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-rw-r--r--compiler/rustc_abi/src/callconv.rs2
-rw-r--r--compiler/rustc_abi/src/extern_abi/mod.rs3
-rw-r--r--compiler/rustc_abi/src/layout.rs7
-rw-r--r--compiler/rustc_abi/src/lib.rs6
-rw-r--r--compiler/rustc_ast/src/ast.rs83
-rw-r--r--compiler/rustc_ast/src/attr/mod.rs335
-rw-r--r--compiler/rustc_ast/src/entry.rs7
-rw-r--r--compiler/rustc_ast/src/expand/allocator.rs2
-rw-r--r--compiler/rustc_ast/src/expand/mod.rs2
-rw-r--r--compiler/rustc_ast/src/format.rs3
-rw-r--r--compiler/rustc_ast/src/lib.rs12
-rw-r--r--compiler/rustc_ast/src/mut_visit.rs7
-rw-r--r--compiler/rustc_ast/src/token.rs13
-rw-r--r--compiler/rustc_ast/src/tokenstream.rs76
-rw-r--r--compiler/rustc_ast/src/util/literal.rs3
-rw-r--r--compiler/rustc_ast/src/util/parser.rs12
-rw-r--r--compiler/rustc_ast/src/visit.rs5
-rw-r--r--compiler/rustc_ast_lowering/src/asm.rs3
-rw-r--r--compiler/rustc_ast_lowering/src/delegation.rs3
-rw-r--r--compiler/rustc_ast_lowering/src/errors.rs3
-rw-r--r--compiler/rustc_ast_lowering/src/expr.rs3
-rw-r--r--compiler/rustc_ast_lowering/src/format.rs3
-rw-r--r--compiler/rustc_ast_lowering/src/item.rs13
-rw-r--r--compiler/rustc_ast_lowering/src/lib.rs49
-rw-r--r--compiler/rustc_ast_lowering/src/pat.rs12
-rw-r--r--compiler/rustc_ast_lowering/src/path.rs3
-rw-r--r--compiler/rustc_ast_passes/Cargo.toml2
-rw-r--r--compiler/rustc_ast_passes/src/ast_validation.rs5
-rw-r--r--compiler/rustc_ast_passes/src/errors.rs3
-rw-r--r--compiler/rustc_ast_passes/src/feature_gate.rs3
-rw-r--r--compiler/rustc_ast_pretty/src/pprust/state.rs34
-rw-r--r--compiler/rustc_ast_pretty/src/pprust/state/item.rs2
-rw-r--r--compiler/rustc_ast_pretty/src/pprust/tests.rs3
-rw-r--r--compiler/rustc_attr/src/builtin.rs1349
-rw-r--r--compiler/rustc_attr_data_structures/Cargo.toml (renamed from compiler/rustc_attr/Cargo.toml)2
-rw-r--r--compiler/rustc_attr_data_structures/src/attributes.rs106
-rw-r--r--compiler/rustc_attr_data_structures/src/lib.rs16
-rw-r--r--compiler/rustc_attr_data_structures/src/stability.rs200
-rw-r--r--compiler/rustc_attr_data_structures/src/version.rs (renamed from compiler/rustc_session/src/version.rs)8
-rw-r--r--compiler/rustc_attr_parsing/Cargo.toml21
-rw-r--r--compiler/rustc_attr_parsing/messages.ftl (renamed from compiler/rustc_attr/messages.ftl)80
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/allow_unstable.rs49
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/cfg.rs253
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/confusables.rs21
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/deprecation.rs148
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/mod.rs17
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/repr.rs215
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/stability.rs384
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/transparency.rs36
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/util.rs36
-rw-r--r--compiler/rustc_attr_parsing/src/lib.rs (renamed from compiler/rustc_attr/src/lib.rs)11
-rw-r--r--compiler/rustc_attr_parsing/src/session_diagnostics.rs (renamed from compiler/rustc_attr/src/session_diagnostics.rs)109
-rw-r--r--compiler/rustc_borrowck/src/dataflow.rs12
-rw-r--r--compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs3
-rw-r--r--compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs3
-rw-r--r--compiler/rustc_borrowck/src/diagnostics/mod.rs3
-rw-r--r--compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs33
-rw-r--r--compiler/rustc_borrowck/src/diagnostics/region_errors.rs29
-rw-r--r--compiler/rustc_borrowck/src/diagnostics/region_name.rs24
-rw-r--r--compiler/rustc_borrowck/src/diagnostics/var_name.rs3
-rw-r--r--compiler/rustc_borrowck/src/lib.rs84
-rw-r--r--compiler/rustc_borrowck/src/member_constraints.rs52
-rw-r--r--compiler/rustc_borrowck/src/nll.rs99
-rw-r--r--compiler/rustc_borrowck/src/polonius/constraints.rs45
-rw-r--r--compiler/rustc_borrowck/src/polonius/dump.rs104
-rw-r--r--compiler/rustc_borrowck/src/polonius/legacy/accesses.rs85
-rw-r--r--compiler/rustc_borrowck/src/polonius/legacy/loan_invalidations.rs (renamed from compiler/rustc_borrowck/src/polonius/loan_invalidations.rs)16
-rw-r--r--compiler/rustc_borrowck/src/polonius/legacy/loan_kills.rs (renamed from compiler/rustc_borrowck/src/polonius/loan_kills.rs)24
-rw-r--r--compiler/rustc_borrowck/src/polonius/legacy/mod.rs223
-rw-r--r--compiler/rustc_borrowck/src/polonius/mod.rs320
-rw-r--r--compiler/rustc_borrowck/src/region_infer/mod.rs19
-rw-r--r--compiler/rustc_borrowck/src/region_infer/opaque_types.rs13
-rw-r--r--compiler/rustc_borrowck/src/region_infer/values.rs5
-rw-r--r--compiler/rustc_borrowck/src/type_check/constraint_conversion.rs21
-rw-r--r--compiler/rustc_borrowck/src/type_check/liveness/mod.rs3
-rw-r--r--compiler/rustc_borrowck/src/type_check/liveness/polonius.rs136
-rw-r--r--compiler/rustc_borrowck/src/type_check/liveness/trace.rs10
-rw-r--r--compiler/rustc_borrowck/src/type_check/mod.rs175
-rw-r--r--compiler/rustc_borrowck/src/type_check/opaque_types.rs335
-rw-r--r--compiler/rustc_borrowck/src/type_check/relate_tys.rs3
-rw-r--r--compiler/rustc_borrowck/src/universal_regions.rs25
-rw-r--r--compiler/rustc_builtin_macros/Cargo.toml2
-rw-r--r--compiler/rustc_builtin_macros/messages.ftl6
-rw-r--r--compiler/rustc_builtin_macros/src/alloc_error_handler.rs3
-rw-r--r--compiler/rustc_builtin_macros/src/asm.rs113
-rw-r--r--compiler/rustc_builtin_macros/src/assert.rs6
-rw-r--r--compiler/rustc_builtin_macros/src/assert/context.rs3
-rw-r--r--compiler/rustc_builtin_macros/src/autodiff.rs5
-rw-r--r--compiler/rustc_builtin_macros/src/cfg.rs7
-rw-r--r--compiler/rustc_builtin_macros/src/cfg_accessible.rs3
-rw-r--r--compiler/rustc_builtin_macros/src/cfg_eval.rs3
-rw-r--r--compiler/rustc_builtin_macros/src/concat.rs2
-rw-r--r--compiler/rustc_builtin_macros/src/concat_idents.rs5
-rw-r--r--compiler/rustc_builtin_macros/src/derive.rs3
-rw-r--r--compiler/rustc_builtin_macros/src/deriving/clone.rs3
-rw-r--r--compiler/rustc_builtin_macros/src/deriving/cmp/eq.rs3
-rw-r--r--compiler/rustc_builtin_macros/src/deriving/cmp/ord.rs3
-rw-r--r--compiler/rustc_builtin_macros/src/deriving/cmp/partial_eq.rs3
-rw-r--r--compiler/rustc_builtin_macros/src/deriving/cmp/partial_ord.rs3
-rw-r--r--compiler/rustc_builtin_macros/src/deriving/coerce_pointee.rs5
-rw-r--r--compiler/rustc_builtin_macros/src/deriving/debug.rs3
-rw-r--r--compiler/rustc_builtin_macros/src/deriving/decodable.rs3
-rw-r--r--compiler/rustc_builtin_macros/src/deriving/default.rs16
-rw-r--r--compiler/rustc_builtin_macros/src/deriving/encodable.rs3
-rw-r--r--compiler/rustc_builtin_macros/src/deriving/generic/mod.rs5
-rw-r--r--compiler/rustc_builtin_macros/src/deriving/generic/ty.rs3
-rw-r--r--compiler/rustc_builtin_macros/src/deriving/hash.rs3
-rw-r--r--compiler/rustc_builtin_macros/src/deriving/mod.rs3
-rw-r--r--compiler/rustc_builtin_macros/src/edition_panic.rs3
-rw-r--r--compiler/rustc_builtin_macros/src/env.rs3
-rw-r--r--compiler/rustc_builtin_macros/src/errors.rs16
-rw-r--r--compiler/rustc_builtin_macros/src/format.rs12
-rw-r--r--compiler/rustc_builtin_macros/src/global_allocator.rs3
-rw-r--r--compiler/rustc_builtin_macros/src/lib.rs2
-rw-r--r--compiler/rustc_builtin_macros/src/pattern_type.rs5
-rw-r--r--compiler/rustc_builtin_macros/src/proc_macro_harness.rs3
-rw-r--r--compiler/rustc_builtin_macros/src/source_util.rs3
-rw-r--r--compiler/rustc_builtin_macros/src/standard_library_imports.rs3
-rw-r--r--compiler/rustc_builtin_macros/src/test.rs3
-rw-r--r--compiler/rustc_builtin_macros/src/test_harness.rs3
-rw-r--r--compiler/rustc_builtin_macros/src/trace_macros.rs9
-rw-r--r--compiler/rustc_builtin_macros/src/util.rs6
-rw-r--r--compiler/rustc_codegen_cranelift/src/compiler_builtins.rs2
-rw-r--r--compiler/rustc_codegen_cranelift/src/discriminant.rs2
-rw-r--r--compiler/rustc_codegen_cranelift/src/driver/jit.rs2
-rw-r--r--compiler/rustc_codegen_cranelift/src/intrinsics/mod.rs2
-rw-r--r--compiler/rustc_codegen_cranelift/src/main_shim.rs3
-rw-r--r--compiler/rustc_codegen_gcc/src/attributes.rs4
-rw-r--r--compiler/rustc_codegen_gcc/src/gcc_util.rs2
-rw-r--r--compiler/rustc_codegen_gcc/src/intrinsic/mod.rs2
-rw-r--r--compiler/rustc_codegen_gcc/src/lib.rs6
-rw-r--r--compiler/rustc_codegen_llvm/Cargo.toml2
-rw-r--r--compiler/rustc_codegen_llvm/src/attributes.rs2
-rw-r--r--compiler/rustc_codegen_llvm/src/back/write.rs3
-rw-r--r--compiler/rustc_codegen_llvm/src/base.rs2
-rw-r--r--compiler/rustc_codegen_llvm/src/callee.rs2
-rw-r--r--compiler/rustc_codegen_llvm/src/coverageinfo/ffi.rs36
-rw-r--r--compiler/rustc_codegen_llvm/src/coverageinfo/llvm_cov.rs5
-rw-r--r--compiler/rustc_codegen_llvm/src/coverageinfo/map_data.rs84
-rw-r--r--compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs204
-rw-r--r--compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/covfun.rs123
-rw-r--r--compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/spans.rs126
-rw-r--r--compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs19
-rw-r--r--compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs2
-rw-r--r--compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs3
-rw-r--r--compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/cpp_like.rs25
-rw-r--r--compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/mod.rs2
-rw-r--r--compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/native.rs4
-rw-r--r--compiler/rustc_codegen_llvm/src/debuginfo/mod.rs3
-rw-r--r--compiler/rustc_codegen_llvm/src/lib.rs3
-rw-r--r--compiler/rustc_codegen_llvm/src/llvm/ffi.rs28
-rw-r--r--compiler/rustc_codegen_llvm/src/llvm_util.rs8
-rw-r--r--compiler/rustc_codegen_llvm/src/type_of.rs2
-rw-r--r--compiler/rustc_codegen_ssa/Cargo.toml7
-rw-r--r--compiler/rustc_codegen_ssa/src/assert_module_sources.rs11
-rw-r--r--compiler/rustc_codegen_ssa/src/back/archive.rs2
-rw-r--r--compiler/rustc_codegen_ssa/src/back/link.rs35
-rw-r--r--compiler/rustc_codegen_ssa/src/back/linker.rs9
-rw-r--r--compiler/rustc_codegen_ssa/src/back/symbol_export.rs3
-rw-r--r--compiler/rustc_codegen_ssa/src/back/write.rs3
-rw-r--r--compiler/rustc_codegen_ssa/src/base.rs8
-rw-r--r--compiler/rustc_codegen_ssa/src/codegen_attrs.rs93
-rw-r--r--compiler/rustc_codegen_ssa/src/debuginfo/mod.rs4
-rw-r--r--compiler/rustc_codegen_ssa/src/errors.rs70
-rw-r--r--compiler/rustc_codegen_ssa/src/lib.rs2
-rw-r--r--compiler/rustc_codegen_ssa/src/mir/debuginfo.rs3
-rw-r--r--compiler/rustc_codegen_ssa/src/mir/naked_asm.rs2
-rw-r--r--compiler/rustc_codegen_ssa/src/mir/place.rs12
-rw-r--r--compiler/rustc_codegen_ssa/src/target_features.rs13
-rw-r--r--compiler/rustc_codegen_ssa/src/traits/backend.rs2
-rw-r--r--compiler/rustc_const_eval/Cargo.toml2
-rw-r--r--compiler/rustc_const_eval/src/check_consts/check.rs2
-rw-r--r--compiler/rustc_const_eval/src/check_consts/mod.rs2
-rw-r--r--compiler/rustc_const_eval/src/check_consts/ops.rs3
-rw-r--r--compiler/rustc_const_eval/src/check_consts/post_drop_elaboration.rs2
-rw-r--r--compiler/rustc_const_eval/src/check_consts/resolver.rs12
-rw-r--r--compiler/rustc_const_eval/src/const_eval/dummy_machine.rs4
-rw-r--r--compiler/rustc_const_eval/src/const_eval/fn_queries.rs5
-rw-r--r--compiler/rustc_const_eval/src/const_eval/machine.rs8
-rw-r--r--compiler/rustc_const_eval/src/interpret/call.rs4
-rw-r--r--compiler/rustc_const_eval/src/interpret/discriminant.rs25
-rw-r--r--compiler/rustc_const_eval/src/interpret/intrinsics.rs2
-rw-r--r--compiler/rustc_const_eval/src/interpret/machine.rs9
-rw-r--r--compiler/rustc_const_eval/src/interpret/operator.rs2
-rw-r--r--compiler/rustc_const_eval/src/interpret/projection.rs2
-rw-r--r--compiler/rustc_const_eval/src/interpret/validity.rs7
-rw-r--r--compiler/rustc_const_eval/src/interpret/visitor.rs4
-rw-r--r--compiler/rustc_const_eval/src/util/caller_location.rs2
-rw-r--r--compiler/rustc_const_eval/src/util/check_validity_requirement.rs1
-rw-r--r--compiler/rustc_driver_impl/Cargo.toml2
-rw-r--r--compiler/rustc_driver_impl/src/lib.rs107
-rw-r--r--compiler/rustc_driver_impl/src/pretty.rs12
-rw-r--r--compiler/rustc_error_codes/src/error_codes/E0665.md25
-rw-r--r--compiler/rustc_errors/Cargo.toml1
-rw-r--r--compiler/rustc_errors/src/diagnostic.rs3
-rw-r--r--compiler/rustc_errors/src/diagnostic_impls.rs3
-rw-r--r--compiler/rustc_errors/src/emitter.rs12
-rw-r--r--compiler/rustc_errors/src/lib.rs8
-rw-r--r--compiler/rustc_errors/src/markdown/parse.rs2
-rw-r--r--compiler/rustc_expand/Cargo.toml2
-rw-r--r--compiler/rustc_expand/src/base.rs35
-rw-r--r--compiler/rustc_expand/src/build.rs3
-rw-r--r--compiler/rustc_expand/src/config.rs7
-rw-r--r--compiler/rustc_expand/src/errors.rs3
-rw-r--r--compiler/rustc_expand/src/expand.rs5
-rw-r--r--compiler/rustc_expand/src/mbe.rs3
-rw-r--r--compiler/rustc_expand/src/mbe/diagnostics.rs3
-rw-r--r--compiler/rustc_expand/src/mbe/macro_check.rs3
-rw-r--r--compiler/rustc_expand/src/mbe/macro_parser.rs3
-rw-r--r--compiler/rustc_expand/src/mbe/macro_rules.rs8
-rw-r--r--compiler/rustc_expand/src/mbe/metavar_expr.rs42
-rw-r--r--compiler/rustc_expand/src/mbe/quoted.rs55
-rw-r--r--compiler/rustc_expand/src/mbe/transcribe.rs5
-rw-r--r--compiler/rustc_expand/src/module.rs9
-rw-r--r--compiler/rustc_expand/src/placeholders.rs3
-rw-r--r--compiler/rustc_expand/src/proc_macro_server.rs13
-rw-r--r--compiler/rustc_feature/src/accepted.rs7
-rw-r--r--compiler/rustc_feature/src/builtin_attrs.rs21
-rw-r--r--compiler/rustc_feature/src/lib.rs2
-rw-r--r--compiler/rustc_feature/src/removed.rs2
-rw-r--r--compiler/rustc_feature/src/unstable.rs9
-rw-r--r--compiler/rustc_hir/Cargo.toml1
-rw-r--r--compiler/rustc_hir/src/arena.rs2
-rw-r--r--compiler/rustc_hir/src/definitions.rs2
-rw-r--r--compiler/rustc_hir/src/hir.rs299
-rw-r--r--compiler/rustc_hir/src/intravisit.rs5
-rw-r--r--compiler/rustc_hir/src/lang_items.rs11
-rw-r--r--compiler/rustc_hir/src/pat_util.rs3
-rw-r--r--compiler/rustc_hir/src/stable_hash_impls.rs10
-rw-r--r--compiler/rustc_hir/src/weak_lang_items.rs2
-rw-r--r--compiler/rustc_hir_analysis/Cargo.toml2
-rw-r--r--compiler/rustc_hir_analysis/messages.ftl6
-rw-r--r--compiler/rustc_hir_analysis/src/check/check.rs6
-rw-r--r--compiler/rustc_hir_analysis/src/check/compare_impl_item.rs8
-rw-r--r--compiler/rustc_hir_analysis/src/check/compare_impl_item/refine.rs11
-rw-r--r--compiler/rustc_hir_analysis/src/check/entry.rs3
-rw-r--r--compiler/rustc_hir_analysis/src/check/intrinsic.rs3
-rw-r--r--compiler/rustc_hir_analysis/src/check/mod.rs3
-rw-r--r--compiler/rustc_hir_analysis/src/check/region.rs22
-rw-r--r--compiler/rustc_hir_analysis/src/check/wfcheck.rs22
-rw-r--r--compiler/rustc_hir_analysis/src/coherence/builtin.rs100
-rw-r--r--compiler/rustc_hir_analysis/src/coherence/inherent_impls.rs3
-rw-r--r--compiler/rustc_hir_analysis/src/coherence/mod.rs4
-rw-r--r--compiler/rustc_hir_analysis/src/collect.rs227
-rw-r--r--compiler/rustc_hir_analysis/src/collect/generics_of.rs3
-rw-r--r--compiler/rustc_hir_analysis/src/collect/item_bounds.rs7
-rw-r--r--compiler/rustc_hir_analysis/src/collect/predicates_of.rs44
-rw-r--r--compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs3
-rw-r--r--compiler/rustc_hir_analysis/src/collect/type_of.rs5
-rw-r--r--compiler/rustc_hir_analysis/src/errors.rs13
-rw-r--r--compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs5
-rw-r--r--compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs52
-rw-r--r--compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs247
-rw-r--r--compiler/rustc_hir_analysis/src/hir_ty_lowering/generics.rs2
-rw-r--r--compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs5
-rw-r--r--compiler/rustc_hir_analysis/src/variance/dump.rs2
-rw-r--r--compiler/rustc_hir_pretty/src/lib.rs127
-rw-r--r--compiler/rustc_hir_typeck/Cargo.toml2
-rw-r--r--compiler/rustc_hir_typeck/src/callee.rs3
-rw-r--r--compiler/rustc_hir_typeck/src/cast.rs15
-rw-r--r--compiler/rustc_hir_typeck/src/check.rs2
-rw-r--r--compiler/rustc_hir_typeck/src/coercion.rs51
-rw-r--r--compiler/rustc_hir_typeck/src/demand.rs5
-rw-r--r--compiler/rustc_hir_typeck/src/errors.rs3
-rw-r--r--compiler/rustc_hir_typeck/src/expr.rs3
-rw-r--r--compiler/rustc_hir_typeck/src/fallback.rs6
-rw-r--r--compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs29
-rw-r--r--compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs3
-rw-r--r--compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs10
-rw-r--r--compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs3
-rw-r--r--compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs20
-rw-r--r--compiler/rustc_hir_typeck/src/method/mod.rs3
-rw-r--r--compiler/rustc_hir_typeck/src/method/prelude_edition_lints.rs12
-rw-r--r--compiler/rustc_hir_typeck/src/method/probe.rs39
-rw-r--r--compiler/rustc_hir_typeck/src/method/suggest.rs6
-rw-r--r--compiler/rustc_hir_typeck/src/op.rs3
-rw-r--r--compiler/rustc_hir_typeck/src/pat.rs104
-rw-r--r--compiler/rustc_hir_typeck/src/place_op.rs3
-rw-r--r--compiler/rustc_hir_typeck/src/upvar.rs5
-rw-r--r--compiler/rustc_hir_typeck/src/writeback.rs15
-rw-r--r--compiler/rustc_incremental/src/assert_dep_graph.rs7
-rw-r--r--compiler/rustc_incremental/src/errors.rs3
-rw-r--r--compiler/rustc_incremental/src/persist/dirty_clean.rs9
-rw-r--r--compiler/rustc_index/Cargo.toml2
-rw-r--r--compiler/rustc_index/src/bit_set.rs8
-rw-r--r--compiler/rustc_index_macros/Cargo.toml1
-rw-r--r--compiler/rustc_infer/src/infer/canonical/query_response.rs14
-rw-r--r--compiler/rustc_infer/src/infer/mod.rs24
-rw-r--r--compiler/rustc_infer/src/infer/opaque_types/mod.rs287
-rw-r--r--compiler/rustc_infer/src/infer/region_constraints/mod.rs36
-rw-r--r--compiler/rustc_infer/src/traits/util.rs3
-rw-r--r--compiler/rustc_interface/Cargo.toml2
-rw-r--r--compiler/rustc_interface/src/interface.rs3
-rw-r--r--compiler/rustc_interface/src/lib.rs6
-rw-r--r--compiler/rustc_interface/src/passes.rs112
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577 files changed, 9775 insertions, 7982 deletions
diff --git a/compiler/rustc_abi/src/callconv.rs b/compiler/rustc_abi/src/callconv.rs
index ee63e46e88c..400395f99ff 100644
--- a/compiler/rustc_abi/src/callconv.rs
+++ b/compiler/rustc_abi/src/callconv.rs
@@ -206,7 +206,7 @@ impl<'a, Ty> TyAndLayout<'a, Ty> {
                 let (mut result, mut total) = from_fields_at(*self, Size::ZERO)?;
 
                 match &self.variants {
-                    abi::Variants::Single { .. } => {}
+                    abi::Variants::Single { .. } | abi::Variants::Empty => {}
                     abi::Variants::Multiple { variants, .. } => {
                         // Treat enum variants like union members.
                         // HACK(eddyb) pretend the `enum` field (discriminant)
diff --git a/compiler/rustc_abi/src/extern_abi/mod.rs b/compiler/rustc_abi/src/extern_abi/mod.rs
index f7e41280131..390f2dbc10f 100644
--- a/compiler/rustc_abi/src/extern_abi/mod.rs
+++ b/compiler/rustc_abi/src/extern_abi/mod.rs
@@ -1,8 +1,7 @@
 use std::fmt;
 
 use rustc_macros::{Decodable, Encodable, HashStable_Generic};
-use rustc_span::symbol::sym;
-use rustc_span::{Span, Symbol};
+use rustc_span::{Span, Symbol, sym};
 
 #[cfg(test)]
 mod tests;
diff --git a/compiler/rustc_abi/src/layout.rs b/compiler/rustc_abi/src/layout.rs
index e6d66f608da..226a46f605c 100644
--- a/compiler/rustc_abi/src/layout.rs
+++ b/compiler/rustc_abi/src/layout.rs
@@ -213,8 +213,9 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
         &self,
     ) -> LayoutData<FieldIdx, VariantIdx> {
         let dl = self.cx.data_layout();
+        // This is also used for uninhabited enums, so we use `Variants::Empty`.
         LayoutData {
-            variants: Variants::Single { index: VariantIdx::new(0) },
+            variants: Variants::Empty,
             fields: FieldsShape::Primitive,
             backend_repr: BackendRepr::Uninhabited,
             largest_niche: None,
@@ -1004,8 +1005,8 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
             Variants::Multiple { tag, tag_encoding, tag_field, .. } => {
                 Variants::Multiple { tag, tag_encoding, tag_field, variants: best_layout.variants }
             }
-            Variants::Single { .. } => {
-                panic!("encountered a single-variant enum during multi-variant layout")
+            Variants::Single { .. } | Variants::Empty => {
+                panic!("encountered a single-variant or empty enum during multi-variant layout")
             }
         };
         Ok(best_layout.layout)
diff --git a/compiler/rustc_abi/src/lib.rs b/compiler/rustc_abi/src/lib.rs
index 15a27c0b6ee..ca15f7d9920 100644
--- a/compiler/rustc_abi/src/lib.rs
+++ b/compiler/rustc_abi/src/lib.rs
@@ -1504,10 +1504,12 @@ impl BackendRepr {
 #[derive(PartialEq, Eq, Hash, Clone, Debug)]
 #[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
 pub enum Variants<FieldIdx: Idx, VariantIdx: Idx> {
+    /// A type with no valid variants. Must be uninhabited.
+    Empty,
+
     /// Single enum variants, structs/tuples, unions, and all non-ADTs.
     Single {
-        /// Always 0 for non-enums/generators.
-        /// For enums without a variant, this is an invalid index!
+        /// Always `0` for types that cannot have multiple variants.
         index: VariantIdx,
     },
 
diff --git a/compiler/rustc_ast/src/ast.rs b/compiler/rustc_ast/src/ast.rs
index f0099fa8adc..cec868e5c8e 100644
--- a/compiler/rustc_ast/src/ast.rs
+++ b/compiler/rustc_ast/src/ast.rs
@@ -19,7 +19,7 @@
 //! - [`UnOp`], [`BinOp`], and [`BinOpKind`]: Unary and binary operators.
 
 use std::borrow::Cow;
-use std::{cmp, fmt, mem};
+use std::{cmp, fmt};
 
 pub use GenericArgs::*;
 pub use UnsafeSource::*;
@@ -31,8 +31,7 @@ use rustc_data_structures::sync::Lrc;
 use rustc_macros::{Decodable, Encodable, HashStable_Generic};
 pub use rustc_span::AttrId;
 use rustc_span::source_map::{Spanned, respan};
-use rustc_span::symbol::{Ident, Symbol, kw, sym};
-use rustc_span::{DUMMY_SP, ErrorGuaranteed, Span};
+use rustc_span::{DUMMY_SP, ErrorGuaranteed, Ident, Span, Symbol, kw, sym};
 use thin_vec::{ThinVec, thin_vec};
 
 pub use crate::format::*;
@@ -859,6 +858,8 @@ pub enum PatKind {
 pub enum PatFieldsRest {
     /// `module::StructName { field, ..}`
     Rest,
+    /// `module::StructName { field, syntax error }`
+    Recovered(ErrorGuaranteed),
     /// `module::StructName { field }`
     None,
 }
@@ -1321,11 +1322,15 @@ impl Expr {
     }
 
     pub fn precedence(&self) -> ExprPrecedence {
-        match self.kind {
-            ExprKind::Closure(..) => ExprPrecedence::Closure,
+        match &self.kind {
+            ExprKind::Closure(closure) => {
+                match closure.fn_decl.output {
+                    FnRetTy::Default(_) => ExprPrecedence::Jump,
+                    FnRetTy::Ty(_) => ExprPrecedence::Unambiguous,
+                }
+            }
 
             ExprKind::Break(..)
-            | ExprKind::Continue(..)
             | ExprKind::Ret(..)
             | ExprKind::Yield(..)
             | ExprKind::Yeet(..)
@@ -1359,6 +1364,7 @@ impl Expr {
             | ExprKind::Block(..)
             | ExprKind::Call(..)
             | ExprKind::ConstBlock(_)
+            | ExprKind::Continue(..)
             | ExprKind::Field(..)
             | ExprKind::ForLoop { .. }
             | ExprKind::FormatArgs(..)
@@ -1758,53 +1764,16 @@ pub enum AttrArgs {
     Eq {
         /// Span of the `=` token.
         eq_span: Span,
-
-        value: AttrArgsEq,
+        expr: P<Expr>,
     },
 }
 
-// The RHS of an `AttrArgs::Eq` starts out as an expression. Once macro
-// expansion is completed, all cases end up either as a meta item literal,
-// which is the form used after lowering to HIR, or as an error.
-#[derive(Clone, Encodable, Decodable, Debug)]
-pub enum AttrArgsEq {
-    Ast(P<Expr>),
-    Hir(MetaItemLit),
-}
-
-impl AttrArgsEq {
-    pub fn span(&self) -> Span {
-        match self {
-            AttrArgsEq::Ast(p) => p.span,
-            AttrArgsEq::Hir(lit) => lit.span,
-        }
-    }
-
-    pub fn unwrap_ast(&self) -> &Expr {
-        match self {
-            AttrArgsEq::Ast(p) => p,
-            AttrArgsEq::Hir(lit) => {
-                unreachable!("in literal form when getting inner tokens: {lit:?}")
-            }
-        }
-    }
-
-    pub fn unwrap_ast_mut(&mut self) -> &mut P<Expr> {
-        match self {
-            AttrArgsEq::Ast(p) => p,
-            AttrArgsEq::Hir(lit) => {
-                unreachable!("in literal form when getting inner tokens: {lit:?}")
-            }
-        }
-    }
-}
-
 impl AttrArgs {
     pub fn span(&self) -> Option<Span> {
         match self {
             AttrArgs::Empty => None,
             AttrArgs::Delimited(args) => Some(args.dspan.entire()),
-            AttrArgs::Eq { eq_span, value } => Some(eq_span.to(value.span())),
+            AttrArgs::Eq { eq_span, expr } => Some(eq_span.to(expr.span)),
         }
     }
 
@@ -1814,27 +1783,7 @@ impl AttrArgs {
         match self {
             AttrArgs::Empty => TokenStream::default(),
             AttrArgs::Delimited(args) => args.tokens.clone(),
-            AttrArgs::Eq { value, .. } => TokenStream::from_ast(value.unwrap_ast()),
-        }
-    }
-}
-
-impl<CTX> HashStable<CTX> for AttrArgs
-where
-    CTX: crate::HashStableContext,
-{
-    fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
-        mem::discriminant(self).hash_stable(ctx, hasher);
-        match self {
-            AttrArgs::Empty => {}
-            AttrArgs::Delimited(args) => args.hash_stable(ctx, hasher),
-            AttrArgs::Eq { value: AttrArgsEq::Ast(expr), .. } => {
-                unreachable!("hash_stable {:?}", expr);
-            }
-            AttrArgs::Eq { eq_span, value: AttrArgsEq::Hir(lit) } => {
-                eq_span.hash_stable(ctx, hasher);
-                lit.hash_stable(ctx, hasher);
-            }
+            AttrArgs::Eq { expr, .. } => TokenStream::from_ast(expr),
         }
     }
 }
@@ -3051,7 +3000,7 @@ impl NormalAttr {
     }
 }
 
-#[derive(Clone, Encodable, Decodable, Debug, HashStable_Generic)]
+#[derive(Clone, Encodable, Decodable, Debug)]
 pub struct AttrItem {
     pub unsafety: Safety,
     pub path: Path,
diff --git a/compiler/rustc_ast/src/attr/mod.rs b/compiler/rustc_ast/src/attr/mod.rs
index 0d79cadef34..97385b2eaab 100644
--- a/compiler/rustc_ast/src/attr/mod.rs
+++ b/compiler/rustc_ast/src/attr/mod.rs
@@ -1,22 +1,23 @@
 //! Functions dealing with attributes and meta items.
 
-use std::iter;
+use std::fmt::Debug;
 use std::sync::atomic::{AtomicU32, Ordering};
 
 use rustc_index::bit_set::GrowableBitSet;
-use rustc_span::Span;
-use rustc_span::symbol::{Ident, Symbol, sym};
+use rustc_span::{Ident, Span, Symbol, sym};
 use smallvec::{SmallVec, smallvec};
 use thin_vec::{ThinVec, thin_vec};
 
 use crate::ast::{
-    AttrArgs, AttrArgsEq, AttrId, AttrItem, AttrKind, AttrStyle, AttrVec, Attribute, DUMMY_NODE_ID,
-    DelimArgs, Expr, ExprKind, LitKind, MetaItem, MetaItemInner, MetaItemKind, MetaItemLit,
-    NormalAttr, Path, PathSegment, Safety,
+    AttrArgs, AttrId, AttrItem, AttrKind, AttrStyle, AttrVec, Attribute, DUMMY_NODE_ID, DelimArgs,
+    Expr, ExprKind, LitKind, MetaItem, MetaItemInner, MetaItemKind, MetaItemLit, NormalAttr, Path,
+    PathSegment, Safety,
 };
 use crate::ptr::P;
 use crate::token::{self, CommentKind, Delimiter, Token};
-use crate::tokenstream::{DelimSpan, LazyAttrTokenStream, Spacing, TokenStream, TokenTree};
+use crate::tokenstream::{
+    DelimSpan, LazyAttrTokenStream, Spacing, TokenStream, TokenStreamIter, TokenTree,
+};
 use crate::util::comments;
 use crate::util::literal::escape_string_symbol;
 
@@ -66,11 +67,27 @@ impl Attribute {
             AttrKind::DocComment(..) => panic!("unexpected doc comment"),
         }
     }
+}
+
+impl AttributeExt for Attribute {
+    fn id(&self) -> AttrId {
+        self.id
+    }
+
+    fn value_span(&self) -> Option<Span> {
+        match &self.kind {
+            AttrKind::Normal(normal) => match &normal.item.args {
+                AttrArgs::Eq { expr, .. } => Some(expr.span),
+                _ => None,
+            },
+            AttrKind::DocComment(..) => None,
+        }
+    }
 
     /// Returns `true` if it is a sugared doc comment (`///` or `//!` for example).
     /// So `#[doc = "doc"]` (which is a doc comment) and `#[doc(...)]` (which is not
     /// a doc comment) will return `false`.
-    pub fn is_doc_comment(&self) -> bool {
+    fn is_doc_comment(&self) -> bool {
         match self.kind {
             AttrKind::Normal(..) => false,
             AttrKind::DocComment(..) => true,
@@ -78,7 +95,7 @@ impl Attribute {
     }
 
     /// For a single-segment attribute, returns its name; otherwise, returns `None`.
-    pub fn ident(&self) -> Option<Ident> {
+    fn ident(&self) -> Option<Ident> {
         match &self.kind {
             AttrKind::Normal(normal) => {
                 if let [ident] = &*normal.item.path.segments {
@@ -91,28 +108,14 @@ impl Attribute {
         }
     }
 
-    pub fn name_or_empty(&self) -> Symbol {
-        self.ident().unwrap_or_else(Ident::empty).name
-    }
-
-    pub fn path(&self) -> SmallVec<[Symbol; 1]> {
-        match &self.kind {
-            AttrKind::Normal(normal) => {
-                normal.item.path.segments.iter().map(|s| s.ident.name).collect()
-            }
-            AttrKind::DocComment(..) => smallvec![sym::doc],
-        }
-    }
-
-    #[inline]
-    pub fn has_name(&self, name: Symbol) -> bool {
+    fn ident_path(&self) -> Option<SmallVec<[Ident; 1]>> {
         match &self.kind {
-            AttrKind::Normal(normal) => normal.item.path == name,
-            AttrKind::DocComment(..) => false,
+            AttrKind::Normal(p) => Some(p.item.path.segments.iter().map(|i| i.ident).collect()),
+            AttrKind::DocComment(_, _) => None,
         }
     }
 
-    pub fn path_matches(&self, name: &[Symbol]) -> bool {
+    fn path_matches(&self, name: &[Symbol]) -> bool {
         match &self.kind {
             AttrKind::Normal(normal) => {
                 normal.item.path.segments.len() == name.len()
@@ -128,7 +131,11 @@ impl Attribute {
         }
     }
 
-    pub fn is_word(&self) -> bool {
+    fn span(&self) -> Span {
+        self.span
+    }
+
+    fn is_word(&self) -> bool {
         if let AttrKind::Normal(normal) = &self.kind {
             matches!(normal.item.args, AttrArgs::Empty)
         } else {
@@ -143,7 +150,7 @@ impl Attribute {
     /// #[attr = ""] // Returns `None`.
     /// #[attr] // Returns `None`.
     /// ```
-    pub fn meta_item_list(&self) -> Option<ThinVec<MetaItemInner>> {
+    fn meta_item_list(&self) -> Option<ThinVec<MetaItemInner>> {
         match &self.kind {
             AttrKind::Normal(normal) => normal.item.meta_item_list(),
             AttrKind::DocComment(..) => None,
@@ -165,7 +172,7 @@ impl Attribute {
     /// ```text
     /// #[attr("value")]
     /// ```
-    pub fn value_str(&self) -> Option<Symbol> {
+    fn value_str(&self) -> Option<Symbol> {
         match &self.kind {
             AttrKind::Normal(normal) => normal.item.value_str(),
             AttrKind::DocComment(..) => None,
@@ -177,7 +184,7 @@ impl Attribute {
     /// * `/** doc */` returns `Some(("doc", CommentKind::Block))`.
     /// * `#[doc = "doc"]` returns `Some(("doc", CommentKind::Line))`.
     /// * `#[doc(...)]` returns `None`.
-    pub fn doc_str_and_comment_kind(&self) -> Option<(Symbol, CommentKind)> {
+    fn doc_str_and_comment_kind(&self) -> Option<(Symbol, CommentKind)> {
         match &self.kind {
             AttrKind::DocComment(kind, data) => Some((*data, *kind)),
             AttrKind::Normal(normal) if normal.item.path == sym::doc => {
@@ -191,7 +198,7 @@ impl Attribute {
     /// * `///doc` returns `Some("doc")`.
     /// * `#[doc = "doc"]` returns `Some("doc")`.
     /// * `#[doc(...)]` returns `None`.
-    pub fn doc_str(&self) -> Option<Symbol> {
+    fn doc_str(&self) -> Option<Symbol> {
         match &self.kind {
             AttrKind::DocComment(.., data) => Some(*data),
             AttrKind::Normal(normal) if normal.item.path == sym::doc => normal.item.value_str(),
@@ -199,14 +206,14 @@ impl Attribute {
         }
     }
 
-    pub fn may_have_doc_links(&self) -> bool {
-        self.doc_str().is_some_and(|s| comments::may_have_doc_links(s.as_str()))
+    fn style(&self) -> AttrStyle {
+        self.style
     }
+}
 
-    pub fn is_proc_macro_attr(&self) -> bool {
-        [sym::proc_macro, sym::proc_macro_attribute, sym::proc_macro_derive]
-            .iter()
-            .any(|kind| self.has_name(*kind))
+impl Attribute {
+    pub fn may_have_doc_links(&self) -> bool {
+        self.doc_str().is_some_and(|s| comments::may_have_doc_links(s.as_str()))
     }
 
     /// Extracts the MetaItem from inside this Attribute.
@@ -268,7 +275,12 @@ impl AttrItem {
     /// ```
     fn value_str(&self) -> Option<Symbol> {
         match &self.args {
-            AttrArgs::Eq { value, .. } => value.value_str(),
+            AttrArgs::Eq { expr, .. } => match expr.kind {
+                ExprKind::Lit(token_lit) => {
+                    LitKind::from_token_lit(token_lit).ok().and_then(|lit| lit.str())
+                }
+                _ => None,
+            },
             AttrArgs::Delimited(_) | AttrArgs::Empty => None,
         }
     }
@@ -287,20 +299,6 @@ impl AttrItem {
     }
 }
 
-impl AttrArgsEq {
-    fn value_str(&self) -> Option<Symbol> {
-        match self {
-            AttrArgsEq::Ast(expr) => match expr.kind {
-                ExprKind::Lit(token_lit) => {
-                    LitKind::from_token_lit(token_lit).ok().and_then(|lit| lit.str())
-                }
-                _ => None,
-            },
-            AttrArgsEq::Hir(lit) => lit.kind.str(),
-        }
-    }
-}
-
 impl MetaItem {
     /// For a single-segment meta item, returns its name; otherwise, returns `None`.
     pub fn ident(&self) -> Option<Ident> {
@@ -368,12 +366,9 @@ impl MetaItem {
         }
     }
 
-    fn from_tokens<'a, I>(tokens: &mut iter::Peekable<I>) -> Option<MetaItem>
-    where
-        I: Iterator<Item = &'a TokenTree>,
-    {
+    fn from_tokens(iter: &mut TokenStreamIter<'_>) -> Option<MetaItem> {
         // FIXME: Share code with `parse_path`.
-        let tt = tokens.next().map(|tt| TokenTree::uninterpolate(tt));
+        let tt = iter.next().map(|tt| TokenTree::uninterpolate(tt));
         let path = match tt.as_deref() {
             Some(&TokenTree::Token(
                 Token { kind: ref kind @ (token::Ident(..) | token::PathSep), span },
@@ -381,9 +376,9 @@ impl MetaItem {
             )) => 'arm: {
                 let mut segments = if let &token::Ident(name, _) = kind {
                     if let Some(TokenTree::Token(Token { kind: token::PathSep, .. }, _)) =
-                        tokens.peek()
+                        iter.peek()
                     {
-                        tokens.next();
+                        iter.next();
                         thin_vec![PathSegment::from_ident(Ident::new(name, span))]
                     } else {
                         break 'arm Path::from_ident(Ident::new(name, span));
@@ -393,16 +388,16 @@ impl MetaItem {
                 };
                 loop {
                     if let Some(&TokenTree::Token(Token { kind: token::Ident(name, _), span }, _)) =
-                        tokens.next().map(|tt| TokenTree::uninterpolate(tt)).as_deref()
+                        iter.next().map(|tt| TokenTree::uninterpolate(tt)).as_deref()
                     {
                         segments.push(PathSegment::from_ident(Ident::new(name, span)));
                     } else {
                         return None;
                     }
                     if let Some(TokenTree::Token(Token { kind: token::PathSep, .. }, _)) =
-                        tokens.peek()
+                        iter.peek()
                     {
-                        tokens.next();
+                        iter.next();
                     } else {
                         break;
                     }
@@ -423,8 +418,8 @@ impl MetaItem {
             }
             _ => return None,
         };
-        let list_closing_paren_pos = tokens.peek().map(|tt| tt.span().hi());
-        let kind = MetaItemKind::from_tokens(tokens)?;
+        let list_closing_paren_pos = iter.peek().map(|tt| tt.span().hi());
+        let kind = MetaItemKind::from_tokens(iter)?;
         let hi = match &kind {
             MetaItemKind::NameValue(lit) => lit.span.hi(),
             MetaItemKind::List(..) => list_closing_paren_pos.unwrap_or(path.span.hi()),
@@ -439,13 +434,14 @@ impl MetaItem {
 }
 
 impl MetaItemKind {
-    fn list_from_tokens(tokens: TokenStream) -> Option<ThinVec<MetaItemInner>> {
-        let mut tokens = tokens.trees().peekable();
+    // public because it can be called in the hir
+    pub fn list_from_tokens(tokens: TokenStream) -> Option<ThinVec<MetaItemInner>> {
+        let mut iter = tokens.iter();
         let mut result = ThinVec::new();
-        while tokens.peek().is_some() {
-            let item = MetaItemInner::from_tokens(&mut tokens)?;
+        while iter.peek().is_some() {
+            let item = MetaItemInner::from_tokens(&mut iter)?;
             result.push(item);
-            match tokens.next() {
+            match iter.next() {
                 None | Some(TokenTree::Token(Token { kind: token::Comma, .. }, _)) => {}
                 _ => return None,
             }
@@ -453,12 +449,10 @@ impl MetaItemKind {
         Some(result)
     }
 
-    fn name_value_from_tokens<'a>(
-        tokens: &mut impl Iterator<Item = &'a TokenTree>,
-    ) -> Option<MetaItemKind> {
-        match tokens.next() {
+    fn name_value_from_tokens(iter: &mut TokenStreamIter<'_>) -> Option<MetaItemKind> {
+        match iter.next() {
             Some(TokenTree::Delimited(.., Delimiter::Invisible(_), inner_tokens)) => {
-                MetaItemKind::name_value_from_tokens(&mut inner_tokens.trees())
+                MetaItemKind::name_value_from_tokens(&mut inner_tokens.iter())
             }
             Some(TokenTree::Token(token, _)) => {
                 MetaItemLit::from_token(token).map(MetaItemKind::NameValue)
@@ -467,19 +461,17 @@ impl MetaItemKind {
         }
     }
 
-    fn from_tokens<'a>(
-        tokens: &mut iter::Peekable<impl Iterator<Item = &'a TokenTree>>,
-    ) -> Option<MetaItemKind> {
-        match tokens.peek() {
+    fn from_tokens(iter: &mut TokenStreamIter<'_>) -> Option<MetaItemKind> {
+        match iter.peek() {
             Some(TokenTree::Delimited(.., Delimiter::Parenthesis, inner_tokens)) => {
                 let inner_tokens = inner_tokens.clone();
-                tokens.next();
+                iter.next();
                 MetaItemKind::list_from_tokens(inner_tokens).map(MetaItemKind::List)
             }
             Some(TokenTree::Delimited(..)) => None,
             Some(TokenTree::Token(Token { kind: token::Eq, .. }, _)) => {
-                tokens.next();
-                MetaItemKind::name_value_from_tokens(tokens)
+                iter.next();
+                MetaItemKind::name_value_from_tokens(iter)
             }
             _ => Some(MetaItemKind::Word),
         }
@@ -492,7 +484,7 @@ impl MetaItemKind {
                 MetaItemKind::list_from_tokens(tokens.clone()).map(MetaItemKind::List)
             }
             AttrArgs::Delimited(..) => None,
-            AttrArgs::Eq { value: AttrArgsEq::Ast(expr), .. } => match expr.kind {
+            AttrArgs::Eq { expr, .. } => match expr.kind {
                 ExprKind::Lit(token_lit) => {
                     // Turn failures to `None`, we'll get parse errors elsewhere.
                     MetaItemLit::from_token_lit(token_lit, expr.span)
@@ -501,9 +493,6 @@ impl MetaItemKind {
                 }
                 _ => None,
             },
-            AttrArgs::Eq { value: AttrArgsEq::Hir(lit), .. } => {
-                Some(MetaItemKind::NameValue(lit.clone()))
-            }
         }
     }
 }
@@ -598,22 +587,19 @@ impl MetaItemInner {
         self.meta_item().is_some()
     }
 
-    fn from_tokens<'a, I>(tokens: &mut iter::Peekable<I>) -> Option<MetaItemInner>
-    where
-        I: Iterator<Item = &'a TokenTree>,
-    {
-        match tokens.peek() {
+    fn from_tokens(iter: &mut TokenStreamIter<'_>) -> Option<MetaItemInner> {
+        match iter.peek() {
             Some(TokenTree::Token(token, _)) if let Some(lit) = MetaItemLit::from_token(token) => {
-                tokens.next();
+                iter.next();
                 return Some(MetaItemInner::Lit(lit));
             }
             Some(TokenTree::Delimited(.., Delimiter::Invisible(_), inner_tokens)) => {
-                tokens.next();
-                return MetaItemInner::from_tokens(&mut inner_tokens.trees().peekable());
+                iter.next();
+                return MetaItemInner::from_tokens(&mut inner_tokens.iter());
             }
             _ => {}
         }
-        MetaItem::from_tokens(tokens).map(MetaItemInner::MetaItem)
+        MetaItem::from_tokens(iter).map(MetaItemInner::MetaItem)
     }
 }
 
@@ -704,26 +690,175 @@ pub fn mk_attr_name_value_str(
         tokens: None,
     });
     let path = Path::from_ident(Ident::new(name, span));
-    let args = AttrArgs::Eq { eq_span: span, value: AttrArgsEq::Ast(expr) };
+    let args = AttrArgs::Eq { eq_span: span, expr };
     mk_attr(g, style, unsafety, path, args, span)
 }
 
-pub fn filter_by_name(attrs: &[Attribute], name: Symbol) -> impl Iterator<Item = &Attribute> {
+pub fn filter_by_name<A: AttributeExt>(attrs: &[A], name: Symbol) -> impl Iterator<Item = &A> {
     attrs.iter().filter(move |attr| attr.has_name(name))
 }
 
-pub fn find_by_name(attrs: &[Attribute], name: Symbol) -> Option<&Attribute> {
+pub fn find_by_name<A: AttributeExt>(attrs: &[A], name: Symbol) -> Option<&A> {
     filter_by_name(attrs, name).next()
 }
 
-pub fn first_attr_value_str_by_name(attrs: &[Attribute], name: Symbol) -> Option<Symbol> {
+pub fn first_attr_value_str_by_name(attrs: &[impl AttributeExt], name: Symbol) -> Option<Symbol> {
     find_by_name(attrs, name).and_then(|attr| attr.value_str())
 }
 
-pub fn contains_name(attrs: &[Attribute], name: Symbol) -> bool {
+pub fn contains_name(attrs: &[impl AttributeExt], name: Symbol) -> bool {
     find_by_name(attrs, name).is_some()
 }
 
 pub fn list_contains_name(items: &[MetaItemInner], name: Symbol) -> bool {
     items.iter().any(|item| item.has_name(name))
 }
+
+impl MetaItemLit {
+    pub fn value_str(&self) -> Option<Symbol> {
+        LitKind::from_token_lit(self.as_token_lit()).ok().and_then(|lit| lit.str())
+    }
+}
+
+pub trait AttributeExt: Debug {
+    fn id(&self) -> AttrId;
+
+    fn name_or_empty(&self) -> Symbol {
+        self.ident().unwrap_or_else(Ident::empty).name
+    }
+
+    /// Get the meta item list, `#[attr(meta item list)]`
+    fn meta_item_list(&self) -> Option<ThinVec<MetaItemInner>>;
+
+    /// Gets the value literal, as string, when using `#[attr = value]`
+    fn value_str(&self) -> Option<Symbol>;
+
+    /// Gets the span of the value literal, as string, when using `#[attr = value]`
+    fn value_span(&self) -> Option<Span>;
+
+    /// For a single-segment attribute, returns its name; otherwise, returns `None`.
+    fn ident(&self) -> Option<Ident>;
+
+    /// Checks whether the path of this attribute matches the name.
+    ///
+    /// Matches one segment of the path to each element in `name`
+    fn path_matches(&self, name: &[Symbol]) -> bool;
+
+    /// Returns `true` if it is a sugared doc comment (`///` or `//!` for example).
+    /// So `#[doc = "doc"]` (which is a doc comment) and `#[doc(...)]` (which is not
+    /// a doc comment) will return `false`.
+    fn is_doc_comment(&self) -> bool;
+
+    #[inline]
+    fn has_name(&self, name: Symbol) -> bool {
+        self.ident().map(|x| x.name == name).unwrap_or(false)
+    }
+
+    /// get the span of the entire attribute
+    fn span(&self) -> Span;
+
+    fn is_word(&self) -> bool;
+
+    fn path(&self) -> SmallVec<[Symbol; 1]> {
+        self.ident_path()
+            .map(|i| i.into_iter().map(|i| i.name).collect())
+            .unwrap_or(smallvec![sym::doc])
+    }
+
+    /// Returns None for doc comments
+    fn ident_path(&self) -> Option<SmallVec<[Ident; 1]>>;
+
+    /// Returns the documentation if this is a doc comment or a sugared doc comment.
+    /// * `///doc` returns `Some("doc")`.
+    /// * `#[doc = "doc"]` returns `Some("doc")`.
+    /// * `#[doc(...)]` returns `None`.
+    fn doc_str(&self) -> Option<Symbol>;
+
+    fn is_proc_macro_attr(&self) -> bool {
+        [sym::proc_macro, sym::proc_macro_attribute, sym::proc_macro_derive]
+            .iter()
+            .any(|kind| self.has_name(*kind))
+    }
+
+    /// Returns the documentation and its kind if this is a doc comment or a sugared doc comment.
+    /// * `///doc` returns `Some(("doc", CommentKind::Line))`.
+    /// * `/** doc */` returns `Some(("doc", CommentKind::Block))`.
+    /// * `#[doc = "doc"]` returns `Some(("doc", CommentKind::Line))`.
+    /// * `#[doc(...)]` returns `None`.
+    fn doc_str_and_comment_kind(&self) -> Option<(Symbol, CommentKind)>;
+
+    fn style(&self) -> AttrStyle;
+}
+
+// FIXME(fn_delegation): use function delegation instead of manually forwarding
+
+impl Attribute {
+    pub fn id(&self) -> AttrId {
+        AttributeExt::id(self)
+    }
+
+    pub fn name_or_empty(&self) -> Symbol {
+        AttributeExt::name_or_empty(self)
+    }
+
+    pub fn meta_item_list(&self) -> Option<ThinVec<MetaItemInner>> {
+        AttributeExt::meta_item_list(self)
+    }
+
+    pub fn value_str(&self) -> Option<Symbol> {
+        AttributeExt::value_str(self)
+    }
+
+    pub fn value_span(&self) -> Option<Span> {
+        AttributeExt::value_span(self)
+    }
+
+    pub fn ident(&self) -> Option<Ident> {
+        AttributeExt::ident(self)
+    }
+
+    pub fn path_matches(&self, name: &[Symbol]) -> bool {
+        AttributeExt::path_matches(self, name)
+    }
+
+    pub fn is_doc_comment(&self) -> bool {
+        AttributeExt::is_doc_comment(self)
+    }
+
+    #[inline]
+    pub fn has_name(&self, name: Symbol) -> bool {
+        AttributeExt::has_name(self, name)
+    }
+
+    pub fn span(&self) -> Span {
+        AttributeExt::span(self)
+    }
+
+    pub fn is_word(&self) -> bool {
+        AttributeExt::is_word(self)
+    }
+
+    pub fn path(&self) -> SmallVec<[Symbol; 1]> {
+        AttributeExt::path(self)
+    }
+
+    pub fn ident_path(&self) -> Option<SmallVec<[Ident; 1]>> {
+        AttributeExt::ident_path(self)
+    }
+
+    pub fn doc_str(&self) -> Option<Symbol> {
+        AttributeExt::doc_str(self)
+    }
+
+    pub fn is_proc_macro_attr(&self) -> bool {
+        AttributeExt::is_proc_macro_attr(self)
+    }
+
+    pub fn doc_str_and_comment_kind(&self) -> Option<(Symbol, CommentKind)> {
+        AttributeExt::doc_str_and_comment_kind(self)
+    }
+
+    pub fn style(&self) -> AttrStyle {
+        AttributeExt::style(self)
+    }
+}
diff --git a/compiler/rustc_ast/src/entry.rs b/compiler/rustc_ast/src/entry.rs
index 45c4caca6e9..ab1413d6080 100644
--- a/compiler/rustc_ast/src/entry.rs
+++ b/compiler/rustc_ast/src/entry.rs
@@ -1,7 +1,6 @@
-use rustc_span::Symbol;
-use rustc_span::symbol::sym;
+use rustc_span::{Symbol, sym};
 
-use crate::{Attribute, attr};
+use crate::attr::{self, AttributeExt};
 
 #[derive(Debug)]
 pub enum EntryPointType {
@@ -37,7 +36,7 @@ pub enum EntryPointType {
 }
 
 pub fn entry_point_type(
-    attrs: &[Attribute],
+    attrs: &[impl AttributeExt],
     at_root: bool,
     name: Option<Symbol>,
 ) -> EntryPointType {
diff --git a/compiler/rustc_ast/src/expand/allocator.rs b/compiler/rustc_ast/src/expand/allocator.rs
index bee7dfb61da..dd8d5ae624a 100644
--- a/compiler/rustc_ast/src/expand/allocator.rs
+++ b/compiler/rustc_ast/src/expand/allocator.rs
@@ -1,5 +1,5 @@
 use rustc_macros::HashStable_Generic;
-use rustc_span::symbol::{Symbol, sym};
+use rustc_span::{Symbol, sym};
 
 #[derive(Clone, Debug, Copy, Eq, PartialEq, HashStable_Generic)]
 pub enum AllocatorKind {
diff --git a/compiler/rustc_ast/src/expand/mod.rs b/compiler/rustc_ast/src/expand/mod.rs
index d259677e98e..04c81629323 100644
--- a/compiler/rustc_ast/src/expand/mod.rs
+++ b/compiler/rustc_ast/src/expand/mod.rs
@@ -1,8 +1,8 @@
 //! Definitions shared by macros / syntax extensions and e.g. `rustc_middle`.
 
 use rustc_macros::{Decodable, Encodable, HashStable_Generic};
+use rustc_span::Ident;
 use rustc_span::def_id::DefId;
-use rustc_span::symbol::Ident;
 
 use crate::MetaItem;
 
diff --git a/compiler/rustc_ast/src/format.rs b/compiler/rustc_ast/src/format.rs
index d5900d83e4d..de628f09853 100644
--- a/compiler/rustc_ast/src/format.rs
+++ b/compiler/rustc_ast/src/format.rs
@@ -1,7 +1,6 @@
 use rustc_data_structures::fx::FxHashMap;
 use rustc_macros::{Decodable, Encodable};
-use rustc_span::Span;
-use rustc_span::symbol::{Ident, Symbol};
+use rustc_span::{Ident, Span, Symbol};
 
 use crate::Expr;
 use crate::ptr::P;
diff --git a/compiler/rustc_ast/src/lib.rs b/compiler/rustc_ast/src/lib.rs
index 7730d0b4b78..6372c66050e 100644
--- a/compiler/rustc_ast/src/lib.rs
+++ b/compiler/rustc_ast/src/lib.rs
@@ -44,20 +44,10 @@ pub mod token;
 pub mod tokenstream;
 pub mod visit;
 
-use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
-
 pub use self::ast::*;
 pub use self::ast_traits::{AstDeref, AstNodeWrapper, HasAttrs, HasNodeId, HasTokens};
 
 /// Requirements for a `StableHashingContext` to be used in this crate.
 /// This is a hack to allow using the `HashStable_Generic` derive macro
 /// instead of implementing everything in `rustc_middle`.
-pub trait HashStableContext: rustc_span::HashStableContext {
-    fn hash_attr(&mut self, _: &ast::Attribute, hasher: &mut StableHasher);
-}
-
-impl<AstCtx: crate::HashStableContext> HashStable<AstCtx> for ast::Attribute {
-    fn hash_stable(&self, hcx: &mut AstCtx, hasher: &mut StableHasher) {
-        hcx.hash_attr(self, hasher)
-    }
-}
+pub trait HashStableContext: rustc_span::HashStableContext {}
diff --git a/compiler/rustc_ast/src/mut_visit.rs b/compiler/rustc_ast/src/mut_visit.rs
index b44e2d9cace..995924c2a29 100644
--- a/compiler/rustc_ast/src/mut_visit.rs
+++ b/compiler/rustc_ast/src/mut_visit.rs
@@ -13,9 +13,8 @@ use std::panic;
 use rustc_data_structures::flat_map_in_place::FlatMapInPlace;
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_data_structures::sync::Lrc;
-use rustc_span::Span;
 use rustc_span::source_map::Spanned;
-use rustc_span::symbol::Ident;
+use rustc_span::{Ident, Span};
 use smallvec::{Array, SmallVec, smallvec};
 use thin_vec::ThinVec;
 
@@ -451,8 +450,8 @@ fn visit_attr_args<T: MutVisitor>(vis: &mut T, args: &mut AttrArgs) {
     match args {
         AttrArgs::Empty => {}
         AttrArgs::Delimited(args) => visit_delim_args(vis, args),
-        AttrArgs::Eq { eq_span, value } => {
-            vis.visit_expr(value.unwrap_ast_mut());
+        AttrArgs::Eq { eq_span, expr } => {
+            vis.visit_expr(expr);
             vis.visit_span(eq_span);
         }
     }
diff --git a/compiler/rustc_ast/src/token.rs b/compiler/rustc_ast/src/token.rs
index 678f43e3511..f639e785bc4 100644
--- a/compiler/rustc_ast/src/token.rs
+++ b/compiler/rustc_ast/src/token.rs
@@ -11,11 +11,10 @@ use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::sync::Lrc;
 use rustc_macros::{Decodable, Encodable, HashStable_Generic};
 use rustc_span::edition::Edition;
+use rustc_span::{DUMMY_SP, ErrorGuaranteed, Span, kw, sym};
 #[allow(clippy::useless_attribute)] // FIXME: following use of `hidden_glob_reexports` incorrectly triggers `useless_attribute` lint.
 #[allow(hidden_glob_reexports)]
-use rustc_span::symbol::{Ident, Symbol};
-use rustc_span::symbol::{kw, sym};
-use rustc_span::{DUMMY_SP, ErrorGuaranteed, Span};
+use rustc_span::{Ident, Symbol};
 
 use crate::ast;
 use crate::ptr::P;
@@ -904,7 +903,8 @@ impl Token {
         self.is_non_raw_ident_where(|id| id.name == kw)
     }
 
-    /// Returns `true` if the token is a given keyword, `kw` or if `case` is `Insensitive` and this token is an identifier equal to `kw` ignoring the case.
+    /// Returns `true` if the token is a given keyword, `kw` or if `case` is `Insensitive` and this
+    /// token is an identifier equal to `kw` ignoring the case.
     pub fn is_keyword_case(&self, kw: Symbol, case: Case) -> bool {
         self.is_keyword(kw)
             || (case == Case::Insensitive
@@ -917,6 +917,11 @@ impl Token {
         self.is_non_raw_ident_where(Ident::is_path_segment_keyword)
     }
 
+    /// Don't use this unless you're doing something very loose and heuristic-y.
+    pub fn is_any_keyword(&self) -> bool {
+        self.is_non_raw_ident_where(Ident::is_any_keyword)
+    }
+
     /// Returns true for reserved identifiers used internally for elided lifetimes,
     /// unnamed method parameters, crate root module, error recovery etc.
     pub fn is_special_ident(&self) -> bool {
diff --git a/compiler/rustc_ast/src/tokenstream.rs b/compiler/rustc_ast/src/tokenstream.rs
index c6b6addc946..e7b393d869d 100644
--- a/compiler/rustc_ast/src/tokenstream.rs
+++ b/compiler/rustc_ast/src/tokenstream.rs
@@ -99,7 +99,7 @@ where
     CTX: crate::HashStableContext,
 {
     fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
-        for sub_tt in self.trees() {
+        for sub_tt in self.iter() {
             sub_tt.hash_stable(hcx, hasher);
         }
     }
@@ -406,7 +406,7 @@ impl Eq for TokenStream {}
 
 impl PartialEq<TokenStream> for TokenStream {
     fn eq(&self, other: &TokenStream) -> bool {
-        self.trees().eq(other.trees())
+        self.iter().eq(other.iter())
     }
 }
 
@@ -423,24 +423,24 @@ impl TokenStream {
         self.0.len()
     }
 
-    pub fn trees(&self) -> RefTokenTreeCursor<'_> {
-        RefTokenTreeCursor::new(self)
+    pub fn get(&self, index: usize) -> Option<&TokenTree> {
+        self.0.get(index)
     }
 
-    pub fn into_trees(self) -> TokenTreeCursor {
-        TokenTreeCursor::new(self)
+    pub fn iter(&self) -> TokenStreamIter<'_> {
+        TokenStreamIter::new(self)
     }
 
     /// Compares two `TokenStream`s, checking equality without regarding span information.
     pub fn eq_unspanned(&self, other: &TokenStream) -> bool {
-        let mut t1 = self.trees();
-        let mut t2 = other.trees();
-        for (t1, t2) in iter::zip(&mut t1, &mut t2) {
-            if !t1.eq_unspanned(t2) {
+        let mut iter1 = self.iter();
+        let mut iter2 = other.iter();
+        for (tt1, tt2) in iter::zip(&mut iter1, &mut iter2) {
+            if !tt1.eq_unspanned(tt2) {
                 return false;
             }
         }
-        t1.next().is_none() && t2.next().is_none()
+        iter1.next().is_none() && iter2.next().is_none()
     }
 
     /// Create a token stream containing a single token with alone spacing. The
@@ -509,7 +509,7 @@ impl TokenStream {
     #[must_use]
     pub fn flattened(&self) -> TokenStream {
         fn can_skip(stream: &TokenStream) -> bool {
-            stream.trees().all(|tree| match tree {
+            stream.iter().all(|tree| match tree {
                 TokenTree::Token(token, _) => !matches!(
                     token.kind,
                     token::NtIdent(..) | token::NtLifetime(..) | token::Interpolated(..)
@@ -522,7 +522,7 @@ impl TokenStream {
             return self.clone();
         }
 
-        self.trees().map(|tree| TokenStream::flatten_token_tree(tree)).collect()
+        self.iter().map(|tree| TokenStream::flatten_token_tree(tree)).collect()
     }
 
     // If `vec` is not empty, try to glue `tt` onto its last token. The return
@@ -665,25 +665,26 @@ impl TokenStream {
     }
 }
 
-/// By-reference iterator over a [`TokenStream`], that produces `&TokenTree`
-/// items.
 #[derive(Clone)]
-pub struct RefTokenTreeCursor<'t> {
+pub struct TokenStreamIter<'t> {
     stream: &'t TokenStream,
     index: usize,
 }
 
-impl<'t> RefTokenTreeCursor<'t> {
+impl<'t> TokenStreamIter<'t> {
     fn new(stream: &'t TokenStream) -> Self {
-        RefTokenTreeCursor { stream, index: 0 }
+        TokenStreamIter { stream, index: 0 }
     }
 
-    pub fn look_ahead(&self, n: usize) -> Option<&TokenTree> {
-        self.stream.0.get(self.index + n)
+    // Peeking could be done via `Peekable`, but most iterators need peeking,
+    // and this is simple and avoids the need to use `peekable` and `Peekable`
+    // at all the use sites.
+    pub fn peek(&self) -> Option<&'t TokenTree> {
+        self.stream.0.get(self.index)
     }
 }
 
-impl<'t> Iterator for RefTokenTreeCursor<'t> {
+impl<'t> Iterator for TokenStreamIter<'t> {
     type Item = &'t TokenTree;
 
     fn next(&mut self) -> Option<&'t TokenTree> {
@@ -694,39 +695,6 @@ impl<'t> Iterator for RefTokenTreeCursor<'t> {
     }
 }
 
-/// Owning by-value iterator over a [`TokenStream`], that produces `&TokenTree`
-/// items.
-///
-/// Doesn't impl `Iterator` because Rust doesn't permit an owning iterator to
-/// return `&T` from `next`; the need for an explicit lifetime in the `Item`
-/// associated type gets in the way. Instead, use `next_ref` (which doesn't
-/// involve associated types) for getting individual elements, or
-/// `RefTokenTreeCursor` if you really want an `Iterator`, e.g. in a `for`
-/// loop.
-#[derive(Clone, Debug)]
-pub struct TokenTreeCursor {
-    pub stream: TokenStream,
-    index: usize,
-}
-
-impl TokenTreeCursor {
-    fn new(stream: TokenStream) -> Self {
-        TokenTreeCursor { stream, index: 0 }
-    }
-
-    #[inline]
-    pub fn next_ref(&mut self) -> Option<&TokenTree> {
-        self.stream.0.get(self.index).map(|tree| {
-            self.index += 1;
-            tree
-        })
-    }
-
-    pub fn look_ahead(&self, n: usize) -> Option<&TokenTree> {
-        self.stream.0.get(self.index + n)
-    }
-}
-
 #[derive(Debug, Copy, Clone, PartialEq, Encodable, Decodable, HashStable_Generic)]
 pub struct DelimSpan {
     pub open: Span,
diff --git a/compiler/rustc_ast/src/util/literal.rs b/compiler/rustc_ast/src/util/literal.rs
index 498df5a7144..4459cb962e8 100644
--- a/compiler/rustc_ast/src/util/literal.rs
+++ b/compiler/rustc_ast/src/util/literal.rs
@@ -5,8 +5,7 @@ use std::{ascii, fmt, str};
 use rustc_lexer::unescape::{
     MixedUnit, Mode, byte_from_char, unescape_byte, unescape_char, unescape_mixed, unescape_unicode,
 };
-use rustc_span::Span;
-use rustc_span::symbol::{Symbol, kw, sym};
+use rustc_span::{Span, Symbol, kw, sym};
 use tracing::debug;
 
 use crate::ast::{self, LitKind, MetaItemLit, StrStyle};
diff --git a/compiler/rustc_ast/src/util/parser.rs b/compiler/rustc_ast/src/util/parser.rs
index e88bf27021a..8f2b7a23c01 100644
--- a/compiler/rustc_ast/src/util/parser.rs
+++ b/compiler/rustc_ast/src/util/parser.rs
@@ -1,4 +1,4 @@
-use rustc_span::symbol::kw;
+use rustc_span::kw;
 
 use crate::ast::{self, BinOpKind};
 use crate::token::{self, BinOpToken, Token};
@@ -153,9 +153,10 @@ impl AssocOp {
         match *self {
             Assign | AssignOp(_) => Fixity::Right,
             As | Multiply | Divide | Modulus | Add | Subtract | ShiftLeft | ShiftRight | BitAnd
-            | BitXor | BitOr | Less | Greater | LessEqual | GreaterEqual | Equal | NotEqual
-            | LAnd | LOr => Fixity::Left,
-            DotDot | DotDotEq => Fixity::None,
+            | BitXor | BitOr | LAnd | LOr => Fixity::Left,
+            Less | Greater | LessEqual | GreaterEqual | Equal | NotEqual | DotDot | DotDotEq => {
+                Fixity::None
+            }
         }
     }
 
@@ -231,8 +232,7 @@ impl AssocOp {
 
 #[derive(Clone, Copy, PartialEq, PartialOrd)]
 pub enum ExprPrecedence {
-    Closure,
-    // return, break, yield
+    // return, break, yield, closures
     Jump,
     // = += -= *= /= %= &= |= ^= <<= >>=
     Assign,
diff --git a/compiler/rustc_ast/src/visit.rs b/compiler/rustc_ast/src/visit.rs
index 22db4438e31..c7cc772dabb 100644
--- a/compiler/rustc_ast/src/visit.rs
+++ b/compiler/rustc_ast/src/visit.rs
@@ -15,8 +15,7 @@
 
 pub use rustc_ast_ir::visit::VisitorResult;
 pub use rustc_ast_ir::{try_visit, visit_opt, walk_list, walk_visitable_list};
-use rustc_span::Span;
-use rustc_span::symbol::Ident;
+use rustc_span::{Ident, Span};
 
 use crate::ast::*;
 use crate::ptr::P;
@@ -1287,7 +1286,7 @@ pub fn walk_attr_args<'a, V: Visitor<'a>>(visitor: &mut V, args: &'a AttrArgs) -
     match args {
         AttrArgs::Empty => {}
         AttrArgs::Delimited(_args) => {}
-        AttrArgs::Eq { value, .. } => try_visit!(visitor.visit_expr(value.unwrap_ast())),
+        AttrArgs::Eq { expr, .. } => try_visit!(visitor.visit_expr(expr)),
     }
     V::Result::output()
 }
diff --git a/compiler/rustc_ast_lowering/src/asm.rs b/compiler/rustc_ast_lowering/src/asm.rs
index 569a15b0e07..2f1f1269ece 100644
--- a/compiler/rustc_ast_lowering/src/asm.rs
+++ b/compiler/rustc_ast_lowering/src/asm.rs
@@ -7,8 +7,7 @@ use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap};
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
 use rustc_session::parse::feature_err;
-use rustc_span::symbol::kw;
-use rustc_span::{Span, sym};
+use rustc_span::{Span, kw, sym};
 use rustc_target::asm;
 
 use super::LoweringContext;
diff --git a/compiler/rustc_ast_lowering/src/delegation.rs b/compiler/rustc_ast_lowering/src/delegation.rs
index 70c94f4019a..758f1dc1c35 100644
--- a/compiler/rustc_ast_lowering/src/delegation.rs
+++ b/compiler/rustc_ast_lowering/src/delegation.rs
@@ -46,8 +46,7 @@ use rustc_errors::ErrorGuaranteed;
 use rustc_hir::def_id::DefId;
 use rustc_middle::span_bug;
 use rustc_middle::ty::{Asyncness, ResolverAstLowering};
-use rustc_span::Span;
-use rustc_span::symbol::Ident;
+use rustc_span::{Ident, Span};
 use rustc_target::spec::abi;
 use {rustc_ast as ast, rustc_hir as hir};
 
diff --git a/compiler/rustc_ast_lowering/src/errors.rs b/compiler/rustc_ast_lowering/src/errors.rs
index 2564d4e2772..f727691bf47 100644
--- a/compiler/rustc_ast_lowering/src/errors.rs
+++ b/compiler/rustc_ast_lowering/src/errors.rs
@@ -1,8 +1,7 @@
 use rustc_errors::codes::*;
 use rustc_errors::{Diag, DiagArgFromDisplay, EmissionGuarantee, SubdiagMessageOp, Subdiagnostic};
 use rustc_macros::{Diagnostic, Subdiagnostic};
-use rustc_span::symbol::Ident;
-use rustc_span::{Span, Symbol};
+use rustc_span::{Ident, Span, Symbol};
 
 #[derive(Diagnostic)]
 #[diag(ast_lowering_generic_type_with_parentheses, code = E0214)]
diff --git a/compiler/rustc_ast_lowering/src/expr.rs b/compiler/rustc_ast_lowering/src/expr.rs
index 32905806343..d16a3ce390d 100644
--- a/compiler/rustc_ast_lowering/src/expr.rs
+++ b/compiler/rustc_ast_lowering/src/expr.rs
@@ -13,8 +13,7 @@ use rustc_middle::span_bug;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::errors::report_lit_error;
 use rustc_span::source_map::{Spanned, respan};
-use rustc_span::symbol::{Ident, Symbol, kw, sym};
-use rustc_span::{DUMMY_SP, DesugaringKind, Span};
+use rustc_span::{DUMMY_SP, DesugaringKind, Ident, Span, Symbol, kw, sym};
 use thin_vec::{ThinVec, thin_vec};
 use visit::{Visitor, walk_expr};
 
diff --git a/compiler/rustc_ast_lowering/src/format.rs b/compiler/rustc_ast_lowering/src/format.rs
index 653116e1fe0..22aa1e6fc20 100644
--- a/compiler/rustc_ast_lowering/src/format.rs
+++ b/compiler/rustc_ast_lowering/src/format.rs
@@ -6,8 +6,7 @@ use rustc_ast::*;
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_hir as hir;
 use rustc_session::config::FmtDebug;
-use rustc_span::symbol::{Ident, kw};
-use rustc_span::{Span, Symbol, sym};
+use rustc_span::{Ident, Span, Symbol, kw, sym};
 
 use super::LoweringContext;
 
diff --git a/compiler/rustc_ast_lowering/src/item.rs b/compiler/rustc_ast_lowering/src/item.rs
index d63131eacb5..2cf6a2a909b 100644
--- a/compiler/rustc_ast_lowering/src/item.rs
+++ b/compiler/rustc_ast_lowering/src/item.rs
@@ -10,8 +10,7 @@ use rustc_index::{IndexSlice, IndexVec};
 use rustc_middle::span_bug;
 use rustc_middle::ty::{ResolverAstLowering, TyCtxt};
 use rustc_span::edit_distance::find_best_match_for_name;
-use rustc_span::symbol::{Ident, kw, sym};
-use rustc_span::{DesugaringKind, Span, Symbol};
+use rustc_span::{DesugaringKind, Ident, Span, Symbol, kw, sym};
 use rustc_target::spec::abi;
 use smallvec::{SmallVec, smallvec};
 use thin_vec::ThinVec;
@@ -176,7 +175,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         id: NodeId,
         hir_id: hir::HirId,
         ident: &mut Ident,
-        attrs: &'hir [Attribute],
+        attrs: &'hir [hir::Attribute],
         vis_span: Span,
         i: &ItemKind,
     ) -> hir::ItemKind<'hir> {
@@ -467,7 +466,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         id: NodeId,
         vis_span: Span,
         ident: &mut Ident,
-        attrs: &'hir [Attribute],
+        attrs: &'hir [hir::Attribute],
     ) -> hir::ItemKind<'hir> {
         let path = &tree.prefix;
         let segments = prefix.segments.iter().chain(path.segments.iter()).cloned().collect();
@@ -1172,9 +1171,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 // we can keep the same name for the parameter.
                 // This lets rustdoc render it correctly in documentation.
                 hir::PatKind::Binding(_, _, ident, _) => (ident, false),
-                hir::PatKind::Wild => {
-                    (Ident::with_dummy_span(rustc_span::symbol::kw::Underscore), false)
-                }
+                hir::PatKind::Wild => (Ident::with_dummy_span(rustc_span::kw::Underscore), false),
                 _ => {
                     // Replace the ident for bindings that aren't simple.
                     let name = format!("__arg{index}");
@@ -1392,7 +1389,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         }
     }
 
-    pub(super) fn lower_safety(&mut self, s: Safety, default: hir::Safety) -> hir::Safety {
+    pub(super) fn lower_safety(&self, s: Safety, default: hir::Safety) -> hir::Safety {
         match s {
             Safety::Unsafe(_) => hir::Safety::Unsafe,
             Safety::Default => default,
diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index e4600b0f636..8438a421226 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -41,7 +41,6 @@
 // tidy-alphabetical-end
 
 use rustc_ast::node_id::NodeMap;
-use rustc_ast::ptr::P;
 use rustc_ast::{self as ast, *};
 use rustc_data_structures::captures::Captures;
 use rustc_data_structures::fingerprint::Fingerprint;
@@ -59,8 +58,7 @@ use rustc_macros::extension;
 use rustc_middle::span_bug;
 use rustc_middle::ty::{ResolverAstLowering, TyCtxt};
 use rustc_session::parse::{add_feature_diagnostics, feature_err};
-use rustc_span::symbol::{Ident, Symbol, kw, sym};
-use rustc_span::{DUMMY_SP, DesugaringKind, Span};
+use rustc_span::{DUMMY_SP, DesugaringKind, Ident, Span, Symbol, kw, sym};
 use smallvec::{SmallVec, smallvec};
 use thin_vec::ThinVec;
 use tracing::{debug, instrument, trace};
@@ -96,7 +94,7 @@ struct LoweringContext<'a, 'hir> {
     /// Bodies inside the owner being lowered.
     bodies: Vec<(hir::ItemLocalId, &'hir hir::Body<'hir>)>,
     /// Attributes inside the owner being lowered.
-    attrs: SortedMap<hir::ItemLocalId, &'hir [Attribute]>,
+    attrs: SortedMap<hir::ItemLocalId, &'hir [hir::Attribute]>,
     /// Collect items that were created by lowering the current owner.
     children: Vec<(LocalDefId, hir::MaybeOwner<'hir>)>,
 
@@ -847,7 +845,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         ret
     }
 
-    fn lower_attrs(&mut self, id: HirId, attrs: &[Attribute]) -> &'hir [Attribute] {
+    fn lower_attrs(&mut self, id: HirId, attrs: &[Attribute]) -> &'hir [hir::Attribute] {
         if attrs.is_empty() {
             &[]
         } else {
@@ -859,25 +857,33 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         }
     }
 
-    fn lower_attr(&self, attr: &Attribute) -> Attribute {
+    fn lower_attr(&self, attr: &Attribute) -> hir::Attribute {
         // Note that we explicitly do not walk the path. Since we don't really
         // lower attributes (we use the AST version) there is nowhere to keep
         // the `HirId`s. We don't actually need HIR version of attributes anyway.
         // Tokens are also not needed after macro expansion and parsing.
         let kind = match attr.kind {
-            AttrKind::Normal(ref normal) => AttrKind::Normal(P(NormalAttr {
-                item: AttrItem {
-                    unsafety: normal.item.unsafety,
-                    path: normal.item.path.clone(),
-                    args: self.lower_attr_args(&normal.item.args),
-                    tokens: None,
+            AttrKind::Normal(ref normal) => hir::AttrKind::Normal(Box::new(hir::AttrItem {
+                unsafety: self.lower_safety(normal.item.unsafety, hir::Safety::Safe),
+                path: hir::AttrPath {
+                    segments: normal
+                        .item
+                        .path
+                        .segments
+                        .iter()
+                        .map(|i| i.ident)
+                        .collect::<Vec<_>>()
+                        .into_boxed_slice(),
+                    span: normal.item.path.span,
                 },
-                tokens: None,
+                args: self.lower_attr_args(&normal.item.args),
             })),
-            AttrKind::DocComment(comment_kind, data) => AttrKind::DocComment(comment_kind, data),
+            AttrKind::DocComment(comment_kind, data) => {
+                hir::AttrKind::DocComment(comment_kind, data)
+            }
         };
 
-        Attribute { kind, id: attr.id, style: attr.style, span: self.lower_span(attr.span) }
+        hir::Attribute { kind, id: attr.id, style: attr.style, span: self.lower_span(attr.span) }
     }
 
     fn alias_attrs(&mut self, id: HirId, target_id: HirId) {
@@ -889,15 +895,14 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         }
     }
 
-    fn lower_attr_args(&self, args: &AttrArgs) -> AttrArgs {
+    fn lower_attr_args(&self, args: &AttrArgs) -> hir::AttrArgs {
         match args {
-            AttrArgs::Empty => AttrArgs::Empty,
-            AttrArgs::Delimited(args) => AttrArgs::Delimited(self.lower_delim_args(args)),
+            AttrArgs::Empty => hir::AttrArgs::Empty,
+            AttrArgs::Delimited(args) => hir::AttrArgs::Delimited(self.lower_delim_args(args)),
             // This is an inert key-value attribute - it will never be visible to macros
             // after it gets lowered to HIR. Therefore, we can extract literals to handle
             // nonterminals in `#[doc]` (e.g. `#[doc = $e]`).
-            &AttrArgs::Eq { eq_span, ref value } => {
-                let expr = value.unwrap_ast();
+            &AttrArgs::Eq { eq_span, ref expr } => {
                 // In valid code the value always ends up as a single literal. Otherwise, a dummy
                 // literal suffices because the error is handled elsewhere.
                 let lit = if let ExprKind::Lit(token_lit) = expr.kind
@@ -913,7 +918,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                         span: DUMMY_SP,
                     }
                 };
-                AttrArgs::Eq { eq_span, value: AttrArgsEq::Hir(lit) }
+                hir::AttrArgs::Eq { eq_span, expr: lit }
             }
         }
     }
@@ -2201,7 +2206,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
 
     fn stmt_let_pat(
         &mut self,
-        attrs: Option<&'hir [Attribute]>,
+        attrs: Option<&'hir [hir::Attribute]>,
         span: Span,
         init: Option<&'hir hir::Expr<'hir>>,
         pat: &'hir hir::Pat<'hir>,
diff --git a/compiler/rustc_ast_lowering/src/pat.rs b/compiler/rustc_ast_lowering/src/pat.rs
index c4bae084a3f..a4ab2561b72 100644
--- a/compiler/rustc_ast_lowering/src/pat.rs
+++ b/compiler/rustc_ast_lowering/src/pat.rs
@@ -3,9 +3,8 @@ use rustc_ast::*;
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_hir as hir;
 use rustc_hir::def::Res;
-use rustc_span::Span;
 use rustc_span::source_map::Spanned;
-use rustc_span::symbol::Ident;
+use rustc_span::{Ident, Span};
 
 use super::errors::{
     ArbitraryExpressionInPattern, ExtraDoubleDot, MisplacedDoubleDot, SubTupleBinding,
@@ -92,7 +91,14 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                                 span: self.lower_span(f.span),
                             }
                         }));
-                        break hir::PatKind::Struct(qpath, fs, *etc == ast::PatFieldsRest::Rest);
+                        break hir::PatKind::Struct(
+                            qpath,
+                            fs,
+                            matches!(
+                                etc,
+                                ast::PatFieldsRest::Rest | ast::PatFieldsRest::Recovered(_)
+                            ),
+                        );
                     }
                     PatKind::Tuple(pats) => {
                         let (pats, ddpos) = self.lower_pat_tuple(pats, "tuple");
diff --git a/compiler/rustc_ast_lowering/src/path.rs b/compiler/rustc_ast_lowering/src/path.rs
index 133793e26ea..043144a5464 100644
--- a/compiler/rustc_ast_lowering/src/path.rs
+++ b/compiler/rustc_ast_lowering/src/path.rs
@@ -6,8 +6,7 @@ use rustc_hir::def::{DefKind, PartialRes, Res};
 use rustc_hir::def_id::DefId;
 use rustc_middle::span_bug;
 use rustc_session::parse::add_feature_diagnostics;
-use rustc_span::symbol::{Ident, kw, sym};
-use rustc_span::{BytePos, DUMMY_SP, DesugaringKind, Span, Symbol};
+use rustc_span::{BytePos, DUMMY_SP, DesugaringKind, Ident, Span, Symbol, kw, sym};
 use smallvec::{SmallVec, smallvec};
 use tracing::{debug, instrument};
 
diff --git a/compiler/rustc_ast_passes/Cargo.toml b/compiler/rustc_ast_passes/Cargo.toml
index eace5ce8208..8046765647e 100644
--- a/compiler/rustc_ast_passes/Cargo.toml
+++ b/compiler/rustc_ast_passes/Cargo.toml
@@ -8,7 +8,7 @@ edition = "2021"
 itertools = "0.12"
 rustc_ast = { path = "../rustc_ast" }
 rustc_ast_pretty = { path = "../rustc_ast_pretty" }
-rustc_attr = { path = "../rustc_attr" }
+rustc_attr_parsing = { path = "../rustc_attr_parsing" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
 rustc_feature = { path = "../rustc_feature" }
diff --git a/compiler/rustc_ast_passes/src/ast_validation.rs b/compiler/rustc_ast_passes/src/ast_validation.rs
index 290c2e52970..d1cf9c53d66 100644
--- a/compiler/rustc_ast_passes/src/ast_validation.rs
+++ b/compiler/rustc_ast_passes/src/ast_validation.rs
@@ -34,8 +34,7 @@ use rustc_session::lint::builtin::{
     PATTERNS_IN_FNS_WITHOUT_BODY,
 };
 use rustc_session::lint::{BuiltinLintDiag, LintBuffer};
-use rustc_span::Span;
-use rustc_span::symbol::{Ident, kw, sym};
+use rustc_span::{Ident, Span, kw, sym};
 use rustc_target::spec::abi;
 use thin_vec::thin_vec;
 
@@ -342,7 +341,7 @@ impl<'a> AstValidator<'a> {
                     sym::forbid,
                     sym::warn,
                 ];
-                !arr.contains(&attr.name_or_empty()) && rustc_attr::is_builtin_attr(attr)
+                !arr.contains(&attr.name_or_empty()) && rustc_attr_parsing::is_builtin_attr(*attr)
             })
             .for_each(|attr| {
                 if attr.is_doc_comment() {
diff --git a/compiler/rustc_ast_passes/src/errors.rs b/compiler/rustc_ast_passes/src/errors.rs
index 9b600e3ee92..0eb2043eaa3 100644
--- a/compiler/rustc_ast_passes/src/errors.rs
+++ b/compiler/rustc_ast_passes/src/errors.rs
@@ -4,8 +4,7 @@ use rustc_ast::ParamKindOrd;
 use rustc_errors::codes::*;
 use rustc_errors::{Applicability, Diag, EmissionGuarantee, SubdiagMessageOp, Subdiagnostic};
 use rustc_macros::{Diagnostic, Subdiagnostic};
-use rustc_span::symbol::Ident;
-use rustc_span::{Span, Symbol};
+use rustc_span::{Ident, Span, Symbol};
 
 use crate::fluent_generated as fluent;
 
diff --git a/compiler/rustc_ast_passes/src/feature_gate.rs b/compiler/rustc_ast_passes/src/feature_gate.rs
index c10b3296497..f885b20c761 100644
--- a/compiler/rustc_ast_passes/src/feature_gate.rs
+++ b/compiler/rustc_ast_passes/src/feature_gate.rs
@@ -4,9 +4,8 @@ use rustc_ast::{NodeId, PatKind, attr, token};
 use rustc_feature::{AttributeGate, BUILTIN_ATTRIBUTE_MAP, BuiltinAttribute, Features, GateIssue};
 use rustc_session::Session;
 use rustc_session::parse::{feature_err, feature_err_issue, feature_warn};
-use rustc_span::Span;
 use rustc_span::source_map::Spanned;
-use rustc_span::symbol::{Symbol, sym};
+use rustc_span::{Span, Symbol, sym};
 use rustc_target::spec::abi;
 use thin_vec::ThinVec;
 
diff --git a/compiler/rustc_ast_pretty/src/pprust/state.rs b/compiler/rustc_ast_pretty/src/pprust/state.rs
index 04ffa2cffe3..172df102929 100644
--- a/compiler/rustc_ast_pretty/src/pprust/state.rs
+++ b/compiler/rustc_ast_pretty/src/pprust/state.rs
@@ -17,15 +17,15 @@ use rustc_ast::tokenstream::{Spacing, TokenStream, TokenTree};
 use rustc_ast::util::classify;
 use rustc_ast::util::comments::{Comment, CommentStyle};
 use rustc_ast::{
-    self as ast, AttrArgs, AttrArgsEq, BindingMode, BlockCheckMode, ByRef, DelimArgs, GenericArg,
-    GenericBound, InlineAsmOperand, InlineAsmOptions, InlineAsmRegOrRegClass,
-    InlineAsmTemplatePiece, PatKind, RangeEnd, RangeSyntax, Safety, SelfKind, Term, attr,
+    self as ast, AttrArgs, BindingMode, BlockCheckMode, ByRef, DelimArgs, GenericArg, GenericBound,
+    InlineAsmOperand, InlineAsmOptions, InlineAsmRegOrRegClass, InlineAsmTemplatePiece, PatKind,
+    RangeEnd, RangeSyntax, Safety, SelfKind, Term, attr,
 };
 use rustc_data_structures::sync::Lrc;
 use rustc_span::edition::Edition;
 use rustc_span::source_map::{SourceMap, Spanned};
-use rustc_span::symbol::{Ident, IdentPrinter, Symbol, kw, sym};
-use rustc_span::{BytePos, CharPos, DUMMY_SP, FileName, Pos, Span};
+use rustc_span::symbol::IdentPrinter;
+use rustc_span::{BytePos, CharPos, DUMMY_SP, FileName, Ident, Pos, Span, Symbol, kw, sym};
 use thin_vec::ThinVec;
 
 use crate::pp::Breaks::{Consistent, Inconsistent};
@@ -359,7 +359,7 @@ fn binop_to_string(op: BinOpToken) -> &'static str {
     }
 }
 
-fn doc_comment_to_string(
+pub fn doc_comment_to_string(
     comment_kind: CommentKind,
     attr_style: ast::AttrStyle,
     data: Symbol,
@@ -648,20 +648,13 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
             AttrArgs::Empty => {
                 self.print_path(&item.path, false, 0);
             }
-            AttrArgs::Eq { value: AttrArgsEq::Ast(expr), .. } => {
+            AttrArgs::Eq { expr, .. } => {
                 self.print_path(&item.path, false, 0);
                 self.space();
                 self.word_space("=");
                 let token_str = self.expr_to_string(expr);
                 self.word(token_str);
             }
-            AttrArgs::Eq { value: AttrArgsEq::Hir(lit), .. } => {
-                self.print_path(&item.path, false, 0);
-                self.space();
-                self.word_space("=");
-                let token_str = self.meta_item_lit_to_string(lit);
-                self.word(token_str);
-            }
         }
         match item.unsafety {
             ast::Safety::Unsafe(_) => self.pclose(),
@@ -732,7 +725,7 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
     // E.g. we have seen cases where a proc macro can handle `a :: b` but not
     // `a::b`. See #117433 for some examples.
     fn print_tts(&mut self, tts: &TokenStream, convert_dollar_crate: bool) {
-        let mut iter = tts.trees().peekable();
+        let mut iter = tts.iter().peekable();
         while let Some(tt) = iter.next() {
             let spacing = self.print_tt(tt, convert_dollar_crate);
             if let Some(next) = iter.peek() {
@@ -1211,8 +1204,10 @@ impl<'a> State<'a> {
             }
             ast::TyKind::Path(Some(qself), path) => self.print_qpath(path, qself, false),
             ast::TyKind::TraitObject(bounds, syntax) => {
-                if *syntax == ast::TraitObjectSyntax::Dyn {
-                    self.word_nbsp("dyn");
+                match syntax {
+                    ast::TraitObjectSyntax::Dyn => self.word_nbsp("dyn"),
+                    ast::TraitObjectSyntax::DynStar => self.word_nbsp("dyn*"),
+                    ast::TraitObjectSyntax::None => {}
                 }
                 self.print_type_bounds(bounds);
             }
@@ -1661,11 +1656,14 @@ impl<'a> State<'a> {
                     },
                     |f| f.pat.span,
                 );
-                if *etc == ast::PatFieldsRest::Rest {
+                if let ast::PatFieldsRest::Rest | ast::PatFieldsRest::Recovered(_) = etc {
                     if !fields.is_empty() {
                         self.word_space(",");
                     }
                     self.word("..");
+                    if let ast::PatFieldsRest::Recovered(_) = etc {
+                        self.word("/* recovered parse error */");
+                    }
                 }
                 if !empty {
                     self.space();
diff --git a/compiler/rustc_ast_pretty/src/pprust/state/item.rs b/compiler/rustc_ast_pretty/src/pprust/state/item.rs
index 1ae765c0130..897c275d850 100644
--- a/compiler/rustc_ast_pretty/src/pprust/state/item.rs
+++ b/compiler/rustc_ast_pretty/src/pprust/state/item.rs
@@ -3,7 +3,7 @@ use itertools::{Itertools, Position};
 use rustc_ast as ast;
 use rustc_ast::ModKind;
 use rustc_ast::ptr::P;
-use rustc_span::symbol::Ident;
+use rustc_span::Ident;
 
 use crate::pp::Breaks::Inconsistent;
 use crate::pprust::state::fixup::FixupContext;
diff --git a/compiler/rustc_ast_pretty/src/pprust/tests.rs b/compiler/rustc_ast_pretty/src/pprust/tests.rs
index 01e5dff34b7..4c42dd1f202 100644
--- a/compiler/rustc_ast_pretty/src/pprust/tests.rs
+++ b/compiler/rustc_ast_pretty/src/pprust/tests.rs
@@ -1,6 +1,5 @@
 use rustc_ast as ast;
-use rustc_span::symbol::Ident;
-use rustc_span::{DUMMY_SP, create_default_session_globals_then};
+use rustc_span::{DUMMY_SP, Ident, create_default_session_globals_then};
 use thin_vec::ThinVec;
 
 use super::*;
diff --git a/compiler/rustc_attr/src/builtin.rs b/compiler/rustc_attr/src/builtin.rs
deleted file mode 100644
index 94f9727eb7f..00000000000
--- a/compiler/rustc_attr/src/builtin.rs
+++ /dev/null
@@ -1,1349 +0,0 @@
-//! Parsing and validation of builtin attributes
-
-use std::num::NonZero;
-
-use rustc_abi::Align;
-use rustc_ast::{
-    self as ast, Attribute, LitKind, MetaItem, MetaItemInner, MetaItemKind, MetaItemLit, NodeId,
-    attr,
-};
-use rustc_ast_pretty::pprust;
-use rustc_errors::ErrorGuaranteed;
-use rustc_feature::{Features, GatedCfg, find_gated_cfg, is_builtin_attr_name};
-use rustc_macros::{Decodable, Encodable, HashStable_Generic};
-use rustc_session::config::ExpectedValues;
-use rustc_session::lint::BuiltinLintDiag;
-use rustc_session::lint::builtin::UNEXPECTED_CFGS;
-use rustc_session::parse::feature_err;
-use rustc_session::{RustcVersion, Session};
-use rustc_span::Span;
-use rustc_span::hygiene::Transparency;
-use rustc_span::symbol::{Symbol, kw, sym};
-
-use crate::fluent_generated;
-use crate::session_diagnostics::{self, IncorrectReprFormatGenericCause};
-
-/// The version placeholder that recently stabilized features contain inside the
-/// `since` field of the `#[stable]` attribute.
-///
-/// For more, see [this pull request](https://github.com/rust-lang/rust/pull/100591).
-pub const VERSION_PLACEHOLDER: &str = "CURRENT_RUSTC_VERSION";
-
-pub fn is_builtin_attr(attr: &Attribute) -> bool {
-    attr.is_doc_comment() || attr.ident().is_some_and(|ident| is_builtin_attr_name(ident.name))
-}
-
-pub(crate) enum UnsupportedLiteralReason {
-    Generic,
-    CfgString,
-    CfgBoolean,
-    DeprecatedString,
-    DeprecatedKvPair,
-}
-
-#[derive(Copy, Clone, PartialEq, Encodable, Decodable, Debug, HashStable_Generic)]
-pub enum InlineAttr {
-    None,
-    Hint,
-    Always,
-    Never,
-}
-
-#[derive(Clone, Encodable, Decodable, Debug, PartialEq, Eq, HashStable_Generic)]
-pub enum InstructionSetAttr {
-    ArmA32,
-    ArmT32,
-}
-
-#[derive(Clone, Encodable, Decodable, Debug, HashStable_Generic)]
-pub enum OptimizeAttr {
-    None,
-    Speed,
-    Size,
-}
-
-/// Represents the following attributes:
-///
-/// - `#[stable]`
-/// - `#[unstable]`
-#[derive(Encodable, Decodable, Copy, Clone, Debug, PartialEq, Eq, Hash)]
-#[derive(HashStable_Generic)]
-pub struct Stability {
-    pub level: StabilityLevel,
-    pub feature: Symbol,
-}
-
-impl Stability {
-    pub fn is_unstable(&self) -> bool {
-        self.level.is_unstable()
-    }
-
-    pub fn is_stable(&self) -> bool {
-        self.level.is_stable()
-    }
-
-    pub fn stable_since(&self) -> Option<StableSince> {
-        self.level.stable_since()
-    }
-}
-
-/// Represents the `#[rustc_const_unstable]` and `#[rustc_const_stable]` attributes.
-#[derive(Encodable, Decodable, Copy, Clone, Debug, PartialEq, Eq, Hash)]
-#[derive(HashStable_Generic)]
-pub struct ConstStability {
-    pub level: StabilityLevel,
-    pub feature: Symbol,
-    /// This is true iff the `const_stable_indirect` attribute is present.
-    pub const_stable_indirect: bool,
-    /// whether the function has a `#[rustc_promotable]` attribute
-    pub promotable: bool,
-}
-
-impl ConstStability {
-    pub fn is_const_unstable(&self) -> bool {
-        self.level.is_unstable()
-    }
-
-    pub fn is_const_stable(&self) -> bool {
-        self.level.is_stable()
-    }
-}
-
-/// Represents the `#[rustc_default_body_unstable]` attribute.
-#[derive(Encodable, Decodable, Copy, Clone, Debug, PartialEq, Eq, Hash)]
-#[derive(HashStable_Generic)]
-pub struct DefaultBodyStability {
-    pub level: StabilityLevel,
-    pub feature: Symbol,
-}
-
-/// The available stability levels.
-#[derive(Encodable, Decodable, PartialEq, Copy, Clone, Debug, Eq, Hash)]
-#[derive(HashStable_Generic)]
-pub enum StabilityLevel {
-    /// `#[unstable]`
-    Unstable {
-        /// Reason for the current stability level.
-        reason: UnstableReason,
-        /// Relevant `rust-lang/rust` issue.
-        issue: Option<NonZero<u32>>,
-        is_soft: bool,
-        /// If part of a feature is stabilized and a new feature is added for the remaining parts,
-        /// then the `implied_by` attribute is used to indicate which now-stable feature previously
-        /// contained an item.
-        ///
-        /// ```pseudo-Rust
-        /// #[unstable(feature = "foo", issue = "...")]
-        /// fn foo() {}
-        /// #[unstable(feature = "foo", issue = "...")]
-        /// fn foobar() {}
-        /// ```
-        ///
-        /// ...becomes...
-        ///
-        /// ```pseudo-Rust
-        /// #[stable(feature = "foo", since = "1.XX.X")]
-        /// fn foo() {}
-        /// #[unstable(feature = "foobar", issue = "...", implied_by = "foo")]
-        /// fn foobar() {}
-        /// ```
-        implied_by: Option<Symbol>,
-    },
-    /// `#[stable]`
-    Stable {
-        /// Rust release which stabilized this feature.
-        since: StableSince,
-        /// Is this item allowed to be referred to on stable, despite being contained in unstable
-        /// modules?
-        allowed_through_unstable_modules: bool,
-    },
-}
-
-/// Rust release in which a feature is stabilized.
-#[derive(Encodable, Decodable, PartialEq, Copy, Clone, Debug, Eq, PartialOrd, Ord, Hash)]
-#[derive(HashStable_Generic)]
-pub enum StableSince {
-    Version(RustcVersion),
-    /// Stabilized in the upcoming version, whatever number that is.
-    Current,
-    /// Failed to parse a stabilization version.
-    Err,
-}
-
-impl StabilityLevel {
-    pub fn is_unstable(&self) -> bool {
-        matches!(self, StabilityLevel::Unstable { .. })
-    }
-    pub fn is_stable(&self) -> bool {
-        matches!(self, StabilityLevel::Stable { .. })
-    }
-    pub fn stable_since(&self) -> Option<StableSince> {
-        match *self {
-            StabilityLevel::Stable { since, .. } => Some(since),
-            StabilityLevel::Unstable { .. } => None,
-        }
-    }
-}
-
-#[derive(Encodable, Decodable, PartialEq, Copy, Clone, Debug, Eq, Hash)]
-#[derive(HashStable_Generic)]
-pub enum UnstableReason {
-    None,
-    Default,
-    Some(Symbol),
-}
-
-impl UnstableReason {
-    fn from_opt_reason(reason: Option<Symbol>) -> Self {
-        // UnstableReason::Default constructed manually
-        match reason {
-            Some(r) => Self::Some(r),
-            None => Self::None,
-        }
-    }
-
-    pub fn to_opt_reason(&self) -> Option<Symbol> {
-        match self {
-            Self::None => None,
-            Self::Default => Some(sym::unstable_location_reason_default),
-            Self::Some(r) => Some(*r),
-        }
-    }
-}
-
-/// Collects stability info from `stable`/`unstable`/`rustc_allowed_through_unstable_modules`
-/// attributes in `attrs`. Returns `None` if no stability attributes are found.
-pub fn find_stability(
-    sess: &Session,
-    attrs: &[Attribute],
-    item_sp: Span,
-) -> Option<(Stability, Span)> {
-    let mut stab: Option<(Stability, Span)> = None;
-    let mut allowed_through_unstable_modules = false;
-
-    for attr in attrs {
-        match attr.name_or_empty() {
-            sym::rustc_allowed_through_unstable_modules => allowed_through_unstable_modules = true,
-            sym::unstable => {
-                if stab.is_some() {
-                    sess.dcx()
-                        .emit_err(session_diagnostics::MultipleStabilityLevels { span: attr.span });
-                    break;
-                }
-
-                if let Some((feature, level)) = parse_unstability(sess, attr) {
-                    stab = Some((Stability { level, feature }, attr.span));
-                }
-            }
-            sym::stable => {
-                if stab.is_some() {
-                    sess.dcx()
-                        .emit_err(session_diagnostics::MultipleStabilityLevels { span: attr.span });
-                    break;
-                }
-                if let Some((feature, level)) = parse_stability(sess, attr) {
-                    stab = Some((Stability { level, feature }, attr.span));
-                }
-            }
-            _ => {}
-        }
-    }
-
-    if allowed_through_unstable_modules {
-        match &mut stab {
-            Some((
-                Stability {
-                    level: StabilityLevel::Stable { allowed_through_unstable_modules, .. },
-                    ..
-                },
-                _,
-            )) => *allowed_through_unstable_modules = true,
-            _ => {
-                sess.dcx()
-                    .emit_err(session_diagnostics::RustcAllowedUnstablePairing { span: item_sp });
-            }
-        }
-    }
-
-    stab
-}
-
-/// Collects stability info from `rustc_const_stable`/`rustc_const_unstable`/`rustc_promotable`
-/// attributes in `attrs`. Returns `None` if no stability attributes are found.
-pub fn find_const_stability(
-    sess: &Session,
-    attrs: &[Attribute],
-    item_sp: Span,
-) -> Option<(ConstStability, Span)> {
-    let mut const_stab: Option<(ConstStability, Span)> = None;
-    let mut promotable = false;
-    let mut const_stable_indirect = false;
-
-    for attr in attrs {
-        match attr.name_or_empty() {
-            sym::rustc_promotable => promotable = true,
-            sym::rustc_const_stable_indirect => const_stable_indirect = true,
-            sym::rustc_const_unstable => {
-                if const_stab.is_some() {
-                    sess.dcx()
-                        .emit_err(session_diagnostics::MultipleStabilityLevels { span: attr.span });
-                    break;
-                }
-
-                if let Some((feature, level)) = parse_unstability(sess, attr) {
-                    const_stab = Some((
-                        ConstStability {
-                            level,
-                            feature,
-                            const_stable_indirect: false,
-                            promotable: false,
-                        },
-                        attr.span,
-                    ));
-                }
-            }
-            sym::rustc_const_stable => {
-                if const_stab.is_some() {
-                    sess.dcx()
-                        .emit_err(session_diagnostics::MultipleStabilityLevels { span: attr.span });
-                    break;
-                }
-                if let Some((feature, level)) = parse_stability(sess, attr) {
-                    const_stab = Some((
-                        ConstStability {
-                            level,
-                            feature,
-                            const_stable_indirect: false,
-                            promotable: false,
-                        },
-                        attr.span,
-                    ));
-                }
-            }
-            _ => {}
-        }
-    }
-
-    // Merge promotable and const_stable_indirect into stability info
-    if promotable {
-        match &mut const_stab {
-            Some((stab, _)) => stab.promotable = promotable,
-            _ => {
-                _ = sess
-                    .dcx()
-                    .emit_err(session_diagnostics::RustcPromotablePairing { span: item_sp })
-            }
-        }
-    }
-    if const_stable_indirect {
-        match &mut const_stab {
-            Some((stab, _)) => {
-                if stab.is_const_unstable() {
-                    stab.const_stable_indirect = true;
-                } else {
-                    _ = sess.dcx().emit_err(session_diagnostics::RustcConstStableIndirectPairing {
-                        span: item_sp,
-                    })
-                }
-            }
-            _ => {
-                // This function has no const stability attribute, but has `const_stable_indirect`.
-                // We ignore that; unmarked functions are subject to recursive const stability
-                // checks by default so we do carry out the user's intent.
-            }
-        }
-    }
-
-    const_stab
-}
-
-/// Calculates the const stability for a const function in a `-Zforce-unstable-if-unmarked` crate
-/// without the `staged_api` feature.
-pub fn unmarked_crate_const_stab(
-    _sess: &Session,
-    attrs: &[Attribute],
-    regular_stab: Stability,
-) -> ConstStability {
-    assert!(regular_stab.level.is_unstable());
-    // The only attribute that matters here is `rustc_const_stable_indirect`.
-    // We enforce recursive const stability rules for those functions.
-    let const_stable_indirect =
-        attrs.iter().any(|a| a.name_or_empty() == sym::rustc_const_stable_indirect);
-    ConstStability {
-        feature: regular_stab.feature,
-        const_stable_indirect,
-        promotable: false,
-        level: regular_stab.level,
-    }
-}
-
-/// Collects stability info from `rustc_default_body_unstable` attributes in `attrs`.
-/// Returns `None` if no stability attributes are found.
-pub fn find_body_stability(
-    sess: &Session,
-    attrs: &[Attribute],
-) -> Option<(DefaultBodyStability, Span)> {
-    let mut body_stab: Option<(DefaultBodyStability, Span)> = None;
-
-    for attr in attrs {
-        if attr.has_name(sym::rustc_default_body_unstable) {
-            if body_stab.is_some() {
-                sess.dcx()
-                    .emit_err(session_diagnostics::MultipleStabilityLevels { span: attr.span });
-                break;
-            }
-
-            if let Some((feature, level)) = parse_unstability(sess, attr) {
-                body_stab = Some((DefaultBodyStability { level, feature }, attr.span));
-            }
-        }
-    }
-
-    body_stab
-}
-
-fn insert_or_error(sess: &Session, meta: &MetaItem, item: &mut Option<Symbol>) -> Option<()> {
-    if item.is_some() {
-        sess.dcx().emit_err(session_diagnostics::MultipleItem {
-            span: meta.span,
-            item: pprust::path_to_string(&meta.path),
-        });
-        None
-    } else if let Some(v) = meta.value_str() {
-        *item = Some(v);
-        Some(())
-    } else {
-        sess.dcx().emit_err(session_diagnostics::IncorrectMetaItem { span: meta.span });
-        None
-    }
-}
-
-/// Read the content of a `stable`/`rustc_const_stable` attribute, and return the feature name and
-/// its stability information.
-fn parse_stability(sess: &Session, attr: &Attribute) -> Option<(Symbol, StabilityLevel)> {
-    let meta = attr.meta()?;
-    let MetaItem { kind: MetaItemKind::List(ref metas), .. } = meta else { return None };
-
-    let mut feature = None;
-    let mut since = None;
-    for meta in metas {
-        let Some(mi) = meta.meta_item() else {
-            sess.dcx().emit_err(session_diagnostics::UnsupportedLiteral {
-                span: meta.span(),
-                reason: UnsupportedLiteralReason::Generic,
-                is_bytestr: false,
-                start_point_span: sess.source_map().start_point(meta.span()),
-            });
-            return None;
-        };
-
-        match mi.name_or_empty() {
-            sym::feature => insert_or_error(sess, mi, &mut feature)?,
-            sym::since => insert_or_error(sess, mi, &mut since)?,
-            _ => {
-                sess.dcx().emit_err(session_diagnostics::UnknownMetaItem {
-                    span: meta.span(),
-                    item: pprust::path_to_string(&mi.path),
-                    expected: &["feature", "since"],
-                });
-                return None;
-            }
-        }
-    }
-
-    let feature = match feature {
-        Some(feature) if rustc_lexer::is_ident(feature.as_str()) => Ok(feature),
-        Some(_bad_feature) => {
-            Err(sess.dcx().emit_err(session_diagnostics::NonIdentFeature { span: attr.span }))
-        }
-        None => Err(sess.dcx().emit_err(session_diagnostics::MissingFeature { span: attr.span })),
-    };
-
-    let since = if let Some(since) = since {
-        if since.as_str() == VERSION_PLACEHOLDER {
-            StableSince::Current
-        } else if let Some(version) = parse_version(since) {
-            StableSince::Version(version)
-        } else {
-            sess.dcx().emit_err(session_diagnostics::InvalidSince { span: attr.span });
-            StableSince::Err
-        }
-    } else {
-        sess.dcx().emit_err(session_diagnostics::MissingSince { span: attr.span });
-        StableSince::Err
-    };
-
-    match feature {
-        Ok(feature) => {
-            let level = StabilityLevel::Stable { since, allowed_through_unstable_modules: false };
-            Some((feature, level))
-        }
-        Err(ErrorGuaranteed { .. }) => None,
-    }
-}
-
-/// Read the content of a `unstable`/`rustc_const_unstable`/`rustc_default_body_unstable`
-/// attribute, and return the feature name and its stability information.
-fn parse_unstability(sess: &Session, attr: &Attribute) -> Option<(Symbol, StabilityLevel)> {
-    let meta = attr.meta()?;
-    let MetaItem { kind: MetaItemKind::List(ref metas), .. } = meta else { return None };
-
-    let mut feature = None;
-    let mut reason = None;
-    let mut issue = None;
-    let mut issue_num = None;
-    let mut is_soft = false;
-    let mut implied_by = None;
-    for meta in metas {
-        let Some(mi) = meta.meta_item() else {
-            sess.dcx().emit_err(session_diagnostics::UnsupportedLiteral {
-                span: meta.span(),
-                reason: UnsupportedLiteralReason::Generic,
-                is_bytestr: false,
-                start_point_span: sess.source_map().start_point(meta.span()),
-            });
-            return None;
-        };
-
-        match mi.name_or_empty() {
-            sym::feature => insert_or_error(sess, mi, &mut feature)?,
-            sym::reason => insert_or_error(sess, mi, &mut reason)?,
-            sym::issue => {
-                insert_or_error(sess, mi, &mut issue)?;
-
-                // These unwraps are safe because `insert_or_error` ensures the meta item
-                // is a name/value pair string literal.
-                issue_num = match issue.unwrap().as_str() {
-                    "none" => None,
-                    issue => match issue.parse::<NonZero<u32>>() {
-                        Ok(num) => Some(num),
-                        Err(err) => {
-                            sess.dcx().emit_err(
-                                session_diagnostics::InvalidIssueString {
-                                    span: mi.span,
-                                    cause: session_diagnostics::InvalidIssueStringCause::from_int_error_kind(
-                                        mi.name_value_literal_span().unwrap(),
-                                        err.kind(),
-                                    ),
-                                },
-                            );
-                            return None;
-                        }
-                    },
-                };
-            }
-            sym::soft => {
-                if !mi.is_word() {
-                    sess.dcx().emit_err(session_diagnostics::SoftNoArgs { span: mi.span });
-                }
-                is_soft = true;
-            }
-            sym::implied_by => insert_or_error(sess, mi, &mut implied_by)?,
-            _ => {
-                sess.dcx().emit_err(session_diagnostics::UnknownMetaItem {
-                    span: meta.span(),
-                    item: pprust::path_to_string(&mi.path),
-                    expected: &["feature", "reason", "issue", "soft", "implied_by"],
-                });
-                return None;
-            }
-        }
-    }
-
-    let feature = match feature {
-        Some(feature) if rustc_lexer::is_ident(feature.as_str()) => Ok(feature),
-        Some(_bad_feature) => {
-            Err(sess.dcx().emit_err(session_diagnostics::NonIdentFeature { span: attr.span }))
-        }
-        None => Err(sess.dcx().emit_err(session_diagnostics::MissingFeature { span: attr.span })),
-    };
-
-    let issue = issue
-        .ok_or_else(|| sess.dcx().emit_err(session_diagnostics::MissingIssue { span: attr.span }));
-
-    match (feature, issue) {
-        (Ok(feature), Ok(_)) => {
-            let level = StabilityLevel::Unstable {
-                reason: UnstableReason::from_opt_reason(reason),
-                issue: issue_num,
-                is_soft,
-                implied_by,
-            };
-            Some((feature, level))
-        }
-        (Err(ErrorGuaranteed { .. }), _) | (_, Err(ErrorGuaranteed { .. })) => None,
-    }
-}
-
-pub fn find_crate_name(attrs: &[Attribute]) -> Option<Symbol> {
-    attr::first_attr_value_str_by_name(attrs, sym::crate_name)
-}
-
-#[derive(Clone, Debug)]
-pub struct Condition {
-    pub name: Symbol,
-    pub name_span: Span,
-    pub value: Option<Symbol>,
-    pub value_span: Option<Span>,
-    pub span: Span,
-}
-
-/// Tests if a cfg-pattern matches the cfg set
-pub fn cfg_matches(
-    cfg: &ast::MetaItemInner,
-    sess: &Session,
-    lint_node_id: NodeId,
-    features: Option<&Features>,
-) -> bool {
-    eval_condition(cfg, sess, features, &mut |cfg| {
-        try_gate_cfg(cfg.name, cfg.span, sess, features);
-        match sess.psess.check_config.expecteds.get(&cfg.name) {
-            Some(ExpectedValues::Some(values)) if !values.contains(&cfg.value) => {
-                sess.psess.buffer_lint(
-                    UNEXPECTED_CFGS,
-                    cfg.span,
-                    lint_node_id,
-                    BuiltinLintDiag::UnexpectedCfgValue(
-                        (cfg.name, cfg.name_span),
-                        cfg.value.map(|v| (v, cfg.value_span.unwrap())),
-                    ),
-                );
-            }
-            None if sess.psess.check_config.exhaustive_names => {
-                sess.psess.buffer_lint(
-                    UNEXPECTED_CFGS,
-                    cfg.span,
-                    lint_node_id,
-                    BuiltinLintDiag::UnexpectedCfgName(
-                        (cfg.name, cfg.name_span),
-                        cfg.value.map(|v| (v, cfg.value_span.unwrap())),
-                    ),
-                );
-            }
-            _ => { /* not unexpected */ }
-        }
-        sess.psess.config.contains(&(cfg.name, cfg.value))
-    })
-}
-
-fn try_gate_cfg(name: Symbol, span: Span, sess: &Session, features: Option<&Features>) {
-    let gate = find_gated_cfg(|sym| sym == name);
-    if let (Some(feats), Some(gated_cfg)) = (features, gate) {
-        gate_cfg(gated_cfg, span, sess, feats);
-    }
-}
-
-#[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
-fn gate_cfg(gated_cfg: &GatedCfg, cfg_span: Span, sess: &Session, features: &Features) {
-    let (cfg, feature, has_feature) = gated_cfg;
-    if !has_feature(features) && !cfg_span.allows_unstable(*feature) {
-        let explain = format!("`cfg({cfg})` is experimental and subject to change");
-        feature_err(sess, *feature, cfg_span, explain).emit();
-    }
-}
-
-/// Parse a rustc version number written inside string literal in an attribute,
-/// like appears in `since = "1.0.0"`. Suffixes like "-dev" and "-nightly" are
-/// not accepted in this position, unlike when parsing CFG_RELEASE.
-pub fn parse_version(s: Symbol) -> Option<RustcVersion> {
-    let mut components = s.as_str().split('-');
-    let d = components.next()?;
-    if components.next().is_some() {
-        return None;
-    }
-    let mut digits = d.splitn(3, '.');
-    let major = digits.next()?.parse().ok()?;
-    let minor = digits.next()?.parse().ok()?;
-    let patch = digits.next().unwrap_or("0").parse().ok()?;
-    Some(RustcVersion { major, minor, patch })
-}
-
-/// Evaluate a cfg-like condition (with `any` and `all`), using `eval` to
-/// evaluate individual items.
-pub fn eval_condition(
-    cfg: &ast::MetaItemInner,
-    sess: &Session,
-    features: Option<&Features>,
-    eval: &mut impl FnMut(Condition) -> bool,
-) -> bool {
-    let dcx = sess.dcx();
-
-    let cfg = match cfg {
-        ast::MetaItemInner::MetaItem(meta_item) => meta_item,
-        ast::MetaItemInner::Lit(MetaItemLit { kind: LitKind::Bool(b), .. }) => {
-            if let Some(features) = features {
-                // we can't use `try_gate_cfg` as symbols don't differentiate between `r#true`
-                // and `true`, and we want to keep the former working without feature gate
-                gate_cfg(
-                    &(
-                        if *b { kw::True } else { kw::False },
-                        sym::cfg_boolean_literals,
-                        |features: &Features| features.cfg_boolean_literals(),
-                    ),
-                    cfg.span(),
-                    sess,
-                    features,
-                );
-            }
-            return *b;
-        }
-        _ => {
-            dcx.emit_err(session_diagnostics::UnsupportedLiteral {
-                span: cfg.span(),
-                reason: UnsupportedLiteralReason::CfgBoolean,
-                is_bytestr: false,
-                start_point_span: sess.source_map().start_point(cfg.span()),
-            });
-            return false;
-        }
-    };
-
-    match &cfg.kind {
-        ast::MetaItemKind::List(mis) if cfg.name_or_empty() == sym::version => {
-            try_gate_cfg(sym::version, cfg.span, sess, features);
-            let (min_version, span) = match &mis[..] {
-                [MetaItemInner::Lit(MetaItemLit { kind: LitKind::Str(sym, ..), span, .. })] => {
-                    (sym, span)
-                }
-                [
-                    MetaItemInner::Lit(MetaItemLit { span, .. })
-                    | MetaItemInner::MetaItem(MetaItem { span, .. }),
-                ] => {
-                    dcx.emit_err(session_diagnostics::ExpectedVersionLiteral { span: *span });
-                    return false;
-                }
-                [..] => {
-                    dcx.emit_err(session_diagnostics::ExpectedSingleVersionLiteral {
-                        span: cfg.span,
-                    });
-                    return false;
-                }
-            };
-            let Some(min_version) = parse_version(*min_version) else {
-                dcx.emit_warn(session_diagnostics::UnknownVersionLiteral { span: *span });
-                return false;
-            };
-
-            // See https://github.com/rust-lang/rust/issues/64796#issuecomment-640851454 for details
-            if sess.psess.assume_incomplete_release {
-                RustcVersion::CURRENT > min_version
-            } else {
-                RustcVersion::CURRENT >= min_version
-            }
-        }
-        ast::MetaItemKind::List(mis) => {
-            for mi in mis.iter() {
-                if mi.meta_item_or_bool().is_none() {
-                    dcx.emit_err(session_diagnostics::UnsupportedLiteral {
-                        span: mi.span(),
-                        reason: UnsupportedLiteralReason::Generic,
-                        is_bytestr: false,
-                        start_point_span: sess.source_map().start_point(mi.span()),
-                    });
-                    return false;
-                }
-            }
-
-            // The unwraps below may look dangerous, but we've already asserted
-            // that they won't fail with the loop above.
-            match cfg.name_or_empty() {
-                sym::any => mis
-                    .iter()
-                    // We don't use any() here, because we want to evaluate all cfg condition
-                    // as eval_condition can (and does) extra checks
-                    .fold(false, |res, mi| res | eval_condition(mi, sess, features, eval)),
-                sym::all => mis
-                    .iter()
-                    // We don't use all() here, because we want to evaluate all cfg condition
-                    // as eval_condition can (and does) extra checks
-                    .fold(true, |res, mi| res & eval_condition(mi, sess, features, eval)),
-                sym::not => {
-                    let [mi] = mis.as_slice() else {
-                        dcx.emit_err(session_diagnostics::ExpectedOneCfgPattern { span: cfg.span });
-                        return false;
-                    };
-
-                    !eval_condition(mi, sess, features, eval)
-                }
-                sym::target => {
-                    if let Some(features) = features
-                        && !features.cfg_target_compact()
-                    {
-                        feature_err(
-                            sess,
-                            sym::cfg_target_compact,
-                            cfg.span,
-                            fluent_generated::attr_unstable_cfg_target_compact,
-                        )
-                        .emit();
-                    }
-
-                    mis.iter().fold(true, |res, mi| {
-                        let Some(mut mi) = mi.meta_item().cloned() else {
-                            dcx.emit_err(session_diagnostics::CfgPredicateIdentifier {
-                                span: mi.span(),
-                            });
-                            return false;
-                        };
-
-                        if let [seg, ..] = &mut mi.path.segments[..] {
-                            seg.ident.name = Symbol::intern(&format!("target_{}", seg.ident.name));
-                        }
-
-                        res & eval_condition(
-                            &ast::MetaItemInner::MetaItem(mi),
-                            sess,
-                            features,
-                            eval,
-                        )
-                    })
-                }
-                _ => {
-                    dcx.emit_err(session_diagnostics::InvalidPredicate {
-                        span: cfg.span,
-                        predicate: pprust::path_to_string(&cfg.path),
-                    });
-                    false
-                }
-            }
-        }
-        ast::MetaItemKind::Word | MetaItemKind::NameValue(..) if cfg.path.segments.len() != 1 => {
-            dcx.emit_err(session_diagnostics::CfgPredicateIdentifier { span: cfg.path.span });
-            true
-        }
-        MetaItemKind::NameValue(lit) if !lit.kind.is_str() => {
-            dcx.emit_err(session_diagnostics::UnsupportedLiteral {
-                span: lit.span,
-                reason: UnsupportedLiteralReason::CfgString,
-                is_bytestr: lit.kind.is_bytestr(),
-                start_point_span: sess.source_map().start_point(lit.span),
-            });
-            true
-        }
-        ast::MetaItemKind::Word | ast::MetaItemKind::NameValue(..) => {
-            let ident = cfg.ident().expect("multi-segment cfg predicate");
-            eval(Condition {
-                name: ident.name,
-                name_span: ident.span,
-                value: cfg.value_str(),
-                value_span: cfg.name_value_literal_span(),
-                span: cfg.span,
-            })
-        }
-    }
-}
-
-#[derive(Copy, Debug, Encodable, Decodable, Clone, HashStable_Generic)]
-pub struct Deprecation {
-    pub since: DeprecatedSince,
-    /// The note to issue a reason.
-    pub note: Option<Symbol>,
-    /// A text snippet used to completely replace any use of the deprecated item in an expression.
-    ///
-    /// This is currently unstable.
-    pub suggestion: Option<Symbol>,
-}
-
-/// Release in which an API is deprecated.
-#[derive(Copy, Debug, Encodable, Decodable, Clone, HashStable_Generic)]
-pub enum DeprecatedSince {
-    RustcVersion(RustcVersion),
-    /// Deprecated in the future ("to be determined").
-    Future,
-    /// `feature(staged_api)` is off. Deprecation versions outside the standard
-    /// library are allowed to be arbitrary strings, for better or worse.
-    NonStandard(Symbol),
-    /// Deprecation version is unspecified but optional.
-    Unspecified,
-    /// Failed to parse a deprecation version, or the deprecation version is
-    /// unspecified and required. An error has already been emitted.
-    Err,
-}
-
-impl Deprecation {
-    /// Whether an item marked with #[deprecated(since = "X")] is currently
-    /// deprecated (i.e., whether X is not greater than the current rustc
-    /// version).
-    pub fn is_in_effect(&self) -> bool {
-        match self.since {
-            DeprecatedSince::RustcVersion(since) => since <= RustcVersion::CURRENT,
-            DeprecatedSince::Future => false,
-            // The `since` field doesn't have semantic purpose without `#![staged_api]`.
-            DeprecatedSince::NonStandard(_) => true,
-            // Assume deprecation is in effect if "since" field is absent or invalid.
-            DeprecatedSince::Unspecified | DeprecatedSince::Err => true,
-        }
-    }
-
-    pub fn is_since_rustc_version(&self) -> bool {
-        matches!(self.since, DeprecatedSince::RustcVersion(_))
-    }
-}
-
-/// Finds the deprecation attribute. `None` if none exists.
-pub fn find_deprecation(
-    sess: &Session,
-    features: &Features,
-    attrs: &[Attribute],
-) -> Option<(Deprecation, Span)> {
-    let mut depr: Option<(Deprecation, Span)> = None;
-    let is_rustc = features.staged_api();
-
-    'outer: for attr in attrs {
-        if !attr.has_name(sym::deprecated) {
-            continue;
-        }
-
-        let Some(meta) = attr.meta() else {
-            continue;
-        };
-        let mut since = None;
-        let mut note = None;
-        let mut suggestion = None;
-        match &meta.kind {
-            MetaItemKind::Word => {}
-            MetaItemKind::NameValue(..) => note = meta.value_str(),
-            MetaItemKind::List(list) => {
-                let get = |meta: &MetaItem, item: &mut Option<Symbol>| {
-                    if item.is_some() {
-                        sess.dcx().emit_err(session_diagnostics::MultipleItem {
-                            span: meta.span,
-                            item: pprust::path_to_string(&meta.path),
-                        });
-                        return false;
-                    }
-                    if let Some(v) = meta.value_str() {
-                        *item = Some(v);
-                        true
-                    } else {
-                        if let Some(lit) = meta.name_value_literal() {
-                            sess.dcx().emit_err(session_diagnostics::UnsupportedLiteral {
-                                span: lit.span,
-                                reason: UnsupportedLiteralReason::DeprecatedString,
-                                is_bytestr: lit.kind.is_bytestr(),
-                                start_point_span: sess.source_map().start_point(lit.span),
-                            });
-                        } else {
-                            sess.dcx().emit_err(session_diagnostics::IncorrectMetaItem {
-                                span: meta.span,
-                            });
-                        }
-
-                        false
-                    }
-                };
-
-                for meta in list {
-                    match meta {
-                        MetaItemInner::MetaItem(mi) => match mi.name_or_empty() {
-                            sym::since => {
-                                if !get(mi, &mut since) {
-                                    continue 'outer;
-                                }
-                            }
-                            sym::note => {
-                                if !get(mi, &mut note) {
-                                    continue 'outer;
-                                }
-                            }
-                            sym::suggestion => {
-                                if !features.deprecated_suggestion() {
-                                    sess.dcx().emit_err(
-                                        session_diagnostics::DeprecatedItemSuggestion {
-                                            span: mi.span,
-                                            is_nightly: sess.is_nightly_build(),
-                                            details: (),
-                                        },
-                                    );
-                                }
-
-                                if !get(mi, &mut suggestion) {
-                                    continue 'outer;
-                                }
-                            }
-                            _ => {
-                                sess.dcx().emit_err(session_diagnostics::UnknownMetaItem {
-                                    span: meta.span(),
-                                    item: pprust::path_to_string(&mi.path),
-                                    expected: if features.deprecated_suggestion() {
-                                        &["since", "note", "suggestion"]
-                                    } else {
-                                        &["since", "note"]
-                                    },
-                                });
-                                continue 'outer;
-                            }
-                        },
-                        MetaItemInner::Lit(lit) => {
-                            sess.dcx().emit_err(session_diagnostics::UnsupportedLiteral {
-                                span: lit.span,
-                                reason: UnsupportedLiteralReason::DeprecatedKvPair,
-                                is_bytestr: false,
-                                start_point_span: sess.source_map().start_point(lit.span),
-                            });
-                            continue 'outer;
-                        }
-                    }
-                }
-            }
-        }
-
-        let since = if let Some(since) = since {
-            if since.as_str() == "TBD" {
-                DeprecatedSince::Future
-            } else if !is_rustc {
-                DeprecatedSince::NonStandard(since)
-            } else if let Some(version) = parse_version(since) {
-                DeprecatedSince::RustcVersion(version)
-            } else {
-                sess.dcx().emit_err(session_diagnostics::InvalidSince { span: attr.span });
-                DeprecatedSince::Err
-            }
-        } else if is_rustc {
-            sess.dcx().emit_err(session_diagnostics::MissingSince { span: attr.span });
-            DeprecatedSince::Err
-        } else {
-            DeprecatedSince::Unspecified
-        };
-
-        if is_rustc && note.is_none() {
-            sess.dcx().emit_err(session_diagnostics::MissingNote { span: attr.span });
-            continue;
-        }
-
-        depr = Some((Deprecation { since, note, suggestion }, attr.span));
-    }
-
-    depr
-}
-
-#[derive(PartialEq, Debug, Encodable, Decodable, Copy, Clone)]
-pub enum ReprAttr {
-    ReprInt(IntType),
-    ReprRust,
-    ReprC,
-    ReprPacked(Align),
-    ReprSimd,
-    ReprTransparent,
-    ReprAlign(Align),
-}
-
-#[derive(Eq, PartialEq, Debug, Copy, Clone)]
-#[derive(Encodable, Decodable, HashStable_Generic)]
-pub enum IntType {
-    SignedInt(ast::IntTy),
-    UnsignedInt(ast::UintTy),
-}
-
-impl IntType {
-    #[inline]
-    pub fn is_signed(self) -> bool {
-        use IntType::*;
-
-        match self {
-            SignedInt(..) => true,
-            UnsignedInt(..) => false,
-        }
-    }
-}
-
-/// Parse #[repr(...)] forms.
-///
-/// Valid repr contents: any of the primitive integral type names (see
-/// `int_type_of_word`, below) to specify enum discriminant type; `C`, to use
-/// the same discriminant size that the corresponding C enum would or C
-/// structure layout, `packed` to remove padding, and `transparent` to delegate representation
-/// concerns to the only non-ZST field.
-pub fn find_repr_attrs(sess: &Session, attr: &Attribute) -> Vec<ReprAttr> {
-    if attr.has_name(sym::repr) { parse_repr_attr(sess, attr) } else { Vec::new() }
-}
-
-pub fn parse_repr_attr(sess: &Session, attr: &Attribute) -> Vec<ReprAttr> {
-    assert!(attr.has_name(sym::repr), "expected `#[repr(..)]`, found: {attr:?}");
-    use ReprAttr::*;
-    let mut acc = Vec::new();
-    let dcx = sess.dcx();
-
-    if let Some(items) = attr.meta_item_list() {
-        for item in items {
-            let mut recognised = false;
-            if item.is_word() {
-                let hint = match item.name_or_empty() {
-                    sym::Rust => Some(ReprRust),
-                    sym::C => Some(ReprC),
-                    sym::packed => Some(ReprPacked(Align::ONE)),
-                    sym::simd => Some(ReprSimd),
-                    sym::transparent => Some(ReprTransparent),
-                    sym::align => {
-                        sess.dcx().emit_err(session_diagnostics::InvalidReprAlignNeedArg {
-                            span: item.span(),
-                        });
-                        recognised = true;
-                        None
-                    }
-                    name => int_type_of_word(name).map(ReprInt),
-                };
-
-                if let Some(h) = hint {
-                    recognised = true;
-                    acc.push(h);
-                }
-            } else if let Some((name, value)) = item.singleton_lit_list() {
-                let mut literal_error = None;
-                let mut err_span = item.span();
-                if name == sym::align {
-                    recognised = true;
-                    match parse_alignment(&value.kind) {
-                        Ok(literal) => acc.push(ReprAlign(literal)),
-                        Err(message) => {
-                            err_span = value.span;
-                            literal_error = Some(message)
-                        }
-                    };
-                } else if name == sym::packed {
-                    recognised = true;
-                    match parse_alignment(&value.kind) {
-                        Ok(literal) => acc.push(ReprPacked(literal)),
-                        Err(message) => {
-                            err_span = value.span;
-                            literal_error = Some(message)
-                        }
-                    };
-                } else if matches!(name, sym::Rust | sym::C | sym::simd | sym::transparent)
-                    || int_type_of_word(name).is_some()
-                {
-                    recognised = true;
-                    sess.dcx().emit_err(session_diagnostics::InvalidReprHintNoParen {
-                        span: item.span(),
-                        name: name.to_ident_string(),
-                    });
-                }
-                if let Some(literal_error) = literal_error {
-                    sess.dcx().emit_err(session_diagnostics::InvalidReprGeneric {
-                        span: err_span,
-                        repr_arg: name.to_ident_string(),
-                        error_part: literal_error,
-                    });
-                }
-            } else if let Some(meta_item) = item.meta_item() {
-                match &meta_item.kind {
-                    MetaItemKind::NameValue(value) => {
-                        if meta_item.has_name(sym::align) || meta_item.has_name(sym::packed) {
-                            let name = meta_item.name_or_empty().to_ident_string();
-                            recognised = true;
-                            sess.dcx().emit_err(session_diagnostics::IncorrectReprFormatGeneric {
-                                span: item.span(),
-                                repr_arg: &name,
-                                cause: IncorrectReprFormatGenericCause::from_lit_kind(
-                                    item.span(),
-                                    &value.kind,
-                                    &name,
-                                ),
-                            });
-                        } else if matches!(
-                            meta_item.name_or_empty(),
-                            sym::Rust | sym::C | sym::simd | sym::transparent
-                        ) || int_type_of_word(meta_item.name_or_empty()).is_some()
-                        {
-                            recognised = true;
-                            sess.dcx().emit_err(session_diagnostics::InvalidReprHintNoValue {
-                                span: meta_item.span,
-                                name: meta_item.name_or_empty().to_ident_string(),
-                            });
-                        }
-                    }
-                    MetaItemKind::List(nested_items) => {
-                        if meta_item.has_name(sym::align) {
-                            recognised = true;
-                            if let [nested_item] = nested_items.as_slice() {
-                                sess.dcx().emit_err(
-                                    session_diagnostics::IncorrectReprFormatExpectInteger {
-                                        span: nested_item.span(),
-                                    },
-                                );
-                            } else {
-                                sess.dcx().emit_err(
-                                    session_diagnostics::IncorrectReprFormatAlignOneArg {
-                                        span: meta_item.span,
-                                    },
-                                );
-                            }
-                        } else if meta_item.has_name(sym::packed) {
-                            recognised = true;
-                            if let [nested_item] = nested_items.as_slice() {
-                                sess.dcx().emit_err(
-                                    session_diagnostics::IncorrectReprFormatPackedExpectInteger {
-                                        span: nested_item.span(),
-                                    },
-                                );
-                            } else {
-                                sess.dcx().emit_err(
-                                    session_diagnostics::IncorrectReprFormatPackedOneOrZeroArg {
-                                        span: meta_item.span,
-                                    },
-                                );
-                            }
-                        } else if matches!(
-                            meta_item.name_or_empty(),
-                            sym::Rust | sym::C | sym::simd | sym::transparent
-                        ) || int_type_of_word(meta_item.name_or_empty()).is_some()
-                        {
-                            recognised = true;
-                            sess.dcx().emit_err(session_diagnostics::InvalidReprHintNoParen {
-                                span: meta_item.span,
-                                name: meta_item.name_or_empty().to_ident_string(),
-                            });
-                        }
-                    }
-                    _ => (),
-                }
-            }
-            if !recognised {
-                // Not a word we recognize. This will be caught and reported by
-                // the `check_mod_attrs` pass, but this pass doesn't always run
-                // (e.g. if we only pretty-print the source), so we have to gate
-                // the `span_delayed_bug` call as follows:
-                if sess.opts.pretty.map_or(true, |pp| pp.needs_analysis()) {
-                    dcx.span_delayed_bug(item.span(), "unrecognized representation hint");
-                }
-            }
-        }
-    }
-    acc
-}
-
-fn int_type_of_word(s: Symbol) -> Option<IntType> {
-    use IntType::*;
-
-    match s {
-        sym::i8 => Some(SignedInt(ast::IntTy::I8)),
-        sym::u8 => Some(UnsignedInt(ast::UintTy::U8)),
-        sym::i16 => Some(SignedInt(ast::IntTy::I16)),
-        sym::u16 => Some(UnsignedInt(ast::UintTy::U16)),
-        sym::i32 => Some(SignedInt(ast::IntTy::I32)),
-        sym::u32 => Some(UnsignedInt(ast::UintTy::U32)),
-        sym::i64 => Some(SignedInt(ast::IntTy::I64)),
-        sym::u64 => Some(UnsignedInt(ast::UintTy::U64)),
-        sym::i128 => Some(SignedInt(ast::IntTy::I128)),
-        sym::u128 => Some(UnsignedInt(ast::UintTy::U128)),
-        sym::isize => Some(SignedInt(ast::IntTy::Isize)),
-        sym::usize => Some(UnsignedInt(ast::UintTy::Usize)),
-        _ => None,
-    }
-}
-
-pub enum TransparencyError {
-    UnknownTransparency(Symbol, Span),
-    MultipleTransparencyAttrs(Span, Span),
-}
-
-pub fn find_transparency(
-    attrs: &[Attribute],
-    macro_rules: bool,
-) -> (Transparency, Option<TransparencyError>) {
-    let mut transparency = None;
-    let mut error = None;
-    for attr in attrs {
-        if attr.has_name(sym::rustc_macro_transparency) {
-            if let Some((_, old_span)) = transparency {
-                error = Some(TransparencyError::MultipleTransparencyAttrs(old_span, attr.span));
-                break;
-            } else if let Some(value) = attr.value_str() {
-                transparency = Some((
-                    match value {
-                        sym::transparent => Transparency::Transparent,
-                        sym::semitransparent => Transparency::SemiTransparent,
-                        sym::opaque => Transparency::Opaque,
-                        _ => {
-                            error = Some(TransparencyError::UnknownTransparency(value, attr.span));
-                            continue;
-                        }
-                    },
-                    attr.span,
-                ));
-            }
-        }
-    }
-    let fallback = if macro_rules { Transparency::SemiTransparent } else { Transparency::Opaque };
-    (transparency.map_or(fallback, |t| t.0), error)
-}
-
-pub fn allow_internal_unstable<'a>(
-    sess: &'a Session,
-    attrs: &'a [Attribute],
-) -> impl Iterator<Item = Symbol> + 'a {
-    allow_unstable(sess, attrs, sym::allow_internal_unstable)
-}
-
-pub fn rustc_allow_const_fn_unstable<'a>(
-    sess: &'a Session,
-    attrs: &'a [Attribute],
-) -> impl Iterator<Item = Symbol> + 'a {
-    allow_unstable(sess, attrs, sym::rustc_allow_const_fn_unstable)
-}
-
-fn allow_unstable<'a>(
-    sess: &'a Session,
-    attrs: &'a [Attribute],
-    symbol: Symbol,
-) -> impl Iterator<Item = Symbol> + 'a {
-    let attrs = attr::filter_by_name(attrs, symbol);
-    let list = attrs
-        .filter_map(move |attr| {
-            attr.meta_item_list().or_else(|| {
-                sess.dcx().emit_err(session_diagnostics::ExpectsFeatureList {
-                    span: attr.span,
-                    name: symbol.to_ident_string(),
-                });
-                None
-            })
-        })
-        .flatten();
-
-    list.into_iter().filter_map(move |it| {
-        let name = it.ident().map(|ident| ident.name);
-        if name.is_none() {
-            sess.dcx().emit_err(session_diagnostics::ExpectsFeatures {
-                span: it.span(),
-                name: symbol.to_ident_string(),
-            });
-        }
-        name
-    })
-}
-
-pub fn parse_alignment(node: &ast::LitKind) -> Result<Align, &'static str> {
-    if let ast::LitKind::Int(literal, ast::LitIntType::Unsuffixed) = node {
-        // `Align::from_bytes` accepts 0 as an input, check is_power_of_two() first
-        if literal.get().is_power_of_two() {
-            // Only possible error is larger than 2^29
-            literal
-                .get()
-                .try_into()
-                .ok()
-                .and_then(|v| Align::from_bytes(v).ok())
-                .ok_or("larger than 2^29")
-        } else {
-            Err("not a power of two")
-        }
-    } else {
-        Err("not an unsuffixed integer")
-    }
-}
-
-/// Read the content of a `rustc_confusables` attribute, and return the list of candidate names.
-pub fn parse_confusables(attr: &Attribute) -> Option<Vec<Symbol>> {
-    let meta = attr.meta()?;
-    let MetaItem { kind: MetaItemKind::List(ref metas), .. } = meta else { return None };
-
-    let mut candidates = Vec::new();
-
-    for meta in metas {
-        let MetaItemInner::Lit(meta_lit) = meta else {
-            return None;
-        };
-        candidates.push(meta_lit.symbol);
-    }
-
-    Some(candidates)
-}
diff --git a/compiler/rustc_attr/Cargo.toml b/compiler/rustc_attr_data_structures/Cargo.toml
index 3b24452450a..2ee58f24470 100644
--- a/compiler/rustc_attr/Cargo.toml
+++ b/compiler/rustc_attr_data_structures/Cargo.toml
@@ -1,5 +1,5 @@
 [package]
-name = "rustc_attr"
+name = "rustc_attr_data_structures"
 version = "0.0.0"
 edition = "2021"
 
diff --git a/compiler/rustc_attr_data_structures/src/attributes.rs b/compiler/rustc_attr_data_structures/src/attributes.rs
new file mode 100644
index 00000000000..8986bec57de
--- /dev/null
+++ b/compiler/rustc_attr_data_structures/src/attributes.rs
@@ -0,0 +1,106 @@
+use rustc_abi::Align;
+use rustc_ast as ast;
+use rustc_macros::{Decodable, Encodable, HashStable_Generic};
+use rustc_span::{Span, Symbol};
+
+use crate::RustcVersion;
+
+#[derive(Copy, Clone, PartialEq, Encodable, Decodable, Debug, HashStable_Generic)]
+pub enum InlineAttr {
+    None,
+    Hint,
+    Always,
+    Never,
+}
+
+#[derive(Clone, Encodable, Decodable, Debug, PartialEq, Eq, HashStable_Generic)]
+pub enum InstructionSetAttr {
+    ArmA32,
+    ArmT32,
+}
+
+#[derive(Clone, Encodable, Decodable, Debug, HashStable_Generic)]
+pub enum OptimizeAttr {
+    None,
+    Speed,
+    Size,
+}
+
+#[derive(Clone, Debug, Encodable, Decodable)]
+pub enum DiagnosticAttribute {
+    // tidy-alphabetical-start
+    DoNotRecommend,
+    OnUnimplemented,
+    // tidy-alphabetical-end
+}
+
+#[derive(PartialEq, Debug, Encodable, Decodable, Copy, Clone)]
+pub enum ReprAttr {
+    ReprInt(IntType),
+    ReprRust,
+    ReprC,
+    ReprPacked(Align),
+    ReprSimd,
+    ReprTransparent,
+    ReprAlign(Align),
+}
+pub use ReprAttr::*;
+
+pub enum TransparencyError {
+    UnknownTransparency(Symbol, Span),
+    MultipleTransparencyAttrs(Span, Span),
+}
+
+#[derive(Eq, PartialEq, Debug, Copy, Clone)]
+#[derive(Encodable, Decodable)]
+pub enum IntType {
+    SignedInt(ast::IntTy),
+    UnsignedInt(ast::UintTy),
+}
+
+#[derive(Copy, Debug, Encodable, Decodable, Clone, HashStable_Generic)]
+pub struct Deprecation {
+    pub since: DeprecatedSince,
+    /// The note to issue a reason.
+    pub note: Option<Symbol>,
+    /// A text snippet used to completely replace any use of the deprecated item in an expression.
+    ///
+    /// This is currently unstable.
+    pub suggestion: Option<Symbol>,
+}
+
+/// Release in which an API is deprecated.
+#[derive(Copy, Debug, Encodable, Decodable, Clone, HashStable_Generic)]
+pub enum DeprecatedSince {
+    RustcVersion(RustcVersion),
+    /// Deprecated in the future ("to be determined").
+    Future,
+    /// `feature(staged_api)` is off. Deprecation versions outside the standard
+    /// library are allowed to be arbitrary strings, for better or worse.
+    NonStandard(Symbol),
+    /// Deprecation version is unspecified but optional.
+    Unspecified,
+    /// Failed to parse a deprecation version, or the deprecation version is
+    /// unspecified and required. An error has already been emitted.
+    Err,
+}
+
+impl Deprecation {
+    /// Whether an item marked with #[deprecated(since = "X")] is currently
+    /// deprecated (i.e., whether X is not greater than the current rustc
+    /// version).
+    pub fn is_in_effect(&self) -> bool {
+        match self.since {
+            DeprecatedSince::RustcVersion(since) => since <= RustcVersion::CURRENT,
+            DeprecatedSince::Future => false,
+            // The `since` field doesn't have semantic purpose without `#![staged_api]`.
+            DeprecatedSince::NonStandard(_) => true,
+            // Assume deprecation is in effect if "since" field is absent or invalid.
+            DeprecatedSince::Unspecified | DeprecatedSince::Err => true,
+        }
+    }
+
+    pub fn is_since_rustc_version(&self) -> bool {
+        matches!(self.since, DeprecatedSince::RustcVersion(_))
+    }
+}
diff --git a/compiler/rustc_attr_data_structures/src/lib.rs b/compiler/rustc_attr_data_structures/src/lib.rs
new file mode 100644
index 00000000000..4f204aeab64
--- /dev/null
+++ b/compiler/rustc_attr_data_structures/src/lib.rs
@@ -0,0 +1,16 @@
+// tidy-alphabetical-start
+#![allow(internal_features)]
+#![doc(rust_logo)]
+#![feature(let_chains)]
+#![feature(rustdoc_internals)]
+#![warn(unreachable_pub)]
+// tidy-alphabetical-end
+
+mod attributes;
+mod stability;
+mod version;
+
+pub use attributes::*;
+pub(crate) use rustc_session::HashStableContext;
+pub use stability::*;
+pub use version::*;
diff --git a/compiler/rustc_attr_data_structures/src/stability.rs b/compiler/rustc_attr_data_structures/src/stability.rs
new file mode 100644
index 00000000000..021fe40e3e0
--- /dev/null
+++ b/compiler/rustc_attr_data_structures/src/stability.rs
@@ -0,0 +1,200 @@
+use std::num::NonZero;
+
+use rustc_macros::{Decodable, Encodable, HashStable_Generic};
+use rustc_span::{Symbol, sym};
+
+use crate::RustcVersion;
+
+/// The version placeholder that recently stabilized features contain inside the
+/// `since` field of the `#[stable]` attribute.
+///
+/// For more, see [this pull request](https://github.com/rust-lang/rust/pull/100591).
+pub const VERSION_PLACEHOLDER: &str = "CURRENT_RUSTC_VERSION";
+
+/// Represents the following attributes:
+///
+/// - `#[stable]`
+/// - `#[unstable]`
+#[derive(Encodable, Decodable, Copy, Clone, Debug, PartialEq, Eq, Hash)]
+#[derive(HashStable_Generic)]
+pub struct Stability {
+    pub level: StabilityLevel,
+    pub feature: Symbol,
+}
+
+impl Stability {
+    pub fn is_unstable(&self) -> bool {
+        self.level.is_unstable()
+    }
+
+    pub fn is_stable(&self) -> bool {
+        self.level.is_stable()
+    }
+
+    pub fn stable_since(&self) -> Option<StableSince> {
+        self.level.stable_since()
+    }
+}
+
+/// Represents the `#[rustc_const_unstable]` and `#[rustc_const_stable]` attributes.
+#[derive(Encodable, Decodable, Copy, Clone, Debug, PartialEq, Eq, Hash)]
+#[derive(HashStable_Generic)]
+pub struct ConstStability {
+    pub level: StabilityLevel,
+    pub feature: Symbol,
+    /// whether the function has a `#[rustc_promotable]` attribute
+    pub promotable: bool,
+    /// This is true iff the `const_stable_indirect` attribute is present.
+    pub const_stable_indirect: bool,
+}
+
+impl ConstStability {
+    pub fn from_partial(
+        PartialConstStability { level, feature, promotable }: PartialConstStability,
+        const_stable_indirect: bool,
+    ) -> Self {
+        Self { const_stable_indirect, level, feature, promotable }
+    }
+
+    /// The stability assigned to unmarked items when -Zforce-unstable-if-unmarked is set.
+    pub fn unmarked(const_stable_indirect: bool, regular_stab: Stability) -> Self {
+        Self {
+            feature: regular_stab.feature,
+            promotable: false,
+            level: regular_stab.level,
+            const_stable_indirect,
+        }
+    }
+
+    pub fn is_const_unstable(&self) -> bool {
+        self.level.is_unstable()
+    }
+
+    pub fn is_const_stable(&self) -> bool {
+        self.level.is_stable()
+    }
+}
+
+/// Excludes `const_stable_indirect`. This is necessary because when `-Zforce-unstable-if-unmarked`
+/// is set, we need to encode standalone `#[rustc_const_stable_indirect]` attributes
+#[derive(Encodable, Decodable, Copy, Clone, Debug, PartialEq, Eq, Hash)]
+#[derive(HashStable_Generic)]
+pub struct PartialConstStability {
+    pub level: StabilityLevel,
+    pub feature: Symbol,
+    /// whether the function has a `#[rustc_promotable]` attribute
+    pub promotable: bool,
+}
+
+impl PartialConstStability {
+    pub fn is_const_unstable(&self) -> bool {
+        self.level.is_unstable()
+    }
+
+    pub fn is_const_stable(&self) -> bool {
+        self.level.is_stable()
+    }
+}
+
+/// The available stability levels.
+#[derive(Encodable, Decodable, PartialEq, Copy, Clone, Debug, Eq, Hash)]
+#[derive(HashStable_Generic)]
+pub enum StabilityLevel {
+    /// `#[unstable]`
+    Unstable {
+        /// Reason for the current stability level.
+        reason: UnstableReason,
+        /// Relevant `rust-lang/rust` issue.
+        issue: Option<NonZero<u32>>,
+        is_soft: bool,
+        /// If part of a feature is stabilized and a new feature is added for the remaining parts,
+        /// then the `implied_by` attribute is used to indicate which now-stable feature previously
+        /// contained an item.
+        ///
+        /// ```pseudo-Rust
+        /// #[unstable(feature = "foo", issue = "...")]
+        /// fn foo() {}
+        /// #[unstable(feature = "foo", issue = "...")]
+        /// fn foobar() {}
+        /// ```
+        ///
+        /// ...becomes...
+        ///
+        /// ```pseudo-Rust
+        /// #[stable(feature = "foo", since = "1.XX.X")]
+        /// fn foo() {}
+        /// #[unstable(feature = "foobar", issue = "...", implied_by = "foo")]
+        /// fn foobar() {}
+        /// ```
+        implied_by: Option<Symbol>,
+    },
+    /// `#[stable]`
+    Stable {
+        /// Rust release which stabilized this feature.
+        since: StableSince,
+        /// Is this item allowed to be referred to on stable, despite being contained in unstable
+        /// modules?
+        allowed_through_unstable_modules: bool,
+    },
+}
+
+/// Rust release in which a feature is stabilized.
+#[derive(Encodable, Decodable, PartialEq, Copy, Clone, Debug, Eq, PartialOrd, Ord, Hash)]
+#[derive(HashStable_Generic)]
+pub enum StableSince {
+    /// also stores the original symbol for printing
+    Version(RustcVersion),
+    /// Stabilized in the upcoming version, whatever number that is.
+    Current,
+    /// Failed to parse a stabilization version.
+    Err,
+}
+
+impl StabilityLevel {
+    pub fn is_unstable(&self) -> bool {
+        matches!(self, StabilityLevel::Unstable { .. })
+    }
+    pub fn is_stable(&self) -> bool {
+        matches!(self, StabilityLevel::Stable { .. })
+    }
+    pub fn stable_since(&self) -> Option<StableSince> {
+        match *self {
+            StabilityLevel::Stable { since, .. } => Some(since),
+            StabilityLevel::Unstable { .. } => None,
+        }
+    }
+}
+
+#[derive(Encodable, Decodable, PartialEq, Copy, Clone, Debug, Eq, Hash)]
+#[derive(HashStable_Generic)]
+pub enum UnstableReason {
+    None,
+    Default,
+    Some(Symbol),
+}
+
+/// Represents the `#[rustc_default_body_unstable]` attribute.
+#[derive(Encodable, Decodable, Copy, Clone, Debug, PartialEq, Eq, Hash)]
+#[derive(HashStable_Generic)]
+pub struct DefaultBodyStability {
+    pub level: StabilityLevel,
+    pub feature: Symbol,
+}
+
+impl UnstableReason {
+    pub fn from_opt_reason(reason: Option<Symbol>) -> Self {
+        // UnstableReason::Default constructed manually
+        match reason {
+            Some(r) => Self::Some(r),
+            None => Self::None,
+        }
+    }
+
+    pub fn to_opt_reason(&self) -> Option<Symbol> {
+        match self {
+            Self::None => None,
+            Self::Default => Some(sym::unstable_location_reason_default),
+            Self::Some(r) => Some(*r),
+        }
+    }
+}
diff --git a/compiler/rustc_session/src/version.rs b/compiler/rustc_attr_data_structures/src/version.rs
index 1696eaf902b..6be875ad4be 100644
--- a/compiler/rustc_session/src/version.rs
+++ b/compiler/rustc_attr_data_structures/src/version.rs
@@ -1,7 +1,5 @@
-use std::borrow::Cow;
 use std::fmt::{self, Display};
 
-use rustc_errors::IntoDiagArg;
 use rustc_macros::{Decodable, Encodable, HashStable_Generic, current_rustc_version};
 
 #[derive(Encodable, Decodable, Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
@@ -21,9 +19,3 @@ impl Display for RustcVersion {
         write!(formatter, "{}.{}.{}", self.major, self.minor, self.patch)
     }
 }
-
-impl IntoDiagArg for RustcVersion {
-    fn into_diag_arg(self) -> rustc_errors::DiagArgValue {
-        rustc_errors::DiagArgValue::Str(Cow::Owned(self.to_string()))
-    }
-}
diff --git a/compiler/rustc_attr_parsing/Cargo.toml b/compiler/rustc_attr_parsing/Cargo.toml
new file mode 100644
index 00000000000..7ccedf40c3f
--- /dev/null
+++ b/compiler/rustc_attr_parsing/Cargo.toml
@@ -0,0 +1,21 @@
+[package]
+name = "rustc_attr_parsing"
+version = "0.0.0"
+edition = "2021"
+
+[dependencies]
+# tidy-alphabetical-start
+rustc_abi = { path = "../rustc_abi" }
+rustc_ast = { path = "../rustc_ast" }
+rustc_ast_pretty = { path = "../rustc_ast_pretty" }
+rustc_attr_data_structures = { path = "../rustc_attr_data_structures" }
+rustc_data_structures = { path = "../rustc_data_structures" }
+rustc_errors = { path = "../rustc_errors" }
+rustc_feature = { path = "../rustc_feature" }
+rustc_fluent_macro = { path = "../rustc_fluent_macro" }
+rustc_lexer = { path = "../rustc_lexer" }
+rustc_macros = { path = "../rustc_macros" }
+rustc_serialize = { path = "../rustc_serialize" }
+rustc_session = { path = "../rustc_session" }
+rustc_span = { path = "../rustc_span" }
+# tidy-alphabetical-end
diff --git a/compiler/rustc_attr/messages.ftl b/compiler/rustc_attr_parsing/messages.ftl
index 235ab7572c4..faa2865cb91 100644
--- a/compiler/rustc_attr/messages.ftl
+++ b/compiler/rustc_attr_parsing/messages.ftl
@@ -1,46 +1,46 @@
-attr_cfg_predicate_identifier =
+attr_parsing_cfg_predicate_identifier =
     `cfg` predicate key must be an identifier
 
-attr_deprecated_item_suggestion =
+attr_parsing_deprecated_item_suggestion =
     suggestions on deprecated items are unstable
     .help = add `#![feature(deprecated_suggestion)]` to the crate root
     .note = see #94785 for more details
 
-attr_expected_one_cfg_pattern =
+attr_parsing_expected_one_cfg_pattern =
     expected 1 cfg-pattern
 
-attr_expected_single_version_literal =
+attr_parsing_expected_single_version_literal =
     expected single version literal
 
-attr_expected_version_literal =
+attr_parsing_expected_version_literal =
     expected a version literal
 
-attr_expects_feature_list =
+attr_parsing_expects_feature_list =
     `{$name}` expects a list of feature names
 
-attr_expects_features =
+attr_parsing_expects_features =
     `{$name}` expects feature names
 
-attr_incorrect_meta_item =
+attr_parsing_incorrect_meta_item =
     incorrect meta item
 
-attr_incorrect_repr_format_align_one_arg =
+attr_parsing_incorrect_repr_format_align_one_arg =
     incorrect `repr(align)` attribute format: `align` takes exactly one argument in parentheses
 
-attr_incorrect_repr_format_expect_literal_integer =
+attr_parsing_incorrect_repr_format_expect_literal_integer =
     incorrect `repr(align)` attribute format: `align` expects a literal integer as argument
 
-attr_incorrect_repr_format_generic =
+attr_parsing_incorrect_repr_format_generic =
     incorrect `repr({$repr_arg})` attribute format
     .suggestion = use parentheses instead
 
-attr_incorrect_repr_format_packed_expect_integer =
+attr_parsing_incorrect_repr_format_packed_expect_integer =
     incorrect `repr(packed)` attribute format: `packed` expects a literal integer as argument
 
-attr_incorrect_repr_format_packed_one_or_zero_arg =
+attr_parsing_incorrect_repr_format_packed_one_or_zero_arg =
     incorrect `repr(packed)` attribute format: `packed` takes exactly one parenthesized argument, or no parentheses at all
 
-attr_invalid_issue_string =
+attr_parsing_invalid_issue_string =
     `issue` must be a non-zero numeric string or "none"
     .must_not_be_zero = `issue` must not be "0", use "none" instead
     .empty = cannot parse integer from empty string
@@ -48,77 +48,77 @@ attr_invalid_issue_string =
     .pos_overflow = number too large to fit in target type
     .neg_overflow = number too small to fit in target type
 
-attr_invalid_predicate =
+attr_parsing_invalid_predicate =
     invalid predicate `{$predicate}`
 
-attr_invalid_repr_align_need_arg =
+attr_parsing_invalid_repr_align_need_arg =
     invalid `repr(align)` attribute: `align` needs an argument
     .suggestion = supply an argument here
 
-attr_invalid_repr_generic =
+attr_parsing_invalid_repr_generic =
     invalid `repr({$repr_arg})` attribute: {$error_part}
 
-attr_invalid_repr_hint_no_paren =
+attr_parsing_invalid_repr_hint_no_paren =
     invalid representation hint: `{$name}` does not take a parenthesized argument list
 
-attr_invalid_repr_hint_no_value =
+attr_parsing_invalid_repr_hint_no_value =
     invalid representation hint: `{$name}` does not take a value
 
-attr_invalid_since =
+attr_parsing_invalid_since =
     'since' must be a Rust version number, such as "1.31.0"
 
-attr_missing_feature =
+attr_parsing_missing_feature =
     missing 'feature'
 
-attr_missing_issue =
+attr_parsing_missing_issue =
     missing 'issue'
 
-attr_missing_note =
+attr_parsing_missing_note =
     missing 'note'
 
-attr_missing_since =
+attr_parsing_missing_since =
     missing 'since'
 
-attr_multiple_item =
+attr_parsing_multiple_item =
     multiple '{$item}' items
 
-attr_multiple_stability_levels =
+attr_parsing_multiple_stability_levels =
     multiple stability levels
 
-attr_non_ident_feature =
+attr_parsing_non_ident_feature =
     'feature' is not an identifier
 
-attr_rustc_allowed_unstable_pairing =
+attr_parsing_rustc_allowed_unstable_pairing =
     `rustc_allowed_through_unstable_modules` attribute must be paired with a `stable` attribute
 
-attr_rustc_const_stable_indirect_pairing =
+attr_parsing_rustc_const_stable_indirect_pairing =
     `const_stable_indirect` attribute does not make sense on `rustc_const_stable` function, its behavior is already implied
 
-attr_rustc_promotable_pairing =
+attr_parsing_rustc_promotable_pairing =
     `rustc_promotable` attribute must be paired with either a `rustc_const_unstable` or a `rustc_const_stable` attribute
 
-attr_soft_no_args =
+attr_parsing_soft_no_args =
     `soft` should not have any arguments
 
-attr_unknown_meta_item =
+attr_parsing_unknown_meta_item =
     unknown meta item '{$item}'
     .label = expected one of {$expected}
 
-attr_unknown_version_literal =
+attr_parsing_unknown_version_literal =
     unknown version literal format, assuming it refers to a future version
 
-attr_unstable_cfg_target_compact =
+attr_parsing_unstable_cfg_target_compact =
     compact `cfg(target(..))` is experimental and subject to change
 
-attr_unsupported_literal_cfg_boolean =
+attr_parsing_unsupported_literal_cfg_boolean =
     literal in `cfg` predicate value must be a boolean
-attr_unsupported_literal_cfg_string =
+attr_parsing_unsupported_literal_cfg_string =
     literal in `cfg` predicate value must be a string
-attr_unsupported_literal_deprecated_kv_pair =
+attr_parsing_unsupported_literal_deprecated_kv_pair =
     item in `deprecated` must be a key/value pair
-attr_unsupported_literal_deprecated_string =
+attr_parsing_unsupported_literal_deprecated_string =
     literal in `deprecated` value must be a string
-attr_unsupported_literal_generic =
+attr_parsing_unsupported_literal_generic =
     unsupported literal
-attr_unsupported_literal_suggestion =
+attr_parsing_unsupported_literal_suggestion =
     consider removing the prefix
diff --git a/compiler/rustc_attr_parsing/src/attributes/allow_unstable.rs b/compiler/rustc_attr_parsing/src/attributes/allow_unstable.rs
new file mode 100644
index 00000000000..471168ed4f5
--- /dev/null
+++ b/compiler/rustc_attr_parsing/src/attributes/allow_unstable.rs
@@ -0,0 +1,49 @@
+use rustc_ast::attr::{AttributeExt, filter_by_name};
+use rustc_session::Session;
+use rustc_span::{Symbol, sym};
+
+use crate::session_diagnostics;
+
+pub fn allow_internal_unstable<'a>(
+    sess: &'a Session,
+    attrs: &'a [impl AttributeExt],
+) -> impl Iterator<Item = Symbol> + 'a {
+    allow_unstable(sess, attrs, sym::allow_internal_unstable)
+}
+
+pub fn rustc_allow_const_fn_unstable<'a>(
+    sess: &'a Session,
+    attrs: &'a [impl AttributeExt],
+) -> impl Iterator<Item = Symbol> + 'a {
+    allow_unstable(sess, attrs, sym::rustc_allow_const_fn_unstable)
+}
+
+fn allow_unstable<'a>(
+    sess: &'a Session,
+    attrs: &'a [impl AttributeExt],
+    symbol: Symbol,
+) -> impl Iterator<Item = Symbol> + 'a {
+    let attrs = filter_by_name(attrs, symbol);
+    let list = attrs
+        .filter_map(move |attr| {
+            attr.meta_item_list().or_else(|| {
+                sess.dcx().emit_err(session_diagnostics::ExpectsFeatureList {
+                    span: attr.span(),
+                    name: symbol.to_ident_string(),
+                });
+                None
+            })
+        })
+        .flatten();
+
+    list.into_iter().filter_map(move |it| {
+        let name = it.ident().map(|ident| ident.name);
+        if name.is_none() {
+            sess.dcx().emit_err(session_diagnostics::ExpectsFeatures {
+                span: it.span(),
+                name: symbol.to_ident_string(),
+            });
+        }
+        name
+    })
+}
diff --git a/compiler/rustc_attr_parsing/src/attributes/cfg.rs b/compiler/rustc_attr_parsing/src/attributes/cfg.rs
new file mode 100644
index 00000000000..bb9aaaa2fea
--- /dev/null
+++ b/compiler/rustc_attr_parsing/src/attributes/cfg.rs
@@ -0,0 +1,253 @@
+//! Parsing and validation of builtin attributes
+
+use rustc_ast::{self as ast, LitKind, MetaItem, MetaItemInner, MetaItemKind, MetaItemLit, NodeId};
+use rustc_ast_pretty::pprust;
+use rustc_attr_data_structures::RustcVersion;
+use rustc_feature::{Features, GatedCfg, find_gated_cfg};
+use rustc_session::Session;
+use rustc_session::config::ExpectedValues;
+use rustc_session::lint::BuiltinLintDiag;
+use rustc_session::lint::builtin::UNEXPECTED_CFGS;
+use rustc_session::parse::feature_err;
+use rustc_span::{Span, Symbol, kw, sym};
+
+use crate::util::UnsupportedLiteralReason;
+use crate::{fluent_generated, parse_version, session_diagnostics};
+
+#[derive(Clone, Debug)]
+pub struct Condition {
+    pub name: Symbol,
+    pub name_span: Span,
+    pub value: Option<Symbol>,
+    pub value_span: Option<Span>,
+    pub span: Span,
+}
+
+/// Tests if a cfg-pattern matches the cfg set
+pub fn cfg_matches(
+    cfg: &ast::MetaItemInner,
+    sess: &Session,
+    lint_node_id: NodeId,
+    features: Option<&Features>,
+) -> bool {
+    eval_condition(cfg, sess, features, &mut |cfg| {
+        try_gate_cfg(cfg.name, cfg.span, sess, features);
+        match sess.psess.check_config.expecteds.get(&cfg.name) {
+            Some(ExpectedValues::Some(values)) if !values.contains(&cfg.value) => {
+                sess.psess.buffer_lint(
+                    UNEXPECTED_CFGS,
+                    cfg.span,
+                    lint_node_id,
+                    BuiltinLintDiag::UnexpectedCfgValue(
+                        (cfg.name, cfg.name_span),
+                        cfg.value.map(|v| (v, cfg.value_span.unwrap())),
+                    ),
+                );
+            }
+            None if sess.psess.check_config.exhaustive_names => {
+                sess.psess.buffer_lint(
+                    UNEXPECTED_CFGS,
+                    cfg.span,
+                    lint_node_id,
+                    BuiltinLintDiag::UnexpectedCfgName(
+                        (cfg.name, cfg.name_span),
+                        cfg.value.map(|v| (v, cfg.value_span.unwrap())),
+                    ),
+                );
+            }
+            _ => { /* not unexpected */ }
+        }
+        sess.psess.config.contains(&(cfg.name, cfg.value))
+    })
+}
+
+fn try_gate_cfg(name: Symbol, span: Span, sess: &Session, features: Option<&Features>) {
+    let gate = find_gated_cfg(|sym| sym == name);
+    if let (Some(feats), Some(gated_cfg)) = (features, gate) {
+        gate_cfg(gated_cfg, span, sess, feats);
+    }
+}
+
+#[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
+fn gate_cfg(gated_cfg: &GatedCfg, cfg_span: Span, sess: &Session, features: &Features) {
+    let (cfg, feature, has_feature) = gated_cfg;
+    if !has_feature(features) && !cfg_span.allows_unstable(*feature) {
+        let explain = format!("`cfg({cfg})` is experimental and subject to change");
+        feature_err(sess, *feature, cfg_span, explain).emit();
+    }
+}
+
+/// Evaluate a cfg-like condition (with `any` and `all`), using `eval` to
+/// evaluate individual items.
+pub fn eval_condition(
+    cfg: &ast::MetaItemInner,
+    sess: &Session,
+    features: Option<&Features>,
+    eval: &mut impl FnMut(Condition) -> bool,
+) -> bool {
+    let dcx = sess.dcx();
+
+    let cfg = match cfg {
+        ast::MetaItemInner::MetaItem(meta_item) => meta_item,
+        ast::MetaItemInner::Lit(MetaItemLit { kind: LitKind::Bool(b), .. }) => {
+            if let Some(features) = features {
+                // we can't use `try_gate_cfg` as symbols don't differentiate between `r#true`
+                // and `true`, and we want to keep the former working without feature gate
+                gate_cfg(
+                    &(
+                        if *b { kw::True } else { kw::False },
+                        sym::cfg_boolean_literals,
+                        |features: &Features| features.cfg_boolean_literals(),
+                    ),
+                    cfg.span(),
+                    sess,
+                    features,
+                );
+            }
+            return *b;
+        }
+        _ => {
+            dcx.emit_err(session_diagnostics::UnsupportedLiteral {
+                span: cfg.span(),
+                reason: UnsupportedLiteralReason::CfgBoolean,
+                is_bytestr: false,
+                start_point_span: sess.source_map().start_point(cfg.span()),
+            });
+            return false;
+        }
+    };
+
+    match &cfg.kind {
+        ast::MetaItemKind::List(mis) if cfg.name_or_empty() == sym::version => {
+            try_gate_cfg(sym::version, cfg.span, sess, features);
+            let (min_version, span) = match &mis[..] {
+                [MetaItemInner::Lit(MetaItemLit { kind: LitKind::Str(sym, ..), span, .. })] => {
+                    (sym, span)
+                }
+                [
+                    MetaItemInner::Lit(MetaItemLit { span, .. })
+                    | MetaItemInner::MetaItem(MetaItem { span, .. }),
+                ] => {
+                    dcx.emit_err(session_diagnostics::ExpectedVersionLiteral { span: *span });
+                    return false;
+                }
+                [..] => {
+                    dcx.emit_err(session_diagnostics::ExpectedSingleVersionLiteral {
+                        span: cfg.span,
+                    });
+                    return false;
+                }
+            };
+            let Some(min_version) = parse_version(*min_version) else {
+                dcx.emit_warn(session_diagnostics::UnknownVersionLiteral { span: *span });
+                return false;
+            };
+
+            // See https://github.com/rust-lang/rust/issues/64796#issuecomment-640851454 for details
+            if sess.psess.assume_incomplete_release {
+                RustcVersion::CURRENT > min_version
+            } else {
+                RustcVersion::CURRENT >= min_version
+            }
+        }
+        ast::MetaItemKind::List(mis) => {
+            for mi in mis.iter() {
+                if mi.meta_item_or_bool().is_none() {
+                    dcx.emit_err(session_diagnostics::UnsupportedLiteral {
+                        span: mi.span(),
+                        reason: UnsupportedLiteralReason::Generic,
+                        is_bytestr: false,
+                        start_point_span: sess.source_map().start_point(mi.span()),
+                    });
+                    return false;
+                }
+            }
+
+            // The unwraps below may look dangerous, but we've already asserted
+            // that they won't fail with the loop above.
+            match cfg.name_or_empty() {
+                sym::any => mis
+                    .iter()
+                    // We don't use any() here, because we want to evaluate all cfg condition
+                    // as eval_condition can (and does) extra checks
+                    .fold(false, |res, mi| res | eval_condition(mi, sess, features, eval)),
+                sym::all => mis
+                    .iter()
+                    // We don't use all() here, because we want to evaluate all cfg condition
+                    // as eval_condition can (and does) extra checks
+                    .fold(true, |res, mi| res & eval_condition(mi, sess, features, eval)),
+                sym::not => {
+                    let [mi] = mis.as_slice() else {
+                        dcx.emit_err(session_diagnostics::ExpectedOneCfgPattern { span: cfg.span });
+                        return false;
+                    };
+
+                    !eval_condition(mi, sess, features, eval)
+                }
+                sym::target => {
+                    if let Some(features) = features
+                        && !features.cfg_target_compact()
+                    {
+                        feature_err(
+                            sess,
+                            sym::cfg_target_compact,
+                            cfg.span,
+                            fluent_generated::attr_parsing_unstable_cfg_target_compact,
+                        )
+                        .emit();
+                    }
+
+                    mis.iter().fold(true, |res, mi| {
+                        let Some(mut mi) = mi.meta_item().cloned() else {
+                            dcx.emit_err(session_diagnostics::CfgPredicateIdentifier {
+                                span: mi.span(),
+                            });
+                            return false;
+                        };
+
+                        if let [seg, ..] = &mut mi.path.segments[..] {
+                            seg.ident.name = Symbol::intern(&format!("target_{}", seg.ident.name));
+                        }
+
+                        res & eval_condition(
+                            &ast::MetaItemInner::MetaItem(mi),
+                            sess,
+                            features,
+                            eval,
+                        )
+                    })
+                }
+                _ => {
+                    dcx.emit_err(session_diagnostics::InvalidPredicate {
+                        span: cfg.span,
+                        predicate: pprust::path_to_string(&cfg.path),
+                    });
+                    false
+                }
+            }
+        }
+        ast::MetaItemKind::Word | MetaItemKind::NameValue(..) if cfg.path.segments.len() != 1 => {
+            dcx.emit_err(session_diagnostics::CfgPredicateIdentifier { span: cfg.path.span });
+            true
+        }
+        MetaItemKind::NameValue(lit) if !lit.kind.is_str() => {
+            dcx.emit_err(session_diagnostics::UnsupportedLiteral {
+                span: lit.span,
+                reason: UnsupportedLiteralReason::CfgString,
+                is_bytestr: lit.kind.is_bytestr(),
+                start_point_span: sess.source_map().start_point(lit.span),
+            });
+            true
+        }
+        ast::MetaItemKind::Word | ast::MetaItemKind::NameValue(..) => {
+            let ident = cfg.ident().expect("multi-segment cfg predicate");
+            eval(Condition {
+                name: ident.name,
+                name_span: ident.span,
+                value: cfg.value_str(),
+                value_span: cfg.name_value_literal_span(),
+                span: cfg.span,
+            })
+        }
+    }
+}
diff --git a/compiler/rustc_attr_parsing/src/attributes/confusables.rs b/compiler/rustc_attr_parsing/src/attributes/confusables.rs
new file mode 100644
index 00000000000..2ced759fd88
--- /dev/null
+++ b/compiler/rustc_attr_parsing/src/attributes/confusables.rs
@@ -0,0 +1,21 @@
+//! Parsing and validation of builtin attributes
+
+use rustc_ast::MetaItemInner;
+use rustc_ast::attr::AttributeExt;
+use rustc_span::Symbol;
+
+/// Read the content of a `rustc_confusables` attribute, and return the list of candidate names.
+pub fn parse_confusables(attr: &impl AttributeExt) -> Option<Vec<Symbol>> {
+    let metas = attr.meta_item_list()?;
+
+    let mut candidates = Vec::new();
+
+    for meta in metas {
+        let MetaItemInner::Lit(meta_lit) = meta else {
+            return None;
+        };
+        candidates.push(meta_lit.symbol);
+    }
+
+    Some(candidates)
+}
diff --git a/compiler/rustc_attr_parsing/src/attributes/deprecation.rs b/compiler/rustc_attr_parsing/src/attributes/deprecation.rs
new file mode 100644
index 00000000000..d7415a7198f
--- /dev/null
+++ b/compiler/rustc_attr_parsing/src/attributes/deprecation.rs
@@ -0,0 +1,148 @@
+//! Parsing and validation of builtin attributes
+
+use rustc_ast::attr::AttributeExt;
+use rustc_ast::{MetaItem, MetaItemInner};
+use rustc_ast_pretty::pprust;
+use rustc_attr_data_structures::{DeprecatedSince, Deprecation};
+use rustc_feature::Features;
+use rustc_session::Session;
+use rustc_span::{Span, Symbol, sym};
+
+use super::util::UnsupportedLiteralReason;
+use crate::{parse_version, session_diagnostics};
+
+/// Finds the deprecation attribute. `None` if none exists.
+pub fn find_deprecation(
+    sess: &Session,
+    features: &Features,
+    attrs: &[impl AttributeExt],
+) -> Option<(Deprecation, Span)> {
+    let mut depr: Option<(Deprecation, Span)> = None;
+    let is_rustc = features.staged_api();
+
+    'outer: for attr in attrs {
+        if !attr.has_name(sym::deprecated) {
+            continue;
+        }
+
+        let mut since = None;
+        let mut note = None;
+        let mut suggestion = None;
+
+        if attr.is_doc_comment() {
+            continue;
+        } else if attr.is_word() {
+        } else if let Some(value) = attr.value_str() {
+            note = Some(value)
+        } else if let Some(list) = attr.meta_item_list() {
+            let get = |meta: &MetaItem, item: &mut Option<Symbol>| {
+                if item.is_some() {
+                    sess.dcx().emit_err(session_diagnostics::MultipleItem {
+                        span: meta.span,
+                        item: pprust::path_to_string(&meta.path),
+                    });
+                    return false;
+                }
+                if let Some(v) = meta.value_str() {
+                    *item = Some(v);
+                    true
+                } else {
+                    if let Some(lit) = meta.name_value_literal() {
+                        sess.dcx().emit_err(session_diagnostics::UnsupportedLiteral {
+                            span: lit.span,
+                            reason: UnsupportedLiteralReason::DeprecatedString,
+                            is_bytestr: lit.kind.is_bytestr(),
+                            start_point_span: sess.source_map().start_point(lit.span),
+                        });
+                    } else {
+                        sess.dcx()
+                            .emit_err(session_diagnostics::IncorrectMetaItem { span: meta.span });
+                    }
+                    false
+                }
+            };
+
+            for meta in &list {
+                match meta {
+                    MetaItemInner::MetaItem(mi) => match mi.name_or_empty() {
+                        sym::since => {
+                            if !get(mi, &mut since) {
+                                continue 'outer;
+                            }
+                        }
+                        sym::note => {
+                            if !get(mi, &mut note) {
+                                continue 'outer;
+                            }
+                        }
+                        sym::suggestion => {
+                            if !features.deprecated_suggestion() {
+                                sess.dcx().emit_err(
+                                    session_diagnostics::DeprecatedItemSuggestion {
+                                        span: mi.span,
+                                        is_nightly: sess.is_nightly_build(),
+                                        details: (),
+                                    },
+                                );
+                            }
+
+                            if !get(mi, &mut suggestion) {
+                                continue 'outer;
+                            }
+                        }
+                        _ => {
+                            sess.dcx().emit_err(session_diagnostics::UnknownMetaItem {
+                                span: meta.span(),
+                                item: pprust::path_to_string(&mi.path),
+                                expected: if features.deprecated_suggestion() {
+                                    &["since", "note", "suggestion"]
+                                } else {
+                                    &["since", "note"]
+                                },
+                            });
+                            continue 'outer;
+                        }
+                    },
+                    MetaItemInner::Lit(lit) => {
+                        sess.dcx().emit_err(session_diagnostics::UnsupportedLiteral {
+                            span: lit.span,
+                            reason: UnsupportedLiteralReason::DeprecatedKvPair,
+                            is_bytestr: false,
+                            start_point_span: sess.source_map().start_point(lit.span),
+                        });
+                        continue 'outer;
+                    }
+                }
+            }
+        } else {
+            continue;
+        }
+
+        let since = if let Some(since) = since {
+            if since.as_str() == "TBD" {
+                DeprecatedSince::Future
+            } else if !is_rustc {
+                DeprecatedSince::NonStandard(since)
+            } else if let Some(version) = parse_version(since) {
+                DeprecatedSince::RustcVersion(version)
+            } else {
+                sess.dcx().emit_err(session_diagnostics::InvalidSince { span: attr.span() });
+                DeprecatedSince::Err
+            }
+        } else if is_rustc {
+            sess.dcx().emit_err(session_diagnostics::MissingSince { span: attr.span() });
+            DeprecatedSince::Err
+        } else {
+            DeprecatedSince::Unspecified
+        };
+
+        if is_rustc && note.is_none() {
+            sess.dcx().emit_err(session_diagnostics::MissingNote { span: attr.span() });
+            continue;
+        }
+
+        depr = Some((Deprecation { since, note, suggestion }, attr.span()));
+    }
+
+    depr
+}
diff --git a/compiler/rustc_attr_parsing/src/attributes/mod.rs b/compiler/rustc_attr_parsing/src/attributes/mod.rs
new file mode 100644
index 00000000000..a78e0b54b64
--- /dev/null
+++ b/compiler/rustc_attr_parsing/src/attributes/mod.rs
@@ -0,0 +1,17 @@
+mod allow_unstable;
+mod cfg;
+mod confusables;
+mod deprecation;
+mod repr;
+mod stability;
+mod transparency;
+
+pub mod util;
+
+pub use allow_unstable::*;
+pub use cfg::*;
+pub use confusables::*;
+pub use deprecation::*;
+pub use repr::*;
+pub use stability::*;
+pub use transparency::*;
diff --git a/compiler/rustc_attr_parsing/src/attributes/repr.rs b/compiler/rustc_attr_parsing/src/attributes/repr.rs
new file mode 100644
index 00000000000..124f0aa3eff
--- /dev/null
+++ b/compiler/rustc_attr_parsing/src/attributes/repr.rs
@@ -0,0 +1,215 @@
+//! Parsing and validation of builtin attributes
+
+use rustc_abi::Align;
+use rustc_ast::attr::AttributeExt;
+use rustc_ast::{self as ast, MetaItemKind};
+use rustc_attr_data_structures::IntType;
+use rustc_attr_data_structures::ReprAttr::*;
+use rustc_session::Session;
+use rustc_span::{Symbol, sym};
+
+use crate::ReprAttr;
+use crate::session_diagnostics::{self, IncorrectReprFormatGenericCause};
+
+/// Parse #[repr(...)] forms.
+///
+/// Valid repr contents: any of the primitive integral type names (see
+/// `int_type_of_word`, below) to specify enum discriminant type; `C`, to use
+/// the same discriminant size that the corresponding C enum would or C
+/// structure layout, `packed` to remove padding, and `transparent` to delegate representation
+/// concerns to the only non-ZST field.
+pub fn find_repr_attrs(sess: &Session, attr: &impl AttributeExt) -> Vec<ReprAttr> {
+    if attr.has_name(sym::repr) { parse_repr_attr(sess, attr) } else { Vec::new() }
+}
+
+pub fn parse_repr_attr(sess: &Session, attr: &impl AttributeExt) -> Vec<ReprAttr> {
+    assert!(attr.has_name(sym::repr), "expected `#[repr(..)]`, found: {attr:?}");
+    let mut acc = Vec::new();
+    let dcx = sess.dcx();
+
+    if let Some(items) = attr.meta_item_list() {
+        for item in items {
+            let mut recognised = false;
+            if item.is_word() {
+                let hint = match item.name_or_empty() {
+                    sym::Rust => Some(ReprRust),
+                    sym::C => Some(ReprC),
+                    sym::packed => Some(ReprPacked(Align::ONE)),
+                    sym::simd => Some(ReprSimd),
+                    sym::transparent => Some(ReprTransparent),
+                    sym::align => {
+                        sess.dcx().emit_err(session_diagnostics::InvalidReprAlignNeedArg {
+                            span: item.span(),
+                        });
+                        recognised = true;
+                        None
+                    }
+                    name => int_type_of_word(name).map(ReprInt),
+                };
+
+                if let Some(h) = hint {
+                    recognised = true;
+                    acc.push(h);
+                }
+            } else if let Some((name, value)) = item.singleton_lit_list() {
+                let mut literal_error = None;
+                let mut err_span = item.span();
+                if name == sym::align {
+                    recognised = true;
+                    match parse_alignment(&value.kind) {
+                        Ok(literal) => acc.push(ReprAlign(literal)),
+                        Err(message) => {
+                            err_span = value.span;
+                            literal_error = Some(message)
+                        }
+                    };
+                } else if name == sym::packed {
+                    recognised = true;
+                    match parse_alignment(&value.kind) {
+                        Ok(literal) => acc.push(ReprPacked(literal)),
+                        Err(message) => {
+                            err_span = value.span;
+                            literal_error = Some(message)
+                        }
+                    };
+                } else if matches!(name, sym::Rust | sym::C | sym::simd | sym::transparent)
+                    || int_type_of_word(name).is_some()
+                {
+                    recognised = true;
+                    sess.dcx().emit_err(session_diagnostics::InvalidReprHintNoParen {
+                        span: item.span(),
+                        name: name.to_ident_string(),
+                    });
+                }
+                if let Some(literal_error) = literal_error {
+                    sess.dcx().emit_err(session_diagnostics::InvalidReprGeneric {
+                        span: err_span,
+                        repr_arg: name.to_ident_string(),
+                        error_part: literal_error,
+                    });
+                }
+            } else if let Some(meta_item) = item.meta_item() {
+                match &meta_item.kind {
+                    MetaItemKind::NameValue(value) => {
+                        if meta_item.has_name(sym::align) || meta_item.has_name(sym::packed) {
+                            let name = meta_item.name_or_empty().to_ident_string();
+                            recognised = true;
+                            sess.dcx().emit_err(session_diagnostics::IncorrectReprFormatGeneric {
+                                span: item.span(),
+                                repr_arg: &name,
+                                cause: IncorrectReprFormatGenericCause::from_lit_kind(
+                                    item.span(),
+                                    &value.kind,
+                                    &name,
+                                ),
+                            });
+                        } else if matches!(
+                            meta_item.name_or_empty(),
+                            sym::Rust | sym::C | sym::simd | sym::transparent
+                        ) || int_type_of_word(meta_item.name_or_empty()).is_some()
+                        {
+                            recognised = true;
+                            sess.dcx().emit_err(session_diagnostics::InvalidReprHintNoValue {
+                                span: meta_item.span,
+                                name: meta_item.name_or_empty().to_ident_string(),
+                            });
+                        }
+                    }
+                    MetaItemKind::List(nested_items) => {
+                        if meta_item.has_name(sym::align) {
+                            recognised = true;
+                            if let [nested_item] = nested_items.as_slice() {
+                                sess.dcx().emit_err(
+                                    session_diagnostics::IncorrectReprFormatExpectInteger {
+                                        span: nested_item.span(),
+                                    },
+                                );
+                            } else {
+                                sess.dcx().emit_err(
+                                    session_diagnostics::IncorrectReprFormatAlignOneArg {
+                                        span: meta_item.span,
+                                    },
+                                );
+                            }
+                        } else if meta_item.has_name(sym::packed) {
+                            recognised = true;
+                            if let [nested_item] = nested_items.as_slice() {
+                                sess.dcx().emit_err(
+                                    session_diagnostics::IncorrectReprFormatPackedExpectInteger {
+                                        span: nested_item.span(),
+                                    },
+                                );
+                            } else {
+                                sess.dcx().emit_err(
+                                    session_diagnostics::IncorrectReprFormatPackedOneOrZeroArg {
+                                        span: meta_item.span,
+                                    },
+                                );
+                            }
+                        } else if matches!(
+                            meta_item.name_or_empty(),
+                            sym::Rust | sym::C | sym::simd | sym::transparent
+                        ) || int_type_of_word(meta_item.name_or_empty()).is_some()
+                        {
+                            recognised = true;
+                            sess.dcx().emit_err(session_diagnostics::InvalidReprHintNoParen {
+                                span: meta_item.span,
+                                name: meta_item.name_or_empty().to_ident_string(),
+                            });
+                        }
+                    }
+                    _ => (),
+                }
+            }
+            if !recognised {
+                // Not a word we recognize. This will be caught and reported by
+                // the `check_mod_attrs` pass, but this pass doesn't always run
+                // (e.g. if we only pretty-print the source), so we have to gate
+                // the `span_delayed_bug` call as follows:
+                if sess.opts.pretty.map_or(true, |pp| pp.needs_analysis()) {
+                    dcx.span_delayed_bug(item.span(), "unrecognized representation hint");
+                }
+            }
+        }
+    }
+    acc
+}
+
+fn int_type_of_word(s: Symbol) -> Option<IntType> {
+    use rustc_attr_data_structures::IntType::*;
+
+    match s {
+        sym::i8 => Some(SignedInt(ast::IntTy::I8)),
+        sym::u8 => Some(UnsignedInt(ast::UintTy::U8)),
+        sym::i16 => Some(SignedInt(ast::IntTy::I16)),
+        sym::u16 => Some(UnsignedInt(ast::UintTy::U16)),
+        sym::i32 => Some(SignedInt(ast::IntTy::I32)),
+        sym::u32 => Some(UnsignedInt(ast::UintTy::U32)),
+        sym::i64 => Some(SignedInt(ast::IntTy::I64)),
+        sym::u64 => Some(UnsignedInt(ast::UintTy::U64)),
+        sym::i128 => Some(SignedInt(ast::IntTy::I128)),
+        sym::u128 => Some(UnsignedInt(ast::UintTy::U128)),
+        sym::isize => Some(SignedInt(ast::IntTy::Isize)),
+        sym::usize => Some(UnsignedInt(ast::UintTy::Usize)),
+        _ => None,
+    }
+}
+
+pub fn parse_alignment(node: &ast::LitKind) -> Result<Align, &'static str> {
+    if let ast::LitKind::Int(literal, ast::LitIntType::Unsuffixed) = node {
+        // `Align::from_bytes` accepts 0 as an input, check is_power_of_two() first
+        if literal.get().is_power_of_two() {
+            // Only possible error is larger than 2^29
+            literal
+                .get()
+                .try_into()
+                .ok()
+                .and_then(|v| Align::from_bytes(v).ok())
+                .ok_or("larger than 2^29")
+        } else {
+            Err("not a power of two")
+        }
+    } else {
+        Err("not an unsuffixed integer")
+    }
+}
diff --git a/compiler/rustc_attr_parsing/src/attributes/stability.rs b/compiler/rustc_attr_parsing/src/attributes/stability.rs
new file mode 100644
index 00000000000..89937e1c593
--- /dev/null
+++ b/compiler/rustc_attr_parsing/src/attributes/stability.rs
@@ -0,0 +1,384 @@
+//! Parsing and validation of builtin attributes
+
+use std::num::NonZero;
+
+use rustc_ast::MetaItem;
+use rustc_ast::attr::AttributeExt;
+use rustc_ast_pretty::pprust;
+use rustc_attr_data_structures::{
+    ConstStability, DefaultBodyStability, Stability, StabilityLevel, StableSince, UnstableReason,
+    VERSION_PLACEHOLDER,
+};
+use rustc_errors::ErrorGuaranteed;
+use rustc_session::Session;
+use rustc_span::{Span, Symbol, sym};
+
+use crate::attributes::util::UnsupportedLiteralReason;
+use crate::{parse_version, session_diagnostics};
+
+/// Collects stability info from `stable`/`unstable`/`rustc_allowed_through_unstable_modules`
+/// attributes in `attrs`. Returns `None` if no stability attributes are found.
+pub fn find_stability(
+    sess: &Session,
+    attrs: &[impl AttributeExt],
+    item_sp: Span,
+) -> Option<(Stability, Span)> {
+    let mut stab: Option<(Stability, Span)> = None;
+    let mut allowed_through_unstable_modules = false;
+
+    for attr in attrs {
+        match attr.name_or_empty() {
+            sym::rustc_allowed_through_unstable_modules => allowed_through_unstable_modules = true,
+            sym::unstable => {
+                if stab.is_some() {
+                    sess.dcx().emit_err(session_diagnostics::MultipleStabilityLevels {
+                        span: attr.span(),
+                    });
+                    break;
+                }
+
+                if let Some((feature, level)) = parse_unstability(sess, attr) {
+                    stab = Some((Stability { level, feature }, attr.span()));
+                }
+            }
+            sym::stable => {
+                if stab.is_some() {
+                    sess.dcx().emit_err(session_diagnostics::MultipleStabilityLevels {
+                        span: attr.span(),
+                    });
+                    break;
+                }
+                if let Some((feature, level)) = parse_stability(sess, attr) {
+                    stab = Some((Stability { level, feature }, attr.span()));
+                }
+            }
+            _ => {}
+        }
+    }
+
+    if allowed_through_unstable_modules {
+        match &mut stab {
+            Some((
+                Stability {
+                    level: StabilityLevel::Stable { allowed_through_unstable_modules, .. },
+                    ..
+                },
+                _,
+            )) => *allowed_through_unstable_modules = true,
+            _ => {
+                sess.dcx()
+                    .emit_err(session_diagnostics::RustcAllowedUnstablePairing { span: item_sp });
+            }
+        }
+    }
+
+    stab
+}
+
+/// Collects stability info from `rustc_const_stable`/`rustc_const_unstable`/`rustc_promotable`
+/// attributes in `attrs`. Returns `None` if no stability attributes are found.
+pub fn find_const_stability(
+    sess: &Session,
+    attrs: &[impl AttributeExt],
+    item_sp: Span,
+) -> Option<(ConstStability, Span)> {
+    let mut const_stab: Option<(ConstStability, Span)> = None;
+    let mut promotable = false;
+    let mut const_stable_indirect = false;
+
+    for attr in attrs {
+        match attr.name_or_empty() {
+            sym::rustc_promotable => promotable = true,
+            sym::rustc_const_stable_indirect => const_stable_indirect = true,
+            sym::rustc_const_unstable => {
+                if const_stab.is_some() {
+                    sess.dcx().emit_err(session_diagnostics::MultipleStabilityLevels {
+                        span: attr.span(),
+                    });
+                    break;
+                }
+
+                if let Some((feature, level)) = parse_unstability(sess, attr) {
+                    const_stab = Some((
+                        ConstStability {
+                            level,
+                            feature,
+                            const_stable_indirect: false,
+                            promotable: false,
+                        },
+                        attr.span(),
+                    ));
+                }
+            }
+            sym::rustc_const_stable => {
+                if const_stab.is_some() {
+                    sess.dcx().emit_err(session_diagnostics::MultipleStabilityLevels {
+                        span: attr.span(),
+                    });
+                    break;
+                }
+                if let Some((feature, level)) = parse_stability(sess, attr) {
+                    const_stab = Some((
+                        ConstStability {
+                            level,
+                            feature,
+                            const_stable_indirect: false,
+                            promotable: false,
+                        },
+                        attr.span(),
+                    ));
+                }
+            }
+            _ => {}
+        }
+    }
+
+    // Merge promotable and const_stable_indirect into stability info
+    if promotable {
+        match &mut const_stab {
+            Some((stab, _)) => stab.promotable = promotable,
+            _ => {
+                _ = sess
+                    .dcx()
+                    .emit_err(session_diagnostics::RustcPromotablePairing { span: item_sp })
+            }
+        }
+    }
+    if const_stable_indirect {
+        match &mut const_stab {
+            Some((stab, _)) => {
+                if stab.is_const_unstable() {
+                    stab.const_stable_indirect = true;
+                } else {
+                    _ = sess.dcx().emit_err(session_diagnostics::RustcConstStableIndirectPairing {
+                        span: item_sp,
+                    })
+                }
+            }
+            _ => {
+                // This function has no const stability attribute, but has `const_stable_indirect`.
+                // We ignore that; unmarked functions are subject to recursive const stability
+                // checks by default so we do carry out the user's intent.
+            }
+        }
+    }
+
+    const_stab
+}
+
+/// Calculates the const stability for a const function in a `-Zforce-unstable-if-unmarked` crate
+/// without the `staged_api` feature.
+pub fn unmarked_crate_const_stab(
+    _sess: &Session,
+    attrs: &[impl AttributeExt],
+    regular_stab: Stability,
+) -> ConstStability {
+    assert!(regular_stab.level.is_unstable());
+    // The only attribute that matters here is `rustc_const_stable_indirect`.
+    // We enforce recursive const stability rules for those functions.
+    let const_stable_indirect =
+        attrs.iter().any(|a| a.name_or_empty() == sym::rustc_const_stable_indirect);
+    ConstStability {
+        feature: regular_stab.feature,
+        const_stable_indirect,
+        promotable: false,
+        level: regular_stab.level,
+    }
+}
+
+/// Collects stability info from `rustc_default_body_unstable` attributes in `attrs`.
+/// Returns `None` if no stability attributes are found.
+pub fn find_body_stability(
+    sess: &Session,
+    attrs: &[impl AttributeExt],
+) -> Option<(DefaultBodyStability, Span)> {
+    let mut body_stab: Option<(DefaultBodyStability, Span)> = None;
+
+    for attr in attrs {
+        if attr.has_name(sym::rustc_default_body_unstable) {
+            if body_stab.is_some() {
+                sess.dcx()
+                    .emit_err(session_diagnostics::MultipleStabilityLevels { span: attr.span() });
+                break;
+            }
+
+            if let Some((feature, level)) = parse_unstability(sess, attr) {
+                body_stab = Some((DefaultBodyStability { level, feature }, attr.span()));
+            }
+        }
+    }
+
+    body_stab
+}
+
+fn insert_or_error(sess: &Session, meta: &MetaItem, item: &mut Option<Symbol>) -> Option<()> {
+    if item.is_some() {
+        sess.dcx().emit_err(session_diagnostics::MultipleItem {
+            span: meta.span,
+            item: pprust::path_to_string(&meta.path),
+        });
+        None
+    } else if let Some(v) = meta.value_str() {
+        *item = Some(v);
+        Some(())
+    } else {
+        sess.dcx().emit_err(session_diagnostics::IncorrectMetaItem { span: meta.span });
+        None
+    }
+}
+
+/// Read the content of a `stable`/`rustc_const_stable` attribute, and return the feature name and
+/// its stability information.
+fn parse_stability(sess: &Session, attr: &impl AttributeExt) -> Option<(Symbol, StabilityLevel)> {
+    let metas = attr.meta_item_list()?;
+
+    let mut feature = None;
+    let mut since = None;
+    for meta in metas {
+        let Some(mi) = meta.meta_item() else {
+            sess.dcx().emit_err(session_diagnostics::UnsupportedLiteral {
+                span: meta.span(),
+                reason: UnsupportedLiteralReason::Generic,
+                is_bytestr: false,
+                start_point_span: sess.source_map().start_point(meta.span()),
+            });
+            return None;
+        };
+
+        match mi.name_or_empty() {
+            sym::feature => insert_or_error(sess, mi, &mut feature)?,
+            sym::since => insert_or_error(sess, mi, &mut since)?,
+            _ => {
+                sess.dcx().emit_err(session_diagnostics::UnknownMetaItem {
+                    span: meta.span(),
+                    item: pprust::path_to_string(&mi.path),
+                    expected: &["feature", "since"],
+                });
+                return None;
+            }
+        }
+    }
+
+    let feature = match feature {
+        Some(feature) if rustc_lexer::is_ident(feature.as_str()) => Ok(feature),
+        Some(_bad_feature) => {
+            Err(sess.dcx().emit_err(session_diagnostics::NonIdentFeature { span: attr.span() }))
+        }
+        None => Err(sess.dcx().emit_err(session_diagnostics::MissingFeature { span: attr.span() })),
+    };
+
+    let since = if let Some(since) = since {
+        if since.as_str() == VERSION_PLACEHOLDER {
+            StableSince::Current
+        } else if let Some(version) = parse_version(since) {
+            StableSince::Version(version)
+        } else {
+            sess.dcx().emit_err(session_diagnostics::InvalidSince { span: attr.span() });
+            StableSince::Err
+        }
+    } else {
+        sess.dcx().emit_err(session_diagnostics::MissingSince { span: attr.span() });
+        StableSince::Err
+    };
+
+    match feature {
+        Ok(feature) => {
+            let level = StabilityLevel::Stable { since, allowed_through_unstable_modules: false };
+            Some((feature, level))
+        }
+        Err(ErrorGuaranteed { .. }) => None,
+    }
+}
+
+/// Read the content of a `unstable`/`rustc_const_unstable`/`rustc_default_body_unstable`
+/// attribute, and return the feature name and its stability information.
+fn parse_unstability(sess: &Session, attr: &impl AttributeExt) -> Option<(Symbol, StabilityLevel)> {
+    let metas = attr.meta_item_list()?;
+
+    let mut feature = None;
+    let mut reason = None;
+    let mut issue = None;
+    let mut issue_num = None;
+    let mut is_soft = false;
+    let mut implied_by = None;
+    for meta in metas {
+        let Some(mi) = meta.meta_item() else {
+            sess.dcx().emit_err(session_diagnostics::UnsupportedLiteral {
+                span: meta.span(),
+                reason: UnsupportedLiteralReason::Generic,
+                is_bytestr: false,
+                start_point_span: sess.source_map().start_point(meta.span()),
+            });
+            return None;
+        };
+
+        match mi.name_or_empty() {
+            sym::feature => insert_or_error(sess, mi, &mut feature)?,
+            sym::reason => insert_or_error(sess, mi, &mut reason)?,
+            sym::issue => {
+                insert_or_error(sess, mi, &mut issue)?;
+
+                // These unwraps are safe because `insert_or_error` ensures the meta item
+                // is a name/value pair string literal.
+                issue_num = match issue.unwrap().as_str() {
+                    "none" => None,
+                    issue => match issue.parse::<NonZero<u32>>() {
+                        Ok(num) => Some(num),
+                        Err(err) => {
+                            sess.dcx().emit_err(
+                                session_diagnostics::InvalidIssueString {
+                                    span: mi.span,
+                                    cause: session_diagnostics::InvalidIssueStringCause::from_int_error_kind(
+                                        mi.name_value_literal_span().unwrap(),
+                                        err.kind(),
+                                    ),
+                                },
+                            );
+                            return None;
+                        }
+                    },
+                };
+            }
+            sym::soft => {
+                if !mi.is_word() {
+                    sess.dcx().emit_err(session_diagnostics::SoftNoArgs { span: mi.span });
+                }
+                is_soft = true;
+            }
+            sym::implied_by => insert_or_error(sess, mi, &mut implied_by)?,
+            _ => {
+                sess.dcx().emit_err(session_diagnostics::UnknownMetaItem {
+                    span: meta.span(),
+                    item: pprust::path_to_string(&mi.path),
+                    expected: &["feature", "reason", "issue", "soft", "implied_by"],
+                });
+                return None;
+            }
+        }
+    }
+
+    let feature = match feature {
+        Some(feature) if rustc_lexer::is_ident(feature.as_str()) => Ok(feature),
+        Some(_bad_feature) => {
+            Err(sess.dcx().emit_err(session_diagnostics::NonIdentFeature { span: attr.span() }))
+        }
+        None => Err(sess.dcx().emit_err(session_diagnostics::MissingFeature { span: attr.span() })),
+    };
+
+    let issue = issue.ok_or_else(|| {
+        sess.dcx().emit_err(session_diagnostics::MissingIssue { span: attr.span() })
+    });
+
+    match (feature, issue) {
+        (Ok(feature), Ok(_)) => {
+            let level = StabilityLevel::Unstable {
+                reason: UnstableReason::from_opt_reason(reason),
+                issue: issue_num,
+                is_soft,
+                implied_by,
+            };
+            Some((feature, level))
+        }
+        (Err(ErrorGuaranteed { .. }), _) | (_, Err(ErrorGuaranteed { .. })) => None,
+    }
+}
diff --git a/compiler/rustc_attr_parsing/src/attributes/transparency.rs b/compiler/rustc_attr_parsing/src/attributes/transparency.rs
new file mode 100644
index 00000000000..f4065a77048
--- /dev/null
+++ b/compiler/rustc_attr_parsing/src/attributes/transparency.rs
@@ -0,0 +1,36 @@
+use rustc_ast::attr::AttributeExt;
+use rustc_attr_data_structures::TransparencyError;
+use rustc_span::hygiene::Transparency;
+use rustc_span::sym;
+
+pub fn find_transparency(
+    attrs: &[impl AttributeExt],
+    macro_rules: bool,
+) -> (Transparency, Option<TransparencyError>) {
+    let mut transparency = None;
+    let mut error = None;
+    for attr in attrs {
+        if attr.has_name(sym::rustc_macro_transparency) {
+            if let Some((_, old_span)) = transparency {
+                error = Some(TransparencyError::MultipleTransparencyAttrs(old_span, attr.span()));
+                break;
+            } else if let Some(value) = attr.value_str() {
+                transparency = Some((
+                    match value {
+                        sym::transparent => Transparency::Transparent,
+                        sym::semitransparent => Transparency::SemiTransparent,
+                        sym::opaque => Transparency::Opaque,
+                        _ => {
+                            error =
+                                Some(TransparencyError::UnknownTransparency(value, attr.span()));
+                            continue;
+                        }
+                    },
+                    attr.span(),
+                ));
+            }
+        }
+    }
+    let fallback = if macro_rules { Transparency::SemiTransparent } else { Transparency::Opaque };
+    (transparency.map_or(fallback, |t| t.0), error)
+}
diff --git a/compiler/rustc_attr_parsing/src/attributes/util.rs b/compiler/rustc_attr_parsing/src/attributes/util.rs
new file mode 100644
index 00000000000..e36f7dfff5a
--- /dev/null
+++ b/compiler/rustc_attr_parsing/src/attributes/util.rs
@@ -0,0 +1,36 @@
+use rustc_ast::attr::{AttributeExt, first_attr_value_str_by_name};
+use rustc_attr_data_structures::RustcVersion;
+use rustc_feature::is_builtin_attr_name;
+use rustc_span::{Symbol, sym};
+
+pub(crate) enum UnsupportedLiteralReason {
+    Generic,
+    CfgString,
+    CfgBoolean,
+    DeprecatedString,
+    DeprecatedKvPair,
+}
+
+pub fn is_builtin_attr(attr: &impl AttributeExt) -> bool {
+    attr.is_doc_comment() || attr.ident().is_some_and(|ident| is_builtin_attr_name(ident.name))
+}
+
+pub fn find_crate_name(attrs: &[impl AttributeExt]) -> Option<Symbol> {
+    first_attr_value_str_by_name(attrs, sym::crate_name)
+}
+
+/// Parse a rustc version number written inside string literal in an attribute,
+/// like appears in `since = "1.0.0"`. Suffixes like "-dev" and "-nightly" are
+/// not accepted in this position, unlike when parsing CFG_RELEASE.
+pub fn parse_version(s: Symbol) -> Option<RustcVersion> {
+    let mut components = s.as_str().split('-');
+    let d = components.next()?;
+    if components.next().is_some() {
+        return None;
+    }
+    let mut digits = d.splitn(3, '.');
+    let major = digits.next()?.parse().ok()?;
+    let minor = digits.next()?.parse().ok()?;
+    let patch = digits.next().unwrap_or("0").parse().ok()?;
+    Some(RustcVersion { major, minor, patch })
+}
diff --git a/compiler/rustc_attr/src/lib.rs b/compiler/rustc_attr_parsing/src/lib.rs
index bb207c5c952..a1264a6875f 100644
--- a/compiler/rustc_attr/src/lib.rs
+++ b/compiler/rustc_attr_parsing/src/lib.rs
@@ -12,14 +12,11 @@
 #![warn(unreachable_pub)]
 // tidy-alphabetical-end
 
-mod builtin;
+mod attributes;
 mod session_diagnostics;
 
-pub use IntType::*;
-pub use ReprAttr::*;
-pub use StabilityLevel::*;
-pub use builtin::*;
-pub use rustc_ast::attr::*;
-pub(crate) use rustc_session::HashStableContext;
+pub use attributes::*;
+pub use rustc_attr_data_structures::*;
+pub use util::{find_crate_name, is_builtin_attr, parse_version};
 
 rustc_fluent_macro::fluent_messages! { "../messages.ftl" }
diff --git a/compiler/rustc_attr/src/session_diagnostics.rs b/compiler/rustc_attr_parsing/src/session_diagnostics.rs
index 9d08a9f5754..b1d8ec49774 100644
--- a/compiler/rustc_attr/src/session_diagnostics.rs
+++ b/compiler/rustc_attr_parsing/src/session_diagnostics.rs
@@ -6,17 +6,18 @@ use rustc_errors::{Applicability, Diag, DiagCtxtHandle, Diagnostic, EmissionGuar
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_span::{Span, Symbol};
 
-use crate::{UnsupportedLiteralReason, fluent_generated as fluent};
+use crate::attributes::util::UnsupportedLiteralReason;
+use crate::fluent_generated as fluent;
 
 #[derive(Diagnostic)]
-#[diag(attr_expected_one_cfg_pattern, code = E0536)]
+#[diag(attr_parsing_expected_one_cfg_pattern, code = E0536)]
 pub(crate) struct ExpectedOneCfgPattern {
     #[primary_span]
     pub span: Span,
 }
 
 #[derive(Diagnostic)]
-#[diag(attr_invalid_predicate, code = E0537)]
+#[diag(attr_parsing_invalid_predicate, code = E0537)]
 pub(crate) struct InvalidPredicate {
     #[primary_span]
     pub span: Span,
@@ -25,7 +26,7 @@ pub(crate) struct InvalidPredicate {
 }
 
 #[derive(Diagnostic)]
-#[diag(attr_multiple_item, code = E0538)]
+#[diag(attr_parsing_multiple_item, code = E0538)]
 pub(crate) struct MultipleItem {
     #[primary_span]
     pub span: Span,
@@ -34,7 +35,7 @@ pub(crate) struct MultipleItem {
 }
 
 #[derive(Diagnostic)]
-#[diag(attr_incorrect_meta_item, code = E0539)]
+#[diag(attr_parsing_incorrect_meta_item, code = E0539)]
 pub(crate) struct IncorrectMetaItem {
     #[primary_span]
     pub span: Span,
@@ -51,38 +52,38 @@ pub(crate) struct UnknownMetaItem<'a> {
 impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for UnknownMetaItem<'_> {
     fn into_diag(self, dcx: DiagCtxtHandle<'a>, level: Level) -> Diag<'a, G> {
         let expected = self.expected.iter().map(|name| format!("`{name}`")).collect::<Vec<_>>();
-        Diag::new(dcx, level, fluent::attr_unknown_meta_item)
+        Diag::new(dcx, level, fluent::attr_parsing_unknown_meta_item)
             .with_span(self.span)
             .with_code(E0541)
             .with_arg("item", self.item)
             .with_arg("expected", expected.join(", "))
-            .with_span_label(self.span, fluent::attr_label)
+            .with_span_label(self.span, fluent::attr_parsing_label)
     }
 }
 
 #[derive(Diagnostic)]
-#[diag(attr_missing_since, code = E0542)]
+#[diag(attr_parsing_missing_since, code = E0542)]
 pub(crate) struct MissingSince {
     #[primary_span]
     pub span: Span,
 }
 
 #[derive(Diagnostic)]
-#[diag(attr_missing_note, code = E0543)]
+#[diag(attr_parsing_missing_note, code = E0543)]
 pub(crate) struct MissingNote {
     #[primary_span]
     pub span: Span,
 }
 
 #[derive(Diagnostic)]
-#[diag(attr_multiple_stability_levels, code = E0544)]
+#[diag(attr_parsing_multiple_stability_levels, code = E0544)]
 pub(crate) struct MultipleStabilityLevels {
     #[primary_span]
     pub span: Span,
 }
 
 #[derive(Diagnostic)]
-#[diag(attr_invalid_issue_string, code = E0545)]
+#[diag(attr_parsing_invalid_issue_string, code = E0545)]
 pub(crate) struct InvalidIssueString {
     #[primary_span]
     pub span: Span,
@@ -95,31 +96,31 @@ pub(crate) struct InvalidIssueString {
 // translatable.
 #[derive(Subdiagnostic)]
 pub(crate) enum InvalidIssueStringCause {
-    #[label(attr_must_not_be_zero)]
+    #[label(attr_parsing_must_not_be_zero)]
     MustNotBeZero {
         #[primary_span]
         span: Span,
     },
 
-    #[label(attr_empty)]
+    #[label(attr_parsing_empty)]
     Empty {
         #[primary_span]
         span: Span,
     },
 
-    #[label(attr_invalid_digit)]
+    #[label(attr_parsing_invalid_digit)]
     InvalidDigit {
         #[primary_span]
         span: Span,
     },
 
-    #[label(attr_pos_overflow)]
+    #[label(attr_parsing_pos_overflow)]
     PosOverflow {
         #[primary_span]
         span: Span,
     },
 
-    #[label(attr_neg_overflow)]
+    #[label(attr_parsing_neg_overflow)]
     NegOverflow {
         #[primary_span]
         span: Span,
@@ -140,21 +141,21 @@ impl InvalidIssueStringCause {
 }
 
 #[derive(Diagnostic)]
-#[diag(attr_missing_feature, code = E0546)]
+#[diag(attr_parsing_missing_feature, code = E0546)]
 pub(crate) struct MissingFeature {
     #[primary_span]
     pub span: Span,
 }
 
 #[derive(Diagnostic)]
-#[diag(attr_non_ident_feature, code = E0546)]
+#[diag(attr_parsing_non_ident_feature, code = E0546)]
 pub(crate) struct NonIdentFeature {
     #[primary_span]
     pub span: Span,
 }
 
 #[derive(Diagnostic)]
-#[diag(attr_missing_issue, code = E0547)]
+#[diag(attr_parsing_missing_issue, code = E0547)]
 pub(crate) struct MissingIssue {
     #[primary_span]
     pub span: Span,
@@ -163,20 +164,20 @@ pub(crate) struct MissingIssue {
 // FIXME: Why is this the same error code as `InvalidReprHintNoParen` and `InvalidReprHintNoValue`?
 // It is more similar to `IncorrectReprFormatGeneric`.
 #[derive(Diagnostic)]
-#[diag(attr_incorrect_repr_format_packed_one_or_zero_arg, code = E0552)]
+#[diag(attr_parsing_incorrect_repr_format_packed_one_or_zero_arg, code = E0552)]
 pub(crate) struct IncorrectReprFormatPackedOneOrZeroArg {
     #[primary_span]
     pub span: Span,
 }
 #[derive(Diagnostic)]
-#[diag(attr_incorrect_repr_format_packed_expect_integer, code = E0552)]
+#[diag(attr_parsing_incorrect_repr_format_packed_expect_integer, code = E0552)]
 pub(crate) struct IncorrectReprFormatPackedExpectInteger {
     #[primary_span]
     pub span: Span,
 }
 
 #[derive(Diagnostic)]
-#[diag(attr_invalid_repr_hint_no_paren, code = E0552)]
+#[diag(attr_parsing_invalid_repr_hint_no_paren, code = E0552)]
 pub(crate) struct InvalidReprHintNoParen {
     #[primary_span]
     pub span: Span,
@@ -185,7 +186,7 @@ pub(crate) struct InvalidReprHintNoParen {
 }
 
 #[derive(Diagnostic)]
-#[diag(attr_invalid_repr_hint_no_value, code = E0552)]
+#[diag(attr_parsing_invalid_repr_hint_no_value, code = E0552)]
 pub(crate) struct InvalidReprHintNoValue {
     #[primary_span]
     pub span: Span,
@@ -204,14 +205,18 @@ pub(crate) struct UnsupportedLiteral {
 impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for UnsupportedLiteral {
     fn into_diag(self, dcx: DiagCtxtHandle<'a>, level: Level) -> Diag<'a, G> {
         let mut diag = Diag::new(dcx, level, match self.reason {
-            UnsupportedLiteralReason::Generic => fluent::attr_unsupported_literal_generic,
-            UnsupportedLiteralReason::CfgString => fluent::attr_unsupported_literal_cfg_string,
-            UnsupportedLiteralReason::CfgBoolean => fluent::attr_unsupported_literal_cfg_boolean,
+            UnsupportedLiteralReason::Generic => fluent::attr_parsing_unsupported_literal_generic,
+            UnsupportedLiteralReason::CfgString => {
+                fluent::attr_parsing_unsupported_literal_cfg_string
+            }
+            UnsupportedLiteralReason::CfgBoolean => {
+                fluent::attr_parsing_unsupported_literal_cfg_boolean
+            }
             UnsupportedLiteralReason::DeprecatedString => {
-                fluent::attr_unsupported_literal_deprecated_string
+                fluent::attr_parsing_unsupported_literal_deprecated_string
             }
             UnsupportedLiteralReason::DeprecatedKvPair => {
-                fluent::attr_unsupported_literal_deprecated_kv_pair
+                fluent::attr_parsing_unsupported_literal_deprecated_kv_pair
             }
         });
         diag.span(self.span);
@@ -219,7 +224,7 @@ impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for UnsupportedLiteral {
         if self.is_bytestr {
             diag.span_suggestion(
                 self.start_point_span,
-                fluent::attr_unsupported_literal_suggestion,
+                fluent::attr_parsing_unsupported_literal_suggestion,
                 "",
                 Applicability::MaybeIncorrect,
             );
@@ -229,7 +234,7 @@ impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for UnsupportedLiteral {
 }
 
 #[derive(Diagnostic)]
-#[diag(attr_invalid_repr_align_need_arg, code = E0589)]
+#[diag(attr_parsing_invalid_repr_align_need_arg, code = E0589)]
 pub(crate) struct InvalidReprAlignNeedArg {
     #[primary_span]
     #[suggestion(code = "align(...)", applicability = "has-placeholders")]
@@ -237,7 +242,7 @@ pub(crate) struct InvalidReprAlignNeedArg {
 }
 
 #[derive(Diagnostic)]
-#[diag(attr_invalid_repr_generic, code = E0589)]
+#[diag(attr_parsing_invalid_repr_generic, code = E0589)]
 pub(crate) struct InvalidReprGeneric<'a> {
     #[primary_span]
     pub span: Span,
@@ -247,21 +252,21 @@ pub(crate) struct InvalidReprGeneric<'a> {
 }
 
 #[derive(Diagnostic)]
-#[diag(attr_incorrect_repr_format_align_one_arg, code = E0693)]
+#[diag(attr_parsing_incorrect_repr_format_align_one_arg, code = E0693)]
 pub(crate) struct IncorrectReprFormatAlignOneArg {
     #[primary_span]
     pub span: Span,
 }
 
 #[derive(Diagnostic)]
-#[diag(attr_incorrect_repr_format_expect_literal_integer, code = E0693)]
+#[diag(attr_parsing_incorrect_repr_format_expect_literal_integer, code = E0693)]
 pub(crate) struct IncorrectReprFormatExpectInteger {
     #[primary_span]
     pub span: Span,
 }
 
 #[derive(Diagnostic)]
-#[diag(attr_incorrect_repr_format_generic, code = E0693)]
+#[diag(attr_parsing_incorrect_repr_format_generic, code = E0693)]
 pub(crate) struct IncorrectReprFormatGeneric<'a> {
     #[primary_span]
     pub span: Span,
@@ -274,7 +279,11 @@ pub(crate) struct IncorrectReprFormatGeneric<'a> {
 
 #[derive(Subdiagnostic)]
 pub(crate) enum IncorrectReprFormatGenericCause<'a> {
-    #[suggestion(attr_suggestion, code = "{name}({int})", applicability = "machine-applicable")]
+    #[suggestion(
+        attr_parsing_suggestion,
+        code = "{name}({int})",
+        applicability = "machine-applicable"
+    )]
     Int {
         #[primary_span]
         span: Span,
@@ -286,7 +295,11 @@ pub(crate) enum IncorrectReprFormatGenericCause<'a> {
         int: u128,
     },
 
-    #[suggestion(attr_suggestion, code = "{name}({symbol})", applicability = "machine-applicable")]
+    #[suggestion(
+        attr_parsing_suggestion,
+        code = "{name}({symbol})",
+        applicability = "machine-applicable"
+    )]
     Symbol {
         #[primary_span]
         span: Span,
@@ -312,35 +325,35 @@ impl<'a> IncorrectReprFormatGenericCause<'a> {
 }
 
 #[derive(Diagnostic)]
-#[diag(attr_rustc_promotable_pairing, code = E0717)]
+#[diag(attr_parsing_rustc_promotable_pairing, code = E0717)]
 pub(crate) struct RustcPromotablePairing {
     #[primary_span]
     pub span: Span,
 }
 
 #[derive(Diagnostic)]
-#[diag(attr_rustc_const_stable_indirect_pairing)]
+#[diag(attr_parsing_rustc_const_stable_indirect_pairing)]
 pub(crate) struct RustcConstStableIndirectPairing {
     #[primary_span]
     pub span: Span,
 }
 
 #[derive(Diagnostic)]
-#[diag(attr_rustc_allowed_unstable_pairing, code = E0789)]
+#[diag(attr_parsing_rustc_allowed_unstable_pairing, code = E0789)]
 pub(crate) struct RustcAllowedUnstablePairing {
     #[primary_span]
     pub span: Span,
 }
 
 #[derive(Diagnostic)]
-#[diag(attr_cfg_predicate_identifier)]
+#[diag(attr_parsing_cfg_predicate_identifier)]
 pub(crate) struct CfgPredicateIdentifier {
     #[primary_span]
     pub span: Span,
 }
 
 #[derive(Diagnostic)]
-#[diag(attr_deprecated_item_suggestion)]
+#[diag(attr_parsing_deprecated_item_suggestion)]
 pub(crate) struct DeprecatedItemSuggestion {
     #[primary_span]
     pub span: Span,
@@ -353,21 +366,21 @@ pub(crate) struct DeprecatedItemSuggestion {
 }
 
 #[derive(Diagnostic)]
-#[diag(attr_expected_single_version_literal)]
+#[diag(attr_parsing_expected_single_version_literal)]
 pub(crate) struct ExpectedSingleVersionLiteral {
     #[primary_span]
     pub span: Span,
 }
 
 #[derive(Diagnostic)]
-#[diag(attr_expected_version_literal)]
+#[diag(attr_parsing_expected_version_literal)]
 pub(crate) struct ExpectedVersionLiteral {
     #[primary_span]
     pub span: Span,
 }
 
 #[derive(Diagnostic)]
-#[diag(attr_expects_feature_list)]
+#[diag(attr_parsing_expects_feature_list)]
 pub(crate) struct ExpectsFeatureList {
     #[primary_span]
     pub span: Span,
@@ -376,7 +389,7 @@ pub(crate) struct ExpectsFeatureList {
 }
 
 #[derive(Diagnostic)]
-#[diag(attr_expects_features)]
+#[diag(attr_parsing_expects_features)]
 pub(crate) struct ExpectsFeatures {
     #[primary_span]
     pub span: Span,
@@ -385,21 +398,21 @@ pub(crate) struct ExpectsFeatures {
 }
 
 #[derive(Diagnostic)]
-#[diag(attr_invalid_since)]
+#[diag(attr_parsing_invalid_since)]
 pub(crate) struct InvalidSince {
     #[primary_span]
     pub span: Span,
 }
 
 #[derive(Diagnostic)]
-#[diag(attr_soft_no_args)]
+#[diag(attr_parsing_soft_no_args)]
 pub(crate) struct SoftNoArgs {
     #[primary_span]
     pub span: Span,
 }
 
 #[derive(Diagnostic)]
-#[diag(attr_unknown_version_literal)]
+#[diag(attr_parsing_unknown_version_literal)]
 pub(crate) struct UnknownVersionLiteral {
     #[primary_span]
     pub span: Span,
diff --git a/compiler/rustc_borrowck/src/dataflow.rs b/compiler/rustc_borrowck/src/dataflow.rs
index dc4eab766c9..abe4d4f20ec 100644
--- a/compiler/rustc_borrowck/src/dataflow.rs
+++ b/compiler/rustc_borrowck/src/dataflow.rs
@@ -12,7 +12,7 @@ use rustc_mir_dataflow::impls::{
     EverInitializedPlaces, EverInitializedPlacesDomain, MaybeUninitializedPlaces,
     MaybeUninitializedPlacesDomain,
 };
-use rustc_mir_dataflow::{Analysis, GenKill, JoinSemiLattice, SwitchIntEdgeEffects};
+use rustc_mir_dataflow::{Analysis, GenKill, JoinSemiLattice};
 use tracing::debug;
 
 use crate::{BorrowSet, PlaceConflictBias, PlaceExt, RegionInferenceContext, places_conflict};
@@ -101,16 +101,6 @@ impl<'a, 'tcx> Analysis<'tcx> for Borrowck<'a, 'tcx> {
         // This is only reachable from `iterate_to_fixpoint`, which this analysis doesn't use.
         unreachable!();
     }
-
-    fn apply_switch_int_edge_effects(
-        &mut self,
-        _block: BasicBlock,
-        _discr: &mir::Operand<'tcx>,
-        _apply_edge_effects: &mut impl SwitchIntEdgeEffects<Self::Domain>,
-    ) {
-        // This is only reachable from `iterate_to_fixpoint`, which this analysis doesn't use.
-        unreachable!();
-    }
 }
 
 impl JoinSemiLattice for BorrowckDomain {
diff --git a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
index 8dcc5324fdf..8e5944d6cf4 100644
--- a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
@@ -34,8 +34,7 @@ use rustc_middle::util::CallKind;
 use rustc_mir_dataflow::move_paths::{InitKind, MoveOutIndex, MovePathIndex};
 use rustc_span::def_id::{DefId, LocalDefId};
 use rustc_span::hygiene::DesugaringKind;
-use rustc_span::symbol::{Ident, kw, sym};
-use rustc_span::{BytePos, Span, Symbol};
+use rustc_span::{BytePos, Ident, Span, Symbol, kw, sym};
 use rustc_trait_selection::error_reporting::InferCtxtErrorExt;
 use rustc_trait_selection::error_reporting::traits::FindExprBySpan;
 use rustc_trait_selection::infer::InferCtxtExt;
diff --git a/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs b/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
index 45a8ef0adb6..22f7f708419 100644
--- a/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
@@ -17,8 +17,7 @@ use rustc_middle::mir::{
 };
 use rustc_middle::ty::adjustment::PointerCoercion;
 use rustc_middle::ty::{self, RegionVid, Ty, TyCtxt};
-use rustc_span::symbol::{Symbol, kw};
-use rustc_span::{DesugaringKind, Span, sym};
+use rustc_span::{DesugaringKind, Span, Symbol, kw, sym};
 use rustc_trait_selection::error_reporting::traits::FindExprBySpan;
 use tracing::{debug, instrument};
 
diff --git a/compiler/rustc_borrowck/src/diagnostics/mod.rs b/compiler/rustc_borrowck/src/diagnostics/mod.rs
index 92afad62aa4..67be6ecdeb3 100644
--- a/compiler/rustc_borrowck/src/diagnostics/mod.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/mod.rs
@@ -20,8 +20,7 @@ use rustc_middle::util::{CallDesugaringKind, call_kind};
 use rustc_mir_dataflow::move_paths::{InitLocation, LookupResult};
 use rustc_span::def_id::LocalDefId;
 use rustc_span::source_map::Spanned;
-use rustc_span::symbol::sym;
-use rustc_span::{DUMMY_SP, Span, Symbol};
+use rustc_span::{DUMMY_SP, Span, Symbol, sym};
 use rustc_trait_selection::error_reporting::InferCtxtErrorExt;
 use rustc_trait_selection::infer::InferCtxtExt;
 use rustc_trait_selection::traits::{
diff --git a/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs b/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
index 4fb7b22f289..2484f817a06 100644
--- a/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
@@ -15,8 +15,7 @@ use rustc_middle::mir::{
     PlaceRef, ProjectionElem,
 };
 use rustc_middle::ty::{self, InstanceKind, Ty, TyCtxt, Upcast};
-use rustc_span::symbol::{Symbol, kw};
-use rustc_span::{BytePos, DesugaringKind, Span, sym};
+use rustc_span::{BytePos, DesugaringKind, Span, Symbol, kw, sym};
 use rustc_trait_selection::error_reporting::InferCtxtErrorExt;
 use rustc_trait_selection::infer::InferCtxtExt;
 use rustc_trait_selection::traits;
@@ -1474,16 +1473,27 @@ fn suggest_ampmut<'tcx>(
     // let x: &i32 = &'a 5;
     //                ^^ lifetime annotation not allowed
     //
-    if let Some(assignment_rhs_span) = opt_assignment_rhs_span
-        && let Ok(src) = tcx.sess.source_map().span_to_snippet(assignment_rhs_span)
-        && let Some(stripped) = src.strip_prefix('&')
+    if let Some(rhs_span) = opt_assignment_rhs_span
+        && let Ok(rhs_str) = tcx.sess.source_map().span_to_snippet(rhs_span)
+        && let Some(rhs_str_no_amp) = rhs_str.strip_prefix('&')
     {
-        let is_raw_ref = stripped.trim_start().starts_with("raw ");
-        // We don't support raw refs yet
-        if is_raw_ref {
-            return None;
+        // Suggest changing `&raw const` to `&raw mut` if applicable.
+        if rhs_str_no_amp.trim_start().strip_prefix("raw const").is_some() {
+            let const_idx = rhs_str.find("const").unwrap() as u32;
+            let const_span = rhs_span
+                .with_lo(rhs_span.lo() + BytePos(const_idx))
+                .with_hi(rhs_span.lo() + BytePos(const_idx + "const".len() as u32));
+
+            return Some(AmpMutSugg {
+                has_sugg: true,
+                span: const_span,
+                suggestion: "mut".to_owned(),
+                additional: None,
+            });
         }
-        let is_mut = if let Some(rest) = stripped.trim_start().strip_prefix("mut") {
+
+        // Figure out if rhs already is `&mut`.
+        let is_mut = if let Some(rest) = rhs_str_no_amp.trim_start().strip_prefix("mut") {
             match rest.chars().next() {
                 // e.g. `&mut x`
                 Some(c) if c.is_whitespace() => true,
@@ -1500,9 +1510,8 @@ fn suggest_ampmut<'tcx>(
         // if the reference is already mutable then there is nothing we can do
         // here.
         if !is_mut {
-            let span = assignment_rhs_span;
             // shrink the span to just after the `&` in `&variable`
-            let span = span.with_lo(span.lo() + BytePos(1)).shrink_to_lo();
+            let span = rhs_span.with_lo(rhs_span.lo() + BytePos(1)).shrink_to_lo();
 
             // FIXME(Ezrashaw): returning is bad because we still might want to
             // update the annotated type, see #106857.
diff --git a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
index 6ea5c44dc01..3555009c63f 100644
--- a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
@@ -15,8 +15,7 @@ use rustc_middle::bug;
 use rustc_middle::hir::place::PlaceBase;
 use rustc_middle::mir::{ConstraintCategory, ReturnConstraint};
 use rustc_middle::ty::{self, GenericArgs, Region, RegionVid, Ty, TyCtxt, TypeVisitor};
-use rustc_span::Span;
-use rustc_span::symbol::{Ident, kw};
+use rustc_span::{Ident, Span, kw};
 use rustc_trait_selection::error_reporting::InferCtxtErrorExt;
 use rustc_trait_selection::error_reporting::infer::nice_region_error::{
     self, HirTraitObjectVisitor, NiceRegionError, TraitObjectVisitor, find_anon_type,
@@ -189,7 +188,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
     /// Returns `true` if a closure is inferred to be an `FnMut` closure.
     fn is_closure_fn_mut(&self, fr: RegionVid) -> bool {
         if let Some(ty::ReLateParam(late_param)) = self.to_error_region(fr).as_deref()
-            && let ty::BoundRegionKind::ClosureEnv = late_param.bound_region
+            && let ty::LateParamRegionKind::ClosureEnv = late_param.kind
             && let DefiningTy::Closure(_, args) = self.regioncx.universal_regions().defining_ty
         {
             return args.as_closure().kind() == ty::ClosureKind::FnMut;
@@ -848,7 +847,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                 return;
             };
 
-            let fn_returns = self.infcx.tcx.return_type_impl_or_dyn_traits(suitable_region.def_id);
+            let fn_returns = self.infcx.tcx.return_type_impl_or_dyn_traits(suitable_region.scope);
 
             let param = if let Some(param) =
                 find_param_with_region(self.infcx.tcx, self.mir_def_id(), f, outlived_f)
@@ -875,7 +874,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                     Some(arg),
                     captures,
                     Some((param.param_ty_span, param.param_ty.to_string())),
-                    Some(suitable_region.def_id),
+                    Some(suitable_region.scope),
                 );
                 return;
             }
@@ -883,7 +882,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
             let Some((alias_tys, alias_span, lt_addition_span)) = self
                 .infcx
                 .tcx
-                .return_type_impl_or_dyn_traits_with_type_alias(suitable_region.def_id)
+                .return_type_impl_or_dyn_traits_with_type_alias(suitable_region.scope)
             else {
                 return;
             };
@@ -1018,18 +1017,20 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
             return;
         };
 
-        let Some((ty_sub, _)) =
-            self.infcx.tcx.is_suitable_region(self.mir_def_id(), sub).and_then(|anon_reg| {
-                find_anon_type(self.infcx.tcx, self.mir_def_id(), sub, &anon_reg.bound_region)
-            })
+        let Some((ty_sub, _)) = self
+            .infcx
+            .tcx
+            .is_suitable_region(self.mir_def_id(), sub)
+            .and_then(|_| find_anon_type(self.infcx.tcx, self.mir_def_id(), sub))
         else {
             return;
         };
 
-        let Some((ty_sup, _)) =
-            self.infcx.tcx.is_suitable_region(self.mir_def_id(), sup).and_then(|anon_reg| {
-                find_anon_type(self.infcx.tcx, self.mir_def_id(), sup, &anon_reg.bound_region)
-            })
+        let Some((ty_sup, _)) = self
+            .infcx
+            .tcx
+            .is_suitable_region(self.mir_def_id(), sup)
+            .and_then(|_| find_anon_type(self.infcx.tcx, self.mir_def_id(), sup))
         else {
             return;
         };
diff --git a/compiler/rustc_borrowck/src/diagnostics/region_name.rs b/compiler/rustc_borrowck/src/diagnostics/region_name.rs
index d49dee85144..bdb880b2bce 100644
--- a/compiler/rustc_borrowck/src/diagnostics/region_name.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/region_name.rs
@@ -11,8 +11,7 @@ use rustc_hir::def::{DefKind, Res};
 use rustc_middle::ty::print::RegionHighlightMode;
 use rustc_middle::ty::{self, GenericArgKind, GenericArgsRef, RegionVid, Ty};
 use rustc_middle::{bug, span_bug};
-use rustc_span::symbol::{Symbol, kw, sym};
-use rustc_span::{DUMMY_SP, Span};
+use rustc_span::{DUMMY_SP, Span, Symbol, kw, sym};
 use rustc_trait_selection::error_reporting::InferCtxtErrorExt;
 use tracing::{debug, instrument};
 
@@ -300,17 +299,17 @@ impl<'tcx> MirBorrowckCtxt<'_, '_, 'tcx> {
                 Some(RegionName { name: kw::StaticLifetime, source: RegionNameSource::Static })
             }
 
-            ty::ReLateParam(late_param) => match late_param.bound_region {
-                ty::BoundRegionKind::Named(region_def_id, name) => {
+            ty::ReLateParam(late_param) => match late_param.kind {
+                ty::LateParamRegionKind::Named(region_def_id, name) => {
                     // Get the span to point to, even if we don't use the name.
                     let span = tcx.hir().span_if_local(region_def_id).unwrap_or(DUMMY_SP);
                     debug!(
                         "bound region named: {:?}, is_named: {:?}",
                         name,
-                        late_param.bound_region.is_named()
+                        late_param.kind.is_named()
                     );
 
-                    if late_param.bound_region.is_named() {
+                    if late_param.kind.is_named() {
                         // A named region that is actually named.
                         Some(RegionName {
                             name,
@@ -332,7 +331,7 @@ impl<'tcx> MirBorrowckCtxt<'_, '_, 'tcx> {
                     }
                 }
 
-                ty::BoundRegionKind::ClosureEnv => {
+                ty::LateParamRegionKind::ClosureEnv => {
                     let def_ty = self.regioncx.universal_regions().defining_ty;
 
                     let closure_kind = match def_ty {
@@ -369,7 +368,7 @@ impl<'tcx> MirBorrowckCtxt<'_, '_, 'tcx> {
                     })
                 }
 
-                ty::BoundRegionKind::Anon => None,
+                ty::LateParamRegionKind::Anon(_) => None,
             },
 
             ty::ReBound(..)
@@ -459,11 +458,8 @@ impl<'tcx> MirBorrowckCtxt<'_, '_, 'tcx> {
     ) -> RegionNameHighlight {
         let mut highlight = RegionHighlightMode::default();
         highlight.highlighting_region_vid(self.infcx.tcx, needle_fr, counter);
-        let type_name = self
-            .infcx
-            .err_ctxt()
-            .extract_inference_diagnostics_data(ty.into(), Some(highlight))
-            .name;
+        let type_name =
+            self.infcx.err_ctxt().extract_inference_diagnostics_data(ty.into(), highlight).name;
 
         debug!(
             "highlight_if_we_cannot_match_hir_ty: type_name={:?} needle_fr={:?}",
@@ -874,7 +870,7 @@ impl<'tcx> MirBorrowckCtxt<'_, '_, 'tcx> {
         let type_name = self
             .infcx
             .err_ctxt()
-            .extract_inference_diagnostics_data(yield_ty.into(), Some(highlight))
+            .extract_inference_diagnostics_data(yield_ty.into(), highlight)
             .name;
 
         let yield_span = match tcx.hir_node(self.mir_hir_id()) {
diff --git a/compiler/rustc_borrowck/src/diagnostics/var_name.rs b/compiler/rustc_borrowck/src/diagnostics/var_name.rs
index bda70241267..191c0444c74 100644
--- a/compiler/rustc_borrowck/src/diagnostics/var_name.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/var_name.rs
@@ -1,8 +1,7 @@
 use rustc_index::IndexSlice;
 use rustc_middle::mir::{Body, Local};
 use rustc_middle::ty::{self, RegionVid, TyCtxt};
-use rustc_span::Span;
-use rustc_span::symbol::Symbol;
+use rustc_span::{Span, Symbol};
 use tracing::debug;
 
 use crate::region_infer::RegionInferenceContext;
diff --git a/compiler/rustc_borrowck/src/lib.rs b/compiler/rustc_borrowck/src/lib.rs
index 18b7984e90d..8ee1b1d0ae6 100644
--- a/compiler/rustc_borrowck/src/lib.rs
+++ b/compiler/rustc_borrowck/src/lib.rs
@@ -141,6 +141,9 @@ fn do_mir_borrowck<'tcx>(
 ) -> (BorrowCheckResult<'tcx>, Option<Box<BodyWithBorrowckFacts<'tcx>>>) {
     let def = input_body.source.def_id().expect_local();
     let infcx = BorrowckInferCtxt::new(tcx, def);
+    if let Some(e) = input_body.tainted_by_errors {
+        infcx.set_tainted_by_errors(e);
+    }
 
     let mut local_names = IndexVec::from_elem(None, &input_body.local_decls);
     for var_debug_info in &input_body.var_debug_info {
@@ -162,13 +165,6 @@ fn do_mir_borrowck<'tcx>(
         }
     }
 
-    let diags = &mut diags::BorrowckDiags::new();
-
-    // Gather the upvars of a closure, if any.
-    if let Some(e) = input_body.tainted_by_errors {
-        infcx.set_tainted_by_errors(e);
-    }
-
     // Replace all regions with fresh inference variables. This
     // requires first making our own copy of the MIR. This copy will
     // be modified (in place) to contain non-lexical lifetimes. It
@@ -206,6 +202,7 @@ fn do_mir_borrowck<'tcx>(
         polonius_output,
         opt_closure_req,
         nll_errors,
+        localized_outlives_constraints,
     } = nll::compute_regions(
         &infcx,
         free_regions,
@@ -224,6 +221,7 @@ fn do_mir_borrowck<'tcx>(
 
     // We also have a `#[rustc_regions]` annotation that causes us to dump
     // information.
+    let diags = &mut diags::BorrowckDiags::new();
     nll::dump_annotation(&infcx, body, &regioncx, &opt_closure_req, &opaque_type_values, diags);
 
     let movable_coroutine =
@@ -318,6 +316,16 @@ fn do_mir_borrowck<'tcx>(
 
     mbcx.report_move_errors();
 
+    // If requested, dump polonius MIR.
+    polonius::dump_polonius_mir(
+        &infcx,
+        body,
+        &regioncx,
+        &borrow_set,
+        localized_outlives_constraints,
+        &opt_closure_req,
+    );
+
     // For each non-user used mutable variable, check if it's been assigned from
     // a user-declared local. If so, then put that local into the used_mut set.
     // Note that this set is expected to be small - only upvars from closures
@@ -337,35 +345,7 @@ fn do_mir_borrowck<'tcx>(
     mbcx.gather_used_muts(temporary_used_locals, unused_mut_locals);
 
     debug!("mbcx.used_mut: {:?}", mbcx.used_mut);
-    let used_mut = std::mem::take(&mut mbcx.used_mut);
-    for local in mbcx.body.mut_vars_and_args_iter().filter(|local| !used_mut.contains(local)) {
-        let local_decl = &mbcx.body.local_decls[local];
-        let lint_root = match &mbcx.body.source_scopes[local_decl.source_info.scope].local_data {
-            ClearCrossCrate::Set(data) => data.lint_root,
-            _ => continue,
-        };
-
-        // Skip over locals that begin with an underscore or have no name
-        match mbcx.local_names[local] {
-            Some(name) => {
-                if name.as_str().starts_with('_') {
-                    continue;
-                }
-            }
-            None => continue,
-        }
-
-        let span = local_decl.source_info.span;
-        if span.desugaring_kind().is_some() {
-            // If the `mut` arises as part of a desugaring, we should ignore it.
-            continue;
-        }
-
-        let mut_span = tcx.sess.source_map().span_until_non_whitespace(span);
-
-        tcx.emit_node_span_lint(UNUSED_MUT, lint_root, span, VarNeedNotMut { span: mut_span })
-    }
-
+    mbcx.lint_unused_mut();
     let tainted_by_errors = mbcx.emit_errors();
 
     let result = BorrowCheckResult {
@@ -2393,6 +2373,38 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, '_, 'tcx> {
         // `BasicBlocks` computes dominators on-demand and caches them.
         self.body.basic_blocks.dominators()
     }
+
+    fn lint_unused_mut(&self) {
+        let tcx = self.infcx.tcx;
+        let body = self.body;
+        for local in body.mut_vars_and_args_iter().filter(|local| !self.used_mut.contains(local)) {
+            let local_decl = &body.local_decls[local];
+            let lint_root = match &body.source_scopes[local_decl.source_info.scope].local_data {
+                ClearCrossCrate::Set(data) => data.lint_root,
+                _ => continue,
+            };
+
+            // Skip over locals that begin with an underscore or have no name
+            match self.local_names[local] {
+                Some(name) => {
+                    if name.as_str().starts_with('_') {
+                        continue;
+                    }
+                }
+                None => continue,
+            }
+
+            let span = local_decl.source_info.span;
+            if span.desugaring_kind().is_some() {
+                // If the `mut` arises as part of a desugaring, we should ignore it.
+                continue;
+            }
+
+            let mut_span = tcx.sess.source_map().span_until_non_whitespace(span);
+
+            tcx.emit_node_span_lint(UNUSED_MUT, lint_root, span, VarNeedNotMut { span: mut_span })
+        }
+    }
 }
 
 mod diags {
diff --git a/compiler/rustc_borrowck/src/member_constraints.rs b/compiler/rustc_borrowck/src/member_constraints.rs
index fc621a3b828..a0adf471fd3 100644
--- a/compiler/rustc_borrowck/src/member_constraints.rs
+++ b/compiler/rustc_borrowck/src/member_constraints.rs
@@ -4,10 +4,9 @@ use std::ops::Index;
 use rustc_data_structures::captures::Captures;
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_index::{IndexSlice, IndexVec};
-use rustc_middle::infer::MemberConstraint;
 use rustc_middle::ty::{self, Ty};
 use rustc_span::Span;
-use tracing::debug;
+use tracing::instrument;
 
 /// Compactly stores a set of `R0 member of [R1...Rn]` constraints,
 /// indexed by the region `R0`.
@@ -23,7 +22,7 @@ where
     /// Stores the data about each `R0 member of [R1..Rn]` constraint.
     /// These are organized into a linked list, so each constraint
     /// contains the index of the next constraint with the same `R0`.
-    constraints: IndexVec<NllMemberConstraintIndex, NllMemberConstraint<'tcx>>,
+    constraints: IndexVec<NllMemberConstraintIndex, MemberConstraint<'tcx>>,
 
     /// Stores the `R1..Rn` regions for *all* sets. For any given
     /// constraint, we keep two indices so that we can pull out a
@@ -33,7 +32,7 @@ where
 
 /// Represents a `R0 member of [R1..Rn]` constraint
 #[derive(Debug)]
-pub(crate) struct NllMemberConstraint<'tcx> {
+pub(crate) struct MemberConstraint<'tcx> {
     next_constraint: Option<NllMemberConstraintIndex>,
 
     /// The span where the hidden type was instantiated.
@@ -70,37 +69,34 @@ impl Default for MemberConstraintSet<'_, ty::RegionVid> {
 }
 
 impl<'tcx> MemberConstraintSet<'tcx, ty::RegionVid> {
+    pub(crate) fn is_empty(&self) -> bool {
+        self.constraints.is_empty()
+    }
+
     /// Pushes a member constraint into the set.
-    ///
-    /// The input member constraint `m_c` is in the form produced by
-    /// the `rustc_middle::infer` code.
-    ///
-    /// The `to_region_vid` callback fn is used to convert the regions
-    /// within into `RegionVid` format -- it typically consults the
-    /// `UniversalRegions` data structure that is known to the caller
-    /// (but which this code is unaware of).
-    pub(crate) fn push_constraint(
+    #[instrument(level = "debug", skip(self))]
+    pub(crate) fn add_member_constraint(
         &mut self,
-        m_c: &MemberConstraint<'tcx>,
-        mut to_region_vid: impl FnMut(ty::Region<'tcx>) -> ty::RegionVid,
+        key: ty::OpaqueTypeKey<'tcx>,
+        hidden_ty: Ty<'tcx>,
+        definition_span: Span,
+        member_region_vid: ty::RegionVid,
+        choice_regions: &[ty::RegionVid],
     ) {
-        debug!("push_constraint(m_c={:?})", m_c);
-        let member_region_vid: ty::RegionVid = to_region_vid(m_c.member_region);
         let next_constraint = self.first_constraints.get(&member_region_vid).cloned();
         let start_index = self.choice_regions.len();
-        let end_index = start_index + m_c.choice_regions.len();
-        debug!("push_constraint: member_region_vid={:?}", member_region_vid);
-        let constraint_index = self.constraints.push(NllMemberConstraint {
+        self.choice_regions.extend(choice_regions);
+        let end_index = self.choice_regions.len();
+        let constraint_index = self.constraints.push(MemberConstraint {
             next_constraint,
             member_region_vid,
-            definition_span: m_c.definition_span,
-            hidden_ty: m_c.hidden_ty,
-            key: m_c.key,
+            definition_span,
+            hidden_ty,
+            key,
             start_index,
             end_index,
         });
         self.first_constraints.insert(member_region_vid, constraint_index);
-        self.choice_regions.extend(m_c.choice_regions.iter().map(|&r| to_region_vid(r)));
     }
 }
 
@@ -182,7 +178,7 @@ where
     /// R0 member of [R1..Rn]
     /// ```
     pub(crate) fn choice_regions(&self, pci: NllMemberConstraintIndex) -> &[ty::RegionVid] {
-        let NllMemberConstraint { start_index, end_index, .. } = &self.constraints[pci];
+        let MemberConstraint { start_index, end_index, .. } = &self.constraints[pci];
         &self.choice_regions[*start_index..*end_index]
     }
 }
@@ -191,9 +187,9 @@ impl<'tcx, R> Index<NllMemberConstraintIndex> for MemberConstraintSet<'tcx, R>
 where
     R: Copy + Eq,
 {
-    type Output = NllMemberConstraint<'tcx>;
+    type Output = MemberConstraint<'tcx>;
 
-    fn index(&self, i: NllMemberConstraintIndex) -> &NllMemberConstraint<'tcx> {
+    fn index(&self, i: NllMemberConstraintIndex) -> &MemberConstraint<'tcx> {
         &self.constraints[i]
     }
 }
@@ -215,7 +211,7 @@ where
 /// target_list: A -> B -> C -> D -> E -> F -> (None)
 /// ```
 fn append_list(
-    constraints: &mut IndexSlice<NllMemberConstraintIndex, NllMemberConstraint<'_>>,
+    constraints: &mut IndexSlice<NllMemberConstraintIndex, MemberConstraint<'_>>,
     target_list: NllMemberConstraintIndex,
     source_list: NllMemberConstraintIndex,
 ) {
diff --git a/compiler/rustc_borrowck/src/nll.rs b/compiler/rustc_borrowck/src/nll.rs
index be02e2f48df..abe27555b18 100644
--- a/compiler/rustc_borrowck/src/nll.rs
+++ b/compiler/rustc_borrowck/src/nll.rs
@@ -21,7 +21,7 @@ use rustc_mir_dataflow::impls::MaybeInitializedPlaces;
 use rustc_mir_dataflow::move_paths::MoveData;
 use rustc_mir_dataflow::points::DenseLocationMap;
 use rustc_session::config::MirIncludeSpans;
-use rustc_span::symbol::sym;
+use rustc_span::sym;
 use tracing::{debug, instrument};
 
 use crate::borrow_set::BorrowSet;
@@ -29,6 +29,7 @@ use crate::consumers::ConsumerOptions;
 use crate::diagnostics::RegionErrors;
 use crate::facts::{AllFacts, AllFactsExt, RustcFacts};
 use crate::location::LocationTable;
+use crate::polonius::LocalizedOutlivesConstraintSet;
 use crate::region_infer::RegionInferenceContext;
 use crate::type_check::{self, MirTypeckResults};
 use crate::universal_regions::UniversalRegions;
@@ -45,6 +46,9 @@ pub(crate) struct NllOutput<'tcx> {
     pub polonius_output: Option<Box<PoloniusOutput>>,
     pub opt_closure_req: Option<ClosureRegionRequirements<'tcx>>,
     pub nll_errors: RegionErrors<'tcx>,
+
+    /// When using `-Zpolonius=next`: the localized typeck and liveness constraints.
+    pub localized_outlives_constraints: Option<LocalizedOutlivesConstraintSet>,
 }
 
 /// Rewrites the regions in the MIR to use NLL variables, also scraping out the set of universal
@@ -116,7 +120,7 @@ pub(crate) fn compute_regions<'a, 'tcx>(
     let var_origins = infcx.get_region_var_origins();
 
     // If requested, emit legacy polonius facts.
-    polonius::emit_facts(
+    polonius::legacy::emit_facts(
         &mut all_facts,
         infcx.tcx,
         location_table,
@@ -124,6 +128,7 @@ pub(crate) fn compute_regions<'a, 'tcx>(
         borrow_set,
         move_data,
         &universal_region_relations,
+        &constraints,
     );
 
     let mut regioncx = RegionInferenceContext::new(
@@ -134,6 +139,15 @@ pub(crate) fn compute_regions<'a, 'tcx>(
         elements,
     );
 
+    // If requested for `-Zpolonius=next`, convert NLL constraints to localized outlives
+    // constraints.
+    let localized_outlives_constraints =
+        if infcx.tcx.sess.opts.unstable_opts.polonius.is_next_enabled() {
+            Some(polonius::create_localized_constraints(&mut regioncx, body))
+        } else {
+            None
+        };
+
     // If requested: dump NLL facts, and run legacy polonius analysis.
     let polonius_output = all_facts.as_ref().and_then(|all_facts| {
         if infcx.tcx.sess.opts.unstable_opts.nll_facts {
@@ -174,6 +188,7 @@ pub(crate) fn compute_regions<'a, 'tcx>(
         polonius_output,
         opt_closure_req: closure_region_requirements,
         nll_errors,
+        localized_outlives_constraints,
     }
 }
 
@@ -214,40 +229,7 @@ pub(super) fn dump_nll_mir<'tcx>(
         &0,
         body,
         |pass_where, out| {
-            match pass_where {
-                // Before the CFG, dump out the values for each region variable.
-                PassWhere::BeforeCFG => {
-                    regioncx.dump_mir(tcx, out)?;
-                    writeln!(out, "|")?;
-
-                    if let Some(closure_region_requirements) = closure_region_requirements {
-                        writeln!(out, "| Free Region Constraints")?;
-                        for_each_region_constraint(tcx, closure_region_requirements, &mut |msg| {
-                            writeln!(out, "| {msg}")
-                        })?;
-                        writeln!(out, "|")?;
-                    }
-
-                    if borrow_set.len() > 0 {
-                        writeln!(out, "| Borrows")?;
-                        for (borrow_idx, borrow_data) in borrow_set.iter_enumerated() {
-                            writeln!(
-                                out,
-                                "| {:?}: issued at {:?} in {:?}",
-                                borrow_idx, borrow_data.reserve_location, borrow_data.region
-                            )?;
-                        }
-                        writeln!(out, "|")?;
-                    }
-                }
-
-                PassWhere::BeforeLocation(_) => {}
-
-                PassWhere::AfterTerminator(_) => {}
-
-                PassWhere::BeforeBlock(_) | PassWhere::AfterLocation(_) | PassWhere::AfterCFG => {}
-            }
-            Ok(())
+            emit_nll_mir(tcx, regioncx, closure_region_requirements, borrow_set, pass_where, out)
         },
         options,
     );
@@ -265,6 +247,51 @@ pub(super) fn dump_nll_mir<'tcx>(
     };
 }
 
+/// Produces the actual NLL MIR sections to emit during the dumping process.
+pub(crate) fn emit_nll_mir<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    regioncx: &RegionInferenceContext<'tcx>,
+    closure_region_requirements: &Option<ClosureRegionRequirements<'tcx>>,
+    borrow_set: &BorrowSet<'tcx>,
+    pass_where: PassWhere,
+    out: &mut dyn io::Write,
+) -> io::Result<()> {
+    match pass_where {
+        // Before the CFG, dump out the values for each region variable.
+        PassWhere::BeforeCFG => {
+            regioncx.dump_mir(tcx, out)?;
+            writeln!(out, "|")?;
+
+            if let Some(closure_region_requirements) = closure_region_requirements {
+                writeln!(out, "| Free Region Constraints")?;
+                for_each_region_constraint(tcx, closure_region_requirements, &mut |msg| {
+                    writeln!(out, "| {msg}")
+                })?;
+                writeln!(out, "|")?;
+            }
+
+            if borrow_set.len() > 0 {
+                writeln!(out, "| Borrows")?;
+                for (borrow_idx, borrow_data) in borrow_set.iter_enumerated() {
+                    writeln!(
+                        out,
+                        "| {:?}: issued at {:?} in {:?}",
+                        borrow_idx, borrow_data.reserve_location, borrow_data.region
+                    )?;
+                }
+                writeln!(out, "|")?;
+            }
+        }
+
+        PassWhere::BeforeLocation(_) => {}
+
+        PassWhere::AfterTerminator(_) => {}
+
+        PassWhere::BeforeBlock(_) | PassWhere::AfterLocation(_) | PassWhere::AfterCFG => {}
+    }
+    Ok(())
+}
+
 #[allow(rustc::diagnostic_outside_of_impl)]
 #[allow(rustc::untranslatable_diagnostic)]
 pub(super) fn dump_annotation<'tcx, 'infcx>(
diff --git a/compiler/rustc_borrowck/src/polonius/constraints.rs b/compiler/rustc_borrowck/src/polonius/constraints.rs
new file mode 100644
index 00000000000..50f59dd0dee
--- /dev/null
+++ b/compiler/rustc_borrowck/src/polonius/constraints.rs
@@ -0,0 +1,45 @@
+use rustc_middle::ty::RegionVid;
+use rustc_mir_dataflow::points::PointIndex;
+
+/// A localized outlives constraint reifies the CFG location where the outlives constraint holds,
+/// within the origins themselves as if they were different from point to point: from `a: b`
+/// outlives constraints to `a@p: b@p`, where `p` is the point in the CFG.
+///
+/// This models two sources of constraints:
+/// - constraints that traverse the subsets between regions at a given point, `a@p: b@p`. These
+///   depend on typeck constraints generated via assignments, calls, etc. (In practice there are
+///   subtleties where a statement's effect only starts being visible at the successor point, via
+///   the "result" of that statement).
+/// - constraints that traverse the CFG via the same region, `a@p: a@q`, where `p` is a predecessor
+///   of `q`. These depend on the liveness of the regions at these points, as well as their
+///   variance.
+///
+/// The `source` origin at `from` flows into the `target` origin at `to`.
+///
+/// This dual of NLL's [crate::constraints::OutlivesConstraint] therefore encodes the
+/// position-dependent outlives constraints used by Polonius, to model the flow-sensitive loan
+/// propagation via reachability within a graph of localized constraints.
+#[derive(Copy, Clone, PartialEq, Eq, Debug, Hash)]
+pub(crate) struct LocalizedOutlivesConstraint {
+    pub source: RegionVid,
+    pub from: PointIndex,
+    pub target: RegionVid,
+    pub to: PointIndex,
+}
+
+/// A container of [LocalizedOutlivesConstraint]s that can be turned into a traversable
+/// `rustc_data_structures` graph.
+#[derive(Clone, Default, Debug)]
+pub(crate) struct LocalizedOutlivesConstraintSet {
+    pub outlives: Vec<LocalizedOutlivesConstraint>,
+}
+
+impl LocalizedOutlivesConstraintSet {
+    pub(crate) fn push(&mut self, constraint: LocalizedOutlivesConstraint) {
+        if constraint.source == constraint.target && constraint.from == constraint.to {
+            // 'a@p: 'a@p is pretty uninteresting
+            return;
+        }
+        self.outlives.push(constraint);
+    }
+}
diff --git a/compiler/rustc_borrowck/src/polonius/dump.rs b/compiler/rustc_borrowck/src/polonius/dump.rs
new file mode 100644
index 00000000000..a6d80149034
--- /dev/null
+++ b/compiler/rustc_borrowck/src/polonius/dump.rs
@@ -0,0 +1,104 @@
+use std::io;
+
+use rustc_middle::mir::pretty::{PrettyPrintMirOptions, dump_mir_with_options};
+use rustc_middle::mir::{Body, ClosureRegionRequirements, PassWhere};
+use rustc_middle::ty::TyCtxt;
+use rustc_session::config::MirIncludeSpans;
+
+use crate::borrow_set::BorrowSet;
+use crate::polonius::{LocalizedOutlivesConstraint, LocalizedOutlivesConstraintSet};
+use crate::{BorrowckInferCtxt, RegionInferenceContext};
+
+/// `-Zdump-mir=polonius` dumps MIR annotated with NLL and polonius specific information.
+// Note: this currently duplicates most of NLL MIR, with some additions for the localized outlives
+// constraints. This is ok for now as this dump will change in the near future to an HTML file to
+// become more useful.
+pub(crate) fn dump_polonius_mir<'tcx>(
+    infcx: &BorrowckInferCtxt<'tcx>,
+    body: &Body<'tcx>,
+    regioncx: &RegionInferenceContext<'tcx>,
+    borrow_set: &BorrowSet<'tcx>,
+    localized_outlives_constraints: Option<LocalizedOutlivesConstraintSet>,
+    closure_region_requirements: &Option<ClosureRegionRequirements<'tcx>>,
+) {
+    let tcx = infcx.tcx;
+    if !tcx.sess.opts.unstable_opts.polonius.is_next_enabled() {
+        return;
+    }
+
+    let localized_outlives_constraints = localized_outlives_constraints
+        .expect("missing localized constraints with `-Zpolonius=next`");
+
+    // We want the NLL extra comments printed by default in NLL MIR dumps (they were removed in
+    // #112346). Specifying `-Z mir-include-spans` on the CLI still has priority: for example,
+    // they're always disabled in mir-opt tests to make working with blessed dumps easier.
+    let options = PrettyPrintMirOptions {
+        include_extra_comments: matches!(
+            tcx.sess.opts.unstable_opts.mir_include_spans,
+            MirIncludeSpans::On | MirIncludeSpans::Nll
+        ),
+    };
+
+    dump_mir_with_options(
+        tcx,
+        false,
+        "polonius",
+        &0,
+        body,
+        |pass_where, out| {
+            emit_polonius_mir(
+                tcx,
+                regioncx,
+                closure_region_requirements,
+                borrow_set,
+                &localized_outlives_constraints,
+                pass_where,
+                out,
+            )
+        },
+        options,
+    );
+}
+
+/// Produces the actual NLL + Polonius MIR sections to emit during the dumping process.
+fn emit_polonius_mir<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    regioncx: &RegionInferenceContext<'tcx>,
+    closure_region_requirements: &Option<ClosureRegionRequirements<'tcx>>,
+    borrow_set: &BorrowSet<'tcx>,
+    localized_outlives_constraints: &LocalizedOutlivesConstraintSet,
+    pass_where: PassWhere,
+    out: &mut dyn io::Write,
+) -> io::Result<()> {
+    // Emit the regular NLL front-matter
+    crate::nll::emit_nll_mir(
+        tcx,
+        regioncx,
+        closure_region_requirements,
+        borrow_set,
+        pass_where.clone(),
+        out,
+    )?;
+
+    let liveness = regioncx.liveness_constraints();
+
+    // Add localized outlives constraints
+    match pass_where {
+        PassWhere::BeforeCFG => {
+            if localized_outlives_constraints.outlives.len() > 0 {
+                writeln!(out, "| Localized constraints")?;
+
+                for constraint in &localized_outlives_constraints.outlives {
+                    let LocalizedOutlivesConstraint { source, from, target, to } = constraint;
+                    let from = liveness.location_from_point(*from);
+                    let to = liveness.location_from_point(*to);
+                    writeln!(out, "| {source:?} at {from:?} -> {target:?} at {to:?}")?;
+                }
+                writeln!(out, "|")?;
+            }
+        }
+        _ => {}
+    }
+
+    Ok(())
+}
diff --git a/compiler/rustc_borrowck/src/polonius/legacy/accesses.rs b/compiler/rustc_borrowck/src/polonius/legacy/accesses.rs
new file mode 100644
index 00000000000..9c4aa8ea1ed
--- /dev/null
+++ b/compiler/rustc_borrowck/src/polonius/legacy/accesses.rs
@@ -0,0 +1,85 @@
+use rustc_middle::mir::visit::{MutatingUseContext, PlaceContext, Visitor};
+use rustc_middle::mir::{Body, Local, Location, Place};
+use rustc_middle::ty::TyCtxt;
+use rustc_mir_dataflow::move_paths::{LookupResult, MoveData};
+use tracing::debug;
+
+use crate::def_use::{self, DefUse};
+use crate::facts::AllFacts;
+use crate::location::{LocationIndex, LocationTable};
+use crate::universal_regions::UniversalRegions;
+
+/// Emit polonius facts for variable defs, uses, drops, and path accesses.
+pub(crate) fn emit_access_facts<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    facts: &mut AllFacts,
+    body: &Body<'tcx>,
+    location_table: &LocationTable,
+    move_data: &MoveData<'tcx>,
+    universal_regions: &UniversalRegions<'tcx>,
+) {
+    let mut extractor = AccessFactsExtractor { facts, move_data, location_table };
+    extractor.visit_body(body);
+
+    for (local, local_decl) in body.local_decls.iter_enumerated() {
+        debug!("add use_of_var_derefs_origin facts - local={:?}, type={:?}", local, local_decl.ty);
+        tcx.for_each_free_region(&local_decl.ty, |region| {
+            let region_vid = universal_regions.to_region_vid(region);
+            facts.use_of_var_derefs_origin.push((local, region_vid.into()));
+        });
+    }
+}
+
+/// MIR visitor extracting point-wise facts about accesses.
+struct AccessFactsExtractor<'a, 'tcx> {
+    facts: &'a mut AllFacts,
+    move_data: &'a MoveData<'tcx>,
+    location_table: &'a LocationTable,
+}
+
+impl<'tcx> AccessFactsExtractor<'_, 'tcx> {
+    fn location_to_index(&self, location: Location) -> LocationIndex {
+        self.location_table.mid_index(location)
+    }
+}
+
+impl<'a, 'tcx> Visitor<'tcx> for AccessFactsExtractor<'a, 'tcx> {
+    fn visit_local(&mut self, local: Local, context: PlaceContext, location: Location) {
+        match def_use::categorize(context) {
+            Some(DefUse::Def) => {
+                debug!("AccessFactsExtractor - emit def");
+                self.facts.var_defined_at.push((local, self.location_to_index(location)));
+            }
+            Some(DefUse::Use) => {
+                debug!("AccessFactsExtractor - emit use");
+                self.facts.var_used_at.push((local, self.location_to_index(location)));
+            }
+            Some(DefUse::Drop) => {
+                debug!("AccessFactsExtractor - emit drop");
+                self.facts.var_dropped_at.push((local, self.location_to_index(location)));
+            }
+            _ => (),
+        }
+    }
+
+    fn visit_place(&mut self, place: &Place<'tcx>, context: PlaceContext, location: Location) {
+        self.super_place(place, context, location);
+
+        match context {
+            PlaceContext::NonMutatingUse(_)
+            | PlaceContext::MutatingUse(MutatingUseContext::Borrow) => {
+                let path = match self.move_data.rev_lookup.find(place.as_ref()) {
+                    LookupResult::Exact(path) | LookupResult::Parent(Some(path)) => path,
+                    _ => {
+                        // There's no path access to emit.
+                        return;
+                    }
+                };
+                debug!("AccessFactsExtractor - emit path access ({path:?}, {location:?})");
+                self.facts.path_accessed_at_base.push((path, self.location_to_index(location)));
+            }
+
+            _ => {}
+        }
+    }
+}
diff --git a/compiler/rustc_borrowck/src/polonius/loan_invalidations.rs b/compiler/rustc_borrowck/src/polonius/legacy/loan_invalidations.rs
index f646beeecf7..0d5b6f3a2c8 100644
--- a/compiler/rustc_borrowck/src/polonius/loan_invalidations.rs
+++ b/compiler/rustc_borrowck/src/polonius/legacy/loan_invalidations.rs
@@ -21,22 +21,22 @@ use crate::{
 /// Emit `loan_invalidated_at` facts.
 pub(super) fn emit_loan_invalidations<'tcx>(
     tcx: TyCtxt<'tcx>,
-    all_facts: &mut AllFacts,
-    location_table: &LocationTable,
+    facts: &mut AllFacts,
     body: &Body<'tcx>,
+    location_table: &LocationTable,
     borrow_set: &BorrowSet<'tcx>,
 ) {
     let dominators = body.basic_blocks.dominators();
     let mut visitor =
-        LoanInvalidationsGenerator { all_facts, borrow_set, tcx, location_table, body, dominators };
+        LoanInvalidationsGenerator { facts, borrow_set, tcx, location_table, body, dominators };
     visitor.visit_body(body);
 }
 
 struct LoanInvalidationsGenerator<'a, 'tcx> {
     tcx: TyCtxt<'tcx>,
-    all_facts: &'a mut AllFacts,
-    location_table: &'a LocationTable,
+    facts: &'a mut AllFacts,
     body: &'a Body<'tcx>,
+    location_table: &'a LocationTable,
     dominators: &'a Dominators<BasicBlock>,
     borrow_set: &'a BorrowSet<'tcx>,
 }
@@ -151,7 +151,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LoanInvalidationsGenerator<'a, 'tcx> {
                 let resume = self.location_table.start_index(resume.start_location());
                 for (i, data) in borrow_set.iter_enumerated() {
                     if borrow_of_local_data(data.borrowed_place) {
-                        self.all_facts.loan_invalidated_at.push((resume, i));
+                        self.facts.loan_invalidated_at.push((resume, i));
                     }
                 }
 
@@ -165,7 +165,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LoanInvalidationsGenerator<'a, 'tcx> {
                 let start = self.location_table.start_index(location);
                 for (i, data) in borrow_set.iter_enumerated() {
                     if borrow_of_local_data(data.borrowed_place) {
-                        self.all_facts.loan_invalidated_at.push((start, i));
+                        self.facts.loan_invalidated_at.push((start, i));
                     }
                 }
             }
@@ -409,7 +409,7 @@ impl<'a, 'tcx> LoanInvalidationsGenerator<'a, 'tcx> {
     /// Generates a new `loan_invalidated_at(L, B)` fact.
     fn emit_loan_invalidated_at(&mut self, b: BorrowIndex, l: Location) {
         let lidx = self.location_table.start_index(l);
-        self.all_facts.loan_invalidated_at.push((lidx, b));
+        self.facts.loan_invalidated_at.push((lidx, b));
     }
 
     fn check_activations(&mut self, location: Location) {
diff --git a/compiler/rustc_borrowck/src/polonius/loan_kills.rs b/compiler/rustc_borrowck/src/polonius/legacy/loan_kills.rs
index 68e0865ab82..fdde9fa0476 100644
--- a/compiler/rustc_borrowck/src/polonius/loan_kills.rs
+++ b/compiler/rustc_borrowck/src/polonius/legacy/loan_kills.rs
@@ -14,12 +14,12 @@ use crate::places_conflict;
 /// Emit `loan_killed_at` and `cfg_edge` facts at the same time.
 pub(super) fn emit_loan_kills<'tcx>(
     tcx: TyCtxt<'tcx>,
-    all_facts: &mut AllFacts,
-    location_table: &LocationTable,
+    facts: &mut AllFacts,
     body: &Body<'tcx>,
+    location_table: &LocationTable,
     borrow_set: &BorrowSet<'tcx>,
 ) {
-    let mut visitor = LoanKillsGenerator { borrow_set, tcx, location_table, all_facts, body };
+    let mut visitor = LoanKillsGenerator { borrow_set, tcx, location_table, facts, body };
     for (bb, data) in body.basic_blocks.iter_enumerated() {
         visitor.visit_basic_block_data(bb, data);
     }
@@ -27,7 +27,7 @@ pub(super) fn emit_loan_kills<'tcx>(
 
 struct LoanKillsGenerator<'a, 'tcx> {
     tcx: TyCtxt<'tcx>,
-    all_facts: &'a mut AllFacts,
+    facts: &'a mut AllFacts,
     location_table: &'a LocationTable,
     borrow_set: &'a BorrowSet<'tcx>,
     body: &'a Body<'tcx>,
@@ -36,12 +36,12 @@ struct LoanKillsGenerator<'a, 'tcx> {
 impl<'a, 'tcx> Visitor<'tcx> for LoanKillsGenerator<'a, 'tcx> {
     fn visit_statement(&mut self, statement: &Statement<'tcx>, location: Location) {
         // Also record CFG facts here.
-        self.all_facts.cfg_edge.push((
+        self.facts.cfg_edge.push((
             self.location_table.start_index(location),
             self.location_table.mid_index(location),
         ));
 
-        self.all_facts.cfg_edge.push((
+        self.facts.cfg_edge.push((
             self.location_table.mid_index(location),
             self.location_table.start_index(location.successor_within_block()),
         ));
@@ -63,15 +63,15 @@ impl<'a, 'tcx> Visitor<'tcx> for LoanKillsGenerator<'a, 'tcx> {
 
     fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location) {
         // Also record CFG facts here.
-        self.all_facts.cfg_edge.push((
+        self.facts.cfg_edge.push((
             self.location_table.start_index(location),
             self.location_table.mid_index(location),
         ));
 
         let successor_blocks = terminator.successors();
-        self.all_facts.cfg_edge.reserve(successor_blocks.size_hint().0);
+        self.facts.cfg_edge.reserve(successor_blocks.size_hint().0);
         for successor_block in successor_blocks {
-            self.all_facts.cfg_edge.push((
+            self.facts.cfg_edge.push((
                 self.location_table.mid_index(location),
                 self.location_table.start_index(successor_block.start_location()),
             ));
@@ -128,7 +128,7 @@ impl<'tcx> LoanKillsGenerator<'_, 'tcx> {
 
                         if places_conflict {
                             let location_index = self.location_table.mid_index(location);
-                            self.all_facts.loan_killed_at.push((borrow_index, location_index));
+                            self.facts.loan_killed_at.push((borrow_index, location_index));
                         }
                     }
                 }
@@ -140,9 +140,9 @@ impl<'tcx> LoanKillsGenerator<'_, 'tcx> {
     fn record_killed_borrows_for_local(&mut self, local: Local, location: Location) {
         if let Some(borrow_indices) = self.borrow_set.local_map.get(&local) {
             let location_index = self.location_table.mid_index(location);
-            self.all_facts.loan_killed_at.reserve(borrow_indices.len());
+            self.facts.loan_killed_at.reserve(borrow_indices.len());
             for &borrow_index in borrow_indices {
-                self.all_facts.loan_killed_at.push((borrow_index, location_index));
+                self.facts.loan_killed_at.push((borrow_index, location_index));
             }
         }
     }
diff --git a/compiler/rustc_borrowck/src/polonius/legacy/mod.rs b/compiler/rustc_borrowck/src/polonius/legacy/mod.rs
new file mode 100644
index 00000000000..60fd2afe63e
--- /dev/null
+++ b/compiler/rustc_borrowck/src/polonius/legacy/mod.rs
@@ -0,0 +1,223 @@
+//! Functions dedicated to fact generation for the `-Zpolonius=legacy` datalog implementation.
+//!
+//! Will be removed in the future, once the in-tree `-Zpolonius=next` implementation reaches feature
+//! parity.
+
+use std::iter;
+
+use either::Either;
+use rustc_middle::mir::{Body, Local, LocalKind, Location, START_BLOCK};
+use rustc_middle::ty::{GenericArg, TyCtxt};
+use rustc_mir_dataflow::move_paths::{InitKind, InitLocation, MoveData};
+use tracing::debug;
+
+use crate::borrow_set::BorrowSet;
+use crate::constraints::OutlivesConstraint;
+use crate::facts::{AllFacts, PoloniusRegionVid};
+use crate::location::LocationTable;
+use crate::type_check::MirTypeckRegionConstraints;
+use crate::type_check::free_region_relations::UniversalRegionRelations;
+use crate::universal_regions::UniversalRegions;
+
+mod accesses;
+mod loan_invalidations;
+mod loan_kills;
+
+/// When requested, emit most of the facts needed by polonius:
+/// - moves and assignments
+/// - universal regions and their relations
+/// - CFG points and edges
+/// - loan kills
+/// - loan invalidations
+/// - access facts such as variable definitions, uses, drops, and path accesses
+/// - outlives constraints
+///
+/// The rest of the facts are emitted during typeck and liveness.
+pub(crate) fn emit_facts<'tcx>(
+    all_facts: &mut Option<AllFacts>,
+    tcx: TyCtxt<'tcx>,
+    location_table: &LocationTable,
+    body: &Body<'tcx>,
+    borrow_set: &BorrowSet<'tcx>,
+    move_data: &MoveData<'tcx>,
+    universal_region_relations: &UniversalRegionRelations<'tcx>,
+    constraints: &MirTypeckRegionConstraints<'tcx>,
+) {
+    let Some(facts) = all_facts else {
+        // We don't do anything if there are no facts to fill.
+        return;
+    };
+    let _prof_timer = tcx.prof.generic_activity("polonius_fact_generation");
+    emit_move_facts(facts, body, location_table, move_data);
+    emit_universal_region_facts(facts, borrow_set, universal_region_relations);
+    loan_kills::emit_loan_kills(tcx, facts, body, location_table, borrow_set);
+    loan_invalidations::emit_loan_invalidations(tcx, facts, body, location_table, borrow_set);
+    accesses::emit_access_facts(
+        tcx,
+        facts,
+        body,
+        location_table,
+        move_data,
+        &universal_region_relations.universal_regions,
+    );
+    emit_outlives_facts(facts, location_table, constraints);
+}
+
+/// Emit facts needed for move/init analysis: moves and assignments.
+fn emit_move_facts(
+    facts: &mut AllFacts,
+    body: &Body<'_>,
+    location_table: &LocationTable,
+    move_data: &MoveData<'_>,
+) {
+    facts.path_is_var.extend(move_data.rev_lookup.iter_locals_enumerated().map(|(l, r)| (r, l)));
+
+    for (child, move_path) in move_data.move_paths.iter_enumerated() {
+        if let Some(parent) = move_path.parent {
+            facts.child_path.push((child, parent));
+        }
+    }
+
+    let fn_entry_start =
+        location_table.start_index(Location { block: START_BLOCK, statement_index: 0 });
+
+    // initialized_at
+    for init in move_data.inits.iter() {
+        match init.location {
+            InitLocation::Statement(location) => {
+                let block_data = &body[location.block];
+                let is_terminator = location.statement_index == block_data.statements.len();
+
+                if is_terminator && init.kind == InitKind::NonPanicPathOnly {
+                    // We are at the terminator of an init that has a panic path,
+                    // and where the init should not happen on panic
+
+                    for successor in block_data.terminator().successors() {
+                        if body[successor].is_cleanup {
+                            continue;
+                        }
+
+                        // The initialization happened in (or rather, when arriving at)
+                        // the successors, but not in the unwind block.
+                        let first_statement = Location { block: successor, statement_index: 0 };
+                        facts
+                            .path_assigned_at_base
+                            .push((init.path, location_table.start_index(first_statement)));
+                    }
+                } else {
+                    // In all other cases, the initialization just happens at the
+                    // midpoint, like any other effect.
+                    facts
+                        .path_assigned_at_base
+                        .push((init.path, location_table.mid_index(location)));
+                }
+            }
+            // Arguments are initialized on function entry
+            InitLocation::Argument(local) => {
+                assert!(body.local_kind(local) == LocalKind::Arg);
+                facts.path_assigned_at_base.push((init.path, fn_entry_start));
+            }
+        }
+    }
+
+    for (local, path) in move_data.rev_lookup.iter_locals_enumerated() {
+        if body.local_kind(local) != LocalKind::Arg {
+            // Non-arguments start out deinitialised; we simulate this with an
+            // initial move:
+            facts.path_moved_at_base.push((path, fn_entry_start));
+        }
+    }
+
+    // moved_out_at
+    // deinitialisation is assumed to always happen!
+    facts
+        .path_moved_at_base
+        .extend(move_data.moves.iter().map(|mo| (mo.path, location_table.mid_index(mo.source))));
+}
+
+/// Emit universal regions facts, and their relations.
+fn emit_universal_region_facts(
+    facts: &mut AllFacts,
+    borrow_set: &BorrowSet<'_>,
+    universal_region_relations: &UniversalRegionRelations<'_>,
+) {
+    // 1: universal regions are modeled in Polonius as a pair:
+    // - the universal region vid itself.
+    // - a "placeholder loan" associated to this universal region. Since they don't exist in
+    //   the `borrow_set`, their `BorrowIndex` are synthesized as the universal region index
+    //   added to the existing number of loans, as if they succeeded them in the set.
+    //
+    let universal_regions = &universal_region_relations.universal_regions;
+    facts
+        .universal_region
+        .extend(universal_regions.universal_regions_iter().map(PoloniusRegionVid::from));
+    let borrow_count = borrow_set.len();
+    debug!(
+        "emit_universal_region_facts: polonius placeholders, num_universals={}, borrow_count={}",
+        universal_regions.len(),
+        borrow_count
+    );
+
+    for universal_region in universal_regions.universal_regions_iter() {
+        let universal_region_idx = universal_region.index();
+        let placeholder_loan_idx = borrow_count + universal_region_idx;
+        facts.placeholder.push((universal_region.into(), placeholder_loan_idx.into()));
+    }
+
+    // 2: the universal region relations `outlives` constraints are emitted as
+    //  `known_placeholder_subset` facts.
+    for (fr1, fr2) in universal_region_relations.known_outlives() {
+        if fr1 != fr2 {
+            debug!(
+                "emit_universal_region_facts: emitting polonius `known_placeholder_subset` \
+                     fr1={:?}, fr2={:?}",
+                fr1, fr2
+            );
+            facts.known_placeholder_subset.push((fr1.into(), fr2.into()));
+        }
+    }
+}
+
+/// For every potentially drop()-touched region `region` in `local`'s type
+/// (`kind`), emit a `drop_of_var_derefs_origin(local, origin)` fact.
+pub(crate) fn emit_drop_facts<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    local: Local,
+    kind: &GenericArg<'tcx>,
+    universal_regions: &UniversalRegions<'tcx>,
+    all_facts: &mut Option<AllFacts>,
+) {
+    debug!("emit_drop_facts(local={:?}, kind={:?}", local, kind);
+    let Some(facts) = all_facts.as_mut() else { return };
+    let _prof_timer = tcx.prof.generic_activity("polonius_fact_generation");
+    tcx.for_each_free_region(kind, |drop_live_region| {
+        let region_vid = universal_regions.to_region_vid(drop_live_region);
+        facts.drop_of_var_derefs_origin.push((local, region_vid.into()));
+    });
+}
+
+/// Emit facts about the outlives constraints: the `subset` base relation, i.e. not a transitive
+/// closure.
+fn emit_outlives_facts<'tcx>(
+    facts: &mut AllFacts,
+    location_table: &LocationTable,
+    constraints: &MirTypeckRegionConstraints<'tcx>,
+) {
+    facts.subset_base.extend(constraints.outlives_constraints.outlives().iter().flat_map(
+        |constraint: &OutlivesConstraint<'_>| {
+            if let Some(from_location) = constraint.locations.from_location() {
+                Either::Left(iter::once((
+                    constraint.sup.into(),
+                    constraint.sub.into(),
+                    location_table.mid_index(from_location),
+                )))
+            } else {
+                Either::Right(
+                    location_table.all_points().map(move |location| {
+                        (constraint.sup.into(), constraint.sub.into(), location)
+                    }),
+                )
+            }
+        },
+    ));
+}
diff --git a/compiler/rustc_borrowck/src/polonius/mod.rs b/compiler/rustc_borrowck/src/polonius/mod.rs
index 9fccc00bdaf..eee5e70efe3 100644
--- a/compiler/rustc_borrowck/src/polonius/mod.rs
+++ b/compiler/rustc_borrowck/src/polonius/mod.rs
@@ -1,184 +1,180 @@
-//! Functions dedicated to fact generation for the `-Zpolonius=legacy` datalog implementation.
+//! Polonius analysis and support code:
+//! - dedicated constraints
+//! - conversion from NLL constraints
+//! - debugging utilities
+//! - etc.
+//!
+//! The current implementation models the flow-sensitive borrow-checking concerns as a graph
+//! containing both information about regions and information about the control flow.
+//!
+//! Loan propagation is seen as a reachability problem (with some subtleties) between where the loan
+//! is introduced and a given point.
+//!
+//! Constraints arising from type-checking allow loans to flow from region to region at the same CFG
+//! point. Constraints arising from liveness allow loans to flow within from point to point, between
+//! live regions at these points.
+//!
+//! Edges can be bidirectional to encode invariant relationships, and loans can flow "back in time"
+//! to traverse these constraints arising earlier in the CFG.
+//!
+//! When incorporating kills in the traversal, the loans reaching a given point are considered live.
+//!
+//! After this, the usual NLL process happens. These live loans are fed into a dataflow analysis
+//! combining them with the points where loans go out of NLL scope (the frontier where they stop
+//! propagating to a live region), to yield the "loans in scope" or "active loans", at a given
+//! point.
+//!
+//! Illegal accesses are still computed by checking whether one of these resulting loans is
+//! invalidated.
+//!
+//! More information on this simple approach can be found in the following links, and in the future
+//! in the rustc dev guide:
+//! - <https://smallcultfollowing.com/babysteps/blog/2023/09/22/polonius-part-1/>
+//! - <https://smallcultfollowing.com/babysteps/blog/2023/09/29/polonius-part-2/>
 //!
-//! Will be removed in the future, once the in-tree `-Zpolonius=next` implementation reaches feature
-//! parity.
-
-use rustc_middle::mir::{Body, LocalKind, Location, START_BLOCK};
-use rustc_middle::ty::TyCtxt;
-use rustc_mir_dataflow::move_paths::{InitKind, InitLocation, MoveData};
-use tracing::debug;
 
-use crate::borrow_set::BorrowSet;
-use crate::facts::{AllFacts, PoloniusRegionVid};
-use crate::location::LocationTable;
-use crate::type_check::free_region_relations::UniversalRegionRelations;
+mod constraints;
+pub(crate) use constraints::*;
+mod dump;
+pub(crate) use dump::dump_polonius_mir;
+pub(crate) mod legacy;
+
+use rustc_middle::mir::{Body, Location};
+use rustc_mir_dataflow::points::PointIndex;
+
+use crate::RegionInferenceContext;
+use crate::constraints::OutlivesConstraint;
+use crate::region_infer::values::LivenessValues;
+use crate::type_check::Locations;
+use crate::universal_regions::UniversalRegions;
+
+/// Creates a constraint set for `-Zpolonius=next` by:
+/// - converting NLL typeck constraints to be localized
+/// - encoding liveness constraints
+pub(crate) fn create_localized_constraints<'tcx>(
+    regioncx: &mut RegionInferenceContext<'tcx>,
+    body: &Body<'tcx>,
+) -> LocalizedOutlivesConstraintSet {
+    let mut localized_outlives_constraints = LocalizedOutlivesConstraintSet::default();
+    convert_typeck_constraints(
+        body,
+        regioncx.liveness_constraints(),
+        regioncx.outlives_constraints(),
+        &mut localized_outlives_constraints,
+    );
+    create_liveness_constraints(
+        body,
+        regioncx.liveness_constraints(),
+        regioncx.universal_regions(),
+        &mut localized_outlives_constraints,
+    );
 
-mod loan_invalidations;
-mod loan_kills;
+    // FIXME: here, we can trace loan reachability in the constraint graph and record this as loan
+    // liveness for the next step in the chain, the NLL loan scope and active loans computations.
 
-/// When requested, emit most of the facts needed by polonius:
-/// - moves and assignments
-/// - universal regions and their relations
-/// - CFG points and edges
-/// - loan kills
-/// - loan invalidations
-///
-/// The rest of the facts are emitted during typeck and liveness.
-pub(crate) fn emit_facts<'tcx>(
-    all_facts: &mut Option<AllFacts>,
-    tcx: TyCtxt<'tcx>,
-    location_table: &LocationTable,
-    body: &Body<'tcx>,
-    borrow_set: &BorrowSet<'tcx>,
-    move_data: &MoveData<'_>,
-    universal_region_relations: &UniversalRegionRelations<'_>,
-) {
-    let Some(all_facts) = all_facts else {
-        // We don't do anything if there are no facts to fill.
-        return;
-    };
-    let _prof_timer = tcx.prof.generic_activity("polonius_fact_generation");
-    emit_move_facts(all_facts, move_data, location_table, body);
-    emit_universal_region_facts(all_facts, borrow_set, universal_region_relations);
-    emit_cfg_and_loan_kills_facts(all_facts, tcx, location_table, body, borrow_set);
-    emit_loan_invalidations_facts(all_facts, tcx, location_table, body, borrow_set);
+    localized_outlives_constraints
 }
 
-/// Emit facts needed for move/init analysis: moves and assignments.
-fn emit_move_facts(
-    all_facts: &mut AllFacts,
-    move_data: &MoveData<'_>,
-    location_table: &LocationTable,
-    body: &Body<'_>,
+/// Propagate loans throughout the subset graph at a given point (with some subtleties around the
+/// location where effects start to be visible).
+fn convert_typeck_constraints<'tcx>(
+    body: &Body<'tcx>,
+    liveness: &LivenessValues,
+    outlives_constraints: impl Iterator<Item = OutlivesConstraint<'tcx>>,
+    localized_outlives_constraints: &mut LocalizedOutlivesConstraintSet,
 ) {
-    all_facts
-        .path_is_var
-        .extend(move_data.rev_lookup.iter_locals_enumerated().map(|(l, r)| (r, l)));
-
-    for (child, move_path) in move_data.move_paths.iter_enumerated() {
-        if let Some(parent) = move_path.parent {
-            all_facts.child_path.push((child, parent));
-        }
-    }
-
-    let fn_entry_start =
-        location_table.start_index(Location { block: START_BLOCK, statement_index: 0 });
-
-    // initialized_at
-    for init in move_data.inits.iter() {
-        match init.location {
-            InitLocation::Statement(location) => {
-                let block_data = &body[location.block];
-                let is_terminator = location.statement_index == block_data.statements.len();
-
-                if is_terminator && init.kind == InitKind::NonPanicPathOnly {
-                    // We are at the terminator of an init that has a panic path,
-                    // and where the init should not happen on panic
-
-                    for successor in block_data.terminator().successors() {
-                        if body[successor].is_cleanup {
-                            continue;
-                        }
-
-                        // The initialization happened in (or rather, when arriving at)
-                        // the successors, but not in the unwind block.
-                        let first_statement = Location { block: successor, statement_index: 0 };
-                        all_facts
-                            .path_assigned_at_base
-                            .push((init.path, location_table.start_index(first_statement)));
+    for outlives_constraint in outlives_constraints {
+        match outlives_constraint.locations {
+            Locations::All(_) => {
+                // For now, turn logical constraints holding at all points into physical edges at
+                // every point in the graph.
+                // FIXME: encode this into *traversal* instead.
+                for (block, bb) in body.basic_blocks.iter_enumerated() {
+                    let statement_count = bb.statements.len();
+                    for statement_index in 0..=statement_count {
+                        let current_location = Location { block, statement_index };
+                        let current_point = liveness.point_from_location(current_location);
+
+                        localized_outlives_constraints.push(LocalizedOutlivesConstraint {
+                            source: outlives_constraint.sup,
+                            from: current_point,
+                            target: outlives_constraint.sub,
+                            to: current_point,
+                        });
                     }
-                } else {
-                    // In all other cases, the initialization just happens at the
-                    // midpoint, like any other effect.
-                    all_facts
-                        .path_assigned_at_base
-                        .push((init.path, location_table.mid_index(location)));
                 }
             }
-            // Arguments are initialized on function entry
-            InitLocation::Argument(local) => {
-                assert!(body.local_kind(local) == LocalKind::Arg);
-                all_facts.path_assigned_at_base.push((init.path, fn_entry_start));
-            }
-        }
-    }
 
-    for (local, path) in move_data.rev_lookup.iter_locals_enumerated() {
-        if body.local_kind(local) != LocalKind::Arg {
-            // Non-arguments start out deinitialised; we simulate this with an
-            // initial move:
-            all_facts.path_moved_at_base.push((path, fn_entry_start));
+            _ => {}
         }
     }
-
-    // moved_out_at
-    // deinitialisation is assumed to always happen!
-    all_facts
-        .path_moved_at_base
-        .extend(move_data.moves.iter().map(|mo| (mo.path, location_table.mid_index(mo.source))));
 }
 
-/// Emit universal regions facts, and their relations.
-fn emit_universal_region_facts(
-    all_facts: &mut AllFacts,
-    borrow_set: &BorrowSet<'_>,
-    universal_region_relations: &UniversalRegionRelations<'_>,
+/// Propagate loans throughout the CFG: for each statement in the MIR, create localized outlives
+/// constraints for loans that are propagated to the next statements.
+pub(crate) fn create_liveness_constraints<'tcx>(
+    body: &Body<'tcx>,
+    liveness: &LivenessValues,
+    universal_regions: &UniversalRegions<'tcx>,
+    localized_outlives_constraints: &mut LocalizedOutlivesConstraintSet,
 ) {
-    // 1: universal regions are modeled in Polonius as a pair:
-    // - the universal region vid itself.
-    // - a "placeholder loan" associated to this universal region. Since they don't exist in
-    //   the `borrow_set`, their `BorrowIndex` are synthesized as the universal region index
-    //   added to the existing number of loans, as if they succeeded them in the set.
-    //
-    let universal_regions = &universal_region_relations.universal_regions;
-    all_facts
-        .universal_region
-        .extend(universal_regions.universal_regions_iter().map(PoloniusRegionVid::from));
-    let borrow_count = borrow_set.len();
-    debug!(
-        "emit_universal_region_facts: polonius placeholders, num_universals={}, borrow_count={}",
-        universal_regions.len(),
-        borrow_count
-    );
-
-    for universal_region in universal_regions.universal_regions_iter() {
-        let universal_region_idx = universal_region.index();
-        let placeholder_loan_idx = borrow_count + universal_region_idx;
-        all_facts.placeholder.push((universal_region.into(), placeholder_loan_idx.into()));
-    }
-
-    // 2: the universal region relations `outlives` constraints are emitted as
-    //  `known_placeholder_subset` facts.
-    for (fr1, fr2) in universal_region_relations.known_outlives() {
-        if fr1 != fr2 {
-            debug!(
-                "emit_universal_region_facts: emitting polonius `known_placeholder_subset` \
-                     fr1={:?}, fr2={:?}",
-                fr1, fr2
-            );
-            all_facts.known_placeholder_subset.push((fr1.into(), fr2.into()));
+    for (block, bb) in body.basic_blocks.iter_enumerated() {
+        let statement_count = bb.statements.len();
+        for statement_index in 0..=statement_count {
+            let current_location = Location { block, statement_index };
+            let current_point = liveness.point_from_location(current_location);
+
+            if statement_index < statement_count {
+                // Intra-block edges, straight line constraints from each point to its successor
+                // within the same block.
+                let next_location = Location { block, statement_index: statement_index + 1 };
+                let next_point = liveness.point_from_location(next_location);
+                propagate_loans_between_points(
+                    current_point,
+                    next_point,
+                    liveness,
+                    universal_regions,
+                    localized_outlives_constraints,
+                );
+            } else {
+                // Inter-block edges, from the block's terminator to each successor block's entry
+                // point.
+                for successor_block in bb.terminator().successors() {
+                    let next_location = Location { block: successor_block, statement_index: 0 };
+                    let next_point = liveness.point_from_location(next_location);
+                    propagate_loans_between_points(
+                        current_point,
+                        next_point,
+                        liveness,
+                        universal_regions,
+                        localized_outlives_constraints,
+                    );
+                }
+            }
         }
     }
 }
 
-/// Emit facts about loan invalidations.
-fn emit_loan_invalidations_facts<'tcx>(
-    all_facts: &mut AllFacts,
-    tcx: TyCtxt<'tcx>,
-    location_table: &LocationTable,
-    body: &Body<'tcx>,
-    borrow_set: &BorrowSet<'tcx>,
-) {
-    loan_invalidations::emit_loan_invalidations(tcx, all_facts, location_table, body, borrow_set);
-}
-
-/// Emit facts about CFG points and edges, as well as locations where loans are killed.
-fn emit_cfg_and_loan_kills_facts<'tcx>(
-    all_facts: &mut AllFacts,
-    tcx: TyCtxt<'tcx>,
-    location_table: &LocationTable,
-    body: &Body<'tcx>,
-    borrow_set: &BorrowSet<'tcx>,
+/// Propagate loans within a region between two points in the CFG, if that region is live at both
+/// the source and target points.
+fn propagate_loans_between_points(
+    current_point: PointIndex,
+    next_point: PointIndex,
+    _liveness: &LivenessValues,
+    universal_regions: &UniversalRegions<'_>,
+    localized_outlives_constraints: &mut LocalizedOutlivesConstraintSet,
 ) {
-    loan_kills::emit_loan_kills(tcx, all_facts, location_table, body, borrow_set);
+    // Universal regions are semantically live at all points.
+    // Note: we always have universal regions but they're not always (or often) involved in the
+    // subset graph. For now, we emit all their edges unconditionally, but some of these subgraphs
+    // will be disconnected from the rest of the graph and thus, unnecessary.
+    // FIXME: only emit the edges of universal regions that existential regions can reach.
+    for region in universal_regions.universal_regions_iter() {
+        localized_outlives_constraints.push(LocalizedOutlivesConstraint {
+            source: region,
+            from: current_point,
+            target: region,
+            to: next_point,
+        });
+    }
 }
diff --git a/compiler/rustc_borrowck/src/region_infer/mod.rs b/compiler/rustc_borrowck/src/region_infer/mod.rs
index 0eecf98a6ed..907a3f16b06 100644
--- a/compiler/rustc_borrowck/src/region_infer/mod.rs
+++ b/compiler/rustc_borrowck/src/region_infer/mod.rs
@@ -571,7 +571,9 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     /// Given a universal region in scope on the MIR, returns the
     /// corresponding index.
     ///
-    /// (Panics if `r` is not a registered universal region.)
+    /// Panics if `r` is not a registered universal region, most notably
+    /// if it is a placeholder. Handling placeholders requires access to the
+    /// `MirTypeckRegionConstraints`.
     pub(crate) fn to_region_vid(&self, r: ty::Region<'tcx>) -> RegionVid {
         self.universal_regions().to_region_vid(r)
     }
@@ -795,7 +797,6 @@ impl<'tcx> RegionInferenceContext<'tcx> {
 
         // If the member region lives in a higher universe, we currently choose
         // the most conservative option by leaving it unchanged.
-
         if !self.constraint_sccs().annotation(scc).min_universe().is_root() {
             return;
         }
@@ -823,12 +824,14 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         }
         debug!(?choice_regions, "after ub");
 
-        // At this point we can pick any member of `choice_regions`, but to avoid potential
-        // non-determinism we will pick the *unique minimum* choice.
+        // At this point we can pick any member of `choice_regions` and would like to choose
+        // it to be a small as possible. To avoid potential non-determinism we will pick the
+        // smallest such choice.
         //
         // Because universal regions are only partially ordered (i.e, not every two regions are
         // comparable), we will ignore any region that doesn't compare to all others when picking
         // the minimum choice.
+        //
         // For example, consider `choice_regions = ['static, 'a, 'b, 'c, 'd, 'e]`, where
         // `'static: 'a, 'static: 'b, 'a: 'c, 'b: 'c, 'c: 'd, 'c: 'e`.
         // `['d, 'e]` are ignored because they do not compare - the same goes for `['a, 'b]`.
@@ -853,6 +856,8 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             return;
         };
 
+        // As we require `'scc: 'min_choice`, we have definitely already computed
+        // its `scc_values` at this point.
         let min_choice_scc = self.constraint_sccs.scc(min_choice);
         debug!(?min_choice, ?min_choice_scc);
         if self.scc_values.add_region(scc, min_choice_scc) {
@@ -2224,13 +2229,17 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     fn scc_representative(&self, scc: ConstraintSccIndex) -> RegionVid {
         self.constraint_sccs.annotation(scc).representative
     }
+
+    pub(crate) fn liveness_constraints(&self) -> &LivenessValues {
+        &self.liveness_constraints
+    }
 }
 
 impl<'tcx> RegionDefinition<'tcx> {
     fn new(universe: ty::UniverseIndex, rv_origin: RegionVariableOrigin) -> Self {
         // Create a new region definition. Note that, for free
         // regions, the `external_name` field gets updated later in
-        // `init_universal_regions`.
+        // `init_free_and_bound_regions`.
 
         let origin = match rv_origin {
             RegionVariableOrigin::Nll(origin) => origin,
diff --git a/compiler/rustc_borrowck/src/region_infer/opaque_types.rs b/compiler/rustc_borrowck/src/region_infer/opaque_types.rs
index 7164a129235..3e16a3ca157 100644
--- a/compiler/rustc_borrowck/src/region_infer/opaque_types.rs
+++ b/compiler/rustc_borrowck/src/region_infer/opaque_types.rs
@@ -134,12 +134,13 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             // the hidden type becomes the opaque type itself. In this case, this was an opaque
             // usage of the opaque type and we can ignore it. This check is mirrored in typeck's
             // writeback.
-            // FIXME(-Znext-solver): This should be unnecessary with the new solver.
-            if let ty::Alias(ty::Opaque, alias_ty) = ty.kind()
-                && alias_ty.def_id == opaque_type_key.def_id.to_def_id()
-                && alias_ty.args == opaque_type_key.args
-            {
-                continue;
+            if !infcx.next_trait_solver() {
+                if let ty::Alias(ty::Opaque, alias_ty) = ty.kind()
+                    && alias_ty.def_id == opaque_type_key.def_id.to_def_id()
+                    && alias_ty.args == opaque_type_key.args
+                {
+                    continue;
+                }
             }
             // Sometimes two opaque types are the same only after we remap the generic parameters
             // back to the opaque type definition. E.g. we may have `OpaqueType<X, Y>` mapped to
diff --git a/compiler/rustc_borrowck/src/region_infer/values.rs b/compiler/rustc_borrowck/src/region_infer/values.rs
index a16bce63839..0b0757f16ab 100644
--- a/compiler/rustc_borrowck/src/region_infer/values.rs
+++ b/compiler/rustc_borrowck/src/region_infer/values.rs
@@ -199,6 +199,11 @@ impl LivenessValues {
         self.elements.point_from_location(location)
     }
 
+    #[inline]
+    pub(crate) fn location_from_point(&self, point: PointIndex) -> Location {
+        self.elements.to_location(point)
+    }
+
     /// When using `-Zpolonius=next`, returns whether the `loan_idx` is live at the given `point`.
     pub(crate) fn is_loan_live_at(&self, loan_idx: BorrowIndex, point: PointIndex) -> bool {
         self.loans
diff --git a/compiler/rustc_borrowck/src/type_check/constraint_conversion.rs b/compiler/rustc_borrowck/src/type_check/constraint_conversion.rs
index 918efac2a20..4b7f5321388 100644
--- a/compiler/rustc_borrowck/src/type_check/constraint_conversion.rs
+++ b/compiler/rustc_borrowck/src/type_check/constraint_conversion.rs
@@ -77,17 +77,7 @@ impl<'a, 'tcx> ConstraintConversion<'a, 'tcx> {
 
     #[instrument(skip(self), level = "debug")]
     pub(super) fn convert_all(&mut self, query_constraints: &QueryRegionConstraints<'tcx>) {
-        let QueryRegionConstraints { outlives, member_constraints } = query_constraints;
-
-        // Annoying: to invoke `self.to_region_vid`, we need access to
-        // `self.constraints`, but we also want to be mutating
-        // `self.member_constraints`. For now, just swap out the value
-        // we want and replace at the end.
-        let mut tmp = std::mem::take(&mut self.constraints.member_constraints);
-        for member_constraint in member_constraints {
-            tmp.push_constraint(member_constraint, |r| self.to_region_vid(r));
-        }
-        self.constraints.member_constraints = tmp;
+        let QueryRegionConstraints { outlives } = query_constraints;
 
         for &(predicate, constraint_category) in outlives {
             self.convert(predicate, constraint_category);
@@ -295,13 +285,8 @@ impl<'a, 'tcx> ConstraintConversion<'a, 'tcx> {
 
         match result {
             Ok(TypeOpOutput { output: ty, constraints, .. }) => {
-                if let Some(constraints) = constraints {
-                    assert!(
-                        constraints.member_constraints.is_empty(),
-                        "no member constraints expected from normalizing: {:#?}",
-                        constraints.member_constraints
-                    );
-                    next_outlives_predicates.extend(constraints.outlives.iter().copied());
+                if let Some(QueryRegionConstraints { outlives }) = constraints {
+                    next_outlives_predicates.extend(outlives.iter().copied());
                 }
                 ty
             }
diff --git a/compiler/rustc_borrowck/src/type_check/liveness/mod.rs b/compiler/rustc_borrowck/src/type_check/liveness/mod.rs
index 20d19a53752..683293bf828 100644
--- a/compiler/rustc_borrowck/src/type_check/liveness/mod.rs
+++ b/compiler/rustc_borrowck/src/type_check/liveness/mod.rs
@@ -17,7 +17,6 @@ use crate::region_infer::values::LivenessValues;
 use crate::universal_regions::UniversalRegions;
 
 mod local_use_map;
-mod polonius;
 mod trace;
 
 /// Combines liveness analysis with initialization analysis to
@@ -45,8 +44,6 @@ pub(super) fn generate<'a, 'tcx>(
     let (relevant_live_locals, boring_locals) =
         compute_relevant_live_locals(typeck.tcx(), &free_regions, body);
 
-    polonius::populate_access_facts(typeck, body, move_data);
-
     trace::trace(
         typeck,
         body,
diff --git a/compiler/rustc_borrowck/src/type_check/liveness/polonius.rs b/compiler/rustc_borrowck/src/type_check/liveness/polonius.rs
deleted file mode 100644
index e8d8ae0850b..00000000000
--- a/compiler/rustc_borrowck/src/type_check/liveness/polonius.rs
+++ /dev/null
@@ -1,136 +0,0 @@
-use rustc_middle::mir::visit::{MutatingUseContext, PlaceContext, Visitor};
-use rustc_middle::mir::{Body, Local, Location, Place};
-use rustc_middle::ty::GenericArg;
-use rustc_mir_dataflow::move_paths::{LookupResult, MoveData, MovePathIndex};
-use tracing::debug;
-
-use super::TypeChecker;
-use crate::def_use::{self, DefUse};
-use crate::location::{LocationIndex, LocationTable};
-
-type VarPointRelation = Vec<(Local, LocationIndex)>;
-type PathPointRelation = Vec<(MovePathIndex, LocationIndex)>;
-
-struct UseFactsExtractor<'a, 'tcx> {
-    var_defined_at: &'a mut VarPointRelation,
-    var_used_at: &'a mut VarPointRelation,
-    location_table: &'a LocationTable,
-    var_dropped_at: &'a mut VarPointRelation,
-    move_data: &'a MoveData<'tcx>,
-    path_accessed_at_base: &'a mut PathPointRelation,
-}
-
-// A Visitor to walk through the MIR and extract point-wise facts
-impl<'tcx> UseFactsExtractor<'_, 'tcx> {
-    fn location_to_index(&self, location: Location) -> LocationIndex {
-        self.location_table.mid_index(location)
-    }
-
-    fn insert_def(&mut self, local: Local, location: Location) {
-        debug!("UseFactsExtractor::insert_def()");
-        self.var_defined_at.push((local, self.location_to_index(location)));
-    }
-
-    fn insert_use(&mut self, local: Local, location: Location) {
-        debug!("UseFactsExtractor::insert_use()");
-        self.var_used_at.push((local, self.location_to_index(location)));
-    }
-
-    fn insert_drop_use(&mut self, local: Local, location: Location) {
-        debug!("UseFactsExtractor::insert_drop_use()");
-        self.var_dropped_at.push((local, self.location_to_index(location)));
-    }
-
-    fn insert_path_access(&mut self, path: MovePathIndex, location: Location) {
-        debug!("UseFactsExtractor::insert_path_access({:?}, {:?})", path, location);
-        self.path_accessed_at_base.push((path, self.location_to_index(location)));
-    }
-
-    fn place_to_mpi(&self, place: &Place<'tcx>) -> Option<MovePathIndex> {
-        match self.move_data.rev_lookup.find(place.as_ref()) {
-            LookupResult::Exact(mpi) => Some(mpi),
-            LookupResult::Parent(mmpi) => mmpi,
-        }
-    }
-}
-
-impl<'a, 'tcx> Visitor<'tcx> for UseFactsExtractor<'a, 'tcx> {
-    fn visit_local(&mut self, local: Local, context: PlaceContext, location: Location) {
-        match def_use::categorize(context) {
-            Some(DefUse::Def) => self.insert_def(local, location),
-            Some(DefUse::Use) => self.insert_use(local, location),
-            Some(DefUse::Drop) => self.insert_drop_use(local, location),
-            _ => (),
-        }
-    }
-
-    fn visit_place(&mut self, place: &Place<'tcx>, context: PlaceContext, location: Location) {
-        self.super_place(place, context, location);
-        match context {
-            PlaceContext::NonMutatingUse(_) => {
-                if let Some(mpi) = self.place_to_mpi(place) {
-                    self.insert_path_access(mpi, location);
-                }
-            }
-
-            PlaceContext::MutatingUse(MutatingUseContext::Borrow) => {
-                if let Some(mpi) = self.place_to_mpi(place) {
-                    self.insert_path_access(mpi, location);
-                }
-            }
-            _ => (),
-        }
-    }
-}
-
-pub(super) fn populate_access_facts<'a, 'tcx>(
-    typeck: &mut TypeChecker<'a, 'tcx>,
-    body: &Body<'tcx>,
-    move_data: &MoveData<'tcx>,
-) {
-    if let Some(facts) = typeck.all_facts.as_mut() {
-        debug!("populate_access_facts()");
-        let location_table = typeck.location_table;
-
-        let mut extractor = UseFactsExtractor {
-            var_defined_at: &mut facts.var_defined_at,
-            var_used_at: &mut facts.var_used_at,
-            var_dropped_at: &mut facts.var_dropped_at,
-            path_accessed_at_base: &mut facts.path_accessed_at_base,
-            location_table,
-            move_data,
-        };
-        extractor.visit_body(body);
-
-        for (local, local_decl) in body.local_decls.iter_enumerated() {
-            debug!(
-                "add use_of_var_derefs_origin facts - local={:?}, type={:?}",
-                local, local_decl.ty
-            );
-            let _prof_timer = typeck.infcx.tcx.prof.generic_activity("polonius_fact_generation");
-            let universal_regions = &typeck.universal_regions;
-            typeck.infcx.tcx.for_each_free_region(&local_decl.ty, |region| {
-                let region_vid = universal_regions.to_region_vid(region);
-                facts.use_of_var_derefs_origin.push((local, region_vid.into()));
-            });
-        }
-    }
-}
-
-/// For every potentially drop()-touched region `region` in `local`'s type
-/// (`kind`), emit a Polonius `use_of_var_derefs_origin(local, origin)` fact.
-pub(super) fn add_drop_of_var_derefs_origin<'tcx>(
-    typeck: &mut TypeChecker<'_, 'tcx>,
-    local: Local,
-    kind: &GenericArg<'tcx>,
-) {
-    debug!("add_drop_of_var_derefs_origin(local={:?}, kind={:?}", local, kind);
-    if let Some(facts) = typeck.all_facts.as_mut() {
-        let _prof_timer = typeck.infcx.tcx.prof.generic_activity("polonius_fact_generation");
-        let universal_regions = &typeck.universal_regions;
-        typeck.infcx.tcx.for_each_free_region(kind, |drop_live_region| {
-            let region_vid = universal_regions.to_region_vid(drop_live_region);
-            facts.drop_of_var_derefs_origin.push((local, region_vid.into()));
-        });
-    }
-}
diff --git a/compiler/rustc_borrowck/src/type_check/liveness/trace.rs b/compiler/rustc_borrowck/src/type_check/liveness/trace.rs
index 3ec36c16cbf..f510d193dd9 100644
--- a/compiler/rustc_borrowck/src/type_check/liveness/trace.rs
+++ b/compiler/rustc_borrowck/src/type_check/liveness/trace.rs
@@ -15,9 +15,9 @@ use rustc_trait_selection::traits::query::type_op::{DropckOutlives, TypeOp, Type
 use tracing::debug;
 
 use crate::location::RichLocation;
+use crate::polonius;
 use crate::region_infer::values::{self, LiveLoans};
 use crate::type_check::liveness::local_use_map::LocalUseMap;
-use crate::type_check::liveness::polonius;
 use crate::type_check::{NormalizeLocation, TypeChecker};
 
 /// This is the heart of the liveness computation. For each variable X
@@ -590,7 +590,13 @@ impl<'tcx> LivenessContext<'_, '_, '_, 'tcx> {
         // the destructor and must be live at this point.
         for &kind in &drop_data.dropck_result.kinds {
             Self::make_all_regions_live(self.elements, self.typeck, kind, live_at);
-            polonius::add_drop_of_var_derefs_origin(self.typeck, dropped_local, &kind);
+            polonius::legacy::emit_drop_facts(
+                self.typeck.tcx(),
+                dropped_local,
+                &kind,
+                self.typeck.universal_regions,
+                self.typeck.all_facts,
+            );
         }
     }
 
diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs
index 90d327b0ad2..4d53c87e3fc 100644
--- a/compiler/rustc_borrowck/src/type_check/mod.rs
+++ b/compiler/rustc_borrowck/src/type_check/mod.rs
@@ -3,7 +3,6 @@
 use std::rc::Rc;
 use std::{fmt, iter, mem};
 
-use either::Either;
 use rustc_abi::{FIRST_VARIANT, FieldIdx};
 use rustc_data_structures::frozen::Frozen;
 use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
@@ -40,11 +39,8 @@ use rustc_mir_dataflow::move_paths::MoveData;
 use rustc_mir_dataflow::points::DenseLocationMap;
 use rustc_span::def_id::CRATE_DEF_ID;
 use rustc_span::source_map::Spanned;
-use rustc_span::symbol::sym;
-use rustc_span::{DUMMY_SP, Span};
-use rustc_trait_selection::traits::query::type_op::custom::{
-    CustomTypeOp, scrape_region_constraints,
-};
+use rustc_span::{DUMMY_SP, Span, sym};
+use rustc_trait_selection::traits::query::type_op::custom::scrape_region_constraints;
 use rustc_trait_selection::traits::query::type_op::{TypeOp, TypeOpOutput};
 use tracing::{debug, instrument, trace};
 
@@ -91,6 +87,7 @@ mod constraint_conversion;
 pub(crate) mod free_region_relations;
 mod input_output;
 pub(crate) mod liveness;
+mod opaque_types;
 mod relate_tys;
 
 /// Type checks the given `mir` in the context of the inference
@@ -107,7 +104,6 @@ mod relate_tys;
 /// # Parameters
 ///
 /// - `infcx` -- inference context to use
-/// - `param_env` -- parameter environment to use for trait solving
 /// - `body` -- MIR body to type-check
 /// - `promoted` -- map of promoted constants within `body`
 /// - `universal_regions` -- the universal regions from `body`s function signature
@@ -155,7 +151,7 @@ pub(crate) fn type_check<'a, 'tcx>(
 
     debug!(?normalized_inputs_and_output);
 
-    let mut checker = TypeChecker {
+    let mut typeck = TypeChecker {
         infcx,
         last_span: body.span,
         body,
@@ -171,93 +167,23 @@ pub(crate) fn type_check<'a, 'tcx>(
         constraints: &mut constraints,
     };
 
-    checker.check_user_type_annotations();
+    typeck.check_user_type_annotations();
 
-    let mut verifier = TypeVerifier { cx: &mut checker, promoted, last_span: body.span };
+    let mut verifier = TypeVerifier { typeck: &mut typeck, promoted, last_span: body.span };
     verifier.visit_body(body);
 
-    checker.typeck_mir(body);
-    checker.equate_inputs_and_outputs(body, &normalized_inputs_and_output);
-    checker.check_signature_annotation(body);
-
-    liveness::generate(&mut checker, body, &elements, flow_inits, move_data);
-
-    translate_outlives_facts(&mut checker);
-    let opaque_type_values = infcx.take_opaque_types();
-
-    let opaque_type_values = opaque_type_values
-        .into_iter()
-        .map(|(opaque_type_key, decl)| {
-            let _: Result<_, ErrorGuaranteed> = checker.fully_perform_op(
-                Locations::All(body.span),
-                ConstraintCategory::OpaqueType,
-                CustomTypeOp::new(
-                    |ocx| {
-                        ocx.infcx.register_member_constraints(
-                            opaque_type_key,
-                            decl.hidden_type.ty,
-                            decl.hidden_type.span,
-                        );
-                        Ok(())
-                    },
-                    "opaque_type_map",
-                ),
-            );
-            let hidden_type = infcx.resolve_vars_if_possible(decl.hidden_type);
-            trace!("finalized opaque type {:?} to {:#?}", opaque_type_key, hidden_type.ty.kind());
-            if hidden_type.has_non_region_infer() {
-                infcx.dcx().span_bug(
-                    decl.hidden_type.span,
-                    format!("could not resolve {:#?}", hidden_type.ty.kind()),
-                );
-            }
+    typeck.typeck_mir(body);
+    typeck.equate_inputs_and_outputs(body, &normalized_inputs_and_output);
+    typeck.check_signature_annotation(body);
 
-            // Convert all regions to nll vars.
-            let (opaque_type_key, hidden_type) =
-                fold_regions(infcx.tcx, (opaque_type_key, hidden_type), |region, _| {
-                    match region.kind() {
-                        ty::ReVar(_) => region,
-                        ty::RePlaceholder(placeholder) => {
-                            checker.constraints.placeholder_region(infcx, placeholder)
-                        }
-                        _ => ty::Region::new_var(
-                            infcx.tcx,
-                            checker.universal_regions.to_region_vid(region),
-                        ),
-                    }
-                });
+    liveness::generate(&mut typeck, body, &elements, flow_inits, move_data);
 
-            (opaque_type_key, hidden_type)
-        })
-        .collect();
+    let opaque_type_values =
+        opaque_types::take_opaques_and_register_member_constraints(&mut typeck);
 
     MirTypeckResults { constraints, universal_region_relations, opaque_type_values }
 }
 
-fn translate_outlives_facts(typeck: &mut TypeChecker<'_, '_>) {
-    if let Some(facts) = typeck.all_facts {
-        let _prof_timer = typeck.infcx.tcx.prof.generic_activity("polonius_fact_generation");
-        let location_table = typeck.location_table;
-        facts.subset_base.extend(
-            typeck.constraints.outlives_constraints.outlives().iter().flat_map(
-                |constraint: &OutlivesConstraint<'_>| {
-                    if let Some(from_location) = constraint.locations.from_location() {
-                        Either::Left(iter::once((
-                            constraint.sup.into(),
-                            constraint.sub.into(),
-                            location_table.mid_index(from_location),
-                        )))
-                    } else {
-                        Either::Right(location_table.all_points().map(move |location| {
-                            (constraint.sup.into(), constraint.sub.into(), location)
-                        }))
-                    }
-                },
-            ),
-        );
-    }
-}
-
 #[track_caller]
 fn mirbug(tcx: TyCtxt<'_>, span: Span, msg: String) {
     // We sometimes see MIR failures (notably predicate failures) due to
@@ -276,7 +202,7 @@ enum FieldAccessError {
 /// type, calling `span_mirbug` and returning an error type if there
 /// is a problem.
 struct TypeVerifier<'a, 'b, 'tcx> {
-    cx: &'a mut TypeChecker<'b, 'tcx>,
+    typeck: &'a mut TypeChecker<'b, 'tcx>,
     promoted: &'b IndexSlice<Promoted, Body<'tcx>>,
     last_span: Span,
 }
@@ -298,9 +224,9 @@ impl<'a, 'b, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'tcx> {
         self.super_const_operand(constant, location);
         let ty = self.sanitize_type(constant, constant.const_.ty());
 
-        self.cx.infcx.tcx.for_each_free_region(&ty, |live_region| {
-            let live_region_vid = self.cx.universal_regions.to_region_vid(live_region);
-            self.cx.constraints.liveness_constraints.add_location(live_region_vid, location);
+        self.typeck.infcx.tcx.for_each_free_region(&ty, |live_region| {
+            let live_region_vid = self.typeck.universal_regions.to_region_vid(live_region);
+            self.typeck.constraints.liveness_constraints.add_location(live_region_vid, location);
         });
 
         // HACK(compiler-errors): Constants that are gathered into Body.required_consts
@@ -312,14 +238,14 @@ impl<'a, 'b, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'tcx> {
         };
 
         if let Some(annotation_index) = constant.user_ty {
-            if let Err(terr) = self.cx.relate_type_and_user_type(
+            if let Err(terr) = self.typeck.relate_type_and_user_type(
                 constant.const_.ty(),
                 ty::Invariant,
                 &UserTypeProjection { base: annotation_index, projs: vec![] },
                 locations,
                 ConstraintCategory::Boring,
             ) {
-                let annotation = &self.cx.user_type_annotations[annotation_index];
+                let annotation = &self.typeck.user_type_annotations[annotation_index];
                 span_mirbug!(
                     self,
                     constant,
@@ -348,9 +274,12 @@ impl<'a, 'b, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'tcx> {
                                      promoted: &Body<'tcx>,
                                      ty,
                                      san_ty| {
-                        if let Err(terr) =
-                            verifier.cx.eq_types(ty, san_ty, locations, ConstraintCategory::Boring)
-                        {
+                        if let Err(terr) = verifier.typeck.eq_types(
+                            ty,
+                            san_ty,
+                            locations,
+                            ConstraintCategory::Boring,
+                        ) {
                             span_mirbug!(
                                 verifier,
                                 promoted,
@@ -368,21 +297,21 @@ impl<'a, 'b, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'tcx> {
                     let promoted_ty = promoted_body.return_ty();
                     check_err(self, promoted_body, ty, promoted_ty);
                 } else {
-                    self.cx.ascribe_user_type(
+                    self.typeck.ascribe_user_type(
                         constant.const_.ty(),
                         ty::UserType::new(ty::UserTypeKind::TypeOf(uv.def, UserArgs {
                             args: uv.args,
                             user_self_ty: None,
                         })),
-                        locations.span(self.cx.body),
+                        locations.span(self.typeck.body),
                     );
                 }
             } else if let Some(static_def_id) = constant.check_static_ptr(tcx) {
                 let unnormalized_ty = tcx.type_of(static_def_id).instantiate_identity();
-                let normalized_ty = self.cx.normalize(unnormalized_ty, locations);
+                let normalized_ty = self.typeck.normalize(unnormalized_ty, locations);
                 let literal_ty = constant.const_.ty().builtin_deref(true).unwrap();
 
-                if let Err(terr) = self.cx.eq_types(
+                if let Err(terr) = self.typeck.eq_types(
                     literal_ty,
                     normalized_ty,
                     locations,
@@ -394,7 +323,7 @@ impl<'a, 'b, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'tcx> {
 
             if let ty::FnDef(def_id, args) = *constant.const_.ty().kind() {
                 let instantiated_predicates = tcx.predicates_of(def_id).instantiate(tcx, args);
-                self.cx.normalize_and_prove_instantiated_predicates(
+                self.typeck.normalize_and_prove_instantiated_predicates(
                     def_id,
                     instantiated_predicates,
                     locations,
@@ -404,7 +333,7 @@ impl<'a, 'b, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'tcx> {
                     tcx.impl_of_method(def_id).map(|imp| tcx.def_kind(imp)),
                     Some(DefKind::Impl { of_trait: true })
                 ));
-                self.cx.prove_predicates(
+                self.typeck.prove_predicates(
                     args.types().map(|ty| ty::ClauseKind::WellFormed(ty.into())),
                     locations,
                     ConstraintCategory::Boring,
@@ -438,7 +367,7 @@ impl<'a, 'b, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'tcx> {
                     local_decl.ty
                 };
 
-                if let Err(terr) = self.cx.relate_type_and_user_type(
+                if let Err(terr) = self.typeck.relate_type_and_user_type(
                     ty,
                     ty::Invariant,
                     user_ty,
@@ -468,11 +397,11 @@ impl<'a, 'b, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'tcx> {
 
 impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
     fn body(&self) -> &Body<'tcx> {
-        self.cx.body
+        self.typeck.body
     }
 
     fn tcx(&self) -> TyCtxt<'tcx> {
-        self.cx.infcx.tcx
+        self.typeck.infcx.tcx
     }
 
     fn sanitize_type(&mut self, parent: &dyn fmt::Debug, ty: Ty<'tcx>) -> Ty<'tcx> {
@@ -522,7 +451,7 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
             // whether the bounds fully apply: in effect, the rule is
             // that if a value of some type could implement `Copy`, then
             // it must.
-            self.cx.prove_trait_ref(
+            self.typeck.prove_trait_ref(
                 trait_ref,
                 location.to_locations(),
                 ConstraintCategory::CopyBound,
@@ -537,7 +466,7 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
         // checker on the promoted MIR, then transfer the constraints back to
         // the main MIR, changing the locations to the provided location.
 
-        let parent_body = mem::replace(&mut self.cx.body, promoted_body);
+        let parent_body = mem::replace(&mut self.typeck.body, promoted_body);
 
         // Use new sets of constraints and closure bounds so that we can
         // modify their locations.
@@ -548,18 +477,18 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
         // Don't try to add borrow_region facts for the promoted MIR
 
         let mut swap_constraints = |this: &mut Self| {
-            mem::swap(this.cx.all_facts, all_facts);
-            mem::swap(&mut this.cx.constraints.outlives_constraints, &mut constraints);
-            mem::swap(&mut this.cx.constraints.liveness_constraints, &mut liveness_constraints);
+            mem::swap(this.typeck.all_facts, all_facts);
+            mem::swap(&mut this.typeck.constraints.outlives_constraints, &mut constraints);
+            mem::swap(&mut this.typeck.constraints.liveness_constraints, &mut liveness_constraints);
         };
 
         swap_constraints(self);
 
         self.visit_body(promoted_body);
 
-        self.cx.typeck_mir(promoted_body);
+        self.typeck.typeck_mir(promoted_body);
 
-        self.cx.body = parent_body;
+        self.typeck.body = parent_body;
         // Merge the outlives constraints back in, at the given location.
         swap_constraints(self);
 
@@ -575,7 +504,7 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
                 // temporary from the user's point of view.
                 constraint.category = ConstraintCategory::Boring;
             }
-            self.cx.constraints.outlives_constraints.push(constraint)
+            self.typeck.constraints.outlives_constraints.push(constraint)
         }
         // If the region is live at least one location in the promoted MIR,
         // then add a liveness constraint to the main MIR for this region
@@ -585,7 +514,7 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
         // unordered.
         #[allow(rustc::potential_query_instability)]
         for region in liveness_constraints.live_regions_unordered() {
-            self.cx.constraints.liveness_constraints.add_location(region, location);
+            self.typeck.constraints.liveness_constraints.add_location(region, location);
         }
     }
 
@@ -669,13 +598,13 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
             },
             ProjectionElem::Field(field, fty) => {
                 let fty = self.sanitize_type(place, fty);
-                let fty = self.cx.normalize(fty, location);
+                let fty = self.typeck.normalize(fty, location);
                 match self.field_ty(place, base, field, location) {
                     Ok(ty) => {
-                        let ty = self.cx.normalize(ty, location);
+                        let ty = self.typeck.normalize(ty, location);
                         debug!(?fty, ?ty);
 
-                        if let Err(terr) = self.cx.relate_types(
+                        if let Err(terr) = self.typeck.relate_types(
                             ty,
                             self.get_ambient_variance(context),
                             fty,
@@ -707,8 +636,8 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
             }
             ProjectionElem::OpaqueCast(ty) => {
                 let ty = self.sanitize_type(place, ty);
-                let ty = self.cx.normalize(ty, location);
-                self.cx
+                let ty = self.typeck.normalize(ty, location);
+                self.typeck
                     .relate_types(
                         ty,
                         self.get_ambient_variance(context),
@@ -817,7 +746,7 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
         };
 
         if let Some(field) = variant.fields.get(field) {
-            Ok(self.cx.normalize(field.ty(tcx, args), location))
+            Ok(self.typeck.normalize(field.ty(tcx, args), location))
         } else {
             Err(FieldAccessError::OutOfRange { field_count: variant.fields.len() })
         }
@@ -981,6 +910,14 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         self.body
     }
 
+    fn to_region_vid(&mut self, r: ty::Region<'tcx>) -> RegionVid {
+        if let ty::RePlaceholder(placeholder) = r.kind() {
+            self.constraints.placeholder_region(self.infcx, placeholder).as_var()
+        } else {
+            self.universal_regions.to_region_vid(r)
+        }
+    }
+
     fn unsized_feature_enabled(&self) -> bool {
         let features = self.tcx().features();
         features.unsized_locals() || features.unsized_fn_params()
diff --git a/compiler/rustc_borrowck/src/type_check/opaque_types.rs b/compiler/rustc_borrowck/src/type_check/opaque_types.rs
new file mode 100644
index 00000000000..edf3b1ae092
--- /dev/null
+++ b/compiler/rustc_borrowck/src/type_check/opaque_types.rs
@@ -0,0 +1,335 @@
+use std::iter;
+
+use rustc_data_structures::fx::FxIndexMap;
+use rustc_middle::span_bug;
+use rustc_middle::ty::fold::fold_regions;
+use rustc_middle::ty::{
+    self, GenericArgKind, OpaqueHiddenType, OpaqueTypeKey, Ty, TyCtxt, TypeSuperVisitable,
+    TypeVisitable, TypeVisitableExt, TypeVisitor,
+};
+use tracing::{debug, trace};
+
+use super::{MemberConstraintSet, TypeChecker};
+
+/// Once we're done with typechecking the body, we take all the opaque types
+/// defined by this function and add their 'member constraints'.
+pub(super) fn take_opaques_and_register_member_constraints<'tcx>(
+    typeck: &mut TypeChecker<'_, 'tcx>,
+) -> FxIndexMap<OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>> {
+    let infcx = typeck.infcx;
+    // Annoying: to invoke `typeck.to_region_vid`, we need access to
+    // `typeck.constraints`, but we also want to be mutating
+    // `typeck.member_constraints`. For now, just swap out the value
+    // we want and replace at the end.
+    let mut member_constraints = std::mem::take(&mut typeck.constraints.member_constraints);
+    let opaque_types = infcx
+        .take_opaque_types()
+        .into_iter()
+        .map(|(opaque_type_key, decl)| {
+            let hidden_type = infcx.resolve_vars_if_possible(decl.hidden_type);
+            register_member_constraints(
+                typeck,
+                &mut member_constraints,
+                opaque_type_key,
+                hidden_type,
+            );
+            trace!("finalized opaque type {:?} to {:#?}", opaque_type_key, hidden_type.ty.kind());
+            if hidden_type.has_non_region_infer() {
+                span_bug!(hidden_type.span, "could not resolve {:?}", hidden_type.ty);
+            }
+
+            // Convert all regions to nll vars.
+            let (opaque_type_key, hidden_type) =
+                fold_regions(infcx.tcx, (opaque_type_key, hidden_type), |r, _| {
+                    ty::Region::new_var(infcx.tcx, typeck.to_region_vid(r))
+                });
+
+            (opaque_type_key, hidden_type)
+        })
+        .collect();
+    assert!(typeck.constraints.member_constraints.is_empty());
+    typeck.constraints.member_constraints = member_constraints;
+    opaque_types
+}
+
+/// Given the map `opaque_types` containing the opaque
+/// `impl Trait` types whose underlying, hidden types are being
+/// inferred, this method adds constraints to the regions
+/// appearing in those underlying hidden types to ensure that they
+/// at least do not refer to random scopes within the current
+/// function. These constraints are not (quite) sufficient to
+/// guarantee that the regions are actually legal values; that
+/// final condition is imposed after region inference is done.
+///
+/// # The Problem
+///
+/// Let's work through an example to explain how it works. Assume
+/// the current function is as follows:
+///
+/// ```text
+/// fn foo<'a, 'b>(..) -> (impl Bar<'a>, impl Bar<'b>)
+/// ```
+///
+/// Here, we have two `impl Trait` types whose values are being
+/// inferred (the `impl Bar<'a>` and the `impl
+/// Bar<'b>`). Conceptually, this is sugar for a setup where we
+/// define underlying opaque types (`Foo1`, `Foo2`) and then, in
+/// the return type of `foo`, we *reference* those definitions:
+///
+/// ```text
+/// type Foo1<'x> = impl Bar<'x>;
+/// type Foo2<'x> = impl Bar<'x>;
+/// fn foo<'a, 'b>(..) -> (Foo1<'a>, Foo2<'b>) { .. }
+///                    //  ^^^^ ^^
+///                    //  |    |
+///                    //  |    args
+///                    //  def_id
+/// ```
+///
+/// As indicating in the comments above, each of those references
+/// is (in the compiler) basically generic parameters (`args`)
+/// applied to the type of a suitable `def_id` (which identifies
+/// `Foo1` or `Foo2`).
+///
+/// Now, at this point in compilation, what we have done is to
+/// replace each of the references (`Foo1<'a>`, `Foo2<'b>`) with
+/// fresh inference variables C1 and C2. We wish to use the values
+/// of these variables to infer the underlying types of `Foo1` and
+/// `Foo2`. That is, this gives rise to higher-order (pattern) unification
+/// constraints like:
+///
+/// ```text
+/// for<'a> (Foo1<'a> = C1)
+/// for<'b> (Foo1<'b> = C2)
+/// ```
+///
+/// For these equation to be satisfiable, the types `C1` and `C2`
+/// can only refer to a limited set of regions. For example, `C1`
+/// can only refer to `'static` and `'a`, and `C2` can only refer
+/// to `'static` and `'b`. The job of this function is to impose that
+/// constraint.
+///
+/// Up to this point, C1 and C2 are basically just random type
+/// inference variables, and hence they may contain arbitrary
+/// regions. In fact, it is fairly likely that they do! Consider
+/// this possible definition of `foo`:
+///
+/// ```text
+/// fn foo<'a, 'b>(x: &'a i32, y: &'b i32) -> (impl Bar<'a>, impl Bar<'b>) {
+///         (&*x, &*y)
+///     }
+/// ```
+///
+/// Here, the values for the concrete types of the two impl
+/// traits will include inference variables:
+///
+/// ```text
+/// &'0 i32
+/// &'1 i32
+/// ```
+///
+/// Ordinarily, the subtyping rules would ensure that these are
+/// sufficiently large. But since `impl Bar<'a>` isn't a specific
+/// type per se, we don't get such constraints by default. This
+/// is where this function comes into play. It adds extra
+/// constraints to ensure that all the regions which appear in the
+/// inferred type are regions that could validly appear.
+///
+/// This is actually a bit of a tricky constraint in general. We
+/// want to say that each variable (e.g., `'0`) can only take on
+/// values that were supplied as arguments to the opaque type
+/// (e.g., `'a` for `Foo1<'a>`) or `'static`, which is always in
+/// scope. We don't have a constraint quite of this kind in the current
+/// region checker.
+///
+/// # The Solution
+///
+/// We generally prefer to make `<=` constraints, since they
+/// integrate best into the region solver. To do that, we find the
+/// "minimum" of all the arguments that appear in the args: that
+/// is, some region which is less than all the others. In the case
+/// of `Foo1<'a>`, that would be `'a` (it's the only choice, after
+/// all). Then we apply that as a least bound to the variables
+/// (e.g., `'a <= '0`).
+///
+/// In some cases, there is no minimum. Consider this example:
+///
+/// ```text
+/// fn baz<'a, 'b>() -> impl Trait<'a, 'b> { ... }
+/// ```
+///
+/// Here we would report a more complex "in constraint", like `'r
+/// in ['a, 'b, 'static]` (where `'r` is some region appearing in
+/// the hidden type).
+///
+/// # Constrain regions, not the hidden concrete type
+///
+/// Note that generating constraints on each region `Rc` is *not*
+/// the same as generating an outlives constraint on `Tc` itself.
+/// For example, if we had a function like this:
+///
+/// ```
+/// # #![feature(type_alias_impl_trait)]
+/// # fn main() {}
+/// # trait Foo<'a> {}
+/// # impl<'a, T> Foo<'a> for (&'a u32, T) {}
+/// fn foo<'a, T>(x: &'a u32, y: T) -> impl Foo<'a> {
+///   (x, y)
+/// }
+///
+/// // Equivalent to:
+/// # mod dummy { use super::*;
+/// type FooReturn<'a, T> = impl Foo<'a>;
+/// fn foo<'a, T>(x: &'a u32, y: T) -> FooReturn<'a, T> {
+///   (x, y)
+/// }
+/// # }
+/// ```
+///
+/// then the hidden type `Tc` would be `(&'0 u32, T)` (where `'0`
+/// is an inference variable). If we generated a constraint that
+/// `Tc: 'a`, then this would incorrectly require that `T: 'a` --
+/// but this is not necessary, because the opaque type we
+/// create will be allowed to reference `T`. So we only generate a
+/// constraint that `'0: 'a`.
+fn register_member_constraints<'tcx>(
+    typeck: &mut TypeChecker<'_, 'tcx>,
+    member_constraints: &mut MemberConstraintSet<'tcx, ty::RegionVid>,
+    opaque_type_key: OpaqueTypeKey<'tcx>,
+    OpaqueHiddenType { span, ty: hidden_ty }: OpaqueHiddenType<'tcx>,
+) {
+    let tcx = typeck.tcx();
+    let hidden_ty = typeck.infcx.resolve_vars_if_possible(hidden_ty);
+    debug!(?hidden_ty);
+
+    let variances = tcx.variances_of(opaque_type_key.def_id);
+    debug!(?variances);
+
+    // For a case like `impl Foo<'a, 'b>`, we would generate a constraint
+    // `'r in ['a, 'b, 'static]` for each region `'r` that appears in the
+    // hidden type (i.e., it must be equal to `'a`, `'b`, or `'static`).
+    //
+    // `conflict1` and `conflict2` are the two region bounds that we
+    // detected which were unrelated. They are used for diagnostics.
+
+    // Create the set of choice regions: each region in the hidden
+    // type can be equal to any of the region parameters of the
+    // opaque type definition.
+    let fr_static = typeck.universal_regions.fr_static;
+    let choice_regions: Vec<_> = opaque_type_key
+        .args
+        .iter()
+        .enumerate()
+        .filter(|(i, _)| variances[*i] == ty::Invariant)
+        .filter_map(|(_, arg)| match arg.unpack() {
+            GenericArgKind::Lifetime(r) => Some(typeck.to_region_vid(r)),
+            GenericArgKind::Type(_) | GenericArgKind::Const(_) => None,
+        })
+        .chain(iter::once(fr_static))
+        .collect();
+
+    // FIXME(#42940): This should use the `FreeRegionsVisitor`, but that's
+    // not currently sound until we have existential regions.
+    hidden_ty.visit_with(&mut ConstrainOpaqueTypeRegionVisitor {
+        tcx,
+        op: |r| {
+            member_constraints.add_member_constraint(
+                opaque_type_key,
+                hidden_ty,
+                span,
+                typeck.to_region_vid(r),
+                &choice_regions,
+            )
+        },
+    });
+}
+
+/// Visitor that requires that (almost) all regions in the type visited outlive
+/// `least_region`. We cannot use `push_outlives_components` because regions in
+/// closure signatures are not included in their outlives components. We need to
+/// ensure all regions outlive the given bound so that we don't end up with,
+/// say, `ReVar` appearing in a return type and causing ICEs when other
+/// functions end up with region constraints involving regions from other
+/// functions.
+///
+/// We also cannot use `for_each_free_region` because for closures it includes
+/// the regions parameters from the enclosing item.
+///
+/// We ignore any type parameters because impl trait values are assumed to
+/// capture all the in-scope type parameters.
+struct ConstrainOpaqueTypeRegionVisitor<'tcx, OP: FnMut(ty::Region<'tcx>)> {
+    tcx: TyCtxt<'tcx>,
+    op: OP,
+}
+
+impl<'tcx, OP> TypeVisitor<TyCtxt<'tcx>> for ConstrainOpaqueTypeRegionVisitor<'tcx, OP>
+where
+    OP: FnMut(ty::Region<'tcx>),
+{
+    fn visit_binder<T: TypeVisitable<TyCtxt<'tcx>>>(&mut self, t: &ty::Binder<'tcx, T>) {
+        t.super_visit_with(self);
+    }
+
+    fn visit_region(&mut self, r: ty::Region<'tcx>) {
+        match *r {
+            // ignore bound regions, keep visiting
+            ty::ReBound(_, _) => {}
+            _ => (self.op)(r),
+        }
+    }
+
+    fn visit_ty(&mut self, ty: Ty<'tcx>) {
+        // We're only interested in types involving regions
+        if !ty.flags().intersects(ty::TypeFlags::HAS_FREE_REGIONS) {
+            return;
+        }
+
+        match ty.kind() {
+            ty::Closure(_, args) => {
+                // Skip lifetime parameters of the enclosing item(s)
+
+                for upvar in args.as_closure().upvar_tys() {
+                    upvar.visit_with(self);
+                }
+                args.as_closure().sig_as_fn_ptr_ty().visit_with(self);
+            }
+
+            ty::CoroutineClosure(_, args) => {
+                // Skip lifetime parameters of the enclosing item(s)
+
+                for upvar in args.as_coroutine_closure().upvar_tys() {
+                    upvar.visit_with(self);
+                }
+
+                args.as_coroutine_closure().signature_parts_ty().visit_with(self);
+            }
+
+            ty::Coroutine(_, args) => {
+                // Skip lifetime parameters of the enclosing item(s)
+                // Also skip the witness type, because that has no free regions.
+
+                for upvar in args.as_coroutine().upvar_tys() {
+                    upvar.visit_with(self);
+                }
+                args.as_coroutine().return_ty().visit_with(self);
+                args.as_coroutine().yield_ty().visit_with(self);
+                args.as_coroutine().resume_ty().visit_with(self);
+            }
+
+            ty::Alias(ty::Opaque, ty::AliasTy { def_id, args, .. }) => {
+                // Skip lifetime parameters that are not captures.
+                let variances = self.tcx.variances_of(*def_id);
+
+                for (v, s) in std::iter::zip(variances, args.iter()) {
+                    if *v != ty::Bivariant {
+                        s.visit_with(self);
+                    }
+                }
+            }
+
+            _ => {
+                ty.super_visit_with(self);
+            }
+        }
+    }
+}
diff --git a/compiler/rustc_borrowck/src/type_check/relate_tys.rs b/compiler/rustc_borrowck/src/type_check/relate_tys.rs
index 752b2bf1a24..59e2eee41d3 100644
--- a/compiler/rustc_borrowck/src/type_check/relate_tys.rs
+++ b/compiler/rustc_borrowck/src/type_check/relate_tys.rs
@@ -13,8 +13,7 @@ use rustc_middle::traits::query::NoSolution;
 use rustc_middle::ty::fold::FnMutDelegate;
 use rustc_middle::ty::relate::combine::{super_combine_consts, super_combine_tys};
 use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitableExt};
-use rustc_span::symbol::sym;
-use rustc_span::{Span, Symbol};
+use rustc_span::{Span, Symbol, sym};
 use tracing::{debug, instrument};
 
 use crate::constraints::OutlivesConstraint;
diff --git a/compiler/rustc_borrowck/src/universal_regions.rs b/compiler/rustc_borrowck/src/universal_regions.rs
index bb64d646ff3..1ac45cbea38 100644
--- a/compiler/rustc_borrowck/src/universal_regions.rs
+++ b/compiler/rustc_borrowck/src/universal_regions.rs
@@ -33,8 +33,7 @@ use rustc_middle::ty::{
     TyCtxt, TypeVisitableExt,
 };
 use rustc_middle::{bug, span_bug};
-use rustc_span::ErrorGuaranteed;
-use rustc_span::symbol::{kw, sym};
+use rustc_span::{ErrorGuaranteed, kw, sym};
 use tracing::{debug, instrument};
 
 use crate::BorrowckInferCtxt;
@@ -843,8 +842,9 @@ impl<'tcx> BorrowckInferCtxt<'tcx> {
     {
         let (value, _map) = self.tcx.instantiate_bound_regions(value, |br| {
             debug!(?br);
+            let kind = ty::LateParamRegionKind::from_bound(br.var, br.kind);
             let liberated_region =
-                ty::Region::new_late_param(self.tcx, all_outlive_scope.to_def_id(), br.kind);
+                ty::Region::new_late_param(self.tcx, all_outlive_scope.to_def_id(), kind);
             let region_vid = {
                 let name = match br.kind.get_name() {
                     Some(name) => name,
@@ -881,6 +881,10 @@ impl<'tcx> UniversalRegionIndices<'tcx> {
     /// reference those regions from the `ParamEnv`. It is also used
     /// during initialization. Relies on the `indices` map having been
     /// fully initialized.
+    ///
+    /// Panics if `r` is not a registered universal region, most notably
+    /// if it is a placeholder. Handling placeholders requires access to the
+    /// `MirTypeckRegionConstraints`.
     fn to_region_vid(&self, r: ty::Region<'tcx>) -> RegionVid {
         if let ty::ReVar(..) = *r {
             r.as_var()
@@ -942,12 +946,13 @@ fn for_each_late_bound_region_in_item<'tcx>(
         return;
     }
 
-    for bound_var in tcx.late_bound_vars(tcx.local_def_id_to_hir_id(mir_def_id)) {
-        let ty::BoundVariableKind::Region(bound_region) = bound_var else {
-            continue;
-        };
-        let liberated_region =
-            ty::Region::new_late_param(tcx, mir_def_id.to_def_id(), bound_region);
-        f(liberated_region);
+    for (idx, bound_var) in
+        tcx.late_bound_vars(tcx.local_def_id_to_hir_id(mir_def_id)).iter().enumerate()
+    {
+        if let ty::BoundVariableKind::Region(kind) = bound_var {
+            let kind = ty::LateParamRegionKind::from_bound(ty::BoundVar::from_usize(idx), kind);
+            let liberated_region = ty::Region::new_late_param(tcx, mir_def_id.to_def_id(), kind);
+            f(liberated_region);
+        }
     }
 }
diff --git a/compiler/rustc_builtin_macros/Cargo.toml b/compiler/rustc_builtin_macros/Cargo.toml
index ef48486f6f1..b50cb35b8e9 100644
--- a/compiler/rustc_builtin_macros/Cargo.toml
+++ b/compiler/rustc_builtin_macros/Cargo.toml
@@ -14,7 +14,7 @@ doctest = false
 # tidy-alphabetical-start
 rustc_ast = { path = "../rustc_ast" }
 rustc_ast_pretty = { path = "../rustc_ast_pretty" }
-rustc_attr = { path = "../rustc_attr" }
+rustc_attr_parsing = { path = "../rustc_attr_parsing" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
 rustc_expand = { path = "../rustc_expand" }
diff --git a/compiler/rustc_builtin_macros/messages.ftl b/compiler/rustc_builtin_macros/messages.ftl
index 87d3d288013..7a31d2a2239 100644
--- a/compiler/rustc_builtin_macros/messages.ftl
+++ b/compiler/rustc_builtin_macros/messages.ftl
@@ -249,9 +249,9 @@ builtin_macros_naked_functions_testing_attribute =
     .label = function marked with testing attribute here
     .naked_attribute = `#[naked]` is incompatible with testing attributes
 
-builtin_macros_no_default_variant = no default declared
-    .help = make a unit variant default by placing `#[default]` above it
-    .suggestion = make `{$ident}` default
+builtin_macros_no_default_variant = `#[derive(Default)]` on enum with no `#[default]`
+    .label = this enum needs a unit variant marked with `#[default]`
+    .suggestion = make this unit variant default by placing `#[default]` on it
 
 builtin_macros_non_abi = at least one abi must be provided as an argument to `clobber_abi`
 
diff --git a/compiler/rustc_builtin_macros/src/alloc_error_handler.rs b/compiler/rustc_builtin_macros/src/alloc_error_handler.rs
index 0caad997b9d..d2b4e1ca824 100644
--- a/compiler/rustc_builtin_macros/src/alloc_error_handler.rs
+++ b/compiler/rustc_builtin_macros/src/alloc_error_handler.rs
@@ -3,8 +3,7 @@ use rustc_ast::{
     self as ast, Fn, FnHeader, FnSig, Generics, ItemKind, Safety, Stmt, StmtKind, TyKind,
 };
 use rustc_expand::base::{Annotatable, ExtCtxt};
-use rustc_span::Span;
-use rustc_span::symbol::{Ident, kw, sym};
+use rustc_span::{Ident, Span, kw, sym};
 use thin_vec::{ThinVec, thin_vec};
 
 use crate::errors;
diff --git a/compiler/rustc_builtin_macros/src/asm.rs b/compiler/rustc_builtin_macros/src/asm.rs
index 14ac3cd74e8..6ae697d4030 100644
--- a/compiler/rustc_builtin_macros/src/asm.rs
+++ b/compiler/rustc_builtin_macros/src/asm.rs
@@ -1,17 +1,16 @@
 use ast::token::IdentIsRaw;
 use lint::BuiltinLintDiag;
-use rustc_ast::AsmMacro;
 use rustc_ast::ptr::P;
-use rustc_ast::token::{self, Delimiter};
 use rustc_ast::tokenstream::TokenStream;
+use rustc_ast::{AsmMacro, token};
 use rustc_data_structures::fx::{FxHashMap, FxIndexMap};
 use rustc_errors::PResult;
 use rustc_expand::base::*;
 use rustc_index::bit_set::GrowableBitSet;
-use rustc_parse::parser::Parser;
+use rustc_parse::exp;
+use rustc_parse::parser::{ExpKeywordPair, Parser};
 use rustc_session::lint;
-use rustc_span::symbol::{Ident, Symbol, kw, sym};
-use rustc_span::{ErrorGuaranteed, InnerSpan, Span};
+use rustc_span::{ErrorGuaranteed, Ident, InnerSpan, Span, Symbol, kw};
 use rustc_target::asm::InlineAsmArch;
 use smallvec::smallvec;
 use {rustc_ast as ast, rustc_parse_format as parse};
@@ -39,16 +38,16 @@ pub struct AsmArgs {
 /// - `Err(_)` if the current token matches the keyword, but was not expected
 fn eat_operand_keyword<'a>(
     p: &mut Parser<'a>,
-    symbol: Symbol,
+    exp: ExpKeywordPair,
     asm_macro: AsmMacro,
 ) -> PResult<'a, bool> {
     if matches!(asm_macro, AsmMacro::Asm) {
-        Ok(p.eat_keyword(symbol))
+        Ok(p.eat_keyword(exp))
     } else {
         let span = p.token.span;
-        if p.eat_keyword_noexpect(symbol) {
+        if p.eat_keyword_noexpect(exp.kw) {
             // in gets printed as `r#in` otherwise
-            let symbol = if symbol == kw::In { "in" } else { symbol.as_str() };
+            let symbol = if exp.kw == kw::In { "in" } else { exp.kw.as_str() };
             Err(p.dcx().create_err(errors::AsmUnsupportedOperand {
                 span,
                 symbol,
@@ -96,13 +95,13 @@ pub fn parse_asm_args<'a>(
 
     let mut allow_templates = true;
     while p.token != token::Eof {
-        if !p.eat(&token::Comma) {
+        if !p.eat(exp!(Comma)) {
             if allow_templates {
                 // After a template string, we always expect *only* a comma...
                 return Err(dcx.create_err(errors::AsmExpectedComma { span: p.token.span }));
             } else {
                 // ...after that delegate to `expect` to also include the other expected tokens.
-                return Err(p.expect(&token::Comma).err().unwrap());
+                return Err(p.expect(exp!(Comma)).err().unwrap());
             }
         }
         if p.token == token::Eof {
@@ -110,14 +109,14 @@ pub fn parse_asm_args<'a>(
         } // accept trailing commas
 
         // Parse clobber_abi
-        if p.eat_keyword(sym::clobber_abi) {
+        if p.eat_keyword(exp!(ClobberAbi)) {
             parse_clobber_abi(p, &mut args)?;
             allow_templates = false;
             continue;
         }
 
         // Parse options
-        if p.eat_keyword(sym::options) {
+        if p.eat_keyword(exp!(Options)) {
             parse_options(p, &mut args, asm_macro)?;
             allow_templates = false;
             continue;
@@ -129,7 +128,7 @@ pub fn parse_asm_args<'a>(
         let name = if p.token.is_ident() && p.look_ahead(1, |t| *t == token::Eq) {
             let (ident, _) = p.token.ident().unwrap();
             p.bump();
-            p.expect(&token::Eq)?;
+            p.expect(exp!(Eq))?;
             allow_templates = false;
             Some(ident.name)
         } else {
@@ -137,57 +136,57 @@ pub fn parse_asm_args<'a>(
         };
 
         let mut explicit_reg = false;
-        let op = if eat_operand_keyword(p, kw::In, asm_macro)? {
+        let op = if eat_operand_keyword(p, exp!(In), asm_macro)? {
             let reg = parse_reg(p, &mut explicit_reg)?;
-            if p.eat_keyword(kw::Underscore) {
+            if p.eat_keyword(exp!(Underscore)) {
                 let err = dcx.create_err(errors::AsmUnderscoreInput { span: p.token.span });
                 return Err(err);
             }
             let expr = p.parse_expr()?;
             ast::InlineAsmOperand::In { reg, expr }
-        } else if eat_operand_keyword(p, sym::out, asm_macro)? {
+        } else if eat_operand_keyword(p, exp!(Out), asm_macro)? {
             let reg = parse_reg(p, &mut explicit_reg)?;
-            let expr = if p.eat_keyword(kw::Underscore) { None } else { Some(p.parse_expr()?) };
+            let expr = if p.eat_keyword(exp!(Underscore)) { None } else { Some(p.parse_expr()?) };
             ast::InlineAsmOperand::Out { reg, expr, late: false }
-        } else if eat_operand_keyword(p, sym::lateout, asm_macro)? {
+        } else if eat_operand_keyword(p, exp!(Lateout), asm_macro)? {
             let reg = parse_reg(p, &mut explicit_reg)?;
-            let expr = if p.eat_keyword(kw::Underscore) { None } else { Some(p.parse_expr()?) };
+            let expr = if p.eat_keyword(exp!(Underscore)) { None } else { Some(p.parse_expr()?) };
             ast::InlineAsmOperand::Out { reg, expr, late: true }
-        } else if eat_operand_keyword(p, sym::inout, asm_macro)? {
+        } else if eat_operand_keyword(p, exp!(Inout), asm_macro)? {
             let reg = parse_reg(p, &mut explicit_reg)?;
-            if p.eat_keyword(kw::Underscore) {
+            if p.eat_keyword(exp!(Underscore)) {
                 let err = dcx.create_err(errors::AsmUnderscoreInput { span: p.token.span });
                 return Err(err);
             }
             let expr = p.parse_expr()?;
-            if p.eat(&token::FatArrow) {
+            if p.eat(exp!(FatArrow)) {
                 let out_expr =
-                    if p.eat_keyword(kw::Underscore) { None } else { Some(p.parse_expr()?) };
+                    if p.eat_keyword(exp!(Underscore)) { None } else { Some(p.parse_expr()?) };
                 ast::InlineAsmOperand::SplitInOut { reg, in_expr: expr, out_expr, late: false }
             } else {
                 ast::InlineAsmOperand::InOut { reg, expr, late: false }
             }
-        } else if eat_operand_keyword(p, sym::inlateout, asm_macro)? {
+        } else if eat_operand_keyword(p, exp!(Inlateout), asm_macro)? {
             let reg = parse_reg(p, &mut explicit_reg)?;
-            if p.eat_keyword(kw::Underscore) {
+            if p.eat_keyword(exp!(Underscore)) {
                 let err = dcx.create_err(errors::AsmUnderscoreInput { span: p.token.span });
                 return Err(err);
             }
             let expr = p.parse_expr()?;
-            if p.eat(&token::FatArrow) {
+            if p.eat(exp!(FatArrow)) {
                 let out_expr =
-                    if p.eat_keyword(kw::Underscore) { None } else { Some(p.parse_expr()?) };
+                    if p.eat_keyword(exp!(Underscore)) { None } else { Some(p.parse_expr()?) };
                 ast::InlineAsmOperand::SplitInOut { reg, in_expr: expr, out_expr, late: true }
             } else {
                 ast::InlineAsmOperand::InOut { reg, expr, late: true }
             }
-        } else if eat_operand_keyword(p, sym::label, asm_macro)? {
+        } else if eat_operand_keyword(p, exp!(Label), asm_macro)? {
             let block = p.parse_block()?;
             ast::InlineAsmOperand::Label { block }
-        } else if p.eat_keyword(kw::Const) {
+        } else if p.eat_keyword(exp!(Const)) {
             let anon_const = p.parse_expr_anon_const()?;
             ast::InlineAsmOperand::Const { anon_const }
-        } else if p.eat_keyword(sym::sym) {
+        } else if p.eat_keyword(exp!(Sym)) {
             let expr = p.parse_expr()?;
             let ast::ExprKind::Path(qself, path) = &expr.kind else {
                 let err = dcx.create_err(errors::AsmSymNoPath { span: expr.span });
@@ -390,31 +389,31 @@ fn parse_options<'a>(
 ) -> PResult<'a, ()> {
     let span_start = p.prev_token.span;
 
-    p.expect(&token::OpenDelim(Delimiter::Parenthesis))?;
-
-    while !p.eat(&token::CloseDelim(Delimiter::Parenthesis)) {
-        const OPTIONS: [(Symbol, ast::InlineAsmOptions); ast::InlineAsmOptions::COUNT] = [
-            (sym::pure, ast::InlineAsmOptions::PURE),
-            (sym::nomem, ast::InlineAsmOptions::NOMEM),
-            (sym::readonly, ast::InlineAsmOptions::READONLY),
-            (sym::preserves_flags, ast::InlineAsmOptions::PRESERVES_FLAGS),
-            (sym::noreturn, ast::InlineAsmOptions::NORETURN),
-            (sym::nostack, ast::InlineAsmOptions::NOSTACK),
-            (sym::may_unwind, ast::InlineAsmOptions::MAY_UNWIND),
-            (sym::att_syntax, ast::InlineAsmOptions::ATT_SYNTAX),
-            (kw::Raw, ast::InlineAsmOptions::RAW),
+    p.expect(exp!(OpenParen))?;
+
+    while !p.eat(exp!(CloseParen)) {
+        const OPTIONS: [(ExpKeywordPair, ast::InlineAsmOptions); ast::InlineAsmOptions::COUNT] = [
+            (exp!(Pure), ast::InlineAsmOptions::PURE),
+            (exp!(Nomem), ast::InlineAsmOptions::NOMEM),
+            (exp!(Readonly), ast::InlineAsmOptions::READONLY),
+            (exp!(PreservesFlags), ast::InlineAsmOptions::PRESERVES_FLAGS),
+            (exp!(Noreturn), ast::InlineAsmOptions::NORETURN),
+            (exp!(Nostack), ast::InlineAsmOptions::NOSTACK),
+            (exp!(MayUnwind), ast::InlineAsmOptions::MAY_UNWIND),
+            (exp!(AttSyntax), ast::InlineAsmOptions::ATT_SYNTAX),
+            (exp!(Raw), ast::InlineAsmOptions::RAW),
         ];
 
         'blk: {
-            for (symbol, option) in OPTIONS {
+            for (exp, option) in OPTIONS {
                 let kw_matched = if asm_macro.is_supported_option(option) {
-                    p.eat_keyword(symbol)
+                    p.eat_keyword(exp)
                 } else {
-                    p.eat_keyword_noexpect(symbol)
+                    p.eat_keyword_noexpect(exp.kw)
                 };
 
                 if kw_matched {
-                    try_set_option(p, args, asm_macro, symbol, option);
+                    try_set_option(p, args, asm_macro, exp.kw, option);
                     break 'blk;
                 }
             }
@@ -423,10 +422,10 @@ fn parse_options<'a>(
         }
 
         // Allow trailing commas
-        if p.eat(&token::CloseDelim(Delimiter::Parenthesis)) {
+        if p.eat(exp!(CloseParen)) {
             break;
         }
-        p.expect(&token::Comma)?;
+        p.expect(exp!(Comma))?;
     }
 
     let new_span = span_start.to(p.prev_token.span);
@@ -438,14 +437,14 @@ fn parse_options<'a>(
 fn parse_clobber_abi<'a>(p: &mut Parser<'a>, args: &mut AsmArgs) -> PResult<'a, ()> {
     let span_start = p.prev_token.span;
 
-    p.expect(&token::OpenDelim(Delimiter::Parenthesis))?;
+    p.expect(exp!(OpenParen))?;
 
-    if p.eat(&token::CloseDelim(Delimiter::Parenthesis)) {
+    if p.eat(exp!(CloseParen)) {
         return Err(p.dcx().create_err(errors::NonABI { span: p.token.span }));
     }
 
     let mut new_abis = Vec::new();
-    while !p.eat(&token::CloseDelim(Delimiter::Parenthesis)) {
+    while !p.eat(exp!(CloseParen)) {
         match p.parse_str_lit() {
             Ok(str_lit) => {
                 new_abis.push((str_lit.symbol_unescaped, str_lit.span));
@@ -457,10 +456,10 @@ fn parse_clobber_abi<'a>(p: &mut Parser<'a>, args: &mut AsmArgs) -> PResult<'a,
         };
 
         // Allow trailing commas
-        if p.eat(&token::CloseDelim(Delimiter::Parenthesis)) {
+        if p.eat(exp!(CloseParen)) {
             break;
         }
-        p.expect(&token::Comma)?;
+        p.expect(exp!(Comma))?;
     }
 
     let full_span = span_start.to(p.prev_token.span);
@@ -483,7 +482,7 @@ fn parse_reg<'a>(
     p: &mut Parser<'a>,
     explicit_reg: &mut bool,
 ) -> PResult<'a, ast::InlineAsmRegOrRegClass> {
-    p.expect(&token::OpenDelim(Delimiter::Parenthesis))?;
+    p.expect(exp!(OpenParen))?;
     let result = match p.token.uninterpolate().kind {
         token::Ident(name, IdentIsRaw::No) => ast::InlineAsmRegOrRegClass::RegClass(name),
         token::Literal(token::Lit { kind: token::LitKind::Str, symbol, suffix: _ }) => {
@@ -497,7 +496,7 @@ fn parse_reg<'a>(
         }
     };
     p.bump();
-    p.expect(&token::CloseDelim(Delimiter::Parenthesis))?;
+    p.expect(exp!(CloseParen))?;
     Ok(result)
 }
 
diff --git a/compiler/rustc_builtin_macros/src/assert.rs b/compiler/rustc_builtin_macros/src/assert.rs
index 599b180f879..c659b1cff59 100644
--- a/compiler/rustc_builtin_macros/src/assert.rs
+++ b/compiler/rustc_builtin_macros/src/assert.rs
@@ -7,9 +7,9 @@ use rustc_ast::{DelimArgs, Expr, ExprKind, MacCall, Path, PathSegment, UnOp, tok
 use rustc_ast_pretty::pprust;
 use rustc_errors::PResult;
 use rustc_expand::base::{DummyResult, ExpandResult, ExtCtxt, MacEager, MacroExpanderResult};
+use rustc_parse::exp;
 use rustc_parse::parser::Parser;
-use rustc_span::symbol::{Ident, Symbol, sym};
-use rustc_span::{DUMMY_SP, Span};
+use rustc_span::{DUMMY_SP, Ident, Span, Symbol, sym};
 use thin_vec::thin_vec;
 
 use crate::edition_panic::use_panic_2021;
@@ -144,7 +144,7 @@ fn parse_assert<'a>(cx: &ExtCtxt<'a>, sp: Span, stream: TokenStream) -> PResult<
             cx.dcx().emit_err(errors::AssertMissingComma { span: parser.token.span, comma });
 
             parse_custom_message(&mut parser)
-        } else if parser.eat(&token::Comma) {
+        } else if parser.eat(exp!(Comma)) {
             parse_custom_message(&mut parser)
         } else {
             None
diff --git a/compiler/rustc_builtin_macros/src/assert/context.rs b/compiler/rustc_builtin_macros/src/assert/context.rs
index eb07975d8af..bb9dc651cec 100644
--- a/compiler/rustc_builtin_macros/src/assert/context.rs
+++ b/compiler/rustc_builtin_macros/src/assert/context.rs
@@ -8,8 +8,7 @@ use rustc_ast::{
 use rustc_ast_pretty::pprust;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_expand::base::ExtCtxt;
-use rustc_span::Span;
-use rustc_span::symbol::{Ident, Symbol, sym};
+use rustc_span::{Ident, Span, Symbol, sym};
 use thin_vec::{ThinVec, thin_vec};
 
 pub(super) struct Context<'cx, 'a> {
diff --git a/compiler/rustc_builtin_macros/src/autodiff.rs b/compiler/rustc_builtin_macros/src/autodiff.rs
index 66bb11ca522..8960cf6ab59 100644
--- a/compiler/rustc_builtin_macros/src/autodiff.rs
+++ b/compiler/rustc_builtin_macros/src/autodiff.rs
@@ -20,8 +20,7 @@ mod llvm_enzyme {
         PatKind, TyKind,
     };
     use rustc_expand::base::{Annotatable, ExtCtxt};
-    use rustc_span::symbol::{Ident, kw, sym};
-    use rustc_span::{Span, Symbol};
+    use rustc_span::{Ident, Span, Symbol, kw, sym};
     use thin_vec::{ThinVec, thin_vec};
     use tracing::{debug, trace};
 
@@ -35,7 +34,7 @@ mod llvm_enzyme {
             FnRetTy::Default(_) => false,
         }
     }
-    fn first_ident(x: &MetaItemInner) -> rustc_span::symbol::Ident {
+    fn first_ident(x: &MetaItemInner) -> rustc_span::Ident {
         let segments = &x.meta_item().unwrap().path.segments;
         assert!(segments.len() == 1);
         segments[0].ident
diff --git a/compiler/rustc_builtin_macros/src/cfg.rs b/compiler/rustc_builtin_macros/src/cfg.rs
index 15993dbf5ec..85b8ef79c05 100644
--- a/compiler/rustc_builtin_macros/src/cfg.rs
+++ b/compiler/rustc_builtin_macros/src/cfg.rs
@@ -6,8 +6,9 @@ use rustc_ast::token;
 use rustc_ast::tokenstream::TokenStream;
 use rustc_errors::PResult;
 use rustc_expand::base::{DummyResult, ExpandResult, ExtCtxt, MacEager, MacroExpanderResult};
+use rustc_parse::exp;
 use rustc_span::Span;
-use {rustc_ast as ast, rustc_attr as attr};
+use {rustc_ast as ast, rustc_attr_parsing as attr};
 
 use crate::errors;
 
@@ -48,9 +49,9 @@ fn parse_cfg<'a>(
 
     let cfg = p.parse_meta_item_inner()?;
 
-    let _ = p.eat(&token::Comma);
+    let _ = p.eat(exp!(Comma));
 
-    if !p.eat(&token::Eof) {
+    if !p.eat(exp!(Eof)) {
         return Err(cx.dcx().create_err(errors::OneCfgPattern { span }));
     }
 
diff --git a/compiler/rustc_builtin_macros/src/cfg_accessible.rs b/compiler/rustc_builtin_macros/src/cfg_accessible.rs
index 23578781a83..5f203dd5d11 100644
--- a/compiler/rustc_builtin_macros/src/cfg_accessible.rs
+++ b/compiler/rustc_builtin_macros/src/cfg_accessible.rs
@@ -4,8 +4,7 @@ use rustc_ast as ast;
 use rustc_expand::base::{Annotatable, ExpandResult, ExtCtxt, Indeterminate, MultiItemModifier};
 use rustc_feature::AttributeTemplate;
 use rustc_parse::validate_attr;
-use rustc_span::Span;
-use rustc_span::symbol::sym;
+use rustc_span::{Span, sym};
 
 use crate::errors;
 
diff --git a/compiler/rustc_builtin_macros/src/cfg_eval.rs b/compiler/rustc_builtin_macros/src/cfg_eval.rs
index d46a1bd3d31..53c61831b42 100644
--- a/compiler/rustc_builtin_macros/src/cfg_eval.rs
+++ b/compiler/rustc_builtin_macros/src/cfg_eval.rs
@@ -12,8 +12,7 @@ use rustc_expand::configure;
 use rustc_feature::Features;
 use rustc_parse::parser::{ForceCollect, Parser};
 use rustc_session::Session;
-use rustc_span::Span;
-use rustc_span::symbol::sym;
+use rustc_span::{Span, sym};
 use smallvec::SmallVec;
 use tracing::instrument;
 
diff --git a/compiler/rustc_builtin_macros/src/concat.rs b/compiler/rustc_builtin_macros/src/concat.rs
index a28801f66dd..c200539e128 100644
--- a/compiler/rustc_builtin_macros/src/concat.rs
+++ b/compiler/rustc_builtin_macros/src/concat.rs
@@ -2,7 +2,7 @@ use rustc_ast::tokenstream::TokenStream;
 use rustc_ast::{ExprKind, LitKind, UnOp};
 use rustc_expand::base::{DummyResult, ExpandResult, ExtCtxt, MacEager, MacroExpanderResult};
 use rustc_session::errors::report_lit_error;
-use rustc_span::symbol::Symbol;
+use rustc_span::Symbol;
 
 use crate::errors;
 use crate::util::get_exprs_from_tts;
diff --git a/compiler/rustc_builtin_macros/src/concat_idents.rs b/compiler/rustc_builtin_macros/src/concat_idents.rs
index b459cc3007d..a721f5b84c5 100644
--- a/compiler/rustc_builtin_macros/src/concat_idents.rs
+++ b/compiler/rustc_builtin_macros/src/concat_idents.rs
@@ -3,8 +3,7 @@ use rustc_ast::token::{self, Token};
 use rustc_ast::tokenstream::{TokenStream, TokenTree};
 use rustc_ast::{AttrVec, DUMMY_NODE_ID, Expr, ExprKind, Path, Ty, TyKind};
 use rustc_expand::base::{DummyResult, ExpandResult, ExtCtxt, MacResult, MacroExpanderResult};
-use rustc_span::Span;
-use rustc_span::symbol::{Ident, Symbol};
+use rustc_span::{Ident, Span, Symbol};
 
 use crate::errors;
 
@@ -19,7 +18,7 @@ pub(crate) fn expand_concat_idents<'cx>(
     }
 
     let mut res_str = String::new();
-    for (i, e) in tts.trees().enumerate() {
+    for (i, e) in tts.iter().enumerate() {
         if i & 1 == 1 {
             match e {
                 TokenTree::Token(Token { kind: token::Comma, .. }, _) => {}
diff --git a/compiler/rustc_builtin_macros/src/derive.rs b/compiler/rustc_builtin_macros/src/derive.rs
index 60450d085f6..2653a9f48b9 100644
--- a/compiler/rustc_builtin_macros/src/derive.rs
+++ b/compiler/rustc_builtin_macros/src/derive.rs
@@ -6,8 +6,7 @@ use rustc_expand::base::{
 use rustc_feature::AttributeTemplate;
 use rustc_parse::validate_attr;
 use rustc_session::Session;
-use rustc_span::symbol::{Ident, sym};
-use rustc_span::{ErrorGuaranteed, Span};
+use rustc_span::{ErrorGuaranteed, Ident, Span, sym};
 
 use crate::cfg_eval::cfg_eval;
 use crate::errors;
diff --git a/compiler/rustc_builtin_macros/src/deriving/clone.rs b/compiler/rustc_builtin_macros/src/deriving/clone.rs
index f79227d52a8..78f50ba8d29 100644
--- a/compiler/rustc_builtin_macros/src/deriving/clone.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/clone.rs
@@ -1,8 +1,7 @@
 use rustc_ast::{self as ast, Generics, ItemKind, MetaItem, VariantData};
 use rustc_data_structures::fx::FxHashSet;
 use rustc_expand::base::{Annotatable, ExtCtxt};
-use rustc_span::Span;
-use rustc_span::symbol::{Ident, kw, sym};
+use rustc_span::{Ident, Span, kw, sym};
 use thin_vec::{ThinVec, thin_vec};
 
 use crate::deriving::generic::ty::*;
diff --git a/compiler/rustc_builtin_macros/src/deriving/cmp/eq.rs b/compiler/rustc_builtin_macros/src/deriving/cmp/eq.rs
index bd6f4eb8d99..5790350203a 100644
--- a/compiler/rustc_builtin_macros/src/deriving/cmp/eq.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/cmp/eq.rs
@@ -1,8 +1,7 @@
 use rustc_ast::{self as ast, MetaItem};
 use rustc_data_structures::fx::FxHashSet;
 use rustc_expand::base::{Annotatable, ExtCtxt};
-use rustc_span::Span;
-use rustc_span::symbol::sym;
+use rustc_span::{Span, sym};
 use thin_vec::{ThinVec, thin_vec};
 
 use crate::deriving::generic::ty::*;
diff --git a/compiler/rustc_builtin_macros/src/deriving/cmp/ord.rs b/compiler/rustc_builtin_macros/src/deriving/cmp/ord.rs
index 433cbfaa6cb..1ed44c20bc6 100644
--- a/compiler/rustc_builtin_macros/src/deriving/cmp/ord.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/cmp/ord.rs
@@ -1,7 +1,6 @@
 use rustc_ast::MetaItem;
 use rustc_expand::base::{Annotatable, ExtCtxt};
-use rustc_span::Span;
-use rustc_span::symbol::{Ident, sym};
+use rustc_span::{Ident, Span, sym};
 use thin_vec::thin_vec;
 
 use crate::deriving::generic::ty::*;
diff --git a/compiler/rustc_builtin_macros/src/deriving/cmp/partial_eq.rs b/compiler/rustc_builtin_macros/src/deriving/cmp/partial_eq.rs
index ae1e5f4a219..4b93b3414c7 100644
--- a/compiler/rustc_builtin_macros/src/deriving/cmp/partial_eq.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/cmp/partial_eq.rs
@@ -1,8 +1,7 @@
 use rustc_ast::ptr::P;
 use rustc_ast::{BinOpKind, BorrowKind, Expr, ExprKind, MetaItem, Mutability};
 use rustc_expand::base::{Annotatable, ExtCtxt};
-use rustc_span::Span;
-use rustc_span::symbol::sym;
+use rustc_span::{Span, sym};
 use thin_vec::thin_vec;
 
 use crate::deriving::generic::ty::*;
diff --git a/compiler/rustc_builtin_macros/src/deriving/cmp/partial_ord.rs b/compiler/rustc_builtin_macros/src/deriving/cmp/partial_ord.rs
index 99a98325053..7958e037555 100644
--- a/compiler/rustc_builtin_macros/src/deriving/cmp/partial_ord.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/cmp/partial_ord.rs
@@ -1,7 +1,6 @@
 use rustc_ast::{ExprKind, ItemKind, MetaItem, PatKind};
 use rustc_expand::base::{Annotatable, ExtCtxt};
-use rustc_span::Span;
-use rustc_span::symbol::{Ident, sym};
+use rustc_span::{Ident, Span, sym};
 use thin_vec::thin_vec;
 
 use crate::deriving::generic::ty::*;
diff --git a/compiler/rustc_builtin_macros/src/deriving/coerce_pointee.rs b/compiler/rustc_builtin_macros/src/deriving/coerce_pointee.rs
index 3bd8f899a4a..49706db0e0b 100644
--- a/compiler/rustc_builtin_macros/src/deriving/coerce_pointee.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/coerce_pointee.rs
@@ -6,12 +6,11 @@ use rustc_ast::{
     self as ast, GenericArg, GenericBound, GenericParamKind, ItemKind, MetaItem,
     TraitBoundModifiers, VariantData, WherePredicate,
 };
-use rustc_attr as attr;
+use rustc_attr_parsing as attr;
 use rustc_data_structures::flat_map_in_place::FlatMapInPlace;
 use rustc_expand::base::{Annotatable, ExtCtxt};
 use rustc_macros::Diagnostic;
-use rustc_span::symbol::{Ident, sym};
-use rustc_span::{Span, Symbol};
+use rustc_span::{Ident, Span, Symbol, sym};
 use thin_vec::{ThinVec, thin_vec};
 
 use crate::errors;
diff --git a/compiler/rustc_builtin_macros/src/deriving/debug.rs b/compiler/rustc_builtin_macros/src/deriving/debug.rs
index 06a598cf3b0..eb01ca3941d 100644
--- a/compiler/rustc_builtin_macros/src/deriving/debug.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/debug.rs
@@ -1,8 +1,7 @@
 use rustc_ast::{self as ast, EnumDef, MetaItem};
 use rustc_expand::base::{Annotatable, ExtCtxt};
 use rustc_session::config::FmtDebug;
-use rustc_span::Span;
-use rustc_span::symbol::{Ident, Symbol, sym};
+use rustc_span::{Ident, Span, Symbol, sym};
 use thin_vec::{ThinVec, thin_vec};
 
 use crate::deriving::generic::ty::*;
diff --git a/compiler/rustc_builtin_macros/src/deriving/decodable.rs b/compiler/rustc_builtin_macros/src/deriving/decodable.rs
index 469092e7b1c..6348560496e 100644
--- a/compiler/rustc_builtin_macros/src/deriving/decodable.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/decodable.rs
@@ -3,8 +3,7 @@
 use rustc_ast::ptr::P;
 use rustc_ast::{self as ast, Expr, MetaItem, Mutability};
 use rustc_expand::base::{Annotatable, ExtCtxt};
-use rustc_span::Span;
-use rustc_span::symbol::{Ident, Symbol, sym};
+use rustc_span::{Ident, Span, Symbol, sym};
 use thin_vec::{ThinVec, thin_vec};
 
 use crate::deriving::generic::ty::*;
diff --git a/compiler/rustc_builtin_macros/src/deriving/default.rs b/compiler/rustc_builtin_macros/src/deriving/default.rs
index 6b1a6effad7..3c7bebd0f19 100644
--- a/compiler/rustc_builtin_macros/src/deriving/default.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/default.rs
@@ -4,8 +4,7 @@ use rustc_ast as ast;
 use rustc_ast::visit::visit_opt;
 use rustc_ast::{EnumDef, VariantData, attr};
 use rustc_expand::base::{Annotatable, DummyResult, ExtCtxt};
-use rustc_span::symbol::{Ident, kw, sym};
-use rustc_span::{ErrorGuaranteed, Span};
+use rustc_span::{ErrorGuaranteed, Ident, Span, kw, sym};
 use smallvec::SmallVec;
 use thin_vec::{ThinVec, thin_vec};
 
@@ -43,7 +42,9 @@ pub(crate) fn expand_deriving_default(
                     StaticStruct(_, fields) => {
                         default_struct_substructure(cx, trait_span, substr, fields)
                     }
-                    StaticEnum(enum_def, _) => default_enum_substructure(cx, trait_span, enum_def),
+                    StaticEnum(enum_def, _) => {
+                        default_enum_substructure(cx, trait_span, enum_def, item.span())
+                    }
                     _ => cx.dcx().span_bug(trait_span, "method in `derive(Default)`"),
                 }
             })),
@@ -97,9 +98,10 @@ fn default_enum_substructure(
     cx: &ExtCtxt<'_>,
     trait_span: Span,
     enum_def: &EnumDef,
+    item_span: Span,
 ) -> BlockOrExpr {
     let expr = match try {
-        let default_variant = extract_default_variant(cx, enum_def, trait_span)?;
+        let default_variant = extract_default_variant(cx, enum_def, trait_span, item_span)?;
         validate_default_attribute(cx, default_variant)?;
         default_variant
     } {
@@ -147,6 +149,7 @@ fn extract_default_variant<'a>(
     cx: &ExtCtxt<'_>,
     enum_def: &'a EnumDef,
     trait_span: Span,
+    item_span: Span,
 ) -> Result<&'a rustc_ast::Variant, ErrorGuaranteed> {
     let default_variants: SmallVec<[_; 1]> = enum_def
         .variants
@@ -164,9 +167,10 @@ fn extract_default_variant<'a>(
                 .filter(|variant| !attr::contains_name(&variant.attrs, sym::non_exhaustive));
 
             let suggs = possible_defaults
-                .map(|v| errors::NoDefaultVariantSugg { span: v.span, ident: v.ident })
+                .map(|v| errors::NoDefaultVariantSugg { span: v.span.shrink_to_lo() })
                 .collect();
-            let guar = cx.dcx().emit_err(errors::NoDefaultVariant { span: trait_span, suggs });
+            let guar =
+                cx.dcx().emit_err(errors::NoDefaultVariant { span: trait_span, item_span, suggs });
 
             return Err(guar);
         }
diff --git a/compiler/rustc_builtin_macros/src/deriving/encodable.rs b/compiler/rustc_builtin_macros/src/deriving/encodable.rs
index 5c7583f2a77..20aacb2caca 100644
--- a/compiler/rustc_builtin_macros/src/deriving/encodable.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/encodable.rs
@@ -87,8 +87,7 @@
 
 use rustc_ast::{AttrVec, ExprKind, MetaItem, Mutability};
 use rustc_expand::base::{Annotatable, ExtCtxt};
-use rustc_span::Span;
-use rustc_span::symbol::{Ident, Symbol, sym};
+use rustc_span::{Ident, Span, Symbol, sym};
 use thin_vec::{ThinVec, thin_vec};
 
 use crate::deriving::generic::ty::*;
diff --git a/compiler/rustc_builtin_macros/src/deriving/generic/mod.rs b/compiler/rustc_builtin_macros/src/deriving/generic/mod.rs
index 846d8784dea..f0a5e44e066 100644
--- a/compiler/rustc_builtin_macros/src/deriving/generic/mod.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/generic/mod.rs
@@ -185,10 +185,9 @@ use rustc_ast::{
     self as ast, AnonConst, BindingMode, ByRef, EnumDef, Expr, GenericArg, GenericParamKind,
     Generics, Mutability, PatKind, VariantData,
 };
-use rustc_attr as attr;
+use rustc_attr_parsing as attr;
 use rustc_expand::base::{Annotatable, ExtCtxt};
-use rustc_span::symbol::{Ident, Symbol, kw, sym};
-use rustc_span::{DUMMY_SP, Span};
+use rustc_span::{DUMMY_SP, Ident, Span, Symbol, kw, sym};
 use thin_vec::{ThinVec, thin_vec};
 use ty::{Bounds, Path, Ref, Self_, Ty};
 
diff --git a/compiler/rustc_builtin_macros/src/deriving/generic/ty.rs b/compiler/rustc_builtin_macros/src/deriving/generic/ty.rs
index b118cbfbd91..af6dc62db7a 100644
--- a/compiler/rustc_builtin_macros/src/deriving/generic/ty.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/generic/ty.rs
@@ -6,8 +6,7 @@ use rustc_ast::ptr::P;
 use rustc_ast::{self as ast, Expr, GenericArg, GenericParamKind, Generics, SelfKind};
 use rustc_expand::base::ExtCtxt;
 use rustc_span::source_map::respan;
-use rustc_span::symbol::{Ident, Symbol, kw};
-use rustc_span::{DUMMY_SP, Span};
+use rustc_span::{DUMMY_SP, Ident, Span, Symbol, kw};
 use thin_vec::ThinVec;
 
 /// A path, e.g., `::std::option::Option::<i32>` (global). Has support
diff --git a/compiler/rustc_builtin_macros/src/deriving/hash.rs b/compiler/rustc_builtin_macros/src/deriving/hash.rs
index 2d1f5b70f77..6e6dbe19e4d 100644
--- a/compiler/rustc_builtin_macros/src/deriving/hash.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/hash.rs
@@ -1,7 +1,6 @@
 use rustc_ast::{MetaItem, Mutability};
 use rustc_expand::base::{Annotatable, ExtCtxt};
-use rustc_span::Span;
-use rustc_span::symbol::sym;
+use rustc_span::{Span, sym};
 use thin_vec::thin_vec;
 
 use crate::deriving::generic::ty::*;
diff --git a/compiler/rustc_builtin_macros/src/deriving/mod.rs b/compiler/rustc_builtin_macros/src/deriving/mod.rs
index 681fbd1651d..ec058b41313 100644
--- a/compiler/rustc_builtin_macros/src/deriving/mod.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/mod.rs
@@ -4,8 +4,7 @@ use rustc_ast as ast;
 use rustc_ast::ptr::P;
 use rustc_ast::{GenericArg, MetaItem};
 use rustc_expand::base::{Annotatable, ExpandResult, ExtCtxt, MultiItemModifier};
-use rustc_span::Span;
-use rustc_span::symbol::{Symbol, sym};
+use rustc_span::{Span, Symbol, sym};
 use thin_vec::{ThinVec, thin_vec};
 
 macro path_local($x:ident) {
diff --git a/compiler/rustc_builtin_macros/src/edition_panic.rs b/compiler/rustc_builtin_macros/src/edition_panic.rs
index c4164a7db9a..b39c9861fd6 100644
--- a/compiler/rustc_builtin_macros/src/edition_panic.rs
+++ b/compiler/rustc_builtin_macros/src/edition_panic.rs
@@ -3,9 +3,8 @@ use rustc_ast::token::Delimiter;
 use rustc_ast::tokenstream::{DelimSpan, TokenStream};
 use rustc_ast::*;
 use rustc_expand::base::*;
-use rustc_span::Span;
 use rustc_span::edition::Edition;
-use rustc_span::symbol::sym;
+use rustc_span::{Span, sym};
 
 /// This expands to either
 /// - `$crate::panic::panic_2015!(...)` or
diff --git a/compiler/rustc_builtin_macros/src/env.rs b/compiler/rustc_builtin_macros/src/env.rs
index 43e2bf1796f..8831261759c 100644
--- a/compiler/rustc_builtin_macros/src/env.rs
+++ b/compiler/rustc_builtin_macros/src/env.rs
@@ -10,8 +10,7 @@ use rustc_ast::token::{self, LitKind};
 use rustc_ast::tokenstream::TokenStream;
 use rustc_ast::{AstDeref, ExprKind, GenericArg, Mutability};
 use rustc_expand::base::{DummyResult, ExpandResult, ExtCtxt, MacEager, MacroExpanderResult};
-use rustc_span::Span;
-use rustc_span::symbol::{Ident, Symbol, kw, sym};
+use rustc_span::{Ident, Span, Symbol, kw, sym};
 use thin_vec::thin_vec;
 
 use crate::errors;
diff --git a/compiler/rustc_builtin_macros/src/errors.rs b/compiler/rustc_builtin_macros/src/errors.rs
index c9bd3371e55..1abdfdb9c65 100644
--- a/compiler/rustc_builtin_macros/src/errors.rs
+++ b/compiler/rustc_builtin_macros/src/errors.rs
@@ -4,8 +4,7 @@ use rustc_errors::{
     SubdiagMessageOp, Subdiagnostic,
 };
 use rustc_macros::{Diagnostic, Subdiagnostic};
-use rustc_span::symbol::Ident;
-use rustc_span::{Span, Symbol};
+use rustc_span::{Ident, Span, Symbol};
 
 #[derive(Diagnostic)]
 #[diag(builtin_macros_requires_cfg_pattern)]
@@ -370,26 +369,21 @@ pub(crate) struct DerivePathArgsValue {
 }
 
 #[derive(Diagnostic)]
-#[diag(builtin_macros_no_default_variant)]
-#[help]
+#[diag(builtin_macros_no_default_variant, code = E0665)]
 pub(crate) struct NoDefaultVariant {
     #[primary_span]
     pub(crate) span: Span,
+    #[label]
+    pub(crate) item_span: Span,
     #[subdiagnostic]
     pub(crate) suggs: Vec<NoDefaultVariantSugg>,
 }
 
 #[derive(Subdiagnostic)]
-#[suggestion(
-    builtin_macros_suggestion,
-    code = "#[default] {ident}",
-    applicability = "maybe-incorrect",
-    style = "tool-only"
-)]
+#[suggestion(builtin_macros_suggestion, code = "#[default] ", applicability = "maybe-incorrect")]
 pub(crate) struct NoDefaultVariantSugg {
     #[primary_span]
     pub(crate) span: Span,
-    pub(crate) ident: Ident,
 }
 
 #[derive(Diagnostic)]
diff --git a/compiler/rustc_builtin_macros/src/format.rs b/compiler/rustc_builtin_macros/src/format.rs
index 32730ac3867..528eb7725f5 100644
--- a/compiler/rustc_builtin_macros/src/format.rs
+++ b/compiler/rustc_builtin_macros/src/format.rs
@@ -12,9 +12,9 @@ use rustc_errors::{Applicability, Diag, MultiSpan, PResult, SingleLabelManySpans
 use rustc_expand::base::*;
 use rustc_lint_defs::builtin::NAMED_ARGUMENTS_USED_POSITIONALLY;
 use rustc_lint_defs::{BufferedEarlyLint, BuiltinLintDiag, LintId};
+use rustc_parse::exp;
 use rustc_parse_format as parse;
-use rustc_span::symbol::{Ident, Symbol};
-use rustc_span::{BytePos, ErrorGuaranteed, InnerSpan, Span};
+use rustc_span::{BytePos, ErrorGuaranteed, Ident, InnerSpan, Span, Symbol};
 
 use crate::errors;
 use crate::util::expr_to_spanned_string;
@@ -94,12 +94,12 @@ fn parse_args<'a>(ecx: &ExtCtxt<'a>, sp: Span, tts: TokenStream) -> PResult<'a,
     let mut first = true;
 
     while p.token != token::Eof {
-        if !p.eat(&token::Comma) {
+        if !p.eat(exp!(Comma)) {
             if first {
-                p.clear_expected_tokens();
+                p.clear_expected_token_types();
             }
 
-            match p.expect(&token::Comma) {
+            match p.expect(exp!(Comma)) {
                 Err(err) => {
                     match token::TokenKind::Comma.similar_tokens() {
                         Some(tks) if tks.contains(&p.token.kind) => {
@@ -123,7 +123,7 @@ fn parse_args<'a>(ecx: &ExtCtxt<'a>, sp: Span, tts: TokenStream) -> PResult<'a,
         match p.token.ident() {
             Some((ident, _)) if p.look_ahead(1, |t| *t == token::Eq) => {
                 p.bump();
-                p.expect(&token::Eq)?;
+                p.expect(exp!(Eq))?;
                 let expr = p.parse_expr()?;
                 if let Some((_, prev)) = args.by_name(ident.name) {
                     ecx.dcx().emit_err(errors::FormatDuplicateArg {
diff --git a/compiler/rustc_builtin_macros/src/global_allocator.rs b/compiler/rustc_builtin_macros/src/global_allocator.rs
index b4b18409a18..8388e9dcafb 100644
--- a/compiler/rustc_builtin_macros/src/global_allocator.rs
+++ b/compiler/rustc_builtin_macros/src/global_allocator.rs
@@ -7,8 +7,7 @@ use rustc_ast::{
     Stmt, StmtKind, Ty, TyKind,
 };
 use rustc_expand::base::{Annotatable, ExtCtxt};
-use rustc_span::Span;
-use rustc_span::symbol::{Ident, Symbol, kw, sym};
+use rustc_span::{Ident, Span, Symbol, kw, sym};
 use thin_vec::{ThinVec, thin_vec};
 
 use crate::errors;
diff --git a/compiler/rustc_builtin_macros/src/lib.rs b/compiler/rustc_builtin_macros/src/lib.rs
index cc4a974e757..6071d36f8eb 100644
--- a/compiler/rustc_builtin_macros/src/lib.rs
+++ b/compiler/rustc_builtin_macros/src/lib.rs
@@ -24,7 +24,7 @@ extern crate proc_macro;
 
 use rustc_expand::base::{MacroExpanderFn, ResolverExpand, SyntaxExtensionKind};
 use rustc_expand::proc_macro::BangProcMacro;
-use rustc_span::symbol::sym;
+use rustc_span::sym;
 
 use crate::deriving::*;
 
diff --git a/compiler/rustc_builtin_macros/src/pattern_type.rs b/compiler/rustc_builtin_macros/src/pattern_type.rs
index 90b5f097b32..a600a9f316a 100644
--- a/compiler/rustc_builtin_macros/src/pattern_type.rs
+++ b/compiler/rustc_builtin_macros/src/pattern_type.rs
@@ -3,7 +3,8 @@ use rustc_ast::tokenstream::TokenStream;
 use rustc_ast::{Pat, Ty, ast};
 use rustc_errors::PResult;
 use rustc_expand::base::{self, DummyResult, ExpandResult, ExtCtxt, MacroExpanderResult};
-use rustc_span::{Span, sym};
+use rustc_parse::exp;
+use rustc_span::Span;
 
 pub(crate) fn expand<'cx>(
     cx: &'cx mut ExtCtxt<'_>,
@@ -24,7 +25,7 @@ fn parse_pat_ty<'a>(cx: &mut ExtCtxt<'a>, stream: TokenStream) -> PResult<'a, (P
     let mut parser = cx.new_parser_from_tts(stream);
 
     let ty = parser.parse_ty()?;
-    parser.expect_keyword(sym::is)?;
+    parser.expect_keyword(exp!(Is))?;
     let pat = parser.parse_pat_no_top_alt(None, None)?;
 
     Ok((ty, pat))
diff --git a/compiler/rustc_builtin_macros/src/proc_macro_harness.rs b/compiler/rustc_builtin_macros/src/proc_macro_harness.rs
index 707c36d5046..dee185ff0c9 100644
--- a/compiler/rustc_builtin_macros/src/proc_macro_harness.rs
+++ b/compiler/rustc_builtin_macros/src/proc_macro_harness.rs
@@ -11,8 +11,7 @@ use rustc_feature::Features;
 use rustc_session::Session;
 use rustc_span::hygiene::AstPass;
 use rustc_span::source_map::SourceMap;
-use rustc_span::symbol::{Ident, Symbol, kw, sym};
-use rustc_span::{DUMMY_SP, Span};
+use rustc_span::{DUMMY_SP, Ident, Span, Symbol, kw, sym};
 use smallvec::smallvec;
 use thin_vec::{ThinVec, thin_vec};
 
diff --git a/compiler/rustc_builtin_macros/src/source_util.rs b/compiler/rustc_builtin_macros/src/source_util.rs
index 946fbe918e6..123b96f6bca 100644
--- a/compiler/rustc_builtin_macros/src/source_util.rs
+++ b/compiler/rustc_builtin_macros/src/source_util.rs
@@ -16,8 +16,7 @@ use rustc_parse::parser::{ForceCollect, Parser};
 use rustc_parse::{new_parser_from_file, unwrap_or_emit_fatal};
 use rustc_session::lint::builtin::INCOMPLETE_INCLUDE;
 use rustc_span::source_map::SourceMap;
-use rustc_span::symbol::Symbol;
-use rustc_span::{Pos, Span};
+use rustc_span::{Pos, Span, Symbol};
 use smallvec::SmallVec;
 
 use crate::errors;
diff --git a/compiler/rustc_builtin_macros/src/standard_library_imports.rs b/compiler/rustc_builtin_macros/src/standard_library_imports.rs
index a3fc53344ab..1a3f4d2d449 100644
--- a/compiler/rustc_builtin_macros/src/standard_library_imports.rs
+++ b/compiler/rustc_builtin_macros/src/standard_library_imports.rs
@@ -3,10 +3,9 @@ use rustc_expand::base::{ExtCtxt, ResolverExpand};
 use rustc_expand::expand::ExpansionConfig;
 use rustc_feature::Features;
 use rustc_session::Session;
-use rustc_span::DUMMY_SP;
 use rustc_span::edition::Edition::*;
 use rustc_span::hygiene::AstPass;
-use rustc_span::symbol::{Ident, Symbol, kw, sym};
+use rustc_span::{DUMMY_SP, Ident, Symbol, kw, sym};
 use thin_vec::thin_vec;
 
 pub fn inject(
diff --git a/compiler/rustc_builtin_macros/src/test.rs b/compiler/rustc_builtin_macros/src/test.rs
index 664e935ee14..3f73ddbdd29 100644
--- a/compiler/rustc_builtin_macros/src/test.rs
+++ b/compiler/rustc_builtin_macros/src/test.rs
@@ -9,8 +9,7 @@ use rustc_ast::{self as ast, GenericParamKind, attr};
 use rustc_ast_pretty::pprust;
 use rustc_errors::{Applicability, Diag, Level};
 use rustc_expand::base::*;
-use rustc_span::symbol::{Ident, Symbol, sym};
-use rustc_span::{ErrorGuaranteed, FileNameDisplayPreference, Span};
+use rustc_span::{ErrorGuaranteed, FileNameDisplayPreference, Ident, Span, Symbol, sym};
 use thin_vec::{ThinVec, thin_vec};
 use tracing::debug;
 
diff --git a/compiler/rustc_builtin_macros/src/test_harness.rs b/compiler/rustc_builtin_macros/src/test_harness.rs
index e7ff65e08f9..46446598943 100644
--- a/compiler/rustc_builtin_macros/src/test_harness.rs
+++ b/compiler/rustc_builtin_macros/src/test_harness.rs
@@ -16,8 +16,7 @@ use rustc_lint_defs::BuiltinLintDiag;
 use rustc_session::Session;
 use rustc_session::lint::builtin::UNNAMEABLE_TEST_ITEMS;
 use rustc_span::hygiene::{AstPass, SyntaxContext, Transparency};
-use rustc_span::symbol::{Ident, Symbol, sym};
-use rustc_span::{DUMMY_SP, Span};
+use rustc_span::{DUMMY_SP, Ident, Span, Symbol, sym};
 use rustc_target::spec::PanicStrategy;
 use smallvec::smallvec;
 use thin_vec::{ThinVec, thin_vec};
diff --git a/compiler/rustc_builtin_macros/src/trace_macros.rs b/compiler/rustc_builtin_macros/src/trace_macros.rs
index e624d1da66b..8264c17b4d1 100644
--- a/compiler/rustc_builtin_macros/src/trace_macros.rs
+++ b/compiler/rustc_builtin_macros/src/trace_macros.rs
@@ -1,7 +1,6 @@
 use rustc_ast::tokenstream::{TokenStream, TokenTree};
 use rustc_expand::base::{DummyResult, ExpandResult, ExtCtxt, MacroExpanderResult};
-use rustc_span::Span;
-use rustc_span::symbol::kw;
+use rustc_span::{Span, kw};
 
 use crate::errors;
 
@@ -10,9 +9,9 @@ pub(crate) fn expand_trace_macros(
     sp: Span,
     tt: TokenStream,
 ) -> MacroExpanderResult<'static> {
-    let mut cursor = tt.trees();
+    let mut iter = tt.iter();
     let mut err = false;
-    let value = match &cursor.next() {
+    let value = match iter.next() {
         Some(TokenTree::Token(token, _)) if token.is_keyword(kw::True) => true,
         Some(TokenTree::Token(token, _)) if token.is_keyword(kw::False) => false,
         _ => {
@@ -20,7 +19,7 @@ pub(crate) fn expand_trace_macros(
             false
         }
     };
-    err |= cursor.next().is_some();
+    err |= iter.next().is_some();
     if err {
         cx.dcx().emit_err(errors::TraceMacros { span: sp });
     } else {
diff --git a/compiler/rustc_builtin_macros/src/util.rs b/compiler/rustc_builtin_macros/src/util.rs
index 2a28dfaf3c4..be12d21a800 100644
--- a/compiler/rustc_builtin_macros/src/util.rs
+++ b/compiler/rustc_builtin_macros/src/util.rs
@@ -7,7 +7,7 @@ use rustc_expand::expand::AstFragment;
 use rustc_feature::AttributeTemplate;
 use rustc_lint_defs::BuiltinLintDiag;
 use rustc_lint_defs::builtin::DUPLICATE_MACRO_ATTRIBUTES;
-use rustc_parse::{parser, validate_attr};
+use rustc_parse::{exp, parser, validate_attr};
 use rustc_session::errors::report_lit_error;
 use rustc_span::{BytePos, Span, Symbol};
 
@@ -204,7 +204,7 @@ pub(crate) fn get_single_expr_from_tts(
         Ok(ret) => ret,
         Err(guar) => return ExpandResult::Ready(Err(guar)),
     };
-    let _ = p.eat(&token::Comma);
+    let _ = p.eat(exp!(Comma));
 
     if p.token != token::Eof {
         cx.dcx().emit_err(errors::OnlyOneArgument { span, name });
@@ -237,7 +237,7 @@ pub(crate) fn get_exprs_from_tts(
         let expr = cx.expander().fully_expand_fragment(AstFragment::Expr(expr)).make_expr();
 
         es.push(expr);
-        if p.eat(&token::Comma) {
+        if p.eat(exp!(Comma)) {
             continue;
         }
         if p.token != token::Eof {
diff --git a/compiler/rustc_codegen_cranelift/src/compiler_builtins.rs b/compiler/rustc_codegen_cranelift/src/compiler_builtins.rs
index 4154a62234c..f8e3a034421 100644
--- a/compiler/rustc_codegen_cranelift/src/compiler_builtins.rs
+++ b/compiler/rustc_codegen_cranelift/src/compiler_builtins.rs
@@ -3,7 +3,7 @@ use std::ffi::c_int;
 #[cfg(feature = "jit")]
 use std::ffi::c_void;
 
-// FIXME replace with core::ffi::c_size_t once stablized
+// FIXME replace with core::ffi::c_size_t once stabilized
 #[allow(non_camel_case_types)]
 #[cfg(feature = "jit")]
 type size_t = usize;
diff --git a/compiler/rustc_codegen_cranelift/src/discriminant.rs b/compiler/rustc_codegen_cranelift/src/discriminant.rs
index 45794a42665..4d0d5dc60eb 100644
--- a/compiler/rustc_codegen_cranelift/src/discriminant.rs
+++ b/compiler/rustc_codegen_cranelift/src/discriminant.rs
@@ -18,6 +18,7 @@ pub(crate) fn codegen_set_discriminant<'tcx>(
         return;
     }
     match layout.variants {
+        Variants::Empty => unreachable!("we already handled uninhabited types"),
         Variants::Single { index } => {
             assert_eq!(index, variant_index);
         }
@@ -85,6 +86,7 @@ pub(crate) fn codegen_get_discriminant<'tcx>(
     }
 
     let (tag_scalar, tag_field, tag_encoding) = match &layout.variants {
+        Variants::Empty => unreachable!("we already handled uninhabited types"),
         Variants::Single { index } => {
             let discr_val = layout
                 .ty
diff --git a/compiler/rustc_codegen_cranelift/src/driver/jit.rs b/compiler/rustc_codegen_cranelift/src/driver/jit.rs
index 4be4291021d..eaab3362c7e 100644
--- a/compiler/rustc_codegen_cranelift/src/driver/jit.rs
+++ b/compiler/rustc_codegen_cranelift/src/driver/jit.rs
@@ -294,7 +294,7 @@ fn dep_symbol_lookup_fn(
     // search path.
     for &cnum in crate_info.used_crates.iter().rev() {
         let src = &crate_info.used_crate_source[&cnum];
-        match data[cnum.as_usize() - 1] {
+        match data[cnum] {
             Linkage::NotLinked | Linkage::IncludedFromDylib => {}
             Linkage::Static => {
                 let name = crate_info.crate_name[&cnum];
diff --git a/compiler/rustc_codegen_cranelift/src/intrinsics/mod.rs b/compiler/rustc_codegen_cranelift/src/intrinsics/mod.rs
index 5f1b71eff6b..2e5813556aa 100644
--- a/compiler/rustc_codegen_cranelift/src/intrinsics/mod.rs
+++ b/compiler/rustc_codegen_cranelift/src/intrinsics/mod.rs
@@ -23,7 +23,7 @@ use rustc_middle::ty::GenericArgsRef;
 use rustc_middle::ty::layout::ValidityRequirement;
 use rustc_middle::ty::print::{with_no_trimmed_paths, with_no_visible_paths};
 use rustc_span::source_map::Spanned;
-use rustc_span::symbol::{Symbol, sym};
+use rustc_span::{Symbol, sym};
 
 pub(crate) use self::llvm::codegen_llvm_intrinsic_call;
 use crate::cast::clif_intcast;
diff --git a/compiler/rustc_codegen_cranelift/src/main_shim.rs b/compiler/rustc_codegen_cranelift/src/main_shim.rs
index e480f21b9df..e6bf0d5b47e 100644
--- a/compiler/rustc_codegen_cranelift/src/main_shim.rs
+++ b/compiler/rustc_codegen_cranelift/src/main_shim.rs
@@ -2,8 +2,7 @@ use cranelift_frontend::{FunctionBuilder, FunctionBuilderContext};
 use rustc_hir::LangItem;
 use rustc_middle::ty::{AssocKind, GenericArg};
 use rustc_session::config::{EntryFnType, sigpipe};
-use rustc_span::DUMMY_SP;
-use rustc_span::symbol::Ident;
+use rustc_span::{DUMMY_SP, Ident};
 
 use crate::prelude::*;
 
diff --git a/compiler/rustc_codegen_gcc/src/attributes.rs b/compiler/rustc_codegen_gcc/src/attributes.rs
index d20e13e15b9..028a5ab5f71 100644
--- a/compiler/rustc_codegen_gcc/src/attributes.rs
+++ b/compiler/rustc_codegen_gcc/src/attributes.rs
@@ -2,8 +2,8 @@
 use gccjit::FnAttribute;
 use gccjit::Function;
 #[cfg(feature = "master")]
-use rustc_attr::InlineAttr;
-use rustc_attr::InstructionSetAttr;
+use rustc_attr_parsing::InlineAttr;
+use rustc_attr_parsing::InstructionSetAttr;
 #[cfg(feature = "master")]
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use rustc_middle::ty;
diff --git a/compiler/rustc_codegen_gcc/src/gcc_util.rs b/compiler/rustc_codegen_gcc/src/gcc_util.rs
index 88e5eefd7a1..058a874501b 100644
--- a/compiler/rustc_codegen_gcc/src/gcc_util.rs
+++ b/compiler/rustc_codegen_gcc/src/gcc_util.rs
@@ -96,7 +96,7 @@ pub(crate) fn global_gcc_features(sess: &Session, diagnostics: bool) -> Vec<Stri
                     }
                     Some((_, stability, _)) => {
                         if let Err(reason) =
-                            stability.compute_toggleability(&sess.target).allow_toggle()
+                            stability.toggle_allowed(&sess.target, enable_disable == '+')
                         {
                             sess.dcx().emit_warn(ForbiddenCTargetFeature { feature, reason });
                         } else if stability.requires_nightly().is_some() {
diff --git a/compiler/rustc_codegen_gcc/src/intrinsic/mod.rs b/compiler/rustc_codegen_gcc/src/intrinsic/mod.rs
index 69326f409bb..78ec9741f57 100644
--- a/compiler/rustc_codegen_gcc/src/intrinsic/mod.rs
+++ b/compiler/rustc_codegen_gcc/src/intrinsic/mod.rs
@@ -66,7 +66,7 @@ fn get_simple_intrinsic<'gcc, 'tcx>(
         sym::log2f64 => "log2",
         sym::fmaf32 => "fmaf",
         sym::fmaf64 => "fma",
-        // FIXME: calling `fma` from libc without FMA target feature uses expensive sofware emulation
+        // FIXME: calling `fma` from libc without FMA target feature uses expensive software emulation
         sym::fmuladdf32 => "fmaf", // TODO: use gcc intrinsic analogous to llvm.fmuladd.f32
         sym::fmuladdf64 => "fma",  // TODO: use gcc intrinsic analogous to llvm.fmuladd.f64
         sym::fabsf32 => "fabsf",
diff --git a/compiler/rustc_codegen_gcc/src/lib.rs b/compiler/rustc_codegen_gcc/src/lib.rs
index 764e84be1fe..f2efa981f97 100644
--- a/compiler/rustc_codegen_gcc/src/lib.rs
+++ b/compiler/rustc_codegen_gcc/src/lib.rs
@@ -35,7 +35,7 @@ extern crate tracing;
 extern crate rustc_abi;
 extern crate rustc_apfloat;
 extern crate rustc_ast;
-extern crate rustc_attr;
+extern crate rustc_attr_parsing;
 extern crate rustc_codegen_ssa;
 extern crate rustc_data_structures;
 extern crate rustc_errors;
@@ -483,9 +483,9 @@ fn target_features_cfg(
         .rust_target_features()
         .iter()
         .filter(|(_, gate, _)| gate.in_cfg())
-        .filter_map(|&(feature, gate, _)| {
+        .filter_map(|(feature, gate, _)| {
             if sess.is_nightly_build() || allow_unstable || gate.requires_nightly().is_none() {
-                Some(feature)
+                Some(*feature)
             } else {
                 None
             }
diff --git a/compiler/rustc_codegen_llvm/Cargo.toml b/compiler/rustc_codegen_llvm/Cargo.toml
index 03a871297c4..689986d642d 100644
--- a/compiler/rustc_codegen_llvm/Cargo.toml
+++ b/compiler/rustc_codegen_llvm/Cargo.toml
@@ -16,7 +16,7 @@ object = { version = "0.36.3", default-features = false, features = ["std", "rea
 rustc-demangle = "0.1.21"
 rustc_abi = { path = "../rustc_abi" }
 rustc_ast = { path = "../rustc_ast" }
-rustc_attr = { path = "../rustc_attr" }
+rustc_attr_parsing = { path = "../rustc_attr_parsing" }
 rustc_codegen_ssa = { path = "../rustc_codegen_ssa" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
diff --git a/compiler/rustc_codegen_llvm/src/attributes.rs b/compiler/rustc_codegen_llvm/src/attributes.rs
index 5552a241060..f8454fd9960 100644
--- a/compiler/rustc_codegen_llvm/src/attributes.rs
+++ b/compiler/rustc_codegen_llvm/src/attributes.rs
@@ -1,6 +1,6 @@
 //! Set and unset common attributes on LLVM values.
 
-use rustc_attr::{InlineAttr, InstructionSetAttr, OptimizeAttr};
+use rustc_attr_parsing::{InlineAttr, InstructionSetAttr, OptimizeAttr};
 use rustc_codegen_ssa::traits::*;
 use rustc_hir::def_id::DefId;
 use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, PatchableFunctionEntry};
diff --git a/compiler/rustc_codegen_llvm/src/back/write.rs b/compiler/rustc_codegen_llvm/src/back/write.rs
index 66ca4e2b473..45294ea35b1 100644
--- a/compiler/rustc_codegen_llvm/src/back/write.rs
+++ b/compiler/rustc_codegen_llvm/src/back/write.rs
@@ -25,8 +25,7 @@ use rustc_session::Session;
 use rustc_session::config::{
     self, Lto, OutputType, Passes, RemapPathScopeComponents, SplitDwarfKind, SwitchWithOptPath,
 };
-use rustc_span::symbol::sym;
-use rustc_span::{BytePos, InnerSpan, Pos, SpanData, SyntaxContext};
+use rustc_span::{BytePos, InnerSpan, Pos, SpanData, SyntaxContext, sym};
 use rustc_target::spec::{CodeModel, RelocModel, SanitizerSet, SplitDebuginfo, TlsModel};
 use tracing::debug;
 
diff --git a/compiler/rustc_codegen_llvm/src/base.rs b/compiler/rustc_codegen_llvm/src/base.rs
index f62310bd948..d05faf5577b 100644
--- a/compiler/rustc_codegen_llvm/src/base.rs
+++ b/compiler/rustc_codegen_llvm/src/base.rs
@@ -23,7 +23,7 @@ use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrs;
 use rustc_middle::mir::mono::{Linkage, Visibility};
 use rustc_middle::ty::TyCtxt;
 use rustc_session::config::DebugInfo;
-use rustc_span::symbol::Symbol;
+use rustc_span::Symbol;
 use rustc_target::spec::SanitizerSet;
 
 use super::ModuleLlvm;
diff --git a/compiler/rustc_codegen_llvm/src/callee.rs b/compiler/rustc_codegen_llvm/src/callee.rs
index ec77f32caf4..aa9a0f34f55 100644
--- a/compiler/rustc_codegen_llvm/src/callee.rs
+++ b/compiler/rustc_codegen_llvm/src/callee.rs
@@ -106,7 +106,7 @@ pub(crate) fn get_fn<'ll, 'tcx>(cx: &CodegenCx<'ll, 'tcx>, instance: Instance<'t
                 // This is a monomorphization of a generic function.
                 if !(cx.tcx.sess.opts.share_generics()
                     || tcx.codegen_fn_attrs(instance_def_id).inline
-                        == rustc_attr::InlineAttr::Never)
+                        == rustc_attr_parsing::InlineAttr::Never)
                 {
                     // When not sharing generics, all instances are in the same
                     // crate and have hidden visibility.
diff --git a/compiler/rustc_codegen_llvm/src/coverageinfo/ffi.rs b/compiler/rustc_codegen_llvm/src/coverageinfo/ffi.rs
index 1f133141c18..b617f4d37f5 100644
--- a/compiler/rustc_codegen_llvm/src/coverageinfo/ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/coverageinfo/ffi.rs
@@ -1,6 +1,4 @@
-use rustc_middle::mir::coverage::{CounterId, CovTerm, ExpressionId, SourceRegion};
-
-use crate::coverageinfo::mapgen::LocalFileId;
+use rustc_middle::mir::coverage::{CounterId, CovTerm, ExpressionId};
 
 /// Must match the layout of `LLVMRustCounterKind`.
 #[derive(Copy, Clone, Debug)]
@@ -126,30 +124,16 @@ pub(crate) struct CoverageSpan {
     /// Local index into the function's local-to-global file ID table.
     /// The value at that index is itself an index into the coverage filename
     /// table in the CGU's `__llvm_covmap` section.
-    file_id: u32,
+    pub(crate) file_id: u32,
 
     /// 1-based starting line of the source code span.
-    start_line: u32,
+    pub(crate) start_line: u32,
     /// 1-based starting column of the source code span.
-    start_col: u32,
+    pub(crate) start_col: u32,
     /// 1-based ending line of the source code span.
-    end_line: u32,
+    pub(crate) end_line: u32,
     /// 1-based ending column of the source code span. High bit must be unset.
-    end_col: u32,
-}
-
-impl CoverageSpan {
-    pub(crate) fn from_source_region(
-        local_file_id: LocalFileId,
-        code_region: &SourceRegion,
-    ) -> Self {
-        let file_id = local_file_id.as_u32();
-        let &SourceRegion { start_line, start_col, end_line, end_col } = code_region;
-        // Internally, LLVM uses the high bit of `end_col` to distinguish between
-        // code regions and gap regions, so it can't be used by the column number.
-        assert!(end_col & (1u32 << 31) == 0, "high bit of `end_col` must be unset: {end_col:#X}");
-        Self { file_id, start_line, start_col, end_line, end_col }
-    }
+    pub(crate) end_col: u32,
 }
 
 /// Holds tables of the various region types in one struct.
@@ -184,7 +168,7 @@ impl Regions {
 #[derive(Clone, Debug)]
 #[repr(C)]
 pub(crate) struct CodeRegion {
-    pub(crate) span: CoverageSpan,
+    pub(crate) cov_span: CoverageSpan,
     pub(crate) counter: Counter,
 }
 
@@ -192,7 +176,7 @@ pub(crate) struct CodeRegion {
 #[derive(Clone, Debug)]
 #[repr(C)]
 pub(crate) struct BranchRegion {
-    pub(crate) span: CoverageSpan,
+    pub(crate) cov_span: CoverageSpan,
     pub(crate) true_counter: Counter,
     pub(crate) false_counter: Counter,
 }
@@ -201,7 +185,7 @@ pub(crate) struct BranchRegion {
 #[derive(Clone, Debug)]
 #[repr(C)]
 pub(crate) struct MCDCBranchRegion {
-    pub(crate) span: CoverageSpan,
+    pub(crate) cov_span: CoverageSpan,
     pub(crate) true_counter: Counter,
     pub(crate) false_counter: Counter,
     pub(crate) mcdc_branch_params: mcdc::BranchParameters,
@@ -211,6 +195,6 @@ pub(crate) struct MCDCBranchRegion {
 #[derive(Clone, Debug)]
 #[repr(C)]
 pub(crate) struct MCDCDecisionRegion {
-    pub(crate) span: CoverageSpan,
+    pub(crate) cov_span: CoverageSpan,
     pub(crate) mcdc_decision_params: mcdc::DecisionParameters,
 }
diff --git a/compiler/rustc_codegen_llvm/src/coverageinfo/llvm_cov.rs b/compiler/rustc_codegen_llvm/src/coverageinfo/llvm_cov.rs
index 086cf1f44a0..2cd7fa3225a 100644
--- a/compiler/rustc_codegen_llvm/src/coverageinfo/llvm_cov.rs
+++ b/compiler/rustc_codegen_llvm/src/coverageinfo/llvm_cov.rs
@@ -40,11 +40,10 @@ pub(crate) fn create_pgo_func_name_var<'ll>(
     }
 }
 
-pub(crate) fn write_filenames_to_buffer<'a>(
-    filenames: impl IntoIterator<Item = &'a str>,
-) -> Vec<u8> {
+pub(crate) fn write_filenames_to_buffer(filenames: &[impl AsRef<str>]) -> Vec<u8> {
     let (pointers, lengths) = filenames
         .into_iter()
+        .map(AsRef::as_ref)
         .map(|s: &str| (s.as_c_char_ptr(), s.len()))
         .unzip::<_, _, Vec<_>, Vec<_>>();
 
diff --git a/compiler/rustc_codegen_llvm/src/coverageinfo/map_data.rs b/compiler/rustc_codegen_llvm/src/coverageinfo/map_data.rs
deleted file mode 100644
index c5d1ebdfe7c..00000000000
--- a/compiler/rustc_codegen_llvm/src/coverageinfo/map_data.rs
+++ /dev/null
@@ -1,84 +0,0 @@
-use rustc_data_structures::captures::Captures;
-use rustc_middle::mir::coverage::{
-    CovTerm, CoverageIdsInfo, Expression, FunctionCoverageInfo, Mapping, MappingKind, Op,
-    SourceRegion,
-};
-
-use crate::coverageinfo::ffi::{Counter, CounterExpression, ExprKind};
-
-pub(crate) struct FunctionCoverage<'tcx> {
-    pub(crate) function_coverage_info: &'tcx FunctionCoverageInfo,
-    /// If `None`, the corresponding function is unused.
-    ids_info: Option<&'tcx CoverageIdsInfo>,
-}
-
-impl<'tcx> FunctionCoverage<'tcx> {
-    pub(crate) fn new_used(
-        function_coverage_info: &'tcx FunctionCoverageInfo,
-        ids_info: &'tcx CoverageIdsInfo,
-    ) -> Self {
-        Self { function_coverage_info, ids_info: Some(ids_info) }
-    }
-
-    pub(crate) fn new_unused(function_coverage_info: &'tcx FunctionCoverageInfo) -> Self {
-        Self { function_coverage_info, ids_info: None }
-    }
-
-    /// Returns true for a used (called) function, and false for an unused function.
-    pub(crate) fn is_used(&self) -> bool {
-        self.ids_info.is_some()
-    }
-
-    /// Return the source hash, generated from the HIR node structure, and used to indicate whether
-    /// or not the source code structure changed between different compilations.
-    pub(crate) fn source_hash(&self) -> u64 {
-        if self.is_used() { self.function_coverage_info.function_source_hash } else { 0 }
-    }
-
-    /// Convert this function's coverage expression data into a form that can be
-    /// passed through FFI to LLVM.
-    pub(crate) fn counter_expressions(
-        &self,
-    ) -> impl Iterator<Item = CounterExpression> + ExactSizeIterator + Captures<'_> {
-        // We know that LLVM will optimize out any unused expressions before
-        // producing the final coverage map, so there's no need to do the same
-        // thing on the Rust side unless we're confident we can do much better.
-        // (See `CounterExpressionsMinimizer` in `CoverageMappingWriter.cpp`.)
-
-        self.function_coverage_info.expressions.iter().map(move |&Expression { lhs, op, rhs }| {
-            CounterExpression {
-                lhs: self.counter_for_term(lhs),
-                kind: match op {
-                    Op::Add => ExprKind::Add,
-                    Op::Subtract => ExprKind::Subtract,
-                },
-                rhs: self.counter_for_term(rhs),
-            }
-        })
-    }
-
-    /// Converts this function's coverage mappings into an intermediate form
-    /// that will be used by `mapgen` when preparing for FFI.
-    pub(crate) fn counter_regions(
-        &self,
-    ) -> impl Iterator<Item = (MappingKind, &SourceRegion)> + ExactSizeIterator {
-        self.function_coverage_info.mappings.iter().map(move |mapping| {
-            let Mapping { kind, source_region } = mapping;
-            let kind =
-                kind.map_terms(|term| if self.is_zero_term(term) { CovTerm::Zero } else { term });
-            (kind, source_region)
-        })
-    }
-
-    fn counter_for_term(&self, term: CovTerm) -> Counter {
-        if self.is_zero_term(term) { Counter::ZERO } else { Counter::from_term(term) }
-    }
-
-    fn is_zero_term(&self, term: CovTerm) -> bool {
-        match self.ids_info {
-            Some(ids_info) => ids_info.is_zero_term(term),
-            // This function is unused, so all coverage counters/expressions are zero.
-            None => true,
-        }
-    }
-}
diff --git a/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs b/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs
index 4f2af732527..b3ad2a0e409 100644
--- a/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs
+++ b/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs
@@ -1,28 +1,28 @@
-use std::iter;
+use std::sync::Arc;
 
-use itertools::Itertools as _;
+use itertools::Itertools;
 use rustc_abi::Align;
 use rustc_codegen_ssa::traits::{
     BaseTypeCodegenMethods, ConstCodegenMethods, StaticCodegenMethods,
 };
-use rustc_data_structures::fx::{FxHashSet, FxIndexMap, FxIndexSet};
+use rustc_data_structures::fx::{FxHashSet, FxIndexMap};
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_index::IndexVec;
+use rustc_middle::mir;
 use rustc_middle::ty::{self, TyCtxt};
-use rustc_middle::{bug, mir};
 use rustc_session::RemapFileNameExt;
 use rustc_session::config::RemapPathScopeComponents;
 use rustc_span::def_id::DefIdSet;
-use rustc_span::{Span, Symbol};
+use rustc_span::{SourceFile, StableSourceFileId};
 use tracing::debug;
 
 use crate::common::CodegenCx;
 use crate::coverageinfo::llvm_cov;
-use crate::coverageinfo::map_data::FunctionCoverage;
 use crate::coverageinfo::mapgen::covfun::prepare_covfun_record;
 use crate::llvm;
 
 mod covfun;
+mod spans;
 
 /// Generates and exports the coverage map, which is embedded in special
 /// linker sections in the final binary.
@@ -49,46 +49,40 @@ pub(crate) fn finalize(cx: &CodegenCx<'_, '_>) {
 
     debug!("Generating coverage map for CodegenUnit: `{}`", cx.codegen_unit.name());
 
-    // In order to show that unused functions have coverage counts of zero (0), LLVM requires the
-    // functions exist. Generate synthetic functions with a (required) single counter, and add the
-    // MIR `Coverage` code regions to the `function_coverage_map`, before calling
-    // `ctx.take_function_coverage_map()`.
-    if cx.codegen_unit.is_code_coverage_dead_code_cgu() {
-        add_unused_functions(cx);
-    }
-
     // FIXME(#132395): Can this be none even when coverage is enabled?
-    let function_coverage_map = match cx.coverage_cx {
-        Some(ref cx) => cx.take_function_coverage_map(),
+    let instances_used = match cx.coverage_cx {
+        Some(ref cx) => cx.instances_used.borrow(),
         None => return,
     };
-    if function_coverage_map.is_empty() {
-        // This CGU has no functions with coverage instrumentation.
-        return;
-    }
-
-    let all_file_names = function_coverage_map
-        .iter()
-        .map(|(_, fn_cov)| fn_cov.function_coverage_info.body_span)
-        .map(|span| span_file_name(tcx, span));
-    let global_file_table = GlobalFileTable::new(all_file_names);
-
-    // Encode all filenames referenced by coverage mappings in this CGU.
-    let filenames_buffer = global_file_table.make_filenames_buffer(tcx);
-    // The `llvm-cov` tool uses this hash to associate each covfun record with
-    // its corresponding filenames table, since the final binary will typically
-    // contain multiple covmap records from different compilation units.
-    let filenames_hash = llvm_cov::hash_bytes(&filenames_buffer);
 
-    let mut unused_function_names = Vec::new();
+    // The order of entries in this global file table needs to be deterministic,
+    // and ideally should also be independent of the details of stable-hashing,
+    // because coverage tests snapshots (`.cov-map`) can observe the order and
+    // would need to be re-blessed if it changes. As long as those requirements
+    // are satisfied, the order can be arbitrary.
+    let mut global_file_table = GlobalFileTable::new();
 
-    let covfun_records = function_coverage_map
-        .into_iter()
-        .filter_map(|(instance, function_coverage)| {
-            prepare_covfun_record(tcx, &global_file_table, instance, &function_coverage)
-        })
+    let mut covfun_records = instances_used
+        .iter()
+        .copied()
+        // Sort by symbol name, so that the global file table is built in an
+        // order that doesn't depend on the stable-hash-based order in which
+        // instances were visited during codegen.
+        .sorted_by_cached_key(|&instance| tcx.symbol_name(instance).name)
+        .filter_map(|instance| prepare_covfun_record(tcx, &mut global_file_table, instance, true))
         .collect::<Vec<_>>();
 
+    // In a single designated CGU, also prepare covfun records for functions
+    // in this crate that were instrumented for coverage, but are unused.
+    if cx.codegen_unit.is_code_coverage_dead_code_cgu() {
+        let mut unused_instances = gather_unused_function_instances(cx);
+        // Sort the unused instances by symbol name, for the same reason as the used ones.
+        unused_instances.sort_by_cached_key(|&instance| tcx.symbol_name(instance).name);
+        covfun_records.extend(unused_instances.into_iter().filter_map(|instance| {
+            prepare_covfun_record(tcx, &mut global_file_table, instance, false)
+        }));
+    }
+
     // If there are no covfun records for this CGU, don't generate a covmap record.
     // Emitting a covmap record without any covfun records causes `llvm-cov` to
     // fail when generating coverage reports, and if there are no covfun records
@@ -98,6 +92,15 @@ pub(crate) fn finalize(cx: &CodegenCx<'_, '_>) {
         return;
     }
 
+    // Encode all filenames referenced by coverage mappings in this CGU.
+    let filenames_buffer = global_file_table.make_filenames_buffer(tcx);
+    // The `llvm-cov` tool uses this hash to associate each covfun record with
+    // its corresponding filenames table, since the final binary will typically
+    // contain multiple covmap records from different compilation units.
+    let filenames_hash = llvm_cov::hash_bytes(&filenames_buffer);
+
+    let mut unused_function_names = vec![];
+
     for covfun in &covfun_records {
         unused_function_names.extend(covfun.mangled_function_name_if_unused());
 
@@ -129,54 +132,51 @@ pub(crate) fn finalize(cx: &CodegenCx<'_, '_>) {
     generate_covmap_record(cx, covmap_version, &filenames_buffer);
 }
 
-/// Maps "global" (per-CGU) file ID numbers to their underlying filenames.
+/// Maps "global" (per-CGU) file ID numbers to their underlying source files.
 struct GlobalFileTable {
-    /// This "raw" table doesn't include the working dir, so a filename's
+    /// This "raw" table doesn't include the working dir, so a file's
     /// global ID is its index in this set **plus one**.
-    raw_file_table: FxIndexSet<Symbol>,
+    raw_file_table: FxIndexMap<StableSourceFileId, Arc<SourceFile>>,
 }
 
 impl GlobalFileTable {
-    fn new(all_file_names: impl IntoIterator<Item = Symbol>) -> Self {
-        // Collect all of the filenames into a set. Filenames usually come in
-        // contiguous runs, so we can dedup adjacent ones to save work.
-        let mut raw_file_table = all_file_names.into_iter().dedup().collect::<FxIndexSet<Symbol>>();
-
-        // Sort the file table by its actual string values, not the arbitrary
-        // ordering of its symbols.
-        raw_file_table.sort_unstable_by(|a, b| a.as_str().cmp(b.as_str()));
-
-        Self { raw_file_table }
+    fn new() -> Self {
+        Self { raw_file_table: FxIndexMap::default() }
     }
 
-    fn global_file_id_for_file_name(&self, file_name: Symbol) -> GlobalFileId {
-        let raw_id = self.raw_file_table.get_index_of(&file_name).unwrap_or_else(|| {
-            bug!("file name not found in prepared global file table: {file_name}");
-        });
+    fn global_file_id_for_file(&mut self, file: &Arc<SourceFile>) -> GlobalFileId {
+        // Ensure the given file has a table entry, and get its index.
+        let entry = self.raw_file_table.entry(file.stable_id);
+        let raw_id = entry.index();
+        entry.or_insert_with(|| Arc::clone(file));
+
         // The raw file table doesn't include an entry for the working dir
         // (which has ID 0), so add 1 to get the correct ID.
         GlobalFileId::from_usize(raw_id + 1)
     }
 
     fn make_filenames_buffer(&self, tcx: TyCtxt<'_>) -> Vec<u8> {
+        let mut table = Vec::with_capacity(self.raw_file_table.len() + 1);
+
         // LLVM Coverage Mapping Format version 6 (zero-based encoded as 5)
         // requires setting the first filename to the compilation directory.
         // Since rustc generates coverage maps with relative paths, the
         // compilation directory can be combined with the relative paths
         // to get absolute paths, if needed.
-        use rustc_session::RemapFileNameExt;
-        use rustc_session::config::RemapPathScopeComponents;
-        let working_dir: &str = &tcx
-            .sess
-            .opts
-            .working_dir
-            .for_scope(tcx.sess, RemapPathScopeComponents::MACRO)
-            .to_string_lossy();
-
-        // Insert the working dir at index 0, before the other filenames.
-        let filenames =
-            iter::once(working_dir).chain(self.raw_file_table.iter().map(Symbol::as_str));
-        llvm_cov::write_filenames_to_buffer(filenames)
+        table.push(
+            tcx.sess
+                .opts
+                .working_dir
+                .for_scope(tcx.sess, RemapPathScopeComponents::MACRO)
+                .to_string_lossy(),
+        );
+
+        // Add the regular entries after the base directory.
+        table.extend(self.raw_file_table.values().map(|file| {
+            file.name.for_scope(tcx.sess, RemapPathScopeComponents::MACRO).to_string_lossy()
+        }));
+
+        llvm_cov::write_filenames_to_buffer(&table)
     }
 }
 
@@ -189,7 +189,7 @@ rustc_index::newtype_index! {
     /// An index into a function's list of global file IDs. That underlying list
     /// of local-to-global mappings will be embedded in the function's record in
     /// the `__llvm_covfun` linker section.
-    pub(crate) struct LocalFileId {}
+    struct LocalFileId {}
 }
 
 /// Holds a mapping from "local" (per-function) file IDs to "global" (per-CGU)
@@ -215,13 +215,6 @@ impl VirtualFileMapping {
     }
 }
 
-fn span_file_name(tcx: TyCtxt<'_>, span: Span) -> Symbol {
-    let source_file = tcx.sess.source_map().lookup_source_file(span.lo());
-    let name =
-        source_file.name.for_scope(tcx.sess, RemapPathScopeComponents::MACRO).to_string_lossy();
-    Symbol::intern(&name)
-}
-
 /// Generates the contents of the covmap record for this CGU, which mostly
 /// consists of a header and a list of filenames. The record is then stored
 /// as a global variable in the `__llvm_covmap` section.
@@ -264,39 +257,35 @@ fn generate_covmap_record<'ll>(cx: &CodegenCx<'ll, '_>, version: u32, filenames_
 /// coverage map (in a single designated CGU) so that we still emit coverage mappings for them.
 /// We also end up adding their symbol names to a special global array that LLVM will include in
 /// its embedded coverage data.
-fn add_unused_functions(cx: &CodegenCx<'_, '_>) {
+fn gather_unused_function_instances<'tcx>(cx: &CodegenCx<'_, 'tcx>) -> Vec<ty::Instance<'tcx>> {
     assert!(cx.codegen_unit.is_code_coverage_dead_code_cgu());
 
     let tcx = cx.tcx;
     let usage = prepare_usage_sets(tcx);
 
     let is_unused_fn = |def_id: LocalDefId| -> bool {
-        let def_id = def_id.to_def_id();
-
-        // To be eligible for "unused function" mappings, a definition must:
-        // - Be function-like
+        // Usage sets expect `DefId`, so convert from `LocalDefId`.
+        let d: DefId = LocalDefId::to_def_id(def_id);
+        // To be potentially eligible for "unused function" mappings, a definition must:
+        // - Be eligible for coverage instrumentation
         // - Not participate directly in codegen (or have lost all its coverage statements)
         // - Not have any coverage statements inlined into codegenned functions
-        tcx.def_kind(def_id).is_fn_like()
-            && (!usage.all_mono_items.contains(&def_id)
-                || usage.missing_own_coverage.contains(&def_id))
-            && !usage.used_via_inlining.contains(&def_id)
+        tcx.is_eligible_for_coverage(def_id)
+            && (!usage.all_mono_items.contains(&d) || usage.missing_own_coverage.contains(&d))
+            && !usage.used_via_inlining.contains(&d)
     };
 
-    // Scan for unused functions that were instrumented for coverage.
-    for def_id in tcx.mir_keys(()).iter().copied().filter(|&def_id| is_unused_fn(def_id)) {
-        // Get the coverage info from MIR, skipping functions that were never instrumented.
-        let body = tcx.optimized_mir(def_id);
-        let Some(function_coverage_info) = body.function_coverage_info.as_deref() else { continue };
-
-        // FIXME(79651): Consider trying to filter out dummy instantiations of
-        // unused generic functions from library crates, because they can produce
-        // "unused instantiation" in coverage reports even when they are actually
-        // used by some downstream crate in the same binary.
+    // FIXME(#79651): Consider trying to filter out dummy instantiations of
+    // unused generic functions from library crates, because they can produce
+    // "unused instantiation" in coverage reports even when they are actually
+    // used by some downstream crate in the same binary.
 
-        debug!("generating unused fn: {def_id:?}");
-        add_unused_function_coverage(cx, def_id, function_coverage_info);
-    }
+    tcx.mir_keys(())
+        .iter()
+        .copied()
+        .filter(|&def_id| is_unused_fn(def_id))
+        .map(|def_id| make_dummy_instance(tcx, def_id))
+        .collect::<Vec<_>>()
 }
 
 struct UsageSets<'tcx> {
@@ -361,16 +350,11 @@ fn prepare_usage_sets<'tcx>(tcx: TyCtxt<'tcx>) -> UsageSets<'tcx> {
     UsageSets { all_mono_items, used_via_inlining, missing_own_coverage }
 }
 
-fn add_unused_function_coverage<'tcx>(
-    cx: &CodegenCx<'_, 'tcx>,
-    def_id: LocalDefId,
-    function_coverage_info: &'tcx mir::coverage::FunctionCoverageInfo,
-) {
-    let tcx = cx.tcx;
-    let def_id = def_id.to_def_id();
+fn make_dummy_instance<'tcx>(tcx: TyCtxt<'tcx>, local_def_id: LocalDefId) -> ty::Instance<'tcx> {
+    let def_id = local_def_id.to_def_id();
 
     // Make a dummy instance that fills in all generics with placeholders.
-    let instance = ty::Instance::new(
+    ty::Instance::new(
         def_id,
         ty::GenericArgs::for_item(tcx, def_id, |param, _| {
             if let ty::GenericParamDefKind::Lifetime = param.kind {
@@ -379,9 +363,5 @@ fn add_unused_function_coverage<'tcx>(
                 tcx.mk_param_from_def(param)
             }
         }),
-    );
-
-    // An unused function's mappings will all be rewritten to map to zero.
-    let function_coverage = FunctionCoverage::new_unused(function_coverage_info);
-    cx.coverage_cx().function_coverage_map.borrow_mut().insert(instance, function_coverage);
+    )
 }
diff --git a/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/covfun.rs b/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/covfun.rs
index 33e7a0f2f20..5428d776f41 100644
--- a/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/covfun.rs
+++ b/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/covfun.rs
@@ -10,15 +10,16 @@ use rustc_abi::Align;
 use rustc_codegen_ssa::traits::{
     BaseTypeCodegenMethods, ConstCodegenMethods, StaticCodegenMethods,
 };
-use rustc_middle::bug;
-use rustc_middle::mir::coverage::MappingKind;
+use rustc_middle::mir::coverage::{
+    CovTerm, CoverageIdsInfo, Expression, FunctionCoverageInfo, Mapping, MappingKind, Op,
+};
 use rustc_middle::ty::{Instance, TyCtxt};
+use rustc_span::Span;
 use rustc_target::spec::HasTargetSpec;
 use tracing::debug;
 
 use crate::common::CodegenCx;
-use crate::coverageinfo::map_data::FunctionCoverage;
-use crate::coverageinfo::mapgen::{GlobalFileTable, VirtualFileMapping, span_file_name};
+use crate::coverageinfo::mapgen::{GlobalFileTable, VirtualFileMapping, spans};
 use crate::coverageinfo::{ffi, llvm_cov};
 use crate::llvm;
 
@@ -45,77 +46,129 @@ impl<'tcx> CovfunRecord<'tcx> {
 
 pub(crate) fn prepare_covfun_record<'tcx>(
     tcx: TyCtxt<'tcx>,
-    global_file_table: &GlobalFileTable,
+    global_file_table: &mut GlobalFileTable,
     instance: Instance<'tcx>,
-    function_coverage: &FunctionCoverage<'tcx>,
+    is_used: bool,
 ) -> Option<CovfunRecord<'tcx>> {
+    let fn_cov_info = tcx.instance_mir(instance.def).function_coverage_info.as_deref()?;
+    let ids_info = tcx.coverage_ids_info(instance.def);
+
+    let expressions = prepare_expressions(fn_cov_info, ids_info, is_used);
+
     let mut covfun = CovfunRecord {
         mangled_function_name: tcx.symbol_name(instance).name,
-        source_hash: function_coverage.source_hash(),
-        is_used: function_coverage.is_used(),
+        source_hash: if is_used { fn_cov_info.function_source_hash } else { 0 },
+        is_used,
         virtual_file_mapping: VirtualFileMapping::default(),
-        expressions: function_coverage.counter_expressions().collect::<Vec<_>>(),
+        expressions,
         regions: ffi::Regions::default(),
     };
 
-    fill_region_tables(tcx, global_file_table, function_coverage, &mut covfun);
+    fill_region_tables(tcx, global_file_table, fn_cov_info, ids_info, &mut covfun);
 
     if covfun.regions.has_no_regions() {
-        if covfun.is_used {
-            bug!("a used function should have had coverage mapping data but did not: {covfun:?}");
-        } else {
-            debug!(?covfun, "unused function had no coverage mapping data");
-            return None;
-        }
+        debug!(?covfun, "function has no mappings to embed; skipping");
+        return None;
     }
 
     Some(covfun)
 }
 
+/// Convert the function's coverage-counter expressions into a form suitable for FFI.
+fn prepare_expressions(
+    fn_cov_info: &FunctionCoverageInfo,
+    ids_info: &CoverageIdsInfo,
+    is_used: bool,
+) -> Vec<ffi::CounterExpression> {
+    // If any counters or expressions were removed by MIR opts, replace their
+    // terms with zero.
+    let counter_for_term = |term| {
+        if !is_used || ids_info.is_zero_term(term) {
+            ffi::Counter::ZERO
+        } else {
+            ffi::Counter::from_term(term)
+        }
+    };
+
+    // We know that LLVM will optimize out any unused expressions before
+    // producing the final coverage map, so there's no need to do the same
+    // thing on the Rust side unless we're confident we can do much better.
+    // (See `CounterExpressionsMinimizer` in `CoverageMappingWriter.cpp`.)
+    fn_cov_info
+        .expressions
+        .iter()
+        .map(move |&Expression { lhs, op, rhs }| ffi::CounterExpression {
+            lhs: counter_for_term(lhs),
+            kind: match op {
+                Op::Add => ffi::ExprKind::Add,
+                Op::Subtract => ffi::ExprKind::Subtract,
+            },
+            rhs: counter_for_term(rhs),
+        })
+        .collect::<Vec<_>>()
+}
+
 /// Populates the mapping region tables in the current function's covfun record.
 fn fill_region_tables<'tcx>(
     tcx: TyCtxt<'tcx>,
-    global_file_table: &GlobalFileTable,
-    function_coverage: &FunctionCoverage<'tcx>,
+    global_file_table: &mut GlobalFileTable,
+    fn_cov_info: &'tcx FunctionCoverageInfo,
+    ids_info: &'tcx CoverageIdsInfo,
     covfun: &mut CovfunRecord<'tcx>,
 ) {
-    let counter_regions = function_coverage.counter_regions();
-    if counter_regions.is_empty() {
-        return;
-    }
-
     // Currently a function's mappings must all be in the same file as its body span.
-    let file_name = span_file_name(tcx, function_coverage.function_coverage_info.body_span);
+    let source_map = tcx.sess.source_map();
+    let source_file = source_map.lookup_source_file(fn_cov_info.body_span.lo());
 
-    // Look up the global file ID for that filename.
-    let global_file_id = global_file_table.global_file_id_for_file_name(file_name);
+    // Look up the global file ID for that file.
+    let global_file_id = global_file_table.global_file_id_for_file(&source_file);
 
     // Associate that global file ID with a local file ID for this function.
     let local_file_id = covfun.virtual_file_mapping.local_id_for_global(global_file_id);
-    debug!("  file id: {local_file_id:?} => {global_file_id:?} = '{file_name:?}'");
 
     let ffi::Regions { code_regions, branch_regions, mcdc_branch_regions, mcdc_decision_regions } =
         &mut covfun.regions;
 
+    let make_cov_span = |span: Span| {
+        spans::make_coverage_span(local_file_id, source_map, fn_cov_info, &source_file, span)
+    };
+    let discard_all = tcx.sess.coverage_discard_all_spans_in_codegen();
+
     // For each counter/region pair in this function+file, convert it to a
     // form suitable for FFI.
-    for (mapping_kind, region) in counter_regions {
-        debug!("Adding counter {mapping_kind:?} to map for {region:?}");
-        let span = ffi::CoverageSpan::from_source_region(local_file_id, region);
-        match mapping_kind {
+    let is_zero_term = |term| !covfun.is_used || ids_info.is_zero_term(term);
+    for &Mapping { ref kind, span } in &fn_cov_info.mappings {
+        // If the mapping refers to counters/expressions that were removed by
+        // MIR opts, replace those occurrences with zero.
+        let kind = kind.map_terms(|term| if is_zero_term(term) { CovTerm::Zero } else { term });
+
+        // Convert the `Span` into coordinates that we can pass to LLVM, or
+        // discard the span if conversion fails. In rare, cases _all_ of a
+        // function's spans are discarded, and the rest of coverage codegen
+        // needs to handle that gracefully to avoid a repeat of #133606.
+        // We don't have a good test case for triggering that organically, so
+        // instead we set `-Zcoverage-options=discard-all-spans-in-codegen`
+        // to force it to occur.
+        let Some(cov_span) = make_cov_span(span) else { continue };
+        if discard_all {
+            continue;
+        }
+
+        match kind {
             MappingKind::Code(term) => {
-                code_regions.push(ffi::CodeRegion { span, counter: ffi::Counter::from_term(term) });
+                code_regions
+                    .push(ffi::CodeRegion { cov_span, counter: ffi::Counter::from_term(term) });
             }
             MappingKind::Branch { true_term, false_term } => {
                 branch_regions.push(ffi::BranchRegion {
-                    span,
+                    cov_span,
                     true_counter: ffi::Counter::from_term(true_term),
                     false_counter: ffi::Counter::from_term(false_term),
                 });
             }
             MappingKind::MCDCBranch { true_term, false_term, mcdc_params } => {
                 mcdc_branch_regions.push(ffi::MCDCBranchRegion {
-                    span,
+                    cov_span,
                     true_counter: ffi::Counter::from_term(true_term),
                     false_counter: ffi::Counter::from_term(false_term),
                     mcdc_branch_params: ffi::mcdc::BranchParameters::from(mcdc_params),
@@ -123,7 +176,7 @@ fn fill_region_tables<'tcx>(
             }
             MappingKind::MCDCDecision(mcdc_decision_params) => {
                 mcdc_decision_regions.push(ffi::MCDCDecisionRegion {
-                    span,
+                    cov_span,
                     mcdc_decision_params: ffi::mcdc::DecisionParameters::from(mcdc_decision_params),
                 });
             }
diff --git a/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/spans.rs b/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/spans.rs
new file mode 100644
index 00000000000..6d1d91340c2
--- /dev/null
+++ b/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/spans.rs
@@ -0,0 +1,126 @@
+use rustc_middle::mir::coverage::FunctionCoverageInfo;
+use rustc_span::source_map::SourceMap;
+use rustc_span::{BytePos, Pos, SourceFile, Span};
+use tracing::debug;
+
+use crate::coverageinfo::ffi;
+use crate::coverageinfo::mapgen::LocalFileId;
+
+/// Converts the span into its start line and column, and end line and column.
+///
+/// Line numbers and column numbers are 1-based. Unlike most column numbers emitted by
+/// the compiler, these column numbers are denoted in **bytes**, because that's what
+/// LLVM's `llvm-cov` tool expects to see in coverage maps.
+///
+/// Returns `None` if the conversion failed for some reason. This shouldn't happen,
+/// but it's hard to rule out entirely (especially in the presence of complex macros
+/// or other expansions), and if it does happen then skipping a span or function is
+/// better than an ICE or `llvm-cov` failure that the user might have no way to avoid.
+pub(crate) fn make_coverage_span(
+    file_id: LocalFileId,
+    source_map: &SourceMap,
+    fn_cov_info: &FunctionCoverageInfo,
+    file: &SourceFile,
+    span: Span,
+) -> Option<ffi::CoverageSpan> {
+    let span = ensure_non_empty_span(source_map, fn_cov_info, span)?;
+
+    let lo = span.lo();
+    let hi = span.hi();
+
+    // Column numbers need to be in bytes, so we can't use the more convenient
+    // `SourceMap` methods for looking up file coordinates.
+    let line_and_byte_column = |pos: BytePos| -> Option<(usize, usize)> {
+        let rpos = file.relative_position(pos);
+        let line_index = file.lookup_line(rpos)?;
+        let line_start = file.lines()[line_index];
+        // Line numbers and column numbers are 1-based, so add 1 to each.
+        Some((line_index + 1, (rpos - line_start).to_usize() + 1))
+    };
+
+    let (mut start_line, start_col) = line_and_byte_column(lo)?;
+    let (mut end_line, end_col) = line_and_byte_column(hi)?;
+
+    // Apply an offset so that code in doctests has correct line numbers.
+    // FIXME(#79417): Currently we have no way to offset doctest _columns_.
+    start_line = source_map.doctest_offset_line(&file.name, start_line);
+    end_line = source_map.doctest_offset_line(&file.name, end_line);
+
+    check_coverage_span(ffi::CoverageSpan {
+        file_id: file_id.as_u32(),
+        start_line: start_line as u32,
+        start_col: start_col as u32,
+        end_line: end_line as u32,
+        end_col: end_col as u32,
+    })
+}
+
+fn ensure_non_empty_span(
+    source_map: &SourceMap,
+    fn_cov_info: &FunctionCoverageInfo,
+    span: Span,
+) -> Option<Span> {
+    if !span.is_empty() {
+        return Some(span);
+    }
+
+    let lo = span.lo();
+    let hi = span.hi();
+
+    // The span is empty, so try to expand it to cover an adjacent '{' or '}',
+    // but only within the bounds of the body span.
+    let try_next = hi < fn_cov_info.body_span.hi();
+    let try_prev = fn_cov_info.body_span.lo() < lo;
+    if !(try_next || try_prev) {
+        return None;
+    }
+
+    source_map
+        .span_to_source(span, |src, start, end| try {
+            // Adjusting span endpoints by `BytePos(1)` is normally a bug,
+            // but in this case we have specifically checked that the character
+            // we're skipping over is one of two specific ASCII characters, so
+            // adjusting by exactly 1 byte is correct.
+            if try_next && src.as_bytes()[end] == b'{' {
+                Some(span.with_hi(hi + BytePos(1)))
+            } else if try_prev && src.as_bytes()[start - 1] == b'}' {
+                Some(span.with_lo(lo - BytePos(1)))
+            } else {
+                None
+            }
+        })
+        .ok()?
+}
+
+/// If `llvm-cov` sees a source region that is improperly ordered (end < start),
+/// it will immediately exit with a fatal error. To prevent that from happening,
+/// discard regions that are improperly ordered, or might be interpreted in a
+/// way that makes them improperly ordered.
+fn check_coverage_span(cov_span: ffi::CoverageSpan) -> Option<ffi::CoverageSpan> {
+    let ffi::CoverageSpan { file_id: _, start_line, start_col, end_line, end_col } = cov_span;
+
+    // Line/column coordinates are supposed to be 1-based. If we ever emit
+    // coordinates of 0, `llvm-cov` might misinterpret them.
+    let all_nonzero = [start_line, start_col, end_line, end_col].into_iter().all(|x| x != 0);
+    // Coverage mappings use the high bit of `end_col` to indicate that a
+    // region is actually a "gap" region, so make sure it's unset.
+    let end_col_has_high_bit_unset = (end_col & (1 << 31)) == 0;
+    // If a region is improperly ordered (end < start), `llvm-cov` will exit
+    // with a fatal error, which is inconvenient for users and hard to debug.
+    let is_ordered = (start_line, start_col) <= (end_line, end_col);
+
+    if all_nonzero && end_col_has_high_bit_unset && is_ordered {
+        Some(cov_span)
+    } else {
+        debug!(
+            ?cov_span,
+            ?all_nonzero,
+            ?end_col_has_high_bit_unset,
+            ?is_ordered,
+            "Skipping source region that would be misinterpreted or rejected by LLVM"
+        );
+        // If this happens in a debug build, ICE to make it easier to notice.
+        debug_assert!(false, "Improper source region: {cov_span:?}");
+        None
+    }
+}
diff --git a/compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs b/compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs
index 82b6677e203..7311cd9d230 100644
--- a/compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs
+++ b/compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs
@@ -5,7 +5,7 @@ use rustc_abi::Size;
 use rustc_codegen_ssa::traits::{
     BuilderMethods, ConstCodegenMethods, CoverageInfoBuilderMethods, MiscCodegenMethods,
 };
-use rustc_data_structures::fx::{FxHashMap, FxIndexMap};
+use rustc_data_structures::fx::{FxHashMap, FxIndexSet};
 use rustc_middle::mir::coverage::CoverageKind;
 use rustc_middle::ty::Instance;
 use rustc_middle::ty::layout::HasTyCtxt;
@@ -13,18 +13,16 @@ use tracing::{debug, instrument};
 
 use crate::builder::Builder;
 use crate::common::CodegenCx;
-use crate::coverageinfo::map_data::FunctionCoverage;
 use crate::llvm;
 
 pub(crate) mod ffi;
 mod llvm_cov;
-pub(crate) mod map_data;
 mod mapgen;
 
 /// Extra per-CGU context/state needed for coverage instrumentation.
 pub(crate) struct CguCoverageContext<'ll, 'tcx> {
     /// Coverage data for each instrumented function identified by DefId.
-    pub(crate) function_coverage_map: RefCell<FxIndexMap<Instance<'tcx>, FunctionCoverage<'tcx>>>,
+    pub(crate) instances_used: RefCell<FxIndexSet<Instance<'tcx>>>,
     pub(crate) pgo_func_name_var_map: RefCell<FxHashMap<Instance<'tcx>, &'ll llvm::Value>>,
     pub(crate) mcdc_condition_bitmap_map: RefCell<FxHashMap<Instance<'tcx>, Vec<&'ll llvm::Value>>>,
 
@@ -34,17 +32,13 @@ pub(crate) struct CguCoverageContext<'ll, 'tcx> {
 impl<'ll, 'tcx> CguCoverageContext<'ll, 'tcx> {
     pub(crate) fn new() -> Self {
         Self {
-            function_coverage_map: Default::default(),
+            instances_used: RefCell::<FxIndexSet<_>>::default(),
             pgo_func_name_var_map: Default::default(),
             mcdc_condition_bitmap_map: Default::default(),
             covfun_section_name: Default::default(),
         }
     }
 
-    fn take_function_coverage_map(&self) -> FxIndexMap<Instance<'tcx>, FunctionCoverage<'tcx>> {
-        self.function_coverage_map.replace(FxIndexMap::default())
-    }
-
     /// LLVM use a temp value to record evaluated mcdc test vector of each decision, which is
     /// called condition bitmap. In order to handle nested decisions, several condition bitmaps can
     /// be allocated for a function body. These values are named `mcdc.addr.{i}` and are a 32-bit
@@ -157,12 +151,7 @@ impl<'tcx> CoverageInfoBuilderMethods<'tcx> for Builder<'_, '_, 'tcx> {
         // Mark the instance as used in this CGU, for coverage purposes.
         // This includes functions that were not partitioned into this CGU,
         // but were MIR-inlined into one of this CGU's functions.
-        coverage_cx.function_coverage_map.borrow_mut().entry(instance).or_insert_with(|| {
-            FunctionCoverage::new_used(
-                function_coverage_info,
-                bx.tcx.coverage_ids_info(instance.def),
-            )
-        });
+        coverage_cx.instances_used.borrow_mut().insert(instance);
 
         match *kind {
             CoverageKind::SpanMarker | CoverageKind::BlockMarker { .. } => unreachable!(
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs b/compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs
index aef8642f199..2c9f1cda13a 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs
@@ -7,7 +7,7 @@ use rustc_hir::def_id::LOCAL_CRATE;
 use rustc_middle::bug;
 use rustc_middle::middle::debugger_visualizer::DebuggerVisualizerType;
 use rustc_session::config::{CrateType, DebugInfo};
-use rustc_span::symbol::sym;
+use rustc_span::sym;
 
 use crate::builder::Builder;
 use crate::common::CodegenCx;
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs b/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
index 59275254022..40248a9009a 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
@@ -16,8 +16,7 @@ use rustc_middle::ty::{
     self, AdtKind, CoroutineArgsExt, Instance, PolyExistentialTraitRef, Ty, TyCtxt, Visibility,
 };
 use rustc_session::config::{self, DebugInfo, Lto};
-use rustc_span::symbol::Symbol;
-use rustc_span::{DUMMY_SP, FileName, FileNameDisplayPreference, SourceFile, hygiene};
+use rustc_span::{DUMMY_SP, FileName, FileNameDisplayPreference, SourceFile, Symbol, hygiene};
 use rustc_symbol_mangling::typeid_for_trait_ref;
 use rustc_target::spec::DebuginfoKind;
 use smallvec::smallvec;
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/cpp_like.rs b/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/cpp_like.rs
index d374767f187..23e11748e52 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/cpp_like.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/cpp_like.rs
@@ -212,21 +212,17 @@ pub(super) fn build_enum_type_di_node<'ll, 'tcx>(
         ),
         |cx, enum_type_di_node| {
             match enum_type_and_layout.variants {
-                Variants::Single { index: variant_index } => {
-                    if enum_adt_def.variants().is_empty() {
-                        // Uninhabited enums have Variants::Single. We don't generate
-                        // any members for them.
-                        return smallvec![];
-                    }
-
-                    build_single_variant_union_fields(
-                        cx,
-                        enum_adt_def,
-                        enum_type_and_layout,
-                        enum_type_di_node,
-                        variant_index,
-                    )
+                Variants::Empty => {
+                    // We don't generate any members for uninhabited types.
+                    return smallvec![];
                 }
+                Variants::Single { index: variant_index } => build_single_variant_union_fields(
+                    cx,
+                    enum_adt_def,
+                    enum_type_and_layout,
+                    enum_type_di_node,
+                    variant_index,
+                ),
                 Variants::Multiple {
                     tag_encoding: TagEncoding::Direct,
                     ref variants,
@@ -303,6 +299,7 @@ pub(super) fn build_coroutine_di_node<'ll, 'tcx>(
                 )
             }
             Variants::Single { .. }
+            | Variants::Empty
             | Variants::Multiple { tag_encoding: TagEncoding::Niche { .. }, .. } => {
                 bug!(
                     "Encountered coroutine with non-direct-tag layout: {:?}",
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/mod.rs b/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/mod.rs
index 65ab22ad89e..9f6a5cc89e0 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/mod.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/mod.rs
@@ -392,7 +392,7 @@ fn compute_discriminant_value<'ll, 'tcx>(
     variant_index: VariantIdx,
 ) -> DiscrResult {
     match enum_type_and_layout.layout.variants() {
-        &Variants::Single { .. } => DiscrResult::NoDiscriminant,
+        &Variants::Single { .. } | &Variants::Empty => DiscrResult::NoDiscriminant,
         &Variants::Multiple { tag_encoding: TagEncoding::Direct, .. } => DiscrResult::Value(
             enum_type_and_layout.ty.discriminant_for_variant(cx.tcx, variant_index).unwrap().val,
         ),
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/native.rs b/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/native.rs
index 241bf167a81..11824398f24 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/native.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/native.rs
@@ -358,8 +358,8 @@ fn build_discr_member_di_node<'ll, 'tcx>(
     let containing_scope = enum_or_coroutine_type_di_node;
 
     match enum_or_coroutine_type_and_layout.layout.variants() {
-        // A single-variant enum has no discriminant.
-        &Variants::Single { .. } => None,
+        // A single-variant or no-variant enum has no discriminant.
+        &Variants::Single { .. } | &Variants::Empty => None,
 
         &Variants::Multiple { tag_field, .. } => {
             let tag_base_type = tag_base_type(cx.tcx, enum_or_coroutine_type_and_layout);
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs b/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs
index a8fdfbed592..fae698bea2a 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs
@@ -19,9 +19,8 @@ use rustc_middle::ty::layout::{HasTypingEnv, LayoutOf};
 use rustc_middle::ty::{self, GenericArgsRef, Instance, Ty, TypeVisitableExt};
 use rustc_session::Session;
 use rustc_session::config::{self, DebugInfo};
-use rustc_span::symbol::Symbol;
 use rustc_span::{
-    BytePos, Pos, SourceFile, SourceFileAndLine, SourceFileHash, Span, StableSourceFileId,
+    BytePos, Pos, SourceFile, SourceFileAndLine, SourceFileHash, Span, StableSourceFileId, Symbol,
 };
 use smallvec::SmallVec;
 use tracing::debug;
diff --git a/compiler/rustc_codegen_llvm/src/lib.rs b/compiler/rustc_codegen_llvm/src/lib.rs
index af8562db054..0de0c6a7a89 100644
--- a/compiler/rustc_codegen_llvm/src/lib.rs
+++ b/compiler/rustc_codegen_llvm/src/lib.rs
@@ -17,6 +17,7 @@
 #![feature(iter_intersperse)]
 #![feature(let_chains)]
 #![feature(rustdoc_internals)]
+#![feature(try_blocks)]
 #![warn(unreachable_pub)]
 // tidy-alphabetical-end
 
@@ -43,7 +44,7 @@ use rustc_middle::ty::TyCtxt;
 use rustc_middle::util::Providers;
 use rustc_session::Session;
 use rustc_session::config::{OptLevel, OutputFilenames, PrintKind, PrintRequest};
-use rustc_span::symbol::Symbol;
+use rustc_span::Symbol;
 
 mod back {
     pub(crate) mod archive;
diff --git a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
index d62632d1431..9a2bfd95562 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
@@ -56,25 +56,6 @@ pub enum LLVMRustResult {
     Failure,
 }
 
-// Rust version of the C struct with the same name in rustc_llvm/llvm-wrapper/RustWrapper.cpp.
-#[repr(C)]
-pub struct LLVMRustCOFFShortExport {
-    pub name: *const c_char,
-    pub ordinal_present: bool,
-    /// value of `ordinal` only important when `ordinal_present` is true
-    pub ordinal: u16,
-}
-
-impl LLVMRustCOFFShortExport {
-    pub fn new(name: *const c_char, ordinal: Option<u16>) -> LLVMRustCOFFShortExport {
-        LLVMRustCOFFShortExport {
-            name,
-            ordinal_present: ordinal.is_some(),
-            ordinal: ordinal.unwrap_or(0),
-        }
-    }
-}
-
 /// Translation of LLVM's MachineTypes enum, defined in llvm\include\llvm\BinaryFormat\COFF.h.
 ///
 /// We include only architectures supported on Windows.
@@ -2347,15 +2328,6 @@ unsafe extern "C" {
     ) -> &'a mut RustArchiveMember<'a>;
     pub fn LLVMRustArchiveMemberFree<'a>(Member: &'a mut RustArchiveMember<'a>);
 
-    pub fn LLVMRustWriteImportLibrary(
-        ImportName: *const c_char,
-        Path: *const c_char,
-        Exports: *const LLVMRustCOFFShortExport,
-        NumExports: usize,
-        Machine: u16,
-        MinGW: bool,
-    ) -> LLVMRustResult;
-
     pub fn LLVMRustSetDataLayoutFromTargetMachine<'a>(M: &'a Module, TM: &'a TargetMachine);
 
     pub fn LLVMRustPositionBuilderAtStart<'a>(B: &Builder<'a>, BB: &'a BasicBlock);
diff --git a/compiler/rustc_codegen_llvm/src/llvm_util.rs b/compiler/rustc_codegen_llvm/src/llvm_util.rs
index bfec7d708cf..628c0b1c29c 100644
--- a/compiler/rustc_codegen_llvm/src/llvm_util.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm_util.rs
@@ -15,7 +15,7 @@ use rustc_fs_util::path_to_c_string;
 use rustc_middle::bug;
 use rustc_session::Session;
 use rustc_session::config::{PrintKind, PrintRequest};
-use rustc_span::symbol::Symbol;
+use rustc_span::Symbol;
 use rustc_target::spec::{MergeFunctions, PanicStrategy, SmallDataThresholdSupport};
 use rustc_target::target_features::{RUSTC_SPECIAL_FEATURES, RUSTC_SPECIFIC_FEATURES};
 
@@ -373,9 +373,9 @@ pub fn target_features_cfg(sess: &Session, allow_unstable: bool) -> Vec<Symbol>
         .rust_target_features()
         .iter()
         .filter(|(_, gate, _)| gate.in_cfg())
-        .filter_map(|&(feature, gate, _)| {
+        .filter_map(|(feature, gate, _)| {
             if sess.is_nightly_build() || allow_unstable || gate.requires_nightly().is_none() {
-                Some(feature)
+                Some(*feature)
             } else {
                 None
             }
@@ -718,7 +718,7 @@ pub(crate) fn global_llvm_features(
                         }
                         Some((_, stability, _)) => {
                             if let Err(reason) =
-                                stability.compute_toggleability(&sess.target).allow_toggle()
+                                stability.toggle_allowed(&sess.target, enable_disable == '+')
                             {
                                 sess.dcx().emit_warn(ForbiddenCTargetFeature { feature, reason });
                             } else if stability.requires_nightly().is_some() {
diff --git a/compiler/rustc_codegen_llvm/src/type_of.rs b/compiler/rustc_codegen_llvm/src/type_of.rs
index 2b05e24a7ba..b0b6da869da 100644
--- a/compiler/rustc_codegen_llvm/src/type_of.rs
+++ b/compiler/rustc_codegen_llvm/src/type_of.rs
@@ -38,7 +38,7 @@ fn uncached_llvm_type<'a, 'tcx>(
             if let (&ty::Adt(def, _), &Variants::Single { index }) =
                 (layout.ty.kind(), &layout.variants)
             {
-                if def.is_enum() && !def.variants().is_empty() {
+                if def.is_enum() {
                     write!(&mut name, "::{}", def.variant(index).name).unwrap();
                 }
             }
diff --git a/compiler/rustc_codegen_ssa/Cargo.toml b/compiler/rustc_codegen_ssa/Cargo.toml
index 450a95ae20c..3a9b4d36807 100644
--- a/compiler/rustc_codegen_ssa/Cargo.toml
+++ b/compiler/rustc_codegen_ssa/Cargo.toml
@@ -8,7 +8,9 @@ edition = "2021"
 ar_archive_writer = "0.4.2"
 arrayvec = { version = "0.7", default-features = false }
 bitflags = "2.4.1"
-cc = "1.1.23"
+# Pinned so `cargo update` bumps don't cause breakage. Please also update the
+# `cc` in `rustc_llvm` if you update the `cc` here.
+cc = "=1.2.5"
 either = "1.5.0"
 itertools = "0.12"
 pathdiff = "0.2.0"
@@ -17,12 +19,13 @@ rustc_abi = { path = "../rustc_abi" }
 rustc_arena = { path = "../rustc_arena" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_ast_pretty = { path = "../rustc_ast_pretty" }
-rustc_attr = { path = "../rustc_attr" }
+rustc_attr_parsing = { path = "../rustc_attr_parsing" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
 rustc_fluent_macro = { path = "../rustc_fluent_macro" }
 rustc_fs_util = { path = "../rustc_fs_util" }
 rustc_hir = { path = "../rustc_hir" }
+rustc_hir_pretty = { path = "../rustc_hir_pretty" }
 rustc_incremental = { path = "../rustc_incremental" }
 rustc_index = { path = "../rustc_index" }
 rustc_macros = { path = "../rustc_macros" }
diff --git a/compiler/rustc_codegen_ssa/src/assert_module_sources.rs b/compiler/rustc_codegen_ssa/src/assert_module_sources.rs
index 11bcd727501..ab65319e3d3 100644
--- a/compiler/rustc_codegen_ssa/src/assert_module_sources.rs
+++ b/compiler/rustc_codegen_ssa/src/assert_module_sources.rs
@@ -26,15 +26,14 @@
 use std::borrow::Cow;
 use std::fmt;
 
-use rustc_ast as ast;
 use rustc_data_structures::unord::{UnordMap, UnordSet};
 use rustc_errors::{DiagArgValue, IntoDiagArg};
+use rustc_hir as hir;
 use rustc_hir::def_id::LOCAL_CRATE;
 use rustc_middle::mir::mono::CodegenUnitNameBuilder;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::Session;
-use rustc_span::symbol::sym;
-use rustc_span::{Span, Symbol};
+use rustc_span::{Span, Symbol, sym};
 use thin_vec::ThinVec;
 use tracing::debug;
 
@@ -77,7 +76,7 @@ struct AssertModuleSource<'tcx> {
 }
 
 impl<'tcx> AssertModuleSource<'tcx> {
-    fn check_attr(&mut self, attr: &ast::Attribute) {
+    fn check_attr(&mut self, attr: &hir::Attribute) {
         let (expected_reuse, comp_kind) = if attr.has_name(sym::rustc_partition_reused) {
             (CguReuse::PreLto, ComparisonKind::AtLeast)
         } else if attr.has_name(sym::rustc_partition_codegened) {
@@ -158,7 +157,7 @@ impl<'tcx> AssertModuleSource<'tcx> {
         );
     }
 
-    fn field(&self, attr: &ast::Attribute, name: Symbol) -> Symbol {
+    fn field(&self, attr: &hir::Attribute, name: Symbol) -> Symbol {
         for item in attr.meta_item_list().unwrap_or_else(ThinVec::new) {
             if item.has_name(name) {
                 if let Some(value) = item.value_str() {
@@ -177,7 +176,7 @@ impl<'tcx> AssertModuleSource<'tcx> {
 
     /// Scan for a `cfg="foo"` attribute and check whether we have a
     /// cfg flag called `foo`.
-    fn check_config(&self, attr: &ast::Attribute) -> bool {
+    fn check_config(&self, attr: &hir::Attribute) -> bool {
         let config = &self.tcx.sess.psess.config;
         let value = self.field(attr, sym::cfg);
         debug!("check_config(config={:?}, value={:?})", config, value);
diff --git a/compiler/rustc_codegen_ssa/src/back/archive.rs b/compiler/rustc_codegen_ssa/src/back/archive.rs
index d4836eb7a1d..d9eece1d8dc 100644
--- a/compiler/rustc_codegen_ssa/src/back/archive.rs
+++ b/compiler/rustc_codegen_ssa/src/back/archive.rs
@@ -14,7 +14,7 @@ use object::read::macho::FatArch;
 use rustc_data_structures::fx::FxIndexSet;
 use rustc_data_structures::memmap::Mmap;
 use rustc_session::Session;
-use rustc_span::symbol::Symbol;
+use rustc_span::Symbol;
 use tempfile::Builder as TempFileBuilder;
 use tracing::trace;
 
diff --git a/compiler/rustc_codegen_ssa/src/back/link.rs b/compiler/rustc_codegen_ssa/src/back/link.rs
index 31ac8c6e66a..4bc064528f3 100644
--- a/compiler/rustc_codegen_ssa/src/back/link.rs
+++ b/compiler/rustc_codegen_ssa/src/back/link.rs
@@ -15,7 +15,7 @@ use rustc_ast::CRATE_NODE_ID;
 use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_data_structures::memmap::Mmap;
 use rustc_data_structures::temp_dir::MaybeTempDir;
-use rustc_errors::{DiagCtxtHandle, FatalError};
+use rustc_errors::DiagCtxtHandle;
 use rustc_fs_util::{fix_windows_verbatim_for_gcc, try_canonicalize};
 use rustc_hir::def_id::{CrateNum, LOCAL_CRATE};
 use rustc_metadata::fs::{METADATA_FILENAME, copy_to_stdout, emit_wrapper_file};
@@ -35,7 +35,7 @@ use rustc_session::utils::NativeLibKind;
 /// For all the linkers we support, and information they might
 /// need out of the shared crate context before we get rid of it.
 use rustc_session::{Session, filesearch};
-use rustc_span::symbol::Symbol;
+use rustc_span::Symbol;
 use rustc_target::spec::crt_objects::CrtObjects;
 use rustc_target::spec::{
     Cc, LinkOutputKind, LinkSelfContainedComponents, LinkSelfContainedDefault, LinkerFeatures,
@@ -234,8 +234,6 @@ pub fn each_linked_rlib(
     crate_type: Option<CrateType>,
     f: &mut dyn FnMut(CrateNum, &Path),
 ) -> Result<(), errors::LinkRlibError> {
-    let crates = info.used_crates.iter();
-
     let fmts = if let Some(crate_type) = crate_type {
         let Some(fmts) = info.dependency_formats.get(&crate_type) else {
             return Err(errors::LinkRlibError::MissingFormat);
@@ -261,8 +259,9 @@ pub fn each_linked_rlib(
         info.dependency_formats.first().unwrap().1
     };
 
-    for &cnum in crates {
-        match fmts.get(cnum.as_usize() - 1) {
+    let used_dep_crates = info.used_crates.iter();
+    for &cnum in used_dep_crates {
+        match fmts.get(cnum) {
             Some(&Linkage::NotLinked | &Linkage::Dynamic | &Linkage::IncludedFromDylib) => continue,
             Some(_) => {}
             None => return Err(errors::LinkRlibError::MissingFormat),
@@ -624,7 +623,7 @@ fn link_staticlib(
 
     let mut all_rust_dylibs = vec![];
     for &cnum in crates {
-        match fmts.get(cnum.as_usize() - 1) {
+        match fmts.get(cnum) {
             Some(&Linkage::Dynamic) => {}
             _ => continue,
         }
@@ -986,12 +985,12 @@ fn link_natively(
                 let mut output = prog.stderr.clone();
                 output.extend_from_slice(&prog.stdout);
                 let escaped_output = escape_linker_output(&output, flavor);
-                // FIXME: Add UI tests for this error.
                 let err = errors::LinkingFailed {
                     linker_path: &linker_path,
                     exit_status: prog.status,
-                    command: &cmd,
+                    command: cmd,
                     escaped_output,
+                    verbose: sess.opts.verbose,
                 };
                 sess.dcx().emit_err(err);
                 // If MSVC's `link.exe` was expected but the return code
@@ -1039,22 +1038,22 @@ fn link_natively(
         Err(e) => {
             let linker_not_found = e.kind() == io::ErrorKind::NotFound;
 
-            if linker_not_found {
-                sess.dcx().emit_err(errors::LinkerNotFound { linker_path, error: e });
+            let err = if linker_not_found {
+                sess.dcx().emit_err(errors::LinkerNotFound { linker_path, error: e })
             } else {
                 sess.dcx().emit_err(errors::UnableToExeLinker {
                     linker_path,
                     error: e,
                     command_formatted: format!("{cmd:?}"),
-                });
-            }
+                })
+            };
 
             if sess.target.is_like_msvc && linker_not_found {
                 sess.dcx().emit_note(errors::MsvcMissingLinker);
                 sess.dcx().emit_note(errors::CheckInstalledVisualStudio);
                 sess.dcx().emit_note(errors::InsufficientVSCodeProduct);
             }
-            FatalError.raise();
+            err.raise_fatal();
         }
     }
 
@@ -2361,8 +2360,8 @@ fn linker_with_args(
         .crate_info
         .native_libraries
         .iter()
-        .filter_map(|(cnum, libraries)| {
-            (dependency_linkage[cnum.as_usize() - 1] != Linkage::Static).then_some(libraries)
+        .filter_map(|(&cnum, libraries)| {
+            (dependency_linkage[cnum] != Linkage::Static).then_some(libraries)
         })
         .flatten()
         .collect::<Vec<_>>();
@@ -2754,7 +2753,7 @@ fn add_upstream_rust_crates(
         // (e.g. `libstd` when `-C prefer-dynamic` is used).
         // FIXME: `dependency_formats` can report `profiler_builtins` as `NotLinked` for some
         // reason, it shouldn't do that because `profiler_builtins` should indeed be linked.
-        let linkage = data[cnum.as_usize() - 1];
+        let linkage = data[cnum];
         let link_static_crate = linkage == Linkage::Static
             || (linkage == Linkage::IncludedFromDylib || linkage == Linkage::NotLinked)
                 && (codegen_results.crate_info.compiler_builtins == Some(cnum)
@@ -2982,7 +2981,7 @@ fn add_dynamic_crate(cmd: &mut dyn Linker, sess: &Session, cratepath: &Path) {
 
 fn relevant_lib(sess: &Session, lib: &NativeLib) -> bool {
     match lib.cfg {
-        Some(ref cfg) => rustc_attr::cfg_matches(cfg, sess, CRATE_NODE_ID, None),
+        Some(ref cfg) => rustc_attr_parsing::cfg_matches(cfg, sess, CRATE_NODE_ID, None),
         None => true,
     }
 }
diff --git a/compiler/rustc_codegen_ssa/src/back/linker.rs b/compiler/rustc_codegen_ssa/src/back/linker.rs
index 301b22f2be4..3c6513ca26b 100644
--- a/compiler/rustc_codegen_ssa/src/back/linker.rs
+++ b/compiler/rustc_codegen_ssa/src/back/linker.rs
@@ -16,7 +16,7 @@ use rustc_middle::middle::exported_symbols::{ExportedSymbol, SymbolExportInfo, S
 use rustc_middle::ty::TyCtxt;
 use rustc_session::Session;
 use rustc_session::config::{self, CrateType, DebugInfo, LinkerPluginLto, Lto, OptLevel, Strip};
-use rustc_span::symbol::sym;
+use rustc_span::sym;
 use rustc_target::spec::{Cc, LinkOutputKind, LinkerFlavor, Lld};
 use tracing::{debug, warn};
 
@@ -1744,15 +1744,10 @@ fn for_each_exported_symbols_include_dep<'tcx>(
     crate_type: CrateType,
     mut callback: impl FnMut(ExportedSymbol<'tcx>, SymbolExportInfo, CrateNum),
 ) {
-    for &(symbol, info) in tcx.exported_symbols(LOCAL_CRATE).iter() {
-        callback(symbol, info, LOCAL_CRATE);
-    }
-
     let formats = tcx.dependency_formats(());
     let deps = &formats[&crate_type];
 
-    for (index, dep_format) in deps.iter().enumerate() {
-        let cnum = CrateNum::new(index + 1);
+    for (cnum, dep_format) in deps.iter_enumerated() {
         // For each dependency that we are linking to statically ...
         if *dep_format == Linkage::Static {
             for &(symbol, info) in tcx.exported_symbols(cnum).iter() {
diff --git a/compiler/rustc_codegen_ssa/src/back/symbol_export.rs b/compiler/rustc_codegen_ssa/src/back/symbol_export.rs
index 788a8a13b3e..60ab2919352 100644
--- a/compiler/rustc_codegen_ssa/src/back/symbol_export.rs
+++ b/compiler/rustc_codegen_ssa/src/back/symbol_export.rs
@@ -311,7 +311,8 @@ fn exported_symbols_provider_local(
             }
 
             if !tcx.sess.opts.share_generics() {
-                if tcx.codegen_fn_attrs(mono_item.def_id()).inline == rustc_attr::InlineAttr::Never
+                if tcx.codegen_fn_attrs(mono_item.def_id()).inline
+                    == rustc_attr_parsing::InlineAttr::Never
                 {
                     // this is OK, we explicitly allow sharing inline(never) across crates even
                     // without share-generics.
diff --git a/compiler/rustc_codegen_ssa/src/back/write.rs b/compiler/rustc_codegen_ssa/src/back/write.rs
index 683defcafee..b40bb4ed5d2 100644
--- a/compiler/rustc_codegen_ssa/src/back/write.rs
+++ b/compiler/rustc_codegen_ssa/src/back/write.rs
@@ -33,8 +33,7 @@ use rustc_session::config::{
     self, CrateType, Lto, OutFileName, OutputFilenames, OutputType, Passes, SwitchWithOptPath,
 };
 use rustc_span::source_map::SourceMap;
-use rustc_span::symbol::sym;
-use rustc_span::{FileName, InnerSpan, Span, SpanData};
+use rustc_span::{FileName, InnerSpan, Span, SpanData, sym};
 use rustc_target::spec::{MergeFunctions, SanitizerSet};
 use tracing::debug;
 
diff --git a/compiler/rustc_codegen_ssa/src/base.rs b/compiler/rustc_codegen_ssa/src/base.rs
index 27c9cb0b31e..77e1fed720d 100644
--- a/compiler/rustc_codegen_ssa/src/base.rs
+++ b/compiler/rustc_codegen_ssa/src/base.rs
@@ -5,7 +5,6 @@ use std::time::{Duration, Instant};
 use itertools::Itertools;
 use rustc_abi::FIRST_VARIANT;
 use rustc_ast::expand::allocator::{ALLOCATOR_METHODS, AllocatorKind, global_fn_name};
-use rustc_attr as attr;
 use rustc_data_structures::fx::{FxHashMap, FxIndexSet};
 use rustc_data_structures::profiling::{get_resident_set_size, print_time_passes_entry};
 use rustc_data_structures::sync::{Lrc, par_map};
@@ -25,12 +24,12 @@ use rustc_middle::ty::layout::{HasTyCtxt, HasTypingEnv, LayoutOf, TyAndLayout};
 use rustc_middle::ty::{self, Instance, Ty, TyCtxt};
 use rustc_session::Session;
 use rustc_session::config::{self, CrateType, EntryFnType, OptLevel, OutputType};
-use rustc_span::symbol::sym;
-use rustc_span::{DUMMY_SP, Symbol};
+use rustc_span::{DUMMY_SP, Symbol, sym};
 use rustc_trait_selection::infer::at::ToTrace;
 use rustc_trait_selection::infer::{BoundRegionConversionTime, TyCtxtInferExt};
 use rustc_trait_selection::traits::{ObligationCause, ObligationCtxt};
 use tracing::{debug, info};
+use {rustc_ast as ast, rustc_attr_parsing as attr};
 
 use crate::assert_module_sources::CguReuse;
 use crate::back::link::are_upstream_rust_objects_already_included;
@@ -873,7 +872,8 @@ impl CrateInfo {
             crate_types.iter().map(|&c| (c, crate::back::linker::linked_symbols(tcx, c))).collect();
         let local_crate_name = tcx.crate_name(LOCAL_CRATE);
         let crate_attrs = tcx.hir().attrs(rustc_hir::CRATE_HIR_ID);
-        let subsystem = attr::first_attr_value_str_by_name(crate_attrs, sym::windows_subsystem);
+        let subsystem =
+            ast::attr::first_attr_value_str_by_name(crate_attrs, sym::windows_subsystem);
         let windows_subsystem = subsystem.map(|subsystem| {
             if subsystem != sym::windows && subsystem != sym::console {
                 tcx.dcx().emit_fatal(errors::InvalidWindowsSubsystem { subsystem });
diff --git a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
index ab2d24e8d2d..cdb72aba36f 100644
--- a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
+++ b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
@@ -1,5 +1,6 @@
-use rustc_ast::{MetaItemInner, MetaItemKind, ast, attr};
-use rustc_attr::{InlineAttr, InstructionSetAttr, OptimizeAttr, list_contains_name};
+use rustc_ast::attr::list_contains_name;
+use rustc_ast::{MetaItemInner, attr};
+use rustc_attr_parsing::{InlineAttr, InstructionSetAttr, OptimizeAttr};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::codes::*;
 use rustc_errors::{DiagMessage, SubdiagMessage, struct_span_code_err};
@@ -15,8 +16,7 @@ use rustc_middle::query::Providers;
 use rustc_middle::ty::{self as ty, TyCtxt};
 use rustc_session::parse::feature_err;
 use rustc_session::{Session, lint};
-use rustc_span::symbol::Ident;
-use rustc_span::{Span, sym};
+use rustc_span::{Ident, Span, sym};
 use rustc_target::spec::{SanitizerSet, abi};
 
 use crate::errors;
@@ -251,7 +251,7 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
             sym::target_feature => {
                 if !tcx.is_closure_like(did.to_def_id())
                     && let Some(fn_sig) = fn_sig()
-                    && fn_sig.skip_binder().safety() == hir::Safety::Safe
+                    && fn_sig.skip_binder().safety().is_safe()
                 {
                     if tcx.sess.target.is_like_wasm || tcx.sess.opts.actually_rustdoc {
                         // The `#[target_feature]` attribute is allowed on
@@ -425,7 +425,7 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
                     && let [item] = items.as_slice()
                     && let Some((sym::align, literal)) = item.singleton_lit_list()
                 {
-                    rustc_attr::parse_alignment(&literal.kind)
+                    rustc_attr_parsing::parse_alignment(&literal.kind)
                         .map_err(|msg| {
                             struct_span_code_err!(
                                 tcx.dcx(),
@@ -525,28 +525,26 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
         if !attr.has_name(sym::inline) {
             return ia;
         }
-        match attr.meta_kind() {
-            Some(MetaItemKind::Word) => InlineAttr::Hint,
-            Some(MetaItemKind::List(ref items)) => {
-                inline_span = Some(attr.span);
-                if items.len() != 1 {
-                    struct_span_code_err!(tcx.dcx(), attr.span, E0534, "expected one argument")
-                        .emit();
-                    InlineAttr::None
-                } else if list_contains_name(items, sym::always) {
-                    InlineAttr::Always
-                } else if list_contains_name(items, sym::never) {
-                    InlineAttr::Never
-                } else {
-                    struct_span_code_err!(tcx.dcx(), items[0].span(), E0535, "invalid argument")
-                        .with_help("valid inline arguments are `always` and `never`")
-                        .emit();
+        if attr.is_word() {
+            InlineAttr::Hint
+        } else if let Some(ref items) = attr.meta_item_list() {
+            inline_span = Some(attr.span);
+            if items.len() != 1 {
+                struct_span_code_err!(tcx.dcx(), attr.span, E0534, "expected one argument").emit();
+                InlineAttr::None
+            } else if list_contains_name(items, sym::always) {
+                InlineAttr::Always
+            } else if list_contains_name(items, sym::never) {
+                InlineAttr::Never
+            } else {
+                struct_span_code_err!(tcx.dcx(), items[0].span(), E0535, "invalid argument")
+                    .with_help("valid inline arguments are `always` and `never`")
+                    .emit();
 
-                    InlineAttr::None
-                }
+                InlineAttr::None
             }
-            Some(MetaItemKind::NameValue(_)) => ia,
-            None => ia,
+        } else {
+            ia
         }
     });
 
@@ -562,27 +560,24 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
             return ia;
         }
         let err = |sp, s| struct_span_code_err!(tcx.dcx(), sp, E0722, "{}", s).emit();
-        match attr.meta_kind() {
-            Some(MetaItemKind::Word) => {
+        if attr.is_word() {
+            err(attr.span, "expected one argument");
+            ia
+        } else if let Some(ref items) = attr.meta_item_list() {
+            inline_span = Some(attr.span);
+            if items.len() != 1 {
                 err(attr.span, "expected one argument");
-                ia
-            }
-            Some(MetaItemKind::List(ref items)) => {
-                inline_span = Some(attr.span);
-                if items.len() != 1 {
-                    err(attr.span, "expected one argument");
-                    OptimizeAttr::None
-                } else if list_contains_name(items, sym::size) {
-                    OptimizeAttr::Size
-                } else if list_contains_name(items, sym::speed) {
-                    OptimizeAttr::Speed
-                } else {
-                    err(items[0].span(), "invalid argument");
-                    OptimizeAttr::None
-                }
+                OptimizeAttr::None
+            } else if list_contains_name(items, sym::size) {
+                OptimizeAttr::Size
+            } else if list_contains_name(items, sym::speed) {
+                OptimizeAttr::Speed
+            } else {
+                err(items[0].span(), "invalid argument");
+                OptimizeAttr::None
             }
-            Some(MetaItemKind::NameValue(_)) => ia,
-            None => ia,
+        } else {
+            OptimizeAttr::None
         }
     });
 
@@ -730,7 +725,7 @@ fn should_inherit_track_caller(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
     false
 }
 
-fn check_link_ordinal(tcx: TyCtxt<'_>, attr: &ast::Attribute) -> Option<u16> {
+fn check_link_ordinal(tcx: TyCtxt<'_>, attr: &hir::Attribute) -> Option<u16> {
     use rustc_ast::{LitIntType, LitKind, MetaItemLit};
     let meta_item_list = attr.meta_item_list();
     let meta_item_list = meta_item_list.as_deref();
@@ -795,7 +790,7 @@ struct MixedExportNameAndNoMangleState<'a> {
     export_name: Option<Span>,
     hir_id: Option<HirId>,
     no_mangle: Option<Span>,
-    no_mangle_attr: Option<&'a ast::Attribute>,
+    no_mangle_attr: Option<&'a hir::Attribute>,
 }
 
 impl<'a> MixedExportNameAndNoMangleState<'a> {
@@ -803,7 +798,7 @@ impl<'a> MixedExportNameAndNoMangleState<'a> {
         self.export_name = Some(span);
     }
 
-    fn track_no_mangle(&mut self, span: Span, hir_id: HirId, attr_name: &'a ast::Attribute) {
+    fn track_no_mangle(&mut self, span: Span, hir_id: HirId, attr_name: &'a hir::Attribute) {
         self.no_mangle = Some(span);
         self.hir_id = Some(hir_id);
         self.no_mangle_attr = Some(attr_name);
@@ -824,7 +819,7 @@ impl<'a> MixedExportNameAndNoMangleState<'a> {
                 no_mangle,
                 errors::MixedExportNameAndNoMangle {
                     no_mangle,
-                    no_mangle_attr: rustc_ast_pretty::pprust::attribute_to_string(no_mangle_attr),
+                    no_mangle_attr: rustc_hir_pretty::attribute_to_string(&tcx, no_mangle_attr),
                     export_name,
                     removal_span: no_mangle,
                 },
diff --git a/compiler/rustc_codegen_ssa/src/debuginfo/mod.rs b/compiler/rustc_codegen_ssa/src/debuginfo/mod.rs
index 88d36b19da4..7c62c03d574 100644
--- a/compiler/rustc_codegen_ssa/src/debuginfo/mod.rs
+++ b/compiler/rustc_codegen_ssa/src/debuginfo/mod.rs
@@ -65,8 +65,8 @@ fn tag_base_type_opt<'tcx>(
     });
 
     match enum_type_and_layout.layout.variants() {
-        // A single-variant enum has no discriminant.
-        Variants::Single { .. } => None,
+        // A single-variant or no-variant enum has no discriminant.
+        Variants::Single { .. } | Variants::Empty => None,
 
         Variants::Multiple { tag_encoding: TagEncoding::Niche { .. }, tag, .. } => {
             // Niche tags are always normalized to unsized integers of the correct size.
diff --git a/compiler/rustc_codegen_ssa/src/errors.rs b/compiler/rustc_codegen_ssa/src/errors.rs
index 00f8654e670..c7213bbc801 100644
--- a/compiler/rustc_codegen_ssa/src/errors.rs
+++ b/compiler/rustc_codegen_ssa/src/errors.rs
@@ -1,6 +1,7 @@
 //! Errors emitted by codegen_ssa
 
 use std::borrow::Cow;
+use std::ffi::OsString;
 use std::io::Error;
 use std::num::ParseIntError;
 use std::path::{Path, PathBuf};
@@ -345,21 +346,82 @@ impl<G: EmissionGuarantee> Diagnostic<'_, G> for ThorinErrorWrapper {
 }
 
 pub(crate) struct LinkingFailed<'a> {
-    pub linker_path: &'a PathBuf,
+    pub linker_path: &'a Path,
     pub exit_status: ExitStatus,
-    pub command: &'a Command,
+    pub command: Command,
     pub escaped_output: String,
+    pub verbose: bool,
 }
 
 impl<G: EmissionGuarantee> Diagnostic<'_, G> for LinkingFailed<'_> {
-    fn into_diag(self, dcx: DiagCtxtHandle<'_>, level: Level) -> Diag<'_, G> {
+    fn into_diag(mut self, dcx: DiagCtxtHandle<'_>, level: Level) -> Diag<'_, G> {
         let mut diag = Diag::new(dcx, level, fluent::codegen_ssa_linking_failed);
         diag.arg("linker_path", format!("{}", self.linker_path.display()));
         diag.arg("exit_status", format!("{}", self.exit_status));
 
         let contains_undefined_ref = self.escaped_output.contains("undefined reference to");
 
-        diag.note(format!("{:?}", self.command)).note(self.escaped_output);
+        if self.verbose {
+            diag.note(format!("{:?}", self.command));
+        } else {
+            enum ArgGroup {
+                Regular(OsString),
+                Objects(usize),
+                Rlibs(PathBuf, Vec<OsString>),
+            }
+
+            // Omit rust object files and fold rlibs in the error by default to make linker errors a
+            // bit less verbose.
+            let orig_args = self.command.take_args();
+            let mut args: Vec<ArgGroup> = vec![];
+            for arg in orig_args {
+                if arg.as_encoded_bytes().ends_with(b".rcgu.o") {
+                    if let Some(ArgGroup::Objects(n)) = args.last_mut() {
+                        *n += 1;
+                    } else {
+                        args.push(ArgGroup::Objects(1));
+                    }
+                } else if arg.as_encoded_bytes().ends_with(b".rlib") {
+                    let rlib_path = Path::new(&arg);
+                    let dir = rlib_path.parent().unwrap();
+                    let filename = rlib_path.file_name().unwrap().to_owned();
+                    if let Some(ArgGroup::Rlibs(parent, rlibs)) = args.last_mut() {
+                        if parent == dir {
+                            rlibs.push(filename);
+                        } else {
+                            args.push(ArgGroup::Rlibs(dir.to_owned(), vec![filename]));
+                        }
+                    } else {
+                        args.push(ArgGroup::Rlibs(dir.to_owned(), vec![filename]));
+                    }
+                } else {
+                    args.push(ArgGroup::Regular(arg));
+                }
+            }
+            self.command.args(args.into_iter().map(|arg_group| match arg_group {
+                ArgGroup::Regular(arg) => arg,
+                ArgGroup::Objects(n) => OsString::from(format!("<{n} object files omitted>")),
+                ArgGroup::Rlibs(dir, rlibs) => {
+                    let mut arg = dir.into_os_string();
+                    arg.push("/{");
+                    let mut first = true;
+                    for rlib in rlibs {
+                        if !first {
+                            arg.push(",");
+                        }
+                        first = false;
+                        arg.push(rlib);
+                    }
+                    arg.push("}");
+                    arg
+                }
+            }));
+
+            diag.note(format!("{:?}", self.command));
+            diag.note("some arguments are omitted. use `--verbose` to show all linker arguments");
+        }
+
+        diag.note(self.escaped_output);
 
         // Trying to match an error from OS linkers
         // which by now we have no way to translate.
diff --git a/compiler/rustc_codegen_ssa/src/lib.rs b/compiler/rustc_codegen_ssa/src/lib.rs
index 7dc8ab38a97..65c6067c740 100644
--- a/compiler/rustc_codegen_ssa/src/lib.rs
+++ b/compiler/rustc_codegen_ssa/src/lib.rs
@@ -42,7 +42,7 @@ use rustc_session::Session;
 use rustc_session::config::{CrateType, OutputFilenames, OutputType, RUST_CGU_EXT};
 use rustc_session::cstore::{self, CrateSource};
 use rustc_session::utils::NativeLibKind;
-use rustc_span::symbol::Symbol;
+use rustc_span::Symbol;
 
 pub mod assert_module_sources;
 pub mod back;
diff --git a/compiler/rustc_codegen_ssa/src/mir/debuginfo.rs b/compiler/rustc_codegen_ssa/src/mir/debuginfo.rs
index d4d7f16db55..843a996d2bf 100644
--- a/compiler/rustc_codegen_ssa/src/mir/debuginfo.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/debuginfo.rs
@@ -10,8 +10,7 @@ use rustc_middle::ty::layout::{LayoutOf, TyAndLayout};
 use rustc_middle::ty::{Instance, Ty};
 use rustc_middle::{bug, mir, ty};
 use rustc_session::config::DebugInfo;
-use rustc_span::symbol::{Symbol, kw};
-use rustc_span::{BytePos, Span, hygiene};
+use rustc_span::{BytePos, Span, Symbol, hygiene, kw};
 
 use super::operand::{OperandRef, OperandValue};
 use super::place::{PlaceRef, PlaceValue};
diff --git a/compiler/rustc_codegen_ssa/src/mir/naked_asm.rs b/compiler/rustc_codegen_ssa/src/mir/naked_asm.rs
index c08758a9796..cac3cc587cb 100644
--- a/compiler/rustc_codegen_ssa/src/mir/naked_asm.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/naked_asm.rs
@@ -1,4 +1,4 @@
-use rustc_attr::InstructionSetAttr;
+use rustc_attr_parsing::InstructionSetAttr;
 use rustc_middle::mir::mono::{Linkage, MonoItem, MonoItemData, Visibility};
 use rustc_middle::mir::{Body, InlineAsmOperand};
 use rustc_middle::ty::layout::{HasTyCtxt, HasTypingEnv, LayoutOf};
diff --git a/compiler/rustc_codegen_ssa/src/mir/place.rs b/compiler/rustc_codegen_ssa/src/mir/place.rs
index c38484109d2..c634f864ffb 100644
--- a/compiler/rustc_codegen_ssa/src/mir/place.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/place.rs
@@ -243,6 +243,7 @@ impl<'a, 'tcx, V: CodegenObject> PlaceRef<'tcx, V> {
             return bx.cx().const_poison(cast_to);
         }
         let (tag_scalar, tag_encoding, tag_field) = match self.layout.variants {
+            Variants::Empty => unreachable!("we already handled uninhabited types"),
             Variants::Single { index } => {
                 let discr_val = self
                     .layout
@@ -365,9 +366,9 @@ impl<'a, 'tcx, V: CodegenObject> PlaceRef<'tcx, V> {
             return;
         }
         match self.layout.variants {
-            Variants::Single { index } => {
-                assert_eq!(index, variant_index);
-            }
+            Variants::Empty => unreachable!("we already handled uninhabited types"),
+            Variants::Single { index } => assert_eq!(index, variant_index),
+
             Variants::Multiple { tag_encoding: TagEncoding::Direct, tag_field, .. } => {
                 let ptr = self.project_field(bx, tag_field);
                 let to =
@@ -422,10 +423,7 @@ impl<'a, 'tcx, V: CodegenObject> PlaceRef<'tcx, V> {
             layout.size
         };
 
-        let llval = bx.inbounds_gep(bx.cx().backend_type(self.layout), self.val.llval, &[
-            bx.cx().const_usize(0),
-            llindex,
-        ]);
+        let llval = bx.inbounds_gep(bx.cx().backend_type(layout), self.val.llval, &[llindex]);
         let align = self.val.align.restrict_for_offset(offset);
         PlaceValue::new_sized(llval, align).with_type(layout)
     }
diff --git a/compiler/rustc_codegen_ssa/src/target_features.rs b/compiler/rustc_codegen_ssa/src/target_features.rs
index fa600ec7166..7e80d014ea2 100644
--- a/compiler/rustc_codegen_ssa/src/target_features.rs
+++ b/compiler/rustc_codegen_ssa/src/target_features.rs
@@ -1,16 +1,15 @@
-use rustc_ast::ast;
-use rustc_attr::InstructionSetAttr;
+use rustc_attr_parsing::InstructionSetAttr;
 use rustc_data_structures::fx::FxIndexSet;
 use rustc_data_structures::unord::{UnordMap, UnordSet};
 use rustc_errors::Applicability;
+use rustc_hir as hir;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{DefId, LOCAL_CRATE, LocalDefId};
 use rustc_middle::middle::codegen_fn_attrs::TargetFeature;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::parse::feature_err;
-use rustc_span::Span;
-use rustc_span::symbol::{Symbol, sym};
+use rustc_span::{Span, Symbol, sym};
 use rustc_target::target_features;
 
 use crate::errors;
@@ -19,7 +18,7 @@ use crate::errors;
 /// Enabled target features are added to `target_features`.
 pub(crate) fn from_target_feature_attr(
     tcx: TyCtxt<'_>,
-    attr: &ast::Attribute,
+    attr: &hir::Attribute,
     rust_target_features: &UnordMap<String, target_features::StabilityComputed>,
     target_features: &mut Vec<TargetFeature>,
 ) {
@@ -65,7 +64,7 @@ pub(crate) fn from_target_feature_attr(
 
             // Only allow target features whose feature gates have been enabled
             // and which are permitted to be toggled.
-            if let Err(reason) = stability.allow_toggle() {
+            if let Err(reason) = stability.toggle_allowed(/*enable*/ true) {
                 tcx.dcx().emit_err(errors::ForbiddenTargetFeatureAttr {
                     span: item.span(),
                     feature,
@@ -160,7 +159,7 @@ pub(crate) fn provide(providers: &mut Providers) {
                     .target
                     .rust_target_features()
                     .iter()
-                    .map(|&(a, b, _)| (a.to_string(), b.compute_toggleability(target)))
+                    .map(|(a, b, _)| (a.to_string(), b.compute_toggleability(target)))
                     .collect()
             }
         },
diff --git a/compiler/rustc_codegen_ssa/src/traits/backend.rs b/compiler/rustc_codegen_ssa/src/traits/backend.rs
index 4b17db2c49e..ebcf118b903 100644
--- a/compiler/rustc_codegen_ssa/src/traits/backend.rs
+++ b/compiler/rustc_codegen_ssa/src/traits/backend.rs
@@ -11,7 +11,7 @@ use rustc_middle::ty::TyCtxt;
 use rustc_middle::util::Providers;
 use rustc_session::Session;
 use rustc_session::config::{self, OutputFilenames, PrintRequest};
-use rustc_span::symbol::Symbol;
+use rustc_span::Symbol;
 
 use super::CodegenObject;
 use super::write::WriteBackendMethods;
diff --git a/compiler/rustc_const_eval/Cargo.toml b/compiler/rustc_const_eval/Cargo.toml
index 41136019a88..7717cd2c696 100644
--- a/compiler/rustc_const_eval/Cargo.toml
+++ b/compiler/rustc_const_eval/Cargo.toml
@@ -9,7 +9,7 @@ either = "1"
 rustc_abi = { path = "../rustc_abi" }
 rustc_apfloat = "0.2.0"
 rustc_ast = { path = "../rustc_ast" }
-rustc_attr = { path = "../rustc_attr" }
+rustc_attr_parsing = { path = "../rustc_attr_parsing" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
 rustc_fluent_macro = { path = "../rustc_fluent_macro" }
diff --git a/compiler/rustc_const_eval/src/check_consts/check.rs b/compiler/rustc_const_eval/src/check_consts/check.rs
index 16610ebfca2..f4257ad9671 100644
--- a/compiler/rustc_const_eval/src/check_consts/check.rs
+++ b/compiler/rustc_const_eval/src/check_consts/check.rs
@@ -6,7 +6,7 @@ use std::mem;
 use std::num::NonZero;
 use std::ops::Deref;
 
-use rustc_attr::{ConstStability, StabilityLevel};
+use rustc_attr_parsing::{ConstStability, StabilityLevel};
 use rustc_errors::{Diag, ErrorGuaranteed};
 use rustc_hir::def_id::DefId;
 use rustc_hir::{self as hir, LangItem};
diff --git a/compiler/rustc_const_eval/src/check_consts/mod.rs b/compiler/rustc_const_eval/src/check_consts/mod.rs
index 80d3c6448aa..ab68691f1b9 100644
--- a/compiler/rustc_const_eval/src/check_consts/mod.rs
+++ b/compiler/rustc_const_eval/src/check_consts/mod.rs
@@ -9,7 +9,7 @@ use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_middle::ty::{self, PolyFnSig, TyCtxt};
 use rustc_middle::{bug, mir};
 use rustc_span::Symbol;
-use {rustc_attr as attr, rustc_hir as hir};
+use {rustc_attr_parsing as attr, rustc_hir as hir};
 
 pub use self::qualifs::Qualif;
 
diff --git a/compiler/rustc_const_eval/src/check_consts/ops.rs b/compiler/rustc_const_eval/src/check_consts/ops.rs
index 23f2aa4d029..afb7900c4b0 100644
--- a/compiler/rustc_const_eval/src/check_consts/ops.rs
+++ b/compiler/rustc_const_eval/src/check_consts/ops.rs
@@ -15,8 +15,7 @@ use rustc_middle::ty::{
     suggest_constraining_type_param,
 };
 use rustc_middle::util::{CallDesugaringKind, CallKind, call_kind};
-use rustc_span::symbol::sym;
-use rustc_span::{BytePos, Pos, Span, Symbol};
+use rustc_span::{BytePos, Pos, Span, Symbol, sym};
 use rustc_trait_selection::traits::SelectionContext;
 use tracing::debug;
 
diff --git a/compiler/rustc_const_eval/src/check_consts/post_drop_elaboration.rs b/compiler/rustc_const_eval/src/check_consts/post_drop_elaboration.rs
index 951e19b470b..16e142a85ee 100644
--- a/compiler/rustc_const_eval/src/check_consts/post_drop_elaboration.rs
+++ b/compiler/rustc_const_eval/src/check_consts/post_drop_elaboration.rs
@@ -1,7 +1,7 @@
 use rustc_middle::mir::visit::Visitor;
 use rustc_middle::mir::{self, BasicBlock, Location};
 use rustc_middle::ty::TyCtxt;
-use rustc_span::symbol::sym;
+use rustc_span::sym;
 use tracing::trace;
 
 use super::ConstCx;
diff --git a/compiler/rustc_const_eval/src/check_consts/resolver.rs b/compiler/rustc_const_eval/src/check_consts/resolver.rs
index 763c37a41af..79df63a9e84 100644
--- a/compiler/rustc_const_eval/src/check_consts/resolver.rs
+++ b/compiler/rustc_const_eval/src/check_consts/resolver.rs
@@ -5,7 +5,7 @@
 use std::fmt;
 use std::marker::PhantomData;
 
-use rustc_index::bit_set::BitSet;
+use rustc_index::bit_set::MixedBitSet;
 use rustc_middle::mir::visit::Visitor;
 use rustc_middle::mir::{
     self, BasicBlock, CallReturnPlaces, Local, Location, Statement, StatementKind, TerminatorEdges,
@@ -246,12 +246,14 @@ where
 }
 
 #[derive(Debug, PartialEq, Eq)]
+/// The state for the `FlowSensitiveAnalysis` dataflow analysis. This domain is likely homogeneous,
+/// and has a big size, so we use a bitset that can be sparse (c.f. issue #134404).
 pub(super) struct State {
     /// Describes whether a local contains qualif.
-    pub qualif: BitSet<Local>,
+    pub qualif: MixedBitSet<Local>,
     /// Describes whether a local's address escaped and it might become qualified as a result an
     /// indirect mutation.
-    pub borrow: BitSet<Local>,
+    pub borrow: MixedBitSet<Local>,
 }
 
 impl Clone for State {
@@ -320,8 +322,8 @@ where
 
     fn bottom_value(&self, body: &mir::Body<'tcx>) -> Self::Domain {
         State {
-            qualif: BitSet::new_empty(body.local_decls.len()),
-            borrow: BitSet::new_empty(body.local_decls.len()),
+            qualif: MixedBitSet::new_empty(body.local_decls.len()),
+            borrow: MixedBitSet::new_empty(body.local_decls.len()),
         }
     }
 
diff --git a/compiler/rustc_const_eval/src/const_eval/dummy_machine.rs b/compiler/rustc_const_eval/src/const_eval/dummy_machine.rs
index 817acfcca74..46dcebc46e9 100644
--- a/compiler/rustc_const_eval/src/const_eval/dummy_machine.rs
+++ b/compiler/rustc_const_eval/src/const_eval/dummy_machine.rs
@@ -1,9 +1,11 @@
 use rustc_middle::mir::interpret::{AllocId, ConstAllocation, InterpResult};
 use rustc_middle::mir::*;
 use rustc_middle::query::TyCtxtAt;
+use rustc_middle::ty::Ty;
 use rustc_middle::ty::layout::TyAndLayout;
 use rustc_middle::{bug, span_bug, ty};
 use rustc_span::def_id::DefId;
+use rustc_target::callconv::FnAbi;
 
 use crate::interpret::{
     self, HasStaticRootDefId, ImmTy, Immediate, InterpCx, PointerArithmetic, interp_ok,
@@ -86,7 +88,7 @@ impl<'tcx> interpret::Machine<'tcx> for DummyMachine {
     fn find_mir_or_eval_fn(
         _ecx: &mut InterpCx<'tcx, Self>,
         _instance: ty::Instance<'tcx>,
-        _abi: rustc_abi::ExternAbi,
+        _abi: &FnAbi<'tcx, Ty<'tcx>>,
         _args: &[interpret::FnArg<'tcx, Self::Provenance>],
         _destination: &interpret::MPlaceTy<'tcx, Self::Provenance>,
         _target: Option<BasicBlock>,
diff --git a/compiler/rustc_const_eval/src/const_eval/fn_queries.rs b/compiler/rustc_const_eval/src/const_eval/fn_queries.rs
index f5396c62433..babf99c4c1f 100644
--- a/compiler/rustc_const_eval/src/const_eval/fn_queries.rs
+++ b/compiler/rustc_const_eval/src/const_eval/fn_queries.rs
@@ -57,9 +57,8 @@ fn is_promotable_const_fn(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
             Some(stab) => {
                 if cfg!(debug_assertions) && stab.promotable {
                     let sig = tcx.fn_sig(def_id);
-                    assert_eq!(
-                        sig.skip_binder().safety(),
-                        hir::Safety::Safe,
+                    assert!(
+                        sig.skip_binder().safety().is_safe(),
                         "don't mark const unsafe fns as promotable",
                         // https://github.com/rust-lang/rust/pull/53851#issuecomment-418760682
                     );
diff --git a/compiler/rustc_const_eval/src/const_eval/machine.rs b/compiler/rustc_const_eval/src/const_eval/machine.rs
index 23683851799..ba7fbb254c6 100644
--- a/compiler/rustc_const_eval/src/const_eval/machine.rs
+++ b/compiler/rustc_const_eval/src/const_eval/machine.rs
@@ -2,7 +2,7 @@ use std::borrow::{Borrow, Cow};
 use std::fmt;
 use std::hash::Hash;
 
-use rustc_abi::{Align, ExternAbi, Size};
+use rustc_abi::{Align, Size};
 use rustc_ast::Mutability;
 use rustc_data_structures::fx::{FxHashMap, FxIndexMap, IndexEntry};
 use rustc_hir::def_id::{DefId, LocalDefId};
@@ -13,8 +13,8 @@ use rustc_middle::query::TyCtxtAt;
 use rustc_middle::ty::layout::{HasTypingEnv, TyAndLayout};
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_middle::{bug, mir};
-use rustc_span::Span;
-use rustc_span::symbol::{Symbol, sym};
+use rustc_span::{Span, Symbol, sym};
+use rustc_target::callconv::FnAbi;
 use tracing::debug;
 
 use super::error::*;
@@ -340,7 +340,7 @@ impl<'tcx> interpret::Machine<'tcx> for CompileTimeMachine<'tcx> {
     fn find_mir_or_eval_fn(
         ecx: &mut InterpCx<'tcx, Self>,
         orig_instance: ty::Instance<'tcx>,
-        _abi: ExternAbi,
+        _abi: &FnAbi<'tcx, Ty<'tcx>>,
         args: &[FnArg<'tcx>],
         dest: &MPlaceTy<'tcx>,
         ret: Option<mir::BasicBlock>,
diff --git a/compiler/rustc_const_eval/src/interpret/call.rs b/compiler/rustc_const_eval/src/interpret/call.rs
index ed4a1a9e647..46720328ea4 100644
--- a/compiler/rustc_const_eval/src/interpret/call.rs
+++ b/compiler/rustc_const_eval/src/interpret/call.rs
@@ -519,7 +519,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                 return M::call_extra_fn(
                     self,
                     extra,
-                    caller_abi,
+                    caller_fn_abi,
                     args,
                     destination,
                     target,
@@ -570,7 +570,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                 let Some((body, instance)) = M::find_mir_or_eval_fn(
                     self,
                     instance,
-                    caller_abi,
+                    caller_fn_abi,
                     args,
                     destination,
                     target,
diff --git a/compiler/rustc_const_eval/src/interpret/discriminant.rs b/compiler/rustc_const_eval/src/interpret/discriminant.rs
index 6faac1582ab..2f0b1cb6d1e 100644
--- a/compiler/rustc_const_eval/src/interpret/discriminant.rs
+++ b/compiler/rustc_const_eval/src/interpret/discriminant.rs
@@ -44,7 +44,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         }
     }
 
-    /// Read discriminant, return the runtime value as well as the variant index.
+    /// Read discriminant, return the variant index.
     /// Can also legally be called on non-enums (e.g. through the discriminant_value intrinsic)!
     ///
     /// Will never return an uninhabited variant.
@@ -65,21 +65,17 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         // We use "tag" to refer to how the discriminant is encoded in memory, which can be either
         // straight-forward (`TagEncoding::Direct`) or with a niche (`TagEncoding::Niche`).
         let (tag_scalar_layout, tag_encoding, tag_field) = match op.layout().variants {
+            Variants::Empty => {
+                throw_ub!(UninhabitedEnumVariantRead(None));
+            }
             Variants::Single { index } => {
-                // Do some extra checks on enums.
-                if ty.is_enum() {
-                    // Hilariously, `Single` is used even for 0-variant enums.
-                    // (See https://github.com/rust-lang/rust/issues/89765).
-                    if ty.ty_adt_def().unwrap().variants().is_empty() {
-                        throw_ub!(UninhabitedEnumVariantRead(index))
-                    }
+                if op.layout().is_uninhabited() {
                     // For consistency with `write_discriminant`, and to make sure that
                     // `project_downcast` cannot fail due to strange layouts, we declare immediate UB
-                    // for uninhabited variants.
-                    if op.layout().for_variant(self, index).is_uninhabited() {
-                        throw_ub!(UninhabitedEnumVariantRead(index))
-                    }
+                    // for uninhabited enums.
+                    throw_ub!(UninhabitedEnumVariantRead(Some(index)));
                 }
+                // Since the type is inhabited, there must be an index.
                 return interp_ok(index);
             }
             Variants::Multiple { tag, ref tag_encoding, tag_field, .. } => {
@@ -199,11 +195,13 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         // `uninhabited_enum_branching` MIR pass. It also ensures consistency with
         // `write_discriminant`.
         if op.layout().for_variant(self, index).is_uninhabited() {
-            throw_ub!(UninhabitedEnumVariantRead(index))
+            throw_ub!(UninhabitedEnumVariantRead(Some(index)))
         }
         interp_ok(index)
     }
 
+    /// Read discriminant, return the user-visible discriminant.
+    /// Can also legally be called on non-enums (e.g. through the discriminant_value intrinsic)!
     pub fn discriminant_for_variant(
         &self,
         ty: Ty<'tcx>,
@@ -243,6 +241,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         }
 
         match layout.variants {
+            abi::Variants::Empty => unreachable!("we already handled uninhabited types"),
             abi::Variants::Single { .. } => {
                 // The tag of a `Single` enum is like the tag of the niched
                 // variant: there's no tag as the discriminant is encoded
diff --git a/compiler/rustc_const_eval/src/interpret/intrinsics.rs b/compiler/rustc_const_eval/src/interpret/intrinsics.rs
index a79923e8555..1af8438534f 100644
--- a/compiler/rustc_const_eval/src/interpret/intrinsics.rs
+++ b/compiler/rustc_const_eval/src/interpret/intrinsics.rs
@@ -11,7 +11,7 @@ use rustc_middle::mir::{self, BinOp, ConstValue, NonDivergingIntrinsic};
 use rustc_middle::ty::layout::{LayoutOf as _, TyAndLayout, ValidityRequirement};
 use rustc_middle::ty::{GenericArgsRef, Ty, TyCtxt};
 use rustc_middle::{bug, ty};
-use rustc_span::symbol::{Symbol, sym};
+use rustc_span::{Symbol, sym};
 use tracing::trace;
 
 use super::memory::MemoryKind;
diff --git a/compiler/rustc_const_eval/src/interpret/machine.rs b/compiler/rustc_const_eval/src/interpret/machine.rs
index 9ac2a024ccf..36e5a2ff750 100644
--- a/compiler/rustc_const_eval/src/interpret/machine.rs
+++ b/compiler/rustc_const_eval/src/interpret/machine.rs
@@ -6,7 +6,7 @@ use std::borrow::{Borrow, Cow};
 use std::fmt::Debug;
 use std::hash::Hash;
 
-use rustc_abi::{Align, ExternAbi, Size};
+use rustc_abi::{Align, Size};
 use rustc_apfloat::{Float, FloatConvert};
 use rustc_ast::{InlineAsmOptions, InlineAsmTemplatePiece};
 use rustc_middle::query::TyCtxtAt;
@@ -15,6 +15,7 @@ use rustc_middle::ty::layout::TyAndLayout;
 use rustc_middle::{mir, ty};
 use rustc_span::Span;
 use rustc_span::def_id::DefId;
+use rustc_target::callconv::FnAbi;
 
 use super::{
     AllocBytes, AllocId, AllocKind, AllocRange, Allocation, CTFE_ALLOC_SALT, ConstAllocation,
@@ -201,7 +202,7 @@ pub trait Machine<'tcx>: Sized {
     fn find_mir_or_eval_fn(
         ecx: &mut InterpCx<'tcx, Self>,
         instance: ty::Instance<'tcx>,
-        abi: ExternAbi,
+        abi: &FnAbi<'tcx, Ty<'tcx>>,
         args: &[FnArg<'tcx, Self::Provenance>],
         destination: &MPlaceTy<'tcx, Self::Provenance>,
         target: Option<mir::BasicBlock>,
@@ -213,7 +214,7 @@ pub trait Machine<'tcx>: Sized {
     fn call_extra_fn(
         ecx: &mut InterpCx<'tcx, Self>,
         fn_val: Self::ExtraFnVal,
-        abi: ExternAbi,
+        abi: &FnAbi<'tcx, Ty<'tcx>>,
         args: &[FnArg<'tcx, Self::Provenance>],
         destination: &MPlaceTy<'tcx, Self::Provenance>,
         target: Option<mir::BasicBlock>,
@@ -656,7 +657,7 @@ pub macro compile_time_machine(<$tcx: lifetime>) {
     fn call_extra_fn(
         _ecx: &mut InterpCx<$tcx, Self>,
         fn_val: !,
-        _abi: ExternAbi,
+        _abi: &FnAbi<$tcx, Ty<$tcx>>,
         _args: &[FnArg<$tcx>],
         _destination: &MPlaceTy<$tcx, Self::Provenance>,
         _target: Option<mir::BasicBlock>,
diff --git a/compiler/rustc_const_eval/src/interpret/operator.rs b/compiler/rustc_const_eval/src/interpret/operator.rs
index 8b7b78c7129..5fa632fc57a 100644
--- a/compiler/rustc_const_eval/src/interpret/operator.rs
+++ b/compiler/rustc_const_eval/src/interpret/operator.rs
@@ -6,7 +6,7 @@ use rustc_middle::mir::interpret::{InterpResult, PointerArithmetic, Scalar};
 use rustc_middle::ty::layout::{LayoutOf, TyAndLayout};
 use rustc_middle::ty::{self, FloatTy, ScalarInt, Ty};
 use rustc_middle::{bug, mir, span_bug};
-use rustc_span::symbol::sym;
+use rustc_span::sym;
 use tracing::trace;
 
 use super::{ImmTy, InterpCx, Machine, MemPlaceMeta, interp_ok, throw_ub};
diff --git a/compiler/rustc_const_eval/src/interpret/projection.rs b/compiler/rustc_const_eval/src/interpret/projection.rs
index 65a93784e2c..996142d7b03 100644
--- a/compiler/rustc_const_eval/src/interpret/projection.rs
+++ b/compiler/rustc_const_eval/src/interpret/projection.rs
@@ -325,7 +325,7 @@ where
         let actual_to = if from_end {
             if from.checked_add(to).is_none_or(|to| to > len) {
                 // This can only be reached in ConstProp and non-rustc-MIR.
-                throw_ub!(BoundsCheckFailed { len: len, index: from.saturating_add(to) });
+                throw_ub!(BoundsCheckFailed { len, index: from.saturating_add(to) });
             }
             len.checked_sub(to).unwrap()
         } else {
diff --git a/compiler/rustc_const_eval/src/interpret/validity.rs b/compiler/rustc_const_eval/src/interpret/validity.rs
index 273eaf42d87..6f101395ccf 100644
--- a/compiler/rustc_const_eval/src/interpret/validity.rs
+++ b/compiler/rustc_const_eval/src/interpret/validity.rs
@@ -26,7 +26,7 @@ use rustc_middle::mir::interpret::{
 };
 use rustc_middle::ty::layout::{LayoutCx, LayoutOf, TyAndLayout};
 use rustc_middle::ty::{self, Ty};
-use rustc_span::symbol::{Symbol, sym};
+use rustc_span::{Symbol, sym};
 use tracing::trace;
 
 use super::machine::AllocMap;
@@ -302,7 +302,7 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValidityVisitor<'rt, 'tcx, M> {
                     };
                 }
             }
-            Variants::Single { .. } => {}
+            Variants::Single { .. } | Variants::Empty => {}
         }
 
         // Now we know we are projecting to a field, so figure out which one.
@@ -344,6 +344,7 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValidityVisitor<'rt, 'tcx, M> {
                         // Inside a variant
                         PathElem::Field(def.variant(index).fields[FieldIdx::from_usize(field)].name)
                     }
+                    Variants::Empty => panic!("there is no field in Variants::Empty types"),
                     Variants::Multiple { .. } => bug!("we handled variants above"),
                 }
             }
@@ -1010,7 +1011,7 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValidityVisitor<'rt, 'tcx, M> {
             }
             // Don't forget potential other variants.
             match &layout.variants {
-                Variants::Single { .. } => {
+                Variants::Single { .. } | Variants::Empty => {
                     // Fully handled above.
                 }
                 Variants::Multiple { variants, .. } => {
diff --git a/compiler/rustc_const_eval/src/interpret/visitor.rs b/compiler/rustc_const_eval/src/interpret/visitor.rs
index 76ab0bb544f..3647c109a6e 100644
--- a/compiler/rustc_const_eval/src/interpret/visitor.rs
+++ b/compiler/rustc_const_eval/src/interpret/visitor.rs
@@ -218,8 +218,8 @@ pub trait ValueVisitor<'tcx, M: Machine<'tcx>>: Sized {
                 // recurse with the inner type
                 self.visit_variant(v, idx, &inner)?;
             }
-            // For single-variant layouts, we already did anything there is to do.
-            Variants::Single { .. } => {}
+            // For single-variant layouts, we already did everything there is to do.
+            Variants::Single { .. } | Variants::Empty => {}
         }
 
         interp_ok(())
diff --git a/compiler/rustc_const_eval/src/util/caller_location.rs b/compiler/rustc_const_eval/src/util/caller_location.rs
index 6593547cd23..6dd9447cf5a 100644
--- a/compiler/rustc_const_eval/src/util/caller_location.rs
+++ b/compiler/rustc_const_eval/src/util/caller_location.rs
@@ -3,7 +3,7 @@ use rustc_middle::query::TyCtxtAt;
 use rustc_middle::ty::layout::LayoutOf;
 use rustc_middle::ty::{self};
 use rustc_middle::{bug, mir};
-use rustc_span::symbol::Symbol;
+use rustc_span::Symbol;
 use tracing::trace;
 
 use crate::const_eval::{CanAccessMutGlobal, CompileTimeInterpCx, mk_eval_cx_to_read_const_val};
diff --git a/compiler/rustc_const_eval/src/util/check_validity_requirement.rs b/compiler/rustc_const_eval/src/util/check_validity_requirement.rs
index 651a797e97c..a729d9325c8 100644
--- a/compiler/rustc_const_eval/src/util/check_validity_requirement.rs
+++ b/compiler/rustc_const_eval/src/util/check_validity_requirement.rs
@@ -155,6 +155,7 @@ fn check_validity_requirement_lax<'tcx>(
     }
 
     match &this.variants {
+        Variants::Empty => return Ok(false),
         Variants::Single { .. } => {
             // All fields of this single variant have already been checked above, there is nothing
             // else to do.
diff --git a/compiler/rustc_driver_impl/Cargo.toml b/compiler/rustc_driver_impl/Cargo.toml
index 81f15ebcbf8..2f0fe64b096 100644
--- a/compiler/rustc_driver_impl/Cargo.toml
+++ b/compiler/rustc_driver_impl/Cargo.toml
@@ -9,7 +9,7 @@ rustc_ast = { path = "../rustc_ast" }
 rustc_ast_lowering = { path = "../rustc_ast_lowering" }
 rustc_ast_passes = { path = "../rustc_ast_passes" }
 rustc_ast_pretty = { path = "../rustc_ast_pretty" }
-rustc_attr = { path = "../rustc_attr" }
+rustc_attr_parsing = { path = "../rustc_attr_parsing" }
 rustc_borrowck = { path = "../rustc_borrowck" }
 rustc_builtin_macros = { path = "../rustc_builtin_macros" }
 rustc_codegen_ssa = { path = "../rustc_codegen_ssa" }
diff --git a/compiler/rustc_driver_impl/src/lib.rs b/compiler/rustc_driver_impl/src/lib.rs
index b80736f41ad..3dc39fc131a 100644
--- a/compiler/rustc_driver_impl/src/lib.rs
+++ b/compiler/rustc_driver_impl/src/lib.rs
@@ -26,7 +26,7 @@ use std::fmt::Write as _;
 use std::fs::{self, File};
 use std::io::{self, IsTerminal, Read, Write};
 use std::panic::{self, PanicHookInfo, catch_unwind};
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
 use std::process::{self, Command, Stdio};
 use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::{Arc, OnceLock};
@@ -45,7 +45,7 @@ use rustc_errors::registry::Registry;
 use rustc_errors::{ColorConfig, DiagCtxt, ErrCode, FatalError, PResult, markdown};
 use rustc_feature::find_gated_cfg;
 use rustc_interface::util::{self, get_codegen_backend};
-use rustc_interface::{Linker, interface, passes};
+use rustc_interface::{Linker, create_and_enter_global_ctxt, interface, passes};
 use rustc_lint::unerased_lint_store;
 use rustc_metadata::creader::MetadataLoader;
 use rustc_metadata::locator;
@@ -112,7 +112,7 @@ pub static DEFAULT_LOCALE_RESOURCES: &[&str] = &[
     crate::DEFAULT_LOCALE_RESOURCE,
     rustc_ast_lowering::DEFAULT_LOCALE_RESOURCE,
     rustc_ast_passes::DEFAULT_LOCALE_RESOURCE,
-    rustc_attr::DEFAULT_LOCALE_RESOURCE,
+    rustc_attr_parsing::DEFAULT_LOCALE_RESOURCE,
     rustc_borrowck::DEFAULT_LOCALE_RESOURCE,
     rustc_builtin_macros::DEFAULT_LOCALE_RESOURCE,
     rustc_codegen_ssa::DEFAULT_LOCALE_RESOURCE,
@@ -387,76 +387,69 @@ fn run_compiler(
             return early_exit();
         }
 
-        let linker = compiler.enter(|queries| {
+        // Parse the crate root source code (doesn't parse submodules yet)
+        // Everything else is parsed during macro expansion.
+        let krate = passes::parse(sess);
+
+        // If pretty printing is requested: Figure out the representation, print it and exit
+        if let Some(pp_mode) = sess.opts.pretty {
+            if pp_mode.needs_ast_map() {
+                create_and_enter_global_ctxt(compiler, krate, |tcx| {
+                    tcx.ensure().early_lint_checks(());
+                    pretty::print(sess, pp_mode, pretty::PrintExtra::NeedsAstMap { tcx });
+                    passes::write_dep_info(tcx);
+                });
+            } else {
+                pretty::print(sess, pp_mode, pretty::PrintExtra::AfterParsing { krate: &krate });
+            }
+            trace!("finished pretty-printing");
+            return early_exit();
+        }
+
+        if callbacks.after_crate_root_parsing(compiler, &krate) == Compilation::Stop {
+            return early_exit();
+        }
+
+        if sess.opts.unstable_opts.parse_crate_root_only {
+            return early_exit();
+        }
+
+        let linker = create_and_enter_global_ctxt(compiler, krate, |tcx| {
             let early_exit = || {
                 sess.dcx().abort_if_errors();
                 None
             };
 
-            // Parse the crate root source code (doesn't parse submodules yet)
-            // Everything else is parsed during macro expansion.
-            queries.parse();
-
-            // If pretty printing is requested: Figure out the representation, print it and exit
-            if let Some(pp_mode) = sess.opts.pretty {
-                if pp_mode.needs_ast_map() {
-                    queries.global_ctxt().enter(|tcx| {
-                        tcx.ensure().early_lint_checks(());
-                        pretty::print(sess, pp_mode, pretty::PrintExtra::NeedsAstMap { tcx });
-                        passes::write_dep_info(tcx);
-                    });
-                } else {
-                    let krate = queries.parse();
-                    pretty::print(sess, pp_mode, pretty::PrintExtra::AfterParsing {
-                        krate: &*krate.borrow(),
-                    });
-                }
-                trace!("finished pretty-printing");
+            // Make sure name resolution and macro expansion is run.
+            let _ = tcx.resolver_for_lowering();
+
+            if let Some(metrics_dir) = &sess.opts.unstable_opts.metrics_dir {
+                dump_feature_usage_metrics(tcx, metrics_dir);
+            }
+
+            if callbacks.after_expansion(compiler, tcx) == Compilation::Stop {
                 return early_exit();
             }
 
-            if callbacks.after_crate_root_parsing(compiler, &*queries.parse().borrow())
-                == Compilation::Stop
+            passes::write_dep_info(tcx);
+
+            if sess.opts.output_types.contains_key(&OutputType::DepInfo)
+                && sess.opts.output_types.len() == 1
             {
                 return early_exit();
             }
 
-            if sess.opts.unstable_opts.parse_crate_root_only {
+            if sess.opts.unstable_opts.no_analysis {
                 return early_exit();
             }
 
-            queries.global_ctxt().enter(|tcx| {
-                // Make sure name resolution and macro expansion is run.
-                let _ = tcx.resolver_for_lowering();
-
-                if let Some(metrics_dir) = &sess.opts.unstable_opts.metrics_dir {
-                    dump_feature_usage_metrics(tcx, metrics_dir);
-                }
-
-                if callbacks.after_expansion(compiler, tcx) == Compilation::Stop {
-                    return early_exit();
-                }
-
-                passes::write_dep_info(tcx);
-
-                if sess.opts.output_types.contains_key(&OutputType::DepInfo)
-                    && sess.opts.output_types.len() == 1
-                {
-                    return early_exit();
-                }
-
-                if sess.opts.unstable_opts.no_analysis {
-                    return early_exit();
-                }
+            tcx.ensure().analysis(());
 
-                tcx.ensure().analysis(());
-
-                if callbacks.after_analysis(compiler, tcx) == Compilation::Stop {
-                    return early_exit();
-                }
+            if callbacks.after_analysis(compiler, tcx) == Compilation::Stop {
+                return early_exit();
+            }
 
-                Some(Linker::codegen_and_build_linker(tcx, &*compiler.codegen_backend))
-            })
+            Some(Linker::codegen_and_build_linker(tcx, &*compiler.codegen_backend))
         });
 
         // Linking is done outside the `compiler.enter()` so that the
@@ -467,7 +460,7 @@ fn run_compiler(
     })
 }
 
-fn dump_feature_usage_metrics(tcxt: TyCtxt<'_>, metrics_dir: &PathBuf) {
+fn dump_feature_usage_metrics(tcxt: TyCtxt<'_>, metrics_dir: &Path) {
     let output_filenames = tcxt.output_filenames(());
     let mut metrics_file_name = std::ffi::OsString::from("unstable_feature_usage_metrics-");
     let mut metrics_path = output_filenames.with_directory_and_extension(metrics_dir, "json");
diff --git a/compiler/rustc_driver_impl/src/pretty.rs b/compiler/rustc_driver_impl/src/pretty.rs
index 5df960be307..93f3d2ab911 100644
--- a/compiler/rustc_driver_impl/src/pretty.rs
+++ b/compiler/rustc_driver_impl/src/pretty.rs
@@ -4,15 +4,13 @@ use std::cell::Cell;
 use std::fmt::Write;
 
 use rustc_ast_pretty::pprust as pprust_ast;
-use rustc_errors::FatalError;
 use rustc_middle::bug;
 use rustc_middle::mir::{write_mir_graphviz, write_mir_pretty};
 use rustc_middle::ty::{self, TyCtxt};
 use rustc_session::Session;
 use rustc_session::config::{OutFileName, PpHirMode, PpMode, PpSourceMode};
 use rustc_smir::rustc_internal::pretty::write_smir_pretty;
-use rustc_span::FileName;
-use rustc_span::symbol::Ident;
+use rustc_span::{FileName, Ident};
 use tracing::debug;
 use {rustc_ast as ast, rustc_hir_pretty as pprust_hir};
 
@@ -312,9 +310,7 @@ pub fn print<'tcx>(sess: &Session, ppm: PpMode, ex: PrintExtra<'tcx>) {
             let tcx = ex.tcx();
             let mut out = String::new();
             rustc_hir_analysis::check_crate(tcx);
-            if tcx.dcx().has_errors().is_some() {
-                FatalError.raise();
-            }
+            tcx.dcx().abort_if_errors();
             debug!("pretty printing THIR tree");
             for did in tcx.hir().body_owners() {
                 let _ = writeln!(out, "{:?}:\n{}\n", did, tcx.thir_tree(did));
@@ -325,9 +321,7 @@ pub fn print<'tcx>(sess: &Session, ppm: PpMode, ex: PrintExtra<'tcx>) {
             let tcx = ex.tcx();
             let mut out = String::new();
             rustc_hir_analysis::check_crate(tcx);
-            if tcx.dcx().has_errors().is_some() {
-                FatalError.raise();
-            }
+            tcx.dcx().abort_if_errors();
             debug!("pretty printing THIR flat");
             for did in tcx.hir().body_owners() {
                 let _ = writeln!(out, "{:?}:\n{}\n", did, tcx.thir_flat(did));
diff --git a/compiler/rustc_error_codes/src/error_codes/E0665.md b/compiler/rustc_error_codes/src/error_codes/E0665.md
index ae54d6d1579..caa94423377 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0665.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0665.md
@@ -1,10 +1,9 @@
-#### Note: this error code is no longer emitted by the compiler.
-
-The `Default` trait was derived on an enum.
+The `Default` trait was derived on an enum without specifying the default
+variant.
 
 Erroneous code example:
 
-```compile_fail
+```compile_fail,E0665
 #[derive(Default)]
 enum Food {
     Sweet,
@@ -16,18 +15,30 @@ The `Default` cannot be derived on an enum for the simple reason that the
 compiler doesn't know which value to pick by default whereas it can for a
 struct as long as all its fields implement the `Default` trait as well.
 
-If you still want to implement `Default` on your enum, you'll have to do it "by
-hand":
+For the case where the desired default variant has no payload, you can
+annotate it with `#[default]` to derive it:
 
 ```
+#[derive(Default)]
 enum Food {
+    #[default]
     Sweet,
     Salty,
 }
+```
+
+In the case where the default variant does have a payload, you will have to
+implement `Default` on your enum manually:
+
+```
+enum Food {
+    Sweet(i32),
+    Salty,
+}
 
 impl Default for Food {
     fn default() -> Food {
-        Food::Sweet
+        Food::Sweet(1)
     }
 }
 ```
diff --git a/compiler/rustc_errors/Cargo.toml b/compiler/rustc_errors/Cargo.toml
index 06bae57638f..66b9adbead0 100644
--- a/compiler/rustc_errors/Cargo.toml
+++ b/compiler/rustc_errors/Cargo.toml
@@ -16,6 +16,7 @@ rustc_error_messages = { path = "../rustc_error_messages" }
 rustc_fluent_macro = { path = "../rustc_fluent_macro" }
 rustc_hir = { path = "../rustc_hir" }
 rustc_index = { path = "../rustc_index" }
+rustc_lexer = { path = "../rustc_lexer" }
 rustc_lint_defs = { path = "../rustc_lint_defs" }
 rustc_macros = { path = "../rustc_macros" }
 rustc_serialize = { path = "../rustc_serialize" }
diff --git a/compiler/rustc_errors/src/diagnostic.rs b/compiler/rustc_errors/src/diagnostic.rs
index 4352de3ad25..05b9cbfbc06 100644
--- a/compiler/rustc_errors/src/diagnostic.rs
+++ b/compiler/rustc_errors/src/diagnostic.rs
@@ -11,8 +11,7 @@ use rustc_error_messages::{FluentValue, fluent_value_from_str_list_sep_by_and};
 use rustc_lint_defs::Applicability;
 use rustc_macros::{Decodable, Encodable};
 use rustc_span::source_map::Spanned;
-use rustc_span::symbol::Symbol;
-use rustc_span::{DUMMY_SP, Span};
+use rustc_span::{DUMMY_SP, Span, Symbol};
 use tracing::debug;
 
 use crate::snippet::Style;
diff --git a/compiler/rustc_errors/src/diagnostic_impls.rs b/compiler/rustc_errors/src/diagnostic_impls.rs
index b4510371323..d179396398f 100644
--- a/compiler/rustc_errors/src/diagnostic_impls.rs
+++ b/compiler/rustc_errors/src/diagnostic_impls.rs
@@ -9,9 +9,8 @@ use rustc_abi::TargetDataLayoutErrors;
 use rustc_ast::util::parser::ExprPrecedence;
 use rustc_ast_pretty::pprust;
 use rustc_macros::Subdiagnostic;
-use rustc_span::Span;
 use rustc_span::edition::Edition;
-use rustc_span::symbol::{Ident, MacroRulesNormalizedIdent, Symbol};
+use rustc_span::{Ident, MacroRulesNormalizedIdent, Span, Symbol};
 use rustc_target::spec::{PanicStrategy, SplitDebuginfo, StackProtector, TargetTuple};
 use rustc_type_ir::{ClosureKind, FloatTy};
 use {rustc_ast as ast, rustc_hir as hir};
diff --git a/compiler/rustc_errors/src/emitter.rs b/compiler/rustc_errors/src/emitter.rs
index ac2f91cdeb3..977721a5b8a 100644
--- a/compiler/rustc_errors/src/emitter.rs
+++ b/compiler/rustc_errors/src/emitter.rs
@@ -19,6 +19,7 @@ use derive_setters::Setters;
 use rustc_data_structures::fx::{FxHashMap, FxIndexMap, FxIndexSet};
 use rustc_data_structures::sync::{DynSend, IntoDynSyncSend, Lrc};
 use rustc_error_messages::{FluentArgs, SpanLabel};
+use rustc_lexer;
 use rustc_lint_defs::pluralize;
 use rustc_span::hygiene::{ExpnKind, MacroKind};
 use rustc_span::source_map::SourceMap;
@@ -1698,9 +1699,14 @@ impl HumanEmitter {
                     if let Some(source_string) =
                         line.line_index.checked_sub(1).and_then(|l| file.get_line(l))
                     {
+                        // Whitespace can only be removed (aka considered leading)
+                        // if the lexer considers it whitespace.
+                        // non-rustc_lexer::is_whitespace() chars are reported as an
+                        // error (ex. no-break-spaces \u{a0}), and thus can't be considered
+                        // for removal during error reporting.
                         let leading_whitespace = source_string
                             .chars()
-                            .take_while(|c| c.is_whitespace())
+                            .take_while(|c| rustc_lexer::is_whitespace(*c))
                             .map(|c| {
                                 match c {
                                     // Tabs are displayed as 4 spaces
@@ -1709,7 +1715,7 @@ impl HumanEmitter {
                                 }
                             })
                             .sum();
-                        if source_string.chars().any(|c| !c.is_whitespace()) {
+                        if source_string.chars().any(|c| !rustc_lexer::is_whitespace(c)) {
                             whitespace_margin = min(whitespace_margin, leading_whitespace);
                         }
                     }
@@ -2523,7 +2529,7 @@ impl HumanEmitter {
                     buffer.puts(*row_num, max_line_num_len + 1, "+ ", Style::Addition);
                 }
                 [] => {
-                    // FIXME: needed? Doesn't get excercised in any test.
+                    // FIXME: needed? Doesn't get exercised in any test.
                     self.draw_col_separator_no_space(buffer, *row_num, max_line_num_len + 1);
                 }
                 _ => {
diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index 25d41462556..58fe3ec4b85 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -1569,18 +1569,18 @@ impl DiagCtxtInner {
                 debug!(?diagnostic);
                 debug!(?self.emitted_diagnostics);
 
-                let already_emitted_sub = |sub: &mut Subdiag| {
+                let not_yet_emitted = |sub: &mut Subdiag| {
                     debug!(?sub);
                     if sub.level != OnceNote && sub.level != OnceHelp {
-                        return false;
+                        return true;
                     }
                     let mut hasher = StableHasher::new();
                     sub.hash(&mut hasher);
                     let diagnostic_hash = hasher.finish();
                     debug!(?diagnostic_hash);
-                    !self.emitted_diagnostics.insert(diagnostic_hash)
+                    self.emitted_diagnostics.insert(diagnostic_hash)
                 };
-                diagnostic.children.extract_if(already_emitted_sub).for_each(|_| {});
+                diagnostic.children.retain_mut(not_yet_emitted);
                 if already_emitted {
                     let msg = "duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`";
                     diagnostic.sub(Note, msg, MultiSpan::new());
diff --git a/compiler/rustc_errors/src/markdown/parse.rs b/compiler/rustc_errors/src/markdown/parse.rs
index 8dd146c1c33..7a991a2ace7 100644
--- a/compiler/rustc_errors/src/markdown/parse.rs
+++ b/compiler/rustc_errors/src/markdown/parse.rs
@@ -346,7 +346,7 @@ fn parse_with_end_pat<'a>(
     None
 }
 
-/// Resturn `(match, residual)` to end of line. The EOL is returned with the
+/// Return `(match, residual)` to end of line. The EOL is returned with the
 /// residual.
 fn parse_to_newline(buf: &[u8]) -> (&[u8], &[u8]) {
     buf.iter().position(|ch| *ch == b'\n').map_or((buf, &[]), |pos| buf.split_at(pos))
diff --git a/compiler/rustc_expand/Cargo.toml b/compiler/rustc_expand/Cargo.toml
index ce014364b0d..eb93972387d 100644
--- a/compiler/rustc_expand/Cargo.toml
+++ b/compiler/rustc_expand/Cargo.toml
@@ -12,7 +12,7 @@ doctest = false
 rustc_ast = { path = "../rustc_ast" }
 rustc_ast_passes = { path = "../rustc_ast_passes" }
 rustc_ast_pretty = { path = "../rustc_ast_pretty" }
-rustc_attr = { path = "../rustc_attr" }
+rustc_attr_parsing = { path = "../rustc_attr_parsing" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
 rustc_feature = { path = "../rustc_feature" }
diff --git a/compiler/rustc_expand/src/base.rs b/compiler/rustc_expand/src/base.rs
index bed500c3032..e6adbc0f0ac 100644
--- a/compiler/rustc_expand/src/base.rs
+++ b/compiler/rustc_expand/src/base.rs
@@ -4,13 +4,13 @@ use std::path::Component::Prefix;
 use std::path::{Path, PathBuf};
 use std::rc::Rc;
 
-use rustc_ast::attr::MarkedAttrs;
+use rustc_ast::attr::{AttributeExt, MarkedAttrs};
 use rustc_ast::ptr::P;
 use rustc_ast::token::Nonterminal;
 use rustc_ast::tokenstream::TokenStream;
 use rustc_ast::visit::{AssocCtxt, Visitor};
 use rustc_ast::{self as ast, AttrVec, Attribute, HasAttrs, Item, NodeId, PatKind};
-use rustc_attr::{self as attr, Deprecation, Stability};
+use rustc_attr_parsing::{self as attr, Deprecation, Stability};
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_data_structures::sync::{self, Lrc};
 use rustc_errors::{DiagCtxtHandle, ErrorGuaranteed, PResult};
@@ -25,8 +25,7 @@ use rustc_span::def_id::{CrateNum, DefId, LocalDefId};
 use rustc_span::edition::Edition;
 use rustc_span::hygiene::{AstPass, ExpnData, ExpnKind, LocalExpnId, MacroKind};
 use rustc_span::source_map::SourceMap;
-use rustc_span::symbol::{Ident, Symbol, kw, sym};
-use rustc_span::{DUMMY_SP, FileName, Span};
+use rustc_span::{DUMMY_SP, FileName, Ident, Span, Symbol, kw, sym};
 use smallvec::{SmallVec, smallvec};
 use thin_vec::ThinVec;
 
@@ -782,10 +781,12 @@ impl SyntaxExtension {
         }
     }
 
-    fn collapse_debuginfo_by_name(attr: &Attribute) -> Result<CollapseMacroDebuginfo, Span> {
+    fn collapse_debuginfo_by_name(
+        attr: &impl AttributeExt,
+    ) -> Result<CollapseMacroDebuginfo, Span> {
         let list = attr.meta_item_list();
         let Some([MetaItemInner::MetaItem(item)]) = list.as_deref() else {
-            return Err(attr.span);
+            return Err(attr.span());
         };
         if !item.is_word() {
             return Err(item.span);
@@ -805,9 +806,9 @@ impl SyntaxExtension {
     /// | (unspecified) | no  | if-ext        | if-ext   | yes |
     /// | external      | no  | if-ext        | if-ext   | yes |
     /// | yes           | yes | yes           | yes      | yes |
-    fn get_collapse_debuginfo(sess: &Session, attrs: &[ast::Attribute], ext: bool) -> bool {
+    fn get_collapse_debuginfo(sess: &Session, attrs: &[impl AttributeExt], ext: bool) -> bool {
         let flag = sess.opts.cg.collapse_macro_debuginfo;
-        let attr = attr::find_by_name(attrs, sym::collapse_debuginfo)
+        let attr = ast::attr::find_by_name(attrs, sym::collapse_debuginfo)
             .and_then(|attr| {
                 Self::collapse_debuginfo_by_name(attr)
                     .map_err(|span| {
@@ -816,7 +817,7 @@ impl SyntaxExtension {
                     .ok()
             })
             .unwrap_or_else(|| {
-                if attr::contains_name(attrs, sym::rustc_builtin_macro) {
+                if ast::attr::contains_name(attrs, sym::rustc_builtin_macro) {
                     CollapseMacroDebuginfo::Yes
                 } else {
                     CollapseMacroDebuginfo::Unspecified
@@ -842,20 +843,20 @@ impl SyntaxExtension {
         helper_attrs: Vec<Symbol>,
         edition: Edition,
         name: Symbol,
-        attrs: &[ast::Attribute],
+        attrs: &[impl AttributeExt],
         is_local: bool,
     ) -> SyntaxExtension {
         let allow_internal_unstable =
-            attr::allow_internal_unstable(sess, attrs).collect::<Vec<Symbol>>();
+            rustc_attr_parsing::allow_internal_unstable(sess, attrs).collect::<Vec<Symbol>>();
 
-        let allow_internal_unsafe = attr::contains_name(attrs, sym::allow_internal_unsafe);
-        let local_inner_macros = attr::find_by_name(attrs, sym::macro_export)
+        let allow_internal_unsafe = ast::attr::contains_name(attrs, sym::allow_internal_unsafe);
+        let local_inner_macros = ast::attr::find_by_name(attrs, sym::macro_export)
             .and_then(|macro_export| macro_export.meta_item_list())
-            .is_some_and(|l| attr::list_contains_name(&l, sym::local_inner_macros));
+            .is_some_and(|l| ast::attr::list_contains_name(&l, sym::local_inner_macros));
         let collapse_debuginfo = Self::get_collapse_debuginfo(sess, attrs, !is_local);
         tracing::debug!(?name, ?local_inner_macros, ?collapse_debuginfo, ?allow_internal_unsafe);
 
-        let (builtin_name, helper_attrs) = attr::find_by_name(attrs, sym::rustc_builtin_macro)
+        let (builtin_name, helper_attrs) = ast::attr::find_by_name(attrs, sym::rustc_builtin_macro)
             .map(|attr| {
                 // Override `helper_attrs` passed above if it's a built-in macro,
                 // marking `proc_macro_derive` macros as built-in is not a realistic use case.
@@ -1305,7 +1306,7 @@ pub fn resolve_path(sess: &Session, path: impl Into<PathBuf>, span: Span) -> PRe
 
 pub fn parse_macro_name_and_helper_attrs(
     dcx: DiagCtxtHandle<'_>,
-    attr: &Attribute,
+    attr: &impl AttributeExt,
     macro_type: &str,
 ) -> Option<(Symbol, Vec<Symbol>)> {
     // Once we've located the `#[proc_macro_derive]` attribute, verify
@@ -1313,7 +1314,7 @@ pub fn parse_macro_name_and_helper_attrs(
     // `#[proc_macro_derive(Foo, attributes(A, ..))]`
     let list = attr.meta_item_list()?;
     let ([trait_attr] | [trait_attr, _]) = list.as_slice() else {
-        dcx.emit_err(errors::AttrNoArguments { span: attr.span });
+        dcx.emit_err(errors::AttrNoArguments { span: attr.span() });
         return None;
     };
     let Some(trait_attr) = trait_attr.meta_item() else {
diff --git a/compiler/rustc_expand/src/build.rs b/compiler/rustc_expand/src/build.rs
index a673e2e3250..22bfda34cc0 100644
--- a/compiler/rustc_expand/src/build.rs
+++ b/compiler/rustc_expand/src/build.rs
@@ -4,8 +4,7 @@ use rustc_ast::{
     self as ast, AttrVec, BlockCheckMode, Expr, LocalKind, MatchKind, PatKind, UnOp, attr, token,
 };
 use rustc_span::source_map::Spanned;
-use rustc_span::symbol::{Ident, Symbol, kw, sym};
-use rustc_span::{DUMMY_SP, Span};
+use rustc_span::{DUMMY_SP, Ident, Span, Symbol, kw, sym};
 use thin_vec::{ThinVec, thin_vec};
 
 use crate::base::ExtCtxt;
diff --git a/compiler/rustc_expand/src/config.rs b/compiler/rustc_expand/src/config.rs
index dc6aa110f45..91624c7554c 100644
--- a/compiler/rustc_expand/src/config.rs
+++ b/compiler/rustc_expand/src/config.rs
@@ -8,7 +8,7 @@ use rustc_ast::tokenstream::{
 use rustc_ast::{
     self as ast, AttrStyle, Attribute, HasAttrs, HasTokens, MetaItem, MetaItemInner, NodeId,
 };
-use rustc_attr as attr;
+use rustc_attr_parsing as attr;
 use rustc_data_structures::flat_map_in_place::FlatMapInPlace;
 use rustc_feature::{
     ACCEPTED_LANG_FEATURES, AttributeSafety, EnabledLangFeature, EnabledLibFeature, Features,
@@ -18,8 +18,7 @@ use rustc_lint_defs::BuiltinLintDiag;
 use rustc_parse::validate_attr;
 use rustc_session::Session;
 use rustc_session::parse::feature_err;
-use rustc_span::Span;
-use rustc_span::symbol::{Symbol, sym};
+use rustc_span::{Span, Symbol, sym};
 use thin_vec::ThinVec;
 use tracing::instrument;
 
@@ -362,7 +361,7 @@ impl<'a> StripUnconfigured<'a> {
         ));
 
         let tokens = Some(LazyAttrTokenStream::new(AttrTokenStream::new(trees)));
-        let attr = attr::mk_attr_from_item(
+        let attr = ast::attr::mk_attr_from_item(
             &self.sess.psess.attr_id_generator,
             item,
             tokens,
diff --git a/compiler/rustc_expand/src/errors.rs b/compiler/rustc_expand/src/errors.rs
index 7bd7c305539..89bdc7b6dfa 100644
--- a/compiler/rustc_expand/src/errors.rs
+++ b/compiler/rustc_expand/src/errors.rs
@@ -4,8 +4,7 @@ use rustc_ast::ast;
 use rustc_errors::codes::*;
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_session::Limit;
-use rustc_span::symbol::{Ident, MacroRulesNormalizedIdent};
-use rustc_span::{Span, Symbol};
+use rustc_span::{Ident, MacroRulesNormalizedIdent, Span, Symbol};
 
 #[derive(Diagnostic)]
 #[diag(expand_expr_repeat_no_syntax_vars)]
diff --git a/compiler/rustc_expand/src/expand.rs b/compiler/rustc_expand/src/expand.rs
index 690e080fbfc..ec497f6f8f1 100644
--- a/compiler/rustc_expand/src/expand.rs
+++ b/compiler/rustc_expand/src/expand.rs
@@ -29,8 +29,7 @@ use rustc_session::lint::builtin::{UNUSED_ATTRIBUTES, UNUSED_DOC_COMMENTS};
 use rustc_session::parse::feature_err;
 use rustc_session::{Limit, Session};
 use rustc_span::hygiene::SyntaxContext;
-use rustc_span::symbol::{Ident, sym};
-use rustc_span::{ErrorGuaranteed, FileName, LocalExpnId, Span};
+use rustc_span::{ErrorGuaranteed, FileName, Ident, LocalExpnId, Span, sym};
 use smallvec::SmallVec;
 
 use crate::base::*;
@@ -1913,7 +1912,7 @@ impl<'a, 'b> InvocationCollector<'a, 'b> {
                     self.cx.current_expansion.lint_node_id,
                     BuiltinLintDiag::UnusedDocComment(attr.span),
                 );
-            } else if rustc_attr::is_builtin_attr(attr) {
+            } else if rustc_attr_parsing::is_builtin_attr(attr) {
                 let attr_name = attr.ident().unwrap().name;
                 // `#[cfg]` and `#[cfg_attr]` are special - they are
                 // eagerly evaluated.
diff --git a/compiler/rustc_expand/src/mbe.rs b/compiler/rustc_expand/src/mbe.rs
index e5d098f63d6..4ff8c02bcdb 100644
--- a/compiler/rustc_expand/src/mbe.rs
+++ b/compiler/rustc_expand/src/mbe.rs
@@ -16,8 +16,7 @@ use metavar_expr::MetaVarExpr;
 use rustc_ast::token::{Delimiter, NonterminalKind, Token, TokenKind};
 use rustc_ast::tokenstream::{DelimSpacing, DelimSpan};
 use rustc_macros::{Decodable, Encodable};
-use rustc_span::Span;
-use rustc_span::symbol::Ident;
+use rustc_span::{Ident, Span};
 
 /// Contains the sub-token-trees of a "delimited" token tree such as `(a b c)`.
 /// The delimiters are not represented explicitly in the `tts` vector.
diff --git a/compiler/rustc_expand/src/mbe/diagnostics.rs b/compiler/rustc_expand/src/mbe/diagnostics.rs
index 77b8d228922..9f48835e15d 100644
--- a/compiler/rustc_expand/src/mbe/diagnostics.rs
+++ b/compiler/rustc_expand/src/mbe/diagnostics.rs
@@ -7,8 +7,7 @@ use rustc_macros::Subdiagnostic;
 use rustc_parse::parser::{Parser, Recovery, token_descr};
 use rustc_session::parse::ParseSess;
 use rustc_span::source_map::SourceMap;
-use rustc_span::symbol::Ident;
-use rustc_span::{ErrorGuaranteed, Span};
+use rustc_span::{ErrorGuaranteed, Ident, Span};
 use tracing::debug;
 
 use super::macro_rules::{NoopTracker, parser_from_cx};
diff --git a/compiler/rustc_expand/src/mbe/macro_check.rs b/compiler/rustc_expand/src/mbe/macro_check.rs
index 1498b9cbd5d..729dec2bfbd 100644
--- a/compiler/rustc_expand/src/mbe/macro_check.rs
+++ b/compiler/rustc_expand/src/mbe/macro_check.rs
@@ -115,8 +115,7 @@ use rustc_lint_defs::BuiltinLintDiag;
 use rustc_session::lint::builtin::{META_VARIABLE_MISUSE, MISSING_FRAGMENT_SPECIFIER};
 use rustc_session::parse::ParseSess;
 use rustc_span::edition::Edition;
-use rustc_span::symbol::{MacroRulesNormalizedIdent, kw};
-use rustc_span::{ErrorGuaranteed, Span};
+use rustc_span::{ErrorGuaranteed, MacroRulesNormalizedIdent, Span, kw};
 use smallvec::SmallVec;
 
 use super::quoted::VALID_FRAGMENT_NAMES_MSG;
diff --git a/compiler/rustc_expand/src/mbe/macro_parser.rs b/compiler/rustc_expand/src/mbe/macro_parser.rs
index 2a8dddc1e00..d709fd79281 100644
--- a/compiler/rustc_expand/src/mbe/macro_parser.rs
+++ b/compiler/rustc_expand/src/mbe/macro_parser.rs
@@ -82,8 +82,7 @@ use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::ErrorGuaranteed;
 use rustc_lint_defs::pluralize;
 use rustc_parse::parser::{ParseNtResult, Parser, token_descr};
-use rustc_span::Span;
-use rustc_span::symbol::{Ident, MacroRulesNormalizedIdent};
+use rustc_span::{Ident, MacroRulesNormalizedIdent, Span};
 
 use crate::mbe::macro_rules::Tracker;
 use crate::mbe::{KleeneOp, TokenTree};
diff --git a/compiler/rustc_expand/src/mbe/macro_rules.rs b/compiler/rustc_expand/src/mbe/macro_rules.rs
index a373c753cc1..7ac9f453bae 100644
--- a/compiler/rustc_expand/src/mbe/macro_rules.rs
+++ b/compiler/rustc_expand/src/mbe/macro_rules.rs
@@ -3,13 +3,14 @@ use std::collections::hash_map::Entry;
 use std::{mem, slice};
 
 use ast::token::IdentIsRaw;
+use rustc_ast::attr::AttributeExt;
 use rustc_ast::token::NtPatKind::*;
 use rustc_ast::token::TokenKind::*;
 use rustc_ast::token::{self, Delimiter, NonterminalKind, Token, TokenKind};
 use rustc_ast::tokenstream::{DelimSpan, TokenStream};
 use rustc_ast::{self as ast, DUMMY_NODE_ID, NodeId};
 use rustc_ast_pretty::pprust;
-use rustc_attr::{self as attr, TransparencyError};
+use rustc_attr_parsing::{self as attr, TransparencyError};
 use rustc_data_structures::fx::{FxHashMap, FxIndexMap};
 use rustc_errors::{Applicability, ErrorGuaranteed};
 use rustc_feature::Features;
@@ -20,10 +21,9 @@ use rustc_lint_defs::builtin::{
 use rustc_parse::parser::{ParseNtResult, Parser, Recovery};
 use rustc_session::Session;
 use rustc_session::parse::ParseSess;
-use rustc_span::Span;
 use rustc_span::edition::Edition;
 use rustc_span::hygiene::Transparency;
-use rustc_span::symbol::{Ident, MacroRulesNormalizedIdent, kw, sym};
+use rustc_span::{Ident, MacroRulesNormalizedIdent, Span, kw, sym};
 use tracing::{debug, instrument, trace, trace_span};
 
 use super::diagnostics;
@@ -371,7 +371,7 @@ pub fn compile_declarative_macro(
     features: &Features,
     macro_def: &ast::MacroDef,
     ident: Ident,
-    attrs: &[ast::Attribute],
+    attrs: &[impl AttributeExt],
     span: Span,
     node_id: NodeId,
     edition: Edition,
diff --git a/compiler/rustc_expand/src/mbe/metavar_expr.rs b/compiler/rustc_expand/src/mbe/metavar_expr.rs
index 810a5d30c7e..1ccb070f83a 100644
--- a/compiler/rustc_expand/src/mbe/metavar_expr.rs
+++ b/compiler/rustc_expand/src/mbe/metavar_expr.rs
@@ -1,12 +1,11 @@
 use rustc_ast::token::{self, Delimiter, IdentIsRaw, Lit, Token, TokenKind};
-use rustc_ast::tokenstream::{RefTokenTreeCursor, TokenStream, TokenTree};
+use rustc_ast::tokenstream::{TokenStream, TokenStreamIter, TokenTree};
 use rustc_ast::{LitIntType, LitKind};
 use rustc_ast_pretty::pprust;
 use rustc_errors::{Applicability, PResult};
 use rustc_macros::{Decodable, Encodable};
 use rustc_session::parse::ParseSess;
-use rustc_span::symbol::Ident;
-use rustc_span::{Span, Symbol};
+use rustc_span::{Ident, Span, Symbol};
 
 pub(crate) const RAW_IDENT_ERR: &str = "`${concat(..)}` currently does not support raw identifiers";
 pub(crate) const UNSUPPORTED_CONCAT_ELEM_ERR: &str = "expected identifier or string literal";
@@ -39,14 +38,14 @@ impl MetaVarExpr {
         outer_span: Span,
         psess: &'psess ParseSess,
     ) -> PResult<'psess, MetaVarExpr> {
-        let mut tts = input.trees();
-        let ident = parse_ident(&mut tts, psess, outer_span)?;
-        let Some(TokenTree::Delimited(.., Delimiter::Parenthesis, args)) = tts.next() else {
+        let mut iter = input.iter();
+        let ident = parse_ident(&mut iter, psess, outer_span)?;
+        let Some(TokenTree::Delimited(.., Delimiter::Parenthesis, args)) = iter.next() else {
             let msg = "meta-variable expression parameter must be wrapped in parentheses";
             return Err(psess.dcx().struct_span_err(ident.span, msg));
         };
-        check_trailing_token(&mut tts, psess)?;
-        let mut iter = args.trees();
+        check_trailing_token(&mut iter, psess)?;
+        let mut iter = args.iter();
         let rslt = match ident.as_str() {
             "concat" => {
                 let mut result = Vec::new();
@@ -74,7 +73,7 @@ impl MetaVarExpr {
                         }
                     };
                     result.push(element);
-                    if iter.look_ahead(0).is_none() {
+                    if iter.peek().is_none() {
                         break;
                     }
                     if !try_eat_comma(&mut iter) {
@@ -143,7 +142,7 @@ pub(crate) enum MetaVarExprConcatElem {
 
 // Checks if there are any remaining tokens. For example, `${ignore(ident ... a b c ...)}`
 fn check_trailing_token<'psess>(
-    iter: &mut RefTokenTreeCursor<'_>,
+    iter: &mut TokenStreamIter<'_>,
     psess: &'psess ParseSess,
 ) -> PResult<'psess, ()> {
     if let Some(tt) = iter.next() {
@@ -159,14 +158,14 @@ fn check_trailing_token<'psess>(
 
 /// Parse a meta-variable `count` expression: `count(ident[, depth])`
 fn parse_count<'psess>(
-    iter: &mut RefTokenTreeCursor<'_>,
+    iter: &mut TokenStreamIter<'_>,
     psess: &'psess ParseSess,
     span: Span,
 ) -> PResult<'psess, MetaVarExpr> {
     eat_dollar(iter, psess, span)?;
     let ident = parse_ident(iter, psess, span)?;
     let depth = if try_eat_comma(iter) {
-        if iter.look_ahead(0).is_none() {
+        if iter.peek().is_none() {
             return Err(psess.dcx().struct_span_err(
                 span,
                 "`count` followed by a comma must have an associated index indicating its depth",
@@ -181,7 +180,7 @@ fn parse_count<'psess>(
 
 /// Parses the depth used by index(depth) and len(depth).
 fn parse_depth<'psess>(
-    iter: &mut RefTokenTreeCursor<'_>,
+    iter: &mut TokenStreamIter<'_>,
     psess: &'psess ParseSess,
     span: Span,
 ) -> PResult<'psess, usize> {
@@ -204,7 +203,7 @@ fn parse_depth<'psess>(
 
 /// Parses an generic ident
 fn parse_ident<'psess>(
-    iter: &mut RefTokenTreeCursor<'_>,
+    iter: &mut TokenStreamIter<'_>,
     psess: &'psess ParseSess,
     fallback_span: Span,
 ) -> PResult<'psess, Ident> {
@@ -236,7 +235,7 @@ fn parse_ident_from_token<'psess>(
 }
 
 fn parse_token<'psess, 't>(
-    iter: &mut RefTokenTreeCursor<'t>,
+    iter: &mut TokenStreamIter<'t>,
     psess: &'psess ParseSess,
     fallback_span: Span,
 ) -> PResult<'psess, &'t Token> {
@@ -251,8 +250,8 @@ fn parse_token<'psess, 't>(
 
 /// Tries to move the iterator forward returning `true` if there is a comma. If not, then the
 /// iterator is not modified and the result is `false`.
-fn try_eat_comma(iter: &mut RefTokenTreeCursor<'_>) -> bool {
-    if let Some(TokenTree::Token(Token { kind: token::Comma, .. }, _)) = iter.look_ahead(0) {
+fn try_eat_comma(iter: &mut TokenStreamIter<'_>) -> bool {
+    if let Some(TokenTree::Token(Token { kind: token::Comma, .. }, _)) = iter.peek() {
         let _ = iter.next();
         return true;
     }
@@ -261,8 +260,8 @@ fn try_eat_comma(iter: &mut RefTokenTreeCursor<'_>) -> bool {
 
 /// Tries to move the iterator forward returning `true` if there is a dollar sign. If not, then the
 /// iterator is not modified and the result is `false`.
-fn try_eat_dollar(iter: &mut RefTokenTreeCursor<'_>) -> bool {
-    if let Some(TokenTree::Token(Token { kind: token::Dollar, .. }, _)) = iter.look_ahead(0) {
+fn try_eat_dollar(iter: &mut TokenStreamIter<'_>) -> bool {
+    if let Some(TokenTree::Token(Token { kind: token::Dollar, .. }, _)) = iter.peek() {
         let _ = iter.next();
         return true;
     }
@@ -271,12 +270,11 @@ fn try_eat_dollar(iter: &mut RefTokenTreeCursor<'_>) -> bool {
 
 /// Expects that the next item is a dollar sign.
 fn eat_dollar<'psess>(
-    iter: &mut RefTokenTreeCursor<'_>,
+    iter: &mut TokenStreamIter<'_>,
     psess: &'psess ParseSess,
     span: Span,
 ) -> PResult<'psess, ()> {
-    if let Some(TokenTree::Token(Token { kind: token::Dollar, .. }, _)) = iter.look_ahead(0) {
-        let _ = iter.next();
+    if try_eat_dollar(iter) {
         return Ok(());
     }
     Err(psess.dcx().struct_span_err(
diff --git a/compiler/rustc_expand/src/mbe/quoted.rs b/compiler/rustc_expand/src/mbe/quoted.rs
index 36094707fac..a27d47892e4 100644
--- a/compiler/rustc_expand/src/mbe/quoted.rs
+++ b/compiler/rustc_expand/src/mbe/quoted.rs
@@ -1,12 +1,12 @@
 use rustc_ast::token::{self, Delimiter, IdentIsRaw, NonterminalKind, Token};
+use rustc_ast::tokenstream::TokenStreamIter;
 use rustc_ast::{NodeId, tokenstream};
 use rustc_ast_pretty::pprust;
 use rustc_feature::Features;
 use rustc_session::Session;
 use rustc_session::parse::feature_err;
-use rustc_span::Span;
 use rustc_span::edition::Edition;
-use rustc_span::symbol::{Ident, kw, sym};
+use rustc_span::{Ident, Span, kw, sym};
 
 use crate::errors;
 use crate::mbe::macro_parser::count_metavar_decls;
@@ -49,25 +49,25 @@ pub(super) fn parse(
 
     // For each token tree in `input`, parse the token into a `self::TokenTree`, consuming
     // additional trees if need be.
-    let mut trees = input.trees().peekable();
-    while let Some(tree) = trees.next() {
+    let mut iter = input.iter();
+    while let Some(tree) = iter.next() {
         // Given the parsed tree, if there is a metavar and we are expecting matchers, actually
         // parse out the matcher (i.e., in `$id:ident` this would parse the `:` and `ident`).
-        let tree = parse_tree(tree, &mut trees, parsing_patterns, sess, node_id, features, edition);
+        let tree = parse_tree(tree, &mut iter, parsing_patterns, sess, node_id, features, edition);
         match tree {
             TokenTree::MetaVar(start_sp, ident) if parsing_patterns => {
                 // Not consuming the next token immediately, as it may not be a colon
-                let span = match trees.peek() {
+                let span = match iter.peek() {
                     Some(&tokenstream::TokenTree::Token(
                         Token { kind: token::Colon, span: colon_span },
                         _,
                     )) => {
                         // Consume the colon first
-                        trees.next();
+                        iter.next();
 
                         // It's ok to consume the next tree no matter how,
                         // since if it's not a token then it will be an invalid declaration.
-                        match trees.next() {
+                        match iter.next() {
                             Some(tokenstream::TokenTree::Token(token, _)) => match token.ident() {
                                 Some((fragment, _)) => {
                                     let span = token.span.with_lo(start_sp.lo());
@@ -143,14 +143,14 @@ fn maybe_emit_macro_metavar_expr_concat_feature(features: &Features, sess: &Sess
 /// # Parameters
 ///
 /// - `tree`: the tree we wish to convert.
-/// - `outer_trees`: an iterator over trees. We may need to read more tokens from it in order to finish
+/// - `outer_iter`: an iterator over trees. We may need to read more tokens from it in order to finish
 ///   converting `tree`
 /// - `parsing_patterns`: same as [parse].
 /// - `sess`: the parsing session. Any errors will be emitted to this session.
 /// - `features`: language features so we can do feature gating.
 fn parse_tree<'a>(
     tree: &'a tokenstream::TokenTree,
-    outer_trees: &mut impl Iterator<Item = &'a tokenstream::TokenTree>,
+    outer_iter: &mut TokenStreamIter<'a>,
     parsing_patterns: bool,
     sess: &Session,
     node_id: NodeId,
@@ -163,15 +163,16 @@ fn parse_tree<'a>(
         &tokenstream::TokenTree::Token(Token { kind: token::Dollar, span: dollar_span }, _) => {
             // FIXME: Handle `Invisible`-delimited groups in a more systematic way
             // during parsing.
-            let mut next = outer_trees.next();
-            let mut trees: Box<dyn Iterator<Item = &tokenstream::TokenTree>>;
-            match next {
+            let mut next = outer_iter.next();
+            let mut iter_storage;
+            let mut iter: &mut TokenStreamIter<'_> = match next {
                 Some(tokenstream::TokenTree::Delimited(.., delim, tts)) if delim.skip() => {
-                    trees = Box::new(tts.trees());
-                    next = trees.next();
+                    iter_storage = tts.iter();
+                    next = iter_storage.next();
+                    &mut iter_storage
                 }
-                _ => trees = Box::new(outer_trees),
-            }
+                _ => outer_iter,
+            };
 
             match next {
                 // `tree` is followed by a delimited set of token trees.
@@ -230,7 +231,7 @@ fn parse_tree<'a>(
                     let sequence = parse(tts, parsing_patterns, sess, node_id, features, edition);
                     // Get the Kleene operator and optional separator
                     let (separator, kleene) =
-                        parse_sep_and_kleene_op(&mut trees, delim_span.entire(), sess);
+                        parse_sep_and_kleene_op(&mut iter, delim_span.entire(), sess);
                     // Count the number of captured "names" (i.e., named metavars)
                     let num_captures =
                         if parsing_patterns { count_metavar_decls(&sequence) } else { 0 };
@@ -313,11 +314,11 @@ fn kleene_op(token: &Token) -> Option<KleeneOp> {
 /// - Ok(Ok((op, span))) if the next token tree is a KleeneOp
 /// - Ok(Err(tok, span)) if the next token tree is a token but not a KleeneOp
 /// - Err(span) if the next token tree is not a token
-fn parse_kleene_op<'a>(
-    input: &mut impl Iterator<Item = &'a tokenstream::TokenTree>,
+fn parse_kleene_op(
+    iter: &mut TokenStreamIter<'_>,
     span: Span,
 ) -> Result<Result<(KleeneOp, Span), Token>, Span> {
-    match input.next() {
+    match iter.next() {
         Some(tokenstream::TokenTree::Token(token, _)) => match kleene_op(token) {
             Some(op) => Ok(Ok((op, token.span))),
             None => Ok(Err(token.clone())),
@@ -334,22 +335,22 @@ fn parse_kleene_op<'a>(
 /// itself. Note that here we are parsing the _macro_ itself, rather than trying to match some
 /// stream of tokens in an invocation of a macro.
 ///
-/// This function will take some input iterator `input` corresponding to `span` and a parsing
-/// session `sess`. If the next one (or possibly two) tokens in `input` correspond to a Kleene
+/// This function will take some input iterator `iter` corresponding to `span` and a parsing
+/// session `sess`. If the next one (or possibly two) tokens in `iter` correspond to a Kleene
 /// operator and separator, then a tuple with `(separator, KleeneOp)` is returned. Otherwise, an
 /// error with the appropriate span is emitted to `sess` and a dummy value is returned.
-fn parse_sep_and_kleene_op<'a>(
-    input: &mut impl Iterator<Item = &'a tokenstream::TokenTree>,
+fn parse_sep_and_kleene_op(
+    iter: &mut TokenStreamIter<'_>,
     span: Span,
     sess: &Session,
 ) -> (Option<Token>, KleeneToken) {
     // We basically look at two token trees here, denoted as #1 and #2 below
-    let span = match parse_kleene_op(input, span) {
+    let span = match parse_kleene_op(iter, span) {
         // #1 is a `?`, `+`, or `*` KleeneOp
         Ok(Ok((op, span))) => return (None, KleeneToken::new(op, span)),
 
         // #1 is a separator followed by #2, a KleeneOp
-        Ok(Err(token)) => match parse_kleene_op(input, token.span) {
+        Ok(Err(token)) => match parse_kleene_op(iter, token.span) {
             // #2 is the `?` Kleene op, which does not take a separator (error)
             Ok(Ok((KleeneOp::ZeroOrOne, span))) => {
                 // Error!
diff --git a/compiler/rustc_expand/src/mbe/transcribe.rs b/compiler/rustc_expand/src/mbe/transcribe.rs
index b77d02e630a..4fb1eadd486 100644
--- a/compiler/rustc_expand/src/mbe/transcribe.rs
+++ b/compiler/rustc_expand/src/mbe/transcribe.rs
@@ -11,8 +11,9 @@ use rustc_parse::lexer::nfc_normalize;
 use rustc_parse::parser::ParseNtResult;
 use rustc_session::parse::{ParseSess, SymbolGallery};
 use rustc_span::hygiene::{LocalExpnId, Transparency};
-use rustc_span::symbol::{Ident, MacroRulesNormalizedIdent, sym};
-use rustc_span::{Span, Symbol, SyntaxContext, with_metavar_spans};
+use rustc_span::{
+    Ident, MacroRulesNormalizedIdent, Span, Symbol, SyntaxContext, sym, with_metavar_spans,
+};
 use smallvec::{SmallVec, smallvec};
 
 use crate::errors::{
diff --git a/compiler/rustc_expand/src/module.rs b/compiler/rustc_expand/src/module.rs
index 85ea42e78ad..9c35b26772b 100644
--- a/compiler/rustc_expand/src/module.rs
+++ b/compiler/rustc_expand/src/module.rs
@@ -2,13 +2,12 @@ use std::iter::once;
 use std::path::{self, Path, PathBuf};
 
 use rustc_ast::ptr::P;
-use rustc_ast::{AttrVec, Attribute, Inline, Item, ModSpans, token};
+use rustc_ast::{AttrVec, Attribute, Inline, Item, ModSpans};
 use rustc_errors::{Diag, ErrorGuaranteed};
-use rustc_parse::{new_parser_from_file, unwrap_or_emit_fatal, validate_attr};
+use rustc_parse::{exp, new_parser_from_file, unwrap_or_emit_fatal, validate_attr};
 use rustc_session::Session;
 use rustc_session::parse::ParseSess;
-use rustc_span::Span;
-use rustc_span::symbol::{Ident, sym};
+use rustc_span::{Ident, Span, sym};
 use thin_vec::ThinVec;
 
 use crate::base::ModuleData;
@@ -71,7 +70,7 @@ pub(crate) fn parse_external_mod(
         let mut parser =
             unwrap_or_emit_fatal(new_parser_from_file(&sess.psess, &mp.file_path, Some(span)));
         let (inner_attrs, items, inner_span) =
-            parser.parse_mod(&token::Eof).map_err(|err| ModError::ParserError(err))?;
+            parser.parse_mod(exp!(Eof)).map_err(|err| ModError::ParserError(err))?;
         attrs.extend(inner_attrs);
         (items, inner_span, mp.file_path)
     };
diff --git a/compiler/rustc_expand/src/placeholders.rs b/compiler/rustc_expand/src/placeholders.rs
index 9e459bd81a1..e969f2d4fb5 100644
--- a/compiler/rustc_expand/src/placeholders.rs
+++ b/compiler/rustc_expand/src/placeholders.rs
@@ -4,8 +4,7 @@ use rustc_ast::token::Delimiter;
 use rustc_ast::visit::AssocCtxt;
 use rustc_ast::{self as ast, Safety};
 use rustc_data_structures::fx::FxHashMap;
-use rustc_span::DUMMY_SP;
-use rustc_span::symbol::Ident;
+use rustc_span::{DUMMY_SP, Ident};
 use smallvec::{SmallVec, smallvec};
 use thin_vec::ThinVec;
 
diff --git a/compiler/rustc_expand/src/proc_macro_server.rs b/compiler/rustc_expand/src/proc_macro_server.rs
index 263df235b3e..7eb09a64e96 100644
--- a/compiler/rustc_expand/src/proc_macro_server.rs
+++ b/compiler/rustc_expand/src/proc_macro_server.rs
@@ -15,11 +15,10 @@ use rustc_data_structures::sync::Lrc;
 use rustc_errors::{Diag, ErrorGuaranteed, MultiSpan, PResult};
 use rustc_parse::lexer::nfc_normalize;
 use rustc_parse::parser::Parser;
-use rustc_parse::{new_parser_from_source_str, source_str_to_stream, unwrap_or_emit_fatal};
+use rustc_parse::{exp, new_parser_from_source_str, source_str_to_stream, unwrap_or_emit_fatal};
 use rustc_session::parse::ParseSess;
 use rustc_span::def_id::CrateNum;
-use rustc_span::symbol::{self, Symbol, sym};
-use rustc_span::{BytePos, FileName, Pos, SourceFile, Span};
+use rustc_span::{BytePos, FileName, Pos, SourceFile, Span, Symbol, sym};
 use smallvec::{SmallVec, smallvec};
 
 use crate::base::ExtCtxt;
@@ -112,9 +111,9 @@ impl FromInternal<(TokenStream, &mut Rustc<'_, '_>)> for Vec<TokenTree<TokenStre
         // Estimate the capacity as `stream.len()` rounded up to the next power
         // of two to limit the number of required reallocations.
         let mut trees = Vec::with_capacity(stream.len().next_power_of_two());
-        let mut cursor = stream.trees();
+        let mut iter = stream.iter();
 
-        while let Some(tree) = cursor.next() {
+        while let Some(tree) = iter.next() {
             let (Token { kind, span }, joint) = match tree.clone() {
                 tokenstream::TokenTree::Delimited(span, _, delim, tts) => {
                     let delimiter = pm::Delimiter::from_internal(delim);
@@ -230,7 +229,7 @@ impl FromInternal<(TokenStream, &mut Rustc<'_, '_>)> for Vec<TokenTree<TokenStre
                 })),
 
                 Lifetime(name, is_raw) => {
-                    let ident = symbol::Ident::new(name, span).without_first_quote();
+                    let ident = rustc_span::Ident::new(name, span).without_first_quote();
                     trees.extend([
                         TokenTree::Punct(Punct { ch: b'\'', joint: true, span }),
                         TokenTree::Ident(Ident { sym: ident.name, is_raw: is_raw.into(), span }),
@@ -474,7 +473,7 @@ impl server::FreeFunctions for Rustc<'_, '_> {
             unwrap_or_emit_fatal(new_parser_from_source_str(self.psess(), name, s.to_owned()));
 
         let first_span = parser.token.span.data();
-        let minus_present = parser.eat(&token::BinOp(token::Minus));
+        let minus_present = parser.eat(exp!(Minus));
 
         let lit_span = parser.token.span.data();
         let token::Literal(mut lit) = parser.token.kind else {
diff --git a/compiler/rustc_feature/src/accepted.rs b/compiler/rustc_feature/src/accepted.rs
index c5913ed27cf..5a9b8c43e74 100644
--- a/compiler/rustc_feature/src/accepted.rs
+++ b/compiler/rustc_feature/src/accepted.rs
@@ -1,6 +1,6 @@
 //! List of the accepted feature gates.
 
-use rustc_span::symbol::sym;
+use rustc_span::sym;
 
 use super::{Feature, to_nonzero};
 
@@ -157,6 +157,9 @@ declare_features! (
     (accepted, const_refs_to_static, "1.83.0", Some(119618)),
     /// Allows implementing `Copy` for closures where possible (RFC 2132).
     (accepted, copy_closures, "1.26.0", Some(44490)),
+    /// Allows function attribute `#[coverage(on/off)]`, to control coverage
+    /// instrumentation of that function.
+    (accepted, coverage_attribute, "CURRENT_RUSTC_VERSION", Some(84605)),
     /// Allows `crate` in paths.
     (accepted, crate_in_paths, "1.30.0", Some(45477)),
     /// Allows users to provide classes for fenced code block using `class:classname`.
@@ -175,6 +178,8 @@ declare_features! (
     (accepted, destructuring_assignment, "1.59.0", Some(71126)),
     /// Allows using the `#[diagnostic]` attribute tool namespace
     (accepted, diagnostic_namespace, "1.78.0", Some(111996)),
+    /// Controls errors in trait implementations.
+    (accepted, do_not_recommend, "CURRENT_RUSTC_VERSION", Some(51992)),
     /// Allows `#[doc(alias = "...")]`.
     (accepted, doc_alias, "1.48.0", Some(50146)),
     /// Allows `..` in tuple (struct) patterns.
diff --git a/compiler/rustc_feature/src/builtin_attrs.rs b/compiler/rustc_feature/src/builtin_attrs.rs
index 3bf485c2eb6..63e5ebb8688 100644
--- a/compiler/rustc_feature/src/builtin_attrs.rs
+++ b/compiler/rustc_feature/src/builtin_attrs.rs
@@ -6,7 +6,7 @@ use AttributeDuplicates::*;
 use AttributeGate::*;
 use AttributeType::*;
 use rustc_data_structures::fx::FxHashMap;
-use rustc_span::symbol::{Symbol, sym};
+use rustc_span::{Symbol, sym};
 
 use crate::{Features, Stability};
 
@@ -480,10 +480,9 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
         template!(List: "address, kcfi, memory, thread"), DuplicatesOk,
         EncodeCrossCrate::No, experimental!(no_sanitize)
     ),
-    gated!(
+    ungated!(
         coverage, Normal, template!(OneOf: &[sym::off, sym::on]),
         ErrorPreceding, EncodeCrossCrate::No,
-        coverage_attribute, experimental!(coverage)
     ),
 
     ungated!(
@@ -913,12 +912,21 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
     rustc_attr!(
         rustc_deny_explicit_impl,
         AttributeType::Normal,
-        template!(List: "implement_via_object = (true|false)"),
+        template!(Word),
         ErrorFollowing,
         EncodeCrossCrate::No,
         "#[rustc_deny_explicit_impl] enforces that a trait can have no user-provided impls"
     ),
     rustc_attr!(
+        rustc_do_not_implement_via_object,
+        AttributeType::Normal,
+        template!(Word),
+        ErrorFollowing,
+        EncodeCrossCrate::No,
+        "#[rustc_do_not_implement_via_object] opts out of the automatic trait impl for trait objects \
+        (`impl Trait for dyn Trait`)"
+    ),
+    rustc_attr!(
         rustc_has_incoherent_inherent_impls, AttributeType::Normal, template!(Word),
         ErrorFollowing, EncodeCrossCrate::Yes,
         "#[rustc_has_incoherent_inherent_impls] allows the addition of incoherent inherent impls for \
@@ -1188,10 +1196,9 @@ pub static BUILTIN_ATTRIBUTE_MAP: LazyLock<FxHashMap<Symbol, &BuiltinAttribute>>
         map
     });
 
-pub fn is_stable_diagnostic_attribute(sym: Symbol, features: &Features) -> bool {
+pub fn is_stable_diagnostic_attribute(sym: Symbol, _features: &Features) -> bool {
     match sym {
-        sym::on_unimplemented => true,
-        sym::do_not_recommend => features.do_not_recommend(),
+        sym::on_unimplemented | sym::do_not_recommend => true,
         _ => false,
     }
 }
diff --git a/compiler/rustc_feature/src/lib.rs b/compiler/rustc_feature/src/lib.rs
index 5d27b8f542c..6db512ace1b 100644
--- a/compiler/rustc_feature/src/lib.rs
+++ b/compiler/rustc_feature/src/lib.rs
@@ -28,7 +28,7 @@ mod tests;
 
 use std::num::NonZero;
 
-use rustc_span::symbol::Symbol;
+use rustc_span::Symbol;
 
 #[derive(Debug, Clone)]
 pub struct Feature {
diff --git a/compiler/rustc_feature/src/removed.rs b/compiler/rustc_feature/src/removed.rs
index e25840ba5fc..388ed9d08fa 100644
--- a/compiler/rustc_feature/src/removed.rs
+++ b/compiler/rustc_feature/src/removed.rs
@@ -1,6 +1,6 @@
 //! List of the removed feature gates.
 
-use rustc_span::symbol::sym;
+use rustc_span::sym;
 
 use super::{Feature, to_nonzero};
 
diff --git a/compiler/rustc_feature/src/unstable.rs b/compiler/rustc_feature/src/unstable.rs
index 45c63b03fe9..ebb07195a28 100644
--- a/compiler/rustc_feature/src/unstable.rs
+++ b/compiler/rustc_feature/src/unstable.rs
@@ -3,8 +3,7 @@
 use std::path::PathBuf;
 
 use rustc_data_structures::fx::FxHashSet;
-use rustc_span::Span;
-use rustc_span::symbol::{Symbol, sym};
+use rustc_span::{Span, Symbol, sym};
 
 use super::{Feature, to_nonzero};
 
@@ -332,6 +331,7 @@ declare_features! (
     (unstable, hexagon_target_feature, "1.27.0", Some(44839)),
     (unstable, lahfsahf_target_feature, "1.78.0", Some(44839)),
     (unstable, loongarch_target_feature, "1.73.0", Some(44839)),
+    (unstable, m68k_target_feature, "CURRENT_RUSTC_VERSION", Some(134328)),
     (unstable, mips_target_feature, "1.27.0", Some(44839)),
     (unstable, powerpc_target_feature, "1.27.0", Some(44839)),
     (unstable, prfchw_target_feature, "1.78.0", Some(44839)),
@@ -447,9 +447,6 @@ declare_features! (
     (unstable, coroutine_clone, "1.65.0", Some(95360)),
     /// Allows defining coroutines.
     (unstable, coroutines, "1.21.0", Some(43122)),
-    /// Allows function attribute `#[coverage(on/off)]`, to control coverage
-    /// instrumentation of that function.
-    (unstable, coverage_attribute, "1.74.0", Some(84605)),
     /// Allows non-builtin attributes in inner attribute position.
     (unstable, custom_inner_attributes, "1.30.0", Some(54726)),
     /// Allows custom test frameworks with `#![test_runner]` and `#[test_case]`.
@@ -465,8 +462,6 @@ declare_features! (
     (unstable, deprecated_suggestion, "1.61.0", Some(94785)),
     /// Allows deref patterns.
     (incomplete, deref_patterns, "1.79.0", Some(87121)),
-    /// Controls errors in trait implementations.
-    (unstable, do_not_recommend, "1.67.0", Some(51992)),
     /// Tells rustdoc to automatically generate `#[doc(cfg(...))]`.
     (unstable, doc_auto_cfg, "1.58.0", Some(43781)),
     /// Allows `#[doc(cfg(...))]`.
diff --git a/compiler/rustc_hir/Cargo.toml b/compiler/rustc_hir/Cargo.toml
index 85c6da83379..5bfc4756ec6 100644
--- a/compiler/rustc_hir/Cargo.toml
+++ b/compiler/rustc_hir/Cargo.toml
@@ -16,5 +16,6 @@ rustc_serialize = { path = "../rustc_serialize" }
 rustc_span = { path = "../rustc_span" }
 rustc_target = { path = "../rustc_target" }
 smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
+thin-vec = "0.2.12"
 tracing = "0.1"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_hir/src/arena.rs b/compiler/rustc_hir/src/arena.rs
index f1f624269ae..88c0d223fd3 100644
--- a/compiler/rustc_hir/src/arena.rs
+++ b/compiler/rustc_hir/src/arena.rs
@@ -6,7 +6,7 @@ macro_rules! arena_types {
         $macro!([
             // HIR types
             [] asm_template: rustc_ast::InlineAsmTemplatePiece,
-            [] attribute: rustc_ast::Attribute,
+            [] attribute: rustc_hir::Attribute,
             [] owner_info: rustc_hir::OwnerInfo<'tcx>,
             [] use_path: rustc_hir::UsePath<'tcx>,
             [] lit: rustc_hir::Lit,
diff --git a/compiler/rustc_hir/src/definitions.rs b/compiler/rustc_hir/src/definitions.rs
index d85f9586d42..dc527240f74 100644
--- a/compiler/rustc_hir/src/definitions.rs
+++ b/compiler/rustc_hir/src/definitions.rs
@@ -11,7 +11,7 @@ use rustc_data_structures::stable_hasher::{Hash64, StableHasher};
 use rustc_data_structures::unord::UnordMap;
 use rustc_index::IndexVec;
 use rustc_macros::{Decodable, Encodable};
-use rustc_span::symbol::{Symbol, kw, sym};
+use rustc_span::{Symbol, kw, sym};
 use tracing::{debug, instrument};
 
 pub use crate::def_id::DefPathHash;
diff --git a/compiler/rustc_hir/src/hir.rs b/compiler/rustc_hir/src/hir.rs
index 357033a9e18..8cea269f298 100644
--- a/compiler/rustc_hir/src/hir.rs
+++ b/compiler/rustc_hir/src/hir.rs
@@ -1,10 +1,13 @@
 use std::fmt;
 
 use rustc_abi::ExternAbi;
+// ignore-tidy-filelength
+use rustc_ast::attr::AttributeExt;
+use rustc_ast::token::CommentKind;
 use rustc_ast::util::parser::{AssocOp, ExprPrecedence};
 use rustc_ast::{
-    self as ast, Attribute, FloatTy, InlineAsmOptions, InlineAsmTemplatePiece, IntTy, Label,
-    LitKind, TraitObjectSyntax, UintTy,
+    self as ast, AttrId, AttrStyle, DelimArgs, FloatTy, InlineAsmOptions, InlineAsmTemplatePiece,
+    IntTy, Label, LitKind, MetaItemInner, MetaItemLit, TraitObjectSyntax, UintTy,
 };
 pub use rustc_ast::{
     BinOp, BinOpKind, BindingMode, BorrowKind, BoundConstness, BoundPolarity, ByRef, CaptureBy,
@@ -17,10 +20,10 @@ use rustc_macros::{Decodable, Encodable, HashStable_Generic};
 use rustc_span::def_id::LocalDefId;
 use rustc_span::hygiene::MacroKind;
 use rustc_span::source_map::Spanned;
-use rustc_span::symbol::{Ident, Symbol, kw, sym};
-use rustc_span::{BytePos, DUMMY_SP, ErrorGuaranteed, Span};
+use rustc_span::{BytePos, DUMMY_SP, ErrorGuaranteed, Ident, Span, Symbol, kw, sym};
 use rustc_target::asm::InlineAsmRegOrRegClass;
 use smallvec::SmallVec;
+use thin_vec::ThinVec;
 use tracing::debug;
 
 use crate::LangItem;
@@ -937,6 +940,250 @@ pub struct ParentedNode<'tcx> {
     pub node: Node<'tcx>,
 }
 
+/// Arguments passed to an attribute macro.
+#[derive(Clone, Debug, HashStable_Generic, Encodable, Decodable)]
+pub enum AttrArgs {
+    /// No arguments: `#[attr]`.
+    Empty,
+    /// Delimited arguments: `#[attr()/[]/{}]`.
+    Delimited(DelimArgs),
+    /// Arguments of a key-value attribute: `#[attr = "value"]`.
+    Eq {
+        /// Span of the `=` token.
+        eq_span: Span,
+        /// The "value".
+        expr: MetaItemLit,
+    },
+}
+
+#[derive(Clone, Debug, Encodable, Decodable)]
+pub enum AttrKind {
+    /// A normal attribute.
+    Normal(Box<AttrItem>),
+
+    /// A doc comment (e.g. `/// ...`, `//! ...`, `/** ... */`, `/*! ... */`).
+    /// Doc attributes (e.g. `#[doc="..."]`) are represented with the `Normal`
+    /// variant (which is much less compact and thus more expensive).
+    DocComment(CommentKind, Symbol),
+}
+
+#[derive(Clone, Debug, HashStable_Generic, Encodable, Decodable)]
+pub struct AttrPath {
+    pub segments: Box<[Ident]>,
+    pub span: Span,
+}
+
+#[derive(Clone, Debug, HashStable_Generic, Encodable, Decodable)]
+pub struct AttrItem {
+    pub unsafety: Safety,
+    // Not lowered to hir::Path because we have no NodeId to resolve to.
+    pub path: AttrPath,
+    pub args: AttrArgs,
+}
+
+#[derive(Clone, Debug, Encodable, Decodable)]
+pub struct Attribute {
+    pub kind: AttrKind,
+    pub id: AttrId,
+    /// Denotes if the attribute decorates the following construct (outer)
+    /// or the construct this attribute is contained within (inner).
+    pub style: AttrStyle,
+    pub span: Span,
+}
+
+impl Attribute {
+    pub fn get_normal_item(&self) -> &AttrItem {
+        match &self.kind {
+            AttrKind::Normal(normal) => &normal,
+            AttrKind::DocComment(..) => panic!("unexpected doc comment"),
+        }
+    }
+
+    pub fn unwrap_normal_item(self) -> AttrItem {
+        match self.kind {
+            AttrKind::Normal(normal) => *normal,
+            AttrKind::DocComment(..) => panic!("unexpected doc comment"),
+        }
+    }
+
+    pub fn value_lit(&self) -> Option<&MetaItemLit> {
+        match &self.kind {
+            AttrKind::Normal(n) => match n.as_ref() {
+                AttrItem { args: AttrArgs::Eq { expr, .. }, .. } => Some(expr),
+                _ => None,
+            },
+            _ => None,
+        }
+    }
+}
+
+impl AttributeExt for Attribute {
+    fn id(&self) -> AttrId {
+        self.id
+    }
+
+    fn meta_item_list(&self) -> Option<ThinVec<ast::MetaItemInner>> {
+        match &self.kind {
+            AttrKind::Normal(n) => match n.as_ref() {
+                AttrItem { args: AttrArgs::Delimited(d), .. } => {
+                    ast::MetaItemKind::list_from_tokens(d.tokens.clone())
+                }
+                _ => None,
+            },
+            _ => None,
+        }
+    }
+
+    fn value_str(&self) -> Option<Symbol> {
+        self.value_lit().and_then(|x| x.value_str())
+    }
+
+    fn value_span(&self) -> Option<Span> {
+        self.value_lit().map(|i| i.span)
+    }
+
+    /// For a single-segment attribute, returns its name; otherwise, returns `None`.
+    fn ident(&self) -> Option<Ident> {
+        match &self.kind {
+            AttrKind::Normal(n) => {
+                if let [ident] = n.path.segments.as_ref() {
+                    Some(*ident)
+                } else {
+                    None
+                }
+            }
+            AttrKind::DocComment(..) => None,
+        }
+    }
+
+    fn path_matches(&self, name: &[Symbol]) -> bool {
+        match &self.kind {
+            AttrKind::Normal(n) => {
+                n.path.segments.len() == name.len()
+                    && n.path.segments.iter().zip(name).all(|(s, n)| s.name == *n)
+            }
+            AttrKind::DocComment(..) => false,
+        }
+    }
+
+    fn is_doc_comment(&self) -> bool {
+        matches!(self.kind, AttrKind::DocComment(..))
+    }
+
+    fn span(&self) -> Span {
+        self.span
+    }
+
+    fn is_word(&self) -> bool {
+        match &self.kind {
+            AttrKind::Normal(n) => {
+                matches!(n.args, AttrArgs::Empty)
+            }
+            AttrKind::DocComment(..) => false,
+        }
+    }
+
+    fn ident_path(&self) -> Option<SmallVec<[Ident; 1]>> {
+        match &self.kind {
+            AttrKind::Normal(n) => Some(n.path.segments.iter().copied().collect()),
+            AttrKind::DocComment(..) => None,
+        }
+    }
+
+    fn doc_str(&self) -> Option<Symbol> {
+        match &self.kind {
+            AttrKind::DocComment(.., data) => Some(*data),
+            AttrKind::Normal(_) if self.has_name(sym::doc) => self.value_str(),
+            _ => None,
+        }
+    }
+    fn doc_str_and_comment_kind(&self) -> Option<(Symbol, CommentKind)> {
+        match &self.kind {
+            AttrKind::DocComment(kind, data) => Some((*data, *kind)),
+            AttrKind::Normal(_) if self.name_or_empty() == sym::doc => {
+                self.value_str().map(|s| (s, CommentKind::Line))
+            }
+            _ => None,
+        }
+    }
+
+    fn style(&self) -> AttrStyle {
+        self.style
+    }
+}
+
+// FIXME(fn_delegation): use function delegation instead of manually forwarding
+impl Attribute {
+    pub fn id(&self) -> AttrId {
+        AttributeExt::id(self)
+    }
+
+    pub fn name_or_empty(&self) -> Symbol {
+        AttributeExt::name_or_empty(self)
+    }
+
+    pub fn meta_item_list(&self) -> Option<ThinVec<MetaItemInner>> {
+        AttributeExt::meta_item_list(self)
+    }
+
+    pub fn value_str(&self) -> Option<Symbol> {
+        AttributeExt::value_str(self)
+    }
+
+    pub fn value_span(&self) -> Option<Span> {
+        AttributeExt::value_span(self)
+    }
+
+    pub fn ident(&self) -> Option<Ident> {
+        AttributeExt::ident(self)
+    }
+
+    pub fn path_matches(&self, name: &[Symbol]) -> bool {
+        AttributeExt::path_matches(self, name)
+    }
+
+    pub fn is_doc_comment(&self) -> bool {
+        AttributeExt::is_doc_comment(self)
+    }
+
+    #[inline]
+    pub fn has_name(&self, name: Symbol) -> bool {
+        AttributeExt::has_name(self, name)
+    }
+
+    pub fn span(&self) -> Span {
+        AttributeExt::span(self)
+    }
+
+    pub fn is_word(&self) -> bool {
+        AttributeExt::is_word(self)
+    }
+
+    pub fn path(&self) -> SmallVec<[Symbol; 1]> {
+        AttributeExt::path(self)
+    }
+
+    pub fn ident_path(&self) -> Option<SmallVec<[Ident; 1]>> {
+        AttributeExt::ident_path(self)
+    }
+
+    pub fn doc_str(&self) -> Option<Symbol> {
+        AttributeExt::doc_str(self)
+    }
+
+    pub fn is_proc_macro_attr(&self) -> bool {
+        AttributeExt::is_proc_macro_attr(self)
+    }
+
+    pub fn doc_str_and_comment_kind(&self) -> Option<(Symbol, CommentKind)> {
+        AttributeExt::doc_str_and_comment_kind(self)
+    }
+
+    pub fn style(&self) -> AttrStyle {
+        AttributeExt::style(self)
+    }
+}
+
 /// Attributes owned by a HIR owner.
 #[derive(Debug)]
 pub struct AttributeMap<'tcx> {
@@ -1696,11 +1943,15 @@ pub struct Expr<'hir> {
 
 impl Expr<'_> {
     pub fn precedence(&self) -> ExprPrecedence {
-        match self.kind {
-            ExprKind::Closure { .. } => ExprPrecedence::Closure,
+        match &self.kind {
+            ExprKind::Closure(closure) => {
+                match closure.fn_decl.output {
+                    FnRetTy::DefaultReturn(_) => ExprPrecedence::Jump,
+                    FnRetTy::Return(_) => ExprPrecedence::Unambiguous,
+                }
+            }
 
             ExprKind::Break(..)
-            | ExprKind::Continue(..)
             | ExprKind::Ret(..)
             | ExprKind::Yield(..)
             | ExprKind::Become(..) => ExprPrecedence::Jump,
@@ -1726,6 +1977,7 @@ impl Expr<'_> {
             | ExprKind::Block(..)
             | ExprKind::Call(..)
             | ExprKind::ConstBlock(_)
+            | ExprKind::Continue(..)
             | ExprKind::Field(..)
             | ExprKind::If(..)
             | ExprKind::Index(..)
@@ -1743,7 +1995,7 @@ impl Expr<'_> {
             | ExprKind::UnsafeBinderCast(..)
             | ExprKind::Err(_) => ExprPrecedence::Unambiguous,
 
-            ExprKind::DropTemps(ref expr, ..) => expr.precedence(),
+            ExprKind::DropTemps(expr, ..) => expr.precedence(),
         }
     }
 
@@ -2025,6 +2277,22 @@ pub fn is_range_literal(expr: &Expr<'_>) -> bool {
     }
 }
 
+/// Checks if the specified expression needs parentheses for prefix
+/// or postfix suggestions to be valid.
+/// For example, `a + b` requires parentheses to suggest `&(a + b)`,
+/// but just `a` does not.
+/// Similarly, `(a + b).c()` also requires parentheses.
+/// This should not be used for other types of suggestions.
+pub fn expr_needs_parens(expr: &Expr<'_>) -> bool {
+    match expr.kind {
+        // parenthesize if needed (Issue #46756)
+        ExprKind::Cast(_, _) | ExprKind::Binary(_, _, _) => true,
+        // parenthesize borrows of range literals (Issue #54505)
+        _ if is_range_literal(expr) => true,
+        _ => false,
+    }
+}
+
 #[derive(Debug, Clone, Copy, HashStable_Generic)]
 pub enum ExprKind<'hir> {
     /// Allow anonymous constants from an inline `const` block
@@ -3418,6 +3686,19 @@ impl Safety {
             Self::Safe => "",
         }
     }
+
+    #[inline]
+    pub fn is_unsafe(self) -> bool {
+        !self.is_safe()
+    }
+
+    #[inline]
+    pub fn is_safe(self) -> bool {
+        match self {
+            Self::Unsafe => false,
+            Self::Safe => true,
+        }
+    }
 }
 
 impl fmt::Display for Safety {
@@ -3462,7 +3743,7 @@ impl FnHeader {
     }
 
     pub fn is_unsafe(&self) -> bool {
-        matches!(&self.safety, Safety::Unsafe)
+        self.safety.is_unsafe()
     }
 }
 
diff --git a/compiler/rustc_hir/src/intravisit.rs b/compiler/rustc_hir/src/intravisit.rs
index 6d481f7536a..387a195cb29 100644
--- a/compiler/rustc_hir/src/intravisit.rs
+++ b/compiler/rustc_hir/src/intravisit.rs
@@ -64,11 +64,10 @@
 //! This order consistency is required in a few places in rustc, for
 //! example coroutine inference, and possibly also HIR borrowck.
 
+use rustc_ast::Label;
 use rustc_ast::visit::{VisitorResult, try_visit, visit_opt, walk_list};
-use rustc_ast::{Attribute, Label};
-use rustc_span::Span;
 use rustc_span::def_id::LocalDefId;
-use rustc_span::symbol::{Ident, Symbol};
+use rustc_span::{Ident, Span, Symbol};
 
 use crate::hir::*;
 
diff --git a/compiler/rustc_hir/src/lang_items.rs b/compiler/rustc_hir/src/lang_items.rs
index 15cb331d07a..fae3b778d7b 100644
--- a/compiler/rustc_hir/src/lang_items.rs
+++ b/compiler/rustc_hir/src/lang_items.rs
@@ -7,12 +7,11 @@
 //! * Traits that represent operators; e.g., `Add`, `Sub`, `Index`.
 //! * Functions called by the compiler itself.
 
-use rustc_ast as ast;
+use rustc_ast::attr::AttributeExt;
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_macros::{Decodable, Encodable, HashStable_Generic};
-use rustc_span::Span;
-use rustc_span::symbol::{Symbol, kw, sym};
+use rustc_span::{Span, Symbol, kw, sym};
 
 use crate::def_id::DefId;
 use crate::{MethodKind, Target};
@@ -153,11 +152,11 @@ impl<CTX> HashStable<CTX> for LangItem {
 
 /// Extracts the first `lang = "$name"` out of a list of attributes.
 /// The `#[panic_handler]` attribute is also extracted out when found.
-pub fn extract(attrs: &[ast::Attribute]) -> Option<(Symbol, Span)> {
+pub fn extract(attrs: &[impl AttributeExt]) -> Option<(Symbol, Span)> {
     attrs.iter().find_map(|attr| {
         Some(match attr {
-            _ if attr.has_name(sym::lang) => (attr.value_str()?, attr.span),
-            _ if attr.has_name(sym::panic_handler) => (sym::panic_impl, attr.span),
+            _ if attr.has_name(sym::lang) => (attr.value_str()?, attr.span()),
+            _ if attr.has_name(sym::panic_handler) => (sym::panic_impl, attr.span()),
             _ => return None,
         })
     })
diff --git a/compiler/rustc_hir/src/pat_util.rs b/compiler/rustc_hir/src/pat_util.rs
index 2ebbb4a06b6..bb853985c7d 100644
--- a/compiler/rustc_hir/src/pat_util.rs
+++ b/compiler/rustc_hir/src/pat_util.rs
@@ -1,7 +1,6 @@
 use std::iter::Enumerate;
 
-use rustc_span::Span;
-use rustc_span::symbol::Ident;
+use rustc_span::{Ident, Span};
 
 use crate::def::{CtorOf, DefKind, Res};
 use crate::def_id::{DefId, DefIdSet};
diff --git a/compiler/rustc_hir/src/stable_hash_impls.rs b/compiler/rustc_hir/src/stable_hash_impls.rs
index fe169e989ec..db0d0fcf3b9 100644
--- a/compiler/rustc_hir/src/stable_hash_impls.rs
+++ b/compiler/rustc_hir/src/stable_hash_impls.rs
@@ -2,7 +2,8 @@ use rustc_data_structures::stable_hasher::{HashStable, StableHasher, ToStableHas
 use rustc_span::def_id::DefPathHash;
 
 use crate::hir::{
-    AttributeMap, BodyId, Crate, ForeignItemId, ImplItemId, ItemId, OwnerNodes, TraitItemId,
+    Attribute, AttributeMap, BodyId, Crate, ForeignItemId, ImplItemId, ItemId, OwnerNodes,
+    TraitItemId,
 };
 use crate::hir_id::{HirId, ItemLocalId};
 
@@ -12,6 +13,7 @@ use crate::hir_id::{HirId, ItemLocalId};
 pub trait HashStableContext:
     rustc_ast::HashStableContext + rustc_target::HashStableContext
 {
+    fn hash_attr(&mut self, _: &Attribute, hasher: &mut StableHasher);
 }
 
 impl<HirCtx: crate::HashStableContext> ToStableHashKey<HirCtx> for HirId {
@@ -113,3 +115,9 @@ impl<HirCtx: crate::HashStableContext> HashStable<HirCtx> for Crate<'_> {
         opt_hir_hash.unwrap().hash_stable(hcx, hasher)
     }
 }
+
+impl<HirCtx: crate::HashStableContext> HashStable<HirCtx> for Attribute {
+    fn hash_stable(&self, hcx: &mut HirCtx, hasher: &mut StableHasher) {
+        hcx.hash_attr(self, hasher)
+    }
+}
diff --git a/compiler/rustc_hir/src/weak_lang_items.rs b/compiler/rustc_hir/src/weak_lang_items.rs
index 337859cd1fb..b4e548effd4 100644
--- a/compiler/rustc_hir/src/weak_lang_items.rs
+++ b/compiler/rustc_hir/src/weak_lang_items.rs
@@ -1,6 +1,6 @@
 //! Validity checking for weak lang items
 
-use rustc_span::symbol::{Symbol, sym};
+use rustc_span::{Symbol, sym};
 
 use crate::LangItem;
 
diff --git a/compiler/rustc_hir_analysis/Cargo.toml b/compiler/rustc_hir_analysis/Cargo.toml
index 581ef2272d1..196d7d99e93 100644
--- a/compiler/rustc_hir_analysis/Cargo.toml
+++ b/compiler/rustc_hir_analysis/Cargo.toml
@@ -13,7 +13,7 @@ itertools = "0.12"
 rustc_abi = { path = "../rustc_abi" }
 rustc_arena = { path = "../rustc_arena" }
 rustc_ast = { path = "../rustc_ast" }
-rustc_attr = { path = "../rustc_attr" }
+rustc_attr_parsing = { path = "../rustc_attr_parsing" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
 rustc_feature = { path = "../rustc_feature" }
diff --git a/compiler/rustc_hir_analysis/messages.ftl b/compiler/rustc_hir_analysis/messages.ftl
index a2df0ba265c..0c3ed9b5c60 100644
--- a/compiler/rustc_hir_analysis/messages.ftl
+++ b/compiler/rustc_hir_analysis/messages.ftl
@@ -249,6 +249,12 @@ hir_analysis_invalid_receiver_ty_help =
 hir_analysis_invalid_receiver_ty_help_no_arbitrary_self_types =
     consider changing to `self`, `&self`, `&mut self`, `self: Box<Self>`, `self: Rc<Self>`, `self: Arc<Self>`, or `self: Pin<P>` (where P is one of the previous types except `Self`)
 
+hir_analysis_invalid_receiver_ty_help_nonnull_note =
+    `NonNull` does not implement `Receiver` because it has methods that may shadow the referent; consider wrapping your `NonNull` in a newtype wrapper for which you implement `Receiver`
+
+hir_analysis_invalid_receiver_ty_help_weak_note =
+    `Weak` does not implement `Receiver` because it has methods that may shadow the referent; consider wrapping your `Weak` in a newtype wrapper for which you implement `Receiver`
+
 hir_analysis_invalid_receiver_ty_no_arbitrary_self_types = invalid `self` parameter type: `{$receiver_ty}`
     .note = type of `self` must be `Self` or a type that dereferences to it
 
diff --git a/compiler/rustc_hir_analysis/src/check/check.rs b/compiler/rustc_hir_analysis/src/check/check.rs
index 022a6d457ec..5548a6a6ef7 100644
--- a/compiler/rustc_hir_analysis/src/check/check.rs
+++ b/compiler/rustc_hir_analysis/src/check/check.rs
@@ -6,7 +6,7 @@ use rustc_data_structures::unord::{UnordMap, UnordSet};
 use rustc_errors::MultiSpan;
 use rustc_errors::codes::*;
 use rustc_hir::def::{CtorKind, DefKind};
-use rustc_hir::{Node, Safety, intravisit};
+use rustc_hir::{Node, intravisit};
 use rustc_infer::infer::{RegionVariableOrigin, TyCtxtInferExt};
 use rustc_infer::traits::{Obligation, ObligationCauseCode};
 use rustc_lint_defs::builtin::{
@@ -31,7 +31,7 @@ use rustc_trait_selection::traits::outlives_bounds::InferCtxtExt as _;
 use rustc_type_ir::fold::TypeFoldable;
 use tracing::{debug, instrument};
 use ty::TypingMode;
-use {rustc_attr as attr, rustc_hir as hir};
+use {rustc_attr_parsing as attr, rustc_hir as hir};
 
 use super::compare_impl_item::check_type_bounds;
 use super::*;
@@ -161,7 +161,7 @@ fn check_unsafe_fields(tcx: TyCtxt<'_>, item_def_id: LocalDefId) {
     };
     let typing_env = ty::TypingEnv::non_body_analysis(tcx, item_def_id);
     for field in def.all_fields() {
-        if field.safety != Safety::Unsafe {
+        if !field.safety.is_unsafe() {
             continue;
         }
         let Ok(field_ty) = tcx.try_normalize_erasing_regions(typing_env, field.ty(tcx, args))
diff --git a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
index e176fc58999..a6b504de3da 100644
--- a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
+++ b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
@@ -430,12 +430,12 @@ fn compare_method_predicate_entailment<'tcx>(
     Ok(())
 }
 
-struct RemapLateBound<'a, 'tcx> {
+struct RemapLateParam<'a, 'tcx> {
     tcx: TyCtxt<'tcx>,
-    mapping: &'a FxIndexMap<ty::BoundRegionKind, ty::BoundRegionKind>,
+    mapping: &'a FxIndexMap<ty::LateParamRegionKind, ty::LateParamRegionKind>,
 }
 
-impl<'tcx> TypeFolder<TyCtxt<'tcx>> for RemapLateBound<'_, 'tcx> {
+impl<'tcx> TypeFolder<TyCtxt<'tcx>> for RemapLateParam<'_, 'tcx> {
     fn cx(&self) -> TyCtxt<'tcx> {
         self.tcx
     }
@@ -445,7 +445,7 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for RemapLateBound<'_, 'tcx> {
             ty::Region::new_late_param(
                 self.tcx,
                 fr.scope,
-                self.mapping.get(&fr.bound_region).copied().unwrap_or(fr.bound_region),
+                self.mapping.get(&fr.kind).copied().unwrap_or(fr.kind),
             )
         } else {
             r
diff --git a/compiler/rustc_hir_analysis/src/check/compare_impl_item/refine.rs b/compiler/rustc_hir_analysis/src/check/compare_impl_item/refine.rs
index 6eac4ac3baf..2b14594ea1b 100644
--- a/compiler/rustc_hir_analysis/src/check/compare_impl_item/refine.rs
+++ b/compiler/rustc_hir_analysis/src/check/compare_impl_item/refine.rs
@@ -289,11 +289,16 @@ fn report_mismatched_rpitit_signature<'tcx>(
         tcx.fn_sig(trait_m_def_id).skip_binder().bound_vars(),
         tcx.fn_sig(impl_m_def_id).skip_binder().bound_vars(),
     )
-    .filter_map(|(impl_bv, trait_bv)| {
+    .enumerate()
+    .filter_map(|(idx, (impl_bv, trait_bv))| {
         if let ty::BoundVariableKind::Region(impl_bv) = impl_bv
             && let ty::BoundVariableKind::Region(trait_bv) = trait_bv
         {
-            Some((impl_bv, trait_bv))
+            let var = ty::BoundVar::from_usize(idx);
+            Some((
+                ty::LateParamRegionKind::from_bound(var, impl_bv),
+                ty::LateParamRegionKind::from_bound(var, trait_bv),
+            ))
         } else {
             None
         }
@@ -301,7 +306,7 @@ fn report_mismatched_rpitit_signature<'tcx>(
     .collect();
 
     let mut return_ty =
-        trait_m_sig.output().fold_with(&mut super::RemapLateBound { tcx, mapping: &mapping });
+        trait_m_sig.output().fold_with(&mut super::RemapLateParam { tcx, mapping: &mapping });
 
     if tcx.asyncness(impl_m_def_id).is_async() && tcx.asyncness(trait_m_def_id).is_async() {
         let ty::Alias(ty::Projection, future_ty) = return_ty.kind() else {
diff --git a/compiler/rustc_hir_analysis/src/check/entry.rs b/compiler/rustc_hir_analysis/src/check/entry.rs
index f3dd13c84b9..245085b332c 100644
--- a/compiler/rustc_hir_analysis/src/check/entry.rs
+++ b/compiler/rustc_hir_analysis/src/check/entry.rs
@@ -7,9 +7,8 @@ use rustc_infer::infer::TyCtxtInferExt;
 use rustc_middle::span_bug;
 use rustc_middle::ty::{self, Ty, TyCtxt, TypingMode};
 use rustc_session::config::EntryFnType;
-use rustc_span::Span;
 use rustc_span::def_id::{CRATE_DEF_ID, DefId, LocalDefId};
-use rustc_span::symbol::sym;
+use rustc_span::{Span, sym};
 use rustc_trait_selection::error_reporting::InferCtxtErrorExt;
 use rustc_trait_selection::traits::{self, ObligationCause, ObligationCauseCode};
 
diff --git a/compiler/rustc_hir_analysis/src/check/intrinsic.rs b/compiler/rustc_hir_analysis/src/check/intrinsic.rs
index 2e6b511412b..39479401910 100644
--- a/compiler/rustc_hir_analysis/src/check/intrinsic.rs
+++ b/compiler/rustc_hir_analysis/src/check/intrinsic.rs
@@ -8,8 +8,7 @@ use rustc_middle::bug;
 use rustc_middle::traits::{ObligationCause, ObligationCauseCode};
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_span::def_id::LocalDefId;
-use rustc_span::symbol::sym;
-use rustc_span::{Span, Symbol};
+use rustc_span::{Span, Symbol, sym};
 
 use crate::check::check_function_signature;
 use crate::errors::{
diff --git a/compiler/rustc_hir_analysis/src/check/mod.rs b/compiler/rustc_hir_analysis/src/check/mod.rs
index 61e203a1ff6..0b0c92a726d 100644
--- a/compiler/rustc_hir_analysis/src/check/mod.rs
+++ b/compiler/rustc_hir_analysis/src/check/mod.rs
@@ -89,8 +89,7 @@ use rustc_middle::ty::{self, GenericArgs, GenericArgsRef, Ty, TyCtxt, TypingMode
 use rustc_middle::{bug, span_bug};
 use rustc_session::parse::feature_err;
 use rustc_span::def_id::CRATE_DEF_ID;
-use rustc_span::symbol::{Ident, kw, sym};
-use rustc_span::{BytePos, DUMMY_SP, Span, Symbol};
+use rustc_span::{BytePos, DUMMY_SP, Ident, Span, Symbol, kw, sym};
 use rustc_trait_selection::error_reporting::InferCtxtErrorExt;
 use rustc_trait_selection::error_reporting::infer::ObligationCauseExt as _;
 use rustc_trait_selection::error_reporting::traits::suggestions::ReturnsVisitor;
diff --git a/compiler/rustc_hir_analysis/src/check/region.rs b/compiler/rustc_hir_analysis/src/check/region.rs
index b9cb48cafdc..ca6729a5bbd 100644
--- a/compiler/rustc_hir_analysis/src/check/region.rs
+++ b/compiler/rustc_hir_analysis/src/check/region.rs
@@ -129,7 +129,7 @@ fn resolve_block<'tcx>(visitor: &mut RegionResolutionVisitor<'tcx>, blk: &'tcx h
                     let mut prev_cx = visitor.cx;
 
                     visitor.enter_scope(Scope {
-                        id: blk.hir_id.local_id,
+                        local_id: blk.hir_id.local_id,
                         data: ScopeData::Remainder(FirstStatementIndex::new(i)),
                     });
                     visitor.cx.var_parent = visitor.cx.parent;
@@ -154,7 +154,7 @@ fn resolve_block<'tcx>(visitor: &mut RegionResolutionVisitor<'tcx>, blk: &'tcx h
                     // the first such subscope, which has the block itself as a
                     // parent.
                     visitor.enter_scope(Scope {
-                        id: blk.hir_id.local_id,
+                        local_id: blk.hir_id.local_id,
                         data: ScopeData::Remainder(FirstStatementIndex::new(i)),
                     });
                     visitor.cx.var_parent = visitor.cx.parent;
@@ -184,7 +184,7 @@ fn resolve_block<'tcx>(visitor: &mut RegionResolutionVisitor<'tcx>, blk: &'tcx h
                 visitor
                     .scope_tree
                     .backwards_incompatible_scope
-                    .insert(local_id, Scope { id: local_id, data: ScopeData::Node });
+                    .insert(local_id, Scope { local_id, data: ScopeData::Node });
             }
             visitor.visit_expr(tail_expr);
         }
@@ -221,7 +221,7 @@ fn resolve_arm<'tcx>(visitor: &mut RegionResolutionVisitor<'tcx>, arm: &'tcx hir
 }
 
 fn resolve_pat<'tcx>(visitor: &mut RegionResolutionVisitor<'tcx>, pat: &'tcx hir::Pat<'tcx>) {
-    visitor.record_child_scope(Scope { id: pat.hir_id.local_id, data: ScopeData::Node });
+    visitor.record_child_scope(Scope { local_id: pat.hir_id.local_id, data: ScopeData::Node });
 
     // If this is a binding then record the lifetime of that binding.
     if let PatKind::Binding(..) = pat.kind {
@@ -485,7 +485,7 @@ fn resolve_expr<'tcx>(visitor: &mut RegionResolutionVisitor<'tcx>, expr: &'tcx h
             } else {
                 ScopeData::IfThen
             };
-            visitor.enter_scope(Scope { id: then.hir_id.local_id, data });
+            visitor.enter_scope(Scope { local_id: then.hir_id.local_id, data });
             visitor.cx.var_parent = visitor.cx.parent;
             visitor.visit_expr(cond);
             visitor.visit_expr(then);
@@ -500,7 +500,7 @@ fn resolve_expr<'tcx>(visitor: &mut RegionResolutionVisitor<'tcx>, expr: &'tcx h
             } else {
                 ScopeData::IfThen
             };
-            visitor.enter_scope(Scope { id: then.hir_id.local_id, data });
+            visitor.enter_scope(Scope { local_id: then.hir_id.local_id, data });
             visitor.cx.var_parent = visitor.cx.parent;
             visitor.visit_expr(cond);
             visitor.visit_expr(then);
@@ -516,7 +516,7 @@ fn resolve_expr<'tcx>(visitor: &mut RegionResolutionVisitor<'tcx>, expr: &'tcx h
 
     if let hir::ExprKind::Yield(_, source) = &expr.kind {
         // Mark this expr's scope and all parent scopes as containing `yield`.
-        let mut scope = Scope { id: expr.hir_id.local_id, data: ScopeData::Node };
+        let mut scope = Scope { local_id: expr.hir_id.local_id, data: ScopeData::Node };
         loop {
             let span = match expr.kind {
                 hir::ExprKind::Yield(expr, hir::YieldSource::Await { .. }) => {
@@ -803,9 +803,9 @@ impl<'tcx> RegionResolutionVisitor<'tcx> {
         // account for the destruction scope representing the scope of
         // the destructors that run immediately after it completes.
         if self.terminating_scopes.contains(&id) {
-            self.enter_scope(Scope { id, data: ScopeData::Destruction });
+            self.enter_scope(Scope { local_id: id, data: ScopeData::Destruction });
         }
-        self.enter_scope(Scope { id, data: ScopeData::Node });
+        self.enter_scope(Scope { local_id: id, data: ScopeData::Node });
     }
 
     fn enter_body(&mut self, hir_id: hir::HirId, f: impl FnOnce(&mut Self)) {
@@ -822,8 +822,8 @@ impl<'tcx> RegionResolutionVisitor<'tcx> {
         let outer_pessimistic_yield = mem::replace(&mut self.pessimistic_yield, false);
         self.terminating_scopes.insert(hir_id.local_id);
 
-        self.enter_scope(Scope { id: hir_id.local_id, data: ScopeData::CallSite });
-        self.enter_scope(Scope { id: hir_id.local_id, data: ScopeData::Arguments });
+        self.enter_scope(Scope { local_id: hir_id.local_id, data: ScopeData::CallSite });
+        self.enter_scope(Scope { local_id: hir_id.local_id, data: ScopeData::Arguments });
 
         f(self);
 
diff --git a/compiler/rustc_hir_analysis/src/check/wfcheck.rs b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
index e6ef29de965..3cddc9642ba 100644
--- a/compiler/rustc_hir_analysis/src/check/wfcheck.rs
+++ b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
@@ -23,8 +23,7 @@ use rustc_middle::ty::{
 };
 use rustc_middle::{bug, span_bug};
 use rustc_session::parse::feature_err;
-use rustc_span::symbol::{Ident, sym};
-use rustc_span::{DUMMY_SP, Span};
+use rustc_span::{DUMMY_SP, Ident, Span, sym};
 use rustc_trait_selection::error_reporting::InferCtxtErrorExt;
 use rustc_trait_selection::regions::InferCtxtRegionExt;
 use rustc_trait_selection::traits::misc::{
@@ -44,6 +43,7 @@ use {rustc_ast as ast, rustc_hir as hir};
 use crate::autoderef::Autoderef;
 use crate::collect::CollectItemTypesVisitor;
 use crate::constrained_generic_params::{Parameter, identify_constrained_generic_params};
+use crate::errors::InvalidReceiverTyHint;
 use crate::{errors, fluent_generated as fluent};
 
 pub(super) struct WfCheckingCtxt<'a, 'tcx> {
@@ -1749,7 +1749,18 @@ fn check_method_receiver<'tcx>(
             {
                 match receiver_validity_err {
                     ReceiverValidityError::DoesNotDeref if arbitrary_self_types_level.is_some() => {
-                        tcx.dcx().emit_err(errors::InvalidReceiverTy { span, receiver_ty })
+                        let hint = match receiver_ty
+                            .builtin_deref(false)
+                            .unwrap_or(receiver_ty)
+                            .ty_adt_def()
+                            .and_then(|adt_def| tcx.get_diagnostic_name(adt_def.did()))
+                        {
+                            Some(sym::RcWeak | sym::ArcWeak) => Some(InvalidReceiverTyHint::Weak),
+                            Some(sym::NonNull) => Some(InvalidReceiverTyHint::NonNull),
+                            _ => None,
+                        };
+
+                        tcx.dcx().emit_err(errors::InvalidReceiverTy { span, receiver_ty, hint })
                     }
                     ReceiverValidityError::DoesNotDeref => {
                         tcx.dcx().emit_err(errors::InvalidReceiverTyNoArbitrarySelfTypes {
@@ -2328,8 +2339,11 @@ fn lint_redundant_lifetimes<'tcx>(
     );
     // If we are in a function, add its late-bound lifetimes too.
     if matches!(def_kind, DefKind::Fn | DefKind::AssocFn) {
-        for var in tcx.fn_sig(owner_id).instantiate_identity().bound_vars() {
+        for (idx, var) in
+            tcx.fn_sig(owner_id).instantiate_identity().bound_vars().iter().enumerate()
+        {
             let ty::BoundVariableKind::Region(kind) = var else { continue };
+            let kind = ty::LateParamRegionKind::from_bound(ty::BoundVar::from_usize(idx), kind);
             lifetimes.push(ty::Region::new_late_param(tcx, owner_id.to_def_id(), kind));
         }
     }
diff --git a/compiler/rustc_hir_analysis/src/coherence/builtin.rs b/compiler/rustc_hir_analysis/src/coherence/builtin.rs
index 2eea65125b0..3b98f358b1e 100644
--- a/compiler/rustc_hir_analysis/src/coherence/builtin.rs
+++ b/compiler/rustc_hir_analysis/src/coherence/builtin.rs
@@ -673,37 +673,6 @@ fn visit_implementation_of_pointer_like(checker: &Checker<'_>) -> Result<(), Err
     let impl_span = tcx.def_span(checker.impl_def_id);
     let self_ty = tcx.impl_trait_ref(checker.impl_def_id).unwrap().instantiate_identity().self_ty();
 
-    // If an ADT is repr(transparent)...
-    if let ty::Adt(def, args) = *self_ty.kind()
-        && def.repr().transparent()
-    {
-        // FIXME(compiler-errors): This should and could be deduplicated into a query.
-        // Find the nontrivial field.
-        let adt_typing_env = ty::TypingEnv::non_body_analysis(tcx, def.did());
-        let nontrivial_field = def.all_fields().find(|field_def| {
-            let field_ty = tcx.type_of(field_def.did).instantiate_identity();
-            !tcx.layout_of(adt_typing_env.as_query_input(field_ty))
-                .is_ok_and(|layout| layout.layout.is_1zst())
-        });
-
-        if let Some(nontrivial_field) = nontrivial_field {
-            // Check that the nontrivial field implements `PointerLike`.
-            let nontrivial_field = nontrivial_field.ty(tcx, args);
-            let (infcx, param_env) = tcx.infer_ctxt().build_with_typing_env(typing_env);
-            let ocx = ObligationCtxt::new(&infcx);
-            ocx.register_bound(
-                ObligationCause::misc(impl_span, checker.impl_def_id),
-                param_env,
-                nontrivial_field,
-                tcx.lang_items().pointer_like().unwrap(),
-            );
-            // FIXME(dyn-star): We should regionck this implementation.
-            if ocx.select_all_or_error().is_empty() {
-                return Ok(());
-            }
-        }
-    }
-
     let is_permitted_primitive = match *self_ty.kind() {
         ty::Adt(def, _) => def.is_box(),
         ty::Uint(..) | ty::Int(..) | ty::RawPtr(..) | ty::Ref(..) | ty::FnPtr(..) => true,
@@ -717,6 +686,74 @@ fn visit_implementation_of_pointer_like(checker: &Checker<'_>) -> Result<(), Err
         return Ok(());
     }
 
+    let why_disqualified = match *self_ty.kind() {
+        // If an ADT is repr(transparent)
+        ty::Adt(self_ty_def, args) => {
+            if self_ty_def.repr().transparent() {
+                // FIXME(compiler-errors): This should and could be deduplicated into a query.
+                // Find the nontrivial field.
+                let adt_typing_env = ty::TypingEnv::non_body_analysis(tcx, self_ty_def.did());
+                let nontrivial_field = self_ty_def.all_fields().find(|field_def| {
+                    let field_ty = tcx.type_of(field_def.did).instantiate_identity();
+                    !tcx.layout_of(adt_typing_env.as_query_input(field_ty))
+                        .is_ok_and(|layout| layout.layout.is_1zst())
+                });
+
+                if let Some(nontrivial_field) = nontrivial_field {
+                    // Check that the nontrivial field implements `PointerLike`.
+                    let nontrivial_field_ty = nontrivial_field.ty(tcx, args);
+                    let (infcx, param_env) = tcx.infer_ctxt().build_with_typing_env(typing_env);
+                    let ocx = ObligationCtxt::new(&infcx);
+                    ocx.register_bound(
+                        ObligationCause::misc(impl_span, checker.impl_def_id),
+                        param_env,
+                        nontrivial_field_ty,
+                        tcx.lang_items().pointer_like().unwrap(),
+                    );
+                    // FIXME(dyn-star): We should regionck this implementation.
+                    if ocx.select_all_or_error().is_empty() {
+                        return Ok(());
+                    } else {
+                        format!(
+                            "the field `{field_name}` of {descr} `{self_ty}` \
+                    does not implement `PointerLike`",
+                            field_name = nontrivial_field.name,
+                            descr = self_ty_def.descr()
+                        )
+                    }
+                } else {
+                    format!(
+                        "the {descr} `{self_ty}` is `repr(transparent)`, \
+                but does not have a non-trivial field (it is zero-sized)",
+                        descr = self_ty_def.descr()
+                    )
+                }
+            } else if self_ty_def.is_box() {
+                // If we got here, then the `layout.is_pointer_like()` check failed
+                // and this box is not a thin pointer.
+
+                String::from("boxes of dynamically-sized types are too large to be `PointerLike`")
+            } else {
+                format!(
+                    "the {descr} `{self_ty}` is not `repr(transparent)`",
+                    descr = self_ty_def.descr()
+                )
+            }
+        }
+        ty::Ref(..) => {
+            // If we got here, then the `layout.is_pointer_like()` check failed
+            // and this reference is not a thin pointer.
+            String::from("references to dynamically-sized types are too large to be `PointerLike`")
+        }
+        ty::Dynamic(..) | ty::Foreign(..) => {
+            String::from("types of dynamic or unknown size may not implement `PointerLike`")
+        }
+        _ => {
+            // This is a white lie; it is true everywhere outside the standard library.
+            format!("only user-defined sized types are eligible for `impl PointerLike`")
+        }
+    };
+
     Err(tcx
         .dcx()
         .struct_span_err(
@@ -724,5 +761,6 @@ fn visit_implementation_of_pointer_like(checker: &Checker<'_>) -> Result<(), Err
             "implementation must be applied to type that has the same ABI as a pointer, \
             or is `repr(transparent)` and whose field is `PointerLike`",
         )
+        .with_note(why_disqualified)
         .emit())
 }
diff --git a/compiler/rustc_hir_analysis/src/coherence/inherent_impls.rs b/compiler/rustc_hir_analysis/src/coherence/inherent_impls.rs
index 2afc2aec1ba..8f6f5b5f222 100644
--- a/compiler/rustc_hir_analysis/src/coherence/inherent_impls.rs
+++ b/compiler/rustc_hir_analysis/src/coherence/inherent_impls.rs
@@ -13,8 +13,7 @@ use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_middle::bug;
 use rustc_middle::ty::fast_reject::{SimplifiedType, TreatParams, simplify_type};
 use rustc_middle::ty::{self, CrateInherentImpls, Ty, TyCtxt};
-use rustc_span::ErrorGuaranteed;
-use rustc_span::symbol::sym;
+use rustc_span::{ErrorGuaranteed, sym};
 
 use crate::errors;
 
diff --git a/compiler/rustc_hir_analysis/src/coherence/mod.rs b/compiler/rustc_hir_analysis/src/coherence/mod.rs
index 3aad4bafeb5..1be4aa2f63a 100644
--- a/compiler/rustc_hir_analysis/src/coherence/mod.rs
+++ b/compiler/rustc_hir_analysis/src/coherence/mod.rs
@@ -206,7 +206,9 @@ fn check_object_overlap<'tcx>(
                 // so this is valid.
             } else {
                 let mut supertrait_def_ids = tcx.supertrait_def_ids(component_def_id);
-                if supertrait_def_ids.any(|d| d == trait_def_id) {
+                if supertrait_def_ids
+                    .any(|d| d == trait_def_id && tcx.trait_def(d).implement_via_object)
+                {
                     let span = tcx.def_span(impl_def_id);
                     return Err(struct_span_code_err!(
                         tcx.dcx(),
diff --git a/compiler/rustc_hir_analysis/src/collect.rs b/compiler/rustc_hir_analysis/src/collect.rs
index 7fb024cce5a..ada70117b62 100644
--- a/compiler/rustc_hir_analysis/src/collect.rs
+++ b/compiler/rustc_hir_analysis/src/collect.rs
@@ -38,8 +38,7 @@ use rustc_middle::ty::fold::fold_regions;
 use rustc_middle::ty::util::{Discr, IntTypeExt};
 use rustc_middle::ty::{self, AdtKind, Const, IsSuggestable, Ty, TyCtxt, TypingMode};
 use rustc_middle::{bug, span_bug};
-use rustc_span::symbol::{Ident, Symbol, kw, sym};
-use rustc_span::{DUMMY_SP, Span};
+use rustc_span::{DUMMY_SP, Ident, Span, Symbol, kw, sym};
 use rustc_trait_selection::error_reporting::traits::suggestions::NextTypeParamName;
 use rustc_trait_selection::infer::InferCtxtExt;
 use rustc_trait_selection::traits::ObligationCtxt;
@@ -1262,49 +1261,8 @@ fn trait_def(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::TraitDef {
             no_dups.then_some(list)
         });
 
-    let mut deny_explicit_impl = false;
-    let mut implement_via_object = true;
-    if let Some(attr) = tcx.get_attr(def_id, sym::rustc_deny_explicit_impl) {
-        deny_explicit_impl = true;
-        let mut seen_attr = false;
-        for meta in attr.meta_item_list().iter().flatten() {
-            if let Some(meta) = meta.meta_item()
-                && meta.name_or_empty() == sym::implement_via_object
-                && let Some(lit) = meta.name_value_literal()
-            {
-                if seen_attr {
-                    tcx.dcx().span_err(meta.span, "duplicated `implement_via_object` meta item");
-                }
-                seen_attr = true;
-
-                match lit.symbol {
-                    kw::True => {
-                        implement_via_object = true;
-                    }
-                    kw::False => {
-                        implement_via_object = false;
-                    }
-                    _ => {
-                        tcx.dcx().span_err(
-                            meta.span,
-                            format!(
-                                "unknown literal passed to `implement_via_object` attribute: {}",
-                                lit.symbol
-                            ),
-                        );
-                    }
-                }
-            } else {
-                tcx.dcx().span_err(
-                    meta.span(),
-                    format!("unknown meta item passed to `rustc_deny_explicit_impl` {meta:?}"),
-                );
-            }
-        }
-        if !seen_attr {
-            tcx.dcx().span_err(attr.span, "missing `implement_via_object` meta item");
-        }
-    }
+    let deny_explicit_impl = tcx.has_attr(def_id, sym::rustc_deny_explicit_impl);
+    let implement_via_object = !tcx.has_attr(def_id, sym::rustc_do_not_implement_via_object);
 
     ty::TraitDef {
         def_id: def_id.to_def_id(),
@@ -1340,7 +1298,7 @@ fn fn_sig(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<'_, ty::PolyFn
             ..
         })
         | Item(hir::Item { kind: ItemKind::Fn(sig, generics, _), .. }) => {
-            infer_return_ty_for_fn_sig(sig, generics, def_id, &icx)
+            lower_fn_sig_recovering_infer_ret_ty(&icx, sig, generics, def_id)
         }
 
         ImplItem(hir::ImplItem { kind: ImplItemKind::Fn(sig, _), generics, .. }) => {
@@ -1357,7 +1315,7 @@ fn fn_sig(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<'_, ty::PolyFn
                     None,
                 )
             } else {
-                infer_return_ty_for_fn_sig(sig, generics, def_id, &icx)
+                lower_fn_sig_recovering_infer_ret_ty(&icx, sig, generics, def_id)
             }
         }
 
@@ -1407,99 +1365,108 @@ fn fn_sig(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<'_, ty::PolyFn
     ty::EarlyBinder::bind(output)
 }
 
-fn infer_return_ty_for_fn_sig<'tcx>(
-    sig: &hir::FnSig<'tcx>,
-    generics: &hir::Generics<'_>,
+fn lower_fn_sig_recovering_infer_ret_ty<'tcx>(
+    icx: &ItemCtxt<'tcx>,
+    sig: &'tcx hir::FnSig<'tcx>,
+    generics: &'tcx hir::Generics<'tcx>,
     def_id: LocalDefId,
+) -> ty::PolyFnSig<'tcx> {
+    if let Some(infer_ret_ty) = sig.decl.output.get_infer_ret_ty() {
+        return recover_infer_ret_ty(icx, infer_ret_ty, generics, def_id);
+    }
+
+    icx.lowerer().lower_fn_ty(
+        icx.tcx().local_def_id_to_hir_id(def_id),
+        sig.header.safety,
+        sig.header.abi,
+        sig.decl,
+        Some(generics),
+        None,
+    )
+}
+
+fn recover_infer_ret_ty<'tcx>(
     icx: &ItemCtxt<'tcx>,
+    infer_ret_ty: &'tcx hir::Ty<'tcx>,
+    generics: &'tcx hir::Generics<'tcx>,
+    def_id: LocalDefId,
 ) -> ty::PolyFnSig<'tcx> {
     let tcx = icx.tcx;
     let hir_id = tcx.local_def_id_to_hir_id(def_id);
 
-    match sig.decl.output.get_infer_ret_ty() {
-        Some(ty) => {
-            let fn_sig = tcx.typeck(def_id).liberated_fn_sigs()[hir_id];
-            // Typeck doesn't expect erased regions to be returned from `type_of`.
-            // This is a heuristic approach. If the scope has region parameters,
-            // we should change fn_sig's lifetime from `ReErased` to `ReError`,
-            // otherwise to `ReStatic`.
-            let has_region_params = generics.params.iter().any(|param| match param.kind {
-                GenericParamKind::Lifetime { .. } => true,
-                _ => false,
-            });
-            let fn_sig = fold_regions(tcx, fn_sig, |r, _| match *r {
-                ty::ReErased => {
-                    if has_region_params {
-                        ty::Region::new_error_with_message(
-                            tcx,
-                            DUMMY_SP,
-                            "erased region is not allowed here in return type",
-                        )
-                    } else {
-                        tcx.lifetimes.re_static
-                    }
-                }
-                _ => r,
-            });
+    let fn_sig = tcx.typeck(def_id).liberated_fn_sigs()[hir_id];
 
-            let mut visitor = HirPlaceholderCollector::default();
-            visitor.visit_ty(ty);
-
-            let mut diag = bad_placeholder(icx.lowerer(), visitor.0, "return type");
-            let ret_ty = fn_sig.output();
-            // Don't leak types into signatures unless they're nameable!
-            // For example, if a function returns itself, we don't want that
-            // recursive function definition to leak out into the fn sig.
-            let mut recovered_ret_ty = None;
-
-            if let Some(suggestable_ret_ty) = ret_ty.make_suggestable(tcx, false, None) {
-                diag.span_suggestion(
-                    ty.span,
-                    "replace with the correct return type",
-                    suggestable_ret_ty,
-                    Applicability::MachineApplicable,
-                );
-                recovered_ret_ty = Some(suggestable_ret_ty);
-            } else if let Some(sugg) = suggest_impl_trait(
-                &tcx.infer_ctxt().build(TypingMode::non_body_analysis()),
-                tcx.param_env(def_id),
-                ret_ty,
-            ) {
-                diag.span_suggestion(
-                    ty.span,
-                    "replace with an appropriate return type",
-                    sugg,
-                    Applicability::MachineApplicable,
-                );
-            } else if ret_ty.is_closure() {
-                diag.help("consider using an `Fn`, `FnMut`, or `FnOnce` trait bound");
-            }
-            // Also note how `Fn` traits work just in case!
-            if ret_ty.is_closure() {
-                diag.note(
-                    "for more information on `Fn` traits and closure types, see \
-                     https://doc.rust-lang.org/book/ch13-01-closures.html",
-                );
+    // Typeck doesn't expect erased regions to be returned from `type_of`.
+    // This is a heuristic approach. If the scope has region parameters,
+    // we should change fn_sig's lifetime from `ReErased` to `ReError`,
+    // otherwise to `ReStatic`.
+    let has_region_params = generics.params.iter().any(|param| match param.kind {
+        GenericParamKind::Lifetime { .. } => true,
+        _ => false,
+    });
+    let fn_sig = fold_regions(tcx, fn_sig, |r, _| match *r {
+        ty::ReErased => {
+            if has_region_params {
+                ty::Region::new_error_with_message(
+                    tcx,
+                    DUMMY_SP,
+                    "erased region is not allowed here in return type",
+                )
+            } else {
+                tcx.lifetimes.re_static
             }
-
-            let guar = diag.emit();
-            ty::Binder::dummy(tcx.mk_fn_sig(
-                fn_sig.inputs().iter().copied(),
-                recovered_ret_ty.unwrap_or_else(|| Ty::new_error(tcx, guar)),
-                fn_sig.c_variadic,
-                fn_sig.safety,
-                fn_sig.abi,
-            ))
         }
-        None => icx.lowerer().lower_fn_ty(
-            hir_id,
-            sig.header.safety,
-            sig.header.abi,
-            sig.decl,
-            Some(generics),
-            None,
-        ),
+        _ => r,
+    });
+
+    let mut visitor = HirPlaceholderCollector::default();
+    visitor.visit_ty(infer_ret_ty);
+
+    let mut diag = bad_placeholder(icx.lowerer(), visitor.0, "return type");
+    let ret_ty = fn_sig.output();
+
+    // Don't leak types into signatures unless they're nameable!
+    // For example, if a function returns itself, we don't want that
+    // recursive function definition to leak out into the fn sig.
+    let mut recovered_ret_ty = None;
+    if let Some(suggestable_ret_ty) = ret_ty.make_suggestable(tcx, false, None) {
+        diag.span_suggestion(
+            infer_ret_ty.span,
+            "replace with the correct return type",
+            suggestable_ret_ty,
+            Applicability::MachineApplicable,
+        );
+        recovered_ret_ty = Some(suggestable_ret_ty);
+    } else if let Some(sugg) = suggest_impl_trait(
+        &tcx.infer_ctxt().build(TypingMode::non_body_analysis()),
+        tcx.param_env(def_id),
+        ret_ty,
+    ) {
+        diag.span_suggestion(
+            infer_ret_ty.span,
+            "replace with an appropriate return type",
+            sugg,
+            Applicability::MachineApplicable,
+        );
+    } else if ret_ty.is_closure() {
+        diag.help("consider using an `Fn`, `FnMut`, or `FnOnce` trait bound");
+    }
+
+    // Also note how `Fn` traits work just in case!
+    if ret_ty.is_closure() {
+        diag.note(
+            "for more information on `Fn` traits and closure types, see \
+                     https://doc.rust-lang.org/book/ch13-01-closures.html",
+        );
     }
+    let guar = diag.emit();
+    ty::Binder::dummy(tcx.mk_fn_sig(
+        fn_sig.inputs().iter().copied(),
+        recovered_ret_ty.unwrap_or_else(|| Ty::new_error(tcx, guar)),
+        fn_sig.c_variadic,
+        fn_sig.safety,
+        fn_sig.abi,
+    ))
 }
 
 pub fn suggest_impl_trait<'tcx>(
diff --git a/compiler/rustc_hir_analysis/src/collect/generics_of.rs b/compiler/rustc_hir_analysis/src/collect/generics_of.rs
index f52d4f42eca..075615de522 100644
--- a/compiler/rustc_hir_analysis/src/collect/generics_of.rs
+++ b/compiler/rustc_hir_analysis/src/collect/generics_of.rs
@@ -8,8 +8,7 @@ use rustc_hir::def::DefKind;
 use rustc_hir::def_id::LocalDefId;
 use rustc_middle::ty::{self, TyCtxt};
 use rustc_session::lint;
-use rustc_span::Span;
-use rustc_span::symbol::{Symbol, kw};
+use rustc_span::{Span, Symbol, kw};
 use tracing::{debug, instrument};
 
 use crate::delegation::inherit_generics_for_delegation_item;
diff --git a/compiler/rustc_hir_analysis/src/collect/item_bounds.rs b/compiler/rustc_hir_analysis/src/collect/item_bounds.rs
index 0b81f469371..d3ff1f7bebe 100644
--- a/compiler/rustc_hir_analysis/src/collect/item_bounds.rs
+++ b/compiler/rustc_hir_analysis/src/collect/item_bounds.rs
@@ -371,10 +371,9 @@ pub(super) fn explicit_item_bounds_with_filter(
                 associated_type_bounds(tcx, def_id, opaque_ty.bounds, opaque_ty.span, filter);
             return ty::EarlyBinder::bind(bounds);
         }
-        Some(ty::ImplTraitInTraitData::Impl { .. }) => span_bug!(
-            tcx.def_span(def_id),
-            "item bounds for RPITIT in impl to be fed on def-id creation"
-        ),
+        Some(ty::ImplTraitInTraitData::Impl { .. }) => {
+            span_bug!(tcx.def_span(def_id), "RPITIT in impl should not have item bounds")
+        }
         None => {}
     }
 
diff --git a/compiler/rustc_hir_analysis/src/collect/predicates_of.rs b/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
index 1a6c0a93436..8f84492146f 100644
--- a/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
+++ b/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
@@ -9,8 +9,7 @@ use rustc_middle::ty::{
     self, GenericPredicates, ImplTraitInTraitData, Ty, TyCtxt, TypeVisitable, TypeVisitor, Upcast,
 };
 use rustc_middle::{bug, span_bug};
-use rustc_span::symbol::Ident;
-use rustc_span::{DUMMY_SP, Span};
+use rustc_span::{DUMMY_SP, Ident, Span};
 use tracing::{debug, instrument, trace};
 
 use super::item_bounds::explicit_item_bounds_with_filter;
@@ -957,6 +956,15 @@ pub(super) fn const_conditions<'tcx>(
         bug!("const_conditions invoked for item that is not conditionally const: {def_id:?}");
     }
 
+    match tcx.opt_rpitit_info(def_id.to_def_id()) {
+        // RPITITs inherit const conditions of their parent fn
+        Some(
+            ty::ImplTraitInTraitData::Impl { fn_def_id }
+            | ty::ImplTraitInTraitData::Trait { fn_def_id, .. },
+        ) => return tcx.const_conditions(fn_def_id),
+        None => {}
+    }
+
     let (generics, trait_def_id_and_supertraits, has_parent) = match tcx.hir_node_by_def_id(def_id)
     {
         Node::Item(item) => match item.kind {
@@ -1060,19 +1068,29 @@ pub(super) fn explicit_implied_const_bounds<'tcx>(
         bug!("const_conditions invoked for item that is not conditionally const: {def_id:?}");
     }
 
-    let bounds = match tcx.hir_node_by_def_id(def_id) {
-        Node::Item(hir::Item { kind: hir::ItemKind::Trait(..), .. }) => {
-            implied_predicates_with_filter(
-                tcx,
-                def_id.to_def_id(),
-                PredicateFilter::SelfConstIfConst,
-            )
-        }
-        Node::TraitItem(hir::TraitItem { kind: hir::TraitItemKind::Type(..), .. })
-        | Node::OpaqueTy(_) => {
+    let bounds = match tcx.opt_rpitit_info(def_id.to_def_id()) {
+        // RPITIT's bounds are the same as opaque type bounds, but with
+        // a projection self type.
+        Some(ty::ImplTraitInTraitData::Trait { .. }) => {
             explicit_item_bounds_with_filter(tcx, def_id, PredicateFilter::ConstIfConst)
         }
-        _ => bug!("explicit_implied_const_bounds called on wrong item: {def_id:?}"),
+        Some(ty::ImplTraitInTraitData::Impl { .. }) => {
+            span_bug!(tcx.def_span(def_id), "RPITIT in impl should not have item bounds")
+        }
+        None => match tcx.hir_node_by_def_id(def_id) {
+            Node::Item(hir::Item { kind: hir::ItemKind::Trait(..), .. }) => {
+                implied_predicates_with_filter(
+                    tcx,
+                    def_id.to_def_id(),
+                    PredicateFilter::SelfConstIfConst,
+                )
+            }
+            Node::TraitItem(hir::TraitItem { kind: hir::TraitItemKind::Type(..), .. })
+            | Node::OpaqueTy(_) => {
+                explicit_item_bounds_with_filter(tcx, def_id, PredicateFilter::ConstIfConst)
+            }
+            _ => bug!("explicit_implied_const_bounds called on wrong item: {def_id:?}"),
+        },
     };
 
     bounds.map_bound(|bounds| {
diff --git a/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs b/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
index 0f797bcdae4..7c65e9613b6 100644
--- a/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
+++ b/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
@@ -26,9 +26,8 @@ use rustc_middle::middle::resolve_bound_vars::*;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::{self, TyCtxt, TypeSuperVisitable, TypeVisitor};
 use rustc_middle::{bug, span_bug};
-use rustc_span::Span;
 use rustc_span::def_id::{DefId, LocalDefId, LocalDefIdMap};
-use rustc_span::symbol::{Ident, sym};
+use rustc_span::{Ident, Span, sym};
 use tracing::{debug, debug_span, instrument};
 
 use crate::errors;
diff --git a/compiler/rustc_hir_analysis/src/collect/type_of.rs b/compiler/rustc_hir_analysis/src/collect/type_of.rs
index 5595504c3d9..c0526903e88 100644
--- a/compiler/rustc_hir_analysis/src/collect/type_of.rs
+++ b/compiler/rustc_hir_analysis/src/collect/type_of.rs
@@ -10,8 +10,7 @@ use rustc_middle::ty::print::with_forced_trimmed_paths;
 use rustc_middle::ty::util::IntTypeExt;
 use rustc_middle::ty::{self, Article, IsSuggestable, Ty, TyCtxt, TypeVisitableExt};
 use rustc_middle::{bug, span_bug};
-use rustc_span::symbol::Ident;
-use rustc_span::{DUMMY_SP, Span};
+use rustc_span::{DUMMY_SP, Ident, Span};
 
 use super::{ItemCtxt, bad_placeholder};
 use crate::errors::TypeofReservedKeywordUsed;
@@ -473,7 +472,7 @@ fn infer_placeholder_type<'tcx>(
 fn check_feature_inherent_assoc_ty(tcx: TyCtxt<'_>, span: Span) {
     if !tcx.features().inherent_associated_types() {
         use rustc_session::parse::feature_err;
-        use rustc_span::symbol::sym;
+        use rustc_span::sym;
         feature_err(
             &tcx.sess,
             sym::inherent_associated_types,
diff --git a/compiler/rustc_hir_analysis/src/errors.rs b/compiler/rustc_hir_analysis/src/errors.rs
index 5ab6faf3b7c..00ba1741ed7 100644
--- a/compiler/rustc_hir_analysis/src/errors.rs
+++ b/compiler/rustc_hir_analysis/src/errors.rs
@@ -6,8 +6,7 @@ use rustc_errors::{
 };
 use rustc_macros::{Diagnostic, LintDiagnostic, Subdiagnostic};
 use rustc_middle::ty::Ty;
-use rustc_span::symbol::Ident;
-use rustc_span::{Span, Symbol};
+use rustc_span::{Ident, Span, Symbol};
 
 use crate::fluent_generated as fluent;
 mod pattern_types;
@@ -1655,6 +1654,14 @@ pub(crate) struct NonConstRange {
     pub span: Span,
 }
 
+#[derive(Subdiagnostic)]
+pub(crate) enum InvalidReceiverTyHint {
+    #[note(hir_analysis_invalid_receiver_ty_help_weak_note)]
+    Weak,
+    #[note(hir_analysis_invalid_receiver_ty_help_nonnull_note)]
+    NonNull,
+}
+
 #[derive(Diagnostic)]
 #[diag(hir_analysis_invalid_receiver_ty_no_arbitrary_self_types, code = E0307)]
 #[note]
@@ -1673,6 +1680,8 @@ pub(crate) struct InvalidReceiverTy<'tcx> {
     #[primary_span]
     pub span: Span,
     pub receiver_ty: Ty<'tcx>,
+    #[subdiagnostic]
+    pub hint: Option<InvalidReceiverTyHint>,
 }
 
 #[derive(Diagnostic)]
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs
index 0404e38a293..e949d4a1126 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs
@@ -9,8 +9,7 @@ use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_middle::bug;
 use rustc_middle::ty::{self as ty, IsSuggestable, Ty, TyCtxt};
-use rustc_span::symbol::Ident;
-use rustc_span::{ErrorGuaranteed, Span, Symbol, sym};
+use rustc_span::{ErrorGuaranteed, Ident, Span, Symbol, kw, sym};
 use rustc_trait_selection::traits;
 use rustc_type_ir::visit::{TypeSuperVisitable, TypeVisitable, TypeVisitableExt, TypeVisitor};
 use smallvec::SmallVec;
@@ -745,7 +744,7 @@ fn check_assoc_const_binding_type<'tcx>(
     let generics = tcx.generics_of(enclosing_item_owner_id);
     for index in collector.params {
         let param = generics.param_at(index as _, tcx);
-        let is_self_param = param.name == rustc_span::symbol::kw::SelfUpper;
+        let is_self_param = param.name == kw::SelfUpper;
         guar.get_or_insert(cx.dcx().emit_err(crate::errors::ParamInTyOfAssocConstBinding {
             span: assoc_const.span,
             assoc_const,
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs
index d3c86989440..71a5727ed6c 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs
@@ -1,9 +1,8 @@
-use rustc_data_structures::fx::{FxHashSet, FxIndexMap, FxIndexSet};
+use rustc_data_structures::fx::{FxHashSet, FxIndexSet};
 use rustc_errors::codes::*;
 use rustc_errors::struct_span_code_err;
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
-use rustc_hir::def_id::DefId;
 use rustc_lint_defs::builtin::UNUSED_ASSOCIATED_TYPE_BOUNDS;
 use rustc_middle::span_bug;
 use rustc_middle::ty::fold::BottomUpFolder;
@@ -11,7 +10,7 @@ use rustc_middle::ty::{
     self, DynKind, ExistentialPredicateStableCmpExt as _, Ty, TyCtxt, TypeFoldable,
     TypeVisitableExt, Upcast,
 };
-use rustc_span::{ErrorGuaranteed, Span};
+use rustc_span::{DUMMY_SP, ErrorGuaranteed, Span};
 use rustc_trait_selection::error_reporting::traits::report_dyn_incompatibility;
 use rustc_trait_selection::traits::{self, hir_ty_lowering_dyn_compatibility_violations};
 use rustc_type_ir::elaborate::ClauseWithSupertraitSpan;
@@ -128,8 +127,9 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             }
         }
 
-        let mut associated_types: FxIndexMap<Span, FxIndexSet<DefId>> = FxIndexMap::default();
+        let mut needed_associated_types = FxIndexSet::default();
 
+        let principal_span = regular_traits.first().map_or(DUMMY_SP, |info| info.bottom().1);
         let regular_traits_refs_spans = trait_bounds
             .into_iter()
             .filter(|(trait_ref, _)| !tcx.trait_is_auto(trait_ref.def_id()));
@@ -145,13 +145,18 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 let bound_predicate = pred.kind();
                 match bound_predicate.skip_binder() {
                     ty::PredicateKind::Clause(ty::ClauseKind::Trait(pred)) => {
-                        let pred = bound_predicate.rebind(pred);
-                        associated_types.entry(original_span).or_default().extend(
-                            tcx.associated_items(pred.def_id())
+                        // FIXME(negative_bounds): Handle this correctly...
+                        let trait_ref =
+                            tcx.anonymize_bound_vars(bound_predicate.rebind(pred.trait_ref));
+                        needed_associated_types.extend(
+                            tcx.associated_items(trait_ref.def_id())
                                 .in_definition_order()
                                 .filter(|item| item.kind == ty::AssocKind::Type)
                                 .filter(|item| !item.is_impl_trait_in_trait())
-                                .map(|item| item.def_id),
+                                // If the associated type has a `where Self: Sized` bound,
+                                // we do not need to constrain the associated type.
+                                .filter(|item| !tcx.generics_require_sized_self(item.def_id))
+                                .map(|item| (item.def_id, trait_ref)),
                         );
                     }
                     ty::PredicateKind::Clause(ty::ClauseKind::Projection(pred)) => {
@@ -201,26 +206,25 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         // So every `Projection` clause is an `Assoc = Foo` bound. `associated_types` contains all associated
         // types's `DefId`, so the following loop removes all the `DefIds` of the associated types that have a
         // corresponding `Projection` clause
-        for def_ids in associated_types.values_mut() {
-            for (projection_bound, span) in &projection_bounds {
-                let def_id = projection_bound.item_def_id();
-                def_ids.swap_remove(&def_id);
-                if tcx.generics_require_sized_self(def_id) {
-                    tcx.emit_node_span_lint(
-                        UNUSED_ASSOCIATED_TYPE_BOUNDS,
-                        hir_id,
-                        *span,
-                        crate::errors::UnusedAssociatedTypeBounds { span: *span },
-                    );
-                }
+        for (projection_bound, span) in &projection_bounds {
+            let def_id = projection_bound.item_def_id();
+            let trait_ref = tcx.anonymize_bound_vars(
+                projection_bound.map_bound(|p| p.projection_term.trait_ref(tcx)),
+            );
+            needed_associated_types.swap_remove(&(def_id, trait_ref));
+            if tcx.generics_require_sized_self(def_id) {
+                tcx.emit_node_span_lint(
+                    UNUSED_ASSOCIATED_TYPE_BOUNDS,
+                    hir_id,
+                    *span,
+                    crate::errors::UnusedAssociatedTypeBounds { span: *span },
+                );
             }
-            // If the associated type has a `where Self: Sized` bound, we do not need to constrain the associated
-            // type in the `dyn Trait`.
-            def_ids.retain(|def_id| !tcx.generics_require_sized_self(def_id));
         }
 
         if let Err(guar) = self.check_for_required_assoc_tys(
-            associated_types,
+            principal_span,
+            needed_associated_types,
             potential_assoc_types,
             hir_trait_bounds,
         ) {
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
index 6e10450313c..0623d35853e 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
@@ -16,8 +16,7 @@ use rustc_middle::ty::{
 };
 use rustc_session::parse::feature_err;
 use rustc_span::edit_distance::find_best_match_for_name;
-use rustc_span::symbol::{Ident, kw, sym};
-use rustc_span::{BytePos, DUMMY_SP, Span, Symbol};
+use rustc_span::{BytePos, DUMMY_SP, Ident, Span, Symbol, kw, sym};
 use rustc_trait_selection::error_reporting::traits::report_dyn_incompatibility;
 use rustc_trait_selection::traits::{
     FulfillmentError, TraitAliasExpansionInfo, dyn_compatibility_violations_for_assoc_item,
@@ -721,51 +720,42 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
     /// emit a generic note suggesting using a `where` clause to constraint instead.
     pub(crate) fn check_for_required_assoc_tys(
         &self,
-        associated_types: FxIndexMap<Span, FxIndexSet<DefId>>,
+        principal_span: Span,
+        missing_assoc_types: FxIndexSet<(DefId, ty::PolyTraitRef<'tcx>)>,
         potential_assoc_types: Vec<usize>,
         trait_bounds: &[hir::PolyTraitRef<'_>],
     ) -> Result<(), ErrorGuaranteed> {
-        if associated_types.values().all(|v| v.is_empty()) {
+        if missing_assoc_types.is_empty() {
             return Ok(());
         }
 
         let tcx = self.tcx();
-        // FIXME: Marked `mut` so that we can replace the spans further below with a more
-        // appropriate one, but this should be handled earlier in the span assignment.
-        let associated_types: FxIndexMap<Span, Vec<_>> = associated_types
+        // FIXME: This logic needs some more care w.r.t handling of conflicts
+        let missing_assoc_types: Vec<_> = missing_assoc_types
             .into_iter()
-            .map(|(span, def_ids)| {
-                (span, def_ids.into_iter().map(|did| tcx.associated_item(did)).collect())
-            })
+            .map(|(def_id, trait_ref)| (tcx.associated_item(def_id), trait_ref))
             .collect();
-        let mut names: FxIndexMap<String, Vec<Symbol>> = Default::default();
+        let mut names: FxIndexMap<_, Vec<Symbol>> = Default::default();
         let mut names_len = 0;
 
         // Account for things like `dyn Foo + 'a`, like in tests `issue-22434.rs` and
         // `issue-22560.rs`.
-        let mut trait_bound_spans: Vec<Span> = vec![];
         let mut dyn_compatibility_violations = Ok(());
-        for (span, items) in &associated_types {
-            if !items.is_empty() {
-                trait_bound_spans.push(*span);
-            }
-            for assoc_item in items {
-                let trait_def_id = assoc_item.container_id(tcx);
-                names.entry(tcx.def_path_str(trait_def_id)).or_default().push(assoc_item.name);
-                names_len += 1;
-
-                let violations =
-                    dyn_compatibility_violations_for_assoc_item(tcx, trait_def_id, *assoc_item);
-                if !violations.is_empty() {
-                    dyn_compatibility_violations = Err(report_dyn_incompatibility(
-                        tcx,
-                        *span,
-                        None,
-                        trait_def_id,
-                        &violations,
-                    )
-                    .emit());
-                }
+        for (assoc_item, trait_ref) in &missing_assoc_types {
+            names.entry(trait_ref).or_default().push(assoc_item.name);
+            names_len += 1;
+
+            let violations =
+                dyn_compatibility_violations_for_assoc_item(tcx, trait_ref.def_id(), *assoc_item);
+            if !violations.is_empty() {
+                dyn_compatibility_violations = Err(report_dyn_incompatibility(
+                    tcx,
+                    principal_span,
+                    None,
+                    trait_ref.def_id(),
+                    &violations,
+                )
+                .emit());
             }
         }
 
@@ -813,6 +803,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             .into_iter()
             .map(|(trait_, mut assocs)| {
                 assocs.sort();
+                let trait_ = trait_.print_trait_sugared();
                 format!("{} in `{trait_}`", match &assocs[..] {
                     [] => String::new(),
                     [only] => format!("`{only}`"),
@@ -826,10 +817,9 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         names.sort();
         let names = names.join(", ");
 
-        trait_bound_spans.sort();
         let mut err = struct_span_code_err!(
             self.dcx(),
-            trait_bound_spans,
+            principal_span,
             E0191,
             "the value of the associated type{} {} must be specified",
             pluralize!(names_len),
@@ -839,81 +829,83 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         let mut types_count = 0;
         let mut where_constraints = vec![];
         let mut already_has_generics_args_suggestion = false;
-        for (span, assoc_items) in &associated_types {
-            let mut names: UnordMap<_, usize> = Default::default();
-            for item in assoc_items {
-                types_count += 1;
-                *names.entry(item.name).or_insert(0) += 1;
-            }
-            let mut dupes = false;
-            let mut shadows = false;
-            for item in assoc_items {
-                let prefix = if names[&item.name] > 1 {
-                    let trait_def_id = item.container_id(tcx);
-                    dupes = true;
-                    format!("{}::", tcx.def_path_str(trait_def_id))
-                } else if bound_names.get(&item.name).is_some_and(|x| x != &item) {
-                    let trait_def_id = item.container_id(tcx);
-                    shadows = true;
-                    format!("{}::", tcx.def_path_str(trait_def_id))
-                } else {
-                    String::new()
-                };
 
-                let mut is_shadowed = false;
-
-                if let Some(assoc_item) = bound_names.get(&item.name)
-                    && assoc_item != &item
-                {
-                    is_shadowed = true;
+        let mut names: UnordMap<_, usize> = Default::default();
+        for (item, _) in &missing_assoc_types {
+            types_count += 1;
+            *names.entry(item.name).or_insert(0) += 1;
+        }
+        let mut dupes = false;
+        let mut shadows = false;
+        for (item, trait_ref) in &missing_assoc_types {
+            let prefix = if names[&item.name] > 1 {
+                let trait_def_id = trait_ref.def_id();
+                dupes = true;
+                format!("{}::", tcx.def_path_str(trait_def_id))
+            } else if bound_names.get(&item.name).is_some_and(|x| *x != item) {
+                let trait_def_id = trait_ref.def_id();
+                shadows = true;
+                format!("{}::", tcx.def_path_str(trait_def_id))
+            } else {
+                String::new()
+            };
 
-                    let rename_message =
-                        if assoc_item.def_id.is_local() { ", consider renaming it" } else { "" };
-                    err.span_label(
-                        tcx.def_span(assoc_item.def_id),
-                        format!("`{}{}` shadowed here{}", prefix, item.name, rename_message),
-                    );
-                }
+            let mut is_shadowed = false;
 
-                let rename_message = if is_shadowed { ", consider renaming it" } else { "" };
+            if let Some(assoc_item) = bound_names.get(&item.name)
+                && *assoc_item != item
+            {
+                is_shadowed = true;
 
-                if let Some(sp) = tcx.hir().span_if_local(item.def_id) {
-                    err.span_label(
-                        sp,
-                        format!("`{}{}` defined here{}", prefix, item.name, rename_message),
-                    );
-                }
+                let rename_message =
+                    if assoc_item.def_id.is_local() { ", consider renaming it" } else { "" };
+                err.span_label(
+                    tcx.def_span(assoc_item.def_id),
+                    format!("`{}{}` shadowed here{}", prefix, item.name, rename_message),
+                );
             }
-            if potential_assoc_types.len() == assoc_items.len() {
-                // When the amount of missing associated types equals the number of
-                // extra type arguments present. A suggesting to replace the generic args with
-                // associated types is already emitted.
-                already_has_generics_args_suggestion = true;
-            } else if let (Ok(snippet), false, false) =
-                (tcx.sess.source_map().span_to_snippet(*span), dupes, shadows)
-            {
-                let types: Vec<_> =
-                    assoc_items.iter().map(|item| format!("{} = Type", item.name)).collect();
-                let code = if snippet.ends_with('>') {
-                    // The user wrote `Trait<'a>` or similar and we don't have a type we can
-                    // suggest, but at least we can clue them to the correct syntax
-                    // `Trait<'a, Item = Type>` while accounting for the `<'a>` in the
-                    // suggestion.
-                    format!("{}, {}>", &snippet[..snippet.len() - 1], types.join(", "))
-                } else if in_expr_or_pat {
-                    // The user wrote `Iterator`, so we don't have a type we can suggest, but at
-                    // least we can clue them to the correct syntax `Iterator::<Item = Type>`.
-                    format!("{}::<{}>", snippet, types.join(", "))
-                } else {
-                    // The user wrote `Iterator`, so we don't have a type we can suggest, but at
-                    // least we can clue them to the correct syntax `Iterator<Item = Type>`.
-                    format!("{}<{}>", snippet, types.join(", "))
-                };
-                suggestions.push((*span, code));
-            } else if dupes {
-                where_constraints.push(*span);
+
+            let rename_message = if is_shadowed { ", consider renaming it" } else { "" };
+
+            if let Some(sp) = tcx.hir().span_if_local(item.def_id) {
+                err.span_label(
+                    sp,
+                    format!("`{}{}` defined here{}", prefix, item.name, rename_message),
+                );
             }
         }
+        if potential_assoc_types.len() == missing_assoc_types.len() {
+            // When the amount of missing associated types equals the number of
+            // extra type arguments present. A suggesting to replace the generic args with
+            // associated types is already emitted.
+            already_has_generics_args_suggestion = true;
+        } else if let (Ok(snippet), false, false) =
+            (tcx.sess.source_map().span_to_snippet(principal_span), dupes, shadows)
+        {
+            let types: Vec<_> = missing_assoc_types
+                .iter()
+                .map(|(item, _)| format!("{} = Type", item.name))
+                .collect();
+            let code = if snippet.ends_with('>') {
+                // The user wrote `Trait<'a>` or similar and we don't have a type we can
+                // suggest, but at least we can clue them to the correct syntax
+                // `Trait<'a, Item = Type>` while accounting for the `<'a>` in the
+                // suggestion.
+                format!("{}, {}>", &snippet[..snippet.len() - 1], types.join(", "))
+            } else if in_expr_or_pat {
+                // The user wrote `Iterator`, so we don't have a type we can suggest, but at
+                // least we can clue them to the correct syntax `Iterator::<Item = Type>`.
+                format!("{}::<{}>", snippet, types.join(", "))
+            } else {
+                // The user wrote `Iterator`, so we don't have a type we can suggest, but at
+                // least we can clue them to the correct syntax `Iterator<Item = Type>`.
+                format!("{}<{}>", snippet, types.join(", "))
+            };
+            suggestions.push((principal_span, code));
+        } else if dupes {
+            where_constraints.push(principal_span);
+        }
+
         let where_msg = "consider introducing a new type parameter, adding `where` constraints \
                          using the fully-qualified path to the associated types";
         if !where_constraints.is_empty() && suggestions.is_empty() {
@@ -924,32 +916,29 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         }
         if suggestions.len() != 1 || already_has_generics_args_suggestion {
             // We don't need this label if there's an inline suggestion, show otherwise.
-            for (span, assoc_items) in &associated_types {
-                let mut names: FxIndexMap<_, usize> = FxIndexMap::default();
-                for item in assoc_items {
-                    types_count += 1;
-                    *names.entry(item.name).or_insert(0) += 1;
-                }
-                let mut label = vec![];
-                for item in assoc_items {
-                    let postfix = if names[&item.name] > 1 {
-                        let trait_def_id = item.container_id(tcx);
-                        format!(" (from trait `{}`)", tcx.def_path_str(trait_def_id))
-                    } else {
-                        String::new()
-                    };
-                    label.push(format!("`{}`{}", item.name, postfix));
-                }
-                if !label.is_empty() {
-                    err.span_label(
-                        *span,
-                        format!(
-                            "associated type{} {} must be specified",
-                            pluralize!(label.len()),
-                            label.join(", "),
-                        ),
-                    );
-                }
+            let mut names: FxIndexMap<_, usize> = FxIndexMap::default();
+            for (item, _) in &missing_assoc_types {
+                types_count += 1;
+                *names.entry(item.name).or_insert(0) += 1;
+            }
+            let mut label = vec![];
+            for (item, trait_ref) in &missing_assoc_types {
+                let postfix = if names[&item.name] > 1 {
+                    format!(" (from trait `{}`)", trait_ref.print_trait_sugared())
+                } else {
+                    String::new()
+                };
+                label.push(format!("`{}`{}", item.name, postfix));
+            }
+            if !label.is_empty() {
+                err.span_label(
+                    principal_span,
+                    format!(
+                        "associated type{} {} must be specified",
+                        pluralize!(label.len()),
+                        label.join(", "),
+                    ),
+                );
             }
         }
         suggestions.sort_by_key(|&(span, _)| span);
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/generics.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/generics.rs
index c3f4fc8699a..df00948dd21 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/generics.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/generics.rs
@@ -9,7 +9,7 @@ use rustc_middle::ty::{
     self, GenericArgsRef, GenericParamDef, GenericParamDefKind, IsSuggestable, Ty,
 };
 use rustc_session::lint::builtin::LATE_BOUND_LIFETIME_ARGUMENTS;
-use rustc_span::symbol::{kw, sym};
+use rustc_span::{kw, sym};
 use smallvec::SmallVec;
 use tracing::{debug, instrument};
 
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
index a357ade0294..b56222763d0 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
@@ -45,8 +45,7 @@ use rustc_middle::ty::{
 use rustc_middle::{bug, span_bug};
 use rustc_session::lint::builtin::AMBIGUOUS_ASSOCIATED_ITEMS;
 use rustc_span::edit_distance::find_best_match_for_name;
-use rustc_span::symbol::{Ident, Symbol, kw};
-use rustc_span::{DUMMY_SP, Span};
+use rustc_span::{DUMMY_SP, Ident, Span, Symbol, kw};
 use rustc_trait_selection::infer::InferCtxtExt;
 use rustc_trait_selection::traits::wf::object_region_bounds;
 use rustc_trait_selection::traits::{self, ObligationCtxt};
@@ -356,7 +355,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 ty::Region::new_late_param(
                     tcx,
                     scope.to_def_id(),
-                    ty::BoundRegionKind::Named(id.to_def_id(), name),
+                    ty::LateParamRegionKind::Named(id.to_def_id(), name),
                 )
 
                 // (*) -- not late-bound, won't change
diff --git a/compiler/rustc_hir_analysis/src/variance/dump.rs b/compiler/rustc_hir_analysis/src/variance/dump.rs
index a0fdf95a831..31f0adf720d 100644
--- a/compiler/rustc_hir_analysis/src/variance/dump.rs
+++ b/compiler/rustc_hir_analysis/src/variance/dump.rs
@@ -2,7 +2,7 @@ use std::fmt::Write;
 
 use rustc_hir::def_id::{CRATE_DEF_ID, LocalDefId};
 use rustc_middle::ty::{GenericArgs, TyCtxt};
-use rustc_span::symbol::sym;
+use rustc_span::sym;
 
 fn format_variances(tcx: TyCtxt<'_>, def_id: LocalDefId) -> String {
     let variances = tcx.variances_of(def_id);
diff --git a/compiler/rustc_hir_pretty/src/lib.rs b/compiler/rustc_hir_pretty/src/lib.rs
index 8dd8a5c98ef..5c1c5892190 100644
--- a/compiler/rustc_hir_pretty/src/lib.rs
+++ b/compiler/rustc_hir_pretty/src/lib.rs
@@ -11,16 +11,17 @@ use std::vec;
 
 use rustc_abi::ExternAbi;
 use rustc_ast::util::parser::{self, AssocOp, ExprPrecedence, Fixity};
+use rustc_ast::{DUMMY_NODE_ID, DelimArgs};
 use rustc_ast_pretty::pp::Breaks::{Consistent, Inconsistent};
 use rustc_ast_pretty::pp::{self, Breaks};
+use rustc_ast_pretty::pprust::state::MacHeader;
 use rustc_ast_pretty::pprust::{Comments, PrintState};
 use rustc_hir::{
     BindingMode, ByRef, ConstArgKind, GenericArg, GenericBound, GenericParam, GenericParamKind,
     HirId, LifetimeParamKind, Node, PatKind, PreciseCapturingArg, RangeEnd, Term,
 };
-use rustc_span::FileName;
 use rustc_span::source_map::SourceMap;
-use rustc_span::symbol::{Ident, Symbol, kw};
+use rustc_span::{FileName, Ident, Span, Symbol, kw};
 use {rustc_ast as ast, rustc_hir as hir};
 
 pub fn id_to_string(map: &dyn rustc_hir::intravisit::Map<'_>, hir_id: HirId) -> String {
@@ -68,15 +69,115 @@ impl PpAnn for &dyn rustc_hir::intravisit::Map<'_> {
 pub struct State<'a> {
     pub s: pp::Printer,
     comments: Option<Comments<'a>>,
-    attrs: &'a dyn Fn(HirId) -> &'a [ast::Attribute],
+    attrs: &'a dyn Fn(HirId) -> &'a [hir::Attribute],
     ann: &'a (dyn PpAnn + 'a),
 }
 
 impl<'a> State<'a> {
-    fn attrs(&self, id: HirId) -> &'a [ast::Attribute] {
+    fn attrs(&self, id: HirId) -> &'a [hir::Attribute] {
         (self.attrs)(id)
     }
 
+    fn print_inner_attributes(&mut self, attrs: &[hir::Attribute]) -> bool {
+        self.print_either_attributes(attrs, ast::AttrStyle::Inner, false, true)
+    }
+
+    fn print_outer_attributes(&mut self, attrs: &[hir::Attribute]) -> bool {
+        self.print_either_attributes(attrs, ast::AttrStyle::Outer, false, true)
+    }
+
+    fn print_either_attributes(
+        &mut self,
+        attrs: &[hir::Attribute],
+        kind: ast::AttrStyle,
+        is_inline: bool,
+        trailing_hardbreak: bool,
+    ) -> bool {
+        let mut printed = false;
+        for attr in attrs {
+            if attr.style == kind {
+                self.print_attribute_inline(attr, is_inline);
+                if is_inline {
+                    self.nbsp();
+                }
+                printed = true;
+            }
+        }
+        if printed && trailing_hardbreak && !is_inline {
+            self.hardbreak_if_not_bol();
+        }
+        printed
+    }
+
+    fn print_attribute_inline(&mut self, attr: &hir::Attribute, is_inline: bool) {
+        if !is_inline {
+            self.hardbreak_if_not_bol();
+        }
+        self.maybe_print_comment(attr.span.lo());
+        match &attr.kind {
+            hir::AttrKind::Normal(normal) => {
+                match attr.style {
+                    ast::AttrStyle::Inner => self.word("#!["),
+                    ast::AttrStyle::Outer => self.word("#["),
+                }
+                if normal.unsafety == hir::Safety::Unsafe {
+                    self.word("unsafe(");
+                }
+                self.print_attr_item(&normal, attr.span);
+                if normal.unsafety == hir::Safety::Unsafe {
+                    self.word(")");
+                }
+                self.word("]");
+            }
+            hir::AttrKind::DocComment(comment_kind, data) => {
+                self.word(rustc_ast_pretty::pprust::state::doc_comment_to_string(
+                    *comment_kind,
+                    attr.style,
+                    *data,
+                ));
+                self.hardbreak()
+            }
+        }
+    }
+
+    fn print_attr_item(&mut self, item: &hir::AttrItem, span: Span) {
+        self.ibox(0);
+        let path = ast::Path {
+            span,
+            segments: item
+                .path
+                .segments
+                .iter()
+                .map(|i| ast::PathSegment { ident: *i, args: None, id: DUMMY_NODE_ID })
+                .collect(),
+            tokens: None,
+        };
+
+        match &item.args {
+            hir::AttrArgs::Delimited(DelimArgs { dspan: _, delim, tokens }) => self
+                .print_mac_common(
+                    Some(MacHeader::Path(&path)),
+                    false,
+                    None,
+                    *delim,
+                    tokens,
+                    true,
+                    span,
+                ),
+            hir::AttrArgs::Empty => {
+                PrintState::print_path(self, &path, false, 0);
+            }
+            hir::AttrArgs::Eq { eq_span: _, expr } => {
+                PrintState::print_path(self, &path, false, 0);
+                self.space();
+                self.word_space("=");
+                let token_str = self.meta_item_lit_to_string(expr);
+                self.word(token_str);
+            }
+        }
+        self.end();
+    }
+
     fn print_node(&mut self, node: Node<'_>) {
         match node {
             Node::Param(a) => self.print_param(a),
@@ -164,7 +265,7 @@ pub fn print_crate<'a>(
     krate: &hir::Mod<'_>,
     filename: FileName,
     input: String,
-    attrs: &'a dyn Fn(HirId) -> &'a [ast::Attribute],
+    attrs: &'a dyn Fn(HirId) -> &'a [hir::Attribute],
     ann: &'a dyn PpAnn,
 ) -> String {
     let mut s = State {
@@ -191,6 +292,10 @@ where
     printer.s.eof()
 }
 
+pub fn attribute_to_string(ann: &dyn PpAnn, attr: &hir::Attribute) -> String {
+    to_string(ann, |s| s.print_attribute_inline(attr, false))
+}
+
 pub fn ty_to_string(ann: &dyn PpAnn, ty: &hir::Ty<'_>) -> String {
     to_string(ann, |s| s.print_type(ty))
 }
@@ -242,7 +347,7 @@ impl<'a> State<'a> {
         self.commasep_cmnt(b, exprs, |s, e| s.print_expr(e), |e| e.span);
     }
 
-    fn print_mod(&mut self, _mod: &hir::Mod<'_>, attrs: &[ast::Attribute]) {
+    fn print_mod(&mut self, _mod: &hir::Mod<'_>, attrs: &[hir::Attribute]) {
         self.print_inner_attributes(attrs);
         for &item_id in _mod.item_ids {
             self.ann.nested(self, Nested::Item(item_id));
@@ -297,8 +402,10 @@ impl<'a> State<'a> {
             }
             hir::TyKind::Path(ref qpath) => self.print_qpath(qpath, false),
             hir::TyKind::TraitObject(bounds, lifetime, syntax) => {
-                if syntax == ast::TraitObjectSyntax::Dyn {
-                    self.word_space("dyn");
+                match syntax {
+                    ast::TraitObjectSyntax::Dyn => self.word_nbsp("dyn"),
+                    ast::TraitObjectSyntax::DynStar => self.word_nbsp("dyn*"),
+                    ast::TraitObjectSyntax::None => {}
                 }
                 let mut first = true;
                 for bound in bounds {
@@ -926,14 +1033,14 @@ impl<'a> State<'a> {
         self.print_block_maybe_unclosed(blk, &[], false)
     }
 
-    fn print_block_with_attrs(&mut self, blk: &hir::Block<'_>, attrs: &[ast::Attribute]) {
+    fn print_block_with_attrs(&mut self, blk: &hir::Block<'_>, attrs: &[hir::Attribute]) {
         self.print_block_maybe_unclosed(blk, attrs, true)
     }
 
     fn print_block_maybe_unclosed(
         &mut self,
         blk: &hir::Block<'_>,
-        attrs: &[ast::Attribute],
+        attrs: &[hir::Attribute],
         close_box: bool,
     ) {
         match blk.rules {
diff --git a/compiler/rustc_hir_typeck/Cargo.toml b/compiler/rustc_hir_typeck/Cargo.toml
index 8ddbb4b3397..1f5acaa58a9 100644
--- a/compiler/rustc_hir_typeck/Cargo.toml
+++ b/compiler/rustc_hir_typeck/Cargo.toml
@@ -9,7 +9,7 @@ itertools = "0.12"
 rustc_abi = { path = "../rustc_abi" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_ast_ir = { path = "../rustc_ast_ir" }
-rustc_attr = { path = "../rustc_attr" }
+rustc_attr_parsing = { path = "../rustc_attr_parsing" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
 rustc_fluent_macro = { path = "../rustc_fluent_macro" }
diff --git a/compiler/rustc_hir_typeck/src/callee.rs b/compiler/rustc_hir_typeck/src/callee.rs
index b430f48965a..9d364775445 100644
--- a/compiler/rustc_hir_typeck/src/callee.rs
+++ b/compiler/rustc_hir_typeck/src/callee.rs
@@ -13,9 +13,8 @@ use rustc_middle::ty::adjustment::{
 };
 use rustc_middle::ty::{self, GenericArgsRef, Ty, TyCtxt, TypeVisitableExt};
 use rustc_middle::{bug, span_bug};
-use rustc_span::Span;
 use rustc_span::def_id::LocalDefId;
-use rustc_span::symbol::{Ident, sym};
+use rustc_span::{Ident, Span, sym};
 use rustc_trait_selection::error_reporting::traits::DefIdOrName;
 use rustc_trait_selection::infer::InferCtxtExt as _;
 use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt as _;
diff --git a/compiler/rustc_hir_typeck/src/cast.rs b/compiler/rustc_hir_typeck/src/cast.rs
index 80b91c21598..8190095971b 100644
--- a/compiler/rustc_hir_typeck/src/cast.rs
+++ b/compiler/rustc_hir_typeck/src/cast.rs
@@ -43,8 +43,7 @@ use rustc_middle::ty::{self, Ty, TyCtxt, TypeAndMut, TypeVisitableExt, VariantDe
 use rustc_middle::{bug, span_bug};
 use rustc_session::lint;
 use rustc_span::def_id::LOCAL_CRATE;
-use rustc_span::symbol::sym;
-use rustc_span::{DUMMY_SP, Span};
+use rustc_span::{DUMMY_SP, Span, sym};
 use rustc_trait_selection::infer::InferCtxtExt;
 use tracing::{debug, instrument};
 
@@ -722,13 +721,11 @@ impl<'a, 'tcx> CastCheck<'tcx> {
         use rustc_middle::ty::cast::IntTy::*;
 
         if self.cast_ty.is_dyn_star() {
-            if fcx.tcx.features().dyn_star() {
-                span_bug!(self.span, "should be handled by `coerce`");
-            } else {
-                // Report "casting is invalid" rather than "non-primitive cast"
-                // if the feature is not enabled.
-                return Err(CastError::IllegalCast);
-            }
+            // This coercion will fail if the feature is not enabled, OR
+            // if the coercion is (currently) illegal (e.g. `dyn* Foo + Send`
+            // to `dyn* Foo`). Report "casting is invalid" rather than
+            // "non-primitive cast".
+            return Err(CastError::IllegalCast);
         }
 
         let (t_from, t_cast) = match (CastTy::from_ty(self.expr_ty), CastTy::from_ty(self.cast_ty))
diff --git a/compiler/rustc_hir_typeck/src/check.rs b/compiler/rustc_hir_typeck/src/check.rs
index 51d78646373..b0698183b57 100644
--- a/compiler/rustc_hir_typeck/src/check.rs
+++ b/compiler/rustc_hir_typeck/src/check.rs
@@ -10,7 +10,7 @@ use rustc_infer::infer::RegionVariableOrigin;
 use rustc_infer::traits::WellFormedLoc;
 use rustc_middle::ty::{self, Binder, Ty, TyCtxt};
 use rustc_span::def_id::LocalDefId;
-use rustc_span::symbol::sym;
+use rustc_span::sym;
 use rustc_trait_selection::traits::{ObligationCause, ObligationCauseCode};
 use tracing::{debug, instrument};
 
diff --git a/compiler/rustc_hir_typeck/src/coercion.rs b/compiler/rustc_hir_typeck/src/coercion.rs
index bf41dcbe4a3..f9e4a592d92 100644
--- a/compiler/rustc_hir_typeck/src/coercion.rs
+++ b/compiler/rustc_hir_typeck/src/coercion.rs
@@ -59,8 +59,7 @@ use rustc_middle::ty::error::TypeError;
 use rustc_middle::ty::visit::TypeVisitableExt;
 use rustc_middle::ty::{self, GenericArgsRef, Ty, TyCtxt};
 use rustc_session::parse::feature_err;
-use rustc_span::symbol::sym;
-use rustc_span::{BytePos, DUMMY_SP, DesugaringKind, Span};
+use rustc_span::{BytePos, DUMMY_SP, DesugaringKind, Span, sym};
 use rustc_trait_selection::infer::InferCtxtExt as _;
 use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt;
 use rustc_trait_selection::traits::{
@@ -738,8 +737,10 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
             return Err(TypeError::Mismatch);
         }
 
-        if let ty::Dynamic(a_data, _, _) = a.kind()
-            && let ty::Dynamic(b_data, _, _) = b.kind()
+        // FIXME(dyn_star): We should probably allow things like casting from
+        // `dyn* Foo + Send` to `dyn* Foo`.
+        if let ty::Dynamic(a_data, _, ty::DynStar) = a.kind()
+            && let ty::Dynamic(b_data, _, ty::DynStar) = b.kind()
             && a_data.principal_def_id() == b_data.principal_def_id()
         {
             return self.unify_and(a, b, |_| vec![]);
@@ -863,7 +864,8 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
             let outer_universe = self.infcx.universe();
 
             let result = if let ty::FnPtr(_, hdr_b) = b.kind()
-                && let (hir::Safety::Safe, hir::Safety::Unsafe) = (fn_ty_a.safety(), hdr_b.safety)
+                && fn_ty_a.safety().is_safe()
+                && hdr_b.safety.is_unsafe()
             {
                 let unsafe_a = self.tcx.safe_to_unsafe_fn_ty(fn_ty_a);
                 self.unify_and(unsafe_a, b, to_unsafe)
@@ -925,7 +927,7 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
 
                     // Safe `#[target_feature]` functions are not assignable to safe fn pointers (RFC 2396).
 
-                    if b_hdr.safety == hir::Safety::Safe
+                    if b_hdr.safety.is_safe()
                         && !self.tcx.codegen_fn_attrs(def_id).target_features.is_empty()
                     {
                         return Err(TypeError::TargetFeatureCast(def_id));
@@ -1315,43 +1317,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }
         }
 
-        // Then try to coerce the previous expressions to the type of the new one.
-        // This requires ensuring there are no coercions applied to *any* of the
-        // previous expressions, other than noop reborrows (ignoring lifetimes).
-        for expr in exprs {
-            let expr = expr.as_coercion_site();
-            let noop = match self.typeck_results.borrow().expr_adjustments(expr) {
-                &[
-                    Adjustment { kind: Adjust::Deref(_), .. },
-                    Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(mutbl_adj)), .. },
-                ] => {
-                    match *self.node_ty(expr.hir_id).kind() {
-                        ty::Ref(_, _, mt_orig) => {
-                            let mutbl_adj: hir::Mutability = mutbl_adj.into();
-                            // Reborrow that we can safely ignore, because
-                            // the next adjustment can only be a Deref
-                            // which will be merged into it.
-                            mutbl_adj == mt_orig
-                        }
-                        _ => false,
-                    }
-                }
-                &[Adjustment { kind: Adjust::NeverToAny, .. }] | &[] => true,
-                _ => false,
-            };
-
-            if !noop {
-                debug!(
-                    "coercion::try_find_coercion_lub: older expression {:?} had adjustments, requiring LUB",
-                    expr,
-                );
-
-                return Err(self
-                    .commit_if_ok(|_| self.at(cause, self.param_env).lub(prev_ty, new_ty))
-                    .unwrap_err());
-            }
-        }
-
         match self.commit_if_ok(|_| coerce.coerce(prev_ty, new_ty)) {
             Err(_) => {
                 // Avoid giving strange errors on failed attempts.
diff --git a/compiler/rustc_hir_typeck/src/demand.rs b/compiler/rustc_hir_typeck/src/demand.rs
index d0272651c08..e51323fc5c8 100644
--- a/compiler/rustc_hir_typeck/src/demand.rs
+++ b/compiler/rustc_hir_typeck/src/demand.rs
@@ -9,8 +9,7 @@ use rustc_middle::ty::error::{ExpectedFound, TypeError};
 use rustc_middle::ty::fold::BottomUpFolder;
 use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_middle::ty::{self, AssocItem, Ty, TypeFoldable, TypeVisitableExt};
-use rustc_span::symbol::sym;
-use rustc_span::{DUMMY_SP, Span};
+use rustc_span::{DUMMY_SP, Ident, Span, sym};
 use rustc_trait_selection::infer::InferCtxtExt;
 use rustc_trait_selection::traits::ObligationCause;
 use tracing::instrument;
@@ -1118,7 +1117,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             Constructor,
         }
         let mut maybe_emit_help = |def_id: hir::def_id::DefId,
-                                   callable: rustc_span::symbol::Ident,
+                                   callable: Ident,
                                    args: &[hir::Expr<'_>],
                                    kind: CallableKind| {
             let arg_idx = args.iter().position(|a| a.hir_id == expr.hir_id).unwrap();
diff --git a/compiler/rustc_hir_typeck/src/errors.rs b/compiler/rustc_hir_typeck/src/errors.rs
index 7746a5a7132..ff09583cc65 100644
--- a/compiler/rustc_hir_typeck/src/errors.rs
+++ b/compiler/rustc_hir_typeck/src/errors.rs
@@ -10,8 +10,7 @@ use rustc_errors::{
 use rustc_macros::{Diagnostic, LintDiagnostic, Subdiagnostic};
 use rustc_middle::ty::{self, Ty};
 use rustc_span::edition::{Edition, LATEST_STABLE_EDITION};
-use rustc_span::symbol::Ident;
-use rustc_span::{Span, Symbol};
+use rustc_span::{Ident, Span, Symbol};
 
 use crate::fluent_generated as fluent;
 
diff --git a/compiler/rustc_hir_typeck/src/expr.rs b/compiler/rustc_hir_typeck/src/expr.rs
index 66978399efb..caea53d9200 100644
--- a/compiler/rustc_hir_typeck/src/expr.rs
+++ b/compiler/rustc_hir_typeck/src/expr.rs
@@ -30,11 +30,10 @@ use rustc_middle::ty::{self, AdtKind, GenericArgsRef, Ty, TypeVisitableExt};
 use rustc_middle::{bug, span_bug};
 use rustc_session::errors::ExprParenthesesNeeded;
 use rustc_session::parse::feature_err;
-use rustc_span::Span;
 use rustc_span::edit_distance::find_best_match_for_name;
 use rustc_span::hygiene::DesugaringKind;
 use rustc_span::source_map::Spanned;
-use rustc_span::symbol::{Ident, Symbol, kw, sym};
+use rustc_span::{Ident, Span, Symbol, kw, sym};
 use rustc_trait_selection::infer::InferCtxtExt;
 use rustc_trait_selection::traits::{self, ObligationCauseCode, ObligationCtxt};
 use tracing::{debug, instrument, trace};
diff --git a/compiler/rustc_hir_typeck/src/fallback.rs b/compiler/rustc_hir_typeck/src/fallback.rs
index b57c248ed2b..c128485d93e 100644
--- a/compiler/rustc_hir_typeck/src/fallback.rs
+++ b/compiler/rustc_hir_typeck/src/fallback.rs
@@ -762,7 +762,7 @@ fn compute_unsafe_infer_vars<'a, 'tcx>(
                     if let Some(def_id) = typeck_results.type_dependent_def_id(ex.hir_id)
                         && let method_ty = self.fcx.tcx.type_of(def_id).instantiate_identity()
                         && let sig = method_ty.fn_sig(self.fcx.tcx)
-                        && let hir::Safety::Unsafe = sig.safety()
+                        && sig.safety().is_unsafe()
                     {
                         let mut collector = InferVarCollector {
                             value: (ex.hir_id, ex.span, UnsafeUseReason::Method),
@@ -782,7 +782,7 @@ fn compute_unsafe_infer_vars<'a, 'tcx>(
 
                     if func_ty.is_fn()
                         && let sig = func_ty.fn_sig(self.fcx.tcx)
-                        && let hir::Safety::Unsafe = sig.safety()
+                        && sig.safety().is_unsafe()
                     {
                         let mut collector = InferVarCollector {
                             value: (ex.hir_id, ex.span, UnsafeUseReason::Call),
@@ -813,7 +813,7 @@ fn compute_unsafe_infer_vars<'a, 'tcx>(
                     // `is_fn` excludes closures, but those can't be unsafe.
                     if ty.is_fn()
                         && let sig = ty.fn_sig(self.fcx.tcx)
-                        && let hir::Safety::Unsafe = sig.safety()
+                        && sig.safety().is_unsafe()
                     {
                         let mut collector = InferVarCollector {
                             value: (ex.hir_id, ex.span, UnsafeUseReason::Path),
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
index 0dacfc9b7bf..364499378b0 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
@@ -29,10 +29,9 @@ use rustc_middle::ty::{
 };
 use rustc_middle::{bug, span_bug};
 use rustc_session::lint;
-use rustc_span::Span;
 use rustc_span::def_id::LocalDefId;
 use rustc_span::hygiene::DesugaringKind;
-use rustc_span::symbol::kw;
+use rustc_span::{Span, kw};
 use rustc_trait_selection::error_reporting::infer::need_type_info::TypeAnnotationNeeded;
 use rustc_trait_selection::traits::{
     self, NormalizeExt, ObligationCauseCode, StructurallyNormalizeExt,
@@ -147,18 +146,21 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         debug!("write_ty({:?}, {:?}) in fcx {}", id, self.resolve_vars_if_possible(ty), self.tag());
         let mut typeck = self.typeck_results.borrow_mut();
         let mut node_ty = typeck.node_types_mut();
-        if let Some(ty) = node_ty.get(id)
-            && let Err(e) = ty.error_reported()
-        {
-            // Do not overwrite nodes that were already marked as `{type error}`. This allows us to
-            // silence unnecessary errors from obligations that were set earlier than a type error
-            // was produced, but that is overwritten by later analysis. This happens in particular
-            // for `Sized` obligations introduced in gather_locals. (#117846)
-            self.set_tainted_by_errors(e);
-            return;
-        }
 
-        node_ty.insert(id, ty);
+        if let Some(prev) = node_ty.insert(id, ty) {
+            if prev.references_error() {
+                node_ty.insert(id, prev);
+            } else if !ty.references_error() {
+                // Could change this to a bug, but there's lots of diagnostic code re-lowering
+                // or re-typechecking nodes that were already typecked.
+                // Lots of that diagnostics code relies on subtle effects of re-lowering, so we'll
+                // let it keep doing that and just ensure that compilation won't succeed.
+                self.dcx().span_delayed_bug(
+                    self.tcx.hir().span(id),
+                    format!("`{prev}` overridden by `{ty}` for {id:?} in {:?}", self.body_id),
+                );
+            }
+        }
 
         if let Err(e) = ty.error_reported() {
             self.set_tainted_by_errors(e);
@@ -1105,7 +1107,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         if let Res::Local(hid) = res {
             let ty = self.local_ty(span, hid);
             let ty = self.normalize(span, ty);
-            self.write_ty(hir_id, ty);
             return (ty, res);
         }
 
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs
index 6eaba641888..ee0436f73e1 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs
@@ -5,8 +5,7 @@ use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::DefId;
 use rustc_infer::traits::ObligationCauseCode;
 use rustc_middle::ty::{self, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitor};
-use rustc_span::Span;
-use rustc_span::symbol::kw;
+use rustc_span::{Span, kw};
 use rustc_trait_selection::traits;
 
 use crate::FnCtxt;
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
index 6b1cceefbee..fffea8f640b 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
@@ -22,8 +22,7 @@ use rustc_middle::ty::visit::TypeVisitableExt;
 use rustc_middle::ty::{self, IsSuggestable, Ty, TyCtxt};
 use rustc_middle::{bug, span_bug};
 use rustc_session::Session;
-use rustc_span::symbol::{Ident, kw};
-use rustc_span::{DUMMY_SP, Span, sym};
+use rustc_span::{DUMMY_SP, Ident, Span, kw, sym};
 use rustc_trait_selection::error_reporting::infer::{FailureCode, ObligationCauseExt};
 use rustc_trait_selection::infer::InferCtxtExt;
 use rustc_trait_selection::traits::{self, ObligationCauseCode, ObligationCtxt, SelectionContext};
@@ -1751,10 +1750,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         }
     }
 
-    pub(in super::super) fn check_decl(&self, decl: Declaration<'tcx>) {
+    pub(in super::super) fn check_decl(&self, decl: Declaration<'tcx>) -> Ty<'tcx> {
         // Determine and write the type which we'll check the pattern against.
         let decl_ty = self.local_ty(decl.span, decl.hir_id);
-        self.write_ty(decl.hir_id, decl_ty);
 
         // Type check the initializer.
         if let Some(ref init) = decl.init {
@@ -1786,11 +1784,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }
             self.diverges.set(previous_diverges);
         }
+        decl_ty
     }
 
     /// Type check a `let` statement.
     fn check_decl_local(&self, local: &'tcx hir::LetStmt<'tcx>) {
-        self.check_decl(local.into());
+        let ty = self.check_decl(local.into());
+        self.write_ty(local.hir_id, ty);
         if local.pat.is_never_pattern() {
             self.diverges.set(Diverges::Always {
                 span: local.pat.span,
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs
index b9011e89f04..d432199f037 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs
@@ -17,8 +17,7 @@ use rustc_infer::infer;
 use rustc_infer::traits::Obligation;
 use rustc_middle::ty::{self, Const, Ty, TyCtxt, TypeVisitableExt};
 use rustc_session::Session;
-use rustc_span::symbol::Ident;
-use rustc_span::{self, DUMMY_SP, Span, sym};
+use rustc_span::{self, DUMMY_SP, Ident, Span, sym};
 use rustc_trait_selection::error_reporting::TypeErrCtxt;
 use rustc_trait_selection::error_reporting::infer::sub_relations::SubRelations;
 use rustc_trait_selection::traits::{ObligationCause, ObligationCauseCode, ObligationCtxt};
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs
index ddcd90a2a9d..964ef5b2106 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs
@@ -10,7 +10,7 @@ use rustc_hir::def::{CtorKind, CtorOf, DefKind, Res};
 use rustc_hir::lang_items::LangItem;
 use rustc_hir::{
     Arm, CoroutineDesugaring, CoroutineKind, CoroutineSource, Expr, ExprKind, GenericBound, HirId,
-    Node, Path, QPath, Stmt, StmtKind, TyKind, WherePredicateKind,
+    Node, Path, QPath, Stmt, StmtKind, TyKind, WherePredicateKind, expr_needs_parens,
 };
 use rustc_hir_analysis::collect::suggest_impl_trait;
 use rustc_hir_analysis::hir_ty_lowering::HirTyLowerer;
@@ -24,8 +24,7 @@ use rustc_middle::ty::{
 };
 use rustc_session::errors::ExprParenthesesNeeded;
 use rustc_span::source_map::Spanned;
-use rustc_span::symbol::{Ident, sym};
-use rustc_span::{Span, Symbol};
+use rustc_span::{Ident, Span, Symbol, sym};
 use rustc_trait_selection::error_reporting::InferCtxtErrorExt;
 use rustc_trait_selection::error_reporting::traits::DefIdOrName;
 use rustc_trait_selection::infer::InferCtxtExt;
@@ -35,7 +34,6 @@ use tracing::{debug, instrument};
 
 use super::FnCtxt;
 use crate::fn_ctxt::rustc_span::BytePos;
-use crate::hir::is_range_literal;
 use crate::method::probe;
 use crate::method::probe::{IsSuggestion, Mode, ProbeScope};
 use crate::{errors, fluent_generated as fluent};
@@ -2648,7 +2646,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     }
 
                     let make_sugg = |expr: &Expr<'_>, span: Span, sugg: &str| {
-                        if self.needs_parentheses(expr) {
+                        if expr_needs_parens(expr) {
                             (
                                 vec![
                                     (span.shrink_to_lo(), format!("{prefix}{sugg}(")),
@@ -2861,7 +2859,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             return None;
                         }
 
-                        if self.needs_parentheses(expr) {
+                        if expr_needs_parens(expr) {
                             return Some((
                                 vec![
                                     (span, format!("{suggestion}(")),
@@ -2902,16 +2900,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         false
     }
 
-    fn needs_parentheses(&self, expr: &hir::Expr<'_>) -> bool {
-        match expr.kind {
-            // parenthesize if needed (Issue #46756)
-            hir::ExprKind::Cast(_, _) | hir::ExprKind::Binary(_, _, _) => true,
-            // parenthesize borrows of range literals (Issue #54505)
-            _ if is_range_literal(expr) => true,
-            _ => false,
-        }
-    }
-
     pub(crate) fn suggest_cast(
         &self,
         err: &mut Diag<'_>,
diff --git a/compiler/rustc_hir_typeck/src/method/mod.rs b/compiler/rustc_hir_typeck/src/method/mod.rs
index e0b6ea0ac9d..4008021c3a8 100644
--- a/compiler/rustc_hir_typeck/src/method/mod.rs
+++ b/compiler/rustc_hir_typeck/src/method/mod.rs
@@ -19,8 +19,7 @@ use rustc_middle::ty::{
     self, GenericArgs, GenericArgsRef, GenericParamDefKind, Ty, TypeVisitableExt,
 };
 use rustc_middle::{bug, span_bug};
-use rustc_span::symbol::Ident;
-use rustc_span::{ErrorGuaranteed, Span};
+use rustc_span::{ErrorGuaranteed, Ident, Span};
 use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt;
 use rustc_trait_selection::traits::{self, NormalizeExt};
 use tracing::{debug, instrument};
diff --git a/compiler/rustc_hir_typeck/src/method/prelude_edition_lints.rs b/compiler/rustc_hir_typeck/src/method/prelude_edition_lints.rs
index b20592c85d2..5ccfcf93f69 100644
--- a/compiler/rustc_hir_typeck/src/method/prelude_edition_lints.rs
+++ b/compiler/rustc_hir_typeck/src/method/prelude_edition_lints.rs
@@ -8,9 +8,7 @@ use rustc_lint::{ARRAY_INTO_ITER, BOXED_SLICE_INTO_ITER};
 use rustc_middle::span_bug;
 use rustc_middle::ty::{self, Ty};
 use rustc_session::lint::builtin::{RUST_2021_PRELUDE_COLLISIONS, RUST_2024_PRELUDE_COLLISIONS};
-use rustc_span::Span;
-use rustc_span::symbol::kw::{Empty, Underscore};
-use rustc_span::symbol::{Ident, sym};
+use rustc_span::{Ident, Span, kw, sym};
 use rustc_trait_selection::infer::InferCtxtExt;
 use tracing::debug;
 
@@ -369,11 +367,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             .collect();
 
         // Find an identifier with which this trait was imported (note that `_` doesn't count).
-        let any_id = import_items
-            .iter()
-            .find_map(|item| if item.ident.name != Underscore { Some(item.ident) } else { None });
+        let any_id = import_items.iter().find_map(|item| {
+            if item.ident.name != kw::Underscore { Some(item.ident) } else { None }
+        });
         if let Some(any_id) = any_id {
-            if any_id.name == Empty {
+            if any_id.name == kw::Empty {
                 // Glob import, so just use its name.
                 return None;
             } else {
diff --git a/compiler/rustc_hir_typeck/src/method/probe.rs b/compiler/rustc_hir_typeck/src/method/probe.rs
index 3b377076545..ace114f1ffa 100644
--- a/compiler/rustc_hir_typeck/src/method/probe.rs
+++ b/compiler/rustc_hir_typeck/src/method/probe.rs
@@ -25,8 +25,7 @@ use rustc_span::def_id::{DefId, LocalDefId};
 use rustc_span::edit_distance::{
     edit_distance_with_substrings, find_best_match_for_name_with_substrings,
 };
-use rustc_span::symbol::{Ident, sym};
-use rustc_span::{DUMMY_SP, Span, Symbol};
+use rustc_span::{DUMMY_SP, Ident, Span, Symbol, sym};
 use rustc_trait_selection::error_reporting::infer::need_type_info::TypeAnnotationNeeded;
 use rustc_trait_selection::infer::InferCtxtExt as _;
 use rustc_trait_selection::traits::query::CanonicalTyGoal;
@@ -1230,23 +1229,16 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                 if let Some(by_value_pick) = by_value_pick {
                     if let Ok(by_value_pick) = by_value_pick.as_ref() {
                         if by_value_pick.kind == PickKind::InherentImplPick {
-                            if let Err(e) = self.check_for_shadowed_autorefd_method(
-                                by_value_pick,
-                                step,
-                                self_ty,
-                                hir::Mutability::Not,
-                                track_unstable_candidates,
-                            ) {
-                                return Some(Err(e));
-                            }
-                            if let Err(e) = self.check_for_shadowed_autorefd_method(
-                                by_value_pick,
-                                step,
-                                self_ty,
-                                hir::Mutability::Mut,
-                                track_unstable_candidates,
-                            ) {
-                                return Some(Err(e));
+                            for mutbl in [hir::Mutability::Not, hir::Mutability::Mut] {
+                                if let Err(e) = self.check_for_shadowed_autorefd_method(
+                                    by_value_pick,
+                                    step,
+                                    self_ty,
+                                    mutbl,
+                                    track_unstable_candidates,
+                                ) {
+                                    return Some(Err(e));
+                                }
                             }
                         }
                     }
@@ -1337,6 +1329,15 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         mutbl: hir::Mutability,
         track_unstable_candidates: bool,
     ) -> Result<(), MethodError<'tcx>> {
+        // The errors emitted by this function are part of
+        // the arbitrary self types work, and should not impact
+        // other users.
+        if !self.tcx.features().arbitrary_self_types()
+            && !self.tcx.features().arbitrary_self_types_pointers()
+        {
+            return Ok(());
+        }
+
         // We don't want to remember any of the diagnostic hints from this
         // shadow search, but we do need to provide Some/None for the
         // unstable_candidates in order to reflect the behavior of the
diff --git a/compiler/rustc_hir_typeck/src/method/suggest.rs b/compiler/rustc_hir_typeck/src/method/suggest.rs
index 6b1a288510a..1de88d52767 100644
--- a/compiler/rustc_hir_typeck/src/method/suggest.rs
+++ b/compiler/rustc_hir_typeck/src/method/suggest.rs
@@ -8,7 +8,7 @@ use std::borrow::Cow;
 
 use hir::Expr;
 use rustc_ast::ast::Mutability;
-use rustc_attr::parse_confusables;
+use rustc_attr_parsing::parse_confusables;
 use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_data_structures::sorted_map::SortedMap;
 use rustc_data_structures::unord::UnordSet;
@@ -27,9 +27,9 @@ use rustc_middle::ty::print::{
 };
 use rustc_middle::ty::{self, GenericArgKind, IsSuggestable, Ty, TyCtxt, TypeVisitableExt};
 use rustc_span::def_id::DefIdSet;
-use rustc_span::symbol::{Ident, kw, sym};
 use rustc_span::{
-    DUMMY_SP, ErrorGuaranteed, ExpnKind, FileName, MacroKind, Span, Symbol, edit_distance,
+    DUMMY_SP, ErrorGuaranteed, ExpnKind, FileName, Ident, MacroKind, Span, Symbol, edit_distance,
+    kw, sym,
 };
 use rustc_trait_selection::error_reporting::traits::DefIdOrName;
 use rustc_trait_selection::error_reporting::traits::on_unimplemented::OnUnimplementedNote;
diff --git a/compiler/rustc_hir_typeck/src/op.rs b/compiler/rustc_hir_typeck/src/op.rs
index 72b930ee84d..805079afdb0 100644
--- a/compiler/rustc_hir_typeck/src/op.rs
+++ b/compiler/rustc_hir_typeck/src/op.rs
@@ -11,9 +11,8 @@ use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_middle::ty::{self, IsSuggestable, Ty, TyCtxt, TypeVisitableExt};
 use rustc_middle::{bug, span_bug};
 use rustc_session::errors::ExprParenthesesNeeded;
-use rustc_span::Span;
 use rustc_span::source_map::Spanned;
-use rustc_span::symbol::{Ident, sym};
+use rustc_span::{Ident, Span, sym};
 use rustc_trait_selection::infer::InferCtxtExt;
 use rustc_trait_selection::traits::{FulfillmentError, Obligation, ObligationCtxt};
 use rustc_type_ir::TyKind::*;
diff --git a/compiler/rustc_hir_typeck/src/pat.rs b/compiler/rustc_hir_typeck/src/pat.rs
index 2a8ed26aa2b..98b28240f4c 100644
--- a/compiler/rustc_hir_typeck/src/pat.rs
+++ b/compiler/rustc_hir_typeck/src/pat.rs
@@ -10,8 +10,12 @@ use rustc_errors::{
 };
 use rustc_hir::def::{CtorKind, DefKind, Res};
 use rustc_hir::pat_util::EnumerateAndAdjustIterator;
-use rustc_hir::{self as hir, BindingMode, ByRef, HirId, LangItem, Mutability, Pat, PatKind};
+use rustc_hir::{
+    self as hir, BindingMode, ByRef, ExprKind, HirId, LangItem, Mutability, Pat, PatKind,
+    expr_needs_parens,
+};
 use rustc_infer::infer;
+use rustc_middle::traits::PatternOriginExpr;
 use rustc_middle::ty::{self, Ty, TypeVisitableExt};
 use rustc_middle::{bug, span_bug};
 use rustc_session::lint::builtin::NON_EXHAUSTIVE_OMITTED_PATTERNS;
@@ -19,8 +23,7 @@ use rustc_session::parse::feature_err;
 use rustc_span::edit_distance::find_best_match_for_name;
 use rustc_span::hygiene::DesugaringKind;
 use rustc_span::source_map::Spanned;
-use rustc_span::symbol::{Ident, kw, sym};
-use rustc_span::{BytePos, DUMMY_SP, Span};
+use rustc_span::{BytePos, DUMMY_SP, Ident, Span, kw, sym};
 use rustc_trait_selection::infer::InferCtxtExt;
 use rustc_trait_selection::traits::{ObligationCause, ObligationCauseCode};
 use tracing::{debug, instrument, trace};
@@ -94,10 +97,32 @@ struct PatInfo<'a, 'tcx> {
 
 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     fn pattern_cause(&self, ti: &TopInfo<'tcx>, cause_span: Span) -> ObligationCause<'tcx> {
+        // If origin_expr exists, then expected represents the type of origin_expr.
+        // If span also exists, then span == origin_expr.span (although it doesn't need to exist).
+        // In that case, we can peel away references from both and treat them
+        // as the same.
+        let origin_expr_info = ti.origin_expr.map(|mut cur_expr| {
+            let mut count = 0;
+
+            // cur_ty may have more layers of references than cur_expr.
+            // We can only make suggestions about cur_expr, however, so we'll
+            // use that as our condition for stopping.
+            while let ExprKind::AddrOf(.., inner) = &cur_expr.kind {
+                cur_expr = inner;
+                count += 1;
+            }
+
+            PatternOriginExpr {
+                peeled_span: cur_expr.span,
+                peeled_count: count,
+                peeled_prefix_suggestion_parentheses: expr_needs_parens(cur_expr),
+            }
+        });
+
         let code = ObligationCauseCode::Pattern {
             span: ti.span,
             root_ty: ti.expected,
-            origin_expr: ti.origin_expr.is_some(),
+            origin_expr: origin_expr_info,
         };
         self.cause(cause_span, code)
     }
@@ -692,12 +717,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     BindingMode(def_br, Mutability::Mut)
                 } else {
                     // `mut` resets the binding mode on edition <= 2021
-                    *self
-                        .typeck_results
-                        .borrow_mut()
-                        .rust_2024_migration_desugared_pats_mut()
-                        .entry(pat_info.top_info.hir_id)
-                        .or_default() |= pat.span.at_least_rust_2024();
+                    self.add_rust_2024_migration_desugared_pat(
+                        pat_info.top_info.hir_id,
+                        pat.span,
+                        ident.span,
+                        "requires binding by-value, but the implicit default is by-reference",
+                    );
                     BindingMode(ByRef::No, Mutability::Mut)
                 }
             }
@@ -705,12 +730,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             BindingMode(ByRef::Yes(_), _) => {
                 if matches!(def_br, ByRef::Yes(_)) {
                     // `ref`/`ref mut` overrides the binding mode on edition <= 2021
-                    *self
-                        .typeck_results
-                        .borrow_mut()
-                        .rust_2024_migration_desugared_pats_mut()
-                        .entry(pat_info.top_info.hir_id)
-                        .or_default() |= pat.span.at_least_rust_2024();
+                    self.add_rust_2024_migration_desugared_pat(
+                        pat_info.top_info.hir_id,
+                        pat.span,
+                        ident.span,
+                        "cannot override to bind by-reference when that is the implicit default",
+                    );
                 }
                 user_bind_annot
             }
@@ -2240,12 +2265,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // Reset binding mode on old editions
             if pat_info.binding_mode != ByRef::No {
                 pat_info.binding_mode = ByRef::No;
-                *self
-                    .typeck_results
-                    .borrow_mut()
-                    .rust_2024_migration_desugared_pats_mut()
-                    .entry(pat_info.top_info.hir_id)
-                    .or_default() |= pat.span.at_least_rust_2024();
+                self.add_rust_2024_migration_desugared_pat(
+                    pat_info.top_info.hir_id,
+                    pat.span,
+                    inner.span,
+                    "cannot implicitly match against multiple layers of reference",
+                )
             }
         }
 
@@ -2604,4 +2629,39 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             _ => (false, ty),
         }
     }
+
+    /// Record a pattern that's invalid under Rust 2024 match ergonomics, along with a problematic
+    /// span, so that the pattern migration lint can desugar it during THIR construction.
+    fn add_rust_2024_migration_desugared_pat(
+        &self,
+        pat_id: HirId,
+        subpat_span: Span,
+        cutoff_span: Span,
+        detailed_label: &str,
+    ) {
+        // Try to trim the span we're labeling to just the `&` or binding mode that's an issue.
+        // If the subpattern's span is is from an expansion, the emitted label will not be trimmed.
+        let source_map = self.tcx.sess.source_map();
+        let cutoff_span = source_map
+            .span_extend_prev_while(cutoff_span, char::is_whitespace)
+            .unwrap_or(cutoff_span);
+        // Ensure we use the syntax context and thus edition of `subpat_span`; this will be a hard
+        // error if the subpattern is of edition >= 2024.
+        let trimmed_span = subpat_span.until(cutoff_span).with_ctxt(subpat_span.ctxt());
+
+        // Only provide a detailed label if the problematic subpattern isn't from an expansion.
+        // In the case that it's from a macro, we'll add a more detailed note in the emitter.
+        let desc = if subpat_span.from_expansion() {
+            "default binding mode is reset within expansion"
+        } else {
+            detailed_label
+        };
+
+        self.typeck_results
+            .borrow_mut()
+            .rust_2024_migration_desugared_pats_mut()
+            .entry(pat_id)
+            .or_default()
+            .push((trimmed_span, desc.to_owned()));
+    }
 }
diff --git a/compiler/rustc_hir_typeck/src/place_op.rs b/compiler/rustc_hir_typeck/src/place_op.rs
index 7c667511aa9..ba635071135 100644
--- a/compiler/rustc_hir_typeck/src/place_op.rs
+++ b/compiler/rustc_hir_typeck/src/place_op.rs
@@ -7,8 +7,7 @@ use rustc_middle::ty::adjustment::{
     PointerCoercion,
 };
 use rustc_middle::ty::{self, Ty};
-use rustc_span::Span;
-use rustc_span::symbol::{Ident, sym};
+use rustc_span::{Ident, Span, sym};
 use tracing::debug;
 use {rustc_ast as ast, rustc_hir as hir};
 
diff --git a/compiler/rustc_hir_typeck/src/upvar.rs b/compiler/rustc_hir_typeck/src/upvar.rs
index 4f283644cbe..b3085843141 100644
--- a/compiler/rustc_hir_typeck/src/upvar.rs
+++ b/compiler/rustc_hir_typeck/src/upvar.rs
@@ -14,7 +14,7 @@
 //! to everything owned by `x`, so the result is the same for something
 //! like `x.f = 5` and so on (presuming `x` is not a borrowed pointer to a
 //! struct). These adjustments are performed in
-//! `adjust_upvar_borrow_kind()` (you can trace backwards through the code
+//! `adjust_for_non_move_closure` (you can trace backwards through the code
 //! from there).
 //!
 //! The fact that we are inferring borrow kinds as we go results in a
@@ -1684,8 +1684,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // want to capture by ref to allow precise capture using reborrows.
             //
             // If the data will be moved out of this place, then the place will be truncated
-            // at the first Deref in `adjust_upvar_borrow_kind_for_consume` and then moved into
-            // the closure.
+            // at the first Deref in `adjust_for_move_closure` and then moved into the closure.
             hir::CaptureBy::Value { .. } if !place.deref_tys().any(Ty::is_ref) => {
                 ty::UpvarCapture::ByValue
             }
diff --git a/compiler/rustc_hir_typeck/src/writeback.rs b/compiler/rustc_hir_typeck/src/writeback.rs
index 6f1e3a0cf8c..5612aa75aae 100644
--- a/compiler/rustc_hir_typeck/src/writeback.rs
+++ b/compiler/rustc_hir_typeck/src/writeback.rs
@@ -15,8 +15,7 @@ use rustc_middle::ty::adjustment::{Adjust, Adjustment, PointerCoercion};
 use rustc_middle::ty::fold::{TypeFoldable, TypeFolder, fold_regions};
 use rustc_middle::ty::visit::TypeVisitableExt;
 use rustc_middle::ty::{self, Ty, TyCtxt, TypeSuperFoldable};
-use rustc_span::Span;
-use rustc_span::symbol::sym;
+use rustc_span::{Span, sym};
 use rustc_trait_selection::error_reporting::infer::need_type_info::TypeAnnotationNeeded;
 use rustc_trait_selection::solve;
 use tracing::{debug, instrument};
@@ -555,11 +554,13 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
             let hidden_type = self.resolve(decl.hidden_type, &decl.hidden_type.span);
             let opaque_type_key = self.resolve(opaque_type_key, &decl.hidden_type.span);
 
-            if let ty::Alias(ty::Opaque, alias_ty) = hidden_type.ty.kind()
-                && alias_ty.def_id == opaque_type_key.def_id.to_def_id()
-                && alias_ty.args == opaque_type_key.args
-            {
-                continue;
+            if !self.fcx.next_trait_solver() {
+                if let ty::Alias(ty::Opaque, alias_ty) = hidden_type.ty.kind()
+                    && alias_ty.def_id == opaque_type_key.def_id.to_def_id()
+                    && alias_ty.args == opaque_type_key.args
+                {
+                    continue;
+                }
             }
 
             // Here we only detect impl trait definition conflicts when they
diff --git a/compiler/rustc_incremental/src/assert_dep_graph.rs b/compiler/rustc_incremental/src/assert_dep_graph.rs
index 1f46155abc8..569034954c3 100644
--- a/compiler/rustc_incremental/src/assert_dep_graph.rs
+++ b/compiler/rustc_incremental/src/assert_dep_graph.rs
@@ -47,10 +47,9 @@ use rustc_middle::dep_graph::{
 use rustc_middle::hir::nested_filter;
 use rustc_middle::ty::TyCtxt;
 use rustc_middle::{bug, span_bug};
-use rustc_span::Span;
-use rustc_span::symbol::{Symbol, sym};
+use rustc_span::{Span, Symbol, sym};
 use tracing::debug;
-use {rustc_ast as ast, rustc_graphviz as dot, rustc_hir as hir};
+use {rustc_graphviz as dot, rustc_hir as hir};
 
 use crate::errors;
 
@@ -106,7 +105,7 @@ struct IfThisChanged<'tcx> {
 }
 
 impl<'tcx> IfThisChanged<'tcx> {
-    fn argument(&self, attr: &ast::Attribute) -> Option<Symbol> {
+    fn argument(&self, attr: &hir::Attribute) -> Option<Symbol> {
         let mut value = None;
         for list_item in attr.meta_item_list().unwrap_or_default() {
             match list_item.ident() {
diff --git a/compiler/rustc_incremental/src/errors.rs b/compiler/rustc_incremental/src/errors.rs
index cb21f975878..b4a207386dc 100644
--- a/compiler/rustc_incremental/src/errors.rs
+++ b/compiler/rustc_incremental/src/errors.rs
@@ -1,8 +1,7 @@
 use std::path::{Path, PathBuf};
 
 use rustc_macros::Diagnostic;
-use rustc_span::symbol::Ident;
-use rustc_span::{Span, Symbol};
+use rustc_span::{Ident, Span, Symbol};
 
 #[derive(Diagnostic)]
 #[diag(incremental_unrecognized_depnode)]
diff --git a/compiler/rustc_incremental/src/persist/dirty_clean.rs b/compiler/rustc_incremental/src/persist/dirty_clean.rs
index 2075d4214c1..b99872e7ae6 100644
--- a/compiler/rustc_incremental/src/persist/dirty_clean.rs
+++ b/compiler/rustc_incremental/src/persist/dirty_clean.rs
@@ -19,16 +19,17 @@
 //! Errors are reported if we are in the suitable configuration but
 //! the required condition is not met.
 
-use rustc_ast::{self as ast, Attribute, MetaItemInner};
+use rustc_ast::{self as ast, MetaItemInner};
 use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::unord::UnordSet;
 use rustc_hir::def_id::LocalDefId;
-use rustc_hir::{ImplItemKind, ItemKind as HirItem, Node as HirNode, TraitItemKind, intravisit};
+use rustc_hir::{
+    Attribute, ImplItemKind, ItemKind as HirItem, Node as HirNode, TraitItemKind, intravisit,
+};
 use rustc_middle::dep_graph::{DepNode, DepNodeExt, label_strs};
 use rustc_middle::hir::nested_filter;
 use rustc_middle::ty::TyCtxt;
-use rustc_span::Span;
-use rustc_span::symbol::{Symbol, sym};
+use rustc_span::{Span, Symbol, sym};
 use thin_vec::ThinVec;
 use tracing::debug;
 
diff --git a/compiler/rustc_index/Cargo.toml b/compiler/rustc_index/Cargo.toml
index 33e8e2824c7..f27db7a5400 100644
--- a/compiler/rustc_index/Cargo.toml
+++ b/compiler/rustc_index/Cargo.toml
@@ -5,7 +5,7 @@ edition = "2021"
 
 [dependencies]
 # tidy-alphabetical-start
-rustc_index_macros = { path = "../rustc_index_macros", default-features = false }
+rustc_index_macros = { path = "../rustc_index_macros" }
 rustc_macros = { path = "../rustc_macros", optional = true }
 rustc_serialize = { path = "../rustc_serialize", optional = true }
 smallvec = "1.8.1"
diff --git a/compiler/rustc_index/src/bit_set.rs b/compiler/rustc_index/src/bit_set.rs
index aba1e938296..664b77fd49e 100644
--- a/compiler/rustc_index/src/bit_set.rs
+++ b/compiler/rustc_index/src/bit_set.rs
@@ -1191,6 +1191,14 @@ impl<T: Idx> MixedBitSet<T> {
         }
     }
 
+    #[inline]
+    pub fn clear(&mut self) {
+        match self {
+            MixedBitSet::Small(set) => set.clear(),
+            MixedBitSet::Large(set) => set.clear(),
+        }
+    }
+
     bit_relations_inherent_impls! {}
 }
 
diff --git a/compiler/rustc_index_macros/Cargo.toml b/compiler/rustc_index_macros/Cargo.toml
index a7c2a1804dd..98bc1b6a29b 100644
--- a/compiler/rustc_index_macros/Cargo.toml
+++ b/compiler/rustc_index_macros/Cargo.toml
@@ -12,5 +12,4 @@ proc-macro2 = "1"
 quote = "1"
 
 [features]
-default = ["nightly"]
 nightly = []
diff --git a/compiler/rustc_infer/src/infer/canonical/query_response.rs b/compiler/rustc_infer/src/infer/canonical/query_response.rs
index 1d3d32ef749..d5aab4781de 100644
--- a/compiler/rustc_infer/src/infer/canonical/query_response.rs
+++ b/compiler/rustc_infer/src/infer/canonical/query_response.rs
@@ -316,16 +316,6 @@ impl<'tcx> InferCtxt<'tcx> {
             }),
         );
 
-        // ...also include the query member constraints.
-        output_query_region_constraints.member_constraints.extend(
-            query_response
-                .value
-                .region_constraints
-                .member_constraints
-                .iter()
-                .map(|p_c| instantiate_value(self.tcx, &result_args, p_c.clone())),
-        );
-
         let user_result: R =
             query_response.instantiate_projected(self.tcx, &result_args, |q_r| q_r.value.clone());
 
@@ -643,7 +633,7 @@ pub fn make_query_region_constraints<'tcx>(
     outlives_obligations: impl Iterator<Item = (Ty<'tcx>, ty::Region<'tcx>, ConstraintCategory<'tcx>)>,
     region_constraints: &RegionConstraintData<'tcx>,
 ) -> QueryRegionConstraints<'tcx> {
-    let RegionConstraintData { constraints, verifys, member_constraints } = region_constraints;
+    let RegionConstraintData { constraints, verifys } = region_constraints;
 
     assert!(verifys.is_empty());
 
@@ -674,5 +664,5 @@ pub fn make_query_region_constraints<'tcx>(
         }))
         .collect();
 
-    QueryRegionConstraints { outlives, member_constraints: member_constraints.clone() }
+    QueryRegionConstraints { outlives }
 }
diff --git a/compiler/rustc_infer/src/infer/mod.rs b/compiler/rustc_infer/src/infer/mod.rs
index 544f941dda5..c5a56005c06 100644
--- a/compiler/rustc_infer/src/infer/mod.rs
+++ b/compiler/rustc_infer/src/infer/mod.rs
@@ -17,7 +17,6 @@ pub use relate::StructurallyRelateAliases;
 pub use relate::combine::PredicateEmittingRelation;
 use rustc_data_structures::captures::Captures;
 use rustc_data_structures::fx::{FxHashSet, FxIndexMap};
-use rustc_data_structures::sync::Lrc;
 use rustc_data_structures::undo_log::{Rollback, UndoLogs};
 use rustc_data_structures::unify as ut;
 use rustc_errors::{DiagCtxtHandle, ErrorGuaranteed};
@@ -41,8 +40,7 @@ use rustc_middle::ty::{
     GenericParamDefKind, InferConst, IntVid, PseudoCanonicalInput, Ty, TyCtxt, TyVid,
     TypeVisitable, TypingEnv, TypingMode,
 };
-use rustc_span::Span;
-use rustc_span::symbol::Symbol;
+use rustc_span::{Span, Symbol};
 use snapshot::undo_log::InferCtxtUndoLogs;
 use tracing::{debug, instrument};
 use type_variable::TypeVariableOrigin;
@@ -686,26 +684,6 @@ impl<'tcx> InferCtxt<'tcx> {
         self.inner.borrow_mut().unwrap_region_constraints().make_subregion(origin, a, b);
     }
 
-    /// Require that the region `r` be equal to one of the regions in
-    /// the set `regions`.
-    #[instrument(skip(self), level = "debug")]
-    pub fn member_constraint(
-        &self,
-        key: ty::OpaqueTypeKey<'tcx>,
-        definition_span: Span,
-        hidden_ty: Ty<'tcx>,
-        region: ty::Region<'tcx>,
-        in_regions: Lrc<Vec<ty::Region<'tcx>>>,
-    ) {
-        self.inner.borrow_mut().unwrap_region_constraints().member_constraint(
-            key,
-            definition_span,
-            hidden_ty,
-            region,
-            in_regions,
-        );
-    }
-
     /// Processes a `Coerce` predicate from the fulfillment context.
     /// This is NOT the preferred way to handle coercion, which is to
     /// invoke `FnCtxt::coerce` or a similar method (see `coercion.rs`).
diff --git a/compiler/rustc_infer/src/infer/opaque_types/mod.rs b/compiler/rustc_infer/src/infer/opaque_types/mod.rs
index b64686afd23..137d438a479 100644
--- a/compiler/rustc_infer/src/infer/opaque_types/mod.rs
+++ b/compiler/rustc_infer/src/infer/opaque_types/mod.rs
@@ -1,6 +1,5 @@
 use hir::def_id::{DefId, LocalDefId};
 use rustc_data_structures::fx::FxIndexMap;
-use rustc_data_structures::sync::Lrc;
 use rustc_hir as hir;
 use rustc_middle::bug;
 use rustc_middle::traits::ObligationCause;
@@ -8,8 +7,7 @@ use rustc_middle::traits::solve::Goal;
 use rustc_middle::ty::error::{ExpectedFound, TypeError};
 use rustc_middle::ty::fold::BottomUpFolder;
 use rustc_middle::ty::{
-    self, GenericArgKind, OpaqueHiddenType, OpaqueTypeKey, Ty, TyCtxt, TypeFoldable,
-    TypeSuperVisitable, TypeVisitable, TypeVisitableExt, TypeVisitor,
+    self, OpaqueHiddenType, OpaqueTypeKey, Ty, TyCtxt, TypeFoldable, TypeVisitableExt,
 };
 use rustc_span::Span;
 use tracing::{debug, instrument};
@@ -181,289 +179,6 @@ impl<'tcx> InferCtxt<'tcx> {
             Err(TypeError::Sorts(ExpectedFound::new(a, b)))
         }
     }
-
-    /// Given the map `opaque_types` containing the opaque
-    /// `impl Trait` types whose underlying, hidden types are being
-    /// inferred, this method adds constraints to the regions
-    /// appearing in those underlying hidden types to ensure that they
-    /// at least do not refer to random scopes within the current
-    /// function. These constraints are not (quite) sufficient to
-    /// guarantee that the regions are actually legal values; that
-    /// final condition is imposed after region inference is done.
-    ///
-    /// # The Problem
-    ///
-    /// Let's work through an example to explain how it works. Assume
-    /// the current function is as follows:
-    ///
-    /// ```text
-    /// fn foo<'a, 'b>(..) -> (impl Bar<'a>, impl Bar<'b>)
-    /// ```
-    ///
-    /// Here, we have two `impl Trait` types whose values are being
-    /// inferred (the `impl Bar<'a>` and the `impl
-    /// Bar<'b>`). Conceptually, this is sugar for a setup where we
-    /// define underlying opaque types (`Foo1`, `Foo2`) and then, in
-    /// the return type of `foo`, we *reference* those definitions:
-    ///
-    /// ```text
-    /// type Foo1<'x> = impl Bar<'x>;
-    /// type Foo2<'x> = impl Bar<'x>;
-    /// fn foo<'a, 'b>(..) -> (Foo1<'a>, Foo2<'b>) { .. }
-    ///                    //  ^^^^ ^^
-    ///                    //  |    |
-    ///                    //  |    args
-    ///                    //  def_id
-    /// ```
-    ///
-    /// As indicating in the comments above, each of those references
-    /// is (in the compiler) basically generic parameters (`args`)
-    /// applied to the type of a suitable `def_id` (which identifies
-    /// `Foo1` or `Foo2`).
-    ///
-    /// Now, at this point in compilation, what we have done is to
-    /// replace each of the references (`Foo1<'a>`, `Foo2<'b>`) with
-    /// fresh inference variables C1 and C2. We wish to use the values
-    /// of these variables to infer the underlying types of `Foo1` and
-    /// `Foo2`. That is, this gives rise to higher-order (pattern) unification
-    /// constraints like:
-    ///
-    /// ```text
-    /// for<'a> (Foo1<'a> = C1)
-    /// for<'b> (Foo1<'b> = C2)
-    /// ```
-    ///
-    /// For these equation to be satisfiable, the types `C1` and `C2`
-    /// can only refer to a limited set of regions. For example, `C1`
-    /// can only refer to `'static` and `'a`, and `C2` can only refer
-    /// to `'static` and `'b`. The job of this function is to impose that
-    /// constraint.
-    ///
-    /// Up to this point, C1 and C2 are basically just random type
-    /// inference variables, and hence they may contain arbitrary
-    /// regions. In fact, it is fairly likely that they do! Consider
-    /// this possible definition of `foo`:
-    ///
-    /// ```text
-    /// fn foo<'a, 'b>(x: &'a i32, y: &'b i32) -> (impl Bar<'a>, impl Bar<'b>) {
-    ///         (&*x, &*y)
-    ///     }
-    /// ```
-    ///
-    /// Here, the values for the concrete types of the two impl
-    /// traits will include inference variables:
-    ///
-    /// ```text
-    /// &'0 i32
-    /// &'1 i32
-    /// ```
-    ///
-    /// Ordinarily, the subtyping rules would ensure that these are
-    /// sufficiently large. But since `impl Bar<'a>` isn't a specific
-    /// type per se, we don't get such constraints by default. This
-    /// is where this function comes into play. It adds extra
-    /// constraints to ensure that all the regions which appear in the
-    /// inferred type are regions that could validly appear.
-    ///
-    /// This is actually a bit of a tricky constraint in general. We
-    /// want to say that each variable (e.g., `'0`) can only take on
-    /// values that were supplied as arguments to the opaque type
-    /// (e.g., `'a` for `Foo1<'a>`) or `'static`, which is always in
-    /// scope. We don't have a constraint quite of this kind in the current
-    /// region checker.
-    ///
-    /// # The Solution
-    ///
-    /// We generally prefer to make `<=` constraints, since they
-    /// integrate best into the region solver. To do that, we find the
-    /// "minimum" of all the arguments that appear in the args: that
-    /// is, some region which is less than all the others. In the case
-    /// of `Foo1<'a>`, that would be `'a` (it's the only choice, after
-    /// all). Then we apply that as a least bound to the variables
-    /// (e.g., `'a <= '0`).
-    ///
-    /// In some cases, there is no minimum. Consider this example:
-    ///
-    /// ```text
-    /// fn baz<'a, 'b>() -> impl Trait<'a, 'b> { ... }
-    /// ```
-    ///
-    /// Here we would report a more complex "in constraint", like `'r
-    /// in ['a, 'b, 'static]` (where `'r` is some region appearing in
-    /// the hidden type).
-    ///
-    /// # Constrain regions, not the hidden concrete type
-    ///
-    /// Note that generating constraints on each region `Rc` is *not*
-    /// the same as generating an outlives constraint on `Tc` itself.
-    /// For example, if we had a function like this:
-    ///
-    /// ```
-    /// # #![feature(type_alias_impl_trait)]
-    /// # fn main() {}
-    /// # trait Foo<'a> {}
-    /// # impl<'a, T> Foo<'a> for (&'a u32, T) {}
-    /// fn foo<'a, T>(x: &'a u32, y: T) -> impl Foo<'a> {
-    ///   (x, y)
-    /// }
-    ///
-    /// // Equivalent to:
-    /// # mod dummy { use super::*;
-    /// type FooReturn<'a, T> = impl Foo<'a>;
-    /// fn foo<'a, T>(x: &'a u32, y: T) -> FooReturn<'a, T> {
-    ///   (x, y)
-    /// }
-    /// # }
-    /// ```
-    ///
-    /// then the hidden type `Tc` would be `(&'0 u32, T)` (where `'0`
-    /// is an inference variable). If we generated a constraint that
-    /// `Tc: 'a`, then this would incorrectly require that `T: 'a` --
-    /// but this is not necessary, because the opaque type we
-    /// create will be allowed to reference `T`. So we only generate a
-    /// constraint that `'0: 'a`.
-    #[instrument(level = "debug", skip(self))]
-    pub fn register_member_constraints(
-        &self,
-        opaque_type_key: OpaqueTypeKey<'tcx>,
-        concrete_ty: Ty<'tcx>,
-        span: Span,
-    ) {
-        let concrete_ty = self.resolve_vars_if_possible(concrete_ty);
-        debug!(?concrete_ty);
-
-        let variances = self.tcx.variances_of(opaque_type_key.def_id);
-        debug!(?variances);
-
-        // For a case like `impl Foo<'a, 'b>`, we would generate a constraint
-        // `'r in ['a, 'b, 'static]` for each region `'r` that appears in the
-        // hidden type (i.e., it must be equal to `'a`, `'b`, or `'static`).
-        //
-        // `conflict1` and `conflict2` are the two region bounds that we
-        // detected which were unrelated. They are used for diagnostics.
-
-        // Create the set of choice regions: each region in the hidden
-        // type can be equal to any of the region parameters of the
-        // opaque type definition.
-        let choice_regions: Lrc<Vec<ty::Region<'tcx>>> = Lrc::new(
-            opaque_type_key
-                .args
-                .iter()
-                .enumerate()
-                .filter(|(i, _)| variances[*i] == ty::Invariant)
-                .filter_map(|(_, arg)| match arg.unpack() {
-                    GenericArgKind::Lifetime(r) => Some(r),
-                    GenericArgKind::Type(_) | GenericArgKind::Const(_) => None,
-                })
-                .chain(std::iter::once(self.tcx.lifetimes.re_static))
-                .collect(),
-        );
-
-        // FIXME(#42940): This should use the `FreeRegionsVisitor`, but that's
-        // not currently sound until we have existential regions.
-        concrete_ty.visit_with(&mut ConstrainOpaqueTypeRegionVisitor {
-            tcx: self.tcx,
-            op: |r| {
-                self.member_constraint(
-                    opaque_type_key,
-                    span,
-                    concrete_ty,
-                    r,
-                    Lrc::clone(&choice_regions),
-                )
-            },
-        });
-    }
-}
-
-/// Visitor that requires that (almost) all regions in the type visited outlive
-/// `least_region`. We cannot use `push_outlives_components` because regions in
-/// closure signatures are not included in their outlives components. We need to
-/// ensure all regions outlive the given bound so that we don't end up with,
-/// say, `ReVar` appearing in a return type and causing ICEs when other
-/// functions end up with region constraints involving regions from other
-/// functions.
-///
-/// We also cannot use `for_each_free_region` because for closures it includes
-/// the regions parameters from the enclosing item.
-///
-/// We ignore any type parameters because impl trait values are assumed to
-/// capture all the in-scope type parameters.
-struct ConstrainOpaqueTypeRegionVisitor<'tcx, OP: FnMut(ty::Region<'tcx>)> {
-    tcx: TyCtxt<'tcx>,
-    op: OP,
-}
-
-impl<'tcx, OP> TypeVisitor<TyCtxt<'tcx>> for ConstrainOpaqueTypeRegionVisitor<'tcx, OP>
-where
-    OP: FnMut(ty::Region<'tcx>),
-{
-    fn visit_binder<T: TypeVisitable<TyCtxt<'tcx>>>(&mut self, t: &ty::Binder<'tcx, T>) {
-        t.super_visit_with(self);
-    }
-
-    fn visit_region(&mut self, r: ty::Region<'tcx>) {
-        match *r {
-            // ignore bound regions, keep visiting
-            ty::ReBound(_, _) => {}
-            _ => (self.op)(r),
-        }
-    }
-
-    fn visit_ty(&mut self, ty: Ty<'tcx>) {
-        // We're only interested in types involving regions
-        if !ty.flags().intersects(ty::TypeFlags::HAS_FREE_REGIONS) {
-            return;
-        }
-
-        match ty.kind() {
-            ty::Closure(_, args) => {
-                // Skip lifetime parameters of the enclosing item(s)
-
-                for upvar in args.as_closure().upvar_tys() {
-                    upvar.visit_with(self);
-                }
-                args.as_closure().sig_as_fn_ptr_ty().visit_with(self);
-            }
-
-            ty::CoroutineClosure(_, args) => {
-                // Skip lifetime parameters of the enclosing item(s)
-
-                for upvar in args.as_coroutine_closure().upvar_tys() {
-                    upvar.visit_with(self);
-                }
-
-                args.as_coroutine_closure().signature_parts_ty().visit_with(self);
-            }
-
-            ty::Coroutine(_, args) => {
-                // Skip lifetime parameters of the enclosing item(s)
-                // Also skip the witness type, because that has no free regions.
-
-                for upvar in args.as_coroutine().upvar_tys() {
-                    upvar.visit_with(self);
-                }
-                args.as_coroutine().return_ty().visit_with(self);
-                args.as_coroutine().yield_ty().visit_with(self);
-                args.as_coroutine().resume_ty().visit_with(self);
-            }
-
-            ty::Alias(ty::Opaque, ty::AliasTy { def_id, args, .. }) => {
-                // Skip lifetime parameters that are not captures.
-                let variances = self.tcx.variances_of(*def_id);
-
-                for (v, s) in std::iter::zip(variances, args.iter()) {
-                    if *v != ty::Bivariant {
-                        s.visit_with(self);
-                    }
-                }
-            }
-
-            _ => {
-                ty.super_visit_with(self);
-            }
-        }
-    }
 }
 
 impl<'tcx> InferCtxt<'tcx> {
diff --git a/compiler/rustc_infer/src/infer/region_constraints/mod.rs b/compiler/rustc_infer/src/infer/region_constraints/mod.rs
index 270217e26b7..6dce4b2b21d 100644
--- a/compiler/rustc_infer/src/infer/region_constraints/mod.rs
+++ b/compiler/rustc_infer/src/infer/region_constraints/mod.rs
@@ -4,7 +4,6 @@ use std::ops::Range;
 use std::{cmp, fmt, mem};
 
 use rustc_data_structures::fx::FxHashMap;
-use rustc_data_structures::sync::Lrc;
 use rustc_data_structures::undo_log::UndoLogs;
 use rustc_data_structures::unify as ut;
 use rustc_index::IndexVec;
@@ -12,7 +11,6 @@ use rustc_macros::{TypeFoldable, TypeVisitable};
 use rustc_middle::infer::unify_key::{RegionVariableValue, RegionVidKey};
 use rustc_middle::ty::{self, ReBound, ReStatic, ReVar, Region, RegionVid, Ty, TyCtxt};
 use rustc_middle::{bug, span_bug};
-use rustc_span::Span;
 use tracing::{debug, instrument};
 
 use self::CombineMapType::*;
@@ -22,8 +20,6 @@ use crate::infer::snapshot::undo_log::{InferCtxtUndoLogs, Snapshot};
 
 mod leak_check;
 
-pub use rustc_middle::infer::MemberConstraint;
-
 #[derive(Clone, Default)]
 pub struct RegionConstraintStorage<'tcx> {
     /// For each `RegionVid`, the corresponding `RegionVariableOrigin`.
@@ -73,11 +69,6 @@ pub struct RegionConstraintData<'tcx> {
     /// be a region variable (or neither, as it happens).
     pub constraints: Vec<(Constraint<'tcx>, SubregionOrigin<'tcx>)>,
 
-    /// Constraints of the form `R0 member of [R1, ..., Rn]`, meaning that
-    /// `R0` must be equal to one of the regions `R1..Rn`. These occur
-    /// with `impl Trait` quite frequently.
-    pub member_constraints: Vec<MemberConstraint<'tcx>>,
-
     /// A "verify" is something that we need to verify after inference
     /// is done, but which does not directly affect inference in any
     /// way.
@@ -466,29 +457,6 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
         }
     }
 
-    pub(super) fn member_constraint(
-        &mut self,
-        key: ty::OpaqueTypeKey<'tcx>,
-        definition_span: Span,
-        hidden_ty: Ty<'tcx>,
-        member_region: ty::Region<'tcx>,
-        choice_regions: Lrc<Vec<ty::Region<'tcx>>>,
-    ) {
-        debug!("member_constraint({:?} in {:#?})", member_region, choice_regions);
-
-        if choice_regions.iter().any(|&r| r == member_region) {
-            return;
-        }
-
-        self.storage.data.member_constraints.push(MemberConstraint {
-            key,
-            definition_span,
-            hidden_ty,
-            member_region,
-            choice_regions,
-        });
-    }
-
     #[instrument(skip(self, origin), level = "debug")]
     pub(super) fn make_subregion(
         &mut self,
@@ -745,8 +713,8 @@ impl<'tcx> RegionConstraintData<'tcx> {
     /// Returns `true` if this region constraint data contains no constraints, and `false`
     /// otherwise.
     pub fn is_empty(&self) -> bool {
-        let RegionConstraintData { constraints, member_constraints, verifys } = self;
-        constraints.is_empty() && member_constraints.is_empty() && verifys.is_empty()
+        let RegionConstraintData { constraints, verifys } = self;
+        constraints.is_empty() && verifys.is_empty()
     }
 }
 
diff --git a/compiler/rustc_infer/src/traits/util.rs b/compiler/rustc_infer/src/traits/util.rs
index a977bd15d3b..ab8ada1596c 100644
--- a/compiler/rustc_infer/src/traits/util.rs
+++ b/compiler/rustc_infer/src/traits/util.rs
@@ -1,7 +1,6 @@
 use rustc_data_structures::fx::FxHashSet;
 use rustc_middle::ty::{self, ToPolyTraitRef, TyCtxt};
-use rustc_span::Span;
-use rustc_span::symbol::Ident;
+use rustc_span::{Ident, Span};
 pub use rustc_type_ir::elaborate::*;
 
 use crate::traits::{self, Obligation, ObligationCauseCode, PredicateObligation};
diff --git a/compiler/rustc_interface/Cargo.toml b/compiler/rustc_interface/Cargo.toml
index 7a2ba07ce87..dcb9c5d22d6 100644
--- a/compiler/rustc_interface/Cargo.toml
+++ b/compiler/rustc_interface/Cargo.toml
@@ -11,7 +11,7 @@ rustc_ast = { path = "../rustc_ast" }
 rustc_ast_lowering = { path = "../rustc_ast_lowering" }
 rustc_ast_passes = { path = "../rustc_ast_passes" }
 rustc_ast_pretty = { path = "../rustc_ast_pretty" }
-rustc_attr = { path = "../rustc_attr" }
+rustc_attr_parsing = { path = "../rustc_attr_parsing" }
 rustc_borrowck = { path = "../rustc_borrowck" }
 rustc_builtin_macros = { path = "../rustc_builtin_macros" }
 rustc_codegen_llvm = { path = "../rustc_codegen_llvm", optional = true }
diff --git a/compiler/rustc_interface/src/interface.rs b/compiler/rustc_interface/src/interface.rs
index 91f190c6a28..1456255ea14 100644
--- a/compiler/rustc_interface/src/interface.rs
+++ b/compiler/rustc_interface/src/interface.rs
@@ -22,9 +22,8 @@ use rustc_session::config::{self, Cfg, CheckCfg, ExpectedValues, Input, OutFileN
 use rustc_session::filesearch::{self, sysroot_candidates};
 use rustc_session::parse::ParseSess;
 use rustc_session::{CompilerIO, EarlyDiagCtxt, Session, lint};
-use rustc_span::FileName;
 use rustc_span::source_map::{FileLoader, RealFileLoader, SourceMapInputs};
-use rustc_span::symbol::sym;
+use rustc_span::{FileName, sym};
 use tracing::trace;
 
 use crate::util;
diff --git a/compiler/rustc_interface/src/lib.rs b/compiler/rustc_interface/src/lib.rs
index 1c4dda2a436..a2a29612e48 100644
--- a/compiler/rustc_interface/src/lib.rs
+++ b/compiler/rustc_interface/src/lib.rs
@@ -8,7 +8,7 @@
 // tidy-alphabetical-end
 
 mod callbacks;
-mod errors;
+pub mod errors;
 pub mod interface;
 pub mod passes;
 mod proc_macro_decls;
@@ -17,8 +17,8 @@ pub mod util;
 
 pub use callbacks::setup_callbacks;
 pub use interface::{Config, run_compiler};
-pub use passes::DEFAULT_QUERY_PROVIDERS;
-pub use queries::{Linker, Queries};
+pub use passes::{DEFAULT_QUERY_PROVIDERS, create_and_enter_global_ctxt, parse};
+pub use queries::Linker;
 
 #[cfg(test)]
 mod tests;
diff --git a/compiler/rustc_interface/src/passes.rs b/compiler/rustc_interface/src/passes.rs
index 430bc7db077..aff66e48fbb 100644
--- a/compiler/rustc_interface/src/passes.rs
+++ b/compiler/rustc_interface/src/passes.rs
@@ -19,7 +19,7 @@ use rustc_incremental::setup_dep_graph;
 use rustc_lint::{BufferedEarlyLint, EarlyCheckNode, LintStore, unerased_lint_store};
 use rustc_metadata::creader::CStore;
 use rustc_middle::arena::Arena;
-use rustc_middle::ty::{self, GlobalCtxt, RegisteredTools, TyCtxt};
+use rustc_middle::ty::{self, CurrentGcx, GlobalCtxt, RegisteredTools, TyCtxt};
 use rustc_middle::util::Providers;
 use rustc_parse::{
     new_parser_from_file, new_parser_from_source_str, unwrap_or_emit_fatal, validate_attr,
@@ -32,8 +32,7 @@ use rustc_session::cstore::Untracked;
 use rustc_session::output::{collect_crate_types, filename_for_input, find_crate_name};
 use rustc_session::search_paths::PathKind;
 use rustc_session::{Limit, Session};
-use rustc_span::symbol::{Symbol, sym};
-use rustc_span::{ErrorGuaranteed, FileName, SourceFileHash, SourceFileHashAlgorithm};
+use rustc_span::{ErrorGuaranteed, FileName, SourceFileHash, SourceFileHashAlgorithm, Symbol, sym};
 use rustc_target::spec::PanicStrategy;
 use rustc_trait_selection::traits;
 use tracing::{info, instrument};
@@ -41,7 +40,7 @@ use tracing::{info, instrument};
 use crate::interface::Compiler;
 use crate::{errors, proc_macro_decls, util};
 
-pub(crate) fn parse<'a>(sess: &'a Session) -> ast::Crate {
+pub fn parse<'a>(sess: &'a Session) -> ast::Crate {
     let krate = sess
         .time("parse_crate", || {
             let mut parser = unwrap_or_emit_fatal(match &sess.io.input {
@@ -76,6 +75,7 @@ fn pre_expansion_lint<'a>(
         || {
             rustc_lint::check_ast_node(
                 sess,
+                None,
                 features,
                 true,
                 lint_store,
@@ -310,6 +310,7 @@ fn early_lint_checks(tcx: TyCtxt<'_>, (): ()) {
     let lint_store = unerased_lint_store(tcx.sess);
     rustc_lint::check_ast_node(
         sess,
+        Some(tcx),
         tcx.features(),
         false,
         lint_store,
@@ -709,13 +710,11 @@ pub static DEFAULT_QUERY_PROVIDERS: LazyLock<Providers> = LazyLock::new(|| {
     *providers
 });
 
-pub(crate) fn create_global_ctxt<'tcx>(
-    compiler: &'tcx Compiler,
+pub fn create_and_enter_global_ctxt<T, F: for<'tcx> FnOnce(TyCtxt<'tcx>) -> T>(
+    compiler: &Compiler,
     mut krate: rustc_ast::Crate,
-    gcx_cell: &'tcx OnceLock<GlobalCtxt<'tcx>>,
-    arena: &'tcx WorkerLocal<Arena<'tcx>>,
-    hir_arena: &'tcx WorkerLocal<rustc_hir::Arena<'tcx>>,
-) -> &'tcx GlobalCtxt<'tcx> {
+    f: F,
+) -> T {
     let sess = &compiler.sess;
 
     rustc_builtin_macros::cmdline_attrs::inject(
@@ -763,44 +762,63 @@ pub(crate) fn create_global_ctxt<'tcx>(
 
     let incremental = dep_graph.is_fully_enabled();
 
-    sess.time("setup_global_ctxt", || {
-        let qcx = gcx_cell.get_or_init(move || {
-            TyCtxt::create_global_ctxt(
-                sess,
-                crate_types,
-                stable_crate_id,
-                arena,
-                hir_arena,
-                untracked,
-                dep_graph,
-                rustc_query_impl::query_callbacks(arena),
-                rustc_query_impl::query_system(
-                    providers.queries,
-                    providers.extern_queries,
-                    query_result_on_disk_cache,
-                    incremental,
-                ),
-                providers.hooks,
-                compiler.current_gcx.clone(),
-            )
-        });
-
-        qcx.enter(|tcx| {
-            let feed = tcx.create_crate_num(stable_crate_id).unwrap();
-            assert_eq!(feed.key(), LOCAL_CRATE);
-            feed.crate_name(crate_name);
+    let gcx_cell = OnceLock::new();
+    let arena = WorkerLocal::new(|_| Arena::default());
+    let hir_arena = WorkerLocal::new(|_| rustc_hir::Arena::default());
+
+    // This closure is necessary to force rustc to perform the correct lifetime
+    // subtyping for GlobalCtxt::enter to be allowed.
+    let inner: Box<
+        dyn for<'tcx> FnOnce(
+            &'tcx Session,
+            CurrentGcx,
+            &'tcx OnceLock<GlobalCtxt<'tcx>>,
+            &'tcx WorkerLocal<Arena<'tcx>>,
+            &'tcx WorkerLocal<rustc_hir::Arena<'tcx>>,
+            F,
+        ) -> T,
+    > = Box::new(move |sess, current_gcx, gcx_cell, arena, hir_arena, f| {
+        TyCtxt::create_global_ctxt(
+            gcx_cell,
+            sess,
+            crate_types,
+            stable_crate_id,
+            arena,
+            hir_arena,
+            untracked,
+            dep_graph,
+            rustc_query_impl::query_callbacks(arena),
+            rustc_query_impl::query_system(
+                providers.queries,
+                providers.extern_queries,
+                query_result_on_disk_cache,
+                incremental,
+            ),
+            providers.hooks,
+            current_gcx,
+            |tcx| {
+                let feed = tcx.create_crate_num(stable_crate_id).unwrap();
+                assert_eq!(feed.key(), LOCAL_CRATE);
+                feed.crate_name(crate_name);
+
+                let feed = tcx.feed_unit_query();
+                feed.features_query(tcx.arena.alloc(rustc_expand::config::features(
+                    tcx.sess,
+                    &pre_configured_attrs,
+                    crate_name,
+                )));
+                feed.crate_for_resolver(tcx.arena.alloc(Steal::new((krate, pre_configured_attrs))));
+                feed.output_filenames(Arc::new(outputs));
+
+                let res = f(tcx);
+                // FIXME maybe run finish even when a fatal error occured? or at least tcx.alloc_self_profile_query_strings()?
+                tcx.finish();
+                res
+            },
+        )
+    });
 
-            let feed = tcx.feed_unit_query();
-            feed.features_query(tcx.arena.alloc(rustc_expand::config::features(
-                sess,
-                &pre_configured_attrs,
-                crate_name,
-            )));
-            feed.crate_for_resolver(tcx.arena.alloc(Steal::new((krate, pre_configured_attrs))));
-            feed.output_filenames(Arc::new(outputs));
-        });
-        qcx
-    })
+    inner(&compiler.sess, compiler.current_gcx.clone(), &gcx_cell, &arena, &hir_arena, f)
 }
 
 /// Runs all analyses that we guarantee to run, even if errors were reported in earlier analyses.
diff --git a/compiler/rustc_interface/src/proc_macro_decls.rs b/compiler/rustc_interface/src/proc_macro_decls.rs
index 2c8014d8b3a..82593dbc2b7 100644
--- a/compiler/rustc_interface/src/proc_macro_decls.rs
+++ b/compiler/rustc_interface/src/proc_macro_decls.rs
@@ -2,7 +2,7 @@ use rustc_ast::attr;
 use rustc_hir::def_id::LocalDefId;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::TyCtxt;
-use rustc_span::symbol::sym;
+use rustc_span::sym;
 
 fn proc_macro_decls_static(tcx: TyCtxt<'_>, (): ()) -> Option<LocalDefId> {
     let mut decls = None;
diff --git a/compiler/rustc_interface/src/queries.rs b/compiler/rustc_interface/src/queries.rs
index bb2ad3b3dd0..c8914c9be9c 100644
--- a/compiler/rustc_interface/src/queries.rs
+++ b/compiler/rustc_interface/src/queries.rs
@@ -1,117 +1,18 @@
 use std::any::Any;
-use std::cell::{RefCell, RefMut};
 use std::sync::Arc;
 
-use rustc_ast as ast;
 use rustc_codegen_ssa::CodegenResults;
 use rustc_codegen_ssa::traits::CodegenBackend;
-use rustc_data_structures::steal::Steal;
 use rustc_data_structures::svh::Svh;
-use rustc_data_structures::sync::{OnceLock, WorkerLocal};
 use rustc_hir::def_id::LOCAL_CRATE;
-use rustc_middle::arena::Arena;
 use rustc_middle::dep_graph::DepGraph;
-use rustc_middle::ty::{GlobalCtxt, TyCtxt};
+use rustc_middle::ty::TyCtxt;
 use rustc_session::Session;
 use rustc_session::config::{self, OutputFilenames, OutputType};
 
 use crate::errors::FailedWritingFile;
-use crate::interface::Compiler;
 use crate::passes;
 
-/// Represent the result of a query.
-///
-/// This result can be stolen once with the [`steal`] method and generated with the [`compute`] method.
-///
-/// [`steal`]: Steal::steal
-/// [`compute`]: Self::compute
-pub struct Query<T> {
-    /// `None` means no value has been computed yet.
-    result: RefCell<Option<Steal<T>>>,
-}
-
-impl<T> Query<T> {
-    fn compute<F: FnOnce() -> T>(&self, f: F) -> QueryResult<'_, T> {
-        QueryResult(RefMut::map(
-            self.result.borrow_mut(),
-            |r: &mut Option<Steal<T>>| -> &mut Steal<T> {
-                r.get_or_insert_with(|| Steal::new(f()))
-            },
-        ))
-    }
-}
-
-pub struct QueryResult<'a, T>(RefMut<'a, Steal<T>>);
-
-impl<'a, T> std::ops::Deref for QueryResult<'a, T> {
-    type Target = RefMut<'a, Steal<T>>;
-
-    fn deref(&self) -> &Self::Target {
-        &self.0
-    }
-}
-
-impl<'a, T> std::ops::DerefMut for QueryResult<'a, T> {
-    fn deref_mut(&mut self) -> &mut Self::Target {
-        &mut self.0
-    }
-}
-
-impl<'a, 'tcx> QueryResult<'a, &'tcx GlobalCtxt<'tcx>> {
-    pub fn enter<T>(&mut self, f: impl FnOnce(TyCtxt<'tcx>) -> T) -> T {
-        (*self.0).borrow().enter(f)
-    }
-}
-
-pub struct Queries<'tcx> {
-    compiler: &'tcx Compiler,
-    gcx_cell: OnceLock<GlobalCtxt<'tcx>>,
-
-    arena: WorkerLocal<Arena<'tcx>>,
-    hir_arena: WorkerLocal<rustc_hir::Arena<'tcx>>,
-
-    parse: Query<ast::Crate>,
-    // This just points to what's in `gcx_cell`.
-    gcx: Query<&'tcx GlobalCtxt<'tcx>>,
-}
-
-impl<'tcx> Queries<'tcx> {
-    pub fn new(compiler: &'tcx Compiler) -> Queries<'tcx> {
-        Queries {
-            compiler,
-            gcx_cell: OnceLock::new(),
-            arena: WorkerLocal::new(|_| Arena::default()),
-            hir_arena: WorkerLocal::new(|_| rustc_hir::Arena::default()),
-            parse: Query { result: RefCell::new(None) },
-            gcx: Query { result: RefCell::new(None) },
-        }
-    }
-
-    pub fn finish(&'tcx self) {
-        if let Some(gcx) = self.gcx_cell.get() {
-            gcx.finish();
-        }
-    }
-
-    pub fn parse(&self) -> QueryResult<'_, ast::Crate> {
-        self.parse.compute(|| passes::parse(&self.compiler.sess))
-    }
-
-    pub fn global_ctxt(&'tcx self) -> QueryResult<'tcx, &'tcx GlobalCtxt<'tcx>> {
-        self.gcx.compute(|| {
-            let krate = self.parse().steal();
-
-            passes::create_global_ctxt(
-                self.compiler,
-                krate,
-                &self.gcx_cell,
-                &self.arena,
-                &self.hir_arena,
-            )
-        })
-    }
-}
-
 pub struct Linker {
     dep_graph: DepGraph,
     output_filenames: Arc<OutputFilenames>,
@@ -186,22 +87,3 @@ impl Linker {
         codegen_backend.link(sess, codegen_results, &self.output_filenames)
     }
 }
-
-impl Compiler {
-    pub fn enter<F, T>(&self, f: F) -> T
-    where
-        F: for<'tcx> FnOnce(&'tcx Queries<'tcx>) -> T,
-    {
-        // Must declare `_timer` first so that it is dropped after `queries`.
-        let _timer;
-        let queries = Queries::new(self);
-        let ret = f(&queries);
-
-        // The timer's lifetime spans the dropping of `queries`, which contains
-        // the global context.
-        _timer = self.sess.timer("free_global_ctxt");
-        queries.finish();
-
-        ret
-    }
-}
diff --git a/compiler/rustc_interface/src/tests.rs b/compiler/rustc_interface/src/tests.rs
index e76e9ca9f85..9ad69039914 100644
--- a/compiler/rustc_interface/src/tests.rs
+++ b/compiler/rustc_interface/src/tests.rs
@@ -23,8 +23,7 @@ use rustc_session::utils::{CanonicalizedPath, NativeLib, NativeLibKind};
 use rustc_session::{CompilerIO, EarlyDiagCtxt, Session, build_session, filesearch, getopts};
 use rustc_span::edition::{DEFAULT_EDITION, Edition};
 use rustc_span::source_map::{RealFileLoader, SourceMapInputs};
-use rustc_span::symbol::sym;
-use rustc_span::{FileName, SourceFileHashAlgorithm};
+use rustc_span::{FileName, SourceFileHashAlgorithm, sym};
 use rustc_target::spec::{
     CodeModel, FramePointer, LinkerFlavorCli, MergeFunctions, OnBrokenPipe, PanicStrategy,
     RelocModel, RelroLevel, SanitizerSet, SplitDebuginfo, StackProtector, TlsModel, WasmCAbi,
@@ -767,7 +766,11 @@ fn test_unstable_options_tracking_hash() {
         })
     );
     tracked!(codegen_backend, Some("abc".to_string()));
-    tracked!(coverage_options, CoverageOptions { level: CoverageLevel::Mcdc, no_mir_spans: true });
+    tracked!(coverage_options, CoverageOptions {
+        level: CoverageLevel::Mcdc,
+        no_mir_spans: true,
+        discard_all_spans_in_codegen: true
+    });
     tracked!(crate_attr, vec!["abc".to_string()]);
     tracked!(cross_crate_inline_threshold, InliningThreshold::Always);
     tracked!(debug_info_for_profiling, true);
diff --git a/compiler/rustc_interface/src/util.rs b/compiler/rustc_interface/src/util.rs
index 2af25bfd3aa..984b8104f53 100644
--- a/compiler/rustc_interface/src/util.rs
+++ b/compiler/rustc_interface/src/util.rs
@@ -18,7 +18,7 @@ use rustc_session::{EarlyDiagCtxt, Session, filesearch};
 use rustc_span::edit_distance::find_best_match_for_name;
 use rustc_span::edition::Edition;
 use rustc_span::source_map::SourceMapInputs;
-use rustc_span::symbol::sym;
+use rustc_span::sym;
 use rustc_target::spec::Target;
 use tracing::info;
 
@@ -453,7 +453,7 @@ pub fn build_output_filenames(attrs: &[ast::Attribute], sess: &Session) -> Outpu
         .opts
         .crate_name
         .clone()
-        .or_else(|| rustc_attr::find_crate_name(attrs).map(|n| n.to_string()));
+        .or_else(|| rustc_attr_parsing::find_crate_name(attrs).map(|n| n.to_string()));
 
     match sess.io.output_file {
         None => {
diff --git a/compiler/rustc_lint/Cargo.toml b/compiler/rustc_lint/Cargo.toml
index ec5f0f06c59..cc5a9029633 100644
--- a/compiler/rustc_lint/Cargo.toml
+++ b/compiler/rustc_lint/Cargo.toml
@@ -8,7 +8,7 @@ edition = "2021"
 rustc_abi = { path = "../rustc_abi" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_ast_pretty = { path = "../rustc_ast_pretty" }
-rustc_attr = { path = "../rustc_attr" }
+rustc_attr_parsing = { path = "../rustc_attr_parsing" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
 rustc_feature = { path = "../rustc_feature" }
diff --git a/compiler/rustc_lint/messages.ftl b/compiler/rustc_lint/messages.ftl
index 01d9ac20fae..7522e21d0ef 100644
--- a/compiler/rustc_lint/messages.ftl
+++ b/compiler/rustc_lint/messages.ftl
@@ -536,9 +536,6 @@ lint_non_camel_case_type = {$sort} `{$name}` should have an upper camel case nam
     .suggestion = convert the identifier to upper camel case
     .label = should have an UpperCamelCase name
 
-lint_non_existent_doc_keyword = found non-existing keyword `{$keyword}` used in `#[doc(keyword = "...")]`
-    .help = only existing keywords are allowed in core/std
-
 lint_non_fmt_panic = panic message is not a string literal
     .note = this usage of `{$name}!()` is deprecated; it will be a hard error in Rust 2021
     .more_info_note = for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/panic-macro-consistency.html>
@@ -806,14 +803,14 @@ lint_unexpected_cfg_add_build_rs_println = or consider adding `{$build_rs_printl
 lint_unexpected_cfg_add_cargo_feature = consider using a Cargo feature instead
 lint_unexpected_cfg_add_cargo_toml_lint_cfg = or consider adding in `Cargo.toml` the `check-cfg` lint config for the lint:{$cargo_toml_lint_cfg}
 lint_unexpected_cfg_add_cmdline_arg = to expect this configuration use `{$cmdline_arg}`
-lint_unexpected_cfg_cargo_update = the {$macro_kind} `{$macro_name}` may come from an old version of it's defining crate, try updating your dependencies with `cargo update`
+lint_unexpected_cfg_cargo_update = the {$macro_kind} `{$macro_name}` may come from an old version of the `{$crate_name}` crate, try updating your dependency with `cargo update -p {$crate_name}`
 
 lint_unexpected_cfg_define_features = consider defining some features in `Cargo.toml`
 lint_unexpected_cfg_doc_cargo = see <https://doc.rust-lang.org/nightly/rustc/check-cfg/cargo-specifics.html> for more information about checking conditional configuration
 lint_unexpected_cfg_doc_rustc = see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
 
 lint_unexpected_cfg_from_external_macro_origin = using a cfg inside a {$macro_kind} will use the cfgs from the destination crate and not the ones from the defining crate
-lint_unexpected_cfg_from_external_macro_refer = try refering to `{$macro_name}` crate for guidance on how handle this unexpected cfg
+lint_unexpected_cfg_from_external_macro_refer = try referring to `{$macro_name}` crate for guidance on how handle this unexpected cfg
 lint_unexpected_cfg_name = unexpected `cfg` condition name: `{$name}`
 lint_unexpected_cfg_name_expected_names = expected names are: {$possibilities}{$and_more ->
         [0] {""}
diff --git a/compiler/rustc_lint/src/builtin.rs b/compiler/rustc_lint/src/builtin.rs
index 3543784bc72..6e823957cc6 100644
--- a/compiler/rustc_lint/src/builtin.rs
+++ b/compiler/rustc_lint/src/builtin.rs
@@ -39,8 +39,7 @@ pub use rustc_session::lint::builtin::*;
 use rustc_session::{declare_lint, declare_lint_pass, impl_lint_pass};
 use rustc_span::edition::Edition;
 use rustc_span::source_map::Spanned;
-use rustc_span::symbol::{Ident, Symbol, kw, sym};
-use rustc_span::{BytePos, InnerSpan, Span};
+use rustc_span::{BytePos, Ident, InnerSpan, Span, Symbol, kw, sym};
 use rustc_target::asm::InlineAsmArch;
 use rustc_trait_selection::infer::{InferCtxtExt, TyCtxtInferExt};
 use rustc_trait_selection::traits::misc::type_allowed_to_implement_copy;
@@ -387,7 +386,7 @@ pub struct MissingDoc;
 
 impl_lint_pass!(MissingDoc => [MISSING_DOCS]);
 
-fn has_doc(attr: &ast::Attribute) -> bool {
+fn has_doc(attr: &hir::Attribute) -> bool {
     if attr.is_doc_comment() {
         return true;
     }
@@ -1012,7 +1011,7 @@ declare_lint_pass!(InvalidNoMangleItems => [NO_MANGLE_CONST_ITEMS, NO_MANGLE_GEN
 impl<'tcx> LateLintPass<'tcx> for InvalidNoMangleItems {
     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
         let attrs = cx.tcx.hir().attrs(it.hir_id());
-        let check_no_mangle_on_generic_fn = |no_mangle_attr: &ast::Attribute,
+        let check_no_mangle_on_generic_fn = |no_mangle_attr: &hir::Attribute,
                                              impl_generics: Option<&hir::Generics<'_>>,
                                              generics: &hir::Generics<'_>,
                                              span| {
@@ -1176,7 +1175,7 @@ declare_lint_pass!(
 );
 
 impl<'tcx> LateLintPass<'tcx> for UnstableFeatures {
-    fn check_attribute(&mut self, cx: &LateContext<'_>, attr: &ast::Attribute) {
+    fn check_attribute(&mut self, cx: &LateContext<'_>, attr: &hir::Attribute) {
         if attr.has_name(sym::feature)
             && let Some(items) = attr.meta_item_list()
         {
@@ -1814,7 +1813,7 @@ declare_lint! {
     "detects edition keywords being used as an identifier",
     @future_incompatible = FutureIncompatibleInfo {
         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2024),
-        reference: "issue #49716 <https://github.com/rust-lang/rust/issues/49716>",
+        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2024/gen-keyword.html>",
     };
 }
 
@@ -1829,7 +1828,7 @@ impl KeywordIdents {
     fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: &TokenStream) {
         // Check if the preceding token is `$`, because we want to allow `$async`, etc.
         let mut prev_dollar = false;
-        for tt in tokens.trees() {
+        for tt in tokens.iter() {
             match tt {
                 // Only report non-raw idents.
                 TokenTree::Token(token, _) => {
diff --git a/compiler/rustc_lint/src/context.rs b/compiler/rustc_lint/src/context.rs
index 44c7888a530..50bb1fb942e 100644
--- a/compiler/rustc_lint/src/context.rs
+++ b/compiler/rustc_lint/src/context.rs
@@ -20,12 +20,11 @@ use rustc_middle::ty::layout::{LayoutError, LayoutOfHelpers, TyAndLayout};
 use rustc_middle::ty::print::{PrintError, PrintTraitRefExt as _, Printer, with_no_trimmed_paths};
 use rustc_middle::ty::{self, GenericArg, RegisteredTools, Ty, TyCtxt, TypingEnv, TypingMode};
 use rustc_session::lint::{
-    BuiltinLintDiag, FutureIncompatibleInfo, Level, Lint, LintBuffer, LintExpectationId, LintId,
+    FutureIncompatibleInfo, Level, Lint, LintBuffer, LintExpectationId, LintId,
 };
 use rustc_session::{LintStoreMarker, Session};
-use rustc_span::Span;
 use rustc_span::edit_distance::find_best_match_for_names;
-use rustc_span::symbol::{Ident, Symbol, sym};
+use rustc_span::{Ident, Span, Symbol, sym};
 use tracing::debug;
 use {rustc_abi as abi, rustc_hir as hir};
 
@@ -33,8 +32,6 @@ use self::TargetLint::*;
 use crate::levels::LintLevelsBuilder;
 use crate::passes::{EarlyLintPassObject, LateLintPassObject};
 
-mod diagnostics;
-
 type EarlyLintPassFactory = dyn Fn() -> EarlyLintPassObject + sync::DynSend + sync::DynSync;
 type LateLintPassFactory =
     dyn for<'tcx> Fn(TyCtxt<'tcx>) -> LateLintPassObject<'tcx> + sync::DynSend + sync::DynSync;
@@ -511,38 +508,6 @@ pub struct EarlyContext<'a> {
     pub buffered: LintBuffer,
 }
 
-impl EarlyContext<'_> {
-    /// Emit a lint at the appropriate level, with an associated span and an existing
-    /// diagnostic.
-    ///
-    /// [`lint_level`]: rustc_middle::lint::lint_level#decorate-signature
-    #[rustc_lint_diagnostics]
-    pub fn span_lint_with_diagnostics(
-        &self,
-        lint: &'static Lint,
-        span: MultiSpan,
-        diagnostic: BuiltinLintDiag,
-    ) {
-        self.opt_span_lint_with_diagnostics(lint, Some(span), diagnostic);
-    }
-
-    /// Emit a lint at the appropriate level, with an optional associated span and an existing
-    /// diagnostic.
-    ///
-    /// [`lint_level`]: rustc_middle::lint::lint_level#decorate-signature
-    #[rustc_lint_diagnostics]
-    pub fn opt_span_lint_with_diagnostics(
-        &self,
-        lint: &'static Lint,
-        span: Option<MultiSpan>,
-        diagnostic: BuiltinLintDiag,
-    ) {
-        self.opt_span_lint(lint, span, |diag| {
-            diagnostics::decorate_lint(self.sess(), diagnostic, diag);
-        });
-    }
-}
-
 pub trait LintContext {
     fn sess(&self) -> &Session;
 
diff --git a/compiler/rustc_lint/src/dangling.rs b/compiler/rustc_lint/src/dangling.rs
index 10769b57a76..98b717a3070 100644
--- a/compiler/rustc_lint/src/dangling.rs
+++ b/compiler/rustc_lint/src/dangling.rs
@@ -4,8 +4,7 @@ use rustc_hir::intravisit::{FnKind, Visitor, walk_expr};
 use rustc_hir::{Block, Body, Expr, ExprKind, FnDecl, LangItem};
 use rustc_middle::ty::{Ty, TyCtxt};
 use rustc_session::{declare_lint, impl_lint_pass};
-use rustc_span::Span;
-use rustc_span::symbol::sym;
+use rustc_span::{Span, sym};
 
 use crate::lints::DanglingPointersFromTemporaries;
 use crate::{LateContext, LateLintPass};
diff --git a/compiler/rustc_lint/src/early.rs b/compiler/rustc_lint/src/early.rs
index a68a2a7f983..bc7cd3d118c 100644
--- a/compiler/rustc_lint/src/early.rs
+++ b/compiler/rustc_lint/src/early.rs
@@ -9,35 +9,39 @@ use rustc_ast::visit::{self as ast_visit, Visitor, walk_list};
 use rustc_ast::{self as ast, HasAttrs};
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_feature::Features;
-use rustc_middle::ty::RegisteredTools;
+use rustc_middle::ty::{RegisteredTools, TyCtxt};
 use rustc_session::Session;
 use rustc_session::lint::{BufferedEarlyLint, LintBuffer, LintPass};
-use rustc_span::Span;
-use rustc_span::symbol::Ident;
+use rustc_span::{Ident, Span};
 use tracing::debug;
 
-use crate::context::{EarlyContext, LintStore};
+use crate::context::{EarlyContext, LintContext, LintStore};
 use crate::passes::{EarlyLintPass, EarlyLintPassObject};
 
+mod diagnostics;
+
 macro_rules! lint_callback { ($cx:expr, $f:ident, $($args:expr),*) => ({
     $cx.pass.$f(&$cx.context, $($args),*);
 }) }
 
 /// Implements the AST traversal for early lint passes. `T` provides the
 /// `check_*` methods.
-pub struct EarlyContextAndPass<'a, T: EarlyLintPass> {
-    context: EarlyContext<'a>,
+pub struct EarlyContextAndPass<'ecx, 'tcx, T: EarlyLintPass> {
+    context: EarlyContext<'ecx>,
+    tcx: Option<TyCtxt<'tcx>>,
     pass: T,
 }
 
-impl<'a, T: EarlyLintPass> EarlyContextAndPass<'a, T> {
+impl<'ecx, 'tcx, T: EarlyLintPass> EarlyContextAndPass<'ecx, 'tcx, T> {
     // This always-inlined function is for the hot call site.
     #[inline(always)]
     #[allow(rustc::diagnostic_outside_of_impl)]
     fn inlined_check_id(&mut self, id: ast::NodeId) {
         for early_lint in self.context.buffered.take(id) {
             let BufferedEarlyLint { span, node_id: _, lint_id, diagnostic } = early_lint;
-            self.context.opt_span_lint_with_diagnostics(lint_id.lint, span, diagnostic);
+            self.context.opt_span_lint(lint_id.lint, span, |diag| {
+                diagnostics::decorate_lint(self.context.sess(), self.tcx, diagnostic, diag);
+            });
         }
     }
 
@@ -49,7 +53,7 @@ impl<'a, T: EarlyLintPass> EarlyContextAndPass<'a, T> {
     /// Merge the lints specified by any lint attributes into the
     /// current lint context, call the provided function, then reset the
     /// lints in effect to their previous state.
-    fn with_lint_attrs<F>(&mut self, id: ast::NodeId, attrs: &'a [ast::Attribute], f: F)
+    fn with_lint_attrs<F>(&mut self, id: ast::NodeId, attrs: &'_ [ast::Attribute], f: F)
     where
         F: FnOnce(&mut Self),
     {
@@ -67,19 +71,21 @@ impl<'a, T: EarlyLintPass> EarlyContextAndPass<'a, T> {
     }
 }
 
-impl<'a, T: EarlyLintPass> ast_visit::Visitor<'a> for EarlyContextAndPass<'a, T> {
-    fn visit_coroutine_kind(&mut self, coroutine_kind: &'a ast::CoroutineKind) -> Self::Result {
+impl<'ast, 'ecx, 'tcx, T: EarlyLintPass> ast_visit::Visitor<'ast>
+    for EarlyContextAndPass<'ecx, 'tcx, T>
+{
+    fn visit_coroutine_kind(&mut self, coroutine_kind: &'ast ast::CoroutineKind) -> Self::Result {
         self.check_id(coroutine_kind.closure_id());
     }
 
-    fn visit_param(&mut self, param: &'a ast::Param) {
+    fn visit_param(&mut self, param: &'ast ast::Param) {
         self.with_lint_attrs(param.id, &param.attrs, |cx| {
             lint_callback!(cx, check_param, param);
             ast_visit::walk_param(cx, param);
         });
     }
 
-    fn visit_item(&mut self, it: &'a ast::Item) {
+    fn visit_item(&mut self, it: &'ast ast::Item) {
         self.with_lint_attrs(it.id, &it.attrs, |cx| {
             lint_callback!(cx, check_item, it);
             ast_visit::walk_item(cx, it);
@@ -87,31 +93,31 @@ impl<'a, T: EarlyLintPass> ast_visit::Visitor<'a> for EarlyContextAndPass<'a, T>
         })
     }
 
-    fn visit_foreign_item(&mut self, it: &'a ast::ForeignItem) {
+    fn visit_foreign_item(&mut self, it: &'ast ast::ForeignItem) {
         self.with_lint_attrs(it.id, &it.attrs, |cx| {
             ast_visit::walk_item(cx, it);
         })
     }
 
-    fn visit_pat(&mut self, p: &'a ast::Pat) {
+    fn visit_pat(&mut self, p: &'ast ast::Pat) {
         lint_callback!(self, check_pat, p);
         self.check_id(p.id);
         ast_visit::walk_pat(self, p);
         lint_callback!(self, check_pat_post, p);
     }
 
-    fn visit_pat_field(&mut self, field: &'a ast::PatField) {
+    fn visit_pat_field(&mut self, field: &'ast ast::PatField) {
         self.with_lint_attrs(field.id, &field.attrs, |cx| {
             ast_visit::walk_pat_field(cx, field);
         });
     }
 
-    fn visit_anon_const(&mut self, c: &'a ast::AnonConst) {
+    fn visit_anon_const(&mut self, c: &'ast ast::AnonConst) {
         self.check_id(c.id);
         ast_visit::walk_anon_const(self, c);
     }
 
-    fn visit_expr(&mut self, e: &'a ast::Expr) {
+    fn visit_expr(&mut self, e: &'ast ast::Expr) {
         self.with_lint_attrs(e.id, &e.attrs, |cx| {
             lint_callback!(cx, check_expr, e);
             ast_visit::walk_expr(cx, e);
@@ -119,13 +125,13 @@ impl<'a, T: EarlyLintPass> ast_visit::Visitor<'a> for EarlyContextAndPass<'a, T>
         })
     }
 
-    fn visit_expr_field(&mut self, f: &'a ast::ExprField) {
+    fn visit_expr_field(&mut self, f: &'ast ast::ExprField) {
         self.with_lint_attrs(f.id, &f.attrs, |cx| {
             ast_visit::walk_expr_field(cx, f);
         })
     }
 
-    fn visit_stmt(&mut self, s: &'a ast::Stmt) {
+    fn visit_stmt(&mut self, s: &'ast ast::Stmt) {
         // Add the statement's lint attributes to our
         // current state when checking the statement itself.
         // This allows us to handle attributes like
@@ -145,33 +151,33 @@ impl<'a, T: EarlyLintPass> ast_visit::Visitor<'a> for EarlyContextAndPass<'a, T>
         ast_visit::walk_stmt(self, s);
     }
 
-    fn visit_fn(&mut self, fk: ast_visit::FnKind<'a>, span: Span, id: ast::NodeId) {
+    fn visit_fn(&mut self, fk: ast_visit::FnKind<'ast>, span: Span, id: ast::NodeId) {
         lint_callback!(self, check_fn, fk, span, id);
         self.check_id(id);
         ast_visit::walk_fn(self, fk);
     }
 
-    fn visit_variant_data(&mut self, s: &'a ast::VariantData) {
+    fn visit_variant_data(&mut self, s: &'ast ast::VariantData) {
         if let Some(ctor_node_id) = s.ctor_node_id() {
             self.check_id(ctor_node_id);
         }
         ast_visit::walk_struct_def(self, s);
     }
 
-    fn visit_field_def(&mut self, s: &'a ast::FieldDef) {
+    fn visit_field_def(&mut self, s: &'ast ast::FieldDef) {
         self.with_lint_attrs(s.id, &s.attrs, |cx| {
             ast_visit::walk_field_def(cx, s);
         })
     }
 
-    fn visit_variant(&mut self, v: &'a ast::Variant) {
+    fn visit_variant(&mut self, v: &'ast ast::Variant) {
         self.with_lint_attrs(v.id, &v.attrs, |cx| {
             lint_callback!(cx, check_variant, v);
             ast_visit::walk_variant(cx, v);
         })
     }
 
-    fn visit_ty(&mut self, t: &'a ast::Ty) {
+    fn visit_ty(&mut self, t: &'ast ast::Ty) {
         lint_callback!(self, check_ty, t);
         self.check_id(t.id);
         ast_visit::walk_ty(self, t);
@@ -181,55 +187,55 @@ impl<'a, T: EarlyLintPass> ast_visit::Visitor<'a> for EarlyContextAndPass<'a, T>
         lint_callback!(self, check_ident, ident);
     }
 
-    fn visit_local(&mut self, l: &'a ast::Local) {
+    fn visit_local(&mut self, l: &'ast ast::Local) {
         self.with_lint_attrs(l.id, &l.attrs, |cx| {
             lint_callback!(cx, check_local, l);
             ast_visit::walk_local(cx, l);
         })
     }
 
-    fn visit_block(&mut self, b: &'a ast::Block) {
+    fn visit_block(&mut self, b: &'ast ast::Block) {
         lint_callback!(self, check_block, b);
         self.check_id(b.id);
         ast_visit::walk_block(self, b);
     }
 
-    fn visit_arm(&mut self, a: &'a ast::Arm) {
+    fn visit_arm(&mut self, a: &'ast ast::Arm) {
         self.with_lint_attrs(a.id, &a.attrs, |cx| {
             lint_callback!(cx, check_arm, a);
             ast_visit::walk_arm(cx, a);
         })
     }
 
-    fn visit_generic_arg(&mut self, arg: &'a ast::GenericArg) {
+    fn visit_generic_arg(&mut self, arg: &'ast ast::GenericArg) {
         lint_callback!(self, check_generic_arg, arg);
         ast_visit::walk_generic_arg(self, arg);
     }
 
-    fn visit_generic_param(&mut self, param: &'a ast::GenericParam) {
+    fn visit_generic_param(&mut self, param: &'ast ast::GenericParam) {
         self.with_lint_attrs(param.id, &param.attrs, |cx| {
             lint_callback!(cx, check_generic_param, param);
             ast_visit::walk_generic_param(cx, param);
         });
     }
 
-    fn visit_generics(&mut self, g: &'a ast::Generics) {
+    fn visit_generics(&mut self, g: &'ast ast::Generics) {
         lint_callback!(self, check_generics, g);
         ast_visit::walk_generics(self, g);
     }
 
-    fn visit_where_predicate(&mut self, p: &'a ast::WherePredicate) {
+    fn visit_where_predicate(&mut self, p: &'ast ast::WherePredicate) {
         lint_callback!(self, enter_where_predicate, p);
         ast_visit::walk_where_predicate(self, p);
         lint_callback!(self, exit_where_predicate, p);
     }
 
-    fn visit_poly_trait_ref(&mut self, t: &'a ast::PolyTraitRef) {
+    fn visit_poly_trait_ref(&mut self, t: &'ast ast::PolyTraitRef) {
         lint_callback!(self, check_poly_trait_ref, t);
         ast_visit::walk_poly_trait_ref(self, t);
     }
 
-    fn visit_assoc_item(&mut self, item: &'a ast::AssocItem, ctxt: ast_visit::AssocCtxt) {
+    fn visit_assoc_item(&mut self, item: &'ast ast::AssocItem, ctxt: ast_visit::AssocCtxt) {
         self.with_lint_attrs(item.id, &item.attrs, |cx| {
             match ctxt {
                 ast_visit::AssocCtxt::Trait => {
@@ -243,32 +249,32 @@ impl<'a, T: EarlyLintPass> ast_visit::Visitor<'a> for EarlyContextAndPass<'a, T>
         });
     }
 
-    fn visit_lifetime(&mut self, lt: &'a ast::Lifetime, _: ast_visit::LifetimeCtxt) {
+    fn visit_lifetime(&mut self, lt: &'ast ast::Lifetime, _: ast_visit::LifetimeCtxt) {
         self.check_id(lt.id);
         ast_visit::walk_lifetime(self, lt);
     }
 
-    fn visit_path(&mut self, p: &'a ast::Path, id: ast::NodeId) {
+    fn visit_path(&mut self, p: &'ast ast::Path, id: ast::NodeId) {
         self.check_id(id);
         ast_visit::walk_path(self, p);
     }
 
-    fn visit_path_segment(&mut self, s: &'a ast::PathSegment) {
+    fn visit_path_segment(&mut self, s: &'ast ast::PathSegment) {
         self.check_id(s.id);
         ast_visit::walk_path_segment(self, s);
     }
 
-    fn visit_attribute(&mut self, attr: &'a ast::Attribute) {
+    fn visit_attribute(&mut self, attr: &'ast ast::Attribute) {
         lint_callback!(self, check_attribute, attr);
         ast_visit::walk_attribute(self, attr);
     }
 
-    fn visit_mac_def(&mut self, mac: &'a ast::MacroDef, id: ast::NodeId) {
+    fn visit_mac_def(&mut self, mac: &'ast ast::MacroDef, id: ast::NodeId) {
         lint_callback!(self, check_mac_def, mac);
         self.check_id(id);
     }
 
-    fn visit_mac_call(&mut self, mac: &'a ast::MacCall) {
+    fn visit_mac_call(&mut self, mac: &'ast ast::MacCall) {
         lint_callback!(self, check_mac, mac);
         ast_visit::walk_mac(self, mac);
     }
@@ -310,28 +316,18 @@ crate::early_lint_methods!(impl_early_lint_pass, []);
 /// This trait generalizes over those nodes.
 pub trait EarlyCheckNode<'a>: Copy {
     fn id(self) -> ast::NodeId;
-    fn attrs<'b>(self) -> &'b [ast::Attribute]
-    where
-        'a: 'b;
-    fn check<'b, T: EarlyLintPass>(self, cx: &mut EarlyContextAndPass<'b, T>)
-    where
-        'a: 'b;
+    fn attrs(self) -> &'a [ast::Attribute];
+    fn check<'ecx, 'tcx, T: EarlyLintPass>(self, cx: &mut EarlyContextAndPass<'ecx, 'tcx, T>);
 }
 
 impl<'a> EarlyCheckNode<'a> for (&'a ast::Crate, &'a [ast::Attribute]) {
     fn id(self) -> ast::NodeId {
         ast::CRATE_NODE_ID
     }
-    fn attrs<'b>(self) -> &'b [ast::Attribute]
-    where
-        'a: 'b,
-    {
+    fn attrs(self) -> &'a [ast::Attribute] {
         self.1
     }
-    fn check<'b, T: EarlyLintPass>(self, cx: &mut EarlyContextAndPass<'b, T>)
-    where
-        'a: 'b,
-    {
+    fn check<'ecx, 'tcx, T: EarlyLintPass>(self, cx: &mut EarlyContextAndPass<'ecx, 'tcx, T>) {
         lint_callback!(cx, check_crate, self.0);
         ast_visit::walk_crate(cx, self.0);
         lint_callback!(cx, check_crate_post, self.0);
@@ -342,16 +338,10 @@ impl<'a> EarlyCheckNode<'a> for (ast::NodeId, &'a [ast::Attribute], &'a [P<ast::
     fn id(self) -> ast::NodeId {
         self.0
     }
-    fn attrs<'b>(self) -> &'b [ast::Attribute]
-    where
-        'a: 'b,
-    {
+    fn attrs(self) -> &'a [ast::Attribute] {
         self.1
     }
-    fn check<'b, T: EarlyLintPass>(self, cx: &mut EarlyContextAndPass<'b, T>)
-    where
-        'a: 'b,
-    {
+    fn check<'ecx, 'tcx, T: EarlyLintPass>(self, cx: &mut EarlyContextAndPass<'ecx, 'tcx, T>) {
         walk_list!(cx, visit_attribute, self.1);
         walk_list!(cx, visit_item, self.2);
     }
@@ -359,6 +349,7 @@ impl<'a> EarlyCheckNode<'a> for (ast::NodeId, &'a [ast::Attribute], &'a [P<ast::
 
 pub fn check_ast_node<'a>(
     sess: &Session,
+    tcx: Option<TyCtxt<'_>>,
     features: &Features,
     pre_expansion: bool,
     lint_store: &LintStore,
@@ -382,22 +373,23 @@ pub fn check_ast_node<'a>(
     let passes =
         if pre_expansion { &lint_store.pre_expansion_passes } else { &lint_store.early_passes };
     if passes.is_empty() {
-        check_ast_node_inner(sess, check_node, context, builtin_lints);
+        check_ast_node_inner(sess, tcx, check_node, context, builtin_lints);
     } else {
         let mut passes: Vec<_> = passes.iter().map(|mk_pass| (mk_pass)()).collect();
         passes.push(Box::new(builtin_lints));
         let pass = RuntimeCombinedEarlyLintPass { passes: &mut passes[..] };
-        check_ast_node_inner(sess, check_node, context, pass);
+        check_ast_node_inner(sess, tcx, check_node, context, pass);
     }
 }
 
 fn check_ast_node_inner<'a, T: EarlyLintPass>(
     sess: &Session,
+    tcx: Option<TyCtxt<'_>>,
     check_node: impl EarlyCheckNode<'a>,
     context: EarlyContext<'_>,
     pass: T,
 ) {
-    let mut cx = EarlyContextAndPass { context, pass };
+    let mut cx = EarlyContextAndPass { context, tcx, pass };
 
     cx.with_lint_attrs(check_node.id(), check_node.attrs(), |cx| check_node.check(cx));
 
diff --git a/compiler/rustc_lint/src/context/diagnostics.rs b/compiler/rustc_lint/src/early/diagnostics.rs
index a3731e31c2b..6d73715562b 100644
--- a/compiler/rustc_lint/src/context/diagnostics.rs
+++ b/compiler/rustc_lint/src/early/diagnostics.rs
@@ -8,17 +8,22 @@ use rustc_errors::{
     Applicability, Diag, DiagArgValue, LintDiagnostic, elided_lifetime_in_path_suggestion,
 };
 use rustc_middle::middle::stability;
+use rustc_middle::ty::TyCtxt;
 use rustc_session::Session;
 use rustc_session::lint::{BuiltinLintDiag, ElidedLifetimeResolution};
-use rustc_span::BytePos;
-use rustc_span::symbol::kw;
+use rustc_span::{BytePos, kw};
 use tracing::debug;
 
 use crate::lints::{self, ElidedNamedLifetime};
 
 mod check_cfg;
 
-pub(super) fn decorate_lint(sess: &Session, diagnostic: BuiltinLintDiag, diag: &mut Diag<'_, ()>) {
+pub(super) fn decorate_lint(
+    sess: &Session,
+    tcx: Option<TyCtxt<'_>>,
+    diagnostic: BuiltinLintDiag,
+    diag: &mut Diag<'_, ()>,
+) {
     match diagnostic {
         BuiltinLintDiag::UnicodeTextFlow(comment_span, content) => {
             let spans: Vec<_> = content
@@ -199,10 +204,10 @@ pub(super) fn decorate_lint(sess: &Session, diagnostic: BuiltinLintDiag, diag: &
             .decorate_lint(diag);
         }
         BuiltinLintDiag::UnexpectedCfgName(name, value) => {
-            check_cfg::unexpected_cfg_name(sess, name, value).decorate_lint(diag);
+            check_cfg::unexpected_cfg_name(sess, tcx, name, value).decorate_lint(diag);
         }
         BuiltinLintDiag::UnexpectedCfgValue(name, value) => {
-            check_cfg::unexpected_cfg_value(sess, name, value).decorate_lint(diag);
+            check_cfg::unexpected_cfg_value(sess, tcx, name, value).decorate_lint(diag);
         }
         BuiltinLintDiag::DeprecatedWhereclauseLocation(left_sp, sugg) => {
             let suggestion = match sugg {
diff --git a/compiler/rustc_lint/src/context/diagnostics/check_cfg.rs b/compiler/rustc_lint/src/early/diagnostics/check_cfg.rs
index 63a722f6067..eebb131599a 100644
--- a/compiler/rustc_lint/src/context/diagnostics/check_cfg.rs
+++ b/compiler/rustc_lint/src/early/diagnostics/check_cfg.rs
@@ -1,10 +1,10 @@
 use rustc_hir::def_id::LOCAL_CRATE;
 use rustc_middle::bug;
+use rustc_middle::ty::TyCtxt;
 use rustc_session::Session;
 use rustc_session::config::ExpectedValues;
 use rustc_span::edit_distance::find_best_match_for_name;
-use rustc_span::symbol::Ident;
-use rustc_span::{ExpnKind, Span, Symbol, sym};
+use rustc_span::{ExpnKind, Ident, Span, Symbol, sym};
 
 use crate::lints;
 
@@ -73,17 +73,20 @@ fn rustc_macro_help(span: Span) -> Option<lints::UnexpectedCfgRustcMacroHelp> {
     }
 }
 
-fn cargo_macro_help(span: Span) -> Option<lints::UnexpectedCfgCargoMacroHelp> {
+fn cargo_macro_help(
+    tcx: Option<TyCtxt<'_>>,
+    span: Span,
+) -> Option<lints::UnexpectedCfgCargoMacroHelp> {
     let oexpn = span.ctxt().outer_expn_data();
     if let Some(def_id) = oexpn.macro_def_id
         && let ExpnKind::Macro(macro_kind, macro_name) = oexpn.kind
         && def_id.krate != LOCAL_CRATE
+        && let Some(tcx) = tcx
     {
         Some(lints::UnexpectedCfgCargoMacroHelp {
             macro_kind: macro_kind.descr(),
             macro_name,
-            // FIXME: Get access to a `TyCtxt` from an `EarlyContext`
-            // crate_name: cx.tcx.crate_name(def_id.krate),
+            crate_name: tcx.crate_name(def_id.krate),
         })
     } else {
         None
@@ -92,6 +95,7 @@ fn cargo_macro_help(span: Span) -> Option<lints::UnexpectedCfgCargoMacroHelp> {
 
 pub(super) fn unexpected_cfg_name(
     sess: &Session,
+    tcx: Option<TyCtxt<'_>>,
     (name, name_span): (Symbol, Span),
     value: Option<(Symbol, Span)>,
 ) -> lints::UnexpectedCfgName {
@@ -223,7 +227,7 @@ pub(super) fn unexpected_cfg_name(
         };
         lints::unexpected_cfg_name::InvocationHelp::Cargo {
             help,
-            macro_help: cargo_macro_help(name_span),
+            macro_help: cargo_macro_help(tcx, name_span),
         }
     } else {
         let help = lints::UnexpectedCfgRustcHelp::new(&inst(EscapeQuotes::No));
@@ -238,6 +242,7 @@ pub(super) fn unexpected_cfg_name(
 
 pub(super) fn unexpected_cfg_value(
     sess: &Session,
+    tcx: Option<TyCtxt<'_>>,
     (name, name_span): (Symbol, Span),
     value: Option<(Symbol, Span)>,
 ) -> lints::UnexpectedCfgValue {
@@ -339,7 +344,7 @@ pub(super) fn unexpected_cfg_value(
         };
         lints::unexpected_cfg_value::InvocationHelp::Cargo {
             help,
-            macro_help: cargo_macro_help(name_span),
+            macro_help: cargo_macro_help(tcx, name_span),
         }
     } else {
         let help = if can_suggest_adding_value {
diff --git a/compiler/rustc_lint/src/enum_intrinsics_non_enums.rs b/compiler/rustc_lint/src/enum_intrinsics_non_enums.rs
index 8e22a9bdc45..6556a8d8f2d 100644
--- a/compiler/rustc_lint/src/enum_intrinsics_non_enums.rs
+++ b/compiler/rustc_lint/src/enum_intrinsics_non_enums.rs
@@ -2,8 +2,7 @@ use rustc_hir as hir;
 use rustc_middle::ty::Ty;
 use rustc_middle::ty::visit::TypeVisitableExt;
 use rustc_session::{declare_lint, declare_lint_pass};
-use rustc_span::Span;
-use rustc_span::symbol::sym;
+use rustc_span::{Span, sym};
 
 use crate::context::LintContext;
 use crate::lints::{EnumIntrinsicsMemDiscriminate, EnumIntrinsicsMemVariant};
diff --git a/compiler/rustc_lint/src/if_let_rescope.rs b/compiler/rustc_lint/src/if_let_rescope.rs
index 1402129195f..259ea908fc6 100644
--- a/compiler/rustc_lint/src/if_let_rescope.rs
+++ b/compiler/rustc_lint/src/if_let_rescope.rs
@@ -84,7 +84,7 @@ declare_lint! {
     rewriting in `match` is an option to preserve the semantics up to Edition 2021",
     @future_incompatible = FutureIncompatibleInfo {
         reason: FutureIncompatibilityReason::EditionSemanticsChange(Edition::Edition2024),
-        reference: "issue #124085 <https://github.com/rust-lang/rust/issues/124085>",
+        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2024/temporary-if-let-scope.html>",
     };
 }
 
diff --git a/compiler/rustc_lint/src/impl_trait_overcaptures.rs b/compiler/rustc_lint/src/impl_trait_overcaptures.rs
index 1aacdbd448c..b5dd6cf16ee 100644
--- a/compiler/rustc_lint/src/impl_trait_overcaptures.rs
+++ b/compiler/rustc_lint/src/impl_trait_overcaptures.rs
@@ -177,7 +177,7 @@ fn check_fn(tcx: TyCtxt<'_>, parent_def_id: LocalDefId) {
         // Lazily compute these two, since they're likely a bit expensive.
         variances: LazyCell::new(|| {
             let mut functional_variances = FunctionalVariances {
-                tcx: tcx,
+                tcx,
                 variances: FxHashMap::default(),
                 ambient_variance: ty::Covariant,
                 generics: tcx.generics_of(parent_def_id),
@@ -325,7 +325,7 @@ where
                         ParamKind::Free(def_id, name) => ty::Region::new_late_param(
                             self.tcx,
                             self.parent_def_id.to_def_id(),
-                            ty::BoundRegionKind::Named(def_id, name),
+                            ty::LateParamRegionKind::Named(def_id, name),
                         ),
                         // Totally ignore late bound args from binders.
                         ParamKind::Late => return true,
@@ -475,7 +475,7 @@ fn extract_def_id_from_arg<'tcx>(
             )
             | ty::ReLateParam(ty::LateParamRegion {
                 scope: _,
-                bound_region: ty::BoundRegionKind::Named(def_id, ..),
+                kind: ty::LateParamRegionKind::Named(def_id, ..),
             }) => def_id,
             _ => unreachable!(),
         },
@@ -544,7 +544,7 @@ impl<'tcx> TypeRelation<TyCtxt<'tcx>> for FunctionalVariances<'tcx> {
             )
             | ty::ReLateParam(ty::LateParamRegion {
                 scope: _,
-                bound_region: ty::BoundRegionKind::Named(def_id, ..),
+                kind: ty::LateParamRegionKind::Named(def_id, ..),
             }) => def_id,
             _ => {
                 return Ok(a);
diff --git a/compiler/rustc_lint/src/internal.rs b/compiler/rustc_lint/src/internal.rs
index 482650e04e8..b31a4c74787 100644
--- a/compiler/rustc_lint/src/internal.rs
+++ b/compiler/rustc_lint/src/internal.rs
@@ -10,13 +10,12 @@ use rustc_hir::{
 };
 use rustc_middle::ty::{self, GenericArgsRef, Ty as MiddleTy};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
-use rustc_span::Span;
 use rustc_span::hygiene::{ExpnKind, MacroKind};
-use rustc_span::symbol::{Symbol, kw, sym};
+use rustc_span::{Span, sym};
 use tracing::debug;
 
 use crate::lints::{
-    BadOptAccessDiag, DefaultHashTypesDiag, DiagOutOfImpl, LintPassByHand, NonExistentDocKeyword,
+    BadOptAccessDiag, DefaultHashTypesDiag, DiagOutOfImpl, LintPassByHand,
     NonGlobImportTypeIrInherent, QueryInstability, QueryUntracked, SpanUseEqCtxtDiag,
     SymbolInternStringLiteralDiag, TyQualified, TykindDiag, TykindKind, TypeIrInherentUsage,
     UntranslatableDiag,
@@ -171,27 +170,11 @@ impl<'tcx> LateLintPass<'tcx> for TyTyKind {
                                 | PatKind::TupleStruct(qpath, ..)
                                 | PatKind::Struct(qpath, ..),
                             ..
-                        }) => {
-                            if let QPath::TypeRelative(qpath_ty, ..) = qpath
-                                && qpath_ty.hir_id == ty.hir_id
-                            {
-                                Some(path.span)
-                            } else {
-                                None
-                            }
-                        }
-                        Node::Expr(Expr { kind: ExprKind::Path(qpath), .. }) => {
-                            if let QPath::TypeRelative(qpath_ty, ..) = qpath
-                                && qpath_ty.hir_id == ty.hir_id
-                            {
-                                Some(path.span)
-                            } else {
-                                None
-                            }
-                        }
-                        // Can't unify these two branches because qpath below is `&&` and above is `&`
-                        // and `A | B` paths don't play well together with adjustments, apparently.
-                        Node::Expr(Expr { kind: ExprKind::Struct(qpath, ..), .. }) => {
+                        })
+                        | Node::Expr(
+                            Expr { kind: ExprKind::Path(qpath), .. }
+                            | &Expr { kind: ExprKind::Struct(qpath, ..), .. },
+                        ) => {
                             if let QPath::TypeRelative(qpath_ty, ..) = qpath
                                 && qpath_ty.hir_id == ty.hir_id
                             {
@@ -376,46 +359,6 @@ impl EarlyLintPass for LintPassImpl {
 }
 
 declare_tool_lint! {
-    /// The `existing_doc_keyword` lint detects use `#[doc()]` keywords
-    /// that don't exist, e.g. `#[doc(keyword = "..")]`.
-    pub rustc::EXISTING_DOC_KEYWORD,
-    Allow,
-    "Check that documented keywords in std and core actually exist",
-    report_in_external_macro: true
-}
-
-declare_lint_pass!(ExistingDocKeyword => [EXISTING_DOC_KEYWORD]);
-
-fn is_doc_keyword(s: Symbol) -> bool {
-    s <= kw::Union
-}
-
-impl<'tcx> LateLintPass<'tcx> for ExistingDocKeyword {
-    fn check_item(&mut self, cx: &LateContext<'_>, item: &rustc_hir::Item<'_>) {
-        for attr in cx.tcx.hir().attrs(item.hir_id()) {
-            if !attr.has_name(sym::doc) {
-                continue;
-            }
-            if let Some(list) = attr.meta_item_list() {
-                for nested in list {
-                    if nested.has_name(sym::keyword) {
-                        let keyword = nested
-                            .value_str()
-                            .expect("#[doc(keyword = \"...\")] expected a value!");
-                        if is_doc_keyword(keyword) {
-                            return;
-                        }
-                        cx.emit_span_lint(EXISTING_DOC_KEYWORD, attr.span, NonExistentDocKeyword {
-                            keyword,
-                        });
-                    }
-                }
-            }
-        }
-    }
-}
-
-declare_tool_lint! {
     /// The `untranslatable_diagnostic` lint detects messages passed to functions with `impl
     /// Into<{D,Subd}iagMessage` parameters without using translatable Fluent strings.
     ///
diff --git a/compiler/rustc_lint/src/levels.rs b/compiler/rustc_lint/src/levels.rs
index 4b1dafbdbee..5a4ed68440a 100644
--- a/compiler/rustc_lint/src/levels.rs
+++ b/compiler/rustc_lint/src/levels.rs
@@ -1,3 +1,4 @@
+use rustc_ast::attr::AttributeExt;
 use rustc_ast_pretty::pprust;
 use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_errors::{Diag, LintDiagnostic, MultiSpan};
@@ -19,8 +20,7 @@ use rustc_session::lint::builtin::{
     UNFULFILLED_LINT_EXPECTATIONS, UNKNOWN_LINTS, UNUSED_ATTRIBUTES,
 };
 use rustc_session::lint::{Level, Lint, LintExpectationId, LintId};
-use rustc_span::symbol::{Symbol, sym};
-use rustc_span::{DUMMY_SP, Span};
+use rustc_span::{DUMMY_SP, Span, Symbol, sym};
 use tracing::{debug, instrument};
 use {rustc_ast as ast, rustc_hir as hir};
 
@@ -371,7 +371,7 @@ impl<'tcx> Visitor<'tcx> for LintLevelMaximum<'tcx> {
 
     /// FIXME(blyxyas): In a future revision, we should also graph #![allow]s,
     /// but that is handled with more care
-    fn visit_attribute(&mut self, attribute: &'tcx ast::Attribute) {
+    fn visit_attribute(&mut self, attribute: &'tcx hir::Attribute) {
         if matches!(
             Level::from_attr(attribute),
             Some(
@@ -383,10 +383,9 @@ impl<'tcx> Visitor<'tcx> for LintLevelMaximum<'tcx> {
             )
         ) {
             let store = unerased_lint_store(self.tcx.sess);
-            let Some(meta) = attribute.meta() else { return };
             // Lint attributes are always a metalist inside a
             // metalist (even with just one lint).
-            let Some(meta_item_list) = meta.meta_item_list() else { return };
+            let Some(meta_item_list) = attribute.meta_item_list() else { return };
 
             for meta_list in meta_item_list {
                 // Convert Path to String
@@ -686,7 +685,12 @@ impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
         };
     }
 
-    fn add(&mut self, attrs: &[ast::Attribute], is_crate_node: bool, source_hir_id: Option<HirId>) {
+    fn add(
+        &mut self,
+        attrs: &[impl AttributeExt],
+        is_crate_node: bool,
+        source_hir_id: Option<HirId>,
+    ) {
         let sess = self.sess;
         for (attr_index, attr) in attrs.iter().enumerate() {
             if attr.has_name(sym::automatically_derived) {
@@ -910,7 +914,7 @@ impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
 
                 let src = LintLevelSource::Node { name, span: sp, reason };
                 for &id in ids {
-                    if self.check_gated_lint(id, attr.span, false) {
+                    if self.check_gated_lint(id, sp, false) {
                         self.insert_spec(id, (level, src));
                     }
                 }
diff --git a/compiler/rustc_lint/src/lib.rs b/compiler/rustc_lint/src/lib.rs
index a99c94592b3..d7f0d2a6941 100644
--- a/compiler/rustc_lint/src/lib.rs
+++ b/compiler/rustc_lint/src/lib.rs
@@ -600,8 +600,6 @@ fn register_internals(store: &mut LintStore) {
     store.register_late_mod_pass(|_| Box::new(DefaultHashTypes));
     store.register_lints(&QueryStability::lint_vec());
     store.register_late_mod_pass(|_| Box::new(QueryStability));
-    store.register_lints(&ExistingDocKeyword::lint_vec());
-    store.register_late_mod_pass(|_| Box::new(ExistingDocKeyword));
     store.register_lints(&TyTyKind::lint_vec());
     store.register_late_mod_pass(|_| Box::new(TyTyKind));
     store.register_lints(&TypeIr::lint_vec());
@@ -629,7 +627,6 @@ fn register_internals(store: &mut LintStore) {
         LintId::of(LINT_PASS_IMPL_WITHOUT_MACRO),
         LintId::of(USAGE_OF_QUALIFIED_TY),
         LintId::of(NON_GLOB_IMPORT_OF_TYPE_IR_INHERENT),
-        LintId::of(EXISTING_DOC_KEYWORD),
         LintId::of(BAD_OPT_ACCESS),
         LintId::of(SPAN_USE_EQ_CTXT),
     ]);
diff --git a/compiler/rustc_lint/src/lints.rs b/compiler/rustc_lint/src/lints.rs
index 5da9f6d2053..ac995b59caf 100644
--- a/compiler/rustc_lint/src/lints.rs
+++ b/compiler/rustc_lint/src/lints.rs
@@ -16,8 +16,7 @@ use rustc_middle::ty::{Clause, PolyExistentialTraitRef, Ty, TyCtxt};
 use rustc_session::Session;
 use rustc_session::lint::AmbiguityErrorDiag;
 use rustc_span::edition::Edition;
-use rustc_span::symbol::{Ident, MacroRulesNormalizedIdent};
-use rustc_span::{Span, Symbol, sym};
+use rustc_span::{Ident, MacroRulesNormalizedIdent, Span, Symbol, kw, sym};
 
 use crate::builtin::{InitError, ShorthandAssocTyCollector, TypeAliasBounds};
 use crate::errors::{OverruledAttributeSub, RequestedLevel};
@@ -951,13 +950,6 @@ pub(crate) struct NonGlobImportTypeIrInherent {
 pub(crate) struct LintPassByHand;
 
 #[derive(LintDiagnostic)]
-#[diag(lint_non_existent_doc_keyword)]
-#[help]
-pub(crate) struct NonExistentDocKeyword {
-    pub keyword: Symbol,
-}
-
-#[derive(LintDiagnostic)]
 #[diag(lint_diag_out_of_impl)]
 pub(crate) struct DiagOutOfImpl;
 
@@ -1816,14 +1808,14 @@ pub(crate) enum AmbiguousWidePointerComparisonsAddrSuggestion<'a> {
 }
 
 #[derive(LintDiagnostic)]
-pub(crate) enum UnpredictableFunctionPointerComparisons<'a> {
+pub(crate) enum UnpredictableFunctionPointerComparisons<'a, 'tcx> {
     #[diag(lint_unpredictable_fn_pointer_comparisons)]
     #[note(lint_note_duplicated_fn)]
     #[note(lint_note_deduplicated_fn)]
     #[note(lint_note_visit_fn_addr_eq)]
     Suggestion {
         #[subdiagnostic]
-        sugg: UnpredictableFunctionPointerComparisonsSuggestion<'a>,
+        sugg: UnpredictableFunctionPointerComparisonsSuggestion<'a, 'tcx>,
     },
     #[diag(lint_unpredictable_fn_pointer_comparisons)]
     #[note(lint_note_duplicated_fn)]
@@ -1833,22 +1825,40 @@ pub(crate) enum UnpredictableFunctionPointerComparisons<'a> {
 }
 
 #[derive(Subdiagnostic)]
-#[multipart_suggestion(
-    lint_fn_addr_eq_suggestion,
-    style = "verbose",
-    applicability = "maybe-incorrect"
-)]
-pub(crate) struct UnpredictableFunctionPointerComparisonsSuggestion<'a> {
-    pub ne: &'a str,
-    pub cast_right: String,
-    pub deref_left: &'a str,
-    pub deref_right: &'a str,
-    #[suggestion_part(code = "{ne}std::ptr::fn_addr_eq({deref_left}")]
-    pub left: Span,
-    #[suggestion_part(code = ", {deref_right}")]
-    pub middle: Span,
-    #[suggestion_part(code = "{cast_right})")]
-    pub right: Span,
+pub(crate) enum UnpredictableFunctionPointerComparisonsSuggestion<'a, 'tcx> {
+    #[multipart_suggestion(
+        lint_fn_addr_eq_suggestion,
+        style = "verbose",
+        applicability = "maybe-incorrect"
+    )]
+    FnAddrEq {
+        ne: &'a str,
+        deref_left: &'a str,
+        deref_right: &'a str,
+        #[suggestion_part(code = "{ne}std::ptr::fn_addr_eq({deref_left}")]
+        left: Span,
+        #[suggestion_part(code = ", {deref_right}")]
+        middle: Span,
+        #[suggestion_part(code = ")")]
+        right: Span,
+    },
+    #[multipart_suggestion(
+        lint_fn_addr_eq_suggestion,
+        style = "verbose",
+        applicability = "maybe-incorrect"
+    )]
+    FnAddrEqWithCast {
+        ne: &'a str,
+        deref_left: &'a str,
+        deref_right: &'a str,
+        fn_sig: rustc_middle::ty::PolyFnSig<'tcx>,
+        #[suggestion_part(code = "{ne}std::ptr::fn_addr_eq({deref_left}")]
+        left: Span,
+        #[suggestion_part(code = ", {deref_right}")]
+        middle: Span,
+        #[suggestion_part(code = " as {fn_sig})")]
+        right: Span,
+    },
 }
 
 pub(crate) struct ImproperCTypes<'a> {
@@ -2187,8 +2197,7 @@ pub(crate) struct UnexpectedCfgRustcMacroHelp {
 pub(crate) struct UnexpectedCfgCargoMacroHelp {
     pub macro_kind: &'static str,
     pub macro_name: Symbol,
-    // FIXME: Figure out a way to get the crate name
-    // crate_name: String,
+    pub crate_name: Symbol,
 }
 
 #[derive(LintDiagnostic)]
@@ -2205,8 +2214,7 @@ pub(crate) struct UnexpectedCfgName {
 pub(crate) mod unexpected_cfg_name {
     use rustc_errors::DiagSymbolList;
     use rustc_macros::Subdiagnostic;
-    use rustc_span::symbol::Ident;
-    use rustc_span::{Span, Symbol};
+    use rustc_span::{Ident, Span, Symbol};
 
     #[derive(Subdiagnostic)]
     pub(crate) enum CodeSuggestion {
@@ -2679,7 +2687,7 @@ impl<G: EmissionGuarantee> LintDiagnostic<'_, G> for ElidedNamedLifetime {
         //  but currently this lint's suggestions can conflict with those of `clippy::needless_lifetimes`:
         //  https://github.com/rust-lang/rust/pull/129840#issuecomment-2323349119
         // HACK: `'static` suggestions will never sonflict, emit only those for now.
-        if name != rustc_span::symbol::kw::StaticLifetime {
+        if name != kw::StaticLifetime {
             return;
         }
         match kind {
diff --git a/compiler/rustc_lint/src/macro_expr_fragment_specifier_2024_migration.rs b/compiler/rustc_lint/src/macro_expr_fragment_specifier_2024_migration.rs
index 23f4f728906..ce280fef8b6 100644
--- a/compiler/rustc_lint/src/macro_expr_fragment_specifier_2024_migration.rs
+++ b/compiler/rustc_lint/src/macro_expr_fragment_specifier_2024_migration.rs
@@ -84,7 +84,7 @@ impl Expr2024 {
         let mut prev_colon = false;
         let mut prev_identifier = false;
         let mut prev_dollar = false;
-        for tt in tokens.trees() {
+        for tt in tokens.iter() {
             debug!(
                 "check_tokens: {:?} - colon {prev_dollar} - ident {prev_identifier} - colon {prev_colon}",
                 tt
diff --git a/compiler/rustc_lint/src/non_ascii_idents.rs b/compiler/rustc_lint/src/non_ascii_idents.rs
index 9b495c19990..593c8616c1d 100644
--- a/compiler/rustc_lint/src/non_ascii_idents.rs
+++ b/compiler/rustc_lint/src/non_ascii_idents.rs
@@ -2,7 +2,7 @@ use rustc_ast as ast;
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_data_structures::unord::UnordMap;
 use rustc_session::{declare_lint, declare_lint_pass};
-use rustc_span::symbol::Symbol;
+use rustc_span::Symbol;
 use unicode_security::general_security_profile::IdentifierType;
 
 use crate::lints::{
@@ -205,7 +205,7 @@ impl EarlyLintPass for NonAsciiIdents {
                     (IdentifierType::Not_NFKC, "Not_NFKC"),
                 ] {
                     let codepoints: Vec<_> =
-                        chars.extract_if(|(_, ty)| *ty == Some(id_ty)).collect();
+                        chars.extract_if(.., |(_, ty)| *ty == Some(id_ty)).collect();
                     if codepoints.is_empty() {
                         continue;
                     }
@@ -217,7 +217,7 @@ impl EarlyLintPass for NonAsciiIdents {
                 }
 
                 let remaining = chars
-                    .extract_if(|(c, _)| !GeneralSecurityProfile::identifier_allowed(*c))
+                    .extract_if(.., |(c, _)| !GeneralSecurityProfile::identifier_allowed(*c))
                     .collect::<Vec<_>>();
                 if !remaining.is_empty() {
                     cx.emit_span_lint(UNCOMMON_CODEPOINTS, sp, IdentifierUncommonCodepoints {
diff --git a/compiler/rustc_lint/src/non_fmt_panic.rs b/compiler/rustc_lint/src/non_fmt_panic.rs
index 36b1ff59c67..6f047b4da49 100644
--- a/compiler/rustc_lint/src/non_fmt_panic.rs
+++ b/compiler/rustc_lint/src/non_fmt_panic.rs
@@ -8,8 +8,7 @@ use rustc_parse_format::{ParseMode, Parser, Piece};
 use rustc_session::lint::FutureIncompatibilityReason;
 use rustc_session::{declare_lint, declare_lint_pass};
 use rustc_span::edition::Edition;
-use rustc_span::symbol::kw;
-use rustc_span::{InnerSpan, Span, Symbol, hygiene, sym};
+use rustc_span::{InnerSpan, Span, Symbol, hygiene, kw, sym};
 use rustc_trait_selection::infer::InferCtxtExt;
 
 use crate::lints::{NonFmtPanicBraces, NonFmtPanicUnused};
diff --git a/compiler/rustc_lint/src/non_local_def.rs b/compiler/rustc_lint/src/non_local_def.rs
index 3c33b2dd478..a1cc3a85109 100644
--- a/compiler/rustc_lint/src/non_local_def.rs
+++ b/compiler/rustc_lint/src/non_local_def.rs
@@ -5,8 +5,7 @@ use rustc_hir::{Body, HirId, Item, ItemKind, Node, Path, TyKind};
 use rustc_middle::ty::TyCtxt;
 use rustc_session::{declare_lint, impl_lint_pass};
 use rustc_span::def_id::{DefId, LOCAL_CRATE};
-use rustc_span::symbol::kw;
-use rustc_span::{ExpnKind, MacroKind, Span, sym};
+use rustc_span::{ExpnKind, MacroKind, Span, kw, sym};
 
 use crate::lints::{NonLocalDefinitionsCargoUpdateNote, NonLocalDefinitionsDiag};
 use crate::{LateContext, LateLintPass, LintContext, fluent_generated as fluent};
diff --git a/compiler/rustc_lint/src/nonstandard_style.rs b/compiler/rustc_lint/src/nonstandard_style.rs
index 4d8ebf2909e..70dce78b572 100644
--- a/compiler/rustc_lint/src/nonstandard_style.rs
+++ b/compiler/rustc_lint/src/nonstandard_style.rs
@@ -1,14 +1,13 @@
 use rustc_abi::ExternAbi;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::intravisit::FnKind;
-use rustc_hir::{GenericParamKind, PatKind};
+use rustc_hir::{AttrArgs, AttrItem, AttrKind, GenericParamKind, PatKind};
 use rustc_middle::ty;
 use rustc_session::config::CrateType;
 use rustc_session::{declare_lint, declare_lint_pass};
 use rustc_span::def_id::LocalDefId;
-use rustc_span::symbol::{Ident, sym};
-use rustc_span::{BytePos, Span};
-use {rustc_ast as ast, rustc_attr as attr, rustc_hir as hir};
+use rustc_span::{BytePos, Ident, Span, sym};
+use {rustc_ast as ast, rustc_attr_parsing as attr, rustc_hir as hir};
 
 use crate::lints::{
     NonCamelCaseType, NonCamelCaseTypeSub, NonSnakeCaseDiag, NonSnakeCaseDiagSub,
@@ -342,35 +341,35 @@ impl<'tcx> LateLintPass<'tcx> for NonSnakeCase {
         let crate_ident = if let Some(name) = &cx.tcx.sess.opts.crate_name {
             Some(Ident::from_str(name))
         } else {
-            attr::find_by_name(cx.tcx.hir().attrs(hir::CRATE_HIR_ID), sym::crate_name)
-                .and_then(|attr| attr.meta())
-                .and_then(|meta| {
-                    meta.name_value_literal().and_then(|lit| {
-                        if let ast::LitKind::Str(name, ..) = lit.kind {
-                            // Discard the double quotes surrounding the literal.
-                            let sp = cx
-                                .sess()
-                                .source_map()
-                                .span_to_snippet(lit.span)
-                                .ok()
-                                .and_then(|snippet| {
-                                    let left = snippet.find('"')?;
-                                    let right =
-                                        snippet.rfind('"').map(|pos| snippet.len() - pos)?;
-
-                                    Some(
-                                        lit.span
-                                            .with_lo(lit.span.lo() + BytePos(left as u32 + 1))
-                                            .with_hi(lit.span.hi() - BytePos(right as u32)),
-                                    )
-                                })
-                                .unwrap_or(lit.span);
-
-                            Some(Ident::new(name, sp))
-                        } else {
-                            None
-                        }
-                    })
+            ast::attr::find_by_name(cx.tcx.hir().attrs(hir::CRATE_HIR_ID), sym::crate_name)
+                .and_then(|attr| {
+                    if let AttrKind::Normal(n) = &attr.kind
+                        && let AttrItem { args: AttrArgs::Eq { eq_span: _, expr: ref lit }, .. } =
+                            n.as_ref()
+                        && let ast::LitKind::Str(name, ..) = lit.kind
+                    {
+                        // Discard the double quotes surrounding the literal.
+                        let sp = cx
+                            .sess()
+                            .source_map()
+                            .span_to_snippet(lit.span)
+                            .ok()
+                            .and_then(|snippet| {
+                                let left = snippet.find('"')?;
+                                let right = snippet.rfind('"').map(|pos| snippet.len() - pos)?;
+
+                                Some(
+                                    lit.span
+                                        .with_lo(lit.span.lo() + BytePos(left as u32 + 1))
+                                        .with_hi(lit.span.hi() - BytePos(right as u32)),
+                                )
+                            })
+                            .unwrap_or(lit.span);
+
+                        Some(Ident::new(name, sp))
+                    } else {
+                        None
+                    }
                 })
         };
 
@@ -502,7 +501,7 @@ impl<'tcx> LateLintPass<'tcx> for NonUpperCaseGlobals {
     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
         let attrs = cx.tcx.hir().attrs(it.hir_id());
         match it.kind {
-            hir::ItemKind::Static(..) if !attr::contains_name(attrs, sym::no_mangle) => {
+            hir::ItemKind::Static(..) if !ast::attr::contains_name(attrs, sym::no_mangle) => {
                 NonUpperCaseGlobals::check_upper_case(cx, "static variable", &it.ident);
             }
             hir::ItemKind::Const(..) => {
diff --git a/compiler/rustc_lint/src/noop_method_call.rs b/compiler/rustc_lint/src/noop_method_call.rs
index 76dc96ae00f..fa519281be5 100644
--- a/compiler/rustc_lint/src/noop_method_call.rs
+++ b/compiler/rustc_lint/src/noop_method_call.rs
@@ -3,7 +3,7 @@ use rustc_hir::{Expr, ExprKind};
 use rustc_middle::ty;
 use rustc_middle::ty::adjustment::Adjust;
 use rustc_session::{declare_lint, declare_lint_pass};
-use rustc_span::symbol::sym;
+use rustc_span::sym;
 
 use crate::context::LintContext;
 use crate::lints::{
diff --git a/compiler/rustc_lint/src/opaque_hidden_inferred_bound.rs b/compiler/rustc_lint/src/opaque_hidden_inferred_bound.rs
index 5de0d4bc870..53a411e2b87 100644
--- a/compiler/rustc_lint/src/opaque_hidden_inferred_bound.rs
+++ b/compiler/rustc_lint/src/opaque_hidden_inferred_bound.rs
@@ -5,8 +5,7 @@ use rustc_middle::ty::fold::BottomUpFolder;
 use rustc_middle::ty::print::{PrintTraitPredicateExt as _, TraitPredPrintModifiersAndPath};
 use rustc_middle::ty::{self, Ty, TypeFoldable};
 use rustc_session::{declare_lint, declare_lint_pass};
-use rustc_span::Span;
-use rustc_span::symbol::kw;
+use rustc_span::{Span, kw};
 use rustc_trait_selection::traits::{self, ObligationCtxt};
 
 use crate::{LateContext, LateLintPass, LintContext};
diff --git a/compiler/rustc_lint/src/pass_by_value.rs b/compiler/rustc_lint/src/pass_by_value.rs
index ec306f5f834..3f264859d48 100644
--- a/compiler/rustc_lint/src/pass_by_value.rs
+++ b/compiler/rustc_lint/src/pass_by_value.rs
@@ -3,7 +3,7 @@ use rustc_hir::def::Res;
 use rustc_hir::{GenericArg, PathSegment, QPath, TyKind};
 use rustc_middle::ty;
 use rustc_session::{declare_lint_pass, declare_tool_lint};
-use rustc_span::symbol::sym;
+use rustc_span::sym;
 
 use crate::lints::PassByValueDiag;
 use crate::{LateContext, LateLintPass, LintContext};
diff --git a/compiler/rustc_lint/src/passes.rs b/compiler/rustc_lint/src/passes.rs
index 9d84d36e779..3a323298bee 100644
--- a/compiler/rustc_lint/src/passes.rs
+++ b/compiler/rustc_lint/src/passes.rs
@@ -42,9 +42,9 @@ macro_rules! late_lint_methods {
             fn check_field_def(a: &'tcx rustc_hir::FieldDef<'tcx>);
             fn check_variant(a: &'tcx rustc_hir::Variant<'tcx>);
             fn check_path(a: &rustc_hir::Path<'tcx>, b: rustc_hir::HirId);
-            fn check_attribute(a: &'tcx rustc_ast::Attribute);
-            fn check_attributes(a: &'tcx [rustc_ast::Attribute]);
-            fn check_attributes_post(a: &'tcx [rustc_ast::Attribute]);
+            fn check_attribute(a: &'tcx rustc_hir::Attribute);
+            fn check_attributes(a: &'tcx [rustc_hir::Attribute]);
+            fn check_attributes_post(a: &'tcx [rustc_hir::Attribute]);
         ]);
     )
 }
@@ -136,7 +136,7 @@ macro_rules! early_lint_methods {
     ($macro:path, $args:tt) => (
         $macro!($args, [
             fn check_param(a: &rustc_ast::Param);
-            fn check_ident(a: &rustc_span::symbol::Ident);
+            fn check_ident(a: &rustc_span::Ident);
             fn check_crate(a: &rustc_ast::Crate);
             fn check_crate_post(a: &rustc_ast::Crate);
             fn check_item(a: &rustc_ast::Item);
diff --git a/compiler/rustc_lint/src/shadowed_into_iter.rs b/compiler/rustc_lint/src/shadowed_into_iter.rs
index a73904cd776..f5ab44d7469 100644
--- a/compiler/rustc_lint/src/shadowed_into_iter.rs
+++ b/compiler/rustc_lint/src/shadowed_into_iter.rs
@@ -61,6 +61,7 @@ declare_lint! {
     "detects calling `into_iter` on boxed slices in Rust 2015, 2018, and 2021",
     @future_incompatible = FutureIncompatibleInfo {
         reason: FutureIncompatibilityReason::EditionSemanticsChange(Edition::Edition2024),
+        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2024/intoiterator-box-slice.html>"
     };
 }
 
diff --git a/compiler/rustc_lint/src/traits.rs b/compiler/rustc_lint/src/traits.rs
index b793ec6a493..a9797c3b32a 100644
--- a/compiler/rustc_lint/src/traits.rs
+++ b/compiler/rustc_lint/src/traits.rs
@@ -1,6 +1,6 @@
 use rustc_hir::{self as hir, LangItem};
 use rustc_session::{declare_lint, declare_lint_pass};
-use rustc_span::symbol::sym;
+use rustc_span::sym;
 
 use crate::lints::{DropGlue, DropTraitConstraintsDiag};
 use crate::{LateContext, LateLintPass, LintContext};
diff --git a/compiler/rustc_lint/src/types.rs b/compiler/rustc_lint/src/types.rs
index 33650be056d..c0371b1f606 100644
--- a/compiler/rustc_lint/src/types.rs
+++ b/compiler/rustc_lint/src/types.rs
@@ -4,7 +4,7 @@ use std::ops::ControlFlow;
 use rustc_abi::{BackendRepr, ExternAbi, TagEncoding, Variants, WrappingRange};
 use rustc_data_structures::fx::FxHashSet;
 use rustc_errors::DiagMessage;
-use rustc_hir::{Expr, ExprKind};
+use rustc_hir::{Expr, ExprKind, LangItem};
 use rustc_middle::bug;
 use rustc_middle::ty::layout::{LayoutOf, SizeSkeleton};
 use rustc_middle::ty::{
@@ -12,8 +12,7 @@ use rustc_middle::ty::{
 };
 use rustc_session::{declare_lint, declare_lint_pass, impl_lint_pass};
 use rustc_span::def_id::LocalDefId;
-use rustc_span::symbol::sym;
-use rustc_span::{Span, Symbol, source_map};
+use rustc_span::{Span, Symbol, source_map, sym};
 use tracing::debug;
 use {rustc_ast as ast, rustc_hir as hir};
 
@@ -445,7 +444,25 @@ fn lint_fn_pointer<'tcx>(
     let (l_ty, l_ty_refs) = peel_refs(l_ty);
     let (r_ty, r_ty_refs) = peel_refs(r_ty);
 
-    if !l_ty.is_fn() || !r_ty.is_fn() {
+    if l_ty.is_fn() && r_ty.is_fn() {
+        // both operands are function pointers, fallthrough
+    } else if let ty::Adt(l_def, l_args) = l_ty.kind()
+        && let ty::Adt(r_def, r_args) = r_ty.kind()
+        && cx.tcx.is_lang_item(l_def.did(), LangItem::Option)
+        && cx.tcx.is_lang_item(r_def.did(), LangItem::Option)
+        && let Some(l_some_arg) = l_args.get(0)
+        && let Some(r_some_arg) = r_args.get(0)
+        && l_some_arg.expect_ty().is_fn()
+        && r_some_arg.expect_ty().is_fn()
+    {
+        // both operands are `Option<{function ptr}>`
+        return cx.emit_span_lint(
+            UNPREDICTABLE_FUNCTION_POINTER_COMPARISONS,
+            e.span,
+            UnpredictableFunctionPointerComparisons::Warn,
+        );
+    } else {
+        // types are not function pointers, nothing to do
         return;
     }
 
@@ -483,29 +500,36 @@ fn lint_fn_pointer<'tcx>(
     let middle = l_span.shrink_to_hi().until(r_span.shrink_to_lo());
     let right = r_span.shrink_to_hi().until(e.span.shrink_to_hi());
 
-    // We only check for a right cast as `FnDef` == `FnPtr` is not possible,
-    // only `FnPtr == FnDef` is possible.
-    let cast_right = if !r_ty.is_fn_ptr() {
-        let fn_sig = r_ty.fn_sig(cx.tcx);
-        format!(" as {fn_sig}")
-    } else {
-        String::new()
-    };
+    let sugg =
+        // We only check for a right cast as `FnDef` == `FnPtr` is not possible,
+        // only `FnPtr == FnDef` is possible.
+        if !r_ty.is_fn_ptr() {
+            let fn_sig = r_ty.fn_sig(cx.tcx);
 
-    cx.emit_span_lint(
-        UNPREDICTABLE_FUNCTION_POINTER_COMPARISONS,
-        e.span,
-        UnpredictableFunctionPointerComparisons::Suggestion {
-            sugg: UnpredictableFunctionPointerComparisonsSuggestion {
+            UnpredictableFunctionPointerComparisonsSuggestion::FnAddrEqWithCast {
                 ne,
+                fn_sig,
                 deref_left,
                 deref_right,
                 left,
                 middle,
                 right,
-                cast_right,
-            },
-        },
+            }
+        } else {
+            UnpredictableFunctionPointerComparisonsSuggestion::FnAddrEq {
+                ne,
+                deref_left,
+                deref_right,
+                left,
+                middle,
+                right,
+            }
+        };
+
+    cx.emit_span_lint(
+        UNPREDICTABLE_FUNCTION_POINTER_COMPARISONS,
+        e.span,
+        UnpredictableFunctionPointerComparisons::Suggestion { sugg },
     );
 }
 
diff --git a/compiler/rustc_lint/src/types/literal.rs b/compiler/rustc_lint/src/types/literal.rs
index dca42fea57d..83942918e3b 100644
--- a/compiler/rustc_lint/src/types/literal.rs
+++ b/compiler/rustc_lint/src/types/literal.rs
@@ -3,7 +3,7 @@ use rustc_abi::{Integer, Size};
 use rustc_middle::ty::Ty;
 use rustc_middle::ty::layout::IntegerExt;
 use rustc_middle::{bug, ty};
-use {rustc_ast as ast, rustc_attr as attr, rustc_hir as hir};
+use {rustc_ast as ast, rustc_attr_parsing as attr, rustc_hir as hir};
 
 use crate::LateContext;
 use crate::context::LintContext;
diff --git a/compiler/rustc_lint/src/unqualified_local_imports.rs b/compiler/rustc_lint/src/unqualified_local_imports.rs
index bea01a33bd6..c9dd6b32d88 100644
--- a/compiler/rustc_lint/src/unqualified_local_imports.rs
+++ b/compiler/rustc_lint/src/unqualified_local_imports.rs
@@ -1,7 +1,7 @@
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::{self as hir};
 use rustc_session::{declare_lint, declare_lint_pass};
-use rustc_span::symbol::kw;
+use rustc_span::kw;
 
 use crate::{LateContext, LateLintPass, LintContext, lints};
 
@@ -31,7 +31,7 @@ declare_lint! {
     ///
     /// This lint is meant to be used with the (unstable) rustfmt setting `group_imports = "StdExternalCrate"`.
     /// That setting makes rustfmt group `self::`, `super::`, and `crate::` imports separately from those
-    /// refering to other crates. However, rustfmt cannot know whether `use c::S;` refers to a local module `c`
+    /// referring to other crates. However, rustfmt cannot know whether `use c::S;` refers to a local module `c`
     /// or an external crate `c`, so it always gets categorized as an import from another crate.
     /// To ensure consistent grouping of imports from the local crate, all local imports must
     /// start with `self::`, `super::`, or `crate::`. This lint can be used to enforce that style.
diff --git a/compiler/rustc_lint/src/unused.rs b/compiler/rustc_lint/src/unused.rs
index 9cad5d98562..2b3cb14f9e9 100644
--- a/compiler/rustc_lint/src/unused.rs
+++ b/compiler/rustc_lint/src/unused.rs
@@ -11,8 +11,7 @@ use rustc_hir::{self as hir, LangItem};
 use rustc_infer::traits::util::elaborate;
 use rustc_middle::ty::{self, Ty, adjustment};
 use rustc_session::{declare_lint, declare_lint_pass, impl_lint_pass};
-use rustc_span::symbol::{Symbol, kw, sym};
-use rustc_span::{BytePos, Span};
+use rustc_span::{BytePos, Span, Symbol, kw, sym};
 use tracing::instrument;
 
 use crate::lints::{
diff --git a/compiler/rustc_lint_defs/src/builtin.rs b/compiler/rustc_lint_defs/src/builtin.rs
index 54e927df3c4..2f23ab27492 100644
--- a/compiler/rustc_lint_defs/src/builtin.rs
+++ b/compiler/rustc_lint_defs/src/builtin.rs
@@ -1677,7 +1677,7 @@ declare_lint! {
     "detects patterns whose meaning will change in Rust 2024",
     @future_incompatible = FutureIncompatibleInfo {
         reason: FutureIncompatibilityReason::EditionSemanticsChange(Edition::Edition2024),
-        reference: "123076",
+        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2024/match-ergonomics.html>",
     };
 }
 
@@ -2606,7 +2606,7 @@ declare_lint! {
     "unsafe operations in unsafe functions without an explicit unsafe block are deprecated",
     @future_incompatible = FutureIncompatibleInfo {
         reason: FutureIncompatibilityReason::EditionSemanticsChange(Edition::Edition2024),
-        reference: "issue #71668 <https://github.com/rust-lang/rust/issues/71668>",
+        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2024/unsafe-op-in-unsafe-fn.html>",
         explain_reason: false
     };
     @edition Edition2024 => Warn;
@@ -4189,7 +4189,7 @@ declare_lint! {
     "never type fallback affecting unsafe function calls",
     @future_incompatible = FutureIncompatibleInfo {
         reason: FutureIncompatibilityReason::EditionAndFutureReleaseSemanticsChange(Edition::Edition2024),
-        reference: "issue #123748 <https://github.com/rust-lang/rust/issues/123748>",
+        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2024/never-type-fallback.html>",
     };
     @edition Edition2024 => Deny;
     report_in_external_macro
@@ -4243,7 +4243,7 @@ declare_lint! {
     "never type fallback affecting unsafe function calls",
     @future_incompatible = FutureIncompatibleInfo {
         reason: FutureIncompatibilityReason::EditionAndFutureReleaseError(Edition::Edition2024),
-        reference: "issue #123748 <https://github.com/rust-lang/rust/issues/123748>",
+        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2024/never-type-fallback.html>",
     };
     report_in_external_macro
 }
@@ -4790,7 +4790,7 @@ declare_lint! {
     "detects unsafe functions being used as safe functions",
     @future_incompatible = FutureIncompatibleInfo {
         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2024),
-        reference: "issue #27970 <https://github.com/rust-lang/rust/issues/27970>",
+        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2024/newly-unsafe-functions.html>",
     };
 }
 
@@ -4826,7 +4826,7 @@ declare_lint! {
     "detects missing unsafe keyword on extern declarations",
     @future_incompatible = FutureIncompatibleInfo {
         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2024),
-        reference: "issue #123743 <https://github.com/rust-lang/rust/issues/123743>",
+        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2024/unsafe-extern.html>",
     };
 }
 
@@ -4867,7 +4867,7 @@ declare_lint! {
     "detects unsafe attributes outside of unsafe",
     @future_incompatible = FutureIncompatibleInfo {
         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2024),
-        reference: "issue #123757 <https://github.com/rust-lang/rust/issues/123757>",
+        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2024/unsafe-attributes.html>",
     };
 }
 
@@ -5069,7 +5069,7 @@ declare_lint! {
     "Detect and warn on significant change in drop order in tail expression location",
     @future_incompatible = FutureIncompatibleInfo {
         reason: FutureIncompatibilityReason::EditionSemanticsChange(Edition::Edition2024),
-        reference: "issue #123739 <https://github.com/rust-lang/rust/issues/123739>",
+        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2024/temporary-tail-expr-scope.html>",
     };
 }
 
@@ -5108,7 +5108,7 @@ declare_lint! {
     "will be parsed as a guarded string in Rust 2024",
     @future_incompatible = FutureIncompatibleInfo {
         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2024),
-        reference: "issue #123735 <https://github.com/rust-lang/rust/issues/123735>",
+        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2024/reserved-syntax.html>",
     };
     crate_level_only
 }
diff --git a/compiler/rustc_lint_defs/src/lib.rs b/compiler/rustc_lint_defs/src/lib.rs
index eb761bd6475..7786d3eb59a 100644
--- a/compiler/rustc_lint_defs/src/lib.rs
+++ b/compiler/rustc_lint_defs/src/lib.rs
@@ -3,8 +3,9 @@
 // tidy-alphabetical-end
 
 use rustc_abi::ExternAbi;
+use rustc_ast::AttrId;
+use rustc_ast::attr::AttributeExt;
 use rustc_ast::node_id::NodeId;
-use rustc_ast::{AttrId, Attribute};
 use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_data_structures::stable_hasher::{
     HashStable, StableCompare, StableHasher, ToStableHashKey,
@@ -14,8 +15,7 @@ use rustc_hir::def::Namespace;
 use rustc_hir::{HashStableContext, HirId, MissingLifetimeKind};
 use rustc_macros::{Decodable, Encodable, HashStable_Generic};
 pub use rustc_span::edition::Edition;
-use rustc_span::symbol::{Ident, MacroRulesNormalizedIdent};
-use rustc_span::{Span, Symbol, sym};
+use rustc_span::{Ident, MacroRulesNormalizedIdent, Span, Symbol, sym};
 use serde::{Deserialize, Serialize};
 
 pub use self::Level::*;
@@ -221,8 +221,8 @@ impl Level {
     }
 
     /// Converts an `Attribute` to a level.
-    pub fn from_attr(attr: &Attribute) -> Option<Self> {
-        Self::from_symbol(attr.name_or_empty(), Some(attr.id))
+    pub fn from_attr(attr: &impl AttributeExt) -> Option<Self> {
+        Self::from_symbol(attr.name_or_empty(), Some(attr.id()))
     }
 
     /// Converts a `Symbol` to a level.
@@ -931,7 +931,7 @@ macro_rules! declare_lint {
             desc: $desc,
             is_externally_loaded: false,
             $($v: true,)*
-            $(feature_gate: Some(rustc_span::symbol::sym::$gate),)?
+            $(feature_gate: Some(rustc_span::sym::$gate),)?
             $(future_incompatible: Some($crate::FutureIncompatibleInfo {
                 reason: $reason,
                 $($field: $val,)*
@@ -976,7 +976,7 @@ macro_rules! declare_tool_lint {
             report_in_external_macro: $external,
             future_incompatible: None,
             is_externally_loaded: true,
-            $(feature_gate: Some(rustc_span::symbol::sym::$gate),)?
+            $(feature_gate: Some(rustc_span::sym::$gate),)?
             crate_level_only: false,
             $(eval_always: $eval_always,)?
             ..$crate::Lint::default_fields_for_macro()
diff --git a/compiler/rustc_llvm/Cargo.toml b/compiler/rustc_llvm/Cargo.toml
index b29d6b79250..79a6454dbb9 100644
--- a/compiler/rustc_llvm/Cargo.toml
+++ b/compiler/rustc_llvm/Cargo.toml
@@ -10,5 +10,7 @@ libc = "0.2.73"
 
 [build-dependencies]
 # tidy-alphabetical-start
-cc = "1.1.23"
+# Pinned so `cargo update` bumps don't cause breakage. Please also update the
+# pinned `cc` in `rustc_codegen_ssa` if you update `cc` here.
+cc = "=1.2.5"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
index b79205ff946..36441a95adb 100644
--- a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
+++ b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
@@ -1796,56 +1796,6 @@ extern "C" LLVMValueRef LLVMRustBuildMaxNum(LLVMBuilderRef B, LLVMValueRef LHS,
   return wrap(unwrap(B)->CreateMaxNum(unwrap(LHS), unwrap(RHS)));
 }
 
-// This struct contains all necessary info about a symbol exported from a DLL.
-struct LLVMRustCOFFShortExport {
-  const char *name;
-  bool ordinal_present;
-  // The value of `ordinal` is only meaningful if `ordinal_present` is true.
-  uint16_t ordinal;
-};
-
-// Machine must be a COFF machine type, as defined in PE specs.
-extern "C" LLVMRustResult
-LLVMRustWriteImportLibrary(const char *ImportName, const char *Path,
-                           const LLVMRustCOFFShortExport *Exports,
-                           size_t NumExports, uint16_t Machine, bool MinGW) {
-  std::vector<llvm::object::COFFShortExport> ConvertedExports;
-  ConvertedExports.reserve(NumExports);
-
-  for (size_t i = 0; i < NumExports; ++i) {
-    bool ordinal_present = Exports[i].ordinal_present;
-    uint16_t ordinal = ordinal_present ? Exports[i].ordinal : 0;
-    ConvertedExports.push_back(llvm::object::COFFShortExport{
-        Exports[i].name, // Name
-        std::string{},   // ExtName
-        std::string{},   // SymbolName
-        std::string{},   // AliasTarget
-#if LLVM_VERSION_GE(19, 0)
-        std::string{}, // ExportAs
-#endif
-        ordinal,         // Ordinal
-        ordinal_present, // Noname
-        false,           // Data
-        false,           // Private
-        false            // Constant
-    });
-  }
-
-  auto Error = llvm::object::writeImportLibrary(
-      ImportName, Path, ConvertedExports,
-      static_cast<llvm::COFF::MachineTypes>(Machine), MinGW);
-  if (Error) {
-    std::string errorString;
-    auto stream = llvm::raw_string_ostream(errorString);
-    stream << Error;
-    stream.flush();
-    LLVMRustSetLastError(errorString.c_str());
-    return LLVMRustResult::Failure;
-  } else {
-    return LLVMRustResult::Success;
-  }
-}
-
 // Transfers ownership of DiagnosticHandler unique_ptr to the caller.
 extern "C" DiagnosticHandler *
 LLVMRustContextGetDiagnosticHandler(LLVMContextRef C) {
diff --git a/compiler/rustc_macros/src/diagnostics/mod.rs b/compiler/rustc_macros/src/diagnostics/mod.rs
index 0f7b8921509..91398f1a9da 100644
--- a/compiler/rustc_macros/src/diagnostics/mod.rs
+++ b/compiler/rustc_macros/src/diagnostics/mod.rs
@@ -16,7 +16,7 @@ use synstructure::Structure;
 /// # extern crate rustc_errors;
 /// # use rustc_errors::Applicability;
 /// # extern crate rustc_span;
-/// # use rustc_span::{symbol::Ident, Span};
+/// # use rustc_span::{Ident, Span};
 /// # extern crate rust_middle;
 /// # use rustc_middle::ty::Ty;
 /// #[derive(Diagnostic)]
diff --git a/compiler/rustc_metadata/Cargo.toml b/compiler/rustc_metadata/Cargo.toml
index 12519be9870..0b9fdbbd3da 100644
--- a/compiler/rustc_metadata/Cargo.toml
+++ b/compiler/rustc_metadata/Cargo.toml
@@ -11,7 +11,7 @@ libloading = "0.8.0"
 odht = { version = "0.3.1", features = ["nightly"] }
 rustc_abi = { path = "../rustc_abi" }
 rustc_ast = { path = "../rustc_ast" }
-rustc_attr = { path = "../rustc_attr" }
+rustc_attr_parsing = { path = "../rustc_attr_parsing" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
 rustc_expand = { path = "../rustc_expand" }
diff --git a/compiler/rustc_metadata/src/creader.rs b/compiler/rustc_metadata/src/creader.rs
index 29dba2bca61..c8715f94d5d 100644
--- a/compiler/rustc_metadata/src/creader.rs
+++ b/compiler/rustc_metadata/src/creader.rs
@@ -17,6 +17,7 @@ use rustc_data_structures::sync::{self, FreezeReadGuard, FreezeWriteGuard};
 use rustc_errors::DiagCtxtHandle;
 use rustc_expand::base::SyntaxExtension;
 use rustc_fs_util::try_canonicalize;
+use rustc_hir as hir;
 use rustc_hir::def_id::{CrateNum, LOCAL_CRATE, LocalDefId, StableCrateId};
 use rustc_hir::definitions::Definitions;
 use rustc_index::IndexVec;
@@ -28,8 +29,7 @@ use rustc_session::lint::{self, BuiltinLintDiag};
 use rustc_session::output::validate_crate_name;
 use rustc_session::search_paths::PathKind;
 use rustc_span::edition::Edition;
-use rustc_span::symbol::{Ident, Symbol, sym};
-use rustc_span::{DUMMY_SP, Span};
+use rustc_span::{DUMMY_SP, Ident, Span, Symbol, sym};
 use rustc_target::spec::{PanicStrategy, Target, TargetTuple};
 use tracing::{debug, info, trace};
 
@@ -97,7 +97,13 @@ impl<'a, 'tcx> CrateLoader<'a, 'tcx> {
 }
 
 pub enum LoadedMacro {
-    MacroDef { def: MacroDef, ident: Ident, attrs: AttrVec, span: Span, edition: Edition },
+    MacroDef {
+        def: MacroDef,
+        ident: Ident,
+        attrs: Vec<hir::Attribute>,
+        span: Span,
+        edition: Edition,
+    },
     ProcMacro(SyntaxExtension),
 }
 
diff --git a/compiler/rustc_metadata/src/dependency_format.rs b/compiler/rustc_metadata/src/dependency_format.rs
index e8de0acb7c9..582c2215d92 100644
--- a/compiler/rustc_metadata/src/dependency_format.rs
+++ b/compiler/rustc_metadata/src/dependency_format.rs
@@ -52,7 +52,8 @@
 //! than finding a number of solutions (there are normally quite a few).
 
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
-use rustc_hir::def_id::CrateNum;
+use rustc_hir::def_id::{CrateNum, LOCAL_CRATE};
+use rustc_index::IndexVec;
 use rustc_middle::bug;
 use rustc_middle::middle::dependency_format::{Dependencies, DependencyList, Linkage};
 use rustc_middle::ty::TyCtxt;
@@ -84,7 +85,7 @@ fn calculate_type(tcx: TyCtxt<'_>, ty: CrateType) -> DependencyList {
     let sess = &tcx.sess;
 
     if !sess.opts.output_types.should_codegen() {
-        return Vec::new();
+        return IndexVec::new();
     }
 
     let preferred_linkage = match ty {
@@ -131,7 +132,7 @@ fn calculate_type(tcx: TyCtxt<'_>, ty: CrateType) -> DependencyList {
 
     match preferred_linkage {
         // If the crate is not linked, there are no link-time dependencies.
-        Linkage::NotLinked => return Vec::new(),
+        Linkage::NotLinked => return IndexVec::new(),
         Linkage::Static => {
             // Attempt static linkage first. For dylibs and executables, we may be
             // able to retry below with dynamic linkage.
@@ -156,7 +157,7 @@ fn calculate_type(tcx: TyCtxt<'_>, ty: CrateType) -> DependencyList {
                     }
                     sess.dcx().emit_err(RlibRequired { crate_name: tcx.crate_name(cnum) });
                 }
-                return Vec::new();
+                return IndexVec::new();
             }
         }
         Linkage::Dynamic | Linkage::IncludedFromDylib => {}
@@ -210,19 +211,32 @@ fn calculate_type(tcx: TyCtxt<'_>, ty: CrateType) -> DependencyList {
 
     // Collect what we've got so far in the return vector.
     let last_crate = tcx.crates(()).len();
-    let mut ret = (1..last_crate + 1)
-        .map(|cnum| match formats.get(&CrateNum::new(cnum)) {
-            Some(&RequireDynamic) => Linkage::Dynamic,
-            Some(&RequireStatic) => Linkage::IncludedFromDylib,
-            None => Linkage::NotLinked,
-        })
-        .collect::<Vec<_>>();
+    let mut ret = IndexVec::new();
+
+    // We need to fill in something for LOCAL_CRATE as IndexVec is a dense map.
+    // Linkage::Static semantically the most correct thing to use as the local
+    // crate is always statically linked into the linker output, even when
+    // linking a dylib. Using Linkage::Static also allow avoiding special cases
+    // for LOCAL_CRATE in some places.
+    assert_eq!(ret.push(Linkage::Static), LOCAL_CRATE);
+
+    for cnum in 1..last_crate + 1 {
+        let cnum = CrateNum::new(cnum);
+        assert_eq!(
+            ret.push(match formats.get(&cnum) {
+                Some(&RequireDynamic) => Linkage::Dynamic,
+                Some(&RequireStatic) => Linkage::IncludedFromDylib,
+                None => Linkage::NotLinked,
+            }),
+            cnum
+        );
+    }
 
     // Run through the dependency list again, and add any missing libraries as
     // static libraries.
     //
     // If the crate hasn't been included yet and it's not actually required
-    // (e.g., it's an allocator) then we skip it here as well.
+    // (e.g., it's a panic runtime) then we skip it here as well.
     for &cnum in tcx.crates(()).iter() {
         let src = tcx.used_crate_source(cnum);
         if src.dylib.is_none()
@@ -232,7 +246,7 @@ fn calculate_type(tcx: TyCtxt<'_>, ty: CrateType) -> DependencyList {
             assert!(src.rlib.is_some() || src.rmeta.is_some());
             info!("adding staticlib: {}", tcx.crate_name(cnum));
             add_library(tcx, cnum, RequireStatic, &mut formats, &mut unavailable_as_static);
-            ret[cnum.as_usize() - 1] = Linkage::Static;
+            ret[cnum] = Linkage::Static;
         }
     }
 
@@ -240,8 +254,7 @@ fn calculate_type(tcx: TyCtxt<'_>, ty: CrateType) -> DependencyList {
     // artifact which means that we may need to inject dependencies of some
     // form.
     //
-    // Things like allocators and panic runtimes may not have been activated
-    // quite yet, so do so here.
+    // Things like panic runtimes may not have been activated quite yet, so do so here.
     activate_injected_dep(CStore::from_tcx(tcx).injected_panic_runtime(), &mut ret, &|cnum| {
         tcx.is_panic_runtime(cnum)
     });
@@ -252,8 +265,10 @@ fn calculate_type(tcx: TyCtxt<'_>, ty: CrateType) -> DependencyList {
     //
     // For situations like this, we perform one last pass over the dependencies,
     // making sure that everything is available in the requested format.
-    for (cnum, kind) in ret.iter().enumerate() {
-        let cnum = CrateNum::new(cnum + 1);
+    for (cnum, kind) in ret.iter_enumerated() {
+        if cnum == LOCAL_CRATE {
+            continue;
+        }
         let src = tcx.used_crate_source(cnum);
         match *kind {
             Linkage::NotLinked | Linkage::IncludedFromDylib => {}
@@ -334,18 +349,21 @@ fn attempt_static(tcx: TyCtxt<'_>, unavailable: &mut Vec<CrateNum>) -> Option<De
 
     // All crates are available in an rlib format, so we're just going to link
     // everything in explicitly so long as it's actually required.
-    let mut ret = tcx
-        .crates(())
-        .iter()
-        .map(|&cnum| match tcx.dep_kind(cnum) {
-            CrateDepKind::Explicit => Linkage::Static,
-            CrateDepKind::MacrosOnly | CrateDepKind::Implicit => Linkage::NotLinked,
-        })
-        .collect::<Vec<_>>();
+    let mut ret = IndexVec::new();
+    assert_eq!(ret.push(Linkage::Static), LOCAL_CRATE);
+    for &cnum in tcx.crates(()) {
+        assert_eq!(
+            ret.push(match tcx.dep_kind(cnum) {
+                CrateDepKind::Explicit => Linkage::Static,
+                CrateDepKind::MacrosOnly | CrateDepKind::Implicit => Linkage::NotLinked,
+            }),
+            cnum
+        );
+    }
 
-    // Our allocator/panic runtime may not have been linked above if it wasn't
-    // explicitly linked, which is the case for any injected dependency. Handle
-    // that here and activate them.
+    // Our panic runtime may not have been linked above if it wasn't explicitly
+    // linked, which is the case for any injected dependency. Handle that here
+    // and activate it.
     activate_injected_dep(CStore::from_tcx(tcx).injected_panic_runtime(), &mut ret, &|cnum| {
         tcx.is_panic_runtime(cnum)
     });
@@ -367,8 +385,7 @@ fn activate_injected_dep(
     list: &mut DependencyList,
     replaces_injected: &dyn Fn(CrateNum) -> bool,
 ) {
-    for (i, slot) in list.iter().enumerate() {
-        let cnum = CrateNum::new(i + 1);
+    for (cnum, slot) in list.iter_enumerated() {
         if !replaces_injected(cnum) {
             continue;
         }
@@ -377,25 +394,23 @@ fn activate_injected_dep(
         }
     }
     if let Some(injected) = injected {
-        let idx = injected.as_usize() - 1;
-        assert_eq!(list[idx], Linkage::NotLinked);
-        list[idx] = Linkage::Static;
+        assert_eq!(list[injected], Linkage::NotLinked);
+        list[injected] = Linkage::Static;
     }
 }
 
-// After the linkage for a crate has been determined we need to verify that
-// there's only going to be one allocator in the output.
-fn verify_ok(tcx: TyCtxt<'_>, list: &[Linkage]) {
+/// After the linkage for a crate has been determined we need to verify that
+/// there's only going to be one panic runtime in the output.
+fn verify_ok(tcx: TyCtxt<'_>, list: &DependencyList) {
     let sess = &tcx.sess;
     if list.is_empty() {
         return;
     }
     let mut panic_runtime = None;
-    for (i, linkage) in list.iter().enumerate() {
+    for (cnum, linkage) in list.iter_enumerated() {
         if let Linkage::NotLinked = *linkage {
             continue;
         }
-        let cnum = CrateNum::new(i + 1);
 
         if tcx.is_panic_runtime(cnum) {
             if let Some((prev, _)) = panic_runtime {
@@ -431,11 +446,10 @@ fn verify_ok(tcx: TyCtxt<'_>, list: &[Linkage]) {
         // strategy. If the dep isn't linked, we ignore it, and if our strategy
         // is abort then it's compatible with everything. Otherwise all crates'
         // panic strategy must match our own.
-        for (i, linkage) in list.iter().enumerate() {
+        for (cnum, linkage) in list.iter_enumerated() {
             if let Linkage::NotLinked = *linkage {
                 continue;
             }
-            let cnum = CrateNum::new(i + 1);
             if cnum == runtime_cnum || tcx.is_compiler_builtins(cnum) {
                 continue;
             }
@@ -450,13 +464,16 @@ fn verify_ok(tcx: TyCtxt<'_>, list: &[Linkage]) {
                 });
             }
 
-            let found_drop_strategy = tcx.panic_in_drop_strategy(cnum);
-            if tcx.sess.opts.unstable_opts.panic_in_drop != found_drop_strategy {
-                sess.dcx().emit_err(IncompatiblePanicInDropStrategy {
-                    crate_name: tcx.crate_name(cnum),
-                    found_strategy: found_drop_strategy,
-                    desired_strategy: tcx.sess.opts.unstable_opts.panic_in_drop,
-                });
+            // panic_in_drop_strategy isn't allowed for LOCAL_CRATE
+            if cnum != LOCAL_CRATE {
+                let found_drop_strategy = tcx.panic_in_drop_strategy(cnum);
+                if tcx.sess.opts.unstable_opts.panic_in_drop != found_drop_strategy {
+                    sess.dcx().emit_err(IncompatiblePanicInDropStrategy {
+                        crate_name: tcx.crate_name(cnum),
+                        found_strategy: found_drop_strategy,
+                        desired_strategy: tcx.sess.opts.unstable_opts.panic_in_drop,
+                    });
+                }
             }
         }
     }
diff --git a/compiler/rustc_metadata/src/locator.rs b/compiler/rustc_metadata/src/locator.rs
index d59ec7af6ec..b9ebf17af24 100644
--- a/compiler/rustc_metadata/src/locator.rs
+++ b/compiler/rustc_metadata/src/locator.rs
@@ -229,8 +229,7 @@ use rustc_session::cstore::CrateSource;
 use rustc_session::filesearch::FileSearch;
 use rustc_session::search_paths::PathKind;
 use rustc_session::utils::CanonicalizedPath;
-use rustc_span::Span;
-use rustc_span::symbol::Symbol;
+use rustc_span::{Span, Symbol};
 use rustc_target::spec::{Target, TargetTuple};
 use tracing::{debug, info};
 
diff --git a/compiler/rustc_metadata/src/native_libs.rs b/compiler/rustc_metadata/src/native_libs.rs
index 8bd2281981b..2a1e4b261e7 100644
--- a/compiler/rustc_metadata/src/native_libs.rs
+++ b/compiler/rustc_metadata/src/native_libs.rs
@@ -3,7 +3,7 @@ use std::path::{Path, PathBuf};
 
 use rustc_abi::ExternAbi;
 use rustc_ast::CRATE_NODE_ID;
-use rustc_attr as attr;
+use rustc_attr_parsing as attr;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_middle::query::LocalCrate;
 use rustc_middle::ty::{self, List, Ty, TyCtxt};
@@ -16,7 +16,7 @@ use rustc_session::parse::feature_err;
 use rustc_session::search_paths::PathKind;
 use rustc_session::utils::NativeLibKind;
 use rustc_span::def_id::{DefId, LOCAL_CRATE};
-use rustc_span::symbol::{Symbol, sym};
+use rustc_span::{Symbol, sym};
 use rustc_target::spec::LinkSelfContainedComponents;
 
 use crate::{errors, fluent_generated};
@@ -544,7 +544,7 @@ impl<'tcx> Collector<'tcx> {
             // can move them to the end of the list below.
             let mut existing = self
                 .libs
-                .extract_if(|lib| {
+                .extract_if(.., |lib| {
                     if lib.name.as_str() == passed_lib.name {
                         // FIXME: This whole logic is questionable, whether modifiers are
                         // involved or not, library reordering and kind overriding without
diff --git a/compiler/rustc_metadata/src/rmeta/decoder.rs b/compiler/rustc_metadata/src/rmeta/decoder.rs
index b9586338655..c2b5e318bda 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder.rs
@@ -31,8 +31,7 @@ use rustc_serialize::{Decodable, Decoder};
 use rustc_session::Session;
 use rustc_session::cstore::{CrateSource, ExternCrate};
 use rustc_span::hygiene::HygieneDecodeContext;
-use rustc_span::symbol::kw;
-use rustc_span::{BytePos, DUMMY_SP, Pos, SpanData, SpanDecoder, SyntaxContext};
+use rustc_span::{BytePos, DUMMY_SP, Pos, SpanData, SpanDecoder, SyntaxContext, kw};
 use tracing::debug;
 
 use crate::creader::CStore;
@@ -874,7 +873,7 @@ impl MetadataBlob {
                         let def_key = root.tables.def_keys.get(blob, item).unwrap().decode(blob);
                         #[cfg_attr(not(bootstrap), allow(rustc::symbol_intern_string_literal))]
                         let def_name = if item == CRATE_DEF_INDEX {
-                            rustc_span::symbol::kw::Crate
+                            kw::Crate
                         } else {
                             def_key
                                 .disambiguated_data
@@ -1369,7 +1368,7 @@ impl<'a> CrateMetadataRef<'a> {
         self,
         id: DefIndex,
         sess: &'a Session,
-    ) -> impl Iterator<Item = ast::Attribute> + 'a {
+    ) -> impl Iterator<Item = hir::Attribute> + 'a {
         self.root
             .tables
             .attributes
@@ -1475,7 +1474,7 @@ impl<'a> CrateMetadataRef<'a> {
     ) -> &'tcx [(CrateNum, LinkagePreference)] {
         tcx.arena.alloc_from_iter(
             self.root.dylib_dependency_formats.decode(self).enumerate().flat_map(|(i, link)| {
-                let cnum = CrateNum::new(i + 1);
+                let cnum = CrateNum::new(i + 1); // We skipped LOCAL_CRATE when encoding
                 link.map(|link| (self.cnum_map[cnum], link))
             }),
         )
diff --git a/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs b/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
index f01ad31d0bb..527f2f10205 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
@@ -1,7 +1,7 @@
 use std::any::Any;
 use std::mem;
 
-use rustc_attr::Deprecation;
+use rustc_attr_parsing::Deprecation;
 use rustc_data_structures::sync::Lrc;
 use rustc_hir::def::{CtorKind, DefKind, Res};
 use rustc_hir::def_id::{CrateNum, DefId, DefIdMap, LOCAL_CRATE};
@@ -17,9 +17,8 @@ use rustc_middle::ty::{self, TyCtxt};
 use rustc_middle::util::Providers;
 use rustc_session::cstore::{CrateStore, ExternCrate};
 use rustc_session::{Session, StableCrateId};
-use rustc_span::Span;
 use rustc_span::hygiene::ExpnId;
-use rustc_span::symbol::{Symbol, kw};
+use rustc_span::{Span, Symbol, kw};
 
 use super::{Decodable, DecodeContext, DecodeIterator};
 use crate::creader::{CStore, LoadedMacro};
@@ -344,7 +343,7 @@ provide! { tcx, def_id, other, cdata,
     }
     associated_item => { cdata.get_associated_item(def_id.index, tcx.sess) }
     inherent_impls => { cdata.get_inherent_implementations_for_type(tcx, def_id.index) }
-    item_attrs => { tcx.arena.alloc_from_iter(cdata.get_item_attrs(def_id.index, tcx.sess)) }
+    attrs_for_def => { tcx.arena.alloc_from_iter(cdata.get_item_attrs(def_id.index, tcx.sess)) }
     is_mir_available => { cdata.is_item_mir_available(def_id.index) }
     is_ctfe_mir_available => { cdata.is_ctfe_mir_available(def_id.index) }
     cross_crate_inlinable => { table_direct }
diff --git a/compiler/rustc_metadata/src/rmeta/encoder.rs b/compiler/rustc_metadata/src/rmeta/encoder.rs
index df5b06c6d16..c538ab99fb5 100644
--- a/compiler/rustc_metadata/src/rmeta/encoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/encoder.rs
@@ -4,7 +4,7 @@ use std::fs::File;
 use std::io::{Read, Seek, Write};
 use std::path::{Path, PathBuf};
 
-use rustc_ast::Attribute;
+use rustc_ast::attr::AttributeExt;
 use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_data_structures::memmap::{Mmap, MmapMut};
 use rustc_data_structures::sync::{Lrc, join, par_for_each_in};
@@ -27,9 +27,9 @@ use rustc_middle::{bug, span_bug};
 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder, opaque};
 use rustc_session::config::{CrateType, OptLevel};
 use rustc_span::hygiene::HygieneEncodeContext;
-use rustc_span::symbol::sym;
 use rustc_span::{
     ExternalSource, FileName, SourceFile, SpanData, SpanEncoder, StableSourceFileId, SyntaxContext,
+    sym,
 };
 use tracing::{debug, instrument, trace};
 
@@ -710,15 +710,18 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
                 has_global_allocator: tcx.has_global_allocator(LOCAL_CRATE),
                 has_alloc_error_handler: tcx.has_alloc_error_handler(LOCAL_CRATE),
                 has_panic_handler: tcx.has_panic_handler(LOCAL_CRATE),
-                has_default_lib_allocator: attr::contains_name(attrs, sym::default_lib_allocator),
+                has_default_lib_allocator: ast::attr::contains_name(
+                    attrs,
+                    sym::default_lib_allocator,
+                ),
                 proc_macro_data,
                 debugger_visualizers,
-                compiler_builtins: attr::contains_name(attrs, sym::compiler_builtins),
-                needs_allocator: attr::contains_name(attrs, sym::needs_allocator),
-                needs_panic_runtime: attr::contains_name(attrs, sym::needs_panic_runtime),
-                no_builtins: attr::contains_name(attrs, sym::no_builtins),
-                panic_runtime: attr::contains_name(attrs, sym::panic_runtime),
-                profiler_runtime: attr::contains_name(attrs, sym::profiler_runtime),
+                compiler_builtins: ast::attr::contains_name(attrs, sym::compiler_builtins),
+                needs_allocator: ast::attr::contains_name(attrs, sym::needs_allocator),
+                needs_panic_runtime: ast::attr::contains_name(attrs, sym::needs_panic_runtime),
+                no_builtins: ast::attr::contains_name(attrs, sym::no_builtins),
+                panic_runtime: ast::attr::contains_name(attrs, sym::panic_runtime),
+                profiler_runtime: ast::attr::contains_name(attrs, sym::profiler_runtime),
                 symbol_mangling_version: tcx.sess.opts.get_symbol_mangling_version(),
 
                 crate_deps,
@@ -814,7 +817,7 @@ struct AnalyzeAttrState<'a> {
 /// visibility: this is a piece of data that can be computed once per defid, and not once per
 /// attribute. Some attributes would only be usable downstream if they are public.
 #[inline]
-fn analyze_attr(attr: &Attribute, state: &mut AnalyzeAttrState<'_>) -> bool {
+fn analyze_attr(attr: &impl AttributeExt, state: &mut AnalyzeAttrState<'_>) -> bool {
     let mut should_encode = false;
     if !rustc_feature::encode_cross_crate(attr.name_or_empty()) {
         // Attributes not marked encode-cross-crate don't need to be encoded for downstream crates.
@@ -1354,7 +1357,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
             .hir()
             .attrs(tcx.local_def_id_to_hir_id(def_id))
             .iter()
-            .filter(|attr| analyze_attr(attr, &mut state));
+            .filter(|attr| analyze_attr(*attr, &mut state));
 
         record_array!(self.tables.attributes[def_id.to_def_id()] <- attr_iter);
 
@@ -1917,11 +1920,11 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
                 // Proc-macros may have attributes like `#[allow_internal_unstable]`,
                 // so downstream crates need access to them.
                 let attrs = hir.attrs(proc_macro);
-                let macro_kind = if attr::contains_name(attrs, sym::proc_macro) {
+                let macro_kind = if ast::attr::contains_name(attrs, sym::proc_macro) {
                     MacroKind::Bang
-                } else if attr::contains_name(attrs, sym::proc_macro_attribute) {
+                } else if ast::attr::contains_name(attrs, sym::proc_macro_attribute) {
                     MacroKind::Attr
-                } else if let Some(attr) = attr::find_by_name(attrs, sym::proc_macro_derive) {
+                } else if let Some(attr) = ast::attr::find_by_name(attrs, sym::proc_macro_derive) {
                     // This unwrap chain should have been checked by the proc-macro harness.
                     name = attr.meta_item_list().unwrap()[0]
                         .meta_item()
@@ -2162,12 +2165,14 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
         empty_proc_macro!(self);
         let formats = self.tcx.dependency_formats(());
         if let Some(arr) = formats.get(&CrateType::Dylib) {
-            return self.lazy_array(arr.iter().map(|slot| match *slot {
-                Linkage::NotLinked | Linkage::IncludedFromDylib => None,
+            return self.lazy_array(arr.iter().skip(1 /* skip LOCAL_CRATE */).map(
+                |slot| match *slot {
+                    Linkage::NotLinked | Linkage::IncludedFromDylib => None,
 
-                Linkage::Dynamic => Some(LinkagePreference::RequireDynamic),
-                Linkage::Static => Some(LinkagePreference::RequireStatic),
-            }));
+                    Linkage::Dynamic => Some(LinkagePreference::RequireDynamic),
+                    Linkage::Static => Some(LinkagePreference::RequireStatic),
+                },
+            ));
         }
         LazyArray::default()
     }
diff --git a/compiler/rustc_metadata/src/rmeta/mod.rs b/compiler/rustc_metadata/src/rmeta/mod.rs
index 4961464833a..64a1c70dd2f 100644
--- a/compiler/rustc_metadata/src/rmeta/mod.rs
+++ b/compiler/rustc_metadata/src/rmeta/mod.rs
@@ -36,11 +36,10 @@ use rustc_session::config::SymbolManglingVersion;
 use rustc_session::cstore::{CrateDepKind, ForeignModule, LinkagePreference, NativeLib};
 use rustc_span::edition::Edition;
 use rustc_span::hygiene::{ExpnIndex, MacroKind, SyntaxContextData};
-use rustc_span::symbol::{Ident, Symbol};
-use rustc_span::{self, ExpnData, ExpnHash, ExpnId, Span};
+use rustc_span::{self, ExpnData, ExpnHash, ExpnId, Ident, Span, Symbol};
 use rustc_target::spec::{PanicStrategy, TargetTuple};
 use table::TableBuilder;
-use {rustc_ast as ast, rustc_attr as attr, rustc_hir as hir};
+use {rustc_ast as ast, rustc_attr_parsing as attr, rustc_hir as hir};
 
 use crate::creader::CrateMetadataRef;
 
@@ -403,7 +402,7 @@ define_tables! {
     cross_crate_inlinable: Table<DefIndex, bool>,
 
 - optional:
-    attributes: Table<DefIndex, LazyArray<ast::Attribute>>,
+    attributes: Table<DefIndex, LazyArray<hir::Attribute>>,
     // For non-reexported names in a module every name is associated with a separate `DefId`,
     // so we can take their names, visibilities etc from other encoded tables.
     module_children_non_reexports: Table<DefIndex, LazyArray<DefIndex>>,
diff --git a/compiler/rustc_middle/Cargo.toml b/compiler/rustc_middle/Cargo.toml
index 3bda3a4aa63..e64500f812a 100644
--- a/compiler/rustc_middle/Cargo.toml
+++ b/compiler/rustc_middle/Cargo.toml
@@ -17,7 +17,7 @@ rustc_apfloat = "0.2.0"
 rustc_arena = { path = "../rustc_arena" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_ast_ir = { path = "../rustc_ast_ir" }
-rustc_attr = { path = "../rustc_attr" }
+rustc_attr_parsing = { path = "../rustc_attr_parsing" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_error_messages = { path = "../rustc_error_messages" } # Used for intra-doc links
 rustc_errors = { path = "../rustc_errors" }
diff --git a/compiler/rustc_middle/src/arena.rs b/compiler/rustc_middle/src/arena.rs
index b664230d10b..750531b638e 100644
--- a/compiler/rustc_middle/src/arena.rs
+++ b/compiler/rustc_middle/src/arena.rs
@@ -85,9 +85,9 @@ macro_rules! arena_types {
             [] upvars_mentioned: rustc_data_structures::fx::FxIndexMap<rustc_hir::HirId, rustc_hir::Upvar>,
             [] dyn_compatibility_violations: rustc_middle::traits::DynCompatibilityViolation,
             [] codegen_unit: rustc_middle::mir::mono::CodegenUnit<'tcx>,
-            [decode] attribute: rustc_ast::Attribute,
-            [] name_set: rustc_data_structures::unord::UnordSet<rustc_span::symbol::Symbol>,
-            [] ordered_name_set: rustc_data_structures::fx::FxIndexSet<rustc_span::symbol::Symbol>,
+            [decode] attribute: rustc_hir::Attribute,
+            [] name_set: rustc_data_structures::unord::UnordSet<rustc_span::Symbol>,
+            [] ordered_name_set: rustc_data_structures::fx::FxIndexSet<rustc_span::Symbol>,
             [] pats: rustc_middle::ty::PatternKind<'tcx>,
 
             // Note that this deliberately duplicates items in the `rustc_hir::arena`,
diff --git a/compiler/rustc_middle/src/dep_graph/dep_node.rs b/compiler/rustc_middle/src/dep_graph/dep_node.rs
index 87bbeb178ee..fcfc31575f8 100644
--- a/compiler/rustc_middle/src/dep_graph/dep_node.rs
+++ b/compiler/rustc_middle/src/dep_graph/dep_node.rs
@@ -64,7 +64,7 @@ pub use rustc_query_system::dep_graph::DepNode;
 use rustc_query_system::dep_graph::FingerprintStyle;
 pub use rustc_query_system::dep_graph::dep_node::DepKind;
 pub(crate) use rustc_query_system::dep_graph::{DepContext, DepNodeParams};
-use rustc_span::symbol::Symbol;
+use rustc_span::Symbol;
 
 use crate::mir::mono::MonoItem;
 use crate::ty::TyCtxt;
diff --git a/compiler/rustc_middle/src/hir/map/mod.rs b/compiler/rustc_middle/src/hir/map/mod.rs
index 0c701c834f2..308078ddf87 100644
--- a/compiler/rustc_middle/src/hir/map/mod.rs
+++ b/compiler/rustc_middle/src/hir/map/mod.rs
@@ -9,11 +9,10 @@ use rustc_hir::def_id::{DefId, LOCAL_CRATE, LocalDefId, LocalModDefId};
 use rustc_hir::definitions::{DefKey, DefPath, DefPathHash};
 use rustc_hir::intravisit::Visitor;
 use rustc_hir::*;
+use rustc_hir_pretty as pprust_hir;
 use rustc_middle::hir::nested_filter;
 use rustc_span::def_id::StableCrateId;
-use rustc_span::symbol::{Ident, Symbol, kw, sym};
-use rustc_span::{ErrorGuaranteed, Span};
-use {rustc_ast as ast, rustc_hir_pretty as pprust_hir};
+use rustc_span::{ErrorGuaranteed, Ident, Span, Symbol, kw, sym};
 
 use crate::hir::ModuleItems;
 use crate::middle::debugger_visualizer::DebuggerVisualizerFile;
@@ -381,7 +380,7 @@ impl<'hir> Map<'hir> {
     /// Gets the attributes on the crate. This is preferable to
     /// invoking `krate.attrs` because it registers a tighter
     /// dep-graph access.
-    pub fn krate_attrs(self) -> &'hir [ast::Attribute] {
+    pub fn krate_attrs(self) -> &'hir [Attribute] {
         self.attrs(CRATE_HIR_ID)
     }
 
@@ -792,7 +791,7 @@ impl<'hir> Map<'hir> {
 
     /// Given a node ID, gets a list of attributes associated with the AST
     /// corresponding to the node-ID.
-    pub fn attrs(self, id: HirId) -> &'hir [ast::Attribute] {
+    pub fn attrs(self, id: HirId) -> &'hir [Attribute] {
         self.tcx.hir_attrs(id.owner).get(id.local_id)
     }
 
diff --git a/compiler/rustc_middle/src/hir/mod.rs b/compiler/rustc_middle/src/hir/mod.rs
index ad0d70152e1..ffefd81cd08 100644
--- a/compiler/rustc_middle/src/hir/mod.rs
+++ b/compiler/rustc_middle/src/hir/mod.rs
@@ -151,7 +151,7 @@ impl<'tcx> TyCtxt<'tcx> {
         self,
         node: OwnerNode<'_>,
         bodies: &SortedMap<ItemLocalId, &Body<'_>>,
-        attrs: &SortedMap<ItemLocalId, &[rustc_ast::Attribute]>,
+        attrs: &SortedMap<ItemLocalId, &[Attribute]>,
     ) -> (Option<Fingerprint>, Option<Fingerprint>) {
         if self.needs_crate_hash() {
             self.with_stable_hashing_context(|mut hcx| {
diff --git a/compiler/rustc_middle/src/infer/canonical.rs b/compiler/rustc_middle/src/infer/canonical.rs
index ac55497f8b3..0f408375e05 100644
--- a/compiler/rustc_middle/src/infer/canonical.rs
+++ b/compiler/rustc_middle/src/infer/canonical.rs
@@ -30,7 +30,6 @@ pub use rustc_type_ir as ir;
 pub use rustc_type_ir::{CanonicalTyVarKind, CanonicalVarKind};
 use smallvec::SmallVec;
 
-use crate::infer::MemberConstraint;
 use crate::mir::ConstraintCategory;
 use crate::ty::{self, GenericArg, List, Ty, TyCtxt, TypeFlags, TypeVisitableExt};
 
@@ -91,14 +90,13 @@ pub struct QueryResponse<'tcx, R> {
 #[derive(HashStable, TypeFoldable, TypeVisitable)]
 pub struct QueryRegionConstraints<'tcx> {
     pub outlives: Vec<QueryOutlivesConstraint<'tcx>>,
-    pub member_constraints: Vec<MemberConstraint<'tcx>>,
 }
 
 impl QueryRegionConstraints<'_> {
     /// Represents an empty (trivially true) set of region
     /// constraints.
     pub fn is_empty(&self) -> bool {
-        self.outlives.is_empty() && self.member_constraints.is_empty()
+        self.outlives.is_empty()
     }
 }
 
diff --git a/compiler/rustc_middle/src/infer/mod.rs b/compiler/rustc_middle/src/infer/mod.rs
index 19fe9e5a54f..3dfcf90cb93 100644
--- a/compiler/rustc_middle/src/infer/mod.rs
+++ b/compiler/rustc_middle/src/infer/mod.rs
@@ -1,34 +1,2 @@
 pub mod canonical;
 pub mod unify_key;
-
-use rustc_data_structures::sync::Lrc;
-use rustc_macros::{HashStable, TypeFoldable, TypeVisitable};
-use rustc_span::Span;
-
-use crate::ty::{OpaqueTypeKey, Region, Ty};
-
-/// Requires that `region` must be equal to one of the regions in `choice_regions`.
-/// We often denote this using the syntax:
-///
-/// ```text
-/// R0 member of [O1..On]
-/// ```
-#[derive(Debug, Clone, PartialEq, Eq, Hash)]
-#[derive(HashStable, TypeFoldable, TypeVisitable)]
-pub struct MemberConstraint<'tcx> {
-    /// The `DefId` and args of the opaque type causing this constraint.
-    /// Used for error reporting.
-    pub key: OpaqueTypeKey<'tcx>,
-
-    /// The span where the hidden type was instantiated.
-    pub definition_span: Span,
-
-    /// The hidden type in which `member_region` appears: used for error reporting.
-    pub hidden_ty: Ty<'tcx>,
-
-    /// The region `R0`.
-    pub member_region: Region<'tcx>,
-
-    /// The options `O1..On`.
-    pub choice_regions: Lrc<Vec<Region<'tcx>>>,
-}
diff --git a/compiler/rustc_middle/src/lint.rs b/compiler/rustc_middle/src/lint.rs
index 971d036fa69..620d9f1c357 100644
--- a/compiler/rustc_middle/src/lint.rs
+++ b/compiler/rustc_middle/src/lint.rs
@@ -9,7 +9,7 @@ use rustc_session::Session;
 use rustc_session::lint::builtin::{self, FORBIDDEN_LINT_GROUPS};
 use rustc_session::lint::{FutureIncompatibilityReason, Level, Lint, LintExpectationId, LintId};
 use rustc_span::hygiene::{ExpnKind, MacroKind};
-use rustc_span::{DUMMY_SP, DesugaringKind, Span, Symbol, symbol};
+use rustc_span::{DUMMY_SP, DesugaringKind, Span, Symbol, kw};
 use tracing::instrument;
 
 use crate::ty::TyCtxt;
@@ -37,7 +37,7 @@ pub enum LintLevelSource {
 impl LintLevelSource {
     pub fn name(&self) -> Symbol {
         match *self {
-            LintLevelSource::Default => symbol::kw::Default,
+            LintLevelSource::Default => kw::Default,
             LintLevelSource::Node { name, .. } => name,
             LintLevelSource::CommandLine(name, _) => name,
         }
diff --git a/compiler/rustc_middle/src/metadata.rs b/compiler/rustc_middle/src/metadata.rs
index c3175c6bdf5..57c8960943b 100644
--- a/compiler/rustc_middle/src/metadata.rs
+++ b/compiler/rustc_middle/src/metadata.rs
@@ -1,7 +1,7 @@
 use rustc_hir::def::Res;
 use rustc_macros::{HashStable, TyDecodable, TyEncodable};
+use rustc_span::Ident;
 use rustc_span::def_id::DefId;
-use rustc_span::symbol::Ident;
 use smallvec::SmallVec;
 
 use crate::ty;
diff --git a/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs b/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs
index 44428471a5f..241767fe249 100644
--- a/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs
+++ b/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs
@@ -1,7 +1,7 @@
 use rustc_abi::Align;
-use rustc_attr::{InlineAttr, InstructionSetAttr, OptimizeAttr};
+use rustc_attr_parsing::{InlineAttr, InstructionSetAttr, OptimizeAttr};
 use rustc_macros::{HashStable, TyDecodable, TyEncodable};
-use rustc_span::symbol::Symbol;
+use rustc_span::Symbol;
 use rustc_target::spec::SanitizerSet;
 
 use crate::mir::mono::Linkage;
diff --git a/compiler/rustc_middle/src/middle/dependency_format.rs b/compiler/rustc_middle/src/middle/dependency_format.rs
index e3b40b64157..4f613e97631 100644
--- a/compiler/rustc_middle/src/middle/dependency_format.rs
+++ b/compiler/rustc_middle/src/middle/dependency_format.rs
@@ -8,13 +8,13 @@
 // this will introduce circular dependency between rustc_metadata and rustc_middle
 
 use rustc_data_structures::fx::FxIndexMap;
+use rustc_hir::def_id::CrateNum;
+use rustc_index::IndexVec;
 use rustc_macros::{Decodable, Encodable, HashStable};
 use rustc_session::config::CrateType;
 
 /// A list of dependencies for a certain crate type.
-///
-/// The length of this vector is the same as the number of external crates used.
-pub type DependencyList = Vec<Linkage>;
+pub type DependencyList = IndexVec<CrateNum, Linkage>;
 
 /// A mapping of all required dependencies for a particular flavor of output.
 ///
diff --git a/compiler/rustc_middle/src/middle/limits.rs b/compiler/rustc_middle/src/middle/limits.rs
index 270bcabcc86..8a367a947d1 100644
--- a/compiler/rustc_middle/src/middle/limits.rs
+++ b/compiler/rustc_middle/src/middle/limits.rs
@@ -10,9 +10,9 @@
 
 use std::num::IntErrorKind;
 
-use rustc_ast::Attribute;
+use rustc_ast::attr::AttributeExt;
 use rustc_session::{Limit, Limits, Session};
-use rustc_span::symbol::{Symbol, sym};
+use rustc_span::{Symbol, sym};
 
 use crate::error::LimitInvalid;
 use crate::query::Providers;
@@ -35,32 +35,36 @@ pub fn provide(providers: &mut Providers) {
     }
 }
 
-pub fn get_recursion_limit(krate_attrs: &[Attribute], sess: &Session) -> Limit {
+pub fn get_recursion_limit(krate_attrs: &[impl AttributeExt], sess: &Session) -> Limit {
     get_limit(krate_attrs, sess, sym::recursion_limit, 128)
 }
 
-fn get_limit(krate_attrs: &[Attribute], sess: &Session, name: Symbol, default: usize) -> Limit {
+fn get_limit(
+    krate_attrs: &[impl AttributeExt],
+    sess: &Session,
+    name: Symbol,
+    default: usize,
+) -> Limit {
     match get_limit_size(krate_attrs, sess, name) {
         Some(size) => Limit::new(size),
         None => Limit::new(default),
     }
 }
 
-pub fn get_limit_size(krate_attrs: &[Attribute], sess: &Session, name: Symbol) -> Option<usize> {
+pub fn get_limit_size(
+    krate_attrs: &[impl AttributeExt],
+    sess: &Session,
+    name: Symbol,
+) -> Option<usize> {
     for attr in krate_attrs {
         if !attr.has_name(name) {
             continue;
         }
 
-        if let Some(s) = attr.value_str() {
-            match s.as_str().parse() {
+        if let Some(sym) = attr.value_str() {
+            match sym.as_str().parse() {
                 Ok(n) => return Some(n),
                 Err(e) => {
-                    let value_span = attr
-                        .meta()
-                        .and_then(|meta| meta.name_value_literal_span())
-                        .unwrap_or(attr.span);
-
                     let error_str = match e.kind() {
                         IntErrorKind::PosOverflow => "`limit` is too large",
                         IntErrorKind::Empty => "`limit` must be a non-negative integer",
@@ -71,7 +75,11 @@ pub fn get_limit_size(krate_attrs: &[Attribute], sess: &Session, name: Symbol) -
                         IntErrorKind::Zero => bug!("zero is a valid `limit`"),
                         kind => bug!("unimplemented IntErrorKind variant: {:?}", kind),
                     };
-                    sess.dcx().emit_err(LimitInvalid { span: attr.span, value_span, error_str });
+                    sess.dcx().emit_err(LimitInvalid {
+                        span: attr.span(),
+                        value_span: attr.value_span().unwrap(),
+                        error_str,
+                    });
                 }
             }
         }
diff --git a/compiler/rustc_middle/src/middle/mod.rs b/compiler/rustc_middle/src/middle/mod.rs
index 83873439bd9..692fe027c49 100644
--- a/compiler/rustc_middle/src/middle/mod.rs
+++ b/compiler/rustc_middle/src/middle/mod.rs
@@ -6,8 +6,7 @@ pub mod lang_items;
 pub mod lib_features {
     use rustc_data_structures::unord::UnordMap;
     use rustc_macros::{HashStable, TyDecodable, TyEncodable};
-    use rustc_span::Span;
-    use rustc_span::symbol::Symbol;
+    use rustc_span::{Span, Symbol};
 
     #[derive(Copy, Clone, Debug, PartialEq, Eq)]
     #[derive(HashStable, TyEncodable, TyDecodable)]
diff --git a/compiler/rustc_middle/src/middle/region.rs b/compiler/rustc_middle/src/middle/region.rs
index 114211b27c1..66861519e17 100644
--- a/compiler/rustc_middle/src/middle/region.rs
+++ b/compiler/rustc_middle/src/middle/region.rs
@@ -84,23 +84,23 @@ use crate::ty::TyCtxt;
 #[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash, Copy, TyEncodable, TyDecodable)]
 #[derive(HashStable)]
 pub struct Scope {
-    pub id: hir::ItemLocalId,
+    pub local_id: hir::ItemLocalId,
     pub data: ScopeData,
 }
 
 impl fmt::Debug for Scope {
     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self.data {
-            ScopeData::Node => write!(fmt, "Node({:?})", self.id),
-            ScopeData::CallSite => write!(fmt, "CallSite({:?})", self.id),
-            ScopeData::Arguments => write!(fmt, "Arguments({:?})", self.id),
-            ScopeData::Destruction => write!(fmt, "Destruction({:?})", self.id),
-            ScopeData::IfThen => write!(fmt, "IfThen({:?})", self.id),
-            ScopeData::IfThenRescope => write!(fmt, "IfThen[edition2024]({:?})", self.id),
+            ScopeData::Node => write!(fmt, "Node({:?})", self.local_id),
+            ScopeData::CallSite => write!(fmt, "CallSite({:?})", self.local_id),
+            ScopeData::Arguments => write!(fmt, "Arguments({:?})", self.local_id),
+            ScopeData::Destruction => write!(fmt, "Destruction({:?})", self.local_id),
+            ScopeData::IfThen => write!(fmt, "IfThen({:?})", self.local_id),
+            ScopeData::IfThenRescope => write!(fmt, "IfThen[edition2024]({:?})", self.local_id),
             ScopeData::Remainder(fsi) => write!(
                 fmt,
                 "Remainder {{ block: {:?}, first_statement_index: {}}}",
-                self.id,
+                self.local_id,
                 fsi.as_u32(),
             ),
         }
@@ -164,18 +164,8 @@ rustc_index::newtype_index! {
 rustc_data_structures::static_assert_size!(ScopeData, 4);
 
 impl Scope {
-    /// Returns an item-local ID associated with this scope.
-    ///
-    /// N.B., likely to be replaced as API is refined; e.g., pnkfelix
-    /// anticipates `fn entry_node_id` and `fn each_exit_node_id`.
-    pub fn item_local_id(&self) -> hir::ItemLocalId {
-        self.id
-    }
-
     pub fn hir_id(&self, scope_tree: &ScopeTree) -> Option<HirId> {
-        scope_tree
-            .root_body
-            .map(|hir_id| HirId { owner: hir_id.owner, local_id: self.item_local_id() })
+        scope_tree.root_body.map(|hir_id| HirId { owner: hir_id.owner, local_id: self.local_id })
     }
 
     /// Returns the span of this `Scope`. Note that in general the
@@ -350,7 +340,7 @@ impl ScopeTree {
 
     pub fn record_var_scope(&mut self, var: hir::ItemLocalId, lifetime: Scope) {
         debug!("record_var_scope(sub={:?}, sup={:?})", var, lifetime);
-        assert!(var != lifetime.item_local_id());
+        assert!(var != lifetime.local_id);
         self.var_map.insert(var, lifetime);
     }
 
@@ -359,7 +349,7 @@ impl ScopeTree {
         match &candidate_type {
             RvalueCandidateType::Borrow { lifetime: Some(lifetime), .. }
             | RvalueCandidateType::Pattern { lifetime: Some(lifetime), .. } => {
-                assert!(var.local_id != lifetime.item_local_id())
+                assert!(var.local_id != lifetime.local_id)
             }
             _ => {}
         }
diff --git a/compiler/rustc_middle/src/middle/stability.rs b/compiler/rustc_middle/src/middle/stability.rs
index 94d13021612..84c3c2eb49e 100644
--- a/compiler/rustc_middle/src/middle/stability.rs
+++ b/compiler/rustc_middle/src/middle/stability.rs
@@ -4,7 +4,7 @@
 use std::num::NonZero;
 
 use rustc_ast::NodeId;
-use rustc_attr::{
+use rustc_attr_parsing::{
     self as attr, ConstStability, DefaultBodyStability, DeprecatedSince, Deprecation, Stability,
 };
 use rustc_data_structures::unord::UnordMap;
@@ -18,8 +18,7 @@ use rustc_session::Session;
 use rustc_session::lint::builtin::{DEPRECATED, DEPRECATED_IN_FUTURE, SOFT_UNSTABLE};
 use rustc_session::lint::{BuiltinLintDiag, DeprecatedSinceKind, Level, Lint, LintBuffer};
 use rustc_session::parse::feature_err_issue;
-use rustc_span::Span;
-use rustc_span::symbol::{Symbol, sym};
+use rustc_span::{Span, Symbol, sym};
 use tracing::debug;
 
 pub use self::StabilityLevel::*;
@@ -392,7 +391,7 @@ impl<'tcx> TyCtxt<'tcx> {
 
         match stability {
             Some(Stability {
-                level: attr::Unstable { reason, issue, is_soft, implied_by },
+                level: attr::StabilityLevel::Unstable { reason, issue, is_soft, implied_by },
                 feature,
                 ..
             }) => {
@@ -475,7 +474,7 @@ impl<'tcx> TyCtxt<'tcx> {
 
         match stability {
             Some(DefaultBodyStability {
-                level: attr::Unstable { reason, issue, is_soft, .. },
+                level: attr::StabilityLevel::Unstable { reason, issue, is_soft, .. },
                 feature,
             }) => {
                 if span.allows_unstable(feature) {
diff --git a/compiler/rustc_middle/src/mir/consts.rs b/compiler/rustc_middle/src/mir/consts.rs
index d8a39191920..1231ea88569 100644
--- a/compiler/rustc_middle/src/mir/consts.rs
+++ b/compiler/rustc_middle/src/mir/consts.rs
@@ -5,7 +5,7 @@ use rustc_hir::def_id::DefId;
 use rustc_macros::{HashStable, Lift, TyDecodable, TyEncodable, TypeFoldable, TypeVisitable};
 use rustc_session::RemapFileNameExt;
 use rustc_session::config::RemapPathScopeComponents;
-use rustc_span::{DUMMY_SP, Span};
+use rustc_span::{DUMMY_SP, Span, Symbol};
 use rustc_type_ir::visit::TypeVisitableExt;
 
 use super::interpret::ReportedErrorInfo;
@@ -569,7 +569,7 @@ impl<'tcx> TyCtxt<'tcx> {
         let topmost = span.ctxt().outer_expn().expansion_cause().unwrap_or(span);
         let caller = self.sess.source_map().lookup_char_pos(topmost.lo());
         self.const_caller_location(
-            rustc_span::symbol::Symbol::intern(
+            Symbol::intern(
                 &caller
                     .file
                     .name
diff --git a/compiler/rustc_middle/src/mir/coverage.rs b/compiler/rustc_middle/src/mir/coverage.rs
index 962176290df..29f26180c97 100644
--- a/compiler/rustc_middle/src/mir/coverage.rs
+++ b/compiler/rustc_middle/src/mir/coverage.rs
@@ -154,22 +154,6 @@ impl Debug for CoverageKind {
     }
 }
 
-#[derive(Clone, TyEncodable, TyDecodable, Hash, HashStable, PartialEq, Eq, PartialOrd, Ord)]
-#[derive(TypeFoldable, TypeVisitable)]
-pub struct SourceRegion {
-    pub start_line: u32,
-    pub start_col: u32,
-    pub end_line: u32,
-    pub end_col: u32,
-}
-
-impl Debug for SourceRegion {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
-        let &Self { start_line, start_col, end_line, end_col } = self;
-        write!(fmt, "{start_line}:{start_col} - {end_line}:{end_col}")
-    }
-}
-
 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, HashStable)]
 #[derive(TyEncodable, TyDecodable, TypeFoldable, TypeVisitable)]
 pub enum Op {
@@ -231,7 +215,7 @@ impl MappingKind {
 #[derive(TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable, TypeVisitable)]
 pub struct Mapping {
     pub kind: MappingKind,
-    pub source_region: SourceRegion,
+    pub span: Span,
 }
 
 /// Stores per-function coverage information attached to a `mir::Body`,
diff --git a/compiler/rustc_middle/src/mir/interpret/error.rs b/compiler/rustc_middle/src/mir/interpret/error.rs
index fbada6ec405..37328470aa7 100644
--- a/compiler/rustc_middle/src/mir/interpret/error.rs
+++ b/compiler/rustc_middle/src/mir/interpret/error.rs
@@ -392,7 +392,7 @@ pub enum UndefinedBehaviorInfo<'tcx> {
     /// A discriminant of an uninhabited enum variant is written.
     UninhabitedEnumVariantWritten(VariantIdx),
     /// An uninhabited enum variant is projected.
-    UninhabitedEnumVariantRead(VariantIdx),
+    UninhabitedEnumVariantRead(Option<VariantIdx>),
     /// Trying to set discriminant to the niched variant, but the value does not match.
     InvalidNichedEnumVariantWritten { enum_ty: Ty<'tcx> },
     /// ABI-incompatible argument types.
diff --git a/compiler/rustc_middle/src/mir/mod.rs b/compiler/rustc_middle/src/mir/mod.rs
index 56340ff0095..98ef7d58a50 100644
--- a/compiler/rustc_middle/src/mir/mod.rs
+++ b/compiler/rustc_middle/src/mir/mod.rs
@@ -26,8 +26,7 @@ use rustc_index::{Idx, IndexSlice, IndexVec};
 use rustc_macros::{HashStable, TyDecodable, TyEncodable, TypeFoldable, TypeVisitable};
 use rustc_serialize::{Decodable, Encodable};
 use rustc_span::source_map::Spanned;
-use rustc_span::symbol::Symbol;
-use rustc_span::{DUMMY_SP, Span};
+use rustc_span::{DUMMY_SP, Span, Symbol};
 use tracing::trace;
 
 pub use self::query::*;
@@ -1349,8 +1348,8 @@ pub struct BasicBlockData<'tcx> {
 }
 
 impl<'tcx> BasicBlockData<'tcx> {
-    pub fn new(terminator: Option<Terminator<'tcx>>) -> BasicBlockData<'tcx> {
-        BasicBlockData { statements: vec![], terminator, is_cleanup: false }
+    pub fn new(terminator: Option<Terminator<'tcx>>, is_cleanup: bool) -> BasicBlockData<'tcx> {
+        BasicBlockData { statements: vec![], terminator, is_cleanup }
     }
 
     /// Accessor for terminator.
diff --git a/compiler/rustc_middle/src/mir/mono.rs b/compiler/rustc_middle/src/mir/mono.rs
index 266dc7ad2b3..27168b2a9f2 100644
--- a/compiler/rustc_middle/src/mir/mono.rs
+++ b/compiler/rustc_middle/src/mir/mono.rs
@@ -1,7 +1,7 @@
 use std::fmt;
 use std::hash::Hash;
 
-use rustc_attr::InlineAttr;
+use rustc_attr_parsing::InlineAttr;
 use rustc_data_structures::base_n::{BaseNString, CASE_INSENSITIVE, ToBaseN};
 use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::fx::FxIndexMap;
@@ -13,8 +13,7 @@ use rustc_index::Idx;
 use rustc_macros::{HashStable, TyDecodable, TyEncodable};
 use rustc_query_system::ich::StableHashingContext;
 use rustc_session::config::OptLevel;
-use rustc_span::Span;
-use rustc_span::symbol::Symbol;
+use rustc_span::{Span, Symbol};
 use rustc_target::spec::SymbolVisibility;
 use tracing::debug;
 
diff --git a/compiler/rustc_middle/src/mir/pretty.rs b/compiler/rustc_middle/src/mir/pretty.rs
index 2bfcd0a6227..2d1a0e36f90 100644
--- a/compiler/rustc_middle/src/mir/pretty.rs
+++ b/compiler/rustc_middle/src/mir/pretty.rs
@@ -23,6 +23,7 @@ pub(crate) const ALIGN: usize = 40;
 
 /// An indication of where we are in the control flow graph. Used for printing
 /// extra information in `dump_mir`
+#[derive(Clone)]
 pub enum PassWhere {
     /// We have not started dumping the control flow graph, but we are about to.
     BeforeCFG,
@@ -603,8 +604,8 @@ fn write_function_coverage_info(
     for (id, expression) in expressions.iter_enumerated() {
         writeln!(w, "{INDENT}coverage {id:?} => {expression:?};")?;
     }
-    for coverage::Mapping { kind, source_region } in mappings {
-        writeln!(w, "{INDENT}coverage {kind:?} => {source_region:?};")?;
+    for coverage::Mapping { kind, span } in mappings {
+        writeln!(w, "{INDENT}coverage {kind:?} => {span:?};")?;
     }
     writeln!(w)?;
 
diff --git a/compiler/rustc_middle/src/mir/query.rs b/compiler/rustc_middle/src/mir/query.rs
index f690359e012..429be9bc725 100644
--- a/compiler/rustc_middle/src/mir/query.rs
+++ b/compiler/rustc_middle/src/mir/query.rs
@@ -11,8 +11,7 @@ use rustc_hir::def_id::LocalDefId;
 use rustc_index::bit_set::BitMatrix;
 use rustc_index::{Idx, IndexVec};
 use rustc_macros::{HashStable, TyDecodable, TyEncodable, TypeFoldable, TypeVisitable};
-use rustc_span::Span;
-use rustc_span::symbol::Symbol;
+use rustc_span::{Span, Symbol};
 use smallvec::SmallVec;
 
 use super::{ConstValue, SourceInfo};
diff --git a/compiler/rustc_middle/src/mir/syntax.rs b/compiler/rustc_middle/src/mir/syntax.rs
index fea940ea47c..0c17a2e0fe5 100644
--- a/compiler/rustc_middle/src/mir/syntax.rs
+++ b/compiler/rustc_middle/src/mir/syntax.rs
@@ -10,10 +10,9 @@ use rustc_hir::CoroutineKind;
 use rustc_hir::def_id::DefId;
 use rustc_index::IndexVec;
 use rustc_macros::{HashStable, TyDecodable, TyEncodable, TypeFoldable, TypeVisitable};
-use rustc_span::Span;
 use rustc_span::def_id::LocalDefId;
 use rustc_span::source_map::Spanned;
-use rustc_span::symbol::Symbol;
+use rustc_span::{Span, Symbol};
 use rustc_target::asm::InlineAsmRegOrRegClass;
 use smallvec::SmallVec;
 
@@ -822,6 +821,11 @@ pub enum TerminatorKind<'tcx> {
     /// continues at the `resume` basic block, with the second argument written to the `resume_arg`
     /// place. If the coroutine is dropped before then, the `drop` basic block is invoked.
     ///
+    /// Note that coroutines can be (unstably) cloned under certain conditions, which means that
+    /// this terminator can **return multiple times**! MIR optimizations that reorder code into
+    /// different basic blocks needs to be aware of that.
+    /// See <https://github.com/rust-lang/rust/issues/95360>.
+    ///
     /// Not permitted in bodies that are not coroutine bodies, or after coroutine lowering.
     ///
     /// **Needs clarification**: What about the evaluation order of the `resume_arg` and `value`?
diff --git a/compiler/rustc_middle/src/query/erase.rs b/compiler/rustc_middle/src/query/erase.rs
index 013847f0b2d..b72c0e776fe 100644
--- a/compiler/rustc_middle/src/query/erase.rs
+++ b/compiler/rustc_middle/src/query/erase.rs
@@ -239,9 +239,9 @@ trivial! {
     bool,
     Option<(rustc_span::def_id::DefId, rustc_session::config::EntryFnType)>,
     Option<rustc_ast::expand::allocator::AllocatorKind>,
-    Option<rustc_attr::ConstStability>,
-    Option<rustc_attr::DefaultBodyStability>,
-    Option<rustc_attr::Stability>,
+    Option<rustc_attr_parsing::ConstStability>,
+    Option<rustc_attr_parsing::DefaultBodyStability>,
+    Option<rustc_attr_parsing::Stability>,
     Option<rustc_data_structures::svh::Svh>,
     Option<rustc_hir::def::DefKind>,
     Option<rustc_hir::CoroutineKind>,
@@ -264,10 +264,10 @@ trivial! {
     Result<rustc_middle::traits::EvaluationResult, rustc_middle::traits::OverflowError>,
     rustc_abi::ReprOptions,
     rustc_ast::expand::allocator::AllocatorKind,
-    rustc_attr::ConstStability,
-    rustc_attr::DefaultBodyStability,
-    rustc_attr::Deprecation,
-    rustc_attr::Stability,
+    rustc_attr_parsing::ConstStability,
+    rustc_attr_parsing::DefaultBodyStability,
+    rustc_attr_parsing::Deprecation,
+    rustc_attr_parsing::Stability,
     rustc_data_structures::svh::Svh,
     rustc_errors::ErrorGuaranteed,
     rustc_hir::Constness,
@@ -332,7 +332,7 @@ trivial! {
     rustc_span::ExpnId,
     rustc_span::Span,
     rustc_span::Symbol,
-    rustc_span::symbol::Ident,
+    rustc_span::Ident,
     rustc_target::spec::PanicStrategy,
     rustc_type_ir::Variance,
     u32,
diff --git a/compiler/rustc_middle/src/query/keys.rs b/compiler/rustc_middle/src/query/keys.rs
index 66fec2dd0f7..e243425c0b7 100644
--- a/compiler/rustc_middle/src/query/keys.rs
+++ b/compiler/rustc_middle/src/query/keys.rs
@@ -4,8 +4,7 @@ use rustc_hir::def_id::{CrateNum, DefId, LOCAL_CRATE, LocalDefId, LocalModDefId,
 use rustc_hir::hir_id::{HirId, OwnerId};
 use rustc_query_system::dep_graph::DepNodeIndex;
 use rustc_query_system::query::{DefIdCache, DefaultCache, SingleCache, VecCache};
-use rustc_span::symbol::{Ident, Symbol};
-use rustc_span::{DUMMY_SP, Span};
+use rustc_span::{DUMMY_SP, Ident, Span, Symbol};
 
 use crate::infer::canonical::CanonicalQueryInput;
 use crate::mir::mono::CollectionMode;
diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs
index cc4e31294bd..2c2dffe8b88 100644
--- a/compiler/rustc_middle/src/query/mod.rs
+++ b/compiler/rustc_middle/src/query/mod.rs
@@ -41,10 +41,9 @@ use rustc_session::cstore::{
 use rustc_session::lint::LintExpectationId;
 use rustc_span::def_id::LOCAL_CRATE;
 use rustc_span::source_map::Spanned;
-use rustc_span::symbol::Symbol;
-use rustc_span::{DUMMY_SP, Span};
+use rustc_span::{DUMMY_SP, Span, Symbol};
 use rustc_target::spec::PanicStrategy;
-use {rustc_abi as abi, rustc_ast as ast, rustc_attr as attr, rustc_hir as hir};
+use {rustc_abi as abi, rustc_ast as ast, rustc_attr_parsing as attr, rustc_hir as hir};
 
 use crate::infer::canonical::{self, Canonical};
 use crate::lint::LintExpectation;
@@ -680,7 +679,7 @@ rustc_queries! {
     /// of supertraits that define the given associated type. This is used to avoid
     /// cycles in resolving type-dependent associated item paths like `T::Item`.
     query explicit_supertraits_containing_assoc_item(
-        key: (DefId, rustc_span::symbol::Ident)
+        key: (DefId, rustc_span::Ident)
     ) -> ty::EarlyBinder<'tcx, &'tcx [(ty::Clause<'tcx>, Span)]> {
         desc { |tcx| "computing the super traits of `{}` with associated type name `{}`",
             tcx.def_path_str(key.0),
@@ -709,7 +708,7 @@ rustc_queries! {
     /// To avoid cycles within the predicates of a single item we compute
     /// per-type-parameter predicates for resolving `T::AssocTy`.
     query type_param_predicates(
-        key: (LocalDefId, LocalDefId, rustc_span::symbol::Ident)
+        key: (LocalDefId, LocalDefId, rustc_span::Ident)
     ) -> ty::EarlyBinder<'tcx, &'tcx [(ty::Clause<'tcx>, Span)]> {
         desc { |tcx| "computing the bounds for type parameter `{}`", tcx.hir().ty_param_name(key.1) }
     }
@@ -1267,7 +1266,7 @@ rustc_queries! {
     /// Returns the attributes on the item at `def_id`.
     ///
     /// Do not use this directly, use `tcx.get_attrs` instead.
-    query item_attrs(def_id: DefId) -> &'tcx [ast::Attribute] {
+    query attrs_for_def(def_id: DefId) -> &'tcx [hir::Attribute] {
         desc { |tcx| "collecting attributes of `{}`", tcx.def_path_str(def_id) }
         separate_provide_extern
     }
@@ -1284,7 +1283,7 @@ rustc_queries! {
         desc { |tcx| "computing target features for inline asm of `{}`", tcx.def_path_str(def_id) }
     }
 
-    query fn_arg_names(def_id: DefId) -> &'tcx [rustc_span::symbol::Ident] {
+    query fn_arg_names(def_id: DefId) -> &'tcx [rustc_span::Ident] {
         desc { |tcx| "looking up function parameter names for `{}`", tcx.def_path_str(def_id) }
         separate_provide_extern
     }
diff --git a/compiler/rustc_middle/src/query/on_disk_cache.rs b/compiler/rustc_middle/src/query/on_disk_cache.rs
index 119a99e1bf7..4a144ebb899 100644
--- a/compiler/rustc_middle/src/query/on_disk_cache.rs
+++ b/compiler/rustc_middle/src/query/on_disk_cache.rs
@@ -798,8 +798,8 @@ macro_rules! impl_ref_decoder {
 
 impl_ref_decoder! {<'tcx>
     Span,
-    rustc_ast::Attribute,
-    rustc_span::symbol::Ident,
+    rustc_hir::Attribute,
+    rustc_span::Ident,
     ty::Variance,
     rustc_span::def_id::DefId,
     rustc_span::def_id::LocalDefId,
diff --git a/compiler/rustc_middle/src/traits/mod.rs b/compiler/rustc_middle/src/traits/mod.rs
index 0a77c3bc42f..b34a1782581 100644
--- a/compiler/rustc_middle/src/traits/mod.rs
+++ b/compiler/rustc_middle/src/traits/mod.rs
@@ -20,8 +20,7 @@ use rustc_macros::{
     Decodable, Encodable, HashStable, TyDecodable, TyEncodable, TypeFoldable, TypeVisitable,
 };
 use rustc_span::def_id::{CRATE_DEF_ID, LocalDefId};
-use rustc_span::symbol::Symbol;
-use rustc_span::{DUMMY_SP, Span};
+use rustc_span::{DUMMY_SP, Span, Symbol};
 // FIXME: Remove this import and import via `solve::`
 pub use rustc_type_ir::solve::BuiltinImplSource;
 use smallvec::{SmallVec, smallvec};
@@ -316,8 +315,8 @@ pub enum ObligationCauseCode<'tcx> {
         span: Option<Span>,
         /// The root expected type induced by a scrutinee or type expression.
         root_ty: Ty<'tcx>,
-        /// Whether the `Span` came from an expression or a type expression.
-        origin_expr: bool,
+        /// Information about the `Span`, if it came from an expression, otherwise `None`.
+        origin_expr: Option<PatternOriginExpr>,
     },
 
     /// Computing common supertype in an if expression
@@ -530,6 +529,25 @@ pub struct MatchExpressionArmCause<'tcx> {
     pub tail_defines_return_position_impl_trait: Option<LocalDefId>,
 }
 
+/// Information about the origin expression of a pattern, relevant to diagnostics.
+/// Fields here refer to the scrutinee of a pattern.
+/// If the scrutinee isn't given in the diagnostic, then this won't exist.
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+#[derive(TypeFoldable, TypeVisitable, HashStable, TyEncodable, TyDecodable)]
+pub struct PatternOriginExpr {
+    /// A span representing the scrutinee expression, with all leading references
+    /// peeled from the expression.
+    /// Only references in the expression are peeled - if the expression refers to a variable
+    /// whose type is a reference, then that reference is kept because it wasn't created
+    /// in the expression.
+    pub peeled_span: Span,
+    /// The number of references that were peeled to produce `peeled_span`.
+    pub peeled_count: usize,
+    /// Does the peeled expression need to be wrapped in parentheses for
+    /// a prefix suggestion (i.e., dereference) to be valid.
+    pub peeled_prefix_suggestion_parentheses: bool,
+}
+
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 #[derive(TypeFoldable, TypeVisitable, HashStable, TyEncodable, TyDecodable)]
 pub struct IfExpressionCause<'tcx> {
diff --git a/compiler/rustc_middle/src/traits/specialization_graph.rs b/compiler/rustc_middle/src/traits/specialization_graph.rs
index 515aabbe2fc..ed7c98ee0e0 100644
--- a/compiler/rustc_middle/src/traits/specialization_graph.rs
+++ b/compiler/rustc_middle/src/traits/specialization_graph.rs
@@ -2,7 +2,7 @@ use rustc_data_structures::fx::FxIndexMap;
 use rustc_errors::ErrorGuaranteed;
 use rustc_hir::def_id::{DefId, DefIdMap};
 use rustc_macros::{HashStable, TyDecodable, TyEncodable};
-use rustc_span::symbol::sym;
+use rustc_span::sym;
 
 use crate::error::StrictCoherenceNeedsNegativeCoherence;
 use crate::ty::fast_reject::SimplifiedType;
diff --git a/compiler/rustc_middle/src/ty/adt.rs b/compiler/rustc_middle/src/ty/adt.rs
index 447cbc8932e..8f4137cc011 100644
--- a/compiler/rustc_middle/src/ty/adt.rs
+++ b/compiler/rustc_middle/src/ty/adt.rs
@@ -17,7 +17,7 @@ use rustc_index::{IndexSlice, IndexVec};
 use rustc_macros::{HashStable, TyDecodable, TyEncodable};
 use rustc_query_system::ich::StableHashingContext;
 use rustc_session::DataTypeKind;
-use rustc_span::symbol::sym;
+use rustc_span::sym;
 use rustc_type_ir::solve::AdtDestructorKind;
 use tracing::{debug, info, trace};
 
diff --git a/compiler/rustc_middle/src/ty/assoc.rs b/compiler/rustc_middle/src/ty/assoc.rs
index 62157d9bfe2..6309dd2e490 100644
--- a/compiler/rustc_middle/src/ty/assoc.rs
+++ b/compiler/rustc_middle/src/ty/assoc.rs
@@ -3,7 +3,7 @@ use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Namespace};
 use rustc_hir::def_id::DefId;
 use rustc_macros::{Decodable, Encodable, HashStable};
-use rustc_span::symbol::{Ident, Symbol};
+use rustc_span::{Ident, Symbol};
 
 use super::{TyCtxt, Visibility};
 use crate::ty;
diff --git a/compiler/rustc_middle/src/ty/closure.rs b/compiler/rustc_middle/src/ty/closure.rs
index 6ab4d76e545..33d39b137b6 100644
--- a/compiler/rustc_middle/src/ty/closure.rs
+++ b/compiler/rustc_middle/src/ty/closure.rs
@@ -7,8 +7,7 @@ use rustc_hir::HirId;
 use rustc_hir::def_id::LocalDefId;
 use rustc_macros::{HashStable, TyDecodable, TyEncodable, TypeFoldable, TypeVisitable};
 use rustc_span::def_id::LocalDefIdMap;
-use rustc_span::symbol::Ident;
-use rustc_span::{Span, Symbol};
+use rustc_span::{Ident, Span, Symbol};
 
 use super::TyCtxt;
 use crate::hir::place::{
diff --git a/compiler/rustc_middle/src/ty/codec.rs b/compiler/rustc_middle/src/ty/codec.rs
index aba5719138c..94bf1aa4f03 100644
--- a/compiler/rustc_middle/src/ty/codec.rs
+++ b/compiler/rustc_middle/src/ty/codec.rs
@@ -548,7 +548,7 @@ macro_rules! impl_arena_copy_decoder {
 
 impl_arena_copy_decoder! {<'tcx>
     Span,
-    rustc_span::symbol::Ident,
+    rustc_span::Ident,
     ty::Variance,
     rustc_span::def_id::DefId,
     rustc_span::def_id::LocalDefId,
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index db1a479f580..977e62becf1 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -10,10 +10,11 @@ use std::cmp::Ordering;
 use std::hash::{Hash, Hasher};
 use std::marker::PhantomData;
 use std::ops::{Bound, Deref};
+use std::sync::OnceLock;
 use std::{fmt, iter, mem};
 
 use rustc_abi::{ExternAbi, FieldIdx, Layout, LayoutData, TargetDataLayout, VariantIdx};
-use rustc_ast::{self as ast, attr};
+use rustc_ast as ast;
 use rustc_data_structures::defer;
 use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::fx::FxHashMap;
@@ -29,13 +30,12 @@ use rustc_data_structures::unord::UnordSet;
 use rustc_errors::{
     Applicability, Diag, DiagCtxtHandle, ErrorGuaranteed, LintDiagnostic, MultiSpan,
 };
-use rustc_hir as hir;
 use rustc_hir::def::{CtorKind, DefKind};
 use rustc_hir::def_id::{CrateNum, DefId, LOCAL_CRATE, LocalDefId};
 use rustc_hir::definitions::Definitions;
 use rustc_hir::intravisit::Visitor;
 use rustc_hir::lang_items::LangItem;
-use rustc_hir::{HirId, Node, TraitCandidate};
+use rustc_hir::{self as hir, Attribute, HirId, Node, TraitCandidate};
 use rustc_index::IndexVec;
 use rustc_macros::{HashStable, TyDecodable, TyEncodable};
 use rustc_query_system::cache::WithDepNode;
@@ -47,8 +47,7 @@ use rustc_session::cstore::{CrateStoreDyn, Untracked};
 use rustc_session::lint::Lint;
 use rustc_session::{Limit, MetadataKind, Session};
 use rustc_span::def_id::{CRATE_DEF_ID, DefPathHash, StableCrateId};
-use rustc_span::symbol::{Ident, Symbol, kw, sym};
-use rustc_span::{DUMMY_SP, Span};
+use rustc_span::{DUMMY_SP, Ident, Span, Symbol, kw, sym};
 use rustc_type_ir::TyKind::*;
 use rustc_type_ir::fold::TypeFoldable;
 use rustc_type_ir::lang_items::TraitSolverLangItem;
@@ -586,7 +585,7 @@ impl<'tcx> Interner for TyCtxt<'tcx> {
     }
 
     fn trait_is_unsafe(self, trait_def_id: Self::DefId) -> bool {
-        self.trait_def(trait_def_id).safety == hir::Safety::Unsafe
+        self.trait_def(trait_def_id).safety.is_unsafe()
     }
 
     fn is_impl_trait_in_trait(self, def_id: DefId) -> bool {
@@ -722,7 +721,7 @@ impl<'tcx> rustc_type_ir::inherent::Safety<TyCtxt<'tcx>> for hir::Safety {
     }
 
     fn is_safe(self) -> bool {
-        matches!(self, hir::Safety::Safe)
+        self.is_safe()
     }
 
     fn prefix_str(self) -> &'static str {
@@ -1119,10 +1118,10 @@ impl<'tcx> CommonConsts<'tcx> {
 /// either a `ReEarlyParam` or `ReLateParam`.
 #[derive(Debug)]
 pub struct FreeRegionInfo {
-    /// `LocalDefId` of the free region.
-    pub def_id: LocalDefId,
-    /// the bound region corresponding to free region.
-    pub bound_region: ty::BoundRegionKind,
+    /// `LocalDefId` of the scope.
+    pub scope: LocalDefId,
+    /// the `DefId` of the free region.
+    pub region_def_id: DefId,
     /// checks if bound region is in Impl Item
     pub is_impl_item: bool,
 }
@@ -1347,46 +1346,6 @@ pub struct GlobalCtxt<'tcx> {
 
     /// Stores memory for globals (statics/consts).
     pub(crate) alloc_map: Lock<interpret::AllocMap<'tcx>>,
-
-    current_gcx: CurrentGcx,
-}
-
-impl<'tcx> GlobalCtxt<'tcx> {
-    /// Installs `self` in a `TyCtxt` and `ImplicitCtxt` for the duration of
-    /// `f`.
-    pub fn enter<F, R>(&'tcx self, f: F) -> R
-    where
-        F: FnOnce(TyCtxt<'tcx>) -> R,
-    {
-        let icx = tls::ImplicitCtxt::new(self);
-
-        // Reset `current_gcx` to `None` when we exit.
-        let _on_drop = defer(move || {
-            *self.current_gcx.value.write() = None;
-        });
-
-        // Set this `GlobalCtxt` as the current one.
-        {
-            let mut guard = self.current_gcx.value.write();
-            assert!(guard.is_none(), "no `GlobalCtxt` is currently set");
-            *guard = Some(self as *const _ as *const ());
-        }
-
-        tls::enter_context(&icx, || f(icx.tcx))
-    }
-
-    pub fn finish(&'tcx self) {
-        // We assume that no queries are run past here. If there are new queries
-        // after this point, they'll show up as "<unknown>" in self-profiling data.
-        self.enter(|tcx| tcx.alloc_self_profile_query_strings());
-
-        self.enter(|tcx| tcx.save_dep_graph());
-        self.enter(|tcx| tcx.query_key_hash_verify_all());
-
-        if let Err((path, error)) = self.dep_graph.finish_encoding() {
-            self.sess.dcx().emit_fatal(crate::error::FailedWritingFile { path: &path, error });
-        }
-    }
 }
 
 /// This is used to get a reference to a `GlobalCtxt` if one is available.
@@ -1530,7 +1489,8 @@ impl<'tcx> TyCtxt<'tcx> {
     /// By only providing the `TyCtxt` inside of the closure we enforce that the type
     /// context and any interned value (types, args, etc.) can only be used while `ty::tls`
     /// has a valid reference to the context, to allow formatting values that need it.
-    pub fn create_global_ctxt(
+    pub fn create_global_ctxt<T>(
+        gcx_cell: &'tcx OnceLock<GlobalCtxt<'tcx>>,
         s: &'tcx Session,
         crate_types: Vec<CrateType>,
         stable_crate_id: StableCrateId,
@@ -1542,7 +1502,8 @@ impl<'tcx> TyCtxt<'tcx> {
         query_system: QuerySystem<'tcx>,
         hooks: crate::hooks::Providers,
         current_gcx: CurrentGcx,
-    ) -> GlobalCtxt<'tcx> {
+        f: impl FnOnce(TyCtxt<'tcx>) -> T,
+    ) -> T {
         let data_layout = s.target.parse_data_layout().unwrap_or_else(|err| {
             s.dcx().emit_fatal(err);
         });
@@ -1551,7 +1512,7 @@ impl<'tcx> TyCtxt<'tcx> {
         let common_lifetimes = CommonLifetimes::new(&interners);
         let common_consts = CommonConsts::new(&interners, &common_types, s, &untracked);
 
-        GlobalCtxt {
+        let gcx = gcx_cell.get_or_init(|| GlobalCtxt {
             sess: s,
             crate_types,
             stable_crate_id,
@@ -1575,8 +1536,23 @@ impl<'tcx> TyCtxt<'tcx> {
             canonical_param_env_cache: Default::default(),
             data_layout,
             alloc_map: Lock::new(interpret::AllocMap::new()),
-            current_gcx,
+        });
+
+        let icx = tls::ImplicitCtxt::new(&gcx);
+
+        // Reset `current_gcx` to `None` when we exit.
+        let _on_drop = defer(|| {
+            *current_gcx.value.write() = None;
+        });
+
+        // Set this `GlobalCtxt` as the current one.
+        {
+            let mut guard = current_gcx.value.write();
+            assert!(guard.is_none(), "no `GlobalCtxt` is currently set");
+            *guard = Some(&gcx as *const _ as *const ());
         }
+
+        tls::enter_context(&icx, || f(icx.tcx))
     }
 
     /// Obtain all lang items of this crate and all dependencies (recursively)
@@ -1983,7 +1959,7 @@ impl<'tcx> TyCtxt<'tcx> {
         generic_param_scope: LocalDefId,
         mut region: Region<'tcx>,
     ) -> Option<FreeRegionInfo> {
-        let (suitable_region_binding_scope, bound_region) = loop {
+        let (suitable_region_binding_scope, region_def_id) = loop {
             let def_id =
                 region.opt_param_def_id(self, generic_param_scope.to_def_id())?.as_local()?;
             let scope = self.local_parent(def_id);
@@ -1993,10 +1969,7 @@ impl<'tcx> TyCtxt<'tcx> {
                 region = self.map_opaque_lifetime_to_parent_lifetime(def_id);
                 continue;
             }
-            break (
-                scope,
-                ty::BoundRegionKind::Named(def_id.into(), self.item_name(def_id.into())),
-            );
+            break (scope, def_id.into());
         };
 
         let is_impl_item = match self.hir_node_by_def_id(suitable_region_binding_scope) {
@@ -2005,7 +1978,7 @@ impl<'tcx> TyCtxt<'tcx> {
             _ => false,
         };
 
-        Some(FreeRegionInfo { def_id: suitable_region_binding_scope, bound_region, is_impl_item })
+        Some(FreeRegionInfo { scope: suitable_region_binding_scope, region_def_id, is_impl_item })
     }
 
     /// Given a `DefId` for an `fn`, return all the `dyn` and `impl` traits in its return type.
@@ -2120,6 +2093,19 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn local_opaque_ty_origin(self, def_id: LocalDefId) -> hir::OpaqueTyOrigin<LocalDefId> {
         self.hir().expect_opaque_ty(def_id).origin
     }
+
+    pub fn finish(self) {
+        // We assume that no queries are run past here. If there are new queries
+        // after this point, they'll show up as "<unknown>" in self-profiling data.
+        self.alloc_self_profile_query_strings();
+
+        self.save_dep_graph();
+        self.query_key_hash_verify_all();
+
+        if let Err((path, error)) = self.dep_graph.finish_encoding() {
+            self.sess.dcx().emit_fatal(crate::error::FailedWritingFile { path: &path, error });
+        }
+    }
 }
 
 macro_rules! nop_lift {
@@ -2521,7 +2507,7 @@ impl<'tcx> TyCtxt<'tcx> {
     /// that is, a `fn` type that is equivalent in every way for being
     /// unsafe.
     pub fn safe_to_unsafe_fn_ty(self, sig: PolyFnSig<'tcx>) -> Ty<'tcx> {
-        assert_eq!(sig.safety(), hir::Safety::Safe);
+        assert!(sig.safety().is_safe());
         Ty::new_fn_ptr(self, sig.map_bound(|sig| ty::FnSig { safety: hir::Safety::Unsafe, ..sig }))
     }
 
@@ -3105,7 +3091,7 @@ impl<'tcx> TyCtxt<'tcx> {
                     return ty::Region::new_late_param(
                         self,
                         new_parent.to_def_id(),
-                        ty::BoundRegionKind::Named(
+                        ty::LateParamRegionKind::Named(
                             lbv.to_def_id(),
                             self.item_name(lbv.to_def_id()),
                         ),
@@ -3239,12 +3225,16 @@ pub fn provide(providers: &mut Providers) {
     providers.extern_mod_stmt_cnum =
         |tcx, id| tcx.resolutions(()).extern_crate_map.get(&id).cloned();
     providers.is_panic_runtime =
-        |tcx, LocalCrate| attr::contains_name(tcx.hir().krate_attrs(), sym::panic_runtime);
+        |tcx, LocalCrate| contains_name(tcx.hir().krate_attrs(), sym::panic_runtime);
     providers.is_compiler_builtins =
-        |tcx, LocalCrate| attr::contains_name(tcx.hir().krate_attrs(), sym::compiler_builtins);
+        |tcx, LocalCrate| contains_name(tcx.hir().krate_attrs(), sym::compiler_builtins);
     providers.has_panic_handler = |tcx, LocalCrate| {
         // We want to check if the panic handler was defined in this crate
         tcx.lang_items().panic_impl().is_some_and(|did| did.is_local())
     };
     providers.source_span = |tcx, def_id| tcx.untracked.source_span.get(def_id).unwrap_or(DUMMY_SP);
 }
+
+pub fn contains_name(attrs: &[Attribute], name: Symbol) -> bool {
+    attrs.iter().any(|x| x.has_name(name))
+}
diff --git a/compiler/rustc_middle/src/ty/diagnostics.rs b/compiler/rustc_middle/src/ty/diagnostics.rs
index 604f1da26c6..406e732744b 100644
--- a/compiler/rustc_middle/src/ty/diagnostics.rs
+++ b/compiler/rustc_middle/src/ty/diagnostics.rs
@@ -309,7 +309,7 @@ pub fn suggest_constraining_type_params<'a>(
         let Some(param) = param else { return false };
 
         {
-            let mut sized_constraints = constraints.extract_if(|(_, def_id, _)| {
+            let mut sized_constraints = constraints.extract_if(.., |(_, def_id, _)| {
                 def_id.is_some_and(|def_id| tcx.is_lang_item(def_id, LangItem::Sized))
             });
             if let Some((_, def_id, _)) = sized_constraints.next() {
diff --git a/compiler/rustc_middle/src/ty/fold.rs b/compiler/rustc_middle/src/ty/fold.rs
index 1b073d3c466..067516917ef 100644
--- a/compiler/rustc_middle/src/ty/fold.rs
+++ b/compiler/rustc_middle/src/ty/fold.rs
@@ -270,7 +270,8 @@ impl<'tcx> TyCtxt<'tcx> {
         T: TypeFoldable<TyCtxt<'tcx>>,
     {
         self.instantiate_bound_regions_uncached(value, |br| {
-            ty::Region::new_late_param(self, all_outlive_scope, br.kind)
+            let kind = ty::LateParamRegionKind::from_bound(br.var, br.kind);
+            ty::Region::new_late_param(self, all_outlive_scope, kind)
         })
     }
 
diff --git a/compiler/rustc_middle/src/ty/generics.rs b/compiler/rustc_middle/src/ty/generics.rs
index ce40ab18261..85d9db7ee74 100644
--- a/compiler/rustc_middle/src/ty/generics.rs
+++ b/compiler/rustc_middle/src/ty/generics.rs
@@ -2,8 +2,7 @@ use rustc_ast as ast;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_hir::def_id::DefId;
 use rustc_macros::{HashStable, TyDecodable, TyEncodable};
-use rustc_span::Span;
-use rustc_span::symbol::{Symbol, kw};
+use rustc_span::{Span, Symbol, kw};
 use tracing::instrument;
 
 use super::{Clause, InstantiatedPredicates, ParamConst, ParamTy, Ty, TyCtxt};
diff --git a/compiler/rustc_middle/src/ty/instance.rs b/compiler/rustc_middle/src/ty/instance.rs
index 1dd564d9798..49b5588e261 100644
--- a/compiler/rustc_middle/src/ty/instance.rs
+++ b/compiler/rustc_middle/src/ty/instance.rs
@@ -202,7 +202,7 @@ impl<'tcx> Instance<'tcx> {
         if !tcx.sess.opts.share_generics()
             // However, if the def_id is marked inline(never), then it's fine to just reuse the
             // upstream monomorphization.
-            && tcx.codegen_fn_attrs(self.def_id()).inline != rustc_attr::InlineAttr::Never
+            && tcx.codegen_fn_attrs(self.def_id()).inline != rustc_attr_parsing::InlineAttr::Never
         {
             return None;
         }
@@ -277,7 +277,7 @@ impl<'tcx> InstanceKind<'tcx> {
         &self,
         tcx: TyCtxt<'tcx>,
         attr: Symbol,
-    ) -> impl Iterator<Item = &'tcx rustc_ast::Attribute> {
+    ) -> impl Iterator<Item = &'tcx hir::Attribute> {
         tcx.get_attrs(self.def_id(), attr)
     }
 
diff --git a/compiler/rustc_middle/src/ty/layout.rs b/compiler/rustc_middle/src/ty/layout.rs
index 07573a79260..367b0c07f9b 100644
--- a/compiler/rustc_middle/src/ty/layout.rs
+++ b/compiler/rustc_middle/src/ty/layout.rs
@@ -16,8 +16,7 @@ use rustc_hir::def_id::DefId;
 use rustc_index::IndexVec;
 use rustc_macros::{HashStable, TyDecodable, TyEncodable, extension};
 use rustc_session::config::OptLevel;
-use rustc_span::symbol::{Symbol, sym};
-use rustc_span::{DUMMY_SP, ErrorGuaranteed, Span};
+use rustc_span::{DUMMY_SP, ErrorGuaranteed, Span, Symbol, sym};
 use rustc_target::callconv::FnAbi;
 use rustc_target::spec::{
     HasTargetSpec, HasWasmCAbiOpt, HasX86AbiOpt, PanicStrategy, Target, WasmCAbi, X86Abi,
@@ -735,21 +734,22 @@ where
         let layout = match this.variants {
             Variants::Single { index }
                 // If all variants but one are uninhabited, the variant layout is the enum layout.
-                if index == variant_index &&
-                // Don't confuse variants of uninhabited enums with the enum itself.
-                // For more details see https://github.com/rust-lang/rust/issues/69763.
-                this.fields != FieldsShape::Primitive =>
+                if index == variant_index =>
             {
                 this.layout
             }
 
-            Variants::Single { index } => {
+            Variants::Single { .. } | Variants::Empty => {
+                // Single-variant and no-variant enums *can* have other variants, but those are
+                // uninhabited. Produce a layout that has the right fields for that variant, so that
+                // the rest of the compiler can project fields etc as usual.
+
                 let tcx = cx.tcx();
                 let typing_env = cx.typing_env();
 
                 // Deny calling for_variant more than once for non-Single enums.
                 if let Ok(original_layout) = tcx.layout_of(typing_env.as_query_input(this.ty)) {
-                    assert_eq!(original_layout.variants, Variants::Single { index });
+                    assert_eq!(original_layout.variants, this.variants);
                 }
 
                 let fields = match this.ty.kind() {
@@ -903,6 +903,7 @@ where
                 ),
 
                 ty::Coroutine(def_id, args) => match this.variants {
+                    Variants::Empty => unreachable!(),
                     Variants::Single { index } => TyMaybeWithLayout::Ty(
                         args.as_coroutine()
                             .state_tys(def_id, tcx)
@@ -928,6 +929,7 @@ where
                             let field = &def.variant(index).fields[FieldIdx::from_usize(i)];
                             TyMaybeWithLayout::Ty(field.ty(tcx, args))
                         }
+                        Variants::Empty => panic!("there is no field in Variants::Empty types"),
 
                         // Discriminant field for enums (where applicable).
                         Variants::Multiple { tag, .. } => {
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index e47b0cf0b3b..5e929fbec0b 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -33,9 +33,9 @@ use rustc_data_structures::intern::Interned;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::steal::Steal;
 use rustc_errors::{Diag, ErrorGuaranteed, StashKey};
+use rustc_hir::LangItem;
 use rustc_hir::def::{CtorKind, CtorOf, DefKind, DocLinkResMap, LifetimeRes, Res};
 use rustc_hir::def_id::{CrateNum, DefId, DefIdMap, LocalDefId, LocalDefIdMap};
-use rustc_hir::{LangItem, Safety};
 use rustc_index::IndexVec;
 use rustc_macros::{
     Decodable, Encodable, HashStable, TyDecodable, TyEncodable, TypeFoldable, TypeVisitable,
@@ -46,13 +46,12 @@ use rustc_serialize::{Decodable, Encodable};
 use rustc_session::lint::LintBuffer;
 pub use rustc_session::lint::RegisteredTools;
 use rustc_span::hygiene::MacroKind;
-use rustc_span::symbol::{Ident, Symbol, kw, sym};
-use rustc_span::{ExpnId, ExpnKind, Span};
+use rustc_span::{ExpnId, ExpnKind, Ident, Span, Symbol, kw, sym};
 pub use rustc_type_ir::relate::VarianceDiagInfo;
 pub use rustc_type_ir::*;
 use tracing::{debug, instrument};
 pub use vtable::*;
-use {rustc_ast as ast, rustc_attr as attr, rustc_hir as hir};
+use {rustc_ast as ast, rustc_attr_parsing as attr, rustc_hir as hir};
 
 pub use self::closure::{
     BorrowKind, CAPTURE_STRUCT_LOCAL, CaptureInfo, CapturedPlace, ClosureTypeInfo,
@@ -84,7 +83,8 @@ pub use self::predicate::{
     TypeOutlivesPredicate,
 };
 pub use self::region::{
-    BoundRegion, BoundRegionKind, EarlyParamRegion, LateParamRegion, Region, RegionKind, RegionVid,
+    BoundRegion, BoundRegionKind, EarlyParamRegion, LateParamRegion, LateParamRegionKind, Region,
+    RegionKind, RegionVid,
 };
 pub use self::rvalue_scopes::RvalueScopes;
 pub use self::sty::{
@@ -972,7 +972,7 @@ pub struct ParamEnv<'tcx> {
 }
 
 impl<'tcx> rustc_type_ir::inherent::ParamEnv<TyCtxt<'tcx>> for ParamEnv<'tcx> {
-    fn caller_bounds(self) -> impl IntoIterator<Item = ty::Clause<'tcx>> {
+    fn caller_bounds(self) -> impl inherent::SliceLike<Item = ty::Clause<'tcx>> {
         self.caller_bounds()
     }
 }
@@ -1281,7 +1281,7 @@ impl VariantDef {
 
     /// Returns whether this variant has unsafe fields.
     pub fn has_unsafe_fields(&self) -> bool {
-        self.fields.iter().any(|x| x.safety == Safety::Unsafe)
+        self.fields.iter().any(|x| x.safety.is_unsafe())
     }
 }
 
@@ -1745,11 +1745,11 @@ impl<'tcx> TyCtxt<'tcx> {
     }
 
     // FIXME(@lcnr): Remove this function.
-    pub fn get_attrs_unchecked(self, did: DefId) -> &'tcx [ast::Attribute] {
+    pub fn get_attrs_unchecked(self, did: DefId) -> &'tcx [hir::Attribute] {
         if let Some(did) = did.as_local() {
             self.hir().attrs(self.local_def_id_to_hir_id(did))
         } else {
-            self.item_attrs(did)
+            self.attrs_for_def(did)
         }
     }
 
@@ -1758,14 +1758,14 @@ impl<'tcx> TyCtxt<'tcx> {
         self,
         did: impl Into<DefId>,
         attr: Symbol,
-    ) -> impl Iterator<Item = &'tcx ast::Attribute> {
+    ) -> impl Iterator<Item = &'tcx hir::Attribute> {
         let did: DefId = did.into();
-        let filter_fn = move |a: &&ast::Attribute| a.has_name(attr);
+        let filter_fn = move |a: &&hir::Attribute| a.has_name(attr);
         if let Some(did) = did.as_local() {
             self.hir().attrs(self.local_def_id_to_hir_id(did)).iter().filter(filter_fn)
         } else {
             debug_assert!(rustc_feature::encode_cross_crate(attr));
-            self.item_attrs(did).iter().filter(filter_fn)
+            self.attrs_for_def(did).iter().filter(filter_fn)
         }
     }
 
@@ -1781,7 +1781,7 @@ impl<'tcx> TyCtxt<'tcx> {
         self,
         did: impl Into<DefId>,
         attr: Symbol,
-    ) -> Option<&'tcx ast::Attribute> {
+    ) -> Option<&'tcx hir::Attribute> {
         let did: DefId = did.into();
         if did.as_local().is_some() {
             // it's a crate local item, we need to check feature flags
@@ -1794,7 +1794,7 @@ impl<'tcx> TyCtxt<'tcx> {
             // we filter out unstable diagnostic attributes before
             // encoding attributes
             debug_assert!(rustc_feature::encode_cross_crate(attr));
-            self.item_attrs(did)
+            self.attrs_for_def(did)
                 .iter()
                 .find(|a| matches!(a.path().as_ref(), [sym::diagnostic, a] if *a == attr))
         }
@@ -1804,19 +1804,19 @@ impl<'tcx> TyCtxt<'tcx> {
         self,
         did: DefId,
         attr: &'attr [Symbol],
-    ) -> impl Iterator<Item = &'tcx ast::Attribute> + 'attr
+    ) -> impl Iterator<Item = &'tcx hir::Attribute> + 'attr
     where
         'tcx: 'attr,
     {
-        let filter_fn = move |a: &&ast::Attribute| a.path_matches(attr);
+        let filter_fn = move |a: &&hir::Attribute| a.path_matches(attr);
         if let Some(did) = did.as_local() {
             self.hir().attrs(self.local_def_id_to_hir_id(did)).iter().filter(filter_fn)
         } else {
-            self.item_attrs(did).iter().filter(filter_fn)
+            self.attrs_for_def(did).iter().filter(filter_fn)
         }
     }
 
-    pub fn get_attr(self, did: impl Into<DefId>, attr: Symbol) -> Option<&'tcx ast::Attribute> {
+    pub fn get_attr(self, did: impl Into<DefId>, attr: Symbol) -> Option<&'tcx hir::Attribute> {
         if cfg!(debug_assertions) && !rustc_feature::is_valid_for_get_attr(attr) {
             let did: DefId = did.into();
             bug!("get_attr: unexpected called with DefId `{:?}`, attr `{:?}`", did, attr);
diff --git a/compiler/rustc_middle/src/ty/parameterized.rs b/compiler/rustc_middle/src/ty/parameterized.rs
index f7322217aa3..86a95827e84 100644
--- a/compiler/rustc_middle/src/ty/parameterized.rs
+++ b/compiler/rustc_middle/src/ty/parameterized.rs
@@ -80,10 +80,10 @@ trivially_parameterized_over_tcx! {
     rustc_ast::Attribute,
     rustc_ast::DelimArgs,
     rustc_ast::expand::StrippedCfgItem<rustc_hir::def_id::DefIndex>,
-    rustc_attr::ConstStability,
-    rustc_attr::DefaultBodyStability,
-    rustc_attr::Deprecation,
-    rustc_attr::Stability,
+    rustc_attr_parsing::ConstStability,
+    rustc_attr_parsing::DefaultBodyStability,
+    rustc_attr_parsing::Deprecation,
+    rustc_attr_parsing::Stability,
     rustc_hir::Constness,
     rustc_hir::Defaultness,
     rustc_hir::Safety,
@@ -109,8 +109,9 @@ trivially_parameterized_over_tcx! {
     rustc_span::Symbol,
     rustc_span::def_id::DefPathHash,
     rustc_span::hygiene::SyntaxContextData,
-    rustc_span::symbol::Ident,
+    rustc_span::Ident,
     rustc_type_ir::Variance,
+    rustc_hir::Attribute,
 }
 
 // HACK(compiler-errors): This macro rule can only take a fake path,
@@ -140,5 +141,5 @@ parameterized_over_tcx! {
     ty::Predicate,
     ty::Clause,
     ty::ClauseKind,
-    ty::ImplTraitHeader
+    ty::ImplTraitHeader,
 }
diff --git a/compiler/rustc_middle/src/ty/print/pretty.rs b/compiler/rustc_middle/src/ty/print/pretty.rs
index 40e0fb0087f..a089eac5d7e 100644
--- a/compiler/rustc_middle/src/ty/print/pretty.rs
+++ b/compiler/rustc_middle/src/ty/print/pretty.rs
@@ -16,8 +16,7 @@ use rustc_hir::definitions::{DefKey, DefPathDataName};
 use rustc_macros::{Lift, extension};
 use rustc_session::Limit;
 use rustc_session::cstore::{ExternCrate, ExternCrateSource};
-use rustc_span::symbol::{Ident, Symbol, kw};
-use rustc_span::{FileNameDisplayPreference, sym};
+use rustc_span::{FileNameDisplayPreference, Ident, Symbol, kw, sym};
 use rustc_type_ir::{Upcast as _, elaborate};
 use smallvec::SmallVec;
 
@@ -2375,8 +2374,8 @@ impl<'tcx> PrettyPrinter<'tcx> for FmtPrinter<'_, 'tcx> {
         match *region {
             ty::ReEarlyParam(ref data) => data.has_name(),
 
+            ty::ReLateParam(ty::LateParamRegion { kind, .. }) => kind.is_named(),
             ty::ReBound(_, ty::BoundRegion { kind: br, .. })
-            | ty::ReLateParam(ty::LateParamRegion { bound_region: br, .. })
             | ty::RePlaceholder(ty::Placeholder {
                 bound: ty::BoundRegion { kind: br, .. }, ..
             }) => {
@@ -2449,8 +2448,13 @@ impl<'tcx> FmtPrinter<'_, 'tcx> {
                     return Ok(());
                 }
             }
+            ty::ReLateParam(ty::LateParamRegion { kind, .. }) => {
+                if let Some(name) = kind.get_name() {
+                    p!(write("{}", name));
+                    return Ok(());
+                }
+            }
             ty::ReBound(_, ty::BoundRegion { kind: br, .. })
-            | ty::ReLateParam(ty::LateParamRegion { bound_region: br, .. })
             | ty::RePlaceholder(ty::Placeholder {
                 bound: ty::BoundRegion { kind: br, .. }, ..
             }) => {
diff --git a/compiler/rustc_middle/src/ty/region.rs b/compiler/rustc_middle/src/ty/region.rs
index 60c2c322d4f..14a2e5befe6 100644
--- a/compiler/rustc_middle/src/ty/region.rs
+++ b/compiler/rustc_middle/src/ty/region.rs
@@ -4,8 +4,7 @@ use rustc_data_structures::intern::Interned;
 use rustc_errors::MultiSpan;
 use rustc_hir::def_id::DefId;
 use rustc_macros::{HashStable, TyDecodable, TyEncodable};
-use rustc_span::symbol::{Symbol, kw, sym};
-use rustc_span::{DUMMY_SP, ErrorGuaranteed};
+use rustc_span::{DUMMY_SP, ErrorGuaranteed, Symbol, kw, sym};
 use rustc_type_ir::RegionKind as IrRegionKind;
 pub use rustc_type_ir::RegionVid;
 use tracing::debug;
@@ -70,9 +69,10 @@ impl<'tcx> Region<'tcx> {
     pub fn new_late_param(
         tcx: TyCtxt<'tcx>,
         scope: DefId,
-        bound_region: ty::BoundRegionKind,
+        kind: LateParamRegionKind,
     ) -> Region<'tcx> {
-        tcx.intern_region(ty::ReLateParam(ty::LateParamRegion { scope, bound_region }))
+        let data = LateParamRegion { scope, kind };
+        tcx.intern_region(ty::ReLateParam(data))
     }
 
     #[inline]
@@ -125,8 +125,8 @@ impl<'tcx> Region<'tcx> {
         match kind {
             ty::ReEarlyParam(region) => Region::new_early_param(tcx, region),
             ty::ReBound(debruijn, region) => Region::new_bound(tcx, debruijn, region),
-            ty::ReLateParam(ty::LateParamRegion { scope, bound_region }) => {
-                Region::new_late_param(tcx, scope, bound_region)
+            ty::ReLateParam(ty::LateParamRegion { scope, kind }) => {
+                Region::new_late_param(tcx, scope, kind)
             }
             ty::ReStatic => tcx.lifetimes.re_static,
             ty::ReVar(vid) => Region::new_var(tcx, vid),
@@ -166,7 +166,7 @@ impl<'tcx> Region<'tcx> {
             match *self {
                 ty::ReEarlyParam(ebr) => Some(ebr.name),
                 ty::ReBound(_, br) => br.kind.get_name(),
-                ty::ReLateParam(fr) => fr.bound_region.get_name(),
+                ty::ReLateParam(fr) => fr.kind.get_name(),
                 ty::ReStatic => Some(kw::StaticLifetime),
                 ty::RePlaceholder(placeholder) => placeholder.bound.kind.get_name(),
                 _ => None,
@@ -188,7 +188,7 @@ impl<'tcx> Region<'tcx> {
         match *self {
             ty::ReEarlyParam(ebr) => ebr.has_name(),
             ty::ReBound(_, br) => br.kind.is_named(),
-            ty::ReLateParam(fr) => fr.bound_region.is_named(),
+            ty::ReLateParam(fr) => fr.kind.is_named(),
             ty::ReStatic => true,
             ty::ReVar(..) => false,
             ty::RePlaceholder(placeholder) => placeholder.bound.kind.is_named(),
@@ -311,7 +311,7 @@ impl<'tcx> Region<'tcx> {
                 Some(tcx.generics_of(binding_item).region_param(ebr, tcx).def_id)
             }
             ty::ReLateParam(ty::LateParamRegion {
-                bound_region: ty::BoundRegionKind::Named(def_id, _),
+                kind: ty::LateParamRegionKind::Named(def_id, _),
                 ..
             }) => Some(def_id),
             _ => None,
@@ -359,7 +359,71 @@ impl std::fmt::Debug for EarlyParamRegion {
 /// different parameters apart.
 pub struct LateParamRegion {
     pub scope: DefId,
-    pub bound_region: BoundRegionKind,
+    pub kind: LateParamRegionKind,
+}
+
+/// When liberating bound regions, we map their [`BoundRegionKind`]
+/// to this as we need to track the index of anonymous regions. We
+/// otherwise end up liberating multiple bound regions to the same
+/// late-bound region.
+#[derive(Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable, Copy)]
+#[derive(HashStable)]
+pub enum LateParamRegionKind {
+    /// An anonymous region parameter for a given fn (&T)
+    ///
+    /// Unlike [`BoundRegionKind::Anon`], this tracks the index of the
+    /// liberated bound region.
+    ///
+    /// We should ideally never liberate anonymous regions, but do so for the
+    /// sake of diagnostics in `FnCtxt::sig_of_closure_with_expectation`.
+    Anon(u32),
+
+    /// Named region parameters for functions (a in &'a T)
+    ///
+    /// The `DefId` is needed to distinguish free regions in
+    /// the event of shadowing.
+    Named(DefId, Symbol),
+
+    /// Anonymous region for the implicit env pointer parameter
+    /// to a closure
+    ClosureEnv,
+}
+
+impl LateParamRegionKind {
+    pub fn from_bound(var: BoundVar, br: BoundRegionKind) -> LateParamRegionKind {
+        match br {
+            BoundRegionKind::Anon => LateParamRegionKind::Anon(var.as_u32()),
+            BoundRegionKind::Named(def_id, name) => LateParamRegionKind::Named(def_id, name),
+            BoundRegionKind::ClosureEnv => LateParamRegionKind::ClosureEnv,
+        }
+    }
+
+    pub fn is_named(&self) -> bool {
+        match *self {
+            LateParamRegionKind::Named(_, name) => {
+                name != kw::UnderscoreLifetime && name != kw::Empty
+            }
+            _ => false,
+        }
+    }
+
+    pub fn get_name(&self) -> Option<Symbol> {
+        if self.is_named() {
+            match *self {
+                LateParamRegionKind::Named(_, name) => return Some(name),
+                _ => unreachable!(),
+            }
+        }
+
+        None
+    }
+
+    pub fn get_id(&self) -> Option<DefId> {
+        match *self {
+            LateParamRegionKind::Named(id, _) => Some(id),
+            _ => None,
+        }
+    }
 }
 
 #[derive(Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable, Copy)]
diff --git a/compiler/rustc_middle/src/ty/rvalue_scopes.rs b/compiler/rustc_middle/src/ty/rvalue_scopes.rs
index 57c2d7623d2..b00c8169a36 100644
--- a/compiler/rustc_middle/src/ty/rvalue_scopes.rs
+++ b/compiler/rustc_middle/src/ty/rvalue_scopes.rs
@@ -35,7 +35,7 @@ impl RvalueScopes {
         // if there's one. Static items, for instance, won't
         // have an enclosing scope, hence no scope will be
         // returned.
-        let mut id = Scope { id: expr_id, data: ScopeData::Node };
+        let mut id = Scope { local_id: expr_id, data: ScopeData::Node };
         let mut backwards_incompatible = None;
 
         while let Some(&(p, _)) = region_scope_tree.parent_map.get(&id) {
@@ -60,7 +60,7 @@ impl RvalueScopes {
                     if backwards_incompatible.is_none() {
                         backwards_incompatible = region_scope_tree
                             .backwards_incompatible_scope
-                            .get(&p.item_local_id())
+                            .get(&p.local_id)
                             .copied();
                     }
                     id = p
@@ -76,7 +76,7 @@ impl RvalueScopes {
     pub fn record_rvalue_scope(&mut self, var: hir::ItemLocalId, lifetime: Option<Scope>) {
         debug!("record_rvalue_scope(var={var:?}, lifetime={lifetime:?})");
         if let Some(lifetime) = lifetime {
-            assert!(var != lifetime.item_local_id());
+            assert!(var != lifetime.local_id);
         }
         self.map.insert(var, lifetime);
     }
diff --git a/compiler/rustc_middle/src/ty/structural_impls.rs b/compiler/rustc_middle/src/ty/structural_impls.rs
index 0af0a5f170d..f38454ceac0 100644
--- a/compiler/rustc_middle/src/ty/structural_impls.rs
+++ b/compiler/rustc_middle/src/ty/structural_impls.rs
@@ -77,7 +77,23 @@ impl fmt::Debug for ty::BoundRegionKind {
 
 impl fmt::Debug for ty::LateParamRegion {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "ReLateParam({:?}, {:?})", self.scope, self.bound_region)
+        write!(f, "ReLateParam({:?}, {:?})", self.scope, self.kind)
+    }
+}
+
+impl fmt::Debug for ty::LateParamRegionKind {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match *self {
+            ty::LateParamRegionKind::Anon(idx) => write!(f, "BrAnon({idx})"),
+            ty::LateParamRegionKind::Named(did, name) => {
+                if did.is_crate_root() {
+                    write!(f, "BrNamed({name})")
+                } else {
+                    write!(f, "BrNamed({did:?}, {name})")
+                }
+            }
+            ty::LateParamRegionKind::ClosureEnv => write!(f, "BrEnv"),
+        }
     }
 }
 
@@ -224,7 +240,6 @@ TrivialTypeTraversalImpls! {
     ::rustc_ast::InlineAsmOptions,
     ::rustc_ast::InlineAsmTemplatePiece,
     ::rustc_ast::NodeId,
-    ::rustc_span::symbol::Symbol,
     ::rustc_hir::def::Res,
     ::rustc_hir::def_id::LocalDefId,
     ::rustc_hir::ByRef,
@@ -252,8 +267,9 @@ TrivialTypeTraversalImpls! {
     crate::ty::Placeholder<ty::BoundVar>,
     crate::ty::LateParamRegion,
     crate::ty::adjustment::PointerCoercion,
+    ::rustc_span::Ident,
     ::rustc_span::Span,
-    ::rustc_span::symbol::Ident,
+    ::rustc_span::Symbol,
     ty::BoundVar,
     ty::ValTree<'tcx>,
 }
diff --git a/compiler/rustc_middle/src/ty/sty.rs b/compiler/rustc_middle/src/ty/sty.rs
index 3fbc23924f5..045c483d6a5 100644
--- a/compiler/rustc_middle/src/ty/sty.rs
+++ b/compiler/rustc_middle/src/ty/sty.rs
@@ -15,8 +15,7 @@ use rustc_hir as hir;
 use rustc_hir::LangItem;
 use rustc_hir::def_id::DefId;
 use rustc_macros::{HashStable, TyDecodable, TyEncodable, TypeFoldable, extension};
-use rustc_span::symbol::{Symbol, sym};
-use rustc_span::{DUMMY_SP, Span};
+use rustc_span::{DUMMY_SP, Span, Symbol, sym};
 use rustc_type_ir::TyKind::*;
 use rustc_type_ir::visit::TypeVisitableExt;
 use rustc_type_ir::{self as ir, BoundVar, CollectAndApply, DynKind};
diff --git a/compiler/rustc_middle/src/ty/trait_def.rs b/compiler/rustc_middle/src/ty/trait_def.rs
index 188107e5d54..743ea33b20a 100644
--- a/compiler/rustc_middle/src/ty/trait_def.rs
+++ b/compiler/rustc_middle/src/ty/trait_def.rs
@@ -70,12 +70,12 @@ pub struct TraitDef {
 
     /// Whether to add a builtin `dyn Trait: Trait` implementation.
     /// This is enabled for all traits except ones marked with
-    /// `#[rustc_deny_explicit_impl(implement_via_object = false)]`.
+    /// `#[rustc_do_not_implement_via_object]`.
     pub implement_via_object: bool,
 
     /// Whether a trait is fully built-in, and any implementation is disallowed.
     /// This only applies to built-in traits, and is marked via
-    /// `#[rustc_deny_explicit_impl(implement_via_object = ...)]`.
+    /// `#[rustc_deny_explicit_impl]`.
     pub deny_explicit_impl: bool,
 }
 
diff --git a/compiler/rustc_middle/src/ty/typeck_results.rs b/compiler/rustc_middle/src/ty/typeck_results.rs
index 551c113aa59..f94f52e4f61 100644
--- a/compiler/rustc_middle/src/ty/typeck_results.rs
+++ b/compiler/rustc_middle/src/ty/typeck_results.rs
@@ -74,9 +74,8 @@ pub struct TypeckResults<'tcx> {
     pat_binding_modes: ItemLocalMap<BindingMode>,
 
     /// Top-level patterns whose match ergonomics need to be desugared by the Rust 2021 -> 2024
-    /// migration lint. The boolean indicates whether the emitted diagnostic should be a hard error
-    /// (if any of the incompatible pattern elements are in edition 2024).
-    rust_2024_migration_desugared_pats: ItemLocalMap<bool>,
+    /// migration lint. Problematic subpatterns are stored in the `Vec` for the lint to highlight.
+    rust_2024_migration_desugared_pats: ItemLocalMap<Vec<(Span, String)>>,
 
     /// Stores the types which were implicitly dereferenced in pattern binding modes
     /// for later usage in THIR lowering. For example,
@@ -419,14 +418,18 @@ impl<'tcx> TypeckResults<'tcx> {
         LocalTableInContextMut { hir_owner: self.hir_owner, data: &mut self.pat_adjustments }
     }
 
-    pub fn rust_2024_migration_desugared_pats(&self) -> LocalTableInContext<'_, bool> {
+    pub fn rust_2024_migration_desugared_pats(
+        &self,
+    ) -> LocalTableInContext<'_, Vec<(Span, String)>> {
         LocalTableInContext {
             hir_owner: self.hir_owner,
             data: &self.rust_2024_migration_desugared_pats,
         }
     }
 
-    pub fn rust_2024_migration_desugared_pats_mut(&mut self) -> LocalTableInContextMut<'_, bool> {
+    pub fn rust_2024_migration_desugared_pats_mut(
+        &mut self,
+    ) -> LocalTableInContextMut<'_, Vec<(Span, String)>> {
         LocalTableInContextMut {
             hir_owner: self.hir_owner,
             data: &mut self.rust_2024_migration_desugared_pats,
diff --git a/compiler/rustc_middle/src/ty/util.rs b/compiler/rustc_middle/src/ty/util.rs
index fda9898ed56..fc3530e3dde 100644
--- a/compiler/rustc_middle/src/ty/util.rs
+++ b/compiler/rustc_middle/src/ty/util.rs
@@ -1291,7 +1291,7 @@ impl<'tcx> Ty<'tcx> {
     /// Checks whether this type is an ADT that has unsafe fields.
     pub fn has_unsafe_fields(self) -> bool {
         if let ty::Adt(adt_def, ..) = self.kind() {
-            adt_def.all_fields().any(|x| x.safety == hir::Safety::Unsafe)
+            adt_def.all_fields().any(|x| x.safety.is_unsafe())
         } else {
             false
         }
diff --git a/compiler/rustc_middle/src/util/call_kind.rs b/compiler/rustc_middle/src/util/call_kind.rs
index df5b73ac1bd..0e395331687 100644
--- a/compiler/rustc_middle/src/util/call_kind.rs
+++ b/compiler/rustc_middle/src/util/call_kind.rs
@@ -4,8 +4,7 @@
 
 use rustc_hir::def_id::DefId;
 use rustc_hir::{LangItem, lang_items};
-use rustc_span::symbol::Ident;
-use rustc_span::{DesugaringKind, Span, sym};
+use rustc_span::{DesugaringKind, Ident, Span, sym};
 use tracing::debug;
 
 use crate::ty::{AssocItemContainer, GenericArgsRef, Instance, Ty, TyCtxt, TypingEnv};
diff --git a/compiler/rustc_mir_build/messages.ftl b/compiler/rustc_mir_build/messages.ftl
index f647486f62a..edba247c7b0 100644
--- a/compiler/rustc_mir_build/messages.ftl
+++ b/compiler/rustc_mir_build/messages.ftl
@@ -285,7 +285,7 @@ mir_build_pointer_pattern = function pointers and raw pointers not derived from
 
 mir_build_privately_uninhabited = pattern `{$witness_1}` is currently uninhabited, but this variant contains private fields which may become inhabited in the future
 
-mir_build_rust_2024_incompatible_pat = patterns are not allowed to reset the default binding mode in edition 2024
+mir_build_rust_2024_incompatible_pat = this pattern relies on behavior which may change in edition 2024
 
 mir_build_rustc_box_attribute_error = `#[rustc_box]` attribute used incorrectly
     .attributes = no other attributes may be applied
diff --git a/compiler/rustc_mir_build/src/build/block.rs b/compiler/rustc_mir_build/src/builder/block.rs
index 89e64015bc4..ba63a97de89 100644
--- a/compiler/rustc_mir_build/src/build/block.rs
+++ b/compiler/rustc_mir_build/src/builder/block.rs
@@ -5,9 +5,9 @@ use rustc_middle::{span_bug, ty};
 use rustc_span::Span;
 use tracing::debug;
 
-use crate::build::ForGuard::OutsideGuard;
-use crate::build::matches::{DeclareLetBindings, EmitStorageLive, ScheduleDrops};
-use crate::build::{BlockAnd, BlockAndExtension, BlockFrame, Builder};
+use crate::builder::ForGuard::OutsideGuard;
+use crate::builder::matches::{DeclareLetBindings, EmitStorageLive, ScheduleDrops};
+use crate::builder::{BlockAnd, BlockAndExtension, BlockFrame, Builder};
 
 impl<'a, 'tcx> Builder<'a, 'tcx> {
     pub(crate) fn ast_block(
diff --git a/compiler/rustc_mir_build/src/build/cfg.rs b/compiler/rustc_mir_build/src/builder/cfg.rs
index 9c5ee5b0996..42212f2518b 100644
--- a/compiler/rustc_mir_build/src/build/cfg.rs
+++ b/compiler/rustc_mir_build/src/builder/cfg.rs
@@ -4,7 +4,7 @@ use rustc_middle::mir::*;
 use rustc_middle::ty::TyCtxt;
 use tracing::debug;
 
-use crate::build::CFG;
+use crate::builder::CFG;
 
 impl<'tcx> CFG<'tcx> {
     pub(crate) fn block_data(&self, blk: BasicBlock) -> &BasicBlockData<'tcx> {
@@ -19,7 +19,7 @@ impl<'tcx> CFG<'tcx> {
     // it as #[inline(never)] to keep rustc's stack use in check.
     #[inline(never)]
     pub(crate) fn start_new_block(&mut self) -> BasicBlock {
-        self.basic_blocks.push(BasicBlockData::new(None))
+        self.basic_blocks.push(BasicBlockData::new(None, false))
     }
 
     pub(crate) fn start_new_cleanup_block(&mut self) -> BasicBlock {
diff --git a/compiler/rustc_mir_build/src/build/coverageinfo.rs b/compiler/rustc_mir_build/src/builder/coverageinfo.rs
index 52a4a4b4b51..a80bd4f3c80 100644
--- a/compiler/rustc_mir_build/src/build/coverageinfo.rs
+++ b/compiler/rustc_mir_build/src/builder/coverageinfo.rs
@@ -8,8 +8,8 @@ use rustc_middle::thir::{ExprId, ExprKind, Pat, Thir};
 use rustc_middle::ty::TyCtxt;
 use rustc_span::def_id::LocalDefId;
 
-use crate::build::coverageinfo::mcdc::MCDCInfoBuilder;
-use crate::build::{Builder, CFG};
+use crate::builder::coverageinfo::mcdc::MCDCInfoBuilder;
+use crate::builder::{Builder, CFG};
 
 mod mcdc;
 
diff --git a/compiler/rustc_mir_build/src/build/coverageinfo/mcdc.rs b/compiler/rustc_mir_build/src/builder/coverageinfo/mcdc.rs
index 343d4000043..6b4871dc1fc 100644
--- a/compiler/rustc_mir_build/src/build/coverageinfo/mcdc.rs
+++ b/compiler/rustc_mir_build/src/builder/coverageinfo/mcdc.rs
@@ -9,7 +9,7 @@ use rustc_middle::thir::LogicalOp;
 use rustc_middle::ty::TyCtxt;
 use rustc_span::Span;
 
-use crate::build::Builder;
+use crate::builder::Builder;
 use crate::errors::MCDCExceedsConditionLimit;
 
 /// LLVM uses `i16` to represent condition id. Hence `i16::MAX` is the hard limit for number of
diff --git a/compiler/rustc_mir_build/src/build/custom/mod.rs b/compiler/rustc_mir_build/src/builder/custom/mod.rs
index e809c9a23f3..ca2e1dd7a1a 100644
--- a/compiler/rustc_mir_build/src/build/custom/mod.rs
+++ b/compiler/rustc_mir_build/src/builder/custom/mod.rs
@@ -17,10 +17,9 @@
 //! terminators, and everything below can be found in the `parse::instruction` submodule.
 //!
 
-use rustc_ast::Attribute;
 use rustc_data_structures::fx::FxHashMap;
-use rustc_hir::HirId;
 use rustc_hir::def_id::DefId;
+use rustc_hir::{Attribute, HirId};
 use rustc_index::{IndexSlice, IndexVec};
 use rustc_middle::mir::*;
 use rustc_middle::span_bug;
@@ -65,7 +64,7 @@ pub(super) fn build_custom_mir<'tcx>(
     };
 
     body.local_decls.push(LocalDecl::new(return_ty, return_ty_span));
-    body.basic_blocks_mut().push(BasicBlockData::new(None));
+    body.basic_blocks_mut().push(BasicBlockData::new(None, false));
     body.source_scopes.push(SourceScopeData {
         span,
         parent_scope: None,
diff --git a/compiler/rustc_mir_build/src/build/custom/parse.rs b/compiler/rustc_mir_build/src/builder/custom/parse.rs
index 538068e1fac..91e284604b6 100644
--- a/compiler/rustc_mir_build/src/build/custom/parse.rs
+++ b/compiler/rustc_mir_build/src/builder/custom/parse.rs
@@ -199,10 +199,12 @@ impl<'a, 'tcx> ParseCtxt<'a, 'tcx> {
         match &self.thir[stmt].kind {
             StmtKind::Let { pattern, initializer: Some(initializer), .. } => {
                 let (var, ..) = self.parse_var(pattern)?;
-                let mut data = BasicBlockData::new(None);
-                data.is_cleanup = parse_by_kind!(self, *initializer, _, "basic block declaration",
-                    @variant(mir_basic_block, Normal) => false,
-                    @variant(mir_basic_block, Cleanup) => true,
+                let data = BasicBlockData::new(
+                    None,
+                    parse_by_kind!(self, *initializer, _, "basic block declaration",
+                        @variant(mir_basic_block, Normal) => false,
+                        @variant(mir_basic_block, Cleanup) => true,
+                    ),
                 );
                 let block = self.body.basic_blocks_mut().push(data);
                 self.block_map.insert(var, block);
@@ -308,8 +310,7 @@ impl<'a, 'tcx> ParseCtxt<'a, 'tcx> {
             ExprKind::Block { block } => &self.thir[*block],
         );
 
-        let mut data = BasicBlockData::new(None);
-        data.is_cleanup = is_cleanup;
+        let mut data = BasicBlockData::new(None, is_cleanup);
         for stmt_id in &*block.stmts {
             let stmt = self.statement_as_expr(*stmt_id)?;
             let span = self.thir[stmt].span;
diff --git a/compiler/rustc_mir_build/src/build/custom/parse/instruction.rs b/compiler/rustc_mir_build/src/builder/custom/parse/instruction.rs
index 67114efdff5..59f440432eb 100644
--- a/compiler/rustc_mir_build/src/build/custom/parse/instruction.rs
+++ b/compiler/rustc_mir_build/src/builder/custom/parse/instruction.rs
@@ -9,8 +9,8 @@ use rustc_span::Span;
 use rustc_span::source_map::Spanned;
 
 use super::{PResult, ParseCtxt, parse_by_kind};
-use crate::build::custom::ParseError;
-use crate::build::expr::as_constant::as_constant_inner;
+use crate::builder::custom::ParseError;
+use crate::builder::expr::as_constant::as_constant_inner;
 
 impl<'a, 'tcx> ParseCtxt<'a, 'tcx> {
     pub(crate) fn parse_statement(&self, expr_id: ExprId) -> PResult<StatementKind<'tcx>> {
diff --git a/compiler/rustc_mir_build/src/build/expr/as_constant.rs b/compiler/rustc_mir_build/src/builder/expr/as_constant.rs
index 640408cb9c8..177c1e33a83 100644
--- a/compiler/rustc_mir_build/src/build/expr/as_constant.rs
+++ b/compiler/rustc_mir_build/src/builder/expr/as_constant.rs
@@ -14,7 +14,7 @@ use rustc_middle::ty::{
 use rustc_middle::{bug, mir, span_bug};
 use tracing::{instrument, trace};
 
-use crate::build::{Builder, parse_float_into_constval};
+use crate::builder::{Builder, parse_float_into_constval};
 
 impl<'a, 'tcx> Builder<'a, 'tcx> {
     /// Compile `expr`, yielding a compile-time constant. Assumes that
diff --git a/compiler/rustc_mir_build/src/build/expr/as_operand.rs b/compiler/rustc_mir_build/src/builder/expr/as_operand.rs
index 777ff9e68f0..63e9b1dc6cd 100644
--- a/compiler/rustc_mir_build/src/build/expr/as_operand.rs
+++ b/compiler/rustc_mir_build/src/builder/expr/as_operand.rs
@@ -4,8 +4,8 @@ use rustc_middle::mir::*;
 use rustc_middle::thir::*;
 use tracing::{debug, instrument};
 
-use crate::build::expr::category::Category;
-use crate::build::{BlockAnd, BlockAndExtension, Builder, NeedsTemporary};
+use crate::builder::expr::category::Category;
+use crate::builder::{BlockAnd, BlockAndExtension, Builder, NeedsTemporary};
 
 impl<'a, 'tcx> Builder<'a, 'tcx> {
     /// Construct a temporary lifetime restricted to just the local scope
diff --git a/compiler/rustc_mir_build/src/build/expr/as_place.rs b/compiler/rustc_mir_build/src/builder/expr/as_place.rs
index 70a74910a68..01aec70f437 100644
--- a/compiler/rustc_mir_build/src/build/expr/as_place.rs
+++ b/compiler/rustc_mir_build/src/builder/expr/as_place.rs
@@ -14,9 +14,9 @@ use rustc_middle::{bug, span_bug};
 use rustc_span::{DesugaringKind, Span};
 use tracing::{debug, instrument, trace};
 
-use crate::build::ForGuard::{OutsideGuard, RefWithinGuard};
-use crate::build::expr::category::Category;
-use crate::build::{BlockAnd, BlockAndExtension, Builder, Capture, CaptureMap};
+use crate::builder::ForGuard::{OutsideGuard, RefWithinGuard};
+use crate::builder::expr::category::Category;
+use crate::builder::{BlockAnd, BlockAndExtension, Builder, Capture, CaptureMap};
 
 /// The "outermost" place that holds this value.
 #[derive(Copy, Clone, Debug, PartialEq)]
@@ -68,7 +68,7 @@ pub(crate) enum PlaceBase {
 /// This is used internally when building a place for an expression like `a.b.c`. The fields `b`
 /// and `c` can be progressively pushed onto the place builder that is created when converting `a`.
 #[derive(Clone, Debug, PartialEq)]
-pub(in crate::build) struct PlaceBuilder<'tcx> {
+pub(in crate::builder) struct PlaceBuilder<'tcx> {
     base: PlaceBase,
     projection: Vec<PlaceElem<'tcx>>,
 }
@@ -249,7 +249,7 @@ fn strip_prefix<'a, 'tcx>(
 }
 
 impl<'tcx> PlaceBuilder<'tcx> {
-    pub(in crate::build) fn to_place(&self, cx: &Builder<'_, 'tcx>) -> Place<'tcx> {
+    pub(in crate::builder) fn to_place(&self, cx: &Builder<'_, 'tcx>) -> Place<'tcx> {
         self.try_to_place(cx).unwrap_or_else(|| match self.base {
             PlaceBase::Local(local) => span_bug!(
                 cx.local_decls[local].source_info.span,
@@ -265,7 +265,7 @@ impl<'tcx> PlaceBuilder<'tcx> {
     }
 
     /// Creates a `Place` or returns `None` if an upvar cannot be resolved
-    pub(in crate::build) fn try_to_place(&self, cx: &Builder<'_, 'tcx>) -> Option<Place<'tcx>> {
+    pub(in crate::builder) fn try_to_place(&self, cx: &Builder<'_, 'tcx>) -> Option<Place<'tcx>> {
         let resolved = self.resolve_upvar(cx);
         let builder = resolved.as_ref().unwrap_or(self);
         let PlaceBase::Local(local) = builder.base else { return None };
@@ -283,7 +283,7 @@ impl<'tcx> PlaceBuilder<'tcx> {
     /// not captured. This can happen because the final mir that will be
     /// generated doesn't require a read for this place. Failures will only
     /// happen inside closures.
-    pub(in crate::build) fn resolve_upvar(
+    pub(in crate::builder) fn resolve_upvar(
         &self,
         cx: &Builder<'_, 'tcx>,
     ) -> Option<PlaceBuilder<'tcx>> {
@@ -647,13 +647,31 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
 
         match place_ty.kind() {
             ty::Array(_elem_ty, len_const) => {
-                // We know how long an array is, so just use that as a constant
-                // directly -- no locals needed. We do need one statement so
-                // that borrow- and initialization-checking consider it used,
-                // though. FIXME: Do we really *need* to count this as a use?
-                // Could partial array tracking work off something else instead?
-                self.cfg.push_fake_read(block, source_info, FakeReadCause::ForIndex, place);
-                let const_ = Const::from_ty_const(*len_const, usize_ty, self.tcx);
+                let ty_const = if let Some((_, len_ty)) = len_const.try_to_valtree()
+                    && len_ty != self.tcx.types.usize
+                {
+                    // Bad const generics can give us a constant from the type that's
+                    // not actually a `usize`, so in that case give an error instead.
+                    // FIXME: It'd be nice if the type checker made sure this wasn't
+                    // possible, instead.
+                    let err = self.tcx.dcx().span_delayed_bug(
+                        span,
+                        format!(
+                            "Array length should have already been a type error, as it's {len_ty:?}"
+                        ),
+                    );
+                    ty::Const::new_error(self.tcx, err)
+                } else {
+                    // We know how long an array is, so just use that as a constant
+                    // directly -- no locals needed. We do need one statement so
+                    // that borrow- and initialization-checking consider it used,
+                    // though. FIXME: Do we really *need* to count this as a use?
+                    // Could partial array tracking work off something else instead?
+                    self.cfg.push_fake_read(block, source_info, FakeReadCause::ForIndex, place);
+                    *len_const
+                };
+
+                let const_ = Const::from_ty_const(ty_const, usize_ty, self.tcx);
                 Operand::Constant(Box::new(ConstOperand { span, user_ty: None, const_ }))
             }
             ty::Slice(_elem_ty) => {
diff --git a/compiler/rustc_mir_build/src/build/expr/as_rvalue.rs b/compiler/rustc_mir_build/src/builder/expr/as_rvalue.rs
index c66af118453..9961c2488ef 100644
--- a/compiler/rustc_mir_build/src/build/expr/as_rvalue.rs
+++ b/compiler/rustc_mir_build/src/builder/expr/as_rvalue.rs
@@ -16,9 +16,9 @@ use rustc_span::source_map::Spanned;
 use rustc_span::{DUMMY_SP, Span};
 use tracing::debug;
 
-use crate::build::expr::as_place::PlaceBase;
-use crate::build::expr::category::{Category, RvalueFunc};
-use crate::build::{BlockAnd, BlockAndExtension, Builder, NeedsTemporary};
+use crate::builder::expr::as_place::PlaceBase;
+use crate::builder::expr::category::{Category, RvalueFunc};
+use crate::builder::{BlockAnd, BlockAndExtension, Builder, NeedsTemporary};
 
 impl<'a, 'tcx> Builder<'a, 'tcx> {
     /// Returns an rvalue suitable for use until the end of the current
diff --git a/compiler/rustc_mir_build/src/build/expr/as_temp.rs b/compiler/rustc_mir_build/src/builder/expr/as_temp.rs
index 466f67b1ba4..2927f5b0c45 100644
--- a/compiler/rustc_mir_build/src/build/expr/as_temp.rs
+++ b/compiler/rustc_mir_build/src/builder/expr/as_temp.rs
@@ -7,8 +7,8 @@ use rustc_middle::mir::*;
 use rustc_middle::thir::*;
 use tracing::{debug, instrument};
 
-use crate::build::scope::DropKind;
-use crate::build::{BlockAnd, BlockAndExtension, Builder};
+use crate::builder::scope::DropKind;
+use crate::builder::{BlockAnd, BlockAndExtension, Builder};
 
 impl<'a, 'tcx> Builder<'a, 'tcx> {
     /// Compile `expr` into a fresh temporary. This is used when building
@@ -75,11 +75,11 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     LocalInfo::BlockTailTemp(tail_info)
                 }
 
-                _ if let Some(Scope { data: ScopeData::IfThenRescope, id }) =
+                _ if let Some(Scope { data: ScopeData::IfThenRescope, local_id }) =
                     temp_lifetime.temp_lifetime =>
                 {
                     LocalInfo::IfThenRescopeTemp {
-                        if_then: HirId { owner: this.hir_id.owner, local_id: id },
+                        if_then: HirId { owner: this.hir_id.owner, local_id },
                     }
                 }
 
diff --git a/compiler/rustc_mir_build/src/build/expr/category.rs b/compiler/rustc_mir_build/src/builder/expr/category.rs
index e0349e3e3f6..e0349e3e3f6 100644
--- a/compiler/rustc_mir_build/src/build/expr/category.rs
+++ b/compiler/rustc_mir_build/src/builder/expr/category.rs
diff --git a/compiler/rustc_mir_build/src/build/expr/into.rs b/compiler/rustc_mir_build/src/builder/expr/into.rs
index a3d5376dcd4..88f63d4e22c 100644
--- a/compiler/rustc_mir_build/src/build/expr/into.rs
+++ b/compiler/rustc_mir_build/src/builder/expr/into.rs
@@ -11,9 +11,9 @@ use rustc_middle::ty::CanonicalUserTypeAnnotation;
 use rustc_span::source_map::Spanned;
 use tracing::{debug, instrument};
 
-use crate::build::expr::category::{Category, RvalueFunc};
-use crate::build::matches::DeclareLetBindings;
-use crate::build::{BlockAnd, BlockAndExtension, BlockFrame, Builder, NeedsTemporary};
+use crate::builder::expr::category::{Category, RvalueFunc};
+use crate::builder::matches::DeclareLetBindings;
+use crate::builder::{BlockAnd, BlockAndExtension, BlockFrame, Builder, NeedsTemporary};
 
 impl<'a, 'tcx> Builder<'a, 'tcx> {
     /// Compile `expr`, storing the result into `destination`, which
@@ -367,14 +367,20 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                             .collect()
                     }
                     AdtExprBase::DefaultFields(field_types) => {
-                        itertools::zip_eq(field_names, &**field_types)
-                            .map(|(n, ty)| match fields_map.get(&n) {
+                        itertools::zip_eq(field_names, field_types)
+                            .map(|(n, &ty)| match fields_map.get(&n) {
                                 Some(v) => v.clone(),
                                 None => match variant.fields[n].value {
                                     Some(def) => {
-                                        let value = Const::from_unevaluated(this.tcx, def)
-                                            .instantiate(this.tcx, args);
-                                        this.literal_operand(expr_span, value)
+                                        let value = Const::Unevaluated(
+                                            UnevaluatedConst::new(def, args),
+                                            ty,
+                                        );
+                                        Operand::Constant(Box::new(ConstOperand {
+                                            span: expr_span,
+                                            user_ty: None,
+                                            const_: value,
+                                        }))
                                     }
                                     None => {
                                         let name = variant.fields[n].name;
diff --git a/compiler/rustc_mir_build/src/build/expr/mod.rs b/compiler/rustc_mir_build/src/builder/expr/mod.rs
index 3de43a3370f..3de43a3370f 100644
--- a/compiler/rustc_mir_build/src/build/expr/mod.rs
+++ b/compiler/rustc_mir_build/src/builder/expr/mod.rs
diff --git a/compiler/rustc_mir_build/src/build/expr/stmt.rs b/compiler/rustc_mir_build/src/builder/expr/stmt.rs
index 15ee6dd014c..4ae3536d9c2 100644
--- a/compiler/rustc_mir_build/src/build/expr/stmt.rs
+++ b/compiler/rustc_mir_build/src/builder/expr/stmt.rs
@@ -5,8 +5,8 @@ use rustc_middle::thir::*;
 use rustc_span::source_map::Spanned;
 use tracing::debug;
 
-use crate::build::scope::BreakableTarget;
-use crate::build::{BlockAnd, BlockAndExtension, BlockFrame, Builder};
+use crate::builder::scope::BreakableTarget;
+use crate::builder::{BlockAnd, BlockAndExtension, BlockFrame, Builder};
 
 impl<'a, 'tcx> Builder<'a, 'tcx> {
     /// Builds a block of MIR statements to evaluate the THIR `expr`.
diff --git a/compiler/rustc_mir_build/src/build/matches/match_pair.rs b/compiler/rustc_mir_build/src/builder/matches/match_pair.rs
index 33fbd7b1a3f..9d59ffc88ba 100644
--- a/compiler/rustc_mir_build/src/build/matches/match_pair.rs
+++ b/compiler/rustc_mir_build/src/builder/matches/match_pair.rs
@@ -2,9 +2,9 @@ use rustc_middle::mir::*;
 use rustc_middle::thir::{self, *};
 use rustc_middle::ty::{self, Ty, TypeVisitableExt};
 
-use crate::build::Builder;
-use crate::build::expr::as_place::{PlaceBase, PlaceBuilder};
-use crate::build::matches::{FlatPat, MatchPairTree, TestCase};
+use crate::builder::Builder;
+use crate::builder::expr::as_place::{PlaceBase, PlaceBuilder};
+use crate::builder::matches::{FlatPat, MatchPairTree, TestCase};
 
 impl<'a, 'tcx> Builder<'a, 'tcx> {
     /// Builds and returns [`MatchPairTree`] subtrees, one for each pattern in
@@ -86,7 +86,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
 impl<'pat, 'tcx> MatchPairTree<'pat, 'tcx> {
     /// Recursively builds a match pair tree for the given pattern and its
     /// subpatterns.
-    pub(in crate::build) fn for_pattern(
+    pub(in crate::builder) fn for_pattern(
         mut place_builder: PlaceBuilder<'tcx>,
         pattern: &'pat Pat<'tcx>,
         cx: &mut Builder<'_, 'tcx>,
diff --git a/compiler/rustc_mir_build/src/build/matches/mod.rs b/compiler/rustc_mir_build/src/builder/matches/mod.rs
index 5791460a6b1..b944d13fb0d 100644
--- a/compiler/rustc_mir_build/src/build/matches/mod.rs
+++ b/compiler/rustc_mir_build/src/builder/matches/mod.rs
@@ -14,14 +14,13 @@ use rustc_middle::middle::region;
 use rustc_middle::mir::{self, *};
 use rustc_middle::thir::{self, *};
 use rustc_middle::ty::{self, CanonicalUserTypeAnnotation, Ty};
-use rustc_span::symbol::Symbol;
-use rustc_span::{BytePos, Pos, Span};
+use rustc_span::{BytePos, Pos, Span, Symbol};
 use tracing::{debug, instrument};
 
-use crate::build::ForGuard::{self, OutsideGuard, RefWithinGuard};
-use crate::build::expr::as_place::PlaceBuilder;
-use crate::build::scope::DropKind;
-use crate::build::{
+use crate::builder::ForGuard::{self, OutsideGuard, RefWithinGuard};
+use crate::builder::expr::as_place::PlaceBuilder;
+use crate::builder::scope::DropKind;
+use crate::builder::{
     BlockAnd, BlockAndExtension, Builder, GuardFrame, GuardFrameLocal, LocalsForNode,
 };
 
diff --git a/compiler/rustc_mir_build/src/build/matches/simplify.rs b/compiler/rustc_mir_build/src/builder/matches/simplify.rs
index 5b402604395..ebaed1e431b 100644
--- a/compiler/rustc_mir_build/src/build/matches/simplify.rs
+++ b/compiler/rustc_mir_build/src/builder/matches/simplify.rs
@@ -16,8 +16,8 @@ use std::mem;
 
 use tracing::{debug, instrument};
 
-use crate::build::Builder;
-use crate::build::matches::{MatchPairTree, PatternExtraData, TestCase};
+use crate::builder::Builder;
+use crate::builder::matches::{MatchPairTree, PatternExtraData, TestCase};
 
 impl<'a, 'tcx> Builder<'a, 'tcx> {
     /// Simplify a list of match pairs so they all require a test. Stores relevant bindings and
diff --git a/compiler/rustc_mir_build/src/build/matches/test.rs b/compiler/rustc_mir_build/src/builder/matches/test.rs
index 4f7bbc4ce3e..8cca84d7fcc 100644
--- a/compiler/rustc_mir_build/src/build/matches/test.rs
+++ b/compiler/rustc_mir_build/src/builder/matches/test.rs
@@ -16,12 +16,11 @@ use rustc_middle::ty::{self, GenericArg, Ty, TyCtxt};
 use rustc_middle::{bug, span_bug};
 use rustc_span::def_id::DefId;
 use rustc_span::source_map::Spanned;
-use rustc_span::symbol::{Symbol, sym};
-use rustc_span::{DUMMY_SP, Span};
+use rustc_span::{DUMMY_SP, Span, Symbol, sym};
 use tracing::{debug, instrument};
 
-use crate::build::Builder;
-use crate::build::matches::{Candidate, MatchPairTree, Test, TestBranch, TestCase, TestKind};
+use crate::builder::Builder;
+use crate::builder::matches::{Candidate, MatchPairTree, Test, TestBranch, TestCase, TestKind};
 
 impl<'a, 'tcx> Builder<'a, 'tcx> {
     /// Identifies what test is needed to decide if `match_pair` is applicable.
diff --git a/compiler/rustc_mir_build/src/build/matches/util.rs b/compiler/rustc_mir_build/src/builder/matches/util.rs
index 555684ded81..1bd399e511b 100644
--- a/compiler/rustc_mir_build/src/build/matches/util.rs
+++ b/compiler/rustc_mir_build/src/builder/matches/util.rs
@@ -4,9 +4,9 @@ use rustc_middle::ty::Ty;
 use rustc_span::Span;
 use tracing::debug;
 
-use crate::build::Builder;
-use crate::build::expr::as_place::PlaceBase;
-use crate::build::matches::{Binding, Candidate, FlatPat, MatchPairTree, TestCase};
+use crate::builder::Builder;
+use crate::builder::expr::as_place::PlaceBase;
+use crate::builder::matches::{Binding, Candidate, FlatPat, MatchPairTree, TestCase};
 
 impl<'a, 'tcx> Builder<'a, 'tcx> {
     /// Creates a false edge to `imaginary_target` and a real edge to
diff --git a/compiler/rustc_mir_build/src/build/misc.rs b/compiler/rustc_mir_build/src/builder/misc.rs
index a14dcad6573..9ea56a9574f 100644
--- a/compiler/rustc_mir_build/src/build/misc.rs
+++ b/compiler/rustc_mir_build/src/builder/misc.rs
@@ -7,7 +7,7 @@ use rustc_span::Span;
 use rustc_trait_selection::infer::InferCtxtExt;
 use tracing::debug;
 
-use crate::build::Builder;
+use crate::builder::Builder;
 
 impl<'a, 'tcx> Builder<'a, 'tcx> {
     /// Adds a new temporary value of type `ty` storing the result of
@@ -56,10 +56,10 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
     pub(crate) fn consume_by_copy_or_move(&self, place: Place<'tcx>) -> Operand<'tcx> {
         let tcx = self.tcx;
         let ty = place.ty(&self.local_decls, tcx).ty;
-        if !self.infcx.type_is_copy_modulo_regions(self.param_env, ty) {
-            Operand::Move(place)
-        } else {
+        if self.infcx.type_is_copy_modulo_regions(self.param_env, ty) {
             Operand::Copy(place)
+        } else {
+            Operand::Move(place)
         }
     }
 }
diff --git a/compiler/rustc_mir_build/src/build/mod.rs b/compiler/rustc_mir_build/src/builder/mod.rs
index f43c29d8f5d..0a60899248a 100644
--- a/compiler/rustc_mir_build/src/build/mod.rs
+++ b/compiler/rustc_mir_build/src/builder/mod.rs
@@ -1,3 +1,8 @@
+//! This module used to be named `build`, but that was causing GitHub's
+//! "Go to file" feature to silently ignore all files in the module, probably
+//! because it assumes that "build" is a build-output directory.
+//! See <https://github.com/rust-lang/rust/pull/134365>.
+
 use itertools::Itertools;
 use rustc_abi::{ExternAbi, FieldIdx};
 use rustc_apfloat::Float;
@@ -19,12 +24,11 @@ use rustc_middle::query::TyCtxtAt;
 use rustc_middle::thir::{self, ExprId, LintLevel, LocalVarId, Param, ParamId, PatKind, Thir};
 use rustc_middle::ty::{self, ScalarInt, Ty, TyCtxt, TypeVisitableExt, TypingMode};
 use rustc_middle::{bug, span_bug};
-use rustc_span::symbol::sym;
-use rustc_span::{Span, Symbol};
+use rustc_span::{Span, Symbol, sym};
 
 use super::lints;
-use crate::build::expr::as_place::PlaceBuilder;
-use crate::build::scope::DropKind;
+use crate::builder::expr::as_place::PlaceBuilder;
+use crate::builder::scope::DropKind;
 
 pub(crate) fn closure_saved_names_of_captured_variables<'tcx>(
     tcx: TyCtxt<'tcx>,
@@ -527,9 +531,9 @@ fn construct_fn<'tcx>(
     );
 
     let call_site_scope =
-        region::Scope { id: body.id().hir_id.local_id, data: region::ScopeData::CallSite };
+        region::Scope { local_id: body.id().hir_id.local_id, data: region::ScopeData::CallSite };
     let arg_scope =
-        region::Scope { id: body.id().hir_id.local_id, data: region::ScopeData::Arguments };
+        region::Scope { local_id: body.id().hir_id.local_id, data: region::ScopeData::Arguments };
     let source_info = builder.source_info(span);
     let call_site_s = (call_site_scope, source_info);
     let _: BlockAnd<()> = builder.in_scope(call_site_s, LintLevel::Inherited, |builder| {
diff --git a/compiler/rustc_mir_build/src/build/scope.rs b/compiler/rustc_mir_build/src/builder/scope.rs
index 636e47b7ad2..35c98037827 100644
--- a/compiler/rustc_mir_build/src/build/scope.rs
+++ b/compiler/rustc_mir_build/src/builder/scope.rs
@@ -89,13 +89,13 @@ use rustc_index::{IndexSlice, IndexVec};
 use rustc_middle::middle::region;
 use rustc_middle::mir::*;
 use rustc_middle::thir::{ExprId, LintLevel};
-use rustc_middle::{bug, span_bug, ty};
+use rustc_middle::{bug, span_bug};
 use rustc_session::lint::Level;
 use rustc_span::source_map::Spanned;
 use rustc_span::{DUMMY_SP, Span};
 use tracing::{debug, instrument};
 
-use crate::build::{BlockAnd, BlockAndExtension, BlockFrame, Builder, CFG};
+use crate::builder::{BlockAnd, BlockAndExtension, BlockFrame, Builder, CFG};
 
 #[derive(Debug)]
 pub(crate) struct Scopes<'tcx> {
@@ -151,15 +151,13 @@ struct DropData {
 
     /// Whether this is a value Drop or a StorageDead.
     kind: DropKind,
-
-    /// Whether this is a backwards-incompatible drop lint
-    backwards_incompatible_lint: bool,
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub(crate) enum DropKind {
     Value,
     Storage,
+    ForLint,
 }
 
 #[derive(Debug)]
@@ -248,7 +246,7 @@ impl Scope {
     /// use of optimizations in the MIR coroutine transform.
     fn needs_cleanup(&self) -> bool {
         self.drops.iter().any(|drop| match drop.kind {
-            DropKind::Value => true,
+            DropKind::Value | DropKind::ForLint => true,
             DropKind::Storage => false,
         })
     }
@@ -277,12 +275,8 @@ impl DropTree {
         // represents the block in the tree that should be jumped to once all
         // of the required drops have been performed.
         let fake_source_info = SourceInfo::outermost(DUMMY_SP);
-        let fake_data = DropData {
-            source_info: fake_source_info,
-            local: Local::MAX,
-            kind: DropKind::Storage,
-            backwards_incompatible_lint: false,
-        };
+        let fake_data =
+            DropData { source_info: fake_source_info, local: Local::MAX, kind: DropKind::Storage };
         let drops = IndexVec::from_raw(vec![DropNode { data: fake_data, next: DropIdx::MAX }]);
         Self { drops, entry_points: Vec::new(), existing_drops_map: FxHashMap::default() }
     }
@@ -411,6 +405,27 @@ impl DropTree {
                     };
                     cfg.terminate(block, drop_node.data.source_info, terminator);
                 }
+                DropKind::ForLint => {
+                    let stmt = Statement {
+                        source_info: drop_node.data.source_info,
+                        kind: StatementKind::BackwardIncompatibleDropHint {
+                            place: Box::new(drop_node.data.local.into()),
+                            reason: BackwardIncompatibleDropReason::Edition2024,
+                        },
+                    };
+                    cfg.push(block, stmt);
+                    let target = blocks[drop_node.next].unwrap();
+                    if target != block {
+                        // Diagnostics don't use this `Span` but debuginfo
+                        // might. Since we don't want breakpoints to be placed
+                        // here, especially when this is on an unwind path, we
+                        // use `DUMMY_SP`.
+                        let source_info =
+                            SourceInfo { span: DUMMY_SP, ..drop_node.data.source_info };
+                        let terminator = TerminatorKind::Goto { target };
+                        cfg.terminate(block, source_info, terminator);
+                    }
+                }
                 // Root nodes don't correspond to a drop.
                 DropKind::Storage if drop_idx == ROOT_NODE => {}
                 DropKind::Storage => {
@@ -770,12 +785,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     let local =
                         place.as_local().unwrap_or_else(|| bug!("projection in tail call args"));
 
-                    Some(DropData {
-                        source_info,
-                        local,
-                        kind: DropKind::Value,
-                        backwards_incompatible_lint: false,
-                    })
+                    Some(DropData { source_info, local, kind: DropKind::Value })
                 }
                 Operand::Constant(_) => None,
             })
@@ -822,6 +832,15 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                         });
                         block = next;
                     }
+                    DropKind::ForLint => {
+                        self.cfg.push(block, Statement {
+                            source_info,
+                            kind: StatementKind::BackwardIncompatibleDropHint {
+                                place: Box::new(local.into()),
+                                reason: BackwardIncompatibleDropReason::Edition2024,
+                            },
+                        });
+                    }
                     DropKind::Storage => {
                         // Only temps and vars need their storage dead.
                         assert!(local.index() > self.arg_count);
@@ -1021,7 +1040,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         drop_kind: DropKind,
     ) {
         let needs_drop = match drop_kind {
-            DropKind::Value => {
+            DropKind::Value | DropKind::ForLint => {
                 if !self.local_decls[local].ty.needs_drop(self.tcx, self.typing_env()) {
                     return;
                 }
@@ -1101,7 +1120,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     source_info: SourceInfo { span: scope_end, scope: scope.source_scope },
                     local,
                     kind: drop_kind,
-                    backwards_incompatible_lint: false,
                 });
 
                 return;
@@ -1119,10 +1137,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         region_scope: region::Scope,
         local: Local,
     ) {
-        if !self.local_decls[local].ty.has_significant_drop(self.tcx, ty::TypingEnv {
-            typing_mode: ty::TypingMode::non_body_analysis(),
-            param_env: self.param_env,
-        }) {
+        if !self.local_decls[local].ty.has_significant_drop(self.tcx, self.typing_env()) {
             return;
         }
         for scope in self.scopes.scopes.iter_mut().rev() {
@@ -1135,8 +1150,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 scope.drops.push(DropData {
                     source_info: SourceInfo { span: scope_end, scope: scope.source_scope },
                     local,
-                    kind: DropKind::Value,
-                    backwards_incompatible_lint: true,
+                    kind: DropKind::ForLint,
                 });
 
                 return;
@@ -1379,12 +1393,23 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
 }
 
 /// Builds drops for `pop_scope` and `leave_top_scope`.
+///
+/// # Parameters
+///
+/// * `unwind_drops`, the drop tree data structure storing what needs to be cleaned up if unwind occurs
+/// * `scope`, describes the drops that will occur on exiting the scope in regular execution
+/// * `block`, the block to branch to once drops are complete (assuming no unwind occurs)
+/// * `unwind_to`, describes the drops that would occur at this point in the code if a
+///   panic occurred (a subset of the drops in `scope`, since we sometimes elide StorageDead and other
+///   instructions on unwinding)
+/// * `storage_dead_on_unwind`, if true, then we should emit `StorageDead` even when unwinding
+/// * `arg_count`, number of MIR local variables corresponding to fn arguments (used to assert that we don't drop those)
 fn build_scope_drops<'tcx>(
     cfg: &mut CFG<'tcx>,
     unwind_drops: &mut DropTree,
     scope: &Scope,
-    mut block: BasicBlock,
-    mut unwind_to: DropIdx,
+    block: BasicBlock,
+    unwind_to: DropIdx,
     storage_dead_on_unwind: bool,
     arg_count: usize,
 ) -> BlockAnd<()> {
@@ -1409,6 +1434,18 @@ fn build_scope_drops<'tcx>(
     // drops for the unwind path should have already been generated by
     // `diverge_cleanup_gen`.
 
+    // `unwind_to` indicates what needs to be dropped should unwinding occur.
+    // This is a subset of what needs to be dropped when exiting the scope.
+    // As we unwind the scope, we will also move `unwind_to` backwards to match,
+    // so that we can use it should a destructor panic.
+    let mut unwind_to = unwind_to;
+
+    // The block that we should jump to after drops complete. We start by building the final drop (`drops[n]`
+    // in the diagram above) and then build the drops (e.g., `drop[1]`, `drop[0]`) that come before it.
+    // block begins as the successor of `drops[n]` and then becomes `drops[n]` so that `drops[n-1]`
+    // will branch to `drops[n]`.
+    let mut block = block;
+
     for drop_data in scope.drops.iter().rev() {
         let source_info = drop_data.source_info;
         let local = drop_data.local;
@@ -1418,6 +1455,9 @@ fn build_scope_drops<'tcx>(
                 // `unwind_to` should drop the value that we're about to
                 // schedule. If dropping this value panics, then we continue
                 // with the *next* value on the unwind path.
+                //
+                // We adjust this BEFORE we create the drop (e.g., `drops[n]`)
+                // because `drops[n]` should unwind to `drops[n-1]`.
                 debug_assert_eq!(unwind_drops.drops[unwind_to].data.local, drop_data.local);
                 debug_assert_eq!(unwind_drops.drops[unwind_to].data.kind, drop_data.kind);
                 unwind_to = unwind_drops.drops[unwind_to].next;
@@ -1430,27 +1470,50 @@ fn build_scope_drops<'tcx>(
                     continue;
                 }
 
-                if drop_data.backwards_incompatible_lint {
-                    cfg.push(block, Statement {
-                        source_info,
-                        kind: StatementKind::BackwardIncompatibleDropHint {
-                            place: Box::new(local.into()),
-                            reason: BackwardIncompatibleDropReason::Edition2024,
-                        },
-                    });
-                } else {
-                    unwind_drops.add_entry_point(block, unwind_to);
-                    let next = cfg.start_new_block();
-                    cfg.terminate(block, source_info, TerminatorKind::Drop {
-                        place: local.into(),
-                        target: next,
-                        unwind: UnwindAction::Continue,
-                        replace: false,
-                    });
-                    block = next;
+                unwind_drops.add_entry_point(block, unwind_to);
+                let next = cfg.start_new_block();
+                cfg.terminate(block, source_info, TerminatorKind::Drop {
+                    place: local.into(),
+                    target: next,
+                    unwind: UnwindAction::Continue,
+                    replace: false,
+                });
+                block = next;
+            }
+            DropKind::ForLint => {
+                // As in the `DropKind::Storage` case below:
+                // normally lint-related drops are not emitted for unwind,
+                // so we can just leave `unwind_to` unmodified, but in some
+                // cases we emit things ALSO on the unwind path, so we need to adjust
+                // `unwind_to` in that case.
+                if storage_dead_on_unwind {
+                    debug_assert_eq!(unwind_drops.drops[unwind_to].data.local, drop_data.local);
+                    debug_assert_eq!(unwind_drops.drops[unwind_to].data.kind, drop_data.kind);
+                    unwind_to = unwind_drops.drops[unwind_to].next;
                 }
+
+                // If the operand has been moved, and we are not on an unwind
+                // path, then don't generate the drop. (We only take this into
+                // account for non-unwind paths so as not to disturb the
+                // caching mechanism.)
+                if scope.moved_locals.iter().any(|&o| o == local) {
+                    continue;
+                }
+
+                cfg.push(block, Statement {
+                    source_info,
+                    kind: StatementKind::BackwardIncompatibleDropHint {
+                        place: Box::new(local.into()),
+                        reason: BackwardIncompatibleDropReason::Edition2024,
+                    },
+                });
             }
             DropKind::Storage => {
+                // Ordinarily, storage-dead nodes are not emitted on unwind, so we don't
+                // need to adjust `unwind_to` on this path. However, in some specific cases
+                // we *do* emit storage-dead nodes on the unwind path, and in that case now that
+                // the storage-dead has completed, we need to adjust the `unwind_to` pointer
+                // so that any future drops we emit will not register storage-dead.
                 if storage_dead_on_unwind {
                     debug_assert_eq!(unwind_drops.drops[unwind_to].data.local, drop_data.local);
                     debug_assert_eq!(unwind_drops.drops[unwind_to].data.kind, drop_data.kind);
@@ -1489,7 +1552,7 @@ impl<'a, 'tcx: 'a> Builder<'a, 'tcx> {
             let mut unwind_indices = IndexVec::from_elem_n(unwind_target, 1);
             for (drop_idx, drop_node) in drops.drops.iter_enumerated().skip(1) {
                 match drop_node.data.kind {
-                    DropKind::Storage => {
+                    DropKind::Storage | DropKind::ForLint => {
                         if is_coroutine {
                             let unwind_drop = self
                                 .scopes
diff --git a/compiler/rustc_mir_build/src/check_unsafety.rs b/compiler/rustc_mir_build/src/check_unsafety.rs
index f37b3f977fa..f7071eb139f 100644
--- a/compiler/rustc_mir_build/src/check_unsafety.rs
+++ b/compiler/rustc_mir_build/src/check_unsafety.rs
@@ -4,7 +4,7 @@ use std::ops::Bound;
 
 use rustc_errors::DiagArgValue;
 use rustc_hir::def::DefKind;
-use rustc_hir::{self as hir, BindingMode, ByRef, HirId, Mutability, Safety};
+use rustc_hir::{self as hir, BindingMode, ByRef, HirId, Mutability};
 use rustc_middle::middle::codegen_fn_attrs::TargetFeature;
 use rustc_middle::mir::BorrowKind;
 use rustc_middle::span_bug;
@@ -15,10 +15,9 @@ use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_session::lint::Level;
 use rustc_session::lint::builtin::{DEPRECATED_SAFE_2024, UNSAFE_OP_IN_UNSAFE_FN, UNUSED_UNSAFE};
 use rustc_span::def_id::{DefId, LocalDefId};
-use rustc_span::symbol::Symbol;
-use rustc_span::{Span, sym};
+use rustc_span::{Span, Symbol, sym};
 
-use crate::build::ExprCategory;
+use crate::builder::ExprCategory;
 use crate::errors::*;
 
 struct UnsafetyVisitor<'a, 'tcx> {
@@ -342,7 +341,7 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for UnsafetyVisitor<'a, 'tcx> {
             PatKind::Leaf { subpatterns, .. } => {
                 if let ty::Adt(adt_def, ..) = pat.ty.kind() {
                     for pat in subpatterns {
-                        if adt_def.non_enum_variant().fields[pat.field].safety == Safety::Unsafe {
+                        if adt_def.non_enum_variant().fields[pat.field].safety.is_unsafe() {
                             self.requires_unsafe(pat.pattern.span, UseOfUnsafeField);
                         }
                     }
@@ -367,7 +366,7 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for UnsafetyVisitor<'a, 'tcx> {
             PatKind::Variant { adt_def, args: _, variant_index, subpatterns } => {
                 for pat in subpatterns {
                     let field = &pat.field;
-                    if adt_def.variant(*variant_index).fields[*field].safety == Safety::Unsafe {
+                    if adt_def.variant(*variant_index).fields[*field].safety.is_unsafe() {
                         self.requires_unsafe(pat.pattern.span, UseOfUnsafeField);
                     }
                 }
@@ -479,7 +478,7 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for UnsafetyVisitor<'a, 'tcx> {
                 return; // don't visit the whole expression
             }
             ExprKind::Call { fun, ty: _, args: _, from_hir_call: _, fn_span: _ } => {
-                if self.thir[fun].ty.fn_sig(self.tcx).safety() == hir::Safety::Unsafe {
+                if self.thir[fun].ty.fn_sig(self.tcx).safety().is_unsafe() {
                     let func_id = if let ty::FnDef(func_id, _) = self.thir[fun].ty.kind() {
                         Some(*func_id)
                     } else {
@@ -623,7 +622,7 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for UnsafetyVisitor<'a, 'tcx> {
             ExprKind::Field { lhs, variant_index, name } => {
                 let lhs = &self.thir[lhs];
                 if let ty::Adt(adt_def, _) = lhs.ty.kind() {
-                    if adt_def.variant(variant_index).fields[name].safety == Safety::Unsafe {
+                    if adt_def.variant(variant_index).fields[name].safety.is_unsafe() {
                         self.requires_unsafe(expr.span, UseOfUnsafeField);
                     } else if adt_def.is_union() {
                         if let Some(assigned_ty) = self.assignment_info {
@@ -1112,11 +1111,7 @@ pub(crate) fn check_unsafety(tcx: TyCtxt<'_>, def: LocalDefId) {
 
     let hir_id = tcx.local_def_id_to_hir_id(def);
     let safety_context = tcx.hir().fn_sig_by_hir_id(hir_id).map_or(SafetyContext::Safe, |fn_sig| {
-        if fn_sig.header.safety == hir::Safety::Unsafe {
-            SafetyContext::UnsafeFn
-        } else {
-            SafetyContext::Safe
-        }
+        if fn_sig.header.safety.is_unsafe() { SafetyContext::UnsafeFn } else { SafetyContext::Safe }
     });
     let body_target_features = &tcx.body_codegen_attrs(def.to_def_id()).target_features;
     let mut warnings = Vec::new();
diff --git a/compiler/rustc_mir_build/src/errors.rs b/compiler/rustc_mir_build/src/errors.rs
index 3632da943e1..be5f8bdffb5 100644
--- a/compiler/rustc_mir_build/src/errors.rs
+++ b/compiler/rustc_mir_build/src/errors.rs
@@ -1,14 +1,13 @@
 use rustc_errors::codes::*;
 use rustc_errors::{
     Applicability, Diag, DiagArgValue, DiagCtxtHandle, Diagnostic, EmissionGuarantee, Level,
-    MultiSpan, SubdiagMessageOp, Subdiagnostic,
+    MultiSpan, SubdiagMessageOp, Subdiagnostic, pluralize,
 };
 use rustc_macros::{Diagnostic, LintDiagnostic, Subdiagnostic};
 use rustc_middle::ty::{self, Ty};
 use rustc_pattern_analysis::errors::Uncovered;
 use rustc_pattern_analysis::rustc::RustcPatCtxt;
-use rustc_span::Span;
-use rustc_span::symbol::Symbol;
+use rustc_span::{Span, Symbol};
 
 use crate::fluent_generated as fluent;
 
@@ -1089,18 +1088,20 @@ pub(crate) enum RustcBoxAttrReason {
 
 #[derive(LintDiagnostic)]
 #[diag(mir_build_rust_2024_incompatible_pat)]
-pub(crate) struct Rust2024IncompatiblePat {
+pub(crate) struct Rust2024IncompatiblePat<'a> {
     #[subdiagnostic]
-    pub(crate) sugg: Rust2024IncompatiblePatSugg,
+    pub(crate) sugg: Rust2024IncompatiblePatSugg<'a>,
 }
 
-pub(crate) struct Rust2024IncompatiblePatSugg {
+pub(crate) struct Rust2024IncompatiblePatSugg<'a> {
     pub(crate) suggestion: Vec<(Span, String)>,
-    /// Whether the incompatibility is a hard error because a relevant span is in edition 2024.
-    pub(crate) is_hard_error: bool,
+    pub(crate) ref_pattern_count: usize,
+    pub(crate) binding_mode_count: usize,
+    /// Labeled spans for subpatterns invalid in Rust 2024.
+    pub(crate) labels: &'a [(Span, String)],
 }
 
-impl Subdiagnostic for Rust2024IncompatiblePatSugg {
+impl<'a> Subdiagnostic for Rust2024IncompatiblePatSugg<'a> {
     fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
         self,
         diag: &mut Diag<'_, G>,
@@ -1112,6 +1113,16 @@ impl Subdiagnostic for Rust2024IncompatiblePatSugg {
             } else {
                 Applicability::MaybeIncorrect
             };
-        diag.multipart_suggestion("desugar the match ergonomics", self.suggestion, applicability);
+        let plural_derefs = pluralize!(self.ref_pattern_count);
+        let and_modes = if self.binding_mode_count > 0 {
+            format!(" and variable binding mode{}", pluralize!(self.binding_mode_count))
+        } else {
+            String::new()
+        };
+        diag.multipart_suggestion_verbose(
+            format!("make the implied reference pattern{plural_derefs}{and_modes} explicit"),
+            self.suggestion,
+            applicability,
+        );
     }
 }
diff --git a/compiler/rustc_mir_build/src/lib.rs b/compiler/rustc_mir_build/src/lib.rs
index 833e5019865..467725841dc 100644
--- a/compiler/rustc_mir_build/src/lib.rs
+++ b/compiler/rustc_mir_build/src/lib.rs
@@ -11,7 +11,10 @@
 #![warn(unreachable_pub)]
 // tidy-alphabetical-end
 
-mod build;
+// The `builder` module used to be named `build`, but that was causing GitHub's
+// "Go to file" feature to silently ignore all files in the module, probably
+// because it assumes that "build" is a build-output directory. See #134365.
+mod builder;
 mod check_tail_calls;
 mod check_unsafety;
 mod errors;
@@ -25,9 +28,9 @@ rustc_fluent_macro::fluent_messages! { "../messages.ftl" }
 pub fn provide(providers: &mut Providers) {
     providers.check_match = thir::pattern::check_match;
     providers.lit_to_const = thir::constant::lit_to_const;
-    providers.hooks.build_mir = build::mir_build;
+    providers.hooks.build_mir = builder::mir_build;
     providers.closure_saved_names_of_captured_variables =
-        build::closure_saved_names_of_captured_variables;
+        builder::closure_saved_names_of_captured_variables;
     providers.check_unsafety = check_unsafety::check_unsafety;
     providers.check_tail_calls = check_tail_calls::check_tail_calls;
     providers.thir_body = thir::cx::thir_body;
diff --git a/compiler/rustc_mir_build/src/thir/constant.rs b/compiler/rustc_mir_build/src/thir/constant.rs
index 30b6718683b..ce1c635d1b9 100644
--- a/compiler/rustc_mir_build/src/thir/constant.rs
+++ b/compiler/rustc_mir_build/src/thir/constant.rs
@@ -5,7 +5,7 @@ use rustc_middle::mir::interpret::{LitToConstError, LitToConstInput};
 use rustc_middle::ty::{self, ScalarInt, TyCtxt, TypeVisitableExt as _};
 use tracing::trace;
 
-use crate::build::parse_float_into_scalar;
+use crate::builder::parse_float_into_scalar;
 
 pub(crate) fn lit_to_const<'tcx>(
     tcx: TyCtxt<'tcx>,
diff --git a/compiler/rustc_mir_build/src/thir/cx/block.rs b/compiler/rustc_mir_build/src/thir/cx/block.rs
index 069c2e7881e..c9df027687a 100644
--- a/compiler/rustc_mir_build/src/thir/cx/block.rs
+++ b/compiler/rustc_mir_build/src/thir/cx/block.rs
@@ -16,7 +16,7 @@ impl<'tcx> Cx<'tcx> {
         let block = Block {
             targeted_by_break: block.targeted_by_break,
             region_scope: region::Scope {
-                id: block.hir_id.local_id,
+                local_id: block.hir_id.local_id,
                 data: region::ScopeData::Node,
             },
             span: block.span,
@@ -51,7 +51,7 @@ impl<'tcx> Cx<'tcx> {
                         let stmt = Stmt {
                             kind: StmtKind::Expr {
                                 scope: region::Scope {
-                                    id: hir_id.local_id,
+                                    local_id: hir_id.local_id,
                                     data: region::ScopeData::Node,
                                 },
                                 expr: self.mirror_expr(expr),
@@ -65,7 +65,7 @@ impl<'tcx> Cx<'tcx> {
                     }
                     hir::StmtKind::Let(local) => {
                         let remainder_scope = region::Scope {
-                            id: block_id,
+                            local_id: block_id,
                             data: region::ScopeData::Remainder(region::FirstStatementIndex::new(
                                 index,
                             )),
@@ -108,7 +108,7 @@ impl<'tcx> Cx<'tcx> {
                             kind: StmtKind::Let {
                                 remainder_scope,
                                 init_scope: region::Scope {
-                                    id: hir_id.local_id,
+                                    local_id: hir_id.local_id,
                                     data: region::ScopeData::Node,
                                 },
                                 pattern,
diff --git a/compiler/rustc_mir_build/src/thir/cx/expr.rs b/compiler/rustc_mir_build/src/thir/cx/expr.rs
index 6770e562d50..0338ac674e5 100644
--- a/compiler/rustc_mir_build/src/thir/cx/expr.rs
+++ b/compiler/rustc_mir_build/src/thir/cx/expr.rs
@@ -25,6 +25,14 @@ use crate::thir::cx::Cx;
 use crate::thir::util::UserAnnotatedTyHelpers;
 
 impl<'tcx> Cx<'tcx> {
+    /// Create a THIR expression for the given HIR expression. This expands all
+    /// adjustments and directly adds the type information from the
+    /// `typeck_results`. See the [dev-guide] for more details.
+    ///
+    /// (The term "mirror" in this case does not refer to "flipped" or
+    /// "reversed".)
+    ///
+    /// [dev-guide]: https://rustc-dev-guide.rust-lang.org/thir.html
     pub(crate) fn mirror_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) -> ExprId {
         // `mirror_expr` is recursing very deep. Make sure the stack doesn't overflow.
         ensure_sufficient_stack(|| self.mirror_expr_inner(expr))
@@ -37,7 +45,7 @@ impl<'tcx> Cx<'tcx> {
     #[instrument(level = "trace", skip(self, hir_expr))]
     pub(super) fn mirror_expr_inner(&mut self, hir_expr: &'tcx hir::Expr<'tcx>) -> ExprId {
         let expr_scope =
-            region::Scope { id: hir_expr.hir_id.local_id, data: region::ScopeData::Node };
+            region::Scope { local_id: hir_expr.hir_id.local_id, data: region::ScopeData::Node };
 
         trace!(?hir_expr.hir_id, ?hir_expr.span);
 
@@ -806,14 +814,20 @@ impl<'tcx> Cx<'tcx> {
             hir::ExprKind::Become(call) => ExprKind::Become { value: self.mirror_expr(call) },
             hir::ExprKind::Break(dest, ref value) => match dest.target_id {
                 Ok(target_id) => ExprKind::Break {
-                    label: region::Scope { id: target_id.local_id, data: region::ScopeData::Node },
+                    label: region::Scope {
+                        local_id: target_id.local_id,
+                        data: region::ScopeData::Node,
+                    },
                     value: value.map(|value| self.mirror_expr(value)),
                 },
                 Err(err) => bug!("invalid loop id for break: {}", err),
             },
             hir::ExprKind::Continue(dest) => match dest.target_id {
                 Ok(loop_id) => ExprKind::Continue {
-                    label: region::Scope { id: loop_id.local_id, data: region::ScopeData::Node },
+                    label: region::Scope {
+                        local_id: loop_id.local_id,
+                        data: region::ScopeData::Node,
+                    },
                 },
                 Err(err) => bug!("invalid loop id for continue: {}", err),
             },
@@ -823,7 +837,7 @@ impl<'tcx> Cx<'tcx> {
             },
             hir::ExprKind::If(cond, then, else_opt) => ExprKind::If {
                 if_then_scope: region::Scope {
-                    id: then.hir_id.local_id,
+                    local_id: then.hir_id.local_id,
                     data: {
                         if expr.span.at_least_rust_2024() {
                             region::ScopeData::IfThenRescope
@@ -1013,7 +1027,7 @@ impl<'tcx> Cx<'tcx> {
             guard: arm.guard.as_ref().map(|g| self.mirror_expr(g)),
             body: self.mirror_expr(arm.body),
             lint_level: LintLevel::Explicit(arm.hir_id),
-            scope: region::Scope { id: arm.hir_id.local_id, data: region::ScopeData::Node },
+            scope: region::Scope { local_id: arm.hir_id.local_id, data: region::ScopeData::Node },
             span: arm.span,
         };
         self.thir.arms.push(arm)
@@ -1189,7 +1203,7 @@ impl<'tcx> Cx<'tcx> {
             .temporary_scope(self.region_scope_tree, closure_expr.hir_id.local_id);
         let var_ty = place.base_ty;
 
-        // The result of capture analysis in `rustc_hir_analysis/check/upvar.rs`represents a captured path
+        // The result of capture analysis in `rustc_hir_typeck/src/upvar.rs` represents a captured path
         // as it's seen for use within the closure and not at the time of closure creation.
         //
         // That is we see expect to see it start from a captured upvar and not something that is local
diff --git a/compiler/rustc_mir_build/src/thir/pattern/mod.rs b/compiler/rustc_mir_build/src/thir/pattern/mod.rs
index 2dbc8b7b573..bdf243c87b6 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/mod.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/mod.rs
@@ -6,6 +6,7 @@ mod const_to_pat;
 use std::cmp::Ordering;
 
 use rustc_abi::{FieldIdx, Integer};
+use rustc_errors::MultiSpan;
 use rustc_errors::codes::*;
 use rustc_hir::def::{CtorOf, DefKind, Res};
 use rustc_hir::pat_util::EnumerateAndAdjustIterator;
@@ -34,7 +35,7 @@ struct PatCtxt<'a, 'tcx> {
     typeck_results: &'a ty::TypeckResults<'tcx>,
 
     /// Used by the Rust 2024 migration lint.
-    rust_2024_migration_suggestion: Option<Rust2024IncompatiblePatSugg>,
+    rust_2024_migration_suggestion: Option<Rust2024IncompatiblePatSugg<'a>>,
 }
 
 pub(super) fn pat_from_hir<'a, 'tcx>(
@@ -50,24 +51,36 @@ pub(super) fn pat_from_hir<'a, 'tcx>(
         rust_2024_migration_suggestion: typeck_results
             .rust_2024_migration_desugared_pats()
             .get(pat.hir_id)
-            .map(|&is_hard_error| Rust2024IncompatiblePatSugg {
+            .map(|labels| Rust2024IncompatiblePatSugg {
                 suggestion: Vec::new(),
-                is_hard_error,
+                ref_pattern_count: 0,
+                binding_mode_count: 0,
+                labels: labels.as_slice(),
             }),
     };
     let result = pcx.lower_pattern(pat);
     debug!("pat_from_hir({:?}) = {:?}", pat, result);
     if let Some(sugg) = pcx.rust_2024_migration_suggestion {
-        if sugg.is_hard_error {
+        let mut spans = MultiSpan::from_spans(sugg.labels.iter().map(|(span, _)| *span).collect());
+        for (span, label) in sugg.labels {
+            spans.push_span_label(*span, label.clone());
+        }
+        // If a relevant span is from at least edition 2024, this is a hard error.
+        let is_hard_error = spans.primary_spans().iter().any(|span| span.at_least_rust_2024());
+        if is_hard_error {
             let mut err =
-                tcx.dcx().struct_span_err(pat.span, fluent::mir_build_rust_2024_incompatible_pat);
+                tcx.dcx().struct_span_err(spans, fluent::mir_build_rust_2024_incompatible_pat);
+            if let Some(info) = lint::builtin::RUST_2024_INCOMPATIBLE_PAT.future_incompatible {
+                // provide the same reference link as the lint
+                err.note(format!("for more information, see {}", info.reference));
+            }
             err.subdiagnostic(sugg);
             err.emit();
         } else {
             tcx.emit_node_span_lint(
                 lint::builtin::RUST_2024_INCOMPATIBLE_PAT,
                 pat.hir_id,
-                pat.span,
+                spans,
                 Rust2024IncompatiblePat { sugg },
             );
         }
@@ -133,6 +146,7 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
                 })
                 .collect();
             s.suggestion.push((pat.span.shrink_to_lo(), suggestion_str));
+            s.ref_pattern_count += adjustments.len();
         };
 
         adjusted_pat
@@ -371,7 +385,8 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
                     s.suggestion.push((
                         pat.span.with_lo(ident.span.lo()).shrink_to_lo(),
                         sugg_str.to_owned(),
-                    ))
+                    ));
+                    s.binding_mode_count += 1;
                 }
 
                 // A ref x pattern is the same node used for x, and as such it has
diff --git a/compiler/rustc_mir_dataflow/src/framework/direction.rs b/compiler/rustc_mir_dataflow/src/framework/direction.rs
index 9d943ebe327..6427fd0fd29 100644
--- a/compiler/rustc_mir_dataflow/src/framework/direction.rs
+++ b/compiler/rustc_mir_dataflow/src/framework/direction.rs
@@ -1,8 +1,6 @@
 use std::ops::RangeInclusive;
 
-use rustc_middle::mir::{
-    self, BasicBlock, CallReturnPlaces, Location, SwitchTargets, TerminatorEdges,
-};
+use rustc_middle::mir::{self, BasicBlock, CallReturnPlaces, Location, TerminatorEdges};
 
 use super::visitor::ResultsVisitor;
 use super::{Analysis, Effect, EffectIndex, Results, SwitchIntTarget};
@@ -78,8 +76,6 @@ impl Direction for Backward {
         for pred in body.basic_blocks.predecessors()[block].iter().copied() {
             match body[pred].terminator().kind {
                 // Apply terminator-specific edge effects.
-                //
-                // FIXME(ecstaticmorse): Avoid cloning the exit state unconditionally.
                 mir::TerminatorKind::Call { destination, target: Some(dest), .. }
                     if dest == block =>
                 {
@@ -115,18 +111,18 @@ impl Direction for Backward {
                 }
 
                 mir::TerminatorKind::SwitchInt { targets: _, ref discr } => {
-                    let mut applier = BackwardSwitchIntEdgeEffectsApplier {
-                        body,
-                        pred,
-                        exit_state,
-                        block,
-                        propagate: &mut propagate,
-                        effects_applied: false,
-                    };
-
-                    analysis.apply_switch_int_edge_effects(pred, discr, &mut applier);
-
-                    if !applier.effects_applied {
+                    if let Some(mut data) = analysis.get_switch_int_data(block, discr) {
+                        let values = &body.basic_blocks.switch_sources()[&(block, pred)];
+                        let targets =
+                            values.iter().map(|&value| SwitchIntTarget { value, target: block });
+
+                        let mut tmp = analysis.bottom_value(body);
+                        for target in targets {
+                            tmp.clone_from(&exit_state);
+                            analysis.apply_switch_int_edge_effect(&mut data, &mut tmp, target);
+                            propagate(pred, &tmp);
+                        }
+                    } else {
                         propagate(pred, exit_state)
                     }
                 }
@@ -245,37 +241,6 @@ impl Direction for Backward {
     }
 }
 
-struct BackwardSwitchIntEdgeEffectsApplier<'mir, 'tcx, D, F> {
-    body: &'mir mir::Body<'tcx>,
-    pred: BasicBlock,
-    exit_state: &'mir mut D,
-    block: BasicBlock,
-    propagate: &'mir mut F,
-    effects_applied: bool,
-}
-
-impl<D, F> super::SwitchIntEdgeEffects<D> for BackwardSwitchIntEdgeEffectsApplier<'_, '_, D, F>
-where
-    D: Clone,
-    F: FnMut(BasicBlock, &D),
-{
-    fn apply(&mut self, mut apply_edge_effect: impl FnMut(&mut D, SwitchIntTarget)) {
-        assert!(!self.effects_applied);
-
-        let values = &self.body.basic_blocks.switch_sources()[&(self.block, self.pred)];
-        let targets = values.iter().map(|&value| SwitchIntTarget { value, target: self.block });
-
-        let mut tmp = None;
-        for target in targets {
-            let tmp = opt_clone_from_or_clone(&mut tmp, self.exit_state);
-            apply_edge_effect(tmp, target);
-            (self.propagate)(self.pred, tmp);
-        }
-
-        self.effects_applied = true;
-    }
-}
-
 /// Dataflow that runs from the entry of a block (the first statement), to its exit (terminator).
 pub struct Forward;
 
@@ -284,7 +249,7 @@ impl Direction for Forward {
 
     fn apply_effects_in_block<'mir, 'tcx, A>(
         analysis: &mut A,
-        _body: &mir::Body<'tcx>,
+        body: &mir::Body<'tcx>,
         state: &mut A::Domain,
         block: BasicBlock,
         block_data: &'mir mir::BasicBlockData<'tcx>,
@@ -324,23 +289,28 @@ impl Direction for Forward {
                 }
             }
             TerminatorEdges::SwitchInt { targets, discr } => {
-                let mut applier = ForwardSwitchIntEdgeEffectsApplier {
-                    exit_state,
-                    targets,
-                    propagate,
-                    effects_applied: false,
-                };
-
-                analysis.apply_switch_int_edge_effects(block, discr, &mut applier);
-
-                let ForwardSwitchIntEdgeEffectsApplier {
-                    exit_state,
-                    mut propagate,
-                    effects_applied,
-                    ..
-                } = applier;
-
-                if !effects_applied {
+                if let Some(mut data) = analysis.get_switch_int_data(block, discr) {
+                    let mut tmp = analysis.bottom_value(body);
+                    for (value, target) in targets.iter() {
+                        tmp.clone_from(&exit_state);
+                        analysis.apply_switch_int_edge_effect(
+                            &mut data,
+                            &mut tmp,
+                            SwitchIntTarget { value: Some(value), target },
+                        );
+                        propagate(target, &tmp);
+                    }
+
+                    // Once we get to the final, "otherwise" branch, there is no need to preserve
+                    // `exit_state`, so pass it directly to `apply_switch_int_edge_effect` to save
+                    // a clone of the dataflow state.
+                    let otherwise = targets.otherwise();
+                    analysis.apply_switch_int_edge_effect(&mut data, exit_state, SwitchIntTarget {
+                        value: None,
+                        target: otherwise,
+                    });
+                    propagate(otherwise, exit_state);
+                } else {
                     for target in targets.all_targets() {
                         propagate(*target, exit_state);
                     }
@@ -454,54 +424,3 @@ impl Direction for Forward {
         vis.visit_block_end(state);
     }
 }
-
-struct ForwardSwitchIntEdgeEffectsApplier<'mir, D, F> {
-    exit_state: &'mir mut D,
-    targets: &'mir SwitchTargets,
-    propagate: F,
-
-    effects_applied: bool,
-}
-
-impl<D, F> super::SwitchIntEdgeEffects<D> for ForwardSwitchIntEdgeEffectsApplier<'_, D, F>
-where
-    D: Clone,
-    F: FnMut(BasicBlock, &D),
-{
-    fn apply(&mut self, mut apply_edge_effect: impl FnMut(&mut D, SwitchIntTarget)) {
-        assert!(!self.effects_applied);
-
-        let mut tmp = None;
-        for (value, target) in self.targets.iter() {
-            let tmp = opt_clone_from_or_clone(&mut tmp, self.exit_state);
-            apply_edge_effect(tmp, SwitchIntTarget { value: Some(value), target });
-            (self.propagate)(target, tmp);
-        }
-
-        // Once we get to the final, "otherwise" branch, there is no need to preserve `exit_state`,
-        // so pass it directly to `apply_edge_effect` to save a clone of the dataflow state.
-        let otherwise = self.targets.otherwise();
-        apply_edge_effect(self.exit_state, SwitchIntTarget { value: None, target: otherwise });
-        (self.propagate)(otherwise, self.exit_state);
-
-        self.effects_applied = true;
-    }
-}
-
-/// An analogue of `Option::get_or_insert_with` that stores a clone of `val` into `opt`, but uses
-/// the more efficient `clone_from` if `opt` was `Some`.
-///
-/// Returns a mutable reference to the new clone that resides in `opt`.
-//
-// FIXME: Figure out how to express this using `Option::clone_from`, or maybe lift it into the
-// standard library?
-fn opt_clone_from_or_clone<'a, T: Clone>(opt: &'a mut Option<T>, val: &T) -> &'a mut T {
-    if opt.is_some() {
-        let ret = opt.as_mut().unwrap();
-        ret.clone_from(val);
-        ret
-    } else {
-        *opt = Some(val.clone());
-        opt.as_mut().unwrap()
-    }
-}
diff --git a/compiler/rustc_mir_dataflow/src/framework/graphviz.rs b/compiler/rustc_mir_dataflow/src/framework/graphviz.rs
index 5b2b128e035..60c97710c7f 100644
--- a/compiler/rustc_mir_dataflow/src/framework/graphviz.rs
+++ b/compiler/rustc_mir_dataflow/src/framework/graphviz.rs
@@ -16,7 +16,7 @@ use rustc_middle::mir::{
 };
 use rustc_middle::ty::TyCtxt;
 use rustc_middle::ty::print::with_no_trimmed_paths;
-use rustc_span::symbol::{Symbol, sym};
+use rustc_span::{Symbol, sym};
 use tracing::debug;
 use {rustc_ast as ast, rustc_graphviz as dot};
 
diff --git a/compiler/rustc_mir_dataflow/src/framework/mod.rs b/compiler/rustc_mir_dataflow/src/framework/mod.rs
index 41df5fae0de..3de2c6e3f47 100644
--- a/compiler/rustc_mir_dataflow/src/framework/mod.rs
+++ b/compiler/rustc_mir_dataflow/src/framework/mod.rs
@@ -103,6 +103,9 @@ pub trait Analysis<'tcx> {
     /// The direction of this analysis. Either `Forward` or `Backward`.
     type Direction: Direction = Forward;
 
+    /// Auxiliary data used for analyzing `SwitchInt` terminators, if necessary.
+    type SwitchIntData = !;
+
     /// A descriptive name for this analysis. Used only for debugging.
     ///
     /// This name should be brief and contain no spaces, periods or other characters that are not
@@ -190,25 +193,36 @@ pub trait Analysis<'tcx> {
     ) {
     }
 
-    /// Updates the current dataflow state with the effect of taking a particular branch in a
-    /// `SwitchInt` terminator.
+    /// Used to update the current dataflow state with the effect of taking a particular branch in
+    /// a `SwitchInt` terminator.
     ///
     /// Unlike the other edge-specific effects, which are allowed to mutate `Self::Domain`
-    /// directly, overriders of this method must pass a callback to
-    /// `SwitchIntEdgeEffects::apply`. The callback will be run once for each outgoing edge and
-    /// will have access to the dataflow state that will be propagated along that edge.
+    /// directly, overriders of this method must return a `Self::SwitchIntData` value (wrapped in
+    /// `Some`). The `apply_switch_int_edge_effect` method will then be called once for each
+    /// outgoing edge and will have access to the dataflow state that will be propagated along that
+    /// edge, and also the `Self::SwitchIntData` value.
     ///
     /// This interface is somewhat more complex than the other visitor-like "effect" methods.
     /// However, it is both more ergonomic—callers don't need to recompute or cache information
     /// about a given `SwitchInt` terminator for each one of its edges—and more efficient—the
     /// engine doesn't need to clone the exit state for a block unless
-    /// `SwitchIntEdgeEffects::apply` is actually called.
-    fn apply_switch_int_edge_effects(
+    /// `get_switch_int_data` is actually called.
+    fn get_switch_int_data(
         &mut self,
-        _block: BasicBlock,
+        _block: mir::BasicBlock,
         _discr: &mir::Operand<'tcx>,
-        _apply_edge_effects: &mut impl SwitchIntEdgeEffects<Self::Domain>,
+    ) -> Option<Self::SwitchIntData> {
+        None
+    }
+
+    /// See comments on `get_switch_int_data`.
+    fn apply_switch_int_edge_effect(
+        &mut self,
+        _data: &mut Self::SwitchIntData,
+        _state: &mut Self::Domain,
+        _edge: SwitchIntTarget,
     ) {
+        unreachable!();
     }
 
     /* Extension methods */
@@ -421,12 +435,5 @@ pub struct SwitchIntTarget {
     pub target: BasicBlock,
 }
 
-/// A type that records the edge-specific effects for a `SwitchInt` terminator.
-pub trait SwitchIntEdgeEffects<D> {
-    /// Calls `apply_edge_effect` for each outgoing edge from a `SwitchInt` terminator and
-    /// records the results.
-    fn apply(&mut self, apply_edge_effect: impl FnMut(&mut D, SwitchIntTarget));
-}
-
 #[cfg(test)]
 mod tests;
diff --git a/compiler/rustc_mir_dataflow/src/framework/visitor.rs b/compiler/rustc_mir_dataflow/src/framework/visitor.rs
index d18e9fa33f0..a03aecee7be 100644
--- a/compiler/rustc_mir_dataflow/src/framework/visitor.rs
+++ b/compiler/rustc_mir_dataflow/src/framework/visitor.rs
@@ -35,7 +35,6 @@ where
 {
     fn visit_block_start(&mut self, _state: &A::Domain) {}
 
-    /// // njn: grep for "before", "primary", etc.
     /// Called after the "early" effect of the given statement is applied to `state`.
     fn visit_after_early_statement_effect(
         &mut self,
diff --git a/compiler/rustc_mir_dataflow/src/impls/initialized.rs b/compiler/rustc_mir_dataflow/src/impls/initialized.rs
index fb02408e17d..769f9c7cfc3 100644
--- a/compiler/rustc_mir_dataflow/src/impls/initialized.rs
+++ b/compiler/rustc_mir_dataflow/src/impls/initialized.rs
@@ -1,20 +1,96 @@
 use std::assert_matches::assert_matches;
 
+use rustc_abi::VariantIdx;
 use rustc_index::Idx;
 use rustc_index::bit_set::{BitSet, MixedBitSet};
 use rustc_middle::bug;
 use rustc_middle::mir::{self, Body, CallReturnPlaces, Location, TerminatorEdges};
+use rustc_middle::ty::util::Discr;
 use rustc_middle::ty::{self, TyCtxt};
 use tracing::{debug, instrument};
 
 use crate::elaborate_drops::DropFlagState;
-use crate::framework::SwitchIntEdgeEffects;
+use crate::framework::SwitchIntTarget;
 use crate::move_paths::{HasMoveData, InitIndex, InitKind, LookupResult, MoveData, MovePathIndex};
 use crate::{
     Analysis, GenKill, MaybeReachable, drop_flag_effects, drop_flag_effects_for_function_entry,
     drop_flag_effects_for_location, on_all_children_bits, on_lookup_result_bits,
 };
 
+// Used by both `MaybeInitializedPlaces` and `MaybeUninitializedPlaces`.
+pub struct MaybePlacesSwitchIntData<'tcx> {
+    enum_place: mir::Place<'tcx>,
+    discriminants: Vec<(VariantIdx, Discr<'tcx>)>,
+    index: usize,
+}
+
+impl<'tcx> MaybePlacesSwitchIntData<'tcx> {
+    // The discriminant order in the `SwitchInt` targets should match the order yielded by
+    // `AdtDef::discriminants`. We rely on this to match each discriminant in the targets to its
+    // corresponding variant in linear time.
+    fn next_discr(&mut self, value: u128) -> VariantIdx {
+        // An out-of-bounds abort will occur if the discriminant ordering isn't as described above.
+        loop {
+            let (variant, discr) = self.discriminants[self.index];
+            self.index += 1;
+            if discr.val == value {
+                return variant;
+            }
+        }
+    }
+}
+
+impl<'tcx> MaybePlacesSwitchIntData<'tcx> {
+    fn new(
+        tcx: TyCtxt<'tcx>,
+        body: &Body<'tcx>,
+        block: mir::BasicBlock,
+        discr: &mir::Operand<'tcx>,
+    ) -> Option<Self> {
+        let Some(discr) = discr.place() else { return None };
+
+        // Inspect a `SwitchInt`-terminated basic block to see if the condition of that `SwitchInt`
+        // is an enum discriminant.
+        //
+        // We expect such blocks to have a call to `discriminant` as their last statement like so:
+        // ```text
+        // ...
+        // _42 = discriminant(_1)
+        // SwitchInt(_42, ..)
+        // ```
+        // If the basic block matches this pattern, this function gathers the place corresponding
+        // to the enum (`_1` in the example above) as well as the discriminants.
+        let block_data = &body[block];
+        for statement in block_data.statements.iter().rev() {
+            match statement.kind {
+                mir::StatementKind::Assign(box (lhs, mir::Rvalue::Discriminant(enum_place)))
+                    if lhs == discr =>
+                {
+                    match enum_place.ty(body, tcx).ty.kind() {
+                        ty::Adt(enum_def, _) => {
+                            return Some(MaybePlacesSwitchIntData {
+                                enum_place,
+                                discriminants: enum_def.discriminants(tcx).collect(),
+                                index: 0,
+                            });
+                        }
+
+                        // `Rvalue::Discriminant` is also used to get the active yield point for a
+                        // coroutine, but we do not need edge-specific effects in that case. This
+                        // may change in the future.
+                        ty::Coroutine(..) => break,
+
+                        t => bug!("`discriminant` called on unexpected type {:?}", t),
+                    }
+                }
+                mir::StatementKind::Coverage(_) => continue,
+                _ => break,
+            }
+        }
+        None
+    }
+}
+
 /// `MaybeInitializedPlaces` tracks all places that might be
 /// initialized upon reaching a particular point in the control flow
 /// for a function.
@@ -247,6 +323,8 @@ impl<'tcx> Analysis<'tcx> for MaybeInitializedPlaces<'_, 'tcx> {
     /// We use a mixed bitset to avoid paying too high a memory footprint.
     type Domain = MaybeReachable<MixedBitSet<MovePathIndex>>;
 
+    type SwitchIntData = MaybePlacesSwitchIntData<'tcx>;
+
     const NAME: &'static str = "maybe_init";
 
     fn bottom_value(&self, _: &mir::Body<'tcx>) -> Self::Domain {
@@ -293,6 +371,8 @@ impl<'tcx> Analysis<'tcx> for MaybeInitializedPlaces<'_, 'tcx> {
         terminator: &'mir mir::Terminator<'tcx>,
         location: Location,
     ) -> TerminatorEdges<'mir, 'tcx> {
+        // Note: `edges` must be computed first because `drop_flag_effects_for_location` can change
+        // the result of `is_unwind_dead`.
         let mut edges = terminator.edges();
         if self.skip_unreachable_unwind
             && let mir::TerminatorKind::Drop { target, unwind, place, replace: _ } = terminator.kind
@@ -326,46 +406,34 @@ impl<'tcx> Analysis<'tcx> for MaybeInitializedPlaces<'_, 'tcx> {
         });
     }
 
-    fn apply_switch_int_edge_effects(
+    fn get_switch_int_data(
         &mut self,
         block: mir::BasicBlock,
         discr: &mir::Operand<'tcx>,
-        edge_effects: &mut impl SwitchIntEdgeEffects<Self::Domain>,
-    ) {
+    ) -> Option<Self::SwitchIntData> {
         if !self.tcx.sess.opts.unstable_opts.precise_enum_drop_elaboration {
-            return;
+            return None;
         }
 
-        let enum_ = discr.place().and_then(|discr| {
-            switch_on_enum_discriminant(self.tcx, self.body, &self.body[block], discr)
-        });
-
-        let Some((enum_place, enum_def)) = enum_ else {
-            return;
-        };
-
-        let mut discriminants = enum_def.discriminants(self.tcx);
-        edge_effects.apply(|state, edge| {
-            let Some(value) = edge.value else {
-                return;
-            };
-
-            // MIR building adds discriminants to the `values` array in the same order as they
-            // are yielded by `AdtDef::discriminants`. We rely on this to match each
-            // discriminant in `values` to its corresponding variant in linear time.
-            let (variant, _) = discriminants
-                .find(|&(_, discr)| discr.val == value)
-                .expect("Order of `AdtDef::discriminants` differed from `SwitchInt::values`");
+        MaybePlacesSwitchIntData::new(self.tcx, self.body, block, discr)
+    }
 
+    fn apply_switch_int_edge_effect(
+        &mut self,
+        data: &mut Self::SwitchIntData,
+        state: &mut Self::Domain,
+        edge: SwitchIntTarget,
+    ) {
+        if let Some(value) = edge.value {
             // Kill all move paths that correspond to variants we know to be inactive along this
             // particular outgoing edge of a `SwitchInt`.
             drop_flag_effects::on_all_inactive_variants(
-                self.move_data(),
-                enum_place,
-                variant,
+                self.move_data,
+                data.enum_place,
+                data.next_discr(value),
                 |mpi| state.kill(mpi),
             );
-        });
+        }
     }
 }
 
@@ -376,6 +444,8 @@ pub type MaybeUninitializedPlacesDomain = MixedBitSet<MovePathIndex>;
 impl<'tcx> Analysis<'tcx> for MaybeUninitializedPlaces<'_, 'tcx> {
     type Domain = MaybeUninitializedPlacesDomain;
 
+    type SwitchIntData = MaybePlacesSwitchIntData<'tcx>;
+
     const NAME: &'static str = "maybe_uninit";
 
     fn bottom_value(&self, _: &mir::Body<'tcx>) -> Self::Domain {
@@ -445,50 +515,38 @@ impl<'tcx> Analysis<'tcx> for MaybeUninitializedPlaces<'_, 'tcx> {
         });
     }
 
-    fn apply_switch_int_edge_effects(
+    fn get_switch_int_data(
         &mut self,
         block: mir::BasicBlock,
         discr: &mir::Operand<'tcx>,
-        edge_effects: &mut impl SwitchIntEdgeEffects<Self::Domain>,
-    ) {
+    ) -> Option<Self::SwitchIntData> {
         if !self.tcx.sess.opts.unstable_opts.precise_enum_drop_elaboration {
-            return;
+            return None;
         }
 
         if !self.mark_inactive_variants_as_uninit {
-            return;
+            return None;
         }
 
-        let enum_ = discr.place().and_then(|discr| {
-            switch_on_enum_discriminant(self.tcx, self.body, &self.body[block], discr)
-        });
-
-        let Some((enum_place, enum_def)) = enum_ else {
-            return;
-        };
-
-        let mut discriminants = enum_def.discriminants(self.tcx);
-        edge_effects.apply(|state, edge| {
-            let Some(value) = edge.value else {
-                return;
-            };
-
-            // MIR building adds discriminants to the `values` array in the same order as they
-            // are yielded by `AdtDef::discriminants`. We rely on this to match each
-            // discriminant in `values` to its corresponding variant in linear time.
-            let (variant, _) = discriminants
-                .find(|&(_, discr)| discr.val == value)
-                .expect("Order of `AdtDef::discriminants` differed from `SwitchInt::values`");
+        MaybePlacesSwitchIntData::new(self.tcx, self.body, block, discr)
+    }
 
+    fn apply_switch_int_edge_effect(
+        &mut self,
+        data: &mut Self::SwitchIntData,
+        state: &mut Self::Domain,
+        edge: SwitchIntTarget,
+    ) {
+        if let Some(value) = edge.value {
             // Mark all move paths that correspond to variants other than this one as maybe
             // uninitialized (in reality, they are *definitely* uninitialized).
             drop_flag_effects::on_all_inactive_variants(
-                self.move_data(),
-                enum_place,
-                variant,
+                self.move_data,
+                data.enum_place,
+                data.next_discr(value),
                 |mpi| state.gen_(mpi),
             );
-        });
+        }
     }
 }
 
@@ -578,45 +636,3 @@ impl<'tcx> Analysis<'tcx> for EverInitializedPlaces<'_, 'tcx> {
         }
     }
 }
-
-/// Inspect a `SwitchInt`-terminated basic block to see if the condition of that `SwitchInt` is
-/// an enum discriminant.
-///
-/// We expect such blocks to have a call to `discriminant` as their last statement like so:
-///
-/// ```text
-/// ...
-/// _42 = discriminant(_1)
-/// SwitchInt(_42, ..)
-/// ```
-///
-/// If the basic block matches this pattern, this function returns the place corresponding to the
-/// enum (`_1` in the example above) as well as the `AdtDef` of that enum.
-fn switch_on_enum_discriminant<'mir, 'tcx>(
-    tcx: TyCtxt<'tcx>,
-    body: &'mir mir::Body<'tcx>,
-    block: &'mir mir::BasicBlockData<'tcx>,
-    switch_on: mir::Place<'tcx>,
-) -> Option<(mir::Place<'tcx>, ty::AdtDef<'tcx>)> {
-    for statement in block.statements.iter().rev() {
-        match &statement.kind {
-            mir::StatementKind::Assign(box (lhs, mir::Rvalue::Discriminant(discriminated)))
-                if *lhs == switch_on =>
-            {
-                match discriminated.ty(body, tcx).ty.kind() {
-                    ty::Adt(def, _) => return Some((*discriminated, *def)),
-
-                    // `Rvalue::Discriminant` is also used to get the active yield point for a
-                    // coroutine, but we do not need edge-specific effects in that case. This may
-                    // change in the future.
-                    ty::Coroutine(..) => return None,
-
-                    t => bug!("`discriminant` called on unexpected type {:?}", t),
-                }
-            }
-            mir::StatementKind::Coverage(_) => continue,
-            _ => return None,
-        }
-    }
-    None
-}
diff --git a/compiler/rustc_mir_dataflow/src/lib.rs b/compiler/rustc_mir_dataflow/src/lib.rs
index 85255db5d9a..0cc79b0c939 100644
--- a/compiler/rustc_mir_dataflow/src/lib.rs
+++ b/compiler/rustc_mir_dataflow/src/lib.rs
@@ -5,6 +5,7 @@
 #![feature(exact_size_is_empty)]
 #![feature(file_buffered)]
 #![feature(let_chains)]
+#![feature(never_type)]
 #![feature(try_blocks)]
 #![warn(unreachable_pub)]
 // tidy-alphabetical-end
@@ -19,8 +20,7 @@ pub use self::drop_flag_effects::{
 };
 pub use self::framework::{
     Analysis, Backward, Direction, EntryStates, Forward, GenKill, JoinSemiLattice, MaybeReachable,
-    Results, ResultsCursor, ResultsVisitor, SwitchIntEdgeEffects, fmt, graphviz, lattice,
-    visit_results,
+    Results, ResultsCursor, ResultsVisitor, fmt, graphviz, lattice, visit_results,
 };
 use self::move_paths::MoveData;
 
diff --git a/compiler/rustc_mir_dataflow/src/rustc_peek.rs b/compiler/rustc_mir_dataflow/src/rustc_peek.rs
index 85cf8ca2104..399141aa921 100644
--- a/compiler/rustc_mir_dataflow/src/rustc_peek.rs
+++ b/compiler/rustc_mir_dataflow/src/rustc_peek.rs
@@ -2,8 +2,7 @@ use rustc_ast::MetaItem;
 use rustc_hir::def_id::DefId;
 use rustc_middle::mir::{self, Body, Local, Location};
 use rustc_middle::ty::{self, Ty, TyCtxt};
-use rustc_span::Span;
-use rustc_span::symbol::{Symbol, sym};
+use rustc_span::{Span, Symbol, sym};
 use tracing::{debug, info};
 
 use crate::errors::{
diff --git a/compiler/rustc_mir_transform/Cargo.toml b/compiler/rustc_mir_transform/Cargo.toml
index 4b648d21084..2f233f787f0 100644
--- a/compiler/rustc_mir_transform/Cargo.toml
+++ b/compiler/rustc_mir_transform/Cargo.toml
@@ -10,7 +10,7 @@ itertools = "0.12"
 rustc_abi = { path = "../rustc_abi" }
 rustc_arena = { path = "../rustc_arena" }
 rustc_ast = { path = "../rustc_ast" }
-rustc_attr = { path = "../rustc_attr" }
+rustc_attr_parsing = { path = "../rustc_attr_parsing" }
 rustc_const_eval = { path = "../rustc_const_eval" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
diff --git a/compiler/rustc_mir_transform/src/coroutine.rs b/compiler/rustc_mir_transform/src/coroutine.rs
index 31d5245fb5c..a3320f99cc3 100644
--- a/compiler/rustc_mir_transform/src/coroutine.rs
+++ b/compiler/rustc_mir_transform/src/coroutine.rs
@@ -73,9 +73,8 @@ use rustc_mir_dataflow::impls::{
     always_storage_live_locals,
 };
 use rustc_mir_dataflow::{Analysis, Results, ResultsVisitor};
-use rustc_span::Span;
 use rustc_span::def_id::{DefId, LocalDefId};
-use rustc_span::symbol::sym;
+use rustc_span::{Span, sym};
 use rustc_target::spec::PanicStrategy;
 use rustc_trait_selection::error_reporting::InferCtxtErrorExt;
 use rustc_trait_selection::infer::TyCtxtInferExt as _;
diff --git a/compiler/rustc_mir_transform/src/coroutine/by_move_body.rs b/compiler/rustc_mir_transform/src/coroutine/by_move_body.rs
index ef61866e902..9f5bb015fa3 100644
--- a/compiler/rustc_mir_transform/src/coroutine/by_move_body.rs
+++ b/compiler/rustc_mir_transform/src/coroutine/by_move_body.rs
@@ -78,7 +78,7 @@ use rustc_middle::hir::place::{Projection, ProjectionKind};
 use rustc_middle::mir::visit::MutVisitor;
 use rustc_middle::mir::{self, dump_mir};
 use rustc_middle::ty::{self, InstanceKind, Ty, TyCtxt, TypeVisitableExt};
-use rustc_span::symbol::kw;
+use rustc_span::kw;
 
 pub(crate) fn coroutine_by_move_body_def_id<'tcx>(
     tcx: TyCtxt<'tcx>,
diff --git a/compiler/rustc_mir_transform/src/coverage/mappings.rs b/compiler/rustc_mir_transform/src/coverage/mappings.rs
index 2db7c6cf1d6..4185b3f4d4d 100644
--- a/compiler/rustc_mir_transform/src/coverage/mappings.rs
+++ b/compiler/rustc_mir_transform/src/coverage/mappings.rs
@@ -80,7 +80,7 @@ pub(super) fn extract_all_mapping_info_from_mir<'tcx>(
     tcx: TyCtxt<'tcx>,
     mir_body: &mir::Body<'tcx>,
     hir_info: &ExtractedHirInfo,
-    basic_coverage_blocks: &CoverageGraph,
+    graph: &CoverageGraph,
 ) -> ExtractedMappings {
     let mut code_mappings = vec![];
     let mut branch_pairs = vec![];
@@ -102,23 +102,23 @@ pub(super) fn extract_all_mapping_info_from_mir<'tcx>(
         }
     } else {
         // Extract coverage spans from MIR statements/terminators as normal.
-        extract_refined_covspans(mir_body, hir_info, basic_coverage_blocks, &mut code_mappings);
+        extract_refined_covspans(mir_body, hir_info, graph, &mut code_mappings);
     }
 
-    branch_pairs.extend(extract_branch_pairs(mir_body, hir_info, basic_coverage_blocks));
+    branch_pairs.extend(extract_branch_pairs(mir_body, hir_info, graph));
 
     extract_mcdc_mappings(
         mir_body,
         tcx,
         hir_info.body_span,
-        basic_coverage_blocks,
+        graph,
         &mut mcdc_bitmap_bits,
         &mut mcdc_degraded_branches,
         &mut mcdc_mappings,
     );
 
     ExtractedMappings {
-        num_bcbs: basic_coverage_blocks.num_nodes(),
+        num_bcbs: graph.num_nodes(),
         code_mappings,
         branch_pairs,
         mcdc_bitmap_bits,
@@ -211,7 +211,7 @@ fn resolve_block_markers(
 pub(super) fn extract_branch_pairs(
     mir_body: &mir::Body<'_>,
     hir_info: &ExtractedHirInfo,
-    basic_coverage_blocks: &CoverageGraph,
+    graph: &CoverageGraph,
 ) -> Vec<BranchPair> {
     let Some(coverage_info_hi) = mir_body.coverage_info_hi.as_deref() else { return vec![] };
 
@@ -228,8 +228,7 @@ pub(super) fn extract_branch_pairs(
             }
             let span = unexpand_into_body_span(raw_span, hir_info.body_span)?;
 
-            let bcb_from_marker =
-                |marker: BlockMarkerId| basic_coverage_blocks.bcb_from_bb(block_markers[marker]?);
+            let bcb_from_marker = |marker: BlockMarkerId| graph.bcb_from_bb(block_markers[marker]?);
 
             let true_bcb = bcb_from_marker(true_marker)?;
             let false_bcb = bcb_from_marker(false_marker)?;
@@ -243,7 +242,7 @@ pub(super) fn extract_mcdc_mappings(
     mir_body: &mir::Body<'_>,
     tcx: TyCtxt<'_>,
     body_span: Span,
-    basic_coverage_blocks: &CoverageGraph,
+    graph: &CoverageGraph,
     mcdc_bitmap_bits: &mut usize,
     mcdc_degraded_branches: &mut impl Extend<MCDCBranch>,
     mcdc_mappings: &mut impl Extend<(MCDCDecision, Vec<MCDCBranch>)>,
@@ -252,8 +251,7 @@ pub(super) fn extract_mcdc_mappings(
 
     let block_markers = resolve_block_markers(coverage_info_hi, mir_body);
 
-    let bcb_from_marker =
-        |marker: BlockMarkerId| basic_coverage_blocks.bcb_from_bb(block_markers[marker]?);
+    let bcb_from_marker = |marker: BlockMarkerId| graph.bcb_from_bb(block_markers[marker]?);
 
     let check_branch_bcb =
         |raw_span: Span, true_marker: BlockMarkerId, false_marker: BlockMarkerId| {
diff --git a/compiler/rustc_mir_transform/src/coverage/mod.rs b/compiler/rustc_mir_transform/src/coverage/mod.rs
index 241c3c79114..57956448414 100644
--- a/compiler/rustc_mir_transform/src/coverage/mod.rs
+++ b/compiler/rustc_mir_transform/src/coverage/mod.rs
@@ -13,16 +13,15 @@ use rustc_hir::intravisit::{Visitor, walk_expr};
 use rustc_middle::hir::map::Map;
 use rustc_middle::hir::nested_filter;
 use rustc_middle::mir::coverage::{
-    CoverageKind, DecisionInfo, FunctionCoverageInfo, Mapping, MappingKind, SourceRegion,
+    CoverageKind, DecisionInfo, FunctionCoverageInfo, Mapping, MappingKind,
 };
 use rustc_middle::mir::{
     self, BasicBlock, BasicBlockData, SourceInfo, Statement, StatementKind, Terminator,
     TerminatorKind,
 };
 use rustc_middle::ty::TyCtxt;
+use rustc_span::Span;
 use rustc_span::def_id::LocalDefId;
-use rustc_span::source_map::SourceMap;
-use rustc_span::{BytePos, Pos, SourceFile, Span};
 use tracing::{debug, debug_span, trace};
 
 use crate::coverage::counters::{CoverageCounters, Site};
@@ -72,16 +71,15 @@ fn instrument_function_for_coverage<'tcx>(tcx: TyCtxt<'tcx>, mir_body: &mut mir:
     let _span = debug_span!("instrument_function_for_coverage", ?def_id).entered();
 
     let hir_info = extract_hir_info(tcx, def_id.expect_local());
-    let basic_coverage_blocks = CoverageGraph::from_mir(mir_body);
+
+    // Build the coverage graph, which is a simplified view of the MIR control-flow
+    // graph that ignores some details not relevant to coverage instrumentation.
+    let graph = CoverageGraph::from_mir(mir_body);
 
     ////////////////////////////////////////////////////
     // Extract coverage spans and other mapping info from MIR.
-    let extracted_mappings = mappings::extract_all_mapping_info_from_mir(
-        tcx,
-        mir_body,
-        &hir_info,
-        &basic_coverage_blocks,
-    );
+    let extracted_mappings =
+        mappings::extract_all_mapping_info_from_mir(tcx, mir_body, &hir_info, &graph);
 
     ////////////////////////////////////////////////////
     // Create an optimized mix of `Counter`s and `Expression`s for the `CoverageGraph`. Ensure
@@ -95,23 +93,18 @@ fn instrument_function_for_coverage<'tcx>(tcx: TyCtxt<'tcx>, mir_body: &mut mir:
     }
 
     let coverage_counters =
-        CoverageCounters::make_bcb_counters(&basic_coverage_blocks, &bcbs_with_counter_mappings);
+        CoverageCounters::make_bcb_counters(&graph, &bcbs_with_counter_mappings);
 
-    let mappings = create_mappings(tcx, &hir_info, &extracted_mappings, &coverage_counters);
+    let mappings = create_mappings(&extracted_mappings, &coverage_counters);
     if mappings.is_empty() {
         // No spans could be converted into valid mappings, so skip this function.
         debug!("no spans could be converted into valid mappings; skipping");
         return;
     }
 
-    inject_coverage_statements(
-        mir_body,
-        &basic_coverage_blocks,
-        &extracted_mappings,
-        &coverage_counters,
-    );
+    inject_coverage_statements(mir_body, &graph, &extracted_mappings, &coverage_counters);
 
-    inject_mcdc_statements(mir_body, &basic_coverage_blocks, &extracted_mappings);
+    inject_mcdc_statements(mir_body, &graph, &extracted_mappings);
 
     let mcdc_num_condition_bitmaps = extracted_mappings
         .mcdc_mappings
@@ -136,18 +129,12 @@ fn instrument_function_for_coverage<'tcx>(tcx: TyCtxt<'tcx>, mir_body: &mut mir:
 ///
 /// Precondition: All BCBs corresponding to those spans have been given
 /// coverage counters.
-fn create_mappings<'tcx>(
-    tcx: TyCtxt<'tcx>,
-    hir_info: &ExtractedHirInfo,
+fn create_mappings(
     extracted_mappings: &ExtractedMappings,
     coverage_counters: &CoverageCounters,
 ) -> Vec<Mapping> {
-    let source_map = tcx.sess.source_map();
-    let file = source_map.lookup_source_file(hir_info.body_span.lo());
-
     let term_for_bcb =
         |bcb| coverage_counters.term_for_bcb(bcb).expect("all BCBs with spans were given counters");
-    let region_for_span = |span: Span| make_source_region(source_map, hir_info, &file, span);
 
     // Fully destructure the mappings struct to make sure we don't miss any kinds.
     let ExtractedMappings {
@@ -160,22 +147,20 @@ fn create_mappings<'tcx>(
     } = extracted_mappings;
     let mut mappings = Vec::new();
 
-    mappings.extend(code_mappings.iter().filter_map(
+    mappings.extend(code_mappings.iter().map(
         // Ordinary code mappings are the simplest kind.
         |&mappings::CodeMapping { span, bcb }| {
-            let source_region = region_for_span(span)?;
             let kind = MappingKind::Code(term_for_bcb(bcb));
-            Some(Mapping { kind, source_region })
+            Mapping { kind, span }
         },
     ));
 
-    mappings.extend(branch_pairs.iter().filter_map(
+    mappings.extend(branch_pairs.iter().map(
         |&mappings::BranchPair { span, true_bcb, false_bcb }| {
             let true_term = term_for_bcb(true_bcb);
             let false_term = term_for_bcb(false_bcb);
             let kind = MappingKind::Branch { true_term, false_term };
-            let source_region = region_for_span(span)?;
-            Some(Mapping { kind, source_region })
+            Mapping { kind, span }
         },
     ));
 
@@ -183,7 +168,7 @@ fn create_mappings<'tcx>(
         |bcb| coverage_counters.term_for_bcb(bcb).expect("all BCBs with spans were given counters");
 
     // MCDC branch mappings are appended with their decisions in case decisions were ignored.
-    mappings.extend(mcdc_degraded_branches.iter().filter_map(
+    mappings.extend(mcdc_degraded_branches.iter().map(
         |&mappings::MCDCBranch {
              span,
              true_bcb,
@@ -192,10 +177,9 @@ fn create_mappings<'tcx>(
              true_index: _,
              false_index: _,
          }| {
-            let source_region = region_for_span(span)?;
             let true_term = term_for_bcb(true_bcb);
             let false_term = term_for_bcb(false_bcb);
-            Some(Mapping { kind: MappingKind::Branch { true_term, false_term }, source_region })
+            Mapping { kind: MappingKind::Branch { true_term, false_term }, span }
         },
     ));
 
@@ -203,7 +187,7 @@ fn create_mappings<'tcx>(
         let num_conditions = branches.len() as u16;
         let conditions = branches
             .into_iter()
-            .filter_map(
+            .map(
                 |&mappings::MCDCBranch {
                      span,
                      true_bcb,
@@ -212,32 +196,28 @@ fn create_mappings<'tcx>(
                      true_index: _,
                      false_index: _,
                  }| {
-                    let source_region = region_for_span(span)?;
                     let true_term = term_for_bcb(true_bcb);
                     let false_term = term_for_bcb(false_bcb);
-                    Some(Mapping {
+                    Mapping {
                         kind: MappingKind::MCDCBranch {
                             true_term,
                             false_term,
                             mcdc_params: condition_info,
                         },
-                        source_region,
-                    })
+                        span,
+                    }
                 },
             )
             .collect::<Vec<_>>();
 
-        if conditions.len() == num_conditions as usize
-            && let Some(source_region) = region_for_span(decision.span)
-        {
+        if conditions.len() == num_conditions as usize {
             // LLVM requires end index for counter mapping regions.
             let kind = MappingKind::MCDCDecision(DecisionInfo {
                 bitmap_idx: (decision.bitmap_idx + decision.num_test_vectors) as u32,
                 num_conditions,
             });
-            mappings.extend(
-                std::iter::once(Mapping { kind, source_region }).chain(conditions.into_iter()),
-            );
+            let span = decision.span;
+            mappings.extend(std::iter::once(Mapping { kind, span }).chain(conditions.into_iter()));
         } else {
             mappings.extend(conditions.into_iter().map(|mapping| {
                 let MappingKind::MCDCBranch { true_term, false_term, mcdc_params: _ } =
@@ -245,10 +225,7 @@ fn create_mappings<'tcx>(
                 else {
                     unreachable!("all mappings here are MCDCBranch as shown above");
                 };
-                Mapping {
-                    kind: MappingKind::Branch { true_term, false_term },
-                    source_region: mapping.source_region,
-                }
+                Mapping { kind: MappingKind::Branch { true_term, false_term }, span: mapping.span }
             }))
         }
     }
@@ -260,7 +237,7 @@ fn create_mappings<'tcx>(
 /// inject any necessary coverage statements into MIR.
 fn inject_coverage_statements<'tcx>(
     mir_body: &mut mir::Body<'tcx>,
-    basic_coverage_blocks: &CoverageGraph,
+    graph: &CoverageGraph,
     extracted_mappings: &ExtractedMappings,
     coverage_counters: &CoverageCounters,
 ) {
@@ -270,12 +247,12 @@ fn inject_coverage_statements<'tcx>(
         // For BCB nodes this is just their first block, but for edges we need
         // to create a new block between the two BCBs, and inject into that.
         let target_bb = match site {
-            Site::Node { bcb } => basic_coverage_blocks[bcb].leader_bb(),
+            Site::Node { bcb } => graph[bcb].leader_bb(),
             Site::Edge { from_bcb, to_bcb } => {
                 // Create a new block between the last block of `from_bcb` and
                 // the first block of `to_bcb`.
-                let from_bb = basic_coverage_blocks[from_bcb].last_bb();
-                let to_bb = basic_coverage_blocks[to_bcb].leader_bb();
+                let from_bb = graph[from_bcb].last_bb();
+                let to_bb = graph[to_bcb].leader_bb();
 
                 let new_bb = inject_edge_counter_basic_block(mir_body, from_bb, to_bb);
                 debug!(
@@ -308,7 +285,7 @@ fn inject_coverage_statements<'tcx>(
         inject_statement(
             mir_body,
             CoverageKind::ExpressionUsed { id: expression_id },
-            basic_coverage_blocks[bcb].leader_bb(),
+            graph[bcb].leader_bb(),
         );
     }
 }
@@ -317,13 +294,13 @@ fn inject_coverage_statements<'tcx>(
 /// For each decision inject statements to update test vector bitmap after it has been evaluated.
 fn inject_mcdc_statements<'tcx>(
     mir_body: &mut mir::Body<'tcx>,
-    basic_coverage_blocks: &CoverageGraph,
+    graph: &CoverageGraph,
     extracted_mappings: &ExtractedMappings,
 ) {
     for (decision, conditions) in &extracted_mappings.mcdc_mappings {
         // Inject test vector update first because `inject_statement` always insert new statement at head.
         for &end in &decision.end_bcbs {
-            let end_bb = basic_coverage_blocks[end].leader_bb();
+            let end_bb = graph[end].leader_bb();
             inject_statement(
                 mir_body,
                 CoverageKind::TestVectorBitmapUpdate {
@@ -344,7 +321,7 @@ fn inject_mcdc_statements<'tcx>(
         } in conditions
         {
             for (index, bcb) in [(false_index, false_bcb), (true_index, true_bcb)] {
-                let bb = basic_coverage_blocks[bcb].leader_bb();
+                let bb = graph[bcb].leader_bb();
                 inject_statement(
                     mir_body,
                     CoverageKind::CondBitmapUpdate {
@@ -391,121 +368,6 @@ fn inject_statement(mir_body: &mut mir::Body<'_>, counter_kind: CoverageKind, bb
     data.statements.insert(0, statement);
 }
 
-fn ensure_non_empty_span(
-    source_map: &SourceMap,
-    hir_info: &ExtractedHirInfo,
-    span: Span,
-) -> Option<Span> {
-    if !span.is_empty() {
-        return Some(span);
-    }
-
-    let lo = span.lo();
-    let hi = span.hi();
-
-    // The span is empty, so try to expand it to cover an adjacent '{' or '}',
-    // but only within the bounds of the body span.
-    let try_next = hi < hir_info.body_span.hi();
-    let try_prev = hir_info.body_span.lo() < lo;
-    if !(try_next || try_prev) {
-        return None;
-    }
-
-    source_map
-        .span_to_source(span, |src, start, end| try {
-            // We're only checking for specific ASCII characters, so we don't
-            // have to worry about multi-byte code points.
-            if try_next && src.as_bytes()[end] == b'{' {
-                Some(span.with_hi(hi + BytePos(1)))
-            } else if try_prev && src.as_bytes()[start - 1] == b'}' {
-                Some(span.with_lo(lo - BytePos(1)))
-            } else {
-                None
-            }
-        })
-        .ok()?
-}
-
-/// Converts the span into its start line and column, and end line and column.
-///
-/// Line numbers and column numbers are 1-based. Unlike most column numbers emitted by
-/// the compiler, these column numbers are denoted in **bytes**, because that's what
-/// LLVM's `llvm-cov` tool expects to see in coverage maps.
-///
-/// Returns `None` if the conversion failed for some reason. This shouldn't happen,
-/// but it's hard to rule out entirely (especially in the presence of complex macros
-/// or other expansions), and if it does happen then skipping a span or function is
-/// better than an ICE or `llvm-cov` failure that the user might have no way to avoid.
-fn make_source_region(
-    source_map: &SourceMap,
-    hir_info: &ExtractedHirInfo,
-    file: &SourceFile,
-    span: Span,
-) -> Option<SourceRegion> {
-    let span = ensure_non_empty_span(source_map, hir_info, span)?;
-
-    let lo = span.lo();
-    let hi = span.hi();
-
-    // Column numbers need to be in bytes, so we can't use the more convenient
-    // `SourceMap` methods for looking up file coordinates.
-    let line_and_byte_column = |pos: BytePos| -> Option<(usize, usize)> {
-        let rpos = file.relative_position(pos);
-        let line_index = file.lookup_line(rpos)?;
-        let line_start = file.lines()[line_index];
-        // Line numbers and column numbers are 1-based, so add 1 to each.
-        Some((line_index + 1, (rpos - line_start).to_usize() + 1))
-    };
-
-    let (mut start_line, start_col) = line_and_byte_column(lo)?;
-    let (mut end_line, end_col) = line_and_byte_column(hi)?;
-
-    // Apply an offset so that code in doctests has correct line numbers.
-    // FIXME(#79417): Currently we have no way to offset doctest _columns_.
-    start_line = source_map.doctest_offset_line(&file.name, start_line);
-    end_line = source_map.doctest_offset_line(&file.name, end_line);
-
-    check_source_region(SourceRegion {
-        start_line: start_line as u32,
-        start_col: start_col as u32,
-        end_line: end_line as u32,
-        end_col: end_col as u32,
-    })
-}
-
-/// If `llvm-cov` sees a source region that is improperly ordered (end < start),
-/// it will immediately exit with a fatal error. To prevent that from happening,
-/// discard regions that are improperly ordered, or might be interpreted in a
-/// way that makes them improperly ordered.
-fn check_source_region(source_region: SourceRegion) -> Option<SourceRegion> {
-    let SourceRegion { start_line, start_col, end_line, end_col } = source_region;
-
-    // Line/column coordinates are supposed to be 1-based. If we ever emit
-    // coordinates of 0, `llvm-cov` might misinterpret them.
-    let all_nonzero = [start_line, start_col, end_line, end_col].into_iter().all(|x| x != 0);
-    // Coverage mappings use the high bit of `end_col` to indicate that a
-    // region is actually a "gap" region, so make sure it's unset.
-    let end_col_has_high_bit_unset = (end_col & (1 << 31)) == 0;
-    // If a region is improperly ordered (end < start), `llvm-cov` will exit
-    // with a fatal error, which is inconvenient for users and hard to debug.
-    let is_ordered = (start_line, start_col) <= (end_line, end_col);
-
-    if all_nonzero && end_col_has_high_bit_unset && is_ordered {
-        Some(source_region)
-    } else {
-        debug!(
-            ?source_region,
-            ?all_nonzero,
-            ?end_col_has_high_bit_unset,
-            ?is_ordered,
-            "Skipping source region that would be misinterpreted or rejected by LLVM"
-        );
-        // If this happens in a debug build, ICE to make it easier to notice.
-        debug_assert!(false, "Improper source region: {source_region:?}");
-        None
-    }
-}
-
 /// Function information extracted from HIR by the coverage instrumentor.
 #[derive(Debug)]
 struct ExtractedHirInfo {
diff --git a/compiler/rustc_mir_transform/src/coverage/spans.rs b/compiler/rustc_mir_transform/src/coverage/spans.rs
index 085c738f1f9..314a86ea52f 100644
--- a/compiler/rustc_mir_transform/src/coverage/spans.rs
+++ b/compiler/rustc_mir_transform/src/coverage/spans.rs
@@ -17,14 +17,13 @@ mod from_mir;
 pub(super) fn extract_refined_covspans(
     mir_body: &mir::Body<'_>,
     hir_info: &ExtractedHirInfo,
-    basic_coverage_blocks: &CoverageGraph,
+    graph: &CoverageGraph,
     code_mappings: &mut impl Extend<mappings::CodeMapping>,
 ) {
-    let ExtractedCovspans { mut covspans } =
-        extract_covspans_from_mir(mir_body, hir_info, basic_coverage_blocks);
+    let ExtractedCovspans { mut covspans } = extract_covspans_from_mir(mir_body, hir_info, graph);
 
     // First, perform the passes that need macro information.
-    covspans.sort_by(|a, b| basic_coverage_blocks.cmp_in_dominator_order(a.bcb, b.bcb));
+    covspans.sort_by(|a, b| graph.cmp_in_dominator_order(a.bcb, b.bcb));
     remove_unwanted_expansion_spans(&mut covspans);
     split_visible_macro_spans(&mut covspans);
 
@@ -34,7 +33,7 @@ pub(super) fn extract_refined_covspans(
     let compare_covspans = |a: &Covspan, b: &Covspan| {
         compare_spans(a.span, b.span)
             // After deduplication, we want to keep only the most-dominated BCB.
-            .then_with(|| basic_coverage_blocks.cmp_in_dominator_order(a.bcb, b.bcb).reverse())
+            .then_with(|| graph.cmp_in_dominator_order(a.bcb, b.bcb).reverse())
     };
     covspans.sort_by(compare_covspans);
 
diff --git a/compiler/rustc_mir_transform/src/coverage/spans/from_mir.rs b/compiler/rustc_mir_transform/src/coverage/spans/from_mir.rs
index 824d657e1fc..26ce743be36 100644
--- a/compiler/rustc_mir_transform/src/coverage/spans/from_mir.rs
+++ b/compiler/rustc_mir_transform/src/coverage/spans/from_mir.rs
@@ -22,13 +22,13 @@ pub(crate) struct ExtractedCovspans {
 pub(crate) fn extract_covspans_from_mir(
     mir_body: &mir::Body<'_>,
     hir_info: &ExtractedHirInfo,
-    basic_coverage_blocks: &CoverageGraph,
+    graph: &CoverageGraph,
 ) -> ExtractedCovspans {
     let &ExtractedHirInfo { body_span, .. } = hir_info;
 
     let mut covspans = vec![];
 
-    for (bcb, bcb_data) in basic_coverage_blocks.iter_enumerated() {
+    for (bcb, bcb_data) in graph.iter_enumerated() {
         bcb_to_initial_coverage_spans(mir_body, body_span, bcb, bcb_data, &mut covspans);
     }
 
diff --git a/compiler/rustc_mir_transform/src/coverage/tests.rs b/compiler/rustc_mir_transform/src/coverage/tests.rs
index 233ca9981c5..b2ee50de50a 100644
--- a/compiler/rustc_mir_transform/src/coverage/tests.rs
+++ b/compiler/rustc_mir_transform/src/coverage/tests.rs
@@ -223,16 +223,12 @@ fn print_mir_graphviz(name: &str, mir_body: &Body<'_>) {
     }
 }
 
-fn print_coverage_graphviz(
-    name: &str,
-    mir_body: &Body<'_>,
-    basic_coverage_blocks: &graph::CoverageGraph,
-) {
+fn print_coverage_graphviz(name: &str, mir_body: &Body<'_>, graph: &graph::CoverageGraph) {
     if PRINT_GRAPHS {
         println!(
             "digraph {} {{\n{}\n}}",
             name,
-            basic_coverage_blocks
+            graph
                 .iter_enumerated()
                 .map(|(bcb, bcb_data)| {
                     format!(
@@ -240,7 +236,7 @@ fn print_coverage_graphviz(
                         bcb,
                         bcb,
                         mir_body[bcb_data.last_bb()].terminator().kind.name(),
-                        basic_coverage_blocks
+                        graph
                             .successors(bcb)
                             .map(|successor| { format!("    {:?} -> {:?};", bcb, successor) })
                             .join("\n")
@@ -300,11 +296,11 @@ fn goto_switchint<'a>() -> Body<'a> {
 
 #[track_caller]
 fn assert_successors(
-    basic_coverage_blocks: &graph::CoverageGraph,
+    graph: &graph::CoverageGraph,
     bcb: BasicCoverageBlock,
     expected_successors: &[BasicCoverageBlock],
 ) {
-    let mut successors = basic_coverage_blocks.successors[bcb].clone();
+    let mut successors = graph.successors[bcb].clone();
     successors.sort_unstable();
     assert_eq!(successors, expected_successors);
 }
@@ -315,8 +311,8 @@ fn test_covgraph_goto_switchint() {
     if false {
         eprintln!("basic_blocks = {}", debug_basic_blocks(&mir_body));
     }
-    let basic_coverage_blocks = graph::CoverageGraph::from_mir(&mir_body);
-    print_coverage_graphviz("covgraph_goto_switchint ", &mir_body, &basic_coverage_blocks);
+    let graph = graph::CoverageGraph::from_mir(&mir_body);
+    print_coverage_graphviz("covgraph_goto_switchint ", &mir_body, &graph);
     /*
     ┌──────────────┐     ┌─────────────────┐
     │ bcb2: Return │ ◀── │ bcb0: SwitchInt │
@@ -328,16 +324,11 @@ fn test_covgraph_goto_switchint() {
                          │  bcb1: Return   │
                          └─────────────────┘
     */
-    assert_eq!(
-        basic_coverage_blocks.num_nodes(),
-        3,
-        "basic_coverage_blocks: {:?}",
-        basic_coverage_blocks.iter_enumerated().collect::<Vec<_>>()
-    );
+    assert_eq!(graph.num_nodes(), 3, "graph: {:?}", graph.iter_enumerated().collect::<Vec<_>>());
 
-    assert_successors(&basic_coverage_blocks, bcb(0), &[bcb(1), bcb(2)]);
-    assert_successors(&basic_coverage_blocks, bcb(1), &[]);
-    assert_successors(&basic_coverage_blocks, bcb(2), &[]);
+    assert_successors(&graph, bcb(0), &[bcb(1), bcb(2)]);
+    assert_successors(&graph, bcb(1), &[]);
+    assert_successors(&graph, bcb(2), &[]);
 }
 
 /// Create a mock `Body` with a loop.
@@ -383,12 +374,8 @@ fn switchint_then_loop_else_return<'a>() -> Body<'a> {
 #[test]
 fn test_covgraph_switchint_then_loop_else_return() {
     let mir_body = switchint_then_loop_else_return();
-    let basic_coverage_blocks = graph::CoverageGraph::from_mir(&mir_body);
-    print_coverage_graphviz(
-        "covgraph_switchint_then_loop_else_return",
-        &mir_body,
-        &basic_coverage_blocks,
-    );
+    let graph = graph::CoverageGraph::from_mir(&mir_body);
+    print_coverage_graphviz("covgraph_switchint_then_loop_else_return", &mir_body, &graph);
     /*
                        ┌─────────────────┐
                        │   bcb0: Call    │
@@ -408,17 +395,12 @@ fn test_covgraph_switchint_then_loop_else_return() {
       │                                     │
       └─────────────────────────────────────┘
     */
-    assert_eq!(
-        basic_coverage_blocks.num_nodes(),
-        4,
-        "basic_coverage_blocks: {:?}",
-        basic_coverage_blocks.iter_enumerated().collect::<Vec<_>>()
-    );
+    assert_eq!(graph.num_nodes(), 4, "graph: {:?}", graph.iter_enumerated().collect::<Vec<_>>());
 
-    assert_successors(&basic_coverage_blocks, bcb(0), &[bcb(1)]);
-    assert_successors(&basic_coverage_blocks, bcb(1), &[bcb(2), bcb(3)]);
-    assert_successors(&basic_coverage_blocks, bcb(2), &[]);
-    assert_successors(&basic_coverage_blocks, bcb(3), &[bcb(1)]);
+    assert_successors(&graph, bcb(0), &[bcb(1)]);
+    assert_successors(&graph, bcb(1), &[bcb(2), bcb(3)]);
+    assert_successors(&graph, bcb(2), &[]);
+    assert_successors(&graph, bcb(3), &[bcb(1)]);
 }
 
 /// Create a mock `Body` with nested loops.
@@ -494,11 +476,11 @@ fn switchint_loop_then_inner_loop_else_break<'a>() -> Body<'a> {
 #[test]
 fn test_covgraph_switchint_loop_then_inner_loop_else_break() {
     let mir_body = switchint_loop_then_inner_loop_else_break();
-    let basic_coverage_blocks = graph::CoverageGraph::from_mir(&mir_body);
+    let graph = graph::CoverageGraph::from_mir(&mir_body);
     print_coverage_graphviz(
         "covgraph_switchint_loop_then_inner_loop_else_break",
         &mir_body,
-        &basic_coverage_blocks,
+        &graph,
     );
     /*
                          ┌─────────────────┐
@@ -531,18 +513,13 @@ fn test_covgraph_switchint_loop_then_inner_loop_else_break() {
       │                                            │
       └────────────────────────────────────────────┘
     */
-    assert_eq!(
-        basic_coverage_blocks.num_nodes(),
-        7,
-        "basic_coverage_blocks: {:?}",
-        basic_coverage_blocks.iter_enumerated().collect::<Vec<_>>()
-    );
-
-    assert_successors(&basic_coverage_blocks, bcb(0), &[bcb(1)]);
-    assert_successors(&basic_coverage_blocks, bcb(1), &[bcb(2), bcb(3)]);
-    assert_successors(&basic_coverage_blocks, bcb(2), &[]);
-    assert_successors(&basic_coverage_blocks, bcb(3), &[bcb(4)]);
-    assert_successors(&basic_coverage_blocks, bcb(4), &[bcb(5), bcb(6)]);
-    assert_successors(&basic_coverage_blocks, bcb(5), &[bcb(1)]);
-    assert_successors(&basic_coverage_blocks, bcb(6), &[bcb(4)]);
+    assert_eq!(graph.num_nodes(), 7, "graph: {:?}", graph.iter_enumerated().collect::<Vec<_>>());
+
+    assert_successors(&graph, bcb(0), &[bcb(1)]);
+    assert_successors(&graph, bcb(1), &[bcb(2), bcb(3)]);
+    assert_successors(&graph, bcb(2), &[]);
+    assert_successors(&graph, bcb(3), &[bcb(4)]);
+    assert_successors(&graph, bcb(4), &[bcb(5), bcb(6)]);
+    assert_successors(&graph, bcb(5), &[bcb(1)]);
+    assert_successors(&graph, bcb(6), &[bcb(4)]);
 }
diff --git a/compiler/rustc_mir_transform/src/cross_crate_inline.rs b/compiler/rustc_mir_transform/src/cross_crate_inline.rs
index 589be81558c..e1f1dd83f0d 100644
--- a/compiler/rustc_mir_transform/src/cross_crate_inline.rs
+++ b/compiler/rustc_mir_transform/src/cross_crate_inline.rs
@@ -1,4 +1,4 @@
-use rustc_attr::InlineAttr;
+use rustc_attr_parsing::InlineAttr;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::LocalDefId;
 use rustc_middle::mir::visit::Visitor;
diff --git a/compiler/rustc_mir_transform/src/early_otherwise_branch.rs b/compiler/rustc_mir_transform/src/early_otherwise_branch.rs
index 17c8348140a..91e1395e764 100644
--- a/compiler/rustc_mir_transform/src/early_otherwise_branch.rs
+++ b/compiler/rustc_mir_transform/src/early_otherwise_branch.rs
@@ -129,18 +129,29 @@ impl<'tcx> crate::MirPass<'tcx> for EarlyOtherwiseBranch {
 
             let mut patch = MirPatch::new(body);
 
-            // create temp to store second discriminant in, `_s` in example above
-            let second_discriminant_temp =
-                patch.new_temp(opt_data.child_ty, opt_data.child_source.span);
+            let (second_discriminant_temp, second_operand) = if opt_data.need_hoist_discriminant {
+                // create temp to store second discriminant in, `_s` in example above
+                let second_discriminant_temp =
+                    patch.new_temp(opt_data.child_ty, opt_data.child_source.span);
 
-            patch.add_statement(parent_end, StatementKind::StorageLive(second_discriminant_temp));
+                patch.add_statement(
+                    parent_end,
+                    StatementKind::StorageLive(second_discriminant_temp),
+                );
 
-            // create assignment of discriminant
-            patch.add_assign(
-                parent_end,
-                Place::from(second_discriminant_temp),
-                Rvalue::Discriminant(opt_data.child_place),
-            );
+                // create assignment of discriminant
+                patch.add_assign(
+                    parent_end,
+                    Place::from(second_discriminant_temp),
+                    Rvalue::Discriminant(opt_data.child_place),
+                );
+                (
+                    Some(second_discriminant_temp),
+                    Operand::Move(Place::from(second_discriminant_temp)),
+                )
+            } else {
+                (None, Operand::Copy(opt_data.child_place))
+            };
 
             // create temp to store inequality comparison between the two discriminants, `_t` in
             // example above
@@ -149,11 +160,9 @@ impl<'tcx> crate::MirPass<'tcx> for EarlyOtherwiseBranch {
             let comp_temp = patch.new_temp(comp_res_type, opt_data.child_source.span);
             patch.add_statement(parent_end, StatementKind::StorageLive(comp_temp));
 
-            // create inequality comparison between the two discriminants
-            let comp_rvalue = Rvalue::BinaryOp(
-                nequal,
-                Box::new((parent_op.clone(), Operand::Move(Place::from(second_discriminant_temp)))),
-            );
+            // create inequality comparison
+            let comp_rvalue =
+                Rvalue::BinaryOp(nequal, Box::new((parent_op.clone(), second_operand)));
             patch.add_statement(
                 parent_end,
                 StatementKind::Assign(Box::new((Place::from(comp_temp), comp_rvalue))),
@@ -170,14 +179,17 @@ impl<'tcx> crate::MirPass<'tcx> for EarlyOtherwiseBranch {
             let eq_targets = SwitchTargets::new(eq_new_targets, parent_targets.otherwise());
 
             // Create `bbEq` in example above
-            let eq_switch = BasicBlockData::new(Some(Terminator {
-                source_info: bbs[parent].terminator().source_info,
-                kind: TerminatorKind::SwitchInt {
-                    // switch on the first discriminant, so we can mark the second one as dead
-                    discr: parent_op,
-                    targets: eq_targets,
-                },
-            }));
+            let eq_switch = BasicBlockData::new(
+                Some(Terminator {
+                    source_info: bbs[parent].terminator().source_info,
+                    kind: TerminatorKind::SwitchInt {
+                        // switch on the first discriminant, so we can mark the second one as dead
+                        discr: parent_op,
+                        targets: eq_targets,
+                    },
+                }),
+                bbs[parent].is_cleanup,
+            );
 
             let eq_bb = patch.new_block(eq_switch);
 
@@ -189,8 +201,13 @@ impl<'tcx> crate::MirPass<'tcx> for EarlyOtherwiseBranch {
                 TerminatorKind::if_(Operand::Move(Place::from(comp_temp)), true_case, false_case),
             );
 
-            // generate StorageDead for the second_discriminant_temp not in use anymore
-            patch.add_statement(parent_end, StatementKind::StorageDead(second_discriminant_temp));
+            if let Some(second_discriminant_temp) = second_discriminant_temp {
+                // generate StorageDead for the second_discriminant_temp not in use anymore
+                patch.add_statement(
+                    parent_end,
+                    StatementKind::StorageDead(second_discriminant_temp),
+                );
+            }
 
             // Generate a StorageDead for comp_temp in each of the targets, since we moved it into
             // the switch
@@ -218,6 +235,7 @@ struct OptimizationData<'tcx> {
     child_place: Place<'tcx>,
     child_ty: Ty<'tcx>,
     child_source: SourceInfo,
+    need_hoist_discriminant: bool,
 }
 
 fn evaluate_candidate<'tcx>(
@@ -226,49 +244,21 @@ fn evaluate_candidate<'tcx>(
     parent: BasicBlock,
 ) -> Option<OptimizationData<'tcx>> {
     let bbs = &body.basic_blocks;
+    // NB: If this BB is a cleanup, we may need to figure out what else needs to be handled.
+    if bbs[parent].is_cleanup {
+        return None;
+    }
     let TerminatorKind::SwitchInt { targets, discr: parent_discr } = &bbs[parent].terminator().kind
     else {
         return None;
     };
     let parent_ty = parent_discr.ty(body.local_decls(), tcx);
-    if !bbs[targets.otherwise()].is_empty_unreachable() {
-        // Someone could write code like this:
-        // ```rust
-        // let Q = val;
-        // if discriminant(P) == otherwise {
-        //     let ptr = &mut Q as *mut _ as *mut u8;
-        //     // It may be difficult for us to effectively determine whether values are valid.
-        //     // Invalid values can come from all sorts of corners.
-        //     unsafe { *ptr = 10; }
-        // }
-        //
-        // match P {
-        //    A => match Q {
-        //        A => {
-        //            // code
-        //        }
-        //        _ => {
-        //            // don't use Q
-        //        }
-        //    }
-        //    _ => {
-        //        // don't use Q
-        //    }
-        // };
-        // ```
-        //
-        // Hoisting the `discriminant(Q)` out of the `A` arm causes us to compute the discriminant
-        // of an invalid value, which is UB.
-        // In order to fix this, **we would either need to show that the discriminant computation of
-        // `place` is computed in all branches**.
-        // FIXME(#95162) For the moment, we adopt a conservative approach and
-        // consider only the `otherwise` branch has no statements and an unreachable terminator.
-        return None;
-    }
     let (_, child) = targets.iter().next()?;
-    let child_terminator = &bbs[child].terminator();
-    let TerminatorKind::SwitchInt { targets: child_targets, discr: child_discr } =
-        &child_terminator.kind
+
+    let Terminator {
+        kind: TerminatorKind::SwitchInt { targets: child_targets, discr: child_discr },
+        source_info,
+    } = bbs[child].terminator()
     else {
         return None;
     };
@@ -276,25 +266,115 @@ fn evaluate_candidate<'tcx>(
     if child_ty != parent_ty {
         return None;
     }
-    let Some(StatementKind::Assign(boxed)) = &bbs[child].statements.first().map(|x| &x.kind) else {
+
+    // We only handle:
+    // ```
+    // bb4: {
+    //     _8 = discriminant((_3.1: Enum1));
+    //    switchInt(move _8) -> [2: bb7, otherwise: bb1];
+    // }
+    // ```
+    // and
+    // ```
+    // bb2: {
+    //     switchInt((_3.1: u64)) -> [1: bb5, otherwise: bb1];
+    // }
+    // ```
+    if bbs[child].statements.len() > 1 {
         return None;
+    }
+
+    // When thie BB has exactly one statement, this statement should be discriminant.
+    let need_hoist_discriminant = bbs[child].statements.len() == 1;
+    let child_place = if need_hoist_discriminant {
+        if !bbs[targets.otherwise()].is_empty_unreachable() {
+            // Someone could write code like this:
+            // ```rust
+            // let Q = val;
+            // if discriminant(P) == otherwise {
+            //     let ptr = &mut Q as *mut _ as *mut u8;
+            //     // It may be difficult for us to effectively determine whether values are valid.
+            //     // Invalid values can come from all sorts of corners.
+            //     unsafe { *ptr = 10; }
+            // }
+            //
+            // match P {
+            //    A => match Q {
+            //        A => {
+            //            // code
+            //        }
+            //        _ => {
+            //            // don't use Q
+            //        }
+            //    }
+            //    _ => {
+            //        // don't use Q
+            //    }
+            // };
+            // ```
+            //
+            // Hoisting the `discriminant(Q)` out of the `A` arm causes us to compute the discriminant of an
+            // invalid value, which is UB.
+            // In order to fix this, **we would either need to show that the discriminant computation of
+            // `place` is computed in all branches**.
+            // FIXME(#95162) For the moment, we adopt a conservative approach and
+            // consider only the `otherwise` branch has no statements and an unreachable terminator.
+            return None;
+        }
+        // Handle:
+        // ```
+        // bb4: {
+        //     _8 = discriminant((_3.1: Enum1));
+        //    switchInt(move _8) -> [2: bb7, otherwise: bb1];
+        // }
+        // ```
+        let [
+            Statement {
+                kind: StatementKind::Assign(box (_, Rvalue::Discriminant(child_place))),
+                ..
+            },
+        ] = bbs[child].statements.as_slice()
+        else {
+            return None;
+        };
+        *child_place
+    } else {
+        // Handle:
+        // ```
+        // bb2: {
+        //     switchInt((_3.1: u64)) -> [1: bb5, otherwise: bb1];
+        // }
+        // ```
+        let Operand::Copy(child_place) = child_discr else {
+            return None;
+        };
+        *child_place
     };
-    let (_, Rvalue::Discriminant(child_place)) = &**boxed else {
-        return None;
+    let destination = if need_hoist_discriminant || bbs[targets.otherwise()].is_empty_unreachable()
+    {
+        child_targets.otherwise()
+    } else {
+        targets.otherwise()
     };
-    let destination = child_targets.otherwise();
 
     // Verify that the optimization is legal for each branch
     for (value, child) in targets.iter() {
-        if !verify_candidate_branch(&bbs[child], value, *child_place, destination) {
+        if !verify_candidate_branch(
+            &bbs[child],
+            value,
+            child_place,
+            destination,
+            need_hoist_discriminant,
+        ) {
             return None;
         }
     }
     Some(OptimizationData {
         destination,
-        child_place: *child_place,
+        child_place,
         child_ty,
-        child_source: child_terminator.source_info,
+        child_source: *source_info,
+        need_hoist_discriminant,
     })
 }
 
@@ -303,31 +383,48 @@ fn verify_candidate_branch<'tcx>(
     value: u128,
     place: Place<'tcx>,
     destination: BasicBlock,
+    need_hoist_discriminant: bool,
 ) -> bool {
-    // In order for the optimization to be correct, the branch must...
-    // ...have exactly one statement
-    if let [statement] = branch.statements.as_slice()
-        // ...assign the discriminant of `place` in that statement
-        && let StatementKind::Assign(boxed) = &statement.kind
-        && let (discr_place, Rvalue::Discriminant(from_place)) = &**boxed
-        && *from_place == place
-        // ...make that assignment to a local
-        && discr_place.projection.is_empty()
-        // ...terminate on a `SwitchInt` that invalidates that local
-        && let TerminatorKind::SwitchInt { discr: switch_op, targets, .. } =
-            &branch.terminator().kind
-        && *switch_op == Operand::Move(*discr_place)
-        // ...fall through to `destination` if the switch misses
-        && destination == targets.otherwise()
-        // ...have a branch for value `value`
-        && let mut iter = targets.iter()
-        && let Some((target_value, _)) = iter.next()
-        && target_value == value
-        // ...and have no more branches
-        && iter.next().is_none()
-    {
-        true
+    // In order for the optimization to be correct, the terminator must be a `SwitchInt`.
+    let TerminatorKind::SwitchInt { discr: switch_op, targets } = &branch.terminator().kind else {
+        return false;
+    };
+    if need_hoist_discriminant {
+        // If we need hoist discriminant, the branch must have exactly one statement.
+        let [statement] = branch.statements.as_slice() else {
+            return false;
+        };
+        // The statement must assign the discriminant of `place`.
+        let StatementKind::Assign(box (discr_place, Rvalue::Discriminant(from_place))) =
+            statement.kind
+        else {
+            return false;
+        };
+        if from_place != place {
+            return false;
+        }
+        // The assignment must invalidate a local that terminate on a `SwitchInt`.
+        if !discr_place.projection.is_empty() || *switch_op != Operand::Move(discr_place) {
+            return false;
+        }
     } else {
-        false
+        // If we don't need hoist discriminant, the branch must not have any statements.
+        if !branch.statements.is_empty() {
+            return false;
+        }
+        // The place on `SwitchInt` must be the same.
+        if *switch_op != Operand::Copy(place) {
+            return false;
+        }
     }
+    // It must fall through to `destination` if the switch misses.
+    if destination != targets.otherwise() {
+        return false;
+    }
+    // It must have exactly one branch for value `value` and have no more branches.
+    let mut iter = targets.iter();
+    let (Some((target_value, _)), None) = (iter.next(), iter.next()) else {
+        return false;
+    };
+    target_value == value
 }
diff --git a/compiler/rustc_mir_transform/src/function_item_references.rs b/compiler/rustc_mir_transform/src/function_item_references.rs
index 2945fc6f3d5..fb21bf9977f 100644
--- a/compiler/rustc_mir_transform/src/function_item_references.rs
+++ b/compiler/rustc_mir_transform/src/function_item_references.rs
@@ -5,9 +5,8 @@ use rustc_middle::mir::visit::Visitor;
 use rustc_middle::mir::*;
 use rustc_middle::ty::{self, EarlyBinder, GenericArgsRef, Ty, TyCtxt};
 use rustc_session::lint::builtin::FUNCTION_ITEM_REFERENCES;
-use rustc_span::Span;
 use rustc_span::source_map::Spanned;
-use rustc_span::symbol::sym;
+use rustc_span::{Span, sym};
 
 use crate::errors;
 
diff --git a/compiler/rustc_mir_transform/src/inline.rs b/compiler/rustc_mir_transform/src/inline.rs
index 79c38b50459..35699acb318 100644
--- a/compiler/rustc_mir_transform/src/inline.rs
+++ b/compiler/rustc_mir_transform/src/inline.rs
@@ -4,7 +4,7 @@ use std::iter;
 use std::ops::{Range, RangeFrom};
 
 use rustc_abi::{ExternAbi, FieldIdx};
-use rustc_attr::InlineAttr;
+use rustc_attr_parsing::InlineAttr;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::DefId;
 use rustc_index::Idx;
@@ -572,11 +572,13 @@ impl<'tcx> Inliner<'tcx> {
         let return_block = if let Some(block) = target {
             // Prepare a new block for code that should execute when call returns. We don't use
             // target block directly since it might have other predecessors.
-            let mut data = BasicBlockData::new(Some(Terminator {
-                source_info: terminator.source_info,
-                kind: TerminatorKind::Goto { target: block },
-            }));
-            data.is_cleanup = caller_body[block].is_cleanup;
+            let data = BasicBlockData::new(
+                Some(Terminator {
+                    source_info: terminator.source_info,
+                    kind: TerminatorKind::Goto { target: block },
+                }),
+                caller_body[block].is_cleanup,
+            );
             Some(caller_body.basic_blocks_mut().push(data))
         } else {
             None
diff --git a/compiler/rustc_mir_transform/src/instsimplify.rs b/compiler/rustc_mir_transform/src/instsimplify.rs
index adc3374df2e..1a65affe812 100644
--- a/compiler/rustc_mir_transform/src/instsimplify.rs
+++ b/compiler/rustc_mir_transform/src/instsimplify.rs
@@ -7,8 +7,7 @@ use rustc_middle::bug;
 use rustc_middle::mir::*;
 use rustc_middle::ty::layout::ValidityRequirement;
 use rustc_middle::ty::{self, GenericArgsRef, Ty, TyCtxt, layout};
-use rustc_span::symbol::Symbol;
-use rustc_span::{DUMMY_SP, sym};
+use rustc_span::{DUMMY_SP, Symbol, sym};
 
 use crate::simplify::simplify_duplicate_switch_targets;
 use crate::take_array;
diff --git a/compiler/rustc_mir_transform/src/jump_threading.rs b/compiler/rustc_mir_transform/src/jump_threading.rs
index beed007589b..8feb90ff7a0 100644
--- a/compiler/rustc_mir_transform/src/jump_threading.rs
+++ b/compiler/rustc_mir_transform/src/jump_threading.rs
@@ -35,7 +35,6 @@
 //! Likewise, applying the optimisation can create a lot of new MIR, so we bound the instruction
 //! cost by `MAX_COST`.
 
-use rustc_abi::{TagEncoding, Variants};
 use rustc_arena::DroplessArena;
 use rustc_const_eval::const_eval::DummyMachine;
 use rustc_const_eval::interpret::{ImmTy, Immediate, InterpCx, OpTy, Projectable};
@@ -565,31 +564,15 @@ impl<'a, 'tcx> TOFinder<'a, 'tcx> {
             StatementKind::SetDiscriminant { box place, variant_index } => {
                 let Some(discr_target) = self.map.find_discr(place.as_ref()) else { return };
                 let enum_ty = place.ty(self.body, self.tcx).ty;
-                // `SetDiscriminant` may be a no-op if the assigned variant is the untagged variant
-                // of a niche encoding. If we cannot ensure that we write to the discriminant, do
-                // nothing.
-                let Ok(enum_layout) = self.ecx.layout_of(enum_ty) else {
+                // `SetDiscriminant` guarantees that the discriminant is now `variant_index`.
+                // Even if the discriminant write does nothing due to niches, it is UB to set the
+                // discriminant when the data does not encode the desired discriminant.
+                let Some(discr) =
+                    self.ecx.discriminant_for_variant(enum_ty, *variant_index).discard_err()
+                else {
                     return;
                 };
-                let writes_discriminant = match enum_layout.variants {
-                    Variants::Single { index } => {
-                        assert_eq!(index, *variant_index);
-                        true
-                    }
-                    Variants::Multiple { tag_encoding: TagEncoding::Direct, .. } => true,
-                    Variants::Multiple {
-                        tag_encoding: TagEncoding::Niche { untagged_variant, .. },
-                        ..
-                    } => *variant_index != untagged_variant,
-                };
-                if writes_discriminant {
-                    let Some(discr) =
-                        self.ecx.discriminant_for_variant(enum_ty, *variant_index).discard_err()
-                    else {
-                        return;
-                    };
-                    self.process_immediate(bb, discr_target, discr, state);
-                }
+                self.process_immediate(bb, discr_target, discr, state);
             }
             // If we expect `lhs ?= true`, we have an opportunity if we assume `lhs == true`.
             StatementKind::Intrinsic(box NonDivergingIntrinsic::Assume(
diff --git a/compiler/rustc_mir_transform/src/large_enums.rs b/compiler/rustc_mir_transform/src/large_enums.rs
index 8be5a63d008..490e7dd8f7e 100644
--- a/compiler/rustc_mir_transform/src/large_enums.rs
+++ b/compiler/rustc_mir_transform/src/large_enums.rs
@@ -216,7 +216,7 @@ impl EnumSizeOpt {
         };
         let layout = tcx.layout_of(typing_env.as_query_input(ty)).ok()?;
         let variants = match &layout.variants {
-            Variants::Single { .. } => return None,
+            Variants::Single { .. } | Variants::Empty => return None,
             Variants::Multiple { tag_encoding: TagEncoding::Niche { .. }, .. } => return None,
 
             Variants::Multiple { variants, .. } if variants.len() <= 1 => return None,
diff --git a/compiler/rustc_mir_transform/src/lower_intrinsics.rs b/compiler/rustc_mir_transform/src/lower_intrinsics.rs
index 6d635606687..942c6144ea6 100644
--- a/compiler/rustc_mir_transform/src/lower_intrinsics.rs
+++ b/compiler/rustc_mir_transform/src/lower_intrinsics.rs
@@ -3,7 +3,7 @@
 use rustc_middle::mir::*;
 use rustc_middle::ty::{self, TyCtxt};
 use rustc_middle::{bug, span_bug};
-use rustc_span::symbol::sym;
+use rustc_span::sym;
 
 use crate::take_array;
 
diff --git a/compiler/rustc_mir_transform/src/shim/async_destructor_ctor.rs b/compiler/rustc_mir_transform/src/shim/async_destructor_ctor.rs
index 139b25be0ab..f01bab75c4a 100644
--- a/compiler/rustc_mir_transform/src/shim/async_destructor_ctor.rs
+++ b/compiler/rustc_mir_transform/src/shim/async_destructor_ctor.rs
@@ -96,7 +96,7 @@ impl<'tcx> AsyncDestructorCtorShimBuilder<'tcx> {
             typing_env,
 
             stack: Vec::with_capacity(Self::MAX_STACK_LEN),
-            last_bb: bbs.push(BasicBlockData::new(None)),
+            last_bb: bbs.push(BasicBlockData::new(None, false)),
             top_cleanup_bb: match tcx.sess.panic_strategy() {
                 PanicStrategy::Unwind => {
                     // Don't drop input arg because it's just a pointer
diff --git a/compiler/rustc_mir_transform/src/unreachable_enum_branching.rs b/compiler/rustc_mir_transform/src/unreachable_enum_branching.rs
index 57e255b7c32..55dcad0680a 100644
--- a/compiler/rustc_mir_transform/src/unreachable_enum_branching.rs
+++ b/compiler/rustc_mir_transform/src/unreachable_enum_branching.rs
@@ -54,6 +54,10 @@ fn variant_discriminants<'tcx>(
     tcx: TyCtxt<'tcx>,
 ) -> FxHashSet<u128> {
     match &layout.variants {
+        Variants::Empty => {
+            // Uninhabited, no valid discriminant.
+            FxHashSet::default()
+        }
         Variants::Single { index } => {
             let mut res = FxHashSet::default();
             res.insert(
diff --git a/compiler/rustc_monomorphize/Cargo.toml b/compiler/rustc_monomorphize/Cargo.toml
index e18441ea7fc..9bdaeb015cd 100644
--- a/compiler/rustc_monomorphize/Cargo.toml
+++ b/compiler/rustc_monomorphize/Cargo.toml
@@ -6,7 +6,7 @@ edition = "2021"
 [dependencies]
 # tidy-alphabetical-start
 rustc_abi = { path = "../rustc_abi" }
-rustc_attr = { path = "../rustc_attr" }
+rustc_attr_parsing = { path = "../rustc_attr_parsing" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
 rustc_fluent_macro = { path = "../rustc_fluent_macro" }
diff --git a/compiler/rustc_monomorphize/src/collector.rs b/compiler/rustc_monomorphize/src/collector.rs
index 480d82c1a38..05d34715314 100644
--- a/compiler/rustc_monomorphize/src/collector.rs
+++ b/compiler/rustc_monomorphize/src/collector.rs
@@ -232,8 +232,7 @@ use rustc_middle::{bug, span_bug};
 use rustc_session::Limit;
 use rustc_session::config::EntryFnType;
 use rustc_span::source_map::{Spanned, dummy_spanned, respan};
-use rustc_span::symbol::sym;
-use rustc_span::{DUMMY_SP, Span};
+use rustc_span::{DUMMY_SP, Span, sym};
 use tracing::{debug, instrument, trace};
 
 use crate::errors::{self, EncounteredErrorWhileInstantiating, NoOptimizedMir, RecursionLimit};
diff --git a/compiler/rustc_monomorphize/src/mono_checks/move_check.rs b/compiler/rustc_monomorphize/src/mono_checks/move_check.rs
index 438d49fd7fb..02b9397f9a9 100644
--- a/compiler/rustc_monomorphize/src/mono_checks/move_check.rs
+++ b/compiler/rustc_monomorphize/src/mono_checks/move_check.rs
@@ -6,9 +6,8 @@ use rustc_middle::mir::{self, Location, traversal};
 use rustc_middle::ty::{self, AssocKind, Instance, Ty, TyCtxt, TypeFoldable};
 use rustc_session::Limit;
 use rustc_session::lint::builtin::LARGE_ASSIGNMENTS;
-use rustc_span::Span;
 use rustc_span::source_map::Spanned;
-use rustc_span::symbol::{Ident, sym};
+use rustc_span::{Ident, Span, sym};
 use tracing::{debug, trace};
 
 use crate::errors::LargeAssignmentsLint;
diff --git a/compiler/rustc_monomorphize/src/partitioning.rs b/compiler/rustc_monomorphize/src/partitioning.rs
index dabce72650a..7b179663430 100644
--- a/compiler/rustc_monomorphize/src/partitioning.rs
+++ b/compiler/rustc_monomorphize/src/partitioning.rs
@@ -117,7 +117,7 @@ use rustc_middle::ty::{self, InstanceKind, TyCtxt};
 use rustc_middle::util::Providers;
 use rustc_session::CodegenUnits;
 use rustc_session::config::{DumpMonoStatsFormat, SwitchWithOptPath};
-use rustc_span::symbol::Symbol;
+use rustc_span::Symbol;
 use rustc_target::spec::SymbolVisibility;
 use tracing::debug;
 
@@ -833,7 +833,8 @@ fn mono_item_visibility<'tcx>(
         return if is_generic
             && (always_export_generics
                 || (can_export_generics
-                    && tcx.codegen_fn_attrs(def_id).inline == rustc_attr::InlineAttr::Never))
+                    && tcx.codegen_fn_attrs(def_id).inline
+                        == rustc_attr_parsing::InlineAttr::Never))
         {
             // If it is an upstream monomorphization and we export generics, we must make
             // it available to downstream crates.
@@ -847,7 +848,7 @@ fn mono_item_visibility<'tcx>(
     if is_generic {
         if always_export_generics
             || (can_export_generics
-                && tcx.codegen_fn_attrs(def_id).inline == rustc_attr::InlineAttr::Never)
+                && tcx.codegen_fn_attrs(def_id).inline == rustc_attr_parsing::InlineAttr::Never)
         {
             if tcx.is_unreachable_local_definition(def_id) {
                 // This instance cannot be used from another crate.
diff --git a/compiler/rustc_next_trait_solver/src/canonicalizer.rs b/compiler/rustc_next_trait_solver/src/canonicalizer.rs
index 63608f9e856..2f7301d8fe5 100644
--- a/compiler/rustc_next_trait_solver/src/canonicalizer.rs
+++ b/compiler/rustc_next_trait_solver/src/canonicalizer.rs
@@ -3,6 +3,7 @@ use std::cmp::Ordering;
 use rustc_type_ir::data_structures::HashMap;
 use rustc_type_ir::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable};
 use rustc_type_ir::inherent::*;
+use rustc_type_ir::solve::{Goal, QueryInput};
 use rustc_type_ir::visit::TypeVisitableExt;
 use rustc_type_ir::{
     self as ty, Canonical, CanonicalTyVarKind, CanonicalVarInfo, CanonicalVarKind, InferCtxtLike,
@@ -17,8 +18,11 @@ use crate::delegate::SolverDelegate;
 /// while canonicalizing the response happens in the context of the
 /// query.
 #[derive(Debug, Clone, Copy)]
-pub enum CanonicalizeMode {
-    Input,
+enum CanonicalizeMode {
+    /// When canonicalizing the `param_env`, we keep `'static` as merging
+    /// trait candidates relies on it when deciding whether a where-bound
+    /// is trivial.
+    Input { keep_static: bool },
     /// FIXME: We currently return region constraints referring to
     /// placeholders and inference variables from a binder instantiated
     /// inside of the query.
@@ -59,15 +63,15 @@ pub struct Canonicalizer<'a, D: SolverDelegate<Interner = I>, I: Interner> {
 }
 
 impl<'a, D: SolverDelegate<Interner = I>, I: Interner> Canonicalizer<'a, D, I> {
-    pub fn canonicalize<T: TypeFoldable<I>>(
+    pub fn canonicalize_response<T: TypeFoldable<I>>(
         delegate: &'a D,
-        canonicalize_mode: CanonicalizeMode,
+        max_input_universe: ty::UniverseIndex,
         variables: &'a mut Vec<I::GenericArg>,
         value: T,
     ) -> ty::Canonical<I, T> {
         let mut canonicalizer = Canonicalizer {
             delegate,
-            canonicalize_mode,
+            canonicalize_mode: CanonicalizeMode::Response { max_input_universe },
 
             variables,
             variable_lookup_table: Default::default(),
@@ -80,9 +84,67 @@ impl<'a, D: SolverDelegate<Interner = I>, I: Interner> Canonicalizer<'a, D, I> {
         let value = value.fold_with(&mut canonicalizer);
         assert!(!value.has_infer(), "unexpected infer in {value:?}");
         assert!(!value.has_placeholders(), "unexpected placeholders in {value:?}");
-
         let (max_universe, variables) = canonicalizer.finalize();
+        Canonical { max_universe, variables, value }
+    }
+
+    /// When canonicalizing query inputs, we keep `'static` in the `param_env`
+    /// but erase it everywhere else. We generally don't want to depend on region
+    /// identity, so while it should not matter whether `'static` is kept in the
+    /// value or opaque type storage as well, this prevents us from accidentally
+    /// relying on it in the future.
+    ///
+    /// We want to keep the option of canonicalizing `'static` to an existential
+    /// variable in the future by changing the way we detect global where-bounds.
+    pub fn canonicalize_input<P: TypeFoldable<I>>(
+        delegate: &'a D,
+        variables: &'a mut Vec<I::GenericArg>,
+        input: QueryInput<I, P>,
+    ) -> ty::Canonical<I, QueryInput<I, P>> {
+        // First canonicalize the `param_env` while keeping `'static`
+        let mut env_canonicalizer = Canonicalizer {
+            delegate,
+            canonicalize_mode: CanonicalizeMode::Input { keep_static: true },
+
+            variables,
+            variable_lookup_table: Default::default(),
+            primitive_var_infos: Vec::new(),
+            binder_index: ty::INNERMOST,
+
+            cache: Default::default(),
+        };
+        let param_env = input.goal.param_env.fold_with(&mut env_canonicalizer);
+        debug_assert_eq!(env_canonicalizer.binder_index, ty::INNERMOST);
+        // Then canonicalize the rest of the input without keeping `'static`
+        // while *mostly* reusing the canonicalizer from above.
+        let mut rest_canonicalizer = Canonicalizer {
+            delegate,
+            canonicalize_mode: CanonicalizeMode::Input { keep_static: false },
+
+            variables: env_canonicalizer.variables,
+            // We're able to reuse the `variable_lookup_table` as whether or not
+            // it already contains an entry for `'static` does not matter.
+            variable_lookup_table: env_canonicalizer.variable_lookup_table,
+            primitive_var_infos: env_canonicalizer.primitive_var_infos,
+            binder_index: ty::INNERMOST,
 
+            // We do not reuse the cache as it may contain entries whose canonicalized
+            // value contains `'static`. While we could alternatively handle this by
+            // checking for `'static` when using cached entries, this does not
+            // feel worth the effort. I do not expect that a `ParamEnv` will ever
+            // contain large enough types for caching to be necessary.
+            cache: Default::default(),
+        };
+
+        let predicate = input.goal.predicate.fold_with(&mut rest_canonicalizer);
+        let goal = Goal { param_env, predicate };
+        let predefined_opaques_in_body =
+            input.predefined_opaques_in_body.fold_with(&mut rest_canonicalizer);
+        let value = QueryInput { goal, predefined_opaques_in_body };
+
+        assert!(!value.has_infer(), "unexpected infer in {value:?}");
+        assert!(!value.has_placeholders(), "unexpected placeholders in {value:?}");
+        let (max_universe, variables) = rest_canonicalizer.finalize();
         Canonical { max_universe, variables, value }
     }
 
@@ -126,7 +188,7 @@ impl<'a, D: SolverDelegate<Interner = I>, I: Interner> Canonicalizer<'a, D, I> {
             // all information which should not matter for the solver.
             //
             // For this we compress universes as much as possible.
-            CanonicalizeMode::Input => {}
+            CanonicalizeMode::Input { .. } => {}
             // When canonicalizing a response we map a universes already entered
             // by the caller to the root universe and only return useful universe
             // information for placeholders and inference variables created inside
@@ -290,17 +352,15 @@ impl<'a, D: SolverDelegate<Interner = I>, I: Interner> Canonicalizer<'a, D, I> {
                 }
             },
             ty::Placeholder(placeholder) => match self.canonicalize_mode {
-                CanonicalizeMode::Input => CanonicalVarKind::PlaceholderTy(PlaceholderLike::new(
-                    placeholder.universe(),
-                    self.variables.len().into(),
-                )),
+                CanonicalizeMode::Input { .. } => CanonicalVarKind::PlaceholderTy(
+                    PlaceholderLike::new(placeholder.universe(), self.variables.len().into()),
+                ),
                 CanonicalizeMode::Response { .. } => CanonicalVarKind::PlaceholderTy(placeholder),
             },
             ty::Param(_) => match self.canonicalize_mode {
-                CanonicalizeMode::Input => CanonicalVarKind::PlaceholderTy(PlaceholderLike::new(
-                    ty::UniverseIndex::ROOT,
-                    self.variables.len().into(),
-                )),
+                CanonicalizeMode::Input { .. } => CanonicalVarKind::PlaceholderTy(
+                    PlaceholderLike::new(ty::UniverseIndex::ROOT, self.variables.len().into()),
+                ),
                 CanonicalizeMode::Response { .. } => panic!("param ty in response: {t:?}"),
             },
             ty::Bool
@@ -357,21 +417,30 @@ impl<D: SolverDelegate<Interner = I>, I: Interner> TypeFolder<I> for Canonicaliz
         let kind = match r.kind() {
             ty::ReBound(..) => return r,
 
-            // We may encounter `ReStatic` in item signatures or the hidden type
-            // of an opaque. `ReErased` should only be encountered in the hidden
+            // We don't canonicalize `ReStatic` in the `param_env` as we use it
+            // when checking whether a `ParamEnv` candidate is global.
+            ty::ReStatic => match self.canonicalize_mode {
+                CanonicalizeMode::Input { keep_static: false } => {
+                    CanonicalVarKind::Region(ty::UniverseIndex::ROOT)
+                }
+                CanonicalizeMode::Input { keep_static: true }
+                | CanonicalizeMode::Response { .. } => return r,
+            },
+
+            // `ReErased` should only be encountered in the hidden
             // type of an opaque for regions that are ignored for the purposes of
             // captures.
             //
             // FIXME: We should investigate the perf implications of not uniquifying
             // `ReErased`. We may be able to short-circuit registering region
             // obligations if we encounter a `ReErased` on one side, for example.
-            ty::ReStatic | ty::ReErased | ty::ReError(_) => match self.canonicalize_mode {
-                CanonicalizeMode::Input => CanonicalVarKind::Region(ty::UniverseIndex::ROOT),
+            ty::ReErased | ty::ReError(_) => match self.canonicalize_mode {
+                CanonicalizeMode::Input { .. } => CanonicalVarKind::Region(ty::UniverseIndex::ROOT),
                 CanonicalizeMode::Response { .. } => return r,
             },
 
             ty::ReEarlyParam(_) | ty::ReLateParam(_) => match self.canonicalize_mode {
-                CanonicalizeMode::Input => CanonicalVarKind::Region(ty::UniverseIndex::ROOT),
+                CanonicalizeMode::Input { .. } => CanonicalVarKind::Region(ty::UniverseIndex::ROOT),
                 CanonicalizeMode::Response { .. } => {
                     panic!("unexpected region in response: {r:?}")
                 }
@@ -379,7 +448,7 @@ impl<D: SolverDelegate<Interner = I>, I: Interner> TypeFolder<I> for Canonicaliz
 
             ty::RePlaceholder(placeholder) => match self.canonicalize_mode {
                 // We canonicalize placeholder regions as existentials in query inputs.
-                CanonicalizeMode::Input => CanonicalVarKind::Region(ty::UniverseIndex::ROOT),
+                CanonicalizeMode::Input { .. } => CanonicalVarKind::Region(ty::UniverseIndex::ROOT),
                 CanonicalizeMode::Response { max_input_universe } => {
                     // If we have a placeholder region inside of a query, it must be from
                     // a new universe.
@@ -397,7 +466,9 @@ impl<D: SolverDelegate<Interner = I>, I: Interner> TypeFolder<I> for Canonicaliz
                     "region vid should have been resolved fully before canonicalization"
                 );
                 match self.canonicalize_mode {
-                    CanonicalizeMode::Input => CanonicalVarKind::Region(ty::UniverseIndex::ROOT),
+                    CanonicalizeMode::Input { keep_static: _ } => {
+                        CanonicalVarKind::Region(ty::UniverseIndex::ROOT)
+                    }
                     CanonicalizeMode::Response { .. } => {
                         CanonicalVarKind::Region(self.delegate.universe_of_lt(vid).unwrap())
                     }
@@ -434,7 +505,7 @@ impl<D: SolverDelegate<Interner = I>, I: Interner> TypeFolder<I> for Canonicaliz
                 ty::InferConst::Fresh(_) => todo!(),
             },
             ty::ConstKind::Placeholder(placeholder) => match self.canonicalize_mode {
-                CanonicalizeMode::Input => CanonicalVarKind::PlaceholderConst(
+                CanonicalizeMode::Input { .. } => CanonicalVarKind::PlaceholderConst(
                     PlaceholderLike::new(placeholder.universe(), self.variables.len().into()),
                 ),
                 CanonicalizeMode::Response { .. } => {
@@ -442,7 +513,7 @@ impl<D: SolverDelegate<Interner = I>, I: Interner> TypeFolder<I> for Canonicaliz
                 }
             },
             ty::ConstKind::Param(_) => match self.canonicalize_mode {
-                CanonicalizeMode::Input => CanonicalVarKind::PlaceholderConst(
+                CanonicalizeMode::Input { .. } => CanonicalVarKind::PlaceholderConst(
                     PlaceholderLike::new(ty::UniverseIndex::ROOT, self.variables.len().into()),
                 ),
                 CanonicalizeMode::Response { .. } => panic!("param ty in response: {c:?}"),
diff --git a/compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs b/compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs
index 198ccb000f3..02f6439b77f 100644
--- a/compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs
@@ -11,6 +11,7 @@ use rustc_type_ir::visit::TypeVisitableExt as _;
 use rustc_type_ir::{self as ty, Interner, TypingMode, Upcast as _, elaborate};
 use tracing::{debug, instrument};
 
+use super::trait_goals::TraitGoalProvenVia;
 use crate::delegate::SolverDelegate;
 use crate::solve::inspect::ProbeKind;
 use crate::solve::{
@@ -337,15 +338,6 @@ where
 
         self.assemble_param_env_candidates(goal, &mut candidates);
 
-        match self.typing_mode() {
-            TypingMode::Coherence => {}
-            TypingMode::Analysis { .. }
-            | TypingMode::PostBorrowckAnalysis { .. }
-            | TypingMode::PostAnalysis => {
-                self.discard_impls_shadowed_by_env(goal, &mut candidates);
-            }
-        }
-
         candidates
     }
 
@@ -500,7 +492,7 @@ where
         goal: Goal<I, G>,
         candidates: &mut Vec<Candidate<I>>,
     ) {
-        for (i, assumption) in goal.param_env.caller_bounds().into_iter().enumerate() {
+        for (i, assumption) in goal.param_env.caller_bounds().iter().enumerate() {
             candidates.extend(G::probe_and_consider_implied_clause(
                 self,
                 CandidateSource::ParamEnv(i),
@@ -733,72 +725,64 @@ where
         })
     }
 
-    /// If there's a where-bound for the current goal, do not use any impl candidates
-    /// to prove the current goal. Most importantly, if there is a where-bound which does
-    /// not specify any associated types, we do not allow normalizing the associated type
-    /// by using an impl, even if it would apply.
+    /// We sadly can't simply take all possible candidates for normalization goals
+    /// and check whether they result in the same constraints. We want to make sure
+    /// that trying to normalize an alias doesn't result in constraints which aren't
+    /// otherwise required.
+    ///
+    /// Most notably, when proving a trait goal by via a where-bound, we should not
+    /// normalize via impls which have stricter region constraints than the where-bound:
+    ///
+    /// ```rust
+    /// trait Trait<'a> {
+    ///     type Assoc;
+    /// }
+    ///
+    /// impl<'a, T: 'a> Trait<'a> for T {
+    ///     type Assoc = u32;
+    /// }
+    ///
+    /// fn with_bound<'a, T: Trait<'a>>(_value: T::Assoc) {}
+    /// ```
     ///
-    ///  <https://github.com/rust-lang/trait-system-refactor-initiative/issues/76>
-    // FIXME(@lcnr): The current structure here makes me unhappy and feels ugly. idk how
-    // to improve this however. However, this should make it fairly straightforward to refine
-    // the filtering going forward, so it seems alright-ish for now.
-    #[instrument(level = "debug", skip(self, goal))]
-    fn discard_impls_shadowed_by_env<G: GoalKind<D>>(
+    /// The where-bound of `with_bound` doesn't specify the associated type, so we would
+    /// only be able to normalize `<T as Trait<'a>>::Assoc` by using the impl. This impl
+    /// adds a `T: 'a` bound however, which would result in a region error. Given that the
+    /// user explicitly wrote that `T: Trait<'a>` holds, this is undesirable and we instead
+    /// treat the alias as rigid.
+    ///
+    /// See trait-system-refactor-initiative#124 for more details.
+    #[instrument(level = "debug", skip(self), ret)]
+    pub(super) fn merge_candidates(
         &mut self,
-        goal: Goal<I, G>,
-        candidates: &mut Vec<Candidate<I>>,
-    ) {
-        let cx = self.cx();
-        let trait_goal: Goal<I, ty::TraitPredicate<I>> =
-            goal.with(cx, goal.predicate.trait_ref(cx));
-
-        let mut trait_candidates_from_env = vec![];
-        self.probe(|_| ProbeKind::ShadowedEnvProbing).enter(|ecx| {
-            ecx.assemble_param_env_candidates(trait_goal, &mut trait_candidates_from_env);
-            ecx.assemble_alias_bound_candidates(trait_goal, &mut trait_candidates_from_env);
-        });
+        proven_via: Option<TraitGoalProvenVia>,
+        candidates: Vec<Candidate<I>>,
+    ) -> QueryResult<I> {
+        let Some(proven_via) = proven_via else {
+            // We don't care about overflow. If proving the trait goal overflowed, then
+            // it's enough to report an overflow error for that, we don't also have to
+            // overflow during normalization.
+            return Ok(self.make_ambiguous_response_no_constraints(MaybeCause::Ambiguity));
+        };
 
-        if !trait_candidates_from_env.is_empty() {
-            let trait_env_result = self.merge_candidates(trait_candidates_from_env);
-            match trait_env_result.unwrap().value.certainty {
-                // If proving the trait goal succeeds by using the env,
-                // we freely drop all impl candidates.
-                //
-                // FIXME(@lcnr): It feels like this could easily hide
-                // a forced ambiguity candidate added earlier.
-                // This feels dangerous.
-                Certainty::Yes => {
-                    candidates.retain(|c| match c.source {
-                        CandidateSource::Impl(_) | CandidateSource::BuiltinImpl(_) => {
-                            debug!(?c, "discard impl candidate");
-                            false
-                        }
-                        CandidateSource::ParamEnv(_) | CandidateSource::AliasBound => true,
-                        CandidateSource::CoherenceUnknowable => panic!("uh oh"),
-                    });
-                }
-                // If it is still ambiguous we instead just force the whole goal
-                // to be ambig and wait for inference constraints. See
-                // tests/ui/traits/next-solver/env-shadows-impls/ambig-env-no-shadow.rs
-                Certainty::Maybe(cause) => {
-                    debug!(?cause, "force ambiguity");
-                    *candidates = self.forced_ambiguity(cause).into_iter().collect();
-                }
-            }
-        }
-    }
+        let responses: Vec<_> = match proven_via {
+            // Even when a trait bound has been proven using a where-bound, we
+            // still need to consider alias-bounds for normalization, see
+            // tests/ui/next-solver/alias-bound-shadowed-by-env.rs.
+            //
+            // FIXME(const_trait_impl): should this behavior also be used by
+            // constness checking. Doing so is *at least theoretically* breaking,
+            // see github.com/rust-lang/rust/issues/133044#issuecomment-2500709754
+            TraitGoalProvenVia::ParamEnv | TraitGoalProvenVia::AliasBound => candidates
+                .iter()
+                .filter(|c| {
+                    matches!(c.source, CandidateSource::AliasBound | CandidateSource::ParamEnv(_))
+                })
+                .map(|c| c.result)
+                .collect(),
+            TraitGoalProvenVia::Misc => candidates.iter().map(|c| c.result).collect(),
+        };
 
-    /// If there are multiple ways to prove a trait or projection goal, we have
-    /// to somehow try to merge the candidates into one. If that fails, we return
-    /// ambiguity.
-    #[instrument(level = "debug", skip(self), ret)]
-    pub(super) fn merge_candidates(&mut self, candidates: Vec<Candidate<I>>) -> QueryResult<I> {
-        // First try merging all candidates. This is complete and fully sound.
-        let responses = candidates.iter().map(|c| c.result).collect::<Vec<_>>();
-        if let Some(result) = self.try_merge_responses(&responses) {
-            return Ok(result);
-        } else {
-            self.flounder(&responses)
-        }
+        self.try_merge_responses(&responses).map_or_else(|| self.flounder(&responses), Ok)
     }
 }
diff --git a/compiler/rustc_next_trait_solver/src/solve/effect_goals.rs b/compiler/rustc_next_trait_solver/src/solve/effect_goals.rs
index 81b5199002b..ce7552e30f0 100644
--- a/compiler/rustc_next_trait_solver/src/solve/effect_goals.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/effect_goals.rs
@@ -4,6 +4,7 @@
 use rustc_type_ir::fast_reject::DeepRejectCtxt;
 use rustc_type_ir::inherent::*;
 use rustc_type_ir::lang_items::TraitSolverLangItem;
+use rustc_type_ir::solve::inspect::ProbeKind;
 use rustc_type_ir::{self as ty, Interner, elaborate};
 use tracing::instrument;
 
@@ -391,6 +392,11 @@ where
         goal: Goal<I, ty::HostEffectPredicate<I>>,
     ) -> QueryResult<I> {
         let candidates = self.assemble_and_evaluate_candidates(goal);
-        self.merge_candidates(candidates)
+        let (_, proven_via) = self.probe(|_| ProbeKind::ShadowedEnvProbing).enter(|ecx| {
+            let trait_goal: Goal<I, ty::TraitPredicate<I>> =
+                goal.with(ecx.cx(), goal.predicate.trait_ref);
+            ecx.compute_trait_goal(trait_goal)
+        })?;
+        self.merge_candidates(proven_via, candidates)
     }
 }
diff --git a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs
index a143af13688..e99cd3d2727 100644
--- a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs
@@ -18,7 +18,7 @@ use rustc_type_ir::relate::solver_relating::RelateExt;
 use rustc_type_ir::{self as ty, Canonical, CanonicalVarValues, InferCtxtLike, Interner};
 use tracing::{debug, instrument, trace};
 
-use crate::canonicalizer::{CanonicalizeMode, Canonicalizer};
+use crate::canonicalizer::Canonicalizer;
 use crate::delegate::SolverDelegate;
 use crate::resolve::EagerResolver;
 use crate::solve::eval_ctxt::NestedGoals;
@@ -60,17 +60,13 @@ where
             (goal, opaque_types).fold_with(&mut EagerResolver::new(self.delegate));
 
         let mut orig_values = Default::default();
-        let canonical = Canonicalizer::canonicalize(
-            self.delegate,
-            CanonicalizeMode::Input,
-            &mut orig_values,
-            QueryInput {
+        let canonical =
+            Canonicalizer::canonicalize_input(self.delegate, &mut orig_values, QueryInput {
                 goal,
                 predefined_opaques_in_body: self
                     .cx()
                     .mk_predefined_opaques_in_body(PredefinedOpaquesData { opaque_types }),
-            },
-        );
+            });
         let query_input = ty::CanonicalQueryInput { canonical, typing_mode: self.typing_mode() };
         (orig_values, query_input)
     }
@@ -148,9 +144,9 @@ where
             .region_constraints
             .retain(|outlives| outlives.0.as_region().map_or(true, |re| re != outlives.1));
 
-        let canonical = Canonicalizer::canonicalize(
+        let canonical = Canonicalizer::canonicalize_response(
             self.delegate,
-            CanonicalizeMode::Response { max_input_universe: self.max_input_universe },
+            self.max_input_universe,
             &mut Default::default(),
             Response {
                 var_values,
@@ -428,12 +424,7 @@ where
     let var_values = CanonicalVarValues { var_values: delegate.cx().mk_args(var_values) };
     let state = inspect::State { var_values, data };
     let state = state.fold_with(&mut EagerResolver::new(delegate));
-    Canonicalizer::canonicalize(
-        delegate,
-        CanonicalizeMode::Response { max_input_universe },
-        &mut vec![],
-        state,
-    )
+    Canonicalizer::canonicalize_response(delegate, max_input_universe, &mut vec![], state)
 }
 
 // FIXME: needs to be pub to be accessed by downstream
diff --git a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs
index 70ceb22bfea..8c74490e0e0 100644
--- a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs
@@ -440,7 +440,7 @@ where
         if let Some(kind) = kind.no_bound_vars() {
             match kind {
                 ty::PredicateKind::Clause(ty::ClauseKind::Trait(predicate)) => {
-                    self.compute_trait_goal(Goal { param_env, predicate })
+                    self.compute_trait_goal(Goal { param_env, predicate }).map(|(r, _via)| r)
                 }
                 ty::PredicateKind::Clause(ty::ClauseKind::HostEffect(predicate)) => {
                     self.compute_host_effect_goal(Goal { param_env, predicate })
diff --git a/compiler/rustc_next_trait_solver/src/solve/mod.rs b/compiler/rustc_next_trait_solver/src/solve/mod.rs
index ebf1013db1e..37678bfd880 100644
--- a/compiler/rustc_next_trait_solver/src/solve/mod.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/mod.rs
@@ -243,22 +243,27 @@ where
             .copied()
     }
 
+    fn bail_with_ambiguity(&mut self, responses: &[CanonicalResponse<I>]) -> CanonicalResponse<I> {
+        debug_assert!(!responses.is_empty());
+        if let Certainty::Maybe(maybe_cause) =
+            responses.iter().fold(Certainty::AMBIGUOUS, |certainty, response| {
+                certainty.unify_with(response.value.certainty)
+            })
+        {
+            self.make_ambiguous_response_no_constraints(maybe_cause)
+        } else {
+            panic!("expected flounder response to be ambiguous")
+        }
+    }
+
     /// If we fail to merge responses we flounder and return overflow or ambiguity.
     #[instrument(level = "trace", skip(self), ret)]
     fn flounder(&mut self, responses: &[CanonicalResponse<I>]) -> QueryResult<I> {
         if responses.is_empty() {
             return Err(NoSolution);
+        } else {
+            Ok(self.bail_with_ambiguity(responses))
         }
-
-        let Certainty::Maybe(maybe_cause) =
-            responses.iter().fold(Certainty::AMBIGUOUS, |certainty, response| {
-                certainty.unify_with(response.value.certainty)
-            })
-        else {
-            panic!("expected flounder response to be ambiguous")
-        };
-
-        Ok(self.make_ambiguous_response_no_constraints(maybe_cause))
     }
 
     /// Normalize a type for when it is structurally matched on.
diff --git a/compiler/rustc_next_trait_solver/src/solve/normalizes_to/mod.rs b/compiler/rustc_next_trait_solver/src/solve/normalizes_to/mod.rs
index 63dbee2640b..b8867192225 100644
--- a/compiler/rustc_next_trait_solver/src/solve/normalizes_to/mod.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/normalizes_to/mod.rs
@@ -88,10 +88,17 @@ where
     /// returns `NoSolution`.
     #[instrument(level = "trace", skip(self), ret)]
     fn normalize_at_least_one_step(&mut self, goal: Goal<I, NormalizesTo<I>>) -> QueryResult<I> {
-        match goal.predicate.alias.kind(self.cx()) {
+        let cx = self.cx();
+        match goal.predicate.alias.kind(cx) {
             ty::AliasTermKind::ProjectionTy | ty::AliasTermKind::ProjectionConst => {
                 let candidates = self.assemble_and_evaluate_candidates(goal);
-                self.merge_candidates(candidates)
+                let (_, proven_via) =
+                    self.probe(|_| ProbeKind::ShadowedEnvProbing).enter(|ecx| {
+                        let trait_goal: Goal<I, ty::TraitPredicate<I>> =
+                            goal.with(cx, goal.predicate.alias.trait_ref(cx));
+                        ecx.compute_trait_goal(trait_goal)
+                    })?;
+                self.merge_candidates(proven_via, candidates)
             }
             ty::AliasTermKind::InherentTy => self.normalize_inherent_associated_type(goal),
             ty::AliasTermKind::OpaqueTy => self.normalize_opaque_type(goal),
diff --git a/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs b/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs
index 12df35d30b8..886cdec0345 100644
--- a/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs
@@ -5,6 +5,7 @@ use rustc_type_ir::data_structures::IndexSet;
 use rustc_type_ir::fast_reject::DeepRejectCtxt;
 use rustc_type_ir::inherent::*;
 use rustc_type_ir::lang_items::TraitSolverLangItem;
+use rustc_type_ir::solve::CanonicalResponse;
 use rustc_type_ir::visit::TypeVisitableExt as _;
 use rustc_type_ir::{self as ty, Interner, TraitPredicate, TypingMode, Upcast as _, elaborate};
 use tracing::{instrument, trace};
@@ -1147,13 +1148,101 @@ where
             ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
         })
     }
+}
+
+/// How we've proven this trait goal.
+///
+/// This is used by `NormalizesTo` goals to only normalize
+/// by using the same 'kind of candidate' we've used to prove
+/// its corresponding trait goal. Most notably, we do not
+/// normalize by using an impl if the trait goal has been
+/// proven via a `ParamEnv` candidate.
+///
+/// This is necessary to avoid unnecessary region constraints,
+/// see trait-system-refactor-initiative#125 for more details.
+#[derive(Debug, Clone, Copy)]
+pub(super) enum TraitGoalProvenVia {
+    /// We've proven the trait goal by something which is
+    /// is not a non-global where-bound or an alias-bound.
+    ///
+    /// This means we don't disable any candidates during
+    /// normalization.
+    Misc,
+    ParamEnv,
+    AliasBound,
+}
+
+impl<D, I> EvalCtxt<'_, D>
+where
+    D: SolverDelegate<Interner = I>,
+    I: Interner,
+{
+    pub(super) fn merge_trait_candidates(
+        &mut self,
+        goal: Goal<I, TraitPredicate<I>>,
+        candidates: Vec<Candidate<I>>,
+    ) -> Result<(CanonicalResponse<I>, Option<TraitGoalProvenVia>), NoSolution> {
+        if let TypingMode::Coherence = self.typing_mode() {
+            let all_candidates: Vec<_> = candidates.into_iter().map(|c| c.result).collect();
+            return if let Some(response) = self.try_merge_responses(&all_candidates) {
+                Ok((response, Some(TraitGoalProvenVia::Misc)))
+            } else {
+                self.flounder(&all_candidates).map(|r| (r, None))
+            };
+        }
+
+        // FIXME: prefer trivial builtin impls
+
+        // If there are non-global where-bounds, prefer where-bounds
+        // (including global ones) over everything else.
+        let has_non_global_where_bounds = candidates.iter().any(|c| match c.source {
+            CandidateSource::ParamEnv(idx) => {
+                let where_bound = goal.param_env.caller_bounds().get(idx);
+                where_bound.has_bound_vars() || !where_bound.is_global()
+            }
+            _ => false,
+        });
+        if has_non_global_where_bounds {
+            let where_bounds: Vec<_> = candidates
+                .iter()
+                .filter(|c| matches!(c.source, CandidateSource::ParamEnv(_)))
+                .map(|c| c.result)
+                .collect();
+
+            return if let Some(response) = self.try_merge_responses(&where_bounds) {
+                Ok((response, Some(TraitGoalProvenVia::ParamEnv)))
+            } else {
+                Ok((self.bail_with_ambiguity(&where_bounds), None))
+            };
+        }
+
+        if candidates.iter().any(|c| matches!(c.source, CandidateSource::AliasBound)) {
+            let alias_bounds: Vec<_> = candidates
+                .iter()
+                .filter(|c| matches!(c.source, CandidateSource::AliasBound))
+                .map(|c| c.result)
+                .collect();
+            return if let Some(response) = self.try_merge_responses(&alias_bounds) {
+                Ok((response, Some(TraitGoalProvenVia::AliasBound)))
+            } else {
+                Ok((self.bail_with_ambiguity(&alias_bounds), None))
+            };
+        }
+
+        let all_candidates: Vec<_> = candidates.into_iter().map(|c| c.result).collect();
+        if let Some(response) = self.try_merge_responses(&all_candidates) {
+            Ok((response, Some(TraitGoalProvenVia::Misc)))
+        } else {
+            self.flounder(&all_candidates).map(|r| (r, None))
+        }
+    }
 
     #[instrument(level = "trace", skip(self))]
     pub(super) fn compute_trait_goal(
         &mut self,
         goal: Goal<I, TraitPredicate<I>>,
-    ) -> QueryResult<I> {
+    ) -> Result<(CanonicalResponse<I>, Option<TraitGoalProvenVia>), NoSolution> {
         let candidates = self.assemble_and_evaluate_candidates(goal);
-        self.merge_candidates(candidates)
+        self.merge_trait_candidates(goal, candidates)
     }
 }
diff --git a/compiler/rustc_parse/src/errors.rs b/compiler/rustc_parse/src/errors.rs
index 4c4e03cdfa3..f78d9dc2bfc 100644
--- a/compiler/rustc_parse/src/errors.rs
+++ b/compiler/rustc_parse/src/errors.rs
@@ -13,8 +13,7 @@ use rustc_errors::{
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_session::errors::ExprParenthesesNeeded;
 use rustc_span::edition::{Edition, LATEST_STABLE_EDITION};
-use rustc_span::symbol::Ident;
-use rustc_span::{Span, Symbol};
+use rustc_span::{Ident, Span, Symbol};
 
 use crate::fluent_generated as fluent;
 use crate::parser::{ForbiddenLetReason, TokenDescription};
diff --git a/compiler/rustc_parse/src/lexer/mod.rs b/compiler/rustc_parse/src/lexer/mod.rs
index 443ddfc94ec..792e2cc26ef 100644
--- a/compiler/rustc_parse/src/lexer/mod.rs
+++ b/compiler/rustc_parse/src/lexer/mod.rs
@@ -14,8 +14,7 @@ use rustc_session::lint::builtin::{
     TEXT_DIRECTION_CODEPOINT_IN_COMMENT,
 };
 use rustc_session::parse::ParseSess;
-use rustc_span::symbol::Symbol;
-use rustc_span::{BytePos, Pos, Span};
+use rustc_span::{BytePos, Pos, Span, Symbol};
 use tracing::debug;
 
 use crate::lexer::diagnostics::TokenTreeDiagInfo;
diff --git a/compiler/rustc_parse/src/lexer/unicode_chars.rs b/compiler/rustc_parse/src/lexer/unicode_chars.rs
index 42eef27803e..ef8d0f96b61 100644
--- a/compiler/rustc_parse/src/lexer/unicode_chars.rs
+++ b/compiler/rustc_parse/src/lexer/unicode_chars.rs
@@ -1,8 +1,7 @@
 //! Characters and their corresponding confusables were collected from
 //! <https://www.unicode.org/Public/security/10.0.0/confusables.txt>
 
-use rustc_span::symbol::kw;
-use rustc_span::{BytePos, Pos, Span};
+use rustc_span::{BytePos, Pos, Span, kw};
 
 use super::Lexer;
 use crate::errors::TokenSubstitution;
diff --git a/compiler/rustc_parse/src/parser/attr.rs b/compiler/rustc_parse/src/parser/attr.rs
index b6fa2099588..2691e6f56d6 100644
--- a/compiler/rustc_parse/src/parser/attr.rs
+++ b/compiler/rustc_parse/src/parser/attr.rs
@@ -1,9 +1,6 @@
-use rustc_ast as ast;
-use rustc_ast::attr;
-use rustc_ast::token::{self, Delimiter};
+use rustc_ast::{self as ast, Attribute, attr, token};
 use rustc_errors::codes::*;
 use rustc_errors::{Diag, PResult};
-use rustc_span::symbol::kw;
 use rustc_span::{BytePos, Span};
 use thin_vec::ThinVec;
 use tracing::debug;
@@ -12,7 +9,7 @@ use super::{
     AttrWrapper, Capturing, FnParseMode, ForceCollect, Parser, ParserRange, PathStyle, Trailing,
     UsePreAttrPos,
 };
-use crate::{errors, fluent_generated as fluent, maybe_whole};
+use crate::{errors, exp, fluent_generated as fluent, maybe_whole};
 
 // Public for rustfmt usage
 #[derive(Debug)]
@@ -47,8 +44,8 @@ impl<'a> Parser<'a> {
         let mut just_parsed_doc_comment = false;
         let start_pos = self.num_bump_calls;
         loop {
-            let attr = if self.check(&token::Pound) {
-                let prev_outer_attr_sp = outer_attrs.last().map(|attr| attr.span);
+            let attr = if self.check(exp!(Pound)) {
+                let prev_outer_attr_sp = outer_attrs.last().map(|attr: &Attribute| attr.span);
 
                 let inner_error_reason = if just_parsed_doc_comment {
                     Some(InnerAttrForbiddenReason::AfterOuterDocComment {
@@ -128,14 +125,14 @@ impl<'a> Parser<'a> {
         let lo = self.token.span;
         // Attributes can't have attributes of their own [Editor's note: not with that attitude]
         self.collect_tokens_no_attrs(|this| {
-            assert!(this.eat(&token::Pound), "parse_attribute called in non-attribute position");
+            assert!(this.eat(exp!(Pound)), "parse_attribute called in non-attribute position");
 
             let style =
-                if this.eat(&token::Not) { ast::AttrStyle::Inner } else { ast::AttrStyle::Outer };
+                if this.eat(exp!(Not)) { ast::AttrStyle::Inner } else { ast::AttrStyle::Outer };
 
-            this.expect(&token::OpenDelim(Delimiter::Bracket))?;
+            this.expect(exp!(OpenBracket))?;
             let item = this.parse_attr_item(ForceCollect::No)?;
-            this.expect(&token::CloseDelim(Delimiter::Bracket))?;
+            this.expect(exp!(CloseBracket))?;
             let attr_sp = lo.to(this.prev_token.span);
 
             // Emit error if inner attribute is encountered and forbidden.
@@ -276,10 +273,10 @@ impl<'a> Parser<'a> {
 
         // Attr items don't have attributes.
         self.collect_tokens(None, AttrWrapper::empty(), force_collect, |this, _empty_attrs| {
-            let is_unsafe = this.eat_keyword(kw::Unsafe);
+            let is_unsafe = this.eat_keyword(exp!(Unsafe));
             let unsafety = if is_unsafe {
                 let unsafe_span = this.prev_token.span;
-                this.expect(&token::OpenDelim(Delimiter::Parenthesis))?;
+                this.expect(exp!(OpenParen))?;
                 ast::Safety::Unsafe(unsafe_span)
             } else {
                 ast::Safety::Default
@@ -288,7 +285,7 @@ impl<'a> Parser<'a> {
             let path = this.parse_path(PathStyle::Mod)?;
             let args = this.parse_attr_args()?;
             if is_unsafe {
-                this.expect(&token::CloseDelim(Delimiter::Parenthesis))?;
+                this.expect(exp!(CloseParen))?;
             }
             Ok((
                 ast::AttrItem { unsafety, path, args, tokens: None },
@@ -308,7 +305,7 @@ impl<'a> Parser<'a> {
         loop {
             let start_pos = self.num_bump_calls;
             // Only try to parse if it is an inner attribute (has `!`).
-            let attr = if self.check(&token::Pound) && self.look_ahead(1, |t| t == &token::Not) {
+            let attr = if self.check(exp!(Pound)) && self.look_ahead(1, |t| t == &token::Not) {
                 Some(self.parse_attribute(InnerAttrPolicy::Permitted)?)
             } else if let token::DocComment(comment_kind, attr_style, data) = self.token.kind {
                 if attr_style == ast::AttrStyle::Inner {
@@ -360,7 +357,7 @@ impl<'a> Parser<'a> {
         &mut self,
     ) -> PResult<'a, (ast::MetaItemInner, Vec<(ast::AttrItem, Span)>)> {
         let cfg_predicate = self.parse_meta_item_inner()?;
-        self.expect(&token::Comma)?;
+        self.expect(exp!(Comma))?;
 
         // Presumably, the majority of the time there will only be one attr.
         let mut expanded_attrs = Vec::with_capacity(1);
@@ -368,7 +365,7 @@ impl<'a> Parser<'a> {
             let lo = self.token.span;
             let item = self.parse_attr_item(ForceCollect::Yes)?;
             expanded_attrs.push((item, lo.to(self.prev_token.span)));
-            if !self.eat(&token::Comma) {
+            if !self.eat(exp!(Comma)) {
                 break;
             }
         }
@@ -382,7 +379,7 @@ impl<'a> Parser<'a> {
         let mut nmis = ThinVec::with_capacity(1);
         while self.token != token::Eof {
             nmis.push(self.parse_meta_item_inner()?);
-            if !self.eat(&token::Comma) {
+            if !self.eat(exp!(Comma)) {
                 break;
             }
         }
@@ -415,13 +412,13 @@ impl<'a> Parser<'a> {
 
         let lo = self.token.span;
         let is_unsafe = if unsafe_allowed == AllowLeadingUnsafe::Yes {
-            self.eat_keyword(kw::Unsafe)
+            self.eat_keyword(exp!(Unsafe))
         } else {
             false
         };
         let unsafety = if is_unsafe {
             let unsafe_span = self.prev_token.span;
-            self.expect(&token::OpenDelim(Delimiter::Parenthesis))?;
+            self.expect(exp!(OpenParen))?;
 
             ast::Safety::Unsafe(unsafe_span)
         } else {
@@ -431,7 +428,7 @@ impl<'a> Parser<'a> {
         let path = self.parse_path(PathStyle::Mod)?;
         let kind = self.parse_meta_item_kind()?;
         if is_unsafe {
-            self.expect(&token::CloseDelim(Delimiter::Parenthesis))?;
+            self.expect(exp!(CloseParen))?;
         }
         let span = lo.to(self.prev_token.span);
 
@@ -439,9 +436,9 @@ impl<'a> Parser<'a> {
     }
 
     pub(crate) fn parse_meta_item_kind(&mut self) -> PResult<'a, ast::MetaItemKind> {
-        Ok(if self.eat(&token::Eq) {
+        Ok(if self.eat(exp!(Eq)) {
             ast::MetaItemKind::NameValue(self.parse_unsuffixed_meta_item_lit()?)
-        } else if self.check(&token::OpenDelim(Delimiter::Parenthesis)) {
+        } else if self.check(exp!(OpenParen)) {
             let (list, _) = self.parse_paren_comma_seq(|p| p.parse_meta_item_inner())?;
             ast::MetaItemKind::List(list)
         } else {
diff --git a/compiler/rustc_parse/src/parser/diagnostics.rs b/compiler/rustc_parse/src/parser/diagnostics.rs
index e5edf605d82..aab4e1b1afc 100644
--- a/compiler/rustc_parse/src/parser/diagnostics.rs
+++ b/compiler/rustc_parse/src/parser/diagnostics.rs
@@ -16,20 +16,21 @@ use rustc_ast_pretty::pprust;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::sync::Lrc;
 use rustc_errors::{
-    Applicability, Diag, DiagCtxtHandle, ErrorGuaranteed, FatalError, PResult, Subdiagnostic,
-    Suggestions, pluralize,
+    Applicability, Diag, DiagCtxtHandle, ErrorGuaranteed, PResult, Subdiagnostic, Suggestions,
+    pluralize,
 };
 use rustc_session::errors::ExprParenthesesNeeded;
 use rustc_span::edit_distance::find_best_match_for_name;
 use rustc_span::source_map::Spanned;
-use rustc_span::symbol::{AllKeywords, Ident, kw, sym};
-use rustc_span::{BytePos, DUMMY_SP, Span, SpanSnippetError, Symbol};
+use rustc_span::symbol::used_keywords;
+use rustc_span::{BytePos, DUMMY_SP, Ident, Span, SpanSnippetError, Symbol, kw, sym};
 use thin_vec::{ThinVec, thin_vec};
 use tracing::{debug, trace};
 
 use super::pat::Expected;
 use super::{
-    BlockMode, CommaRecoveryMode, Parser, PathStyle, Restrictions, SemiColonMode, SeqSep, TokenType,
+    BlockMode, CommaRecoveryMode, ExpTokenPair, Parser, PathStyle, Restrictions, SemiColonMode,
+    SeqSep, TokenType,
 };
 use crate::errors::{
     AddParen, AmbiguousPlus, AsyncMoveBlockIn2015, AttributeOnParamType, AwaitSuggestion,
@@ -47,7 +48,7 @@ use crate::errors::{
     UnexpectedConstParamDeclarationSugg, UnmatchedAngleBrackets, UseEqInstead, WrapType,
 };
 use crate::parser::attr::InnerAttrPolicy;
-use crate::{fluent_generated as fluent, parser};
+use crate::{exp, fluent_generated as fluent};
 
 /// Creates a placeholder argument.
 pub(super) fn dummy_arg(ident: Ident, guar: ErrorGuaranteed) -> Param {
@@ -462,8 +463,8 @@ impl<'a> Parser<'a> {
 
     pub(super) fn expected_one_of_not_found(
         &mut self,
-        edible: &[TokenKind],
-        inedible: &[TokenKind],
+        edible: &[ExpTokenPair<'_>],
+        inedible: &[ExpTokenPair<'_>],
     ) -> PResult<'a, ErrorGuaranteed> {
         debug!("expected_one_of_not_found(edible: {:?}, inedible: {:?})", edible, inedible);
         fn tokens_to_string(tokens: &[TokenType]) -> String {
@@ -483,49 +484,17 @@ impl<'a> Parser<'a> {
             })
         }
 
-        self.expected_tokens.extend(edible.iter().chain(inedible).cloned().map(TokenType::Token));
-        let mut expected = self
-            .expected_tokens
-            .iter()
-            .filter(|token| {
-                // Filter out suggestions that suggest the same token which was found and deemed incorrect.
-                fn is_ident_eq_keyword(found: &TokenKind, expected: &TokenType) -> bool {
-                    if let TokenKind::Ident(current_sym, _) = found
-                        && let TokenType::Keyword(suggested_sym) = expected
-                    {
-                        return current_sym == suggested_sym;
-                    }
-                    false
-                }
-
-                if **token != parser::TokenType::Token(self.token.kind.clone()) {
-                    let eq = is_ident_eq_keyword(&self.token.kind, &token);
-                    // If the suggestion is a keyword and the found token is an ident,
-                    // the content of which are equal to the suggestion's content,
-                    // we can remove that suggestion (see the `return false` below).
-
-                    // If this isn't the case however, and the suggestion is a token the
-                    // content of which is the same as the found token's, we remove it as well.
-                    if !eq {
-                        if let TokenType::Token(kind) = token {
-                            if self.token == *kind {
-                                return false;
-                            }
-                        }
-                        return true;
-                    }
-                }
-                false
-            })
-            .cloned()
-            .collect::<Vec<_>>();
+        for exp in edible.iter().chain(inedible.iter()) {
+            self.expected_token_types.insert(exp.token_type);
+        }
+        let mut expected: Vec<_> = self.expected_token_types.iter().collect();
         expected.sort_by_cached_key(|x| x.to_string());
         expected.dedup();
 
         let sm = self.psess.source_map();
 
         // Special-case "expected `;`" errors.
-        if expected.contains(&TokenType::Token(token::Semi)) {
+        if expected.contains(&TokenType::Semi) {
             // If the user is trying to write a ternary expression, recover it and
             // return an Err to prevent a cascade of irrelevant diagnostics.
             if self.prev_token == token::Question
@@ -577,7 +546,7 @@ impl<'a> Parser<'a> {
                     || (sm.is_multiline(
                         self.prev_token.span.shrink_to_hi().until(self.token.span.shrink_to_lo()),
                     ) && t == &token::Pound)
-            }) && !expected.contains(&TokenType::Token(token::Comma))
+            }) && !expected.contains(&TokenType::Comma)
             {
                 // Missing semicolon typo. This is triggered if the next token could either start a
                 // new statement or is a block close. For example:
@@ -597,7 +566,7 @@ impl<'a> Parser<'a> {
 
         if self.token == TokenKind::EqEq
             && self.prev_token.is_ident()
-            && expected.iter().any(|tok| matches!(tok, TokenType::Token(TokenKind::Eq)))
+            && expected.contains(&TokenType::Eq)
         {
             // Likely typo: `=` → `==` in let expr or enum item
             return Err(self.dcx().create_err(UseEqInstead { span: self.token.span }));
@@ -636,15 +605,8 @@ impl<'a> Parser<'a> {
 
         // Look for usages of '=>' where '>=' was probably intended
         if self.token == token::FatArrow
-            && expected
-                .iter()
-                .any(|tok| matches!(tok, TokenType::Operator | TokenType::Token(TokenKind::Le)))
-            && !expected.iter().any(|tok| {
-                matches!(
-                    tok,
-                    TokenType::Token(TokenKind::FatArrow) | TokenType::Token(TokenKind::Comma)
-                )
-            })
+            && expected.iter().any(|tok| matches!(tok, TokenType::Operator | TokenType::Le))
+            && !expected.iter().any(|tok| matches!(tok, TokenType::FatArrow | TokenType::Comma))
         {
             err.span_suggestion(
                 self.token.span,
@@ -741,7 +703,7 @@ impl<'a> Parser<'a> {
         };
 
         if self.check_too_many_raw_str_terminators(&mut err) {
-            if expected.contains(&TokenType::Token(token::Semi)) && self.eat(&token::Semi) {
+            if expected.contains(&TokenType::Semi) && self.eat(exp!(Semi)) {
                 let guar = err.emit();
                 return Ok(guar);
             } else {
@@ -785,17 +747,15 @@ impl<'a> Parser<'a> {
         let Some((curr_ident, _)) = self.token.ident() else {
             return;
         };
-        let expected_tokens: &[TokenType] =
+        let expected_token_types: &[TokenType] =
             expected.len().checked_sub(10).map_or(&expected, |index| &expected[index..]);
-        let expected_keywords: Vec<Symbol> = expected_tokens
-            .iter()
-            .filter_map(|token| if let TokenType::Keyword(kw) = token { Some(*kw) } else { None })
-            .collect();
-
-        // When there are a few keywords in the last ten elements of `self.expected_tokens` and the current
-        // token is an identifier, it's probably a misspelled keyword.
-        // This handles code like `async Move {}`, misspelled `if` in match guard, misspelled `else` in `if`-`else`
-        // and mispelled `where` in a where clause.
+        let expected_keywords: Vec<Symbol> =
+            expected_token_types.iter().filter_map(|token| token.is_keyword()).collect();
+
+        // When there are a few keywords in the last ten elements of `self.expected_token_types`
+        // and the current token is an identifier, it's probably a misspelled keyword. This handles
+        // code like `async Move {}`, misspelled `if` in match guard, misspelled `else` in
+        // `if`-`else` and mispelled `where` in a where clause.
         if !expected_keywords.is_empty()
             && !curr_ident.is_used_keyword()
             && let Some(misspelled_kw) = find_similar_kw(curr_ident, &expected_keywords)
@@ -811,12 +771,12 @@ impl<'a> Parser<'a> {
             // so that it gets generated only when the diagnostic needs it.
             // Also, it is unlikely that this list is generated multiple times because the
             // parser halts after execution hits this path.
-            let all_keywords = AllKeywords::new().collect_used(|| prev_ident.span.edition());
+            let all_keywords = used_keywords(|| prev_ident.span.edition());
 
             // Otherwise, check the previous token with all the keywords as possible candidates.
             // This handles code like `Struct Human;` and `While a < b {}`.
-            // We check the previous token only when the current token is an identifier to avoid false
-            // positives like suggesting keyword `for` for `extern crate foo {}`.
+            // We check the previous token only when the current token is an identifier to avoid
+            // false positives like suggesting keyword `for` for `extern crate foo {}`.
             if let Some(misspelled_kw) = find_similar_kw(prev_ident, &all_keywords) {
                 err.subdiagnostic(misspelled_kw);
                 // We don't want other suggestions to be added as they are most likely meaningless
@@ -1052,7 +1012,7 @@ impl<'a> Parser<'a> {
                 (Err(snapshot_err), Err(err)) => {
                     // We don't know what went wrong, emit the normal error.
                     snapshot_err.cancel();
-                    self.consume_block(Delimiter::Brace, ConsumeClosingDelim::Yes);
+                    self.consume_block(exp!(OpenBrace), exp!(CloseBrace), ConsumeClosingDelim::Yes);
                     Err(err)
                 }
                 (Ok(_), Ok(mut tail)) => {
@@ -1089,7 +1049,7 @@ impl<'a> Parser<'a> {
                     Applicability::MaybeIncorrect,
                 );
                 let guar = err.emit();
-                self.eat_to_tokens(&[&token::CloseDelim(Delimiter::Brace)]);
+                self.eat_to_tokens(&[exp!(CloseBrace)]);
                 guar
             }
             token::OpenDelim(Delimiter::Parenthesis)
@@ -1097,7 +1057,7 @@ impl<'a> Parser<'a> {
             {
                 // We are within a function call or tuple, we can emit the error
                 // and recover.
-                self.eat_to_tokens(&[&token::CloseDelim(Delimiter::Parenthesis), &token::Comma]);
+                self.eat_to_tokens(&[exp!(CloseParen), exp!(Comma)]);
 
                 err.multipart_suggestion_verbose(
                     "you might have meant to open the body of the closure",
@@ -1124,11 +1084,11 @@ impl<'a> Parser<'a> {
         Ok(self.mk_expr_err(lo.to(self.token.span), guar))
     }
 
-    /// Eats and discards tokens until one of `kets` is encountered. Respects token trees,
+    /// Eats and discards tokens until one of `closes` is encountered. Respects token trees,
     /// passes through any errors encountered. Used for error recovery.
-    pub(super) fn eat_to_tokens(&mut self, kets: &[&TokenKind]) {
-        if let Err(err) =
-            self.parse_seq_to_before_tokens(kets, &[], SeqSep::none(), |p| Ok(p.parse_token_tree()))
+    pub(super) fn eat_to_tokens(&mut self, closes: &[ExpTokenPair<'_>]) {
+        if let Err(err) = self
+            .parse_seq_to_before_tokens(closes, &[], SeqSep::none(), |p| Ok(p.parse_token_tree()))
         {
             err.cancel();
         }
@@ -1147,7 +1107,7 @@ impl<'a> Parser<'a> {
     pub(super) fn check_trailing_angle_brackets(
         &mut self,
         segment: &PathSegment,
-        end: &[&TokenKind],
+        end: &[ExpTokenPair<'_>],
     ) -> Option<ErrorGuaranteed> {
         if !self.may_recover() {
             return None;
@@ -1230,7 +1190,7 @@ impl<'a> Parser<'a> {
         // second case.
         if self.look_ahead(position, |t| {
             trace!("check_trailing_angle_brackets: t={:?}", t);
-            end.contains(&&t.kind)
+            end.iter().any(|exp| exp.tok == &t.kind)
         }) {
             // Eat from where we started until the end token so that parsing can continue
             // as if we didn't have those extra angle brackets.
@@ -1298,11 +1258,11 @@ impl<'a> Parser<'a> {
     ) -> PResult<'a, ErrorGuaranteed> {
         if let ExprKind::Binary(binop, _, _) = &expr.kind
             && let ast::BinOpKind::Lt = binop.node
-            && self.eat(&token::Comma)
+            && self.eat(exp!(Comma))
         {
             let x = self.parse_seq_to_before_end(
-                &token::Gt,
-                SeqSep::trailing_allowed(token::Comma),
+                exp!(Gt),
+                SeqSep::trailing_allowed(exp!(Comma)),
                 |p| match p.parse_generic_arg(None)? {
                     Some(arg) => Ok(arg),
                     // If we didn't eat a generic arg, then we should error.
@@ -1311,7 +1271,7 @@ impl<'a> Parser<'a> {
             );
             match x {
                 Ok((_, _, Recovered::No)) => {
-                    if self.eat(&token::Gt) {
+                    if self.eat(exp!(Gt)) {
                         // We made sense of it. Improve the error message.
                         e.span_suggestion_verbose(
                             binop.span.shrink_to_lo(),
@@ -1874,7 +1834,7 @@ impl<'a> Parser<'a> {
         ty_span: Span,
         ty: P<Ty>,
     ) -> PResult<'a, P<T>> {
-        self.expect(&token::PathSep)?;
+        self.expect(exp!(PathSep))?;
 
         let mut path = ast::Path { segments: ThinVec::new(), span: DUMMY_SP, tokens: None };
         self.parse_path_segments(&mut path.segments, T::PATH_STYLE, None)?;
@@ -1956,10 +1916,10 @@ impl<'a> Parser<'a> {
     }
 
     pub(super) fn expect_semi(&mut self) -> PResult<'a, ()> {
-        if self.eat(&token::Semi) || self.recover_colon_as_semi() {
+        if self.eat(exp!(Semi)) || self.recover_colon_as_semi() {
             return Ok(());
         }
-        self.expect(&token::Semi).map(drop) // Error unconditionally
+        self.expect(exp!(Semi)).map(drop) // Error unconditionally
     }
 
     pub(super) fn recover_colon_as_semi(&mut self) -> bool {
@@ -2004,15 +1964,15 @@ impl<'a> Parser<'a> {
     }
 
     fn recover_await_macro(&mut self) -> PResult<'a, (Span, P<Expr>, bool)> {
-        self.expect(&token::Not)?;
-        self.expect(&token::OpenDelim(Delimiter::Parenthesis))?;
+        self.expect(exp!(Not))?;
+        self.expect(exp!(OpenParen))?;
         let expr = self.parse_expr()?;
-        self.expect(&token::CloseDelim(Delimiter::Parenthesis))?;
+        self.expect(exp!(CloseParen))?;
         Ok((self.prev_token.span, expr, false))
     }
 
     fn recover_await_prefix(&mut self, await_sp: Span) -> PResult<'a, (Span, P<Expr>, bool)> {
-        let is_question = self.eat(&token::Question); // Handle `await? <expr>`.
+        let is_question = self.eat(exp!(Question)); // Handle `await? <expr>`.
         let expr = if self.token == token::OpenDelim(Delimiter::Brace) {
             // Handle `await { <expr> }`.
             // This needs to be handled separately from the next arm to avoid
@@ -2074,7 +2034,7 @@ impl<'a> Parser<'a> {
             let try_span = lo.to(self.token.span); //we take the try!( span
             self.bump(); //remove (
             let is_empty = self.token == token::CloseDelim(Delimiter::Parenthesis); //check if the block is empty
-            self.consume_block(Delimiter::Parenthesis, ConsumeClosingDelim::No); //eat the block
+            self.consume_block(exp!(OpenParen), exp!(CloseParen), ConsumeClosingDelim::No); //eat the block
             let hi = self.token.span;
             self.bump(); //remove )
             let mut err = self.dcx().struct_span_err(lo.to(hi), "use of deprecated `try` macro");
@@ -2130,13 +2090,14 @@ impl<'a> Parser<'a> {
 
     pub(super) fn recover_seq_parse_error(
         &mut self,
-        delim: Delimiter,
+        open: ExpTokenPair<'_>,
+        close: ExpTokenPair<'_>,
         lo: Span,
         err: Diag<'a>,
     ) -> P<Expr> {
         let guar = err.emit();
         // Recover from parse error, callers expect the closing delim to be consumed.
-        self.consume_block(delim, ConsumeClosingDelim::Yes);
+        self.consume_block(open, close, ConsumeClosingDelim::Yes);
         self.mk_expr(lo.to(self.prev_token.span), ExprKind::Err(guar))
     }
 
@@ -2225,7 +2186,7 @@ impl<'a> Parser<'a> {
     }
 
     pub(super) fn check_for_for_in_in_typo(&mut self, in_span: Span) {
-        if self.eat_keyword(kw::In) {
+        if self.eat_keyword(exp!(In)) {
             // a common typo: `for _ in in bar {}`
             self.dcx().emit_err(InInTypo {
                 span: self.prev_token.span,
@@ -2366,7 +2327,7 @@ impl<'a> Parser<'a> {
 
     pub(super) fn recover_arg_parse(&mut self) -> PResult<'a, (P<ast::Pat>, P<ast::Ty>)> {
         let pat = self.parse_pat_no_top_alt(Some(Expected::ArgumentName), None)?;
-        self.expect(&token::Colon)?;
+        self.expect(exp!(Colon))?;
         let ty = self.parse_ty()?;
 
         self.dcx().emit_err(PatternMethodParamWithoutBody { span: pat.span });
@@ -2384,12 +2345,17 @@ impl<'a> Parser<'a> {
         Ok(param)
     }
 
-    pub(super) fn consume_block(&mut self, delim: Delimiter, consume_close: ConsumeClosingDelim) {
+    pub(super) fn consume_block(
+        &mut self,
+        open: ExpTokenPair<'_>,
+        close: ExpTokenPair<'_>,
+        consume_close: ConsumeClosingDelim,
+    ) {
         let mut brace_depth = 0;
         loop {
-            if self.eat(&token::OpenDelim(delim)) {
+            if self.eat(open) {
                 brace_depth += 1;
-            } else if self.check(&token::CloseDelim(delim)) {
+            } else if self.check(close) {
                 if brace_depth == 0 {
                     if let ConsumeClosingDelim::Yes = consume_close {
                         // Some of the callers of this method expect to be able to parse the
@@ -2545,7 +2511,7 @@ impl<'a> Parser<'a> {
         match self.recover_const_arg(arg.span(), err) {
             Ok(arg) => {
                 args.push(AngleBracketedArg::Arg(arg));
-                if self.eat(&token::Comma) {
+                if self.eat(exp!(Comma)) {
                     return Ok(true); // Continue
                 }
             }
@@ -3016,7 +2982,7 @@ impl<'a> Parser<'a> {
     /// Check for exclusive ranges written as `..<`
     pub(crate) fn maybe_err_dotdotlt_syntax(&self, maybe_lt: Token, mut err: Diag<'a>) -> Diag<'a> {
         if maybe_lt == token::Lt
-            && (self.expected_tokens.contains(&TokenType::Token(token::Gt))
+            && (self.expected_token_types.contains(TokenType::Gt)
                 || matches!(self.token.kind, token::Literal(..)))
         {
             err.span_suggestion(
@@ -3057,17 +3023,10 @@ impl<'a> Parser<'a> {
     }
 
     pub(super) fn recover_vcs_conflict_marker(&mut self) {
-        if let Err(err) = self.err_vcs_conflict_marker() {
-            err.emit();
-            FatalError.raise();
-        }
-    }
-
-    pub(crate) fn err_vcs_conflict_marker(&mut self) -> PResult<'a, ()> {
         // <<<<<<<
         let Some(start) = self.conflict_marker(&TokenKind::BinOp(token::Shl), &TokenKind::Lt)
         else {
-            return Ok(());
+            return;
         };
         let mut spans = Vec::with_capacity(3);
         spans.push(start);
@@ -3097,7 +3056,7 @@ impl<'a> Parser<'a> {
             self.bump();
         }
 
-        let mut err = self.dcx().struct_span_err(spans, "encountered diff marker");
+        let mut err = self.dcx().struct_span_fatal(spans, "encountered diff marker");
         match middlediff3 {
             // We're using diff3
             Some(middlediff3) => {
@@ -3140,15 +3099,15 @@ impl<'a> Parser<'a> {
              visit <https://git-scm.com/book/en/v2/Git-Tools-Advanced-Merging#_checking_out_conflicts>",
         );
 
-        Err(err)
+        err.emit();
     }
 
     /// Parse and throw away a parenthesized comma separated
     /// sequence of patterns until `)` is reached.
     fn skip_pat_list(&mut self) -> PResult<'a, ()> {
-        while !self.check(&token::CloseDelim(Delimiter::Parenthesis)) {
+        while !self.check(exp!(CloseParen)) {
             self.parse_pat_no_top_alt(None, None)?;
-            if !self.eat(&token::Comma) {
+            if !self.eat(exp!(Comma)) {
                 return Ok(());
             }
         }
diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index a2136399b0c..7533e75ffe2 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -8,6 +8,7 @@ use ast::token::IdentIsRaw;
 use ast::{CoroutineKind, ForLoopKind, GenBlockKind, MatchKind, Pat, Path, PathSegment, Recovered};
 use rustc_ast::ptr::P;
 use rustc_ast::token::{self, Delimiter, Token, TokenKind};
+use rustc_ast::tokenstream::TokenTree;
 use rustc_ast::util::case::Case;
 use rustc_ast::util::classify;
 use rustc_ast::util::parser::{AssocOp, ExprPrecedence, Fixity, prec_let_scrutinee_needs_par};
@@ -26,8 +27,7 @@ use rustc_session::errors::{ExprParenthesesNeeded, report_lit_error};
 use rustc_session::lint::BuiltinLintDiag;
 use rustc_session::lint::builtin::BREAK_WITH_LABEL_AND_LOOP;
 use rustc_span::source_map::{self, Spanned};
-use rustc_span::symbol::{Ident, Symbol, kw, sym};
-use rustc_span::{BytePos, ErrorGuaranteed, Pos, Span};
+use rustc_span::{BytePos, ErrorGuaranteed, Ident, Pos, Span, Symbol, kw, sym};
 use thin_vec::{ThinVec, thin_vec};
 use tracing::instrument;
 
@@ -35,10 +35,10 @@ use super::diagnostics::SnapshotParser;
 use super::pat::{CommaRecoveryMode, Expected, RecoverColon, RecoverComma};
 use super::ty::{AllowPlus, RecoverQPath, RecoverReturnSign};
 use super::{
-    AttrWrapper, BlockMode, ClosureSpans, ForceCollect, Parser, PathStyle, Restrictions,
-    SemiColonMode, SeqSep, TokenType, Trailing, UsePreAttrPos,
+    AttrWrapper, BlockMode, ClosureSpans, ExpTokenPair, ForceCollect, Parser, PathStyle,
+    Restrictions, SemiColonMode, SeqSep, TokenType, Trailing, UsePreAttrPos,
 };
-use crate::{errors, maybe_recover_from_interpolated_ty_qpath};
+use crate::{errors, exp, maybe_recover_from_interpolated_ty_qpath};
 
 #[derive(Debug)]
 pub(super) enum DestructuredFloat {
@@ -153,7 +153,7 @@ impl<'a> Parser<'a> {
             return Ok((lhs, parsed_something));
         }
 
-        self.expected_tokens.push(TokenType::Operator);
+        self.expected_token_types.insert(TokenType::Operator);
         while let Some(op) = self.check_assoc_op() {
             let lhs_span = self.interpolated_or_expr_span(&lhs);
             let cur_op_span = self.token.span;
@@ -279,13 +279,9 @@ impl<'a> Parser<'a> {
                 break;
             }
 
-            let fixity = op.fixity();
-            let min_prec = match fixity {
+            let min_prec = match op.fixity() {
                 Fixity::Right => Bound::Included(prec),
-                Fixity::Left => Bound::Excluded(prec),
-                // We currently have no non-associative operators that are not handled above by
-                // the special cases. The code is here only for future convenience.
-                Fixity::None => Bound::Excluded(prec),
+                Fixity::Left | Fixity::None => Bound::Excluded(prec),
             };
             let (rhs, _) = self.with_res(restrictions - Restrictions::STMT_EXPR, |this| {
                 let attrs = this.parse_outer_attributes()?;
@@ -337,10 +333,6 @@ impl<'a> Parser<'a> {
                     self.dcx().span_bug(span, "AssocOp should have been handled by special case")
                 }
             };
-
-            if let Fixity::None = fixity {
-                break;
-            }
         }
 
         Ok((lhs, parsed_something))
@@ -873,9 +865,9 @@ impl<'a> Parser<'a> {
 
     /// Parse `mut?` or `raw [ const | mut ]`.
     fn parse_borrow_modifiers(&mut self) -> (ast::BorrowKind, ast::Mutability) {
-        if self.check_keyword(kw::Raw) && self.look_ahead(1, Token::is_mutability) {
+        if self.check_keyword(exp!(Raw)) && self.look_ahead(1, Token::is_mutability) {
             // `raw [ const | mut ]`.
-            let found_raw = self.eat_keyword(kw::Raw);
+            let found_raw = self.eat_keyword(exp!(Raw));
             assert!(found_raw);
             let mutability = self.parse_const_or_mut().unwrap();
             (ast::BorrowKind::Raw, mutability)
@@ -908,7 +900,7 @@ impl<'a> Parser<'a> {
                         // a `return` which could be suggested otherwise.
                         self.eat_noexpect(&token::Question)
                     } else {
-                        self.eat(&token::Question)
+                        self.eat(exp!(Question))
                     };
                 if has_question {
                     // `expr?`
@@ -926,7 +918,7 @@ impl<'a> Parser<'a> {
                     self.dcx().emit_err(errors::ExprRArrowCall { span });
                     true
                 } else {
-                    self.eat(&token::Dot)
+                    self.eat(exp!(Dot))
                 };
                 if has_dot {
                     // expr.f
@@ -1251,7 +1243,7 @@ impl<'a> Parser<'a> {
             .map(|args| self.mk_expr(lo.to(self.prev_token.span), self.mk_call(fun, args)));
         match self.maybe_recover_struct_lit_bad_delims(lo, open_paren, seq, snapshot) {
             Ok(expr) => expr,
-            Err(err) => self.recover_seq_parse_error(Delimiter::Parenthesis, lo, err),
+            Err(err) => self.recover_seq_parse_error(exp!(OpenParen), exp!(CloseParen), lo, err),
         }
     }
 
@@ -1268,10 +1260,8 @@ impl<'a> Parser<'a> {
         match (self.may_recover(), seq, snapshot) {
             (true, Err(err), Some((mut snapshot, ExprKind::Path(None, path)))) => {
                 snapshot.bump(); // `(`
-                match snapshot.parse_struct_fields(path.clone(), false, Delimiter::Parenthesis) {
-                    Ok((fields, ..))
-                        if snapshot.eat(&token::CloseDelim(Delimiter::Parenthesis)) =>
-                    {
+                match snapshot.parse_struct_fields(path.clone(), false, exp!(CloseParen)) {
+                    Ok((fields, ..)) if snapshot.eat(exp!(CloseParen)) => {
                         // We are certain we have `Enum::Foo(a: 3, b: 4)`, suggest
                         // `Enum::Foo { a: 3, b: 4 }` or `Enum::Foo(3, 4)`.
                         self.restore_snapshot(snapshot);
@@ -1328,7 +1318,7 @@ impl<'a> Parser<'a> {
         self.bump(); // `[`
         let index = self.parse_expr()?;
         self.suggest_missing_semicolon_before_array(prev_span, open_delim_span)?;
-        self.expect(&token::CloseDelim(Delimiter::Bracket))?;
+        self.expect(exp!(CloseBracket))?;
         Ok(self.mk_expr(
             lo.to(self.prev_token.span),
             self.mk_index(base, index, open_delim_span.to(self.prev_token.span)),
@@ -1337,12 +1327,12 @@ impl<'a> Parser<'a> {
 
     /// Assuming we have just parsed `.`, continue parsing into an expression.
     fn parse_dot_suffix(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
-        if self.token.uninterpolated_span().at_least_rust_2018() && self.eat_keyword(kw::Await) {
+        if self.token.uninterpolated_span().at_least_rust_2018() && self.eat_keyword(exp!(Await)) {
             return Ok(self.mk_await_expr(self_arg, lo));
         }
 
         // Post-fix match
-        if self.eat_keyword(kw::Match) {
+        if self.eat_keyword(exp!(Match)) {
             let match_span = self.prev_token.span;
             self.psess.gated_spans.gate(sym::postfix_match, match_span);
             return self.parse_match_block(lo, match_span, self_arg, MatchKind::Postfix);
@@ -1350,10 +1340,10 @@ impl<'a> Parser<'a> {
 
         let fn_span_lo = self.token.span;
         let mut seg = self.parse_path_segment(PathStyle::Expr, None)?;
-        self.check_trailing_angle_brackets(&seg, &[&token::OpenDelim(Delimiter::Parenthesis)]);
+        self.check_trailing_angle_brackets(&seg, &[exp!(OpenParen)]);
         self.check_turbofish_missing_angle_brackets(&mut seg);
 
-        if self.check(&token::OpenDelim(Delimiter::Parenthesis)) {
+        if self.check(exp!(OpenParen)) {
             // Method call `expr.f()`
             let args = self.parse_expr_paren_seq()?;
             let fn_span = fn_span_lo.to(self.prev_token.span);
@@ -1415,18 +1405,18 @@ impl<'a> Parser<'a> {
 
         let restrictions = self.restrictions;
         self.with_res(restrictions - Restrictions::ALLOW_LET, |this| {
-            // Note: when adding new syntax here, don't forget to adjust `TokenKind::can_begin_expr()`.
+            // Note: adding new syntax here? Don't forget to adjust `TokenKind::can_begin_expr()`.
             let lo = this.token.span;
             if let token::Literal(_) = this.token.kind {
                 // This match arm is a special-case of the `_` match arm below and
                 // could be removed without changing functionality, but it's faster
                 // to have it here, especially for programs with large constants.
                 this.parse_expr_lit()
-            } else if this.check(&token::OpenDelim(Delimiter::Parenthesis)) {
+            } else if this.check(exp!(OpenParen)) {
                 this.parse_expr_tuple_parens(restrictions)
-            } else if this.check(&token::OpenDelim(Delimiter::Brace)) {
+            } else if this.check(exp!(OpenBrace)) {
                 this.parse_expr_block(None, lo, BlockCheckMode::Default)
-            } else if this.check(&token::BinOp(token::Or)) || this.check(&token::OrOr) {
+            } else if this.check(exp!(Or)) || this.check(exp!(OrOr)) {
                 this.parse_expr_closure().map_err(|mut err| {
                     // If the input is something like `if a { 1 } else { 2 } | if a { 3 } else { 4 }`
                     // then suggest parens around the lhs.
@@ -1435,41 +1425,41 @@ impl<'a> Parser<'a> {
                     }
                     err
                 })
-            } else if this.check(&token::OpenDelim(Delimiter::Bracket)) {
-                this.parse_expr_array_or_repeat(Delimiter::Bracket)
+            } else if this.check(exp!(OpenBracket)) {
+                this.parse_expr_array_or_repeat(exp!(CloseBracket))
             } else if this.is_builtin() {
                 this.parse_expr_builtin()
             } else if this.check_path() {
                 this.parse_expr_path_start()
-            } else if this.check_keyword(kw::Move)
-                || this.check_keyword(kw::Static)
+            } else if this.check_keyword(exp!(Move))
+                || this.check_keyword(exp!(Static))
                 || this.check_const_closure()
             {
                 this.parse_expr_closure()
-            } else if this.eat_keyword(kw::If) {
+            } else if this.eat_keyword(exp!(If)) {
                 this.parse_expr_if()
-            } else if this.check_keyword(kw::For) {
+            } else if this.check_keyword(exp!(For)) {
                 if this.choose_generics_over_qpath(1) {
                     this.parse_expr_closure()
                 } else {
-                    assert!(this.eat_keyword(kw::For));
+                    assert!(this.eat_keyword(exp!(For)));
                     this.parse_expr_for(None, lo)
                 }
-            } else if this.eat_keyword(kw::While) {
+            } else if this.eat_keyword(exp!(While)) {
                 this.parse_expr_while(None, lo)
             } else if let Some(label) = this.eat_label() {
                 this.parse_expr_labeled(label, true)
-            } else if this.eat_keyword(kw::Loop) {
+            } else if this.eat_keyword(exp!(Loop)) {
                 this.parse_expr_loop(None, lo).map_err(|mut err| {
                     err.span_label(lo, "while parsing this `loop` expression");
                     err
                 })
-            } else if this.eat_keyword(kw::Match) {
+            } else if this.eat_keyword(exp!(Match)) {
                 this.parse_expr_match().map_err(|mut err| {
                     err.span_label(lo, "while parsing this `match` expression");
                     err
                 })
-            } else if this.eat_keyword(kw::Unsafe) {
+            } else if this.eat_keyword(exp!(Unsafe)) {
                 this.parse_expr_block(None, lo, BlockCheckMode::Unsafe(ast::UserProvided)).map_err(
                     |mut err| {
                         err.span_label(lo, "while parsing this `unsafe` expression");
@@ -1481,23 +1471,23 @@ impl<'a> Parser<'a> {
             } else if this.may_recover() && this.is_do_catch_block() {
                 this.recover_do_catch()
             } else if this.is_try_block() {
-                this.expect_keyword(kw::Try)?;
+                this.expect_keyword(exp!(Try))?;
                 this.parse_try_block(lo)
-            } else if this.eat_keyword(kw::Return) {
+            } else if this.eat_keyword(exp!(Return)) {
                 this.parse_expr_return()
-            } else if this.eat_keyword(kw::Continue) {
+            } else if this.eat_keyword(exp!(Continue)) {
                 this.parse_expr_continue(lo)
-            } else if this.eat_keyword(kw::Break) {
+            } else if this.eat_keyword(exp!(Break)) {
                 this.parse_expr_break()
-            } else if this.eat_keyword(kw::Yield) {
+            } else if this.eat_keyword(exp!(Yield)) {
                 this.parse_expr_yield()
             } else if this.is_do_yeet() {
                 this.parse_expr_yeet()
-            } else if this.eat_keyword(kw::Become) {
+            } else if this.eat_keyword(exp!(Become)) {
                 this.parse_expr_become()
-            } else if this.check_keyword(kw::Let) {
+            } else if this.check_keyword(exp!(Let)) {
                 this.parse_expr_let(restrictions)
-            } else if this.eat_keyword(kw::Underscore) {
+            } else if this.eat_keyword(exp!(Underscore)) {
                 Ok(this.mk_expr(this.prev_token.span, ExprKind::Underscore))
             } else if this.token.uninterpolated_span().at_least_rust_2018() {
                 // `Span::at_least_rust_2018()` is somewhat expensive; don't get it repeatedly.
@@ -1505,11 +1495,11 @@ impl<'a> Parser<'a> {
                     // check for `gen {}` and `gen move {}`
                     // or `async gen {}` and `async gen move {}`
                     && (this.is_gen_block(kw::Gen, 0)
-                        || (this.check_keyword(kw::Async) && this.is_gen_block(kw::Gen, 1)))
+                        || (this.check_keyword(exp!(Async)) && this.is_gen_block(kw::Gen, 1)))
                 {
                     // FIXME: (async) gen closures aren't yet parsed.
                     this.parse_gen_block()
-                } else if this.check_keyword(kw::Async) {
+                } else if this.check_keyword(exp!(Async)) {
                     // FIXME(gen_blocks): Parse `gen async` and suggest swap
                     if this.is_gen_block(kw::Async, 0) {
                         // Check for `async {` and `async move {`,
@@ -1541,15 +1531,20 @@ impl<'a> Parser<'a> {
 
     fn parse_expr_tuple_parens(&mut self, restrictions: Restrictions) -> PResult<'a, P<Expr>> {
         let lo = self.token.span;
-        self.expect(&token::OpenDelim(Delimiter::Parenthesis))?;
+        self.expect(exp!(OpenParen))?;
         let (es, trailing_comma) = match self.parse_seq_to_end(
-            &token::CloseDelim(Delimiter::Parenthesis),
-            SeqSep::trailing_allowed(token::Comma),
+            exp!(CloseParen),
+            SeqSep::trailing_allowed(exp!(Comma)),
             |p| p.parse_expr_catch_underscore(restrictions.intersection(Restrictions::ALLOW_LET)),
         ) {
             Ok(x) => x,
             Err(err) => {
-                return Ok(self.recover_seq_parse_error(Delimiter::Parenthesis, lo, err));
+                return Ok(self.recover_seq_parse_error(
+                    exp!(OpenParen),
+                    exp!(CloseParen),
+                    lo,
+                    err,
+                ));
             }
         };
         let kind = if es.len() == 1 && matches!(trailing_comma, Trailing::No) {
@@ -1563,25 +1558,24 @@ impl<'a> Parser<'a> {
         self.maybe_recover_from_bad_qpath(expr)
     }
 
-    fn parse_expr_array_or_repeat(&mut self, close_delim: Delimiter) -> PResult<'a, P<Expr>> {
+    fn parse_expr_array_or_repeat(&mut self, close: ExpTokenPair<'_>) -> PResult<'a, P<Expr>> {
         let lo = self.token.span;
         self.bump(); // `[` or other open delim
 
-        let close = &token::CloseDelim(close_delim);
         let kind = if self.eat(close) {
             // Empty vector
             ExprKind::Array(ThinVec::new())
         } else {
             // Non-empty vector
             let first_expr = self.parse_expr()?;
-            if self.eat(&token::Semi) {
+            if self.eat(exp!(Semi)) {
                 // Repeating array syntax: `[ 0; 512 ]`
                 let count = self.parse_expr_anon_const()?;
                 self.expect(close)?;
                 ExprKind::Repeat(first_expr, count)
-            } else if self.eat(&token::Comma) {
+            } else if self.eat(exp!(Comma)) {
                 // Vector with two or more elements.
-                let sep = SeqSep::trailing_allowed(token::Comma);
+                let sep = SeqSep::trailing_allowed(exp!(Comma));
                 let (mut exprs, _) = self.parse_seq_to_end(close, sep, |p| p.parse_expr())?;
                 exprs.insert(0, first_expr);
                 ExprKind::Array(exprs)
@@ -1615,7 +1609,7 @@ impl<'a> Parser<'a> {
         };
 
         // `!`, as an operator, is prefix, so we know this isn't that.
-        let (span, kind) = if self.eat(&token::Not) {
+        let (span, kind) = if self.eat(exp!(Not)) {
             // MACRO INVOCATION expression
             if qself.is_some() {
                 self.dcx().emit_err(errors::MacroInvocationWithQualifiedPath(path.span));
@@ -1623,7 +1617,7 @@ impl<'a> Parser<'a> {
             let lo = path.span;
             let mac = P(MacCall { path, args: self.parse_delim_args()? });
             (lo.to(self.prev_token.span), ExprKind::MacCall(mac))
-        } else if self.check(&token::OpenDelim(Delimiter::Brace))
+        } else if self.check(exp!(OpenBrace))
             && let Some(expr) = self.maybe_parse_struct_expr(&qself, &path)
         {
             if qself.is_some() {
@@ -1646,13 +1640,13 @@ impl<'a> Parser<'a> {
     ) -> PResult<'a, P<Expr>> {
         let lo = label_.ident.span;
         let label = Some(label_);
-        let ate_colon = self.eat(&token::Colon);
+        let ate_colon = self.eat(exp!(Colon));
         let tok_sp = self.token.span;
-        let expr = if self.eat_keyword(kw::While) {
+        let expr = if self.eat_keyword(exp!(While)) {
             self.parse_expr_while(label, lo)
-        } else if self.eat_keyword(kw::For) {
+        } else if self.eat_keyword(exp!(For)) {
             self.parse_expr_for(label, lo)
-        } else if self.eat_keyword(kw::Loop) {
+        } else if self.eat_keyword(exp!(Loop)) {
             self.parse_expr_loop(label, lo)
         } else if self.check_noexpect(&token::OpenDelim(Delimiter::Brace))
             || self.token.is_whole_block()
@@ -1958,7 +1952,7 @@ impl<'a> Parser<'a> {
         self.psess.gated_spans.gate(sym::builtin_syntax, ident.span);
         self.bump();
 
-        self.expect(&TokenKind::OpenDelim(Delimiter::Parenthesis))?;
+        self.expect(exp!(OpenParen))?;
         let ret = if let Some(res) = parse(self, lo, ident)? {
             Ok(res)
         } else {
@@ -1968,7 +1962,7 @@ impl<'a> Parser<'a> {
             });
             return Err(err);
         };
-        self.expect(&TokenKind::CloseDelim(Delimiter::Parenthesis))?;
+        self.expect(exp!(CloseParen))?;
 
         ret
     }
@@ -1976,14 +1970,12 @@ impl<'a> Parser<'a> {
     /// Built-in macro for `offset_of!` expressions.
     pub(crate) fn parse_expr_offset_of(&mut self, lo: Span) -> PResult<'a, P<Expr>> {
         let container = self.parse_ty()?;
-        self.expect(&TokenKind::Comma)?;
+        self.expect(exp!(Comma))?;
 
         let fields = self.parse_floating_field_access()?;
         let trailing_comma = self.eat_noexpect(&TokenKind::Comma);
 
-        if let Err(mut e) =
-            self.expect_one_of(&[], &[TokenKind::CloseDelim(Delimiter::Parenthesis)])
-        {
+        if let Err(mut e) = self.expect_one_of(&[], &[exp!(CloseParen)]) {
             if trailing_comma {
                 e.note("unexpected third argument to offset_of");
             } else {
@@ -2006,7 +1998,7 @@ impl<'a> Parser<'a> {
     /// Built-in macro for type ascription expressions.
     pub(crate) fn parse_expr_type_ascribe(&mut self, lo: Span) -> PResult<'a, P<Expr>> {
         let expr = self.parse_expr()?;
-        self.expect(&token::Comma)?;
+        self.expect(exp!(Comma))?;
         let ty = self.parse_ty()?;
         let span = lo.to(self.token.span);
         Ok(self.mk_expr(span, ExprKind::Type(expr, ty)))
@@ -2018,7 +2010,7 @@ impl<'a> Parser<'a> {
         kind: UnsafeBinderCastKind,
     ) -> PResult<'a, P<Expr>> {
         let expr = self.parse_expr()?;
-        let ty = if self.eat(&TokenKind::Comma) { Some(self.parse_ty()?) } else { None };
+        let ty = if self.eat(exp!(Comma)) { Some(self.parse_ty()?) } else { None };
         let span = lo.to(self.token.span);
         Ok(self.mk_expr(span, ExprKind::UnsafeBinderCast(kind, expr, ty)))
     }
@@ -2214,7 +2206,7 @@ impl<'a> Parser<'a> {
         }
 
         let lo = self.token.span;
-        let minus_present = self.eat(&token::BinOp(token::Minus));
+        let minus_present = self.eat(exp!(Minus));
         let (token_lit, span) = self.parse_token_lit()?;
         let expr = self.mk_expr(span, ExprKind::Lit(token_lit));
 
@@ -2236,7 +2228,7 @@ impl<'a> Parser<'a> {
     /// expression.
     fn maybe_suggest_brackets_instead_of_braces(&mut self, lo: Span) -> Option<P<Expr>> {
         let mut snapshot = self.create_snapshot_for_diagnostic();
-        match snapshot.parse_expr_array_or_repeat(Delimiter::Brace) {
+        match snapshot.parse_expr_array_or_repeat(exp!(CloseBrace)) {
             Ok(arr) => {
                 let guar = self.dcx().emit_err(errors::ArrayBracketsInsteadOfSpaces {
                     span: arr.span,
@@ -2272,8 +2264,8 @@ impl<'a> Parser<'a> {
             let mut snapshot = self.create_snapshot_for_diagnostic();
             snapshot.bump();
             match snapshot.parse_seq_to_before_end(
-                &token::CloseDelim(Delimiter::Bracket),
-                SeqSep::trailing_allowed(token::Comma),
+                exp!(CloseBracket),
+                SeqSep::trailing_allowed(exp!(Comma)),
                 |p| p.parse_expr(),
             ) {
                 Ok(_)
@@ -2337,7 +2329,7 @@ impl<'a> Parser<'a> {
         let lo = self.token.span;
 
         let before = self.prev_token.clone();
-        let binder = if self.check_keyword(kw::For) {
+        let binder = if self.check_keyword(exp!(For)) {
             let lo = self.token.span;
             let (lifetime_defs, _) = self.parse_late_bound_lifetime_defs()?;
             let span = lo.to(self.prev_token.span);
@@ -2352,7 +2344,7 @@ impl<'a> Parser<'a> {
         let constness = self.parse_closure_constness();
 
         let movability =
-            if self.eat_keyword(kw::Static) { Movability::Static } else { Movability::Movable };
+            if self.eat_keyword(exp!(Static)) { Movability::Static } else { Movability::Movable };
 
         let coroutine_kind = if self.token.uninterpolated_span().at_least_rust_2018() {
             self.parse_coroutine_kind(Case::Sensitive)
@@ -2393,7 +2385,8 @@ impl<'a> Parser<'a> {
         }
 
         if self.token == TokenKind::Semi
-            && matches!(self.token_cursor.stack.last(), Some((.., Delimiter::Parenthesis)))
+            && let Some(last) = self.token_cursor.stack.last()
+            && let Some(TokenTree::Delimited(_, _, Delimiter::Parenthesis, _)) = last.curr()
             && self.may_recover()
         {
             // It is likely that the closure body is a block but where the
@@ -2432,10 +2425,10 @@ impl<'a> Parser<'a> {
 
     /// Parses an optional `move` prefix to a closure-like construct.
     fn parse_capture_clause(&mut self) -> PResult<'a, CaptureBy> {
-        if self.eat_keyword(kw::Move) {
+        if self.eat_keyword(exp!(Move)) {
             let move_kw_span = self.prev_token.span;
             // Check for `move async` and recover
-            if self.check_keyword(kw::Async) {
+            if self.check_keyword(exp!(Async)) {
                 let move_async_span = self.token.span.with_lo(self.prev_token.span.data().lo);
                 Err(self
                     .dcx()
@@ -2452,15 +2445,15 @@ impl<'a> Parser<'a> {
     fn parse_fn_block_decl(&mut self) -> PResult<'a, (P<FnDecl>, Span)> {
         let arg_start = self.token.span.lo();
 
-        let inputs = if self.eat(&token::OrOr) {
+        let inputs = if self.eat(exp!(OrOr)) {
             ThinVec::new()
         } else {
-            self.expect(&token::BinOp(token::Or))?;
+            self.expect(exp!(Or))?;
             let args = self
                 .parse_seq_to_before_tokens(
-                    &[&token::BinOp(token::Or)],
+                    &[exp!(Or)],
                     &[&token::OrOr],
-                    SeqSep::trailing_allowed(token::Comma),
+                    SeqSep::trailing_allowed(exp!(Comma)),
                     |p| p.parse_fn_block_param(),
                 )?
                 .0;
@@ -2480,7 +2473,7 @@ impl<'a> Parser<'a> {
         let attrs = self.parse_outer_attributes()?;
         self.collect_tokens(None, attrs, ForceCollect::No, |this, attrs| {
             let pat = this.parse_pat_no_top_alt(Some(Expected::ParameterName), None)?;
-            let ty = if this.eat(&token::Colon) {
+            let ty = if this.eat(exp!(Colon)) {
                 this.parse_ty()?
             } else {
                 this.mk_ty(pat.span, TyKind::Infer)
@@ -2565,7 +2558,7 @@ impl<'a> Parser<'a> {
         } else {
             let attrs = self.parse_outer_attributes()?; // For recovery.
             let maybe_fatarrow = self.token.clone();
-            let block = if self.check(&token::OpenDelim(Delimiter::Brace)) {
+            let block = if self.check(exp!(OpenBrace)) {
                 self.parse_block()?
             } else if let Some(block) = recover_block_from_condition(self) {
                 block
@@ -2608,7 +2601,7 @@ impl<'a> Parser<'a> {
             self.error_on_if_block_attrs(lo, false, block.span, attrs);
             block
         };
-        let els = if self.eat_keyword(kw::Else) { Some(self.parse_expr_else()?) } else { None };
+        let els = if self.eat_keyword(exp!(Else)) { Some(self.parse_expr_else()?) } else { None };
         Ok(self.mk_expr(lo.to(self.prev_token.span), ExprKind::If(cond, thn, els)))
     }
 
@@ -2661,7 +2654,7 @@ impl<'a> Parser<'a> {
             });
             self.bump();
         } else {
-            self.expect(&token::Eq)?;
+            self.expect(exp!(Eq))?;
         }
         let attrs = self.parse_outer_attributes()?;
         let (expr, _) =
@@ -2674,9 +2667,9 @@ impl<'a> Parser<'a> {
     fn parse_expr_else(&mut self) -> PResult<'a, P<Expr>> {
         let else_span = self.prev_token.span; // `else`
         let attrs = self.parse_outer_attributes()?; // For recovery.
-        let expr = if self.eat_keyword(kw::If) {
+        let expr = if self.eat_keyword(exp!(If)) {
             ensure_sufficient_stack(|| self.parse_expr_if())?
-        } else if self.check(&TokenKind::OpenDelim(Delimiter::Brace)) {
+        } else if self.check(exp!(OpenBrace)) {
             self.parse_simple_block()?
         } else {
             let snapshot = self.create_snapshot_for_diagnostic();
@@ -2718,7 +2711,7 @@ impl<'a> Parser<'a> {
                 //         while true {}
                 //     }
                 //     ^
-                    if self.check(&TokenKind::OpenDelim(Delimiter::Brace))
+                    if self.check(exp!(OpenBrace))
                         && (classify::expr_requires_semi_to_be_stmt(&cond)
                             || matches!(cond.kind, ExprKind::MacCall(..)))
                     =>
@@ -2804,7 +2797,7 @@ impl<'a> Parser<'a> {
             begin_paren,
         ) {
             (Ok(pat), _) => pat, // Happy path.
-            (Err(err), Some((start_span, left))) if self.eat_keyword(kw::In) => {
+            (Err(err), Some((start_span, left))) if self.eat_keyword(exp!(In)) => {
                 // We know for sure we have seen `for ($SOMETHING in`. In the happy path this would
                 // happen right before the return of this method.
                 let attrs = self.parse_outer_attributes()?;
@@ -2838,7 +2831,7 @@ impl<'a> Parser<'a> {
             }
             (Err(err), _) => return Err(err), // Some other error, bubble up.
         };
-        if !self.eat_keyword(kw::In) {
+        if !self.eat_keyword(exp!(In)) {
             self.error_missing_in_for_loop();
         }
         self.check_for_for_in_in_typo(self.prev_token.span);
@@ -2850,7 +2843,7 @@ impl<'a> Parser<'a> {
     /// Parses `for await? <src_pat> in <src_expr> <src_loop_block>` (`for` token already eaten).
     fn parse_expr_for(&mut self, opt_label: Option<Label>, lo: Span) -> PResult<'a, P<Expr>> {
         let is_await =
-            self.token.uninterpolated_span().at_least_rust_2018() && self.eat_keyword(kw::Await);
+            self.token.uninterpolated_span().at_least_rust_2018() && self.eat_keyword(exp!(Await));
 
         if is_await {
             self.psess.gated_spans.gate(sym::async_for_loop, self.prev_token.span);
@@ -2980,7 +2973,7 @@ impl<'a> Parser<'a> {
         scrutinee: P<Expr>,
         match_kind: MatchKind,
     ) -> PResult<'a, P<Expr>> {
-        if let Err(mut e) = self.expect(&token::OpenDelim(Delimiter::Brace)) {
+        if let Err(mut e) = self.expect(exp!(OpenBrace)) {
             if self.token == token::Semi {
                 e.span_suggestion_short(
                     match_span,
@@ -3120,7 +3113,7 @@ impl<'a> Parser<'a> {
 
             let span_before_body = this.prev_token.span;
             let arm_body;
-            let is_fat_arrow = this.check(&token::FatArrow);
+            let is_fat_arrow = this.check(exp!(FatArrow));
             let is_almost_fat_arrow = TokenKind::FatArrow
                 .similar_tokens()
                 .is_some_and(|similar_tokens| similar_tokens.contains(&this.token.kind));
@@ -3133,17 +3126,15 @@ impl<'a> Parser<'a> {
             let mut result = if armless {
                 // A pattern without a body, allowed for never patterns.
                 arm_body = None;
-                this.expect_one_of(&[token::Comma], &[token::CloseDelim(Delimiter::Brace)]).map(
-                    |x| {
-                        // Don't gate twice
-                        if !pat.contains_never_pattern() {
-                            this.psess.gated_spans.gate(sym::never_patterns, pat.span);
-                        }
-                        x
-                    },
-                )
+                this.expect_one_of(&[exp!(Comma)], &[exp!(CloseBrace)]).map(|x| {
+                    // Don't gate twice
+                    if !pat.contains_never_pattern() {
+                        this.psess.gated_spans.gate(sym::never_patterns, pat.span);
+                    }
+                    x
+                })
             } else {
-                if let Err(mut err) = this.expect(&token::FatArrow) {
+                if let Err(mut err) = this.expect(exp!(FatArrow)) {
                     // We might have a `=>` -> `=` or `->` typo (issue #89396).
                     if is_almost_fat_arrow {
                         err.span_suggestion(
@@ -3183,7 +3174,7 @@ impl<'a> Parser<'a> {
                 if !require_comma {
                     arm_body = Some(expr);
                     // Eat a comma if it exists, though.
-                    let _ = this.eat(&token::Comma);
+                    let _ = this.eat(exp!(Comma));
                     Ok(Recovered::No)
                 } else if let Some((span, guar)) =
                     this.parse_arm_body_missing_braces(&expr, arrow_span)
@@ -3194,42 +3185,40 @@ impl<'a> Parser<'a> {
                 } else {
                     let expr_span = expr.span;
                     arm_body = Some(expr);
-                    this.expect_one_of(&[token::Comma], &[token::CloseDelim(Delimiter::Brace)])
-                        .map_err(|mut err| {
-                            if this.token == token::FatArrow {
-                                let sm = this.psess.source_map();
-                                if let Ok(expr_lines) = sm.span_to_lines(expr_span)
-                                    && let Ok(arm_start_lines) = sm.span_to_lines(arm_start_span)
-                                    && arm_start_lines.lines[0].end_col
-                                        == expr_lines.lines[0].end_col
-                                    && expr_lines.lines.len() == 2
-                                {
-                                    // We check whether there's any trailing code in the parse span,
-                                    // if there isn't, we very likely have the following:
-                                    //
-                                    // X |     &Y => "y"
-                                    //   |        --    - missing comma
-                                    //   |        |
-                                    //   |        arrow_span
-                                    // X |     &X => "x"
-                                    //   |      - ^^ self.token.span
-                                    //   |      |
-                                    //   |      parsed until here as `"y" & X`
-                                    err.span_suggestion_short(
-                                        arm_start_span.shrink_to_hi(),
-                                        "missing a comma here to end this `match` arm",
-                                        ",",
-                                        Applicability::MachineApplicable,
-                                    );
-                                }
-                            } else {
-                                err.span_label(
-                                    arrow_span,
-                                    "while parsing the `match` arm starting here",
+                    this.expect_one_of(&[exp!(Comma)], &[exp!(CloseBrace)]).map_err(|mut err| {
+                        if this.token == token::FatArrow {
+                            let sm = this.psess.source_map();
+                            if let Ok(expr_lines) = sm.span_to_lines(expr_span)
+                                && let Ok(arm_start_lines) = sm.span_to_lines(arm_start_span)
+                                && arm_start_lines.lines[0].end_col == expr_lines.lines[0].end_col
+                                && expr_lines.lines.len() == 2
+                            {
+                                // We check whether there's any trailing code in the parse span,
+                                // if there isn't, we very likely have the following:
+                                //
+                                // X |     &Y => "y"
+                                //   |        --    - missing comma
+                                //   |        |
+                                //   |        arrow_span
+                                // X |     &X => "x"
+                                //   |      - ^^ self.token.span
+                                //   |      |
+                                //   |      parsed until here as `"y" & X`
+                                err.span_suggestion_short(
+                                    arm_start_span.shrink_to_hi(),
+                                    "missing a comma here to end this `match` arm",
+                                    ",",
+                                    Applicability::MachineApplicable,
                                 );
                             }
-                            err
-                        })
+                        } else {
+                            err.span_label(
+                                arrow_span,
+                                "while parsing the `match` arm starting here",
+                            );
+                        }
+                        err
+                    })
                 }
             };
 
@@ -3266,7 +3255,7 @@ impl<'a> Parser<'a> {
                         )
                         .map_err(|err| err.cancel())
                         .is_ok();
-                    if pattern_follows && snapshot.check(&TokenKind::FatArrow) {
+                    if pattern_follows && snapshot.check(exp!(FatArrow)) {
                         err.cancel();
                         let guar = this.dcx().emit_err(errors::MissingCommaAfterMatchArm {
                             span: arm_span.shrink_to_hi(),
@@ -3308,7 +3297,7 @@ impl<'a> Parser<'a> {
                 _ => (false, true),
             }
         }
-        if !self.eat_keyword(kw::If) {
+        if !self.eat_keyword(exp!(If)) {
             // No match arm guard present.
             return Ok(None);
         }
@@ -3383,7 +3372,7 @@ impl<'a> Parser<'a> {
                     // errors.
                     self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore);
                     let msg = "you might have meant to start a match arm after the match guard";
-                    if self.eat(&token::CloseDelim(Delimiter::Brace)) {
+                    if self.eat(exp!(CloseBrace)) {
                         let applicability = if self.token != token::FatArrow {
                             // We have high confidence that we indeed didn't have a struct
                             // literal in the match guard, but rather we had some operation
@@ -3408,7 +3397,7 @@ impl<'a> Parser<'a> {
     /// Parses a `try {...}` expression (`try` token already eaten).
     fn parse_try_block(&mut self, span_lo: Span) -> PResult<'a, P<Expr>> {
         let (attrs, body) = self.parse_inner_attrs_and_block()?;
-        if self.eat_keyword(kw::Catch) {
+        if self.eat_keyword(exp!(Catch)) {
             Err(self.dcx().create_err(errors::CatchAfterTry { span: self.prev_token.span }))
         } else {
             let span = span_lo.to(body.span);
@@ -3439,10 +3428,10 @@ impl<'a> Parser<'a> {
     /// Parses an `async move? {...}` or `gen move? {...}` expression.
     fn parse_gen_block(&mut self) -> PResult<'a, P<Expr>> {
         let lo = self.token.span;
-        let kind = if self.eat_keyword(kw::Async) {
-            if self.eat_keyword(kw::Gen) { GenBlockKind::AsyncGen } else { GenBlockKind::Async }
+        let kind = if self.eat_keyword(exp!(Async)) {
+            if self.eat_keyword(exp!(Gen)) { GenBlockKind::AsyncGen } else { GenBlockKind::Async }
         } else {
-            assert!(self.eat_keyword(kw::Gen));
+            assert!(self.eat_keyword(exp!(Gen)));
             GenBlockKind::Gen
         };
         match kind {
@@ -3503,7 +3492,7 @@ impl<'a> Parser<'a> {
     ) -> Option<PResult<'a, P<Expr>>> {
         let struct_allowed = !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
         if struct_allowed || self.is_certainly_not_a_block() {
-            if let Err(err) = self.expect(&token::OpenDelim(Delimiter::Brace)) {
+            if let Err(err) = self.expect(exp!(OpenBrace)) {
                 return Some(Err(err));
             }
             let expr = self.parse_expr_struct(qself.clone(), path.clone(), true);
@@ -3526,7 +3515,7 @@ impl<'a> Parser<'a> {
         &mut self,
         pth: ast::Path,
         recover: bool,
-        close_delim: Delimiter,
+        close: ExpTokenPair<'_>,
     ) -> PResult<
         'a,
         (
@@ -3545,11 +3534,11 @@ impl<'a> Parser<'a> {
             errors::HelpUseLatestEdition::new().add_to_diag(e);
         };
 
-        while self.token != token::CloseDelim(close_delim) {
-            if self.eat(&token::DotDot) || self.recover_struct_field_dots(close_delim) {
+        while self.token != *close.tok {
+            if self.eat(exp!(DotDot)) || self.recover_struct_field_dots(close.tok) {
                 let exp_span = self.prev_token.span;
                 // We permit `.. }` on the left-hand side of a destructuring assignment.
-                if self.check(&token::CloseDelim(close_delim)) {
+                if self.check(close) {
                     base = ast::StructRest::Rest(self.prev_token.span);
                     break;
                 }
@@ -3624,7 +3613,7 @@ impl<'a> Parser<'a> {
                             Applicability::MaybeIncorrect,
                         );
                     }
-                    if in_if_guard && close_delim == Delimiter::Brace {
+                    if in_if_guard && close.token_type == TokenType::CloseBrace {
                         return Err(e);
                     }
 
@@ -3654,9 +3643,9 @@ impl<'a> Parser<'a> {
             let is_shorthand = parsed_field.as_ref().is_ok_and(|f| f.is_shorthand);
             // A shorthand field can be turned into a full field with `:`.
             // We should point this out.
-            self.check_or_expected(!is_shorthand, TokenType::Token(token::Colon));
+            self.check_or_expected(!is_shorthand, TokenType::Colon);
 
-            match self.expect_one_of(&[token::Comma], &[token::CloseDelim(close_delim)]) {
+            match self.expect_one_of(&[exp!(Comma)], &[close]) {
                 Ok(_) => {
                     if let Ok(f) = parsed_field.or_else(|guar| field_ident(self, guar).ok_or(guar))
                     {
@@ -3688,7 +3677,7 @@ impl<'a> Parser<'a> {
                         fields.push(f);
                     }
                     self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
-                    let _ = self.eat(&token::Comma);
+                    let _ = self.eat(exp!(Comma));
                 }
             }
         }
@@ -3704,9 +3693,9 @@ impl<'a> Parser<'a> {
     ) -> PResult<'a, P<Expr>> {
         let lo = pth.span;
         let (fields, base, recovered_async) =
-            self.parse_struct_fields(pth.clone(), recover, Delimiter::Brace)?;
+            self.parse_struct_fields(pth.clone(), recover, exp!(CloseBrace))?;
         let span = lo.to(self.token.span);
-        self.expect(&token::CloseDelim(Delimiter::Brace))?;
+        self.expect(exp!(CloseBrace))?;
         let expr = if let Some(guar) = recovered_async {
             ExprKind::Err(guar)
         } else {
@@ -3726,10 +3715,8 @@ impl<'a> Parser<'a> {
         self.recover_stmt();
     }
 
-    fn recover_struct_field_dots(&mut self, close_delim: Delimiter) -> bool {
-        if !self.look_ahead(1, |t| *t == token::CloseDelim(close_delim))
-            && self.eat(&token::DotDotDot)
-        {
+    fn recover_struct_field_dots(&mut self, close: &TokenKind) -> bool {
+        if !self.look_ahead(1, |t| t == close) && self.eat(exp!(DotDotDot)) {
             // recover from typo of `...`, suggest `..`
             let span = self.prev_token.span;
             self.dcx().emit_err(errors::MissingDotDot { token_span: span, sugg_span: span });
diff --git a/compiler/rustc_parse/src/parser/generics.rs b/compiler/rustc_parse/src/parser/generics.rs
index 76ecb77d750..b1b84b0b701 100644
--- a/compiler/rustc_parse/src/parser/generics.rs
+++ b/compiler/rustc_parse/src/parser/generics.rs
@@ -4,8 +4,7 @@ use rustc_ast::{
     WhereClause, token,
 };
 use rustc_errors::{Applicability, PResult};
-use rustc_span::Span;
-use rustc_span::symbol::{Ident, kw};
+use rustc_span::{Ident, Span, kw};
 use thin_vec::ThinVec;
 
 use super::{ForceCollect, Parser, Trailing, UsePreAttrPos};
@@ -14,6 +13,7 @@ use crate::errors::{
     UnexpectedSelfInGenericParameters, WhereClauseBeforeTupleStructBody,
     WhereClauseBeforeTupleStructBodySugg,
 };
+use crate::exp;
 
 enum PredicateKindOrStructBody {
     PredicateKind(ast::WherePredicateKind),
@@ -53,7 +53,7 @@ impl<'a> Parser<'a> {
 
         // Parse optional colon and param bounds.
         let mut colon_span = None;
-        let bounds = if self.eat(&token::Colon) {
+        let bounds = if self.eat(exp!(Colon)) {
             colon_span = Some(self.prev_token.span);
             // recover from `impl Trait` in type param bound
             if self.token.is_keyword(kw::Impl) {
@@ -90,7 +90,7 @@ impl<'a> Parser<'a> {
             Vec::new()
         };
 
-        let default = if self.eat(&token::Eq) { Some(self.parse_ty()?) } else { None };
+        let default = if self.eat(exp!(Eq)) { Some(self.parse_ty()?) } else { None };
         Ok(GenericParam {
             ident,
             id: ast::DUMMY_NODE_ID,
@@ -108,13 +108,13 @@ impl<'a> Parser<'a> {
     ) -> PResult<'a, GenericParam> {
         let const_span = self.token.span;
 
-        self.expect_keyword(kw::Const)?;
+        self.expect_keyword(exp!(Const))?;
         let ident = self.parse_ident()?;
-        self.expect(&token::Colon)?;
+        self.expect(exp!(Colon))?;
         let ty = self.parse_ty()?;
 
         // Parse optional const generics default value.
-        let default = if self.eat(&token::Eq) { Some(self.parse_const_arg()?) } else { None };
+        let default = if self.eat(exp!(Eq)) { Some(self.parse_const_arg()?) } else { None };
 
         Ok(GenericParam {
             ident,
@@ -133,11 +133,11 @@ impl<'a> Parser<'a> {
         mistyped_const_ident: Ident,
     ) -> PResult<'a, GenericParam> {
         let ident = self.parse_ident()?;
-        self.expect(&token::Colon)?;
+        self.expect(exp!(Colon))?;
         let ty = self.parse_ty()?;
 
         // Parse optional const generics default value.
-        let default = if self.eat(&token::Eq) { Some(self.parse_const_arg()?) } else { None };
+        let default = if self.eat(exp!(Eq)) { Some(self.parse_const_arg()?) } else { None };
 
         self.dcx()
             .struct_span_err(
@@ -178,13 +178,13 @@ impl<'a> Parser<'a> {
                         .emit_err(UnexpectedSelfInGenericParameters { span: this.prev_token.span });
 
                     // Eat a trailing comma, if it exists.
-                    let _ = this.eat(&token::Comma);
+                    let _ = this.eat(exp!(Comma));
                 }
 
                 let param = if this.check_lifetime() {
                     let lifetime = this.expect_lifetime();
                     // Parse lifetime parameter.
-                    let (colon_span, bounds) = if this.eat(&token::Colon) {
+                    let (colon_span, bounds) = if this.eat(exp!(Colon)) {
                         (Some(this.prev_token.span), this.parse_lt_param_bounds())
                     } else {
                         (None, Vec::new())
@@ -210,7 +210,7 @@ impl<'a> Parser<'a> {
                         is_placeholder: false,
                         colon_span,
                     })
-                } else if this.check_keyword(kw::Const) {
+                } else if this.check_keyword(exp!(Const)) {
                     // Parse const parameter.
                     Some(this.parse_const_param(attrs)?)
                 } else if this.check_ident() {
@@ -247,7 +247,7 @@ impl<'a> Parser<'a> {
                     return Ok((None, Trailing::No, UsePreAttrPos::No));
                 };
 
-                if !this.eat(&token::Comma) {
+                if !this.eat(exp!(Comma)) {
                     done = true;
                 }
                 // We just ate the comma, so no need to capture the trailing token.
@@ -325,7 +325,7 @@ impl<'a> Parser<'a> {
         };
         let mut tuple_struct_body = None;
 
-        if !self.eat_keyword(kw::Where) {
+        if !self.eat_keyword(exp!(Where)) {
             return Ok((where_clause, None));
         }
         where_clause.has_where_token = true;
@@ -345,7 +345,7 @@ impl<'a> Parser<'a> {
             let kind = if self.check_lifetime() && self.look_ahead(1, |t| !t.is_like_plus()) {
                 let lifetime = self.expect_lifetime();
                 // Bounds starting with a colon are mandatory, but possibly empty.
-                self.expect(&token::Colon)?;
+                self.expect(exp!(Colon))?;
                 let bounds = self.parse_lt_param_bounds();
                 ast::WherePredicateKind::RegionPredicate(ast::WhereRegionPredicate {
                     lifetime,
@@ -371,7 +371,7 @@ impl<'a> Parser<'a> {
             });
 
             let prev_token = self.prev_token.span;
-            let ate_comma = self.eat(&token::Comma);
+            let ate_comma = self.eat(exp!(Comma));
 
             if self.eat_keyword_noexpect(kw::Where) {
                 self.dcx().emit_err(MultipleWhereClauses {
@@ -465,7 +465,7 @@ impl<'a> Parser<'a> {
         // Parse type with mandatory colon and (possibly empty) bounds,
         // or with mandatory equality sign and the second type.
         let ty = self.parse_ty_for_where_clause()?;
-        if self.eat(&token::Colon) {
+        if self.eat(exp!(Colon)) {
             let bounds = self.parse_generic_bounds()?;
             Ok(ast::WherePredicateKind::BoundPredicate(ast::WhereBoundPredicate {
                 bound_generic_params: lifetime_defs,
@@ -474,7 +474,7 @@ impl<'a> Parser<'a> {
             }))
         // FIXME: Decide what should be used here, `=` or `==`.
         // FIXME: We are just dropping the binders in lifetime_defs on the floor here.
-        } else if self.eat(&token::Eq) || self.eat(&token::EqEq) {
+        } else if self.eat(exp!(Eq)) || self.eat(exp!(EqEq)) {
             let rhs_ty = self.parse_ty()?;
             Ok(ast::WherePredicateKind::EqPredicate(ast::WhereEqPredicate { lhs_ty: ty, rhs_ty }))
         } else {
diff --git a/compiler/rustc_parse/src/parser/item.rs b/compiler/rustc_parse/src/parser/item.rs
index e27fc963eb9..f3e56be9f6e 100644
--- a/compiler/rustc_parse/src/parser/item.rs
+++ b/compiler/rustc_parse/src/parser/item.rs
@@ -13,37 +13,36 @@ use rustc_errors::codes::*;
 use rustc_errors::{Applicability, PResult, StashKey, struct_span_code_err};
 use rustc_span::edit_distance::edit_distance;
 use rustc_span::edition::Edition;
-use rustc_span::symbol::{Ident, Symbol, kw, sym};
-use rustc_span::{DUMMY_SP, ErrorGuaranteed, Span, source_map};
+use rustc_span::{DUMMY_SP, ErrorGuaranteed, Ident, Span, Symbol, kw, source_map, sym};
 use thin_vec::{ThinVec, thin_vec};
 use tracing::debug;
 
 use super::diagnostics::{ConsumeClosingDelim, dummy_arg};
 use super::ty::{AllowPlus, RecoverQPath, RecoverReturnSign};
 use super::{
-    AttrWrapper, FollowedByType, ForceCollect, Parser, PathStyle, Trailing, UsePreAttrPos,
+    AttrWrapper, ExpKeywordPair, ExpTokenPair, FollowedByType, ForceCollect, Parser, PathStyle,
+    Trailing, UsePreAttrPos,
 };
 use crate::errors::{self, MacroExpandsToAdtField};
-use crate::{fluent_generated as fluent, maybe_whole};
+use crate::{exp, fluent_generated as fluent, maybe_whole};
 
 impl<'a> Parser<'a> {
     /// Parses a source module as a crate. This is the main entry point for the parser.
     pub fn parse_crate_mod(&mut self) -> PResult<'a, ast::Crate> {
-        let (attrs, items, spans) = self.parse_mod(&token::Eof)?;
+        let (attrs, items, spans) = self.parse_mod(exp!(Eof))?;
         Ok(ast::Crate { attrs, items, spans, id: DUMMY_NODE_ID, is_placeholder: false })
     }
 
     /// Parses a `mod <foo> { ... }` or `mod <foo>;` item.
     fn parse_item_mod(&mut self, attrs: &mut AttrVec) -> PResult<'a, ItemInfo> {
         let safety = self.parse_safety(Case::Sensitive);
-        self.expect_keyword(kw::Mod)?;
+        self.expect_keyword(exp!(Mod))?;
         let id = self.parse_ident()?;
-        let mod_kind = if self.eat(&token::Semi) {
+        let mod_kind = if self.eat(exp!(Semi)) {
             ModKind::Unloaded
         } else {
-            self.expect(&token::OpenDelim(Delimiter::Brace))?;
-            let (inner_attrs, items, inner_span) =
-                self.parse_mod(&token::CloseDelim(Delimiter::Brace))?;
+            self.expect(exp!(OpenBrace))?;
+            let (inner_attrs, items, inner_span) = self.parse_mod(exp!(CloseBrace))?;
             attrs.extend(inner_attrs);
             ModKind::Loaded(items, Inline::Yes, inner_span, Ok(()))
         };
@@ -56,7 +55,7 @@ impl<'a> Parser<'a> {
     /// - `}` for mod items
     pub fn parse_mod(
         &mut self,
-        term: &TokenKind,
+        term: ExpTokenPair<'_>,
     ) -> PResult<'a, (AttrVec, ThinVec<P<Item>>, ModSpans)> {
         let lo = self.token.span;
         let attrs = self.parse_inner_attributes()?;
@@ -210,15 +209,15 @@ impl<'a> Parser<'a> {
         let check_pub = def == &Defaultness::Final;
         let mut def_ = || mem::replace(def, Defaultness::Final);
 
-        let info = if self.eat_keyword_case(kw::Use, case) {
+        let info = if self.eat_keyword_case(exp!(Use), case) {
             self.parse_use_item()?
         } else if self.check_fn_front_matter(check_pub, case) {
             // FUNCTION ITEM
             let (ident, sig, generics, body) =
                 self.parse_fn(attrs, fn_parse_mode, lo, vis, case)?;
             (ident, ItemKind::Fn(Box::new(Fn { defaultness: def_(), sig, generics, body })))
-        } else if self.eat_keyword(kw::Extern) {
-            if self.eat_keyword(kw::Crate) {
+        } else if self.eat_keyword(exp!(Extern)) {
+            if self.eat_keyword(exp!(Crate)) {
                 // EXTERN CRATE
                 self.parse_item_extern_crate()?
             } else {
@@ -228,7 +227,7 @@ impl<'a> Parser<'a> {
         } else if self.is_unsafe_foreign_mod() {
             // EXTERN BLOCK
             let safety = self.parse_safety(Case::Sensitive);
-            self.expect_keyword(kw::Extern)?;
+            self.expect_keyword(exp!(Extern))?;
             self.parse_item_foreign_mod(attrs, safety)?
         } else if self.is_static_global() {
             let safety = self.parse_safety(Case::Sensitive);
@@ -256,28 +255,28 @@ impl<'a> Parser<'a> {
                     })),
                 )
             }
-        } else if self.check_keyword(kw::Trait) || self.check_auto_or_unsafe_trait_item() {
+        } else if self.check_keyword(exp!(Trait)) || self.check_auto_or_unsafe_trait_item() {
             // TRAIT ITEM
             self.parse_item_trait(attrs, lo)?
-        } else if self.check_keyword(kw::Impl)
-            || self.check_keyword(kw::Unsafe) && self.is_keyword_ahead(1, &[kw::Impl])
+        } else if self.check_keyword(exp!(Impl))
+            || self.check_keyword(exp!(Unsafe)) && self.is_keyword_ahead(1, &[kw::Impl])
         {
             // IMPL ITEM
             self.parse_item_impl(attrs, def_())?
         } else if self.is_reuse_path_item() {
             self.parse_item_delegation()?
-        } else if self.check_keyword(kw::Mod)
-            || self.check_keyword(kw::Unsafe) && self.is_keyword_ahead(1, &[kw::Mod])
+        } else if self.check_keyword(exp!(Mod))
+            || self.check_keyword(exp!(Unsafe)) && self.is_keyword_ahead(1, &[kw::Mod])
         {
             // MODULE ITEM
             self.parse_item_mod(attrs)?
-        } else if self.eat_keyword(kw::Type) {
+        } else if self.eat_keyword(exp!(Type)) {
             // TYPE ITEM
             self.parse_type_alias(def_())?
-        } else if self.eat_keyword(kw::Enum) {
+        } else if self.eat_keyword(exp!(Enum)) {
             // ENUM ITEM
             self.parse_item_enum()?
-        } else if self.eat_keyword(kw::Struct) {
+        } else if self.eat_keyword(exp!(Struct)) {
             // STRUCT ITEM
             self.parse_item_struct()?
         } else if self.is_kw_followed_by_ident(kw::Union) {
@@ -287,7 +286,7 @@ impl<'a> Parser<'a> {
         } else if self.is_builtin() {
             // BUILTIN# ITEM
             return self.parse_item_builtin();
-        } else if self.eat_keyword(kw::Macro) {
+        } else if self.eat_keyword(exp!(Macro)) {
             // MACROS 2.0 ITEM
             self.parse_item_decl_macro(lo)?
         } else if let IsMacroRulesItem::Yes { has_bang } = self.is_macro_rules_item() {
@@ -408,13 +407,13 @@ impl<'a> Parser<'a> {
         };
 
         let mut found_generics = false;
-        if self.check(&token::Lt) {
+        if self.check(exp!(Lt)) {
             found_generics = true;
-            self.eat_to_tokens(&[&token::Gt]);
+            self.eat_to_tokens(&[exp!(Gt)]);
             self.bump(); // `>`
         }
 
-        let err = if self.check(&token::OpenDelim(Delimiter::Brace)) {
+        let err = if self.check(exp!(OpenBrace)) {
             // possible struct or enum definition where `struct` or `enum` was forgotten
             if self.look_ahead(1, |t| *t == token::CloseDelim(Delimiter::Brace)) {
                 // `S {}` could be unit enum or struct
@@ -427,25 +426,23 @@ impl<'a> Parser<'a> {
             } else {
                 Some(errors::MissingKeywordForItemDefinition::Enum { span, insert_span, ident })
             }
-        } else if self.check(&token::OpenDelim(Delimiter::Parenthesis)) {
+        } else if self.check(exp!(OpenParen)) {
             // possible function or tuple struct definition where `fn` or `struct` was forgotten
             self.bump(); // `(`
             let is_method = self.recover_self_param();
 
-            self.consume_block(Delimiter::Parenthesis, ConsumeClosingDelim::Yes);
+            self.consume_block(exp!(OpenParen), exp!(CloseParen), ConsumeClosingDelim::Yes);
 
-            let err = if self.check(&token::RArrow)
-                || self.check(&token::OpenDelim(Delimiter::Brace))
-            {
-                self.eat_to_tokens(&[&token::OpenDelim(Delimiter::Brace)]);
+            let err = if self.check(exp!(RArrow)) || self.check(exp!(OpenBrace)) {
+                self.eat_to_tokens(&[exp!(OpenBrace)]);
                 self.bump(); // `{`
-                self.consume_block(Delimiter::Brace, ConsumeClosingDelim::Yes);
+                self.consume_block(exp!(OpenBrace), exp!(CloseBrace), ConsumeClosingDelim::Yes);
                 if is_method {
                     errors::MissingKeywordForItemDefinition::Method { span, insert_span, ident }
                 } else {
                     errors::MissingKeywordForItemDefinition::Function { span, insert_span, ident }
                 }
-            } else if is_pub && self.check(&token::Semi) {
+            } else if is_pub && self.check(exp!(Semi)) {
                 errors::MissingKeywordForItemDefinition::Struct { span, insert_span, ident }
             } else {
                 errors::MissingKeywordForItemDefinition::Ambiguous {
@@ -480,7 +477,7 @@ impl<'a> Parser<'a> {
     /// Parses an item macro, e.g., `item!();`.
     fn parse_item_macro(&mut self, vis: &Visibility) -> PResult<'a, MacCall> {
         let path = self.parse_path(PathStyle::Mod)?; // `foo::bar`
-        self.expect(&token::Not)?; // `!`
+        self.expect(exp!(Not))?; // `!`
         match self.parse_delim_args() {
             // `( .. )` or `[ .. ]` (followed by `;`), or `{ .. }`.
             Ok(args) => {
@@ -540,7 +537,7 @@ impl<'a> Parser<'a> {
 
     fn parse_polarity(&mut self) -> ast::ImplPolarity {
         // Disambiguate `impl !Trait for Type { ... }` and `impl ! { ... }` for the never type.
-        if self.check(&token::Not) && self.look_ahead(1, |t| t.can_begin_type()) {
+        if self.check(exp!(Not)) && self.look_ahead(1, |t| t.can_begin_type()) {
             self.bump(); // `!`
             ast::ImplPolarity::Negative(self.prev_token.span)
         } else {
@@ -568,7 +565,7 @@ impl<'a> Parser<'a> {
         defaultness: Defaultness,
     ) -> PResult<'a, ItemInfo> {
         let safety = self.parse_safety(Case::Sensitive);
-        self.expect_keyword(kw::Impl)?;
+        self.expect_keyword(exp!(Impl))?;
 
         // First, parse generic parameters if necessary.
         let mut generics = if self.choose_generics_over_qpath(0) {
@@ -618,7 +615,7 @@ impl<'a> Parser<'a> {
         };
 
         // If `for` is missing we try to recover.
-        let has_for = self.eat_keyword(kw::For);
+        let has_for = self.eat_keyword(exp!(For));
         let missing_for_span = self.prev_token.span.between(self.token.span);
 
         let ty_second = if self.token == token::DotDot {
@@ -703,7 +700,7 @@ impl<'a> Parser<'a> {
 
     fn parse_item_delegation(&mut self) -> PResult<'a, ItemInfo> {
         let span = self.token.span;
-        self.expect_keyword(kw::Reuse)?;
+        self.expect_keyword(exp!(Reuse))?;
 
         let (qself, path) = if self.eat_lt() {
             let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
@@ -713,23 +710,23 @@ impl<'a> Parser<'a> {
         };
 
         let rename = |this: &mut Self| {
-            Ok(if this.eat_keyword(kw::As) { Some(this.parse_ident()?) } else { None })
+            Ok(if this.eat_keyword(exp!(As)) { Some(this.parse_ident()?) } else { None })
         };
         let body = |this: &mut Self| {
-            Ok(if this.check(&token::OpenDelim(Delimiter::Brace)) {
+            Ok(if this.check(exp!(OpenBrace)) {
                 Some(this.parse_block()?)
             } else {
-                this.expect(&token::Semi)?;
+                this.expect(exp!(Semi))?;
                 None
             })
         };
 
         let (ident, item_kind) = if self.eat_path_sep() {
-            let suffixes = if self.eat(&token::BinOp(token::Star)) {
+            let suffixes = if self.eat(exp!(Star)) {
                 None
             } else {
                 let parse_suffix = |p: &mut Self| Ok((p.parse_path_segment_ident()?, rename(p)?));
-                Some(self.parse_delim_comma_seq(Delimiter::Brace, parse_suffix)?.0)
+                Some(self.parse_delim_comma_seq(exp!(OpenBrace), exp!(CloseBrace), parse_suffix)?.0)
             };
             let deleg = DelegationMac { qself, prefix: path, suffixes, body: body(self)? };
             (Ident::empty(), ItemKind::DelegationMac(Box::new(deleg)))
@@ -767,11 +764,11 @@ impl<'a> Parser<'a> {
             return Ok(ThinVec::new());
         }
 
-        self.expect(&token::OpenDelim(Delimiter::Brace))?;
+        self.expect(exp!(OpenBrace))?;
         attrs.extend(self.parse_inner_attributes()?);
 
         let mut items = ThinVec::new();
-        while !self.eat(&token::CloseDelim(Delimiter::Brace)) {
+        while !self.eat(exp!(CloseBrace)) {
             if self.recover_doc_comment_before_brace() {
                 continue;
             }
@@ -812,7 +809,7 @@ impl<'a> Parser<'a> {
 
                     let mut err =
                         self.dcx().struct_span_err(non_item_span, "non-item in item list");
-                    self.consume_block(Delimiter::Brace, ConsumeClosingDelim::Yes);
+                    self.consume_block(exp!(OpenBrace), exp!(CloseBrace), ConsumeClosingDelim::Yes);
                     if is_let {
                         err.span_suggestion_verbose(
                             non_item_span,
@@ -838,7 +835,7 @@ impl<'a> Parser<'a> {
                 }
                 Ok(Some(item)) => items.extend(item),
                 Err(err) => {
-                    self.consume_block(Delimiter::Brace, ConsumeClosingDelim::Yes);
+                    self.consume_block(exp!(OpenBrace), exp!(CloseBrace), ConsumeClosingDelim::Yes);
                     err.with_span_label(
                         open_brace_span,
                         "while parsing this item list starting here",
@@ -881,7 +878,7 @@ impl<'a> Parser<'a> {
         // We are interested in `default` followed by another identifier.
         // However, we must avoid keywords that occur as binary operators.
         // Currently, the only applicable keyword is `as` (`default as Ty`).
-        if self.check_keyword(kw::Default)
+        if self.check_keyword(exp!(Default))
             && self.look_ahead(1, |t| t.is_non_raw_ident_where(|i| i.name != kw::As))
         {
             self.bump(); // `default`
@@ -894,33 +891,33 @@ impl<'a> Parser<'a> {
     /// Is this an `(unsafe auto? | auto) trait` item?
     fn check_auto_or_unsafe_trait_item(&mut self) -> bool {
         // auto trait
-        self.check_keyword(kw::Auto) && self.is_keyword_ahead(1, &[kw::Trait])
+        self.check_keyword(exp!(Auto)) && self.is_keyword_ahead(1, &[kw::Trait])
             // unsafe auto trait
-            || self.check_keyword(kw::Unsafe) && self.is_keyword_ahead(1, &[kw::Trait, kw::Auto])
+            || self.check_keyword(exp!(Unsafe)) && self.is_keyword_ahead(1, &[kw::Trait, kw::Auto])
     }
 
     /// Parses `unsafe? auto? trait Foo { ... }` or `trait Foo = Bar;`.
     fn parse_item_trait(&mut self, attrs: &mut AttrVec, lo: Span) -> PResult<'a, ItemInfo> {
         let safety = self.parse_safety(Case::Sensitive);
         // Parse optional `auto` prefix.
-        let is_auto = if self.eat_keyword(kw::Auto) {
+        let is_auto = if self.eat_keyword(exp!(Auto)) {
             self.psess.gated_spans.gate(sym::auto_traits, self.prev_token.span);
             IsAuto::Yes
         } else {
             IsAuto::No
         };
 
-        self.expect_keyword(kw::Trait)?;
+        self.expect_keyword(exp!(Trait))?;
         let ident = self.parse_ident()?;
         let mut generics = self.parse_generics()?;
 
         // Parse optional colon and supertrait bounds.
-        let had_colon = self.eat(&token::Colon);
+        let had_colon = self.eat(exp!(Colon));
         let span_at_colon = self.prev_token.span;
         let bounds = if had_colon { self.parse_generic_bounds()? } else { Vec::new() };
 
         let span_before_eq = self.prev_token.span;
-        if self.eat(&token::Eq) {
+        if self.eat(exp!(Eq)) {
             // It's a trait alias.
             if had_colon {
                 let span = span_at_colon.to(span_before_eq);
@@ -1008,11 +1005,10 @@ impl<'a> Parser<'a> {
         let mut generics = self.parse_generics()?;
 
         // Parse optional colon and param bounds.
-        let bounds =
-            if self.eat(&token::Colon) { self.parse_generic_bounds()? } else { Vec::new() };
+        let bounds = if self.eat(exp!(Colon)) { self.parse_generic_bounds()? } else { Vec::new() };
         let before_where_clause = self.parse_where_clause()?;
 
-        let ty = if self.eat(&token::Eq) { Some(self.parse_ty()?) } else { None };
+        let ty = if self.eat(exp!(Eq)) { Some(self.parse_ty()?) } else { None };
 
         let after_where_clause = self.parse_where_clause()?;
 
@@ -1065,46 +1061,44 @@ impl<'a> Parser<'a> {
 
         let mut prefix =
             ast::Path { segments: ThinVec::new(), span: lo.shrink_to_lo(), tokens: None };
-        let kind = if self.check(&token::OpenDelim(Delimiter::Brace))
-            || self.check(&token::BinOp(token::Star))
-            || self.is_import_coupler()
-        {
-            // `use *;` or `use ::*;` or `use {...};` or `use ::{...};`
-            let mod_sep_ctxt = self.token.span.ctxt();
-            if self.eat_path_sep() {
-                prefix
-                    .segments
-                    .push(PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt)));
-            }
-
-            self.parse_use_tree_glob_or_nested()?
-        } else {
-            // `use path::*;` or `use path::{...};` or `use path;` or `use path as bar;`
-            prefix = self.parse_path(PathStyle::Mod)?;
+        let kind =
+            if self.check(exp!(OpenBrace)) || self.check(exp!(Star)) || self.is_import_coupler() {
+                // `use *;` or `use ::*;` or `use {...};` or `use ::{...};`
+                let mod_sep_ctxt = self.token.span.ctxt();
+                if self.eat_path_sep() {
+                    prefix
+                        .segments
+                        .push(PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt)));
+                }
 
-            if self.eat_path_sep() {
                 self.parse_use_tree_glob_or_nested()?
             } else {
-                // Recover from using a colon as path separator.
-                while self.eat_noexpect(&token::Colon) {
-                    self.dcx()
-                        .emit_err(errors::SingleColonImportPath { span: self.prev_token.span });
-
-                    // We parse the rest of the path and append it to the original prefix.
-                    self.parse_path_segments(&mut prefix.segments, PathStyle::Mod, None)?;
-                    prefix.span = lo.to(self.prev_token.span);
-                }
+                // `use path::*;` or `use path::{...};` or `use path;` or `use path as bar;`
+                prefix = self.parse_path(PathStyle::Mod)?;
 
-                UseTreeKind::Simple(self.parse_rename()?)
-            }
-        };
+                if self.eat_path_sep() {
+                    self.parse_use_tree_glob_or_nested()?
+                } else {
+                    // Recover from using a colon as path separator.
+                    while self.eat_noexpect(&token::Colon) {
+                        self.dcx()
+                            .emit_err(errors::SingleColonImportPath { span: self.prev_token.span });
+
+                        // We parse the rest of the path and append it to the original prefix.
+                        self.parse_path_segments(&mut prefix.segments, PathStyle::Mod, None)?;
+                        prefix.span = lo.to(self.prev_token.span);
+                    }
+
+                    UseTreeKind::Simple(self.parse_rename()?)
+                }
+            };
 
         Ok(UseTree { prefix, kind, span: lo.to(self.prev_token.span) })
     }
 
     /// Parses `*` or `{...}`.
     fn parse_use_tree_glob_or_nested(&mut self) -> PResult<'a, UseTreeKind> {
-        Ok(if self.eat(&token::BinOp(token::Star)) {
+        Ok(if self.eat(exp!(Star)) {
             UseTreeKind::Glob
         } else {
             let lo = self.token.span;
@@ -1121,7 +1115,7 @@ impl<'a> Parser<'a> {
     /// USE_TREE_LIST = ∅ | (USE_TREE `,`)* USE_TREE [`,`]
     /// ```
     fn parse_use_tree_list(&mut self) -> PResult<'a, ThinVec<(UseTree, ast::NodeId)>> {
-        self.parse_delim_comma_seq(Delimiter::Brace, |p| {
+        self.parse_delim_comma_seq(exp!(OpenBrace), exp!(CloseBrace), |p| {
             p.recover_vcs_conflict_marker();
             Ok((p.parse_use_tree()?, DUMMY_NODE_ID))
         })
@@ -1129,7 +1123,11 @@ impl<'a> Parser<'a> {
     }
 
     fn parse_rename(&mut self) -> PResult<'a, Option<Ident>> {
-        if self.eat_keyword(kw::As) { self.parse_ident_or_underscore().map(Some) } else { Ok(None) }
+        if self.eat_keyword(exp!(As)) {
+            self.parse_ident_or_underscore().map(Some)
+        } else {
+            Ok(None)
+        }
     }
 
     fn parse_ident_or_underscore(&mut self) -> PResult<'a, Ident> {
@@ -1169,15 +1167,15 @@ impl<'a> Parser<'a> {
             self.parse_ident()
         }?;
 
-        let dash = token::BinOp(token::BinOpToken::Minus);
-        if self.token != dash {
+        let dash = exp!(Minus);
+        if self.token != *dash.tok {
             return Ok(ident);
         }
 
         // Accept `extern crate name-like-this` for better diagnostics.
         let mut dashes = vec![];
         let mut idents = vec![];
-        while self.eat(&dash) {
+        while self.eat(dash) {
             dashes.push(self.prev_token.span);
             idents.push(self.parse_ident()?);
         }
@@ -1218,9 +1216,9 @@ impl<'a> Parser<'a> {
             && self.token.is_keyword(kw::Unsafe)
             && self.look_ahead(1, |t| *t == token::OpenDelim(Delimiter::Brace))
         {
-            self.expect(&token::OpenDelim(Delimiter::Brace)).unwrap_err().emit();
+            self.expect(exp!(OpenBrace)).unwrap_err().emit();
             safety = Safety::Unsafe(self.token.span);
-            let _ = self.eat_keyword(kw::Unsafe);
+            let _ = self.eat_keyword(exp!(Unsafe));
         }
         let module = ast::ForeignMod {
             extern_span,
@@ -1286,7 +1284,7 @@ impl<'a> Parser<'a> {
     }
 
     fn is_static_global(&mut self) -> bool {
-        if self.check_keyword(kw::Static) {
+        if self.check_keyword(exp!(Static)) {
             // Check if this could be a closure.
             !self.look_ahead(1, |token| {
                 if token.is_keyword(kw::Move) {
@@ -1295,20 +1293,19 @@ impl<'a> Parser<'a> {
                 matches!(token.kind, token::BinOp(token::Or) | token::OrOr)
             })
         } else {
-            let quals: &[Symbol] = &[kw::Unsafe, kw::Safe];
             // `$qual static`
-            quals.iter().any(|&kw| self.check_keyword(kw))
+            (self.check_keyword(exp!(Unsafe)) || self.check_keyword(exp!(Safe)))
                 && self.look_ahead(1, |t| t.is_keyword(kw::Static))
         }
     }
 
     /// Recover on `const mut` with `const` already eaten.
     fn recover_const_mut(&mut self, const_span: Span) {
-        if self.eat_keyword(kw::Mut) {
+        if self.eat_keyword(exp!(Mut)) {
             let span = self.prev_token.span;
             self.dcx()
                 .emit_err(errors::ConstGlobalCannotBeMutable { ident_span: span, const_span });
-        } else if self.eat_keyword(kw::Let) {
+        } else if self.eat_keyword(exp!(Let)) {
             let span = self.prev_token.span;
             self.dcx().emit_err(errors::ConstLetMutuallyExclusive { span: const_span.to(span) });
         }
@@ -1373,14 +1370,13 @@ impl<'a> Parser<'a> {
 
         // Parse the type of a static item. That is, the `":" $ty` fragment.
         // FIXME: This could maybe benefit from `.may_recover()`?
-        let ty = match (self.eat(&token::Colon), self.check(&token::Eq) | self.check(&token::Semi))
-        {
+        let ty = match (self.eat(exp!(Colon)), self.check(exp!(Eq)) | self.check(exp!(Semi))) {
             (true, false) => self.parse_ty()?,
             // If there wasn't a `:` or the colon was followed by a `=` or `;`, recover a missing type.
             (colon, _) => self.recover_missing_global_item_type(colon, Some(mutability)),
         };
 
-        let expr = if self.eat(&token::Eq) { Some(self.parse_expr()?) } else { None };
+        let expr = if self.eat(exp!(Eq)) { Some(self.parse_expr()?) } else { None };
 
         self.expect_semi()?;
 
@@ -1406,8 +1402,8 @@ impl<'a> Parser<'a> {
         // Parse the type of a constant item. That is, the `":" $ty` fragment.
         // FIXME: This could maybe benefit from `.may_recover()`?
         let ty = match (
-            self.eat(&token::Colon),
-            self.check(&token::Eq) | self.check(&token::Semi) | self.check_keyword(kw::Where),
+            self.eat(exp!(Colon)),
+            self.check(exp!(Eq)) | self.check(exp!(Semi)) | self.check_keyword(exp!(Where)),
         ) {
             (true, false) => self.parse_ty()?,
             // If there wasn't a `:` or the colon was followed by a `=`, `;` or `where`, recover a missing type.
@@ -1419,7 +1415,7 @@ impl<'a> Parser<'a> {
         let before_where_clause =
             if self.may_recover() { self.parse_where_clause()? } else { WhereClause::default() };
 
-        let expr = if self.eat(&token::Eq) { Some(self.parse_expr()?) } else { None };
+        let expr = if self.eat(exp!(Eq)) { Some(self.parse_expr()?) } else { None };
 
         let after_where_clause = self.parse_where_clause()?;
 
@@ -1532,31 +1528,33 @@ impl<'a> Parser<'a> {
             self.bump();
             (thin_vec![], Trailing::No)
         } else {
-            self.parse_delim_comma_seq(Delimiter::Brace, |p| p.parse_enum_variant(id.span))
-                .map_err(|mut err| {
-                    err.span_label(id.span, "while parsing this enum");
-                    if self.token == token::Colon {
-                        let snapshot = self.create_snapshot_for_diagnostic();
-                        self.bump();
-                        match self.parse_ty() {
-                            Ok(_) => {
-                                err.span_suggestion_verbose(
-                                    prev_span,
-                                    "perhaps you meant to use `struct` here",
-                                    "struct",
-                                    Applicability::MaybeIncorrect,
-                                );
-                            }
-                            Err(e) => {
-                                e.cancel();
-                            }
+            self.parse_delim_comma_seq(exp!(OpenBrace), exp!(CloseBrace), |p| {
+                p.parse_enum_variant(id.span)
+            })
+            .map_err(|mut err| {
+                err.span_label(id.span, "while parsing this enum");
+                if self.token == token::Colon {
+                    let snapshot = self.create_snapshot_for_diagnostic();
+                    self.bump();
+                    match self.parse_ty() {
+                        Ok(_) => {
+                            err.span_suggestion_verbose(
+                                prev_span,
+                                "perhaps you meant to use `struct` here",
+                                "struct",
+                                Applicability::MaybeIncorrect,
+                            );
+                        }
+                        Err(e) => {
+                            e.cancel();
                         }
-                        self.restore_snapshot(snapshot);
                     }
-                    self.eat_to_tokens(&[&token::CloseDelim(Delimiter::Brace)]);
-                    self.bump(); // }
-                    err
-                })?
+                    self.restore_snapshot(snapshot);
+                }
+                self.eat_to_tokens(&[exp!(CloseBrace)]);
+                self.bump(); // }
+                err
+            })?
         };
 
         let enum_definition = EnumDef { variants: variants.into_iter().flatten().collect() };
@@ -1589,7 +1587,7 @@ impl<'a> Parser<'a> {
                 return Ok((None, Trailing::from(this.token == token::Comma), UsePreAttrPos::No));
             }
 
-            let struct_def = if this.check(&token::OpenDelim(Delimiter::Brace)) {
+            let struct_def = if this.check(exp!(OpenBrace)) {
                 // Parse a struct variant.
                 let (fields, recovered) =
                     match this.parse_record_struct_body("struct", ident.span, false) {
@@ -1599,7 +1597,7 @@ impl<'a> Parser<'a> {
                                 // We handle `enum` to `struct` suggestion in the caller.
                                 return Err(err);
                             }
-                            this.eat_to_tokens(&[&token::CloseDelim(Delimiter::Brace)]);
+                            this.eat_to_tokens(&[exp!(CloseBrace)]);
                             this.bump(); // }
                             err.span_label(span, "while parsing this enum");
                             err.help(help);
@@ -1608,7 +1606,7 @@ impl<'a> Parser<'a> {
                         }
                     };
                 VariantData::Struct { fields, recovered }
-            } else if this.check(&token::OpenDelim(Delimiter::Parenthesis)) {
+            } else if this.check(exp!(OpenParen)) {
                 let body = match this.parse_tuple_struct_body() {
                     Ok(body) => body,
                     Err(mut err) => {
@@ -1616,7 +1614,7 @@ impl<'a> Parser<'a> {
                             // We handle `enum` to `struct` suggestion in the caller.
                             return Err(err);
                         }
-                        this.eat_to_tokens(&[&token::CloseDelim(Delimiter::Parenthesis)]);
+                        this.eat_to_tokens(&[exp!(CloseParen)]);
                         this.bump(); // )
                         err.span_label(span, "while parsing this enum");
                         err.help(help);
@@ -1630,7 +1628,7 @@ impl<'a> Parser<'a> {
             };
 
             let disr_expr =
-                if this.eat(&token::Eq) { Some(this.parse_expr_anon_const()?) } else { None };
+                if this.eat(exp!(Eq)) { Some(this.parse_expr_anon_const()?) } else { None };
 
             let vr = ast::Variant {
                 ident,
@@ -1681,7 +1679,7 @@ impl<'a> Parser<'a> {
                 let body = VariantData::Tuple(body, DUMMY_NODE_ID);
                 self.expect_semi()?;
                 body
-            } else if self.eat(&token::Semi) {
+            } else if self.eat(exp!(Semi)) {
                 // If we see a: `struct Foo<T> where T: Copy;` style decl.
                 VariantData::Unit(DUMMY_NODE_ID)
             } else {
@@ -1694,7 +1692,7 @@ impl<'a> Parser<'a> {
                 VariantData::Struct { fields, recovered }
             }
         // No `where` so: `struct Foo<T>;`
-        } else if self.eat(&token::Semi) {
+        } else if self.eat(exp!(Semi)) {
             VariantData::Unit(DUMMY_NODE_ID)
         // Record-style struct definition
         } else if self.token == token::OpenDelim(Delimiter::Brace) {
@@ -1763,14 +1761,18 @@ impl<'a> Parser<'a> {
     ) -> PResult<'a, (ThinVec<FieldDef>, Recovered)> {
         let mut fields = ThinVec::new();
         let mut recovered = Recovered::No;
-        if self.eat(&token::OpenDelim(Delimiter::Brace)) {
+        if self.eat(exp!(OpenBrace)) {
             while self.token != token::CloseDelim(Delimiter::Brace) {
                 match self.parse_field_def(adt_ty) {
                     Ok(field) => {
                         fields.push(field);
                     }
                     Err(mut err) => {
-                        self.consume_block(Delimiter::Brace, ConsumeClosingDelim::No);
+                        self.consume_block(
+                            exp!(OpenBrace),
+                            exp!(CloseBrace),
+                            ConsumeClosingDelim::No,
+                        );
                         err.span_label(ident_span, format!("while parsing this {adt_ty}"));
                         let guar = err.emit();
                         recovered = Recovered::Yes(guar);
@@ -1778,7 +1780,7 @@ impl<'a> Parser<'a> {
                     }
                 }
             }
-            self.expect(&token::CloseDelim(Delimiter::Brace))?;
+            self.expect(exp!(CloseBrace))?;
         } else {
             let token_str = super::token_descr(&self.token);
             let where_str = if parsed_where { "" } else { "`where`, or " };
@@ -1793,7 +1795,7 @@ impl<'a> Parser<'a> {
 
     fn parse_unsafe_field(&mut self) -> Safety {
         // not using parse_safety as that also accepts `safe`.
-        if self.eat_keyword(kw::Unsafe) {
+        if self.eat_keyword(exp!(Unsafe)) {
             let span = self.prev_token.span;
             self.psess.gated_spans.gate(sym::unsafe_fields, span);
             Safety::Unsafe(span)
@@ -1901,7 +1903,7 @@ impl<'a> Parser<'a> {
         if self.token == token::Comma {
             seen_comma = true;
         }
-        if self.eat(&token::Semi) {
+        if self.eat(exp!(Semi)) {
             let sp = self.prev_token.span;
             let mut err =
                 self.dcx().struct_span_err(sp, format!("{adt_ty} fields are separated by `,`"));
@@ -1925,7 +1927,7 @@ impl<'a> Parser<'a> {
                     missing_comma: None,
                 };
                 self.bump(); // consume the doc comment
-                let comma_after_doc_seen = self.eat(&token::Comma);
+                let comma_after_doc_seen = self.eat(exp!(Comma));
                 // `seen_comma` is always false, because we are inside doc block
                 // condition is here to make code more readable
                 if !seen_comma && comma_after_doc_seen {
@@ -1950,13 +1952,13 @@ impl<'a> Parser<'a> {
                 if let TyKind::Path(_, Path { segments, .. }) = &a_var.ty.kind {
                     if let Some(last_segment) = segments.last() {
                         let guar = self.check_trailing_angle_brackets(last_segment, &[
-                            &token::Comma,
-                            &token::CloseDelim(Delimiter::Brace),
+                            exp!(Comma),
+                            exp!(CloseBrace),
                         ]);
                         if let Some(_guar) = guar {
                             // Handle a case like `Vec<u8>>,` where we can continue parsing fields
                             // after the comma
-                            let _ = self.eat(&token::Comma);
+                            let _ = self.eat(exp!(Comma));
 
                             // `check_trailing_angle_brackets` already emitted a nicer error, as
                             // proven by the presence of `_guar`. We can continue parsing.
@@ -1989,7 +1991,7 @@ impl<'a> Parser<'a> {
     }
 
     fn expect_field_ty_separator(&mut self) -> PResult<'a, ()> {
-        if let Err(err) = self.expect(&token::Colon) {
+        if let Err(err) = self.expect(exp!(Colon)) {
             let sm = self.psess.source_map();
             let eq_typo = self.token == token::Eq && self.look_ahead(1, |t| t.is_path_start());
             let semi_typo = self.token == token::Semi
@@ -2097,7 +2099,7 @@ impl<'a> Parser<'a> {
                         self.expected_ident_found_err()
                     }
                 }
-            } else if self.eat_keyword(kw::Struct) {
+            } else if self.eat_keyword(exp!(Struct)) {
                 match self.parse_item_struct() {
                     Ok((ident, _)) => self
                         .dcx()
@@ -2154,12 +2156,12 @@ impl<'a> Parser<'a> {
     /// ```
     fn parse_item_decl_macro(&mut self, lo: Span) -> PResult<'a, ItemInfo> {
         let ident = self.parse_ident()?;
-        let body = if self.check(&token::OpenDelim(Delimiter::Brace)) {
+        let body = if self.check(exp!(OpenBrace)) {
             self.parse_delim_args()? // `MacBody`
-        } else if self.check(&token::OpenDelim(Delimiter::Parenthesis)) {
+        } else if self.check(exp!(OpenParen)) {
             let params = self.parse_token_tree(); // `MacParams`
             let pspan = params.span();
-            if !self.check(&token::OpenDelim(Delimiter::Brace)) {
+            if !self.check(exp!(OpenBrace)) {
                 self.unexpected()?;
             }
             let body = self.parse_token_tree(); // `MacBody`
@@ -2179,7 +2181,7 @@ impl<'a> Parser<'a> {
 
     /// Is this a possibly malformed start of a `macro_rules! foo` item definition?
     fn is_macro_rules_item(&mut self) -> IsMacroRulesItem {
-        if self.check_keyword(kw::MacroRules) {
+        if self.check_keyword(exp!(MacroRules)) {
             let macro_rules_span = self.token.span;
 
             if self.look_ahead(1, |t| *t == token::Not) && self.look_ahead(2, |t| t.is_ident()) {
@@ -2204,14 +2206,14 @@ impl<'a> Parser<'a> {
         vis: &Visibility,
         has_bang: bool,
     ) -> PResult<'a, ItemInfo> {
-        self.expect_keyword(kw::MacroRules)?; // `macro_rules`
+        self.expect_keyword(exp!(MacroRules))?; // `macro_rules`
 
         if has_bang {
-            self.expect(&token::Not)?; // `!`
+            self.expect(exp!(Not))?; // `!`
         }
         let ident = self.parse_ident()?;
 
-        if self.eat(&token::Not) {
+        if self.eat(exp!(Not)) {
             // Handle macro_rules! foo!
             let span = self.prev_token.span;
             self.dcx().emit_err(errors::MacroNameRemoveBang { span });
@@ -2241,7 +2243,7 @@ impl<'a> Parser<'a> {
     }
 
     fn eat_semi_for_macro_if_needed(&mut self, args: &DelimArgs) {
-        if args.need_semicolon() && !self.eat(&token::Semi) {
+        if args.need_semicolon() && !self.eat(exp!(Semi)) {
             self.report_invalid_macro_expansion_item(args);
         }
     }
@@ -2417,11 +2419,8 @@ impl<'a> Parser<'a> {
         req_body: bool,
         fn_params_end: Option<Span>,
     ) -> PResult<'a, ErrorGuaranteed> {
-        let expected = if req_body {
-            &[token::OpenDelim(Delimiter::Brace)][..]
-        } else {
-            &[token::Semi, token::OpenDelim(Delimiter::Brace)]
-        };
+        let expected: &[_] =
+            if req_body { &[exp!(OpenBrace)] } else { &[exp!(Semi), exp!(OpenBrace)] };
         match self.expected_one_of_not_found(&[], expected) {
             Ok(error_guaranteed) => Ok(error_guaranteed),
             Err(mut err) => {
@@ -2506,14 +2505,14 @@ impl<'a> Parser<'a> {
             self.token == TokenKind::Semi
         } else {
             // Only include `;` in list of expected tokens if body is not required
-            self.check(&TokenKind::Semi)
+            self.check(exp!(Semi))
         };
         let (inner_attrs, body) = if has_semi {
             // Include the trailing semicolon in the span of the signature
             self.expect_semi()?;
             *sig_hi = self.prev_token.span;
             (AttrVec::new(), None)
-        } else if self.check(&token::OpenDelim(Delimiter::Brace)) || self.token.is_whole_block() {
+        } else if self.check(exp!(OpenBrace)) || self.token.is_whole_block() {
             self.parse_block_common(self.token.span, BlockCheckMode::Default, false)
                 .map(|(attrs, body)| (attrs, Some(body)))?
         } else if self.token == token::Eq {
@@ -2541,21 +2540,28 @@ impl<'a> Parser<'a> {
     /// `check_pub` adds additional `pub` to the checks in case users place it
     /// wrongly, can be used to ensure `pub` never comes after `default`.
     pub(super) fn check_fn_front_matter(&mut self, check_pub: bool, case: Case) -> bool {
-        const ALL_QUALS: &[Symbol] =
-            &[kw::Pub, kw::Gen, kw::Const, kw::Async, kw::Unsafe, kw::Safe, kw::Extern];
+        const ALL_QUALS: &[ExpKeywordPair] = &[
+            exp!(Pub),
+            exp!(Gen),
+            exp!(Const),
+            exp!(Async),
+            exp!(Unsafe),
+            exp!(Safe),
+            exp!(Extern),
+        ];
 
         // We use an over-approximation here.
         // `const const`, `fn const` won't parse, but we're not stepping over other syntax either.
         // `pub` is added in case users got confused with the ordering like `async pub fn`,
         // only if it wasn't preceded by `default` as `default pub` is invalid.
-        let quals: &[Symbol] = if check_pub {
+        let quals: &[_] = if check_pub {
             ALL_QUALS
         } else {
-            &[kw::Gen, kw::Const, kw::Async, kw::Unsafe, kw::Safe, kw::Extern]
+            &[exp!(Gen), exp!(Const), exp!(Async), exp!(Unsafe), exp!(Safe), exp!(Extern)]
         };
-        self.check_keyword_case(kw::Fn, case) // Definitely an `fn`.
+        self.check_keyword_case(exp!(Fn), case) // Definitely an `fn`.
             // `$qual fn` or `$qual $qual`:
-            || quals.iter().any(|&kw| self.check_keyword_case(kw, case))
+            || quals.iter().any(|&exp| self.check_keyword_case(exp, case))
                 && self.look_ahead(1, |t| {
                     // `$qual fn`, e.g. `const fn` or `async fn`.
                     t.is_keyword_case(kw::Fn, case)
@@ -2563,12 +2569,14 @@ impl<'a> Parser<'a> {
                     || (
                         (
                             t.is_non_raw_ident_where(|i|
-                                quals.contains(&i.name)
+                                quals.iter().any(|exp| exp.kw == i.name)
                                     // Rule out 2015 `const async: T = val`.
                                     && i.is_reserved()
                             )
                             || case == Case::Insensitive
-                                && t.is_non_raw_ident_where(|i| quals.iter().any(|qual| qual.as_str() == i.name.as_str().to_lowercase()))
+                                && t.is_non_raw_ident_where(|i| quals.iter().any(|exp| {
+                                    exp.kw.as_str() == i.name.as_str().to_lowercase()
+                                }))
                         )
                         // Rule out `unsafe extern {`.
                         && !self.is_unsafe_foreign_mod()
@@ -2576,12 +2584,13 @@ impl<'a> Parser<'a> {
                         && !self.is_async_gen_block())
                 })
             // `extern ABI fn`
-            || self.check_keyword_case(kw::Extern, case)
+            || self.check_keyword_case(exp!(Extern), case)
                 && self.look_ahead(1, |t| t.can_begin_string_literal())
                 && (self.look_ahead(2, |t| t.is_keyword_case(kw::Fn, case)) ||
-                    // this branch is only for better diagnostics; `pub`, `unsafe`, etc. are not allowed here
+                    // This branch is only for better diagnostics; `pub`, `unsafe`, etc. are not
+                    // allowed here.
                     (self.may_recover()
-                        && self.look_ahead(2, |t| ALL_QUALS.iter().any(|&kw| t.is_keyword(kw)))
+                        && self.look_ahead(2, |t| ALL_QUALS.iter().any(|exp| t.is_keyword(exp.kw)))
                         && self.look_ahead(3, |t| t.is_keyword_case(kw::Fn, case))))
     }
 
@@ -2629,9 +2638,9 @@ impl<'a> Parser<'a> {
             Some(CoroutineKind::Async { .. }) | None => {}
         }
 
-        if !self.eat_keyword_case(kw::Fn, case) {
+        if !self.eat_keyword_case(exp!(Fn), case) {
             // It is possible for `expect_one_of` to recover given the contents of
-            // `self.expected_tokens`, therefore, do not use `self.unexpected()` which doesn't
+            // `self.expected_token_types`, therefore, do not use `self.unexpected()` which doesn't
             // account for this.
             match self.expect_one_of(&[], &[]) {
                 Ok(Recovered::Yes(_)) => {}
@@ -2649,7 +2658,7 @@ impl<'a> Parser<'a> {
                     let mut recover_safety = safety;
                     // This will allow the machine fix to directly place the keyword in the correct place or to indicate
                     // that the keyword is already present and the second instance should be removed.
-                    let wrong_kw = if self.check_keyword(kw::Const) {
+                    let wrong_kw = if self.check_keyword(exp!(Const)) {
                         match constness {
                             Const::Yes(sp) => Some(WrongKw::Duplicated(sp)),
                             Const::No => {
@@ -2657,7 +2666,7 @@ impl<'a> Parser<'a> {
                                 Some(WrongKw::Misplaced(async_start_sp))
                             }
                         }
-                    } else if self.check_keyword(kw::Async) {
+                    } else if self.check_keyword(exp!(Async)) {
                         match coroutine_kind {
                             Some(CoroutineKind::Async { span, .. }) => {
                                 Some(WrongKw::Duplicated(span))
@@ -2683,7 +2692,7 @@ impl<'a> Parser<'a> {
                                 Some(WrongKw::Misplaced(unsafe_start_sp))
                             }
                         }
-                    } else if self.check_keyword(kw::Unsafe) {
+                    } else if self.check_keyword(exp!(Unsafe)) {
                         match safety {
                             Safety::Unsafe(sp) => Some(WrongKw::Duplicated(sp)),
                             Safety::Safe(sp) => {
@@ -2695,7 +2704,7 @@ impl<'a> Parser<'a> {
                                 Some(WrongKw::Misplaced(ext_start_sp))
                             }
                         }
-                    } else if self.check_keyword(kw::Safe) {
+                    } else if self.check_keyword(exp!(Safe)) {
                         match safety {
                             Safety::Safe(sp) => Some(WrongKw::Duplicated(sp)),
                             Safety::Unsafe(sp) => {
@@ -2741,7 +2750,7 @@ impl<'a> Parser<'a> {
                         }
                     }
                     // Recover incorrect visibility order such as `async pub`
-                    else if self.check_keyword(kw::Pub) {
+                    else if self.check_keyword(exp!(Pub)) {
                         let sp = sp_start.to(self.prev_token.span);
                         if let Ok(snippet) = self.span_to_snippet(sp) {
                             let current_vis = match self.parse_visibility(FollowedByType::No) {
@@ -2844,7 +2853,7 @@ impl<'a> Parser<'a> {
                 };
                 p.restore_snapshot(snapshot);
                 // Skip every token until next possible arg or end.
-                p.eat_to_tokens(&[&token::Comma, &token::CloseDelim(Delimiter::Parenthesis)]);
+                p.eat_to_tokens(&[exp!(Comma), exp!(CloseParen)]);
                 // Create a placeholder argument for proper arg count (issue #34264).
                 Ok(dummy_arg(Ident::new(kw::Empty, lo.to(p.prev_token.span)), guar))
             });
@@ -2955,7 +2964,7 @@ impl<'a> Parser<'a> {
         let parse_self_possibly_typed = |this: &mut Self, m| {
             let eself_ident = expect_self_ident(this);
             let eself_hi = this.prev_token.span;
-            let eself = if this.eat(&token::Colon) {
+            let eself = if this.eat(exp!(Colon)) {
                 SelfKind::Explicit(this.parse_ty()?, m)
             } else {
                 SelfKind::Value(m)
diff --git a/compiler/rustc_parse/src/parser/mod.rs b/compiler/rustc_parse/src/parser/mod.rs
index 37556c064d8..2637ea268c8 100644
--- a/compiler/rustc_parse/src/parser/mod.rs
+++ b/compiler/rustc_parse/src/parser/mod.rs
@@ -8,6 +8,7 @@ mod nonterminal;
 mod pat;
 mod path;
 mod stmt;
+pub mod token_type;
 mod ty;
 
 use std::assert_matches::debug_assert_matches;
@@ -24,14 +25,12 @@ use rustc_ast::ptr::P;
 use rustc_ast::token::{
     self, Delimiter, IdentIsRaw, InvisibleOrigin, MetaVarKind, Nonterminal, Token, TokenKind,
 };
-use rustc_ast::tokenstream::{
-    AttrsTarget, DelimSpacing, DelimSpan, Spacing, TokenStream, TokenTree, TokenTreeCursor,
-};
+use rustc_ast::tokenstream::{AttrsTarget, Spacing, TokenStream, TokenTree};
 use rustc_ast::util::case::Case;
 use rustc_ast::{
-    self as ast, AnonConst, AttrArgs, AttrArgsEq, AttrId, ByRef, Const, CoroutineKind,
-    DUMMY_NODE_ID, DelimArgs, Expr, ExprKind, Extern, HasAttrs, HasTokens, Mutability, Recovered,
-    Safety, StrLit, Visibility, VisibilityKind,
+    self as ast, AnonConst, AttrArgs, AttrId, ByRef, Const, CoroutineKind, DUMMY_NODE_ID,
+    DelimArgs, Expr, ExprKind, Extern, HasAttrs, HasTokens, Mutability, Recovered, Safety, StrLit,
+    Visibility, VisibilityKind,
 };
 use rustc_ast_pretty::pprust;
 use rustc_data_structures::fx::FxHashMap;
@@ -39,14 +38,16 @@ use rustc_data_structures::sync::Lrc;
 use rustc_errors::{Applicability, Diag, FatalError, MultiSpan, PResult};
 use rustc_index::interval::IntervalSet;
 use rustc_session::parse::ParseSess;
-use rustc_span::symbol::{Ident, Symbol, kw, sym};
-use rustc_span::{DUMMY_SP, Span};
+use rustc_span::{DUMMY_SP, Ident, Span, Symbol, kw, sym};
 use thin_vec::ThinVec;
+use token_type::TokenTypeSet;
+pub use token_type::{ExpKeywordPair, ExpTokenPair, TokenType};
 use tracing::debug;
 
 use crate::errors::{
     self, IncorrectVisibilityRestriction, MismatchedClosingDelimiter, NonStringAbiLiteral,
 };
+use crate::exp;
 use crate::lexer::UnmatchedDelim;
 
 #[cfg(test)]
@@ -144,7 +145,7 @@ pub struct Parser<'a> {
     pub prev_token: Token,
     pub capture_cfg: bool,
     restrictions: Restrictions,
-    expected_tokens: Vec<TokenType>,
+    expected_token_types: TokenTypeSet,
     token_cursor: TokenCursor,
     // The number of calls to `bump`, i.e. the position in the token stream.
     num_bump_calls: u32,
@@ -187,9 +188,9 @@ pub struct Parser<'a> {
     recovery: Recovery,
 }
 
-// This type is used a lot, e.g. it's cloned when matching many declarative macro rules with nonterminals. Make sure
-// it doesn't unintentionally get bigger.
-#[cfg(target_pointer_width = "64")]
+// This type is used a lot, e.g. it's cloned when matching many declarative macro rules with
+// nonterminals. Make sure it doesn't unintentionally get bigger.
+#[cfg(all(target_pointer_width = "64", not(target_arch = "s390x")))]
 rustc_data_structures::static_assert_size!(Parser<'_>, 288);
 
 /// Stores span information about a closure.
@@ -273,21 +274,48 @@ struct CaptureState {
     seen_attrs: IntervalSet<AttrId>,
 }
 
-/// Iterator over a `TokenStream` that produces `Token`s. It's a bit odd that
+#[derive(Clone, Debug)]
+struct TokenTreeCursor {
+    stream: TokenStream,
+    /// Points to the current token tree in the stream. In `TokenCursor::curr`,
+    /// this can be any token tree. In `TokenCursor::stack`, this is always a
+    /// `TokenTree::Delimited`.
+    index: usize,
+}
+
+impl TokenTreeCursor {
+    #[inline]
+    fn new(stream: TokenStream) -> Self {
+        TokenTreeCursor { stream, index: 0 }
+    }
+
+    #[inline]
+    fn curr(&self) -> Option<&TokenTree> {
+        self.stream.get(self.index)
+    }
+
+    #[inline]
+    fn bump(&mut self) {
+        self.index += 1;
+    }
+}
+
+/// A `TokenStream` cursor that produces `Token`s. It's a bit odd that
 /// we (a) lex tokens into a nice tree structure (`TokenStream`), and then (b)
 /// use this type to emit them as a linear sequence. But a linear sequence is
 /// what the parser expects, for the most part.
 #[derive(Clone, Debug)]
 struct TokenCursor {
-    // Cursor for the current (innermost) token stream. The delimiters for this
-    // token stream are found in `self.stack.last()`; when that is `None` then
-    // we are in the outermost token stream which never has delimiters.
-    tree_cursor: TokenTreeCursor,
-
-    // Token streams surrounding the current one. The delimiters for stack[n]'s
-    // tokens are in `stack[n-1]`. `stack[0]` (when present) has no delimiters
-    // because it's the outermost token stream which never has delimiters.
-    stack: Vec<(TokenTreeCursor, DelimSpan, DelimSpacing, Delimiter)>,
+    // Cursor for the current (innermost) token stream. The index within the
+    // cursor can point to any token tree in the stream (or one past the end).
+    // The delimiters for this token stream are found in `self.stack.last()`;
+    // if that is `None` we are in the outermost token stream which never has
+    // delimiters.
+    curr: TokenTreeCursor,
+
+    // Token streams surrounding the current one. The index within each cursor
+    // always points to a `TokenTree::Delimited`.
+    stack: Vec<TokenTreeCursor>,
 }
 
 impl TokenCursor {
@@ -302,32 +330,33 @@ impl TokenCursor {
             // FIXME: we currently don't return `Delimiter::Invisible` open/close delims. To fix
             // #67062 we will need to, whereupon the `delim != Delimiter::Invisible` conditions
             // below can be removed.
-            if let Some(tree) = self.tree_cursor.next_ref() {
+            if let Some(tree) = self.curr.curr() {
                 match tree {
                     &TokenTree::Token(ref token, spacing) => {
                         debug_assert!(!matches!(
                             token.kind,
                             token::OpenDelim(_) | token::CloseDelim(_)
                         ));
-                        return (token.clone(), spacing);
+                        let res = (token.clone(), spacing);
+                        self.curr.bump();
+                        return res;
                     }
                     &TokenTree::Delimited(sp, spacing, delim, ref tts) => {
-                        let trees = tts.clone().into_trees();
-                        self.stack.push((
-                            mem::replace(&mut self.tree_cursor, trees),
-                            sp,
-                            spacing,
-                            delim,
-                        ));
+                        let trees = TokenTreeCursor::new(tts.clone());
+                        self.stack.push(mem::replace(&mut self.curr, trees));
                         if !delim.skip() {
                             return (Token::new(token::OpenDelim(delim), sp.open), spacing.open);
                         }
                         // No open delimiter to return; continue on to the next iteration.
                     }
                 };
-            } else if let Some((tree_cursor, span, spacing, delim)) = self.stack.pop() {
+            } else if let Some(parent) = self.stack.pop() {
                 // We have exhausted this token stream. Move back to its parent token stream.
-                self.tree_cursor = tree_cursor;
+                let Some(&TokenTree::Delimited(span, spacing, delim, _)) = parent.curr() else {
+                    panic!("parent should be Delimited")
+                };
+                self.curr = parent;
+                self.curr.bump(); // move past the `Delimited`
                 if !delim.skip() {
                     return (Token::new(token::CloseDelim(delim), span.close), spacing.close);
                 }
@@ -342,48 +371,21 @@ impl TokenCursor {
     }
 }
 
-#[derive(Debug, Clone, PartialEq)]
-enum TokenType {
-    Token(TokenKind),
-    Keyword(Symbol),
-    Operator,
-    Lifetime,
-    Ident,
-    Path,
-    Type,
-    Const,
-}
-
-impl TokenType {
-    fn to_string(&self) -> String {
-        match self {
-            TokenType::Token(t) => format!("`{}`", pprust::token_kind_to_string(t)),
-            TokenType::Keyword(kw) => format!("`{kw}`"),
-            TokenType::Operator => "an operator".to_string(),
-            TokenType::Lifetime => "lifetime".to_string(),
-            TokenType::Ident => "identifier".to_string(),
-            TokenType::Path => "path".to_string(),
-            TokenType::Type => "type".to_string(),
-            TokenType::Const => "a const expression".to_string(),
-        }
-    }
-}
-
 /// A sequence separator.
 #[derive(Debug)]
-struct SeqSep {
+struct SeqSep<'a> {
     /// The separator token.
-    sep: Option<TokenKind>,
+    sep: Option<ExpTokenPair<'a>>,
     /// `true` if a trailing separator is allowed.
     trailing_sep_allowed: bool,
 }
 
-impl SeqSep {
-    fn trailing_allowed(t: TokenKind) -> SeqSep {
-        SeqSep { sep: Some(t), trailing_sep_allowed: true }
+impl<'a> SeqSep<'a> {
+    fn trailing_allowed(sep: ExpTokenPair<'a>) -> SeqSep<'a> {
+        SeqSep { sep: Some(sep), trailing_sep_allowed: true }
     }
 
-    fn none() -> SeqSep {
+    fn none() -> SeqSep<'a> {
         SeqSep { sep: None, trailing_sep_allowed: false }
     }
 }
@@ -465,8 +467,8 @@ impl<'a> Parser<'a> {
             prev_token: Token::dummy(),
             capture_cfg: false,
             restrictions: Restrictions::empty(),
-            expected_tokens: Vec::new(),
-            token_cursor: TokenCursor { tree_cursor: stream.into_trees(), stack: Vec::new() },
+            expected_token_types: TokenTypeSet::new(),
+            token_cursor: TokenCursor { curr: TokenTreeCursor::new(stream), stack: Vec::new() },
             num_bump_calls: 0,
             break_last_token: 0,
             unmatched_angle_bracket_count: 0,
@@ -528,16 +530,16 @@ impl<'a> Parser<'a> {
     }
 
     /// Expects and consumes the token `t`. Signals an error if the next token is not `t`.
-    pub fn expect(&mut self, t: &TokenKind) -> PResult<'a, Recovered> {
-        if self.expected_tokens.is_empty() {
-            if self.token == *t {
+    pub fn expect(&mut self, exp: ExpTokenPair<'_>) -> PResult<'a, Recovered> {
+        if self.expected_token_types.is_empty() {
+            if self.token == *exp.tok {
                 self.bump();
                 Ok(Recovered::No)
             } else {
-                self.unexpected_try_recover(t)
+                self.unexpected_try_recover(exp.tok)
             }
         } else {
-            self.expect_one_of(slice::from_ref(t), &[])
+            self.expect_one_of(slice::from_ref(&exp), &[])
         }
     }
 
@@ -546,13 +548,13 @@ impl<'a> Parser<'a> {
     /// anything. Signal a fatal error if next token is unexpected.
     fn expect_one_of(
         &mut self,
-        edible: &[TokenKind],
-        inedible: &[TokenKind],
+        edible: &[ExpTokenPair<'_>],
+        inedible: &[ExpTokenPair<'_>],
     ) -> PResult<'a, Recovered> {
-        if edible.contains(&self.token.kind) {
+        if edible.iter().any(|exp| exp.tok == &self.token.kind) {
             self.bump();
             Ok(Recovered::No)
-        } else if inedible.contains(&self.token.kind) {
+        } else if inedible.iter().any(|exp| exp.tok == &self.token.kind) {
             // leave it in the input
             Ok(Recovered::No)
         } else if self.token != token::Eof
@@ -594,13 +596,13 @@ impl<'a> Parser<'a> {
 
     /// Checks if the next token is `tok`, and returns `true` if so.
     ///
-    /// This method will automatically add `tok` to `expected_tokens` if `tok` is not
+    /// This method will automatically add `tok` to `expected_token_types` if `tok` is not
     /// encountered.
     #[inline]
-    fn check(&mut self, tok: &TokenKind) -> bool {
-        let is_present = self.token == *tok;
+    fn check(&mut self, exp: ExpTokenPair<'_>) -> bool {
+        let is_present = self.token == *exp.tok;
         if !is_present {
-            self.expected_tokens.push(TokenType::Token(tok.clone()));
+            self.expected_token_types.insert(exp.token_type);
         }
         is_present
     }
@@ -628,8 +630,8 @@ impl<'a> Parser<'a> {
     /// Consumes a token 'tok' if it exists. Returns whether the given token was present.
     #[inline]
     #[must_use]
-    pub fn eat(&mut self, tok: &TokenKind) -> bool {
-        let is_present = self.check(tok);
+    pub fn eat(&mut self, exp: ExpTokenPair<'_>) -> bool {
+        let is_present = self.check(exp);
         if is_present {
             self.bump()
         }
@@ -640,22 +642,23 @@ impl<'a> Parser<'a> {
     /// An expectation is also added for diagnostics purposes.
     #[inline]
     #[must_use]
-    fn check_keyword(&mut self, kw: Symbol) -> bool {
-        self.expected_tokens.push(TokenType::Keyword(kw));
-        self.token.is_keyword(kw)
+    fn check_keyword(&mut self, exp: ExpKeywordPair) -> bool {
+        let is_keyword = self.token.is_keyword(exp.kw);
+        if !is_keyword {
+            self.expected_token_types.insert(exp.token_type);
+        }
+        is_keyword
     }
 
     #[inline]
     #[must_use]
-    fn check_keyword_case(&mut self, kw: Symbol, case: Case) -> bool {
-        if self.check_keyword(kw) {
-            return true;
-        }
-
+    fn check_keyword_case(&mut self, exp: ExpKeywordPair, case: Case) -> bool {
+        if self.check_keyword(exp) {
+            true
         // Do an ASCII case-insensitive match, because all keywords are ASCII.
-        if case == Case::Insensitive
+        } else if case == Case::Insensitive
             && let Some((ident, IdentIsRaw::No)) = self.token.ident()
-            && ident.as_str().eq_ignore_ascii_case(kw.as_str())
+            && ident.as_str().eq_ignore_ascii_case(exp.kw.as_str())
         {
             true
         } else {
@@ -668,13 +671,12 @@ impl<'a> Parser<'a> {
     // Public for rustc_builtin_macros and rustfmt usage.
     #[inline]
     #[must_use]
-    pub fn eat_keyword(&mut self, kw: Symbol) -> bool {
-        if self.check_keyword(kw) {
+    pub fn eat_keyword(&mut self, exp: ExpKeywordPair) -> bool {
+        let is_keyword = self.check_keyword(exp);
+        if is_keyword {
             self.bump();
-            true
-        } else {
-            false
         }
+        is_keyword
     }
 
     /// Eats a keyword, optionally ignoring the case.
@@ -682,21 +684,19 @@ impl<'a> Parser<'a> {
     /// This is useful for recovery.
     #[inline]
     #[must_use]
-    fn eat_keyword_case(&mut self, kw: Symbol, case: Case) -> bool {
-        if self.eat_keyword(kw) {
-            return true;
-        }
-
-        if case == Case::Insensitive
+    fn eat_keyword_case(&mut self, exp: ExpKeywordPair, case: Case) -> bool {
+        if self.eat_keyword(exp) {
+            true
+        } else if case == Case::Insensitive
             && let Some((ident, IdentIsRaw::No)) = self.token.ident()
-            && ident.as_str().to_lowercase() == kw.as_str().to_lowercase()
+            && ident.as_str().to_lowercase() == exp.kw.as_str().to_lowercase()
         {
-            self.dcx().emit_err(errors::KwBadCase { span: ident.span, kw: kw.as_str() });
+            self.dcx().emit_err(errors::KwBadCase { span: ident.span, kw: exp.kw.as_str() });
             self.bump();
-            return true;
+            true
+        } else {
+            false
         }
-
-        false
     }
 
     /// If the next token is the given keyword, eats it and returns `true`.
@@ -705,19 +705,18 @@ impl<'a> Parser<'a> {
     #[inline]
     #[must_use]
     pub fn eat_keyword_noexpect(&mut self, kw: Symbol) -> bool {
-        if self.token.is_keyword(kw) {
+        let is_keyword = self.token.is_keyword(kw);
+        if is_keyword {
             self.bump();
-            true
-        } else {
-            false
         }
+        is_keyword
     }
 
     /// If the given word is not a keyword, signals an error.
     /// If the next token is not the given word, signals an error.
     /// Otherwise, eats it.
-    pub fn expect_keyword(&mut self, kw: Symbol) -> PResult<'a, ()> {
-        if !self.eat_keyword(kw) { self.unexpected() } else { Ok(()) }
+    pub fn expect_keyword(&mut self, exp: ExpKeywordPair) -> PResult<'a, ()> {
+        if !self.eat_keyword(exp) { self.unexpected() } else { Ok(()) }
     }
 
     /// Is the given keyword `kw` followed by a non-reserved identifier?
@@ -726,13 +725,11 @@ impl<'a> Parser<'a> {
     }
 
     #[inline]
-    fn check_or_expected(&mut self, ok: bool, typ: TokenType) -> bool {
-        if ok {
-            true
-        } else {
-            self.expected_tokens.push(typ);
-            false
+    fn check_or_expected(&mut self, ok: bool, token_type: TokenType) -> bool {
+        if !ok {
+            self.expected_token_types.insert(token_type);
         }
+        ok
     }
 
     fn check_ident(&mut self) -> bool {
@@ -775,22 +772,19 @@ impl<'a> Parser<'a> {
     /// Otherwise returns `false`.
     #[inline]
     fn check_plus(&mut self) -> bool {
-        self.check_or_expected(
-            self.token.is_like_plus(),
-            TokenType::Token(token::BinOp(token::Plus)),
-        )
+        self.check_or_expected(self.token.is_like_plus(), TokenType::Plus)
     }
 
     /// Eats the expected token if it's present possibly breaking
     /// compound tokens like multi-character operators in process.
     /// Returns `true` if the token was eaten.
-    fn break_and_eat(&mut self, expected: TokenKind) -> bool {
-        if self.token == expected {
+    fn break_and_eat(&mut self, exp: ExpTokenPair<'_>) -> bool {
+        if self.token == *exp.tok {
             self.bump();
             return true;
         }
         match self.token.kind.break_two_token_op(1) {
-            Some((first, second)) if first == expected => {
+            Some((first, second)) if first == *exp.tok => {
                 let first_span = self.psess.source_map().start_point(self.token.span);
                 let second_span = self.token.span.with_lo(first_span.hi());
                 self.token = Token::new(first, first_span);
@@ -807,7 +801,7 @@ impl<'a> Parser<'a> {
                 true
             }
             _ => {
-                self.expected_tokens.push(TokenType::Token(expected));
+                self.expected_token_types.insert(exp.token_type);
                 false
             }
         }
@@ -815,24 +809,24 @@ impl<'a> Parser<'a> {
 
     /// Eats `+` possibly breaking tokens like `+=` in process.
     fn eat_plus(&mut self) -> bool {
-        self.break_and_eat(token::BinOp(token::Plus))
+        self.break_and_eat(exp!(Plus))
     }
 
     /// Eats `&` possibly breaking tokens like `&&` in process.
     /// Signals an error if `&` is not eaten.
     fn expect_and(&mut self) -> PResult<'a, ()> {
-        if self.break_and_eat(token::BinOp(token::And)) { Ok(()) } else { self.unexpected() }
+        if self.break_and_eat(exp!(And)) { Ok(()) } else { self.unexpected() }
     }
 
     /// Eats `|` possibly breaking tokens like `||` in process.
     /// Signals an error if `|` was not eaten.
     fn expect_or(&mut self) -> PResult<'a, ()> {
-        if self.break_and_eat(token::BinOp(token::Or)) { Ok(()) } else { self.unexpected() }
+        if self.break_and_eat(exp!(Or)) { Ok(()) } else { self.unexpected() }
     }
 
     /// Eats `<` possibly breaking tokens like `<<` in process.
     fn eat_lt(&mut self) -> bool {
-        let ate = self.break_and_eat(token::Lt);
+        let ate = self.break_and_eat(exp!(Lt));
         if ate {
             // See doc comment for `unmatched_angle_bracket_count`.
             self.unmatched_angle_bracket_count += 1;
@@ -850,7 +844,7 @@ impl<'a> Parser<'a> {
     /// Eats `>` possibly breaking tokens like `>>` in process.
     /// Signals an error if `>` was not eaten.
     fn expect_gt(&mut self) -> PResult<'a, ()> {
-        if self.break_and_eat(token::Gt) {
+        if self.break_and_eat(exp!(Gt)) {
             // See doc comment for `unmatched_angle_bracket_count`.
             if self.unmatched_angle_bracket_count > 0 {
                 self.unmatched_angle_bracket_count -= 1;
@@ -862,14 +856,14 @@ impl<'a> Parser<'a> {
         }
     }
 
-    /// Checks if the next token is contained within `kets`, and returns `true` if so.
+    /// Checks if the next token is contained within `closes`, and returns `true` if so.
     fn expect_any_with_type(
         &mut self,
-        kets_expected: &[&TokenKind],
-        kets_not_expected: &[&TokenKind],
+        closes_expected: &[ExpTokenPair<'_>],
+        closes_not_expected: &[&TokenKind],
     ) -> bool {
-        kets_expected.iter().any(|k| self.check(k))
-            || kets_not_expected.iter().any(|k| self.check_noexpect(k))
+        closes_expected.iter().any(|&close| self.check(close))
+            || closes_not_expected.iter().any(|k| self.check_noexpect(k))
     }
 
     /// Parses a sequence until the specified delimiters. The function
@@ -877,9 +871,9 @@ impl<'a> Parser<'a> {
     /// closing bracket.
     fn parse_seq_to_before_tokens<T>(
         &mut self,
-        kets_expected: &[&TokenKind],
-        kets_not_expected: &[&TokenKind],
-        sep: SeqSep,
+        closes_expected: &[ExpTokenPair<'_>],
+        closes_not_expected: &[&TokenKind],
+        sep: SeqSep<'_>,
         mut f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
     ) -> PResult<'a, (ThinVec<T>, Trailing, Recovered)> {
         let mut first = true;
@@ -887,17 +881,17 @@ impl<'a> Parser<'a> {
         let mut trailing = Trailing::No;
         let mut v = ThinVec::new();
 
-        while !self.expect_any_with_type(kets_expected, kets_not_expected) {
+        while !self.expect_any_with_type(closes_expected, closes_not_expected) {
             if let token::CloseDelim(..) | token::Eof = self.token.kind {
                 break;
             }
-            if let Some(t) = &sep.sep {
+            if let Some(exp) = sep.sep {
                 if first {
                     // no separator for the first element
                     first = false;
                 } else {
                     // check for separator
-                    match self.expect(t) {
+                    match self.expect(exp) {
                         Ok(Recovered::No) => {
                             self.current_closure.take();
                         }
@@ -908,7 +902,7 @@ impl<'a> Parser<'a> {
                         }
                         Err(mut expect_err) => {
                             let sp = self.prev_token.span.shrink_to_hi();
-                            let token_str = pprust::token_kind_to_string(t);
+                            let token_str = pprust::token_kind_to_string(exp.tok);
 
                             match self.current_closure.take() {
                                 Some(closure_spans) if self.token == TokenKind::Semi => {
@@ -928,7 +922,7 @@ impl<'a> Parser<'a> {
 
                                 _ => {
                                     // Attempt to keep parsing if it was a similar separator.
-                                    if let Some(tokens) = t.similar_tokens() {
+                                    if let Some(tokens) = exp.tok.similar_tokens() {
                                         if tokens.contains(&self.token.kind) {
                                             self.bump();
                                         }
@@ -978,15 +972,17 @@ impl<'a> Parser<'a> {
                                     // Parsing failed, therefore it must be something more serious
                                     // than just a missing separator.
                                     for xx in &e.children {
-                                        // propagate the help message from sub error 'e' to main error 'expect_err;
+                                        // Propagate the help message from sub error `e` to main
+                                        // error `expect_err`.
                                         expect_err.children.push(xx.clone());
                                     }
                                     e.cancel();
                                     if self.token == token::Colon {
-                                        // we will try to recover in `maybe_recover_struct_lit_bad_delims`
+                                        // We will try to recover in
+                                        // `maybe_recover_struct_lit_bad_delims`.
                                         return Err(expect_err);
-                                    } else if let [token::CloseDelim(Delimiter::Parenthesis)] =
-                                        kets_expected
+                                    } else if let [exp] = closes_expected
+                                        && exp.token_type == TokenType::CloseParen
                                     {
                                         return Err(expect_err);
                                     } else {
@@ -1000,7 +996,7 @@ impl<'a> Parser<'a> {
                 }
             }
             if sep.trailing_sep_allowed
-                && self.expect_any_with_type(kets_expected, kets_not_expected)
+                && self.expect_any_with_type(closes_expected, closes_not_expected)
             {
                 trailing = Trailing::Yes;
                 break;
@@ -1020,7 +1016,7 @@ impl<'a> Parser<'a> {
     ) -> PResult<'a, ()> {
         let initial_semicolon = self.token.span;
 
-        while self.eat(&TokenKind::Semi) {
+        while self.eat(exp!(Semi)) {
             let _ = self.parse_stmt_without_recovery(false, ForceCollect::No).unwrap_or_else(|e| {
                 e.cancel();
                 None
@@ -1076,11 +1072,11 @@ impl<'a> Parser<'a> {
     /// closing bracket.
     fn parse_seq_to_before_end<T>(
         &mut self,
-        ket: &TokenKind,
-        sep: SeqSep,
+        close: ExpTokenPair<'_>,
+        sep: SeqSep<'_>,
         f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
     ) -> PResult<'a, (ThinVec<T>, Trailing, Recovered)> {
-        self.parse_seq_to_before_tokens(&[ket], &[], sep, f)
+        self.parse_seq_to_before_tokens(&[close], &[], sep, f)
     }
 
     /// Parses a sequence, including only the closing delimiter. The function
@@ -1088,15 +1084,15 @@ impl<'a> Parser<'a> {
     /// closing bracket.
     fn parse_seq_to_end<T>(
         &mut self,
-        ket: &TokenKind,
-        sep: SeqSep,
+        close: ExpTokenPair<'_>,
+        sep: SeqSep<'_>,
         f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
     ) -> PResult<'a, (ThinVec<T>, Trailing)> {
-        let (val, trailing, recovered) = self.parse_seq_to_before_end(ket, sep, f)?;
-        if matches!(recovered, Recovered::No) && !self.eat(ket) {
+        let (val, trailing, recovered) = self.parse_seq_to_before_end(close, sep, f)?;
+        if matches!(recovered, Recovered::No) && !self.eat(close) {
             self.dcx().span_delayed_bug(
                 self.token.span,
-                "recovered but `parse_seq_to_before_end` did not give us the ket token",
+                "recovered but `parse_seq_to_before_end` did not give us the close token",
             );
         }
         Ok((val, trailing))
@@ -1107,13 +1103,13 @@ impl<'a> Parser<'a> {
     /// closing bracket.
     fn parse_unspanned_seq<T>(
         &mut self,
-        bra: &TokenKind,
-        ket: &TokenKind,
-        sep: SeqSep,
+        open: ExpTokenPair<'_>,
+        close: ExpTokenPair<'_>,
+        sep: SeqSep<'_>,
         f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
     ) -> PResult<'a, (ThinVec<T>, Trailing)> {
-        self.expect(bra)?;
-        self.parse_seq_to_end(ket, sep, f)
+        self.expect(open)?;
+        self.parse_seq_to_end(close, sep, f)
     }
 
     /// Parses a comma-separated sequence, including both delimiters.
@@ -1121,15 +1117,11 @@ impl<'a> Parser<'a> {
     /// closing bracket.
     fn parse_delim_comma_seq<T>(
         &mut self,
-        delim: Delimiter,
+        open: ExpTokenPair<'_>,
+        close: ExpTokenPair<'_>,
         f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
     ) -> PResult<'a, (ThinVec<T>, Trailing)> {
-        self.parse_unspanned_seq(
-            &token::OpenDelim(delim),
-            &token::CloseDelim(delim),
-            SeqSep::trailing_allowed(token::Comma),
-            f,
-        )
+        self.parse_unspanned_seq(open, close, SeqSep::trailing_allowed(exp!(Comma)), f)
     }
 
     /// Parses a comma-separated sequence delimited by parentheses (e.g. `(x, y)`).
@@ -1139,7 +1131,7 @@ impl<'a> Parser<'a> {
         &mut self,
         f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
     ) -> PResult<'a, (ThinVec<T>, Trailing)> {
-        self.parse_delim_comma_seq(Delimiter::Parenthesis, f)
+        self.parse_delim_comma_seq(exp!(OpenParen), exp!(CloseParen), f)
     }
 
     /// Advance the parser by one token using provided token as the next one.
@@ -1155,7 +1147,7 @@ impl<'a> Parser<'a> {
         self.token_spacing = next_spacing;
 
         // Diagnostics.
-        self.expected_tokens.clear();
+        self.expected_token_types.clear();
     }
 
     /// Advance the parser by one token.
@@ -1192,7 +1184,7 @@ impl<'a> Parser<'a> {
         if dist == 1 {
             // The index is zero because the tree cursor's index always points
             // to the next token to be gotten.
-            match self.token_cursor.tree_cursor.look_ahead(0) {
+            match self.token_cursor.curr.curr() {
                 Some(tree) => {
                     // Indexing stayed within the current token tree.
                     match tree {
@@ -1202,12 +1194,13 @@ impl<'a> Parser<'a> {
                                 return looker(&Token::new(token::OpenDelim(delim), dspan.open));
                             }
                         }
-                    };
+                    }
                 }
                 None => {
                     // The tree cursor lookahead went (one) past the end of the
                     // current token tree. Try to return a close delimiter.
-                    if let Some(&(_, span, _, delim)) = self.token_cursor.stack.last()
+                    if let Some(last) = self.token_cursor.stack.last()
+                        && let Some(&TokenTree::Delimited(span, _, delim, _)) = last.curr()
                         && !delim.skip()
                     {
                         // We are not in the outermost token stream, so we have
@@ -1244,11 +1237,11 @@ impl<'a> Parser<'a> {
     /// Parses asyncness: `async` or nothing.
     fn parse_coroutine_kind(&mut self, case: Case) -> Option<CoroutineKind> {
         let span = self.token.uninterpolated_span();
-        if self.eat_keyword_case(kw::Async, case) {
+        if self.eat_keyword_case(exp!(Async), case) {
             // FIXME(gen_blocks): Do we want to unconditionally parse `gen` and then
             // error if edition <= 2024, like we do with async and edition <= 2018?
             if self.token.uninterpolated_span().at_least_rust_2024()
-                && self.eat_keyword_case(kw::Gen, case)
+                && self.eat_keyword_case(exp!(Gen), case)
             {
                 let gen_span = self.prev_token.uninterpolated_span();
                 Some(CoroutineKind::AsyncGen {
@@ -1264,7 +1257,7 @@ impl<'a> Parser<'a> {
                 })
             }
         } else if self.token.uninterpolated_span().at_least_rust_2024()
-            && self.eat_keyword_case(kw::Gen, case)
+            && self.eat_keyword_case(exp!(Gen), case)
         {
             Some(CoroutineKind::Gen {
                 span,
@@ -1278,9 +1271,9 @@ impl<'a> Parser<'a> {
 
     /// Parses fn unsafety: `unsafe`, `safe` or nothing.
     fn parse_safety(&mut self, case: Case) -> Safety {
-        if self.eat_keyword_case(kw::Unsafe, case) {
+        if self.eat_keyword_case(exp!(Unsafe), case) {
             Safety::Unsafe(self.prev_token.uninterpolated_span())
-        } else if self.eat_keyword_case(kw::Safe, case) {
+        } else if self.eat_keyword_case(exp!(Safe), case) {
             Safety::Safe(self.prev_token.uninterpolated_span())
         } else {
             Safety::Default
@@ -1306,7 +1299,7 @@ impl<'a> Parser<'a> {
         if (self.check_const_closure() == is_closure)
             && !self
                 .look_ahead(1, |t| *t == token::OpenDelim(Delimiter::Brace) || t.is_whole_block())
-            && self.eat_keyword_case(kw::Const, case)
+            && self.eat_keyword_case(exp!(Const), case)
         {
             Const::Yes(self.prev_token.uninterpolated_span())
         } else {
@@ -1319,7 +1312,7 @@ impl<'a> Parser<'a> {
         if pat {
             self.psess.gated_spans.gate(sym::inline_const_pat, span);
         }
-        self.expect_keyword(kw::Const)?;
+        self.expect_keyword(exp!(Const))?;
         let (attrs, blk) = self.parse_inner_attrs_and_block()?;
         let anon_const = AnonConst {
             id: DUMMY_NODE_ID,
@@ -1331,19 +1324,19 @@ impl<'a> Parser<'a> {
 
     /// Parses mutability (`mut` or nothing).
     fn parse_mutability(&mut self) -> Mutability {
-        if self.eat_keyword(kw::Mut) { Mutability::Mut } else { Mutability::Not }
+        if self.eat_keyword(exp!(Mut)) { Mutability::Mut } else { Mutability::Not }
     }
 
     /// Parses reference binding mode (`ref`, `ref mut`, or nothing).
     fn parse_byref(&mut self) -> ByRef {
-        if self.eat_keyword(kw::Ref) { ByRef::Yes(self.parse_mutability()) } else { ByRef::No }
+        if self.eat_keyword(exp!(Ref)) { ByRef::Yes(self.parse_mutability()) } else { ByRef::No }
     }
 
     /// Possibly parses mutability (`const` or `mut`).
     fn parse_const_or_mut(&mut self) -> Option<Mutability> {
-        if self.eat_keyword(kw::Mut) {
+        if self.eat_keyword(exp!(Mut)) {
             Some(Mutability::Mut)
-        } else if self.eat_keyword(kw::Const) {
+        } else if self.eat_keyword(exp!(Const)) {
             Some(Mutability::Not)
         } else {
             None
@@ -1374,18 +1367,18 @@ impl<'a> Parser<'a> {
     fn parse_attr_args(&mut self) -> PResult<'a, AttrArgs> {
         Ok(if let Some(args) = self.parse_delim_args_inner() {
             AttrArgs::Delimited(args)
-        } else if self.eat(&token::Eq) {
+        } else if self.eat(exp!(Eq)) {
             let eq_span = self.prev_token.span;
-            AttrArgs::Eq { eq_span, value: AttrArgsEq::Ast(self.parse_expr_force_collect()?) }
+            AttrArgs::Eq { eq_span, expr: self.parse_expr_force_collect()? }
         } else {
             AttrArgs::Empty
         })
     }
 
     fn parse_delim_args_inner(&mut self) -> Option<DelimArgs> {
-        let delimited = self.check(&token::OpenDelim(Delimiter::Parenthesis))
-            || self.check(&token::OpenDelim(Delimiter::Bracket))
-            || self.check(&token::OpenDelim(Delimiter::Brace));
+        let delimited = self.check(exp!(OpenParen))
+            || self.check(exp!(OpenBracket))
+            || self.check(exp!(OpenBrace));
 
         delimited.then(|| {
             let TokenTree::Delimited(dspan, _, delim, tokens) = self.parse_token_tree() else {
@@ -1399,9 +1392,10 @@ impl<'a> Parser<'a> {
     pub fn parse_token_tree(&mut self) -> TokenTree {
         match self.token.kind {
             token::OpenDelim(..) => {
-                // Grab the tokens within the delimiters.
-                let stream = self.token_cursor.tree_cursor.stream.clone();
-                let (_, span, spacing, delim) = *self.token_cursor.stack.last().unwrap();
+                // Clone the `TokenTree::Delimited` that we are currently
+                // within. That's what we are going to return.
+                let tree = self.token_cursor.stack.last().unwrap().curr().unwrap().clone();
+                debug_assert_matches!(tree, TokenTree::Delimited(..));
 
                 // Advance the token cursor through the entire delimited
                 // sequence. After getting the `OpenDelim` we are *within* the
@@ -1421,7 +1415,7 @@ impl<'a> Parser<'a> {
 
                 // Consume close delimiter
                 self.bump();
-                TokenTree::Delimited(span, spacing, delim, stream)
+                tree
             }
             token::CloseDelim(_) | token::Eof => unreachable!(),
             _ => {
@@ -1463,7 +1457,7 @@ impl<'a> Parser<'a> {
     pub fn parse_visibility(&mut self, fbt: FollowedByType) -> PResult<'a, Visibility> {
         maybe_whole!(self, NtVis, |vis| vis.into_inner());
 
-        if !self.eat_keyword(kw::Pub) {
+        if !self.eat_keyword(exp!(Pub)) {
             // We need a span for our `Spanned<VisibilityKind>`, but there's inherently no
             // keyword to grab a span from for inherited visibility; an empty span at the
             // beginning of the current token would seem to be the "Schelling span".
@@ -1475,7 +1469,7 @@ impl<'a> Parser<'a> {
         }
         let lo = self.prev_token.span;
 
-        if self.check(&token::OpenDelim(Delimiter::Parenthesis)) {
+        if self.check(exp!(OpenParen)) {
             // We don't `self.bump()` the `(` yet because this might be a struct definition where
             // `()` or a tuple might be allowed. For example, `struct Struct(pub (), pub (usize));`.
             // Because of this, we only `bump` the `(` if we're assured it is appropriate to do so
@@ -1485,7 +1479,7 @@ impl<'a> Parser<'a> {
                 self.bump(); // `(`
                 self.bump(); // `in`
                 let path = self.parse_path(PathStyle::Mod)?; // `path`
-                self.expect(&token::CloseDelim(Delimiter::Parenthesis))?; // `)`
+                self.expect(exp!(CloseParen))?; // `)`
                 let vis = VisibilityKind::Restricted {
                     path: P(path),
                     id: ast::DUMMY_NODE_ID,
@@ -1502,7 +1496,7 @@ impl<'a> Parser<'a> {
                 // Parse `pub(crate)`, `pub(self)`, or `pub(super)`.
                 self.bump(); // `(`
                 let path = self.parse_path(PathStyle::Mod)?; // `crate`/`super`/`self`
-                self.expect(&token::CloseDelim(Delimiter::Parenthesis))?; // `)`
+                self.expect(exp!(CloseParen))?; // `)`
                 let vis = VisibilityKind::Restricted {
                     path: P(path),
                     id: ast::DUMMY_NODE_ID,
@@ -1528,7 +1522,7 @@ impl<'a> Parser<'a> {
     fn recover_incorrect_vis_restriction(&mut self) -> PResult<'a, ()> {
         self.bump(); // `(`
         let path = self.parse_path(PathStyle::Mod)?;
-        self.expect(&token::CloseDelim(Delimiter::Parenthesis))?; // `)`
+        self.expect(exp!(CloseParen))?; // `)`
 
         let path_str = pprust::path_to_string(&path);
         self.dcx()
@@ -1539,7 +1533,7 @@ impl<'a> Parser<'a> {
 
     /// Parses `extern string_literal?`.
     fn parse_extern(&mut self, case: Case) -> Extern {
-        if self.eat_keyword_case(kw::Extern, case) {
+        if self.eat_keyword_case(exp!(Extern), case) {
             let mut extern_span = self.prev_token.span;
             let abi = self.parse_abi();
             if let Some(abi) = abi {
@@ -1579,7 +1573,7 @@ impl<'a> Parser<'a> {
 
     /// Checks for `::` or, potentially, `:::` and then look ahead after it.
     fn check_path_sep_and_look_ahead(&mut self, looker: impl Fn(&Token) -> bool) -> bool {
-        if self.check(&token::PathSep) {
+        if self.check(exp!(PathSep)) {
             if self.may_recover() && self.look_ahead(1, |t| t.kind == token::Colon) {
                 debug_assert!(!self.look_ahead(1, &looker), "Looker must not match on colon");
                 self.look_ahead(2, looker)
@@ -1643,8 +1637,8 @@ impl<'a> Parser<'a> {
         DebugParser { parser: self, lookahead }
     }
 
-    pub fn clear_expected_tokens(&mut self) {
-        self.expected_tokens.clear();
+    pub fn clear_expected_token_types(&mut self) {
+        self.expected_token_types.clear();
     }
 
     pub fn approx_token_stream_pos(&self) -> u32 {
diff --git a/compiler/rustc_parse/src/parser/mut_visit/tests.rs b/compiler/rustc_parse/src/parser/mut_visit/tests.rs
index b82c295732d..46c678c3902 100644
--- a/compiler/rustc_parse/src/parser/mut_visit/tests.rs
+++ b/compiler/rustc_parse/src/parser/mut_visit/tests.rs
@@ -1,8 +1,7 @@
 use rustc_ast as ast;
 use rustc_ast::mut_visit::MutVisitor;
 use rustc_ast_pretty::pprust;
-use rustc_span::create_default_session_globals_then;
-use rustc_span::symbol::Ident;
+use rustc_span::{Ident, create_default_session_globals_then};
 
 use crate::parser::tests::{matches_codepattern, string_to_crate};
 
diff --git a/compiler/rustc_parse/src/parser/nonterminal.rs b/compiler/rustc_parse/src/parser/nonterminal.rs
index 752a52b382b..67cabb757e9 100644
--- a/compiler/rustc_parse/src/parser/nonterminal.rs
+++ b/compiler/rustc_parse/src/parser/nonterminal.rs
@@ -9,7 +9,7 @@ use rustc_ast::token::{
 use rustc_ast_pretty::pprust;
 use rustc_data_structures::sync::Lrc;
 use rustc_errors::PResult;
-use rustc_span::symbol::{Ident, kw};
+use rustc_span::{Ident, kw};
 
 use crate::errors::UnexpectedNonterminal;
 use crate::parser::pat::{CommaRecoveryMode, RecoverColon, RecoverComma};
diff --git a/compiler/rustc_parse/src/parser/pat.rs b/compiler/rustc_parse/src/parser/pat.rs
index 4cda887a02b..5ad3da2196f 100644
--- a/compiler/rustc_parse/src/parser/pat.rs
+++ b/compiler/rustc_parse/src/parser/pat.rs
@@ -13,8 +13,7 @@ use rustc_ast_pretty::pprust;
 use rustc_errors::{Applicability, Diag, DiagArgValue, PResult, StashKey};
 use rustc_session::errors::ExprParenthesesNeeded;
 use rustc_span::source_map::{Spanned, respan};
-use rustc_span::symbol::{Ident, kw, sym};
-use rustc_span::{BytePos, ErrorGuaranteed, Span};
+use rustc_span::{BytePos, ErrorGuaranteed, Ident, Span, kw, sym};
 use thin_vec::{ThinVec, thin_vec};
 
 use super::{ForceCollect, Parser, PathStyle, Restrictions, Trailing, UsePreAttrPos};
@@ -31,7 +30,7 @@ use crate::errors::{
     UnexpectedVertVertInPattern, WrapInParens,
 };
 use crate::parser::expr::{DestructuredFloat, could_be_unclosed_char_literal};
-use crate::{maybe_recover_from_interpolated_ty_qpath, maybe_whole};
+use crate::{exp, maybe_recover_from_interpolated_ty_qpath, maybe_whole};
 
 #[derive(PartialEq, Copy, Clone)]
 pub enum Expected {
@@ -111,7 +110,7 @@ impl<'a> Parser<'a> {
     ) -> PResult<'a, P<Pat>> {
         let pat = self.parse_pat_no_top_guard(expected, rc, ra, rt)?;
 
-        if self.eat_keyword(kw::If) {
+        if self.eat_keyword(exp!(If)) {
             let cond = self.parse_expr()?;
             // Feature-gate guard patterns
             self.psess.gated_spans.gate(sym::guard_patterns, cond.span);
@@ -194,7 +193,7 @@ impl<'a> Parser<'a> {
 
         // If the next token is not a `|`,
         // this is not an or-pattern and we should exit here.
-        if !self.check(&token::BinOp(token::Or)) && self.token != token::OrOr {
+        if !self.check(exp!(Or)) && self.token != token::OrOr {
             // If we parsed a leading `|` which should be gated,
             // then we should really gate the leading `|`.
             // This complicated procedure is done purely for diagnostics UX.
@@ -264,7 +263,7 @@ impl<'a> Parser<'a> {
             CommaRecoveryMode::LikelyTuple,
             Some(syntax_loc),
         )?;
-        let colon = self.eat(&token::Colon);
+        let colon = self.eat(exp!(Colon));
 
         if let PatKind::Or(pats) = &pat.kind {
             let span = pat.span;
@@ -328,7 +327,7 @@ impl<'a> Parser<'a> {
             self.dcx().emit_err(UnexpectedVertVertInPattern { span: self.token.span, start: lo });
             self.bump();
             EatOrResult::AteOr
-        } else if self.eat(&token::BinOp(token::Or)) {
+        } else if self.eat(exp!(Or)) {
             EatOrResult::AteOr
         } else {
             EatOrResult::None
@@ -715,40 +714,41 @@ impl<'a> Parser<'a> {
             lo = self.token.span;
         }
 
-        let pat = if self.check(&token::BinOp(token::And)) || self.token == token::AndAnd {
+        let pat = if self.check(exp!(And)) || self.token == token::AndAnd {
             self.parse_pat_deref(expected)?
-        } else if self.check(&token::OpenDelim(Delimiter::Parenthesis)) {
+        } else if self.check(exp!(OpenParen)) {
             self.parse_pat_tuple_or_parens()?
-        } else if self.check(&token::OpenDelim(Delimiter::Bracket)) {
+        } else if self.check(exp!(OpenBracket)) {
             // Parse `[pat, pat,...]` as a slice pattern.
-            let (pats, _) = self.parse_delim_comma_seq(Delimiter::Bracket, |p| {
-                p.parse_pat_allow_top_guard(
-                    None,
-                    RecoverComma::No,
-                    RecoverColon::No,
-                    CommaRecoveryMode::EitherTupleOrPipe,
-                )
-            })?;
+            let (pats, _) =
+                self.parse_delim_comma_seq(exp!(OpenBracket), exp!(CloseBracket), |p| {
+                    p.parse_pat_allow_top_guard(
+                        None,
+                        RecoverComma::No,
+                        RecoverColon::No,
+                        CommaRecoveryMode::EitherTupleOrPipe,
+                    )
+                })?;
             PatKind::Slice(pats)
-        } else if self.check(&token::DotDot) && !self.is_pat_range_end_start(1) {
+        } else if self.check(exp!(DotDot)) && !self.is_pat_range_end_start(1) {
             // A rest pattern `..`.
             self.bump(); // `..`
             PatKind::Rest
-        } else if self.check(&token::DotDotDot) && !self.is_pat_range_end_start(1) {
+        } else if self.check(exp!(DotDotDot)) && !self.is_pat_range_end_start(1) {
             self.recover_dotdotdot_rest_pat(lo)
         } else if let Some(form) = self.parse_range_end() {
             self.parse_pat_range_to(form)? // `..=X`, `...X`, or `..X`.
-        } else if self.eat(&token::Not) {
+        } else if self.eat(exp!(Not)) {
             // Parse `!`
             self.psess.gated_spans.gate(sym::never_patterns, self.prev_token.span);
             PatKind::Never
-        } else if self.eat_keyword(kw::Underscore) {
+        } else if self.eat_keyword(exp!(Underscore)) {
             // Parse `_`
             PatKind::Wild
-        } else if self.eat_keyword(kw::Mut) {
+        } else if self.eat_keyword(exp!(Mut)) {
             self.parse_pat_ident_mut()?
-        } else if self.eat_keyword(kw::Ref) {
-            if self.check_keyword(kw::Box) {
+        } else if self.eat_keyword(exp!(Ref)) {
+            if self.check_keyword(exp!(Box)) {
                 // Suggest `box ref`.
                 let span = self.prev_token.span.to(self.token.span);
                 self.bump();
@@ -757,7 +757,7 @@ impl<'a> Parser<'a> {
             // Parse ref ident @ pat / ref mut ident @ pat
             let mutbl = self.parse_mutability();
             self.parse_pat_ident(BindingMode(ByRef::Yes(mutbl), Mutability::Not), syntax_loc)?
-        } else if self.eat_keyword(kw::Box) {
+        } else if self.eat_keyword(exp!(Box)) {
             self.parse_pat_box()?
         } else if self.check_inline_const(0) {
             // Parse `const pat`
@@ -794,14 +794,14 @@ impl<'a> Parser<'a> {
             };
             let span = lo.to(self.prev_token.span);
 
-            if qself.is_none() && self.check(&token::Not) {
+            if qself.is_none() && self.check(exp!(Not)) {
                 self.parse_pat_mac_invoc(path)?
             } else if let Some(form) = self.parse_range_end() {
                 let begin = self.mk_expr(span, ExprKind::Path(qself, path));
                 self.parse_pat_range_begin_with(begin, form)?
-            } else if self.check(&token::OpenDelim(Delimiter::Brace)) {
+            } else if self.check(exp!(OpenBrace)) {
                 self.parse_pat_struct(qself, path)?
-            } else if self.check(&token::OpenDelim(Delimiter::Parenthesis)) {
+            } else if self.check(exp!(OpenParen)) {
                 self.parse_pat_tuple_struct(qself, path)?
             } else {
                 match self.maybe_recover_trailing_expr(span, false) {
@@ -1107,7 +1107,7 @@ impl<'a> Parser<'a> {
     /// Eat any extraneous `mut`s and error + recover if we ate any.
     fn recover_additional_muts(&mut self) {
         let lo = self.token.span;
-        while self.eat_keyword(kw::Mut) {}
+        while self.eat_keyword(exp!(Mut)) {}
         if lo == self.token.span {
             return;
         }
@@ -1148,11 +1148,11 @@ impl<'a> Parser<'a> {
 
     /// Parses the range pattern end form `".." | "..." | "..=" ;`.
     fn parse_range_end(&mut self) -> Option<Spanned<RangeEnd>> {
-        let re = if self.eat(&token::DotDotDot) {
+        let re = if self.eat(exp!(DotDotDot)) {
             RangeEnd::Included(RangeSyntax::DotDotDot)
-        } else if self.eat(&token::DotDotEq) {
+        } else if self.eat(exp!(DotDotEq)) {
             RangeEnd::Included(RangeSyntax::DotDotEq)
-        } else if self.eat(&token::DotDot) {
+        } else if self.eat(exp!(DotDot)) {
             RangeEnd::Excluded
         } else {
             return None;
@@ -1272,7 +1272,7 @@ impl<'a> Parser<'a> {
 
         // recover trailing `)`
         if let Some(open_paren) = open_paren {
-            self.expect(&token::CloseDelim(Delimiter::Parenthesis))?;
+            self.expect(exp!(CloseParen))?;
 
             self.dcx().emit_err(UnexpectedParenInRangePat {
                 span: vec![open_paren, self.prev_token.span],
@@ -1332,7 +1332,7 @@ impl<'a> Parser<'a> {
             }));
         }
 
-        let sub = if self.eat(&token::At) {
+        let sub = if self.eat(exp!(At)) {
             Some(self.parse_pat_no_top_alt(Some(Expected::BindingPattern), None)?)
         } else {
             None
@@ -1371,10 +1371,10 @@ impl<'a> Parser<'a> {
         self.bump();
         let (fields, etc) = self.parse_pat_fields().unwrap_or_else(|mut e| {
             e.span_label(path.span, "while parsing the fields for this pattern");
-            e.emit();
+            let guar = e.emit();
             self.recover_stmt();
             // When recovering, pretend we had `Foo { .. }`, to avoid cascading errors.
-            (ThinVec::new(), PatFieldsRest::Rest)
+            (ThinVec::new(), PatFieldsRest::Recovered(guar))
         });
         self.bump();
         Ok(PatKind::Struct(qself, path, fields, etc))
@@ -1448,7 +1448,7 @@ impl<'a> Parser<'a> {
 
             // We cannot use `parse_pat_ident()` since it will complain `box`
             // is not an identifier.
-            let sub = if self.eat(&token::At) {
+            let sub = if self.eat(exp!(At)) {
                 Some(self.parse_pat_no_top_alt(Some(Expected::BindingPattern), None)?)
             } else {
                 None
@@ -1505,9 +1505,9 @@ impl<'a> Parser<'a> {
             }
             ate_comma = false;
 
-            if self.check(&token::DotDot)
+            if self.check(exp!(DotDot))
                 || self.check_noexpect(&token::DotDotDot)
-                || self.check_keyword(kw::Underscore)
+                || self.check_keyword(exp!(Underscore))
             {
                 etc = PatFieldsRest::Rest;
                 let mut etc_sp = self.token.span;
@@ -1595,7 +1595,7 @@ impl<'a> Parser<'a> {
                         return Err(err);
                     }
                 }?;
-                ate_comma = this.eat(&token::Comma);
+                ate_comma = this.eat(exp!(Comma));
 
                 last_non_comma_dotdot_span = Some(this.prev_token.span);
 
@@ -1648,7 +1648,7 @@ impl<'a> Parser<'a> {
                 ident: prev_field,
             })
         } else {
-            self.dcx().create_err(AtInStructPattern { span: span })
+            self.dcx().create_err(AtInStructPattern { span })
         }
     }
 
@@ -1707,7 +1707,7 @@ impl<'a> Parser<'a> {
             (pat, fieldname, false)
         } else {
             // Parsing a pattern of the form `(box) (ref) (mut) fieldname`.
-            let is_box = self.eat_keyword(kw::Box);
+            let is_box = self.eat_keyword(exp!(Box));
             let boxed_span = self.token.span;
             let mutability = self.parse_mutability();
             let by_ref = self.parse_byref();
diff --git a/compiler/rustc_parse/src/parser/path.rs b/compiler/rustc_parse/src/parser/path.rs
index 6a7029a8f1c..39737b9e137 100644
--- a/compiler/rustc_parse/src/parser/path.rs
+++ b/compiler/rustc_parse/src/parser/path.rs
@@ -9,8 +9,7 @@ use rustc_ast::{
     Path, PathSegment, QSelf,
 };
 use rustc_errors::{Applicability, Diag, PResult};
-use rustc_span::symbol::{Ident, kw, sym};
-use rustc_span::{BytePos, Span};
+use rustc_span::{BytePos, Ident, Span, kw, sym};
 use thin_vec::ThinVec;
 use tracing::debug;
 
@@ -18,7 +17,7 @@ use super::ty::{AllowPlus, RecoverQPath, RecoverReturnSign};
 use super::{Parser, Restrictions, TokenType};
 use crate::errors::{PathSingleColon, PathTripleColon};
 use crate::parser::{CommaRecoveryMode, RecoverColon, RecoverComma};
-use crate::{errors, maybe_whole};
+use crate::{errors, exp, maybe_whole};
 
 /// Specifies how to parse a path.
 #[derive(Copy, Clone, PartialEq)]
@@ -81,7 +80,7 @@ impl<'a> Parser<'a> {
         // above). `path_span` has the span of that path, or an empty
         // span in the case of something like `<T>::Bar`.
         let (mut path, path_span);
-        if self.eat_keyword(kw::As) {
+        if self.eat_keyword(exp!(As)) {
             let path_lo = self.token.span;
             path = self.parse_path(PathStyle::Type)?;
             path_span = path_lo.to(self.prev_token.span);
@@ -91,7 +90,7 @@ impl<'a> Parser<'a> {
         }
 
         // See doc comment for `unmatched_angle_bracket_count`.
-        self.expect(&token::Gt)?;
+        self.expect(exp!(Gt))?;
         if self.unmatched_angle_bracket_count > 0 {
             self.unmatched_angle_bracket_count -= 1;
             debug!("parse_qpath: (decrement) count={:?}", self.unmatched_angle_bracket_count);
@@ -99,7 +98,7 @@ impl<'a> Parser<'a> {
 
         let is_import_coupler = self.is_import_coupler();
         if !is_import_coupler && !self.recover_colon_before_qpath_proj() {
-            self.expect(&token::PathSep)?;
+            self.expect(exp!(PathSep))?;
         }
 
         let qself = P(QSelf { ty, path_span, position: path.segments.len() });
@@ -243,7 +242,7 @@ impl<'a> Parser<'a> {
                 // `PathStyle::Expr` is only provided at the root invocation and never in
                 // `parse_path_segment` to recurse and therefore can be checked to maintain
                 // this invariant.
-                self.check_trailing_angle_brackets(&segment, &[&token::PathSep]);
+                self.check_trailing_angle_brackets(&segment, &[exp!(PathSep)]);
             }
             segments.push(segment);
 
@@ -276,7 +275,7 @@ impl<'a> Parser<'a> {
     /// Eat `::` or, potentially, `:::`.
     #[must_use]
     pub(super) fn eat_path_sep(&mut self) -> bool {
-        let result = self.eat(&token::PathSep);
+        let result = self.eat(exp!(PathSep));
         if result && self.may_recover() {
             if self.eat_noexpect(&token::Colon) {
                 self.dcx().emit_err(PathTripleColon { span: self.prev_token.span });
@@ -301,10 +300,8 @@ impl<'a> Parser<'a> {
             )
         };
         let check_args_start = |this: &mut Self| {
-            this.expected_tokens.extend_from_slice(&[
-                TokenType::Token(token::Lt),
-                TokenType::Token(token::OpenDelim(Delimiter::Parenthesis)),
-            ]);
+            this.expected_token_types.insert(TokenType::Lt);
+            this.expected_token_types.insert(TokenType::OpenParen);
             is_args_start(&this.token)
         };
 
@@ -368,7 +365,7 @@ impl<'a> Parser<'a> {
                 {
                     self.bump(); // (
                     self.bump(); // ..
-                    self.expect(&token::CloseDelim(Delimiter::Parenthesis))?;
+                    self.expect(exp!(CloseParen))?;
                     let span = lo.to(self.prev_token.span);
 
                     self.psess.gated_spans.gate(sym::return_type_notation, span);
@@ -600,8 +597,7 @@ impl<'a> Parser<'a> {
                 // When encountering severely malformed code where there are several levels of
                 // nested unclosed angle args (`f::<f::<f::<f::<...`), we avoid severe O(n^2)
                 // behavior by bailing out earlier (#117080).
-                e.emit();
-                rustc_errors::FatalError.raise();
+                e.emit().raise_fatal();
             }
             Err(e) if is_first_invocation && self.unmatched_angle_bracket_count > 0 => {
                 self.angle_bracket_nesting -= 1;
@@ -662,12 +658,12 @@ impl<'a> Parser<'a> {
         let mut args = ThinVec::new();
         while let Some(arg) = self.parse_angle_arg(ty_generics)? {
             args.push(arg);
-            if !self.eat(&token::Comma) {
+            if !self.eat(exp!(Comma)) {
                 if self.check_noexpect(&TokenKind::Semi)
                     && self.look_ahead(1, |t| t.is_ident() || t.is_lifetime())
                 {
                     // Add `>` to the list of expected tokens.
-                    self.check(&token::Gt);
+                    self.check(exp!(Gt));
                     // Handle `,` to `;` substitution
                     let mut err = self.unexpected().unwrap_err();
                     self.bump();
@@ -706,7 +702,7 @@ impl<'a> Parser<'a> {
                 // is present and then use that info to push the other token onto the tokens list
                 let separated =
                     self.check_noexpect(&token::Colon) || self.check_noexpect(&token::Eq);
-                if separated && (self.check(&token::Colon) | self.check(&token::Eq)) {
+                if separated && (self.check(exp!(Colon)) | self.check(exp!(Eq))) {
                     let arg_span = arg.span();
                     let (binder, ident, gen_args) = match self.get_ident_from_generic_arg(&arg) {
                         Ok(ident_gen_args) => ident_gen_args,
@@ -721,9 +717,9 @@ impl<'a> Parser<'a> {
                             "`for<...>` is not allowed on associated type bounds",
                         ));
                     }
-                    let kind = if self.eat(&token::Colon) {
+                    let kind = if self.eat(exp!(Colon)) {
                         AssocItemConstraintKind::Bound { bounds: self.parse_generic_bounds()? }
-                    } else if self.eat(&token::Eq) {
+                    } else if self.eat(exp!(Eq)) {
                         self.parse_assoc_equality_term(
                             ident,
                             gen_args.as_ref(),
@@ -744,8 +740,8 @@ impl<'a> Parser<'a> {
                     if self.prev_token.is_ident()
                         && (self.token.is_ident() || self.look_ahead(1, |token| token.is_ident()))
                     {
-                        self.check(&token::Colon);
-                        self.check(&token::Eq);
+                        self.check(exp!(Colon));
+                        self.check(exp!(Eq));
                     }
                     Ok(Some(AngleBracketedArg::Arg(arg)))
                 }
diff --git a/compiler/rustc_parse/src/parser/stmt.rs b/compiler/rustc_parse/src/parser/stmt.rs
index 5fa2e01fc86..1ddb5fc0a11 100644
--- a/compiler/rustc_parse/src/parser/stmt.rs
+++ b/compiler/rustc_parse/src/parser/stmt.rs
@@ -12,8 +12,7 @@ use rustc_ast::{
     LocalKind, MacCall, MacCallStmt, MacStmtStyle, Recovered, Stmt, StmtKind,
 };
 use rustc_errors::{Applicability, Diag, PResult};
-use rustc_span::symbol::{Ident, kw, sym};
-use rustc_span::{BytePos, ErrorGuaranteed, Span};
+use rustc_span::{BytePos, ErrorGuaranteed, Ident, Span, kw, sym};
 use thin_vec::{ThinVec, thin_vec};
 
 use super::attr::InnerAttrForbiddenReason;
@@ -25,7 +24,7 @@ use super::{
     Trailing, UsePreAttrPos,
 };
 use crate::errors::MalformedLoopLabel;
-use crate::{errors, maybe_whole};
+use crate::{errors, exp, maybe_whole};
 
 impl<'a> Parser<'a> {
     /// Parses a statement. This stops just before trailing semicolons on everything but items.
@@ -72,7 +71,7 @@ impl<'a> Parser<'a> {
 
         let stmt = if self.token.is_keyword(kw::Let) {
             self.collect_tokens(None, attrs, force_collect, |this, attrs| {
-                this.expect_keyword(kw::Let)?;
+                this.expect_keyword(exp!(Let))?;
                 let local = this.parse_local(attrs)?;
                 let trailing = Trailing::from(capture_semi && this.token == token::Semi);
                 Ok((
@@ -141,7 +140,7 @@ impl<'a> Parser<'a> {
             force_collect,
         )? {
             self.mk_stmt(lo.to(item.span), StmtKind::Item(P(item)))
-        } else if self.eat(&token::Semi) {
+        } else if self.eat(exp!(Semi)) {
             // Do not attempt to parse an expression if we're done here.
             self.error_outer_attrs(attrs);
             self.mk_stmt(lo, StmtKind::Empty)
@@ -157,7 +156,7 @@ impl<'a> Parser<'a> {
                     Ok((expr, Trailing::No, UsePreAttrPos::Yes))
                 },
             )?;
-            if matches!(e.kind, ExprKind::Assign(..)) && self.eat_keyword(kw::Else) {
+            if matches!(e.kind, ExprKind::Assign(..)) && self.eat_keyword(exp!(Else)) {
                 let bl = self.parse_block()?;
                 // Destructuring assignment ... else.
                 // This is not allowed, but point it out in a nice way.
@@ -177,7 +176,7 @@ impl<'a> Parser<'a> {
         let stmt = self.collect_tokens(None, attrs, ForceCollect::No, |this, attrs| {
             let path = this.parse_path(PathStyle::Expr)?;
 
-            if this.eat(&token::Not) {
+            if this.eat(exp!(Not)) {
                 let stmt_mac = this.parse_stmt_mac(lo, attrs, path)?;
                 return Ok((
                     stmt_mac,
@@ -186,7 +185,7 @@ impl<'a> Parser<'a> {
                 ));
             }
 
-            let expr = if this.eat(&token::OpenDelim(Delimiter::Brace)) {
+            let expr = if this.eat(exp!(OpenBrace)) {
                 this.parse_expr_struct(None, path, true)?
             } else {
                 let hi = this.prev_token.span;
@@ -371,7 +370,7 @@ impl<'a> Parser<'a> {
         let kind = match init {
             None => LocalKind::Decl,
             Some(init) => {
-                if self.eat_keyword(kw::Else) {
+                if self.eat_keyword(exp!(Else)) {
                     if self.token.is_keyword(kw::If) {
                         // `let...else if`. Emit the same error that `parse_block()` would,
                         // but explicitly point out that this pattern is not allowed.
@@ -450,7 +449,7 @@ impl<'a> Parser<'a> {
                 self.bump();
                 true
             }
-            _ => self.eat(&token::Eq),
+            _ => self.eat(exp!(Eq)),
         };
 
         Ok(if eq_consumed || eq_optional { Some(self.parse_expr()?) } else { None })
@@ -510,7 +509,7 @@ impl<'a> Parser<'a> {
             Ok(Some(Stmt { kind: StmtKind::Empty, .. })) => {}
             Ok(Some(stmt)) => {
                 let stmt_own_line = self.psess.source_map().is_line_before_span_empty(sp);
-                let stmt_span = if stmt_own_line && self.eat(&token::Semi) {
+                let stmt_span = if stmt_own_line && self.eat(exp!(Semi)) {
                     // Expand the span to include the semicolon.
                     stmt.span.with_hi(self.prev_token.span.hi())
                 } else {
@@ -652,7 +651,7 @@ impl<'a> Parser<'a> {
 
         let maybe_ident = self.prev_token.clone();
         self.maybe_recover_unexpected_block_label();
-        if !self.eat(&token::OpenDelim(Delimiter::Brace)) {
+        if !self.eat(exp!(OpenBrace)) {
             return self.error_block_no_opening_brace();
         }
 
@@ -679,7 +678,7 @@ impl<'a> Parser<'a> {
     ) -> PResult<'a, P<Block>> {
         let mut stmts = ThinVec::new();
         let mut snapshot = None;
-        while !self.eat(&token::CloseDelim(Delimiter::Brace)) {
+        while !self.eat(exp!(CloseBrace)) {
             if self.token == token::Eof {
                 break;
             }
@@ -746,6 +745,51 @@ impl<'a> Parser<'a> {
         Ok(self.mk_block(stmts, s, lo.to(self.prev_token.span)))
     }
 
+    fn recover_missing_dot(&mut self, err: &mut Diag<'_>) {
+        let Some((ident, _)) = self.token.ident() else {
+            return;
+        };
+        if let Some(c) = ident.name.as_str().chars().next()
+            && c.is_uppercase()
+        {
+            return;
+        }
+        if self.token.is_reserved_ident() && !self.token.is_ident_named(kw::Await) {
+            return;
+        }
+        if self.prev_token.is_reserved_ident() && self.prev_token.is_ident_named(kw::Await) {
+            // Likely `foo.await bar`
+        } else if !self.prev_token.is_reserved_ident() && self.prev_token.is_ident() {
+            // Likely `foo bar`
+        } else if self.prev_token.kind == token::Question {
+            // `foo? bar`
+        } else if self.prev_token.kind == token::CloseDelim(Delimiter::Parenthesis) {
+            // `foo() bar`
+        } else {
+            return;
+        }
+        if self.token.span == self.prev_token.span {
+            // Account for syntax errors in proc-macros.
+            return;
+        }
+        if self.look_ahead(1, |t| [token::Semi, token::Question, token::Dot].contains(&t.kind)) {
+            err.span_suggestion_verbose(
+                self.prev_token.span.between(self.token.span),
+                "you might have meant to write a field access",
+                ".".to_string(),
+                Applicability::MaybeIncorrect,
+            );
+        }
+        if self.look_ahead(1, |t| t.kind == token::OpenDelim(Delimiter::Parenthesis)) {
+            err.span_suggestion_verbose(
+                self.prev_token.span.between(self.token.span),
+                "you might have meant to write a method call",
+                ".".to_string(),
+                Applicability::MaybeIncorrect,
+            );
+        }
+    }
+
     /// Parses a statement, including the trailing semicolon.
     pub fn parse_full_stmt(
         &mut self,
@@ -782,8 +826,7 @@ impl<'a> Parser<'a> {
             {
                 // Just check for errors and recover; do not eat semicolon yet.
 
-                let expect_result =
-                    self.expect_one_of(&[], &[token::Semi, token::CloseDelim(Delimiter::Brace)]);
+                let expect_result = self.expect_one_of(&[], &[exp!(Semi), exp!(CloseBrace)]);
 
                 // Try to both emit a better diagnostic, and avoid further errors by replacing
                 // the `expr` with `ExprKind::Err`.
@@ -853,7 +896,8 @@ impl<'a> Parser<'a> {
                             Some(if recover.no() {
                                 res?
                             } else {
-                                res.unwrap_or_else(|e| {
+                                res.unwrap_or_else(|mut e| {
+                                    self.recover_missing_dot(&mut e);
                                     let guar = e.emit();
                                     self.recover_stmt();
                                     guar
@@ -874,7 +918,12 @@ impl<'a> Parser<'a> {
                 // We might be at the `,` in `let x = foo<bar, baz>;`. Try to recover.
                 match &mut local.kind {
                     LocalKind::Init(expr) | LocalKind::InitElse(expr, _) => {
-                        self.check_mistyped_turbofish_with_multiple_type_params(e, expr)?;
+                        self.check_mistyped_turbofish_with_multiple_type_params(e, expr).map_err(
+                            |mut e| {
+                                self.recover_missing_dot(&mut e);
+                                e
+                            },
+                        )?;
                         // We found `foo<bar, baz>`, have we fully recovered?
                         self.expect_semi()?;
                     }
@@ -931,7 +980,7 @@ impl<'a> Parser<'a> {
             }
         }
 
-        if add_semi_to_stmt || (eat_semi && self.eat(&token::Semi)) {
+        if add_semi_to_stmt || (eat_semi && self.eat(exp!(Semi))) {
             stmt = stmt.add_trailing_semicolon();
         }
 
diff --git a/compiler/rustc_parse/src/parser/tests.rs b/compiler/rustc_parse/src/parser/tests.rs
index 1813960dad0..3f8d66c2c95 100644
--- a/compiler/rustc_parse/src/parser/tests.rs
+++ b/compiler/rustc_parse/src/parser/tests.rs
@@ -18,8 +18,9 @@ use rustc_errors::emitter::{HumanEmitter, OutputTheme};
 use rustc_errors::{DiagCtxt, MultiSpan, PResult};
 use rustc_session::parse::ParseSess;
 use rustc_span::source_map::{FilePathMapping, SourceMap};
-use rustc_span::symbol::{Symbol, kw, sym};
-use rustc_span::{BytePos, FileName, Pos, Span, create_default_session_globals_then};
+use rustc_span::{
+    BytePos, FileName, Pos, Span, Symbol, create_default_session_globals_then, kw, sym,
+};
 use termcolor::WriteColor;
 
 use crate::parser::{ForceCollect, Parser};
@@ -2285,7 +2286,7 @@ fn bad_path_expr_1() {
 fn string_to_tts_macro() {
     create_default_session_globals_then(|| {
         let stream = string_to_stream("macro_rules! zip (($a)=>($a))".to_string());
-        let tts = &stream.trees().collect::<Vec<_>>()[..];
+        let tts = &stream.iter().collect::<Vec<_>>()[..];
 
         match tts {
             [
@@ -2297,14 +2298,14 @@ fn string_to_tts_macro() {
                 TokenTree::Token(Token { kind: token::Ident(name_zip, IdentIsRaw::No), .. }, _),
                 TokenTree::Delimited(.., macro_delim, macro_tts),
             ] if name_macro_rules == &kw::MacroRules && name_zip.as_str() == "zip" => {
-                let tts = &macro_tts.trees().collect::<Vec<_>>();
+                let tts = &macro_tts.iter().collect::<Vec<_>>();
                 match &tts[..] {
                     [
                         TokenTree::Delimited(.., first_delim, first_tts),
                         TokenTree::Token(Token { kind: token::FatArrow, .. }, _),
                         TokenTree::Delimited(.., second_delim, second_tts),
                     ] if macro_delim == &Delimiter::Parenthesis => {
-                        let tts = &first_tts.trees().collect::<Vec<_>>();
+                        let tts = &first_tts.iter().collect::<Vec<_>>();
                         match &tts[..] {
                             [
                                 TokenTree::Token(Token { kind: token::Dollar, .. }, _),
@@ -2316,7 +2317,7 @@ fn string_to_tts_macro() {
                             }
                             _ => panic!("value 3: {:?} {:?}", first_delim, first_tts),
                         }
-                        let tts = &second_tts.trees().collect::<Vec<_>>();
+                        let tts = &second_tts.iter().collect::<Vec<_>>();
                         match &tts[..] {
                             [
                                 TokenTree::Token(Token { kind: token::Dollar, .. }, _),
@@ -2544,7 +2545,7 @@ fn ttdelim_span() {
         .unwrap();
 
         let ast::ExprKind::MacCall(mac) = &expr.kind else { panic!("not a macro") };
-        let span = mac.args.tokens.trees().last().unwrap().span();
+        let span = mac.args.tokens.iter().last().unwrap().span();
 
         match psess.source_map().span_to_snippet(span) {
             Ok(s) => assert_eq!(&s[..], "{ body }"),
diff --git a/compiler/rustc_parse/src/parser/token_type.rs b/compiler/rustc_parse/src/parser/token_type.rs
new file mode 100644
index 00000000000..73f3ac001c8
--- /dev/null
+++ b/compiler/rustc_parse/src/parser/token_type.rs
@@ -0,0 +1,631 @@
+use rustc_ast::token::TokenKind;
+use rustc_span::symbol::{Symbol, kw, sym};
+
+/// Used in "expected"/"expected one of" error messages. Tokens are added here
+/// as necessary. Tokens with values (e.g. literals, identifiers) are
+/// represented by a single variant (e.g. `Literal`, `Ident`).
+///
+/// It's an awkward representation, but it's important for performance. It's a
+/// C-style parameterless enum so that `TokenTypeSet` can be a bitset. This is
+/// important because `Parser::expected_token_types` is very hot. `TokenType`
+/// used to have variants with parameters (e.g. all the keywords were in a
+/// single `Keyword` variant with a `Symbol` parameter) and
+/// `Parser::expected_token_types` was a `Vec<TokenType>` which was much slower
+/// to manipulate.
+///
+/// We really want to keep the number of variants to 128 or fewer, so that
+/// `TokenTypeSet` can be implemented with a `u128`.
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub enum TokenType {
+    // Expression-operator symbols
+    Eq,
+    Lt,
+    Le,
+    EqEq,
+    Gt,
+    AndAnd,
+    OrOr,
+    Not,
+    Tilde,
+
+    // BinOps
+    Plus,
+    Minus,
+    Star,
+    And,
+    Or,
+
+    // Structural symbols
+    At,
+    Dot,
+    DotDot,
+    DotDotDot,
+    DotDotEq,
+    Comma,
+    Semi,
+    Colon,
+    PathSep,
+    RArrow,
+    FatArrow,
+    Pound,
+    Question,
+    OpenParen,
+    CloseParen,
+    OpenBrace,
+    CloseBrace,
+    OpenBracket,
+    CloseBracket,
+    Eof,
+
+    // Token types with some details elided.
+    /// Any operator.
+    Operator,
+    /// Any identifier token.
+    Ident,
+    /// Any lifetime token.
+    Lifetime,
+    /// Any token that can start a path.
+    Path,
+    /// Any token that can start a type.
+    Type,
+    /// Any token that can start a const expression.
+    Const,
+
+    // Keywords
+    // tidy-alphabetical-start
+    KwAs,
+    KwAsync,
+    KwAuto,
+    KwAwait,
+    KwBecome,
+    KwBox,
+    KwBreak,
+    KwCatch,
+    KwConst,
+    KwContinue,
+    KwCrate,
+    KwDefault,
+    KwDyn,
+    KwElse,
+    KwEnum,
+    KwExtern,
+    KwFn,
+    KwFor,
+    KwGen,
+    KwIf,
+    KwImpl,
+    KwIn,
+    KwLet,
+    KwLoop,
+    KwMacro,
+    KwMacroRules,
+    KwMatch,
+    KwMod,
+    KwMove,
+    KwMut,
+    KwPub,
+    KwRaw,
+    KwRef,
+    KwReturn,
+    KwReuse,
+    KwSafe,
+    KwSelfUpper,
+    KwStatic,
+    KwStruct,
+    KwTrait,
+    KwTry,
+    KwType,
+    KwUnderscore,
+    KwUnsafe,
+    KwUse,
+    KwWhere,
+    KwWhile,
+    KwYield,
+    // tidy-alphabetical-end
+
+    // Keyword-like symbols.
+    // tidy-alphabetical-start
+    SymAttSyntax,
+    SymClobberAbi,
+    SymInlateout,
+    SymInout,
+    SymIs,
+    SymLabel,
+    SymLateout,
+    SymMayUnwind,
+    SymNomem,
+    SymNoreturn,
+    SymNostack,
+    SymOptions,
+    SymOut,
+    SymPreservesFlags,
+    SymPure,
+    SymReadonly,
+    SymSym,
+    // tidy-alphabetical-end
+}
+
+// Macro to avoid repetitive boilerplate code.
+macro_rules! from_u32_match {
+    ($val:ident; $($tok:ident,)+) => {
+        // A more obvious formulation would be `0 => TokenType::Eq`. But
+        // this formulation with the guard lets us avoid specifying a
+        // specific integer for each variant.
+        match $val {
+            $(
+                t if t == TokenType::$tok as u32 => TokenType::$tok,
+            )+
+            _ => panic!("unhandled value: {}", $val),
+        }
+    };
+}
+
+impl TokenType {
+    fn from_u32(val: u32) -> TokenType {
+        let token_type = from_u32_match! { val;
+            Eq,
+            Lt,
+            Le,
+            EqEq,
+            Gt,
+            AndAnd,
+            OrOr,
+            Not,
+            Tilde,
+
+            Plus,
+            Minus,
+            Star,
+            And,
+            Or,
+
+            At,
+            Dot,
+            DotDot,
+            DotDotDot,
+            DotDotEq,
+            Comma,
+            Semi,
+            Colon,
+            PathSep,
+            RArrow,
+            FatArrow,
+            Pound,
+            Question,
+            OpenParen,
+            CloseParen,
+            OpenBrace,
+            CloseBrace,
+            OpenBracket,
+            CloseBracket,
+            Eof,
+
+            Operator,
+            Ident,
+            Lifetime,
+            Path,
+            Type,
+            Const,
+
+            KwAs,
+            KwAsync,
+            KwAuto,
+            KwAwait,
+            KwBecome,
+            KwBox,
+            KwBreak,
+            KwCatch,
+            KwConst,
+            KwContinue,
+            KwCrate,
+            KwDefault,
+            KwDyn,
+            KwElse,
+            KwEnum,
+            KwExtern,
+            KwFn,
+            KwFor,
+            KwGen,
+            KwIf,
+            KwImpl,
+            KwIn,
+            KwLet,
+            KwLoop,
+            KwMacro,
+            KwMacroRules,
+            KwMatch,
+            KwMod,
+            KwMove,
+            KwMut,
+            KwPub,
+            KwRaw,
+            KwRef,
+            KwReturn,
+            KwReuse,
+            KwSafe,
+            KwSelfUpper,
+            KwStatic,
+            KwStruct,
+            KwTrait,
+            KwTry,
+            KwType,
+            KwUnderscore,
+            KwUnsafe,
+            KwUse,
+            KwWhere,
+            KwWhile,
+            KwYield,
+
+            SymAttSyntax,
+            SymClobberAbi,
+            SymInlateout,
+            SymInout,
+            SymIs,
+            SymLabel,
+            SymLateout,
+            SymMayUnwind,
+            SymNomem,
+            SymNoreturn,
+            SymNostack,
+            SymOptions,
+            SymOut,
+            SymPreservesFlags,
+            SymPure,
+            SymReadonly,
+            SymSym,
+        };
+        token_type
+    }
+
+    pub(super) fn is_keyword(&self) -> Option<Symbol> {
+        match self {
+            TokenType::KwAs => Some(kw::As),
+            TokenType::KwAsync => Some(kw::Async),
+            TokenType::KwAuto => Some(kw::Auto),
+            TokenType::KwAwait => Some(kw::Await),
+            TokenType::KwBecome => Some(kw::Become),
+            TokenType::KwBox => Some(kw::Box),
+            TokenType::KwBreak => Some(kw::Break),
+            TokenType::KwCatch => Some(kw::Catch),
+            TokenType::KwConst => Some(kw::Const),
+            TokenType::KwContinue => Some(kw::Continue),
+            TokenType::KwCrate => Some(kw::Crate),
+            TokenType::KwDefault => Some(kw::Default),
+            TokenType::KwDyn => Some(kw::Dyn),
+            TokenType::KwElse => Some(kw::Else),
+            TokenType::KwEnum => Some(kw::Enum),
+            TokenType::KwExtern => Some(kw::Extern),
+            TokenType::KwFn => Some(kw::Fn),
+            TokenType::KwFor => Some(kw::For),
+            TokenType::KwGen => Some(kw::Gen),
+            TokenType::KwIf => Some(kw::If),
+            TokenType::KwImpl => Some(kw::Impl),
+            TokenType::KwIn => Some(kw::In),
+            TokenType::KwLet => Some(kw::Let),
+            TokenType::KwLoop => Some(kw::Loop),
+            TokenType::KwMacroRules => Some(kw::MacroRules),
+            TokenType::KwMacro => Some(kw::Macro),
+            TokenType::KwMatch => Some(kw::Match),
+            TokenType::KwMod => Some(kw::Mod),
+            TokenType::KwMove => Some(kw::Move),
+            TokenType::KwMut => Some(kw::Mut),
+            TokenType::KwPub => Some(kw::Pub),
+            TokenType::KwRaw => Some(kw::Raw),
+            TokenType::KwRef => Some(kw::Ref),
+            TokenType::KwReturn => Some(kw::Return),
+            TokenType::KwReuse => Some(kw::Reuse),
+            TokenType::KwSafe => Some(kw::Safe),
+            TokenType::KwSelfUpper => Some(kw::SelfUpper),
+            TokenType::KwStatic => Some(kw::Static),
+            TokenType::KwStruct => Some(kw::Struct),
+            TokenType::KwTrait => Some(kw::Trait),
+            TokenType::KwTry => Some(kw::Try),
+            TokenType::KwType => Some(kw::Type),
+            TokenType::KwUnderscore => Some(kw::Underscore),
+            TokenType::KwUnsafe => Some(kw::Unsafe),
+            TokenType::KwUse => Some(kw::Use),
+            TokenType::KwWhere => Some(kw::Where),
+            TokenType::KwWhile => Some(kw::While),
+            TokenType::KwYield => Some(kw::Yield),
+
+            TokenType::SymAttSyntax => Some(sym::att_syntax),
+            TokenType::SymClobberAbi => Some(sym::clobber_abi),
+            TokenType::SymInlateout => Some(sym::inlateout),
+            TokenType::SymInout => Some(sym::inout),
+            TokenType::SymIs => Some(sym::is),
+            TokenType::SymLabel => Some(sym::label),
+            TokenType::SymLateout => Some(sym::lateout),
+            TokenType::SymMayUnwind => Some(sym::may_unwind),
+            TokenType::SymNomem => Some(sym::nomem),
+            TokenType::SymNoreturn => Some(sym::noreturn),
+            TokenType::SymNostack => Some(sym::nostack),
+            TokenType::SymOptions => Some(sym::options),
+            TokenType::SymOut => Some(sym::out),
+            TokenType::SymPreservesFlags => Some(sym::preserves_flags),
+            TokenType::SymPure => Some(sym::pure),
+            TokenType::SymReadonly => Some(sym::readonly),
+            TokenType::SymSym => Some(sym::sym),
+            _ => None,
+        }
+    }
+
+    // The output should be the same as that produced by
+    // `rustc_ast_pretty::pprust::token_to_string`.
+    pub(super) fn to_string(&self) -> String {
+        match self {
+            TokenType::Eq => "`=`",
+            TokenType::Lt => "`<`",
+            TokenType::Le => "`<=`",
+            TokenType::EqEq => "`==`",
+            TokenType::Gt => "`>`",
+            TokenType::AndAnd => "`&&`",
+            TokenType::OrOr => "`||`",
+            TokenType::Not => "`!`",
+            TokenType::Tilde => "`~`",
+
+            TokenType::Plus => "`+`",
+            TokenType::Minus => "`-`",
+            TokenType::Star => "`*`",
+            TokenType::And => "`&`",
+            TokenType::Or => "`|`",
+
+            TokenType::At => "`@`",
+            TokenType::Dot => "`.`",
+            TokenType::DotDot => "`..`",
+            TokenType::DotDotDot => "`...`",
+            TokenType::DotDotEq => "`..=`",
+            TokenType::Comma => "`,`",
+            TokenType::Semi => "`;`",
+            TokenType::Colon => "`:`",
+            TokenType::PathSep => "`::`",
+            TokenType::RArrow => "`->`",
+            TokenType::FatArrow => "`=>`",
+            TokenType::Pound => "`#`",
+            TokenType::Question => "`?`",
+            TokenType::OpenParen => "`(`",
+            TokenType::CloseParen => "`)`",
+            TokenType::OpenBrace => "`{`",
+            TokenType::CloseBrace => "`}`",
+            TokenType::OpenBracket => "`[`",
+            TokenType::CloseBracket => "`]`",
+            TokenType::Eof => "<eof>",
+
+            TokenType::Operator => "an operator",
+            TokenType::Ident => "identifier",
+            TokenType::Lifetime => "lifetime",
+            TokenType::Path => "path",
+            TokenType::Type => "type",
+            TokenType::Const => "a const expression",
+
+            _ => return format!("`{}`", self.is_keyword().unwrap()),
+        }
+        .to_string()
+    }
+}
+
+/// Used by various `Parser` methods such as `check` and `eat`. The first field
+/// is always by used those methods. The second field is only used when the
+/// first field doesn't match.
+#[derive(Clone, Copy, Debug)]
+pub struct ExpTokenPair<'a> {
+    pub tok: &'a TokenKind,
+    pub token_type: TokenType,
+}
+
+/// Used by various `Parser` methods such as `check_keyword` and `eat_keyword`.
+/// The first field is always used by those methods. The second field is only
+/// used when the first field doesn't match.
+#[derive(Clone, Copy)]
+pub struct ExpKeywordPair {
+    pub kw: Symbol,
+    pub token_type: TokenType,
+}
+
+// Gets a statically-known `ExpTokenPair` pair (for non-keywords) or
+// `ExpKeywordPair` (for keywords), as used with various `check`/`expect`
+// methods in `Parser`.
+//
+// The name is short because it's used a lot.
+#[macro_export]
+// We don't use the normal `#[rustfmt::skip]` here because that triggers a
+// bogus "macro-expanded `macro_export` macros from the current crate cannot be
+// referred to by absolute paths" error, ugh. See #52234.
+#[cfg_attr(rustfmt, rustfmt::skip)]
+macro_rules! exp {
+    // `ExpTokenPair` helper rules.
+    (@tok, $tok:ident) => {
+        $crate::parser::token_type::ExpTokenPair {
+            tok: &rustc_ast::token::$tok,
+            token_type: $crate::parser::token_type::TokenType::$tok
+        }
+    };
+    (@binop, $op:ident) => {
+        $crate::parser::token_type::ExpTokenPair {
+            tok: &rustc_ast::token::BinOp(rustc_ast::token::BinOpToken::$op),
+            token_type: $crate::parser::token_type::TokenType::$op,
+        }
+    };
+    (@open, $delim:ident, $token_type:ident) => {
+        $crate::parser::token_type::ExpTokenPair {
+            tok: &rustc_ast::token::OpenDelim(rustc_ast::token::Delimiter::$delim),
+            token_type: $crate::parser::token_type::TokenType::$token_type,
+        }
+    };
+    (@close, $delim:ident, $token_type:ident) => {
+        $crate::parser::token_type::ExpTokenPair {
+            tok: &rustc_ast::token::CloseDelim(rustc_ast::token::Delimiter::$delim),
+            token_type: $crate::parser::token_type::TokenType::$token_type,
+        }
+    };
+
+    // `ExpKeywordPair` helper rules.
+    (@kw, $kw:ident, $token_type:ident) => {
+        $crate::parser::token_type::ExpKeywordPair {
+            kw: rustc_span::symbol::kw::$kw,
+            token_type: $crate::parser::token_type::TokenType::$token_type,
+        }
+    };
+    (@sym, $kw:ident, $token_type:ident) => {
+        $crate::parser::token_type::ExpKeywordPair {
+            kw: rustc_span::symbol::sym::$kw,
+            token_type: $crate::parser::token_type::TokenType::$token_type,
+        }
+    };
+
+    (Eq)             => { exp!(@tok, Eq) };
+    (Lt)             => { exp!(@tok, Lt) };
+    (Le)             => { exp!(@tok, Le) };
+    (EqEq)           => { exp!(@tok, EqEq) };
+    (Gt)             => { exp!(@tok, Gt) };
+    (AndAnd)         => { exp!(@tok, AndAnd) };
+    (OrOr)           => { exp!(@tok, OrOr) };
+    (Not)            => { exp!(@tok, Not) };
+    (Tilde)          => { exp!(@tok, Tilde) };
+    (At)             => { exp!(@tok, At) };
+    (Dot)            => { exp!(@tok, Dot) };
+    (DotDot)         => { exp!(@tok, DotDot) };
+    (DotDotDot)      => { exp!(@tok, DotDotDot) };
+    (DotDotEq)       => { exp!(@tok, DotDotEq) };
+    (Comma)          => { exp!(@tok, Comma) };
+    (Semi)           => { exp!(@tok, Semi) };
+    (Colon)          => { exp!(@tok, Colon) };
+    (PathSep)        => { exp!(@tok, PathSep) };
+    (RArrow)         => { exp!(@tok, RArrow) };
+    (FatArrow)       => { exp!(@tok, FatArrow) };
+    (Pound)          => { exp!(@tok, Pound) };
+    (Question)       => { exp!(@tok, Question) };
+    (Eof)            => { exp!(@tok, Eof) };
+
+    (Plus)           => { exp!(@binop, Plus) };
+    (Minus)          => { exp!(@binop, Minus) };
+    (Star)           => { exp!(@binop, Star) };
+    (And)            => { exp!(@binop, And) };
+    (Or)             => { exp!(@binop, Or) };
+
+    (OpenParen)      => { exp!(@open,  Parenthesis, OpenParen) };
+    (OpenBrace)      => { exp!(@open,  Brace,       OpenBrace) };
+    (OpenBracket)    => { exp!(@open,  Bracket,     OpenBracket) };
+    (CloseParen)     => { exp!(@close, Parenthesis, CloseParen) };
+    (CloseBrace)     => { exp!(@close, Brace,       CloseBrace) };
+    (CloseBracket)   => { exp!(@close, Bracket,     CloseBracket) };
+
+    (As)             => { exp!(@kw, As,         KwAs) };
+    (Async)          => { exp!(@kw, Async,      KwAsync) };
+    (Auto)           => { exp!(@kw, Auto,       KwAuto) };
+    (Await)          => { exp!(@kw, Await,      KwAwait) };
+    (Become)         => { exp!(@kw, Become,     KwBecome) };
+    (Box)            => { exp!(@kw, Box,        KwBox) };
+    (Break)          => { exp!(@kw, Break,      KwBreak) };
+    (Catch)          => { exp!(@kw, Catch,      KwCatch) };
+    (Const)          => { exp!(@kw, Const,      KwConst) };
+    (Continue)       => { exp!(@kw, Continue,   KwContinue) };
+    (Crate)          => { exp!(@kw, Crate,      KwCrate) };
+    (Default)        => { exp!(@kw, Default,    KwDefault) };
+    (Dyn)            => { exp!(@kw, Dyn,        KwDyn) };
+    (Else)           => { exp!(@kw, Else,       KwElse) };
+    (Enum)           => { exp!(@kw, Enum,       KwEnum) };
+    (Extern)         => { exp!(@kw, Extern,     KwExtern) };
+    (Fn)             => { exp!(@kw, Fn,         KwFn) };
+    (For)            => { exp!(@kw, For,        KwFor) };
+    (Gen)            => { exp!(@kw, Gen,        KwGen) };
+    (If)             => { exp!(@kw, If,         KwIf) };
+    (Impl)           => { exp!(@kw, Impl,       KwImpl) };
+    (In)             => { exp!(@kw, In,         KwIn) };
+    (Let)            => { exp!(@kw, Let,        KwLet) };
+    (Loop)           => { exp!(@kw, Loop,       KwLoop) };
+    (Macro)          => { exp!(@kw, Macro,      KwMacro) };
+    (MacroRules)     => { exp!(@kw, MacroRules, KwMacroRules) };
+    (Match)          => { exp!(@kw, Match,      KwMatch) };
+    (Mod)            => { exp!(@kw, Mod,        KwMod) };
+    (Move)           => { exp!(@kw, Move,       KwMove) };
+    (Mut)            => { exp!(@kw, Mut,        KwMut) };
+    (Pub)            => { exp!(@kw, Pub,        KwPub) };
+    (Raw)            => { exp!(@kw, Raw,        KwRaw) };
+    (Ref)            => { exp!(@kw, Ref,        KwRef) };
+    (Return)         => { exp!(@kw, Return,     KwReturn) };
+    (Reuse)          => { exp!(@kw, Reuse,      KwReuse) };
+    (Safe)           => { exp!(@kw, Safe,       KwSafe) };
+    (SelfUpper)      => { exp!(@kw, SelfUpper,  KwSelfUpper) };
+    (Static)         => { exp!(@kw, Static,     KwStatic) };
+    (Struct)         => { exp!(@kw, Struct,     KwStruct) };
+    (Trait)          => { exp!(@kw, Trait,      KwTrait) };
+    (Try)            => { exp!(@kw, Try,        KwTry) };
+    (Type)           => { exp!(@kw, Type,       KwType) };
+    (Underscore)     => { exp!(@kw, Underscore, KwUnderscore) };
+    (Unsafe)         => { exp!(@kw, Unsafe,     KwUnsafe) };
+    (Use)            => { exp!(@kw, Use,        KwUse) };
+    (Where)          => { exp!(@kw, Where,      KwWhere) };
+    (While)          => { exp!(@kw, While,      KwWhile) };
+    (Yield)          => { exp!(@kw, Yield,      KwYield) };
+
+    (AttSyntax)      => { exp!(@sym, att_syntax,      SymAttSyntax) };
+    (ClobberAbi)     => { exp!(@sym, clobber_abi,     SymClobberAbi) };
+    (Inlateout)      => { exp!(@sym, inlateout,       SymInlateout) };
+    (Inout)          => { exp!(@sym, inout,           SymInout) };
+    (Is)             => { exp!(@sym, is,              SymIs) };
+    (Label)          => { exp!(@sym, label,           SymLabel) };
+    (Lateout)        => { exp!(@sym, lateout,         SymLateout) };
+    (MayUnwind)      => { exp!(@sym, may_unwind,      SymMayUnwind) };
+    (Nomem)          => { exp!(@sym, nomem,           SymNomem) };
+    (Noreturn)       => { exp!(@sym, noreturn,        SymNoreturn) };
+    (Nostack)        => { exp!(@sym, nostack,         SymNostack) };
+    (Options)        => { exp!(@sym, options,         SymOptions) };
+    (Out)            => { exp!(@sym, out,             SymOut) };
+    (PreservesFlags) => { exp!(@sym, preserves_flags, SymPreservesFlags) };
+    (Pure)           => { exp!(@sym, pure,            SymPure) };
+    (Readonly)       => { exp!(@sym, readonly,        SymReadonly) };
+    (Sym)            => { exp!(@sym, sym,             SymSym) };
+}
+
+/// A bitset type designed specifically for `Parser::expected_token_types`,
+/// which is very hot. `u128` is the smallest integer that will fit every
+/// `TokenType` value.
+#[derive(Clone, Copy)]
+pub(super) struct TokenTypeSet(u128);
+
+impl TokenTypeSet {
+    pub(super) fn new() -> TokenTypeSet {
+        TokenTypeSet(0)
+    }
+
+    pub(super) fn is_empty(&self) -> bool {
+        self.0 == 0
+    }
+
+    pub(super) fn insert(&mut self, token_type: TokenType) {
+        self.0 = self.0 | (1u128 << token_type as u32)
+    }
+
+    pub(super) fn clear(&mut self) {
+        self.0 = 0
+    }
+
+    pub(super) fn contains(&self, token_type: TokenType) -> bool {
+        self.0 & (1u128 << token_type as u32) != 0
+    }
+
+    pub(super) fn iter(&self) -> TokenTypeSetIter {
+        TokenTypeSetIter(*self)
+    }
+}
+
+// The `TokenTypeSet` is a copy of the set being iterated. It initially holds
+// the entire set. Each bit is cleared as it is returned. We have finished once
+// it is all zeroes.
+pub(super) struct TokenTypeSetIter(TokenTypeSet);
+
+impl Iterator for TokenTypeSetIter {
+    type Item = TokenType;
+
+    fn next(&mut self) -> Option<TokenType> {
+        let num_bits: u32 = (std::mem::size_of_val(&self.0.0) * 8) as u32;
+        assert_eq!(num_bits, 128);
+        let z = self.0.0.trailing_zeros();
+        if z == num_bits {
+            None
+        } else {
+            self.0.0 &= !(1 << z); // clear the trailing 1 bit
+            Some(TokenType::from_u32(z))
+        }
+    }
+}
diff --git a/compiler/rustc_parse/src/parser/tokenstream/tests.rs b/compiler/rustc_parse/src/parser/tokenstream/tests.rs
index b13b68c266a..037b5b1a9de 100644
--- a/compiler/rustc_parse/src/parser/tokenstream/tests.rs
+++ b/compiler/rustc_parse/src/parser/tokenstream/tests.rs
@@ -23,8 +23,8 @@ fn test_concat() {
         let mut eq_res = TokenStream::default();
         eq_res.push_stream(test_fst);
         eq_res.push_stream(test_snd);
-        assert_eq!(test_res.trees().count(), 5);
-        assert_eq!(eq_res.trees().count(), 5);
+        assert_eq!(test_res.iter().count(), 5);
+        assert_eq!(eq_res.iter().count(), 5);
         assert_eq!(test_res.eq_unspanned(&eq_res), true);
     })
 }
@@ -33,7 +33,7 @@ fn test_concat() {
 fn test_to_from_bijection() {
     create_default_session_globals_then(|| {
         let test_start = string_to_ts("foo::bar(baz)");
-        let test_end = test_start.trees().cloned().collect();
+        let test_end = test_start.iter().cloned().collect();
         assert_eq!(test_start, test_end)
     })
 }
@@ -105,6 +105,6 @@ fn test_dotdotdot() {
         stream.push_tree(TokenTree::token_joint(token::Dot, sp(1, 2)));
         stream.push_tree(TokenTree::token_alone(token::Dot, sp(2, 3)));
         assert!(stream.eq_unspanned(&string_to_ts("...")));
-        assert_eq!(stream.trees().count(), 1);
+        assert_eq!(stream.iter().count(), 1);
     })
 }
diff --git a/compiler/rustc_parse/src/parser/ty.rs b/compiler/rustc_parse/src/parser/ty.rs
index f696074e66a..6497d19a173 100644
--- a/compiler/rustc_parse/src/parser/ty.rs
+++ b/compiler/rustc_parse/src/parser/ty.rs
@@ -8,8 +8,7 @@ use rustc_ast::{
     TyKind, UnsafeBinderTy,
 };
 use rustc_errors::{Applicability, PResult};
-use rustc_span::symbol::{Ident, kw, sym};
-use rustc_span::{ErrorGuaranteed, Span};
+use rustc_span::{ErrorGuaranteed, Ident, Span, kw, sym};
 use thin_vec::{ThinVec, thin_vec};
 
 use super::{Parser, PathStyle, SeqSep, TokenType, Trailing};
@@ -19,7 +18,7 @@ use crate::errors::{
     HelpUseLatestEdition, InvalidDynKeyword, LifetimeAfterMut, NeedPlusAfterTraitObjectLifetime,
     NestedCVariadicType, ReturnTypesUseThinArrow,
 };
-use crate::{maybe_recover_from_interpolated_ty_qpath, maybe_whole};
+use crate::{exp, maybe_recover_from_interpolated_ty_qpath, maybe_whole};
 
 /// Signals whether parsing a type should allow `+`.
 ///
@@ -204,7 +203,7 @@ impl<'a> Parser<'a> {
         recover_return_sign: RecoverReturnSign,
     ) -> PResult<'a, FnRetTy> {
         let lo = self.prev_token.span;
-        Ok(if self.eat(&token::RArrow) {
+        Ok(if self.eat(exp!(RArrow)) {
             // FIXME(Centril): Can we unconditionally `allow_plus`?
             let ty = self.parse_ty_common(
                 allow_plus,
@@ -252,28 +251,28 @@ impl<'a> Parser<'a> {
 
         let lo = self.token.span;
         let mut impl_dyn_multi = false;
-        let kind = if self.check(&token::OpenDelim(Delimiter::Parenthesis)) {
+        let kind = if self.check(exp!(OpenParen)) {
             self.parse_ty_tuple_or_parens(lo, allow_plus)?
-        } else if self.eat(&token::Not) {
+        } else if self.eat(exp!(Not)) {
             // Never type `!`
             TyKind::Never
-        } else if self.eat(&token::BinOp(token::Star)) {
+        } else if self.eat(exp!(Star)) {
             self.parse_ty_ptr()?
-        } else if self.eat(&token::OpenDelim(Delimiter::Bracket)) {
+        } else if self.eat(exp!(OpenBracket)) {
             self.parse_array_or_slice_ty()?
-        } else if self.check(&token::BinOp(token::And)) || self.check(&token::AndAnd) {
+        } else if self.check(exp!(And)) || self.check(exp!(AndAnd)) {
             // Reference
             self.expect_and()?;
             self.parse_borrowed_pointee()?
         } else if self.eat_keyword_noexpect(kw::Typeof) {
             self.parse_typeof_ty()?
-        } else if self.eat_keyword(kw::Underscore) {
+        } else if self.eat_keyword(exp!(Underscore)) {
             // A type to be inferred `_`
             TyKind::Infer
         } else if self.check_fn_front_matter(false, Case::Sensitive) {
             // Function pointer type
             self.parse_ty_bare_fn(lo, ThinVec::new(), None, recover_return_sign)?
-        } else if self.check_keyword(kw::For) {
+        } else if self.check_keyword(exp!(For)) {
             // Function pointer type or bound list (trait object type) starting with a poly-trait.
             //   `for<'lt> [unsafe] [extern "ABI"] fn (&'lt S) -> T`
             //   `for<'lt> Trait1<'lt> + Trait2 + 'a`
@@ -325,7 +324,7 @@ impl<'a> Parser<'a> {
                     self.parse_remaining_bounds_path(lifetime_defs, path, lo, parse_plus)?
                 }
             }
-        } else if self.eat_keyword(kw::Impl) {
+        } else if self.eat_keyword(exp!(Impl)) {
             self.parse_impl_ty(&mut impl_dyn_multi)?
         } else if self.is_explicit_dyn_type() {
             self.parse_dyn_ty(&mut impl_dyn_multi)?
@@ -337,7 +336,7 @@ impl<'a> Parser<'a> {
             self.parse_path_start_ty(lo, allow_plus, ty_generics)?
         } else if self.can_begin_bound() {
             self.parse_bare_trait_object(lo, allow_plus)?
-        } else if self.eat(&token::DotDotDot) {
+        } else if self.eat(exp!(DotDotDot)) {
             match allow_c_variadic {
                 AllowCVariadic::Yes => TyKind::CVarArgs,
                 AllowCVariadic::No => {
@@ -348,7 +347,7 @@ impl<'a> Parser<'a> {
                     TyKind::Err(guar)
                 }
             }
-        } else if self.check_keyword(kw::Unsafe)
+        } else if self.check_keyword(exp!(Unsafe))
             && self.look_ahead(1, |tok| matches!(tok.kind, token::Lt))
         {
             self.parse_unsafe_binder_ty()?
@@ -375,7 +374,7 @@ impl<'a> Parser<'a> {
 
     fn parse_unsafe_binder_ty(&mut self) -> PResult<'a, TyKind> {
         let lo = self.token.span;
-        assert!(self.eat_keyword(kw::Unsafe));
+        assert!(self.eat_keyword(exp!(Unsafe)));
         self.expect_lt()?;
         let generic_params = self.parse_generic_params()?;
         self.expect_gt()?;
@@ -488,16 +487,16 @@ impl<'a> Parser<'a> {
             Err(err) => return Err(err),
         };
 
-        let ty = if self.eat(&token::Semi) {
+        let ty = if self.eat(exp!(Semi)) {
             let mut length = self.parse_expr_anon_const()?;
-            if let Err(e) = self.expect(&token::CloseDelim(Delimiter::Bracket)) {
+            if let Err(e) = self.expect(exp!(CloseBracket)) {
                 // Try to recover from `X<Y, ...>` when `X::<Y, ...>` works
                 self.check_mistyped_turbofish_with_multiple_type_params(e, &mut length.value)?;
-                self.expect(&token::CloseDelim(Delimiter::Bracket))?;
+                self.expect(exp!(CloseBracket))?;
             }
             TyKind::Array(elt_ty, length)
         } else {
-            self.expect(&token::CloseDelim(Delimiter::Bracket))?;
+            self.expect(exp!(CloseBracket))?;
             TyKind::Slice(elt_ty)
         };
 
@@ -580,9 +579,9 @@ impl<'a> Parser<'a> {
     // Parses the `typeof(EXPR)`.
     // To avoid ambiguity, the type is surrounded by parentheses.
     fn parse_typeof_ty(&mut self) -> PResult<'a, TyKind> {
-        self.expect(&token::OpenDelim(Delimiter::Parenthesis))?;
+        self.expect(exp!(OpenParen))?;
         let expr = self.parse_expr_anon_const()?;
-        self.expect(&token::CloseDelim(Delimiter::Parenthesis))?;
+        self.expect(exp!(CloseParen))?;
         Ok(TyKind::Typeof(expr))
     }
 
@@ -698,15 +697,15 @@ impl<'a> Parser<'a> {
         let lo = self.token.span;
         self.expect_lt()?;
         let (args, _, _) = self.parse_seq_to_before_tokens(
-            &[&TokenKind::Gt],
+            &[exp!(Gt)],
             &[
                 &TokenKind::Ge,
                 &TokenKind::BinOp(BinOpToken::Shr),
                 &TokenKind::BinOpEq(BinOpToken::Shr),
             ],
-            SeqSep::trailing_allowed(token::Comma),
+            SeqSep::trailing_allowed(exp!(Comma)),
             |self_| {
-                if self_.check_keyword(kw::SelfUpper) {
+                if self_.check_keyword(exp!(SelfUpper)) {
                     self_.bump();
                     Ok(PreciseCapturingArg::Arg(
                         ast::Path::from_ident(self_.prev_token.ident().unwrap().0),
@@ -730,7 +729,7 @@ impl<'a> Parser<'a> {
 
     /// Is a `dyn B0 + ... + Bn` type allowed here?
     fn is_explicit_dyn_type(&mut self) -> bool {
-        self.check_keyword(kw::Dyn)
+        self.check_keyword(exp!(Dyn))
             && (self.token.uninterpolated_span().at_least_rust_2018()
                 || self.look_ahead(1, |t| {
                     (can_begin_dyn_bound_in_edition_2015(t) || *t == TokenKind::BinOp(token::Star))
@@ -746,7 +745,7 @@ impl<'a> Parser<'a> {
         self.bump(); // `dyn`
 
         // parse dyn* types
-        let syntax = if self.eat(&TokenKind::BinOp(token::Star)) {
+        let syntax = if self.eat(exp!(Star)) {
             self.psess.gated_spans.gate(sym::dyn_star, lo.to(self.prev_token.span));
             TraitObjectSyntax::DynStar
         } else {
@@ -773,7 +772,7 @@ impl<'a> Parser<'a> {
     ) -> PResult<'a, TyKind> {
         // Simple path
         let path = self.parse_path_inner(PathStyle::Type, ty_generics)?;
-        if self.eat(&token::Not) {
+        if self.eat(exp!(Not)) {
             // Macro invocation in type position
             Ok(TyKind::MacCall(P(MacCall { path, args: self.parse_delim_args()? })))
         } else if allow_plus == AllowPlus::Yes && self.check_plus() {
@@ -826,14 +825,14 @@ impl<'a> Parser<'a> {
     fn can_begin_bound(&mut self) -> bool {
         self.check_path()
             || self.check_lifetime()
-            || self.check(&token::Not)
-            || self.check(&token::Question)
-            || self.check(&token::Tilde)
-            || self.check_keyword(kw::For)
-            || self.check(&token::OpenDelim(Delimiter::Parenthesis))
-            || self.check_keyword(kw::Const)
-            || self.check_keyword(kw::Async)
-            || self.check_keyword(kw::Use)
+            || self.check(exp!(Not))
+            || self.check(exp!(Question))
+            || self.check(exp!(Tilde))
+            || self.check_keyword(exp!(For))
+            || self.check(exp!(OpenParen))
+            || self.check_keyword(exp!(Const))
+            || self.check_keyword(exp!(Async))
+            || self.check_keyword(exp!(Use))
     }
 
     /// Parses a bound according to the grammar:
@@ -843,11 +842,11 @@ impl<'a> Parser<'a> {
     fn parse_generic_bound(&mut self) -> PResult<'a, GenericBound> {
         let lo = self.token.span;
         let leading_token = self.prev_token.clone();
-        let has_parens = self.eat(&token::OpenDelim(Delimiter::Parenthesis));
+        let has_parens = self.eat(exp!(OpenParen));
 
         let bound = if self.token.is_lifetime() {
             self.parse_generic_lt_bound(lo, has_parens)?
-        } else if self.eat_keyword(kw::Use) {
+        } else if self.eat_keyword(exp!(Use)) {
             // parse precise captures, if any. This is `use<'lt, 'lt, P, P>`; a list of
             // lifetimes and ident params (including SelfUpper). These are validated later
             // for order, duplication, and whether they actually reference params.
@@ -920,7 +919,7 @@ impl<'a> Parser<'a> {
 
     /// Recover on `('lifetime)` with `(` already eaten.
     fn recover_paren_lifetime(&mut self, lo: Span) -> PResult<'a, ()> {
-        self.expect(&token::CloseDelim(Delimiter::Parenthesis))?;
+        self.expect(exp!(CloseParen))?;
         let span = lo.to(self.prev_token.span);
         let sugg = errors::RemoveParens { lo, hi: self.prev_token.span };
 
@@ -941,13 +940,13 @@ impl<'a> Parser<'a> {
     /// See `parse_generic_ty_bound` for the complete grammar of trait bound modifiers.
     fn parse_trait_bound_modifiers(&mut self) -> PResult<'a, TraitBoundModifiers> {
         let modifier_lo = self.token.span;
-        let constness = if self.eat(&token::Tilde) {
+        let constness = if self.eat(exp!(Tilde)) {
             let tilde = self.prev_token.span;
-            self.expect_keyword(kw::Const)?;
+            self.expect_keyword(exp!(Const))?;
             let span = tilde.to(self.prev_token.span);
             self.psess.gated_spans.gate(sym::const_trait_impl, span);
             BoundConstness::Maybe(span)
-        } else if self.eat_keyword(kw::Const) {
+        } else if self.eat_keyword(exp!(Const)) {
             self.psess.gated_spans.gate(sym::const_trait_impl, self.prev_token.span);
             BoundConstness::Always(self.prev_token.span)
         } else {
@@ -955,7 +954,7 @@ impl<'a> Parser<'a> {
         };
 
         let asyncness = if self.token.uninterpolated_span().at_least_rust_2018()
-            && self.eat_keyword(kw::Async)
+            && self.eat_keyword(exp!(Async))
         {
             self.psess.gated_spans.gate(sym::async_trait_bounds, self.prev_token.span);
             BoundAsyncness::Async(self.prev_token.span)
@@ -975,9 +974,9 @@ impl<'a> Parser<'a> {
         };
         let modifier_hi = self.prev_token.span;
 
-        let polarity = if self.eat(&token::Question) {
+        let polarity = if self.eat(exp!(Question)) {
             BoundPolarity::Maybe(self.prev_token.span)
-        } else if self.eat(&token::Not) {
+        } else if self.eat(exp!(Not)) {
             self.psess.gated_spans.gate(sym::negative_bounds, self.prev_token.span);
             BoundPolarity::Negative(self.prev_token.span)
         } else {
@@ -1123,7 +1122,7 @@ impl<'a> Parser<'a> {
             if self.token.is_like_plus() && leading_token.is_keyword(kw::Dyn) {
                 let bounds = vec![];
                 self.parse_remaining_bounds(bounds, true)?;
-                self.expect(&token::CloseDelim(Delimiter::Parenthesis))?;
+                self.expect(exp!(CloseParen))?;
                 self.dcx().emit_err(errors::IncorrectParensTraitBounds {
                     span: vec![lo, self.prev_token.span],
                     sugg: errors::IncorrectParensTraitBoundsSugg {
@@ -1132,7 +1131,7 @@ impl<'a> Parser<'a> {
                     },
                 });
             } else {
-                self.expect(&token::CloseDelim(Delimiter::Parenthesis))?;
+                self.expect(exp!(CloseParen))?;
             }
         }
 
@@ -1177,7 +1176,7 @@ impl<'a> Parser<'a> {
     pub(super) fn parse_late_bound_lifetime_defs(
         &mut self,
     ) -> PResult<'a, (ThinVec<GenericParam>, Option<Span>)> {
-        if self.eat_keyword(kw::For) {
+        if self.eat_keyword(exp!(For)) {
             let lo = self.token.span;
             self.expect_lt()?;
             let params = self.parse_generic_params()?;
@@ -1281,7 +1280,7 @@ impl<'a> Parser<'a> {
     }
 
     pub(super) fn check_lifetime(&mut self) -> bool {
-        self.expected_tokens.push(TokenType::Lifetime);
+        self.expected_token_types.insert(TokenType::Lifetime);
         self.token.is_lifetime()
     }
 
diff --git a/compiler/rustc_parse/src/validate_attr.rs b/compiler/rustc_parse/src/validate_attr.rs
index aab3f10bc66..8b6b37c0f8f 100644
--- a/compiler/rustc_parse/src/validate_attr.rs
+++ b/compiler/rustc_parse/src/validate_attr.rs
@@ -3,8 +3,7 @@
 use rustc_ast::token::Delimiter;
 use rustc_ast::tokenstream::DelimSpan;
 use rustc_ast::{
-    self as ast, AttrArgs, AttrArgsEq, Attribute, DelimArgs, MetaItem, MetaItemInner, MetaItemKind,
-    Safety,
+    self as ast, AttrArgs, Attribute, DelimArgs, MetaItem, MetaItemInner, MetaItemKind, Safety,
 };
 use rustc_errors::{Applicability, FatalError, PResult};
 use rustc_feature::{AttributeSafety, AttributeTemplate, BUILTIN_ATTRIBUTE_MAP, BuiltinAttribute};
@@ -70,7 +69,7 @@ pub fn parse_meta<'a>(psess: &'a ParseSess, attr: &Attribute) -> PResult<'a, Met
                     parse_in(psess, tokens.clone(), "meta list", |p| p.parse_meta_seq_top())?;
                 MetaItemKind::List(nmis)
             }
-            AttrArgs::Eq { value: AttrArgsEq::Ast(expr), .. } => {
+            AttrArgs::Eq { expr, .. } => {
                 if let ast::ExprKind::Lit(token_lit) = expr.kind {
                     let res = ast::MetaItemLit::from_token_lit(token_lit, expr.span);
                     let res = match res {
@@ -116,9 +115,6 @@ pub fn parse_meta<'a>(psess: &'a ParseSess, attr: &Attribute) -> PResult<'a, Met
                     return Err(err);
                 }
             }
-            AttrArgs::Eq { value: AttrArgsEq::Hir(lit), .. } => {
-                MetaItemKind::NameValue(lit.clone())
-            }
         },
     })
 }
diff --git a/compiler/rustc_passes/Cargo.toml b/compiler/rustc_passes/Cargo.toml
index ed5991459ac..2b8a3b9ce23 100644
--- a/compiler/rustc_passes/Cargo.toml
+++ b/compiler/rustc_passes/Cargo.toml
@@ -8,7 +8,7 @@ edition = "2021"
 rustc_abi = { path = "../rustc_abi" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_ast_pretty = { path = "../rustc_ast_pretty" }
-rustc_attr = { path = "../rustc_attr" }
+rustc_attr_parsing = { path = "../rustc_attr_parsing" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
 rustc_expand = { path = "../rustc_expand" }
@@ -16,7 +16,6 @@ rustc_feature = { path = "../rustc_feature" }
 rustc_fluent_macro = { path = "../rustc_fluent_macro" }
 rustc_hir = { path = "../rustc_hir" }
 rustc_index = { path = "../rustc_index" }
-rustc_lexer = { path = "../rustc_lexer" }
 rustc_macros = { path = "../rustc_macros" }
 rustc_middle = { path = "../rustc_middle" }
 rustc_privacy = { path = "../rustc_privacy" }
diff --git a/compiler/rustc_passes/messages.ftl b/compiler/rustc_passes/messages.ftl
index 7a0a518bb51..ba3101e9058 100644
--- a/compiler/rustc_passes/messages.ftl
+++ b/compiler/rustc_passes/messages.ftl
@@ -211,8 +211,9 @@ passes_doc_invalid =
 passes_doc_keyword_empty_mod =
     `#[doc(keyword = "...")]` should be used on empty modules
 
-passes_doc_keyword_invalid_ident =
-    `{$doc_keyword}` is not a valid identifier
+passes_doc_keyword_not_keyword =
+    nonexistent keyword `{$keyword}` used in `#[doc(keyword = "...")]`
+    .help = only existing keywords are allowed in core/std
 
 passes_doc_keyword_not_mod =
     `#[doc(keyword = "...")]` should be used on modules
@@ -356,6 +357,9 @@ passes_ignored_derived_impls =
 passes_implied_feature_not_exist =
     feature `{$implied_by}` implying `{$feature}` does not exist
 
+passes_incorrect_do_not_recommend_args =
+    `#[diagnostic::do_not_recommend]` does not expect any arguments
+
 passes_incorrect_do_not_recommend_location =
     `#[diagnostic::do_not_recommend]` can only be placed on trait implementations
 
@@ -562,6 +566,10 @@ passes_no_sanitize =
     `#[no_sanitize({$attr_str})]` should be applied to {$accepted_kind}
     .label = not {$accepted_kind}
 
+passes_non_exaustive_with_default_field_values =
+    `#[non_exhaustive]` can't be used to annotate items with default field values
+    .label = this struct has default field values
+
 passes_non_exported_macro_invalid_attrs =
     attribute should be applied to function or closure
     .label = not a function or closure
diff --git a/compiler/rustc_passes/src/abi_test.rs b/compiler/rustc_passes/src/abi_test.rs
index 4db8584b884..75a1bb39a74 100644
--- a/compiler/rustc_passes/src/abi_test.rs
+++ b/compiler/rustc_passes/src/abi_test.rs
@@ -1,11 +1,11 @@
-use rustc_ast::Attribute;
+use rustc_hir::Attribute;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::LocalDefId;
 use rustc_middle::span_bug;
 use rustc_middle::ty::layout::{FnAbiError, LayoutError};
 use rustc_middle::ty::{self, GenericArgs, Instance, Ty, TyCtxt};
 use rustc_span::source_map::Spanned;
-use rustc_span::symbol::sym;
+use rustc_span::sym;
 use rustc_target::abi::call::FnAbi;
 
 use super::layout_test::ensure_wf;
diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs
index 074fe77324f..8cf20a378d4 100644
--- a/compiler/rustc_passes/src/check_attr.rs
+++ b/compiler/rustc_passes/src/check_attr.rs
@@ -7,17 +7,15 @@
 use std::cell::Cell;
 use std::collections::hash_map::Entry;
 
-use rustc_ast::{
-    AttrKind, AttrStyle, Attribute, LitKind, MetaItemInner, MetaItemKind, MetaItemLit, ast,
-};
+use rustc_ast::{AttrStyle, LitKind, MetaItemInner, MetaItemKind, MetaItemLit, ast};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::{Applicability, DiagCtxtHandle, IntoDiagArg, MultiSpan, StashKey};
 use rustc_feature::{AttributeDuplicates, AttributeType, BUILTIN_ATTRIBUTE_MAP, BuiltinAttribute};
 use rustc_hir::def_id::LocalModDefId;
 use rustc_hir::intravisit::{self, Visitor};
 use rustc_hir::{
-    self as hir, self, AssocItemKind, CRATE_HIR_ID, CRATE_OWNER_ID, FnSig, ForeignItem, HirId,
-    Item, ItemKind, MethodKind, Safety, Target, TraitItem,
+    self as hir, self, AssocItemKind, AttrKind, Attribute, CRATE_HIR_ID, CRATE_OWNER_ID, FnSig,
+    ForeignItem, HirId, Item, ItemKind, MethodKind, Safety, Target, TraitItem,
 };
 use rustc_macros::LintDiagnostic;
 use rustc_middle::hir::nested_filter;
@@ -32,8 +30,7 @@ use rustc_session::lint::builtin::{
     UNKNOWN_OR_MALFORMED_DIAGNOSTIC_ATTRIBUTES, UNUSED_ATTRIBUTES,
 };
 use rustc_session::parse::feature_err;
-use rustc_span::symbol::{Symbol, kw, sym};
-use rustc_span::{BytePos, DUMMY_SP, Span};
+use rustc_span::{BytePos, DUMMY_SP, Span, Symbol, kw, sym};
 use rustc_target::abi::Size;
 use rustc_target::spec::abi::Abi;
 use rustc_trait_selection::error_reporting::InferCtxtErrorExt;
@@ -118,7 +115,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
         for attr in attrs {
             match attr.path().as_slice() {
                 [sym::diagnostic, sym::do_not_recommend, ..] => {
-                    self.check_do_not_recommend(attr.span, hir_id, target)
+                    self.check_do_not_recommend(attr.span, hir_id, target, attr, item)
                 }
                 [sym::diagnostic, sym::on_unimplemented, ..] => {
                     self.check_diagnostic_on_unimplemented(attr.span, hir_id, target)
@@ -127,7 +124,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                 [sym::coverage, ..] => self.check_coverage(attr, span, target),
                 [sym::optimize, ..] => self.check_optimize(hir_id, attr, span, target),
                 [sym::no_sanitize, ..] => self.check_no_sanitize(attr, span, target),
-                [sym::non_exhaustive, ..] => self.check_non_exhaustive(hir_id, attr, span, target),
+                [sym::non_exhaustive, ..] => self.check_non_exhaustive(hir_id, attr, span, target, item),
                 [sym::marker, ..] => self.check_marker(hir_id, attr, span, target),
                 [sym::target_feature, ..] => {
                     self.check_target_feature(hir_id, attr, span, target, attrs)
@@ -189,6 +186,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                 [sym::rustc_coinductive, ..]
                 | [sym::rustc_must_implement_one_of, ..]
                 | [sym::rustc_deny_explicit_impl, ..]
+                | [sym::rustc_do_not_implement_via_object, ..]
                 | [sym::const_trait, ..] => self.check_must_be_applied_to_trait(attr, span, target),
                 [sym::collapse_debuginfo, ..] => self.check_collapse_debuginfo(attr, span, target),
                 [sym::must_not_suspend, ..] => self.check_must_not_suspend(attr, span, target),
@@ -351,8 +349,21 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
     }
 
     /// Checks if `#[diagnostic::do_not_recommend]` is applied on a trait impl.
-    fn check_do_not_recommend(&self, attr_span: Span, hir_id: HirId, target: Target) {
-        if !matches!(target, Target::Impl) {
+    fn check_do_not_recommend(
+        &self,
+        attr_span: Span,
+        hir_id: HirId,
+        target: Target,
+        attr: &Attribute,
+        item: Option<ItemLike<'_>>,
+    ) {
+        if !matches!(target, Target::Impl)
+            || matches!(
+                item,
+                Some(ItemLike::Item(hir::Item {  kind: hir::ItemKind::Impl(_impl),.. }))
+                    if _impl.of_trait.is_none()
+            )
+        {
             self.tcx.emit_node_span_lint(
                 UNKNOWN_OR_MALFORMED_DIAGNOSTIC_ATTRIBUTES,
                 hir_id,
@@ -360,6 +371,14 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                 errors::IncorrectDoNotRecommendLocation,
             );
         }
+        if !attr.is_word() {
+            self.tcx.emit_node_span_lint(
+                UNKNOWN_OR_MALFORMED_DIAGNOSTIC_ATTRIBUTES,
+                hir_id,
+                attr_span,
+                errors::DoNotRecommendDoesNotExpectArgs,
+            );
+        }
     }
 
     /// Checks if `#[diagnostic::on_unimplemented]` is applied to a trait definition
@@ -666,9 +685,30 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
     }
 
     /// Checks if the `#[non_exhaustive]` attribute on an `item` is valid.
-    fn check_non_exhaustive(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) {
+    fn check_non_exhaustive(
+        &self,
+        hir_id: HirId,
+        attr: &Attribute,
+        span: Span,
+        target: Target,
+        item: Option<ItemLike<'_>>,
+    ) {
         match target {
-            Target::Struct | Target::Enum | Target::Variant => {}
+            Target::Struct => {
+                if let Some(ItemLike::Item(hir::Item {
+                    kind: hir::ItemKind::Struct(hir::VariantData::Struct { fields, .. }, _),
+                    ..
+                })) = item
+                    && !fields.is_empty()
+                    && fields.iter().any(|f| f.default.is_some())
+                {
+                    self.dcx().emit_err(errors::NonExhaustiveWithDefaultFieldValues {
+                        attr_span: attr.span,
+                        defn_span: span,
+                    });
+                }
+            }
+            Target::Enum | Target::Variant => {}
             // FIXME(#80564): We permit struct fields, match arms and macro defs to have an
             // `#[non_exhaustive]` attribute with just a lint, because we previously
             // erroneously allowed it and some crates used it accidentally, to be compatible
@@ -715,7 +755,8 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
         attrs: &[Attribute],
     ) {
         match target {
-            Target::Fn => {
+            Target::Method(MethodKind::Trait { body: true } | MethodKind::Inherent)
+            | Target::Fn => {
                 // `#[target_feature]` is not allowed in lang items.
                 if let Some((lang_item, _)) = hir::lang_items::extract(attrs)
                     // Calling functions with `#[target_feature]` is
@@ -732,7 +773,6 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                     });
                 }
             }
-            Target::Method(MethodKind::Trait { body: true } | MethodKind::Inherent) => {}
             // FIXME: #[target_feature] was previously erroneously allowed on statements and some
             // crates used this, so only emit a warning.
             Target::Statement => {
@@ -914,6 +954,13 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
     }
 
     fn check_doc_keyword(&self, meta: &MetaItemInner, hir_id: HirId) {
+        fn is_doc_keyword(s: Symbol) -> bool {
+            // FIXME: Once rustdoc can handle URL conflicts on case insensitive file systems, we
+            // can remove the `SelfTy` case here, remove `sym::SelfTy`, and update the
+            // `#[doc(keyword = "SelfTy")` attribute in `library/std/src/keyword_docs.rs`.
+            s <= kw::Union || s == sym::SelfTy
+        }
+
         let doc_keyword = meta.value_str().unwrap_or(kw::Empty);
         if doc_keyword == kw::Empty {
             self.doc_attr_str_error(meta, "keyword");
@@ -935,10 +982,10 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                 return;
             }
         }
-        if !rustc_lexer::is_ident(doc_keyword.as_str()) {
-            self.dcx().emit_err(errors::DocKeywordInvalidIdent {
+        if !is_doc_keyword(doc_keyword) {
+            self.dcx().emit_err(errors::DocKeywordNotKeyword {
                 span: meta.name_value_literal_span().unwrap_or_else(|| meta.span()),
-                doc_keyword,
+                keyword: doc_keyword,
             });
         }
     }
@@ -1176,10 +1223,8 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
         specified_inline: &mut Option<(bool, Span)>,
         aliases: &mut FxHashMap<String, Span>,
     ) {
-        if let Some(mi) = attr.meta()
-            && let Some(list) = mi.meta_item_list()
-        {
-            for meta in list {
+        if let Some(list) = attr.meta_item_list() {
+            for meta in &list {
                 if let Some(i_meta) = meta.meta_item() {
                     match i_meta.name_or_empty() {
                         sym::alias => {
@@ -1279,7 +1324,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                                             AttrStyle::Inner => "!",
                                             AttrStyle::Outer => "",
                                         },
-                                        sugg: (attr.meta().unwrap().span, applicability),
+                                        sugg: (attr.span, applicability),
                                     },
                                 );
                             } else if i_meta.has_name(sym::passes)
@@ -2141,10 +2186,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
     fn check_confusables(&self, attr: &Attribute, target: Target) {
         match target {
             Target::Method(MethodKind::Inherent) => {
-                let Some(meta) = attr.meta() else {
-                    return;
-                };
-                let ast::MetaItem { kind: MetaItemKind::List(ref metas), .. } = meta else {
+                let Some(metas) = attr.meta_item_list() else {
                     return;
                 };
 
@@ -2602,7 +2644,7 @@ fn check_invalid_crate_level_attr(tcx: TyCtxt<'_>, attrs: &[Attribute]) {
 
                     if let AttrKind::Normal(ref p) = attr.kind {
                         tcx.dcx().try_steal_replace_and_emit_err(
-                            p.item.path.span,
+                            p.path.span,
                             StashKey::UndeterminedMacroResolution,
                             err,
                         );
diff --git a/compiler/rustc_passes/src/dead.rs b/compiler/rustc_passes/src/dead.rs
index ecf8d34ad84..c5dc8e68fe8 100644
--- a/compiler/rustc_passes/src/dead.rs
+++ b/compiler/rustc_passes/src/dead.rs
@@ -22,7 +22,7 @@ use rustc_middle::ty::{self, TyCtxt};
 use rustc_middle::{bug, span_bug};
 use rustc_session::lint;
 use rustc_session::lint::builtin::DEAD_CODE;
-use rustc_span::symbol::{Symbol, sym};
+use rustc_span::{Symbol, sym};
 
 use crate::errors::{
     ChangeFields, IgnoredDerivedImpls, MultipleDeadCodes, ParentInfo, UselessAssignment,
diff --git a/compiler/rustc_passes/src/diagnostic_items.rs b/compiler/rustc_passes/src/diagnostic_items.rs
index 1c3d3bf3dea..7b02aecdfae 100644
--- a/compiler/rustc_passes/src/diagnostic_items.rs
+++ b/compiler/rustc_passes/src/diagnostic_items.rs
@@ -9,13 +9,12 @@
 //!
 //! * Compiler internal types like `Ty` and `TyCtxt`
 
-use rustc_ast as ast;
-use rustc_hir::OwnerId;
 use rustc_hir::diagnostic_items::DiagnosticItems;
+use rustc_hir::{Attribute, OwnerId};
 use rustc_middle::query::{LocalCrate, Providers};
 use rustc_middle::ty::TyCtxt;
 use rustc_span::def_id::{DefId, LOCAL_CRATE};
-use rustc_span::symbol::{Symbol, sym};
+use rustc_span::{Symbol, sym};
 
 use crate::errors::DuplicateDiagnosticItemInCrate;
 
@@ -55,7 +54,7 @@ fn report_duplicate_item(
 }
 
 /// Extract the first `rustc_diagnostic_item = "$name"` out of a list of attributes.
-fn extract(attrs: &[ast::Attribute]) -> Option<Symbol> {
+fn extract(attrs: &[Attribute]) -> Option<Symbol> {
     attrs.iter().find_map(|attr| {
         if attr.has_name(sym::rustc_diagnostic_item) { attr.value_str() } else { None }
     })
diff --git a/compiler/rustc_passes/src/entry.rs b/compiler/rustc_passes/src/entry.rs
index 690808e7527..4949a4316a7 100644
--- a/compiler/rustc_passes/src/entry.rs
+++ b/compiler/rustc_passes/src/entry.rs
@@ -8,8 +8,7 @@ use rustc_middle::query::Providers;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::RemapFileNameExt;
 use rustc_session::config::{CrateType, EntryFnType, RemapPathScopeComponents, sigpipe};
-use rustc_span::symbol::sym;
-use rustc_span::{Span, Symbol};
+use rustc_span::{Span, Symbol, sym};
 
 use crate::errors::{
     AttrOnlyInFunctions, ExternMain, MultipleRustcMain, MultipleStartFunctions, NoMainErr,
diff --git a/compiler/rustc_passes/src/errors.rs b/compiler/rustc_passes/src/errors.rs
index fdc7e1bba2f..163325f2a3c 100644
--- a/compiler/rustc_passes/src/errors.rs
+++ b/compiler/rustc_passes/src/errors.rs
@@ -20,6 +20,10 @@ use crate::lang_items::Duplicate;
 #[diag(passes_incorrect_do_not_recommend_location)]
 pub(crate) struct IncorrectDoNotRecommendLocation;
 
+#[derive(LintDiagnostic)]
+#[diag(passes_incorrect_do_not_recommend_args)]
+pub(crate) struct DoNotRecommendDoesNotExpectArgs;
+
 #[derive(Diagnostic)]
 #[diag(passes_autodiff_attr)]
 pub(crate) struct AutoDiffAttr {
@@ -116,6 +120,15 @@ pub(crate) struct NonExhaustiveWrongLocation {
 }
 
 #[derive(Diagnostic)]
+#[diag(passes_non_exaustive_with_default_field_values)]
+pub(crate) struct NonExhaustiveWithDefaultFieldValues {
+    #[primary_span]
+    pub attr_span: Span,
+    #[label]
+    pub defn_span: Span,
+}
+
+#[derive(Diagnostic)]
 #[diag(passes_should_be_applied_to_trait)]
 pub(crate) struct AttrShouldBeAppliedToTrait {
     #[primary_span]
@@ -216,18 +229,19 @@ pub(crate) struct DocKeywordEmptyMod {
 }
 
 #[derive(Diagnostic)]
-#[diag(passes_doc_keyword_not_mod)]
-pub(crate) struct DocKeywordNotMod {
+#[diag(passes_doc_keyword_not_keyword)]
+#[help]
+pub(crate) struct DocKeywordNotKeyword {
     #[primary_span]
     pub span: Span,
+    pub keyword: Symbol,
 }
 
 #[derive(Diagnostic)]
-#[diag(passes_doc_keyword_invalid_ident)]
-pub(crate) struct DocKeywordInvalidIdent {
+#[diag(passes_doc_keyword_not_mod)]
+pub(crate) struct DocKeywordNotMod {
     #[primary_span]
     pub span: Span,
-    pub doc_keyword: Symbol,
 }
 
 #[derive(Diagnostic)]
diff --git a/compiler/rustc_passes/src/input_stats.rs b/compiler/rustc_passes/src/input_stats.rs
index 7ccbc7bdc57..f9cb8c9b927 100644
--- a/compiler/rustc_passes/src/input_stats.rs
+++ b/compiler/rustc_passes/src/input_stats.rs
@@ -22,6 +22,10 @@ impl NodeStats {
     fn new() -> NodeStats {
         NodeStats { count: 0, size: 0 }
     }
+
+    fn accum_size(&self) -> usize {
+        self.count * self.size
+    }
 }
 
 struct Node {
@@ -121,11 +125,9 @@ impl<'k> StatCollector<'k> {
         // We will soon sort, so the initial order does not matter.
         #[allow(rustc::potential_query_instability)]
         let mut nodes: Vec<_> = self.nodes.iter().collect();
-        nodes.sort_by_cached_key(|(label, node)| {
-            (node.stats.count * node.stats.size, label.to_owned())
-        });
+        nodes.sort_by_cached_key(|(label, node)| (node.stats.accum_size(), label.to_owned()));
 
-        let total_size = nodes.iter().map(|(_, node)| node.stats.count * node.stats.size).sum();
+        let total_size = nodes.iter().map(|(_, node)| node.stats.accum_size()).sum();
         let total_count = nodes.iter().map(|(_, node)| node.stats.count).sum();
 
         eprintln!("{prefix} {title}");
@@ -138,7 +140,7 @@ impl<'k> StatCollector<'k> {
         let percent = |m, n| (m * 100) as f64 / n as f64;
 
         for (label, node) in nodes {
-            let size = node.stats.count * node.stats.size;
+            let size = node.stats.accum_size();
             eprintln!(
                 "{} {:<18}{:>10} ({:4.1}%){:>14}{:>14}",
                 prefix,
@@ -152,10 +154,12 @@ impl<'k> StatCollector<'k> {
                 // We will soon sort, so the initial order does not matter.
                 #[allow(rustc::potential_query_instability)]
                 let mut subnodes: Vec<_> = node.subnodes.iter().collect();
-                subnodes.sort_by_key(|(_, subnode)| subnode.count * subnode.size);
+                subnodes.sort_by_cached_key(|(label, subnode)| {
+                    (subnode.accum_size(), label.to_owned())
+                });
 
                 for (label, subnode) in subnodes {
-                    let size = subnode.count * subnode.size;
+                    let size = subnode.accum_size();
                     eprintln!(
                         "{} - {:<18}{:>10} ({:4.1}%){:>14}",
                         prefix,
@@ -500,7 +504,7 @@ impl<'v> hir_visit::Visitor<'v> for StatCollector<'v> {
         hir_visit::walk_assoc_item_constraint(self, constraint)
     }
 
-    fn visit_attribute(&mut self, attr: &'v ast::Attribute) {
+    fn visit_attribute(&mut self, attr: &'v hir::Attribute) {
         self.record("Attribute", None, attr);
     }
 
diff --git a/compiler/rustc_passes/src/lang_items.rs b/compiler/rustc_passes/src/lang_items.rs
index 19f00aa3c1b..fe1140d893e 100644
--- a/compiler/rustc_passes/src/lang_items.rs
+++ b/compiler/rustc_passes/src/lang_items.rs
@@ -16,8 +16,7 @@ use rustc_hir::{LangItem, LanguageItems, MethodKind, Target};
 use rustc_middle::query::Providers;
 use rustc_middle::ty::{ResolverAstLowering, TyCtxt};
 use rustc_session::cstore::ExternCrate;
-use rustc_span::Span;
-use rustc_span::symbol::kw::Empty;
+use rustc_span::{Span, kw};
 
 use crate::errors::{
     DuplicateLangItem, IncorrectTarget, LangItemOnIncorrectTarget, UnknownLangItem,
@@ -99,7 +98,7 @@ impl<'ast, 'tcx> LanguageItemCollector<'ast, 'tcx> {
         {
             let lang_item_name = lang_item.name();
             let crate_name = self.tcx.crate_name(item_def_id.krate);
-            let mut dependency_of = Empty;
+            let mut dependency_of = kw::Empty;
             let is_local = item_def_id.is_local();
             let path = if is_local {
                 String::new()
@@ -113,8 +112,8 @@ impl<'ast, 'tcx> LanguageItemCollector<'ast, 'tcx> {
             };
 
             let first_defined_span = self.item_spans.get(&original_def_id).copied();
-            let mut orig_crate_name = Empty;
-            let mut orig_dependency_of = Empty;
+            let mut orig_crate_name = kw::Empty;
+            let mut orig_dependency_of = kw::Empty;
             let orig_is_local = original_def_id.is_local();
             let orig_path = if orig_is_local {
                 String::new()
diff --git a/compiler/rustc_passes/src/layout_test.rs b/compiler/rustc_passes/src/layout_test.rs
index bb90b5a1e31..1133cf93304 100644
--- a/compiler/rustc_passes/src/layout_test.rs
+++ b/compiler/rustc_passes/src/layout_test.rs
@@ -1,13 +1,12 @@
 use rustc_abi::{HasDataLayout, TargetDataLayout};
-use rustc_ast::Attribute;
+use rustc_hir::Attribute;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::LocalDefId;
 use rustc_middle::span_bug;
 use rustc_middle::ty::layout::{HasTyCtxt, HasTypingEnv, LayoutError, LayoutOfHelpers};
 use rustc_middle::ty::{self, Ty, TyCtxt};
-use rustc_span::Span;
 use rustc_span::source_map::Spanned;
-use rustc_span::symbol::sym;
+use rustc_span::{Span, sym};
 use rustc_trait_selection::error_reporting::InferCtxtErrorExt;
 use rustc_trait_selection::infer::TyCtxtInferExt;
 use rustc_trait_selection::traits;
diff --git a/compiler/rustc_passes/src/lib_features.rs b/compiler/rustc_passes/src/lib_features.rs
index 8a360c017ad..600c46eb3d0 100644
--- a/compiler/rustc_passes/src/lib_features.rs
+++ b/compiler/rustc_passes/src/lib_features.rs
@@ -4,15 +4,14 @@
 //! but are not declared in one single location (unlike lang features), which means we need to
 //! collect them instead.
 
-use rustc_ast::Attribute;
-use rustc_attr::VERSION_PLACEHOLDER;
+use rustc_attr_parsing::VERSION_PLACEHOLDER;
+use rustc_hir::Attribute;
 use rustc_hir::intravisit::Visitor;
 use rustc_middle::hir::nested_filter;
 use rustc_middle::middle::lib_features::{FeatureStability, LibFeatures};
 use rustc_middle::query::{LocalCrate, Providers};
 use rustc_middle::ty::TyCtxt;
-use rustc_span::symbol::Symbol;
-use rustc_span::{Span, sym};
+use rustc_span::{Span, Symbol, sym};
 
 use crate::errors::{FeaturePreviouslyDeclared, FeatureStableTwice};
 
diff --git a/compiler/rustc_passes/src/liveness.rs b/compiler/rustc_passes/src/liveness.rs
index 034f7308c4a..b85a987c641 100644
--- a/compiler/rustc_passes/src/liveness.rs
+++ b/compiler/rustc_passes/src/liveness.rs
@@ -96,8 +96,7 @@ use rustc_middle::query::Providers;
 use rustc_middle::span_bug;
 use rustc_middle::ty::{self, RootVariableMinCaptureList, Ty, TyCtxt};
 use rustc_session::lint;
-use rustc_span::symbol::{Symbol, kw, sym};
-use rustc_span::{BytePos, Span};
+use rustc_span::{BytePos, Span, Symbol, kw, sym};
 use tracing::{debug, instrument};
 
 use self::LiveNodeKind::*;
diff --git a/compiler/rustc_passes/src/naked_functions.rs b/compiler/rustc_passes/src/naked_functions.rs
index 766a9e1bdad..cad488bd71d 100644
--- a/compiler/rustc_passes/src/naked_functions.rs
+++ b/compiler/rustc_passes/src/naked_functions.rs
@@ -10,8 +10,7 @@ use rustc_middle::query::Providers;
 use rustc_middle::span_bug;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::lint::builtin::UNDEFINED_NAKED_FUNCTION_ABI;
-use rustc_span::Span;
-use rustc_span::symbol::sym;
+use rustc_span::{Span, sym};
 use rustc_target::spec::abi::Abi;
 
 use crate::errors::{
diff --git a/compiler/rustc_passes/src/stability.rs b/compiler/rustc_passes/src/stability.rs
index 2809ad453ff..d3637dac6b7 100644
--- a/compiler/rustc_passes/src/stability.rs
+++ b/compiler/rustc_passes/src/stability.rs
@@ -4,9 +4,9 @@
 use std::mem::replace;
 use std::num::NonZero;
 
-use rustc_attr::{
+use rustc_attr_parsing::{
     self as attr, ConstStability, DeprecatedSince, Stability, StabilityLevel, StableSince,
-    Unstable, UnstableReason, VERSION_PLACEHOLDER,
+    UnstableReason, VERSION_PLACEHOLDER,
 };
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_data_structures::unord::{ExtendUnord, UnordMap, UnordSet};
@@ -25,8 +25,7 @@ use rustc_middle::query::Providers;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::lint;
 use rustc_session::lint::builtin::{INEFFECTIVE_UNSTABLE_TRAIT_IMPL, USELESS_DEPRECATED};
-use rustc_span::Span;
-use rustc_span::symbol::{Symbol, sym};
+use rustc_span::{Span, Symbol, sym};
 use tracing::{debug, info};
 
 use crate::errors;
@@ -199,7 +198,7 @@ impl<'a, 'tcx> Annotator<'a, 'tcx> {
             // this is *almost surely* an accident.
             if let (
                 &Some(DeprecatedSince::RustcVersion(dep_since)),
-                &attr::Stable { since: stab_since, .. },
+                &attr::StabilityLevel::Stable { since: stab_since, .. },
             ) = (&depr.as_ref().map(|(d, _)| d.since), &stab.level)
             {
                 match stab_since {
@@ -224,15 +223,17 @@ impl<'a, 'tcx> Annotator<'a, 'tcx> {
 
             // Stable *language* features shouldn't be used as unstable library features.
             // (Not doing this for stable library features is checked by tidy.)
-            if let Stability { level: Unstable { .. }, feature } = stab {
+            if let Stability { level: StabilityLevel::Unstable { .. }, feature } = stab {
                 if ACCEPTED_LANG_FEATURES.iter().find(|f| f.name == feature).is_some() {
                     self.tcx
                         .dcx()
                         .emit_err(errors::UnstableAttrForAlreadyStableFeature { span, item_sp });
                 }
             }
-            if let Stability { level: Unstable { implied_by: Some(implied_by), .. }, feature } =
-                stab
+            if let Stability {
+                level: StabilityLevel::Unstable { implied_by: Some(implied_by), .. },
+                feature,
+            } = stab
             {
                 self.index.implications.insert(implied_by, feature);
             }
@@ -278,8 +279,10 @@ impl<'a, 'tcx> Annotator<'a, 'tcx> {
 
         // Stable *language* features shouldn't be used as unstable library features.
         // (Not doing this for stable library features is checked by tidy.)
-        if let Some((ConstStability { level: Unstable { .. }, feature, .. }, const_span)) =
-            const_stab
+        if let Some((
+            ConstStability { level: StabilityLevel::Unstable { .. }, feature, .. },
+            const_span,
+        )) = const_stab
         {
             if ACCEPTED_LANG_FEATURES.iter().find(|f| f.name == feature).is_some() {
                 self.tcx.dcx().emit_err(errors::UnstableAttrForAlreadyStableFeature {
@@ -314,7 +317,7 @@ impl<'a, 'tcx> Annotator<'a, 'tcx> {
         });
 
         if let Some(ConstStability {
-            level: Unstable { implied_by: Some(implied_by), .. },
+            level: StabilityLevel::Unstable { implied_by: Some(implied_by), .. },
             feature,
             ..
         }) = const_stab
@@ -780,7 +783,11 @@ impl<'tcx> Visitor<'tcx> for Checker<'tcx> {
                     // error if all involved types and traits are stable, because
                     // it will have no effect.
                     // See: https://github.com/rust-lang/rust/issues/55436
-                    if let Some((Stability { level: attr::Unstable { .. }, .. }, span)) = stab {
+                    if let Some((
+                        Stability { level: attr::StabilityLevel::Unstable { .. }, .. },
+                        span,
+                    )) = stab
+                    {
                         let mut c = CheckTraitImplStable { tcx: self.tcx, fully_stable: true };
                         c.visit_ty(self_ty);
                         c.visit_trait_ref(t);
diff --git a/compiler/rustc_privacy/Cargo.toml b/compiler/rustc_privacy/Cargo.toml
index f998e0ff154..eb48155919f 100644
--- a/compiler/rustc_privacy/Cargo.toml
+++ b/compiler/rustc_privacy/Cargo.toml
@@ -6,7 +6,7 @@ edition = "2021"
 [dependencies]
 # tidy-alphabetical-start
 rustc_ast = { path = "../rustc_ast" }
-rustc_attr = { path = "../rustc_attr" }
+rustc_attr_parsing = { path = "../rustc_attr_parsing" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
 rustc_fluent_macro = { path = "../rustc_fluent_macro" }
diff --git a/compiler/rustc_privacy/src/lib.rs b/compiler/rustc_privacy/src/lib.rs
index 3057f13e3a7..c50c9007a01 100644
--- a/compiler/rustc_privacy/src/lib.rs
+++ b/compiler/rustc_privacy/src/lib.rs
@@ -37,11 +37,10 @@ use rustc_middle::ty::{
 };
 use rustc_middle::{bug, span_bug};
 use rustc_session::lint;
-use rustc_span::Span;
 use rustc_span::hygiene::Transparency;
-use rustc_span::symbol::{Ident, kw, sym};
+use rustc_span::{Ident, Span, kw, sym};
 use tracing::debug;
-use {rustc_attr as attr, rustc_hir as hir};
+use {rustc_attr_parsing as attr, rustc_hir as hir};
 
 rustc_fluent_macro::fluent_messages! { "../messages.ftl" }
 
diff --git a/compiler/rustc_query_system/src/ich/hcx.rs b/compiler/rustc_query_system/src/ich/hcx.rs
index ad4b194eb50..6b737ceb50a 100644
--- a/compiler/rustc_query_system/src/ich/hcx.rs
+++ b/compiler/rustc_query_system/src/ich/hcx.rs
@@ -6,8 +6,7 @@ use rustc_hir::definitions::DefPathHash;
 use rustc_session::Session;
 use rustc_session::cstore::Untracked;
 use rustc_span::source_map::SourceMap;
-use rustc_span::symbol::Symbol;
-use rustc_span::{BytePos, CachingSourceMapView, DUMMY_SP, SourceFile, Span, SpanData};
+use rustc_span::{BytePos, CachingSourceMapView, DUMMY_SP, SourceFile, Span, SpanData, Symbol};
 
 use crate::ich;
 
diff --git a/compiler/rustc_query_system/src/ich/impls_syntax.rs b/compiler/rustc_query_system/src/ich/impls_syntax.rs
index 5a72e80a0a5..480fd497728 100644
--- a/compiler/rustc_query_system/src/ich/impls_syntax.rs
+++ b/compiler/rustc_query_system/src/ich/impls_syntax.rs
@@ -1,18 +1,17 @@
 //! This module contains `HashStable` implementations for various data types
-//! from `rustc_ast` in no particular order.
+//! from various crates in no particular order.
 
-use std::assert_matches::assert_matches;
-
-use rustc_ast as ast;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
+use rustc_hir as hir;
 use rustc_span::SourceFile;
 use smallvec::SmallVec;
 
 use crate::ich::StableHashingContext;
 
 impl<'ctx> rustc_target::HashStableContext for StableHashingContext<'ctx> {}
+impl<'ctx> rustc_ast::HashStableContext for StableHashingContext<'ctx> {}
 
-impl<'a> HashStable<StableHashingContext<'a>> for [ast::Attribute] {
+impl<'a> HashStable<StableHashingContext<'a>> for [hir::Attribute] {
     fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
         if self.is_empty() {
             self.len().hash_stable(hcx, hasher);
@@ -20,7 +19,7 @@ impl<'a> HashStable<StableHashingContext<'a>> for [ast::Attribute] {
         }
 
         // Some attributes are always ignored during hashing.
-        let filtered: SmallVec<[&ast::Attribute; 8]> = self
+        let filtered: SmallVec<[&hir::Attribute; 8]> = self
             .iter()
             .filter(|attr| {
                 !attr.is_doc_comment()
@@ -35,30 +34,23 @@ impl<'a> HashStable<StableHashingContext<'a>> for [ast::Attribute] {
     }
 }
 
-impl<'ctx> rustc_ast::HashStableContext for StableHashingContext<'ctx> {
-    fn hash_attr(&mut self, attr: &ast::Attribute, hasher: &mut StableHasher) {
+impl<'ctx> rustc_hir::HashStableContext for StableHashingContext<'ctx> {
+    fn hash_attr(&mut self, attr: &hir::Attribute, hasher: &mut StableHasher) {
         // Make sure that these have been filtered out.
         debug_assert!(!attr.ident().is_some_and(|ident| self.is_ignored_attr(ident.name)));
         debug_assert!(!attr.is_doc_comment());
 
-        let ast::Attribute { kind, id: _, style, span } = attr;
-        if let ast::AttrKind::Normal(normal) = kind {
-            normal.item.hash_stable(self, hasher);
+        let hir::Attribute { kind, id: _, style, span } = attr;
+        if let hir::AttrKind::Normal(item) = kind {
+            item.hash_stable(self, hasher);
             style.hash_stable(self, hasher);
             span.hash_stable(self, hasher);
-            assert_matches!(
-                normal.tokens.as_ref(),
-                None,
-                "Tokens should have been removed during lowering!"
-            );
         } else {
             unreachable!();
         }
     }
 }
 
-impl<'ctx> rustc_hir::HashStableContext for StableHashingContext<'ctx> {}
-
 impl<'a> HashStable<StableHashingContext<'a>> for SourceFile {
     fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
         let SourceFile {
diff --git a/compiler/rustc_query_system/src/ich/mod.rs b/compiler/rustc_query_system/src/ich/mod.rs
index 8f28b1d4c80..852d93b711f 100644
--- a/compiler/rustc_query_system/src/ich/mod.rs
+++ b/compiler/rustc_query_system/src/ich/mod.rs
@@ -1,6 +1,6 @@
 //! ICH - Incremental Compilation Hash
 
-use rustc_span::symbol::{Symbol, sym};
+use rustc_span::{Symbol, sym};
 
 pub use self::hcx::StableHashingContext;
 
diff --git a/compiler/rustc_resolve/Cargo.toml b/compiler/rustc_resolve/Cargo.toml
index b71853b871d..309227176d4 100644
--- a/compiler/rustc_resolve/Cargo.toml
+++ b/compiler/rustc_resolve/Cargo.toml
@@ -10,7 +10,7 @@ pulldown-cmark = { version = "0.11", features = ["html"], default-features = fal
 rustc_arena = { path = "../rustc_arena" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_ast_pretty = { path = "../rustc_ast_pretty" }
-rustc_attr = { path = "../rustc_attr" }
+rustc_attr_parsing = { path = "../rustc_attr_parsing" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
 rustc_expand = { path = "../rustc_expand" }
diff --git a/compiler/rustc_resolve/src/build_reduced_graph.rs b/compiler/rustc_resolve/src/build_reduced_graph.rs
index 924b8afa329..3fe1eed243f 100644
--- a/compiler/rustc_resolve/src/build_reduced_graph.rs
+++ b/compiler/rustc_resolve/src/build_reduced_graph.rs
@@ -12,7 +12,7 @@ use rustc_ast::{
     self as ast, AssocItem, AssocItemKind, Block, ForeignItem, ForeignItemKind, Impl, Item,
     ItemKind, MetaItemKind, NodeId, StmtKind,
 };
-use rustc_attr as attr;
+use rustc_attr_parsing as attr;
 use rustc_data_structures::sync::Lrc;
 use rustc_expand::base::ResolverExpand;
 use rustc_expand::expand::AstFragment;
@@ -22,9 +22,8 @@ use rustc_metadata::creader::LoadedMacro;
 use rustc_middle::metadata::ModChild;
 use rustc_middle::ty::Feed;
 use rustc_middle::{bug, ty};
-use rustc_span::Span;
 use rustc_span::hygiene::{ExpnId, LocalExpnId, MacroKind};
-use rustc_span::symbol::{Ident, Symbol, kw, sym};
+use rustc_span::{Ident, Span, Symbol, kw, sym};
 use tracing::debug;
 
 use crate::Namespace::{MacroNS, TypeNS, ValueNS};
@@ -634,7 +633,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
             }
             ast::UseTreeKind::Glob => {
                 let kind = ImportKind::Glob {
-                    is_prelude: attr::contains_name(&item.attrs, sym::prelude_import),
+                    is_prelude: ast::attr::contains_name(&item.attrs, sym::prelude_import),
                     max_vis: Cell::new(None),
                     id,
                 };
@@ -777,7 +776,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
                     expansion.to_expn_id(),
                     item.span,
                     parent.no_implicit_prelude
-                        || attr::contains_name(&item.attrs, sym::no_implicit_prelude),
+                        || ast::attr::contains_name(&item.attrs, sym::no_implicit_prelude),
                 );
                 self.r.define(parent, ident, TypeNS, (module, vis, sp, expansion));
 
@@ -835,7 +834,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
                     // If the structure is marked as non_exhaustive then lower the visibility
                     // to within the crate.
                     let mut ctor_vis = if vis.is_public()
-                        && attr::contains_name(&item.attrs, sym::non_exhaustive)
+                        && ast::attr::contains_name(&item.attrs, sym::non_exhaustive)
                     {
                         ty::Visibility::Restricted(CRATE_DEF_ID)
                     } else {
@@ -1176,11 +1175,11 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
     }
 
     fn proc_macro_stub(&self, item: &ast::Item) -> Option<(MacroKind, Ident, Span)> {
-        if attr::contains_name(&item.attrs, sym::proc_macro) {
+        if ast::attr::contains_name(&item.attrs, sym::proc_macro) {
             return Some((MacroKind::Bang, item.ident, item.span));
-        } else if attr::contains_name(&item.attrs, sym::proc_macro_attribute) {
+        } else if ast::attr::contains_name(&item.attrs, sym::proc_macro_attribute) {
             return Some((MacroKind::Attr, item.ident, item.span));
-        } else if let Some(attr) = attr::find_by_name(&item.attrs, sym::proc_macro_derive) {
+        } else if let Some(attr) = ast::attr::find_by_name(&item.attrs, sym::proc_macro_derive) {
             if let Some(meta_item_inner) =
                 attr.meta_item_list().and_then(|list| list.get(0).cloned())
             {
@@ -1233,7 +1232,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
         if macro_rules {
             let ident = ident.normalize_to_macros_2_0();
             self.r.macro_names.insert(ident);
-            let is_macro_export = attr::contains_name(&item.attrs, sym::macro_export);
+            let is_macro_export = ast::attr::contains_name(&item.attrs, sym::macro_export);
             let vis = if is_macro_export {
                 ty::Visibility::Public
             } else {
@@ -1507,7 +1506,7 @@ impl<'a, 'ra, 'tcx> Visitor<'a> for BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
 
         // If the variant is marked as non_exhaustive then lower the visibility to within the crate.
         let ctor_vis =
-            if vis.is_public() && attr::contains_name(&variant.attrs, sym::non_exhaustive) {
+            if vis.is_public() && ast::attr::contains_name(&variant.attrs, sym::non_exhaustive) {
                 ty::Visibility::Restricted(CRATE_DEF_ID)
             } else {
                 vis
diff --git a/compiler/rustc_resolve/src/check_unused.rs b/compiler/rustc_resolve/src/check_unused.rs
index e36055e8575..5a605df88c2 100644
--- a/compiler/rustc_resolve/src/check_unused.rs
+++ b/compiler/rustc_resolve/src/check_unused.rs
@@ -33,8 +33,7 @@ use rustc_session::lint::BuiltinLintDiag;
 use rustc_session::lint::builtin::{
     MACRO_USE_EXTERN_CRATE, UNUSED_EXTERN_CRATES, UNUSED_IMPORTS, UNUSED_QUALIFICATIONS,
 };
-use rustc_span::symbol::{Ident, kw};
-use rustc_span::{DUMMY_SP, Span};
+use rustc_span::{DUMMY_SP, Ident, Span, kw};
 
 use crate::imports::{Import, ImportKind};
 use crate::{LexicalScopeBinding, NameBindingKind, Resolver, module_to_string};
diff --git a/compiler/rustc_resolve/src/def_collector.rs b/compiler/rustc_resolve/src/def_collector.rs
index 66492842581..87024c487df 100644
--- a/compiler/rustc_resolve/src/def_collector.rs
+++ b/compiler/rustc_resolve/src/def_collector.rs
@@ -7,9 +7,8 @@ use rustc_expand::expand::AstFragment;
 use rustc_hir as hir;
 use rustc_hir::def::{CtorKind, CtorOf, DefKind};
 use rustc_hir::def_id::LocalDefId;
-use rustc_span::Span;
 use rustc_span::hygiene::LocalExpnId;
-use rustc_span::symbol::{Symbol, kw, sym};
+use rustc_span::{Span, Symbol, kw, sym};
 use tracing::debug;
 
 use crate::{ImplTraitContext, InvocationParent, Resolver};
@@ -356,6 +355,7 @@ impl<'a, 'ra, 'tcx> visit::Visitor<'a> for DefCollector<'a, 'ra, 'tcx> {
                 let kind = match self.impl_trait_context {
                     ImplTraitContext::Universal => DefKind::TyParam,
                     ImplTraitContext::Existential => DefKind::OpaqueTy,
+                    ImplTraitContext::InBinding => return visit::walk_ty(self, ty),
                 };
                 let id = self.create_def(*id, name, kind, ty.span);
                 match self.impl_trait_context {
@@ -365,6 +365,7 @@ impl<'a, 'ra, 'tcx> visit::Visitor<'a> for DefCollector<'a, 'ra, 'tcx> {
                     ImplTraitContext::Existential => {
                         self.with_parent(id, |this| visit::walk_ty(this, ty))
                     }
+                    ImplTraitContext::InBinding => unreachable!(),
                 };
             }
             _ => visit::walk_ty(self, ty),
@@ -374,6 +375,13 @@ impl<'a, 'ra, 'tcx> visit::Visitor<'a> for DefCollector<'a, 'ra, 'tcx> {
     fn visit_stmt(&mut self, stmt: &'a Stmt) {
         match stmt.kind {
             StmtKind::MacCall(..) => self.visit_macro_invoc(stmt.id),
+            // FIXME(impl_trait_in_bindings): We don't really have a good way of
+            // introducing the right `ImplTraitContext` here for all the cases we
+            // care about, in case we want to introduce ITIB to other positions
+            // such as turbofishes (e.g. `foo::<impl Fn()>(|| {})`).
+            StmtKind::Let(ref local) => self.with_impl_trait(ImplTraitContext::InBinding, |this| {
+                visit::walk_local(this, local)
+            }),
             _ => visit::walk_stmt(self, stmt),
         }
     }
diff --git a/compiler/rustc_resolve/src/diagnostics.rs b/compiler/rustc_resolve/src/diagnostics.rs
index 368eb3c26c7..9795299ed6d 100644
--- a/compiler/rustc_resolve/src/diagnostics.rs
+++ b/compiler/rustc_resolve/src/diagnostics.rs
@@ -28,8 +28,7 @@ use rustc_span::edit_distance::find_best_match_for_name;
 use rustc_span::edition::Edition;
 use rustc_span::hygiene::MacroKind;
 use rustc_span::source_map::SourceMap;
-use rustc_span::symbol::{Ident, Symbol, kw, sym};
-use rustc_span::{BytePos, Span, SyntaxContext};
+use rustc_span::{BytePos, Ident, Span, Symbol, SyntaxContext, kw, sym};
 use thin_vec::{ThinVec, thin_vec};
 use tracing::debug;
 
@@ -2817,11 +2816,11 @@ fn show_candidates(
         path_strings.sort_by(|a, b| a.0.cmp(&b.0));
         path_strings.dedup_by(|a, b| a.0 == b.0);
         let core_path_strings =
-            path_strings.extract_if(|p| p.0.starts_with("core::")).collect::<Vec<_>>();
+            path_strings.extract_if(.., |p| p.0.starts_with("core::")).collect::<Vec<_>>();
         let std_path_strings =
-            path_strings.extract_if(|p| p.0.starts_with("std::")).collect::<Vec<_>>();
+            path_strings.extract_if(.., |p| p.0.starts_with("std::")).collect::<Vec<_>>();
         let foreign_crate_path_strings =
-            path_strings.extract_if(|p| !p.0.starts_with("crate::")).collect::<Vec<_>>();
+            path_strings.extract_if(.., |p| !p.0.starts_with("crate::")).collect::<Vec<_>>();
 
         // We list the `crate` local paths first.
         // Then we list the `std`/`core` paths.
diff --git a/compiler/rustc_resolve/src/errors.rs b/compiler/rustc_resolve/src/errors.rs
index 24f5a812a82..3bfe98f7091 100644
--- a/compiler/rustc_resolve/src/errors.rs
+++ b/compiler/rustc_resolve/src/errors.rs
@@ -1,8 +1,7 @@
 use rustc_errors::codes::*;
 use rustc_errors::{Applicability, ElidedLifetimeInPathSubdiag, MultiSpan};
 use rustc_macros::{Diagnostic, Subdiagnostic};
-use rustc_span::Span;
-use rustc_span::symbol::{Ident, Symbol};
+use rustc_span::{Ident, Span, Symbol};
 
 use crate::Res;
 use crate::late::PatternSource;
diff --git a/compiler/rustc_resolve/src/ident.rs b/compiler/rustc_resolve/src/ident.rs
index 5906a682f3e..45e87edc53e 100644
--- a/compiler/rustc_resolve/src/ident.rs
+++ b/compiler/rustc_resolve/src/ident.rs
@@ -9,8 +9,7 @@ use rustc_session::lint::builtin::PROC_MACRO_DERIVE_RESOLUTION_FALLBACK;
 use rustc_session::parse::feature_err;
 use rustc_span::def_id::LocalDefId;
 use rustc_span::hygiene::{ExpnId, ExpnKind, LocalExpnId, MacroKind, SyntaxContext};
-use rustc_span::symbol::{Ident, kw};
-use rustc_span::{Span, sym};
+use rustc_span::{Ident, Span, kw, sym};
 use tracing::{debug, instrument};
 
 use crate::errors::{ParamKindInEnumDiscriminant, ParamKindInNonTrivialAnonConst};
diff --git a/compiler/rustc_resolve/src/imports.rs b/compiler/rustc_resolve/src/imports.rs
index 2ed3f4d2c4f..5b1d8d622bd 100644
--- a/compiler/rustc_resolve/src/imports.rs
+++ b/compiler/rustc_resolve/src/imports.rs
@@ -17,10 +17,9 @@ use rustc_session::lint::builtin::{
     AMBIGUOUS_GLOB_REEXPORTS, HIDDEN_GLOB_REEXPORTS, PUB_USE_OF_PRIVATE_EXTERN_CRATE,
     REDUNDANT_IMPORTS, UNUSED_IMPORTS,
 };
-use rustc_span::Span;
 use rustc_span::edit_distance::find_best_match_for_name;
 use rustc_span::hygiene::LocalExpnId;
-use rustc_span::symbol::{Ident, Symbol, kw};
+use rustc_span::{Ident, Span, Symbol, kw};
 use smallvec::SmallVec;
 use tracing::debug;
 
diff --git a/compiler/rustc_resolve/src/late.rs b/compiler/rustc_resolve/src/late.rs
index bde11428d40..7324d3fe786 100644
--- a/compiler/rustc_resolve/src/late.rs
+++ b/compiler/rustc_resolve/src/late.rs
@@ -19,7 +19,9 @@ use rustc_ast::visit::{
 use rustc_ast::*;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap};
 use rustc_errors::codes::*;
-use rustc_errors::{Applicability, DiagArgValue, IntoDiagArg, StashKey, Suggestions};
+use rustc_errors::{
+    Applicability, DiagArgValue, ErrorGuaranteed, IntoDiagArg, StashKey, Suggestions,
+};
 use rustc_hir::def::Namespace::{self, *};
 use rustc_hir::def::{self, CtorKind, DefKind, LifetimeRes, NonMacroAttrKind, PartialRes, PerNS};
 use rustc_hir::def_id::{CRATE_DEF_ID, DefId, LOCAL_CRATE, LocalDefId};
@@ -31,8 +33,7 @@ use rustc_session::config::{CrateType, ResolveDocLinks};
 use rustc_session::lint::{self, BuiltinLintDiag};
 use rustc_session::parse::feature_err;
 use rustc_span::source_map::{Spanned, respan};
-use rustc_span::symbol::{Ident, Symbol, kw, sym};
-use rustc_span::{BytePos, Span, SyntaxContext};
+use rustc_span::{BytePos, Ident, Span, Symbol, SyntaxContext, kw, sym};
 use smallvec::{SmallVec, smallvec};
 use tracing::{debug, instrument, trace};
 
@@ -264,12 +265,17 @@ impl RibKind<'_> {
 #[derive(Debug)]
 pub(crate) struct Rib<'ra, R = Res> {
     pub bindings: IdentMap<R>,
+    pub patterns_with_skipped_bindings: FxHashMap<DefId, Vec<(Span, Result<(), ErrorGuaranteed>)>>,
     pub kind: RibKind<'ra>,
 }
 
 impl<'ra, R> Rib<'ra, R> {
     fn new(kind: RibKind<'ra>) -> Rib<'ra, R> {
-        Rib { bindings: Default::default(), kind }
+        Rib {
+            bindings: Default::default(),
+            patterns_with_skipped_bindings: Default::default(),
+            kind,
+        }
     }
 }
 
@@ -3775,6 +3781,7 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
     /// When a whole or-pattern has been dealt with, the thing happens.
     ///
     /// See the implementation and `fresh_binding` for more details.
+    #[tracing::instrument(skip(self, bindings), level = "debug")]
     fn resolve_pattern_inner(
         &mut self,
         pat: &Pat,
@@ -3783,7 +3790,6 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
     ) {
         // Visit all direct subpatterns of this pattern.
         pat.walk(&mut |pat| {
-            debug!("resolve_pattern pat={:?} node={:?}", pat, pat.kind);
             match pat.kind {
                 PatKind::Ident(bmode, ident, ref sub) => {
                     // First try to resolve the identifier as some existing entity,
@@ -3809,8 +3815,9 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
                 PatKind::Path(ref qself, ref path) => {
                     self.smart_resolve_path(pat.id, qself, path, PathSource::Pat);
                 }
-                PatKind::Struct(ref qself, ref path, ..) => {
+                PatKind::Struct(ref qself, ref path, ref _fields, ref rest) => {
                     self.smart_resolve_path(pat.id, qself, path, PathSource::Struct);
+                    self.record_patterns_with_skipped_bindings(pat, rest);
                 }
                 PatKind::Or(ref ps) => {
                     // Add a new set of bindings to the stack. `Or` here records that when a
@@ -3843,6 +3850,30 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
         });
     }
 
+    fn record_patterns_with_skipped_bindings(&mut self, pat: &Pat, rest: &ast::PatFieldsRest) {
+        match rest {
+            ast::PatFieldsRest::Rest | ast::PatFieldsRest::Recovered(_) => {
+                // Record that the pattern doesn't introduce all the bindings it could.
+                if let Some(partial_res) = self.r.partial_res_map.get(&pat.id)
+                    && let Some(res) = partial_res.full_res()
+                    && let Some(def_id) = res.opt_def_id()
+                {
+                    self.ribs[ValueNS]
+                        .last_mut()
+                        .unwrap()
+                        .patterns_with_skipped_bindings
+                        .entry(def_id)
+                        .or_default()
+                        .push((pat.span, match rest {
+                            ast::PatFieldsRest::Recovered(guar) => Err(*guar),
+                            _ => Ok(()),
+                        }));
+                }
+            }
+            ast::PatFieldsRest::None => {}
+        }
+    }
+
     fn fresh_binding(
         &mut self,
         ident: Ident,
@@ -4294,7 +4325,7 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
 
     #[inline]
     /// If we're actually rustdoc then avoid giving a name resolution error for `cfg()` items or
-    // an invalid `use foo::*;` was found, which can cause unbounded ammounts of "item not found"
+    // an invalid `use foo::*;` was found, which can cause unbounded amounts of "item not found"
     // errors. We silence them all.
     fn should_report_errs(&self) -> bool {
         !(self.r.tcx.sess.opts.actually_rustdoc && self.in_func_body)
diff --git a/compiler/rustc_resolve/src/late/diagnostics.rs b/compiler/rustc_resolve/src/late/diagnostics.rs
index 09f3e848766..6ee02e9f47f 100644
--- a/compiler/rustc_resolve/src/late/diagnostics.rs
+++ b/compiler/rustc_resolve/src/late/diagnostics.rs
@@ -27,8 +27,7 @@ use rustc_session::{Session, lint};
 use rustc_span::edit_distance::find_best_match_for_name;
 use rustc_span::edition::Edition;
 use rustc_span::hygiene::MacroKind;
-use rustc_span::symbol::{Ident, Symbol, kw, sym};
-use rustc_span::{DUMMY_SP, Span};
+use rustc_span::{DUMMY_SP, Ident, Span, Symbol, kw, sym};
 use thin_vec::ThinVec;
 use tracing::debug;
 
@@ -430,6 +429,7 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
         let mut err = self.r.dcx().struct_span_err(base_error.span, base_error.msg.clone());
         err.code(code);
 
+        self.detect_missing_binding_available_from_pattern(&mut err, path, following_seg);
         self.suggest_at_operator_in_slice_pat_with_range(&mut err, path);
         self.suggest_swapping_misplaced_self_ty_and_trait(&mut err, source, res, base_error.span);
 
@@ -628,7 +628,7 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
         // Try to filter out intrinsics candidates, as long as we have
         // some other candidates to suggest.
         let intrinsic_candidates: Vec<_> = candidates
-            .extract_if(|sugg| {
+            .extract_if(.., |sugg| {
                 let path = path_names_to_string(&sugg.path);
                 path.starts_with("core::intrinsics::") || path.starts_with("std::intrinsics::")
             })
@@ -1120,6 +1120,48 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
         true
     }
 
+    fn detect_missing_binding_available_from_pattern(
+        &mut self,
+        err: &mut Diag<'_>,
+        path: &[Segment],
+        following_seg: Option<&Segment>,
+    ) {
+        let [segment] = path else { return };
+        let None = following_seg else { return };
+        for rib in self.ribs[ValueNS].iter().rev() {
+            for (def_id, spans) in &rib.patterns_with_skipped_bindings {
+                if let Some(fields) = self.r.field_idents(*def_id) {
+                    for field in fields {
+                        if field.name == segment.ident.name {
+                            if spans.iter().all(|(_, had_error)| had_error.is_err()) {
+                                // This resolution error will likely be fixed by fixing a
+                                // syntax error in a pattern, so it is irrelevant to the user.
+                                let multispan: MultiSpan =
+                                    spans.iter().map(|(s, _)| *s).collect::<Vec<_>>().into();
+                                err.span_note(
+                                    multispan,
+                                    "this pattern had a recovered parse error which likely lost \
+                                     the expected fields",
+                                );
+                                err.downgrade_to_delayed_bug();
+                            }
+                            let ty = self.r.tcx.item_name(*def_id);
+                            for (span, _) in spans {
+                                err.span_label(
+                                    *span,
+                                    format!(
+                                        "this pattern doesn't include `{field}`, which is \
+                                         available in `{ty}`",
+                                    ),
+                                );
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+
     fn suggest_at_operator_in_slice_pat_with_range(
         &mut self,
         err: &mut Diag<'_>,
diff --git a/compiler/rustc_resolve/src/lib.rs b/compiler/rustc_resolve/src/lib.rs
index 94adfcd3b91..7b950b97d30 100644
--- a/compiler/rustc_resolve/src/lib.rs
+++ b/compiler/rustc_resolve/src/lib.rs
@@ -70,8 +70,7 @@ use rustc_query_system::ich::StableHashingContext;
 use rustc_session::lint::builtin::PRIVATE_MACRO_USE;
 use rustc_session::lint::{BuiltinLintDiag, LintBuffer};
 use rustc_span::hygiene::{ExpnId, LocalExpnId, MacroKind, SyntaxContext, Transparency};
-use rustc_span::symbol::{Ident, Symbol, kw, sym};
-use rustc_span::{DUMMY_SP, Span};
+use rustc_span::{DUMMY_SP, Ident, Span, Symbol, kw, sym};
 use smallvec::{SmallVec, smallvec};
 use tracing::debug;
 
@@ -190,6 +189,7 @@ impl InvocationParent {
 enum ImplTraitContext {
     Existential,
     Universal,
+    InBinding,
 }
 
 /// Used for tracking import use types which will be used for redundant import checking.
diff --git a/compiler/rustc_resolve/src/macros.rs b/compiler/rustc_resolve/src/macros.rs
index 669a9c2428f..b24e343c58d 100644
--- a/compiler/rustc_resolve/src/macros.rs
+++ b/compiler/rustc_resolve/src/macros.rs
@@ -4,10 +4,11 @@
 use std::cell::Cell;
 use std::mem;
 
+use rustc_ast::attr::AttributeExt;
 use rustc_ast::expand::StrippedCfgItem;
 use rustc_ast::{self as ast, Crate, Inline, ItemKind, ModKind, NodeId, attr};
 use rustc_ast_pretty::pprust;
-use rustc_attr::StabilityLevel;
+use rustc_attr_parsing::StabilityLevel;
 use rustc_data_structures::intern::Interned;
 use rustc_data_structures::sync::Lrc;
 use rustc_errors::{Applicability, StashKey};
@@ -32,8 +33,7 @@ use rustc_session::parse::feature_err;
 use rustc_span::edit_distance::edit_distance;
 use rustc_span::edition::Edition;
 use rustc_span::hygiene::{self, AstPass, ExpnData, ExpnKind, LocalExpnId, MacroKind};
-use rustc_span::symbol::{Ident, Symbol, kw, sym};
-use rustc_span::{DUMMY_SP, Span};
+use rustc_span::{DUMMY_SP, Ident, Span, Symbol, kw, sym};
 
 use crate::Namespace::*;
 use crate::errors::{
@@ -689,8 +689,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             && let [namespace, attribute, ..] = &*path.segments
             && namespace.ident.name == sym::diagnostic
             && !(attribute.ident.name == sym::on_unimplemented
-                || (attribute.ident.name == sym::do_not_recommend
-                    && self.tcx.features().do_not_recommend()))
+                || attribute.ident.name == sym::do_not_recommend)
         {
             let distance =
                 edit_distance(attribute.ident.name.as_str(), sym::on_unimplemented.as_str(), 5);
@@ -1126,7 +1125,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         &mut self,
         macro_def: &ast::MacroDef,
         ident: Ident,
-        attrs: &[ast::Attribute],
+        attrs: &[impl AttributeExt],
         span: Span,
         node_id: NodeId,
         edition: Edition,
diff --git a/compiler/rustc_resolve/src/rustdoc.rs b/compiler/rustc_resolve/src/rustdoc.rs
index 65128ceb866..84e43d0e016 100644
--- a/compiler/rustc_resolve/src/rustdoc.rs
+++ b/compiler/rustc_resolve/src/rustdoc.rs
@@ -5,12 +5,13 @@ use pulldown_cmark::{
     BrokenLink, BrokenLinkCallback, CowStr, Event, LinkType, Options, Parser, Tag,
 };
 use rustc_ast as ast;
+use rustc_ast::attr::AttributeExt;
 use rustc_ast::util::comments::beautify_doc_string;
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_middle::ty::TyCtxt;
 use rustc_span::def_id::DefId;
-use rustc_span::symbol::{Symbol, kw, sym};
-use rustc_span::{DUMMY_SP, InnerSpan, Span};
+use rustc_span::{DUMMY_SP, InnerSpan, Span, Symbol, kw, sym};
+use thin_vec::ThinVec;
 use tracing::{debug, trace};
 
 #[derive(Clone, Copy, PartialEq, Eq, Debug)]
@@ -192,19 +193,24 @@ pub fn add_doc_fragment(out: &mut String, frag: &DocFragment) {
     }
 }
 
-pub fn attrs_to_doc_fragments<'a>(
-    attrs: impl Iterator<Item = (&'a ast::Attribute, Option<DefId>)>,
+pub fn attrs_to_doc_fragments<'a, A: AttributeExt + Clone + 'a>(
+    attrs: impl Iterator<Item = (&'a A, Option<DefId>)>,
     doc_only: bool,
-) -> (Vec<DocFragment>, ast::AttrVec) {
+) -> (Vec<DocFragment>, ThinVec<A>) {
     let mut doc_fragments = Vec::new();
-    let mut other_attrs = ast::AttrVec::new();
+    let mut other_attrs = ThinVec::<A>::new();
     for (attr, item_id) in attrs {
         if let Some((doc_str, comment_kind)) = attr.doc_str_and_comment_kind() {
             let doc = beautify_doc_string(doc_str, comment_kind);
             let (span, kind) = if attr.is_doc_comment() {
-                (attr.span, DocFragmentKind::SugaredDoc)
+                (attr.span(), DocFragmentKind::SugaredDoc)
             } else {
-                (span_for_value(attr), DocFragmentKind::RawDoc)
+                (
+                    attr.value_span()
+                        .map(|i| i.with_ctxt(attr.span().ctxt()))
+                        .unwrap_or(attr.span()),
+                    DocFragmentKind::RawDoc,
+                )
             };
             let fragment = DocFragment { span, doc, kind, item_id, indent: 0 };
             doc_fragments.push(fragment);
@@ -218,16 +224,6 @@ pub fn attrs_to_doc_fragments<'a>(
     (doc_fragments, other_attrs)
 }
 
-fn span_for_value(attr: &ast::Attribute) -> Span {
-    if let ast::AttrKind::Normal(normal) = &attr.kind
-        && let ast::AttrArgs::Eq { value, .. } = &normal.item.args
-    {
-        value.span().with_ctxt(attr.span.ctxt())
-    } else {
-        attr.span
-    }
-}
-
 /// Return the doc-comments on this item, grouped by the module they came from.
 /// The module can be different if this is a re-export with added documentation.
 ///
@@ -353,12 +349,15 @@ pub fn strip_generics_from_path(path_str: &str) -> Result<Box<str>, MalformedGen
 ///
 //// If there are no doc-comments, return true.
 /// FIXME(#78591): Support both inner and outer attributes on the same item.
-pub fn inner_docs(attrs: &[ast::Attribute]) -> bool {
-    attrs.iter().find(|a| a.doc_str().is_some()).map_or(true, |a| a.style == ast::AttrStyle::Inner)
+pub fn inner_docs(attrs: &[impl AttributeExt]) -> bool {
+    attrs
+        .iter()
+        .find(|a| a.doc_str().is_some())
+        .map_or(true, |a| a.style() == ast::AttrStyle::Inner)
 }
 
 /// Has `#[rustc_doc_primitive]` or `#[doc(keyword)]`.
-pub fn has_primitive_or_keyword_docs(attrs: &[ast::Attribute]) -> bool {
+pub fn has_primitive_or_keyword_docs(attrs: &[impl AttributeExt]) -> bool {
     for attr in attrs {
         if attr.has_name(sym::rustc_doc_primitive) {
             return true;
@@ -408,7 +407,7 @@ pub fn may_be_doc_link(link_type: LinkType) -> bool {
 
 /// Simplified version of `preprocessed_markdown_links` from rustdoc.
 /// Must return at least the same links as it, but may add some more links on top of that.
-pub(crate) fn attrs_to_preprocessed_links(attrs: &[ast::Attribute]) -> Vec<Box<str>> {
+pub(crate) fn attrs_to_preprocessed_links<A: AttributeExt + Clone>(attrs: &[A]) -> Vec<Box<str>> {
     let (doc_fragments, _) = attrs_to_doc_fragments(attrs.iter().map(|attr| (attr, None)), true);
     let doc = prepare_to_doc_link_resolution(&doc_fragments).into_values().next().unwrap();
 
diff --git a/compiler/rustc_session/src/config.rs b/compiler/rustc_session/src/config.rs
index 936c2ca87d6..047e920e688 100644
--- a/compiler/rustc_session/src/config.rs
+++ b/compiler/rustc_session/src/config.rs
@@ -147,18 +147,24 @@ pub enum InstrumentCoverage {
     Yes,
 }
 
-/// Individual flag values controlled by `-Z coverage-options`.
+/// Individual flag values controlled by `-Zcoverage-options`.
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, Default)]
 pub struct CoverageOptions {
     pub level: CoverageLevel,
 
-    /// `-Z coverage-options=no-mir-spans`: Don't extract block coverage spans
+    /// `-Zcoverage-options=no-mir-spans`: Don't extract block coverage spans
     /// from MIR statements/terminators, making it easier to inspect/debug
     /// branch and MC/DC coverage mappings.
     ///
     /// For internal debugging only. If other code changes would make it hard
     /// to keep supporting this flag, remove it.
     pub no_mir_spans: bool,
+
+    /// `-Zcoverage-options=discard-all-spans-in-codegen`: During codgen,
+    /// discard all coverage spans as though they were invalid. Needed by
+    /// regression tests for #133606, because we don't have an easy way to
+    /// reproduce it from actual source code.
+    pub discard_all_spans_in_codegen: bool,
 }
 
 /// Controls whether branch coverage or MC/DC coverage is enabled.
@@ -1076,7 +1082,7 @@ impl OutputFilenames {
         self.with_directory_and_extension(&self.out_directory, extension)
     }
 
-    pub fn with_directory_and_extension(&self, directory: &PathBuf, extension: &str) -> PathBuf {
+    pub fn with_directory_and_extension(&self, directory: &Path, extension: &str) -> PathBuf {
         let mut path = directory.join(&self.filestem);
         path.set_extension(extension);
         path
diff --git a/compiler/rustc_session/src/config/cfg.rs b/compiler/rustc_session/src/config/cfg.rs
index 43cf1324edd..3426858495b 100644
--- a/compiler/rustc_session/src/config/cfg.rs
+++ b/compiler/rustc_session/src/config/cfg.rs
@@ -28,7 +28,7 @@ use rustc_ast::ast;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
 use rustc_lint_defs::BuiltinLintDiag;
 use rustc_lint_defs::builtin::EXPLICIT_BUILTIN_CFGS_IN_FLAGS;
-use rustc_span::symbol::{Symbol, sym};
+use rustc_span::{Symbol, sym};
 use rustc_target::spec::{PanicStrategy, RelocModel, SanitizerSet, TARGETS, Target, TargetTuple};
 
 use crate::Session;
diff --git a/compiler/rustc_session/src/cstore.rs b/compiler/rustc_session/src/cstore.rs
index 3e2cbc18933..c8a5c22ad12 100644
--- a/compiler/rustc_session/src/cstore.rs
+++ b/compiler/rustc_session/src/cstore.rs
@@ -13,8 +13,7 @@ use rustc_hir::def_id::{
 };
 use rustc_hir::definitions::{DefKey, DefPath, DefPathHash, Definitions};
 use rustc_macros::{Decodable, Encodable, HashStable_Generic};
-use rustc_span::Span;
-use rustc_span::symbol::Symbol;
+use rustc_span::{Span, Symbol};
 
 use crate::search_paths::PathKind;
 use crate::utils::NativeLibKind;
@@ -43,7 +42,7 @@ pub enum CrateDepKind {
     /// A dependency that is only used for its macros.
     MacrosOnly,
     /// A dependency that is always injected into the dependency list and so
-    /// doesn't need to be linked to an rlib, e.g., the injected allocator.
+    /// doesn't need to be linked to an rlib, e.g., the injected panic runtime.
     Implicit,
     /// A dependency that is required by an rlib version of this crate.
     /// Ordinary `extern crate`s result in `Explicit` dependencies.
diff --git a/compiler/rustc_session/src/lib.rs b/compiler/rustc_session/src/lib.rs
index 0b4470b2b0f..dcf86d1a408 100644
--- a/compiler/rustc_session/src/lib.rs
+++ b/compiler/rustc_session/src/lib.rs
@@ -29,9 +29,6 @@ pub mod output;
 
 pub use getopts;
 
-mod version;
-pub use version::RustcVersion;
-
 rustc_fluent_macro::fluent_messages! { "../messages.ftl" }
 
 /// Requirements for a `StableHashingContext` to be used in this crate.
diff --git a/compiler/rustc_session/src/options.rs b/compiler/rustc_session/src/options.rs
index 3873a203bd3..3772a4a08af 100644
--- a/compiler/rustc_session/src/options.rs
+++ b/compiler/rustc_session/src/options.rs
@@ -1037,6 +1037,7 @@ pub mod parse {
                 "condition" => slot.level = CoverageLevel::Condition,
                 "mcdc" => slot.level = CoverageLevel::Mcdc,
                 "no-mir-spans" => slot.no_mir_spans = true,
+                "discard-all-spans-in-codegen" => slot.discard_all_spans_in_codegen = true,
                 _ => return false,
             }
         }
diff --git a/compiler/rustc_session/src/output.rs b/compiler/rustc_session/src/output.rs
index 2b2ba50d3fb..ff0419d06bf 100644
--- a/compiler/rustc_session/src/output.rs
+++ b/compiler/rustc_session/src/output.rs
@@ -3,9 +3,7 @@
 use std::path::Path;
 
 use rustc_ast::{self as ast, attr};
-use rustc_errors::FatalError;
-use rustc_span::symbol::sym;
-use rustc_span::{Span, Symbol};
+use rustc_span::{Span, Symbol, sym};
 
 use crate::Session;
 use crate::config::{self, CrateType, Input, OutFileName, OutputFilenames, OutputType};
@@ -91,11 +89,10 @@ pub fn find_crate_name(sess: &Session, attrs: &[ast::Attribute]) -> Symbol {
 }
 
 pub fn validate_crate_name(sess: &Session, s: Symbol, sp: Option<Span>) {
-    let mut err_count = 0;
+    let mut guar = None;
     {
         if s.is_empty() {
-            err_count += 1;
-            sess.dcx().emit_err(CrateNameEmpty { span: sp });
+            guar = Some(sess.dcx().emit_err(CrateNameEmpty { span: sp }));
         }
         for c in s.as_str().chars() {
             if c.is_alphanumeric() {
@@ -104,8 +101,7 @@ pub fn validate_crate_name(sess: &Session, s: Symbol, sp: Option<Span>) {
             if c == '_' {
                 continue;
             }
-            err_count += 1;
-            sess.dcx().emit_err(InvalidCharacterInCrateName {
+            guar = Some(sess.dcx().emit_err(InvalidCharacterInCrateName {
                 span: sp,
                 character: c,
                 crate_name: s,
@@ -114,12 +110,12 @@ pub fn validate_crate_name(sess: &Session, s: Symbol, sp: Option<Span>) {
                 } else {
                     None
                 },
-            });
+            }));
         }
     }
 
-    if err_count > 0 {
-        FatalError.raise();
+    if let Some(guar) = guar {
+        guar.raise_fatal();
     }
 }
 
diff --git a/compiler/rustc_session/src/parse.rs b/compiler/rustc_session/src/parse.rs
index 21c11655110..90361efed84 100644
--- a/compiler/rustc_session/src/parse.rs
+++ b/compiler/rustc_session/src/parse.rs
@@ -79,7 +79,7 @@ impl SymbolGallery {
 
 // todo: this function now accepts `Session` instead of `ParseSess` and should be relocated
 /// Construct a diagnostic for a language feature error due to the given `span`.
-/// The `feature`'s `Symbol` is the one you used in `unstable.rs` and `rustc_span::symbols`.
+/// The `feature`'s `Symbol` is the one you used in `unstable.rs` and `rustc_span::symbol`.
 #[track_caller]
 pub fn feature_err(
     sess: &Session,
diff --git a/compiler/rustc_session/src/session.rs b/compiler/rustc_session/src/session.rs
index 9f6106f9cfb..54bb4622963 100644
--- a/compiler/rustc_session/src/session.rs
+++ b/compiler/rustc_session/src/session.rs
@@ -352,6 +352,11 @@ impl Session {
         self.opts.unstable_opts.coverage_options.no_mir_spans
     }
 
+    /// True if `-Zcoverage-options=discard-all-spans-in-codegen` was passed.
+    pub fn coverage_discard_all_spans_in_codegen(&self) -> bool {
+        self.opts.unstable_opts.coverage_options.discard_all_spans_in_codegen
+    }
+
     pub fn is_sanitizer_cfi_enabled(&self) -> bool {
         self.opts.unstable_opts.sanitizer.contains(SanitizerSet::CFI)
     }
diff --git a/compiler/rustc_smir/Cargo.toml b/compiler/rustc_smir/Cargo.toml
index 1230667ee91..29ce24e8b78 100644
--- a/compiler/rustc_smir/Cargo.toml
+++ b/compiler/rustc_smir/Cargo.toml
@@ -7,9 +7,9 @@ edition = "2021"
 # tidy-alphabetical-start
 rustc_abi = { path = "../rustc_abi" }
 rustc_ast = { path = "../rustc_ast" }
-rustc_ast_pretty = { path = "../rustc_ast_pretty" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_hir = { path = "../rustc_hir" }
+rustc_hir_pretty = { path = "../rustc_hir_pretty" }
 rustc_middle = { path = "../rustc_middle" }
 rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
diff --git a/compiler/rustc_smir/src/rustc_internal/mod.rs b/compiler/rustc_smir/src/rustc_internal/mod.rs
index 64d241067a8..dc63ea1999e 100644
--- a/compiler/rustc_smir/src/rustc_internal/mod.rs
+++ b/compiler/rustc_smir/src/rustc_internal/mod.rs
@@ -318,7 +318,7 @@ macro_rules! run_driver {
     ($args:expr, $callback:expr $(, $with_tcx:ident)?) => {{
         use rustc_driver::{Callbacks, Compilation, RunCompiler};
         use rustc_middle::ty::TyCtxt;
-        use rustc_interface::{interface, Queries};
+        use rustc_interface::interface;
         use stable_mir::CompilerError;
         use std::ops::ControlFlow;
 
diff --git a/compiler/rustc_smir/src/rustc_smir/context.rs b/compiler/rustc_smir/src/rustc_smir/context.rs
index 9025b47c422..9793a4d4162 100644
--- a/compiler/rustc_smir/src/rustc_smir/context.rs
+++ b/compiler/rustc_smir/src/rustc_smir/context.rs
@@ -251,11 +251,10 @@ impl<'tcx> Context for TablesWrapper<'tcx> {
         let mut tables = self.0.borrow_mut();
         let tcx = tables.tcx;
         let did = tables[def_id];
-        let attr_name: Vec<_> =
-            attr.iter().map(|seg| rustc_span::symbol::Symbol::intern(&seg)).collect();
+        let attr_name: Vec<_> = attr.iter().map(|seg| rustc_span::Symbol::intern(&seg)).collect();
         tcx.get_attrs_by_path(did, &attr_name)
             .map(|attribute| {
-                let attr_str = rustc_ast_pretty::pprust::attribute_to_string(attribute);
+                let attr_str = rustc_hir_pretty::attribute_to_string(&tcx, attribute);
                 let span = attribute.span;
                 stable_mir::crate_def::Attribute::new(attr_str, span.stable(&mut *tables))
             })
@@ -266,17 +265,16 @@ impl<'tcx> Context for TablesWrapper<'tcx> {
         let mut tables = self.0.borrow_mut();
         let tcx = tables.tcx;
         let did = tables[def_id];
-        let filter_fn = move |a: &&rustc_ast::ast::Attribute| {
-            matches!(a.kind, rustc_ast::ast::AttrKind::Normal(_))
-        };
+        let filter_fn =
+            move |a: &&rustc_hir::Attribute| matches!(a.kind, rustc_hir::AttrKind::Normal(_));
         let attrs_iter = if let Some(did) = did.as_local() {
             tcx.hir().attrs(tcx.local_def_id_to_hir_id(did)).iter().filter(filter_fn)
         } else {
-            tcx.item_attrs(did).iter().filter(filter_fn)
+            tcx.attrs_for_def(did).iter().filter(filter_fn)
         };
         attrs_iter
             .map(|attribute| {
-                let attr_str = rustc_ast_pretty::pprust::attribute_to_string(attribute);
+                let attr_str = rustc_hir_pretty::attribute_to_string(&tcx, attribute);
                 let span = attribute.span;
                 stable_mir::crate_def::Attribute::new(attr_str, span.stable(&mut *tables))
             })
diff --git a/compiler/rustc_smir/src/rustc_smir/convert/abi.rs b/compiler/rustc_smir/src/rustc_smir/convert/abi.rs
index af24fd23f50..b39a15a8633 100644
--- a/compiler/rustc_smir/src/rustc_smir/convert/abi.rs
+++ b/compiler/rustc_smir/src/rustc_smir/convert/abi.rs
@@ -167,6 +167,7 @@ impl<'tcx> Stable<'tcx> for rustc_abi::Variants<rustc_abi::FieldIdx, rustc_abi::
             rustc_abi::Variants::Single { index } => {
                 VariantsShape::Single { index: index.stable(tables) }
             }
+            rustc_abi::Variants::Empty => VariantsShape::Empty,
             rustc_abi::Variants::Multiple { tag, tag_encoding, tag_field, variants } => {
                 VariantsShape::Multiple {
                     tag: tag.stable(tables),
diff --git a/compiler/rustc_span/src/edit_distance.rs b/compiler/rustc_span/src/edit_distance.rs
index 4f120db48f0..8a2baaa42e2 100644
--- a/compiler/rustc_span/src/edit_distance.rs
+++ b/compiler/rustc_span/src/edit_distance.rs
@@ -11,7 +11,7 @@
 
 use std::{cmp, mem};
 
-use crate::symbol::Symbol;
+use crate::Symbol;
 
 #[cfg(test)]
 mod tests;
diff --git a/compiler/rustc_span/src/lib.rs b/compiler/rustc_span/src/lib.rs
index bd8b93bb4d1..d5c2a337b4c 100644
--- a/compiler/rustc_span/src/lib.rs
+++ b/compiler/rustc_span/src/lib.rs
@@ -25,7 +25,6 @@
 #![feature(hash_set_entry)]
 #![feature(if_let_guard)]
 #![feature(let_chains)]
-#![feature(min_specialization)]
 #![feature(negative_impls)]
 #![feature(read_buf)]
 #![feature(round_char_boundary)]
@@ -68,7 +67,7 @@ mod span_encoding;
 pub use span_encoding::{DUMMY_SP, Span};
 
 pub mod symbol;
-pub use symbol::{Symbol, sym};
+pub use symbol::{Ident, MacroRulesNormalizedIdent, Symbol, kw, sym};
 
 mod analyze_source_file;
 pub mod fatal_error;
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index e3708896ba9..123e4b1f01f 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -20,18 +20,26 @@ mod tests;
 
 // The proc macro code for this is in `compiler/rustc_macros/src/symbols.rs`.
 symbols! {
-    // If you modify this list, adjust `is_special`, `is_used_keyword`/`is_unused_keyword`
-    // and `AllKeywords`.
+    // This list includes things that are definitely keywords (e.g. `if`),
+    // a few things that are definitely not keywords (e.g. the empty symbol,
+    // `{{root}}`) and things where there is disagreement between people and/or
+    // documents (such as the Rust Reference) about whether it is a keyword
+    // (e.g. `_`).
+    //
+    // If you modify this list, adjust any relevant `Symbol::{is,can_be}_*` predicates and
+    // `used_keywords`.
     // But this should rarely be necessary if the keywords are kept in alphabetic order.
     Keywords {
         // Special reserved identifiers used internally for elided lifetimes,
         // unnamed method parameters, crate root module, error recovery etc.
+        // Matching predicates: `is_any_keyword`, `is_special`/`is_reserved`
         Empty:              "",
         PathRoot:           "{{root}}",
         DollarCrate:        "$crate",
         Underscore:         "_",
 
         // Keywords that are used in stable Rust.
+        // Matching predicates: `is_any_keyword`, `is_used_keyword_always`/`is_reserved`
         As:                 "as",
         Break:              "break",
         Const:              "const",
@@ -69,6 +77,7 @@ symbols! {
         While:              "while",
 
         // Keywords that are used in unstable Rust or reserved for future use.
+        // Matching predicates: `is_any_keyword`, `is_unused_keyword_always`/`is_reserved`
         Abstract:           "abstract",
         Become:             "become",
         Box:                "box",
@@ -83,23 +92,29 @@ symbols! {
         Yield:              "yield",
 
         // Edition-specific keywords that are used in stable Rust.
+        // Matching predicates: `is_any_keyword`, `is_used_keyword_conditional`/`is_reserved` (if
+        // the edition suffices)
         Async:              "async", // >= 2018 Edition only
         Await:              "await", // >= 2018 Edition only
         Dyn:                "dyn", // >= 2018 Edition only
 
         // Edition-specific keywords that are used in unstable Rust or reserved for future use.
+        // Matching predicates: `is_any_keyword`, `is_unused_keyword_conditional`/`is_reserved` (if
+        // the edition suffices)
+        Gen:                "gen", // >= 2024 Edition only
         Try:                "try", // >= 2018 Edition only
 
-        // Special lifetime names
+        // "Lifetime keywords": regular keywords with a leading `'`.
+        // Matching predicates: `is_any_keyword`
         UnderscoreLifetime: "'_",
         StaticLifetime:     "'static",
 
         // Weak keywords, have special meaning only in specific contexts.
+        // Matching predicates: `is_any_keyword`
         Auto:               "auto",
         Builtin:            "builtin",
         Catch:              "catch",
         Default:            "default",
-        Gen:                "gen",
         MacroRules:         "macro_rules",
         Raw:                "raw",
         Reuse:              "reuse",
@@ -306,6 +321,7 @@ symbols! {
         RwLockWriteGuard,
         Saturating,
         SeekFrom,
+        SelfTy,
         Send,
         SeqCst,
         Sized,
@@ -1190,6 +1206,7 @@ symbols! {
         loongarch_target_feature,
         loop_break_value,
         lt,
+        m68k_target_feature,
         macro_at_most_once_rep,
         macro_attributes_in_derive_output,
         macro_escape,
@@ -1700,6 +1717,7 @@ symbols! {
         rustc_diagnostic_macros,
         rustc_dirty,
         rustc_do_not_const_check,
+        rustc_do_not_implement_via_object,
         rustc_doc_primitive,
         rustc_driver,
         rustc_dummy,
@@ -2476,13 +2494,6 @@ impl fmt::Display for Symbol {
     }
 }
 
-// takes advantage of `str::to_string` specialization
-impl ToString for Symbol {
-    fn to_string(&self) -> String {
-        self.as_str().to_string()
-    }
-}
-
 impl<CTX> HashStable<CTX> for Symbol {
     #[inline]
     fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
@@ -2594,6 +2605,11 @@ pub mod sym {
 }
 
 impl Symbol {
+    /// Don't use this unless you're doing something very loose and heuristic-y.
+    pub fn is_any_keyword(self) -> bool {
+        self >= kw::As && self <= kw::Yeet
+    }
+
     fn is_special(self) -> bool {
         self <= kw::Underscore
     }
@@ -2611,8 +2627,8 @@ impl Symbol {
     }
 
     fn is_unused_keyword_conditional(self, edition: impl Copy + FnOnce() -> Edition) -> bool {
-        self == kw::Try && edition().at_least_rust_2018()
-            || self == kw::Gen && edition().at_least_rust_2024()
+        self == kw::Gen && edition().at_least_rust_2024()
+            || self == kw::Try && edition().at_least_rust_2018()
     }
 
     pub fn is_reserved(self, edition: impl Copy + FnOnce() -> Edition) -> bool {
@@ -2650,6 +2666,11 @@ impl Symbol {
 }
 
 impl Ident {
+    /// Don't use this unless you're doing something very loose and heuristic-y.
+    pub fn is_any_keyword(self) -> bool {
+        self.name.is_any_keyword()
+    }
+
     /// Returns `true` for reserved identifiers used internally for elided lifetimes,
     /// unnamed method parameters, crate root module, error recovery etc.
     pub fn is_special(self) -> bool {
@@ -2688,41 +2709,19 @@ impl Ident {
     }
 }
 
-/// An iterator over all the keywords in Rust.
-#[derive(Copy, Clone)]
-pub struct AllKeywords {
-    curr_idx: u32,
-    end_idx: u32,
-}
-
-impl AllKeywords {
-    /// Initialize a new iterator over all the keywords.
-    ///
-    /// *Note:* Please update this if a new keyword is added beyond the current
-    /// range.
-    pub fn new() -> Self {
-        AllKeywords { curr_idx: kw::Empty.as_u32(), end_idx: kw::Yeet.as_u32() }
-    }
-
-    /// Collect all the keywords in a given edition into a vector.
-    pub fn collect_used(&self, edition: impl Copy + FnOnce() -> Edition) -> Vec<Symbol> {
-        self.filter(|&keyword| {
-            keyword.is_used_keyword_always() || keyword.is_used_keyword_conditional(edition)
+/// Collect all the keywords in a given edition into a vector.
+///
+/// *Note:* Please update this if a new keyword is added beyond the current
+/// range.
+pub fn used_keywords(edition: impl Copy + FnOnce() -> Edition) -> Vec<Symbol> {
+    (kw::Empty.as_u32()..kw::Yeet.as_u32())
+        .filter_map(|kw| {
+            let kw = Symbol::new(kw);
+            if kw.is_used_keyword_always() || kw.is_used_keyword_conditional(edition) {
+                Some(kw)
+            } else {
+                None
+            }
         })
         .collect()
-    }
-}
-
-impl Iterator for AllKeywords {
-    type Item = Symbol;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        if self.curr_idx <= self.end_idx {
-            let keyword = Symbol::new(self.curr_idx);
-            self.curr_idx += 1;
-            Some(keyword)
-        } else {
-            None
-        }
-    }
 }
diff --git a/compiler/rustc_symbol_mangling/src/test.rs b/compiler/rustc_symbol_mangling/src/test.rs
index 73bd8d7555b..7fda81126c4 100644
--- a/compiler/rustc_symbol_mangling/src/test.rs
+++ b/compiler/rustc_symbol_mangling/src/test.rs
@@ -7,7 +7,7 @@
 use rustc_hir::def_id::LocalDefId;
 use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_middle::ty::{GenericArgs, Instance, TyCtxt};
-use rustc_span::symbol::{Symbol, sym};
+use rustc_span::{Symbol, sym};
 
 use crate::errors::{Kind, TestOutput};
 
diff --git a/compiler/rustc_symbol_mangling/src/v0.rs b/compiler/rustc_symbol_mangling/src/v0.rs
index def741e3546..a801b3e53a1 100644
--- a/compiler/rustc_symbol_mangling/src/v0.rs
+++ b/compiler/rustc_symbol_mangling/src/v0.rs
@@ -17,7 +17,7 @@ use rustc_middle::ty::{
     self, EarlyBinder, FloatTy, GenericArg, GenericArgKind, Instance, IntTy, ReifyReason, Ty,
     TyCtxt, TypeVisitable, TypeVisitableExt, UintTy,
 };
-use rustc_span::symbol::kw;
+use rustc_span::kw;
 
 pub(super) fn mangle<'tcx>(
     tcx: TyCtxt<'tcx>,
@@ -439,7 +439,7 @@ impl<'tcx> Printer<'tcx> for SymbolMangler<'tcx> {
                 let sig = sig_tys.with(hdr);
                 self.push("F");
                 self.in_binder(&sig, |cx, sig| {
-                    if sig.safety == hir::Safety::Unsafe {
+                    if sig.safety.is_unsafe() {
                         cx.push("U");
                     }
                     match sig.abi {
diff --git a/compiler/rustc_target/src/asm/mod.rs b/compiler/rustc_target/src/asm/mod.rs
index 204d5d53361..1292f46f0c9 100644
--- a/compiler/rustc_target/src/asm/mod.rs
+++ b/compiler/rustc_target/src/asm/mod.rs
@@ -35,7 +35,7 @@ macro_rules! def_reg_class {
         impl $arch_regclass {
             pub fn name(self) -> rustc_span::Symbol {
                 match self {
-                    $(Self::$class => rustc_span::symbol::sym::$class,)*
+                    $(Self::$class => rustc_span::sym::$class,)*
                 }
             }
 
@@ -511,7 +511,7 @@ impl InlineAsmRegClass {
             Self::Msp430(r) => r.name(),
             Self::M68k(r) => r.name(),
             Self::CSKY(r) => r.name(),
-            Self::Err => rustc_span::symbol::sym::reg,
+            Self::Err => rustc_span::sym::reg,
         }
     }
 
diff --git a/compiler/rustc_target/src/callconv/loongarch.rs b/compiler/rustc_target/src/callconv/loongarch.rs
index d1234c3cc91..8bf61cb1337 100644
--- a/compiler/rustc_target/src/callconv/loongarch.rs
+++ b/compiler/rustc_target/src/callconv/loongarch.rs
@@ -116,7 +116,7 @@ where
             FieldsShape::Arbitrary { .. } => {
                 match arg_layout.variants {
                     abi::Variants::Multiple { .. } => return Err(CannotUseFpConv),
-                    abi::Variants::Single { .. } => (),
+                    abi::Variants::Single { .. } | abi::Variants::Empty => (),
                 }
                 for i in arg_layout.fields.index_by_increasing_offset() {
                     let field = arg_layout.field(cx, i);
diff --git a/compiler/rustc_target/src/callconv/riscv.rs b/compiler/rustc_target/src/callconv/riscv.rs
index c0298edb5ab..4d858392c97 100644
--- a/compiler/rustc_target/src/callconv/riscv.rs
+++ b/compiler/rustc_target/src/callconv/riscv.rs
@@ -122,7 +122,7 @@ where
             FieldsShape::Arbitrary { .. } => {
                 match arg_layout.variants {
                     abi::Variants::Multiple { .. } => return Err(CannotUseFpConv),
-                    abi::Variants::Single { .. } => (),
+                    abi::Variants::Single { .. } | abi::Variants::Empty => (),
                 }
                 for i in arg_layout.fields.index_by_increasing_offset() {
                     let field = arg_layout.field(cx, i);
diff --git a/compiler/rustc_target/src/callconv/x86_64.rs b/compiler/rustc_target/src/callconv/x86_64.rs
index bd101b23ea1..37aecf323a1 100644
--- a/compiler/rustc_target/src/callconv/x86_64.rs
+++ b/compiler/rustc_target/src/callconv/x86_64.rs
@@ -65,7 +65,7 @@ where
                 }
 
                 match &layout.variants {
-                    abi::Variants::Single { .. } => {}
+                    abi::Variants::Single { .. } | abi::Variants::Empty => {}
                     abi::Variants::Multiple { variants, .. } => {
                         // Treat enum variants like union members.
                         for variant_idx in variants.indices() {
diff --git a/compiler/rustc_target/src/spec/mod.rs b/compiler/rustc_target/src/spec/mod.rs
index 7d308c6c662..ad746d3f26b 100644
--- a/compiler/rustc_target/src/spec/mod.rs
+++ b/compiler/rustc_target/src/spec/mod.rs
@@ -46,7 +46,7 @@ use rustc_data_structures::fx::FxHashSet;
 use rustc_fs_util::try_canonicalize;
 use rustc_macros::{Decodable, Encodable, HashStable_Generic};
 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
-use rustc_span::symbol::{Symbol, kw, sym};
+use rustc_span::{Symbol, kw, sym};
 use serde_json::Value;
 use tracing::debug;
 
@@ -2213,6 +2213,10 @@ pub struct TargetOptions {
     /// `-Ctarget-cpu` but can be overwritten with `-Ctarget-features`.
     /// Corresponds to `llc -mattr=$features`.
     /// Note that these are LLVM feature names, not Rust feature names!
+    ///
+    /// Generally it is a bad idea to use negative target features because they often interact very
+    /// poorly with how `-Ctarget-cpu` works. Instead, try to use a lower "base CPU" and enable the
+    /// features you want to use.
     pub features: StaticCow<str>,
     /// Direct or use GOT indirect to reference external data symbols
     pub direct_access_external_data: Option<bool>,
@@ -2605,15 +2609,11 @@ impl TargetOptions {
     }
 
     pub(crate) fn has_feature(&self, search_feature: &str) -> bool {
-        self.features.split(',').any(|f| {
-            if let Some(f) = f.strip_prefix('+')
-                && f == search_feature
-            {
-                true
-            } else {
-                false
-            }
-        })
+        self.features.split(',').any(|f| f.strip_prefix('+').is_some_and(|f| f == search_feature))
+    }
+
+    pub(crate) fn has_neg_feature(&self, search_feature: &str) -> bool {
+        self.features.split(',').any(|f| f.strip_prefix('-').is_some_and(|f| f == search_feature))
     }
 }
 
@@ -3166,7 +3166,7 @@ impl Target {
                 // Note that the `lp64e` is still unstable as it's not (yet) part of the ELF psABI.
                 check_matches!(
                     &*self.llvm_abiname,
-                    "lp64" | "lp64f" | "lp64d" | "lp64q" | "lp64e",
+                    "lp64" | "lp64f" | "lp64d" | "lp64e",
                     "invalid RISC-V ABI name"
                 );
             }
diff --git a/compiler/rustc_target/src/spec/targets/powerpc64le_unknown_linux_musl.rs b/compiler/rustc_target/src/spec/targets/powerpc64le_unknown_linux_musl.rs
index 952a00c52a2..f763c37f535 100644
--- a/compiler/rustc_target/src/spec/targets/powerpc64le_unknown_linux_musl.rs
+++ b/compiler/rustc_target/src/spec/targets/powerpc64le_unknown_linux_musl.rs
@@ -13,8 +13,8 @@ pub(crate) fn target() -> Target {
         llvm_target: "powerpc64le-unknown-linux-musl".into(),
         metadata: crate::spec::TargetMetadata {
             description: Some("64-bit PowerPC Linux with musl 1.2.3, Little Endian".into()),
-            tier: Some(3),
-            host_tools: Some(false),
+            tier: Some(2),
+            host_tools: Some(true),
             std: Some(true),
         },
         pointer_width: 64,
diff --git a/compiler/rustc_target/src/spec/targets/sparcv9_sun_solaris.rs b/compiler/rustc_target/src/spec/targets/sparcv9_sun_solaris.rs
index fdc9628f78e..770da60da9e 100644
--- a/compiler/rustc_target/src/spec/targets/sparcv9_sun_solaris.rs
+++ b/compiler/rustc_target/src/spec/targets/sparcv9_sun_solaris.rs
@@ -13,7 +13,7 @@ pub(crate) fn target() -> Target {
     Target {
         llvm_target: "sparcv9-sun-solaris".into(),
         metadata: crate::spec::TargetMetadata {
-            description: Some("SPARC Solaris 11, illumos".into()),
+            description: Some("SPARC Solaris 11.4".into()),
             tier: Some(2),
             host_tools: Some(false),
             std: Some(true),
diff --git a/compiler/rustc_target/src/spec/targets/x86_64_pc_solaris.rs b/compiler/rustc_target/src/spec/targets/x86_64_pc_solaris.rs
index 28dd3c426c7..843568a4792 100644
--- a/compiler/rustc_target/src/spec/targets/x86_64_pc_solaris.rs
+++ b/compiler/rustc_target/src/spec/targets/x86_64_pc_solaris.rs
@@ -13,7 +13,7 @@ pub(crate) fn target() -> Target {
     Target {
         llvm_target: "x86_64-pc-solaris".into(),
         metadata: crate::spec::TargetMetadata {
-            description: Some("64-bit Solaris 11, illumos".into()),
+            description: Some("64-bit Solaris 11.4".into()),
             tier: Some(2),
             host_tools: Some(false),
             std: Some(true),
diff --git a/compiler/rustc_target/src/target_features.rs b/compiler/rustc_target/src/target_features.rs
index 29d3f826a15..5372437b0d2 100644
--- a/compiler/rustc_target/src/target_features.rs
+++ b/compiler/rustc_target/src/target_features.rs
@@ -3,7 +3,7 @@
 //! and Rust adds some features that do not correspond to LLVM features at all.
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
-use rustc_span::symbol::{Symbol, sym};
+use rustc_span::{Symbol, sym};
 
 use crate::spec::Target;
 
@@ -20,7 +20,7 @@ pub const RUSTC_SPECIAL_FEATURES: &[&str] = &["backchain"];
 /// `Toggleability` is the type storing whether (un)stable features can be toggled:
 /// this is initially a function since it can depend on `Target`, but for stable hashing
 /// it needs to be something hashable to we have to make the type generic.
-#[derive(Debug, Clone, Copy)]
+#[derive(Debug, Clone)]
 pub enum Stability<Toggleability> {
     /// This target feature is stable, it can be used in `#[target_feature]` and
     /// `#[cfg(target_feature)]`.
@@ -39,16 +39,26 @@ pub enum Stability<Toggleability> {
         allow_toggle: Toggleability,
     },
     /// This feature can not be set via `-Ctarget-feature` or `#[target_feature]`, it can only be
-    /// set in the basic target definition. It is never set in `cfg(target_feature)`. Used in
+    /// set in the target spec. It is never set in `cfg(target_feature)`. Used in
     /// particular for features that change the floating-point ABI.
     Forbidden { reason: &'static str },
 }
 
-/// `Stability` where `allow_toggle` has not been computed yet.
 /// Returns `Ok` if the toggle is allowed, `Err` with an explanation of not.
-pub type StabilityUncomputed = Stability<fn(&Target) -> Result<(), &'static str>>;
+/// The `bool` indicates whether the feature is being enabled (`true`) or disabled.
+pub type AllowToggleUncomputed = fn(&Target, bool) -> Result<(), &'static str>;
+
+/// The computed result of whether a feature can be enabled/disabled on the current target.
+#[derive(Debug, Clone)]
+pub struct AllowToggleComputed {
+    enable: Result<(), &'static str>,
+    disable: Result<(), &'static str>,
+}
+
+/// `Stability` where `allow_toggle` has not been computed yet.
+pub type StabilityUncomputed = Stability<AllowToggleUncomputed>;
 /// `Stability` where `allow_toggle` has already been computed.
-pub type StabilityComputed = Stability<Result<(), &'static str>>;
+pub type StabilityComputed = Stability<AllowToggleComputed>;
 
 impl<CTX, Toggleability: HashStable<CTX>> HashStable<CTX> for Stability<Toggleability> {
     #[inline]
@@ -69,11 +79,20 @@ impl<CTX, Toggleability: HashStable<CTX>> HashStable<CTX> for Stability<Toggleab
     }
 }
 
+impl<CTX> HashStable<CTX> for AllowToggleComputed {
+    #[inline]
+    fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
+        let AllowToggleComputed { enable, disable } = self;
+        enable.hash_stable(hcx, hasher);
+        disable.hash_stable(hcx, hasher);
+    }
+}
+
 impl<Toggleability> Stability<Toggleability> {
     /// Returns whether the feature can be used in `cfg(target_feature)` ever.
     /// (It might still be nightly-only even if this returns `true`, so make sure to also check
     /// `requires_nightly`.)
-    pub fn in_cfg(self) -> bool {
+    pub fn in_cfg(&self) -> bool {
         !matches!(self, Stability::Forbidden { .. })
     }
 
@@ -85,8 +104,8 @@ impl<Toggleability> Stability<Toggleability> {
     /// Before calling this, ensure the feature is even permitted for this use:
     /// - for `#[target_feature]`/`-Ctarget-feature`, check `allow_toggle()`
     /// - for `cfg(target_feature)`, check `in_cfg`
-    pub fn requires_nightly(self) -> Option<Symbol> {
-        match self {
+    pub fn requires_nightly(&self) -> Option<Symbol> {
+        match *self {
             Stability::Unstable { nightly_feature, .. } => Some(nightly_feature),
             Stability::Stable { .. } => None,
             Stability::Forbidden { .. } => panic!("forbidden features should not reach this far"),
@@ -95,35 +114,49 @@ impl<Toggleability> Stability<Toggleability> {
 }
 
 impl StabilityUncomputed {
-    pub fn compute_toggleability(self, target: &Target) -> StabilityComputed {
+    pub fn compute_toggleability(&self, target: &Target) -> StabilityComputed {
         use Stability::*;
-        match self {
-            Stable { allow_toggle } => Stable { allow_toggle: allow_toggle(target) },
+        let compute = |f: AllowToggleUncomputed| AllowToggleComputed {
+            enable: f(target, true),
+            disable: f(target, false),
+        };
+        match *self {
+            Stable { allow_toggle } => Stable { allow_toggle: compute(allow_toggle) },
             Unstable { nightly_feature, allow_toggle } => {
-                Unstable { nightly_feature, allow_toggle: allow_toggle(target) }
+                Unstable { nightly_feature, allow_toggle: compute(allow_toggle) }
             }
             Forbidden { reason } => Forbidden { reason },
         }
     }
+
+    pub fn toggle_allowed(&self, target: &Target, enable: bool) -> Result<(), &'static str> {
+        use Stability::*;
+        match *self {
+            Stable { allow_toggle } => allow_toggle(target, enable),
+            Unstable { allow_toggle, .. } => allow_toggle(target, enable),
+            Forbidden { reason } => Err(reason),
+        }
+    }
 }
 
 impl StabilityComputed {
     /// Returns whether the feature may be toggled via `#[target_feature]` or `-Ctarget-feature`.
     /// (It might still be nightly-only even if this returns `true`, so make sure to also check
     /// `requires_nightly`.)
-    pub fn allow_toggle(self) -> Result<(), &'static str> {
-        match self {
+    pub fn toggle_allowed(&self, enable: bool) -> Result<(), &'static str> {
+        let allow_toggle = match self {
             Stability::Stable { allow_toggle } => allow_toggle,
             Stability::Unstable { allow_toggle, .. } => allow_toggle,
-            Stability::Forbidden { reason } => Err(reason),
-        }
+            Stability::Forbidden { reason } => return Err(reason),
+        };
+        if enable { allow_toggle.enable } else { allow_toggle.disable }
     }
 }
 
 // Constructors for the list below, defaulting to "always allow toggle".
-const STABLE: StabilityUncomputed = Stability::Stable { allow_toggle: |_target| Ok(()) };
+const STABLE: StabilityUncomputed = Stability::Stable { allow_toggle: |_target, _enable| Ok(()) };
 const fn unstable(nightly_feature: Symbol) -> StabilityUncomputed {
-    Stability::Unstable { nightly_feature, allow_toggle: |_target| Ok(()) }
+    Stability::Unstable { nightly_feature, allow_toggle: |_target, _enable| Ok(()) }
 }
 
 // Here we list target features that rustc "understands": they can be used in `#[target_feature]`
@@ -184,7 +217,7 @@ const ARM_FEATURES: &[(&str, StabilityUncomputed, ImpliedFeatures)] = &[
         "fpregs",
         Stability::Unstable {
             nightly_feature: sym::arm_target_feature,
-            allow_toggle: |target: &Target| {
+            allow_toggle: |target: &Target, _enable| {
                 // Only allow toggling this if the target has `soft-float` set. With `soft-float`,
                 // `fpregs` isn't needed so changing it cannot affect the ABI.
                 if target.has_feature("soft-float") {
@@ -257,6 +290,7 @@ const AARCH64_FEATURES: &[(&str, StabilityUncomputed, ImpliedFeatures)] = &[
     ("flagm", STABLE, &[]),
     // FEAT_FLAGM2
     ("flagm2", unstable(sym::aarch64_unstable_target_feature), &[]),
+    ("fp-armv8", Stability::Forbidden { reason: "Rust ties `fp-armv8` to `neon`" }, &[]),
     // FEAT_FP16
     // Rust ties FP and Neon: https://github.com/rust-lang/rust/pull/91608
     ("fp16", STABLE, &["neon"]),
@@ -292,7 +326,28 @@ const AARCH64_FEATURES: &[(&str, StabilityUncomputed, ImpliedFeatures)] = &[
     // FEAT_MTE & FEAT_MTE2
     ("mte", STABLE, &[]),
     // FEAT_AdvSimd & FEAT_FP
-    ("neon", STABLE, &[]),
+    (
+        "neon",
+        Stability::Stable {
+            allow_toggle: |target, enable| {
+                if target.abi == "softfloat" {
+                    // `neon` has no ABI implications for softfloat targets, we can allow this.
+                    Ok(())
+                } else if enable
+                    && !target.has_neg_feature("fp-armv8")
+                    && !target.has_neg_feature("neon")
+                {
+                    // neon is enabled by default, and has not been disabled, so enabling it again
+                    // is redundant and we can permit it. Forbidding this would be a breaking change
+                    // since this feature is stable.
+                    Ok(())
+                } else {
+                    Err("unsound on hard-float targets because it changes float ABI")
+                }
+            },
+        },
+        &[],
+    ),
     // FEAT_PAUTH (address authentication)
     ("paca", STABLE, &[]),
     // FEAT_PAUTH (generic authentication)
@@ -481,7 +536,7 @@ const X86_FEATURES: &[(&str, StabilityUncomputed, ImpliedFeatures)] = &[
         "x87",
         Stability::Unstable {
             nightly_feature: sym::x87_target_feature,
-            allow_toggle: |target: &Target| {
+            allow_toggle: |target: &Target, _enable| {
                 // Only allow toggling this if the target has `soft-float` set. With `soft-float`,
                 // `fpregs` isn't needed so changing it cannot affect the ABI.
                 if target.has_feature("soft-float") {
@@ -535,9 +590,76 @@ const RISCV_FEATURES: &[(&str, StabilityUncomputed, ImpliedFeatures)] = &[
     // tidy-alphabetical-start
     ("a", STABLE, &["zaamo", "zalrsc"]),
     ("c", STABLE, &[]),
-    ("d", unstable(sym::riscv_target_feature), &["f"]),
-    ("e", unstable(sym::riscv_target_feature), &[]),
-    ("f", unstable(sym::riscv_target_feature), &[]),
+    (
+        "d",
+        Stability::Unstable {
+            nightly_feature: sym::riscv_target_feature,
+            allow_toggle: |target, enable| match &*target.llvm_abiname {
+                "ilp32d" | "lp64d" if !enable => {
+                    // The ABI requires the `d` feature, so it cannot be disabled.
+                    Err("feature is required by ABI")
+                }
+                "ilp32e" if enable => {
+                    // ilp32e is incompatible with features that need aligned load/stores > 32 bits,
+                    // like `d`.
+                    Err("feature is incompatible with ABI")
+                }
+                _ => Ok(()),
+            },
+        },
+        &["f"],
+    ),
+    (
+        "e",
+        Stability::Unstable {
+            // Given that this is a negative feature, consider this before stabilizing:
+            // does it really make sense to enable this feature in an individual
+            // function with `#[target_feature]`?
+            nightly_feature: sym::riscv_target_feature,
+            allow_toggle: |target, enable| {
+                match &*target.llvm_abiname {
+                    _ if !enable => {
+                        // Disabling this feature means we can use more registers (x16-x31).
+                        // The "e" ABIs treat them as caller-save, so it is safe to use them only
+                        // in some parts of a program while the rest doesn't know they even exist.
+                        // On other ABIs, the feature is already disabled anyway.
+                        Ok(())
+                    }
+                    "ilp32e" | "lp64e" => {
+                        // Embedded ABIs should already have the feature anyway, it's fine to enable
+                        // it again from an ABI perspective.
+                        Ok(())
+                    }
+                    _ => {
+                        // *Not* an embedded ABI. Enabling `e` is invalid.
+                        Err("feature is incompatible with ABI")
+                    }
+                }
+            },
+        },
+        &[],
+    ),
+    (
+        "f",
+        Stability::Unstable {
+            nightly_feature: sym::riscv_target_feature,
+            allow_toggle: |target, enable| {
+                match &*target.llvm_abiname {
+                    "ilp32f" | "ilp32d" | "lp64f" | "lp64d" if !enable => {
+                        // The ABI requires the `f` feature, so it cannot be disabled.
+                        Err("feature is required by ABI")
+                    }
+                    _ => Ok(()),
+                }
+            },
+        },
+        &[],
+    ),
+    (
+        "forced-atomics",
+        Stability::Forbidden { reason: "unsound because it changes the ABI of atomic operations" },
+        &[],
+    ),
     ("m", STABLE, &[]),
     ("relax", unstable(sym::riscv_target_feature), &[]),
     ("unaligned-scalar-mem", unstable(sym::riscv_target_feature), &[]),
@@ -668,6 +790,20 @@ const SPARC_FEATURES: &[(&str, StabilityUncomputed, ImpliedFeatures)] = &[
     // tidy-alphabetical-end
 ];
 
+const M68K_FEATURES: &[(&str, StabilityUncomputed, ImpliedFeatures)] = &[
+    // tidy-alphabetical-start
+    ("isa-68000", unstable(sym::m68k_target_feature), &[]),
+    ("isa-68010", unstable(sym::m68k_target_feature), &["isa-68000"]),
+    ("isa-68020", unstable(sym::m68k_target_feature), &["isa-68010"]),
+    ("isa-68030", unstable(sym::m68k_target_feature), &["isa-68020"]),
+    ("isa-68040", unstable(sym::m68k_target_feature), &["isa-68030", "isa-68882"]),
+    ("isa-68060", unstable(sym::m68k_target_feature), &["isa-68040"]),
+    // FPU
+    ("isa-68881", unstable(sym::m68k_target_feature), &[]),
+    ("isa-68882", unstable(sym::m68k_target_feature), &["isa-68881"]),
+    // tidy-alphabetical-end
+];
+
 /// When rustdoc is running, provide a list of all known features so that all their respective
 /// primitives may be documented.
 ///
@@ -687,6 +823,7 @@ pub fn all_rust_features() -> impl Iterator<Item = (&'static str, StabilityUncom
         .chain(LOONGARCH_FEATURES)
         .chain(IBMZ_FEATURES)
         .chain(SPARC_FEATURES)
+        .chain(M68K_FEATURES)
         .cloned()
         .map(|(f, s, _)| (f, s))
 }
@@ -734,6 +871,7 @@ impl Target {
             "loongarch64" => LOONGARCH_FEATURES,
             "s390x" => IBMZ_FEATURES,
             "sparc" | "sparc64" => SPARC_FEATURES,
+            "m68k" => M68K_FEATURES,
             _ => &[],
         }
     }
@@ -751,7 +889,7 @@ impl Target {
             "sparc" | "sparc64" => SPARC_FEATURES_FOR_CORRECT_VECTOR_ABI,
             "hexagon" => HEXAGON_FEATURES_FOR_CORRECT_VECTOR_ABI,
             "mips" | "mips32r6" | "mips64" | "mips64r6" => MIPS_FEATURES_FOR_CORRECT_VECTOR_ABI,
-            "bpf" => &[], // no vector ABI
+            "bpf" | "m68k" => &[], // no vector ABI
             "csky" => CSKY_FEATURES_FOR_CORRECT_VECTOR_ABI,
             // FIXME: for some tier3 targets, we are overly cautious and always give warnings
             // when passing args in vector registers.
diff --git a/compiler/rustc_trait_selection/Cargo.toml b/compiler/rustc_trait_selection/Cargo.toml
index e29ed9a4b56..b13a753c4ed 100644
--- a/compiler/rustc_trait_selection/Cargo.toml
+++ b/compiler/rustc_trait_selection/Cargo.toml
@@ -9,7 +9,7 @@ itertools = "0.12"
 rustc_abi = { path = "../rustc_abi" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_ast_ir = { path = "../rustc_ast_ir" }
-rustc_attr = { path = "../rustc_attr" }
+rustc_attr_parsing = { path = "../rustc_attr_parsing" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
 rustc_fluent_macro = { path = "../rustc_fluent_macro" }
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
index f856a8d7abb..ee5ce19cb4d 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
@@ -63,10 +63,11 @@ use rustc_hir::{self as hir};
 use rustc_macros::extension;
 use rustc_middle::bug;
 use rustc_middle::dep_graph::DepContext;
+use rustc_middle::traits::PatternOriginExpr;
 use rustc_middle::ty::error::{ExpectedFound, TypeError, TypeErrorToStringExt};
 use rustc_middle::ty::print::{PrintError, PrintTraitRefExt as _, with_forced_trimmed_paths};
 use rustc_middle::ty::{
-    self, List, Region, Ty, TyCtxt, TypeFoldable, TypeSuperVisitable, TypeVisitable,
+    self, List, ParamEnv, Region, Ty, TyCtxt, TypeFoldable, TypeSuperVisitable, TypeVisitable,
     TypeVisitableExt,
 };
 use rustc_span::def_id::LOCAL_CRATE;
@@ -77,7 +78,7 @@ use crate::error_reporting::TypeErrCtxt;
 use crate::errors::{ObligationCauseFailureCode, TypeErrorAdditionalDiags};
 use crate::infer;
 use crate::infer::relate::{self, RelateResult, TypeRelation};
-use crate::infer::{InferCtxt, TypeTrace, ValuePairs};
+use crate::infer::{InferCtxt, InferCtxtExt as _, TypeTrace, ValuePairs};
 use crate::solve::deeply_normalize_for_diagnostics;
 use crate::traits::{
     IfExpressionCause, MatchExpressionArmCause, ObligationCause, ObligationCauseCode,
@@ -433,15 +434,22 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         cause: &ObligationCause<'tcx>,
         exp_found: Option<ty::error::ExpectedFound<Ty<'tcx>>>,
         terr: TypeError<'tcx>,
+        param_env: Option<ParamEnv<'tcx>>,
     ) {
         match *cause.code() {
-            ObligationCauseCode::Pattern { origin_expr: true, span: Some(span), root_ty } => {
-                let ty = self.resolve_vars_if_possible(root_ty);
-                if !matches!(ty.kind(), ty::Infer(ty::InferTy::TyVar(_) | ty::InferTy::FreshTy(_)))
-                {
+            ObligationCauseCode::Pattern {
+                origin_expr: Some(origin_expr),
+                span: Some(span),
+                root_ty,
+            } => {
+                let expected_ty = self.resolve_vars_if_possible(root_ty);
+                if !matches!(
+                    expected_ty.kind(),
+                    ty::Infer(ty::InferTy::TyVar(_) | ty::InferTy::FreshTy(_))
+                ) {
                     // don't show type `_`
                     if span.desugaring_kind() == Some(DesugaringKind::ForLoop)
-                        && let ty::Adt(def, args) = ty.kind()
+                        && let ty::Adt(def, args) = expected_ty.kind()
                         && Some(def.did()) == self.tcx.get_diagnostic_item(sym::Option)
                     {
                         err.span_label(
@@ -449,22 +457,48 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                             format!("this is an iterator with items of type `{}`", args.type_at(0)),
                         );
                     } else {
-                        err.span_label(span, format!("this expression has type `{ty}`"));
+                        err.span_label(span, format!("this expression has type `{expected_ty}`"));
                     }
                 }
                 if let Some(ty::error::ExpectedFound { found, .. }) = exp_found
-                    && ty.boxed_ty() == Some(found)
-                    && let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span)
+                    && let Ok(mut peeled_snippet) =
+                        self.tcx.sess.source_map().span_to_snippet(origin_expr.peeled_span)
                 {
-                    err.span_suggestion(
-                        span,
-                        "consider dereferencing the boxed value",
-                        format!("*{snippet}"),
-                        Applicability::MachineApplicable,
-                    );
+                    // Parentheses are needed for cases like as casts.
+                    // We use the peeled_span for deref suggestions.
+                    // It's also safe to use for box, since box only triggers if there
+                    // wasn't a reference to begin with.
+                    if origin_expr.peeled_prefix_suggestion_parentheses {
+                        peeled_snippet = format!("({peeled_snippet})");
+                    }
+
+                    // Try giving a box suggestion first, as it is a special case of the
+                    // deref suggestion.
+                    if expected_ty.boxed_ty() == Some(found) {
+                        err.span_suggestion_verbose(
+                            span,
+                            "consider dereferencing the boxed value",
+                            format!("*{peeled_snippet}"),
+                            Applicability::MachineApplicable,
+                        );
+                    } else if let Some(param_env) = param_env
+                        && let Some(prefix) = self.should_deref_suggestion_on_mismatch(
+                            param_env,
+                            found,
+                            expected_ty,
+                            origin_expr,
+                        )
+                    {
+                        err.span_suggestion_verbose(
+                            span,
+                            "consider dereferencing to access the inner value using the Deref trait",
+                            format!("{prefix}{peeled_snippet}"),
+                            Applicability::MaybeIncorrect,
+                        );
+                    }
                 }
             }
-            ObligationCauseCode::Pattern { origin_expr: false, span: Some(span), .. } => {
+            ObligationCauseCode::Pattern { origin_expr: None, span: Some(span), .. } => {
                 err.span_label(span, "expected due to this");
             }
             ObligationCauseCode::BlockTailExpression(
@@ -618,6 +652,45 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         }
     }
 
+    /// Determines whether deref_to == <deref_from as Deref>::Target, and if so,
+    /// returns a prefix that should be added to deref_from as a suggestion.
+    fn should_deref_suggestion_on_mismatch(
+        &self,
+        param_env: ParamEnv<'tcx>,
+        deref_to: Ty<'tcx>,
+        deref_from: Ty<'tcx>,
+        origin_expr: PatternOriginExpr,
+    ) -> Option<String> {
+        // origin_expr contains stripped away versions of our expression.
+        // We'll want to use that to avoid suggesting things like *&x.
+        // However, the type that we have access to hasn't been stripped away,
+        // so we need to ignore the first n dereferences, where n is the number
+        // that's been stripped away in origin_expr.
+
+        // Find a way to autoderef from deref_from to deref_to.
+        let Some((num_derefs, (after_deref_ty, _))) = (self.autoderef_steps)(deref_from)
+            .into_iter()
+            .enumerate()
+            .find(|(_, (ty, _))| self.infcx.can_eq(param_env, *ty, deref_to))
+        else {
+            return None;
+        };
+
+        if num_derefs <= origin_expr.peeled_count {
+            return None;
+        }
+
+        let deref_part = "*".repeat(num_derefs - origin_expr.peeled_count);
+
+        // If the user used a reference in the original expression, they probably
+        // want the suggestion to still give a reference.
+        if deref_from.is_ref() && !after_deref_ty.is_ref() {
+            Some(format!("&{deref_part}"))
+        } else {
+            Some(deref_part)
+        }
+    }
+
     /// Given that `other_ty` is the same as a type argument for `name` in `sub`, populate `value`
     /// highlighting `name` and every type argument that isn't at `pos` (which is `other_ty`), and
     /// populate `other_value` with `other_ty`.
@@ -751,7 +824,9 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
     fn cmp_fn_sig(
         &self,
         sig1: &ty::PolyFnSig<'tcx>,
+        fn_def1: Option<(DefId, &'tcx [ty::GenericArg<'tcx>])>,
         sig2: &ty::PolyFnSig<'tcx>,
+        fn_def2: Option<(DefId, &'tcx [ty::GenericArg<'tcx>])>,
     ) -> (DiagStyledString, DiagStyledString) {
         let sig1 = &(self.normalize_fn_sig)(*sig1);
         let sig2 = &(self.normalize_fn_sig)(*sig2);
@@ -857,6 +932,25 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
             (values.1).0.extend(x2.0);
         }
 
+        let fmt = |(did, args)| format!(" {{{}}}", self.tcx.def_path_str_with_args(did, args));
+
+        match (fn_def1, fn_def2) {
+            (None, None) => {}
+            (Some(fn_def1), Some(fn_def2)) => {
+                let path1 = fmt(fn_def1);
+                let path2 = fmt(fn_def2);
+                let same_path = path1 == path2;
+                values.0.push(path1, !same_path);
+                values.1.push(path2, !same_path);
+            }
+            (Some(fn_def1), None) => {
+                values.0.push_highlighted(fmt(fn_def1));
+            }
+            (None, Some(fn_def2)) => {
+                values.1.push_highlighted(fmt(fn_def2));
+            }
+        }
+
         values
     }
 
@@ -1245,36 +1339,21 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
             (ty::FnDef(did1, args1), ty::FnDef(did2, args2)) => {
                 let sig1 = self.tcx.fn_sig(*did1).instantiate(self.tcx, args1);
                 let sig2 = self.tcx.fn_sig(*did2).instantiate(self.tcx, args2);
-                let mut values = self.cmp_fn_sig(&sig1, &sig2);
-                let path1 = format!(" {{{}}}", self.tcx.def_path_str_with_args(*did1, args1));
-                let path2 = format!(" {{{}}}", self.tcx.def_path_str_with_args(*did2, args2));
-                let same_path = path1 == path2;
-                values.0.push(path1, !same_path);
-                values.1.push(path2, !same_path);
-                values
+                self.cmp_fn_sig(&sig1, Some((*did1, args1)), &sig2, Some((*did2, args2)))
             }
 
             (ty::FnDef(did1, args1), ty::FnPtr(sig_tys2, hdr2)) => {
                 let sig1 = self.tcx.fn_sig(*did1).instantiate(self.tcx, args1);
-                let mut values = self.cmp_fn_sig(&sig1, &sig_tys2.with(*hdr2));
-                values.0.push_highlighted(format!(
-                    " {{{}}}",
-                    self.tcx.def_path_str_with_args(*did1, args1)
-                ));
-                values
+                self.cmp_fn_sig(&sig1, Some((*did1, args1)), &sig_tys2.with(*hdr2), None)
             }
 
             (ty::FnPtr(sig_tys1, hdr1), ty::FnDef(did2, args2)) => {
                 let sig2 = self.tcx.fn_sig(*did2).instantiate(self.tcx, args2);
-                let mut values = self.cmp_fn_sig(&sig_tys1.with(*hdr1), &sig2);
-                values
-                    .1
-                    .push_normal(format!(" {{{}}}", self.tcx.def_path_str_with_args(*did2, args2)));
-                values
+                self.cmp_fn_sig(&sig_tys1.with(*hdr1), None, &sig2, Some((*did2, args2)))
             }
 
             (ty::FnPtr(sig_tys1, hdr1), ty::FnPtr(sig_tys2, hdr2)) => {
-                self.cmp_fn_sig(&sig_tys1.with(*hdr1), &sig_tys2.with(*hdr2))
+                self.cmp_fn_sig(&sig_tys1.with(*hdr1), None, &sig_tys2.with(*hdr2), None)
             }
 
             _ => {
@@ -1406,8 +1485,8 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
             Variable(ty::error::ExpectedFound<Ty<'a>>),
             Fixed(&'static str),
         }
-        let (expected_found, exp_found, is_simple_error, values) = match values {
-            None => (None, Mismatch::Fixed("type"), false, None),
+        let (expected_found, exp_found, is_simple_error, values, param_env) = match values {
+            None => (None, Mismatch::Fixed("type"), false, None, None),
             Some(ty::ParamEnvAnd { param_env, value: values }) => {
                 let mut values = self.resolve_vars_if_possible(values);
                 if self.next_trait_solver() {
@@ -1459,7 +1538,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                     diag.downgrade_to_delayed_bug();
                     return;
                 };
-                (Some(vals), exp_found, is_simple_error, Some(values))
+                (Some(vals), exp_found, is_simple_error, Some(values), Some(param_env))
             }
         };
 
@@ -1791,7 +1870,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
 
         // It reads better to have the error origin as the final
         // thing.
-        self.note_error_origin(diag, cause, exp_found, terr);
+        self.note_error_origin(diag, cause, exp_found, terr, param_env);
 
         debug!(?diag);
     }
@@ -2029,7 +2108,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                 if exp_found.references_error() {
                     return None;
                 }
-                let (exp, fnd) = self.cmp_fn_sig(&exp_found.expected, &exp_found.found);
+                let (exp, fnd) = self.cmp_fn_sig(&exp_found.expected, None, &exp_found.found, None);
                 Some((exp, fnd, None))
             }
         }
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/need_type_info.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/need_type_info.rs
index af3b5e0d5d4..2dcf3760d2f 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/need_type_info.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/need_type_info.rs
@@ -17,10 +17,10 @@ use rustc_middle::ty::{
     self, GenericArg, GenericArgKind, GenericArgsRef, InferConst, IsSuggestable, Ty, TyCtxt,
     TypeFoldable, TypeFolder, TypeSuperFoldable, TypeckResults,
 };
-use rustc_span::symbol::{Ident, sym};
-use rustc_span::{BytePos, DUMMY_SP, FileName, Span};
+use rustc_span::{BytePos, DUMMY_SP, FileName, Ident, Span, sym};
 use tracing::{debug, instrument, warn};
 
+use super::nice_region_error::placeholder_error::Highlighted;
 use crate::error_reporting::TypeErrCtxt;
 use crate::errors::{
     AmbiguousImpl, AmbiguousReturn, AnnotationRequired, InferenceBadError,
@@ -279,8 +279,9 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
     pub fn extract_inference_diagnostics_data(
         &self,
         arg: GenericArg<'tcx>,
-        highlight: Option<ty::print::RegionHighlightMode<'tcx>>,
+        highlight: ty::print::RegionHighlightMode<'tcx>,
     ) -> InferenceDiagnosticsData {
+        let tcx = self.tcx;
         match arg.unpack() {
             GenericArgKind::Type(ty) => {
                 if let ty::Infer(ty::TyVar(ty_vid)) = *ty.kind() {
@@ -300,13 +301,9 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                     }
                 }
 
-                let mut printer = ty::print::FmtPrinter::new(self.tcx, Namespace::TypeNS);
-                if let Some(highlight) = highlight {
-                    printer.region_highlight_mode = highlight;
-                }
-                ty.print(&mut printer).unwrap();
                 InferenceDiagnosticsData {
-                    name: printer.into_buffer(),
+                    name: Highlighted { highlight, ns: Namespace::TypeNS, tcx, value: ty }
+                        .to_string(),
                     span: None,
                     kind: UnderspecifiedArgKind::Type { prefix: ty.prefix_string(self.tcx) },
                     parent: None,
@@ -325,13 +322,9 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                     }
 
                     debug_assert!(!origin.span.is_dummy());
-                    let mut printer = ty::print::FmtPrinter::new(self.tcx, Namespace::ValueNS);
-                    if let Some(highlight) = highlight {
-                        printer.region_highlight_mode = highlight;
-                    }
-                    ct.print(&mut printer).unwrap();
                     InferenceDiagnosticsData {
-                        name: printer.into_buffer(),
+                        name: Highlighted { highlight, ns: Namespace::ValueNS, tcx, value: ct }
+                            .to_string(),
                         span: Some(origin.span),
                         kind: UnderspecifiedArgKind::Const { is_parameter: false },
                         parent: None,
@@ -343,13 +336,9 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                     // FIXME: Ideally we should look into the generic constant
                     // to figure out which inference var is actually unresolved so that
                     // this path is unreachable.
-                    let mut printer = ty::print::FmtPrinter::new(self.tcx, Namespace::ValueNS);
-                    if let Some(highlight) = highlight {
-                        printer.region_highlight_mode = highlight;
-                    }
-                    ct.print(&mut printer).unwrap();
                     InferenceDiagnosticsData {
-                        name: printer.into_buffer(),
+                        name: Highlighted { highlight, ns: Namespace::ValueNS, tcx, value: ct }
+                            .to_string(),
                         span: None,
                         kind: UnderspecifiedArgKind::Const { is_parameter: false },
                         parent: None,
@@ -422,7 +411,8 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         should_label_span: bool,
     ) -> Diag<'a> {
         let arg = self.resolve_vars_if_possible(arg);
-        let arg_data = self.extract_inference_diagnostics_data(arg, None);
+        let arg_data =
+            self.extract_inference_diagnostics_data(arg, ty::print::RegionHighlightMode::default());
 
         let Some(typeck_results) = &self.typeck_results else {
             // If we don't have any typeck results we're outside
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/different_lifetimes.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/different_lifetimes.rs
index 7f847253439..9cb58a9d45b 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/different_lifetimes.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/different_lifetimes.rs
@@ -63,26 +63,16 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
         }
 
         // Determine whether the sub and sup consist of both anonymous (elided) regions.
-        let anon_reg_sup = self.tcx().is_suitable_region(self.generic_param_scope, sup)?;
+        let sup_info = self.tcx().is_suitable_region(self.generic_param_scope, sup)?;
 
-        let anon_reg_sub = self.tcx().is_suitable_region(self.generic_param_scope, sub)?;
-        let scope_def_id_sup = anon_reg_sup.def_id;
-        let bregion_sup = anon_reg_sup.bound_region;
-        let scope_def_id_sub = anon_reg_sub.def_id;
-        let bregion_sub = anon_reg_sub.bound_region;
+        let sub_info = self.tcx().is_suitable_region(self.generic_param_scope, sub)?;
 
-        let ty_sup = find_anon_type(self.tcx(), self.generic_param_scope, sup, &bregion_sup)?;
+        let ty_sup = find_anon_type(self.tcx(), self.generic_param_scope, sup)?;
 
-        let ty_sub = find_anon_type(self.tcx(), self.generic_param_scope, sub, &bregion_sub)?;
+        let ty_sub = find_anon_type(self.tcx(), self.generic_param_scope, sub)?;
 
-        debug!(
-            "try_report_anon_anon_conflict: found_param1={:?} sup={:?} br1={:?}",
-            ty_sub, sup, bregion_sup
-        );
-        debug!(
-            "try_report_anon_anon_conflict: found_param2={:?} sub={:?} br2={:?}",
-            ty_sup, sub, bregion_sub
-        );
+        debug!("try_report_anon_anon_conflict: found_param1={:?} sup={:?}", ty_sub, sup);
+        debug!("try_report_anon_anon_conflict: found_param2={:?} sub={:?}", ty_sup, sub);
 
         let (ty_sup, ty_fndecl_sup) = ty_sup;
         let (ty_sub, ty_fndecl_sub) = ty_sub;
@@ -93,9 +83,9 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
             self.find_param_with_region(sub, sub)?;
 
         let sup_is_ret_type =
-            self.is_return_type_anon(scope_def_id_sup, bregion_sup, ty_fndecl_sup);
+            self.is_return_type_anon(sup_info.scope, sup_info.region_def_id, ty_fndecl_sup);
         let sub_is_ret_type =
-            self.is_return_type_anon(scope_def_id_sub, bregion_sub, ty_fndecl_sub);
+            self.is_return_type_anon(sub_info.scope, sub_info.region_def_id, ty_fndecl_sub);
 
         debug!(
             "try_report_anon_anon_conflict: sub_is_ret_type={:?} sup_is_ret_type={:?}",
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/find_anon_type.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/find_anon_type.rs
index cd621fd1a39..2a487a48a8e 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/find_anon_type.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/find_anon_type.rs
@@ -1,7 +1,7 @@
 use core::ops::ControlFlow;
 
 use rustc_hir as hir;
-use rustc_hir::def_id::LocalDefId;
+use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::intravisit::{self, Visitor};
 use rustc_middle::hir::map::Map;
 use rustc_middle::hir::nested_filter;
@@ -28,16 +28,15 @@ pub fn find_anon_type<'tcx>(
     tcx: TyCtxt<'tcx>,
     generic_param_scope: LocalDefId,
     region: Region<'tcx>,
-    br: &ty::BoundRegionKind,
 ) -> Option<(&'tcx hir::Ty<'tcx>, &'tcx hir::FnSig<'tcx>)> {
     let anon_reg = tcx.is_suitable_region(generic_param_scope, region)?;
-    let fn_sig = tcx.hir_node_by_def_id(anon_reg.def_id).fn_sig()?;
+    let fn_sig = tcx.hir_node_by_def_id(anon_reg.scope).fn_sig()?;
 
     fn_sig
         .decl
         .inputs
         .iter()
-        .find_map(|arg| find_component_for_bound_region(tcx, arg, br))
+        .find_map(|arg| find_component_for_bound_region(tcx, arg, anon_reg.region_def_id))
         .map(|ty| (ty, fn_sig))
 }
 
@@ -46,9 +45,9 @@ pub fn find_anon_type<'tcx>(
 fn find_component_for_bound_region<'tcx>(
     tcx: TyCtxt<'tcx>,
     arg: &'tcx hir::Ty<'tcx>,
-    br: &ty::BoundRegionKind,
+    region_def_id: DefId,
 ) -> Option<&'tcx hir::Ty<'tcx>> {
-    FindNestedTypeVisitor { tcx, bound_region: *br, current_index: ty::INNERMOST }
+    FindNestedTypeVisitor { tcx, region_def_id, current_index: ty::INNERMOST }
         .visit_ty(arg)
         .break_value()
 }
@@ -62,9 +61,8 @@ fn find_component_for_bound_region<'tcx>(
 // specific part of the type in the error message.
 struct FindNestedTypeVisitor<'tcx> {
     tcx: TyCtxt<'tcx>,
-    // The bound_region corresponding to the Refree(freeregion)
-    // associated with the anonymous region we are looking for.
-    bound_region: ty::BoundRegionKind,
+    // The `DefId` of the region we're looking for.
+    region_def_id: DefId,
     current_index: ty::DebruijnIndex,
 }
 
@@ -96,16 +94,13 @@ impl<'tcx> Visitor<'tcx> for FindNestedTypeVisitor<'tcx> {
             hir::TyKind::Ref(lifetime, _) => {
                 // the lifetime of the Ref
                 let hir_id = lifetime.hir_id;
-                match (self.tcx.named_bound_var(hir_id), self.bound_region) {
+                match self.tcx.named_bound_var(hir_id) {
                     // Find the index of the named region that was part of the
                     // error. We will then search the function parameters for a bound
                     // region at the right depth with the same index
-                    (
-                        Some(rbv::ResolvedArg::EarlyBound(id)),
-                        ty::BoundRegionKind::Named(def_id, _),
-                    ) => {
-                        debug!("EarlyBound id={:?} def_id={:?}", id, def_id);
-                        if id.to_def_id() == def_id {
+                    Some(rbv::ResolvedArg::EarlyBound(id)) => {
+                        debug!("EarlyBound id={:?}", id);
+                        if id.to_def_id() == self.region_def_id {
                             return ControlFlow::Break(arg);
                         }
                     }
@@ -113,31 +108,25 @@ impl<'tcx> Visitor<'tcx> for FindNestedTypeVisitor<'tcx> {
                     // Find the index of the named region that was part of the
                     // error. We will then search the function parameters for a bound
                     // region at the right depth with the same index
-                    (
-                        Some(rbv::ResolvedArg::LateBound(debruijn_index, _, id)),
-                        ty::BoundRegionKind::Named(def_id, _),
-                    ) => {
+                    Some(rbv::ResolvedArg::LateBound(debruijn_index, _, id)) => {
                         debug!(
                             "FindNestedTypeVisitor::visit_ty: LateBound depth = {:?}",
                             debruijn_index
                         );
-                        debug!("LateBound id={:?} def_id={:?}", id, def_id);
-                        if debruijn_index == self.current_index && id.to_def_id() == def_id {
+                        debug!("LateBound id={:?}", id);
+                        if debruijn_index == self.current_index
+                            && id.to_def_id() == self.region_def_id
+                        {
                             return ControlFlow::Break(arg);
                         }
                     }
 
-                    (
-                        Some(
-                            rbv::ResolvedArg::StaticLifetime
-                            | rbv::ResolvedArg::Free(_, _)
-                            | rbv::ResolvedArg::EarlyBound(_)
-                            | rbv::ResolvedArg::LateBound(_, _, _)
-                            | rbv::ResolvedArg::Error(_),
-                        )
-                        | None,
-                        _,
-                    ) => {
+                    Some(
+                        rbv::ResolvedArg::StaticLifetime
+                        | rbv::ResolvedArg::Free(_, _)
+                        | rbv::ResolvedArg::Error(_),
+                    )
+                    | None => {
                         debug!("no arg found");
                     }
                 }
@@ -151,7 +140,7 @@ impl<'tcx> Visitor<'tcx> for FindNestedTypeVisitor<'tcx> {
                 return if intravisit::walk_ty(
                     &mut TyPathVisitor {
                         tcx: self.tcx,
-                        bound_region: self.bound_region,
+                        region_def_id: self.region_def_id,
                         current_index: self.current_index,
                     },
                     arg,
@@ -179,7 +168,7 @@ impl<'tcx> Visitor<'tcx> for FindNestedTypeVisitor<'tcx> {
 // specific part of the type in the error message.
 struct TyPathVisitor<'tcx> {
     tcx: TyCtxt<'tcx>,
-    bound_region: ty::BoundRegionKind,
+    region_def_id: DefId,
     current_index: ty::DebruijnIndex,
 }
 
@@ -192,38 +181,29 @@ impl<'tcx> Visitor<'tcx> for TyPathVisitor<'tcx> {
     }
 
     fn visit_lifetime(&mut self, lifetime: &hir::Lifetime) -> Self::Result {
-        match (self.tcx.named_bound_var(lifetime.hir_id), self.bound_region) {
+        match self.tcx.named_bound_var(lifetime.hir_id) {
             // the lifetime of the TyPath!
-            (Some(rbv::ResolvedArg::EarlyBound(id)), ty::BoundRegionKind::Named(def_id, _)) => {
-                debug!("EarlyBound id={:?} def_id={:?}", id, def_id);
-                if id.to_def_id() == def_id {
+            Some(rbv::ResolvedArg::EarlyBound(id)) => {
+                debug!("EarlyBound id={:?}", id);
+                if id.to_def_id() == self.region_def_id {
                     return ControlFlow::Break(());
                 }
             }
 
-            (
-                Some(rbv::ResolvedArg::LateBound(debruijn_index, _, id)),
-                ty::BoundRegionKind::Named(def_id, _),
-            ) => {
+            Some(rbv::ResolvedArg::LateBound(debruijn_index, _, id)) => {
                 debug!("FindNestedTypeVisitor::visit_ty: LateBound depth = {:?}", debruijn_index,);
                 debug!("id={:?}", id);
-                debug!("def_id={:?}", def_id);
-                if debruijn_index == self.current_index && id.to_def_id() == def_id {
+                if debruijn_index == self.current_index && id.to_def_id() == self.region_def_id {
                     return ControlFlow::Break(());
                 }
             }
 
-            (
-                Some(
-                    rbv::ResolvedArg::StaticLifetime
-                    | rbv::ResolvedArg::EarlyBound(_)
-                    | rbv::ResolvedArg::LateBound(_, _, _)
-                    | rbv::ResolvedArg::Free(_, _)
-                    | rbv::ResolvedArg::Error(_),
-                )
-                | None,
-                _,
-            ) => {
+            Some(
+                rbv::ResolvedArg::StaticLifetime
+                | rbv::ResolvedArg::Free(_, _)
+                | rbv::ResolvedArg::Error(_),
+            )
+            | None => {
                 debug!("no arg found");
             }
         }
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/named_anon_conflict.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/named_anon_conflict.rs
index 9fa5a8ac637..aa7935a29f0 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/named_anon_conflict.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/named_anon_conflict.rs
@@ -3,7 +3,7 @@
 
 use rustc_errors::Diag;
 use rustc_middle::ty;
-use rustc_span::symbol::kw;
+use rustc_span::kw;
 use tracing::debug;
 
 use crate::error_reporting::infer::nice_region_error::NiceRegionError;
@@ -54,13 +54,13 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
         let param = anon_param_info.param;
         let new_ty = anon_param_info.param_ty;
         let new_ty_span = anon_param_info.param_ty_span;
-        let br = anon_param_info.bound_region;
         let is_first = anon_param_info.is_first;
-        let scope_def_id = region_info.def_id;
+        let scope_def_id = region_info.scope;
         let is_impl_item = region_info.is_impl_item;
 
-        match br {
-            ty::BoundRegionKind::Named(_, kw::UnderscoreLifetime) | ty::BoundRegionKind::Anon => {}
+        match anon_param_info.kind {
+            ty::LateParamRegionKind::Named(_, kw::UnderscoreLifetime)
+            | ty::LateParamRegionKind::Anon(_) => {}
             _ => {
                 /* not an anonymous region */
                 debug!("try_report_named_anon_conflict: not an anonymous region");
@@ -73,7 +73,7 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
             return None;
         }
 
-        if find_anon_type(self.tcx(), self.generic_param_scope, anon, &br).is_some()
+        if find_anon_type(self.tcx(), self.generic_param_scope, anon).is_some()
             && self.is_self_anon(is_first, scope_def_id)
         {
             return None;
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/placeholder_error.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/placeholder_error.rs
index 4398af76ab2..aaaefd81d19 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/placeholder_error.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/placeholder_error.rs
@@ -21,9 +21,10 @@ use crate::traits::{ObligationCause, ObligationCauseCode};
 // HACK(eddyb) maybe move this in a more central location.
 #[derive(Copy, Clone)]
 pub struct Highlighted<'tcx, T> {
-    tcx: TyCtxt<'tcx>,
-    highlight: RegionHighlightMode<'tcx>,
-    value: T,
+    pub tcx: TyCtxt<'tcx>,
+    pub highlight: RegionHighlightMode<'tcx>,
+    pub value: T,
+    pub ns: Namespace,
 }
 
 impl<'tcx, T> IntoDiagArg for Highlighted<'tcx, T>
@@ -37,7 +38,7 @@ where
 
 impl<'tcx, T> Highlighted<'tcx, T> {
     fn map<U>(self, f: impl FnOnce(T) -> U) -> Highlighted<'tcx, U> {
-        Highlighted { tcx: self.tcx, highlight: self.highlight, value: f(self.value) }
+        Highlighted { tcx: self.tcx, highlight: self.highlight, value: f(self.value), ns: self.ns }
     }
 }
 
@@ -46,7 +47,7 @@ where
     T: for<'a> Print<'tcx, FmtPrinter<'a, 'tcx>>,
 {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        let mut printer = ty::print::FmtPrinter::new(self.tcx, Namespace::TypeNS);
+        let mut printer = ty::print::FmtPrinter::new(self.tcx, self.ns);
         printer.region_highlight_mode = self.highlight;
 
         self.value.print(&mut printer)?;
@@ -381,6 +382,7 @@ impl<'tcx> NiceRegionError<'_, 'tcx> {
             tcx: self.tcx(),
             highlight: RegionHighlightMode::default(),
             value: trait_ref,
+            ns: Namespace::TypeNS,
         };
 
         let same_self_type = actual_trait_ref.self_ty() == expected_trait_ref.self_ty();
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/static_impl_trait.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/static_impl_trait.rs
index 9a7bdaa5b57..3416a17624e 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/static_impl_trait.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/static_impl_trait.rs
@@ -11,9 +11,8 @@ use rustc_hir::{
 use rustc_middle::ty::{
     self, AssocItemContainer, StaticLifetimeVisitor, Ty, TyCtxt, TypeSuperVisitable, TypeVisitor,
 };
-use rustc_span::Span;
 use rustc_span::def_id::LocalDefId;
-use rustc_span::symbol::Ident;
+use rustc_span::{Ident, Span};
 use tracing::debug;
 
 use crate::error_reporting::infer::nice_region_error::NiceRegionError;
@@ -50,7 +49,7 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
                     // This may have a closure and it would cause ICE
                     // through `find_param_with_region` (#78262).
                     let anon_reg_sup = tcx.is_suitable_region(self.generic_param_scope, *sup_r)?;
-                    let fn_returns = tcx.return_type_impl_or_dyn_traits(anon_reg_sup.def_id);
+                    let fn_returns = tcx.return_type_impl_or_dyn_traits(anon_reg_sup.scope);
                     if fn_returns.is_empty() {
                         return None;
                     }
@@ -196,7 +195,7 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
 
         let mut err = self.tcx().dcx().create_err(diag);
 
-        let fn_returns = tcx.return_type_impl_or_dyn_traits(anon_reg_sup.def_id);
+        let fn_returns = tcx.return_type_impl_or_dyn_traits(anon_reg_sup.scope);
 
         let mut override_error_code = None;
         if let SubregionOrigin::Subtype(box TypeTrace { cause, .. }) = &sup_origin
@@ -250,7 +249,7 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
             Some(arg),
             captures,
             Some((param.param_ty_span, param.param_ty.to_string())),
-            Some(anon_reg_sup.def_id),
+            Some(anon_reg_sup.scope),
         );
 
         let reported = err.emit();
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/trait_impl_difference.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/trait_impl_difference.rs
index 592ade8ede2..95dd1b28a39 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/trait_impl_difference.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/trait_impl_difference.rs
@@ -2,18 +2,19 @@
 
 use rustc_errors::ErrorGuaranteed;
 use rustc_hir as hir;
-use rustc_hir::def::Res;
+use rustc_hir::def::{Namespace, Res};
 use rustc_hir::def_id::DefId;
 use rustc_hir::intravisit::Visitor;
 use rustc_middle::hir::nested_filter;
 use rustc_middle::traits::ObligationCauseCode;
 use rustc_middle::ty::error::ExpectedFound;
 use rustc_middle::ty::print::RegionHighlightMode;
-use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitor};
+use rustc_middle::ty::{self, TyCtxt, TypeVisitable};
 use rustc_span::Span;
 use tracing::debug;
 
 use crate::error_reporting::infer::nice_region_error::NiceRegionError;
+use crate::error_reporting::infer::nice_region_error::placeholder_error::Highlighted;
 use crate::errors::{ConsiderBorrowingParamHelp, RelationshipHelp, TraitImplDiff};
 use crate::infer::{RegionResolutionError, Subtype, ValuePairs};
 
@@ -32,19 +33,14 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
             _,
         ) = error.clone()
             && let (Subtype(sup_trace), Subtype(sub_trace)) = (&sup_origin, &sub_origin)
-            && let ObligationCauseCode::CompareImplItem { trait_item_def_id, .. } =
+            && let &ObligationCauseCode::CompareImplItem { trait_item_def_id, .. } =
                 sub_trace.cause.code()
             && sub_trace.values == sup_trace.values
             && let ValuePairs::PolySigs(ExpectedFound { expected, found }) = sub_trace.values
         {
             // FIXME(compiler-errors): Don't like that this needs `Ty`s, but
             // all of the region highlighting machinery only deals with those.
-            let guar = self.emit_err(
-                var_origin.span(),
-                Ty::new_fn_ptr(self.cx.tcx, expected),
-                Ty::new_fn_ptr(self.cx.tcx, found),
-                *trait_item_def_id,
-            );
+            let guar = self.emit_err(var_origin.span(), expected, found, trait_item_def_id);
             return Some(guar);
         }
         None
@@ -53,11 +49,11 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
     fn emit_err(
         &self,
         sp: Span,
-        expected: Ty<'tcx>,
-        found: Ty<'tcx>,
-        trait_def_id: DefId,
+        expected: ty::PolyFnSig<'tcx>,
+        found: ty::PolyFnSig<'tcx>,
+        trait_item_def_id: DefId,
     ) -> ErrorGuaranteed {
-        let trait_sp = self.tcx().def_span(trait_def_id);
+        let trait_sp = self.tcx().def_span(trait_item_def_id);
 
         // Mark all unnamed regions in the type with a number.
         // This diagnostic is called in response to lifetime errors, so be informative.
@@ -67,10 +63,10 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
         }
 
         impl<'tcx> HighlightBuilder<'tcx> {
-            fn build(ty: Ty<'tcx>) -> RegionHighlightMode<'tcx> {
+            fn build(sig: ty::PolyFnSig<'tcx>) -> RegionHighlightMode<'tcx> {
                 let mut builder =
                     HighlightBuilder { highlight: RegionHighlightMode::default(), counter: 1 };
-                builder.visit_ty(ty);
+                sig.visit_with(&mut builder);
                 builder.highlight
             }
         }
@@ -85,16 +81,21 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
         }
 
         let expected_highlight = HighlightBuilder::build(expected);
-        let expected = self
-            .cx
-            .extract_inference_diagnostics_data(expected.into(), Some(expected_highlight))
-            .name;
+        let tcx = self.cx.tcx;
+        let expected = Highlighted {
+            highlight: expected_highlight,
+            ns: Namespace::TypeNS,
+            tcx,
+            value: expected,
+        }
+        .to_string();
         let found_highlight = HighlightBuilder::build(found);
         let found =
-            self.cx.extract_inference_diagnostics_data(found.into(), Some(found_highlight)).name;
+            Highlighted { highlight: found_highlight, ns: Namespace::TypeNS, tcx, value: found }
+                .to_string();
 
         // Get the span of all the used type parameters in the method.
-        let assoc_item = self.tcx().associated_item(trait_def_id);
+        let assoc_item = self.tcx().associated_item(trait_item_def_id);
         let mut visitor = TypeParamSpanVisitor { tcx: self.tcx(), types: vec![] };
         match assoc_item.kind {
             ty::AssocKind::Fn => {
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/util.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/util.rs
index 218d2e753ef..445937ad169 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/util.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/util.rs
@@ -2,7 +2,7 @@
 //! anonymous regions.
 
 use rustc_hir as hir;
-use rustc_hir::def_id::LocalDefId;
+use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_middle::ty::fold::fold_regions;
 use rustc_middle::ty::{self, Binder, Region, Ty, TyCtxt, TypeFoldable};
 use rustc_span::Span;
@@ -17,8 +17,8 @@ pub struct AnonymousParamInfo<'tcx> {
     pub param: &'tcx hir::Param<'tcx>,
     /// The type corresponding to the anonymous region parameter.
     pub param_ty: Ty<'tcx>,
-    /// The ty::BoundRegionKind corresponding to the anonymous region.
-    pub bound_region: ty::BoundRegionKind,
+    /// The `ty::LateParamRegionKind` corresponding to the anonymous region.
+    pub kind: ty::LateParamRegionKind,
     /// The `Span` of the parameter type.
     pub param_ty_span: Span,
     /// Signals that the argument is the first parameter in the declaration.
@@ -43,11 +43,11 @@ pub fn find_param_with_region<'tcx>(
     anon_region: Region<'tcx>,
     replace_region: Region<'tcx>,
 ) -> Option<AnonymousParamInfo<'tcx>> {
-    let (id, bound_region) = match *anon_region {
-        ty::ReLateParam(late_param) => (late_param.scope, late_param.bound_region),
+    let (id, kind) = match *anon_region {
+        ty::ReLateParam(late_param) => (late_param.scope, late_param.kind),
         ty::ReEarlyParam(ebr) => {
             let region_def = tcx.generics_of(generic_param_scope).region_param(ebr, tcx).def_id;
-            (tcx.parent(region_def), ty::BoundRegionKind::Named(region_def, ebr.name))
+            (tcx.parent(region_def), ty::LateParamRegionKind::Named(region_def, ebr.name))
         }
         _ => return None, // not a free region
     };
@@ -96,13 +96,7 @@ pub fn find_param_with_region<'tcx>(
                 let ty_hir_id = fn_decl.inputs[index].hir_id;
                 let param_ty_span = hir.span(ty_hir_id);
                 let is_first = index == 0;
-                AnonymousParamInfo {
-                    param,
-                    param_ty: new_param_ty,
-                    param_ty_span,
-                    bound_region,
-                    is_first,
-                }
+                AnonymousParamInfo { param, param_ty: new_param_ty, param_ty_span, kind, is_first }
             })
         })
 }
@@ -122,7 +116,7 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
     pub(super) fn is_return_type_anon(
         &self,
         scope_def_id: LocalDefId,
-        br: ty::BoundRegionKind,
+        region_def_id: DefId,
         hir_sig: &hir::FnSig<'_>,
     ) -> Option<Span> {
         let fn_ty = self.tcx().type_of(scope_def_id).instantiate_identity();
@@ -135,8 +129,8 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
                 None
             };
             return match future_output {
-                Some(output) if self.includes_region(output, br) => Some(span),
-                None if self.includes_region(ret_ty, br) => Some(span),
+                Some(output) if self.includes_region(output, region_def_id) => Some(span),
+                None if self.includes_region(ret_ty, region_def_id) => Some(span),
                 _ => None,
             };
         }
@@ -146,12 +140,15 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
     fn includes_region(
         &self,
         ty: Binder<'tcx, impl TypeFoldable<TyCtxt<'tcx>>>,
-        region: ty::BoundRegionKind,
+        region_def_id: DefId,
     ) -> bool {
         let late_bound_regions = self.tcx().collect_referenced_late_bound_regions(ty);
         // We are only checking is any region meets the condition so order doesn't matter
         #[allow(rustc::potential_query_instability)]
-        late_bound_regions.iter().any(|r| *r == region)
+        late_bound_regions.iter().any(|r| match *r {
+            ty::BoundRegionKind::Named(def_id, _) => def_id == region_def_id,
+            _ => false,
+        })
     }
 
     // Here we check for the case where anonymous region
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/note.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/note.rs
index c4dac1a936c..beae9962f7f 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/note.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/note.rs
@@ -3,7 +3,7 @@ use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_middle::traits::ObligationCauseCode;
 use rustc_middle::ty::error::TypeError;
 use rustc_middle::ty::{self, IsSuggestable, Region, Ty};
-use rustc_span::symbol::kw;
+use rustc_span::kw;
 use tracing::debug;
 
 use super::ObligationCauseAsDiagArg;
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/region.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/region.rs
index 9fd7dccc57c..98b5fb2052f 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/region.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/region.rs
@@ -12,8 +12,7 @@ use rustc_middle::bug;
 use rustc_middle::traits::ObligationCauseCode;
 use rustc_middle::ty::error::TypeError;
 use rustc_middle::ty::{self, IsSuggestable, Region, Ty, TyCtxt, TypeVisitableExt as _};
-use rustc_span::symbol::kw;
-use rustc_span::{BytePos, ErrorGuaranteed, Span, Symbol};
+use rustc_span::{BytePos, ErrorGuaranteed, Span, Symbol, kw};
 use rustc_type_ir::Upcast as _;
 use tracing::{debug, instrument};
 
@@ -790,7 +789,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                 let lifetime_scope = match sub.kind() {
                     ty::ReStatic => hir::def_id::CRATE_DEF_ID,
                     _ => match self.tcx.is_suitable_region(generic_param_scope, sub) {
-                        Some(info) => info.def_id,
+                        Some(info) => info.scope,
                         None => generic_param_scope,
                     },
                 };
@@ -864,13 +863,13 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
             }
         }
 
-        let (lifetime_def_id, lifetime_scope) =
-            match self.tcx.is_suitable_region(generic_param_scope, lifetime) {
-                Some(info) if !lifetime.has_name() => {
-                    (info.bound_region.get_id().unwrap().expect_local(), info.def_id)
-                }
-                _ => return lifetime.get_name_or_anon().to_string(),
-            };
+        let (lifetime_def_id, lifetime_scope) = match self
+            .tcx
+            .is_suitable_region(generic_param_scope, lifetime)
+        {
+            Some(info) if !lifetime.has_name() => (info.region_def_id.expect_local(), info.scope),
+            _ => return lifetime.get_name_or_anon().to_string(),
+        };
 
         let new_lt = {
             let generics = self.tcx.generics_of(lifetime_scope);
@@ -1096,14 +1095,13 @@ fn msg_span_from_named_region<'tcx>(
             (text, Some(span))
         }
         ty::ReLateParam(ref fr) => {
-            if !fr.bound_region.is_named()
-                && let Some((ty, _)) =
-                    find_anon_type(tcx, generic_param_scope, region, &fr.bound_region)
+            if !fr.kind.is_named()
+                && let Some((ty, _)) = find_anon_type(tcx, generic_param_scope, region)
             {
                 ("the anonymous lifetime defined here".to_string(), Some(ty.span))
             } else {
-                match fr.bound_region {
-                    ty::BoundRegionKind::Named(param_def_id, name) => {
+                match fr.kind {
+                    ty::LateParamRegionKind::Named(param_def_id, name) => {
                         let span = tcx.def_span(param_def_id);
                         let text = if name == kw::UnderscoreLifetime {
                             "the anonymous lifetime as defined here".to_string()
@@ -1112,7 +1110,7 @@ fn msg_span_from_named_region<'tcx>(
                         };
                         (text, Some(span))
                     }
-                    ty::BoundRegionKind::Anon => (
+                    ty::LateParamRegionKind::Anon(_) => (
                         "the anonymous lifetime as defined here".to_string(),
                         Some(tcx.def_span(generic_param_scope)),
                     ),
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/suggest.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/suggest.rs
index fc2d0ba36f0..08775df5ac9 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/suggest.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/suggest.rs
@@ -210,7 +210,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
             (Some(ty), _) if self.same_type_modulo_infer(ty, exp_found.found) => match cause.code()
             {
                 ObligationCauseCode::Pattern { span: Some(then_span), origin_expr, .. } => {
-                    origin_expr.then_some(ConsiderAddingAwait::FutureSugg {
+                    origin_expr.is_some().then_some(ConsiderAddingAwait::FutureSugg {
                         span: then_span.shrink_to_hi(),
                     })
                 }
diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs
index 4fb02f60943..d41f8f46c17 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs
@@ -27,8 +27,7 @@ use rustc_middle::ty::{
     self, ToPolyTraitRef, TraitRef, Ty, TyCtxt, TypeFoldable, TypeVisitableExt, Upcast,
 };
 use rustc_middle::{bug, span_bug};
-use rustc_span::symbol::sym;
-use rustc_span::{BytePos, DUMMY_SP, Span, Symbol};
+use rustc_span::{BytePos, DUMMY_SP, Span, Symbol, sym};
 use tracing::{debug, instrument};
 
 use super::on_unimplemented::{AppendConstMessage, OnUnimplementedNote};
diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/on_unimplemented.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/on_unimplemented.rs
index f10314c1c9e..a401fcf3505 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/traits/on_unimplemented.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/on_unimplemented.rs
@@ -1,21 +1,21 @@
 use std::iter;
 use std::path::PathBuf;
 
-use rustc_ast::{AttrArgs, AttrKind, Attribute, MetaItemInner};
+use rustc_ast::MetaItemInner;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::codes::*;
 use rustc_errors::{ErrorGuaranteed, struct_span_code_err};
 use rustc_hir::def_id::{DefId, LocalDefId};
+use rustc_hir::{AttrArgs, AttrKind, Attribute};
 use rustc_macros::LintDiagnostic;
 use rustc_middle::bug;
 use rustc_middle::ty::print::PrintTraitRefExt as _;
 use rustc_middle::ty::{self, GenericArgsRef, GenericParamDefKind, ToPolyTraitRef, TyCtxt};
 use rustc_parse_format::{ParseMode, Parser, Piece, Position};
 use rustc_session::lint::builtin::UNKNOWN_OR_MALFORMED_DIAGNOSTIC_ATTRIBUTES;
-use rustc_span::Span;
-use rustc_span::symbol::{Symbol, kw, sym};
+use rustc_span::{Span, Symbol, kw, sym};
 use tracing::{debug, info};
-use {rustc_attr as attr, rustc_hir as hir};
+use {rustc_attr_parsing as attr, rustc_hir as hir};
 
 use super::{ObligationCauseCode, PredicateObligation};
 use crate::error_reporting::TypeErrCtxt;
@@ -639,7 +639,7 @@ impl<'tcx> OnUnimplementedDirective {
                 let report_span = match &item.args {
                     AttrArgs::Empty => item.path.span,
                     AttrArgs::Delimited(args) => args.dspan.entire(),
-                    AttrArgs::Eq { eq_span, value } => eq_span.to(value.span()),
+                    AttrArgs::Eq { eq_span, expr } => eq_span.to(expr.span),
                 };
 
                 if let Some(item_def_id) = item_def_id.as_local() {
@@ -654,7 +654,7 @@ impl<'tcx> OnUnimplementedDirective {
             }
         } else if is_diagnostic_namespace_variant {
             match &attr.kind {
-                AttrKind::Normal(p) if !matches!(p.item.args, AttrArgs::Empty) => {
+                AttrKind::Normal(p) if !matches!(p.args, AttrArgs::Empty) => {
                     if let Some(item_def_id) = item_def_id.as_local() {
                         tcx.emit_node_span_lint(
                             UNKNOWN_OR_MALFORMED_DIAGNOSTIC_ATTRIBUTES,
diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/overflow.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/overflow.rs
index c47c2169691..d82acc4e054 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/traits/overflow.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/overflow.rs
@@ -1,8 +1,6 @@
 use std::fmt;
 
-use rustc_errors::{
-    Diag, E0275, EmissionGuarantee, ErrorGuaranteed, FatalError, struct_span_code_err,
-};
+use rustc_errors::{Diag, E0275, EmissionGuarantee, ErrorGuaranteed, struct_span_code_err};
 use rustc_hir::def::Namespace;
 use rustc_hir::def_id::LOCAL_CRATE;
 use rustc_infer::traits::{Obligation, PredicateObligation};
@@ -52,8 +50,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
     ) -> ! {
         let mut err = self.build_overflow_error(cause, span, suggest_increasing_limit);
         mutate(&mut err);
-        err.emit();
-        FatalError.raise();
+        err.emit().raise_fatal();
     }
 
     pub fn build_overflow_error(
diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
index 94682f501a8..6a8f7f4ee35 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
@@ -20,7 +20,8 @@ use rustc_hir::def_id::DefId;
 use rustc_hir::intravisit::Visitor;
 use rustc_hir::lang_items::LangItem;
 use rustc_hir::{
-    CoroutineDesugaring, CoroutineKind, CoroutineSource, Expr, HirId, Node, is_range_literal,
+    CoroutineDesugaring, CoroutineKind, CoroutineSource, Expr, HirId, Node, expr_needs_parens,
+    is_range_literal,
 };
 use rustc_infer::infer::{BoundRegionConversionTime, DefineOpaqueTypes, InferCtxt, InferOk};
 use rustc_middle::hir::map;
@@ -37,8 +38,9 @@ use rustc_middle::ty::{
 };
 use rustc_middle::{bug, span_bug};
 use rustc_span::def_id::LocalDefId;
-use rustc_span::symbol::{Ident, Symbol, kw, sym};
-use rustc_span::{BytePos, DUMMY_SP, DesugaringKind, ExpnKind, MacroKind, Span};
+use rustc_span::{
+    BytePos, DUMMY_SP, DesugaringKind, ExpnKind, Ident, MacroKind, Span, Symbol, kw, sym,
+};
 use tracing::{debug, instrument};
 
 use super::{
@@ -1391,13 +1393,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                         let Some(expr) = expr_finder.result else {
                             return false;
                         };
-                        let needs_parens = match expr.kind {
-                            // parenthesize if needed (Issue #46756)
-                            hir::ExprKind::Cast(_, _) | hir::ExprKind::Binary(_, _, _) => true,
-                            // parenthesize borrows of range literals (Issue #54505)
-                            _ if is_range_literal(expr) => true,
-                            _ => false,
-                        };
+                        let needs_parens = expr_needs_parens(expr);
 
                         let span = if needs_parens { span } else { span.shrink_to_lo() };
                         let suggestions = if !needs_parens {
diff --git a/compiler/rustc_trait_selection/src/errors.rs b/compiler/rustc_trait_selection/src/errors.rs
index 68fe90f0de2..700c79a7065 100644
--- a/compiler/rustc_trait_selection/src/errors.rs
+++ b/compiler/rustc_trait_selection/src/errors.rs
@@ -14,8 +14,7 @@ use rustc_hir::{FnRetTy, GenericParamKind, Node};
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_middle::ty::print::{PrintTraitRefExt as _, TraitRefPrintOnlyTraitPath};
 use rustc_middle::ty::{self, Binder, ClosureKind, FnSig, PolyTraitRef, Region, Ty, TyCtxt};
-use rustc_span::symbol::{Ident, Symbol, kw};
-use rustc_span::{BytePos, Span};
+use rustc_span::{BytePos, Ident, Span, Symbol, kw};
 
 use crate::error_reporting::infer::ObligationCauseAsDiagArg;
 use crate::error_reporting::infer::need_type_info::UnderspecifiedArgKind;
@@ -517,7 +516,7 @@ impl Subdiagnostic for AddLifetimeParamsSuggestion<'_> {
                 return false;
             };
 
-            let node = self.tcx.hir_node_by_def_id(anon_reg.def_id);
+            let node = self.tcx.hir_node_by_def_id(anon_reg.scope);
             let is_impl = matches!(&node, hir::Node::ImplItem(_));
             let (generics, parent_generics) = match node {
                 hir::Node::Item(&hir::Item {
@@ -527,7 +526,7 @@ impl Subdiagnostic for AddLifetimeParamsSuggestion<'_> {
                 | hir::Node::TraitItem(&hir::TraitItem { ref generics, .. })
                 | hir::Node::ImplItem(&hir::ImplItem { ref generics, .. }) => (
                     generics,
-                    match self.tcx.parent_hir_node(self.tcx.local_def_id_to_hir_id(anon_reg.def_id))
+                    match self.tcx.parent_hir_node(self.tcx.local_def_id_to_hir_id(anon_reg.scope))
                     {
                         hir::Node::Item(hir::Item {
                             kind: hir::ItemKind::Trait(_, _, ref generics, ..),
diff --git a/compiler/rustc_trait_selection/src/errors/note_and_explain.rs b/compiler/rustc_trait_selection/src/errors/note_and_explain.rs
index cc0a637a78e..b752dbf3093 100644
--- a/compiler/rustc_trait_selection/src/errors/note_and_explain.rs
+++ b/compiler/rustc_trait_selection/src/errors/note_and_explain.rs
@@ -2,8 +2,7 @@ use rustc_errors::{Diag, EmissionGuarantee, IntoDiagArg, SubdiagMessageOp, Subdi
 use rustc_hir::def_id::LocalDefId;
 use rustc_middle::bug;
 use rustc_middle::ty::{self, TyCtxt};
-use rustc_span::Span;
-use rustc_span::symbol::kw;
+use rustc_span::{Span, kw};
 
 use crate::error_reporting::infer::nice_region_error::find_anon_type;
 use crate::fluent_generated as fluent;
@@ -40,15 +39,14 @@ impl<'a> DescriptionCtx<'a> {
                 }
             }
             ty::ReLateParam(ref fr) => {
-                if !fr.bound_region.is_named()
-                    && let Some((ty, _)) =
-                        find_anon_type(tcx, generic_param_scope, region, &fr.bound_region)
+                if !fr.kind.is_named()
+                    && let Some((ty, _)) = find_anon_type(tcx, generic_param_scope, region)
                 {
                     (Some(ty.span), "defined_here", String::new())
                 } else {
                     let scope = fr.scope.expect_local();
-                    match fr.bound_region {
-                        ty::BoundRegionKind::Named(_, name) => {
+                    match fr.kind {
+                        ty::LateParamRegionKind::Named(_, name) => {
                             let span = if let Some(param) = tcx
                                 .hir()
                                 .get_generics(scope)
@@ -64,7 +62,7 @@ impl<'a> DescriptionCtx<'a> {
                                 (Some(span), "as_defined", name.to_string())
                             }
                         }
-                        ty::BoundRegionKind::Anon => {
+                        ty::LateParamRegionKind::Anon(_) => {
                             let span = Some(tcx.def_span(scope));
                             (span, "defined_here", String::new())
                         }
diff --git a/compiler/rustc_trait_selection/src/lib.rs b/compiler/rustc_trait_selection/src/lib.rs
index 11d72106b22..1af383e9200 100644
--- a/compiler/rustc_trait_selection/src/lib.rs
+++ b/compiler/rustc_trait_selection/src/lib.rs
@@ -23,6 +23,7 @@
 #![feature(extract_if)]
 #![feature(if_let_guard)]
 #![feature(iter_intersperse)]
+#![feature(iterator_try_reduce)]
 #![feature(let_chains)]
 #![feature(never_type)]
 #![feature(rustdoc_internals)]
diff --git a/compiler/rustc_trait_selection/src/solve/delegate.rs b/compiler/rustc_trait_selection/src/solve/delegate.rs
index 97cde67799c..9b8c9ff6bb8 100644
--- a/compiler/rustc_trait_selection/src/solve/delegate.rs
+++ b/compiler/rustc_trait_selection/src/solve/delegate.rs
@@ -123,8 +123,6 @@ impl<'tcx> rustc_next_trait_solver::delegate::SolverDelegate for SolverDelegate<
             )
         });
 
-        assert_eq!(region_constraints.member_constraints, vec![]);
-
         let mut seen = FxHashSet::default();
         region_constraints
             .outlives
diff --git a/compiler/rustc_trait_selection/src/traits/coherence.rs b/compiler/rustc_trait_selection/src/traits/coherence.rs
index a98871b2d60..971d3a81102 100644
--- a/compiler/rustc_trait_selection/src/traits/coherence.rs
+++ b/compiler/rustc_trait_selection/src/traits/coherence.rs
@@ -21,8 +21,7 @@ use rustc_middle::ty::visit::{TypeSuperVisitable, TypeVisitable, TypeVisitableEx
 use rustc_middle::ty::{self, Ty, TyCtxt, TypingMode};
 pub use rustc_next_trait_solver::coherence::*;
 use rustc_next_trait_solver::solve::SolverDelegateEvalExt;
-use rustc_span::symbol::sym;
-use rustc_span::{DUMMY_SP, Span};
+use rustc_span::{DUMMY_SP, Span, sym};
 use tracing::{debug, instrument, warn};
 
 use super::ObligationCtxt;
diff --git a/compiler/rustc_trait_selection/src/traits/misc.rs b/compiler/rustc_trait_selection/src/traits/misc.rs
index d216ae72913..7a67b943e94 100644
--- a/compiler/rustc_trait_selection/src/traits/misc.rs
+++ b/compiler/rustc_trait_selection/src/traits/misc.rs
@@ -84,7 +84,7 @@ pub fn type_allowed_to_implement_copy<'tcx>(
         return Err(CopyImplementationError::HasDestructor);
     }
 
-    if impl_safety == hir::Safety::Safe && self_type.has_unsafe_fields() {
+    if impl_safety.is_safe() && self_type.has_unsafe_fields() {
         return Err(CopyImplementationError::HasUnsafeFields);
     }
 
diff --git a/compiler/rustc_trait_selection/src/traits/mod.rs b/compiler/rustc_trait_selection/src/traits/mod.rs
index 069fab6a6e6..1dcd0d0dfb8 100644
--- a/compiler/rustc_trait_selection/src/traits/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/mod.rs
@@ -447,7 +447,7 @@ pub fn normalize_param_env_or_error<'tcx>(
     // This works fairly well because trait matching does not actually care about param-env
     // TypeOutlives predicates - these are normally used by regionck.
     let outlives_predicates: Vec<_> = predicates
-        .extract_if(|predicate| {
+        .extract_if(.., |predicate| {
             matches!(predicate.kind().skip_binder(), ty::ClauseKind::TypeOutlives(..))
         })
         .collect();
@@ -599,7 +599,7 @@ pub fn try_evaluate_const<'tcx>(
                 // even though it is not something we should ever actually encounter.
                 //
                 // Array repeat expr counts are allowed to syntactically use generic parameters
-                // but must not actually depend on them in order to evalaute succesfully. This means
+                // but must not actually depend on them in order to evalaute successfully. This means
                 // that it is actually fine to evalaute them in their own environment rather than with
                 // the actually provided generic arguments.
                 tcx.dcx().delayed_bug(
diff --git a/compiler/rustc_trait_selection/src/traits/outlives_bounds.rs b/compiler/rustc_trait_selection/src/traits/outlives_bounds.rs
index 88c11e55b7a..23dabe32ff2 100644
--- a/compiler/rustc_trait_selection/src/traits/outlives_bounds.rs
+++ b/compiler/rustc_trait_selection/src/traits/outlives_bounds.rs
@@ -4,11 +4,10 @@ use rustc_infer::infer::resolve::OpportunisticRegionResolver;
 use rustc_infer::traits::query::type_op::ImpliedOutlivesBounds;
 use rustc_macros::extension;
 use rustc_middle::infer::canonical::{OriginalQueryValues, QueryRegionConstraints};
-use rustc_middle::span_bug;
 pub use rustc_middle::traits::query::OutlivesBound;
 use rustc_middle::ty::{self, ParamEnv, Ty, TypeFolder, TypeVisitableExt};
 use rustc_span::def_id::LocalDefId;
-use tracing::{debug, instrument};
+use tracing::instrument;
 
 use crate::infer::InferCtxt;
 use crate::traits::{ObligationCause, ObligationCtxt};
@@ -86,16 +85,12 @@ fn implied_outlives_bounds<'a, 'tcx>(
     bounds.retain(|bound| !bound.has_placeholders());
 
     if !constraints.is_empty() {
-        debug!(?constraints);
-        if !constraints.member_constraints.is_empty() {
-            span_bug!(span, "{:#?}", constraints.member_constraints);
-        }
-
+        let QueryRegionConstraints { outlives } = constraints;
         // Instantiation may have produced new inference variables and constraints on those
         // variables. Process these constraints.
         let ocx = ObligationCtxt::new(infcx);
         let cause = ObligationCause::misc(span, body_id);
-        for &constraint in &constraints.outlives {
+        for &constraint in &outlives {
             ocx.register_obligation(infcx.query_outlives_constraint_to_obligation(
                 constraint,
                 cause.clone(),
diff --git a/compiler/rustc_trait_selection/src/traits/project.rs b/compiler/rustc_trait_selection/src/traits/project.rs
index 5f1dbfeedfb..4bccd3450bc 100644
--- a/compiler/rustc_trait_selection/src/traits/project.rs
+++ b/compiler/rustc_trait_selection/src/traits/project.rs
@@ -17,7 +17,7 @@ use rustc_middle::ty::fold::TypeFoldable;
 use rustc_middle::ty::visit::TypeVisitableExt;
 use rustc_middle::ty::{self, Term, Ty, TyCtxt, TypingMode, Upcast};
 use rustc_middle::{bug, span_bug};
-use rustc_span::symbol::sym;
+use rustc_span::sym;
 use thin_vec::thin_vec;
 use tracing::{debug, instrument};
 
diff --git a/compiler/rustc_trait_selection/src/traits/query/type_op/mod.rs b/compiler/rustc_trait_selection/src/traits/query/type_op/mod.rs
index a618d96ce95..54fce914bb6 100644
--- a/compiler/rustc_trait_selection/src/traits/query/type_op/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/query/type_op/mod.rs
@@ -180,11 +180,8 @@ where
             span,
         )?;
         output.error_info = error_info;
-        if let Some(constraints) = output.constraints {
-            region_constraints
-                .member_constraints
-                .extend(constraints.member_constraints.iter().cloned());
-            region_constraints.outlives.extend(constraints.outlives.iter().cloned());
+        if let Some(QueryRegionConstraints { outlives }) = output.constraints {
+            region_constraints.outlives.extend(outlives.iter().cloned());
         }
         output.constraints = if region_constraints.is_empty() {
             None
diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
index 25fe43e3a0e..0462b1d9ee7 100644
--- a/compiler/rustc_trait_selection/src/traits/select/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -31,8 +31,7 @@ use rustc_middle::ty::{
     self, GenericArgsRef, PolyProjectionPredicate, Ty, TyCtxt, TypeFoldable, TypeVisitableExt,
     TypingMode, Upcast,
 };
-use rustc_span::Symbol;
-use rustc_span::symbol::sym;
+use rustc_span::{Symbol, sym};
 use tracing::{debug, instrument, trace};
 
 use self::EvaluationResult::*;
@@ -445,7 +444,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
 
         // Winnow, but record the exact outcome of evaluation, which
         // is needed for specialization. Propagate overflow if it occurs.
-        let mut candidates = candidates
+        let candidates = candidates
             .into_iter()
             .map(|c| match self.evaluate_candidate(stack, &c) {
                 Ok(eval) if eval.may_apply() => {
@@ -458,40 +457,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             .flat_map(Result::transpose)
             .collect::<Result<Vec<_>, _>>()?;
 
-        debug!(?stack, ?candidates, "winnowed to {} candidates", candidates.len());
-
-        let has_non_region_infer = stack.obligation.predicate.has_non_region_infer();
-
-        // If there are STILL multiple candidates, we can further
-        // reduce the list by dropping duplicates -- including
-        // resolving specializations.
-        if candidates.len() > 1 {
-            let mut i = 0;
-            while i < candidates.len() {
-                let should_drop_i = (0..candidates.len()).filter(|&j| i != j).any(|j| {
-                    self.candidate_should_be_dropped_in_favor_of(
-                        &candidates[i],
-                        &candidates[j],
-                        has_non_region_infer,
-                    ) == DropVictim::Yes
-                });
-                if should_drop_i {
-                    debug!(candidate = ?candidates[i], "Dropping candidate #{}/{}", i, candidates.len());
-                    candidates.swap_remove(i);
-                } else {
-                    debug!(candidate = ?candidates[i], "Retaining candidate #{}/{}", i, candidates.len());
-                    i += 1;
-
-                    // If there are *STILL* multiple candidates, give up
-                    // and report ambiguity.
-                    if i > 1 {
-                        debug!("multiple matches, ambig");
-                        return Ok(None);
-                    }
-                }
-            }
-        }
-
+        debug!(?stack, ?candidates, "{} potentially applicable candidates", candidates.len());
         // If there are *NO* candidates, then there are no impls --
         // that we know of, anyway. Note that in the case where there
         // are unbound type variables within the obligation, it might
@@ -508,13 +474,18 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             // to have emitted at least one.
             if stack.obligation.predicate.references_error() {
                 debug!(?stack.obligation.predicate, "found error type in predicate, treating as ambiguous");
-                return Ok(None);
+                Ok(None)
+            } else {
+                Err(Unimplemented)
+            }
+        } else {
+            let has_non_region_infer = stack.obligation.predicate.has_non_region_infer();
+            if let Some(candidate) = self.winnow_candidates(has_non_region_infer, candidates) {
+                self.filter_reservation_impls(candidate)
+            } else {
+                Ok(None)
             }
-            return Err(Unimplemented);
         }
-
-        // Just one candidate left.
-        self.filter_reservation_impls(candidates.pop().unwrap().candidate)
     }
 
     ///////////////////////////////////////////////////////////////////////////
@@ -1803,18 +1774,6 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
     }
 }
 
-#[derive(Debug, Copy, Clone, PartialEq, Eq)]
-enum DropVictim {
-    Yes,
-    No,
-}
-
-impl DropVictim {
-    fn drop_if(should_drop: bool) -> DropVictim {
-        if should_drop { DropVictim::Yes } else { DropVictim::No }
-    }
-}
-
 /// ## Winnowing
 ///
 /// Winnowing is the process of attempting to resolve ambiguity by
@@ -1822,131 +1781,149 @@ impl DropVictim {
 /// type variables and then we also attempt to evaluate recursive
 /// bounds to see if they are satisfied.
 impl<'tcx> SelectionContext<'_, 'tcx> {
-    /// Returns `DropVictim::Yes` if `victim` should be dropped in favor of
-    /// `other`. Generally speaking we will drop duplicate
-    /// candidates and prefer where-clause candidates.
+    /// If there are multiple ways to prove a trait goal, we make some
+    /// *fairly arbitrary* choices about which candidate is actually used.
     ///
-    /// See the comment for "SelectionCandidate" for more details.
-    #[instrument(level = "debug", skip(self))]
-    fn candidate_should_be_dropped_in_favor_of(
+    /// For more details, look at the implementation of this method :)
+    #[instrument(level = "debug", skip(self), ret)]
+    fn winnow_candidates(
         &mut self,
-        victim: &EvaluatedCandidate<'tcx>,
-        other: &EvaluatedCandidate<'tcx>,
         has_non_region_infer: bool,
-    ) -> DropVictim {
-        if victim.candidate == other.candidate {
-            return DropVictim::Yes;
+        mut candidates: Vec<EvaluatedCandidate<'tcx>>,
+    ) -> Option<SelectionCandidate<'tcx>> {
+        if candidates.len() == 1 {
+            return Some(candidates.pop().unwrap().candidate);
+        }
+
+        // We prefer trivial builtin candidates, i.e. builtin impls without any nested
+        // requirements, over all others. This is a fix for #53123 and prevents winnowing
+        // from accidentally extending the lifetime of a variable.
+        let mut trivial_builtin = candidates
+            .iter()
+            .filter(|c| matches!(c.candidate, BuiltinCandidate { has_nested: false }));
+        if let Some(_trivial) = trivial_builtin.next() {
+            // There should only ever be a single trivial builtin candidate
+            // as they would otherwise overlap.
+            debug_assert_eq!(trivial_builtin.next(), None);
+            return Some(BuiltinCandidate { has_nested: false });
         }
 
-        // Check if a bound would previously have been removed when normalizing
-        // the param_env so that it can be given the lowest priority. See
-        // #50825 for the motivation for this.
-        let is_global =
-            |cand: ty::PolyTraitPredicate<'tcx>| cand.is_global() && !cand.has_bound_vars();
+        // Before we consider where-bounds, we have to deduplicate them here and also
+        // drop where-bounds in case the same where-bound exists without bound vars.
+        // This is necessary as elaborating super-trait bounds may result in duplicates.
+        'search_victim: loop {
+            for (i, this) in candidates.iter().enumerate() {
+                let ParamCandidate(this) = this.candidate else { continue };
+                for (j, other) in candidates.iter().enumerate() {
+                    if i == j {
+                        continue;
+                    }
 
-        // (*) Prefer `BuiltinCandidate { has_nested: false }`, `PointeeCandidate`,
-        // or `DiscriminantKindCandidate` to anything else.
-        //
-        // This is a fix for #53123 and prevents winnowing from accidentally extending the
-        // lifetime of a variable.
-        match (&other.candidate, &victim.candidate) {
-            // FIXME(@jswrenn): this should probably be more sophisticated
-            (TransmutabilityCandidate, _) | (_, TransmutabilityCandidate) => DropVictim::No,
-
-            // (*)
-            (BuiltinCandidate { has_nested: false }, _) => DropVictim::Yes,
-            (_, BuiltinCandidate { has_nested: false }) => DropVictim::No,
-
-            (ParamCandidate(other), ParamCandidate(victim)) => {
-                let same_except_bound_vars = other.skip_binder().trait_ref
-                    == victim.skip_binder().trait_ref
-                    && other.skip_binder().polarity == victim.skip_binder().polarity
-                    && !other.skip_binder().trait_ref.has_escaping_bound_vars();
-                if same_except_bound_vars {
-                    // See issue #84398. In short, we can generate multiple ParamCandidates which are
-                    // the same except for unused bound vars. Just pick the one with the fewest bound vars
-                    // or the current one if tied (they should both evaluate to the same answer). This is
-                    // probably best characterized as a "hack", since we might prefer to just do our
-                    // best to *not* create essentially duplicate candidates in the first place.
-                    DropVictim::drop_if(other.bound_vars().len() <= victim.bound_vars().len())
-                } else {
-                    DropVictim::No
+                    let ParamCandidate(other) = other.candidate else { continue };
+                    if this == other {
+                        candidates.remove(j);
+                        continue 'search_victim;
+                    }
+
+                    if this.skip_binder().trait_ref == other.skip_binder().trait_ref
+                        && this.skip_binder().polarity == other.skip_binder().polarity
+                        && !this.skip_binder().trait_ref.has_escaping_bound_vars()
+                    {
+                        candidates.remove(j);
+                        continue 'search_victim;
+                    }
                 }
             }
 
-            (
-                ParamCandidate(other_cand),
-                ImplCandidate(..)
-                | AutoImplCandidate
-                | ClosureCandidate { .. }
-                | AsyncClosureCandidate
-                | AsyncFnKindHelperCandidate
-                | CoroutineCandidate
-                | FutureCandidate
-                | IteratorCandidate
-                | AsyncIteratorCandidate
-                | FnPointerCandidate { .. }
-                | BuiltinObjectCandidate
-                | BuiltinUnsizeCandidate
-                | TraitUpcastingUnsizeCandidate(_)
-                | BuiltinCandidate { .. }
-                | TraitAliasCandidate
-                | ObjectCandidate(_)
-                | ProjectionCandidate(_),
-            ) => {
-                // We have a where clause so don't go around looking
-                // for impls. Arbitrarily give param candidates priority
-                // over projection and object candidates.
-                //
-                // Global bounds from the where clause should be ignored
-                // here (see issue #50825).
-                DropVictim::drop_if(!is_global(*other_cand))
-            }
-            (ObjectCandidate(_) | ProjectionCandidate(_), ParamCandidate(victim_cand)) => {
-                // Prefer these to a global where-clause bound
-                // (see issue #50825).
-                if is_global(*victim_cand) { DropVictim::Yes } else { DropVictim::No }
+            break;
+        }
+
+        // The next highest priority is for non-global where-bounds. However, while we don't
+        // prefer global where-clauses here, we do bail with ambiguity when encountering both
+        // a global and a non-global where-clause.
+        //
+        // Our handling of where-bounds is generally fairly messy but necessary for backwards
+        // compatability, see #50825 for why we need to handle global where-bounds like this.
+        let is_global = |c: ty::PolyTraitPredicate<'tcx>| c.is_global() && !c.has_bound_vars();
+        let param_candidates = candidates
+            .iter()
+            .filter_map(|c| if let ParamCandidate(p) = c.candidate { Some(p) } else { None });
+        let mut has_global_bounds = false;
+        let mut param_candidate = None;
+        for c in param_candidates {
+            if is_global(c) {
+                has_global_bounds = true;
+            } else if param_candidate.replace(c).is_some() {
+                // Ambiguity, two potentially different where-clauses
+                return None;
             }
-            (
-                ImplCandidate(_)
-                | AutoImplCandidate
-                | ClosureCandidate { .. }
-                | AsyncClosureCandidate
-                | AsyncFnKindHelperCandidate
-                | CoroutineCandidate
-                | FutureCandidate
-                | IteratorCandidate
-                | AsyncIteratorCandidate
-                | FnPointerCandidate { .. }
-                | BuiltinObjectCandidate
-                | BuiltinUnsizeCandidate
-                | TraitUpcastingUnsizeCandidate(_)
-                | BuiltinCandidate { has_nested: true }
-                | TraitAliasCandidate,
-                ParamCandidate(victim_cand),
-            ) => {
-                // Prefer these to a global where-clause bound
-                // (see issue #50825).
-                DropVictim::drop_if(
-                    is_global(*victim_cand) && other.evaluation.must_apply_modulo_regions(),
-                )
+        }
+        if let Some(predicate) = param_candidate {
+            // Ambiguity, a global and a non-global where-bound.
+            if has_global_bounds {
+                return None;
+            } else {
+                return Some(ParamCandidate(predicate));
             }
+        }
+
+        // Prefer alias-bounds over blanket impls for rigid associated types. This is
+        // fairly arbitrary but once again necessary for backwards compatibility.
+        // If there are multiple applicable candidates which don't affect type inference,
+        // choose the one with the lowest index.
+        let alias_bound = candidates
+            .iter()
+            .filter_map(|c| if let ProjectionCandidate(i) = c.candidate { Some(i) } else { None })
+            .try_reduce(|c1, c2| if has_non_region_infer { None } else { Some(c1.min(c2)) });
+        match alias_bound {
+            Some(Some(index)) => return Some(ProjectionCandidate(index)),
+            Some(None) => {}
+            None => return None,
+        }
+
+        // Need to prioritize builtin trait object impls as `<dyn Any as Any>::type_id`
+        // should use the vtable method and not the method provided by the user-defined
+        // impl `impl<T: ?Sized> Any for T { .. }`. This really shouldn't exist but is
+        // necessary due to #57893. We again arbitrarily prefer the applicable candidate
+        // with the lowest index.
+        let object_bound = candidates
+            .iter()
+            .filter_map(|c| if let ObjectCandidate(i) = c.candidate { Some(i) } else { None })
+            .try_reduce(|c1, c2| if has_non_region_infer { None } else { Some(c1.min(c2)) });
+        match object_bound {
+            Some(Some(index)) => return Some(ObjectCandidate(index)),
+            Some(None) => {}
+            None => return None,
+        }
 
-            (ProjectionCandidate(i), ProjectionCandidate(j))
-            | (ObjectCandidate(i), ObjectCandidate(j)) => {
-                // Arbitrarily pick the lower numbered candidate for backwards
-                // compatibility reasons. Don't let this affect inference.
-                DropVictim::drop_if(i < j && !has_non_region_infer)
+        // Finally, handle overlapping user-written impls.
+        let impls = candidates.iter().filter_map(|c| {
+            if let ImplCandidate(def_id) = c.candidate {
+                Some((def_id, c.evaluation))
+            } else {
+                None
             }
-            (ObjectCandidate(_), ProjectionCandidate(_))
-            | (ProjectionCandidate(_), ObjectCandidate(_)) => {
-                bug!("Have both object and projection candidate")
+        });
+        let mut impl_candidate = None;
+        for c in impls {
+            if let Some(prev) = impl_candidate.replace(c) {
+                if self.prefer_lhs_over_victim(has_non_region_infer, c, prev) {
+                    // Ok, prefer `c` over the previous entry
+                } else if self.prefer_lhs_over_victim(has_non_region_infer, prev, c) {
+                    // Ok, keep `prev` instead of the new entry
+                    impl_candidate = Some(prev);
+                } else {
+                    // Ambiguity, two potentially different where-clauses
+                    return None;
+                }
             }
-
-            // Arbitrarily give projection and object candidates priority.
-            (
-                ObjectCandidate(_) | ProjectionCandidate(_),
-                ImplCandidate(..)
+        }
+        if let Some((def_id, _evaluation)) = impl_candidate {
+            // Don't use impl candidates which overlap with other candidates.
+            // This should pretty much only ever happen with malformed impls.
+            if candidates.iter().all(|c| match c.candidate {
+                BuiltinCandidate { has_nested: _ }
+                | TransmutabilityCandidate
                 | AutoImplCandidate
                 | ClosureCandidate { .. }
                 | AsyncClosureCandidate
@@ -1955,155 +1932,113 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
                 | FutureCandidate
                 | IteratorCandidate
                 | AsyncIteratorCandidate
-                | FnPointerCandidate { .. }
-                | BuiltinObjectCandidate
-                | BuiltinUnsizeCandidate
+                | FnPointerCandidate
+                | TraitAliasCandidate
                 | TraitUpcastingUnsizeCandidate(_)
-                | BuiltinCandidate { .. }
-                | TraitAliasCandidate,
-            ) => DropVictim::Yes,
-
-            (
-                ImplCandidate(..)
-                | AutoImplCandidate
-                | ClosureCandidate { .. }
-                | AsyncClosureCandidate
-                | AsyncFnKindHelperCandidate
-                | CoroutineCandidate
-                | FutureCandidate
-                | IteratorCandidate
-                | AsyncIteratorCandidate
-                | FnPointerCandidate { .. }
                 | BuiltinObjectCandidate
-                | BuiltinUnsizeCandidate
-                | TraitUpcastingUnsizeCandidate(_)
-                | BuiltinCandidate { .. }
-                | TraitAliasCandidate,
-                ObjectCandidate(_) | ProjectionCandidate(_),
-            ) => DropVictim::No,
-
-            (&ImplCandidate(other_def), &ImplCandidate(victim_def)) => {
-                // See if we can toss out `victim` based on specialization.
-                // While this requires us to know *for sure* that the `other` impl applies
-                // we still use modulo regions here.
-                //
-                // This is fine as specialization currently assumes that specializing
-                // impls have to be always applicable, meaning that the only allowed
-                // region constraints may be constraints also present on the default impl.
-                let tcx = self.tcx();
-                if other.evaluation.must_apply_modulo_regions()
-                    && tcx.specializes((other_def, victim_def))
-                {
-                    return DropVictim::Yes;
-                }
-
-                match tcx.impls_are_allowed_to_overlap(other_def, victim_def) {
-                    // For #33140 the impl headers must be exactly equal, the trait must not have
-                    // any associated items and there are no where-clauses.
-                    //
-                    // We can just arbitrarily drop one of the impls.
-                    Some(ty::ImplOverlapKind::FutureCompatOrderDepTraitObjects) => {
-                        assert_eq!(other.evaluation, victim.evaluation);
-                        DropVictim::Yes
-                    }
-                    // For candidates which already reference errors it doesn't really
-                    // matter what we do 🤷
-                    Some(ty::ImplOverlapKind::Permitted { marker: false }) => {
-                        DropVictim::drop_if(other.evaluation.must_apply_considering_regions())
-                    }
-                    Some(ty::ImplOverlapKind::Permitted { marker: true }) => {
-                        // Subtle: If the predicate we are evaluating has inference
-                        // variables, do *not* allow discarding candidates due to
-                        // marker trait impls.
-                        //
-                        // Without this restriction, we could end up accidentally
-                        // constraining inference variables based on an arbitrarily
-                        // chosen trait impl.
-                        //
-                        // Imagine we have the following code:
-                        //
-                        // ```rust
-                        // #[marker] trait MyTrait {}
-                        // impl MyTrait for u8 {}
-                        // impl MyTrait for bool {}
-                        // ```
-                        //
-                        // And we are evaluating the predicate `<_#0t as MyTrait>`.
-                        //
-                        // During selection, we will end up with one candidate for each
-                        // impl of `MyTrait`. If we were to discard one impl in favor
-                        // of the other, we would be left with one candidate, causing
-                        // us to "successfully" select the predicate, unifying
-                        // _#0t with (for example) `u8`.
-                        //
-                        // However, we have no reason to believe that this unification
-                        // is correct - we've essentially just picked an arbitrary
-                        // *possibility* for _#0t, and required that this be the *only*
-                        // possibility.
-                        //
-                        // Eventually, we will either:
-                        // 1) Unify all inference variables in the predicate through
-                        // some other means (e.g. type-checking of a function). We will
-                        // then be in a position to drop marker trait candidates
-                        // without constraining inference variables (since there are
-                        // none left to constrain)
-                        // 2) Be left with some unconstrained inference variables. We
-                        // will then correctly report an inference error, since the
-                        // existence of multiple marker trait impls tells us nothing
-                        // about which one should actually apply.
-                        DropVictim::drop_if(
-                            !has_non_region_infer
-                                && other.evaluation.must_apply_considering_regions(),
-                        )
-                    }
-                    None => DropVictim::No,
-                }
+                | BuiltinUnsizeCandidate => false,
+                // Non-global param candidates have already been handled, global
+                // where-bounds get ignored.
+                ParamCandidate(_) | ImplCandidate(_) => true,
+                ProjectionCandidate(_) | ObjectCandidate(_) => unreachable!(),
+            }) {
+                return Some(ImplCandidate(def_id));
+            } else {
+                return None;
             }
+        }
 
-            (AutoImplCandidate, ImplCandidate(_)) | (ImplCandidate(_), AutoImplCandidate) => {
-                DropVictim::No
-            }
+        if candidates.len() == 1 {
+            Some(candidates.pop().unwrap().candidate)
+        } else {
+            // Also try ignoring all global where-bounds and check whether we end
+            // with a unique candidate in this case.
+            let mut not_a_global_where_bound = candidates
+                .into_iter()
+                .filter(|c| !matches!(c.candidate, ParamCandidate(p) if is_global(p)));
+            not_a_global_where_bound
+                .next()
+                .map(|c| c.candidate)
+                .filter(|_| not_a_global_where_bound.next().is_none())
+        }
+    }
 
-            (AutoImplCandidate, _) | (_, AutoImplCandidate) => {
-                bug!(
-                    "default implementations shouldn't be recorded \
-                    when there are other global candidates: {:?} {:?}",
-                    other,
-                    victim
-                );
+    fn prefer_lhs_over_victim(
+        &self,
+        has_non_region_infer: bool,
+        (lhs, lhs_evaluation): (DefId, EvaluationResult),
+        (victim, victim_evaluation): (DefId, EvaluationResult),
+    ) -> bool {
+        let tcx = self.tcx();
+        // See if we can toss out `victim` based on specialization.
+        //
+        // While this requires us to know *for sure* that the `lhs` impl applies
+        // we still use modulo regions here. This is fine as specialization currently
+        // assumes that specializing impls have to be always applicable, meaning that
+        // the only allowed region constraints may be constraints also present on the default impl.
+        if lhs_evaluation.must_apply_modulo_regions() {
+            if tcx.specializes((lhs, victim)) {
+                return true;
             }
+        }
 
-            // Everything else is ambiguous
-            (
-                ImplCandidate(_)
-                | ClosureCandidate { .. }
-                | AsyncClosureCandidate
-                | AsyncFnKindHelperCandidate
-                | CoroutineCandidate
-                | FutureCandidate
-                | IteratorCandidate
-                | AsyncIteratorCandidate
-                | FnPointerCandidate { .. }
-                | BuiltinObjectCandidate
-                | BuiltinUnsizeCandidate
-                | TraitUpcastingUnsizeCandidate(_)
-                | BuiltinCandidate { has_nested: true }
-                | TraitAliasCandidate,
-                ImplCandidate(_)
-                | ClosureCandidate { .. }
-                | AsyncClosureCandidate
-                | AsyncFnKindHelperCandidate
-                | CoroutineCandidate
-                | FutureCandidate
-                | IteratorCandidate
-                | AsyncIteratorCandidate
-                | FnPointerCandidate { .. }
-                | BuiltinObjectCandidate
-                | BuiltinUnsizeCandidate
-                | TraitUpcastingUnsizeCandidate(_)
-                | BuiltinCandidate { has_nested: true }
-                | TraitAliasCandidate,
-            ) => DropVictim::No,
+        match tcx.impls_are_allowed_to_overlap(lhs, victim) {
+            // For #33140 the impl headers must be exactly equal, the trait must not have
+            // any associated items and there are no where-clauses.
+            //
+            // We can just arbitrarily drop one of the impls.
+            Some(ty::ImplOverlapKind::FutureCompatOrderDepTraitObjects) => {
+                assert_eq!(lhs_evaluation, victim_evaluation);
+                true
+            }
+            // For candidates which already reference errors it doesn't really
+            // matter what we do 🤷
+            Some(ty::ImplOverlapKind::Permitted { marker: false }) => {
+                lhs_evaluation.must_apply_considering_regions()
+            }
+            Some(ty::ImplOverlapKind::Permitted { marker: true }) => {
+                // Subtle: If the predicate we are evaluating has inference
+                // variables, do *not* allow discarding candidates due to
+                // marker trait impls.
+                //
+                // Without this restriction, we could end up accidentally
+                // constraining inference variables based on an arbitrarily
+                // chosen trait impl.
+                //
+                // Imagine we have the following code:
+                //
+                // ```rust
+                // #[marker] trait MyTrait {}
+                // impl MyTrait for u8 {}
+                // impl MyTrait for bool {}
+                // ```
+                //
+                // And we are evaluating the predicate `<_#0t as MyTrait>`.
+                //
+                // During selection, we will end up with one candidate for each
+                // impl of `MyTrait`. If we were to discard one impl in favor
+                // of the other, we would be left with one candidate, causing
+                // us to "successfully" select the predicate, unifying
+                // _#0t with (for example) `u8`.
+                //
+                // However, we have no reason to believe that this unification
+                // is correct - we've essentially just picked an arbitrary
+                // *possibility* for _#0t, and required that this be the *only*
+                // possibility.
+                //
+                // Eventually, we will either:
+                // 1) Unify all inference variables in the predicate through
+                // some other means (e.g. type-checking of a function). We will
+                // then be in a position to drop marker trait candidates
+                // without constraining inference variables (since there are
+                // none left to constrain)
+                // 2) Be left with some unconstrained inference variables. We
+                // will then correctly report an inference error, since the
+                // existence of multiple marker trait impls tells us nothing
+                // about which one should actually apply.
+                !has_non_region_infer && lhs_evaluation.must_apply_considering_regions()
+            }
+            None => false,
         }
     }
 }
diff --git a/compiler/rustc_trait_selection/src/traits/specialize/mod.rs b/compiler/rustc_trait_selection/src/traits/specialize/mod.rs
index 1430cfae51f..401b41c796d 100644
--- a/compiler/rustc_trait_selection/src/traits/specialize/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/specialize/mod.rs
@@ -483,15 +483,19 @@ fn report_negative_positive_conflict<'tcx>(
     negative_impl_def_id: DefId,
     positive_impl_def_id: DefId,
 ) -> ErrorGuaranteed {
-    tcx.dcx()
-        .create_err(NegativePositiveConflict {
-            impl_span: tcx.def_span(local_impl_def_id),
-            trait_desc: overlap.trait_ref,
-            self_ty: overlap.self_ty,
-            negative_impl_span: tcx.span_of_impl(negative_impl_def_id),
-            positive_impl_span: tcx.span_of_impl(positive_impl_def_id),
-        })
-        .emit()
+    let mut diag = tcx.dcx().create_err(NegativePositiveConflict {
+        impl_span: tcx.def_span(local_impl_def_id),
+        trait_desc: overlap.trait_ref,
+        self_ty: overlap.self_ty,
+        negative_impl_span: tcx.span_of_impl(negative_impl_def_id),
+        positive_impl_span: tcx.span_of_impl(positive_impl_def_id),
+    });
+
+    for cause in &overlap.intercrate_ambiguity_causes {
+        cause.add_intercrate_ambiguity_hint(&mut diag);
+    }
+
+    diag.emit()
 }
 
 fn report_conflicting_impls<'tcx>(
diff --git a/compiler/rustc_transmute/src/layout/tree.rs b/compiler/rustc_transmute/src/layout/tree.rs
index 83463babc4f..6ce9969aefe 100644
--- a/compiler/rustc_transmute/src/layout/tree.rs
+++ b/compiler/rustc_transmute/src/layout/tree.rs
@@ -338,16 +338,11 @@ pub(crate) mod rustc {
                 };
 
             match layout.variants() {
+                Variants::Empty => Ok(Self::uninhabited()),
                 Variants::Single { index } => {
-                    // Hilariously, `Single` is used even for 0-variant enums;
-                    // `index` is just junk in that case.
-                    if ty.ty_adt_def().unwrap().variants().is_empty() {
-                        Ok(Self::uninhabited())
-                    } else {
-                        // `Variants::Single` on enums with variants denotes that
-                        // the enum delegates its layout to the variant at `index`.
-                        layout_of_variant(*index, None)
-                    }
+                    // `Variants::Single` on enums with variants denotes that
+                    // the enum delegates its layout to the variant at `index`.
+                    layout_of_variant(*index, None)
                 }
                 Variants::Multiple { tag, tag_encoding, tag_field, .. } => {
                     // `Variants::Multiple` denotes an enum with multiple
@@ -500,6 +495,10 @@ pub(crate) mod rustc {
         (ty, layout): (Ty<'tcx>, Layout<'tcx>),
         i: FieldIdx,
     ) -> Ty<'tcx> {
+        // We cannot use `ty_and_layout_field` to retrieve the field type, since
+        // `ty_and_layout_field` erases regions in the returned type. We must
+        // not erase regions here, since we may need to ultimately emit outlives
+        // obligations as a consequence of the transmutability analysis.
         match ty.kind() {
             ty::Adt(def, args) => {
                 match layout.variants {
@@ -507,6 +506,7 @@ pub(crate) mod rustc {
                         let field = &def.variant(index).fields[i];
                         field.ty(cx.tcx(), args)
                     }
+                    Variants::Empty => panic!("there is no field in Variants::Empty types"),
                     // Discriminant field for enums (where applicable).
                     Variants::Multiple { tag, .. } => {
                         assert_eq!(i.as_usize(), 0);
diff --git a/compiler/rustc_transmute/src/lib.rs b/compiler/rustc_transmute/src/lib.rs
index f7651e49cdd..ad86813c87e 100644
--- a/compiler/rustc_transmute/src/lib.rs
+++ b/compiler/rustc_transmute/src/lib.rs
@@ -131,7 +131,7 @@ mod rustc {
             c: Const<'tcx>,
         ) -> Option<Self> {
             use rustc_middle::ty::ScalarInt;
-            use rustc_span::symbol::sym;
+            use rustc_span::sym;
 
             let Some((cv, ty)) = c.try_to_valtree() else {
                 return None;
diff --git a/compiler/rustc_ty_utils/src/assoc.rs b/compiler/rustc_ty_utils/src/assoc.rs
index f97e8d48c8e..8f9f66db1bd 100644
--- a/compiler/rustc_ty_utils/src/assoc.rs
+++ b/compiler/rustc_ty_utils/src/assoc.rs
@@ -6,7 +6,7 @@ use rustc_hir::intravisit::{self, Visitor};
 use rustc_middle::query::Providers;
 use rustc_middle::ty::{self, ImplTraitInTraitData, TyCtxt};
 use rustc_middle::{bug, span_bug};
-use rustc_span::symbol::kw;
+use rustc_span::kw;
 
 pub(crate) fn provide(providers: &mut Providers) {
     *providers = Providers {
diff --git a/compiler/rustc_ty_utils/src/layout.rs b/compiler/rustc_ty_utils/src/layout.rs
index 0d656f1b63b..a3b2ed07d4b 100644
--- a/compiler/rustc_ty_utils/src/layout.rs
+++ b/compiler/rustc_ty_utils/src/layout.rs
@@ -23,8 +23,7 @@ use rustc_middle::ty::{
     TypeVisitableExt,
 };
 use rustc_session::{DataTypeKind, FieldInfo, FieldKind, SizeKind, VariantInfo};
-use rustc_span::sym;
-use rustc_span::symbol::Symbol;
+use rustc_span::{Symbol, sym};
 use tracing::{debug, instrument, trace};
 use {rustc_abi as abi, rustc_hir as hir};
 
@@ -1105,15 +1104,13 @@ fn variant_info_for_adt<'tcx>(
     };
 
     match layout.variants {
+        Variants::Empty => (vec![], None),
+
         Variants::Single { index } => {
-            if !adt_def.variants().is_empty() && layout.fields != FieldsShape::Primitive {
-                debug!("print-type-size `{:#?}` variant {}", layout, adt_def.variant(index).name);
-                let variant_def = &adt_def.variant(index);
-                let fields: Vec<_> = variant_def.fields.iter().map(|f| f.name).collect();
-                (vec![build_variant_info(Some(variant_def.name), &fields, layout)], None)
-            } else {
-                (vec![], None)
-            }
+            debug!("print-type-size `{:#?}` variant {}", layout, adt_def.variant(index).name);
+            let variant_def = &adt_def.variant(index);
+            let fields: Vec<_> = variant_def.fields.iter().map(|f| f.name).collect();
+            (vec![build_variant_info(Some(variant_def.name), &fields, layout)], None)
         }
 
         Variants::Multiple { tag, ref tag_encoding, .. } => {
diff --git a/compiler/rustc_ty_utils/src/layout/invariant.rs b/compiler/rustc_ty_utils/src/layout/invariant.rs
index f39b87622f4..8d5403ed324 100644
--- a/compiler/rustc_ty_utils/src/layout/invariant.rs
+++ b/compiler/rustc_ty_utils/src/layout/invariant.rs
@@ -241,63 +241,81 @@ pub(super) fn layout_sanity_check<'tcx>(cx: &LayoutCx<'tcx>, layout: &TyAndLayou
 
     check_layout_abi(cx, layout);
 
-    if let Variants::Multiple { variants, tag, tag_encoding, .. } = &layout.variants {
-        if let TagEncoding::Niche { niche_start, untagged_variant, niche_variants } = tag_encoding {
-            let niche_size = tag.size(cx);
-            assert!(*niche_start <= niche_size.unsigned_int_max());
-            for (idx, variant) in variants.iter_enumerated() {
-                // Ensure all inhabited variants are accounted for.
-                if !variant.is_uninhabited() {
-                    assert!(idx == *untagged_variant || niche_variants.contains(&idx));
-                }
-            }
+    match &layout.variants {
+        Variants::Empty => {
+            assert!(layout.is_uninhabited());
         }
-        for variant in variants.iter() {
-            // No nested "multiple".
-            assert_matches!(variant.variants, Variants::Single { .. });
-            // Variants should have the same or a smaller size as the full thing,
-            // and same for alignment.
-            if variant.size > layout.size {
-                bug!(
-                    "Type with size {} bytes has variant with size {} bytes: {layout:#?}",
-                    layout.size.bytes(),
-                    variant.size.bytes(),
-                )
+        Variants::Single { index } => {
+            if let Some(variants) = layout.ty.variant_range(tcx) {
+                assert!(variants.contains(index));
+            } else {
+                // Types without variants use `0` as dummy variant index.
+                assert!(index.as_u32() == 0);
             }
-            if variant.align.abi > layout.align.abi {
-                bug!(
-                    "Type with alignment {} bytes has variant with alignment {} bytes: {layout:#?}",
-                    layout.align.abi.bytes(),
-                    variant.align.abi.bytes(),
-                )
-            }
-            // Skip empty variants.
-            if variant.size == Size::ZERO || variant.fields.count() == 0 || variant.is_uninhabited()
+        }
+        Variants::Multiple { variants, tag, tag_encoding, .. } => {
+            if let TagEncoding::Niche { niche_start, untagged_variant, niche_variants } =
+                tag_encoding
             {
-                // These are never actually accessed anyway, so we can skip the coherence check
-                // for them. They also fail that check, since they have
-                // `Aggregate`/`Uninhabited` ABI even when the main type is
-                // `Scalar`/`ScalarPair`. (Note that sometimes, variants with fields have size
-                // 0, and sometimes, variants without fields have non-0 size.)
-                continue;
+                let niche_size = tag.size(cx);
+                assert!(*niche_start <= niche_size.unsigned_int_max());
+                for (idx, variant) in variants.iter_enumerated() {
+                    // Ensure all inhabited variants are accounted for.
+                    if !variant.is_uninhabited() {
+                        assert!(idx == *untagged_variant || niche_variants.contains(&idx));
+                    }
+                }
             }
-            // The top-level ABI and the ABI of the variants should be coherent.
-            let scalar_coherent =
-                |s1: Scalar, s2: Scalar| s1.size(cx) == s2.size(cx) && s1.align(cx) == s2.align(cx);
-            let abi_coherent = match (layout.backend_repr, variant.backend_repr) {
-                (BackendRepr::Scalar(s1), BackendRepr::Scalar(s2)) => scalar_coherent(s1, s2),
-                (BackendRepr::ScalarPair(a1, b1), BackendRepr::ScalarPair(a2, b2)) => {
-                    scalar_coherent(a1, a2) && scalar_coherent(b1, b2)
+            for variant in variants.iter() {
+                // No nested "multiple".
+                assert_matches!(variant.variants, Variants::Single { .. });
+                // Variants should have the same or a smaller size as the full thing,
+                // and same for alignment.
+                if variant.size > layout.size {
+                    bug!(
+                        "Type with size {} bytes has variant with size {} bytes: {layout:#?}",
+                        layout.size.bytes(),
+                        variant.size.bytes(),
+                    )
+                }
+                if variant.align.abi > layout.align.abi {
+                    bug!(
+                        "Type with alignment {} bytes has variant with alignment {} bytes: {layout:#?}",
+                        layout.align.abi.bytes(),
+                        variant.align.abi.bytes(),
+                    )
+                }
+                // Skip empty variants.
+                if variant.size == Size::ZERO
+                    || variant.fields.count() == 0
+                    || variant.is_uninhabited()
+                {
+                    // These are never actually accessed anyway, so we can skip the coherence check
+                    // for them. They also fail that check, since they have
+                    // `Aggregate`/`Uninhabited` ABI even when the main type is
+                    // `Scalar`/`ScalarPair`. (Note that sometimes, variants with fields have size
+                    // 0, and sometimes, variants without fields have non-0 size.)
+                    continue;
+                }
+                // The top-level ABI and the ABI of the variants should be coherent.
+                let scalar_coherent = |s1: Scalar, s2: Scalar| {
+                    s1.size(cx) == s2.size(cx) && s1.align(cx) == s2.align(cx)
+                };
+                let abi_coherent = match (layout.backend_repr, variant.backend_repr) {
+                    (BackendRepr::Scalar(s1), BackendRepr::Scalar(s2)) => scalar_coherent(s1, s2),
+                    (BackendRepr::ScalarPair(a1, b1), BackendRepr::ScalarPair(a2, b2)) => {
+                        scalar_coherent(a1, a2) && scalar_coherent(b1, b2)
+                    }
+                    (BackendRepr::Uninhabited, _) => true,
+                    (BackendRepr::Memory { .. }, _) => true,
+                    _ => false,
+                };
+                if !abi_coherent {
+                    bug!(
+                        "Variant ABI is incompatible with top-level ABI:\nvariant={:#?}\nTop-level: {layout:#?}",
+                        variant
+                    );
                 }
-                (BackendRepr::Uninhabited, _) => true,
-                (BackendRepr::Memory { .. }, _) => true,
-                _ => false,
-            };
-            if !abi_coherent {
-                bug!(
-                    "Variant ABI is incompatible with top-level ABI:\nvariant={:#?}\nTop-level: {layout:#?}",
-                    variant
-                );
             }
         }
     }
diff --git a/compiler/rustc_type_ir/src/elaborate.rs b/compiler/rustc_type_ir/src/elaborate.rs
index 0d574445df8..923b74abdfd 100644
--- a/compiler/rustc_type_ir/src/elaborate.rs
+++ b/compiler/rustc_type_ir/src/elaborate.rs
@@ -72,7 +72,7 @@ impl<I: Interner> Elaboratable<I> for ClauseWithSupertraitSpan<I> {
         _parent_trait_pred: crate::Binder<I, crate::TraitPredicate<I>>,
         _index: usize,
     ) -> Self {
-        ClauseWithSupertraitSpan { pred: clause.as_predicate(), supertrait_span: supertrait_span }
+        ClauseWithSupertraitSpan { pred: clause.as_predicate(), supertrait_span }
     }
 }
 
diff --git a/compiler/rustc_type_ir/src/inherent.rs b/compiler/rustc_type_ir/src/inherent.rs
index f45c94127bd..2db40accda3 100644
--- a/compiler/rustc_type_ir/src/inherent.rs
+++ b/compiler/rustc_type_ir/src/inherent.rs
@@ -543,7 +543,7 @@ pub trait AdtDef<I: Interner>: Copy + Debug + Hash + Eq {
 }
 
 pub trait ParamEnv<I: Interner>: Copy + Debug + Hash + Eq + TypeFoldable<I> {
-    fn caller_bounds(self) -> impl IntoIterator<Item = I::Clause>;
+    fn caller_bounds(self) -> impl SliceLike<Item = I::Clause>;
 }
 
 pub trait Features<I: Interner>: Copy {
diff --git a/compiler/stable_mir/src/abi.rs b/compiler/stable_mir/src/abi.rs
index 2ac30b5aff1..17e6a852022 100644
--- a/compiler/stable_mir/src/abi.rs
+++ b/compiler/stable_mir/src/abi.rs
@@ -180,6 +180,9 @@ impl FieldsShape {
 
 #[derive(Clone, Debug, PartialEq, Eq, Hash, Serialize)]
 pub enum VariantsShape {
+    /// A type with no valid variants. Must be uninhabited.
+    Empty,
+
     /// Single enum variants, structs/tuples, unions, and all non-ADTs.
     Single { index: VariantIdx },