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-rw-r--r--compiler/rustc_ast/src/ast.rs101
-rw-r--r--compiler/rustc_ast/src/util/literal.rs6
-rw-r--r--compiler/rustc_ast_ir/Cargo.toml6
-rw-r--r--compiler/rustc_ast_ir/src/lib.rs210
-rw-r--r--compiler/rustc_ast_lowering/Cargo.toml1
-rw-r--r--compiler/rustc_ast_lowering/src/expr.rs22
-rw-r--r--compiler/rustc_ast_lowering/src/index.rs2
-rw-r--r--compiler/rustc_ast_lowering/src/item.rs4
-rw-r--r--compiler/rustc_ast_lowering/src/lib.rs2
-rw-r--r--compiler/rustc_ast_passes/messages.ftl4
-rw-r--r--compiler/rustc_ast_passes/src/ast_validation.rs47
-rw-r--r--compiler/rustc_ast_passes/src/errors.rs20
-rw-r--r--compiler/rustc_attr_data_structures/Cargo.toml16
-rw-r--r--compiler/rustc_attr_data_structures/src/lints.rs16
-rw-r--r--compiler/rustc_attr_parsing/Cargo.toml1
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/allow_unstable.rs2
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/body.rs15
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/cfg.rs3
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/cfg_old.rs2
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/codegen_attrs.rs10
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/confusables.rs2
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/deprecation.rs2
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/dummy.rs2
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/inline.rs4
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/link_attrs.rs4
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/lint_helpers.rs2
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/loop_match.rs2
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/macro_attrs.rs2
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/mod.rs3
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/must_use.rs2
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/no_implicit_prelude.rs2
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/non_exhaustive.rs2
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/path.rs2
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/proc_macro_attrs.rs2
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/repr.rs2
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/rustc_internal.rs2
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/semantics.rs2
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/stability.rs9
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/test_attrs.rs4
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/traits.rs2
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/transparency.rs2
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/util.rs2
-rw-r--r--compiler/rustc_attr_parsing/src/context.rs88
-rw-r--r--compiler/rustc_attr_parsing/src/lib.rs10
-rw-r--r--compiler/rustc_attr_parsing/src/lints.rs2
-rw-r--r--compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs43
-rw-r--r--compiler/rustc_borrowck/src/diagnostics/mod.rs16
-rw-r--r--compiler/rustc_borrowck/src/region_infer/mod.rs2
-rw-r--r--compiler/rustc_borrowck/src/type_check/input_output.rs1
-rw-r--r--compiler/rustc_borrowck/src/type_check/mod.rs110
-rw-r--r--compiler/rustc_borrowck/src/type_check/relate_tys.rs4
-rw-r--r--compiler/rustc_builtin_macros/Cargo.toml1
-rw-r--r--compiler/rustc_builtin_macros/src/deriving/generic/mod.rs2
-rw-r--r--compiler/rustc_builtin_macros/src/proc_macro_harness.rs2
-rw-r--r--compiler/rustc_codegen_cranelift/scripts/setup_rust_fork.sh1
-rwxr-xr-xcompiler/rustc_codegen_cranelift/scripts/test_rustc_tests.sh2
-rw-r--r--compiler/rustc_codegen_gcc/build_system/src/abi_test.rs2
-rw-r--r--compiler/rustc_codegen_gcc/build_system/src/fuzz.rs8
-rw-r--r--compiler/rustc_codegen_gcc/build_system/src/test.rs7
-rw-r--r--compiler/rustc_codegen_gcc/messages.ftl2
-rw-r--r--compiler/rustc_codegen_gcc/patches/0001-Add-stdarch-Cargo.toml-for-testing.patch23
-rw-r--r--compiler/rustc_codegen_gcc/rust-toolchain2
-rw-r--r--compiler/rustc_codegen_gcc/src/allocator.rs14
-rw-r--r--compiler/rustc_codegen_gcc/src/attributes.rs4
-rw-r--r--compiler/rustc_codegen_gcc/src/builder.rs41
-rw-r--r--compiler/rustc_codegen_gcc/src/callee.rs2
-rw-r--r--compiler/rustc_codegen_gcc/src/debuginfo.rs3
-rw-r--r--compiler/rustc_codegen_gcc/src/errors.rs4
-rw-r--r--compiler/rustc_codegen_gcc/src/int.rs76
-rw-r--r--compiler/rustc_codegen_gcc/src/intrinsic/archs.rs60
-rw-r--r--compiler/rustc_codegen_gcc/src/intrinsic/mod.rs9
-rw-r--r--compiler/rustc_codegen_gcc/src/intrinsic/simd.rs81
-rw-r--r--compiler/rustc_codegen_gcc/src/lib.rs6
-rw-r--r--compiler/rustc_codegen_gcc/tests/failing-lto-tests.txt2
-rw-r--r--compiler/rustc_codegen_gcc/tests/failing-run-make-tests.txt1
-rw-r--r--compiler/rustc_codegen_gcc/tests/failing-ui-tests.txt8
-rw-r--r--compiler/rustc_codegen_gcc/tools/cspell_dicts/rustc_codegen_gcc.txt3
-rw-r--r--compiler/rustc_codegen_llvm/Cargo.toml6
-rw-r--r--compiler/rustc_codegen_llvm/src/attributes.rs2
-rw-r--r--compiler/rustc_codegen_llvm/src/base.rs12
-rw-r--r--compiler/rustc_codegen_llvm/src/builder.rs25
-rw-r--r--compiler/rustc_codegen_llvm/src/callee.rs2
-rw-r--r--compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs47
-rw-r--r--compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/covfun.rs29
-rw-r--r--compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/spans.rs28
-rw-r--r--compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs62
-rw-r--r--compiler/rustc_codegen_llvm/src/debuginfo/mod.rs36
-rw-r--r--compiler/rustc_codegen_llvm/src/llvm/ffi.rs11
-rw-r--r--compiler/rustc_codegen_ssa/Cargo.toml1
-rw-r--r--compiler/rustc_codegen_ssa/src/back/link.rs5
-rw-r--r--compiler/rustc_codegen_ssa/src/back/symbol_export.rs2
-rw-r--r--compiler/rustc_codegen_ssa/src/back/write.rs4
-rw-r--r--compiler/rustc_codegen_ssa/src/base.rs2
-rw-r--r--compiler/rustc_codegen_ssa/src/codegen_attrs.rs536
-rw-r--r--compiler/rustc_codegen_ssa/src/mir/block.rs73
-rw-r--r--compiler/rustc_codegen_ssa/src/mir/naked_asm.rs2
-rw-r--r--compiler/rustc_codegen_ssa/src/target_features.rs2
-rw-r--r--compiler/rustc_codegen_ssa/src/traits/builder.rs12
-rw-r--r--compiler/rustc_codegen_ssa/src/traits/debuginfo.rs2
-rw-r--r--compiler/rustc_const_eval/Cargo.toml1
-rw-r--r--compiler/rustc_const_eval/src/check_consts/check.rs15
-rw-r--r--compiler/rustc_const_eval/src/check_consts/mod.rs5
-rw-r--r--compiler/rustc_const_eval/src/interpret/call.rs10
-rw-r--r--compiler/rustc_const_eval/src/interpret/eval_context.rs6
-rw-r--r--compiler/rustc_const_eval/src/interpret/memory.rs8
-rw-r--r--compiler/rustc_const_eval/src/interpret/operand.rs25
-rw-r--r--compiler/rustc_const_eval/src/interpret/place.rs5
-rw-r--r--compiler/rustc_const_eval/src/interpret/projection.rs9
-rw-r--r--compiler/rustc_const_eval/src/interpret/stack.rs6
-rw-r--r--compiler/rustc_const_eval/src/interpret/step.rs22
-rw-r--r--compiler/rustc_const_eval/src/interpret/util.rs102
-rw-r--r--compiler/rustc_const_eval/src/interpret/visitor.rs15
-rw-r--r--compiler/rustc_const_eval/src/lib.rs1
-rw-r--r--compiler/rustc_const_eval/src/util/caller_location.rs10
-rw-r--r--compiler/rustc_const_eval/src/util/type_name.rs24
-rw-r--r--compiler/rustc_driver_impl/Cargo.toml2
-rw-r--r--compiler/rustc_error_codes/src/error_codes/E0562.md9
-rw-r--r--compiler/rustc_errors/Cargo.toml3
-rw-r--r--compiler/rustc_errors/src/diagnostic_impls.rs2
-rw-r--r--compiler/rustc_errors/src/emitter.rs144
-rw-r--r--compiler/rustc_errors/src/lib.rs11
-rw-r--r--compiler/rustc_expand/Cargo.toml1
-rw-r--r--compiler/rustc_expand/src/base.rs3
-rw-r--r--compiler/rustc_expand/src/expand.rs3
-rw-r--r--compiler/rustc_expand/src/mbe/macro_rules.rs3
-rw-r--r--compiler/rustc_feature/Cargo.toml2
-rw-r--r--compiler/rustc_feature/src/builtin_attrs.rs9
-rw-r--r--compiler/rustc_feature/src/removed.rs2
-rw-r--r--compiler/rustc_feature/src/unstable.rs2
-rw-r--r--compiler/rustc_hir/Cargo.toml2
-rw-r--r--compiler/rustc_hir/src/attrs/data_structures.rs (renamed from compiler/rustc_attr_data_structures/src/attributes.rs)15
-rw-r--r--compiler/rustc_hir/src/attrs/encode_cross_crate.rs (renamed from compiler/rustc_attr_data_structures/src/encode_cross_crate.rs)4
-rw-r--r--compiler/rustc_hir/src/attrs/mod.rs54
-rw-r--r--compiler/rustc_hir/src/attrs/pretty_printing.rs (renamed from compiler/rustc_attr_data_structures/src/lib.rs)67
-rw-r--r--compiler/rustc_hir/src/def.rs4
-rw-r--r--compiler/rustc_hir/src/hir.rs27
-rw-r--r--compiler/rustc_hir/src/intravisit.rs16
-rw-r--r--compiler/rustc_hir/src/lib.rs5
-rw-r--r--compiler/rustc_hir/src/lints.rs26
-rw-r--r--compiler/rustc_hir/src/stability.rs (renamed from compiler/rustc_attr_data_structures/src/stability.rs)3
-rw-r--r--compiler/rustc_hir/src/stable_hash_impls.rs6
-rw-r--r--compiler/rustc_hir/src/version.rs (renamed from compiler/rustc_attr_data_structures/src/version.rs)2
-rw-r--r--compiler/rustc_hir_analysis/Cargo.toml1
-rw-r--r--compiler/rustc_hir_analysis/src/check/check.rs14
-rw-r--r--compiler/rustc_hir_analysis/src/check/compare_impl_item.rs20
-rw-r--r--compiler/rustc_hir_analysis/src/check/entry.rs4
-rw-r--r--compiler/rustc_hir_analysis/src/check/mod.rs2
-rw-r--r--compiler/rustc_hir_analysis/src/coherence/inherent_impls.rs3
-rw-r--r--compiler/rustc_hir_analysis/src/collect.rs4
-rw-r--r--compiler/rustc_hir_analysis/src/collect/generics_of.rs212
-rw-r--r--compiler/rustc_hir_analysis/src/collect/item_bounds.rs10
-rw-r--r--compiler/rustc_hir_analysis/src/collect/predicates_of.rs3
-rw-r--r--compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs2
-rw-r--r--compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs4
-rw-r--r--compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs14
-rw-r--r--compiler/rustc_hir_pretty/Cargo.toml1
-rw-r--r--compiler/rustc_hir_pretty/src/lib.rs2
-rw-r--r--compiler/rustc_hir_typeck/Cargo.toml1
-rw-r--r--compiler/rustc_hir_typeck/src/closure.rs5
-rw-r--r--compiler/rustc_hir_typeck/src/coercion.rs12
-rw-r--r--compiler/rustc_hir_typeck/src/expr.rs4
-rw-r--r--compiler/rustc_hir_typeck/src/fallback.rs3
-rw-r--r--compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs25
-rw-r--r--compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs8
-rw-r--r--compiler/rustc_hir_typeck/src/lib.rs21
-rw-r--r--compiler/rustc_hir_typeck/src/loops.rs54
-rw-r--r--compiler/rustc_hir_typeck/src/method/confirm.rs30
-rw-r--r--compiler/rustc_hir_typeck/src/method/mod.rs21
-rw-r--r--compiler/rustc_hir_typeck/src/method/probe.rs2
-rw-r--r--compiler/rustc_hir_typeck/src/method/suggest.rs12
-rw-r--r--compiler/rustc_hir_typeck/src/naked_functions.rs4
-rw-r--r--compiler/rustc_hir_typeck/src/typeck_root_ctxt.rs24
-rw-r--r--compiler/rustc_hir_typeck/src/upvar.rs4
-rw-r--r--compiler/rustc_index/Cargo.toml2
-rw-r--r--compiler/rustc_index_macros/Cargo.toml7
-rw-r--r--compiler/rustc_infer/src/infer/at.rs2
-rw-r--r--compiler/rustc_infer/src/infer/canonical/canonicalizer.rs8
-rw-r--r--compiler/rustc_infer/src/infer/canonical/instantiate.rs4
-rw-r--r--compiler/rustc_infer/src/infer/canonical/query_response.rs31
-rw-r--r--compiler/rustc_infer/src/infer/context.rs4
-rw-r--r--compiler/rustc_infer/src/infer/lexical_region_resolve/mod.rs234
-rw-r--r--compiler/rustc_infer/src/infer/mod.rs71
-rw-r--r--compiler/rustc_infer/src/infer/outlives/mod.rs8
-rw-r--r--compiler/rustc_infer/src/infer/outlives/obligations.rs3
-rw-r--r--compiler/rustc_infer/src/infer/region_constraints/leak_check.rs29
-rw-r--r--compiler/rustc_infer/src/infer/region_constraints/mod.rs50
-rw-r--r--compiler/rustc_infer/src/infer/relate/generalize.rs36
-rw-r--r--compiler/rustc_infer/src/infer/relate/higher_ranked.rs4
-rw-r--r--compiler/rustc_infer/src/infer/snapshot/undo_log.rs8
-rw-r--r--compiler/rustc_interface/src/passes.rs8
-rw-r--r--compiler/rustc_interface/src/tests.rs4
-rw-r--r--compiler/rustc_lint/Cargo.toml1
-rw-r--r--compiler/rustc_lint/messages.ftl6
-rw-r--r--compiler/rustc_lint/src/builtin.rs4
-rw-r--r--compiler/rustc_lint/src/context.rs23
-rw-r--r--compiler/rustc_lint/src/dangling.rs152
-rw-r--r--compiler/rustc_lint/src/default_could_be_derived.rs3
-rw-r--r--compiler/rustc_lint/src/foreign_modules.rs3
-rw-r--r--compiler/rustc_lint/src/lints.rs16
-rw-r--r--compiler/rustc_lint/src/nonstandard_style.rs4
-rw-r--r--compiler/rustc_lint/src/pass_by_value.rs4
-rw-r--r--compiler/rustc_lint/src/types/literal.rs8
-rw-r--r--compiler/rustc_lint/src/unused.rs4
-rw-r--r--compiler/rustc_lint_defs/src/builtin.rs1
-rw-r--r--compiler/rustc_llvm/Cargo.toml2
-rw-r--r--compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp26
-rw-r--r--compiler/rustc_macros/src/lib.rs2
-rw-r--r--compiler/rustc_metadata/Cargo.toml1
-rw-r--r--compiler/rustc_metadata/src/creader.rs25
-rw-r--r--compiler/rustc_metadata/src/native_libs.rs3
-rw-r--r--compiler/rustc_metadata/src/rmeta/decoder.rs8
-rw-r--r--compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs31
-rw-r--r--compiler/rustc_metadata/src/rmeta/def_path_hash_map.rs5
-rw-r--r--compiler/rustc_metadata/src/rmeta/encoder.rs3
-rw-r--r--compiler/rustc_metadata/src/rmeta/mod.rs45
-rw-r--r--compiler/rustc_metadata/src/rmeta/parameterized.rs166
-rw-r--r--compiler/rustc_middle/Cargo.toml1
-rw-r--r--compiler/rustc_middle/src/arena.rs2
-rw-r--r--compiler/rustc_middle/src/hir/map.rs14
-rw-r--r--compiler/rustc_middle/src/hir/mod.rs68
-rw-r--r--compiler/rustc_middle/src/lib.rs1
-rw-r--r--compiler/rustc_middle/src/middle/codegen_fn_attrs.rs2
-rw-r--r--compiler/rustc_middle/src/middle/stability.rs12
-rw-r--r--compiler/rustc_middle/src/mir/interpret/error.rs41
-rw-r--r--compiler/rustc_middle/src/mir/mod.rs3
-rw-r--r--compiler/rustc_middle/src/mir/mono.rs2
-rw-r--r--compiler/rustc_middle/src/mir/pretty.rs40
-rw-r--r--compiler/rustc_middle/src/mir/visit.rs34
-rw-r--r--compiler/rustc_middle/src/query/erase.rs14
-rw-r--r--compiler/rustc_middle/src/query/mod.rs23
-rw-r--r--compiler/rustc_middle/src/ty/adt.rs4
-rw-r--r--compiler/rustc_middle/src/ty/assoc.rs3
-rw-r--r--compiler/rustc_middle/src/ty/codec.rs3
-rw-r--r--compiler/rustc_middle/src/ty/consts.rs14
-rw-r--r--compiler/rustc_middle/src/ty/context.rs8
-rw-r--r--compiler/rustc_middle/src/ty/error.rs24
-rw-r--r--compiler/rustc_middle/src/ty/fold.rs24
-rw-r--r--compiler/rustc_middle/src/ty/generic_args.rs29
-rw-r--r--compiler/rustc_middle/src/ty/instance.rs8
-rw-r--r--compiler/rustc_middle/src/ty/mod.rs189
-rw-r--r--compiler/rustc_middle/src/ty/parameterized.rs155
-rw-r--r--compiler/rustc_middle/src/ty/predicate.rs12
-rw-r--r--compiler/rustc_middle/src/ty/print/mod.rs44
-rw-r--r--compiler/rustc_middle/src/ty/print/pretty.rs912
-rw-r--r--compiler/rustc_middle/src/ty/region.rs20
-rw-r--r--compiler/rustc_middle/src/ty/structural_impls.rs60
-rw-r--r--compiler/rustc_middle/src/ty/sty.rs12
-rw-r--r--compiler/rustc_middle/src/ty/typeck_results.rs6
-rw-r--r--compiler/rustc_mir_build/Cargo.toml2
-rw-r--r--compiler/rustc_mir_build/messages.ftl2
-rw-r--r--compiler/rustc_mir_build/src/builder/expr/as_operand.rs4
-rw-r--r--compiler/rustc_mir_build/src/check_tail_calls.rs77
-rw-r--r--compiler/rustc_mir_build/src/errors.rs4
-rw-r--r--compiler/rustc_mir_build/src/thir/cx/expr.rs7
-rw-r--r--compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs3
-rw-r--r--compiler/rustc_mir_dataflow/src/impls/initialized.rs3
-rw-r--r--compiler/rustc_mir_transform/Cargo.toml1
-rw-r--r--compiler/rustc_mir_transform/src/check_inline.rs2
-rw-r--r--compiler/rustc_mir_transform/src/coverage/mappings.rs20
-rw-r--r--compiler/rustc_mir_transform/src/coverage/query.rs3
-rw-r--r--compiler/rustc_mir_transform/src/coverage/spans.rs52
-rw-r--r--compiler/rustc_mir_transform/src/cross_crate_inline.rs2
-rw-r--r--compiler/rustc_mir_transform/src/ctfe_limit.rs2
-rw-r--r--compiler/rustc_mir_transform/src/elaborate_drop.rs58
-rw-r--r--compiler/rustc_mir_transform/src/inline.rs2
-rw-r--r--compiler/rustc_mir_transform/src/simplify.rs1
-rw-r--r--compiler/rustc_mir_transform/src/sroa.rs6
-rw-r--r--compiler/rustc_mir_transform/src/validate.rs2
-rw-r--r--compiler/rustc_monomorphize/Cargo.toml1
-rw-r--r--compiler/rustc_monomorphize/src/collector.rs2
-rw-r--r--compiler/rustc_monomorphize/src/partitioning.rs2
-rw-r--r--compiler/rustc_next_trait_solver/Cargo.toml2
-rw-r--r--compiler/rustc_next_trait_solver/src/canonicalizer.rs72
-rw-r--r--compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs76
-rw-r--r--compiler/rustc_next_trait_solver/src/solve/assembly/structural_traits.rs20
-rw-r--r--compiler/rustc_next_trait_solver/src/solve/effect_goals.rs4
-rw-r--r--compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs11
-rw-r--r--compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs32
-rw-r--r--compiler/rustc_next_trait_solver/src/solve/mod.rs71
-rw-r--r--compiler/rustc_next_trait_solver/src/solve/normalizes_to/mod.rs4
-rw-r--r--compiler/rustc_next_trait_solver/src/solve/trait_goals.rs41
-rw-r--r--compiler/rustc_parse/Cargo.toml3
-rw-r--r--compiler/rustc_parse/messages.ftl11
-rw-r--r--compiler/rustc_parse/src/errors.rs28
-rw-r--r--compiler/rustc_parse/src/parser/expr.rs13
-rw-r--r--compiler/rustc_parse/src/parser/item.rs3
-rw-r--r--compiler/rustc_parse/src/parser/path.rs31
-rw-r--r--compiler/rustc_parse/src/parser/ty.rs28
-rw-r--r--compiler/rustc_parse/src/validate_attr.rs2
-rw-r--r--compiler/rustc_passes/Cargo.toml1
-rw-r--r--compiler/rustc_passes/src/check_attr.rs23
-rw-r--r--compiler/rustc_passes/src/check_export.rs3
-rw-r--r--compiler/rustc_passes/src/dead.rs467
-rw-r--r--compiler/rustc_passes/src/lib.rs1
-rw-r--r--compiler/rustc_passes/src/lib_features.rs4
-rw-r--r--compiler/rustc_passes/src/liveness.rs4
-rw-r--r--compiler/rustc_passes/src/stability.rs33
-rw-r--r--compiler/rustc_pattern_analysis/Cargo.toml5
-rw-r--r--compiler/rustc_privacy/Cargo.toml1
-rw-r--r--compiler/rustc_privacy/src/lib.rs249
-rw-r--r--compiler/rustc_proc_macro/Cargo.toml4
-rw-r--r--compiler/rustc_public/Cargo.toml2
-rw-r--r--compiler/rustc_query_system/Cargo.toml1
-rw-r--r--compiler/rustc_query_system/src/ich/hcx.rs1
-rw-r--r--compiler/rustc_resolve/Cargo.toml2
-rw-r--r--compiler/rustc_resolve/src/build_reduced_graph.rs44
-rw-r--r--compiler/rustc_resolve/src/diagnostics.rs39
-rw-r--r--compiler/rustc_resolve/src/errors.rs52
-rw-r--r--compiler/rustc_resolve/src/late.rs10
-rw-r--r--compiler/rustc_resolve/src/late/diagnostics.rs22
-rw-r--r--compiler/rustc_resolve/src/lib.rs83
-rw-r--r--compiler/rustc_resolve/src/macros.rs3
-rw-r--r--compiler/rustc_sanitizers/Cargo.toml6
-rw-r--r--compiler/rustc_session/src/config.rs9
-rw-r--r--compiler/rustc_session/src/options.rs4
-rw-r--r--compiler/rustc_session/src/session.rs17
-rw-r--r--compiler/rustc_span/src/hygiene.rs4
-rw-r--r--compiler/rustc_symbol_mangling/Cargo.toml1
-rw-r--r--compiler/rustc_symbol_mangling/src/legacy.rs65
-rw-r--r--compiler/rustc_symbol_mangling/src/v0.rs86
-rw-r--r--compiler/rustc_target/src/spec/targets/hexagon_unknown_linux_musl.rs1
-rw-r--r--compiler/rustc_target/src/spec/targets/mips64_unknown_linux_muslabi64.rs2
-rw-r--r--compiler/rustc_target/src/spec/targets/powerpc64_unknown_linux_musl.rs2
-rw-r--r--compiler/rustc_target/src/spec/targets/powerpc_unknown_linux_musl.rs2
-rw-r--r--compiler/rustc_target/src/spec/targets/powerpc_unknown_linux_muslspe.rs2
-rw-r--r--compiler/rustc_target/src/spec/targets/riscv32gc_unknown_linux_musl.rs2
-rw-r--r--compiler/rustc_target/src/spec/targets/s390x_unknown_linux_musl.rs2
-rw-r--r--compiler/rustc_target/src/spec/targets/thumbv7neon_unknown_linux_musleabihf.rs2
-rw-r--r--compiler/rustc_thread_pool/Cargo.toml1
-rw-r--r--compiler/rustc_thread_pool/src/scope/mod.rs6
-rw-r--r--compiler/rustc_thread_pool/src/sleep/mod.rs2
-rw-r--r--compiler/rustc_trait_selection/Cargo.toml1
-rw-r--r--compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs16
-rw-r--r--compiler/rustc_trait_selection/src/error_reporting/infer/need_type_info.rs51
-rw-r--r--compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/placeholder_error.rs8
-rw-r--r--compiler/rustc_trait_selection/src/error_reporting/infer/note_and_explain.rs7
-rw-r--r--compiler/rustc_trait_selection/src/error_reporting/infer/region.rs2
-rw-r--r--compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs6
-rw-r--r--compiler/rustc_trait_selection/src/error_reporting/traits/overflow.rs6
-rw-r--r--compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs9
-rw-r--r--compiler/rustc_trait_selection/src/solve/delegate.rs8
-rw-r--r--compiler/rustc_trait_selection/src/solve/fulfill.rs31
-rw-r--r--compiler/rustc_trait_selection/src/traits/auto_trait.rs44
-rw-r--r--compiler/rustc_trait_selection/src/traits/coherence.rs30
-rw-r--r--compiler/rustc_trait_selection/src/traits/mod.rs5
-rw-r--r--compiler/rustc_trait_selection/src/traits/query/dropck_outlives.rs7
-rw-r--r--compiler/rustc_trait_selection/src/traits/query/type_op/ascribe_user_type.rs2
-rw-r--r--compiler/rustc_trait_selection/src/traits/query/type_op/custom.rs1
-rw-r--r--compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs64
-rw-r--r--compiler/rustc_trait_selection/src/traits/select/mod.rs16
-rw-r--r--compiler/rustc_trait_selection/src/traits/util.rs4
-rw-r--r--compiler/rustc_traits/src/coroutine_witnesses.rs1
-rw-r--r--compiler/rustc_traits/src/implied_outlives_bounds.rs4
-rw-r--r--compiler/rustc_traits/src/type_op.rs4
-rw-r--r--compiler/rustc_transmute/Cargo.toml2
-rw-r--r--compiler/rustc_ty_utils/src/needs_drop.rs43
-rw-r--r--compiler/rustc_type_ir/Cargo.toml10
-rw-r--r--compiler/rustc_type_ir/src/binder.rs25
-rw-r--r--compiler/rustc_type_ir/src/flags.rs11
-rw-r--r--compiler/rustc_type_ir/src/infer_ctxt.rs4
-rw-r--r--compiler/rustc_type_ir/src/inherent.rs2
-rw-r--r--compiler/rustc_type_ir/src/lib.rs12
-rw-r--r--compiler/rustc_type_ir/src/predicate.rs26
-rw-r--r--compiler/rustc_type_ir/src/ty_kind.rs176
-rw-r--r--compiler/rustc_type_ir/src/ty_kind/closure.rs27
365 files changed, 4928 insertions, 3868 deletions
diff --git a/compiler/rustc_ast/src/ast.rs b/compiler/rustc_ast/src/ast.rs
index 984b280e81b..fdff18ffd47 100644
--- a/compiler/rustc_ast/src/ast.rs
+++ b/compiler/rustc_ast/src/ast.rs
@@ -23,7 +23,7 @@ use std::{cmp, fmt};
 
 pub use GenericArgs::*;
 pub use UnsafeSource::*;
-pub use rustc_ast_ir::{Movability, Mutability, Pinnedness};
+pub use rustc_ast_ir::{FloatTy, IntTy, Movability, Mutability, Pinnedness, UintTy};
 use rustc_data_structures::packed::Pu128;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::stack::ensure_sufficient_stack;
@@ -2285,105 +2285,6 @@ pub struct FnSig {
     pub span: Span,
 }
 
-#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
-#[derive(Encodable, Decodable, HashStable_Generic)]
-pub enum FloatTy {
-    F16,
-    F32,
-    F64,
-    F128,
-}
-
-impl FloatTy {
-    pub fn name_str(self) -> &'static str {
-        match self {
-            FloatTy::F16 => "f16",
-            FloatTy::F32 => "f32",
-            FloatTy::F64 => "f64",
-            FloatTy::F128 => "f128",
-        }
-    }
-
-    pub fn name(self) -> Symbol {
-        match self {
-            FloatTy::F16 => sym::f16,
-            FloatTy::F32 => sym::f32,
-            FloatTy::F64 => sym::f64,
-            FloatTy::F128 => sym::f128,
-        }
-    }
-}
-
-#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
-#[derive(Encodable, Decodable, HashStable_Generic)]
-pub enum IntTy {
-    Isize,
-    I8,
-    I16,
-    I32,
-    I64,
-    I128,
-}
-
-impl IntTy {
-    pub fn name_str(&self) -> &'static str {
-        match *self {
-            IntTy::Isize => "isize",
-            IntTy::I8 => "i8",
-            IntTy::I16 => "i16",
-            IntTy::I32 => "i32",
-            IntTy::I64 => "i64",
-            IntTy::I128 => "i128",
-        }
-    }
-
-    pub fn name(&self) -> Symbol {
-        match *self {
-            IntTy::Isize => sym::isize,
-            IntTy::I8 => sym::i8,
-            IntTy::I16 => sym::i16,
-            IntTy::I32 => sym::i32,
-            IntTy::I64 => sym::i64,
-            IntTy::I128 => sym::i128,
-        }
-    }
-}
-
-#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Copy, Debug)]
-#[derive(Encodable, Decodable, HashStable_Generic)]
-pub enum UintTy {
-    Usize,
-    U8,
-    U16,
-    U32,
-    U64,
-    U128,
-}
-
-impl UintTy {
-    pub fn name_str(&self) -> &'static str {
-        match *self {
-            UintTy::Usize => "usize",
-            UintTy::U8 => "u8",
-            UintTy::U16 => "u16",
-            UintTy::U32 => "u32",
-            UintTy::U64 => "u64",
-            UintTy::U128 => "u128",
-        }
-    }
-
-    pub fn name(&self) -> Symbol {
-        match *self {
-            UintTy::Usize => sym::usize,
-            UintTy::U8 => sym::u8,
-            UintTy::U16 => sym::u16,
-            UintTy::U32 => sym::u32,
-            UintTy::U64 => sym::u64,
-            UintTy::U128 => sym::u128,
-        }
-    }
-}
-
 /// A constraint on an associated item.
 ///
 /// ### Examples
diff --git a/compiler/rustc_ast/src/util/literal.rs b/compiler/rustc_ast/src/util/literal.rs
index 2dfd695d880..e9cf3cf0737 100644
--- a/compiler/rustc_ast/src/util/literal.rs
+++ b/compiler/rustc_ast/src/util/literal.rs
@@ -190,15 +190,15 @@ impl fmt::Display for LitKind {
             LitKind::Int(n, ty) => {
                 write!(f, "{n}")?;
                 match ty {
-                    ast::LitIntType::Unsigned(ty) => write!(f, "{}", ty.name())?,
-                    ast::LitIntType::Signed(ty) => write!(f, "{}", ty.name())?,
+                    ast::LitIntType::Unsigned(ty) => write!(f, "{}", ty.name_str())?,
+                    ast::LitIntType::Signed(ty) => write!(f, "{}", ty.name_str())?,
                     ast::LitIntType::Unsuffixed => {}
                 }
             }
             LitKind::Float(symbol, ty) => {
                 write!(f, "{symbol}")?;
                 match ty {
-                    ast::LitFloatType::Suffixed(ty) => write!(f, "{}", ty.name())?,
+                    ast::LitFloatType::Suffixed(ty) => write!(f, "{}", ty.name_str())?,
                     ast::LitFloatType::Unsuffixed => {}
                 }
             }
diff --git a/compiler/rustc_ast_ir/Cargo.toml b/compiler/rustc_ast_ir/Cargo.toml
index 76bdd9f7eb6..1d21a07dc44 100644
--- a/compiler/rustc_ast_ir/Cargo.toml
+++ b/compiler/rustc_ast_ir/Cargo.toml
@@ -8,12 +8,16 @@ edition = "2024"
 rustc_data_structures = { path = "../rustc_data_structures", optional = true }
 rustc_macros = { path = "../rustc_macros", optional = true }
 rustc_serialize = { path = "../rustc_serialize", optional = true }
+rustc_span = { path = "../rustc_span", optional = true }
 # tidy-alphabetical-end
 
 [features]
+# tidy-alphabetical-start
 default = ["nightly"]
 nightly = [
-    "dep:rustc_serialize",
     "dep:rustc_data_structures",
     "dep:rustc_macros",
+    "dep:rustc_serialize",
+    "dep:rustc_span",
 ]
+# tidy-alphabetical-end
diff --git a/compiler/rustc_ast_ir/src/lib.rs b/compiler/rustc_ast_ir/src/lib.rs
index 0898433a74c..8f2a37c1210 100644
--- a/compiler/rustc_ast_ir/src/lib.rs
+++ b/compiler/rustc_ast_ir/src/lib.rs
@@ -11,11 +11,221 @@
 #![cfg_attr(feature = "nightly", feature(rustc_attrs))]
 // tidy-alphabetical-end
 
+use std::fmt;
+
 #[cfg(feature = "nightly")]
 use rustc_macros::{Decodable_NoContext, Encodable_NoContext, HashStable_NoContext};
+#[cfg(feature = "nightly")]
+use rustc_span::{Symbol, sym};
 
 pub mod visit;
 
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+#[cfg_attr(
+    feature = "nightly",
+    derive(Encodable_NoContext, Decodable_NoContext, HashStable_NoContext)
+)]
+pub enum IntTy {
+    Isize,
+    I8,
+    I16,
+    I32,
+    I64,
+    I128,
+}
+
+impl IntTy {
+    pub fn name_str(&self) -> &'static str {
+        match *self {
+            IntTy::Isize => "isize",
+            IntTy::I8 => "i8",
+            IntTy::I16 => "i16",
+            IntTy::I32 => "i32",
+            IntTy::I64 => "i64",
+            IntTy::I128 => "i128",
+        }
+    }
+
+    #[cfg(feature = "nightly")]
+    pub fn name(self) -> Symbol {
+        match self {
+            IntTy::Isize => sym::isize,
+            IntTy::I8 => sym::i8,
+            IntTy::I16 => sym::i16,
+            IntTy::I32 => sym::i32,
+            IntTy::I64 => sym::i64,
+            IntTy::I128 => sym::i128,
+        }
+    }
+
+    pub fn bit_width(&self) -> Option<u64> {
+        Some(match *self {
+            IntTy::Isize => return None,
+            IntTy::I8 => 8,
+            IntTy::I16 => 16,
+            IntTy::I32 => 32,
+            IntTy::I64 => 64,
+            IntTy::I128 => 128,
+        })
+    }
+
+    pub fn normalize(&self, target_width: u32) -> Self {
+        match self {
+            IntTy::Isize => match target_width {
+                16 => IntTy::I16,
+                32 => IntTy::I32,
+                64 => IntTy::I64,
+                _ => unreachable!(),
+            },
+            _ => *self,
+        }
+    }
+
+    pub fn to_unsigned(self) -> UintTy {
+        match self {
+            IntTy::Isize => UintTy::Usize,
+            IntTy::I8 => UintTy::U8,
+            IntTy::I16 => UintTy::U16,
+            IntTy::I32 => UintTy::U32,
+            IntTy::I64 => UintTy::U64,
+            IntTy::I128 => UintTy::U128,
+        }
+    }
+}
+
+impl fmt::Debug for IntTy {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{}", self.name_str())
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Copy)]
+#[cfg_attr(
+    feature = "nightly",
+    derive(Encodable_NoContext, Decodable_NoContext, HashStable_NoContext)
+)]
+pub enum UintTy {
+    Usize,
+    U8,
+    U16,
+    U32,
+    U64,
+    U128,
+}
+
+impl UintTy {
+    pub fn name_str(&self) -> &'static str {
+        match *self {
+            UintTy::Usize => "usize",
+            UintTy::U8 => "u8",
+            UintTy::U16 => "u16",
+            UintTy::U32 => "u32",
+            UintTy::U64 => "u64",
+            UintTy::U128 => "u128",
+        }
+    }
+
+    #[cfg(feature = "nightly")]
+    pub fn name(self) -> Symbol {
+        match self {
+            UintTy::Usize => sym::usize,
+            UintTy::U8 => sym::u8,
+            UintTy::U16 => sym::u16,
+            UintTy::U32 => sym::u32,
+            UintTy::U64 => sym::u64,
+            UintTy::U128 => sym::u128,
+        }
+    }
+
+    pub fn bit_width(&self) -> Option<u64> {
+        Some(match *self {
+            UintTy::Usize => return None,
+            UintTy::U8 => 8,
+            UintTy::U16 => 16,
+            UintTy::U32 => 32,
+            UintTy::U64 => 64,
+            UintTy::U128 => 128,
+        })
+    }
+
+    pub fn normalize(&self, target_width: u32) -> Self {
+        match self {
+            UintTy::Usize => match target_width {
+                16 => UintTy::U16,
+                32 => UintTy::U32,
+                64 => UintTy::U64,
+                _ => unreachable!(),
+            },
+            _ => *self,
+        }
+    }
+
+    pub fn to_signed(self) -> IntTy {
+        match self {
+            UintTy::Usize => IntTy::Isize,
+            UintTy::U8 => IntTy::I8,
+            UintTy::U16 => IntTy::I16,
+            UintTy::U32 => IntTy::I32,
+            UintTy::U64 => IntTy::I64,
+            UintTy::U128 => IntTy::I128,
+        }
+    }
+}
+
+impl fmt::Debug for UintTy {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{}", self.name_str())
+    }
+}
+
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+#[cfg_attr(
+    feature = "nightly",
+    derive(Encodable_NoContext, Decodable_NoContext, HashStable_NoContext)
+)]
+pub enum FloatTy {
+    F16,
+    F32,
+    F64,
+    F128,
+}
+
+impl FloatTy {
+    pub fn name_str(self) -> &'static str {
+        match self {
+            FloatTy::F16 => "f16",
+            FloatTy::F32 => "f32",
+            FloatTy::F64 => "f64",
+            FloatTy::F128 => "f128",
+        }
+    }
+
+    #[cfg(feature = "nightly")]
+    pub fn name(self) -> Symbol {
+        match self {
+            FloatTy::F16 => sym::f16,
+            FloatTy::F32 => sym::f32,
+            FloatTy::F64 => sym::f64,
+            FloatTy::F128 => sym::f128,
+        }
+    }
+
+    pub fn bit_width(self) -> u64 {
+        match self {
+            FloatTy::F16 => 16,
+            FloatTy::F32 => 32,
+            FloatTy::F64 => 64,
+            FloatTy::F128 => 128,
+        }
+    }
+}
+
+impl fmt::Debug for FloatTy {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{}", self.name_str())
+    }
+}
+
 /// The movability of a coroutine / closure literal:
 /// whether a coroutine contains self-references, causing it to be `!Unpin`.
 #[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, Copy)]
diff --git a/compiler/rustc_ast_lowering/Cargo.toml b/compiler/rustc_ast_lowering/Cargo.toml
index dc571f5c367..6ac258155fe 100644
--- a/compiler/rustc_ast_lowering/Cargo.toml
+++ b/compiler/rustc_ast_lowering/Cargo.toml
@@ -11,7 +11,6 @@ doctest = false
 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_attr_parsing = { path = "../rustc_attr_parsing" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
diff --git a/compiler/rustc_ast_lowering/src/expr.rs b/compiler/rustc_ast_lowering/src/expr.rs
index 657792c9397..fb42cfea30b 100644
--- a/compiler/rustc_ast_lowering/src/expr.rs
+++ b/compiler/rustc_ast_lowering/src/expr.rs
@@ -4,11 +4,11 @@ use std::sync::Arc;
 use rustc_ast::ptr::P as AstP;
 use rustc_ast::*;
 use rustc_ast_pretty::pprust::expr_to_string;
-use rustc_attr_data_structures::{AttributeKind, find_attr};
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_hir as hir;
-use rustc_hir::HirId;
+use rustc_hir::attrs::AttributeKind;
 use rustc_hir::def::{DefKind, Res};
+use rustc_hir::{HirId, find_attr};
 use rustc_middle::span_bug;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::errors::report_lit_error;
@@ -98,7 +98,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
             }
 
             let expr_hir_id = self.lower_node_id(e.id);
-            self.lower_attrs(expr_hir_id, &e.attrs, e.span);
+            let attrs = self.lower_attrs(expr_hir_id, &e.attrs, e.span);
 
             let kind = match &e.kind {
                 ExprKind::Array(exprs) => hir::ExprKind::Array(self.lower_exprs(exprs)),
@@ -232,10 +232,10 @@ impl<'hir> LoweringContext<'_, 'hir> {
                         *fn_arg_span,
                     ),
                     None => self.lower_expr_closure(
+                        attrs,
                         binder,
                         *capture_clause,
                         e.id,
-                        expr_hir_id,
                         *constness,
                         *movability,
                         fn_decl,
@@ -1052,10 +1052,10 @@ impl<'hir> LoweringContext<'_, 'hir> {
 
     fn lower_expr_closure(
         &mut self,
+        attrs: &[rustc_hir::Attribute],
         binder: &ClosureBinder,
         capture_clause: CaptureBy,
         closure_id: NodeId,
-        closure_hir_id: hir::HirId,
         constness: Const,
         movability: Movability,
         decl: &FnDecl,
@@ -1067,15 +1067,9 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let (binder_clause, generic_params) = self.lower_closure_binder(binder);
 
         let (body_id, closure_kind) = self.with_new_scopes(fn_decl_span, move |this| {
-            let mut coroutine_kind = if this
-                .attrs
-                .get(&closure_hir_id.local_id)
-                .is_some_and(|attrs| attrs.iter().any(|attr| attr.has_name(sym::coroutine)))
-            {
-                Some(hir::CoroutineKind::Coroutine(Movability::Movable))
-            } else {
-                None
-            };
+
+            let mut coroutine_kind = find_attr!(attrs, AttributeKind::Coroutine(_) => hir::CoroutineKind::Coroutine(Movability::Movable));
+
             // FIXME(contracts): Support contracts on closures?
             let body_id = this.lower_fn_body(decl, None, |this| {
                 this.coroutine_kind = coroutine_kind;
diff --git a/compiler/rustc_ast_lowering/src/index.rs b/compiler/rustc_ast_lowering/src/index.rs
index 5b63206d7d6..5f8933aa2be 100644
--- a/compiler/rustc_ast_lowering/src/index.rs
+++ b/compiler/rustc_ast_lowering/src/index.rs
@@ -311,7 +311,7 @@ impl<'a, 'hir> Visitor<'hir> for NodeCollector<'a, 'hir> {
         );
 
         self.with_parent(const_arg.hir_id, |this| {
-            intravisit::walk_ambig_const_arg(this, const_arg);
+            intravisit::walk_const_arg(this, const_arg);
         });
     }
 
diff --git a/compiler/rustc_ast_lowering/src/item.rs b/compiler/rustc_ast_lowering/src/item.rs
index 1899dcda361..9f54af57528 100644
--- a/compiler/rustc_ast_lowering/src/item.rs
+++ b/compiler/rustc_ast_lowering/src/item.rs
@@ -2,11 +2,11 @@ use rustc_abi::ExternAbi;
 use rustc_ast::ptr::P;
 use rustc_ast::visit::AssocCtxt;
 use rustc_ast::*;
-use rustc_attr_data_structures::{AttributeKind, find_attr};
 use rustc_errors::{E0570, ErrorGuaranteed, struct_span_code_err};
+use rustc_hir::attrs::AttributeKind;
 use rustc_hir::def::{DefKind, PerNS, Res};
 use rustc_hir::def_id::{CRATE_DEF_ID, LocalDefId};
-use rustc_hir::{self as hir, HirId, LifetimeSource, PredicateOrigin};
+use rustc_hir::{self as hir, HirId, LifetimeSource, PredicateOrigin, find_attr};
 use rustc_index::{IndexSlice, IndexVec};
 use rustc_middle::span_bug;
 use rustc_middle::ty::{ResolverAstLowering, TyCtxt};
diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index 189c82b614c..d097e3cbaa8 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -675,7 +675,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         let bodies = SortedMap::from_presorted_elements(bodies);
 
         // Don't hash unless necessary, because it's expensive.
-        let (opt_hash_including_bodies, attrs_hash, delayed_lints_hash) =
+        let rustc_middle::hir::Hashes { opt_hash_including_bodies, attrs_hash, delayed_lints_hash } =
             self.tcx.hash_owner_nodes(node, &bodies, &attrs, &delayed_lints, define_opaque);
         let num_nodes = self.item_local_id_counter.as_usize();
         let (nodes, parenting) = index::index_hir(self.tcx, node, &bodies, num_nodes);
diff --git a/compiler/rustc_ast_passes/messages.ftl b/compiler/rustc_ast_passes/messages.ftl
index 9b9c1105e47..53e64439afc 100644
--- a/compiler/rustc_ast_passes/messages.ftl
+++ b/compiler/rustc_ast_passes/messages.ftl
@@ -241,6 +241,10 @@ ast_passes_tilde_const_disallowed = `[const]` is not allowed here
     .trait_assoc_ty = associated types in non-`const` traits cannot have `[const]` trait bounds
     .trait_impl_assoc_ty = associated types in non-const impls cannot have `[const]` trait bounds
     .inherent_assoc_ty = inherent associated types cannot have `[const]` trait bounds
+    .struct = structs cannot have `[const]` trait bounds
+    .enum = enums cannot have `[const]` trait bounds
+    .union = unions cannot have `[const]` trait bounds
+    .anon_const = anonymous constants cannot have `[const]` trait bounds
     .object = trait objects cannot have `[const]` trait bounds
     .item = this item cannot have `[const]` trait bounds
 
diff --git a/compiler/rustc_ast_passes/src/ast_validation.rs b/compiler/rustc_ast_passes/src/ast_validation.rs
index e99e5cc4ae6..1c1c5f82f3e 100644
--- a/compiler/rustc_ast_passes/src/ast_validation.rs
+++ b/compiler/rustc_ast_passes/src/ast_validation.rs
@@ -1128,7 +1128,9 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                         );
                     }
                 }
-                visit::walk_item(self, item)
+                self.with_tilde_const(Some(TildeConstReason::Enum { span: item.span }), |this| {
+                    visit::walk_item(this, item)
+                });
             }
             ItemKind::Trait(box Trait {
                 constness,
@@ -1179,26 +1181,32 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                 }
                 visit::walk_item(self, item)
             }
-            ItemKind::Struct(ident, generics, vdata) => match vdata {
-                VariantData::Struct { fields, .. } => {
-                    self.visit_attrs_vis_ident(&item.attrs, &item.vis, ident);
-                    self.visit_generics(generics);
-                    walk_list!(self, visit_field_def, fields);
-                }
-                _ => visit::walk_item(self, item),
-            },
+            ItemKind::Struct(ident, generics, vdata) => {
+                self.with_tilde_const(Some(TildeConstReason::Struct { span: item.span }), |this| {
+                    match vdata {
+                        VariantData::Struct { fields, .. } => {
+                            this.visit_attrs_vis_ident(&item.attrs, &item.vis, ident);
+                            this.visit_generics(generics);
+                            walk_list!(this, visit_field_def, fields);
+                        }
+                        _ => visit::walk_item(this, item),
+                    }
+                })
+            }
             ItemKind::Union(ident, generics, vdata) => {
                 if vdata.fields().is_empty() {
                     self.dcx().emit_err(errors::FieldlessUnion { span: item.span });
                 }
-                match vdata {
-                    VariantData::Struct { fields, .. } => {
-                        self.visit_attrs_vis_ident(&item.attrs, &item.vis, ident);
-                        self.visit_generics(generics);
-                        walk_list!(self, visit_field_def, fields);
+                self.with_tilde_const(Some(TildeConstReason::Union { span: item.span }), |this| {
+                    match vdata {
+                        VariantData::Struct { fields, .. } => {
+                            this.visit_attrs_vis_ident(&item.attrs, &item.vis, ident);
+                            this.visit_generics(generics);
+                            walk_list!(this, visit_field_def, fields);
+                        }
+                        _ => visit::walk_item(this, item),
                     }
-                    _ => visit::walk_item(self, item),
-                }
+                });
             }
             ItemKind::Const(box ConstItem { defaultness, expr, .. }) => {
                 self.check_defaultness(item.span, *defaultness);
@@ -1627,6 +1635,13 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
             _ => self.with_in_trait_impl(None, |this| visit::walk_assoc_item(this, item, ctxt)),
         }
     }
+
+    fn visit_anon_const(&mut self, anon_const: &'a AnonConst) {
+        self.with_tilde_const(
+            Some(TildeConstReason::AnonConst { span: anon_const.value.span }),
+            |this| visit::walk_anon_const(this, anon_const),
+        )
+    }
 }
 
 /// When encountering an equality constraint in a `where` clause, emit an error. If the code seems
diff --git a/compiler/rustc_ast_passes/src/errors.rs b/compiler/rustc_ast_passes/src/errors.rs
index 2e3b1510755..60f47490f12 100644
--- a/compiler/rustc_ast_passes/src/errors.rs
+++ b/compiler/rustc_ast_passes/src/errors.rs
@@ -624,6 +624,26 @@ pub(crate) enum TildeConstReason {
         #[primary_span]
         span: Span,
     },
+    #[note(ast_passes_struct)]
+    Struct {
+        #[primary_span]
+        span: Span,
+    },
+    #[note(ast_passes_enum)]
+    Enum {
+        #[primary_span]
+        span: Span,
+    },
+    #[note(ast_passes_union)]
+    Union {
+        #[primary_span]
+        span: Span,
+    },
+    #[note(ast_passes_anon_const)]
+    AnonConst {
+        #[primary_span]
+        span: Span,
+    },
     #[note(ast_passes_object)]
     TraitObject,
     #[note(ast_passes_item)]
diff --git a/compiler/rustc_attr_data_structures/Cargo.toml b/compiler/rustc_attr_data_structures/Cargo.toml
deleted file mode 100644
index b18923c337f..00000000000
--- a/compiler/rustc_attr_data_structures/Cargo.toml
+++ /dev/null
@@ -1,16 +0,0 @@
-[package]
-name = "rustc_attr_data_structures"
-version = "0.0.0"
-edition = "2024"
-
-[dependencies]
-# 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_macros = {path = "../rustc_macros"}
-rustc_serialize = {path = "../rustc_serialize"}
-rustc_span = {path = "../rustc_span"}
-thin-vec = "0.2.12"
-# tidy-alphabetical-end
diff --git a/compiler/rustc_attr_data_structures/src/lints.rs b/compiler/rustc_attr_data_structures/src/lints.rs
deleted file mode 100644
index 60ca4d43ce9..00000000000
--- a/compiler/rustc_attr_data_structures/src/lints.rs
+++ /dev/null
@@ -1,16 +0,0 @@
-use rustc_macros::HashStable_Generic;
-use rustc_span::Span;
-
-#[derive(Clone, Debug, HashStable_Generic)]
-pub struct AttributeLint<Id> {
-    pub id: Id,
-    pub span: Span,
-    pub kind: AttributeLintKind,
-}
-
-#[derive(Clone, Debug, HashStable_Generic)]
-pub enum AttributeLintKind {
-    UnusedDuplicate { this: Span, other: Span, warning: bool },
-    IllFormedAttributeInput { suggestions: Vec<String> },
-    EmptyAttribute { first_span: Span },
-}
diff --git a/compiler/rustc_attr_parsing/Cargo.toml b/compiler/rustc_attr_parsing/Cargo.toml
index 32029137268..cec9d62e656 100644
--- a/compiler/rustc_attr_parsing/Cargo.toml
+++ b/compiler/rustc_attr_parsing/Cargo.toml
@@ -8,7 +8,6 @@ edition = "2024"
 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_errors = { path = "../rustc_errors" }
 rustc_feature = { path = "../rustc_feature" }
 rustc_fluent_macro = { path = "../rustc_fluent_macro" }
diff --git a/compiler/rustc_attr_parsing/src/attributes/allow_unstable.rs b/compiler/rustc_attr_parsing/src/attributes/allow_unstable.rs
index a6bd2306ec5..95104b896ac 100644
--- a/compiler/rustc_attr_parsing/src/attributes/allow_unstable.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/allow_unstable.rs
@@ -1,7 +1,7 @@
 use std::iter;
 
-use rustc_attr_data_structures::AttributeKind;
 use rustc_feature::{AttributeTemplate, template};
+use rustc_hir::attrs::AttributeKind;
 use rustc_span::{Span, Symbol, sym};
 
 use super::{CombineAttributeParser, ConvertFn};
diff --git a/compiler/rustc_attr_parsing/src/attributes/body.rs b/compiler/rustc_attr_parsing/src/attributes/body.rs
new file mode 100644
index 00000000000..ab9330216f6
--- /dev/null
+++ b/compiler/rustc_attr_parsing/src/attributes/body.rs
@@ -0,0 +1,15 @@
+//! Attributes that can be found in function body.
+
+use rustc_hir::attrs::AttributeKind;
+use rustc_span::{Symbol, sym};
+
+use super::{NoArgsAttributeParser, OnDuplicate};
+use crate::context::Stage;
+
+pub(crate) struct CoroutineParser;
+
+impl<S: Stage> NoArgsAttributeParser<S> for CoroutineParser {
+    const PATH: &[Symbol] = &[sym::coroutine];
+    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Error;
+    const CREATE: fn(rustc_span::Span) -> AttributeKind = |span| AttributeKind::Coroutine(span);
+}
diff --git a/compiler/rustc_attr_parsing/src/attributes/cfg.rs b/compiler/rustc_attr_parsing/src/attributes/cfg.rs
index 6373cf6e08a..947be28bc95 100644
--- a/compiler/rustc_attr_parsing/src/attributes/cfg.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/cfg.rs
@@ -1,6 +1,7 @@
 use rustc_ast::{LitKind, NodeId};
-use rustc_attr_data_structures::{CfgEntry, RustcVersion};
 use rustc_feature::{AttributeTemplate, Features, template};
+use rustc_hir::RustcVersion;
+use rustc_hir::attrs::CfgEntry;
 use rustc_session::Session;
 use rustc_session::config::ExpectedValues;
 use rustc_session::lint::BuiltinLintDiag;
diff --git a/compiler/rustc_attr_parsing/src/attributes/cfg_old.rs b/compiler/rustc_attr_parsing/src/attributes/cfg_old.rs
index c5025a8b6ea..3257d898ecc 100644
--- a/compiler/rustc_attr_parsing/src/attributes/cfg_old.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/cfg_old.rs
@@ -1,7 +1,7 @@
 use rustc_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_hir::RustcVersion;
 use rustc_session::Session;
 use rustc_session::config::ExpectedValues;
 use rustc_session::lint::builtin::UNEXPECTED_CFGS;
diff --git a/compiler/rustc_attr_parsing/src/attributes/codegen_attrs.rs b/compiler/rustc_attr_parsing/src/attributes/codegen_attrs.rs
index afa9abed0bb..c5fb11dbf6a 100644
--- a/compiler/rustc_attr_parsing/src/attributes/codegen_attrs.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/codegen_attrs.rs
@@ -1,5 +1,5 @@
-use rustc_attr_data_structures::{AttributeKind, CoverageAttrKind, OptimizeAttr, UsedBy};
 use rustc_feature::{AttributeTemplate, template};
+use rustc_hir::attrs::{AttributeKind, CoverageAttrKind, OptimizeAttr, UsedBy};
 use rustc_session::parse::feature_err;
 use rustc_span::{Span, Symbol, sym};
 
@@ -374,11 +374,3 @@ impl<S: Stage> CombineAttributeParser<S> for TargetFeatureParser {
         features
     }
 }
-
-pub(crate) struct OmitGdbPrettyPrinterSectionParser;
-
-impl<S: Stage> NoArgsAttributeParser<S> for OmitGdbPrettyPrinterSectionParser {
-    const PATH: &[Symbol] = &[sym::omit_gdb_pretty_printer_section];
-    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Error;
-    const CREATE: fn(Span) -> AttributeKind = |_| AttributeKind::OmitGdbPrettyPrinterSection;
-}
diff --git a/compiler/rustc_attr_parsing/src/attributes/confusables.rs b/compiler/rustc_attr_parsing/src/attributes/confusables.rs
index c911908dfb3..7d24c89a6e8 100644
--- a/compiler/rustc_attr_parsing/src/attributes/confusables.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/confusables.rs
@@ -1,5 +1,5 @@
-use rustc_attr_data_structures::AttributeKind;
 use rustc_feature::template;
+use rustc_hir::attrs::AttributeKind;
 use rustc_span::{Span, Symbol, sym};
 use thin_vec::ThinVec;
 
diff --git a/compiler/rustc_attr_parsing/src/attributes/deprecation.rs b/compiler/rustc_attr_parsing/src/attributes/deprecation.rs
index 08cf1ab5d19..38ec4bd5645 100644
--- a/compiler/rustc_attr_parsing/src/attributes/deprecation.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/deprecation.rs
@@ -1,5 +1,5 @@
-use rustc_attr_data_structures::{AttributeKind, DeprecatedSince, Deprecation};
 use rustc_feature::{AttributeTemplate, template};
+use rustc_hir::attrs::{AttributeKind, DeprecatedSince, Deprecation};
 use rustc_span::{Span, Symbol, sym};
 
 use super::util::parse_version;
diff --git a/compiler/rustc_attr_parsing/src/attributes/dummy.rs b/compiler/rustc_attr_parsing/src/attributes/dummy.rs
index e5e1c3bb6b6..bbcd9ab530c 100644
--- a/compiler/rustc_attr_parsing/src/attributes/dummy.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/dummy.rs
@@ -1,5 +1,5 @@
-use rustc_attr_data_structures::AttributeKind;
 use rustc_feature::{AttributeTemplate, template};
+use rustc_hir::attrs::AttributeKind;
 use rustc_span::{Symbol, sym};
 
 use crate::attributes::{AttributeOrder, OnDuplicate, SingleAttributeParser};
diff --git a/compiler/rustc_attr_parsing/src/attributes/inline.rs b/compiler/rustc_attr_parsing/src/attributes/inline.rs
index fe812175218..8437713206e 100644
--- a/compiler/rustc_attr_parsing/src/attributes/inline.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/inline.rs
@@ -2,9 +2,9 @@
 //                      note: need to model better how duplicate attr errors work when not using
 //                      SingleAttributeParser which is what we have two of here.
 
-use rustc_attr_data_structures::lints::AttributeLintKind;
-use rustc_attr_data_structures::{AttributeKind, InlineAttr};
 use rustc_feature::{AttributeTemplate, template};
+use rustc_hir::attrs::{AttributeKind, InlineAttr};
+use rustc_hir::lints::AttributeLintKind;
 use rustc_span::{Symbol, sym};
 
 use super::{AcceptContext, AttributeOrder, OnDuplicate};
diff --git a/compiler/rustc_attr_parsing/src/attributes/link_attrs.rs b/compiler/rustc_attr_parsing/src/attributes/link_attrs.rs
index 960cebd8925..7eab3090870 100644
--- a/compiler/rustc_attr_parsing/src/attributes/link_attrs.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/link_attrs.rs
@@ -1,6 +1,6 @@
-use rustc_attr_data_structures::AttributeKind;
-use rustc_attr_data_structures::AttributeKind::{LinkName, LinkOrdinal, LinkSection};
 use rustc_feature::{AttributeTemplate, template};
+use rustc_hir::attrs::AttributeKind;
+use rustc_hir::attrs::AttributeKind::{LinkName, LinkOrdinal, LinkSection};
 use rustc_span::{Span, Symbol, sym};
 
 use crate::attributes::{
diff --git a/compiler/rustc_attr_parsing/src/attributes/lint_helpers.rs b/compiler/rustc_attr_parsing/src/attributes/lint_helpers.rs
index 0eceff53e8b..9530fec07d6 100644
--- a/compiler/rustc_attr_parsing/src/attributes/lint_helpers.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/lint_helpers.rs
@@ -1,4 +1,4 @@
-use rustc_attr_data_structures::AttributeKind;
+use rustc_hir::attrs::AttributeKind;
 use rustc_span::{Span, Symbol, sym};
 
 use crate::attributes::{NoArgsAttributeParser, OnDuplicate};
diff --git a/compiler/rustc_attr_parsing/src/attributes/loop_match.rs b/compiler/rustc_attr_parsing/src/attributes/loop_match.rs
index 80808b90dc6..868c113a6d1 100644
--- a/compiler/rustc_attr_parsing/src/attributes/loop_match.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/loop_match.rs
@@ -1,4 +1,4 @@
-use rustc_attr_data_structures::AttributeKind;
+use rustc_hir::attrs::AttributeKind;
 use rustc_span::{Span, Symbol, sym};
 
 use crate::attributes::{NoArgsAttributeParser, OnDuplicate};
diff --git a/compiler/rustc_attr_parsing/src/attributes/macro_attrs.rs b/compiler/rustc_attr_parsing/src/attributes/macro_attrs.rs
index eade49180ac..886f7a889d3 100644
--- a/compiler/rustc_attr_parsing/src/attributes/macro_attrs.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/macro_attrs.rs
@@ -1,6 +1,6 @@
-use rustc_attr_data_structures::{AttributeKind, MacroUseArgs};
 use rustc_errors::DiagArgValue;
 use rustc_feature::{AttributeTemplate, template};
+use rustc_hir::attrs::{AttributeKind, MacroUseArgs};
 use rustc_span::{Span, Symbol, sym};
 use thin_vec::ThinVec;
 
diff --git a/compiler/rustc_attr_parsing/src/attributes/mod.rs b/compiler/rustc_attr_parsing/src/attributes/mod.rs
index 0c10517d044..f7946ade6d2 100644
--- a/compiler/rustc_attr_parsing/src/attributes/mod.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/mod.rs
@@ -16,8 +16,8 @@
 
 use std::marker::PhantomData;
 
-use rustc_attr_data_structures::AttributeKind;
 use rustc_feature::{AttributeTemplate, template};
+use rustc_hir::attrs::AttributeKind;
 use rustc_span::{Span, Symbol};
 use thin_vec::ThinVec;
 
@@ -26,6 +26,7 @@ use crate::parser::ArgParser;
 use crate::session_diagnostics::UnusedMultiple;
 
 pub(crate) mod allow_unstable;
+pub(crate) mod body;
 pub(crate) mod cfg;
 pub(crate) mod cfg_old;
 pub(crate) mod codegen_attrs;
diff --git a/compiler/rustc_attr_parsing/src/attributes/must_use.rs b/compiler/rustc_attr_parsing/src/attributes/must_use.rs
index 42af3ed0bfa..d767abbc250 100644
--- a/compiler/rustc_attr_parsing/src/attributes/must_use.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/must_use.rs
@@ -1,6 +1,6 @@
-use rustc_attr_data_structures::AttributeKind;
 use rustc_errors::DiagArgValue;
 use rustc_feature::{AttributeTemplate, template};
+use rustc_hir::attrs::AttributeKind;
 use rustc_span::{Symbol, sym};
 
 use crate::attributes::{AttributeOrder, OnDuplicate, SingleAttributeParser};
diff --git a/compiler/rustc_attr_parsing/src/attributes/no_implicit_prelude.rs b/compiler/rustc_attr_parsing/src/attributes/no_implicit_prelude.rs
index 47cc925f7f6..40f8d00685e 100644
--- a/compiler/rustc_attr_parsing/src/attributes/no_implicit_prelude.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/no_implicit_prelude.rs
@@ -1,4 +1,4 @@
-use rustc_attr_data_structures::AttributeKind;
+use rustc_hir::attrs::AttributeKind;
 use rustc_span::{Span, sym};
 
 use crate::attributes::{NoArgsAttributeParser, OnDuplicate};
diff --git a/compiler/rustc_attr_parsing/src/attributes/non_exhaustive.rs b/compiler/rustc_attr_parsing/src/attributes/non_exhaustive.rs
index 94f6a65c74e..361ac8e959d 100644
--- a/compiler/rustc_attr_parsing/src/attributes/non_exhaustive.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/non_exhaustive.rs
@@ -1,4 +1,4 @@
-use rustc_attr_data_structures::AttributeKind;
+use rustc_hir::attrs::AttributeKind;
 use rustc_span::{Span, Symbol, sym};
 
 use crate::attributes::{NoArgsAttributeParser, OnDuplicate};
diff --git a/compiler/rustc_attr_parsing/src/attributes/path.rs b/compiler/rustc_attr_parsing/src/attributes/path.rs
index febb1b45a18..5700d780d71 100644
--- a/compiler/rustc_attr_parsing/src/attributes/path.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/path.rs
@@ -1,5 +1,5 @@
-use rustc_attr_data_structures::AttributeKind;
 use rustc_feature::{AttributeTemplate, template};
+use rustc_hir::attrs::AttributeKind;
 use rustc_span::{Symbol, sym};
 
 use crate::attributes::{AttributeOrder, OnDuplicate, SingleAttributeParser};
diff --git a/compiler/rustc_attr_parsing/src/attributes/proc_macro_attrs.rs b/compiler/rustc_attr_parsing/src/attributes/proc_macro_attrs.rs
index 4de77dc268e..b156a7c5845 100644
--- a/compiler/rustc_attr_parsing/src/attributes/proc_macro_attrs.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/proc_macro_attrs.rs
@@ -1,5 +1,5 @@
-use rustc_attr_data_structures::AttributeKind;
 use rustc_feature::{AttributeTemplate, template};
+use rustc_hir::attrs::AttributeKind;
 use rustc_span::{Span, Symbol, sym};
 use thin_vec::ThinVec;
 
diff --git a/compiler/rustc_attr_parsing/src/attributes/repr.rs b/compiler/rustc_attr_parsing/src/attributes/repr.rs
index 521acbb607c..6087afe6ded 100644
--- a/compiler/rustc_attr_parsing/src/attributes/repr.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/repr.rs
@@ -1,7 +1,7 @@
 use rustc_abi::Align;
 use rustc_ast::{IntTy, LitIntType, LitKind, UintTy};
-use rustc_attr_data_structures::{AttributeKind, IntType, ReprAttr};
 use rustc_feature::{AttributeTemplate, template};
+use rustc_hir::attrs::{AttributeKind, IntType, ReprAttr};
 use rustc_span::{DUMMY_SP, Span, Symbol, sym};
 
 use super::{AcceptMapping, AttributeParser, CombineAttributeParser, ConvertFn, FinalizeContext};
diff --git a/compiler/rustc_attr_parsing/src/attributes/rustc_internal.rs b/compiler/rustc_attr_parsing/src/attributes/rustc_internal.rs
index 7ca951dc0bb..b465d2e62ff 100644
--- a/compiler/rustc_attr_parsing/src/attributes/rustc_internal.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/rustc_internal.rs
@@ -1,5 +1,5 @@
-use rustc_attr_data_structures::AttributeKind;
 use rustc_feature::{AttributeTemplate, template};
+use rustc_hir::attrs::AttributeKind;
 use rustc_span::{Symbol, sym};
 
 use crate::attributes::{AttributeOrder, OnDuplicate, SingleAttributeParser};
diff --git a/compiler/rustc_attr_parsing/src/attributes/semantics.rs b/compiler/rustc_attr_parsing/src/attributes/semantics.rs
index 74fdff5d2e1..70a8a002099 100644
--- a/compiler/rustc_attr_parsing/src/attributes/semantics.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/semantics.rs
@@ -1,4 +1,4 @@
-use rustc_attr_data_structures::AttributeKind;
+use rustc_hir::attrs::AttributeKind;
 use rustc_span::{Span, Symbol, sym};
 
 use crate::attributes::{NoArgsAttributeParser, OnDuplicate};
diff --git a/compiler/rustc_attr_parsing/src/attributes/stability.rs b/compiler/rustc_attr_parsing/src/attributes/stability.rs
index c54fc6b41f8..3c4ec133d51 100644
--- a/compiler/rustc_attr_parsing/src/attributes/stability.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/stability.rs
@@ -1,11 +1,12 @@
 use std::num::NonZero;
 
-use rustc_attr_data_structures::{
-    AttributeKind, DefaultBodyStability, PartialConstStability, Stability, StabilityLevel,
-    StableSince, UnstableReason, VERSION_PLACEHOLDER,
-};
 use rustc_errors::ErrorGuaranteed;
 use rustc_feature::template;
+use rustc_hir::attrs::AttributeKind;
+use rustc_hir::{
+    DefaultBodyStability, PartialConstStability, Stability, StabilityLevel, StableSince,
+    UnstableReason, VERSION_PLACEHOLDER,
+};
 use rustc_span::{Ident, Span, Symbol, sym};
 
 use super::util::parse_version;
diff --git a/compiler/rustc_attr_parsing/src/attributes/test_attrs.rs b/compiler/rustc_attr_parsing/src/attributes/test_attrs.rs
index ee81f64860f..a90ed830cd1 100644
--- a/compiler/rustc_attr_parsing/src/attributes/test_attrs.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/test_attrs.rs
@@ -1,6 +1,6 @@
-use rustc_attr_data_structures::AttributeKind;
-use rustc_attr_data_structures::lints::AttributeLintKind;
 use rustc_feature::{AttributeTemplate, template};
+use rustc_hir::attrs::AttributeKind;
+use rustc_hir::lints::AttributeLintKind;
 use rustc_span::{Symbol, sym};
 
 use crate::attributes::{AttributeOrder, OnDuplicate, SingleAttributeParser};
diff --git a/compiler/rustc_attr_parsing/src/attributes/traits.rs b/compiler/rustc_attr_parsing/src/attributes/traits.rs
index e69a533699b..a954617ca57 100644
--- a/compiler/rustc_attr_parsing/src/attributes/traits.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/traits.rs
@@ -1,7 +1,7 @@
 use core::mem;
 
-use rustc_attr_data_structures::AttributeKind;
 use rustc_feature::{AttributeTemplate, template};
+use rustc_hir::attrs::AttributeKind;
 use rustc_span::{Span, Symbol, sym};
 
 use crate::attributes::{
diff --git a/compiler/rustc_attr_parsing/src/attributes/transparency.rs b/compiler/rustc_attr_parsing/src/attributes/transparency.rs
index c9fdc57cc06..1c57dc1ebe2 100644
--- a/compiler/rustc_attr_parsing/src/attributes/transparency.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/transparency.rs
@@ -1,5 +1,5 @@
-use rustc_attr_data_structures::AttributeKind;
 use rustc_feature::{AttributeTemplate, template};
+use rustc_hir::attrs::AttributeKind;
 use rustc_span::hygiene::Transparency;
 use rustc_span::{Symbol, sym};
 
diff --git a/compiler/rustc_attr_parsing/src/attributes/util.rs b/compiler/rustc_attr_parsing/src/attributes/util.rs
index 503d2f1fae1..10134915b27 100644
--- a/compiler/rustc_attr_parsing/src/attributes/util.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/util.rs
@@ -1,6 +1,6 @@
 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_hir::RustcVersion;
 use rustc_span::{Symbol, sym};
 
 /// Parse a rustc version number written inside string literal in an attribute,
diff --git a/compiler/rustc_attr_parsing/src/context.rs b/compiler/rustc_attr_parsing/src/context.rs
index 9b86d101840..911d2e13310 100644
--- a/compiler/rustc_attr_parsing/src/context.rs
+++ b/compiler/rustc_attr_parsing/src/context.rs
@@ -5,10 +5,10 @@ use std::sync::LazyLock;
 
 use private::Sealed;
 use rustc_ast::{self as ast, LitKind, MetaItemLit, NodeId};
-use rustc_attr_data_structures::AttributeKind;
-use rustc_attr_data_structures::lints::{AttributeLint, AttributeLintKind};
 use rustc_errors::{DiagCtxtHandle, Diagnostic};
 use rustc_feature::{AttributeTemplate, Features};
+use rustc_hir::attrs::AttributeKind;
+use rustc_hir::lints::{AttributeLint, AttributeLintKind};
 use rustc_hir::{AttrArgs, AttrItem, AttrPath, Attribute, HashIgnoredAttrId, HirId};
 use rustc_session::Session;
 use rustc_span::{DUMMY_SP, ErrorGuaranteed, Span, Symbol, sym};
@@ -16,10 +16,10 @@ use rustc_span::{DUMMY_SP, ErrorGuaranteed, Span, Symbol, sym};
 use crate::attributes::allow_unstable::{
     AllowConstFnUnstableParser, AllowInternalUnstableParser, UnstableFeatureBoundParser,
 };
+use crate::attributes::body::CoroutineParser;
 use crate::attributes::codegen_attrs::{
-    ColdParser, CoverageParser, ExportNameParser, NakedParser, NoMangleParser,
-    OmitGdbPrettyPrinterSectionParser, OptimizeParser, TargetFeatureParser, TrackCallerParser,
-    UsedParser,
+    ColdParser, CoverageParser, ExportNameParser, NakedParser, NoMangleParser, OptimizeParser,
+    TargetFeatureParser, TrackCallerParser, UsedParser,
 };
 use crate::attributes::confusables::ConfusablesParser;
 use crate::attributes::deprecation::DeprecationParser;
@@ -62,15 +62,23 @@ use crate::attributes::{AttributeParser as _, Combine, Single, WithoutArgs};
 use crate::parser::{ArgParser, MetaItemParser, PathParser};
 use crate::session_diagnostics::{AttributeParseError, AttributeParseErrorReason, UnknownMetaItem};
 
-macro_rules! group_type {
-    ($stage: ty) => {
-         LazyLock<(
-            BTreeMap<&'static [Symbol], Vec<(AttributeTemplate, Box<dyn for<'sess, 'a> Fn(&mut AcceptContext<'_, 'sess, $stage>, &ArgParser<'a>) + Send + Sync>)>>,
-            Vec<Box<dyn Send + Sync + Fn(&mut FinalizeContext<'_, '_, $stage>) -> Option<AttributeKind>>>
-        )>
-    };
+type GroupType<S> = LazyLock<GroupTypeInner<S>>;
+
+struct GroupTypeInner<S: Stage> {
+    accepters: BTreeMap<&'static [Symbol], Vec<GroupTypeInnerAccept<S>>>,
+    finalizers: Vec<FinalizeFn<S>>,
+}
+
+struct GroupTypeInnerAccept<S: Stage> {
+    template: AttributeTemplate,
+    accept_fn: AcceptFn<S>,
 }
 
+type AcceptFn<S> =
+    Box<dyn for<'sess, 'a> Fn(&mut AcceptContext<'_, 'sess, S>, &ArgParser<'a>) + Send + Sync>;
+type FinalizeFn<S> =
+    Box<dyn Send + Sync + Fn(&mut FinalizeContext<'_, '_, S>) -> Option<AttributeKind>>;
+
 macro_rules! attribute_parsers {
     (
         pub(crate) static $name: ident = [$($names: ty),* $(,)?];
@@ -93,11 +101,11 @@ macro_rules! attribute_parsers {
         }
     };
     (
-        @[$ty: ty] pub(crate) static $name: ident = [$($names: ty),* $(,)?];
+        @[$stage: ty] pub(crate) static $name: ident = [$($names: ty),* $(,)?];
     ) => {
-        pub(crate) static $name: group_type!($ty) = LazyLock::new(|| {
-            let mut accepts = BTreeMap::<_, Vec<(AttributeTemplate, Box<dyn for<'sess, 'a> Fn(&mut AcceptContext<'_, 'sess, $ty>, &ArgParser<'a>) + Send + Sync>)>>::new();
-            let mut finalizes = Vec::<Box<dyn Send + Sync + Fn(&mut FinalizeContext<'_, '_, $ty>) -> Option<AttributeKind>>>::new();
+        pub(crate) static $name: GroupType<$stage> = LazyLock::new(|| {
+            let mut accepts = BTreeMap::<_, Vec<GroupTypeInnerAccept<$stage>>>::new();
+            let mut finalizes = Vec::<FinalizeFn<$stage>>::new();
             $(
                 {
                     thread_local! {
@@ -105,11 +113,14 @@ macro_rules! attribute_parsers {
                     };
 
                     for (path, template, accept_fn) in <$names>::ATTRIBUTES {
-                        accepts.entry(*path).or_default().push((*template, Box::new(|cx, args| {
-                            STATE_OBJECT.with_borrow_mut(|s| {
-                                accept_fn(s, cx, args)
+                        accepts.entry(*path).or_default().push(GroupTypeInnerAccept {
+                            template: *template,
+                            accept_fn: Box::new(|cx, args| {
+                                STATE_OBJECT.with_borrow_mut(|s| {
+                                    accept_fn(s, cx, args)
+                                })
                             })
-                        })));
+                        });
                     }
 
                     finalizes.push(Box::new(|cx| {
@@ -119,7 +130,7 @@ macro_rules! attribute_parsers {
                 }
             )*
 
-            (accepts, finalizes)
+            GroupTypeInner { accepters:accepts, finalizers:finalizes }
         });
     };
 }
@@ -174,6 +185,7 @@ attribute_parsers!(
         Single<WithoutArgs<ConstContinueParser>>,
         Single<WithoutArgs<ConstStabilityIndirectParser>>,
         Single<WithoutArgs<ConstTraitParser>>,
+        Single<WithoutArgs<CoroutineParser>>,
         Single<WithoutArgs<DenyExplicitImplParser>>,
         Single<WithoutArgs<DoNotImplementViaObjectParser>>,
         Single<WithoutArgs<ExportStableParser>>,
@@ -187,7 +199,6 @@ attribute_parsers!(
         Single<WithoutArgs<NoImplicitPreludeParser>>,
         Single<WithoutArgs<NoMangleParser>>,
         Single<WithoutArgs<NonExhaustiveParser>>,
-        Single<WithoutArgs<OmitGdbPrettyPrinterSectionParser>>,
         Single<WithoutArgs<ParenSugarParser>>,
         Single<WithoutArgs<PassByValueParser>>,
         Single<WithoutArgs<PointeeParser>>,
@@ -213,24 +224,24 @@ mod private {
 #[allow(private_interfaces)]
 pub trait Stage: Sized + 'static + Sealed {
     type Id: Copy;
-    const SHOULD_EMIT_LINTS: bool;
 
-    fn parsers() -> &'static group_type!(Self);
+    fn parsers() -> &'static GroupType<Self>;
 
     fn emit_err<'sess>(
         &self,
         sess: &'sess Session,
         diag: impl for<'x> Diagnostic<'x>,
     ) -> ErrorGuaranteed;
+
+    fn should_emit(&self) -> ShouldEmit;
 }
 
 // allow because it's a sealed trait
 #[allow(private_interfaces)]
 impl Stage for Early {
     type Id = NodeId;
-    const SHOULD_EMIT_LINTS: bool = false;
 
-    fn parsers() -> &'static group_type!(Self) {
+    fn parsers() -> &'static GroupType<Self> {
         &early::ATTRIBUTE_PARSERS
     }
     fn emit_err<'sess>(
@@ -244,15 +255,18 @@ impl Stage for Early {
             sess.dcx().create_err(diag).delay_as_bug()
         }
     }
+
+    fn should_emit(&self) -> ShouldEmit {
+        self.emit_errors
+    }
 }
 
 // allow because it's a sealed trait
 #[allow(private_interfaces)]
 impl Stage for Late {
     type Id = HirId;
-    const SHOULD_EMIT_LINTS: bool = true;
 
-    fn parsers() -> &'static group_type!(Self) {
+    fn parsers() -> &'static GroupType<Self> {
         &late::ATTRIBUTE_PARSERS
     }
     fn emit_err<'sess>(
@@ -262,6 +276,10 @@ impl Stage for Late {
     ) -> ErrorGuaranteed {
         tcx.dcx().emit_err(diag)
     }
+
+    fn should_emit(&self) -> ShouldEmit {
+        ShouldEmit::ErrorsAndLints
+    }
 }
 
 /// used when parsing attributes for miscellaneous things *before* ast lowering
@@ -300,7 +318,7 @@ impl<'f, 'sess: 'f, S: Stage> SharedContext<'f, 'sess, S> {
     /// must be delayed until after HIR is built. This method will take care of the details of
     /// that.
     pub(crate) fn emit_lint(&mut self, lint: AttributeLintKind, span: Span) {
-        if !S::SHOULD_EMIT_LINTS {
+        if !self.stage.should_emit().should_emit() {
             return;
         }
         let id = self.target_id;
@@ -811,8 +829,8 @@ impl<'sess, S: Stage> AttributeParser<'sess, S> {
                     let args = parser.args();
                     let parts = path.segments().map(|i| i.name).collect::<Vec<_>>();
 
-                    if let Some(accepts) = S::parsers().0.get(parts.as_slice()) {
-                        for (template, accept) in accepts {
+                    if let Some(accepts) = S::parsers().accepters.get(parts.as_slice()) {
+                        for accept in accepts {
                             let mut cx: AcceptContext<'_, 'sess, S> = AcceptContext {
                                 shared: SharedContext {
                                     cx: self,
@@ -821,11 +839,11 @@ impl<'sess, S: Stage> AttributeParser<'sess, S> {
                                     emit_lint: &mut emit_lint,
                                 },
                                 attr_span: lower_span(attr.span),
-                                template,
+                                template: &accept.template,
                                 attr_path: path.get_attribute_path(),
                             };
 
-                            accept(&mut cx, args)
+                            (accept.accept_fn)(&mut cx, args)
                         }
                     } else {
                         // If we're here, we must be compiling a tool attribute... Or someone
@@ -856,7 +874,7 @@ impl<'sess, S: Stage> AttributeParser<'sess, S> {
         }
 
         let mut parsed_attributes = Vec::new();
-        for f in &S::parsers().1 {
+        for f in &S::parsers().finalizers {
             if let Some(attr) = f(&mut FinalizeContext {
                 shared: SharedContext {
                     cx: self,
@@ -877,7 +895,7 @@ impl<'sess, S: Stage> AttributeParser<'sess, S> {
 
     /// Returns whether there is a parser for an attribute with this name
     pub fn is_parsed_attribute(path: &[Symbol]) -> bool {
-        Late::parsers().0.contains_key(path)
+        Late::parsers().accepters.contains_key(path)
     }
 
     fn lower_attr_args(&self, args: &ast::AttrArgs, lower_span: impl Fn(Span) -> Span) -> AttrArgs {
diff --git a/compiler/rustc_attr_parsing/src/lib.rs b/compiler/rustc_attr_parsing/src/lib.rs
index dc54cb6b840..fc1377e5314 100644
--- a/compiler/rustc_attr_parsing/src/lib.rs
+++ b/compiler/rustc_attr_parsing/src/lib.rs
@@ -1,13 +1,13 @@
 //! Centralized logic for parsing and attributes.
 //!
 //! ## Architecture
-//! This crate is part of a series of crates that handle attribute processing.
-//! - [rustc_attr_data_structures](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_attr_data_structures/index.html): Defines the data structures that store parsed attributes
+//! This crate is part of a series of crates and modules that handle attribute processing.
+//! - [rustc_hir::attrs](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_hir/index.html): Defines the data structures that store parsed attributes
 //! - [rustc_attr_parsing](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_attr_parsing/index.html): This crate, handles the parsing of attributes
-//! - (planned) rustc_attr_validation: Will handle attribute validation
+//! - (planned) rustc_attr_validation: Will handle attribute validation, logic currently handled in `rustc_passes`
 //!
 //! The separation between data structures and parsing follows the principle of separation of concerns.
-//! Data structures (`rustc_attr_data_structures`) define what attributes look like after parsing.
+//! Data structures (`rustc_hir::attrs`) define what attributes look like after parsing.
 //! This crate (`rustc_attr_parsing`) handles how to convert raw tokens into those structures.
 //! This split allows other parts of the compiler to use the data structures without needing
 //! the parsing logic, making the codebase more modular and maintainable.
@@ -62,7 +62,7 @@
 //! a "stability" of an item. So, the stability attribute has an
 //! [`AttributeParser`](attributes::AttributeParser) that recognizes both the `#[stable()]`
 //! and `#[unstable()]` syntactic attributes, and at the end produce a single
-//! [`AttributeKind::Stability`](rustc_attr_data_structures::AttributeKind::Stability).
+//! [`AttributeKind::Stability`](rustc_hir::attrs::AttributeKind::Stability).
 //!
 //! When multiple instances of the same attribute are allowed, they're combined into a single
 //! semantic attribute. For example:
diff --git a/compiler/rustc_attr_parsing/src/lints.rs b/compiler/rustc_attr_parsing/src/lints.rs
index e648ca4fdf8..22f5531bc80 100644
--- a/compiler/rustc_attr_parsing/src/lints.rs
+++ b/compiler/rustc_attr_parsing/src/lints.rs
@@ -1,6 +1,6 @@
-use rustc_attr_data_structures::lints::{AttributeLint, AttributeLintKind};
 use rustc_errors::{DiagArgValue, LintEmitter};
 use rustc_hir::HirId;
+use rustc_hir::lints::{AttributeLint, AttributeLintKind};
 
 use crate::session_diagnostics;
 
diff --git a/compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs b/compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs
index 0de4bd67f0c..76da9dc8832 100644
--- a/compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs
@@ -3,7 +3,7 @@ use std::rc::Rc;
 
 use rustc_errors::Diag;
 use rustc_hir::def_id::LocalDefId;
-use rustc_infer::infer::region_constraints::{Constraint, RegionConstraintData};
+use rustc_infer::infer::region_constraints::{Constraint, ConstraintKind, RegionConstraintData};
 use rustc_infer::infer::{
     InferCtxt, RegionResolutionError, RegionVariableOrigin, SubregionOrigin, TyCtxtInferExt as _,
 };
@@ -277,7 +277,7 @@ where
         // `QueryNormalizeExt::query_normalize` used in the query and `normalize` called below:
         // the former fails to normalize the `nll/relate_tys/impl-fn-ignore-binder-via-bottom.rs`
         // test. Check after #85499 lands to see if its fixes have erased this difference.
-        let (param_env, value) = key.into_parts();
+        let ty::ParamEnvAnd { param_env, value } = key;
         let _ = ocx.normalize(&cause, param_env, value.value);
 
         let diag = try_extract_error_from_fulfill_cx(
@@ -324,7 +324,7 @@ where
             mbcx.infcx.tcx.infer_ctxt().build_with_canonical(cause.span, &self.canonical_query);
         let ocx = ObligationCtxt::new(&infcx);
 
-        let (param_env, value) = key.into_parts();
+        let ty::ParamEnvAnd { param_env, value } = key;
         let _ = ocx.deeply_normalize(&cause, param_env, value.value);
 
         let diag = try_extract_error_from_fulfill_cx(
@@ -454,25 +454,24 @@ fn try_extract_error_from_region_constraints<'a, 'tcx>(
             (RePlaceholder(a_p), RePlaceholder(b_p)) => a_p.bound == b_p.bound,
             _ => a_region == b_region,
         };
-    let mut check =
-        |constraint: &Constraint<'tcx>, cause: &SubregionOrigin<'tcx>, exact| match *constraint {
-            Constraint::RegSubReg(sub, sup)
-                if ((exact && sup == placeholder_region)
-                    || (!exact && regions_the_same(sup, placeholder_region)))
-                    && sup != sub =>
-            {
-                Some((sub, cause.clone()))
-            }
-            Constraint::VarSubReg(vid, sup)
-                if (exact
-                    && sup == placeholder_region
-                    && !universe_of_region(vid).can_name(placeholder_universe))
-                    || (!exact && regions_the_same(sup, placeholder_region)) =>
-            {
-                Some((ty::Region::new_var(infcx.tcx, vid), cause.clone()))
-            }
-            _ => None,
-        };
+    let mut check = |c: &Constraint<'tcx>, cause: &SubregionOrigin<'tcx>, exact| match c.kind {
+        ConstraintKind::RegSubReg
+            if ((exact && c.sup == placeholder_region)
+                || (!exact && regions_the_same(c.sup, placeholder_region)))
+                && c.sup != c.sub =>
+        {
+            Some((c.sub, cause.clone()))
+        }
+        ConstraintKind::VarSubReg
+            if (exact
+                && c.sup == placeholder_region
+                && !universe_of_region(c.sub.as_var()).can_name(placeholder_universe))
+                || (!exact && regions_the_same(c.sup, placeholder_region)) =>
+        {
+            Some((c.sub, cause.clone()))
+        }
+        _ => None,
+    };
 
     let mut find_culprit = |exact_match: bool| {
         region_constraints
diff --git a/compiler/rustc_borrowck/src/diagnostics/mod.rs b/compiler/rustc_borrowck/src/diagnostics/mod.rs
index 56fdaf1c724..34bed375cb9 100644
--- a/compiler/rustc_borrowck/src/diagnostics/mod.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/mod.rs
@@ -613,7 +613,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
     /// Return the name of the provided `Ty` (that must be a reference) with a synthesized lifetime
     /// name where required.
     pub(super) fn get_name_for_ty(&self, ty: Ty<'tcx>, counter: usize) -> String {
-        let mut printer = ty::print::FmtPrinter::new(self.infcx.tcx, Namespace::TypeNS);
+        let mut p = ty::print::FmtPrinter::new(self.infcx.tcx, Namespace::TypeNS);
 
         // We need to add synthesized lifetimes where appropriate. We do
         // this by hooking into the pretty printer and telling it to label the
@@ -624,19 +624,19 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                 | ty::RePlaceholder(ty::PlaceholderRegion {
                     bound: ty::BoundRegion { kind: br, .. },
                     ..
-                }) => printer.region_highlight_mode.highlighting_bound_region(br, counter),
+                }) => p.region_highlight_mode.highlighting_bound_region(br, counter),
                 _ => {}
             }
         }
 
-        ty.print(&mut printer).unwrap();
-        printer.into_buffer()
+        ty.print(&mut p).unwrap();
+        p.into_buffer()
     }
 
     /// Returns the name of the provided `Ty` (that must be a reference)'s region with a
     /// synthesized lifetime name where required.
     pub(super) fn get_region_name_for_ty(&self, ty: Ty<'tcx>, counter: usize) -> String {
-        let mut printer = ty::print::FmtPrinter::new(self.infcx.tcx, Namespace::TypeNS);
+        let mut p = ty::print::FmtPrinter::new(self.infcx.tcx, Namespace::TypeNS);
 
         let region = if let ty::Ref(region, ..) = ty.kind() {
             match region.kind() {
@@ -644,7 +644,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                 | ty::RePlaceholder(ty::PlaceholderRegion {
                     bound: ty::BoundRegion { kind: br, .. },
                     ..
-                }) => printer.region_highlight_mode.highlighting_bound_region(br, counter),
+                }) => p.region_highlight_mode.highlighting_bound_region(br, counter),
                 _ => {}
             }
             region
@@ -652,8 +652,8 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
             bug!("ty for annotation of borrow region is not a reference");
         };
 
-        region.print(&mut printer).unwrap();
-        printer.into_buffer()
+        region.print(&mut p).unwrap();
+        p.into_buffer()
     }
 
     /// Add a note to region errors and borrow explanations when higher-ranked regions in predicates
diff --git a/compiler/rustc_borrowck/src/region_infer/mod.rs b/compiler/rustc_borrowck/src/region_infer/mod.rs
index 68f1637e07e..f1320048533 100644
--- a/compiler/rustc_borrowck/src/region_infer/mod.rs
+++ b/compiler/rustc_borrowck/src/region_infer/mod.rs
@@ -417,7 +417,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     /// minimum values.
     ///
     /// For example:
-    /// ```
+    /// ```ignore (illustrative)
     /// fn foo<'a, 'b>( /* ... */ ) where 'a: 'b { /* ... */ }
     /// ```
     /// would initialize two variables like so:
diff --git a/compiler/rustc_borrowck/src/type_check/input_output.rs b/compiler/rustc_borrowck/src/type_check/input_output.rs
index 99392ea1915..eb31b5de05d 100644
--- a/compiler/rustc_borrowck/src/type_check/input_output.rs
+++ b/compiler/rustc_borrowck/src/type_check/input_output.rs
@@ -86,7 +86,6 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                         // them with fresh ty vars.
                         resume_ty: next_ty_var(),
                         yield_ty: next_ty_var(),
-                        witness: next_ty_var(),
                     },
                 )
                 .args,
diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs
index f5fedbf95c1..148d0de3bab 100644
--- a/compiler/rustc_borrowck/src/type_check/mod.rs
+++ b/compiler/rustc_borrowck/src/type_check/mod.rs
@@ -769,9 +769,13 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
             }
             TerminatorKind::Call { func, args, .. }
             | TerminatorKind::TailCall { func, args, .. } => {
-                let call_source = match term.kind {
-                    TerminatorKind::Call { call_source, .. } => call_source,
-                    TerminatorKind::TailCall { .. } => CallSource::Normal,
+                let (call_source, destination, is_diverging) = match term.kind {
+                    TerminatorKind::Call { call_source, destination, target, .. } => {
+                        (call_source, destination, target.is_none())
+                    }
+                    TerminatorKind::TailCall { .. } => {
+                        (CallSource::Normal, RETURN_PLACE.into(), false)
+                    }
                     _ => unreachable!(),
                 };
 
@@ -845,9 +849,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                     );
                 }
 
-                if let TerminatorKind::Call { destination, target, .. } = term.kind {
-                    self.check_call_dest(term, &sig, destination, target, term_location);
-                }
+                self.check_call_dest(term, &sig, destination, is_diverging, term_location);
 
                 // The ordinary liveness rules will ensure that all
                 // regions in the type of the callee are live here. We
@@ -1874,65 +1876,61 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         term: &Terminator<'tcx>,
         sig: &ty::FnSig<'tcx>,
         destination: Place<'tcx>,
-        target: Option<BasicBlock>,
+        is_diverging: bool,
         term_location: Location,
     ) {
         let tcx = self.tcx();
-        match target {
-            Some(_) => {
-                let dest_ty = destination.ty(self.body, tcx).ty;
-                let dest_ty = self.normalize(dest_ty, term_location);
-                let category = match destination.as_local() {
-                    Some(RETURN_PLACE) => {
-                        if let DefiningTy::Const(def_id, _) | DefiningTy::InlineConst(def_id, _) =
-                            self.universal_regions.defining_ty
-                        {
-                            if tcx.is_static(def_id) {
-                                ConstraintCategory::UseAsStatic
-                            } else {
-                                ConstraintCategory::UseAsConst
-                            }
+        if is_diverging {
+            // The signature in this call can reference region variables,
+            // so erase them before calling a query.
+            let output_ty = self.tcx().erase_regions(sig.output());
+            if !output_ty
+                .is_privately_uninhabited(self.tcx(), self.infcx.typing_env(self.infcx.param_env))
+            {
+                span_mirbug!(self, term, "call to converging function {:?} w/o dest", sig);
+            }
+        } else {
+            let dest_ty = destination.ty(self.body, tcx).ty;
+            let dest_ty = self.normalize(dest_ty, term_location);
+            let category = match destination.as_local() {
+                Some(RETURN_PLACE) => {
+                    if let DefiningTy::Const(def_id, _) | DefiningTy::InlineConst(def_id, _) =
+                        self.universal_regions.defining_ty
+                    {
+                        if tcx.is_static(def_id) {
+                            ConstraintCategory::UseAsStatic
                         } else {
-                            ConstraintCategory::Return(ReturnConstraint::Normal)
+                            ConstraintCategory::UseAsConst
                         }
+                    } else {
+                        ConstraintCategory::Return(ReturnConstraint::Normal)
                     }
-                    Some(l) if !self.body.local_decls[l].is_user_variable() => {
-                        ConstraintCategory::Boring
-                    }
-                    // The return type of a call is interesting for diagnostics.
-                    _ => ConstraintCategory::Assignment,
-                };
-
-                let locations = term_location.to_locations();
-
-                if let Err(terr) = self.sub_types(sig.output(), dest_ty, locations, category) {
-                    span_mirbug!(
-                        self,
-                        term,
-                        "call dest mismatch ({:?} <- {:?}): {:?}",
-                        dest_ty,
-                        sig.output(),
-                        terr
-                    );
                 }
-
-                // When `unsized_fn_params` is not enabled,
-                // this check is done at `check_local`.
-                if self.unsized_feature_enabled() {
-                    let span = term.source_info.span;
-                    self.ensure_place_sized(dest_ty, span);
+                Some(l) if !self.body.local_decls[l].is_user_variable() => {
+                    ConstraintCategory::Boring
                 }
+                // The return type of a call is interesting for diagnostics.
+                _ => ConstraintCategory::Assignment,
+            };
+
+            let locations = term_location.to_locations();
+
+            if let Err(terr) = self.sub_types(sig.output(), dest_ty, locations, category) {
+                span_mirbug!(
+                    self,
+                    term,
+                    "call dest mismatch ({:?} <- {:?}): {:?}",
+                    dest_ty,
+                    sig.output(),
+                    terr
+                );
             }
-            None => {
-                // The signature in this call can reference region variables,
-                // so erase them before calling a query.
-                let output_ty = self.tcx().erase_regions(sig.output());
-                if !output_ty.is_privately_uninhabited(
-                    self.tcx(),
-                    self.infcx.typing_env(self.infcx.param_env),
-                ) {
-                    span_mirbug!(self, term, "call to converging function {:?} w/o dest", sig);
-                }
+
+            // When `unsized_fn_params` is not enabled,
+            // this check is done at `check_local`.
+            if self.unsized_feature_enabled() {
+                let span = term.source_info.span;
+                self.ensure_place_sized(dest_ty, span);
             }
         }
     }
diff --git a/compiler/rustc_borrowck/src/type_check/relate_tys.rs b/compiler/rustc_borrowck/src/type_check/relate_tys.rs
index e023300f1c2..bb72d1d52f3 100644
--- a/compiler/rustc_borrowck/src/type_check/relate_tys.rs
+++ b/compiler/rustc_borrowck/src/type_check/relate_tys.rs
@@ -187,7 +187,7 @@ impl<'a, 'b, 'tcx> NllTypeRelating<'a, 'b, 'tcx> {
                 types: &mut |_bound_ty: ty::BoundTy| {
                     unreachable!("we only replace regions in nll_relate, not types")
                 },
-                consts: &mut |_bound_var: ty::BoundVar| {
+                consts: &mut |_bound_const: ty::BoundConst| {
                     unreachable!("we only replace regions in nll_relate, not consts")
                 },
             };
@@ -226,7 +226,7 @@ impl<'a, 'b, 'tcx> NllTypeRelating<'a, 'b, 'tcx> {
             types: &mut |_bound_ty: ty::BoundTy| {
                 unreachable!("we only replace regions in nll_relate, not types")
             },
-            consts: &mut |_bound_var: ty::BoundVar| {
+            consts: &mut |_bound_const: ty::BoundConst| {
                 unreachable!("we only replace regions in nll_relate, not consts")
             },
         };
diff --git a/compiler/rustc_builtin_macros/Cargo.toml b/compiler/rustc_builtin_macros/Cargo.toml
index 4c1264c6f1c..e56b9e641a1 100644
--- a/compiler/rustc_builtin_macros/Cargo.toml
+++ b/compiler/rustc_builtin_macros/Cargo.toml
@@ -10,7 +10,6 @@ doctest = false
 # tidy-alphabetical-start
 rustc_ast = { path = "../rustc_ast" }
 rustc_ast_pretty = { path = "../rustc_ast_pretty" }
-rustc_attr_data_structures = { path = "../rustc_attr_data_structures" }
 rustc_attr_parsing = { path = "../rustc_attr_parsing" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
diff --git a/compiler/rustc_builtin_macros/src/deriving/generic/mod.rs b/compiler/rustc_builtin_macros/src/deriving/generic/mod.rs
index b24e5563761..fc9eed24ee0 100644
--- a/compiler/rustc_builtin_macros/src/deriving/generic/mod.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/generic/mod.rs
@@ -187,10 +187,10 @@ use rustc_ast::{
     self as ast, AnonConst, AttrArgs, BindingMode, ByRef, DelimArgs, EnumDef, Expr, GenericArg,
     GenericParamKind, Generics, Mutability, PatKind, Safety, VariantData,
 };
-use rustc_attr_data_structures::{AttributeKind, ReprPacked};
 use rustc_attr_parsing::AttributeParser;
 use rustc_expand::base::{Annotatable, ExtCtxt};
 use rustc_hir::Attribute;
+use rustc_hir::attrs::{AttributeKind, ReprPacked};
 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/proc_macro_harness.rs b/compiler/rustc_builtin_macros/src/proc_macro_harness.rs
index 09f5e6f6efc..df70c93c1c2 100644
--- a/compiler/rustc_builtin_macros/src/proc_macro_harness.rs
+++ b/compiler/rustc_builtin_macros/src/proc_macro_harness.rs
@@ -4,12 +4,12 @@ use rustc_ast::ptr::P;
 use rustc_ast::visit::{self, Visitor};
 use rustc_ast::{self as ast, HasNodeId, NodeId, attr};
 use rustc_ast_pretty::pprust;
-use rustc_attr_data_structures::AttributeKind;
 use rustc_attr_parsing::AttributeParser;
 use rustc_errors::DiagCtxtHandle;
 use rustc_expand::base::{ExtCtxt, ResolverExpand};
 use rustc_expand::expand::{AstFragment, ExpansionConfig};
 use rustc_feature::Features;
+use rustc_hir::attrs::AttributeKind;
 use rustc_session::Session;
 use rustc_span::hygiene::AstPass;
 use rustc_span::source_map::SourceMap;
diff --git a/compiler/rustc_codegen_cranelift/scripts/setup_rust_fork.sh b/compiler/rustc_codegen_cranelift/scripts/setup_rust_fork.sh
index 532702bb1a4..492f4dc4452 100644
--- a/compiler/rustc_codegen_cranelift/scripts/setup_rust_fork.sh
+++ b/compiler/rustc_codegen_cranelift/scripts/setup_rust_fork.sh
@@ -33,6 +33,7 @@ rustc = "$(pwd)/../dist/bin/rustc-clif"
 cargo = "$(rustup which cargo)"
 full-bootstrap = true
 local-rebuild = true
+compiletest-allow-stage0 = true
 
 [rust]
 download-rustc = false
diff --git a/compiler/rustc_codegen_cranelift/scripts/test_rustc_tests.sh b/compiler/rustc_codegen_cranelift/scripts/test_rustc_tests.sh
index 7e356b4b462..52e02c857c7 100755
--- a/compiler/rustc_codegen_cranelift/scripts/test_rustc_tests.sh
+++ b/compiler/rustc_codegen_cranelift/scripts/test_rustc_tests.sh
@@ -166,5 +166,5 @@ index 073116933bd..c3e4578204d 100644
 EOF
 
 echo "[TEST] rustc test suite"
-COMPILETEST_FORCE_STAGE0=1 ./x.py test --stage 0 --test-args=--no-capture tests/{codegen-units,run-make,ui,incremental}
+./x.py test --stage 0 --test-args=--no-capture tests/{codegen-units,run-make,ui,incremental}
 popd
diff --git a/compiler/rustc_codegen_gcc/build_system/src/abi_test.rs b/compiler/rustc_codegen_gcc/build_system/src/abi_test.rs
index 3c1531be27a..a85886d87f3 100644
--- a/compiler/rustc_codegen_gcc/build_system/src/abi_test.rs
+++ b/compiler/rustc_codegen_gcc/build_system/src/abi_test.rs
@@ -31,7 +31,7 @@ pub fn run() -> Result<(), String> {
         Some("clones/abi-cafe".as_ref()),
         true,
     )
-    .map_err(|err| (format!("Git clone failed with message: {err:?}!")))?;
+    .map_err(|err| format!("Git clone failed with message: {err:?}!"))?;
     // Configure abi-cafe to use the exact same rustc version we use - this is crucial.
     // Otherwise, the concept of ABI compatibility becomes meanignless.
     std::fs::copy("rust-toolchain", "clones/abi-cafe/rust-toolchain")
diff --git a/compiler/rustc_codegen_gcc/build_system/src/fuzz.rs b/compiler/rustc_codegen_gcc/build_system/src/fuzz.rs
index 453211366b3..9714ce29af9 100644
--- a/compiler/rustc_codegen_gcc/build_system/src/fuzz.rs
+++ b/compiler/rustc_codegen_gcc/build_system/src/fuzz.rs
@@ -43,18 +43,18 @@ pub fn run() -> Result<(), String> {
             "--start" => {
                 start =
                     str::parse(&args.next().ok_or_else(|| "Fuzz start not provided!".to_string())?)
-                        .map_err(|err| (format!("Fuzz start not a number {err:?}!")))?;
+                        .map_err(|err| format!("Fuzz start not a number {err:?}!"))?;
             }
             "--count" => {
                 count =
                     str::parse(&args.next().ok_or_else(|| "Fuzz count not provided!".to_string())?)
-                        .map_err(|err| (format!("Fuzz count not a number {err:?}!")))?;
+                        .map_err(|err| format!("Fuzz count not a number {err:?}!"))?;
             }
             "-j" | "--jobs" => {
                 threads = str::parse(
                     &args.next().ok_or_else(|| "Fuzz thread count not provided!".to_string())?,
                 )
-                .map_err(|err| (format!("Fuzz thread count not a number {err:?}!")))?;
+                .map_err(|err| format!("Fuzz thread count not a number {err:?}!"))?;
             }
             _ => return Err(format!("Unknown option {arg}")),
         }
@@ -66,7 +66,7 @@ pub fn run() -> Result<(), String> {
         Some("clones/rustlantis".as_ref()),
         true,
     )
-    .map_err(|err| (format!("Git clone failed with message: {err:?}!")))?;
+    .map_err(|err| format!("Git clone failed with message: {err:?}!"))?;
 
     // Ensure that we are on the newest rustlantis commit.
     let cmd: &[&dyn AsRef<OsStr>] = &[&"git", &"pull", &"origin"];
diff --git a/compiler/rustc_codegen_gcc/build_system/src/test.rs b/compiler/rustc_codegen_gcc/build_system/src/test.rs
index bc0fdd40b6e..2c8271c36a9 100644
--- a/compiler/rustc_codegen_gcc/build_system/src/test.rs
+++ b/compiler/rustc_codegen_gcc/build_system/src/test.rs
@@ -561,8 +561,6 @@ fn asm_tests(env: &Env, args: &TestArg) -> Result<(), String> {
     // FIXME: create a function "display_if_not_quiet" or something along the line.
     println!("[TEST] rustc asm test suite");
 
-    env.insert("COMPILETEST_FORCE_STAGE0".to_string(), "1".to_string());
-
     let codegen_backend_path = format!(
         "{pwd}/target/{channel}/librustc_codegen_gcc.{dylib_ext}",
         pwd = std::env::current_dir()
@@ -588,6 +586,8 @@ fn asm_tests(env: &Env, args: &TestArg) -> Result<(), String> {
             &"always",
             &"--stage",
             &"0",
+            &"--set",
+            &"build.compiletest-allow-stage0=true",
             &"tests/assembly-llvm/asm",
             &"--compiletest-rustc-args",
             &rustc_args,
@@ -1047,7 +1047,6 @@ where
 
     // FIXME: create a function "display_if_not_quiet" or something along the line.
     println!("[TEST] rustc {test_type} test suite");
-    env.insert("COMPILETEST_FORCE_STAGE0".to_string(), "1".to_string());
 
     let extra =
         if args.is_using_gcc_master_branch() { "" } else { " -Csymbol-mangling-version=v0" };
@@ -1070,6 +1069,8 @@ where
             &"always",
             &"--stage",
             &"0",
+            &"--set",
+            &"build.compiletest-allow-stage0=true",
             &format!("tests/{test_type}"),
             &"--compiletest-rustc-args",
             &rustc_args,
diff --git a/compiler/rustc_codegen_gcc/messages.ftl b/compiler/rustc_codegen_gcc/messages.ftl
index a70ac08f01a..b9b77b7d18c 100644
--- a/compiler/rustc_codegen_gcc/messages.ftl
+++ b/compiler/rustc_codegen_gcc/messages.ftl
@@ -4,3 +4,5 @@ codegen_gcc_unwinding_inline_asm =
 codegen_gcc_copy_bitcode = failed to copy bitcode to object file: {$err}
 
 codegen_gcc_lto_bitcode_from_rlib = failed to get bitcode from object file for LTO ({$gcc_err})
+
+codegen_gcc_explicit_tail_calls_unsupported = explicit tail calls with the 'become' keyword are not implemented in the GCC backend
diff --git a/compiler/rustc_codegen_gcc/patches/0001-Add-stdarch-Cargo.toml-for-testing.patch b/compiler/rustc_codegen_gcc/patches/0001-Add-stdarch-Cargo.toml-for-testing.patch
index 9cc377850b9..3a8c37a8b8d 100644
--- a/compiler/rustc_codegen_gcc/patches/0001-Add-stdarch-Cargo.toml-for-testing.patch
+++ b/compiler/rustc_codegen_gcc/patches/0001-Add-stdarch-Cargo.toml-for-testing.patch
@@ -1,29 +1,28 @@
-From b8f3eed3053c9333b5dfbeaeb2a6a65a4b3156df Mon Sep 17 00:00:00 2001
-From: Antoni Boucher <bouanto@zoho.com>
-Date: Tue, 29 Aug 2023 13:06:34 -0400
+From 190e26c9274b3c93a9ee3516b395590e6bd9213b Mon Sep 17 00:00:00 2001
+From: None <none@example.com>
+Date: Sun, 3 Aug 2025 19:54:56 -0400
 Subject: [PATCH] Patch 0001-Add-stdarch-Cargo.toml-for-testing.patch
 
 ---
- library/stdarch/Cargo.toml | 23 +++++++++++++++++++++++
- 1 file changed, 23 insertions(+)
+ library/stdarch/Cargo.toml | 20 ++++++++++++++++++++
+ 1 file changed, 20 insertions(+)
  create mode 100644 library/stdarch/Cargo.toml
 
 diff --git a/library/stdarch/Cargo.toml b/library/stdarch/Cargo.toml
 new file mode 100644
-index 0000000..4c63700
+index 0000000..bd6725c
 --- /dev/null
 +++ b/library/stdarch/Cargo.toml
-@@ -0,0 +1,21 @@
+@@ -0,0 +1,20 @@
 +[workspace]
 +resolver = "1"
 +members = [
-+  "crates/core_arch",
-+  "crates/std_detect",
-+  "crates/stdarch-gen-arm",
++  "crates/*",
 +  #"examples/"
 +]
 +exclude = [
-+  "crates/wasm-assert-instr-tests"
++  "crates/wasm-assert-instr-tests",
++  "rust_programs",
 +]
 +
 +[profile.release]
@@ -36,5 +35,5 @@ index 0000000..4c63700
 +opt-level = 3
 +incremental = true
 -- 
-2.42.0
+2.50.1
 
diff --git a/compiler/rustc_codegen_gcc/rust-toolchain b/compiler/rustc_codegen_gcc/rust-toolchain
index 2fe8ec4647f..058e734be5c 100644
--- a/compiler/rustc_codegen_gcc/rust-toolchain
+++ b/compiler/rustc_codegen_gcc/rust-toolchain
@@ -1,3 +1,3 @@
 [toolchain]
-channel = "nightly-2025-07-04"
+channel = "nightly-2025-08-03"
 components = ["rust-src", "rustc-dev", "llvm-tools-preview"]
diff --git a/compiler/rustc_codegen_gcc/src/allocator.rs b/compiler/rustc_codegen_gcc/src/allocator.rs
index 0d8dc93274f..2a95a7368aa 100644
--- a/compiler/rustc_codegen_gcc/src/allocator.rs
+++ b/compiler/rustc_codegen_gcc/src/allocator.rs
@@ -99,11 +99,15 @@ fn create_const_value_function(
     let func = context.new_function(None, FunctionType::Exported, output, &[], name, false);
 
     #[cfg(feature = "master")]
-    func.add_attribute(FnAttribute::Visibility(symbol_visibility_to_gcc(
-        tcx.sess.default_visibility(),
-    )));
-
-    func.add_attribute(FnAttribute::AlwaysInline);
+    {
+        func.add_attribute(FnAttribute::Visibility(symbol_visibility_to_gcc(
+            tcx.sess.default_visibility(),
+        )));
+
+        // FIXME(antoyo): cg_llvm sets AlwaysInline, but AlwaysInline is different in GCC and using
+        // it here will causes linking errors when using LTO.
+        func.add_attribute(FnAttribute::Inline);
+    }
 
     if tcx.sess.must_emit_unwind_tables() {
         // TODO(antoyo): emit unwind tables.
diff --git a/compiler/rustc_codegen_gcc/src/attributes.rs b/compiler/rustc_codegen_gcc/src/attributes.rs
index 7a1ae6ca9c8..04b43bb8bb7 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_data_structures::InlineAttr;
-use rustc_attr_data_structures::InstructionSetAttr;
+use rustc_hir::attrs::InlineAttr;
+use rustc_hir::attrs::InstructionSetAttr;
 #[cfg(feature = "master")]
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 #[cfg(feature = "master")]
diff --git a/compiler/rustc_codegen_gcc/src/builder.rs b/compiler/rustc_codegen_gcc/src/builder.rs
index a4ec4bf8dea..34ade3d025f 100644
--- a/compiler/rustc_codegen_gcc/src/builder.rs
+++ b/compiler/rustc_codegen_gcc/src/builder.rs
@@ -34,6 +34,7 @@ use rustc_target::spec::{HasTargetSpec, HasX86AbiOpt, Target, X86Abi};
 
 use crate::common::{SignType, TypeReflection, type_is_pointer};
 use crate::context::CodegenCx;
+use crate::errors;
 use crate::intrinsic::llvm;
 use crate::type_of::LayoutGccExt;
 
@@ -539,9 +540,15 @@ impl<'a, 'gcc, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'gcc, 'tcx> {
 
     fn ret(&mut self, mut value: RValue<'gcc>) {
         let expected_return_type = self.current_func().get_return_type();
-        if !expected_return_type.is_compatible_with(value.get_type()) {
-            // NOTE: due to opaque pointers now being used, we need to cast here.
-            value = self.context.new_cast(self.location, value, expected_return_type);
+        let value_type = value.get_type();
+        if !expected_return_type.is_compatible_with(value_type) {
+            // NOTE: due to opaque pointers now being used, we need to (bit)cast here.
+            if self.is_native_int_type(value_type) && self.is_native_int_type(expected_return_type)
+            {
+                value = self.context.new_cast(self.location, value, expected_return_type);
+            } else {
+                value = self.context.new_bitcast(self.location, value, expected_return_type);
+            }
         }
         self.llbb().end_with_return(self.location, value);
     }
@@ -1278,11 +1285,19 @@ impl<'a, 'gcc, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'gcc, 'tcx> {
 
     fn intcast(
         &mut self,
-        value: RValue<'gcc>,
+        mut value: RValue<'gcc>,
         dest_typ: Type<'gcc>,
-        _is_signed: bool,
+        is_signed: bool,
     ) -> RValue<'gcc> {
-        // NOTE: is_signed is for value, not dest_typ.
+        let value_type = value.get_type();
+        if is_signed && !value_type.is_signed(self.cx) {
+            let signed_type = value_type.to_signed(self.cx);
+            value = self.gcc_int_cast(value, signed_type);
+        } else if !is_signed && value_type.is_signed(self.cx) {
+            let unsigned_type = value_type.to_unsigned(self.cx);
+            value = self.gcc_int_cast(value, unsigned_type);
+        }
+
         self.gcc_int_cast(value, dest_typ)
     }
 
@@ -1742,6 +1757,20 @@ impl<'a, 'gcc, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'gcc, 'tcx> {
         call
     }
 
+    fn tail_call(
+        &mut self,
+        _llty: Self::Type,
+        _fn_attrs: Option<&CodegenFnAttrs>,
+        _fn_abi: &FnAbi<'tcx, Ty<'tcx>>,
+        _llfn: Self::Value,
+        _args: &[Self::Value],
+        _funclet: Option<&Self::Funclet>,
+        _instance: Option<Instance<'tcx>>,
+    ) {
+        // FIXME: implement support for explicit tail calls like rustc_codegen_llvm.
+        self.tcx.dcx().emit_fatal(errors::ExplicitTailCallsUnsupported);
+    }
+
     fn zext(&mut self, value: RValue<'gcc>, dest_typ: Type<'gcc>) -> RValue<'gcc> {
         // FIXME(antoyo): this does not zero-extend.
         self.gcc_int_cast(value, dest_typ)
diff --git a/compiler/rustc_codegen_gcc/src/callee.rs b/compiler/rustc_codegen_gcc/src/callee.rs
index e7ca95af594..8487a85bd03 100644
--- a/compiler/rustc_codegen_gcc/src/callee.rs
+++ b/compiler/rustc_codegen_gcc/src/callee.rs
@@ -106,7 +106,7 @@ pub fn get_fn<'gcc, 'tcx>(cx: &CodegenCx<'gcc, 'tcx>, instance: Instance<'tcx>)
                 // This is a monomorphization of a generic function.
                 if !(cx.tcx.sess.opts.share_generics()
                     || tcx.codegen_instance_attrs(instance.def).inline
-                        == rustc_attr_data_structures::InlineAttr::Never)
+                        == rustc_hir::attrs::InlineAttr::Never)
                 {
                     // When not sharing generics, all instances are in the same
                     // crate and have hidden visibility.
diff --git a/compiler/rustc_codegen_gcc/src/debuginfo.rs b/compiler/rustc_codegen_gcc/src/debuginfo.rs
index 4c8585192a1..4c0b6439523 100644
--- a/compiler/rustc_codegen_gcc/src/debuginfo.rs
+++ b/compiler/rustc_codegen_gcc/src/debuginfo.rs
@@ -254,7 +254,8 @@ impl<'gcc, 'tcx> DebugInfoCodegenMethods<'tcx> for CodegenCx<'gcc, 'tcx> {
         // TODO(antoyo): implement.
     }
 
-    fn debuginfo_finalize(&self) {
+    fn debuginfo_finalize(&mut self) {
+        // TODO: emit section `.debug_gdb_scripts`.
         self.context.set_debug_info(true)
     }
 
diff --git a/compiler/rustc_codegen_gcc/src/errors.rs b/compiler/rustc_codegen_gcc/src/errors.rs
index 0aa16bd88b4..b252c39c0c0 100644
--- a/compiler/rustc_codegen_gcc/src/errors.rs
+++ b/compiler/rustc_codegen_gcc/src/errors.rs
@@ -19,3 +19,7 @@ pub(crate) struct CopyBitcode {
 pub(crate) struct LtoBitcodeFromRlib {
     pub gcc_err: String,
 }
+
+#[derive(Diagnostic)]
+#[diag(codegen_gcc_explicit_tail_calls_unsupported)]
+pub(crate) struct ExplicitTailCallsUnsupported;
diff --git a/compiler/rustc_codegen_gcc/src/int.rs b/compiler/rustc_codegen_gcc/src/int.rs
index 6f21ce9352b..9fb7f6bad68 100644
--- a/compiler/rustc_codegen_gcc/src/int.rs
+++ b/compiler/rustc_codegen_gcc/src/int.rs
@@ -4,12 +4,15 @@
 
 // cSpell:words cmpti divti modti mulodi muloti udivti umodti
 
-use gccjit::{BinaryOp, ComparisonOp, FunctionType, Location, RValue, ToRValue, Type, UnaryOp};
+use gccjit::{
+    BinaryOp, CType, ComparisonOp, FunctionType, Location, RValue, ToRValue, Type, UnaryOp,
+};
 use rustc_abi::{CanonAbi, Endian, ExternAbi};
 use rustc_codegen_ssa::common::{IntPredicate, TypeKind};
 use rustc_codegen_ssa::traits::{BackendTypes, BaseTypeCodegenMethods, BuilderMethods, OverflowOp};
 use rustc_middle::ty::{self, Ty};
 use rustc_target::callconv::{ArgAbi, ArgAttributes, FnAbi, PassMode};
+use rustc_type_ir::{Interner, TyKind};
 
 use crate::builder::{Builder, ToGccComp};
 use crate::common::{SignType, TypeReflection};
@@ -167,9 +170,9 @@ impl<'a, 'gcc, 'tcx> Builder<'a, 'gcc, 'tcx> {
                 if a_type.is_vector() {
                     // Vector types need to be bitcast.
                     // TODO(antoyo): perhaps use __builtin_convertvector for vector casting.
-                    b = self.context.new_bitcast(self.location, b, a.get_type());
+                    b = self.context.new_bitcast(self.location, b, a_type);
                 } else {
-                    b = self.context.new_cast(self.location, b, a.get_type());
+                    b = self.context.new_cast(self.location, b, a_type);
                 }
             }
             self.context.new_binary_op(self.location, operation, a_type, a, b)
@@ -216,13 +219,22 @@ impl<'a, 'gcc, 'tcx> Builder<'a, 'gcc, 'tcx> {
         operation_name: &str,
         signed: bool,
         a: RValue<'gcc>,
-        b: RValue<'gcc>,
+        mut b: RValue<'gcc>,
     ) -> RValue<'gcc> {
         let a_type = a.get_type();
         let b_type = b.get_type();
         if (self.is_native_int_type_or_bool(a_type) && self.is_native_int_type_or_bool(b_type))
             || (a_type.is_vector() && b_type.is_vector())
         {
+            if !a_type.is_compatible_with(b_type) {
+                if a_type.is_vector() {
+                    // Vector types need to be bitcast.
+                    // TODO(antoyo): perhaps use __builtin_convertvector for vector casting.
+                    b = self.context.new_bitcast(self.location, b, a_type);
+                } else {
+                    b = self.context.new_cast(self.location, b, a_type);
+                }
+            }
             self.context.new_binary_op(self.location, operation, a_type, a, b)
         } else {
             debug_assert!(a_type.dyncast_array().is_some());
@@ -351,6 +363,11 @@ impl<'a, 'gcc, 'tcx> Builder<'a, 'gcc, 'tcx> {
             // TODO(antoyo): is it correct to use rhs type instead of the parameter typ?
             .new_local(self.location, rhs.get_type(), "binopResult")
             .get_address(self.location);
+        let new_type = type_kind_to_gcc_type(new_kind);
+        let new_type = self.context.new_c_type(new_type);
+        let lhs = self.context.new_cast(self.location, lhs, new_type);
+        let rhs = self.context.new_cast(self.location, rhs, new_type);
+        let res = self.context.new_cast(self.location, res, new_type.make_pointer());
         let overflow = self.overflow_call(intrinsic, &[lhs, rhs, res], None);
         (res.dereference(self.location).to_rvalue(), overflow)
     }
@@ -477,11 +494,27 @@ impl<'a, 'gcc, 'tcx> Builder<'a, 'gcc, 'tcx> {
             let lhs_low = self.context.new_cast(self.location, self.low(lhs), unsigned_type);
             let rhs_low = self.context.new_cast(self.location, self.low(rhs), unsigned_type);
 
+            let mut lhs_high = self.high(lhs);
+            let mut rhs_high = self.high(rhs);
+
+            match op {
+                IntPredicate::IntUGT
+                | IntPredicate::IntUGE
+                | IntPredicate::IntULT
+                | IntPredicate::IntULE => {
+                    lhs_high = self.context.new_cast(self.location, lhs_high, unsigned_type);
+                    rhs_high = self.context.new_cast(self.location, rhs_high, unsigned_type);
+                }
+                // TODO(antoyo): we probably need to handle signed comparison for unsigned
+                // integers.
+                _ => (),
+            }
+
             let condition = self.context.new_comparison(
                 self.location,
                 ComparisonOp::LessThan,
-                self.high(lhs),
-                self.high(rhs),
+                lhs_high,
+                rhs_high,
             );
             self.llbb().end_with_conditional(self.location, condition, block1, block2);
 
@@ -495,8 +528,8 @@ impl<'a, 'gcc, 'tcx> Builder<'a, 'gcc, 'tcx> {
             let condition = self.context.new_comparison(
                 self.location,
                 ComparisonOp::GreaterThan,
-                self.high(lhs),
-                self.high(rhs),
+                lhs_high,
+                rhs_high,
             );
             block2.end_with_conditional(self.location, condition, block3, block4);
 
@@ -620,7 +653,7 @@ impl<'a, 'gcc, 'tcx> Builder<'a, 'gcc, 'tcx> {
         }
     }
 
-    pub fn gcc_xor(&self, a: RValue<'gcc>, b: RValue<'gcc>) -> RValue<'gcc> {
+    pub fn gcc_xor(&self, a: RValue<'gcc>, mut b: RValue<'gcc>) -> RValue<'gcc> {
         let a_type = a.get_type();
         let b_type = b.get_type();
         if a_type.is_vector() && b_type.is_vector() {
@@ -628,6 +661,9 @@ impl<'a, 'gcc, 'tcx> Builder<'a, 'gcc, 'tcx> {
             a ^ b
         } else if self.is_native_int_type_or_bool(a_type) && self.is_native_int_type_or_bool(b_type)
         {
+            if !a_type.is_compatible_with(b_type) {
+                b = self.context.new_cast(self.location, b, a_type);
+            }
             a ^ b
         } else {
             self.concat_low_high_rvalues(
@@ -1042,3 +1078,25 @@ impl<'gcc, 'tcx> CodegenCx<'gcc, 'tcx> {
         self.context.new_array_constructor(None, typ, &values)
     }
 }
+
+fn type_kind_to_gcc_type<I: Interner>(kind: TyKind<I>) -> CType {
+    use rustc_middle::ty::IntTy::*;
+    use rustc_middle::ty::UintTy::*;
+    use rustc_middle::ty::{Int, Uint};
+
+    match kind {
+        Int(I8) => CType::Int8t,
+        Int(I16) => CType::Int16t,
+        Int(I32) => CType::Int32t,
+        Int(I64) => CType::Int64t,
+        Int(I128) => CType::Int128t,
+
+        Uint(U8) => CType::UInt8t,
+        Uint(U16) => CType::UInt16t,
+        Uint(U32) => CType::UInt32t,
+        Uint(U64) => CType::UInt64t,
+        Uint(U128) => CType::UInt128t,
+
+        _ => unimplemented!("Kind: {:?}", kind),
+    }
+}
diff --git a/compiler/rustc_codegen_gcc/src/intrinsic/archs.rs b/compiler/rustc_codegen_gcc/src/intrinsic/archs.rs
index 915ed875e32..d1b2a93243d 100644
--- a/compiler/rustc_codegen_gcc/src/intrinsic/archs.rs
+++ b/compiler/rustc_codegen_gcc/src/intrinsic/archs.rs
@@ -95,8 +95,11 @@ fn map_arch_intrinsic(full_name: &str) -> &'static str {
                     "cubema" => "__builtin_amdgcn_cubema",
                     "cubesc" => "__builtin_amdgcn_cubesc",
                     "cubetc" => "__builtin_amdgcn_cubetc",
+                    "cvt.f16.bf8" => "__builtin_amdgcn_cvt_f16_bf8",
+                    "cvt.f16.fp8" => "__builtin_amdgcn_cvt_f16_fp8",
                     "cvt.f32.bf8" => "__builtin_amdgcn_cvt_f32_bf8",
                     "cvt.f32.fp8" => "__builtin_amdgcn_cvt_f32_fp8",
+                    "cvt.f32.fp8.e5m3" => "__builtin_amdgcn_cvt_f32_fp8_e5m3",
                     "cvt.off.f32.i4" => "__builtin_amdgcn_cvt_off_f32_i4",
                     "cvt.pk.bf8.f32" => "__builtin_amdgcn_cvt_pk_bf8_f32",
                     "cvt.pk.f16.bf8" => "__builtin_amdgcn_cvt_pk_f16_bf8",
@@ -181,6 +184,12 @@ fn map_arch_intrinsic(full_name: &str) -> &'static str {
                     "dot4.f32.fp8.bf8" => "__builtin_amdgcn_dot4_f32_fp8_bf8",
                     "dot4.f32.fp8.fp8" => "__builtin_amdgcn_dot4_f32_fp8_fp8",
                     "ds.add.gs.reg.rtn" => "__builtin_amdgcn_ds_add_gs_reg_rtn",
+                    "ds.atomic.async.barrier.arrive.b64" => {
+                        "__builtin_amdgcn_ds_atomic_async_barrier_arrive_b64"
+                    }
+                    "ds.atomic.barrier.arrive.rtn.b64" => {
+                        "__builtin_amdgcn_ds_atomic_barrier_arrive_rtn_b64"
+                    }
                     "ds.bpermute" => "__builtin_amdgcn_ds_bpermute",
                     "ds.bpermute.fi.b32" => "__builtin_amdgcn_ds_bpermute_fi_b32",
                     "ds.gws.barrier" => "__builtin_amdgcn_ds_gws_barrier",
@@ -198,8 +207,32 @@ fn map_arch_intrinsic(full_name: &str) -> &'static str {
                     "fdot2.f16.f16" => "__builtin_amdgcn_fdot2_f16_f16",
                     "fdot2.f32.bf16" => "__builtin_amdgcn_fdot2_f32_bf16",
                     "fdot2c.f32.bf16" => "__builtin_amdgcn_fdot2c_f32_bf16",
+                    "flat.prefetch" => "__builtin_amdgcn_flat_prefetch",
                     "fmul.legacy" => "__builtin_amdgcn_fmul_legacy",
+                    "global.load.async.to.lds.b128" => {
+                        "__builtin_amdgcn_global_load_async_to_lds_b128"
+                    }
+                    "global.load.async.to.lds.b32" => {
+                        "__builtin_amdgcn_global_load_async_to_lds_b32"
+                    }
+                    "global.load.async.to.lds.b64" => {
+                        "__builtin_amdgcn_global_load_async_to_lds_b64"
+                    }
+                    "global.load.async.to.lds.b8" => "__builtin_amdgcn_global_load_async_to_lds_b8",
                     "global.load.lds" => "__builtin_amdgcn_global_load_lds",
+                    "global.prefetch" => "__builtin_amdgcn_global_prefetch",
+                    "global.store.async.from.lds.b128" => {
+                        "__builtin_amdgcn_global_store_async_from_lds_b128"
+                    }
+                    "global.store.async.from.lds.b32" => {
+                        "__builtin_amdgcn_global_store_async_from_lds_b32"
+                    }
+                    "global.store.async.from.lds.b64" => {
+                        "__builtin_amdgcn_global_store_async_from_lds_b64"
+                    }
+                    "global.store.async.from.lds.b8" => {
+                        "__builtin_amdgcn_global_store_async_from_lds_b8"
+                    }
                     "groupstaticsize" => "__builtin_amdgcn_groupstaticsize",
                     "iglp.opt" => "__builtin_amdgcn_iglp_opt",
                     "implicit.buffer.ptr" => "__builtin_amdgcn_implicit_buffer_ptr",
@@ -291,6 +324,7 @@ fn map_arch_intrinsic(full_name: &str) -> &'static str {
                     "s.incperflevel" => "__builtin_amdgcn_s_incperflevel",
                     "s.memrealtime" => "__builtin_amdgcn_s_memrealtime",
                     "s.memtime" => "__builtin_amdgcn_s_memtime",
+                    "s.monitor.sleep" => "__builtin_amdgcn_s_monitor_sleep",
                     "s.sendmsg" => "__builtin_amdgcn_s_sendmsg",
                     "s.sendmsghalt" => "__builtin_amdgcn_s_sendmsghalt",
                     "s.setprio" => "__builtin_amdgcn_s_setprio",
@@ -300,11 +334,15 @@ fn map_arch_intrinsic(full_name: &str) -> &'static str {
                     "s.sleep.var" => "__builtin_amdgcn_s_sleep_var",
                     "s.ttracedata" => "__builtin_amdgcn_s_ttracedata",
                     "s.ttracedata.imm" => "__builtin_amdgcn_s_ttracedata_imm",
+                    "s.wait.asynccnt" => "__builtin_amdgcn_s_wait_asynccnt",
                     "s.wait.event.export.ready" => "__builtin_amdgcn_s_wait_event_export_ready",
+                    "s.wait.tensorcnt" => "__builtin_amdgcn_s_wait_tensorcnt",
                     "s.waitcnt" => "__builtin_amdgcn_s_waitcnt",
                     "sad.hi.u8" => "__builtin_amdgcn_sad_hi_u8",
                     "sad.u16" => "__builtin_amdgcn_sad_u16",
                     "sad.u8" => "__builtin_amdgcn_sad_u8",
+                    "sat.pk4.i4.i8" => "__builtin_amdgcn_sat_pk4_i4_i8",
+                    "sat.pk4.u4.u8" => "__builtin_amdgcn_sat_pk4_u4_u8",
                     "sched.barrier" => "__builtin_amdgcn_sched_barrier",
                     "sched.group.barrier" => "__builtin_amdgcn_sched_group_barrier",
                     "sdot2" => "__builtin_amdgcn_sdot2",
@@ -346,8 +384,13 @@ fn map_arch_intrinsic(full_name: &str) -> &'static str {
                     "smfmac.i32.16x16x64.i8" => "__builtin_amdgcn_smfmac_i32_16x16x64_i8",
                     "smfmac.i32.32x32x32.i8" => "__builtin_amdgcn_smfmac_i32_32x32x32_i8",
                     "smfmac.i32.32x32x64.i8" => "__builtin_amdgcn_smfmac_i32_32x32x64_i8",
+                    "struct.ptr.buffer.load.lds" => "__builtin_amdgcn_struct_ptr_buffer_load_lds",
                     "sudot4" => "__builtin_amdgcn_sudot4",
                     "sudot8" => "__builtin_amdgcn_sudot8",
+                    "tensor.load.to.lds" => "__builtin_amdgcn_tensor_load_to_lds",
+                    "tensor.load.to.lds.d2" => "__builtin_amdgcn_tensor_load_to_lds_d2",
+                    "tensor.store.from.lds" => "__builtin_amdgcn_tensor_store_from_lds",
+                    "tensor.store.from.lds.d2" => "__builtin_amdgcn_tensor_store_from_lds_d2",
                     "udot2" => "__builtin_amdgcn_udot2",
                     "udot4" => "__builtin_amdgcn_udot4",
                     "udot8" => "__builtin_amdgcn_udot8",
@@ -6326,6 +6369,23 @@ fn map_arch_intrinsic(full_name: &str) -> &'static str {
             }
             s390(name, full_name)
         }
+        "spv" => {
+            #[allow(non_snake_case)]
+            fn spv(name: &str, full_name: &str) -> &'static str {
+                match name {
+                    // spv
+                    "num.subgroups" => "__builtin_spirv_num_subgroups",
+                    "subgroup.id" => "__builtin_spirv_subgroup_id",
+                    "subgroup.local.invocation.id" => {
+                        "__builtin_spirv_subgroup_local_invocation_id"
+                    }
+                    "subgroup.max.size" => "__builtin_spirv_subgroup_max_size",
+                    "subgroup.size" => "__builtin_spirv_subgroup_size",
+                    _ => unimplemented!("***** unsupported LLVM intrinsic {full_name}"),
+                }
+            }
+            spv(name, full_name)
+        }
         "ve" => {
             #[allow(non_snake_case)]
             fn ve(name: &str, full_name: &str) -> &'static str {
diff --git a/compiler/rustc_codegen_gcc/src/intrinsic/mod.rs b/compiler/rustc_codegen_gcc/src/intrinsic/mod.rs
index 0753ac1aeb8..eb0a5336a1f 100644
--- a/compiler/rustc_codegen_gcc/src/intrinsic/mod.rs
+++ b/compiler/rustc_codegen_gcc/src/intrinsic/mod.rs
@@ -925,10 +925,17 @@ impl<'a, 'gcc, 'tcx> Builder<'a, 'gcc, 'tcx> {
         // TODO(antoyo): use width?
         let arg_type = arg.get_type();
         let result_type = self.u32_type;
+        let arg = if arg_type.is_signed(self.cx) {
+            let new_type = arg_type.to_unsigned(self.cx);
+            self.gcc_int_cast(arg, new_type)
+        } else {
+            arg
+        };
+        let arg_type = arg.get_type();
         let count_leading_zeroes =
             // TODO(antoyo): write a new function Type::is_compatible_with(&Type) and use it here
             // instead of using is_uint().
-            if arg_type.is_uint(self.cx) {
+            if arg_type.is_uchar(self.cx) || arg_type.is_ushort(self.cx) || arg_type.is_uint(self.cx) {
                 "__builtin_clz"
             }
             else if arg_type.is_ulong(self.cx) {
diff --git a/compiler/rustc_codegen_gcc/src/intrinsic/simd.rs b/compiler/rustc_codegen_gcc/src/intrinsic/simd.rs
index 350915a277e..fdc15d580ef 100644
--- a/compiler/rustc_codegen_gcc/src/intrinsic/simd.rs
+++ b/compiler/rustc_codegen_gcc/src/intrinsic/simd.rs
@@ -206,6 +206,28 @@ pub fn generic_simd_intrinsic<'a, 'gcc, 'tcx>(
         );
     }
 
+    #[cfg(feature = "master")]
+    if name == sym::simd_funnel_shl {
+        return Ok(simd_funnel_shift(
+            bx,
+            args[0].immediate(),
+            args[1].immediate(),
+            args[2].immediate(),
+            true,
+        ));
+    }
+
+    #[cfg(feature = "master")]
+    if name == sym::simd_funnel_shr {
+        return Ok(simd_funnel_shift(
+            bx,
+            args[0].immediate(),
+            args[1].immediate(),
+            args[2].immediate(),
+            false,
+        ));
+    }
+
     if name == sym::simd_bswap {
         return Ok(simd_bswap(bx, args[0].immediate()));
     }
@@ -1434,3 +1456,62 @@ pub fn generic_simd_intrinsic<'a, 'gcc, 'tcx>(
 
     unimplemented!("simd {}", name);
 }
+
+#[cfg(feature = "master")]
+fn simd_funnel_shift<'a, 'gcc, 'tcx>(
+    bx: &mut Builder<'a, 'gcc, 'tcx>,
+    a: RValue<'gcc>,
+    b: RValue<'gcc>,
+    shift: RValue<'gcc>,
+    shift_left: bool,
+) -> RValue<'gcc> {
+    use crate::common::SignType;
+
+    let a_type = a.get_type();
+    let vector_type = a_type.unqualified().dyncast_vector().expect("vector type");
+    let num_units = vector_type.get_num_units();
+    let elem_type = vector_type.get_element_type();
+
+    let (new_int_type, int_shift_val, int_mask) = if elem_type.is_compatible_with(bx.u8_type)
+        || elem_type.is_compatible_with(bx.i8_type)
+    {
+        (bx.u16_type, 8, u8::MAX as u64)
+    } else if elem_type.is_compatible_with(bx.u16_type) || elem_type.is_compatible_with(bx.i16_type)
+    {
+        (bx.u32_type, 16, u16::MAX as u64)
+    } else if elem_type.is_compatible_with(bx.u32_type) || elem_type.is_compatible_with(bx.i32_type)
+    {
+        (bx.u64_type, 32, u32::MAX as u64)
+    } else if elem_type.is_compatible_with(bx.u64_type) || elem_type.is_compatible_with(bx.i64_type)
+    {
+        (bx.u128_type, 64, u64::MAX)
+    } else {
+        unimplemented!("funnel shift on {:?}", elem_type);
+    };
+
+    let int_mask = bx.context.new_rvalue_from_long(new_int_type, int_mask as i64);
+    let int_shift_val = bx.context.new_rvalue_from_int(new_int_type, int_shift_val);
+    let mut elements = vec![];
+    let unsigned_type = elem_type.to_unsigned(bx);
+    for i in 0..num_units {
+        let index = bx.context.new_rvalue_from_int(bx.int_type, i as i32);
+        let a_val = bx.context.new_vector_access(None, a, index).to_rvalue();
+        let a_val = bx.context.new_bitcast(None, a_val, unsigned_type);
+        // TODO: we probably need to use gcc_int_cast instead.
+        let a_val = bx.gcc_int_cast(a_val, new_int_type);
+        let b_val = bx.context.new_vector_access(None, b, index).to_rvalue();
+        let b_val = bx.context.new_bitcast(None, b_val, unsigned_type);
+        let b_val = bx.gcc_int_cast(b_val, new_int_type);
+        let shift_val = bx.context.new_vector_access(None, shift, index).to_rvalue();
+        let shift_val = bx.gcc_int_cast(shift_val, new_int_type);
+        let mut val = a_val << int_shift_val | b_val;
+        if shift_left {
+            val = (val << shift_val) >> int_shift_val;
+        } else {
+            val = (val >> shift_val) & int_mask;
+        }
+        let val = bx.gcc_int_cast(val, elem_type);
+        elements.push(val);
+    }
+    bx.context.new_rvalue_from_vector(None, a_type, &elements)
+}
diff --git a/compiler/rustc_codegen_gcc/src/lib.rs b/compiler/rustc_codegen_gcc/src/lib.rs
index a3120682500..b11f11d38e3 100644
--- a/compiler/rustc_codegen_gcc/src/lib.rs
+++ b/compiler/rustc_codegen_gcc/src/lib.rs
@@ -35,7 +35,6 @@ extern crate tracing;
 extern crate rustc_abi;
 extern crate rustc_apfloat;
 extern crate rustc_ast;
-extern crate rustc_attr_data_structures;
 extern crate rustc_codegen_ssa;
 extern crate rustc_data_structures;
 extern crate rustc_errors;
@@ -51,6 +50,7 @@ extern crate rustc_session;
 extern crate rustc_span;
 extern crate rustc_symbol_mangling;
 extern crate rustc_target;
+extern crate rustc_type_ir;
 
 // This prevents duplicating functions and statics that are already part of the host rustc process.
 #[allow(unused_extern_crates)]
@@ -363,9 +363,9 @@ impl WriteBackendMethods for GccCodegenBackend {
         _exported_symbols_for_lto: &[String],
         each_linked_rlib_for_lto: &[PathBuf],
         modules: Vec<FatLtoInput<Self>>,
-        diff_fncs: Vec<AutoDiffItem>,
+        diff_functions: Vec<AutoDiffItem>,
     ) -> Result<ModuleCodegen<Self::Module>, FatalError> {
-        if !diff_fncs.is_empty() {
+        if !diff_functions.is_empty() {
             unimplemented!();
         }
 
diff --git a/compiler/rustc_codegen_gcc/tests/failing-lto-tests.txt b/compiler/rustc_codegen_gcc/tests/failing-lto-tests.txt
index b9126fb73a7..bf0633f7320 100644
--- a/compiler/rustc_codegen_gcc/tests/failing-lto-tests.txt
+++ b/compiler/rustc_codegen_gcc/tests/failing-lto-tests.txt
@@ -28,6 +28,6 @@ tests/ui/macros/macro-comma-behavior-rpass.rs
 tests/ui/macros/rfc-2011-nicer-assert-messages/assert-with-custom-errors-does-not-create-unnecessary-code.rs
 tests/ui/macros/rfc-2011-nicer-assert-messages/feature-gate-generic_assert.rs
 tests/ui/macros/stringify.rs
-tests/ui/reexport-test-harness-main.rs
 tests/ui/rfcs/rfc-1937-termination-trait/termination-trait-in-test.rs
 tests/ui/binding/fn-arg-incomplete-pattern-drop-order.rs
+tests/ui/lto/debuginfo-lto-alloc.rs
diff --git a/compiler/rustc_codegen_gcc/tests/failing-run-make-tests.txt b/compiler/rustc_codegen_gcc/tests/failing-run-make-tests.txt
index 842533cd3c6..29032b321fa 100644
--- a/compiler/rustc_codegen_gcc/tests/failing-run-make-tests.txt
+++ b/compiler/rustc_codegen_gcc/tests/failing-run-make-tests.txt
@@ -6,7 +6,6 @@ tests/run-make/doctests-keep-binaries/
 tests/run-make/doctests-runtool/
 tests/run-make/emit-shared-files/
 tests/run-make/exit-code/
-tests/run-make/issue-22131/
 tests/run-make/issue-64153/
 tests/run-make/llvm-ident/
 tests/run-make/native-link-modifier-bundle/
diff --git a/compiler/rustc_codegen_gcc/tests/failing-ui-tests.txt b/compiler/rustc_codegen_gcc/tests/failing-ui-tests.txt
index 6979c04d534..41fb4729c07 100644
--- a/compiler/rustc_codegen_gcc/tests/failing-ui-tests.txt
+++ b/compiler/rustc_codegen_gcc/tests/failing-ui-tests.txt
@@ -10,11 +10,10 @@ tests/ui/iterators/iter-sum-overflow-overflow-checks.rs
 tests/ui/mir/mir_drop_order.rs
 tests/ui/mir/mir_let_chains_drop_order.rs
 tests/ui/mir/mir_match_guard_let_chains_drop_order.rs
-tests/ui/oom_unwind.rs
+tests/ui/panics/oom-panic-unwind.rs
 tests/ui/panic-runtime/abort-link-to-unwinding-crates.rs
 tests/ui/panic-runtime/abort.rs
 tests/ui/panic-runtime/link-to-abort.rs
-tests/ui/unwind-no-uwtable.rs
 tests/ui/parser/unclosed-delimiter-in-dep.rs
 tests/ui/consts/missing_span_in_backtrace.rs
 tests/ui/drop/dynamic-drop.rs
@@ -82,3 +81,8 @@ tests/ui/coroutine/panic-drops.rs
 tests/ui/coroutine/panic-safe.rs
 tests/ui/process/nofile-limit.rs
 tests/ui/simd/intrinsic/generic-arithmetic-pass.rs
+tests/ui/linking/no-gc-encapsulation-symbols.rs
+tests/ui/panics/unwind-force-no-unwind-tables.rs
+tests/ui/attributes/fn-align-dyn.rs
+tests/ui/linkage-attr/raw-dylib/elf/glibc-x86_64.rs
+tests/ui/explicit-tail-calls/recursion-etc.rs
diff --git a/compiler/rustc_codegen_gcc/tools/cspell_dicts/rustc_codegen_gcc.txt b/compiler/rustc_codegen_gcc/tools/cspell_dicts/rustc_codegen_gcc.txt
index 31023e50ffa..4fb018b3ecd 100644
--- a/compiler/rustc_codegen_gcc/tools/cspell_dicts/rustc_codegen_gcc.txt
+++ b/compiler/rustc_codegen_gcc/tools/cspell_dicts/rustc_codegen_gcc.txt
@@ -8,6 +8,7 @@ clzll
 cmse
 codegened
 csky
+ctfe
 ctlz
 ctpop
 cttz
@@ -25,6 +26,7 @@ fwrapv
 gimple
 hrtb
 immediates
+interner
 liblto
 llbb
 llcx
@@ -47,6 +49,7 @@ mavx
 mcmodel
 minimumf
 minnumf
+miri
 monomorphization
 monomorphizations
 monomorphized
diff --git a/compiler/rustc_codegen_llvm/Cargo.toml b/compiler/rustc_codegen_llvm/Cargo.toml
index 5ab22f8fc4d..2d11628250c 100644
--- a/compiler/rustc_codegen_llvm/Cargo.toml
+++ b/compiler/rustc_codegen_llvm/Cargo.toml
@@ -19,7 +19,6 @@ object = { version = "0.37.0", default-features = false, features = ["std", "rea
 rustc-demangle = "0.1.21"
 rustc_abi = { path = "../rustc_abi" }
 rustc_ast = { path = "../rustc_ast" }
-rustc_attr_data_structures = { path = "../rustc_attr_data_structures" }
 rustc_codegen_ssa = { path = "../rustc_codegen_ssa" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
@@ -38,11 +37,14 @@ rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
 rustc_symbol_mangling = { path = "../rustc_symbol_mangling" }
 rustc_target = { path = "../rustc_target" }
-serde = { version = "1", features = [ "derive" ]}
+serde = { version = "1", features = ["derive"] }
 serde_json = "1"
 smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
 tracing = "0.1"
 # tidy-alphabetical-end
 
 [features]
+# tidy-alphabetical-start
 check_only = ["rustc_llvm/check_only"]
+# tidy-alphabetical-end
+
diff --git a/compiler/rustc_codegen_llvm/src/attributes.rs b/compiler/rustc_codegen_llvm/src/attributes.rs
index c32f11b27f3..c548f467583 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_data_structures::{InlineAttr, InstructionSetAttr, OptimizeAttr};
 use rustc_codegen_ssa::traits::*;
+use rustc_hir::attrs::{InlineAttr, InstructionSetAttr, OptimizeAttr};
 use rustc_hir::def_id::DefId;
 use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, PatchableFunctionEntry};
 use rustc_middle::ty::{self, TyCtxt};
diff --git a/compiler/rustc_codegen_llvm/src/base.rs b/compiler/rustc_codegen_llvm/src/base.rs
index 5dda836988c..d7da03bf490 100644
--- a/compiler/rustc_codegen_llvm/src/base.rs
+++ b/compiler/rustc_codegen_llvm/src/base.rs
@@ -109,11 +109,16 @@ pub(crate) fn compile_codegen_unit(
             }
 
             // Finalize code coverage by injecting the coverage map. Note, the coverage map will
-            // also be added to the `llvm.compiler.used` variable, created next.
+            // also be added to the `llvm.compiler.used` variable, created below.
             if cx.sess().instrument_coverage() {
                 cx.coverageinfo_finalize();
             }
 
+            // Finalize debuginfo. This adds to `llvm.used`, created below.
+            if cx.sess().opts.debuginfo != DebugInfo::None {
+                cx.debuginfo_finalize();
+            }
+
             // Create the llvm.used and llvm.compiler.used variables.
             if !cx.used_statics.is_empty() {
                 cx.create_used_variable_impl(c"llvm.used", &cx.used_statics);
@@ -130,11 +135,6 @@ pub(crate) fn compile_codegen_unit(
                     llvm::LLVMDeleteGlobal(old_g);
                 }
             }
-
-            // Finalize debuginfo
-            if cx.sess().opts.debuginfo != DebugInfo::None {
-                cx.debuginfo_finalize();
-            }
         }
 
         ModuleCodegen::new_regular(cgu_name.to_string(), llvm_module)
diff --git a/compiler/rustc_codegen_llvm/src/builder.rs b/compiler/rustc_codegen_llvm/src/builder.rs
index f712b3b83fa..da2a153d819 100644
--- a/compiler/rustc_codegen_llvm/src/builder.rs
+++ b/compiler/rustc_codegen_llvm/src/builder.rs
@@ -15,6 +15,7 @@ use rustc_codegen_ssa::mir::place::PlaceRef;
 use rustc_codegen_ssa::traits::*;
 use rustc_data_structures::small_c_str::SmallCStr;
 use rustc_hir::def_id::DefId;
+use rustc_middle::bug;
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrs;
 use rustc_middle::ty::layout::{
     FnAbiError, FnAbiOfHelpers, FnAbiRequest, HasTypingEnv, LayoutError, LayoutOfHelpers,
@@ -24,7 +25,7 @@ use rustc_middle::ty::{self, Instance, Ty, TyCtxt};
 use rustc_sanitizers::{cfi, kcfi};
 use rustc_session::config::OptLevel;
 use rustc_span::Span;
-use rustc_target::callconv::FnAbi;
+use rustc_target::callconv::{FnAbi, PassMode};
 use rustc_target::spec::{HasTargetSpec, SanitizerSet, Target};
 use smallvec::SmallVec;
 use tracing::{debug, instrument};
@@ -1431,6 +1432,28 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         call
     }
 
+    fn tail_call(
+        &mut self,
+        llty: Self::Type,
+        fn_attrs: Option<&CodegenFnAttrs>,
+        fn_abi: &FnAbi<'tcx, Ty<'tcx>>,
+        llfn: Self::Value,
+        args: &[Self::Value],
+        funclet: Option<&Self::Funclet>,
+        instance: Option<Instance<'tcx>>,
+    ) {
+        let call = self.call(llty, fn_attrs, Some(fn_abi), llfn, args, funclet, instance);
+        llvm::LLVMRustSetTailCallKind(call, llvm::TailCallKind::MustTail);
+
+        match &fn_abi.ret.mode {
+            PassMode::Ignore | PassMode::Indirect { .. } => self.ret_void(),
+            PassMode::Direct(_) | PassMode::Pair { .. } => self.ret(call),
+            mode @ PassMode::Cast { .. } => {
+                bug!("Encountered `PassMode::{mode:?}` during codegen")
+            }
+        }
+    }
+
     fn zext(&mut self, val: &'ll Value, dest_ty: &'ll Type) -> &'ll Value {
         unsafe { llvm::LLVMBuildZExt(self.llbuilder, val, dest_ty, UNNAMED) }
     }
diff --git a/compiler/rustc_codegen_llvm/src/callee.rs b/compiler/rustc_codegen_llvm/src/callee.rs
index 5a3dd90ab24..791a71d73ae 100644
--- a/compiler/rustc_codegen_llvm/src/callee.rs
+++ b/compiler/rustc_codegen_llvm/src/callee.rs
@@ -103,7 +103,7 @@ 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_instance_attrs(instance.def).inline
-                    == rustc_attr_data_structures::InlineAttr::Never)
+                    == rustc_hir::attrs::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/mapgen.rs b/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs
index 8c9dfcfd18c..d1cb95507d9 100644
--- a/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs
+++ b/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs
@@ -1,3 +1,4 @@
+use std::assert_matches::assert_matches;
 use std::sync::Arc;
 
 use itertools::Itertools;
@@ -5,6 +6,7 @@ use rustc_abi::Align;
 use rustc_codegen_ssa::traits::{BaseTypeCodegenMethods, ConstCodegenMethods};
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_index::IndexVec;
+use rustc_macros::TryFromU32;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::RemapFileNameExt;
 use rustc_session::config::RemapPathScopeComponents;
@@ -20,6 +22,23 @@ mod covfun;
 mod spans;
 mod unused;
 
+/// Version number that will be included the `__llvm_covmap` section header.
+/// Corresponds to LLVM's `llvm::coverage::CovMapVersion` (in `CoverageMapping.h`),
+/// or at least the subset that we know and care about.
+///
+/// Note that version `n` is encoded as `(n-1)`.
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, TryFromU32)]
+enum CovmapVersion {
+    /// Used by LLVM 18 onwards.
+    Version7 = 6,
+}
+
+impl CovmapVersion {
+    fn to_u32(self) -> u32 {
+        self as u32
+    }
+}
+
 /// Generates and exports the coverage map, which is embedded in special
 /// linker sections in the final binary.
 ///
@@ -29,19 +48,13 @@ pub(crate) fn finalize(cx: &mut CodegenCx<'_, '_>) {
     let tcx = cx.tcx;
 
     // Ensure that LLVM is using a version of the coverage mapping format that
-    // agrees with our Rust-side code. Expected versions (encoded as n-1) are:
-    // - `CovMapVersion::Version7` (6) used by LLVM 18-19
-    let covmap_version = {
-        let llvm_covmap_version = llvm_cov::mapping_version();
-        let expected_versions = 6..=6;
-        assert!(
-            expected_versions.contains(&llvm_covmap_version),
-            "Coverage mapping version exposed by `llvm-wrapper` is out of sync; \
-            expected {expected_versions:?} but was {llvm_covmap_version}"
-        );
-        // This is the version number that we will embed in the covmap section:
-        llvm_covmap_version
-    };
+    // agrees with our Rust-side code. Expected versions are:
+    // - `Version7` (6) used by LLVM 18 onwards.
+    let covmap_version =
+        CovmapVersion::try_from(llvm_cov::mapping_version()).unwrap_or_else(|raw_version: u32| {
+            panic!("unknown coverage mapping version reported by `llvm-wrapper`: {raw_version}")
+        });
+    assert_matches!(covmap_version, CovmapVersion::Version7);
 
     debug!("Generating coverage map for CodegenUnit: `{}`", cx.codegen_unit.name());
 
@@ -201,7 +214,11 @@ impl VirtualFileMapping {
 /// 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.
-fn generate_covmap_record<'ll>(cx: &mut CodegenCx<'ll, '_>, version: u32, filenames_buffer: &[u8]) {
+fn generate_covmap_record<'ll>(
+    cx: &mut CodegenCx<'ll, '_>,
+    version: CovmapVersion,
+    filenames_buffer: &[u8],
+) {
     // A covmap record consists of four target-endian u32 values, followed by
     // the encoded filenames table. Two of the header fields are unused in
     // modern versions of the LLVM coverage mapping format, and are always 0.
@@ -212,7 +229,7 @@ fn generate_covmap_record<'ll>(cx: &mut CodegenCx<'ll, '_>, version: u32, filena
             cx.const_u32(0), // (unused)
             cx.const_u32(filenames_buffer.len() as u32),
             cx.const_u32(0), // (unused)
-            cx.const_u32(version),
+            cx.const_u32(version.to_u32()),
         ],
         /* packed */ false,
     );
diff --git a/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/covfun.rs b/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/covfun.rs
index b704cf2b1cd..fd1e7f7f160 100644
--- a/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/covfun.rs
+++ b/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/covfun.rs
@@ -27,6 +27,9 @@ use crate::llvm;
 /// the final record that will be embedded in the `__llvm_covfun` section.
 #[derive(Debug)]
 pub(crate) struct CovfunRecord<'tcx> {
+    /// Not used directly, but helpful in debug messages.
+    _instance: Instance<'tcx>,
+
     mangled_function_name: &'tcx str,
     source_hash: u64,
     is_used: bool,
@@ -55,6 +58,7 @@ pub(crate) fn prepare_covfun_record<'tcx>(
     let expressions = prepare_expressions(ids_info);
 
     let mut covfun = CovfunRecord {
+        _instance: instance,
         mangled_function_name: tcx.symbol_name(instance).name,
         source_hash: if is_used { fn_cov_info.function_source_hash } else { 0 },
         is_used,
@@ -102,11 +106,21 @@ fn fill_region_tables<'tcx>(
     ids_info: &'tcx CoverageIdsInfo,
     covfun: &mut CovfunRecord<'tcx>,
 ) {
+    // If this function is unused, replace all counters with zero.
+    let counter_for_bcb = |bcb: BasicCoverageBlock| -> ffi::Counter {
+        let term = if covfun.is_used {
+            ids_info.term_for_bcb[bcb].expect("every BCB in a mapping was given a term")
+        } else {
+            CovTerm::Zero
+        };
+        ffi::Counter::from_term(term)
+    };
+
     // Currently a function's mappings must all be in the same file, so use the
     // first mapping's span to determine the file.
     let source_map = tcx.sess.source_map();
     let Some(first_span) = (try { fn_cov_info.mappings.first()?.span }) else {
-        debug_assert!(false, "function has no mappings: {:?}", covfun.mangled_function_name);
+        debug_assert!(false, "function has no mappings: {covfun:?}");
         return;
     };
     let source_file = source_map.lookup_source_file(first_span.lo());
@@ -117,7 +131,7 @@ fn fill_region_tables<'tcx>(
     // codegen needs to handle that gracefully to avoid #133606.
     // It's hard for tests to trigger this organically, so instead we set
     // `-Zcoverage-options=discard-all-spans-in-codegen` to force it to occur.
-    let discard_all = tcx.sess.coverage_discard_all_spans_in_codegen();
+    let discard_all = tcx.sess.coverage_options().discard_all_spans_in_codegen;
     let make_coords = |span: Span| {
         if discard_all { None } else { spans::make_coords(source_map, &source_file, span) }
     };
@@ -133,16 +147,6 @@ fn fill_region_tables<'tcx>(
     // For each counter/region pair in this function+file, convert it to a
     // form suitable for FFI.
     for &Mapping { ref kind, span } in &fn_cov_info.mappings {
-        // If this function is unused, replace all counters with zero.
-        let counter_for_bcb = |bcb: BasicCoverageBlock| -> ffi::Counter {
-            let term = if covfun.is_used {
-                ids_info.term_for_bcb[bcb].expect("every BCB in a mapping was given a term")
-            } else {
-                CovTerm::Zero
-            };
-            ffi::Counter::from_term(term)
-        };
-
         let Some(coords) = make_coords(span) else { continue };
         let cov_span = coords.make_coverage_span(local_file_id);
 
@@ -184,6 +188,7 @@ pub(crate) fn generate_covfun_record<'tcx>(
     covfun: &CovfunRecord<'tcx>,
 ) {
     let &CovfunRecord {
+        _instance,
         mangled_function_name,
         source_hash,
         is_used,
diff --git a/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/spans.rs b/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/spans.rs
index 39a59560c9d..574463be7ff 100644
--- a/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/spans.rs
+++ b/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/spans.rs
@@ -39,7 +39,10 @@ impl Coords {
 /// 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_coords(source_map: &SourceMap, file: &SourceFile, span: Span) -> Option<Coords> {
-    let span = ensure_non_empty_span(source_map, span)?;
+    if span.is_empty() {
+        debug_assert!(false, "can't make coords from empty span: {span:?}");
+        return None;
+    }
 
     let lo = span.lo();
     let hi = span.hi();
@@ -70,29 +73,6 @@ pub(crate) fn make_coords(source_map: &SourceMap, file: &SourceFile, span: Span)
     })
 }
 
-fn ensure_non_empty_span(source_map: &SourceMap, span: Span) -> Option<Span> {
-    if !span.is_empty() {
-        return Some(span);
-    }
-
-    // The span is empty, so try to enlarge it to cover an adjacent '{' or '}'.
-    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 src.as_bytes().get(end).copied() == Some(b'{') {
-                Some(span.with_hi(span.hi() + BytePos(1)))
-            } else if start > 0 && src.as_bytes()[start - 1] == b'}' {
-                Some(span.with_lo(span.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
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs b/compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs
index 61555ac2f6f..fccd32dec95 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs
@@ -1,12 +1,13 @@
 // .debug_gdb_scripts binary section.
 
-use rustc_attr_data_structures::{AttributeKind, find_attr};
-use rustc_codegen_ssa::base::collect_debugger_visualizers_transitive;
+use std::collections::BTreeSet;
+use std::ffi::CString;
+
 use rustc_codegen_ssa::traits::*;
 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_session::config::DebugInfo;
 
 use crate::builder::Builder;
 use crate::common::CodegenCx;
@@ -32,7 +33,12 @@ pub(crate) fn insert_reference_to_gdb_debug_scripts_section_global(bx: &mut Buil
 pub(crate) fn get_or_insert_gdb_debug_scripts_section_global<'ll>(
     cx: &CodegenCx<'ll, '_>,
 ) -> &'ll Value {
-    let c_section_var_name = c"__rustc_debug_gdb_scripts_section__";
+    let c_section_var_name = CString::new(format!(
+        "__rustc_debug_gdb_scripts_section_{}_{:08x}",
+        cx.tcx.crate_name(LOCAL_CRATE),
+        cx.tcx.stable_crate_id(LOCAL_CRATE),
+    ))
+    .unwrap();
     let section_var_name = c_section_var_name.to_str().unwrap();
 
     let section_var = unsafe { llvm::LLVMGetNamedGlobal(cx.llmod, c_section_var_name.as_ptr()) };
@@ -45,10 +51,14 @@ pub(crate) fn get_or_insert_gdb_debug_scripts_section_global<'ll>(
 
         // Next, add the pretty printers that were specified via the `#[debugger_visualizer]`
         // attribute.
-        let visualizers = collect_debugger_visualizers_transitive(
-            cx.tcx,
-            DebuggerVisualizerType::GdbPrettyPrinter,
-        );
+        let visualizers = cx
+            .tcx
+            .debugger_visualizers(LOCAL_CRATE)
+            .iter()
+            .filter(|visualizer| {
+                visualizer.visualizer_type == DebuggerVisualizerType::GdbPrettyPrinter
+            })
+            .collect::<BTreeSet<_>>();
         let crate_name = cx.tcx.crate_name(LOCAL_CRATE);
         for (index, visualizer) in visualizers.iter().enumerate() {
             // The initial byte `4` instructs GDB that the following pretty printer
@@ -85,39 +95,5 @@ pub(crate) fn get_or_insert_gdb_debug_scripts_section_global<'ll>(
 }
 
 pub(crate) fn needs_gdb_debug_scripts_section(cx: &CodegenCx<'_, '_>) -> bool {
-    let omit_gdb_pretty_printer_section =
-        find_attr!(cx.tcx.hir_krate_attrs(), AttributeKind::OmitGdbPrettyPrinterSection);
-
-    // To ensure the section `__rustc_debug_gdb_scripts_section__` will not create
-    // ODR violations at link time, this section will not be emitted for rlibs since
-    // each rlib could produce a different set of visualizers that would be embedded
-    // in the `.debug_gdb_scripts` section. For that reason, we make sure that the
-    // section is only emitted for leaf crates.
-    let embed_visualizers = cx.tcx.crate_types().iter().any(|&crate_type| match crate_type {
-        CrateType::Executable
-        | CrateType::Dylib
-        | CrateType::Cdylib
-        | CrateType::Staticlib
-        | CrateType::Sdylib => {
-            // These are crate types for which we will embed pretty printers since they
-            // are treated as leaf crates.
-            true
-        }
-        CrateType::ProcMacro => {
-            // We could embed pretty printers for proc macro crates too but it does not
-            // seem like a good default, since this is a rare use case and we don't
-            // want to slow down the common case.
-            false
-        }
-        CrateType::Rlib => {
-            // As per the above description, embedding pretty printers for rlibs could
-            // lead to ODR violations so we skip this crate type as well.
-            false
-        }
-    });
-
-    !omit_gdb_pretty_printer_section
-        && cx.sess().opts.debuginfo != DebugInfo::None
-        && cx.sess().target.emit_debug_gdb_scripts
-        && embed_visualizers
+    cx.sess().opts.debuginfo != DebugInfo::None && cx.sess().target.emit_debug_gdb_scripts
 }
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs b/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs
index 6cbf2dbf7d3..c911435967c 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs
@@ -30,7 +30,7 @@ use tracing::debug;
 
 use self::metadata::{UNKNOWN_COLUMN_NUMBER, UNKNOWN_LINE_NUMBER, file_metadata, type_di_node};
 use self::namespace::mangled_name_of_instance;
-use self::utils::{DIB, create_DIArray, is_node_local_to_unit};
+use self::utils::{DIB, create_DIArray, debug_context, is_node_local_to_unit};
 use crate::builder::Builder;
 use crate::common::{AsCCharPtr, CodegenCx};
 use crate::llvm;
@@ -131,20 +131,28 @@ impl<'ll, 'tcx> CodegenUnitDebugContext<'ll, 'tcx> {
 }
 
 /// Creates any deferred debug metadata nodes
-pub(crate) fn finalize(cx: &CodegenCx<'_, '_>) {
-    if let Some(dbg_cx) = &cx.dbg_cx {
-        debug!("finalize");
-
-        if gdb::needs_gdb_debug_scripts_section(cx) {
-            // Add a .debug_gdb_scripts section to this compile-unit. This will
-            // cause GDB to try and load the gdb_load_rust_pretty_printers.py file,
-            // which activates the Rust pretty printers for binary this section is
-            // contained in.
-            gdb::get_or_insert_gdb_debug_scripts_section_global(cx);
-        }
+pub(crate) fn finalize(cx: &mut CodegenCx<'_, '_>) {
+    if cx.dbg_cx.is_none() {
+        return;
+    }
+
+    debug!("finalize");
 
-        dbg_cx.finalize(cx.sess());
+    if gdb::needs_gdb_debug_scripts_section(cx) {
+        // Add a .debug_gdb_scripts section to this compile-unit. This will
+        // cause GDB to try and load the gdb_load_rust_pretty_printers.py file,
+        // which activates the Rust pretty printers for binary this section is
+        // contained in.
+        let section_var = gdb::get_or_insert_gdb_debug_scripts_section_global(cx);
+
+        // Make sure that the linker doesn't optimize the global away. Adding
+        // it to `llvm.used` has the advantage that it works even in no_std
+        // binaries, where we don't have a main shim and thus don't emit a
+        // volatile load to preserve the global.
+        cx.add_used_global(section_var);
     }
+
+    debug_context(cx).finalize(cx.sess());
 }
 
 impl<'ll> Builder<'_, 'll, '_> {
@@ -614,7 +622,7 @@ impl<'ll, 'tcx> DebugInfoCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
         metadata::extend_scope_to_file(self, scope_metadata, file)
     }
 
-    fn debuginfo_finalize(&self) {
+    fn debuginfo_finalize(&mut self) {
         finalize(self)
     }
 
diff --git a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
index 0d0cb5f139e..2443194ff48 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
@@ -97,6 +97,16 @@ pub(crate) enum ModuleFlagMergeBehavior {
 
 // Consts for the LLVM CallConv type, pre-cast to usize.
 
+#[derive(Copy, Clone, PartialEq, Debug)]
+#[repr(C)]
+#[allow(dead_code)]
+pub(crate) enum TailCallKind {
+    None = 0,
+    Tail = 1,
+    MustTail = 2,
+    NoTail = 3,
+}
+
 /// LLVM CallingConv::ID. Should we wrap this?
 ///
 /// See <https://github.com/llvm/llvm-project/blob/main/llvm/include/llvm/IR/CallingConv.h>
@@ -1186,6 +1196,7 @@ unsafe extern "C" {
     pub(crate) safe fn LLVMIsGlobalConstant(GlobalVar: &Value) -> Bool;
     pub(crate) safe fn LLVMSetGlobalConstant(GlobalVar: &Value, IsConstant: Bool);
     pub(crate) safe fn LLVMSetTailCall(CallInst: &Value, IsTailCall: Bool);
+    pub(crate) safe fn LLVMRustSetTailCallKind(CallInst: &Value, Kind: TailCallKind);
 
     // Operations on attributes
     pub(crate) fn LLVMCreateStringAttribute(
diff --git a/compiler/rustc_codegen_ssa/Cargo.toml b/compiler/rustc_codegen_ssa/Cargo.toml
index 94501da69a7..30956fd1855 100644
--- a/compiler/rustc_codegen_ssa/Cargo.toml
+++ b/compiler/rustc_codegen_ssa/Cargo.toml
@@ -17,7 +17,6 @@ regex = "1.4"
 rustc_abi = { path = "../rustc_abi" }
 rustc_arena = { path = "../rustc_arena" }
 rustc_ast = { path = "../rustc_ast" }
-rustc_attr_data_structures = { path = "../rustc_attr_data_structures" }
 rustc_attr_parsing = { path = "../rustc_attr_parsing" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
diff --git a/compiler/rustc_codegen_ssa/src/back/link.rs b/compiler/rustc_codegen_ssa/src/back/link.rs
index 162fbf3d6e2..b69fbf61185 100644
--- a/compiler/rustc_codegen_ssa/src/back/link.rs
+++ b/compiler/rustc_codegen_ssa/src/back/link.rs
@@ -1011,11 +1011,12 @@ fn link_natively(
             (Strip::Debuginfo, _) => {
                 strip_with_external_utility(sess, stripcmd, out_filename, &["--strip-debug"])
             }
-            // Per the manpage, `-x` is the maximum safe strip level for dynamic libraries. (#93988)
+
+            // Per the manpage, --discard-all is the maximum safe strip level for dynamic libraries. (#93988)
             (
                 Strip::Symbols,
                 CrateType::Dylib | CrateType::Cdylib | CrateType::ProcMacro | CrateType::Sdylib,
-            ) => strip_with_external_utility(sess, stripcmd, out_filename, &["-x"]),
+            ) => strip_with_external_utility(sess, stripcmd, out_filename, &["--discard-all"]),
             (Strip::Symbols, _) => {
                 strip_with_external_utility(sess, stripcmd, out_filename, &["--strip-all"])
             }
diff --git a/compiler/rustc_codegen_ssa/src/back/symbol_export.rs b/compiler/rustc_codegen_ssa/src/back/symbol_export.rs
index 297bdec2bc2..4b4b39f5353 100644
--- a/compiler/rustc_codegen_ssa/src/back/symbol_export.rs
+++ b/compiler/rustc_codegen_ssa/src/back/symbol_export.rs
@@ -384,7 +384,7 @@ fn exported_generic_symbols_provider_local<'tcx>(
 
             if !tcx.sess.opts.share_generics() {
                 if tcx.codegen_fn_attrs(mono_item.def_id()).inline
-                    == rustc_attr_data_structures::InlineAttr::Never
+                    == rustc_hir::attrs::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 6773d3e24e9..aa29afb7f5b 100644
--- a/compiler/rustc_codegen_ssa/src/back/write.rs
+++ b/compiler/rustc_codegen_ssa/src/back/write.rs
@@ -214,7 +214,9 @@ impl ModuleConfig {
                 false
             ),
             emit_obj,
-            emit_thin_lto: sess.opts.unstable_opts.emit_thin_lto,
+            // thin lto summaries prevent fat lto, so do not emit them if fat
+            // lto is requested. See PR #136840 for background information.
+            emit_thin_lto: sess.opts.unstable_opts.emit_thin_lto && sess.lto() != Lto::Fat,
             emit_thin_lto_summary: if_regular!(
                 sess.opts.output_types.contains_key(&OutputType::ThinLinkBitcode),
                 false
diff --git a/compiler/rustc_codegen_ssa/src/base.rs b/compiler/rustc_codegen_ssa/src/base.rs
index a5807c56e31..b4556ced0b3 100644
--- a/compiler/rustc_codegen_ssa/src/base.rs
+++ b/compiler/rustc_codegen_ssa/src/base.rs
@@ -7,11 +7,11 @@ use itertools::Itertools;
 use rustc_abi::FIRST_VARIANT;
 use rustc_ast as ast;
 use rustc_ast::expand::allocator::AllocatorKind;
-use rustc_attr_data_structures::OptimizeAttr;
 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::{IntoDynSyncSend, par_map};
 use rustc_data_structures::unord::UnordMap;
+use rustc_hir::attrs::OptimizeAttr;
 use rustc_hir::def_id::{DefId, LOCAL_CRATE};
 use rustc_hir::lang_items::LangItem;
 use rustc_hir::{ItemId, Target};
diff --git a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
index e187331c696..7f54a47327a 100644
--- a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
+++ b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
@@ -3,13 +3,11 @@ use std::str::FromStr;
 use rustc_abi::{Align, ExternAbi};
 use rustc_ast::expand::autodiff_attrs::{AutoDiffAttrs, DiffActivity, DiffMode};
 use rustc_ast::{LitKind, MetaItem, MetaItemInner, attr};
-use rustc_attr_data_structures::{
-    AttributeKind, InlineAttr, InstructionSetAttr, OptimizeAttr, UsedBy, find_attr,
-};
+use rustc_hir::attrs::{AttributeKind, InlineAttr, InstructionSetAttr, UsedBy};
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{DefId, LOCAL_CRATE, LocalDefId};
 use rustc_hir::weak_lang_items::WEAK_LANG_ITEMS;
-use rustc_hir::{self as hir, LangItem, lang_items};
+use rustc_hir::{self as hir, Attribute, LangItem, find_attr, lang_items};
 use rustc_middle::middle::codegen_fn_attrs::{
     CodegenFnAttrFlags, CodegenFnAttrs, PatchableFunctionEntry,
 };
@@ -53,77 +51,196 @@ fn linkage_by_name(tcx: TyCtxt<'_>, def_id: LocalDefId, name: &str) -> Linkage {
     }
 }
 
-fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
-    if cfg!(debug_assertions) {
-        let def_kind = tcx.def_kind(did);
-        assert!(
-            def_kind.has_codegen_attrs(),
-            "unexpected `def_kind` in `codegen_fn_attrs`: {def_kind:?}",
-        );
+/// In some cases, attributes are only valid on functions, but it's the `check_attr`
+/// pass that checks that they aren't used anywhere else, rather than this module.
+/// In these cases, we bail from performing further checks that are only meaningful for
+/// functions (such as calling `fn_sig`, which ICEs if given a non-function). We also
+/// report a delayed bug, just in case `check_attr` isn't doing its job.
+fn try_fn_sig<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    did: LocalDefId,
+    attr_span: Span,
+) -> Option<ty::EarlyBinder<'tcx, ty::PolyFnSig<'tcx>>> {
+    use DefKind::*;
+
+    let def_kind = tcx.def_kind(did);
+    if let Fn | AssocFn | Variant | Ctor(..) = def_kind {
+        Some(tcx.fn_sig(did))
+    } else {
+        tcx.dcx().span_delayed_bug(attr_span, "this attribute can only be applied to functions");
+        None
     }
+}
 
-    let attrs = tcx.hir_attrs(tcx.local_def_id_to_hir_id(did));
-    let mut codegen_fn_attrs = CodegenFnAttrs::new();
-    if tcx.should_inherit_track_caller(did) {
-        codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
+// FIXME(jdonszelmann): remove when instruction_set becomes a parsed attr
+fn parse_instruction_set_attr(tcx: TyCtxt<'_>, attr: &Attribute) -> Option<InstructionSetAttr> {
+    let list = attr.meta_item_list()?;
+
+    match &list[..] {
+        [MetaItemInner::MetaItem(set)] => {
+            let segments = set.path.segments.iter().map(|x| x.ident.name).collect::<Vec<_>>();
+            match segments.as_slice() {
+                [sym::arm, sym::a32 | sym::t32] if !tcx.sess.target.has_thumb_interworking => {
+                    tcx.dcx().emit_err(errors::UnsupportedInstructionSet { span: attr.span() });
+                    None
+                }
+                [sym::arm, sym::a32] => Some(InstructionSetAttr::ArmA32),
+                [sym::arm, sym::t32] => Some(InstructionSetAttr::ArmT32),
+                _ => {
+                    tcx.dcx().emit_err(errors::InvalidInstructionSet { span: attr.span() });
+                    None
+                }
+            }
+        }
+        [] => {
+            tcx.dcx().emit_err(errors::BareInstructionSet { span: attr.span() });
+            None
+        }
+        _ => {
+            tcx.dcx().emit_err(errors::MultipleInstructionSet { span: attr.span() });
+            None
+        }
     }
+}
+
+// FIXME(jdonszelmann): remove when linkage becomes a parsed attr
+fn parse_linkage_attr(tcx: TyCtxt<'_>, did: LocalDefId, attr: &Attribute) -> Option<Linkage> {
+    let val = attr.value_str()?;
+    let linkage = linkage_by_name(tcx, did, val.as_str());
+    Some(linkage)
+}
+
+// FIXME(jdonszelmann): remove when no_sanitize becomes a parsed attr
+fn parse_no_sanitize_attr(tcx: TyCtxt<'_>, attr: &Attribute) -> Option<SanitizerSet> {
+    let list = attr.meta_item_list()?;
+    let mut sanitizer_set = SanitizerSet::empty();
+
+    for item in list.iter() {
+        match item.name() {
+            Some(sym::address) => {
+                sanitizer_set |= SanitizerSet::ADDRESS | SanitizerSet::KERNELADDRESS
+            }
+            Some(sym::cfi) => sanitizer_set |= SanitizerSet::CFI,
+            Some(sym::kcfi) => sanitizer_set |= SanitizerSet::KCFI,
+            Some(sym::memory) => sanitizer_set |= SanitizerSet::MEMORY,
+            Some(sym::memtag) => sanitizer_set |= SanitizerSet::MEMTAG,
+            Some(sym::shadow_call_stack) => sanitizer_set |= SanitizerSet::SHADOWCALLSTACK,
+            Some(sym::thread) => sanitizer_set |= SanitizerSet::THREAD,
+            Some(sym::hwaddress) => sanitizer_set |= SanitizerSet::HWADDRESS,
+            _ => {
+                tcx.dcx().emit_err(errors::InvalidNoSanitize { span: item.span() });
+            }
+        }
+    }
+
+    Some(sanitizer_set)
+}
+
+// FIXME(jdonszelmann): remove when patchable_function_entry becomes a parsed attr
+fn parse_patchable_function_entry(
+    tcx: TyCtxt<'_>,
+    attr: &Attribute,
+) -> Option<PatchableFunctionEntry> {
+    attr.meta_item_list().and_then(|l| {
+        let mut prefix = None;
+        let mut entry = None;
+        for item in l {
+            let Some(meta_item) = item.meta_item() else {
+                tcx.dcx().emit_err(errors::ExpectedNameValuePair { span: item.span() });
+                continue;
+            };
+
+            let Some(name_value_lit) = meta_item.name_value_literal() else {
+                tcx.dcx().emit_err(errors::ExpectedNameValuePair { span: item.span() });
+                continue;
+            };
+
+            let attrib_to_write = match meta_item.name() {
+                Some(sym::prefix_nops) => &mut prefix,
+                Some(sym::entry_nops) => &mut entry,
+                _ => {
+                    tcx.dcx().emit_err(errors::UnexpectedParameterName {
+                        span: item.span(),
+                        prefix_nops: sym::prefix_nops,
+                        entry_nops: sym::entry_nops,
+                    });
+                    continue;
+                }
+            };
+
+            let rustc_ast::LitKind::Int(val, _) = name_value_lit.kind else {
+                tcx.dcx().emit_err(errors::InvalidLiteralValue { span: name_value_lit.span });
+                continue;
+            };
+
+            let Ok(val) = val.get().try_into() else {
+                tcx.dcx().emit_err(errors::OutOfRangeInteger { span: name_value_lit.span });
+                continue;
+            };
+
+            *attrib_to_write = Some(val);
+        }
+
+        if let (None, None) = (prefix, entry) {
+            tcx.dcx().span_err(attr.span(), "must specify at least one parameter");
+        }
+
+        Some(PatchableFunctionEntry::from_prefix_and_entry(prefix.unwrap_or(0), entry.unwrap_or(0)))
+    })
+}
+
+/// Spans that are collected when processing built-in attributes,
+/// that are useful for emitting diagnostics later.
+#[derive(Default)]
+struct InterestingAttributeDiagnosticSpans {
+    link_ordinal: Option<Span>,
+    no_sanitize: Option<Span>,
+    inline: Option<Span>,
+    no_mangle: Option<Span>,
+}
+
+/// Process the builtin attrs ([`hir::Attribute`]) on the item.
+/// Many of them directly translate to codegen attrs.
+fn process_builtin_attrs(
+    tcx: TyCtxt<'_>,
+    did: LocalDefId,
+    attrs: &[Attribute],
+    codegen_fn_attrs: &mut CodegenFnAttrs,
+) -> InterestingAttributeDiagnosticSpans {
+    let mut interesting_spans = InterestingAttributeDiagnosticSpans::default();
+    let rust_target_features = tcx.rust_target_features(LOCAL_CRATE);
 
     // If our rustc version supports autodiff/enzyme, then we call our handler
     // to check for any `#[rustc_autodiff(...)]` attributes.
+    // FIXME(jdonszelmann): merge with loop below
     if cfg!(llvm_enzyme) {
         let ad = autodiff_attrs(tcx, did.into());
         codegen_fn_attrs.autodiff_item = ad;
     }
 
-    // When `no_builtins` is applied at the crate level, we should add the
-    // `no-builtins` attribute to each function to ensure it takes effect in LTO.
-    let crate_attrs = tcx.hir_attrs(rustc_hir::CRATE_HIR_ID);
-    let no_builtins = attr::contains_name(crate_attrs, sym::no_builtins);
-    if no_builtins {
-        codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_BUILTINS;
-    }
-
-    let rust_target_features = tcx.rust_target_features(LOCAL_CRATE);
-
-    let mut link_ordinal_span = None;
-    let mut no_sanitize_span = None;
-
     for attr in attrs.iter() {
-        // In some cases, attribute are only valid on functions, but it's the `check_attr`
-        // pass that check that they aren't used anywhere else, rather this module.
-        // In these cases, we bail from performing further checks that are only meaningful for
-        // functions (such as calling `fn_sig`, which ICEs if given a non-function). We also
-        // report a delayed bug, just in case `check_attr` isn't doing its job.
-        let fn_sig = |attr_span| {
-            use DefKind::*;
-
-            let def_kind = tcx.def_kind(did);
-            if let Fn | AssocFn | Variant | Ctor(..) = def_kind {
-                Some(tcx.fn_sig(did))
-            } else {
-                tcx.dcx()
-                    .span_delayed_bug(attr_span, "this attribute can only be applied to functions");
-                None
-            }
-        };
-
         if let hir::Attribute::Parsed(p) = attr {
             match p {
                 AttributeKind::Cold(_) => codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD,
                 AttributeKind::ExportName { name, .. } => {
-                    codegen_fn_attrs.export_name = Some(*name);
+                    codegen_fn_attrs.export_name = Some(*name)
+                }
+                AttributeKind::Inline(inline, span) => {
+                    codegen_fn_attrs.inline = *inline;
+                    interesting_spans.inline = Some(*span);
                 }
                 AttributeKind::Naked(_) => codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED,
                 AttributeKind::Align { align, .. } => codegen_fn_attrs.alignment = Some(*align),
                 AttributeKind::LinkName { name, .. } => codegen_fn_attrs.link_name = Some(*name),
                 AttributeKind::LinkOrdinal { ordinal, span } => {
                     codegen_fn_attrs.link_ordinal = Some(*ordinal);
-                    link_ordinal_span = Some(*span);
+                    interesting_spans.link_ordinal = Some(*span);
                 }
                 AttributeKind::LinkSection { name, .. } => {
                     codegen_fn_attrs.link_section = Some(*name)
                 }
                 AttributeKind::NoMangle(attr_span) => {
+                    interesting_spans.no_mangle = Some(*attr_span);
                     if tcx.opt_item_name(did.to_def_id()).is_some() {
                         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
                     } else {
@@ -137,6 +254,7 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
                         });
                     }
                 }
+                AttributeKind::Optimize(optimize, _) => codegen_fn_attrs.optimize = *optimize,
                 AttributeKind::TargetFeature(features, attr_span) => {
                     let Some(sig) = tcx.hir_node_by_def_id(did).fn_sig() else {
                         tcx.dcx().span_delayed_bug(*attr_span, "target_feature applied to non-fn");
@@ -184,7 +302,7 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
                     let is_closure = tcx.is_closure_like(did.to_def_id());
 
                     if !is_closure
-                        && let Some(fn_sig) = fn_sig(*attr_span)
+                        && let Some(fn_sig) = try_fn_sig(tcx, did, *attr_span)
                         && fn_sig.skip_binder().abi() != ExternAbi::Rust
                     {
                         tcx.dcx().emit_err(errors::RequiresRustAbi { span: *attr_span });
@@ -232,155 +350,49 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
             }
             sym::thread_local => codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL,
             sym::linkage => {
-                if let Some(val) = attr.value_str() {
-                    let linkage = Some(linkage_by_name(tcx, did, val.as_str()));
-                    if tcx.is_foreign_item(did) {
-                        codegen_fn_attrs.import_linkage = linkage;
-
-                        if tcx.is_mutable_static(did.into()) {
-                            let mut diag = tcx.dcx().struct_span_err(
-                                attr.span(),
-                                "extern mutable statics are not allowed with `#[linkage]`",
-                            );
-                            diag.note(
-                                "marking the extern static mutable would allow changing which \
-                                 symbol the static references rather than make the target of the \
-                                 symbol mutable",
-                            );
-                            diag.emit();
-                        }
-                    } else {
-                        codegen_fn_attrs.linkage = linkage;
+                let linkage = parse_linkage_attr(tcx, did, attr);
+
+                if tcx.is_foreign_item(did) {
+                    codegen_fn_attrs.import_linkage = linkage;
+
+                    if tcx.is_mutable_static(did.into()) {
+                        let mut diag = tcx.dcx().struct_span_err(
+                            attr.span(),
+                            "extern mutable statics are not allowed with `#[linkage]`",
+                        );
+                        diag.note(
+                            "marking the extern static mutable would allow changing which \
+                            symbol the static references rather than make the target of the \
+                            symbol mutable",
+                        );
+                        diag.emit();
                     }
+                } else {
+                    codegen_fn_attrs.linkage = linkage;
                 }
             }
             sym::no_sanitize => {
-                no_sanitize_span = Some(attr.span());
-                if let Some(list) = attr.meta_item_list() {
-                    for item in list.iter() {
-                        match item.name() {
-                            Some(sym::address) => {
-                                codegen_fn_attrs.no_sanitize |=
-                                    SanitizerSet::ADDRESS | SanitizerSet::KERNELADDRESS
-                            }
-                            Some(sym::cfi) => codegen_fn_attrs.no_sanitize |= SanitizerSet::CFI,
-                            Some(sym::kcfi) => codegen_fn_attrs.no_sanitize |= SanitizerSet::KCFI,
-                            Some(sym::memory) => {
-                                codegen_fn_attrs.no_sanitize |= SanitizerSet::MEMORY
-                            }
-                            Some(sym::memtag) => {
-                                codegen_fn_attrs.no_sanitize |= SanitizerSet::MEMTAG
-                            }
-                            Some(sym::shadow_call_stack) => {
-                                codegen_fn_attrs.no_sanitize |= SanitizerSet::SHADOWCALLSTACK
-                            }
-                            Some(sym::thread) => {
-                                codegen_fn_attrs.no_sanitize |= SanitizerSet::THREAD
-                            }
-                            Some(sym::hwaddress) => {
-                                codegen_fn_attrs.no_sanitize |= SanitizerSet::HWADDRESS
-                            }
-                            _ => {
-                                tcx.dcx().emit_err(errors::InvalidNoSanitize { span: item.span() });
-                            }
-                        }
-                    }
-                }
+                interesting_spans.no_sanitize = Some(attr.span());
+                codegen_fn_attrs.no_sanitize |=
+                    parse_no_sanitize_attr(tcx, attr).unwrap_or_default();
             }
             sym::instruction_set => {
-                codegen_fn_attrs.instruction_set =
-                    attr.meta_item_list().and_then(|l| match &l[..] {
-                        [MetaItemInner::MetaItem(set)] => {
-                            let segments =
-                                set.path.segments.iter().map(|x| x.ident.name).collect::<Vec<_>>();
-                            match segments.as_slice() {
-                                [sym::arm, sym::a32 | sym::t32]
-                                    if !tcx.sess.target.has_thumb_interworking =>
-                                {
-                                    tcx.dcx().emit_err(errors::UnsupportedInstructionSet {
-                                        span: attr.span(),
-                                    });
-                                    None
-                                }
-                                [sym::arm, sym::a32] => Some(InstructionSetAttr::ArmA32),
-                                [sym::arm, sym::t32] => Some(InstructionSetAttr::ArmT32),
-                                _ => {
-                                    tcx.dcx().emit_err(errors::InvalidInstructionSet {
-                                        span: attr.span(),
-                                    });
-                                    None
-                                }
-                            }
-                        }
-                        [] => {
-                            tcx.dcx().emit_err(errors::BareInstructionSet { span: attr.span() });
-                            None
-                        }
-                        _ => {
-                            tcx.dcx()
-                                .emit_err(errors::MultipleInstructionSet { span: attr.span() });
-                            None
-                        }
-                    })
+                codegen_fn_attrs.instruction_set = parse_instruction_set_attr(tcx, attr)
             }
             sym::patchable_function_entry => {
-                codegen_fn_attrs.patchable_function_entry = attr.meta_item_list().and_then(|l| {
-                    let mut prefix = None;
-                    let mut entry = None;
-                    for item in l {
-                        let Some(meta_item) = item.meta_item() else {
-                            tcx.dcx().emit_err(errors::ExpectedNameValuePair { span: item.span() });
-                            continue;
-                        };
-
-                        let Some(name_value_lit) = meta_item.name_value_literal() else {
-                            tcx.dcx().emit_err(errors::ExpectedNameValuePair { span: item.span() });
-                            continue;
-                        };
-
-                        let attrib_to_write = match meta_item.name() {
-                            Some(sym::prefix_nops) => &mut prefix,
-                            Some(sym::entry_nops) => &mut entry,
-                            _ => {
-                                tcx.dcx().emit_err(errors::UnexpectedParameterName {
-                                    span: item.span(),
-                                    prefix_nops: sym::prefix_nops,
-                                    entry_nops: sym::entry_nops,
-                                });
-                                continue;
-                            }
-                        };
-
-                        let rustc_ast::LitKind::Int(val, _) = name_value_lit.kind else {
-                            tcx.dcx().emit_err(errors::InvalidLiteralValue {
-                                span: name_value_lit.span,
-                            });
-                            continue;
-                        };
-
-                        let Ok(val) = val.get().try_into() else {
-                            tcx.dcx()
-                                .emit_err(errors::OutOfRangeInteger { span: name_value_lit.span });
-                            continue;
-                        };
-
-                        *attrib_to_write = Some(val);
-                    }
-
-                    if let (None, None) = (prefix, entry) {
-                        tcx.dcx().span_err(attr.span(), "must specify at least one parameter");
-                    }
-
-                    Some(PatchableFunctionEntry::from_prefix_and_entry(
-                        prefix.unwrap_or(0),
-                        entry.unwrap_or(0),
-                    ))
-                })
+                codegen_fn_attrs.patchable_function_entry =
+                    parse_patchable_function_entry(tcx, attr);
             }
             _ => {}
         }
     }
 
+    interesting_spans
+}
+
+/// Applies overrides for codegen fn attrs. These often have a specific reason why they're necessary.
+/// Please comment why when adding a new one!
+fn apply_overrides(tcx: TyCtxt<'_>, did: LocalDefId, codegen_fn_attrs: &mut CodegenFnAttrs) {
     // Apply the minimum function alignment here. This ensures that a function's alignment is
     // determined by the `-C` flags of the crate it is defined in, not the `-C` flags of the crate
     // it happens to be codegen'd (or const-eval'd) in.
@@ -390,15 +402,6 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
     // On trait methods, inherit the `#[align]` of the trait's method prototype.
     codegen_fn_attrs.alignment = Ord::max(codegen_fn_attrs.alignment, tcx.inherited_align(did));
 
-    let inline_span;
-    (codegen_fn_attrs.inline, inline_span) = if let Some((inline_attr, span)) =
-        find_attr!(attrs, AttributeKind::Inline(i, span) => (*i, *span))
-    {
-        (inline_attr, Some(span))
-    } else {
-        (InlineAttr::None, None)
-    };
-
     // naked function MUST NOT be inlined! This attribute is required for the rust compiler itself,
     // but not for the code generation backend because at that point the naked function will just be
     // a declaration, with a definition provided in global assembly.
@@ -406,9 +409,6 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
         codegen_fn_attrs.inline = InlineAttr::Never;
     }
 
-    codegen_fn_attrs.optimize =
-        find_attr!(attrs, AttributeKind::Optimize(i, _) => *i).unwrap_or(OptimizeAttr::Default);
-
     // #73631: closures inherit `#[target_feature]` annotations
     //
     // If this closure is marked `#[inline(always)]`, simply skip adding `#[target_feature]`.
@@ -431,6 +431,26 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
         }
     }
 
+    // When `no_builtins` is applied at the crate level, we should add the
+    // `no-builtins` attribute to each function to ensure it takes effect in LTO.
+    let crate_attrs = tcx.hir_attrs(rustc_hir::CRATE_HIR_ID);
+    let no_builtins = attr::contains_name(crate_attrs, sym::no_builtins);
+    if no_builtins {
+        codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_BUILTINS;
+    }
+
+    // inherit track-caller properly
+    if tcx.should_inherit_track_caller(did) {
+        codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
+    }
+}
+
+fn check_result(
+    tcx: TyCtxt<'_>,
+    did: LocalDefId,
+    interesting_spans: InterestingAttributeDiagnosticSpans,
+    codegen_fn_attrs: &CodegenFnAttrs,
+) {
     // If a function uses `#[target_feature]` it can't be inlined into general
     // purpose functions as they wouldn't have the right target features
     // enabled. For that reason we also forbid `#[inline(always)]` as it can't be
@@ -446,14 +466,16 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
     // llvm/llvm-project#70563).
     if !codegen_fn_attrs.target_features.is_empty()
         && matches!(codegen_fn_attrs.inline, InlineAttr::Always)
-        && let Some(span) = inline_span
+        && let Some(span) = interesting_spans.inline
     {
         tcx.dcx().span_err(span, "cannot use `#[inline(always)]` with `#[target_feature]`");
     }
 
+    // warn that inline has no effect when no_sanitize is present
     if !codegen_fn_attrs.no_sanitize.is_empty()
         && codegen_fn_attrs.inline.always()
-        && let (Some(no_sanitize_span), Some(inline_span)) = (no_sanitize_span, inline_span)
+        && let (Some(no_sanitize_span), Some(inline_span)) =
+            (interesting_spans.no_sanitize, interesting_spans.inline)
     {
         let hir_id = tcx.local_def_id_to_hir_id(did);
         tcx.node_span_lint(lint::builtin::INLINE_NO_SANITIZE, hir_id, no_sanitize_span, |lint| {
@@ -462,14 +484,55 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
         })
     }
 
+    // error when specifying link_name together with link_ordinal
+    if let Some(_) = codegen_fn_attrs.link_name
+        && let Some(_) = codegen_fn_attrs.link_ordinal
+    {
+        let msg = "cannot use `#[link_name]` with `#[link_ordinal]`";
+        if let Some(span) = interesting_spans.link_ordinal {
+            tcx.dcx().span_err(span, msg);
+        } else {
+            tcx.dcx().err(msg);
+        }
+    }
+
+    if let Some(features) = check_tied_features(
+        tcx.sess,
+        &codegen_fn_attrs
+            .target_features
+            .iter()
+            .map(|features| (features.name.as_str(), true))
+            .collect(),
+    ) {
+        let span =
+            find_attr!(tcx.get_all_attrs(did), AttributeKind::TargetFeature(_, span) => *span)
+                .unwrap_or_else(|| tcx.def_span(did));
+
+        tcx.dcx()
+            .create_err(errors::TargetFeatureDisableOrEnable {
+                features,
+                span: Some(span),
+                missing_features: Some(errors::MissingFeatures),
+            })
+            .emit();
+    }
+}
+
+fn handle_lang_items(
+    tcx: TyCtxt<'_>,
+    did: LocalDefId,
+    interesting_spans: &InterestingAttributeDiagnosticSpans,
+    attrs: &[Attribute],
+    codegen_fn_attrs: &mut CodegenFnAttrs,
+) {
+    let lang_item = lang_items::extract(attrs).and_then(|(name, _)| LangItem::from_name(name));
+
     // Weak lang items have the same semantics as "std internal" symbols in the
     // sense that they're preserved through all our LTO passes and only
     // strippable by the linker.
     //
     // Additionally weak lang items have predetermined symbol names.
-    if let Some((name, _)) = lang_items::extract(attrs)
-        && let Some(lang_item) = LangItem::from_name(name)
-    {
+    if let Some(lang_item) = lang_item {
         if WEAK_LANG_ITEMS.contains(&lang_item) {
             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
         }
@@ -478,20 +541,15 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
             codegen_fn_attrs.link_name = Some(link_name);
         }
     }
-    check_link_name_xor_ordinal(tcx, &codegen_fn_attrs, link_ordinal_span);
 
+    // error when using no_mangle on a lang item item
     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL)
         && codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::NO_MANGLE)
     {
-        let no_mangle_span =
-            find_attr!(attrs, AttributeKind::NoMangle(no_mangle_span) => *no_mangle_span)
-                .unwrap_or_default();
-        let lang_item =
-            lang_items::extract(attrs).map_or(None, |(name, _span)| LangItem::from_name(name));
         let mut err = tcx
             .dcx()
             .struct_span_err(
-                no_mangle_span,
+                interesting_spans.no_mangle.unwrap_or_default(),
                 "`#[no_mangle]` cannot be used on internal language items",
             )
             .with_note("Rustc requires this item to have a specific mangled name.")
@@ -508,28 +566,33 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
         }
         err.emit();
     }
+}
 
-    if let Some(features) = check_tied_features(
-        tcx.sess,
-        &codegen_fn_attrs
-            .target_features
-            .iter()
-            .map(|features| (features.name.as_str(), true))
-            .collect(),
-    ) {
-        let span =
-            find_attr!(tcx.get_all_attrs(did), AttributeKind::TargetFeature(_, span) => *span)
-                .unwrap_or_else(|| tcx.def_span(did));
-
-        tcx.dcx()
-            .create_err(errors::TargetFeatureDisableOrEnable {
-                features,
-                span: Some(span),
-                missing_features: Some(errors::MissingFeatures),
-            })
-            .emit();
+/// Generate the [`CodegenFnAttrs`] for an item (identified by the [`LocalDefId`]).
+///
+/// This happens in 4 stages:
+/// - apply built-in attributes that directly translate to codegen attributes.
+/// - handle lang items. These have special codegen attrs applied to them.
+/// - apply overrides, like minimum requirements for alignment and other settings that don't rely directly the built-in attrs on the item.
+///   overrides come after applying built-in attributes since they may only apply when certain attributes were already set in the stage before.
+/// - check that the result is valid. There's various ways in which this may not be the case, such as certain combinations of attrs.
+fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
+    if cfg!(debug_assertions) {
+        let def_kind = tcx.def_kind(did);
+        assert!(
+            def_kind.has_codegen_attrs(),
+            "unexpected `def_kind` in `codegen_fn_attrs`: {def_kind:?}",
+        );
     }
 
+    let mut codegen_fn_attrs = CodegenFnAttrs::new();
+    let attrs = tcx.hir_attrs(tcx.local_def_id_to_hir_id(did));
+
+    let interesting_spans = process_builtin_attrs(tcx, did, attrs, &mut codegen_fn_attrs);
+    handle_lang_items(tcx, did, &interesting_spans, attrs, &mut codegen_fn_attrs);
+    apply_overrides(tcx, did, &mut codegen_fn_attrs);
+    check_result(tcx, did, interesting_spans, &codegen_fn_attrs);
+
     codegen_fn_attrs
 }
 
@@ -555,27 +618,12 @@ fn inherited_align<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> Option<Align> {
     tcx.codegen_fn_attrs(opt_trait_item(tcx, def_id)?).alignment
 }
 
-fn check_link_name_xor_ordinal(
-    tcx: TyCtxt<'_>,
-    codegen_fn_attrs: &CodegenFnAttrs,
-    inline_span: Option<Span>,
-) {
-    if codegen_fn_attrs.link_name.is_none() || codegen_fn_attrs.link_ordinal.is_none() {
-        return;
-    }
-    let msg = "cannot use `#[link_name]` with `#[link_ordinal]`";
-    if let Some(span) = inline_span {
-        tcx.dcx().span_err(span, msg);
-    } else {
-        tcx.dcx().err(msg);
-    }
-}
-
 /// We now check the #\[rustc_autodiff\] attributes which we generated from the #[autodiff(...)]
 /// macros. There are two forms. The pure one without args to mark primal functions (the functions
 /// being differentiated). The other form is #[rustc_autodiff(Mode, ActivityList)] on top of the
 /// placeholder functions. We wrote the rustc_autodiff attributes ourself, so this should never
 /// panic, unless we introduced a bug when parsing the autodiff macro.
+//FIXME(jdonszelmann): put in the main loop. No need to have two..... :/ Let's do that when we make autodiff parsed.
 fn autodiff_attrs(tcx: TyCtxt<'_>, id: DefId) -> Option<AutoDiffAttrs> {
     let attrs = tcx.get_attrs(id, sym::rustc_autodiff);
 
diff --git a/compiler/rustc_codegen_ssa/src/mir/block.rs b/compiler/rustc_codegen_ssa/src/mir/block.rs
index bde63fd501a..e96590441fa 100644
--- a/compiler/rustc_codegen_ssa/src/mir/block.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/block.rs
@@ -35,6 +35,14 @@ enum MergingSucc {
     True,
 }
 
+/// Indicates to the call terminator codegen whether a cal
+/// is a normal call or an explicit tail call.
+#[derive(Debug, PartialEq)]
+enum CallKind {
+    Normal,
+    Tail,
+}
+
 /// Used by `FunctionCx::codegen_terminator` for emitting common patterns
 /// e.g., creating a basic block, calling a function, etc.
 struct TerminatorCodegenHelper<'tcx> {
@@ -160,6 +168,7 @@ impl<'a, 'tcx> TerminatorCodegenHelper<'tcx> {
         mut unwind: mir::UnwindAction,
         lifetime_ends_after_call: &[(Bx::Value, Size)],
         instance: Option<Instance<'tcx>>,
+        kind: CallKind,
         mergeable_succ: bool,
     ) -> MergingSucc {
         let tcx = bx.tcx();
@@ -221,6 +230,11 @@ impl<'a, 'tcx> TerminatorCodegenHelper<'tcx> {
             }
         };
 
+        if kind == CallKind::Tail {
+            bx.tail_call(fn_ty, fn_attrs, fn_abi, fn_ptr, llargs, self.funclet(fx), instance);
+            return MergingSucc::False;
+        }
+
         if let Some(unwind_block) = unwind_block {
             let ret_llbb = if let Some((_, target)) = destination {
                 fx.llbb(target)
@@ -659,6 +673,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             unwind,
             &[],
             Some(drop_instance),
+            CallKind::Normal,
             !maybe_null && mergeable_succ,
         )
     }
@@ -747,8 +762,19 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         let (fn_abi, llfn, instance) = common::build_langcall(bx, span, lang_item);
 
         // Codegen the actual panic invoke/call.
-        let merging_succ =
-            helper.do_call(self, bx, fn_abi, llfn, &args, None, unwind, &[], Some(instance), false);
+        let merging_succ = helper.do_call(
+            self,
+            bx,
+            fn_abi,
+            llfn,
+            &args,
+            None,
+            unwind,
+            &[],
+            Some(instance),
+            CallKind::Normal,
+            false,
+        );
         assert_eq!(merging_succ, MergingSucc::False);
         MergingSucc::False
     }
@@ -777,6 +803,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             mir::UnwindAction::Unreachable,
             &[],
             Some(instance),
+            CallKind::Normal,
             false,
         );
         assert_eq!(merging_succ, MergingSucc::False);
@@ -845,6 +872,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             unwind,
             &[],
             Some(instance),
+            CallKind::Normal,
             mergeable_succ,
         ))
     }
@@ -860,6 +888,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         target: Option<mir::BasicBlock>,
         unwind: mir::UnwindAction,
         fn_span: Span,
+        kind: CallKind,
         mergeable_succ: bool,
     ) -> MergingSucc {
         let source_info = mir::SourceInfo { span: fn_span, ..terminator.source_info };
@@ -1003,8 +1032,13 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         // We still need to call `make_return_dest` even if there's no `target`, since
         // `fn_abi.ret` could be `PassMode::Indirect`, even if it is uninhabited,
         // and `make_return_dest` adds the return-place indirect pointer to `llargs`.
-        let return_dest = self.make_return_dest(bx, destination, &fn_abi.ret, &mut llargs);
-        let destination = target.map(|target| (return_dest, target));
+        let destination = match kind {
+            CallKind::Normal => {
+                let return_dest = self.make_return_dest(bx, destination, &fn_abi.ret, &mut llargs);
+                target.map(|target| (return_dest, target))
+            }
+            CallKind::Tail => None,
+        };
 
         // Split the rust-call tupled arguments off.
         let (first_args, untuple) = if sig.abi() == ExternAbi::RustCall
@@ -1020,6 +1054,14 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         // to generate `lifetime_end` when the call returns.
         let mut lifetime_ends_after_call: Vec<(Bx::Value, Size)> = Vec::new();
         'make_args: for (i, arg) in first_args.iter().enumerate() {
+            if kind == CallKind::Tail && matches!(fn_abi.args[i].mode, PassMode::Indirect { .. }) {
+                // FIXME: https://github.com/rust-lang/rust/pull/144232#discussion_r2218543841
+                span_bug!(
+                    fn_span,
+                    "arguments using PassMode::Indirect are currently not supported for tail calls"
+                );
+            }
+
             let mut op = self.codegen_operand(bx, &arg.node);
 
             if let (0, Some(ty::InstanceKind::Virtual(_, idx))) = (i, instance.map(|i| i.def)) {
@@ -1147,6 +1189,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             unwind,
             &lifetime_ends_after_call,
             instance,
+            kind,
             mergeable_succ,
         )
     }
@@ -1388,15 +1431,23 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 target,
                 unwind,
                 fn_span,
+                CallKind::Normal,
                 mergeable_succ(),
             ),
-            mir::TerminatorKind::TailCall { .. } => {
-                // FIXME(explicit_tail_calls): implement tail calls in ssa backend
-                span_bug!(
-                    terminator.source_info.span,
-                    "`TailCall` terminator is not yet supported by `rustc_codegen_ssa`"
-                )
-            }
+            mir::TerminatorKind::TailCall { ref func, ref args, fn_span } => self
+                .codegen_call_terminator(
+                    helper,
+                    bx,
+                    terminator,
+                    func,
+                    args,
+                    mir::Place::from(mir::RETURN_PLACE),
+                    None,
+                    mir::UnwindAction::Unreachable,
+                    fn_span,
+                    CallKind::Tail,
+                    mergeable_succ(),
+                ),
             mir::TerminatorKind::CoroutineDrop | mir::TerminatorKind::Yield { .. } => {
                 bug!("coroutine ops in codegen")
             }
diff --git a/compiler/rustc_codegen_ssa/src/mir/naked_asm.rs b/compiler/rustc_codegen_ssa/src/mir/naked_asm.rs
index 42e435cf0a3..2a9b5c9019b 100644
--- a/compiler/rustc_codegen_ssa/src/mir/naked_asm.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/naked_asm.rs
@@ -1,5 +1,5 @@
 use rustc_abi::{BackendRepr, Float, Integer, Primitive, RegKind};
-use rustc_attr_data_structures::InstructionSetAttr;
+use rustc_hir::attrs::InstructionSetAttr;
 use rustc_middle::mir::mono::{Linkage, MonoItemData, Visibility};
 use rustc_middle::mir::{InlineAsmOperand, START_BLOCK};
 use rustc_middle::ty::layout::{FnAbiOf, LayoutOf, TyAndLayout};
diff --git a/compiler/rustc_codegen_ssa/src/target_features.rs b/compiler/rustc_codegen_ssa/src/target_features.rs
index def4ec13e87..d984156c674 100644
--- a/compiler/rustc_codegen_ssa/src/target_features.rs
+++ b/compiler/rustc_codegen_ssa/src/target_features.rs
@@ -1,6 +1,6 @@
-use rustc_attr_data_structures::InstructionSetAttr;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
 use rustc_data_structures::unord::{UnordMap, UnordSet};
+use rustc_hir::attrs::InstructionSetAttr;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{DefId, LOCAL_CRATE, LocalDefId};
 use rustc_middle::middle::codegen_fn_attrs::TargetFeature;
diff --git a/compiler/rustc_codegen_ssa/src/traits/builder.rs b/compiler/rustc_codegen_ssa/src/traits/builder.rs
index 979456a6ba7..4b18146863b 100644
--- a/compiler/rustc_codegen_ssa/src/traits/builder.rs
+++ b/compiler/rustc_codegen_ssa/src/traits/builder.rs
@@ -595,6 +595,18 @@ pub trait BuilderMethods<'a, 'tcx>:
         funclet: Option<&Self::Funclet>,
         instance: Option<Instance<'tcx>>,
     ) -> Self::Value;
+
+    fn tail_call(
+        &mut self,
+        llty: Self::Type,
+        fn_attrs: Option<&CodegenFnAttrs>,
+        fn_abi: &FnAbi<'tcx, Ty<'tcx>>,
+        llfn: Self::Value,
+        args: &[Self::Value],
+        funclet: Option<&Self::Funclet>,
+        instance: Option<Instance<'tcx>>,
+    );
+
     fn zext(&mut self, val: Self::Value, dest_ty: Self::Type) -> Self::Value;
 
     fn apply_attrs_to_cleanup_callsite(&mut self, llret: Self::Value);
diff --git a/compiler/rustc_codegen_ssa/src/traits/debuginfo.rs b/compiler/rustc_codegen_ssa/src/traits/debuginfo.rs
index b9d4950e0ad..30a3bd5abe4 100644
--- a/compiler/rustc_codegen_ssa/src/traits/debuginfo.rs
+++ b/compiler/rustc_codegen_ssa/src/traits/debuginfo.rs
@@ -50,7 +50,7 @@ pub trait DebugInfoCodegenMethods<'tcx>: BackendTypes {
         scope_metadata: Self::DIScope,
         file: &SourceFile,
     ) -> Self::DIScope;
-    fn debuginfo_finalize(&self);
+    fn debuginfo_finalize(&mut self);
 
     // FIXME(eddyb) find a common convention for all of the debuginfo-related
     // names (choose between `dbg`, `debug`, `debuginfo`, `debug_info` etc.).
diff --git a/compiler/rustc_const_eval/Cargo.toml b/compiler/rustc_const_eval/Cargo.toml
index 93d0d5b9a71..51dcee8d882 100644
--- a/compiler/rustc_const_eval/Cargo.toml
+++ b/compiler/rustc_const_eval/Cargo.toml
@@ -9,7 +9,6 @@ either = "1"
 rustc_abi = { path = "../rustc_abi" }
 rustc_apfloat = "0.2.0"
 rustc_ast = { path = "../rustc_ast" }
-rustc_attr_data_structures = { path = "../rustc_attr_data_structures" }
 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 44e5d1d5ee7..8e2c138282a 100644
--- a/compiler/rustc_const_eval/src/check_consts/check.rs
+++ b/compiler/rustc_const_eval/src/check_consts/check.rs
@@ -6,7 +6,6 @@ use std::mem;
 use std::num::NonZero;
 use std::ops::Deref;
 
-use rustc_attr_data_structures as attrs;
 use rustc_errors::{Diag, ErrorGuaranteed};
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::DefId;
@@ -466,7 +465,7 @@ impl<'mir, 'tcx> Checker<'mir, 'tcx> {
     /// Check the const stability of the given item (fn or trait).
     fn check_callee_stability(&mut self, def_id: DefId) {
         match self.tcx.lookup_const_stability(def_id) {
-            Some(attrs::ConstStability { level: attrs::StabilityLevel::Stable { .. }, .. }) => {
+            Some(hir::ConstStability { level: hir::StabilityLevel::Stable { .. }, .. }) => {
                 // All good.
             }
             None => {
@@ -482,8 +481,8 @@ impl<'mir, 'tcx> Checker<'mir, 'tcx> {
                     });
                 }
             }
-            Some(attrs::ConstStability {
-                level: attrs::StabilityLevel::Unstable { implied_by: implied_feature, issue, .. },
+            Some(hir::ConstStability {
+                level: hir::StabilityLevel::Unstable { implied_by: implied_feature, issue, .. },
                 feature,
                 ..
             }) => {
@@ -891,8 +890,8 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                                 });
                             }
                         }
-                        Some(attrs::ConstStability {
-                            level: attrs::StabilityLevel::Unstable { .. },
+                        Some(hir::ConstStability {
+                            level: hir::StabilityLevel::Unstable { .. },
                             feature,
                             ..
                         }) => {
@@ -902,8 +901,8 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                                 const_stable_indirect: is_const_stable,
                             });
                         }
-                        Some(attrs::ConstStability {
-                            level: attrs::StabilityLevel::Stable { .. },
+                        Some(hir::ConstStability {
+                            level: hir::StabilityLevel::Stable { .. },
                             ..
                         }) => {
                             // All good. Note that a `#[rustc_const_stable]` intrinsic (meaning it
diff --git a/compiler/rustc_const_eval/src/check_consts/mod.rs b/compiler/rustc_const_eval/src/check_consts/mod.rs
index ebf18c6f2ac..4a88d039ef3 100644
--- a/compiler/rustc_const_eval/src/check_consts/mod.rs
+++ b/compiler/rustc_const_eval/src/check_consts/mod.rs
@@ -5,11 +5,12 @@
 //! it finds operations that are invalid in a certain context.
 
 use rustc_errors::DiagCtxtHandle;
+use rustc_hir::attrs::AttributeKind;
 use rustc_hir::def_id::{DefId, LocalDefId};
+use rustc_hir::{self as hir, find_attr};
 use rustc_middle::ty::{self, PolyFnSig, TyCtxt};
 use rustc_middle::{bug, mir};
 use rustc_span::Symbol;
-use {rustc_attr_data_structures as attrs, rustc_hir as hir};
 
 pub use self::qualifs::Qualif;
 
@@ -82,7 +83,7 @@ pub fn rustc_allow_const_fn_unstable(
 ) -> bool {
     let attrs = tcx.hir_attrs(tcx.local_def_id_to_hir_id(def_id));
 
-    attrs::find_attr!(attrs, attrs::AttributeKind::AllowConstFnUnstable(syms, _) if syms.contains(&feature_gate))
+    find_attr!(attrs, AttributeKind::AllowConstFnUnstable(syms, _) if syms.contains(&feature_gate))
 }
 
 /// Returns `true` if the given `def_id` (trait or function) is "safe to expose on stable".
diff --git a/compiler/rustc_const_eval/src/interpret/call.rs b/compiler/rustc_const_eval/src/interpret/call.rs
index 5b3adba0265..b8a65369825 100644
--- a/compiler/rustc_const_eval/src/interpret/call.rs
+++ b/compiler/rustc_const_eval/src/interpret/call.rs
@@ -11,6 +11,7 @@ use rustc_middle::ty::{self, AdtDef, Instance, Ty, VariantDef};
 use rustc_middle::{bug, mir, span_bug};
 use rustc_span::sym;
 use rustc_target::callconv::{ArgAbi, FnAbi, PassMode};
+use tracing::field::Empty;
 use tracing::{info, instrument, trace};
 
 use super::{
@@ -18,7 +19,8 @@ use super::{
     Projectable, Provenance, ReturnAction, ReturnContinuation, Scalar, StackPopInfo, interp_ok,
     throw_ub, throw_ub_custom, throw_unsup_format,
 };
-use crate::fluent_generated as fluent;
+use crate::interpret::EnteredTraceSpan;
+use crate::{enter_trace_span, fluent_generated as fluent};
 
 /// An argument passed to a function.
 #[derive(Clone, Debug)]
@@ -344,6 +346,8 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         destination: &PlaceTy<'tcx, M::Provenance>,
         mut cont: ReturnContinuation,
     ) -> InterpResult<'tcx> {
+        let _span = enter_trace_span!(M, step::init_stack_frame, %instance, tracing_separate_thread = Empty);
+
         // Compute callee information.
         // FIXME: for variadic support, do we have to somehow determine callee's extra_args?
         let callee_fn_abi = self.fn_abi_of_instance(instance, ty::List::empty())?;
@@ -523,7 +527,9 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         target: Option<mir::BasicBlock>,
         unwind: mir::UnwindAction,
     ) -> InterpResult<'tcx> {
-        trace!("init_fn_call: {:#?}", fn_val);
+        let _span =
+            enter_trace_span!(M, step::init_fn_call, tracing_separate_thread = Empty, ?fn_val)
+                .or_if_tracing_disabled(|| trace!("init_fn_call: {:#?}", fn_val));
 
         let instance = match fn_val {
             FnVal::Instance(instance) => instance,
diff --git a/compiler/rustc_const_eval/src/interpret/eval_context.rs b/compiler/rustc_const_eval/src/interpret/eval_context.rs
index 0a8591ca140..c4b705d7124 100644
--- a/compiler/rustc_const_eval/src/interpret/eval_context.rs
+++ b/compiler/rustc_const_eval/src/interpret/eval_context.rs
@@ -113,7 +113,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
     /// See [LayoutOf::layout_of] for the original documentation.
     #[inline(always)]
     pub fn layout_of(&self, ty: Ty<'tcx>) -> <Self as LayoutOfHelpers<'tcx>>::LayoutOfResult {
-        let _span = enter_trace_span!(M, "InterpCx::layout_of", ty = ?ty.kind());
+        let _span = enter_trace_span!(M, layouting::layout_of, ty = ?ty.kind());
         LayoutOf::layout_of(self, ty)
     }
 
@@ -126,7 +126,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         sig: ty::PolyFnSig<'tcx>,
         extra_args: &'tcx ty::List<Ty<'tcx>>,
     ) -> <Self as FnAbiOfHelpers<'tcx>>::FnAbiOfResult {
-        let _span = enter_trace_span!(M, "InterpCx::fn_abi_of_fn_ptr", ?sig, ?extra_args);
+        let _span = enter_trace_span!(M, layouting::fn_abi_of_fn_ptr, ?sig, ?extra_args);
         FnAbiOf::fn_abi_of_fn_ptr(self, sig, extra_args)
     }
 
@@ -139,7 +139,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         instance: ty::Instance<'tcx>,
         extra_args: &'tcx ty::List<Ty<'tcx>>,
     ) -> <Self as FnAbiOfHelpers<'tcx>>::FnAbiOfResult {
-        let _span = enter_trace_span!(M, "InterpCx::fn_abi_of_instance", ?instance, ?extra_args);
+        let _span = enter_trace_span!(M, layouting::fn_abi_of_instance, ?instance, ?extra_args);
         FnAbiOf::fn_abi_of_instance(self, instance, extra_args)
     }
 }
diff --git a/compiler/rustc_const_eval/src/interpret/memory.rs b/compiler/rustc_const_eval/src/interpret/memory.rs
index 47bebf5371a..23b40894f16 100644
--- a/compiler/rustc_const_eval/src/interpret/memory.rs
+++ b/compiler/rustc_const_eval/src/interpret/memory.rs
@@ -937,8 +937,12 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         // (both global from `alloc_map` and local from `extra_fn_ptr_map`)
         if let Some(fn_val) = self.get_fn_alloc(id) {
             let align = match fn_val {
-                FnVal::Instance(instance) => {
-                    self.tcx.codegen_instance_attrs(instance.def).alignment.unwrap_or(Align::ONE)
+                FnVal::Instance(_instance) => {
+                    // FIXME: Until we have a clear design for the effects of align(N) functions
+                    // on the address of function pointers, we don't consider the align(N)
+                    // attribute on functions in the interpreter.
+                    // See <https://github.com/rust-lang/rust/issues/144661> for more context.
+                    Align::ONE
                 }
                 // Machine-specific extra functions currently do not support alignment restrictions.
                 FnVal::Other(_) => Align::ONE,
diff --git a/compiler/rustc_const_eval/src/interpret/operand.rs b/compiler/rustc_const_eval/src/interpret/operand.rs
index 21afd082a05..14541809070 100644
--- a/compiler/rustc_const_eval/src/interpret/operand.rs
+++ b/compiler/rustc_const_eval/src/interpret/operand.rs
@@ -13,6 +13,7 @@ use rustc_middle::ty::print::{FmtPrinter, PrettyPrinter};
 use rustc_middle::ty::{ConstInt, ScalarInt, Ty, TyCtxt};
 use rustc_middle::{bug, mir, span_bug, ty};
 use rustc_span::DUMMY_SP;
+use tracing::field::Empty;
 use tracing::trace;
 
 use super::{
@@ -20,6 +21,7 @@ use super::{
     OffsetMode, PlaceTy, Pointer, Projectable, Provenance, Scalar, alloc_range, err_ub,
     from_known_layout, interp_ok, mir_assign_valid_types, throw_ub,
 };
+use crate::enter_trace_span;
 
 /// An `Immediate` represents a single immediate self-contained Rust value.
 ///
@@ -186,18 +188,18 @@ pub struct ImmTy<'tcx, Prov: Provenance = CtfeProvenance> {
 impl<Prov: Provenance> std::fmt::Display for ImmTy<'_, Prov> {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         /// Helper function for printing a scalar to a FmtPrinter
-        fn p<'a, 'tcx, Prov: Provenance>(
-            cx: &mut FmtPrinter<'a, 'tcx>,
+        fn print_scalar<'a, 'tcx, Prov: Provenance>(
+            p: &mut FmtPrinter<'a, 'tcx>,
             s: Scalar<Prov>,
             ty: Ty<'tcx>,
         ) -> Result<(), std::fmt::Error> {
             match s {
-                Scalar::Int(int) => cx.pretty_print_const_scalar_int(int, ty, true),
+                Scalar::Int(int) => p.pretty_print_const_scalar_int(int, ty, true),
                 Scalar::Ptr(ptr, _sz) => {
                     // Just print the ptr value. `pretty_print_const_scalar_ptr` would also try to
                     // print what is points to, which would fail since it has no access to the local
                     // memory.
-                    cx.pretty_print_const_pointer(ptr, ty)
+                    p.pretty_print_const_pointer(ptr, ty)
                 }
             }
         }
@@ -205,8 +207,9 @@ impl<Prov: Provenance> std::fmt::Display for ImmTy<'_, Prov> {
             match self.imm {
                 Immediate::Scalar(s) => {
                     if let Some(ty) = tcx.lift(self.layout.ty) {
-                        let s =
-                            FmtPrinter::print_string(tcx, Namespace::ValueNS, |cx| p(cx, s, ty))?;
+                        let s = FmtPrinter::print_string(tcx, Namespace::ValueNS, |p| {
+                            print_scalar(p, s, ty)
+                        })?;
                         f.write_str(&s)?;
                         return Ok(());
                     }
@@ -770,6 +773,13 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         mir_place: mir::Place<'tcx>,
         layout: Option<TyAndLayout<'tcx>>,
     ) -> InterpResult<'tcx, OpTy<'tcx, M::Provenance>> {
+        let _span = enter_trace_span!(
+            M,
+            step::eval_place_to_op,
+            ?mir_place,
+            tracing_separate_thread = Empty
+        );
+
         // Do not use the layout passed in as argument if the base we are looking at
         // here is not the entire place.
         let layout = if mir_place.projection.is_empty() { layout } else { None };
@@ -813,6 +823,9 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         mir_op: &mir::Operand<'tcx>,
         layout: Option<TyAndLayout<'tcx>>,
     ) -> InterpResult<'tcx, OpTy<'tcx, M::Provenance>> {
+        let _span =
+            enter_trace_span!(M, step::eval_operand, ?mir_op, tracing_separate_thread = Empty);
+
         use rustc_middle::mir::Operand::*;
         let op = match mir_op {
             // FIXME: do some more logic on `move` to invalidate the old location
diff --git a/compiler/rustc_const_eval/src/interpret/place.rs b/compiler/rustc_const_eval/src/interpret/place.rs
index e2284729efd..45c4edb8503 100644
--- a/compiler/rustc_const_eval/src/interpret/place.rs
+++ b/compiler/rustc_const_eval/src/interpret/place.rs
@@ -9,6 +9,7 @@ use rustc_abi::{BackendRepr, HasDataLayout, Size};
 use rustc_middle::ty::Ty;
 use rustc_middle::ty::layout::TyAndLayout;
 use rustc_middle::{bug, mir, span_bug};
+use tracing::field::Empty;
 use tracing::{instrument, trace};
 
 use super::{
@@ -16,6 +17,7 @@ use super::{
     InterpResult, Machine, MemoryKind, Misalignment, OffsetMode, OpTy, Operand, Pointer,
     Projectable, Provenance, Scalar, alloc_range, interp_ok, mir_assign_valid_types,
 };
+use crate::enter_trace_span;
 
 #[derive(Copy, Clone, Hash, PartialEq, Eq, Debug)]
 /// Information required for the sound usage of a `MemPlace`.
@@ -524,6 +526,9 @@ where
         &self,
         mir_place: mir::Place<'tcx>,
     ) -> InterpResult<'tcx, PlaceTy<'tcx, M::Provenance>> {
+        let _span =
+            enter_trace_span!(M, step::eval_place, ?mir_place, tracing_separate_thread = Empty);
+
         let mut place = self.local_to_place(mir_place.local)?;
         // Using `try_fold` turned out to be bad for performance, hence the loop.
         for elem in mir_place.projection.iter() {
diff --git a/compiler/rustc_const_eval/src/interpret/projection.rs b/compiler/rustc_const_eval/src/interpret/projection.rs
index f72c4418081..d05871bfc77 100644
--- a/compiler/rustc_const_eval/src/interpret/projection.rs
+++ b/compiler/rustc_const_eval/src/interpret/projection.rs
@@ -199,6 +199,15 @@ where
         base.offset_with_meta(offset, OffsetMode::Inbounds, meta, field_layout, self)
     }
 
+    /// Projects multiple fields at once. See [`Self::project_field`] for details.
+    pub fn project_fields<P: Projectable<'tcx, M::Provenance>, const N: usize>(
+        &self,
+        base: &P,
+        fields: [FieldIdx; N],
+    ) -> InterpResult<'tcx, [P; N]> {
+        fields.try_map(|field| self.project_field(base, field))
+    }
+
     /// Downcasting to an enum variant.
     pub fn project_downcast<P: Projectable<'tcx, M::Provenance>>(
         &self,
diff --git a/compiler/rustc_const_eval/src/interpret/stack.rs b/compiler/rustc_const_eval/src/interpret/stack.rs
index 2e99bb4209f..73cc87508ef 100644
--- a/compiler/rustc_const_eval/src/interpret/stack.rs
+++ b/compiler/rustc_const_eval/src/interpret/stack.rs
@@ -397,11 +397,11 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         // Finish things up.
         M::after_stack_push(self)?;
         self.frame_mut().loc = Left(mir::Location::START);
-        // `tracing_separate_thread` is used to instruct the chrome_tracing [tracing::Layer] in Miri
+        // `tracing_separate_thread` is used to instruct the tracing_chrome [tracing::Layer] in Miri
         // to put the "frame" span on a separate trace thread/line than other spans, to make the
-        // visualization in https://ui.perfetto.dev easier to interpret. It is set to a value of
+        // visualization in <https://ui.perfetto.dev> easier to interpret. It is set to a value of
         // [tracing::field::Empty] so that other tracing layers (e.g. the logger) will ignore it.
-        let span = info_span!("frame", tracing_separate_thread = Empty, "{}", instance);
+        let span = info_span!("frame", tracing_separate_thread = Empty, frame = %instance);
         self.frame_mut().tracing_span.enter(span);
 
         interp_ok(())
diff --git a/compiler/rustc_const_eval/src/interpret/step.rs b/compiler/rustc_const_eval/src/interpret/step.rs
index 629dcc3523c..9df49c0f4cc 100644
--- a/compiler/rustc_const_eval/src/interpret/step.rs
+++ b/compiler/rustc_const_eval/src/interpret/step.rs
@@ -9,13 +9,15 @@ use rustc_middle::ty::{self, Instance, Ty};
 use rustc_middle::{bug, mir, span_bug};
 use rustc_span::source_map::Spanned;
 use rustc_target::callconv::FnAbi;
+use tracing::field::Empty;
 use tracing::{info, instrument, trace};
 
 use super::{
     FnArg, FnVal, ImmTy, Immediate, InterpCx, InterpResult, Machine, MemPlaceMeta, PlaceTy,
     Projectable, Scalar, interp_ok, throw_ub, throw_unsup_format,
 };
-use crate::util;
+use crate::interpret::EnteredTraceSpan;
+use crate::{enter_trace_span, util};
 
 struct EvaluatedCalleeAndArgs<'tcx, M: Machine<'tcx>> {
     callee: FnVal<'tcx, M::ExtraFnVal>,
@@ -74,7 +76,14 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
     ///
     /// This does NOT move the statement counter forward, the caller has to do that!
     pub fn eval_statement(&mut self, stmt: &mir::Statement<'tcx>) -> InterpResult<'tcx> {
-        info!("{:?}", stmt);
+        let _span = enter_trace_span!(
+            M,
+            step::eval_statement,
+            stmt = ?stmt.kind,
+            span = ?stmt.source_info.span,
+            tracing_separate_thread = Empty,
+        )
+        .or_if_tracing_disabled(|| info!(stmt = ?stmt.kind));
 
         use rustc_middle::mir::StatementKind::*;
 
@@ -456,7 +465,14 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
     }
 
     fn eval_terminator(&mut self, terminator: &mir::Terminator<'tcx>) -> InterpResult<'tcx> {
-        info!("{:?}", terminator.kind);
+        let _span = enter_trace_span!(
+            M,
+            step::eval_terminator,
+            terminator = ?terminator.kind,
+            span = ?terminator.source_info.span,
+            tracing_separate_thread = Empty,
+        )
+        .or_if_tracing_disabled(|| info!(terminator = ?terminator.kind));
 
         use rustc_middle::mir::TerminatorKind::*;
         match terminator.kind {
diff --git a/compiler/rustc_const_eval/src/interpret/util.rs b/compiler/rustc_const_eval/src/interpret/util.rs
index 72650d545c3..71800950faa 100644
--- a/compiler/rustc_const_eval/src/interpret/util.rs
+++ b/compiler/rustc_const_eval/src/interpret/util.rs
@@ -48,18 +48,104 @@ pub(crate) fn create_static_alloc<'tcx>(
 
 /// A marker trait returned by [crate::interpret::Machine::enter_trace_span], identifying either a
 /// real [tracing::span::EnteredSpan] in case tracing is enabled, or the dummy type `()` when
-/// tracing is disabled.
-pub trait EnteredTraceSpan {}
-impl EnteredTraceSpan for () {}
-impl EnteredTraceSpan for tracing::span::EnteredSpan {}
+/// tracing is disabled. Also see [crate::enter_trace_span!] below.
+pub trait EnteredTraceSpan {
+    /// Allows executing an alternative function when tracing is disabled. Useful for example if you
+    /// want to open a trace span when tracing is enabled, and alternatively just log a line when
+    /// tracing is disabled.
+    fn or_if_tracing_disabled(self, f: impl FnOnce()) -> Self;
+}
+impl EnteredTraceSpan for () {
+    fn or_if_tracing_disabled(self, f: impl FnOnce()) -> Self {
+        f(); // tracing is disabled, execute the function
+        self
+    }
+}
+impl EnteredTraceSpan for tracing::span::EnteredSpan {
+    fn or_if_tracing_disabled(self, _f: impl FnOnce()) -> Self {
+        self // tracing is enabled, don't execute anything
+    }
+}
 
-/// Shortand for calling [crate::interpret::Machine::enter_trace_span] on a [tracing::info_span].
+/// Shortand for calling [crate::interpret::Machine::enter_trace_span] on a [tracing::info_span!].
 /// This is supposed to be compiled out when [crate::interpret::Machine::enter_trace_span] has the
 /// default implementation (i.e. when it does not actually enter the span but instead returns `()`).
+/// This macro takes a type implementing the [crate::interpret::Machine] trait as its first argument
+/// and otherwise accepts the same syntax as [tracing::span!] (see some tips below).
 /// Note: the result of this macro **must be used** because the span is exited when it's dropped.
+///
+/// ### Syntax accepted by this macro
+///
+/// The full documentation for the [tracing::span!] syntax can be found at [tracing] under "Using the
+/// Macros". A few possibly confusing syntaxes are listed here:
+/// ```rust
+/// # use rustc_const_eval::enter_trace_span;
+/// # type M = rustc_const_eval::const_eval::CompileTimeMachine<'static>;
+/// # let my_display_var = String::new();
+/// # let my_debug_var = String::new();
+/// // logs a span named "hello" with a field named "arg" of value 42 (works only because
+/// // 42 implements the tracing::Value trait, otherwise use one of the options below)
+/// let _span = enter_trace_span!(M, "hello", arg = 42);
+/// // logs a field called "my_display_var" using the Display implementation
+/// let _span = enter_trace_span!(M, "hello", %my_display_var);
+/// // logs a field called "my_debug_var" using the Debug implementation
+/// let _span = enter_trace_span!(M, "hello", ?my_debug_var);
+///  ```
+///
+/// ### `NAME::SUBNAME` syntax
+///
+/// In addition to the syntax accepted by [tracing::span!], this macro optionally allows passing
+/// the span name (i.e. the first macro argument) in the form `NAME::SUBNAME` (without quotes) to
+/// indicate that the span has name "NAME" (usually the name of the component) and has an additional
+/// more specific name "SUBNAME" (usually the function name). The latter is passed to the [tracing]
+/// infrastructure as a span field with the name "NAME". This allows not being distracted by
+/// subnames when looking at the trace in <https://ui.perfetto.dev>, but when deeper introspection
+/// is needed within a component, it's still possible to view the subnames directly in the UI by
+/// selecting a span, clicking on the "NAME" argument on the right, and clicking on "Visualize
+/// argument values".
+/// ```rust
+/// # use rustc_const_eval::enter_trace_span;
+/// # type M = rustc_const_eval::const_eval::CompileTimeMachine<'static>;
+/// // for example, the first will expand to the second
+/// let _span = enter_trace_span!(M, borrow_tracker::on_stack_pop, /* ... */);
+/// let _span = enter_trace_span!(M, "borrow_tracker", borrow_tracker = "on_stack_pop", /* ... */);
+/// ```
+///
+/// ### `tracing_separate_thread` parameter
+///
+/// This macro was introduced to obtain better traces of Miri without impacting release performance.
+/// Miri saves traces using the the `tracing_chrome` `tracing::Layer` so that they can be visualized
+/// in <https://ui.perfetto.dev>. To instruct `tracing_chrome` to put some spans on a separate trace
+/// thread/line than other spans when viewed in <https://ui.perfetto.dev>, you can pass
+/// `tracing_separate_thread = tracing::field::Empty` to the tracing macros. This is useful to
+/// separate out spans which just indicate the current step or program frame being processed by the
+/// interpreter. You should use a value of [tracing::field::Empty] so that other tracing layers
+/// (e.g. the logger) will ignore the `tracing_separate_thread` field. For example:
+/// ```rust
+/// # use rustc_const_eval::enter_trace_span;
+/// # type M = rustc_const_eval::const_eval::CompileTimeMachine<'static>;
+/// let _span = enter_trace_span!(M, step::eval_statement, tracing_separate_thread = tracing::field::Empty);
+/// ```
+///
+/// ### Executing something else when tracing is disabled
+///
+/// [crate::interpret::Machine::enter_trace_span] returns [EnteredTraceSpan], on which you can call
+/// [EnteredTraceSpan::or_if_tracing_disabled], to e.g. log a line as an alternative to the tracing
+/// span for when tracing is disabled. For example:
+/// ```rust
+/// # use rustc_const_eval::enter_trace_span;
+/// # use rustc_const_eval::interpret::EnteredTraceSpan;
+/// # type M = rustc_const_eval::const_eval::CompileTimeMachine<'static>;
+/// let _span = enter_trace_span!(M, step::eval_statement)
+///     .or_if_tracing_disabled(|| tracing::info!("eval_statement"));
+/// ```
 #[macro_export]
 macro_rules! enter_trace_span {
-    ($machine:ident, $($tt:tt)*) => {
-        $machine::enter_trace_span(|| tracing::info_span!($($tt)*))
-    }
+    ($machine:ty, $name:ident :: $subname:ident $($tt:tt)*) => {
+        $crate::enter_trace_span!($machine, stringify!($name), $name = %stringify!($subname) $($tt)*)
+    };
+
+    ($machine:ty, $($tt:tt)*) => {
+        <$machine as $crate::interpret::Machine>::enter_trace_span(|| tracing::info_span!($($tt)*))
+    };
 }
diff --git a/compiler/rustc_const_eval/src/interpret/visitor.rs b/compiler/rustc_const_eval/src/interpret/visitor.rs
index a27b6646131..82c50fac6c0 100644
--- a/compiler/rustc_const_eval/src/interpret/visitor.rs
+++ b/compiler/rustc_const_eval/src/interpret/visitor.rs
@@ -121,25 +121,24 @@ pub trait ValueVisitor<'tcx, M: Machine<'tcx>>: Sized {
 
                 // `Box` has two fields: the pointer we care about, and the allocator.
                 assert_eq!(v.layout().fields.count(), 2, "`Box` must have exactly 2 fields");
-                let (unique_ptr, alloc) = (
-                    self.ecx().project_field(v, FieldIdx::ZERO)?,
-                    self.ecx().project_field(v, FieldIdx::ONE)?,
-                );
+                let [unique_ptr, alloc] =
+                    self.ecx().project_fields(v, [FieldIdx::ZERO, FieldIdx::ONE])?;
+
                 // Unfortunately there is some type junk in the way here: `unique_ptr` is a `Unique`...
                 // (which means another 2 fields, the second of which is a `PhantomData`)
                 assert_eq!(unique_ptr.layout().fields.count(), 2);
-                let (nonnull_ptr, phantom) = (
-                    self.ecx().project_field(&unique_ptr, FieldIdx::ZERO)?,
-                    self.ecx().project_field(&unique_ptr, FieldIdx::ONE)?,
-                );
+                let [nonnull_ptr, phantom] =
+                    self.ecx().project_fields(&unique_ptr, [FieldIdx::ZERO, FieldIdx::ONE])?;
                 assert!(
                     phantom.layout().ty.ty_adt_def().is_some_and(|adt| adt.is_phantom_data()),
                     "2nd field of `Unique` should be PhantomData but is {:?}",
                     phantom.layout().ty,
                 );
+
                 // ... that contains a `NonNull`... (gladly, only a single field here)
                 assert_eq!(nonnull_ptr.layout().fields.count(), 1);
                 let raw_ptr = self.ecx().project_field(&nonnull_ptr, FieldIdx::ZERO)?; // the actual raw ptr
+
                 // ... whose only field finally is a raw ptr we can dereference.
                 self.visit_box(ty, &raw_ptr)?;
 
diff --git a/compiler/rustc_const_eval/src/lib.rs b/compiler/rustc_const_eval/src/lib.rs
index bf7a79dcb20..3840cdf7575 100644
--- a/compiler/rustc_const_eval/src/lib.rs
+++ b/compiler/rustc_const_eval/src/lib.rs
@@ -2,6 +2,7 @@
 #![allow(internal_features)]
 #![allow(rustc::diagnostic_outside_of_impl)]
 #![doc(rust_logo)]
+#![feature(array_try_map)]
 #![feature(assert_matches)]
 #![feature(box_patterns)]
 #![feature(decl_macro)]
diff --git a/compiler/rustc_const_eval/src/util/caller_location.rs b/compiler/rustc_const_eval/src/util/caller_location.rs
index c437934eaab..5249b32eca4 100644
--- a/compiler/rustc_const_eval/src/util/caller_location.rs
+++ b/compiler/rustc_const_eval/src/util/caller_location.rs
@@ -42,12 +42,12 @@ fn alloc_caller_location<'tcx>(
     let location = ecx.allocate(loc_layout, MemoryKind::CallerLocation).unwrap();
 
     // Initialize fields.
-    ecx.write_immediate(filename, &ecx.project_field(&location, FieldIdx::from_u32(0)).unwrap())
-        .expect("writing to memory we just allocated cannot fail");
-    ecx.write_scalar(line, &ecx.project_field(&location, FieldIdx::from_u32(1)).unwrap())
-        .expect("writing to memory we just allocated cannot fail");
-    ecx.write_scalar(col, &ecx.project_field(&location, FieldIdx::from_u32(2)).unwrap())
+    let [filename_field, line_field, col_field] =
+        ecx.project_fields(&location, [0, 1, 2].map(FieldIdx::from_u32)).unwrap();
+    ecx.write_immediate(filename, &filename_field)
         .expect("writing to memory we just allocated cannot fail");
+    ecx.write_scalar(line, &line_field).expect("writing to memory we just allocated cannot fail");
+    ecx.write_scalar(col, &col_field).expect("writing to memory we just allocated cannot fail");
 
     location
 }
diff --git a/compiler/rustc_const_eval/src/util/type_name.rs b/compiler/rustc_const_eval/src/util/type_name.rs
index e8f2728a772..e6b9759819f 100644
--- a/compiler/rustc_const_eval/src/util/type_name.rs
+++ b/compiler/rustc_const_eval/src/util/type_name.rs
@@ -4,7 +4,7 @@ use rustc_data_structures::intern::Interned;
 use rustc_hir::def_id::CrateNum;
 use rustc_hir::definitions::DisambiguatedDefPathData;
 use rustc_middle::bug;
-use rustc_middle::ty::print::{PrettyPrinter, Print, PrintError, Printer};
+use rustc_middle::ty::print::{PrettyPrinter, PrintError, Printer};
 use rustc_middle::ty::{self, GenericArg, GenericArgKind, Ty, TyCtxt};
 
 struct AbsolutePathPrinter<'tcx> {
@@ -18,7 +18,7 @@ impl<'tcx> Printer<'tcx> for AbsolutePathPrinter<'tcx> {
     }
 
     fn print_region(&mut self, _region: ty::Region<'_>) -> Result<(), PrintError> {
-        Ok(())
+        unreachable!(); // because `<Self As PrettyPrinter>::should_print_region` returns false
     }
 
     fn print_type(&mut self, ty: Ty<'tcx>) -> Result<(), PrintError> {
@@ -89,7 +89,6 @@ impl<'tcx> Printer<'tcx> for AbsolutePathPrinter<'tcx> {
     fn path_append_impl(
         &mut self,
         print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
-        _disambiguated_data: &DisambiguatedDefPathData,
         self_ty: Ty<'tcx>,
         trait_ref: Option<ty::TraitRef<'tcx>>,
     ) -> Result<(), PrintError> {
@@ -138,19 +137,6 @@ impl<'tcx> PrettyPrinter<'tcx> for AbsolutePathPrinter<'tcx> {
     fn should_print_region(&self, _region: ty::Region<'_>) -> bool {
         false
     }
-    fn comma_sep<T>(&mut self, mut elems: impl Iterator<Item = T>) -> Result<(), PrintError>
-    where
-        T: Print<'tcx, Self>,
-    {
-        if let Some(first) = elems.next() {
-            first.print(self)?;
-            for elem in elems {
-                self.path.push_str(", ");
-                elem.print(self)?;
-            }
-        }
-        Ok(())
-    }
 
     fn generic_delimiters(
         &mut self,
@@ -179,7 +165,7 @@ impl Write for AbsolutePathPrinter<'_> {
 }
 
 pub fn type_name<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> String {
-    let mut printer = AbsolutePathPrinter { tcx, path: String::new() };
-    printer.print_type(ty).unwrap();
-    printer.path
+    let mut p = AbsolutePathPrinter { tcx, path: String::new() };
+    p.print_type(ty).unwrap();
+    p.path
 }
diff --git a/compiler/rustc_driver_impl/Cargo.toml b/compiler/rustc_driver_impl/Cargo.toml
index 0d6b49607eb..ae1dbd2cf51 100644
--- a/compiler/rustc_driver_impl/Cargo.toml
+++ b/compiler/rustc_driver_impl/Cargo.toml
@@ -4,8 +4,8 @@ version = "0.0.0"
 edition = "2024"
 
 [dependencies]
-jiff = { version = "0.2.5", default-features = false, features = ["std"] }
 # tidy-alphabetical-start
+jiff = { version = "0.2.5", default-features = false, features = ["std"] }
 rustc_abi = { path = "../rustc_abi" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_ast_lowering = { path = "../rustc_ast_lowering" }
diff --git a/compiler/rustc_error_codes/src/error_codes/E0562.md b/compiler/rustc_error_codes/src/error_codes/E0562.md
index 95f038df56d..af7b219fb12 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0562.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0562.md
@@ -1,5 +1,4 @@
-Abstract return types (written `impl Trait` for some trait `Trait`) are only
-allowed as function and inherent impl return types.
+`impl Trait` is only allowed as a function return and argument type.
 
 Erroneous code example:
 
@@ -14,7 +13,7 @@ fn main() {
 }
 ```
 
-Make sure `impl Trait` only appears in return-type position.
+Make sure `impl Trait` appears in a function signature.
 
 ```
 fn count_to_n(n: usize) -> impl Iterator<Item=usize> {
@@ -28,6 +27,6 @@ fn main() {
 }
 ```
 
-See [RFC 1522] for more details.
+See the [reference] for more details on `impl Trait`.
 
-[RFC 1522]: https://github.com/rust-lang/rfcs/blob/master/text/1522-conservative-impl-trait.md
+[reference]: https://doc.rust-lang.org/stable/reference/types/impl-trait.html
diff --git a/compiler/rustc_errors/Cargo.toml b/compiler/rustc_errors/Cargo.toml
index c4181a62a35..3e8cf6207ae 100644
--- a/compiler/rustc_errors/Cargo.toml
+++ b/compiler/rustc_errors/Cargo.toml
@@ -10,7 +10,6 @@ derive_setters = "0.1.6"
 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_error_codes = { path = "../rustc_error_codes" }
 rustc_error_messages = { path = "../rustc_error_messages" }
@@ -25,7 +24,7 @@ rustc_serialize = { path = "../rustc_serialize" }
 rustc_span = { path = "../rustc_span" }
 rustc_target = { path = "../rustc_target" }
 rustc_type_ir = { path = "../rustc_type_ir" }
-serde = { version = "1.0.125", features = [ "derive" ] }
+serde = { version = "1.0.125", features = ["derive"] }
 serde_json = "1.0.59"
 termcolor = "1.2.0"
 termize = "0.2"
diff --git a/compiler/rustc_errors/src/diagnostic_impls.rs b/compiler/rustc_errors/src/diagnostic_impls.rs
index eeb9ac28808..eca5806fac5 100644
--- a/compiler/rustc_errors/src/diagnostic_impls.rs
+++ b/compiler/rustc_errors/src/diagnostic_impls.rs
@@ -8,7 +8,7 @@ use std::process::ExitStatus;
 use rustc_abi::TargetDataLayoutErrors;
 use rustc_ast::util::parser::ExprPrecedence;
 use rustc_ast_pretty::pprust;
-use rustc_attr_data_structures::RustcVersion;
+use rustc_hir::RustcVersion;
 use rustc_macros::Subdiagnostic;
 use rustc_span::edition::Edition;
 use rustc_span::{Ident, MacroRulesNormalizedIdent, Span, Symbol};
diff --git a/compiler/rustc_errors/src/emitter.rs b/compiler/rustc_errors/src/emitter.rs
index 46a4a186824..84970e7c162 100644
--- a/compiler/rustc_errors/src/emitter.rs
+++ b/compiler/rustc_errors/src/emitter.rs
@@ -262,19 +262,11 @@ pub trait Emitter {
                     format!("help: {msg}")
                 } else {
                     // Show the default suggestion text with the substitution
-                    format!(
-                        "help: {}{}: `{}`",
-                        msg,
-                        if self
-                            .source_map()
-                            .is_some_and(|sm| is_case_difference(sm, snippet, part.span,))
-                        {
-                            " (notice the capitalization)"
-                        } else {
-                            ""
-                        },
-                        snippet,
-                    )
+                    let confusion_type = self
+                        .source_map()
+                        .map(|sm| detect_confusion_type(sm, snippet, part.span))
+                        .unwrap_or(ConfusionType::None);
+                    format!("help: {}{}: `{}`", msg, confusion_type.label_text(), snippet,)
                 };
                 primary_span.push_span_label(part.span, msg);
 
@@ -1597,8 +1589,9 @@ impl HumanEmitter {
             annotated_files.swap(0, pos);
         }
 
+        let annotated_files_len = annotated_files.len();
         // Print out the annotate source lines that correspond with the error
-        for annotated_file in annotated_files {
+        for (file_idx, annotated_file) in annotated_files.into_iter().enumerate() {
             // we can't annotate anything if the source is unavailable.
             if !should_show_source_code(
                 &self.ignored_directories_in_source_blocks,
@@ -1855,7 +1848,9 @@ impl HumanEmitter {
                         width_offset,
                         code_offset,
                         margin,
-                        !is_cont && line_idx + 1 == annotated_file.lines.len(),
+                        !is_cont
+                            && file_idx + 1 == annotated_files_len
+                            && line_idx + 1 == annotated_file.lines.len(),
                     );
 
                     let mut to_add = FxHashMap::default();
@@ -2028,12 +2023,12 @@ impl HumanEmitter {
         buffer.append(0, ": ", Style::HeaderMsg);
 
         let mut msg = vec![(suggestion.msg.to_owned(), Style::NoStyle)];
-        if suggestions
-            .iter()
-            .take(MAX_SUGGESTIONS)
-            .any(|(_, _, _, only_capitalization)| *only_capitalization)
+        if let Some(confusion_type) =
+            suggestions.iter().take(MAX_SUGGESTIONS).find_map(|(_, _, _, confusion_type)| {
+                if confusion_type.has_confusion() { Some(*confusion_type) } else { None }
+            })
         {
-            msg.push((" (notice the capitalization difference)".into(), Style::NoStyle));
+            msg.push((confusion_type.label_text().into(), Style::NoStyle));
         }
         self.msgs_to_buffer(
             &mut buffer,
@@ -2985,7 +2980,7 @@ impl HumanEmitter {
     fn secondary_file_start(&self) -> &'static str {
         match self.theme {
             OutputTheme::Ascii => "::: ",
-            OutputTheme::Unicode => " ⸬ ",
+            OutputTheme::Unicode => " ⸬  ",
         }
     }
 
@@ -3528,24 +3523,107 @@ pub fn is_different(sm: &SourceMap, suggested: &str, sp: Span) -> bool {
 }
 
 /// Whether the original and suggested code are visually similar enough to warrant extra wording.
-pub fn is_case_difference(sm: &SourceMap, suggested: &str, sp: Span) -> bool {
-    // FIXME: this should probably be extended to also account for `FO0` → `FOO` and unicode.
+pub fn detect_confusion_type(sm: &SourceMap, suggested: &str, sp: Span) -> ConfusionType {
     let found = match sm.span_to_snippet(sp) {
         Ok(snippet) => snippet,
         Err(e) => {
             warn!(error = ?e, "Invalid span {:?}", sp);
-            return false;
+            return ConfusionType::None;
         }
     };
-    let ascii_confusables = &['c', 'f', 'i', 'k', 'o', 's', 'u', 'v', 'w', 'x', 'y', 'z'];
-    // All the chars that differ in capitalization are confusable (above):
-    let confusable = iter::zip(found.chars(), suggested.chars())
-        .filter(|(f, s)| f != s)
-        .all(|(f, s)| ascii_confusables.contains(&f) || ascii_confusables.contains(&s));
-    confusable && found.to_lowercase() == suggested.to_lowercase()
-            // FIXME: We sometimes suggest the same thing we already have, which is a
-            //        bug, but be defensive against that here.
-            && found != suggested
+
+    let mut has_case_confusion = false;
+    let mut has_digit_letter_confusion = false;
+
+    if found.len() == suggested.len() {
+        let mut has_case_diff = false;
+        let mut has_digit_letter_confusable = false;
+        let mut has_other_diff = false;
+
+        let ascii_confusables = &['c', 'f', 'i', 'k', 'o', 's', 'u', 'v', 'w', 'x', 'y', 'z'];
+
+        let digit_letter_confusables = [('0', 'O'), ('1', 'l'), ('5', 'S'), ('8', 'B'), ('9', 'g')];
+
+        for (f, s) in iter::zip(found.chars(), suggested.chars()) {
+            if f != s {
+                if f.to_lowercase().to_string() == s.to_lowercase().to_string() {
+                    // Check for case differences (any character that differs only in case)
+                    if ascii_confusables.contains(&f) || ascii_confusables.contains(&s) {
+                        has_case_diff = true;
+                    } else {
+                        has_other_diff = true;
+                    }
+                } else if digit_letter_confusables.contains(&(f, s))
+                    || digit_letter_confusables.contains(&(s, f))
+                {
+                    // Check for digit-letter confusables (like 0 vs O, 1 vs l, etc.)
+                    has_digit_letter_confusable = true;
+                } else {
+                    has_other_diff = true;
+                }
+            }
+        }
+
+        // If we have case differences and no other differences
+        if has_case_diff && !has_other_diff && found != suggested {
+            has_case_confusion = true;
+        }
+        if has_digit_letter_confusable && !has_other_diff && found != suggested {
+            has_digit_letter_confusion = true;
+        }
+    }
+
+    match (has_case_confusion, has_digit_letter_confusion) {
+        (true, true) => ConfusionType::Both,
+        (true, false) => ConfusionType::Case,
+        (false, true) => ConfusionType::DigitLetter,
+        (false, false) => ConfusionType::None,
+    }
+}
+
+/// Represents the type of confusion detected between original and suggested code.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum ConfusionType {
+    /// No confusion detected
+    None,
+    /// Only case differences (e.g., "hello" vs "Hello")
+    Case,
+    /// Only digit-letter confusion (e.g., "0" vs "O", "1" vs "l")
+    DigitLetter,
+    /// Both case and digit-letter confusion
+    Both,
+}
+
+impl ConfusionType {
+    /// Returns the appropriate label text for this confusion type.
+    pub fn label_text(&self) -> &'static str {
+        match self {
+            ConfusionType::None => "",
+            ConfusionType::Case => " (notice the capitalization)",
+            ConfusionType::DigitLetter => " (notice the digit/letter confusion)",
+            ConfusionType::Both => " (notice the capitalization and digit/letter confusion)",
+        }
+    }
+
+    /// Combines two confusion types. If either is `Both`, the result is `Both`.
+    /// If one is `Case` and the other is `DigitLetter`, the result is `Both`.
+    /// Otherwise, returns the non-`None` type, or `None` if both are `None`.
+    pub fn combine(self, other: ConfusionType) -> ConfusionType {
+        match (self, other) {
+            (ConfusionType::None, other) => other,
+            (this, ConfusionType::None) => this,
+            (ConfusionType::Both, _) | (_, ConfusionType::Both) => ConfusionType::Both,
+            (ConfusionType::Case, ConfusionType::DigitLetter)
+            | (ConfusionType::DigitLetter, ConfusionType::Case) => ConfusionType::Both,
+            (ConfusionType::Case, ConfusionType::Case) => ConfusionType::Case,
+            (ConfusionType::DigitLetter, ConfusionType::DigitLetter) => ConfusionType::DigitLetter,
+        }
+    }
+
+    /// Returns true if this confusion type represents any kind of confusion.
+    pub fn has_confusion(&self) -> bool {
+        *self != ConfusionType::None
+    }
 }
 
 pub(crate) fn should_show_source_code(
diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index 381d780077d..2534cddf105 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -50,7 +50,7 @@ pub use diagnostic_impls::{
     IndicateAnonymousLifetime, SingleLabelManySpans,
 };
 pub use emitter::ColorConfig;
-use emitter::{DynEmitter, Emitter, is_case_difference, is_different};
+use emitter::{ConfusionType, DynEmitter, Emitter, detect_confusion_type, is_different};
 use rustc_data_structures::AtomicRef;
 use rustc_data_structures::fx::{FxHashSet, FxIndexMap, FxIndexSet};
 use rustc_data_structures::stable_hasher::StableHasher;
@@ -308,7 +308,7 @@ impl CodeSuggestion {
     pub(crate) fn splice_lines(
         &self,
         sm: &SourceMap,
-    ) -> Vec<(String, Vec<SubstitutionPart>, Vec<Vec<SubstitutionHighlight>>, bool)> {
+    ) -> Vec<(String, Vec<SubstitutionPart>, Vec<Vec<SubstitutionHighlight>>, ConfusionType)> {
         // For the `Vec<Vec<SubstitutionHighlight>>` value, the first level of the vector
         // corresponds to the output snippet's lines, while the second level corresponds to the
         // substrings within that line that should be highlighted.
@@ -414,14 +414,15 @@ impl CodeSuggestion {
                 // We need to keep track of the difference between the existing code and the added
                 // or deleted code in order to point at the correct column *after* substitution.
                 let mut acc = 0;
-                let mut only_capitalization = false;
+                let mut confusion_type = ConfusionType::None;
                 for part in &mut substitution.parts {
                     // If this is a replacement of, e.g. `"a"` into `"ab"`, adjust the
                     // suggestion and snippet to look as if we just suggested to add
                     // `"b"`, which is typically much easier for the user to understand.
                     part.trim_trivial_replacements(sm);
 
-                    only_capitalization |= is_case_difference(sm, &part.snippet, part.span);
+                    let part_confusion = detect_confusion_type(sm, &part.snippet, part.span);
+                    confusion_type = confusion_type.combine(part_confusion);
                     let cur_lo = sm.lookup_char_pos(part.span.lo());
                     if prev_hi.line == cur_lo.line {
                         let mut count =
@@ -511,7 +512,7 @@ impl CodeSuggestion {
                 if highlights.iter().all(|parts| parts.is_empty()) {
                     None
                 } else {
-                    Some((buf, substitution.parts, highlights, only_capitalization))
+                    Some((buf, substitution.parts, highlights, confusion_type))
                 }
             })
             .collect()
diff --git a/compiler/rustc_expand/Cargo.toml b/compiler/rustc_expand/Cargo.toml
index 57dd3a3128d..f897833d85c 100644
--- a/compiler/rustc_expand/Cargo.toml
+++ b/compiler/rustc_expand/Cargo.toml
@@ -12,7 +12,6 @@ doctest = false
 rustc_ast = { path = "../rustc_ast" }
 rustc_ast_passes = { path = "../rustc_ast_passes" }
 rustc_ast_pretty = { path = "../rustc_ast_pretty" }
-rustc_attr_data_structures = { path = "../rustc_attr_data_structures" }
 rustc_attr_parsing = { path = "../rustc_attr_parsing" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
diff --git a/compiler/rustc_expand/src/base.rs b/compiler/rustc_expand/src/base.rs
index c01320fc644..1a9832b2fe2 100644
--- a/compiler/rustc_expand/src/base.rs
+++ b/compiler/rustc_expand/src/base.rs
@@ -12,12 +12,13 @@ use rustc_ast::token::MetaVarKind;
 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_data_structures::{AttributeKind, CfgEntry, Deprecation, Stability, find_attr};
 use rustc_data_structures::fx::{FxHashMap, FxIndexMap};
 use rustc_data_structures::sync;
 use rustc_errors::{DiagCtxtHandle, ErrorGuaranteed, PResult};
 use rustc_feature::Features;
 use rustc_hir as hir;
+use rustc_hir::attrs::{AttributeKind, CfgEntry, Deprecation};
+use rustc_hir::{Stability, find_attr};
 use rustc_lint_defs::{BufferedEarlyLint, RegisteredTools};
 use rustc_parse::MACRO_ARGUMENTS;
 use rustc_parse::parser::{ForceCollect, Parser};
diff --git a/compiler/rustc_expand/src/expand.rs b/compiler/rustc_expand/src/expand.rs
index 0517fd0419d..f02aa6c120f 100644
--- a/compiler/rustc_expand/src/expand.rs
+++ b/compiler/rustc_expand/src/expand.rs
@@ -1411,9 +1411,8 @@ impl InvocationCollectorNode for P<ast::Item> {
                     }
                 }
             }
-
             let mut idents = Vec::new();
-            collect_use_tree_leaves(ut, &mut idents);
+            collect_use_tree_leaves(&ut, &mut idents);
             idents
         } else {
             self.kind.ident().into_iter().collect()
diff --git a/compiler/rustc_expand/src/mbe/macro_rules.rs b/compiler/rustc_expand/src/mbe/macro_rules.rs
index febe6f8b88c..52d38c35f98 100644
--- a/compiler/rustc_expand/src/mbe/macro_rules.rs
+++ b/compiler/rustc_expand/src/mbe/macro_rules.rs
@@ -10,11 +10,12 @@ use rustc_ast::token::{self, 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_data_structures::{AttributeKind, find_attr};
 use rustc_data_structures::fx::{FxHashMap, FxIndexMap};
 use rustc_errors::{Applicability, Diag, ErrorGuaranteed};
 use rustc_feature::Features;
 use rustc_hir as hir;
+use rustc_hir::attrs::AttributeKind;
+use rustc_hir::find_attr;
 use rustc_lint_defs::BuiltinLintDiag;
 use rustc_lint_defs::builtin::{
     RUST_2021_INCOMPATIBLE_OR_PATTERNS, SEMICOLON_IN_EXPRESSIONS_FROM_MACROS,
diff --git a/compiler/rustc_feature/Cargo.toml b/compiler/rustc_feature/Cargo.toml
index 78d7b698b72..a4746ac455c 100644
--- a/compiler/rustc_feature/Cargo.toml
+++ b/compiler/rustc_feature/Cargo.toml
@@ -5,8 +5,8 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-rustc_attr_data_structures = { path = "../rustc_attr_data_structures" }
 rustc_data_structures = { path = "../rustc_data_structures" }
+rustc_hir = { path = "../rustc_hir" }
 rustc_span = { path = "../rustc_span" }
 serde = { version = "1.0.125", features = ["derive"] }
 serde_json = "1.0.59"
diff --git a/compiler/rustc_feature/src/builtin_attrs.rs b/compiler/rustc_feature/src/builtin_attrs.rs
index 96df6aa19bc..5c63d4808db 100644
--- a/compiler/rustc_feature/src/builtin_attrs.rs
+++ b/compiler/rustc_feature/src/builtin_attrs.rs
@@ -5,8 +5,8 @@ use std::sync::LazyLock;
 use AttributeDuplicates::*;
 use AttributeGate::*;
 use AttributeType::*;
-use rustc_attr_data_structures::EncodeCrossCrate;
 use rustc_data_structures::fx::FxHashMap;
+use rustc_hir::attrs::EncodeCrossCrate;
 use rustc_span::edition::Edition;
 use rustc_span::{Symbol, sym};
 
@@ -112,7 +112,7 @@ pub enum AttributeGate {
     Ungated,
 }
 
-// FIXME(jdonszelmann): move to rustc_attr_data_structures
+// FIXME(jdonszelmann): move to rustc_hir::attrs
 /// A template that the attribute input must match.
 /// Only top-level shape (`#[attr]` vs `#[attr(...)]` vs `#[attr = ...]`) is considered now.
 #[derive(Clone, Copy, Default)]
@@ -1257,11 +1257,6 @@ pub static BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
         TEST, rustc_dummy, Normal, template!(Word /* doesn't matter*/),
         DuplicatesOk, EncodeCrossCrate::No
     ),
-    gated!(
-        omit_gdb_pretty_printer_section, Normal, template!(Word),
-        WarnFollowing, EncodeCrossCrate::No,
-        "the `#[omit_gdb_pretty_printer_section]` attribute is just used for the Rust test suite",
-    ),
     rustc_attr!(
         TEST, pattern_complexity_limit, CrateLevel, template!(NameValueStr: "N"),
         ErrorFollowing, EncodeCrossCrate::No,
diff --git a/compiler/rustc_feature/src/removed.rs b/compiler/rustc_feature/src/removed.rs
index 7e174c465d5..4eee79a2a71 100644
--- a/compiler/rustc_feature/src/removed.rs
+++ b/compiler/rustc_feature/src/removed.rs
@@ -199,6 +199,8 @@ declare_features! (
     /// Renamed to `dyn_compatible_for_dispatch`.
     (removed, object_safe_for_dispatch, "1.83.0", Some(43561),
      Some("renamed to `dyn_compatible_for_dispatch`"), 131511),
+    /// Allows using `#[omit_gdb_pretty_printer_section]`.
+    (removed, omit_gdb_pretty_printer_section, "CURRENT_RUSTC_VERSION", None, None, 144738),
     /// Allows using `#[on_unimplemented(..)]` on traits.
     /// (Moved to `rustc_attrs`.)
     (removed, on_unimplemented, "1.40.0", None, None, 65794),
diff --git a/compiler/rustc_feature/src/unstable.rs b/compiler/rustc_feature/src/unstable.rs
index e985e04ba33..1303b3317e0 100644
--- a/compiler/rustc_feature/src/unstable.rs
+++ b/compiler/rustc_feature/src/unstable.rs
@@ -225,8 +225,6 @@ declare_features! (
     (unstable, multiple_supertrait_upcastable, "1.69.0", None),
     /// Allow negative trait bounds. This is an internal-only feature for testing the trait solver!
     (internal, negative_bounds, "1.71.0", None),
-    /// Allows using `#[omit_gdb_pretty_printer_section]`.
-    (internal, omit_gdb_pretty_printer_section, "1.5.0", None),
     /// Set the maximum pattern complexity allowed (not limited by default).
     (internal, pattern_complexity_limit, "1.78.0", None),
     /// Allows using pattern types.
diff --git a/compiler/rustc_hir/Cargo.toml b/compiler/rustc_hir/Cargo.toml
index 7ca8539845a..539d2e6f0b1 100644
--- a/compiler/rustc_hir/Cargo.toml
+++ b/compiler/rustc_hir/Cargo.toml
@@ -9,7 +9,7 @@ odht = { version = "0.3.1", features = ["nightly"] }
 rustc_abi = { path = "../rustc_abi" }
 rustc_arena = { path = "../rustc_arena" }
 rustc_ast = { path = "../rustc_ast" }
-rustc_attr_data_structures = { path = "../rustc_attr_data_structures" }
+rustc_ast_pretty = { path = "../rustc_ast_pretty" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_hashes = { path = "../rustc_hashes" }
 rustc_index = { path = "../rustc_index" }
diff --git a/compiler/rustc_attr_data_structures/src/attributes.rs b/compiler/rustc_hir/src/attrs/data_structures.rs
index 55019cd57a7..d9d2ec48948 100644
--- a/compiler/rustc_attr_data_structures/src/attributes.rs
+++ b/compiler/rustc_hir/src/attrs/data_structures.rs
@@ -1,12 +1,15 @@
+pub use ReprAttr::*;
 use rustc_abi::Align;
 use rustc_ast::token::CommentKind;
-use rustc_ast::{self as ast, AttrStyle};
+use rustc_ast::{AttrStyle, ast};
 use rustc_macros::{Decodable, Encodable, HashStable_Generic, PrintAttribute};
+use rustc_span::def_id::DefId;
 use rustc_span::hygiene::Transparency;
 use rustc_span::{Ident, Span, Symbol};
 use thin_vec::ThinVec;
 
-use crate::{DefaultBodyStability, PartialConstStability, PrintAttribute, RustcVersion, Stability};
+use crate::attrs::pretty_printing::PrintAttribute;
+use crate::{DefaultBodyStability, PartialConstStability, RustcVersion, Stability};
 
 #[derive(Copy, Clone, PartialEq, Encodable, Decodable, Debug, HashStable_Generic, PrintAttribute)]
 pub enum InlineAttr {
@@ -68,8 +71,6 @@ pub enum ReprAttr {
     ReprTransparent,
     ReprAlign(Align),
 }
-pub use ReprAttr::*;
-use rustc_span::def_id::DefId;
 
 pub enum TransparencyError {
     UnknownTransparency(Symbol, Span),
@@ -296,6 +297,9 @@ pub enum AttributeKind {
     /// Represents `#[const_trait]`.
     ConstTrait(Span),
 
+    /// Represents `#[coroutine]`.
+    Coroutine(Span),
+
     /// Represents `#[coverage(..)]`.
     Coverage(Span, CoverageAttrKind),
 
@@ -390,9 +394,6 @@ pub enum AttributeKind {
     /// Represents `#[non_exhaustive]`
     NonExhaustive(Span),
 
-    /// Represents `#[omit_gdb_pretty_printer_section]`
-    OmitGdbPrettyPrinterSection,
-
     /// Represents `#[optimize(size|speed)]`
     Optimize(OptimizeAttr, Span),
 
diff --git a/compiler/rustc_attr_data_structures/src/encode_cross_crate.rs b/compiler/rustc_hir/src/attrs/encode_cross_crate.rs
index af2d46d0bc7..b66e5bbeabe 100644
--- a/compiler/rustc_attr_data_structures/src/encode_cross_crate.rs
+++ b/compiler/rustc_hir/src/attrs/encode_cross_crate.rs
@@ -1,4 +1,4 @@
-use crate::AttributeKind;
+use crate::attrs::AttributeKind;
 
 #[derive(PartialEq)]
 pub enum EncodeCrossCrate {
@@ -28,6 +28,7 @@ impl AttributeKind {
             ConstStability { .. } => Yes,
             ConstStabilityIndirect => No,
             ConstTrait(..) => No,
+            Coroutine(..) => No,
             Coverage(..) => No,
             DenyExplicitImpl(..) => No,
             Deprecation { .. } => Yes,
@@ -55,7 +56,6 @@ impl AttributeKind {
             NoImplicitPrelude(..) => No,
             NoMangle(..) => Yes,      // Needed for rustdoc
             NonExhaustive(..) => Yes, // Needed for rustdoc
-            OmitGdbPrettyPrinterSection => No,
             Optimize(..) => No,
             ParenSugar(..) => No,
             PassByValue(..) => Yes,
diff --git a/compiler/rustc_hir/src/attrs/mod.rs b/compiler/rustc_hir/src/attrs/mod.rs
new file mode 100644
index 00000000000..482e6c90739
--- /dev/null
+++ b/compiler/rustc_hir/src/attrs/mod.rs
@@ -0,0 +1,54 @@
+//! Data structures for representing parsed attributes in the Rust compiler.
+//! Formerly `rustc_attr_data_structures`.
+//!
+//! For detailed documentation about attribute processing,
+//! see [rustc_attr_parsing](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_attr_parsing/index.html).
+
+pub use data_structures::*;
+pub use encode_cross_crate::EncodeCrossCrate;
+pub use pretty_printing::PrintAttribute;
+
+mod data_structures;
+mod encode_cross_crate;
+mod pretty_printing;
+
+/// Finds attributes in sequences of attributes by pattern matching.
+///
+/// A little like `matches` but for attributes.
+///
+/// ```rust,ignore (illustrative)
+/// // finds the repr attribute
+/// if let Some(r) = find_attr!(attrs, AttributeKind::Repr(r) => r) {
+///
+/// }
+///
+/// // checks if one has matched
+/// if find_attr!(attrs, AttributeKind::Repr(_)) {
+///
+/// }
+/// ```
+///
+/// Often this requires you to first end up with a list of attributes.
+/// A common way to get those is through `tcx.get_all_attrs(did)`
+#[macro_export]
+macro_rules! find_attr {
+    ($attributes_list: expr, $pattern: pat $(if $guard: expr)?) => {{
+        $crate::find_attr!($attributes_list, $pattern $(if $guard)? => ()).is_some()
+    }};
+
+    ($attributes_list: expr, $pattern: pat $(if $guard: expr)? => $e: expr) => {{
+        'done: {
+            for i in $attributes_list {
+                let i: &rustc_hir::Attribute = i;
+                match i {
+                    rustc_hir::Attribute::Parsed($pattern) $(if $guard)? => {
+                        break 'done Some($e);
+                    }
+                    _ => {}
+                }
+            }
+
+            None
+        }
+    }};
+}
diff --git a/compiler/rustc_attr_data_structures/src/lib.rs b/compiler/rustc_hir/src/attrs/pretty_printing.rs
index 4c5af805ca9..e44b29141da 100644
--- a/compiler/rustc_attr_data_structures/src/lib.rs
+++ b/compiler/rustc_hir/src/attrs/pretty_printing.rs
@@ -1,38 +1,12 @@
-//! Data structures for representing parsed attributes in the Rust compiler.
-//! For detailed documentation about attribute processing,
-//! see [rustc_attr_parsing](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_attr_parsing/index.html).
-
-// tidy-alphabetical-start
-#![allow(internal_features)]
-#![doc(rust_logo)]
-#![feature(rustdoc_internals)]
-// tidy-alphabetical-end
-
-mod attributes;
-mod encode_cross_crate;
-mod stability;
-mod version;
-
-pub mod lints;
-
 use std::num::NonZero;
 
-pub use attributes::*;
-pub use encode_cross_crate::EncodeCrossCrate;
 use rustc_abi::Align;
 use rustc_ast::token::CommentKind;
 use rustc_ast::{AttrStyle, IntTy, UintTy};
 use rustc_ast_pretty::pp::Printer;
 use rustc_span::hygiene::Transparency;
 use rustc_span::{ErrorGuaranteed, Ident, Span, Symbol};
-pub use stability::*;
 use thin_vec::ThinVec;
-pub use version::*;
-
-/// 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_ast::HashStableContext + rustc_abi::HashStableContext {}
 
 /// This trait is used to print attributes in `rustc_hir_pretty`.
 ///
@@ -173,44 +147,3 @@ print_tup!(A B C D E F G H);
 print_skip!(Span, (), ErrorGuaranteed);
 print_disp!(u16, bool, NonZero<u32>);
 print_debug!(Symbol, Ident, UintTy, IntTy, Align, AttrStyle, CommentKind, Transparency);
-
-/// Finds attributes in sequences of attributes by pattern matching.
-///
-/// A little like `matches` but for attributes.
-///
-/// ```rust,ignore (illustrative)
-/// // finds the repr attribute
-/// if let Some(r) = find_attr!(attrs, AttributeKind::Repr(r) => r) {
-///
-/// }
-///
-/// // checks if one has matched
-/// if find_attr!(attrs, AttributeKind::Repr(_)) {
-///
-/// }
-/// ```
-///
-/// Often this requires you to first end up with a list of attributes.
-/// A common way to get those is through `tcx.get_all_attrs(did)`
-#[macro_export]
-macro_rules! find_attr {
-    ($attributes_list: expr, $pattern: pat $(if $guard: expr)?) => {{
-        $crate::find_attr!($attributes_list, $pattern $(if $guard)? => ()).is_some()
-    }};
-
-    ($attributes_list: expr, $pattern: pat $(if $guard: expr)? => $e: expr) => {{
-        'done: {
-            for i in $attributes_list {
-                let i: &rustc_hir::Attribute = i;
-                match i {
-                    rustc_hir::Attribute::Parsed($pattern) $(if $guard)? => {
-                        break 'done Some($e);
-                    }
-                    _ => {}
-                }
-            }
-
-            None
-        }
-    }};
-}
diff --git a/compiler/rustc_hir/src/def.rs b/compiler/rustc_hir/src/def.rs
index 3fee9af01b3..2201d493f2d 100644
--- a/compiler/rustc_hir/src/def.rs
+++ b/compiler/rustc_hir/src/def.rs
@@ -360,7 +360,7 @@ impl DefKind {
 /// For example, everything prefixed with `/* Res */` in this example has
 /// an associated `Res`:
 ///
-/// ```
+/// ```ignore (illustrative)
 /// fn str_to_string(s: & /* Res */ str) -> /* Res */ String {
 ///     /* Res */ String::from(/* Res */ s)
 /// }
@@ -421,7 +421,7 @@ pub enum Res<Id = hir::HirId> {
     /// }
     ///
     /// impl Foo for Bar {
-    ///     fn foo() -> Box<Self> { // SelfTyAlias
+    ///     fn foo() -> Box<Self /* SelfTyAlias */> {
     ///         let _: Self;        // SelfTyAlias
     ///
     ///         todo!()
diff --git a/compiler/rustc_hir/src/hir.rs b/compiler/rustc_hir/src/hir.rs
index 4ccc2e5a97c..c30c830f9af 100644
--- a/compiler/rustc_hir/src/hir.rs
+++ b/compiler/rustc_hir/src/hir.rs
@@ -14,7 +14,6 @@ pub use rustc_ast::{
     BoundConstness, BoundPolarity, ByRef, CaptureBy, DelimArgs, ImplPolarity, IsAuto,
     MetaItemInner, MetaItemLit, Movability, Mutability, UnOp,
 };
-use rustc_attr_data_structures::AttributeKind;
 use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::sorted_map::SortedMap;
 use rustc_data_structures::tagged_ptr::TaggedRef;
@@ -30,6 +29,7 @@ use thin_vec::ThinVec;
 use tracing::debug;
 
 use crate::LangItem;
+use crate::attrs::AttributeKind;
 use crate::def::{CtorKind, DefKind, PerNS, Res};
 use crate::def_id::{DefId, LocalDefIdMap};
 pub(crate) use crate::hir_id::{HirId, ItemLocalId, ItemLocalMap, OwnerId};
@@ -412,10 +412,8 @@ impl<'hir> PathSegment<'hir> {
 /// that are [just paths](ConstArgKind::Path) (currently just bare const params)
 /// versus const args that are literals or have arbitrary computations (e.g., `{ 1 + 3 }`).
 ///
-/// The `Unambig` generic parameter represents whether the position this const is from is
-/// unambiguously a const or ambiguous as to whether it is a type or a const. When in an
-/// ambiguous context the parameter is instantiated with an uninhabited type making the
-/// [`ConstArgKind::Infer`] variant unusable and [`GenericArg::Infer`] is used instead.
+/// For an explanation of the `Unambig` generic parameter see the dev-guide:
+/// <https://rustc-dev-guide.rust-lang.org/hir/ambig-unambig-ty-and-consts.html>
 #[derive(Clone, Copy, Debug, HashStable_Generic)]
 #[repr(C)]
 pub struct ConstArg<'hir, Unambig = ()> {
@@ -427,7 +425,7 @@ pub struct ConstArg<'hir, Unambig = ()> {
 impl<'hir> ConstArg<'hir, AmbigArg> {
     /// Converts a `ConstArg` in an ambiguous position to one in an unambiguous position.
     ///
-    /// Functions accepting an unambiguous consts may expect the [`ConstArgKind::Infer`] variant
+    /// Functions accepting unambiguous consts may expect the [`ConstArgKind::Infer`] variant
     /// to be used. Care should be taken to separately handle infer consts when calling this
     /// function as it cannot be handled by downstream code making use of the returned const.
     ///
@@ -3016,7 +3014,7 @@ impl fmt::Display for LoopIdError {
     }
 }
 
-#[derive(Copy, Clone, Debug, HashStable_Generic)]
+#[derive(Copy, Clone, Debug, PartialEq, HashStable_Generic)]
 pub struct Destination {
     /// This is `Some(_)` iff there is an explicit user-specified 'label
     pub label: Option<Label>,
@@ -3314,14 +3312,12 @@ impl<'hir> AssocItemConstraintKind<'hir> {
 #[derive(Debug, Clone, Copy, HashStable_Generic)]
 pub enum AmbigArg {}
 
-#[derive(Debug, Clone, Copy, HashStable_Generic)]
-#[repr(C)]
 /// Represents a type in the `HIR`.
 ///
-/// The `Unambig` generic parameter represents whether the position this type is from is
-/// unambiguously a type or ambiguous as to whether it is a type or a const. When in an
-/// ambiguous context the parameter is instantiated with an uninhabited type making the
-/// [`TyKind::Infer`] variant unusable and [`GenericArg::Infer`] is used instead.
+/// For an explanation of the `Unambig` generic parameter see the dev-guide:
+/// <https://rustc-dev-guide.rust-lang.org/hir/ambig-unambig-ty-and-consts.html>
+#[derive(Debug, Clone, Copy, HashStable_Generic)]
+#[repr(C)]
 pub struct Ty<'hir, Unambig = ()> {
     #[stable_hasher(ignore)]
     pub hir_id: HirId,
@@ -3656,9 +3652,12 @@ pub enum InferDelegationKind {
 }
 
 /// The various kinds of types recognized by the compiler.
-#[derive(Debug, Clone, Copy, HashStable_Generic)]
+///
+/// For an explanation of the `Unambig` generic parameter see the dev-guide:
+/// <https://rustc-dev-guide.rust-lang.org/hir/ambig-unambig-ty-and-consts.html>
 // SAFETY: `repr(u8)` is required so that `TyKind<()>` and `TyKind<!>` are layout compatible
 #[repr(u8, C)]
+#[derive(Debug, Clone, Copy, HashStable_Generic)]
 pub enum TyKind<'hir, Unambig = ()> {
     /// Actual type should be inherited from `DefId` signature
     InferDelegation(DefId, InferDelegationKind),
diff --git a/compiler/rustc_hir/src/intravisit.rs b/compiler/rustc_hir/src/intravisit.rs
index f33915d5b07..23fa466859a 100644
--- a/compiler/rustc_hir/src/intravisit.rs
+++ b/compiler/rustc_hir/src/intravisit.rs
@@ -364,9 +364,6 @@ pub trait Visitor<'v>: Sized {
     /// All types are treated as ambiguous types for the purposes of hir visiting in
     /// order to ensure that visitors can handle infer vars without it being too error-prone.
     ///
-    /// See the doc comments on [`Ty`] for an explanation of what it means for a type to be
-    /// ambiguous.
-    ///
     /// The [`Visitor::visit_infer`] method should be overridden in order to handle infer vars.
     fn visit_ty(&mut self, t: &'v Ty<'v, AmbigArg>) -> Self::Result {
         walk_ty(self, t)
@@ -375,12 +372,9 @@ pub trait Visitor<'v>: Sized {
     /// All consts are treated as ambiguous consts for the purposes of hir visiting in
     /// order to ensure that visitors can handle infer vars without it being too error-prone.
     ///
-    /// See the doc comments on [`ConstArg`] for an explanation of what it means for a const to be
-    /// ambiguous.
-    ///
     /// The [`Visitor::visit_infer`] method should be overridden in order to handle infer vars.
     fn visit_const_arg(&mut self, c: &'v ConstArg<'v, AmbigArg>) -> Self::Result {
-        walk_ambig_const_arg(self, c)
+        walk_const_arg(self, c)
     }
 
     #[allow(unused_variables)]
@@ -522,7 +516,7 @@ pub trait VisitorExt<'v>: Visitor<'v> {
     /// Named `visit_const_arg_unambig` instead of `visit_unambig_const_arg` to aid in
     /// discovery by IDes when `v.visit_const_arg` is written.
     fn visit_const_arg_unambig(&mut self, c: &'v ConstArg<'v>) -> Self::Result {
-        walk_const_arg(self, c)
+        walk_unambig_const_arg(self, c)
     }
 }
 impl<'v, V: Visitor<'v>> VisitorExt<'v> for V {}
@@ -985,7 +979,6 @@ pub fn walk_unambig_ty<'v, V: Visitor<'v>>(visitor: &mut V, typ: &'v Ty<'v>) ->
         Some(ambig_ty) => visitor.visit_ty(ambig_ty),
         None => {
             let Ty { hir_id, span, kind: _ } = typ;
-            try_visit!(visitor.visit_id(*hir_id));
             visitor.visit_infer(*hir_id, *span, InferKind::Ty(typ))
         }
     }
@@ -1043,7 +1036,7 @@ pub fn walk_ty<'v, V: Visitor<'v>>(visitor: &mut V, typ: &'v Ty<'v, AmbigArg>) -
     V::Result::output()
 }
 
-pub fn walk_const_arg<'v, V: Visitor<'v>>(
+pub fn walk_unambig_const_arg<'v, V: Visitor<'v>>(
     visitor: &mut V,
     const_arg: &'v ConstArg<'v>,
 ) -> V::Result {
@@ -1051,13 +1044,12 @@ pub fn walk_const_arg<'v, V: Visitor<'v>>(
         Some(ambig_ct) => visitor.visit_const_arg(ambig_ct),
         None => {
             let ConstArg { hir_id, kind: _ } = const_arg;
-            try_visit!(visitor.visit_id(*hir_id));
             visitor.visit_infer(*hir_id, const_arg.span(), InferKind::Const(const_arg))
         }
     }
 }
 
-pub fn walk_ambig_const_arg<'v, V: Visitor<'v>>(
+pub fn walk_const_arg<'v, V: Visitor<'v>>(
     visitor: &mut V,
     const_arg: &'v ConstArg<'v, AmbigArg>,
 ) -> V::Result {
diff --git a/compiler/rustc_hir/src/lib.rs b/compiler/rustc_hir/src/lib.rs
index dafd31336fb..f1212d07ff6 100644
--- a/compiler/rustc_hir/src/lib.rs
+++ b/compiler/rustc_hir/src/lib.rs
@@ -18,6 +18,7 @@
 extern crate self as rustc_hir;
 
 mod arena;
+pub mod attrs;
 pub mod def;
 pub mod def_path_hash_map;
 pub mod definitions;
@@ -29,8 +30,10 @@ pub mod intravisit;
 pub mod lang_items;
 pub mod lints;
 pub mod pat_util;
+mod stability;
 mod stable_hash_impls;
 mod target;
+mod version;
 pub mod weak_lang_items;
 
 #[cfg(test)]
@@ -40,7 +43,9 @@ mod tests;
 pub use hir::*;
 pub use hir_id::*;
 pub use lang_items::{LangItem, LanguageItems};
+pub use stability::*;
 pub use stable_hash_impls::HashStableContext;
 pub use target::{MethodKind, Target};
+pub use version::*;
 
 arena_types!(rustc_arena::declare_arena);
diff --git a/compiler/rustc_hir/src/lints.rs b/compiler/rustc_hir/src/lints.rs
index 7be6c32e57e..c55a41eb2b7 100644
--- a/compiler/rustc_hir/src/lints.rs
+++ b/compiler/rustc_hir/src/lints.rs
@@ -1,9 +1,16 @@
-use rustc_attr_data_structures::lints::AttributeLint;
 use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_macros::HashStable_Generic;
+use rustc_span::Span;
 
 use crate::HirId;
 
+#[derive(Debug)]
+pub struct DelayedLints {
+    pub lints: Box<[DelayedLint]>,
+    // Only present when the crate hash is needed.
+    pub opt_hash: Option<Fingerprint>,
+}
+
 /// During ast lowering, no lints can be emitted.
 /// That is because lints attach to nodes either in the AST, or on the built HIR.
 /// When attached to AST nodes, they're emitted just before building HIR,
@@ -15,9 +22,16 @@ pub enum DelayedLint {
     AttributeParsing(AttributeLint<HirId>),
 }
 
-#[derive(Debug)]
-pub struct DelayedLints {
-    pub lints: Box<[DelayedLint]>,
-    // Only present when the crate hash is needed.
-    pub opt_hash: Option<Fingerprint>,
+#[derive(Clone, Debug, HashStable_Generic)]
+pub struct AttributeLint<Id> {
+    pub id: Id,
+    pub span: Span,
+    pub kind: AttributeLintKind,
+}
+
+#[derive(Clone, Debug, HashStable_Generic)]
+pub enum AttributeLintKind {
+    UnusedDuplicate { this: Span, other: Span, warning: bool },
+    IllFormedAttributeInput { suggestions: Vec<String> },
+    EmptyAttribute { first_span: Span },
 }
diff --git a/compiler/rustc_attr_data_structures/src/stability.rs b/compiler/rustc_hir/src/stability.rs
index bd31c062117..2b3a2a79316 100644
--- a/compiler/rustc_attr_data_structures/src/stability.rs
+++ b/compiler/rustc_hir/src/stability.rs
@@ -3,7 +3,8 @@ use std::num::NonZero;
 use rustc_macros::{Decodable, Encodable, HashStable_Generic, PrintAttribute};
 use rustc_span::{ErrorGuaranteed, Symbol, sym};
 
-use crate::{PrintAttribute, RustcVersion};
+use crate::RustcVersion;
+use crate::attrs::PrintAttribute;
 
 /// The version placeholder that recently stabilized features contain inside the
 /// `since` field of the `#[stable]` attribute.
diff --git a/compiler/rustc_hir/src/stable_hash_impls.rs b/compiler/rustc_hir/src/stable_hash_impls.rs
index 6acf1524b60..ecc608d437b 100644
--- a/compiler/rustc_hir/src/stable_hash_impls.rs
+++ b/compiler/rustc_hir/src/stable_hash_impls.rs
@@ -11,11 +11,7 @@ use crate::lints::DelayedLints;
 /// 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_attr_data_structures::HashStableContext
-    + rustc_ast::HashStableContext
-    + rustc_abi::HashStableContext
-{
+pub trait HashStableContext: rustc_ast::HashStableContext + rustc_abi::HashStableContext {
     fn hash_attr_id(&mut self, id: &HashIgnoredAttrId, hasher: &mut StableHasher);
 }
 
diff --git a/compiler/rustc_attr_data_structures/src/version.rs b/compiler/rustc_hir/src/version.rs
index 030e9520940..ab5ab026b4c 100644
--- a/compiler/rustc_attr_data_structures/src/version.rs
+++ b/compiler/rustc_hir/src/version.rs
@@ -5,7 +5,7 @@ use rustc_macros::{
     Decodable, Encodable, HashStable_Generic, PrintAttribute, current_rustc_version,
 };
 
-use crate::PrintAttribute;
+use crate::attrs::PrintAttribute;
 
 #[derive(Encodable, Decodable, Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
 #[derive(HashStable_Generic, PrintAttribute)]
diff --git a/compiler/rustc_hir_analysis/Cargo.toml b/compiler/rustc_hir_analysis/Cargo.toml
index 5d6c49ee862..e5017794d8f 100644
--- a/compiler/rustc_hir_analysis/Cargo.toml
+++ b/compiler/rustc_hir_analysis/Cargo.toml
@@ -13,7 +13,6 @@ itertools = "0.12"
 rustc_abi = { path = "../rustc_abi" }
 rustc_arena = { path = "../rustc_arena" }
 rustc_ast = { path = "../rustc_ast" }
-rustc_attr_data_structures = { path = "../rustc_attr_data_structures" }
 rustc_attr_parsing = { path = "../rustc_attr_parsing" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
diff --git a/compiler/rustc_hir_analysis/src/check/check.rs b/compiler/rustc_hir_analysis/src/check/check.rs
index 6e63ce31024..161a8566b04 100644
--- a/compiler/rustc_hir_analysis/src/check/check.rs
+++ b/compiler/rustc_hir_analysis/src/check/check.rs
@@ -2,13 +2,14 @@ use std::cell::LazyCell;
 use std::ops::ControlFlow;
 
 use rustc_abi::{ExternAbi, FieldIdx};
-use rustc_attr_data_structures::ReprAttr::ReprPacked;
-use rustc_attr_data_structures::{AttributeKind, find_attr};
 use rustc_data_structures::unord::{UnordMap, UnordSet};
 use rustc_errors::codes::*;
 use rustc_errors::{EmissionGuarantee, MultiSpan};
+use rustc_hir as hir;
+use rustc_hir::attrs::AttributeKind;
+use rustc_hir::attrs::ReprAttr::ReprPacked;
 use rustc_hir::def::{CtorKind, DefKind};
-use rustc_hir::{LangItem, Node, intravisit};
+use rustc_hir::{LangItem, Node, attrs, find_attr, intravisit};
 use rustc_infer::infer::{RegionVariableOrigin, TyCtxtInferExt};
 use rustc_infer::traits::{Obligation, ObligationCauseCode, WellFormedLoc};
 use rustc_lint_defs::builtin::{
@@ -32,7 +33,6 @@ use rustc_trait_selection::traits;
 use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt;
 use tracing::{debug, instrument};
 use ty::TypingMode;
-use {rustc_attr_data_structures as attrs, rustc_hir as hir};
 
 use super::compare_impl_item::check_type_bounds;
 use super::*;
@@ -1401,7 +1401,7 @@ fn check_simd(tcx: TyCtxt<'_>, sp: Span, def_id: LocalDefId) {
 pub(super) fn check_packed(tcx: TyCtxt<'_>, sp: Span, def: ty::AdtDef<'_>) {
     let repr = def.repr();
     if repr.packed() {
-        if let Some(reprs) = attrs::find_attr!(tcx.get_all_attrs(def.did()), attrs::AttributeKind::Repr { reprs, .. } => reprs)
+        if let Some(reprs) = find_attr!(tcx.get_all_attrs(def.did()), attrs::AttributeKind::Repr { reprs, .. } => reprs)
         {
             for (r, _) in reprs {
                 if let ReprPacked(pack) = r
@@ -1536,7 +1536,7 @@ pub(super) fn check_transparent<'tcx>(tcx: TyCtxt<'tcx>, adt: ty::AdtDef<'tcx>)
                 ty::Array(ty, _) => check_non_exhaustive(tcx, *ty),
                 ty::Adt(def, args) => {
                     if !def.did().is_local()
-                        && !attrs::find_attr!(
+                        && !find_attr!(
                             tcx.get_all_attrs(def.did()),
                             AttributeKind::PubTransparent(_)
                         )
@@ -1622,7 +1622,7 @@ fn check_enum(tcx: TyCtxt<'_>, def_id: LocalDefId) {
     def.destructor(tcx); // force the destructor to be evaluated
 
     if def.variants().is_empty() {
-        attrs::find_attr!(
+        find_attr!(
             tcx.get_all_attrs(def_id),
             attrs::AttributeKind::Repr { reprs, first_span } => {
                 struct_span_code_err!(
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 e24426f9fed..6767e5ed88d 100644
--- a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
+++ b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
@@ -356,14 +356,14 @@ fn compare_method_predicate_entailment<'tcx>(
     }
 
     if !(impl_sig, trait_sig).references_error() {
-        ocx.register_obligation(traits::Obligation::new(
-            infcx.tcx,
-            cause,
-            param_env,
-            ty::ClauseKind::WellFormed(
-                Ty::new_fn_ptr(tcx, ty::Binder::dummy(unnormalized_impl_sig)).into(),
-            ),
-        ));
+        for ty in unnormalized_impl_sig.inputs_and_output {
+            ocx.register_obligation(traits::Obligation::new(
+                infcx.tcx,
+                cause.clone(),
+                param_env,
+                ty::ClauseKind::WellFormed(ty.into()),
+            ));
+        }
     }
 
     // Check that all obligations are satisfied by the implementation's
@@ -425,7 +425,7 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for RemapLateParam<'tcx> {
 ///
 /// trait Foo {
 ///     fn bar() -> impl Deref<Target = impl Sized>;
-///              // ^- RPITIT #1        ^- RPITIT #2
+///     //          ^- RPITIT #1        ^- RPITIT #2
 /// }
 ///
 /// impl Foo for () {
@@ -2498,7 +2498,7 @@ fn param_env_with_gat_bounds<'tcx>(
                     ty::Const::new_bound(
                         tcx,
                         ty::INNERMOST,
-                        ty::BoundVar::from_usize(bound_vars.len() - 1),
+                        ty::BoundConst { var: ty::BoundVar::from_usize(bound_vars.len() - 1) },
                     )
                     .into()
                 }
diff --git a/compiler/rustc_hir_analysis/src/check/entry.rs b/compiler/rustc_hir_analysis/src/check/entry.rs
index b556683e80a..97787270be7 100644
--- a/compiler/rustc_hir_analysis/src/check/entry.rs
+++ b/compiler/rustc_hir_analysis/src/check/entry.rs
@@ -1,9 +1,9 @@
 use std::ops::Not;
 
 use rustc_abi::ExternAbi;
-use rustc_attr_data_structures::{AttributeKind, find_attr};
 use rustc_hir as hir;
-use rustc_hir::Node;
+use rustc_hir::attrs::AttributeKind;
+use rustc_hir::{Node, find_attr};
 use rustc_infer::infer::TyCtxtInferExt;
 use rustc_middle::span_bug;
 use rustc_middle::ty::{self, TyCtxt, TypingMode};
diff --git a/compiler/rustc_hir_analysis/src/check/mod.rs b/compiler/rustc_hir_analysis/src/check/mod.rs
index b2cfab37c1f..85445cb3c00 100644
--- a/compiler/rustc_hir_analysis/src/check/mod.rs
+++ b/compiler/rustc_hir_analysis/src/check/mod.rs
@@ -493,7 +493,7 @@ fn suggestion_signature<'tcx>(
     let args = ty::GenericArgs::identity_for_item(tcx, assoc.def_id).rebase_onto(
         tcx,
         assoc.container_id(tcx),
-        impl_trait_ref.with_self_ty(tcx, tcx.types.self_param).args,
+        impl_trait_ref.with_replaced_self_ty(tcx, tcx.types.self_param).args,
     );
 
     match assoc.kind {
diff --git a/compiler/rustc_hir_analysis/src/coherence/inherent_impls.rs b/compiler/rustc_hir_analysis/src/coherence/inherent_impls.rs
index 80bf13dc4b7..38ae7852ca9 100644
--- a/compiler/rustc_hir_analysis/src/coherence/inherent_impls.rs
+++ b/compiler/rustc_hir_analysis/src/coherence/inherent_impls.rs
@@ -7,10 +7,11 @@
 //! `tcx.inherent_impls(def_id)`). That value, however,
 //! is computed by selecting an idea from this table.
 
-use rustc_attr_data_structures::{AttributeKind, find_attr};
 use rustc_hir as hir;
+use rustc_hir::attrs::AttributeKind;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{DefId, LocalDefId};
+use rustc_hir::find_attr;
 use rustc_middle::bug;
 use rustc_middle::ty::fast_reject::{SimplifiedType, TreatParams, simplify_type};
 use rustc_middle::ty::{self, CrateInherentImpls, Ty, TyCtxt};
diff --git a/compiler/rustc_hir_analysis/src/collect.rs b/compiler/rustc_hir_analysis/src/collect.rs
index afe79bed851..8ccbfbbb3b4 100644
--- a/compiler/rustc_hir_analysis/src/collect.rs
+++ b/compiler/rustc_hir_analysis/src/collect.rs
@@ -21,16 +21,16 @@ use std::ops::Bound;
 
 use rustc_abi::ExternAbi;
 use rustc_ast::Recovered;
-use rustc_attr_data_structures::{AttributeKind, find_attr};
 use rustc_data_structures::fx::{FxHashSet, FxIndexMap};
 use rustc_data_structures::unord::UnordMap;
 use rustc_errors::{
     Applicability, Diag, DiagCtxtHandle, E0228, ErrorGuaranteed, StashKey, struct_span_code_err,
 };
+use rustc_hir::attrs::AttributeKind;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::intravisit::{InferKind, Visitor, VisitorExt};
-use rustc_hir::{self as hir, GenericParamKind, HirId, Node, PreciseCapturingArgKind};
+use rustc_hir::{self as hir, GenericParamKind, HirId, Node, PreciseCapturingArgKind, find_attr};
 use rustc_infer::infer::{InferCtxt, TyCtxtInferExt};
 use rustc_infer::traits::{DynCompatibilityViolation, ObligationCause};
 use rustc_middle::query::Providers;
diff --git a/compiler/rustc_hir_analysis/src/collect/generics_of.rs b/compiler/rustc_hir_analysis/src/collect/generics_of.rs
index 31e9c3b80fb..ce0e51f106f 100644
--- a/compiler/rustc_hir_analysis/src/collect/generics_of.rs
+++ b/compiler/rustc_hir_analysis/src/collect/generics_of.rs
@@ -223,60 +223,27 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
             "synthetic HIR should have its `generics_of` explicitly fed"
         ),
 
-        _ => span_bug!(tcx.def_span(def_id), "unhandled node {node:?}"),
+        _ => span_bug!(tcx.def_span(def_id), "generics_of: unexpected node kind {node:?}"),
     };
 
-    enum Defaults {
-        Allowed,
-        // See #36887
-        FutureCompatDisallowed,
-        Deny,
-    }
-
-    let hir_generics = node.generics().unwrap_or(hir::Generics::empty());
-    let (opt_self, allow_defaults) = match node {
-        Node::Item(item) => {
-            match item.kind {
-                ItemKind::Trait(..) | ItemKind::TraitAlias(..) => {
-                    // Add in the self type parameter.
-                    //
-                    // Something of a hack: use the node id for the trait, also as
-                    // the node id for the Self type parameter.
-                    let opt_self = Some(ty::GenericParamDef {
-                        index: 0,
-                        name: kw::SelfUpper,
-                        def_id: def_id.to_def_id(),
-                        pure_wrt_drop: false,
-                        kind: ty::GenericParamDefKind::Type {
-                            has_default: false,
-                            synthetic: false,
-                        },
-                    });
-
-                    (opt_self, Defaults::Allowed)
-                }
-                ItemKind::TyAlias(..)
-                | ItemKind::Enum(..)
-                | ItemKind::Struct(..)
-                | ItemKind::Union(..) => (None, Defaults::Allowed),
-                ItemKind::Const(..) => (None, Defaults::Deny),
-                _ => (None, Defaults::FutureCompatDisallowed),
-            }
-        }
-
-        Node::OpaqueTy(..) => (None, Defaults::Allowed),
-
-        // GATs
-        Node::TraitItem(item) if matches!(item.kind, TraitItemKind::Type(..)) => {
-            (None, Defaults::Deny)
-        }
-        Node::ImplItem(item) if matches!(item.kind, ImplItemKind::Type(..)) => {
-            (None, Defaults::Deny)
-        }
-
-        _ => (None, Defaults::FutureCompatDisallowed),
+    // Add in the self type parameter.
+    let opt_self = if let Node::Item(item) = node
+        && let ItemKind::Trait(..) | ItemKind::TraitAlias(..) = item.kind
+    {
+        // Something of a hack: We reuse the node ID of the trait for the self type parameter.
+        Some(ty::GenericParamDef {
+            index: 0,
+            name: kw::SelfUpper,
+            def_id: def_id.to_def_id(),
+            pure_wrt_drop: false,
+            kind: ty::GenericParamDefKind::Type { has_default: false, synthetic: false },
+        })
+    } else {
+        None
     };
 
+    let param_default_policy = param_default_policy(node);
+    let hir_generics = node.generics().unwrap_or(hir::Generics::empty());
     let has_self = opt_self.is_some();
     let mut parent_has_self = false;
     let mut own_start = has_self as u32;
@@ -312,60 +279,53 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
         prev + type_start
     };
 
-    const TYPE_DEFAULT_NOT_ALLOWED: &'static str = "defaults for type parameters are only allowed in \
-    `struct`, `enum`, `type`, or `trait` definitions";
-
-    own_params.extend(hir_generics.params.iter().filter_map(|param| match param.kind {
-        GenericParamKind::Lifetime { .. } => None,
-        GenericParamKind::Type { default, synthetic, .. } => {
-            if default.is_some() {
-                match allow_defaults {
-                    Defaults::Allowed => {}
-                    Defaults::FutureCompatDisallowed => {
-                        tcx.node_span_lint(
-                            lint::builtin::INVALID_TYPE_PARAM_DEFAULT,
-                            param.hir_id,
-                            param.span,
-                            |lint| {
-                                lint.primary_message(TYPE_DEFAULT_NOT_ALLOWED);
-                            },
-                        );
-                    }
-                    Defaults::Deny => {
-                        tcx.dcx().span_err(param.span, TYPE_DEFAULT_NOT_ALLOWED);
+    own_params.extend(hir_generics.params.iter().filter_map(|param| {
+        const MESSAGE: &str = "defaults for generic parameters are not allowed here";
+        let kind = match param.kind {
+            GenericParamKind::Lifetime { .. } => return None,
+            GenericParamKind::Type { default, synthetic } => {
+                if default.is_some() {
+                    match param_default_policy.expect("no policy for generic param default") {
+                        ParamDefaultPolicy::Allowed => {}
+                        ParamDefaultPolicy::FutureCompatForbidden => {
+                            tcx.node_span_lint(
+                                lint::builtin::INVALID_TYPE_PARAM_DEFAULT,
+                                param.hir_id,
+                                param.span,
+                                |lint| {
+                                    lint.primary_message(MESSAGE);
+                                },
+                            );
+                        }
+                        ParamDefaultPolicy::Forbidden => {
+                            tcx.dcx().span_err(param.span, MESSAGE);
+                        }
                     }
                 }
-            }
 
-            let kind = ty::GenericParamDefKind::Type { has_default: default.is_some(), synthetic };
-
-            Some(ty::GenericParamDef {
-                index: next_index(),
-                name: param.name.ident().name,
-                def_id: param.def_id.to_def_id(),
-                pure_wrt_drop: param.pure_wrt_drop,
-                kind,
-            })
-        }
-        GenericParamKind::Const { ty: _, default, synthetic } => {
-            if !matches!(allow_defaults, Defaults::Allowed) && default.is_some() {
-                tcx.dcx().span_err(
-                    param.span,
-                    "defaults for const parameters are only allowed in \
-                    `struct`, `enum`, `type`, or `trait` definitions",
-                );
+                ty::GenericParamDefKind::Type { has_default: default.is_some(), synthetic }
             }
+            GenericParamKind::Const { ty: _, default, synthetic } => {
+                if default.is_some() {
+                    match param_default_policy.expect("no policy for generic param default") {
+                        ParamDefaultPolicy::Allowed => {}
+                        ParamDefaultPolicy::FutureCompatForbidden
+                        | ParamDefaultPolicy::Forbidden => {
+                            tcx.dcx().span_err(param.span, MESSAGE);
+                        }
+                    }
+                }
 
-            let index = next_index();
-
-            Some(ty::GenericParamDef {
-                index,
-                name: param.name.ident().name,
-                def_id: param.def_id.to_def_id(),
-                pure_wrt_drop: param.pure_wrt_drop,
-                kind: ty::GenericParamDefKind::Const { has_default: default.is_some(), synthetic },
-            })
-        }
+                ty::GenericParamDefKind::Const { has_default: default.is_some(), synthetic }
+            }
+        };
+        Some(ty::GenericParamDef {
+            index: next_index(),
+            name: param.name.ident().name,
+            def_id: param.def_id.to_def_id(),
+            pure_wrt_drop: param.pure_wrt_drop,
+            kind,
+        })
     }));
 
     // provide junk type parameter defs - the only place that
@@ -379,20 +339,14 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
         // for info on the usage of each of these fields.
         let dummy_args = match kind {
             ClosureKind::Closure => &["<closure_kind>", "<closure_signature>", "<upvars>"][..],
-            ClosureKind::Coroutine(_) => &[
-                "<coroutine_kind>",
-                "<resume_ty>",
-                "<yield_ty>",
-                "<return_ty>",
-                "<witness>",
-                "<upvars>",
-            ][..],
+            ClosureKind::Coroutine(_) => {
+                &["<coroutine_kind>", "<resume_ty>", "<yield_ty>", "<return_ty>", "<upvars>"][..]
+            }
             ClosureKind::CoroutineClosure(_) => &[
                 "<closure_kind>",
                 "<closure_signature_parts>",
                 "<upvars>",
                 "<bound_captures_by_ref>",
-                "<witness>",
             ][..],
         };
 
@@ -444,6 +398,48 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
     }
 }
 
+#[derive(Clone, Copy)]
+enum ParamDefaultPolicy {
+    Allowed,
+    /// Tracked in <https://github.com/rust-lang/rust/issues/36887>.
+    FutureCompatForbidden,
+    Forbidden,
+}
+
+fn param_default_policy(node: Node<'_>) -> Option<ParamDefaultPolicy> {
+    use rustc_hir::*;
+
+    Some(match node {
+        Node::Item(item) => match item.kind {
+            ItemKind::Trait(..)
+            | ItemKind::TraitAlias(..)
+            | ItemKind::TyAlias(..)
+            | ItemKind::Enum(..)
+            | ItemKind::Struct(..)
+            | ItemKind::Union(..) => ParamDefaultPolicy::Allowed,
+            ItemKind::Fn { .. } | ItemKind::Impl(_) => ParamDefaultPolicy::FutureCompatForbidden,
+            // Re. GCI, we're not bound by backward compatibility.
+            ItemKind::Const(..) => ParamDefaultPolicy::Forbidden,
+            _ => return None,
+        },
+        Node::TraitItem(item) => match item.kind {
+            // Re. GATs and GACs (generic_const_items), we're not bound by backward compatibility.
+            TraitItemKind::Const(..) | TraitItemKind::Type(..) => ParamDefaultPolicy::Forbidden,
+            TraitItemKind::Fn(..) => ParamDefaultPolicy::FutureCompatForbidden,
+        },
+        Node::ImplItem(item) => match item.kind {
+            // Re. GATs and GACs (generic_const_items), we're not bound by backward compatibility.
+            ImplItemKind::Const(..) | ImplItemKind::Type(..) => ParamDefaultPolicy::Forbidden,
+            ImplItemKind::Fn(..) => ParamDefaultPolicy::FutureCompatForbidden,
+        },
+        // Generic params are (semantically) invalid on foreign items. Still, for maximum forward
+        // compatibility, let's hard-reject defaults on them.
+        Node::ForeignItem(_) => ParamDefaultPolicy::Forbidden,
+        Node::OpaqueTy(..) => ParamDefaultPolicy::Allowed,
+        _ => return None,
+    })
+}
+
 fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option<Span> {
     struct LateBoundRegionsDetector<'tcx> {
         tcx: TyCtxt<'tcx>,
diff --git a/compiler/rustc_hir_analysis/src/collect/item_bounds.rs b/compiler/rustc_hir_analysis/src/collect/item_bounds.rs
index 548ba343aae..ba54fa8cc0d 100644
--- a/compiler/rustc_hir_analysis/src/collect/item_bounds.rs
+++ b/compiler/rustc_hir_analysis/src/collect/item_bounds.rs
@@ -189,7 +189,7 @@ fn remap_gat_vars_and_recurse_into_nested_projections<'tcx>(
             }
             ty::GenericArgKind::Const(ct) => {
                 if let ty::ConstKind::Bound(ty::INNERMOST, bv) = ct.kind() {
-                    mapping.insert(bv, tcx.mk_param_from_def(param))
+                    mapping.insert(bv.var, tcx.mk_param_from_def(param))
                 } else {
                     return None;
                 }
@@ -307,16 +307,16 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for MapAndCompressBoundVars<'tcx> {
             return ct;
         }
 
-        if let ty::ConstKind::Bound(binder, old_var) = ct.kind()
+        if let ty::ConstKind::Bound(binder, old_bound) = ct.kind()
             && self.binder == binder
         {
-            let mapped = if let Some(mapped) = self.mapping.get(&old_var) {
+            let mapped = if let Some(mapped) = self.mapping.get(&old_bound.var) {
                 mapped.expect_const()
             } else {
                 let var = ty::BoundVar::from_usize(self.still_bound_vars.len());
                 self.still_bound_vars.push(ty::BoundVariableKind::Const);
-                let mapped = ty::Const::new_bound(self.tcx, ty::INNERMOST, var);
-                self.mapping.insert(old_var, mapped.into());
+                let mapped = ty::Const::new_bound(self.tcx, ty::INNERMOST, ty::BoundConst { var });
+                self.mapping.insert(old_bound.var, mapped.into());
                 mapped
             };
 
diff --git a/compiler/rustc_hir_analysis/src/collect/predicates_of.rs b/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
index cc53919626e..522409a5ee5 100644
--- a/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
+++ b/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
@@ -1,11 +1,12 @@
 use std::assert_matches::assert_matches;
 
 use hir::Node;
-use rustc_attr_data_structures::{AttributeKind, find_attr};
 use rustc_data_structures::fx::FxIndexSet;
 use rustc_hir as hir;
+use rustc_hir::attrs::AttributeKind;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{DefId, LocalDefId};
+use rustc_hir::find_attr;
 use rustc_middle::ty::{
     self, GenericPredicates, ImplTraitInTraitData, Ty, TyCtxt, TypeVisitable, TypeVisitor, Upcast,
 };
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 7760642d8fb..386e1091ac4 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs
@@ -1077,7 +1077,7 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for GenericParamAndBoundVarCollector<'_, 't
             ty::ConstKind::Param(param) => {
                 self.params.insert(param.index);
             }
-            ty::ConstKind::Bound(db, ty::BoundVar { .. }) if db >= self.depth => {
+            ty::ConstKind::Bound(db, _) if db >= self.depth => {
                 let guar = self.cx.dcx().delayed_bug("unexpected escaping late-bound const var");
                 return ControlFlow::Break(guar);
             }
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 f73442fdebd..3e446b7c656 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
@@ -888,8 +888,8 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 ty::PredicateKind::Clause(ty::ClauseKind::Projection(pred)) => {
                     // `<Foo as Iterator>::Item = String`.
                     let projection_term = pred.projection_term;
-                    let quiet_projection_term =
-                        projection_term.with_self_ty(tcx, Ty::new_var(tcx, ty::TyVid::ZERO));
+                    let quiet_projection_term = projection_term
+                        .with_replaced_self_ty(tcx, Ty::new_var(tcx, ty::TyVid::ZERO));
 
                     let term = pred.term;
                     let obligation = format!("{projection_term} = {term}");
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 d7687998358..7e2bfa9f920 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
@@ -2037,9 +2037,9 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 match prim_ty {
                     hir::PrimTy::Bool => tcx.types.bool,
                     hir::PrimTy::Char => tcx.types.char,
-                    hir::PrimTy::Int(it) => Ty::new_int(tcx, ty::int_ty(it)),
-                    hir::PrimTy::Uint(uit) => Ty::new_uint(tcx, ty::uint_ty(uit)),
-                    hir::PrimTy::Float(ft) => Ty::new_float(tcx, ty::float_ty(ft)),
+                    hir::PrimTy::Int(it) => Ty::new_int(tcx, it),
+                    hir::PrimTy::Uint(uit) => Ty::new_uint(tcx, uit),
+                    hir::PrimTy::Float(ft) => Ty::new_float(tcx, ft),
                     hir::PrimTy::Str => tcx.types.str_,
                 }
             }
@@ -2107,9 +2107,11 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 let name = tcx.item_name(param_def_id);
                 ty::Const::new_param(tcx, ty::ParamConst::new(index, name))
             }
-            Some(rbv::ResolvedArg::LateBound(debruijn, index, _)) => {
-                ty::Const::new_bound(tcx, debruijn, ty::BoundVar::from_u32(index))
-            }
+            Some(rbv::ResolvedArg::LateBound(debruijn, index, _)) => ty::Const::new_bound(
+                tcx,
+                debruijn,
+                ty::BoundConst { var: ty::BoundVar::from_u32(index) },
+            ),
             Some(rbv::ResolvedArg::Error(guar)) => ty::Const::new_error(tcx, guar),
             arg => bug!("unexpected bound var resolution for {:?}: {arg:?}", path_hir_id),
         }
diff --git a/compiler/rustc_hir_pretty/Cargo.toml b/compiler/rustc_hir_pretty/Cargo.toml
index 91da8cb3fc5..f5d7dbd3f96 100644
--- a/compiler/rustc_hir_pretty/Cargo.toml
+++ b/compiler/rustc_hir_pretty/Cargo.toml
@@ -8,7 +8,6 @@ edition = "2024"
 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_hir = { path = "../rustc_hir" }
 rustc_span = { path = "../rustc_span" }
 # tidy-alphabetical-end
diff --git a/compiler/rustc_hir_pretty/src/lib.rs b/compiler/rustc_hir_pretty/src/lib.rs
index bda02042aa6..235eec96d74 100644
--- a/compiler/rustc_hir_pretty/src/lib.rs
+++ b/compiler/rustc_hir_pretty/src/lib.rs
@@ -15,7 +15,7 @@ use rustc_ast_pretty::pp::Breaks::{Consistent, Inconsistent};
 use rustc_ast_pretty::pp::{self, BoxMarker, Breaks};
 use rustc_ast_pretty::pprust::state::MacHeader;
 use rustc_ast_pretty::pprust::{Comments, PrintState};
-use rustc_attr_data_structures::{AttributeKind, PrintAttribute};
+use rustc_hir::attrs::{AttributeKind, PrintAttribute};
 use rustc_hir::{
     BindingMode, ByRef, ConstArgKind, GenericArg, GenericBound, GenericParam, GenericParamKind,
     HirId, ImplicitSelfKind, LifetimeParamKind, Node, PatKind, PreciseCapturingArg, RangeEnd, Term,
diff --git a/compiler/rustc_hir_typeck/Cargo.toml b/compiler/rustc_hir_typeck/Cargo.toml
index c963f0ddefd..f00125c3e09 100644
--- a/compiler/rustc_hir_typeck/Cargo.toml
+++ b/compiler/rustc_hir_typeck/Cargo.toml
@@ -8,7 +8,6 @@ edition = "2024"
 itertools = "0.12"
 rustc_abi = { path = "../rustc_abi" }
 rustc_ast = { path = "../rustc_ast" }
-rustc_attr_data_structures = { path = "../rustc_attr_data_structures" }
 rustc_attr_parsing = { path = "../rustc_attr_parsing" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
diff --git a/compiler/rustc_hir_typeck/src/closure.rs b/compiler/rustc_hir_typeck/src/closure.rs
index a413f805873..82b7c578a1f 100644
--- a/compiler/rustc_hir_typeck/src/closure.rs
+++ b/compiler/rustc_hir_typeck/src/closure.rs
@@ -161,8 +161,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 // Resume type defaults to `()` if the coroutine has no argument.
                 let resume_ty = liberated_sig.inputs().get(0).copied().unwrap_or(tcx.types.unit);
 
-                let interior = Ty::new_coroutine_witness(tcx, expr_def_id.to_def_id(), parent_args);
-
                 // Coroutines that come from coroutine closures have not yet determined
                 // their kind ty, so make a fresh infer var which will be constrained
                 // later during upvar analysis. Regular coroutines always have the kind
@@ -182,7 +180,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         resume_ty,
                         yield_ty,
                         return_ty: liberated_sig.output(),
-                        witness: interior,
                         tupled_upvars_ty,
                     },
                 );
@@ -210,7 +207,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 };
                 // Compute all of the variables that will be used to populate the coroutine.
                 let resume_ty = self.next_ty_var(expr_span);
-                let interior = self.next_ty_var(expr_span);
 
                 let closure_kind_ty = match expected_kind {
                     Some(kind) => Ty::from_closure_kind(tcx, kind),
@@ -243,7 +239,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         ),
                         tupled_upvars_ty,
                         coroutine_captures_by_ref_ty,
-                        coroutine_witness_ty: interior,
                     },
                 );
 
diff --git a/compiler/rustc_hir_typeck/src/coercion.rs b/compiler/rustc_hir_typeck/src/coercion.rs
index 6d67535da5f..e66601631fc 100644
--- a/compiler/rustc_hir_typeck/src/coercion.rs
+++ b/compiler/rustc_hir_typeck/src/coercion.rs
@@ -37,10 +37,10 @@
 
 use std::ops::Deref;
 
-use rustc_attr_data_structures::InlineAttr;
 use rustc_errors::codes::*;
 use rustc_errors::{Applicability, Diag, struct_span_code_err};
 use rustc_hir as hir;
+use rustc_hir::attrs::InlineAttr;
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir_analysis::hir_ty_lowering::HirTyLowerer;
 use rustc_infer::infer::relate::RelateResult;
@@ -1800,11 +1800,13 @@ impl<'tcx, 'exprs, E: AsCoercionSite> CoerceMany<'tcx, 'exprs, E> {
                             .kind()
                             .map_bound(|clause| match clause {
                                 ty::ClauseKind::Trait(trait_pred) => Some(ty::ClauseKind::Trait(
-                                    trait_pred.with_self_ty(fcx.tcx, ty),
+                                    trait_pred.with_replaced_self_ty(fcx.tcx, ty),
                                 )),
-                                ty::ClauseKind::Projection(proj_pred) => Some(
-                                    ty::ClauseKind::Projection(proj_pred.with_self_ty(fcx.tcx, ty)),
-                                ),
+                                ty::ClauseKind::Projection(proj_pred) => {
+                                    Some(ty::ClauseKind::Projection(
+                                        proj_pred.with_replaced_self_ty(fcx.tcx, ty),
+                                    ))
+                                }
                                 _ => None,
                             })
                             .transpose()?;
diff --git a/compiler/rustc_hir_typeck/src/expr.rs b/compiler/rustc_hir_typeck/src/expr.rs
index 08e8164078c..454ec7ddcaf 100644
--- a/compiler/rustc_hir_typeck/src/expr.rs
+++ b/compiler/rustc_hir_typeck/src/expr.rs
@@ -7,7 +7,6 @@
 
 use rustc_abi::{FIRST_VARIANT, FieldIdx};
 use rustc_ast::util::parser::ExprPrecedence;
-use rustc_attr_data_structures::{AttributeKind, find_attr};
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_data_structures::unord::UnordMap;
@@ -16,10 +15,11 @@ use rustc_errors::{
     Applicability, Diag, ErrorGuaranteed, MultiSpan, StashKey, Subdiagnostic, listify, pluralize,
     struct_span_code_err,
 };
+use rustc_hir::attrs::AttributeKind;
 use rustc_hir::def::{CtorKind, DefKind, Res};
 use rustc_hir::def_id::DefId;
 use rustc_hir::lang_items::LangItem;
-use rustc_hir::{ExprKind, HirId, QPath};
+use rustc_hir::{ExprKind, HirId, QPath, find_attr};
 use rustc_hir_analysis::NoVariantNamed;
 use rustc_hir_analysis::hir_ty_lowering::{FeedConstTy, HirTyLowerer as _};
 use rustc_infer::infer::{self, DefineOpaqueTypes, InferOk, RegionVariableOrigin};
diff --git a/compiler/rustc_hir_typeck/src/fallback.rs b/compiler/rustc_hir_typeck/src/fallback.rs
index 9406697dfed..ef88e02fd98 100644
--- a/compiler/rustc_hir_typeck/src/fallback.rs
+++ b/compiler/rustc_hir_typeck/src/fallback.rs
@@ -18,6 +18,7 @@ use rustc_span::{DUMMY_SP, Span};
 use rustc_trait_selection::traits::{ObligationCause, ObligationCtxt};
 use tracing::debug;
 
+use crate::typeck_root_ctxt::InferVarInfo;
 use crate::{FnCtxt, errors};
 
 #[derive(Copy, Clone)]
@@ -345,7 +346,7 @@ impl<'tcx> FnCtxt<'_, 'tcx> {
                 .map(|(_, info)| *info)
                 .collect();
 
-            let found_infer_var_info = ty::InferVarInfo {
+            let found_infer_var_info = InferVarInfo {
                 self_in_trait: infer_var_infos.items().any(|info| info.self_in_trait),
                 output: infer_var_infos.items().any(|info| info.output),
             };
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 4e4bf8a5562..ed88e32a273 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
@@ -17,6 +17,21 @@ enum ClauseFlavor {
     Const,
 }
 
+#[derive(Copy, Clone, PartialEq, Eq, Debug)]
+enum ParamTerm {
+    Ty(ty::ParamTy),
+    Const(ty::ParamConst),
+}
+
+impl ParamTerm {
+    fn index(self) -> usize {
+        match self {
+            ParamTerm::Ty(ty) => ty.index as usize,
+            ParamTerm::Const(ct) => ct.index as usize,
+        }
+    }
+}
+
 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     pub(crate) fn adjust_fulfillment_error_for_expr_obligation(
         &self,
@@ -77,17 +92,17 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 _ => return false,
             };
 
-        let find_param_matching = |matches: &dyn Fn(ty::ParamTerm) -> bool| {
+        let find_param_matching = |matches: &dyn Fn(ParamTerm) -> bool| {
             predicate_args.iter().find_map(|arg| {
                 arg.walk().find_map(|arg| {
                     if let ty::GenericArgKind::Type(ty) = arg.kind()
                         && let ty::Param(param_ty) = *ty.kind()
-                        && matches(ty::ParamTerm::Ty(param_ty))
+                        && matches(ParamTerm::Ty(param_ty))
                     {
                         Some(arg)
                     } else if let ty::GenericArgKind::Const(ct) = arg.kind()
                         && let ty::ConstKind::Param(param_ct) = ct.kind()
-                        && matches(ty::ParamTerm::Const(param_ct))
+                        && matches(ParamTerm::Const(param_ct))
                     {
                         Some(arg)
                     } else {
@@ -106,14 +121,14 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // from a trait or impl, for example.
         let mut fallback_param_to_point_at = find_param_matching(&|param_term| {
             self.tcx.parent(generics.param_at(param_term.index(), self.tcx).def_id) != def_id
-                && !matches!(param_term, ty::ParamTerm::Ty(ty) if ty.name == kw::SelfUpper)
+                && !matches!(param_term, ParamTerm::Ty(ty) if ty.name == kw::SelfUpper)
         });
         // Finally, the `Self` parameter is possibly the reason that the predicate
         // is unsatisfied. This is less likely to be true for methods, because
         // method probe means that we already kinda check that the predicates due
         // to the `Self` type are true.
         let mut self_param_to_point_at = find_param_matching(
-            &|param_term| matches!(param_term, ty::ParamTerm::Ty(ty) if ty.name == kw::SelfUpper),
+            &|param_term| matches!(param_term, ParamTerm::Ty(ty) if ty.name == kw::SelfUpper),
         );
 
         // Finally, for ambiguity-related errors, we actually want to look
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
index 719989d5793..36abd7c8555 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
@@ -1658,8 +1658,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             ),
             ast::LitKind::Byte(_) => tcx.types.u8,
             ast::LitKind::Char(_) => tcx.types.char,
-            ast::LitKind::Int(_, ast::LitIntType::Signed(t)) => Ty::new_int(tcx, ty::int_ty(t)),
-            ast::LitKind::Int(_, ast::LitIntType::Unsigned(t)) => Ty::new_uint(tcx, ty::uint_ty(t)),
+            ast::LitKind::Int(_, ast::LitIntType::Signed(t)) => Ty::new_int(tcx, t),
+            ast::LitKind::Int(_, ast::LitIntType::Unsigned(t)) => Ty::new_uint(tcx, t),
             ast::LitKind::Int(i, ast::LitIntType::Unsuffixed) => {
                 let opt_ty = expected.to_option(self).and_then(|ty| match ty.kind() {
                     ty::Int(_) | ty::Uint(_) => Some(ty),
@@ -1686,9 +1686,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 });
                 opt_ty.unwrap_or_else(|| self.next_int_var())
             }
-            ast::LitKind::Float(_, ast::LitFloatType::Suffixed(t)) => {
-                Ty::new_float(tcx, ty::float_ty(t))
-            }
+            ast::LitKind::Float(_, ast::LitFloatType::Suffixed(t)) => Ty::new_float(tcx, t),
             ast::LitKind::Float(_, ast::LitFloatType::Unsuffixed) => {
                 let opt_ty = expected.to_option(self).and_then(|ty| match ty.kind() {
                     ty::Float(_) => Some(ty),
diff --git a/compiler/rustc_hir_typeck/src/lib.rs b/compiler/rustc_hir_typeck/src/lib.rs
index 9e324286fa1..aae870f7ee3 100644
--- a/compiler/rustc_hir_typeck/src/lib.rs
+++ b/compiler/rustc_hir_typeck/src/lib.rs
@@ -42,18 +42,18 @@ mod writeback;
 
 pub use coercion::can_coerce;
 use fn_ctxt::FnCtxt;
-use rustc_attr_data_structures::{AttributeKind, find_attr};
 use rustc_data_structures::unord::UnordSet;
 use rustc_errors::codes::*;
 use rustc_errors::{Applicability, ErrorGuaranteed, pluralize, struct_span_code_err};
 use rustc_hir as hir;
+use rustc_hir::attrs::AttributeKind;
 use rustc_hir::def::{DefKind, Res};
-use rustc_hir::{HirId, HirIdMap, Node};
+use rustc_hir::{HirId, HirIdMap, Node, find_attr};
 use rustc_hir_analysis::check::{check_abi, check_custom_abi};
 use rustc_hir_analysis::hir_ty_lowering::HirTyLowerer;
 use rustc_infer::traits::{ObligationCauseCode, ObligationInspector, WellFormedLoc};
 use rustc_middle::query::Providers;
-use rustc_middle::ty::{self, Ty, TyCtxt};
+use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitableExt};
 use rustc_middle::{bug, span_bug};
 use rustc_session::config;
 use rustc_span::Span;
@@ -259,6 +259,21 @@ fn typeck_with_inspect<'tcx>(
 
     let typeck_results = fcx.resolve_type_vars_in_body(body);
 
+    // Handle potentially region dependent goals, see `InferCtxt::in_hir_typeck`.
+    if let None = fcx.infcx.tainted_by_errors() {
+        for obligation in fcx.take_hir_typeck_potentially_region_dependent_goals() {
+            let obligation = fcx.resolve_vars_if_possible(obligation);
+            if obligation.has_non_region_infer() {
+                bug!("unexpected inference variable after writeback: {obligation:?}");
+            }
+            fcx.register_predicate(obligation);
+        }
+        fcx.select_obligations_where_possible(|_| {});
+        if let None = fcx.infcx.tainted_by_errors() {
+            fcx.report_ambiguity_errors();
+        }
+    }
+
     fcx.detect_opaque_types_added_during_writeback();
 
     // Consistency check our TypeckResults instance can hold all ItemLocalIds
diff --git a/compiler/rustc_hir_typeck/src/loops.rs b/compiler/rustc_hir_typeck/src/loops.rs
index 80eab578f13..acfa5c473aa 100644
--- a/compiler/rustc_hir_typeck/src/loops.rs
+++ b/compiler/rustc_hir_typeck/src/loops.rs
@@ -2,13 +2,12 @@ use std::collections::BTreeMap;
 use std::fmt;
 
 use Context::*;
-use rustc_ast::Label;
-use rustc_attr_data_structures::{AttributeKind, find_attr};
 use rustc_hir as hir;
+use rustc_hir::attrs::AttributeKind;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::LocalDefId;
 use rustc_hir::intravisit::{self, Visitor};
-use rustc_hir::{Destination, Node};
+use rustc_hir::{Destination, Node, find_attr};
 use rustc_middle::hir::nested_filter;
 use rustc_middle::span_bug;
 use rustc_middle::ty::TyCtxt;
@@ -42,8 +41,8 @@ enum Context {
     ConstBlock,
     /// E.g. `#[loop_match] loop { state = 'label: { /* ... */ } }`.
     LoopMatch {
-        /// The label of the labeled block (not of the loop itself).
-        labeled_block: Label,
+        /// The destination pointing to the labeled block (not to the loop itself).
+        labeled_block: Destination,
     },
 }
 
@@ -186,18 +185,18 @@ impl<'hir> Visitor<'hir> for CheckLoopVisitor<'hir> {
             {
                 self.with_context(UnlabeledBlock(b.span.shrink_to_lo()), |v| v.visit_block(b));
             }
-            hir::ExprKind::Break(break_label, ref opt_expr) => {
+            hir::ExprKind::Break(break_destination, ref opt_expr) => {
                 if let Some(e) = opt_expr {
                     self.visit_expr(e);
                 }
 
-                if self.require_label_in_labeled_block(e.span, &break_label, "break") {
+                if self.require_label_in_labeled_block(e.span, &break_destination, "break") {
                     // If we emitted an error about an unlabeled break in a labeled
                     // block, we don't need any further checking for this break any more
                     return;
                 }
 
-                let loop_id = match break_label.target_id {
+                let loop_id = match break_destination.target_id {
                     Ok(loop_id) => Some(loop_id),
                     Err(hir::LoopIdError::OutsideLoopScope) => None,
                     Err(hir::LoopIdError::UnlabeledCfInWhileCondition) => {
@@ -212,18 +211,25 @@ impl<'hir> Visitor<'hir> for CheckLoopVisitor<'hir> {
 
                 // A `#[const_continue]` must break to a block in a `#[loop_match]`.
                 if find_attr!(self.tcx.hir_attrs(e.hir_id), AttributeKind::ConstContinue(_)) {
-                    if let Some(break_label) = break_label.label {
-                        let is_target_label = |cx: &Context| match cx {
-                            Context::LoopMatch { labeled_block } => {
-                                break_label.ident.name == labeled_block.ident.name
-                            }
-                            _ => false,
-                        };
+                    let Some(label) = break_destination.label else {
+                        let span = e.span;
+                        self.tcx.dcx().emit_fatal(ConstContinueBadLabel { span });
+                    };
 
-                        if !self.cx_stack.iter().rev().any(is_target_label) {
-                            let span = break_label.ident.span;
-                            self.tcx.dcx().emit_fatal(ConstContinueBadLabel { span });
+                    let is_target_label = |cx: &Context| match cx {
+                        Context::LoopMatch { labeled_block } => {
+                            // NOTE: with macro expansion, the label's span might be different here
+                            // even though it does still refer to the same HIR node. A block
+                            // can't have two labels, so the hir_id is a unique identifier.
+                            assert!(labeled_block.target_id.is_ok()); // see `is_loop_match`.
+                            break_destination.target_id == labeled_block.target_id
                         }
+                        _ => false,
+                    };
+
+                    if !self.cx_stack.iter().rev().any(is_target_label) {
+                        let span = label.ident.span;
+                        self.tcx.dcx().emit_fatal(ConstContinueBadLabel { span });
                     }
                 }
 
@@ -249,7 +255,7 @@ impl<'hir> Visitor<'hir> for CheckLoopVisitor<'hir> {
                         Some(kind) => {
                             let suggestion = format!(
                                 "break{}",
-                                break_label
+                                break_destination
                                     .label
                                     .map_or_else(String::new, |l| format!(" {}", l.ident))
                             );
@@ -259,7 +265,7 @@ impl<'hir> Visitor<'hir> for CheckLoopVisitor<'hir> {
                                 kind: kind.name(),
                                 suggestion,
                                 loop_label,
-                                break_label: break_label.label,
+                                break_label: break_destination.label,
                                 break_expr_kind: &break_expr.kind,
                                 break_expr_span: break_expr.span,
                             });
@@ -268,7 +274,7 @@ impl<'hir> Visitor<'hir> for CheckLoopVisitor<'hir> {
                 }
 
                 let sp_lo = e.span.with_lo(e.span.lo() + BytePos("break".len() as u32));
-                let label_sp = match break_label.label {
+                let label_sp = match break_destination.label {
                     Some(label) => sp_lo.with_hi(label.ident.span.hi()),
                     None => sp_lo.shrink_to_lo(),
                 };
@@ -416,7 +422,7 @@ impl<'hir> CheckLoopVisitor<'hir> {
         &self,
         e: &'hir hir::Expr<'hir>,
         body: &'hir hir::Block<'hir>,
-    ) -> Option<Label> {
+    ) -> Option<Destination> {
         if !find_attr!(self.tcx.hir_attrs(e.hir_id), AttributeKind::LoopMatch(_)) {
             return None;
         }
@@ -438,8 +444,8 @@ impl<'hir> CheckLoopVisitor<'hir> {
 
         let hir::ExprKind::Assign(_, rhs_expr, _) = loop_body_expr.kind else { return None };
 
-        let hir::ExprKind::Block(_, label) = rhs_expr.kind else { return None };
+        let hir::ExprKind::Block(block, label) = rhs_expr.kind else { return None };
 
-        label
+        Some(Destination { label, target_id: Ok(block.hir_id) })
     }
 }
diff --git a/compiler/rustc_hir_typeck/src/method/confirm.rs b/compiler/rustc_hir_typeck/src/method/confirm.rs
index 8d9f7eaf177..a23910a2006 100644
--- a/compiler/rustc_hir_typeck/src/method/confirm.rs
+++ b/compiler/rustc_hir_typeck/src/method/confirm.rs
@@ -116,7 +116,7 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
         // If there is a `Self: Sized` bound and `Self` is a trait object, it is possible that
         // something which derefs to `Self` actually implements the trait and the caller
         // wanted to make a static dispatch on it but forgot to import the trait.
-        // See test `tests/ui/issue-35976.rs`.
+        // See test `tests/ui/issues/issue-35976.rs`.
         //
         // In that case, we'll error anyway, but we'll also re-run the search with all traits
         // in scope, and if we find another method which can be used, we'll output an
@@ -142,7 +142,6 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
 
         let (method_sig, method_predicates) =
             self.normalize(self.span, (method_sig, method_predicates));
-        let method_sig = ty::Binder::dummy(method_sig);
 
         // Make sure nobody calls `drop()` explicitly.
         self.check_for_illegal_method_calls(pick);
@@ -154,20 +153,11 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
         // We won't add these if we encountered an illegal sized bound, so that we can use
         // a custom error in that case.
         if illegal_sized_bound.is_none() {
-            self.add_obligations(
-                Ty::new_fn_ptr(self.tcx, method_sig),
-                all_args,
-                method_predicates,
-                pick.item.def_id,
-            );
+            self.add_obligations(method_sig, all_args, method_predicates, pick.item.def_id);
         }
 
         // Create the final `MethodCallee`.
-        let callee = MethodCallee {
-            def_id: pick.item.def_id,
-            args: all_args,
-            sig: method_sig.skip_binder(),
-        };
+        let callee = MethodCallee { def_id: pick.item.def_id, args: all_args, sig: method_sig };
         ConfirmResult { callee, illegal_sized_bound }
     }
 
@@ -601,14 +591,14 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
 
     fn add_obligations(
         &mut self,
-        fty: Ty<'tcx>,
+        sig: ty::FnSig<'tcx>,
         all_args: GenericArgsRef<'tcx>,
         method_predicates: ty::InstantiatedPredicates<'tcx>,
         def_id: DefId,
     ) {
         debug!(
-            "add_obligations: fty={:?} all_args={:?} method_predicates={:?} def_id={:?}",
-            fty, all_args, method_predicates, def_id
+            "add_obligations: sig={:?} all_args={:?} method_predicates={:?} def_id={:?}",
+            sig, all_args, method_predicates, def_id
         );
 
         // FIXME: could replace with the following, but we already calculated `method_predicates`,
@@ -637,7 +627,13 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
         // the function type must also be well-formed (this is not
         // implied by the args being well-formed because of inherent
         // impls and late-bound regions - see issue #28609).
-        self.register_wf_obligation(fty.into(), self.span, ObligationCauseCode::WellFormed(None));
+        for ty in sig.inputs_and_output {
+            self.register_wf_obligation(
+                ty.into(),
+                self.span,
+                ObligationCauseCode::WellFormed(None),
+            );
+        }
     }
 
     ///////////////////////////////////////////////////////////////////////////
diff --git a/compiler/rustc_hir_typeck/src/method/mod.rs b/compiler/rustc_hir_typeck/src/method/mod.rs
index 316468b0a5d..e37ea031672 100644
--- a/compiler/rustc_hir_typeck/src/method/mod.rs
+++ b/compiler/rustc_hir_typeck/src/method/mod.rs
@@ -428,19 +428,18 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         ));
 
         // Also add an obligation for the method type being well-formed.
-        let method_ty = Ty::new_fn_ptr(tcx, ty::Binder::dummy(fn_sig));
         debug!(
-            "lookup_method_in_trait: matched method method_ty={:?} obligation={:?}",
-            method_ty, obligation
+            "lookup_method_in_trait: matched method fn_sig={:?} obligation={:?}",
+            fn_sig, obligation
         );
-        obligations.push(traits::Obligation::new(
-            tcx,
-            obligation.cause,
-            self.param_env,
-            ty::Binder::dummy(ty::PredicateKind::Clause(ty::ClauseKind::WellFormed(
-                method_ty.into(),
-            ))),
-        ));
+        for ty in fn_sig.inputs_and_output {
+            obligations.push(traits::Obligation::new(
+                tcx,
+                obligation.cause.clone(),
+                self.param_env,
+                ty::Binder::dummy(ty::PredicateKind::Clause(ty::ClauseKind::WellFormed(ty.into()))),
+            ));
+        }
 
         let callee = MethodCallee { def_id, args, sig: fn_sig };
         debug!("callee = {:?}", callee);
diff --git a/compiler/rustc_hir_typeck/src/method/probe.rs b/compiler/rustc_hir_typeck/src/method/probe.rs
index 1f3969bd93c..3ca3b56b87e 100644
--- a/compiler/rustc_hir_typeck/src/method/probe.rs
+++ b/compiler/rustc_hir_typeck/src/method/probe.rs
@@ -2051,7 +2051,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
     /// probe. This will result in a pending obligation so when more type-info is available we can
     /// make the final decision.
     ///
-    /// Example (`tests/ui/method-two-trait-defer-resolution-1.rs`):
+    /// Example (`tests/ui/methods/method-two-trait-defer-resolution-1.rs`):
     ///
     /// ```ignore (illustrative)
     /// trait Foo { ... }
diff --git a/compiler/rustc_hir_typeck/src/method/suggest.rs b/compiler/rustc_hir_typeck/src/method/suggest.rs
index e64af8fb7b3..0c0cc752b01 100644
--- a/compiler/rustc_hir_typeck/src/method/suggest.rs
+++ b/compiler/rustc_hir_typeck/src/method/suggest.rs
@@ -9,7 +9,6 @@ use std::path::PathBuf;
 
 use hir::Expr;
 use rustc_ast::ast::Mutability;
-use rustc_attr_data_structures::{AttributeKind, find_attr};
 use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_data_structures::sorted_map::SortedMap;
 use rustc_data_structures::unord::UnordSet;
@@ -17,11 +16,12 @@ use rustc_errors::codes::*;
 use rustc_errors::{
     Applicability, Diag, DiagStyledString, MultiSpan, StashKey, pluralize, struct_span_code_err,
 };
+use rustc_hir::attrs::AttributeKind;
 use rustc_hir::def::{CtorKind, DefKind, Res};
 use rustc_hir::def_id::DefId;
 use rustc_hir::intravisit::{self, Visitor};
 use rustc_hir::lang_items::LangItem;
-use rustc_hir::{self as hir, ExprKind, HirId, Node, PathSegment, QPath};
+use rustc_hir::{self as hir, ExprKind, HirId, Node, PathSegment, QPath, find_attr};
 use rustc_infer::infer::{BoundRegionConversionTime, RegionVariableOrigin};
 use rustc_middle::bug;
 use rustc_middle::ty::fast_reject::{DeepRejectCtxt, TreatParams, simplify_type};
@@ -1053,8 +1053,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         let pred = bound_predicate.rebind(pred);
                         // `<Foo as Iterator>::Item = String`.
                         let projection_term = pred.skip_binder().projection_term;
-                        let quiet_projection_term =
-                            projection_term.with_self_ty(tcx, Ty::new_var(tcx, ty::TyVid::ZERO));
+                        let quiet_projection_term = projection_term
+                            .with_replaced_self_ty(tcx, Ty::new_var(tcx, ty::TyVid::ZERO));
 
                         let term = pred.skip_binder().term;
 
@@ -2157,7 +2157,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                     self.tcx,
                                     self.fresh_args_for_item(sugg_span, impl_did),
                                 )
-                                .with_self_ty(self.tcx, rcvr_ty),
+                                .with_replaced_self_ty(self.tcx, rcvr_ty),
                             idx,
                             sugg_span,
                             item,
@@ -2196,7 +2196,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                 trait_did,
                                 self.fresh_args_for_item(sugg_span, trait_did),
                             )
-                            .with_self_ty(self.tcx, rcvr_ty),
+                            .with_replaced_self_ty(self.tcx, rcvr_ty),
                             idx,
                             sugg_span,
                             item,
diff --git a/compiler/rustc_hir_typeck/src/naked_functions.rs b/compiler/rustc_hir_typeck/src/naked_functions.rs
index d055fa68fc3..d3fd63d871a 100644
--- a/compiler/rustc_hir_typeck/src/naked_functions.rs
+++ b/compiler/rustc_hir_typeck/src/naked_functions.rs
@@ -1,10 +1,10 @@
 //! Checks validity of naked functions.
 
-use rustc_attr_data_structures::{AttributeKind, find_attr};
 use rustc_hir as hir;
+use rustc_hir::attrs::AttributeKind;
 use rustc_hir::def_id::LocalDefId;
 use rustc_hir::intravisit::Visitor;
-use rustc_hir::{ExprKind, HirIdSet, StmtKind};
+use rustc_hir::{ExprKind, HirIdSet, StmtKind, find_attr};
 use rustc_middle::span_bug;
 use rustc_middle::ty::TyCtxt;
 use rustc_span::Span;
diff --git a/compiler/rustc_hir_typeck/src/typeck_root_ctxt.rs b/compiler/rustc_hir_typeck/src/typeck_root_ctxt.rs
index 6a985fc91e7..d8d217ca800 100644
--- a/compiler/rustc_hir_typeck/src/typeck_root_ctxt.rs
+++ b/compiler/rustc_hir_typeck/src/typeck_root_ctxt.rs
@@ -17,6 +17,19 @@ use tracing::{debug, instrument};
 
 use super::callee::DeferredCallResolution;
 
+#[derive(Debug, Default, Copy, Clone)]
+pub(crate) struct InferVarInfo {
+    /// This is true if we identified that this Ty (`?T`) is found in a `?T: Foo`
+    /// obligation, where:
+    ///
+    ///  * `Foo` is not `Sized`
+    ///  * `(): Foo` may be satisfied
+    pub self_in_trait: bool,
+    /// This is true if we identified that this Ty (`?T`) is found in a `<_ as
+    /// _>::AssocType = ?T`
+    pub output: bool,
+}
+
 /// Data shared between a "typeck root" and its nested bodies,
 /// e.g. closures defined within the function. For example:
 /// ```ignore (illustrative)
@@ -71,7 +84,7 @@ pub(crate) struct TypeckRootCtxt<'tcx> {
     /// fallback. See the `fallback` module for details.
     pub(super) diverging_type_vars: RefCell<UnordSet<Ty<'tcx>>>,
 
-    pub(super) infer_var_info: RefCell<UnordMap<ty::TyVid, ty::InferVarInfo>>,
+    pub(super) infer_var_info: RefCell<UnordMap<ty::TyVid, InferVarInfo>>,
 }
 
 impl<'tcx> Deref for TypeckRootCtxt<'tcx> {
@@ -85,8 +98,11 @@ impl<'tcx> TypeckRootCtxt<'tcx> {
     pub(crate) fn new(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> Self {
         let hir_owner = tcx.local_def_id_to_hir_id(def_id).owner;
 
-        let infcx =
-            tcx.infer_ctxt().ignoring_regions().build(TypingMode::typeck_for_body(tcx, def_id));
+        let infcx = tcx
+            .infer_ctxt()
+            .ignoring_regions()
+            .in_hir_typeck()
+            .build(TypingMode::typeck_for_body(tcx, def_id));
         let typeck_results = RefCell::new(ty::TypeckResults::new(hir_owner));
         let fulfillment_cx = RefCell::new(<dyn TraitEngine<'_, _>>::new(&infcx));
 
@@ -151,7 +167,7 @@ impl<'tcx> TypeckRootCtxt<'tcx> {
                 obligation.predicate.kind().rebind(
                     // (*) binder moved here
                     ty::PredicateKind::Clause(ty::ClauseKind::Trait(
-                        tpred.with_self_ty(self.tcx, new_self_ty),
+                        tpred.with_replaced_self_ty(self.tcx, new_self_ty),
                     )),
                 ),
             );
diff --git a/compiler/rustc_hir_typeck/src/upvar.rs b/compiler/rustc_hir_typeck/src/upvar.rs
index df38c3a1214..50fa3f2cc9d 100644
--- a/compiler/rustc_hir_typeck/src/upvar.rs
+++ b/compiler/rustc_hir_typeck/src/upvar.rs
@@ -2391,13 +2391,11 @@ fn migration_suggestion_for_2229(
 /// let mut p = Point { x: 10, y: 10 };
 ///
 /// let c = || {
-///     p.x     += 10;
-/// // ^ E1 ^
+///     p.x += 10; // E1
 ///     // ...
 ///     // More code
 ///     // ...
 ///     p.x += 10; // E2
-/// // ^ E2 ^
 /// };
 /// ```
 /// `CaptureKind` associated with both `E1` and `E2` will be ByRef(MutBorrow),
diff --git a/compiler/rustc_index/Cargo.toml b/compiler/rustc_index/Cargo.toml
index 3d83a3c98da..e46a1a7f760 100644
--- a/compiler/rustc_index/Cargo.toml
+++ b/compiler/rustc_index/Cargo.toml
@@ -15,8 +15,8 @@ smallvec = "1.8.1"
 # tidy-alphabetical-start
 default = ["nightly"]
 nightly = [
-    "dep:rustc_serialize",
     "dep:rustc_macros",
+    "dep:rustc_serialize",
     "rustc_index_macros/nightly",
 ]
 rustc_randomized_layouts = []
diff --git a/compiler/rustc_index_macros/Cargo.toml b/compiler/rustc_index_macros/Cargo.toml
index 891e7ded619..34f3109a526 100644
--- a/compiler/rustc_index_macros/Cargo.toml
+++ b/compiler/rustc_index_macros/Cargo.toml
@@ -7,9 +7,14 @@ edition = "2024"
 proc-macro = true
 
 [dependencies]
-syn = { version = "2.0.9", features = ["full", "extra-traits"] }
+# tidy-alphabetical-start
 proc-macro2 = "1"
 quote = "1"
+syn = { version = "2.0.9", features = ["full", "extra-traits"] }
+# tidy-alphabetical-end
 
 [features]
+# tidy-alphabetical-start
 nightly = []
+# tidy-alphabetical-end
+
diff --git a/compiler/rustc_infer/src/infer/at.rs b/compiler/rustc_infer/src/infer/at.rs
index 5fe795bd23a..ad19cdef4e7 100644
--- a/compiler/rustc_infer/src/infer/at.rs
+++ b/compiler/rustc_infer/src/infer/at.rs
@@ -71,6 +71,7 @@ impl<'tcx> InferCtxt<'tcx> {
             tcx: self.tcx,
             typing_mode: self.typing_mode,
             considering_regions: self.considering_regions,
+            in_hir_typeck: self.in_hir_typeck,
             skip_leak_check: self.skip_leak_check,
             inner: self.inner.clone(),
             lexical_region_resolutions: self.lexical_region_resolutions.clone(),
@@ -95,6 +96,7 @@ impl<'tcx> InferCtxt<'tcx> {
             tcx: self.tcx,
             typing_mode,
             considering_regions: self.considering_regions,
+            in_hir_typeck: self.in_hir_typeck,
             skip_leak_check: self.skip_leak_check,
             inner: self.inner.clone(),
             lexical_region_resolutions: self.lexical_region_resolutions.clone(),
diff --git a/compiler/rustc_infer/src/infer/canonical/canonicalizer.rs b/compiler/rustc_infer/src/infer/canonical/canonicalizer.rs
index 060447ba720..3ad14dc79d5 100644
--- a/compiler/rustc_infer/src/infer/canonical/canonicalizer.rs
+++ b/compiler/rustc_infer/src/infer/canonical/canonicalizer.rs
@@ -44,7 +44,7 @@ impl<'tcx> InferCtxt<'tcx> {
     where
         V: TypeFoldable<TyCtxt<'tcx>>,
     {
-        let (param_env, value) = value.into_parts();
+        let ty::ParamEnvAnd { param_env, value } = value;
         let canonical_param_env = self.tcx.canonical_param_env_cache.get_or_insert(
             self.tcx,
             param_env,
@@ -752,7 +752,8 @@ impl<'cx, 'tcx> Canonicalizer<'cx, 'tcx> {
     ) -> Ty<'tcx> {
         debug_assert!(!self.infcx.is_some_and(|infcx| ty_var != infcx.shallow_resolve(ty_var)));
         let var = self.canonical_var(var_kind, ty_var.into());
-        Ty::new_bound(self.tcx, self.binder_index, var.into())
+        let bt = ty::BoundTy { var, kind: ty::BoundTyKind::Anon };
+        Ty::new_bound(self.tcx, self.binder_index, bt)
     }
 
     /// Given a type variable `const_var` of the given kind, first check
@@ -768,6 +769,7 @@ impl<'cx, 'tcx> Canonicalizer<'cx, 'tcx> {
             !self.infcx.is_some_and(|infcx| ct_var != infcx.shallow_resolve_const(ct_var))
         );
         let var = self.canonical_var(var_kind, ct_var.into());
-        ty::Const::new_bound(self.tcx, self.binder_index, var)
+        let bc = ty::BoundConst { var };
+        ty::Const::new_bound(self.tcx, self.binder_index, bc)
     }
 }
diff --git a/compiler/rustc_infer/src/infer/canonical/instantiate.rs b/compiler/rustc_infer/src/infer/canonical/instantiate.rs
index 2385c68ef6b..cc052fbd85c 100644
--- a/compiler/rustc_infer/src/infer/canonical/instantiate.rs
+++ b/compiler/rustc_infer/src/infer/canonical/instantiate.rs
@@ -133,7 +133,7 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for CanonicalInstantiator<'tcx> {
     fn fold_const(&mut self, ct: ty::Const<'tcx>) -> ty::Const<'tcx> {
         match ct.kind() {
             ty::ConstKind::Bound(debruijn, bound_const) if debruijn == self.current_index => {
-                self.var_values[bound_const.as_usize()].expect_const()
+                self.var_values[bound_const.var.as_usize()].expect_const()
             }
             _ => ct.super_fold_with(self),
         }
@@ -217,7 +217,7 @@ fn highest_var_in_clauses<'tcx>(c: ty::Clauses<'tcx>) -> usize {
             if let ty::ConstKind::Bound(debruijn, bound_const) = ct.kind()
                 && debruijn == self.current_index
             {
-                self.max_var = self.max_var.max(bound_const.as_usize());
+                self.max_var = self.max_var.max(bound_const.var.as_usize());
             } else if ct.has_vars_bound_at_or_above(self.current_index) {
                 ct.super_visit_with(self);
             }
diff --git a/compiler/rustc_infer/src/infer/canonical/query_response.rs b/compiler/rustc_infer/src/infer/canonical/query_response.rs
index 6be53c948c8..09578598114 100644
--- a/compiler/rustc_infer/src/infer/canonical/query_response.rs
+++ b/compiler/rustc_infer/src/infer/canonical/query_response.rs
@@ -21,7 +21,7 @@ use crate::infer::canonical::{
     Canonical, CanonicalQueryResponse, CanonicalVarValues, Certainty, OriginalQueryValues,
     QueryRegionConstraints, QueryResponse,
 };
-use crate::infer::region_constraints::{Constraint, RegionConstraintData};
+use crate::infer::region_constraints::RegionConstraintData;
 use crate::infer::{
     DefineOpaqueTypes, InferCtxt, InferOk, InferResult, SubregionOrigin, TypeOutlivesConstraint,
 };
@@ -105,8 +105,6 @@ impl<'tcx> InferCtxt<'tcx> {
     where
         T: Debug + TypeFoldable<TyCtxt<'tcx>>,
     {
-        let tcx = self.tcx;
-
         // Select everything, returning errors.
         let errors = fulfill_cx.select_all_or_error(self);
 
@@ -120,7 +118,6 @@ impl<'tcx> InferCtxt<'tcx> {
         debug!(?region_obligations);
         let region_constraints = self.with_region_constraints(|region_constraints| {
             make_query_region_constraints(
-                tcx,
                 region_obligations,
                 region_constraints,
                 region_assumptions,
@@ -433,12 +430,12 @@ impl<'tcx> InferCtxt<'tcx> {
                 }
                 GenericArgKind::Lifetime(result_value) => {
                     // e.g., here `result_value` might be `'?1` in the example above...
-                    if let ty::ReBound(debruijn, br) = result_value.kind() {
+                    if let ty::ReBound(debruijn, b) = result_value.kind() {
                         // ... in which case we would set `canonical_vars[0]` to `Some('static)`.
 
                         // We only allow a `ty::INNERMOST` index in generic parameters.
                         assert_eq!(debruijn, ty::INNERMOST);
-                        opt_values[br.var] = Some(*original_value);
+                        opt_values[b.var] = Some(*original_value);
                     }
                 }
                 GenericArgKind::Const(result_value) => {
@@ -447,7 +444,7 @@ impl<'tcx> InferCtxt<'tcx> {
 
                         // We only allow a `ty::INNERMOST` index in generic parameters.
                         assert_eq!(debruijn, ty::INNERMOST);
-                        opt_values[b] = Some(*original_value);
+                        opt_values[b.var] = Some(*original_value);
                     }
                 }
             }
@@ -587,7 +584,6 @@ impl<'tcx> InferCtxt<'tcx> {
 /// Given the region obligations and constraints scraped from the infcx,
 /// creates query region constraints.
 pub fn make_query_region_constraints<'tcx>(
-    tcx: TyCtxt<'tcx>,
     outlives_obligations: Vec<TypeOutlivesConstraint<'tcx>>,
     region_constraints: &RegionConstraintData<'tcx>,
     assumptions: Vec<ty::ArgOutlivesPredicate<'tcx>>,
@@ -600,22 +596,9 @@ pub fn make_query_region_constraints<'tcx>(
 
     let outlives: Vec<_> = constraints
         .iter()
-        .map(|(k, origin)| {
-            let constraint = match *k {
-                // Swap regions because we are going from sub (<=) to outlives
-                // (>=).
-                Constraint::VarSubVar(v1, v2) => ty::OutlivesPredicate(
-                    ty::Region::new_var(tcx, v2).into(),
-                    ty::Region::new_var(tcx, v1),
-                ),
-                Constraint::VarSubReg(v1, r2) => {
-                    ty::OutlivesPredicate(r2.into(), ty::Region::new_var(tcx, v1))
-                }
-                Constraint::RegSubVar(r1, v2) => {
-                    ty::OutlivesPredicate(ty::Region::new_var(tcx, v2).into(), r1)
-                }
-                Constraint::RegSubReg(r1, r2) => ty::OutlivesPredicate(r2.into(), r1),
-            };
+        .map(|(c, origin)| {
+            // Swap regions because we are going from sub (<=) to outlives (>=).
+            let constraint = ty::OutlivesPredicate(c.sup.into(), c.sub);
             (constraint, origin.to_constraint_category())
         })
         .chain(outlives_obligations.into_iter().map(|obl| {
diff --git a/compiler/rustc_infer/src/infer/context.rs b/compiler/rustc_infer/src/infer/context.rs
index bb9c8850093..21e999b080d 100644
--- a/compiler/rustc_infer/src/infer/context.rs
+++ b/compiler/rustc_infer/src/infer/context.rs
@@ -22,6 +22,10 @@ impl<'tcx> rustc_type_ir::InferCtxtLike for InferCtxt<'tcx> {
         self.next_trait_solver
     }
 
+    fn in_hir_typeck(&self) -> bool {
+        self.in_hir_typeck
+    }
+
     fn typing_mode(&self) -> ty::TypingMode<'tcx> {
         self.typing_mode()
     }
diff --git a/compiler/rustc_infer/src/infer/lexical_region_resolve/mod.rs b/compiler/rustc_infer/src/infer/lexical_region_resolve/mod.rs
index 2185886901e..3adcfb42727 100644
--- a/compiler/rustc_infer/src/infer/lexical_region_resolve/mod.rs
+++ b/compiler/rustc_infer/src/infer/lexical_region_resolve/mod.rs
@@ -19,7 +19,7 @@ use tracing::{debug, instrument};
 
 use super::outlives::test_type_match;
 use crate::infer::region_constraints::{
-    Constraint, GenericKind, RegionConstraintData, VarInfos, VerifyBound,
+    Constraint, ConstraintKind, GenericKind, RegionConstraintData, VarInfos, VerifyBound,
 };
 use crate::infer::{RegionRelations, RegionVariableOrigin, SubregionOrigin};
 
@@ -187,91 +187,96 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> {
         let mut constraints = IndexVec::from_elem(Vec::new(), &var_values.values);
         // Tracks the changed region vids.
         let mut changes = Vec::new();
-        for (constraint, _) in &self.data.constraints {
-            match *constraint {
-                Constraint::RegSubVar(a_region, b_vid) => {
-                    let b_data = var_values.value_mut(b_vid);
-
-                    if self.expand_node(a_region, b_vid, b_data) {
-                        changes.push(b_vid);
+        for (c, _) in &self.data.constraints {
+            match c.kind {
+                ConstraintKind::RegSubVar => {
+                    let sup_vid = c.sup.as_var();
+                    let sup_data = var_values.value_mut(sup_vid);
+
+                    if self.expand_node(c.sub, sup_vid, sup_data) {
+                        changes.push(sup_vid);
                     }
                 }
-                Constraint::VarSubVar(a_vid, b_vid) => match *var_values.value(a_vid) {
-                    VarValue::ErrorValue => continue,
-                    VarValue::Empty(a_universe) => {
-                        let b_data = var_values.value_mut(b_vid);
-
-                        let changed = match *b_data {
-                            VarValue::Empty(b_universe) => {
-                                // Empty regions are ordered according to the universe
-                                // they are associated with.
-                                let ui = a_universe.min(b_universe);
-
-                                debug!(
-                                    "Expanding value of {:?} \
+                ConstraintKind::VarSubVar => {
+                    let sub_vid = c.sub.as_var();
+                    let sup_vid = c.sup.as_var();
+                    match *var_values.value(sub_vid) {
+                        VarValue::ErrorValue => continue,
+                        VarValue::Empty(sub_universe) => {
+                            let sup_data = var_values.value_mut(sup_vid);
+
+                            let changed = match *sup_data {
+                                VarValue::Empty(sup_universe) => {
+                                    // Empty regions are ordered according to the universe
+                                    // they are associated with.
+                                    let ui = sub_universe.min(sup_universe);
+
+                                    debug!(
+                                        "Expanding value of {:?} \
                                     from empty lifetime with universe {:?} \
                                     to empty lifetime with universe {:?}",
-                                    b_vid, b_universe, ui
-                                );
+                                        sup_vid, sup_universe, ui
+                                    );
 
-                                *b_data = VarValue::Empty(ui);
-                                true
-                            }
-                            VarValue::Value(cur_region) => {
-                                match cur_region.kind() {
-                                    // If this empty region is from a universe that can name the
-                                    // placeholder universe, then the LUB is the Placeholder region
-                                    // (which is the cur_region). Otherwise, the LUB is the Static
-                                    // lifetime.
-                                    RePlaceholder(placeholder)
-                                        if !a_universe.can_name(placeholder.universe) =>
-                                    {
-                                        let lub = self.tcx().lifetimes.re_static;
-                                        debug!(
-                                            "Expanding value of {:?} from {:?} to {:?}",
-                                            b_vid, cur_region, lub
-                                        );
-
-                                        *b_data = VarValue::Value(lub);
-                                        true
+                                    *sup_data = VarValue::Empty(ui);
+                                    true
+                                }
+                                VarValue::Value(cur_region) => {
+                                    match cur_region.kind() {
+                                        // If this empty region is from a universe that can name
+                                        // the placeholder universe, then the LUB is the
+                                        // Placeholder region (which is the cur_region). Otherwise,
+                                        // the LUB is the Static lifetime.
+                                        RePlaceholder(placeholder)
+                                            if !sub_universe.can_name(placeholder.universe) =>
+                                        {
+                                            let lub = self.tcx().lifetimes.re_static;
+                                            debug!(
+                                                "Expanding value of {:?} from {:?} to {:?}",
+                                                sup_vid, cur_region, lub
+                                            );
+
+                                            *sup_data = VarValue::Value(lub);
+                                            true
+                                        }
+
+                                        _ => false,
                                     }
-
-                                    _ => false,
                                 }
-                            }
 
-                            VarValue::ErrorValue => false,
-                        };
+                                VarValue::ErrorValue => false,
+                            };
 
-                        if changed {
-                            changes.push(b_vid);
-                        }
-                        match b_data {
-                            VarValue::Value(Region(Interned(ReStatic, _)))
-                            | VarValue::ErrorValue => (),
-                            _ => {
-                                constraints[a_vid].push((a_vid, b_vid));
-                                constraints[b_vid].push((a_vid, b_vid));
+                            if changed {
+                                changes.push(sup_vid);
+                            }
+                            match sup_data {
+                                VarValue::Value(Region(Interned(ReStatic, _)))
+                                | VarValue::ErrorValue => (),
+                                _ => {
+                                    constraints[sub_vid].push((sub_vid, sup_vid));
+                                    constraints[sup_vid].push((sub_vid, sup_vid));
+                                }
                             }
                         }
-                    }
-                    VarValue::Value(a_region) => {
-                        let b_data = var_values.value_mut(b_vid);
+                        VarValue::Value(sub_region) => {
+                            let sup_data = var_values.value_mut(sup_vid);
 
-                        if self.expand_node(a_region, b_vid, b_data) {
-                            changes.push(b_vid);
-                        }
-                        match b_data {
-                            VarValue::Value(Region(Interned(ReStatic, _)))
-                            | VarValue::ErrorValue => (),
-                            _ => {
-                                constraints[a_vid].push((a_vid, b_vid));
-                                constraints[b_vid].push((a_vid, b_vid));
+                            if self.expand_node(sub_region, sup_vid, sup_data) {
+                                changes.push(sup_vid);
+                            }
+                            match sup_data {
+                                VarValue::Value(Region(Interned(ReStatic, _)))
+                                | VarValue::ErrorValue => (),
+                                _ => {
+                                    constraints[sub_vid].push((sub_vid, sup_vid));
+                                    constraints[sup_vid].push((sub_vid, sup_vid));
+                                }
                             }
                         }
                     }
-                },
-                Constraint::RegSubReg(..) | Constraint::VarSubReg(..) => {
+                }
+                ConstraintKind::RegSubReg | ConstraintKind::VarSubReg => {
                     // These constraints are checked after expansion
                     // is done, in `collect_errors`.
                     continue;
@@ -528,49 +533,48 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> {
         var_data: &mut LexicalRegionResolutions<'tcx>,
         errors: &mut Vec<RegionResolutionError<'tcx>>,
     ) {
-        for (constraint, origin) in &self.data.constraints {
-            debug!(?constraint, ?origin);
-            match *constraint {
-                Constraint::RegSubVar(..) | Constraint::VarSubVar(..) => {
+        for (c, origin) in &self.data.constraints {
+            debug!(?c, ?origin);
+            match c.kind {
+                ConstraintKind::RegSubVar | ConstraintKind::VarSubVar => {
                     // Expansion will ensure that these constraints hold. Ignore.
                 }
 
-                Constraint::RegSubReg(sub, sup) => {
-                    if self.sub_concrete_regions(sub, sup) {
+                ConstraintKind::RegSubReg => {
+                    if self.sub_concrete_regions(c.sub, c.sup) {
                         continue;
                     }
 
                     debug!(
-                        "region error at {:?}: \
-                         cannot verify that {:?} <= {:?}",
-                        origin, sub, sup
+                        "region error at {:?}: cannot verify that {:?} <= {:?}",
+                        origin, c.sub, c.sup
                     );
 
                     errors.push(RegionResolutionError::ConcreteFailure(
                         (*origin).clone(),
-                        sub,
-                        sup,
+                        c.sub,
+                        c.sup,
                     ));
                 }
 
-                Constraint::VarSubReg(a_vid, b_region) => {
-                    let a_data = var_data.value_mut(a_vid);
-                    debug!("contraction: {:?} == {:?}, {:?}", a_vid, a_data, b_region);
+                ConstraintKind::VarSubReg => {
+                    let sub_vid = c.sub.as_var();
+                    let sub_data = var_data.value_mut(sub_vid);
+                    debug!("contraction: {:?} == {:?}, {:?}", sub_vid, sub_data, c.sup);
 
-                    let VarValue::Value(a_region) = *a_data else {
+                    let VarValue::Value(sub_region) = *sub_data else {
                         continue;
                     };
 
                     // Do not report these errors immediately:
                     // instead, set the variable value to error and
                     // collect them later.
-                    if !self.sub_concrete_regions(a_region, b_region) {
+                    if !self.sub_concrete_regions(sub_region, c.sup) {
                         debug!(
-                            "region error at {:?}: \
-                            cannot verify that {:?}={:?} <= {:?}",
-                            origin, a_vid, a_region, b_region
+                            "region error at {:?}: cannot verify that {:?}={:?} <= {:?}",
+                            origin, sub_vid, sub_region, c.sup
                         );
-                        *a_data = VarValue::ErrorValue;
+                        *sub_data = VarValue::ErrorValue;
                     }
                 }
             }
@@ -682,18 +686,20 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> {
         let dummy_source = graph.add_node(());
         let dummy_sink = graph.add_node(());
 
-        for (constraint, _) in &self.data.constraints {
-            match *constraint {
-                Constraint::VarSubVar(a_id, b_id) => {
-                    graph.add_edge(NodeIndex(a_id.index()), NodeIndex(b_id.index()), *constraint);
+        for (c, _) in &self.data.constraints {
+            match c.kind {
+                ConstraintKind::VarSubVar => {
+                    let sub_vid = c.sub.as_var();
+                    let sup_vid = c.sup.as_var();
+                    graph.add_edge(NodeIndex(sub_vid.index()), NodeIndex(sup_vid.index()), *c);
                 }
-                Constraint::RegSubVar(_, b_id) => {
-                    graph.add_edge(dummy_source, NodeIndex(b_id.index()), *constraint);
+                ConstraintKind::RegSubVar => {
+                    graph.add_edge(dummy_source, NodeIndex(c.sup.as_var().index()), *c);
                 }
-                Constraint::VarSubReg(a_id, _) => {
-                    graph.add_edge(NodeIndex(a_id.index()), dummy_sink, *constraint);
+                ConstraintKind::VarSubReg => {
+                    graph.add_edge(NodeIndex(c.sub.as_var().index()), dummy_sink, *c);
                 }
-                Constraint::RegSubReg(..) => {
+                ConstraintKind::RegSubReg => {
                     // this would be an edge from `dummy_source` to
                     // `dummy_sink`; just ignore it.
                 }
@@ -878,26 +884,30 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> {
 
             let source_node_index = NodeIndex(source_vid.index());
             for (_, edge) in graph.adjacent_edges(source_node_index, dir) {
-                match edge.data {
-                    Constraint::VarSubVar(from_vid, to_vid) => {
+                let get_origin =
+                    || this.constraints.iter().find(|(c, _)| *c == edge.data).unwrap().1.clone();
+
+                match edge.data.kind {
+                    ConstraintKind::VarSubVar => {
+                        let from_vid = edge.data.sub.as_var();
+                        let to_vid = edge.data.sup.as_var();
                         let opp_vid = if from_vid == source_vid { to_vid } else { from_vid };
                         if state.set.insert(opp_vid) {
                             state.stack.push(opp_vid);
                         }
                     }
 
-                    Constraint::RegSubVar(region, _) | Constraint::VarSubReg(_, region) => {
-                        let origin = this
-                            .constraints
-                            .iter()
-                            .find(|(c, _)| *c == edge.data)
-                            .unwrap()
-                            .1
-                            .clone();
-                        state.result.push(RegionAndOrigin { region, origin });
+                    ConstraintKind::RegSubVar => {
+                        let origin = get_origin();
+                        state.result.push(RegionAndOrigin { region: edge.data.sub, origin });
+                    }
+
+                    ConstraintKind::VarSubReg => {
+                        let origin = get_origin();
+                        state.result.push(RegionAndOrigin { region: edge.data.sup, origin });
                     }
 
-                    Constraint::RegSubReg(..) => panic!(
+                    ConstraintKind::RegSubReg => panic!(
                         "cannot reach reg-sub-reg edge in region inference \
                          post-processing"
                     ),
diff --git a/compiler/rustc_infer/src/infer/mod.rs b/compiler/rustc_infer/src/infer/mod.rs
index 2d269e320b6..7379df7c7c7 100644
--- a/compiler/rustc_infer/src/infer/mod.rs
+++ b/compiler/rustc_infer/src/infer/mod.rs
@@ -37,10 +37,11 @@ use snapshot::undo_log::InferCtxtUndoLogs;
 use tracing::{debug, instrument};
 use type_variable::TypeVariableOrigin;
 
-use crate::infer::region_constraints::UndoLog;
+use crate::infer::snapshot::undo_log::UndoLog;
 use crate::infer::unify_key::{ConstVariableOrigin, ConstVariableValue, ConstVidKey};
 use crate::traits::{
-    self, ObligationCause, ObligationInspector, PredicateObligations, TraitEngine,
+    self, ObligationCause, ObligationInspector, PredicateObligation, PredicateObligations,
+    TraitEngine,
 };
 
 pub mod at;
@@ -156,6 +157,12 @@ pub struct InferCtxtInner<'tcx> {
     /// which may cause types to no longer be considered well-formed.
     region_assumptions: Vec<ty::ArgOutlivesPredicate<'tcx>>,
 
+    /// `-Znext-solver`: Successfully proven goals during HIR typeck which
+    /// reference inference variables and get reproven after writeback.
+    ///
+    /// See the documentation of `InferCtxt::in_hir_typeck` for more details.
+    hir_typeck_potentially_region_dependent_goals: Vec<PredicateObligation<'tcx>>,
+
     /// Caches for opaque type inference.
     opaque_type_storage: OpaqueTypeStorage<'tcx>,
 }
@@ -173,6 +180,7 @@ impl<'tcx> InferCtxtInner<'tcx> {
             region_constraint_storage: Some(Default::default()),
             region_obligations: Default::default(),
             region_assumptions: Default::default(),
+            hir_typeck_potentially_region_dependent_goals: Default::default(),
             opaque_type_storage: Default::default(),
         }
     }
@@ -244,9 +252,29 @@ pub struct InferCtxt<'tcx> {
     typing_mode: TypingMode<'tcx>,
 
     /// Whether this inference context should care about region obligations in
-    /// the root universe. Most notably, this is used during hir typeck as region
+    /// the root universe. Most notably, this is used during HIR typeck as region
     /// solving is left to borrowck instead.
     pub considering_regions: bool,
+    /// `-Znext-solver`: Whether this inference context is used by HIR typeck. If so, we
+    /// need to make sure we don't rely on region identity in the trait solver or when
+    /// relating types. This is necessary as borrowck starts by replacing each occurrence of a
+    /// free region with a unique inference variable. If HIR typeck ends up depending on two
+    /// regions being equal we'd get unexpected mismatches between HIR typeck and MIR typeck,
+    /// resulting in an ICE.
+    ///
+    /// The trait solver sometimes depends on regions being identical. As a concrete example
+    /// the trait solver ignores other candidates if one candidate exists without any constraints.
+    /// The goal `&'a u32: Equals<&'a u32>` has no constraints right now. If we replace each
+    /// occurrence of `'a` with a unique region the goal now equates these regions. See
+    /// the tests in trait-system-refactor-initiative#27 for concrete examples.
+    ///
+    /// We handle this by *uniquifying* region when canonicalizing root goals during HIR typeck.
+    /// This is still insufficient as inference variables may *hide* region variables, so e.g.
+    /// `dyn TwoSuper<?x, ?x>: Super<?x>` may hold but MIR typeck could end up having to prove
+    /// `dyn TwoSuper<&'0 (), &'1 ()>: Super<&'2 ()>` which is now ambiguous. Because of this we
+    /// stash all successfully proven goals which reference inference variables and then reprove
+    /// them after writeback.
+    pub in_hir_typeck: bool,
 
     /// If set, this flag causes us to skip the 'leak check' during
     /// higher-ranked subtyping operations. This flag is a temporary one used
@@ -506,6 +534,7 @@ pub struct TypeOutlivesConstraint<'tcx> {
 pub struct InferCtxtBuilder<'tcx> {
     tcx: TyCtxt<'tcx>,
     considering_regions: bool,
+    in_hir_typeck: bool,
     skip_leak_check: bool,
     /// Whether we should use the new trait solver in the local inference context,
     /// which affects things like which solver is used in `predicate_may_hold`.
@@ -518,6 +547,7 @@ impl<'tcx> TyCtxt<'tcx> {
         InferCtxtBuilder {
             tcx: self,
             considering_regions: true,
+            in_hir_typeck: false,
             skip_leak_check: false,
             next_trait_solver: self.next_trait_solver_globally(),
         }
@@ -535,6 +565,11 @@ impl<'tcx> InferCtxtBuilder<'tcx> {
         self
     }
 
+    pub fn in_hir_typeck(mut self) -> Self {
+        self.in_hir_typeck = true;
+        self
+    }
+
     pub fn skip_leak_check(mut self, skip_leak_check: bool) -> Self {
         self.skip_leak_check = skip_leak_check;
         self
@@ -568,12 +603,18 @@ impl<'tcx> InferCtxtBuilder<'tcx> {
     }
 
     pub fn build(&mut self, typing_mode: TypingMode<'tcx>) -> InferCtxt<'tcx> {
-        let InferCtxtBuilder { tcx, considering_regions, skip_leak_check, next_trait_solver } =
-            *self;
+        let InferCtxtBuilder {
+            tcx,
+            considering_regions,
+            in_hir_typeck,
+            skip_leak_check,
+            next_trait_solver,
+        } = *self;
         InferCtxt {
             tcx,
             typing_mode,
             considering_regions,
+            in_hir_typeck,
             skip_leak_check,
             inner: RefCell::new(InferCtxtInner::new()),
             lexical_region_resolutions: RefCell::new(None),
@@ -978,6 +1019,22 @@ impl<'tcx> InferCtxt<'tcx> {
         }
     }
 
+    pub fn push_hir_typeck_potentially_region_dependent_goal(
+        &self,
+        goal: PredicateObligation<'tcx>,
+    ) {
+        let mut inner = self.inner.borrow_mut();
+        inner.undo_log.push(UndoLog::PushHirTypeckPotentiallyRegionDependentGoal);
+        inner.hir_typeck_potentially_region_dependent_goals.push(goal);
+    }
+
+    pub fn take_hir_typeck_potentially_region_dependent_goals(
+        &self,
+    ) -> Vec<PredicateObligation<'tcx>> {
+        assert!(!self.in_snapshot(), "cannot take goals in a snapshot");
+        std::mem::take(&mut self.inner.borrow_mut().hir_typeck_potentially_region_dependent_goals)
+    }
+
     pub fn ty_to_string(&self, t: Ty<'tcx>) -> String {
         self.resolve_vars_if_possible(t).to_string()
     }
@@ -1208,8 +1265,8 @@ impl<'tcx> InferCtxt<'tcx> {
             fn replace_ty(&mut self, bt: ty::BoundTy) -> Ty<'tcx> {
                 self.args[bt.var.index()].expect_ty()
             }
-            fn replace_const(&mut self, bv: ty::BoundVar) -> ty::Const<'tcx> {
-                self.args[bv.index()].expect_const()
+            fn replace_const(&mut self, bc: ty::BoundConst) -> ty::Const<'tcx> {
+                self.args[bc.var.index()].expect_const()
             }
         }
         let delegate = ToFreshVars { args };
diff --git a/compiler/rustc_infer/src/infer/outlives/mod.rs b/compiler/rustc_infer/src/infer/outlives/mod.rs
index 19911bfbd48..c992cda8aae 100644
--- a/compiler/rustc_infer/src/infer/outlives/mod.rs
+++ b/compiler/rustc_infer/src/infer/outlives/mod.rs
@@ -10,7 +10,7 @@ use super::region_constraints::{RegionConstraintData, UndoLog};
 use super::{InferCtxt, RegionResolutionError, SubregionOrigin};
 use crate::infer::free_regions::RegionRelations;
 use crate::infer::lexical_region_resolve;
-use crate::infer::region_constraints::Constraint;
+use crate::infer::region_constraints::ConstraintKind;
 
 pub mod env;
 pub mod for_liveness;
@@ -70,10 +70,10 @@ impl<'tcx> InferCtxt<'tcx> {
         // Filter out any region-region outlives assumptions that are implied by
         // coroutine well-formedness.
         if self.tcx.sess.opts.unstable_opts.higher_ranked_assumptions {
-            storage.data.constraints.retain(|(constraint, _)| match *constraint {
-                Constraint::RegSubReg(r1, r2) => !outlives_env
+            storage.data.constraints.retain(|(c, _)| match c.kind {
+                ConstraintKind::RegSubReg => !outlives_env
                     .higher_ranked_assumptions()
-                    .contains(&ty::OutlivesPredicate(r2.into(), r1)),
+                    .contains(&ty::OutlivesPredicate(c.sup.into(), c.sub)),
                 _ => true,
             });
         }
diff --git a/compiler/rustc_infer/src/infer/outlives/obligations.rs b/compiler/rustc_infer/src/infer/outlives/obligations.rs
index a8520c0e71d..b989d419057 100644
--- a/compiler/rustc_infer/src/infer/outlives/obligations.rs
+++ b/compiler/rustc_infer/src/infer/outlives/obligations.rs
@@ -36,7 +36,7 @@
 //! fn bar<T>(a: T, b: impl for<'a> Fn(&'a T)) {}
 //! fn foo<T>(x: T) {
 //!     bar(x, |y| { /* ... */})
-//!          // ^ closure arg
+//!     //      ^ closure arg
 //! }
 //! ```
 //!
@@ -177,6 +177,7 @@ impl<'tcx> InferCtxt<'tcx> {
     }
 
     pub fn take_registered_region_assumptions(&self) -> Vec<ty::ArgOutlivesPredicate<'tcx>> {
+        assert!(!self.in_snapshot(), "cannot take registered region assumptions in a snapshot");
         std::mem::take(&mut self.inner.borrow_mut().region_assumptions)
     }
 
diff --git a/compiler/rustc_infer/src/infer/region_constraints/leak_check.rs b/compiler/rustc_infer/src/infer/region_constraints/leak_check.rs
index e332b6d0447..4d76bc2e17a 100644
--- a/compiler/rustc_infer/src/infer/region_constraints/leak_check.rs
+++ b/compiler/rustc_infer/src/infer/region_constraints/leak_check.rs
@@ -83,7 +83,7 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
             return Ok(());
         }
 
-        let mini_graph = MiniGraph::new(tcx, &self, only_consider_snapshot);
+        let mini_graph = MiniGraph::new(&self, only_consider_snapshot);
 
         let mut leak_check = LeakCheck::new(tcx, outer_universe, max_universe, mini_graph, self);
         leak_check.assign_placeholder_values()?;
@@ -359,7 +359,6 @@ struct MiniGraph<'tcx> {
 
 impl<'tcx> MiniGraph<'tcx> {
     fn new(
-        tcx: TyCtxt<'tcx>,
         region_constraints: &RegionConstraintCollector<'_, 'tcx>,
         only_consider_snapshot: Option<&CombinedSnapshot<'tcx>>,
     ) -> Self {
@@ -368,7 +367,6 @@ impl<'tcx> MiniGraph<'tcx> {
 
         // Note that if `R2: R1`, we get a callback `r1, r2`, so `target` is first parameter.
         Self::iterate_region_constraints(
-            tcx,
             region_constraints,
             only_consider_snapshot,
             |target, source| {
@@ -384,33 +382,18 @@ impl<'tcx> MiniGraph<'tcx> {
 
     /// Invokes `each_edge(R1, R2)` for each edge where `R2: R1`
     fn iterate_region_constraints(
-        tcx: TyCtxt<'tcx>,
         region_constraints: &RegionConstraintCollector<'_, 'tcx>,
         only_consider_snapshot: Option<&CombinedSnapshot<'tcx>>,
         mut each_edge: impl FnMut(ty::Region<'tcx>, ty::Region<'tcx>),
     ) {
-        let mut each_constraint = |constraint| match constraint {
-            &Constraint::VarSubVar(a, b) => {
-                each_edge(ty::Region::new_var(tcx, a), ty::Region::new_var(tcx, b));
-            }
-            &Constraint::RegSubVar(a, b) => {
-                each_edge(a, ty::Region::new_var(tcx, b));
-            }
-            &Constraint::VarSubReg(a, b) => {
-                each_edge(ty::Region::new_var(tcx, a), b);
-            }
-            &Constraint::RegSubReg(a, b) => {
-                each_edge(a, b);
-            }
-        };
-
         if let Some(snapshot) = only_consider_snapshot {
             for undo_entry in
                 region_constraints.undo_log.region_constraints_in_snapshot(&snapshot.undo_snapshot)
             {
                 match undo_entry {
                     &AddConstraint(i) => {
-                        each_constraint(&region_constraints.data().constraints[i].0);
+                        let c = region_constraints.data().constraints[i].0;
+                        each_edge(c.sub, c.sup);
                     }
                     &AddVerify(i) => span_bug!(
                         region_constraints.data().verifys[i].origin.span(),
@@ -420,11 +403,7 @@ impl<'tcx> MiniGraph<'tcx> {
                 }
             }
         } else {
-            region_constraints
-                .data()
-                .constraints
-                .iter()
-                .for_each(|(constraint, _)| each_constraint(constraint));
+            region_constraints.data().constraints.iter().for_each(|(c, _)| each_edge(c.sub, c.sup))
         }
     }
 
diff --git a/compiler/rustc_infer/src/infer/region_constraints/mod.rs b/compiler/rustc_infer/src/infer/region_constraints/mod.rs
index a1744b4df80..85f5e55a8e1 100644
--- a/compiler/rustc_infer/src/infer/region_constraints/mod.rs
+++ b/compiler/rustc_infer/src/infer/region_constraints/mod.rs
@@ -80,31 +80,37 @@ pub struct RegionConstraintData<'tcx> {
 
 /// Represents a constraint that influences the inference process.
 #[derive(Clone, Copy, PartialEq, Eq, Debug, Hash)]
-pub enum Constraint<'tcx> {
+pub enum ConstraintKind {
     /// A region variable is a subregion of another.
-    VarSubVar(RegionVid, RegionVid),
+    VarSubVar,
 
     /// A concrete region is a subregion of region variable.
-    RegSubVar(Region<'tcx>, RegionVid),
+    RegSubVar,
 
     /// A region variable is a subregion of a concrete region. This does not
     /// directly affect inference, but instead is checked after
     /// inference is complete.
-    VarSubReg(RegionVid, Region<'tcx>),
+    VarSubReg,
 
     /// A constraint where neither side is a variable. This does not
     /// directly affect inference, but instead is checked after
     /// inference is complete.
-    RegSubReg(Region<'tcx>, Region<'tcx>),
+    RegSubReg,
+}
+
+/// Represents a constraint that influences the inference process.
+#[derive(Clone, Copy, PartialEq, Eq, Debug, Hash)]
+pub struct Constraint<'tcx> {
+    pub kind: ConstraintKind,
+    // If `kind` is `VarSubVar` or `VarSubReg`, this must be a `ReVar`.
+    pub sub: Region<'tcx>,
+    // If `kind` is `VarSubVar` or `RegSubVar`, this must be a `ReVar`.
+    pub sup: Region<'tcx>,
 }
 
 impl Constraint<'_> {
     pub fn involves_placeholders(&self) -> bool {
-        match self {
-            Constraint::VarSubVar(_, _) => false,
-            Constraint::VarSubReg(_, r) | Constraint::RegSubVar(r, _) => r.is_placeholder(),
-            Constraint::RegSubReg(r, s) => r.is_placeholder() || s.is_placeholder(),
-        }
+        self.sub.is_placeholder() || self.sup.is_placeholder()
     }
 }
 
@@ -471,16 +477,24 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
                 // all regions are subregions of static, so we can ignore this
             }
             (ReVar(sub_id), ReVar(sup_id)) => {
-                self.add_constraint(Constraint::VarSubVar(sub_id, sup_id), origin);
-            }
-            (_, ReVar(sup_id)) => {
-                self.add_constraint(Constraint::RegSubVar(sub, sup_id), origin);
-            }
-            (ReVar(sub_id), _) => {
-                self.add_constraint(Constraint::VarSubReg(sub_id, sup), origin);
+                if sub_id != sup_id {
+                    self.add_constraint(
+                        Constraint { kind: ConstraintKind::VarSubVar, sub, sup },
+                        origin,
+                    );
+                }
             }
+            (_, ReVar(_)) => self
+                .add_constraint(Constraint { kind: ConstraintKind::RegSubVar, sub, sup }, origin),
+            (ReVar(_), _) => self
+                .add_constraint(Constraint { kind: ConstraintKind::VarSubReg, sub, sup }, origin),
             _ => {
-                self.add_constraint(Constraint::RegSubReg(sub, sup), origin);
+                if sub != sup {
+                    self.add_constraint(
+                        Constraint { kind: ConstraintKind::RegSubReg, sub, sup },
+                        origin,
+                    )
+                }
             }
         }
     }
diff --git a/compiler/rustc_infer/src/infer/relate/generalize.rs b/compiler/rustc_infer/src/infer/relate/generalize.rs
index 9e451f16a9d..a000bb1123c 100644
--- a/compiler/rustc_infer/src/infer/relate/generalize.rs
+++ b/compiler/rustc_infer/src/infer/relate/generalize.rs
@@ -19,6 +19,24 @@ use crate::infer::type_variable::TypeVariableValue;
 use crate::infer::unify_key::ConstVariableValue;
 use crate::infer::{InferCtxt, RegionVariableOrigin, relate};
 
+#[derive(Copy, Clone, Eq, PartialEq, Debug)]
+enum TermVid {
+    Ty(ty::TyVid),
+    Const(ty::ConstVid),
+}
+
+impl From<ty::TyVid> for TermVid {
+    fn from(value: ty::TyVid) -> Self {
+        TermVid::Ty(value)
+    }
+}
+
+impl From<ty::ConstVid> for TermVid {
+    fn from(value: ty::ConstVid) -> Self {
+        TermVid::Const(value)
+    }
+}
+
 impl<'tcx> InferCtxt<'tcx> {
     /// The idea is that we should ensure that the type variable `target_vid`
     /// is equal to, a subtype of, or a supertype of `source_ty`.
@@ -238,20 +256,18 @@ impl<'tcx> InferCtxt<'tcx> {
         &self,
         span: Span,
         structurally_relate_aliases: StructurallyRelateAliases,
-        target_vid: impl Into<ty::TermVid>,
+        target_vid: impl Into<TermVid>,
         ambient_variance: ty::Variance,
         source_term: T,
     ) -> RelateResult<'tcx, Generalization<T>> {
         assert!(!source_term.has_escaping_bound_vars());
         let (for_universe, root_vid) = match target_vid.into() {
-            ty::TermVid::Ty(ty_vid) => {
-                (self.probe_ty_var(ty_vid).unwrap_err(), ty::TermVid::Ty(self.root_var(ty_vid)))
+            TermVid::Ty(ty_vid) => {
+                (self.probe_ty_var(ty_vid).unwrap_err(), TermVid::Ty(self.root_var(ty_vid)))
             }
-            ty::TermVid::Const(ct_vid) => (
+            TermVid::Const(ct_vid) => (
                 self.probe_const_var(ct_vid).unwrap_err(),
-                ty::TermVid::Const(
-                    self.inner.borrow_mut().const_unification_table().find(ct_vid).vid,
-                ),
+                TermVid::Const(self.inner.borrow_mut().const_unification_table().find(ct_vid).vid),
             ),
         };
 
@@ -299,7 +315,7 @@ struct Generalizer<'me, 'tcx> {
     /// The vid of the type variable that is in the process of being
     /// instantiated. If we find this within the value we are folding,
     /// that means we would have created a cyclic value.
-    root_vid: ty::TermVid,
+    root_vid: TermVid,
 
     /// The universe of the type variable that is in the process of being
     /// instantiated. If we find anything that this universe cannot name,
@@ -469,7 +485,7 @@ impl<'tcx> TypeRelation<TyCtxt<'tcx>> for Generalizer<'_, 'tcx> {
             ty::Infer(ty::TyVar(vid)) => {
                 let mut inner = self.infcx.inner.borrow_mut();
                 let vid = inner.type_variables().root_var(vid);
-                if ty::TermVid::Ty(vid) == self.root_vid {
+                if TermVid::Ty(vid) == self.root_vid {
                     // If sub-roots are equal, then `root_vid` and
                     // `vid` are related via subtyping.
                     Err(self.cyclic_term_error())
@@ -621,7 +637,7 @@ impl<'tcx> TypeRelation<TyCtxt<'tcx>> for Generalizer<'_, 'tcx> {
                 // If root const vids are equal, then `root_vid` and
                 // `vid` are related and we'd be inferring an infinitely
                 // deep const.
-                if ty::TermVid::Const(
+                if TermVid::Const(
                     self.infcx.inner.borrow_mut().const_unification_table().find(vid).vid,
                 ) == self.root_vid
                 {
diff --git a/compiler/rustc_infer/src/infer/relate/higher_ranked.rs b/compiler/rustc_infer/src/infer/relate/higher_ranked.rs
index 2143f72a3b0..16fe591b29b 100644
--- a/compiler/rustc_infer/src/infer/relate/higher_ranked.rs
+++ b/compiler/rustc_infer/src/infer/relate/higher_ranked.rs
@@ -45,10 +45,10 @@ impl<'tcx> InferCtxt<'tcx> {
                     ty::PlaceholderType { universe: next_universe, bound: bound_ty },
                 )
             },
-            consts: &mut |bound_var: ty::BoundVar| {
+            consts: &mut |bound_const: ty::BoundConst| {
                 ty::Const::new_placeholder(
                     self.tcx,
-                    ty::PlaceholderConst { universe: next_universe, bound: bound_var },
+                    ty::PlaceholderConst { universe: next_universe, bound: bound_const },
                 )
             },
         };
diff --git a/compiler/rustc_infer/src/infer/snapshot/undo_log.rs b/compiler/rustc_infer/src/infer/snapshot/undo_log.rs
index 40e4c329446..fcc0ab3af41 100644
--- a/compiler/rustc_infer/src/infer/snapshot/undo_log.rs
+++ b/compiler/rustc_infer/src/infer/snapshot/undo_log.rs
@@ -29,6 +29,7 @@ pub(crate) enum UndoLog<'tcx> {
     ProjectionCache(traits::UndoLog<'tcx>),
     PushTypeOutlivesConstraint,
     PushRegionAssumption,
+    PushHirTypeckPotentiallyRegionDependentGoal,
 }
 
 macro_rules! impl_from {
@@ -79,7 +80,12 @@ impl<'tcx> Rollback<UndoLog<'tcx>> for InferCtxtInner<'tcx> {
                 assert_matches!(popped, Some(_), "pushed region constraint but could not pop it");
             }
             UndoLog::PushRegionAssumption => {
-                self.region_assumptions.pop();
+                let popped = self.region_assumptions.pop();
+                assert_matches!(popped, Some(_), "pushed region assumption but could not pop it");
+            }
+            UndoLog::PushHirTypeckPotentiallyRegionDependentGoal => {
+                let popped = self.hir_typeck_potentially_region_dependent_goals.pop();
+                assert_matches!(popped, Some(_), "pushed goal but could not pop it");
             }
         }
     }
diff --git a/compiler/rustc_interface/src/passes.rs b/compiler/rustc_interface/src/passes.rs
index 057fbe2fc4e..8dec8069bc7 100644
--- a/compiler/rustc_interface/src/passes.rs
+++ b/compiler/rustc_interface/src/passes.rs
@@ -29,7 +29,7 @@ use rustc_parse::{
     new_parser_from_file, new_parser_from_source_str, unwrap_or_emit_fatal, validate_attr,
 };
 use rustc_passes::{abi_test, input_stats, layout_test};
-use rustc_resolve::Resolver;
+use rustc_resolve::{Resolver, ResolverOutputs};
 use rustc_session::config::{CrateType, Input, OutFileName, OutputFilenames, OutputType};
 use rustc_session::cstore::Untracked;
 use rustc_session::output::{collect_crate_types, filename_for_input};
@@ -793,7 +793,7 @@ fn resolver_for_lowering_raw<'tcx>(
     // Make sure we don't mutate the cstore from here on.
     tcx.untracked().cstore.freeze();
 
-    let ty::ResolverOutputs {
+    let ResolverOutputs {
         global_ctxt: untracked_resolutions,
         ast_lowering: untracked_resolver_for_lowering,
     } = resolver.into_outputs();
@@ -1151,7 +1151,9 @@ fn analysis(tcx: TyCtxt<'_>, (): ()) {
 
                 parallel!(
                     {
-                        tcx.ensure_ok().check_private_in_public(());
+                        tcx.par_hir_for_each_module(|module| {
+                            tcx.ensure_ok().check_private_in_public(module)
+                        })
                     },
                     {
                         tcx.par_hir_for_each_module(|module| {
diff --git a/compiler/rustc_interface/src/tests.rs b/compiler/rustc_interface/src/tests.rs
index 8771bb44050..86faab62d03 100644
--- a/compiler/rustc_interface/src/tests.rs
+++ b/compiler/rustc_interface/src/tests.rs
@@ -778,8 +778,8 @@ fn test_unstable_options_tracking_hash() {
         coverage_options,
         CoverageOptions {
             level: CoverageLevel::Mcdc,
-            no_mir_spans: true,
-            discard_all_spans_in_codegen: true
+            // (don't collapse test-only options onto the same line)
+            discard_all_spans_in_codegen: true,
         }
     );
     tracked!(crate_attr, vec!["abc".to_string()]);
diff --git a/compiler/rustc_lint/Cargo.toml b/compiler/rustc_lint/Cargo.toml
index 64751eaf1fe..7718f16984d 100644
--- a/compiler/rustc_lint/Cargo.toml
+++ b/compiler/rustc_lint/Cargo.toml
@@ -8,7 +8,6 @@ edition = "2024"
 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_attr_parsing = { path = "../rustc_attr_parsing" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
diff --git a/compiler/rustc_lint/messages.ftl b/compiler/rustc_lint/messages.ftl
index 69fe7fe83ff..4d0c0c94a81 100644
--- a/compiler/rustc_lint/messages.ftl
+++ b/compiler/rustc_lint/messages.ftl
@@ -207,6 +207,12 @@ lint_confusable_identifier_pair = found both `{$existing_sym}` and `{$sym}` as i
 
 lint_custom_inner_attribute_unstable = custom inner attributes are unstable
 
+lint_dangling_pointers_from_locals = a dangling pointer will be produced because the local variable `{$local_var_name}` will be dropped
+    .ret_ty = return type of the {$fn_kind} is `{$ret_ty}`
+    .local_var = `{$local_var_name}` is part the {$fn_kind} and will be dropped at the end of the {$fn_kind}
+    .created_at = dangling pointer created here
+    .note = pointers do not have a lifetime; after returning, the `{$local_var_ty}` will be deallocated at the end of the {$fn_kind} because nothing is referencing it as far as the type system is concerned
+
 lint_dangling_pointers_from_temporaries = a dangling pointer will be produced because the temporary `{$ty}` will be dropped
     .label_ptr = this pointer will immediately be invalid
     .label_temporary = this `{$ty}` is deallocated at the end of the statement, bind it to a variable to extend its lifetime
diff --git a/compiler/rustc_lint/src/builtin.rs b/compiler/rustc_lint/src/builtin.rs
index 152971c4ed6..c893b723375 100644
--- a/compiler/rustc_lint/src/builtin.rs
+++ b/compiler/rustc_lint/src/builtin.rs
@@ -21,14 +21,14 @@ use rustc_ast::tokenstream::{TokenStream, TokenTree};
 use rustc_ast::visit::{FnCtxt, FnKind};
 use rustc_ast::{self as ast, *};
 use rustc_ast_pretty::pprust::expr_to_string;
-use rustc_attr_data_structures::{AttributeKind, find_attr};
 use rustc_errors::{Applicability, LintDiagnostic};
 use rustc_feature::GateIssue;
 use rustc_hir as hir;
+use rustc_hir::attrs::AttributeKind;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::{CRATE_DEF_ID, DefId, LocalDefId};
 use rustc_hir::intravisit::FnKind as HirFnKind;
-use rustc_hir::{Body, FnDecl, PatKind, PredicateOrigin};
+use rustc_hir::{Body, FnDecl, PatKind, PredicateOrigin, find_attr};
 use rustc_middle::bug;
 use rustc_middle::lint::LevelAndSource;
 use rustc_middle::ty::layout::LayoutOf;
diff --git a/compiler/rustc_lint/src/context.rs b/compiler/rustc_lint/src/context.rs
index b694d3dd49b..11181d10af5 100644
--- a/compiler/rustc_lint/src/context.rs
+++ b/compiler/rustc_lint/src/context.rs
@@ -756,22 +756,22 @@ impl<'tcx> LateContext<'tcx> {
             }
 
             fn print_region(&mut self, _region: ty::Region<'_>) -> Result<(), PrintError> {
-                Ok(())
+                unreachable!(); // because `path_generic_args` ignores the `GenericArgs`
             }
 
             fn print_type(&mut self, _ty: Ty<'tcx>) -> Result<(), PrintError> {
-                Ok(())
+                unreachable!(); // because `path_generic_args` ignores the `GenericArgs`
             }
 
             fn print_dyn_existential(
                 &mut self,
                 _predicates: &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
             ) -> Result<(), PrintError> {
-                Ok(())
+                unreachable!(); // because `path_generic_args` ignores the `GenericArgs`
             }
 
             fn print_const(&mut self, _ct: ty::Const<'tcx>) -> Result<(), PrintError> {
-                Ok(())
+                unreachable!(); // because `path_generic_args` ignores the `GenericArgs`
             }
 
             fn path_crate(&mut self, cnum: CrateNum) -> Result<(), PrintError> {
@@ -784,10 +784,10 @@ impl<'tcx> LateContext<'tcx> {
                 self_ty: Ty<'tcx>,
                 trait_ref: Option<ty::TraitRef<'tcx>>,
             ) -> Result<(), PrintError> {
-                if trait_ref.is_none() {
-                    if let ty::Adt(def, args) = self_ty.kind() {
-                        return self.print_def_path(def.did(), args);
-                    }
+                if trait_ref.is_none()
+                    && let ty::Adt(def, args) = self_ty.kind()
+                {
+                    return self.print_def_path(def.did(), args);
                 }
 
                 // This shouldn't ever be needed, but just in case:
@@ -803,7 +803,6 @@ impl<'tcx> LateContext<'tcx> {
             fn path_append_impl(
                 &mut self,
                 print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
-                _disambiguated_data: &DisambiguatedDefPathData,
                 self_ty: Ty<'tcx>,
                 trait_ref: Option<ty::TraitRef<'tcx>>,
             ) -> Result<(), PrintError> {
@@ -854,9 +853,9 @@ impl<'tcx> LateContext<'tcx> {
             }
         }
 
-        let mut printer = AbsolutePathPrinter { tcx: self.tcx, path: vec![] };
-        printer.print_def_path(def_id, &[]).unwrap();
-        printer.path
+        let mut p = AbsolutePathPrinter { tcx: self.tcx, path: vec![] };
+        p.print_def_path(def_id, &[]).unwrap();
+        p.path
     }
 
     /// Returns the associated type `name` for `self_ty` as an implementation of `trait_id`.
diff --git a/compiler/rustc_lint/src/dangling.rs b/compiler/rustc_lint/src/dangling.rs
index c737919db9c..af4457f4314 100644
--- a/compiler/rustc_lint/src/dangling.rs
+++ b/compiler/rustc_lint/src/dangling.rs
@@ -1,13 +1,14 @@
 use rustc_ast::visit::{visit_opt, walk_list};
-use rustc_attr_data_structures::{AttributeKind, find_attr};
+use rustc_hir::attrs::AttributeKind;
+use rustc_hir::def::Res;
 use rustc_hir::def_id::LocalDefId;
 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_hir::{Block, Body, Expr, ExprKind, FnDecl, FnRetTy, LangItem, TyKind, find_attr};
+use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_session::{declare_lint, impl_lint_pass};
 use rustc_span::{Span, sym};
 
-use crate::lints::DanglingPointersFromTemporaries;
+use crate::lints::{DanglingPointersFromLocals, DanglingPointersFromTemporaries};
 use crate::{LateContext, LateLintPass};
 
 declare_lint! {
@@ -42,6 +43,36 @@ declare_lint! {
     "detects getting a pointer from a temporary"
 }
 
+declare_lint! {
+    /// The `dangling_pointers_from_locals` lint detects getting a pointer to data
+    /// of a local that will be dropped at the end of the function.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// fn f() -> *const u8 {
+    ///     let x = 0;
+    ///     &x // returns a dangling ptr to `x`
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// Returning a pointer from a local value will not prolong its lifetime,
+    /// which means that the value can be dropped and the allocation freed
+    /// while the pointer still exists, making the pointer dangling.
+    /// This is not an error (as far as the type system is concerned)
+    /// but probably is not what the user intended either.
+    ///
+    /// If you need stronger guarantees, consider using references instead,
+    /// as they are statically verified by the borrow-checker to never dangle.
+    pub DANGLING_POINTERS_FROM_LOCALS,
+    Warn,
+    "detects returning a pointer from a local variable"
+}
+
 /// FIXME: false negatives (i.e. the lint is not emitted when it should be)
 /// 1. Ways to get a temporary that are not recognized:
 ///    - `owning_temporary.field`
@@ -53,20 +84,123 @@ declare_lint! {
 #[derive(Clone, Copy, Default)]
 pub(crate) struct DanglingPointers;
 
-impl_lint_pass!(DanglingPointers => [DANGLING_POINTERS_FROM_TEMPORARIES]);
+impl_lint_pass!(DanglingPointers => [DANGLING_POINTERS_FROM_TEMPORARIES, DANGLING_POINTERS_FROM_LOCALS]);
 
 // This skips over const blocks, but they cannot use or return a dangling pointer anyways.
 impl<'tcx> LateLintPass<'tcx> for DanglingPointers {
     fn check_fn(
         &mut self,
         cx: &LateContext<'tcx>,
-        _: FnKind<'tcx>,
-        _: &'tcx FnDecl<'tcx>,
+        fn_kind: FnKind<'tcx>,
+        fn_decl: &'tcx FnDecl<'tcx>,
         body: &'tcx Body<'tcx>,
         _: Span,
-        _: LocalDefId,
+        def_id: LocalDefId,
     ) {
-        DanglingPointerSearcher { cx, inside_call_args: false }.visit_body(body)
+        DanglingPointerSearcher { cx, inside_call_args: false }.visit_body(body);
+
+        if let FnRetTy::Return(ret_ty) = &fn_decl.output
+            && let TyKind::Ptr(_) = ret_ty.kind
+        {
+            // get the return type of the function or closure
+            let ty = match cx.tcx.type_of(def_id).instantiate_identity().kind() {
+                ty::FnDef(..) => cx.tcx.fn_sig(def_id).instantiate_identity(),
+                ty::Closure(_, args) => args.as_closure().sig(),
+                _ => return,
+            };
+            let ty = ty.output();
+
+            // this type is only used for layout computation and pretty-printing, neither of them rely on regions
+            let ty = cx.tcx.instantiate_bound_regions_with_erased(ty);
+
+            // verify that we have a pointer type
+            let inner_ty = match ty.kind() {
+                ty::RawPtr(inner_ty, _) => *inner_ty,
+                _ => return,
+            };
+
+            if cx
+                .tcx
+                .layout_of(cx.typing_env().as_query_input(inner_ty))
+                .is_ok_and(|layout| !layout.is_1zst())
+            {
+                let dcx = &DanglingPointerLocalContext {
+                    body: def_id,
+                    fn_ret: ty,
+                    fn_ret_span: ret_ty.span,
+                    fn_ret_inner: inner_ty,
+                    fn_kind: match fn_kind {
+                        FnKind::ItemFn(..) => "function",
+                        FnKind::Method(..) => "method",
+                        FnKind::Closure => "closure",
+                    },
+                };
+
+                // look for `return`s
+                DanglingPointerReturnSearcher { cx, dcx }.visit_body(body);
+
+                // analyze implicit return expression
+                if let ExprKind::Block(block, None) = &body.value.kind
+                    && let innermost_block = block.innermost_block()
+                    && let Some(expr) = innermost_block.expr
+                {
+                    lint_addr_of_local(cx, dcx, expr);
+                }
+            }
+        }
+    }
+}
+
+struct DanglingPointerLocalContext<'tcx> {
+    body: LocalDefId,
+    fn_ret: Ty<'tcx>,
+    fn_ret_span: Span,
+    fn_ret_inner: Ty<'tcx>,
+    fn_kind: &'static str,
+}
+
+struct DanglingPointerReturnSearcher<'lcx, 'tcx> {
+    cx: &'lcx LateContext<'tcx>,
+    dcx: &'lcx DanglingPointerLocalContext<'tcx>,
+}
+
+impl<'tcx> Visitor<'tcx> for DanglingPointerReturnSearcher<'_, 'tcx> {
+    fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) -> Self::Result {
+        if let ExprKind::Ret(Some(expr)) = expr.kind {
+            lint_addr_of_local(self.cx, self.dcx, expr);
+        }
+        walk_expr(self, expr)
+    }
+}
+
+/// Look for `&<path_to_local_in_same_body>` pattern and emit lint for it
+fn lint_addr_of_local<'a>(
+    cx: &LateContext<'a>,
+    dcx: &DanglingPointerLocalContext<'a>,
+    expr: &'a Expr<'a>,
+) {
+    // peel casts as they do not interest us here, we want the inner expression.
+    let (inner, _) = super::utils::peel_casts(cx, expr);
+
+    if let ExprKind::AddrOf(_, _, inner_of) = inner.kind
+        && let ExprKind::Path(ref qpath) = inner_of.peel_blocks().kind
+        && let Res::Local(from) = cx.qpath_res(qpath, inner_of.hir_id)
+        && cx.tcx.hir_enclosing_body_owner(from) == dcx.body
+    {
+        cx.tcx.emit_node_span_lint(
+            DANGLING_POINTERS_FROM_LOCALS,
+            expr.hir_id,
+            expr.span,
+            DanglingPointersFromLocals {
+                ret_ty: dcx.fn_ret,
+                ret_ty_span: dcx.fn_ret_span,
+                fn_kind: dcx.fn_kind,
+                local_var: cx.tcx.hir_span(from),
+                local_var_name: cx.tcx.hir_ident(from),
+                local_var_ty: dcx.fn_ret_inner,
+                created_at: (expr.hir_id != inner.hir_id).then_some(inner.span),
+            },
+        );
     }
 }
 
diff --git a/compiler/rustc_lint/src/default_could_be_derived.rs b/compiler/rustc_lint/src/default_could_be_derived.rs
index b5fc083a095..7c39d8917ce 100644
--- a/compiler/rustc_lint/src/default_could_be_derived.rs
+++ b/compiler/rustc_lint/src/default_could_be_derived.rs
@@ -1,7 +1,8 @@
-use rustc_attr_data_structures::{AttributeKind, find_attr};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::{Applicability, Diag};
 use rustc_hir as hir;
+use rustc_hir::attrs::AttributeKind;
+use rustc_hir::find_attr;
 use rustc_middle::ty;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::{declare_lint, impl_lint_pass};
diff --git a/compiler/rustc_lint/src/foreign_modules.rs b/compiler/rustc_lint/src/foreign_modules.rs
index d6c402d481f..759e6c927b8 100644
--- a/compiler/rustc_lint/src/foreign_modules.rs
+++ b/compiler/rustc_lint/src/foreign_modules.rs
@@ -1,9 +1,10 @@
 use rustc_abi::FIRST_VARIANT;
-use rustc_attr_data_structures::{AttributeKind, find_attr};
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_data_structures::unord::{UnordMap, UnordSet};
 use rustc_hir as hir;
+use rustc_hir::attrs::AttributeKind;
 use rustc_hir::def::DefKind;
+use rustc_hir::find_attr;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::{self, AdtDef, Instance, Ty, TyCtxt};
 use rustc_session::declare_lint;
diff --git a/compiler/rustc_lint/src/lints.rs b/compiler/rustc_lint/src/lints.rs
index fd8d0f832aa..ef63c0dee8c 100644
--- a/compiler/rustc_lint/src/lints.rs
+++ b/compiler/rustc_lint/src/lints.rs
@@ -1188,6 +1188,22 @@ pub(crate) struct DanglingPointersFromTemporaries<'tcx> {
     pub temporary_span: Span,
 }
 
+#[derive(LintDiagnostic)]
+#[diag(lint_dangling_pointers_from_locals)]
+#[note]
+pub(crate) struct DanglingPointersFromLocals<'tcx> {
+    pub ret_ty: Ty<'tcx>,
+    #[label(lint_ret_ty)]
+    pub ret_ty_span: Span,
+    pub fn_kind: &'static str,
+    #[label(lint_local_var)]
+    pub local_var: Span,
+    pub local_var_name: Ident,
+    pub local_var_ty: Ty<'tcx>,
+    #[label(lint_created_at)]
+    pub created_at: Option<Span>,
+}
+
 // multiple_supertrait_upcastable.rs
 #[derive(LintDiagnostic)]
 #[diag(lint_multiple_supertrait_upcastable)]
diff --git a/compiler/rustc_lint/src/nonstandard_style.rs b/compiler/rustc_lint/src/nonstandard_style.rs
index 76e374deef6..7e5f43ba77f 100644
--- a/compiler/rustc_lint/src/nonstandard_style.rs
+++ b/compiler/rustc_lint/src/nonstandard_style.rs
@@ -1,11 +1,11 @@
 use rustc_abi::ExternAbi;
-use rustc_attr_data_structures::{AttributeKind, ReprAttr, find_attr};
 use rustc_attr_parsing::AttributeParser;
 use rustc_errors::Applicability;
+use rustc_hir::attrs::{AttributeKind, ReprAttr};
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::DefId;
 use rustc_hir::intravisit::{FnKind, Visitor};
-use rustc_hir::{AttrArgs, AttrItem, Attribute, GenericParamKind, PatExprKind, PatKind};
+use rustc_hir::{AttrArgs, AttrItem, Attribute, GenericParamKind, PatExprKind, PatKind, find_attr};
 use rustc_middle::hir::nested_filter::All;
 use rustc_middle::ty;
 use rustc_session::config::CrateType;
diff --git a/compiler/rustc_lint/src/pass_by_value.rs b/compiler/rustc_lint/src/pass_by_value.rs
index a3cf3d568b1..4f65acd8001 100644
--- a/compiler/rustc_lint/src/pass_by_value.rs
+++ b/compiler/rustc_lint/src/pass_by_value.rs
@@ -1,6 +1,6 @@
-use rustc_attr_data_structures::{AttributeKind, find_attr};
+use rustc_hir::attrs::AttributeKind;
 use rustc_hir::def::Res;
-use rustc_hir::{self as hir, AmbigArg, GenericArg, PathSegment, QPath, TyKind};
+use rustc_hir::{self as hir, AmbigArg, GenericArg, PathSegment, QPath, TyKind, find_attr};
 use rustc_middle::ty;
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 
diff --git a/compiler/rustc_lint/src/types/literal.rs b/compiler/rustc_lint/src/types/literal.rs
index 2bac58ba23d..1febbff4bbf 100644
--- a/compiler/rustc_lint/src/types/literal.rs
+++ b/compiler/rustc_lint/src/types/literal.rs
@@ -1,11 +1,11 @@
 use hir::{ExprKind, Node, is_range_literal};
 use rustc_abi::{Integer, Size};
-use rustc_hir::HirId;
+use rustc_hir::{HirId, attrs};
 use rustc_middle::ty::Ty;
 use rustc_middle::ty::layout::IntegerExt;
 use rustc_middle::{bug, ty};
 use rustc_span::Span;
-use {rustc_ast as ast, rustc_attr_data_structures as attrs, rustc_hir as hir};
+use {rustc_ast as ast, rustc_hir as hir};
 
 use crate::LateContext;
 use crate::context::LintContext;
@@ -272,7 +272,7 @@ fn lint_int_literal<'tcx>(
                 cx,
                 hir_id,
                 span,
-                attrs::IntType::SignedInt(ty::ast_int_ty(t)),
+                attrs::IntType::SignedInt(t),
                 Integer::from_int_ty(cx, t).size(),
                 repr_str,
                 v,
@@ -358,7 +358,7 @@ fn lint_uint_literal<'tcx>(
                 cx,
                 hir_id,
                 span,
-                attrs::IntType::UnsignedInt(ty::ast_uint_ty(t)),
+                attrs::IntType::UnsignedInt(t),
                 Integer::from_uint_ty(cx, t).size(),
                 repr_str,
                 lit_val,
diff --git a/compiler/rustc_lint/src/unused.rs b/compiler/rustc_lint/src/unused.rs
index 00e40b515a3..22d89d24612 100644
--- a/compiler/rustc_lint/src/unused.rs
+++ b/compiler/rustc_lint/src/unused.rs
@@ -2,12 +2,12 @@ use std::iter;
 
 use rustc_ast::util::{classify, parser};
 use rustc_ast::{self as ast, ExprKind, FnRetTy, HasAttrs as _, StmtKind};
-use rustc_attr_data_structures::{AttributeKind, find_attr};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::{MultiSpan, pluralize};
+use rustc_hir::attrs::AttributeKind;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::DefId;
-use rustc_hir::{self as hir, LangItem};
+use rustc_hir::{self as hir, LangItem, find_attr};
 use rustc_infer::traits::util::elaborate;
 use rustc_middle::ty::{self, Ty, adjustment};
 use rustc_session::{declare_lint, declare_lint_pass, impl_lint_pass};
diff --git a/compiler/rustc_lint_defs/src/builtin.rs b/compiler/rustc_lint_defs/src/builtin.rs
index b1edb5c3044..3b84c6b6110 100644
--- a/compiler/rustc_lint_defs/src/builtin.rs
+++ b/compiler/rustc_lint_defs/src/builtin.rs
@@ -125,6 +125,7 @@ declare_lint_pass! {
         UNSAFE_OP_IN_UNSAFE_FN,
         UNSTABLE_NAME_COLLISIONS,
         UNSTABLE_SYNTAX_PRE_EXPANSION,
+        UNSUPPORTED_CALLING_CONVENTIONS,
         UNUSED_ASSIGNMENTS,
         UNUSED_ASSOCIATED_TYPE_BOUNDS,
         UNUSED_ATTRIBUTES,
diff --git a/compiler/rustc_llvm/Cargo.toml b/compiler/rustc_llvm/Cargo.toml
index 85a2a9c09f0..cd352ce3d0f 100644
--- a/compiler/rustc_llvm/Cargo.toml
+++ b/compiler/rustc_llvm/Cargo.toml
@@ -16,5 +16,7 @@ cc = "=1.2.16"
 # tidy-alphabetical-end
 
 [features]
+# tidy-alphabetical-start
 # Used by ./x.py check --compile-time-deps to skip building C++ code
 check_only = []
+# tidy-alphabetical-end
diff --git a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
index c9814beedd6..588d867bbbf 100644
--- a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
+++ b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
@@ -1986,3 +1986,29 @@ extern "C" void LLVMRustSetNoSanitizeHWAddress(LLVMValueRef Global) {
   MD.NoHWAddress = true;
   GV.setSanitizerMetadata(MD);
 }
+
+enum class LLVMRustTailCallKind {
+  None = 0,
+  Tail = 1,
+  MustTail = 2,
+  NoTail = 3
+};
+
+extern "C" void LLVMRustSetTailCallKind(LLVMValueRef Call,
+                                        LLVMRustTailCallKind Kind) {
+  CallInst *CI = unwrap<CallInst>(Call);
+  switch (Kind) {
+  case LLVMRustTailCallKind::None:
+    CI->setTailCallKind(CallInst::TCK_None);
+    break;
+  case LLVMRustTailCallKind::Tail:
+    CI->setTailCallKind(CallInst::TCK_Tail);
+    break;
+  case LLVMRustTailCallKind::MustTail:
+    CI->setTailCallKind(CallInst::TCK_MustTail);
+    break;
+  case LLVMRustTailCallKind::NoTail:
+    CI->setTailCallKind(CallInst::TCK_NoTail);
+    break;
+  }
+}
diff --git a/compiler/rustc_macros/src/lib.rs b/compiler/rustc_macros/src/lib.rs
index 101f5ccb7a4..803b3621c88 100644
--- a/compiler/rustc_macros/src/lib.rs
+++ b/compiler/rustc_macros/src/lib.rs
@@ -187,7 +187,7 @@ decl_derive! {
 decl_derive! {
     [PrintAttribute] =>
     /// Derives `PrintAttribute` for `AttributeKind`.
-    /// This macro is pretty specific to `rustc_attr_data_structures` and likely not that useful in
+    /// This macro is pretty specific to `rustc_hir::attrs` and likely not that useful in
     /// other places. It's deriving something close to `Debug` without printing some extraneous
     /// things like spans.
     print_attribute::print_attribute
diff --git a/compiler/rustc_metadata/Cargo.toml b/compiler/rustc_metadata/Cargo.toml
index 0edc1d18ecc..1b40d9f684e 100644
--- a/compiler/rustc_metadata/Cargo.toml
+++ b/compiler/rustc_metadata/Cargo.toml
@@ -10,7 +10,6 @@ libloading = "0.8.0"
 odht = { version = "0.3.1", features = ["nightly"] }
 rustc_abi = { path = "../rustc_abi" }
 rustc_ast = { path = "../rustc_ast" }
-rustc_attr_data_structures = { path = "../rustc_attr_data_structures" }
 rustc_attr_parsing = { path = "../rustc_attr_parsing" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
diff --git a/compiler/rustc_metadata/src/creader.rs b/compiler/rustc_metadata/src/creader.rs
index 438eff33054..6bfb3769f24 100644
--- a/compiler/rustc_metadata/src/creader.rs
+++ b/compiler/rustc_metadata/src/creader.rs
@@ -12,6 +12,7 @@ use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::owned_slice::OwnedSlice;
 use rustc_data_structures::svh::Svh;
 use rustc_data_structures::sync::{self, FreezeReadGuard, FreezeWriteGuard};
+use rustc_data_structures::unord::UnordMap;
 use rustc_expand::base::SyntaxExtension;
 use rustc_fs_util::try_canonicalize;
 use rustc_hir as hir;
@@ -69,6 +70,9 @@ pub struct CStore {
     /// This crate has a `#[alloc_error_handler]` item.
     has_alloc_error_handler: bool,
 
+    /// Names that were used to load the crates via `extern crate` or paths.
+    resolved_externs: UnordMap<Symbol, CrateNum>,
+
     /// Unused externs of the crate
     unused_externs: Vec<Symbol>,
 
@@ -249,6 +253,22 @@ impl CStore {
         self.metas[cnum] = Some(Box::new(data));
     }
 
+    /// Save the name used to resolve the extern crate in the local crate
+    ///
+    /// The name isn't always the crate's own name, because `sess.opts.externs` can assign it another name.
+    /// It's also not always the same as the `DefId`'s symbol due to renames `extern crate resolved_name as defid_name`.
+    pub(crate) fn set_resolved_extern_crate_name(&mut self, name: Symbol, extern_crate: CrateNum) {
+        self.resolved_externs.insert(name, extern_crate);
+    }
+
+    /// Crate resolved and loaded via the given extern name
+    /// (corresponds to names in `sess.opts.externs`)
+    ///
+    /// May be `None` if the crate wasn't used
+    pub fn resolved_extern_crate(&self, externs_name: Symbol) -> Option<CrateNum> {
+        self.resolved_externs.get(&externs_name).copied()
+    }
+
     pub(crate) fn iter_crate_data(&self) -> impl Iterator<Item = (CrateNum, &CrateMetadata)> {
         self.metas
             .iter_enumerated()
@@ -475,6 +495,7 @@ impl CStore {
             alloc_error_handler_kind: None,
             has_global_allocator: false,
             has_alloc_error_handler: false,
+            resolved_externs: UnordMap::default(),
             unused_externs: Vec::new(),
             used_extern_options: Default::default(),
         }
@@ -511,7 +532,7 @@ impl CStore {
             // We're also sure to compare *paths*, not actual byte slices. The
             // `source` stores paths which are normalized which may be different
             // from the strings on the command line.
-            let source = self.get_crate_data(cnum).cdata.source();
+            let source = data.source();
             if let Some(entry) = externs.get(name.as_str()) {
                 // Only use `--extern crate_name=path` here, not `--extern crate_name`.
                 if let Some(mut files) = entry.files() {
@@ -1308,6 +1329,7 @@ impl CStore {
                 let path_len = definitions.def_path(def_id).data.len();
                 self.update_extern_crate(
                     cnum,
+                    name,
                     ExternCrate {
                         src: ExternCrateSource::Extern(def_id.to_def_id()),
                         span: item.span,
@@ -1332,6 +1354,7 @@ impl CStore {
 
         self.update_extern_crate(
             cnum,
+            name,
             ExternCrate {
                 src: ExternCrateSource::Path,
                 span,
diff --git a/compiler/rustc_metadata/src/native_libs.rs b/compiler/rustc_metadata/src/native_libs.rs
index ed0f084ea83..8855766ca98 100644
--- a/compiler/rustc_metadata/src/native_libs.rs
+++ b/compiler/rustc_metadata/src/native_libs.rs
@@ -3,9 +3,10 @@ use std::path::{Path, PathBuf};
 
 use rustc_abi::ExternAbi;
 use rustc_ast::CRATE_NODE_ID;
-use rustc_attr_data_structures::{AttributeKind, find_attr};
 use rustc_attr_parsing as attr;
 use rustc_data_structures::fx::FxHashSet;
+use rustc_hir::attrs::AttributeKind;
+use rustc_hir::find_attr;
 use rustc_middle::query::LocalCrate;
 use rustc_middle::ty::{self, List, Ty, TyCtxt};
 use rustc_session::Session;
diff --git a/compiler/rustc_metadata/src/rmeta/decoder.rs b/compiler/rustc_metadata/src/rmeta/decoder.rs
index e6aedc61338..00c97a2f738 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder.rs
@@ -1937,9 +1937,13 @@ impl CrateMetadata {
         self.root.decode_target_modifiers(&self.blob).collect()
     }
 
-    pub(crate) fn update_extern_crate(&mut self, new_extern_crate: ExternCrate) -> bool {
+    /// Keep `new_extern_crate` if it looks better in diagnostics
+    pub(crate) fn update_extern_crate_diagnostics(
+        &mut self,
+        new_extern_crate: ExternCrate,
+    ) -> bool {
         let update =
-            Some(new_extern_crate.rank()) > self.extern_crate.as_ref().map(ExternCrate::rank);
+            self.extern_crate.as_ref().is_none_or(|old| old.rank() < new_extern_crate.rank());
         if update {
             self.extern_crate = Some(new_extern_crate);
         }
diff --git a/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs b/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
index 57a672c45f7..0f3896fd9be 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
@@ -2,7 +2,7 @@ use std::any::Any;
 use std::mem;
 use std::sync::Arc;
 
-use rustc_attr_data_structures::Deprecation;
+use rustc_hir::attrs::Deprecation;
 use rustc_hir::def::{CtorKind, DefKind};
 use rustc_hir::def_id::{CrateNum, DefId, DefIdMap, LOCAL_CRATE};
 use rustc_hir::definitions::{DefKey, DefPath, DefPathHash};
@@ -627,14 +627,37 @@ impl CStore {
         }
     }
 
-    pub(crate) fn update_extern_crate(&mut self, cnum: CrateNum, extern_crate: ExternCrate) {
+    /// Track how an extern crate has been loaded. Called after resolving an import in the local crate.
+    ///
+    /// * the `name` is for [`Self::set_resolved_extern_crate_name`] saving `--extern name=`
+    /// * `extern_crate` is for diagnostics
+    pub(crate) fn update_extern_crate(
+        &mut self,
+        cnum: CrateNum,
+        name: Symbol,
+        extern_crate: ExternCrate,
+    ) {
+        debug_assert_eq!(
+            extern_crate.dependency_of, LOCAL_CRATE,
+            "this function should not be called on transitive dependencies"
+        );
+        self.set_resolved_extern_crate_name(name, cnum);
+        self.update_transitive_extern_crate_diagnostics(cnum, extern_crate);
+    }
+
+    /// `CrateMetadata` uses `ExternCrate` only for diagnostics
+    fn update_transitive_extern_crate_diagnostics(
+        &mut self,
+        cnum: CrateNum,
+        extern_crate: ExternCrate,
+    ) {
         let cmeta = self.get_crate_data_mut(cnum);
-        if cmeta.update_extern_crate(extern_crate) {
+        if cmeta.update_extern_crate_diagnostics(extern_crate) {
             // Propagate the extern crate info to dependencies if it was updated.
             let extern_crate = ExternCrate { dependency_of: cnum, ..extern_crate };
             let dependencies = mem::take(&mut cmeta.dependencies);
             for &dep_cnum in &dependencies {
-                self.update_extern_crate(dep_cnum, extern_crate);
+                self.update_transitive_extern_crate_diagnostics(dep_cnum, extern_crate);
             }
             self.get_crate_data_mut(cnum).dependencies = dependencies;
         }
diff --git a/compiler/rustc_metadata/src/rmeta/def_path_hash_map.rs b/compiler/rustc_metadata/src/rmeta/def_path_hash_map.rs
index 19369425f81..f3917b55782 100644
--- a/compiler/rustc_metadata/src/rmeta/def_path_hash_map.rs
+++ b/compiler/rustc_metadata/src/rmeta/def_path_hash_map.rs
@@ -1,6 +1,5 @@
 use rustc_data_structures::owned_slice::OwnedSlice;
 use rustc_hir::def_path_hash_map::{Config as HashMapConfig, DefPathHashMap};
-use rustc_middle::parameterized_over_tcx;
 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
 use rustc_span::def_id::{DefIndex, DefPathHash};
 
@@ -11,10 +10,6 @@ pub(crate) enum DefPathHashMapRef<'tcx> {
     BorrowedFromTcx(&'tcx DefPathHashMap),
 }
 
-parameterized_over_tcx! {
-    DefPathHashMapRef,
-}
-
 impl DefPathHashMapRef<'_> {
     #[inline]
     pub(crate) fn def_path_hash_to_def_index(&self, def_path_hash: &DefPathHash) -> DefIndex {
diff --git a/compiler/rustc_metadata/src/rmeta/encoder.rs b/compiler/rustc_metadata/src/rmeta/encoder.rs
index 4075bee707c..ff9f77be945 100644
--- a/compiler/rustc_metadata/src/rmeta/encoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/encoder.rs
@@ -5,7 +5,6 @@ use std::io::{Read, Seek, Write};
 use std::path::{Path, PathBuf};
 use std::sync::Arc;
 
-use rustc_attr_data_structures::{AttributeKind, EncodeCrossCrate, find_attr};
 use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_data_structures::memmap::{Mmap, MmapMut};
 use rustc_data_structures::sync::{join, par_for_each_in};
@@ -13,8 +12,10 @@ use rustc_data_structures::temp_dir::MaybeTempDir;
 use rustc_data_structures::thousands::usize_with_underscores;
 use rustc_feature::Features;
 use rustc_hir as hir;
+use rustc_hir::attrs::{AttributeKind, EncodeCrossCrate};
 use rustc_hir::def_id::{CRATE_DEF_ID, CRATE_DEF_INDEX, LOCAL_CRATE, LocalDefId, LocalDefIdSet};
 use rustc_hir::definitions::DefPathData;
+use rustc_hir::find_attr;
 use rustc_hir_pretty::id_to_string;
 use rustc_middle::dep_graph::WorkProductId;
 use rustc_middle::middle::dependency_format::Linkage;
diff --git a/compiler/rustc_metadata/src/rmeta/mod.rs b/compiler/rustc_metadata/src/rmeta/mod.rs
index 915c9731688..99174e4ad2f 100644
--- a/compiler/rustc_metadata/src/rmeta/mod.rs
+++ b/compiler/rustc_metadata/src/rmeta/mod.rs
@@ -6,15 +6,16 @@ use decoder::{DecodeContext, Metadata};
 use def_path_hash_map::DefPathHashMapRef;
 use encoder::EncodeContext;
 pub use encoder::{EncodedMetadata, encode_metadata, rendered_const};
+pub(crate) use parameterized::ParameterizedOverTcx;
 use rustc_abi::{FieldIdx, ReprOptions, VariantIdx};
-use rustc_attr_data_structures::StrippedCfgItem;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::svh::Svh;
-use rustc_hir::PreciseCapturingArgKind;
+use rustc_hir::attrs::StrippedCfgItem;
 use rustc_hir::def::{CtorKind, DefKind, DocLinkResMap};
 use rustc_hir::def_id::{CrateNum, DefId, DefIdMap, DefIndex, DefPathHash, StableCrateId};
 use rustc_hir::definitions::DefKey;
 use rustc_hir::lang_items::LangItem;
+use rustc_hir::{PreciseCapturingArgKind, attrs};
 use rustc_index::IndexVec;
 use rustc_index::bit_set::DenseBitSet;
 use rustc_macros::{
@@ -26,12 +27,10 @@ use rustc_middle::middle::debugger_visualizer::DebuggerVisualizerFile;
 use rustc_middle::middle::exported_symbols::{ExportedSymbol, SymbolExportInfo};
 use rustc_middle::middle::lib_features::FeatureStability;
 use rustc_middle::middle::resolve_bound_vars::ObjectLifetimeDefault;
+use rustc_middle::mir;
 use rustc_middle::ty::fast_reject::SimplifiedType;
-use rustc_middle::ty::{
-    self, DeducedParamAttrs, ParameterizedOverTcx, Ty, TyCtxt, UnusedGenericParams,
-};
+use rustc_middle::ty::{self, DeducedParamAttrs, Ty, TyCtxt, UnusedGenericParams};
 use rustc_middle::util::Providers;
-use rustc_middle::{mir, trivially_parameterized_over_tcx};
 use rustc_serialize::opaque::FileEncoder;
 use rustc_session::config::{SymbolManglingVersion, TargetModifier};
 use rustc_session::cstore::{CrateDepKind, ForeignModule, LinkagePreference, NativeLib};
@@ -40,13 +39,14 @@ use rustc_span::hygiene::{ExpnIndex, MacroKind, SyntaxContextKey};
 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_data_structures as attrs, rustc_hir as hir};
+use {rustc_ast as ast, rustc_hir as hir};
 
 use crate::creader::CrateMetadataRef;
 
 mod decoder;
 mod def_path_hash_map;
 mod encoder;
+mod parameterized;
 mod table;
 
 pub(crate) fn rustc_version(cfg_version: &'static str) -> String {
@@ -86,10 +86,6 @@ struct LazyValue<T> {
     _marker: PhantomData<fn() -> T>,
 }
 
-impl<T: ParameterizedOverTcx> ParameterizedOverTcx for LazyValue<T> {
-    type Value<'tcx> = LazyValue<T::Value<'tcx>>;
-}
-
 impl<T> LazyValue<T> {
     fn from_position(position: NonZero<usize>) -> LazyValue<T> {
         LazyValue { position, _marker: PhantomData }
@@ -112,10 +108,6 @@ struct LazyArray<T> {
     _marker: PhantomData<fn() -> T>,
 }
 
-impl<T: ParameterizedOverTcx> ParameterizedOverTcx for LazyArray<T> {
-    type Value<'tcx> = LazyArray<T::Value<'tcx>>;
-}
-
 impl<T> Default for LazyArray<T> {
     fn default() -> LazyArray<T> {
         LazyArray::from_position_and_num_elems(NonZero::new(1).unwrap(), 0)
@@ -143,10 +135,6 @@ struct LazyTable<I, T> {
     _marker: PhantomData<fn(I) -> T>,
 }
 
-impl<I: 'static, T: ParameterizedOverTcx> ParameterizedOverTcx for LazyTable<I, T> {
-    type Value<'tcx> = LazyTable<I, T::Value<'tcx>>;
-}
-
 impl<I, T> LazyTable<I, T> {
     fn from_position_and_encoded_size(
         position: NonZero<usize>,
@@ -200,7 +188,7 @@ type ExpnHashTable = LazyTable<ExpnIndex, Option<LazyValue<ExpnHash>>>;
 #[derive(MetadataEncodable, MetadataDecodable)]
 pub(crate) struct ProcMacroData {
     proc_macro_decls_static: DefIndex,
-    stability: Option<attrs::Stability>,
+    stability: Option<hir::Stability>,
     macros: LazyArray<DefIndex>,
 }
 
@@ -422,9 +410,9 @@ define_tables! {
     safety: Table<DefIndex, hir::Safety>,
     def_span: Table<DefIndex, LazyValue<Span>>,
     def_ident_span: Table<DefIndex, LazyValue<Span>>,
-    lookup_stability: Table<DefIndex, LazyValue<attrs::Stability>>,
-    lookup_const_stability: Table<DefIndex, LazyValue<attrs::ConstStability>>,
-    lookup_default_body_stability: Table<DefIndex, LazyValue<attrs::DefaultBodyStability>>,
+    lookup_stability: Table<DefIndex, LazyValue<hir::Stability>>,
+    lookup_const_stability: Table<DefIndex, LazyValue<hir::ConstStability>>,
+    lookup_default_body_stability: Table<DefIndex, LazyValue<hir::DefaultBodyStability>>,
     lookup_deprecation_entry: Table<DefIndex, LazyValue<attrs::Deprecation>>,
     explicit_predicates_of: Table<DefIndex, LazyValue<ty::GenericPredicates<'static>>>,
     generics_of: Table<DefIndex, LazyValue<ty::Generics>>,
@@ -594,14 +582,3 @@ pub fn provide(providers: &mut Providers) {
     encoder::provide(providers);
     decoder::provide(providers);
 }
-
-trivially_parameterized_over_tcx! {
-    VariantData,
-    RawDefId,
-    TraitImpls,
-    IncoherentImpls,
-    CrateHeader,
-    CrateRoot,
-    CrateDep,
-    AttrFlags,
-}
diff --git a/compiler/rustc_metadata/src/rmeta/parameterized.rs b/compiler/rustc_metadata/src/rmeta/parameterized.rs
new file mode 100644
index 00000000000..d632e65104a
--- /dev/null
+++ b/compiler/rustc_metadata/src/rmeta/parameterized.rs
@@ -0,0 +1,166 @@
+use std::hash::Hash;
+
+use rustc_data_structures::unord::UnordMap;
+use rustc_hir::def_id::DefIndex;
+use rustc_index::{Idx, IndexVec};
+use rustc_middle::ty::{Binder, EarlyBinder};
+use rustc_span::Symbol;
+
+use crate::rmeta::{LazyArray, LazyTable, LazyValue};
+
+pub(crate) trait ParameterizedOverTcx: 'static {
+    type Value<'tcx>;
+}
+
+impl<T: ParameterizedOverTcx> ParameterizedOverTcx for Option<T> {
+    type Value<'tcx> = Option<T::Value<'tcx>>;
+}
+
+impl<A: ParameterizedOverTcx, B: ParameterizedOverTcx> ParameterizedOverTcx for (A, B) {
+    type Value<'tcx> = (A::Value<'tcx>, B::Value<'tcx>);
+}
+
+impl<T: ParameterizedOverTcx> ParameterizedOverTcx for Vec<T> {
+    type Value<'tcx> = Vec<T::Value<'tcx>>;
+}
+
+impl<I: Idx + 'static, T: ParameterizedOverTcx> ParameterizedOverTcx for IndexVec<I, T> {
+    type Value<'tcx> = IndexVec<I, T::Value<'tcx>>;
+}
+
+impl<I: Hash + Eq + 'static, T: ParameterizedOverTcx> ParameterizedOverTcx for UnordMap<I, T> {
+    type Value<'tcx> = UnordMap<I, T::Value<'tcx>>;
+}
+
+impl<T: ParameterizedOverTcx> ParameterizedOverTcx for Binder<'static, T> {
+    type Value<'tcx> = Binder<'tcx, T::Value<'tcx>>;
+}
+
+impl<T: ParameterizedOverTcx> ParameterizedOverTcx for EarlyBinder<'static, T> {
+    type Value<'tcx> = EarlyBinder<'tcx, T::Value<'tcx>>;
+}
+
+impl<T: ParameterizedOverTcx> ParameterizedOverTcx for LazyValue<T> {
+    type Value<'tcx> = LazyValue<T::Value<'tcx>>;
+}
+
+impl<T: ParameterizedOverTcx> ParameterizedOverTcx for LazyArray<T> {
+    type Value<'tcx> = LazyArray<T::Value<'tcx>>;
+}
+
+impl<I: 'static, T: ParameterizedOverTcx> ParameterizedOverTcx for LazyTable<I, T> {
+    type Value<'tcx> = LazyTable<I, T::Value<'tcx>>;
+}
+
+macro_rules! trivially_parameterized_over_tcx {
+    ($($ty:ty),+ $(,)?) => {
+        $(
+            impl ParameterizedOverTcx for $ty {
+                #[allow(unused_lifetimes)]
+                type Value<'tcx> = $ty;
+            }
+        )*
+    }
+}
+
+trivially_parameterized_over_tcx! {
+    bool,
+    u64,
+    usize,
+    std::string::String,
+    // tidy-alphabetical-start
+    crate::rmeta::AttrFlags,
+    crate::rmeta::CrateDep,
+    crate::rmeta::CrateHeader,
+    crate::rmeta::CrateRoot,
+    crate::rmeta::IncoherentImpls,
+    crate::rmeta::RawDefId,
+    crate::rmeta::TraitImpls,
+    crate::rmeta::VariantData,
+    rustc_abi::ReprOptions,
+    rustc_ast::DelimArgs,
+    rustc_hir::Attribute,
+    rustc_hir::ConstStability,
+    rustc_hir::Constness,
+    rustc_hir::CoroutineKind,
+    rustc_hir::DefaultBodyStability,
+    rustc_hir::Defaultness,
+    rustc_hir::LangItem,
+    rustc_hir::OpaqueTyOrigin<rustc_hir::def_id::DefId>,
+    rustc_hir::PreciseCapturingArgKind<Symbol, Symbol>,
+    rustc_hir::Safety,
+    rustc_hir::Stability,
+    rustc_hir::attrs::Deprecation,
+    rustc_hir::attrs::StrippedCfgItem<rustc_hir::def_id::DefIndex>,
+    rustc_hir::def::DefKind,
+    rustc_hir::def::DocLinkResMap,
+    rustc_hir::def_id::DefId,
+    rustc_hir::def_id::DefIndex,
+    rustc_hir::definitions::DefKey,
+    rustc_index::bit_set::DenseBitSet<u32>,
+    rustc_middle::metadata::ModChild,
+    rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrs,
+    rustc_middle::middle::debugger_visualizer::DebuggerVisualizerFile,
+    rustc_middle::middle::exported_symbols::SymbolExportInfo,
+    rustc_middle::middle::lib_features::FeatureStability,
+    rustc_middle::middle::resolve_bound_vars::ObjectLifetimeDefault,
+    rustc_middle::mir::ConstQualifs,
+    rustc_middle::ty::AnonConstKind,
+    rustc_middle::ty::AssocItemContainer,
+    rustc_middle::ty::AsyncDestructor,
+    rustc_middle::ty::Asyncness,
+    rustc_middle::ty::DeducedParamAttrs,
+    rustc_middle::ty::Destructor,
+    rustc_middle::ty::Generics,
+    rustc_middle::ty::ImplTraitInTraitData,
+    rustc_middle::ty::IntrinsicDef,
+    rustc_middle::ty::TraitDef,
+    rustc_middle::ty::Variance,
+    rustc_middle::ty::Visibility<DefIndex>,
+    rustc_middle::ty::adjustment::CoerceUnsizedInfo,
+    rustc_middle::ty::fast_reject::SimplifiedType,
+    rustc_session::config::TargetModifier,
+    rustc_session::cstore::ForeignModule,
+    rustc_session::cstore::LinkagePreference,
+    rustc_session::cstore::NativeLib,
+    rustc_span::ExpnData,
+    rustc_span::ExpnHash,
+    rustc_span::ExpnId,
+    rustc_span::Ident,
+    rustc_span::SourceFile,
+    rustc_span::Span,
+    rustc_span::Symbol,
+    rustc_span::hygiene::SyntaxContextKey,
+    // tidy-alphabetical-end
+}
+
+// HACK(compiler-errors): This macro rule can only take a fake path,
+// not a real, due to parsing ambiguity reasons.
+macro_rules! parameterized_over_tcx {
+    ($($( $fake_path:ident )::+ ),+ $(,)?) => {
+        $(
+            impl ParameterizedOverTcx for $( $fake_path )::+ <'static> {
+                type Value<'tcx> = $( $fake_path )::+ <'tcx>;
+            }
+        )*
+    }
+}
+
+parameterized_over_tcx! {
+    // tidy-alphabetical-start
+    crate::rmeta::DefPathHashMapRef,
+    rustc_middle::middle::exported_symbols::ExportedSymbol,
+    rustc_middle::mir::Body,
+    rustc_middle::mir::CoroutineLayout,
+    rustc_middle::mir::interpret::ConstAllocation,
+    rustc_middle::ty::Clause,
+    rustc_middle::ty::ClauseKind,
+    rustc_middle::ty::Const,
+    rustc_middle::ty::ConstConditions,
+    rustc_middle::ty::FnSig,
+    rustc_middle::ty::GenericPredicates,
+    rustc_middle::ty::ImplTraitHeader,
+    rustc_middle::ty::TraitRef,
+    rustc_middle::ty::Ty,
+    // tidy-alphabetical-end
+}
diff --git a/compiler/rustc_middle/Cargo.toml b/compiler/rustc_middle/Cargo.toml
index edd0af6e4f5..fbcce16cedc 100644
--- a/compiler/rustc_middle/Cargo.toml
+++ b/compiler/rustc_middle/Cargo.toml
@@ -14,7 +14,6 @@ rustc_apfloat = "0.2.0"
 rustc_arena = { path = "../rustc_arena" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_ast_ir = { path = "../rustc_ast_ir" }
-rustc_attr_data_structures = { path = "../rustc_attr_data_structures" }
 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 43a7af9ce38..4b6e38cd52d 100644
--- a/compiler/rustc_middle/src/arena.rs
+++ b/compiler/rustc_middle/src/arena.rs
@@ -110,7 +110,7 @@ macro_rules! arena_types {
             [] external_constraints: rustc_middle::traits::solve::ExternalConstraintsData<rustc_middle::ty::TyCtxt<'tcx>>,
             [] predefined_opaques_in_body: rustc_middle::traits::solve::PredefinedOpaquesData<rustc_middle::ty::TyCtxt<'tcx>>,
             [decode] doc_link_resolutions: rustc_hir::def::DocLinkResMap,
-            [] stripped_cfg_items: rustc_attr_data_structures::StrippedCfgItem,
+            [] stripped_cfg_items: rustc_hir::attrs::StrippedCfgItem,
             [] mod_child: rustc_middle::metadata::ModChild,
             [] features: rustc_feature::Features,
             [decode] specialization_graph: rustc_middle::traits::specialization_graph::Graph,
diff --git a/compiler/rustc_middle/src/hir/map.rs b/compiler/rustc_middle/src/hir/map.rs
index 42a1e7377f4..4370816d38e 100644
--- a/compiler/rustc_middle/src/hir/map.rs
+++ b/compiler/rustc_middle/src/hir/map.rs
@@ -4,11 +4,11 @@
 
 use rustc_abi::ExternAbi;
 use rustc_ast::visit::{VisitorResult, walk_list};
-use rustc_attr_data_structures::{AttributeKind, find_attr};
 use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::svh::Svh;
 use rustc_data_structures::sync::{DynSend, DynSync, par_for_each_in, try_par_for_each_in};
+use rustc_hir::attrs::AttributeKind;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::{DefId, LOCAL_CRATE, LocalDefId, LocalModDefId};
 use rustc_hir::definitions::{DefKey, DefPath, DefPathHash};
@@ -533,8 +533,10 @@ impl<'tcx> TyCtxt<'tcx> {
     /// ```
     /// fn foo(x: usize) -> bool {
     ///     if x == 1 {
-    ///         true  // If `get_fn_id_for_return_block` gets passed the `id` corresponding
-    ///     } else {  // to this, it will return `foo`'s `HirId`.
+    ///         // If `get_fn_id_for_return_block` gets passed the `id` corresponding to this, it
+    ///         // will return `foo`'s `HirId`.
+    ///         true
+    ///     } else {
     ///         false
     ///     }
     /// }
@@ -543,8 +545,10 @@ impl<'tcx> TyCtxt<'tcx> {
     /// ```compile_fail,E0308
     /// fn foo(x: usize) -> bool {
     ///     loop {
-    ///         true  // If `get_fn_id_for_return_block` gets passed the `id` corresponding
-    ///     }         // to this, it will return `None`.
+    ///         // If `get_fn_id_for_return_block` gets passed the `id` corresponding to this, it
+    ///         // will return `None`.
+    ///         true
+    ///     }
     ///     false
     /// }
     /// ```
diff --git a/compiler/rustc_middle/src/hir/mod.rs b/compiler/rustc_middle/src/hir/mod.rs
index 6c07e49734a..67bc89692ff 100644
--- a/compiler/rustc_middle/src/hir/mod.rs
+++ b/compiler/rustc_middle/src/hir/mod.rs
@@ -174,36 +174,52 @@ impl<'tcx> TyCtxt<'tcx> {
         attrs: &SortedMap<ItemLocalId, &[Attribute]>,
         delayed_lints: &[DelayedLint],
         define_opaque: Option<&[(Span, LocalDefId)]>,
-    ) -> (Option<Fingerprint>, Option<Fingerprint>, Option<Fingerprint>) {
-        if self.needs_crate_hash() {
-            self.with_stable_hashing_context(|mut hcx| {
-                let mut stable_hasher = StableHasher::new();
-                node.hash_stable(&mut hcx, &mut stable_hasher);
-                // Bodies are stored out of line, so we need to pull them explicitly in the hash.
-                bodies.hash_stable(&mut hcx, &mut stable_hasher);
-                let h1 = stable_hasher.finish();
-
-                let mut stable_hasher = StableHasher::new();
-                attrs.hash_stable(&mut hcx, &mut stable_hasher);
-
-                // Hash the defined opaque types, which are not present in the attrs.
-                define_opaque.hash_stable(&mut hcx, &mut stable_hasher);
-
-                let h2 = stable_hasher.finish();
-
-                // hash lints emitted during ast lowering
-                let mut stable_hasher = StableHasher::new();
-                delayed_lints.hash_stable(&mut hcx, &mut stable_hasher);
-                let h3 = stable_hasher.finish();
-
-                (Some(h1), Some(h2), Some(h3))
-            })
-        } else {
-            (None, None, None)
+    ) -> Hashes {
+        if !self.needs_crate_hash() {
+            return Hashes {
+                opt_hash_including_bodies: None,
+                attrs_hash: None,
+                delayed_lints_hash: None,
+            };
         }
+
+        self.with_stable_hashing_context(|mut hcx| {
+            let mut stable_hasher = StableHasher::new();
+            node.hash_stable(&mut hcx, &mut stable_hasher);
+            // Bodies are stored out of line, so we need to pull them explicitly in the hash.
+            bodies.hash_stable(&mut hcx, &mut stable_hasher);
+            let h1 = stable_hasher.finish();
+
+            let mut stable_hasher = StableHasher::new();
+            attrs.hash_stable(&mut hcx, &mut stable_hasher);
+
+            // Hash the defined opaque types, which are not present in the attrs.
+            define_opaque.hash_stable(&mut hcx, &mut stable_hasher);
+
+            let h2 = stable_hasher.finish();
+
+            // hash lints emitted during ast lowering
+            let mut stable_hasher = StableHasher::new();
+            delayed_lints.hash_stable(&mut hcx, &mut stable_hasher);
+            let h3 = stable_hasher.finish();
+
+            Hashes {
+                opt_hash_including_bodies: Some(h1),
+                attrs_hash: Some(h2),
+                delayed_lints_hash: Some(h3),
+            }
+        })
     }
 }
 
+/// Hashes computed by [`TyCtxt::hash_owner_nodes`] if necessary.
+#[derive(Clone, Copy, Debug)]
+pub struct Hashes {
+    pub opt_hash_including_bodies: Option<Fingerprint>,
+    pub attrs_hash: Option<Fingerprint>,
+    pub delayed_lints_hash: Option<Fingerprint>,
+}
+
 pub fn provide(providers: &mut Providers) {
     providers.hir_crate_items = map::hir_crate_items;
     providers.crate_hash = map::crate_hash;
diff --git a/compiler/rustc_middle/src/lib.rs b/compiler/rustc_middle/src/lib.rs
index 803b645c8f7..e5cc23c213d 100644
--- a/compiler/rustc_middle/src/lib.rs
+++ b/compiler/rustc_middle/src/lib.rs
@@ -57,6 +57,7 @@
 #![feature(sized_hierarchy)]
 #![feature(try_blocks)]
 #![feature(try_trait_v2)]
+#![feature(try_trait_v2_residual)]
 #![feature(try_trait_v2_yeet)]
 #![feature(type_alias_impl_trait)]
 #![feature(yeet_expr)]
diff --git a/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs b/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs
index 34a29acdc85..94384e64afd 100644
--- a/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs
+++ b/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs
@@ -2,7 +2,7 @@ use std::borrow::Cow;
 
 use rustc_abi::Align;
 use rustc_ast::expand::autodiff_attrs::AutoDiffAttrs;
-use rustc_attr_data_structures::{InlineAttr, InstructionSetAttr, OptimizeAttr};
+use rustc_hir::attrs::{InlineAttr, InstructionSetAttr, OptimizeAttr};
 use rustc_macros::{HashStable, TyDecodable, TyEncodable};
 use rustc_span::Symbol;
 use rustc_target::spec::SanitizerSet;
diff --git a/compiler/rustc_middle/src/middle/stability.rs b/compiler/rustc_middle/src/middle/stability.rs
index dc9311188e8..4a19cf1563c 100644
--- a/compiler/rustc_middle/src/middle/stability.rs
+++ b/compiler/rustc_middle/src/middle/stability.rs
@@ -4,13 +4,11 @@
 use std::num::NonZero;
 
 use rustc_ast::NodeId;
-use rustc_attr_data_structures::{
-    self as attrs, ConstStability, DefaultBodyStability, DeprecatedSince, Deprecation, Stability,
-};
 use rustc_errors::{Applicability, Diag, EmissionGuarantee};
 use rustc_feature::GateIssue;
+use rustc_hir::attrs::{DeprecatedSince, Deprecation};
 use rustc_hir::def_id::{DefId, LocalDefId};
-use rustc_hir::{self as hir, HirId};
+use rustc_hir::{self as hir, ConstStability, DefaultBodyStability, HirId, Stability};
 use rustc_macros::{Decodable, Encodable, HashStable, Subdiagnostic};
 use rustc_session::Session;
 use rustc_session::lint::builtin::{DEPRECATED, DEPRECATED_IN_FUTURE, SOFT_UNSTABLE};
@@ -368,7 +366,7 @@ impl<'tcx> TyCtxt<'tcx> {
 
         match stability {
             Some(Stability {
-                level: attrs::StabilityLevel::Unstable { reason, issue, is_soft, implied_by, .. },
+                level: hir::StabilityLevel::Unstable { reason, issue, is_soft, implied_by, .. },
                 feature,
                 ..
             }) => {
@@ -451,7 +449,7 @@ impl<'tcx> TyCtxt<'tcx> {
 
         match stability {
             Some(DefaultBodyStability {
-                level: attrs::StabilityLevel::Unstable { reason, issue, is_soft, .. },
+                level: hir::StabilityLevel::Unstable { reason, issue, is_soft, .. },
                 feature,
             }) => {
                 if span.allows_unstable(feature) {
@@ -600,7 +598,7 @@ impl<'tcx> TyCtxt<'tcx> {
 
         match stability {
             Some(ConstStability {
-                level: attrs::StabilityLevel::Unstable { reason, issue, is_soft, implied_by, .. },
+                level: hir::StabilityLevel::Unstable { reason, issue, is_soft, implied_by, .. },
                 feature,
                 ..
             }) => {
diff --git a/compiler/rustc_middle/src/mir/interpret/error.rs b/compiler/rustc_middle/src/mir/interpret/error.rs
index 3e895c6b280..77427a12d11 100644
--- a/compiler/rustc_middle/src/mir/interpret/error.rs
+++ b/compiler/rustc_middle/src/mir/interpret/error.rs
@@ -793,36 +793,37 @@ impl Drop for Guard {
 /// We also make things panic if this type is ever implicitly dropped.
 #[derive(Debug)]
 #[must_use]
-pub struct InterpResult_<'tcx, T> {
+pub struct InterpResult<'tcx, T = ()> {
     res: Result<T, InterpErrorInfo<'tcx>>,
     guard: Guard,
 }
 
-// Type alias to be able to set a default type argument.
-pub type InterpResult<'tcx, T = ()> = InterpResult_<'tcx, T>;
-
-impl<'tcx, T> ops::Try for InterpResult_<'tcx, T> {
+impl<'tcx, T> ops::Try for InterpResult<'tcx, T> {
     type Output = T;
-    type Residual = InterpResult_<'tcx, convert::Infallible>;
+    type Residual = InterpResult<'tcx, convert::Infallible>;
 
     #[inline]
     fn from_output(output: Self::Output) -> Self {
-        InterpResult_::new(Ok(output))
+        InterpResult::new(Ok(output))
     }
 
     #[inline]
     fn branch(self) -> ops::ControlFlow<Self::Residual, Self::Output> {
         match self.disarm() {
             Ok(v) => ops::ControlFlow::Continue(v),
-            Err(e) => ops::ControlFlow::Break(InterpResult_::new(Err(e))),
+            Err(e) => ops::ControlFlow::Break(InterpResult::new(Err(e))),
         }
     }
 }
 
-impl<'tcx, T> ops::FromResidual for InterpResult_<'tcx, T> {
+impl<'tcx, T> ops::Residual<T> for InterpResult<'tcx, convert::Infallible> {
+    type TryType = InterpResult<'tcx, T>;
+}
+
+impl<'tcx, T> ops::FromResidual for InterpResult<'tcx, T> {
     #[inline]
     #[track_caller]
-    fn from_residual(residual: InterpResult_<'tcx, convert::Infallible>) -> Self {
+    fn from_residual(residual: InterpResult<'tcx, convert::Infallible>) -> Self {
         match residual.disarm() {
             Err(e) => Self::new(Err(e)),
         }
@@ -830,7 +831,7 @@ impl<'tcx, T> ops::FromResidual for InterpResult_<'tcx, T> {
 }
 
 // Allow `yeet`ing `InterpError` in functions returning `InterpResult_`.
-impl<'tcx, T> ops::FromResidual<ops::Yeet<InterpErrorKind<'tcx>>> for InterpResult_<'tcx, T> {
+impl<'tcx, T> ops::FromResidual<ops::Yeet<InterpErrorKind<'tcx>>> for InterpResult<'tcx, T> {
     #[inline]
     fn from_residual(ops::Yeet(e): ops::Yeet<InterpErrorKind<'tcx>>) -> Self {
         Self::new(Err(e.into()))
@@ -840,7 +841,7 @@ impl<'tcx, T> ops::FromResidual<ops::Yeet<InterpErrorKind<'tcx>>> for InterpResu
 // Allow `?` on `Result<_, InterpError>` in functions returning `InterpResult_`.
 // This is useful e.g. for `option.ok_or_else(|| err_ub!(...))`.
 impl<'tcx, T, E: Into<InterpErrorInfo<'tcx>>> ops::FromResidual<Result<convert::Infallible, E>>
-    for InterpResult_<'tcx, T>
+    for InterpResult<'tcx, T>
 {
     #[inline]
     fn from_residual(residual: Result<convert::Infallible, E>) -> Self {
@@ -863,7 +864,7 @@ impl<'tcx, T, V: FromIterator<T>> FromIterator<InterpResult<'tcx, T>> for Interp
     }
 }
 
-impl<'tcx, T> InterpResult_<'tcx, T> {
+impl<'tcx, T> InterpResult<'tcx, T> {
     #[inline(always)]
     fn new(res: Result<T, InterpErrorInfo<'tcx>>) -> Self {
         Self { res, guard: Guard }
@@ -890,7 +891,7 @@ impl<'tcx, T> InterpResult_<'tcx, T> {
 
     #[inline]
     pub fn map<U>(self, f: impl FnOnce(T) -> U) -> InterpResult<'tcx, U> {
-        InterpResult_::new(self.disarm().map(f))
+        InterpResult::new(self.disarm().map(f))
     }
 
     #[inline]
@@ -898,7 +899,7 @@ impl<'tcx, T> InterpResult_<'tcx, T> {
         self,
         f: impl FnOnce(InterpErrorInfo<'tcx>) -> InterpErrorInfo<'tcx>,
     ) -> InterpResult<'tcx, T> {
-        InterpResult_::new(self.disarm().map_err(f))
+        InterpResult::new(self.disarm().map_err(f))
     }
 
     #[inline]
@@ -906,7 +907,7 @@ impl<'tcx, T> InterpResult_<'tcx, T> {
         self,
         f: impl FnOnce(InterpErrorKind<'tcx>) -> InterpErrorKind<'tcx>,
     ) -> InterpResult<'tcx, T> {
-        InterpResult_::new(self.disarm().map_err(|mut e| {
+        InterpResult::new(self.disarm().map_err(|mut e| {
             e.0.kind = f(e.0.kind);
             e
         }))
@@ -914,7 +915,7 @@ impl<'tcx, T> InterpResult_<'tcx, T> {
 
     #[inline]
     pub fn inspect_err_kind(self, f: impl FnOnce(&InterpErrorKind<'tcx>)) -> InterpResult<'tcx, T> {
-        InterpResult_::new(self.disarm().inspect_err(|e| f(&e.0.kind)))
+        InterpResult::new(self.disarm().inspect_err(|e| f(&e.0.kind)))
     }
 
     #[inline]
@@ -937,7 +938,7 @@ impl<'tcx, T> InterpResult_<'tcx, T> {
 
     #[inline]
     pub fn and_then<U>(self, f: impl FnOnce(T) -> InterpResult<'tcx, U>) -> InterpResult<'tcx, U> {
-        InterpResult_::new(self.disarm().and_then(|t| f(t).disarm()))
+        InterpResult::new(self.disarm().and_then(|t| f(t).disarm()))
     }
 
     /// Returns success if both `self` and `other` succeed, while ensuring we don't
@@ -952,7 +953,7 @@ impl<'tcx, T> InterpResult_<'tcx, T> {
                 // Discard the other error.
                 drop(other.disarm());
                 // Return `self`.
-                InterpResult_::new(Err(e))
+                InterpResult::new(Err(e))
             }
         }
     }
@@ -960,5 +961,5 @@ impl<'tcx, T> InterpResult_<'tcx, T> {
 
 #[inline(always)]
 pub fn interp_ok<'tcx, T>(x: T) -> InterpResult<'tcx, T> {
-    InterpResult_::new(Ok(x))
+    InterpResult::new(Ok(x))
 }
diff --git a/compiler/rustc_middle/src/mir/mod.rs b/compiler/rustc_middle/src/mir/mod.rs
index e819aa2d8f8..c55c7fc6002 100644
--- a/compiler/rustc_middle/src/mir/mod.rs
+++ b/compiler/rustc_middle/src/mir/mod.rs
@@ -1017,7 +1017,8 @@ pub struct LocalDecl<'tcx> {
     /// ```
     /// fn foo(x: &str) {
     ///     #[allow(unused_mut)]
-    ///     let mut x: u32 = { // <- one unused mut
+    ///     let mut x: u32 = {
+    ///         //^ one unused mut
     ///         let mut y: u32 = x.parse().unwrap();
     ///         y + 2
     ///     };
diff --git a/compiler/rustc_middle/src/mir/mono.rs b/compiler/rustc_middle/src/mir/mono.rs
index 105736b9e24..e5864660575 100644
--- a/compiler/rustc_middle/src/mir/mono.rs
+++ b/compiler/rustc_middle/src/mir/mono.rs
@@ -3,7 +3,6 @@ use std::fmt;
 use std::hash::Hash;
 
 use rustc_ast::expand::autodiff_attrs::AutoDiffItem;
-use rustc_attr_data_structures::InlineAttr;
 use rustc_data_structures::base_n::{BaseNString, CASE_INSENSITIVE, ToBaseN};
 use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::fx::FxIndexMap;
@@ -11,6 +10,7 @@ use rustc_data_structures::stable_hasher::{HashStable, StableHasher, ToStableHas
 use rustc_data_structures::unord::UnordMap;
 use rustc_hashes::Hash128;
 use rustc_hir::ItemId;
+use rustc_hir::attrs::InlineAttr;
 use rustc_hir::def_id::{CrateNum, DefId, DefIdSet, LOCAL_CRATE};
 use rustc_index::Idx;
 use rustc_macros::{HashStable, TyDecodable, TyEncodable};
diff --git a/compiler/rustc_middle/src/mir/pretty.rs b/compiler/rustc_middle/src/mir/pretty.rs
index 809cdb329f7..ed067d49127 100644
--- a/compiler/rustc_middle/src/mir/pretty.rs
+++ b/compiler/rustc_middle/src/mir/pretty.rs
@@ -970,11 +970,11 @@ impl<'tcx> TerminatorKind<'tcx> {
             Call { func, args, destination, .. } => {
                 write!(fmt, "{destination:?} = ")?;
                 write!(fmt, "{func:?}(")?;
-                for (index, arg) in args.iter().map(|a| &a.node).enumerate() {
+                for (index, arg) in args.iter().enumerate() {
                     if index > 0 {
                         write!(fmt, ", ")?;
                     }
-                    write!(fmt, "{arg:?}")?;
+                    write!(fmt, "{:?}", arg.node)?;
                 }
                 write!(fmt, ")")
             }
@@ -984,7 +984,7 @@ impl<'tcx> TerminatorKind<'tcx> {
                     if index > 0 {
                         write!(fmt, ", ")?;
                     }
-                    write!(fmt, "{:?}", arg)?;
+                    write!(fmt, "{:?}", arg.node)?;
                 }
                 write!(fmt, ")")
             }
@@ -1197,8 +1197,8 @@ impl<'tcx> Debug for Rvalue<'tcx> {
                         ty::tls::with(|tcx| {
                             let variant_def = &tcx.adt_def(adt_did).variant(variant);
                             let args = tcx.lift(args).expect("could not lift for printing");
-                            let name = FmtPrinter::print_string(tcx, Namespace::ValueNS, |cx| {
-                                cx.print_def_path(variant_def.def_id, args)
+                            let name = FmtPrinter::print_string(tcx, Namespace::ValueNS, |p| {
+                                p.print_def_path(variant_def.def_id, args)
                             })?;
 
                             match variant_def.ctor_kind() {
@@ -1473,9 +1473,9 @@ impl<'tcx> Visitor<'tcx> for ExtraComments<'tcx> {
             };
 
             let fmt_valtree = |cv: &ty::Value<'tcx>| {
-                let mut cx = FmtPrinter::new(self.tcx, Namespace::ValueNS);
-                cx.pretty_print_const_valtree(*cv, /*print_ty*/ true).unwrap();
-                cx.into_buffer()
+                let mut p = FmtPrinter::new(self.tcx, Namespace::ValueNS);
+                p.pretty_print_const_valtree(*cv, /*print_ty*/ true).unwrap();
+                p.into_buffer()
             };
 
             let val = match const_ {
@@ -1967,10 +1967,10 @@ fn pretty_print_const_value_tcx<'tcx>(
                             .expect("destructed mir constant of adt without variant idx");
                         let variant_def = &def.variant(variant_idx);
                         let args = tcx.lift(args).unwrap();
-                        let mut cx = FmtPrinter::new(tcx, Namespace::ValueNS);
-                        cx.print_alloc_ids = true;
-                        cx.print_value_path(variant_def.def_id, args)?;
-                        fmt.write_str(&cx.into_buffer())?;
+                        let mut p = FmtPrinter::new(tcx, Namespace::ValueNS);
+                        p.print_alloc_ids = true;
+                        p.print_value_path(variant_def.def_id, args)?;
+                        fmt.write_str(&p.into_buffer())?;
 
                         match variant_def.ctor_kind() {
                             Some(CtorKind::Const) => {}
@@ -2001,18 +2001,18 @@ fn pretty_print_const_value_tcx<'tcx>(
             }
         }
         (ConstValue::Scalar(scalar), _) => {
-            let mut cx = FmtPrinter::new(tcx, Namespace::ValueNS);
-            cx.print_alloc_ids = true;
+            let mut p = FmtPrinter::new(tcx, Namespace::ValueNS);
+            p.print_alloc_ids = true;
             let ty = tcx.lift(ty).unwrap();
-            cx.pretty_print_const_scalar(scalar, ty)?;
-            fmt.write_str(&cx.into_buffer())?;
+            p.pretty_print_const_scalar(scalar, ty)?;
+            fmt.write_str(&p.into_buffer())?;
             return Ok(());
         }
         (ConstValue::ZeroSized, ty::FnDef(d, s)) => {
-            let mut cx = FmtPrinter::new(tcx, Namespace::ValueNS);
-            cx.print_alloc_ids = true;
-            cx.print_value_path(*d, s)?;
-            fmt.write_str(&cx.into_buffer())?;
+            let mut p = FmtPrinter::new(tcx, Namespace::ValueNS);
+            p.print_alloc_ids = true;
+            p.print_value_path(*d, s)?;
+            fmt.write_str(&p.into_buffer())?;
             return Ok(());
         }
         // FIXME(oli-obk): also pretty print arrays and other aggregate constants by reading
diff --git a/compiler/rustc_middle/src/mir/visit.rs b/compiler/rustc_middle/src/mir/visit.rs
index 929ebe1aee1..42a68b29ec7 100644
--- a/compiler/rustc_middle/src/mir/visit.rs
+++ b/compiler/rustc_middle/src/mir/visit.rs
@@ -1205,18 +1205,19 @@ macro_rules! visit_place_fns {
             self.super_projection_elem(place_ref, elem, context, location);
         }
 
-        fn super_place(&mut self, place: &Place<'tcx>, context: PlaceContext, location: Location) {
-            let mut context = context;
-
-            if !place.projection.is_empty() {
-                if context.is_use() {
-                    // ^ Only change the context if it is a real use, not a "use" in debuginfo.
-                    context = if context.is_mutating_use() {
-                        PlaceContext::MutatingUse(MutatingUseContext::Projection)
-                    } else {
-                        PlaceContext::NonMutatingUse(NonMutatingUseContext::Projection)
-                    };
-                }
+        fn super_place(
+            &mut self,
+            place: &Place<'tcx>,
+            mut context: PlaceContext,
+            location: Location,
+        ) {
+            if !place.projection.is_empty() && context.is_use() {
+                // ^ Only change the context if it is a real use, not a "use" in debuginfo.
+                context = if context.is_mutating_use() {
+                    PlaceContext::MutatingUse(MutatingUseContext::Projection)
+                } else {
+                    PlaceContext::NonMutatingUse(NonMutatingUseContext::Projection)
+                };
             }
 
             self.visit_local(place.local, context, location);
@@ -1239,7 +1240,7 @@ macro_rules! visit_place_fns {
             &mut self,
             _place_ref: PlaceRef<'tcx>,
             elem: PlaceElem<'tcx>,
-            _context: PlaceContext,
+            context: PlaceContext,
             location: Location,
         ) {
             match elem {
@@ -1252,7 +1253,12 @@ macro_rules! visit_place_fns {
                 ProjectionElem::Index(local) => {
                     self.visit_local(
                         local,
-                        PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy),
+                        if context.is_use() {
+                            // ^ Only change the context if it is a real use, not a "use" in debuginfo.
+                            PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy)
+                        } else {
+                            context
+                        },
                         location,
                     );
                 }
diff --git a/compiler/rustc_middle/src/query/erase.rs b/compiler/rustc_middle/src/query/erase.rs
index dab5900b4ab..a8b357bf105 100644
--- a/compiler/rustc_middle/src/query/erase.rs
+++ b/compiler/rustc_middle/src/query/erase.rs
@@ -246,9 +246,9 @@ trivial! {
     bool,
     Option<(rustc_span::def_id::DefId, rustc_session::config::EntryFnType)>,
     Option<rustc_ast::expand::allocator::AllocatorKind>,
-    Option<rustc_attr_data_structures::ConstStability>,
-    Option<rustc_attr_data_structures::DefaultBodyStability>,
-    Option<rustc_attr_data_structures::Stability>,
+    Option<rustc_hir::ConstStability>,
+    Option<rustc_hir::DefaultBodyStability>,
+    Option<rustc_hir::Stability>,
     Option<rustc_data_structures::svh::Svh>,
     Option<rustc_hir::def::DefKind>,
     Option<rustc_hir::CoroutineKind>,
@@ -272,13 +272,12 @@ trivial! {
     Result<rustc_middle::traits::EvaluationResult, rustc_middle::traits::OverflowError>,
     rustc_abi::ReprOptions,
     rustc_ast::expand::allocator::AllocatorKind,
-    rustc_attr_data_structures::ConstStability,
-    rustc_attr_data_structures::DefaultBodyStability,
-    rustc_attr_data_structures::Deprecation,
-    rustc_attr_data_structures::Stability,
+    rustc_hir::DefaultBodyStability,
+    rustc_hir::attrs::Deprecation,
     rustc_data_structures::svh::Svh,
     rustc_errors::ErrorGuaranteed,
     rustc_hir::Constness,
+    rustc_hir::ConstStability,
     rustc_hir::def_id::DefId,
     rustc_hir::def_id::DefIndex,
     rustc_hir::def_id::LocalDefId,
@@ -293,6 +292,7 @@ trivial! {
     rustc_hir::LangItem,
     rustc_hir::OpaqueTyOrigin<rustc_hir::def_id::DefId>,
     rustc_hir::OwnerId,
+    rustc_hir::Stability,
     rustc_hir::Upvar,
     rustc_index::bit_set::FiniteBitSet<u32>,
     rustc_middle::middle::dependency_format::Linkage,
diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs
index b0d579a546f..a4589576594 100644
--- a/compiler/rustc_middle/src/query/mod.rs
+++ b/compiler/rustc_middle/src/query/mod.rs
@@ -70,7 +70,6 @@ use std::sync::Arc;
 use rustc_abi::Align;
 use rustc_arena::TypedArena;
 use rustc_ast::expand::allocator::AllocatorKind;
-use rustc_attr_data_structures::StrippedCfgItem;
 use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_data_structures::sorted_map::SortedMap;
@@ -78,6 +77,7 @@ use rustc_data_structures::steal::Steal;
 use rustc_data_structures::svh::Svh;
 use rustc_data_structures::unord::{UnordMap, UnordSet};
 use rustc_errors::ErrorGuaranteed;
+use rustc_hir::attrs::StrippedCfgItem;
 use rustc_hir::def::{DefKind, DocLinkResMap};
 use rustc_hir::def_id::{
     CrateNum, DefId, DefIdMap, LocalDefId, LocalDefIdMap, LocalDefIdSet, LocalModDefId,
@@ -101,7 +101,7 @@ use rustc_span::def_id::LOCAL_CRATE;
 use rustc_span::source_map::Spanned;
 use rustc_span::{DUMMY_SP, Span, Symbol};
 use rustc_target::spec::PanicStrategy;
-use {rustc_abi as abi, rustc_ast as ast, rustc_attr_data_structures as attr, rustc_hir as hir};
+use {rustc_abi as abi, rustc_ast as ast, rustc_hir as hir};
 
 use crate::infer::canonical::{self, Canonical};
 use crate::lint::LintExpectation;
@@ -1178,11 +1178,10 @@ rustc_queries! {
 
     /// Return the live symbols in the crate for dead code check.
     ///
-    /// The second return value maps from ADTs to ignored derived traits (e.g. Debug and Clone) and
-    /// their respective impl (i.e., part of the derive macro)
+    /// The second return value maps from ADTs to ignored derived traits (e.g. Debug and Clone).
     query live_symbols_and_ignored_derived_traits(_: ()) -> &'tcx (
         LocalDefIdSet,
-        LocalDefIdMap<FxIndexSet<(DefId, DefId)>>
+        LocalDefIdMap<FxIndexSet<DefId>>,
     ) {
         arena_cache
         desc { "finding live symbols in crate" }
@@ -1390,9 +1389,11 @@ rustc_queries! {
         eval_always
         desc { "checking effective visibilities" }
     }
-    query check_private_in_public(_: ()) {
-        eval_always
-        desc { "checking for private elements in public interfaces" }
+    query check_private_in_public(module_def_id: LocalModDefId) {
+        desc { |tcx|
+            "checking for private elements in public interfaces for {}",
+            describe_as_module(module_def_id, tcx)
+        }
     }
 
     query reachable_set(_: ()) -> &'tcx LocalDefIdSet {
@@ -1455,19 +1456,19 @@ rustc_queries! {
         cache_on_disk_if { true }
     }
 
-    query lookup_stability(def_id: DefId) -> Option<attr::Stability> {
+    query lookup_stability(def_id: DefId) -> Option<hir::Stability> {
         desc { |tcx| "looking up stability of `{}`", tcx.def_path_str(def_id) }
         cache_on_disk_if { def_id.is_local() }
         separate_provide_extern
     }
 
-    query lookup_const_stability(def_id: DefId) -> Option<attr::ConstStability> {
+    query lookup_const_stability(def_id: DefId) -> Option<hir::ConstStability> {
         desc { |tcx| "looking up const stability of `{}`", tcx.def_path_str(def_id) }
         cache_on_disk_if { def_id.is_local() }
         separate_provide_extern
     }
 
-    query lookup_default_body_stability(def_id: DefId) -> Option<attr::DefaultBodyStability> {
+    query lookup_default_body_stability(def_id: DefId) -> Option<hir::DefaultBodyStability> {
         desc { |tcx| "looking up default body stability of `{}`", tcx.def_path_str(def_id) }
         separate_provide_extern
     }
diff --git a/compiler/rustc_middle/src/ty/adt.rs b/compiler/rustc_middle/src/ty/adt.rs
index 3bf80d37e65..df82c7a826b 100644
--- a/compiler/rustc_middle/src/ty/adt.rs
+++ b/compiler/rustc_middle/src/ty/adt.rs
@@ -4,15 +4,15 @@ use std::ops::Range;
 use std::str;
 
 use rustc_abi::{FIRST_VARIANT, ReprOptions, VariantIdx};
-use rustc_attr_data_structures::{AttributeKind, find_attr};
 use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::intern::Interned;
 use rustc_data_structures::stable_hasher::{HashStable, HashingControls, StableHasher};
 use rustc_errors::ErrorGuaranteed;
+use rustc_hir::attrs::AttributeKind;
 use rustc_hir::def::{CtorKind, DefKind, Res};
 use rustc_hir::def_id::DefId;
-use rustc_hir::{self as hir, LangItem};
+use rustc_hir::{self as hir, LangItem, find_attr};
 use rustc_index::{IndexSlice, IndexVec};
 use rustc_macros::{HashStable, TyDecodable, TyEncodable};
 use rustc_query_system::ich::StableHashingContext;
diff --git a/compiler/rustc_middle/src/ty/assoc.rs b/compiler/rustc_middle/src/ty/assoc.rs
index 1d15e4de7b6..a902a8a61e5 100644
--- a/compiler/rustc_middle/src/ty/assoc.rs
+++ b/compiler/rustc_middle/src/ty/assoc.rs
@@ -1,8 +1,9 @@
-use rustc_attr_data_structures::{AttributeKind, find_attr};
 use rustc_data_structures::sorted_map::SortedIndexMultiMap;
 use rustc_hir as hir;
+use rustc_hir::attrs::AttributeKind;
 use rustc_hir::def::{DefKind, Namespace};
 use rustc_hir::def_id::DefId;
+use rustc_hir::find_attr;
 use rustc_macros::{Decodable, Encodable, HashStable};
 use rustc_span::{Ident, Symbol};
 
diff --git a/compiler/rustc_middle/src/ty/codec.rs b/compiler/rustc_middle/src/ty/codec.rs
index 335b889b14d..95759d1f31a 100644
--- a/compiler/rustc_middle/src/ty/codec.rs
+++ b/compiler/rustc_middle/src/ty/codec.rs
@@ -510,12 +510,9 @@ impl_decodable_via_ref! {
     &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
     &'tcx traits::ImplSource<'tcx, ()>,
     &'tcx mir::Body<'tcx>,
-    &'tcx mir::ConcreteOpaqueTypes<'tcx>,
     &'tcx ty::List<ty::BoundVariableKind>,
     &'tcx ty::List<ty::Pattern<'tcx>>,
     &'tcx ty::ListWithCachedTypeInfo<ty::Clause<'tcx>>,
-    &'tcx ty::List<FieldIdx>,
-    &'tcx ty::List<(VariantIdx, FieldIdx)>,
 }
 
 #[macro_export]
diff --git a/compiler/rustc_middle/src/ty/consts.rs b/compiler/rustc_middle/src/ty/consts.rs
index fd1aa4042bc..614b6471f18 100644
--- a/compiler/rustc_middle/src/ty/consts.rs
+++ b/compiler/rustc_middle/src/ty/consts.rs
@@ -93,9 +93,9 @@ impl<'tcx> Const<'tcx> {
     pub fn new_bound(
         tcx: TyCtxt<'tcx>,
         debruijn: ty::DebruijnIndex,
-        var: ty::BoundVar,
+        bound_const: ty::BoundConst,
     ) -> Const<'tcx> {
-        Const::new(tcx, ty::ConstKind::Bound(debruijn, var))
+        Const::new(tcx, ty::ConstKind::Bound(debruijn, bound_const))
     }
 
     #[inline]
@@ -168,12 +168,16 @@ impl<'tcx> rustc_type_ir::inherent::Const<TyCtxt<'tcx>> for Const<'tcx> {
         Const::new_var(tcx, vid)
     }
 
-    fn new_bound(interner: TyCtxt<'tcx>, debruijn: ty::DebruijnIndex, var: ty::BoundVar) -> Self {
-        Const::new_bound(interner, debruijn, var)
+    fn new_bound(
+        interner: TyCtxt<'tcx>,
+        debruijn: ty::DebruijnIndex,
+        bound_const: ty::BoundConst,
+    ) -> Self {
+        Const::new_bound(interner, debruijn, bound_const)
     }
 
     fn new_anon_bound(tcx: TyCtxt<'tcx>, debruijn: ty::DebruijnIndex, var: ty::BoundVar) -> Self {
-        Const::new_bound(tcx, debruijn, var)
+        Const::new_bound(tcx, debruijn, ty::BoundConst { var })
     }
 
     fn new_placeholder(tcx: TyCtxt<'tcx>, placeholder: ty::PlaceholderConst) -> Self {
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index 6f21160d1f6..db56082c71a 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -17,7 +17,6 @@ use std::{fmt, iter, mem};
 
 use rustc_abi::{ExternAbi, FieldIdx, Layout, LayoutData, TargetDataLayout, VariantIdx};
 use rustc_ast as ast;
-use rustc_attr_data_structures::{AttributeKind, find_attr};
 use rustc_data_structures::defer;
 use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::fx::FxHashMap;
@@ -33,12 +32,13 @@ use rustc_data_structures::sync::{
 use rustc_errors::{
     Applicability, Diag, DiagCtxtHandle, ErrorGuaranteed, LintDiagnostic, LintEmitter, MultiSpan,
 };
+use rustc_hir::attrs::AttributeKind;
 use rustc_hir::def::{CtorKind, DefKind};
 use rustc_hir::def_id::{CrateNum, DefId, LOCAL_CRATE, LocalDefId};
 use rustc_hir::definitions::{DefPathData, Definitions, DisambiguatorState};
 use rustc_hir::intravisit::VisitorExt;
 use rustc_hir::lang_items::LangItem;
-use rustc_hir::{self as hir, Attribute, HirId, Node, TraitCandidate};
+use rustc_hir::{self as hir, Attribute, HirId, Node, TraitCandidate, find_attr};
 use rustc_index::IndexVec;
 use rustc_macros::{HashStable, TyDecodable, TyEncodable};
 use rustc_query_system::cache::WithDepNode;
@@ -152,7 +152,7 @@ impl<'tcx> Interner for TyCtxt<'tcx> {
     type PlaceholderConst = ty::PlaceholderConst;
 
     type ParamConst = ty::ParamConst;
-    type BoundConst = ty::BoundVar;
+    type BoundConst = ty::BoundConst;
     type ValueConst = ty::Value<'tcx>;
     type ExprConst = ty::Expr<'tcx>;
     type ValTree = ty::ValTree<'tcx>;
@@ -1381,7 +1381,7 @@ impl<'tcx> TyCtxtFeed<'tcx, LocalDefId> {
         let bodies = Default::default();
         let attrs = hir::AttributeMap::EMPTY;
 
-        let (opt_hash_including_bodies, _, _) =
+        let rustc_middle::hir::Hashes { opt_hash_including_bodies, .. } =
             self.tcx.hash_owner_nodes(node, &bodies, &attrs.map, &[], attrs.define_opaque);
         let node = node.into();
         self.opt_hir_owner_nodes(Some(self.tcx.arena.alloc(hir::OwnerNodes {
diff --git a/compiler/rustc_middle/src/ty/error.rs b/compiler/rustc_middle/src/ty/error.rs
index 13723874ad3..c24dc983d21 100644
--- a/compiler/rustc_middle/src/ty/error.rs
+++ b/compiler/rustc_middle/src/ty/error.rs
@@ -213,13 +213,13 @@ impl<'tcx> Ty<'tcx> {
 }
 
 impl<'tcx> TyCtxt<'tcx> {
-    pub fn string_with_limit<T>(self, p: T, length_limit: usize) -> String
+    pub fn string_with_limit<T>(self, t: T, length_limit: usize) -> String
     where
         T: Copy + for<'a, 'b> Lift<TyCtxt<'b>, Lifted: Print<'b, FmtPrinter<'a, 'b>>>,
     {
         let mut type_limit = 50;
-        let regular = FmtPrinter::print_string(self, hir::def::Namespace::TypeNS, |cx| {
-            self.lift(p).expect("could not lift for printing").print(cx)
+        let regular = FmtPrinter::print_string(self, hir::def::Namespace::TypeNS, |p| {
+            self.lift(t).expect("could not lift for printing").print(p)
         })
         .expect("could not write to `String`");
         if regular.len() <= length_limit {
@@ -229,16 +229,16 @@ impl<'tcx> TyCtxt<'tcx> {
         loop {
             // Look for the longest properly trimmed path that still fits in length_limit.
             short = with_forced_trimmed_paths!({
-                let mut cx = FmtPrinter::new_with_limit(
+                let mut p = FmtPrinter::new_with_limit(
                     self,
                     hir::def::Namespace::TypeNS,
                     rustc_session::Limit(type_limit),
                 );
-                self.lift(p)
+                self.lift(t)
                     .expect("could not lift for printing")
-                    .print(&mut cx)
+                    .print(&mut p)
                     .expect("could not print type");
-                cx.into_buffer()
+                p.into_buffer()
             });
             if short.len() <= length_limit || type_limit == 0 {
                 break;
@@ -252,12 +252,12 @@ impl<'tcx> TyCtxt<'tcx> {
     /// `tcx.short_string(ty, diag.long_ty_path())`. The diagnostic itself is the one that keeps
     /// the existence of a "long type" anywhere in the diagnostic, so the note telling the user
     /// where we wrote the file to is only printed once.
-    pub fn short_string<T>(self, p: T, path: &mut Option<PathBuf>) -> String
+    pub fn short_string<T>(self, t: T, path: &mut Option<PathBuf>) -> String
     where
         T: Copy + Hash + for<'a, 'b> Lift<TyCtxt<'b>, Lifted: Print<'b, FmtPrinter<'a, 'b>>>,
     {
-        let regular = FmtPrinter::print_string(self, hir::def::Namespace::TypeNS, |cx| {
-            self.lift(p).expect("could not lift for printing").print(cx)
+        let regular = FmtPrinter::print_string(self, hir::def::Namespace::TypeNS, |p| {
+            self.lift(t).expect("could not lift for printing").print(p)
         })
         .expect("could not write to `String`");
 
@@ -270,13 +270,13 @@ impl<'tcx> TyCtxt<'tcx> {
         if regular.len() <= width * 2 / 3 {
             return regular;
         }
-        let short = self.string_with_limit(p, length_limit);
+        let short = self.string_with_limit(t, length_limit);
         if regular == short {
             return regular;
         }
         // Ensure we create an unique file for the type passed in when we create a file.
         let mut s = DefaultHasher::new();
-        p.hash(&mut s);
+        t.hash(&mut s);
         let hash = s.finish();
         *path = Some(path.take().unwrap_or_else(|| {
             self.output_filenames(()).temp_path_for_diagnostic(&format!("long-type-{hash}.txt"))
diff --git a/compiler/rustc_middle/src/ty/fold.rs b/compiler/rustc_middle/src/ty/fold.rs
index b2057fa36d7..7d56ec1635f 100644
--- a/compiler/rustc_middle/src/ty/fold.rs
+++ b/compiler/rustc_middle/src/ty/fold.rs
@@ -3,7 +3,7 @@ use rustc_hir::def_id::DefId;
 use rustc_type_ir::data_structures::DelayedMap;
 
 use crate::ty::{
-    self, Binder, BoundTy, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable,
+    self, Binder, BoundConst, BoundTy, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable,
     TypeVisitableExt,
 };
 
@@ -60,7 +60,7 @@ where
 pub trait BoundVarReplacerDelegate<'tcx> {
     fn replace_region(&mut self, br: ty::BoundRegion) -> ty::Region<'tcx>;
     fn replace_ty(&mut self, bt: ty::BoundTy) -> Ty<'tcx>;
-    fn replace_const(&mut self, bv: ty::BoundVar) -> ty::Const<'tcx>;
+    fn replace_const(&mut self, bc: ty::BoundConst) -> ty::Const<'tcx>;
 }
 
 /// A simple delegate taking 3 mutable functions. The used functions must
@@ -69,7 +69,7 @@ pub trait BoundVarReplacerDelegate<'tcx> {
 pub struct FnMutDelegate<'a, 'tcx> {
     pub regions: &'a mut (dyn FnMut(ty::BoundRegion) -> ty::Region<'tcx> + 'a),
     pub types: &'a mut (dyn FnMut(ty::BoundTy) -> Ty<'tcx> + 'a),
-    pub consts: &'a mut (dyn FnMut(ty::BoundVar) -> ty::Const<'tcx> + 'a),
+    pub consts: &'a mut (dyn FnMut(ty::BoundConst) -> ty::Const<'tcx> + 'a),
 }
 
 impl<'a, 'tcx> BoundVarReplacerDelegate<'tcx> for FnMutDelegate<'a, 'tcx> {
@@ -79,8 +79,8 @@ impl<'a, 'tcx> BoundVarReplacerDelegate<'tcx> for FnMutDelegate<'a, 'tcx> {
     fn replace_ty(&mut self, bt: ty::BoundTy) -> Ty<'tcx> {
         (self.types)(bt)
     }
-    fn replace_const(&mut self, bv: ty::BoundVar) -> ty::Const<'tcx> {
-        (self.consts)(bv)
+    fn replace_const(&mut self, bc: ty::BoundConst) -> ty::Const<'tcx> {
+        (self.consts)(bc)
     }
 }
 
@@ -300,7 +300,13 @@ impl<'tcx> TyCtxt<'tcx> {
                         ty::BoundTy { var: shift_bv(t.var), kind: t.kind },
                     )
                 },
-                consts: &mut |c| ty::Const::new_bound(self, ty::INNERMOST, shift_bv(c)),
+                consts: &mut |c| {
+                    ty::Const::new_bound(
+                        self,
+                        ty::INNERMOST,
+                        ty::BoundConst { var: shift_bv(c.var) },
+                    )
+                },
             },
         )
     }
@@ -343,12 +349,12 @@ impl<'tcx> TyCtxt<'tcx> {
                     .expect_ty();
                 Ty::new_bound(self.tcx, ty::INNERMOST, BoundTy { var, kind })
             }
-            fn replace_const(&mut self, bv: ty::BoundVar) -> ty::Const<'tcx> {
-                let entry = self.map.entry(bv);
+            fn replace_const(&mut self, bc: ty::BoundConst) -> ty::Const<'tcx> {
+                let entry = self.map.entry(bc.var);
                 let index = entry.index();
                 let var = ty::BoundVar::from_usize(index);
                 let () = entry.or_insert_with(|| ty::BoundVariableKind::Const).expect_const();
-                ty::Const::new_bound(self.tcx, ty::INNERMOST, var)
+                ty::Const::new_bound(self.tcx, ty::INNERMOST, BoundConst { var })
             }
         }
 
diff --git a/compiler/rustc_middle/src/ty/generic_args.rs b/compiler/rustc_middle/src/ty/generic_args.rs
index 7d34d8df3f3..b02abb5ab43 100644
--- a/compiler/rustc_middle/src/ty/generic_args.rs
+++ b/compiler/rustc_middle/src/ty/generic_args.rs
@@ -96,14 +96,12 @@ impl<'tcx> rustc_type_ir::inherent::GenericArgs<TyCtxt<'tcx>> for ty::GenericArg
                 signature_parts_ty,
                 tupled_upvars_ty,
                 coroutine_captures_by_ref_ty,
-                coroutine_witness_ty,
             ] => ty::CoroutineClosureArgsParts {
                 parent_args,
                 closure_kind_ty: closure_kind_ty.expect_ty(),
                 signature_parts_ty: signature_parts_ty.expect_ty(),
                 tupled_upvars_ty: tupled_upvars_ty.expect_ty(),
                 coroutine_captures_by_ref_ty: coroutine_captures_by_ref_ty.expect_ty(),
-                coroutine_witness_ty: coroutine_witness_ty.expect_ty(),
             },
             _ => bug!("closure args missing synthetics"),
         }
@@ -111,23 +109,16 @@ impl<'tcx> rustc_type_ir::inherent::GenericArgs<TyCtxt<'tcx>> for ty::GenericArg
 
     fn split_coroutine_args(self) -> ty::CoroutineArgsParts<TyCtxt<'tcx>> {
         match self[..] {
-            [
-                ref parent_args @ ..,
-                kind_ty,
-                resume_ty,
-                yield_ty,
-                return_ty,
-                witness,
-                tupled_upvars_ty,
-            ] => ty::CoroutineArgsParts {
-                parent_args,
-                kind_ty: kind_ty.expect_ty(),
-                resume_ty: resume_ty.expect_ty(),
-                yield_ty: yield_ty.expect_ty(),
-                return_ty: return_ty.expect_ty(),
-                witness: witness.expect_ty(),
-                tupled_upvars_ty: tupled_upvars_ty.expect_ty(),
-            },
+            [ref parent_args @ .., kind_ty, resume_ty, yield_ty, return_ty, tupled_upvars_ty] => {
+                ty::CoroutineArgsParts {
+                    parent_args,
+                    kind_ty: kind_ty.expect_ty(),
+                    resume_ty: resume_ty.expect_ty(),
+                    yield_ty: yield_ty.expect_ty(),
+                    return_ty: return_ty.expect_ty(),
+                    tupled_upvars_ty: tupled_upvars_ty.expect_ty(),
+                }
+            }
             _ => bug!("coroutine args missing synthetics"),
         }
     }
diff --git a/compiler/rustc_middle/src/ty/instance.rs b/compiler/rustc_middle/src/ty/instance.rs
index d5767ca3786..16873b6ee21 100644
--- a/compiler/rustc_middle/src/ty/instance.rs
+++ b/compiler/rustc_middle/src/ty/instance.rs
@@ -212,7 +212,7 @@ 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_data_structures::InlineAttr::Never
+            && tcx.codegen_fn_attrs(self.def_id()).inline != rustc_hir::attrs::InlineAttr::Never
         {
             return None;
         }
@@ -397,13 +397,13 @@ pub fn fmt_instance(
     ty::tls::with(|tcx| {
         let args = tcx.lift(instance.args).expect("could not lift for printing");
 
-        let mut cx = if let Some(type_length) = type_length {
+        let mut p = if let Some(type_length) = type_length {
             FmtPrinter::new_with_limit(tcx, Namespace::ValueNS, type_length)
         } else {
             FmtPrinter::new(tcx, Namespace::ValueNS)
         };
-        cx.print_def_path(instance.def_id(), args)?;
-        let s = cx.into_buffer();
+        p.print_def_path(instance.def_id(), args)?;
+        let s = p.into_buffer();
         f.write_str(&s)
     })?;
 
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index bb70c61cd14..0deb2482c6f 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -27,17 +27,17 @@ pub use intrinsic::IntrinsicDef;
 use rustc_abi::{Align, FieldIdx, Integer, IntegerType, ReprFlags, ReprOptions, VariantIdx};
 use rustc_ast::node_id::NodeMap;
 pub use rustc_ast_ir::{Movability, Mutability, try_visit};
-use rustc_attr_data_structures::{AttributeKind, StrippedCfgItem, find_attr};
 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap, FxIndexSet};
 use rustc_data_structures::intern::Interned;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::steal::Steal;
 use rustc_data_structures::unord::{UnordMap, UnordSet};
 use rustc_errors::{Diag, ErrorGuaranteed};
-use rustc_hir::LangItem;
+use rustc_hir::attrs::{AttributeKind, StrippedCfgItem};
 use rustc_hir::def::{CtorKind, CtorOf, DefKind, DocLinkResMap, LifetimeRes, Res};
 use rustc_hir::def_id::{CrateNum, DefId, DefIdMap, LocalDefId, LocalDefIdMap};
 use rustc_hir::definitions::DisambiguatorState;
+use rustc_hir::{LangItem, attrs as attr, find_attr};
 use rustc_index::IndexVec;
 use rustc_index::bit_set::BitMatrix;
 use rustc_macros::{
@@ -49,7 +49,7 @@ use rustc_serialize::{Decodable, Encodable};
 use rustc_session::lint::LintBuffer;
 pub use rustc_session::lint::RegisteredTools;
 use rustc_span::hygiene::MacroKind;
-use rustc_span::{DUMMY_SP, ExpnId, ExpnKind, Ident, Span, Symbol, kw, sym};
+use rustc_span::{DUMMY_SP, ExpnId, ExpnKind, Ident, Span, Symbol, sym};
 pub use rustc_type_ir::data_structures::{DelayedMap, DelayedSet};
 pub use rustc_type_ir::fast_reject::DeepRejectCtxt;
 #[allow(
@@ -65,7 +65,7 @@ pub use rustc_type_ir::*;
 use rustc_type_ir::{InferCtxtLike, Interner};
 use tracing::{debug, instrument};
 pub use vtable::*;
-use {rustc_ast as ast, rustc_attr_data_structures as attr, rustc_hir as hir};
+use {rustc_ast as ast, rustc_hir as hir};
 
 pub use self::closure::{
     BorrowKind, CAPTURE_STRUCT_LOCAL, CaptureInfo, CapturedPlace, ClosureTypeInfo,
@@ -85,7 +85,6 @@ pub use self::fold::*;
 pub use self::instance::{Instance, InstanceKind, ReifyReason, ShortInstance, UnusedGenericParams};
 pub use self::list::{List, ListWithCachedTypeInfo};
 pub use self::opaque_types::OpaqueTypeKey;
-pub use self::parameterized::ParameterizedOverTcx;
 pub use self::pattern::{Pattern, PatternKind};
 pub use self::predicate::{
     AliasTerm, ArgOutlivesPredicate, Clause, ClauseKind, CoercePredicate, ExistentialPredicate,
@@ -158,7 +157,6 @@ mod instance;
 mod intrinsic;
 mod list;
 mod opaque_types;
-mod parameterized;
 mod predicate;
 mod region;
 mod rvalue_scopes;
@@ -170,11 +168,6 @@ mod visit;
 
 // Data types
 
-pub struct ResolverOutputs {
-    pub global_ctxt: ResolverGlobalCtxt,
-    pub ast_lowering: ResolverAstLowering,
-}
-
 #[derive(Debug, HashStable)]
 pub struct ResolverGlobalCtxt {
     pub visibilities_for_hashing: Vec<(LocalDefId, Visibility)>,
@@ -255,18 +248,6 @@ impl MainDefinition {
     }
 }
 
-/// The "header" of an impl is everything outside the body: a Self type, a trait
-/// ref (in the case of a trait impl), and a set of predicates (from the
-/// bounds / where-clauses).
-#[derive(Clone, Debug, TypeFoldable, TypeVisitable)]
-pub struct ImplHeader<'tcx> {
-    pub impl_def_id: DefId,
-    pub impl_args: ty::GenericArgsRef<'tcx>,
-    pub self_ty: Ty<'tcx>,
-    pub trait_ref: Option<TraitRef<'tcx>>,
-    pub predicates: Vec<Predicate<'tcx>>,
-}
-
 #[derive(Copy, Clone, Debug, TyEncodable, TyDecodable, HashStable)]
 pub struct ImplTraitHeader<'tcx> {
     pub trait_ref: ty::EarlyBinder<'tcx, ty::TraitRef<'tcx>>,
@@ -470,14 +451,6 @@ impl<'tcx> rustc_type_ir::Flags for Ty<'tcx> {
     }
 }
 
-impl EarlyParamRegion {
-    /// Does this early bound region have a name? Early bound regions normally
-    /// always have names except when using anonymous lifetimes (`'_`).
-    pub fn is_named(&self) -> bool {
-        self.name != kw::UnderscoreLifetime
-    }
-}
-
 /// The crate outlives map is computed during typeck and contains the
 /// outlives of every item in the local crate. You should not use it
 /// directly, because to do so will make your pass dependent on the
@@ -698,39 +671,6 @@ impl<'tcx> TermKind<'tcx> {
     }
 }
 
-#[derive(Copy, Clone, PartialEq, Eq, Debug)]
-pub enum ParamTerm {
-    Ty(ParamTy),
-    Const(ParamConst),
-}
-
-impl ParamTerm {
-    pub fn index(self) -> usize {
-        match self {
-            ParamTerm::Ty(ty) => ty.index as usize,
-            ParamTerm::Const(ct) => ct.index as usize,
-        }
-    }
-}
-
-#[derive(Copy, Clone, Eq, PartialEq, Debug)]
-pub enum TermVid {
-    Ty(ty::TyVid),
-    Const(ty::ConstVid),
-}
-
-impl From<ty::TyVid> for TermVid {
-    fn from(value: ty::TyVid) -> Self {
-        TermVid::Ty(value)
-    }
-}
-
-impl From<ty::ConstVid> for TermVid {
-    fn from(value: ty::ConstVid) -> Self {
-        TermVid::Const(value)
-    }
-}
-
 /// Represents the bounds declared on a particular set of type
 /// parameters. Should eventually be generalized into a flag list of
 /// where-clauses. You can obtain an `InstantiatedPredicates` list from a
@@ -968,34 +908,43 @@ impl<'tcx> rustc_type_ir::inherent::PlaceholderLike<TyCtxt<'tcx>> for Placeholde
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, HashStable)]
 #[derive(TyEncodable, TyDecodable)]
-pub struct BoundConst<'tcx> {
+pub struct BoundConst {
     pub var: BoundVar,
-    pub ty: Ty<'tcx>,
 }
 
-pub type PlaceholderConst = Placeholder<BoundVar>;
+impl<'tcx> rustc_type_ir::inherent::BoundVarLike<TyCtxt<'tcx>> for BoundConst {
+    fn var(self) -> BoundVar {
+        self.var
+    }
+
+    fn assert_eq(self, var: ty::BoundVariableKind) {
+        var.expect_const()
+    }
+}
+
+pub type PlaceholderConst = Placeholder<BoundConst>;
 
 impl<'tcx> rustc_type_ir::inherent::PlaceholderLike<TyCtxt<'tcx>> for PlaceholderConst {
-    type Bound = BoundVar;
+    type Bound = BoundConst;
 
     fn universe(self) -> UniverseIndex {
         self.universe
     }
 
     fn var(self) -> BoundVar {
-        self.bound
+        self.bound.var
     }
 
     fn with_updated_universe(self, ui: UniverseIndex) -> Self {
         Placeholder { universe: ui, ..self }
     }
 
-    fn new(ui: UniverseIndex, bound: BoundVar) -> Self {
+    fn new(ui: UniverseIndex, bound: BoundConst) -> Self {
         Placeholder { universe: ui, bound }
     }
 
     fn new_anon(ui: UniverseIndex, var: BoundVar) -> Self {
-        Placeholder { universe: ui, bound: var }
+        Placeholder { universe: ui, bound: BoundConst { var } }
     }
 }
 
@@ -1069,12 +1018,6 @@ pub struct ParamEnvAnd<'tcx, T> {
     pub value: T,
 }
 
-impl<'tcx, T> ParamEnvAnd<'tcx, T> {
-    pub fn into_parts(self) -> (ParamEnv<'tcx>, T) {
-        (self.param_env, self.value)
-    }
-}
-
 /// The environment in which to do trait solving.
 ///
 /// Most of the time you only need to care about the `ParamEnv`
@@ -1525,7 +1468,7 @@ impl<'tcx> TyCtxt<'tcx> {
         }
 
         if let Some(reprs) =
-            attr::find_attr!(self.get_all_attrs(did), AttributeKind::Repr { reprs, .. } => reprs)
+            find_attr!(self.get_all_attrs(did), AttributeKind::Repr { reprs, .. } => reprs)
         {
             for (r, _) in reprs {
                 flags.insert(match *r {
@@ -1770,15 +1713,6 @@ impl<'tcx> TyCtxt<'tcx> {
         }
     }
 
-    // FIXME(@lcnr): Remove this function.
-    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.attrs_for_def(did)
-        }
-    }
-
     /// Gets all attributes with the given name.
     pub fn get_attrs(
         self,
@@ -1790,7 +1724,8 @@ impl<'tcx> TyCtxt<'tcx> {
 
     /// Gets all attributes.
     ///
-    /// To see if an item has a specific attribute, you should use [`rustc_attr_data_structures::find_attr!`] so you can use matching.
+    /// To see if an item has a specific attribute, you should use
+    /// [`rustc_hir::find_attr!`] so you can use matching.
     pub fn get_all_attrs(self, did: impl Into<DefId>) -> &'tcx [hir::Attribute] {
         let did: DefId = did.into();
         if let Some(did) = did.as_local() {
@@ -2198,59 +2133,6 @@ impl<'tcx> TyCtxt<'tcx> {
     }
 }
 
-pub fn int_ty(ity: ast::IntTy) -> IntTy {
-    match ity {
-        ast::IntTy::Isize => IntTy::Isize,
-        ast::IntTy::I8 => IntTy::I8,
-        ast::IntTy::I16 => IntTy::I16,
-        ast::IntTy::I32 => IntTy::I32,
-        ast::IntTy::I64 => IntTy::I64,
-        ast::IntTy::I128 => IntTy::I128,
-    }
-}
-
-pub fn uint_ty(uty: ast::UintTy) -> UintTy {
-    match uty {
-        ast::UintTy::Usize => UintTy::Usize,
-        ast::UintTy::U8 => UintTy::U8,
-        ast::UintTy::U16 => UintTy::U16,
-        ast::UintTy::U32 => UintTy::U32,
-        ast::UintTy::U64 => UintTy::U64,
-        ast::UintTy::U128 => UintTy::U128,
-    }
-}
-
-pub fn float_ty(fty: ast::FloatTy) -> FloatTy {
-    match fty {
-        ast::FloatTy::F16 => FloatTy::F16,
-        ast::FloatTy::F32 => FloatTy::F32,
-        ast::FloatTy::F64 => FloatTy::F64,
-        ast::FloatTy::F128 => FloatTy::F128,
-    }
-}
-
-pub fn ast_int_ty(ity: IntTy) -> ast::IntTy {
-    match ity {
-        IntTy::Isize => ast::IntTy::Isize,
-        IntTy::I8 => ast::IntTy::I8,
-        IntTy::I16 => ast::IntTy::I16,
-        IntTy::I32 => ast::IntTy::I32,
-        IntTy::I64 => ast::IntTy::I64,
-        IntTy::I128 => ast::IntTy::I128,
-    }
-}
-
-pub fn ast_uint_ty(uty: UintTy) -> ast::UintTy {
-    match uty {
-        UintTy::Usize => ast::UintTy::Usize,
-        UintTy::U8 => ast::UintTy::U8,
-        UintTy::U16 => ast::UintTy::U16,
-        UintTy::U32 => ast::UintTy::U32,
-        UintTy::U64 => ast::UintTy::U64,
-        UintTy::U128 => ast::UintTy::U128,
-    }
-}
-
 pub fn provide(providers: &mut Providers) {
     closure::provide(providers);
     context::provide(providers);
@@ -2304,34 +2186,9 @@ impl<'tcx> fmt::Debug for SymbolName<'tcx> {
     }
 }
 
-#[derive(Debug, Default, Copy, Clone)]
-pub struct InferVarInfo {
-    /// This is true if we identified that this Ty (`?T`) is found in a `?T: Foo`
-    /// obligation, where:
-    ///
-    ///  * `Foo` is not `Sized`
-    ///  * `(): Foo` may be satisfied
-    pub self_in_trait: bool,
-    /// This is true if we identified that this Ty (`?T`) is found in a `<_ as
-    /// _>::AssocType = ?T`
-    pub output: bool,
-}
-
 /// The constituent parts of a type level constant of kind ADT or array.
 #[derive(Copy, Clone, Debug, HashStable)]
 pub struct DestructuredConst<'tcx> {
     pub variant: Option<VariantIdx>,
     pub fields: &'tcx [ty::Const<'tcx>],
 }
-
-// Some types are used a lot. Make sure they don't unintentionally get bigger.
-#[cfg(target_pointer_width = "64")]
-mod size_asserts {
-    use rustc_data_structures::static_assert_size;
-
-    use super::*;
-    // tidy-alphabetical-start
-    static_assert_size!(PredicateKind<'_>, 32);
-    static_assert_size!(WithCachedTypeInfo<TyKind<'_>>, 48);
-    // tidy-alphabetical-end
-}
diff --git a/compiler/rustc_middle/src/ty/parameterized.rs b/compiler/rustc_middle/src/ty/parameterized.rs
deleted file mode 100644
index dbacbe21edb..00000000000
--- a/compiler/rustc_middle/src/ty/parameterized.rs
+++ /dev/null
@@ -1,155 +0,0 @@
-use std::hash::Hash;
-
-use rustc_data_structures::unord::UnordMap;
-use rustc_hir::def_id::DefIndex;
-use rustc_index::{Idx, IndexVec};
-use rustc_span::Symbol;
-
-use crate::ty;
-
-pub trait ParameterizedOverTcx: 'static {
-    type Value<'tcx>;
-}
-
-impl<T: ParameterizedOverTcx> ParameterizedOverTcx for &'static [T] {
-    type Value<'tcx> = &'tcx [T::Value<'tcx>];
-}
-
-impl<T: ParameterizedOverTcx> ParameterizedOverTcx for Option<T> {
-    type Value<'tcx> = Option<T::Value<'tcx>>;
-}
-
-impl<A: ParameterizedOverTcx, B: ParameterizedOverTcx> ParameterizedOverTcx for (A, B) {
-    type Value<'tcx> = (A::Value<'tcx>, B::Value<'tcx>);
-}
-
-impl<T: ParameterizedOverTcx> ParameterizedOverTcx for Vec<T> {
-    type Value<'tcx> = Vec<T::Value<'tcx>>;
-}
-
-impl<I: Idx + 'static, T: ParameterizedOverTcx> ParameterizedOverTcx for IndexVec<I, T> {
-    type Value<'tcx> = IndexVec<I, T::Value<'tcx>>;
-}
-
-impl<I: Hash + Eq + 'static, T: ParameterizedOverTcx> ParameterizedOverTcx for UnordMap<I, T> {
-    type Value<'tcx> = UnordMap<I, T::Value<'tcx>>;
-}
-
-impl<T: ParameterizedOverTcx> ParameterizedOverTcx for ty::Binder<'static, T> {
-    type Value<'tcx> = ty::Binder<'tcx, T::Value<'tcx>>;
-}
-
-impl<T: ParameterizedOverTcx> ParameterizedOverTcx for ty::EarlyBinder<'static, T> {
-    type Value<'tcx> = ty::EarlyBinder<'tcx, T::Value<'tcx>>;
-}
-
-#[macro_export]
-macro_rules! trivially_parameterized_over_tcx {
-    ($($ty:ty),+ $(,)?) => {
-        $(
-            impl $crate::ty::ParameterizedOverTcx for $ty {
-                #[allow(unused_lifetimes)]
-                type Value<'tcx> = $ty;
-            }
-        )*
-    }
-}
-
-trivially_parameterized_over_tcx! {
-    usize,
-    (),
-    u32,
-    u64,
-    bool,
-    std::string::String,
-    crate::metadata::ModChild,
-    crate::middle::codegen_fn_attrs::CodegenFnAttrs,
-    crate::middle::debugger_visualizer::DebuggerVisualizerFile,
-    crate::middle::exported_symbols::SymbolExportInfo,
-    crate::middle::lib_features::FeatureStability,
-    crate::middle::resolve_bound_vars::ObjectLifetimeDefault,
-    crate::mir::ConstQualifs,
-    ty::AsyncDestructor,
-    ty::AssocItemContainer,
-    ty::Asyncness,
-    ty::AnonConstKind,
-    ty::DeducedParamAttrs,
-    ty::Destructor,
-    ty::Generics,
-    ty::ImplPolarity,
-    ty::ImplTraitInTraitData,
-    ty::ReprOptions,
-    ty::TraitDef,
-    ty::UnusedGenericParams,
-    ty::Visibility<DefIndex>,
-    ty::adjustment::CoerceUnsizedInfo,
-    ty::fast_reject::SimplifiedType,
-    ty::IntrinsicDef,
-    rustc_ast::Attribute,
-    rustc_ast::DelimArgs,
-    rustc_attr_data_structures::StrippedCfgItem<rustc_hir::def_id::DefIndex>,
-    rustc_attr_data_structures::ConstStability,
-    rustc_attr_data_structures::DefaultBodyStability,
-    rustc_attr_data_structures::Deprecation,
-    rustc_attr_data_structures::Stability,
-    rustc_hir::Constness,
-    rustc_hir::Defaultness,
-    rustc_hir::Safety,
-    rustc_hir::CoroutineKind,
-    rustc_hir::IsAsync,
-    rustc_hir::LangItem,
-    rustc_hir::def::DefKind,
-    rustc_hir::def::DocLinkResMap,
-    rustc_hir::def_id::DefId,
-    rustc_hir::def_id::DefIndex,
-    rustc_hir::definitions::DefKey,
-    rustc_hir::OpaqueTyOrigin<rustc_hir::def_id::DefId>,
-    rustc_hir::PreciseCapturingArgKind<Symbol, Symbol>,
-    rustc_index::bit_set::DenseBitSet<u32>,
-    rustc_index::bit_set::FiniteBitSet<u32>,
-    rustc_session::cstore::ForeignModule,
-    rustc_session::cstore::LinkagePreference,
-    rustc_session::cstore::NativeLib,
-    rustc_session::config::TargetModifier,
-    rustc_span::ExpnData,
-    rustc_span::ExpnHash,
-    rustc_span::ExpnId,
-    rustc_span::SourceFile,
-    rustc_span::Span,
-    rustc_span::Symbol,
-    rustc_span::def_id::DefPathHash,
-    rustc_span::hygiene::SyntaxContextKey,
-    rustc_span::Ident,
-    rustc_type_ir::Variance,
-    rustc_hir::Attribute,
-}
-
-// HACK(compiler-errors): This macro rule can only take a fake path,
-// not a real, due to parsing ambiguity reasons.
-#[macro_export]
-macro_rules! parameterized_over_tcx {
-    ($($($fake_path:ident)::+),+ $(,)?) => {
-        $(
-            impl $crate::ty::ParameterizedOverTcx for $($fake_path)::+<'static> {
-                type Value<'tcx> = $($fake_path)::+<'tcx>;
-            }
-        )*
-    }
-}
-
-parameterized_over_tcx! {
-    crate::middle::exported_symbols::ExportedSymbol,
-    crate::mir::Body,
-    crate::mir::CoroutineLayout,
-    crate::mir::interpret::ConstAllocation,
-    ty::Ty,
-    ty::FnSig,
-    ty::GenericPredicates,
-    ty::ConstConditions,
-    ty::TraitRef,
-    ty::Const,
-    ty::Predicate,
-    ty::Clause,
-    ty::ClauseKind,
-    ty::ImplTraitHeader,
-}
diff --git a/compiler/rustc_middle/src/ty/predicate.rs b/compiler/rustc_middle/src/ty/predicate.rs
index 46f254e9d30..73a6f1829af 100644
--- a/compiler/rustc_middle/src/ty/predicate.rs
+++ b/compiler/rustc_middle/src/ty/predicate.rs
@@ -704,3 +704,15 @@ impl<'tcx> Predicate<'tcx> {
         }
     }
 }
+
+// Some types are used a lot. Make sure they don't unintentionally get bigger.
+#[cfg(target_pointer_width = "64")]
+mod size_asserts {
+    use rustc_data_structures::static_assert_size;
+
+    use super::*;
+    // tidy-alphabetical-start
+    static_assert_size!(PredicateKind<'_>, 32);
+    static_assert_size!(WithCachedTypeInfo<PredicateKind<'_>>, 56);
+    // tidy-alphabetical-end
+}
diff --git a/compiler/rustc_middle/src/ty/print/mod.rs b/compiler/rustc_middle/src/ty/print/mod.rs
index 9172c5d3ab7..8a125c7fe28 100644
--- a/compiler/rustc_middle/src/ty/print/mod.rs
+++ b/compiler/rustc_middle/src/ty/print/mod.rs
@@ -18,7 +18,7 @@ use super::Lift;
 pub type PrintError = std::fmt::Error;
 
 pub trait Print<'tcx, P> {
-    fn print(&self, cx: &mut P) -> Result<(), PrintError>;
+    fn print(&self, p: &mut P) -> Result<(), PrintError>;
 }
 
 /// Interface for outputting user-facing "type-system entities"
@@ -88,7 +88,6 @@ pub trait Printer<'tcx>: Sized {
     fn path_append_impl(
         &mut self,
         print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
-        disambiguated_data: &DisambiguatedDefPathData,
         self_ty: Ty<'tcx>,
         trait_ref: Option<ty::TraitRef<'tcx>>,
     ) -> Result<(), PrintError>;
@@ -148,7 +147,7 @@ pub trait Printer<'tcx>: Sized {
                                 && args.len() > parent_args.len()
                             {
                                 return self.path_generic_args(
-                                    |cx| cx.print_def_path(def_id, parent_args),
+                                    |p| p.print_def_path(def_id, parent_args),
                                     &args[..parent_args.len() + 1][..1],
                                 );
                             } else {
@@ -170,7 +169,7 @@ pub trait Printer<'tcx>: Sized {
                             if !generics.is_own_empty() && args.len() >= generics.count() {
                                 let args = generics.own_args_no_defaults(self.tcx(), args);
                                 return self.path_generic_args(
-                                    |cx| cx.print_def_path(def_id, parent_args),
+                                    |p| p.print_def_path(def_id, parent_args),
                                     args,
                                 );
                             }
@@ -186,16 +185,16 @@ pub trait Printer<'tcx>: Sized {
                 }
 
                 self.path_append(
-                    |cx: &mut Self| {
+                    |p: &mut Self| {
                         if trait_qualify_parent {
                             let trait_ref = ty::TraitRef::new(
-                                cx.tcx(),
+                                p.tcx(),
                                 parent_def_id,
                                 parent_args.iter().copied(),
                             );
-                            cx.path_qualified(trait_ref.self_ty(), Some(trait_ref))
+                            p.path_qualified(trait_ref.self_ty(), Some(trait_ref))
                         } else {
-                            cx.print_def_path(parent_def_id, parent_args)
+                            p.print_def_path(parent_def_id, parent_args)
                         }
                     },
                     &key.disambiguated_data,
@@ -236,12 +235,7 @@ pub trait Printer<'tcx>: Sized {
             // If the impl is not co-located with either self-type or
             // trait-type, then fallback to a format that identifies
             // the module more clearly.
-            self.path_append_impl(
-                |cx| cx.print_def_path(parent_def_id, &[]),
-                &key.disambiguated_data,
-                self_ty,
-                impl_trait_ref,
-            )
+            self.path_append_impl(|p| p.print_def_path(parent_def_id, &[]), self_ty, impl_trait_ref)
         } else {
             // Otherwise, try to give a good form that would be valid language
             // syntax. Preferably using associated item notation.
@@ -312,26 +306,26 @@ pub fn characteristic_def_id_of_type(ty: Ty<'_>) -> Option<DefId> {
 }
 
 impl<'tcx, P: Printer<'tcx>> Print<'tcx, P> for ty::Region<'tcx> {
-    fn print(&self, cx: &mut P) -> Result<(), PrintError> {
-        cx.print_region(*self)
+    fn print(&self, p: &mut P) -> Result<(), PrintError> {
+        p.print_region(*self)
     }
 }
 
 impl<'tcx, P: Printer<'tcx>> Print<'tcx, P> for Ty<'tcx> {
-    fn print(&self, cx: &mut P) -> Result<(), PrintError> {
-        cx.print_type(*self)
+    fn print(&self, p: &mut P) -> Result<(), PrintError> {
+        p.print_type(*self)
     }
 }
 
 impl<'tcx, P: Printer<'tcx>> Print<'tcx, P> for &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>> {
-    fn print(&self, cx: &mut P) -> Result<(), PrintError> {
-        cx.print_dyn_existential(self)
+    fn print(&self, p: &mut P) -> Result<(), PrintError> {
+        p.print_dyn_existential(self)
     }
 }
 
 impl<'tcx, P: Printer<'tcx>> Print<'tcx, P> for ty::Const<'tcx> {
-    fn print(&self, cx: &mut P) -> Result<(), PrintError> {
-        cx.print_const(*self)
+    fn print(&self, p: &mut P) -> Result<(), PrintError> {
+        p.print_const(*self)
     }
 }
 
@@ -351,9 +345,9 @@ where
 {
     fn print(t: &T, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         ty::tls::with(|tcx| {
-            let mut cx = FmtPrinter::new(tcx, Namespace::TypeNS);
-            tcx.lift(*t).expect("could not lift for printing").print(&mut cx)?;
-            fmt.write_str(&cx.into_buffer())?;
+            let mut p = FmtPrinter::new(tcx, Namespace::TypeNS);
+            tcx.lift(*t).expect("could not lift for printing").print(&mut p)?;
+            fmt.write_str(&p.into_buffer())?;
             Ok(())
         })
     }
diff --git a/compiler/rustc_middle/src/ty/print/pretty.rs b/compiler/rustc_middle/src/ty/print/pretty.rs
index 5c44b10ba71..b381d62be47 100644
--- a/compiler/rustc_middle/src/ty/print/pretty.rs
+++ b/compiler/rustc_middle/src/ty/print/pretty.rs
@@ -29,33 +29,6 @@ use crate::ty::{
     TypeFoldable, TypeSuperFoldable, TypeSuperVisitable, TypeVisitable, TypeVisitableExt,
 };
 
-macro_rules! p {
-    (@$lit:literal) => {
-        write!(scoped_cx!(), $lit)?
-    };
-    (@write($($data:expr),+)) => {
-        write!(scoped_cx!(), $($data),+)?
-    };
-    (@print($x:expr)) => {
-        $x.print(scoped_cx!())?
-    };
-    (@$method:ident($($arg:expr),*)) => {
-        scoped_cx!().$method($($arg),*)?
-    };
-    ($($elem:tt $(($($args:tt)*))?),+) => {{
-        $(p!(@ $elem $(($($args)*))?);)+
-    }};
-}
-macro_rules! define_scoped_cx {
-    ($cx:ident) => {
-        macro_rules! scoped_cx {
-            () => {
-                $cx
-            };
-        }
-    };
-}
-
 thread_local! {
     static FORCE_IMPL_FILENAME_LINE: Cell<bool> = const { Cell::new(false) };
     static SHOULD_PREFIX_WITH_CRATE: Cell<bool> = const { Cell::new(false) };
@@ -689,12 +662,11 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
             }
         }
 
-        self.generic_delimiters(|cx| {
-            define_scoped_cx!(cx);
-
-            p!(print(self_ty));
+        self.generic_delimiters(|p| {
+            self_ty.print(p)?;
             if let Some(trait_ref) = trait_ref {
-                p!(" as ", print(trait_ref.print_only_trait_path()));
+                write!(p, " as ")?;
+                trait_ref.print_only_trait_path().print(p)?;
             }
             Ok(())
         })
@@ -708,121 +680,121 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
     ) -> Result<(), PrintError> {
         print_prefix(self)?;
 
-        self.generic_delimiters(|cx| {
-            define_scoped_cx!(cx);
-
-            p!("impl ");
+        self.generic_delimiters(|p| {
+            write!(p, "impl ")?;
             if let Some(trait_ref) = trait_ref {
-                p!(print(trait_ref.print_only_trait_path()), " for ");
+                trait_ref.print_only_trait_path().print(p)?;
+                write!(p, " for ")?;
             }
-            p!(print(self_ty));
+            self_ty.print(p)?;
 
             Ok(())
         })
     }
 
     fn pretty_print_type(&mut self, ty: Ty<'tcx>) -> Result<(), PrintError> {
-        define_scoped_cx!(self);
-
         match *ty.kind() {
-            ty::Bool => p!("bool"),
-            ty::Char => p!("char"),
-            ty::Int(t) => p!(write("{}", t.name_str())),
-            ty::Uint(t) => p!(write("{}", t.name_str())),
-            ty::Float(t) => p!(write("{}", t.name_str())),
+            ty::Bool => write!(self, "bool")?,
+            ty::Char => write!(self, "char")?,
+            ty::Int(t) => write!(self, "{}", t.name_str())?,
+            ty::Uint(t) => write!(self, "{}", t.name_str())?,
+            ty::Float(t) => write!(self, "{}", t.name_str())?,
             ty::Pat(ty, pat) => {
-                p!("(", print(ty), ") is ", write("{pat:?}"))
+                write!(self, "(")?;
+                ty.print(self)?;
+                write!(self, ") is {pat:?}")?;
             }
             ty::RawPtr(ty, mutbl) => {
-                p!(write("*{} ", mutbl.ptr_str()));
-                p!(print(ty))
+                write!(self, "*{} ", mutbl.ptr_str())?;
+                ty.print(self)?;
             }
             ty::Ref(r, ty, mutbl) => {
-                p!("&");
+                write!(self, "&")?;
                 if self.should_print_region(r) {
-                    p!(print(r), " ");
+                    r.print(self)?;
+                    write!(self, " ")?;
                 }
-                p!(print(ty::TypeAndMut { ty, mutbl }))
+                ty::TypeAndMut { ty, mutbl }.print(self)?;
             }
-            ty::Never => p!("!"),
+            ty::Never => write!(self, "!")?,
             ty::Tuple(tys) => {
-                p!("(", comma_sep(tys.iter()));
+                write!(self, "(")?;
+                self.comma_sep(tys.iter())?;
                 if tys.len() == 1 {
-                    p!(",");
+                    write!(self, ",")?;
                 }
-                p!(")")
+                write!(self, ")")?;
             }
             ty::FnDef(def_id, args) => {
                 if with_reduced_queries() {
-                    p!(print_def_path(def_id, args));
+                    self.print_def_path(def_id, args)?;
                 } else {
                     let mut sig = self.tcx().fn_sig(def_id).instantiate(self.tcx(), args);
                     if self.tcx().codegen_fn_attrs(def_id).safe_target_features {
-                        p!("#[target_features] ");
+                        write!(self, "#[target_features] ")?;
                         sig = sig.map_bound(|mut sig| {
                             sig.safety = hir::Safety::Safe;
                             sig
                         });
                     }
-                    p!(print(sig), " {{", print_value_path(def_id, args), "}}");
+                    sig.print(self)?;
+                    write!(self, " {{")?;
+                    self.print_value_path(def_id, args)?;
+                    write!(self, "}}")?;
                 }
             }
-            ty::FnPtr(ref sig_tys, hdr) => p!(print(sig_tys.with(hdr))),
+            ty::FnPtr(ref sig_tys, hdr) => sig_tys.with(hdr).print(self)?,
             ty::UnsafeBinder(ref bound_ty) => {
-                self.wrap_binder(bound_ty, WrapBinderMode::Unsafe, |ty, cx| {
-                    cx.pretty_print_type(*ty)
+                self.wrap_binder(bound_ty, WrapBinderMode::Unsafe, |ty, p| {
+                    p.pretty_print_type(*ty)
                 })?;
             }
             ty::Infer(infer_ty) => {
                 if self.should_print_verbose() {
-                    p!(write("{:?}", ty.kind()));
+                    write!(self, "{:?}", ty.kind())?;
                     return Ok(());
                 }
 
                 if let ty::TyVar(ty_vid) = infer_ty {
                     if let Some(name) = self.ty_infer_name(ty_vid) {
-                        p!(write("{}", name))
+                        write!(self, "{name}")?;
                     } else {
-                        p!(write("{}", infer_ty))
+                        write!(self, "{infer_ty}")?;
                     }
                 } else {
-                    p!(write("{}", infer_ty))
+                    write!(self, "{infer_ty}")?;
                 }
             }
-            ty::Error(_) => p!("{{type error}}"),
-            ty::Param(ref param_ty) => p!(print(param_ty)),
+            ty::Error(_) => write!(self, "{{type error}}")?,
+            ty::Param(ref param_ty) => param_ty.print(self)?,
             ty::Bound(debruijn, bound_ty) => match bound_ty.kind {
                 ty::BoundTyKind::Anon => {
                     rustc_type_ir::debug_bound_var(self, debruijn, bound_ty.var)?
                 }
                 ty::BoundTyKind::Param(def_id) => match self.should_print_verbose() {
-                    true => p!(write("{:?}", ty.kind())),
-                    false => p!(write("{}", self.tcx().item_name(def_id))),
+                    true => write!(self, "{:?}", ty.kind())?,
+                    false => write!(self, "{}", self.tcx().item_name(def_id))?,
                 },
             },
-            ty::Adt(def, args) => {
-                p!(print_def_path(def.did(), args));
-            }
+            ty::Adt(def, args) => self.print_def_path(def.did(), args)?,
             ty::Dynamic(data, r, repr) => {
                 let print_r = self.should_print_region(r);
                 if print_r {
-                    p!("(");
+                    write!(self, "(")?;
                 }
                 match repr {
-                    ty::Dyn => p!("dyn "),
+                    ty::Dyn => write!(self, "dyn ")?,
                 }
-                p!(print(data));
+                data.print(self)?;
                 if print_r {
-                    p!(" + ", print(r), ")");
+                    write!(self, " + ")?;
+                    r.print(self)?;
+                    write!(self, ")")?;
                 }
             }
-            ty::Foreign(def_id) => {
-                p!(print_def_path(def_id, &[]));
-            }
-            ty::Alias(ty::Projection | ty::Inherent | ty::Free, ref data) => {
-                p!(print(data))
-            }
-            ty::Placeholder(placeholder) => p!(print(placeholder)),
+            ty::Foreign(def_id) => self.print_def_path(def_id, &[])?,
+            ty::Alias(ty::Projection | ty::Inherent | ty::Free, ref data) => data.print(self)?,
+            ty::Placeholder(placeholder) => placeholder.print(self)?,
             ty::Alias(ty::Opaque, ty::AliasTy { def_id, args, .. }) => {
                 // We use verbose printing in 'NO_QUERIES' mode, to
                 // avoid needing to call `predicates_of`. This should
@@ -834,7 +806,7 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                 // example.]
                 if self.should_print_verbose() {
                     // FIXME(eddyb) print this with `print_def_path`.
-                    p!(write("Opaque({:?}, {})", def_id, args.print_as_list()));
+                    write!(self, "Opaque({:?}, {})", def_id, args.print_as_list())?;
                     return Ok(());
                 }
 
@@ -849,17 +821,17 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                             if d == def_id {
                                 // If the type alias directly starts with the `impl` of the
                                 // opaque type we're printing, then skip the `::{opaque#1}`.
-                                p!(print_def_path(parent, args));
+                                self.print_def_path(parent, args)?;
                                 return Ok(());
                             }
                         }
                         // Complex opaque type, e.g. `type Foo = (i32, impl Debug);`
-                        p!(print_def_path(def_id, args));
+                        self.print_def_path(def_id, args)?;
                         return Ok(());
                     }
                     _ => {
                         if with_reduced_queries() {
-                            p!(print_def_path(def_id, &[]));
+                            self.print_def_path(def_id, &[])?;
                             return Ok(());
                         } else {
                             return self.pretty_print_opaque_impl_type(def_id, args);
@@ -867,9 +839,9 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                     }
                 }
             }
-            ty::Str => p!("str"),
+            ty::Str => write!(self, "str")?,
             ty::Coroutine(did, args) => {
-                p!("{{");
+                write!(self, "{{")?;
                 let coroutine_kind = self.tcx().coroutine_kind(did).unwrap();
                 let should_print_movability = self.should_print_verbose()
                     || matches!(coroutine_kind, hir::CoroutineKind::Coroutine(_));
@@ -877,12 +849,12 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                 if should_print_movability {
                     match coroutine_kind.movability() {
                         hir::Movability::Movable => {}
-                        hir::Movability::Static => p!("static "),
+                        hir::Movability::Static => write!(self, "static ")?,
                     }
                 }
 
                 if !self.should_print_verbose() {
-                    p!(write("{}", coroutine_kind));
+                    write!(self, "{coroutine_kind}")?;
                     if coroutine_kind.is_fn_like() {
                         // If we are printing an `async fn` coroutine type, then give the path
                         // of the fn, instead of its span, because that will in most cases be
@@ -891,68 +863,71 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                         // This will look like:
                         //    {async fn body of some_fn()}
                         let did_of_the_fn_item = self.tcx().parent(did);
-                        p!(" of ", print_def_path(did_of_the_fn_item, args), "()");
+                        write!(self, " of ")?;
+                        self.print_def_path(did_of_the_fn_item, args)?;
+                        write!(self, "()")?;
                     } else if let Some(local_did) = did.as_local() {
                         let span = self.tcx().def_span(local_did);
-                        p!(write(
+                        write!(
+                            self,
                             "@{}",
                             // This may end up in stderr diagnostics but it may also be emitted
                             // into MIR. Hence we use the remapped path if available
                             self.tcx().sess.source_map().span_to_embeddable_string(span)
-                        ));
+                        )?;
                     } else {
-                        p!("@", print_def_path(did, args));
+                        write!(self, "@")?;
+                        self.print_def_path(did, args)?;
                     }
                 } else {
-                    p!(print_def_path(did, args));
-                    p!(
-                        " upvar_tys=",
-                        print(args.as_coroutine().tupled_upvars_ty()),
-                        " resume_ty=",
-                        print(args.as_coroutine().resume_ty()),
-                        " yield_ty=",
-                        print(args.as_coroutine().yield_ty()),
-                        " return_ty=",
-                        print(args.as_coroutine().return_ty()),
-                        " witness=",
-                        print(args.as_coroutine().witness())
-                    );
+                    self.print_def_path(did, args)?;
+                    write!(self, " upvar_tys=")?;
+                    args.as_coroutine().tupled_upvars_ty().print(self)?;
+                    write!(self, " resume_ty=")?;
+                    args.as_coroutine().resume_ty().print(self)?;
+                    write!(self, " yield_ty=")?;
+                    args.as_coroutine().yield_ty().print(self)?;
+                    write!(self, " return_ty=")?;
+                    args.as_coroutine().return_ty().print(self)?;
                 }
 
-                p!("}}")
+                write!(self, "}}")?
             }
             ty::CoroutineWitness(did, args) => {
-                p!(write("{{"));
+                write!(self, "{{")?;
                 if !self.tcx().sess.verbose_internals() {
-                    p!("coroutine witness");
+                    write!(self, "coroutine witness")?;
                     if let Some(did) = did.as_local() {
                         let span = self.tcx().def_span(did);
-                        p!(write(
+                        write!(
+                            self,
                             "@{}",
                             // This may end up in stderr diagnostics but it may also be emitted
                             // into MIR. Hence we use the remapped path if available
                             self.tcx().sess.source_map().span_to_embeddable_string(span)
-                        ));
+                        )?;
                     } else {
-                        p!(write("@"), print_def_path(did, args));
+                        write!(self, "@")?;
+                        self.print_def_path(did, args)?;
                     }
                 } else {
-                    p!(print_def_path(did, args));
+                    self.print_def_path(did, args)?;
                 }
 
-                p!("}}")
+                write!(self, "}}")?
             }
             ty::Closure(did, args) => {
-                p!(write("{{"));
+                write!(self, "{{")?;
                 if !self.should_print_verbose() {
-                    p!(write("closure"));
+                    write!(self, "closure")?;
                     if self.should_truncate() {
                         write!(self, "@...}}")?;
                         return Ok(());
                     } else {
                         if let Some(did) = did.as_local() {
                             if self.tcx().sess.opts.unstable_opts.span_free_formats {
-                                p!("@", print_def_path(did.to_def_id(), args));
+                                write!(self, "@")?;
+                                self.print_def_path(did.to_def_id(), args)?;
                             } else {
                                 let span = self.tcx().def_span(did);
                                 let preference = if with_forced_trimmed_paths() {
@@ -960,54 +935,56 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                                 } else {
                                     FileNameDisplayPreference::Remapped
                                 };
-                                p!(write(
+                                write!(
+                                    self,
                                     "@{}",
-                                    // This may end up in stderr diagnostics but it may also be emitted
-                                    // into MIR. Hence we use the remapped path if available
+                                    // This may end up in stderr diagnostics but it may also be
+                                    // emitted into MIR. Hence we use the remapped path if
+                                    // available
                                     self.tcx().sess.source_map().span_to_string(span, preference)
-                                ));
+                                )?;
                             }
                         } else {
-                            p!(write("@"), print_def_path(did, args));
+                            write!(self, "@")?;
+                            self.print_def_path(did, args)?;
                         }
                     }
                 } else {
-                    p!(print_def_path(did, args));
-                    p!(
-                        " closure_kind_ty=",
-                        print(args.as_closure().kind_ty()),
-                        " closure_sig_as_fn_ptr_ty=",
-                        print(args.as_closure().sig_as_fn_ptr_ty()),
-                        " upvar_tys=",
-                        print(args.as_closure().tupled_upvars_ty())
-                    );
+                    self.print_def_path(did, args)?;
+                    write!(self, " closure_kind_ty=")?;
+                    args.as_closure().kind_ty().print(self)?;
+                    write!(self, " closure_sig_as_fn_ptr_ty=")?;
+                    args.as_closure().sig_as_fn_ptr_ty().print(self)?;
+                    write!(self, " upvar_tys=")?;
+                    args.as_closure().tupled_upvars_ty().print(self)?;
                 }
-                p!("}}");
+                write!(self, "}}")?;
             }
             ty::CoroutineClosure(did, args) => {
-                p!(write("{{"));
+                write!(self, "{{")?;
                 if !self.should_print_verbose() {
                     match self.tcx().coroutine_kind(self.tcx().coroutine_for_closure(did)).unwrap()
                     {
                         hir::CoroutineKind::Desugared(
                             hir::CoroutineDesugaring::Async,
                             hir::CoroutineSource::Closure,
-                        ) => p!("async closure"),
+                        ) => write!(self, "async closure")?,
                         hir::CoroutineKind::Desugared(
                             hir::CoroutineDesugaring::AsyncGen,
                             hir::CoroutineSource::Closure,
-                        ) => p!("async gen closure"),
+                        ) => write!(self, "async gen closure")?,
                         hir::CoroutineKind::Desugared(
                             hir::CoroutineDesugaring::Gen,
                             hir::CoroutineSource::Closure,
-                        ) => p!("gen closure"),
+                        ) => write!(self, "gen closure")?,
                         _ => unreachable!(
                             "coroutine from coroutine-closure should have CoroutineSource::Closure"
                         ),
                     }
                     if let Some(did) = did.as_local() {
                         if self.tcx().sess.opts.unstable_opts.span_free_formats {
-                            p!("@", print_def_path(did.to_def_id(), args));
+                            write!(self, "@")?;
+                            self.print_def_path(did.to_def_id(), args)?;
                         } else {
                             let span = self.tcx().def_span(did);
                             let preference = if with_forced_trimmed_paths() {
@@ -1015,35 +992,43 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                             } else {
                                 FileNameDisplayPreference::Remapped
                             };
-                            p!(write(
+                            write!(
+                                self,
                                 "@{}",
                                 // This may end up in stderr diagnostics but it may also be emitted
                                 // into MIR. Hence we use the remapped path if available
                                 self.tcx().sess.source_map().span_to_string(span, preference)
-                            ));
+                            )?;
                         }
                     } else {
-                        p!(write("@"), print_def_path(did, args));
+                        write!(self, "@")?;
+                        self.print_def_path(did, args)?;
                     }
                 } else {
-                    p!(print_def_path(did, args));
-                    p!(
-                        " closure_kind_ty=",
-                        print(args.as_coroutine_closure().kind_ty()),
-                        " signature_parts_ty=",
-                        print(args.as_coroutine_closure().signature_parts_ty()),
-                        " upvar_tys=",
-                        print(args.as_coroutine_closure().tupled_upvars_ty()),
-                        " coroutine_captures_by_ref_ty=",
-                        print(args.as_coroutine_closure().coroutine_captures_by_ref_ty()),
-                        " coroutine_witness_ty=",
-                        print(args.as_coroutine_closure().coroutine_witness_ty())
-                    );
+                    self.print_def_path(did, args)?;
+                    write!(self, " closure_kind_ty=")?;
+                    args.as_coroutine_closure().kind_ty().print(self)?;
+                    write!(self, " signature_parts_ty=")?;
+                    args.as_coroutine_closure().signature_parts_ty().print(self)?;
+                    write!(self, " upvar_tys=")?;
+                    args.as_coroutine_closure().tupled_upvars_ty().print(self)?;
+                    write!(self, " coroutine_captures_by_ref_ty=")?;
+                    args.as_coroutine_closure().coroutine_captures_by_ref_ty().print(self)?;
                 }
-                p!("}}");
+                write!(self, "}}")?;
+            }
+            ty::Array(ty, sz) => {
+                write!(self, "[")?;
+                ty.print(self)?;
+                write!(self, "; ")?;
+                sz.print(self)?;
+                write!(self, "]")?;
+            }
+            ty::Slice(ty) => {
+                write!(self, "[")?;
+                ty.print(self)?;
+                write!(self, "]")?;
             }
-            ty::Array(ty, sz) => p!("[", print(ty), "; ", print(sz), "]"),
-            ty::Slice(ty) => p!("[", print(ty), "]"),
         }
 
         Ok(())
@@ -1141,25 +1126,25 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                 self.wrap_binder(
                     &bound_args_and_self_ty,
                     WrapBinderMode::ForAll,
-                    |(args, _), cx| {
-                        define_scoped_cx!(cx);
-                        p!(write("{}", tcx.item_name(trait_def_id)));
-                        p!("(");
+                    |(args, _), p| {
+                        write!(p, "{}", tcx.item_name(trait_def_id))?;
+                        write!(p, "(")?;
 
                         for (idx, ty) in args.iter().enumerate() {
                             if idx > 0 {
-                                p!(", ");
+                                write!(p, ", ")?;
                             }
-                            p!(print(ty));
+                            ty.print(p)?;
                         }
 
-                        p!(")");
+                        write!(p, ")")?;
                         if let Some(ty) = return_ty.skip_binder().as_type() {
                             if !ty.is_unit() {
-                                p!(" -> ", print(return_ty));
+                                write!(p, " -> ")?;
+                                return_ty.print(p)?;
                             }
                         }
-                        p!(write("{}", if paren_needed { ")" } else { "" }));
+                        write!(p, "{}", if paren_needed { ")" } else { "" })?;
 
                         first = false;
                         Ok(())
@@ -1185,13 +1170,11 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
         for (trait_pred, assoc_items) in traits {
             write!(self, "{}", if first { "" } else { " + " })?;
 
-            self.wrap_binder(&trait_pred, WrapBinderMode::ForAll, |trait_pred, cx| {
-                define_scoped_cx!(cx);
-
+            self.wrap_binder(&trait_pred, WrapBinderMode::ForAll, |trait_pred, p| {
                 if trait_pred.polarity == ty::PredicatePolarity::Negative {
-                    p!("!");
+                    write!(p, "!")?;
                 }
-                p!(print(trait_pred.trait_ref.print_only_trait_name()));
+                trait_pred.trait_ref.print_only_trait_name().print(p)?;
 
                 let generics = tcx.generics_of(trait_pred.def_id());
                 let own_args = generics.own_args_no_defaults(tcx, trait_pred.trait_ref.args);
@@ -1201,32 +1184,32 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
 
                     for ty in own_args {
                         if first {
-                            p!("<");
+                            write!(p, "<")?;
                             first = false;
                         } else {
-                            p!(", ");
+                            write!(p, ", ")?;
                         }
-                        p!(print(ty));
+                        ty.print(p)?;
                     }
 
                     for (assoc_item_def_id, term) in assoc_items {
                         if first {
-                            p!("<");
+                            write!(p, "<")?;
                             first = false;
                         } else {
-                            p!(", ");
+                            write!(p, ", ")?;
                         }
 
-                        p!(write("{} = ", tcx.associated_item(assoc_item_def_id).name()));
+                        write!(p, "{} = ", tcx.associated_item(assoc_item_def_id).name())?;
 
                         match term.skip_binder().kind() {
-                            TermKind::Ty(ty) => p!(print(ty)),
-                            TermKind::Const(c) => p!(print(c)),
+                            TermKind::Ty(ty) => ty.print(p)?,
+                            TermKind::Const(c) => c.print(p)?,
                         };
                     }
 
                     if !first {
-                        p!(">");
+                        write!(p, ">")?;
                     }
                 }
 
@@ -1326,9 +1309,9 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
     ) -> Result<(), PrintError> {
         let def_key = self.tcx().def_key(alias_ty.def_id);
         self.path_generic_args(
-            |cx| {
-                cx.path_append(
-                    |cx| cx.path_qualified(alias_ty.self_ty(), None),
+            |p| {
+                p.path_append(
+                    |p| p.path_qualified(alias_ty.self_ty(), None),
                     &def_key.disambiguated_data,
                 )
             },
@@ -1392,23 +1375,22 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
         let mut first = true;
 
         if let Some(bound_principal) = predicates.principal() {
-            self.wrap_binder(&bound_principal, WrapBinderMode::ForAll, |principal, cx| {
-                define_scoped_cx!(cx);
-                p!(print_def_path(principal.def_id, &[]));
+            self.wrap_binder(&bound_principal, WrapBinderMode::ForAll, |principal, p| {
+                p.print_def_path(principal.def_id, &[])?;
 
                 let mut resugared = false;
 
                 // Special-case `Fn(...) -> ...` and re-sugar it.
-                let fn_trait_kind = cx.tcx().fn_trait_kind_from_def_id(principal.def_id);
-                if !cx.should_print_verbose() && fn_trait_kind.is_some() {
+                let fn_trait_kind = p.tcx().fn_trait_kind_from_def_id(principal.def_id);
+                if !p.should_print_verbose() && fn_trait_kind.is_some() {
                     if let ty::Tuple(tys) = principal.args.type_at(0).kind() {
                         let mut projections = predicates.projection_bounds();
                         if let (Some(proj), None) = (projections.next(), projections.next()) {
-                            p!(pretty_fn_sig(
+                            p.pretty_fn_sig(
                                 tys,
                                 false,
-                                proj.skip_binder().term.as_type().expect("Return type was a const")
-                            ));
+                                proj.skip_binder().term.as_type().expect("Return type was a const"),
+                            )?;
                             resugared = true;
                         }
                     }
@@ -1418,18 +1400,18 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                 // in order to place the projections inside the `<...>`.
                 if !resugared {
                     let principal_with_self =
-                        principal.with_self_ty(cx.tcx(), cx.tcx().types.trait_object_dummy_self);
+                        principal.with_self_ty(p.tcx(), p.tcx().types.trait_object_dummy_self);
 
-                    let args = cx
+                    let args = p
                         .tcx()
                         .generics_of(principal_with_self.def_id)
-                        .own_args_no_defaults(cx.tcx(), principal_with_self.args);
+                        .own_args_no_defaults(p.tcx(), principal_with_self.args);
 
                     let bound_principal_with_self = bound_principal
-                        .with_self_ty(cx.tcx(), cx.tcx().types.trait_object_dummy_self);
+                        .with_self_ty(p.tcx(), p.tcx().types.trait_object_dummy_self);
 
-                    let clause: ty::Clause<'tcx> = bound_principal_with_self.upcast(cx.tcx());
-                    let super_projections: Vec<_> = elaborate::elaborate(cx.tcx(), [clause])
+                    let clause: ty::Clause<'tcx> = bound_principal_with_self.upcast(p.tcx());
+                    let super_projections: Vec<_> = elaborate::elaborate(p.tcx(), [clause])
                         .filter_only_self()
                         .filter_map(|clause| clause.as_projection_clause())
                         .collect();
@@ -1440,15 +1422,15 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                             // Filter out projections that are implied by the super predicates.
                             let proj_is_implied = super_projections.iter().any(|&super_proj| {
                                 let super_proj = super_proj.map_bound(|super_proj| {
-                                    ty::ExistentialProjection::erase_self_ty(cx.tcx(), super_proj)
+                                    ty::ExistentialProjection::erase_self_ty(p.tcx(), super_proj)
                                 });
 
                                 // This function is sometimes called on types with erased and
                                 // anonymized regions, but the super projections can still
                                 // contain named regions. So we erase and anonymize everything
                                 // here to compare the types modulo regions below.
-                                let proj = cx.tcx().erase_regions(proj);
-                                let super_proj = cx.tcx().erase_regions(super_proj);
+                                let proj = p.tcx().erase_regions(proj);
+                                let super_proj = p.tcx().erase_regions(super_proj);
 
                                 proj == super_proj
                             });
@@ -1462,16 +1444,16 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                         .collect();
 
                     projections
-                        .sort_by_cached_key(|proj| cx.tcx().item_name(proj.def_id).to_string());
+                        .sort_by_cached_key(|proj| p.tcx().item_name(proj.def_id).to_string());
 
                     if !args.is_empty() || !projections.is_empty() {
-                        p!(generic_delimiters(|cx| {
-                            cx.comma_sep(args.iter().copied())?;
+                        p.generic_delimiters(|p| {
+                            p.comma_sep(args.iter().copied())?;
                             if !args.is_empty() && !projections.is_empty() {
-                                write!(cx, ", ")?;
+                                write!(p, ", ")?;
                             }
-                            cx.comma_sep(projections.iter().copied())
-                        }));
+                            p.comma_sep(projections.iter().copied())
+                        })?;
                     }
                 }
                 Ok(())
@@ -1480,11 +1462,9 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
             first = false;
         }
 
-        define_scoped_cx!(self);
-
         // Builtin bounds.
         // FIXME(eddyb) avoid printing twice (needed to ensure
-        // that the auto traits are sorted *and* printed via cx).
+        // that the auto traits are sorted *and* printed via p).
         let mut auto_traits: Vec<_> = predicates.auto_traits().collect();
 
         // The auto traits come ordered by `DefPathHash`. While
@@ -1498,11 +1478,11 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
 
         for def_id in auto_traits {
             if !first {
-                p!(" + ");
+                write!(self, " + ")?;
             }
             first = false;
 
-            p!(print_def_path(def_id, &[]));
+            self.print_def_path(def_id, &[])?;
         }
 
         Ok(())
@@ -1514,18 +1494,18 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
         c_variadic: bool,
         output: Ty<'tcx>,
     ) -> Result<(), PrintError> {
-        define_scoped_cx!(self);
-
-        p!("(", comma_sep(inputs.iter().copied()));
+        write!(self, "(")?;
+        self.comma_sep(inputs.iter().copied())?;
         if c_variadic {
             if !inputs.is_empty() {
-                p!(", ");
+                write!(self, ", ")?;
             }
-            p!("...");
+            write!(self, "...")?;
         }
-        p!(")");
+        write!(self, ")")?;
         if !output.is_unit() {
-            p!(" -> ", print(output));
+            write!(self, " -> ")?;
+            output.print(self)?;
         }
 
         Ok(())
@@ -1536,10 +1516,8 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
         ct: ty::Const<'tcx>,
         print_ty: bool,
     ) -> Result<(), PrintError> {
-        define_scoped_cx!(self);
-
         if self.should_print_verbose() {
-            p!(write("{:?}", ct));
+            write!(self, "{ct:?}")?;
             return Ok(());
         }
 
@@ -1547,25 +1525,28 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
             ty::ConstKind::Unevaluated(ty::UnevaluatedConst { def, args }) => {
                 match self.tcx().def_kind(def) {
                     DefKind::Const | DefKind::AssocConst => {
-                        p!(print_value_path(def, args))
+                        self.print_value_path(def, args)?;
                     }
                     DefKind::AnonConst => {
                         if def.is_local()
                             && let span = self.tcx().def_span(def)
                             && let Ok(snip) = self.tcx().sess.source_map().span_to_snippet(span)
                         {
-                            p!(write("{}", snip))
+                            write!(self, "{snip}")?;
                         } else {
-                            // Do not call `print_value_path` as if a parent of this anon const is an impl it will
-                            // attempt to print out the impl trait ref i.e. `<T as Trait>::{constant#0}`. This would
-                            // cause printing to enter an infinite recursion if the anon const is in the self type i.e.
-                            // `impl<T: Default> Default for [T; 32 - 1 - 1 - 1] {`
-                            // where we would try to print `<[T; /* print `constant#0` again */] as Default>::{constant#0}`
-                            p!(write(
+                            // Do not call `print_value_path` as if a parent of this anon const is
+                            // an impl it will attempt to print out the impl trait ref i.e. `<T as
+                            // Trait>::{constant#0}`. This would cause printing to enter an
+                            // infinite recursion if the anon const is in the self type i.e.
+                            // `impl<T: Default> Default for [T; 32 - 1 - 1 - 1] {` where we would
+                            // try to print
+                            // `<[T; /* print constant#0 again */] as // Default>::{constant#0}`.
+                            write!(
+                                self,
                                 "{}::{}",
                                 self.tcx().crate_name(def.krate),
                                 self.tcx().def_path(def).to_string_no_crate_verbose()
-                            ))
+                            )?;
                         }
                     }
                     defkind => bug!("`{:?}` has unexpected defkind {:?}", ct, defkind),
@@ -1573,11 +1554,11 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
             }
             ty::ConstKind::Infer(infer_ct) => match infer_ct {
                 ty::InferConst::Var(ct_vid) if let Some(name) = self.const_infer_name(ct_vid) => {
-                    p!(write("{}", name))
+                    write!(self, "{name}")?;
                 }
                 _ => write!(self, "_")?,
             },
-            ty::ConstKind::Param(ParamConst { name, .. }) => p!(write("{}", name)),
+            ty::ConstKind::Param(ParamConst { name, .. }) => write!(self, "{name}")?,
             ty::ConstKind::Value(cv) => {
                 return self.pretty_print_const_valtree(cv, print_ty);
             }
@@ -1585,11 +1566,11 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
             ty::ConstKind::Bound(debruijn, bound_var) => {
                 rustc_type_ir::debug_bound_var(self, debruijn, bound_var)?
             }
-            ty::ConstKind::Placeholder(placeholder) => p!(write("{placeholder:?}")),
+            ty::ConstKind::Placeholder(placeholder) => write!(self, "{placeholder:?}")?,
             // FIXME(generic_const_exprs):
             // write out some legible representation of an abstract const?
             ty::ConstKind::Expr(expr) => self.pretty_print_const_expr(expr, print_ty)?,
-            ty::ConstKind::Error(_) => p!("{{const error}}"),
+            ty::ConstKind::Error(_) => write!(self, "{{const error}}")?,
         };
         Ok(())
     }
@@ -1599,7 +1580,6 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
         expr: Expr<'tcx>,
         print_ty: bool,
     ) -> Result<(), PrintError> {
-        define_scoped_cx!(self);
         match expr.kind {
             ty::ExprKind::Binop(op) => {
                 let (_, _, c1, c2) = expr.binop_args();
@@ -1638,7 +1618,7 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                     |this| this.pretty_print_const(c1, print_ty),
                     lhs_parenthesized,
                 )?;
-                p!(write(" {formatted_op} "));
+                write!(self, " {formatted_op} ")?;
                 self.maybe_parenthesized(
                     |this| this.pretty_print_const(c2, print_ty),
                     rhs_parenthesized,
@@ -1661,7 +1641,7 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                     ty::ConstKind::Expr(_) => true,
                     _ => false,
                 };
-                p!(write("{formatted_op}"));
+                write!(self, "{formatted_op}")?;
                 self.maybe_parenthesized(
                     |this| this.pretty_print_const(ct, print_ty),
                     parenthesized,
@@ -1672,7 +1652,9 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
 
                 write!(self, "(")?;
                 self.pretty_print_const(fn_def, print_ty)?;
-                p!(")(", comma_sep(fn_args), ")");
+                write!(self, ")(")?;
+                self.comma_sep(fn_args)?;
+                write!(self, ")")?;
             }
             ty::ExprKind::Cast(kind) => {
                 let (_, value, to_ty) = expr.cast_args();
@@ -1722,8 +1704,6 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
         ptr: Pointer,
         ty: Ty<'tcx>,
     ) -> Result<(), PrintError> {
-        define_scoped_cx!(self);
-
         let (prov, offset) = ptr.prov_and_relative_offset();
         match ty.kind() {
             // Byte strings (&[u8; N])
@@ -1738,19 +1718,19 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                             if let Ok(byte_str) =
                                 alloc.inner().get_bytes_strip_provenance(&self.tcx(), range)
                             {
-                                p!(pretty_print_byte_str(byte_str))
+                                self.pretty_print_byte_str(byte_str)?;
                             } else {
-                                p!("<too short allocation>")
+                                write!(self, "<too short allocation>")?;
                             }
                         }
                         // FIXME: for statics, vtables, and functions, we could in principle print more detail.
                         Some(GlobalAlloc::Static(def_id)) => {
-                            p!(write("<static({:?})>", def_id))
+                            write!(self, "<static({def_id:?})>")?;
                         }
-                        Some(GlobalAlloc::Function { .. }) => p!("<function>"),
-                        Some(GlobalAlloc::VTable(..)) => p!("<vtable>"),
-                        Some(GlobalAlloc::TypeId { .. }) => p!("<typeid>"),
-                        None => p!("<dangling pointer>"),
+                        Some(GlobalAlloc::Function { .. }) => write!(self, "<function>")?,
+                        Some(GlobalAlloc::VTable(..)) => write!(self, "<vtable>")?,
+                        Some(GlobalAlloc::TypeId { .. }) => write!(self, "<typeid>")?,
+                        None => write!(self, "<dangling pointer>")?,
                     }
                     return Ok(());
                 }
@@ -1782,40 +1762,38 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
         ty: Ty<'tcx>,
         print_ty: bool,
     ) -> Result<(), PrintError> {
-        define_scoped_cx!(self);
-
         match ty.kind() {
             // Bool
-            ty::Bool if int == ScalarInt::FALSE => p!("false"),
-            ty::Bool if int == ScalarInt::TRUE => p!("true"),
+            ty::Bool if int == ScalarInt::FALSE => write!(self, "false")?,
+            ty::Bool if int == ScalarInt::TRUE => write!(self, "true")?,
             // Float
             ty::Float(fty) => match fty {
                 ty::FloatTy::F16 => {
                     let val = Half::try_from(int).unwrap();
-                    p!(write("{}{}f16", val, if val.is_finite() { "" } else { "_" }))
+                    write!(self, "{}{}f16", val, if val.is_finite() { "" } else { "_" })?;
                 }
                 ty::FloatTy::F32 => {
                     let val = Single::try_from(int).unwrap();
-                    p!(write("{}{}f32", val, if val.is_finite() { "" } else { "_" }))
+                    write!(self, "{}{}f32", val, if val.is_finite() { "" } else { "_" })?;
                 }
                 ty::FloatTy::F64 => {
                     let val = Double::try_from(int).unwrap();
-                    p!(write("{}{}f64", val, if val.is_finite() { "" } else { "_" }))
+                    write!(self, "{}{}f64", val, if val.is_finite() { "" } else { "_" })?;
                 }
                 ty::FloatTy::F128 => {
                     let val = Quad::try_from(int).unwrap();
-                    p!(write("{}{}f128", val, if val.is_finite() { "" } else { "_" }))
+                    write!(self, "{}{}f128", val, if val.is_finite() { "" } else { "_" })?;
                 }
             },
             // Int
             ty::Uint(_) | ty::Int(_) => {
                 let int =
                     ConstInt::new(int, matches!(ty.kind(), ty::Int(_)), ty.is_ptr_sized_integral());
-                if print_ty { p!(write("{:#?}", int)) } else { p!(write("{:?}", int)) }
+                if print_ty { write!(self, "{int:#?}")? } else { write!(self, "{int:?}")? }
             }
             // Char
             ty::Char if char::try_from(int).is_ok() => {
-                p!(write("{:?}", char::try_from(int).unwrap()))
+                write!(self, "{:?}", char::try_from(int).unwrap())?;
             }
             // Pointer types
             ty::Ref(..) | ty::RawPtr(_, _) | ty::FnPtr(..) => {
@@ -1831,7 +1809,7 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
             }
             ty::Pat(base_ty, pat) if self.tcx().validate_scalar_in_layout(int, ty) => {
                 self.pretty_print_const_scalar_int(int, *base_ty, print_ty)?;
-                p!(write(" is {pat:?}"));
+                write!(self, " is {pat:?}")?;
             }
             // Nontrivial types with scalar bit representation
             _ => {
@@ -1880,10 +1858,10 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
         cv: ty::Value<'tcx>,
         print_ty: bool,
     ) -> Result<(), PrintError> {
-        define_scoped_cx!(self);
-
         if with_reduced_queries() || self.should_print_verbose() {
-            p!(write("ValTree({:?}: ", cv.valtree), print(cv.ty), ")");
+            write!(self, "ValTree({:?}: ", cv.valtree)?;
+            cv.ty.print(self)?;
+            write!(self, ")")?;
             return Ok(());
         }
 
@@ -1904,13 +1882,13 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                     let bytes = cv.try_to_raw_bytes(self.tcx()).unwrap_or_else(|| {
                         bug!("expected to convert valtree to raw bytes for type {:?}", cv.ty)
                     });
-                    p!(write("{:?}", String::from_utf8_lossy(bytes)));
+                    write!(self, "{:?}", String::from_utf8_lossy(bytes))?;
                     return Ok(());
                 }
                 _ => {
                     let cv = ty::Value { valtree: cv.valtree, ty: inner_ty };
-                    p!("&");
-                    p!(pretty_print_const_valtree(cv, print_ty));
+                    write!(self, "&")?;
+                    self.pretty_print_const_valtree(cv, print_ty)?;
                     return Ok(());
                 }
             },
@@ -1918,8 +1896,8 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                 let bytes = cv.try_to_raw_bytes(self.tcx()).unwrap_or_else(|| {
                     bug!("expected to convert valtree to raw bytes for type {:?}", t)
                 });
-                p!("*");
-                p!(pretty_print_byte_str(bytes));
+                write!(self, "*")?;
+                self.pretty_print_byte_str(bytes)?;
                 return Ok(());
             }
             // Aggregates, printed as array/tuple/struct/variant construction syntax.
@@ -1932,14 +1910,17 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                 let fields = contents.fields.iter().copied();
                 match *cv.ty.kind() {
                     ty::Array(..) => {
-                        p!("[", comma_sep(fields), "]");
+                        write!(self, "[")?;
+                        self.comma_sep(fields)?;
+                        write!(self, "]")?;
                     }
                     ty::Tuple(..) => {
-                        p!("(", comma_sep(fields));
+                        write!(self, "(")?;
+                        self.comma_sep(fields)?;
                         if contents.fields.len() == 1 {
-                            p!(",");
+                            write!(self, ",")?;
                         }
-                        p!(")");
+                        write!(self, ")")?;
                     }
                     ty::Adt(def, _) if def.variants().is_empty() => {
                         self.typed_value(
@@ -1955,23 +1936,26 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                         let variant_idx =
                             contents.variant.expect("destructed const of adt without variant idx");
                         let variant_def = &def.variant(variant_idx);
-                        p!(print_value_path(variant_def.def_id, args));
+                        self.print_value_path(variant_def.def_id, args)?;
                         match variant_def.ctor_kind() {
                             Some(CtorKind::Const) => {}
                             Some(CtorKind::Fn) => {
-                                p!("(", comma_sep(fields), ")");
+                                write!(self, "(")?;
+                                self.comma_sep(fields)?;
+                                write!(self, ")")?;
                             }
                             None => {
-                                p!(" {{ ");
+                                write!(self, " {{ ")?;
                                 let mut first = true;
                                 for (field_def, field) in iter::zip(&variant_def.fields, fields) {
                                     if !first {
-                                        p!(", ");
+                                        write!(self, ", ")?;
                                     }
-                                    p!(write("{}: ", field_def.name), print(field));
+                                    write!(self, "{}: ", field_def.name)?;
+                                    field.print(self)?;
                                     first = false;
                                 }
-                                p!(" }}");
+                                write!(self, " }}")?;
                             }
                         }
                     }
@@ -1980,7 +1964,7 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                 return Ok(());
             }
             (ty::ValTreeKind::Leaf(leaf), ty::Ref(_, inner_ty, _)) => {
-                p!(write("&"));
+                write!(self, "&")?;
                 return self.pretty_print_const_scalar_int(*leaf, inner_ty, print_ty);
             }
             (ty::ValTreeKind::Leaf(leaf), _) => {
@@ -1988,7 +1972,7 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
             }
             (_, ty::FnDef(def_id, args)) => {
                 // Never allowed today, but we still encounter them in invalid const args.
-                p!(print_value_path(def_id, args));
+                self.print_value_path(def_id, args)?;
                 return Ok(());
             }
             // FIXME(oli-obk): also pretty print arrays and other aggregate constants by reading
@@ -1998,12 +1982,13 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
 
         // fallback
         if cv.valtree.is_zst() {
-            p!(write("<ZST>"));
+            write!(self, "<ZST>")?;
         } else {
-            p!(write("{:?}", cv.valtree));
+            write!(self, "{:?}", cv.valtree)?;
         }
         if print_ty {
-            p!(": ", print(cv.ty));
+            write!(self, ": ")?;
+            cv.ty.print(self)?;
         }
         Ok(())
     }
@@ -2016,20 +2001,19 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
         let kind = closure.kind_ty().to_opt_closure_kind().unwrap_or(ty::ClosureKind::Fn);
 
         write!(self, "impl ")?;
-        self.wrap_binder(&sig, WrapBinderMode::ForAll, |sig, cx| {
-            define_scoped_cx!(cx);
-
-            p!(write("{kind}("));
+        self.wrap_binder(&sig, WrapBinderMode::ForAll, |sig, p| {
+            write!(p, "{kind}(")?;
             for (i, arg) in sig.inputs()[0].tuple_fields().iter().enumerate() {
                 if i > 0 {
-                    p!(", ");
+                    write!(p, ", ")?;
                 }
-                p!(print(arg));
+                arg.print(p)?;
             }
-            p!(")");
+            write!(p, ")")?;
 
             if !sig.output().is_unit() {
-                p!(" -> ", print(sig.output()));
+                write!(p, " -> ")?;
+                sig.output().print(p)?;
             }
 
             Ok(())
@@ -2040,15 +2024,9 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
         &mut self,
         constness: ty::BoundConstness,
     ) -> Result<(), PrintError> {
-        define_scoped_cx!(self);
-
         match constness {
-            ty::BoundConstness::Const => {
-                p!("const ");
-            }
-            ty::BoundConstness::Maybe => {
-                p!("[const] ");
-            }
+            ty::BoundConstness::Const => write!(self, "const ")?,
+            ty::BoundConstness::Maybe => write!(self, "[const] ")?,
         }
         Ok(())
     }
@@ -2065,10 +2043,10 @@ pub(crate) fn pretty_print_const<'tcx>(
 ) -> fmt::Result {
     ty::tls::with(|tcx| {
         let literal = tcx.lift(c).unwrap();
-        let mut cx = FmtPrinter::new(tcx, Namespace::ValueNS);
-        cx.print_alloc_ids = true;
-        cx.pretty_print_const(literal, print_types)?;
-        fmt.write_str(&cx.into_buffer())?;
+        let mut p = FmtPrinter::new(tcx, Namespace::ValueNS);
+        p.print_alloc_ids = true;
+        p.pretty_print_const(literal, print_types)?;
+        fmt.write_str(&p.into_buffer())?;
         Ok(())
     })
 }
@@ -2188,7 +2166,7 @@ impl<'t> TyCtxt<'t> {
         let ns = guess_def_namespace(self, def_id);
         debug!("def_path_str: def_id={:?}, ns={:?}", def_id, ns);
 
-        FmtPrinter::print_string(self, ns, |cx| cx.print_def_path(def_id, args)).unwrap()
+        FmtPrinter::print_string(self, ns, |p| p.print_def_path(def_id, args)).unwrap()
     }
 
     pub fn value_path_str_with_args(
@@ -2200,7 +2178,7 @@ impl<'t> TyCtxt<'t> {
         let ns = guess_def_namespace(self, def_id);
         debug!("value_path_str: def_id={:?}, ns={:?}", def_id, ns);
 
-        FmtPrinter::print_string(self, ns, |cx| cx.print_value_path(def_id, args)).unwrap()
+        FmtPrinter::print_string(self, ns, |p| p.print_value_path(def_id, args)).unwrap()
     }
 }
 
@@ -2362,15 +2340,14 @@ impl<'tcx> Printer<'tcx> for FmtPrinter<'_, 'tcx> {
     fn path_append_impl(
         &mut self,
         print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
-        _disambiguated_data: &DisambiguatedDefPathData,
         self_ty: Ty<'tcx>,
         trait_ref: Option<ty::TraitRef<'tcx>>,
     ) -> Result<(), PrintError> {
         self.pretty_path_append_impl(
-            |cx| {
-                print_prefix(cx)?;
-                if !cx.empty_path {
-                    write!(cx, "::")?;
+            |p| {
+                print_prefix(p)?;
+                if !p.empty_path {
+                    write!(p, "::")?;
                 }
 
                 Ok(())
@@ -2424,7 +2401,7 @@ impl<'tcx> Printer<'tcx> for FmtPrinter<'_, 'tcx> {
             if self.in_value {
                 write!(self, "::")?;
             }
-            self.generic_delimiters(|cx| cx.comma_sep(args.iter().copied()))
+            self.generic_delimiters(|p| p.comma_sep(args.iter().copied()))
         } else {
             Ok(())
         }
@@ -2460,7 +2437,7 @@ impl<'tcx> PrettyPrinter<'tcx> for FmtPrinter<'_, 'tcx> {
     where
         T: Print<'tcx, Self> + TypeFoldable<TyCtxt<'tcx>>,
     {
-        self.pretty_print_in_binder(value)
+        self.wrap_binder(value, WrapBinderMode::ForAll, |new_value, this| new_value.print(this))
     }
 
     fn wrap_binder<T, C: FnOnce(&T, &mut Self) -> Result<(), PrintError>>(
@@ -2472,7 +2449,12 @@ impl<'tcx> PrettyPrinter<'tcx> for FmtPrinter<'_, 'tcx> {
     where
         T: TypeFoldable<TyCtxt<'tcx>>,
     {
-        self.pretty_wrap_binder(value, mode, f)
+        let old_region_index = self.region_index;
+        let (new_value, _) = self.name_all_regions(value, mode)?;
+        f(&new_value, self)?;
+        self.region_index = old_region_index;
+        self.binder_depth -= 1;
+        Ok(())
     }
 
     fn typed_value(
@@ -2556,11 +2538,10 @@ impl<'tcx> PrettyPrinter<'tcx> for FmtPrinter<'_, 'tcx> {
         ty: Ty<'tcx>,
     ) -> Result<(), PrintError> {
         let print = |this: &mut Self| {
-            define_scoped_cx!(this);
             if this.print_alloc_ids {
-                p!(write("{:?}", p));
+                write!(this, "{p:?}")?;
             } else {
-                p!("&_");
+                write!(this, "&_")?;
             }
             Ok(())
         };
@@ -2571,17 +2552,15 @@ impl<'tcx> PrettyPrinter<'tcx> for FmtPrinter<'_, 'tcx> {
 // HACK(eddyb) limited to `FmtPrinter` because of `region_highlight_mode`.
 impl<'tcx> FmtPrinter<'_, 'tcx> {
     pub fn pretty_print_region(&mut self, region: ty::Region<'tcx>) -> Result<(), fmt::Error> {
-        define_scoped_cx!(self);
-
         // Watch out for region highlights.
         let highlight = self.region_highlight_mode;
         if let Some(n) = highlight.region_highlighted(region) {
-            p!(write("'{}", n));
+            write!(self, "'{n}")?;
             return Ok(());
         }
 
         if self.should_print_verbose() {
-            p!(write("{:?}", region));
+            write!(self, "{region:?}")?;
             return Ok(());
         }
 
@@ -2593,12 +2572,12 @@ impl<'tcx> FmtPrinter<'_, 'tcx> {
         // `explain_region()` or `note_and_explain_region()`.
         match region.kind() {
             ty::ReEarlyParam(data) => {
-                p!(write("{}", data.name));
+                write!(self, "{}", data.name)?;
                 return Ok(());
             }
             ty::ReLateParam(ty::LateParamRegion { kind, .. }) => {
                 if let Some(name) = kind.get_name(self.tcx) {
-                    p!(write("{}", name));
+                    write!(self, "{name}")?;
                     return Ok(());
                 }
             }
@@ -2607,31 +2586,31 @@ impl<'tcx> FmtPrinter<'_, 'tcx> {
                 bound: ty::BoundRegion { kind: br, .. }, ..
             }) => {
                 if let Some(name) = br.get_name(self.tcx) {
-                    p!(write("{}", name));
+                    write!(self, "{name}")?;
                     return Ok(());
                 }
 
                 if let Some((region, counter)) = highlight.highlight_bound_region {
                     if br == region {
-                        p!(write("'{}", counter));
+                        write!(self, "'{counter}")?;
                         return Ok(());
                     }
                 }
             }
             ty::ReVar(region_vid) if identify_regions => {
-                p!(write("{:?}", region_vid));
+                write!(self, "{region_vid:?}")?;
                 return Ok(());
             }
             ty::ReVar(_) => {}
             ty::ReErased => {}
             ty::ReError(_) => {}
             ty::ReStatic => {
-                p!("'static");
+                write!(self, "'static")?;
                 return Ok(());
             }
         }
 
-        p!("'_");
+        write!(self, "'_")?;
 
         Ok(())
     }
@@ -2749,17 +2728,17 @@ impl<'tcx> FmtPrinter<'_, 'tcx> {
         debug!("self.used_region_names: {:?}", self.used_region_names);
 
         let mut empty = true;
-        let mut start_or_continue = |cx: &mut Self, start: &str, cont: &str| {
+        let mut start_or_continue = |p: &mut Self, start: &str, cont: &str| {
             let w = if empty {
                 empty = false;
                 start
             } else {
                 cont
             };
-            let _ = write!(cx, "{w}");
+            let _ = write!(p, "{w}");
         };
-        let do_continue = |cx: &mut Self, cont: Symbol| {
-            let _ = write!(cx, "{cont}");
+        let do_continue = |p: &mut Self, cont: Symbol| {
+            let _ = write!(p, "{cont}");
         };
 
         let possible_names = ('a'..='z').rev().map(|s| Symbol::intern(&format!("'{s}")));
@@ -2859,38 +2838,6 @@ impl<'tcx> FmtPrinter<'_, 'tcx> {
         Ok((new_value, map))
     }
 
-    pub fn pretty_print_in_binder<T>(
-        &mut self,
-        value: &ty::Binder<'tcx, T>,
-    ) -> Result<(), fmt::Error>
-    where
-        T: Print<'tcx, Self> + TypeFoldable<TyCtxt<'tcx>>,
-    {
-        let old_region_index = self.region_index;
-        let (new_value, _) = self.name_all_regions(value, WrapBinderMode::ForAll)?;
-        new_value.print(self)?;
-        self.region_index = old_region_index;
-        self.binder_depth -= 1;
-        Ok(())
-    }
-
-    pub fn pretty_wrap_binder<T, C: FnOnce(&T, &mut Self) -> Result<(), fmt::Error>>(
-        &mut self,
-        value: &ty::Binder<'tcx, T>,
-        mode: WrapBinderMode,
-        f: C,
-    ) -> Result<(), fmt::Error>
-    where
-        T: TypeFoldable<TyCtxt<'tcx>>,
-    {
-        let old_region_index = self.region_index;
-        let (new_value, _) = self.name_all_regions(value, mode)?;
-        f(&new_value, self)?;
-        self.region_index = old_region_index;
-        self.binder_depth -= 1;
-        Ok(())
-    }
-
     fn prepare_region_info<T>(&mut self, value: &ty::Binder<'tcx, T>)
     where
         T: TypeFoldable<TyCtxt<'tcx>>,
@@ -2944,8 +2891,8 @@ impl<'tcx, T, P: PrettyPrinter<'tcx>> Print<'tcx, P> for ty::Binder<'tcx, T>
 where
     T: Print<'tcx, P> + TypeFoldable<TyCtxt<'tcx>>,
 {
-    fn print(&self, cx: &mut P) -> Result<(), PrintError> {
-        cx.print_in_binder(self)
+    fn print(&self, p: &mut P) -> Result<(), PrintError> {
+        p.print_in_binder(self)
     }
 }
 
@@ -2953,9 +2900,10 @@ impl<'tcx, T, P: PrettyPrinter<'tcx>> Print<'tcx, P> for ty::OutlivesPredicate<'
 where
     T: Print<'tcx, P>,
 {
-    fn print(&self, cx: &mut P) -> Result<(), PrintError> {
-        define_scoped_cx!(cx);
-        p!(print(self.0), ": ", print(self.1));
+    fn print(&self, p: &mut P) -> Result<(), PrintError> {
+        self.0.print(p)?;
+        write!(p, ": ")?;
+        self.1.print(p)?;
         Ok(())
     }
 }
@@ -3094,11 +3042,11 @@ macro_rules! forward_display_to_print {
         $(#[allow(unused_lifetimes)] impl<'tcx> fmt::Display for $ty {
             fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
                 ty::tls::with(|tcx| {
-                    let mut cx = FmtPrinter::new(tcx, Namespace::TypeNS);
+                    let mut p = FmtPrinter::new(tcx, Namespace::TypeNS);
                     tcx.lift(*self)
                         .expect("could not lift for printing")
-                        .print(&mut cx)?;
-                    f.write_str(&cx.into_buffer())?;
+                        .print(&mut p)?;
+                    f.write_str(&p.into_buffer())?;
                     Ok(())
                 })
             }
@@ -3107,10 +3055,9 @@ macro_rules! forward_display_to_print {
 }
 
 macro_rules! define_print {
-    (($self:ident, $cx:ident): $($ty:ty $print:block)+) => {
+    (($self:ident, $p:ident): $($ty:ty $print:block)+) => {
         $(impl<'tcx, P: PrettyPrinter<'tcx>> Print<'tcx, P> for $ty {
-            fn print(&$self, $cx: &mut P) -> Result<(), PrintError> {
-                define_scoped_cx!($cx);
+            fn print(&$self, $p: &mut P) -> Result<(), PrintError> {
                 let _: () = $print;
                 Ok(())
             }
@@ -3119,8 +3066,8 @@ macro_rules! define_print {
 }
 
 macro_rules! define_print_and_forward_display {
-    (($self:ident, $cx:ident): $($ty:ty $print:block)+) => {
-        define_print!(($self, $cx): $($ty $print)*);
+    (($self:ident, $p:ident): $($ty:ty $print:block)+) => {
+        define_print!(($self, $p): $($ty $print)*);
         forward_display_to_print!($($ty),+);
     };
 }
@@ -3133,37 +3080,38 @@ forward_display_to_print! {
 }
 
 define_print! {
-    (self, cx):
+    (self, p):
 
     ty::FnSig<'tcx> {
-        p!(write("{}", self.safety.prefix_str()));
+        write!(p, "{}", self.safety.prefix_str())?;
 
         if self.abi != ExternAbi::Rust {
-            p!(write("extern {} ", self.abi));
+            write!(p, "extern {} ", self.abi)?;
         }
 
-        p!("fn", pretty_fn_sig(self.inputs(), self.c_variadic, self.output()));
+        write!(p, "fn")?;
+        p.pretty_fn_sig(self.inputs(), self.c_variadic, self.output())?;
     }
 
     ty::TraitRef<'tcx> {
-        p!(write("<{} as {}>", self.self_ty(), self.print_only_trait_path()))
+        write!(p, "<{} as {}>", self.self_ty(), self.print_only_trait_path())?;
     }
 
     ty::AliasTy<'tcx> {
         let alias_term: ty::AliasTerm<'tcx> = (*self).into();
-        p!(print(alias_term))
+        alias_term.print(p)?;
     }
 
     ty::AliasTerm<'tcx> {
-        match self.kind(cx.tcx()) {
-            ty::AliasTermKind::InherentTy | ty::AliasTermKind::InherentConst => p!(pretty_print_inherent_projection(*self)),
+        match self.kind(p.tcx()) {
+            ty::AliasTermKind::InherentTy | ty::AliasTermKind::InherentConst => p.pretty_print_inherent_projection(*self)?,
             ty::AliasTermKind::ProjectionTy => {
-                if !(cx.should_print_verbose() || with_reduced_queries())
-                    && cx.tcx().is_impl_trait_in_trait(self.def_id)
+                if !(p.should_print_verbose() || with_reduced_queries())
+                    && p.tcx().is_impl_trait_in_trait(self.def_id)
                 {
-                    p!(pretty_print_rpitit(self.def_id, self.args))
+                    p.pretty_print_rpitit(self.def_id, self.args)?;
                 } else {
-                    p!(print_def_path(self.def_id, self.args));
+                    p.print_def_path(self.def_id, self.args)?;
                 }
             }
             ty::AliasTermKind::FreeTy
@@ -3171,17 +3119,18 @@ define_print! {
             | ty::AliasTermKind::OpaqueTy
             | ty::AliasTermKind::UnevaluatedConst
             | ty::AliasTermKind::ProjectionConst => {
-                p!(print_def_path(self.def_id, self.args));
+                p.print_def_path(self.def_id, self.args)?;
             }
         }
     }
 
     ty::TraitPredicate<'tcx> {
-        p!(print(self.trait_ref.self_ty()), ": ");
+        self.trait_ref.self_ty().print(p)?;
+        write!(p, ": ")?;
         if let ty::PredicatePolarity::Negative = self.polarity {
-            p!("!");
+            write!(p, "!")?;
         }
-        p!(print(self.trait_ref.print_trait_sugared()))
+        self.trait_ref.print_trait_sugared().print(p)?;
     }
 
     ty::HostEffectPredicate<'tcx> {
@@ -3189,196 +3138,223 @@ define_print! {
             ty::BoundConstness::Const => { "const" }
             ty::BoundConstness::Maybe => { "[const]" }
         };
-        p!(print(self.trait_ref.self_ty()), ": {constness} ");
-        p!(print(self.trait_ref.print_trait_sugared()))
+        self.trait_ref.self_ty().print(p)?;
+        write!(p, ": {constness} ")?;
+        self.trait_ref.print_trait_sugared().print(p)?;
     }
 
     ty::TypeAndMut<'tcx> {
-        p!(write("{}", self.mutbl.prefix_str()), print(self.ty))
+        write!(p, "{}", self.mutbl.prefix_str())?;
+        self.ty.print(p)?;
     }
 
     ty::ClauseKind<'tcx> {
         match *self {
-            ty::ClauseKind::Trait(ref data) => {
-                p!(print(data))
-            }
-            ty::ClauseKind::RegionOutlives(predicate) => p!(print(predicate)),
-            ty::ClauseKind::TypeOutlives(predicate) => p!(print(predicate)),
-            ty::ClauseKind::Projection(predicate) => p!(print(predicate)),
-            ty::ClauseKind::HostEffect(predicate) => p!(print(predicate)),
+            ty::ClauseKind::Trait(ref data) => data.print(p)?,
+            ty::ClauseKind::RegionOutlives(predicate) => predicate.print(p)?,
+            ty::ClauseKind::TypeOutlives(predicate) => predicate.print(p)?,
+            ty::ClauseKind::Projection(predicate) => predicate.print(p)?,
+            ty::ClauseKind::HostEffect(predicate) => predicate.print(p)?,
             ty::ClauseKind::ConstArgHasType(ct, ty) => {
-                p!("the constant `", print(ct), "` has type `", print(ty), "`")
+                write!(p, "the constant `")?;
+                ct.print(p)?;
+                write!(p, "` has type `")?;
+                ty.print(p)?;
+                write!(p, "`")?;
             },
-            ty::ClauseKind::WellFormed(term) => p!(print(term), " well-formed"),
+            ty::ClauseKind::WellFormed(term) => {
+                term.print(p)?;
+                write!(p, " well-formed")?;
+            }
             ty::ClauseKind::ConstEvaluatable(ct) => {
-                p!("the constant `", print(ct), "` can be evaluated")
+                write!(p, "the constant `")?;
+                ct.print(p)?;
+                write!(p, "` can be evaluated")?;
+            }
+            ty::ClauseKind::UnstableFeature(symbol) => {
+                write!(p, "unstable feature: ")?;
+                write!(p, "`{symbol}`")?;
             }
-            ty::ClauseKind::UnstableFeature(symbol) => p!("unstable feature: ", write("`{}`", symbol)),
         }
     }
 
     ty::PredicateKind<'tcx> {
         match *self {
-            ty::PredicateKind::Clause(data) => {
-                p!(print(data))
-            }
-            ty::PredicateKind::Subtype(predicate) => p!(print(predicate)),
-            ty::PredicateKind::Coerce(predicate) => p!(print(predicate)),
+            ty::PredicateKind::Clause(data) => data.print(p)?,
+            ty::PredicateKind::Subtype(predicate) => predicate.print(p)?,
+            ty::PredicateKind::Coerce(predicate) => predicate.print(p)?,
             ty::PredicateKind::DynCompatible(trait_def_id) => {
-                p!("the trait `", print_def_path(trait_def_id, &[]), "` is dyn-compatible")
+                write!(p, "the trait `")?;
+                p.print_def_path(trait_def_id, &[])?;
+                write!(p, "` is dyn-compatible")?;
             }
             ty::PredicateKind::ConstEquate(c1, c2) => {
-                p!("the constant `", print(c1), "` equals `", print(c2), "`")
+                write!(p, "the constant `")?;
+                c1.print(p)?;
+                write!(p, "` equals `")?;
+                c2.print(p)?;
+                write!(p, "`")?;
+            }
+            ty::PredicateKind::Ambiguous => write!(p, "ambiguous")?,
+            ty::PredicateKind::NormalizesTo(data) => data.print(p)?,
+            ty::PredicateKind::AliasRelate(t1, t2, dir) => {
+                t1.print(p)?;
+                write!(p, " {dir} ")?;
+                t2.print(p)?;
             }
-            ty::PredicateKind::Ambiguous => p!("ambiguous"),
-            ty::PredicateKind::NormalizesTo(data) => p!(print(data)),
-            ty::PredicateKind::AliasRelate(t1, t2, dir) => p!(print(t1), write(" {} ", dir), print(t2)),
         }
     }
 
     ty::ExistentialPredicate<'tcx> {
         match *self {
-            ty::ExistentialPredicate::Trait(x) => p!(print(x)),
-            ty::ExistentialPredicate::Projection(x) => p!(print(x)),
-            ty::ExistentialPredicate::AutoTrait(def_id) => {
-                p!(print_def_path(def_id, &[]));
-            }
+            ty::ExistentialPredicate::Trait(x) => x.print(p)?,
+            ty::ExistentialPredicate::Projection(x) => x.print(p)?,
+            ty::ExistentialPredicate::AutoTrait(def_id) => p.print_def_path(def_id, &[])?,
         }
     }
 
     ty::ExistentialTraitRef<'tcx> {
         // Use a type that can't appear in defaults of type parameters.
-        let dummy_self = Ty::new_fresh(cx.tcx(), 0);
-        let trait_ref = self.with_self_ty(cx.tcx(), dummy_self);
-        p!(print(trait_ref.print_only_trait_path()))
+        let dummy_self = Ty::new_fresh(p.tcx(), 0);
+        let trait_ref = self.with_self_ty(p.tcx(), dummy_self);
+        trait_ref.print_only_trait_path().print(p)?;
     }
 
     ty::ExistentialProjection<'tcx> {
-        let name = cx.tcx().associated_item(self.def_id).name();
+        let name = p.tcx().associated_item(self.def_id).name();
         // The args don't contain the self ty (as it has been erased) but the corresp.
         // generics do as the trait always has a self ty param. We need to offset.
-        let args = &self.args[cx.tcx().generics_of(self.def_id).parent_count - 1..];
-        p!(path_generic_args(|cx| write!(cx, "{name}"), args), " = ", print(self.term))
+        let args = &self.args[p.tcx().generics_of(self.def_id).parent_count - 1..];
+        p.path_generic_args(|p| write!(p, "{name}"), args)?;
+        write!(p, " = ")?;
+        self.term.print(p)?;
     }
 
     ty::ProjectionPredicate<'tcx> {
-        p!(print(self.projection_term), " == ");
-        cx.reset_type_limit();
-        p!(print(self.term))
+        self.projection_term.print(p)?;
+        write!(p, " == ")?;
+        p.reset_type_limit();
+        self.term.print(p)?;
     }
 
     ty::SubtypePredicate<'tcx> {
-        p!(print(self.a), " <: ");
-        cx.reset_type_limit();
-        p!(print(self.b))
+        self.a.print(p)?;
+        write!(p, " <: ")?;
+        p.reset_type_limit();
+        self.b.print(p)?;
     }
 
     ty::CoercePredicate<'tcx> {
-        p!(print(self.a), " -> ");
-        cx.reset_type_limit();
-        p!(print(self.b))
+        self.a.print(p)?;
+        write!(p, " -> ")?;
+        p.reset_type_limit();
+        self.b.print(p)?;
     }
 
     ty::NormalizesTo<'tcx> {
-        p!(print(self.alias), " normalizes-to ");
-        cx.reset_type_limit();
-        p!(print(self.term))
+        self.alias.print(p)?;
+        write!(p, " normalizes-to ")?;
+        p.reset_type_limit();
+        self.term.print(p)?;
     }
 }
 
 define_print_and_forward_display! {
-    (self, cx):
+    (self, p):
 
     &'tcx ty::List<Ty<'tcx>> {
-        p!("{{", comma_sep(self.iter()), "}}")
+        write!(p, "{{")?;
+        p.comma_sep(self.iter())?;
+        write!(p, "}}")?;
     }
 
     TraitRefPrintOnlyTraitPath<'tcx> {
-        p!(print_def_path(self.0.def_id, self.0.args));
+        p.print_def_path(self.0.def_id, self.0.args)?;
     }
 
     TraitRefPrintSugared<'tcx> {
         if !with_reduced_queries()
-            && cx.tcx().trait_def(self.0.def_id).paren_sugar
+            && p.tcx().trait_def(self.0.def_id).paren_sugar
             && let ty::Tuple(args) = self.0.args.type_at(1).kind()
         {
-            p!(write("{}", cx.tcx().item_name(self.0.def_id)), "(");
+            write!(p, "{}(", p.tcx().item_name(self.0.def_id))?;
             for (i, arg) in args.iter().enumerate() {
                 if i > 0 {
-                    p!(", ");
+                    write!(p, ", ")?;
                 }
-                p!(print(arg));
+                arg.print(p)?;
             }
-            p!(")");
+            write!(p, ")")?;
         } else {
-            p!(print_def_path(self.0.def_id, self.0.args));
+            p.print_def_path(self.0.def_id, self.0.args)?;
         }
     }
 
     TraitRefPrintOnlyTraitName<'tcx> {
-        p!(print_def_path(self.0.def_id, &[]));
+        p.print_def_path(self.0.def_id, &[])?;
     }
 
     TraitPredPrintModifiersAndPath<'tcx> {
         if let ty::PredicatePolarity::Negative = self.0.polarity {
-            p!("!")
+            write!(p, "!")?;
         }
-        p!(print(self.0.trait_ref.print_trait_sugared()));
+        self.0.trait_ref.print_trait_sugared().print(p)?;
     }
 
     TraitPredPrintWithBoundConstness<'tcx> {
-        p!(print(self.0.trait_ref.self_ty()), ": ");
+        self.0.trait_ref.self_ty().print(p)?;
+        write!(p, ": ")?;
         if let Some(constness) = self.1 {
-            p!(pretty_print_bound_constness(constness));
+            p.pretty_print_bound_constness(constness)?;
         }
         if let ty::PredicatePolarity::Negative = self.0.polarity {
-            p!("!");
+            write!(p, "!")?;
         }
-        p!(print(self.0.trait_ref.print_trait_sugared()))
+        self.0.trait_ref.print_trait_sugared().print(p)?;
     }
 
     PrintClosureAsImpl<'tcx> {
-        p!(pretty_closure_as_impl(self.closure))
+        p.pretty_closure_as_impl(self.closure)?;
     }
 
     ty::ParamTy {
-        p!(write("{}", self.name))
+        write!(p, "{}", self.name)?;
     }
 
     ty::PlaceholderType {
         match self.bound.kind {
-            ty::BoundTyKind::Anon => p!(write("{self:?}")),
-            ty::BoundTyKind::Param(def_id) => match cx.should_print_verbose() {
-                true => p!(write("{self:?}")),
-                false => p!(write("{}", cx.tcx().item_name(def_id))),
+            ty::BoundTyKind::Anon => write!(p, "{self:?}")?,
+            ty::BoundTyKind::Param(def_id) => match p.should_print_verbose() {
+                true => write!(p, "{self:?}")?,
+                false => write!(p, "{}", p.tcx().item_name(def_id))?,
             },
         }
     }
 
     ty::ParamConst {
-        p!(write("{}", self.name))
+        write!(p, "{}", self.name)?;
     }
 
     ty::Term<'tcx> {
       match self.kind() {
-        ty::TermKind::Ty(ty) => p!(print(ty)),
-        ty::TermKind::Const(c) => p!(print(c)),
+        ty::TermKind::Ty(ty) => ty.print(p)?,
+        ty::TermKind::Const(c) => c.print(p)?,
       }
     }
 
     ty::Predicate<'tcx> {
-        p!(print(self.kind()))
+        self.kind().print(p)?;
     }
 
     ty::Clause<'tcx> {
-        p!(print(self.kind()))
+        self.kind().print(p)?;
     }
 
     GenericArg<'tcx> {
         match self.kind() {
-            GenericArgKind::Lifetime(lt) => p!(print(lt)),
-            GenericArgKind::Type(ty) => p!(print(ty)),
-            GenericArgKind::Const(ct) => p!(print(ct)),
+            GenericArgKind::Lifetime(lt) => lt.print(p)?,
+            GenericArgKind::Type(ty) => ty.print(p)?,
+            GenericArgKind::Const(ct) => ct.print(p)?,
         }
     }
 }
diff --git a/compiler/rustc_middle/src/ty/region.rs b/compiler/rustc_middle/src/ty/region.rs
index 5cf96072177..3a7852dea06 100644
--- a/compiler/rustc_middle/src/ty/region.rs
+++ b/compiler/rustc_middle/src/ty/region.rs
@@ -324,6 +324,14 @@ pub struct EarlyParamRegion {
     pub name: Symbol,
 }
 
+impl EarlyParamRegion {
+    /// Does this early bound region have a name? Early bound regions normally
+    /// always have names except when using anonymous lifetimes (`'_`).
+    pub fn is_named(&self) -> bool {
+        self.name != kw::UnderscoreLifetime
+    }
+}
+
 impl rustc_type_ir::inherent::ParamLike for EarlyParamRegion {
     fn index(self) -> u32 {
         self.index
@@ -487,3 +495,15 @@ impl BoundRegionKind {
         }
     }
 }
+
+// Some types are used a lot. Make sure they don't unintentionally get bigger.
+#[cfg(target_pointer_width = "64")]
+mod size_asserts {
+    use rustc_data_structures::static_assert_size;
+
+    use super::*;
+    // tidy-alphabetical-start
+    static_assert_size!(RegionKind<'_>, 20);
+    static_assert_size!(ty::WithCachedTypeInfo<RegionKind<'_>>, 48);
+    // tidy-alphabetical-end
+}
diff --git a/compiler/rustc_middle/src/ty/structural_impls.rs b/compiler/rustc_middle/src/ty/structural_impls.rs
index a5fdce93e4b..0e2aff6f9bd 100644
--- a/compiler/rustc_middle/src/ty/structural_impls.rs
+++ b/compiler/rustc_middle/src/ty/structural_impls.rs
@@ -25,8 +25,8 @@ impl fmt::Debug for ty::TraitDef {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         ty::tls::with(|tcx| {
             with_no_trimmed_paths!({
-                let s = FmtPrinter::print_string(tcx, Namespace::TypeNS, |cx| {
-                    cx.print_def_path(self.def_id, &[])
+                let s = FmtPrinter::print_string(tcx, Namespace::TypeNS, |p| {
+                    p.print_def_path(self.def_id, &[])
                 })?;
                 f.write_str(&s)
             })
@@ -38,8 +38,8 @@ impl<'tcx> fmt::Debug for ty::AdtDef<'tcx> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         ty::tls::with(|tcx| {
             with_no_trimmed_paths!({
-                let s = FmtPrinter::print_string(tcx, Namespace::TypeNS, |cx| {
-                    cx.print_def_path(self.did(), &[])
+                let s = FmtPrinter::print_string(tcx, Namespace::TypeNS, |p| {
+                    p.print_def_path(self.did(), &[])
                 })?;
                 f.write_str(&s)
             })
@@ -170,9 +170,9 @@ impl<'tcx> fmt::Debug for ty::Const<'tcx> {
         if let ConstKind::Value(cv) = self.kind() {
             return ty::tls::with(move |tcx| {
                 let cv = tcx.lift(cv).unwrap();
-                let mut cx = FmtPrinter::new(tcx, Namespace::ValueNS);
-                cx.pretty_print_const_valtree(cv, /*print_ty*/ true)?;
-                f.write_str(&cx.into_buffer())
+                let mut p = FmtPrinter::new(tcx, Namespace::ValueNS);
+                p.pretty_print_const_valtree(cv, /*print_ty*/ true)?;
+                f.write_str(&p.into_buffer())
             });
         }
         // Fall back to something verbose.
@@ -232,6 +232,7 @@ TrivialLiftImpls! {
     crate::mir::Promoted,
     crate::mir::interpret::AllocId,
     crate::mir::interpret::Scalar,
+    crate::ty::ParamConst,
     rustc_abi::ExternAbi,
     rustc_abi::Size,
     rustc_hir::Safety,
@@ -271,10 +272,6 @@ TrivialTypeTraversalImpls! {
     crate::ty::AssocItem,
     crate::ty::AssocKind,
     crate::ty::BoundRegion,
-    crate::ty::BoundVar,
-    crate::ty::InferConst,
-    crate::ty::Placeholder<crate::ty::BoundRegion>,
-    crate::ty::Placeholder<ty::BoundVar>,
     crate::ty::UserTypeAnnotationIndex,
     crate::ty::ValTree<'tcx>,
     crate::ty::abstract_const::NotConstEvaluatable,
@@ -302,9 +299,8 @@ TrivialTypeTraversalImpls! {
 // interners).
 TrivialTypeTraversalAndLiftImpls! {
     // tidy-alphabetical-start
-    crate::ty::ParamConst,
     crate::ty::ParamTy,
-    crate::ty::Placeholder<crate::ty::BoundTy>,
+    crate::ty::PlaceholderType,
     crate::ty::instance::ReifyReason,
     rustc_hir::def_id::DefId,
     // tidy-alphabetical-end
@@ -673,30 +669,30 @@ impl<'tcx> TypeSuperFoldable<TyCtxt<'tcx>> for ty::Const<'tcx> {
         folder: &mut F,
     ) -> Result<Self, F::Error> {
         let kind = match self.kind() {
-            ConstKind::Param(p) => ConstKind::Param(p.try_fold_with(folder)?),
-            ConstKind::Infer(i) => ConstKind::Infer(i.try_fold_with(folder)?),
-            ConstKind::Bound(d, b) => {
-                ConstKind::Bound(d.try_fold_with(folder)?, b.try_fold_with(folder)?)
-            }
-            ConstKind::Placeholder(p) => ConstKind::Placeholder(p.try_fold_with(folder)?),
             ConstKind::Unevaluated(uv) => ConstKind::Unevaluated(uv.try_fold_with(folder)?),
             ConstKind::Value(v) => ConstKind::Value(v.try_fold_with(folder)?),
-            ConstKind::Error(e) => ConstKind::Error(e.try_fold_with(folder)?),
             ConstKind::Expr(e) => ConstKind::Expr(e.try_fold_with(folder)?),
+
+            ConstKind::Param(_)
+            | ConstKind::Infer(_)
+            | ConstKind::Bound(..)
+            | ConstKind::Placeholder(_)
+            | ConstKind::Error(_) => return Ok(self),
         };
         if kind != self.kind() { Ok(folder.cx().mk_ct_from_kind(kind)) } else { Ok(self) }
     }
 
     fn super_fold_with<F: TypeFolder<TyCtxt<'tcx>>>(self, folder: &mut F) -> Self {
         let kind = match self.kind() {
-            ConstKind::Param(p) => ConstKind::Param(p.fold_with(folder)),
-            ConstKind::Infer(i) => ConstKind::Infer(i.fold_with(folder)),
-            ConstKind::Bound(d, b) => ConstKind::Bound(d.fold_with(folder), b.fold_with(folder)),
-            ConstKind::Placeholder(p) => ConstKind::Placeholder(p.fold_with(folder)),
             ConstKind::Unevaluated(uv) => ConstKind::Unevaluated(uv.fold_with(folder)),
             ConstKind::Value(v) => ConstKind::Value(v.fold_with(folder)),
-            ConstKind::Error(e) => ConstKind::Error(e.fold_with(folder)),
             ConstKind::Expr(e) => ConstKind::Expr(e.fold_with(folder)),
+
+            ConstKind::Param(_)
+            | ConstKind::Infer(_)
+            | ConstKind::Bound(..)
+            | ConstKind::Placeholder(_)
+            | ConstKind::Error(_) => return self,
         };
         if kind != self.kind() { folder.cx().mk_ct_from_kind(kind) } else { self }
     }
@@ -705,17 +701,15 @@ impl<'tcx> TypeSuperFoldable<TyCtxt<'tcx>> for ty::Const<'tcx> {
 impl<'tcx> TypeSuperVisitable<TyCtxt<'tcx>> for ty::Const<'tcx> {
     fn super_visit_with<V: TypeVisitor<TyCtxt<'tcx>>>(&self, visitor: &mut V) -> V::Result {
         match self.kind() {
-            ConstKind::Param(p) => p.visit_with(visitor),
-            ConstKind::Infer(i) => i.visit_with(visitor),
-            ConstKind::Bound(d, b) => {
-                try_visit!(d.visit_with(visitor));
-                b.visit_with(visitor)
-            }
-            ConstKind::Placeholder(p) => p.visit_with(visitor),
             ConstKind::Unevaluated(uv) => uv.visit_with(visitor),
             ConstKind::Value(v) => v.visit_with(visitor),
-            ConstKind::Error(e) => e.visit_with(visitor),
             ConstKind::Expr(e) => e.visit_with(visitor),
+            ConstKind::Error(e) => e.visit_with(visitor),
+
+            ConstKind::Param(_)
+            | ConstKind::Infer(_)
+            | ConstKind::Bound(..)
+            | ConstKind::Placeholder(_) => V::Result::output(),
         }
     }
 }
diff --git a/compiler/rustc_middle/src/ty/sty.rs b/compiler/rustc_middle/src/ty/sty.rs
index 4569596cfbe..72474a60566 100644
--- a/compiler/rustc_middle/src/ty/sty.rs
+++ b/compiler/rustc_middle/src/ty/sty.rs
@@ -403,12 +403,6 @@ pub enum BoundTyKind {
     Param(DefId),
 }
 
-impl From<BoundVar> for BoundTy {
-    fn from(var: BoundVar) -> Self {
-        BoundTy { var, kind: BoundTyKind::Anon }
-    }
-}
-
 /// Constructors for `Ty`
 impl<'tcx> Ty<'tcx> {
     /// Avoid using this in favour of more specific `new_*` methods, where possible.
@@ -1462,7 +1456,7 @@ impl<'tcx> Ty<'tcx> {
         }
     }
 
-    /// Returns the type and mutability of `*ty`.
+    /// Returns the type of `*ty`.
     ///
     /// The parameter `explicit` indicates if this is an *explicit* dereference.
     /// Some types -- notably raw ptrs -- can only be dereferenced explicitly.
@@ -2040,7 +2034,7 @@ mod size_asserts {
 
     use super::*;
     // tidy-alphabetical-start
-    static_assert_size!(ty::RegionKind<'_>, 20);
-    static_assert_size!(ty::TyKind<'_>, 24);
+    static_assert_size!(TyKind<'_>, 24);
+    static_assert_size!(ty::WithCachedTypeInfo<TyKind<'_>>, 48);
     // tidy-alphabetical-end
 }
diff --git a/compiler/rustc_middle/src/ty/typeck_results.rs b/compiler/rustc_middle/src/ty/typeck_results.rs
index 88583407d25..6b187c5325a 100644
--- a/compiler/rustc_middle/src/ty/typeck_results.rs
+++ b/compiler/rustc_middle/src/ty/typeck_results.rs
@@ -789,10 +789,10 @@ impl<'tcx> IsIdentity for CanonicalUserType<'tcx> {
                         },
 
                         GenericArgKind::Lifetime(r) => match r.kind() {
-                            ty::ReBound(debruijn, br) => {
+                            ty::ReBound(debruijn, b) => {
                                 // We only allow a `ty::INNERMOST` index in generic parameters.
                                 assert_eq!(debruijn, ty::INNERMOST);
-                                cvar == br.var
+                                cvar == b.var
                             }
                             _ => false,
                         },
@@ -801,7 +801,7 @@ impl<'tcx> IsIdentity for CanonicalUserType<'tcx> {
                             ty::ConstKind::Bound(debruijn, b) => {
                                 // We only allow a `ty::INNERMOST` index in generic parameters.
                                 assert_eq!(debruijn, ty::INNERMOST);
-                                cvar == b
+                                cvar == b.var
                             }
                             _ => false,
                         },
diff --git a/compiler/rustc_mir_build/Cargo.toml b/compiler/rustc_mir_build/Cargo.toml
index c4c2d8a7ac8..f756f0a19ee 100644
--- a/compiler/rustc_mir_build/Cargo.toml
+++ b/compiler/rustc_mir_build/Cargo.toml
@@ -6,12 +6,10 @@ edition = "2024"
 [dependencies]
 # tidy-alphabetical-start
 itertools = "0.12"
-
 rustc_abi = { path = "../rustc_abi" }
 rustc_apfloat = "0.2.0"
 rustc_arena = { path = "../rustc_arena" }
 rustc_ast = { path = "../rustc_ast" }
-rustc_attr_data_structures = { path = "../rustc_attr_data_structures" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
 rustc_fluent_macro = { path = "../rustc_fluent_macro" }
diff --git a/compiler/rustc_mir_build/messages.ftl b/compiler/rustc_mir_build/messages.ftl
index abfe8eb66dd..287639de663 100644
--- a/compiler/rustc_mir_build/messages.ftl
+++ b/compiler/rustc_mir_build/messages.ftl
@@ -87,7 +87,7 @@ mir_build_confused = missing patterns are not covered because `{$variable}` is i
 mir_build_const_continue_bad_const = could not determine the target branch for this `#[const_continue]`
     .label = this value is too generic
 
-mir_build_const_continue_missing_value = a `#[const_continue]` must break to a label with a value
+mir_build_const_continue_missing_label_or_value = a `#[const_continue]` must break to a label with a value
 
 mir_build_const_continue_not_const = could not determine the target branch for this `#[const_continue]`
     .help = try extracting the expression into a `const` item
diff --git a/compiler/rustc_mir_build/src/builder/expr/as_operand.rs b/compiler/rustc_mir_build/src/builder/expr/as_operand.rs
index 982e7aa8246..6a422223990 100644
--- a/compiler/rustc_mir_build/src/builder/expr/as_operand.rs
+++ b/compiler/rustc_mir_build/src/builder/expr/as_operand.rs
@@ -57,7 +57,9 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
     /// ```
     /// #![feature(unsized_fn_params)]
     /// # use core::fmt::Debug;
-    /// fn foo(_p: dyn Debug) { /* ... */ }
+    /// fn foo(_p: dyn Debug) {
+    ///     /* ... */
+    /// }
     ///
     /// fn bar(box_p: Box<dyn Debug>) { foo(*box_p); }
     /// ```
diff --git a/compiler/rustc_mir_build/src/check_tail_calls.rs b/compiler/rustc_mir_build/src/check_tail_calls.rs
index 18db8c1debb..3ecccb422c4 100644
--- a/compiler/rustc_mir_build/src/check_tail_calls.rs
+++ b/compiler/rustc_mir_build/src/check_tail_calls.rs
@@ -60,9 +60,13 @@ impl<'tcx> TailCallCkVisitor<'_, 'tcx> {
         let BodyTy::Fn(caller_sig) = self.thir.body_type else {
             span_bug!(
                 call.span,
-                "`become` outside of functions should have been disallowed by hit_typeck"
+                "`become` outside of functions should have been disallowed by hir_typeck"
             )
         };
+        // While the `caller_sig` does have its regions erased, it does not have its
+        // binders anonymized. We call `erase_regions` once again to anonymize any binders
+        // within the signature, such as in function pointer or `dyn Trait` args.
+        let caller_sig = self.tcx.erase_regions(caller_sig);
 
         let ExprKind::Scope { value, .. } = call.kind else {
             span_bug!(call.span, "expected scope, found: {call:?}")
@@ -89,22 +93,39 @@ impl<'tcx> TailCallCkVisitor<'_, 'tcx> {
             self.report_op(ty, args, fn_span, expr);
         }
 
-        // Closures in thir look something akin to
-        // `for<'a> extern "rust-call" fn(&'a [closure@...], ()) -> <[closure@...] as FnOnce<()>>::Output {<[closure@...] as Fn<()>>::call}`
-        // So we have to check for them in this weird way...
         if let &ty::FnDef(did, args) = ty.kind() {
+            // Closures in thir look something akin to
+            // `for<'a> extern "rust-call" fn(&'a [closure@...], ()) -> <[closure@...] as FnOnce<()>>::Output {<[closure@...] as Fn<()>>::call}`
+            // So we have to check for them in this weird way...
             let parent = self.tcx.parent(did);
             if self.tcx.fn_trait_kind_from_def_id(parent).is_some()
-                && args.first().and_then(|arg| arg.as_type()).is_some_and(Ty::is_closure)
+                && let Some(this) = args.first()
+                && let Some(this) = this.as_type()
             {
-                self.report_calling_closure(&self.thir[fun], args[1].as_type().unwrap(), expr);
+                if this.is_closure() {
+                    self.report_calling_closure(&self.thir[fun], args[1].as_type().unwrap(), expr);
+                } else {
+                    // This can happen when tail calling `Box` that wraps a function
+                    self.report_nonfn_callee(fn_span, self.thir[fun].span, this);
+                }
 
                 // Tail calling is likely to cause unrelated errors (ABI, argument mismatches),
                 // skip them, producing an error about calling a closure is enough.
                 return;
             };
+
+            if self.tcx.intrinsic(did).is_some() {
+                self.report_calling_intrinsic(expr);
+            }
         }
 
+        let (ty::FnDef(..) | ty::FnPtr(..)) = ty.kind() else {
+            self.report_nonfn_callee(fn_span, self.thir[fun].span, ty);
+
+            // `fn_sig` below panics otherwise
+            return;
+        };
+
         // Erase regions since tail calls don't care about lifetimes
         let callee_sig =
             self.tcx.normalize_erasing_late_bound_regions(self.typing_env, ty.fn_sig(self.tcx));
@@ -280,6 +301,50 @@ impl<'tcx> TailCallCkVisitor<'_, 'tcx> {
         self.found_errors = Err(err);
     }
 
+    fn report_calling_intrinsic(&mut self, expr: &Expr<'_>) {
+        let err = self
+            .tcx
+            .dcx()
+            .struct_span_err(expr.span, "tail calling intrinsics is not allowed")
+            .emit();
+
+        self.found_errors = Err(err);
+    }
+
+    fn report_nonfn_callee(&mut self, call_sp: Span, fun_sp: Span, ty: Ty<'_>) {
+        let mut err = self
+            .tcx
+            .dcx()
+            .struct_span_err(
+                call_sp,
+                "tail calls can only be performed with function definitions or pointers",
+            )
+            .with_note(format!("callee has type `{ty}`"));
+
+        let mut ty = ty;
+        let mut refs = 0;
+        while ty.is_box() || ty.is_ref() {
+            ty = ty.builtin_deref(false).unwrap();
+            refs += 1;
+        }
+
+        if refs > 0 && ty.is_fn() {
+            let thing = if ty.is_fn_ptr() { "pointer" } else { "definition" };
+
+            let derefs =
+                std::iter::once('(').chain(std::iter::repeat_n('*', refs)).collect::<String>();
+
+            err.multipart_suggestion(
+                format!("consider dereferencing the expression to get a function {thing}"),
+                vec![(fun_sp.shrink_to_lo(), derefs), (fun_sp.shrink_to_hi(), ")".to_owned())],
+                Applicability::MachineApplicable,
+            );
+        }
+
+        let err = err.emit();
+        self.found_errors = Err(err);
+    }
+
     fn report_abi_mismatch(&mut self, sp: Span, caller_abi: ExternAbi, callee_abi: ExternAbi) {
         let err = self
             .tcx
diff --git a/compiler/rustc_mir_build/src/errors.rs b/compiler/rustc_mir_build/src/errors.rs
index f1fbd5c4a49..1a52c6c85cb 100644
--- a/compiler/rustc_mir_build/src/errors.rs
+++ b/compiler/rustc_mir_build/src/errors.rs
@@ -1254,8 +1254,8 @@ pub(crate) struct ConstContinueBadConst {
 }
 
 #[derive(Diagnostic)]
-#[diag(mir_build_const_continue_missing_value)]
-pub(crate) struct ConstContinueMissingValue {
+#[diag(mir_build_const_continue_missing_label_or_value)]
+pub(crate) struct ConstContinueMissingLabelOrValue {
     #[primary_span]
     pub span: Span,
 }
diff --git a/compiler/rustc_mir_build/src/thir/cx/expr.rs b/compiler/rustc_mir_build/src/thir/cx/expr.rs
index 16df58cd76d..81b0e21a5f5 100644
--- a/compiler/rustc_mir_build/src/thir/cx/expr.rs
+++ b/compiler/rustc_mir_build/src/thir/cx/expr.rs
@@ -1,10 +1,11 @@
 use itertools::Itertools;
 use rustc_abi::{FIRST_VARIANT, FieldIdx};
 use rustc_ast::UnsafeBinderCastKind;
-use rustc_attr_data_structures::{AttributeKind, find_attr};
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_hir as hir;
+use rustc_hir::attrs::AttributeKind;
 use rustc_hir::def::{CtorKind, CtorOf, DefKind, Res};
+use rustc_hir::find_attr;
 use rustc_index::Idx;
 use rustc_middle::hir::place::{
     Place as HirPlace, PlaceBase as HirPlaceBase, ProjectionKind as HirProjectionKind,
@@ -851,9 +852,9 @@ impl<'tcx> ThirBuildCx<'tcx> {
                 if find_attr!(self.tcx.hir_attrs(expr.hir_id), AttributeKind::ConstContinue(_)) {
                     match dest.target_id {
                         Ok(target_id) => {
-                            let Some(value) = value else {
+                            let (Some(value), Some(_)) = (value, dest.label) else {
                                 let span = expr.span;
-                                self.tcx.dcx().emit_fatal(ConstContinueMissingValue { span })
+                                self.tcx.dcx().emit_fatal(ConstContinueMissingLabelOrValue { span })
                             };
 
                             ExprKind::ConstContinue {
diff --git a/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs b/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs
index 91fcbb9390f..a501cdf88c2 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs
@@ -2,10 +2,11 @@ use core::ops::ControlFlow;
 
 use rustc_abi::{FieldIdx, VariantIdx};
 use rustc_apfloat::Float;
-use rustc_attr_data_structures::{AttributeKind, find_attr};
 use rustc_data_structures::fx::FxHashSet;
 use rustc_errors::Diag;
 use rustc_hir as hir;
+use rustc_hir::attrs::AttributeKind;
+use rustc_hir::find_attr;
 use rustc_index::Idx;
 use rustc_infer::infer::TyCtxtInferExt;
 use rustc_infer::traits::Obligation;
diff --git a/compiler/rustc_mir_dataflow/src/impls/initialized.rs b/compiler/rustc_mir_dataflow/src/impls/initialized.rs
index 117525eb777..5937d68f389 100644
--- a/compiler/rustc_mir_dataflow/src/impls/initialized.rs
+++ b/compiler/rustc_mir_dataflow/src/impls/initialized.rs
@@ -108,6 +108,7 @@ impl<'tcx> MaybePlacesSwitchIntData<'tcx> {
 ///
 /// ```rust
 /// struct S;
+/// #[rustfmt::skip]
 /// fn foo(pred: bool) {                        // maybe-init:
 ///                                             // {}
 ///     let a = S; let mut b = S; let c; let d; // {a, b}
@@ -197,6 +198,7 @@ impl<'a, 'tcx> HasMoveData<'tcx> for MaybeInitializedPlaces<'a, 'tcx> {
 ///
 /// ```rust
 /// struct S;
+/// #[rustfmt::skip]
 /// fn foo(pred: bool) {                        // maybe-uninit:
 ///                                             // {a, b, c, d}
 ///     let a = S; let mut b = S; let c; let d; // {      c, d}
@@ -289,6 +291,7 @@ impl<'tcx> HasMoveData<'tcx> for MaybeUninitializedPlaces<'_, 'tcx> {
 ///
 /// ```rust
 /// struct S;
+/// #[rustfmt::skip]
 /// fn foo(pred: bool) {                        // ever-init:
 ///                                             // {          }
 ///     let a = S; let mut b = S; let c; let d; // {a, b      }
diff --git a/compiler/rustc_mir_transform/Cargo.toml b/compiler/rustc_mir_transform/Cargo.toml
index a7d0b3acbe4..08c43a4648c 100644
--- a/compiler/rustc_mir_transform/Cargo.toml
+++ b/compiler/rustc_mir_transform/Cargo.toml
@@ -10,7 +10,6 @@ itertools = "0.12"
 rustc_abi = { path = "../rustc_abi" }
 rustc_arena = { path = "../rustc_arena" }
 rustc_ast = { path = "../rustc_ast" }
-rustc_attr_data_structures = { path = "../rustc_attr_data_structures" }
 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/check_inline.rs b/compiler/rustc_mir_transform/src/check_inline.rs
index 14d9532894f..af6da209081 100644
--- a/compiler/rustc_mir_transform/src/check_inline.rs
+++ b/compiler/rustc_mir_transform/src/check_inline.rs
@@ -1,7 +1,7 @@
 //! Check that a body annotated with `#[rustc_force_inline]` will not fail to inline based on its
 //! definition alone (irrespective of any specific caller).
 
-use rustc_attr_data_structures::InlineAttr;
+use rustc_hir::attrs::InlineAttr;
 use rustc_hir::def_id::DefId;
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use rustc_middle::mir::{Body, TerminatorKind};
diff --git a/compiler/rustc_mir_transform/src/coverage/mappings.rs b/compiler/rustc_mir_transform/src/coverage/mappings.rs
index b4b4d0416fb..b0e24cf2bdb 100644
--- a/compiler/rustc_mir_transform/src/coverage/mappings.rs
+++ b/compiler/rustc_mir_transform/src/coverage/mappings.rs
@@ -10,7 +10,7 @@ use rustc_middle::ty::TyCtxt;
 use rustc_span::Span;
 
 use crate::coverage::ExtractedHirInfo;
-use crate::coverage::graph::{BasicCoverageBlock, CoverageGraph, START_BCB};
+use crate::coverage::graph::{BasicCoverageBlock, CoverageGraph};
 use crate::coverage::spans::extract_refined_covspans;
 use crate::coverage::unexpand::unexpand_into_body_span;
 use crate::errors::MCDCExceedsTestVectorLimit;
@@ -82,22 +82,8 @@ pub(super) fn extract_all_mapping_info_from_mir<'tcx>(
     let mut mcdc_degraded_branches = vec![];
     let mut mcdc_mappings = vec![];
 
-    if hir_info.is_async_fn || tcx.sess.coverage_no_mir_spans() {
-        // An async function desugars into a function that returns a future,
-        // with the user code wrapped in a closure. Any spans in the desugared
-        // outer function will be unhelpful, so just keep the signature span
-        // and ignore all of the spans in the MIR body.
-        //
-        // When debugging flag `-Zcoverage-options=no-mir-spans` is set, we need
-        // to give the same treatment to _all_ functions, because `llvm-cov`
-        // seems to ignore functions that don't have any ordinary code spans.
-        if let Some(span) = hir_info.fn_sig_span {
-            code_mappings.push(CodeMapping { span, bcb: START_BCB });
-        }
-    } else {
-        // Extract coverage spans from MIR statements/terminators as normal.
-        extract_refined_covspans(tcx, mir_body, hir_info, graph, &mut code_mappings);
-    }
+    // Extract ordinary code mappings from MIR statement/terminator spans.
+    extract_refined_covspans(tcx, mir_body, hir_info, graph, &mut code_mappings);
 
     branch_pairs.extend(extract_branch_pairs(mir_body, hir_info, graph));
 
diff --git a/compiler/rustc_mir_transform/src/coverage/query.rs b/compiler/rustc_mir_transform/src/coverage/query.rs
index 73795e47d2e..c195ca51540 100644
--- a/compiler/rustc_mir_transform/src/coverage/query.rs
+++ b/compiler/rustc_mir_transform/src/coverage/query.rs
@@ -1,4 +1,5 @@
-use rustc_attr_data_structures::{AttributeKind, CoverageAttrKind, find_attr};
+use rustc_hir::attrs::{AttributeKind, CoverageAttrKind};
+use rustc_hir::find_attr;
 use rustc_index::bit_set::DenseBitSet;
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use rustc_middle::mir::coverage::{BasicCoverageBlock, CoverageIdsInfo, CoverageKind, MappingKind};
diff --git a/compiler/rustc_mir_transform/src/coverage/spans.rs b/compiler/rustc_mir_transform/src/coverage/spans.rs
index ec76076020e..0ee42abb195 100644
--- a/compiler/rustc_mir_transform/src/coverage/spans.rs
+++ b/compiler/rustc_mir_transform/src/coverage/spans.rs
@@ -1,7 +1,9 @@
 use rustc_data_structures::fx::FxHashSet;
 use rustc_middle::mir;
+use rustc_middle::mir::coverage::START_BCB;
 use rustc_middle::ty::TyCtxt;
-use rustc_span::{DesugaringKind, ExpnKind, MacroKind, Span};
+use rustc_span::source_map::SourceMap;
+use rustc_span::{BytePos, DesugaringKind, ExpnKind, MacroKind, Span};
 use tracing::instrument;
 
 use crate::coverage::graph::{BasicCoverageBlock, CoverageGraph};
@@ -15,8 +17,19 @@ pub(super) fn extract_refined_covspans<'tcx>(
     mir_body: &mir::Body<'tcx>,
     hir_info: &ExtractedHirInfo,
     graph: &CoverageGraph,
-    code_mappings: &mut impl Extend<mappings::CodeMapping>,
+    code_mappings: &mut Vec<mappings::CodeMapping>,
 ) {
+    if hir_info.is_async_fn {
+        // An async function desugars into a function that returns a future,
+        // with the user code wrapped in a closure. Any spans in the desugared
+        // outer function will be unhelpful, so just keep the signature span
+        // and ignore all of the spans in the MIR body.
+        if let Some(span) = hir_info.fn_sig_span {
+            code_mappings.push(mappings::CodeMapping { span, bcb: START_BCB });
+        }
+        return;
+    }
+
     let &ExtractedHirInfo { body_span, .. } = hir_info;
 
     let raw_spans = from_mir::extract_raw_spans_from_mir(mir_body, graph);
@@ -83,8 +96,18 @@ pub(super) fn extract_refined_covspans<'tcx>(
     // Discard any span that overlaps with a hole.
     discard_spans_overlapping_holes(&mut covspans, &holes);
 
-    // Perform more refinement steps after holes have been dealt with.
+    // Discard spans that overlap in unwanted ways.
     let mut covspans = remove_unwanted_overlapping_spans(covspans);
+
+    // For all empty spans, either enlarge them to be non-empty, or discard them.
+    let source_map = tcx.sess.source_map();
+    covspans.retain_mut(|covspan| {
+        let Some(span) = ensure_non_empty_span(source_map, covspan.span) else { return false };
+        covspan.span = span;
+        true
+    });
+
+    // Merge covspans that can be merged.
     covspans.dedup_by(|b, a| a.merge_if_eligible(b));
 
     code_mappings.extend(covspans.into_iter().map(|Covspan { span, bcb }| {
@@ -230,3 +253,26 @@ fn compare_spans(a: Span, b: Span) -> std::cmp::Ordering {
         // - Both have the same start and span A extends further right
         .then_with(|| Ord::cmp(&a.hi(), &b.hi()).reverse())
 }
+
+fn ensure_non_empty_span(source_map: &SourceMap, span: Span) -> Option<Span> {
+    if !span.is_empty() {
+        return Some(span);
+    }
+
+    // The span is empty, so try to enlarge it to cover an adjacent '{' or '}'.
+    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 src.as_bytes().get(end).copied() == Some(b'{') {
+                Some(span.with_hi(span.hi() + BytePos(1)))
+            } else if start > 0 && src.as_bytes()[start - 1] == b'}' {
+                Some(span.with_lo(span.lo() - BytePos(1)))
+            } else {
+                None
+            }
+        })
+        .ok()?
+}
diff --git a/compiler/rustc_mir_transform/src/cross_crate_inline.rs b/compiler/rustc_mir_transform/src/cross_crate_inline.rs
index 6d7b7e10ef6..b186c2bd775 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_data_structures::InlineAttr;
+use rustc_hir::attrs::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/ctfe_limit.rs b/compiler/rustc_mir_transform/src/ctfe_limit.rs
index fb17cca30f4..ac46336b834 100644
--- a/compiler/rustc_mir_transform/src/ctfe_limit.rs
+++ b/compiler/rustc_mir_transform/src/ctfe_limit.rs
@@ -18,7 +18,7 @@ impl<'tcx> crate::MirPass<'tcx> for CtfeLimit {
             .basic_blocks
             .iter_enumerated()
             .filter_map(|(node, node_data)| {
-                if matches!(node_data.terminator().kind, TerminatorKind::Call { .. })
+                if matches!(node_data.terminator().kind, TerminatorKind::Call { .. } | TerminatorKind::TailCall { .. })
                     // Back edges in a CFG indicate loops
                     || has_back_edge(doms, node, node_data)
                 {
diff --git a/compiler/rustc_mir_transform/src/elaborate_drop.rs b/compiler/rustc_mir_transform/src/elaborate_drop.rs
index de96b1f255a..4f3c53d761f 100644
--- a/compiler/rustc_mir_transform/src/elaborate_drop.rs
+++ b/compiler/rustc_mir_transform/src/elaborate_drop.rs
@@ -611,6 +611,7 @@ where
     ///
     /// For example, with 3 fields, the drop ladder is
     ///
+    /// ```text
     /// .d0:
     ///     ELAB(drop location.0 [target=.d1, unwind=.c1])
     /// .d1:
@@ -621,8 +622,10 @@ where
     ///     ELAB(drop location.1 [target=.c2])
     /// .c2:
     ///     ELAB(drop location.2 [target=`self.unwind`])
+    /// ```
     ///
     /// For possible-async drops in coroutines we also need dropline ladder
+    /// ```text
     /// .d0 (mainline):
     ///     ELAB(drop location.0 [target=.d1, unwind=.c1, drop=.e1])
     /// .d1 (mainline):
@@ -637,6 +640,7 @@ where
     ///     ELAB(drop location.1 [target=.e2, unwind=.c2])
     /// .e2 (dropline):
     ///     ELAB(drop location.2 [target=`self.drop`, unwind=`self.unwind`])
+    /// ```
     ///
     /// NOTE: this does not clear the master drop flag, so you need
     /// to point succ/unwind on a `drop_ladder_bottom`.
@@ -761,24 +765,37 @@ where
 
         let skip_contents = adt.is_union() || adt.is_manually_drop();
         let contents_drop = if skip_contents {
+            if adt.has_dtor(self.tcx()) && self.elaborator.get_drop_flag(self.path).is_some() {
+                // the top-level drop flag is usually cleared by open_drop_for_adt_contents
+                // types with destructors would still need an empty drop ladder to clear it
+
+                // however, these types are only open dropped in `DropShimElaborator`
+                // which does not have drop flags
+                // a future box-like "DerefMove" trait would allow for this case to happen
+                span_bug!(self.source_info.span, "open dropping partially moved union");
+            }
+
             (self.succ, self.unwind, self.dropline)
         } else {
             self.open_drop_for_adt_contents(adt, args)
         };
 
-        if adt.is_box() {
-            // we need to drop the inside of the box before running the destructor
-            let succ = self.destructor_call_block_sync((contents_drop.0, contents_drop.1));
-            let unwind = contents_drop
-                .1
-                .map(|unwind| self.destructor_call_block_sync((unwind, Unwind::InCleanup)));
-            let dropline = contents_drop
-                .2
-                .map(|dropline| self.destructor_call_block_sync((dropline, contents_drop.1)));
-
-            self.open_drop_for_box_contents(adt, args, succ, unwind, dropline)
-        } else if adt.has_dtor(self.tcx()) {
-            self.destructor_call_block(contents_drop)
+        if adt.has_dtor(self.tcx()) {
+            let destructor_block = if adt.is_box() {
+                // we need to drop the inside of the box before running the destructor
+                let succ = self.destructor_call_block_sync((contents_drop.0, contents_drop.1));
+                let unwind = contents_drop
+                    .1
+                    .map(|unwind| self.destructor_call_block_sync((unwind, Unwind::InCleanup)));
+                let dropline = contents_drop
+                    .2
+                    .map(|dropline| self.destructor_call_block_sync((dropline, contents_drop.1)));
+                self.open_drop_for_box_contents(adt, args, succ, unwind, dropline)
+            } else {
+                self.destructor_call_block(contents_drop)
+            };
+
+            self.drop_flag_test_block(destructor_block, contents_drop.0, contents_drop.1)
         } else {
             contents_drop.0
         }
@@ -982,12 +999,7 @@ where
             unwind.is_cleanup(),
         );
 
-        let destructor_block = self.elaborator.patch().new_block(result);
-
-        let block_start = Location { block: destructor_block, statement_index: 0 };
-        self.elaborator.clear_drop_flag(block_start, self.path, DropFlagMode::Shallow);
-
-        self.drop_flag_test_block(destructor_block, succ, unwind)
+        self.elaborator.patch().new_block(result)
     }
 
     fn destructor_call_block(
@@ -1002,13 +1014,7 @@ where
             && !unwind.is_cleanup()
             && ty.is_async_drop(self.tcx(), self.elaborator.typing_env())
         {
-            let destructor_block =
-                self.build_async_drop(self.place, ty, None, succ, unwind, dropline, true);
-
-            let block_start = Location { block: destructor_block, statement_index: 0 };
-            self.elaborator.clear_drop_flag(block_start, self.path, DropFlagMode::Shallow);
-
-            self.drop_flag_test_block(destructor_block, succ, unwind)
+            self.build_async_drop(self.place, ty, None, succ, unwind, dropline, true)
         } else {
             self.destructor_call_block_sync((succ, unwind))
         }
diff --git a/compiler/rustc_mir_transform/src/inline.rs b/compiler/rustc_mir_transform/src/inline.rs
index 1c0fc774867..3d49eb4e8ef 100644
--- a/compiler/rustc_mir_transform/src/inline.rs
+++ b/compiler/rustc_mir_transform/src/inline.rs
@@ -5,7 +5,7 @@ use std::iter;
 use std::ops::{Range, RangeFrom};
 
 use rustc_abi::{ExternAbi, FieldIdx};
-use rustc_attr_data_structures::{InlineAttr, OptimizeAttr};
+use rustc_hir::attrs::{InlineAttr, OptimizeAttr};
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::DefId;
 use rustc_index::Idx;
diff --git a/compiler/rustc_mir_transform/src/simplify.rs b/compiler/rustc_mir_transform/src/simplify.rs
index db933da6413..468ef742dfb 100644
--- a/compiler/rustc_mir_transform/src/simplify.rs
+++ b/compiler/rustc_mir_transform/src/simplify.rs
@@ -225,6 +225,7 @@ impl<'a, 'tcx> CfgSimplifier<'a, 'tcx> {
             current = target;
         }
         let last = current;
+        *changed |= *start != last;
         *start = last;
         while let Some((current, mut terminator)) = terminators.pop() {
             let Terminator { kind: TerminatorKind::Goto { ref mut target }, .. } = terminator
diff --git a/compiler/rustc_mir_transform/src/sroa.rs b/compiler/rustc_mir_transform/src/sroa.rs
index 80c4b58a574..38769885f36 100644
--- a/compiler/rustc_mir_transform/src/sroa.rs
+++ b/compiler/rustc_mir_transform/src/sroa.rs
@@ -72,8 +72,12 @@ fn escaping_locals<'tcx>(
             return true;
         }
         if let ty::Adt(def, _args) = ty.kind()
-            && tcx.is_lang_item(def.did(), LangItem::DynMetadata)
+            && (def.repr().simd() || tcx.is_lang_item(def.did(), LangItem::DynMetadata))
         {
+            // Exclude #[repr(simd)] types so that they are not de-optimized into an array
+            // (MCP#838 banned projections into SIMD types, but if the value is unused
+            // this pass sees "all the uses are of the fields" and expands it.)
+
             // codegen wants to see the `DynMetadata<T>`,
             // not the inner reference-to-opaque-type.
             return true;
diff --git a/compiler/rustc_mir_transform/src/validate.rs b/compiler/rustc_mir_transform/src/validate.rs
index 98d12bf0a38..99e4782e470 100644
--- a/compiler/rustc_mir_transform/src/validate.rs
+++ b/compiler/rustc_mir_transform/src/validate.rs
@@ -1,9 +1,9 @@
 //! Validates the MIR to ensure that invariants are upheld.
 
 use rustc_abi::{ExternAbi, FIRST_VARIANT, Size};
-use rustc_attr_data_structures::InlineAttr;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_hir::LangItem;
+use rustc_hir::attrs::InlineAttr;
 use rustc_index::IndexVec;
 use rustc_index::bit_set::DenseBitSet;
 use rustc_infer::infer::TyCtxtInferExt;
diff --git a/compiler/rustc_monomorphize/Cargo.toml b/compiler/rustc_monomorphize/Cargo.toml
index 063fc8f1c74..0ed5b4fc0d0 100644
--- a/compiler/rustc_monomorphize/Cargo.toml
+++ b/compiler/rustc_monomorphize/Cargo.toml
@@ -7,7 +7,6 @@ edition = "2024"
 # tidy-alphabetical-start
 rustc_abi = { path = "../rustc_abi" }
 rustc_ast = { path = "../rustc_ast" }
-rustc_attr_data_structures = { path = "../rustc_attr_data_structures" }
 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 1bfd83d97ac..35b80a9b96f 100644
--- a/compiler/rustc_monomorphize/src/collector.rs
+++ b/compiler/rustc_monomorphize/src/collector.rs
@@ -208,11 +208,11 @@
 use std::cell::OnceCell;
 use std::path::PathBuf;
 
-use rustc_attr_data_structures::InlineAttr;
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_data_structures::sync::{MTLock, par_for_each_in};
 use rustc_data_structures::unord::{UnordMap, UnordSet};
 use rustc_hir as hir;
+use rustc_hir::attrs::InlineAttr;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{DefId, DefIdMap, LocalDefId};
 use rustc_hir::lang_items::LangItem;
diff --git a/compiler/rustc_monomorphize/src/partitioning.rs b/compiler/rustc_monomorphize/src/partitioning.rs
index cee15e0f696..d76b27d9970 100644
--- a/compiler/rustc_monomorphize/src/partitioning.rs
+++ b/compiler/rustc_monomorphize/src/partitioning.rs
@@ -100,11 +100,11 @@ use std::fs::{self, File};
 use std::io::Write;
 use std::path::{Path, PathBuf};
 
-use rustc_attr_data_structures::InlineAttr;
 use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_data_structures::sync;
 use rustc_data_structures::unord::{UnordMap, UnordSet};
 use rustc_hir::LangItem;
+use rustc_hir::attrs::InlineAttr;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{DefId, DefIdSet, LOCAL_CRATE};
 use rustc_hir::definitions::DefPathDataName;
diff --git a/compiler/rustc_next_trait_solver/Cargo.toml b/compiler/rustc_next_trait_solver/Cargo.toml
index 36d53901d9e..05bcabad02f 100644
--- a/compiler/rustc_next_trait_solver/Cargo.toml
+++ b/compiler/rustc_next_trait_solver/Cargo.toml
@@ -15,6 +15,7 @@ tracing = "0.1"
 # tidy-alphabetical-end
 
 [features]
+# tidy-alphabetical-start
 default = ["nightly"]
 nightly = [
     "dep:rustc_data_structures",
@@ -22,3 +23,4 @@ nightly = [
     "rustc_index/nightly",
     "rustc_type_ir/nightly",
 ]
+# tidy-alphabetical-end
diff --git a/compiler/rustc_next_trait_solver/src/canonicalizer.rs b/compiler/rustc_next_trait_solver/src/canonicalizer.rs
index a418aa82100..1bc35e599c7 100644
--- a/compiler/rustc_next_trait_solver/src/canonicalizer.rs
+++ b/compiler/rustc_next_trait_solver/src/canonicalizer.rs
@@ -19,6 +19,20 @@ const NEEDS_CANONICAL: TypeFlags = TypeFlags::from_bits(
 )
 .unwrap();
 
+#[derive(Debug, Clone, Copy)]
+enum CanonicalizeInputKind {
+    /// When canonicalizing the `param_env`, we keep `'static` as merging
+    /// trait candidates relies on it when deciding whether a where-bound
+    /// is trivial.
+    ParamEnv,
+    /// When canonicalizing predicates, we don't keep `'static`. If we're
+    /// currently outside of the trait solver and canonicalize the root goal
+    /// during HIR typeck, we replace each occurance of a region with a
+    /// unique region variable. See the comment on `InferCtxt::in_hir_typeck`
+    /// for more details.
+    Predicate { is_hir_typeck_root_goal: bool },
+}
+
 /// Whether we're canonicalizing a query input or the query response.
 ///
 /// When canonicalizing an input we're in the context of the caller
@@ -26,10 +40,7 @@ const NEEDS_CANONICAL: TypeFlags = TypeFlags::from_bits(
 /// query.
 #[derive(Debug, Clone, Copy)]
 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 },
+    Input(CanonicalizeInputKind),
     /// FIXME: We currently return region constraints referring to
     /// placeholders and inference variables from a binder instantiated
     /// inside of the query.
@@ -122,7 +133,7 @@ impl<'a, D: SolverDelegate<Interner = I>, I: Interner> Canonicalizer<'a, D, I> {
                     let mut variables = Vec::new();
                     let mut env_canonicalizer = Canonicalizer {
                         delegate,
-                        canonicalize_mode: CanonicalizeMode::Input { keep_static: true },
+                        canonicalize_mode: CanonicalizeMode::Input(CanonicalizeInputKind::ParamEnv),
 
                         variables: &mut variables,
                         variable_lookup_table: Default::default(),
@@ -154,7 +165,7 @@ impl<'a, D: SolverDelegate<Interner = I>, I: Interner> Canonicalizer<'a, D, I> {
         } else {
             let mut env_canonicalizer = Canonicalizer {
                 delegate,
-                canonicalize_mode: CanonicalizeMode::Input { keep_static: true },
+                canonicalize_mode: CanonicalizeMode::Input(CanonicalizeInputKind::ParamEnv),
 
                 variables,
                 variable_lookup_table: Default::default(),
@@ -180,6 +191,7 @@ impl<'a, D: SolverDelegate<Interner = I>, I: Interner> Canonicalizer<'a, D, I> {
     pub fn canonicalize_input<P: TypeFoldable<I>>(
         delegate: &'a D,
         variables: &'a mut Vec<I::GenericArg>,
+        is_hir_typeck_root_goal: bool,
         input: QueryInput<I, P>,
     ) -> ty::Canonical<I, QueryInput<I, P>> {
         // First canonicalize the `param_env` while keeping `'static`
@@ -189,7 +201,9 @@ impl<'a, D: SolverDelegate<Interner = I>, I: Interner> Canonicalizer<'a, D, I> {
         // while *mostly* reusing the canonicalizer from above.
         let mut rest_canonicalizer = Canonicalizer {
             delegate,
-            canonicalize_mode: CanonicalizeMode::Input { keep_static: false },
+            canonicalize_mode: CanonicalizeMode::Input(CanonicalizeInputKind::Predicate {
+                is_hir_typeck_root_goal,
+            }),
 
             variables,
             variable_lookup_table,
@@ -296,7 +310,7 @@ impl<'a, D: SolverDelegate<Interner = I>, I: Interner> Canonicalizer<'a, D, I> {
         }
     }
 
-    fn cached_fold_ty(&mut self, t: I::Ty) -> I::Ty {
+    fn inner_fold_ty(&mut self, t: I::Ty) -> I::Ty {
         let kind = match t.kind() {
             ty::Infer(i) => match i {
                 ty::TyVar(vid) => {
@@ -413,10 +427,10 @@ impl<D: SolverDelegate<Interner = I>, I: Interner> TypeFolder<I> for Canonicaliz
             // 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 } => {
+                CanonicalizeMode::Input(CanonicalizeInputKind::Predicate { .. }) => {
                     CanonicalVarKind::Region(ty::UniverseIndex::ROOT)
                 }
-                CanonicalizeMode::Input { keep_static: true }
+                CanonicalizeMode::Input(CanonicalizeInputKind::ParamEnv)
                 | CanonicalizeMode::Response { .. } => return r,
             },
 
@@ -428,12 +442,12 @@ impl<D: SolverDelegate<Interner = I>, I: Interner> TypeFolder<I> for Canonicaliz
             // `ReErased`. We may be able to short-circuit registering region
             // obligations if we encounter a `ReErased` on one side, for example.
             ty::ReErased | ty::ReError(_) => match self.canonicalize_mode {
-                CanonicalizeMode::Input { .. } => CanonicalVarKind::Region(ty::UniverseIndex::ROOT),
+                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:?}")
                 }
@@ -441,7 +455,7 @@ 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.
@@ -459,9 +473,7 @@ 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 { keep_static: _ } => {
-                        CanonicalVarKind::Region(ty::UniverseIndex::ROOT)
-                    }
+                    CanonicalizeMode::Input(_) => CanonicalVarKind::Region(ty::UniverseIndex::ROOT),
                     CanonicalizeMode::Response { .. } => {
                         CanonicalVarKind::Region(self.delegate.universe_of_lt(vid).unwrap())
                     }
@@ -469,16 +481,34 @@ impl<D: SolverDelegate<Interner = I>, I: Interner> TypeFolder<I> for Canonicaliz
             }
         };
 
-        let var = self.get_or_insert_bound_var(r, kind);
+        let var = if let CanonicalizeMode::Input(CanonicalizeInputKind::Predicate {
+            is_hir_typeck_root_goal: true,
+        }) = self.canonicalize_mode
+        {
+            let var = ty::BoundVar::from(self.variables.len());
+            self.variables.push(r.into());
+            self.var_kinds.push(kind);
+            var
+        } else {
+            self.get_or_insert_bound_var(r, kind)
+        };
 
         Region::new_anon_bound(self.cx(), self.binder_index, var)
     }
 
     fn fold_ty(&mut self, t: I::Ty) -> I::Ty {
-        if let Some(&ty) = self.cache.get(&(self.binder_index, t)) {
+        if let CanonicalizeMode::Input(CanonicalizeInputKind::Predicate {
+            is_hir_typeck_root_goal: true,
+        }) = self.canonicalize_mode
+        {
+            // If we're canonicalizing a root goal during HIR typeck, we
+            // must not use the `cache` as we want to map each occurrence
+            // of a region to a unique existential variable.
+            self.inner_fold_ty(t)
+        } else if let Some(&ty) = self.cache.get(&(self.binder_index, t)) {
             ty
         } else {
-            let res = self.cached_fold_ty(t);
+            let res = self.inner_fold_ty(t);
             let old = self.cache.insert((self.binder_index, t), res);
             assert_eq!(old, None);
             res
@@ -541,9 +571,9 @@ impl<D: SolverDelegate<Interner = I>, I: Interner> TypeFolder<I> for Canonicaliz
 
     fn fold_clauses(&mut self, c: I::Clauses) -> I::Clauses {
         match self.canonicalize_mode {
-            CanonicalizeMode::Input { keep_static: true }
+            CanonicalizeMode::Input(CanonicalizeInputKind::ParamEnv)
             | CanonicalizeMode::Response { max_input_universe: _ } => {}
-            CanonicalizeMode::Input { keep_static: false } => {
+            CanonicalizeMode::Input(CanonicalizeInputKind::Predicate { .. }) => {
                 panic!("erasing 'static in env")
             }
         }
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 b2d40146348..5e08c3a03d8 100644
--- a/compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs
@@ -21,7 +21,7 @@ use crate::delegate::SolverDelegate;
 use crate::solve::inspect::ProbeKind;
 use crate::solve::{
     BuiltinImplSource, CandidateSource, CanonicalResponse, Certainty, EvalCtxt, Goal, GoalSource,
-    MaybeCause, NoSolution, ParamEnvSource, QueryResult,
+    MaybeCause, NoSolution, ParamEnvSource, QueryResult, has_no_inference_or_external_constraints,
 };
 
 enum AliasBoundKind {
@@ -50,7 +50,7 @@ where
 
     fn trait_ref(self, cx: I) -> ty::TraitRef<I>;
 
-    fn with_self_ty(self, cx: I, self_ty: I::Ty) -> Self;
+    fn with_replaced_self_ty(self, cx: I, self_ty: I::Ty) -> Self;
 
     fn trait_def_id(self, cx: I) -> I::DefId;
 
@@ -376,8 +376,8 @@ where
             return self.forced_ambiguity(MaybeCause::Ambiguity).into_iter().collect();
         }
 
-        let goal: Goal<I, G> =
-            goal.with(self.cx(), goal.predicate.with_self_ty(self.cx(), normalized_self_ty));
+        let goal: Goal<I, G> = goal
+            .with(self.cx(), goal.predicate.with_replaced_self_ty(self.cx(), normalized_self_ty));
         // Vars that show up in the rest of the goal substs may have been constrained by
         // normalizing the self type as well, since type variables are not uniquified.
         let goal = self.resolve_vars_if_possible(goal);
@@ -395,9 +395,30 @@ where
 
         match assemble_from {
             AssembleCandidatesFrom::All => {
-                self.assemble_impl_candidates(goal, &mut candidates);
                 self.assemble_builtin_impl_candidates(goal, &mut candidates);
-                self.assemble_object_bound_candidates(goal, &mut candidates);
+                // For performance we only assemble impls if there are no candidates
+                // which would shadow them. This is necessary to avoid hangs in rayon,
+                // see trait-system-refactor-initiative#109 for more details.
+                //
+                // We always assemble builtin impls as trivial builtin impls have a higher
+                // priority than where-clauses.
+                //
+                // We only do this if any such candidate applies without any constraints
+                // as we may want to weaken inference guidance in the future and don't want
+                // to worry about causing major performance regressions when doing so.
+                // See trait-system-refactor-initiative#226 for some ideas here.
+                if TypingMode::Coherence == self.typing_mode()
+                    || !candidates.iter().any(|c| {
+                        matches!(
+                            c.source,
+                            CandidateSource::ParamEnv(ParamEnvSource::NonGlobal)
+                                | CandidateSource::AliasBound
+                        ) && has_no_inference_or_external_constraints(c.result)
+                    })
+                {
+                    self.assemble_impl_candidates(goal, &mut candidates);
+                    self.assemble_object_bound_candidates(goal, &mut candidates);
+                }
             }
             AssembleCandidatesFrom::EnvAndBounds => {}
         }
@@ -938,36 +959,23 @@ where
                 // 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`.
-                let candidates_from_env_and_bounds: Vec<_> = self
+                let mut candidates: Vec<_> = self
                     .assemble_and_evaluate_candidates(goal, AssembleCandidatesFrom::EnvAndBounds);
 
                 // We still need to prefer where-bounds over alias-bounds however.
                 // See `tests/ui/winnowing/norm-where-bound-gt-alias-bound.rs`.
-                let mut considered_candidates: Vec<_> = if candidates_from_env_and_bounds
-                    .iter()
-                    .any(|c| matches!(c.source, CandidateSource::ParamEnv(_)))
-                {
-                    candidates_from_env_and_bounds
-                        .into_iter()
-                        .filter(|c| matches!(c.source, CandidateSource::ParamEnv(_)))
-                        .map(|c| c.result)
-                        .collect()
-                } else {
-                    candidates_from_env_and_bounds.into_iter().map(|c| c.result).collect()
-                };
-
-                // If the trait goal has been proven by using the environment, we want to treat
-                // aliases as rigid if there are no applicable projection bounds in the environment.
-                if considered_candidates.is_empty() {
-                    if let Ok(response) = inject_normalize_to_rigid_candidate(self) {
-                        considered_candidates.push(response);
-                    }
+                if candidates.iter().any(|c| matches!(c.source, CandidateSource::ParamEnv(_))) {
+                    candidates.retain(|c| matches!(c.source, CandidateSource::ParamEnv(_)));
+                } else if candidates.is_empty() {
+                    // If the trait goal has been proven by using the environment, we want to treat
+                    // aliases as rigid if there are no applicable projection bounds in the environment.
+                    return inject_normalize_to_rigid_candidate(self);
                 }
 
-                if let Some(response) = self.try_merge_responses(&considered_candidates) {
+                if let Some(response) = self.try_merge_candidates(&candidates) {
                     Ok(response)
                 } else {
-                    self.flounder(&considered_candidates)
+                    self.flounder(&candidates)
                 }
             }
             TraitGoalProvenVia::Misc => {
@@ -977,11 +985,9 @@ where
                 // Prefer "orphaned" param-env normalization predicates, which are used
                 // (for example, and ideally only) when proving item bounds for an impl.
                 let candidates_from_env: Vec<_> = candidates
-                    .iter()
-                    .filter(|c| matches!(c.source, CandidateSource::ParamEnv(_)))
-                    .map(|c| c.result)
+                    .extract_if(.., |c| matches!(c.source, CandidateSource::ParamEnv(_)))
                     .collect();
-                if let Some(response) = self.try_merge_responses(&candidates_from_env) {
+                if let Some(response) = self.try_merge_candidates(&candidates_from_env) {
                     return Ok(response);
                 }
 
@@ -991,12 +997,10 @@ where
                 // means we can just ignore inference constraints and don't have to special-case
                 // constraining the normalized-to `term`.
                 self.filter_specialized_impls(AllowInferenceConstraints::Yes, &mut candidates);
-
-                let responses: Vec<_> = candidates.iter().map(|c| c.result).collect();
-                if let Some(response) = self.try_merge_responses(&responses) {
+                if let Some(response) = self.try_merge_candidates(&candidates) {
                     Ok(response)
                 } else {
-                    self.flounder(&responses)
+                    self.flounder(&candidates)
                 }
             }
         }
diff --git a/compiler/rustc_next_trait_solver/src/solve/assembly/structural_traits.rs b/compiler/rustc_next_trait_solver/src/solve/assembly/structural_traits.rs
index c0bebdf6fb6..faa86734d08 100644
--- a/compiler/rustc_next_trait_solver/src/solve/assembly/structural_traits.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/assembly/structural_traits.rs
@@ -75,9 +75,16 @@ where
             Ok(ty::Binder::dummy(vec![args.as_coroutine_closure().tupled_upvars_ty()]))
         }
 
-        ty::Coroutine(_, args) => {
+        ty::Coroutine(def_id, args) => {
             let coroutine_args = args.as_coroutine();
-            Ok(ty::Binder::dummy(vec![coroutine_args.tupled_upvars_ty(), coroutine_args.witness()]))
+            Ok(ty::Binder::dummy(vec![
+                coroutine_args.tupled_upvars_ty(),
+                Ty::new_coroutine_witness(
+                    ecx.cx(),
+                    def_id,
+                    ecx.cx().mk_args(coroutine_args.parent_args().as_slice()),
+                ),
+            ]))
         }
 
         ty::CoroutineWitness(def_id, args) => Ok(ecx
@@ -245,7 +252,14 @@ where
             Movability::Movable => {
                 if ecx.cx().features().coroutine_clone() {
                     let coroutine = args.as_coroutine();
-                    Ok(ty::Binder::dummy(vec![coroutine.tupled_upvars_ty(), coroutine.witness()]))
+                    Ok(ty::Binder::dummy(vec![
+                        coroutine.tupled_upvars_ty(),
+                        Ty::new_coroutine_witness(
+                            ecx.cx(),
+                            def_id,
+                            ecx.cx().mk_args(coroutine.parent_args().as_slice()),
+                        ),
+                    ]))
                 } else {
                     Err(NoSolution)
                 }
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 61f3f9367f0..9a22bf58c03 100644
--- a/compiler/rustc_next_trait_solver/src/solve/effect_goals.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/effect_goals.rs
@@ -29,8 +29,8 @@ where
         self.trait_ref
     }
 
-    fn with_self_ty(self, cx: I, self_ty: I::Ty) -> Self {
-        self.with_self_ty(cx, self_ty)
+    fn with_replaced_self_ty(self, cx: I, self_ty: I::Ty) -> Self {
+        self.with_replaced_self_ty(cx, self_ty)
     }
 
     fn trait_def_id(self, _: I) -> I::DefId {
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 5ed316aa6b1..74c5b49ea92 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
@@ -53,20 +53,19 @@ where
 {
     /// Canonicalizes the goal remembering the original values
     /// for each bound variable.
+    ///
+    /// This expects `goal` and `opaque_types` to be eager resolved.
     pub(super) fn canonicalize_goal(
         &self,
+        is_hir_typeck_root_goal: bool,
         goal: Goal<I, I::Predicate>,
+        opaque_types: Vec<(ty::OpaqueTypeKey<I>, I::Ty)>,
     ) -> (Vec<I::GenericArg>, CanonicalInput<I, I::Predicate>) {
-        // We only care about one entry per `OpaqueTypeKey` here,
-        // so we only canonicalize the lookup table and ignore
-        // duplicate entries.
-        let opaque_types = self.delegate.clone_opaque_types_lookup_table();
-        let (goal, opaque_types) = eager_resolve_vars(self.delegate, (goal, opaque_types));
-
         let mut orig_values = Default::default();
         let canonical = Canonicalizer::canonicalize_input(
             self.delegate,
             &mut orig_values,
+            is_hir_typeck_root_goal,
             QueryInput {
                 goal,
                 predefined_opaques_in_body: self
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 ce9b794d40d..8671cc7c3d3 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
@@ -20,6 +20,7 @@ use super::has_only_region_constraints;
 use crate::coherence;
 use crate::delegate::SolverDelegate;
 use crate::placeholder::BoundVarReplacer;
+use crate::resolve::eager_resolve_vars;
 use crate::solve::inspect::{self, ProofTreeBuilder};
 use crate::solve::search_graph::SearchGraph;
 use crate::solve::ty::may_use_unstable_feature;
@@ -440,6 +441,7 @@ where
             return Ok((
                 NestedNormalizationGoals::empty(),
                 GoalEvaluation {
+                    goal,
                     certainty: Certainty::Maybe(stalled_on.stalled_cause),
                     has_changed: HasChanged::No,
                     stalled_on: Some(stalled_on),
@@ -447,7 +449,16 @@ where
             ));
         }
 
-        let (orig_values, canonical_goal) = self.canonicalize_goal(goal);
+        // We only care about one entry per `OpaqueTypeKey` here,
+        // so we only canonicalize the lookup table and ignore
+        // duplicate entries.
+        let opaque_types = self.delegate.clone_opaque_types_lookup_table();
+        let (goal, opaque_types) = eager_resolve_vars(self.delegate, (goal, opaque_types));
+
+        let is_hir_typeck_root_goal = matches!(goal_evaluation_kind, GoalEvaluationKind::Root)
+            && self.delegate.in_hir_typeck();
+        let (orig_values, canonical_goal) =
+            self.canonicalize_goal(is_hir_typeck_root_goal, goal, opaque_types);
         let mut goal_evaluation =
             self.inspect.new_goal_evaluation(goal, &orig_values, goal_evaluation_kind);
         let canonical_result = self.search_graph.evaluate_goal(
@@ -525,7 +536,10 @@ where
             },
         };
 
-        Ok((normalization_nested_goals, GoalEvaluation { certainty, has_changed, stalled_on }))
+        Ok((
+            normalization_nested_goals,
+            GoalEvaluation { goal, certainty, has_changed, stalled_on },
+        ))
     }
 
     pub(super) fn compute_goal(&mut self, goal: Goal<I, I::Predicate>) -> QueryResult<I> {
@@ -661,7 +675,7 @@ where
 
                 let (
                     NestedNormalizationGoals(nested_goals),
-                    GoalEvaluation { certainty, stalled_on, has_changed: _ },
+                    GoalEvaluation { goal, certainty, stalled_on, has_changed: _ },
                 ) = self.evaluate_goal_raw(
                     GoalEvaluationKind::Nested,
                     source,
@@ -699,7 +713,15 @@ where
                 // FIXME: Do we need to eagerly resolve here? Or should we check
                 // if the cache key has any changed vars?
                 let with_resolved_vars = self.resolve_vars_if_possible(goal);
-                if pred.alias != goal.predicate.as_normalizes_to().unwrap().skip_binder().alias {
+                if pred.alias
+                    != with_resolved_vars
+                        .predicate
+                        .as_normalizes_to()
+                        .unwrap()
+                        .no_bound_vars()
+                        .unwrap()
+                        .alias
+                {
                     unchanged_certainty = None;
                 }
 
@@ -711,7 +733,7 @@ where
                     }
                 }
             } else {
-                let GoalEvaluation { certainty, has_changed, stalled_on } =
+                let GoalEvaluation { goal, certainty, has_changed, stalled_on } =
                     self.evaluate_goal(GoalEvaluationKind::Nested, source, goal, stalled_on)?;
                 if has_changed == HasChanged::Yes {
                     unchanged_certainty = None;
diff --git a/compiler/rustc_next_trait_solver/src/solve/mod.rs b/compiler/rustc_next_trait_solver/src/solve/mod.rs
index 5ea3f0d1061..2feebe270a6 100644
--- a/compiler/rustc_next_trait_solver/src/solve/mod.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/mod.rs
@@ -29,6 +29,7 @@ use tracing::instrument;
 
 pub use self::eval_ctxt::{EvalCtxt, GenerateProofTree, SolverDelegateEvalExt};
 use crate::delegate::SolverDelegate;
+use crate::solve::assembly::Candidate;
 
 /// How many fixpoint iterations we should attempt inside of the solver before bailing
 /// with overflow.
@@ -244,52 +245,51 @@ where
     ///
     /// In this case we tend to flounder and return ambiguity by calling `[EvalCtxt::flounder]`.
     #[instrument(level = "trace", skip(self), ret)]
-    fn try_merge_responses(
+    fn try_merge_candidates(
         &mut self,
-        responses: &[CanonicalResponse<I>],
+        candidates: &[Candidate<I>],
     ) -> Option<CanonicalResponse<I>> {
-        if responses.is_empty() {
+        if candidates.is_empty() {
             return None;
         }
 
-        // FIXME(-Znext-solver): Add support to merge region constraints in
-        // responses to deal with trait-system-refactor-initiative#27.
-        let one = responses[0];
-        if responses[1..].iter().all(|&resp| resp == one) {
+        let one: CanonicalResponse<I> = candidates[0].result;
+        if candidates[1..].iter().all(|candidate| candidate.result == one) {
             return Some(one);
         }
 
-        responses
+        candidates
             .iter()
-            .find(|response| {
-                response.value.certainty == Certainty::Yes
-                    && has_no_inference_or_external_constraints(**response)
+            .find(|candidate| {
+                candidate.result.value.certainty == Certainty::Yes
+                    && has_no_inference_or_external_constraints(candidate.result)
             })
-            .copied()
+            .map(|candidate| candidate.result)
     }
 
-    fn bail_with_ambiguity(&mut self, responses: &[CanonicalResponse<I>]) -> CanonicalResponse<I> {
-        debug_assert!(responses.len() > 1);
-        let maybe_cause = responses.iter().fold(MaybeCause::Ambiguity, |maybe_cause, response| {
-            // Pull down the certainty of `Certainty::Yes` to ambiguity when combining
-            // these responses, b/c we're combining more than one response and this we
-            // don't know which one applies.
-            let candidate = match response.value.certainty {
-                Certainty::Yes => MaybeCause::Ambiguity,
-                Certainty::Maybe(candidate) => candidate,
-            };
-            maybe_cause.or(candidate)
-        });
+    fn bail_with_ambiguity(&mut self, candidates: &[Candidate<I>]) -> CanonicalResponse<I> {
+        debug_assert!(candidates.len() > 1);
+        let maybe_cause =
+            candidates.iter().fold(MaybeCause::Ambiguity, |maybe_cause, candidates| {
+                // Pull down the certainty of `Certainty::Yes` to ambiguity when combining
+                // these responses, b/c we're combining more than one response and this we
+                // don't know which one applies.
+                let candidate = match candidates.result.value.certainty {
+                    Certainty::Yes => MaybeCause::Ambiguity,
+                    Certainty::Maybe(candidate) => candidate,
+                };
+                maybe_cause.or(candidate)
+            });
         self.make_ambiguous_response_no_constraints(maybe_cause)
     }
 
     /// 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() {
+    fn flounder(&mut self, candidates: &[Candidate<I>]) -> QueryResult<I> {
+        if candidates.is_empty() {
             return Err(NoSolution);
         } else {
-            Ok(self.bail_with_ambiguity(responses))
+            Ok(self.bail_with_ambiguity(candidates))
         }
     }
 
@@ -388,6 +388,23 @@ fn response_no_constraints_raw<I: Interner>(
 
 /// The result of evaluating a goal.
 pub struct GoalEvaluation<I: Interner> {
+    /// The goal we've evaluated. This is the input goal, but potentially with its
+    /// inference variables resolved. This never applies any inference constraints
+    /// from evaluating the goal.
+    ///
+    /// We rely on this to check whether root goals in HIR typeck had an unresolved
+    /// type inference variable in the input. We must not resolve this after evaluating
+    /// the goal as even if the inference variable has been resolved by evaluating the
+    /// goal itself, this goal may still end up failing due to region uniquification
+    /// later on.
+    ///
+    /// This is used as a minor optimization to avoid re-resolving inference variables
+    /// when reevaluating ambiguous goals. E.g. if we've got a goal `?x: Trait` with `?x`
+    /// already being constrained to `Vec<?y>`, then the first evaluation resolves it to
+    /// `Vec<?y>: Trait`. If this goal is still ambiguous and we later resolve `?y` to `u32`,
+    /// then reevaluating this goal now only needs to resolve `?y` while it would otherwise
+    /// have to resolve both `?x` and `?y`,
+    pub goal: Goal<I, I::Predicate>,
     pub certainty: Certainty,
     pub has_changed: HasChanged,
     /// If the [`Certainty`] was `Maybe`, then keep track of whether the goal has changed
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 1e0a90eb2ee..93434dce79f 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
@@ -99,8 +99,8 @@ where
         self.alias.trait_ref(cx)
     }
 
-    fn with_self_ty(self, cx: I, self_ty: I::Ty) -> Self {
-        self.with_self_ty(cx, self_ty)
+    fn with_replaced_self_ty(self, cx: I, self_ty: I::Ty) -> Self {
+        self.with_replaced_self_ty(cx, self_ty)
     }
 
     fn trait_def_id(self, cx: I) -> I::DefId {
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 650b85d99d2..60bae738e61 100644
--- a/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs
@@ -33,8 +33,8 @@ where
         self.trait_ref
     }
 
-    fn with_self_ty(self, cx: I, self_ty: I::Ty) -> Self {
-        self.with_self_ty(cx, self_ty)
+    fn with_replaced_self_ty(self, cx: I, self_ty: I::Ty) -> Self {
+        self.with_replaced_self_ty(cx, self_ty)
     }
 
     fn trait_def_id(self, _: I) -> I::DefId {
@@ -229,7 +229,7 @@ where
         }
 
         // We need to make sure to stall any coroutines we are inferring to avoid query cycles.
-        if let Some(cand) = ecx.try_stall_coroutine_witness(goal.predicate.self_ty()) {
+        if let Some(cand) = ecx.try_stall_coroutine(goal.predicate.self_ty()) {
             return cand;
         }
 
@@ -294,7 +294,7 @@ where
         }
 
         // We need to make sure to stall any coroutines we are inferring to avoid query cycles.
-        if let Some(cand) = ecx.try_stall_coroutine_witness(goal.predicate.self_ty()) {
+        if let Some(cand) = ecx.try_stall_coroutine(goal.predicate.self_ty()) {
             return cand;
         }
 
@@ -1263,7 +1263,9 @@ where
             let goals =
                 ecx.enter_forall(constituent_tys(ecx, goal.predicate.self_ty())?, |ecx, tys| {
                     tys.into_iter()
-                        .map(|ty| goal.with(ecx.cx(), goal.predicate.with_self_ty(ecx.cx(), ty)))
+                        .map(|ty| {
+                            goal.with(ecx.cx(), goal.predicate.with_replaced_self_ty(ecx.cx(), ty))
+                        })
                         .collect::<Vec<_>>()
                 });
             ecx.add_goals(GoalSource::ImplWhereBound, goals);
@@ -1344,11 +1346,10 @@ where
         mut 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) {
+            return if let Some(response) = self.try_merge_candidates(&candidates) {
                 Ok((response, Some(TraitGoalProvenVia::Misc)))
             } else {
-                self.flounder(&all_candidates).map(|r| (r, None))
+                self.flounder(&candidates).map(|r| (r, None))
             };
         }
 
@@ -1373,11 +1374,9 @@ where
             .any(|c| matches!(c.source, CandidateSource::ParamEnv(ParamEnvSource::NonGlobal)));
         if has_non_global_where_bounds {
             let where_bounds: Vec<_> = candidates
-                .iter()
-                .filter(|c| matches!(c.source, CandidateSource::ParamEnv(_)))
-                .map(|c| c.result)
+                .extract_if(.., |c| matches!(c.source, CandidateSource::ParamEnv(_)))
                 .collect();
-            return if let Some(response) = self.try_merge_responses(&where_bounds) {
+            return if let Some(response) = self.try_merge_candidates(&where_bounds) {
                 Ok((response, Some(TraitGoalProvenVia::ParamEnv)))
             } else {
                 Ok((self.bail_with_ambiguity(&where_bounds), None))
@@ -1386,11 +1385,9 @@ where
 
         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)
+                .extract_if(.., |c| matches!(c.source, CandidateSource::AliasBound))
                 .collect();
-            return if let Some(response) = self.try_merge_responses(&alias_bounds) {
+            return if let Some(response) = self.try_merge_candidates(&alias_bounds) {
                 Ok((response, Some(TraitGoalProvenVia::AliasBound)))
             } else {
                 Ok((self.bail_with_ambiguity(&alias_bounds), None))
@@ -1415,11 +1412,10 @@ where
             TraitGoalProvenVia::Misc
         };
 
-        let all_candidates: Vec<_> = candidates.into_iter().map(|c| c.result).collect();
-        if let Some(response) = self.try_merge_responses(&all_candidates) {
+        if let Some(response) = self.try_merge_candidates(&candidates) {
             Ok((response, Some(proven_via)))
         } else {
-            self.flounder(&all_candidates).map(|r| (r, None))
+            self.flounder(&candidates).map(|r| (r, None))
         }
     }
 
@@ -1432,11 +1428,8 @@ where
         self.merge_trait_candidates(candidates)
     }
 
-    fn try_stall_coroutine_witness(
-        &mut self,
-        self_ty: I::Ty,
-    ) -> Option<Result<Candidate<I>, NoSolution>> {
-        if let ty::CoroutineWitness(def_id, _) = self_ty.kind() {
+    fn try_stall_coroutine(&mut self, self_ty: I::Ty) -> Option<Result<Candidate<I>, NoSolution>> {
+        if let ty::Coroutine(def_id, _) = self_ty.kind() {
             match self.typing_mode() {
                 TypingMode::Analysis {
                     defining_opaque_types_and_generators: stalled_generators,
diff --git a/compiler/rustc_parse/Cargo.toml b/compiler/rustc_parse/Cargo.toml
index 88f93782de1..0ae0b613fa2 100644
--- a/compiler/rustc_parse/Cargo.toml
+++ b/compiler/rustc_parse/Cargo.toml
@@ -26,5 +26,8 @@ unicode-width = "0.2.0"
 # tidy-alphabetical-end
 
 [dev-dependencies]
+# tidy-alphabetical-start
 termcolor = "1.2"
+# tidy-alphabetical-end
+
 
diff --git a/compiler/rustc_parse/messages.ftl b/compiler/rustc_parse/messages.ftl
index 859118a4ade..7059ffbf375 100644
--- a/compiler/rustc_parse/messages.ftl
+++ b/compiler/rustc_parse/messages.ftl
@@ -71,6 +71,17 @@ parse_attr_without_generics = attribute without generic parameters
 parse_attribute_on_param_type = attributes cannot be applied to a function parameter's type
     .label = attributes are not allowed here
 
+parse_attribute_on_type = attributes cannot be applied to types
+    .label = attributes are not allowed here
+    .suggestion = remove attribute from here
+
+parse_attribute_on_generic_arg = attributes cannot be applied to generic arguments
+    .label = attributes are not allowed here
+    .suggestion = remove attribute from here
+
+parse_attribute_on_empty_type = attributes cannot be applied here
+    .label = attributes are not allowed here
+
 parse_bad_assoc_type_bounds = bounds on associated types do not belong here
     .label = belongs in `where` clause
 
diff --git a/compiler/rustc_parse/src/errors.rs b/compiler/rustc_parse/src/errors.rs
index 4aaaba01fae..48ff0394d46 100644
--- a/compiler/rustc_parse/src/errors.rs
+++ b/compiler/rustc_parse/src/errors.rs
@@ -1490,6 +1490,34 @@ pub(crate) struct AttributeOnParamType {
 }
 
 #[derive(Diagnostic)]
+#[diag(parse_attribute_on_type)]
+pub(crate) struct AttributeOnType {
+    #[primary_span]
+    #[label]
+    pub span: Span,
+    #[suggestion(code = "", applicability = "machine-applicable", style = "tool-only")]
+    pub fix_span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(parse_attribute_on_generic_arg)]
+pub(crate) struct AttributeOnGenericArg {
+    #[primary_span]
+    #[label]
+    pub span: Span,
+    #[suggestion(code = "", applicability = "machine-applicable", style = "tool-only")]
+    pub fix_span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(parse_attribute_on_empty_type)]
+pub(crate) struct AttributeOnEmptyType {
+    #[primary_span]
+    #[label]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
 #[diag(parse_pattern_method_param_without_body, code = E0642)]
 pub(crate) struct PatternMethodParamWithoutBody {
     #[primary_span]
diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index 54d8a791025..35b987cf50f 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -263,10 +263,11 @@ impl<'a> Parser<'a> {
                 continue;
             }
 
+            let op_span = op.span;
             let op = op.node;
             // Special cases:
             if op == AssocOp::Cast {
-                lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?;
+                lhs = self.parse_assoc_op_cast(lhs, lhs_span, op_span, ExprKind::Cast)?;
                 continue;
             } else if let AssocOp::Range(limits) = op {
                 // If we didn't have to handle `x..`/`x..=`, it would be pretty easy to
@@ -284,7 +285,7 @@ impl<'a> Parser<'a> {
                 this.parse_expr_assoc_with(min_prec, attrs)
             })?;
 
-            let span = self.mk_expr_sp(&lhs, lhs_span, rhs.span);
+            let span = self.mk_expr_sp(&lhs, lhs_span, op_span, rhs.span);
             lhs = match op {
                 AssocOp::Binary(ast_op) => {
                     let binary = self.mk_binary(source_map::respan(cur_op_span, ast_op), lhs, rhs);
@@ -429,7 +430,7 @@ impl<'a> Parser<'a> {
             None
         };
         let rhs_span = rhs.as_ref().map_or(cur_op_span, |x| x.span);
-        let span = self.mk_expr_sp(&lhs, lhs.span, rhs_span);
+        let span = self.mk_expr_sp(&lhs, lhs.span, cur_op_span, rhs_span);
         let range = self.mk_range(Some(lhs), rhs, limits);
         Ok(self.mk_expr(span, range))
     }
@@ -654,10 +655,11 @@ impl<'a> Parser<'a> {
         &mut self,
         lhs: P<Expr>,
         lhs_span: Span,
+        op_span: Span,
         expr_kind: fn(P<Expr>, P<Ty>) -> ExprKind,
     ) -> PResult<'a, P<Expr>> {
         let mk_expr = |this: &mut Self, lhs: P<Expr>, rhs: P<Ty>| {
-            this.mk_expr(this.mk_expr_sp(&lhs, lhs_span, rhs.span), expr_kind(lhs, rhs))
+            this.mk_expr(this.mk_expr_sp(&lhs, lhs_span, op_span, rhs.span), expr_kind(lhs, rhs))
         };
 
         // Save the state of the parser before parsing type normally, in case there is a
@@ -4005,11 +4007,12 @@ impl<'a> Parser<'a> {
 
     /// Create expression span ensuring the span of the parent node
     /// is larger than the span of lhs and rhs, including the attributes.
-    fn mk_expr_sp(&self, lhs: &P<Expr>, lhs_span: Span, rhs_span: Span) -> Span {
+    fn mk_expr_sp(&self, lhs: &P<Expr>, lhs_span: Span, op_span: Span, rhs_span: Span) -> Span {
         lhs.attrs
             .iter()
             .find(|a| a.style == AttrStyle::Outer)
             .map_or(lhs_span, |a| a.span)
+            .to(op_span)
             .to(rhs_span)
     }
 
diff --git a/compiler/rustc_parse/src/parser/item.rs b/compiler/rustc_parse/src/parser/item.rs
index 65d84b3e3d9..cb7c5649433 100644
--- a/compiler/rustc_parse/src/parser/item.rs
+++ b/compiler/rustc_parse/src/parser/item.rs
@@ -885,6 +885,9 @@ impl<'a> Parser<'a> {
     /// Parses `unsafe? auto? trait Foo { ... }` or `trait Foo = Bar;`.
     fn parse_item_trait(&mut self, attrs: &mut AttrVec, lo: Span) -> PResult<'a, ItemKind> {
         let constness = self.parse_constness(Case::Sensitive);
+        if let Const::Yes(span) = constness {
+            self.psess.gated_spans.gate(sym::const_trait_impl, span);
+        }
         let safety = self.parse_safety(Case::Sensitive);
         // Parse optional `auto` prefix.
         let is_auto = if self.eat_keyword(exp!(Auto)) {
diff --git a/compiler/rustc_parse/src/parser/path.rs b/compiler/rustc_parse/src/parser/path.rs
index 1f4049f197f..8e65ab99c5e 100644
--- a/compiler/rustc_parse/src/parser/path.rs
+++ b/compiler/rustc_parse/src/parser/path.rs
@@ -17,11 +17,11 @@ use super::ty::{AllowPlus, RecoverQPath, RecoverReturnSign};
 use super::{Parser, Restrictions, TokenType};
 use crate::ast::{PatKind, TyKind};
 use crate::errors::{
-    self, FnPathFoundNamedParams, PathFoundAttributeInParams, PathFoundCVariadicParams,
-    PathSingleColon, PathTripleColon,
+    self, AttributeOnEmptyType, AttributeOnGenericArg, FnPathFoundNamedParams,
+    PathFoundAttributeInParams, PathFoundCVariadicParams, PathSingleColon, PathTripleColon,
 };
 use crate::exp;
-use crate::parser::{CommaRecoveryMode, RecoverColon, RecoverComma};
+use crate::parser::{CommaRecoveryMode, ExprKind, RecoverColon, RecoverComma};
 
 /// Specifies how to parse a path.
 #[derive(Copy, Clone, PartialEq)]
@@ -880,6 +880,12 @@ impl<'a> Parser<'a> {
         &mut self,
         ty_generics: Option<&Generics>,
     ) -> PResult<'a, Option<GenericArg>> {
+        let mut attr_span: Option<Span> = None;
+        if self.token == token::Pound && self.look_ahead(1, |t| *t == token::OpenBracket) {
+            let attrs_wrapper = self.parse_outer_attributes()?;
+            let raw_attrs = attrs_wrapper.take_for_recovery(self.psess);
+            attr_span = Some(raw_attrs[0].span.to(raw_attrs.last().unwrap().span));
+        }
         let start = self.token.span;
         let arg = if self.check_lifetime() && self.look_ahead(1, |t| !t.is_like_plus()) {
             // Parse lifetime argument.
@@ -934,6 +940,9 @@ impl<'a> Parser<'a> {
             }
         } else if self.token.is_keyword(kw::Const) {
             return self.recover_const_param_declaration(ty_generics);
+        } else if let Some(attr_span) = attr_span {
+            let diag = self.dcx().create_err(AttributeOnEmptyType { span: attr_span });
+            return Err(diag);
         } else {
             // Fall back by trying to parse a const-expr expression. If we successfully do so,
             // then we should report an error that it needs to be wrapped in braces.
@@ -953,6 +962,22 @@ impl<'a> Parser<'a> {
                 }
             }
         };
+
+        if let Some(attr_span) = attr_span {
+            let guar = self.dcx().emit_err(AttributeOnGenericArg {
+                span: attr_span,
+                fix_span: attr_span.until(arg.span()),
+            });
+            return Ok(Some(match arg {
+                GenericArg::Type(_) => GenericArg::Type(self.mk_ty(attr_span, TyKind::Err(guar))),
+                GenericArg::Const(_) => {
+                    let error_expr = self.mk_expr(attr_span, ExprKind::Err(guar));
+                    GenericArg::Const(AnonConst { id: ast::DUMMY_NODE_ID, value: error_expr })
+                }
+                GenericArg::Lifetime(lt) => GenericArg::Lifetime(lt),
+            }));
+        }
+
         Ok(Some(arg))
     }
 
diff --git a/compiler/rustc_parse/src/parser/ty.rs b/compiler/rustc_parse/src/parser/ty.rs
index 740dd10ea8b..59048e42e6f 100644
--- a/compiler/rustc_parse/src/parser/ty.rs
+++ b/compiler/rustc_parse/src/parser/ty.rs
@@ -14,10 +14,10 @@ use thin_vec::{ThinVec, thin_vec};
 
 use super::{Parser, PathStyle, SeqSep, TokenType, Trailing};
 use crate::errors::{
-    self, DynAfterMut, ExpectedFnPathFoundFnKeyword, ExpectedMutOrConstInRawPointerType,
-    FnPtrWithGenerics, FnPtrWithGenericsSugg, HelpUseLatestEdition, InvalidDynKeyword,
-    LifetimeAfterMut, NeedPlusAfterTraitObjectLifetime, NestedCVariadicType,
-    ReturnTypesUseThinArrow,
+    self, AttributeOnEmptyType, AttributeOnType, DynAfterMut, ExpectedFnPathFoundFnKeyword,
+    ExpectedMutOrConstInRawPointerType, FnPtrWithGenerics, FnPtrWithGenericsSugg,
+    HelpUseLatestEdition, InvalidDynKeyword, LifetimeAfterMut, NeedPlusAfterTraitObjectLifetime,
+    NestedCVariadicType, ReturnTypesUseThinArrow,
 };
 use crate::parser::item::FrontMatterParsingMode;
 use crate::{exp, maybe_recover_from_interpolated_ty_qpath};
@@ -253,7 +253,27 @@ impl<'a> Parser<'a> {
     ) -> PResult<'a, P<Ty>> {
         let allow_qpath_recovery = recover_qpath == RecoverQPath::Yes;
         maybe_recover_from_interpolated_ty_qpath!(self, allow_qpath_recovery);
+        if self.token == token::Pound && self.look_ahead(1, |t| *t == token::OpenBracket) {
+            let attrs_wrapper = self.parse_outer_attributes()?;
+            let raw_attrs = attrs_wrapper.take_for_recovery(self.psess);
+            let attr_span = raw_attrs[0].span.to(raw_attrs.last().unwrap().span);
+            let (full_span, guar) = match self.parse_ty() {
+                Ok(ty) => {
+                    let full_span = attr_span.until(ty.span);
+                    let guar = self
+                        .dcx()
+                        .emit_err(AttributeOnType { span: attr_span, fix_span: full_span });
+                    (attr_span, guar)
+                }
+                Err(err) => {
+                    err.cancel();
+                    let guar = self.dcx().emit_err(AttributeOnEmptyType { span: attr_span });
+                    (attr_span, guar)
+                }
+            };
 
+            return Ok(self.mk_ty(full_span, TyKind::Err(guar)));
+        }
         if let Some(ty) = self.eat_metavar_seq_with_matcher(
             |mv_kind| matches!(mv_kind, MetaVarKind::Ty { .. }),
             |this| this.parse_ty_no_question_mark_recover(),
diff --git a/compiler/rustc_parse/src/validate_attr.rs b/compiler/rustc_parse/src/validate_attr.rs
index bc4c605afad..a7f8d3b9139 100644
--- a/compiler/rustc_parse/src/validate_attr.rs
+++ b/compiler/rustc_parse/src/validate_attr.rs
@@ -106,7 +106,7 @@ pub fn parse_meta<'a>(psess: &'a ParseSess, attr: &Attribute) -> PResult<'a, Met
                     res
                 } else {
                     // Example cases:
-                    // - `#[foo = 1+1]`: results in `ast::ExprKind::BinOp`.
+                    // - `#[foo = 1+1]`: results in `ast::ExprKind::Binary`.
                     // - `#[foo = include_str!("nonexistent-file.rs")]`:
                     //   results in `ast::ExprKind::Err`. In that case we delay
                     //   the error because an earlier error will have already
diff --git a/compiler/rustc_passes/Cargo.toml b/compiler/rustc_passes/Cargo.toml
index 503fc98da76..ba81ef3103b 100644
--- a/compiler/rustc_passes/Cargo.toml
+++ b/compiler/rustc_passes/Cargo.toml
@@ -9,7 +9,6 @@ rustc_abi = { path = "../rustc_abi" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_ast_lowering = { path = "../rustc_ast_lowering" }
 rustc_ast_pretty = { path = "../rustc_ast_pretty" }
-rustc_attr_data_structures = { path = "../rustc_attr_data_structures" }
 rustc_attr_parsing = { path = "../rustc_attr_parsing" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs
index 0b329cc38b0..890028d977d 100644
--- a/compiler/rustc_passes/src/check_attr.rs
+++ b/compiler/rustc_passes/src/check_attr.rs
@@ -11,10 +11,6 @@ use std::slice;
 
 use rustc_abi::{Align, ExternAbi, Size};
 use rustc_ast::{AttrStyle, LitKind, MetaItemInner, MetaItemKind, ast, join_path_syms};
-use rustc_attr_data_structures::{
-    AttributeKind, InlineAttr, PartialConstStability, ReprAttr, Stability, StabilityLevel,
-    find_attr,
-};
 use rustc_attr_parsing::{AttributeParser, Late};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::{Applicability, DiagCtxtHandle, IntoDiagArg, MultiSpan, StashKey};
@@ -22,12 +18,14 @@ use rustc_feature::{
     ACCEPTED_LANG_FEATURES, AttributeDuplicates, AttributeType, BUILTIN_ATTRIBUTE_MAP,
     BuiltinAttribute,
 };
+use rustc_hir::attrs::{AttributeKind, InlineAttr, ReprAttr};
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::LocalModDefId;
 use rustc_hir::intravisit::{self, Visitor};
 use rustc_hir::{
-    self as hir, self, Attribute, CRATE_HIR_ID, CRATE_OWNER_ID, FnSig, ForeignItem, HirId, Item,
-    ItemKind, MethodKind, Safety, Target, TraitItem,
+    self as hir, Attribute, CRATE_HIR_ID, CRATE_OWNER_ID, FnSig, ForeignItem, HirId, Item,
+    ItemKind, MethodKind, PartialConstStability, Safety, Stability, StabilityLevel, Target,
+    TraitItem, find_attr,
 };
 use rustc_macros::LintDiagnostic;
 use rustc_middle::hir::nested_filter;
@@ -291,8 +289,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                     | AttributeKind::MacroTransparency(_)
                     | AttributeKind::Pointee(..)
                     | AttributeKind::Dummy
-                    | AttributeKind::RustcBuiltinMacro { .. }
-                    | AttributeKind::OmitGdbPrettyPrinterSection,
+                    | AttributeKind::RustcBuiltinMacro { .. },
                 ) => { /* do nothing  */ }
                 Attribute::Parsed(AttributeKind::AsPtr(attr_span)) => {
                     self.check_applied_to_fn_or_method(hir_id, *attr_span, span, target)
@@ -327,6 +324,9 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                 &Attribute::Parsed(AttributeKind::Coverage(attr_span, _)) => {
                     self.check_coverage(attr_span, span, target)
                 }
+                &Attribute::Parsed(AttributeKind::Coroutine(attr_span)) => {
+                    self.check_coroutine(attr_span, target)
+                }
                 Attribute::Unparsed(attr_item) => {
                     style = Some(attr_item.style);
                     match attr.path().as_slice() {
@@ -393,9 +393,6 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                         [sym::autodiff_forward, ..] | [sym::autodiff_reverse, ..] => {
                             self.check_autodiff(hir_id, attr, span, target)
                         }
-                        [sym::coroutine, ..] => {
-                            self.check_coroutine(attr, target);
-                        }
                         [sym::linkage, ..] => self.check_linkage(attr, span, target),
                         [
                             // ok
@@ -2654,11 +2651,11 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
         }
     }
 
-    fn check_coroutine(&self, attr: &Attribute, target: Target) {
+    fn check_coroutine(&self, attr_span: Span, target: Target) {
         match target {
             Target::Closure => return,
             _ => {
-                self.dcx().emit_err(errors::CoroutineOnNonClosure { span: attr.span() });
+                self.dcx().emit_err(errors::CoroutineOnNonClosure { span: attr_span });
             }
         }
     }
diff --git a/compiler/rustc_passes/src/check_export.rs b/compiler/rustc_passes/src/check_export.rs
index b1f4584c2a8..6eded3a9eb9 100644
--- a/compiler/rustc_passes/src/check_export.rs
+++ b/compiler/rustc_passes/src/check_export.rs
@@ -2,11 +2,12 @@ use std::iter;
 use std::ops::ControlFlow;
 
 use rustc_abi::ExternAbi;
-use rustc_attr_data_structures::{AttributeKind, find_attr};
 use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_hir as hir;
+use rustc_hir::attrs::AttributeKind;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{DefId, LocalDefId};
+use rustc_hir::find_attr;
 use rustc_hir::intravisit::{self, Visitor};
 use rustc_middle::hir::nested_filter;
 use rustc_middle::middle::privacy::{EffectiveVisibility, Level};
diff --git a/compiler/rustc_passes/src/dead.rs b/compiler/rustc_passes/src/dead.rs
index a90d1af87ca..fa9d0c7b1b7 100644
--- a/compiler/rustc_passes/src/dead.rs
+++ b/compiler/rustc_passes/src/dead.rs
@@ -5,7 +5,6 @@
 
 use std::mem;
 
-use hir::ItemKind;
 use hir::def_id::{LocalDefIdMap, LocalDefIdSet};
 use rustc_abi::FieldIdx;
 use rustc_data_structures::fx::FxIndexSet;
@@ -14,7 +13,7 @@ use rustc_errors::MultiSpan;
 use rustc_hir::def::{CtorOf, DefKind, Res};
 use rustc_hir::def_id::{DefId, LocalDefId, LocalModDefId};
 use rustc_hir::intravisit::{self, Visitor};
-use rustc_hir::{self as hir, ImplItem, ImplItemKind, Node, PatKind, QPath, TyKind};
+use rustc_hir::{self as hir, Node, PatKind, QPath};
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use rustc_middle::middle::privacy::Level;
 use rustc_middle::query::Providers;
@@ -28,37 +27,43 @@ use crate::errors::{
     ChangeFields, IgnoredDerivedImpls, MultipleDeadCodes, ParentInfo, UselessAssignment,
 };
 
-// Any local node that may call something in its body block should be
-// explored. For example, if it's a live Node::Item that is a
-// function, then we should explore its block to check for codes that
-// may need to be marked as live.
+/// Any local definition that may call something in its body block should be explored. For example,
+/// if it's a live function, then we should explore its block to check for codes that may need to
+/// be marked as live.
 fn should_explore(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {
-    matches!(
-        tcx.hir_node_by_def_id(def_id),
-        Node::Item(..)
-            | Node::ImplItem(..)
-            | Node::ForeignItem(..)
-            | Node::TraitItem(..)
-            | Node::Variant(..)
-            | Node::AnonConst(..)
-            | Node::OpaqueTy(..)
-    )
-}
-
-/// Returns the local def id of the ADT if the given ty refers to a local one.
-fn local_adt_def_of_ty<'tcx>(ty: &hir::Ty<'tcx>) -> Option<LocalDefId> {
-    match ty.kind {
-        TyKind::Path(QPath::Resolved(_, path)) => {
-            if let Res::Def(def_kind, def_id) = path.res
-                && let Some(local_def_id) = def_id.as_local()
-                && matches!(def_kind, DefKind::Struct | DefKind::Enum | DefKind::Union)
-            {
-                Some(local_def_id)
-            } else {
-                None
-            }
-        }
-        _ => None,
+    match tcx.def_kind(def_id) {
+        DefKind::Mod
+        | DefKind::Struct
+        | DefKind::Union
+        | DefKind::Enum
+        | DefKind::Variant
+        | DefKind::Trait
+        | DefKind::TyAlias
+        | DefKind::ForeignTy
+        | DefKind::TraitAlias
+        | DefKind::AssocTy
+        | DefKind::Fn
+        | DefKind::Const
+        | DefKind::Static { .. }
+        | DefKind::AssocFn
+        | DefKind::AssocConst
+        | DefKind::Macro(_)
+        | DefKind::GlobalAsm
+        | DefKind::Impl { .. }
+        | DefKind::OpaqueTy
+        | DefKind::AnonConst
+        | DefKind::InlineConst
+        | DefKind::ExternCrate
+        | DefKind::Use
+        | DefKind::Ctor(..)
+        | DefKind::ForeignMod => true,
+
+        DefKind::TyParam
+        | DefKind::ConstParam
+        | DefKind::Field
+        | DefKind::LifetimeParam
+        | DefKind::Closure
+        | DefKind::SyntheticCoroutineBody => false,
     }
 }
 
@@ -74,17 +79,16 @@ struct MarkSymbolVisitor<'tcx> {
     worklist: Vec<(LocalDefId, ComesFromAllowExpect)>,
     tcx: TyCtxt<'tcx>,
     maybe_typeck_results: Option<&'tcx ty::TypeckResults<'tcx>>,
+    scanned: UnordSet<(LocalDefId, ComesFromAllowExpect)>,
     live_symbols: LocalDefIdSet,
     repr_unconditionally_treats_fields_as_live: bool,
     repr_has_repr_simd: bool,
     in_pat: bool,
     ignore_variant_stack: Vec<DefId>,
-    // maps from tuple struct constructors to tuple struct items
-    struct_constructors: LocalDefIdMap<LocalDefId>,
     // maps from ADTs to ignored derived traits (e.g. Debug and Clone)
     // and the span of their respective impl (i.e., part of the derive
     // macro)
-    ignored_derived_traits: LocalDefIdMap<FxIndexSet<(DefId, DefId)>>,
+    ignored_derived_traits: LocalDefIdMap<FxIndexSet<DefId>>,
 }
 
 impl<'tcx> MarkSymbolVisitor<'tcx> {
@@ -99,7 +103,7 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {
 
     fn check_def_id(&mut self, def_id: DefId) {
         if let Some(def_id) = def_id.as_local() {
-            if should_explore(self.tcx, def_id) || self.struct_constructors.contains_key(&def_id) {
+            if should_explore(self.tcx, def_id) {
                 self.worklist.push((def_id, ComesFromAllowExpect::No));
             }
             self.live_symbols.insert(def_id);
@@ -318,13 +322,12 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {
     }
 
     fn mark_live_symbols(&mut self) {
-        let mut scanned = UnordSet::default();
         while let Some(work) = self.worklist.pop() {
-            if !scanned.insert(work) {
+            if !self.scanned.insert(work) {
                 continue;
             }
 
-            let (id, comes_from_allow_expect) = work;
+            let (mut id, comes_from_allow_expect) = work;
 
             // Avoid accessing the HIR for the synthesized associated type generated for RPITITs.
             if self.tcx.is_impl_trait_in_trait(id.to_def_id()) {
@@ -332,9 +335,11 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {
                 continue;
             }
 
-            // in the case of tuple struct constructors we want to check the item, not the generated
-            // tuple struct constructor function
-            let id = self.struct_constructors.get(&id).copied().unwrap_or(id);
+            // in the case of tuple struct constructors we want to check the item,
+            // not the generated tuple struct constructor function
+            if let DefKind::Ctor(..) = self.tcx.def_kind(id) {
+                id = self.tcx.local_parent(id);
+            }
 
             // When using `#[allow]` or `#[expect]` of `dead_code`, we do a QOL improvement
             // by declaring fn calls, statics, ... within said items as live, as well as
@@ -380,10 +385,7 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {
                 if let ty::Adt(adt_def, _) = trait_ref.self_ty().kind()
                     && let Some(adt_def_id) = adt_def.did().as_local()
                 {
-                    self.ignored_derived_traits
-                        .entry(adt_def_id)
-                        .or_default()
-                        .insert((trait_of, impl_of));
+                    self.ignored_derived_traits.entry(adt_def_id).or_default().insert(trait_of);
                 }
                 return true;
             }
@@ -478,24 +480,24 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {
     /// `local_def_id` points to an impl or an impl item,
     /// both impl and impl item that may be passed to this function are of a trait,
     /// and added into the unsolved_items during `create_and_seed_worklist`
-    fn check_impl_or_impl_item_live(
-        &mut self,
-        impl_id: hir::ItemId,
-        local_def_id: LocalDefId,
-    ) -> bool {
-        let trait_def_id = match self.tcx.def_kind(local_def_id) {
+    fn check_impl_or_impl_item_live(&mut self, local_def_id: LocalDefId) -> bool {
+        let (impl_block_id, trait_def_id) = match self.tcx.def_kind(local_def_id) {
             // assoc impl items of traits are live if the corresponding trait items are live
-            DefKind::AssocConst | DefKind::AssocTy | DefKind::AssocFn => self
-                .tcx
-                .associated_item(local_def_id)
-                .trait_item_def_id
-                .and_then(|def_id| def_id.as_local()),
+            DefKind::AssocConst | DefKind::AssocTy | DefKind::AssocFn => (
+                self.tcx.local_parent(local_def_id),
+                self.tcx
+                    .associated_item(local_def_id)
+                    .trait_item_def_id
+                    .and_then(|def_id| def_id.as_local()),
+            ),
             // impl items are live if the corresponding traits are live
-            DefKind::Impl { of_trait: true } => self
-                .tcx
-                .impl_trait_ref(impl_id.owner_id.def_id)
-                .and_then(|trait_ref| trait_ref.skip_binder().def_id.as_local()),
-            _ => None,
+            DefKind::Impl { of_trait: true } => (
+                local_def_id,
+                self.tcx
+                    .impl_trait_ref(local_def_id)
+                    .and_then(|trait_ref| trait_ref.skip_binder().def_id.as_local()),
+            ),
+            _ => bug!(),
         };
 
         if let Some(trait_def_id) = trait_def_id
@@ -505,9 +507,9 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {
         }
 
         // The impl or impl item is used if the corresponding trait or trait item is used and the ty is used.
-        if let Some(local_def_id) =
-            local_adt_def_of_ty(self.tcx.hir_item(impl_id).expect_impl().self_ty)
-            && !self.live_symbols.contains(&local_def_id)
+        if let ty::Adt(adt, _) = self.tcx.type_of(impl_block_id).instantiate_identity().kind()
+            && let Some(adt_def_id) = adt.did().as_local()
+            && !self.live_symbols.contains(&adt_def_id)
         {
             return false;
         }
@@ -714,139 +716,86 @@ fn has_allow_dead_code_or_lang_attr(
     }
 }
 
-// These check_* functions seeds items that
-//   1) We want to explicitly consider as live:
-//     * Item annotated with #[allow(dead_code)]
-//         - This is done so that if we want to suppress warnings for a
-//           group of dead functions, we only have to annotate the "root".
-//           For example, if both `f` and `g` are dead and `f` calls `g`,
-//           then annotating `f` with `#[allow(dead_code)]` will suppress
-//           warning for both `f` and `g`.
-//     * Item annotated with #[lang=".."]
-//         - This is because lang items are always callable from elsewhere.
-//   or
-//   2) We are not sure to be live or not
-//     * Implementations of traits and trait methods
-fn check_item<'tcx>(
+/// Examine the given definition and record it in the worklist if it should be considered live.
+///
+/// We want to explicitly consider as live:
+/// * Item annotated with #[allow(dead_code)]
+///       This is done so that if we want to suppress warnings for a
+///       group of dead functions, we only have to annotate the "root".
+///       For example, if both `f` and `g` are dead and `f` calls `g`,
+///       then annotating `f` with `#[allow(dead_code)]` will suppress
+///       warning for both `f` and `g`.
+///
+/// * Item annotated with #[lang=".."]
+///       Lang items are always callable from elsewhere.
+///
+/// For trait methods and implementations of traits, we are not certain that the definitions are
+/// live at this stage. We record them in `unsolved_items` for later examination.
+fn maybe_record_as_seed<'tcx>(
     tcx: TyCtxt<'tcx>,
+    owner_id: hir::OwnerId,
     worklist: &mut Vec<(LocalDefId, ComesFromAllowExpect)>,
-    struct_constructors: &mut LocalDefIdMap<LocalDefId>,
-    unsolved_items: &mut Vec<(hir::ItemId, LocalDefId)>,
-    id: hir::ItemId,
+    unsolved_items: &mut Vec<LocalDefId>,
 ) {
-    let allow_dead_code = has_allow_dead_code_or_lang_attr(tcx, id.owner_id.def_id);
+    let allow_dead_code = has_allow_dead_code_or_lang_attr(tcx, owner_id.def_id);
     if let Some(comes_from_allow) = allow_dead_code {
-        worklist.push((id.owner_id.def_id, comes_from_allow));
+        worklist.push((owner_id.def_id, comes_from_allow));
     }
 
-    match tcx.def_kind(id.owner_id) {
+    match tcx.def_kind(owner_id) {
         DefKind::Enum => {
-            let item = tcx.hir_item(id);
-            if let hir::ItemKind::Enum(_, _, ref enum_def) = item.kind {
-                if let Some(comes_from_allow) = allow_dead_code {
-                    worklist.extend(
-                        enum_def.variants.iter().map(|variant| (variant.def_id, comes_from_allow)),
-                    );
-                }
-
-                for variant in enum_def.variants {
-                    if let Some(ctor_def_id) = variant.data.ctor_def_id() {
-                        struct_constructors.insert(ctor_def_id, variant.def_id);
-                    }
-                }
+            if let Some(comes_from_allow) = allow_dead_code {
+                let adt = tcx.adt_def(owner_id);
+                worklist.extend(
+                    adt.variants()
+                        .iter()
+                        .map(|variant| (variant.def_id.expect_local(), comes_from_allow)),
+                );
             }
         }
-        DefKind::Impl { of_trait } => {
-            if let Some(comes_from_allow) =
-                has_allow_dead_code_or_lang_attr(tcx, id.owner_id.def_id)
-            {
-                worklist.push((id.owner_id.def_id, comes_from_allow));
-            } else if of_trait {
-                unsolved_items.push((id, id.owner_id.def_id));
-            }
-
-            for def_id in tcx.associated_item_def_ids(id.owner_id) {
-                let local_def_id = def_id.expect_local();
-
-                if let Some(comes_from_allow) = has_allow_dead_code_or_lang_attr(tcx, local_def_id)
-                {
-                    worklist.push((local_def_id, comes_from_allow));
-                } else if of_trait {
-                    // We only care about associated items of traits,
-                    // because they cannot be visited directly,
-                    // so we later mark them as live if their corresponding traits
-                    // or trait items and self types are both live,
-                    // but inherent associated items can be visited and marked directly.
-                    unsolved_items.push((id, local_def_id));
+        DefKind::AssocFn | DefKind::AssocConst | DefKind::AssocTy => {
+            if allow_dead_code.is_none() {
+                let parent = tcx.local_parent(owner_id.def_id);
+                match tcx.def_kind(parent) {
+                    DefKind::Impl { of_trait: false } | DefKind::Trait => {}
+                    DefKind::Impl { of_trait: true } => {
+                        // We only care about associated items of traits,
+                        // because they cannot be visited directly,
+                        // so we later mark them as live if their corresponding traits
+                        // or trait items and self types are both live,
+                        // but inherent associated items can be visited and marked directly.
+                        unsolved_items.push(owner_id.def_id);
+                    }
+                    _ => bug!(),
                 }
             }
         }
-        DefKind::Struct => {
-            let item = tcx.hir_item(id);
-            if let hir::ItemKind::Struct(_, _, ref variant_data) = item.kind
-                && let Some(ctor_def_id) = variant_data.ctor_def_id()
-            {
-                struct_constructors.insert(ctor_def_id, item.owner_id.def_id);
+        DefKind::Impl { of_trait: true } => {
+            if allow_dead_code.is_none() {
+                unsolved_items.push(owner_id.def_id);
             }
         }
         DefKind::GlobalAsm => {
             // global_asm! is always live.
-            worklist.push((id.owner_id.def_id, ComesFromAllowExpect::No));
+            worklist.push((owner_id.def_id, ComesFromAllowExpect::No));
         }
         DefKind::Const => {
-            let item = tcx.hir_item(id);
-            if let hir::ItemKind::Const(ident, ..) = item.kind
-                && ident.name == kw::Underscore
-            {
+            if tcx.item_name(owner_id.def_id) == kw::Underscore {
                 // `const _` is always live, as that syntax only exists for the side effects
                 // of type checking and evaluating the constant expression, and marking them
                 // as dead code would defeat that purpose.
-                worklist.push((id.owner_id.def_id, ComesFromAllowExpect::No));
+                worklist.push((owner_id.def_id, ComesFromAllowExpect::No));
             }
         }
         _ => {}
     }
 }
 
-fn check_trait_item(
-    tcx: TyCtxt<'_>,
-    worklist: &mut Vec<(LocalDefId, ComesFromAllowExpect)>,
-    id: hir::TraitItemId,
-) {
-    use hir::TraitItemKind::{Const, Fn, Type};
-
-    let trait_item = tcx.hir_trait_item(id);
-    if matches!(trait_item.kind, Const(_, Some(_)) | Type(_, Some(_)) | Fn(..))
-        && let Some(comes_from_allow) =
-            has_allow_dead_code_or_lang_attr(tcx, trait_item.owner_id.def_id)
-    {
-        worklist.push((trait_item.owner_id.def_id, comes_from_allow));
-    }
-}
-
-fn check_foreign_item(
-    tcx: TyCtxt<'_>,
-    worklist: &mut Vec<(LocalDefId, ComesFromAllowExpect)>,
-    id: hir::ForeignItemId,
-) {
-    if matches!(tcx.def_kind(id.owner_id), DefKind::Static { .. } | DefKind::Fn)
-        && let Some(comes_from_allow) = has_allow_dead_code_or_lang_attr(tcx, id.owner_id.def_id)
-    {
-        worklist.push((id.owner_id.def_id, comes_from_allow));
-    }
-}
-
 fn create_and_seed_worklist(
     tcx: TyCtxt<'_>,
-) -> (
-    Vec<(LocalDefId, ComesFromAllowExpect)>,
-    LocalDefIdMap<LocalDefId>,
-    Vec<(hir::ItemId, LocalDefId)>,
-) {
+) -> (Vec<(LocalDefId, ComesFromAllowExpect)>, Vec<LocalDefId>) {
     let effective_visibilities = &tcx.effective_visibilities(());
-    // see `MarkSymbolVisitor::struct_constructors`
     let mut unsolved_impl_item = Vec::new();
-    let mut struct_constructors = Default::default();
     let mut worklist = effective_visibilities
         .iter()
         .filter_map(|(&id, effective_vis)| {
@@ -863,54 +812,49 @@ fn create_and_seed_worklist(
         .collect::<Vec<_>>();
 
     let crate_items = tcx.hir_crate_items(());
-    for id in crate_items.free_items() {
-        check_item(tcx, &mut worklist, &mut struct_constructors, &mut unsolved_impl_item, id);
-    }
-
-    for id in crate_items.trait_items() {
-        check_trait_item(tcx, &mut worklist, id);
-    }
-
-    for id in crate_items.foreign_items() {
-        check_foreign_item(tcx, &mut worklist, id);
+    for id in crate_items.owners() {
+        maybe_record_as_seed(tcx, id, &mut worklist, &mut unsolved_impl_item);
     }
 
-    (worklist, struct_constructors, unsolved_impl_item)
+    (worklist, unsolved_impl_item)
 }
 
 fn live_symbols_and_ignored_derived_traits(
     tcx: TyCtxt<'_>,
     (): (),
-) -> (LocalDefIdSet, LocalDefIdMap<FxIndexSet<(DefId, DefId)>>) {
-    let (worklist, struct_constructors, mut unsolved_items) = create_and_seed_worklist(tcx);
+) -> (LocalDefIdSet, LocalDefIdMap<FxIndexSet<DefId>>) {
+    let (worklist, mut unsolved_items) = create_and_seed_worklist(tcx);
     let mut symbol_visitor = MarkSymbolVisitor {
         worklist,
         tcx,
         maybe_typeck_results: None,
+        scanned: Default::default(),
         live_symbols: Default::default(),
         repr_unconditionally_treats_fields_as_live: false,
         repr_has_repr_simd: false,
         in_pat: false,
         ignore_variant_stack: vec![],
-        struct_constructors,
         ignored_derived_traits: Default::default(),
     };
     symbol_visitor.mark_live_symbols();
-    let mut items_to_check;
-    (items_to_check, unsolved_items) =
-        unsolved_items.into_iter().partition(|&(impl_id, local_def_id)| {
-            symbol_visitor.check_impl_or_impl_item_live(impl_id, local_def_id)
-        });
+
+    // We have marked the primary seeds as live. We now need to process unsolved items from traits
+    // and trait impls: add them to the work list if the trait or the implemented type is live.
+    let mut items_to_check: Vec<_> = unsolved_items
+        .extract_if(.., |&mut local_def_id| {
+            symbol_visitor.check_impl_or_impl_item_live(local_def_id)
+        })
+        .collect();
 
     while !items_to_check.is_empty() {
-        symbol_visitor.worklist =
-            items_to_check.into_iter().map(|(_, id)| (id, ComesFromAllowExpect::No)).collect();
+        symbol_visitor
+            .worklist
+            .extend(items_to_check.drain(..).map(|id| (id, ComesFromAllowExpect::No)));
         symbol_visitor.mark_live_symbols();
 
-        (items_to_check, unsolved_items) =
-            unsolved_items.into_iter().partition(|&(impl_id, local_def_id)| {
-                symbol_visitor.check_impl_or_impl_item_live(impl_id, local_def_id)
-            });
+        items_to_check.extend(unsolved_items.extract_if(.., |&mut local_def_id| {
+            symbol_visitor.check_impl_or_impl_item_live(local_def_id)
+        }));
     }
 
     (symbol_visitor.live_symbols, symbol_visitor.ignored_derived_traits)
@@ -925,7 +869,7 @@ struct DeadItem {
 struct DeadVisitor<'tcx> {
     tcx: TyCtxt<'tcx>,
     live_symbols: &'tcx LocalDefIdSet,
-    ignored_derived_traits: &'tcx LocalDefIdMap<FxIndexSet<(DefId, DefId)>>,
+    ignored_derived_traits: &'tcx LocalDefIdMap<FxIndexSet<DefId>>,
 }
 
 enum ShouldWarnAboutField {
@@ -984,25 +928,7 @@ impl<'tcx> DeadVisitor<'tcx> {
         parent_item: Option<LocalDefId>,
         report_on: ReportOn,
     ) {
-        fn get_parent_if_enum_variant<'tcx>(
-            tcx: TyCtxt<'tcx>,
-            may_variant: LocalDefId,
-        ) -> LocalDefId {
-            if let Node::Variant(_) = tcx.hir_node_by_def_id(may_variant)
-                && let Some(enum_did) = tcx.opt_parent(may_variant.to_def_id())
-                && let Some(enum_local_id) = enum_did.as_local()
-                && let Node::Item(item) = tcx.hir_node_by_def_id(enum_local_id)
-                && let ItemKind::Enum(..) = item.kind
-            {
-                enum_local_id
-            } else {
-                may_variant
-            }
-        }
-
-        let Some(&first_item) = dead_codes.first() else {
-            return;
-        };
+        let Some(&first_item) = dead_codes.first() else { return };
         let tcx = self.tcx;
 
         let first_lint_level = first_item.level;
@@ -1011,81 +937,54 @@ impl<'tcx> DeadVisitor<'tcx> {
         let names: Vec<_> = dead_codes.iter().map(|item| item.name).collect();
         let spans: Vec<_> = dead_codes
             .iter()
-            .map(|item| match tcx.def_ident_span(item.def_id) {
-                Some(s) => s.with_ctxt(tcx.def_span(item.def_id).ctxt()),
-                None => tcx.def_span(item.def_id),
+            .map(|item| {
+                let span = tcx.def_span(item.def_id);
+                let ident_span = tcx.def_ident_span(item.def_id);
+                // FIXME(cjgillot) this SyntaxContext manipulation does not make any sense.
+                ident_span.map(|s| s.with_ctxt(span.ctxt())).unwrap_or(span)
             })
             .collect();
 
-        let descr = tcx.def_descr(first_item.def_id.to_def_id());
+        let mut descr = tcx.def_descr(first_item.def_id.to_def_id());
         // `impl` blocks are "batched" and (unlike other batching) might
         // contain different kinds of associated items.
-        let descr = if dead_codes.iter().any(|item| tcx.def_descr(item.def_id.to_def_id()) != descr)
-        {
-            "associated item"
-        } else {
-            descr
-        };
+        if dead_codes.iter().any(|item| tcx.def_descr(item.def_id.to_def_id()) != descr) {
+            descr = "associated item"
+        }
+
         let num = dead_codes.len();
         let multiple = num > 6;
         let name_list = names.into();
 
-        let parent_info = if let Some(parent_item) = parent_item {
+        let parent_info = parent_item.map(|parent_item| {
             let parent_descr = tcx.def_descr(parent_item.to_def_id());
             let span = if let DefKind::Impl { .. } = tcx.def_kind(parent_item) {
                 tcx.def_span(parent_item)
             } else {
                 tcx.def_ident_span(parent_item).unwrap()
             };
-            Some(ParentInfo { num, descr, parent_descr, span })
-        } else {
-            None
-        };
+            ParentInfo { num, descr, parent_descr, span }
+        });
 
-        let encl_def_id = parent_item.unwrap_or(first_item.def_id);
-        // If parent of encl_def_id is an enum, use the parent ID instead.
-        let encl_def_id = get_parent_if_enum_variant(tcx, encl_def_id);
+        let mut encl_def_id = parent_item.unwrap_or(first_item.def_id);
+        // `ignored_derived_traits` is computed for the enum, not for the variants.
+        if let DefKind::Variant = tcx.def_kind(encl_def_id) {
+            encl_def_id = tcx.local_parent(encl_def_id);
+        }
 
         let ignored_derived_impls =
-            if let Some(ign_traits) = self.ignored_derived_traits.get(&encl_def_id) {
+            self.ignored_derived_traits.get(&encl_def_id).map(|ign_traits| {
                 let trait_list = ign_traits
                     .iter()
-                    .map(|(trait_id, _)| self.tcx.item_name(*trait_id))
+                    .map(|trait_id| self.tcx.item_name(*trait_id))
                     .collect::<Vec<_>>();
                 let trait_list_len = trait_list.len();
-                Some(IgnoredDerivedImpls {
+                IgnoredDerivedImpls {
                     name: self.tcx.item_name(encl_def_id.to_def_id()),
                     trait_list: trait_list.into(),
                     trait_list_len,
-                })
-            } else {
-                None
-            };
-
-        let enum_variants_with_same_name = dead_codes
-            .iter()
-            .filter_map(|dead_item| {
-                if let Node::ImplItem(ImplItem {
-                    kind: ImplItemKind::Fn(..) | ImplItemKind::Const(..),
-                    ..
-                }) = tcx.hir_node_by_def_id(dead_item.def_id)
-                    && let Some(impl_did) = tcx.opt_parent(dead_item.def_id.to_def_id())
-                    && let DefKind::Impl { of_trait: false } = tcx.def_kind(impl_did)
-                    && let ty::Adt(maybe_enum, _) = tcx.type_of(impl_did).skip_binder().kind()
-                    && maybe_enum.is_enum()
-                    && let Some(variant) =
-                        maybe_enum.variants().iter().find(|i| i.name == dead_item.name)
-                {
-                    Some(crate::errors::EnumVariantSameName {
-                        dead_descr: tcx.def_descr(dead_item.def_id.to_def_id()),
-                        dead_name: dead_item.name,
-                        variant_span: tcx.def_span(variant.def_id),
-                    })
-                } else {
-                    None
                 }
-            })
-            .collect();
+            });
 
         let diag = match report_on {
             ReportOn::TupleField => {
@@ -1132,16 +1031,42 @@ impl<'tcx> DeadVisitor<'tcx> {
                     ignored_derived_impls,
                 }
             }
-            ReportOn::NamedField => MultipleDeadCodes::DeadCodes {
-                multiple,
-                num,
-                descr,
-                participle,
-                name_list,
-                parent_info,
-                ignored_derived_impls,
-                enum_variants_with_same_name,
-            },
+            ReportOn::NamedField => {
+                let enum_variants_with_same_name = dead_codes
+                    .iter()
+                    .filter_map(|dead_item| {
+                        if let DefKind::AssocFn | DefKind::AssocConst =
+                            tcx.def_kind(dead_item.def_id)
+                            && let impl_did = tcx.local_parent(dead_item.def_id)
+                            && let DefKind::Impl { of_trait: false } = tcx.def_kind(impl_did)
+                            && let ty::Adt(maybe_enum, _) =
+                                tcx.type_of(impl_did).instantiate_identity().kind()
+                            && maybe_enum.is_enum()
+                            && let Some(variant) =
+                                maybe_enum.variants().iter().find(|i| i.name == dead_item.name)
+                        {
+                            Some(crate::errors::EnumVariantSameName {
+                                dead_descr: tcx.def_descr(dead_item.def_id.to_def_id()),
+                                dead_name: dead_item.name,
+                                variant_span: tcx.def_span(variant.def_id),
+                            })
+                        } else {
+                            None
+                        }
+                    })
+                    .collect();
+
+                MultipleDeadCodes::DeadCodes {
+                    multiple,
+                    num,
+                    descr,
+                    participle,
+                    name_list,
+                    parent_info,
+                    ignored_derived_impls,
+                    enum_variants_with_same_name,
+                }
+            }
         };
 
         let hir_id = tcx.local_def_id_to_hir_id(first_item.def_id);
diff --git a/compiler/rustc_passes/src/lib.rs b/compiler/rustc_passes/src/lib.rs
index af7ecf0830c..2ad0b5ff60e 100644
--- a/compiler/rustc_passes/src/lib.rs
+++ b/compiler/rustc_passes/src/lib.rs
@@ -8,6 +8,7 @@
 #![allow(internal_features)]
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
 #![doc(rust_logo)]
+#![feature(if_let_guard)]
 #![feature(map_try_insert)]
 #![feature(rustdoc_internals)]
 // tidy-alphabetical-end
diff --git a/compiler/rustc_passes/src/lib_features.rs b/compiler/rustc_passes/src/lib_features.rs
index 35d2a655991..8d0ef88610a 100644
--- a/compiler/rustc_passes/src/lib_features.rs
+++ b/compiler/rustc_passes/src/lib_features.rs
@@ -4,9 +4,9 @@
 //! but are not declared in one single location (unlike lang features), which means we need to
 //! collect them instead.
 
-use rustc_attr_data_structures::{AttributeKind, StabilityLevel, StableSince};
-use rustc_hir::Attribute;
+use rustc_hir::attrs::AttributeKind;
 use rustc_hir::intravisit::Visitor;
+use rustc_hir::{Attribute, StabilityLevel, StableSince};
 use rustc_middle::hir::nested_filter;
 use rustc_middle::middle::lib_features::{FeatureStability, LibFeatures};
 use rustc_middle::query::{LocalCrate, Providers};
diff --git a/compiler/rustc_passes/src/liveness.rs b/compiler/rustc_passes/src/liveness.rs
index 7350c6a5a82..801a533c943 100644
--- a/compiler/rustc_passes/src/liveness.rs
+++ b/compiler/rustc_passes/src/liveness.rs
@@ -85,13 +85,13 @@ use std::io;
 use std::io::prelude::*;
 use std::rc::Rc;
 
-use rustc_attr_data_structures::{AttributeKind, find_attr};
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_hir as hir;
+use rustc_hir::attrs::AttributeKind;
 use rustc_hir::def::*;
 use rustc_hir::def_id::LocalDefId;
 use rustc_hir::intravisit::{self, Visitor};
-use rustc_hir::{Expr, HirId, HirIdMap, HirIdSet};
+use rustc_hir::{Expr, HirId, HirIdMap, HirIdSet, find_attr};
 use rustc_index::IndexVec;
 use rustc_middle::query::Providers;
 use rustc_middle::span_bug;
diff --git a/compiler/rustc_passes/src/stability.rs b/compiler/rustc_passes/src/stability.rs
index 9ed7293873f..c5056b9df76 100644
--- a/compiler/rustc_passes/src/stability.rs
+++ b/compiler/rustc_passes/src/stability.rs
@@ -4,17 +4,18 @@
 use std::num::NonZero;
 
 use rustc_ast_lowering::stability::extern_abi_stability;
-use rustc_attr_data_structures::{
-    self as attrs, AttributeKind, ConstStability, DefaultBodyStability, DeprecatedSince, Stability,
-    StabilityLevel, StableSince, UnstableReason, VERSION_PLACEHOLDER, find_attr,
-};
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_data_structures::unord::{ExtendUnord, UnordMap, UnordSet};
 use rustc_feature::{EnabledLangFeature, EnabledLibFeature};
+use rustc_hir::attrs::{AttributeKind, DeprecatedSince};
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::{CRATE_DEF_ID, LOCAL_CRATE, LocalDefId, LocalModDefId};
 use rustc_hir::intravisit::{self, Visitor, VisitorExt};
-use rustc_hir::{self as hir, AmbigArg, FieldDef, Item, ItemKind, TraitRef, Ty, TyKind, Variant};
+use rustc_hir::{
+    self as hir, AmbigArg, ConstStability, DefaultBodyStability, FieldDef, Item, ItemKind,
+    Stability, StabilityLevel, StableSince, TraitRef, Ty, TyKind, UnstableReason,
+    VERSION_PLACEHOLDER, Variant, find_attr,
+};
 use rustc_middle::hir::nested_filter;
 use rustc_middle::middle::lib_features::{FeatureStability, LibFeatures};
 use rustc_middle::middle::privacy::EffectiveVisibilities;
@@ -96,7 +97,7 @@ fn annotation_kind(tcx: TyCtxt<'_>, def_id: LocalDefId) -> AnnotationKind {
 
 fn lookup_deprecation_entry(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Option<DeprecationEntry> {
     let attrs = tcx.hir_attrs(tcx.local_def_id_to_hir_id(def_id));
-    let depr = attrs::find_attr!(attrs,
+    let depr = find_attr!(attrs,
         AttributeKind::Deprecation { deprecation, span: _ } => *deprecation
     );
 
@@ -128,7 +129,7 @@ fn inherit_stability(def_kind: DefKind) -> bool {
 /// while maintaining the invariant that all sysroot crates are unstable
 /// by default and are unable to be used.
 const FORCE_UNSTABLE: Stability = Stability {
-    level: attrs::StabilityLevel::Unstable {
+    level: StabilityLevel::Unstable {
         reason: UnstableReason::Default,
         issue: NonZero::new(27812),
         is_soft: false,
@@ -161,8 +162,7 @@ fn lookup_stability(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Option<Stability> {
 
     // # Regular stability
     let attrs = tcx.hir_attrs(tcx.local_def_id_to_hir_id(def_id));
-    let stab =
-        attrs::find_attr!(attrs, AttributeKind::Stability { stability, span: _ } => *stability);
+    let stab = find_attr!(attrs, AttributeKind::Stability { stability, span: _ } => *stability);
 
     if let Some(stab) = stab {
         return Some(stab);
@@ -197,7 +197,7 @@ fn lookup_default_body_stability(
 
     let attrs = tcx.hir_attrs(tcx.local_def_id_to_hir_id(def_id));
     // FIXME: check that this item can have body stability
-    attrs::find_attr!(attrs, AttributeKind::BodyStability { stability, .. } => *stability)
+    find_attr!(attrs, AttributeKind::BodyStability { stability, .. } => *stability)
 }
 
 #[instrument(level = "debug", skip(tcx))]
@@ -224,7 +224,8 @@ fn lookup_const_stability(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Option<ConstSt
 
     let attrs = tcx.hir_attrs(tcx.local_def_id_to_hir_id(def_id));
     let const_stability_indirect = find_attr!(attrs, AttributeKind::ConstStabilityIndirect);
-    let const_stab = attrs::find_attr!(attrs, AttributeKind::ConstStability { stability, span: _ } => *stability);
+    let const_stab =
+        find_attr!(attrs, AttributeKind::ConstStability { stability, span: _ } => *stability);
 
     // After checking the immediate attributes, get rid of the span and compute implied
     // const stability: inherit feature gate from regular stability.
@@ -376,7 +377,7 @@ impl<'tcx> MissingStabilityAnnotations<'tcx> {
         macro_rules! find_attr_span {
             ($name:ident) => {{
                 let attrs = self.tcx.hir_attrs(self.tcx.local_def_id_to_hir_id(def_id));
-                attrs::find_attr!(attrs, AttributeKind::$name { span, .. } => *span)
+                find_attr!(attrs, AttributeKind::$name { span, .. } => *span)
             }}
         }
 
@@ -403,7 +404,7 @@ impl<'tcx> MissingStabilityAnnotations<'tcx> {
             // this is *almost surely* an accident.
             if let Some(depr) = depr
                 && let DeprecatedSince::RustcVersion(dep_since) = depr.attr.since
-                && let attrs::StabilityLevel::Stable { since: stab_since, .. } = stab.level
+                && let StabilityLevel::Stable { since: stab_since, .. } = stab.level
                 && let Some(span) = find_attr_span!(Stability)
             {
                 let item_sp = self.tcx.def_span(def_id);
@@ -644,10 +645,10 @@ impl<'tcx> Visitor<'tcx> for Checker<'tcx> {
                 let features = self.tcx.features();
                 if features.staged_api() {
                     let attrs = self.tcx.hir_attrs(item.hir_id());
-                    let stab = attrs::find_attr!(attrs, AttributeKind::Stability{stability, span} => (*stability, *span));
+                    let stab = find_attr!(attrs, AttributeKind::Stability{stability, span} => (*stability, *span));
 
                     // FIXME(jdonszelmann): make it impossible to miss the or_else in the typesystem
-                    let const_stab = attrs::find_attr!(attrs, AttributeKind::ConstStability{stability, ..} => *stability);
+                    let const_stab = find_attr!(attrs, AttributeKind::ConstStability{stability, ..} => *stability);
 
                     let unstable_feature_stab =
                         find_attr!(attrs, AttributeKind::UnstableFeatureBound(i) => i)
@@ -670,7 +671,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'tcx> {
                     // impl Foo for Bar {}
                     // ```
                     if let Some((
-                        Stability { level: attrs::StabilityLevel::Unstable { .. }, feature },
+                        Stability { level: StabilityLevel::Unstable { .. }, feature },
                         span,
                     )) = stab
                     {
diff --git a/compiler/rustc_pattern_analysis/Cargo.toml b/compiler/rustc_pattern_analysis/Cargo.toml
index 40d549630ac..a59f7bbeb9e 100644
--- a/compiler/rustc_pattern_analysis/Cargo.toml
+++ b/compiler/rustc_pattern_analysis/Cargo.toml
@@ -6,7 +6,6 @@ edition = "2024"
 [dependencies]
 # tidy-alphabetical-start
 rustc-hash = "2.0.0"
-
 rustc_abi = { path = "../rustc_abi", optional = true }
 rustc_apfloat = "0.2.0"
 rustc_arena = { path = "../rustc_arena", optional = true }
@@ -24,10 +23,13 @@ tracing = "0.1"
 # tidy-alphabetical-end
 
 [dev-dependencies]
+# tidy-alphabetical-start
 tracing-subscriber = { version = "0.3.3", default-features = false, features = ["fmt", "env-filter", "ansi"] }
 tracing-tree = "0.3.0"
+# tidy-alphabetical-end
 
 [features]
+# tidy-alphabetical-start
 default = ["rustc"]
 rustc = [
     "dep:rustc_abi",
@@ -43,3 +45,4 @@ rustc = [
     "smallvec/may_dangle",
     "rustc_index/nightly",
 ]
+# tidy-alphabetical-end
diff --git a/compiler/rustc_privacy/Cargo.toml b/compiler/rustc_privacy/Cargo.toml
index 109a7bf49fe..c8bfdb91304 100644
--- a/compiler/rustc_privacy/Cargo.toml
+++ b/compiler/rustc_privacy/Cargo.toml
@@ -6,7 +6,6 @@ edition = "2024"
 [dependencies]
 # tidy-alphabetical-start
 rustc_ast = { path = "../rustc_ast" }
-rustc_attr_data_structures = { path = "../rustc_attr_data_structures" }
 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 b4fa11a8eb3..5d02c02b23c 100644
--- a/compiler/rustc_privacy/src/lib.rs
+++ b/compiler/rustc_privacy/src/lib.rs
@@ -23,10 +23,12 @@ use rustc_ast::visit::{VisitorResult, try_visit};
 use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::intern::Interned;
 use rustc_errors::{MultiSpan, listify};
+use rustc_hir as hir;
+use rustc_hir::attrs::AttributeKind;
 use rustc_hir::def::{DefKind, Res};
-use rustc_hir::def_id::{CRATE_DEF_ID, DefId, LocalDefId, LocalModDefId};
+use rustc_hir::def_id::{DefId, LocalDefId, LocalModDefId};
 use rustc_hir::intravisit::{self, InferKind, Visitor};
-use rustc_hir::{AmbigArg, ForeignItemId, ItemId, PatKind};
+use rustc_hir::{AmbigArg, ForeignItemId, ItemId, OwnerId, PatKind, find_attr};
 use rustc_middle::middle::privacy::{EffectiveVisibilities, EffectiveVisibility, Level};
 use rustc_middle::query::Providers;
 use rustc_middle::ty::print::PrintTraitRefExt as _;
@@ -39,7 +41,6 @@ use rustc_session::lint;
 use rustc_span::hygiene::Transparency;
 use rustc_span::{Ident, Span, Symbol, sym};
 use tracing::debug;
-use {rustc_attr_data_structures as attrs, rustc_hir as hir};
 
 rustc_fluent_macro::fluent_messages! { "../messages.ftl" }
 
@@ -495,7 +496,7 @@ impl<'tcx> EmbargoVisitor<'tcx> {
         let hir_id = self.tcx.local_def_id_to_hir_id(local_def_id);
         let attrs = self.tcx.hir_attrs(hir_id);
 
-        if attrs::find_attr!(attrs, attrs::AttributeKind::MacroTransparency(x) => *x)
+        if find_attr!(attrs, AttributeKind::MacroTransparency(x) => *x)
             .unwrap_or(Transparency::fallback(md.macro_rules))
             != Transparency::Opaque
         {
@@ -598,7 +599,7 @@ impl<'tcx> EmbargoVisitor<'tcx> {
             DefKind::Struct | DefKind::Union => {
                 // While structs and unions have type privacy, their fields do not.
                 let struct_def = self.tcx.adt_def(def_id);
-                for field in struct_def.non_enum_variant().fields.iter() {
+                for field in &struct_def.non_enum_variant().fields {
                     let def_id = field.did.expect_local();
                     let field_vis = self.tcx.local_visibility(def_id);
                     if field_vis.is_accessible_from(module, self.tcx) {
@@ -636,45 +637,49 @@ impl<'tcx> EmbargoVisitor<'tcx> {
     }
 }
 
-impl<'tcx> Visitor<'tcx> for EmbargoVisitor<'tcx> {
-    fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
+impl<'tcx> EmbargoVisitor<'tcx> {
+    fn check_def_id(&mut self, owner_id: OwnerId) {
         // Update levels of nested things and mark all items
         // in interfaces of reachable items as reachable.
-        let item_ev = self.get(item.owner_id.def_id);
-        match item.kind {
+        let item_ev = self.get(owner_id.def_id);
+        match self.tcx.def_kind(owner_id) {
             // The interface is empty, and no nested items.
-            hir::ItemKind::Use(..)
-            | hir::ItemKind::ExternCrate(..)
-            | hir::ItemKind::GlobalAsm { .. } => {}
-            // The interface is empty, and all nested items are processed by `visit_item`.
-            hir::ItemKind::Mod(..) => {}
-            hir::ItemKind::Macro(_, macro_def, _) => {
+            DefKind::Use | DefKind::ExternCrate | DefKind::GlobalAsm => {}
+            // The interface is empty, and all nested items are processed by `check_def_id`.
+            DefKind::Mod => {}
+            DefKind::Macro { .. } => {
                 if let Some(item_ev) = item_ev {
-                    self.update_reachability_from_macro(item.owner_id.def_id, macro_def, item_ev);
+                    let (_, macro_def, _) =
+                        self.tcx.hir_expect_item(owner_id.def_id).expect_macro();
+                    self.update_reachability_from_macro(owner_id.def_id, macro_def, item_ev);
                 }
             }
-            hir::ItemKind::Const(..)
-            | hir::ItemKind::Static(..)
-            | hir::ItemKind::Fn { .. }
-            | hir::ItemKind::TyAlias(..) => {
+            DefKind::ForeignTy
+            | DefKind::Const
+            | DefKind::Static { .. }
+            | DefKind::Fn
+            | DefKind::TyAlias => {
                 if let Some(item_ev) = item_ev {
-                    self.reach(item.owner_id.def_id, item_ev).generics().predicates().ty();
+                    self.reach(owner_id.def_id, item_ev).generics().predicates().ty();
                 }
             }
-            hir::ItemKind::Trait(.., trait_item_refs) => {
+            DefKind::Trait => {
                 if let Some(item_ev) = item_ev {
-                    self.reach(item.owner_id.def_id, item_ev).generics().predicates();
+                    self.reach(owner_id.def_id, item_ev).generics().predicates();
 
-                    for trait_item_ref in trait_item_refs {
-                        self.update(trait_item_ref.owner_id.def_id, item_ev, Level::Reachable);
+                    for assoc_item in self.tcx.associated_items(owner_id).in_definition_order() {
+                        if assoc_item.is_impl_trait_in_trait() {
+                            continue;
+                        }
+
+                        let def_id = assoc_item.def_id.expect_local();
+                        self.update(def_id, item_ev, Level::Reachable);
 
                         let tcx = self.tcx;
-                        let mut reach = self.reach(trait_item_ref.owner_id.def_id, item_ev);
+                        let mut reach = self.reach(def_id, item_ev);
                         reach.generics().predicates();
 
-                        if let DefKind::AssocTy = tcx.def_kind(trait_item_ref.owner_id)
-                            && !tcx.defaultness(trait_item_ref.owner_id).has_value()
-                        {
+                        if assoc_item.is_type() && !assoc_item.defaultness(tcx).has_value() {
                             // No type to visit.
                         } else {
                             reach.ty();
@@ -682,12 +687,12 @@ impl<'tcx> Visitor<'tcx> for EmbargoVisitor<'tcx> {
                     }
                 }
             }
-            hir::ItemKind::TraitAlias(..) => {
+            DefKind::TraitAlias => {
                 if let Some(item_ev) = item_ev {
-                    self.reach(item.owner_id.def_id, item_ev).generics().predicates();
+                    self.reach(owner_id.def_id, item_ev).generics().predicates();
                 }
             }
-            hir::ItemKind::Impl(impl_) => {
+            DefKind::Impl { of_trait } => {
                 // Type inference is very smart sometimes. It can make an impl reachable even some
                 // components of its type or trait are unreachable. E.g. methods of
                 // `impl ReachableTrait<UnreachableTy> for ReachableTy<UnreachableTy> { ... }`
@@ -699,19 +704,23 @@ impl<'tcx> Visitor<'tcx> for EmbargoVisitor<'tcx> {
                 // without knowing both "shallow" version of its self type and "shallow" version of
                 // its trait if it exists (which require reaching the `DefId`s in them).
                 let item_ev = EffectiveVisibility::of_impl::<true>(
-                    item.owner_id.def_id,
+                    owner_id.def_id,
                     self.tcx,
                     &self.effective_visibilities,
                 );
 
-                self.update_eff_vis(item.owner_id.def_id, item_ev, None, Level::Direct);
+                self.update_eff_vis(owner_id.def_id, item_ev, None, Level::Direct);
+
+                self.reach(owner_id.def_id, item_ev).generics().predicates().ty().trait_ref();
 
-                self.reach(item.owner_id.def_id, item_ev).generics().predicates().ty().trait_ref();
+                for assoc_item in self.tcx.associated_items(owner_id).in_definition_order() {
+                    if assoc_item.is_impl_trait_in_trait() {
+                        continue;
+                    }
 
-                for impl_item_ref in impl_.items {
-                    let def_id = impl_item_ref.owner_id.def_id;
+                    let def_id = assoc_item.def_id.expect_local();
                     let max_vis =
-                        impl_.of_trait.is_none().then(|| self.tcx.local_visibility(def_id));
+                        if of_trait { None } else { Some(self.tcx.local_visibility(def_id)) };
                     self.update_eff_vis(def_id, item_ev, max_vis, Level::Direct);
 
                     if let Some(impl_item_ev) = self.get(def_id) {
@@ -719,65 +728,76 @@ impl<'tcx> Visitor<'tcx> for EmbargoVisitor<'tcx> {
                     }
                 }
             }
-            hir::ItemKind::Enum(_, _, ref def) => {
+            DefKind::Enum => {
                 if let Some(item_ev) = item_ev {
-                    self.reach(item.owner_id.def_id, item_ev).generics().predicates();
+                    self.reach(owner_id.def_id, item_ev).generics().predicates();
                 }
-                for variant in def.variants {
+                let def = self.tcx.adt_def(owner_id);
+                for variant in def.variants() {
                     if let Some(item_ev) = item_ev {
-                        self.update(variant.def_id, item_ev, Level::Reachable);
+                        self.update(variant.def_id.expect_local(), item_ev, Level::Reachable);
                     }
 
-                    if let Some(variant_ev) = self.get(variant.def_id) {
-                        if let Some(ctor_def_id) = variant.data.ctor_def_id() {
-                            self.update(ctor_def_id, variant_ev, Level::Reachable);
+                    if let Some(variant_ev) = self.get(variant.def_id.expect_local()) {
+                        if let Some(ctor_def_id) = variant.ctor_def_id() {
+                            self.update(ctor_def_id.expect_local(), variant_ev, Level::Reachable);
                         }
 
-                        for field in variant.data.fields() {
-                            self.update(field.def_id, variant_ev, Level::Reachable);
-                            self.reach(field.def_id, variant_ev).ty();
+                        for field in &variant.fields {
+                            let field = field.did.expect_local();
+                            self.update(field, variant_ev, Level::Reachable);
+                            self.reach(field, variant_ev).ty();
                         }
                         // Corner case: if the variant is reachable, but its
                         // enum is not, make the enum reachable as well.
-                        self.reach(item.owner_id.def_id, variant_ev).ty();
+                        self.reach(owner_id.def_id, variant_ev).ty();
                     }
-                    if let Some(ctor_def_id) = variant.data.ctor_def_id() {
-                        if let Some(ctor_ev) = self.get(ctor_def_id) {
-                            self.reach(item.owner_id.def_id, ctor_ev).ty();
+                    if let Some(ctor_def_id) = variant.ctor_def_id() {
+                        if let Some(ctor_ev) = self.get(ctor_def_id.expect_local()) {
+                            self.reach(owner_id.def_id, ctor_ev).ty();
                         }
                     }
                 }
             }
-            hir::ItemKind::ForeignMod { items, .. } => {
-                for foreign_item in items {
-                    if let Some(foreign_item_ev) = self.get(foreign_item.owner_id.def_id) {
-                        self.reach(foreign_item.owner_id.def_id, foreign_item_ev)
-                            .generics()
-                            .predicates()
-                            .ty();
-                    }
-                }
-            }
-            hir::ItemKind::Struct(_, _, ref struct_def)
-            | hir::ItemKind::Union(_, _, ref struct_def) => {
+            DefKind::Struct | DefKind::Union => {
+                let def = self.tcx.adt_def(owner_id).non_enum_variant();
                 if let Some(item_ev) = item_ev {
-                    self.reach(item.owner_id.def_id, item_ev).generics().predicates();
-                    for field in struct_def.fields() {
-                        self.update(field.def_id, item_ev, Level::Reachable);
-                        if let Some(field_ev) = self.get(field.def_id) {
-                            self.reach(field.def_id, field_ev).ty();
+                    self.reach(owner_id.def_id, item_ev).generics().predicates();
+                    for field in &def.fields {
+                        let field = field.did.expect_local();
+                        self.update(field, item_ev, Level::Reachable);
+                        if let Some(field_ev) = self.get(field) {
+                            self.reach(field, field_ev).ty();
                         }
                     }
                 }
-                if let Some(ctor_def_id) = struct_def.ctor_def_id() {
+                if let Some(ctor_def_id) = def.ctor_def_id() {
                     if let Some(item_ev) = item_ev {
-                        self.update(ctor_def_id, item_ev, Level::Reachable);
+                        self.update(ctor_def_id.expect_local(), item_ev, Level::Reachable);
                     }
-                    if let Some(ctor_ev) = self.get(ctor_def_id) {
-                        self.reach(item.owner_id.def_id, ctor_ev).ty();
+                    if let Some(ctor_ev) = self.get(ctor_def_id.expect_local()) {
+                        self.reach(owner_id.def_id, ctor_ev).ty();
                     }
                 }
             }
+            // Contents are checked directly.
+            DefKind::ForeignMod => {}
+            DefKind::Field
+            | DefKind::Variant
+            | DefKind::AssocFn
+            | DefKind::AssocTy
+            | DefKind::AssocConst
+            | DefKind::TyParam
+            | DefKind::AnonConst
+            | DefKind::InlineConst
+            | DefKind::OpaqueTy
+            | DefKind::Closure
+            | DefKind::SyntheticCoroutineBody
+            | DefKind::ConstParam
+            | DefKind::LifetimeParam
+            | DefKind::Ctor(..) => {
+                bug!("should be checked while checking parent")
+            }
         }
     }
 }
@@ -838,7 +858,7 @@ pub struct TestReachabilityVisitor<'a, 'tcx> {
 }
 
 impl<'a, 'tcx> TestReachabilityVisitor<'a, 'tcx> {
-    fn effective_visibility_diagnostic(&mut self, def_id: LocalDefId) {
+    fn effective_visibility_diagnostic(&self, def_id: LocalDefId) {
         if self.tcx.has_attr(def_id, sym::rustc_effective_visibility) {
             let mut error_msg = String::new();
             let span = self.tcx.def_span(def_id.to_def_id());
@@ -858,43 +878,35 @@ impl<'a, 'tcx> TestReachabilityVisitor<'a, 'tcx> {
     }
 }
 
-impl<'a, 'tcx> Visitor<'tcx> for TestReachabilityVisitor<'a, 'tcx> {
-    fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
-        self.effective_visibility_diagnostic(item.owner_id.def_id);
+impl<'a, 'tcx> TestReachabilityVisitor<'a, 'tcx> {
+    fn check_def_id(&self, owner_id: OwnerId) {
+        self.effective_visibility_diagnostic(owner_id.def_id);
 
-        match item.kind {
-            hir::ItemKind::Enum(_, _, ref def) => {
-                for variant in def.variants.iter() {
-                    self.effective_visibility_diagnostic(variant.def_id);
-                    if let Some(ctor_def_id) = variant.data.ctor_def_id() {
-                        self.effective_visibility_diagnostic(ctor_def_id);
+        match self.tcx.def_kind(owner_id) {
+            DefKind::Enum => {
+                let def = self.tcx.adt_def(owner_id.def_id);
+                for variant in def.variants() {
+                    self.effective_visibility_diagnostic(variant.def_id.expect_local());
+                    if let Some(ctor_def_id) = variant.ctor_def_id() {
+                        self.effective_visibility_diagnostic(ctor_def_id.expect_local());
                     }
-                    for field in variant.data.fields() {
-                        self.effective_visibility_diagnostic(field.def_id);
+                    for field in &variant.fields {
+                        self.effective_visibility_diagnostic(field.did.expect_local());
                     }
                 }
             }
-            hir::ItemKind::Struct(_, _, ref def) | hir::ItemKind::Union(_, _, ref def) => {
+            DefKind::Struct | DefKind::Union => {
+                let def = self.tcx.adt_def(owner_id.def_id).non_enum_variant();
                 if let Some(ctor_def_id) = def.ctor_def_id() {
-                    self.effective_visibility_diagnostic(ctor_def_id);
+                    self.effective_visibility_diagnostic(ctor_def_id.expect_local());
                 }
-                for field in def.fields() {
-                    self.effective_visibility_diagnostic(field.def_id);
+                for field in &def.fields {
+                    self.effective_visibility_diagnostic(field.did.expect_local());
                 }
             }
             _ => {}
         }
     }
-
-    fn visit_trait_item(&mut self, item: &'tcx hir::TraitItem<'tcx>) {
-        self.effective_visibility_diagnostic(item.owner_id.def_id);
-    }
-    fn visit_impl_item(&mut self, item: &'tcx hir::ImplItem<'tcx>) {
-        self.effective_visibility_diagnostic(item.owner_id.def_id);
-    }
-    fn visit_foreign_item(&mut self, item: &'tcx hir::ForeignItem<'tcx>) {
-        self.effective_visibility_diagnostic(item.owner_id.def_id);
-    }
 }
 
 //////////////////////////////////////////////////////////////////////////////////////
@@ -1422,8 +1434,6 @@ impl SearchInterfaceForPrivateItemsVisitor<'_> {
         };
 
         let vis = self.tcx.local_visibility(local_def_id);
-        let span = self.tcx.def_span(self.item_def_id.to_def_id());
-        let vis_span = self.tcx.def_span(def_id);
         if self.in_assoc_ty && !vis.is_at_least(self.required_visibility, self.tcx) {
             let vis_descr = match vis {
                 ty::Visibility::Public => "public",
@@ -1440,6 +1450,8 @@ impl SearchInterfaceForPrivateItemsVisitor<'_> {
                 }
             };
 
+            let span = self.tcx.def_span(self.item_def_id.to_def_id());
+            let vis_span = self.tcx.def_span(def_id);
             self.tcx.dcx().emit_err(InPublicInterface {
                 span,
                 vis_descr,
@@ -1462,6 +1474,8 @@ impl SearchInterfaceForPrivateItemsVisitor<'_> {
             } else {
                 lint::builtin::PRIVATE_BOUNDS
             };
+            let span = self.tcx.def_span(self.item_def_id.to_def_id());
+            let vis_span = self.tcx.def_span(def_id);
             self.tcx.emit_node_span_lint(
                 lint,
                 self.tcx.local_def_id_to_hir_id(self.item_def_id),
@@ -1593,7 +1607,7 @@ impl<'tcx> PrivateItemsInPublicInterfacesChecker<'_, 'tcx> {
         self.effective_visibilities.effective_vis(def_id).copied()
     }
 
-    fn check_item(&mut self, id: ItemId) {
+    fn check_item(&self, id: ItemId) {
         let tcx = self.tcx;
         let def_id = id.owner_id.def_id;
         let item_visibility = tcx.local_visibility(def_id);
@@ -1721,7 +1735,7 @@ impl<'tcx> PrivateItemsInPublicInterfacesChecker<'_, 'tcx> {
         }
     }
 
-    fn check_foreign_item(&mut self, id: ForeignItemId) {
+    fn check_foreign_item(&self, id: ForeignItemId) {
         let tcx = self.tcx;
         let def_id = id.owner_id.def_id;
         let item_visibility = tcx.local_visibility(def_id);
@@ -1835,8 +1849,14 @@ fn effective_visibilities(tcx: TyCtxt<'_>, (): ()) -> &EffectiveVisibilities {
         visitor.changed = false;
     }
 
+    let crate_items = tcx.hir_crate_items(());
     loop {
-        tcx.hir_visit_all_item_likes_in_crate(&mut visitor);
+        for id in crate_items.free_items() {
+            visitor.check_def_id(id.owner_id);
+        }
+        for id in crate_items.foreign_items() {
+            visitor.check_def_id(id.owner_id);
+        }
         if visitor.changed {
             visitor.changed = false;
         } else {
@@ -1845,24 +1865,21 @@ fn effective_visibilities(tcx: TyCtxt<'_>, (): ()) -> &EffectiveVisibilities {
     }
     visitor.effective_visibilities.check_invariants(tcx);
 
-    let mut check_visitor =
+    let check_visitor =
         TestReachabilityVisitor { tcx, effective_visibilities: &visitor.effective_visibilities };
-    check_visitor.effective_visibility_diagnostic(CRATE_DEF_ID);
-    tcx.hir_visit_all_item_likes_in_crate(&mut check_visitor);
+    for id in crate_items.owners() {
+        check_visitor.check_def_id(id);
+    }
 
     tcx.arena.alloc(visitor.effective_visibilities)
 }
 
-fn check_private_in_public(tcx: TyCtxt<'_>, (): ()) {
+fn check_private_in_public(tcx: TyCtxt<'_>, module_def_id: LocalModDefId) {
     let effective_visibilities = tcx.effective_visibilities(());
     // Check for private types in public interfaces.
-    let mut checker = PrivateItemsInPublicInterfacesChecker { tcx, effective_visibilities };
+    let checker = PrivateItemsInPublicInterfacesChecker { tcx, effective_visibilities };
 
-    let crate_items = tcx.hir_crate_items(());
-    for id in crate_items.free_items() {
-        checker.check_item(id);
-    }
-    for id in crate_items.foreign_items() {
-        checker.check_foreign_item(id);
-    }
+    let crate_items = tcx.hir_module_items(module_def_id);
+    let _ = crate_items.par_items(|id| Ok(checker.check_item(id)));
+    let _ = crate_items.par_foreign_items(|id| Ok(checker.check_foreign_item(id)));
 }
diff --git a/compiler/rustc_proc_macro/Cargo.toml b/compiler/rustc_proc_macro/Cargo.toml
index 762acf9a1eb..beb95aa3b52 100644
--- a/compiler/rustc_proc_macro/Cargo.toml
+++ b/compiler/rustc_proc_macro/Cargo.toml
@@ -15,7 +15,11 @@ test = false
 doctest = false
 
 [dependencies]
+# tidy-alphabetical-start
 rustc-literal-escaper = "0.0.5"
+# tidy-alphabetical-end
 
 [features]
+# tidy-alphabetical-start
 rustc-dep-of-std = []
+# tidy-alphabetical-end
diff --git a/compiler/rustc_public/Cargo.toml b/compiler/rustc_public/Cargo.toml
index fa782166e4f..70af30c1a5f 100644
--- a/compiler/rustc_public/Cargo.toml
+++ b/compiler/rustc_public/Cargo.toml
@@ -18,7 +18,9 @@ tracing = "0.1"
 # tidy-alphabetical-end
 
 [features]
+# tidy-alphabetical-start
 # Provides access to APIs that expose internals of the rust compiler.
 # APIs enabled by this feature are unstable. They can be removed or modified
 # at any point and they are not included in the crate's semantic versioning.
 rustc_internal = []
+# tidy-alphabetical-end
diff --git a/compiler/rustc_query_system/Cargo.toml b/compiler/rustc_query_system/Cargo.toml
index 3d2d879a764..7480ba03474 100644
--- a/compiler/rustc_query_system/Cargo.toml
+++ b/compiler/rustc_query_system/Cargo.toml
@@ -8,7 +8,6 @@ edition = "2024"
 parking_lot = "0.12"
 rustc_abi = { path = "../rustc_abi" }
 rustc_ast = { path = "../rustc_ast" }
-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" }
diff --git a/compiler/rustc_query_system/src/ich/hcx.rs b/compiler/rustc_query_system/src/ich/hcx.rs
index 96d0c02c4a6..be838f689e5 100644
--- a/compiler/rustc_query_system/src/ich/hcx.rs
+++ b/compiler/rustc_query_system/src/ich/hcx.rs
@@ -129,4 +129,3 @@ impl<'a> rustc_span::HashStableContext for StableHashingContext<'a> {
 }
 
 impl<'a> rustc_session::HashStableContext for StableHashingContext<'a> {}
-impl<'a> rustc_attr_data_structures::HashStableContext for StableHashingContext<'a> {}
diff --git a/compiler/rustc_resolve/Cargo.toml b/compiler/rustc_resolve/Cargo.toml
index 1238ce0125a..eb98a6e85c0 100644
--- a/compiler/rustc_resolve/Cargo.toml
+++ b/compiler/rustc_resolve/Cargo.toml
@@ -6,12 +6,12 @@ edition = "2024"
 [dependencies]
 # tidy-alphabetical-start
 bitflags = "2.4.1"
+indexmap = "2.4.0"
 itertools = "0.12"
 pulldown-cmark = { version = "0.11", features = ["html"], default-features = false }
 rustc_arena = { path = "../rustc_arena" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_ast_pretty = { path = "../rustc_ast_pretty" }
-rustc_attr_data_structures = { path = "../rustc_attr_data_structures" }
 rustc_attr_parsing = { path = "../rustc_attr_parsing" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
diff --git a/compiler/rustc_resolve/src/build_reduced_graph.rs b/compiler/rustc_resolve/src/build_reduced_graph.rs
index 7912345ec56..d9671c43b3d 100644
--- a/compiler/rustc_resolve/src/build_reduced_graph.rs
+++ b/compiler/rustc_resolve/src/build_reduced_graph.rs
@@ -13,12 +13,12 @@ use rustc_ast::{
     self as ast, AssocItem, AssocItemKind, Block, ConstItem, Delegation, Fn, ForeignItem,
     ForeignItemKind, Impl, Item, ItemKind, NodeId, StaticItem, StmtKind, TyAlias,
 };
-use rustc_attr_data_structures::{AttributeKind, MacroUseArgs};
 use rustc_attr_parsing as attr;
 use rustc_attr_parsing::AttributeParser;
 use rustc_expand::base::ResolverExpand;
 use rustc_expand::expand::AstFragment;
 use rustc_hir::Attribute;
+use rustc_hir::attrs::{AttributeKind, MacroUseArgs};
 use rustc_hir::def::{self, *};
 use rustc_hir::def_id::{CRATE_DEF_ID, DefId, LocalDefId};
 use rustc_index::bit_set::DenseBitSet;
@@ -968,7 +968,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
         }
         self.r.potentially_unused_imports.push(import);
         let imported_binding = self.r.import(binding, import);
-        if parent == self.r.graph_root {
+        if ident.name != kw::Underscore && parent == self.r.graph_root {
             let ident = ident.normalize_to_macros_2_0();
             if let Some(entry) = self.r.extern_prelude.get(&ident)
                 && expansion != LocalExpnId::ROOT
@@ -984,23 +984,29 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
                 // more details: https://github.com/rust-lang/rust/pull/111761
                 return;
             }
-            let entry = self.r.extern_prelude.entry(ident).or_insert(ExternPreludeEntry {
-                binding: Cell::new(None),
-                introduced_by_item: true,
-            });
-            if orig_name.is_some() {
-                entry.introduced_by_item = true;
-            }
-            // Binding from `extern crate` item in source code can replace
-            // a binding from `--extern` on command line here.
-            if !entry.is_import() {
-                entry.binding.set(Some(imported_binding));
-            } else if ident.name != kw::Underscore {
-                self.r.dcx().span_delayed_bug(
-                    item.span,
-                    format!("it had been define the external module '{ident}' multiple times"),
-                );
-            }
+
+            use indexmap::map::Entry;
+            match self.r.extern_prelude.entry(ident) {
+                Entry::Occupied(mut occupied) => {
+                    let entry = occupied.get_mut();
+                    if let Some(old_binding) = entry.binding.get()
+                        && old_binding.is_import()
+                    {
+                        let msg = format!("extern crate `{ident}` already in extern prelude");
+                        self.r.tcx.dcx().span_delayed_bug(item.span, msg);
+                    } else {
+                        // Binding from `extern crate` item in source code can replace
+                        // a binding from `--extern` on command line here.
+                        entry.binding.set(Some(imported_binding));
+                        entry.introduced_by_item = orig_name.is_some();
+                    }
+                    entry
+                }
+                Entry::Vacant(vacant) => vacant.insert(ExternPreludeEntry {
+                    binding: Cell::new(Some(imported_binding)),
+                    introduced_by_item: true,
+                }),
+            };
         }
         self.r.define_binding_local(parent, ident, TypeNS, imported_binding);
     }
diff --git a/compiler/rustc_resolve/src/diagnostics.rs b/compiler/rustc_resolve/src/diagnostics.rs
index 3af69b28780..d18554bba1b 100644
--- a/compiler/rustc_resolve/src/diagnostics.rs
+++ b/compiler/rustc_resolve/src/diagnostics.rs
@@ -4,9 +4,6 @@ use rustc_ast::{
     self as ast, CRATE_NODE_ID, Crate, ItemKind, ModKind, NodeId, Path, join_path_idents,
 };
 use rustc_ast_pretty::pprust;
-use rustc_attr_data_structures::{
-    self as attr, AttributeKind, CfgEntry, Stability, StrippedCfgItem, find_attr,
-};
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_data_structures::unord::{UnordMap, UnordSet};
 use rustc_errors::codes::*;
@@ -15,10 +12,11 @@ use rustc_errors::{
     report_ambiguity_error, struct_span_code_err,
 };
 use rustc_feature::BUILTIN_ATTRIBUTES;
-use rustc_hir::PrimTy;
+use rustc_hir::attrs::{AttributeKind, CfgEntry, StrippedCfgItem};
 use rustc_hir::def::Namespace::{self, *};
 use rustc_hir::def::{self, CtorKind, CtorOf, DefKind, NonMacroAttrKind, PerNS};
 use rustc_hir::def_id::{CRATE_DEF_ID, DefId};
+use rustc_hir::{PrimTy, Stability, StabilityLevel, find_attr};
 use rustc_middle::bug;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::Session;
@@ -803,10 +801,12 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                     }
                     err.multipart_suggestion(msg, suggestions, applicability);
                 }
-                if let Some(ModuleOrUniformRoot::Module(module)) = module
-                    && let Some(module) = module.opt_def_id()
-                    && let Some(segment) = segment
-                {
+
+                if let Some(segment) = segment {
+                    let module = match module {
+                        Some(ModuleOrUniformRoot::Module(m)) if let Some(id) = m.opt_def_id() => id,
+                        _ => CRATE_DEF_ID.to_def_id(),
+                    };
                     self.find_cfg_stripped(&mut err, &segment, module);
                 }
 
@@ -1098,7 +1098,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                     }
                 }
                 Scope::ExternPrelude => {
-                    suggestions.extend(this.extern_prelude.iter().filter_map(|(ident, _)| {
+                    suggestions.extend(this.extern_prelude.keys().filter_map(|ident| {
                         let res = Res::Def(DefKind::Mod, CRATE_DEF_ID.to_def_id());
                         filter_fn(res).then_some(TypoSuggestion::typo_from_ident(*ident, res))
                     }));
@@ -1362,9 +1362,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
 
         match self.tcx.lookup_stability(did) {
             Some(Stability {
-                level: attr::StabilityLevel::Unstable { implied_by, .. },
-                feature,
-                ..
+                level: StabilityLevel::Unstable { implied_by, .. }, feature, ..
             }) => {
                 if span.allows_unstable(feature) {
                     true
@@ -1411,7 +1409,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         );
 
         if lookup_ident.span.at_least_rust_2018() {
-            for ident in self.extern_prelude.clone().into_keys() {
+            for &ident in self.extern_prelude.keys() {
                 if ident.span.from_expansion() {
                     // Idents are adjusted to the root context before being
                     // resolved in the extern prelude, so reporting this to the
@@ -2843,16 +2841,13 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                 continue;
             }
 
-            let note = errors::FoundItemConfigureOut { span: ident.span };
-            err.subdiagnostic(note);
-
-            if let CfgEntry::NameValue { value: Some((feature, _)), .. } = cfg.0 {
-                let note = errors::ItemWasBehindFeature { feature, span: cfg.1 };
-                err.subdiagnostic(note);
+            let item_was = if let CfgEntry::NameValue { value: Some((feature, _)), .. } = cfg.0 {
+                errors::ItemWas::BehindFeature { feature, span: cfg.1 }
             } else {
-                let note = errors::ItemWasCfgOut { span: cfg.1 };
-                err.subdiagnostic(note);
-            }
+                errors::ItemWas::CfgOut { span: cfg.1 }
+            };
+            let note = errors::FoundItemConfigureOut { span: ident.span, item_was };
+            err.subdiagnostic(note);
         }
     }
 }
diff --git a/compiler/rustc_resolve/src/errors.rs b/compiler/rustc_resolve/src/errors.rs
index d6b1e4de6ea..2747ba135ed 100644
--- a/compiler/rustc_resolve/src/errors.rs
+++ b/compiler/rustc_resolve/src/errors.rs
@@ -1,10 +1,13 @@
 use rustc_errors::codes::*;
-use rustc_errors::{Applicability, ElidedLifetimeInPathSubdiag, MultiSpan};
+use rustc_errors::{
+    Applicability, Diag, ElidedLifetimeInPathSubdiag, EmissionGuarantee, IntoDiagArg, MultiSpan,
+    Subdiagnostic,
+};
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_span::{Ident, Span, Symbol};
 
-use crate::Res;
 use crate::late::PatternSource;
+use crate::{Res, fluent_generated as fluent};
 
 #[derive(Diagnostic)]
 #[diag(resolve_generic_params_from_outer_item, code = E0401)]
@@ -1201,26 +1204,35 @@ pub(crate) struct IdentInScopeButItIsDesc<'a> {
     pub(crate) imported_ident_desc: &'a str,
 }
 
-#[derive(Subdiagnostic)]
-#[note(resolve_found_an_item_configured_out)]
 pub(crate) struct FoundItemConfigureOut {
-    #[primary_span]
-    pub(crate) span: Span,
-}
-
-#[derive(Subdiagnostic)]
-#[note(resolve_item_was_behind_feature)]
-pub(crate) struct ItemWasBehindFeature {
-    pub(crate) feature: Symbol,
-    #[primary_span]
-    pub(crate) span: Span,
-}
-
-#[derive(Subdiagnostic)]
-#[note(resolve_item_was_cfg_out)]
-pub(crate) struct ItemWasCfgOut {
-    #[primary_span]
     pub(crate) span: Span,
+    pub(crate) item_was: ItemWas,
+}
+
+pub(crate) enum ItemWas {
+    BehindFeature { feature: Symbol, span: Span },
+    CfgOut { span: Span },
+}
+
+impl Subdiagnostic for FoundItemConfigureOut {
+    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
+        let mut multispan: MultiSpan = self.span.into();
+        match self.item_was {
+            ItemWas::BehindFeature { feature, span } => {
+                let key = "feature".into();
+                let value = feature.into_diag_arg(&mut None);
+                let msg = diag.dcx.eagerly_translate_to_string(
+                    fluent::resolve_item_was_behind_feature,
+                    [(&key, &value)].into_iter(),
+                );
+                multispan.push_span_label(span, msg);
+            }
+            ItemWas::CfgOut { span } => {
+                multispan.push_span_label(span, fluent::resolve_item_was_cfg_out);
+            }
+        }
+        diag.span_note(multispan, fluent::resolve_found_an_item_configured_out);
+    }
 }
 
 #[derive(Diagnostic)]
diff --git a/compiler/rustc_resolve/src/late.rs b/compiler/rustc_resolve/src/late.rs
index 261d099abdc..163e4b5b7a9 100644
--- a/compiler/rustc_resolve/src/late.rs
+++ b/compiler/rustc_resolve/src/late.rs
@@ -4231,13 +4231,21 @@ impl<'a, 'ast, 'ra, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
                 //
                 // And that's what happens below - we're just mixing both messages
                 // into a single one.
+                let failed_to_resolve = match parent_err.node {
+                    ResolutionError::FailedToResolve { .. } => true,
+                    _ => false,
+                };
                 let mut parent_err = this.r.into_struct_error(parent_err.span, parent_err.node);
 
                 // overwrite all properties with the parent's error message
                 err.messages = take(&mut parent_err.messages);
                 err.code = take(&mut parent_err.code);
                 swap(&mut err.span, &mut parent_err.span);
-                err.children = take(&mut parent_err.children);
+                if failed_to_resolve {
+                    err.children = take(&mut parent_err.children);
+                } else {
+                    err.children.append(&mut parent_err.children);
+                }
                 err.sort_span = parent_err.sort_span;
                 err.is_lint = parent_err.is_lint.clone();
 
diff --git a/compiler/rustc_resolve/src/late/diagnostics.rs b/compiler/rustc_resolve/src/late/diagnostics.rs
index 98e48664e68..c8ca57a380f 100644
--- a/compiler/rustc_resolve/src/late/diagnostics.rs
+++ b/compiler/rustc_resolve/src/late/diagnostics.rs
@@ -525,9 +525,8 @@ impl<'ast, 'ra, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
         }
         self.err_code_special_cases(&mut err, source, path, span);
 
-        if let Some(module) = base_error.module {
-            self.r.find_cfg_stripped(&mut err, &path.last().unwrap().ident.name, module);
-        }
+        let module = base_error.module.unwrap_or_else(|| CRATE_DEF_ID.to_def_id());
+        self.r.find_cfg_stripped(&mut err, &path.last().unwrap().ident.name, module);
 
         (err, candidates)
     }
@@ -2477,19 +2476,10 @@ impl<'ast, 'ra, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
                     } else {
                         // Items from the prelude
                         if !module.no_implicit_prelude {
-                            let extern_prelude = self.r.extern_prelude.clone();
-                            names.extend(extern_prelude.iter().flat_map(|(ident, _)| {
-                                self.r
-                                    .cstore_mut()
-                                    .maybe_process_path_extern(self.r.tcx, ident.name)
-                                    .and_then(|crate_id| {
-                                        let crate_mod =
-                                            Res::Def(DefKind::Mod, crate_id.as_def_id());
-
-                                        filter_fn(crate_mod).then(|| {
-                                            TypoSuggestion::typo_from_ident(*ident, crate_mod)
-                                        })
-                                    })
+                            names.extend(self.r.extern_prelude.keys().flat_map(|ident| {
+                                let res = Res::Def(DefKind::Mod, CRATE_DEF_ID.to_def_id());
+                                filter_fn(res)
+                                    .then_some(TypoSuggestion::typo_from_ident(*ident, res))
                             }));
 
                             if let Some(prelude) = self.r.prelude {
diff --git a/compiler/rustc_resolve/src/lib.rs b/compiler/rustc_resolve/src/lib.rs
index 88dfb50b47d..6b034c5129f 100644
--- a/compiler/rustc_resolve/src/lib.rs
+++ b/compiler/rustc_resolve/src/lib.rs
@@ -41,7 +41,6 @@ use rustc_ast::{
     self as ast, AngleBracketedArg, CRATE_NODE_ID, Crate, Expr, ExprKind, GenericArg, GenericArgs,
     LitKind, NodeId, Path, attr,
 };
-use rustc_attr_data_structures::StrippedCfgItem;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap, FxIndexSet};
 use rustc_data_structures::intern::Interned;
 use rustc_data_structures::steal::Steal;
@@ -50,6 +49,7 @@ use rustc_data_structures::unord::{UnordMap, UnordSet};
 use rustc_errors::{Applicability, Diag, ErrCode, ErrorGuaranteed};
 use rustc_expand::base::{DeriveResolution, SyntaxExtension, SyntaxExtensionKind};
 use rustc_feature::BUILTIN_ATTRIBUTES;
+use rustc_hir::attrs::StrippedCfgItem;
 use rustc_hir::def::Namespace::{self, *};
 use rustc_hir::def::{
     self, CtorOf, DefKind, DocLinkResMap, LifetimeRes, NonMacroAttrKind, PartialRes, PerNS,
@@ -64,8 +64,8 @@ use rustc_middle::middle::privacy::EffectiveVisibilities;
 use rustc_middle::query::Providers;
 use rustc_middle::span_bug;
 use rustc_middle::ty::{
-    self, DelegationFnSig, Feed, MainDefinition, RegisteredTools, ResolverGlobalCtxt,
-    ResolverOutputs, TyCtxt, TyCtxtFeed, Visibility,
+    self, DelegationFnSig, Feed, MainDefinition, RegisteredTools, ResolverAstLowering,
+    ResolverGlobalCtxt, TyCtxt, TyCtxtFeed, Visibility,
 };
 use rustc_query_system::ich::StableHashingContext;
 use rustc_session::lint::builtin::PRIVATE_MACRO_USE;
@@ -1037,6 +1037,11 @@ impl MacroData {
     }
 }
 
+pub struct ResolverOutputs {
+    pub global_ctxt: ResolverGlobalCtxt,
+    pub ast_lowering: ResolverAstLowering,
+}
+
 /// The main resolver class.
 ///
 /// This is the visitor that walks the whole crate.
@@ -1482,13 +1487,23 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         let mut invocation_parents = FxHashMap::default();
         invocation_parents.insert(LocalExpnId::ROOT, InvocationParent::ROOT);
 
-        let mut extern_prelude: FxIndexMap<Ident, ExternPreludeEntry<'_>> = tcx
+        let mut extern_prelude: FxIndexMap<_, _> = tcx
             .sess
             .opts
             .externs
             .iter()
-            .filter(|(_, entry)| entry.add_prelude)
-            .map(|(name, _)| (Ident::from_str(name), Default::default()))
+            .filter_map(|(name, entry)| {
+                // Make sure `self`, `super`, `_` etc do not get into extern prelude.
+                // FIXME: reject `--extern self` and similar in option parsing instead.
+                if entry.add_prelude
+                    && let name = Symbol::intern(name)
+                    && name.can_be_raw()
+                {
+                    Some((Ident::with_dummy_span(name), Default::default()))
+                } else {
+                    None
+                }
+            })
             .collect();
 
         if !attr::contains_name(attrs, sym::no_core) {
@@ -2163,40 +2178,42 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
     }
 
     fn extern_prelude_get(&mut self, ident: Ident, finalize: bool) -> Option<NameBinding<'ra>> {
-        if ident.is_path_segment_keyword() {
-            // Make sure `self`, `super` etc produce an error when passed to here.
-            return None;
-        }
-
-        let norm_ident = ident.normalize_to_macros_2_0();
-        let binding = self.extern_prelude.get(&norm_ident).cloned().and_then(|entry| {
-            Some(if let Some(binding) = entry.binding.get() {
+        let mut record_use = None;
+        let entry = self.extern_prelude.get(&ident.normalize_to_macros_2_0());
+        let binding = entry.and_then(|entry| match entry.binding.get() {
+            Some(binding) if binding.is_import() => {
                 if finalize {
-                    if !entry.is_import() {
-                        self.cstore_mut().process_path_extern(self.tcx, ident.name, ident.span);
-                    } else if entry.introduced_by_item {
-                        self.record_use(ident, binding, Used::Other);
-                    }
+                    record_use = Some(binding);
                 }
-                binding
-            } else {
+                Some(binding)
+            }
+            Some(binding) => {
+                if finalize {
+                    self.cstore_mut().process_path_extern(self.tcx, ident.name, ident.span);
+                }
+                Some(binding)
+            }
+            None => {
                 let crate_id = if finalize {
-                    let Some(crate_id) =
-                        self.cstore_mut().process_path_extern(self.tcx, ident.name, ident.span)
-                    else {
-                        return Some(self.dummy_binding);
-                    };
-                    crate_id
+                    self.cstore_mut().process_path_extern(self.tcx, ident.name, ident.span)
                 } else {
-                    self.cstore_mut().maybe_process_path_extern(self.tcx, ident.name)?
+                    self.cstore_mut().maybe_process_path_extern(self.tcx, ident.name)
                 };
-                let res = Res::Def(DefKind::Mod, crate_id.as_def_id());
-                self.arenas.new_pub_res_binding(res, DUMMY_SP, LocalExpnId::ROOT)
-            })
+                match crate_id {
+                    Some(crate_id) => {
+                        let res = Res::Def(DefKind::Mod, crate_id.as_def_id());
+                        let binding =
+                            self.arenas.new_pub_res_binding(res, DUMMY_SP, LocalExpnId::ROOT);
+                        entry.binding.set(Some(binding));
+                        Some(binding)
+                    }
+                    None => finalize.then_some(self.dummy_binding),
+                }
+            }
         });
 
-        if let Some(entry) = self.extern_prelude.get(&norm_ident) {
-            entry.binding.set(binding);
+        if let Some(binding) = record_use {
+            self.record_use(ident, binding, Used::Scope);
         }
 
         binding
diff --git a/compiler/rustc_resolve/src/macros.rs b/compiler/rustc_resolve/src/macros.rs
index 20504ea609d..4e3c0cd5bc0 100644
--- a/compiler/rustc_resolve/src/macros.rs
+++ b/compiler/rustc_resolve/src/macros.rs
@@ -8,7 +8,6 @@ use std::sync::Arc;
 
 use rustc_ast::{self as ast, Crate, NodeId, attr};
 use rustc_ast_pretty::pprust;
-use rustc_attr_data_structures::{CfgEntry, StabilityLevel, StrippedCfgItem};
 use rustc_errors::{Applicability, DiagCtxtHandle, StashKey};
 use rustc_expand::base::{
     Annotatable, DeriveResolution, Indeterminate, ResolverExpand, SyntaxExtension,
@@ -18,6 +17,8 @@ use rustc_expand::expand::{
     AstFragment, AstFragmentKind, Invocation, InvocationKind, SupportsMacroExpansion,
 };
 use rustc_expand::{MacroRulesMacroExpander, compile_declarative_macro};
+use rustc_hir::StabilityLevel;
+use rustc_hir::attrs::{CfgEntry, StrippedCfgItem};
 use rustc_hir::def::{self, DefKind, Namespace, NonMacroAttrKind};
 use rustc_hir::def_id::{CrateNum, DefId, LocalDefId};
 use rustc_middle::middle::stability;
diff --git a/compiler/rustc_sanitizers/Cargo.toml b/compiler/rustc_sanitizers/Cargo.toml
index 66488bc9625..9069d2c233d 100644
--- a/compiler/rustc_sanitizers/Cargo.toml
+++ b/compiler/rustc_sanitizers/Cargo.toml
@@ -4,9 +4,8 @@ version = "0.0.0"
 edition = "2024"
 
 [dependencies]
+# tidy-alphabetical-start
 bitflags = "2.5.0"
-tracing = "0.1"
-twox-hash = "1.6.3"
 rustc_abi = { path = "../rustc_abi" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_hir = { path = "../rustc_hir" }
@@ -14,3 +13,6 @@ rustc_middle = { path = "../rustc_middle" }
 rustc_span = { path = "../rustc_span" }
 rustc_target = { path = "../rustc_target" }
 rustc_trait_selection = { path = "../rustc_trait_selection" }
+tracing = "0.1"
+twox-hash = "1.6.3"
+# tidy-alphabetical-end
diff --git a/compiler/rustc_session/src/config.rs b/compiler/rustc_session/src/config.rs
index 8f624e0fb2f..cfeadf3c759 100644
--- a/compiler/rustc_session/src/config.rs
+++ b/compiler/rustc_session/src/config.rs
@@ -182,14 +182,7 @@ pub enum InstrumentCoverage {
 pub struct CoverageOptions {
     pub level: CoverageLevel,
 
-    /// `-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,
-
+    /// **(internal test-only flag)**
     /// `-Zcoverage-options=discard-all-spans-in-codegen`: During codegen,
     /// discard all coverage spans as though they were invalid. Needed by
     /// regression tests for #133606, because we don't have an easy way to
diff --git a/compiler/rustc_session/src/options.rs b/compiler/rustc_session/src/options.rs
index 44b35e8921e..880b08d4444 100644
--- a/compiler/rustc_session/src/options.rs
+++ b/compiler/rustc_session/src/options.rs
@@ -755,8 +755,7 @@ mod desc {
     pub(crate) const parse_linker_flavor: &str = ::rustc_target::spec::LinkerFlavorCli::one_of();
     pub(crate) const parse_dump_mono_stats: &str = "`markdown` (default) or `json`";
     pub(crate) const parse_instrument_coverage: &str = parse_bool;
-    pub(crate) const parse_coverage_options: &str =
-        "`block` | `branch` | `condition` | `mcdc` | `no-mir-spans`";
+    pub(crate) const parse_coverage_options: &str = "`block` | `branch` | `condition` | `mcdc`";
     pub(crate) const parse_instrument_xray: &str = "either a boolean (`yes`, `no`, `on`, `off`, etc), or a comma separated list of settings: `always` or `never` (mutually exclusive), `ignore-loops`, `instruction-threshold=N`, `skip-entry`, `skip-exit`";
     pub(crate) const parse_unpretty: &str = "`string` or `string=string`";
     pub(crate) const parse_treat_err_as_bug: &str = "either no value or a non-negative number";
@@ -1460,7 +1459,6 @@ pub mod parse {
                 "branch" => slot.level = CoverageLevel::Branch,
                 "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/session.rs b/compiler/rustc_session/src/session.rs
index e7097ec8327..b94636fea94 100644
--- a/compiler/rustc_session/src/session.rs
+++ b/compiler/rustc_session/src/session.rs
@@ -39,8 +39,8 @@ use rustc_target::spec::{
 use crate::code_stats::CodeStats;
 pub use crate::code_stats::{DataTypeKind, FieldInfo, FieldKind, SizeKind, VariantInfo};
 use crate::config::{
-    self, CoverageLevel, CrateType, DebugInfo, ErrorOutputType, FunctionReturn, Input,
-    InstrumentCoverage, OptLevel, OutFileName, OutputType, RemapPathScopeComponents,
+    self, CoverageLevel, CoverageOptions, CrateType, DebugInfo, ErrorOutputType, FunctionReturn,
+    Input, InstrumentCoverage, OptLevel, OutFileName, OutputType, RemapPathScopeComponents,
     SwitchWithOptPath,
 };
 use crate::filesearch::FileSearch;
@@ -359,14 +359,11 @@ impl Session {
             && self.opts.unstable_opts.coverage_options.level >= CoverageLevel::Mcdc
     }
 
-    /// True if `-Zcoverage-options=no-mir-spans` was passed.
-    pub fn coverage_no_mir_spans(&self) -> bool {
-        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
+    /// Provides direct access to the `CoverageOptions` struct, so that
+    /// individual flags for debugging/testing coverage instrumetation don't
+    /// need separate accessors.
+    pub fn coverage_options(&self) -> &CoverageOptions {
+        &self.opts.unstable_opts.coverage_options
     }
 
     pub fn is_sanitizer_cfi_enabled(&self) -> bool {
diff --git a/compiler/rustc_span/src/hygiene.rs b/compiler/rustc_span/src/hygiene.rs
index 97d1d9c2d2a..19494ffc37e 100644
--- a/compiler/rustc_span/src/hygiene.rs
+++ b/compiler/rustc_span/src/hygiene.rs
@@ -768,7 +768,9 @@ impl SyntaxContext {
     ///
     /// ```rust
     /// #![feature(decl_macro)]
-    /// mod foo { pub fn f() {} } // `f`'s `SyntaxContext` is empty.
+    /// mod foo {
+    ///     pub fn f() {} // `f`'s `SyntaxContext` is empty.
+    /// }
     /// m!(f);
     /// macro m($f:ident) {
     ///     mod bar {
diff --git a/compiler/rustc_symbol_mangling/Cargo.toml b/compiler/rustc_symbol_mangling/Cargo.toml
index 12fe6b719f9..0df9c7682bf 100644
--- a/compiler/rustc_symbol_mangling/Cargo.toml
+++ b/compiler/rustc_symbol_mangling/Cargo.toml
@@ -7,7 +7,6 @@ edition = "2024"
 # tidy-alphabetical-start
 punycode = "0.4.0"
 rustc-demangle = "0.1.21"
-
 rustc_abi = { path = "../rustc_abi" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
diff --git a/compiler/rustc_symbol_mangling/src/legacy.rs b/compiler/rustc_symbol_mangling/src/legacy.rs
index 12d1de46313..aa8292c0504 100644
--- a/compiler/rustc_symbol_mangling/src/legacy.rs
+++ b/compiler/rustc_symbol_mangling/src/legacy.rs
@@ -58,59 +58,57 @@ pub(super) fn mangle<'tcx>(
 
     let hash = get_symbol_hash(tcx, instance, instance_ty, instantiating_crate);
 
-    let mut printer = SymbolPrinter { tcx, path: SymbolPath::new(), keep_within_component: false };
-    printer
-        .print_def_path(
-            def_id,
-            if let ty::InstanceKind::DropGlue(_, _)
-            | ty::InstanceKind::AsyncDropGlueCtorShim(_, _)
-            | ty::InstanceKind::FutureDropPollShim(_, _, _) = instance.def
-            {
-                // Add the name of the dropped type to the symbol name
-                &*instance.args
-            } else if let ty::InstanceKind::AsyncDropGlue(_, ty) = instance.def {
-                let ty::Coroutine(_, cor_args) = ty.kind() else {
-                    bug!();
-                };
-                let drop_ty = cor_args.first().unwrap().expect_ty();
-                tcx.mk_args(&[GenericArg::from(drop_ty)])
-            } else {
-                &[]
-            },
-        )
-        .unwrap();
+    let mut p = SymbolPrinter { tcx, path: SymbolPath::new(), keep_within_component: false };
+    p.print_def_path(
+        def_id,
+        if let ty::InstanceKind::DropGlue(_, _)
+        | ty::InstanceKind::AsyncDropGlueCtorShim(_, _)
+        | ty::InstanceKind::FutureDropPollShim(_, _, _) = instance.def
+        {
+            // Add the name of the dropped type to the symbol name
+            &*instance.args
+        } else if let ty::InstanceKind::AsyncDropGlue(_, ty) = instance.def {
+            let ty::Coroutine(_, cor_args) = ty.kind() else {
+                bug!();
+            };
+            let drop_ty = cor_args.first().unwrap().expect_ty();
+            tcx.mk_args(&[GenericArg::from(drop_ty)])
+        } else {
+            &[]
+        },
+    )
+    .unwrap();
 
     match instance.def {
         ty::InstanceKind::ThreadLocalShim(..) => {
-            printer.write_str("{{tls-shim}}").unwrap();
+            p.write_str("{{tls-shim}}").unwrap();
         }
         ty::InstanceKind::VTableShim(..) => {
-            printer.write_str("{{vtable-shim}}").unwrap();
+            p.write_str("{{vtable-shim}}").unwrap();
         }
         ty::InstanceKind::ReifyShim(_, reason) => {
-            printer.write_str("{{reify-shim").unwrap();
+            p.write_str("{{reify-shim").unwrap();
             match reason {
-                Some(ReifyReason::FnPtr) => printer.write_str("-fnptr").unwrap(),
-                Some(ReifyReason::Vtable) => printer.write_str("-vtable").unwrap(),
+                Some(ReifyReason::FnPtr) => p.write_str("-fnptr").unwrap(),
+                Some(ReifyReason::Vtable) => p.write_str("-vtable").unwrap(),
                 None => (),
             }
-            printer.write_str("}}").unwrap();
+            p.write_str("}}").unwrap();
         }
         // FIXME(async_closures): This shouldn't be needed when we fix
         // `Instance::ty`/`Instance::def_id`.
         ty::InstanceKind::ConstructCoroutineInClosureShim { receiver_by_ref, .. } => {
-            printer
-                .write_str(if receiver_by_ref { "{{by-move-shim}}" } else { "{{by-ref-shim}}" })
+            p.write_str(if receiver_by_ref { "{{by-move-shim}}" } else { "{{by-ref-shim}}" })
                 .unwrap();
         }
         _ => {}
     }
 
     if let ty::InstanceKind::FutureDropPollShim(..) = instance.def {
-        let _ = printer.write_str("{{drop-shim}}");
+        let _ = p.write_str("{{drop-shim}}");
     }
 
-    printer.path.finish(hash)
+    p.path.finish(hash)
 }
 
 fn get_symbol_hash<'tcx>(
@@ -236,7 +234,7 @@ impl<'tcx> Printer<'tcx> for SymbolPrinter<'tcx> {
     }
 
     fn print_region(&mut self, _region: ty::Region<'_>) -> Result<(), PrintError> {
-        Ok(())
+        unreachable!(); // because `<Self As PrettyPrinter>::should_print_region` returns false
     }
 
     fn print_type(&mut self, ty: Ty<'tcx>) -> Result<(), PrintError> {
@@ -334,7 +332,6 @@ impl<'tcx> Printer<'tcx> for SymbolPrinter<'tcx> {
     fn path_append_impl(
         &mut self,
         print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
-        _disambiguated_data: &DisambiguatedDefPathData,
         self_ty: Ty<'tcx>,
         trait_ref: Option<ty::TraitRef<'tcx>>,
     ) -> Result<(), PrintError> {
@@ -460,6 +457,8 @@ impl<'tcx> PrettyPrinter<'tcx> for SymbolPrinter<'tcx> {
     fn should_print_region(&self, _region: ty::Region<'_>) -> bool {
         false
     }
+
+    // Identical to `PrettyPrinter::comma_sep` except there is no space after each comma.
     fn comma_sep<T>(&mut self, mut elems: impl Iterator<Item = T>) -> Result<(), PrintError>
     where
         T: Print<'tcx, Self>,
diff --git a/compiler/rustc_symbol_mangling/src/v0.rs b/compiler/rustc_symbol_mangling/src/v0.rs
index fe0f8e6113e..c2458ae814b 100644
--- a/compiler/rustc_symbol_mangling/src/v0.rs
+++ b/compiler/rustc_symbol_mangling/src/v0.rs
@@ -33,7 +33,7 @@ pub(super) fn mangle<'tcx>(
     let args = tcx.normalize_erasing_regions(ty::TypingEnv::fully_monomorphized(), instance.args);
 
     let prefix = "_R";
-    let mut cx: SymbolMangler<'_> = SymbolMangler {
+    let mut p: SymbolMangler<'_> = SymbolMangler {
         tcx,
         start_offset: prefix.len(),
         is_exportable,
@@ -69,16 +69,16 @@ pub(super) fn mangle<'tcx>(
             bug!();
         };
         let drop_ty = cor_args.first().unwrap().expect_ty();
-        cx.print_def_path(def_id, tcx.mk_args(&[GenericArg::from(drop_ty)])).unwrap()
+        p.print_def_path(def_id, tcx.mk_args(&[GenericArg::from(drop_ty)])).unwrap()
     } else if let Some(shim_kind) = shim_kind {
-        cx.path_append_ns(|cx| cx.print_def_path(def_id, args), 'S', 0, shim_kind).unwrap()
+        p.path_append_ns(|p| p.print_def_path(def_id, args), 'S', 0, shim_kind).unwrap()
     } else {
-        cx.print_def_path(def_id, args).unwrap()
+        p.print_def_path(def_id, args).unwrap()
     };
     if let Some(instantiating_crate) = instantiating_crate {
-        cx.print_def_path(instantiating_crate.as_def_id(), &[]).unwrap();
+        p.print_def_path(instantiating_crate.as_def_id(), &[]).unwrap();
     }
-    std::mem::take(&mut cx.out)
+    std::mem::take(&mut p.out)
 }
 
 pub fn mangle_internal_symbol<'tcx>(tcx: TyCtxt<'tcx>, item_name: &str) -> String {
@@ -88,7 +88,7 @@ pub fn mangle_internal_symbol<'tcx>(tcx: TyCtxt<'tcx>, item_name: &str) -> Strin
     }
 
     let prefix = "_R";
-    let mut cx: SymbolMangler<'_> = SymbolMangler {
+    let mut p: SymbolMangler<'_> = SymbolMangler {
         tcx,
         start_offset: prefix.len(),
         is_exportable: false,
@@ -99,10 +99,10 @@ pub fn mangle_internal_symbol<'tcx>(tcx: TyCtxt<'tcx>, item_name: &str) -> Strin
         out: String::from(prefix),
     };
 
-    cx.path_append_ns(
-        |cx| {
-            cx.push("C");
-            cx.push_disambiguator({
+    p.path_append_ns(
+        |p| {
+            p.push("C");
+            p.push_disambiguator({
                 let mut hasher = StableHasher::new();
                 // Incorporate the rustc version to ensure #[rustc_std_internal_symbol] functions
                 // get a different symbol name depending on the rustc version.
@@ -114,7 +114,7 @@ pub fn mangle_internal_symbol<'tcx>(tcx: TyCtxt<'tcx>, item_name: &str) -> Strin
                 let hash: Hash64 = hasher.finish();
                 hash.as_u64()
             });
-            cx.push_ident("__rustc");
+            p.push_ident("__rustc");
             Ok(())
         },
         'v',
@@ -123,7 +123,7 @@ pub fn mangle_internal_symbol<'tcx>(tcx: TyCtxt<'tcx>, item_name: &str) -> Strin
     )
     .unwrap();
 
-    std::mem::take(&mut cx.out)
+    std::mem::take(&mut p.out)
 }
 
 pub(super) fn mangle_typeid_for_trait_ref<'tcx>(
@@ -131,7 +131,7 @@ pub(super) fn mangle_typeid_for_trait_ref<'tcx>(
     trait_ref: ty::ExistentialTraitRef<'tcx>,
 ) -> String {
     // FIXME(flip1995): See comment in `mangle_typeid_for_fnabi`.
-    let mut cx = SymbolMangler {
+    let mut p = SymbolMangler {
         tcx,
         start_offset: 0,
         is_exportable: false,
@@ -141,8 +141,8 @@ pub(super) fn mangle_typeid_for_trait_ref<'tcx>(
         binders: vec![],
         out: String::new(),
     };
-    cx.print_def_path(trait_ref.def_id, &[]).unwrap();
-    std::mem::take(&mut cx.out)
+    p.print_def_path(trait_ref.def_id, &[]).unwrap();
+    std::mem::take(&mut p.out)
 }
 
 struct BinderLevel {
@@ -368,7 +368,7 @@ impl<'tcx> Printer<'tcx> for SymbolMangler<'tcx> {
             self.path_generic_args(
                 |this| {
                     this.path_append_ns(
-                        |cx| cx.print_def_path(parent_def_id, &[]),
+                        |p| p.print_def_path(parent_def_id, &[]),
                         'I',
                         key.disambiguated_data.disambiguator as u64,
                         "",
@@ -425,7 +425,6 @@ impl<'tcx> Printer<'tcx> for SymbolMangler<'tcx> {
             ty::Bool => "b",
             ty::Char => "c",
             ty::Str => "e",
-            ty::Tuple(_) if ty.is_unit() => "u",
             ty::Int(IntTy::I8) => "a",
             ty::Int(IntTy::I16) => "s",
             ty::Int(IntTy::I32) => "l",
@@ -444,12 +443,12 @@ impl<'tcx> Printer<'tcx> for SymbolMangler<'tcx> {
             ty::Float(FloatTy::F128) => "C4f128",
             ty::Never => "z",
 
+            ty::Tuple(_) if ty.is_unit() => "u",
+
             // Should only be encountered within the identity-substituted
             // impl header of an item nested within an impl item.
             ty::Param(_) => "p",
 
-            ty::Bound(..) | ty::Placeholder(_) | ty::Infer(_) | ty::Error(_) => bug!(),
-
             _ => "",
         };
         if !basic_type.is_empty() {
@@ -468,11 +467,9 @@ impl<'tcx> Printer<'tcx> for SymbolMangler<'tcx> {
                 unreachable!()
             }
             ty::Tuple(_) if ty.is_unit() => unreachable!(),
+            ty::Param(_) => unreachable!(),
 
-            // Placeholders, also handled as part of basic types.
-            ty::Param(_) | ty::Bound(..) | ty::Placeholder(_) | ty::Infer(_) | ty::Error(_) => {
-                unreachable!()
-            }
+            ty::Bound(..) | ty::Placeholder(_) | ty::Infer(_) | ty::Error(_) => bug!(),
 
             ty::Ref(r, ty, mutbl) => {
                 self.push(match mutbl {
@@ -542,31 +539,31 @@ impl<'tcx> Printer<'tcx> for SymbolMangler<'tcx> {
             ty::FnPtr(sig_tys, hdr) => {
                 let sig = sig_tys.with(hdr);
                 self.push("F");
-                self.wrap_binder(&sig, |cx, sig| {
+                self.wrap_binder(&sig, |p, sig| {
                     if sig.safety.is_unsafe() {
-                        cx.push("U");
+                        p.push("U");
                     }
                     match sig.abi {
                         ExternAbi::Rust => {}
-                        ExternAbi::C { unwind: false } => cx.push("KC"),
+                        ExternAbi::C { unwind: false } => p.push("KC"),
                         abi => {
-                            cx.push("K");
+                            p.push("K");
                             let name = abi.as_str();
                             if name.contains('-') {
-                                cx.push_ident(&name.replace('-', "_"));
+                                p.push_ident(&name.replace('-', "_"));
                             } else {
-                                cx.push_ident(name);
+                                p.push_ident(name);
                             }
                         }
                     }
                     for &ty in sig.inputs() {
-                        ty.print(cx)?;
+                        ty.print(p)?;
                     }
                     if sig.c_variadic {
-                        cx.push("v");
+                        p.push("v");
                     }
-                    cx.push("E");
-                    sig.output().print(cx)
+                    p.push("E");
+                    sig.output().print(p)
                 })?;
             }
 
@@ -623,7 +620,7 @@ impl<'tcx> Printer<'tcx> for SymbolMangler<'tcx> {
         // [<Trait> [{<Projection>}]] [{<Auto>}]
         // Since any predicates after the first one shouldn't change the binders,
         // just put them all in the binders of the first.
-        self.wrap_binder(&predicates[0], |cx, _| {
+        self.wrap_binder(&predicates[0], |p, _| {
             for predicate in predicates.iter() {
                 // It would be nice to be able to validate bound vars here, but
                 // projections can actually include bound vars from super traits
@@ -632,21 +629,21 @@ impl<'tcx> Printer<'tcx> for SymbolMangler<'tcx> {
                 match predicate.as_ref().skip_binder() {
                     ty::ExistentialPredicate::Trait(trait_ref) => {
                         // Use a type that can't appear in defaults of type parameters.
-                        let dummy_self = Ty::new_fresh(cx.tcx, 0);
-                        let trait_ref = trait_ref.with_self_ty(cx.tcx, dummy_self);
-                        cx.print_def_path(trait_ref.def_id, trait_ref.args)?;
+                        let dummy_self = Ty::new_fresh(p.tcx, 0);
+                        let trait_ref = trait_ref.with_self_ty(p.tcx, dummy_self);
+                        p.print_def_path(trait_ref.def_id, trait_ref.args)?;
                     }
                     ty::ExistentialPredicate::Projection(projection) => {
-                        let name = cx.tcx.associated_item(projection.def_id).name();
-                        cx.push("p");
-                        cx.push_ident(name.as_str());
+                        let name = p.tcx.associated_item(projection.def_id).name();
+                        p.push("p");
+                        p.push_ident(name.as_str());
                         match projection.term.kind() {
-                            ty::TermKind::Ty(ty) => ty.print(cx),
-                            ty::TermKind::Const(c) => c.print(cx),
+                            ty::TermKind::Ty(ty) => ty.print(p),
+                            ty::TermKind::Const(c) => c.print(p),
                         }?;
                     }
                     ty::ExistentialPredicate::AutoTrait(def_id) => {
-                        cx.print_def_path(*def_id, &[])?;
+                        p.print_def_path(*def_id, &[])?;
                     }
                 }
             }
@@ -849,7 +846,6 @@ impl<'tcx> Printer<'tcx> for SymbolMangler<'tcx> {
     fn path_append_impl(
         &mut self,
         _: impl FnOnce(&mut Self) -> Result<(), PrintError>,
-        _: &DisambiguatedDefPathData,
         _: Ty<'tcx>,
         _: Option<ty::TraitRef<'tcx>>,
     ) -> Result<(), PrintError> {
diff --git a/compiler/rustc_target/src/spec/targets/hexagon_unknown_linux_musl.rs b/compiler/rustc_target/src/spec/targets/hexagon_unknown_linux_musl.rs
index f7416a7e0fd..1abf0537cda 100644
--- a/compiler/rustc_target/src/spec/targets/hexagon_unknown_linux_musl.rs
+++ b/compiler/rustc_target/src/spec/targets/hexagon_unknown_linux_musl.rs
@@ -7,7 +7,6 @@ pub(crate) fn target() -> Target {
     // FIXME: HVX length defaults are per-CPU
     base.features = "-small-data,+hvx-length128b".into();
 
-    base.crt_static_default = false;
     base.has_rpath = true;
     base.linker_flavor = LinkerFlavor::Unix(Cc::Yes);
 
diff --git a/compiler/rustc_target/src/spec/targets/mips64_unknown_linux_muslabi64.rs b/compiler/rustc_target/src/spec/targets/mips64_unknown_linux_muslabi64.rs
index f95ce756354..94ecd3590a9 100644
--- a/compiler/rustc_target/src/spec/targets/mips64_unknown_linux_muslabi64.rs
+++ b/compiler/rustc_target/src/spec/targets/mips64_unknown_linux_muslabi64.rs
@@ -23,8 +23,6 @@ pub(crate) fn target() -> Target {
             abi: "abi64".into(),
             endian: Endian::Big,
             mcount: "_mcount".into(),
-            // FIXME(compiler-team#422): musl targets should be dynamically linked by default.
-            crt_static_default: true,
             llvm_abiname: "n64".into(),
             ..base
         },
diff --git a/compiler/rustc_target/src/spec/targets/powerpc64_unknown_linux_musl.rs b/compiler/rustc_target/src/spec/targets/powerpc64_unknown_linux_musl.rs
index 4dc76f0936c..482b6790dad 100644
--- a/compiler/rustc_target/src/spec/targets/powerpc64_unknown_linux_musl.rs
+++ b/compiler/rustc_target/src/spec/targets/powerpc64_unknown_linux_musl.rs
@@ -10,8 +10,6 @@ pub(crate) fn target() -> Target {
     base.add_pre_link_args(LinkerFlavor::Gnu(Cc::Yes, Lld::No), &["-m64"]);
     base.max_atomic_width = Some(64);
     base.stack_probes = StackProbeType::Inline;
-    // FIXME(compiler-team#422): musl targets should be dynamically linked by default.
-    base.crt_static_default = true;
     base.abi = "elfv2".into();
     base.llvm_abiname = "elfv2".into();
 
diff --git a/compiler/rustc_target/src/spec/targets/powerpc_unknown_linux_musl.rs b/compiler/rustc_target/src/spec/targets/powerpc_unknown_linux_musl.rs
index 316b62d941b..f39142d0101 100644
--- a/compiler/rustc_target/src/spec/targets/powerpc_unknown_linux_musl.rs
+++ b/compiler/rustc_target/src/spec/targets/powerpc_unknown_linux_musl.rs
@@ -9,8 +9,6 @@ pub(crate) fn target() -> Target {
     base.add_pre_link_args(LinkerFlavor::Gnu(Cc::Yes, Lld::No), &["-m32"]);
     base.max_atomic_width = Some(32);
     base.stack_probes = StackProbeType::Inline;
-    // FIXME(compiler-team#422): musl targets should be dynamically linked by default.
-    base.crt_static_default = true;
 
     Target {
         llvm_target: "powerpc-unknown-linux-musl".into(),
diff --git a/compiler/rustc_target/src/spec/targets/powerpc_unknown_linux_muslspe.rs b/compiler/rustc_target/src/spec/targets/powerpc_unknown_linux_muslspe.rs
index 30d0d9cb60a..8ddb45483b3 100644
--- a/compiler/rustc_target/src/spec/targets/powerpc_unknown_linux_muslspe.rs
+++ b/compiler/rustc_target/src/spec/targets/powerpc_unknown_linux_muslspe.rs
@@ -9,8 +9,6 @@ pub(crate) fn target() -> Target {
     base.add_pre_link_args(LinkerFlavor::Gnu(Cc::Yes, Lld::No), &["-mspe"]);
     base.max_atomic_width = Some(32);
     base.stack_probes = StackProbeType::Inline;
-    // FIXME(compiler-team#422): musl targets should be dynamically linked by default.
-    base.crt_static_default = true;
 
     Target {
         llvm_target: "powerpc-unknown-linux-muslspe".into(),
diff --git a/compiler/rustc_target/src/spec/targets/riscv32gc_unknown_linux_musl.rs b/compiler/rustc_target/src/spec/targets/riscv32gc_unknown_linux_musl.rs
index 938b39b10c6..eb592cca1c8 100644
--- a/compiler/rustc_target/src/spec/targets/riscv32gc_unknown_linux_musl.rs
+++ b/compiler/rustc_target/src/spec/targets/riscv32gc_unknown_linux_musl.rs
@@ -23,8 +23,6 @@ pub(crate) fn target() -> Target {
             llvm_abiname: "ilp32d".into(),
             max_atomic_width: Some(32),
             supported_split_debuginfo: Cow::Borrowed(&[SplitDebuginfo::Off]),
-            // FIXME(compiler-team#422): musl targets should be dynamically linked by default.
-            crt_static_default: true,
             ..base::linux_musl::opts()
         },
     }
diff --git a/compiler/rustc_target/src/spec/targets/s390x_unknown_linux_musl.rs b/compiler/rustc_target/src/spec/targets/s390x_unknown_linux_musl.rs
index e9522ac760e..0cdbb626739 100644
--- a/compiler/rustc_target/src/spec/targets/s390x_unknown_linux_musl.rs
+++ b/compiler/rustc_target/src/spec/targets/s390x_unknown_linux_musl.rs
@@ -13,8 +13,6 @@ pub(crate) fn target() -> Target {
     base.stack_probes = StackProbeType::Inline;
     base.supported_sanitizers =
         SanitizerSet::ADDRESS | SanitizerSet::LEAK | SanitizerSet::MEMORY | SanitizerSet::THREAD;
-    // FIXME(compiler-team#422): musl targets should be dynamically linked by default.
-    base.crt_static_default = true;
 
     Target {
         llvm_target: "s390x-unknown-linux-musl".into(),
diff --git a/compiler/rustc_target/src/spec/targets/thumbv7neon_unknown_linux_musleabihf.rs b/compiler/rustc_target/src/spec/targets/thumbv7neon_unknown_linux_musleabihf.rs
index 81c502bfead..e026595439f 100644
--- a/compiler/rustc_target/src/spec/targets/thumbv7neon_unknown_linux_musleabihf.rs
+++ b/compiler/rustc_target/src/spec/targets/thumbv7neon_unknown_linux_musleabihf.rs
@@ -27,8 +27,6 @@ pub(crate) fn target() -> Target {
             features: "+v7,+thumb-mode,+thumb2,+vfp3,+neon".into(),
             max_atomic_width: Some(64),
             mcount: "\u{1}mcount".into(),
-            // FIXME(compiler-team#422): musl targets should be dynamically linked by default.
-            crt_static_default: true,
             ..base::linux_musl::opts()
         },
     }
diff --git a/compiler/rustc_thread_pool/Cargo.toml b/compiler/rustc_thread_pool/Cargo.toml
index b0194834264..c92984470b7 100644
--- a/compiler/rustc_thread_pool/Cargo.toml
+++ b/compiler/rustc_thread_pool/Cargo.toml
@@ -7,7 +7,6 @@ authors = [
 ]
 description = "Core APIs for Rayon - fork for rustc"
 license = "MIT OR Apache-2.0"
-rust-version = "1.63"
 edition = "2021"
 readme = "README.md"
 keywords = ["parallel", "thread", "concurrency", "join", "performance"]
diff --git a/compiler/rustc_thread_pool/src/scope/mod.rs b/compiler/rustc_thread_pool/src/scope/mod.rs
index 38230383965..677009a9bc3 100644
--- a/compiler/rustc_thread_pool/src/scope/mod.rs
+++ b/compiler/rustc_thread_pool/src/scope/mod.rs
@@ -501,9 +501,9 @@ impl<'scope> Scope<'scope> {
     /// let mut value_c = None;
     /// rayon::scope(|s| {
     ///     s.spawn(|s1| {
-    ///           // ^ this is the same scope as `s`; this handle `s1`
-    ///           //   is intended for use by the spawned task,
-    ///           //   since scope handles cannot cross thread boundaries.
+    ///         //   ^ this is the same scope as `s`; this handle `s1`
+    ///         //     is intended for use by the spawned task,
+    ///         //     since scope handles cannot cross thread boundaries.
     ///
     ///         value_a = Some(22);
     ///
diff --git a/compiler/rustc_thread_pool/src/sleep/mod.rs b/compiler/rustc_thread_pool/src/sleep/mod.rs
index 31bf7184b42..aa666609214 100644
--- a/compiler/rustc_thread_pool/src/sleep/mod.rs
+++ b/compiler/rustc_thread_pool/src/sleep/mod.rs
@@ -44,7 +44,7 @@ impl SleepData {
 /// jobs are published, and it either blocks threads or wakes them in response to these
 /// events. See the [`README.md`] in this module for more details.
 ///
-/// [`README.md`] README.md
+/// [`README.md`]: README.md
 pub(super) struct Sleep {
     /// One "sleep state" per worker. Used to track if a worker is sleeping and to have
     /// them block.
diff --git a/compiler/rustc_trait_selection/Cargo.toml b/compiler/rustc_trait_selection/Cargo.toml
index 62f1d908601..1071105522d 100644
--- a/compiler/rustc_trait_selection/Cargo.toml
+++ b/compiler/rustc_trait_selection/Cargo.toml
@@ -8,7 +8,6 @@ edition = "2024"
 itertools = "0.12"
 rustc_abi = { path = "../rustc_abi" }
 rustc_ast = { path = "../rustc_ast" }
-rustc_attr_data_structures = {path = "../rustc_attr_data_structures"}
 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 b9acadc406e..ed8229154a9 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
@@ -235,28 +235,29 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
             }
 
             fn print_region(&mut self, _region: ty::Region<'_>) -> Result<(), PrintError> {
-                Err(fmt::Error)
+                unreachable!(); // because `path_generic_args` ignores the `GenericArgs`
             }
 
             fn print_type(&mut self, _ty: Ty<'tcx>) -> Result<(), PrintError> {
-                Err(fmt::Error)
+                unreachable!(); // because `path_generic_args` ignores the `GenericArgs`
             }
 
             fn print_dyn_existential(
                 &mut self,
                 _predicates: &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
             ) -> Result<(), PrintError> {
-                Err(fmt::Error)
+                unreachable!(); // because `path_generic_args` ignores the `GenericArgs`
             }
 
             fn print_const(&mut self, _ct: ty::Const<'tcx>) -> Result<(), PrintError> {
-                Err(fmt::Error)
+                unreachable!(); // because `path_generic_args` ignores the `GenericArgs`
             }
 
             fn path_crate(&mut self, cnum: CrateNum) -> Result<(), PrintError> {
                 self.segments = vec![self.tcx.crate_name(cnum)];
                 Ok(())
             }
+
             fn path_qualified(
                 &mut self,
                 _self_ty: Ty<'tcx>,
@@ -268,12 +269,12 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
             fn path_append_impl(
                 &mut self,
                 _print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
-                _disambiguated_data: &DisambiguatedDefPathData,
                 _self_ty: Ty<'tcx>,
                 _trait_ref: Option<ty::TraitRef<'tcx>>,
             ) -> Result<(), PrintError> {
                 Err(fmt::Error)
             }
+
             fn path_append(
                 &mut self,
                 print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
@@ -283,6 +284,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                 self.segments.push(disambiguated_data.as_sym(true));
                 Ok(())
             }
+
             fn path_generic_args(
                 &mut self,
                 print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
@@ -298,8 +300,8 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
             // let _ = [{struct Foo; Foo}, {struct Foo; Foo}];
             if did1.krate != did2.krate {
                 let abs_path = |def_id| {
-                    let mut printer = AbsolutePathPrinter { tcx: self.tcx, segments: vec![] };
-                    printer.print_def_path(def_id, &[]).map(|_| printer.segments)
+                    let mut p = AbsolutePathPrinter { tcx: self.tcx, segments: vec![] };
+                    p.print_def_path(def_id, &[]).map(|_| p.segments)
                 };
 
                 // We compare strings because DefPath can be different
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 022d549a9df..966f117a1bf 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
@@ -244,7 +244,7 @@ impl<'a, 'tcx> TypeFolder<TyCtxt<'tcx>> for ClosureEraser<'a, 'tcx> {
 }
 
 fn fmt_printer<'a, 'tcx>(infcx: &'a InferCtxt<'tcx>, ns: Namespace) -> FmtPrinter<'a, 'tcx> {
-    let mut printer = FmtPrinter::new(infcx.tcx, ns);
+    let mut p = FmtPrinter::new(infcx.tcx, ns);
     let ty_getter = move |ty_vid| {
         if infcx.probe_ty_var(ty_vid).is_ok() {
             warn!("resolved ty var in error message");
@@ -270,11 +270,11 @@ fn fmt_printer<'a, 'tcx>(infcx: &'a InferCtxt<'tcx>, ns: Namespace) -> FmtPrinte
             None
         }
     };
-    printer.ty_infer_name_resolver = Some(Box::new(ty_getter));
+    p.ty_infer_name_resolver = Some(Box::new(ty_getter));
     let const_getter =
         move |ct_vid| Some(infcx.tcx.item_name(infcx.const_var_origin(ct_vid)?.param_def_id?));
-    printer.const_infer_name_resolver = Some(Box::new(const_getter));
-    printer
+    p.const_infer_name_resolver = Some(Box::new(const_getter));
+    p
 }
 
 fn ty_to_string<'tcx>(
@@ -282,7 +282,7 @@ fn ty_to_string<'tcx>(
     ty: Ty<'tcx>,
     called_method_def_id: Option<DefId>,
 ) -> String {
-    let mut printer = fmt_printer(infcx, Namespace::TypeNS);
+    let mut p = fmt_printer(infcx, Namespace::TypeNS);
     let ty = infcx.resolve_vars_if_possible(ty);
     // We use `fn` ptr syntax for closures, but this only works when the closure does not capture
     // anything. We also remove all type parameters that are fully known to the type system.
@@ -292,8 +292,8 @@ fn ty_to_string<'tcx>(
         // We don't want the regular output for `fn`s because it includes its path in
         // invalid pseudo-syntax, we want the `fn`-pointer output instead.
         (ty::FnDef(..), _) => {
-            ty.fn_sig(infcx.tcx).print(&mut printer).unwrap();
-            printer.into_buffer()
+            ty.fn_sig(infcx.tcx).print(&mut p).unwrap();
+            p.into_buffer()
         }
         (_, Some(def_id))
             if ty.is_ty_or_numeric_infer()
@@ -303,8 +303,8 @@ fn ty_to_string<'tcx>(
         }
         _ if ty.is_ty_or_numeric_infer() => "/* Type */".to_string(),
         _ => {
-            ty.print(&mut printer).unwrap();
-            printer.into_buffer()
+            ty.print(&mut p).unwrap();
+            p.into_buffer()
         }
     }
 }
@@ -561,21 +561,20 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                 {
                     "Vec<_>".to_string()
                 } else {
-                    let mut printer = fmt_printer(self, Namespace::TypeNS);
-                    printer
-                        .comma_sep(generic_args.iter().copied().map(|arg| {
-                            if arg.is_suggestable(self.tcx, true) {
-                                return arg;
-                            }
+                    let mut p = fmt_printer(self, Namespace::TypeNS);
+                    p.comma_sep(generic_args.iter().copied().map(|arg| {
+                        if arg.is_suggestable(self.tcx, true) {
+                            return arg;
+                        }
 
-                            match arg.kind() {
-                                GenericArgKind::Lifetime(_) => bug!("unexpected lifetime"),
-                                GenericArgKind::Type(_) => self.next_ty_var(DUMMY_SP).into(),
-                                GenericArgKind::Const(_) => self.next_const_var(DUMMY_SP).into(),
-                            }
-                        }))
-                        .unwrap();
-                    printer.into_buffer()
+                        match arg.kind() {
+                            GenericArgKind::Lifetime(_) => bug!("unexpected lifetime"),
+                            GenericArgKind::Type(_) => self.next_ty_var(DUMMY_SP).into(),
+                            GenericArgKind::Const(_) => self.next_const_var(DUMMY_SP).into(),
+                        }
+                    }))
+                    .unwrap();
+                    p.into_buffer()
                 };
 
                 if !have_turbofish {
@@ -589,9 +588,9 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
             InferSourceKind::FullyQualifiedMethodCall { receiver, successor, args, def_id } => {
                 let placeholder = Some(self.next_ty_var(DUMMY_SP));
                 if let Some(args) = args.make_suggestable(self.infcx.tcx, true, placeholder) {
-                    let mut printer = fmt_printer(self, Namespace::ValueNS);
-                    printer.print_def_path(def_id, args).unwrap();
-                    let def_path = printer.into_buffer();
+                    let mut p = fmt_printer(self, Namespace::ValueNS);
+                    p.print_def_path(def_id, args).unwrap();
+                    let def_path = p.into_buffer();
 
                     // We only care about whether we have to add `&` or `&mut ` for now.
                     // This is the case if the last adjustment is a borrow and the
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 64fc365c44a..373b756dcdb 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
@@ -47,11 +47,11 @@ 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, self.ns);
-        printer.region_highlight_mode = self.highlight;
+        let mut p = ty::print::FmtPrinter::new(self.tcx, self.ns);
+        p.region_highlight_mode = self.highlight;
 
-        self.value.print(&mut printer)?;
-        f.write_str(&printer.into_buffer())
+        self.value.print(&mut p)?;
+        f.write_str(&p.into_buffer())
     }
 }
 
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/note_and_explain.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/note_and_explain.rs
index db35c988bf7..129d0963a75 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/note_and_explain.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/note_and_explain.rs
@@ -1,8 +1,9 @@
-use rustc_attr_data_structures::{AttributeKind, find_attr};
 use rustc_errors::Applicability::{MachineApplicable, MaybeIncorrect};
 use rustc_errors::{Diag, MultiSpan, pluralize};
 use rustc_hir as hir;
+use rustc_hir::attrs::AttributeKind;
 use rustc_hir::def::DefKind;
+use rustc_hir::find_attr;
 use rustc_middle::traits::{ObligationCause, ObligationCauseCode};
 use rustc_middle::ty::error::{ExpectedFound, TypeError};
 use rustc_middle::ty::fast_reject::DeepRejectCtxt;
@@ -945,8 +946,8 @@ fn foo(&self) -> Self::T { String::new() }
     }
 
     pub fn format_generic_args(&self, args: &[ty::GenericArg<'tcx>]) -> String {
-        FmtPrinter::print_string(self.tcx, hir::def::Namespace::TypeNS, |cx| {
-            cx.path_generic_args(|_| Ok(()), args)
+        FmtPrinter::print_string(self.tcx, hir::def::Namespace::TypeNS, |p| {
+            p.path_generic_args(|_| Ok(()), args)
         })
         .expect("could not write to `String`.")
     }
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 f3441a8d72a..7369134420c 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/region.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/region.rs
@@ -581,7 +581,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         let trait_args = trait_ref
             .instantiate_identity()
             // Replace the explicit self type with `Self` for better suggestion rendering
-            .with_self_ty(self.tcx, Ty::new_param(self.tcx, 0, kw::SelfUpper))
+            .with_replaced_self_ty(self.tcx, Ty::new_param(self.tcx, 0, kw::SelfUpper))
             .args;
         let trait_item_args = ty::GenericArgs::identity_for_item(self.tcx, impl_item_def_id)
             .rebase_onto(self.tcx, impl_def_id, trait_args);
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 1ac309da101..a9e346a5cdb 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
@@ -512,7 +512,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                             && self.fallback_has_occurred
                         {
                             let predicate = leaf_trait_predicate.map_bound(|trait_pred| {
-                                trait_pred.with_self_ty(self.tcx, tcx.types.unit)
+                                trait_pred.with_replaced_self_ty(self.tcx, tcx.types.unit)
                             });
                             let unit_obligation = obligation.with(tcx, predicate);
                             if self.predicate_may_hold(&unit_obligation) {
@@ -2364,8 +2364,8 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         param_env: ty::ParamEnv<'tcx>,
         trait_ref_and_ty: ty::Binder<'tcx, (ty::TraitPredicate<'tcx>, Ty<'tcx>)>,
     ) -> PredicateObligation<'tcx> {
-        let trait_pred =
-            trait_ref_and_ty.map_bound(|(tr, new_self_ty)| tr.with_self_ty(self.tcx, new_self_ty));
+        let trait_pred = trait_ref_and_ty
+            .map_bound(|(tr, new_self_ty)| tr.with_replaced_self_ty(self.tcx, new_self_ty));
 
         Obligation::new(self.tcx, ObligationCause::dummy(), param_env, trait_pred)
     }
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 d929ecf68bf..4f1f5c330e5 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/traits/overflow.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/overflow.rs
@@ -66,10 +66,10 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
             if s.len() > 50 {
                 // We don't need to save the type to a file, we will be talking about this type already
                 // in a separate note when we explain the obligation, so it will be available that way.
-                let mut cx: FmtPrinter<'_, '_> =
+                let mut p: FmtPrinter<'_, '_> =
                     FmtPrinter::new_with_limit(tcx, Namespace::TypeNS, rustc_session::Limit(6));
-                value.print(&mut cx).unwrap();
-                cx.into_buffer()
+                value.print(&mut p).unwrap();
+                p.into_buffer()
             } else {
                 s
             }
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 c182fd99b17..718cff6d135 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
@@ -3942,7 +3942,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
             if let hir::Expr { kind: hir::ExprKind::MethodCall(_, rcvr, _, _), .. } = expr
                 && let Some(ty) = typeck_results.node_type_opt(rcvr.hir_id)
                 && let Some(failed_pred) = failed_pred.as_trait_clause()
-                && let pred = failed_pred.map_bound(|pred| pred.with_self_ty(tcx, ty))
+                && let pred = failed_pred.map_bound(|pred| pred.with_replaced_self_ty(tcx, ty))
                 && self.predicate_must_hold_modulo_regions(&Obligation::misc(
                     tcx, expr.span, body_id, param_env, pred,
                 ))
@@ -4624,9 +4624,10 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         let Some(root_pred) = root_obligation.predicate.as_trait_clause() else { return };
 
         let trait_ref = root_pred.map_bound(|root_pred| {
-            root_pred
-                .trait_ref
-                .with_self_ty(self.tcx, Ty::new_tup(self.tcx, &[root_pred.trait_ref.self_ty()]))
+            root_pred.trait_ref.with_replaced_self_ty(
+                self.tcx,
+                Ty::new_tup(self.tcx, &[root_pred.trait_ref.self_ty()]),
+            )
         });
 
         let obligation =
diff --git a/compiler/rustc_trait_selection/src/solve/delegate.rs b/compiler/rustc_trait_selection/src/solve/delegate.rs
index 7426504e139..e6a2761db5a 100644
--- a/compiler/rustc_trait_selection/src/solve/delegate.rs
+++ b/compiler/rustc_trait_selection/src/solve/delegate.rs
@@ -135,6 +135,13 @@ impl<'tcx> rustc_next_trait_solver::delegate::SolverDelegate for SolverDelegate<
                     None
                 }
             }
+            ty::PredicateKind::Clause(ty::ClauseKind::ConstArgHasType(ct, _)) => {
+                if self.shallow_resolve_const(ct).is_ct_infer() {
+                    Some(Certainty::AMBIGUOUS)
+                } else {
+                    None
+                }
+            }
             ty::PredicateKind::Clause(ty::ClauseKind::WellFormed(arg)) => {
                 let arg = self.shallow_resolve_term(arg);
                 if arg.is_trivially_wf(self.tcx) {
@@ -205,7 +212,6 @@ impl<'tcx> rustc_next_trait_solver::delegate::SolverDelegate for SolverDelegate<
         let region_assumptions = self.0.inner.borrow().region_assumptions().to_owned();
         let region_constraints = self.0.with_region_constraints(|region_constraints| {
             make_query_region_constraints(
-                self.tcx,
                 region_obligations,
                 region_constraints,
                 region_assumptions,
diff --git a/compiler/rustc_trait_selection/src/solve/fulfill.rs b/compiler/rustc_trait_selection/src/solve/fulfill.rs
index 3ce0f025512..3f628d80662 100644
--- a/compiler/rustc_trait_selection/src/solve/fulfill.rs
+++ b/compiler/rustc_trait_selection/src/solve/fulfill.rs
@@ -197,6 +197,12 @@ where
                     delegate.compute_goal_fast_path(goal, obligation.cause.span)
                 {
                     match certainty {
+                        // This fast path doesn't depend on region identity so it doesn't
+                        // matter if the goal contains inference variables or not, so we
+                        // don't need to call `push_hir_typeck_potentially_region_dependent_goal`
+                        // here.
+                        //
+                        // Only goals proven via the trait solver should be region dependent.
                         Certainty::Yes => {}
                         Certainty::Maybe(_) => {
                             self.obligations.register(obligation, None);
@@ -207,7 +213,7 @@ where
 
                 let result = delegate.evaluate_root_goal(goal, obligation.cause.span, stalled_on);
                 self.inspect_evaluated_obligation(infcx, &obligation, &result);
-                let GoalEvaluation { certainty, has_changed, stalled_on } = match result {
+                let GoalEvaluation { goal, certainty, has_changed, stalled_on } = match result {
                     Ok(result) => result,
                     Err(NoSolution) => {
                         errors.push(E::from_solver_error(
@@ -218,6 +224,10 @@ where
                     }
                 };
 
+                // We've resolved the goal in `evaluate_root_goal`, avoid redoing this work
+                // in the next iteration. This does not resolve the inference variables
+                // constrained by evaluating the goal.
+                obligation.predicate = goal.predicate;
                 if has_changed == HasChanged::Yes {
                     // We increment the recursion depth here to track the number of times
                     // this goal has resulted in inference progress. This doesn't precisely
@@ -230,7 +240,22 @@ where
                 }
 
                 match certainty {
-                    Certainty::Yes => {}
+                    Certainty::Yes => {
+                        // Goals may depend on structural identity. Region uniquification at the
+                        // start of MIR borrowck may cause things to no longer be so, potentially
+                        // causing an ICE.
+                        //
+                        // While we uniquify root goals in HIR this does not handle cases where
+                        // regions are hidden inside of a type or const inference variable.
+                        //
+                        // FIXME(-Znext-solver): This does not handle inference variables hidden
+                        // inside of an opaque type, e.g. if there's `Opaque = (?x, ?x)` in the
+                        // storage, we can also rely on structural identity of `?x` even if we
+                        // later uniquify it in MIR borrowck.
+                        if infcx.in_hir_typeck && obligation.has_non_region_infer() {
+                            infcx.push_hir_typeck_potentially_region_dependent_goal(obligation);
+                        }
+                    }
                     Certainty::Maybe(_) => self.obligations.register(obligation, stalled_on),
                 }
             }
@@ -330,7 +355,7 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for StalledOnCoroutines<'tcx> {
             return ControlFlow::Continue(());
         }
 
-        if let ty::CoroutineWitness(def_id, _) = *ty.kind()
+        if let ty::Coroutine(def_id, _) = *ty.kind()
             && def_id.as_local().is_some_and(|def_id| self.stalled_coroutines.contains(&def_id))
         {
             ControlFlow::Break(())
diff --git a/compiler/rustc_trait_selection/src/traits/auto_trait.rs b/compiler/rustc_trait_selection/src/traits/auto_trait.rs
index 759db1d18c0..c63cc0e17ab 100644
--- a/compiler/rustc_trait_selection/src/traits/auto_trait.rs
+++ b/compiler/rustc_trait_selection/src/traits/auto_trait.rs
@@ -13,7 +13,7 @@ use tracing::debug;
 
 use super::*;
 use crate::errors::UnableToConstructConstantValue;
-use crate::infer::region_constraints::{Constraint, RegionConstraintData};
+use crate::infer::region_constraints::{ConstraintKind, RegionConstraintData};
 use crate::regions::OutlivesEnvironmentBuildExt;
 use crate::traits::project::ProjectAndUnifyResult;
 
@@ -452,37 +452,41 @@ impl<'tcx> AutoTraitFinder<'tcx> {
         let mut vid_map = FxIndexMap::<RegionTarget<'cx>, RegionDeps<'cx>>::default();
         let mut finished_map = FxIndexMap::default();
 
-        for (constraint, _) in &regions.constraints {
-            match constraint {
-                &Constraint::VarSubVar(r1, r2) => {
+        for (c, _) in &regions.constraints {
+            match c.kind {
+                ConstraintKind::VarSubVar => {
+                    let sub_vid = c.sub.as_var();
+                    let sup_vid = c.sup.as_var();
                     {
-                        let deps1 = vid_map.entry(RegionTarget::RegionVid(r1)).or_default();
-                        deps1.larger.insert(RegionTarget::RegionVid(r2));
+                        let deps1 = vid_map.entry(RegionTarget::RegionVid(sub_vid)).or_default();
+                        deps1.larger.insert(RegionTarget::RegionVid(sup_vid));
                     }
 
-                    let deps2 = vid_map.entry(RegionTarget::RegionVid(r2)).or_default();
-                    deps2.smaller.insert(RegionTarget::RegionVid(r1));
+                    let deps2 = vid_map.entry(RegionTarget::RegionVid(sup_vid)).or_default();
+                    deps2.smaller.insert(RegionTarget::RegionVid(sub_vid));
                 }
-                &Constraint::RegSubVar(region, vid) => {
+                ConstraintKind::RegSubVar => {
+                    let sup_vid = c.sup.as_var();
                     {
-                        let deps1 = vid_map.entry(RegionTarget::Region(region)).or_default();
-                        deps1.larger.insert(RegionTarget::RegionVid(vid));
+                        let deps1 = vid_map.entry(RegionTarget::Region(c.sub)).or_default();
+                        deps1.larger.insert(RegionTarget::RegionVid(sup_vid));
                     }
 
-                    let deps2 = vid_map.entry(RegionTarget::RegionVid(vid)).or_default();
-                    deps2.smaller.insert(RegionTarget::Region(region));
+                    let deps2 = vid_map.entry(RegionTarget::RegionVid(sup_vid)).or_default();
+                    deps2.smaller.insert(RegionTarget::Region(c.sub));
                 }
-                &Constraint::VarSubReg(vid, region) => {
-                    finished_map.insert(vid, region);
+                ConstraintKind::VarSubReg => {
+                    let sub_vid = c.sub.as_var();
+                    finished_map.insert(sub_vid, c.sup);
                 }
-                &Constraint::RegSubReg(r1, r2) => {
+                ConstraintKind::RegSubReg => {
                     {
-                        let deps1 = vid_map.entry(RegionTarget::Region(r1)).or_default();
-                        deps1.larger.insert(RegionTarget::Region(r2));
+                        let deps1 = vid_map.entry(RegionTarget::Region(c.sub)).or_default();
+                        deps1.larger.insert(RegionTarget::Region(c.sup));
                     }
 
-                    let deps2 = vid_map.entry(RegionTarget::Region(r2)).or_default();
-                    deps2.smaller.insert(RegionTarget::Region(r1));
+                    let deps2 = vid_map.entry(RegionTarget::Region(c.sup)).or_default();
+                    deps2.smaller.insert(RegionTarget::Region(c.sub));
                 }
             }
         }
diff --git a/compiler/rustc_trait_selection/src/traits/coherence.rs b/compiler/rustc_trait_selection/src/traits/coherence.rs
index 07e78da37b3..39afd77a8b6 100644
--- a/compiler/rustc_trait_selection/src/traits/coherence.rs
+++ b/compiler/rustc_trait_selection/src/traits/coherence.rs
@@ -12,6 +12,7 @@ use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{CRATE_DEF_ID, DefId};
 use rustc_infer::infer::{DefineOpaqueTypes, InferCtxt, TyCtxtInferExt};
 use rustc_infer::traits::PredicateObligations;
+use rustc_macros::{TypeFoldable, TypeVisitable};
 use rustc_middle::bug;
 use rustc_middle::traits::query::NoSolution;
 use rustc_middle::traits::solve::{CandidateSource, Certainty, Goal};
@@ -37,8 +38,20 @@ use crate::traits::{
     SelectionContext, SkipLeakCheck, util,
 };
 
+/// The "header" of an impl is everything outside the body: a Self type, a trait
+/// ref (in the case of a trait impl), and a set of predicates (from the
+/// bounds / where-clauses).
+#[derive(Clone, Debug, TypeFoldable, TypeVisitable)]
+pub struct ImplHeader<'tcx> {
+    pub impl_def_id: DefId,
+    pub impl_args: ty::GenericArgsRef<'tcx>,
+    pub self_ty: Ty<'tcx>,
+    pub trait_ref: Option<ty::TraitRef<'tcx>>,
+    pub predicates: Vec<ty::Predicate<'tcx>>,
+}
+
 pub struct OverlapResult<'tcx> {
-    pub impl_header: ty::ImplHeader<'tcx>,
+    pub impl_header: ImplHeader<'tcx>,
     pub intercrate_ambiguity_causes: FxIndexSet<IntercrateAmbiguityCause<'tcx>>,
 
     /// `true` if the overlap might've been permitted before the shift
@@ -151,11 +164,11 @@ pub fn overlapping_impls(
     }
 }
 
-fn fresh_impl_header<'tcx>(infcx: &InferCtxt<'tcx>, impl_def_id: DefId) -> ty::ImplHeader<'tcx> {
+fn fresh_impl_header<'tcx>(infcx: &InferCtxt<'tcx>, impl_def_id: DefId) -> ImplHeader<'tcx> {
     let tcx = infcx.tcx;
     let impl_args = infcx.fresh_args_for_item(DUMMY_SP, impl_def_id);
 
-    ty::ImplHeader {
+    ImplHeader {
         impl_def_id,
         impl_args,
         self_ty: tcx.type_of(impl_def_id).instantiate(tcx, impl_args),
@@ -173,7 +186,7 @@ fn fresh_impl_header_normalized<'tcx>(
     infcx: &InferCtxt<'tcx>,
     param_env: ty::ParamEnv<'tcx>,
     impl_def_id: DefId,
-) -> ty::ImplHeader<'tcx> {
+) -> ImplHeader<'tcx> {
     let header = fresh_impl_header(infcx, impl_def_id);
 
     let InferOk { value: mut header, obligations } =
@@ -287,8 +300,8 @@ fn overlap<'tcx>(
 fn equate_impl_headers<'tcx>(
     infcx: &InferCtxt<'tcx>,
     param_env: ty::ParamEnv<'tcx>,
-    impl1: &ty::ImplHeader<'tcx>,
-    impl2: &ty::ImplHeader<'tcx>,
+    impl1: &ImplHeader<'tcx>,
+    impl2: &ImplHeader<'tcx>,
 ) -> Option<PredicateObligations<'tcx>> {
     let result =
         match (impl1.trait_ref, impl2.trait_ref) {
@@ -535,7 +548,10 @@ fn plug_infer_with_placeholders<'tcx>(
                         ct,
                         ty::Const::new_placeholder(
                             self.infcx.tcx,
-                            ty::Placeholder { universe: self.universe, bound: self.next_var() },
+                            ty::Placeholder {
+                                universe: self.universe,
+                                bound: ty::BoundConst { var: self.next_var() },
+                            },
                         ),
                     )
                 else {
diff --git a/compiler/rustc_trait_selection/src/traits/mod.rs b/compiler/rustc_trait_selection/src/traits/mod.rs
index 9b5e59ce0fd..08315dbd21f 100644
--- a/compiler/rustc_trait_selection/src/traits/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/mod.rs
@@ -706,7 +706,10 @@ fn replace_param_and_infer_args_with_placeholder<'tcx>(
                 self.idx += 1;
                 ty::Const::new_placeholder(
                     self.tcx,
-                    ty::PlaceholderConst { universe: ty::UniverseIndex::ROOT, bound: idx },
+                    ty::PlaceholderConst {
+                        universe: ty::UniverseIndex::ROOT,
+                        bound: ty::BoundConst { var: idx },
+                    },
                 )
             } else {
                 c.super_fold_with(self)
diff --git a/compiler/rustc_trait_selection/src/traits/query/dropck_outlives.rs b/compiler/rustc_trait_selection/src/traits/query/dropck_outlives.rs
index 38cfdcdc22d..b1b331d1b61 100644
--- a/compiler/rustc_trait_selection/src/traits/query/dropck_outlives.rs
+++ b/compiler/rustc_trait_selection/src/traits/query/dropck_outlives.rs
@@ -318,7 +318,7 @@ pub fn dtorck_constraint_for_ty_inner<'tcx>(
             })
         }
 
-        ty::Coroutine(_, args) => {
+        ty::Coroutine(def_id, args) => {
             // rust-lang/rust#49918: types can be constructed, stored
             // in the interior, and sit idle when coroutine yields
             // (and is subsequently dropped).
@@ -346,7 +346,10 @@ pub fn dtorck_constraint_for_ty_inner<'tcx>(
             // While we conservatively assume that all coroutines require drop
             // to avoid query cycles during MIR building, we can check the actual
             // witness during borrowck to avoid unnecessary liveness constraints.
-            if args.witness().needs_drop(tcx, tcx.erase_regions(typing_env)) {
+            let typing_env = tcx.erase_regions(typing_env);
+            if tcx.mir_coroutine_witnesses(def_id).is_some_and(|witness| {
+                witness.field_tys.iter().any(|field| field.ty.needs_drop(tcx, typing_env))
+            }) {
                 constraints.outlives.extend(args.upvar_tys().iter().map(ty::GenericArg::from));
                 constraints.outlives.push(args.resume_ty().into());
             }
diff --git a/compiler/rustc_trait_selection/src/traits/query/type_op/ascribe_user_type.rs b/compiler/rustc_trait_selection/src/traits/query/type_op/ascribe_user_type.rs
index 81b5a131a32..78e7aef78f1 100644
--- a/compiler/rustc_trait_selection/src/traits/query/type_op/ascribe_user_type.rs
+++ b/compiler/rustc_trait_selection/src/traits/query/type_op/ascribe_user_type.rs
@@ -44,7 +44,7 @@ pub fn type_op_ascribe_user_type_with_span<'tcx>(
     key: ParamEnvAnd<'tcx, AscribeUserType<'tcx>>,
     span: Span,
 ) -> Result<(), NoSolution> {
-    let (param_env, AscribeUserType { mir_ty, user_ty }) = key.into_parts();
+    let ty::ParamEnvAnd { param_env, value: AscribeUserType { mir_ty, user_ty } } = key;
     debug!("type_op_ascribe_user_type: mir_ty={:?} user_ty={:?}", mir_ty, user_ty);
     match user_ty.kind {
         UserTypeKind::Ty(user_ty) => relate_mir_and_user_ty(ocx, param_env, span, mir_ty, user_ty)?,
diff --git a/compiler/rustc_trait_selection/src/traits/query/type_op/custom.rs b/compiler/rustc_trait_selection/src/traits/query/type_op/custom.rs
index f027ba1c5cb..0ca2d216228 100644
--- a/compiler/rustc_trait_selection/src/traits/query/type_op/custom.rs
+++ b/compiler/rustc_trait_selection/src/traits/query/type_op/custom.rs
@@ -108,7 +108,6 @@ where
     let region_assumptions = infcx.take_registered_region_assumptions();
     let region_constraint_data = infcx.take_and_reset_region_constraints();
     let region_constraints = query_response::make_query_region_constraints(
-        infcx.tcx,
         region_obligations,
         &region_constraint_data,
         region_assumptions,
diff --git a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
index 2c7089507a8..62795c8a3a6 100644
--- a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
@@ -794,18 +794,25 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                     // The auto impl might apply; we don't know.
                     candidates.ambiguous = true;
                 }
-                ty::Coroutine(coroutine_def_id, _)
-                    if self.tcx().is_lang_item(def_id, LangItem::Unpin) =>
-                {
-                    match self.tcx().coroutine_movability(coroutine_def_id) {
-                        hir::Movability::Static => {
-                            // Immovable coroutines are never `Unpin`, so
-                            // suppress the normal auto-impl candidate for it.
+                ty::Coroutine(coroutine_def_id, _) => {
+                    if self.tcx().is_lang_item(def_id, LangItem::Unpin) {
+                        match self.tcx().coroutine_movability(coroutine_def_id) {
+                            hir::Movability::Static => {
+                                // Immovable coroutines are never `Unpin`, so
+                                // suppress the normal auto-impl candidate for it.
+                            }
+                            hir::Movability::Movable => {
+                                // Movable coroutines are always `Unpin`, so add an
+                                // unconditional builtin candidate with no sub-obligations.
+                                candidates.vec.push(BuiltinCandidate);
+                            }
                         }
-                        hir::Movability::Movable => {
-                            // Movable coroutines are always `Unpin`, so add an
-                            // unconditional builtin candidate.
-                            candidates.vec.push(BuiltinCandidate);
+                    } else {
+                        if self.should_stall_coroutine(coroutine_def_id) {
+                            candidates.ambiguous = true;
+                        } else {
+                            // Coroutines implement all other auto traits normally.
+                            candidates.vec.push(AutoImplCandidate);
                         }
                     }
                 }
@@ -842,12 +849,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                     }
                 }
 
-                ty::CoroutineWitness(def_id, _) => {
-                    if self.should_stall_coroutine_witness(def_id) {
-                        candidates.ambiguous = true;
-                    } else {
-                        candidates.vec.push(AutoImplCandidate);
-                    }
+                ty::CoroutineWitness(..) => {
+                    candidates.vec.push(AutoImplCandidate);
                 }
 
                 ty::Bool
@@ -866,7 +869,6 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 | ty::FnPtr(..)
                 | ty::Closure(..)
                 | ty::CoroutineClosure(..)
-                | ty::Coroutine(..)
                 | ty::Never
                 | ty::Tuple(_)
                 | ty::UnsafeBinder(_) => {
@@ -1153,15 +1155,18 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             ty::Ref(_, _, hir::Mutability::Mut) => {}
 
             ty::Coroutine(coroutine_def_id, args) => {
+                if self.should_stall_coroutine(coroutine_def_id) {
+                    candidates.ambiguous = true;
+                    return;
+                }
+
                 match self.tcx().coroutine_movability(coroutine_def_id) {
                     hir::Movability::Static => {}
                     hir::Movability::Movable => {
                         if self.tcx().features().coroutine_clone() {
                             let resolved_upvars =
                                 self.infcx.shallow_resolve(args.as_coroutine().tupled_upvars_ty());
-                            let resolved_witness =
-                                self.infcx.shallow_resolve(args.as_coroutine().witness());
-                            if resolved_upvars.is_ty_var() || resolved_witness.is_ty_var() {
+                            if resolved_upvars.is_ty_var() {
                                 // Not yet resolved.
                                 candidates.ambiguous = true;
                             } else {
@@ -1194,12 +1199,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 }
             }
 
-            ty::CoroutineWitness(coroutine_def_id, _) => {
-                if self.should_stall_coroutine_witness(coroutine_def_id) {
-                    candidates.ambiguous = true;
-                } else {
-                    candidates.vec.push(SizedCandidate);
-                }
+            ty::CoroutineWitness(..) => {
+                candidates.vec.push(SizedCandidate);
             }
 
             // Fallback to whatever user-defined impls or param-env clauses exist in this case.
@@ -1238,7 +1239,6 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             | ty::RawPtr(..)
             | ty::Char
             | ty::Ref(..)
-            | ty::Coroutine(..)
             | ty::Array(..)
             | ty::Closure(..)
             | ty::CoroutineClosure(..)
@@ -1247,14 +1247,18 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 candidates.vec.push(SizedCandidate);
             }
 
-            ty::CoroutineWitness(coroutine_def_id, _) => {
-                if self.should_stall_coroutine_witness(coroutine_def_id) {
+            ty::Coroutine(coroutine_def_id, _) => {
+                if self.should_stall_coroutine(coroutine_def_id) {
                     candidates.ambiguous = true;
                 } else {
                     candidates.vec.push(SizedCandidate);
                 }
             }
 
+            ty::CoroutineWitness(..) => {
+                candidates.vec.push(SizedCandidate);
+            }
+
             // Conditionally `Sized`.
             ty::Tuple(..) | ty::Pat(..) | ty::Adt(..) | ty::UnsafeBinder(_) => {
                 candidates.vec.push(SizedCandidate);
diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
index d7c3543cb3f..7ea1548f8f2 100644
--- a/compiler/rustc_trait_selection/src/traits/select/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -2196,7 +2196,11 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
                                 args.as_coroutine()
                                     .upvar_tys()
                                     .iter()
-                                    .chain([args.as_coroutine().witness()])
+                                    .chain([Ty::new_coroutine_witness(
+                                        self.tcx(),
+                                        coroutine_def_id,
+                                        self.tcx().mk_args(args.as_coroutine().parent_args()),
+                                    )])
                                     .collect::<Vec<_>>(),
                             )
                         } else {
@@ -2327,9 +2331,13 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
                 ty::Binder::dummy(AutoImplConstituents { types: vec![ty], assumptions: vec![] })
             }
 
-            ty::Coroutine(_, args) => {
+            ty::Coroutine(def_id, args) => {
                 let ty = self.infcx.shallow_resolve(args.as_coroutine().tupled_upvars_ty());
-                let witness = args.as_coroutine().witness();
+                let witness = Ty::new_coroutine_witness(
+                    self.tcx(),
+                    def_id,
+                    self.tcx().mk_args(args.as_coroutine().parent_args()),
+                );
                 ty::Binder::dummy(AutoImplConstituents {
                     types: [ty].into_iter().chain(iter::once(witness)).collect(),
                     assumptions: vec![],
@@ -2841,7 +2849,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
         obligations
     }
 
-    fn should_stall_coroutine_witness(&self, def_id: DefId) -> bool {
+    fn should_stall_coroutine(&self, def_id: DefId) -> bool {
         match self.infcx.typing_mode() {
             TypingMode::Analysis { defining_opaque_types_and_generators: stalled_generators } => {
                 def_id.as_local().is_some_and(|def_id| stalled_generators.contains(&def_id))
diff --git a/compiler/rustc_trait_selection/src/traits/util.rs b/compiler/rustc_trait_selection/src/traits/util.rs
index c3d60ec45c4..83c0969762f 100644
--- a/compiler/rustc_trait_selection/src/traits/util.rs
+++ b/compiler/rustc_trait_selection/src/traits/util.rs
@@ -222,7 +222,7 @@ pub struct PlaceholderReplacer<'a, 'tcx> {
     infcx: &'a InferCtxt<'tcx>,
     mapped_regions: FxIndexMap<ty::PlaceholderRegion, ty::BoundRegion>,
     mapped_types: FxIndexMap<ty::PlaceholderType, ty::BoundTy>,
-    mapped_consts: FxIndexMap<ty::PlaceholderConst, ty::BoundVar>,
+    mapped_consts: FxIndexMap<ty::PlaceholderConst, ty::BoundConst>,
     universe_indices: &'a [Option<ty::UniverseIndex>],
     current_index: ty::DebruijnIndex,
 }
@@ -232,7 +232,7 @@ impl<'a, 'tcx> PlaceholderReplacer<'a, 'tcx> {
         infcx: &'a InferCtxt<'tcx>,
         mapped_regions: FxIndexMap<ty::PlaceholderRegion, ty::BoundRegion>,
         mapped_types: FxIndexMap<ty::PlaceholderType, ty::BoundTy>,
-        mapped_consts: FxIndexMap<ty::PlaceholderConst, ty::BoundVar>,
+        mapped_consts: FxIndexMap<ty::PlaceholderConst, ty::BoundConst>,
         universe_indices: &'a [Option<ty::UniverseIndex>],
         value: T,
     ) -> T {
diff --git a/compiler/rustc_traits/src/coroutine_witnesses.rs b/compiler/rustc_traits/src/coroutine_witnesses.rs
index 87d17f3e131..8a2a0832ddb 100644
--- a/compiler/rustc_traits/src/coroutine_witnesses.rs
+++ b/compiler/rustc_traits/src/coroutine_witnesses.rs
@@ -70,7 +70,6 @@ fn compute_assumptions<'tcx>(
         let region_constraints = infcx.take_and_reset_region_constraints();
 
         let outlives = make_query_region_constraints(
-            tcx,
             region_obligations,
             &region_constraints,
             region_assumptions,
diff --git a/compiler/rustc_traits/src/implied_outlives_bounds.rs b/compiler/rustc_traits/src/implied_outlives_bounds.rs
index 6fb483e6dac..397c24ff70c 100644
--- a/compiler/rustc_traits/src/implied_outlives_bounds.rs
+++ b/compiler/rustc_traits/src/implied_outlives_bounds.rs
@@ -7,7 +7,7 @@ use rustc_infer::infer::canonical::{self, Canonical};
 use rustc_infer::traits::query::OutlivesBound;
 use rustc_infer::traits::query::type_op::ImpliedOutlivesBounds;
 use rustc_middle::query::Providers;
-use rustc_middle::ty::TyCtxt;
+use rustc_middle::ty::{ParamEnvAnd, TyCtxt};
 use rustc_span::DUMMY_SP;
 use rustc_trait_selection::infer::InferCtxtBuilderExt;
 use rustc_trait_selection::traits::query::type_op::implied_outlives_bounds::compute_implied_outlives_bounds_inner;
@@ -25,7 +25,7 @@ fn implied_outlives_bounds<'tcx>(
     NoSolution,
 > {
     tcx.infer_ctxt().enter_canonical_trait_query(&goal, |ocx, key| {
-        let (param_env, ImpliedOutlivesBounds { ty }) = key.into_parts();
+        let ParamEnvAnd { param_env, value: ImpliedOutlivesBounds { ty } } = key;
         compute_implied_outlives_bounds_inner(
             ocx,
             param_env,
diff --git a/compiler/rustc_traits/src/type_op.rs b/compiler/rustc_traits/src/type_op.rs
index e58ad639d20..f77e1994cf4 100644
--- a/compiler/rustc_traits/src/type_op.rs
+++ b/compiler/rustc_traits/src/type_op.rs
@@ -43,7 +43,7 @@ fn type_op_normalize<'tcx, T>(
 where
     T: fmt::Debug + TypeFoldable<TyCtxt<'tcx>>,
 {
-    let (param_env, Normalize { value }) = key.into_parts();
+    let ParamEnvAnd { param_env, value: Normalize { value } } = key;
     let Normalized { value, obligations } =
         ocx.infcx.at(&ObligationCause::dummy(), param_env).query_normalize(value)?;
     ocx.register_obligations(obligations);
@@ -96,6 +96,6 @@ pub fn type_op_prove_predicate_with_cause<'tcx>(
     key: ParamEnvAnd<'tcx, ProvePredicate<'tcx>>,
     cause: ObligationCause<'tcx>,
 ) {
-    let (param_env, ProvePredicate { predicate }) = key.into_parts();
+    let ParamEnvAnd { param_env, value: ProvePredicate { predicate } } = key;
     ocx.register_obligation(Obligation::new(ocx.infcx.tcx, cause, param_env, predicate));
 }
diff --git a/compiler/rustc_transmute/Cargo.toml b/compiler/rustc_transmute/Cargo.toml
index 246b66d3d03..e61717e5e9c 100644
--- a/compiler/rustc_transmute/Cargo.toml
+++ b/compiler/rustc_transmute/Cargo.toml
@@ -20,9 +20,11 @@ itertools = "0.12"
 # tidy-alphabetical-end
 
 [features]
+# tidy-alphabetical-start
 rustc = [
     "dep:rustc_abi",
     "dep:rustc_hir",
     "dep:rustc_middle",
     "dep:rustc_span",
 ]
+# tidy-alphabetical-end
diff --git a/compiler/rustc_ty_utils/src/needs_drop.rs b/compiler/rustc_ty_utils/src/needs_drop.rs
index c3b04c20f4b..13d56889bd1 100644
--- a/compiler/rustc_ty_utils/src/needs_drop.rs
+++ b/compiler/rustc_ty_utils/src/needs_drop.rs
@@ -101,9 +101,6 @@ fn has_significant_drop_raw<'tcx>(
 struct NeedsDropTypes<'tcx, F> {
     tcx: TyCtxt<'tcx>,
     typing_env: ty::TypingEnv<'tcx>,
-    /// Whether to reveal coroutine witnesses, this is set
-    /// to `false` unless we compute `needs_drop` for a coroutine witness.
-    reveal_coroutine_witnesses: bool,
     query_ty: Ty<'tcx>,
     seen_tys: FxHashSet<Ty<'tcx>>,
     /// A stack of types left to process, and the recursion depth when we
@@ -115,6 +112,15 @@ struct NeedsDropTypes<'tcx, F> {
     adt_components: F,
     /// Set this to true if an exhaustive list of types involved in
     /// drop obligation is requested.
+    // FIXME: Calling this bool `exhaustive` is confusing and possibly a footgun,
+    // since it does two things: It makes the iterator yield *all* of the types
+    // that need drop, and it also affects the computation of the drop components
+    // on `Coroutine`s. The latter is somewhat confusing, and probably should be
+    // a function of `typing_env`. See the HACK comment below for why this is
+    // necessary. If this isn't possible, then we probably should turn this into
+    // a `NeedsDropMode` so that we can have a variant like `CollectAllSignificantDrops`,
+    // which will more accurately indicate that we want *all* of the *significant*
+    // drops, which are the two important behavioral changes toggled by this bool.
     exhaustive: bool,
 }
 
@@ -131,7 +137,6 @@ impl<'tcx, F> NeedsDropTypes<'tcx, F> {
         Self {
             tcx,
             typing_env,
-            reveal_coroutine_witnesses: exhaustive,
             seen_tys,
             query_ty: ty,
             unchecked_tys: vec![(ty, 0)],
@@ -195,23 +200,27 @@ where
                     // for the coroutine witness and check whether any of the contained types
                     // need to be dropped, and only require the captured types to be live
                     // if they do.
-                    ty::Coroutine(_, args) => {
-                        if self.reveal_coroutine_witnesses {
-                            queue_type(self, args.as_coroutine().witness());
+                    ty::Coroutine(def_id, args) => {
+                        // FIXME: See FIXME on `exhaustive` field above.
+                        if self.exhaustive {
+                            for upvar in args.as_coroutine().upvar_tys() {
+                                queue_type(self, upvar);
+                            }
+                            queue_type(self, args.as_coroutine().resume_ty());
+                            if let Some(witness) = tcx.mir_coroutine_witnesses(def_id) {
+                                for field_ty in &witness.field_tys {
+                                    queue_type(
+                                        self,
+                                        EarlyBinder::bind(field_ty.ty).instantiate(tcx, args),
+                                    );
+                                }
+                            }
                         } else {
                             return Some(self.always_drop_component(ty));
                         }
                     }
-                    ty::CoroutineWitness(def_id, args) => {
-                        if let Some(witness) = tcx.mir_coroutine_witnesses(def_id) {
-                            self.reveal_coroutine_witnesses = true;
-                            for field_ty in &witness.field_tys {
-                                queue_type(
-                                    self,
-                                    EarlyBinder::bind(field_ty.ty).instantiate(tcx, args),
-                                );
-                            }
-                        }
+                    ty::CoroutineWitness(..) => {
+                        unreachable!("witness should be handled in parent");
                     }
 
                     ty::UnsafeBinder(bound_ty) => {
diff --git a/compiler/rustc_type_ir/Cargo.toml b/compiler/rustc_type_ir/Cargo.toml
index 4bd7bfe79be..e7fee574dd4 100644
--- a/compiler/rustc_type_ir/Cargo.toml
+++ b/compiler/rustc_type_ir/Cargo.toml
@@ -23,14 +23,16 @@ tracing = "0.1"
 # tidy-alphabetical-end
 
 [features]
+# tidy-alphabetical-start
 default = ["nightly"]
 nightly = [
-    "dep:rustc_serialize",
-    "dep:rustc_span",
     "dep:rustc_data_structures",
     "dep:rustc_macros",
+    "dep:rustc_serialize",
+    "dep:rustc_span",
+    "rustc_ast_ir/nightly",
+    "rustc_index/nightly",
     "smallvec/may_dangle",
     "smallvec/union",
-    "rustc_index/nightly",
-    "rustc_ast_ir/nightly",
 ]
+# tidy-alphabetical-end
diff --git a/compiler/rustc_type_ir/src/binder.rs b/compiler/rustc_type_ir/src/binder.rs
index a7b915c4845..189afa32852 100644
--- a/compiler/rustc_type_ir/src/binder.rs
+++ b/compiler/rustc_type_ir/src/binder.rs
@@ -274,8 +274,9 @@ impl<I: Interner, T: IntoIterator> Binder<I, T> {
 pub struct ValidateBoundVars<I: Interner> {
     bound_vars: I::BoundVarKinds,
     binder_index: ty::DebruijnIndex,
-    // We may encounter the same variable at different levels of binding, so
-    // this can't just be `Ty`
+    // We only cache types because any complex const will have to step through
+    // a type at some point anyways. We may encounter the same variable at
+    // different levels of binding, so this can't just be `Ty`.
     visited: SsoHashSet<(ty::DebruijnIndex, I::Ty)>,
 }
 
@@ -319,6 +320,24 @@ impl<I: Interner> TypeVisitor<I> for ValidateBoundVars<I> {
         t.super_visit_with(self)
     }
 
+    fn visit_const(&mut self, c: I::Const) -> Self::Result {
+        if c.outer_exclusive_binder() < self.binder_index {
+            return ControlFlow::Break(());
+        }
+        match c.kind() {
+            ty::ConstKind::Bound(debruijn, bound_const) if debruijn == self.binder_index => {
+                let idx = bound_const.var().as_usize();
+                if self.bound_vars.len() <= idx {
+                    panic!("Not enough bound vars: {:?} not found in {:?}", c, self.bound_vars);
+                }
+                bound_const.assert_eq(self.bound_vars.get(idx).unwrap());
+            }
+            _ => {}
+        };
+
+        c.super_visit_with(self)
+    }
+
     fn visit_region(&mut self, r: I::Region) -> Self::Result {
         match r.kind() {
             ty::ReBound(index, br) if index == self.binder_index => {
@@ -357,7 +376,7 @@ impl<I: Interner> TypeVisitor<I> for ValidateBoundVars<I> {
 pub struct EarlyBinder<I: Interner, T> {
     value: T,
     #[derive_where(skip(Debug))]
-    _tcx: PhantomData<I>,
+    _tcx: PhantomData<fn() -> I>,
 }
 
 /// For early binders, you should first call `instantiate` before using any visitors.
diff --git a/compiler/rustc_type_ir/src/flags.rs b/compiler/rustc_type_ir/src/flags.rs
index d7b9e0ca340..23b7f55fbbe 100644
--- a/compiler/rustc_type_ir/src/flags.rs
+++ b/compiler/rustc_type_ir/src/flags.rs
@@ -131,10 +131,7 @@ bitflags::bitflags! {
         /// Does this have any binders with bound vars (e.g. that need to be anonymized)?
         const HAS_BINDER_VARS             = 1 << 23;
 
-        /// Does this type have any coroutine witnesses in it?
-        // FIXME: This should probably be changed to track whether the type has any
-        // *coroutines* in it, though this will happen if we remove coroutine witnesses
-        // altogether.
+        /// Does this type have any coroutines in it?
         const HAS_TY_CORO                 = 1 << 24;
     }
 }
@@ -246,11 +243,13 @@ impl<I: Interner> FlagComputation<I> {
                 self.add_flags(TypeFlags::HAS_TY_PARAM);
             }
 
-            ty::Closure(_, args) | ty::Coroutine(_, args) | ty::CoroutineClosure(_, args) => {
+            ty::Closure(_, args)
+            | ty::CoroutineClosure(_, args)
+            | ty::CoroutineWitness(_, args) => {
                 self.add_args(args.as_slice());
             }
 
-            ty::CoroutineWitness(_, args) => {
+            ty::Coroutine(_, args) => {
                 self.add_flags(TypeFlags::HAS_TY_CORO);
                 self.add_args(args.as_slice());
             }
diff --git a/compiler/rustc_type_ir/src/infer_ctxt.rs b/compiler/rustc_type_ir/src/infer_ctxt.rs
index e86a2305e23..b4873c8c71c 100644
--- a/compiler/rustc_type_ir/src/infer_ctxt.rs
+++ b/compiler/rustc_type_ir/src/infer_ctxt.rs
@@ -148,6 +148,10 @@ pub trait InferCtxtLike: Sized {
         true
     }
 
+    fn in_hir_typeck(&self) -> bool {
+        false
+    }
+
     fn typing_mode(&self) -> TypingMode<Self::Interner>;
 
     fn universe(&self) -> ty::UniverseIndex;
diff --git a/compiler/rustc_type_ir/src/inherent.rs b/compiler/rustc_type_ir/src/inherent.rs
index 0e307e15d5b..1a6c99ce7de 100644
--- a/compiler/rustc_type_ir/src/inherent.rs
+++ b/compiler/rustc_type_ir/src/inherent.rs
@@ -251,7 +251,7 @@ pub trait Const<I: Interner<Const = Self>>:
 
     fn new_var(interner: I, var: ty::ConstVid) -> Self;
 
-    fn new_bound(interner: I, debruijn: ty::DebruijnIndex, var: I::BoundConst) -> Self;
+    fn new_bound(interner: I, debruijn: ty::DebruijnIndex, bound_const: I::BoundConst) -> Self;
 
     fn new_anon_bound(interner: I, debruijn: ty::DebruijnIndex, var: ty::BoundVar) -> Self;
 
diff --git a/compiler/rustc_type_ir/src/lib.rs b/compiler/rustc_type_ir/src/lib.rs
index a483c18813b..50b588029ae 100644
--- a/compiler/rustc_type_ir/src/lib.rs
+++ b/compiler/rustc_type_ir/src/lib.rs
@@ -75,7 +75,7 @@ pub use pattern::*;
 pub use predicate::*;
 pub use predicate_kind::*;
 pub use region_kind::*;
-pub use rustc_ast_ir::{Movability, Mutability, Pinnedness};
+pub use rustc_ast_ir::{FloatTy, IntTy, Movability, Mutability, Pinnedness, UintTy};
 pub use ty_info::*;
 pub use ty_kind::*;
 pub use upcast::*;
@@ -387,16 +387,6 @@ rustc_index::newtype_index! {
     pub struct BoundVar {}
 }
 
-impl<I: Interner> inherent::BoundVarLike<I> for BoundVar {
-    fn var(self) -> BoundVar {
-        self
-    }
-
-    fn assert_eq(self, _var: I::BoundVarKind) {
-        unreachable!("FIXME: We really should have a separate `BoundConst` for consts")
-    }
-}
-
 /// Represents the various closure traits in the language. This
 /// will determine the type of the environment (`self`, in the
 /// desugaring) argument that the closure expects.
diff --git a/compiler/rustc_type_ir/src/predicate.rs b/compiler/rustc_type_ir/src/predicate.rs
index 4643cd0ab85..c9489c98cce 100644
--- a/compiler/rustc_type_ir/src/predicate.rs
+++ b/compiler/rustc_type_ir/src/predicate.rs
@@ -97,7 +97,7 @@ impl<I: Interner> TraitRef<I> {
         )
     }
 
-    pub fn with_self_ty(self, interner: I, self_ty: I::Ty) -> Self {
+    pub fn with_replaced_self_ty(self, interner: I, self_ty: I::Ty) -> Self {
         TraitRef::new(
             interner,
             self.def_id,
@@ -146,8 +146,11 @@ pub struct TraitPredicate<I: Interner> {
 }
 
 impl<I: Interner> TraitPredicate<I> {
-    pub fn with_self_ty(self, interner: I, self_ty: I::Ty) -> Self {
-        Self { trait_ref: self.trait_ref.with_self_ty(interner, self_ty), polarity: self.polarity }
+    pub fn with_replaced_self_ty(self, interner: I, self_ty: I::Ty) -> Self {
+        Self {
+            trait_ref: self.trait_ref.with_replaced_self_ty(interner, self_ty),
+            polarity: self.polarity,
+        }
     }
 
     pub fn def_id(self) -> I::DefId {
@@ -645,7 +648,7 @@ impl<I: Interner> AliasTerm<I> {
         self.args.type_at(0)
     }
 
-    pub fn with_self_ty(self, interner: I, self_ty: I::Ty) -> Self {
+    pub fn with_replaced_self_ty(self, interner: I, self_ty: I::Ty) -> Self {
         AliasTerm::new(
             interner,
             self.def_id,
@@ -756,8 +759,11 @@ impl<I: Interner> ProjectionPredicate<I> {
         self.projection_term.self_ty()
     }
 
-    pub fn with_self_ty(self, interner: I, self_ty: I::Ty) -> ProjectionPredicate<I> {
-        Self { projection_term: self.projection_term.with_self_ty(interner, self_ty), ..self }
+    pub fn with_replaced_self_ty(self, interner: I, self_ty: I::Ty) -> ProjectionPredicate<I> {
+        Self {
+            projection_term: self.projection_term.with_replaced_self_ty(interner, self_ty),
+            ..self
+        }
     }
 
     pub fn trait_def_id(self, interner: I) -> I::DefId {
@@ -814,8 +820,8 @@ impl<I: Interner> NormalizesTo<I> {
         self.alias.self_ty()
     }
 
-    pub fn with_self_ty(self, interner: I, self_ty: I::Ty) -> NormalizesTo<I> {
-        Self { alias: self.alias.with_self_ty(interner, self_ty), ..self }
+    pub fn with_replaced_self_ty(self, interner: I, self_ty: I::Ty) -> NormalizesTo<I> {
+        Self { alias: self.alias.with_replaced_self_ty(interner, self_ty), ..self }
     }
 
     pub fn trait_def_id(self, interner: I) -> I::DefId {
@@ -849,8 +855,8 @@ impl<I: Interner> HostEffectPredicate<I> {
         self.trait_ref.self_ty()
     }
 
-    pub fn with_self_ty(self, interner: I, self_ty: I::Ty) -> Self {
-        Self { trait_ref: self.trait_ref.with_self_ty(interner, self_ty), ..self }
+    pub fn with_replaced_self_ty(self, interner: I, self_ty: I::Ty) -> Self {
+        Self { trait_ref: self.trait_ref.with_replaced_self_ty(interner, self_ty), ..self }
     }
 
     pub fn def_id(self) -> I::DefId {
diff --git a/compiler/rustc_type_ir/src/ty_kind.rs b/compiler/rustc_type_ir/src/ty_kind.rs
index 7c665424750..73aeab5092d 100644
--- a/compiler/rustc_type_ir/src/ty_kind.rs
+++ b/compiler/rustc_type_ir/src/ty_kind.rs
@@ -15,7 +15,7 @@ pub use self::closure::*;
 use crate::inherent::*;
 #[cfg(feature = "nightly")]
 use crate::visit::TypeVisitable;
-use crate::{self as ty, DebruijnIndex, Interner};
+use crate::{self as ty, DebruijnIndex, FloatTy, IntTy, Interner, UintTy};
 
 mod closure;
 
@@ -475,7 +475,7 @@ impl<I: Interner> AliasTy<I> {
         self.args.type_at(0)
     }
 
-    pub fn with_self_ty(self, interner: I, self_ty: I::Ty) -> Self {
+    pub fn with_replaced_self_ty(self, interner: I, self_ty: I::Ty) -> Self {
         AliasTy::new(
             interner,
             self.def_id,
@@ -509,160 +509,6 @@ impl<I: Interner> AliasTy<I> {
     }
 }
 
-#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
-#[cfg_attr(
-    feature = "nightly",
-    derive(Encodable_NoContext, Decodable_NoContext, HashStable_NoContext)
-)]
-pub enum IntTy {
-    Isize,
-    I8,
-    I16,
-    I32,
-    I64,
-    I128,
-}
-
-impl IntTy {
-    pub fn name_str(&self) -> &'static str {
-        match *self {
-            IntTy::Isize => "isize",
-            IntTy::I8 => "i8",
-            IntTy::I16 => "i16",
-            IntTy::I32 => "i32",
-            IntTy::I64 => "i64",
-            IntTy::I128 => "i128",
-        }
-    }
-
-    pub fn bit_width(&self) -> Option<u64> {
-        Some(match *self {
-            IntTy::Isize => return None,
-            IntTy::I8 => 8,
-            IntTy::I16 => 16,
-            IntTy::I32 => 32,
-            IntTy::I64 => 64,
-            IntTy::I128 => 128,
-        })
-    }
-
-    pub fn normalize(&self, target_width: u32) -> Self {
-        match self {
-            IntTy::Isize => match target_width {
-                16 => IntTy::I16,
-                32 => IntTy::I32,
-                64 => IntTy::I64,
-                _ => unreachable!(),
-            },
-            _ => *self,
-        }
-    }
-
-    pub fn to_unsigned(self) -> UintTy {
-        match self {
-            IntTy::Isize => UintTy::Usize,
-            IntTy::I8 => UintTy::U8,
-            IntTy::I16 => UintTy::U16,
-            IntTy::I32 => UintTy::U32,
-            IntTy::I64 => UintTy::U64,
-            IntTy::I128 => UintTy::U128,
-        }
-    }
-}
-
-#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Copy)]
-#[cfg_attr(
-    feature = "nightly",
-    derive(Encodable_NoContext, Decodable_NoContext, HashStable_NoContext)
-)]
-pub enum UintTy {
-    Usize,
-    U8,
-    U16,
-    U32,
-    U64,
-    U128,
-}
-
-impl UintTy {
-    pub fn name_str(&self) -> &'static str {
-        match *self {
-            UintTy::Usize => "usize",
-            UintTy::U8 => "u8",
-            UintTy::U16 => "u16",
-            UintTy::U32 => "u32",
-            UintTy::U64 => "u64",
-            UintTy::U128 => "u128",
-        }
-    }
-
-    pub fn bit_width(&self) -> Option<u64> {
-        Some(match *self {
-            UintTy::Usize => return None,
-            UintTy::U8 => 8,
-            UintTy::U16 => 16,
-            UintTy::U32 => 32,
-            UintTy::U64 => 64,
-            UintTy::U128 => 128,
-        })
-    }
-
-    pub fn normalize(&self, target_width: u32) -> Self {
-        match self {
-            UintTy::Usize => match target_width {
-                16 => UintTy::U16,
-                32 => UintTy::U32,
-                64 => UintTy::U64,
-                _ => unreachable!(),
-            },
-            _ => *self,
-        }
-    }
-
-    pub fn to_signed(self) -> IntTy {
-        match self {
-            UintTy::Usize => IntTy::Isize,
-            UintTy::U8 => IntTy::I8,
-            UintTy::U16 => IntTy::I16,
-            UintTy::U32 => IntTy::I32,
-            UintTy::U64 => IntTy::I64,
-            UintTy::U128 => IntTy::I128,
-        }
-    }
-}
-
-#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
-#[cfg_attr(
-    feature = "nightly",
-    derive(Encodable_NoContext, Decodable_NoContext, HashStable_NoContext)
-)]
-pub enum FloatTy {
-    F16,
-    F32,
-    F64,
-    F128,
-}
-
-impl FloatTy {
-    pub fn name_str(self) -> &'static str {
-        match self {
-            FloatTy::F16 => "f16",
-            FloatTy::F32 => "f32",
-            FloatTy::F64 => "f64",
-            FloatTy::F128 => "f128",
-        }
-    }
-
-    pub fn bit_width(self) -> u64 {
-        match self {
-            FloatTy::F16 => 16,
-            FloatTy::F32 => 32,
-            FloatTy::F64 => 64,
-            FloatTy::F128 => 128,
-        }
-    }
-}
-
 #[derive(Clone, Copy, PartialEq, Eq, Debug)]
 pub enum IntVarValue {
     Unknown,
@@ -860,24 +706,6 @@ impl fmt::Display for InferTy {
     }
 }
 
-impl fmt::Debug for IntTy {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "{}", self.name_str())
-    }
-}
-
-impl fmt::Debug for UintTy {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "{}", self.name_str())
-    }
-}
-
-impl fmt::Debug for FloatTy {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "{}", self.name_str())
-    }
-}
-
 impl fmt::Debug for InferTy {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         use InferTy::*;
diff --git a/compiler/rustc_type_ir/src/ty_kind/closure.rs b/compiler/rustc_type_ir/src/ty_kind/closure.rs
index d1ca9bdb7fb..c32f8339d0b 100644
--- a/compiler/rustc_type_ir/src/ty_kind/closure.rs
+++ b/compiler/rustc_type_ir/src/ty_kind/closure.rs
@@ -101,7 +101,6 @@ use crate::{self as ty, Interner};
 ///   `yield` inside the coroutine.
 /// * `GR`: The "return type", which is the type of value returned upon
 ///   completion of the coroutine.
-/// * `GW`: The "coroutine witness".
 #[derive_where(Clone, Copy, PartialEq, Eq, Hash, Debug; I: Interner)]
 #[derive(TypeVisitable_Generic, TypeFoldable_Generic, Lift_Generic)]
 pub struct ClosureArgs<I: Interner> {
@@ -239,8 +238,6 @@ pub struct CoroutineClosureArgsParts<I: Interner> {
     /// while the `tupled_upvars_ty`, representing the by-move version of the same
     /// captures, will be `(String,)`.
     pub coroutine_captures_by_ref_ty: I::Ty,
-    /// Witness type returned by the generator produced by this coroutine-closure.
-    pub coroutine_witness_ty: I::Ty,
 }
 
 impl<I: Interner> CoroutineClosureArgs<I> {
@@ -251,7 +248,6 @@ impl<I: Interner> CoroutineClosureArgs<I> {
                 parts.signature_parts_ty.into(),
                 parts.tupled_upvars_ty.into(),
                 parts.coroutine_captures_by_ref_ty.into(),
-                parts.coroutine_witness_ty.into(),
             ])),
         }
     }
@@ -292,7 +288,6 @@ impl<I: Interner> CoroutineClosureArgs<I> {
     }
 
     pub fn coroutine_closure_sig(self) -> ty::Binder<I, CoroutineClosureSignature<I>> {
-        let interior = self.coroutine_witness_ty();
         let ty::FnPtr(sig_tys, hdr) = self.signature_parts_ty().kind() else { panic!() };
         sig_tys.map_bound(|sig_tys| {
             let [resume_ty, tupled_inputs_ty] = *sig_tys.inputs().as_slice() else {
@@ -302,7 +297,6 @@ impl<I: Interner> CoroutineClosureArgs<I> {
                 panic!()
             };
             CoroutineClosureSignature {
-                interior,
                 tupled_inputs_ty,
                 resume_ty,
                 yield_ty,
@@ -318,10 +312,6 @@ impl<I: Interner> CoroutineClosureArgs<I> {
         self.split().coroutine_captures_by_ref_ty
     }
 
-    pub fn coroutine_witness_ty(self) -> I::Ty {
-        self.split().coroutine_witness_ty
-    }
-
     pub fn has_self_borrows(&self) -> bool {
         match self.coroutine_captures_by_ref_ty().kind() {
             ty::FnPtr(sig_tys, _) => sig_tys
@@ -361,7 +351,6 @@ impl<I: Interner> TypeVisitor<I> for HasRegionsBoundAt {
 #[derive_where(Clone, Copy, PartialEq, Eq, Hash, Debug; I: Interner)]
 #[derive(TypeVisitable_Generic, TypeFoldable_Generic)]
 pub struct CoroutineClosureSignature<I: Interner> {
-    pub interior: I::Ty,
     pub tupled_inputs_ty: I::Ty,
     pub resume_ty: I::Ty,
     pub yield_ty: I::Ty,
@@ -407,7 +396,6 @@ impl<I: Interner> CoroutineClosureSignature<I> {
                 resume_ty: self.resume_ty,
                 yield_ty: self.yield_ty,
                 return_ty: self.return_ty,
-                witness: self.interior,
                 tupled_upvars_ty,
             },
         );
@@ -587,11 +575,6 @@ pub struct CoroutineArgsParts<I: Interner> {
     pub yield_ty: I::Ty,
     pub return_ty: I::Ty,
 
-    /// The interior type of the coroutine.
-    /// Represents all types that are stored in locals
-    /// in the coroutine's body.
-    pub witness: I::Ty,
-
     /// The upvars captured by the closure. Remains an inference variable
     /// until the upvar analysis, which happens late in HIR typeck.
     pub tupled_upvars_ty: I::Ty,
@@ -607,7 +590,6 @@ impl<I: Interner> CoroutineArgs<I> {
                 parts.resume_ty.into(),
                 parts.yield_ty.into(),
                 parts.return_ty.into(),
-                parts.witness.into(),
                 parts.tupled_upvars_ty.into(),
             ])),
         }
@@ -629,15 +611,6 @@ impl<I: Interner> CoroutineArgs<I> {
         self.split().kind_ty
     }
 
-    /// This describes the types that can be contained in a coroutine.
-    /// It will be a type variable initially and unified in the last stages of typeck of a body.
-    /// It contains a tuple of all the types that could end up on a coroutine frame.
-    /// The state transformation MIR pass may only produce layouts which mention types
-    /// in this tuple. Upvars are not counted here.
-    pub fn witness(self) -> I::Ty {
-        self.split().witness
-    }
-
     /// Returns an iterator over the list of types of captured paths by the coroutine.
     /// In case there was a type error in figuring out the types of the captured path, an
     /// empty iterator is returned.