about summary refs log tree commit diff
path: root/compiler
diff options
context:
space:
mode:
Diffstat (limited to 'compiler')
-rw-r--r--compiler/rustc_abi/Cargo.toml2
-rw-r--r--compiler/rustc_abi/src/extern_abi.rs3
-rw-r--r--compiler/rustc_ast/src/ast.rs4
-rw-r--r--compiler/rustc_ast/src/token.rs22
-rw-r--r--compiler/rustc_ast/src/tokenstream.rs6
-rw-r--r--compiler/rustc_ast_lowering/src/item.rs4
-rw-r--r--compiler/rustc_ast_passes/Cargo.toml1
-rw-r--r--compiler/rustc_ast_passes/messages.ftl8
-rw-r--r--compiler/rustc_ast_passes/src/ast_validation.rs21
-rw-r--r--compiler/rustc_ast_passes/src/errors.rs19
-rw-r--r--compiler/rustc_ast_passes/src/feature_gate.rs1
-rw-r--r--compiler/rustc_ast_pretty/src/pprust/state.rs17
-rw-r--r--compiler/rustc_attr_parsing/Cargo.toml2
-rw-r--r--compiler/rustc_attr_parsing/messages.ftl21
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/allow_unstable.rs10
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/body.rs8
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/codegen_attrs.rs250
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/confusables.rs15
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/crate_level.rs33
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/deprecation.rs23
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/dummy.rs4
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/inline.rs14
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/link_attrs.rs43
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/lint_helpers.rs7
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/loop_match.rs7
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/macro_attrs.rs16
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/mod.rs11
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/must_use.rs28
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/no_implicit_prelude.rs7
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/non_exhaustive.rs7
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/path.rs9
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/prelude.rs20
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/proc_macro_attrs.rs26
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/prototype.rs11
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/repr.rs16
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/rustc_internal.rs12
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/semantics.rs5
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/stability.rs10
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/test_attrs.rs12
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/traits.rs16
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/transparency.rs12
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/util.rs39
-rw-r--r--compiler/rustc_attr_parsing/src/context.rs636
-rw-r--r--compiler/rustc_attr_parsing/src/interface.rs370
-rw-r--r--compiler/rustc_attr_parsing/src/lib.rs23
-rw-r--r--compiler/rustc_attr_parsing/src/lints.rs27
-rw-r--r--compiler/rustc_attr_parsing/src/parser.rs483
-rw-r--r--compiler/rustc_attr_parsing/src/session_diagnostics.rs116
-rw-r--r--compiler/rustc_attr_parsing/src/target_checking.rs247
-rw-r--r--compiler/rustc_attr_parsing/src/validate_attr.rs (renamed from compiler/rustc_parse/src/validate_attr.rs)22
-rw-r--r--compiler/rustc_borrowck/src/dataflow.rs44
-rw-r--r--compiler/rustc_borrowck/src/diagnostics/opaque_types.rs56
-rw-r--r--compiler/rustc_borrowck/src/diagnostics/region_errors.rs41
-rw-r--r--compiler/rustc_borrowck/src/handle_placeholders.rs12
-rw-r--r--compiler/rustc_borrowck/src/lib.rs33
-rw-r--r--compiler/rustc_borrowck/src/member_constraints.rs226
-rw-r--r--compiler/rustc_borrowck/src/region_infer/mod.rs348
-rw-r--r--compiler/rustc_borrowck/src/region_infer/opaque_types.rs299
-rw-r--r--compiler/rustc_borrowck/src/region_infer/opaque_types/member_constraints.rs194
-rw-r--r--compiler/rustc_borrowck/src/region_infer/opaque_types/mod.rs697
-rw-r--r--compiler/rustc_borrowck/src/region_infer/opaque_types/region_ctxt.rs114
-rw-r--r--compiler/rustc_borrowck/src/region_infer/reverse_sccs.rs10
-rw-r--r--compiler/rustc_borrowck/src/root_cx.rs15
-rw-r--r--compiler/rustc_borrowck/src/type_check/canonical.rs105
-rw-r--r--compiler/rustc_borrowck/src/type_check/constraint_conversion.rs20
-rw-r--r--compiler/rustc_borrowck/src/type_check/free_region_relations.rs32
-rw-r--r--compiler/rustc_borrowck/src/type_check/liveness/trace.rs2
-rw-r--r--compiler/rustc_borrowck/src/type_check/mod.rs189
-rw-r--r--compiler/rustc_borrowck/src/type_check/opaque_types.rs333
-rw-r--r--compiler/rustc_borrowck/src/type_check/relate_tys.rs9
-rw-r--r--compiler/rustc_builtin_macros/src/cfg_accessible.rs2
-rw-r--r--compiler/rustc_builtin_macros/src/derive.rs2
-rw-r--r--compiler/rustc_builtin_macros/src/deriving/from.rs71
-rw-r--r--compiler/rustc_builtin_macros/src/format.rs8
-rw-r--r--compiler/rustc_builtin_macros/src/lib.rs1
-rw-r--r--compiler/rustc_builtin_macros/src/test_harness.rs2
-rw-r--r--compiler/rustc_builtin_macros/src/util.rs3
-rw-r--r--compiler/rustc_codegen_llvm/src/abi.rs7
-rw-r--r--compiler/rustc_codegen_llvm/src/allocator.rs6
-rw-r--r--compiler/rustc_codegen_llvm/src/asm.rs11
-rw-r--r--compiler/rustc_codegen_llvm/src/attributes.rs12
-rw-r--r--compiler/rustc_codegen_llvm/src/back/write.rs2
-rw-r--r--compiler/rustc_codegen_llvm/src/builder.rs49
-rw-r--r--compiler/rustc_codegen_llvm/src/builder/autodiff.rs4
-rw-r--r--compiler/rustc_codegen_llvm/src/common.rs10
-rw-r--r--compiler/rustc_codegen_llvm/src/context.rs11
-rw-r--r--compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs2
-rw-r--r--compiler/rustc_codegen_llvm/src/debuginfo/metadata/type_map.rs54
-rw-r--r--compiler/rustc_codegen_llvm/src/debuginfo/namespace.rs2
-rw-r--r--compiler/rustc_codegen_llvm/src/intrinsic.rs8
-rw-r--r--compiler/rustc_codegen_llvm/src/llvm/ffi.rs59
-rw-r--r--compiler/rustc_codegen_llvm/src/llvm/mod.rs4
-rw-r--r--compiler/rustc_codegen_llvm/src/llvm_util.rs3
-rw-r--r--compiler/rustc_codegen_llvm/src/mono_item.rs2
-rw-r--r--compiler/rustc_codegen_llvm/src/type_.rs12
-rw-r--r--compiler/rustc_codegen_ssa/messages.ftl3
-rw-r--r--compiler/rustc_codegen_ssa/src/back/link.rs9
-rw-r--r--compiler/rustc_codegen_ssa/src/back/link/raw_dylib.rs13
-rw-r--r--compiler/rustc_codegen_ssa/src/base.rs2
-rw-r--r--compiler/rustc_codegen_ssa/src/codegen_attrs.rs124
-rw-r--r--compiler/rustc_codegen_ssa/src/errors.rs8
-rw-r--r--compiler/rustc_codegen_ssa/src/target_features.rs13
-rw-r--r--compiler/rustc_const_eval/src/const_eval/machine.rs118
-rw-r--r--compiler/rustc_const_eval/src/interpret/call.rs12
-rw-r--r--compiler/rustc_const_eval/src/interpret/eval_context.rs4
-rw-r--r--compiler/rustc_const_eval/src/interpret/place.rs6
-rw-r--r--compiler/rustc_const_eval/src/interpret/stack.rs5
-rw-r--r--compiler/rustc_const_eval/src/interpret/step.rs78
-rw-r--r--compiler/rustc_const_eval/src/interpret/validity.rs4
-rw-r--r--compiler/rustc_const_eval/src/util/type_name.rs37
-rw-r--r--compiler/rustc_data_structures/src/lib.rs1
-rw-r--r--compiler/rustc_data_structures/src/union_find.rs (renamed from compiler/rustc_mir_transform/src/coverage/counters/union_find.rs)10
-rw-r--r--compiler/rustc_data_structures/src/union_find/tests.rs (renamed from compiler/rustc_mir_transform/src/coverage/counters/union_find/tests.rs)0
-rw-r--r--compiler/rustc_error_messages/Cargo.toml2
-rw-r--r--compiler/rustc_error_messages/src/diagnostic_impls.rs205
-rw-r--r--compiler/rustc_error_messages/src/lib.rs53
-rw-r--r--compiler/rustc_errors/Cargo.toml4
-rw-r--r--compiler/rustc_errors/src/codes.rs2
-rw-r--r--compiler/rustc_errors/src/decorate_diag.rs85
-rw-r--r--compiler/rustc_errors/src/diagnostic.rs87
-rw-r--r--compiler/rustc_errors/src/diagnostic_impls.rs326
-rw-r--r--compiler/rustc_errors/src/emitter.rs4
-rw-r--r--compiler/rustc_errors/src/lib.rs26
-rw-r--r--compiler/rustc_expand/src/base.rs4
-rw-r--r--compiler/rustc_expand/src/config.rs14
-rw-r--r--compiler/rustc_expand/src/expand.rs34
-rw-r--r--compiler/rustc_expand/src/mbe/macro_rules.rs1
-rw-r--r--compiler/rustc_expand/src/module.rs5
-rw-r--r--compiler/rustc_expand/src/proc_macro_server.rs16
-rw-r--r--compiler/rustc_feature/src/builtin_attrs.rs8
-rw-r--r--compiler/rustc_feature/src/unstable.rs3
-rw-r--r--compiler/rustc_hir/Cargo.toml2
-rw-r--r--compiler/rustc_hir/src/attrs/data_structures.rs41
-rw-r--r--compiler/rustc_hir/src/attrs/encode_cross_crate.rs9
-rw-r--r--compiler/rustc_hir/src/attrs/pretty_printing.rs13
-rw-r--r--compiler/rustc_hir/src/def.rs14
-rw-r--r--compiler/rustc_hir/src/hir.rs19
-rw-r--r--compiler/rustc_hir/src/lang_items.rs3
-rw-r--r--compiler/rustc_hir/src/lib.rs6
-rw-r--r--compiler/rustc_hir/src/lints.rs6
-rw-r--r--compiler/rustc_hir/src/stable_hash_impls.rs21
-rw-r--r--compiler/rustc_hir/src/target.rs2
-rw-r--r--compiler/rustc_hir/src/version.rs8
-rw-r--r--compiler/rustc_hir_analysis/messages.ftl4
-rw-r--r--compiler/rustc_hir_analysis/src/check/check.rs26
-rw-r--r--compiler/rustc_hir_analysis/src/check/intrinsic.rs6
-rw-r--r--compiler/rustc_hir_analysis/src/check/mod.rs1
-rw-r--r--compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs21
-rw-r--r--compiler/rustc_hir_analysis/src/errors.rs11
-rw-r--r--compiler/rustc_hir_analysis/src/lib.rs2
-rw-r--r--compiler/rustc_hir_id/Cargo.toml13
-rw-r--r--compiler/rustc_hir_id/src/lib.rs (renamed from compiler/rustc_hir/src/hir_id.rs)31
-rw-r--r--compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs8
-rw-r--r--compiler/rustc_hir_typeck/src/intrinsicck.rs211
-rw-r--r--compiler/rustc_hir_typeck/src/lib.rs27
-rw-r--r--compiler/rustc_hir_typeck/src/method/probe.rs27
-rw-r--r--compiler/rustc_hir_typeck/src/method/suggest.rs123
-rw-r--r--compiler/rustc_hir_typeck/src/opaque_types.rs215
-rw-r--r--compiler/rustc_hir_typeck/src/writeback.rs74
-rw-r--r--compiler/rustc_index/src/bit_set.rs253
-rw-r--r--compiler/rustc_index/src/bit_set/tests.rs56
-rw-r--r--compiler/rustc_infer/src/infer/context.rs4
-rw-r--r--compiler/rustc_infer/src/infer/mod.rs25
-rw-r--r--compiler/rustc_interface/src/interface.rs4
-rw-r--r--compiler/rustc_interface/src/passes.rs34
-rw-r--r--compiler/rustc_interface/src/tests.rs1
-rw-r--r--compiler/rustc_interface/src/util.rs15
-rw-r--r--compiler/rustc_lexer/src/lib.rs4
-rw-r--r--compiler/rustc_lint/messages.ftl35
-rw-r--r--compiler/rustc_lint/src/builtin.rs2
-rw-r--r--compiler/rustc_lint/src/context.rs14
-rw-r--r--compiler/rustc_lint/src/early.rs10
-rw-r--r--compiler/rustc_lint/src/early/diagnostics.rs43
-rw-r--r--compiler/rustc_lint/src/foreign_modules.rs2
-rw-r--r--compiler/rustc_lint/src/internal.rs137
-rw-r--r--compiler/rustc_lint/src/lib.rs5
-rw-r--r--compiler/rustc_lint/src/lifetime_syntax.rs8
-rw-r--r--compiler/rustc_lint/src/lints.rs148
-rw-r--r--compiler/rustc_lint/src/nonstandard_style.rs52
-rw-r--r--compiler/rustc_lint/src/transmute.rs92
-rw-r--r--compiler/rustc_lint_defs/Cargo.toml3
-rw-r--r--compiler/rustc_lint_defs/src/lib.rs91
-rw-r--r--compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp8
-rw-r--r--compiler/rustc_macros/src/print_attribute.rs60
-rw-r--r--compiler/rustc_metadata/src/native_libs.rs2
-rw-r--r--compiler/rustc_middle/src/lib.rs1
-rw-r--r--compiler/rustc_middle/src/lint.rs29
-rw-r--r--compiler/rustc_middle/src/middle/codegen_fn_attrs.rs33
-rw-r--r--compiler/rustc_middle/src/middle/stability.rs4
-rw-r--r--compiler/rustc_middle/src/mir/interpret/allocation/provenance_map.rs11
-rw-r--r--compiler/rustc_middle/src/mir/mono.rs23
-rw-r--r--compiler/rustc_middle/src/mir/pretty.rs5
-rw-r--r--compiler/rustc_middle/src/mir/statement.rs36
-rw-r--r--compiler/rustc_middle/src/mir/syntax.rs5
-rw-r--r--compiler/rustc_middle/src/mir/visit.rs9
-rw-r--r--compiler/rustc_middle/src/query/mod.rs21
-rw-r--r--compiler/rustc_middle/src/query/on_disk_cache.rs51
-rw-r--r--compiler/rustc_middle/src/traits/mod.rs23
-rw-r--r--compiler/rustc_middle/src/ty/context.rs9
-rw-r--r--compiler/rustc_middle/src/ty/diagnostics.rs4
-rw-r--r--compiler/rustc_middle/src/ty/mod.rs10
-rw-r--r--compiler/rustc_middle/src/ty/print/mod.rs16
-rw-r--r--compiler/rustc_middle/src/ty/sty.rs40
-rw-r--r--compiler/rustc_middle/src/ty/typeck_results.rs17
-rw-r--r--compiler/rustc_mir_build/src/builder/coverageinfo.rs15
-rw-r--r--compiler/rustc_mir_build/src/builder/mod.rs22
-rw-r--r--compiler/rustc_mir_build/src/check_tail_calls.rs41
-rw-r--r--compiler/rustc_mir_build/src/check_unsafety.rs4
-rw-r--r--compiler/rustc_mir_dataflow/Cargo.toml1
-rw-r--r--compiler/rustc_mir_dataflow/src/framework/graphviz.rs2
-rw-r--r--compiler/rustc_mir_dataflow/src/move_paths/abs_domain.rs38
-rw-r--r--compiler/rustc_mir_dataflow/src/move_paths/builder.rs5
-rw-r--r--compiler/rustc_mir_dataflow/src/move_paths/mod.rs17
-rw-r--r--compiler/rustc_mir_dataflow/src/rustc_peek.rs2
-rw-r--r--compiler/rustc_mir_transform/src/check_enums.rs15
-rw-r--r--compiler/rustc_mir_transform/src/coverage/counters.rs1
-rw-r--r--compiler/rustc_mir_transform/src/coverage/counters/node_flow.rs3
-rw-r--r--compiler/rustc_mir_transform/src/gvn.rs62
-rw-r--r--compiler/rustc_mir_transform/src/ref_prop.rs39
-rw-r--r--compiler/rustc_next_trait_solver/src/canonicalizer.rs35
-rw-r--r--compiler/rustc_next_trait_solver/src/solve/assembly/structural_traits.rs24
-rw-r--r--compiler/rustc_next_trait_solver/src/solve/effect_goals.rs18
-rw-r--r--compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs2
-rw-r--r--compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs30
-rw-r--r--compiler/rustc_next_trait_solver/src/solve/normalizes_to/opaque_types.rs174
-rw-r--r--compiler/rustc_next_trait_solver/src/solve/trait_goals.rs17
-rw-r--r--compiler/rustc_parse/Cargo.toml1
-rw-r--r--compiler/rustc_parse/messages.ftl32
-rw-r--r--compiler/rustc_parse/src/errors.rs143
-rw-r--r--compiler/rustc_parse/src/lexer/mod.rs21
-rw-r--r--compiler/rustc_parse/src/lib.rs33
-rw-r--r--compiler/rustc_parse/src/parser/attr.rs2
-rw-r--r--compiler/rustc_parse/src/parser/diagnostics.rs18
-rw-r--r--compiler/rustc_parse/src/parser/expr.rs28
-rw-r--r--compiler/rustc_parse/src/parser/generics.rs11
-rw-r--r--compiler/rustc_parse/src/parser/item.rs6
-rw-r--r--compiler/rustc_parse/src/parser/mod.rs96
-rw-r--r--compiler/rustc_parse/src/parser/path.rs4
-rw-r--r--compiler/rustc_parse/src/parser/token_type.rs6
-rw-r--r--compiler/rustc_parse/src/parser/ty.rs177
-rw-r--r--compiler/rustc_passes/messages.ftl4
-rw-r--r--compiler/rustc_passes/src/check_attr.rs161
-rw-r--r--compiler/rustc_passes/src/dead.rs29
-rw-r--r--compiler/rustc_passes/src/errors.rs8
-rw-r--r--compiler/rustc_pattern_analysis/src/rustc/print.rs22
-rw-r--r--compiler/rustc_resolve/messages.ftl3
-rw-r--r--compiler/rustc_resolve/src/build_reduced_graph.rs9
-rw-r--r--compiler/rustc_resolve/src/diagnostics.rs12
-rw-r--r--compiler/rustc_resolve/src/errors.rs11
-rw-r--r--compiler/rustc_resolve/src/ident.rs61
-rw-r--r--compiler/rustc_resolve/src/imports.rs16
-rw-r--r--compiler/rustc_resolve/src/late.rs2
-rw-r--r--compiler/rustc_resolve/src/late/diagnostics.rs35
-rw-r--r--compiler/rustc_resolve/src/lib.rs36
-rw-r--r--compiler/rustc_resolve/src/macros.rs8
-rw-r--r--compiler/rustc_session/Cargo.toml4
-rw-r--r--compiler/rustc_session/messages.ftl6
-rw-r--r--compiler/rustc_session/src/config/cfg.rs5
-rw-r--r--compiler/rustc_session/src/errors.rs16
-rw-r--r--compiler/rustc_session/src/options.rs2
-rw-r--r--compiler/rustc_session/src/parse.rs14
-rw-r--r--compiler/rustc_session/src/session.rs44
-rw-r--r--compiler/rustc_span/src/caching_source_map_view.rs30
-rw-r--r--compiler/rustc_span/src/source_map.rs14
-rw-r--r--compiler/rustc_span/src/span_encoding.rs5
-rw-r--r--compiler/rustc_span/src/symbol.rs78
-rw-r--r--compiler/rustc_symbol_mangling/src/lib.rs50
-rw-r--r--compiler/rustc_target/Cargo.toml1
-rw-r--r--compiler/rustc_target/src/callconv/mod.rs1
-rw-r--r--compiler/rustc_target/src/spec/mod.rs14
-rw-r--r--compiler/rustc_target/src/spec/targets/aarch64_be_unknown_hermit.rs25
-rw-r--r--compiler/rustc_target/src/spec/targets/aarch64_nintendo_switch_freestanding.rs2
-rw-r--r--compiler/rustc_target/src/spec/targets/armv7a_vex_v5_linker_script.ld27
-rw-r--r--compiler/rustc_target/src/spec/targets/x86_64_apple_darwin.rs2
-rw-r--r--compiler/rustc_target/src/target_features.rs1
-rw-r--r--compiler/rustc_trait_selection/src/error_reporting/infer/note_and_explain.rs2
-rw-r--r--compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs47
-rw-r--r--compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs98
-rw-r--r--compiler/rustc_trait_selection/src/opaque_types.rs55
-rw-r--r--compiler/rustc_trait_selection/src/solve/fulfill.rs4
-rw-r--r--compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs27
-rw-r--r--compiler/rustc_trait_selection/src/traits/query/type_op/custom.rs9
-rw-r--r--compiler/rustc_trait_selection/src/traits/query/type_op/mod.rs16
-rw-r--r--compiler/rustc_trait_selection/src/traits/select/mod.rs61
-rw-r--r--compiler/rustc_trait_selection/src/traits/util.rs8
-rw-r--r--compiler/rustc_traits/Cargo.toml1
-rw-r--r--compiler/rustc_traits/src/coroutine_witnesses.rs2
-rw-r--r--compiler/rustc_traits/src/dropck_outlives.rs2
-rw-r--r--compiler/rustc_ty_utils/src/abi.rs1
-rw-r--r--compiler/rustc_type_ir/Cargo.toml2
-rw-r--r--compiler/rustc_type_ir/src/infer_ctxt.rs4
-rw-r--r--compiler/rustc_type_ir/src/inherent.rs6
-rw-r--r--compiler/rustc_type_ir/src/ir_print.rs49
-rw-r--r--compiler/rustc_type_ir/src/region_kind.rs2
294 files changed, 6587 insertions, 5289 deletions
diff --git a/compiler/rustc_abi/Cargo.toml b/compiler/rustc_abi/Cargo.toml
index 5f9afc46a1a..83d96d8d04d 100644
--- a/compiler/rustc_abi/Cargo.toml
+++ b/compiler/rustc_abi/Cargo.toml
@@ -9,6 +9,7 @@ bitflags = "2.4.1"
 rand = { version = "0.9.0", default-features = false, optional = true }
 rand_xoshiro = { version = "0.7.0", optional = true }
 rustc_data_structures = { path = "../rustc_data_structures", optional = true }
+rustc_error_messages = { path = "../rustc_error_messages", optional = true }
 rustc_hashes = { path = "../rustc_hashes" }
 rustc_index = { path = "../rustc_index", default-features = false }
 rustc_macros = { path = "../rustc_macros", optional = true }
@@ -24,6 +25,7 @@ default = ["nightly", "randomize"]
 # without depending on rustc_data_structures, rustc_macros and rustc_serialize
 nightly = [
     "dep:rustc_data_structures",
+    "dep:rustc_error_messages",
     "dep:rustc_macros",
     "dep:rustc_serialize",
     "dep:rustc_span",
diff --git a/compiler/rustc_abi/src/extern_abi.rs b/compiler/rustc_abi/src/extern_abi.rs
index 29a3678abf3..41d744e1946 100644
--- a/compiler/rustc_abi/src/extern_abi.rs
+++ b/compiler/rustc_abi/src/extern_abi.rs
@@ -223,6 +223,9 @@ impl StableOrd for ExternAbi {
     const THIS_IMPLEMENTATION_HAS_BEEN_TRIPLE_CHECKED: () = ();
 }
 
+#[cfg(feature = "nightly")]
+rustc_error_messages::into_diag_arg_using_display!(ExternAbi);
+
 impl ExternAbi {
     /// An ABI "like Rust"
     ///
diff --git a/compiler/rustc_ast/src/ast.rs b/compiler/rustc_ast/src/ast.rs
index 87c9c797ea5..de3e0e0c87f 100644
--- a/compiler/rustc_ast/src/ast.rs
+++ b/compiler/rustc_ast/src/ast.rs
@@ -3137,7 +3137,7 @@ impl FnRetTy {
 #[derive(Clone, Copy, PartialEq, Encodable, Decodable, Debug, Walkable)]
 pub enum Inline {
     Yes,
-    No,
+    No { had_parse_error: Result<(), ErrorGuaranteed> },
 }
 
 /// Module item kind.
@@ -3147,7 +3147,7 @@ pub enum ModKind {
     /// or with definition outlined to a separate file `mod foo;` and already loaded from it.
     /// The inner span is from the first token past `{` to the last token until `}`,
     /// or from the first to the last token in the loaded file.
-    Loaded(ThinVec<Box<Item>>, Inline, ModSpans, Result<(), ErrorGuaranteed>),
+    Loaded(ThinVec<Box<Item>>, Inline, ModSpans),
     /// Module with definition outlined to a separate file `mod foo;` but not yet loaded from it.
     Unloaded,
 }
diff --git a/compiler/rustc_ast/src/token.rs b/compiler/rustc_ast/src/token.rs
index fc816f2cb79..ea98bebd305 100644
--- a/compiler/rustc_ast/src/token.rs
+++ b/compiler/rustc_ast/src/token.rs
@@ -7,6 +7,7 @@ pub use NtPatKind::*;
 pub use TokenKind::*;
 use rustc_macros::{Decodable, Encodable, HashStable_Generic};
 use rustc_span::edition::Edition;
+use rustc_span::symbol::IdentPrintMode;
 use rustc_span::{DUMMY_SP, ErrorGuaranteed, Span, kw, sym};
 #[allow(clippy::useless_attribute)] // FIXME: following use of `hidden_glob_reexports` incorrectly triggers `useless_attribute` lint.
 #[allow(hidden_glob_reexports)]
@@ -344,15 +345,24 @@ pub enum IdentIsRaw {
     Yes,
 }
 
-impl From<bool> for IdentIsRaw {
-    fn from(b: bool) -> Self {
-        if b { Self::Yes } else { Self::No }
+impl IdentIsRaw {
+    pub fn to_print_mode_ident(self) -> IdentPrintMode {
+        match self {
+            IdentIsRaw::No => IdentPrintMode::Normal,
+            IdentIsRaw::Yes => IdentPrintMode::RawIdent,
+        }
+    }
+    pub fn to_print_mode_lifetime(self) -> IdentPrintMode {
+        match self {
+            IdentIsRaw::No => IdentPrintMode::Normal,
+            IdentIsRaw::Yes => IdentPrintMode::RawLifetime,
+        }
     }
 }
 
-impl From<IdentIsRaw> for bool {
-    fn from(is_raw: IdentIsRaw) -> bool {
-        matches!(is_raw, IdentIsRaw::Yes)
+impl From<bool> for IdentIsRaw {
+    fn from(b: bool) -> Self {
+        if b { Self::Yes } else { Self::No }
     }
 }
 
diff --git a/compiler/rustc_ast/src/tokenstream.rs b/compiler/rustc_ast/src/tokenstream.rs
index e55399adfb8..f4f35a4d2ee 100644
--- a/compiler/rustc_ast/src/tokenstream.rs
+++ b/compiler/rustc_ast/src/tokenstream.rs
@@ -907,6 +907,12 @@ impl TokenTreeCursor {
     pub fn bump(&mut self) {
         self.index += 1;
     }
+
+    // For skipping ahead in rare circumstances.
+    #[inline]
+    pub fn bump_to_end(&mut self) {
+        self.index = self.stream.len();
+    }
 }
 
 /// A `TokenStream` cursor that produces `Token`s. It's a bit odd that
diff --git a/compiler/rustc_ast_lowering/src/item.rs b/compiler/rustc_ast_lowering/src/item.rs
index 72817a0a9a0..bb559bd8921 100644
--- a/compiler/rustc_ast_lowering/src/item.rs
+++ b/compiler/rustc_ast_lowering/src/item.rs
@@ -251,7 +251,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
             ItemKind::Mod(_, ident, mod_kind) => {
                 let ident = self.lower_ident(*ident);
                 match mod_kind {
-                    ModKind::Loaded(items, _, spans, _) => {
+                    ModKind::Loaded(items, _, spans) => {
                         hir::ItemKind::Mod(ident, self.lower_mod(items, spans))
                     }
                     ModKind::Unloaded => panic!("`mod` items should have been loaded by now"),
@@ -1596,7 +1596,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let safety = self.lower_safety(h.safety, default_safety);
 
         // Treat safe `#[target_feature]` functions as unsafe, but also remember that we did so.
-        let safety = if find_attr!(attrs, AttributeKind::TargetFeature { .. })
+        let safety = if find_attr!(attrs, AttributeKind::TargetFeature { was_forced: false, .. })
             && safety.is_safe()
             && !self.tcx.sess.target.is_like_wasm
         {
diff --git a/compiler/rustc_ast_passes/Cargo.toml b/compiler/rustc_ast_passes/Cargo.toml
index 1940628b44a..3e04f8b11ec 100644
--- a/compiler/rustc_ast_passes/Cargo.toml
+++ b/compiler/rustc_ast_passes/Cargo.toml
@@ -15,7 +15,6 @@ rustc_errors = { path = "../rustc_errors" }
 rustc_feature = { path = "../rustc_feature" }
 rustc_fluent_macro = { path = "../rustc_fluent_macro" }
 rustc_macros = { path = "../rustc_macros" }
-rustc_parse = { path = "../rustc_parse" }
 rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
 rustc_target = { path = "../rustc_target" }
diff --git a/compiler/rustc_ast_passes/messages.ftl b/compiler/rustc_ast_passes/messages.ftl
index 73cbcdd30ce..a95f1443968 100644
--- a/compiler/rustc_ast_passes/messages.ftl
+++ b/compiler/rustc_ast_passes/messages.ftl
@@ -20,6 +20,10 @@ ast_passes_abi_must_not_have_return_type=
     .note = functions with the {$abi} ABI cannot have a return type
     .help = remove the return type
 
+ast_passes_abi_x86_interrupt =
+    invalid signature for `extern "x86-interrupt"` function
+    .note = functions with the "x86-interrupt" ABI must be have either 1 or 2 parameters (but found {$param_count})
+
 ast_passes_assoc_const_without_body =
     associated constant in `impl` without body
     .suggestion = provide a definition for the constant
@@ -109,6 +113,10 @@ ast_passes_extern_without_abi = `extern` declarations without an explicit ABI ar
     .suggestion = specify an ABI
     .help = prior to Rust 2024, a default ABI was inferred
 
+ast_passes_extern_without_abi_sugg = `extern` declarations without an explicit ABI are deprecated
+    .label = ABI should be specified here
+    .suggestion = explicitly specify the {$default_abi} ABI
+
 ast_passes_feature_on_non_nightly = `#![feature]` may not be used on the {$channel} release channel
     .suggestion = remove the attribute
     .stable_since = the feature `{$name}` has been stable since `{$since}` and no longer requires an attribute to enable
diff --git a/compiler/rustc_ast_passes/src/ast_validation.rs b/compiler/rustc_ast_passes/src/ast_validation.rs
index 0c72f319007..6133cc3548b 100644
--- a/compiler/rustc_ast_passes/src/ast_validation.rs
+++ b/compiler/rustc_ast_passes/src/ast_validation.rs
@@ -25,16 +25,16 @@ use rustc_abi::{CanonAbi, ExternAbi, InterruptKind};
 use rustc_ast::visit::{AssocCtxt, BoundKind, FnCtxt, FnKind, Visitor, walk_list};
 use rustc_ast::*;
 use rustc_ast_pretty::pprust::{self, State};
+use rustc_attr_parsing::validate_attr;
 use rustc_data_structures::fx::FxIndexMap;
-use rustc_errors::DiagCtxtHandle;
+use rustc_errors::{DiagCtxtHandle, LintBuffer};
 use rustc_feature::Features;
-use rustc_parse::validate_attr;
 use rustc_session::Session;
+use rustc_session::lint::BuiltinLintDiag;
 use rustc_session::lint::builtin::{
     DEPRECATED_WHERE_CLAUSE_LOCATION, MISSING_ABI, MISSING_UNSAFE_ON_EXTERN,
     PATTERNS_IN_FNS_WITHOUT_BODY,
 };
-use rustc_session::lint::{BuiltinLintDiag, LintBuffer};
 use rustc_span::{Ident, Span, kw, sym};
 use rustc_target::spec::{AbiMap, AbiMapping};
 use thin_vec::thin_vec;
@@ -405,6 +405,17 @@ impl<'a> AstValidator<'a> {
                         if let InterruptKind::X86 = interrupt_kind {
                             // "x86-interrupt" is special because it does have arguments.
                             // FIXME(workingjubilee): properly lint on acceptable input types.
+                            let inputs = &sig.decl.inputs;
+                            let param_count = inputs.len();
+                            if !matches!(param_count, 1 | 2) {
+                                let mut spans: Vec<Span> =
+                                    inputs.iter().map(|arg| arg.span).collect();
+                                if spans.is_empty() {
+                                    spans = vec![sig.span];
+                                }
+                                self.dcx().emit_err(errors::AbiX86Interrupt { spans, param_count });
+                            }
+
                             if let FnRetTy::Ty(ref ret_ty) = sig.decl.output
                                 && match &ret_ty.kind {
                                     TyKind::Never => false,
@@ -865,7 +876,7 @@ impl<'a> AstValidator<'a> {
                 MISSING_ABI,
                 id,
                 span,
-                BuiltinLintDiag::MissingAbi(span, ExternAbi::FALLBACK),
+                errors::MissingAbiSugg { span, default_abi: ExternAbi::FALLBACK },
             )
         }
     }
@@ -1169,7 +1180,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                     self.dcx().emit_err(errors::UnsafeItem { span, kind: "module" });
                 }
                 // Ensure that `path` attributes on modules are recorded as used (cf. issue #35584).
-                if !matches!(mod_kind, ModKind::Loaded(_, Inline::Yes, _, _))
+                if !matches!(mod_kind, ModKind::Loaded(_, Inline::Yes, _))
                     && !attr::contains_name(&item.attrs, sym::path)
                 {
                     self.check_mod_file_item_asciionly(*ident);
diff --git a/compiler/rustc_ast_passes/src/errors.rs b/compiler/rustc_ast_passes/src/errors.rs
index 5ecc0d21411..ae8f056cb4e 100644
--- a/compiler/rustc_ast_passes/src/errors.rs
+++ b/compiler/rustc_ast_passes/src/errors.rs
@@ -4,7 +4,7 @@ use rustc_abi::ExternAbi;
 use rustc_ast::ParamKindOrd;
 use rustc_errors::codes::*;
 use rustc_errors::{Applicability, Diag, EmissionGuarantee, Subdiagnostic};
-use rustc_macros::{Diagnostic, Subdiagnostic};
+use rustc_macros::{Diagnostic, LintDiagnostic, Subdiagnostic};
 use rustc_span::{Ident, Span, Symbol};
 
 use crate::fluent_generated as fluent;
@@ -815,6 +815,14 @@ pub(crate) struct MissingAbi {
     pub span: Span,
 }
 
+#[derive(LintDiagnostic)]
+#[diag(ast_passes_extern_without_abi_sugg)]
+pub(crate) struct MissingAbiSugg {
+    #[suggestion(code = "extern {default_abi}", applicability = "machine-applicable")]
+    pub span: Span,
+    pub default_abi: ExternAbi,
+}
+
 #[derive(Diagnostic)]
 #[diag(ast_passes_abi_custom_safe_foreign_function)]
 pub(crate) struct AbiCustomSafeForeignFunction {
@@ -891,3 +899,12 @@ pub(crate) struct AbiMustNotHaveReturnType {
     pub span: Span,
     pub abi: ExternAbi,
 }
+
+#[derive(Diagnostic)]
+#[diag(ast_passes_abi_x86_interrupt)]
+#[note]
+pub(crate) struct AbiX86Interrupt {
+    #[primary_span]
+    pub spans: Vec<Span>,
+    pub param_count: usize,
+}
diff --git a/compiler/rustc_ast_passes/src/feature_gate.rs b/compiler/rustc_ast_passes/src/feature_gate.rs
index c9344a76a7b..e763c9d69fc 100644
--- a/compiler/rustc_ast_passes/src/feature_gate.rs
+++ b/compiler/rustc_ast_passes/src/feature_gate.rs
@@ -524,6 +524,7 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session, features: &Features) {
     gate_all!(where_clause_attrs, "attributes in `where` clause are unstable");
     gate_all!(super_let, "`super let` is experimental");
     gate_all!(frontmatter, "frontmatters are experimental");
+    gate_all!(coroutines, "coroutine syntax is experimental");
 
     if !visitor.features.never_patterns() {
         if let Some(spans) = spans.get(&sym::never_patterns) {
diff --git a/compiler/rustc_ast_pretty/src/pprust/state.rs b/compiler/rustc_ast_pretty/src/pprust/state.rs
index 85f76036df7..a056ce3e29d 100644
--- a/compiler/rustc_ast_pretty/src/pprust/state.rs
+++ b/compiler/rustc_ast_pretty/src/pprust/state.rs
@@ -10,7 +10,7 @@ use std::borrow::Cow;
 use std::sync::Arc;
 
 use rustc_ast::attr::AttrIdGenerator;
-use rustc_ast::token::{self, CommentKind, Delimiter, IdentIsRaw, Token, TokenKind};
+use rustc_ast::token::{self, CommentKind, Delimiter, Token, TokenKind};
 use rustc_ast::tokenstream::{Spacing, TokenStream, TokenTree};
 use rustc_ast::util::classify;
 use rustc_ast::util::comments::{Comment, CommentStyle};
@@ -441,7 +441,7 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
     fn print_generic_args(&mut self, args: &ast::GenericArgs, colons_before_params: bool);
 
     fn print_ident(&mut self, ident: Ident) {
-        self.word(IdentPrinter::for_ast_ident(ident, ident.is_raw_guess()).to_string());
+        self.word(IdentPrinter::for_ast_ident(ident, ident.guess_print_mode()).to_string());
         self.ann_post(ident)
     }
 
@@ -1015,17 +1015,16 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
 
             /* Name components */
             token::Ident(name, is_raw) => {
-                IdentPrinter::new(name, is_raw.into(), convert_dollar_crate).to_string().into()
+                IdentPrinter::new(name, is_raw.to_print_mode_ident(), convert_dollar_crate)
+                    .to_string()
+                    .into()
             }
             token::NtIdent(ident, is_raw) => {
-                IdentPrinter::for_ast_ident(ident, is_raw.into()).to_string().into()
+                IdentPrinter::for_ast_ident(ident, is_raw.to_print_mode_ident()).to_string().into()
             }
 
-            token::Lifetime(name, IdentIsRaw::No)
-            | token::NtLifetime(Ident { name, .. }, IdentIsRaw::No) => name.to_string().into(),
-            token::Lifetime(name, IdentIsRaw::Yes)
-            | token::NtLifetime(Ident { name, .. }, IdentIsRaw::Yes) => {
-                format!("'r#{}", &name.as_str()[1..]).into()
+            token::Lifetime(name, is_raw) | token::NtLifetime(Ident { name, .. }, is_raw) => {
+                IdentPrinter::new(name, is_raw.to_print_mode_lifetime(), None).to_string().into()
             }
 
             /* Other */
diff --git a/compiler/rustc_attr_parsing/Cargo.toml b/compiler/rustc_attr_parsing/Cargo.toml
index bac89373b67..fd8f7ffb2ed 100644
--- a/compiler/rustc_attr_parsing/Cargo.toml
+++ b/compiler/rustc_attr_parsing/Cargo.toml
@@ -5,7 +5,6 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-itertools = "0.12"
 rustc_abi = { path = "../rustc_abi" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_ast_pretty = { path = "../rustc_ast_pretty" }
@@ -15,6 +14,7 @@ rustc_fluent_macro = { path = "../rustc_fluent_macro" }
 rustc_hir = { path = "../rustc_hir" }
 rustc_lexer = { path = "../rustc_lexer" }
 rustc_macros = { path = "../rustc_macros" }
+rustc_parse = { path = "../rustc_parse" }
 rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
 thin-vec = "0.2.12"
diff --git a/compiler/rustc_attr_parsing/messages.ftl b/compiler/rustc_attr_parsing/messages.ftl
index 4fb66a81652..40e9d597530 100644
--- a/compiler/rustc_attr_parsing/messages.ftl
+++ b/compiler/rustc_attr_parsing/messages.ftl
@@ -12,9 +12,11 @@ attr_parsing_empty_attribute =
 
 attr_parsing_invalid_target = `#[{$name}]` attribute cannot be used on {$target}
     .help = `#[{$name}]` can {$only}be applied to {$applied}
+    .suggestion = remove the attribute
 attr_parsing_invalid_target_lint = `#[{$name}]` attribute cannot be used on {$target}
     .warn = {-attr_parsing_previously_accepted}
     .help = `#[{$name}]` can {$only}be applied to {$applied}
+    .suggestion = remove the attribute
 
 attr_parsing_empty_confusables =
     expected at least one confusable name
@@ -168,3 +170,22 @@ attr_parsing_unused_multiple =
 
 -attr_parsing_previously_accepted =
     this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+
+attr_parsing_meta_bad_delim = wrong meta list delimiters
+attr_parsing_meta_bad_delim_suggestion = the delimiters should be `(` and `)`
+
+attr_parsing_unsafe_attr_outside_unsafe = unsafe attribute used without unsafe
+    .label = usage of unsafe attribute
+attr_parsing_unsafe_attr_outside_unsafe_suggestion = wrap the attribute in `unsafe(...)`
+
+attr_parsing_invalid_attr_unsafe = `{$name}` is not an unsafe attribute
+    .label = this is not an unsafe attribute
+    .suggestion = remove the `unsafe(...)`
+    .note = extraneous unsafe is not allowed in attributes
+
+attr_parsing_invalid_meta_item = expected a literal (`1u8`, `1.0f32`, `"string"`, etc.) here, found {$descr}
+    .remove_neg_sugg = negative numbers are not literals, try removing the `-` sign
+    .quote_ident_sugg = surround the identifier with quotation marks to make it into a string literal
+
+attr_parsing_suffixed_literal_in_attribute = suffixed literals are not allowed in attributes
+    .help = instead of using a suffixed literal (`1u8`, `1.0f32`, etc.), use an unsuffixed version (`1`, `1.0`, etc.)
diff --git a/compiler/rustc_attr_parsing/src/attributes/allow_unstable.rs b/compiler/rustc_attr_parsing/src/attributes/allow_unstable.rs
index 4d995027814..088fa73d742 100644
--- a/compiler/rustc_attr_parsing/src/attributes/allow_unstable.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/allow_unstable.rs
@@ -1,14 +1,6 @@
 use std::iter;
 
-use rustc_feature::{AttributeTemplate, template};
-use rustc_hir::attrs::AttributeKind;
-use rustc_hir::{MethodKind, Target};
-use rustc_span::{Span, Symbol, sym};
-
-use super::{CombineAttributeParser, ConvertFn};
-use crate::context::MaybeWarn::{Allow, Warn};
-use crate::context::{AcceptContext, AllowedTargets, Stage};
-use crate::parser::ArgParser;
+use super::prelude::*;
 use crate::session_diagnostics;
 
 pub(crate) struct AllowInternalUnstableParser;
diff --git a/compiler/rustc_attr_parsing/src/attributes/body.rs b/compiler/rustc_attr_parsing/src/attributes/body.rs
index 88540384621..a1492d76194 100644
--- a/compiler/rustc_attr_parsing/src/attributes/body.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/body.rs
@@ -1,12 +1,6 @@
 //! Attributes that can be found in function body.
 
-use rustc_hir::Target;
-use rustc_hir::attrs::AttributeKind;
-use rustc_span::{Symbol, sym};
-
-use super::{NoArgsAttributeParser, OnDuplicate};
-use crate::context::MaybeWarn::Allow;
-use crate::context::{AllowedTargets, Stage};
+use super::prelude::*;
 
 pub(crate) struct CoroutineParser;
 
diff --git a/compiler/rustc_attr_parsing/src/attributes/codegen_attrs.rs b/compiler/rustc_attr_parsing/src/attributes/codegen_attrs.rs
index 6ea073896c2..ffdacff7152 100644
--- a/compiler/rustc_attr_parsing/src/attributes/codegen_attrs.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/codegen_attrs.rs
@@ -1,16 +1,7 @@
-use rustc_feature::{AttributeTemplate, template};
-use rustc_hir::attrs::{AttributeKind, CoverageAttrKind, OptimizeAttr, UsedBy};
-use rustc_hir::{MethodKind, Target};
+use rustc_hir::attrs::{CoverageAttrKind, OptimizeAttr, SanitizerSet, UsedBy};
 use rustc_session::parse::feature_err;
-use rustc_span::{Span, Symbol, sym};
-
-use super::{
-    AcceptMapping, AttributeOrder, AttributeParser, CombineAttributeParser, ConvertFn,
-    NoArgsAttributeParser, OnDuplicate, SingleAttributeParser,
-};
-use crate::context::MaybeWarn::{Allow, Warn};
-use crate::context::{AcceptContext, AllowedTargets, FinalizeContext, Stage};
-use crate::parser::ArgParser;
+
+use super::prelude::*;
 use crate::session_diagnostics::{NakedFunctionIncompatibleAttribute, NullOnExport};
 
 pub(crate) struct OptimizeParser;
@@ -44,7 +35,7 @@ impl<S: Stage> SingleAttributeParser<S> for OptimizeParser {
             Some(sym::speed) => OptimizeAttr::Speed,
             Some(sym::none) => OptimizeAttr::DoNotOptimize,
             _ => {
-                cx.expected_specific_argument(single.span(), vec!["size", "speed", "none"]);
+                cx.expected_specific_argument(single.span(), &[sym::size, sym::speed, sym::none]);
                 OptimizeAttr::Default
             }
         };
@@ -91,7 +82,7 @@ impl<S: Stage> SingleAttributeParser<S> for CoverageParser {
 
     fn convert(cx: &mut AcceptContext<'_, '_, S>, args: &ArgParser<'_>) -> Option<AttributeKind> {
         let Some(args) = args.list() else {
-            cx.expected_specific_argument_and_list(cx.attr_span, vec!["on", "off"]);
+            cx.expected_specific_argument_and_list(cx.attr_span, &[sym::on, sym::off]);
             return None;
         };
 
@@ -100,7 +91,8 @@ impl<S: Stage> SingleAttributeParser<S> for CoverageParser {
             return None;
         };
 
-        let fail_incorrect_argument = |span| cx.expected_specific_argument(span, vec!["on", "off"]);
+        let fail_incorrect_argument =
+            |span| cx.expected_specific_argument(span, &[sym::on, sym::off]);
 
         let Some(arg) = arg.meta_item() else {
             fail_incorrect_argument(args.span);
@@ -135,6 +127,7 @@ impl<S: Stage> SingleAttributeParser<S> for ExportNameParser {
         Warn(Target::Field),
         Warn(Target::Arm),
         Warn(Target::MacroDef),
+        Warn(Target::MacroCall),
     ]);
     const TEMPLATE: AttributeTemplate = template!(NameValueStr: "name");
 
@@ -182,6 +175,7 @@ impl<S: Stage> AttributeParser<S> for NakedParser {
         Allow(Target::Method(MethodKind::Inherent)),
         Allow(Target::Method(MethodKind::Trait { body: true })),
         Allow(Target::Method(MethodKind::TraitImpl)),
+        Warn(Target::MacroCall),
     ]);
 
     fn finalize(self, cx: &FinalizeContext<'_, '_, S>) -> Option<AttributeKind> {
@@ -286,6 +280,7 @@ impl<S: Stage> NoArgsAttributeParser<S> for TrackCallerParser {
         Warn(Target::MacroDef),
         Warn(Target::Arm),
         Warn(Target::Field),
+        Warn(Target::MacroCall),
     ]);
     const CREATE: fn(Span) -> AttributeKind = AttributeKind::TrackCaller;
 }
@@ -352,7 +347,7 @@ impl<S: Stage> AttributeParser<S> for UsedParser {
                             UsedBy::Linker
                         }
                         _ => {
-                            cx.expected_specific_argument(l.span(), vec!["compiler", "linker"]);
+                            cx.expected_specific_argument(l.span(), &[sym::compiler, sym::linker]);
                             return;
                         }
                     }
@@ -373,7 +368,8 @@ impl<S: Stage> AttributeParser<S> for UsedParser {
             }
         },
     )];
-    const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(&[Allow(Target::Static)]);
+    const ALLOWED_TARGETS: AllowedTargets =
+        AllowedTargets::AllowList(&[Allow(Target::Static), Warn(Target::MacroCall)]);
 
     fn finalize(self, _cx: &FinalizeContext<'_, '_, S>) -> Option<AttributeKind> {
         // Ratcheting behaviour, if both `linker` and `compiler` are specified, use `linker`
@@ -385,57 +381,68 @@ impl<S: Stage> AttributeParser<S> for UsedParser {
     }
 }
 
+fn parse_tf_attribute<'c, S: Stage>(
+    cx: &'c mut AcceptContext<'_, '_, S>,
+    args: &'c ArgParser<'_>,
+) -> impl IntoIterator<Item = (Symbol, Span)> + 'c {
+    let mut features = Vec::new();
+    let ArgParser::List(list) = args else {
+        cx.expected_list(cx.attr_span);
+        return features;
+    };
+    if list.is_empty() {
+        cx.warn_empty_attribute(cx.attr_span);
+        return features;
+    }
+    for item in list.mixed() {
+        let Some(name_value) = item.meta_item() else {
+            cx.expected_name_value(item.span(), Some(sym::enable));
+            return features;
+        };
+
+        // Validate name
+        let Some(name) = name_value.path().word_sym() else {
+            cx.expected_name_value(name_value.path().span(), Some(sym::enable));
+            return features;
+        };
+        if name != sym::enable {
+            cx.expected_name_value(name_value.path().span(), Some(sym::enable));
+            return features;
+        }
+
+        // Use value
+        let Some(name_value) = name_value.args().name_value() else {
+            cx.expected_name_value(item.span(), Some(sym::enable));
+            return features;
+        };
+        let Some(value_str) = name_value.value_as_str() else {
+            cx.expected_string_literal(name_value.value_span, Some(name_value.value_as_lit()));
+            return features;
+        };
+        for feature in value_str.as_str().split(",") {
+            features.push((Symbol::intern(feature), item.span()));
+        }
+    }
+    features
+}
+
 pub(crate) struct TargetFeatureParser;
 
 impl<S: Stage> CombineAttributeParser<S> for TargetFeatureParser {
     type Item = (Symbol, Span);
     const PATH: &[Symbol] = &[sym::target_feature];
-    const CONVERT: ConvertFn<Self::Item> = |items, span| AttributeKind::TargetFeature(items, span);
+    const CONVERT: ConvertFn<Self::Item> = |items, span| AttributeKind::TargetFeature {
+        features: items,
+        attr_span: span,
+        was_forced: false,
+    };
     const TEMPLATE: AttributeTemplate = template!(List: &["enable = \"feat1, feat2\""]);
 
     fn extend<'c>(
         cx: &'c mut AcceptContext<'_, '_, S>,
         args: &'c ArgParser<'_>,
     ) -> impl IntoIterator<Item = Self::Item> + 'c {
-        let mut features = Vec::new();
-        let ArgParser::List(list) = args else {
-            cx.expected_list(cx.attr_span);
-            return features;
-        };
-        if list.is_empty() {
-            cx.warn_empty_attribute(cx.attr_span);
-            return features;
-        }
-        for item in list.mixed() {
-            let Some(name_value) = item.meta_item() else {
-                cx.expected_name_value(item.span(), Some(sym::enable));
-                return features;
-            };
-
-            // Validate name
-            let Some(name) = name_value.path().word_sym() else {
-                cx.expected_name_value(name_value.path().span(), Some(sym::enable));
-                return features;
-            };
-            if name != sym::enable {
-                cx.expected_name_value(name_value.path().span(), Some(sym::enable));
-                return features;
-            }
-
-            // Use value
-            let Some(name_value) = name_value.args().name_value() else {
-                cx.expected_name_value(item.span(), Some(sym::enable));
-                return features;
-            };
-            let Some(value_str) = name_value.value_as_str() else {
-                cx.expected_string_literal(name_value.value_span, Some(name_value.value_as_lit()));
-                return features;
-            };
-            for feature in value_str.as_str().split(",") {
-                features.push((Symbol::intern(feature), item.span()));
-            }
-        }
-        features
+        parse_tf_attribute(cx, args)
     }
 
     const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(&[
@@ -447,5 +454,134 @@ impl<S: Stage> CombineAttributeParser<S> for TargetFeatureParser {
         Warn(Target::Field),
         Warn(Target::Arm),
         Warn(Target::MacroDef),
+        Warn(Target::MacroCall),
+    ]);
+}
+
+pub(crate) struct ForceTargetFeatureParser;
+
+impl<S: Stage> CombineAttributeParser<S> for ForceTargetFeatureParser {
+    type Item = (Symbol, Span);
+    const PATH: &[Symbol] = &[sym::force_target_feature];
+    const CONVERT: ConvertFn<Self::Item> = |items, span| AttributeKind::TargetFeature {
+        features: items,
+        attr_span: span,
+        was_forced: true,
+    };
+    const TEMPLATE: AttributeTemplate = template!(List: &["enable = \"feat1, feat2\""]);
+    const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(&[
+        Allow(Target::Fn),
+        Allow(Target::Method(MethodKind::Inherent)),
+        Allow(Target::Method(MethodKind::Trait { body: true })),
+        Allow(Target::Method(MethodKind::TraitImpl)),
+    ]);
+
+    fn extend<'c>(
+        cx: &'c mut AcceptContext<'_, '_, S>,
+        args: &'c ArgParser<'_>,
+    ) -> impl IntoIterator<Item = Self::Item> + 'c {
+        parse_tf_attribute(cx, args)
+    }
+}
+
+pub(crate) struct SanitizeParser;
+
+impl<S: Stage> SingleAttributeParser<S> for SanitizeParser {
+    const PATH: &[Symbol] = &[sym::sanitize];
+
+    // FIXME: still checked in check_attrs.rs
+    const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(ALL_TARGETS);
+
+    const TEMPLATE: AttributeTemplate = template!(List: &[
+        r#"address = "on|off""#,
+        r#"kernel_address = "on|off""#,
+        r#"cfi = "on|off""#,
+        r#"hwaddress = "on|off""#,
+        r#"kcfi = "on|off""#,
+        r#"memory = "on|off""#,
+        r#"memtag = "on|off""#,
+        r#"shadow_call_stack = "on|off""#,
+        r#"thread = "on|off""#
     ]);
+
+    const ATTRIBUTE_ORDER: AttributeOrder = AttributeOrder::KeepOutermost;
+    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Error;
+
+    fn convert(cx: &mut AcceptContext<'_, '_, S>, args: &ArgParser<'_>) -> Option<AttributeKind> {
+        let Some(list) = args.list() else {
+            cx.expected_list(cx.attr_span);
+            return None;
+        };
+
+        let mut on_set = SanitizerSet::empty();
+        let mut off_set = SanitizerSet::empty();
+
+        for item in list.mixed() {
+            let Some(item) = item.meta_item() else {
+                cx.expected_name_value(item.span(), None);
+                continue;
+            };
+
+            let path = item.path().word_sym();
+            let Some(value) = item.args().name_value() else {
+                cx.expected_name_value(item.span(), path);
+                continue;
+            };
+
+            let mut apply = |s: SanitizerSet| {
+                let is_on = match value.value_as_str() {
+                    Some(sym::on) => true,
+                    Some(sym::off) => false,
+                    Some(_) => {
+                        cx.expected_specific_argument_strings(
+                            value.value_span,
+                            &[sym::on, sym::off],
+                        );
+                        return;
+                    }
+                    None => {
+                        cx.expected_string_literal(value.value_span, Some(value.value_as_lit()));
+                        return;
+                    }
+                };
+
+                if is_on {
+                    on_set |= s;
+                } else {
+                    off_set |= s;
+                }
+            };
+
+            match path {
+                Some(sym::address) | Some(sym::kernel_address) => {
+                    apply(SanitizerSet::ADDRESS | SanitizerSet::KERNELADDRESS)
+                }
+                Some(sym::cfi) => apply(SanitizerSet::CFI),
+                Some(sym::kcfi) => apply(SanitizerSet::KCFI),
+                Some(sym::memory) => apply(SanitizerSet::MEMORY),
+                Some(sym::memtag) => apply(SanitizerSet::MEMTAG),
+                Some(sym::shadow_call_stack) => apply(SanitizerSet::SHADOWCALLSTACK),
+                Some(sym::thread) => apply(SanitizerSet::THREAD),
+                Some(sym::hwaddress) => apply(SanitizerSet::HWADDRESS),
+                _ => {
+                    cx.expected_specific_argument_strings(
+                        item.path().span(),
+                        &[
+                            sym::address,
+                            sym::cfi,
+                            sym::kcfi,
+                            sym::memory,
+                            sym::memtag,
+                            sym::shadow_call_stack,
+                            sym::thread,
+                            sym::hwaddress,
+                        ],
+                    );
+                    continue;
+                }
+            }
+        }
+
+        Some(AttributeKind::Sanitize { on_set, off_set, span: cx.attr_span })
+    }
 }
diff --git a/compiler/rustc_attr_parsing/src/attributes/confusables.rs b/compiler/rustc_attr_parsing/src/attributes/confusables.rs
index 00f949c82c5..97e78dfb136 100644
--- a/compiler/rustc_attr_parsing/src/attributes/confusables.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/confusables.rs
@@ -1,13 +1,6 @@
-use rustc_feature::template;
-use rustc_hir::attrs::AttributeKind;
-use rustc_hir::{MethodKind, Target};
-use rustc_span::{Span, Symbol, sym};
-use thin_vec::ThinVec;
-
-use super::{AcceptMapping, AttributeParser};
-use crate::context::MaybeWarn::Allow;
-use crate::context::{AllowedTargets, FinalizeContext, Stage};
-use crate::session_diagnostics;
+use super::prelude::*;
+use crate::session_diagnostics::EmptyConfusables;
+
 #[derive(Default)]
 pub(crate) struct ConfusablesParser {
     confusables: ThinVec<Symbol>,
@@ -25,7 +18,7 @@ impl<S: Stage> AttributeParser<S> for ConfusablesParser {
             };
 
             if list.is_empty() {
-                cx.emit_err(session_diagnostics::EmptyConfusables { span: cx.attr_span });
+                cx.emit_err(EmptyConfusables { span: cx.attr_span });
             }
 
             for param in list.mixed() {
diff --git a/compiler/rustc_attr_parsing/src/attributes/crate_level.rs b/compiler/rustc_attr_parsing/src/attributes/crate_level.rs
new file mode 100644
index 00000000000..9175d7479e1
--- /dev/null
+++ b/compiler/rustc_attr_parsing/src/attributes/crate_level.rs
@@ -0,0 +1,33 @@
+use super::prelude::*;
+
+pub(crate) struct CrateNameParser;
+
+impl<S: Stage> SingleAttributeParser<S> for CrateNameParser {
+    const PATH: &[Symbol] = &[sym::crate_name];
+    const ATTRIBUTE_ORDER: AttributeOrder = AttributeOrder::KeepOutermost;
+    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::WarnButFutureError;
+    const TEMPLATE: AttributeTemplate = template!(NameValueStr: "name");
+
+    // FIXME: crate name is allowed on all targets and ignored,
+    //        even though it should only be valid on crates of course
+    const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(ALL_TARGETS);
+
+    fn convert(cx: &mut AcceptContext<'_, '_, S>, args: &ArgParser<'_>) -> Option<AttributeKind> {
+        let ArgParser::NameValue(n) = args else {
+            cx.expected_name_value(cx.attr_span, None);
+            return None;
+        };
+
+        let Some(name) = n.value_as_str() else {
+            cx.expected_string_literal(n.value_span, Some(n.value_as_lit()));
+            return None;
+        };
+
+        Some(AttributeKind::CrateName {
+            name,
+            name_span: n.value_span,
+            attr_span: cx.attr_span,
+            style: cx.attr_style,
+        })
+    }
+}
diff --git a/compiler/rustc_attr_parsing/src/attributes/deprecation.rs b/compiler/rustc_attr_parsing/src/attributes/deprecation.rs
index d3a61f3a653..31c698228ef 100644
--- a/compiler/rustc_attr_parsing/src/attributes/deprecation.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/deprecation.rs
@@ -1,14 +1,11 @@
-use rustc_feature::{AttributeTemplate, template};
-use rustc_hir::attrs::{AttributeKind, DeprecatedSince, Deprecation};
-use rustc_hir::{MethodKind, Target};
-use rustc_span::{Span, Symbol, sym};
+use rustc_hir::attrs::{DeprecatedSince, Deprecation};
 
+use super::prelude::*;
 use super::util::parse_version;
-use super::{AttributeOrder, OnDuplicate, SingleAttributeParser};
-use crate::context::MaybeWarn::{Allow, Error};
-use crate::context::{AcceptContext, AllowedTargets, Stage};
-use crate::parser::ArgParser;
-use crate::session_diagnostics;
+use crate::session_diagnostics::{
+    DeprecatedItemSuggestion, InvalidSince, MissingNote, MissingSince,
+};
+
 pub(crate) struct DeprecationParser;
 
 fn get<S: Stage>(
@@ -102,7 +99,7 @@ impl<S: Stage> SingleAttributeParser<S> for DeprecationParser {
                         }
                         Some(name @ sym::suggestion) => {
                             if !features.deprecated_suggestion() {
-                                cx.emit_err(session_diagnostics::DeprecatedItemSuggestion {
+                                cx.emit_err(DeprecatedItemSuggestion {
                                     span: param.span(),
                                     is_nightly: cx.sess().is_nightly_build(),
                                     details: (),
@@ -144,18 +141,18 @@ impl<S: Stage> SingleAttributeParser<S> for DeprecationParser {
             } else if let Some(version) = parse_version(since) {
                 DeprecatedSince::RustcVersion(version)
             } else {
-                cx.emit_err(session_diagnostics::InvalidSince { span: cx.attr_span });
+                cx.emit_err(InvalidSince { span: cx.attr_span });
                 DeprecatedSince::Err
             }
         } else if is_rustc {
-            cx.emit_err(session_diagnostics::MissingSince { span: cx.attr_span });
+            cx.emit_err(MissingSince { span: cx.attr_span });
             DeprecatedSince::Err
         } else {
             DeprecatedSince::Unspecified
         };
 
         if is_rustc && note.is_none() {
-            cx.emit_err(session_diagnostics::MissingNote { span: cx.attr_span });
+            cx.emit_err(MissingNote { span: cx.attr_span });
             return None;
         }
 
diff --git a/compiler/rustc_attr_parsing/src/attributes/dummy.rs b/compiler/rustc_attr_parsing/src/attributes/dummy.rs
index 85842b1b5c5..7293cee842c 100644
--- a/compiler/rustc_attr_parsing/src/attributes/dummy.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/dummy.rs
@@ -3,8 +3,10 @@ use rustc_hir::attrs::AttributeKind;
 use rustc_span::{Symbol, sym};
 
 use crate::attributes::{AttributeOrder, OnDuplicate, SingleAttributeParser};
-use crate::context::{ALL_TARGETS, AcceptContext, AllowedTargets, Stage};
+use crate::context::{AcceptContext, Stage};
 use crate::parser::ArgParser;
+use crate::target_checking::{ALL_TARGETS, AllowedTargets};
+
 pub(crate) struct DummyParser;
 impl<S: Stage> SingleAttributeParser<S> for DummyParser {
     const PATH: &[Symbol] = &[sym::rustc_dummy];
diff --git a/compiler/rustc_attr_parsing/src/attributes/inline.rs b/compiler/rustc_attr_parsing/src/attributes/inline.rs
index 33c21bad240..a73430c9d00 100644
--- a/compiler/rustc_attr_parsing/src/attributes/inline.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/inline.rs
@@ -2,17 +2,10 @@
 //                      note: need to model better how duplicate attr errors work when not using
 //                      SingleAttributeParser which is what we have two of here.
 
-use rustc_feature::{AttributeTemplate, template};
 use rustc_hir::attrs::{AttributeKind, InlineAttr};
-use rustc_hir::lints::AttributeLintKind;
-use rustc_hir::{MethodKind, Target};
-use rustc_span::{Symbol, sym};
 
-use super::{AcceptContext, AttributeOrder, OnDuplicate};
-use crate::attributes::SingleAttributeParser;
-use crate::context::MaybeWarn::{Allow, Warn};
-use crate::context::{AllowedTargets, Stage};
-use crate::parser::ArgParser;
+use super::prelude::*;
+
 pub(crate) struct InlineParser;
 
 impl<S: Stage> SingleAttributeParser<S> for InlineParser {
@@ -32,6 +25,7 @@ impl<S: Stage> SingleAttributeParser<S> for InlineParser {
         Warn(Target::MacroDef),
         Warn(Target::Arm),
         Warn(Target::AssocConst),
+        Warn(Target::MacroCall),
     ]);
     const TEMPLATE: AttributeTemplate = template!(
         Word,
@@ -56,7 +50,7 @@ impl<S: Stage> SingleAttributeParser<S> for InlineParser {
                         Some(AttributeKind::Inline(InlineAttr::Never, cx.attr_span))
                     }
                     _ => {
-                        cx.expected_specific_argument(l.span(), vec!["always", "never"]);
+                        cx.expected_specific_argument(l.span(), &[sym::always, sym::never]);
                         return None;
                     }
                 }
diff --git a/compiler/rustc_attr_parsing/src/attributes/link_attrs.rs b/compiler/rustc_attr_parsing/src/attributes/link_attrs.rs
index 552b9dfabc2..5e4551ccd79 100644
--- a/compiler/rustc_attr_parsing/src/attributes/link_attrs.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/link_attrs.rs
@@ -1,16 +1,10 @@
-use rustc_feature::{AttributeTemplate, template};
 use rustc_hir::attrs::AttributeKind::{LinkName, LinkOrdinal, LinkSection};
-use rustc_hir::attrs::{AttributeKind, Linkage};
-use rustc_hir::{MethodKind, Target};
-use rustc_span::{Span, Symbol, sym};
-
-use crate::attributes::{
-    AttributeOrder, NoArgsAttributeParser, OnDuplicate, SingleAttributeParser,
-};
-use crate::context::MaybeWarn::Allow;
-use crate::context::{ALL_TARGETS, AcceptContext, AllowedTargets, Stage, parse_single_integer};
-use crate::parser::ArgParser;
+use rustc_hir::attrs::Linkage;
+
+use super::prelude::*;
+use super::util::parse_single_integer;
 use crate::session_diagnostics::{LinkOrdinalOutOfRange, NullOnLinkSection};
+
 pub(crate) struct LinkNameParser;
 
 impl<S: Stage> SingleAttributeParser<S> for LinkNameParser {
@@ -116,8 +110,11 @@ impl<S: Stage> SingleAttributeParser<S> for LinkOrdinalParser {
     const PATH: &[Symbol] = &[sym::link_ordinal];
     const ATTRIBUTE_ORDER: AttributeOrder = AttributeOrder::KeepOutermost;
     const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Error;
-    const ALLOWED_TARGETS: AllowedTargets =
-        AllowedTargets::AllowList(&[Allow(Target::ForeignFn), Allow(Target::ForeignStatic)]);
+    const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(&[
+        Allow(Target::ForeignFn),
+        Allow(Target::ForeignStatic),
+        Warn(Target::MacroCall),
+    ]);
     const TEMPLATE: AttributeTemplate = template!(
         List: &["ordinal"],
         "https://doc.rust-lang.org/reference/items/external-blocks.html#the-link_ordinal-attribute"
@@ -212,16 +209,16 @@ impl<S: Stage> SingleAttributeParser<S> for LinkageParser {
             _ => {
                 cx.expected_specific_argument(
                     name_value.value_span,
-                    vec![
-                        "available_externally",
-                        "common",
-                        "extern_weak",
-                        "external",
-                        "internal",
-                        "linkonce",
-                        "linkonce_odr",
-                        "weak",
-                        "weak_odr",
+                    &[
+                        sym::available_externally,
+                        sym::common,
+                        sym::extern_weak,
+                        sym::external,
+                        sym::internal,
+                        sym::linkonce,
+                        sym::linkonce_odr,
+                        sym::weak,
+                        sym::weak_odr,
                     ],
                 );
                 return None;
diff --git a/compiler/rustc_attr_parsing/src/attributes/lint_helpers.rs b/compiler/rustc_attr_parsing/src/attributes/lint_helpers.rs
index 2b586d4003c..63b0809d0d8 100644
--- a/compiler/rustc_attr_parsing/src/attributes/lint_helpers.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/lint_helpers.rs
@@ -1,10 +1,5 @@
-use rustc_hir::attrs::AttributeKind;
-use rustc_hir::{MethodKind, Target};
-use rustc_span::{Span, Symbol, sym};
+use super::prelude::*;
 
-use crate::attributes::{NoArgsAttributeParser, OnDuplicate};
-use crate::context::MaybeWarn::{Allow, Error};
-use crate::context::{AllowedTargets, Stage};
 pub(crate) struct AsPtrParser;
 impl<S: Stage> NoArgsAttributeParser<S> for AsPtrParser {
     const PATH: &[Symbol] = &[sym::rustc_as_ptr];
diff --git a/compiler/rustc_attr_parsing/src/attributes/loop_match.rs b/compiler/rustc_attr_parsing/src/attributes/loop_match.rs
index 242e2f2c1bc..528090b8673 100644
--- a/compiler/rustc_attr_parsing/src/attributes/loop_match.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/loop_match.rs
@@ -1,10 +1,5 @@
-use rustc_hir::Target;
-use rustc_hir::attrs::AttributeKind;
-use rustc_span::{Span, Symbol, sym};
+use super::prelude::*;
 
-use crate::attributes::{NoArgsAttributeParser, OnDuplicate};
-use crate::context::MaybeWarn::Allow;
-use crate::context::{AllowedTargets, Stage};
 pub(crate) struct LoopMatchParser;
 impl<S: Stage> NoArgsAttributeParser<S> for LoopMatchParser {
     const PATH: &[Symbol] = &[sym::loop_match];
diff --git a/compiler/rustc_attr_parsing/src/attributes/macro_attrs.rs b/compiler/rustc_attr_parsing/src/attributes/macro_attrs.rs
index 8928129c201..180130c7be4 100644
--- a/compiler/rustc_attr_parsing/src/attributes/macro_attrs.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/macro_attrs.rs
@@ -1,15 +1,9 @@
 use rustc_errors::DiagArgValue;
-use rustc_feature::{AttributeTemplate, template};
-use rustc_hir::Target;
-use rustc_hir::attrs::{AttributeKind, MacroUseArgs};
-use rustc_span::{Span, Symbol, sym};
-use thin_vec::ThinVec;
+use rustc_hir::attrs::MacroUseArgs;
+
+use super::prelude::*;
+use crate::session_diagnostics::IllFormedAttributeInputLint;
 
-use crate::attributes::{AcceptMapping, AttributeParser, NoArgsAttributeParser, OnDuplicate};
-use crate::context::MaybeWarn::{Allow, Error, Warn};
-use crate::context::{AcceptContext, AllowedTargets, FinalizeContext, Stage};
-use crate::parser::ArgParser;
-use crate::session_diagnostics;
 pub(crate) struct MacroEscapeParser;
 impl<S: Stage> NoArgsAttributeParser<S> for MacroEscapeParser {
     const PATH: &[Symbol] = &[sym::macro_escape];
@@ -108,7 +102,7 @@ impl<S: Stage> AttributeParser<S> for MacroUseParser {
                 }
                 ArgParser::NameValue(_) => {
                     let suggestions = MACRO_USE_TEMPLATE.suggestions(cx.attr_style, sym::macro_use);
-                    cx.emit_err(session_diagnostics::IllFormedAttributeInputLint {
+                    cx.emit_err(IllFormedAttributeInputLint {
                         num_suggestions: suggestions.len(),
                         suggestions: DiagArgValue::StrListSepByAnd(
                             suggestions.into_iter().map(|s| format!("`{s}`").into()).collect(),
diff --git a/compiler/rustc_attr_parsing/src/attributes/mod.rs b/compiler/rustc_attr_parsing/src/attributes/mod.rs
index 3d6e26a24b8..9dad9c893f0 100644
--- a/compiler/rustc_attr_parsing/src/attributes/mod.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/mod.rs
@@ -7,9 +7,9 @@
 //! Specifically, you might not care about managing the state of your [`AttributeParser`]
 //! state machine yourself. In this case you can choose to implement:
 //!
-//! - [`SingleAttributeParser`]: makes it easy to implement an attribute which should error if it
+//! - [`SingleAttributeParser`](crate::attributes::SingleAttributeParser): makes it easy to implement an attribute which should error if it
 //! appears more than once in a list of attributes
-//! - [`CombineAttributeParser`]: makes it easy to implement an attribute which should combine the
+//! - [`CombineAttributeParser`](crate::attributes::CombineAttributeParser): makes it easy to implement an attribute which should combine the
 //! contents of attributes, if an attribute appear multiple times in a list
 //!
 //! Attributes should be added to `crate::context::ATTRIBUTE_PARSERS` to be parsed.
@@ -21,9 +21,13 @@ use rustc_hir::attrs::AttributeKind;
 use rustc_span::{Span, Symbol};
 use thin_vec::ThinVec;
 
-use crate::context::{AcceptContext, AllowedTargets, FinalizeContext, Stage};
+use crate::context::{AcceptContext, FinalizeContext, Stage};
 use crate::parser::ArgParser;
 use crate::session_diagnostics::UnusedMultiple;
+use crate::target_checking::AllowedTargets;
+
+/// All the parsers require roughly the same imports, so this prelude has most of the often-needed ones.
+mod prelude;
 
 pub(crate) mod allow_unstable;
 pub(crate) mod body;
@@ -31,6 +35,7 @@ pub(crate) mod cfg;
 pub(crate) mod cfg_old;
 pub(crate) mod codegen_attrs;
 pub(crate) mod confusables;
+pub(crate) mod crate_level;
 pub(crate) mod deprecation;
 pub(crate) mod dummy;
 pub(crate) mod inline;
diff --git a/compiler/rustc_attr_parsing/src/attributes/must_use.rs b/compiler/rustc_attr_parsing/src/attributes/must_use.rs
index b0ee3d1ba6e..e6a5141d783 100644
--- a/compiler/rustc_attr_parsing/src/attributes/must_use.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/must_use.rs
@@ -1,19 +1,29 @@
 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};
-use crate::context::{ALL_TARGETS, AcceptContext, AllowedTargets, Stage};
-use crate::parser::ArgParser;
-use crate::session_diagnostics;
+use super::prelude::*;
+use crate::session_diagnostics::IllFormedAttributeInputLint;
+
 pub(crate) struct MustUseParser;
 
 impl<S: Stage> SingleAttributeParser<S> for MustUseParser {
     const PATH: &[Symbol] = &[sym::must_use];
     const ATTRIBUTE_ORDER: AttributeOrder = AttributeOrder::KeepOutermost;
     const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::WarnButFutureError;
-    const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(ALL_TARGETS); //FIXME Still checked fully in `check_attr.rs`
+    const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowListWarnRest(&[
+        Allow(Target::Fn),
+        Allow(Target::Enum),
+        Allow(Target::Struct),
+        Allow(Target::Union),
+        Allow(Target::Method(MethodKind::Trait { body: false })),
+        Allow(Target::Method(MethodKind::Trait { body: true })),
+        Allow(Target::Method(MethodKind::Inherent)),
+        Allow(Target::ForeignFn),
+        // `impl Trait` in return position can trip
+        // `unused_must_use` if `Trait` is marked as
+        // `#[must_use]`
+        Allow(Target::Trait),
+        Error(Target::WherePredicate),
+    ]);
     const TEMPLATE: AttributeTemplate = template!(
         Word, NameValueStr: "reason",
         "https://doc.rust-lang.org/reference/attributes/diagnostics.html#the-must_use-attribute"
@@ -37,7 +47,7 @@ impl<S: Stage> SingleAttributeParser<S> for MustUseParser {
                 ArgParser::List(_) => {
                     let suggestions = <Self as SingleAttributeParser<S>>::TEMPLATE
                         .suggestions(cx.attr_style, "must_use");
-                    cx.emit_err(session_diagnostics::IllFormedAttributeInputLint {
+                    cx.emit_err(IllFormedAttributeInputLint {
                         num_suggestions: suggestions.len(),
                         suggestions: DiagArgValue::StrListSepByAnd(
                             suggestions.into_iter().map(|s| format!("`{s}`").into()).collect(),
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 589faf38f73..40073ea0f46 100644
--- a/compiler/rustc_attr_parsing/src/attributes/no_implicit_prelude.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/no_implicit_prelude.rs
@@ -1,10 +1,5 @@
-use rustc_hir::Target;
-use rustc_hir::attrs::AttributeKind;
-use rustc_span::{Span, sym};
+use super::prelude::*;
 
-use crate::attributes::{NoArgsAttributeParser, OnDuplicate};
-use crate::context::MaybeWarn::Allow;
-use crate::context::{AllowedTargets, Stage};
 pub(crate) struct NoImplicitPreludeParser;
 
 impl<S: Stage> NoArgsAttributeParser<S> for NoImplicitPreludeParser {
diff --git a/compiler/rustc_attr_parsing/src/attributes/non_exhaustive.rs b/compiler/rustc_attr_parsing/src/attributes/non_exhaustive.rs
index 41e9ca4de41..fc41c073fd2 100644
--- a/compiler/rustc_attr_parsing/src/attributes/non_exhaustive.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/non_exhaustive.rs
@@ -3,8 +3,10 @@ use rustc_hir::attrs::AttributeKind;
 use rustc_span::{Span, Symbol, sym};
 
 use crate::attributes::{NoArgsAttributeParser, OnDuplicate};
-use crate::context::MaybeWarn::{Allow, Warn};
-use crate::context::{AllowedTargets, Stage};
+use crate::context::Stage;
+use crate::target_checking::AllowedTargets;
+use crate::target_checking::Policy::{Allow, Warn};
+
 pub(crate) struct NonExhaustiveParser;
 
 impl<S: Stage> NoArgsAttributeParser<S> for NonExhaustiveParser {
@@ -17,6 +19,7 @@ impl<S: Stage> NoArgsAttributeParser<S> for NonExhaustiveParser {
         Warn(Target::Field),
         Warn(Target::Arm),
         Warn(Target::MacroDef),
+        Warn(Target::MacroCall),
     ]);
     const CREATE: fn(Span) -> AttributeKind = AttributeKind::NonExhaustive;
 }
diff --git a/compiler/rustc_attr_parsing/src/attributes/path.rs b/compiler/rustc_attr_parsing/src/attributes/path.rs
index f9191d1abed..e4cb806bb42 100644
--- a/compiler/rustc_attr_parsing/src/attributes/path.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/path.rs
@@ -1,12 +1,5 @@
-use rustc_feature::{AttributeTemplate, template};
-use rustc_hir::Target;
-use rustc_hir::attrs::AttributeKind;
-use rustc_span::{Symbol, sym};
+use super::prelude::*;
 
-use crate::attributes::{AttributeOrder, OnDuplicate, SingleAttributeParser};
-use crate::context::MaybeWarn::{Allow, Error};
-use crate::context::{AcceptContext, AllowedTargets, Stage};
-use crate::parser::ArgParser;
 pub(crate) struct PathParser;
 
 impl<S: Stage> SingleAttributeParser<S> for PathParser {
diff --git a/compiler/rustc_attr_parsing/src/attributes/prelude.rs b/compiler/rustc_attr_parsing/src/attributes/prelude.rs
new file mode 100644
index 00000000000..2bcdee55c75
--- /dev/null
+++ b/compiler/rustc_attr_parsing/src/attributes/prelude.rs
@@ -0,0 +1,20 @@
+// parsing
+// templates
+pub(super) use rustc_feature::{AttributeTemplate, template};
+// data structures
+pub(super) use rustc_hir::attrs::AttributeKind;
+pub(super) use rustc_hir::lints::AttributeLintKind;
+pub(super) use rustc_hir::{MethodKind, Target};
+pub(super) use rustc_span::{DUMMY_SP, Ident, Span, Symbol, sym};
+pub(super) use thin_vec::ThinVec;
+
+pub(super) use crate::attributes::{
+    AcceptMapping, AttributeOrder, AttributeParser, CombineAttributeParser, ConvertFn,
+    NoArgsAttributeParser, OnDuplicate, SingleAttributeParser,
+};
+// contexts
+pub(super) use crate::context::{AcceptContext, FinalizeContext, Stage};
+pub(super) use crate::parser::*;
+// target checking
+pub(super) use crate::target_checking::Policy::{Allow, Error, Warn};
+pub(super) use crate::target_checking::{ALL_TARGETS, AllowedTargets};
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 4624fa36287..b9929d6f1f8 100644
--- a/compiler/rustc_attr_parsing/src/attributes/proc_macro_attrs.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/proc_macro_attrs.rs
@@ -1,21 +1,13 @@
-use rustc_feature::{AttributeTemplate, template};
-use rustc_hir::Target;
-use rustc_hir::attrs::AttributeKind;
-use rustc_span::{Span, Symbol, sym};
-use thin_vec::ThinVec;
+use super::prelude::*;
+
+const PROC_MACRO_ALLOWED_TARGETS: AllowedTargets =
+    AllowedTargets::AllowList(&[Allow(Target::Fn), Warn(Target::Crate), Warn(Target::MacroCall)]);
 
-use crate::attributes::{
-    AttributeOrder, NoArgsAttributeParser, OnDuplicate, SingleAttributeParser,
-};
-use crate::context::MaybeWarn::{Allow, Warn};
-use crate::context::{AcceptContext, AllowedTargets, Stage};
-use crate::parser::ArgParser;
 pub(crate) struct ProcMacroParser;
 impl<S: Stage> NoArgsAttributeParser<S> for ProcMacroParser {
     const PATH: &[Symbol] = &[sym::proc_macro];
     const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Error;
-    const ALLOWED_TARGETS: AllowedTargets =
-        AllowedTargets::AllowList(&[Allow(Target::Fn), Warn(Target::Crate)]);
+    const ALLOWED_TARGETS: AllowedTargets = PROC_MACRO_ALLOWED_TARGETS;
     const CREATE: fn(Span) -> AttributeKind = AttributeKind::ProcMacro;
 }
 
@@ -23,8 +15,7 @@ pub(crate) struct ProcMacroAttributeParser;
 impl<S: Stage> NoArgsAttributeParser<S> for ProcMacroAttributeParser {
     const PATH: &[Symbol] = &[sym::proc_macro_attribute];
     const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Error;
-    const ALLOWED_TARGETS: AllowedTargets =
-        AllowedTargets::AllowList(&[Allow(Target::Fn), Warn(Target::Crate)]);
+    const ALLOWED_TARGETS: AllowedTargets = PROC_MACRO_ALLOWED_TARGETS;
     const CREATE: fn(Span) -> AttributeKind = AttributeKind::ProcMacroAttribute;
 }
 
@@ -33,8 +24,7 @@ impl<S: Stage> SingleAttributeParser<S> for ProcMacroDeriveParser {
     const PATH: &[Symbol] = &[sym::proc_macro_derive];
     const ATTRIBUTE_ORDER: AttributeOrder = AttributeOrder::KeepOutermost;
     const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Error;
-    const ALLOWED_TARGETS: AllowedTargets =
-        AllowedTargets::AllowList(&[Allow(Target::Fn), Warn(Target::Crate)]);
+    const ALLOWED_TARGETS: AllowedTargets = PROC_MACRO_ALLOWED_TARGETS;
     const TEMPLATE: AttributeTemplate = template!(
         List: &["TraitName", "TraitName, attributes(name1, name2, ...)"],
         "https://doc.rust-lang.org/reference/procedural-macros.html#derive-macros"
@@ -110,7 +100,7 @@ fn parse_derive_like<S: Stage>(
             return None;
         };
         if !attr_list.path().word_is(sym::attributes) {
-            cx.expected_specific_argument(attrs.span(), vec!["attributes"]);
+            cx.expected_specific_argument(attrs.span(), &[sym::attributes]);
             return None;
         }
         let Some(attr_list) = attr_list.args().list() else {
diff --git a/compiler/rustc_attr_parsing/src/attributes/prototype.rs b/compiler/rustc_attr_parsing/src/attributes/prototype.rs
index fb1e47298b4..80fe82bf542 100644
--- a/compiler/rustc_attr_parsing/src/attributes/prototype.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/prototype.rs
@@ -7,8 +7,10 @@ use rustc_span::{Span, Symbol, sym};
 
 use super::{AttributeOrder, OnDuplicate};
 use crate::attributes::SingleAttributeParser;
-use crate::context::{AcceptContext, AllowedTargets, MaybeWarn, Stage};
+use crate::context::{AcceptContext, Stage};
 use crate::parser::ArgParser;
+use crate::target_checking::AllowedTargets;
+use crate::target_checking::Policy::Allow;
 
 pub(crate) struct CustomMirParser;
 
@@ -19,8 +21,7 @@ impl<S: Stage> SingleAttributeParser<S> for CustomMirParser {
 
     const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Error;
 
-    const ALLOWED_TARGETS: AllowedTargets =
-        AllowedTargets::AllowList(&[MaybeWarn::Allow(Target::Fn)]);
+    const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(&[Allow(Target::Fn)]);
 
     const TEMPLATE: AttributeTemplate = template!(List: &[r#"dialect = "...", phase = "...""#]);
 
@@ -108,7 +109,7 @@ fn parse_dialect<S: Stage>(
         sym::runtime => MirDialect::Runtime,
 
         _ => {
-            cx.expected_specific_argument(span, vec!["analysis", "built", "runtime"]);
+            cx.expected_specific_argument(span, &[sym::analysis, sym::built, sym::runtime]);
             *failed = true;
             return None;
         }
@@ -130,7 +131,7 @@ fn parse_phase<S: Stage>(
         sym::optimized => MirPhase::Optimized,
 
         _ => {
-            cx.expected_specific_argument(span, vec!["initial", "post-cleanup", "optimized"]);
+            cx.expected_specific_argument(span, &[sym::initial, sym::post_cleanup, sym::optimized]);
             *failed = true;
             return None;
         }
diff --git a/compiler/rustc_attr_parsing/src/attributes/repr.rs b/compiler/rustc_attr_parsing/src/attributes/repr.rs
index 7ab58ed9347..23aabd15597 100644
--- a/compiler/rustc_attr_parsing/src/attributes/repr.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/repr.rs
@@ -1,16 +1,10 @@
 use rustc_abi::Align;
 use rustc_ast::{IntTy, LitIntType, LitKind, UintTy};
-use rustc_feature::{AttributeTemplate, template};
-use rustc_hir::attrs::{AttributeKind, IntType, ReprAttr};
-use rustc_hir::{MethodKind, Target};
-use rustc_span::{DUMMY_SP, Span, Symbol, sym};
-
-use super::{AcceptMapping, AttributeParser, CombineAttributeParser, ConvertFn, FinalizeContext};
-use crate::context::MaybeWarn::Allow;
-use crate::context::{ALL_TARGETS, AcceptContext, AllowedTargets, Stage};
-use crate::parser::{ArgParser, MetaItemListParser, MetaItemParser};
-use crate::session_diagnostics;
-use crate::session_diagnostics::IncorrectReprFormatGenericCause;
+use rustc_hir::attrs::{IntType, ReprAttr};
+
+use super::prelude::*;
+use crate::session_diagnostics::{self, IncorrectReprFormatGenericCause};
+
 /// Parse #[repr(...)] forms.
 ///
 /// Valid repr contents: any of the primitive integral type names (see
diff --git a/compiler/rustc_attr_parsing/src/attributes/rustc_internal.rs b/compiler/rustc_attr_parsing/src/attributes/rustc_internal.rs
index efd7b650e44..a995549fc7c 100644
--- a/compiler/rustc_attr_parsing/src/attributes/rustc_internal.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/rustc_internal.rs
@@ -1,12 +1,6 @@
-use rustc_feature::{AttributeTemplate, template};
-use rustc_hir::Target;
-use rustc_hir::attrs::AttributeKind;
-use rustc_span::{Symbol, sym};
-
-use crate::attributes::{AttributeOrder, OnDuplicate, SingleAttributeParser};
-use crate::context::MaybeWarn::Allow;
-use crate::context::{AcceptContext, AllowedTargets, Stage, parse_single_integer};
-use crate::parser::ArgParser;
+use super::prelude::*;
+use super::util::parse_single_integer;
+
 pub(crate) struct RustcLayoutScalarValidRangeStart;
 
 impl<S: Stage> SingleAttributeParser<S> for RustcLayoutScalarValidRangeStart {
diff --git a/compiler/rustc_attr_parsing/src/attributes/semantics.rs b/compiler/rustc_attr_parsing/src/attributes/semantics.rs
index d4ad861a3a2..d7f62483297 100644
--- a/compiler/rustc_attr_parsing/src/attributes/semantics.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/semantics.rs
@@ -1,8 +1,5 @@
-use rustc_hir::attrs::AttributeKind;
-use rustc_span::{Span, Symbol, sym};
+use super::prelude::*;
 
-use crate::attributes::{NoArgsAttributeParser, OnDuplicate};
-use crate::context::{ALL_TARGETS, AllowedTargets, Stage};
 pub(crate) struct MayDangleParser;
 impl<S: Stage> NoArgsAttributeParser<S> for MayDangleParser {
     const PATH: &[Symbol] = &[sym::may_dangle];
diff --git a/compiler/rustc_attr_parsing/src/attributes/stability.rs b/compiler/rustc_attr_parsing/src/attributes/stability.rs
index 5a26178f84b..b94e23477ff 100644
--- a/compiler/rustc_attr_parsing/src/attributes/stability.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/stability.rs
@@ -1,20 +1,13 @@
 use std::num::NonZero;
 
 use rustc_errors::ErrorGuaranteed;
-use rustc_feature::template;
-use rustc_hir::attrs::AttributeKind;
 use rustc_hir::{
     DefaultBodyStability, MethodKind, PartialConstStability, Stability, StabilityLevel,
     StableSince, Target, UnstableReason, VERSION_PLACEHOLDER,
 };
-use rustc_span::{Ident, Span, Symbol, sym};
 
+use super::prelude::*;
 use super::util::parse_version;
-use super::{AcceptMapping, AttributeParser, OnDuplicate};
-use crate::attributes::NoArgsAttributeParser;
-use crate::context::MaybeWarn::Allow;
-use crate::context::{AcceptContext, AllowedTargets, FinalizeContext, Stage};
-use crate::parser::{ArgParser, MetaItemParser};
 use crate::session_diagnostics::{self, UnsupportedLiteralReason};
 
 macro_rules! reject_outside_std {
@@ -54,6 +47,7 @@ const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(&[
     Allow(Target::Static),
     Allow(Target::ForeignFn),
     Allow(Target::ForeignStatic),
+    Allow(Target::ExternCrate),
 ]);
 
 #[derive(Default)]
diff --git a/compiler/rustc_attr_parsing/src/attributes/test_attrs.rs b/compiler/rustc_attr_parsing/src/attributes/test_attrs.rs
index 164c680b8a8..510ff1ded49 100644
--- a/compiler/rustc_attr_parsing/src/attributes/test_attrs.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/test_attrs.rs
@@ -1,13 +1,5 @@
-use rustc_feature::{AttributeTemplate, template};
-use rustc_hir::Target;
-use rustc_hir::attrs::AttributeKind;
-use rustc_hir::lints::AttributeLintKind;
-use rustc_span::{Symbol, sym};
+use super::prelude::*;
 
-use crate::attributes::{AttributeOrder, OnDuplicate, SingleAttributeParser};
-use crate::context::MaybeWarn::{Allow, Error};
-use crate::context::{AcceptContext, AllowedTargets, Stage};
-use crate::parser::ArgParser;
 pub(crate) struct IgnoreParser;
 
 impl<S: Stage> SingleAttributeParser<S> for IgnoreParser {
@@ -89,7 +81,7 @@ impl<S: Stage> SingleAttributeParser<S> for ShouldPanicParser {
                         return None;
                     };
                     if !single.path().word_is(sym::expected) {
-                        cx.expected_specific_argument_strings(list.span, vec!["expected"]);
+                        cx.expected_specific_argument_strings(list.span, &[sym::expected]);
                         return None;
                     }
                     let Some(nv) = single.args().name_value() else {
diff --git a/compiler/rustc_attr_parsing/src/attributes/traits.rs b/compiler/rustc_attr_parsing/src/attributes/traits.rs
index ee9d7ba99cd..89ac1b07d16 100644
--- a/compiler/rustc_attr_parsing/src/attributes/traits.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/traits.rs
@@ -1,16 +1,14 @@
-use core::mem;
-
-use rustc_feature::{AttributeTemplate, template};
-use rustc_hir::attrs::AttributeKind;
-use rustc_hir::{MethodKind, Target};
-use rustc_span::{Span, Symbol, sym};
+use std::mem;
 
+use super::prelude::*;
 use crate::attributes::{
     AttributeOrder, NoArgsAttributeParser, OnDuplicate, SingleAttributeParser,
 };
-use crate::context::MaybeWarn::{Allow, Warn};
-use crate::context::{ALL_TARGETS, AcceptContext, AllowedTargets, Stage};
+use crate::context::{AcceptContext, Stage};
 use crate::parser::ArgParser;
+use crate::target_checking::Policy::{Allow, Warn};
+use crate::target_checking::{ALL_TARGETS, AllowedTargets};
+
 pub(crate) struct SkipDuringMethodDispatchParser;
 impl<S: Stage> SingleAttributeParser<S> for SkipDuringMethodDispatchParser {
     const PATH: &[Symbol] = &[sym::rustc_skip_during_method_dispatch];
@@ -44,7 +42,7 @@ impl<S: Stage> SingleAttributeParser<S> for SkipDuringMethodDispatchParser {
                 Some(key @ sym::array) => (key, &mut array),
                 Some(key @ sym::boxed_slice) => (key, &mut boxed_slice),
                 _ => {
-                    cx.expected_specific_argument(path.span(), vec!["array", "boxed_slice"]);
+                    cx.expected_specific_argument(path.span(), &[sym::array, sym::boxed_slice]);
                     continue;
                 }
             };
diff --git a/compiler/rustc_attr_parsing/src/attributes/transparency.rs b/compiler/rustc_attr_parsing/src/attributes/transparency.rs
index 0ffcf434b52..ea1f5549c4e 100644
--- a/compiler/rustc_attr_parsing/src/attributes/transparency.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/transparency.rs
@@ -1,13 +1,7 @@
-use rustc_feature::{AttributeTemplate, template};
-use rustc_hir::Target;
-use rustc_hir::attrs::AttributeKind;
 use rustc_span::hygiene::Transparency;
-use rustc_span::{Symbol, sym};
 
-use super::{AttributeOrder, OnDuplicate, SingleAttributeParser};
-use crate::context::MaybeWarn::Allow;
-use crate::context::{AcceptContext, AllowedTargets, Stage};
-use crate::parser::ArgParser;
+use super::prelude::*;
+
 pub(crate) struct TransparencyParser;
 
 // FIXME(jdonszelmann): make these proper diagnostics
@@ -35,7 +29,7 @@ impl<S: Stage> SingleAttributeParser<S> for TransparencyParser {
             Some(_) => {
                 cx.expected_specific_argument_strings(
                     nv.value_span,
-                    vec!["transparent", "semitransparent", "opaque"],
+                    &[sym::transparent, sym::semitransparent, sym::opaque],
                 );
                 None
             }
diff --git a/compiler/rustc_attr_parsing/src/attributes/util.rs b/compiler/rustc_attr_parsing/src/attributes/util.rs
index 10134915b27..77e8c32e59d 100644
--- a/compiler/rustc_attr_parsing/src/attributes/util.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/util.rs
@@ -1,8 +1,12 @@
-use rustc_ast::attr::{AttributeExt, first_attr_value_str_by_name};
+use rustc_ast::LitKind;
+use rustc_ast::attr::AttributeExt;
 use rustc_feature::is_builtin_attr_name;
 use rustc_hir::RustcVersion;
 use rustc_span::{Symbol, sym};
 
+use crate::context::{AcceptContext, Stage};
+use crate::parser::ArgParser;
+
 /// Parse a rustc version number written inside string literal in an attribute,
 /// like appears in `since = "1.0.0"`. Suffixes like "-dev" and "-nightly" are
 /// not accepted in this position, unlike when parsing CFG_RELEASE.
@@ -23,10 +27,6 @@ pub fn is_builtin_attr(attr: &impl AttributeExt) -> bool {
     attr.is_doc_comment() || attr.ident().is_some_and(|ident| is_builtin_attr_name(ident.name))
 }
 
-pub fn find_crate_name(attrs: &[impl AttributeExt]) -> Option<Symbol> {
-    first_attr_value_str_by_name(attrs, sym::crate_name)
-}
-
 pub fn is_doc_alias_attrs_contain_symbol<'tcx, T: AttributeExt + 'tcx>(
     attrs: impl Iterator<Item = &'tcx T>,
     symbol: Symbol,
@@ -56,3 +56,32 @@ pub fn is_doc_alias_attrs_contain_symbol<'tcx, T: AttributeExt + 'tcx>(
     }
     false
 }
+
+/// Parse a single integer.
+///
+/// Used by attributes that take a single integer as argument, such as
+/// `#[link_ordinal]` and `#[rustc_layout_scalar_valid_range_start]`.
+/// `cx` is the context given to the attribute.
+/// `args` is the parser for the attribute arguments.
+pub(crate) fn parse_single_integer<S: Stage>(
+    cx: &mut AcceptContext<'_, '_, S>,
+    args: &ArgParser<'_>,
+) -> Option<u128> {
+    let Some(list) = args.list() else {
+        cx.expected_list(cx.attr_span);
+        return None;
+    };
+    let Some(single) = list.single() else {
+        cx.expected_single_argument(list.span);
+        return None;
+    };
+    let Some(lit) = single.lit() else {
+        cx.expected_integer_literal(single.span());
+        return None;
+    };
+    let LitKind::Int(num, _ty) = lit.kind else {
+        cx.expected_integer_literal(single.span());
+        return None;
+    };
+    Some(num.0)
+}
diff --git a/compiler/rustc_attr_parsing/src/context.rs b/compiler/rustc_attr_parsing/src/context.rs
index c0d3bc99ba9..d4b9cfe00ad 100644
--- a/compiler/rustc_attr_parsing/src/context.rs
+++ b/compiler/rustc_attr_parsing/src/context.rs
@@ -3,28 +3,28 @@ use std::collections::BTreeMap;
 use std::ops::{Deref, DerefMut};
 use std::sync::LazyLock;
 
-use itertools::Itertools;
 use private::Sealed;
-use rustc_ast::{self as ast, AttrStyle, LitKind, MetaItemLit, NodeId};
-use rustc_errors::{DiagCtxtHandle, Diagnostic};
-use rustc_feature::{AttributeTemplate, Features};
+use rustc_ast::{AttrStyle, MetaItemLit, NodeId};
+use rustc_errors::{Diag, Diagnostic, Level};
+use rustc_feature::AttributeTemplate;
 use rustc_hir::attrs::AttributeKind;
 use rustc_hir::lints::{AttributeLint, AttributeLintKind};
-use rustc_hir::{
-    AttrArgs, AttrItem, AttrPath, Attribute, HashIgnoredAttrId, HirId, MethodKind, Target,
-};
+use rustc_hir::{AttrPath, HirId};
 use rustc_session::Session;
-use rustc_span::{DUMMY_SP, ErrorGuaranteed, Span, Symbol, sym};
+use rustc_span::{ErrorGuaranteed, Span, Symbol};
 
+use crate::AttributeParser;
 use crate::attributes::allow_unstable::{
     AllowConstFnUnstableParser, AllowInternalUnstableParser, UnstableFeatureBoundParser,
 };
 use crate::attributes::body::CoroutineParser;
 use crate::attributes::codegen_attrs::{
-    ColdParser, CoverageParser, ExportNameParser, NakedParser, NoMangleParser, OptimizeParser,
-    TargetFeatureParser, TrackCallerParser, UsedParser,
+    ColdParser, CoverageParser, ExportNameParser, ForceTargetFeatureParser, NakedParser,
+    NoMangleParser, OptimizeParser, SanitizeParser, TargetFeatureParser, TrackCallerParser,
+    UsedParser,
 };
 use crate::attributes::confusables::ConfusablesParser;
+use crate::attributes::crate_level::CrateNameParser;
 use crate::attributes::deprecation::DeprecationParser;
 use crate::attributes::dummy::DummyParser;
 use crate::attributes::inline::{InlineParser, RustcForceInlineParser};
@@ -65,23 +65,21 @@ use crate::attributes::traits::{
 };
 use crate::attributes::transparency::TransparencyParser;
 use crate::attributes::{AttributeParser as _, Combine, Single, WithoutArgs};
-use crate::context::MaybeWarn::{Allow, Error, Warn};
-use crate::parser::{ArgParser, MetaItemParser, PathParser};
-use crate::session_diagnostics::{
-    AttributeParseError, AttributeParseErrorReason, InvalidTarget, UnknownMetaItem,
-};
+use crate::parser::{ArgParser, PathParser};
+use crate::session_diagnostics::{AttributeParseError, AttributeParseErrorReason, UnknownMetaItem};
+use crate::target_checking::AllowedTargets;
 
 type GroupType<S> = LazyLock<GroupTypeInner<S>>;
 
-struct GroupTypeInner<S: Stage> {
-    accepters: BTreeMap<&'static [Symbol], Vec<GroupTypeInnerAccept<S>>>,
-    finalizers: Vec<FinalizeFn<S>>,
+pub(super) struct GroupTypeInner<S: Stage> {
+    pub(super) accepters: BTreeMap<&'static [Symbol], Vec<GroupTypeInnerAccept<S>>>,
+    pub(super) finalizers: Vec<FinalizeFn<S>>,
 }
 
-struct GroupTypeInnerAccept<S: Stage> {
-    template: AttributeTemplate,
-    accept_fn: AcceptFn<S>,
-    allowed_targets: AllowedTargets,
+pub(super) struct GroupTypeInnerAccept<S: Stage> {
+    pub(super) template: AttributeTemplate,
+    pub(super) accept_fn: AcceptFn<S>,
+    pub(super) allowed_targets: AllowedTargets,
 }
 
 type AcceptFn<S> =
@@ -161,6 +159,7 @@ attribute_parsers!(
         // tidy-alphabetical-start
         Combine<AllowConstFnUnstableParser>,
         Combine<AllowInternalUnstableParser>,
+        Combine<ForceTargetFeatureParser>,
         Combine<ReprParser>,
         Combine<TargetFeatureParser>,
         Combine<UnstableFeatureBoundParser>,
@@ -168,6 +167,7 @@ attribute_parsers!(
 
         // tidy-alphabetical-start
         Single<CoverageParser>,
+        Single<CrateNameParser>,
         Single<CustomMirParser>,
         Single<DeprecationParser>,
         Single<DummyParser>,
@@ -187,6 +187,7 @@ attribute_parsers!(
         Single<RustcLayoutScalarValidRangeEnd>,
         Single<RustcLayoutScalarValidRangeStart>,
         Single<RustcObjectLifetimeDefaultParser>,
+        Single<SanitizeParser>,
         Single<ShouldPanicParser>,
         Single<SkipDuringMethodDispatchParser>,
         Single<TransparencyParser>,
@@ -264,11 +265,7 @@ impl Stage for Early {
         sess: &'sess Session,
         diag: impl for<'x> Diagnostic<'x>,
     ) -> ErrorGuaranteed {
-        if self.emit_errors.should_emit() {
-            sess.dcx().emit_err(diag)
-        } else {
-            sess.dcx().create_err(diag).delay_as_bug()
-        }
+        self.should_emit().emit_err(sess.dcx().create_err(diag))
     }
 
     fn should_emit(&self) -> ShouldEmit {
@@ -315,7 +312,9 @@ pub struct AcceptContext<'f, 'sess, S: Stage> {
     /// The span of the attribute currently being parsed
     pub(crate) attr_span: Span,
 
+    /// Whether it is an inner or outer attribute
     pub(crate) attr_style: AttrStyle,
+
     /// The expected structure of the attribute.
     ///
     /// Used in reporting errors to give a hint to users what the attribute *should* look like.
@@ -334,7 +333,7 @@ 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 !self.stage.should_emit().should_emit() {
+        if matches!(self.stage.should_emit(), ShouldEmit::Nothing) {
             return;
         }
         let id = self.target_id;
@@ -506,10 +505,11 @@ impl<'f, 'sess: 'f, S: Stage> AcceptContext<'f, 'sess, S> {
         })
     }
 
+    /// produces an error along the lines of `expected one of [foo, meow]`
     pub(crate) fn expected_specific_argument(
         &self,
         span: Span,
-        possibilities: Vec<&'static str>,
+        possibilities: &[Symbol],
     ) -> ErrorGuaranteed {
         self.emit_err(AttributeParseError {
             span,
@@ -525,10 +525,12 @@ impl<'f, 'sess: 'f, S: Stage> AcceptContext<'f, 'sess, S> {
         })
     }
 
+    /// produces an error along the lines of `expected one of [foo, meow] as an argument`.
+    /// i.e. slightly different wording to [`expected_specific_argument`](Self::expected_specific_argument).
     pub(crate) fn expected_specific_argument_and_list(
         &self,
         span: Span,
-        possibilities: Vec<&'static str>,
+        possibilities: &[Symbol],
     ) -> ErrorGuaranteed {
         self.emit_err(AttributeParseError {
             span,
@@ -544,10 +546,11 @@ impl<'f, 'sess: 'f, S: Stage> AcceptContext<'f, 'sess, S> {
         })
     }
 
+    /// produces an error along the lines of `expected one of ["foo", "meow"]`
     pub(crate) fn expected_specific_argument_strings(
         &self,
         span: Span,
-        possibilities: Vec<&'static str>,
+        possibilities: &[Symbol],
     ) -> ErrorGuaranteed {
         self.emit_err(AttributeParseError {
             span,
@@ -595,7 +598,7 @@ pub struct SharedContext<'p, 'sess, S: Stage> {
     /// The id ([`NodeId`] if `S` is `Early`, [`HirId`] if `S` is `Late`) of the syntactical component this attribute was applied to
     pub(crate) target_id: S::Id,
 
-    emit_lint: &'p mut dyn FnMut(AttributeLint<S::Id>),
+    pub(crate) emit_lint: &'p mut dyn FnMut(AttributeLint<S::Id>),
 }
 
 /// Context given to every attribute parser during finalization.
@@ -648,8 +651,13 @@ pub enum OmitDoc {
     Skip,
 }
 
-#[derive(Copy, Clone)]
+#[derive(Copy, Clone, Debug)]
 pub enum ShouldEmit {
+    /// The operations will emit errors, and lints, and errors are fatal.
+    ///
+    /// Only relevant when early parsing, in late parsing equivalent to `ErrorsAndLints`.
+    /// Late parsing is never fatal, and instead tries to emit as many diagnostics as possible.
+    EarlyFatal,
     /// The operation will emit errors and lints.
     /// This is usually what you need.
     ErrorsAndLints,
@@ -659,564 +667,12 @@ pub enum ShouldEmit {
 }
 
 impl ShouldEmit {
-    pub fn should_emit(&self) -> bool {
-        match self {
-            ShouldEmit::ErrorsAndLints => true,
-            ShouldEmit::Nothing => false,
-        }
-    }
-}
-
-#[derive(Debug)]
-pub(crate) enum AllowedTargets {
-    AllowList(&'static [MaybeWarn]),
-    AllowListWarnRest(&'static [MaybeWarn]),
-}
-
-pub(crate) enum AllowedResult {
-    Allowed,
-    Warn,
-    Error,
-}
-
-impl AllowedTargets {
-    pub(crate) fn is_allowed(&self, target: Target) -> AllowedResult {
-        match self {
-            AllowedTargets::AllowList(list) => {
-                if list.contains(&Allow(target)) {
-                    AllowedResult::Allowed
-                } else if list.contains(&Warn(target)) {
-                    AllowedResult::Warn
-                } else {
-                    AllowedResult::Error
-                }
-            }
-            AllowedTargets::AllowListWarnRest(list) => {
-                if list.contains(&Allow(target)) {
-                    AllowedResult::Allowed
-                } else if list.contains(&Error(target)) {
-                    AllowedResult::Error
-                } else {
-                    AllowedResult::Warn
-                }
-            }
-        }
-    }
-
-    pub(crate) fn allowed_targets(&self) -> Vec<Target> {
+    pub(crate) fn emit_err(&self, diag: Diag<'_>) -> ErrorGuaranteed {
         match self {
-            AllowedTargets::AllowList(list) => list,
-            AllowedTargets::AllowListWarnRest(list) => list,
+            ShouldEmit::EarlyFatal if diag.level() == Level::DelayedBug => diag.emit(),
+            ShouldEmit::EarlyFatal => diag.upgrade_to_fatal().emit(),
+            ShouldEmit::ErrorsAndLints => diag.emit(),
+            ShouldEmit::Nothing => diag.delay_as_bug(),
         }
-        .iter()
-        .filter_map(|target| match target {
-            Allow(target) => Some(*target),
-            Warn(_) => None,
-            Error(_) => None,
-        })
-        .collect()
-    }
-}
-
-#[derive(Debug, Eq, PartialEq)]
-pub(crate) enum MaybeWarn {
-    Allow(Target),
-    Warn(Target),
-    Error(Target),
-}
-
-/// Context created once, for example as part of the ast lowering
-/// context, through which all attributes can be lowered.
-pub struct AttributeParser<'sess, S: Stage = Late> {
-    pub(crate) tools: Vec<Symbol>,
-    features: Option<&'sess Features>,
-    sess: &'sess Session,
-    stage: S,
-
-    /// *Only* parse attributes with this symbol.
-    ///
-    /// Used in cases where we want the lowering infrastructure for parse just a single attribute.
-    parse_only: Option<Symbol>,
-}
-
-impl<'sess> AttributeParser<'sess, Early> {
-    /// This method allows you to parse attributes *before* you have access to features or tools.
-    /// One example where this is necessary, is to parse `feature` attributes themselves for
-    /// example.
-    ///
-    /// Try to use this as little as possible. Attributes *should* be lowered during
-    /// `rustc_ast_lowering`. Some attributes require access to features to parse, which would
-    /// crash if you tried to do so through [`parse_limited`](Self::parse_limited).
-    ///
-    /// To make sure use is limited, supply a `Symbol` you'd like to parse. Only attributes with
-    /// that symbol are picked out of the list of instructions and parsed. Those are returned.
-    ///
-    /// No diagnostics will be emitted when parsing limited. Lints are not emitted at all, while
-    /// errors will be emitted as a delayed bugs. in other words, we *expect* attributes parsed
-    /// with `parse_limited` to be reparsed later during ast lowering where we *do* emit the errors
-    pub fn parse_limited(
-        sess: &'sess Session,
-        attrs: &[ast::Attribute],
-        sym: Symbol,
-        target_span: Span,
-        target_node_id: NodeId,
-        features: Option<&'sess Features>,
-    ) -> Option<Attribute> {
-        let mut p = Self {
-            features,
-            tools: Vec::new(),
-            parse_only: Some(sym),
-            sess,
-            stage: Early { emit_errors: ShouldEmit::Nothing },
-        };
-        let mut parsed = p.parse_attribute_list(
-            attrs,
-            target_span,
-            target_node_id,
-            Target::Crate, // Does not matter, we're not going to emit errors anyways
-            OmitDoc::Skip,
-            std::convert::identity,
-            |_lint| {
-                panic!("can't emit lints here for now (nothing uses this atm)");
-            },
-        );
-        assert!(parsed.len() <= 1);
-
-        parsed.pop()
-    }
-
-    pub fn parse_single<T>(
-        sess: &'sess Session,
-        attr: &ast::Attribute,
-        target_span: Span,
-        target_node_id: NodeId,
-        features: Option<&'sess Features>,
-        emit_errors: ShouldEmit,
-        parse_fn: fn(cx: &mut AcceptContext<'_, '_, Early>, item: &ArgParser<'_>) -> T,
-        template: &AttributeTemplate,
-    ) -> T {
-        let mut parser = Self {
-            features,
-            tools: Vec::new(),
-            parse_only: None,
-            sess,
-            stage: Early { emit_errors },
-        };
-        let ast::AttrKind::Normal(normal_attr) = &attr.kind else {
-            panic!("parse_single called on a doc attr")
-        };
-        let meta_parser = MetaItemParser::from_attr(normal_attr, parser.dcx());
-        let path = meta_parser.path();
-        let args = meta_parser.args();
-        let mut cx: AcceptContext<'_, 'sess, Early> = AcceptContext {
-            shared: SharedContext {
-                cx: &mut parser,
-                target_span,
-                target_id: target_node_id,
-                emit_lint: &mut |_lint| {
-                    panic!("can't emit lints here for now (nothing uses this atm)");
-                },
-            },
-            attr_span: attr.span,
-            attr_style: attr.style,
-            template,
-            attr_path: path.get_attribute_path(),
-        };
-        parse_fn(&mut cx, args)
-    }
-}
-
-impl<'sess, S: Stage> AttributeParser<'sess, S> {
-    pub fn new(
-        sess: &'sess Session,
-        features: &'sess Features,
-        tools: Vec<Symbol>,
-        stage: S,
-    ) -> Self {
-        Self { features: Some(features), tools, parse_only: None, sess, stage }
-    }
-
-    pub(crate) fn sess(&self) -> &'sess Session {
-        &self.sess
-    }
-
-    pub(crate) fn features(&self) -> &'sess Features {
-        self.features.expect("features not available at this point in the compiler")
     }
-
-    pub(crate) fn features_option(&self) -> Option<&'sess Features> {
-        self.features
-    }
-
-    pub(crate) fn dcx(&self) -> DiagCtxtHandle<'sess> {
-        self.sess().dcx()
-    }
-
-    /// Parse a list of attributes.
-    ///
-    /// `target_span` is the span of the thing this list of attributes is applied to,
-    /// and when `omit_doc` is set, doc attributes are filtered out.
-    pub fn parse_attribute_list(
-        &mut self,
-        attrs: &[ast::Attribute],
-        target_span: Span,
-        target_id: S::Id,
-        target: Target,
-        omit_doc: OmitDoc,
-
-        lower_span: impl Copy + Fn(Span) -> Span,
-        mut emit_lint: impl FnMut(AttributeLint<S::Id>),
-    ) -> Vec<Attribute> {
-        let mut attributes = Vec::new();
-        let mut attr_paths = Vec::new();
-
-        for attr in attrs {
-            // If we're only looking for a single attribute, skip all the ones we don't care about.
-            if let Some(expected) = self.parse_only {
-                if !attr.has_name(expected) {
-                    continue;
-                }
-            }
-
-            // Sometimes, for example for `#![doc = include_str!("readme.md")]`,
-            // doc still contains a non-literal. You might say, when we're lowering attributes
-            // that's expanded right? But no, sometimes, when parsing attributes on macros,
-            // we already use the lowering logic and these are still there. So, when `omit_doc`
-            // is set we *also* want to ignore these.
-            if omit_doc == OmitDoc::Skip && attr.has_name(sym::doc) {
-                continue;
-            }
-
-            match &attr.kind {
-                ast::AttrKind::DocComment(comment_kind, symbol) => {
-                    if omit_doc == OmitDoc::Skip {
-                        continue;
-                    }
-
-                    attributes.push(Attribute::Parsed(AttributeKind::DocComment {
-                        style: attr.style,
-                        kind: *comment_kind,
-                        span: lower_span(attr.span),
-                        comment: *symbol,
-                    }))
-                }
-                // // FIXME: make doc attributes go through a proper attribute parser
-                // ast::AttrKind::Normal(n) if n.has_name(sym::doc) => {
-                //     let p = GenericMetaItemParser::from_attr(&n, self.dcx());
-                //
-                //     attributes.push(Attribute::Parsed(AttributeKind::DocComment {
-                //         style: attr.style,
-                //         kind: CommentKind::Line,
-                //         span: attr.span,
-                //         comment: p.args().name_value(),
-                //     }))
-                // }
-                ast::AttrKind::Normal(n) => {
-                    attr_paths.push(PathParser::Ast(&n.item.path));
-
-                    let parser = MetaItemParser::from_attr(n, self.dcx());
-                    let path = parser.path();
-                    let args = parser.args();
-                    let parts = path.segments().map(|i| i.name).collect::<Vec<_>>();
-
-                    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,
-                                    target_span,
-                                    target_id,
-                                    emit_lint: &mut emit_lint,
-                                },
-                                attr_span: lower_span(attr.span),
-                                attr_style: attr.style,
-                                template: &accept.template,
-                                attr_path: path.get_attribute_path(),
-                            };
-
-                            (accept.accept_fn)(&mut cx, args);
-
-                            if self.stage.should_emit().should_emit() {
-                                match accept.allowed_targets.is_allowed(target) {
-                                    AllowedResult::Allowed => {}
-                                    AllowedResult::Warn => {
-                                        let allowed_targets =
-                                            accept.allowed_targets.allowed_targets();
-                                        let (applied, only) = allowed_targets_applied(
-                                            allowed_targets,
-                                            target,
-                                            self.features,
-                                        );
-                                        emit_lint(AttributeLint {
-                                            id: target_id,
-                                            span: attr.span,
-                                            kind: AttributeLintKind::InvalidTarget {
-                                                name: parts[0],
-                                                target,
-                                                only: if only { "only " } else { "" },
-                                                applied,
-                                            },
-                                        });
-                                    }
-                                    AllowedResult::Error => {
-                                        let allowed_targets =
-                                            accept.allowed_targets.allowed_targets();
-                                        let (applied, only) = allowed_targets_applied(
-                                            allowed_targets,
-                                            target,
-                                            self.features,
-                                        );
-                                        self.dcx().emit_err(InvalidTarget {
-                                            span: attr.span,
-                                            name: parts[0],
-                                            target: target.plural_name(),
-                                            only: if only { "only " } else { "" },
-                                            applied,
-                                        });
-                                    }
-                                }
-                            }
-                        }
-                    } else {
-                        // If we're here, we must be compiling a tool attribute... Or someone
-                        // forgot to parse their fancy new attribute. Let's warn them in any case.
-                        // If you are that person, and you really think your attribute should
-                        // remain unparsed, carefully read the documentation in this module and if
-                        // you still think so you can add an exception to this assertion.
-
-                        // FIXME(jdonszelmann): convert other attributes, and check with this that
-                        // we caught em all
-                        // const FIXME_TEMPORARY_ATTR_ALLOWLIST: &[Symbol] = &[sym::cfg];
-                        // assert!(
-                        //     self.tools.contains(&parts[0]) || true,
-                        //     // || FIXME_TEMPORARY_ATTR_ALLOWLIST.contains(&parts[0]),
-                        //     "attribute {path} wasn't parsed and isn't a know tool attribute",
-                        // );
-
-                        attributes.push(Attribute::Unparsed(Box::new(AttrItem {
-                            path: AttrPath::from_ast(&n.item.path),
-                            args: self.lower_attr_args(&n.item.args, lower_span),
-                            id: HashIgnoredAttrId { attr_id: attr.id },
-                            style: attr.style,
-                            span: lower_span(attr.span),
-                        })));
-                    }
-                }
-            }
-        }
-
-        let mut parsed_attributes = Vec::new();
-        for f in &S::parsers().finalizers {
-            if let Some(attr) = f(&mut FinalizeContext {
-                shared: SharedContext {
-                    cx: self,
-                    target_span,
-                    target_id,
-                    emit_lint: &mut emit_lint,
-                },
-                all_attrs: &attr_paths,
-            }) {
-                parsed_attributes.push(Attribute::Parsed(attr));
-            }
-        }
-
-        attributes.extend(parsed_attributes);
-
-        attributes
-    }
-
-    /// Returns whether there is a parser for an attribute with this name
-    pub fn is_parsed_attribute(path: &[Symbol]) -> bool {
-        Late::parsers().accepters.contains_key(path)
-    }
-
-    fn lower_attr_args(&self, args: &ast::AttrArgs, lower_span: impl Fn(Span) -> Span) -> AttrArgs {
-        match args {
-            ast::AttrArgs::Empty => AttrArgs::Empty,
-            ast::AttrArgs::Delimited(args) => AttrArgs::Delimited(args.clone()),
-            // This is an inert key-value attribute - it will never be visible to macros
-            // after it gets lowered to HIR. Therefore, we can extract literals to handle
-            // nonterminals in `#[doc]` (e.g. `#[doc = $e]`).
-            ast::AttrArgs::Eq { eq_span, expr } => {
-                // In valid code the value always ends up as a single literal. Otherwise, a dummy
-                // literal suffices because the error is handled elsewhere.
-                let lit = if let ast::ExprKind::Lit(token_lit) = expr.kind
-                    && let Ok(lit) =
-                        ast::MetaItemLit::from_token_lit(token_lit, lower_span(expr.span))
-                {
-                    lit
-                } else {
-                    let guar = self.dcx().span_delayed_bug(
-                        args.span().unwrap_or(DUMMY_SP),
-                        "expr in place where literal is expected (builtin attr parsing)",
-                    );
-                    ast::MetaItemLit {
-                        symbol: sym::dummy,
-                        suffix: None,
-                        kind: ast::LitKind::Err(guar),
-                        span: DUMMY_SP,
-                    }
-                };
-                AttrArgs::Eq { eq_span: lower_span(*eq_span), expr: lit }
-            }
-        }
-    }
-}
-
-/// Takes a list of `allowed_targets` for an attribute, and the `target` the attribute was applied to.
-/// Does some heuristic-based filtering to remove uninteresting targets, and formats the targets into a string
-pub(crate) fn allowed_targets_applied(
-    mut allowed_targets: Vec<Target>,
-    target: Target,
-    features: Option<&Features>,
-) -> (String, bool) {
-    // Remove unstable targets from `allowed_targets` if their features are not enabled
-    if let Some(features) = features {
-        if !features.fn_delegation() {
-            allowed_targets.retain(|t| !matches!(t, Target::Delegation { .. }));
-        }
-        if !features.stmt_expr_attributes() {
-            allowed_targets.retain(|t| !matches!(t, Target::Expression | Target::Statement));
-        }
-        if !features.extern_types() {
-            allowed_targets.retain(|t| !matches!(t, Target::ForeignTy));
-        }
-    }
-
-    // We define groups of "similar" targets.
-    // If at least two of the targets are allowed, and the `target` is not in the group,
-    // we collapse the entire group to a single entry to simplify the target list
-    const FUNCTION_LIKE: &[Target] = &[
-        Target::Fn,
-        Target::Closure,
-        Target::ForeignFn,
-        Target::Method(MethodKind::Inherent),
-        Target::Method(MethodKind::Trait { body: false }),
-        Target::Method(MethodKind::Trait { body: true }),
-        Target::Method(MethodKind::TraitImpl),
-    ];
-    const METHOD_LIKE: &[Target] = &[
-        Target::Method(MethodKind::Inherent),
-        Target::Method(MethodKind::Trait { body: false }),
-        Target::Method(MethodKind::Trait { body: true }),
-        Target::Method(MethodKind::TraitImpl),
-    ];
-    const IMPL_LIKE: &[Target] =
-        &[Target::Impl { of_trait: false }, Target::Impl { of_trait: true }];
-    const ADT_LIKE: &[Target] = &[Target::Struct, Target::Enum];
-
-    let mut added_fake_targets = Vec::new();
-    filter_targets(
-        &mut allowed_targets,
-        FUNCTION_LIKE,
-        "functions",
-        target,
-        &mut added_fake_targets,
-    );
-    filter_targets(&mut allowed_targets, METHOD_LIKE, "methods", target, &mut added_fake_targets);
-    filter_targets(&mut allowed_targets, IMPL_LIKE, "impl blocks", target, &mut added_fake_targets);
-    filter_targets(&mut allowed_targets, ADT_LIKE, "data types", target, &mut added_fake_targets);
-
-    // If there is now only 1 target left, show that as the only possible target
-    (
-        added_fake_targets
-            .iter()
-            .copied()
-            .chain(allowed_targets.iter().map(|t| t.plural_name()))
-            .join(", "),
-        allowed_targets.len() + added_fake_targets.len() == 1,
-    )
-}
-
-fn filter_targets(
-    allowed_targets: &mut Vec<Target>,
-    target_group: &'static [Target],
-    target_group_name: &'static str,
-    target: Target,
-    added_fake_targets: &mut Vec<&'static str>,
-) {
-    if target_group.contains(&target) {
-        return;
-    }
-    if allowed_targets.iter().filter(|at| target_group.contains(at)).count() < 2 {
-        return;
-    }
-    allowed_targets.retain(|t| !target_group.contains(t));
-    added_fake_targets.push(target_group_name);
-}
-
-/// This is the list of all targets to which a attribute can be applied
-/// This is used for:
-/// - `rustc_dummy`, which can be applied to all targets
-/// - Attributes that are not parted to the new target system yet can use this list as a placeholder
-pub(crate) const ALL_TARGETS: &'static [MaybeWarn] = &[
-    Allow(Target::ExternCrate),
-    Allow(Target::Use),
-    Allow(Target::Static),
-    Allow(Target::Const),
-    Allow(Target::Fn),
-    Allow(Target::Closure),
-    Allow(Target::Mod),
-    Allow(Target::ForeignMod),
-    Allow(Target::GlobalAsm),
-    Allow(Target::TyAlias),
-    Allow(Target::Enum),
-    Allow(Target::Variant),
-    Allow(Target::Struct),
-    Allow(Target::Field),
-    Allow(Target::Union),
-    Allow(Target::Trait),
-    Allow(Target::TraitAlias),
-    Allow(Target::Impl { of_trait: false }),
-    Allow(Target::Impl { of_trait: true }),
-    Allow(Target::Expression),
-    Allow(Target::Statement),
-    Allow(Target::Arm),
-    Allow(Target::AssocConst),
-    Allow(Target::Method(MethodKind::Inherent)),
-    Allow(Target::Method(MethodKind::Trait { body: false })),
-    Allow(Target::Method(MethodKind::Trait { body: true })),
-    Allow(Target::Method(MethodKind::TraitImpl)),
-    Allow(Target::AssocTy),
-    Allow(Target::ForeignFn),
-    Allow(Target::ForeignStatic),
-    Allow(Target::ForeignTy),
-    Allow(Target::MacroDef),
-    Allow(Target::Param),
-    Allow(Target::PatField),
-    Allow(Target::ExprField),
-    Allow(Target::WherePredicate),
-    Allow(Target::MacroCall),
-    Allow(Target::Crate),
-    Allow(Target::Delegation { mac: false }),
-    Allow(Target::Delegation { mac: true }),
-];
-
-/// Parse a single integer.
-///
-/// Used by attributes that take a single integer as argument, such as
-/// `#[link_ordinal]` and `#[rustc_layout_scalar_valid_range_start]`.
-/// `cx` is the context given to the attribute.
-/// `args` is the parser for the attribute arguments.
-pub(crate) fn parse_single_integer<S: Stage>(
-    cx: &mut AcceptContext<'_, '_, S>,
-    args: &ArgParser<'_>,
-) -> Option<u128> {
-    let Some(list) = args.list() else {
-        cx.expected_list(cx.attr_span);
-        return None;
-    };
-    let Some(single) = list.single() else {
-        cx.expected_single_argument(list.span);
-        return None;
-    };
-    let Some(lit) = single.lit() else {
-        cx.expected_integer_literal(single.span());
-        return None;
-    };
-    let LitKind::Int(num, _ty) = lit.kind else {
-        cx.expected_integer_literal(single.span());
-        return None;
-    };
-    Some(num.0)
 }
diff --git a/compiler/rustc_attr_parsing/src/interface.rs b/compiler/rustc_attr_parsing/src/interface.rs
new file mode 100644
index 00000000000..60523c2877c
--- /dev/null
+++ b/compiler/rustc_attr_parsing/src/interface.rs
@@ -0,0 +1,370 @@
+use std::borrow::Cow;
+
+use rustc_ast as ast;
+use rustc_ast::NodeId;
+use rustc_errors::DiagCtxtHandle;
+use rustc_feature::{AttributeTemplate, Features};
+use rustc_hir::attrs::AttributeKind;
+use rustc_hir::lints::AttributeLint;
+use rustc_hir::{AttrArgs, AttrItem, AttrPath, Attribute, HashIgnoredAttrId, Target};
+use rustc_session::Session;
+use rustc_span::{DUMMY_SP, Span, Symbol, sym};
+
+use crate::context::{AcceptContext, FinalizeContext, SharedContext, Stage};
+use crate::parser::{ArgParser, MetaItemParser, PathParser};
+use crate::{Early, Late, OmitDoc, ShouldEmit};
+
+/// Context created once, for example as part of the ast lowering
+/// context, through which all attributes can be lowered.
+pub struct AttributeParser<'sess, S: Stage = Late> {
+    pub(crate) tools: Vec<Symbol>,
+    pub(crate) features: Option<&'sess Features>,
+    pub(crate) sess: &'sess Session,
+    pub(crate) stage: S,
+
+    /// *Only* parse attributes with this symbol.
+    ///
+    /// Used in cases where we want the lowering infrastructure for parse just a single attribute.
+    parse_only: Option<Symbol>,
+}
+
+impl<'sess> AttributeParser<'sess, Early> {
+    /// This method allows you to parse attributes *before* you have access to features or tools.
+    /// One example where this is necessary, is to parse `feature` attributes themselves for
+    /// example.
+    ///
+    /// Try to use this as little as possible. Attributes *should* be lowered during
+    /// `rustc_ast_lowering`. Some attributes require access to features to parse, which would
+    /// crash if you tried to do so through [`parse_limited`](Self::parse_limited).
+    ///
+    /// To make sure use is limited, supply a `Symbol` you'd like to parse. Only attributes with
+    /// that symbol are picked out of the list of instructions and parsed. Those are returned.
+    ///
+    /// No diagnostics will be emitted when parsing limited. Lints are not emitted at all, while
+    /// errors will be emitted as a delayed bugs. in other words, we *expect* attributes parsed
+    /// with `parse_limited` to be reparsed later during ast lowering where we *do* emit the errors
+    pub fn parse_limited(
+        sess: &'sess Session,
+        attrs: &[ast::Attribute],
+        sym: Symbol,
+        target_span: Span,
+        target_node_id: NodeId,
+        features: Option<&'sess Features>,
+    ) -> Option<Attribute> {
+        Self::parse_limited_should_emit(
+            sess,
+            attrs,
+            sym,
+            target_span,
+            target_node_id,
+            features,
+            ShouldEmit::Nothing,
+        )
+    }
+
+    /// Usually you want `parse_limited`, which defaults to no errors.
+    pub fn parse_limited_should_emit(
+        sess: &'sess Session,
+        attrs: &[ast::Attribute],
+        sym: Symbol,
+        target_span: Span,
+        target_node_id: NodeId,
+        features: Option<&'sess Features>,
+        should_emit: ShouldEmit,
+    ) -> Option<Attribute> {
+        let mut parsed = Self::parse_limited_all(
+            sess,
+            attrs,
+            Some(sym),
+            Target::Crate, // Does not matter, we're not going to emit errors anyways
+            target_span,
+            target_node_id,
+            features,
+            should_emit,
+        );
+        assert!(parsed.len() <= 1);
+        parsed.pop()
+    }
+
+    pub fn parse_limited_all(
+        sess: &'sess Session,
+        attrs: &[ast::Attribute],
+        parse_only: Option<Symbol>,
+        target: Target,
+        target_span: Span,
+        target_node_id: NodeId,
+        features: Option<&'sess Features>,
+        emit_errors: ShouldEmit,
+    ) -> Vec<Attribute> {
+        let mut p =
+            Self { features, tools: Vec::new(), parse_only, sess, stage: Early { emit_errors } };
+        p.parse_attribute_list(
+            attrs,
+            target_span,
+            target_node_id,
+            target,
+            OmitDoc::Skip,
+            std::convert::identity,
+            |lint| {
+                crate::lints::emit_attribute_lint(&lint, sess);
+            },
+        )
+    }
+
+    pub fn parse_single<T>(
+        sess: &'sess Session,
+        attr: &ast::Attribute,
+        target_span: Span,
+        target_node_id: NodeId,
+        features: Option<&'sess Features>,
+        emit_errors: ShouldEmit,
+        parse_fn: fn(cx: &mut AcceptContext<'_, '_, Early>, item: &ArgParser<'_>) -> Option<T>,
+        template: &AttributeTemplate,
+    ) -> Option<T> {
+        let mut parser = Self {
+            features,
+            tools: Vec::new(),
+            parse_only: None,
+            sess,
+            stage: Early { emit_errors },
+        };
+        let ast::AttrKind::Normal(normal_attr) = &attr.kind else {
+            panic!("parse_single called on a doc attr")
+        };
+        let parts =
+            normal_attr.item.path.segments.iter().map(|seg| seg.ident.name).collect::<Vec<_>>();
+        let meta_parser = MetaItemParser::from_attr(normal_attr, &parts, &sess.psess, emit_errors)?;
+        let path = meta_parser.path();
+        let args = meta_parser.args();
+        let mut cx: AcceptContext<'_, 'sess, Early> = AcceptContext {
+            shared: SharedContext {
+                cx: &mut parser,
+                target_span,
+                target_id: target_node_id,
+                emit_lint: &mut |lint| {
+                    crate::lints::emit_attribute_lint(&lint, sess);
+                },
+            },
+            attr_span: attr.span,
+            attr_style: attr.style,
+            template,
+            attr_path: path.get_attribute_path(),
+        };
+        parse_fn(&mut cx, args)
+    }
+}
+
+impl<'sess, S: Stage> AttributeParser<'sess, S> {
+    pub fn new(
+        sess: &'sess Session,
+        features: &'sess Features,
+        tools: Vec<Symbol>,
+        stage: S,
+    ) -> Self {
+        Self { features: Some(features), tools, parse_only: None, sess, stage }
+    }
+
+    pub(crate) fn sess(&self) -> &'sess Session {
+        &self.sess
+    }
+
+    pub(crate) fn features(&self) -> &'sess Features {
+        self.features.expect("features not available at this point in the compiler")
+    }
+
+    pub(crate) fn features_option(&self) -> Option<&'sess Features> {
+        self.features
+    }
+
+    pub(crate) fn dcx(&self) -> DiagCtxtHandle<'sess> {
+        self.sess().dcx()
+    }
+
+    /// Parse a list of attributes.
+    ///
+    /// `target_span` is the span of the thing this list of attributes is applied to,
+    /// and when `omit_doc` is set, doc attributes are filtered out.
+    pub fn parse_attribute_list(
+        &mut self,
+        attrs: &[ast::Attribute],
+        target_span: Span,
+        target_id: S::Id,
+        target: Target,
+        omit_doc: OmitDoc,
+
+        lower_span: impl Copy + Fn(Span) -> Span,
+        mut emit_lint: impl FnMut(AttributeLint<S::Id>),
+    ) -> Vec<Attribute> {
+        let mut attributes = Vec::new();
+        let mut attr_paths = Vec::new();
+
+        for attr in attrs {
+            // If we're only looking for a single attribute, skip all the ones we don't care about.
+            if let Some(expected) = self.parse_only {
+                if !attr.has_name(expected) {
+                    continue;
+                }
+            }
+
+            // Sometimes, for example for `#![doc = include_str!("readme.md")]`,
+            // doc still contains a non-literal. You might say, when we're lowering attributes
+            // that's expanded right? But no, sometimes, when parsing attributes on macros,
+            // we already use the lowering logic and these are still there. So, when `omit_doc`
+            // is set we *also* want to ignore these.
+            if omit_doc == OmitDoc::Skip && attr.has_name(sym::doc) {
+                continue;
+            }
+
+            match &attr.kind {
+                ast::AttrKind::DocComment(comment_kind, symbol) => {
+                    if omit_doc == OmitDoc::Skip {
+                        continue;
+                    }
+
+                    attributes.push(Attribute::Parsed(AttributeKind::DocComment {
+                        style: attr.style,
+                        kind: *comment_kind,
+                        span: lower_span(attr.span),
+                        comment: *symbol,
+                    }))
+                }
+                // // FIXME: make doc attributes go through a proper attribute parser
+                // ast::AttrKind::Normal(n) if n.has_name(sym::doc) => {
+                //     let p = GenericMetaItemParser::from_attr(&n, self.dcx());
+                //
+                //     attributes.push(Attribute::Parsed(AttributeKind::DocComment {
+                //         style: attr.style,
+                //         kind: CommentKind::Line,
+                //         span: attr.span,
+                //         comment: p.args().name_value(),
+                //     }))
+                // }
+                ast::AttrKind::Normal(n) => {
+                    attr_paths.push(PathParser(Cow::Borrowed(&n.item.path)));
+
+                    let parts =
+                        n.item.path.segments.iter().map(|seg| seg.ident.name).collect::<Vec<_>>();
+
+                    if let Some(accepts) = S::parsers().accepters.get(parts.as_slice()) {
+                        let Some(parser) = MetaItemParser::from_attr(
+                            n,
+                            &parts,
+                            &self.sess.psess,
+                            self.stage.should_emit(),
+                        ) else {
+                            continue;
+                        };
+                        let path = parser.path();
+                        let args = parser.args();
+                        for accept in accepts {
+                            let mut cx: AcceptContext<'_, 'sess, S> = AcceptContext {
+                                shared: SharedContext {
+                                    cx: self,
+                                    target_span,
+                                    target_id,
+                                    emit_lint: &mut emit_lint,
+                                },
+                                attr_span: lower_span(attr.span),
+                                attr_style: attr.style,
+                                template: &accept.template,
+                                attr_path: path.get_attribute_path(),
+                            };
+
+                            (accept.accept_fn)(&mut cx, args);
+
+                            if !matches!(self.stage.should_emit(), ShouldEmit::Nothing) {
+                                self.check_target(
+                                    path.get_attribute_path(),
+                                    attr.span,
+                                    &accept.allowed_targets,
+                                    target,
+                                    target_id,
+                                    &mut emit_lint,
+                                );
+                            }
+                        }
+                    } else {
+                        // If we're here, we must be compiling a tool attribute... Or someone
+                        // forgot to parse their fancy new attribute. Let's warn them in any case.
+                        // If you are that person, and you really think your attribute should
+                        // remain unparsed, carefully read the documentation in this module and if
+                        // you still think so you can add an exception to this assertion.
+
+                        // FIXME(jdonszelmann): convert other attributes, and check with this that
+                        // we caught em all
+                        // const FIXME_TEMPORARY_ATTR_ALLOWLIST: &[Symbol] = &[sym::cfg];
+                        // assert!(
+                        //     self.tools.contains(&parts[0]) || true,
+                        //     // || FIXME_TEMPORARY_ATTR_ALLOWLIST.contains(&parts[0]),
+                        //     "attribute {path} wasn't parsed and isn't a know tool attribute",
+                        // );
+
+                        attributes.push(Attribute::Unparsed(Box::new(AttrItem {
+                            path: AttrPath::from_ast(&n.item.path),
+                            args: self.lower_attr_args(&n.item.args, lower_span),
+                            id: HashIgnoredAttrId { attr_id: attr.id },
+                            style: attr.style,
+                            span: lower_span(attr.span),
+                        })));
+                    }
+                }
+            }
+        }
+
+        let mut parsed_attributes = Vec::new();
+        for f in &S::parsers().finalizers {
+            if let Some(attr) = f(&mut FinalizeContext {
+                shared: SharedContext {
+                    cx: self,
+                    target_span,
+                    target_id,
+                    emit_lint: &mut emit_lint,
+                },
+                all_attrs: &attr_paths,
+            }) {
+                parsed_attributes.push(Attribute::Parsed(attr));
+            }
+        }
+
+        attributes.extend(parsed_attributes);
+
+        attributes
+    }
+
+    /// Returns whether there is a parser for an attribute with this name
+    pub fn is_parsed_attribute(path: &[Symbol]) -> bool {
+        Late::parsers().accepters.contains_key(path)
+    }
+
+    fn lower_attr_args(&self, args: &ast::AttrArgs, lower_span: impl Fn(Span) -> Span) -> AttrArgs {
+        match args {
+            ast::AttrArgs::Empty => AttrArgs::Empty,
+            ast::AttrArgs::Delimited(args) => AttrArgs::Delimited(args.clone()),
+            // This is an inert key-value attribute - it will never be visible to macros
+            // after it gets lowered to HIR. Therefore, we can extract literals to handle
+            // nonterminals in `#[doc]` (e.g. `#[doc = $e]`).
+            ast::AttrArgs::Eq { eq_span, expr } => {
+                // In valid code the value always ends up as a single literal. Otherwise, a dummy
+                // literal suffices because the error is handled elsewhere.
+                let lit = if let ast::ExprKind::Lit(token_lit) = expr.kind
+                    && let Ok(lit) =
+                        ast::MetaItemLit::from_token_lit(token_lit, lower_span(expr.span))
+                {
+                    lit
+                } else {
+                    let guar = self.dcx().span_delayed_bug(
+                        args.span().unwrap_or(DUMMY_SP),
+                        "expr in place where literal is expected (builtin attr parsing)",
+                    );
+                    ast::MetaItemLit {
+                        symbol: sym::dummy,
+                        suffix: None,
+                        kind: ast::LitKind::Err(guar),
+                        span: DUMMY_SP,
+                    }
+                };
+                AttrArgs::Eq { eq_span: lower_span(*eq_span), expr: lit }
+            }
+        }
+    }
+}
diff --git a/compiler/rustc_attr_parsing/src/lib.rs b/compiler/rustc_attr_parsing/src/lib.rs
index fc1377e5314..4dd908cdc40 100644
--- a/compiler/rustc_attr_parsing/src/lib.rs
+++ b/compiler/rustc_attr_parsing/src/lib.rs
@@ -84,18 +84,31 @@
 // tidy-alphabetical-end
 
 #[macro_use]
+/// All the individual attribute parsers for each of rustc's built-in attributes.
 mod attributes;
+
+/// All the important types given to attribute parsers when parsing
 pub(crate) mod context;
-mod lints;
+
+/// Code that other crates interact with, to actually parse a list (or sometimes single)
+/// attribute.
+mod interface;
+
+/// Despite this entire module called attribute parsing and the term being a little overloaded,
+/// in this module the code lives that actually breaks up tokenstreams into semantic pieces of attributes,
+/// like lists or name-value pairs.
 pub mod parser;
+
+mod lints;
 mod session_diagnostics;
+mod target_checking;
+pub mod validate_attr;
 
 pub use attributes::cfg::{CFG_TEMPLATE, EvalConfigResult, eval_config_entry, parse_cfg_attr};
 pub use attributes::cfg_old::*;
-pub use attributes::util::{
-    find_crate_name, is_builtin_attr, is_doc_alias_attrs_contain_symbol, parse_version,
-};
-pub use context::{AttributeParser, Early, Late, OmitDoc, ShouldEmit};
+pub use attributes::util::{is_builtin_attr, is_doc_alias_attrs_contain_symbol, parse_version};
+pub use context::{Early, Late, OmitDoc, ShouldEmit};
+pub use interface::AttributeParser;
 pub use lints::emit_attribute_lint;
 
 rustc_fluent_macro::fluent_messages! { "../messages.ftl" }
diff --git a/compiler/rustc_attr_parsing/src/lints.rs b/compiler/rustc_attr_parsing/src/lints.rs
index 733225bab59..84ae19c4fc6 100644
--- a/compiler/rustc_attr_parsing/src/lints.rs
+++ b/compiler/rustc_attr_parsing/src/lints.rs
@@ -1,11 +1,13 @@
+use std::borrow::Cow;
+
 use rustc_errors::{DiagArgValue, LintEmitter};
+use rustc_hir::Target;
 use rustc_hir::lints::{AttributeLint, AttributeLintKind};
-use rustc_hir::{HirId, Target};
 use rustc_span::sym;
 
 use crate::session_diagnostics;
 
-pub fn emit_attribute_lint<L: LintEmitter>(lint: &AttributeLint<HirId>, lint_emitter: L) {
+pub fn emit_attribute_lint<L: LintEmitter>(lint: &AttributeLint<L::Id>, lint_emitter: L) {
     let AttributeLint { id, span, kind } = lint;
 
     match kind {
@@ -35,12 +37,18 @@ pub fn emit_attribute_lint<L: LintEmitter>(lint: &AttributeLint<HirId>, lint_emi
             *first_span,
             session_diagnostics::EmptyAttributeList { attr_span: *first_span },
         ),
-        &AttributeLintKind::InvalidTarget { name, target, ref applied, only } => lint_emitter
+        AttributeLintKind::InvalidTarget { name, target, applied, only } => lint_emitter
             .emit_node_span_lint(
                 // This check is here because `deprecated` had its own lint group and removing this would be a breaking change
-                if name == sym::deprecated
-                    && ![Target::Closure, Target::Expression, Target::Statement, Target::Arm]
-                        .contains(&target)
+                if name.segments[0].name == sym::deprecated
+                    && ![
+                        Target::Closure,
+                        Target::Expression,
+                        Target::Statement,
+                        Target::Arm,
+                        Target::MacroCall,
+                    ]
+                    .contains(target)
                 {
                     rustc_session::lint::builtin::USELESS_DEPRECATED
                 } else {
@@ -49,10 +57,13 @@ pub fn emit_attribute_lint<L: LintEmitter>(lint: &AttributeLint<HirId>, lint_emi
                 *id,
                 *span,
                 session_diagnostics::InvalidTargetLint {
-                    name,
+                    name: name.clone(),
                     target: target.plural_name(),
-                    applied: applied.clone(),
+                    applied: DiagArgValue::StrListSepByAnd(
+                        applied.into_iter().map(|i| Cow::Owned(i.to_string())).collect(),
+                    ),
                     only,
+                    attr_span: *span,
                 },
             ),
     }
diff --git a/compiler/rustc_attr_parsing/src/parser.rs b/compiler/rustc_attr_parsing/src/parser.rs
index aecaae947c9..6d3cf684296 100644
--- a/compiler/rustc_attr_parsing/src/parser.rs
+++ b/compiler/rustc_attr_parsing/src/parser.rs
@@ -3,45 +3,30 @@
 //!
 //! FIXME(jdonszelmann): delete `rustc_ast/attr/mod.rs`
 
+use std::borrow::Cow;
 use std::fmt::{Debug, Display};
-use std::iter::Peekable;
 
-use rustc_ast::token::{self, Delimiter, Token};
-use rustc_ast::tokenstream::{TokenStreamIter, TokenTree};
+use rustc_ast::token::{self, Delimiter, MetaVarKind};
+use rustc_ast::tokenstream::TokenStream;
 use rustc_ast::{AttrArgs, DelimArgs, Expr, ExprKind, LitKind, MetaItemLit, NormalAttr, Path};
 use rustc_ast_pretty::pprust;
-use rustc_errors::DiagCtxtHandle;
+use rustc_errors::PResult;
 use rustc_hir::{self as hir, AttrPath};
-use rustc_span::{ErrorGuaranteed, Ident, Span, Symbol, kw, sym};
-
-pub struct SegmentIterator<'a> {
-    offset: usize,
-    path: &'a PathParser<'a>,
-}
-
-impl<'a> Iterator for SegmentIterator<'a> {
-    type Item = &'a Ident;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        if self.offset >= self.path.len() {
-            return None;
-        }
-
-        let res = match self.path {
-            PathParser::Ast(ast_path) => &ast_path.segments[self.offset].ident,
-            PathParser::Attr(attr_path) => &attr_path.segments[self.offset],
-        };
-
-        self.offset += 1;
-        Some(res)
-    }
-}
+use rustc_parse::exp;
+use rustc_parse::parser::{Parser, PathStyle, token_descr};
+use rustc_session::errors::report_lit_error;
+use rustc_session::parse::ParseSess;
+use rustc_span::{ErrorGuaranteed, Ident, Span, Symbol, sym};
+use thin_vec::ThinVec;
+
+use crate::ShouldEmit;
+use crate::session_diagnostics::{
+    InvalidMetaItem, InvalidMetaItemQuoteIdentSugg, InvalidMetaItemRemoveNegSugg, MetaBadDelim,
+    MetaBadDelimSugg, SuffixedLiteralInAttribute,
+};
 
 #[derive(Clone, Debug)]
-pub enum PathParser<'a> {
-    Ast(&'a Path),
-    Attr(AttrPath),
-}
+pub struct PathParser<'a>(pub Cow<'a, Path>);
 
 impl<'a> PathParser<'a> {
     pub fn get_attribute_path(&self) -> hir::AttrPath {
@@ -52,21 +37,15 @@ impl<'a> PathParser<'a> {
     }
 
     pub fn segments(&'a self) -> impl Iterator<Item = &'a Ident> {
-        SegmentIterator { offset: 0, path: self }
+        self.0.segments.iter().map(|seg| &seg.ident)
     }
 
     pub fn span(&self) -> Span {
-        match self {
-            PathParser::Ast(path) => path.span,
-            PathParser::Attr(attr_path) => attr_path.span,
-        }
+        self.0.span
     }
 
     pub fn len(&self) -> usize {
-        match self {
-            PathParser::Ast(path) => path.segments.len(),
-            PathParser::Attr(attr_path) => attr_path.segments.len(),
-        }
+        self.0.segments.len()
     }
 
     pub fn segments_is(&self, segments: &[Symbol]) -> bool {
@@ -99,10 +78,7 @@ impl<'a> PathParser<'a> {
 
 impl Display for PathParser<'_> {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        match self {
-            PathParser::Ast(path) => write!(f, "{}", pprust::path_to_string(path)),
-            PathParser::Attr(attr_path) => write!(f, "{attr_path}"),
-        }
+        write!(f, "{}", pprust::path_to_string(&self.0))
     }
 }
 
@@ -123,21 +99,39 @@ impl<'a> ArgParser<'a> {
         }
     }
 
-    pub fn from_attr_args<'sess>(value: &'a AttrArgs, dcx: DiagCtxtHandle<'sess>) -> Self {
-        match value {
+    pub fn from_attr_args<'sess>(
+        value: &'a AttrArgs,
+        parts: &[Symbol],
+        psess: &'sess ParseSess,
+        should_emit: ShouldEmit,
+    ) -> Option<Self> {
+        Some(match value {
             AttrArgs::Empty => Self::NoArgs,
-            AttrArgs::Delimited(args) if args.delim == Delimiter::Parenthesis => {
-                Self::List(MetaItemListParser::new(args, dcx))
-            }
             AttrArgs::Delimited(args) => {
-                Self::List(MetaItemListParser { sub_parsers: vec![], span: args.dspan.entire() })
+                // The arguments of rustc_dummy are not validated if the arguments are delimited
+                if parts == &[sym::rustc_dummy] {
+                    return Some(ArgParser::List(MetaItemListParser {
+                        sub_parsers: ThinVec::new(),
+                        span: args.dspan.entire(),
+                    }));
+                }
+
+                if args.delim != Delimiter::Parenthesis {
+                    psess.dcx().emit_err(MetaBadDelim {
+                        span: args.dspan.entire(),
+                        sugg: MetaBadDelimSugg { open: args.dspan.open, close: args.dspan.close },
+                    });
+                    return None;
+                }
+
+                Self::List(MetaItemListParser::new(args, psess, should_emit)?)
             }
             AttrArgs::Eq { eq_span, expr } => Self::NameValue(NameValueParser {
                 eq_span: *eq_span,
-                value: expr_to_lit(dcx, &expr, *eq_span),
+                value: expr_to_lit(psess, &expr, expr.span, should_emit)?,
                 value_span: expr.span,
             }),
-        }
+        })
     }
 
     /// Asserts that this MetaItem is a list
@@ -249,11 +243,16 @@ impl<'a> Debug for MetaItemParser<'a> {
 impl<'a> MetaItemParser<'a> {
     /// Create a new parser from a [`NormalAttr`], which is stored inside of any
     /// [`ast::Attribute`](rustc_ast::Attribute)
-    pub fn from_attr<'sess>(attr: &'a NormalAttr, dcx: DiagCtxtHandle<'sess>) -> Self {
-        Self {
-            path: PathParser::Ast(&attr.item.path),
-            args: ArgParser::from_attr_args(&attr.item.args, dcx),
-        }
+    pub fn from_attr<'sess>(
+        attr: &'a NormalAttr,
+        parts: &[Symbol],
+        psess: &'sess ParseSess,
+        should_emit: ShouldEmit,
+    ) -> Option<Self> {
+        Some(Self {
+            path: PathParser(Cow::Borrowed(&attr.item.path)),
+            args: ArgParser::from_attr_args(&attr.item.args, parts, psess, should_emit)?,
+        })
     }
 }
 
@@ -318,215 +317,235 @@ impl NameValueParser {
     }
 }
 
-fn expr_to_lit(dcx: DiagCtxtHandle<'_>, expr: &Expr, span: Span) -> MetaItemLit {
-    // In valid code the value always ends up as a single literal. Otherwise, a dummy
-    // literal suffices because the error is handled elsewhere.
-    if let ExprKind::Lit(token_lit) = expr.kind
-        && let Ok(lit) = MetaItemLit::from_token_lit(token_lit, expr.span)
-    {
-        lit
+fn expr_to_lit(
+    psess: &ParseSess,
+    expr: &Expr,
+    span: Span,
+    should_emit: ShouldEmit,
+) -> Option<MetaItemLit> {
+    if let ExprKind::Lit(token_lit) = expr.kind {
+        let res = MetaItemLit::from_token_lit(token_lit, expr.span);
+        match res {
+            Ok(lit) => {
+                if token_lit.suffix.is_some() {
+                    should_emit.emit_err(
+                        psess.dcx().create_err(SuffixedLiteralInAttribute { span: lit.span }),
+                    );
+                    None
+                } else {
+                    if !lit.kind.is_unsuffixed() {
+                        // Emit error and continue, we can still parse the attribute as if the suffix isn't there
+                        should_emit.emit_err(
+                            psess.dcx().create_err(SuffixedLiteralInAttribute { span: lit.span }),
+                        );
+                    }
+
+                    Some(lit)
+                }
+            }
+            Err(err) => {
+                let guar = report_lit_error(psess, err, token_lit, expr.span);
+                let lit = MetaItemLit {
+                    symbol: token_lit.symbol,
+                    suffix: token_lit.suffix,
+                    kind: LitKind::Err(guar),
+                    span: expr.span,
+                };
+                Some(lit)
+            }
+        }
     } else {
-        let guar = dcx.span_delayed_bug(
-            span,
-            "expr in place where literal is expected (builtin attr parsing)",
-        );
-        MetaItemLit { symbol: sym::dummy, suffix: None, kind: LitKind::Err(guar), span }
+        if matches!(should_emit, ShouldEmit::Nothing) {
+            return None;
+        }
+
+        // Example cases:
+        // - `#[foo = 1+1]`: results in `ast::ExprKind::BinOp`.
+        // - `#[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
+        //   been reported.
+        let msg = "attribute value must be a literal";
+        let err = psess.dcx().struct_span_err(span, msg);
+        should_emit.emit_err(err);
+        None
     }
 }
 
 struct MetaItemListParserContext<'a, 'sess> {
-    // the tokens inside the delimiters, so `#[some::attr(a b c)]` would have `a b c` inside
-    inside_delimiters: Peekable<TokenStreamIter<'a>>,
-    dcx: DiagCtxtHandle<'sess>,
+    parser: &'a mut Parser<'sess>,
+    should_emit: ShouldEmit,
 }
 
 impl<'a, 'sess> MetaItemListParserContext<'a, 'sess> {
-    fn done(&mut self) -> bool {
-        self.inside_delimiters.peek().is_none()
-    }
-
-    fn next_path(&mut self) -> Option<AttrPath> {
-        // FIXME: Share code with `parse_path`.
-        let tt = self.inside_delimiters.next().map(|tt| TokenTree::uninterpolate(tt));
-
-        match tt.as_deref()? {
-            &TokenTree::Token(
-                Token { kind: ref kind @ (token::Ident(..) | token::PathSep), span },
-                _,
-            ) => {
-                // here we have either an ident or pathsep `::`.
-
-                let mut segments = if let &token::Ident(name, _) = kind {
-                    // when we lookahead another pathsep, more path's coming
-                    if let Some(TokenTree::Token(Token { kind: token::PathSep, .. }, _)) =
-                        self.inside_delimiters.peek()
-                    {
-                        self.inside_delimiters.next();
-                        vec![Ident::new(name, span)]
-                    } else {
-                        // else we have a single identifier path, that's all
-                        return Some(AttrPath {
-                            segments: vec![Ident::new(name, span)].into_boxed_slice(),
-                            span,
-                        });
-                    }
-                } else {
-                    // if `::` is all we get, we just got a path root
-                    vec![Ident::new(kw::PathRoot, span)]
-                };
+    fn parse_unsuffixed_meta_item_lit(&mut self) -> PResult<'sess, MetaItemLit> {
+        let uninterpolated_span = self.parser.token_uninterpolated_span();
+        let Some(token_lit) = self.parser.eat_token_lit() else {
+            return self.parser.handle_missing_lit(Parser::mk_meta_item_lit_char);
+        };
 
-                // one segment accepted. accept n more
-                loop {
-                    // another ident?
-                    if let Some(&TokenTree::Token(Token { kind: token::Ident(name, _), span }, _)) =
-                        self.inside_delimiters
-                            .next()
-                            .map(|tt| TokenTree::uninterpolate(tt))
-                            .as_deref()
-                    {
-                        segments.push(Ident::new(name, span));
-                    } else {
-                        return None;
-                    }
-                    // stop unless we see another `::`
-                    if let Some(TokenTree::Token(Token { kind: token::PathSep, .. }, _)) =
-                        self.inside_delimiters.peek()
-                    {
-                        self.inside_delimiters.next();
-                    } else {
-                        break;
-                    }
-                }
-                let span = span.with_hi(segments.last().unwrap().span.hi());
-                Some(AttrPath { segments: segments.into_boxed_slice(), span })
-            }
-            TokenTree::Token(Token { kind, .. }, _) if kind.is_delim() => None,
-            _ => {
-                // malformed attributes can get here. We can't crash, but somewhere else should've
-                // already warned for this.
-                None
+        let lit = match MetaItemLit::from_token_lit(token_lit, self.parser.prev_token.span) {
+            Ok(lit) => lit,
+            Err(err) => {
+                let guar =
+                    report_lit_error(&self.parser.psess, err, token_lit, uninterpolated_span);
+                // Pack possible quotes and prefixes from the original literal into
+                // the error literal's symbol so they can be pretty-printed faithfully.
+                let suffixless_lit = token::Lit::new(token_lit.kind, token_lit.symbol, None);
+                let symbol = Symbol::intern(&suffixless_lit.to_string());
+                let token_lit = token::Lit::new(token::Err(guar), symbol, token_lit.suffix);
+                MetaItemLit::from_token_lit(token_lit, uninterpolated_span).unwrap()
             }
+        };
+
+        if !lit.kind.is_unsuffixed() {
+            // Emit error and continue, we can still parse the attribute as if the suffix isn't there
+            self.should_emit.emit_err(
+                self.parser.dcx().create_err(SuffixedLiteralInAttribute { span: lit.span }),
+            );
         }
-    }
 
-    fn value(&mut self) -> Option<MetaItemLit> {
-        match self.inside_delimiters.next() {
-            Some(TokenTree::Delimited(.., Delimiter::Invisible(_), inner_tokens)) => {
-                MetaItemListParserContext {
-                    inside_delimiters: inner_tokens.iter().peekable(),
-                    dcx: self.dcx,
-                }
-                .value()
-            }
-            Some(TokenTree::Token(token, _)) => MetaItemLit::from_token(token),
-            _ => None,
+        Ok(lit)
+    }
+
+    fn parse_attr_item(&mut self) -> PResult<'sess, MetaItemParser<'static>> {
+        if let Some(MetaVarKind::Meta { has_meta_form }) = self.parser.token.is_metavar_seq() {
+            return if has_meta_form {
+                let attr_item = self
+                    .parser
+                    .eat_metavar_seq(MetaVarKind::Meta { has_meta_form: true }, |this| {
+                        MetaItemListParserContext { parser: this, should_emit: self.should_emit }
+                            .parse_attr_item()
+                    })
+                    .unwrap();
+                Ok(attr_item)
+            } else {
+                self.parser.unexpected_any()
+            };
         }
+
+        let path = self.parser.parse_path(PathStyle::Mod)?;
+
+        // Check style of arguments that this meta item has
+        let args = if self.parser.check(exp!(OpenParen)) {
+            let start = self.parser.token.span;
+            let (sub_parsers, _) = self.parser.parse_paren_comma_seq(|parser| {
+                MetaItemListParserContext { parser, should_emit: self.should_emit }
+                    .parse_meta_item_inner()
+            })?;
+            let end = self.parser.prev_token.span;
+            ArgParser::List(MetaItemListParser { sub_parsers, span: start.with_hi(end.hi()) })
+        } else if self.parser.eat(exp!(Eq)) {
+            let eq_span = self.parser.prev_token.span;
+            let value = self.parse_unsuffixed_meta_item_lit()?;
+
+            ArgParser::NameValue(NameValueParser { eq_span, value, value_span: value.span })
+        } else {
+            ArgParser::NoArgs
+        };
+
+        Ok(MetaItemParser { path: PathParser(Cow::Owned(path)), args })
     }
 
-    /// parses one element on the inside of a list attribute like `#[my_attr( <insides> )]`
-    ///
-    /// parses a path followed be either:
-    /// 1. nothing (a word attr)
-    /// 2. a parenthesized list
-    /// 3. an equals sign and a literal (name-value)
-    ///
-    /// Can also parse *just* a literal. This is for cases like as `#[my_attr("literal")]`
-    /// where no path is given before the literal
-    ///
-    /// Some exceptions too for interpolated attributes which are already pre-processed
-    fn next(&mut self) -> Option<MetaItemOrLitParser<'a>> {
-        // a list element is either a literal
-        if let Some(TokenTree::Token(token, _)) = self.inside_delimiters.peek()
-            && let Some(lit) = MetaItemLit::from_token(token)
-        {
-            self.inside_delimiters.next();
-            return Some(MetaItemOrLitParser::Lit(lit));
-        } else if let Some(TokenTree::Delimited(.., Delimiter::Invisible(_), inner_tokens)) =
-            self.inside_delimiters.peek()
+    fn parse_meta_item_inner(&mut self) -> PResult<'sess, MetaItemOrLitParser<'static>> {
+        match self.parse_unsuffixed_meta_item_lit() {
+            Ok(lit) => return Ok(MetaItemOrLitParser::Lit(lit)),
+            Err(err) => err.cancel(), // we provide a better error below
+        }
+
+        match self.parse_attr_item() {
+            Ok(mi) => return Ok(MetaItemOrLitParser::MetaItemParser(mi)),
+            Err(err) => err.cancel(), // we provide a better error below
+        }
+
+        let mut err = InvalidMetaItem {
+            span: self.parser.token.span,
+            descr: token_descr(&self.parser.token),
+            quote_ident_sugg: None,
+            remove_neg_sugg: None,
+        };
+
+        // Suggest quoting idents, e.g. in `#[cfg(key = value)]`. We don't use `Token::ident` and
+        // don't `uninterpolate` the token to avoid suggesting anything butchered or questionable
+        // when macro metavariables are involved.
+        if self.parser.prev_token == token::Eq
+            && let token::Ident(..) = self.parser.token.kind
         {
-            self.inside_delimiters.next();
-            return MetaItemListParserContext {
-                inside_delimiters: inner_tokens.iter().peekable(),
-                dcx: self.dcx,
+            let before = self.parser.token.span.shrink_to_lo();
+            while let token::Ident(..) = self.parser.token.kind {
+                self.parser.bump();
             }
-            .next();
+            err.quote_ident_sugg = Some(InvalidMetaItemQuoteIdentSugg {
+                before,
+                after: self.parser.prev_token.span.shrink_to_hi(),
+            });
         }
 
-        // or a path.
-        let path = self.next_path()?;
-
-        // Paths can be followed by:
-        // - `(more meta items)` (another list)
-        // - `= lit` (a name-value)
-        // - nothing
-        Some(MetaItemOrLitParser::MetaItemParser(match self.inside_delimiters.peek() {
-            Some(TokenTree::Delimited(dspan, _, Delimiter::Parenthesis, inner_tokens)) => {
-                self.inside_delimiters.next();
-
-                MetaItemParser {
-                    path: PathParser::Attr(path),
-                    args: ArgParser::List(MetaItemListParser::new_tts(
-                        inner_tokens.iter(),
-                        dspan.entire(),
-                        self.dcx,
-                    )),
-                }
-            }
-            Some(TokenTree::Delimited(_, ..)) => {
-                self.inside_delimiters.next();
-                // self.dcx.span_delayed_bug(span.entire(), "wrong delimiters");
-                return None;
-            }
-            Some(TokenTree::Token(Token { kind: token::Eq, span }, _)) => {
-                self.inside_delimiters.next();
-                let value = self.value()?;
-                MetaItemParser {
-                    path: PathParser::Attr(path),
-                    args: ArgParser::NameValue(NameValueParser {
-                        eq_span: *span,
-                        value_span: value.span,
-                        value,
-                    }),
-                }
-            }
-            _ => MetaItemParser { path: PathParser::Attr(path), args: ArgParser::NoArgs },
-        }))
+        if self.parser.token == token::Minus
+            && self
+                .parser
+                .look_ahead(1, |t| matches!(t.kind, rustc_ast::token::TokenKind::Literal { .. }))
+        {
+            err.remove_neg_sugg =
+                Some(InvalidMetaItemRemoveNegSugg { negative_sign: self.parser.token.span });
+            self.parser.bump();
+            self.parser.bump();
+        }
+
+        Err(self.parser.dcx().create_err(err))
     }
 
-    fn parse(mut self, span: Span) -> MetaItemListParser<'a> {
-        let mut sub_parsers = Vec::new();
+    fn parse(
+        tokens: TokenStream,
+        psess: &'sess ParseSess,
+        span: Span,
+        should_emit: ShouldEmit,
+    ) -> PResult<'sess, MetaItemListParser<'static>> {
+        let mut parser = Parser::new(psess, tokens, None);
+        let mut this = MetaItemListParserContext { parser: &mut parser, should_emit };
 
-        while !self.done() {
-            let Some(n) = self.next() else {
-                continue;
-            };
-            sub_parsers.push(n);
+        // Presumably, the majority of the time there will only be one attr.
+        let mut sub_parsers = ThinVec::with_capacity(1);
+        while this.parser.token != token::Eof {
+            sub_parsers.push(this.parse_meta_item_inner()?);
 
-            match self.inside_delimiters.peek() {
-                None | Some(TokenTree::Token(Token { kind: token::Comma, .. }, _)) => {
-                    self.inside_delimiters.next();
-                }
-                Some(_) => {}
+            if !this.parser.eat(exp!(Comma)) {
+                break;
             }
         }
 
-        MetaItemListParser { sub_parsers, span }
+        if parser.token != token::Eof {
+            parser.unexpected()?;
+        }
+
+        Ok(MetaItemListParser { sub_parsers, span })
     }
 }
 
 #[derive(Debug, Clone)]
 pub struct MetaItemListParser<'a> {
-    sub_parsers: Vec<MetaItemOrLitParser<'a>>,
+    sub_parsers: ThinVec<MetaItemOrLitParser<'a>>,
     pub span: Span,
 }
 
 impl<'a> MetaItemListParser<'a> {
-    fn new<'sess>(delim: &'a DelimArgs, dcx: DiagCtxtHandle<'sess>) -> Self {
-        MetaItemListParser::new_tts(delim.tokens.iter(), delim.dspan.entire(), dcx)
-    }
-
-    fn new_tts<'sess>(tts: TokenStreamIter<'a>, span: Span, dcx: DiagCtxtHandle<'sess>) -> Self {
-        MetaItemListParserContext { inside_delimiters: tts.peekable(), dcx }.parse(span)
+    fn new<'sess>(
+        delim: &'a DelimArgs,
+        psess: &'sess ParseSess,
+        should_emit: ShouldEmit,
+    ) -> Option<Self> {
+        match MetaItemListParserContext::parse(
+            delim.tokens.clone(),
+            psess,
+            delim.dspan.entire(),
+            should_emit,
+        ) {
+            Ok(s) => Some(s),
+            Err(e) => {
+                should_emit.emit_err(e);
+                None
+            }
+        }
     }
 
     /// Lets you pick and choose as what you want to parse each element in the list
diff --git a/compiler/rustc_attr_parsing/src/session_diagnostics.rs b/compiler/rustc_attr_parsing/src/session_diagnostics.rs
index c65937b35b3..72bee0ddfbf 100644
--- a/compiler/rustc_attr_parsing/src/session_diagnostics.rs
+++ b/compiler/rustc_attr_parsing/src/session_diagnostics.rs
@@ -1,6 +1,6 @@
 use std::num::IntErrorKind;
 
-use rustc_ast::{self as ast, AttrStyle};
+use rustc_ast::{self as ast, AttrStyle, Path};
 use rustc_errors::codes::*;
 use rustc_errors::{
     Applicability, Diag, DiagArgValue, DiagCtxtHandle, Diagnostic, EmissionGuarantee, Level,
@@ -485,10 +485,12 @@ pub(crate) struct EmptyAttributeList {
 #[warning]
 #[help]
 pub(crate) struct InvalidTargetLint {
-    pub name: Symbol,
+    pub name: AttrPath,
     pub target: &'static str,
-    pub applied: String,
+    pub applied: DiagArgValue,
     pub only: &'static str,
+    #[suggestion(code = "", applicability = "machine-applicable", style = "tool-only")]
+    pub attr_span: Span,
 }
 
 #[derive(Diagnostic)]
@@ -496,10 +498,11 @@ pub(crate) struct InvalidTargetLint {
 #[diag(attr_parsing_invalid_target)]
 pub(crate) struct InvalidTarget {
     #[primary_span]
+    #[suggestion(code = "", applicability = "machine-applicable", style = "tool-only")]
     pub span: Span,
-    pub name: Symbol,
+    pub name: AttrPath,
     pub target: &'static str,
-    pub applied: String,
+    pub applied: DiagArgValue,
     pub only: &'static str,
 }
 
@@ -555,7 +558,7 @@ pub(crate) struct LinkOrdinalOutOfRange {
     pub ordinal: u128,
 }
 
-pub(crate) enum AttributeParseErrorReason {
+pub(crate) enum AttributeParseErrorReason<'a> {
     ExpectedNoArgs,
     ExpectedStringLiteral {
         byte_string: Option<Span>,
@@ -568,7 +571,7 @@ pub(crate) enum AttributeParseErrorReason {
     ExpectedNameValue(Option<Symbol>),
     DuplicateKey(Symbol),
     ExpectedSpecificArgument {
-        possibilities: Vec<&'static str>,
+        possibilities: &'a [Symbol],
         strings: bool,
         /// Should we tell the user to write a list when they didn't?
         list: bool,
@@ -576,16 +579,16 @@ pub(crate) enum AttributeParseErrorReason {
     ExpectedIdentifier,
 }
 
-pub(crate) struct AttributeParseError {
+pub(crate) struct AttributeParseError<'a> {
     pub(crate) span: Span,
     pub(crate) attr_span: Span,
     pub(crate) attr_style: AttrStyle,
     pub(crate) template: AttributeTemplate,
     pub(crate) attribute: AttrPath,
-    pub(crate) reason: AttributeParseErrorReason,
+    pub(crate) reason: AttributeParseErrorReason<'a>,
 }
 
-impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for AttributeParseError {
+impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for AttributeParseError<'_> {
     fn into_diag(self, dcx: DiagCtxtHandle<'a>, level: Level) -> Diag<'a, G> {
         let name = self.attribute.to_string();
 
@@ -654,7 +657,7 @@ impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for AttributeParseError {
                 list: false,
             } => {
                 let quote = if strings { '"' } else { '`' };
-                match possibilities.as_slice() {
+                match possibilities {
                     &[] => {}
                     &[x] => {
                         diag.span_label(
@@ -684,7 +687,7 @@ impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for AttributeParseError {
                 list: true,
             } => {
                 let quote = if strings { '"' } else { '`' };
-                match possibilities.as_slice() {
+                match possibilities {
                     &[] => {}
                     &[x] => {
                         diag.span_label(
@@ -734,3 +737,92 @@ impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for AttributeParseError {
         diag
     }
 }
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_invalid_attr_unsafe)]
+#[note]
+pub(crate) struct InvalidAttrUnsafe {
+    #[primary_span]
+    #[label]
+    pub span: Span,
+    pub name: Path,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_unsafe_attr_outside_unsafe)]
+pub(crate) struct UnsafeAttrOutsideUnsafe {
+    #[primary_span]
+    #[label]
+    pub span: Span,
+    #[subdiagnostic]
+    pub suggestion: UnsafeAttrOutsideUnsafeSuggestion,
+}
+
+#[derive(Subdiagnostic)]
+#[multipart_suggestion(
+    attr_parsing_unsafe_attr_outside_unsafe_suggestion,
+    applicability = "machine-applicable"
+)]
+pub(crate) struct UnsafeAttrOutsideUnsafeSuggestion {
+    #[suggestion_part(code = "unsafe(")]
+    pub left: Span,
+    #[suggestion_part(code = ")")]
+    pub right: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_meta_bad_delim)]
+pub(crate) struct MetaBadDelim {
+    #[primary_span]
+    pub span: Span,
+    #[subdiagnostic]
+    pub sugg: MetaBadDelimSugg,
+}
+
+#[derive(Subdiagnostic)]
+#[multipart_suggestion(
+    attr_parsing_meta_bad_delim_suggestion,
+    applicability = "machine-applicable"
+)]
+pub(crate) struct MetaBadDelimSugg {
+    #[suggestion_part(code = "(")]
+    pub open: Span,
+    #[suggestion_part(code = ")")]
+    pub close: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_invalid_meta_item)]
+pub(crate) struct InvalidMetaItem {
+    #[primary_span]
+    pub span: Span,
+    pub descr: String,
+    #[subdiagnostic]
+    pub quote_ident_sugg: Option<InvalidMetaItemQuoteIdentSugg>,
+    #[subdiagnostic]
+    pub remove_neg_sugg: Option<InvalidMetaItemRemoveNegSugg>,
+}
+
+#[derive(Subdiagnostic)]
+#[multipart_suggestion(attr_parsing_quote_ident_sugg, applicability = "machine-applicable")]
+pub(crate) struct InvalidMetaItemQuoteIdentSugg {
+    #[suggestion_part(code = "\"")]
+    pub before: Span,
+    #[suggestion_part(code = "\"")]
+    pub after: Span,
+}
+
+#[derive(Subdiagnostic)]
+#[multipart_suggestion(attr_parsing_remove_neg_sugg, applicability = "machine-applicable")]
+pub(crate) struct InvalidMetaItemRemoveNegSugg {
+    #[suggestion_part(code = "")]
+    pub negative_sign: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_suffixed_literal_in_attribute)]
+#[help]
+pub(crate) struct SuffixedLiteralInAttribute {
+    #[primary_span]
+    pub span: Span,
+}
diff --git a/compiler/rustc_attr_parsing/src/target_checking.rs b/compiler/rustc_attr_parsing/src/target_checking.rs
new file mode 100644
index 00000000000..9568b791b3f
--- /dev/null
+++ b/compiler/rustc_attr_parsing/src/target_checking.rs
@@ -0,0 +1,247 @@
+use std::borrow::Cow;
+
+use rustc_errors::DiagArgValue;
+use rustc_feature::Features;
+use rustc_hir::lints::{AttributeLint, AttributeLintKind};
+use rustc_hir::{AttrPath, MethodKind, Target};
+use rustc_span::Span;
+
+use crate::AttributeParser;
+use crate::context::Stage;
+use crate::session_diagnostics::InvalidTarget;
+
+#[derive(Debug)]
+pub(crate) enum AllowedTargets {
+    AllowList(&'static [Policy]),
+    AllowListWarnRest(&'static [Policy]),
+}
+
+pub(crate) enum AllowedResult {
+    Allowed,
+    Warn,
+    Error,
+}
+
+impl AllowedTargets {
+    pub(crate) fn is_allowed(&self, target: Target) -> AllowedResult {
+        match self {
+            AllowedTargets::AllowList(list) => {
+                if list.contains(&Policy::Allow(target)) {
+                    AllowedResult::Allowed
+                } else if list.contains(&Policy::Warn(target)) {
+                    AllowedResult::Warn
+                } else {
+                    AllowedResult::Error
+                }
+            }
+            AllowedTargets::AllowListWarnRest(list) => {
+                if list.contains(&Policy::Allow(target)) {
+                    AllowedResult::Allowed
+                } else if list.contains(&Policy::Error(target)) {
+                    AllowedResult::Error
+                } else {
+                    AllowedResult::Warn
+                }
+            }
+        }
+    }
+
+    pub(crate) fn allowed_targets(&self) -> Vec<Target> {
+        match self {
+            AllowedTargets::AllowList(list) => list,
+            AllowedTargets::AllowListWarnRest(list) => list,
+        }
+        .iter()
+        .filter_map(|target| match target {
+            Policy::Allow(target) => Some(*target),
+            Policy::Warn(_) => None,
+            Policy::Error(_) => None,
+        })
+        .collect()
+    }
+}
+
+#[derive(Debug, Eq, PartialEq)]
+pub(crate) enum Policy {
+    Allow(Target),
+    Warn(Target),
+    Error(Target),
+}
+
+impl<S: Stage> AttributeParser<'_, S> {
+    pub(crate) fn check_target(
+        &self,
+        attr_name: AttrPath,
+        attr_span: Span,
+        allowed_targets: &AllowedTargets,
+        target: Target,
+        target_id: S::Id,
+        mut emit_lint: impl FnMut(AttributeLint<S::Id>),
+    ) {
+        match allowed_targets.is_allowed(target) {
+            AllowedResult::Allowed => {}
+            AllowedResult::Warn => {
+                let allowed_targets = allowed_targets.allowed_targets();
+                let (applied, only) =
+                    allowed_targets_applied(allowed_targets, target, self.features);
+                emit_lint(AttributeLint {
+                    id: target_id,
+                    span: attr_span,
+                    kind: AttributeLintKind::InvalidTarget {
+                        name: attr_name,
+                        target,
+                        only: if only { "only " } else { "" },
+                        applied,
+                    },
+                });
+            }
+            AllowedResult::Error => {
+                let allowed_targets = allowed_targets.allowed_targets();
+                let (applied, only) =
+                    allowed_targets_applied(allowed_targets, target, self.features);
+                self.dcx().emit_err(InvalidTarget {
+                    span: attr_span,
+                    name: attr_name,
+                    target: target.plural_name(),
+                    only: if only { "only " } else { "" },
+                    applied: DiagArgValue::StrListSepByAnd(
+                        applied.into_iter().map(Cow::Owned).collect(),
+                    ),
+                });
+            }
+        }
+    }
+}
+
+/// Takes a list of `allowed_targets` for an attribute, and the `target` the attribute was applied to.
+/// Does some heuristic-based filtering to remove uninteresting targets, and formats the targets into a string
+pub(crate) fn allowed_targets_applied(
+    mut allowed_targets: Vec<Target>,
+    target: Target,
+    features: Option<&Features>,
+) -> (Vec<String>, bool) {
+    // Remove unstable targets from `allowed_targets` if their features are not enabled
+    if let Some(features) = features {
+        if !features.fn_delegation() {
+            allowed_targets.retain(|t| !matches!(t, Target::Delegation { .. }));
+        }
+        if !features.stmt_expr_attributes() {
+            allowed_targets.retain(|t| !matches!(t, Target::Expression | Target::Statement));
+        }
+        if !features.extern_types() {
+            allowed_targets.retain(|t| !matches!(t, Target::ForeignTy));
+        }
+    }
+
+    // We define groups of "similar" targets.
+    // If at least two of the targets are allowed, and the `target` is not in the group,
+    // we collapse the entire group to a single entry to simplify the target list
+    const FUNCTION_LIKE: &[Target] = &[
+        Target::Fn,
+        Target::Closure,
+        Target::ForeignFn,
+        Target::Method(MethodKind::Inherent),
+        Target::Method(MethodKind::Trait { body: false }),
+        Target::Method(MethodKind::Trait { body: true }),
+        Target::Method(MethodKind::TraitImpl),
+    ];
+    const METHOD_LIKE: &[Target] = &[
+        Target::Method(MethodKind::Inherent),
+        Target::Method(MethodKind::Trait { body: false }),
+        Target::Method(MethodKind::Trait { body: true }),
+        Target::Method(MethodKind::TraitImpl),
+    ];
+    const IMPL_LIKE: &[Target] =
+        &[Target::Impl { of_trait: false }, Target::Impl { of_trait: true }];
+    const ADT_LIKE: &[Target] = &[Target::Struct, Target::Enum];
+
+    let mut added_fake_targets = Vec::new();
+    filter_targets(
+        &mut allowed_targets,
+        FUNCTION_LIKE,
+        "functions",
+        target,
+        &mut added_fake_targets,
+    );
+    filter_targets(&mut allowed_targets, METHOD_LIKE, "methods", target, &mut added_fake_targets);
+    filter_targets(&mut allowed_targets, IMPL_LIKE, "impl blocks", target, &mut added_fake_targets);
+    filter_targets(&mut allowed_targets, ADT_LIKE, "data types", target, &mut added_fake_targets);
+
+    // If there is now only 1 target left, show that as the only possible target
+    (
+        added_fake_targets
+            .iter()
+            .copied()
+            .chain(allowed_targets.iter().map(|t| t.plural_name()))
+            .map(|i| i.to_string())
+            .collect(),
+        allowed_targets.len() + added_fake_targets.len() == 1,
+    )
+}
+
+fn filter_targets(
+    allowed_targets: &mut Vec<Target>,
+    target_group: &'static [Target],
+    target_group_name: &'static str,
+    target: Target,
+    added_fake_targets: &mut Vec<&'static str>,
+) {
+    if target_group.contains(&target) {
+        return;
+    }
+    if allowed_targets.iter().filter(|at| target_group.contains(at)).count() < 2 {
+        return;
+    }
+    allowed_targets.retain(|t| !target_group.contains(t));
+    added_fake_targets.push(target_group_name);
+}
+
+/// This is the list of all targets to which a attribute can be applied
+/// This is used for:
+/// - `rustc_dummy`, which can be applied to all targets
+/// - Attributes that are not parted to the new target system yet can use this list as a placeholder
+pub(crate) const ALL_TARGETS: &'static [Policy] = {
+    use Policy::Allow;
+    &[
+        Allow(Target::ExternCrate),
+        Allow(Target::Use),
+        Allow(Target::Static),
+        Allow(Target::Const),
+        Allow(Target::Fn),
+        Allow(Target::Closure),
+        Allow(Target::Mod),
+        Allow(Target::ForeignMod),
+        Allow(Target::GlobalAsm),
+        Allow(Target::TyAlias),
+        Allow(Target::Enum),
+        Allow(Target::Variant),
+        Allow(Target::Struct),
+        Allow(Target::Field),
+        Allow(Target::Union),
+        Allow(Target::Trait),
+        Allow(Target::TraitAlias),
+        Allow(Target::Impl { of_trait: false }),
+        Allow(Target::Impl { of_trait: true }),
+        Allow(Target::Expression),
+        Allow(Target::Statement),
+        Allow(Target::Arm),
+        Allow(Target::AssocConst),
+        Allow(Target::Method(MethodKind::Inherent)),
+        Allow(Target::Method(MethodKind::Trait { body: false })),
+        Allow(Target::Method(MethodKind::Trait { body: true })),
+        Allow(Target::Method(MethodKind::TraitImpl)),
+        Allow(Target::AssocTy),
+        Allow(Target::ForeignFn),
+        Allow(Target::ForeignStatic),
+        Allow(Target::ForeignTy),
+        Allow(Target::MacroDef),
+        Allow(Target::Param),
+        Allow(Target::PatField),
+        Allow(Target::ExprField),
+        Allow(Target::WherePredicate),
+        Allow(Target::MacroCall),
+        Allow(Target::Crate),
+        Allow(Target::Delegation { mac: false }),
+        Allow(Target::Delegation { mac: true }),
+    ]
+};
diff --git a/compiler/rustc_parse/src/validate_attr.rs b/compiler/rustc_attr_parsing/src/validate_attr.rs
index 68ef6d6f32c..7a7624893bd 100644
--- a/compiler/rustc_parse/src/validate_attr.rs
+++ b/compiler/rustc_attr_parsing/src/validate_attr.rs
@@ -8,16 +8,16 @@ use rustc_ast::{
     self as ast, AttrArgs, Attribute, DelimArgs, MetaItem, MetaItemInner, MetaItemKind, NodeId,
     Path, Safety,
 };
-use rustc_attr_parsing::{AttributeParser, Late};
 use rustc_errors::{Applicability, DiagCtxtHandle, FatalError, PResult};
 use rustc_feature::{AttributeSafety, AttributeTemplate, BUILTIN_ATTRIBUTE_MAP, BuiltinAttribute};
+use rustc_parse::parse_in;
 use rustc_session::errors::report_lit_error;
 use rustc_session::lint::BuiltinLintDiag;
 use rustc_session::lint::builtin::{ILL_FORMED_ATTRIBUTE_INPUT, UNSAFE_ATTR_OUTSIDE_UNSAFE};
 use rustc_session::parse::ParseSess;
 use rustc_span::{Span, Symbol, sym};
 
-use crate::{errors, parse_in};
+use crate::{AttributeParser, Late, session_diagnostics as errors};
 
 pub fn check_attr(psess: &ParseSess, attr: &Attribute, id: NodeId) {
     if attr.is_doc_comment() || attr.has_name(sym::cfg_trace) || attr.has_name(sym::cfg_attr_trace)
@@ -33,7 +33,10 @@ pub fn check_attr(psess: &ParseSess, attr: &Attribute, id: NodeId) {
     // Check input tokens for built-in and key-value attributes.
     match builtin_attr_info {
         // `rustc_dummy` doesn't have any restrictions specific to built-in attributes.
-        Some(BuiltinAttribute { name, template, .. }) if *name != sym::rustc_dummy => {
+        Some(BuiltinAttribute { name, template, .. }) => {
+            if AttributeParser::<Late>::is_parsed_attribute(slice::from_ref(&name)) {
+                return;
+            }
             match parse_meta(psess, attr) {
                 // Don't check safety again, we just did that
                 Ok(meta) => {
@@ -133,16 +136,6 @@ fn check_meta_bad_delim(psess: &ParseSess, span: DelimSpan, delim: Delimiter) {
     });
 }
 
-pub(super) fn check_cfg_attr_bad_delim(psess: &ParseSess, span: DelimSpan, delim: Delimiter) {
-    if let Delimiter::Parenthesis = delim {
-        return;
-    }
-    psess.dcx().emit_err(errors::CfgAttrBadDelim {
-        span: span.entire(),
-        sugg: errors::MetaBadDelimSugg { open: span.open, close: span.close },
-    });
-}
-
 /// Checks that the given meta-item is compatible with this `AttributeTemplate`.
 fn is_attr_template_compatible(template: &AttributeTemplate, meta: &ast::MetaItemKind) -> bool {
     let is_one_allowed_subword = |items: &[MetaItemInner]| match items {
@@ -269,9 +262,6 @@ pub fn check_builtin_meta_item(
 ) {
     if !is_attr_template_compatible(&template, &meta.kind) {
         // attrs with new parsers are locally validated so excluded here
-        if AttributeParser::<Late>::is_parsed_attribute(slice::from_ref(&name)) {
-            return;
-        }
         emit_malformed_attribute(psess, style, meta.span, name, template);
     }
 
diff --git a/compiler/rustc_borrowck/src/dataflow.rs b/compiler/rustc_borrowck/src/dataflow.rs
index 57db2e9fb57..d3f6c01ab8c 100644
--- a/compiler/rustc_borrowck/src/dataflow.rs
+++ b/compiler/rustc_borrowck/src/dataflow.rs
@@ -1,7 +1,6 @@
 use std::fmt;
 
 use rustc_data_structures::fx::FxIndexMap;
-use rustc_data_structures::graph;
 use rustc_index::bit_set::{DenseBitSet, MixedBitSet};
 use rustc_middle::mir::{
     self, BasicBlock, Body, CallReturnPlaces, Location, Place, TerminatorEdges,
@@ -317,9 +316,8 @@ impl<'tcx> PoloniusOutOfScopePrecomputer<'_, 'tcx> {
             loans_out_of_scope_at_location: FxIndexMap::default(),
         };
         for (loan_idx, loan_data) in borrow_set.iter_enumerated() {
-            let issuing_region = loan_data.region;
             let loan_issued_at = loan_data.reserve_location;
-            prec.precompute_loans_out_of_scope(loan_idx, issuing_region, loan_issued_at);
+            prec.precompute_loans_out_of_scope(loan_idx, loan_issued_at);
         }
 
         prec.loans_out_of_scope_at_location
@@ -328,45 +326,7 @@ impl<'tcx> PoloniusOutOfScopePrecomputer<'_, 'tcx> {
     /// Loans are in scope while they are live: whether they are contained within any live region.
     /// In the location-insensitive analysis, a loan will be contained in a region if the issuing
     /// region can reach it in the subset graph. So this is a reachability problem.
-    fn precompute_loans_out_of_scope(
-        &mut self,
-        loan_idx: BorrowIndex,
-        issuing_region: RegionVid,
-        loan_issued_at: Location,
-    ) {
-        let sccs = self.regioncx.constraint_sccs();
-        let universal_regions = self.regioncx.universal_regions();
-
-        // The loop below was useful for the location-insensitive analysis but shouldn't be
-        // impactful in the location-sensitive case. It seems that it does, however, as without it a
-        // handful of tests fail. That likely means some liveness or outlives data related to choice
-        // regions is missing
-        // FIXME: investigate the impact of loans traversing applied member constraints and why some
-        // tests fail otherwise.
-        //
-        // We first handle the cases where the loan doesn't go out of scope, depending on the
-        // issuing region's successors.
-        for successor in graph::depth_first_search(&self.regioncx.region_graph(), issuing_region) {
-            // Via applied member constraints
-            //
-            // The issuing region can flow into the choice regions, and they are either:
-            // - placeholders or free regions themselves,
-            // - or also transitively outlive a free region.
-            //
-            // That is to say, if there are applied member constraints here, the loan escapes the
-            // function and cannot go out of scope. We could early return here.
-            //
-            // For additional insurance via fuzzing and crater, we verify that the constraint's min
-            // choice indeed escapes the function. In the future, we could e.g. turn this check into
-            // a debug assert and early return as an optimization.
-            let scc = sccs.scc(successor);
-            for constraint in self.regioncx.applied_member_constraints(scc) {
-                if universal_regions.is_universal_region(constraint.min_choice) {
-                    return;
-                }
-            }
-        }
-
+    fn precompute_loans_out_of_scope(&mut self, loan_idx: BorrowIndex, loan_issued_at: Location) {
         let first_block = loan_issued_at.block;
         let first_bb_data = &self.body.basic_blocks[first_block];
 
diff --git a/compiler/rustc_borrowck/src/diagnostics/opaque_types.rs b/compiler/rustc_borrowck/src/diagnostics/opaque_types.rs
index 83fe4a9f98f..f77f759035b 100644
--- a/compiler/rustc_borrowck/src/diagnostics/opaque_types.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/opaque_types.rs
@@ -13,6 +13,8 @@ use rustc_middle::mir::{self, ConstraintCategory, Location};
 use rustc_middle::ty::{
     self, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitableExt, TypeVisitor,
 };
+use rustc_span::Span;
+use rustc_trait_selection::error_reporting::infer::region::unexpected_hidden_region_diagnostic;
 use rustc_trait_selection::errors::impl_trait_overcapture_suggestion;
 
 use crate::MirBorrowckCtxt;
@@ -26,13 +28,61 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
         if errors.is_empty() {
             return;
         }
+
+        let infcx = self.infcx;
         let mut guar = None;
+        let mut last_unexpected_hidden_region: Option<(Span, Ty<'_>, ty::OpaqueTypeKey<'tcx>)> =
+            None;
         for error in errors {
             guar = Some(match error {
-                DeferredOpaqueTypeError::InvalidOpaqueTypeArgs(err) => err.report(self.infcx),
+                DeferredOpaqueTypeError::InvalidOpaqueTypeArgs(err) => err.report(infcx),
                 DeferredOpaqueTypeError::LifetimeMismatchOpaqueParam(err) => {
-                    self.infcx.dcx().emit_err(err)
+                    infcx.dcx().emit_err(err)
+                }
+                DeferredOpaqueTypeError::UnexpectedHiddenRegion {
+                    opaque_type_key,
+                    hidden_type,
+                    member_region,
+                } => {
+                    let named_ty =
+                        self.regioncx.name_regions_for_member_constraint(infcx.tcx, hidden_type.ty);
+                    let named_key = self
+                        .regioncx
+                        .name_regions_for_member_constraint(infcx.tcx, opaque_type_key);
+                    let named_region =
+                        self.regioncx.name_regions_for_member_constraint(infcx.tcx, member_region);
+                    let diag = unexpected_hidden_region_diagnostic(
+                        infcx,
+                        self.mir_def_id(),
+                        hidden_type.span,
+                        named_ty,
+                        named_region,
+                        named_key,
+                    );
+                    if last_unexpected_hidden_region
+                        != Some((hidden_type.span, named_ty, named_key))
+                    {
+                        last_unexpected_hidden_region =
+                            Some((hidden_type.span, named_ty, named_key));
+                        diag.emit()
+                    } else {
+                        diag.delay_as_bug()
+                    }
                 }
+                DeferredOpaqueTypeError::NonDefiningUseInDefiningScope {
+                    span,
+                    opaque_type_key,
+                } => infcx.dcx().span_err(
+                    span,
+                    format!(
+                        "non-defining use of `{}` in the defining scope",
+                        Ty::new_opaque(
+                            infcx.tcx,
+                            opaque_type_key.def_id.to_def_id(),
+                            opaque_type_key.args
+                        )
+                    ),
+                ),
             });
         }
         let guar = guar.unwrap();
@@ -194,7 +244,7 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for FindOpaqueRegion<'_, 'tcx> {
 
                 // Find a path between the borrow region and our opaque capture.
                 if let Some((path, _)) =
-                    self.regioncx.find_constraint_paths_between_regions(self.borrow_region, |r| {
+                    self.regioncx.find_constraint_path_between_regions(self.borrow_region, |r| {
                         r == opaque_region_vid
                     })
                 {
diff --git a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
index fe4e1b6011e..c7d2267e5f7 100644
--- a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
@@ -23,7 +23,6 @@ use rustc_trait_selection::error_reporting::infer::nice_region_error::{
     self, HirTraitObjectVisitor, NiceRegionError, TraitObjectVisitor, find_anon_type,
     find_param_with_region, suggest_adding_lifetime_params,
 };
-use rustc_trait_selection::error_reporting::infer::region::unexpected_hidden_region_diagnostic;
 use rustc_trait_selection::infer::InferCtxtExt;
 use rustc_trait_selection::traits::{Obligation, ObligationCtxt};
 use tracing::{debug, instrument, trace};
@@ -105,18 +104,6 @@ pub(crate) enum RegionErrorKind<'tcx> {
     /// A generic bound failure for a type test (`T: 'a`).
     TypeTestError { type_test: TypeTest<'tcx> },
 
-    /// An unexpected hidden region for an opaque type.
-    UnexpectedHiddenRegion {
-        /// The span for the member constraint.
-        span: Span,
-        /// The hidden type.
-        hidden_ty: Ty<'tcx>,
-        /// The opaque type.
-        key: ty::OpaqueTypeKey<'tcx>,
-        /// The unexpected region.
-        member_region: ty::Region<'tcx>,
-    },
-
     /// Higher-ranked subtyping error.
     BoundUniversalRegionError {
         /// The placeholder free region.
@@ -323,11 +310,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
     pub(crate) fn report_region_errors(&mut self, nll_errors: RegionErrors<'tcx>) {
         // Iterate through all the errors, producing a diagnostic for each one. The diagnostics are
         // buffered in the `MirBorrowckCtxt`.
-
         let mut outlives_suggestion = OutlivesSuggestionBuilder::default();
-        let mut last_unexpected_hidden_region: Option<(Span, Ty<'_>, ty::OpaqueTypeKey<'tcx>)> =
-            None;
-
         for (nll_error, _) in nll_errors.into_iter() {
             match nll_error {
                 RegionErrorKind::TypeTestError { type_test } => {
@@ -378,30 +361,6 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                     }
                 }
 
-                RegionErrorKind::UnexpectedHiddenRegion { span, hidden_ty, key, member_region } => {
-                    let named_ty =
-                        self.regioncx.name_regions_for_member_constraint(self.infcx.tcx, hidden_ty);
-                    let named_key =
-                        self.regioncx.name_regions_for_member_constraint(self.infcx.tcx, key);
-                    let named_region = self
-                        .regioncx
-                        .name_regions_for_member_constraint(self.infcx.tcx, member_region);
-                    let diag = unexpected_hidden_region_diagnostic(
-                        self.infcx,
-                        self.mir_def_id(),
-                        span,
-                        named_ty,
-                        named_region,
-                        named_key,
-                    );
-                    if last_unexpected_hidden_region != Some((span, named_ty, named_key)) {
-                        self.buffer_error(diag);
-                        last_unexpected_hidden_region = Some((span, named_ty, named_key));
-                    } else {
-                        diag.delay_as_bug();
-                    }
-                }
-
                 RegionErrorKind::BoundUniversalRegionError {
                     longer_fr,
                     placeholder,
diff --git a/compiler/rustc_borrowck/src/handle_placeholders.rs b/compiler/rustc_borrowck/src/handle_placeholders.rs
index 1614c112ab5..4661906fbeb 100644
--- a/compiler/rustc_borrowck/src/handle_placeholders.rs
+++ b/compiler/rustc_borrowck/src/handle_placeholders.rs
@@ -15,7 +15,6 @@ use tracing::debug;
 use crate::constraints::{ConstraintSccIndex, OutlivesConstraintSet};
 use crate::consumers::OutlivesConstraint;
 use crate::diagnostics::UniverseInfo;
-use crate::member_constraints::MemberConstraintSet;
 use crate::region_infer::values::{LivenessValues, PlaceholderIndices};
 use crate::region_infer::{ConstraintSccs, RegionDefinition, Representative, TypeTest};
 use crate::ty::VarianceDiagInfo;
@@ -30,7 +29,6 @@ pub(crate) struct LoweredConstraints<'tcx> {
     pub(crate) constraint_sccs: Sccs<RegionVid, ConstraintSccIndex>,
     pub(crate) definitions: Frozen<IndexVec<RegionVid, RegionDefinition<'tcx>>>,
     pub(crate) scc_annotations: IndexVec<ConstraintSccIndex, RegionTracker>,
-    pub(crate) member_constraints: MemberConstraintSet<'tcx, RegionVid>,
     pub(crate) outlives_constraints: Frozen<OutlivesConstraintSet<'tcx>>,
     pub(crate) type_tests: Vec<TypeTest<'tcx>>,
     pub(crate) liveness_constraints: LivenessValues,
@@ -147,9 +145,10 @@ impl scc::Annotation for RegionTracker {
 
 /// Determines if the region variable definitions contain
 /// placeholders, and compute them for later use.
-fn region_definitions<'tcx>(
-    universal_regions: &UniversalRegions<'tcx>,
+// FIXME: This is also used by opaque type handling. Move it to a separate file.
+pub(super) fn region_definitions<'tcx>(
     infcx: &BorrowckInferCtxt<'tcx>,
+    universal_regions: &UniversalRegions<'tcx>,
 ) -> (Frozen<IndexVec<RegionVid, RegionDefinition<'tcx>>>, bool) {
     let var_infos = infcx.get_region_var_infos();
     // Create a RegionDefinition for each inference variable. This happens here because
@@ -213,14 +212,13 @@ pub(crate) fn compute_sccs_applying_placeholder_outlives_constraints<'tcx>(
     infcx: &BorrowckInferCtxt<'tcx>,
 ) -> LoweredConstraints<'tcx> {
     let universal_regions = &universal_region_relations.universal_regions;
-    let (definitions, has_placeholders) = region_definitions(universal_regions, infcx);
+    let (definitions, has_placeholders) = region_definitions(infcx, universal_regions);
 
     let MirTypeckRegionConstraints {
         placeholder_indices,
         placeholder_index_to_region: _,
         liveness_constraints,
         mut outlives_constraints,
-        member_constraints,
         universe_causes,
         type_tests,
     } = constraints;
@@ -246,7 +244,6 @@ pub(crate) fn compute_sccs_applying_placeholder_outlives_constraints<'tcx>(
 
         return LoweredConstraints {
             type_tests,
-            member_constraints,
             constraint_sccs,
             scc_annotations: scc_annotations.scc_to_annotation,
             definitions,
@@ -283,7 +280,6 @@ pub(crate) fn compute_sccs_applying_placeholder_outlives_constraints<'tcx>(
         constraint_sccs,
         definitions,
         scc_annotations,
-        member_constraints,
         outlives_constraints: Frozen::freeze(outlives_constraints),
         type_tests,
         liveness_constraints,
diff --git a/compiler/rustc_borrowck/src/lib.rs b/compiler/rustc_borrowck/src/lib.rs
index d76d6a04e6e..ce78ae203a4 100644
--- a/compiler/rustc_borrowck/src/lib.rs
+++ b/compiler/rustc_borrowck/src/lib.rs
@@ -78,7 +78,6 @@ mod dataflow;
 mod def_use;
 mod diagnostics;
 mod handle_placeholders;
-mod member_constraints;
 mod nll;
 mod path_utils;
 mod place_ext;
@@ -301,7 +300,7 @@ fn do_mir_borrowck<'tcx>(
     def: LocalDefId,
 ) -> PropagatedBorrowCheckResults<'tcx> {
     let tcx = root_cx.tcx;
-    let infcx = BorrowckInferCtxt::new(tcx, def);
+    let infcx = BorrowckInferCtxt::new(tcx, def, root_cx.root_def_id());
     let (input_body, promoted) = tcx.mir_promoted(def);
     let input_body: &Body<'_> = &input_body.borrow();
     let input_promoted: &IndexSlice<_, _> = &promoted.borrow();
@@ -335,9 +334,10 @@ fn do_mir_borrowck<'tcx>(
 
     // Run the MIR type-checker.
     let MirTypeckResults {
-        constraints,
+        mut constraints,
         universal_region_relations,
-        opaque_type_values,
+        region_bound_pairs,
+        known_type_outlives_obligations,
         polonius_context,
     } = type_check::type_check(
         root_cx,
@@ -352,6 +352,17 @@ fn do_mir_borrowck<'tcx>(
         Rc::clone(&location_map),
     );
 
+    let opaque_type_errors = region_infer::opaque_types::handle_opaque_type_uses(
+        root_cx,
+        &infcx,
+        &body,
+        &universal_region_relations,
+        &region_bound_pairs,
+        &known_type_outlives_obligations,
+        &location_map,
+        &mut constraints,
+    );
+
     // Compute non-lexical lifetimes using the constraints computed
     // by typechecking the MIR body.
     let nll::NllOutput {
@@ -375,8 +386,6 @@ fn do_mir_borrowck<'tcx>(
         polonius_context,
     );
 
-    let opaque_type_errors = regioncx.infer_opaque_types(root_cx, &infcx, opaque_type_values);
-
     // Dump MIR results into a file, if that is enabled. This lets us
     // write unit-tests, as well as helping with debugging.
     nll::dump_nll_mir(&infcx, body, &regioncx, &opt_closure_req, &borrow_set);
@@ -581,12 +590,13 @@ fn get_flow_results<'a, 'tcx>(
 
 pub(crate) struct BorrowckInferCtxt<'tcx> {
     pub(crate) infcx: InferCtxt<'tcx>,
-    pub(crate) reg_var_to_origin: RefCell<FxIndexMap<ty::RegionVid, RegionCtxt>>,
+    pub(crate) root_def_id: LocalDefId,
     pub(crate) param_env: ParamEnv<'tcx>,
+    pub(crate) reg_var_to_origin: RefCell<FxIndexMap<ty::RegionVid, RegionCtxt>>,
 }
 
 impl<'tcx> BorrowckInferCtxt<'tcx> {
-    pub(crate) fn new(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> Self {
+    pub(crate) fn new(tcx: TyCtxt<'tcx>, def_id: LocalDefId, root_def_id: LocalDefId) -> Self {
         let typing_mode = if tcx.use_typing_mode_borrowck() {
             TypingMode::borrowck(tcx, def_id)
         } else {
@@ -594,7 +604,12 @@ impl<'tcx> BorrowckInferCtxt<'tcx> {
         };
         let infcx = tcx.infer_ctxt().build(typing_mode);
         let param_env = tcx.param_env(def_id);
-        BorrowckInferCtxt { infcx, reg_var_to_origin: RefCell::new(Default::default()), param_env }
+        BorrowckInferCtxt {
+            infcx,
+            root_def_id,
+            reg_var_to_origin: RefCell::new(Default::default()),
+            param_env,
+        }
     }
 
     pub(crate) fn next_region_var<F>(
diff --git a/compiler/rustc_borrowck/src/member_constraints.rs b/compiler/rustc_borrowck/src/member_constraints.rs
deleted file mode 100644
index bdd0f6fe11e..00000000000
--- a/compiler/rustc_borrowck/src/member_constraints.rs
+++ /dev/null
@@ -1,226 +0,0 @@
-use std::hash::Hash;
-use std::ops::Index;
-
-use rustc_data_structures::fx::FxIndexMap;
-use rustc_index::{IndexSlice, IndexVec};
-use rustc_middle::ty::{self, Ty};
-use rustc_span::Span;
-use tracing::instrument;
-
-/// Compactly stores a set of `R0 member of [R1...Rn]` constraints,
-/// indexed by the region `R0`.
-#[derive(Debug)]
-pub(crate) struct MemberConstraintSet<'tcx, R>
-where
-    R: Copy + Eq,
-{
-    /// Stores the first "member" constraint for a given `R0`. This is an
-    /// index into the `constraints` vector below.
-    first_constraints: FxIndexMap<R, NllMemberConstraintIndex>,
-
-    /// Stores the data about each `R0 member of [R1..Rn]` constraint.
-    /// These are organized into a linked list, so each constraint
-    /// contains the index of the next constraint with the same `R0`.
-    constraints: IndexVec<NllMemberConstraintIndex, MemberConstraint<'tcx>>,
-
-    /// Stores the `R1..Rn` regions for *all* sets. For any given
-    /// constraint, we keep two indices so that we can pull out a
-    /// slice.
-    choice_regions: Vec<ty::RegionVid>,
-}
-
-/// Represents a `R0 member of [R1..Rn]` constraint
-#[derive(Debug)]
-pub(crate) struct MemberConstraint<'tcx> {
-    next_constraint: Option<NllMemberConstraintIndex>,
-
-    /// The span where the hidden type was instantiated.
-    pub(crate) definition_span: Span,
-
-    /// The hidden type in which `R0` appears. (Used in error reporting.)
-    pub(crate) hidden_ty: Ty<'tcx>,
-
-    pub(crate) key: ty::OpaqueTypeKey<'tcx>,
-
-    /// The region `R0`.
-    pub(crate) member_region_vid: ty::RegionVid,
-
-    /// Index of `R1` in `choice_regions` vector from `MemberConstraintSet`.
-    start_index: usize,
-
-    /// Index of `Rn` in `choice_regions` vector from `MemberConstraintSet`.
-    end_index: usize,
-}
-
-rustc_index::newtype_index! {
-    #[debug_format = "MemberConstraintIndex({})"]
-    pub(crate) struct NllMemberConstraintIndex {}
-}
-
-impl Default for MemberConstraintSet<'_, ty::RegionVid> {
-    fn default() -> Self {
-        Self {
-            first_constraints: Default::default(),
-            constraints: Default::default(),
-            choice_regions: Default::default(),
-        }
-    }
-}
-
-impl<'tcx> MemberConstraintSet<'tcx, ty::RegionVid> {
-    pub(crate) fn is_empty(&self) -> bool {
-        self.constraints.is_empty()
-    }
-
-    /// Pushes a member constraint into the set.
-    #[instrument(level = "debug", skip(self))]
-    pub(crate) fn add_member_constraint(
-        &mut self,
-        key: ty::OpaqueTypeKey<'tcx>,
-        hidden_ty: Ty<'tcx>,
-        definition_span: Span,
-        member_region_vid: ty::RegionVid,
-        choice_regions: &[ty::RegionVid],
-    ) {
-        let next_constraint = self.first_constraints.get(&member_region_vid).cloned();
-        let start_index = self.choice_regions.len();
-        self.choice_regions.extend(choice_regions);
-        let end_index = self.choice_regions.len();
-        let constraint_index = self.constraints.push(MemberConstraint {
-            next_constraint,
-            member_region_vid,
-            definition_span,
-            hidden_ty,
-            key,
-            start_index,
-            end_index,
-        });
-        self.first_constraints.insert(member_region_vid, constraint_index);
-    }
-}
-
-impl<'tcx, R1> MemberConstraintSet<'tcx, R1>
-where
-    R1: Copy + Hash + Eq,
-{
-    /// Remap the "member region" key using `map_fn`, producing a new
-    /// member constraint set. This is used in the NLL code to map from
-    /// the original `RegionVid` to an scc index. In some cases, we
-    /// may have multiple `R1` values mapping to the same `R2` key -- that
-    /// is ok, the two sets will be merged.
-    pub(crate) fn into_mapped<R2>(
-        self,
-        mut map_fn: impl FnMut(R1) -> R2,
-    ) -> MemberConstraintSet<'tcx, R2>
-    where
-        R2: Copy + Hash + Eq,
-    {
-        // We can re-use most of the original data, just tweaking the
-        // linked list links a bit.
-        //
-        // For example if we had two keys `Ra` and `Rb` that both now
-        // wind up mapped to the same key `S`, we would append the
-        // linked list for `Ra` onto the end of the linked list for
-        // `Rb` (or vice versa) -- this basically just requires
-        // rewriting the final link from one list to point at the other
-        // other (see `append_list`).
-
-        let MemberConstraintSet { first_constraints, mut constraints, choice_regions } = self;
-
-        let mut first_constraints2 = FxIndexMap::default();
-        first_constraints2.reserve(first_constraints.len());
-
-        for (r1, start1) in first_constraints {
-            let r2 = map_fn(r1);
-            if let Some(&start2) = first_constraints2.get(&r2) {
-                append_list(&mut constraints, start1, start2);
-            }
-            first_constraints2.insert(r2, start1);
-        }
-
-        MemberConstraintSet { first_constraints: first_constraints2, constraints, choice_regions }
-    }
-}
-
-impl<'tcx, R> MemberConstraintSet<'tcx, R>
-where
-    R: Copy + Hash + Eq,
-{
-    pub(crate) fn all_indices(&self) -> impl Iterator<Item = NllMemberConstraintIndex> {
-        self.constraints.indices()
-    }
-
-    /// Iterate down the constraint indices associated with a given
-    /// peek-region. You can then use `choice_regions` and other
-    /// methods to access data.
-    pub(crate) fn indices(
-        &self,
-        member_region_vid: R,
-    ) -> impl Iterator<Item = NllMemberConstraintIndex> {
-        let mut next = self.first_constraints.get(&member_region_vid).cloned();
-        std::iter::from_fn(move || -> Option<NllMemberConstraintIndex> {
-            if let Some(current) = next {
-                next = self.constraints[current].next_constraint;
-                Some(current)
-            } else {
-                None
-            }
-        })
-    }
-
-    /// Returns the "choice regions" for a given member
-    /// constraint. This is the `R1..Rn` from a constraint like:
-    ///
-    /// ```text
-    /// R0 member of [R1..Rn]
-    /// ```
-    pub(crate) fn choice_regions(&self, pci: NllMemberConstraintIndex) -> &[ty::RegionVid] {
-        let MemberConstraint { start_index, end_index, .. } = &self.constraints[pci];
-        &self.choice_regions[*start_index..*end_index]
-    }
-}
-
-impl<'tcx, R> Index<NllMemberConstraintIndex> for MemberConstraintSet<'tcx, R>
-where
-    R: Copy + Eq,
-{
-    type Output = MemberConstraint<'tcx>;
-
-    fn index(&self, i: NllMemberConstraintIndex) -> &MemberConstraint<'tcx> {
-        &self.constraints[i]
-    }
-}
-
-/// Given a linked list starting at `source_list` and another linked
-/// list starting at `target_list`, modify `target_list` so that it is
-/// followed by `source_list`.
-///
-/// Before:
-///
-/// ```text
-/// target_list: A -> B -> C -> (None)
-/// source_list: D -> E -> F -> (None)
-/// ```
-///
-/// After:
-///
-/// ```text
-/// target_list: A -> B -> C -> D -> E -> F -> (None)
-/// ```
-fn append_list(
-    constraints: &mut IndexSlice<NllMemberConstraintIndex, MemberConstraint<'_>>,
-    target_list: NllMemberConstraintIndex,
-    source_list: NllMemberConstraintIndex,
-) {
-    let mut p = target_list;
-    loop {
-        let r = &mut constraints[p];
-        match r.next_constraint {
-            Some(q) => p = q,
-            None => {
-                r.next_constraint = Some(source_list);
-                return;
-            }
-        }
-    }
-}
diff --git a/compiler/rustc_borrowck/src/region_infer/mod.rs b/compiler/rustc_borrowck/src/region_infer/mod.rs
index c76c5c17431..3d95eb4663a 100644
--- a/compiler/rustc_borrowck/src/region_infer/mod.rs
+++ b/compiler/rustc_borrowck/src/region_infer/mod.rs
@@ -1,8 +1,6 @@
-use std::cell::OnceCell;
 use std::collections::VecDeque;
 use std::rc::Rc;
 
-use rustc_data_structures::binary_search_util;
 use rustc_data_structures::frozen::Frozen;
 use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_data_structures::graph::scc::{self, Sccs};
@@ -24,15 +22,13 @@ use rustc_span::hygiene::DesugaringKind;
 use rustc_span::{DUMMY_SP, Span};
 use tracing::{Level, debug, enabled, instrument, trace};
 
-use crate::constraints::graph::{self, NormalConstraintGraph, RegionGraph};
+use crate::constraints::graph::NormalConstraintGraph;
 use crate::constraints::{ConstraintSccIndex, OutlivesConstraint, OutlivesConstraintSet};
 use crate::dataflow::BorrowIndex;
 use crate::diagnostics::{RegionErrorKind, RegionErrors, UniverseInfo};
 use crate::handle_placeholders::{LoweredConstraints, RegionTracker};
-use crate::member_constraints::{MemberConstraintSet, NllMemberConstraintIndex};
 use crate::polonius::LiveLoans;
 use crate::polonius::legacy::PoloniusOutput;
-use crate::region_infer::reverse_sccs::ReverseSccGraph;
 use crate::region_infer::values::{LivenessValues, RegionElement, RegionValues, ToElementIndex};
 use crate::type_check::Locations;
 use crate::type_check::free_region_relations::UniversalRegionRelations;
@@ -120,20 +116,6 @@ pub struct RegionInferenceContext<'tcx> {
 
     scc_annotations: IndexVec<ConstraintSccIndex, RegionTracker>,
 
-    /// Reverse of the SCC constraint graph --  i.e., an edge `A -> B` exists if
-    /// `B: A`. This is used to compute the universal regions that are required
-    /// to outlive a given SCC.
-    rev_scc_graph: OnceCell<ReverseSccGraph>,
-
-    /// The "R0 member of [R1..Rn]" constraints, indexed by SCC.
-    member_constraints: Rc<MemberConstraintSet<'tcx, ConstraintSccIndex>>,
-
-    /// Records the member constraints that we applied to each scc.
-    /// This is useful for error reporting. Once constraint
-    /// propagation is done, this vector is sorted according to
-    /// `member_region_scc`.
-    member_constraints_applied: Vec<AppliedMemberConstraint>,
-
     /// Map universe indexes to information on why we created it.
     universe_causes: FxIndexMap<ty::UniverseIndex, UniverseInfo<'tcx>>,
 
@@ -150,32 +132,6 @@ pub struct RegionInferenceContext<'tcx> {
     universal_region_relations: Frozen<UniversalRegionRelations<'tcx>>,
 }
 
-/// Each time that `apply_member_constraint` is successful, it appends
-/// one of these structs to the `member_constraints_applied` field.
-/// This is used in error reporting to trace out what happened.
-///
-/// The way that `apply_member_constraint` works is that it effectively
-/// adds a new lower bound to the SCC it is analyzing: so you wind up
-/// with `'R: 'O` where `'R` is the pick-region and `'O` is the
-/// minimal viable option.
-#[derive(Debug)]
-pub(crate) struct AppliedMemberConstraint {
-    /// The SCC that was affected. (The "member region".)
-    ///
-    /// The vector if `AppliedMemberConstraint` elements is kept sorted
-    /// by this field.
-    pub(crate) member_region_scc: ConstraintSccIndex,
-
-    /// The "best option" that `apply_member_constraint` found -- this was
-    /// added as an "ad-hoc" lower-bound to `member_region_scc`.
-    pub(crate) min_choice: ty::RegionVid,
-
-    /// The "member constraint index" -- we can find out details about
-    /// the constraint from
-    /// `set.member_constraints[member_constraint_index]`.
-    pub(crate) member_constraint_index: NllMemberConstraintIndex,
-}
-
 #[derive(Debug)]
 pub(crate) struct RegionDefinition<'tcx> {
     /// What kind of variable is this -- a free region? existential
@@ -268,7 +224,6 @@ enum Trace<'a, 'tcx> {
     StartRegion,
     FromGraph(&'a OutlivesConstraint<'tcx>),
     FromStatic(RegionVid),
-    FromMember(RegionVid, RegionVid, Span),
     NotVisited,
 }
 
@@ -363,7 +318,6 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             liveness_constraints,
             universe_causes,
             placeholder_indices,
-            member_constraints,
         } = lowered_constraints;
 
         debug!("universal_regions: {:#?}", universal_region_relations.universal_regions);
@@ -385,9 +339,6 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             scc_values.merge_liveness(scc, region, &liveness_constraints);
         }
 
-        let member_constraints =
-            Rc::new(member_constraints.into_mapped(|r| constraint_sccs.scc(r)));
-
         let mut result = Self {
             definitions,
             liveness_constraints,
@@ -395,9 +346,6 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             constraint_graph,
             constraint_sccs,
             scc_annotations,
-            rev_scc_graph: OnceCell::new(),
-            member_constraints,
-            member_constraints_applied: Vec::new(),
             universe_causes,
             scc_values,
             type_tests,
@@ -550,19 +498,6 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         self.scc_values.placeholders_contained_in(scc)
     }
 
-    /// Once region solving has completed, this function will return the member constraints that
-    /// were applied to the value of a given SCC `scc`. See `AppliedMemberConstraint`.
-    pub(crate) fn applied_member_constraints(
-        &self,
-        scc: ConstraintSccIndex,
-    ) -> &[AppliedMemberConstraint] {
-        binary_search_util::binary_search_slice(
-            &self.member_constraints_applied,
-            |applied| applied.member_region_scc,
-            &scc,
-        )
-    }
-
     /// Performs region inference and report errors if we see any
     /// unsatisfiable constraints. If this is a closure, returns the
     /// region requirements to propagate to our creator, if any.
@@ -607,12 +542,6 @@ impl<'tcx> RegionInferenceContext<'tcx> {
 
         debug!(?errors_buffer);
 
-        if errors_buffer.is_empty() {
-            self.check_member_constraints(infcx, &mut errors_buffer);
-        }
-
-        debug!(?errors_buffer);
-
         let outlives_requirements = outlives_requirements.unwrap_or_default();
 
         if outlives_requirements.is_empty() {
@@ -642,146 +571,15 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         });
 
         // To propagate constraints, we walk the DAG induced by the
-        // SCC. For each SCC, we visit its successors and compute
+        // SCC. For each SCC `A`, we visit its successors and compute
         // their values, then we union all those values to get our
         // own.
-        for scc in self.constraint_sccs.all_sccs() {
-            self.compute_value_for_scc(scc);
-        }
-
-        // Sort the applied member constraints so we can binary search
-        // through them later.
-        self.member_constraints_applied.sort_by_key(|applied| applied.member_region_scc);
-    }
-
-    /// Computes the value of the SCC `scc_a`, which has not yet been
-    /// computed, by unioning the values of its successors.
-    /// Assumes that all successors have been computed already
-    /// (which is assured by iterating over SCCs in dependency order).
-    #[instrument(skip(self), level = "debug")]
-    fn compute_value_for_scc(&mut self, scc_a: ConstraintSccIndex) {
-        // Walk each SCC `B` such that `A: B`...
-        for &scc_b in self.constraint_sccs.successors(scc_a) {
-            debug!(?scc_b);
-            self.scc_values.add_region(scc_a, scc_b);
-        }
-
-        // Now take member constraints into account.
-        let member_constraints = Rc::clone(&self.member_constraints);
-        for m_c_i in member_constraints.indices(scc_a) {
-            self.apply_member_constraint(scc_a, m_c_i, member_constraints.choice_regions(m_c_i));
-        }
-
-        debug!(value = ?self.scc_values.region_value_str(scc_a));
-    }
-
-    /// Invoked for each `R0 member of [R1..Rn]` constraint.
-    ///
-    /// `scc` is the SCC containing R0, and `choice_regions` are the
-    /// `R1..Rn` regions -- they are always known to be universal
-    /// regions (and if that's not true, we just don't attempt to
-    /// enforce the constraint).
-    ///
-    /// The current value of `scc` at the time the method is invoked
-    /// is considered a *lower bound*. If possible, we will modify
-    /// the constraint to set it equal to one of the option regions.
-    /// If we make any changes, returns true, else false.
-    ///
-    /// This function only adds the member constraints to the region graph,
-    /// it does not check them. They are later checked in
-    /// `check_member_constraints` after the region graph has been computed.
-    #[instrument(skip(self, member_constraint_index), level = "debug")]
-    fn apply_member_constraint(
-        &mut self,
-        scc: ConstraintSccIndex,
-        member_constraint_index: NllMemberConstraintIndex,
-        choice_regions: &[ty::RegionVid],
-    ) {
-        // Create a mutable vector of the options. We'll try to winnow
-        // them down.
-        let mut choice_regions: Vec<ty::RegionVid> = choice_regions.to_vec();
-
-        // Convert to the SCC representative: sometimes we have inference
-        // variables in the member constraint that wind up equated with
-        // universal regions. The scc representative is the minimal numbered
-        // one from the corresponding scc so it will be the universal region
-        // if one exists.
-        for c_r in &mut choice_regions {
-            let scc = self.constraint_sccs.scc(*c_r);
-            *c_r = self.scc_representative(scc);
-        }
-
-        // If the member region lives in a higher universe, we currently choose
-        // the most conservative option by leaving it unchanged.
-        if !self.max_placeholder_universe_reached(scc).is_root() {
-            return;
-        }
-
-        // The existing value for `scc` is a lower-bound. This will
-        // consist of some set `{P} + {LB}` of points `{P}` and
-        // lower-bound free regions `{LB}`. As each choice region `O`
-        // is a free region, it will outlive the points. But we can
-        // only consider the option `O` if `O: LB`.
-        choice_regions.retain(|&o_r| {
-            self.scc_values
-                .universal_regions_outlived_by(scc)
-                .all(|lb| self.universal_region_relations.outlives(o_r, lb))
-        });
-        debug!(?choice_regions, "after lb");
-
-        // Now find all the *upper bounds* -- that is, each UB is a
-        // free region that must outlive the member region `R0` (`UB:
-        // R0`). Therefore, we need only keep an option `O` if `UB: O`
-        // for all UB.
-        let universal_region_relations = &self.universal_region_relations;
-        for ub in self.reverse_scc_graph().upper_bounds(scc) {
-            debug!(?ub);
-            choice_regions.retain(|&o_r| universal_region_relations.outlives(ub, o_r));
-        }
-        debug!(?choice_regions, "after ub");
-
-        // At this point we can pick any member of `choice_regions` and would like to choose
-        // it to be a small as possible. To avoid potential non-determinism we will pick the
-        // smallest such choice.
-        //
-        // Because universal regions are only partially ordered (i.e, not every two regions are
-        // comparable), we will ignore any region that doesn't compare to all others when picking
-        // the minimum choice.
-        //
-        // For example, consider `choice_regions = ['static, 'a, 'b, 'c, 'd, 'e]`, where
-        // `'static: 'a, 'static: 'b, 'a: 'c, 'b: 'c, 'c: 'd, 'c: 'e`.
-        // `['d, 'e]` are ignored because they do not compare - the same goes for `['a, 'b]`.
-        let totally_ordered_subset = choice_regions.iter().copied().filter(|&r1| {
-            choice_regions.iter().all(|&r2| {
-                self.universal_region_relations.outlives(r1, r2)
-                    || self.universal_region_relations.outlives(r2, r1)
-            })
-        });
-        // Now we're left with `['static, 'c]`. Pick `'c` as the minimum!
-        let Some(min_choice) = totally_ordered_subset.reduce(|r1, r2| {
-            let r1_outlives_r2 = self.universal_region_relations.outlives(r1, r2);
-            let r2_outlives_r1 = self.universal_region_relations.outlives(r2, r1);
-            match (r1_outlives_r2, r2_outlives_r1) {
-                (true, true) => r1.min(r2),
-                (true, false) => r2,
-                (false, true) => r1,
-                (false, false) => bug!("incomparable regions in total order"),
+        for scc_a in self.constraint_sccs.all_sccs() {
+            // Walk each SCC `B` such that `A: B`...
+            for &scc_b in self.constraint_sccs.successors(scc_a) {
+                debug!(?scc_b);
+                self.scc_values.add_region(scc_a, scc_b);
             }
-        }) else {
-            debug!("no unique minimum choice");
-            return;
-        };
-
-        // As we require `'scc: 'min_choice`, we have definitely already computed
-        // its `scc_values` at this point.
-        let min_choice_scc = self.constraint_sccs.scc(min_choice);
-        debug!(?min_choice, ?min_choice_scc);
-        if self.scc_values.add_region(scc, min_choice_scc) {
-            self.member_constraints_applied.push(AppliedMemberConstraint {
-                member_region_scc: scc,
-                min_choice,
-                member_constraint_index,
-            });
         }
     }
 
@@ -1376,13 +1174,6 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         self.scc_annotations[scc].max_nameable_universe()
     }
 
-    pub(crate) fn max_placeholder_universe_reached(
-        &self,
-        scc: ConstraintSccIndex,
-    ) -> UniverseIndex {
-        self.scc_annotations[scc].max_placeholder_universe_reached()
-    }
-
     /// Checks the final value for the free region `fr` to see if it
     /// grew too large. In particular, examine what `end(X)` points
     /// wound up in `fr`'s final value; for each `end(X)` where `X !=
@@ -1551,43 +1342,6 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         }
     }
 
-    #[instrument(level = "debug", skip(self, infcx, errors_buffer))]
-    fn check_member_constraints(
-        &self,
-        infcx: &InferCtxt<'tcx>,
-        errors_buffer: &mut RegionErrors<'tcx>,
-    ) {
-        let member_constraints = Rc::clone(&self.member_constraints);
-        for m_c_i in member_constraints.all_indices() {
-            debug!(?m_c_i);
-            let m_c = &member_constraints[m_c_i];
-            let member_region_vid = m_c.member_region_vid;
-            debug!(
-                ?member_region_vid,
-                value = ?self.region_value_str(member_region_vid),
-            );
-            let choice_regions = member_constraints.choice_regions(m_c_i);
-            debug!(?choice_regions);
-
-            // Did the member region wind up equal to any of the option regions?
-            if let Some(o) =
-                choice_regions.iter().find(|&&o_r| self.eval_equal(o_r, m_c.member_region_vid))
-            {
-                debug!("evaluated as equal to {:?}", o);
-                continue;
-            }
-
-            // If not, report an error.
-            let member_region = ty::Region::new_var(infcx.tcx, member_region_vid);
-            errors_buffer.push(RegionErrorKind::UnexpectedHiddenRegion {
-                span: m_c.definition_span,
-                hidden_ty: m_c.hidden_ty,
-                key: m_c.key,
-                member_region,
-            });
-        }
-    }
-
     /// We have a constraint `fr1: fr2` that is not satisfied, where
     /// `fr2` represents some universal region. Here, `r` is some
     /// region where we know that `fr1: r` and this function has the
@@ -1651,19 +1405,40 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     }
 
     /// Walks the graph of constraints (where `'a: 'b` is considered
-    /// an edge `'a -> 'b`) to find all paths from `from_region` to
-    /// `to_region`. The paths are accumulated into the vector
-    /// `results`. The paths are stored as a series of
-    /// `ConstraintIndex` values -- in other words, a list of *edges*.
+    /// an edge `'a -> 'b`) to find a path from `from_region` to
+    /// `to_region`.
     ///
     /// Returns: a series of constraints as well as the region `R`
     /// that passed the target test.
     #[instrument(skip(self, target_test), ret)]
-    pub(crate) fn find_constraint_paths_between_regions(
+    pub(crate) fn find_constraint_path_between_regions(
         &self,
         from_region: RegionVid,
         target_test: impl Fn(RegionVid) -> bool,
     ) -> Option<(Vec<OutlivesConstraint<'tcx>>, RegionVid)> {
+        self.find_constraint_path_between_regions_inner(true, from_region, &target_test).or_else(
+            || self.find_constraint_path_between_regions_inner(false, from_region, &target_test),
+        )
+    }
+
+    /// The constraints we get from equating the hidden type of each use of an opaque
+    /// with its final concrete type may end up getting preferred over other, potentially
+    /// longer constraint paths.
+    ///
+    /// Given that we compute the final concrete type by relying on this existing constraint
+    /// path, this can easily end up hiding the actual reason for why we require these regions
+    /// to be equal.
+    ///
+    /// To handle this, we first look at the path while ignoring these constraints and then
+    /// retry while considering them. This is not perfect, as the `from_region` may have already
+    /// been partially related to its argument region, so while we rely on a member constraint
+    /// to get a complete path, the most relevant step of that path already existed before then.
+    fn find_constraint_path_between_regions_inner(
+        &self,
+        ignore_opaque_type_constraints: bool,
+        from_region: RegionVid,
+        target_test: impl Fn(RegionVid) -> bool,
+    ) -> Option<(Vec<OutlivesConstraint<'tcx>>, RegionVid)> {
         let mut context = IndexVec::from_elem(Trace::NotVisited, &self.definitions);
         context[from_region] = Trace::StartRegion;
 
@@ -1677,7 +1452,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
 
         while let Some(r) = deque.pop_front() {
             debug!(
-                "find_constraint_paths_between_regions: from_region={:?} r={:?} value={}",
+                "find_constraint_path_between_regions: from_region={:?} r={:?} value={}",
                 from_region,
                 r,
                 self.region_value_str(r),
@@ -1711,20 +1486,6 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                             result.push(c);
                         }
 
-                        Trace::FromMember(sup, sub, span) => {
-                            let c = OutlivesConstraint {
-                                sup,
-                                sub,
-                                locations: Locations::All(span),
-                                span,
-                                category: ConstraintCategory::OpaqueType,
-                                variance_info: ty::VarianceDiagInfo::default(),
-                                from_closure: false,
-                            };
-                            p = c.sup;
-                            result.push(c);
-                        }
-
                         Trace::StartRegion => {
                             result.reverse();
                             return Some((result, r));
@@ -1763,23 +1524,21 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                 let edges = self.constraint_graph.outgoing_edges_from_graph(r, &self.constraints);
                 // This loop can be hot.
                 for constraint in edges {
-                    if matches!(constraint.category, ConstraintCategory::IllegalUniverse) {
-                        debug!("Ignoring illegal universe constraint: {constraint:?}");
-                        continue;
+                    match constraint.category {
+                        ConstraintCategory::IllegalUniverse => {
+                            debug!("Ignoring illegal universe constraint: {constraint:?}");
+                            continue;
+                        }
+                        ConstraintCategory::OpaqueType if ignore_opaque_type_constraints => {
+                            debug!("Ignoring member constraint: {constraint:?}");
+                            continue;
+                        }
+                        _ => {}
                     }
                     debug_assert_eq!(constraint.sup, r);
                     handle_trace(constraint.sub, Trace::FromGraph(constraint));
                 }
             }
-
-            // Member constraints can also give rise to `'r: 'x` edges that
-            // were not part of the graph initially, so watch out for those.
-            // (But they are extremely rare; this loop is very cold.)
-            for constraint in self.applied_member_constraints(self.constraint_sccs.scc(r)) {
-                let sub = constraint.min_choice;
-                let p_c = &self.member_constraints[constraint.member_constraint_index];
-                handle_trace(sub, Trace::FromMember(r, sub, p_c.definition_span));
-            }
         }
 
         None
@@ -1790,7 +1549,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     pub(crate) fn find_sub_region_live_at(&self, fr1: RegionVid, location: Location) -> RegionVid {
         trace!(scc = ?self.constraint_sccs.scc(fr1));
         trace!(universe = ?self.max_nameable_universe(self.constraint_sccs.scc(fr1)));
-        self.find_constraint_paths_between_regions(fr1, |r| {
+        self.find_constraint_path_between_regions(fr1, |r| {
             // First look for some `r` such that `fr1: r` and `r` is live at `location`
             trace!(?r, liveness_constraints=?self.liveness_constraints.pretty_print_live_points(r));
             self.liveness_constraints.is_live_at(r, location)
@@ -1800,9 +1559,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             // `fr1: r` and `r` is a placeholder from some universe
             // `fr1` cannot name. This would force `fr1` to be
             // `'static`.
-            self.find_constraint_paths_between_regions(fr1, |r| {
-                self.cannot_name_placeholder(fr1, r)
-            })
+            self.find_constraint_path_between_regions(fr1, |r| self.cannot_name_placeholder(fr1, r))
         })
         .or_else(|| {
             // If we fail to find THAT, it may be that `fr1` is a
@@ -1815,9 +1572,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             // must be able to name the universe of R2, because R2 will
             // be at least `'empty(Universe(R2))`, and `R1` must be at
             // larger than that.
-            self.find_constraint_paths_between_regions(fr1, |r| {
-                self.cannot_name_placeholder(r, fr1)
-            })
+            self.find_constraint_path_between_regions(fr1, |r| self.cannot_name_placeholder(r, fr1))
         })
         .map(|(_path, r)| r)
         .unwrap()
@@ -1873,9 +1628,9 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     ) -> (BlameConstraint<'tcx>, Vec<OutlivesConstraint<'tcx>>) {
         // Find all paths
         let (path, target_region) = self
-            .find_constraint_paths_between_regions(from_region, target_test)
+            .find_constraint_path_between_regions(from_region, target_test)
             .or_else(|| {
-                self.find_constraint_paths_between_regions(from_region, |r| {
+                self.find_constraint_path_between_regions(from_region, |r| {
                     self.cannot_name_placeholder(from_region, r)
                 })
             })
@@ -2111,11 +1866,6 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         &self.constraint_sccs
     }
 
-    /// Access to the region graph, built from the outlives constraints.
-    pub(crate) fn region_graph(&self) -> RegionGraph<'_, 'tcx, graph::Normal> {
-        self.constraint_graph.region_graph(&self.constraints, self.universal_regions().fr_static)
-    }
-
     /// Returns the representative `RegionVid` for a given SCC.
     /// See `RegionTracker` for how a region variable ID is chosen.
     ///
diff --git a/compiler/rustc_borrowck/src/region_infer/opaque_types.rs b/compiler/rustc_borrowck/src/region_infer/opaque_types.rs
deleted file mode 100644
index 23c4554aa15..00000000000
--- a/compiler/rustc_borrowck/src/region_infer/opaque_types.rs
+++ /dev/null
@@ -1,299 +0,0 @@
-use rustc_data_structures::fx::FxIndexMap;
-use rustc_infer::infer::{InferCtxt, NllRegionVariableOrigin};
-use rustc_macros::extension;
-use rustc_middle::ty::{
-    self, DefiningScopeKind, OpaqueHiddenType, OpaqueTypeKey, Ty, TyCtxt, TypeFoldable,
-    TypeVisitableExt, fold_regions,
-};
-use rustc_span::Span;
-use rustc_trait_selection::opaque_types::{
-    InvalidOpaqueTypeArgs, check_opaque_type_parameter_valid,
-};
-use tracing::{debug, instrument};
-
-use super::RegionInferenceContext;
-use crate::BorrowCheckRootCtxt;
-use crate::session_diagnostics::LifetimeMismatchOpaqueParam;
-use crate::universal_regions::RegionClassification;
-
-pub(crate) enum DeferredOpaqueTypeError<'tcx> {
-    InvalidOpaqueTypeArgs(InvalidOpaqueTypeArgs<'tcx>),
-    LifetimeMismatchOpaqueParam(LifetimeMismatchOpaqueParam<'tcx>),
-}
-
-impl<'tcx> RegionInferenceContext<'tcx> {
-    /// Resolve any opaque types that were encountered while borrow checking
-    /// this item. This is then used to get the type in the `type_of` query.
-    ///
-    /// For example consider `fn f<'a>(x: &'a i32) -> impl Sized + 'a { x }`.
-    /// This is lowered to give HIR something like
-    ///
-    /// type f<'a>::_Return<'_x> = impl Sized + '_x;
-    /// fn f<'a>(x: &'a i32) -> f<'a>::_Return<'a> { x }
-    ///
-    /// When checking the return type record the type from the return and the
-    /// type used in the return value. In this case they might be `_Return<'1>`
-    /// and `&'2 i32` respectively.
-    ///
-    /// Once we to this method, we have completed region inference and want to
-    /// call `infer_opaque_definition_from_instantiation` to get the inferred
-    /// type of `_Return<'_x>`. `infer_opaque_definition_from_instantiation`
-    /// compares lifetimes directly, so we need to map the inference variables
-    /// back to concrete lifetimes: `'static`, `ReEarlyParam` or `ReLateParam`.
-    ///
-    /// First we map the regions in the generic parameters `_Return<'1>` to
-    /// their `external_name` giving `_Return<'a>`. This step is a bit involved.
-    /// See the [rustc-dev-guide chapter] for more info.
-    ///
-    /// Then we map all the lifetimes in the concrete type to an equal
-    /// universal region that occurs in the opaque type's args, in this case
-    /// this would result in `&'a i32`. We only consider regions in the args
-    /// in case there is an equal region that does not. For example, this should
-    /// be allowed:
-    /// `fn f<'a: 'b, 'b: 'a>(x: *mut &'b i32) -> impl Sized + 'a { x }`
-    ///
-    /// This will then allow `infer_opaque_definition_from_instantiation` to
-    /// determine that `_Return<'_x> = &'_x i32`.
-    ///
-    /// There's a slight complication around closures. Given
-    /// `fn f<'a: 'a>() { || {} }` the closure's type is something like
-    /// `f::<'a>::{{closure}}`. The region parameter from f is essentially
-    /// ignored by type checking so ends up being inferred to an empty region.
-    /// Calling `universal_upper_bound` for such a region gives `fr_fn_body`,
-    /// which has no `external_name` in which case we use `'{erased}` as the
-    /// region to pass to `infer_opaque_definition_from_instantiation`.
-    ///
-    /// [rustc-dev-guide chapter]:
-    /// https://rustc-dev-guide.rust-lang.org/opaque-types-region-infer-restrictions.html
-    #[instrument(level = "debug", skip(self, root_cx, infcx))]
-    pub(crate) fn infer_opaque_types(
-        &self,
-        root_cx: &mut BorrowCheckRootCtxt<'tcx>,
-        infcx: &InferCtxt<'tcx>,
-        opaque_ty_decls: FxIndexMap<OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>>,
-    ) -> Vec<DeferredOpaqueTypeError<'tcx>> {
-        let mut errors = Vec::new();
-        let mut decls_modulo_regions: FxIndexMap<OpaqueTypeKey<'tcx>, (OpaqueTypeKey<'tcx>, Span)> =
-            FxIndexMap::default();
-
-        for (opaque_type_key, concrete_type) in opaque_ty_decls {
-            debug!(?opaque_type_key, ?concrete_type);
-
-            let mut arg_regions: Vec<(ty::RegionVid, ty::Region<'_>)> =
-                vec![(self.universal_regions().fr_static, infcx.tcx.lifetimes.re_static)];
-
-            let opaque_type_key =
-                opaque_type_key.fold_captured_lifetime_args(infcx.tcx, |region| {
-                    // Use the SCC representative instead of directly using `region`.
-                    // See [rustc-dev-guide chapter] § "Strict lifetime equality".
-                    let scc = self.constraint_sccs.scc(region.as_var());
-                    let vid = self.scc_representative(scc);
-                    let named = match self.definitions[vid].origin {
-                        // Iterate over all universal regions in a consistent order and find the
-                        // *first* equal region. This makes sure that equal lifetimes will have
-                        // the same name and simplifies subsequent handling.
-                        // See [rustc-dev-guide chapter] § "Semantic lifetime equality".
-                        NllRegionVariableOrigin::FreeRegion => self
-                            .universal_regions()
-                            .universal_regions_iter()
-                            .filter(|&ur| {
-                                // See [rustc-dev-guide chapter] § "Closure restrictions".
-                                !matches!(
-                                    self.universal_regions().region_classification(ur),
-                                    Some(RegionClassification::External)
-                                )
-                            })
-                            .find(|&ur| self.universal_region_relations.equal(vid, ur))
-                            .map(|ur| self.definitions[ur].external_name.unwrap()),
-                        NllRegionVariableOrigin::Placeholder(placeholder) => {
-                            Some(ty::Region::new_placeholder(infcx.tcx, placeholder))
-                        }
-                        NllRegionVariableOrigin::Existential { .. } => None,
-                    }
-                    .unwrap_or_else(|| {
-                        ty::Region::new_error_with_message(
-                            infcx.tcx,
-                            concrete_type.span,
-                            "opaque type with non-universal region args",
-                        )
-                    });
-
-                    arg_regions.push((vid, named));
-                    named
-                });
-            debug!(?opaque_type_key, ?arg_regions);
-
-            let concrete_type = fold_regions(infcx.tcx, concrete_type, |region, _| {
-                arg_regions
-                    .iter()
-                    .find(|&&(arg_vid, _)| self.eval_equal(region.as_var(), arg_vid))
-                    .map(|&(_, arg_named)| arg_named)
-                    .unwrap_or(infcx.tcx.lifetimes.re_erased)
-            });
-            debug!(?concrete_type);
-
-            let ty = match infcx
-                .infer_opaque_definition_from_instantiation(opaque_type_key, concrete_type)
-            {
-                Ok(ty) => ty,
-                Err(err) => {
-                    errors.push(DeferredOpaqueTypeError::InvalidOpaqueTypeArgs(err));
-                    continue;
-                }
-            };
-
-            // Sometimes, when the hidden type is an inference variable, it can happen that
-            // the hidden type becomes the opaque type itself. In this case, this was an opaque
-            // usage of the opaque type and we can ignore it. This check is mirrored in typeck's
-            // writeback.
-            if !infcx.next_trait_solver() {
-                if let ty::Alias(ty::Opaque, alias_ty) = ty.kind()
-                    && alias_ty.def_id == opaque_type_key.def_id.to_def_id()
-                    && alias_ty.args == opaque_type_key.args
-                {
-                    continue;
-                }
-            }
-
-            root_cx.add_concrete_opaque_type(
-                opaque_type_key.def_id,
-                OpaqueHiddenType { span: concrete_type.span, ty },
-            );
-
-            // Check that all opaque types have the same region parameters if they have the same
-            // non-region parameters. This is necessary because within the new solver we perform
-            // various query operations modulo regions, and thus could unsoundly select some impls
-            // that don't hold.
-            if let Some((prev_decl_key, prev_span)) = decls_modulo_regions.insert(
-                infcx.tcx.erase_regions(opaque_type_key),
-                (opaque_type_key, concrete_type.span),
-            ) && let Some((arg1, arg2)) = std::iter::zip(
-                prev_decl_key.iter_captured_args(infcx.tcx).map(|(_, arg)| arg),
-                opaque_type_key.iter_captured_args(infcx.tcx).map(|(_, arg)| arg),
-            )
-            .find(|(arg1, arg2)| arg1 != arg2)
-            {
-                errors.push(DeferredOpaqueTypeError::LifetimeMismatchOpaqueParam(
-                    LifetimeMismatchOpaqueParam {
-                        arg: arg1,
-                        prev: arg2,
-                        span: prev_span,
-                        prev_span: concrete_type.span,
-                    },
-                ));
-            }
-        }
-
-        errors
-    }
-
-    /// Map the regions in the type to named regions. This is similar to what
-    /// `infer_opaque_types` does, but can infer any universal region, not only
-    /// ones from the args for the opaque type. It also doesn't double check
-    /// that the regions produced are in fact equal to the named region they are
-    /// replaced with. This is fine because this function is only to improve the
-    /// region names in error messages.
-    ///
-    /// This differs from `MirBorrowckCtxt::name_regions` since it is particularly
-    /// lax with mapping region vids that are *shorter* than a universal region to
-    /// that universal region. This is useful for member region constraints since
-    /// we want to suggest a universal region name to capture even if it's technically
-    /// not equal to the error region.
-    pub(crate) fn name_regions_for_member_constraint<T>(&self, tcx: TyCtxt<'tcx>, ty: T) -> T
-    where
-        T: TypeFoldable<TyCtxt<'tcx>>,
-    {
-        fold_regions(tcx, ty, |region, _| match region.kind() {
-            ty::ReVar(vid) => {
-                let scc = self.constraint_sccs.scc(vid);
-
-                // Special handling of higher-ranked regions.
-                if !self.max_nameable_universe(scc).is_root() {
-                    match self.scc_values.placeholders_contained_in(scc).enumerate().last() {
-                        // If the region contains a single placeholder then they're equal.
-                        Some((0, placeholder)) => {
-                            return ty::Region::new_placeholder(tcx, placeholder);
-                        }
-
-                        // Fallback: this will produce a cryptic error message.
-                        _ => return region,
-                    }
-                }
-
-                // Find something that we can name
-                let upper_bound = self.approx_universal_upper_bound(vid);
-                if let Some(universal_region) = self.definitions[upper_bound].external_name {
-                    return universal_region;
-                }
-
-                // Nothing exact found, so we pick a named upper bound, if there's only one.
-                // If there's >1 universal region, then we probably are dealing w/ an intersection
-                // region which cannot be mapped back to a universal.
-                // FIXME: We could probably compute the LUB if there is one.
-                let scc = self.constraint_sccs.scc(vid);
-                let upper_bounds: Vec<_> = self
-                    .reverse_scc_graph()
-                    .upper_bounds(scc)
-                    .filter_map(|vid| self.definitions[vid].external_name)
-                    .filter(|r| !r.is_static())
-                    .collect();
-                match &upper_bounds[..] {
-                    [universal_region] => *universal_region,
-                    _ => region,
-                }
-            }
-            _ => region,
-        })
-    }
-}
-
-#[extension(pub trait InferCtxtExt<'tcx>)]
-impl<'tcx> InferCtxt<'tcx> {
-    /// Given the fully resolved, instantiated type for an opaque
-    /// type, i.e., the value of an inference variable like C1 or C2
-    /// (*), computes the "definition type" for an opaque type
-    /// definition -- that is, the inferred value of `Foo1<'x>` or
-    /// `Foo2<'x>` that we would conceptually use in its definition:
-    /// ```ignore (illustrative)
-    /// type Foo1<'x> = impl Bar<'x> = AAA;  // <-- this type AAA
-    /// type Foo2<'x> = impl Bar<'x> = BBB;  // <-- or this type BBB
-    /// fn foo<'a, 'b>(..) -> (Foo1<'a>, Foo2<'b>) { .. }
-    /// ```
-    /// Note that these values are defined in terms of a distinct set of
-    /// generic parameters (`'x` instead of `'a`) from C1 or C2. The main
-    /// purpose of this function is to do that translation.
-    ///
-    /// (*) C1 and C2 were introduced in the comments on
-    /// `register_member_constraints`. Read that comment for more context.
-    ///
-    /// # Parameters
-    ///
-    /// - `def_id`, the `impl Trait` type
-    /// - `args`, the args used to instantiate this opaque type
-    /// - `instantiated_ty`, the inferred type C1 -- fully resolved, lifted version of
-    ///   `opaque_defn.concrete_ty`
-    #[instrument(level = "debug", skip(self))]
-    fn infer_opaque_definition_from_instantiation(
-        &self,
-        opaque_type_key: OpaqueTypeKey<'tcx>,
-        instantiated_ty: OpaqueHiddenType<'tcx>,
-    ) -> Result<Ty<'tcx>, InvalidOpaqueTypeArgs<'tcx>> {
-        check_opaque_type_parameter_valid(
-            self,
-            opaque_type_key,
-            instantiated_ty.span,
-            DefiningScopeKind::MirBorrowck,
-        )?;
-
-        let definition_ty = instantiated_ty
-            .remap_generic_params_to_declaration_params(
-                opaque_type_key,
-                self.tcx,
-                DefiningScopeKind::MirBorrowck,
-            )
-            .ty;
-
-        definition_ty.error_reported()?;
-        Ok(definition_ty)
-    }
-}
diff --git a/compiler/rustc_borrowck/src/region_infer/opaque_types/member_constraints.rs b/compiler/rustc_borrowck/src/region_infer/opaque_types/member_constraints.rs
new file mode 100644
index 00000000000..667fc440ac0
--- /dev/null
+++ b/compiler/rustc_borrowck/src/region_infer/opaque_types/member_constraints.rs
@@ -0,0 +1,194 @@
+use rustc_data_structures::fx::FxHashMap;
+use rustc_hir::def_id::DefId;
+use rustc_middle::bug;
+use rustc_middle::ty::{
+    self, GenericArgsRef, Region, RegionVid, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable,
+    TypeVisitor,
+};
+use tracing::{debug, instrument};
+
+use super::DefiningUse;
+use super::region_ctxt::RegionCtxt;
+use crate::constraints::ConstraintSccIndex;
+
+pub(super) fn apply_member_constraints<'tcx>(
+    rcx: &mut RegionCtxt<'_, 'tcx>,
+    defining_uses: &[DefiningUse<'tcx>],
+) {
+    // Start by collecting the member constraints of all defining uses.
+    //
+    // Applying member constraints can influence other member constraints,
+    // so we first collect and then apply them.
+    let mut member_constraints = Default::default();
+    for defining_use in defining_uses {
+        let mut visitor = CollectMemberConstraintsVisitor {
+            rcx,
+            defining_use,
+            member_constraints: &mut member_constraints,
+        };
+        defining_use.hidden_type.ty.visit_with(&mut visitor);
+    }
+
+    // Now walk over the region graph, visiting the smallest regions first and then all
+    // regions which have to outlive that one.
+    //
+    // Whenever we encounter a member region, we mutate the value of this SCC. This is
+    // as if we'd introduce new outlives constraints. However, we discard these region
+    // values after we've inferred the hidden types of opaques and apply the region
+    // constraints by simply equating the actual hidden type with the inferred one.
+    debug!(?member_constraints);
+    for scc_a in rcx.constraint_sccs.all_sccs() {
+        debug!(?scc_a);
+        // Start by  adding the region values required by outlives constraints. This
+        // matches how we compute the final region values in `fn compute_regions`.
+        //
+        // We need to do this here to get a lower bound when applying member constraints.
+        // This propagates the region values added by previous member constraints.
+        for &scc_b in rcx.constraint_sccs.successors(scc_a) {
+            debug!(?scc_b);
+            rcx.scc_values.add_region(scc_a, scc_b);
+        }
+
+        for defining_use in member_constraints.get(&scc_a).into_iter().flatten() {
+            apply_member_constraint(rcx, scc_a, &defining_use.arg_regions);
+        }
+    }
+}
+
+#[instrument(level = "debug", skip(rcx))]
+fn apply_member_constraint<'tcx>(
+    rcx: &mut RegionCtxt<'_, 'tcx>,
+    member: ConstraintSccIndex,
+    arg_regions: &[RegionVid],
+) {
+    // If the member region lives in a higher universe, we currently choose
+    // the most conservative option by leaving it unchanged.
+    if !rcx.max_placeholder_universe_reached(member).is_root() {
+        return;
+    }
+
+    // The existing value of `'member` is a lower-bound. If its is already larger than
+    // some universal region, we cannot equate it with that region. Said differently, we
+    // ignore choice regions which are smaller than this member region.
+    let mut choice_regions = arg_regions
+        .iter()
+        .copied()
+        .map(|r| rcx.representative(r).rvid())
+        .filter(|&choice_region| {
+            rcx.scc_values.universal_regions_outlived_by(member).all(|lower_bound| {
+                rcx.universal_region_relations.outlives(choice_region, lower_bound)
+            })
+        })
+        .collect::<Vec<_>>();
+    debug!(?choice_regions, "after enforcing lower-bound");
+
+    // Now find all the *upper bounds* -- that is, each UB is a
+    // free region that must outlive the member region `R0` (`UB:
+    // R0`). Therefore, we need only keep an option `O` if `UB: O`
+    // for all UB.
+    //
+    // If we have a requirement `'upper_bound: 'member`, equating `'member`
+    // with some region `'choice` means we now also require `'upper_bound: 'choice`.
+    // Avoid choice regions for which this does not hold.
+    for ub in rcx.rev_scc_graph.upper_bounds(member) {
+        choice_regions
+            .retain(|&choice_region| rcx.universal_region_relations.outlives(ub, choice_region));
+    }
+    debug!(?choice_regions, "after enforcing upper-bound");
+
+    // At this point we can pick any member of `choice_regions` and would like to choose
+    // it to be a small as possible. To avoid potential non-determinism we will pick the
+    // smallest such choice.
+    //
+    // Because universal regions are only partially ordered (i.e, not every two regions are
+    // comparable), we will ignore any region that doesn't compare to all others when picking
+    // the minimum choice.
+    //
+    // For example, consider `choice_regions = ['static, 'a, 'b, 'c, 'd, 'e]`, where
+    // `'static: 'a, 'static: 'b, 'a: 'c, 'b: 'c, 'c: 'd, 'c: 'e`.
+    // `['d, 'e]` are ignored because they do not compare - the same goes for `['a, 'b]`.
+    let totally_ordered_subset = choice_regions.iter().copied().filter(|&r1| {
+        choice_regions.iter().all(|&r2| {
+            rcx.universal_region_relations.outlives(r1, r2)
+                || rcx.universal_region_relations.outlives(r2, r1)
+        })
+    });
+    // Now we're left with `['static, 'c]`. Pick `'c` as the minimum!
+    let Some(min_choice) = totally_ordered_subset.reduce(|r1, r2| {
+        let r1_outlives_r2 = rcx.universal_region_relations.outlives(r1, r2);
+        let r2_outlives_r1 = rcx.universal_region_relations.outlives(r2, r1);
+        match (r1_outlives_r2, r2_outlives_r1) {
+            (true, true) => r1.min(r2),
+            (true, false) => r2,
+            (false, true) => r1,
+            (false, false) => bug!("incomparable regions in total order"),
+        }
+    }) else {
+        debug!("no unique minimum choice");
+        return;
+    };
+
+    debug!(?min_choice);
+    // Lift the member region to be at least as large as this `min_choice` by directly
+    // mutating the `scc_values` as we compute it. This acts as if we've added a
+    // `'member: 'min_choice` while not recomputing sccs. This means different sccs
+    // may now actually be equal.
+    let min_choice_scc = rcx.constraint_sccs.scc(min_choice);
+    rcx.scc_values.add_region(member, min_choice_scc);
+}
+
+struct CollectMemberConstraintsVisitor<'a, 'b, 'tcx> {
+    rcx: &'a RegionCtxt<'a, 'tcx>,
+    defining_use: &'b DefiningUse<'tcx>,
+    member_constraints: &'a mut FxHashMap<ConstraintSccIndex, Vec<&'b DefiningUse<'tcx>>>,
+}
+impl<'tcx> CollectMemberConstraintsVisitor<'_, '_, 'tcx> {
+    fn cx(&self) -> TyCtxt<'tcx> {
+        self.rcx.infcx.tcx
+    }
+    fn visit_closure_args(&mut self, def_id: DefId, args: GenericArgsRef<'tcx>) {
+        let generics = self.cx().generics_of(def_id);
+        for arg in args.iter().skip(generics.parent_count) {
+            arg.visit_with(self);
+        }
+    }
+}
+impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for CollectMemberConstraintsVisitor<'_, '_, 'tcx> {
+    fn visit_region(&mut self, r: Region<'tcx>) {
+        match r.kind() {
+            ty::ReBound(..) => return,
+            ty::ReVar(vid) => {
+                let scc = self.rcx.constraint_sccs.scc(vid);
+                self.member_constraints.entry(scc).or_default().push(self.defining_use);
+            }
+            _ => unreachable!(),
+        }
+    }
+
+    fn visit_ty(&mut self, ty: Ty<'tcx>) {
+        if !ty.flags().intersects(ty::TypeFlags::HAS_FREE_REGIONS) {
+            return;
+        }
+
+        match *ty.kind() {
+            ty::Closure(def_id, args)
+            | ty::CoroutineClosure(def_id, args)
+            | ty::Coroutine(def_id, args) => self.visit_closure_args(def_id, args),
+
+            ty::Alias(kind, ty::AliasTy { def_id, args, .. })
+                if let Some(variances) = self.cx().opt_alias_variances(kind, def_id) =>
+            {
+                // Skip lifetime parameters that are not captured, since they do
+                // not need member constraints registered for them; we'll erase
+                // them (and hopefully in the future replace them with placeholders).
+                for (&v, arg) in std::iter::zip(variances, args.iter()) {
+                    if v != ty::Bivariant {
+                        arg.visit_with(self)
+                    }
+                }
+            }
+
+            _ => ty.super_visit_with(self),
+        }
+    }
+}
diff --git a/compiler/rustc_borrowck/src/region_infer/opaque_types/mod.rs b/compiler/rustc_borrowck/src/region_infer/opaque_types/mod.rs
new file mode 100644
index 00000000000..bee82e17835
--- /dev/null
+++ b/compiler/rustc_borrowck/src/region_infer/opaque_types/mod.rs
@@ -0,0 +1,697 @@
+use std::iter;
+use std::rc::Rc;
+
+use rustc_data_structures::frozen::Frozen;
+use rustc_data_structures::fx::FxIndexMap;
+use rustc_hir::def_id::DefId;
+use rustc_infer::infer::outlives::env::RegionBoundPairs;
+use rustc_infer::infer::{InferCtxt, NllRegionVariableOrigin, OpaqueTypeStorageEntries};
+use rustc_infer::traits::ObligationCause;
+use rustc_macros::extension;
+use rustc_middle::mir::{Body, ConstraintCategory};
+use rustc_middle::ty::{
+    self, DefiningScopeKind, FallibleTypeFolder, GenericArg, GenericArgsRef, OpaqueHiddenType,
+    OpaqueTypeKey, Region, RegionVid, Ty, TyCtxt, TypeFoldable, TypeSuperFoldable,
+    TypeVisitableExt, fold_regions,
+};
+use rustc_mir_dataflow::points::DenseLocationMap;
+use rustc_span::Span;
+use rustc_trait_selection::opaque_types::{
+    NonDefiningUseReason, opaque_type_has_defining_use_args,
+};
+use rustc_trait_selection::solve::NoSolution;
+use rustc_trait_selection::traits::query::type_op::custom::CustomTypeOp;
+use tracing::{debug, instrument};
+
+use super::reverse_sccs::ReverseSccGraph;
+use crate::consumers::RegionInferenceContext;
+use crate::session_diagnostics::LifetimeMismatchOpaqueParam;
+use crate::type_check::canonical::fully_perform_op_raw;
+use crate::type_check::free_region_relations::UniversalRegionRelations;
+use crate::type_check::{Locations, MirTypeckRegionConstraints};
+use crate::universal_regions::{RegionClassification, UniversalRegions};
+use crate::{BorrowCheckRootCtxt, BorrowckInferCtxt};
+
+mod member_constraints;
+mod region_ctxt;
+
+use member_constraints::apply_member_constraints;
+use region_ctxt::RegionCtxt;
+
+/// We defer errors from [fn handle_opaque_type_uses] and only report them
+/// if there are no `RegionErrors`. If there are region errors, it's likely
+/// that errors here are caused by them and don't need to be handled separately.
+pub(crate) enum DeferredOpaqueTypeError<'tcx> {
+    InvalidOpaqueTypeArgs(NonDefiningUseReason<'tcx>),
+    LifetimeMismatchOpaqueParam(LifetimeMismatchOpaqueParam<'tcx>),
+    UnexpectedHiddenRegion {
+        /// The opaque type.
+        opaque_type_key: OpaqueTypeKey<'tcx>,
+        /// The hidden type containing the member region.
+        hidden_type: OpaqueHiddenType<'tcx>,
+        /// The unexpected region.
+        member_region: Region<'tcx>,
+    },
+    NonDefiningUseInDefiningScope {
+        span: Span,
+        opaque_type_key: OpaqueTypeKey<'tcx>,
+    },
+}
+
+/// This looks at all uses of opaque types in their defining scope inside
+/// of this function.
+///
+/// It first uses all defining uses to compute the actual concrete type of each
+/// opaque type definition.
+///
+/// We then apply this inferred type to actually check all uses of the opaque.
+pub(crate) fn handle_opaque_type_uses<'tcx>(
+    root_cx: &mut BorrowCheckRootCtxt<'tcx>,
+    infcx: &BorrowckInferCtxt<'tcx>,
+    body: &Body<'tcx>,
+    universal_region_relations: &Frozen<UniversalRegionRelations<'tcx>>,
+    region_bound_pairs: &RegionBoundPairs<'tcx>,
+    known_type_outlives_obligations: &[ty::PolyTypeOutlivesPredicate<'tcx>],
+    location_map: &Rc<DenseLocationMap>,
+    constraints: &mut MirTypeckRegionConstraints<'tcx>,
+) -> Vec<DeferredOpaqueTypeError<'tcx>> {
+    let tcx = infcx.tcx;
+    let opaque_types = infcx.clone_opaque_types();
+    if opaque_types.is_empty() {
+        return Vec::new();
+    }
+
+    // We need to eagerly map all regions to NLL vars here, as we need to make sure we've
+    // introduced nll vars for all used placeholders.
+    //
+    // We need to resolve inference vars as even though we're in MIR typeck, we may still
+    // encounter inference variables, e.g. when checking user types.
+    let opaque_types_storage_num_entries = infcx.inner.borrow_mut().opaque_types().num_entries();
+    let opaque_types = opaque_types
+        .into_iter()
+        .map(|entry| {
+            fold_regions(tcx, infcx.resolve_vars_if_possible(entry), |r, _| {
+                let vid = if let ty::RePlaceholder(placeholder) = r.kind() {
+                    constraints.placeholder_region(infcx, placeholder).as_var()
+                } else {
+                    universal_region_relations.universal_regions.to_region_vid(r)
+                };
+                Region::new_var(tcx, vid)
+            })
+        })
+        .collect::<Vec<_>>();
+
+    debug!(?opaque_types);
+
+    let errors = compute_concrete_opaque_types(
+        root_cx,
+        infcx,
+        constraints,
+        universal_region_relations,
+        Rc::clone(location_map),
+        &opaque_types,
+    );
+
+    if !errors.is_empty() {
+        return errors;
+    }
+
+    let errors = apply_computed_concrete_opaque_types(
+        root_cx,
+        infcx,
+        body,
+        &universal_region_relations.universal_regions,
+        region_bound_pairs,
+        known_type_outlives_obligations,
+        constraints,
+        &opaque_types,
+    );
+
+    detect_opaque_types_added_while_handling_opaque_types(infcx, opaque_types_storage_num_entries);
+
+    errors
+}
+
+/// Maps an NLL var to a deterministically chosen equal universal region.
+///
+/// See the corresponding [rustc-dev-guide chapter] for more details. This
+/// ignores changes to the region values due to member constraints. Applying
+/// member constraints does not impact the result of this function.
+///
+/// [rustc-dev-guide chapter]: https://rustc-dev-guide.rust-lang.org/borrow_check/opaque-types-region-inference-restrictions.html
+fn nll_var_to_universal_region<'tcx>(
+    rcx: &RegionCtxt<'_, 'tcx>,
+    r: RegionVid,
+) -> Option<Region<'tcx>> {
+    // Use the SCC representative instead of directly using `region`.
+    // See [rustc-dev-guide chapter] § "Strict lifetime equality".
+    let vid = rcx.representative(r).rvid();
+    match rcx.definitions[vid].origin {
+        // Iterate over all universal regions in a consistent order and find the
+        // *first* equal region. This makes sure that equal lifetimes will have
+        // the same name and simplifies subsequent handling.
+        // See [rustc-dev-guide chapter] § "Semantic lifetime equality".
+        NllRegionVariableOrigin::FreeRegion => rcx
+            .universal_regions()
+            .universal_regions_iter()
+            .filter(|&ur| {
+                // See [rustc-dev-guide chapter] § "Closure restrictions".
+                !matches!(
+                    rcx.universal_regions().region_classification(ur),
+                    Some(RegionClassification::External)
+                )
+            })
+            .find(|&ur| rcx.universal_region_relations.equal(vid, ur))
+            .map(|ur| rcx.definitions[ur].external_name.unwrap()),
+        NllRegionVariableOrigin::Placeholder(placeholder) => {
+            Some(ty::Region::new_placeholder(rcx.infcx.tcx, placeholder))
+        }
+        // If `r` were equal to any universal region, its SCC representative
+        // would have been set to a free region.
+        NllRegionVariableOrigin::Existential { .. } => None,
+    }
+}
+
+#[derive(Debug)]
+struct DefiningUse<'tcx> {
+    /// The opaque type using non NLL vars. This uses the actual
+    /// free regions and placeholders. This is necessary
+    /// to interact with code outside of `rustc_borrowck`.
+    opaque_type_key: OpaqueTypeKey<'tcx>,
+    arg_regions: Vec<RegionVid>,
+    hidden_type: OpaqueHiddenType<'tcx>,
+}
+
+/// This computes the actual hidden types of the opaque types and maps them to their
+/// definition sites. Outside of registering the computed concrete types this function
+/// does not mutate the current borrowck state.
+///
+/// While it may fail to infer the hidden type and return errors, we always apply
+/// the computed concrete hidden type to all opaque type uses to check whether they
+/// are correct. This is necessary to support non-defining uses of opaques in their
+/// defining scope.
+///
+/// It also means that this whole function is not really soundness critical as we
+/// recheck all uses of the opaques regardless.
+fn compute_concrete_opaque_types<'tcx>(
+    root_cx: &mut BorrowCheckRootCtxt<'tcx>,
+    infcx: &BorrowckInferCtxt<'tcx>,
+    constraints: &MirTypeckRegionConstraints<'tcx>,
+    universal_region_relations: &Frozen<UniversalRegionRelations<'tcx>>,
+    location_map: Rc<DenseLocationMap>,
+    opaque_types: &[(OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>)],
+) -> Vec<DeferredOpaqueTypeError<'tcx>> {
+    let mut errors = Vec::new();
+    // When computing the hidden type we need to track member constraints.
+    // We don't mutate the region graph used by `fn compute_regions` but instead
+    // manually track region information via a `RegionCtxt`. We discard this
+    // information at the end of this function.
+    let mut rcx = RegionCtxt::new(infcx, universal_region_relations, location_map, constraints);
+
+    // We start by checking each use of an opaque type during type check and
+    // check whether the generic arguments of the opaque type are fully
+    // universal, if so, it's a defining use.
+    let defining_uses = collect_defining_uses(root_cx, &mut rcx, opaque_types, &mut errors);
+
+    // We now compute and apply member constraints for all regions in the hidden
+    // types of each defining use. This mutates the region values of the `rcx` which
+    // is used when mapping the defining uses to the definition site.
+    apply_member_constraints(&mut rcx, &defining_uses);
+
+    // After applying member constraints, we now check whether all member regions ended
+    // up equal to one of their choice regions and compute the actual concrete type of
+    // the opaque type definition. This is stored in the `root_cx`.
+    compute_concrete_types_from_defining_uses(root_cx, &rcx, &defining_uses, &mut errors);
+    errors
+}
+
+#[instrument(level = "debug", skip_all, ret)]
+fn collect_defining_uses<'tcx>(
+    root_cx: &mut BorrowCheckRootCtxt<'tcx>,
+    rcx: &mut RegionCtxt<'_, 'tcx>,
+    opaque_types: &[(OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>)],
+    errors: &mut Vec<DeferredOpaqueTypeError<'tcx>>,
+) -> Vec<DefiningUse<'tcx>> {
+    let infcx = rcx.infcx;
+    let mut defining_uses = vec![];
+    for &(opaque_type_key, hidden_type) in opaque_types {
+        let non_nll_opaque_type_key = opaque_type_key.fold_captured_lifetime_args(infcx.tcx, |r| {
+            nll_var_to_universal_region(&rcx, r.as_var()).unwrap_or(r)
+        });
+        if let Err(err) = opaque_type_has_defining_use_args(
+            infcx,
+            non_nll_opaque_type_key,
+            hidden_type.span,
+            DefiningScopeKind::MirBorrowck,
+        ) {
+            // A non-defining use. This is a hard error on stable and gets ignored
+            // with `TypingMode::Borrowck`.
+            if infcx.tcx.use_typing_mode_borrowck() {
+                match err {
+                    NonDefiningUseReason::Tainted(guar) => root_cx.add_concrete_opaque_type(
+                        opaque_type_key.def_id,
+                        OpaqueHiddenType::new_error(infcx.tcx, guar),
+                    ),
+                    _ => debug!(?non_nll_opaque_type_key, ?err, "ignoring non-defining use"),
+                }
+            } else {
+                errors.push(DeferredOpaqueTypeError::InvalidOpaqueTypeArgs(err));
+            }
+            continue;
+        }
+
+        // We use the original `opaque_type_key` to compute the `arg_regions`.
+        let arg_regions = iter::once(rcx.universal_regions().fr_static)
+            .chain(
+                opaque_type_key
+                    .iter_captured_args(infcx.tcx)
+                    .filter_map(|(_, arg)| arg.as_region())
+                    .map(Region::as_var),
+            )
+            .collect();
+        defining_uses.push(DefiningUse {
+            opaque_type_key: non_nll_opaque_type_key,
+            arg_regions,
+            hidden_type,
+        });
+    }
+
+    defining_uses
+}
+
+fn compute_concrete_types_from_defining_uses<'tcx>(
+    root_cx: &mut BorrowCheckRootCtxt<'tcx>,
+    rcx: &RegionCtxt<'_, 'tcx>,
+    defining_uses: &[DefiningUse<'tcx>],
+    errors: &mut Vec<DeferredOpaqueTypeError<'tcx>>,
+) {
+    let infcx = rcx.infcx;
+    let tcx = infcx.tcx;
+    let mut decls_modulo_regions: FxIndexMap<OpaqueTypeKey<'tcx>, (OpaqueTypeKey<'tcx>, Span)> =
+        FxIndexMap::default();
+    for &DefiningUse { opaque_type_key, ref arg_regions, hidden_type } in defining_uses {
+        // After applying member constraints, we now map all regions in the hidden type
+        // to the `arg_regions` of this defining use. In case a region in the hidden type
+        // ended up not being equal to any such region, we error.
+        let hidden_type =
+            match hidden_type.try_fold_with(&mut ToArgRegionsFolder::new(rcx, arg_regions)) {
+                Ok(hidden_type) => hidden_type,
+                Err(r) => {
+                    errors.push(DeferredOpaqueTypeError::UnexpectedHiddenRegion {
+                        hidden_type,
+                        opaque_type_key,
+                        member_region: ty::Region::new_var(tcx, r),
+                    });
+                    let guar = tcx.dcx().span_delayed_bug(
+                        hidden_type.span,
+                        "opaque type with non-universal region args",
+                    );
+                    ty::OpaqueHiddenType::new_error(tcx, guar)
+                }
+            };
+
+        // Now that we mapped the member regions to their final value,
+        // map the arguments of the opaque type key back to the parameters
+        // of the opaque type definition.
+        let ty = infcx
+            .infer_opaque_definition_from_instantiation(opaque_type_key, hidden_type)
+            .unwrap_or_else(|_| {
+                Ty::new_error_with_message(
+                    rcx.infcx.tcx,
+                    hidden_type.span,
+                    "deferred invalid opaque type args",
+                )
+            });
+
+        // Sometimes, when the hidden type is an inference variable, it can happen that
+        // the hidden type becomes the opaque type itself. In this case, this was an opaque
+        // usage of the opaque type and we can ignore it. This check is mirrored in typeck's
+        // writeback.
+        if !rcx.infcx.tcx.use_typing_mode_borrowck() {
+            if let ty::Alias(ty::Opaque, alias_ty) = ty.kind()
+                && alias_ty.def_id == opaque_type_key.def_id.to_def_id()
+                && alias_ty.args == opaque_type_key.args
+            {
+                continue;
+            }
+        }
+
+        // Check that all opaque types have the same region parameters if they have the same
+        // non-region parameters. This is necessary because within the new solver we perform
+        // various query operations modulo regions, and thus could unsoundly select some impls
+        // that don't hold.
+        //
+        // FIXME(-Znext-solver): This isn't necessary after all. We can remove this check again.
+        if let Some((prev_decl_key, prev_span)) = decls_modulo_regions.insert(
+            rcx.infcx.tcx.erase_regions(opaque_type_key),
+            (opaque_type_key, hidden_type.span),
+        ) && let Some((arg1, arg2)) = std::iter::zip(
+            prev_decl_key.iter_captured_args(infcx.tcx).map(|(_, arg)| arg),
+            opaque_type_key.iter_captured_args(infcx.tcx).map(|(_, arg)| arg),
+        )
+        .find(|(arg1, arg2)| arg1 != arg2)
+        {
+            errors.push(DeferredOpaqueTypeError::LifetimeMismatchOpaqueParam(
+                LifetimeMismatchOpaqueParam {
+                    arg: arg1,
+                    prev: arg2,
+                    span: prev_span,
+                    prev_span: hidden_type.span,
+                },
+            ));
+        }
+        root_cx.add_concrete_opaque_type(
+            opaque_type_key.def_id,
+            OpaqueHiddenType { span: hidden_type.span, ty },
+        );
+    }
+}
+
+/// A folder to map the regions in the hidden type to their corresponding `arg_regions`.
+///
+/// This folder has to differentiate between member regions and other regions in the hidden
+/// type. Member regions have to be equal to one of the `arg_regions` while other regions simply
+/// get treated as an existential region in the opaque if they are not. Existential
+/// regions are currently represented using `'erased`.
+struct ToArgRegionsFolder<'a, 'tcx> {
+    rcx: &'a RegionCtxt<'a, 'tcx>,
+    // When folding closure args or bivariant alias arguments, we simply
+    // ignore non-member regions. However, we still need to map member
+    // regions to their arg region even if its in a closure argument.
+    //
+    // See tests/ui/type-alias-impl-trait/closure_wf_outlives.rs for an example.
+    erase_unknown_regions: bool,
+    arg_regions: &'a [RegionVid],
+}
+
+impl<'a, 'tcx> ToArgRegionsFolder<'a, 'tcx> {
+    fn new(
+        rcx: &'a RegionCtxt<'a, 'tcx>,
+        arg_regions: &'a [RegionVid],
+    ) -> ToArgRegionsFolder<'a, 'tcx> {
+        ToArgRegionsFolder { rcx, erase_unknown_regions: false, arg_regions }
+    }
+
+    fn fold_non_member_arg(&mut self, arg: GenericArg<'tcx>) -> GenericArg<'tcx> {
+        let prev = self.erase_unknown_regions;
+        self.erase_unknown_regions = true;
+        let res = arg.try_fold_with(self).unwrap();
+        self.erase_unknown_regions = prev;
+        res
+    }
+
+    fn fold_closure_args(
+        &mut self,
+        def_id: DefId,
+        args: GenericArgsRef<'tcx>,
+    ) -> Result<GenericArgsRef<'tcx>, RegionVid> {
+        let generics = self.cx().generics_of(def_id);
+        self.cx().mk_args_from_iter(args.iter().enumerate().map(|(index, arg)| {
+            if index < generics.parent_count {
+                Ok(self.fold_non_member_arg(arg))
+            } else {
+                arg.try_fold_with(self)
+            }
+        }))
+    }
+}
+impl<'tcx> FallibleTypeFolder<TyCtxt<'tcx>> for ToArgRegionsFolder<'_, 'tcx> {
+    type Error = RegionVid;
+    fn cx(&self) -> TyCtxt<'tcx> {
+        self.rcx.infcx.tcx
+    }
+
+    fn try_fold_region(&mut self, r: Region<'tcx>) -> Result<Region<'tcx>, RegionVid> {
+        match r.kind() {
+            // ignore bound regions, keep visiting
+            ty::ReBound(_, _) => Ok(r),
+            _ => {
+                let r = r.as_var();
+                if let Some(arg_region) = self
+                    .arg_regions
+                    .iter()
+                    .copied()
+                    .find(|&arg_vid| self.rcx.eval_equal(r, arg_vid))
+                    .and_then(|r| nll_var_to_universal_region(self.rcx, r))
+                {
+                    Ok(arg_region)
+                } else if self.erase_unknown_regions {
+                    Ok(self.cx().lifetimes.re_erased)
+                } else {
+                    Err(r)
+                }
+            }
+        }
+    }
+
+    fn try_fold_ty(&mut self, ty: Ty<'tcx>) -> Result<Ty<'tcx>, RegionVid> {
+        if !ty.flags().intersects(ty::TypeFlags::HAS_FREE_REGIONS) {
+            return Ok(ty);
+        }
+
+        let tcx = self.cx();
+        Ok(match *ty.kind() {
+            ty::Closure(def_id, args) => {
+                Ty::new_closure(tcx, def_id, self.fold_closure_args(def_id, args)?)
+            }
+
+            ty::CoroutineClosure(def_id, args) => {
+                Ty::new_coroutine_closure(tcx, def_id, self.fold_closure_args(def_id, args)?)
+            }
+
+            ty::Coroutine(def_id, args) => {
+                Ty::new_coroutine(tcx, def_id, self.fold_closure_args(def_id, args)?)
+            }
+
+            ty::Alias(kind, ty::AliasTy { def_id, args, .. })
+                if let Some(variances) = tcx.opt_alias_variances(kind, def_id) =>
+            {
+                let args = tcx.mk_args_from_iter(std::iter::zip(variances, args.iter()).map(
+                    |(&v, s)| {
+                        if v == ty::Bivariant {
+                            Ok(self.fold_non_member_arg(s))
+                        } else {
+                            s.try_fold_with(self)
+                        }
+                    },
+                ))?;
+                ty::AliasTy::new_from_args(tcx, def_id, args).to_ty(tcx)
+            }
+
+            _ => ty.try_super_fold_with(self)?,
+        })
+    }
+}
+
+/// This function is what actually applies member constraints to the borrowck
+/// state. It is also responsible to check all uses of the opaques in their
+/// defining scope.
+///
+/// It does this by equating the hidden type of each use with the instantiated final
+/// hidden type of the opaque.
+fn apply_computed_concrete_opaque_types<'tcx>(
+    root_cx: &mut BorrowCheckRootCtxt<'tcx>,
+    infcx: &BorrowckInferCtxt<'tcx>,
+    body: &Body<'tcx>,
+    universal_regions: &UniversalRegions<'tcx>,
+    region_bound_pairs: &RegionBoundPairs<'tcx>,
+    known_type_outlives_obligations: &[ty::PolyTypeOutlivesPredicate<'tcx>],
+    constraints: &mut MirTypeckRegionConstraints<'tcx>,
+    opaque_types: &[(OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>)],
+) -> Vec<DeferredOpaqueTypeError<'tcx>> {
+    let tcx = infcx.tcx;
+    let mut errors = Vec::new();
+    for &(key, hidden_type) in opaque_types {
+        let Some(expected) = root_cx.get_concrete_opaque_type(key.def_id) else {
+            assert!(tcx.use_typing_mode_borrowck(), "non-defining use in defining scope");
+            errors.push(DeferredOpaqueTypeError::NonDefiningUseInDefiningScope {
+                span: hidden_type.span,
+                opaque_type_key: key,
+            });
+            let guar = tcx.dcx().span_delayed_bug(
+                hidden_type.span,
+                "non-defining use in the defining scope with no defining uses",
+            );
+            root_cx.add_concrete_opaque_type(key.def_id, OpaqueHiddenType::new_error(tcx, guar));
+            continue;
+        };
+
+        // We erase all non-member region of the opaque and need to treat these as existentials.
+        let expected = ty::fold_regions(tcx, expected.instantiate(tcx, key.args), |re, _dbi| {
+            match re.kind() {
+                ty::ReErased => infcx.next_nll_region_var(
+                    NllRegionVariableOrigin::Existential { name: None },
+                    || crate::RegionCtxt::Existential(None),
+                ),
+                _ => re,
+            }
+        });
+
+        // We now simply equate the expected with the actual hidden type.
+        let locations = Locations::All(hidden_type.span);
+        if let Err(guar) = fully_perform_op_raw(
+            infcx,
+            body,
+            universal_regions,
+            region_bound_pairs,
+            known_type_outlives_obligations,
+            constraints,
+            locations,
+            ConstraintCategory::OpaqueType,
+            CustomTypeOp::new(
+                |ocx| {
+                    let cause = ObligationCause::misc(
+                        hidden_type.span,
+                        body.source.def_id().expect_local(),
+                    );
+                    // We need to normalize both types in the old solver before equatingt them.
+                    let actual_ty = ocx.normalize(&cause, infcx.param_env, hidden_type.ty);
+                    let expected_ty = ocx.normalize(&cause, infcx.param_env, expected.ty);
+                    ocx.eq(&cause, infcx.param_env, actual_ty, expected_ty).map_err(|_| NoSolution)
+                },
+                "equating opaque types",
+            ),
+        ) {
+            root_cx.add_concrete_opaque_type(key.def_id, OpaqueHiddenType::new_error(tcx, guar));
+        }
+    }
+    errors
+}
+
+/// In theory `apply_concrete_opaque_types` could introduce new uses of opaque types.
+/// We do not check these new uses so this could be unsound.
+///
+/// We detect any new uses and simply delay a bug if they occur. If this results in
+/// an ICE we can properly handle this, but we haven't encountered any such test yet.
+///
+/// See the related comment in `FnCtxt::detect_opaque_types_added_during_writeback`.
+fn detect_opaque_types_added_while_handling_opaque_types<'tcx>(
+    infcx: &InferCtxt<'tcx>,
+    opaque_types_storage_num_entries: OpaqueTypeStorageEntries,
+) {
+    for (key, hidden_type) in infcx
+        .inner
+        .borrow_mut()
+        .opaque_types()
+        .opaque_types_added_since(opaque_types_storage_num_entries)
+    {
+        let opaque_type_string = infcx.tcx.def_path_str(key.def_id);
+        let msg = format!("unexpected cyclic definition of `{opaque_type_string}`");
+        infcx.dcx().span_delayed_bug(hidden_type.span, msg);
+    }
+
+    let _ = infcx.take_opaque_types();
+}
+
+impl<'tcx> RegionInferenceContext<'tcx> {
+    /// Map the regions in the type to named regions. This is similar to what
+    /// `infer_opaque_types` does, but can infer any universal region, not only
+    /// ones from the args for the opaque type. It also doesn't double check
+    /// that the regions produced are in fact equal to the named region they are
+    /// replaced with. This is fine because this function is only to improve the
+    /// region names in error messages.
+    ///
+    /// This differs from `MirBorrowckCtxt::name_regions` since it is particularly
+    /// lax with mapping region vids that are *shorter* than a universal region to
+    /// that universal region. This is useful for member region constraints since
+    /// we want to suggest a universal region name to capture even if it's technically
+    /// not equal to the error region.
+    pub(crate) fn name_regions_for_member_constraint<T>(&self, tcx: TyCtxt<'tcx>, ty: T) -> T
+    where
+        T: TypeFoldable<TyCtxt<'tcx>>,
+    {
+        fold_regions(tcx, ty, |region, _| match region.kind() {
+            ty::ReVar(vid) => {
+                let scc = self.constraint_sccs.scc(vid);
+
+                // Special handling of higher-ranked regions.
+                if !self.max_nameable_universe(scc).is_root() {
+                    match self.scc_values.placeholders_contained_in(scc).enumerate().last() {
+                        // If the region contains a single placeholder then they're equal.
+                        Some((0, placeholder)) => {
+                            return ty::Region::new_placeholder(tcx, placeholder);
+                        }
+
+                        // Fallback: this will produce a cryptic error message.
+                        _ => return region,
+                    }
+                }
+
+                // Find something that we can name
+                let upper_bound = self.approx_universal_upper_bound(vid);
+                if let Some(universal_region) = self.definitions[upper_bound].external_name {
+                    return universal_region;
+                }
+
+                // Nothing exact found, so we pick a named upper bound, if there's only one.
+                // If there's >1 universal region, then we probably are dealing w/ an intersection
+                // region which cannot be mapped back to a universal.
+                // FIXME: We could probably compute the LUB if there is one.
+                let scc = self.constraint_sccs.scc(vid);
+                let rev_scc_graph =
+                    ReverseSccGraph::compute(&self.constraint_sccs, self.universal_regions());
+                let upper_bounds: Vec<_> = rev_scc_graph
+                    .upper_bounds(scc)
+                    .filter_map(|vid| self.definitions[vid].external_name)
+                    .filter(|r| !r.is_static())
+                    .collect();
+                match &upper_bounds[..] {
+                    [universal_region] => *universal_region,
+                    _ => region,
+                }
+            }
+            _ => region,
+        })
+    }
+}
+
+#[extension(pub trait InferCtxtExt<'tcx>)]
+impl<'tcx> InferCtxt<'tcx> {
+    /// Given the fully resolved, instantiated type for an opaque
+    /// type, i.e., the value of an inference variable like C1 or C2
+    /// (*), computes the "definition type" for an opaque type
+    /// definition -- that is, the inferred value of `Foo1<'x>` or
+    /// `Foo2<'x>` that we would conceptually use in its definition:
+    /// ```ignore (illustrative)
+    /// type Foo1<'x> = impl Bar<'x> = AAA;  // <-- this type AAA
+    /// type Foo2<'x> = impl Bar<'x> = BBB;  // <-- or this type BBB
+    /// fn foo<'a, 'b>(..) -> (Foo1<'a>, Foo2<'b>) { .. }
+    /// ```
+    /// Note that these values are defined in terms of a distinct set of
+    /// generic parameters (`'x` instead of `'a`) from C1 or C2. The main
+    /// purpose of this function is to do that translation.
+    ///
+    /// (*) C1 and C2 were introduced in the comments on
+    /// `register_member_constraints`. Read that comment for more context.
+    ///
+    /// # Parameters
+    ///
+    /// - `def_id`, the `impl Trait` type
+    /// - `args`, the args used to instantiate this opaque type
+    /// - `instantiated_ty`, the inferred type C1 -- fully resolved, lifted version of
+    ///   `opaque_defn.concrete_ty`
+    #[instrument(level = "debug", skip(self))]
+    fn infer_opaque_definition_from_instantiation(
+        &self,
+        opaque_type_key: OpaqueTypeKey<'tcx>,
+        instantiated_ty: OpaqueHiddenType<'tcx>,
+    ) -> Result<Ty<'tcx>, NonDefiningUseReason<'tcx>> {
+        opaque_type_has_defining_use_args(
+            self,
+            opaque_type_key,
+            instantiated_ty.span,
+            DefiningScopeKind::MirBorrowck,
+        )?;
+
+        let definition_ty = instantiated_ty
+            .remap_generic_params_to_declaration_params(
+                opaque_type_key,
+                self.tcx,
+                DefiningScopeKind::MirBorrowck,
+            )
+            .ty;
+
+        definition_ty.error_reported()?;
+        Ok(definition_ty)
+    }
+}
diff --git a/compiler/rustc_borrowck/src/region_infer/opaque_types/region_ctxt.rs b/compiler/rustc_borrowck/src/region_infer/opaque_types/region_ctxt.rs
new file mode 100644
index 00000000000..88326e4eebf
--- /dev/null
+++ b/compiler/rustc_borrowck/src/region_infer/opaque_types/region_ctxt.rs
@@ -0,0 +1,114 @@
+use std::rc::Rc;
+
+use rustc_data_structures::frozen::Frozen;
+use rustc_index::IndexVec;
+use rustc_infer::infer::NllRegionVariableOrigin;
+use rustc_middle::ty::{RegionVid, UniverseIndex};
+use rustc_mir_dataflow::points::DenseLocationMap;
+
+use crate::BorrowckInferCtxt;
+use crate::constraints::ConstraintSccIndex;
+use crate::handle_placeholders::{SccAnnotations, region_definitions};
+use crate::region_infer::reverse_sccs::ReverseSccGraph;
+use crate::region_infer::values::RegionValues;
+use crate::region_infer::{ConstraintSccs, RegionDefinition, RegionTracker, Representative};
+use crate::type_check::MirTypeckRegionConstraints;
+use crate::type_check::free_region_relations::UniversalRegionRelations;
+use crate::universal_regions::UniversalRegions;
+
+/// A slimmed down version of [crate::region_infer::RegionInferenceContext] used
+/// only by opaque type handling.
+pub(super) struct RegionCtxt<'a, 'tcx> {
+    pub(super) infcx: &'a BorrowckInferCtxt<'tcx>,
+    pub(super) definitions: Frozen<IndexVec<RegionVid, RegionDefinition<'tcx>>>,
+    pub(super) universal_region_relations: &'a UniversalRegionRelations<'tcx>,
+    pub(super) constraint_sccs: ConstraintSccs,
+    pub(super) scc_annotations: IndexVec<ConstraintSccIndex, RegionTracker>,
+    pub(super) rev_scc_graph: ReverseSccGraph,
+    pub(super) scc_values: RegionValues<ConstraintSccIndex>,
+}
+
+impl<'a, 'tcx> RegionCtxt<'a, 'tcx> {
+    /// Creates a new `RegionCtxt` used to compute defining opaque type uses.
+    ///
+    /// This does not yet propagate region values. This is instead done lazily
+    /// when applying member constraints.
+    pub(super) fn new(
+        infcx: &'a BorrowckInferCtxt<'tcx>,
+        universal_region_relations: &'a Frozen<UniversalRegionRelations<'tcx>>,
+        location_map: Rc<DenseLocationMap>,
+        constraints: &MirTypeckRegionConstraints<'tcx>,
+    ) -> RegionCtxt<'a, 'tcx> {
+        let universal_regions = &universal_region_relations.universal_regions;
+        let (definitions, _has_placeholders) = region_definitions(infcx, universal_regions);
+        let mut scc_annotations = SccAnnotations::init(&definitions);
+        let constraint_sccs = ConstraintSccs::new_with_annotation(
+            &constraints
+                .outlives_constraints
+                .graph(definitions.len())
+                .region_graph(&constraints.outlives_constraints, universal_regions.fr_static),
+            &mut scc_annotations,
+        );
+        let scc_annotations = scc_annotations.scc_to_annotation;
+
+        // Unlike the `RegionInferenceContext`, we only care about free regions
+        // and fully ignore liveness and placeholders.
+        let placeholder_indices = Default::default();
+        let mut scc_values =
+            RegionValues::new(location_map, universal_regions.len(), placeholder_indices);
+        for variable in definitions.indices() {
+            let scc = constraint_sccs.scc(variable);
+            match definitions[variable].origin {
+                NllRegionVariableOrigin::FreeRegion => {
+                    scc_values.add_element(scc, variable);
+                }
+                _ => {}
+            }
+        }
+
+        let rev_scc_graph = ReverseSccGraph::compute(&constraint_sccs, universal_regions);
+        RegionCtxt {
+            infcx,
+            definitions,
+            universal_region_relations,
+            constraint_sccs,
+            scc_annotations,
+            rev_scc_graph,
+            scc_values,
+        }
+    }
+
+    pub(super) fn representative(&self, vid: RegionVid) -> Representative {
+        let scc = self.constraint_sccs.scc(vid);
+        self.scc_annotations[scc].representative
+    }
+
+    pub(crate) fn max_placeholder_universe_reached(
+        &self,
+        scc: ConstraintSccIndex,
+    ) -> UniverseIndex {
+        self.scc_annotations[scc].max_placeholder_universe_reached()
+    }
+
+    pub(super) fn universal_regions(&self) -> &UniversalRegions<'tcx> {
+        &self.universal_region_relations.universal_regions
+    }
+
+    pub(super) fn eval_equal(&self, r1_vid: RegionVid, r2_vid: RegionVid) -> bool {
+        let r1 = self.constraint_sccs.scc(r1_vid);
+        let r2 = self.constraint_sccs.scc(r2_vid);
+
+        if r1 == r2 {
+            return true;
+        }
+
+        let universal_outlives = |sub, sup| {
+            self.scc_values.universal_regions_outlived_by(sub).all(|r1| {
+                self.scc_values
+                    .universal_regions_outlived_by(sup)
+                    .any(|r2| self.universal_region_relations.outlives(r2, r1))
+            })
+        };
+        universal_outlives(r1, r2) && universal_outlives(r2, r1)
+    }
+}
diff --git a/compiler/rustc_borrowck/src/region_infer/reverse_sccs.rs b/compiler/rustc_borrowck/src/region_infer/reverse_sccs.rs
index 604265f8940..e8da85eccef 100644
--- a/compiler/rustc_borrowck/src/region_infer/reverse_sccs.rs
+++ b/compiler/rustc_borrowck/src/region_infer/reverse_sccs.rs
@@ -5,7 +5,6 @@ use rustc_data_structures::graph;
 use rustc_data_structures::graph::vec_graph::VecGraph;
 use rustc_middle::ty::RegionVid;
 
-use crate::RegionInferenceContext;
 use crate::constraints::ConstraintSccIndex;
 use crate::region_infer::ConstraintSccs;
 use crate::universal_regions::UniversalRegions;
@@ -57,12 +56,3 @@ impl ReverseSccGraph {
             .filter(move |r| duplicates.insert(*r))
     }
 }
-
-impl RegionInferenceContext<'_> {
-    /// Return the reverse graph of the region SCCs, initialising it if needed.
-    pub(super) fn reverse_scc_graph(&self) -> &ReverseSccGraph {
-        self.rev_scc_graph.get_or_init(|| {
-            ReverseSccGraph::compute(&self.constraint_sccs, self.universal_regions())
-        })
-    }
-}
diff --git a/compiler/rustc_borrowck/src/root_cx.rs b/compiler/rustc_borrowck/src/root_cx.rs
index 9b1d12aede5..4e90ae391bb 100644
--- a/compiler/rustc_borrowck/src/root_cx.rs
+++ b/compiler/rustc_borrowck/src/root_cx.rs
@@ -2,7 +2,7 @@ use rustc_abi::FieldIdx;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_hir::def_id::LocalDefId;
 use rustc_middle::bug;
-use rustc_middle::ty::{OpaqueHiddenType, Ty, TyCtxt, TypeVisitableExt};
+use rustc_middle::ty::{EarlyBinder, OpaqueHiddenType, Ty, TyCtxt, TypeVisitableExt};
 use rustc_span::ErrorGuaranteed;
 use smallvec::SmallVec;
 
@@ -19,7 +19,7 @@ pub(super) struct BorrowCheckRootCtxt<'tcx> {
     tainted_by_errors: Option<ErrorGuaranteed>,
     /// This should be `None` during normal compilation. See [`crate::consumers`] for more
     /// information on how this is used.
-    pub(crate) consumer: Option<BorrowckConsumer<'tcx>>,
+    pub consumer: Option<BorrowckConsumer<'tcx>>,
 }
 
 impl<'tcx> BorrowCheckRootCtxt<'tcx> {
@@ -38,6 +38,10 @@ impl<'tcx> BorrowCheckRootCtxt<'tcx> {
         }
     }
 
+    pub(super) fn root_def_id(&self) -> LocalDefId {
+        self.root_def_id
+    }
+
     /// Collect all defining uses of opaque types inside of this typeck root. This
     /// expects the hidden type to be mapped to the definition parameters of the opaque
     /// and errors if we end up with distinct hidden types.
@@ -67,6 +71,13 @@ impl<'tcx> BorrowCheckRootCtxt<'tcx> {
         }
     }
 
+    pub(super) fn get_concrete_opaque_type(
+        &mut self,
+        def_id: LocalDefId,
+    ) -> Option<EarlyBinder<'tcx, OpaqueHiddenType<'tcx>>> {
+        self.concrete_opaque_types.0.get(&def_id).map(|ty| EarlyBinder::bind(*ty))
+    }
+
     pub(super) fn set_tainted_by_errors(&mut self, guar: ErrorGuaranteed) {
         self.tainted_by_errors = Some(guar);
     }
diff --git a/compiler/rustc_borrowck/src/type_check/canonical.rs b/compiler/rustc_borrowck/src/type_check/canonical.rs
index b3fa786a517..2627ed899a9 100644
--- a/compiler/rustc_borrowck/src/type_check/canonical.rs
+++ b/compiler/rustc_borrowck/src/type_check/canonical.rs
@@ -2,8 +2,9 @@ use std::fmt;
 
 use rustc_errors::ErrorGuaranteed;
 use rustc_infer::infer::canonical::Canonical;
+use rustc_infer::infer::outlives::env::RegionBoundPairs;
 use rustc_middle::bug;
-use rustc_middle::mir::ConstraintCategory;
+use rustc_middle::mir::{Body, ConstraintCategory};
 use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable, Upcast};
 use rustc_span::Span;
 use rustc_span::def_id::DefId;
@@ -14,7 +15,68 @@ use rustc_trait_selection::traits::query::type_op::{self, TypeOpOutput};
 use tracing::{debug, instrument};
 
 use super::{Locations, NormalizeLocation, TypeChecker};
+use crate::BorrowckInferCtxt;
 use crate::diagnostics::ToUniverseInfo;
+use crate::type_check::{MirTypeckRegionConstraints, constraint_conversion};
+use crate::universal_regions::UniversalRegions;
+
+#[instrument(skip(infcx, constraints, op), level = "trace")]
+pub(crate) fn fully_perform_op_raw<'tcx, R: fmt::Debug, Op>(
+    infcx: &BorrowckInferCtxt<'tcx>,
+    body: &Body<'tcx>,
+    universal_regions: &UniversalRegions<'tcx>,
+    region_bound_pairs: &RegionBoundPairs<'tcx>,
+    known_type_outlives_obligations: &[ty::PolyTypeOutlivesPredicate<'tcx>],
+    constraints: &mut MirTypeckRegionConstraints<'tcx>,
+    locations: Locations,
+    category: ConstraintCategory<'tcx>,
+    op: Op,
+) -> Result<R, ErrorGuaranteed>
+where
+    Op: type_op::TypeOp<'tcx, Output = R>,
+    Op::ErrorInfo: ToUniverseInfo<'tcx>,
+{
+    let old_universe = infcx.universe();
+
+    let TypeOpOutput { output, constraints: query_constraints, error_info } =
+        op.fully_perform(infcx, infcx.root_def_id, locations.span(body))?;
+    if cfg!(debug_assertions) {
+        let data = infcx.take_and_reset_region_constraints();
+        if !data.is_empty() {
+            panic!("leftover region constraints: {data:#?}");
+        }
+    }
+
+    debug!(?output, ?query_constraints);
+
+    if let Some(data) = query_constraints {
+        constraint_conversion::ConstraintConversion::new(
+            infcx,
+            universal_regions,
+            region_bound_pairs,
+            known_type_outlives_obligations,
+            locations,
+            locations.span(body),
+            category,
+            constraints,
+        )
+        .convert_all(data);
+    }
+
+    // If the query has created new universes and errors are going to be emitted, register the
+    // cause of these new universes for improved diagnostics.
+    let universe = infcx.universe();
+    if old_universe != universe
+        && let Some(error_info) = error_info
+    {
+        let universe_info = error_info.to_universe_info(old_universe);
+        for u in (old_universe + 1)..=universe {
+            constraints.universe_causes.insert(u, universe_info.clone());
+        }
+    }
+
+    Ok(output)
+}
 
 impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
     /// Given some operation `op` that manipulates types, proves
@@ -38,36 +100,17 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         Op: type_op::TypeOp<'tcx, Output = R>,
         Op::ErrorInfo: ToUniverseInfo<'tcx>,
     {
-        let old_universe = self.infcx.universe();
-
-        let TypeOpOutput { output, constraints, error_info } =
-            op.fully_perform(self.infcx, locations.span(self.body))?;
-        if cfg!(debug_assertions) {
-            let data = self.infcx.take_and_reset_region_constraints();
-            if !data.is_empty() {
-                panic!("leftover region constraints: {data:#?}");
-            }
-        }
-
-        debug!(?output, ?constraints);
-
-        if let Some(data) = constraints {
-            self.push_region_constraints(locations, category, data);
-        }
-
-        // If the query has created new universes and errors are going to be emitted, register the
-        // cause of these new universes for improved diagnostics.
-        let universe = self.infcx.universe();
-        if old_universe != universe
-            && let Some(error_info) = error_info
-        {
-            let universe_info = error_info.to_universe_info(old_universe);
-            for u in (old_universe + 1)..=universe {
-                self.constraints.universe_causes.insert(u, universe_info.clone());
-            }
-        }
-
-        Ok(output)
+        fully_perform_op_raw(
+            self.infcx,
+            self.body,
+            self.universal_regions,
+            self.region_bound_pairs,
+            self.known_type_outlives_obligations,
+            self.constraints,
+            locations,
+            category,
+            op,
+        )
     }
 
     pub(super) fn instantiate_canonical<T>(
diff --git a/compiler/rustc_borrowck/src/type_check/constraint_conversion.rs b/compiler/rustc_borrowck/src/type_check/constraint_conversion.rs
index 9bb96b94506..703223e2e54 100644
--- a/compiler/rustc_borrowck/src/type_check/constraint_conversion.rs
+++ b/compiler/rustc_borrowck/src/type_check/constraint_conversion.rs
@@ -1,10 +1,10 @@
 use rustc_data_structures::fx::FxHashSet;
 use rustc_hir::def_id::LocalDefId;
+use rustc_infer::infer::SubregionOrigin;
 use rustc_infer::infer::canonical::QueryRegionConstraints;
 use rustc_infer::infer::outlives::env::RegionBoundPairs;
 use rustc_infer::infer::outlives::obligations::{TypeOutlives, TypeOutlivesDelegate};
 use rustc_infer::infer::region_constraints::{GenericKind, VerifyBound};
-use rustc_infer::infer::{InferCtxt, SubregionOrigin};
 use rustc_infer::traits::query::type_op::DeeplyNormalize;
 use rustc_middle::bug;
 use rustc_middle::ty::{
@@ -18,10 +18,12 @@ use crate::constraints::OutlivesConstraint;
 use crate::region_infer::TypeTest;
 use crate::type_check::{Locations, MirTypeckRegionConstraints};
 use crate::universal_regions::UniversalRegions;
-use crate::{ClosureOutlivesSubject, ClosureRegionRequirements, ConstraintCategory};
+use crate::{
+    BorrowckInferCtxt, ClosureOutlivesSubject, ClosureRegionRequirements, ConstraintCategory,
+};
 
 pub(crate) struct ConstraintConversion<'a, 'tcx> {
-    infcx: &'a InferCtxt<'tcx>,
+    infcx: &'a BorrowckInferCtxt<'tcx>,
     universal_regions: &'a UniversalRegions<'tcx>,
     /// Each RBP `GK: 'a` is assumed to be true. These encode
     /// relationships like `T: 'a` that are added via implicit bounds
@@ -34,7 +36,6 @@ pub(crate) struct ConstraintConversion<'a, 'tcx> {
     /// logic expecting to see (e.g.) `ReStatic`, and if we supplied
     /// our special inference variable there, we would mess that up.
     region_bound_pairs: &'a RegionBoundPairs<'tcx>,
-    param_env: ty::ParamEnv<'tcx>,
     known_type_outlives_obligations: &'a [ty::PolyTypeOutlivesPredicate<'tcx>],
     locations: Locations,
     span: Span,
@@ -45,10 +46,9 @@ pub(crate) struct ConstraintConversion<'a, 'tcx> {
 
 impl<'a, 'tcx> ConstraintConversion<'a, 'tcx> {
     pub(crate) fn new(
-        infcx: &'a InferCtxt<'tcx>,
+        infcx: &'a BorrowckInferCtxt<'tcx>,
         universal_regions: &'a UniversalRegions<'tcx>,
         region_bound_pairs: &'a RegionBoundPairs<'tcx>,
-        param_env: ty::ParamEnv<'tcx>,
         known_type_outlives_obligations: &'a [ty::PolyTypeOutlivesPredicate<'tcx>],
         locations: Locations,
         span: Span,
@@ -59,7 +59,6 @@ impl<'a, 'tcx> ConstraintConversion<'a, 'tcx> {
             infcx,
             universal_regions,
             region_bound_pairs,
-            param_env,
             known_type_outlives_obligations,
             locations,
             span,
@@ -286,8 +285,11 @@ impl<'a, 'tcx> ConstraintConversion<'a, 'tcx> {
             ConstraintCategory<'tcx>,
         )>,
     ) -> Ty<'tcx> {
-        match self.param_env.and(DeeplyNormalize { value: ty }).fully_perform(self.infcx, self.span)
-        {
+        match self.infcx.param_env.and(DeeplyNormalize { value: ty }).fully_perform(
+            self.infcx,
+            self.infcx.root_def_id,
+            self.span,
+        ) {
             Ok(TypeOpOutput { output: ty, constraints, .. }) => {
                 // FIXME(higher_ranked_auto): What should we do with the assumptions here?
                 if let Some(QueryRegionConstraints { outlives, assumptions: _ }) = constraints {
diff --git a/compiler/rustc_borrowck/src/type_check/free_region_relations.rs b/compiler/rustc_borrowck/src/type_check/free_region_relations.rs
index f642d34ea67..7bf2df91470 100644
--- a/compiler/rustc_borrowck/src/type_check/free_region_relations.rs
+++ b/compiler/rustc_borrowck/src/type_check/free_region_relations.rs
@@ -2,9 +2,9 @@ use rustc_data_structures::frozen::Frozen;
 use rustc_data_structures::transitive_relation::{TransitiveRelation, TransitiveRelationBuilder};
 use rustc_hir::def::DefKind;
 use rustc_infer::infer::canonical::QueryRegionConstraints;
+use rustc_infer::infer::outlives;
 use rustc_infer::infer::outlives::env::RegionBoundPairs;
 use rustc_infer::infer::region_constraints::GenericKind;
-use rustc_infer::infer::{InferCtxt, outlives};
 use rustc_infer::traits::query::type_op::DeeplyNormalize;
 use rustc_middle::mir::ConstraintCategory;
 use rustc_middle::traits::query::OutlivesBound;
@@ -14,6 +14,7 @@ use rustc_trait_selection::traits::query::type_op::{self, TypeOp};
 use tracing::{debug, instrument};
 use type_op::TypeOpOutput;
 
+use crate::BorrowckInferCtxt;
 use crate::type_check::{Locations, MirTypeckRegionConstraints, constraint_conversion};
 use crate::universal_regions::UniversalRegions;
 
@@ -47,14 +48,12 @@ pub(crate) struct CreateResult<'tcx> {
 }
 
 pub(crate) fn create<'tcx>(
-    infcx: &InferCtxt<'tcx>,
-    param_env: ty::ParamEnv<'tcx>,
+    infcx: &BorrowckInferCtxt<'tcx>,
     universal_regions: UniversalRegions<'tcx>,
     constraints: &mut MirTypeckRegionConstraints<'tcx>,
 ) -> CreateResult<'tcx> {
     UniversalRegionRelationsBuilder {
         infcx,
-        param_env,
         constraints,
         universal_regions,
         region_bound_pairs: Default::default(),
@@ -177,8 +176,7 @@ impl UniversalRegionRelations<'_> {
 }
 
 struct UniversalRegionRelationsBuilder<'a, 'tcx> {
-    infcx: &'a InferCtxt<'tcx>,
-    param_env: ty::ParamEnv<'tcx>,
+    infcx: &'a BorrowckInferCtxt<'tcx>,
     universal_regions: UniversalRegions<'tcx>,
     constraints: &'a mut MirTypeckRegionConstraints<'tcx>,
 
@@ -205,7 +203,7 @@ impl<'tcx> UniversalRegionRelationsBuilder<'_, 'tcx> {
 
         // Insert the `'a: 'b` we know from the predicates.
         // This does not consider the type-outlives.
-        let param_env = self.param_env;
+        let param_env = self.infcx.param_env;
         self.add_outlives_bounds(outlives::explicit_outlives_bounds(param_env));
 
         // - outlives is reflexive, so `'r: 'r` for every region `'r`
@@ -263,7 +261,7 @@ impl<'tcx> UniversalRegionRelationsBuilder<'_, 'tcx> {
             let TypeOpOutput { output: norm_ty, constraints: constraints_normalize, .. } =
                 param_env
                     .and(DeeplyNormalize { value: ty })
-                    .fully_perform(self.infcx, span)
+                    .fully_perform(self.infcx, self.infcx.root_def_id, span)
                     .unwrap_or_else(|guar| TypeOpOutput {
                         output: Ty::new_error(self.infcx.tcx, guar),
                         constraints: None,
@@ -298,8 +296,9 @@ impl<'tcx> UniversalRegionRelationsBuilder<'_, 'tcx> {
         // Add implied bounds from impl header.
         if matches!(tcx.def_kind(defining_ty_def_id), DefKind::AssocFn | DefKind::AssocConst) {
             for &(ty, _) in tcx.assumed_wf_types(tcx.local_parent(defining_ty_def_id)) {
-                let result: Result<_, ErrorGuaranteed> =
-                    param_env.and(DeeplyNormalize { value: ty }).fully_perform(self.infcx, span);
+                let result: Result<_, ErrorGuaranteed> = param_env
+                    .and(DeeplyNormalize { value: ty })
+                    .fully_perform(self.infcx, self.infcx.root_def_id, span);
                 let Ok(TypeOpOutput { output: norm_ty, constraints: c, .. }) = result else {
                     continue;
                 };
@@ -318,7 +317,6 @@ impl<'tcx> UniversalRegionRelationsBuilder<'_, 'tcx> {
                 self.infcx,
                 &self.universal_regions,
                 &self.region_bound_pairs,
-                param_env,
                 &known_type_outlives_obligations,
                 Locations::All(span),
                 span,
@@ -353,10 +351,11 @@ impl<'tcx> UniversalRegionRelationsBuilder<'_, 'tcx> {
                 output: normalized_outlives,
                 constraints: constraints_normalize,
                 error_info: _,
-            }) = self
-                .param_env
-                .and(DeeplyNormalize { value: outlives })
-                .fully_perform(self.infcx, span)
+            }) = self.infcx.param_env.and(DeeplyNormalize { value: outlives }).fully_perform(
+                self.infcx,
+                self.infcx.root_def_id,
+                span,
+            )
             else {
                 self.infcx.dcx().delayed_bug(format!("could not normalize {outlives:?}"));
                 return;
@@ -381,9 +380,10 @@ impl<'tcx> UniversalRegionRelationsBuilder<'_, 'tcx> {
         span: Span,
     ) -> Option<&'tcx QueryRegionConstraints<'tcx>> {
         let TypeOpOutput { output: bounds, constraints, .. } = self
+            .infcx
             .param_env
             .and(type_op::ImpliedOutlivesBounds { ty })
-            .fully_perform(self.infcx, span)
+            .fully_perform(self.infcx, self.infcx.root_def_id, span)
             .map_err(|_: ErrorGuaranteed| debug!("failed to compute implied bounds {:?}", ty))
             .ok()?;
         debug!(?bounds, ?constraints);
diff --git a/compiler/rustc_borrowck/src/type_check/liveness/trace.rs b/compiler/rustc_borrowck/src/type_check/liveness/trace.rs
index 5d30fa71e92..b704d8f0a76 100644
--- a/compiler/rustc_borrowck/src/type_check/liveness/trace.rs
+++ b/compiler/rustc_borrowck/src/type_check/liveness/trace.rs
@@ -640,7 +640,7 @@ impl<'tcx> LivenessContext<'_, '_, 'tcx> {
 
         let op = typeck.infcx.param_env.and(DropckOutlives { dropped_ty });
 
-        match op.fully_perform(typeck.infcx, DUMMY_SP) {
+        match op.fully_perform(typeck.infcx, typeck.root_cx.root_def_id(), DUMMY_SP) {
             Ok(TypeOpOutput { output, constraints, .. }) => {
                 DropData { dropck_result: output, region_constraint_data: constraints }
             }
diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs
index a960b96b91c..0d363935f14 100644
--- a/compiler/rustc_borrowck/src/type_check/mod.rs
+++ b/compiler/rustc_borrowck/src/type_check/mod.rs
@@ -26,8 +26,7 @@ use rustc_middle::ty::adjustment::PointerCoercion;
 use rustc_middle::ty::cast::CastTy;
 use rustc_middle::ty::{
     self, CanonicalUserTypeAnnotation, CanonicalUserTypeAnnotations, CoroutineArgsExt,
-    GenericArgsRef, OpaqueHiddenType, OpaqueTypeKey, RegionVid, Ty, TyCtxt, TypeVisitableExt,
-    UserArgs, UserTypeAnnotationIndex, fold_regions,
+    GenericArgsRef, Ty, TyCtxt, TypeVisitableExt, UserArgs, UserTypeAnnotationIndex, fold_regions,
 };
 use rustc_middle::{bug, span_bug};
 use rustc_mir_dataflow::move_paths::MoveData;
@@ -35,6 +34,7 @@ use rustc_mir_dataflow::points::DenseLocationMap;
 use rustc_span::def_id::CRATE_DEF_ID;
 use rustc_span::source_map::Spanned;
 use rustc_span::{Span, sym};
+use rustc_trait_selection::infer::InferCtxtExt;
 use rustc_trait_selection::traits::query::type_op::custom::scrape_region_constraints;
 use rustc_trait_selection::traits::query::type_op::{TypeOp, TypeOpOutput};
 use tracing::{debug, instrument, trace};
@@ -42,7 +42,6 @@ use tracing::{debug, instrument, trace};
 use crate::borrow_set::BorrowSet;
 use crate::constraints::{OutlivesConstraint, OutlivesConstraintSet};
 use crate::diagnostics::UniverseInfo;
-use crate::member_constraints::MemberConstraintSet;
 use crate::polonius::legacy::{PoloniusFacts, PoloniusLocationTable};
 use crate::polonius::{PoloniusContext, PoloniusLivenessContext};
 use crate::region_infer::TypeTest;
@@ -67,12 +66,11 @@ macro_rules! span_mirbug {
     })
 }
 
-mod canonical;
+pub(crate) mod canonical;
 mod constraint_conversion;
 pub(crate) mod free_region_relations;
 mod input_output;
 pub(crate) mod liveness;
-mod opaque_types;
 mod relate_tys;
 
 /// Type checks the given `mir` in the context of the inference
@@ -114,7 +112,6 @@ pub(crate) fn type_check<'tcx>(
         placeholder_index_to_region: IndexVec::default(),
         liveness_constraints: LivenessValues::with_specific_points(Rc::clone(&location_map)),
         outlives_constraints: OutlivesConstraintSet::default(),
-        member_constraints: MemberConstraintSet::default(),
         type_tests: Vec::default(),
         universe_causes: FxIndexMap::default(),
     };
@@ -124,7 +121,7 @@ pub(crate) fn type_check<'tcx>(
         region_bound_pairs,
         normalized_inputs_and_output,
         known_type_outlives_obligations,
-    } = free_region_relations::create(infcx, infcx.param_env, universal_regions, &mut constraints);
+    } = free_region_relations::create(infcx, universal_regions, &mut constraints);
 
     let pre_obligations = infcx.take_registered_region_obligations();
     assert!(
@@ -170,9 +167,6 @@ pub(crate) fn type_check<'tcx>(
 
     liveness::generate(&mut typeck, &location_map, move_data);
 
-    let opaque_type_values =
-        opaque_types::take_opaques_and_register_member_constraints(&mut typeck);
-
     // We're done with typeck, we can finalize the polonius liveness context for region inference.
     let polonius_context = typeck.polonius_liveness.take().map(|liveness_context| {
         PoloniusContext::create_from_liveness(
@@ -187,7 +181,6 @@ pub(crate) fn type_check<'tcx>(
     if let Some(guar) = universal_region_relations.universal_regions.encountered_re_error() {
         debug!("encountered an error region; removing constraints!");
         constraints.outlives_constraints = Default::default();
-        constraints.member_constraints = Default::default();
         constraints.type_tests = Default::default();
         root_cx.set_tainted_by_errors(guar);
         infcx.set_tainted_by_errors(guar);
@@ -196,7 +189,8 @@ pub(crate) fn type_check<'tcx>(
     MirTypeckResults {
         constraints,
         universal_region_relations,
-        opaque_type_values,
+        region_bound_pairs,
+        known_type_outlives_obligations,
         polonius_context,
     }
 }
@@ -245,7 +239,8 @@ struct TypeChecker<'a, 'tcx> {
 pub(crate) struct MirTypeckResults<'tcx> {
     pub(crate) constraints: MirTypeckRegionConstraints<'tcx>,
     pub(crate) universal_region_relations: Frozen<UniversalRegionRelations<'tcx>>,
-    pub(crate) opaque_type_values: FxIndexMap<OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>>,
+    pub(crate) region_bound_pairs: Frozen<RegionBoundPairs<'tcx>>,
+    pub(crate) known_type_outlives_obligations: Frozen<Vec<ty::PolyTypeOutlivesPredicate<'tcx>>>,
     pub(crate) polonius_context: Option<PoloniusContext>,
 }
 
@@ -277,8 +272,6 @@ pub(crate) struct MirTypeckRegionConstraints<'tcx> {
 
     pub(crate) outlives_constraints: OutlivesConstraintSet<'tcx>,
 
-    pub(crate) member_constraints: MemberConstraintSet<'tcx, RegionVid>,
-
     pub(crate) universe_causes: FxIndexMap<ty::UniverseIndex, UniverseInfo<'tcx>>,
 
     pub(crate) type_tests: Vec<TypeTest<'tcx>>,
@@ -287,7 +280,7 @@ pub(crate) struct MirTypeckRegionConstraints<'tcx> {
 impl<'tcx> MirTypeckRegionConstraints<'tcx> {
     /// Creates a `Region` for a given `PlaceholderRegion`, or returns the
     /// region that corresponds to a previously created one.
-    fn placeholder_region(
+    pub(crate) fn placeholder_region(
         &mut self,
         infcx: &InferCtxt<'tcx>,
         placeholder: ty::PlaceholderRegion,
@@ -380,14 +373,6 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         self.body
     }
 
-    fn to_region_vid(&mut self, r: ty::Region<'tcx>) -> RegionVid {
-        if let ty::RePlaceholder(placeholder) = r.kind() {
-            self.constraints.placeholder_region(self.infcx, placeholder).as_var()
-        } else {
-            self.universal_regions.to_region_vid(r)
-        }
-    }
-
     fn unsized_feature_enabled(&self) -> bool {
         self.tcx().features().unsized_fn_params()
     }
@@ -424,7 +409,6 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             self.infcx,
             self.universal_regions,
             self.region_bound_pairs,
-            self.infcx.param_env,
             self.known_type_outlives_obligations,
             locations,
             locations.span(self.body),
@@ -1471,68 +1455,79 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                     }
                     CastKind::PtrToPtr => {
                         let ty_from = op.ty(self.body, tcx);
-                        let cast_ty_from = CastTy::from_ty(ty_from);
-                        let cast_ty_to = CastTy::from_ty(*ty);
-                        match (cast_ty_from, cast_ty_to) {
-                            (Some(CastTy::Ptr(src)), Some(CastTy::Ptr(dst))) => {
-                                let src_tail = self.struct_tail(src.ty, location);
-                                let dst_tail = self.struct_tail(dst.ty, location);
-
-                                // This checks (lifetime part of) vtable validity for pointer casts,
-                                // which is irrelevant when there are aren't principal traits on
-                                // both sides (aka only auto traits).
-                                //
-                                // Note that other checks (such as denying `dyn Send` -> `dyn
-                                // Debug`) are in `rustc_hir_typeck`.
-                                if let ty::Dynamic(src_tty, _src_lt, ty::Dyn) = *src_tail.kind()
-                                    && let ty::Dynamic(dst_tty, dst_lt, ty::Dyn) = *dst_tail.kind()
-                                    && src_tty.principal().is_some()
-                                    && dst_tty.principal().is_some()
-                                {
-                                    // Remove auto traits.
-                                    // Auto trait checks are handled in `rustc_hir_typeck` as FCW.
-                                    let src_obj = Ty::new_dynamic(
-                                        tcx,
-                                        tcx.mk_poly_existential_predicates(
-                                            &src_tty.without_auto_traits().collect::<Vec<_>>(),
-                                        ),
-                                        // FIXME: Once we disallow casting `*const dyn Trait + 'short`
-                                        // to `*const dyn Trait + 'long`, then this can just be `src_lt`.
-                                        dst_lt,
-                                        ty::Dyn,
-                                    );
-                                    let dst_obj = Ty::new_dynamic(
-                                        tcx,
-                                        tcx.mk_poly_existential_predicates(
-                                            &dst_tty.without_auto_traits().collect::<Vec<_>>(),
-                                        ),
-                                        dst_lt,
-                                        ty::Dyn,
-                                    );
-
-                                    debug!(?src_tty, ?dst_tty, ?src_obj, ?dst_obj);
-
-                                    self.sub_types(
-                                        src_obj,
-                                        dst_obj,
-                                        location.to_locations(),
-                                        ConstraintCategory::Cast {
-                                            is_implicit_coercion: false,
-                                            unsize_to: None,
-                                        },
-                                    )
-                                    .unwrap();
-                                }
-                            }
-                            _ => {
-                                span_mirbug!(
-                                    self,
-                                    rvalue,
-                                    "Invalid PtrToPtr cast {:?} -> {:?}",
-                                    ty_from,
-                                    ty
-                                )
-                            }
+                        let Some(CastTy::Ptr(src)) = CastTy::from_ty(ty_from) else {
+                            unreachable!();
+                        };
+                        let Some(CastTy::Ptr(dst)) = CastTy::from_ty(*ty) else {
+                            unreachable!();
+                        };
+
+                        if self.infcx.type_is_sized_modulo_regions(self.infcx.param_env, dst.ty) {
+                            // Wide to thin ptr cast. This may even occur in an env with
+                            // impossible predicates, such as `where dyn Trait: Sized`.
+                            // In this case, we don't want to fall into the case below,
+                            // since the types may not actually be equatable, but it's
+                            // fine to perform this operation in an impossible env.
+                            let trait_ref = ty::TraitRef::new(
+                                tcx,
+                                tcx.require_lang_item(LangItem::Sized, self.last_span),
+                                [dst.ty],
+                            );
+                            self.prove_trait_ref(
+                                trait_ref,
+                                location.to_locations(),
+                                ConstraintCategory::Cast {
+                                    is_implicit_coercion: true,
+                                    unsize_to: None,
+                                },
+                            );
+                        } else if let ty::Dynamic(src_tty, _src_lt, ty::Dyn) =
+                            *self.struct_tail(src.ty, location).kind()
+                            && let ty::Dynamic(dst_tty, dst_lt, ty::Dyn) =
+                                *self.struct_tail(dst.ty, location).kind()
+                            && src_tty.principal().is_some()
+                            && dst_tty.principal().is_some()
+                        {
+                            // This checks (lifetime part of) vtable validity for pointer casts,
+                            // which is irrelevant when there are aren't principal traits on
+                            // both sides (aka only auto traits).
+                            //
+                            // Note that other checks (such as denying `dyn Send` -> `dyn
+                            // Debug`) are in `rustc_hir_typeck`.
+
+                            // Remove auto traits.
+                            // Auto trait checks are handled in `rustc_hir_typeck` as FCW.
+                            let src_obj = Ty::new_dynamic(
+                                tcx,
+                                tcx.mk_poly_existential_predicates(
+                                    &src_tty.without_auto_traits().collect::<Vec<_>>(),
+                                ),
+                                // FIXME: Once we disallow casting `*const dyn Trait + 'short`
+                                // to `*const dyn Trait + 'long`, then this can just be `src_lt`.
+                                dst_lt,
+                                ty::Dyn,
+                            );
+                            let dst_obj = Ty::new_dynamic(
+                                tcx,
+                                tcx.mk_poly_existential_predicates(
+                                    &dst_tty.without_auto_traits().collect::<Vec<_>>(),
+                                ),
+                                dst_lt,
+                                ty::Dyn,
+                            );
+
+                            debug!(?src_tty, ?dst_tty, ?src_obj, ?dst_obj);
+
+                            self.sub_types(
+                                src_obj,
+                                dst_obj,
+                                location.to_locations(),
+                                ConstraintCategory::Cast {
+                                    is_implicit_coercion: false,
+                                    unsize_to: None,
+                                },
+                            )
+                            .unwrap();
                         }
                     }
                     CastKind::Transmute => {
@@ -1895,7 +1890,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             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);
+                span_mirbug!(self, term, "call to non-diverging function {:?} w/o dest", sig);
             }
         } else {
             let dest_ty = destination.ty(self.body, tcx).ty;
@@ -2474,12 +2469,12 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         args: GenericArgsRef<'tcx>,
         locations: Locations,
     ) -> ty::InstantiatedPredicates<'tcx> {
+        let root_def_id = self.root_cx.root_def_id();
         if let Some(closure_requirements) = &self.root_cx.closure_requirements(def_id) {
             constraint_conversion::ConstraintConversion::new(
                 self.infcx,
                 self.universal_regions,
                 self.region_bound_pairs,
-                self.infcx.param_env,
                 self.known_type_outlives_obligations,
                 locations,
                 self.body.span,             // irrelevant; will be overridden.
@@ -2489,9 +2484,8 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             .apply_closure_requirements(closure_requirements, def_id, args);
         }
 
-        // Now equate closure args to regions inherited from `typeck_root_def_id`. Fixes #98589.
-        let typeck_root_def_id = tcx.typeck_root_def_id(self.body.source.def_id());
-        let typeck_root_args = ty::GenericArgs::identity_for_item(tcx, typeck_root_def_id);
+        // Now equate closure args to regions inherited from `root_def_id`. Fixes #98589.
+        let typeck_root_args = ty::GenericArgs::identity_for_item(tcx, root_def_id);
 
         let parent_args = match tcx.def_kind(def_id) {
             // We don't want to dispatch on 3 different kind of closures here, so take
@@ -2566,17 +2560,14 @@ impl<'tcx> TypeOp<'tcx> for InstantiateOpaqueType<'tcx> {
     fn fully_perform(
         mut self,
         infcx: &InferCtxt<'tcx>,
+        root_def_id: LocalDefId,
         span: Span,
     ) -> Result<TypeOpOutput<'tcx, Self>, ErrorGuaranteed> {
-        let (mut output, region_constraints) = scrape_region_constraints(
-            infcx,
-            |ocx| {
+        let (mut output, region_constraints) =
+            scrape_region_constraints(infcx, root_def_id, "InstantiateOpaqueType", span, |ocx| {
                 ocx.register_obligations(self.obligations.clone());
                 Ok(())
-            },
-            "InstantiateOpaqueType",
-            span,
-        )?;
+            })?;
         self.region_constraints = Some(region_constraints);
         output.error_info = Some(self);
         Ok(output)
diff --git a/compiler/rustc_borrowck/src/type_check/opaque_types.rs b/compiler/rustc_borrowck/src/type_check/opaque_types.rs
deleted file mode 100644
index 5a422483eef..00000000000
--- a/compiler/rustc_borrowck/src/type_check/opaque_types.rs
+++ /dev/null
@@ -1,333 +0,0 @@
-use std::iter;
-
-use rustc_data_structures::fx::FxIndexMap;
-use rustc_middle::span_bug;
-use rustc_middle::ty::{
-    self, GenericArgKind, OpaqueHiddenType, OpaqueTypeKey, Ty, TyCtxt, TypeSuperVisitable,
-    TypeVisitable, TypeVisitableExt, TypeVisitor, fold_regions,
-};
-use tracing::{debug, trace};
-
-use super::{MemberConstraintSet, TypeChecker};
-
-/// Once we're done with typechecking the body, we take all the opaque types
-/// defined by this function and add their 'member constraints'.
-pub(super) fn take_opaques_and_register_member_constraints<'tcx>(
-    typeck: &mut TypeChecker<'_, 'tcx>,
-) -> FxIndexMap<OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>> {
-    let infcx = typeck.infcx;
-    // Annoying: to invoke `typeck.to_region_vid`, we need access to
-    // `typeck.constraints`, but we also want to be mutating
-    // `typeck.member_constraints`. For now, just swap out the value
-    // we want and replace at the end.
-    let mut member_constraints = std::mem::take(&mut typeck.constraints.member_constraints);
-    let opaque_types = infcx
-        .take_opaque_types()
-        .into_iter()
-        .map(|(opaque_type_key, hidden_type)| {
-            let hidden_type = infcx.resolve_vars_if_possible(hidden_type);
-            register_member_constraints(
-                typeck,
-                &mut member_constraints,
-                opaque_type_key,
-                hidden_type,
-            );
-            trace!("finalized opaque type {:?} to {:#?}", opaque_type_key, hidden_type.ty.kind());
-            if hidden_type.has_non_region_infer() {
-                span_bug!(hidden_type.span, "could not resolve {:?}", hidden_type.ty);
-            }
-
-            // Convert all regions to nll vars.
-            let (opaque_type_key, hidden_type) =
-                fold_regions(infcx.tcx, (opaque_type_key, hidden_type), |r, _| {
-                    ty::Region::new_var(infcx.tcx, typeck.to_region_vid(r))
-                });
-
-            (opaque_type_key, hidden_type)
-        })
-        .collect();
-    assert!(typeck.constraints.member_constraints.is_empty());
-    typeck.constraints.member_constraints = member_constraints;
-    opaque_types
-}
-
-/// Given the map `opaque_types` containing the opaque
-/// `impl Trait` types whose underlying, hidden types are being
-/// inferred, this method adds constraints to the regions
-/// appearing in those underlying hidden types to ensure that they
-/// at least do not refer to random scopes within the current
-/// function. These constraints are not (quite) sufficient to
-/// guarantee that the regions are actually legal values; that
-/// final condition is imposed after region inference is done.
-///
-/// # The Problem
-///
-/// Let's work through an example to explain how it works. Assume
-/// the current function is as follows:
-///
-/// ```text
-/// fn foo<'a, 'b>(..) -> (impl Bar<'a>, impl Bar<'b>)
-/// ```
-///
-/// Here, we have two `impl Trait` types whose values are being
-/// inferred (the `impl Bar<'a>` and the `impl
-/// Bar<'b>`). Conceptually, this is sugar for a setup where we
-/// define underlying opaque types (`Foo1`, `Foo2`) and then, in
-/// the return type of `foo`, we *reference* those definitions:
-///
-/// ```text
-/// type Foo1<'x> = impl Bar<'x>;
-/// type Foo2<'x> = impl Bar<'x>;
-/// fn foo<'a, 'b>(..) -> (Foo1<'a>, Foo2<'b>) { .. }
-///                    //  ^^^^ ^^
-///                    //  |    |
-///                    //  |    args
-///                    //  def_id
-/// ```
-///
-/// As indicating in the comments above, each of those references
-/// is (in the compiler) basically generic parameters (`args`)
-/// applied to the type of a suitable `def_id` (which identifies
-/// `Foo1` or `Foo2`).
-///
-/// Now, at this point in compilation, what we have done is to
-/// replace each of the references (`Foo1<'a>`, `Foo2<'b>`) with
-/// fresh inference variables C1 and C2. We wish to use the values
-/// of these variables to infer the underlying types of `Foo1` and
-/// `Foo2`. That is, this gives rise to higher-order (pattern) unification
-/// constraints like:
-///
-/// ```text
-/// for<'a> (Foo1<'a> = C1)
-/// for<'b> (Foo1<'b> = C2)
-/// ```
-///
-/// For these equation to be satisfiable, the types `C1` and `C2`
-/// can only refer to a limited set of regions. For example, `C1`
-/// can only refer to `'static` and `'a`, and `C2` can only refer
-/// to `'static` and `'b`. The job of this function is to impose that
-/// constraint.
-///
-/// Up to this point, C1 and C2 are basically just random type
-/// inference variables, and hence they may contain arbitrary
-/// regions. In fact, it is fairly likely that they do! Consider
-/// this possible definition of `foo`:
-///
-/// ```text
-/// fn foo<'a, 'b>(x: &'a i32, y: &'b i32) -> (impl Bar<'a>, impl Bar<'b>) {
-///         (&*x, &*y)
-///     }
-/// ```
-///
-/// Here, the values for the concrete types of the two impl
-/// traits will include inference variables:
-///
-/// ```text
-/// &'0 i32
-/// &'1 i32
-/// ```
-///
-/// Ordinarily, the subtyping rules would ensure that these are
-/// sufficiently large. But since `impl Bar<'a>` isn't a specific
-/// type per se, we don't get such constraints by default. This
-/// is where this function comes into play. It adds extra
-/// constraints to ensure that all the regions which appear in the
-/// inferred type are regions that could validly appear.
-///
-/// This is actually a bit of a tricky constraint in general. We
-/// want to say that each variable (e.g., `'0`) can only take on
-/// values that were supplied as arguments to the opaque type
-/// (e.g., `'a` for `Foo1<'a>`) or `'static`, which is always in
-/// scope. We don't have a constraint quite of this kind in the current
-/// region checker.
-///
-/// # The Solution
-///
-/// We generally prefer to make `<=` constraints, since they
-/// integrate best into the region solver. To do that, we find the
-/// "minimum" of all the arguments that appear in the args: that
-/// is, some region which is less than all the others. In the case
-/// of `Foo1<'a>`, that would be `'a` (it's the only choice, after
-/// all). Then we apply that as a least bound to the variables
-/// (e.g., `'a <= '0`).
-///
-/// In some cases, there is no minimum. Consider this example:
-///
-/// ```text
-/// fn baz<'a, 'b>() -> impl Trait<'a, 'b> { ... }
-/// ```
-///
-/// Here we would report a more complex "in constraint", like `'r
-/// in ['a, 'b, 'static]` (where `'r` is some region appearing in
-/// the hidden type).
-///
-/// # Constrain regions, not the hidden concrete type
-///
-/// Note that generating constraints on each region `Rc` is *not*
-/// the same as generating an outlives constraint on `Tc` itself.
-/// For example, if we had a function like this:
-///
-/// ```
-/// # #![feature(type_alias_impl_trait)]
-/// # fn main() {}
-/// # trait Foo<'a> {}
-/// # impl<'a, T> Foo<'a> for (&'a u32, T) {}
-/// fn foo<'a, T>(x: &'a u32, y: T) -> impl Foo<'a> {
-///   (x, y)
-/// }
-///
-/// // Equivalent to:
-/// # mod dummy { use super::*;
-/// type FooReturn<'a, T> = impl Foo<'a>;
-/// #[define_opaque(FooReturn)]
-/// fn foo<'a, T>(x: &'a u32, y: T) -> FooReturn<'a, T> {
-///   (x, y)
-/// }
-/// # }
-/// ```
-///
-/// then the hidden type `Tc` would be `(&'0 u32, T)` (where `'0`
-/// is an inference variable). If we generated a constraint that
-/// `Tc: 'a`, then this would incorrectly require that `T: 'a` --
-/// but this is not necessary, because the opaque type we
-/// create will be allowed to reference `T`. So we only generate a
-/// constraint that `'0: 'a`.
-fn register_member_constraints<'tcx>(
-    typeck: &mut TypeChecker<'_, 'tcx>,
-    member_constraints: &mut MemberConstraintSet<'tcx, ty::RegionVid>,
-    opaque_type_key: OpaqueTypeKey<'tcx>,
-    OpaqueHiddenType { span, ty: hidden_ty }: OpaqueHiddenType<'tcx>,
-) {
-    let tcx = typeck.tcx();
-    let hidden_ty = typeck.infcx.resolve_vars_if_possible(hidden_ty);
-    debug!(?hidden_ty);
-
-    let variances = tcx.variances_of(opaque_type_key.def_id);
-    debug!(?variances);
-
-    // For a case like `impl Foo<'a, 'b>`, we would generate a constraint
-    // `'r in ['a, 'b, 'static]` for each region `'r` that appears in the
-    // hidden type (i.e., it must be equal to `'a`, `'b`, or `'static`).
-    //
-    // `conflict1` and `conflict2` are the two region bounds that we
-    // detected which were unrelated. They are used for diagnostics.
-
-    // Create the set of choice regions: each region in the hidden
-    // type can be equal to any of the region parameters of the
-    // opaque type definition.
-    let fr_static = typeck.universal_regions.fr_static;
-    let choice_regions: Vec<_> = opaque_type_key
-        .args
-        .iter()
-        .enumerate()
-        .filter(|(i, _)| variances[*i] == ty::Invariant)
-        .filter_map(|(_, arg)| match arg.kind() {
-            GenericArgKind::Lifetime(r) => Some(typeck.to_region_vid(r)),
-            GenericArgKind::Type(_) | GenericArgKind::Const(_) => None,
-        })
-        .chain(iter::once(fr_static))
-        .collect();
-
-    // FIXME(#42940): This should use the `FreeRegionsVisitor`, but that's
-    // not currently sound until we have existential regions.
-    hidden_ty.visit_with(&mut ConstrainOpaqueTypeRegionVisitor {
-        tcx,
-        op: |r| {
-            member_constraints.add_member_constraint(
-                opaque_type_key,
-                hidden_ty,
-                span,
-                typeck.to_region_vid(r),
-                &choice_regions,
-            )
-        },
-    });
-}
-
-/// Visitor that requires that (almost) all regions in the type visited outlive
-/// `least_region`. We cannot use `push_outlives_components` because regions in
-/// closure signatures are not included in their outlives components. We need to
-/// ensure all regions outlive the given bound so that we don't end up with,
-/// say, `ReVar` appearing in a return type and causing ICEs when other
-/// functions end up with region constraints involving regions from other
-/// functions.
-///
-/// We also cannot use `for_each_free_region` because for closures it includes
-/// the regions parameters from the enclosing item.
-///
-/// We ignore any type parameters because impl trait values are assumed to
-/// capture all the in-scope type parameters.
-struct ConstrainOpaqueTypeRegionVisitor<'tcx, OP: FnMut(ty::Region<'tcx>)> {
-    tcx: TyCtxt<'tcx>,
-    op: OP,
-}
-
-impl<'tcx, OP> TypeVisitor<TyCtxt<'tcx>> for ConstrainOpaqueTypeRegionVisitor<'tcx, OP>
-where
-    OP: FnMut(ty::Region<'tcx>),
-{
-    fn visit_region(&mut self, r: ty::Region<'tcx>) {
-        match r.kind() {
-            // ignore bound regions, keep visiting
-            ty::ReBound(_, _) => {}
-            _ => (self.op)(r),
-        }
-    }
-
-    fn visit_ty(&mut self, ty: Ty<'tcx>) {
-        // We're only interested in types involving regions
-        if !ty.flags().intersects(ty::TypeFlags::HAS_FREE_REGIONS) {
-            return;
-        }
-
-        match *ty.kind() {
-            ty::Closure(_, args) => {
-                // Skip lifetime parameters of the enclosing item(s)
-
-                for upvar in args.as_closure().upvar_tys() {
-                    upvar.visit_with(self);
-                }
-                args.as_closure().sig_as_fn_ptr_ty().visit_with(self);
-            }
-
-            ty::CoroutineClosure(_, args) => {
-                // Skip lifetime parameters of the enclosing item(s)
-
-                for upvar in args.as_coroutine_closure().upvar_tys() {
-                    upvar.visit_with(self);
-                }
-
-                args.as_coroutine_closure().signature_parts_ty().visit_with(self);
-            }
-
-            ty::Coroutine(_, args) => {
-                // Skip lifetime parameters of the enclosing item(s)
-                // Also skip the witness type, because that has no free regions.
-
-                for upvar in args.as_coroutine().upvar_tys() {
-                    upvar.visit_with(self);
-                }
-                args.as_coroutine().return_ty().visit_with(self);
-                args.as_coroutine().yield_ty().visit_with(self);
-                args.as_coroutine().resume_ty().visit_with(self);
-            }
-
-            ty::Alias(kind, ty::AliasTy { def_id, args, .. })
-                if let Some(variances) = self.tcx.opt_alias_variances(kind, def_id) =>
-            {
-                // Skip lifetime parameters that are not captured, since they do
-                // not need member constraints registered for them; we'll erase
-                // them (and hopefully in the future replace them with placeholders).
-                for (v, s) in std::iter::zip(variances, args.iter()) {
-                    if *v != ty::Bivariant {
-                        s.visit_with(self);
-                    }
-                }
-            }
-
-            _ => {
-                ty.super_visit_with(self);
-            }
-        }
-    }
-}
diff --git a/compiler/rustc_borrowck/src/type_check/relate_tys.rs b/compiler/rustc_borrowck/src/type_check/relate_tys.rs
index 84ca9bad2c1..7ac2dff12f7 100644
--- a/compiler/rustc_borrowck/src/type_check/relate_tys.rs
+++ b/compiler/rustc_borrowck/src/type_check/relate_tys.rs
@@ -124,8 +124,13 @@ impl<'a, 'b, 'tcx> NllTypeRelating<'a, 'b, 'tcx> {
         // by using `ty_vid rel B` and then finally and end by equating `ty_vid` to
         // the opaque.
         let mut enable_subtyping = |ty, opaque_is_expected| {
-            let ty_vid = infcx.next_ty_var_id_in_universe(self.span(), ty::UniverseIndex::ROOT);
-
+            // We create the fresh inference variable in the highest universe.
+            // In theory we could limit it to the highest universe in the args of
+            // the opaque but that isn't really worth the effort.
+            //
+            // We'll make sure that the opaque type can actually name everything
+            // in its hidden type later on.
+            let ty_vid = infcx.next_ty_vid(self.span());
             let variance = if opaque_is_expected {
                 self.ambient_variance
             } else {
diff --git a/compiler/rustc_builtin_macros/src/cfg_accessible.rs b/compiler/rustc_builtin_macros/src/cfg_accessible.rs
index f7d8f4aa783..48d80004cdd 100644
--- a/compiler/rustc_builtin_macros/src/cfg_accessible.rs
+++ b/compiler/rustc_builtin_macros/src/cfg_accessible.rs
@@ -1,9 +1,9 @@
 //! Implementation of the `#[cfg_accessible(path)]` attribute macro.
 
 use rustc_ast as ast;
+use rustc_attr_parsing::validate_attr;
 use rustc_expand::base::{Annotatable, ExpandResult, ExtCtxt, Indeterminate, MultiItemModifier};
 use rustc_feature::AttributeTemplate;
-use rustc_parse::validate_attr;
 use rustc_span::{Span, sym};
 
 use crate::errors;
diff --git a/compiler/rustc_builtin_macros/src/derive.rs b/compiler/rustc_builtin_macros/src/derive.rs
index a33eca43de5..09d827b0635 100644
--- a/compiler/rustc_builtin_macros/src/derive.rs
+++ b/compiler/rustc_builtin_macros/src/derive.rs
@@ -1,10 +1,10 @@
 use rustc_ast as ast;
 use rustc_ast::{GenericParamKind, ItemKind, MetaItemInner, MetaItemKind, StmtKind};
+use rustc_attr_parsing::validate_attr;
 use rustc_expand::base::{
     Annotatable, DeriveResolution, ExpandResult, ExtCtxt, Indeterminate, MultiItemModifier,
 };
 use rustc_feature::AttributeTemplate;
-use rustc_parse::validate_attr;
 use rustc_session::Session;
 use rustc_span::{ErrorGuaranteed, Ident, Span, sym};
 
diff --git a/compiler/rustc_builtin_macros/src/deriving/from.rs b/compiler/rustc_builtin_macros/src/deriving/from.rs
index ef0e6ca324a..ab25de7c917 100644
--- a/compiler/rustc_builtin_macros/src/deriving/from.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/from.rs
@@ -27,21 +27,39 @@ pub(crate) fn expand_deriving_from(
         cx.dcx().bug("derive(From) used on something else than an item");
     };
 
-    // #[derive(From)] is currently usable only on structs with exactly one field.
-    let field = if let ItemKind::Struct(_, _, data) = &item.kind
-        && let [field] = data.fields()
-    {
-        Some(field.clone())
-    } else {
-        None
+    let err_span = || {
+        let item_span = item.kind.ident().map(|ident| ident.span).unwrap_or(item.span);
+        MultiSpan::from_spans(vec![span, item_span])
     };
 
-    let from_type = match &field {
-        Some(field) => Ty::AstTy(field.ty.clone()),
-        // We don't have a type to put into From<...> if we don't have a single field, so just put
-        // unit there.
-        None => Ty::Unit,
+    // `#[derive(From)]` is currently usable only on structs with exactly one field.
+    let field = match &item.kind {
+        ItemKind::Struct(_, _, data) => {
+            if let [field] = data.fields() {
+                Ok(field.clone())
+            } else {
+                let guar = cx.dcx().emit_err(errors::DeriveFromWrongFieldCount {
+                    span: err_span(),
+                    multiple_fields: data.fields().len() > 1,
+                });
+                Err(guar)
+            }
+        }
+        ItemKind::Enum(_, _, _) | ItemKind::Union(_, _, _) => {
+            let guar = cx.dcx().emit_err(errors::DeriveFromWrongTarget {
+                span: err_span(),
+                kind: &format!("{} {}", item.kind.article(), item.kind.descr()),
+            });
+            Err(guar)
+        }
+        _ => cx.dcx().bug("Invalid derive(From) ADT input"),
     };
+
+    let from_type = Ty::AstTy(match field {
+        Ok(ref field) => field.ty.clone(),
+        Err(guar) => cx.ty(span, ast::TyKind::Err(guar)),
+    });
+
     let path =
         Path::new_(pathvec_std!(convert::From), vec![Box::new(from_type.clone())], PathKind::Std);
 
@@ -71,34 +89,17 @@ pub(crate) fn expand_deriving_from(
             attributes: thin_vec![cx.attr_word(sym::inline, span)],
             fieldless_variants_strategy: FieldlessVariantsStrategy::Default,
             combine_substructure: combine_substructure(Box::new(|cx, span, substructure| {
-                let Some(field) = &field else {
-                    let item_span = item.kind.ident().map(|ident| ident.span).unwrap_or(item.span);
-                    let err_span = MultiSpan::from_spans(vec![span, item_span]);
-                    let error = match &item.kind {
-                        ItemKind::Struct(_, _, data) => {
-                            cx.dcx().emit_err(errors::DeriveFromWrongFieldCount {
-                                span: err_span,
-                                multiple_fields: data.fields().len() > 1,
-                            })
-                        }
-                        ItemKind::Enum(_, _, _) | ItemKind::Union(_, _, _) => {
-                            cx.dcx().emit_err(errors::DeriveFromWrongTarget {
-                                span: err_span,
-                                kind: &format!("{} {}", item.kind.article(), item.kind.descr()),
-                            })
-                        }
-                        _ => cx.dcx().bug("Invalid derive(From) ADT input"),
-                    };
-
-                    return BlockOrExpr::new_expr(DummyResult::raw_expr(span, Some(error)));
+                let field = match field {
+                    Ok(ref field) => field,
+                    Err(guar) => {
+                        return BlockOrExpr::new_expr(DummyResult::raw_expr(span, Some(guar)));
+                    }
                 };
 
                 let self_kw = Ident::new(kw::SelfUpper, span);
                 let expr: Box<ast::Expr> = match substructure.fields {
                     SubstructureFields::StaticStruct(variant, _) => match variant {
-                        // Self {
-                        //     field: value
-                        // }
+                        // Self { field: value }
                         VariantData::Struct { .. } => cx.expr_struct_ident(
                             span,
                             self_kw,
diff --git a/compiler/rustc_builtin_macros/src/format.rs b/compiler/rustc_builtin_macros/src/format.rs
index ec613b7b710..6415e55e0b0 100644
--- a/compiler/rustc_builtin_macros/src/format.rs
+++ b/compiler/rustc_builtin_macros/src/format.rs
@@ -10,11 +10,12 @@ use rustc_ast::{
 };
 use rustc_data_structures::fx::FxHashSet;
 use rustc_errors::{
-    Applicability, Diag, MultiSpan, PResult, SingleLabelManySpans, listify, pluralize,
+    Applicability, BufferedEarlyLint, Diag, MultiSpan, PResult, SingleLabelManySpans, listify,
+    pluralize,
 };
 use rustc_expand::base::*;
 use rustc_lint_defs::builtin::NAMED_ARGUMENTS_USED_POSITIONALLY;
-use rustc_lint_defs::{BufferedEarlyLint, BuiltinLintDiag, LintId};
+use rustc_lint_defs::{BuiltinLintDiag, LintId};
 use rustc_parse::exp;
 use rustc_parse_format as parse;
 use rustc_span::{BytePos, ErrorGuaranteed, Ident, InnerSpan, Span, Symbol};
@@ -595,7 +596,8 @@ fn make_format_args(
                     named_arg_sp: arg_name.span,
                     named_arg_name: arg_name.name.to_string(),
                     is_formatting_arg: matches!(used_as, Width | Precision),
-                },
+                }
+                .into(),
             });
         }
     }
diff --git a/compiler/rustc_builtin_macros/src/lib.rs b/compiler/rustc_builtin_macros/src/lib.rs
index 86a4927f390..1bcea95fbb7 100644
--- a/compiler/rustc_builtin_macros/src/lib.rs
+++ b/compiler/rustc_builtin_macros/src/lib.rs
@@ -8,7 +8,6 @@
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
 #![doc(rust_logo)]
 #![feature(assert_matches)]
-#![feature(autodiff)]
 #![feature(box_patterns)]
 #![feature(decl_macro)]
 #![feature(if_let_guard)]
diff --git a/compiler/rustc_builtin_macros/src/test_harness.rs b/compiler/rustc_builtin_macros/src/test_harness.rs
index e803f3be82b..a9d91f77560 100644
--- a/compiler/rustc_builtin_macros/src/test_harness.rs
+++ b/compiler/rustc_builtin_macros/src/test_harness.rs
@@ -141,7 +141,7 @@ impl<'a> MutVisitor for TestHarnessGenerator<'a> {
         if let ast::ItemKind::Mod(
             _,
             _,
-            ModKind::Loaded(.., ast::ModSpans { inner_span: span, .. }, _),
+            ModKind::Loaded(.., ast::ModSpans { inner_span: span, .. }),
         ) = item.kind
         {
             let prev_tests = mem::take(&mut self.tests);
diff --git a/compiler/rustc_builtin_macros/src/util.rs b/compiler/rustc_builtin_macros/src/util.rs
index f00c170e485..3a4585d5be9 100644
--- a/compiler/rustc_builtin_macros/src/util.rs
+++ b/compiler/rustc_builtin_macros/src/util.rs
@@ -1,12 +1,13 @@
 use rustc_ast::tokenstream::TokenStream;
 use rustc_ast::{self as ast, AttrStyle, Attribute, MetaItem, attr, token};
+use rustc_attr_parsing::validate_attr;
 use rustc_errors::{Applicability, Diag, ErrorGuaranteed};
 use rustc_expand::base::{Annotatable, ExpandResult, ExtCtxt};
 use rustc_expand::expand::AstFragment;
 use rustc_feature::AttributeTemplate;
 use rustc_lint_defs::BuiltinLintDiag;
 use rustc_lint_defs::builtin::DUPLICATE_MACRO_ATTRIBUTES;
-use rustc_parse::{exp, parser, validate_attr};
+use rustc_parse::{exp, parser};
 use rustc_session::errors::report_lit_error;
 use rustc_span::{BytePos, Span, Symbol};
 
diff --git a/compiler/rustc_codegen_llvm/src/abi.rs b/compiler/rustc_codegen_llvm/src/abi.rs
index 043123fcab2..399f8b6e762 100644
--- a/compiler/rustc_codegen_llvm/src/abi.rs
+++ b/compiler/rustc_codegen_llvm/src/abi.rs
@@ -42,12 +42,13 @@ trait ArgAttributesExt {
 const ABI_AFFECTING_ATTRIBUTES: [(ArgAttribute, llvm::AttributeKind); 1] =
     [(ArgAttribute::InReg, llvm::AttributeKind::InReg)];
 
-const OPTIMIZATION_ATTRIBUTES: [(ArgAttribute, llvm::AttributeKind); 5] = [
+const OPTIMIZATION_ATTRIBUTES: [(ArgAttribute, llvm::AttributeKind); 6] = [
     (ArgAttribute::NoAlias, llvm::AttributeKind::NoAlias),
     (ArgAttribute::NoCapture, llvm::AttributeKind::NoCapture),
     (ArgAttribute::NonNull, llvm::AttributeKind::NonNull),
     (ArgAttribute::ReadOnly, llvm::AttributeKind::ReadOnly),
     (ArgAttribute::NoUndef, llvm::AttributeKind::NoUndef),
+    (ArgAttribute::CapturesReadOnly, llvm::AttributeKind::CapturesReadOnly),
 ];
 
 fn get_attrs<'ll>(this: &ArgAttributes, cx: &CodegenCx<'ll, '_>) -> SmallVec<[&'ll Attribute; 8]> {
@@ -83,6 +84,10 @@ fn get_attrs<'ll>(this: &ArgAttributes, cx: &CodegenCx<'ll, '_>) -> SmallVec<[&'
         }
         for (attr, llattr) in OPTIMIZATION_ATTRIBUTES {
             if regular.contains(attr) {
+                // captures(address, read_provenance) is only available since LLVM 21.
+                if attr == ArgAttribute::CapturesReadOnly && llvm_util::get_version() < (21, 0, 0) {
+                    continue;
+                }
                 attrs.push(llattr.create_attr(cx.llcx));
             }
         }
diff --git a/compiler/rustc_codegen_llvm/src/allocator.rs b/compiler/rustc_codegen_llvm/src/allocator.rs
index 23610aa856c..df3e49279d9 100644
--- a/compiler/rustc_codegen_llvm/src/allocator.rs
+++ b/compiler/rustc_codegen_llvm/src/allocator.rs
@@ -12,7 +12,7 @@ use smallvec::SmallVec;
 
 use crate::builder::SBuilder;
 use crate::declare::declare_simple_fn;
-use crate::llvm::{self, False, True, Type, Value};
+use crate::llvm::{self, FALSE, TRUE, Type, Value};
 use crate::{SimpleCx, attributes, debuginfo, llvm_util};
 
 pub(crate) unsafe fn codegen(
@@ -80,7 +80,7 @@ pub(crate) unsafe fn codegen(
             &cx,
             &mangle_internal_symbol(tcx, OomStrategy::SYMBOL),
             &i8,
-            &llvm::LLVMConstInt(i8, tcx.sess.opts.unstable_opts.oom.should_panic() as u64, False),
+            &llvm::LLVMConstInt(i8, tcx.sess.opts.unstable_opts.oom.should_panic() as u64, FALSE),
         );
 
         // __rust_no_alloc_shim_is_unstable_v2
@@ -201,7 +201,7 @@ fn create_wrapper_function(
             .map(|(i, _)| llvm::get_param(llfn, i as c_uint))
             .collect::<Vec<_>>();
         let ret = bx.call(ty, callee, &args, None);
-        llvm::LLVMSetTailCall(ret, True);
+        llvm::LLVMSetTailCall(ret, TRUE);
         if output.is_some() {
             bx.ret(ret);
         } else {
diff --git a/compiler/rustc_codegen_llvm/src/asm.rs b/compiler/rustc_codegen_llvm/src/asm.rs
index a643a91141e..38c1d3b53e8 100644
--- a/compiler/rustc_codegen_llvm/src/asm.rs
+++ b/compiler/rustc_codegen_llvm/src/asm.rs
@@ -16,6 +16,7 @@ use tracing::debug;
 use crate::builder::Builder;
 use crate::common::Funclet;
 use crate::context::CodegenCx;
+use crate::llvm::ToLlvmBool;
 use crate::type_::Type;
 use crate::type_of::LayoutLlvmExt;
 use crate::value::Value;
@@ -470,10 +471,6 @@ pub(crate) fn inline_asm_call<'ll>(
     dest: Option<&'ll llvm::BasicBlock>,
     catch_funclet: Option<(&'ll llvm::BasicBlock, Option<&Funclet<'ll>>)>,
 ) -> Option<&'ll Value> {
-    let volatile = if volatile { llvm::True } else { llvm::False };
-    let alignstack = if alignstack { llvm::True } else { llvm::False };
-    let can_throw = if unwind { llvm::True } else { llvm::False };
-
     let argtys = inputs
         .iter()
         .map(|v| {
@@ -500,10 +497,10 @@ pub(crate) fn inline_asm_call<'ll>(
             asm.len(),
             cons.as_ptr(),
             cons.len(),
-            volatile,
-            alignstack,
+            volatile.to_llvm_bool(),
+            alignstack.to_llvm_bool(),
             dia,
-            can_throw,
+            unwind.to_llvm_bool(),
         )
     };
 
diff --git a/compiler/rustc_codegen_llvm/src/attributes.rs b/compiler/rustc_codegen_llvm/src/attributes.rs
index a6daacd95ef..5affb26483a 100644
--- a/compiler/rustc_codegen_llvm/src/attributes.rs
+++ b/compiler/rustc_codegen_llvm/src/attributes.rs
@@ -420,6 +420,16 @@ pub(crate) fn llfn_attrs_from_instance<'ll, 'tcx>(
         || codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::ALLOCATOR_ZEROED)
     {
         to_add.push(create_alloc_family_attr(cx.llcx));
+        if let Some(zv) =
+            cx.tcx.get_attr(instance.def_id(), rustc_span::sym::rustc_allocator_zeroed_variant)
+            && let Some(name) = zv.value_str()
+        {
+            to_add.push(llvm::CreateAttrStringValue(
+                cx.llcx,
+                "alloc-variant-zeroed",
+                &mangle_internal_symbol(cx.tcx, name.as_str()),
+            ));
+        }
         // apply to argument place instead of function
         let alloc_align = AttributeKind::AllocAlign.create_attr(cx.llcx);
         attributes::apply_to_llfn(llfn, AttributePlace::Argument(1), &[alloc_align]);
@@ -497,7 +507,7 @@ pub(crate) fn llfn_attrs_from_instance<'ll, 'tcx>(
             to_add.push(llvm::CreateAttrStringValue(cx.llcx, "wasm-import-module", module));
 
             let name =
-                codegen_fn_attrs.link_name.unwrap_or_else(|| cx.tcx.item_name(instance.def_id()));
+                codegen_fn_attrs.symbol_name.unwrap_or_else(|| cx.tcx.item_name(instance.def_id()));
             let name = name.as_str();
             to_add.push(llvm::CreateAttrStringValue(cx.llcx, "wasm-import-name", name));
         }
diff --git a/compiler/rustc_codegen_llvm/src/back/write.rs b/compiler/rustc_codegen_llvm/src/back/write.rs
index 62998003ca1..7c65d667bda 100644
--- a/compiler/rustc_codegen_llvm/src/back/write.rs
+++ b/compiler/rustc_codegen_llvm/src/back/write.rs
@@ -1110,7 +1110,7 @@ fn embed_bitcode(
 
         llvm::set_section(llglobal, bitcode_section_name(cgcx));
         llvm::set_linkage(llglobal, llvm::Linkage::PrivateLinkage);
-        llvm::LLVMSetGlobalConstant(llglobal, llvm::True);
+        llvm::LLVMSetGlobalConstant(llglobal, llvm::TRUE);
 
         let llconst = common::bytes_in_context(llcx, &[]);
         let llglobal = llvm::add_global(llmod, common::val_ty(llconst), c"rustc.embedded.cmdline");
diff --git a/compiler/rustc_codegen_llvm/src/builder.rs b/compiler/rustc_codegen_llvm/src/builder.rs
index 427c75d40e9..37379586d58 100644
--- a/compiler/rustc_codegen_llvm/src/builder.rs
+++ b/compiler/rustc_codegen_llvm/src/builder.rs
@@ -35,7 +35,7 @@ use crate::attributes;
 use crate::common::Funclet;
 use crate::context::{CodegenCx, FullCx, GenericCx, SCx};
 use crate::llvm::{
-    self, AtomicOrdering, AtomicRmwBinOp, BasicBlock, False, GEPNoWrapFlags, Metadata, True,
+    self, AtomicOrdering, AtomicRmwBinOp, BasicBlock, GEPNoWrapFlags, Metadata, TRUE, ToLlvmBool,
 };
 use crate::type_::Type;
 use crate::type_of::LayoutLlvmExt;
@@ -493,8 +493,8 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         unsafe {
             let add = llvm::LLVMBuildAdd(self.llbuilder, a, b, UNNAMED);
             if llvm::LLVMIsAInstruction(add).is_some() {
-                llvm::LLVMSetNUW(add, True);
-                llvm::LLVMSetNSW(add, True);
+                llvm::LLVMSetNUW(add, TRUE);
+                llvm::LLVMSetNSW(add, TRUE);
             }
             add
         }
@@ -503,8 +503,8 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         unsafe {
             let sub = llvm::LLVMBuildSub(self.llbuilder, a, b, UNNAMED);
             if llvm::LLVMIsAInstruction(sub).is_some() {
-                llvm::LLVMSetNUW(sub, True);
-                llvm::LLVMSetNSW(sub, True);
+                llvm::LLVMSetNUW(sub, TRUE);
+                llvm::LLVMSetNSW(sub, TRUE);
             }
             sub
         }
@@ -513,8 +513,8 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         unsafe {
             let mul = llvm::LLVMBuildMul(self.llbuilder, a, b, UNNAMED);
             if llvm::LLVMIsAInstruction(mul).is_some() {
-                llvm::LLVMSetNUW(mul, True);
-                llvm::LLVMSetNSW(mul, True);
+                llvm::LLVMSetNUW(mul, TRUE);
+                llvm::LLVMSetNSW(mul, TRUE);
             }
             mul
         }
@@ -528,7 +528,7 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
             // an instruction, so we need to check before setting the flag.
             // (See also `LLVMBuildNUWNeg` which also needs a check.)
             if llvm::LLVMIsAInstruction(or).is_some() {
-                llvm::LLVMSetIsDisjoint(or, True);
+                llvm::LLVMSetIsDisjoint(or, TRUE);
             }
             or
         }
@@ -629,7 +629,7 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
     fn volatile_load(&mut self, ty: &'ll Type, ptr: &'ll Value) -> &'ll Value {
         unsafe {
             let load = llvm::LLVMBuildLoad2(self.llbuilder, ty, ptr, UNNAMED);
-            llvm::LLVMSetVolatile(load, llvm::True);
+            llvm::LLVMSetVolatile(load, llvm::TRUE);
             load
         }
     }
@@ -717,7 +717,7 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
             let mut const_llval = None;
             let llty = place.layout.llvm_type(self);
             if let Some(global) = llvm::LLVMIsAGlobalVariable(place.val.llval) {
-                if llvm::LLVMIsGlobalConstant(global) == llvm::True {
+                if llvm::LLVMIsGlobalConstant(global).is_true() {
                     if let Some(init) = llvm::LLVMGetInitializer(global) {
                         if self.val_ty(init) == llty {
                             const_llval = Some(init);
@@ -838,7 +838,7 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
                 if flags.contains(MemFlags::UNALIGNED) { 1 } else { align.bytes() as c_uint };
             llvm::LLVMSetAlignment(store, align);
             if flags.contains(MemFlags::VOLATILE) {
-                llvm::LLVMSetVolatile(store, llvm::True);
+                llvm::LLVMSetVolatile(store, llvm::TRUE);
             }
             if flags.contains(MemFlags::NONTEMPORAL) {
                 // Make sure that the current target architectures supports "sane" non-temporal
@@ -956,7 +956,7 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         let trunc = self.trunc(val, dest_ty);
         unsafe {
             if llvm::LLVMIsAInstruction(trunc).is_some() {
-                llvm::LLVMSetNUW(trunc, True);
+                llvm::LLVMSetNUW(trunc, TRUE);
             }
         }
         trunc
@@ -968,7 +968,7 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         let trunc = self.trunc(val, dest_ty);
         unsafe {
             if llvm::LLVMIsAInstruction(trunc).is_some() {
-                llvm::LLVMSetNSW(trunc, True);
+                llvm::LLVMSetNSW(trunc, TRUE);
             }
         }
         trunc
@@ -1067,13 +1067,7 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
 
     fn intcast(&mut self, val: &'ll Value, dest_ty: &'ll Type, is_signed: bool) -> &'ll Value {
         unsafe {
-            llvm::LLVMBuildIntCast2(
-                self.llbuilder,
-                val,
-                dest_ty,
-                if is_signed { True } else { False },
-                UNNAMED,
-            )
+            llvm::LLVMBuildIntCast2(self.llbuilder, val, dest_ty, is_signed.to_llvm_bool(), UNNAMED)
         }
     }
 
@@ -1229,7 +1223,7 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         let ty = self.type_struct(&[self.type_ptr(), self.type_i32()], false);
         let landing_pad = self.landing_pad(ty, pers_fn, 0);
         unsafe {
-            llvm::LLVMSetCleanup(landing_pad, llvm::True);
+            llvm::LLVMSetCleanup(landing_pad, llvm::TRUE);
         }
         (self.extract_value(landing_pad, 0), self.extract_value(landing_pad, 1))
     }
@@ -1317,7 +1311,6 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         failure_order: rustc_middle::ty::AtomicOrdering,
         weak: bool,
     ) -> (&'ll Value, &'ll Value) {
-        let weak = if weak { llvm::True } else { llvm::False };
         unsafe {
             let value = llvm::LLVMBuildAtomicCmpXchg(
                 self.llbuilder,
@@ -1326,9 +1319,9 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
                 src,
                 AtomicOrdering::from_generic(order),
                 AtomicOrdering::from_generic(failure_order),
-                llvm::False, // SingleThreaded
+                llvm::FALSE, // SingleThreaded
             );
-            llvm::LLVMSetWeak(value, weak);
+            llvm::LLVMSetWeak(value, weak.to_llvm_bool());
             let val = self.extract_value(value, 0);
             let success = self.extract_value(value, 1);
             (val, success)
@@ -1353,7 +1346,7 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
                 dst,
                 src,
                 AtomicOrdering::from_generic(order),
-                llvm::False, // SingleThreaded
+                llvm::FALSE, // SingleThreaded
             )
         };
         if ret_ptr && self.val_ty(res) != self.type_ptr() {
@@ -1368,14 +1361,14 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         scope: SynchronizationScope,
     ) {
         let single_threaded = match scope {
-            SynchronizationScope::SingleThread => llvm::True,
-            SynchronizationScope::CrossThread => llvm::False,
+            SynchronizationScope::SingleThread => true,
+            SynchronizationScope::CrossThread => false,
         };
         unsafe {
             llvm::LLVMBuildFence(
                 self.llbuilder,
                 AtomicOrdering::from_generic(order),
-                single_threaded,
+                single_threaded.to_llvm_bool(),
                 UNNAMED,
             );
         }
diff --git a/compiler/rustc_codegen_llvm/src/builder/autodiff.rs b/compiler/rustc_codegen_llvm/src/builder/autodiff.rs
index e2df3265f6f..6ddf53cdc87 100644
--- a/compiler/rustc_codegen_llvm/src/builder/autodiff.rs
+++ b/compiler/rustc_codegen_llvm/src/builder/autodiff.rs
@@ -11,7 +11,7 @@ use crate::builder::{Builder, PlaceRef, UNNAMED};
 use crate::context::SimpleCx;
 use crate::declare::declare_simple_fn;
 use crate::llvm;
-use crate::llvm::{Metadata, True, Type};
+use crate::llvm::{Metadata, TRUE, Type};
 use crate::value::Value;
 
 pub(crate) fn adjust_activity_to_abi<'tcx>(
@@ -293,7 +293,7 @@ pub(crate) fn generate_enzyme_call<'ll, 'tcx>(
     //   ret double %0
     // }
     // ```
-    let enzyme_ty = unsafe { llvm::LLVMFunctionType(ret_ty, ptr::null(), 0, True) };
+    let enzyme_ty = unsafe { llvm::LLVMFunctionType(ret_ty, ptr::null(), 0, TRUE) };
 
     // FIXME(ZuseZ4): the CC/Addr/Vis values are best effort guesses, we should look at tests and
     // think a bit more about what should go here.
diff --git a/compiler/rustc_codegen_llvm/src/common.rs b/compiler/rustc_codegen_llvm/src/common.rs
index f29fefb66f0..11b79a7fe68 100644
--- a/compiler/rustc_codegen_llvm/src/common.rs
+++ b/compiler/rustc_codegen_llvm/src/common.rs
@@ -20,7 +20,7 @@ use tracing::debug;
 use crate::consts::const_alloc_to_llvm;
 pub(crate) use crate::context::CodegenCx;
 use crate::context::{GenericCx, SCx};
-use crate::llvm::{self, BasicBlock, Bool, ConstantInt, False, Metadata, True};
+use crate::llvm::{self, BasicBlock, ConstantInt, FALSE, Metadata, TRUE, ToLlvmBool};
 use crate::type_::Type;
 use crate::value::Value;
 
@@ -158,7 +158,7 @@ impl<'ll, 'tcx> ConstCodegenMethods for CodegenCx<'ll, 'tcx> {
             self.type_kind(t) == TypeKind::Integer,
             "only allows integer types in const_int"
         );
-        unsafe { llvm::LLVMConstInt(t, i as u64, True) }
+        unsafe { llvm::LLVMConstInt(t, i as u64, TRUE) }
     }
 
     fn const_u8(&self, i: u8) -> &'ll Value {
@@ -192,7 +192,7 @@ impl<'ll, 'tcx> ConstCodegenMethods for CodegenCx<'ll, 'tcx> {
             self.type_kind(t) == TypeKind::Integer,
             "only allows integer types in const_uint"
         );
-        unsafe { llvm::LLVMConstInt(t, i, False) }
+        unsafe { llvm::LLVMConstInt(t, i, FALSE) }
     }
 
     fn const_uint_big(&self, t: &'ll Type, u: u128) -> &'ll Value {
@@ -377,7 +377,7 @@ pub(crate) fn val_ty(v: &Value) -> &Type {
 pub(crate) fn bytes_in_context<'ll>(llcx: &'ll llvm::Context, bytes: &[u8]) -> &'ll Value {
     unsafe {
         let ptr = bytes.as_ptr() as *const c_char;
-        llvm::LLVMConstStringInContext2(llcx, ptr, bytes.len(), True)
+        llvm::LLVMConstStringInContext2(llcx, ptr, bytes.len(), TRUE)
     }
 }
 
@@ -392,7 +392,7 @@ fn struct_in_context<'ll>(
     packed: bool,
 ) -> &'ll Value {
     let len = c_uint::try_from(elts.len()).expect("LLVMConstStructInContext elements len overflow");
-    unsafe { llvm::LLVMConstStructInContext(llcx, elts.as_ptr(), len, packed as Bool) }
+    unsafe { llvm::LLVMConstStructInContext(llcx, elts.as_ptr(), len, packed.to_llvm_bool()) }
 }
 
 #[inline]
diff --git a/compiler/rustc_codegen_llvm/src/context.rs b/compiler/rustc_codegen_llvm/src/context.rs
index 2d91ae64e2d..4fd6110ac4a 100644
--- a/compiler/rustc_codegen_llvm/src/context.rs
+++ b/compiler/rustc_codegen_llvm/src/context.rs
@@ -471,6 +471,15 @@ pub(crate) unsafe fn create_module<'ll>(
         }
     }
 
+    if sess.opts.unstable_opts.indirect_branch_cs_prefix {
+        llvm::add_module_flag_u32(
+            llmod,
+            llvm::ModuleFlagMergeBehavior::Override,
+            "indirect_branch_cs_prefix",
+            1,
+        );
+    }
+
     match (sess.opts.unstable_opts.small_data_threshold, sess.target.small_data_threshold_support())
     {
         // Set up the small-data optimization limit for architectures that use
@@ -692,7 +701,7 @@ impl<'ll, CX: Borrow<SCx<'ll>>> GenericCx<'ll, CX> {
     }
 
     pub(crate) fn get_const_int(&self, ty: &'ll Type, val: u64) -> &'ll Value {
-        unsafe { llvm::LLVMConstInt(ty, val, llvm::False) }
+        unsafe { llvm::LLVMConstInt(ty, val, llvm::FALSE) }
     }
 
     pub(crate) fn get_const_i64(&self, n: u64) -> &'ll Value {
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs b/compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs
index 6eb7042da61..7a6dc008c7b 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs
@@ -72,7 +72,7 @@ pub(crate) fn get_or_insert_gdb_debug_scripts_section_global<'ll>(
                 .unwrap_or_else(|| bug!("symbol `{}` is already defined", section_var_name));
             llvm::set_section(section_var, c".debug_gdb_scripts");
             llvm::set_initializer(section_var, cx.const_bytes(section_contents));
-            llvm::LLVMSetGlobalConstant(section_var, llvm::True);
+            llvm::LLVMSetGlobalConstant(section_var, llvm::TRUE);
             llvm::set_unnamed_address(section_var, llvm::UnnamedAddr::Global);
             llvm::set_linkage(section_var, llvm::Linkage::LinkOnceODRLinkage);
             // This should make sure that the whole section is not larger than
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/metadata/type_map.rs b/compiler/rustc_codegen_llvm/src/debuginfo/metadata/type_map.rs
index d1502d2b1e6..18a783a348a 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/metadata/type_map.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/metadata/type_map.rs
@@ -276,7 +276,7 @@ pub(super) fn build_type_with_children<'ll, 'tcx>(
         && let ty::Adt(adt_def, args) = ty.kind()
     {
         let def_id = adt_def.did();
-        // If any sub type reference the original type definition and the sub type has a type
+        // If any child type references the original type definition and the child type has a type
         // parameter that strictly contains the original parameter, the original type is a recursive
         // type that can expanding indefinitely. Example,
         // ```
@@ -285,21 +285,43 @@ pub(super) fn build_type_with_children<'ll, 'tcx>(
         //     Item(T),
         // }
         // ```
-        let is_expanding_recursive = adt_def.is_enum()
-            && debug_context(cx).adt_stack.borrow().iter().any(|(parent_def_id, parent_args)| {
-                if def_id == *parent_def_id {
-                    args.iter().zip(parent_args.iter()).any(|(arg, parent_arg)| {
-                        if let (Some(arg), Some(parent_arg)) = (arg.as_type(), parent_arg.as_type())
-                        {
-                            arg != parent_arg && arg.contains(parent_arg)
-                        } else {
-                            false
-                        }
-                    })
-                } else {
-                    false
-                }
-            });
+        let is_expanding_recursive = {
+            let stack = debug_context(cx).adt_stack.borrow();
+            stack
+                .iter()
+                .enumerate()
+                .rev()
+                .skip(1)
+                .filter(|(_, (ancestor_def_id, _))| def_id == *ancestor_def_id)
+                .any(|(ancestor_index, (_, ancestor_args))| {
+                    args.iter()
+                        .zip(ancestor_args.iter())
+                        .filter_map(|(arg, ancestor_arg)| arg.as_type().zip(ancestor_arg.as_type()))
+                        .any(|(arg, ancestor_arg)|
+                            // Strictly contains.
+                            (arg != ancestor_arg && arg.contains(ancestor_arg))
+                            // Check all types between current and ancestor use the
+                            // ancestor_arg.
+                            // Otherwise, duplicate wrappers in normal recursive type may be
+                            // regarded as expanding.
+                            // ```
+                            // struct Recursive {
+                            //     a: Box<Box<Recursive>>,
+                            // }
+                            // ```
+                            // It can produce an ADT stack like this,
+                            // - Box<Recursive>
+                            // - Recursive
+                            // - Box<Box<Recursive>>
+                            && stack[ancestor_index + 1..stack.len()].iter().all(
+                                |(_, intermediate_args)|
+                                    intermediate_args
+                                        .iter()
+                                        .filter_map(|arg| arg.as_type())
+                                        .any(|mid_arg| mid_arg.contains(ancestor_arg))
+                            ))
+                })
+        };
         if is_expanding_recursive {
             // FIXME: indicate that this is an expanding recursive type in stub metadata?
             return DINodeCreationResult::new(stub_info.metadata, false);
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/namespace.rs b/compiler/rustc_codegen_llvm/src/debuginfo/namespace.rs
index b4d639368b0..1dcf4ff3062 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/namespace.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/namespace.rs
@@ -38,7 +38,7 @@ pub(crate) fn item_namespace<'ll>(cx: &CodegenCx<'ll, '_>, def_id: DefId) -> &'l
             parent_scope,
             namespace_name_string.as_ptr(),
             namespace_name_string.len(),
-            llvm::False, // ExportSymbols (only relevant for C++ anonymous namespaces)
+            llvm::FALSE, // ExportSymbols (only relevant for C++ anonymous namespaces)
         )
     };
 
diff --git a/compiler/rustc_codegen_llvm/src/intrinsic.rs b/compiler/rustc_codegen_llvm/src/intrinsic.rs
index 4935f8d7dff..49d3dedbeab 100644
--- a/compiler/rustc_codegen_llvm/src/intrinsic.rs
+++ b/compiler/rustc_codegen_llvm/src/intrinsic.rs
@@ -330,10 +330,16 @@ impl<'ll, 'tcx> IntrinsicCallBuilderMethods<'tcx> for Builder<'_, 'll, 'tcx> {
                     _ => bug!(),
                 };
                 let ptr = args[0].immediate();
+                let locality = fn_args.const_at(1).to_value().valtree.unwrap_leaf().to_i32();
                 self.call_intrinsic(
                     "llvm.prefetch",
                     &[self.val_ty(ptr)],
-                    &[ptr, self.const_i32(rw), args[1].immediate(), self.const_i32(cache_type)],
+                    &[
+                        ptr,
+                        self.const_i32(rw),
+                        self.const_i32(locality),
+                        self.const_i32(cache_type),
+                    ],
                 )
             }
             sym::carrying_mul_add => {
diff --git a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
index 55d26a97e2d..fa2802a891f 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
@@ -11,9 +11,8 @@
 //! the need for an extra cast from `*const u8` on the Rust side.
 
 #![allow(non_camel_case_types)]
-#![allow(non_upper_case_globals)]
 
-use std::fmt::Debug;
+use std::fmt::{self, Debug};
 use std::marker::PhantomData;
 use std::num::NonZero;
 use std::ptr;
@@ -33,10 +32,59 @@ use crate::llvm;
 
 /// In the LLVM-C API, boolean values are passed as `typedef int LLVMBool`,
 /// which has a different ABI from Rust or C++ `bool`.
-pub(crate) type Bool = c_int;
+///
+/// This wrapper does not implement `PartialEq`.
+/// To test the underlying boolean value, use [`Self::is_true`].
+#[derive(Clone, Copy)]
+#[repr(transparent)]
+pub(crate) struct Bool {
+    value: c_int,
+}
+
+pub(crate) const TRUE: Bool = Bool::TRUE;
+pub(crate) const FALSE: Bool = Bool::FALSE;
+
+impl Bool {
+    pub(crate) const TRUE: Self = Self { value: 1 };
+    pub(crate) const FALSE: Self = Self { value: 0 };
+
+    pub(crate) const fn from_bool(rust_bool: bool) -> Self {
+        if rust_bool { Self::TRUE } else { Self::FALSE }
+    }
+
+    /// Converts this LLVM-C boolean to a Rust `bool`
+    pub(crate) fn is_true(self) -> bool {
+        // Since we're interacting with a C API, follow the C convention of
+        // treating any nonzero value as true.
+        self.value != Self::FALSE.value
+    }
+}
 
-pub(crate) const True: Bool = 1 as Bool;
-pub(crate) const False: Bool = 0 as Bool;
+impl Debug for Bool {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self.value {
+            0 => f.write_str("FALSE"),
+            1 => f.write_str("TRUE"),
+            // As with `Self::is_true`, treat any nonzero value as true.
+            v => write!(f, "TRUE ({v})"),
+        }
+    }
+}
+
+/// Convenience trait to convert `bool` to `llvm::Bool` with an explicit method call.
+///
+/// Being able to write `b.to_llvm_bool()` is less noisy than `llvm::Bool::from(b)`,
+/// while being more explicit and less mistake-prone than something like `b.into()`.
+pub(crate) trait ToLlvmBool: Copy {
+    fn to_llvm_bool(self) -> llvm::Bool;
+}
+
+impl ToLlvmBool for bool {
+    #[inline(always)]
+    fn to_llvm_bool(self) -> llvm::Bool {
+        llvm::Bool::from_bool(self)
+    }
+}
 
 /// Wrapper for a raw enum value returned from LLVM's C APIs.
 ///
@@ -251,6 +299,7 @@ pub(crate) enum AttributeKind {
     Writable = 42,
     DeadOnUnwind = 43,
     DeadOnReturn = 44,
+    CapturesReadOnly = 45,
 }
 
 /// LLVMIntPredicate
diff --git a/compiler/rustc_codegen_llvm/src/llvm/mod.rs b/compiler/rustc_codegen_llvm/src/llvm/mod.rs
index 7fea7b79a8c..6adabe53129 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/mod.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/mod.rs
@@ -215,7 +215,7 @@ pub(crate) fn set_initializer(llglobal: &Value, constant_val: &Value) {
 }
 
 pub(crate) fn set_global_constant(llglobal: &Value, is_constant: bool) {
-    LLVMSetGlobalConstant(llglobal, if is_constant { ffi::True } else { ffi::False });
+    LLVMSetGlobalConstant(llglobal, is_constant.to_llvm_bool());
 }
 
 pub(crate) fn get_linkage(llglobal: &Value) -> Linkage {
@@ -229,7 +229,7 @@ pub(crate) fn set_linkage(llglobal: &Value, linkage: Linkage) {
 }
 
 pub(crate) fn is_declaration(llglobal: &Value) -> bool {
-    unsafe { LLVMIsDeclaration(llglobal) == ffi::True }
+    unsafe { LLVMIsDeclaration(llglobal) }.is_true()
 }
 
 pub(crate) fn get_visibility(llglobal: &Value) -> Visibility {
diff --git a/compiler/rustc_codegen_llvm/src/llvm_util.rs b/compiler/rustc_codegen_llvm/src/llvm_util.rs
index 28d2100f478..d5025bb405c 100644
--- a/compiler/rustc_codegen_llvm/src/llvm_util.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm_util.rs
@@ -26,7 +26,7 @@ static INIT: Once = Once::new();
 pub(crate) fn init(sess: &Session) {
     unsafe {
         // Before we touch LLVM, make sure that multithreading is enabled.
-        if llvm::LLVMIsMultithreaded() != 1 {
+        if !llvm::LLVMIsMultithreaded().is_true() {
             bug!("LLVM compiled without support for threads");
         }
         INIT.call_once(|| {
@@ -277,6 +277,7 @@ pub(crate) fn to_llvm_features<'a>(sess: &Session, s: &'a str) -> Option<LLVMFea
         {
             None
         }
+        ("loongarch32" | "loongarch64", "32s") if get_version().0 < 21 => None,
         // Filter out features that are not supported by the current LLVM version
         ("riscv32" | "riscv64", "zacas") if get_version().0 < 20 => None,
         (
diff --git a/compiler/rustc_codegen_llvm/src/mono_item.rs b/compiler/rustc_codegen_llvm/src/mono_item.rs
index 5075befae8a..52eefe2d4d2 100644
--- a/compiler/rustc_codegen_llvm/src/mono_item.rs
+++ b/compiler/rustc_codegen_llvm/src/mono_item.rs
@@ -133,7 +133,7 @@ impl CodegenCx<'_, '_> {
 
         // Thread-local variables generally don't support copy relocations.
         let is_thread_local_var = llvm::LLVMIsAGlobalVariable(llval)
-            .is_some_and(|v| llvm::LLVMIsThreadLocal(v) == llvm::True);
+            .is_some_and(|v| llvm::LLVMIsThreadLocal(v).is_true());
         if is_thread_local_var {
             return false;
         }
diff --git a/compiler/rustc_codegen_llvm/src/type_.rs b/compiler/rustc_codegen_llvm/src/type_.rs
index f02d16baf94..9ecaf5f24fe 100644
--- a/compiler/rustc_codegen_llvm/src/type_.rs
+++ b/compiler/rustc_codegen_llvm/src/type_.rs
@@ -15,7 +15,7 @@ use rustc_target::callconv::{CastTarget, FnAbi};
 use crate::abi::{FnAbiLlvmExt, LlvmType};
 use crate::context::{CodegenCx, GenericCx, SCx};
 pub(crate) use crate::llvm::Type;
-use crate::llvm::{Bool, False, Metadata, True};
+use crate::llvm::{FALSE, Metadata, TRUE, ToLlvmBool};
 use crate::type_of::LayoutLlvmExt;
 use crate::value::Value;
 use crate::{common, llvm};
@@ -53,7 +53,9 @@ impl<'ll, CX: Borrow<SCx<'ll>>> GenericCx<'ll, CX> {
     }
 
     pub(crate) fn set_struct_body(&self, ty: &'ll Type, els: &[&'ll Type], packed: bool) {
-        unsafe { llvm::LLVMStructSetBody(ty, els.as_ptr(), els.len() as c_uint, packed as Bool) }
+        unsafe {
+            llvm::LLVMStructSetBody(ty, els.as_ptr(), els.len() as c_uint, packed.to_llvm_bool())
+        }
     }
     pub(crate) fn type_void(&self) -> &'ll Type {
         unsafe { llvm::LLVMVoidTypeInContext(self.llcx()) }
@@ -139,7 +141,7 @@ impl<'ll, CX: Borrow<SCx<'ll>>> GenericCx<'ll, CX> {
     }
 
     pub(crate) fn type_variadic_func(&self, args: &[&'ll Type], ret: &'ll Type) -> &'ll Type {
-        unsafe { llvm::LLVMFunctionType(ret, args.as_ptr(), args.len() as c_uint, True) }
+        unsafe { llvm::LLVMFunctionType(ret, args.as_ptr(), args.len() as c_uint, TRUE) }
     }
 
     pub(crate) fn type_i1(&self) -> &'ll Type {
@@ -152,7 +154,7 @@ impl<'ll, CX: Borrow<SCx<'ll>>> GenericCx<'ll, CX> {
                 self.llcx(),
                 els.as_ptr(),
                 els.len() as c_uint,
-                packed as Bool,
+                packed.to_llvm_bool(),
             )
         }
     }
@@ -200,7 +202,7 @@ impl<'ll, CX: Borrow<SCx<'ll>>> BaseTypeCodegenMethods for GenericCx<'ll, CX> {
     }
 
     fn type_func(&self, args: &[&'ll Type], ret: &'ll Type) -> &'ll Type {
-        unsafe { llvm::LLVMFunctionType(ret, args.as_ptr(), args.len() as c_uint, False) }
+        unsafe { llvm::LLVMFunctionType(ret, args.as_ptr(), args.len() as c_uint, FALSE) }
     }
 
     fn type_kind(&self, ty: &'ll Type) -> TypeKind {
diff --git a/compiler/rustc_codegen_ssa/messages.ftl b/compiler/rustc_codegen_ssa/messages.ftl
index 42ba0154192..44b9941691a 100644
--- a/compiler/rustc_codegen_ssa/messages.ftl
+++ b/compiler/rustc_codegen_ssa/messages.ftl
@@ -171,9 +171,6 @@ codegen_ssa_invalid_monomorphization_unsupported_symbol = invalid monomorphizati
 
 codegen_ssa_invalid_monomorphization_unsupported_symbol_of_size = invalid monomorphization of `{$name}` intrinsic: unsupported {$symbol} from `{$in_ty}` with element `{$in_elem}` of size `{$size}` to `{$ret_ty}`
 
-codegen_ssa_invalid_sanitize = invalid argument for `sanitize`
-    .note = expected one of: `address`, `kernel_address`, `cfi`, `hwaddress`, `kcfi`, `memory`, `memtag`, `shadow_call_stack`, or `thread`
-
 codegen_ssa_invalid_windows_subsystem = invalid windows subsystem `{$subsystem}`, only `windows` and `console` are allowed
 
 codegen_ssa_ld64_unimplemented_modifier = `as-needed` modifier not implemented yet for ld64
diff --git a/compiler/rustc_codegen_ssa/src/back/link.rs b/compiler/rustc_codegen_ssa/src/back/link.rs
index 4ebe59dc2a7..c3777f64e9e 100644
--- a/compiler/rustc_codegen_ssa/src/back/link.rs
+++ b/compiler/rustc_codegen_ssa/src/back/link.rs
@@ -2435,6 +2435,13 @@ fn linker_with_args(
     // Passed after compiler-generated options to support manual overriding when necessary.
     add_user_defined_link_args(cmd, sess);
 
+    // ------------ Builtin configurable linker scripts ------------
+    // The user's link args should be able to overwrite symbols in the compiler's
+    // linker script that were weakly defined (i.e. defined with `PROVIDE()`). For this
+    // to work correctly, the user needs to be able to specify linker arguments like
+    // `--defsym` and `--script` *before* any builtin linker scripts are evaluated.
+    add_link_script(cmd, sess, tmpdir, crate_type);
+
     // ------------ Object code and libraries, order-dependent ------------
 
     // Post-link CRT objects.
@@ -2469,8 +2476,6 @@ fn add_order_independent_options(
 
     let apple_sdk_root = add_apple_sdk(cmd, sess, flavor);
 
-    add_link_script(cmd, sess, tmpdir, crate_type);
-
     if sess.target.os == "fuchsia"
         && crate_type == CrateType::Executable
         && !matches!(flavor, LinkerFlavor::Gnu(Cc::Yes, _))
diff --git a/compiler/rustc_codegen_ssa/src/back/link/raw_dylib.rs b/compiler/rustc_codegen_ssa/src/back/link/raw_dylib.rs
index b9e0c957363..509168b2cd2 100644
--- a/compiler/rustc_codegen_ssa/src/back/link/raw_dylib.rs
+++ b/compiler/rustc_codegen_ssa/src/back/link/raw_dylib.rs
@@ -307,11 +307,14 @@ fn create_elf_raw_dylib_stub(sess: &Session, soname: &str, symbols: &[DllImport]
     stub.reserve_section_headers();
     stub.reserve_dynsym();
     stub.reserve_dynstr();
+    let verdef_count = 1 + vers.len();
+    let mut dynamic_entries = 2; // DT_SONAME, DT_NULL
     if !vers.is_empty() {
         stub.reserve_gnu_versym();
-        stub.reserve_gnu_verdef(1 + vers.len(), 1 + vers.len());
+        stub.reserve_gnu_verdef(verdef_count, verdef_count);
+        dynamic_entries += 1; // DT_VERDEFNUM
     }
-    stub.reserve_dynamic(2); // DT_SONAME, DT_NULL
+    stub.reserve_dynamic(dynamic_entries);
 
     // First write the ELF header with the arch information.
     let e_machine = match (arch, sub_arch) {
@@ -443,9 +446,13 @@ fn create_elf_raw_dylib_stub(sess: &Session, soname: &str, symbols: &[DllImport]
     // .dynamic
     // the DT_SONAME will be used by the linker to populate DT_NEEDED
     // which the loader uses to find the library.
-    // DT_NULL terminates the .dynamic table.
     stub.write_align_dynamic();
     stub.write_dynamic_string(elf::DT_SONAME, soname);
+    // LSB section "2.7. Symbol Versioning" requires `DT_VERDEFNUM` to be reliable.
+    if verdef_count > 1 {
+        stub.write_dynamic(elf::DT_VERDEFNUM, verdef_count as u64);
+    }
+    // DT_NULL terminates the .dynamic table.
     stub.write_dynamic(elf::DT_NULL, 0);
 
     stub_buf
diff --git a/compiler/rustc_codegen_ssa/src/base.rs b/compiler/rustc_codegen_ssa/src/base.rs
index 67cd1f4cd41..8abaf201aba 100644
--- a/compiler/rustc_codegen_ssa/src/base.rs
+++ b/compiler/rustc_codegen_ssa/src/base.rs
@@ -858,7 +858,7 @@ pub fn is_call_from_compiler_builtins_to_upstream_monomorphization<'tcx>(
     instance: Instance<'tcx>,
 ) -> bool {
     fn is_llvm_intrinsic(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
-        if let Some(name) = tcx.codegen_fn_attrs(def_id).link_name {
+        if let Some(name) = tcx.codegen_fn_attrs(def_id).symbol_name {
             name.as_str().starts_with("llvm.")
         } else {
             false
diff --git a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
index bf14c02a09c..6b0bd64102c 100644
--- a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
+++ b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
@@ -6,7 +6,6 @@ use rustc_ast::{LitKind, MetaItem, MetaItemInner, 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, Attribute, LangItem, find_attr, lang_items};
 use rustc_middle::middle::codegen_fn_attrs::{
     CodegenFnAttrFlags, CodegenFnAttrs, PatchableFunctionEntry,
@@ -156,7 +155,7 @@ fn process_builtin_attrs(
             match p {
                 AttributeKind::Cold(_) => codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD,
                 AttributeKind::ExportName { name, .. } => {
-                    codegen_fn_attrs.export_name = Some(*name)
+                    codegen_fn_attrs.symbol_name = Some(*name)
                 }
                 AttributeKind::Inline(inline, span) => {
                     codegen_fn_attrs.inline = *inline;
@@ -164,7 +163,13 @@ fn process_builtin_attrs(
                 }
                 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::LinkName { name, .. } => {
+                    // FIXME Remove check for foreign functions once #[link_name] on non-foreign
+                    // functions is a hard error
+                    if tcx.is_foreign_item(did) {
+                        codegen_fn_attrs.symbol_name = Some(*name);
+                    }
+                }
                 AttributeKind::LinkOrdinal { ordinal, span } => {
                     codegen_fn_attrs.link_ordinal = Some(*ordinal);
                     interesting_spans.link_ordinal = Some(*span);
@@ -188,7 +193,7 @@ fn process_builtin_attrs(
                     }
                 }
                 AttributeKind::Optimize(optimize, _) => codegen_fn_attrs.optimize = *optimize,
-                AttributeKind::TargetFeature(features, attr_span) => {
+                AttributeKind::TargetFeature { features, attr_span, was_forced } => {
                     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");
                         continue;
@@ -196,7 +201,7 @@ fn process_builtin_attrs(
                     let safe_target_features =
                         matches!(sig.header.safety, hir::HeaderSafety::SafeTargetFeatures);
                     codegen_fn_attrs.safe_target_features = safe_target_features;
-                    if safe_target_features {
+                    if safe_target_features && !was_forced {
                         if tcx.sess.target.is_like_wasm || tcx.sess.opts.actually_rustdoc {
                             // The `#[target_feature]` attribute is allowed on
                             // WebAssembly targets on all functions. Prior to stabilizing
@@ -227,6 +232,7 @@ fn process_builtin_attrs(
                         tcx,
                         did,
                         features,
+                        *was_forced,
                         rust_target_features,
                         &mut codegen_fn_attrs.target_features,
                     );
@@ -287,6 +293,9 @@ fn process_builtin_attrs(
                         codegen_fn_attrs.linkage = linkage;
                     }
                 }
+                AttributeKind::Sanitize { span, .. } => {
+                    interesting_spans.sanitize = Some(*span);
+                }
                 _ => {}
             }
         }
@@ -304,7 +313,6 @@ fn process_builtin_attrs(
                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR_ZEROED
             }
             sym::thread_local => codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL,
-            sym::sanitize => interesting_spans.sanitize = Some(attr.span()),
             sym::instruction_set => {
                 codegen_fn_attrs.instruction_set = parse_instruction_set_attr(tcx, attr)
             }
@@ -382,7 +390,7 @@ fn apply_overrides(tcx: TyCtxt<'_>, did: LocalDefId, codegen_fn_attrs: &mut Code
             // * `#[rustc_std_internal_symbol]` mangles the symbol name in a special way
             //   both for exports and imports through foreign items. This is handled further,
             //   during symbol mangling logic.
-        } else if codegen_fn_attrs.link_name.is_some() {
+        } else if codegen_fn_attrs.symbol_name.is_some() {
             // * This can be overridden with the `#[link_name]` attribute
         } else {
             // NOTE: there's one more exception that we cannot apply here. On wasm,
@@ -437,7 +445,7 @@ fn check_result(
     }
 
     // error when specifying link_name together with link_ordinal
-    if let Some(_) = codegen_fn_attrs.link_name
+    if let Some(_) = codegen_fn_attrs.symbol_name
         && let Some(_) = codegen_fn_attrs.link_ordinal
     {
         let msg = "cannot use `#[link_name]` with `#[link_ordinal]`";
@@ -457,7 +465,7 @@ fn check_result(
             .collect(),
     ) {
         let span =
-            find_attr!(tcx.get_all_attrs(did), AttributeKind::TargetFeature(_, span) => *span)
+            find_attr!(tcx.get_all_attrs(did), AttributeKind::TargetFeature{attr_span: span, ..} => *span)
                 .unwrap_or_else(|| tcx.def_span(did));
 
         tcx.dcx()
@@ -484,14 +492,11 @@ fn handle_lang_items(
     // strippable by the linker.
     //
     // Additionally weak lang items have predetermined symbol names.
-    if let Some(lang_item) = lang_item {
-        if WEAK_LANG_ITEMS.contains(&lang_item) {
-            codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
-        }
-        if let Some(link_name) = lang_item.link_name() {
-            codegen_fn_attrs.export_name = Some(link_name);
-            codegen_fn_attrs.link_name = Some(link_name);
-        }
+    if let Some(lang_item) = lang_item
+        && let Some(link_name) = lang_item.link_name()
+    {
+        codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
+        codegen_fn_attrs.symbol_name = Some(link_name);
     }
 
     // error when using no_mangle on a lang item item
@@ -557,79 +562,9 @@ fn opt_trait_item(tcx: TyCtxt<'_>, def_id: DefId) -> Option<DefId> {
     }
 }
 
-/// For an attr that has the `sanitize` attribute, read the list of
-/// disabled sanitizers. `current_attr` holds the information about
-/// previously parsed attributes.
-fn parse_sanitize_attr(
-    tcx: TyCtxt<'_>,
-    attr: &Attribute,
-    current_attr: SanitizerSet,
-) -> SanitizerSet {
-    let mut result = current_attr;
-    if let Some(list) = attr.meta_item_list() {
-        for item in list.iter() {
-            let MetaItemInner::MetaItem(set) = item else {
-                tcx.dcx().emit_err(errors::InvalidSanitize { span: attr.span() });
-                break;
-            };
-            let segments = set.path.segments.iter().map(|x| x.ident.name).collect::<Vec<_>>();
-            match segments.as_slice() {
-                // Similar to clang, sanitize(address = ..) and
-                // sanitize(kernel_address = ..) control both ASan and KASan
-                // Source: https://reviews.llvm.org/D44981.
-                [sym::address] | [sym::kernel_address] if set.value_str() == Some(sym::off) => {
-                    result |= SanitizerSet::ADDRESS | SanitizerSet::KERNELADDRESS
-                }
-                [sym::address] | [sym::kernel_address] if set.value_str() == Some(sym::on) => {
-                    result &= !SanitizerSet::ADDRESS;
-                    result &= !SanitizerSet::KERNELADDRESS;
-                }
-                [sym::cfi] if set.value_str() == Some(sym::off) => result |= SanitizerSet::CFI,
-                [sym::cfi] if set.value_str() == Some(sym::on) => result &= !SanitizerSet::CFI,
-                [sym::kcfi] if set.value_str() == Some(sym::off) => result |= SanitizerSet::KCFI,
-                [sym::kcfi] if set.value_str() == Some(sym::on) => result &= !SanitizerSet::KCFI,
-                [sym::memory] if set.value_str() == Some(sym::off) => {
-                    result |= SanitizerSet::MEMORY
-                }
-                [sym::memory] if set.value_str() == Some(sym::on) => {
-                    result &= !SanitizerSet::MEMORY
-                }
-                [sym::memtag] if set.value_str() == Some(sym::off) => {
-                    result |= SanitizerSet::MEMTAG
-                }
-                [sym::memtag] if set.value_str() == Some(sym::on) => {
-                    result &= !SanitizerSet::MEMTAG
-                }
-                [sym::shadow_call_stack] if set.value_str() == Some(sym::off) => {
-                    result |= SanitizerSet::SHADOWCALLSTACK
-                }
-                [sym::shadow_call_stack] if set.value_str() == Some(sym::on) => {
-                    result &= !SanitizerSet::SHADOWCALLSTACK
-                }
-                [sym::thread] if set.value_str() == Some(sym::off) => {
-                    result |= SanitizerSet::THREAD
-                }
-                [sym::thread] if set.value_str() == Some(sym::on) => {
-                    result &= !SanitizerSet::THREAD
-                }
-                [sym::hwaddress] if set.value_str() == Some(sym::off) => {
-                    result |= SanitizerSet::HWADDRESS
-                }
-                [sym::hwaddress] if set.value_str() == Some(sym::on) => {
-                    result &= !SanitizerSet::HWADDRESS
-                }
-                _ => {
-                    tcx.dcx().emit_err(errors::InvalidSanitize { span: attr.span() });
-                }
-            }
-        }
-    }
-    result
-}
-
 fn disabled_sanitizers_for(tcx: TyCtxt<'_>, did: LocalDefId) -> SanitizerSet {
     // Backtrack to the crate root.
-    let disabled = match tcx.opt_local_parent(did) {
+    let mut disabled = match tcx.opt_local_parent(did) {
         // Check the parent (recursively).
         Some(parent) => tcx.disabled_sanitizers_for(parent),
         // We reached the crate root without seeing an attribute, so
@@ -638,8 +573,17 @@ fn disabled_sanitizers_for(tcx: TyCtxt<'_>, did: LocalDefId) -> SanitizerSet {
     };
 
     // Check for a sanitize annotation directly on this def.
-    if let Some(attr) = tcx.get_attr(did, sym::sanitize) {
-        return parse_sanitize_attr(tcx, attr, disabled);
+    if let Some((on_set, off_set)) = find_attr!(tcx.get_all_attrs(did), AttributeKind::Sanitize {on_set, off_set, ..} => (on_set, off_set))
+    {
+        // the on set is the set of sanitizers explicitly enabled.
+        // we mask those out since we want the set of disabled sanitizers here
+        disabled &= !*on_set;
+        // the off set is the set of sanitizers explicitly disabled.
+        // we or those in here.
+        disabled |= *off_set;
+        // the on set and off set are distjoint since there's a third option: unset.
+        // a node may not set the sanitizer setting in which case it inherits from parents.
+        // the code above in this function does this backtracking
     }
     disabled
 }
diff --git a/compiler/rustc_codegen_ssa/src/errors.rs b/compiler/rustc_codegen_ssa/src/errors.rs
index 209c78ddeda..fb5a8205140 100644
--- a/compiler/rustc_codegen_ssa/src/errors.rs
+++ b/compiler/rustc_codegen_ssa/src/errors.rs
@@ -1121,14 +1121,6 @@ impl IntoDiagArg for ExpectedPointerMutability {
 }
 
 #[derive(Diagnostic)]
-#[diag(codegen_ssa_invalid_sanitize)]
-#[note]
-pub(crate) struct InvalidSanitize {
-    #[primary_span]
-    pub span: Span,
-}
-
-#[derive(Diagnostic)]
 #[diag(codegen_ssa_target_feature_safe_trait)]
 pub(crate) struct TargetFeatureSafeTrait {
     #[primary_span]
diff --git a/compiler/rustc_codegen_ssa/src/target_features.rs b/compiler/rustc_codegen_ssa/src/target_features.rs
index 7e4341a8236..54584999d61 100644
--- a/compiler/rustc_codegen_ssa/src/target_features.rs
+++ b/compiler/rustc_codegen_ssa/src/target_features.rs
@@ -3,7 +3,7 @@ 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;
+use rustc_middle::middle::codegen_fn_attrs::{TargetFeature, TargetFeatureKind};
 use rustc_middle::query::Providers;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::Session;
@@ -22,6 +22,7 @@ pub(crate) fn from_target_feature_attr(
     tcx: TyCtxt<'_>,
     did: LocalDefId,
     features: &[(Symbol, Span)],
+    was_forced: bool,
     rust_target_features: &UnordMap<String, target_features::Stability>,
     target_features: &mut Vec<TargetFeature>,
 ) {
@@ -88,7 +89,14 @@ pub(crate) fn from_target_feature_attr(
                         }
                     }
                 }
-                target_features.push(TargetFeature { name, implied: name != feature })
+                let kind = if name != feature {
+                    TargetFeatureKind::Implied
+                } else if was_forced {
+                    TargetFeatureKind::Forced
+                } else {
+                    TargetFeatureKind::Enabled
+                };
+                target_features.push(TargetFeature { name, kind })
             }
         }
     }
@@ -180,6 +188,7 @@ fn parse_rust_feature_flag<'a>(
             while let Some(new_feature) = new_features.pop() {
                 if features.insert(new_feature) {
                     if let Some(implied_features) = inverse_implied_features.get(&new_feature) {
+                        #[allow(rustc::potential_query_instability)]
                         new_features.extend(implied_features)
                     }
                 }
diff --git a/compiler/rustc_const_eval/src/const_eval/machine.rs b/compiler/rustc_const_eval/src/const_eval/machine.rs
index da954cf4ed7..fccb6b171b1 100644
--- a/compiler/rustc_const_eval/src/const_eval/machine.rs
+++ b/compiler/rustc_const_eval/src/const_eval/machine.rs
@@ -280,22 +280,110 @@ impl<'tcx> CompileTimeInterpCx<'tcx> {
         interp_ok(match (a, b) {
             // Comparisons between integers are always known.
             (Scalar::Int(a), Scalar::Int(b)) => (a == b) as u8,
-            // Comparisons of null with an arbitrary scalar can be known if `scalar_may_be_null`
-            // indicates that the scalar can definitely *not* be null.
-            (Scalar::Int(int), ptr) | (ptr, Scalar::Int(int))
-                if int.is_null() && !self.scalar_may_be_null(ptr)? =>
-            {
-                0
+            // Comparing a pointer `ptr` with an integer `int` is equivalent to comparing
+            // `ptr-int` with null, so we can reduce this case to a `scalar_may_be_null` test.
+            (Scalar::Int(int), Scalar::Ptr(ptr, _)) | (Scalar::Ptr(ptr, _), Scalar::Int(int)) => {
+                let int = int.to_target_usize(*self.tcx);
+                // The `wrapping_neg` here may produce a value that is not
+                // a valid target usize any more... but `wrapping_offset` handles that correctly.
+                let offset_ptr = ptr.wrapping_offset(Size::from_bytes(int.wrapping_neg()), self);
+                if !self.scalar_may_be_null(Scalar::from_pointer(offset_ptr, self))? {
+                    // `ptr.wrapping_sub(int)` is definitely not equal to `0`, so `ptr != int`
+                    0
+                } else {
+                    // `ptr.wrapping_sub(int)` could be equal to `0`, but might not be,
+                    // so we cannot know for sure if `ptr == int` or not
+                    2
+                }
+            }
+            (Scalar::Ptr(a, _), Scalar::Ptr(b, _)) => {
+                let (a_prov, a_offset) = a.prov_and_relative_offset();
+                let (b_prov, b_offset) = b.prov_and_relative_offset();
+                let a_allocid = a_prov.alloc_id();
+                let b_allocid = b_prov.alloc_id();
+                let a_info = self.get_alloc_info(a_allocid);
+                let b_info = self.get_alloc_info(b_allocid);
+
+                // Check if the pointers cannot be equal due to alignment
+                if a_info.align > Align::ONE && b_info.align > Align::ONE {
+                    let min_align = Ord::min(a_info.align.bytes(), b_info.align.bytes());
+                    let a_residue = a_offset.bytes() % min_align;
+                    let b_residue = b_offset.bytes() % min_align;
+                    if a_residue != b_residue {
+                        // If the two pointers have a different residue modulo their
+                        // common alignment, they cannot be equal.
+                        return interp_ok(0);
+                    }
+                    // The pointers have the same residue modulo their common alignment,
+                    // so they could be equal. Try the other checks.
+                }
+
+                if let (Some(GlobalAlloc::Static(a_did)), Some(GlobalAlloc::Static(b_did))) = (
+                    self.tcx.try_get_global_alloc(a_allocid),
+                    self.tcx.try_get_global_alloc(b_allocid),
+                ) {
+                    if a_allocid == b_allocid {
+                        debug_assert_eq!(
+                            a_did, b_did,
+                            "different static item DefIds had same AllocId? {a_allocid:?} == {b_allocid:?}, {a_did:?} != {b_did:?}"
+                        );
+                        // Comparing two pointers into the same static. As per
+                        // https://doc.rust-lang.org/nightly/reference/items/static-items.html#r-items.static.intro
+                        // a static cannot be duplicated, so if two pointers are into the same
+                        // static, they are equal if and only if their offsets are equal.
+                        (a_offset == b_offset) as u8
+                    } else {
+                        debug_assert_ne!(
+                            a_did, b_did,
+                            "same static item DefId had two different AllocIds? {a_allocid:?} != {b_allocid:?}, {a_did:?} == {b_did:?}"
+                        );
+                        // Comparing two pointers into the different statics.
+                        // We can never determine for sure that two pointers into different statics
+                        // are *equal*, but we can know that they are *inequal* if they are both
+                        // strictly in-bounds (i.e. in-bounds and not one-past-the-end) of
+                        // their respective static, as different non-zero-sized statics cannot
+                        // overlap or be deduplicated as per
+                        // https://doc.rust-lang.org/nightly/reference/items/static-items.html#r-items.static.intro
+                        // (non-deduplication), and
+                        // https://doc.rust-lang.org/nightly/reference/items/static-items.html#r-items.static.storage-disjointness
+                        // (non-overlapping).
+                        if a_offset < a_info.size && b_offset < b_info.size {
+                            0
+                        } else {
+                            // Otherwise, conservatively say we don't know.
+                            // There are some cases we could still return `0` for, e.g.
+                            // if the pointers being equal would require their statics to overlap
+                            // one or more bytes, but for simplicity we currently only check
+                            // strictly in-bounds pointers.
+                            2
+                        }
+                    }
+                } else {
+                    // All other cases we conservatively say we don't know.
+                    //
+                    // For comparing statics to non-statics, as per https://doc.rust-lang.org/nightly/reference/items/static-items.html#r-items.static.storage-disjointness
+                    // immutable statics can overlap with other kinds of allocations sometimes.
+                    //
+                    // FIXME: We could be more decisive for (non-zero-sized) mutable statics,
+                    // which cannot overlap with other kinds of allocations.
+                    //
+                    // Functions and vtables can be duplicated and deduplicated, so we
+                    // cannot be sure of runtime equality of pointers to the same one, or the
+                    // runtime inequality of pointers to different ones (see e.g. #73722),
+                    // so comparing those should return 2, whether they are the same allocation
+                    // or not.
+                    //
+                    // `GlobalAlloc::TypeId` exists mostly to prevent consteval from comparing
+                    // `TypeId`s, so comparing those should always return 2, whether they are the
+                    // same allocation or not.
+                    //
+                    // FIXME: We could revisit comparing pointers into the same
+                    // `GlobalAlloc::Memory` once https://github.com/rust-lang/rust/issues/128775
+                    // is fixed (but they can be deduplicated, so comparing pointers into different
+                    // ones should return 2).
+                    2
+                }
             }
-            // Other ways of comparing integers and pointers can never be known for sure.
-            (Scalar::Int { .. }, Scalar::Ptr(..)) | (Scalar::Ptr(..), Scalar::Int { .. }) => 2,
-            // FIXME: return a `1` for when both sides are the same pointer, *except* that
-            // some things (like functions and vtables) do not have stable addresses
-            // so we need to be careful around them (see e.g. #73722).
-            // FIXME: return `0` for at least some comparisons where we can reliably
-            // determine the result of runtime inequality tests at compile-time.
-            // Examples include comparison of addresses in different static items.
-            (Scalar::Ptr(..), Scalar::Ptr(..)) => 2,
         })
     }
 }
diff --git a/compiler/rustc_const_eval/src/interpret/call.rs b/compiler/rustc_const_eval/src/interpret/call.rs
index 64cb934ac8d..4cb88d44e1b 100644
--- a/compiler/rustc_const_eval/src/interpret/call.rs
+++ b/compiler/rustc_const_eval/src/interpret/call.rs
@@ -27,8 +27,9 @@ use crate::{enter_trace_span, fluent_generated as fluent};
 pub enum FnArg<'tcx, Prov: Provenance = CtfeProvenance> {
     /// Pass a copy of the given operand.
     Copy(OpTy<'tcx, Prov>),
-    /// Allow for the argument to be passed in-place: destroy the value originally stored at that place and
-    /// make the place inaccessible for the duration of the function call.
+    /// Allow for the argument to be passed in-place: destroy the value originally stored at that
+    /// place and make the place inaccessible for the duration of the function call. This *must* be
+    /// an in-memory place so that we can do the proper alias checks.
     InPlace(MPlaceTy<'tcx, Prov>),
 }
 
@@ -379,6 +380,11 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
             }
         }
 
+        // *Before* pushing the new frame, determine whether the return destination is in memory.
+        // Need to use `place_to_op` to be *sure* we get the mplace if there is one.
+        let destination_mplace = self.place_to_op(destination)?.as_mplace_or_imm().left();
+
+        // Push the "raw" frame -- this leaves locals uninitialized.
         self.push_stack_frame_raw(instance, body, destination, cont)?;
 
         // If an error is raised here, pop the frame again to get an accurate backtrace.
@@ -496,7 +502,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
 
             // Protect return place for in-place return value passing.
             // We only need to protect anything if this is actually an in-memory place.
-            if let Left(mplace) = destination.as_mplace_or_local() {
+            if let Some(mplace) = destination_mplace {
                 M::protect_in_place_function_argument(self, &mplace)?;
             }
 
diff --git a/compiler/rustc_const_eval/src/interpret/eval_context.rs b/compiler/rustc_const_eval/src/interpret/eval_context.rs
index a8a1ac1c980..9681d89ce35 100644
--- a/compiler/rustc_const_eval/src/interpret/eval_context.rs
+++ b/compiler/rustc_const_eval/src/interpret/eval_context.rs
@@ -325,8 +325,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         let _trace = enter_trace_span!(
             M,
             "instantiate_from_frame_and_normalize_erasing_regions",
-            "{}",
-            frame.instance
+            %frame.instance
         );
         frame
             .instance
@@ -583,6 +582,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         span: Span,
         layout: Option<TyAndLayout<'tcx>>,
     ) -> InterpResult<'tcx, OpTy<'tcx, M::Provenance>> {
+        let _trace = enter_trace_span!(M, const_eval::eval_mir_constant, ?val);
         let const_val = val.eval(*self.tcx, self.typing_env, span).map_err(|err| {
                 if M::ALL_CONSTS_ARE_PRECHECKED {
                     match err {
diff --git a/compiler/rustc_const_eval/src/interpret/place.rs b/compiler/rustc_const_eval/src/interpret/place.rs
index e7fe4c0b34f..a86fdf80f60 100644
--- a/compiler/rustc_const_eval/src/interpret/place.rs
+++ b/compiler/rustc_const_eval/src/interpret/place.rs
@@ -234,6 +234,12 @@ impl<'tcx, Prov: Provenance> PlaceTy<'tcx, Prov> {
     }
 
     /// A place is either an mplace or some local.
+    ///
+    /// Note that the return value can be different even for logically identical places!
+    /// Specifically, if a local is stored in-memory, this may return `Local` or `MPlaceTy`
+    /// depending on how the place was constructed. In other words, seeing `Local` here does *not*
+    /// imply that this place does not point to memory. Every caller must therefore always handle
+    /// both cases.
     #[inline(always)]
     pub fn as_mplace_or_local(
         &self,
diff --git a/compiler/rustc_const_eval/src/interpret/stack.rs b/compiler/rustc_const_eval/src/interpret/stack.rs
index 73cc87508ef..7cabfd96121 100644
--- a/compiler/rustc_const_eval/src/interpret/stack.rs
+++ b/compiler/rustc_const_eval/src/interpret/stack.rs
@@ -20,7 +20,7 @@ use super::{
     MemoryKind, Operand, PlaceTy, Pointer, Provenance, ReturnAction, Scalar, from_known_layout,
     interp_ok, throw_ub, throw_unsup,
 };
-use crate::errors;
+use crate::{enter_trace_span, errors};
 
 // The Phantomdata exists to prevent this type from being `Send`. If it were sent across a thread
 // boundary and dropped in the other thread, it would exit the span in the other thread.
@@ -386,6 +386,9 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
 
         // Make sure all the constants required by this frame evaluate successfully (post-monomorphization check).
         for &const_ in body.required_consts() {
+            // We can't use `eval_mir_constant` here as that assumes that all required consts have
+            // already been checked, so we need a separate tracing call.
+            let _trace = enter_trace_span!(M, const_eval::required_consts, ?const_.const_);
             let c =
                 self.instantiate_from_current_frame_and_normalize_erasing_regions(const_.const_)?;
             c.eval(*self.tcx, self.typing_env, const_.span).map_err(|err| {
diff --git a/compiler/rustc_const_eval/src/interpret/step.rs b/compiler/rustc_const_eval/src/interpret/step.rs
index f1995b3f132..23d362de308 100644
--- a/compiler/rustc_const_eval/src/interpret/step.rs
+++ b/compiler/rustc_const_eval/src/interpret/step.rs
@@ -2,8 +2,11 @@
 //!
 //! The main entry point is the `step` method.
 
+use std::iter;
+
 use either::Either;
 use rustc_abi::{FIRST_VARIANT, FieldIdx};
+use rustc_data_structures::fx::FxHashSet;
 use rustc_index::IndexSlice;
 use rustc_middle::ty::{self, Instance, Ty};
 use rustc_middle::{bug, mir, span_bug};
@@ -389,8 +392,9 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
 
     /// Evaluate the arguments of a function call
     fn eval_fn_call_argument(
-        &self,
+        &mut self,
         op: &mir::Operand<'tcx>,
+        move_definitely_disjoint: bool,
     ) -> InterpResult<'tcx, FnArg<'tcx, M::Provenance>> {
         interp_ok(match op {
             mir::Operand::Copy(_) | mir::Operand::Constant(_) => {
@@ -399,24 +403,19 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                 FnArg::Copy(op)
             }
             mir::Operand::Move(place) => {
-                // If this place lives in memory, preserve its location.
-                // We call `place_to_op` which will be an `MPlaceTy` whenever there exists
-                // an mplace for this place. (This is in contrast to `PlaceTy::as_mplace_or_local`
-                // which can return a local even if that has an mplace.)
                 let place = self.eval_place(*place)?;
-                let op = self.place_to_op(&place)?;
-
-                match op.as_mplace_or_imm() {
-                    Either::Left(mplace) => FnArg::InPlace(mplace),
-                    Either::Right(_imm) => {
-                        // This argument doesn't live in memory, so there's no place
-                        // to make inaccessible during the call.
-                        // We rely on there not being any stray `PlaceTy` that would let the
-                        // caller directly access this local!
-                        // This is also crucial for tail calls, where we want the `FnArg` to
-                        // stay valid when the old stack frame gets popped.
-                        FnArg::Copy(op)
+                if move_definitely_disjoint {
+                    // We still have to ensure that no *other* pointers are used to access this place,
+                    // so *if* it is in memory then we have to treat it as `InPlace`.
+                    // Use `place_to_op` to guarantee that we notice it being in memory.
+                    let op = self.place_to_op(&place)?;
+                    match op.as_mplace_or_imm() {
+                        Either::Left(mplace) => FnArg::InPlace(mplace),
+                        Either::Right(_imm) => FnArg::Copy(op),
                     }
+                } else {
+                    // We have to force this into memory to detect aliasing among `Move` arguments.
+                    FnArg::InPlace(self.force_allocation(&place)?)
                 }
             }
         })
@@ -425,18 +424,53 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
     /// Shared part of `Call` and `TailCall` implementation — finding and evaluating all the
     /// necessary information about callee and arguments to make a call.
     fn eval_callee_and_args(
-        &self,
+        &mut self,
         terminator: &mir::Terminator<'tcx>,
         func: &mir::Operand<'tcx>,
         args: &[Spanned<mir::Operand<'tcx>>],
+        dest: &mir::Place<'tcx>,
     ) -> InterpResult<'tcx, EvaluatedCalleeAndArgs<'tcx, M>> {
         let func = self.eval_operand(func, None)?;
+
+        // Evaluating function call arguments. The tricky part here is dealing with `Move`
+        // arguments: we have to ensure no two such arguments alias. This would be most easily done
+        // by just forcing them all into memory and then doing the usual in-place argument
+        // protection, but then we'd force *a lot* of arguments into memory. So we do some syntactic
+        // pre-processing here where if all `move` arguments are syntactically distinct local
+        // variables (and none is indirect), we can skip the in-memory forcing.
+        // We have to include `dest` in that list so that we can detect aliasing of an in-place
+        // argument with the return place.
+        let move_definitely_disjoint = 'move_definitely_disjoint: {
+            let mut previous_locals = FxHashSet::<mir::Local>::default();
+            for place in args
+                .iter()
+                .filter_map(|a| {
+                    // We only have to care about `Move` arguments.
+                    if let mir::Operand::Move(place) = &a.node { Some(place) } else { None }
+                })
+                .chain(iter::once(dest))
+            {
+                if place.is_indirect_first_projection() {
+                    // An indirect in-place argument could alias with anything else...
+                    break 'move_definitely_disjoint false;
+                }
+                if !previous_locals.insert(place.local) {
+                    // This local is the base for two arguments! They might overlap.
+                    break 'move_definitely_disjoint false;
+                }
+            }
+            // We found no violation so they are all definitely disjoint.
+            true
+        };
         let args = args
             .iter()
-            .map(|arg| self.eval_fn_call_argument(&arg.node))
+            .map(|arg| self.eval_fn_call_argument(&arg.node, move_definitely_disjoint))
             .collect::<InterpResult<'tcx, Vec<_>>>()?;
 
-        let fn_sig_binder = func.layout.ty.fn_sig(*self.tcx);
+        let fn_sig_binder = {
+            let _trace = enter_trace_span!(M, "fn_sig", ty = ?func.layout.ty.kind());
+            func.layout.ty.fn_sig(*self.tcx)
+        };
         let fn_sig = self.tcx.normalize_erasing_late_bound_regions(self.typing_env, fn_sig_binder);
         let extra_args = &args[fn_sig.inputs().len()..];
         let extra_args =
@@ -519,7 +553,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                 let old_loc = self.frame().loc;
 
                 let EvaluatedCalleeAndArgs { callee, args, fn_sig, fn_abi, with_caller_location } =
-                    self.eval_callee_and_args(terminator, func, args)?;
+                    self.eval_callee_and_args(terminator, func, args, &destination)?;
 
                 let destination = self.eval_place(destination)?;
                 self.init_fn_call(
@@ -542,7 +576,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                 let old_frame_idx = self.frame_idx();
 
                 let EvaluatedCalleeAndArgs { callee, args, fn_sig, fn_abi, with_caller_location } =
-                    self.eval_callee_and_args(terminator, func, args)?;
+                    self.eval_callee_and_args(terminator, func, args, &mir::Place::return_place())?;
 
                 self.init_fn_tail_call(callee, (fn_sig.abi, fn_abi), &args, with_caller_location)?;
 
diff --git a/compiler/rustc_const_eval/src/interpret/validity.rs b/compiler/rustc_const_eval/src/interpret/validity.rs
index 5e8bee65706..02e3d90f4af 100644
--- a/compiler/rustc_const_eval/src/interpret/validity.rs
+++ b/compiler/rustc_const_eval/src/interpret/validity.rs
@@ -1418,7 +1418,9 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         let _trace = enter_trace_span!(
             M,
             "validate_operand",
-            "recursive={recursive}, reset_provenance_and_padding={reset_provenance_and_padding}, val={val:?}"
+            recursive,
+            reset_provenance_and_padding,
+            ?val,
         );
 
         // Note that we *could* actually be in CTFE here with `-Zextra-const-ub-checks`, but it's
diff --git a/compiler/rustc_const_eval/src/util/type_name.rs b/compiler/rustc_const_eval/src/util/type_name.rs
index 13cc607135a..2ae6655901b 100644
--- a/compiler/rustc_const_eval/src/util/type_name.rs
+++ b/compiler/rustc_const_eval/src/util/type_name.rs
@@ -1,7 +1,7 @@
 use std::fmt::Write;
 
 use rustc_data_structures::intern::Interned;
-use rustc_hir::def_id::CrateNum;
+use rustc_hir::def_id::{CrateNum, DefId};
 use rustc_hir::definitions::DisambiguatedDefPathData;
 use rustc_middle::bug;
 use rustc_middle::ty::print::{PrettyPrinter, PrintError, Printer};
@@ -132,15 +132,44 @@ impl<'tcx> Printer<'tcx> for TypeNamePrinter<'tcx> {
             Ok(())
         }
     }
+
+    fn print_coroutine_with_kind(
+        &mut self,
+        def_id: DefId,
+        parent_args: &'tcx [GenericArg<'tcx>],
+        kind: Ty<'tcx>,
+    ) -> Result<(), PrintError> {
+        self.print_def_path(def_id, parent_args)?;
+
+        let ty::Coroutine(_, args) = self.tcx.type_of(def_id).instantiate_identity().kind() else {
+            // Could be `ty::Error`.
+            return Ok(());
+        };
+
+        let default_kind = args.as_coroutine().kind_ty();
+
+        match kind.to_opt_closure_kind() {
+            _ if kind == default_kind => {
+                // No need to mark the closure if it's the deduced coroutine kind.
+            }
+            Some(ty::ClosureKind::Fn) | None => {
+                // Should never happen. Just don't mark anything rather than panicking.
+            }
+            Some(ty::ClosureKind::FnMut) => self.path.push_str("::{{call_mut}}"),
+            Some(ty::ClosureKind::FnOnce) => self.path.push_str("::{{call_once}}"),
+        }
+
+        Ok(())
+    }
 }
 
 impl<'tcx> PrettyPrinter<'tcx> for TypeNamePrinter<'tcx> {
-    fn should_print_optional_region(&self, _region: ty::Region<'_>) -> bool {
+    fn should_print_optional_region(&self, region: ty::Region<'_>) -> bool {
         // Bound regions are always printed (as `'_`), which gives some idea that they are special,
         // even though the `for` is omitted by the pretty printer.
         // E.g. `for<'a, 'b> fn(&'a u32, &'b u32)` is printed as "fn(&'_ u32, &'_ u32)".
-        match _region.kind() {
-            ty::ReErased => false,
+        match region.kind() {
+            ty::ReErased | ty::ReEarlyParam(_) => false,
             ty::ReBound(..) => true,
             _ => unreachable!(),
         }
diff --git a/compiler/rustc_data_structures/src/lib.rs b/compiler/rustc_data_structures/src/lib.rs
index 53178d09348..17da3ea83c8 100644
--- a/compiler/rustc_data_structures/src/lib.rs
+++ b/compiler/rustc_data_structures/src/lib.rs
@@ -77,6 +77,7 @@ pub mod thinvec;
 pub mod thousands;
 pub mod transitive_relation;
 pub mod unhash;
+pub mod union_find;
 pub mod unord;
 pub mod vec_cache;
 pub mod work_queue;
diff --git a/compiler/rustc_mir_transform/src/coverage/counters/union_find.rs b/compiler/rustc_data_structures/src/union_find.rs
index a826a953fa6..ef73cd7ab40 100644
--- a/compiler/rustc_mir_transform/src/coverage/counters/union_find.rs
+++ b/compiler/rustc_data_structures/src/union_find.rs
@@ -9,7 +9,7 @@ mod tests;
 /// Simple implementation of a union-find data structure, i.e. a disjoint-set
 /// forest.
 #[derive(Debug)]
-pub(crate) struct UnionFind<Key: Idx> {
+pub struct UnionFind<Key: Idx> {
     table: IndexVec<Key, UnionFindEntry<Key>>,
 }
 
@@ -28,7 +28,7 @@ struct UnionFindEntry<Key> {
 impl<Key: Idx> UnionFind<Key> {
     /// Creates a new disjoint-set forest containing the keys `0..num_keys`.
     /// Initially, every key is part of its own one-element set.
-    pub(crate) fn new(num_keys: usize) -> Self {
+    pub fn new(num_keys: usize) -> Self {
         // Initially, every key is the root of its own set, so its parent is itself.
         Self { table: IndexVec::from_fn_n(|key| UnionFindEntry { parent: key, rank: 0 }, num_keys) }
     }
@@ -38,7 +38,7 @@ impl<Key: Idx> UnionFind<Key> {
     ///
     /// Also updates internal data structures to make subsequent `find`
     /// operations faster.
-    pub(crate) fn find(&mut self, key: Key) -> Key {
+    pub fn find(&mut self, key: Key) -> Key {
         // Loop until we find a key that is its own parent.
         let mut curr = key;
         while let parent = self.table[curr].parent
@@ -60,7 +60,7 @@ impl<Key: Idx> UnionFind<Key> {
     /// Merges the set containing `a` and the set containing `b` into one set.
     ///
     /// Returns the common root of both keys, after the merge.
-    pub(crate) fn unify(&mut self, a: Key, b: Key) -> Key {
+    pub fn unify(&mut self, a: Key, b: Key) -> Key {
         let mut a = self.find(a);
         let mut b = self.find(b);
 
@@ -90,7 +90,7 @@ impl<Key: Idx> UnionFind<Key> {
 
     /// Takes a "snapshot" of the current state of this disjoint-set forest, in
     /// the form of a vector that directly maps each key to its current root.
-    pub(crate) fn snapshot(&mut self) -> IndexVec<Key, Key> {
+    pub fn snapshot(&mut self) -> IndexVec<Key, Key> {
         self.table.indices().map(|key| self.find(key)).collect()
     }
 }
diff --git a/compiler/rustc_mir_transform/src/coverage/counters/union_find/tests.rs b/compiler/rustc_data_structures/src/union_find/tests.rs
index 34a4e4f8e6e..34a4e4f8e6e 100644
--- a/compiler/rustc_mir_transform/src/coverage/counters/union_find/tests.rs
+++ b/compiler/rustc_data_structures/src/union_find/tests.rs
diff --git a/compiler/rustc_error_messages/Cargo.toml b/compiler/rustc_error_messages/Cargo.toml
index 0951859fa53..552ad672752 100644
--- a/compiler/rustc_error_messages/Cargo.toml
+++ b/compiler/rustc_error_messages/Cargo.toml
@@ -11,6 +11,8 @@ icu_list = "1.2"
 icu_locid = "1.2"
 icu_provider_adapters = "1.2"
 intl-memoizer = "0.5.1"
+rustc_ast = { path = "../rustc_ast" }
+rustc_ast_pretty = { path = "../rustc_ast_pretty" }
 rustc_baked_icu_data = { path = "../rustc_baked_icu_data" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_macros = { path = "../rustc_macros" }
diff --git a/compiler/rustc_error_messages/src/diagnostic_impls.rs b/compiler/rustc_error_messages/src/diagnostic_impls.rs
new file mode 100644
index 00000000000..3b664cce577
--- /dev/null
+++ b/compiler/rustc_error_messages/src/diagnostic_impls.rs
@@ -0,0 +1,205 @@
+use std::backtrace::Backtrace;
+use std::borrow::Cow;
+use std::fmt;
+use std::num::ParseIntError;
+use std::path::{Path, PathBuf};
+use std::process::ExitStatus;
+
+use rustc_ast as ast;
+use rustc_ast_pretty::pprust;
+use rustc_span::edition::Edition;
+
+use crate::{DiagArgValue, IntoDiagArg};
+
+pub struct DiagArgFromDisplay<'a>(pub &'a dyn fmt::Display);
+
+impl IntoDiagArg for DiagArgFromDisplay<'_> {
+    fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+        self.0.to_string().into_diag_arg(path)
+    }
+}
+
+impl<'a> From<&'a dyn fmt::Display> for DiagArgFromDisplay<'a> {
+    fn from(t: &'a dyn fmt::Display) -> Self {
+        DiagArgFromDisplay(t)
+    }
+}
+
+impl<'a, T: fmt::Display> From<&'a T> for DiagArgFromDisplay<'a> {
+    fn from(t: &'a T) -> Self {
+        DiagArgFromDisplay(t)
+    }
+}
+
+impl<'a, T: Clone + IntoDiagArg> IntoDiagArg for &'a T {
+    fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+        self.clone().into_diag_arg(path)
+    }
+}
+
+#[macro_export]
+macro_rules! into_diag_arg_using_display {
+    ($( $ty:ty ),+ $(,)?) => {
+        $(
+            impl $crate::IntoDiagArg for $ty {
+                fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> $crate::DiagArgValue {
+                    self.to_string().into_diag_arg(path)
+                }
+            }
+        )+
+    }
+}
+
+macro_rules! into_diag_arg_for_number {
+    ($( $ty:ty ),+ $(,)?) => {
+        $(
+            impl $crate::IntoDiagArg for $ty {
+                fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> $crate::DiagArgValue {
+                    // Convert to a string if it won't fit into `Number`.
+                    #[allow(irrefutable_let_patterns)]
+                    if let Ok(n) = TryInto::<i32>::try_into(self) {
+                        $crate::DiagArgValue::Number(n)
+                    } else {
+                        self.to_string().into_diag_arg(path)
+                    }
+                }
+            }
+        )+
+    }
+}
+
+into_diag_arg_using_display!(
+    ast::ParamKindOrd,
+    std::io::Error,
+    Box<dyn std::error::Error>,
+    std::num::NonZero<u32>,
+    Edition,
+    rustc_span::Ident,
+    rustc_span::MacroRulesNormalizedIdent,
+    ParseIntError,
+    ExitStatus,
+);
+
+into_diag_arg_for_number!(i8, u8, i16, u16, i32, u32, i64, u64, i128, u128, isize, usize);
+
+impl IntoDiagArg for bool {
+    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+        if self {
+            DiagArgValue::Str(Cow::Borrowed("true"))
+        } else {
+            DiagArgValue::Str(Cow::Borrowed("false"))
+        }
+    }
+}
+
+impl IntoDiagArg for char {
+    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+        DiagArgValue::Str(Cow::Owned(format!("{self:?}")))
+    }
+}
+
+impl IntoDiagArg for Vec<char> {
+    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+        DiagArgValue::StrListSepByAnd(
+            self.into_iter().map(|c| Cow::Owned(format!("{c:?}"))).collect(),
+        )
+    }
+}
+
+impl IntoDiagArg for rustc_span::Symbol {
+    fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+        self.to_ident_string().into_diag_arg(path)
+    }
+}
+
+impl<'a> IntoDiagArg for &'a str {
+    fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+        self.to_string().into_diag_arg(path)
+    }
+}
+
+impl IntoDiagArg for String {
+    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+        DiagArgValue::Str(Cow::Owned(self))
+    }
+}
+
+impl<'a> IntoDiagArg for Cow<'a, str> {
+    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+        DiagArgValue::Str(Cow::Owned(self.into_owned()))
+    }
+}
+
+impl<'a> IntoDiagArg for &'a Path {
+    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+        DiagArgValue::Str(Cow::Owned(self.display().to_string()))
+    }
+}
+
+impl IntoDiagArg for PathBuf {
+    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+        DiagArgValue::Str(Cow::Owned(self.display().to_string()))
+    }
+}
+
+impl IntoDiagArg for ast::Expr {
+    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+        DiagArgValue::Str(Cow::Owned(pprust::expr_to_string(&self)))
+    }
+}
+
+impl IntoDiagArg for ast::Path {
+    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+        DiagArgValue::Str(Cow::Owned(pprust::path_to_string(&self)))
+    }
+}
+
+impl IntoDiagArg for ast::token::Token {
+    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+        DiagArgValue::Str(pprust::token_to_string(&self))
+    }
+}
+
+impl IntoDiagArg for ast::token::TokenKind {
+    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+        DiagArgValue::Str(pprust::token_kind_to_string(&self))
+    }
+}
+
+impl IntoDiagArg for std::ffi::CString {
+    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+        DiagArgValue::Str(Cow::Owned(self.to_string_lossy().into_owned()))
+    }
+}
+
+impl IntoDiagArg for rustc_data_structures::small_c_str::SmallCStr {
+    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+        DiagArgValue::Str(Cow::Owned(self.to_string_lossy().into_owned()))
+    }
+}
+
+impl IntoDiagArg for ast::Visibility {
+    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+        let s = pprust::vis_to_string(&self);
+        let s = s.trim_end().to_string();
+        DiagArgValue::Str(Cow::Owned(s))
+    }
+}
+
+impl IntoDiagArg for Backtrace {
+    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+        DiagArgValue::Str(Cow::from(self.to_string()))
+    }
+}
+
+impl IntoDiagArg for ast::util::parser::ExprPrecedence {
+    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+        DiagArgValue::Number(self as i32)
+    }
+}
+
+impl IntoDiagArg for ast::FloatTy {
+    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+        DiagArgValue::Str(Cow::Borrowed(self.name_str()))
+    }
+}
diff --git a/compiler/rustc_error_messages/src/lib.rs b/compiler/rustc_error_messages/src/lib.rs
index 4b3ecad307f..d8bacbe762b 100644
--- a/compiler/rustc_error_messages/src/lib.rs
+++ b/compiler/rustc_error_messages/src/lib.rs
@@ -23,6 +23,9 @@ use rustc_span::Span;
 use tracing::{instrument, trace};
 pub use unic_langid::{LanguageIdentifier, langid};
 
+mod diagnostic_impls;
+pub use diagnostic_impls::DiagArgFromDisplay;
+
 pub type FluentBundle =
     IntoDynSyncSend<fluent_bundle::bundle::FluentBundle<FluentResource, IntlLangMemoizer>>;
 
@@ -589,3 +592,53 @@ pub fn fluent_value_from_str_list_sep_by_and(l: Vec<Cow<'_, str>>) -> FluentValu
 
     FluentValue::Custom(Box::new(FluentStrListSepByAnd(l)))
 }
+
+/// Simplified version of `FluentArg` that can implement `Encodable` and `Decodable`. Collection of
+/// `DiagArg` are converted to `FluentArgs` (consuming the collection) at the start of diagnostic
+/// emission.
+pub type DiagArg<'iter> = (&'iter DiagArgName, &'iter DiagArgValue);
+
+/// Name of a diagnostic argument.
+pub type DiagArgName = Cow<'static, str>;
+
+/// Simplified version of `FluentValue` that can implement `Encodable` and `Decodable`. Converted
+/// to a `FluentValue` by the emitter to be used in diagnostic translation.
+#[derive(Clone, Debug, PartialEq, Eq, Hash, Encodable, Decodable)]
+pub enum DiagArgValue {
+    Str(Cow<'static, str>),
+    // This gets converted to a `FluentNumber`, which is an `f64`. An `i32`
+    // safely fits in an `f64`. Any integers bigger than that will be converted
+    // to strings in `into_diag_arg` and stored using the `Str` variant.
+    Number(i32),
+    StrListSepByAnd(Vec<Cow<'static, str>>),
+}
+
+/// Converts a value of a type into a `DiagArg` (typically a field of an `Diag` struct).
+/// Implemented as a custom trait rather than `From` so that it is implemented on the type being
+/// converted rather than on `DiagArgValue`, which enables types from other `rustc_*` crates to
+/// implement this.
+pub trait IntoDiagArg {
+    /// Convert `Self` into a `DiagArgValue` suitable for rendering in a diagnostic.
+    ///
+    /// It takes a `path` where "long values" could be written to, if the `DiagArgValue` is too big
+    /// for displaying on the terminal. This path comes from the `Diag` itself. When rendering
+    /// values that come from `TyCtxt`, like `Ty<'_>`, they can use `TyCtxt::short_string`. If a
+    /// value has no shortening logic that could be used, the argument can be safely ignored.
+    fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> DiagArgValue;
+}
+
+impl IntoDiagArg for DiagArgValue {
+    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+        self
+    }
+}
+
+impl From<DiagArgValue> for FluentValue<'static> {
+    fn from(val: DiagArgValue) -> Self {
+        match val {
+            DiagArgValue::Str(s) => From::from(s),
+            DiagArgValue::Number(n) => From::from(n),
+            DiagArgValue::StrListSepByAnd(l) => fluent_value_from_str_list_sep_by_and(l),
+        }
+    }
+}
diff --git a/compiler/rustc_errors/Cargo.toml b/compiler/rustc_errors/Cargo.toml
index 3e8cf6207ae..7912b8e6098 100644
--- a/compiler/rustc_errors/Cargo.toml
+++ b/compiler/rustc_errors/Cargo.toml
@@ -9,21 +9,17 @@ annotate-snippets = "0.11"
 derive_setters = "0.1.6"
 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_error_codes = { path = "../rustc_error_codes" }
 rustc_error_messages = { path = "../rustc_error_messages" }
 rustc_fluent_macro = { path = "../rustc_fluent_macro" }
 rustc_hashes = { path = "../rustc_hashes" }
-rustc_hir = { path = "../rustc_hir" }
 rustc_index = { path = "../rustc_index" }
 rustc_lexer = { path = "../rustc_lexer" }
 rustc_lint_defs = { path = "../rustc_lint_defs" }
 rustc_macros = { path = "../rustc_macros" }
 rustc_serialize = { path = "../rustc_serialize" }
 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_json = "1.0.59"
 termcolor = "1.2.0"
diff --git a/compiler/rustc_errors/src/codes.rs b/compiler/rustc_errors/src/codes.rs
index 947cf27ca79..787a8af99b1 100644
--- a/compiler/rustc_errors/src/codes.rs
+++ b/compiler/rustc_errors/src/codes.rs
@@ -20,6 +20,8 @@ impl fmt::Display for ErrCode {
     }
 }
 
+rustc_error_messages::into_diag_arg_using_display!(ErrCode);
+
 macro_rules! define_error_code_constants_and_diagnostics_table {
     ($($name:ident: $num:literal,)*) => (
         $(
diff --git a/compiler/rustc_errors/src/decorate_diag.rs b/compiler/rustc_errors/src/decorate_diag.rs
new file mode 100644
index 00000000000..5aef26ccf97
--- /dev/null
+++ b/compiler/rustc_errors/src/decorate_diag.rs
@@ -0,0 +1,85 @@
+/// This module provides types and traits for buffering lints until later in compilation.
+use rustc_ast::node_id::NodeId;
+use rustc_data_structures::fx::FxIndexMap;
+use rustc_error_messages::MultiSpan;
+use rustc_lint_defs::{BuiltinLintDiag, Lint, LintId};
+
+use crate::{DynSend, LintDiagnostic, LintDiagnosticBox};
+
+/// We can't implement `LintDiagnostic` for `BuiltinLintDiag`, because decorating some of its
+/// variants requires types we don't have yet. So, handle that case separately.
+pub enum DecorateDiagCompat {
+    Dynamic(Box<dyn for<'a> LintDiagnosticBox<'a, ()> + DynSend + 'static>),
+    Builtin(BuiltinLintDiag),
+}
+
+impl std::fmt::Debug for DecorateDiagCompat {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("DecorateDiagCompat").finish()
+    }
+}
+
+impl !LintDiagnostic<'_, ()> for BuiltinLintDiag {}
+
+impl<D: for<'a> LintDiagnostic<'a, ()> + DynSend + 'static> From<D> for DecorateDiagCompat {
+    #[inline]
+    fn from(d: D) -> Self {
+        Self::Dynamic(Box::new(d))
+    }
+}
+
+impl From<BuiltinLintDiag> for DecorateDiagCompat {
+    #[inline]
+    fn from(b: BuiltinLintDiag) -> Self {
+        Self::Builtin(b)
+    }
+}
+
+/// Lints that are buffered up early on in the `Session` before the
+/// `LintLevels` is calculated.
+#[derive(Debug)]
+pub struct BufferedEarlyLint {
+    /// The span of code that we are linting on.
+    pub span: Option<MultiSpan>,
+
+    /// The `NodeId` of the AST node that generated the lint.
+    pub node_id: NodeId,
+
+    /// A lint Id that can be passed to
+    /// `rustc_lint::early::EarlyContextAndPass::check_id`.
+    pub lint_id: LintId,
+
+    /// Customization of the `Diag<'_>` for the lint.
+    pub diagnostic: DecorateDiagCompat,
+}
+
+#[derive(Default, Debug)]
+pub struct LintBuffer {
+    pub map: FxIndexMap<NodeId, Vec<BufferedEarlyLint>>,
+}
+
+impl LintBuffer {
+    pub fn add_early_lint(&mut self, early_lint: BufferedEarlyLint) {
+        self.map.entry(early_lint.node_id).or_default().push(early_lint);
+    }
+
+    pub fn take(&mut self, id: NodeId) -> Vec<BufferedEarlyLint> {
+        // FIXME(#120456) - is `swap_remove` correct?
+        self.map.swap_remove(&id).unwrap_or_default()
+    }
+
+    pub fn buffer_lint(
+        &mut self,
+        lint: &'static Lint,
+        node_id: NodeId,
+        span: impl Into<MultiSpan>,
+        decorate: impl Into<DecorateDiagCompat>,
+    ) {
+        self.add_early_lint(BufferedEarlyLint {
+            lint_id: LintId::of(lint),
+            node_id,
+            span: Some(span.into()),
+            diagnostic: decorate.into(),
+        });
+    }
+}
diff --git a/compiler/rustc_errors/src/diagnostic.rs b/compiler/rustc_errors/src/diagnostic.rs
index e579370ce4e..96a4ed3218f 100644
--- a/compiler/rustc_errors/src/diagnostic.rs
+++ b/compiler/rustc_errors/src/diagnostic.rs
@@ -8,7 +8,7 @@ use std::path::PathBuf;
 use std::thread::panicking;
 
 use rustc_data_structures::fx::FxIndexMap;
-use rustc_error_messages::{FluentValue, fluent_value_from_str_list_sep_by_and};
+use rustc_error_messages::{DiagArgName, DiagArgValue, IntoDiagArg};
 use rustc_lint_defs::{Applicability, LintExpectationId};
 use rustc_macros::{Decodable, Encodable};
 use rustc_span::source_map::Spanned;
@@ -22,26 +22,6 @@ use crate::{
     Suggestions,
 };
 
-/// Simplified version of `FluentArg` that can implement `Encodable` and `Decodable`. Collection of
-/// `DiagArg` are converted to `FluentArgs` (consuming the collection) at the start of diagnostic
-/// emission.
-pub type DiagArg<'iter> = (&'iter DiagArgName, &'iter DiagArgValue);
-
-/// Name of a diagnostic argument.
-pub type DiagArgName = Cow<'static, str>;
-
-/// Simplified version of `FluentValue` that can implement `Encodable` and `Decodable`. Converted
-/// to a `FluentValue` by the emitter to be used in diagnostic translation.
-#[derive(Clone, Debug, PartialEq, Eq, Hash, Encodable, Decodable)]
-pub enum DiagArgValue {
-    Str(Cow<'static, str>),
-    // This gets converted to a `FluentNumber`, which is an `f64`. An `i32`
-    // safely fits in an `f64`. Any integers bigger than that will be converted
-    // to strings in `into_diag_arg` and stored using the `Str` variant.
-    Number(i32),
-    StrListSepByAnd(Vec<Cow<'static, str>>),
-}
-
 pub type DiagArgMap = FxIndexMap<DiagArgName, DiagArgValue>;
 
 /// Trait for types that `Diag::emit` can return as a "guarantee" (or "proof")
@@ -143,36 +123,6 @@ where
     }
 }
 
-/// Converts a value of a type into a `DiagArg` (typically a field of an `Diag` struct).
-/// Implemented as a custom trait rather than `From` so that it is implemented on the type being
-/// converted rather than on `DiagArgValue`, which enables types from other `rustc_*` crates to
-/// implement this.
-pub trait IntoDiagArg {
-    /// Convert `Self` into a `DiagArgValue` suitable for rendering in a diagnostic.
-    ///
-    /// It takes a `path` where "long values" could be written to, if the `DiagArgValue` is too big
-    /// for displaying on the terminal. This path comes from the `Diag` itself. When rendering
-    /// values that come from `TyCtxt`, like `Ty<'_>`, they can use `TyCtxt::short_string`. If a
-    /// value has no shortening logic that could be used, the argument can be safely ignored.
-    fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> DiagArgValue;
-}
-
-impl IntoDiagArg for DiagArgValue {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        self
-    }
-}
-
-impl From<DiagArgValue> for FluentValue<'static> {
-    fn from(val: DiagArgValue) -> Self {
-        match val {
-            DiagArgValue::Str(s) => From::from(s),
-            DiagArgValue::Number(n) => From::from(n),
-            DiagArgValue::StrListSepByAnd(l) => fluent_value_from_str_list_sep_by_and(l),
-        }
-    }
-}
-
 /// Trait implemented by error types. This should not be implemented manually. Instead, use
 /// `#[derive(Subdiagnostic)]` -- see [rustc_macros::Subdiagnostic].
 #[rustc_diagnostic_item = "Subdiagnostic"]
@@ -188,10 +138,20 @@ where
 /// `#[derive(LintDiagnostic)]` -- see [rustc_macros::LintDiagnostic].
 #[rustc_diagnostic_item = "LintDiagnostic"]
 pub trait LintDiagnostic<'a, G: EmissionGuarantee> {
-    /// Decorate and emit a lint.
+    /// Decorate a lint with the information from this type.
     fn decorate_lint<'b>(self, diag: &'b mut Diag<'a, G>);
 }
 
+pub trait LintDiagnosticBox<'a, G: EmissionGuarantee> {
+    fn decorate_lint_box<'b>(self: Box<Self>, diag: &'b mut Diag<'a, G>);
+}
+
+impl<'a, G: EmissionGuarantee, D: LintDiagnostic<'a, G>> LintDiagnosticBox<'a, G> for D {
+    fn decorate_lint_box<'b>(self: Box<Self>, diag: &'b mut Diag<'a, G>) {
+        self.decorate_lint(diag);
+    }
+}
+
 #[derive(Clone, Debug, Encodable, Decodable)]
 pub(crate) struct DiagLocation {
     file: Cow<'static, str>,
@@ -617,6 +577,29 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
         self.level = Level::DelayedBug;
     }
 
+    /// Make emitting this diagnostic fatal
+    ///
+    /// Changes the level of this diagnostic to Fatal, and importantly also changes the emission guarantee.
+    /// This is sound for errors that would otherwise be printed, but now simply exit the process instead.
+    /// This function still gives an emission guarantee, the guarantee is now just that it exits fatally.
+    /// For delayed bugs this is different, since those are buffered. If we upgrade one to fatal, another
+    /// might now be ignored.
+    #[rustc_lint_diagnostics]
+    #[track_caller]
+    pub fn upgrade_to_fatal(mut self) -> Diag<'a, FatalAbort> {
+        assert!(
+            matches!(self.level, Level::Error),
+            "upgrade_to_fatal: cannot upgrade {:?} to Fatal: not an error",
+            self.level
+        );
+        self.level = Level::Fatal;
+
+        // Take is okay since we immediately rewrap it in another diagnostic.
+        // i.e. we do emit it despite defusing the original diagnostic's drop bomb.
+        let diag = self.diag.take();
+        Diag { dcx: self.dcx, diag, _marker: PhantomData }
+    }
+
     with_fn! { with_span_label,
     /// Appends a labeled span to the diagnostic.
     ///
diff --git a/compiler/rustc_errors/src/diagnostic_impls.rs b/compiler/rustc_errors/src/diagnostic_impls.rs
index 698b6b8d504..435d16a8380 100644
--- a/compiler/rustc_errors/src/diagnostic_impls.rs
+++ b/compiler/rustc_errors/src/diagnostic_impls.rs
@@ -1,340 +1,22 @@
-use std::backtrace::Backtrace;
 use std::borrow::Cow;
-use std::fmt;
-use std::num::ParseIntError;
-use std::path::{Path, PathBuf};
-use std::process::ExitStatus;
 
 use rustc_abi::TargetDataLayoutErrors;
-use rustc_ast::util::parser::ExprPrecedence;
-use rustc_ast_pretty::pprust;
-use rustc_hir::RustcVersion;
-use rustc_hir::attrs::{MirDialect, MirPhase};
+use rustc_error_messages::{DiagArgValue, IntoDiagArg};
 use rustc_macros::Subdiagnostic;
-use rustc_span::edition::Edition;
-use rustc_span::{Ident, MacroRulesNormalizedIdent, Span, Symbol};
-use rustc_target::spec::{PanicStrategy, SplitDebuginfo, StackProtector, TargetTuple};
-use rustc_type_ir::{ClosureKind, FloatTy};
-use {rustc_ast as ast, rustc_hir as hir};
+use rustc_span::{Span, Symbol};
 
 use crate::diagnostic::DiagLocation;
 use crate::{
-    Diag, DiagArgValue, DiagCtxtHandle, Diagnostic, EmissionGuarantee, ErrCode, IntoDiagArg, Level,
-    Subdiagnostic, fluent_generated as fluent,
+    Diag, DiagCtxtHandle, Diagnostic, EmissionGuarantee, Level, Subdiagnostic,
+    fluent_generated as fluent,
 };
 
-pub struct DiagArgFromDisplay<'a>(pub &'a dyn fmt::Display);
-
-impl IntoDiagArg for DiagArgFromDisplay<'_> {
-    fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        self.0.to_string().into_diag_arg(path)
-    }
-}
-
-impl<'a> From<&'a dyn fmt::Display> for DiagArgFromDisplay<'a> {
-    fn from(t: &'a dyn fmt::Display) -> Self {
-        DiagArgFromDisplay(t)
-    }
-}
-
-impl<'a, T: fmt::Display> From<&'a T> for DiagArgFromDisplay<'a> {
-    fn from(t: &'a T) -> Self {
-        DiagArgFromDisplay(t)
-    }
-}
-
-impl<'a, T: Clone + IntoDiagArg> IntoDiagArg for &'a T {
-    fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        self.clone().into_diag_arg(path)
-    }
-}
-
-#[macro_export]
-macro_rules! into_diag_arg_using_display {
-    ($( $ty:ty ),+ $(,)?) => {
-        $(
-            impl IntoDiagArg for $ty {
-                fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-                    self.to_string().into_diag_arg(path)
-                }
-            }
-        )+
-    }
-}
-
-macro_rules! into_diag_arg_for_number {
-    ($( $ty:ty ),+ $(,)?) => {
-        $(
-            impl IntoDiagArg for $ty {
-                fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-                    // Convert to a string if it won't fit into `Number`.
-                    #[allow(irrefutable_let_patterns)]
-                    if let Ok(n) = TryInto::<i32>::try_into(self) {
-                        DiagArgValue::Number(n)
-                    } else {
-                        self.to_string().into_diag_arg(path)
-                    }
-                }
-            }
-        )+
-    }
-}
-
-into_diag_arg_using_display!(
-    ast::ParamKindOrd,
-    std::io::Error,
-    Box<dyn std::error::Error>,
-    std::num::NonZero<u32>,
-    hir::Target,
-    Edition,
-    Ident,
-    MacroRulesNormalizedIdent,
-    ParseIntError,
-    StackProtector,
-    &TargetTuple,
-    SplitDebuginfo,
-    ExitStatus,
-    ErrCode,
-    rustc_abi::ExternAbi,
-);
-
-impl IntoDiagArg for RustcVersion {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::Owned(self.to_string()))
-    }
-}
-
-impl<I: rustc_type_ir::Interner> IntoDiagArg for rustc_type_ir::TraitRef<I> {
-    fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        self.to_string().into_diag_arg(path)
-    }
-}
-
-impl<I: rustc_type_ir::Interner> IntoDiagArg for rustc_type_ir::ExistentialTraitRef<I> {
-    fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        self.to_string().into_diag_arg(path)
-    }
-}
-
-impl<I: rustc_type_ir::Interner> IntoDiagArg for rustc_type_ir::UnevaluatedConst<I> {
-    fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        format!("{self:?}").into_diag_arg(path)
-    }
-}
-
-impl<I: rustc_type_ir::Interner> IntoDiagArg for rustc_type_ir::FnSig<I> {
-    fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        format!("{self:?}").into_diag_arg(path)
-    }
-}
-
-impl<I: rustc_type_ir::Interner, T> IntoDiagArg for rustc_type_ir::Binder<I, T>
-where
-    T: IntoDiagArg,
-{
-    fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        self.skip_binder().into_diag_arg(path)
-    }
-}
-
-into_diag_arg_for_number!(i8, u8, i16, u16, i32, u32, i64, u64, i128, u128, isize, usize);
-
-impl IntoDiagArg for bool {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        if self {
-            DiagArgValue::Str(Cow::Borrowed("true"))
-        } else {
-            DiagArgValue::Str(Cow::Borrowed("false"))
-        }
-    }
-}
-
-impl IntoDiagArg for char {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::Owned(format!("{self:?}")))
-    }
-}
-
-impl IntoDiagArg for Vec<char> {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::StrListSepByAnd(
-            self.into_iter().map(|c| Cow::Owned(format!("{c:?}"))).collect(),
-        )
-    }
-}
-
-impl IntoDiagArg for Symbol {
-    fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        self.to_ident_string().into_diag_arg(path)
-    }
-}
-
-impl<'a> IntoDiagArg for &'a str {
-    fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        self.to_string().into_diag_arg(path)
-    }
-}
-
-impl IntoDiagArg for String {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::Owned(self))
-    }
-}
-
-impl<'a> IntoDiagArg for Cow<'a, str> {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::Owned(self.into_owned()))
-    }
-}
-
-impl<'a> IntoDiagArg for &'a Path {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::Owned(self.display().to_string()))
-    }
-}
-
-impl IntoDiagArg for PathBuf {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::Owned(self.display().to_string()))
-    }
-}
-
-impl IntoDiagArg for PanicStrategy {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::Owned(self.desc().to_string()))
-    }
-}
-
-impl IntoDiagArg for hir::ConstContext {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::Borrowed(match self {
-            hir::ConstContext::ConstFn => "const_fn",
-            hir::ConstContext::Static(_) => "static",
-            hir::ConstContext::Const { .. } => "const",
-        }))
-    }
-}
-
-impl IntoDiagArg for ast::Expr {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::Owned(pprust::expr_to_string(&self)))
-    }
-}
-
-impl IntoDiagArg for ast::Path {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::Owned(pprust::path_to_string(&self)))
-    }
-}
-
-impl IntoDiagArg for ast::token::Token {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(pprust::token_to_string(&self))
-    }
-}
-
-impl IntoDiagArg for ast::token::TokenKind {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(pprust::token_kind_to_string(&self))
-    }
-}
-
-impl IntoDiagArg for FloatTy {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::Borrowed(self.name_str()))
-    }
-}
-
-impl IntoDiagArg for std::ffi::CString {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::Owned(self.to_string_lossy().into_owned()))
-    }
-}
-
-impl IntoDiagArg for rustc_data_structures::small_c_str::SmallCStr {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::Owned(self.to_string_lossy().into_owned()))
-    }
-}
-
-impl IntoDiagArg for ast::Visibility {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        let s = pprust::vis_to_string(&self);
-        let s = s.trim_end().to_string();
-        DiagArgValue::Str(Cow::Owned(s))
-    }
-}
-
-impl IntoDiagArg for rustc_lint_defs::Level {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::Borrowed(self.to_cmd_flag()))
-    }
-}
-
-impl<Id> IntoDiagArg for hir::def::Res<Id> {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::Borrowed(self.descr()))
-    }
-}
-
 impl IntoDiagArg for DiagLocation {
     fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
         DiagArgValue::Str(Cow::from(self.to_string()))
     }
 }
 
-impl IntoDiagArg for Backtrace {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::from(self.to_string()))
-    }
-}
-
-impl IntoDiagArg for Level {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::from(self.to_string()))
-    }
-}
-
-impl IntoDiagArg for ClosureKind {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(self.as_str().into())
-    }
-}
-
-impl IntoDiagArg for hir::def::Namespace {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::Borrowed(self.descr()))
-    }
-}
-
-impl IntoDiagArg for ExprPrecedence {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Number(self as i32)
-    }
-}
-
-impl IntoDiagArg for MirDialect {
-    fn into_diag_arg(self, _path: &mut Option<PathBuf>) -> DiagArgValue {
-        let arg = match self {
-            MirDialect::Analysis => "analysis",
-            MirDialect::Built => "built",
-            MirDialect::Runtime => "runtime",
-        };
-        DiagArgValue::Str(Cow::Borrowed(arg))
-    }
-}
-
-impl IntoDiagArg for MirPhase {
-    fn into_diag_arg(self, _path: &mut Option<PathBuf>) -> DiagArgValue {
-        let arg = match self {
-            MirPhase::Initial => "initial",
-            MirPhase::PostCleanup => "post-cleanup",
-            MirPhase::Optimized => "optimized",
-        };
-        DiagArgValue::Str(Cow::Borrowed(arg))
-    }
-}
-
 #[derive(Clone)]
 pub struct DiagSymbolList<S = Symbol>(Vec<S>);
 
diff --git a/compiler/rustc_errors/src/emitter.rs b/compiler/rustc_errors/src/emitter.rs
index 97c47fa9b9a..749bba5de12 100644
--- a/compiler/rustc_errors/src/emitter.rs
+++ b/compiler/rustc_errors/src/emitter.rs
@@ -17,7 +17,7 @@ use std::path::Path;
 use std::sync::Arc;
 
 use derive_setters::Setters;
-use rustc_data_structures::fx::{FxHashMap, FxIndexMap, FxIndexSet};
+use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_data_structures::sync::{DynSend, IntoDynSyncSend};
 use rustc_error_messages::{FluentArgs, SpanLabel};
 use rustc_lexer;
@@ -1853,7 +1853,7 @@ impl HumanEmitter {
                             && line_idx + 1 == annotated_file.lines.len(),
                     );
 
-                    let mut to_add = FxHashMap::default();
+                    let mut to_add = FxIndexMap::default();
 
                     for (depth, style) in depths {
                         // FIXME(#120456) - is `swap_remove` correct?
diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index 2534cddf105..71fc54f0d33 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -40,13 +40,13 @@ use std::{fmt, panic};
 
 use Level::*;
 pub use codes::*;
+pub use decorate_diag::{BufferedEarlyLint, DecorateDiagCompat, LintBuffer};
 pub use diagnostic::{
-    BugAbort, Diag, DiagArg, DiagArgMap, DiagArgName, DiagArgValue, DiagInner, DiagStyledString,
-    Diagnostic, EmissionGuarantee, FatalAbort, IntoDiagArg, LintDiagnostic, StringPart, Subdiag,
-    Subdiagnostic,
+    BugAbort, Diag, DiagArgMap, DiagInner, DiagStyledString, Diagnostic, EmissionGuarantee,
+    FatalAbort, LintDiagnostic, LintDiagnosticBox, StringPart, Subdiag, Subdiagnostic,
 };
 pub use diagnostic_impls::{
-    DiagArgFromDisplay, DiagSymbolList, ElidedLifetimeInPathSubdiag, ExpectedLifetimeParameter,
+    DiagSymbolList, ElidedLifetimeInPathSubdiag, ExpectedLifetimeParameter,
     IndicateAnonymousLifetime, SingleLabelManySpans,
 };
 pub use emitter::ColorConfig;
@@ -56,11 +56,11 @@ use rustc_data_structures::fx::{FxHashSet, FxIndexMap, FxIndexSet};
 use rustc_data_structures::stable_hasher::StableHasher;
 use rustc_data_structures::sync::{DynSend, Lock};
 pub use rustc_error_messages::{
-    DiagMessage, FluentBundle, LanguageIdentifier, LazyFallbackBundle, MultiSpan, SpanLabel,
-    SubdiagMessage, fallback_fluent_bundle, fluent_bundle,
+    DiagArg, DiagArgFromDisplay, DiagArgName, DiagArgValue, DiagMessage, FluentBundle, IntoDiagArg,
+    LanguageIdentifier, LazyFallbackBundle, MultiSpan, SpanLabel, SubdiagMessage,
+    fallback_fluent_bundle, fluent_bundle, into_diag_arg_using_display,
 };
 use rustc_hashes::Hash128;
-use rustc_hir::HirId;
 pub use rustc_lint_defs::{Applicability, listify, pluralize};
 use rustc_lint_defs::{Lint, LintExpectationId};
 use rustc_macros::{Decodable, Encodable};
@@ -80,6 +80,7 @@ use crate::timings::TimingRecord;
 
 pub mod annotate_snippet_emitter_writer;
 pub mod codes;
+mod decorate_diag;
 mod diagnostic;
 mod diagnostic_impls;
 pub mod emitter;
@@ -108,13 +109,14 @@ rustc_data_structures::static_assert_size!(PResult<'_, bool>, 24);
 /// Used to avoid depending on `rustc_middle` in `rustc_attr_parsing`.
 /// Always the `TyCtxt`.
 pub trait LintEmitter: Copy {
+    type Id: Copy;
     #[track_caller]
     fn emit_node_span_lint(
         self,
         lint: &'static Lint,
-        hir_id: HirId,
+        hir_id: Self::Id,
         span: impl Into<MultiSpan>,
-        decorator: impl for<'a> LintDiagnostic<'a, ()>,
+        decorator: impl for<'a> LintDiagnostic<'a, ()> + DynSend + 'static,
     );
 }
 
@@ -1999,6 +2001,12 @@ impl Level {
     }
 }
 
+impl IntoDiagArg for Level {
+    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+        DiagArgValue::Str(Cow::from(self.to_string()))
+    }
+}
+
 // FIXME(eddyb) this doesn't belong here AFAICT, should be moved to callsite.
 pub fn elided_lifetime_in_path_suggestion(
     source_map: &SourceMap,
diff --git a/compiler/rustc_expand/src/base.rs b/compiler/rustc_expand/src/base.rs
index f2c15071532..8ff21509f4a 100644
--- a/compiler/rustc_expand/src/base.rs
+++ b/compiler/rustc_expand/src/base.rs
@@ -13,13 +13,13 @@ use rustc_ast::visit::{AssocCtxt, Visitor};
 use rustc_ast::{self as ast, AttrVec, Attribute, HasAttrs, Item, NodeId, PatKind};
 use rustc_data_structures::fx::{FxHashMap, FxIndexMap};
 use rustc_data_structures::sync;
-use rustc_errors::{DiagCtxtHandle, ErrorGuaranteed, PResult};
+use rustc_errors::{BufferedEarlyLint, DiagCtxtHandle, ErrorGuaranteed, PResult};
 use rustc_feature::Features;
 use rustc_hir as hir;
 use rustc_hir::attrs::{AttributeKind, CfgEntry, Deprecation};
 use rustc_hir::def::MacroKinds;
 use rustc_hir::{Stability, find_attr};
-use rustc_lint_defs::{BufferedEarlyLint, RegisteredTools};
+use rustc_lint_defs::RegisteredTools;
 use rustc_parse::MACRO_ARGUMENTS;
 use rustc_parse::parser::{ForceCollect, Parser};
 use rustc_session::config::CollapseMacroDebuginfo;
diff --git a/compiler/rustc_expand/src/config.rs b/compiler/rustc_expand/src/config.rs
index 83a8d601afe..15419ab7423 100644
--- a/compiler/rustc_expand/src/config.rs
+++ b/compiler/rustc_expand/src/config.rs
@@ -11,8 +11,10 @@ use rustc_ast::{
     NodeId, NormalAttr,
 };
 use rustc_attr_parsing as attr;
+use rustc_attr_parsing::validate_attr::deny_builtin_meta_unsafety;
 use rustc_attr_parsing::{
     AttributeParser, CFG_TEMPLATE, EvalConfigResult, ShouldEmit, eval_config_entry, parse_cfg_attr,
+    validate_attr,
 };
 use rustc_data_structures::flat_map_in_place::FlatMapInPlace;
 use rustc_feature::{
@@ -20,8 +22,6 @@ use rustc_feature::{
     REMOVED_LANG_FEATURES, UNSTABLE_LANG_FEATURES,
 };
 use rustc_lint_defs::BuiltinLintDiag;
-use rustc_parse::validate_attr;
-use rustc_parse::validate_attr::deny_builtin_meta_unsafety;
 use rustc_session::Session;
 use rustc_session::parse::feature_err;
 use rustc_span::{STDLIB_STABLE_CRATES, Span, Symbol, sym};
@@ -415,16 +415,6 @@ impl<'a> StripUnconfigured<'a> {
         node: NodeId,
         emit_errors: ShouldEmit,
     ) -> EvalConfigResult {
-        // We need to run this to do basic validation of the attribute, such as that lits are valid, etc
-        // FIXME(jdonszelmann) this should not be necessary in the future
-        match validate_attr::parse_meta(&self.sess.psess, attr) {
-            Ok(_) => {}
-            Err(err) => {
-                err.emit();
-                return EvalConfigResult::True;
-            }
-        }
-
         // Unsafety check needs to be done explicitly here because this attribute will be removed before the normal check
         deny_builtin_meta_unsafety(
             self.sess.dcx(),
diff --git a/compiler/rustc_expand/src/expand.rs b/compiler/rustc_expand/src/expand.rs
index 1f7f4c7d856..dbb4a9de9e0 100644
--- a/compiler/rustc_expand/src/expand.rs
+++ b/compiler/rustc_expand/src/expand.rs
@@ -1,7 +1,7 @@
 use std::path::PathBuf;
 use std::rc::Rc;
 use std::sync::Arc;
-use std::{iter, mem};
+use std::{iter, mem, slice};
 
 use rustc_ast::mut_visit::*;
 use rustc_ast::tokenstream::TokenStream;
@@ -12,16 +12,17 @@ use rustc_ast::{
     MetaItemKind, ModKind, NodeId, PatKind, StmtKind, TyKind, token,
 };
 use rustc_ast_pretty::pprust;
-use rustc_attr_parsing::{EvalConfigResult, ShouldEmit};
+use rustc_attr_parsing::{AttributeParser, Early, EvalConfigResult, ShouldEmit, validate_attr};
 use rustc_data_structures::flat_map_in_place::FlatMapInPlace;
+use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_errors::PResult;
 use rustc_feature::Features;
+use rustc_hir::Target;
 use rustc_hir::def::MacroKinds;
 use rustc_parse::parser::{
     AttemptLocalParseRecovery, CommaRecoveryMode, ForceCollect, Parser, RecoverColon, RecoverComma,
     token_descr,
 };
-use rustc_parse::validate_attr;
 use rustc_session::lint::BuiltinLintDiag;
 use rustc_session::lint::builtin::{UNUSED_ATTRIBUTES, UNUSED_DOC_COMMENTS};
 use rustc_session::parse::feature_err;
@@ -801,7 +802,8 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                                     ItemKind::Mod(
                                         _,
                                         _,
-                                        ModKind::Unloaded | ModKind::Loaded(_, Inline::No, _, _),
+                                        ModKind::Unloaded
+                                            | ModKind::Loaded(_, Inline::No { .. }, _),
                                     )
                                 ) =>
                         {
@@ -1035,7 +1037,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
             fn visit_item(&mut self, item: &'ast ast::Item) {
                 match &item.kind {
                     ItemKind::Mod(_, _, mod_kind)
-                        if !matches!(mod_kind, ModKind::Loaded(_, Inline::Yes, _, _)) =>
+                        if !matches!(mod_kind, ModKind::Loaded(_, Inline::Yes, _)) =>
                     {
                         feature_err(
                             self.sess,
@@ -1346,7 +1348,7 @@ impl InvocationCollectorNode for Box<ast::Item> {
         let ItemKind::Mod(_, ident, ref mut mod_kind) = node.kind else { unreachable!() };
         let ecx = &mut collector.cx;
         let (file_path, dir_path, dir_ownership) = match mod_kind {
-            ModKind::Loaded(_, inline, _, _) => {
+            ModKind::Loaded(_, inline, _) => {
                 // Inline `mod foo { ... }`, but we still need to push directories.
                 let (dir_path, dir_ownership) = mod_dir_path(
                     ecx.sess,
@@ -1360,7 +1362,7 @@ impl InvocationCollectorNode for Box<ast::Item> {
                 // This lets `parse_external_mod` catch cycles if it's self-referential.
                 let file_path = match inline {
                     Inline::Yes => None,
-                    Inline::No => mod_file_path_from_attr(ecx.sess, &attrs, &dir_path),
+                    Inline::No { .. } => mod_file_path_from_attr(ecx.sess, &attrs, &dir_path),
                 };
                 node.attrs = attrs;
                 (file_path, dir_path, dir_ownership)
@@ -1396,7 +1398,7 @@ impl InvocationCollectorNode for Box<ast::Item> {
                     );
                 }
 
-                *mod_kind = ModKind::Loaded(items, Inline::No, spans, had_parse_error);
+                *mod_kind = ModKind::Loaded(items, Inline::No { had_parse_error }, spans);
                 node.attrs = attrs;
                 if node.attrs.len() > old_attrs_len {
                     // If we loaded an out-of-line module and added some inner attributes,
@@ -2157,6 +2159,16 @@ impl<'a, 'b> InvocationCollector<'a, 'b> {
                 attr,
                 self.cx.current_expansion.lint_node_id,
             );
+            AttributeParser::parse_limited_all(
+                self.cx.sess,
+                slice::from_ref(attr),
+                None,
+                Target::MacroCall,
+                call.span(),
+                self.cx.current_expansion.lint_node_id,
+                Some(self.cx.ecfg.features),
+                ShouldEmit::ErrorsAndLints,
+            );
 
             let current_span = if let Some(sp) = span { sp.to(attr.span) } else { attr.span };
             span = Some(current_span);
@@ -2172,7 +2184,9 @@ impl<'a, 'b> InvocationCollector<'a, 'b> {
                     self.cx.current_expansion.lint_node_id,
                     BuiltinLintDiag::UnusedDocComment(attr.span),
                 );
-            } else if rustc_attr_parsing::is_builtin_attr(attr) {
+            } else if rustc_attr_parsing::is_builtin_attr(attr)
+                && !AttributeParser::<Early>::is_parsed_attribute(&attr.path())
+            {
                 let attr_name = attr.ident().unwrap().name;
                 // `#[cfg]` and `#[cfg_attr]` are special - they are
                 // eagerly evaluated.
@@ -2468,7 +2482,7 @@ impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
         if let Some(attr) = node.attrs.first() {
             self.cfg().maybe_emit_expr_attr_err(attr);
         }
-        self.visit_node(node)
+        ensure_sufficient_stack(|| self.visit_node(node))
     }
 
     fn visit_method_receiver_expr(&mut self, node: &mut ast::Expr) {
diff --git a/compiler/rustc_expand/src/mbe/macro_rules.rs b/compiler/rustc_expand/src/mbe/macro_rules.rs
index bced02ae4da..8b43f852b26 100644
--- a/compiler/rustc_expand/src/mbe/macro_rules.rs
+++ b/compiler/rustc_expand/src/mbe/macro_rules.rs
@@ -596,6 +596,7 @@ pub(super) fn try_match_macro_attr<'matcher, T: Tracker<'matcher>>(
         match result {
             Success(body_named_matches) => {
                 psess.gated_spans.merge(gated_spans_snapshot);
+                #[allow(rustc::potential_query_instability)]
                 named_matches.extend(body_named_matches);
                 return Ok((i, rule, named_matches));
             }
diff --git a/compiler/rustc_expand/src/module.rs b/compiler/rustc_expand/src/module.rs
index 662c67f2d3f..19f3cdbc549 100644
--- a/compiler/rustc_expand/src/module.rs
+++ b/compiler/rustc_expand/src/module.rs
@@ -2,8 +2,9 @@ use std::iter::once;
 use std::path::{self, Path, PathBuf};
 
 use rustc_ast::{AttrVec, Attribute, Inline, Item, ModSpans};
+use rustc_attr_parsing::validate_attr;
 use rustc_errors::{Diag, ErrorGuaranteed};
-use rustc_parse::{exp, new_parser_from_file, unwrap_or_emit_fatal, validate_attr};
+use rustc_parse::{exp, new_parser_from_file, unwrap_or_emit_fatal};
 use rustc_session::Session;
 use rustc_session::parse::ParseSess;
 use rustc_span::{Ident, Span, sym};
@@ -120,7 +121,7 @@ pub(crate) fn mod_dir_path(
 
             (dir_path, dir_ownership)
         }
-        Inline::No => {
+        Inline::No { .. } => {
             // FIXME: This is a subset of `parse_external_mod` without actual parsing,
             // check whether the logic for unloaded, loaded and inline modules can be unified.
             let file_path = mod_file_path(sess, ident, attrs, &module.dir_path, dir_ownership)
diff --git a/compiler/rustc_expand/src/proc_macro_server.rs b/compiler/rustc_expand/src/proc_macro_server.rs
index fd71f2ce948..5b1d3d6d35b 100644
--- a/compiler/rustc_expand/src/proc_macro_server.rs
+++ b/compiler/rustc_expand/src/proc_macro_server.rs
@@ -250,12 +250,14 @@ impl FromInternal<(TokenStream, &mut Rustc<'_, '_>)> for Vec<TokenTree<TokenStre
                 Question => op("?"),
                 SingleQuote => op("'"),
 
-                Ident(sym, is_raw) => {
-                    trees.push(TokenTree::Ident(Ident { sym, is_raw: is_raw.into(), span }))
-                }
+                Ident(sym, is_raw) => trees.push(TokenTree::Ident(Ident {
+                    sym,
+                    is_raw: matches!(is_raw, IdentIsRaw::Yes),
+                    span,
+                })),
                 NtIdent(ident, is_raw) => trees.push(TokenTree::Ident(Ident {
                     sym: ident.name,
-                    is_raw: is_raw.into(),
+                    is_raw: matches!(is_raw, IdentIsRaw::Yes),
                     span: ident.span,
                 })),
 
@@ -263,7 +265,11 @@ impl FromInternal<(TokenStream, &mut Rustc<'_, '_>)> for Vec<TokenTree<TokenStre
                     let ident = rustc_span::Ident::new(name, span).without_first_quote();
                     trees.extend([
                         TokenTree::Punct(Punct { ch: b'\'', joint: true, span }),
-                        TokenTree::Ident(Ident { sym: ident.name, is_raw: is_raw.into(), span }),
+                        TokenTree::Ident(Ident {
+                            sym: ident.name,
+                            is_raw: matches!(is_raw, IdentIsRaw::Yes),
+                            span,
+                        }),
                     ]);
                 }
                 NtLifetime(ident, is_raw) => {
diff --git a/compiler/rustc_feature/src/builtin_attrs.rs b/compiler/rustc_feature/src/builtin_attrs.rs
index 3b11a2bc7df..e81003b1897 100644
--- a/compiler/rustc_feature/src/builtin_attrs.rs
+++ b/compiler/rustc_feature/src/builtin_attrs.rs
@@ -745,6 +745,10 @@ pub static BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
         ErrorPreceding, EncodeCrossCrate::No
     ),
     gated!(
+        unsafe force_target_feature, Normal, template!(List: &[r#"enable = "name""#]),
+        DuplicatesOk, EncodeCrossCrate::No, effective_target_features, experimental!(force_target_feature)
+    ),
+    gated!(
         sanitize, Normal, template!(List: &[r#"address = "on|off""#, r#"kernel_address = "on|off""#, r#"cfi = "on|off""#, r#"hwaddress = "on|off""#, r#"kcfi = "on|off""#, r#"memory = "on|off""#, r#"memtag = "on|off""#, r#"shadow_call_stack = "on|off""#, r#"thread = "on|off""#]), ErrorPreceding,
         EncodeCrossCrate::No, sanitize, experimental!(sanitize),
     ),
@@ -996,6 +1000,10 @@ pub static BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
         rustc_allocator_zeroed, Normal, template!(Word), WarnFollowing,
         EncodeCrossCrate::No,
     ),
+    rustc_attr!(
+        rustc_allocator_zeroed_variant, Normal, template!(NameValueStr: "function"), ErrorPreceding,
+        EncodeCrossCrate::Yes,
+    ),
     gated!(
         default_lib_allocator, Normal, template!(Word), WarnFollowing,
         EncodeCrossCrate::No, allocator_internals, experimental!(default_lib_allocator),
diff --git a/compiler/rustc_feature/src/unstable.rs b/compiler/rustc_feature/src/unstable.rs
index 746871982ce..92b435b4b01 100644
--- a/compiler/rustc_feature/src/unstable.rs
+++ b/compiler/rustc_feature/src/unstable.rs
@@ -480,6 +480,8 @@ declare_features! (
     (unstable, doc_cfg_hide, "1.57.0", Some(43781)),
     /// Allows `#[doc(masked)]`.
     (unstable, doc_masked, "1.21.0", Some(44027)),
+    /// Allows features to allow target_feature to better interact with traits.
+    (incomplete, effective_target_features, "CURRENT_RUSTC_VERSION", Some(143352)),
     /// Allows the .use postfix syntax `x.use` and use closures `use |x| { ... }`
     (incomplete, ergonomic_clones, "1.87.0", Some(132290)),
     /// Allows exhaustive pattern matching on types that contain uninhabited types.
@@ -614,6 +616,7 @@ declare_features! (
     (unstable, proc_macro_hygiene, "1.30.0", Some(54727)),
     /// Allows the use of raw-dylibs on ELF platforms
     (incomplete, raw_dylib_elf, "1.87.0", Some(135694)),
+    (unstable, reborrow, "CURRENT_RUSTC_VERSION", Some(145612)),
     /// Makes `&` and `&mut` patterns eat only one layer of references in Rust 2024.
     (incomplete, ref_pat_eat_one_layer_2024, "1.79.0", Some(123076)),
     /// Makes `&` and `&mut` patterns eat only one layer of references in Rust 2024—structural variant
diff --git a/compiler/rustc_hir/Cargo.toml b/compiler/rustc_hir/Cargo.toml
index 71496b7ec32..1008a3e787d 100644
--- a/compiler/rustc_hir/Cargo.toml
+++ b/compiler/rustc_hir/Cargo.toml
@@ -12,7 +12,9 @@ rustc_arena = { path = "../rustc_arena" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_ast_pretty = { path = "../rustc_ast_pretty" }
 rustc_data_structures = { path = "../rustc_data_structures" }
+rustc_error_messages = { path = "../rustc_error_messages" }
 rustc_hashes = { path = "../rustc_hashes" }
+rustc_hir_id = { path = "../rustc_hir_id" }
 rustc_index = { path = "../rustc_index" }
 rustc_macros = { path = "../rustc_macros" }
 rustc_serialize = { path = "../rustc_serialize" }
diff --git a/compiler/rustc_hir/src/attrs/data_structures.rs b/compiler/rustc_hir/src/attrs/data_structures.rs
index 31715955ed3..09da5772d23 100644
--- a/compiler/rustc_hir/src/attrs/data_structures.rs
+++ b/compiler/rustc_hir/src/attrs/data_structures.rs
@@ -1,11 +1,16 @@
+use std::borrow::Cow;
+use std::path::PathBuf;
+
 pub use ReprAttr::*;
 use rustc_abi::Align;
 use rustc_ast::token::CommentKind;
 use rustc_ast::{AttrStyle, ast};
+use rustc_error_messages::{DiagArgValue, IntoDiagArg};
 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};
+pub use rustc_target::spec::SanitizerSet;
 use thin_vec::ThinVec;
 
 use crate::attrs::pretty_printing::PrintAttribute;
@@ -213,6 +218,17 @@ pub enum MirDialect {
     Runtime,
 }
 
+impl IntoDiagArg for MirDialect {
+    fn into_diag_arg(self, _path: &mut Option<PathBuf>) -> DiagArgValue {
+        let arg = match self {
+            MirDialect::Analysis => "analysis",
+            MirDialect::Built => "built",
+            MirDialect::Runtime => "runtime",
+        };
+        DiagArgValue::Str(Cow::Borrowed(arg))
+    }
+}
+
 #[derive(Clone, Copy, Decodable, Debug, Encodable, PartialEq)]
 #[derive(HashStable_Generic, PrintAttribute)]
 pub enum MirPhase {
@@ -221,6 +237,17 @@ pub enum MirPhase {
     Optimized,
 }
 
+impl IntoDiagArg for MirPhase {
+    fn into_diag_arg(self, _path: &mut Option<PathBuf>) -> DiagArgValue {
+        let arg = match self {
+            MirPhase::Initial => "initial",
+            MirPhase::PostCleanup => "post-cleanup",
+            MirPhase::Optimized => "optimized",
+        };
+        DiagArgValue::Str(Cow::Borrowed(arg))
+    }
+}
+
 /// Represents parsed *built-in* inert attributes.
 ///
 /// ## Overview
@@ -340,6 +367,9 @@ pub enum AttributeKind {
     /// Represents `#[coverage(..)]`.
     Coverage(Span, CoverageAttrKind),
 
+    /// Represents `#[crate_name = ...]`
+    CrateName { name: Symbol, name_span: Span, attr_span: Span, style: AttrStyle },
+
     /// Represents `#[custom_mir]`.
     CustomMir(Option<(MirDialect, Span)>, Option<(MirPhase, Span)>, Span),
 
@@ -479,6 +509,12 @@ pub enum AttributeKind {
     /// Represents `#[rustc_object_lifetime_default]`.
     RustcObjectLifetimeDefault,
 
+    /// Represents `#[sanitize]`
+    ///
+    /// the on set and off set are distjoint since there's a third option: unset.
+    /// a node may not set the sanitizer setting in which case it inherits from parents.
+    Sanitize { on_set: SanitizerSet, off_set: SanitizerSet, span: Span },
+
     /// Represents `#[should_panic]`
     ShouldPanic { reason: Option<Symbol>, span: Span },
 
@@ -498,8 +534,9 @@ pub enum AttributeKind {
     /// Represents `#[rustc_std_internal_symbol]`.
     StdInternalSymbol(Span),
 
-    /// Represents `#[target_feature(enable = "...")]`
-    TargetFeature(ThinVec<(Symbol, Span)>, Span),
+    /// Represents `#[target_feature(enable = "...")]` and
+    /// `#[unsafe(force_target_feature(enable = "...")]`.
+    TargetFeature { features: ThinVec<(Symbol, Span)>, attr_span: Span, was_forced: bool },
 
     /// Represents `#[track_caller]`
     TrackCaller(Span),
diff --git a/compiler/rustc_hir/src/attrs/encode_cross_crate.rs b/compiler/rustc_hir/src/attrs/encode_cross_crate.rs
index defabdccc02..e5329c104bb 100644
--- a/compiler/rustc_hir/src/attrs/encode_cross_crate.rs
+++ b/compiler/rustc_hir/src/attrs/encode_cross_crate.rs
@@ -7,6 +7,11 @@ pub enum EncodeCrossCrate {
 }
 
 impl AttributeKind {
+    /// Whether this attribute should be encoded in metadata files.
+    ///
+    /// If this is "Yes", then another crate can do `tcx.get_all_attrs(did)` for a did in this crate, and get the attribute.
+    /// When this is No, the attribute is filtered out while encoding and other crate won't be able to observe it.
+    /// This can be unexpectedly good for performance, so unless necessary for cross-crate compilation, prefer No.
     pub fn encode_cross_crate(&self) -> EncodeCrossCrate {
         use AttributeKind::*;
         use EncodeCrossCrate::*;
@@ -31,6 +36,7 @@ impl AttributeKind {
             ConstTrait(..) => No,
             Coroutine(..) => No,
             Coverage(..) => No,
+            CrateName { .. } => No,
             CustomMir(_, _, _) => Yes,
             DenyExplicitImpl(..) => No,
             Deprecation { .. } => Yes,
@@ -73,12 +79,13 @@ impl AttributeKind {
             RustcLayoutScalarValidRangeEnd(..) => Yes,
             RustcLayoutScalarValidRangeStart(..) => Yes,
             RustcObjectLifetimeDefault => No,
+            Sanitize { .. } => No,
             ShouldPanic { .. } => No,
             SkipDuringMethodDispatch { .. } => No,
             SpecializationTrait(..) => No,
             Stability { .. } => Yes,
             StdInternalSymbol(..) => No,
-            TargetFeature(..) => No,
+            TargetFeature { .. } => No,
             TrackCaller(..) => Yes,
             TypeConst(..) => Yes,
             UnsafeSpecializationMarker(..) => No,
diff --git a/compiler/rustc_hir/src/attrs/pretty_printing.rs b/compiler/rustc_hir/src/attrs/pretty_printing.rs
index e44b29141da..e65de25b451 100644
--- a/compiler/rustc_hir/src/attrs/pretty_printing.rs
+++ b/compiler/rustc_hir/src/attrs/pretty_printing.rs
@@ -6,6 +6,7 @@ use rustc_ast::{AttrStyle, IntTy, UintTy};
 use rustc_ast_pretty::pp::Printer;
 use rustc_span::hygiene::Transparency;
 use rustc_span::{ErrorGuaranteed, Ident, Span, Symbol};
+use rustc_target::spec::SanitizerSet;
 use thin_vec::ThinVec;
 
 /// This trait is used to print attributes in `rustc_hir_pretty`.
@@ -146,4 +147,14 @@ macro_rules! print_tup {
 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);
+print_debug!(
+    Symbol,
+    Ident,
+    UintTy,
+    IntTy,
+    Align,
+    AttrStyle,
+    CommentKind,
+    Transparency,
+    SanitizerSet,
+);
diff --git a/compiler/rustc_hir/src/def.rs b/compiler/rustc_hir/src/def.rs
index 79319e24266..8af4740f376 100644
--- a/compiler/rustc_hir/src/def.rs
+++ b/compiler/rustc_hir/src/def.rs
@@ -1,10 +1,12 @@
 use std::array::IntoIter;
+use std::borrow::Cow;
 use std::fmt::Debug;
 
 use rustc_ast as ast;
 use rustc_ast::NodeId;
 use rustc_data_structures::stable_hasher::ToStableHashKey;
 use rustc_data_structures::unord::UnordMap;
+use rustc_error_messages::{DiagArgValue, IntoDiagArg};
 use rustc_macros::{Decodable, Encodable, HashStable_Generic};
 use rustc_span::Symbol;
 use rustc_span::def_id::{DefId, LocalDefId};
@@ -586,6 +588,12 @@ pub enum Res<Id = hir::HirId> {
     Err,
 }
 
+impl<Id> IntoDiagArg for Res<Id> {
+    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+        DiagArgValue::Str(Cow::Borrowed(self.descr()))
+    }
+}
+
 /// The result of resolving a path before lowering to HIR,
 /// with "module" segments resolved and associated item
 /// segments deferred to type checking.
@@ -673,6 +681,12 @@ impl Namespace {
     }
 }
 
+impl IntoDiagArg for Namespace {
+    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+        DiagArgValue::Str(Cow::Borrowed(self.descr()))
+    }
+}
+
 impl<CTX: crate::HashStableContext> ToStableHashKey<CTX> for Namespace {
     type KeyType = Namespace;
 
diff --git a/compiler/rustc_hir/src/hir.rs b/compiler/rustc_hir/src/hir.rs
index 2c8986b7c7d..e397c286de2 100644
--- a/compiler/rustc_hir/src/hir.rs
+++ b/compiler/rustc_hir/src/hir.rs
@@ -1,4 +1,5 @@
 // ignore-tidy-filelength
+use std::borrow::Cow;
 use std::fmt;
 
 use rustc_abi::ExternAbi;
@@ -17,6 +18,7 @@ pub use rustc_ast::{
 use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::sorted_map::SortedMap;
 use rustc_data_structures::tagged_ptr::TaggedRef;
+use rustc_error_messages::{DiagArgValue, IntoDiagArg};
 use rustc_index::IndexVec;
 use rustc_macros::{Decodable, Encodable, HashStable_Generic};
 use rustc_span::def_id::LocalDefId;
@@ -1159,6 +1161,12 @@ pub struct AttrPath {
     pub span: Span,
 }
 
+impl IntoDiagArg for AttrPath {
+    fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+        self.to_string().into_diag_arg(path)
+    }
+}
+
 impl AttrPath {
     pub fn from_ast(path: &ast::Path) -> Self {
         AttrPath {
@@ -2259,8 +2267,15 @@ impl fmt::Display for ConstContext {
     }
 }
 
-// NOTE: `IntoDiagArg` impl for `ConstContext` lives in `rustc_errors`
-// due to a cyclical dependency between hir and that crate.
+impl IntoDiagArg for ConstContext {
+    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+        DiagArgValue::Str(Cow::Borrowed(match self {
+            ConstContext::ConstFn => "const_fn",
+            ConstContext::Static(_) => "static",
+            ConstContext::Const { .. } => "const",
+        }))
+    }
+}
 
 /// A literal.
 pub type Lit = Spanned<LitKind>;
diff --git a/compiler/rustc_hir/src/lang_items.rs b/compiler/rustc_hir/src/lang_items.rs
index 905b84a8cbe..0464665b41f 100644
--- a/compiler/rustc_hir/src/lang_items.rs
+++ b/compiler/rustc_hir/src/lang_items.rs
@@ -437,6 +437,9 @@ language_item_table! {
     DefaultTrait1,           sym::default_trait1,      default_trait1_trait,       Target::Trait,          GenericRequirement::None;
 
     ContractCheckEnsures,     sym::contract_check_ensures,      contract_check_ensures_fn,      Target::Fn, GenericRequirement::None;
+
+    // Reborrowing related lang-items
+    Reborrow,                sym::reborrow,            reborrow,                   Target::Trait,          GenericRequirement::Exact(0);
 }
 
 /// The requirement imposed on the generics of a lang item
diff --git a/compiler/rustc_hir/src/lib.rs b/compiler/rustc_hir/src/lib.rs
index f1212d07ff6..78fc63753a2 100644
--- a/compiler/rustc_hir/src/lib.rs
+++ b/compiler/rustc_hir/src/lib.rs
@@ -3,14 +3,11 @@
 //! [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/hir.html
 
 // tidy-alphabetical-start
-#![allow(internal_features)]
 #![feature(associated_type_defaults)]
 #![feature(closure_track_caller)]
 #![feature(debug_closure_helpers)]
 #![feature(exhaustive_patterns)]
-#![feature(negative_impls)]
 #![feature(never_type)]
-#![feature(rustc_attrs)]
 #![feature(variant_count)]
 #![recursion_limit = "256"]
 // tidy-alphabetical-end
@@ -25,7 +22,7 @@ pub mod definitions;
 pub mod diagnostic_items;
 pub use rustc_span::def_id;
 mod hir;
-pub mod hir_id;
+pub use rustc_hir_id::{self as hir_id, *};
 pub mod intravisit;
 pub mod lang_items;
 pub mod lints;
@@ -41,7 +38,6 @@ mod tests;
 
 #[doc(no_inline)]
 pub use hir::*;
-pub use hir_id::*;
 pub use lang_items::{LangItem, LanguageItems};
 pub use stability::*;
 pub use stable_hash_impls::HashStableContext;
diff --git a/compiler/rustc_hir/src/lints.rs b/compiler/rustc_hir/src/lints.rs
index e3cde2d3bb6..061ec786dc8 100644
--- a/compiler/rustc_hir/src/lints.rs
+++ b/compiler/rustc_hir/src/lints.rs
@@ -1,8 +1,8 @@
 use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_macros::HashStable_Generic;
-use rustc_span::{Span, Symbol};
+use rustc_span::Span;
 
-use crate::{HirId, Target};
+use crate::{AttrPath, HirId, Target};
 
 #[derive(Debug)]
 pub struct DelayedLints {
@@ -34,5 +34,5 @@ pub enum AttributeLintKind {
     UnusedDuplicate { this: Span, other: Span, warning: bool },
     IllFormedAttributeInput { suggestions: Vec<String> },
     EmptyAttribute { first_span: Span },
-    InvalidTarget { name: Symbol, target: Target, applied: String, only: &'static str },
+    InvalidTarget { name: AttrPath, target: Target, applied: Vec<String>, only: &'static str },
 }
diff --git a/compiler/rustc_hir/src/stable_hash_impls.rs b/compiler/rustc_hir/src/stable_hash_impls.rs
index ecc608d437b..16e8bac3d8a 100644
--- a/compiler/rustc_hir/src/stable_hash_impls.rs
+++ b/compiler/rustc_hir/src/stable_hash_impls.rs
@@ -5,7 +5,7 @@ use crate::HashIgnoredAttrId;
 use crate::hir::{
     AttributeMap, BodyId, Crate, ForeignItemId, ImplItemId, ItemId, OwnerNodes, TraitItemId,
 };
-use crate::hir_id::{HirId, ItemLocalId};
+use crate::hir_id::ItemLocalId;
 use crate::lints::DelayedLints;
 
 /// Requirements for a `StableHashingContext` to be used in this crate.
@@ -15,25 +15,6 @@ pub trait HashStableContext: rustc_ast::HashStableContext + rustc_abi::HashStabl
     fn hash_attr_id(&mut self, id: &HashIgnoredAttrId, hasher: &mut StableHasher);
 }
 
-impl<HirCtx: crate::HashStableContext> ToStableHashKey<HirCtx> for HirId {
-    type KeyType = (DefPathHash, ItemLocalId);
-
-    #[inline]
-    fn to_stable_hash_key(&self, hcx: &HirCtx) -> (DefPathHash, ItemLocalId) {
-        let def_path_hash = self.owner.def_id.to_stable_hash_key(hcx);
-        (def_path_hash, self.local_id)
-    }
-}
-
-impl<HirCtx: crate::HashStableContext> ToStableHashKey<HirCtx> for ItemLocalId {
-    type KeyType = ItemLocalId;
-
-    #[inline]
-    fn to_stable_hash_key(&self, _: &HirCtx) -> ItemLocalId {
-        *self
-    }
-}
-
 impl<HirCtx: crate::HashStableContext> ToStableHashKey<HirCtx> for BodyId {
     type KeyType = (DefPathHash, ItemLocalId);
 
diff --git a/compiler/rustc_hir/src/target.rs b/compiler/rustc_hir/src/target.rs
index f68dad3a5e8..dcac51b10b4 100644
--- a/compiler/rustc_hir/src/target.rs
+++ b/compiler/rustc_hir/src/target.rs
@@ -79,6 +79,8 @@ impl Display for Target {
     }
 }
 
+rustc_error_messages::into_diag_arg_using_display!(Target);
+
 impl Target {
     pub fn is_associated_item(self) -> bool {
         match self {
diff --git a/compiler/rustc_hir/src/version.rs b/compiler/rustc_hir/src/version.rs
index ab5ab026b4c..bc2c38a4935 100644
--- a/compiler/rustc_hir/src/version.rs
+++ b/compiler/rustc_hir/src/version.rs
@@ -1,6 +1,8 @@
+use std::borrow::Cow;
 use std::fmt::{self, Display};
 use std::sync::OnceLock;
 
+use rustc_error_messages::{DiagArgValue, IntoDiagArg};
 use rustc_macros::{
     Decodable, Encodable, HashStable_Generic, PrintAttribute, current_rustc_version,
 };
@@ -45,3 +47,9 @@ impl Display for RustcVersion {
         write!(formatter, "{}.{}.{}", self.major, self.minor, self.patch)
     }
 }
+
+impl IntoDiagArg for RustcVersion {
+    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+        DiagArgValue::Str(Cow::Owned(self.to_string()))
+    }
+}
diff --git a/compiler/rustc_hir_analysis/messages.ftl b/compiler/rustc_hir_analysis/messages.ftl
index 2428c1aa29f..06f2ec512ab 100644
--- a/compiler/rustc_hir_analysis/messages.ftl
+++ b/compiler/rustc_hir_analysis/messages.ftl
@@ -509,10 +509,6 @@ hir_analysis_supertrait_item_shadowee = item from `{$supertrait}` is shadowed by
 
 hir_analysis_supertrait_item_shadowing = trait item `{$item}` from `{$subtrait}` shadows identically named item from supertrait
 
-hir_analysis_tait_forward_compat2 = item does not constrain `{$opaque_type}`
-    .note = consider removing `#[define_opaque]` or adding an empty `#[define_opaque()]`
-    .opaque = this opaque type is supposed to be constrained
-
 hir_analysis_target_feature_on_main = `main` function is not allowed to have `#[target_feature]`
 
 hir_analysis_too_large_static = extern static is too large for the target architecture
diff --git a/compiler/rustc_hir_analysis/src/check/check.rs b/compiler/rustc_hir_analysis/src/check/check.rs
index 161a8566b04..eccb88a938f 100644
--- a/compiler/rustc_hir_analysis/src/check/check.rs
+++ b/compiler/rustc_hir_analysis/src/check/check.rs
@@ -2053,3 +2053,29 @@ pub(super) fn check_coroutine_obligations(
 
     Ok(())
 }
+
+pub(super) fn check_potentially_region_dependent_goals<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    def_id: LocalDefId,
+) -> Result<(), ErrorGuaranteed> {
+    if !tcx.next_trait_solver_globally() {
+        return Ok(());
+    }
+    let typeck_results = tcx.typeck(def_id);
+    let param_env = tcx.param_env(def_id);
+
+    // We use `TypingMode::Borrowck` as we want to use the opaque types computed by HIR typeck.
+    let typing_mode = TypingMode::borrowck(tcx, def_id);
+    let infcx = tcx.infer_ctxt().ignoring_regions().build(typing_mode);
+    let ocx = ObligationCtxt::new_with_diagnostics(&infcx);
+    for (predicate, cause) in &typeck_results.potentially_region_dependent_goals {
+        let predicate = fold_regions(tcx, *predicate, |_, _| {
+            infcx.next_region_var(RegionVariableOrigin::Misc(cause.span))
+        });
+        ocx.register_obligation(Obligation::new(tcx, cause.clone(), param_env, predicate));
+    }
+
+    let errors = ocx.select_all_or_error();
+    debug!(?errors);
+    if errors.is_empty() { Ok(()) } else { Err(infcx.err_ctxt().report_fulfillment_errors(errors)) }
+}
diff --git a/compiler/rustc_hir_analysis/src/check/intrinsic.rs b/compiler/rustc_hir_analysis/src/check/intrinsic.rs
index f50aed0b3c2..cfc6bc2f3a0 100644
--- a/compiler/rustc_hir_analysis/src/check/intrinsic.rs
+++ b/compiler/rustc_hir_analysis/src/check/intrinsic.rs
@@ -136,6 +136,10 @@ fn intrinsic_operation_unsafety(tcx: TyCtxt<'_>, intrinsic_id: LocalDefId) -> hi
         | sym::round_ties_even_f64
         | sym::round_ties_even_f128
         | sym::autodiff
+        | sym::prefetch_read_data
+        | sym::prefetch_write_data
+        | sym::prefetch_read_instruction
+        | sym::prefetch_write_instruction
         | sym::const_eval_select => hir::Safety::Safe,
         _ => hir::Safety::Unsafe,
     };
@@ -218,7 +222,7 @@ pub(crate) fn check_intrinsic_type(
         | sym::prefetch_write_data
         | sym::prefetch_read_instruction
         | sym::prefetch_write_instruction => {
-            (1, 0, vec![Ty::new_imm_ptr(tcx, param(0)), tcx.types.i32], tcx.types.unit)
+            (1, 1, vec![Ty::new_imm_ptr(tcx, param(0))], tcx.types.unit)
         }
         sym::needs_drop => (1, 0, vec![], tcx.types.bool),
 
diff --git a/compiler/rustc_hir_analysis/src/check/mod.rs b/compiler/rustc_hir_analysis/src/check/mod.rs
index 85445cb3c00..2e4b151d4dc 100644
--- a/compiler/rustc_hir_analysis/src/check/mod.rs
+++ b/compiler/rustc_hir_analysis/src/check/mod.rs
@@ -109,6 +109,7 @@ pub(super) fn provide(providers: &mut Providers) {
         collect_return_position_impl_trait_in_trait_tys,
         compare_impl_item: compare_impl_item::compare_impl_item,
         check_coroutine_obligations: check::check_coroutine_obligations,
+        check_potentially_region_dependent_goals: check::check_potentially_region_dependent_goals,
         check_type_wf: wfcheck::check_type_wf,
         check_well_formed: wfcheck::check_well_formed,
         ..*providers
diff --git a/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs b/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
index 50e20a19eda..b6d898886ac 100644
--- a/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
+++ b/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
@@ -4,9 +4,10 @@ use rustc_hir::{self as hir, Expr, ImplItem, Item, Node, TraitItem, def, intravi
 use rustc_middle::bug;
 use rustc_middle::hir::nested_filter;
 use rustc_middle::ty::{self, DefiningScopeKind, Ty, TyCtxt, TypeVisitableExt};
+use rustc_trait_selection::opaque_types::report_item_does_not_constrain_error;
 use tracing::{debug, instrument, trace};
 
-use crate::errors::{TaitForwardCompat2, UnconstrainedOpaqueType};
+use crate::errors::UnconstrainedOpaqueType;
 
 /// Checks "defining uses" of opaque `impl Trait` in associated types.
 /// These can only be defined by associated items of the same trait.
@@ -127,14 +128,11 @@ impl<'tcx> TaitConstraintLocator<'tcx> {
     }
 
     fn non_defining_use_in_defining_scope(&mut self, item_def_id: LocalDefId) {
-        let guar = self.tcx.dcx().emit_err(TaitForwardCompat2 {
-            span: self
-                .tcx
-                .def_ident_span(item_def_id)
-                .unwrap_or_else(|| self.tcx.def_span(item_def_id)),
-            opaque_type_span: self.tcx.def_span(self.def_id),
-            opaque_type: self.tcx.def_path_str(self.def_id),
-        });
+        // We make sure that all opaque types get defined while
+        // type checking the defining scope, so this error is unreachable
+        // with the new solver.
+        assert!(!self.tcx.next_trait_solver_globally());
+        let guar = report_item_does_not_constrain_error(self.tcx, item_def_id, self.def_id, None);
         self.insert_found(ty::OpaqueHiddenType::new_error(self.tcx, guar));
     }
 
@@ -252,9 +250,7 @@ pub(super) fn find_opaque_ty_constraints_for_rpit<'tcx>(
             } else if let Some(hidden_ty) = tables.concrete_opaque_types.get(&def_id) {
                 hidden_ty.ty
             } else {
-                // FIXME(-Znext-solver): This should not be necessary and we should
-                // instead rely on inference variable fallback inside of typeck itself.
-
+                assert!(!tcx.next_trait_solver_globally());
                 // We failed to resolve the opaque type or it
                 // resolves to itself. We interpret this as the
                 // no values of the hidden type ever being constructed,
@@ -273,6 +269,7 @@ pub(super) fn find_opaque_ty_constraints_for_rpit<'tcx>(
                     if let Err(guar) = hir_ty.error_reported() {
                         Ty::new_error(tcx, guar)
                     } else {
+                        assert!(!tcx.next_trait_solver_globally());
                         hir_ty
                     }
                 }
diff --git a/compiler/rustc_hir_analysis/src/errors.rs b/compiler/rustc_hir_analysis/src/errors.rs
index 26a98722b34..6565ad7cf53 100644
--- a/compiler/rustc_hir_analysis/src/errors.rs
+++ b/compiler/rustc_hir_analysis/src/errors.rs
@@ -410,17 +410,6 @@ pub(crate) struct UnconstrainedOpaqueType {
     pub what: &'static str,
 }
 
-#[derive(Diagnostic)]
-#[diag(hir_analysis_tait_forward_compat2)]
-#[note]
-pub(crate) struct TaitForwardCompat2 {
-    #[primary_span]
-    pub span: Span,
-    #[note(hir_analysis_opaque)]
-    pub opaque_type_span: Span,
-    pub opaque_type: String,
-}
-
 pub(crate) struct MissingTypeParams {
     pub span: Span,
     pub def_span: Span,
diff --git a/compiler/rustc_hir_analysis/src/lib.rs b/compiler/rustc_hir_analysis/src/lib.rs
index 3a153ab089a..44a5ceed469 100644
--- a/compiler/rustc_hir_analysis/src/lib.rs
+++ b/compiler/rustc_hir_analysis/src/lib.rs
@@ -82,7 +82,7 @@ mod coherence;
 mod collect;
 mod constrained_generic_params;
 mod delegation;
-mod errors;
+pub mod errors;
 pub mod hir_ty_lowering;
 pub mod hir_wf_check;
 mod impl_wf_check;
diff --git a/compiler/rustc_hir_id/Cargo.toml b/compiler/rustc_hir_id/Cargo.toml
new file mode 100644
index 00000000000..c357a4f62d9
--- /dev/null
+++ b/compiler/rustc_hir_id/Cargo.toml
@@ -0,0 +1,13 @@
+[package]
+name = "rustc_hir_id"
+version = "0.0.0"
+edition = "2024"
+
+[dependencies]
+# tidy-alphabetical-start
+rustc_data_structures = { path = "../rustc_data_structures" }
+rustc_index = { path = "../rustc_index" }
+rustc_macros = { path = "../rustc_macros" }
+rustc_serialize = { path = "../rustc_serialize" }
+rustc_span = { path = "../rustc_span" }
+# tidy-alphabetical-end
diff --git a/compiler/rustc_hir/src/hir_id.rs b/compiler/rustc_hir_id/src/lib.rs
index b48a081d371..d07bc88e66a 100644
--- a/compiler/rustc_hir/src/hir_id.rs
+++ b/compiler/rustc_hir_id/src/lib.rs
@@ -1,11 +1,15 @@
+//! Library containing Id types from `rustc_hir`, split out so crates can use it without depending
+//! on all of `rustc_hir` (which is large and depends on other large things like `rustc_target`).
+#![allow(internal_features)]
+#![feature(negative_impls)]
+#![feature(rustc_attrs)]
+
 use std::fmt::{self, Debug};
 
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher, StableOrd, ToStableHashKey};
 use rustc_macros::{Decodable, Encodable, HashStable_Generic};
-use rustc_span::HashStableContext;
-use rustc_span::def_id::DefPathHash;
-
-use crate::def_id::{CRATE_DEF_ID, DefId, DefIndex, LocalDefId};
+pub use rustc_span::HashStableContext;
+use rustc_span::def_id::{CRATE_DEF_ID, DefId, DefIndex, DefPathHash, LocalDefId};
 
 #[derive(Copy, Clone, PartialEq, Eq, Hash, Encodable, Decodable)]
 pub struct OwnerId {
@@ -171,3 +175,22 @@ pub const CRATE_HIR_ID: HirId =
     HirId { owner: OwnerId { def_id: CRATE_DEF_ID }, local_id: ItemLocalId::ZERO };
 
 pub const CRATE_OWNER_ID: OwnerId = OwnerId { def_id: CRATE_DEF_ID };
+
+impl<CTX: rustc_span::HashStableContext> ToStableHashKey<CTX> for HirId {
+    type KeyType = (DefPathHash, ItemLocalId);
+
+    #[inline]
+    fn to_stable_hash_key(&self, hcx: &CTX) -> (DefPathHash, ItemLocalId) {
+        let def_path_hash = self.owner.def_id.to_stable_hash_key(hcx);
+        (def_path_hash, self.local_id)
+    }
+}
+
+impl<CTX: HashStableContext> ToStableHashKey<CTX> for ItemLocalId {
+    type KeyType = ItemLocalId;
+
+    #[inline]
+    fn to_stable_hash_key(&self, _: &CTX) -> ItemLocalId {
+        *self
+    }
+}
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
index b80a2af3100..5aec50c8b53 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
@@ -83,14 +83,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         *self.deferred_cast_checks.borrow_mut() = deferred_cast_checks;
     }
 
-    pub(in super::super) fn check_transmutes(&self) {
-        let mut deferred_transmute_checks = self.deferred_transmute_checks.borrow_mut();
-        debug!("FnCtxt::check_transmutes: {} deferred checks", deferred_transmute_checks.len());
-        for (from, to, hir_id) in deferred_transmute_checks.drain(..) {
-            self.check_transmute(from, to, hir_id);
-        }
-    }
-
     pub(in super::super) fn check_asms(&self) {
         let mut deferred_asm_checks = self.deferred_asm_checks.borrow_mut();
         debug!("FnCtxt::check_asm: {} deferred checks", deferred_asm_checks.len());
diff --git a/compiler/rustc_hir_typeck/src/intrinsicck.rs b/compiler/rustc_hir_typeck/src/intrinsicck.rs
index 194e420b606..7567f8ba348 100644
--- a/compiler/rustc_hir_typeck/src/intrinsicck.rs
+++ b/compiler/rustc_hir_typeck/src/intrinsicck.rs
@@ -7,11 +7,10 @@ use rustc_hir as hir;
 use rustc_index::Idx;
 use rustc_middle::bug;
 use rustc_middle::ty::layout::{LayoutError, SizeSkeleton};
-use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitableExt};
+use rustc_middle::ty::{self, Ty, TyCtxt};
+use rustc_span::def_id::LocalDefId;
 use tracing::trace;
 
-use super::FnCtxt;
-
 /// If the type is `Option<T>`, it will return `T`, otherwise
 /// the type itself. Works on most `Option`-like types.
 fn unpack_option_like<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Ty<'tcx> {
@@ -39,119 +38,117 @@ fn unpack_option_like<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Ty<'tcx> {
     ty
 }
 
-impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
-    /// FIXME: Move this check out of typeck, since it'll easily cycle when revealing opaques,
-    /// and we shouldn't need to check anything here if the typeck results are tainted.
-    pub(crate) fn check_transmute(&self, from: Ty<'tcx>, to: Ty<'tcx>, hir_id: HirId) {
-        let tcx = self.tcx;
-        let dl = &tcx.data_layout;
-        let span = tcx.hir_span(hir_id);
-        let normalize = |ty| {
-            let ty = self.resolve_vars_if_possible(ty);
-            if let Ok(ty) =
-                self.tcx.try_normalize_erasing_regions(self.typing_env(self.param_env), ty)
-            {
-                ty
+/// Try to display a sensible error with as much information as possible.
+fn skeleton_string<'tcx>(
+    ty: Ty<'tcx>,
+    sk: Result<SizeSkeleton<'tcx>, &'tcx LayoutError<'tcx>>,
+) -> String {
+    match sk {
+        Ok(SizeSkeleton::Pointer { tail, .. }) => format!("pointer to `{tail}`"),
+        Ok(SizeSkeleton::Known(size, _)) => {
+            if let Some(v) = u128::from(size.bytes()).checked_mul(8) {
+                format!("{v} bits")
             } else {
-                Ty::new_error_with_message(
-                    tcx,
-                    span,
-                    "tried to normalize non-wf type in check_transmute",
-                )
+                // `u128` should definitely be able to hold the size of different architectures
+                // larger sizes should be reported as error `are too big for the target architecture`
+                // otherwise we have a bug somewhere
+                bug!("{:?} overflow for u128", size)
             }
-        };
-        let from = normalize(from);
-        let to = normalize(to);
-        trace!(?from, ?to);
-        if from.has_non_region_infer() || to.has_non_region_infer() {
-            // Note: this path is currently not reached in any test, so any
-            // example that triggers this would be worth minimizing and
-            // converting into a test.
-            self.dcx().span_bug(span, "argument to transmute has inference variables");
         }
-        // Transmutes that are only changing lifetimes are always ok.
-        if from == to {
-            return;
+        Ok(SizeSkeleton::Generic(size)) => {
+            format!("generic size {size}")
+        }
+        Err(LayoutError::TooGeneric(bad)) => {
+            if *bad == ty {
+                "this type does not have a fixed size".to_owned()
+            } else {
+                format!("size can vary because of {bad}")
+            }
+        }
+        Err(err) => err.to_string(),
+    }
+}
+
+fn check_transmute<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    typing_env: ty::TypingEnv<'tcx>,
+    from: Ty<'tcx>,
+    to: Ty<'tcx>,
+    hir_id: HirId,
+) {
+    let span = || tcx.hir_span(hir_id);
+    let normalize = |ty| {
+        if let Ok(ty) = tcx.try_normalize_erasing_regions(typing_env, ty) {
+            ty
+        } else {
+            Ty::new_error_with_message(
+                tcx,
+                span(),
+                format!("tried to normalize non-wf type {ty:#?} in check_transmute"),
+            )
         }
+    };
 
-        let skel = |ty| SizeSkeleton::compute(ty, tcx, self.typing_env(self.param_env));
-        let sk_from = skel(from);
-        let sk_to = skel(to);
-        trace!(?sk_from, ?sk_to);
+    let from = normalize(from);
+    let to = normalize(to);
+    trace!(?from, ?to);
 
-        // Check for same size using the skeletons.
-        if let (Ok(sk_from), Ok(sk_to)) = (sk_from, sk_to) {
-            if sk_from.same_size(sk_to) {
-                return;
-            }
+    // Transmutes that are only changing lifetimes are always ok.
+    if from == to {
+        return;
+    }
 
-            // Special-case transmuting from `typeof(function)` and
-            // `Option<typeof(function)>` to present a clearer error.
-            let from = unpack_option_like(tcx, from);
-            if let (&ty::FnDef(..), SizeSkeleton::Known(size_to, _)) = (from.kind(), sk_to)
-                && size_to == Pointer(dl.instruction_address_space).size(&tcx)
-            {
-                struct_span_code_err!(self.dcx(), span, E0591, "can't transmute zero-sized type")
-                    .with_note(format!("source type: {from}"))
-                    .with_note(format!("target type: {to}"))
-                    .with_help("cast with `as` to a pointer instead")
-                    .emit();
-                return;
-            }
+    let sk_from = SizeSkeleton::compute(from, tcx, typing_env);
+    let sk_to = SizeSkeleton::compute(to, tcx, typing_env);
+    trace!(?sk_from, ?sk_to);
+
+    // Check for same size using the skeletons.
+    if let Ok(sk_from) = sk_from
+        && let Ok(sk_to) = sk_to
+    {
+        if sk_from.same_size(sk_to) {
+            return;
         }
 
-        // Try to display a sensible error with as much information as possible.
-        let skeleton_string = |ty: Ty<'tcx>, sk: Result<_, &_>| match sk {
-            Ok(SizeSkeleton::Pointer { tail, .. }) => format!("pointer to `{tail}`"),
-            Ok(SizeSkeleton::Known(size, _)) => {
-                if let Some(v) = u128::from(size.bytes()).checked_mul(8) {
-                    format!("{v} bits")
-                } else {
-                    // `u128` should definitely be able to hold the size of different architectures
-                    // larger sizes should be reported as error `are too big for the target architecture`
-                    // otherwise we have a bug somewhere
-                    bug!("{:?} overflow for u128", size)
-                }
-            }
-            Ok(SizeSkeleton::Generic(size)) => {
-                if let Some(size) =
-                    self.try_structurally_resolve_const(span, size).try_to_target_usize(tcx)
-                {
-                    format!("{size} bytes")
-                } else {
-                    format!("generic size {size}")
-                }
-            }
-            Err(LayoutError::TooGeneric(bad)) => {
-                if *bad == ty {
-                    "this type does not have a fixed size".to_owned()
-                } else {
-                    format!("size can vary because of {bad}")
-                }
-            }
-            Err(err) => err.to_string(),
-        };
-
-        let mut err = struct_span_code_err!(
-            self.dcx(),
-            span,
-            E0512,
-            "cannot transmute between types of different sizes, \
-                                        or dependently-sized types"
-        );
-        if from == to {
-            err.note(format!("`{from}` does not have a fixed size"));
-            err.emit();
-        } else {
-            err.note(format!("source type: `{}` ({})", from, skeleton_string(from, sk_from)))
-                .note(format!("target type: `{}` ({})", to, skeleton_string(to, sk_to)));
-            if let Err(LayoutError::ReferencesError(_)) = sk_from {
-                err.delay_as_bug();
-            } else if let Err(LayoutError::ReferencesError(_)) = sk_to {
-                err.delay_as_bug();
-            } else {
-                err.emit();
-            }
+        // Special-case transmuting from `typeof(function)` and
+        // `Option<typeof(function)>` to present a clearer error.
+        let from = unpack_option_like(tcx, from);
+        if let ty::FnDef(..) = from.kind()
+            && let SizeSkeleton::Known(size_to, _) = sk_to
+            && size_to == Pointer(tcx.data_layout.instruction_address_space).size(&tcx)
+        {
+            struct_span_code_err!(tcx.sess.dcx(), span(), E0591, "can't transmute zero-sized type")
+                .with_note(format!("source type: {from}"))
+                .with_note(format!("target type: {to}"))
+                .with_help("cast with `as` to a pointer instead")
+                .emit();
+            return;
         }
     }
+
+    let mut err = struct_span_code_err!(
+        tcx.sess.dcx(),
+        span(),
+        E0512,
+        "cannot transmute between types of different sizes, or dependently-sized types"
+    );
+    if from == to {
+        err.note(format!("`{from}` does not have a fixed size"));
+        err.emit();
+    } else {
+        err.note(format!("source type: `{}` ({})", from, skeleton_string(from, sk_from)));
+        err.note(format!("target type: `{}` ({})", to, skeleton_string(to, sk_to)));
+        err.emit();
+    }
+}
+
+pub(crate) fn check_transmutes(tcx: TyCtxt<'_>, owner: LocalDefId) {
+    assert!(!tcx.is_typeck_child(owner.to_def_id()));
+    let typeck_results = tcx.typeck(owner);
+    let None = typeck_results.tainted_by_errors else { return };
+
+    let typing_env = ty::TypingEnv::post_analysis(tcx, owner);
+    for &(from, to, hir_id) in &typeck_results.transmutes_to_check {
+        check_transmute(tcx, typing_env, from, to, hir_id);
+    }
 }
diff --git a/compiler/rustc_hir_typeck/src/lib.rs b/compiler/rustc_hir_typeck/src/lib.rs
index aae870f7ee3..879b7472736 100644
--- a/compiler/rustc_hir_typeck/src/lib.rs
+++ b/compiler/rustc_hir_typeck/src/lib.rs
@@ -53,7 +53,7 @@ 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, TypeVisitableExt};
+use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_middle::{bug, span_bug};
 use rustc_session::config;
 use rustc_span::Span;
@@ -247,33 +247,21 @@ fn typeck_with_inspect<'tcx>(
 
     debug!(pending_obligations = ?fcx.fulfillment_cx.borrow().pending_obligations());
 
-    if let None = fcx.infcx.tainted_by_errors() {
-        fcx.report_ambiguity_errors();
+    // We need to handle opaque types before emitting ambiguity errors as applying
+    // defining uses may guide type inference.
+    if fcx.next_trait_solver() {
+        fcx.handle_opaque_type_uses_next();
     }
 
+    fcx.select_obligations_where_possible(|_| {});
     if let None = fcx.infcx.tainted_by_errors() {
-        fcx.check_transmutes();
+        fcx.report_ambiguity_errors();
     }
 
     fcx.check_asms();
 
     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
@@ -555,6 +543,7 @@ pub fn provide(providers: &mut Providers) {
         method_autoderef_steps: method::probe::method_autoderef_steps,
         typeck,
         used_trait_imports,
+        check_transmutes: intrinsicck::check_transmutes,
         ..*providers
     };
 }
diff --git a/compiler/rustc_hir_typeck/src/method/probe.rs b/compiler/rustc_hir_typeck/src/method/probe.rs
index 3ca3b56b87e..f5c3ebd8375 100644
--- a/compiler/rustc_hir_typeck/src/method/probe.rs
+++ b/compiler/rustc_hir_typeck/src/method/probe.rs
@@ -909,6 +909,10 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         debug_assert_matches!(param_ty.kind(), ty::Param(_));
 
         let tcx = self.tcx;
+
+        // We use `DeepRejectCtxt` here which may return false positive on where clauses
+        // with alias self types. We need to later on reject these as inherent candidates
+        // in `consider_probe`.
         let bounds = self.param_env.caller_bounds().iter().filter_map(|predicate| {
             let bound_predicate = predicate.kind();
             match bound_predicate.skip_binder() {
@@ -1945,6 +1949,29 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                     );
                     (xform_self_ty, xform_ret_ty) =
                         self.xform_self_ty(probe.item, trait_ref.self_ty(), trait_ref.args);
+
+                    if matches!(probe.kind, WhereClauseCandidate(_)) {
+                        // `WhereClauseCandidate` requires that the self type is a param,
+                        // because it has special behavior with candidate preference as an
+                        // inherent pick.
+                        match ocx.structurally_normalize_ty(
+                            cause,
+                            self.param_env,
+                            trait_ref.self_ty(),
+                        ) {
+                            Ok(ty) => {
+                                if !matches!(ty.kind(), ty::Param(_)) {
+                                    debug!("--> not a param ty: {xform_self_ty:?}");
+                                    return ProbeResult::NoMatch;
+                                }
+                            }
+                            Err(errors) => {
+                                debug!("--> cannot relate self-types {:?}", errors);
+                                return ProbeResult::NoMatch;
+                            }
+                        }
+                    }
+
                     xform_self_ty = ocx.normalize(cause, self.param_env, xform_self_ty);
                     match ocx.relate(cause, self.param_env, self.variance(), self_ty, xform_self_ty)
                     {
diff --git a/compiler/rustc_hir_typeck/src/method/suggest.rs b/compiler/rustc_hir_typeck/src/method/suggest.rs
index 824d592fa6c..c8f6c06b720 100644
--- a/compiler/rustc_hir_typeck/src/method/suggest.rs
+++ b/compiler/rustc_hir_typeck/src/method/suggest.rs
@@ -13,9 +13,7 @@ use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_data_structures::sorted_map::SortedMap;
 use rustc_data_structures::unord::UnordSet;
 use rustc_errors::codes::*;
-use rustc_errors::{
-    Applicability, Diag, DiagStyledString, MultiSpan, StashKey, pluralize, struct_span_code_err,
-};
+use rustc_errors::{Applicability, Diag, 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;
@@ -1560,11 +1558,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             );
         }
 
-        if rcvr_ty.is_numeric() && rcvr_ty.is_fresh()
-            || restrict_type_params
-            || suggested_derive
-            || self.lookup_alternative_tuple_impls(&mut err, &unsatisfied_predicates)
-        {
+        if rcvr_ty.is_numeric() && rcvr_ty.is_fresh() || restrict_type_params || suggested_derive {
         } else {
             self.suggest_traits_to_import(
                 &mut err,
@@ -1741,119 +1735,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         err.emit()
     }
 
-    /// If the predicate failure is caused by an unmet bound on a tuple, recheck if the bound would
-    /// succeed if all the types on the tuple had no borrows. This is a common problem for libraries
-    /// like Bevy and ORMs, which rely heavily on traits being implemented on tuples.
-    fn lookup_alternative_tuple_impls(
-        &self,
-        err: &mut Diag<'_>,
-        unsatisfied_predicates: &[(
-            ty::Predicate<'tcx>,
-            Option<ty::Predicate<'tcx>>,
-            Option<ObligationCause<'tcx>>,
-        )],
-    ) -> bool {
-        let mut found_tuple = false;
-        for (pred, root, _ob) in unsatisfied_predicates {
-            let mut preds = vec![pred];
-            if let Some(root) = root {
-                // We will look at both the current predicate and the root predicate that caused it
-                // to be needed. If calling something like `<(A, &B)>::default()`, then `pred` is
-                // `&B: Default` and `root` is `(A, &B): Default`, which is the one we are checking
-                // for further down, so we check both.
-                preds.push(root);
-            }
-            for pred in preds {
-                if let Some(clause) = pred.as_clause()
-                    && let Some(clause) = clause.as_trait_clause()
-                    && let ty = clause.self_ty().skip_binder()
-                    && let ty::Tuple(types) = ty.kind()
-                {
-                    let path = clause.skip_binder().trait_ref.print_only_trait_path();
-                    let def_id = clause.def_id();
-                    let ty = Ty::new_tup(
-                        self.tcx,
-                        self.tcx.mk_type_list_from_iter(types.iter().map(|ty| ty.peel_refs())),
-                    );
-                    let args = ty::GenericArgs::for_item(self.tcx, def_id, |param, _| {
-                        if param.index == 0 {
-                            ty.into()
-                        } else {
-                            self.infcx.var_for_def(DUMMY_SP, param)
-                        }
-                    });
-                    if self
-                        .infcx
-                        .type_implements_trait(def_id, args, self.param_env)
-                        .must_apply_modulo_regions()
-                    {
-                        // "`Trait` is implemented for `(A, B)` but not for `(A, &B)`"
-                        let mut msg = DiagStyledString::normal(format!("`{path}` "));
-                        msg.push_highlighted("is");
-                        msg.push_normal(" implemented for `(");
-                        let len = types.len();
-                        for (i, t) in types.iter().enumerate() {
-                            msg.push(
-                                format!("{}", with_forced_trimmed_paths!(t.peel_refs())),
-                                t.peel_refs() != t,
-                            );
-                            if i < len - 1 {
-                                msg.push_normal(", ");
-                            }
-                        }
-                        msg.push_normal(")` but ");
-                        msg.push_highlighted("not");
-                        msg.push_normal(" for `(");
-                        for (i, t) in types.iter().enumerate() {
-                            msg.push(
-                                format!("{}", with_forced_trimmed_paths!(t)),
-                                t.peel_refs() != t,
-                            );
-                            if i < len - 1 {
-                                msg.push_normal(", ");
-                            }
-                        }
-                        msg.push_normal(")`");
-
-                        // Find the span corresponding to the impl that was found to point at it.
-                        if let Some(impl_span) = self
-                            .tcx
-                            .all_impls(def_id)
-                            .filter(|&impl_def_id| {
-                                let header = self.tcx.impl_trait_header(impl_def_id).unwrap();
-                                let trait_ref = header.trait_ref.instantiate(
-                                    self.tcx,
-                                    self.infcx.fresh_args_for_item(DUMMY_SP, impl_def_id),
-                                );
-
-                                let value = ty::fold_regions(self.tcx, ty, |_, _| {
-                                    self.tcx.lifetimes.re_erased
-                                });
-                                // FIXME: Don't bother dealing with non-lifetime binders here...
-                                if value.has_escaping_bound_vars() {
-                                    return false;
-                                }
-                                self.infcx.can_eq(ty::ParamEnv::empty(), trait_ref.self_ty(), value)
-                                    && header.polarity == ty::ImplPolarity::Positive
-                            })
-                            .map(|impl_def_id| self.tcx.def_span(impl_def_id))
-                            .next()
-                        {
-                            err.highlighted_span_note(impl_span, msg.0);
-                        } else {
-                            err.highlighted_note(msg.0);
-                        }
-                        found_tuple = true;
-                    }
-                    // If `pred` was already on the tuple, we don't need to look at the root
-                    // obligation too.
-                    break;
-                }
-            }
-        }
-        found_tuple
-    }
-
     /// If an appropriate error source is not found, check method chain for possible candidates
     fn lookup_segments_chain_for_no_match_method(
         &self,
diff --git a/compiler/rustc_hir_typeck/src/opaque_types.rs b/compiler/rustc_hir_typeck/src/opaque_types.rs
index e0224f8c6e1..97feac3d009 100644
--- a/compiler/rustc_hir_typeck/src/opaque_types.rs
+++ b/compiler/rustc_hir_typeck/src/opaque_types.rs
@@ -1,5 +1,218 @@
-use super::FnCtxt;
+use rustc_hir::def::DefKind;
+use rustc_infer::traits::ObligationCause;
+use rustc_middle::ty::{
+    self, DefiningScopeKind, EarlyBinder, OpaqueHiddenType, OpaqueTypeKey, TypeVisitableExt,
+    TypingMode,
+};
+use rustc_trait_selection::error_reporting::infer::need_type_info::TypeAnnotationNeeded;
+use rustc_trait_selection::opaque_types::{
+    NonDefiningUseReason, opaque_type_has_defining_use_args, report_item_does_not_constrain_error,
+};
+use rustc_trait_selection::solve;
+use tracing::{debug, instrument};
+
+use crate::FnCtxt;
+
 impl<'tcx> FnCtxt<'_, 'tcx> {
+    /// This takes all the opaque type uses during HIR typeck. It first computes
+    /// the concrete hidden type by iterating over all defining uses.
+    ///
+    /// A use during HIR typeck is defining if all non-lifetime arguments are
+    /// unique generic parameters and the hidden type does not reference any
+    /// inference variables.
+    ///
+    /// It then uses these defining uses to guide inference for all other uses.
+    #[instrument(level = "debug", skip(self))]
+    pub(super) fn handle_opaque_type_uses_next(&mut self) {
+        // We clone the opaques instead of stealing them here as they are still used for
+        // normalization in the next generation trait solver.
+        let mut opaque_types: Vec<_> = self.infcx.clone_opaque_types();
+        let num_entries = self.inner.borrow_mut().opaque_types().num_entries();
+        let prev = self.checked_opaque_types_storage_entries.replace(Some(num_entries));
+        debug_assert_eq!(prev, None);
+        for entry in &mut opaque_types {
+            *entry = self.resolve_vars_if_possible(*entry);
+        }
+        debug!(?opaque_types);
+
+        self.compute_concrete_opaque_types(&opaque_types);
+        self.apply_computed_concrete_opaque_types(&opaque_types);
+    }
+}
+
+enum UsageKind<'tcx> {
+    None,
+    NonDefiningUse(OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>),
+    UnconstrainedHiddenType(OpaqueHiddenType<'tcx>),
+    HasDefiningUse,
+}
+
+impl<'tcx> UsageKind<'tcx> {
+    fn merge(&mut self, other: UsageKind<'tcx>) {
+        match (&*self, &other) {
+            (UsageKind::HasDefiningUse, _) | (_, UsageKind::None) => unreachable!(),
+            (UsageKind::None, _) => *self = other,
+            // When mergining non-defining uses, prefer earlier ones. This means
+            // the error happens as early as possible.
+            (
+                UsageKind::NonDefiningUse(..) | UsageKind::UnconstrainedHiddenType(..),
+                UsageKind::NonDefiningUse(..),
+            ) => {}
+            // When merging unconstrained hidden types, we prefer later ones. This is
+            // used as in most cases, the defining use is the final return statement
+            // of our function, and other uses with defining arguments are likely not
+            // intended to be defining.
+            (
+                UsageKind::NonDefiningUse(..) | UsageKind::UnconstrainedHiddenType(..),
+                UsageKind::UnconstrainedHiddenType(..) | UsageKind::HasDefiningUse,
+            ) => *self = other,
+        }
+    }
+}
+
+impl<'tcx> FnCtxt<'_, 'tcx> {
+    fn compute_concrete_opaque_types(
+        &mut self,
+        opaque_types: &[(OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>)],
+    ) {
+        let tcx = self.tcx;
+        let TypingMode::Analysis { defining_opaque_types_and_generators } = self.typing_mode()
+        else {
+            unreachable!();
+        };
+
+        for def_id in defining_opaque_types_and_generators {
+            match tcx.def_kind(def_id) {
+                DefKind::OpaqueTy => {}
+                DefKind::Closure => continue,
+                _ => unreachable!("not opaque or generator: {def_id:?}"),
+            }
+
+            let mut usage_kind = UsageKind::None;
+            for &(opaque_type_key, hidden_type) in opaque_types {
+                if opaque_type_key.def_id != def_id {
+                    continue;
+                }
+
+                usage_kind.merge(self.consider_opaque_type_use(opaque_type_key, hidden_type));
+                if let UsageKind::HasDefiningUse = usage_kind {
+                    break;
+                }
+            }
+
+            let guar = match usage_kind {
+                UsageKind::None => {
+                    if let Some(guar) = self.tainted_by_errors() {
+                        guar
+                    } else {
+                        report_item_does_not_constrain_error(self.tcx, self.body_id, def_id, None)
+                    }
+                }
+                UsageKind::NonDefiningUse(opaque_type_key, hidden_type) => {
+                    report_item_does_not_constrain_error(
+                        self.tcx,
+                        self.body_id,
+                        def_id,
+                        Some((opaque_type_key, hidden_type.span)),
+                    )
+                }
+                UsageKind::UnconstrainedHiddenType(hidden_type) => {
+                    let infer_var = hidden_type
+                        .ty
+                        .walk()
+                        .filter_map(ty::GenericArg::as_term)
+                        .find(|term| term.is_infer())
+                        .unwrap_or_else(|| hidden_type.ty.into());
+                    self.err_ctxt()
+                        .emit_inference_failure_err(
+                            self.body_id,
+                            hidden_type.span,
+                            infer_var,
+                            TypeAnnotationNeeded::E0282,
+                            false,
+                        )
+                        .emit()
+                }
+                UsageKind::HasDefiningUse => continue,
+            };
+
+            self.typeck_results
+                .borrow_mut()
+                .concrete_opaque_types
+                .insert(def_id, OpaqueHiddenType::new_error(tcx, guar));
+            self.set_tainted_by_errors(guar);
+        }
+    }
+
+    fn consider_opaque_type_use(
+        &mut self,
+        opaque_type_key: OpaqueTypeKey<'tcx>,
+        hidden_type: OpaqueHiddenType<'tcx>,
+    ) -> UsageKind<'tcx> {
+        if let Err(err) = opaque_type_has_defining_use_args(
+            &self,
+            opaque_type_key,
+            hidden_type.span,
+            DefiningScopeKind::HirTypeck,
+        ) {
+            match err {
+                NonDefiningUseReason::Tainted(guar) => {
+                    self.typeck_results.borrow_mut().concrete_opaque_types.insert(
+                        opaque_type_key.def_id,
+                        OpaqueHiddenType::new_error(self.tcx, guar),
+                    );
+                    return UsageKind::HasDefiningUse;
+                }
+                _ => return UsageKind::NonDefiningUse(opaque_type_key, hidden_type),
+            };
+        }
+
+        // We ignore uses of the opaque if they have any inference variables
+        // as this can frequently happen with recursive calls.
+        //
+        // See `tests/ui/traits/next-solver/opaques/universal-args-non-defining.rs`.
+        if hidden_type.ty.has_non_region_infer() {
+            return UsageKind::UnconstrainedHiddenType(hidden_type);
+        }
+
+        let cause = ObligationCause::misc(hidden_type.span, self.body_id);
+        let at = self.at(&cause, self.param_env);
+        let hidden_type = match solve::deeply_normalize(at, hidden_type) {
+            Ok(hidden_type) => hidden_type,
+            Err(errors) => {
+                let guar = self.err_ctxt().report_fulfillment_errors(errors);
+                OpaqueHiddenType::new_error(self.tcx, guar)
+            }
+        };
+        let hidden_type = hidden_type.remap_generic_params_to_declaration_params(
+            opaque_type_key,
+            self.tcx,
+            DefiningScopeKind::HirTypeck,
+        );
+
+        let prev = self
+            .typeck_results
+            .borrow_mut()
+            .concrete_opaque_types
+            .insert(opaque_type_key.def_id, hidden_type);
+        assert!(prev.is_none());
+        UsageKind::HasDefiningUse
+    }
+
+    fn apply_computed_concrete_opaque_types(
+        &mut self,
+        opaque_types: &[(OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>)],
+    ) {
+        let tcx = self.tcx;
+        for &(key, hidden_type) in opaque_types {
+            let expected =
+                *self.typeck_results.borrow_mut().concrete_opaque_types.get(&key.def_id).unwrap();
+
+            let expected = EarlyBinder::bind(expected.ty).instantiate(tcx, key.args);
+            self.demand_eqtype(hidden_type.span, expected, hidden_type.ty);
+        }
+    }
+
     /// We may in theory add further uses of an opaque after cloning the opaque
     /// types storage during writeback when computing the defining uses.
     ///
diff --git a/compiler/rustc_hir_typeck/src/writeback.rs b/compiler/rustc_hir_typeck/src/writeback.rs
index 093de950d63..253eacbf353 100644
--- a/compiler/rustc_hir_typeck/src/writeback.rs
+++ b/compiler/rustc_hir_typeck/src/writeback.rs
@@ -27,7 +27,7 @@ use rustc_middle::ty::{
 };
 use rustc_span::{Span, sym};
 use rustc_trait_selection::error_reporting::infer::need_type_info::TypeAnnotationNeeded;
-use rustc_trait_selection::opaque_types::check_opaque_type_parameter_valid;
+use rustc_trait_selection::opaque_types::opaque_type_has_defining_use_args;
 use rustc_trait_selection::solve;
 use tracing::{debug, instrument};
 
@@ -74,7 +74,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         wbcx.visit_user_provided_tys();
         wbcx.visit_user_provided_sigs();
         wbcx.visit_coroutine_interior();
+        wbcx.visit_transmutes();
         wbcx.visit_offset_of_container_types();
+        wbcx.visit_potentially_region_dependent_goals();
 
         wbcx.typeck_results.rvalue_scopes =
             mem::take(&mut self.typeck_results.borrow_mut().rvalue_scopes);
@@ -532,8 +534,36 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
         }
     }
 
+    fn visit_transmutes(&mut self) {
+        let tcx = self.tcx();
+        let fcx_typeck_results = self.fcx.typeck_results.borrow();
+        assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
+        for &(from, to, hir_id) in self.fcx.deferred_transmute_checks.borrow().iter() {
+            let span = tcx.hir_span(hir_id);
+            let from = self.resolve(from, &span);
+            let to = self.resolve(to, &span);
+            self.typeck_results.transmutes_to_check.push((from, to, hir_id));
+        }
+    }
+
+    fn visit_opaque_types_next(&mut self) {
+        let mut fcx_typeck_results = self.fcx.typeck_results.borrow_mut();
+        assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
+        for hidden_ty in fcx_typeck_results.concrete_opaque_types.values() {
+            assert!(!hidden_ty.has_infer());
+        }
+
+        assert_eq!(self.typeck_results.concrete_opaque_types.len(), 0);
+        self.typeck_results.concrete_opaque_types =
+            mem::take(&mut fcx_typeck_results.concrete_opaque_types);
+    }
+
     #[instrument(skip(self), level = "debug")]
     fn visit_opaque_types(&mut self) {
+        if self.fcx.next_trait_solver() {
+            return self.visit_opaque_types_next();
+        }
+
         let tcx = self.tcx();
         // We clone the opaques instead of stealing them here as they are still used for
         // normalization in the next generation trait solver.
@@ -544,17 +574,14 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
         for (opaque_type_key, hidden_type) in opaque_types {
             let hidden_type = self.resolve(hidden_type, &hidden_type.span);
             let opaque_type_key = self.resolve(opaque_type_key, &hidden_type.span);
-
-            if !self.fcx.next_trait_solver() {
-                if let ty::Alias(ty::Opaque, alias_ty) = hidden_type.ty.kind()
-                    && alias_ty.def_id == opaque_type_key.def_id.to_def_id()
-                    && alias_ty.args == opaque_type_key.args
-                {
-                    continue;
-                }
+            if let ty::Alias(ty::Opaque, alias_ty) = hidden_type.ty.kind()
+                && alias_ty.def_id == opaque_type_key.def_id.to_def_id()
+                && alias_ty.args == opaque_type_key.args
+            {
+                continue;
             }
 
-            if let Err(err) = check_opaque_type_parameter_valid(
+            if let Err(err) = opaque_type_has_defining_use_args(
                 &self.fcx,
                 opaque_type_key,
                 hidden_type.span,
@@ -762,6 +789,32 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
         }
     }
 
+    fn visit_potentially_region_dependent_goals(&mut self) {
+        let obligations = self.fcx.take_hir_typeck_potentially_region_dependent_goals();
+        if let None = self.fcx.tainted_by_errors() {
+            for obligation in obligations {
+                let (predicate, mut cause) =
+                    self.fcx.resolve_vars_if_possible((obligation.predicate, obligation.cause));
+                if predicate.has_non_region_infer() {
+                    self.fcx.dcx().span_delayed_bug(
+                        cause.span,
+                        format!("unexpected inference variable after writeback: {predicate:?}"),
+                    );
+                } else {
+                    let predicate = self.tcx().erase_regions(predicate);
+                    if cause.has_infer() || cause.has_placeholders() {
+                        // We can't use the the obligation cause as it references
+                        // information local to this query.
+                        cause = self.fcx.misc(cause.span);
+                    }
+                    self.typeck_results
+                        .potentially_region_dependent_goals
+                        .insert((predicate, cause));
+                }
+            }
+        }
+    }
+
     fn resolve<T>(&mut self, value: T, span: &dyn Locatable) -> T
     where
         T: TypeFoldable<TyCtxt<'tcx>>,
@@ -883,6 +936,7 @@ impl<'cx, 'tcx> Resolver<'cx, 'tcx> {
         }
     }
 
+    #[instrument(level = "debug", skip(self, outer_exclusive_binder, new_err))]
     fn handle_term<T>(
         &mut self,
         value: T,
diff --git a/compiler/rustc_index/src/bit_set.rs b/compiler/rustc_index/src/bit_set.rs
index 645d95b1dba..684bd34f909 100644
--- a/compiler/rustc_index/src/bit_set.rs
+++ b/compiler/rustc_index/src/bit_set.rs
@@ -491,19 +491,15 @@ pub struct ChunkedBitSet<T> {
     marker: PhantomData<T>,
 }
 
-// Note: the chunk domain size is duplicated in each variant. This is a bit
-// inconvenient, but it allows the type size to be smaller than if we had an
-// outer struct containing a chunk domain size plus the `Chunk`, because the
-// compiler can place the chunk domain size after the tag.
+// NOTE: The chunk size is computed on-the-fly on each manipulation of a chunk.
+// This avoids storing it, as it's almost always CHUNK_BITS except for the last one.
 #[derive(Clone, Debug, PartialEq, Eq)]
 enum Chunk {
     /// A chunk that is all zeros; we don't represent the zeros explicitly.
-    /// The `ChunkSize` is always non-zero.
-    Zeros(ChunkSize),
+    Zeros,
 
     /// A chunk that is all ones; we don't represent the ones explicitly.
-    /// `ChunkSize` is always non-zero.
-    Ones(ChunkSize),
+    Ones,
 
     /// A chunk that has a mix of zeros and ones, which are represented
     /// explicitly and densely. It never has all zeros or all ones.
@@ -514,16 +510,14 @@ enum Chunk {
     /// to store the length, which would make this type larger. These excess
     /// words are always zero, as are any excess bits in the final in-use word.
     ///
-    /// The first `ChunkSize` field is always non-zero.
-    ///
-    /// The second `ChunkSize` field is the count of 1s set in the chunk, and
+    /// The `ChunkSize` field is the count of 1s set in the chunk, and
     /// must satisfy `0 < count < chunk_domain_size`.
     ///
     /// The words are within an `Rc` because it's surprisingly common to
     /// duplicate an entire chunk, e.g. in `ChunkedBitSet::clone_from()`, or
     /// when a `Mixed` chunk is union'd into a `Zeros` chunk. When we do need
     /// to modify a chunk we use `Rc::make_mut`.
-    Mixed(ChunkSize, ChunkSize, Rc<[Word; CHUNK_WORDS]>),
+    Mixed(ChunkSize, Rc<[Word; CHUNK_WORDS]>),
 }
 
 // This type is used a lot. Make sure it doesn't unintentionally get bigger.
@@ -535,6 +529,22 @@ impl<T> ChunkedBitSet<T> {
         self.domain_size
     }
 
+    #[inline]
+    fn last_chunk_size(&self) -> ChunkSize {
+        let n = self.domain_size % CHUNK_BITS;
+        if n == 0 { CHUNK_BITS as ChunkSize } else { n as ChunkSize }
+    }
+
+    /// All the chunks have a chunk_domain_size of `CHUNK_BITS` except the final one.
+    #[inline]
+    fn chunk_domain_size(&self, chunk: usize) -> ChunkSize {
+        if chunk == self.chunks.len() - 1 {
+            self.last_chunk_size()
+        } else {
+            CHUNK_BITS as ChunkSize
+        }
+    }
+
     #[cfg(test)]
     fn assert_valid(&self) {
         if self.domain_size == 0 {
@@ -544,8 +554,9 @@ impl<T> ChunkedBitSet<T> {
 
         assert!((self.chunks.len() - 1) * CHUNK_BITS <= self.domain_size);
         assert!(self.chunks.len() * CHUNK_BITS >= self.domain_size);
-        for chunk in self.chunks.iter() {
-            chunk.assert_valid();
+        for (chunk_index, chunk) in self.chunks.iter().enumerate() {
+            let chunk_domain_size = self.chunk_domain_size(chunk_index);
+            chunk.assert_valid(chunk_domain_size);
         }
     }
 }
@@ -556,16 +567,7 @@ impl<T: Idx> ChunkedBitSet<T> {
         let chunks = if domain_size == 0 {
             Box::new([])
         } else {
-            // All the chunks have a chunk_domain_size of `CHUNK_BITS` except
-            // the final one.
-            let final_chunk_domain_size = {
-                let n = domain_size % CHUNK_BITS;
-                if n == 0 { CHUNK_BITS } else { n }
-            };
-            let mut chunks =
-                vec![Chunk::new(CHUNK_BITS, is_empty); num_chunks(domain_size)].into_boxed_slice();
-            *chunks.last_mut().unwrap() = Chunk::new(final_chunk_domain_size, is_empty);
-            chunks
+            vec![if is_empty { Zeros } else { Ones }; num_chunks(domain_size)].into_boxed_slice()
         };
         ChunkedBitSet { domain_size, chunks, marker: PhantomData }
     }
@@ -594,11 +596,15 @@ impl<T: Idx> ChunkedBitSet<T> {
 
     /// Count the number of bits in the set.
     pub fn count(&self) -> usize {
-        self.chunks.iter().map(|chunk| chunk.count()).sum()
+        self.chunks
+            .iter()
+            .enumerate()
+            .map(|(index, chunk)| chunk.count(self.chunk_domain_size(index)))
+            .sum()
     }
 
     pub fn is_empty(&self) -> bool {
-        self.chunks.iter().all(|chunk| matches!(chunk, Zeros(..)))
+        self.chunks.iter().all(|chunk| matches!(chunk, Zeros))
     }
 
     /// Returns `true` if `self` contains `elem`.
@@ -607,9 +613,9 @@ impl<T: Idx> ChunkedBitSet<T> {
         assert!(elem.index() < self.domain_size);
         let chunk = &self.chunks[chunk_index(elem)];
         match &chunk {
-            Zeros(_) => false,
-            Ones(_) => true,
-            Mixed(_, _, words) => {
+            Zeros => false,
+            Ones => true,
+            Mixed(_, words) => {
                 let (word_index, mask) = chunk_word_index_and_mask(elem);
                 (words[word_index] & mask) != 0
             }
@@ -625,9 +631,10 @@ impl<T: Idx> ChunkedBitSet<T> {
     pub fn insert(&mut self, elem: T) -> bool {
         assert!(elem.index() < self.domain_size);
         let chunk_index = chunk_index(elem);
+        let chunk_domain_size = self.chunk_domain_size(chunk_index);
         let chunk = &mut self.chunks[chunk_index];
         match *chunk {
-            Zeros(chunk_domain_size) => {
+            Zeros => {
                 if chunk_domain_size > 1 {
                     #[cfg(feature = "nightly")]
                     let mut words = {
@@ -649,14 +656,14 @@ impl<T: Idx> ChunkedBitSet<T> {
 
                     let (word_index, mask) = chunk_word_index_and_mask(elem);
                     words_ref[word_index] |= mask;
-                    *chunk = Mixed(chunk_domain_size, 1, words);
+                    *chunk = Mixed(1, words);
                 } else {
-                    *chunk = Ones(chunk_domain_size);
+                    *chunk = Ones;
                 }
                 true
             }
-            Ones(_) => false,
-            Mixed(chunk_domain_size, ref mut count, ref mut words) => {
+            Ones => false,
+            Mixed(ref mut count, ref mut words) => {
                 // We skip all the work if the bit is already set.
                 let (word_index, mask) = chunk_word_index_and_mask(elem);
                 if (words[word_index] & mask) == 0 {
@@ -665,7 +672,7 @@ impl<T: Idx> ChunkedBitSet<T> {
                         let words = Rc::make_mut(words);
                         words[word_index] |= mask;
                     } else {
-                        *chunk = Ones(chunk_domain_size);
+                        *chunk = Ones;
                     }
                     true
                 } else {
@@ -678,11 +685,7 @@ impl<T: Idx> ChunkedBitSet<T> {
     /// Sets all bits to true.
     pub fn insert_all(&mut self) {
         for chunk in self.chunks.iter_mut() {
-            *chunk = match *chunk {
-                Zeros(chunk_domain_size)
-                | Ones(chunk_domain_size)
-                | Mixed(chunk_domain_size, ..) => Ones(chunk_domain_size),
-            }
+            *chunk = Ones;
         }
     }
 
@@ -690,10 +693,11 @@ impl<T: Idx> ChunkedBitSet<T> {
     pub fn remove(&mut self, elem: T) -> bool {
         assert!(elem.index() < self.domain_size);
         let chunk_index = chunk_index(elem);
+        let chunk_domain_size = self.chunk_domain_size(chunk_index);
         let chunk = &mut self.chunks[chunk_index];
         match *chunk {
-            Zeros(_) => false,
-            Ones(chunk_domain_size) => {
+            Zeros => false,
+            Ones => {
                 if chunk_domain_size > 1 {
                     #[cfg(feature = "nightly")]
                     let mut words = {
@@ -722,13 +726,13 @@ impl<T: Idx> ChunkedBitSet<T> {
                     );
                     let (word_index, mask) = chunk_word_index_and_mask(elem);
                     words_ref[word_index] &= !mask;
-                    *chunk = Mixed(chunk_domain_size, chunk_domain_size - 1, words);
+                    *chunk = Mixed(chunk_domain_size - 1, words);
                 } else {
-                    *chunk = Zeros(chunk_domain_size);
+                    *chunk = Zeros;
                 }
                 true
             }
-            Mixed(chunk_domain_size, ref mut count, ref mut words) => {
+            Mixed(ref mut count, ref mut words) => {
                 // We skip all the work if the bit is already clear.
                 let (word_index, mask) = chunk_word_index_and_mask(elem);
                 if (words[word_index] & mask) != 0 {
@@ -737,7 +741,7 @@ impl<T: Idx> ChunkedBitSet<T> {
                         let words = Rc::make_mut(words);
                         words[word_index] &= !mask;
                     } else {
-                        *chunk = Zeros(chunk_domain_size);
+                        *chunk = Zeros
                     }
                     true
                 } else {
@@ -748,11 +752,12 @@ impl<T: Idx> ChunkedBitSet<T> {
     }
 
     fn chunk_iter(&self, chunk_index: usize) -> ChunkIter<'_> {
+        let chunk_domain_size = self.chunk_domain_size(chunk_index);
         match self.chunks.get(chunk_index) {
-            Some(Zeros(_chunk_domain_size)) => ChunkIter::Zeros,
-            Some(Ones(chunk_domain_size)) => ChunkIter::Ones(0..*chunk_domain_size as usize),
-            Some(Mixed(chunk_domain_size, _, words)) => {
-                let num_words = num_words(*chunk_domain_size as usize);
+            Some(Zeros) => ChunkIter::Zeros,
+            Some(Ones) => ChunkIter::Ones(0..chunk_domain_size as usize),
+            Some(Mixed(_, words)) => {
+                let num_words = num_words(chunk_domain_size as usize);
                 ChunkIter::Mixed(BitIter::new(&words[0..num_words]))
             }
             None => ChunkIter::Finished,
@@ -765,23 +770,33 @@ impl<T: Idx> ChunkedBitSet<T> {
 impl<T: Idx> BitRelations<ChunkedBitSet<T>> for ChunkedBitSet<T> {
     fn union(&mut self, other: &ChunkedBitSet<T>) -> bool {
         assert_eq!(self.domain_size, other.domain_size);
-        debug_assert_eq!(self.chunks.len(), other.chunks.len());
+
+        let num_chunks = self.chunks.len();
+        debug_assert_eq!(num_chunks, other.chunks.len());
+
+        let last_chunk_size = self.last_chunk_size();
+        debug_assert_eq!(last_chunk_size, other.last_chunk_size());
 
         let mut changed = false;
-        for (mut self_chunk, other_chunk) in self.chunks.iter_mut().zip(other.chunks.iter()) {
+        for (chunk_index, (mut self_chunk, other_chunk)) in
+            self.chunks.iter_mut().zip(other.chunks.iter()).enumerate()
+        {
+            let chunk_domain_size = if chunk_index + 1 == num_chunks {
+                last_chunk_size
+            } else {
+                CHUNK_BITS as ChunkSize
+            };
+
             match (&mut self_chunk, &other_chunk) {
-                (_, Zeros(_)) | (Ones(_), _) => {}
-                (Zeros(self_chunk_domain_size), Ones(other_chunk_domain_size))
-                | (Mixed(self_chunk_domain_size, ..), Ones(other_chunk_domain_size))
-                | (Zeros(self_chunk_domain_size), Mixed(other_chunk_domain_size, ..)) => {
+                (_, Zeros) | (Ones, _) => {}
+                (Zeros, Ones) | (Mixed(..), Ones) | (Zeros, Mixed(..)) => {
                     // `other_chunk` fully overwrites `self_chunk`
-                    debug_assert_eq!(self_chunk_domain_size, other_chunk_domain_size);
                     *self_chunk = other_chunk.clone();
                     changed = true;
                 }
                 (
-                    Mixed(self_chunk_domain_size, self_chunk_count, self_chunk_words),
-                    Mixed(_other_chunk_domain_size, _other_chunk_count, other_chunk_words),
+                    Mixed(self_chunk_count, self_chunk_words),
+                    Mixed(_other_chunk_count, other_chunk_words),
                 ) => {
                     // First check if the operation would change
                     // `self_chunk.words`. If not, we can avoid allocating some
@@ -789,7 +804,7 @@ impl<T: Idx> BitRelations<ChunkedBitSet<T>> for ChunkedBitSet<T> {
                     // performance win. Also, we only need to operate on the
                     // in-use words, hence the slicing.
                     let op = |a, b| a | b;
-                    let num_words = num_words(*self_chunk_domain_size as usize);
+                    let num_words = num_words(chunk_domain_size as usize);
                     if bitwise_changes(
                         &self_chunk_words[0..num_words],
                         &other_chunk_words[0..num_words],
@@ -806,8 +821,8 @@ impl<T: Idx> BitRelations<ChunkedBitSet<T>> for ChunkedBitSet<T> {
                             .iter()
                             .map(|w| w.count_ones() as ChunkSize)
                             .sum();
-                        if *self_chunk_count == *self_chunk_domain_size {
-                            *self_chunk = Ones(*self_chunk_domain_size);
+                        if *self_chunk_count == chunk_domain_size {
+                            *self_chunk = Ones;
                         }
                         changed = true;
                     }
@@ -819,36 +834,41 @@ impl<T: Idx> BitRelations<ChunkedBitSet<T>> for ChunkedBitSet<T> {
 
     fn subtract(&mut self, other: &ChunkedBitSet<T>) -> bool {
         assert_eq!(self.domain_size, other.domain_size);
-        debug_assert_eq!(self.chunks.len(), other.chunks.len());
+
+        let num_chunks = self.chunks.len();
+        debug_assert_eq!(num_chunks, other.chunks.len());
+
+        let last_chunk_size = self.last_chunk_size();
+        debug_assert_eq!(last_chunk_size, other.last_chunk_size());
 
         let mut changed = false;
-        for (mut self_chunk, other_chunk) in self.chunks.iter_mut().zip(other.chunks.iter()) {
+        for (chunk_index, (mut self_chunk, other_chunk)) in
+            self.chunks.iter_mut().zip(other.chunks.iter()).enumerate()
+        {
+            let chunk_domain_size = if chunk_index + 1 == num_chunks {
+                last_chunk_size
+            } else {
+                CHUNK_BITS as ChunkSize
+            };
+
             match (&mut self_chunk, &other_chunk) {
-                (Zeros(..), _) | (_, Zeros(..)) => {}
-                (
-                    Ones(self_chunk_domain_size) | Mixed(self_chunk_domain_size, _, _),
-                    Ones(other_chunk_domain_size),
-                ) => {
-                    debug_assert_eq!(self_chunk_domain_size, other_chunk_domain_size);
+                (Zeros, _) | (_, Zeros) => {}
+                (Ones | Mixed(_, _), Ones) => {
                     changed = true;
-                    *self_chunk = Zeros(*self_chunk_domain_size);
+                    *self_chunk = Zeros;
                 }
-                (
-                    Ones(self_chunk_domain_size),
-                    Mixed(other_chunk_domain_size, other_chunk_count, other_chunk_words),
-                ) => {
-                    debug_assert_eq!(self_chunk_domain_size, other_chunk_domain_size);
+                (Ones, Mixed(other_chunk_count, other_chunk_words)) => {
                     changed = true;
-                    let num_words = num_words(*self_chunk_domain_size as usize);
+                    let num_words = num_words(chunk_domain_size as usize);
                     debug_assert!(num_words > 0 && num_words <= CHUNK_WORDS);
                     let mut tail_mask =
-                        1 << (*other_chunk_domain_size - ((num_words - 1) * WORD_BITS) as u16) - 1;
+                        1 << (chunk_domain_size - ((num_words - 1) * WORD_BITS) as u16) - 1;
                     let mut self_chunk_words = **other_chunk_words;
                     for word in self_chunk_words[0..num_words].iter_mut().rev() {
                         *word = !*word & tail_mask;
                         tail_mask = u64::MAX;
                     }
-                    let self_chunk_count = *self_chunk_domain_size - *other_chunk_count;
+                    let self_chunk_count = chunk_domain_size - *other_chunk_count;
                     debug_assert_eq!(
                         self_chunk_count,
                         self_chunk_words[0..num_words]
@@ -856,16 +876,15 @@ impl<T: Idx> BitRelations<ChunkedBitSet<T>> for ChunkedBitSet<T> {
                             .map(|w| w.count_ones() as ChunkSize)
                             .sum()
                     );
-                    *self_chunk =
-                        Mixed(*self_chunk_domain_size, self_chunk_count, Rc::new(self_chunk_words));
+                    *self_chunk = Mixed(self_chunk_count, Rc::new(self_chunk_words));
                 }
                 (
-                    Mixed(self_chunk_domain_size, self_chunk_count, self_chunk_words),
-                    Mixed(_other_chunk_domain_size, _other_chunk_count, other_chunk_words),
+                    Mixed(self_chunk_count, self_chunk_words),
+                    Mixed(_other_chunk_count, other_chunk_words),
                 ) => {
                     // See [`<Self as BitRelations<ChunkedBitSet<T>>>::union`] for the explanation
                     let op = |a: u64, b: u64| a & !b;
-                    let num_words = num_words(*self_chunk_domain_size as usize);
+                    let num_words = num_words(chunk_domain_size as usize);
                     if bitwise_changes(
                         &self_chunk_words[0..num_words],
                         &other_chunk_words[0..num_words],
@@ -883,7 +902,7 @@ impl<T: Idx> BitRelations<ChunkedBitSet<T>> for ChunkedBitSet<T> {
                             .map(|w| w.count_ones() as ChunkSize)
                             .sum();
                         if *self_chunk_count == 0 {
-                            *self_chunk = Zeros(*self_chunk_domain_size);
+                            *self_chunk = Zeros;
                         }
                         changed = true;
                     }
@@ -895,28 +914,36 @@ impl<T: Idx> BitRelations<ChunkedBitSet<T>> for ChunkedBitSet<T> {
 
     fn intersect(&mut self, other: &ChunkedBitSet<T>) -> bool {
         assert_eq!(self.domain_size, other.domain_size);
-        debug_assert_eq!(self.chunks.len(), other.chunks.len());
+
+        let num_chunks = self.chunks.len();
+        debug_assert_eq!(num_chunks, other.chunks.len());
+
+        let last_chunk_size = self.last_chunk_size();
+        debug_assert_eq!(last_chunk_size, other.last_chunk_size());
 
         let mut changed = false;
-        for (mut self_chunk, other_chunk) in self.chunks.iter_mut().zip(other.chunks.iter()) {
+        for (chunk_index, (mut self_chunk, other_chunk)) in
+            self.chunks.iter_mut().zip(other.chunks.iter()).enumerate()
+        {
+            let chunk_domain_size = if chunk_index + 1 == num_chunks {
+                last_chunk_size
+            } else {
+                CHUNK_BITS as ChunkSize
+            };
+
             match (&mut self_chunk, &other_chunk) {
-                (Zeros(..), _) | (_, Ones(..)) => {}
-                (
-                    Ones(self_chunk_domain_size),
-                    Zeros(other_chunk_domain_size) | Mixed(other_chunk_domain_size, ..),
-                )
-                | (Mixed(self_chunk_domain_size, ..), Zeros(other_chunk_domain_size)) => {
-                    debug_assert_eq!(self_chunk_domain_size, other_chunk_domain_size);
+                (Zeros, _) | (_, Ones) => {}
+                (Ones, Zeros | Mixed(..)) | (Mixed(..), Zeros) => {
                     changed = true;
                     *self_chunk = other_chunk.clone();
                 }
                 (
-                    Mixed(self_chunk_domain_size, self_chunk_count, self_chunk_words),
-                    Mixed(_other_chunk_domain_size, _other_chunk_count, other_chunk_words),
+                    Mixed(self_chunk_count, self_chunk_words),
+                    Mixed(_other_chunk_count, other_chunk_words),
                 ) => {
                     // See [`<Self as BitRelations<ChunkedBitSet<T>>>::union`] for the explanation
                     let op = |a, b| a & b;
-                    let num_words = num_words(*self_chunk_domain_size as usize);
+                    let num_words = num_words(chunk_domain_size as usize);
                     if bitwise_changes(
                         &self_chunk_words[0..num_words],
                         &other_chunk_words[0..num_words],
@@ -934,7 +961,7 @@ impl<T: Idx> BitRelations<ChunkedBitSet<T>> for ChunkedBitSet<T> {
                             .map(|w| w.count_ones() as ChunkSize)
                             .sum();
                         if *self_chunk_count == 0 {
-                            *self_chunk = Zeros(*self_chunk_domain_size);
+                            *self_chunk = Zeros;
                         }
                         changed = true;
                     }
@@ -964,7 +991,7 @@ impl<T: Idx> BitRelations<ChunkedBitSet<T>> for DenseBitSet<T> {
                 words = &mut words[..CHUNK_WORDS];
             }
             match chunk {
-                Zeros(..) => {
+                Zeros => {
                     for word in words {
                         if *word != 0 {
                             changed = true;
@@ -972,8 +999,8 @@ impl<T: Idx> BitRelations<ChunkedBitSet<T>> for DenseBitSet<T> {
                         }
                     }
                 }
-                Ones(..) => (),
-                Mixed(_, _, data) => {
+                Ones => (),
+                Mixed(_, data) => {
                     for (i, word) in words.iter_mut().enumerate() {
                         let new_val = *word & data[i];
                         if new_val != *word {
@@ -1053,13 +1080,11 @@ impl<'a, T: Idx> Iterator for ChunkedBitIter<'a, T> {
 
 impl Chunk {
     #[cfg(test)]
-    fn assert_valid(&self) {
+    fn assert_valid(&self, chunk_domain_size: ChunkSize) {
+        assert!(chunk_domain_size as usize <= CHUNK_BITS);
         match *self {
-            Zeros(chunk_domain_size) | Ones(chunk_domain_size) => {
-                assert!(chunk_domain_size as usize <= CHUNK_BITS);
-            }
-            Mixed(chunk_domain_size, count, ref words) => {
-                assert!(chunk_domain_size as usize <= CHUNK_BITS);
+            Zeros | Ones => {}
+            Mixed(count, ref words) => {
                 assert!(0 < count && count < chunk_domain_size);
 
                 // Check the number of set bits matches `count`.
@@ -1083,18 +1108,12 @@ impl Chunk {
         }
     }
 
-    fn new(chunk_domain_size: usize, is_empty: bool) -> Self {
-        debug_assert!(0 < chunk_domain_size && chunk_domain_size <= CHUNK_BITS);
-        let chunk_domain_size = chunk_domain_size as ChunkSize;
-        if is_empty { Zeros(chunk_domain_size) } else { Ones(chunk_domain_size) }
-    }
-
     /// Count the number of 1s in the chunk.
-    fn count(&self) -> usize {
+    fn count(&self, chunk_domain_size: ChunkSize) -> usize {
         match *self {
-            Zeros(_) => 0,
-            Ones(chunk_domain_size) => chunk_domain_size as usize,
-            Mixed(_, count, _) => count as usize,
+            Zeros => 0,
+            Ones => chunk_domain_size as usize,
+            Mixed(count, _) => count as usize,
         }
     }
 }
diff --git a/compiler/rustc_index/src/bit_set/tests.rs b/compiler/rustc_index/src/bit_set/tests.rs
index 9ce4cf4293f..deddc872614 100644
--- a/compiler/rustc_index/src/bit_set/tests.rs
+++ b/compiler/rustc_index/src/bit_set/tests.rs
@@ -120,8 +120,9 @@ fn chunked_bitset() {
     let mut b1 = ChunkedBitSet::<usize>::new_empty(1);
     assert_eq!(
         b1,
-        ChunkedBitSet { domain_size: 1, chunks: Box::new([Zeros(1)]), marker: PhantomData }
+        ChunkedBitSet { domain_size: 1, chunks: Box::new([Zeros]), marker: PhantomData }
     );
+    assert_eq!(b1.chunk_domain_size(0), 1);
 
     b1.assert_valid();
     assert!(!b1.contains(0));
@@ -129,12 +130,12 @@ fn chunked_bitset() {
     assert!(b1.insert(0));
     assert!(b1.contains(0));
     assert_eq!(b1.count(), 1);
-    assert_eq!(b1.chunks(), [Ones(1)]);
+    assert_eq!(b1.chunks(), [Ones]);
     assert!(!b1.insert(0));
     assert!(b1.remove(0));
     assert!(!b1.contains(0));
     assert_eq!(b1.count(), 0);
-    assert_eq!(b1.chunks(), [Zeros(1)]);
+    assert_eq!(b1.chunks(), [Zeros]);
     b1.assert_valid();
 
     //-----------------------------------------------------------------------
@@ -142,8 +143,9 @@ fn chunked_bitset() {
     let mut b100 = ChunkedBitSet::<usize>::new_filled(100);
     assert_eq!(
         b100,
-        ChunkedBitSet { domain_size: 100, chunks: Box::new([Ones(100)]), marker: PhantomData }
+        ChunkedBitSet { domain_size: 100, chunks: Box::new([Ones]), marker: PhantomData }
     );
+    assert_eq!(b100.chunk_domain_size(0), 100);
 
     b100.assert_valid();
     for i in 0..100 {
@@ -152,7 +154,7 @@ fn chunked_bitset() {
     assert_eq!(b100.count(), 100);
     assert!(b100.remove(3));
     assert!(b100.insert(3));
-    assert_eq!(b100.chunks(), vec![Ones(100)]);
+    assert_eq!(b100.chunks(), vec![Ones]);
     assert!(
         b100.remove(20) && b100.remove(30) && b100.remove(40) && b100.remove(99) && b100.insert(30)
     );
@@ -161,7 +163,6 @@ fn chunked_bitset() {
     assert_eq!(
         b100.chunks(),
         vec![Mixed(
-            100,
             97,
             #[rustfmt::skip]
             Rc::new([
@@ -180,7 +181,7 @@ fn chunked_bitset() {
         }
     }
     assert_eq!(num_removed, 97);
-    assert_eq!(b100.chunks(), vec![Zeros(100)]);
+    assert_eq!(b100.chunks(), vec![Zeros]);
     b100.assert_valid();
 
     //-----------------------------------------------------------------------
@@ -188,23 +189,21 @@ fn chunked_bitset() {
     let mut b2548 = ChunkedBitSet::<usize>::new_empty(2548);
     assert_eq!(
         b2548,
-        ChunkedBitSet {
-            domain_size: 2548,
-            chunks: Box::new([Zeros(2048), Zeros(500)]),
-            marker: PhantomData,
-        }
+        ChunkedBitSet { domain_size: 2548, chunks: Box::new([Zeros, Zeros]), marker: PhantomData }
     );
+    assert_eq!(b2548.chunk_domain_size(0), 2048);
+    assert_eq!(b2548.chunk_domain_size(1), 500);
 
     b2548.assert_valid();
     b2548.insert(14);
     b2548.remove(14);
-    assert_eq!(b2548.chunks(), vec![Zeros(2048), Zeros(500)]);
+    assert_eq!(b2548.chunks(), vec![Zeros, Zeros]);
     b2548.insert_all();
     for i in 0..2548 {
         assert!(b2548.contains(i));
     }
     assert_eq!(b2548.count(), 2548);
-    assert_eq!(b2548.chunks(), vec![Ones(2048), Ones(500)]);
+    assert_eq!(b2548.chunks(), vec![Ones, Ones]);
     b2548.assert_valid();
 
     //-----------------------------------------------------------------------
@@ -212,12 +211,10 @@ fn chunked_bitset() {
     let mut b4096 = ChunkedBitSet::<usize>::new_empty(4096);
     assert_eq!(
         b4096,
-        ChunkedBitSet {
-            domain_size: 4096,
-            chunks: Box::new([Zeros(2048), Zeros(2048)]),
-            marker: PhantomData,
-        }
+        ChunkedBitSet { domain_size: 4096, chunks: Box::new([Zeros, Zeros]), marker: PhantomData }
     );
+    assert_eq!(b4096.chunk_domain_size(0), 2048);
+    assert_eq!(b4096.chunk_domain_size(1), 2048);
 
     b4096.assert_valid();
     for i in 0..4096 {
@@ -231,11 +228,11 @@ fn chunked_bitset() {
         b4096.chunks(),
         #[rustfmt::skip]
         vec![
-            Mixed(2048, 1, Rc::new([
+            Mixed(1, Rc::new([
                 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
                 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
             ])),
-            Mixed(2048, 1, Rc::new([
+            Mixed(1, Rc::new([
                 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
                 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x8000_0000_0000_0000
             ])),
@@ -251,10 +248,15 @@ fn chunked_bitset() {
         b10000,
         ChunkedBitSet {
             domain_size: 10000,
-            chunks: Box::new([Zeros(2048), Zeros(2048), Zeros(2048), Zeros(2048), Zeros(1808),]),
+            chunks: Box::new([Zeros, Zeros, Zeros, Zeros, Zeros,]),
             marker: PhantomData,
         }
     );
+    assert_eq!(b10000.chunk_domain_size(0), 2048);
+    assert_eq!(b10000.chunk_domain_size(1), 2048);
+    assert_eq!(b10000.chunk_domain_size(2), 2048);
+    assert_eq!(b10000.chunk_domain_size(3), 2048);
+    assert_eq!(b10000.chunk_domain_size(4), 1808);
 
     b10000.assert_valid();
     assert!(b10000.insert(3000) && b10000.insert(5000));
@@ -262,17 +264,17 @@ fn chunked_bitset() {
         b10000.chunks(),
         #[rustfmt::skip]
         vec![
-            Zeros(2048),
-            Mixed(2048, 1, Rc::new([
+            Zeros,
+            Mixed(1, Rc::new([
                 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x0100_0000_0000_0000, 0,
                 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
             ])),
-            Mixed(2048, 1, Rc::new([
+            Mixed(1, Rc::new([
                 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x0100, 0,
                 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
             ])),
-            Zeros(2048),
-            Zeros(1808),
+            Zeros,
+            Zeros,
         ],
     );
     let mut b10000b = ChunkedBitSet::<usize>::new_empty(10000);
diff --git a/compiler/rustc_infer/src/infer/context.rs b/compiler/rustc_infer/src/infer/context.rs
index 21e999b080d..bb9c8850093 100644
--- a/compiler/rustc_infer/src/infer/context.rs
+++ b/compiler/rustc_infer/src/infer/context.rs
@@ -22,10 +22,6 @@ 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/mod.rs b/compiler/rustc_infer/src/infer/mod.rs
index 82d4856df39..d1507f08c06 100644
--- a/compiler/rustc_infer/src/infer/mod.rs
+++ b/compiler/rustc_infer/src/infer/mod.rs
@@ -158,7 +158,8 @@ pub struct InferCtxtInner<'tcx> {
     region_assumptions: Vec<ty::ArgOutlivesPredicate<'tcx>>,
 
     /// `-Znext-solver`: Successfully proven goals during HIR typeck which
-    /// reference inference variables and get reproven after writeback.
+    /// reference inference variables and get reproven in case MIR type check
+    /// fails to prove something.
     ///
     /// See the documentation of `InferCtxt::in_hir_typeck` for more details.
     hir_typeck_potentially_region_dependent_goals: Vec<PredicateObligation<'tcx>>,
@@ -782,22 +783,30 @@ impl<'tcx> InferCtxt<'tcx> {
         self.inner.borrow_mut().type_variables().num_vars()
     }
 
-    pub fn next_ty_var(&self, span: Span) -> Ty<'tcx> {
-        self.next_ty_var_with_origin(TypeVariableOrigin { span, param_def_id: None })
+    pub fn next_ty_vid(&self, span: Span) -> TyVid {
+        self.next_ty_vid_with_origin(TypeVariableOrigin { span, param_def_id: None })
     }
 
-    pub fn next_ty_var_with_origin(&self, origin: TypeVariableOrigin) -> Ty<'tcx> {
-        let vid = self.inner.borrow_mut().type_variables().new_var(self.universe(), origin);
-        Ty::new_var(self.tcx, vid)
+    pub fn next_ty_vid_with_origin(&self, origin: TypeVariableOrigin) -> TyVid {
+        self.inner.borrow_mut().type_variables().new_var(self.universe(), origin)
     }
 
-    pub fn next_ty_var_id_in_universe(&self, span: Span, universe: ty::UniverseIndex) -> TyVid {
+    pub fn next_ty_vid_in_universe(&self, span: Span, universe: ty::UniverseIndex) -> TyVid {
         let origin = TypeVariableOrigin { span, param_def_id: None };
         self.inner.borrow_mut().type_variables().new_var(universe, origin)
     }
 
+    pub fn next_ty_var(&self, span: Span) -> Ty<'tcx> {
+        self.next_ty_var_with_origin(TypeVariableOrigin { span, param_def_id: None })
+    }
+
+    pub fn next_ty_var_with_origin(&self, origin: TypeVariableOrigin) -> Ty<'tcx> {
+        let vid = self.next_ty_vid_with_origin(origin);
+        Ty::new_var(self.tcx, vid)
+    }
+
     pub fn next_ty_var_in_universe(&self, span: Span, universe: ty::UniverseIndex) -> Ty<'tcx> {
-        let vid = self.next_ty_var_id_in_universe(span, universe);
+        let vid = self.next_ty_vid_in_universe(span, universe);
         Ty::new_var(self.tcx, vid)
     }
 
diff --git a/compiler/rustc_interface/src/interface.rs b/compiler/rustc_interface/src/interface.rs
index c46e879b976..8f131f45bbd 100644
--- a/compiler/rustc_interface/src/interface.rs
+++ b/compiler/rustc_interface/src/interface.rs
@@ -285,7 +285,9 @@ pub(crate) fn parse_check_cfg(dcx: DiagCtxtHandle<'_>, specs: Vec<String>) -> Ch
                     .expecteds
                     .entry(name.name)
                     .and_modify(|v| match v {
-                        ExpectedValues::Some(v) if !values_any_specified => {
+                        ExpectedValues::Some(v) if !values_any_specified =>
+                        {
+                            #[allow(rustc::potential_query_instability)]
                             v.extend(values.clone())
                         }
                         ExpectedValues::Some(_) => *v = ExpectedValues::Any,
diff --git a/compiler/rustc_interface/src/passes.rs b/compiler/rustc_interface/src/passes.rs
index 3ba224723e3..bc5ef04079e 100644
--- a/compiler/rustc_interface/src/passes.rs
+++ b/compiler/rustc_interface/src/passes.rs
@@ -6,6 +6,7 @@ use std::sync::{Arc, LazyLock, OnceLock};
 use std::{env, fs, iter};
 
 use rustc_ast as ast;
+use rustc_attr_parsing::{AttributeParser, ShouldEmit, validate_attr};
 use rustc_codegen_ssa::traits::CodegenBackend;
 use rustc_data_structures::jobserver::Proxy;
 use rustc_data_structures::steal::Steal;
@@ -15,6 +16,7 @@ use rustc_errors::timings::TimingSection;
 use rustc_expand::base::{ExtCtxt, LintStoreExpand};
 use rustc_feature::Features;
 use rustc_fs_util::try_canonicalize;
+use rustc_hir::attrs::AttributeKind;
 use rustc_hir::def_id::{LOCAL_CRATE, StableCrateId, StableCrateIdMap};
 use rustc_hir::definitions::Definitions;
 use rustc_incremental::setup_dep_graph;
@@ -25,9 +27,7 @@ use rustc_middle::arena::Arena;
 use rustc_middle::dep_graph::DepsType;
 use rustc_middle::ty::{self, CurrentGcx, GlobalCtxt, RegisteredTools, TyCtxt};
 use rustc_middle::util::Providers;
-use rustc_parse::{
-    new_parser_from_file, new_parser_from_source_str, unwrap_or_emit_fatal, validate_attr,
-};
+use rustc_parse::{new_parser_from_file, new_parser_from_source_str, unwrap_or_emit_fatal};
 use rustc_passes::{abi_test, input_stats, layout_test};
 use rustc_resolve::{Resolver, ResolverOutputs};
 use rustc_session::config::{CrateType, Input, OutFileName, OutputFilenames, OutputType};
@@ -1081,7 +1081,8 @@ fn run_required_analyses(tcx: TyCtxt<'_>) {
             if !tcx.is_typeck_child(def_id.to_def_id()) {
                 // Child unsafety and borrowck happens together with the parent
                 tcx.ensure_ok().check_unsafety(def_id);
-                tcx.ensure_ok().mir_borrowck(def_id)
+                tcx.ensure_ok().mir_borrowck(def_id);
+                tcx.ensure_ok().check_transmutes(def_id);
             }
             tcx.ensure_ok().has_ffi_unwind_calls(def_id);
 
@@ -1244,8 +1245,7 @@ pub fn get_crate_name(sess: &Session, krate_attrs: &[ast::Attribute]) -> Symbol
     // in all code paths that require the crate name very early on, namely before
     // macro expansion.
 
-    let attr_crate_name =
-        validate_and_find_value_str_builtin_attr(sym::crate_name, sess, krate_attrs);
+    let attr_crate_name = parse_crate_name(sess, krate_attrs, ShouldEmit::EarlyFatal);
 
     let validate = |name, span| {
         rustc_session::output::validate_crate_name(sess, name, span);
@@ -1283,6 +1283,28 @@ pub fn get_crate_name(sess: &Session, krate_attrs: &[ast::Attribute]) -> Symbol
     sym::rust_out
 }
 
+pub(crate) fn parse_crate_name(
+    sess: &Session,
+    attrs: &[ast::Attribute],
+    emit_errors: ShouldEmit,
+) -> Option<(Symbol, Span)> {
+    let rustc_hir::Attribute::Parsed(AttributeKind::CrateName { name, name_span, .. }) =
+        AttributeParser::parse_limited_should_emit(
+            sess,
+            &attrs,
+            sym::crate_name,
+            DUMMY_SP,
+            rustc_ast::node_id::CRATE_NODE_ID,
+            None,
+            emit_errors,
+        )?
+    else {
+        unreachable!("crate_name is the only attr we could've parsed here");
+    };
+
+    Some((name, name_span))
+}
+
 fn get_recursion_limit(krate_attrs: &[ast::Attribute], sess: &Session) -> Limit {
     // We don't permit macro calls inside of the attribute (e.g., #![recursion_limit = `expand!()`])
     // because that would require expanding this while in the middle of expansion, which needs to
diff --git a/compiler/rustc_interface/src/tests.rs b/compiler/rustc_interface/src/tests.rs
index 0a764808f95..4425877308a 100644
--- a/compiler/rustc_interface/src/tests.rs
+++ b/compiler/rustc_interface/src/tests.rs
@@ -807,6 +807,7 @@ fn test_unstable_options_tracking_hash() {
     tracked!(hint_mostly_unused, true);
     tracked!(human_readable_cgu_names, true);
     tracked!(incremental_ignore_spans, true);
+    tracked!(indirect_branch_cs_prefix, true);
     tracked!(inline_mir, Some(true));
     tracked!(inline_mir_hint_threshold, Some(123));
     tracked!(inline_mir_threshold, Some(123));
diff --git a/compiler/rustc_interface/src/util.rs b/compiler/rustc_interface/src/util.rs
index 0ca4fcc66ca..04006f3e446 100644
--- a/compiler/rustc_interface/src/util.rs
+++ b/compiler/rustc_interface/src/util.rs
@@ -5,14 +5,15 @@ use std::sync::{Arc, OnceLock};
 use std::{env, thread};
 
 use rustc_ast as ast;
+use rustc_attr_parsing::{ShouldEmit, validate_attr};
 use rustc_codegen_ssa::traits::CodegenBackend;
 use rustc_data_structures::jobserver::Proxy;
 use rustc_data_structures::sync;
+use rustc_errors::LintBuffer;
 use rustc_metadata::{DylibError, load_symbol_from_dylib};
 use rustc_middle::ty::CurrentGcx;
-use rustc_parse::validate_attr;
 use rustc_session::config::{Cfg, OutFileName, OutputFilenames, OutputTypes, Sysroot, host_tuple};
-use rustc_session::lint::{self, BuiltinLintDiag, LintBuffer};
+use rustc_session::lint::{self, BuiltinLintDiag};
 use rustc_session::output::{CRATE_TYPES, categorize_crate_type};
 use rustc_session::{EarlyDiagCtxt, Session, filesearch};
 use rustc_span::edit_distance::find_best_match_for_name;
@@ -23,6 +24,7 @@ use rustc_target::spec::Target;
 use tracing::info;
 
 use crate::errors;
+use crate::passes::parse_crate_name;
 
 /// Function pointer type that constructs a new CodegenBackend.
 type MakeBackendFn = fn() -> Box<dyn CodegenBackend>;
@@ -519,11 +521,10 @@ pub fn build_output_filenames(attrs: &[ast::Attribute], sess: &Session) -> Outpu
         sess.dcx().emit_fatal(errors::MultipleOutputTypesToStdout);
     }
 
-    let crate_name = sess
-        .opts
-        .crate_name
-        .clone()
-        .or_else(|| rustc_attr_parsing::find_crate_name(attrs).map(|n| n.to_string()));
+    let crate_name =
+        sess.opts.crate_name.clone().or_else(|| {
+            parse_crate_name(sess, attrs, ShouldEmit::Nothing).map(|i| i.0.to_string())
+        });
 
     match sess.io.output_file {
         None => {
diff --git a/compiler/rustc_lexer/src/lib.rs b/compiler/rustc_lexer/src/lib.rs
index e80196ed567..483cc3e93dc 100644
--- a/compiler/rustc_lexer/src/lib.rs
+++ b/compiler/rustc_lexer/src/lib.rs
@@ -540,11 +540,11 @@ impl Cursor<'_> {
         // whitespace between the opening and the infostring.
         self.eat_while(|ch| ch != '\n' && is_whitespace(ch));
 
-        // copied from `eat_identifier`, but allows `.` in infostring to allow something like
+        // copied from `eat_identifier`, but allows `-` and `.` in infostring to allow something like
         // `---Cargo.toml` as a valid opener
         if is_id_start(self.first()) {
             self.bump();
-            self.eat_while(|c| is_id_continue(c) || c == '.');
+            self.eat_while(|c| is_id_continue(c) || c == '-' || c == '.');
         }
 
         self.eat_while(|ch| ch != '\n' && is_whitespace(ch));
diff --git a/compiler/rustc_lint/messages.ftl b/compiler/rustc_lint/messages.ftl
index c485e6fc849..417e5a97069 100644
--- a/compiler/rustc_lint/messages.ftl
+++ b/compiler/rustc_lint/messages.ftl
@@ -205,8 +205,6 @@ lint_confusable_identifier_pair = found both `{$existing_sym}` and `{$sym}` as i
     .current_use = this identifier can be confused with `{$existing_sym}`
     .other_use = other identifier used here
 
-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}
@@ -271,10 +269,6 @@ lint_expectation = this lint expectation is unfulfilled
 lint_extern_crate_not_idiomatic = `extern crate` is not idiomatic in the new edition
     .suggestion = convert it to a `use`
 
-lint_extern_without_abi = `extern` declarations without an explicit ABI are deprecated
-    .label = ABI should be specified here
-    .suggestion = explicitly specify the {$default_abi} ABI
-
 lint_for_loops_over_fallibles =
     for loop over {$article} `{$ref_prefix}{$ty}`. This is more readably written as an `if let` statement
     .suggestion = consider using `if let` to clear intent
@@ -294,19 +288,6 @@ lint_hidden_glob_reexport = private item shadows public glob re-export
 
 lint_hidden_lifetime_parameters = hidden lifetime parameters in types are deprecated
 
-lint_hidden_unicode_codepoints = unicode codepoint changing visible direction of text present in {$label}
-    .label = this {$label} contains {$count ->
-        [one] an invisible
-        *[other] invisible
-    } unicode text flow control {$count ->
-        [one] codepoint
-        *[other] codepoints
-    }
-    .note = these kind of unicode codepoints change the way text flows on applications that support them, but can cause confusion because they change the order of characters on the screen
-    .suggestion_remove = if their presence wasn't intentional, you can remove them
-    .suggestion_escape = if you want to keep them but make them visible in your source code, you can escape them
-    .no_suggestion_note_escape = if you want to keep them but make them visible in your source code, you can escape them: {$escaped}
-
 lint_identifier_non_ascii_char = identifier contains non-ASCII characters
 
 lint_identifier_uncommon_codepoints = identifier contains {$codepoints_len ->
@@ -431,8 +412,6 @@ lint_improper_ctypes_union_non_exhaustive = this union is non-exhaustive
 lint_incomplete_include =
     include macro expected single expression in source
 
-lint_inner_macro_attribute_unstable = inner macro attributes are unstable
-
 lint_invalid_asm_label_binary = avoid using labels containing only the digits `0` and `1` in inline assembly
     .label = use a different label that doesn't start with `0` or `1`
     .help = start numbering with `2` instead
@@ -483,6 +462,14 @@ lint_invalid_reference_casting_note_book = for more information, visit <https://
 
 lint_invalid_reference_casting_note_ty_has_interior_mutability = even for types with interior mutability, the only legal way to obtain a mutable pointer from a shared reference is through `UnsafeCell::get`
 
+lint_int_to_ptr_transmutes = transmuting an integer to a pointer creates a pointer without provenance
+    .note = this is dangerous because dereferencing the resulting pointer is undefined behavior
+    .note_exposed_provenance = exposed provenance semantics can be used to create a pointer based on some previously exposed provenance
+    .help_transmute = for more information about transmute, see <https://doc.rust-lang.org/std/mem/fn.transmute.html#transmutation-between-pointers-and-integers>
+    .help_exposed_provenance = for more information about exposed provenance, see <https://doc.rust-lang.org/std/ptr/index.html#exposed-provenance>
+    .suggestion_with_exposed_provenance = use `std::ptr::with_exposed_provenance{$suffix}` instead to use a previously exposed provenance
+    .suggestion_without_provenance_mut = if you truly mean to create a pointer without provenance, use `std::ptr::without_provenance_mut`
+
 lint_legacy_derive_helpers = derive helper attribute is used before it is introduced
     .label = the attribute is introduced here
 
@@ -732,7 +719,7 @@ lint_pattern_in_foreign = patterns aren't allowed in foreign function declaratio
 lint_private_extern_crate_reexport = extern crate `{$ident}` is private and cannot be re-exported
     .suggestion = consider making the `extern crate` item publicly accessible
 
-lint_proc_macro_derive_resolution_fallback = cannot find {$ns} `{$ident}` in this scope
+lint_proc_macro_derive_resolution_fallback = cannot find {$ns_descr} `{$ident}` in this scope
     .label = names from parent modules are not accessible without an explicit import
 
 lint_query_instability = using `{$query}` can result in unstable query results
@@ -870,10 +857,6 @@ lint_undropped_manually_drops = calls to `std::mem::drop` with `std::mem::Manual
     .label = argument has type `{$arg_ty}`
     .suggestion = use `std::mem::ManuallyDrop::into_inner` to get the inner value
 
-lint_unexpected_builtin_cfg = unexpected `--cfg {$cfg}` flag
-    .controlled_by = config `{$cfg_name}` is only supposed to be controlled by `{$controlled_by}`
-    .incoherent = manually setting a built-in cfg can and does create incoherent behaviors
-
 lint_unexpected_cfg_add_build_rs_println = or consider adding `{$build_rs_println}` to the top of the `build.rs`
 lint_unexpected_cfg_add_cargo_feature = consider using a Cargo feature instead
 lint_unexpected_cfg_add_cargo_toml_lint_cfg = or consider adding in `Cargo.toml` the `check-cfg` lint config for the lint:{$cargo_toml_lint_cfg}
diff --git a/compiler/rustc_lint/src/builtin.rs b/compiler/rustc_lint/src/builtin.rs
index 8006cfcf30f..c3c0a34df71 100644
--- a/compiler/rustc_lint/src/builtin.rs
+++ b/compiler/rustc_lint/src/builtin.rs
@@ -3097,7 +3097,7 @@ impl EarlyLintPass for SpecialModuleName {
             if let ast::ItemKind::Mod(
                 _,
                 ident,
-                ast::ModKind::Unloaded | ast::ModKind::Loaded(_, ast::Inline::No, _, _),
+                ast::ModKind::Unloaded | ast::ModKind::Loaded(_, ast::Inline::No { .. }, _),
             ) = item.kind
             {
                 if item.attrs.iter().any(|a| a.has_name(sym::path)) {
diff --git a/compiler/rustc_lint/src/context.rs b/compiler/rustc_lint/src/context.rs
index cb159a0b914..0669da1a025 100644
--- a/compiler/rustc_lint/src/context.rs
+++ b/compiler/rustc_lint/src/context.rs
@@ -11,7 +11,7 @@ use rustc_ast::util::parser::ExprPrecedence;
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_data_structures::sync;
 use rustc_data_structures::unord::UnordMap;
-use rustc_errors::{Diag, LintDiagnostic, MultiSpan};
+use rustc_errors::{Diag, LintBuffer, LintDiagnostic, MultiSpan};
 use rustc_feature::Features;
 use rustc_hir::def::Res;
 use rustc_hir::def_id::{CrateNum, DefId};
@@ -23,8 +23,8 @@ use rustc_middle::middle::privacy::EffectiveVisibilities;
 use rustc_middle::ty::layout::{LayoutError, LayoutOfHelpers, TyAndLayout};
 use rustc_middle::ty::print::{PrintError, PrintTraitRefExt as _, Printer, with_no_trimmed_paths};
 use rustc_middle::ty::{self, GenericArg, RegisteredTools, Ty, TyCtxt, TypingEnv, TypingMode};
-use rustc_session::lint::{FutureIncompatibleInfo, Lint, LintBuffer, LintExpectationId, LintId};
-use rustc_session::{LintStoreMarker, Session};
+use rustc_session::lint::{FutureIncompatibleInfo, Lint, LintExpectationId, LintId};
+use rustc_session::{DynLintStore, Session};
 use rustc_span::edit_distance::find_best_match_for_names;
 use rustc_span::{Ident, Span, Symbol, sym};
 use tracing::debug;
@@ -62,7 +62,13 @@ pub struct LintStore {
     lint_groups: FxIndexMap<&'static str, LintGroup>,
 }
 
-impl LintStoreMarker for LintStore {}
+impl DynLintStore for LintStore {
+    fn lint_groups_iter(&self) -> Box<dyn Iterator<Item = rustc_session::LintGroup> + '_> {
+        Box::new(self.get_lint_groups().map(|(name, lints, is_externally_loaded)| {
+            rustc_session::LintGroup { name, lints, is_externally_loaded }
+        }))
+    }
+}
 
 /// The target of the `by_name` map, which accounts for renaming/deprecation.
 #[derive(Debug)]
diff --git a/compiler/rustc_lint/src/early.rs b/compiler/rustc_lint/src/early.rs
index 58205087def..dff1fc43670 100644
--- a/compiler/rustc_lint/src/early.rs
+++ b/compiler/rustc_lint/src/early.rs
@@ -7,10 +7,11 @@
 use rustc_ast::visit::{self as ast_visit, Visitor, walk_list};
 use rustc_ast::{self as ast, HasAttrs};
 use rustc_data_structures::stack::ensure_sufficient_stack;
+use rustc_errors::{BufferedEarlyLint, DecorateDiagCompat, LintBuffer};
 use rustc_feature::Features;
 use rustc_middle::ty::{RegisteredTools, TyCtxt};
 use rustc_session::Session;
-use rustc_session::lint::{BufferedEarlyLint, LintBuffer, LintPass};
+use rustc_session::lint::LintPass;
 use rustc_span::{Ident, Span};
 use tracing::debug;
 
@@ -36,8 +37,11 @@ impl<'ecx, 'tcx, T: EarlyLintPass> EarlyContextAndPass<'ecx, 'tcx, T> {
     fn check_id(&mut self, id: ast::NodeId) {
         for early_lint in self.context.buffered.take(id) {
             let BufferedEarlyLint { span, node_id: _, lint_id, diagnostic } = early_lint;
-            self.context.opt_span_lint(lint_id.lint, span, |diag| {
-                diagnostics::decorate_builtin_lint(self.context.sess(), self.tcx, diagnostic, diag);
+            self.context.opt_span_lint(lint_id.lint, span, |diag| match diagnostic {
+                DecorateDiagCompat::Builtin(b) => {
+                    diagnostics::decorate_builtin_lint(self.context.sess(), self.tcx, b, diag);
+                }
+                DecorateDiagCompat::Dynamic(d) => d.decorate_lint_box(diag),
             });
         }
     }
diff --git a/compiler/rustc_lint/src/early/diagnostics.rs b/compiler/rustc_lint/src/early/diagnostics.rs
index 678d3d1f8ed..7300490b838 100644
--- a/compiler/rustc_lint/src/early/diagnostics.rs
+++ b/compiler/rustc_lint/src/early/diagnostics.rs
@@ -64,10 +64,12 @@ pub fn decorate_builtin_lint(
             }
             .decorate_lint(diag);
         }
-        BuiltinLintDiag::ProcMacroDeriveResolutionFallback { span: macro_span, ns, ident } => {
-            lints::ProcMacroDeriveResolutionFallback { span: macro_span, ns, ident }
-                .decorate_lint(diag)
-        }
+        BuiltinLintDiag::ProcMacroDeriveResolutionFallback {
+            span: macro_span,
+            ns_descr,
+            ident,
+        } => lints::ProcMacroDeriveResolutionFallback { span: macro_span, ns_descr, ident }
+            .decorate_lint(diag),
         BuiltinLintDiag::MacroExpandedMacroExportsAccessedByAbsolutePaths(span_def) => {
             lints::MacroExpandedMacroExportsAccessedByAbsolutePaths { definition: span_def }
                 .decorate_lint(diag)
@@ -156,9 +158,6 @@ pub fn decorate_builtin_lint(
             }
             .decorate_lint(diag);
         }
-        BuiltinLintDiag::MissingAbi(label_span, default_abi) => {
-            lints::MissingAbi { span: label_span, default_abi }.decorate_lint(diag);
-        }
         BuiltinLintDiag::LegacyDeriveHelpers(label_span) => {
             lints::LegacyDeriveHelpers { span: label_span }.decorate_lint(diag);
         }
@@ -184,27 +183,6 @@ pub fn decorate_builtin_lint(
                 lints::ReservedMultihash { suggestion }.decorate_lint(diag);
             }
         }
-        BuiltinLintDiag::HiddenUnicodeCodepoints {
-            label,
-            count,
-            span_label,
-            labels,
-            escape,
-            spans,
-        } => {
-            lints::HiddenUnicodeCodepointsDiag {
-                label: &label,
-                count,
-                span_label,
-                labels: labels.map(|spans| lints::HiddenUnicodeCodepointsDiagLabels { spans }),
-                sub: if escape {
-                    lints::HiddenUnicodeCodepointsDiagSub::Escape { spans }
-                } else {
-                    lints::HiddenUnicodeCodepointsDiagSub::NoEscape { spans }
-                },
-            }
-            .decorate_lint(diag);
-        }
         BuiltinLintDiag::UnusedBuiltinAttribute {
             attr_name,
             macro_name,
@@ -464,17 +442,8 @@ pub fn decorate_builtin_lint(
             }
             .decorate_lint(diag)
         }
-        BuiltinLintDiag::InnerAttributeUnstable { is_macro } => if is_macro {
-            lints::InnerAttributeUnstable::InnerMacroAttribute
-        } else {
-            lints::InnerAttributeUnstable::CustomInnerAttribute
-        }
-        .decorate_lint(diag),
         BuiltinLintDiag::OutOfScopeMacroCalls { span, path, location } => {
             lints::OutOfScopeMacroCalls { span, path, location }.decorate_lint(diag)
         }
-        BuiltinLintDiag::UnexpectedBuiltinCfg { cfg, cfg_name, controlled_by } => {
-            lints::UnexpectedBuiltinCfg { cfg, cfg_name, controlled_by }.decorate_lint(diag)
-        }
     }
 }
diff --git a/compiler/rustc_lint/src/foreign_modules.rs b/compiler/rustc_lint/src/foreign_modules.rs
index 759e6c927b8..3267e70f1de 100644
--- a/compiler/rustc_lint/src/foreign_modules.rs
+++ b/compiler/rustc_lint/src/foreign_modules.rs
@@ -179,7 +179,7 @@ impl ClashingExternDeclarations {
 /// symbol's name.
 fn name_of_extern_decl(tcx: TyCtxt<'_>, fi: hir::OwnerId) -> SymbolName {
     if let Some((overridden_link_name, overridden_link_name_span)) =
-        tcx.codegen_fn_attrs(fi).link_name.map(|overridden_link_name| {
+        tcx.codegen_fn_attrs(fi).symbol_name.map(|overridden_link_name| {
             // FIXME: Instead of searching through the attributes again to get span
             // information, we could have codegen_fn_attrs also give span information back for
             // where the attribute was defined. However, until this is found to be a
diff --git a/compiler/rustc_lint/src/internal.rs b/compiler/rustc_lint/src/internal.rs
index 016ff17f5d7..929fc8207b0 100644
--- a/compiler/rustc_lint/src/internal.rs
+++ b/compiler/rustc_lint/src/internal.rs
@@ -1,10 +1,10 @@
 //! Some lints that are only useful in the compiler or crates that use compiler internals, such as
 //! Clippy.
 
-use rustc_hir::HirId;
 use rustc_hir::def::Res;
 use rustc_hir::def_id::DefId;
-use rustc_middle::ty::{self, GenericArgsRef, Ty as MiddleTy};
+use rustc_hir::{Expr, ExprKind, HirId};
+use rustc_middle::ty::{self, GenericArgsRef, PredicatePolarity, Ty};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 use rustc_span::hygiene::{ExpnKind, MacroKind};
 use rustc_span::{Span, sym};
@@ -56,25 +56,6 @@ impl LateLintPass<'_> for DefaultHashTypes {
     }
 }
 
-/// Helper function for lints that check for expressions with calls and use typeck results to
-/// get the `DefId` and `GenericArgsRef` of the function.
-fn typeck_results_of_method_fn<'tcx>(
-    cx: &LateContext<'tcx>,
-    expr: &hir::Expr<'_>,
-) -> Option<(Span, DefId, ty::GenericArgsRef<'tcx>)> {
-    match expr.kind {
-        hir::ExprKind::MethodCall(segment, ..)
-            if let Some(def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id) =>
-        {
-            Some((segment.ident.span, def_id, cx.typeck_results().node_args(expr.hir_id)))
-        }
-        _ => match cx.typeck_results().node_type(expr.hir_id).kind() {
-            &ty::FnDef(def_id, args) => Some((expr.span, def_id, args)),
-            _ => None,
-        },
-    }
-}
-
 declare_tool_lint! {
     /// The `potential_query_instability` lint detects use of methods which can lead to
     /// potential query instability, such as iterating over a `HashMap`.
@@ -101,10 +82,12 @@ declare_tool_lint! {
 
 declare_lint_pass!(QueryStability => [POTENTIAL_QUERY_INSTABILITY, UNTRACKED_QUERY_INFORMATION]);
 
-impl LateLintPass<'_> for QueryStability {
-    fn check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
-        let Some((span, def_id, args)) = typeck_results_of_method_fn(cx, expr) else { return };
-        if let Ok(Some(instance)) = ty::Instance::try_resolve(cx.tcx, cx.typing_env(), def_id, args)
+impl<'tcx> LateLintPass<'tcx> for QueryStability {
+    fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
+        if let Some((callee_def_id, span, generic_args, _recv, _args)) =
+            get_callee_span_generic_args_and_args(cx, expr)
+            && let Ok(Some(instance)) =
+                ty::Instance::try_resolve(cx.tcx, cx.typing_env(), callee_def_id, generic_args)
         {
             let def_id = instance.def_id();
             if cx.tcx.has_attr(def_id, sym::rustc_lint_query_instability) {
@@ -113,7 +96,15 @@ impl LateLintPass<'_> for QueryStability {
                     span,
                     QueryInstability { query: cx.tcx.item_name(def_id) },
                 );
+            } else if has_unstable_into_iter_predicate(cx, callee_def_id, generic_args) {
+                let call_span = span.with_hi(expr.span.hi());
+                cx.emit_span_lint(
+                    POTENTIAL_QUERY_INSTABILITY,
+                    call_span,
+                    QueryInstability { query: sym::into_iter },
+                );
             }
+
             if cx.tcx.has_attr(def_id, sym::rustc_lint_untracked_query_information) {
                 cx.emit_span_lint(
                     UNTRACKED_QUERY_INFORMATION,
@@ -125,6 +116,69 @@ impl LateLintPass<'_> for QueryStability {
     }
 }
 
+fn has_unstable_into_iter_predicate<'tcx>(
+    cx: &LateContext<'tcx>,
+    callee_def_id: DefId,
+    generic_args: GenericArgsRef<'tcx>,
+) -> bool {
+    let Some(into_iterator_def_id) = cx.tcx.get_diagnostic_item(sym::IntoIterator) else {
+        return false;
+    };
+    let Some(into_iter_fn_def_id) = cx.tcx.lang_items().into_iter_fn() else {
+        return false;
+    };
+    let predicates = cx.tcx.predicates_of(callee_def_id).instantiate(cx.tcx, generic_args);
+    for (predicate, _) in predicates {
+        let Some(trait_pred) = predicate.as_trait_clause() else {
+            continue;
+        };
+        if trait_pred.def_id() != into_iterator_def_id
+            || trait_pred.polarity() != PredicatePolarity::Positive
+        {
+            continue;
+        }
+        // `IntoIterator::into_iter` has no additional method args.
+        let into_iter_fn_args =
+            cx.tcx.instantiate_bound_regions_with_erased(trait_pred).trait_ref.args;
+        let Ok(Some(instance)) = ty::Instance::try_resolve(
+            cx.tcx,
+            cx.typing_env(),
+            into_iter_fn_def_id,
+            into_iter_fn_args,
+        ) else {
+            continue;
+        };
+        // Does the input type's `IntoIterator` implementation have the
+        // `rustc_lint_query_instability` attribute on its `into_iter` method?
+        if cx.tcx.has_attr(instance.def_id(), sym::rustc_lint_query_instability) {
+            return true;
+        }
+    }
+    false
+}
+
+/// Checks whether an expression is a function or method call and, if so, returns its `DefId`,
+/// `Span`, `GenericArgs`, and arguments. This is a slight augmentation of a similarly named Clippy
+/// function, `get_callee_generic_args_and_args`.
+fn get_callee_span_generic_args_and_args<'tcx>(
+    cx: &LateContext<'tcx>,
+    expr: &'tcx Expr<'tcx>,
+) -> Option<(DefId, Span, GenericArgsRef<'tcx>, Option<&'tcx Expr<'tcx>>, &'tcx [Expr<'tcx>])> {
+    if let ExprKind::Call(callee, args) = expr.kind
+        && let callee_ty = cx.typeck_results().expr_ty(callee)
+        && let ty::FnDef(callee_def_id, generic_args) = callee_ty.kind()
+    {
+        return Some((*callee_def_id, callee.span, generic_args, None, args));
+    }
+    if let ExprKind::MethodCall(segment, recv, args, _) = expr.kind
+        && let Some(method_def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id)
+    {
+        let generic_args = cx.typeck_results().node_args(expr.hir_id);
+        return Some((method_def_id, segment.ident.span, generic_args, Some(recv), args));
+    }
+    None
+}
+
 declare_tool_lint! {
     /// The `usage_of_ty_tykind` lint detects usages of `ty::TyKind::<kind>`,
     /// where `ty::<kind>` would suffice.
@@ -461,33 +515,22 @@ declare_tool_lint! {
 declare_lint_pass!(Diagnostics => [UNTRANSLATABLE_DIAGNOSTIC, DIAGNOSTIC_OUTSIDE_OF_IMPL]);
 
 impl LateLintPass<'_> for Diagnostics {
-    fn check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
+    fn check_expr<'tcx>(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>) {
         let collect_args_tys_and_spans = |args: &[hir::Expr<'_>], reserve_one_extra: bool| {
             let mut result = Vec::with_capacity(args.len() + usize::from(reserve_one_extra));
             result.extend(args.iter().map(|arg| (cx.typeck_results().expr_ty(arg), arg.span)));
             result
         };
         // Only check function calls and method calls.
-        let (span, def_id, fn_gen_args, arg_tys_and_spans) = match expr.kind {
-            hir::ExprKind::Call(callee, args) => {
-                match cx.typeck_results().node_type(callee.hir_id).kind() {
-                    &ty::FnDef(def_id, fn_gen_args) => {
-                        (callee.span, def_id, fn_gen_args, collect_args_tys_and_spans(args, false))
-                    }
-                    _ => return, // occurs for fns passed as args
-                }
-            }
-            hir::ExprKind::MethodCall(_segment, _recv, args, _span) => {
-                let Some((span, def_id, fn_gen_args)) = typeck_results_of_method_fn(cx, expr)
-                else {
-                    return;
-                };
-                let mut args = collect_args_tys_and_spans(args, true);
-                args.insert(0, (cx.tcx.types.self_param, _recv.span)); // dummy inserted for `self`
-                (span, def_id, fn_gen_args, args)
-            }
-            _ => return,
+        let Some((def_id, span, fn_gen_args, recv, args)) =
+            get_callee_span_generic_args_and_args(cx, expr)
+        else {
+            return;
         };
+        let mut arg_tys_and_spans = collect_args_tys_and_spans(args, recv.is_some());
+        if let Some(recv) = recv {
+            arg_tys_and_spans.insert(0, (cx.tcx.types.self_param, recv.span)); // dummy inserted for `self`
+        }
 
         Self::diagnostic_outside_of_impl(cx, span, expr.hir_id, def_id, fn_gen_args);
         Self::untranslatable_diagnostic(cx, def_id, &arg_tys_and_spans);
@@ -496,7 +539,7 @@ impl LateLintPass<'_> for Diagnostics {
 
 impl Diagnostics {
     // Is the type `{D,Subd}iagMessage`?
-    fn is_diag_message<'cx>(cx: &LateContext<'cx>, ty: MiddleTy<'cx>) -> bool {
+    fn is_diag_message<'cx>(cx: &LateContext<'cx>, ty: Ty<'cx>) -> bool {
         if let Some(adt_def) = ty.ty_adt_def()
             && let Some(name) = cx.tcx.get_diagnostic_name(adt_def.did())
             && matches!(name, sym::DiagMessage | sym::SubdiagMessage)
@@ -510,7 +553,7 @@ impl Diagnostics {
     fn untranslatable_diagnostic<'cx>(
         cx: &LateContext<'cx>,
         def_id: DefId,
-        arg_tys_and_spans: &[(MiddleTy<'cx>, Span)],
+        arg_tys_and_spans: &[(Ty<'cx>, Span)],
     ) {
         let fn_sig = cx.tcx.fn_sig(def_id).instantiate_identity().skip_binder();
         let predicates = cx.tcx.predicates_of(def_id).instantiate_identity(cx.tcx).predicates;
diff --git a/compiler/rustc_lint/src/lib.rs b/compiler/rustc_lint/src/lib.rs
index f06757b3c23..bdbac7fc4d1 100644
--- a/compiler/rustc_lint/src/lib.rs
+++ b/compiler/rustc_lint/src/lib.rs
@@ -133,10 +133,9 @@ pub use early::{EarlyCheckNode, check_ast_node};
 pub use late::{check_crate, late_lint_mod, unerased_lint_store};
 pub use levels::LintLevelsBuilder;
 pub use passes::{EarlyLintPass, LateLintPass};
+pub use rustc_errors::BufferedEarlyLint;
 pub use rustc_session::lint::Level::{self, *};
-pub use rustc_session::lint::{
-    BufferedEarlyLint, FutureIncompatibleInfo, Lint, LintId, LintPass, LintVec,
-};
+pub use rustc_session::lint::{FutureIncompatibleInfo, Lint, LintId, LintPass, LintVec};
 
 rustc_fluent_macro::fluent_messages! { "../messages.ftl" }
 
diff --git a/compiler/rustc_lint/src/lifetime_syntax.rs b/compiler/rustc_lint/src/lifetime_syntax.rs
index 464f4fc34b9..413525eb6e5 100644
--- a/compiler/rustc_lint/src/lifetime_syntax.rs
+++ b/compiler/rustc_lint/src/lifetime_syntax.rs
@@ -214,9 +214,9 @@ impl<T> LifetimeSyntaxCategories<Vec<T>> {
         }
     }
 
-    pub fn flatten(&self) -> impl Iterator<Item = &T> {
-        let Self { hidden, elided, named } = self;
-        [hidden.iter(), elided.iter(), named.iter()].into_iter().flatten()
+    pub fn iter_unnamed(&self) -> impl Iterator<Item = &T> {
+        let Self { hidden, elided, named: _ } = self;
+        [hidden.iter(), elided.iter()].into_iter().flatten()
     }
 }
 
@@ -495,7 +495,7 @@ fn emit_mismatch_diagnostic<'tcx>(
 
     cx.emit_span_lint(
         MISMATCHED_LIFETIME_SYNTAXES,
-        inputs.flatten().copied().collect::<Vec<_>>(),
+        inputs.iter_unnamed().chain(outputs.iter_unnamed()).copied().collect::<Vec<_>>(),
         lints::MismatchedLifetimeSyntaxes { inputs, outputs, suggestions },
     );
 }
diff --git a/compiler/rustc_lint/src/lints.rs b/compiler/rustc_lint/src/lints.rs
index a6d59af6900..426500dda4a 100644
--- a/compiler/rustc_lint/src/lints.rs
+++ b/compiler/rustc_lint/src/lints.rs
@@ -1,14 +1,14 @@
+// ignore-tidy-filelength
+
 #![allow(rustc::untranslatable_diagnostic)]
 use std::num::NonZero;
 
-use rustc_abi::ExternAbi;
 use rustc_errors::codes::*;
 use rustc_errors::{
     Applicability, Diag, DiagArgValue, DiagMessage, DiagStyledString, ElidedLifetimeInPathSubdiag,
     EmissionGuarantee, LintDiagnostic, MultiSpan, Subdiagnostic, SuggestionStyle,
 };
 use rustc_hir as hir;
-use rustc_hir::def::Namespace;
 use rustc_hir::def_id::DefId;
 use rustc_hir::intravisit::VisitorExt;
 use rustc_macros::{LintDiagnostic, Subdiagnostic};
@@ -817,80 +817,6 @@ pub(crate) enum InvalidReferenceCastingDiag<'tcx> {
     },
 }
 
-// hidden_unicode_codepoints.rs
-#[derive(LintDiagnostic)]
-#[diag(lint_hidden_unicode_codepoints)]
-#[note]
-pub(crate) struct HiddenUnicodeCodepointsDiag<'a> {
-    pub label: &'a str,
-    pub count: usize,
-    #[label]
-    pub span_label: Span,
-    #[subdiagnostic]
-    pub labels: Option<HiddenUnicodeCodepointsDiagLabels>,
-    #[subdiagnostic]
-    pub sub: HiddenUnicodeCodepointsDiagSub,
-}
-
-pub(crate) struct HiddenUnicodeCodepointsDiagLabels {
-    pub spans: Vec<(char, Span)>,
-}
-
-impl Subdiagnostic for HiddenUnicodeCodepointsDiagLabels {
-    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
-        for (c, span) in self.spans {
-            diag.span_label(span, format!("{c:?}"));
-        }
-    }
-}
-
-pub(crate) enum HiddenUnicodeCodepointsDiagSub {
-    Escape { spans: Vec<(char, Span)> },
-    NoEscape { spans: Vec<(char, Span)> },
-}
-
-// Used because of multiple multipart_suggestion and note
-impl Subdiagnostic for HiddenUnicodeCodepointsDiagSub {
-    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
-        match self {
-            HiddenUnicodeCodepointsDiagSub::Escape { spans } => {
-                diag.multipart_suggestion_with_style(
-                    fluent::lint_suggestion_remove,
-                    spans.iter().map(|(_, span)| (*span, "".to_string())).collect(),
-                    Applicability::MachineApplicable,
-                    SuggestionStyle::HideCodeAlways,
-                );
-                diag.multipart_suggestion(
-                    fluent::lint_suggestion_escape,
-                    spans
-                        .into_iter()
-                        .map(|(c, span)| {
-                            let c = format!("{c:?}");
-                            (span, c[1..c.len() - 1].to_string())
-                        })
-                        .collect(),
-                    Applicability::MachineApplicable,
-                );
-            }
-            HiddenUnicodeCodepointsDiagSub::NoEscape { spans } => {
-                // FIXME: in other suggestions we've reversed the inner spans of doc comments. We
-                // should do the same here to provide the same good suggestions as we do for
-                // literals above.
-                diag.arg(
-                    "escaped",
-                    spans
-                        .into_iter()
-                        .map(|(c, _)| format!("{c:?}"))
-                        .collect::<Vec<String>>()
-                        .join(", "),
-                );
-                diag.note(fluent::lint_suggestion_remove);
-                diag.note(fluent::lint_no_suggestion_note_escape);
-            }
-        }
-    }
-}
-
 // map_unit_fn.rs
 #[derive(LintDiagnostic)]
 #[diag(lint_map_unit_fn)]
@@ -1618,6 +1544,48 @@ impl<'a> LintDiagnostic<'a, ()> for DropGlue<'_> {
     }
 }
 
+// transmute.rs
+#[derive(LintDiagnostic)]
+#[diag(lint_int_to_ptr_transmutes)]
+#[note]
+#[note(lint_note_exposed_provenance)]
+#[help(lint_suggestion_without_provenance_mut)]
+#[help(lint_help_transmute)]
+#[help(lint_help_exposed_provenance)]
+pub(crate) struct IntegerToPtrTransmutes<'tcx> {
+    #[subdiagnostic]
+    pub suggestion: IntegerToPtrTransmutesSuggestion<'tcx>,
+}
+
+#[derive(Subdiagnostic)]
+pub(crate) enum IntegerToPtrTransmutesSuggestion<'tcx> {
+    #[multipart_suggestion(
+        lint_suggestion_with_exposed_provenance,
+        applicability = "machine-applicable",
+        style = "verbose"
+    )]
+    ToPtr {
+        dst: Ty<'tcx>,
+        suffix: &'static str,
+        #[suggestion_part(code = "std::ptr::with_exposed_provenance{suffix}::<{dst}>(")]
+        start_call: Span,
+    },
+    #[multipart_suggestion(
+        lint_suggestion_with_exposed_provenance,
+        applicability = "machine-applicable",
+        style = "verbose"
+    )]
+    ToRef {
+        dst: Ty<'tcx>,
+        suffix: &'static str,
+        ref_mutbl: &'static str,
+        #[suggestion_part(
+            code = "&{ref_mutbl}*std::ptr::with_exposed_provenance{suffix}::<{dst}>("
+        )]
+        start_call: Span,
+    },
+}
+
 // types.rs
 #[derive(LintDiagnostic)]
 #[diag(lint_range_endpoint_out_of_range)]
@@ -2568,16 +2536,6 @@ pub(crate) mod unexpected_cfg_value {
 }
 
 #[derive(LintDiagnostic)]
-#[diag(lint_unexpected_builtin_cfg)]
-#[note(lint_controlled_by)]
-#[note(lint_incoherent)]
-pub(crate) struct UnexpectedBuiltinCfg {
-    pub(crate) cfg: String,
-    pub(crate) cfg_name: Symbol,
-    pub(crate) controlled_by: &'static str,
-}
-
-#[derive(LintDiagnostic)]
 #[diag(lint_macro_use_deprecated)]
 #[help]
 pub(crate) struct MacroUseDeprecated;
@@ -2691,14 +2649,6 @@ pub(crate) struct IllFormedAttributeInput {
 }
 
 #[derive(LintDiagnostic)]
-pub(crate) enum InnerAttributeUnstable {
-    #[diag(lint_inner_macro_attribute_unstable)]
-    InnerMacroAttribute,
-    #[diag(lint_custom_inner_attribute_unstable)]
-    CustomInnerAttribute,
-}
-
-#[derive(LintDiagnostic)]
 #[diag(lint_unknown_diagnostic_attribute)]
 pub(crate) struct UnknownDiagnosticAttribute {
     #[subdiagnostic]
@@ -2769,7 +2719,7 @@ pub(crate) struct AbsPathWithModuleSugg {
 pub(crate) struct ProcMacroDeriveResolutionFallback {
     #[label]
     pub span: Span,
-    pub ns: Namespace,
+    pub ns_descr: &'static str,
     pub ident: Ident,
 }
 
@@ -2891,14 +2841,6 @@ pub(crate) struct PatternsInFnsWithoutBodySub {
 }
 
 #[derive(LintDiagnostic)]
-#[diag(lint_extern_without_abi)]
-pub(crate) struct MissingAbi {
-    #[suggestion(code = "extern {default_abi}", applicability = "machine-applicable")]
-    pub span: Span,
-    pub default_abi: ExternAbi,
-}
-
-#[derive(LintDiagnostic)]
 #[diag(lint_legacy_derive_helpers)]
 pub(crate) struct LegacyDeriveHelpers {
     #[label]
diff --git a/compiler/rustc_lint/src/nonstandard_style.rs b/compiler/rustc_lint/src/nonstandard_style.rs
index 8fafaa33d0c..65075cfecfa 100644
--- a/compiler/rustc_lint/src/nonstandard_style.rs
+++ b/compiler/rustc_lint/src/nonstandard_style.rs
@@ -5,7 +5,7 @@ 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, find_attr};
+use rustc_hir::{Attribute, GenericParamKind, PatExprKind, PatKind, find_attr};
 use rustc_middle::hir::nested_filter::All;
 use rustc_middle::ty;
 use rustc_session::config::CrateType;
@@ -343,35 +343,27 @@ impl<'tcx> LateLintPass<'tcx> for NonSnakeCase {
         let crate_ident = if let Some(name) = &cx.tcx.sess.opts.crate_name {
             Some(Ident::from_str(name))
         } else {
-            ast::attr::find_by_name(cx.tcx.hir_attrs(hir::CRATE_HIR_ID), sym::crate_name).and_then(
-                |attr| {
-                    if let Attribute::Unparsed(n) = attr
-                        && let AttrItem { args: AttrArgs::Eq { eq_span: _, expr: lit }, .. } =
-                            n.as_ref()
-                        && let ast::LitKind::Str(name, ..) = lit.kind
-                    {
-                        // Discard the double quotes surrounding the literal.
-                        let sp = cx
-                            .sess()
-                            .source_map()
-                            .span_to_snippet(lit.span)
-                            .ok()
-                            .and_then(|snippet| {
-                                let left = snippet.find('"')?;
-                                let right = snippet.rfind('"').map(|pos| snippet.len() - pos)?;
-
-                                Some(
-                                    lit.span
-                                        .with_lo(lit.span.lo() + BytePos(left as u32 + 1))
-                                        .with_hi(lit.span.hi() - BytePos(right as u32)),
-                                )
-                            })
-                            .unwrap_or(lit.span);
-
-                        Some(Ident::new(name, sp))
-                    } else {
-                        None
-                    }
+            find_attr!(cx.tcx.hir_attrs(hir::CRATE_HIR_ID), AttributeKind::CrateName{name, name_span,..} => (name, name_span)).map(
+                |(&name, &span)| {
+                    // Discard the double quotes surrounding the literal.
+                    let sp = cx
+                        .sess()
+                        .source_map()
+                        .span_to_snippet(span)
+                        .ok()
+                        .and_then(|snippet| {
+                            let left = snippet.find('"')?;
+                            let right = snippet.rfind('"').map(|pos| snippet.len() - pos)?;
+
+                            Some(
+                                span
+                                    .with_lo(span.lo() + BytePos(left as u32 + 1))
+                                    .with_hi(span.hi() - BytePos(right as u32)),
+                            )
+                        })
+                        .unwrap_or(span);
+
+                    Ident::new(name, sp)
                 },
             )
         };
diff --git a/compiler/rustc_lint/src/transmute.rs b/compiler/rustc_lint/src/transmute.rs
index bc1d4587d07..239c8649041 100644
--- a/compiler/rustc_lint/src/transmute.rs
+++ b/compiler/rustc_lint/src/transmute.rs
@@ -1,3 +1,4 @@
+use rustc_ast::LitKind;
 use rustc_errors::Applicability;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::LocalDefId;
@@ -7,6 +8,7 @@ use rustc_middle::ty::{self, Ty};
 use rustc_session::{declare_lint, impl_lint_pass};
 use rustc_span::sym;
 
+use crate::lints::{IntegerToPtrTransmutes, IntegerToPtrTransmutesSuggestion};
 use crate::{LateContext, LateLintPass};
 
 declare_lint! {
@@ -67,9 +69,44 @@ declare_lint! {
     "detects transmutes that can also be achieved by other operations"
 }
 
+declare_lint! {
+    /// The `integer_to_ptr_transmutes` lint detects integer to pointer
+    /// transmutes where the resulting pointers are undefined behavior to dereference.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// fn foo(a: usize) -> *const u8 {
+    ///    unsafe {
+    ///        std::mem::transmute::<usize, *const u8>(a)
+    ///    }
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// Any attempt to use the resulting pointers are undefined behavior as the resulting
+    /// pointers won't have any provenance.
+    ///
+    /// Alternatively, [`std::ptr::with_exposed_provenance`] should be used, as they do not
+    /// carry the provenance requirement. If wanting to create pointers without provenance
+    /// [`std::ptr::without_provenance`] should be used instead.
+    ///
+    /// See [`std::mem::transmute`] in the reference for more details.
+    ///
+    /// [`std::mem::transmute`]: https://doc.rust-lang.org/std/mem/fn.transmute.html
+    /// [`std::ptr::with_exposed_provenance`]: https://doc.rust-lang.org/std/ptr/fn.with_exposed_provenance.html
+    /// [`std::ptr::without_provenance`]: https://doc.rust-lang.org/std/ptr/fn.without_provenance.html
+    pub INTEGER_TO_PTR_TRANSMUTES,
+    Warn,
+    "detects integer to pointer transmutes",
+}
+
 pub(crate) struct CheckTransmutes;
 
-impl_lint_pass!(CheckTransmutes => [PTR_TO_INTEGER_TRANSMUTE_IN_CONSTS, UNNECESSARY_TRANSMUTES]);
+impl_lint_pass!(CheckTransmutes => [PTR_TO_INTEGER_TRANSMUTE_IN_CONSTS, UNNECESSARY_TRANSMUTES, INTEGER_TO_PTR_TRANSMUTES]);
 
 impl<'tcx> LateLintPass<'tcx> for CheckTransmutes {
     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>) {
@@ -94,9 +131,62 @@ impl<'tcx> LateLintPass<'tcx> for CheckTransmutes {
 
         check_ptr_transmute_in_const(cx, expr, body_owner_def_id, const_context, src, dst);
         check_unnecessary_transmute(cx, expr, callee, arg, const_context, src, dst);
+        check_int_to_ptr_transmute(cx, expr, arg, src, dst);
     }
 }
 
+/// Check for transmutes from integer to pointers (*const/*mut and &/&mut).
+///
+/// Using the resulting pointers would be undefined behavior.
+fn check_int_to_ptr_transmute<'tcx>(
+    cx: &LateContext<'tcx>,
+    expr: &'tcx hir::Expr<'tcx>,
+    arg: &'tcx hir::Expr<'tcx>,
+    src: Ty<'tcx>,
+    dst: Ty<'tcx>,
+) {
+    if !matches!(src.kind(), ty::Uint(_) | ty::Int(_)) {
+        return;
+    }
+    let (ty::Ref(_, inner_ty, mutbl) | ty::RawPtr(inner_ty, mutbl)) = dst.kind() else {
+        return;
+    };
+    // bail-out if the argument is literal 0 as we have other lints for those cases
+    if matches!(arg.kind, hir::ExprKind::Lit(hir::Lit { node: LitKind::Int(v, _), .. }) if v == 0) {
+        return;
+    }
+    // bail-out if the inner type is a ZST
+    let Ok(layout_inner_ty) = cx.tcx.layout_of(cx.typing_env().as_query_input(*inner_ty)) else {
+        return;
+    };
+    if layout_inner_ty.is_1zst() {
+        return;
+    }
+
+    let suffix = if mutbl.is_mut() { "_mut" } else { "" };
+    cx.tcx.emit_node_span_lint(
+        INTEGER_TO_PTR_TRANSMUTES,
+        expr.hir_id,
+        expr.span,
+        IntegerToPtrTransmutes {
+            suggestion: if dst.is_ref() {
+                IntegerToPtrTransmutesSuggestion::ToRef {
+                    dst: *inner_ty,
+                    suffix,
+                    ref_mutbl: mutbl.prefix_str(),
+                    start_call: expr.span.shrink_to_lo().until(arg.span),
+                }
+            } else {
+                IntegerToPtrTransmutesSuggestion::ToPtr {
+                    dst: *inner_ty,
+                    suffix,
+                    start_call: expr.span.shrink_to_lo().until(arg.span),
+                }
+            },
+        },
+    );
+}
+
 /// Check for transmutes that exhibit undefined behavior.
 /// For example, transmuting pointers to integers in a const context.
 ///
diff --git a/compiler/rustc_lint_defs/Cargo.toml b/compiler/rustc_lint_defs/Cargo.toml
index 9ab350daf69..c8201d5ea8c 100644
--- a/compiler/rustc_lint_defs/Cargo.toml
+++ b/compiler/rustc_lint_defs/Cargo.toml
@@ -5,11 +5,10 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-rustc_abi = { path = "../rustc_abi" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_error_messages = { path = "../rustc_error_messages" }
-rustc_hir = { path = "../rustc_hir" }
+rustc_hir_id = { path = "../rustc_hir_id" }
 rustc_macros = { path = "../rustc_macros" }
 rustc_serialize = { path = "../rustc_serialize" }
 rustc_span = { path = "../rustc_span" }
diff --git a/compiler/rustc_lint_defs/src/lib.rs b/compiler/rustc_lint_defs/src/lib.rs
index 3bb7bbce567..2e84233e5a5 100644
--- a/compiler/rustc_lint_defs/src/lib.rs
+++ b/compiler/rustc_lint_defs/src/lib.rs
@@ -1,16 +1,15 @@
-use rustc_abi::ExternAbi;
+use std::borrow::Cow;
+
 use rustc_ast::AttrId;
 use rustc_ast::attr::AttributeExt;
-use rustc_ast::node_id::NodeId;
-use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
+use rustc_data_structures::fx::FxIndexSet;
 use rustc_data_structures::stable_hasher::{
     HashStable, StableCompare, StableHasher, ToStableHashKey,
 };
-use rustc_error_messages::{DiagMessage, MultiSpan};
-use rustc_hir::def::Namespace;
-use rustc_hir::def_id::DefPathHash;
-use rustc_hir::{HashStableContext, HirId, ItemLocalId};
+use rustc_error_messages::{DiagArgValue, DiagMessage, IntoDiagArg, MultiSpan};
+use rustc_hir_id::{HashStableContext, HirId, ItemLocalId};
 use rustc_macros::{Decodable, Encodable, HashStable_Generic};
+use rustc_span::def_id::DefPathHash;
 pub use rustc_span::edition::Edition;
 use rustc_span::{Ident, MacroRulesNormalizedIdent, Span, Symbol, sym};
 use serde::{Deserialize, Serialize};
@@ -138,7 +137,7 @@ impl LintExpectationId {
     }
 }
 
-impl<HCX: rustc_hir::HashStableContext> HashStable<HCX> for LintExpectationId {
+impl<HCX: HashStableContext> HashStable<HCX> for LintExpectationId {
     #[inline]
     fn hash_stable(&self, hcx: &mut HCX, hasher: &mut StableHasher) {
         match self {
@@ -156,7 +155,7 @@ impl<HCX: rustc_hir::HashStableContext> HashStable<HCX> for LintExpectationId {
     }
 }
 
-impl<HCX: rustc_hir::HashStableContext> ToStableHashKey<HCX> for LintExpectationId {
+impl<HCX: HashStableContext> ToStableHashKey<HCX> for LintExpectationId {
     type KeyType = (DefPathHash, ItemLocalId, u16, u16);
 
     #[inline]
@@ -297,6 +296,12 @@ impl Level {
     }
 }
 
+impl IntoDiagArg for Level {
+    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+        DiagArgValue::Str(Cow::Borrowed(self.to_cmd_flag()))
+    }
+}
+
 /// Specification of a single lint.
 #[derive(Copy, Clone, Debug)]
 pub struct Lint {
@@ -617,7 +622,7 @@ pub enum BuiltinLintDiag {
     AbsPathWithModule(Span),
     ProcMacroDeriveResolutionFallback {
         span: Span,
-        ns: Namespace,
+        ns_descr: &'static str,
         ident: Ident,
     },
     MacroExpandedMacroExportsAccessedByAbsolutePaths(Span),
@@ -641,7 +646,6 @@ pub enum BuiltinLintDiag {
         path: String,
         since_kind: DeprecatedSinceKind,
     },
-    MissingAbi(Span, ExternAbi),
     UnusedDocComment(Span),
     UnusedBuiltinAttribute {
         attr_name: Symbol,
@@ -664,14 +668,6 @@ pub enum BuiltinLintDiag {
         is_string: bool,
         suggestion: Span,
     },
-    HiddenUnicodeCodepoints {
-        label: String,
-        count: usize,
-        span_label: Span,
-        labels: Option<Vec<(char, Span)>>,
-        escape: bool,
-        spans: Vec<(char, Span)>,
-    },
     TrailingMacro(bool, Ident),
     BreakWithLabelAndLoop(Span),
     UnicodeTextFlow(Span, String),
@@ -796,68 +792,11 @@ pub enum BuiltinLintDiag {
         suggestions: Vec<String>,
         docs: Option<&'static str>,
     },
-    InnerAttributeUnstable {
-        is_macro: bool,
-    },
     OutOfScopeMacroCalls {
         span: Span,
         path: String,
         location: String,
     },
-    UnexpectedBuiltinCfg {
-        cfg: String,
-        cfg_name: Symbol,
-        controlled_by: &'static str,
-    },
-}
-
-/// Lints that are buffered up early on in the `Session` before the
-/// `LintLevels` is calculated.
-#[derive(Debug)]
-pub struct BufferedEarlyLint {
-    /// The span of code that we are linting on.
-    pub span: Option<MultiSpan>,
-
-    /// The `NodeId` of the AST node that generated the lint.
-    pub node_id: NodeId,
-
-    /// A lint Id that can be passed to
-    /// `rustc_lint::early::EarlyContextAndPass::check_id`.
-    pub lint_id: LintId,
-
-    /// Customization of the `Diag<'_>` for the lint.
-    pub diagnostic: BuiltinLintDiag,
-}
-
-#[derive(Default, Debug)]
-pub struct LintBuffer {
-    pub map: FxIndexMap<NodeId, Vec<BufferedEarlyLint>>,
-}
-
-impl LintBuffer {
-    pub fn add_early_lint(&mut self, early_lint: BufferedEarlyLint) {
-        self.map.entry(early_lint.node_id).or_default().push(early_lint);
-    }
-
-    pub fn take(&mut self, id: NodeId) -> Vec<BufferedEarlyLint> {
-        // FIXME(#120456) - is `swap_remove` correct?
-        self.map.swap_remove(&id).unwrap_or_default()
-    }
-
-    pub fn buffer_lint(
-        &mut self,
-        lint: &'static Lint,
-        node_id: NodeId,
-        span: impl Into<MultiSpan>,
-        diagnostic: BuiltinLintDiag,
-    ) {
-        self.add_early_lint(BufferedEarlyLint {
-            lint_id: LintId::of(lint),
-            node_id,
-            span: Some(span.into()),
-            diagnostic,
-        });
-    }
 }
 
 pub type RegisteredTools = FxIndexSet<Ident>;
diff --git a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
index e4fe1fc2e42..e699e4b9c13 100644
--- a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
+++ b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
@@ -278,6 +278,7 @@ enum class LLVMRustAttributeKind {
   Writable = 42,
   DeadOnUnwind = 43,
   DeadOnReturn = 44,
+  CapturesReadOnly = 45,
 };
 
 static Attribute::AttrKind fromRust(LLVMRustAttributeKind Kind) {
@@ -376,6 +377,8 @@ static Attribute::AttrKind fromRust(LLVMRustAttributeKind Kind) {
 #else
     report_fatal_error("DeadOnReturn attribute requires LLVM 21 or later");
 #endif
+  case LLVMRustAttributeKind::CapturesReadOnly:
+    report_fatal_error("Should be handled separately");
   }
   report_fatal_error("bad LLVMRustAttributeKind");
 }
@@ -430,6 +433,11 @@ LLVMRustCreateAttrNoValue(LLVMContextRef C, LLVMRustAttributeKind RustAttr) {
   if (RustAttr == LLVMRustAttributeKind::NoCapture) {
     return wrap(Attribute::getWithCaptureInfo(*unwrap(C), CaptureInfo::none()));
   }
+  if (RustAttr == LLVMRustAttributeKind::CapturesReadOnly) {
+    return wrap(Attribute::getWithCaptureInfo(
+        *unwrap(C), CaptureInfo(CaptureComponents::Address |
+                                CaptureComponents::ReadProvenance)));
+  }
 #endif
   return wrap(Attribute::get(*unwrap(C), fromRust(RustAttr)));
 }
diff --git a/compiler/rustc_macros/src/print_attribute.rs b/compiler/rustc_macros/src/print_attribute.rs
index 9023520c750..0114e0dfde0 100644
--- a/compiler/rustc_macros/src/print_attribute.rs
+++ b/compiler/rustc_macros/src/print_attribute.rs
@@ -4,7 +4,7 @@ use syn::spanned::Spanned;
 use syn::{Data, Fields, Ident};
 use synstructure::Structure;
 
-fn print_fields(name: &Ident, fields: &Fields) -> (TokenStream, TokenStream, TokenStream) {
+fn print_fields(name: &Ident, fields: &Fields) -> (TokenStream, TokenStream) {
     let string_name = name.to_string();
     let mut disps = vec![quote! {let mut __printed_anything = false;}];
 
@@ -43,7 +43,6 @@ fn print_fields(name: &Ident, fields: &Fields) -> (TokenStream, TokenStream, Tok
                     #(#disps)*
                     __p.word("}");
                 },
-                quote! { true },
             )
         }
         Fields::Unnamed(fields_unnamed) => {
@@ -76,10 +75,9 @@ fn print_fields(name: &Ident, fields: &Fields) -> (TokenStream, TokenStream, Tok
                     #(#disps)*
                     __p.pclose();
                 },
-                quote! { true },
             )
         }
-        Fields::Unit => (quote! {}, quote! { __p.word(#string_name) }, quote! { true }),
+        Fields::Unit => (quote! {}, quote! { __p.word(#string_name) }),
     }
 }
 
@@ -89,51 +87,33 @@ pub(crate) fn print_attribute(input: Structure<'_>) -> TokenStream {
     };
 
     // Must be applied to an enum type.
-    let (code, printed) = match &input.ast().data {
+    let code = match &input.ast().data {
         Data::Enum(e) => {
-            let (arms, printed) = e
+            let arms = e
                 .variants
                 .iter()
                 .map(|x| {
                     let ident = &x.ident;
-                    let (pat, code, printed) = print_fields(ident, &x.fields);
+                    let (pat, code) = print_fields(ident, &x.fields);
 
-                    (
-                        quote! {
-                            Self::#ident #pat => {#code}
-                        },
-                        quote! {
-                            Self::#ident #pat => {#printed}
-                        },
-                    )
+                    quote! {
+                        Self::#ident #pat => {#code}
+                    }
                 })
-                .unzip::<_, _, Vec<_>, Vec<_>>();
+                .collect::<Vec<_>>();
 
-            (
-                quote! {
-                    match self {
-                        #(#arms)*
-                    }
-                },
-                quote! {
-                    match self {
-                        #(#printed)*
-                    }
-                },
-            )
+            quote! {
+                match self {
+                    #(#arms)*
+                }
+            }
         }
         Data::Struct(s) => {
-            let (pat, code, printed) = print_fields(&input.ast().ident, &s.fields);
-            (
-                quote! {
-                    let Self #pat = self;
-                    #code
-                },
-                quote! {
-                    let Self #pat = self;
-                    #printed
-                },
-            )
+            let (pat, code) = print_fields(&input.ast().ident, &s.fields);
+            quote! {
+                let Self #pat = self;
+                #code
+            }
         }
         Data::Union(u) => {
             return span_error(u.union_token.span(), "can't derive PrintAttribute on unions");
@@ -144,7 +124,7 @@ pub(crate) fn print_attribute(input: Structure<'_>) -> TokenStream {
     input.gen_impl(quote! {
         #[allow(unused)]
         gen impl PrintAttribute for @Self {
-            fn should_render(&self) -> bool { #printed }
+            fn should_render(&self) -> bool { true }
             fn print_attribute(&self, __p: &mut rustc_ast_pretty::pp::Printer) { #code }
         }
     })
diff --git a/compiler/rustc_metadata/src/native_libs.rs b/compiler/rustc_metadata/src/native_libs.rs
index 958e314efab..63f1b51df1c 100644
--- a/compiler/rustc_metadata/src/native_libs.rs
+++ b/compiler/rustc_metadata/src/native_libs.rs
@@ -701,7 +701,7 @@ impl<'tcx> Collector<'tcx> {
             .link_ordinal
             .map_or(import_name_type, |ord| Some(PeImportNameType::Ordinal(ord)));
 
-        let name = codegen_fn_attrs.link_name.unwrap_or_else(|| self.tcx.item_name(item));
+        let name = codegen_fn_attrs.symbol_name.unwrap_or_else(|| self.tcx.item_name(item));
 
         if self.tcx.sess.target.binary_format == BinaryFormat::Elf {
             let name = name.as_str();
diff --git a/compiler/rustc_middle/src/lib.rs b/compiler/rustc_middle/src/lib.rs
index e5cc23c213d..cf0549fa668 100644
--- a/compiler/rustc_middle/src/lib.rs
+++ b/compiler/rustc_middle/src/lib.rs
@@ -60,6 +60,7 @@
 #![feature(try_trait_v2_residual)]
 #![feature(try_trait_v2_yeet)]
 #![feature(type_alias_impl_trait)]
+#![feature(unwrap_infallible)]
 #![feature(yeet_expr)]
 #![recursion_limit = "256"]
 // tidy-alphabetical-end
diff --git a/compiler/rustc_middle/src/lint.rs b/compiler/rustc_middle/src/lint.rs
index 341a735f88f..f70b7b6fad7 100644
--- a/compiler/rustc_middle/src/lint.rs
+++ b/compiler/rustc_middle/src/lint.rs
@@ -211,11 +211,28 @@ impl LintExpectation {
 }
 
 fn explain_lint_level_source(
+    sess: &Session,
     lint: &'static Lint,
     level: Level,
     src: LintLevelSource,
     err: &mut Diag<'_, ()>,
 ) {
+    // Find the name of the lint group that contains the given lint.
+    // Assumes the lint only belongs to one group.
+    let lint_group_name = |lint| {
+        let lint_groups_iter = sess.lint_groups_iter();
+        let lint_id = LintId::of(lint);
+        lint_groups_iter
+            .filter(|lint_group| !lint_group.is_externally_loaded)
+            .find(|lint_group| {
+                lint_group
+                    .lints
+                    .iter()
+                    .find(|lint_group_lint| **lint_group_lint == lint_id)
+                    .is_some()
+            })
+            .map(|lint_group| lint_group.name)
+    };
     let name = lint.name_lower();
     if let Level::Allow = level {
         // Do not point at `#[allow(compat_lint)]` as the reason for a compatibility lint
@@ -224,7 +241,15 @@ fn explain_lint_level_source(
     }
     match src {
         LintLevelSource::Default => {
-            err.note_once(format!("`#[{}({})]` on by default", level.as_str(), name));
+            let level_str = level.as_str();
+            match lint_group_name(lint) {
+                Some(group_name) => {
+                    err.note_once(format!("`#[{level_str}({name})]` (part of `#[{level_str}({group_name})]`) on by default"));
+                }
+                None => {
+                    err.note_once(format!("`#[{level_str}({name})]` on by default"));
+                }
+            }
         }
         LintLevelSource::CommandLine(lint_flag_val, orig_level) => {
             let flag = orig_level.to_cmd_flag();
@@ -427,7 +452,7 @@ pub fn lint_level(
             decorate(&mut err);
         }
 
-        explain_lint_level_source(lint, level, src, &mut err);
+        explain_lint_level_source(sess, lint, level, src, &mut err);
         err.emit()
     }
     lint_level_impl(sess, lint, level, span, Box::new(decorate))
diff --git a/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs b/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs
index da17ac04c76..78cafe8566b 100644
--- a/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs
+++ b/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs
@@ -35,14 +35,10 @@ pub struct CodegenFnAttrs {
     pub inline: InlineAttr,
     /// Parsed representation of the `#[optimize]` attribute
     pub optimize: OptimizeAttr,
-    /// The `#[export_name = "..."]` attribute, indicating a custom symbol a
-    /// function should be exported under
-    pub export_name: Option<Symbol>,
-    /// The `#[link_name = "..."]` attribute, indicating a custom symbol an
-    /// imported function should be imported as. Note that `export_name`
-    /// probably isn't set when this is set, this is for foreign items while
-    /// `#[export_name]` is for Rust-defined functions.
-    pub link_name: Option<Symbol>,
+    /// The name this function will be imported/exported under. This can be set
+    /// using the `#[export_name = "..."]` or `#[link_name = "..."]` attribute
+    /// depending on if this is a function definition or foreign function.
+    pub symbol_name: Option<Symbol>,
     /// The `#[link_ordinal = "..."]` attribute, indicating an ordinal an
     /// imported function has in the dynamic library. Note that this must not
     /// be set when `link_name` is set. This is for foreign items with the
@@ -76,13 +72,23 @@ pub struct CodegenFnAttrs {
     pub patchable_function_entry: Option<PatchableFunctionEntry>,
 }
 
+#[derive(Copy, Clone, Debug, TyEncodable, TyDecodable, HashStable, PartialEq, Eq)]
+pub enum TargetFeatureKind {
+    /// The feature is implied by another feature, rather than explicitly added by the
+    /// `#[target_feature]` attribute
+    Implied,
+    /// The feature is added by the regular `target_feature` attribute.
+    Enabled,
+    /// The feature is added by the unsafe `force_target_feature` attribute.
+    Forced,
+}
+
 #[derive(Copy, Clone, Debug, TyEncodable, TyDecodable, HashStable)]
 pub struct TargetFeature {
     /// The name of the target feature (e.g. "avx")
     pub name: Symbol,
-    /// The feature is implied by another feature, rather than explicitly added by the
-    /// `#[target_feature]` attribute
-    pub implied: bool,
+    /// The way this feature was enabled.
+    pub kind: TargetFeatureKind,
 }
 
 #[derive(Copy, Clone, Debug, TyEncodable, TyDecodable, HashStable)]
@@ -167,8 +173,7 @@ impl CodegenFnAttrs {
             flags: CodegenFnAttrFlags::empty(),
             inline: InlineAttr::None,
             optimize: OptimizeAttr::Default,
-            export_name: None,
-            link_name: None,
+            symbol_name: None,
             link_ordinal: None,
             target_features: vec![],
             safe_target_features: false,
@@ -196,7 +201,7 @@ impl CodegenFnAttrs {
 
         self.flags.contains(CodegenFnAttrFlags::NO_MANGLE)
             || self.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL)
-            || self.export_name.is_some()
+            || self.symbol_name.is_some()
             || match self.linkage {
                 // These are private, so make sure we don't try to consider
                 // them external.
diff --git a/compiler/rustc_middle/src/middle/stability.rs b/compiler/rustc_middle/src/middle/stability.rs
index 4a19cf1563c..18520089e3e 100644
--- a/compiler/rustc_middle/src/middle/stability.rs
+++ b/compiler/rustc_middle/src/middle/stability.rs
@@ -4,7 +4,7 @@
 use std::num::NonZero;
 
 use rustc_ast::NodeId;
-use rustc_errors::{Applicability, Diag, EmissionGuarantee};
+use rustc_errors::{Applicability, Diag, EmissionGuarantee, LintBuffer};
 use rustc_feature::GateIssue;
 use rustc_hir::attrs::{DeprecatedSince, Deprecation};
 use rustc_hir::def_id::{DefId, LocalDefId};
@@ -12,7 +12,7 @@ use rustc_hir::{self as hir, ConstStability, DefaultBodyStability, HirId, Stabil
 use rustc_macros::{Decodable, Encodable, HashStable, Subdiagnostic};
 use rustc_session::Session;
 use rustc_session::lint::builtin::{DEPRECATED, DEPRECATED_IN_FUTURE, SOFT_UNSTABLE};
-use rustc_session::lint::{BuiltinLintDiag, DeprecatedSinceKind, Level, Lint, LintBuffer};
+use rustc_session::lint::{BuiltinLintDiag, DeprecatedSinceKind, Level, Lint};
 use rustc_session::parse::feature_err_issue;
 use rustc_span::{Span, Symbol, sym};
 use tracing::debug;
diff --git a/compiler/rustc_middle/src/mir/interpret/allocation/provenance_map.rs b/compiler/rustc_middle/src/mir/interpret/allocation/provenance_map.rs
index ea8596ea286..dbbd95408c8 100644
--- a/compiler/rustc_middle/src/mir/interpret/allocation/provenance_map.rs
+++ b/compiler/rustc_middle/src/mir/interpret/allocation/provenance_map.rs
@@ -120,6 +120,17 @@ impl<Prov: Provenance> ProvenanceMap<Prov> {
         }
     }
 
+    /// Gets the provenances of all bytes (including from pointers) in a range.
+    pub fn get_range(
+        &self,
+        cx: &impl HasDataLayout,
+        range: AllocRange,
+    ) -> impl Iterator<Item = Prov> {
+        let ptr_provs = self.range_ptrs_get(range, cx).iter().map(|(_, p)| *p);
+        let byte_provs = self.range_bytes_get(range).iter().map(|(_, (p, _))| *p);
+        ptr_provs.chain(byte_provs)
+    }
+
     /// Attempt to merge per-byte provenance back into ptr chunks, if the right fragments
     /// sit next to each other. Return `false` is that is not possible due to partial pointers.
     pub fn merge_bytes(&mut self, cx: &impl HasDataLayout) -> bool {
diff --git a/compiler/rustc_middle/src/mir/mono.rs b/compiler/rustc_middle/src/mir/mono.rs
index 0e6f797b1e4..533066bdef9 100644
--- a/compiler/rustc_middle/src/mir/mono.rs
+++ b/compiler/rustc_middle/src/mir/mono.rs
@@ -548,10 +548,27 @@ impl<'tcx> CodegenUnit<'tcx> {
 
         let mut items: Vec<_> = self.items().iter().map(|(&i, &data)| (i, data)).collect();
         if !tcx.sess.opts.unstable_opts.codegen_source_order {
-            // It's already deterministic, so we can just use it.
-            return items;
+            // In this case, we do not need to keep the items in any specific order, as the input
+            // is already deterministic.
+            //
+            // However, it seems that moving related things (such as different
+            // monomorphizations of the same function) close to one another is actually beneficial
+            // for LLVM performance.
+            // LLVM will codegen the items in the order we pass them to it, and when it handles
+            // similar things in succession, it seems that it leads to better cache utilization,
+            // less branch mispredictions and in general to better performance.
+            // For example, if we have functions `a`, `c::<u32>`, `b`, `c::<i16>`, `d` and
+            // `c::<bool>`, it seems that it helps LLVM's performance to codegen the three `c`
+            // instantiations right after one another, as they will likely reference similar types,
+            // call similar functions, etc.
+            //
+            // See https://github.com/rust-lang/rust/pull/145358 for more details.
+            //
+            // Sorting by symbol name should not incur any new non-determinism.
+            items.sort_by_cached_key(|&(i, _)| i.symbol_name(tcx));
+        } else {
+            items.sort_by_cached_key(|&(i, _)| item_sort_key(tcx, i));
         }
-        items.sort_by_cached_key(|&(i, _)| item_sort_key(tcx, i));
         items
     }
 
diff --git a/compiler/rustc_middle/src/mir/pretty.rs b/compiler/rustc_middle/src/mir/pretty.rs
index f2d5b13cbc8..128ae8549f7 100644
--- a/compiler/rustc_middle/src/mir/pretty.rs
+++ b/compiler/rustc_middle/src/mir/pretty.rs
@@ -929,7 +929,10 @@ impl<'tcx> TerminatorKind<'tcx> {
             }
             Yield { value, resume_arg, .. } => write!(fmt, "{resume_arg:?} = yield({value:?})"),
             Unreachable => write!(fmt, "unreachable"),
-            Drop { place, .. } => write!(fmt, "drop({place:?})"),
+            Drop { place, async_fut: None, .. } => write!(fmt, "drop({place:?})"),
+            Drop { place, async_fut: Some(async_fut), .. } => {
+                write!(fmt, "async drop({place:?}; poll={async_fut:?})")
+            }
             Call { func, args, destination, .. } => {
                 write!(fmt, "{destination:?} = ")?;
                 write!(fmt, "{func:?}(")?;
diff --git a/compiler/rustc_middle/src/mir/statement.rs b/compiler/rustc_middle/src/mir/statement.rs
index 683d7b48617..6e52bc775ef 100644
--- a/compiler/rustc_middle/src/mir/statement.rs
+++ b/compiler/rustc_middle/src/mir/statement.rs
@@ -160,7 +160,11 @@ impl<'tcx> PlaceTy<'tcx> {
     /// Convenience wrapper around `projection_ty_core` for `PlaceElem`,
     /// where we can just use the `Ty` that is already stored inline on
     /// field projection elems.
-    pub fn projection_ty(self, tcx: TyCtxt<'tcx>, elem: PlaceElem<'tcx>) -> PlaceTy<'tcx> {
+    pub fn projection_ty<V: ::std::fmt::Debug>(
+        self,
+        tcx: TyCtxt<'tcx>,
+        elem: ProjectionElem<V, Ty<'tcx>>,
+    ) -> PlaceTy<'tcx> {
         self.projection_ty_core(tcx, &elem, |ty| ty, |_, _, _, ty| ty, |ty| ty)
     }
 
@@ -290,6 +294,36 @@ impl<V, T> ProjectionElem<V, T> {
             Self::UnwrapUnsafeBinder(..) => false,
         }
     }
+
+    /// Returns the `ProjectionKind` associated to this projection.
+    pub fn kind(self) -> ProjectionKind {
+        self.try_map(|_| Some(()), |_| ()).unwrap()
+    }
+
+    /// Apply functions to types and values in this projection and return the result.
+    pub fn try_map<V2, T2>(
+        self,
+        v: impl FnOnce(V) -> Option<V2>,
+        t: impl FnOnce(T) -> T2,
+    ) -> Option<ProjectionElem<V2, T2>> {
+        Some(match self {
+            ProjectionElem::Deref => ProjectionElem::Deref,
+            ProjectionElem::Downcast(name, read_variant) => {
+                ProjectionElem::Downcast(name, read_variant)
+            }
+            ProjectionElem::Field(f, ty) => ProjectionElem::Field(f, t(ty)),
+            ProjectionElem::ConstantIndex { offset, min_length, from_end } => {
+                ProjectionElem::ConstantIndex { offset, min_length, from_end }
+            }
+            ProjectionElem::Subslice { from, to, from_end } => {
+                ProjectionElem::Subslice { from, to, from_end }
+            }
+            ProjectionElem::OpaqueCast(ty) => ProjectionElem::OpaqueCast(t(ty)),
+            ProjectionElem::Subtype(ty) => ProjectionElem::Subtype(t(ty)),
+            ProjectionElem::UnwrapUnsafeBinder(ty) => ProjectionElem::UnwrapUnsafeBinder(t(ty)),
+            ProjectionElem::Index(val) => ProjectionElem::Index(v(val)?),
+        })
+    }
 }
 
 /// Alias for projections as they appear in `UserTypeProjection`, where we
diff --git a/compiler/rustc_middle/src/mir/syntax.rs b/compiler/rustc_middle/src/mir/syntax.rs
index 6039a03aa29..3b8def67f92 100644
--- a/compiler/rustc_middle/src/mir/syntax.rs
+++ b/compiler/rustc_middle/src/mir/syntax.rs
@@ -1371,12 +1371,7 @@ pub enum Rvalue<'tcx> {
 
     /// Creates an array where each element is the value of the operand.
     ///
-    /// This is the cause of a bug in the case where the repetition count is zero because the value
-    /// is not dropped, see [#74836].
-    ///
     /// Corresponds to source code like `[x; 32]`.
-    ///
-    /// [#74836]: https://github.com/rust-lang/rust/issues/74836
     Repeat(Operand<'tcx>, ty::Const<'tcx>),
 
     /// Creates a reference of the indicated kind to the place.
diff --git a/compiler/rustc_middle/src/mir/visit.rs b/compiler/rustc_middle/src/mir/visit.rs
index 42a68b29ec7..904d78d69b6 100644
--- a/compiler/rustc_middle/src/mir/visit.rs
+++ b/compiler/rustc_middle/src/mir/visit.rs
@@ -531,13 +531,20 @@ macro_rules! make_mir_visitor {
                         unwind: _,
                         replace: _,
                         drop: _,
-                        async_fut: _,
+                        async_fut,
                     } => {
                         self.visit_place(
                             place,
                             PlaceContext::MutatingUse(MutatingUseContext::Drop),
                             location
                         );
+                        if let Some(async_fut) = async_fut {
+                            self.visit_local(
+                                $(&$mutability)? *async_fut,
+                                PlaceContext::MutatingUse(MutatingUseContext::Borrow),
+                                location
+                            );
+                        }
                     }
 
                     TerminatorKind::Call {
diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs
index 3bb8353f49e..7bd8a0525a2 100644
--- a/compiler/rustc_middle/src/query/mod.rs
+++ b/compiler/rustc_middle/src/query/mod.rs
@@ -696,6 +696,22 @@ rustc_queries! {
         return_result_from_ensure_ok
     }
 
+    /// Used in case `mir_borrowck` fails to prove an obligation. We generally assume that
+    /// all goals we prove in MIR type check hold as we've already checked them in HIR typeck.
+    ///
+    /// However, we replace each free region in the MIR body with a unique region inference
+    /// variable. As we may rely on structural identity when proving goals this may cause a
+    /// goal to no longer hold. We store obligations for which this may happen during HIR
+    /// typeck in the `TypeckResults`. We then uniquify and reprove them in case MIR typeck
+    /// encounters an unexpected error. We expect this to result in an error when used and
+    /// delay a bug if it does not.
+    query check_potentially_region_dependent_goals(key: LocalDefId) -> Result<(), ErrorGuaranteed> {
+        desc {
+            |tcx| "reproving potentially region dependent HIR typeck goals for `{}",
+            tcx.def_path_str(key)
+        }
+    }
+
     /// MIR after our optimization passes have run. This is MIR that is ready
     /// for codegen. This is also the only query that can fetch non-local MIR, at present.
     query optimized_mir(key: DefId) -> &'tcx mir::Body<'tcx> {
@@ -1116,6 +1132,11 @@ rustc_queries! {
     }
 
     /// Unsafety-check this `LocalDefId`.
+    query check_transmutes(key: LocalDefId) {
+        desc { |tcx| "check transmute calls inside `{}`", tcx.def_path_str(key) }
+    }
+
+    /// Unsafety-check this `LocalDefId`.
     query check_unsafety(key: LocalDefId) {
         desc { |tcx| "unsafety-checking `{}`", tcx.def_path_str(key) }
     }
diff --git a/compiler/rustc_middle/src/query/on_disk_cache.rs b/compiler/rustc_middle/src/query/on_disk_cache.rs
index a7ac3442898..546791135ba 100644
--- a/compiler/rustc_middle/src/query/on_disk_cache.rs
+++ b/compiler/rustc_middle/src/query/on_disk_cache.rs
@@ -645,34 +645,29 @@ impl<'a, 'tcx> SpanDecoder for CacheDecoder<'a, 'tcx> {
         let parent = Option::<LocalDefId>::decode(self);
         let tag: u8 = Decodable::decode(self);
 
-        if tag == TAG_PARTIAL_SPAN {
-            return Span::new(BytePos(0), BytePos(0), ctxt, parent);
-        } else if tag == TAG_RELATIVE_SPAN {
-            let dlo = u32::decode(self);
-            let dto = u32::decode(self);
-
-            let enclosing = self.tcx.source_span_untracked(parent.unwrap()).data_untracked();
-            let span = Span::new(
-                enclosing.lo + BytePos::from_u32(dlo),
-                enclosing.lo + BytePos::from_u32(dto),
-                ctxt,
-                parent,
-            );
-
-            return span;
-        } else {
-            debug_assert_eq!(tag, TAG_FULL_SPAN);
-        }
-
-        let file_lo_index = SourceFileIndex::decode(self);
-        let line_lo = usize::decode(self);
-        let col_lo = RelativeBytePos::decode(self);
-        let len = BytePos::decode(self);
-
-        let file_lo = self.file_index_to_file(file_lo_index);
-        let lo = file_lo.lines()[line_lo - 1] + col_lo;
-        let lo = file_lo.absolute_position(lo);
-        let hi = lo + len;
+        let (lo, hi) = match tag {
+            TAG_PARTIAL_SPAN => (BytePos(0), BytePos(0)),
+            TAG_RELATIVE_SPAN => {
+                let dlo = u32::decode(self);
+                let dto = u32::decode(self);
+
+                let enclosing = self.tcx.source_span_untracked(parent.unwrap()).data_untracked();
+                (enclosing.lo + BytePos::from_u32(dlo), enclosing.lo + BytePos::from_u32(dto))
+            }
+            TAG_FULL_SPAN => {
+                let file_lo_index = SourceFileIndex::decode(self);
+                let line_lo = usize::decode(self);
+                let col_lo = RelativeBytePos::decode(self);
+                let len = BytePos::decode(self);
+
+                let file_lo = self.file_index_to_file(file_lo_index);
+                let lo = file_lo.lines()[line_lo - 1] + col_lo;
+                let lo = file_lo.absolute_position(lo);
+                let hi = lo + len;
+                (lo, hi)
+            }
+            _ => unreachable!(),
+        };
 
         Span::new(lo, hi, ctxt, parent)
     }
diff --git a/compiler/rustc_middle/src/traits/mod.rs b/compiler/rustc_middle/src/traits/mod.rs
index 5bdde3a514e..32f91bfba6b 100644
--- a/compiler/rustc_middle/src/traits/mod.rs
+++ b/compiler/rustc_middle/src/traits/mod.rs
@@ -760,6 +760,9 @@ pub enum DynCompatibilityViolation {
     // Supertrait has a non-lifetime `for<T>` binder.
     SupertraitNonLifetimeBinder(SmallVec<[Span; 1]>),
 
+    // Trait has a `const Trait` supertrait.
+    SupertraitConst(SmallVec<[Span; 1]>),
+
     /// Method has something illegal.
     Method(Symbol, MethodViolationCode, Span),
 
@@ -785,6 +788,9 @@ impl DynCompatibilityViolation {
             DynCompatibilityViolation::SupertraitNonLifetimeBinder(_) => {
                 "where clause cannot reference non-lifetime `for<...>` variables".into()
             }
+            DynCompatibilityViolation::SupertraitConst(_) => {
+                "it cannot have a `const` supertrait".into()
+            }
             DynCompatibilityViolation::Method(name, MethodViolationCode::StaticMethod(_), _) => {
                 format!("associated function `{name}` has no `self` parameter").into()
             }
@@ -842,7 +848,8 @@ impl DynCompatibilityViolation {
         match self {
             DynCompatibilityViolation::SizedSelf(_)
             | DynCompatibilityViolation::SupertraitSelf(_)
-            | DynCompatibilityViolation::SupertraitNonLifetimeBinder(..) => {
+            | DynCompatibilityViolation::SupertraitNonLifetimeBinder(..)
+            | DynCompatibilityViolation::SupertraitConst(_) => {
                 DynCompatibilityViolationSolution::None
             }
             DynCompatibilityViolation::Method(
@@ -873,15 +880,17 @@ impl DynCompatibilityViolation {
         match self {
             DynCompatibilityViolation::SupertraitSelf(spans)
             | DynCompatibilityViolation::SizedSelf(spans)
-            | DynCompatibilityViolation::SupertraitNonLifetimeBinder(spans) => spans.clone(),
+            | DynCompatibilityViolation::SupertraitNonLifetimeBinder(spans)
+            | DynCompatibilityViolation::SupertraitConst(spans) => spans.clone(),
             DynCompatibilityViolation::AssocConst(_, span)
             | DynCompatibilityViolation::GAT(_, span)
-            | DynCompatibilityViolation::Method(_, _, span)
-                if *span != DUMMY_SP =>
-            {
-                smallvec![*span]
+            | DynCompatibilityViolation::Method(_, _, span) => {
+                if *span != DUMMY_SP {
+                    smallvec![*span]
+                } else {
+                    smallvec![]
+                }
             }
-            _ => smallvec![],
         }
     }
 }
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index 49a4733de3b..4990a85466e 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -33,7 +33,7 @@ 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::{CtorKind, CtorOf, DefKind};
 use rustc_hir::def_id::{CrateNum, DefId, LOCAL_CRATE, LocalDefId};
 use rustc_hir::definitions::{DefPathData, Definitions, DisambiguatorState};
 use rustc_hir::intravisit::VisitorExt;
@@ -445,7 +445,10 @@ impl<'tcx> Interner for TyCtxt<'tcx> {
     }
 
     fn fn_is_const(self, def_id: DefId) -> bool {
-        debug_assert_matches!(self.def_kind(def_id), DefKind::Fn | DefKind::AssocFn);
+        debug_assert_matches!(
+            self.def_kind(def_id),
+            DefKind::Fn | DefKind::AssocFn | DefKind::Ctor(CtorOf::Struct, CtorKind::Fn)
+        );
         self.is_conditionally_const(def_id)
     }
 
@@ -1418,6 +1421,8 @@ pub struct TyCtxt<'tcx> {
 }
 
 impl<'tcx> LintEmitter for TyCtxt<'tcx> {
+    type Id = HirId;
+
     fn emit_node_span_lint(
         self,
         lint: &'static Lint,
diff --git a/compiler/rustc_middle/src/ty/diagnostics.rs b/compiler/rustc_middle/src/ty/diagnostics.rs
index b3042904a29..b9a6f67ab0d 100644
--- a/compiler/rustc_middle/src/ty/diagnostics.rs
+++ b/compiler/rustc_middle/src/ty/diagnostics.rs
@@ -23,7 +23,7 @@ impl IntoDiagArg for Ty<'_> {
     fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> rustc_errors::DiagArgValue {
         ty::tls::with(|tcx| {
             let ty = tcx.short_string(self, path);
-            rustc_errors::DiagArgValue::Str(std::borrow::Cow::Owned(ty))
+            DiagArgValue::Str(std::borrow::Cow::Owned(ty))
         })
     }
 }
@@ -32,7 +32,7 @@ impl IntoDiagArg for Instance<'_> {
     fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> rustc_errors::DiagArgValue {
         ty::tls::with(|tcx| {
             let instance = tcx.short_string_namespace(self, path, Namespace::ValueNS);
-            rustc_errors::DiagArgValue::Str(std::borrow::Cow::Owned(instance))
+            DiagArgValue::Str(std::borrow::Cow::Owned(instance))
         })
     }
 }
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index e70c98ab704..e567ba05f61 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -32,7 +32,7 @@ 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_errors::{Diag, ErrorGuaranteed, LintBuffer};
 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};
@@ -46,7 +46,6 @@ use rustc_macros::{
 };
 use rustc_query_system::ich::StableHashingContext;
 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, sym};
@@ -830,14 +829,15 @@ impl<'tcx> OpaqueHiddenType<'tcx> {
         // Convert the type from the function into a type valid outside by mapping generic
         // parameters to into the context of the opaque.
         //
-        // We erase regions when doing this during HIR typeck.
+        // We erase regions when doing this during HIR typeck. We manually use `fold_regions`
+        // here as we do not want to anonymize bound variables.
         let this = match defining_scope_kind {
-            DefiningScopeKind::HirTypeck => tcx.erase_regions(self),
+            DefiningScopeKind::HirTypeck => fold_regions(tcx, self, |_, _| tcx.lifetimes.re_erased),
             DefiningScopeKind::MirBorrowck => self,
         };
         let result = this.fold_with(&mut opaque_types::ReverseMapper::new(tcx, map, self.span));
         if cfg!(debug_assertions) && matches!(defining_scope_kind, DefiningScopeKind::HirTypeck) {
-            assert_eq!(result.ty, tcx.erase_regions(result.ty));
+            assert_eq!(result.ty, fold_regions(tcx, result.ty, |_, _| tcx.lifetimes.re_erased));
         }
         result
     }
diff --git a/compiler/rustc_middle/src/ty/print/mod.rs b/compiler/rustc_middle/src/ty/print/mod.rs
index e6feafea122..9e6f277ef77 100644
--- a/compiler/rustc_middle/src/ty/print/mod.rs
+++ b/compiler/rustc_middle/src/ty/print/mod.rs
@@ -124,6 +124,15 @@ pub trait Printer<'tcx>: Sized {
         trait_ref: Option<ty::TraitRef<'tcx>>,
     ) -> Result<(), PrintError>;
 
+    fn print_coroutine_with_kind(
+        &mut self,
+        def_id: DefId,
+        parent_args: &'tcx [GenericArg<'tcx>],
+        kind: Ty<'tcx>,
+    ) -> Result<(), PrintError> {
+        self.print_path_with_generic_args(|p| p.print_def_path(def_id, parent_args), &[kind.into()])
+    }
+
     // Defaults (should not be overridden):
 
     #[instrument(skip(self), level = "debug")]
@@ -162,9 +171,10 @@ pub trait Printer<'tcx>: Sized {
                             )) = self.tcx().coroutine_kind(def_id)
                                 && args.len() > parent_args.len()
                             {
-                                return self.print_path_with_generic_args(
-                                    |p| p.print_def_path(def_id, parent_args),
-                                    &args[..parent_args.len() + 1][..1],
+                                return self.print_coroutine_with_kind(
+                                    def_id,
+                                    parent_args,
+                                    args[parent_args.len()].expect_ty(),
                                 );
                             } else {
                                 // Closures' own generics are only captures, don't print them.
diff --git a/compiler/rustc_middle/src/ty/sty.rs b/compiler/rustc_middle/src/ty/sty.rs
index 72474a60566..755fc68d86f 100644
--- a/compiler/rustc_middle/src/ty/sty.rs
+++ b/compiler/rustc_middle/src/ty/sty.rs
@@ -821,10 +821,38 @@ impl<'tcx> Ty<'tcx> {
     #[inline]
     pub fn new_coroutine_witness(
         tcx: TyCtxt<'tcx>,
-        id: DefId,
+        def_id: DefId,
         args: GenericArgsRef<'tcx>,
     ) -> Ty<'tcx> {
-        Ty::new(tcx, CoroutineWitness(id, args))
+        if cfg!(debug_assertions) {
+            tcx.debug_assert_args_compatible(tcx.typeck_root_def_id(def_id), args);
+        }
+        Ty::new(tcx, CoroutineWitness(def_id, args))
+    }
+
+    pub fn new_coroutine_witness_for_coroutine(
+        tcx: TyCtxt<'tcx>,
+        def_id: DefId,
+        coroutine_args: GenericArgsRef<'tcx>,
+    ) -> Ty<'tcx> {
+        tcx.debug_assert_args_compatible(def_id, coroutine_args);
+        // HACK: Coroutine witness types are lifetime erased, so they
+        // never reference any lifetime args from the coroutine. We erase
+        // the regions here since we may get into situations where a
+        // coroutine is recursively contained within itself, leading to
+        // witness types that differ by region args. This means that
+        // cycle detection in fulfillment will not kick in, which leads
+        // to unnecessary overflows in async code. See the issue:
+        // <https://github.com/rust-lang/rust/issues/145151>.
+        let args =
+            ty::GenericArgs::for_item(tcx, tcx.typeck_root_def_id(def_id), |def, _| {
+                match def.kind {
+                    ty::GenericParamDefKind::Lifetime => tcx.lifetimes.re_erased.into(),
+                    ty::GenericParamDefKind::Type { .. }
+                    | ty::GenericParamDefKind::Const { .. } => coroutine_args[def.index as usize],
+                }
+            });
+        Ty::new_coroutine_witness(tcx, def_id, args)
     }
 
     // misc
@@ -985,6 +1013,14 @@ impl<'tcx> rustc_type_ir::inherent::Ty<TyCtxt<'tcx>> for Ty<'tcx> {
         Ty::new_coroutine_witness(interner, def_id, args)
     }
 
+    fn new_coroutine_witness_for_coroutine(
+        interner: TyCtxt<'tcx>,
+        def_id: DefId,
+        coroutine_args: ty::GenericArgsRef<'tcx>,
+    ) -> Self {
+        Ty::new_coroutine_witness_for_coroutine(interner, def_id, coroutine_args)
+    }
+
     fn new_ptr(interner: TyCtxt<'tcx>, ty: Self, mutbl: hir::Mutability) -> Self {
         Ty::new_ptr(interner, ty, mutbl)
     }
diff --git a/compiler/rustc_middle/src/ty/typeck_results.rs b/compiler/rustc_middle/src/ty/typeck_results.rs
index 6b187c5325a..8dd80aab946 100644
--- a/compiler/rustc_middle/src/ty/typeck_results.rs
+++ b/compiler/rustc_middle/src/ty/typeck_results.rs
@@ -206,10 +206,25 @@ pub struct TypeckResults<'tcx> {
     /// formatting modified file tests/ui/coroutine/retain-resume-ref.rs
     pub coroutine_stalled_predicates: FxIndexSet<(ty::Predicate<'tcx>, ObligationCause<'tcx>)>,
 
+    /// Goals proven during HIR typeck which may be potentially region dependent.
+    ///
+    /// Borrowck *uniquifies* regions which may cause these goal to be ambiguous in MIR
+    /// type check. We ICE if goals fail in borrowck to detect bugs during MIR building or
+    /// missed checks in HIR typeck. To avoid ICE due to region dependence we store all
+    /// goals which may be region dependent and reprove them in case borrowck encounters
+    /// an error.
+    pub potentially_region_dependent_goals:
+        FxIndexSet<(ty::Predicate<'tcx>, ObligationCause<'tcx>)>,
+
     /// Contains the data for evaluating the effect of feature `capture_disjoint_fields`
     /// on closure size.
     pub closure_size_eval: LocalDefIdMap<ClosureSizeProfileData<'tcx>>,
 
+    /// Stores the types involved in calls to `transmute` intrinsic. These are meant to be checked
+    /// outside of typeck and borrowck to avoid cycles with opaque types and coroutine layout
+    /// computation.
+    pub transmutes_to_check: Vec<(Ty<'tcx>, Ty<'tcx>, HirId)>,
+
     /// Container types and field indices of `offset_of!` expressions
     offset_of_data: ItemLocalMap<(Ty<'tcx>, Vec<(VariantIdx, FieldIdx)>)>,
 }
@@ -240,7 +255,9 @@ impl<'tcx> TypeckResults<'tcx> {
             closure_fake_reads: Default::default(),
             rvalue_scopes: Default::default(),
             coroutine_stalled_predicates: Default::default(),
+            potentially_region_dependent_goals: Default::default(),
             closure_size_eval: Default::default(),
+            transmutes_to_check: Default::default(),
             offset_of_data: Default::default(),
         }
     }
diff --git a/compiler/rustc_mir_build/src/builder/coverageinfo.rs b/compiler/rustc_mir_build/src/builder/coverageinfo.rs
index 14199c20921..091b9dad5bc 100644
--- a/compiler/rustc_mir_build/src/builder/coverageinfo.rs
+++ b/compiler/rustc_mir_build/src/builder/coverageinfo.rs
@@ -157,6 +157,21 @@ impl CoverageInfoBuilder {
         // if there's nothing interesting in it.
         Box::new(CoverageInfoHi { num_block_markers, branch_spans })
     }
+
+    pub(crate) fn as_done(&self) -> Box<CoverageInfoHi> {
+        let &Self { nots: _, markers: BlockMarkerGen { num_block_markers }, ref branch_info } =
+            self;
+
+        let branch_spans = branch_info
+            .as_ref()
+            .map(|branch_info| branch_info.branch_spans.as_slice())
+            .unwrap_or_default()
+            .to_owned();
+
+        // For simplicity, always return an info struct (without Option), even
+        // if there's nothing interesting in it.
+        Box::new(CoverageInfoHi { num_block_markers, branch_spans })
+    }
 }
 
 impl<'tcx> Builder<'_, 'tcx> {
diff --git a/compiler/rustc_mir_build/src/builder/mod.rs b/compiler/rustc_mir_build/src/builder/mod.rs
index 9570760f943..6a8f0b21ee0 100644
--- a/compiler/rustc_mir_build/src/builder/mod.rs
+++ b/compiler/rustc_mir_build/src/builder/mod.rs
@@ -790,6 +790,28 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         builder
     }
 
+    #[allow(dead_code)]
+    fn dump_for_debugging(&self) {
+        let mut body = Body::new(
+            MirSource::item(self.def_id.to_def_id()),
+            self.cfg.basic_blocks.clone(),
+            self.source_scopes.clone(),
+            self.local_decls.clone(),
+            self.canonical_user_type_annotations.clone(),
+            self.arg_count.clone(),
+            self.var_debug_info.clone(),
+            self.fn_span.clone(),
+            self.coroutine.clone(),
+            None,
+        );
+        body.coverage_info_hi = self.coverage_info.as_ref().map(|b| b.as_done());
+
+        use rustc_middle::mir::pretty;
+        let options = pretty::PrettyPrintMirOptions::from_cli(self.tcx);
+        pretty::write_mir_fn(self.tcx, &body, &mut |_, _| Ok(()), &mut std::io::stdout(), options)
+            .unwrap();
+    }
+
     fn finish(self) -> Body<'tcx> {
         let mut body = Body::new(
             MirSource::item(self.def_id.to_def_id()),
diff --git a/compiler/rustc_mir_build/src/check_tail_calls.rs b/compiler/rustc_mir_build/src/check_tail_calls.rs
index d4b6da2c14b..e0cbe8519ed 100644
--- a/compiler/rustc_mir_build/src/check_tail_calls.rs
+++ b/compiler/rustc_mir_build/src/check_tail_calls.rs
@@ -135,30 +135,23 @@ impl<'tcx> TailCallCkVisitor<'_, 'tcx> {
             self.report_abi_mismatch(expr.span, caller_sig.abi, callee_sig.abi);
         }
 
+        // FIXME(explicit_tail_calls): this currently fails for cases where opaques are used.
+        // e.g.
+        // ```
+        // fn a() -> impl Sized { become b() } // ICE
+        // fn b() -> u8 { 0 }
+        // ```
+        // we should think what is the expected behavior here.
+        // (we should probably just accept this by revealing opaques?)
         if caller_sig.inputs_and_output != callee_sig.inputs_and_output {
-            if caller_sig.inputs() != callee_sig.inputs() {
-                self.report_arguments_mismatch(
-                    expr.span,
-                    self.tcx.liberate_late_bound_regions(
-                        CRATE_DEF_ID.to_def_id(),
-                        self.caller_ty.fn_sig(self.tcx),
-                    ),
-                    self.tcx
-                        .liberate_late_bound_regions(CRATE_DEF_ID.to_def_id(), ty.fn_sig(self.tcx)),
-                );
-            }
-
-            // FIXME(explicit_tail_calls): this currently fails for cases where opaques are used.
-            // e.g.
-            // ```
-            // fn a() -> impl Sized { become b() } // ICE
-            // fn b() -> u8 { 0 }
-            // ```
-            // we should think what is the expected behavior here.
-            // (we should probably just accept this by revealing opaques?)
-            if caller_sig.output() != callee_sig.output() {
-                span_bug!(expr.span, "hir typeck should have checked the return type already");
-            }
+            self.report_signature_mismatch(
+                expr.span,
+                self.tcx.liberate_late_bound_regions(
+                    CRATE_DEF_ID.to_def_id(),
+                    self.caller_ty.fn_sig(self.tcx),
+                ),
+                self.tcx.liberate_late_bound_regions(CRATE_DEF_ID.to_def_id(), ty.fn_sig(self.tcx)),
+            );
         }
 
         {
@@ -365,7 +358,7 @@ impl<'tcx> TailCallCkVisitor<'_, 'tcx> {
         self.found_errors = Err(err);
     }
 
-    fn report_arguments_mismatch(
+    fn report_signature_mismatch(
         &mut self,
         sp: Span,
         caller_sig: ty::FnSig<'_>,
diff --git a/compiler/rustc_mir_build/src/check_unsafety.rs b/compiler/rustc_mir_build/src/check_unsafety.rs
index cdab785e842..b5e165c7517 100644
--- a/compiler/rustc_mir_build/src/check_unsafety.rs
+++ b/compiler/rustc_mir_build/src/check_unsafety.rs
@@ -8,7 +8,7 @@ use rustc_errors::DiagArgValue;
 use rustc_hir::attrs::AttributeKind;
 use rustc_hir::def::DefKind;
 use rustc_hir::{self as hir, BindingMode, ByRef, HirId, Mutability, find_attr};
-use rustc_middle::middle::codegen_fn_attrs::TargetFeature;
+use rustc_middle::middle::codegen_fn_attrs::{TargetFeature, TargetFeatureKind};
 use rustc_middle::mir::BorrowKind;
 use rustc_middle::span_bug;
 use rustc_middle::thir::visit::Visitor;
@@ -522,7 +522,7 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for UnsafetyVisitor<'a, 'tcx> {
                             .iter()
                             .copied()
                             .filter(|feature| {
-                                !feature.implied
+                                feature.kind == TargetFeatureKind::Enabled
                                     && !self
                                         .body_target_features
                                         .iter()
diff --git a/compiler/rustc_mir_dataflow/Cargo.toml b/compiler/rustc_mir_dataflow/Cargo.toml
index 293bcbef21b..9621f9f20bd 100644
--- a/compiler/rustc_mir_dataflow/Cargo.toml
+++ b/compiler/rustc_mir_dataflow/Cargo.toml
@@ -13,7 +13,6 @@ rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
 rustc_fluent_macro = { path = "../rustc_fluent_macro" }
 rustc_graphviz = { path = "../rustc_graphviz" }
-rustc_hir = { path = "../rustc_hir" }
 rustc_index = { path = "../rustc_index" }
 rustc_macros = { path = "../rustc_macros" }
 rustc_middle = { path = "../rustc_middle" }
diff --git a/compiler/rustc_mir_dataflow/src/framework/graphviz.rs b/compiler/rustc_mir_dataflow/src/framework/graphviz.rs
index f86a15a8f92..372a3f3a8b8 100644
--- a/compiler/rustc_mir_dataflow/src/framework/graphviz.rs
+++ b/compiler/rustc_mir_dataflow/src/framework/graphviz.rs
@@ -8,7 +8,6 @@ use std::sync::OnceLock;
 use std::{io, ops, str};
 
 use regex::Regex;
-use rustc_hir::def_id::DefId;
 use rustc_index::bit_set::DenseBitSet;
 use rustc_middle::mir::{
     self, BasicBlock, Body, Location, create_dump_file, dump_enabled, graphviz_safe_def_name,
@@ -16,6 +15,7 @@ use rustc_middle::mir::{
 };
 use rustc_middle::ty::TyCtxt;
 use rustc_middle::ty::print::with_no_trimmed_paths;
+use rustc_span::def_id::DefId;
 use rustc_span::{Symbol, sym};
 use tracing::debug;
 use {rustc_ast as ast, rustc_graphviz as dot};
diff --git a/compiler/rustc_mir_dataflow/src/move_paths/abs_domain.rs b/compiler/rustc_mir_dataflow/src/move_paths/abs_domain.rs
deleted file mode 100644
index d056ad3d4b4..00000000000
--- a/compiler/rustc_mir_dataflow/src/move_paths/abs_domain.rs
+++ /dev/null
@@ -1,38 +0,0 @@
-//! The move-analysis portion of borrowck needs to work in an abstract
-//! domain of lifted `Place`s. Most of the `Place` variants fall into a
-//! one-to-one mapping between the concrete and abstract (e.g., a
-//! field-deref on a local variable, `x.field`, has the same meaning
-//! in both domains). Indexed projections are the exception: `a[x]`
-//! needs to be treated as mapping to the same move path as `a[y]` as
-//! well as `a[13]`, etc. So we map these `x`/`y` values to `()`.
-//!
-//! (In theory, the analysis could be extended to work with sets of
-//! paths, so that `a[0]` and `a[13]` could be kept distinct, while
-//! `a[x]` would still overlap them both. But that is not this
-//! representation does today.)
-
-use rustc_middle::mir::{PlaceElem, ProjectionElem, ProjectionKind};
-
-pub(crate) trait Lift {
-    fn lift(&self) -> ProjectionKind;
-}
-
-impl<'tcx> Lift for PlaceElem<'tcx> {
-    fn lift(&self) -> ProjectionKind {
-        match *self {
-            ProjectionElem::Deref => ProjectionElem::Deref,
-            ProjectionElem::Field(f, _ty) => ProjectionElem::Field(f, ()),
-            ProjectionElem::OpaqueCast(_ty) => ProjectionElem::OpaqueCast(()),
-            ProjectionElem::Index(_i) => ProjectionElem::Index(()),
-            ProjectionElem::Subslice { from, to, from_end } => {
-                ProjectionElem::Subslice { from, to, from_end }
-            }
-            ProjectionElem::ConstantIndex { offset, min_length, from_end } => {
-                ProjectionElem::ConstantIndex { offset, min_length, from_end }
-            }
-            ProjectionElem::Downcast(a, u) => ProjectionElem::Downcast(a, u),
-            ProjectionElem::Subtype(_ty) => ProjectionElem::Subtype(()),
-            ProjectionElem::UnwrapUnsafeBinder(_ty) => ProjectionElem::UnwrapUnsafeBinder(()),
-        }
-    }
-}
diff --git a/compiler/rustc_mir_dataflow/src/move_paths/builder.rs b/compiler/rustc_mir_dataflow/src/move_paths/builder.rs
index 8bbc89fdcec..48718cad597 100644
--- a/compiler/rustc_mir_dataflow/src/move_paths/builder.rs
+++ b/compiler/rustc_mir_dataflow/src/move_paths/builder.rs
@@ -7,7 +7,6 @@ use rustc_middle::{bug, span_bug};
 use smallvec::{SmallVec, smallvec};
 use tracing::debug;
 
-use super::abs_domain::Lift;
 use super::{
     Init, InitIndex, InitKind, InitLocation, LocationMap, LookupResult, MoveData, MoveOut,
     MoveOutIndex, MovePath, MovePathIndex, MovePathLookup,
@@ -241,7 +240,7 @@ impl<'a, 'tcx, F: Fn(Ty<'tcx>) -> bool> MoveDataBuilder<'a, 'tcx, F> {
             if union_path.is_none() {
                 // inlined from add_move_path because of a borrowck conflict with the iterator
                 base =
-                    *data.rev_lookup.projections.entry((base, elem.lift())).or_insert_with(|| {
+                    *data.rev_lookup.projections.entry((base, elem.kind())).or_insert_with(|| {
                         new_move_path(
                             &mut data.move_paths,
                             &mut data.path_map,
@@ -272,7 +271,7 @@ impl<'a, 'tcx, F: Fn(Ty<'tcx>) -> bool> MoveDataBuilder<'a, 'tcx, F> {
             tcx,
             ..
         } = self;
-        *rev_lookup.projections.entry((base, elem.lift())).or_insert_with(move || {
+        *rev_lookup.projections.entry((base, elem.kind())).or_insert_with(move || {
             new_move_path(move_paths, path_map, init_path_map, Some(base), mk_place(*tcx))
         })
     }
diff --git a/compiler/rustc_mir_dataflow/src/move_paths/mod.rs b/compiler/rustc_mir_dataflow/src/move_paths/mod.rs
index 18985ba0da2..466416d63f5 100644
--- a/compiler/rustc_mir_dataflow/src/move_paths/mod.rs
+++ b/compiler/rustc_mir_dataflow/src/move_paths/mod.rs
@@ -1,3 +1,15 @@
+//! The move-analysis portion of borrowck needs to work in an abstract domain of lifted `Place`s.
+//! Most of the `Place` variants fall into a one-to-one mapping between the concrete and abstract
+//! (e.g., a field projection on a local variable, `x.field`, has the same meaning in both
+//! domains). In other words, all field projections for the same field on the same local do not
+//! have meaningfully different types if ever. Indexed projections are the exception: `a[x]` needs
+//! to be treated as mapping to the same move path as `a[y]` as well as `a[13]`, etc. So we map
+//! these `x`/`y` values to `()`.
+//!
+//! (In theory, the analysis could be extended to work with sets of paths, so that `a[0]` and
+//! `a[13]` could be kept distinct, while `a[x]` would still overlap them both. But that is not
+//! what this representation does today.)
+
 use std::fmt;
 use std::ops::{Index, IndexMut};
 
@@ -8,11 +20,8 @@ use rustc_middle::ty::{Ty, TyCtxt};
 use rustc_span::Span;
 use smallvec::SmallVec;
 
-use self::abs_domain::Lift;
 use crate::un_derefer::UnDerefer;
 
-mod abs_domain;
-
 rustc_index::newtype_index! {
     #[orderable]
     #[debug_format = "mp{}"]
@@ -324,7 +333,7 @@ impl<'tcx> MovePathLookup<'tcx> {
         };
 
         for (_, elem) in self.un_derefer.iter_projections(place) {
-            if let Some(&subpath) = self.projections.get(&(result, elem.lift())) {
+            if let Some(&subpath) = self.projections.get(&(result, elem.kind())) {
                 result = subpath;
             } else {
                 return LookupResult::Parent(Some(result));
diff --git a/compiler/rustc_mir_dataflow/src/rustc_peek.rs b/compiler/rustc_mir_dataflow/src/rustc_peek.rs
index 1682f332857..a899ec1fa88 100644
--- a/compiler/rustc_mir_dataflow/src/rustc_peek.rs
+++ b/compiler/rustc_mir_dataflow/src/rustc_peek.rs
@@ -1,7 +1,7 @@
 use rustc_ast::MetaItem;
-use rustc_hir::def_id::DefId;
 use rustc_middle::mir::{self, Body, Local, Location};
 use rustc_middle::ty::{self, Ty, TyCtxt};
+use rustc_span::def_id::DefId;
 use rustc_span::{Span, Symbol, sym};
 use tracing::{debug, info};
 
diff --git a/compiler/rustc_mir_transform/src/check_enums.rs b/compiler/rustc_mir_transform/src/check_enums.rs
index 33a87cb9873..12447dc7cbb 100644
--- a/compiler/rustc_mir_transform/src/check_enums.rs
+++ b/compiler/rustc_mir_transform/src/check_enums.rs
@@ -48,6 +48,21 @@ impl<'tcx> crate::MirPass<'tcx> for CheckEnums {
                     let new_block = split_block(basic_blocks, location);
 
                     match check {
+                        EnumCheckType::Direct { op_size, .. }
+                        | EnumCheckType::WithNiche { op_size, .. }
+                            if op_size.bytes() == 0 =>
+                        {
+                            // It is never valid to use a ZST as a discriminant for an inhabited enum, but that will
+                            // have been caught by the type checker. Do nothing but ensure that a bug has been signaled.
+                            tcx.dcx().span_delayed_bug(
+                                source_info.span,
+                                "cannot build enum discriminant from zero-sized type",
+                            );
+                            basic_blocks[block].terminator = Some(Terminator {
+                                source_info,
+                                kind: TerminatorKind::Goto { target: new_block },
+                            });
+                        }
                         EnumCheckType::Direct { source_op, discr, op_size, valid_discrs } => {
                             insert_direct_enum_check(
                                 tcx,
diff --git a/compiler/rustc_mir_transform/src/coverage/counters.rs b/compiler/rustc_mir_transform/src/coverage/counters.rs
index 5568d42ab8f..879a20e771d 100644
--- a/compiler/rustc_mir_transform/src/coverage/counters.rs
+++ b/compiler/rustc_mir_transform/src/coverage/counters.rs
@@ -16,7 +16,6 @@ use crate::coverage::graph::{BasicCoverageBlock, CoverageGraph};
 
 mod balanced_flow;
 pub(crate) mod node_flow;
-mod union_find;
 
 /// Struct containing the results of [`prepare_bcb_counters_data`].
 pub(crate) struct BcbCountersData {
diff --git a/compiler/rustc_mir_transform/src/coverage/counters/node_flow.rs b/compiler/rustc_mir_transform/src/coverage/counters/node_flow.rs
index 91ed54b8b59..e063f75887b 100644
--- a/compiler/rustc_mir_transform/src/coverage/counters/node_flow.rs
+++ b/compiler/rustc_mir_transform/src/coverage/counters/node_flow.rs
@@ -7,13 +7,12 @@
 //! (Knuth & Stevenson, 1973).
 
 use rustc_data_structures::graph;
+use rustc_data_structures::union_find::UnionFind;
 use rustc_index::bit_set::DenseBitSet;
 use rustc_index::{Idx, IndexSlice, IndexVec};
 pub(crate) use rustc_middle::mir::coverage::NodeFlowData;
 use rustc_middle::mir::coverage::Op;
 
-use crate::coverage::counters::union_find::UnionFind;
-
 #[cfg(test)]
 mod tests;
 
diff --git a/compiler/rustc_mir_transform/src/gvn.rs b/compiler/rustc_mir_transform/src/gvn.rs
index 952da2cdf72..5a13394543b 100644
--- a/compiler/rustc_mir_transform/src/gvn.rs
+++ b/compiler/rustc_mir_transform/src/gvn.rs
@@ -447,26 +447,9 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
 
             Projection(base, elem) => {
                 let base = self.evaluated[base].as_ref()?;
-                let elem = match elem {
-                    ProjectionElem::Deref => ProjectionElem::Deref,
-                    ProjectionElem::Downcast(name, read_variant) => {
-                        ProjectionElem::Downcast(name, read_variant)
-                    }
-                    ProjectionElem::Field(f, ()) => ProjectionElem::Field(f, ty.ty),
-                    ProjectionElem::ConstantIndex { offset, min_length, from_end } => {
-                        ProjectionElem::ConstantIndex { offset, min_length, from_end }
-                    }
-                    ProjectionElem::Subslice { from, to, from_end } => {
-                        ProjectionElem::Subslice { from, to, from_end }
-                    }
-                    ProjectionElem::OpaqueCast(()) => ProjectionElem::OpaqueCast(ty.ty),
-                    ProjectionElem::Subtype(()) => ProjectionElem::Subtype(ty.ty),
-                    ProjectionElem::UnwrapUnsafeBinder(()) => {
-                        ProjectionElem::UnwrapUnsafeBinder(ty.ty)
-                    }
-                    // This should have been replaced by a `ConstantIndex` earlier.
-                    ProjectionElem::Index(_) => return None,
-                };
+                // `Index` by constants should have been replaced by `ConstantIndex` by
+                // `simplify_place_projection`.
+                let elem = elem.try_map(|_| None, |()| ty.ty)?;
                 self.ecx.project(base, elem).discard_err()?
             }
             Address { place, kind: _, provenance: _ } => {
@@ -476,13 +459,11 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
                 let local = self.locals[place.local]?;
                 let pointer = self.evaluated[local].as_ref()?;
                 let mut mplace = self.ecx.deref_pointer(pointer).discard_err()?;
-                for proj in place.projection.iter().skip(1) {
-                    // We have no call stack to associate a local with a value, so we cannot
-                    // interpret indexing.
-                    if matches!(proj, ProjectionElem::Index(_)) {
-                        return None;
-                    }
-                    mplace = self.ecx.project(&mplace, proj).discard_err()?;
+                for elem in place.projection.iter().skip(1) {
+                    // `Index` by constants should have been replaced by `ConstantIndex` by
+                    // `simplify_place_projection`.
+                    let elem = elem.try_map(|_| None, |ty| ty)?;
+                    mplace = self.ecx.project(&mplace, elem).discard_err()?;
                 }
                 let pointer = mplace.to_ref(&self.ecx);
                 ImmTy::from_immediate(pointer, ty).into()
@@ -902,27 +883,14 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
         proj: ProjectionElem<VnIndex, ()>,
         loc: Location,
     ) -> Option<PlaceElem<'tcx>> {
-        Some(match proj {
-            ProjectionElem::Deref => ProjectionElem::Deref,
-            ProjectionElem::Field(idx, ()) => ProjectionElem::Field(idx, ty),
-            ProjectionElem::Index(idx) => {
-                let Some(local) = self.try_as_local(idx, loc) else {
-                    return None;
-                };
+        proj.try_map(
+            |value| {
+                let local = self.try_as_local(value, loc)?;
                 self.reused_locals.insert(local);
-                ProjectionElem::Index(local)
-            }
-            ProjectionElem::ConstantIndex { offset, min_length, from_end } => {
-                ProjectionElem::ConstantIndex { offset, min_length, from_end }
-            }
-            ProjectionElem::Subslice { from, to, from_end } => {
-                ProjectionElem::Subslice { from, to, from_end }
-            }
-            ProjectionElem::Downcast(symbol, idx) => ProjectionElem::Downcast(symbol, idx),
-            ProjectionElem::OpaqueCast(()) => ProjectionElem::OpaqueCast(ty),
-            ProjectionElem::Subtype(()) => ProjectionElem::Subtype(ty),
-            ProjectionElem::UnwrapUnsafeBinder(()) => ProjectionElem::UnwrapUnsafeBinder(ty),
-        })
+                Some(local)
+            },
+            |()| ty,
+        )
     }
 
     fn simplify_aggregate_to_copy(
diff --git a/compiler/rustc_mir_transform/src/ref_prop.rs b/compiler/rustc_mir_transform/src/ref_prop.rs
index d1c2d6b508f..6f61215cee2 100644
--- a/compiler/rustc_mir_transform/src/ref_prop.rs
+++ b/compiler/rustc_mir_transform/src/ref_prop.rs
@@ -79,6 +79,7 @@ impl<'tcx> crate::MirPass<'tcx> for ReferencePropagation {
     #[instrument(level = "trace", skip(self, tcx, body))]
     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
         debug!(def_id = ?body.source.def_id());
+        move_to_copy_pointers(tcx, body);
         while propagate_ssa(tcx, body) {}
     }
 
@@ -87,11 +88,43 @@ impl<'tcx> crate::MirPass<'tcx> for ReferencePropagation {
     }
 }
 
+/// The SSA analysis done by [`SsaLocals`] treats [`Operand::Move`] as a read, even though in
+/// general [`Operand::Move`] represents pass-by-pointer where the callee can overwrite the
+/// pointee (Miri always considers the place deinitialized). CopyProp has a similar trick to
+/// turn [`Operand::Move`] into [`Operand::Copy`] when required for an optimization, but in this
+/// pass we just turn all moves of pointers into copies because pointers should be by-value anyway.
+fn move_to_copy_pointers<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
+    let mut visitor = MoveToCopyVisitor { tcx, local_decls: &body.local_decls };
+    for (bb, data) in body.basic_blocks.as_mut_preserves_cfg().iter_enumerated_mut() {
+        visitor.visit_basic_block_data(bb, data);
+    }
+
+    struct MoveToCopyVisitor<'a, 'tcx> {
+        tcx: TyCtxt<'tcx>,
+        local_decls: &'a IndexVec<Local, LocalDecl<'tcx>>,
+    }
+
+    impl<'a, 'tcx> MutVisitor<'tcx> for MoveToCopyVisitor<'a, 'tcx> {
+        fn tcx(&self) -> TyCtxt<'tcx> {
+            self.tcx
+        }
+
+        fn visit_operand(&mut self, operand: &mut Operand<'tcx>, loc: Location) {
+            if let Operand::Move(place) = *operand {
+                if place.ty(self.local_decls, self.tcx).ty.is_any_ptr() {
+                    *operand = Operand::Copy(place);
+                }
+            }
+            self.super_operand(operand, loc);
+        }
+    }
+}
+
 fn propagate_ssa<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) -> bool {
     let typing_env = body.typing_env(tcx);
     let ssa = SsaLocals::new(tcx, body, typing_env);
 
-    let mut replacer = compute_replacement(tcx, body, &ssa);
+    let mut replacer = compute_replacement(tcx, body, ssa);
     debug!(?replacer.targets);
     debug!(?replacer.allowed_replacements);
     debug!(?replacer.storage_to_remove);
@@ -119,7 +152,7 @@ enum Value<'tcx> {
 fn compute_replacement<'tcx>(
     tcx: TyCtxt<'tcx>,
     body: &Body<'tcx>,
-    ssa: &SsaLocals,
+    ssa: SsaLocals,
 ) -> Replacer<'tcx> {
     let always_live_locals = always_storage_live_locals(body);
 
@@ -138,7 +171,7 @@ fn compute_replacement<'tcx>(
     // reborrowed references.
     let mut storage_to_remove = DenseBitSet::new_empty(body.local_decls.len());
 
-    let fully_replaceable_locals = fully_replaceable_locals(ssa);
+    let fully_replaceable_locals = fully_replaceable_locals(&ssa);
 
     // Returns true iff we can use `place` as a pointee.
     //
diff --git a/compiler/rustc_next_trait_solver/src/canonicalizer.rs b/compiler/rustc_next_trait_solver/src/canonicalizer.rs
index 1bc35e599c7..da05c49756f 100644
--- a/compiler/rustc_next_trait_solver/src/canonicalizer.rs
+++ b/compiler/rustc_next_trait_solver/src/canonicalizer.rs
@@ -25,12 +25,8 @@ enum CanonicalizeInputKind {
     /// 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 },
+    /// When canonicalizing predicates, we don't keep `'static`.
+    Predicate,
 }
 
 /// Whether we're canonicalizing a query input or the query response.
@@ -191,7 +187,6 @@ 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`
@@ -201,9 +196,7 @@ 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(CanonicalizeInputKind::Predicate {
-                is_hir_typeck_root_goal,
-            }),
+            canonicalize_mode: CanonicalizeMode::Input(CanonicalizeInputKind::Predicate),
 
             variables,
             variable_lookup_table,
@@ -481,31 +474,13 @@ impl<D: SolverDelegate<Interner = I>, I: Interner> TypeFolder<I> for Canonicaliz
             }
         };
 
-        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)
-        };
+        let var = 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 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)) {
+        if let Some(&ty) = self.cache.get(&(self.binder_index, t)) {
             ty
         } else {
             let res = self.inner_fold_ty(t);
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 faa86734d08..d25e74e7335 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
@@ -75,17 +75,10 @@ where
             Ok(ty::Binder::dummy(vec![args.as_coroutine_closure().tupled_upvars_ty()]))
         }
 
-        ty::Coroutine(def_id, args) => {
-            let coroutine_args = args.as_coroutine();
-            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::Coroutine(def_id, args) => Ok(ty::Binder::dummy(vec![
+            args.as_coroutine().tupled_upvars_ty(),
+            Ty::new_coroutine_witness_for_coroutine(ecx.cx(), def_id, args),
+        ])),
 
         ty::CoroutineWitness(def_id, args) => Ok(ecx
             .cx()
@@ -251,14 +244,9 @@ where
             Movability::Static => Err(NoSolution),
             Movability::Movable => {
                 if ecx.cx().features().coroutine_clone() {
-                    let coroutine = args.as_coroutine();
                     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()),
-                        ),
+                        args.as_coroutine().tupled_upvars_ty(),
+                        Ty::new_coroutine_witness_for_coroutine(ecx.cx(), def_id, args),
                     ]))
                 } 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 9a22bf58c03..b7ae9994c62 100644
--- a/compiler/rustc_next_trait_solver/src/solve/effect_goals.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/effect_goals.rs
@@ -6,7 +6,7 @@ use rustc_type_ir::inherent::*;
 use rustc_type_ir::lang_items::TraitSolverLangItem;
 use rustc_type_ir::solve::SizedTraitKind;
 use rustc_type_ir::solve::inspect::ProbeKind;
-use rustc_type_ir::{self as ty, Interner, elaborate};
+use rustc_type_ir::{self as ty, Interner, TypingMode, elaborate};
 use tracing::instrument;
 
 use super::assembly::{Candidate, structural_traits};
@@ -135,12 +135,16 @@ where
         }
 
         let impl_polarity = cx.impl_polarity(impl_def_id);
-        match impl_polarity {
+        let certainty = match impl_polarity {
             ty::ImplPolarity::Negative => return Err(NoSolution),
-            ty::ImplPolarity::Reservation => {
-                unimplemented!("reservation impl for const trait: {:?}", goal)
-            }
-            ty::ImplPolarity::Positive => {}
+            ty::ImplPolarity::Reservation => match ecx.typing_mode() {
+                TypingMode::Coherence => Certainty::AMBIGUOUS,
+                TypingMode::Analysis { .. }
+                | TypingMode::Borrowck { .. }
+                | TypingMode::PostBorrowckAnalysis { .. }
+                | TypingMode::PostAnalysis => return Err(NoSolution),
+            },
+            ty::ImplPolarity::Positive => Certainty::Yes,
         };
 
         if !cx.impl_is_const(impl_def_id) {
@@ -171,7 +175,7 @@ where
                 });
             ecx.add_goals(GoalSource::ImplWhereBound, const_conditions);
 
-            ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
+            ecx.evaluate_added_goals_and_make_canonical_response(certainty)
         })
     }
 
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 74c5b49ea92..4644b145b18 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
@@ -57,7 +57,6 @@ where
     /// 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>) {
@@ -65,7 +64,6 @@ where
         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 a4738306181..4f87902e46e 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
@@ -4,7 +4,6 @@ use std::ops::ControlFlow;
 #[cfg(feature = "nightly")]
 use rustc_macros::HashStable_NoContext;
 use rustc_type_ir::data_structures::{HashMap, HashSet};
-use rustc_type_ir::fast_reject::DeepRejectCtxt;
 use rustc_type_ir::inherent::*;
 use rustc_type_ir::relate::Relate;
 use rustc_type_ir::relate::solver_relating::RelateExt;
@@ -459,10 +458,7 @@ where
         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 (orig_values, canonical_goal) = self.canonicalize_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(
@@ -1131,6 +1127,7 @@ where
         self.delegate.fetch_eligible_assoc_item(goal_trait_ref, trait_assoc_def_id, impl_def_id)
     }
 
+    #[instrument(level = "debug", skip(self), ret)]
     pub(super) fn register_hidden_type_in_storage(
         &mut self,
         opaque_type_key: ty::OpaqueTypeKey<I>,
@@ -1157,29 +1154,6 @@ where
         self.add_goals(GoalSource::AliasWellFormed, goals);
     }
 
-    // Do something for each opaque/hidden pair defined with `def_id` in the
-    // current inference context.
-    pub(super) fn probe_existing_opaque_ty(
-        &mut self,
-        key: ty::OpaqueTypeKey<I>,
-    ) -> Option<(ty::OpaqueTypeKey<I>, I::Ty)> {
-        // We shouldn't have any duplicate entries when using
-        // this function during `TypingMode::Analysis`.
-        let duplicate_entries = self.delegate.clone_duplicate_opaque_types();
-        assert!(duplicate_entries.is_empty(), "unexpected duplicates: {duplicate_entries:?}");
-        let mut matching = self.delegate.clone_opaque_types_lookup_table().into_iter().filter(
-            |(candidate_key, _)| {
-                candidate_key.def_id == key.def_id
-                    && DeepRejectCtxt::relate_rigid_rigid(self.cx())
-                        .args_may_unify(candidate_key.args, key.args)
-            },
-        );
-        let first = matching.next();
-        let second = matching.next();
-        assert_eq!(second, None);
-        first
-    }
-
     // Try to evaluate a const, or return `None` if the const is too generic.
     // This doesn't mean the const isn't evaluatable, though, and should be treated
     // as an ambiguity rather than no-solution.
diff --git a/compiler/rustc_next_trait_solver/src/solve/normalizes_to/opaque_types.rs b/compiler/rustc_next_trait_solver/src/solve/normalizes_to/opaque_types.rs
index df3ad1e468b..a5f857a1dd8 100644
--- a/compiler/rustc_next_trait_solver/src/solve/normalizes_to/opaque_types.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/normalizes_to/opaque_types.rs
@@ -1,13 +1,12 @@
 //! Computes a normalizes-to (projection) goal for opaque types. This goal
 //! behaves differently depending on the current `TypingMode`.
 
-use rustc_index::bit_set::GrowableBitSet;
 use rustc_type_ir::inherent::*;
 use rustc_type_ir::solve::GoalSource;
 use rustc_type_ir::{self as ty, Interner, TypingMode, fold_regions};
 
 use crate::delegate::SolverDelegate;
-use crate::solve::{Certainty, EvalCtxt, Goal, NoSolution, QueryResult, inspect};
+use crate::solve::{Certainty, EvalCtxt, Goal, QueryResult};
 
 impl<D, I> EvalCtxt<'_, D>
 where
@@ -39,100 +38,68 @@ where
                 self.add_goal(GoalSource::Misc, goal.with(cx, ty::PredicateKind::Ambiguous));
                 self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
             }
-            TypingMode::Analysis { defining_opaque_types_and_generators } => {
+            TypingMode::Analysis {
+                defining_opaque_types_and_generators: defining_opaque_types,
+            }
+            | TypingMode::Borrowck { defining_opaque_types } => {
                 let Some(def_id) = opaque_ty
                     .def_id
                     .as_local()
-                    .filter(|&def_id| defining_opaque_types_and_generators.contains(&def_id))
+                    .filter(|&def_id| defining_opaque_types.contains(&def_id))
                 else {
+                    // If we're not in the defining scope, treat the alias as rigid.
                     self.structurally_instantiate_normalizes_to_term(goal, goal.predicate.alias);
                     return self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes);
                 };
 
-                // FIXME: This may have issues when the args contain aliases...
-                match uses_unique_placeholders_ignoring_regions(self.cx(), opaque_ty.args) {
-                    Err(NotUniqueParam::NotParam(param)) if param.is_non_region_infer() => {
-                        return self.evaluate_added_goals_and_make_canonical_response(
-                            Certainty::AMBIGUOUS,
-                        );
-                    }
-                    Err(_) => {
-                        return Err(NoSolution);
-                    }
-                    Ok(()) => {}
-                }
-                // Prefer opaques registered already.
-                let opaque_type_key = ty::OpaqueTypeKey { def_id, args: opaque_ty.args };
-                // FIXME: This also unifies the previous hidden type with the expected.
+                // We structurally normalize the args so that we're able to detect defining uses
+                // later on.
                 //
-                // If that fails, we insert `expected` as a new hidden type instead of
-                // eagerly emitting an error.
-                let existing = self.probe_existing_opaque_ty(opaque_type_key);
-                if let Some((candidate_key, candidate_ty)) = existing {
-                    return self
-                        .probe(|result| inspect::ProbeKind::OpaqueTypeStorageLookup {
-                            result: *result,
-                        })
-                        .enter(|ecx| {
-                            for (a, b) in std::iter::zip(
-                                candidate_key.args.iter(),
-                                opaque_type_key.args.iter(),
-                            ) {
-                                ecx.eq(goal.param_env, a, b)?;
-                            }
-                            ecx.eq(goal.param_env, candidate_ty, expected)?;
-                            ecx.add_item_bounds_for_hidden_type(
-                                def_id.into(),
-                                candidate_key.args,
-                                goal.param_env,
-                                candidate_ty,
-                            );
-                            ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
-                        });
-                }
+                // This reduces the amount of duplicate definitions in the `opaque_type_storage` and
+                // strengthens inference. This causes us to subtly depend on the normalization behavior
+                // when inferring the hidden type of opaques.
+                //
+                // E.g. it's observable that we don't normalize nested aliases with bound vars in
+                // `structurally_normalize` and because we use structural lookup, we also don't
+                // reuse an entry for `Tait<for<'a> fn(&'a ())>` for `Tait<for<'b> fn(&'b ())>`.
+                let normalized_args =
+                    cx.mk_args_from_iter(opaque_ty.args.iter().map(|arg| match arg.kind() {
+                        ty::GenericArgKind::Lifetime(lt) => Ok(lt.into()),
+                        ty::GenericArgKind::Type(ty) => {
+                            self.structurally_normalize_ty(goal.param_env, ty).map(Into::into)
+                        }
+                        ty::GenericArgKind::Const(ct) => {
+                            self.structurally_normalize_const(goal.param_env, ct).map(Into::into)
+                        }
+                    }))?;
 
-                // Otherwise, define a new opaque type
-                let prev = self.register_hidden_type_in_storage(opaque_type_key, expected);
-                assert_eq!(prev, None);
-                self.add_item_bounds_for_hidden_type(
-                    def_id.into(),
-                    opaque_ty.args,
-                    goal.param_env,
-                    expected,
-                );
-                self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
-            }
-            // Very similar to `TypingMode::Analysis` with some notably differences:
-            // - we accept opaque types even if they have non-universal arguments
-            // - we do a structural lookup instead of semantically unifying regions
-            // - the hidden type starts out as the type from HIR typeck with fresh region
-            //   variables instead of a fully unconstrained inference variable
-            TypingMode::Borrowck { defining_opaque_types } => {
-                let Some(def_id) = opaque_ty
-                    .def_id
-                    .as_local()
-                    .filter(|&def_id| defining_opaque_types.contains(&def_id))
-                else {
-                    self.structurally_instantiate_normalizes_to_term(goal, goal.predicate.alias);
-                    return self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes);
-                };
+                let opaque_type_key = ty::OpaqueTypeKey { def_id, args: normalized_args };
+                if let Some(prev) = self.register_hidden_type_in_storage(opaque_type_key, expected)
+                {
+                    self.eq(goal.param_env, expected, prev)?;
+                } else {
+                    // During HIR typeck, opaque types start out as unconstrained
+                    // inference variables. In borrowck we instead use the type
+                    // computed in HIR typeck as the initial value.
+                    match self.typing_mode() {
+                        TypingMode::Analysis { .. } => {}
+                        TypingMode::Borrowck { .. } => {
+                            let actual = cx
+                                .type_of_opaque_hir_typeck(def_id)
+                                .instantiate(cx, opaque_ty.args);
+                            let actual = fold_regions(cx, actual, |re, _dbi| match re.kind() {
+                                ty::ReErased => self.next_region_var(),
+                                _ => re,
+                            });
+                            self.eq(goal.param_env, expected, actual)?;
+                        }
+                        _ => unreachable!(),
+                    }
+                }
 
-                let opaque_type_key = ty::OpaqueTypeKey { def_id, args: opaque_ty.args };
-                let actual = self
-                    .register_hidden_type_in_storage(opaque_type_key, expected)
-                    .unwrap_or_else(|| {
-                        let actual =
-                            cx.type_of_opaque_hir_typeck(def_id).instantiate(cx, opaque_ty.args);
-                        let actual = fold_regions(cx, actual, |re, _dbi| match re.kind() {
-                            ty::ReErased => self.next_region_var(),
-                            _ => re,
-                        });
-                        actual
-                    });
-                self.eq(goal.param_env, expected, actual)?;
                 self.add_item_bounds_for_hidden_type(
                     def_id.into(),
-                    opaque_ty.args,
+                    normalized_args,
                     goal.param_env,
                     expected,
                 );
@@ -168,44 +135,3 @@ where
         }
     }
 }
-
-/// Checks whether each generic argument is simply a unique generic placeholder.
-///
-/// FIXME: Interner argument is needed to constrain the `I` parameter.
-fn uses_unique_placeholders_ignoring_regions<I: Interner>(
-    _cx: I,
-    args: I::GenericArgs,
-) -> Result<(), NotUniqueParam<I>> {
-    let mut seen = GrowableBitSet::default();
-    for arg in args.iter() {
-        match arg.kind() {
-            // Ignore regions, since we can't resolve those in a canonicalized
-            // query in the trait solver.
-            ty::GenericArgKind::Lifetime(_) => {}
-            ty::GenericArgKind::Type(t) => match t.kind() {
-                ty::Placeholder(p) => {
-                    if !seen.insert(p.var()) {
-                        return Err(NotUniqueParam::DuplicateParam(t.into()));
-                    }
-                }
-                _ => return Err(NotUniqueParam::NotParam(t.into())),
-            },
-            ty::GenericArgKind::Const(c) => match c.kind() {
-                ty::ConstKind::Placeholder(p) => {
-                    if !seen.insert(p.var()) {
-                        return Err(NotUniqueParam::DuplicateParam(c.into()));
-                    }
-                }
-                _ => return Err(NotUniqueParam::NotParam(c.into())),
-            },
-        }
-    }
-
-    Ok(())
-}
-
-// FIXME: This should check for dupes and non-params first, then infer vars.
-enum NotUniqueParam<I: Interner> {
-    DuplicateParam(I::GenericArg),
-    NotParam(I::GenericArg),
-}
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 04ede365a21..891ecab041a 100644
--- a/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs
@@ -6,8 +6,8 @@ use rustc_type_ir::inherent::*;
 use rustc_type_ir::lang_items::TraitSolverLangItem;
 use rustc_type_ir::solve::{CanonicalResponse, SizedTraitKind};
 use rustc_type_ir::{
-    self as ty, Interner, Movability, TraitPredicate, TraitRef, TypeVisitableExt as _, TypingMode,
-    Upcast as _, elaborate,
+    self as ty, Interner, Movability, PredicatePolarity, TraitPredicate, TraitRef,
+    TypeVisitableExt as _, TypingMode, Upcast as _, elaborate,
 };
 use tracing::{debug, instrument, trace};
 
@@ -133,19 +133,26 @@ where
             cx: I,
             clause_def_id: I::DefId,
             goal_def_id: I::DefId,
+            polarity: PredicatePolarity,
         ) -> bool {
             clause_def_id == goal_def_id
             // PERF(sized-hierarchy): Sizedness supertraits aren't elaborated to improve perf, so
             // check for a `MetaSized` supertrait being matched against a `Sized` assumption.
             //
             // `PointeeSized` bounds are syntactic sugar for a lack of bounds so don't need this.
-                || (cx.is_lang_item(clause_def_id, TraitSolverLangItem::Sized)
+                || (polarity == PredicatePolarity::Positive
+                    && cx.is_lang_item(clause_def_id, TraitSolverLangItem::Sized)
                     && cx.is_lang_item(goal_def_id, TraitSolverLangItem::MetaSized))
         }
 
         if let Some(trait_clause) = assumption.as_trait_clause()
             && trait_clause.polarity() == goal.predicate.polarity
-            && trait_def_id_matches(ecx.cx(), trait_clause.def_id(), goal.predicate.def_id())
+            && trait_def_id_matches(
+                ecx.cx(),
+                trait_clause.def_id(),
+                goal.predicate.def_id(),
+                goal.predicate.polarity,
+            )
             && DeepRejectCtxt::relate_rigid_rigid(ecx.cx()).args_may_unify(
                 goal.predicate.trait_ref.args,
                 trait_clause.skip_binder().trait_ref.args,
@@ -168,6 +175,8 @@ where
         // PERF(sized-hierarchy): Sizedness supertraits aren't elaborated to improve perf, so
         // check for a `Sized` subtrait when looking for `MetaSized`. `PointeeSized` bounds
         // are syntactic sugar for a lack of bounds so don't need this.
+        // We don't need to check polarity, `fast_reject_assumption` already rejected non-`Positive`
+        // polarity `Sized` assumptions as matching non-`Positive` `MetaSized` goals.
         if ecx.cx().is_lang_item(goal.predicate.def_id(), TraitSolverLangItem::MetaSized)
             && ecx.cx().is_lang_item(trait_clause.def_id(), TraitSolverLangItem::Sized)
         {
diff --git a/compiler/rustc_parse/Cargo.toml b/compiler/rustc_parse/Cargo.toml
index 0ae0b613fa2..6d738a10371 100644
--- a/compiler/rustc_parse/Cargo.toml
+++ b/compiler/rustc_parse/Cargo.toml
@@ -9,7 +9,6 @@ bitflags = "2.4.1"
 rustc-literal-escaper = "0.0.5"
 rustc_ast = { path = "../rustc_ast" }
 rustc_ast_pretty = { path = "../rustc_ast_pretty" }
-rustc_attr_parsing = { path = "../rustc_attr_parsing" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
 rustc_feature = { path = "../rustc_feature" }
diff --git a/compiler/rustc_parse/messages.ftl b/compiler/rustc_parse/messages.ftl
index 9e0075c21b9..4ca2f57bd87 100644
--- a/compiler/rustc_parse/messages.ftl
+++ b/compiler/rustc_parse/messages.ftl
@@ -359,6 +359,20 @@ parse_generics_in_path = unexpected generic arguments in path
 
 parse_help_set_edition_cargo = set `edition = "{$edition}"` in `Cargo.toml`
 parse_help_set_edition_standalone = pass `--edition {$edition}` to `rustc`
+
+parse_hidden_unicode_codepoints = unicode codepoint changing visible direction of text present in {$label}
+    .label = this {$label} contains {$count ->
+        [one] an invisible
+        *[other] invisible
+    } unicode text flow control {$count ->
+        [one] codepoint
+        *[other] codepoints
+    }
+    .note = these kind of unicode codepoints change the way text flows on applications that support them, but can cause confusion because they change the order of characters on the screen
+    .suggestion_remove = if their presence wasn't intentional, you can remove them
+    .suggestion_escape = if you want to keep them but make them visible in your source code, you can escape them
+    .no_suggestion_note_escape = if you want to keep them but make them visible in your source code, you can escape them: {$escaped}
+
 parse_if_expression_missing_condition = missing condition for `if` expression
     .condition_label = expected condition here
     .block_label = if this block is the condition of the `if` expression, then it must be followed by another block
@@ -436,11 +450,6 @@ parse_inner_doc_comment_not_permitted = expected outer doc comment
     .label_does_not_annotate_this = the inner doc comment doesn't annotate this {$item}
     .sugg_change_inner_to_outer = to annotate the {$item}, change the doc comment from inner to outer style
 
-parse_invalid_attr_unsafe = `{$name}` is not an unsafe attribute
-    .label = this is not an unsafe attribute
-    .suggestion = remove the `unsafe(...)`
-    .note = extraneous unsafe is not allowed in attributes
-
 parse_invalid_block_macro_segment = cannot use a `block` macro fragment here
     .label = the `block` fragment is within this context
     .suggestion = wrap this in another block
@@ -468,9 +477,6 @@ parse_invalid_dyn_keyword = invalid `dyn` keyword
 parse_invalid_expression_in_let_else = a `{$operator}` expression cannot be directly assigned in `let...else`
 parse_invalid_identifier_with_leading_number = identifiers cannot start with a number
 
-parse_invalid_label =
-    invalid label name `{$name}`
-
 parse_invalid_literal_suffix_on_tuple_index = suffixes on a tuple index are invalid
     .label = invalid suffix `{$suffix}`
     .tuple_exception_line_1 = `{$suffix}` is *temporarily* accepted on tuple index fields as it was incorrectly accepted on stable for a few releases
@@ -500,6 +506,8 @@ parse_invalid_unicode_escape = invalid unicode character escape
 parse_invalid_variable_declaration =
     invalid variable declaration
 
+parse_keyword_label = labels cannot use keyword names
+
 parse_keyword_lifetime =
     lifetimes cannot use keyword names
 
@@ -601,7 +609,6 @@ parse_maybe_report_ambiguous_plus =
     ambiguous `+` in a type
     .suggestion = use parentheses to disambiguate
 
-parse_meta_bad_delim = wrong meta list delimiters
 parse_meta_bad_delim_suggestion = the delimiters should be `(` and `)`
 
 parse_mismatched_closing_delimiter = mismatched closing delimiter: `{$delimiter}`
@@ -748,9 +755,6 @@ parse_parentheses_with_struct_fields = invalid `struct` delimiters or `fn` call
     .suggestion_braces_for_struct = if `{$type}` is a struct, use braces as delimiters
     .suggestion_no_fields_for_fn = if `{$type}` is a function, use the arguments directly
 
-parse_parenthesized_lifetime = parenthesized lifetime bounds are not supported
-parse_parenthesized_lifetime_suggestion = remove the parentheses
-
 parse_path_double_colon = path separator must be a double colon
     .suggestion = use a double colon instead
 
@@ -993,10 +997,6 @@ parse_unmatched_angle_brackets = {$num_extra_brackets ->
            *[other] remove extra angle brackets
         }
 
-parse_unsafe_attr_outside_unsafe = unsafe attribute used without unsafe
-    .label = usage of unsafe attribute
-parse_unsafe_attr_outside_unsafe_suggestion = wrap the attribute in `unsafe(...)`
-
 
 parse_unskipped_whitespace = whitespace symbol '{$ch}' is not skipped
     .label = {parse_unskipped_whitespace}
diff --git a/compiler/rustc_parse/src/errors.rs b/compiler/rustc_parse/src/errors.rs
index a105dd1909e..797d4830c2f 100644
--- a/compiler/rustc_parse/src/errors.rs
+++ b/compiler/rustc_parse/src/errors.rs
@@ -8,8 +8,9 @@ use rustc_ast::{Path, Visibility};
 use rustc_errors::codes::*;
 use rustc_errors::{
     Applicability, Diag, DiagCtxtHandle, Diagnostic, EmissionGuarantee, Level, Subdiagnostic,
+    SuggestionStyle,
 };
-use rustc_macros::{Diagnostic, Subdiagnostic};
+use rustc_macros::{Diagnostic, LintDiagnostic, Subdiagnostic};
 use rustc_session::errors::ExprParenthesesNeeded;
 use rustc_span::edition::{Edition, LATEST_STABLE_EDITION};
 use rustc_span::{Ident, Span, Symbol};
@@ -2228,11 +2229,10 @@ pub(crate) struct KeywordLifetime {
 }
 
 #[derive(Diagnostic)]
-#[diag(parse_invalid_label)]
-pub(crate) struct InvalidLabel {
+#[diag(parse_keyword_label)]
+pub(crate) struct KeywordLabel {
     #[primary_span]
     pub span: Span,
-    pub name: Symbol,
 }
 
 #[derive(Diagnostic)]
@@ -3163,27 +3163,6 @@ pub(crate) struct ModifierLifetime {
     pub modifier: &'static str,
 }
 
-#[derive(Subdiagnostic)]
-#[multipart_suggestion(
-    parse_parenthesized_lifetime_suggestion,
-    applicability = "machine-applicable"
-)]
-pub(crate) struct RemoveParens {
-    #[suggestion_part(code = "")]
-    pub lo: Span,
-    #[suggestion_part(code = "")]
-    pub hi: Span,
-}
-
-#[derive(Diagnostic)]
-#[diag(parse_parenthesized_lifetime)]
-pub(crate) struct ParenthesizedLifetime {
-    #[primary_span]
-    pub span: Span,
-    #[subdiagnostic]
-    pub sugg: RemoveParens,
-}
-
 #[derive(Diagnostic)]
 #[diag(parse_underscore_literal_suffix)]
 pub(crate) struct UnderscoreLiteralSuffix {
@@ -3367,15 +3346,6 @@ pub(crate) struct KwBadCase<'a> {
 }
 
 #[derive(Diagnostic)]
-#[diag(parse_meta_bad_delim)]
-pub(crate) struct MetaBadDelim {
-    #[primary_span]
-    pub span: Span,
-    #[subdiagnostic]
-    pub sugg: MetaBadDelimSugg,
-}
-
-#[derive(Diagnostic)]
 #[diag(parse_cfg_attr_bad_delim)]
 pub(crate) struct CfgAttrBadDelim {
     #[primary_span]
@@ -3515,38 +3485,6 @@ pub(crate) struct DotDotRangeAttribute {
 }
 
 #[derive(Diagnostic)]
-#[diag(parse_invalid_attr_unsafe)]
-#[note]
-pub(crate) struct InvalidAttrUnsafe {
-    #[primary_span]
-    #[label]
-    pub span: Span,
-    pub name: Path,
-}
-
-#[derive(Diagnostic)]
-#[diag(parse_unsafe_attr_outside_unsafe)]
-pub(crate) struct UnsafeAttrOutsideUnsafe {
-    #[primary_span]
-    #[label]
-    pub span: Span,
-    #[subdiagnostic]
-    pub suggestion: UnsafeAttrOutsideUnsafeSuggestion,
-}
-
-#[derive(Subdiagnostic)]
-#[multipart_suggestion(
-    parse_unsafe_attr_outside_unsafe_suggestion,
-    applicability = "machine-applicable"
-)]
-pub(crate) struct UnsafeAttrOutsideUnsafeSuggestion {
-    #[suggestion_part(code = "unsafe(")]
-    pub left: Span,
-    #[suggestion_part(code = ")")]
-    pub right: Span,
-}
-
-#[derive(Diagnostic)]
 #[diag(parse_binder_before_modifiers)]
 pub(crate) struct BinderBeforeModifiers {
     #[primary_span]
@@ -3664,3 +3602,76 @@ pub(crate) struct ExpectedRegisterClassOrExplicitRegister {
     #[primary_span]
     pub(crate) span: Span,
 }
+
+#[derive(LintDiagnostic)]
+#[diag(parse_hidden_unicode_codepoints)]
+#[note]
+pub(crate) struct HiddenUnicodeCodepointsDiag {
+    pub label: String,
+    pub count: usize,
+    #[label]
+    pub span_label: Span,
+    #[subdiagnostic]
+    pub labels: Option<HiddenUnicodeCodepointsDiagLabels>,
+    #[subdiagnostic]
+    pub sub: HiddenUnicodeCodepointsDiagSub,
+}
+
+pub(crate) struct HiddenUnicodeCodepointsDiagLabels {
+    pub spans: Vec<(char, Span)>,
+}
+
+impl Subdiagnostic for HiddenUnicodeCodepointsDiagLabels {
+    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
+        for (c, span) in self.spans {
+            diag.span_label(span, format!("{c:?}"));
+        }
+    }
+}
+
+pub(crate) enum HiddenUnicodeCodepointsDiagSub {
+    Escape { spans: Vec<(char, Span)> },
+    NoEscape { spans: Vec<(char, Span)> },
+}
+
+// Used because of multiple multipart_suggestion and note
+impl Subdiagnostic for HiddenUnicodeCodepointsDiagSub {
+    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
+        match self {
+            HiddenUnicodeCodepointsDiagSub::Escape { spans } => {
+                diag.multipart_suggestion_with_style(
+                    fluent::parse_suggestion_remove,
+                    spans.iter().map(|(_, span)| (*span, "".to_string())).collect(),
+                    Applicability::MachineApplicable,
+                    SuggestionStyle::HideCodeAlways,
+                );
+                diag.multipart_suggestion(
+                    fluent::parse_suggestion_escape,
+                    spans
+                        .into_iter()
+                        .map(|(c, span)| {
+                            let c = format!("{c:?}");
+                            (span, c[1..c.len() - 1].to_string())
+                        })
+                        .collect(),
+                    Applicability::MachineApplicable,
+                );
+            }
+            HiddenUnicodeCodepointsDiagSub::NoEscape { spans } => {
+                // FIXME: in other suggestions we've reversed the inner spans of doc comments. We
+                // should do the same here to provide the same good suggestions as we do for
+                // literals above.
+                diag.arg(
+                    "escaped",
+                    spans
+                        .into_iter()
+                        .map(|(c, _)| format!("{c:?}"))
+                        .collect::<Vec<String>>()
+                        .join(", "),
+                );
+                diag.note(fluent::parse_suggestion_remove);
+                diag.note(fluent::parse_no_suggestion_note_escape);
+            }
+        }
+    }
+}
diff --git a/compiler/rustc_parse/src/lexer/mod.rs b/compiler/rustc_parse/src/lexer/mod.rs
index 85af5a615ae..9792240a548 100644
--- a/compiler/rustc_parse/src/lexer/mod.rs
+++ b/compiler/rustc_parse/src/lexer/mod.rs
@@ -49,6 +49,7 @@ pub(crate) fn lex_token_trees<'psess, 'src>(
     mut src: &'src str,
     mut start_pos: BytePos,
     override_span: Option<Span>,
+    frontmatter_allowed: FrontmatterAllowed,
 ) -> Result<TokenStream, Vec<Diag<'psess>>> {
     // Skip `#!`, if present.
     if let Some(shebang_len) = rustc_lexer::strip_shebang(src) {
@@ -56,7 +57,7 @@ pub(crate) fn lex_token_trees<'psess, 'src>(
         start_pos = start_pos + BytePos::from_usize(shebang_len);
     }
 
-    let cursor = Cursor::new(src, FrontmatterAllowed::Yes);
+    let cursor = Cursor::new(src, frontmatter_allowed);
     let mut lexer = Lexer {
         psess,
         start_pos,
@@ -542,21 +543,21 @@ impl<'psess, 'src> Lexer<'psess, 'src> {
             })
             .collect();
 
+        let label = label.to_string();
         let count = spans.len();
-        let labels = point_at_inner_spans.then_some(spans.clone());
+        let labels = point_at_inner_spans
+            .then_some(errors::HiddenUnicodeCodepointsDiagLabels { spans: spans.clone() });
+        let sub = if point_at_inner_spans && !spans.is_empty() {
+            errors::HiddenUnicodeCodepointsDiagSub::Escape { spans }
+        } else {
+            errors::HiddenUnicodeCodepointsDiagSub::NoEscape { spans }
+        };
 
         self.psess.buffer_lint(
             TEXT_DIRECTION_CODEPOINT_IN_LITERAL,
             span,
             ast::CRATE_NODE_ID,
-            BuiltinLintDiag::HiddenUnicodeCodepoints {
-                label: label.to_string(),
-                count,
-                span_label: span,
-                labels,
-                escape: point_at_inner_spans && !spans.is_empty(),
-                spans,
-            },
+            errors::HiddenUnicodeCodepointsDiag { label, count, span_label: span, labels, sub },
         );
     }
 
diff --git a/compiler/rustc_parse/src/lib.rs b/compiler/rustc_parse/src/lib.rs
index 2050c5f9608..48289b2e8ab 100644
--- a/compiler/rustc_parse/src/lib.rs
+++ b/compiler/rustc_parse/src/lib.rs
@@ -16,10 +16,11 @@ use std::str::Utf8Error;
 use std::sync::Arc;
 
 use rustc_ast as ast;
-use rustc_ast::tokenstream::TokenStream;
+use rustc_ast::tokenstream::{DelimSpan, TokenStream};
 use rustc_ast::{AttrItem, Attribute, MetaItemInner, token};
 use rustc_ast_pretty::pprust;
 use rustc_errors::{Diag, EmissionGuarantee, FatalError, PResult, pluralize};
+use rustc_lexer::FrontmatterAllowed;
 use rustc_session::parse::ParseSess;
 use rustc_span::source_map::SourceMap;
 use rustc_span::{FileName, SourceFile, Span};
@@ -30,8 +31,9 @@ pub const MACRO_ARGUMENTS: Option<&str> = Some("macro arguments");
 #[macro_use]
 pub mod parser;
 use parser::Parser;
+use rustc_ast::token::Delimiter;
+
 pub mod lexer;
-pub mod validate_attr;
 
 mod errors;
 
@@ -146,7 +148,7 @@ fn new_parser_from_source_file(
     source_file: Arc<SourceFile>,
 ) -> Result<Parser<'_>, Vec<Diag<'_>>> {
     let end_pos = source_file.end_position();
-    let stream = source_file_to_stream(psess, source_file, None)?;
+    let stream = source_file_to_stream(psess, source_file, None, FrontmatterAllowed::Yes)?;
     let mut parser = Parser::new(psess, stream, None);
     if parser.token == token::Eof {
         parser.token.span = Span::new(end_pos, end_pos, parser.token.span.ctxt(), None);
@@ -161,7 +163,9 @@ pub fn source_str_to_stream(
     override_span: Option<Span>,
 ) -> Result<TokenStream, Vec<Diag<'_>>> {
     let source_file = psess.source_map().new_source_file(name, source);
-    source_file_to_stream(psess, source_file, override_span)
+    // used mainly for `proc_macro` and the likes, not for our parsing purposes, so don't parse
+    // frontmatters as frontmatters.
+    source_file_to_stream(psess, source_file, override_span, FrontmatterAllowed::No)
 }
 
 /// Given a source file, produces a sequence of token trees. Returns any buffered errors from
@@ -170,6 +174,7 @@ fn source_file_to_stream<'psess>(
     psess: &'psess ParseSess,
     source_file: Arc<SourceFile>,
     override_span: Option<Span>,
+    frontmatter_allowed: FrontmatterAllowed,
 ) -> Result<TokenStream, Vec<Diag<'psess>>> {
     let src = source_file.src.as_ref().unwrap_or_else(|| {
         psess.dcx().bug(format!(
@@ -178,7 +183,13 @@ fn source_file_to_stream<'psess>(
         ));
     });
 
-    lexer::lex_token_trees(psess, src.as_str(), source_file.start_pos, override_span)
+    lexer::lex_token_trees(
+        psess,
+        src.as_str(),
+        source_file.start_pos,
+        override_span,
+        frontmatter_allowed,
+    )
 }
 
 /// Runs the given subparser `f` on the tokens of the given `attr`'s item.
@@ -225,7 +236,7 @@ pub fn parse_cfg_attr(
         ast::AttrArgs::Delimited(ast::DelimArgs { dspan, delim, ref tokens })
             if !tokens.is_empty() =>
         {
-            crate::validate_attr::check_cfg_attr_bad_delim(psess, dspan, delim);
+            check_cfg_attr_bad_delim(psess, dspan, delim);
             match parse_in(psess, tokens.clone(), "`cfg_attr` input", |p| p.parse_cfg_attr()) {
                 Ok(r) => return Some(r),
                 Err(e) => {
@@ -244,3 +255,13 @@ pub fn parse_cfg_attr(
     }
     None
 }
+
+fn check_cfg_attr_bad_delim(psess: &ParseSess, span: DelimSpan, delim: Delimiter) {
+    if let Delimiter::Parenthesis = delim {
+        return;
+    }
+    psess.dcx().emit_err(errors::CfgAttrBadDelim {
+        span: span.entire(),
+        sugg: errors::MetaBadDelimSugg { open: span.open, close: span.close },
+    });
+}
diff --git a/compiler/rustc_parse/src/parser/attr.rs b/compiler/rustc_parse/src/parser/attr.rs
index 7f6afeba28c..acd338156ce 100644
--- a/compiler/rustc_parse/src/parser/attr.rs
+++ b/compiler/rustc_parse/src/parser/attr.rs
@@ -399,7 +399,7 @@ impl<'a> Parser<'a> {
     }
 
     /// Matches `COMMASEP(meta_item_inner)`.
-    pub(crate) fn parse_meta_seq_top(&mut self) -> PResult<'a, ThinVec<ast::MetaItemInner>> {
+    pub fn parse_meta_seq_top(&mut self) -> PResult<'a, ThinVec<ast::MetaItemInner>> {
         // Presumably, the majority of the time there will only be one attr.
         let mut nmis = ThinVec::with_capacity(1);
         while self.token != token::Eof {
diff --git a/compiler/rustc_parse/src/parser/diagnostics.rs b/compiler/rustc_parse/src/parser/diagnostics.rs
index 220e4ac18fc..a28af7833c3 100644
--- a/compiler/rustc_parse/src/parser/diagnostics.rs
+++ b/compiler/rustc_parse/src/parser/diagnostics.rs
@@ -463,8 +463,8 @@ impl<'a> Parser<'a> {
 
     pub(super) fn expected_one_of_not_found(
         &mut self,
-        edible: &[ExpTokenPair<'_>],
-        inedible: &[ExpTokenPair<'_>],
+        edible: &[ExpTokenPair],
+        inedible: &[ExpTokenPair],
     ) -> PResult<'a, ErrorGuaranteed> {
         debug!("expected_one_of_not_found(edible: {:?}, inedible: {:?})", edible, inedible);
         fn tokens_to_string(tokens: &[TokenType]) -> String {
@@ -1092,7 +1092,7 @@ impl<'a> Parser<'a> {
 
     /// Eats and discards tokens until one of `closes` is encountered. Respects token trees,
     /// passes through any errors encountered. Used for error recovery.
-    pub(super) fn eat_to_tokens(&mut self, closes: &[ExpTokenPair<'_>]) {
+    pub(super) fn eat_to_tokens(&mut self, closes: &[ExpTokenPair]) {
         if let Err(err) = self
             .parse_seq_to_before_tokens(closes, &[], SeqSep::none(), |p| Ok(p.parse_token_tree()))
         {
@@ -1113,7 +1113,7 @@ impl<'a> Parser<'a> {
     pub(super) fn check_trailing_angle_brackets(
         &mut self,
         segment: &PathSegment,
-        end: &[ExpTokenPair<'_>],
+        end: &[ExpTokenPair],
     ) -> Option<ErrorGuaranteed> {
         if !self.may_recover() {
             return None;
@@ -1196,7 +1196,7 @@ impl<'a> Parser<'a> {
         // second case.
         if self.look_ahead(position, |t| {
             trace!("check_trailing_angle_brackets: t={:?}", t);
-            end.iter().any(|exp| exp.tok == &t.kind)
+            end.iter().any(|exp| exp.tok == t.kind)
         }) {
             // Eat from where we started until the end token so that parsing can continue
             // as if we didn't have those extra angle brackets.
@@ -2120,8 +2120,8 @@ impl<'a> Parser<'a> {
 
     pub(super) fn recover_seq_parse_error(
         &mut self,
-        open: ExpTokenPair<'_>,
-        close: ExpTokenPair<'_>,
+        open: ExpTokenPair,
+        close: ExpTokenPair,
         lo: Span,
         err: Diag<'a>,
     ) -> Box<Expr> {
@@ -2386,8 +2386,8 @@ impl<'a> Parser<'a> {
 
     pub(super) fn consume_block(
         &mut self,
-        open: ExpTokenPair<'_>,
-        close: ExpTokenPair<'_>,
+        open: ExpTokenPair,
+        close: ExpTokenPair,
         consume_close: ConsumeClosingDelim,
     ) {
         let mut brace_depth = 0;
diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index d0604f76317..f0f58e901a9 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -1598,7 +1598,7 @@ impl<'a> Parser<'a> {
         self.maybe_recover_from_bad_qpath(expr)
     }
 
-    fn parse_expr_array_or_repeat(&mut self, close: ExpTokenPair<'_>) -> PResult<'a, Box<Expr>> {
+    fn parse_expr_array_or_repeat(&mut self, close: ExpTokenPair) -> PResult<'a, Box<Expr>> {
         let lo = self.token.span;
         self.bump(); // `[` or other open delim
 
@@ -2077,7 +2077,7 @@ impl<'a> Parser<'a> {
         (token::Lit { symbol: name, suffix: None, kind: token::Char }, span)
     }
 
-    fn mk_meta_item_lit_char(name: Symbol, span: Span) -> MetaItemLit {
+    pub fn mk_meta_item_lit_char(name: Symbol, span: Span) -> MetaItemLit {
         ast::MetaItemLit {
             symbol: name,
             suffix: None,
@@ -2086,7 +2086,7 @@ impl<'a> Parser<'a> {
         }
     }
 
-    fn handle_missing_lit<L>(
+    pub fn handle_missing_lit<L>(
         &mut self,
         mk_lit_char: impl FnOnce(Symbol, Span) -> L,
     ) -> PResult<'a, L> {
@@ -2156,7 +2156,7 @@ impl<'a> Parser<'a> {
 
     /// Keep this in sync with `Token::can_begin_literal_maybe_minus` and
     /// `Lit::from_token` (excluding unary negation).
-    fn eat_token_lit(&mut self) -> Option<token::Lit> {
+    pub fn eat_token_lit(&mut self) -> Option<token::Lit> {
         let check_expr = |expr: Box<Expr>| {
             if let ast::ExprKind::Lit(token_lit) = expr.kind {
                 Some(token_lit)
@@ -2397,20 +2397,24 @@ impl<'a> Parser<'a> {
         let before = self.prev_token;
         let binder = if self.check_keyword(exp!(For)) {
             let lo = self.token.span;
-            let (lifetime_defs, _) = self.parse_late_bound_lifetime_defs()?;
+            let (bound_vars, _) = self.parse_higher_ranked_binder()?;
             let span = lo.to(self.prev_token.span);
 
             self.psess.gated_spans.gate(sym::closure_lifetime_binder, span);
 
-            ClosureBinder::For { span, generic_params: lifetime_defs }
+            ClosureBinder::For { span, generic_params: bound_vars }
         } else {
             ClosureBinder::NotPresent
         };
 
         let constness = self.parse_closure_constness();
 
-        let movability =
-            if self.eat_keyword(exp!(Static)) { Movability::Static } else { Movability::Movable };
+        let movability = if self.eat_keyword(exp!(Static)) {
+            self.psess.gated_spans.gate(sym::coroutines, self.prev_token.span);
+            Movability::Static
+        } else {
+            Movability::Movable
+        };
 
         let coroutine_kind = if self.token_uninterpolated_span().at_least_rust_2018() {
             self.parse_coroutine_kind(Case::Sensitive)
@@ -3090,7 +3094,7 @@ impl<'a> Parser<'a> {
         if let Some((ident, is_raw)) = self.token.lifetime() {
             // Disallow `'fn`, but with a better error message than `expect_lifetime`.
             if matches!(is_raw, IdentIsRaw::No) && ident.without_first_quote().is_reserved() {
-                self.dcx().emit_err(errors::InvalidLabel { span: ident.span, name: ident.name });
+                self.dcx().emit_err(errors::KeywordLabel { span: ident.span });
             }
 
             self.bump();
@@ -3657,7 +3661,7 @@ impl<'a> Parser<'a> {
         &mut self,
         pth: ast::Path,
         recover: bool,
-        close: ExpTokenPair<'_>,
+        close: ExpTokenPair,
     ) -> PResult<
         'a,
         (
@@ -3676,8 +3680,8 @@ impl<'a> Parser<'a> {
             errors::HelpUseLatestEdition::new().add_to_diag(e);
         };
 
-        while self.token != *close.tok {
-            if self.eat(exp!(DotDot)) || self.recover_struct_field_dots(close.tok) {
+        while self.token != close.tok {
+            if self.eat(exp!(DotDot)) || self.recover_struct_field_dots(&close.tok) {
                 let exp_span = self.prev_token.span;
                 // We permit `.. }` on the left-hand side of a destructuring assignment.
                 if self.check(close) {
diff --git a/compiler/rustc_parse/src/parser/generics.rs b/compiler/rustc_parse/src/parser/generics.rs
index 4a8530a2b38..eb684c3a62f 100644
--- a/compiler/rustc_parse/src/parser/generics.rs
+++ b/compiler/rustc_parse/src/parser/generics.rs
@@ -172,8 +172,11 @@ impl<'a> Parser<'a> {
         })
     }
 
-    /// Parses a (possibly empty) list of lifetime and type parameters, possibly including
-    /// a trailing comma and erroneous trailing attributes.
+    /// Parse a (possibly empty) list of generic (lifetime, type, const) parameters.
+    ///
+    /// ```ebnf
+    /// GenericParams = (GenericParam ("," GenericParam)* ","?)?
+    /// ```
     pub(super) fn parse_generic_params(&mut self) -> PResult<'a, ThinVec<ast::GenericParam>> {
         let mut params = ThinVec::new();
         let mut done = false;
@@ -520,7 +523,7 @@ impl<'a> Parser<'a> {
         // * `for<'a> Trait1<'a>: Trait2<'a /* ok */>`
         // * `(for<'a> Trait1<'a>): Trait2<'a /* not ok */>`
         // * `for<'a> for<'b> Trait1<'a, 'b>: Trait2<'a /* ok */, 'b /* not ok */>`
-        let (lifetime_defs, _) = self.parse_late_bound_lifetime_defs()?;
+        let (bound_vars, _) = self.parse_higher_ranked_binder()?;
 
         // Parse type with mandatory colon and (possibly empty) bounds,
         // or with mandatory equality sign and the second type.
@@ -528,7 +531,7 @@ impl<'a> Parser<'a> {
         if self.eat(exp!(Colon)) {
             let bounds = self.parse_generic_bounds()?;
             Ok(ast::WherePredicateKind::BoundPredicate(ast::WhereBoundPredicate {
-                bound_generic_params: lifetime_defs,
+                bound_generic_params: bound_vars,
                 bounded_ty: ty,
                 bounds,
             }))
diff --git a/compiler/rustc_parse/src/parser/item.rs b/compiler/rustc_parse/src/parser/item.rs
index ca89eb1e2cf..eb264f59fed 100644
--- a/compiler/rustc_parse/src/parser/item.rs
+++ b/compiler/rustc_parse/src/parser/item.rs
@@ -43,7 +43,7 @@ impl<'a> Parser<'a> {
             self.expect(exp!(OpenBrace))?;
             let (inner_attrs, items, inner_span) = self.parse_mod(exp!(CloseBrace))?;
             attrs.extend(inner_attrs);
-            ModKind::Loaded(items, Inline::Yes, inner_span, Ok(()))
+            ModKind::Loaded(items, Inline::Yes, inner_span)
         };
         Ok(ItemKind::Mod(safety, ident, mod_kind))
     }
@@ -54,7 +54,7 @@ impl<'a> Parser<'a> {
     /// - `}` for mod items
     pub fn parse_mod(
         &mut self,
-        term: ExpTokenPair<'_>,
+        term: ExpTokenPair,
     ) -> PResult<'a, (AttrVec, ThinVec<Box<Item>>, ModSpans)> {
         let lo = self.token.span;
         let attrs = self.parse_inner_attributes()?;
@@ -1201,7 +1201,7 @@ impl<'a> Parser<'a> {
         }?;
 
         let dash = exp!(Minus);
-        if self.token != *dash.tok {
+        if self.token != dash.tok {
             return Ok(ident);
         }
 
diff --git a/compiler/rustc_parse/src/parser/mod.rs b/compiler/rustc_parse/src/parser/mod.rs
index 41ed1f95a01..15598f32429 100644
--- a/compiler/rustc_parse/src/parser/mod.rs
+++ b/compiler/rustc_parse/src/parser/mod.rs
@@ -24,7 +24,7 @@ pub use diagnostics::AttemptLocalParseRecovery;
 pub(crate) use expr::ForbiddenLetReason;
 pub(crate) use item::{FnContext, FnParseMode};
 pub use pat::{CommaRecoveryMode, RecoverColon, RecoverComma};
-use path::PathStyle;
+pub use path::PathStyle;
 use rustc_ast::token::{
     self, IdentIsRaw, InvisibleOrigin, MetaVarKind, NtExprKind, NtPatKind, Token, TokenKind,
 };
@@ -261,19 +261,19 @@ struct CaptureState {
 
 /// A sequence separator.
 #[derive(Debug)]
-struct SeqSep<'a> {
+struct SeqSep {
     /// The separator token.
-    sep: Option<ExpTokenPair<'a>>,
+    sep: Option<ExpTokenPair>,
     /// `true` if a trailing separator is allowed.
     trailing_sep_allowed: bool,
 }
 
-impl<'a> SeqSep<'a> {
-    fn trailing_allowed(sep: ExpTokenPair<'a>) -> SeqSep<'a> {
+impl SeqSep {
+    fn trailing_allowed(sep: ExpTokenPair) -> SeqSep {
         SeqSep { sep: Some(sep), trailing_sep_allowed: true }
     }
 
-    fn none() -> SeqSep<'a> {
+    fn none() -> SeqSep {
         SeqSep { sep: None, trailing_sep_allowed: false }
     }
 }
@@ -285,7 +285,7 @@ pub enum FollowedByType {
 }
 
 #[derive(Copy, Clone, Debug)]
-enum Trailing {
+pub enum Trailing {
     No,
     Yes,
 }
@@ -425,13 +425,13 @@ impl<'a> Parser<'a> {
     }
 
     /// Expects and consumes the token `t`. Signals an error if the next token is not `t`.
-    pub fn expect(&mut self, exp: ExpTokenPair<'_>) -> PResult<'a, Recovered> {
+    pub fn expect(&mut self, exp: ExpTokenPair) -> PResult<'a, Recovered> {
         if self.expected_token_types.is_empty() {
-            if self.token == *exp.tok {
+            if self.token == exp.tok {
                 self.bump();
                 Ok(Recovered::No)
             } else {
-                self.unexpected_try_recover(exp.tok)
+                self.unexpected_try_recover(&exp.tok)
             }
         } else {
             self.expect_one_of(slice::from_ref(&exp), &[])
@@ -443,13 +443,13 @@ impl<'a> Parser<'a> {
     /// anything. Signal a fatal error if next token is unexpected.
     fn expect_one_of(
         &mut self,
-        edible: &[ExpTokenPair<'_>],
-        inedible: &[ExpTokenPair<'_>],
+        edible: &[ExpTokenPair],
+        inedible: &[ExpTokenPair],
     ) -> PResult<'a, Recovered> {
-        if edible.iter().any(|exp| exp.tok == &self.token.kind) {
+        if edible.iter().any(|exp| exp.tok == self.token.kind) {
             self.bump();
             Ok(Recovered::No)
-        } else if inedible.iter().any(|exp| exp.tok == &self.token.kind) {
+        } else if inedible.iter().any(|exp| exp.tok == self.token.kind) {
             // leave it in the input
             Ok(Recovered::No)
         } else if self.token != token::Eof
@@ -494,8 +494,8 @@ impl<'a> Parser<'a> {
     /// This method will automatically add `tok` to `expected_token_types` if `tok` is not
     /// encountered.
     #[inline]
-    fn check(&mut self, exp: ExpTokenPair<'_>) -> bool {
-        let is_present = self.token == *exp.tok;
+    pub fn check(&mut self, exp: ExpTokenPair) -> bool {
+        let is_present = self.token == exp.tok;
         if !is_present {
             self.expected_token_types.insert(exp.token_type);
         }
@@ -542,7 +542,7 @@ impl<'a> Parser<'a> {
     /// Consumes a token 'tok' if it exists. Returns whether the given token was present.
     #[inline]
     #[must_use]
-    pub fn eat(&mut self, exp: ExpTokenPair<'_>) -> bool {
+    pub fn eat(&mut self, exp: ExpTokenPair) -> bool {
         let is_present = self.check(exp);
         if is_present {
             self.bump()
@@ -633,7 +633,7 @@ impl<'a> Parser<'a> {
     }
 
     /// Consume a sequence produced by a metavar expansion, if present.
-    fn eat_metavar_seq<T>(
+    pub fn eat_metavar_seq<T>(
         &mut self,
         mv_kind: MetaVarKind,
         f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
@@ -745,13 +745,13 @@ impl<'a> Parser<'a> {
     /// Eats the expected token if it's present possibly breaking
     /// compound tokens like multi-character operators in process.
     /// Returns `true` if the token was eaten.
-    fn break_and_eat(&mut self, exp: ExpTokenPair<'_>) -> bool {
-        if self.token == *exp.tok {
+    fn break_and_eat(&mut self, exp: ExpTokenPair) -> bool {
+        if self.token == exp.tok {
             self.bump();
             return true;
         }
         match self.token.kind.break_two_token_op(1) {
-            Some((first, second)) if first == *exp.tok => {
+            Some((first, second)) if first == exp.tok => {
                 let first_span = self.psess.source_map().start_point(self.token.span);
                 let second_span = self.token.span.with_lo(first_span.hi());
                 self.token = Token::new(first, first_span);
@@ -826,7 +826,7 @@ impl<'a> Parser<'a> {
     /// Checks if the next token is contained within `closes`, and returns `true` if so.
     fn expect_any_with_type(
         &mut self,
-        closes_expected: &[ExpTokenPair<'_>],
+        closes_expected: &[ExpTokenPair],
         closes_not_expected: &[&TokenKind],
     ) -> bool {
         closes_expected.iter().any(|&close| self.check(close))
@@ -838,9 +838,9 @@ impl<'a> Parser<'a> {
     /// closing bracket.
     fn parse_seq_to_before_tokens<T>(
         &mut self,
-        closes_expected: &[ExpTokenPair<'_>],
+        closes_expected: &[ExpTokenPair],
         closes_not_expected: &[&TokenKind],
-        sep: SeqSep<'_>,
+        sep: SeqSep,
         mut f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
     ) -> PResult<'a, (ThinVec<T>, Trailing, Recovered)> {
         let mut first = true;
@@ -869,7 +869,7 @@ impl<'a> Parser<'a> {
                         }
                         Err(mut expect_err) => {
                             let sp = self.prev_token.span.shrink_to_hi();
-                            let token_str = pprust::token_kind_to_string(exp.tok);
+                            let token_str = pprust::token_kind_to_string(&exp.tok);
 
                             match self.current_closure.take() {
                                 Some(closure_spans) if self.token == TokenKind::Semi => {
@@ -1039,8 +1039,8 @@ impl<'a> Parser<'a> {
     /// closing bracket.
     fn parse_seq_to_before_end<T>(
         &mut self,
-        close: ExpTokenPair<'_>,
-        sep: SeqSep<'_>,
+        close: ExpTokenPair,
+        sep: SeqSep,
         f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
     ) -> PResult<'a, (ThinVec<T>, Trailing, Recovered)> {
         self.parse_seq_to_before_tokens(&[close], &[], sep, f)
@@ -1051,8 +1051,8 @@ impl<'a> Parser<'a> {
     /// closing bracket.
     fn parse_seq_to_end<T>(
         &mut self,
-        close: ExpTokenPair<'_>,
-        sep: SeqSep<'_>,
+        close: ExpTokenPair,
+        sep: SeqSep,
         f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
     ) -> PResult<'a, (ThinVec<T>, Trailing)> {
         let (val, trailing, recovered) = self.parse_seq_to_before_end(close, sep, f)?;
@@ -1070,9 +1070,9 @@ impl<'a> Parser<'a> {
     /// closing bracket.
     fn parse_unspanned_seq<T>(
         &mut self,
-        open: ExpTokenPair<'_>,
-        close: ExpTokenPair<'_>,
-        sep: SeqSep<'_>,
+        open: ExpTokenPair,
+        close: ExpTokenPair,
+        sep: SeqSep,
         f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
     ) -> PResult<'a, (ThinVec<T>, Trailing)> {
         self.expect(open)?;
@@ -1084,8 +1084,8 @@ impl<'a> Parser<'a> {
     /// closing bracket.
     fn parse_delim_comma_seq<T>(
         &mut self,
-        open: ExpTokenPair<'_>,
-        close: ExpTokenPair<'_>,
+        open: ExpTokenPair,
+        close: ExpTokenPair,
         f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
     ) -> PResult<'a, (ThinVec<T>, Trailing)> {
         self.parse_unspanned_seq(open, close, SeqSep::trailing_allowed(exp!(Comma)), f)
@@ -1094,7 +1094,7 @@ impl<'a> Parser<'a> {
     /// Parses a comma-separated sequence delimited by parentheses (e.g. `(x, y)`).
     /// The function `f` must consume tokens until reaching the next separator or
     /// closing bracket.
-    fn parse_paren_comma_seq<T>(
+    pub fn parse_paren_comma_seq<T>(
         &mut self,
         f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
     ) -> PResult<'a, (ThinVec<T>, Trailing)> {
@@ -1355,7 +1355,8 @@ impl<'a> Parser<'a> {
             AttrArgs::Delimited(args)
         } else if self.eat(exp!(Eq)) {
             let eq_span = self.prev_token.span;
-            AttrArgs::Eq { eq_span, expr: self.parse_expr_force_collect()? }
+            let expr = self.parse_expr_force_collect()?;
+            AttrArgs::Eq { eq_span, expr }
         } else {
             AttrArgs::Empty
         })
@@ -1388,15 +1389,26 @@ impl<'a> Parser<'a> {
             // matching `CloseDelim` we are *after* the delimited sequence,
             // i.e. at depth `d - 1`.
             let target_depth = self.token_cursor.stack.len() - 1;
-            loop {
-                // Advance one token at a time, so `TokenCursor::next()`
-                // can capture these tokens if necessary.
+
+            if let Capturing::No = self.capture_state.capturing {
+                // We are not capturing tokens, so skip to the end of the
+                // delimited sequence. This is a perf win when dealing with
+                // declarative macros that pass large `tt` fragments through
+                // multiple rules, as seen in the uom-0.37.0 crate.
+                self.token_cursor.curr.bump_to_end();
                 self.bump();
-                if self.token_cursor.stack.len() == target_depth {
-                    debug_assert!(self.token.kind.close_delim().is_some());
-                    break;
+                debug_assert_eq!(self.token_cursor.stack.len(), target_depth);
+            } else {
+                loop {
+                    // Advance one token at a time, so `TokenCursor::next()`
+                    // can capture these tokens if necessary.
+                    self.bump();
+                    if self.token_cursor.stack.len() == target_depth {
+                        break;
+                    }
                 }
             }
+            debug_assert!(self.token.kind.close_delim().is_some());
 
             // Consume close delimiter
             self.bump();
diff --git a/compiler/rustc_parse/src/parser/path.rs b/compiler/rustc_parse/src/parser/path.rs
index 37fc723cd89..86045648859 100644
--- a/compiler/rustc_parse/src/parser/path.rs
+++ b/compiler/rustc_parse/src/parser/path.rs
@@ -26,7 +26,7 @@ use crate::parser::{
 
 /// Specifies how to parse a path.
 #[derive(Copy, Clone, PartialEq)]
-pub(super) enum PathStyle {
+pub enum PathStyle {
     /// In some contexts, notably in expressions, paths with generic arguments are ambiguous
     /// with something else. For example, in expressions `segment < ....` can be interpreted
     /// as a comparison and `segment ( ....` can be interpreted as a function call.
@@ -150,7 +150,7 @@ impl<'a> Parser<'a> {
         true
     }
 
-    pub(super) fn parse_path(&mut self, style: PathStyle) -> PResult<'a, Path> {
+    pub fn parse_path(&mut self, style: PathStyle) -> PResult<'a, Path> {
         self.parse_path_inner(style, None)
     }
 
diff --git a/compiler/rustc_parse/src/parser/token_type.rs b/compiler/rustc_parse/src/parser/token_type.rs
index b91548196a3..bd4bb368df0 100644
--- a/compiler/rustc_parse/src/parser/token_type.rs
+++ b/compiler/rustc_parse/src/parser/token_type.rs
@@ -416,8 +416,8 @@ impl TokenType {
 /// is always by used those methods. The second field is only used when the
 /// first field doesn't match.
 #[derive(Clone, Copy, Debug)]
-pub struct ExpTokenPair<'a> {
-    pub tok: &'a TokenKind,
+pub struct ExpTokenPair {
+    pub tok: TokenKind,
     pub token_type: TokenType,
 }
 
@@ -444,7 +444,7 @@ macro_rules! exp {
     // `ExpTokenPair` helper rules.
     (@tok, $tok:ident) => {
         $crate::parser::token_type::ExpTokenPair {
-            tok: &rustc_ast::token::$tok,
+            tok: rustc_ast::token::$tok,
             token_type: $crate::parser::token_type::TokenType::$tok
         }
     };
diff --git a/compiler/rustc_parse/src/parser/ty.rs b/compiler/rustc_parse/src/parser/ty.rs
index 290f0a440af..6168647183f 100644
--- a/compiler/rustc_parse/src/parser/ty.rs
+++ b/compiler/rustc_parse/src/parser/ty.rs
@@ -137,14 +137,37 @@ impl<'a> Parser<'a> {
     /// The difference from `parse_ty` is that this version allows `...`
     /// (`CVarArgs`) at the top level of the type.
     pub(super) fn parse_ty_for_param(&mut self) -> PResult<'a, Box<Ty>> {
-        self.parse_ty_common(
+        let ty = self.parse_ty_common(
             AllowPlus::Yes,
             AllowCVariadic::Yes,
             RecoverQPath::Yes,
             RecoverReturnSign::Yes,
             None,
             RecoverQuestionMark::Yes,
-        )
+        )?;
+
+        // Recover a trailing `= EXPR` if present.
+        if self.may_recover()
+            && self.check_noexpect(&token::Eq)
+            && self.look_ahead(1, |tok| tok.can_begin_expr())
+        {
+            let snapshot = self.create_snapshot_for_diagnostic();
+            self.bump();
+            let eq_span = self.prev_token.span;
+            match self.parse_expr() {
+                Ok(e) => {
+                    self.dcx()
+                        .struct_span_err(eq_span.to(e.span), "parameter defaults are not supported")
+                        .emit();
+                }
+                Err(diag) => {
+                    diag.cancel();
+                    self.restore_snapshot(snapshot);
+                }
+            }
+        }
+
+        Ok(ty)
     }
 
     /// Parses a type in restricted contexts where `+` is not permitted.
@@ -308,11 +331,11 @@ impl<'a> Parser<'a> {
             // Function pointer type or bound list (trait object type) starting with a poly-trait.
             //   `for<'lt> [unsafe] [extern "ABI"] fn (&'lt S) -> T`
             //   `for<'lt> Trait1<'lt> + Trait2 + 'a`
-            let (lifetime_defs, _) = self.parse_late_bound_lifetime_defs()?;
+            let (bound_vars, _) = self.parse_higher_ranked_binder()?;
             if self.check_fn_front_matter(false, Case::Sensitive) {
                 self.parse_ty_fn_ptr(
                     lo,
-                    lifetime_defs,
+                    bound_vars,
                     Some(self.prev_token.span.shrink_to_lo()),
                     recover_return_sign,
                 )?
@@ -326,7 +349,7 @@ impl<'a> Parser<'a> {
                     let path = self.parse_path(PathStyle::Type)?;
                     let parse_plus = allow_plus == AllowPlus::Yes && self.check_plus();
                     let kind = self.parse_remaining_bounds_path(
-                        lifetime_defs,
+                        bound_vars,
                         path,
                         lo,
                         parse_plus,
@@ -359,7 +382,7 @@ impl<'a> Parser<'a> {
                     let path = self.parse_path(PathStyle::Type)?;
                     let parse_plus = allow_plus == AllowPlus::Yes && self.check_plus();
                     self.parse_remaining_bounds_path(
-                        lifetime_defs,
+                        bound_vars,
                         path,
                         lo,
                         parse_plus,
@@ -443,7 +466,7 @@ impl<'a> Parser<'a> {
             let ty = ts.into_iter().next().unwrap();
             let maybe_bounds = allow_plus == AllowPlus::Yes && self.token.is_like_plus();
             match ty.kind {
-                // `(TY_BOUND_NOPAREN) + BOUND + ...`.
+                // `"(" BareTraitBound ")" "+" Bound "+" ...`.
                 TyKind::Path(None, path) if maybe_bounds => self.parse_remaining_bounds_path(
                     ThinVec::new(),
                     path,
@@ -853,10 +876,13 @@ impl<'a> Parser<'a> {
         Ok(TyKind::ImplTrait(ast::DUMMY_NODE_ID, bounds))
     }
 
-    fn parse_precise_capturing_args(
-        &mut self,
-    ) -> PResult<'a, (ThinVec<PreciseCapturingArg>, Span)> {
-        let lo = self.token.span;
+    /// Parse a use-bound aka precise capturing list.
+    ///
+    /// ```ebnf
+    /// UseBound = "use" "<" (PreciseCapture ("," PreciseCapture)* ","?)? ">"
+    /// PreciseCapture = "Self" | Ident | Lifetime
+    /// ```
+    fn parse_use_bound(&mut self, lo: Span, parens: ast::Parens) -> PResult<'a, GenericBound> {
         self.expect_lt()?;
         let (args, _, _) = self.parse_seq_to_before_tokens(
             &[exp!(Gt)],
@@ -882,7 +908,13 @@ impl<'a> Parser<'a> {
             },
         )?;
         self.expect_gt()?;
-        Ok((args, lo.to(self.prev_token.span)))
+
+        if let ast::Parens::Yes = parens {
+            self.expect(exp!(CloseParen))?;
+            self.report_parenthesized_bound(lo, self.prev_token.span, "precise capturing lists");
+        }
+
+        Ok(GenericBound::Use(args, lo.to(self.prev_token.span)))
     }
 
     /// Is a `dyn B0 + ... + Bn` type allowed here?
@@ -940,9 +972,10 @@ impl<'a> Parser<'a> {
         self.parse_generic_bounds_common(AllowPlus::Yes)
     }
 
-    /// Parses bounds of a type parameter `BOUND + BOUND + ...`, possibly with trailing `+`.
+    /// Parse generic bounds.
     ///
-    /// See `parse_generic_bound` for the `BOUND` grammar.
+    /// Only if `allow_plus` this parses a `+`-separated list of bounds (trailing `+` is admitted).
+    /// Otherwise, this only parses a single bound or none.
     fn parse_generic_bounds_common(&mut self, allow_plus: AllowPlus) -> PResult<'a, GenericBounds> {
         let mut bounds = Vec::new();
 
@@ -988,48 +1021,56 @@ impl<'a> Parser<'a> {
             || self.check_keyword(exp!(Use))
     }
 
-    /// Parses a bound according to the grammar:
+    /// Parse a bound.
+    ///
     /// ```ebnf
-    /// BOUND = TY_BOUND | LT_BOUND
+    /// Bound = LifetimeBound | UseBound | TraitBound
     /// ```
     fn parse_generic_bound(&mut self) -> PResult<'a, GenericBound> {
-        let lo = self.token.span;
         let leading_token = self.prev_token;
+        let lo = self.token.span;
+
+        // We only admit parenthesized *trait* bounds. However, we want to gracefully recover from
+        // other kinds of parenthesized bounds, so parse the opening parenthesis *here*.
+        //
+        // In the future we might want to lift this syntactic restriction and
+        // introduce "`GenericBound::Paren(Box<GenericBound>)`".
         let parens = if self.eat(exp!(OpenParen)) { ast::Parens::Yes } else { ast::Parens::No };
 
-        let bound = if self.token.is_lifetime() {
-            self.parse_generic_lt_bound(lo, parens)?
+        if self.token.is_lifetime() {
+            self.parse_lifetime_bound(lo, parens)
         } else if self.eat_keyword(exp!(Use)) {
-            // parse precise captures, if any. This is `use<'lt, 'lt, P, P>`; a list of
-            // lifetimes and ident params (including SelfUpper). These are validated later
-            // for order, duplication, and whether they actually reference params.
-            let use_span = self.prev_token.span;
-            let (args, args_span) = self.parse_precise_capturing_args()?;
-            GenericBound::Use(args, use_span.to(args_span))
+            self.parse_use_bound(lo, parens)
         } else {
-            self.parse_generic_ty_bound(lo, parens, &leading_token)?
-        };
-
-        Ok(bound)
+            self.parse_trait_bound(lo, parens, &leading_token)
+        }
     }
 
-    /// Parses a lifetime ("outlives") bound, e.g. `'a`, according to:
+    /// Parse a lifetime-bound aka outlives-bound.
+    ///
     /// ```ebnf
-    /// LT_BOUND = LIFETIME
+    /// LifetimeBound = Lifetime
     /// ```
-    fn parse_generic_lt_bound(
-        &mut self,
-        lo: Span,
-        parens: ast::Parens,
-    ) -> PResult<'a, GenericBound> {
+    fn parse_lifetime_bound(&mut self, lo: Span, parens: ast::Parens) -> PResult<'a, GenericBound> {
         let lt = self.expect_lifetime();
-        let bound = GenericBound::Outlives(lt);
+
         if let ast::Parens::Yes = parens {
-            // FIXME(Centril): Consider not erroring here and accepting `('lt)` instead,
-            // possibly introducing `GenericBound::Paren(Box<GenericBound>)`?
-            self.recover_paren_lifetime(lo)?;
+            self.expect(exp!(CloseParen))?;
+            self.report_parenthesized_bound(lo, self.prev_token.span, "lifetime bounds");
         }
-        Ok(bound)
+
+        Ok(GenericBound::Outlives(lt))
+    }
+
+    fn report_parenthesized_bound(&self, lo: Span, hi: Span, kind: &str) -> ErrorGuaranteed {
+        let mut diag =
+            self.dcx().struct_span_err(lo.to(hi), format!("{kind} may not be parenthesized"));
+        diag.multipart_suggestion(
+            "remove the parentheses",
+            vec![(lo, String::new()), (hi, String::new())],
+            Applicability::MachineApplicable,
+        );
+        diag.emit()
     }
 
     /// Emits an error if any trait bound modifiers were present.
@@ -1074,27 +1115,17 @@ impl<'a> Parser<'a> {
         unreachable!("lifetime bound intercepted in `parse_generic_ty_bound` but no modifiers?")
     }
 
-    /// Recover on `('lifetime)` with `(` already eaten.
-    fn recover_paren_lifetime(&mut self, lo: Span) -> PResult<'a, ()> {
-        self.expect(exp!(CloseParen))?;
-        let span = lo.to(self.prev_token.span);
-        let sugg = errors::RemoveParens { lo, hi: self.prev_token.span };
-
-        self.dcx().emit_err(errors::ParenthesizedLifetime { span, sugg });
-        Ok(())
-    }
-
     /// Parses the modifiers that may precede a trait in a bound, e.g. `?Trait` or `[const] Trait`.
     ///
     /// If no modifiers are present, this does not consume any tokens.
     ///
     /// ```ebnf
-    /// CONSTNESS = [["["] "const" ["]"]]
-    /// ASYNCNESS = ["async"]
-    /// POLARITY = ["?" | "!"]
+    /// Constness = ("const" | "[" "const" "]")?
+    /// Asyncness = "async"?
+    /// Polarity = ("?" | "!")?
     /// ```
     ///
-    /// See `parse_generic_ty_bound` for the complete grammar of trait bound modifiers.
+    /// See `parse_trait_bound` for more context.
     fn parse_trait_bound_modifiers(&mut self) -> PResult<'a, TraitBoundModifiers> {
         let modifier_lo = self.token.span;
         let constness = self.parse_bound_constness()?;
@@ -1187,20 +1218,21 @@ impl<'a> Parser<'a> {
         })
     }
 
-    /// Parses a type bound according to:
+    /// Parse a trait bound.
+    ///
     /// ```ebnf
-    /// TY_BOUND = TY_BOUND_NOPAREN | (TY_BOUND_NOPAREN)
-    /// TY_BOUND_NOPAREN = [for<GENERIC_PARAMS> CONSTNESS ASYNCNESS | POLARITY] SIMPLE_PATH
+    /// TraitBound = BareTraitBound | "(" BareTraitBound ")"
+    /// BareTraitBound =
+    ///     (HigherRankedBinder Constness Asyncness | Polarity)
+    ///     TypePath
     /// ```
-    ///
-    /// For example, this grammar accepts `for<'a: 'b> [const] ?m::Trait<'a>`.
-    fn parse_generic_ty_bound(
+    fn parse_trait_bound(
         &mut self,
         lo: Span,
         parens: ast::Parens,
         leading_token: &Token,
     ) -> PResult<'a, GenericBound> {
-        let (mut lifetime_defs, binder_span) = self.parse_late_bound_lifetime_defs()?;
+        let (mut bound_vars, binder_span) = self.parse_higher_ranked_binder()?;
 
         let modifiers_lo = self.token.span;
         let modifiers = self.parse_trait_bound_modifiers()?;
@@ -1223,11 +1255,11 @@ impl<'a> Parser<'a> {
         // e.g. `T: for<'a> 'a` or `T: [const] 'a`.
         if self.token.is_lifetime() {
             let _: ErrorGuaranteed = self.error_lt_bound_with_modifiers(modifiers, binder_span);
-            return self.parse_generic_lt_bound(lo, parens);
+            return self.parse_lifetime_bound(lo, parens);
         }
 
-        if let (more_lifetime_defs, Some(binder_span)) = self.parse_late_bound_lifetime_defs()? {
-            lifetime_defs.extend(more_lifetime_defs);
+        if let (more_bound_vars, Some(binder_span)) = self.parse_higher_ranked_binder()? {
+            bound_vars.extend(more_bound_vars);
             self.dcx().emit_err(errors::BinderBeforeModifiers { binder_span, modifiers_span });
         }
 
@@ -1287,7 +1319,7 @@ impl<'a> Parser<'a> {
         };
 
         if self.may_recover() && self.token == TokenKind::OpenParen {
-            self.recover_fn_trait_with_lifetime_params(&mut path, &mut lifetime_defs)?;
+            self.recover_fn_trait_with_lifetime_params(&mut path, &mut bound_vars)?;
         }
 
         if let ast::Parens::Yes = parens {
@@ -1310,7 +1342,7 @@ impl<'a> Parser<'a> {
         }
 
         let poly_trait =
-            PolyTraitRef::new(lifetime_defs, path, modifiers, lo.to(self.prev_token.span), parens);
+            PolyTraitRef::new(bound_vars, path, modifiers, lo.to(self.prev_token.span), parens);
         Ok(GenericBound::Trait(poly_trait))
     }
 
@@ -1349,8 +1381,12 @@ impl<'a> Parser<'a> {
         }
     }
 
-    /// Optionally parses `for<$generic_params>`.
-    pub(super) fn parse_late_bound_lifetime_defs(
+    /// Parse an optional higher-ranked binder.
+    ///
+    /// ```ebnf
+    /// HigherRankedBinder = ("for" "<" GenericParams ">")?
+    /// ```
+    pub(super) fn parse_higher_ranked_binder(
         &mut self,
     ) -> PResult<'a, (ThinVec<GenericParam>, Option<Span>)> {
         if self.eat_keyword(exp!(For)) {
@@ -1466,8 +1502,7 @@ impl<'a> Parser<'a> {
     pub(super) fn expect_lifetime(&mut self) -> Lifetime {
         if let Some((ident, is_raw)) = self.token.lifetime() {
             if matches!(is_raw, IdentIsRaw::No)
-                && ident.without_first_quote().is_reserved()
-                && ![kw::UnderscoreLifetime, kw::StaticLifetime].contains(&ident.name)
+                && ident.without_first_quote().is_reserved_lifetime()
             {
                 self.dcx().emit_err(errors::KeywordLifetime { span: ident.span });
             }
diff --git a/compiler/rustc_passes/messages.ftl b/compiler/rustc_passes/messages.ftl
index 03096f205c6..00a41e31a02 100644
--- a/compiler/rustc_passes/messages.ftl
+++ b/compiler/rustc_passes/messages.ftl
@@ -432,10 +432,6 @@ passes_must_not_suspend =
     `must_not_suspend` attribute should be applied to a struct, enum, union, or trait
     .label = is not a struct, enum, union, or trait
 
-passes_must_use_no_effect =
-    `#[must_use]` has no effect when applied to {$target}
-    .suggestion = remove the attribute
-
 passes_no_link =
     attribute should be applied to an `extern crate` item
     .label = not an `extern crate` item
diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs
index c1a212d7ab5..7aef60b7b91 100644
--- a/compiler/rustc_passes/src/check_attr.rs
+++ b/compiler/rustc_passes/src/check_attr.rs
@@ -18,7 +18,7 @@ use rustc_feature::{
     ACCEPTED_LANG_FEATURES, AttributeDuplicates, AttributeType, BUILTIN_ATTRIBUTE_MAP,
     BuiltinAttribute,
 };
-use rustc_hir::attrs::{AttributeKind, InlineAttr, MirDialect, MirPhase, ReprAttr};
+use rustc_hir::attrs::{AttributeKind, InlineAttr, MirDialect, MirPhase, ReprAttr, SanitizerSet};
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::LocalModDefId;
 use rustc_hir::intravisit::{self, Visitor};
@@ -167,7 +167,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                 Attribute::Parsed(AttributeKind::Deprecation { .. }) => {
                     self.check_deprecated(hir_id, attr, span, target)
                 }
-                Attribute::Parsed(AttributeKind::TargetFeature(_, attr_span)) => {
+                Attribute::Parsed(AttributeKind::TargetFeature{ attr_span, ..}) => {
                     self.check_target_feature(hir_id, *attr_span, target, attrs)
                 }
                 Attribute::Parsed(AttributeKind::RustcObjectLifetimeDefault) => {
@@ -194,12 +194,12 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                 Attribute::Parsed(AttributeKind::MayDangle(attr_span)) => {
                     self.check_may_dangle(hir_id, *attr_span)
                 }
-                Attribute::Parsed(AttributeKind::MustUse { span, .. }) => {
-                    self.check_must_use(hir_id, *span, target)
-                }
                 &Attribute::Parsed(AttributeKind::CustomMir(dialect, phase, attr_span)) => {
                     self.check_custom_mir(dialect, phase, attr_span)
                 }
+                &Attribute::Parsed(AttributeKind::Sanitize { on_set, off_set, span: attr_span}) => {
+                    self.check_sanitize(attr_span, on_set | off_set, span, target);
+                },
                 Attribute::Parsed(
                     AttributeKind::BodyStability { .. }
                     | AttributeKind::ConstStabilityIndirect
@@ -249,7 +249,9 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                     | AttributeKind::Coverage (..)
                     | AttributeKind::ShouldPanic { .. }
                     | AttributeKind::Coroutine(..)
-                    | AttributeKind::Linkage(..),
+                    | AttributeKind::Linkage(..)
+                    | AttributeKind::MustUse { .. }
+                    | AttributeKind::CrateName { .. }
                 ) => { /* do nothing  */ }
                 Attribute::Unparsed(attr_item) => {
                     style = Some(attr_item.style);
@@ -260,9 +262,6 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                         [sym::diagnostic, sym::on_unimplemented, ..] => {
                             self.check_diagnostic_on_unimplemented(attr.span(), hir_id, target)
                         }
-                        [sym::sanitize, ..] => {
-                            self.check_sanitize(attr, span, target)
-                        }
                         [sym::thread_local, ..] => self.check_thread_local(attr, span, target),
                         [sym::doc, ..] => self.check_doc_attrs(
                             attr,
@@ -369,22 +368,49 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
             let builtin = attr.ident().and_then(|ident| BUILTIN_ATTRIBUTE_MAP.get(&ident.name));
 
             if hir_id != CRATE_HIR_ID {
-                if let Some(BuiltinAttribute { type_: AttributeType::CrateLevel, .. }) =
-                    attr.ident().and_then(|ident| BUILTIN_ATTRIBUTE_MAP.get(&ident.name))
-                {
-                    match style {
-                        Some(ast::AttrStyle::Outer) => self.tcx.emit_node_span_lint(
+                match attr {
+                    // FIXME(jdonszelmann) move to attribute parsing when validation gets better there
+                    &Attribute::Parsed(AttributeKind::CrateName {
+                        attr_span: span, style, ..
+                    }) => match style {
+                        ast::AttrStyle::Outer => self.tcx.emit_node_span_lint(
                             UNUSED_ATTRIBUTES,
                             hir_id,
-                            attr.span(),
+                            span,
                             errors::OuterCrateLevelAttr,
                         ),
-                        Some(ast::AttrStyle::Inner) | None => self.tcx.emit_node_span_lint(
+                        ast::AttrStyle::Inner => self.tcx.emit_node_span_lint(
                             UNUSED_ATTRIBUTES,
                             hir_id,
-                            attr.span(),
+                            span,
                             errors::InnerCrateLevelAttr,
                         ),
+                    },
+                    Attribute::Parsed(_) => { /* not crate-level */ }
+                    Attribute::Unparsed(attr) => {
+                        // FIXME(jdonszelmann): remove once all crate-level attrs are parsed and caught by
+                        // the above
+                        if let Some(BuiltinAttribute { type_: AttributeType::CrateLevel, .. }) =
+                            attr.path
+                                .segments
+                                .first()
+                                .and_then(|ident| BUILTIN_ATTRIBUTE_MAP.get(&ident.name))
+                        {
+                            match attr.style {
+                                ast::AttrStyle::Outer => self.tcx.emit_node_span_lint(
+                                    UNUSED_ATTRIBUTES,
+                                    hir_id,
+                                    attr.span,
+                                    errors::OuterCrateLevelAttr,
+                                ),
+                                ast::AttrStyle::Inner => self.tcx.emit_node_span_lint(
+                                    UNUSED_ATTRIBUTES,
+                                    hir_id,
+                                    attr.span,
+                                    errors::InnerCrateLevelAttr,
+                                ),
+                            }
+                        }
                     }
                 }
             }
@@ -485,42 +511,48 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
 
     /// Checks that the `#[sanitize(..)]` attribute is applied to a
     /// function/closure/method, or to an impl block or module.
-    fn check_sanitize(&self, attr: &Attribute, target_span: Span, target: Target) {
+    fn check_sanitize(
+        &self,
+        attr_span: Span,
+        set: SanitizerSet,
+        target_span: Span,
+        target: Target,
+    ) {
         let mut not_fn_impl_mod = None;
         let mut no_body = None;
 
-        if let Some(list) = attr.meta_item_list() {
-            for item in list.iter() {
-                let MetaItemInner::MetaItem(set) = item else {
-                    return;
-                };
-                let segments = set.path.segments.iter().map(|x| x.ident.name).collect::<Vec<_>>();
-                match target {
-                    Target::Fn
-                    | Target::Closure
-                    | Target::Method(MethodKind::Trait { body: true } | MethodKind::Inherent)
-                    | Target::Impl { .. }
-                    | Target::Mod => return,
-                    Target::Static if matches!(segments.as_slice(), [sym::address]) => return,
-
-                    // These are "functions", but they aren't allowed because they don't
-                    // have a body, so the usual explanation would be confusing.
-                    Target::Method(MethodKind::Trait { body: false }) | Target::ForeignFn => {
-                        no_body = Some(target_span);
-                    }
+        match target {
+            Target::Fn
+            | Target::Closure
+            | Target::Method(MethodKind::Trait { body: true } | MethodKind::Inherent)
+            | Target::Impl { .. }
+            | Target::Mod => return,
+            Target::Static
+                // if we mask out the address bits, i.e. *only* address was set,
+                // we allow it
+                if set & !(SanitizerSet::ADDRESS | SanitizerSet::KERNELADDRESS)
+                    == SanitizerSet::empty() =>
+            {
+                return;
+            }
 
-                    _ => {
-                        not_fn_impl_mod = Some(target_span);
-                    }
-                }
+            // These are "functions", but they aren't allowed because they don't
+            // have a body, so the usual explanation would be confusing.
+            Target::Method(MethodKind::Trait { body: false }) | Target::ForeignFn => {
+                no_body = Some(target_span);
+            }
+
+            _ => {
+                not_fn_impl_mod = Some(target_span);
             }
-            self.dcx().emit_err(errors::SanitizeAttributeNotAllowed {
-                attr_span: attr.span(),
-                not_fn_impl_mod,
-                no_body,
-                help: (),
-            });
         }
+
+        self.dcx().emit_err(errors::SanitizeAttributeNotAllowed {
+            attr_span,
+            not_fn_impl_mod,
+            no_body,
+            help: (),
+        });
     }
 
     /// Checks if `#[naked]` is applied to a function definition.
@@ -1263,41 +1295,6 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
         }
     }
 
-    /// Warns against some misuses of `#[must_use]`
-    fn check_must_use(&self, hir_id: HirId, attr_span: Span, target: Target) {
-        if matches!(
-            target,
-            Target::Fn
-                | Target::Enum
-                | Target::Struct
-                | Target::Union
-                | Target::Method(MethodKind::Trait { body: false } | MethodKind::Inherent)
-                | Target::ForeignFn
-                // `impl Trait` in return position can trip
-                // `unused_must_use` if `Trait` is marked as
-                // `#[must_use]`
-                | Target::Trait
-        ) {
-            return;
-        }
-
-        // `#[must_use]` can be applied to a trait method definition with a default body
-        if let Target::Method(MethodKind::Trait { body: true }) = target
-            && let parent_def_id = self.tcx.hir_get_parent_item(hir_id).def_id
-            && let containing_item = self.tcx.hir_expect_item(parent_def_id)
-            && let hir::ItemKind::Trait(..) = containing_item.kind
-        {
-            return;
-        }
-
-        self.tcx.emit_node_span_lint(
-            UNUSED_ATTRIBUTES,
-            hir_id,
-            attr_span,
-            errors::MustUseNoEffect { target: target.plural_name(), attr_span },
-        );
-    }
-
     /// Checks if `#[must_not_suspend]` is applied to a struct, enum, union, or trait.
     fn check_must_not_suspend(&self, attr: &Attribute, span: Span, target: Target) {
         match target {
diff --git a/compiler/rustc_passes/src/dead.rs b/compiler/rustc_passes/src/dead.rs
index 08d06402000..10cd9df4816 100644
--- a/compiler/rustc_passes/src/dead.rs
+++ b/compiler/rustc_passes/src/dead.rs
@@ -8,7 +8,6 @@ use std::mem;
 use hir::def_id::{LocalDefIdMap, LocalDefIdSet};
 use rustc_abi::FieldIdx;
 use rustc_data_structures::fx::FxIndexSet;
-use rustc_data_structures::unord::UnordSet;
 use rustc_errors::MultiSpan;
 use rustc_hir::def::{CtorOf, DefKind, Res};
 use rustc_hir::def_id::{DefId, LocalDefId, LocalModDefId};
@@ -79,7 +78,7 @@ struct MarkSymbolVisitor<'tcx> {
     worklist: Vec<(LocalDefId, ComesFromAllowExpect)>,
     tcx: TyCtxt<'tcx>,
     maybe_typeck_results: Option<&'tcx ty::TypeckResults<'tcx>>,
-    scanned: UnordSet<(LocalDefId, ComesFromAllowExpect)>,
+    scanned: LocalDefIdSet,
     live_symbols: LocalDefIdSet,
     repr_unconditionally_treats_fields_as_live: bool,
     repr_has_repr_simd: bool,
@@ -321,18 +320,8 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {
 
     fn mark_live_symbols(&mut self) {
         while let Some(work) = self.worklist.pop() {
-            if !self.scanned.insert(work) {
-                continue;
-            }
-
             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()) {
-                self.live_symbols.insert(id);
-                continue;
-            }
-
             // 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) {
@@ -360,9 +349,23 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {
             // this "duplication" is essential as otherwise a function with `#[expect]`
             // called from a `pub fn` may be falsely reported as not live, falsely
             // triggering the `unfulfilled_lint_expectations` lint.
-            if comes_from_allow_expect != ComesFromAllowExpect::Yes {
+            match comes_from_allow_expect {
+                ComesFromAllowExpect::Yes => {}
+                ComesFromAllowExpect::No => {
+                    self.live_symbols.insert(id);
+                }
+            }
+
+            if !self.scanned.insert(id) {
+                continue;
+            }
+
+            // Avoid accessing the HIR for the synthesized associated type generated for RPITITs.
+            if self.tcx.is_impl_trait_in_trait(id.to_def_id()) {
                 self.live_symbols.insert(id);
+                continue;
             }
+
             self.visit_node(self.tcx.hir_node_by_def_id(id));
         }
     }
diff --git a/compiler/rustc_passes/src/errors.rs b/compiler/rustc_passes/src/errors.rs
index ab46ac2dd8b..4fec6b0798a 100644
--- a/compiler/rustc_passes/src/errors.rs
+++ b/compiler/rustc_passes/src/errors.rs
@@ -358,14 +358,6 @@ pub(crate) struct BothFfiConstAndPure {
     pub attr_span: Span,
 }
 
-#[derive(LintDiagnostic)]
-#[diag(passes_must_use_no_effect)]
-pub(crate) struct MustUseNoEffect {
-    pub target: &'static str,
-    #[suggestion(code = "", applicability = "machine-applicable", style = "tool-only")]
-    pub attr_span: Span,
-}
-
 #[derive(Diagnostic)]
 #[diag(passes_must_not_suspend)]
 pub(crate) struct MustNotSuspend {
diff --git a/compiler/rustc_pattern_analysis/src/rustc/print.rs b/compiler/rustc_pattern_analysis/src/rustc/print.rs
index 7649f72f868..cdf62c2553d 100644
--- a/compiler/rustc_pattern_analysis/src/rustc/print.rs
+++ b/compiler/rustc_pattern_analysis/src/rustc/print.rs
@@ -101,23 +101,11 @@ pub(crate) fn write_struct_like<'tcx>(
     let num_fields = variant_and_name.as_ref().map_or(subpatterns.len(), |(v, _)| v.fields.len());
     if num_fields != 0 || variant_and_name.is_none() {
         write!(f, "(")?;
-        for i in 0..num_fields {
-            write!(f, "{}", start_or_comma())?;
-
-            // Common case: the field is where we expect it.
-            if let Some(p) = subpatterns.get(i) {
-                if p.field.index() == i {
-                    write!(f, "{}", p.pattern)?;
-                    continue;
-                }
-            }
-
-            // Otherwise, we have to go looking for it.
-            if let Some(p) = subpatterns.iter().find(|p| p.field.index() == i) {
-                write!(f, "{}", p.pattern)?;
-            } else {
-                write!(f, "_")?;
-            }
+        for FieldPat { pattern, .. } in subpatterns {
+            write!(f, "{}{pattern}", start_or_comma())?;
+        }
+        if matches!(ty.kind(), ty::Tuple(..)) && num_fields == 1 {
+            write!(f, ",")?;
         }
         write!(f, ")")?;
     }
diff --git a/compiler/rustc_resolve/messages.ftl b/compiler/rustc_resolve/messages.ftl
index 05b5abc3dc6..47280a93677 100644
--- a/compiler/rustc_resolve/messages.ftl
+++ b/compiler/rustc_resolve/messages.ftl
@@ -93,6 +93,9 @@ resolve_consider_adding_a_derive =
 resolve_consider_adding_macro_export =
     consider adding a `#[macro_export]` to the macro in the imported module
 
+resolve_consider_marking_as_pub_crate =
+    in case you want to use the macro within this crate only, reduce the visibility to `pub(crate)`
+
 resolve_consider_declaring_with_pub =
     consider declaring type or module `{$ident}` with `pub`
 
diff --git a/compiler/rustc_resolve/src/build_reduced_graph.rs b/compiler/rustc_resolve/src/build_reduced_graph.rs
index 2f1c9fe4c1d..f75a625a279 100644
--- a/compiler/rustc_resolve/src/build_reduced_graph.rs
+++ b/compiler/rustc_resolve/src/build_reduced_graph.rs
@@ -11,7 +11,7 @@ use std::sync::Arc;
 use rustc_ast::visit::{self, AssocCtxt, Visitor, WalkItemKind};
 use rustc_ast::{
     self as ast, AssocItem, AssocItemKind, Block, ConstItem, Delegation, Fn, ForeignItem,
-    ForeignItemKind, Item, ItemKind, NodeId, StaticItem, StmtKind, TyAlias,
+    ForeignItemKind, Inline, Item, ItemKind, NodeId, StaticItem, StmtKind, TyAlias,
 };
 use rustc_attr_parsing as attr;
 use rustc_attr_parsing::AttributeParser;
@@ -485,6 +485,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
             root_span,
             root_id,
             vis,
+            vis_span: item.vis.span,
         });
 
         self.r.indeterminate_imports.push(import);
@@ -812,7 +813,8 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
             ItemKind::Mod(_, ident, ref mod_kind) => {
                 self.r.define_local(parent, ident, TypeNS, res, vis, sp, expansion);
 
-                if let ast::ModKind::Loaded(_, _, _, Err(_)) = mod_kind {
+                if let ast::ModKind::Loaded(_, Inline::No { had_parse_error: Err(_) }, _) = mod_kind
+                {
                     self.r.mods_with_parse_errors.insert(def_id);
                 }
                 self.parent_scope.module = self.r.new_local_module(
@@ -977,6 +979,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
             span: item.span,
             module_path: Vec::new(),
             vis,
+            vis_span: item.vis.span,
         });
         if used {
             self.r.import_use_map.insert(import, Used::Other);
@@ -1111,6 +1114,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
                 span,
                 module_path: Vec::new(),
                 vis: Visibility::Restricted(CRATE_DEF_ID),
+                vis_span: item.vis.span,
             })
         };
 
@@ -1281,6 +1285,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
                     span,
                     module_path: Vec::new(),
                     vis,
+                    vis_span: item.vis.span,
                 });
                 self.r.import_use_map.insert(import, Used::Other);
                 let import_binding = self.r.import(binding, import);
diff --git a/compiler/rustc_resolve/src/diagnostics.rs b/compiler/rustc_resolve/src/diagnostics.rs
index ff39ba46d97..337e7d2dd86 100644
--- a/compiler/rustc_resolve/src/diagnostics.rs
+++ b/compiler/rustc_resolve/src/diagnostics.rs
@@ -1020,11 +1020,11 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         &mut self,
         suggestions: &mut Vec<TypoSuggestion>,
         scope_set: ScopeSet<'ra>,
-        parent_scope: &ParentScope<'ra>,
+        ps: &ParentScope<'ra>,
         ctxt: SyntaxContext,
         filter_fn: &impl Fn(Res) -> bool,
     ) {
-        self.cm().visit_scopes(scope_set, parent_scope, ctxt, |this, scope, use_prelude, _| {
+        self.cm().visit_scopes(scope_set, ps, ctxt, None, |this, scope, use_prelude, _| {
             match scope {
                 Scope::DeriveHelpers(expn_id) => {
                     let res = Res::NonMacroAttr(NonMacroAttrKind::DeriveHelper);
@@ -1557,7 +1557,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             });
         }
         for ns in [Namespace::MacroNS, Namespace::TypeNS, Namespace::ValueNS] {
-            let Ok(binding) = self.cm().early_resolve_ident_in_lexical_scope(
+            let Ok(binding) = self.cm().resolve_ident_in_scope_set(
                 ident,
                 ScopeSet::All(ns),
                 parent_scope,
@@ -2371,7 +2371,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                     }
                 } else {
                     self.cm()
-                        .early_resolve_ident_in_lexical_scope(
+                        .resolve_ident_in_scope_set(
                             ident,
                             ScopeSet::All(ns_to_try),
                             parent_scope,
@@ -2474,7 +2474,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                     },
                 )
             });
-            if let Ok(binding) = self.cm().early_resolve_ident_in_lexical_scope(
+            if let Ok(binding) = self.cm().resolve_ident_in_scope_set(
                 ident,
                 ScopeSet::All(ValueNS),
                 parent_scope,
@@ -3410,7 +3410,7 @@ impl<'tcx> visit::Visitor<'tcx> for UsePlacementFinder {
 
     fn visit_item(&mut self, item: &'tcx ast::Item) {
         if self.target_module == item.id {
-            if let ItemKind::Mod(_, _, ModKind::Loaded(items, _inline, mod_spans, _)) = &item.kind {
+            if let ItemKind::Mod(_, _, ModKind::Loaded(items, _inline, mod_spans)) = &item.kind {
                 let inject = mod_spans.inject_use_span;
                 if is_span_suitable_for_use_injection(inject) {
                     self.first_legal_span = Some(inject);
diff --git a/compiler/rustc_resolve/src/errors.rs b/compiler/rustc_resolve/src/errors.rs
index a1d62ba7a68..63d6fa23a14 100644
--- a/compiler/rustc_resolve/src/errors.rs
+++ b/compiler/rustc_resolve/src/errors.rs
@@ -776,6 +776,17 @@ pub(crate) struct ConsiderAddingMacroExport {
 }
 
 #[derive(Subdiagnostic)]
+#[suggestion(
+    resolve_consider_marking_as_pub_crate,
+    code = "pub(crate)",
+    applicability = "maybe-incorrect"
+)]
+pub(crate) struct ConsiderMarkingAsPubCrate {
+    #[primary_span]
+    pub(crate) vis_span: Span,
+}
+
+#[derive(Subdiagnostic)]
 #[note(resolve_consider_marking_as_pub)]
 pub(crate) struct ConsiderMarkingAsPub {
     #[primary_span]
diff --git a/compiler/rustc_resolve/src/ident.rs b/compiler/rustc_resolve/src/ident.rs
index c1b3aff4e69..dae42645bec 100644
--- a/compiler/rustc_resolve/src/ident.rs
+++ b/compiler/rustc_resolve/src/ident.rs
@@ -19,7 +19,7 @@ use crate::{
     AmbiguityError, AmbiguityErrorMisc, AmbiguityKind, BindingKey, CmResolver, Determinacy,
     Finalize, ImportKind, LexicalScopeBinding, Module, ModuleKind, ModuleOrUniformRoot,
     NameBinding, NameBindingKind, ParentScope, PathResult, PrivacyError, Res, ResolutionError,
-    Resolver, Scope, ScopeSet, Segment, Used, Weak, errors,
+    Resolver, Scope, ScopeSet, Segment, Stage, Used, Weak, errors,
 };
 
 #[derive(Copy, Clone)]
@@ -49,6 +49,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         scope_set: ScopeSet<'ra>,
         parent_scope: &ParentScope<'ra>,
         ctxt: SyntaxContext,
+        derive_fallback_lint_id: Option<NodeId>,
         mut visitor: impl FnMut(
             &mut CmResolver<'r, 'ra, 'tcx>,
             Scope<'ra>,
@@ -99,15 +100,13 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
 
         let rust_2015 = ctxt.edition().is_rust_2015();
         let (ns, macro_kind) = match scope_set {
-            ScopeSet::All(ns)
-            | ScopeSet::ModuleAndExternPrelude(ns, _)
-            | ScopeSet::Late(ns, ..) => (ns, None),
+            ScopeSet::All(ns) | ScopeSet::ModuleAndExternPrelude(ns, _) => (ns, None),
             ScopeSet::ExternPrelude => (TypeNS, None),
             ScopeSet::Macro(macro_kind) => (MacroNS, Some(macro_kind)),
         };
         let module = match scope_set {
             // Start with the specified module.
-            ScopeSet::Late(_, module, _) | ScopeSet::ModuleAndExternPrelude(_, module) => module,
+            ScopeSet::ModuleAndExternPrelude(_, module) => module,
             // Jump out of trait or enum modules, they do not act as scopes.
             _ => parent_scope.module.nearest_item_scope(),
         };
@@ -193,10 +192,6 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                 },
                 Scope::Module(module, prev_lint_id) => {
                     use_prelude = !module.no_implicit_prelude;
-                    let derive_fallback_lint_id = match scope_set {
-                        ScopeSet::Late(.., lint_id) => lint_id,
-                        _ => None,
-                    };
                     match self.hygienic_lexical_parent(module, &mut ctxt, derive_fallback_lint_id) {
                         Some((parent_module, lint_id)) => {
                             Scope::Module(parent_module, lint_id.or(prev_lint_id))
@@ -349,11 +344,13 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                 return Some(LexicalScopeBinding::Item(binding));
             } else if let RibKind::Module(module) = rib.kind {
                 // Encountered a module item, abandon ribs and look into that module and preludes.
+                let parent_scope = &ParentScope { module, ..*parent_scope };
+                let finalize = finalize.map(|f| Finalize { stage: Stage::Late, ..f });
                 return self
                     .cm()
-                    .early_resolve_ident_in_lexical_scope(
+                    .resolve_ident_in_scope_set(
                         orig_ident,
-                        ScopeSet::Late(ns, module, finalize.map(|finalize| finalize.node_id)),
+                        ScopeSet::All(ns),
                         parent_scope,
                         finalize,
                         finalize.is_some(),
@@ -376,13 +373,9 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         unreachable!()
     }
 
-    /// Resolve an identifier in lexical scope.
-    /// This is a variation of `fn resolve_ident_in_lexical_scope` that can be run during
-    /// expansion and import resolution (perhaps they can be merged in the future).
-    /// The function is used for resolving initial segments of macro paths (e.g., `foo` in
-    /// `foo::bar!();` or `foo!();`) and also for import paths on 2018 edition.
+    /// Resolve an identifier in the specified set of scopes.
     #[instrument(level = "debug", skip(self))]
-    pub(crate) fn early_resolve_ident_in_lexical_scope<'r>(
+    pub(crate) fn resolve_ident_in_scope_set<'r>(
         self: CmResolver<'r, 'ra, 'tcx>,
         orig_ident: Ident,
         scope_set: ScopeSet<'ra>,
@@ -411,9 +404,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         }
 
         let (ns, macro_kind) = match scope_set {
-            ScopeSet::All(ns)
-            | ScopeSet::ModuleAndExternPrelude(ns, _)
-            | ScopeSet::Late(ns, ..) => (ns, None),
+            ScopeSet::All(ns) | ScopeSet::ModuleAndExternPrelude(ns, _) => (ns, None),
             ScopeSet::ExternPrelude => (TypeNS, None),
             ScopeSet::Macro(macro_kind) => (MacroNS, Some(macro_kind)),
         };
@@ -437,10 +428,15 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         }
 
         // Go through all the scopes and try to resolve the name.
+        let derive_fallback_lint_id = match finalize {
+            Some(Finalize { node_id, stage: Stage::Late, .. }) => Some(node_id),
+            _ => None,
+        };
         let break_result = self.visit_scopes(
             scope_set,
             parent_scope,
             orig_ident.span.ctxt(),
+            derive_fallback_lint_id,
             |this, scope, use_prelude, ctxt| {
                 let ident = Ident::new(orig_ident.name, orig_ident.span.with_ctxt(ctxt));
                 let result = match scope {
@@ -510,11 +506,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                             ident,
                             ns,
                             adjusted_parent_scope,
-                            if matches!(scope_set, ScopeSet::Late(..)) {
-                                Shadowing::Unrestricted
-                            } else {
-                                Shadowing::Restricted
-                            },
+                            Shadowing::Restricted,
                             adjusted_finalize,
                             ignore_binding,
                             ignore_import,
@@ -528,7 +520,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                                         orig_ident.span,
                                         BuiltinLintDiag::ProcMacroDeriveResolutionFallback {
                                             span: orig_ident.span,
-                                            ns,
+                                            ns_descr: ns.descr(),
                                             ident,
                                         },
                                     );
@@ -643,7 +635,11 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                             return None;
                         }
 
-                        if finalize.is_none() || matches!(scope_set, ScopeSet::Late(..)) {
+                        // Below we report various ambiguity errors.
+                        // We do not need to report them if we are either in speculative resolution,
+                        // or in late resolution when everything is already imported and expanded
+                        // and no ambiguities exist.
+                        if matches!(finalize, None | Some(Finalize { stage: Stage::Late, .. })) {
                             return Some(Ok(binding));
                         }
 
@@ -811,7 +807,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             ModuleOrUniformRoot::Module(module) => module,
             ModuleOrUniformRoot::ModuleAndExternPrelude(module) => {
                 assert_eq!(shadowing, Shadowing::Unrestricted);
-                let binding = self.early_resolve_ident_in_lexical_scope(
+                let binding = self.resolve_ident_in_scope_set(
                     ident,
                     ScopeSet::ModuleAndExternPrelude(ns, module),
                     parent_scope,
@@ -827,7 +823,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                 return if ns != TypeNS {
                     Err((Determined, Weak::No))
                 } else {
-                    let binding = self.early_resolve_ident_in_lexical_scope(
+                    let binding = self.resolve_ident_in_scope_set(
                         ident,
                         ScopeSet::ExternPrelude,
                         parent_scope,
@@ -852,7 +848,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                     }
                 }
 
-                let binding = self.early_resolve_ident_in_lexical_scope(
+                let binding = self.resolve_ident_in_scope_set(
                     ident,
                     ScopeSet::All(ns),
                     parent_scope,
@@ -945,7 +941,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         // Now we are in situation when new item/import can appear only from a glob or a macro
         // expansion. With restricted shadowing names from globs and macro expansions cannot
         // shadow names from outer scopes, so we can freely fallback from module search to search
-        // in outer scopes. For `early_resolve_ident_in_lexical_scope` to continue search in outer
+        // in outer scopes. For `resolve_ident_in_scope_set` to continue search in outer
         // scopes we return `Undetermined` with `Weak::Yes`.
 
         // Check if one of unexpanded macros can still define the name,
@@ -1040,6 +1036,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         // Forbid expanded shadowing to avoid time travel.
         if let Some(shadowed_glob) = shadowed_glob
             && shadowing == Shadowing::Restricted
+            && finalize.stage == Stage::Early
             && binding.expansion != LocalExpnId::ROOT
             && binding.res() != shadowed_glob.res()
         {
@@ -1635,7 +1632,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                     _ => Err(Determinacy::determined(finalize.is_some())),
                 }
             } else {
-                self.reborrow().early_resolve_ident_in_lexical_scope(
+                self.reborrow().resolve_ident_in_scope_set(
                     ident,
                     ScopeSet::All(ns),
                     parent_scope,
diff --git a/compiler/rustc_resolve/src/imports.rs b/compiler/rustc_resolve/src/imports.rs
index 7c93fdb88ee..d7fc028287f 100644
--- a/compiler/rustc_resolve/src/imports.rs
+++ b/compiler/rustc_resolve/src/imports.rs
@@ -30,7 +30,7 @@ use crate::diagnostics::{DiagMode, Suggestion, import_candidates};
 use crate::errors::{
     CannotBeReexportedCratePublic, CannotBeReexportedCratePublicNS, CannotBeReexportedPrivate,
     CannotBeReexportedPrivateNS, CannotDetermineImportResolution, CannotGlobImportAllCrates,
-    ConsiderAddingMacroExport, ConsiderMarkingAsPub,
+    ConsiderAddingMacroExport, ConsiderMarkingAsPub, ConsiderMarkingAsPubCrate,
 };
 use crate::{
     AmbiguityError, AmbiguityKind, BindingKey, CmResolver, Determinacy, Finalize, ImportSuggestion,
@@ -184,6 +184,9 @@ pub(crate) struct ImportData<'ra> {
     /// |`use foo`        | `ModuleOrUniformRoot::CurrentScope`           | - |
     pub imported_module: Cell<Option<ModuleOrUniformRoot<'ra>>>,
     pub vis: Visibility,
+
+    /// Span of the visibility.
+    pub vis_span: Span,
 }
 
 /// All imports are unique and allocated on a same arena,
@@ -866,7 +869,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             }
             ImportKind::Glob { .. } => {
                 // FIXME: Use mutable resolver directly as a hack, this should be an output of
-                // specualtive resolution.
+                // speculative resolution.
                 self.get_mut_unchecked().resolve_glob_import(import);
                 return 0;
             }
@@ -903,7 +906,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                         // We need the `target`, `source` can be extracted.
                         let imported_binding = this.import(binding, import);
                         // FIXME: Use mutable resolver directly as a hack, this should be an output of
-                        // specualtive resolution.
+                        // speculative resolution.
                         this.get_mut_unchecked().define_binding_local(
                             parent,
                             target,
@@ -917,7 +920,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                         if target.name != kw::Underscore {
                             let key = BindingKey::new(target, ns);
                             // FIXME: Use mutable resolver directly as a hack, this should be an output of
-                            // specualtive resolution.
+                            // speculative resolution.
                             this.get_mut_unchecked().update_local_resolution(
                                 parent,
                                 key,
@@ -1368,6 +1371,9 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                             err.subdiagnostic( ConsiderAddingMacroExport {
                                 span: binding.span,
                             });
+                            err.subdiagnostic( ConsiderMarkingAsPubCrate {
+                                vis_span: import.vis_span,
+                            });
                         }
                         _ => {
                             err.subdiagnostic( ConsiderMarkingAsPub {
@@ -1440,7 +1446,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                     return;
                 }
 
-                match this.cm().early_resolve_ident_in_lexical_scope(
+                match this.cm().resolve_ident_in_scope_set(
                     target,
                     ScopeSet::All(ns),
                     &import.parent_scope,
diff --git a/compiler/rustc_resolve/src/late.rs b/compiler/rustc_resolve/src/late.rs
index 5200f9340e1..679e663f886 100644
--- a/compiler/rustc_resolve/src/late.rs
+++ b/compiler/rustc_resolve/src/late.rs
@@ -4270,7 +4270,7 @@ impl<'a, 'ast, 'ra, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
                         if path.len() == 2
                             && let [segment] = prefix_path
                         {
-                            // Delay to check whether methond name is an associated function or not
+                            // Delay to check whether method name is an associated function or not
                             // ```
                             // let foo = Foo {};
                             // foo::bar(); // possibly suggest to foo.bar();
diff --git a/compiler/rustc_resolve/src/late/diagnostics.rs b/compiler/rustc_resolve/src/late/diagnostics.rs
index 9b201e40d13..80b2095d8cc 100644
--- a/compiler/rustc_resolve/src/late/diagnostics.rs
+++ b/compiler/rustc_resolve/src/late/diagnostics.rs
@@ -38,8 +38,8 @@ use crate::late::{
 };
 use crate::ty::fast_reject::SimplifiedType;
 use crate::{
-    Module, ModuleKind, ModuleOrUniformRoot, PathResult, PathSource, Resolver, ScopeSet, Segment,
-    errors, path_names_to_string,
+    Module, ModuleKind, ModuleOrUniformRoot, ParentScope, PathResult, PathSource, Resolver,
+    ScopeSet, Segment, errors, path_names_to_string,
 };
 
 type Res = def::Res<ast::NodeId>;
@@ -2460,10 +2460,11 @@ impl<'ast, 'ra, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
                     self.r.add_module_candidates(module, &mut names, &filter_fn, Some(ctxt));
                 } else if let RibKind::Module(module) = rib.kind {
                     // Encountered a module item, abandon ribs and look into that module and preludes.
+                    let parent_scope = &ParentScope { module, ..self.parent_scope };
                     self.r.add_scope_set_candidates(
                         &mut names,
-                        ScopeSet::Late(ns, module, None),
-                        &self.parent_scope,
+                        ScopeSet::All(ns),
+                        parent_scope,
                         ctxt,
                         filter_fn,
                     );
@@ -3094,7 +3095,7 @@ impl<'ast, 'ra, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
         } else {
             self.suggest_introducing_lifetime(
                 &mut err,
-                Some(lifetime_ref.ident.name.as_str()),
+                Some(lifetime_ref.ident),
                 |err, _, span, message, suggestion, span_suggs| {
                     err.multipart_suggestion_verbose(
                         message,
@@ -3112,7 +3113,7 @@ impl<'ast, 'ra, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
     fn suggest_introducing_lifetime(
         &self,
         err: &mut Diag<'_>,
-        name: Option<&str>,
+        name: Option<Ident>,
         suggest: impl Fn(
             &mut Diag<'_>,
             bool,
@@ -3159,7 +3160,7 @@ impl<'ast, 'ra, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
                     let mut rm_inner_binders: FxIndexSet<Span> = Default::default();
                     let (span, sugg) = if span.is_empty() {
                         let mut binder_idents: FxIndexSet<Ident> = Default::default();
-                        binder_idents.insert(Ident::from_str(name.unwrap_or("'a")));
+                        binder_idents.insert(name.unwrap_or(Ident::from_str("'a")));
 
                         // We need to special case binders in the following situation:
                         // Change `T: for<'a> Trait<T> + 'b` to `for<'a, 'b> T: Trait<T> + 'b`
@@ -3189,16 +3190,11 @@ impl<'ast, 'ra, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
                             }
                         }
 
-                        let binders_sugg = binder_idents.into_iter().enumerate().fold(
-                            "".to_string(),
-                            |mut binders, (i, x)| {
-                                if i != 0 {
-                                    binders += ", ";
-                                }
-                                binders += x.as_str();
-                                binders
-                            },
-                        );
+                        let binders_sugg: String = binder_idents
+                            .into_iter()
+                            .map(|ident| ident.to_string())
+                            .intersperse(", ".to_owned())
+                            .collect();
                         let sugg = format!(
                             "{}<{}>{}",
                             if higher_ranked { "for" } else { "" },
@@ -3214,7 +3210,8 @@ impl<'ast, 'ra, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
                             .source_map()
                             .span_through_char(span, '<')
                             .shrink_to_hi();
-                        let sugg = format!("{}, ", name.unwrap_or("'a"));
+                        let sugg =
+                            format!("{}, ", name.map(|i| i.to_string()).as_deref().unwrap_or("'a"));
                         (span, sugg)
                     };
 
@@ -3222,7 +3219,7 @@ impl<'ast, 'ra, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
                         let message = Cow::from(format!(
                             "consider making the {} lifetime-generic with a new `{}` lifetime",
                             kind.descr(),
-                            name.unwrap_or("'a"),
+                            name.map(|i| i.to_string()).as_deref().unwrap_or("'a"),
                         ));
                         should_continue = suggest(
                             err,
diff --git a/compiler/rustc_resolve/src/lib.rs b/compiler/rustc_resolve/src/lib.rs
index c0a46e3b16b..2afb52ef4d4 100644
--- a/compiler/rustc_resolve/src/lib.rs
+++ b/compiler/rustc_resolve/src/lib.rs
@@ -49,7 +49,7 @@ use rustc_data_structures::intern::Interned;
 use rustc_data_structures::steal::Steal;
 use rustc_data_structures::sync::{FreezeReadGuard, FreezeWriteGuard};
 use rustc_data_structures::unord::{UnordMap, UnordSet};
-use rustc_errors::{Applicability, Diag, ErrCode, ErrorGuaranteed};
+use rustc_errors::{Applicability, Diag, ErrCode, ErrorGuaranteed, LintBuffer};
 use rustc_expand::base::{DeriveResolution, SyntaxExtension, SyntaxExtensionKind};
 use rustc_feature::BUILTIN_ATTRIBUTES;
 use rustc_hir::attrs::StrippedCfgItem;
@@ -72,8 +72,8 @@ use rustc_middle::ty::{
     ResolverGlobalCtxt, TyCtxt, TyCtxtFeed, Visibility,
 };
 use rustc_query_system::ich::StableHashingContext;
+use rustc_session::lint::BuiltinLintDiag;
 use rustc_session::lint::builtin::PRIVATE_MACRO_USE;
-use rustc_session::lint::{BuiltinLintDiag, LintBuffer};
 use rustc_span::hygiene::{ExpnId, LocalExpnId, MacroKind, SyntaxContext, Transparency};
 use rustc_span::{DUMMY_SP, Ident, Macros20NormalizedIdent, Span, Symbol, kw, sym};
 use smallvec::{SmallVec, smallvec};
@@ -156,11 +156,8 @@ enum ScopeSet<'ra> {
     ModuleAndExternPrelude(Namespace, Module<'ra>),
     /// Just two extern prelude scopes.
     ExternPrelude,
-    /// All scopes with macro namespace and the given macro kind restriction.
+    /// Same as `All(MacroNS)`, but with the given macro kind restriction.
     Macro(MacroKind),
-    /// All scopes with the given namespace, used for partially performing late resolution.
-    /// The node id enables lints and is used for reporting them.
-    Late(Namespace, Module<'ra>, Option<NodeId>),
 }
 
 /// Everything you need to know about a name's location to resolve it.
@@ -781,7 +778,10 @@ impl<'ra> std::ops::Deref for Module<'ra> {
 
 impl<'ra> fmt::Debug for Module<'ra> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "{:?}", self.res())
+        match self.kind {
+            ModuleKind::Block => write!(f, "block"),
+            ModuleKind::Def(..) => write!(f, "{:?}", self.res()),
+        }
     }
 }
 
@@ -1885,7 +1885,8 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             }
         }
 
-        self.cm().visit_scopes(ScopeSet::All(TypeNS), parent_scope, ctxt, |this, scope, _, _| {
+        let scope_set = ScopeSet::All(TypeNS);
+        self.cm().visit_scopes(scope_set, parent_scope, ctxt, None, |this, scope, _, _| {
             match scope {
                 Scope::Module(module, _) => {
                     this.get_mut().traits_in_module(module, assoc_item, &mut found_traits);
@@ -2452,6 +2453,17 @@ fn module_to_string(mut module: Module<'_>) -> Option<String> {
     Some(names_to_string(names.iter().rev().copied()))
 }
 
+#[derive(Copy, Clone, PartialEq, Debug)]
+enum Stage {
+    /// Resolving an import or a macro.
+    /// Used when macro expansion is either not yet finished, or we are finalizing its results.
+    /// Used by default as a more restrictive variant that can produce additional errors.
+    Early,
+    /// Resolving something in late resolution when all imports are resolved
+    /// and all macros are expanded.
+    Late,
+}
+
 #[derive(Copy, Clone, Debug)]
 struct Finalize {
     /// Node ID for linting.
@@ -2464,9 +2476,11 @@ struct Finalize {
     root_span: Span,
     /// Whether to report privacy errors or silently return "no resolution" for them,
     /// similarly to speculative resolution.
-    report_private: bool,
+    report_private: bool = true,
     /// Tracks whether an item is used in scope or used relatively to a module.
-    used: Used,
+    used: Used = Used::Other,
+    /// Finalizing early or late resolution.
+    stage: Stage = Stage::Early,
 }
 
 impl Finalize {
@@ -2475,7 +2489,7 @@ impl Finalize {
     }
 
     fn with_root_span(node_id: NodeId, path_span: Span, root_span: Span) -> Finalize {
-        Finalize { node_id, path_span, root_span, report_private: true, used: Used::Other }
+        Finalize { node_id, path_span, root_span, .. }
     }
 }
 
diff --git a/compiler/rustc_resolve/src/macros.rs b/compiler/rustc_resolve/src/macros.rs
index 72ed8990241..5fa87b4cd9b 100644
--- a/compiler/rustc_resolve/src/macros.rs
+++ b/compiler/rustc_resolve/src/macros.rs
@@ -789,7 +789,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             self.prohibit_imported_non_macro_attrs(None, res.ok(), path_span);
             res
         } else {
-            let binding = self.reborrow().early_resolve_ident_in_lexical_scope(
+            let binding = self.reborrow().resolve_ident_in_scope_set(
                 path[0].ident,
                 ScopeSet::Macro(kind),
                 parent_scope,
@@ -951,7 +951,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         // FIXME: Should be an output of Speculative Resolution.
         let macro_resolutions = self.single_segment_macro_resolutions.take();
         for (ident, kind, parent_scope, initial_binding, sugg_span) in macro_resolutions {
-            match self.cm().early_resolve_ident_in_lexical_scope(
+            match self.cm().resolve_ident_in_scope_set(
                 ident,
                 ScopeSet::Macro(kind),
                 &parent_scope,
@@ -1006,7 +1006,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
 
         let builtin_attrs = mem::take(&mut self.builtin_attrs);
         for (ident, parent_scope) in builtin_attrs {
-            let _ = self.cm().early_resolve_ident_in_lexical_scope(
+            let _ = self.cm().resolve_ident_in_scope_set(
                 ident,
                 ScopeSet::Macro(MacroKind::Attr),
                 &parent_scope,
@@ -1112,7 +1112,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             // If such resolution is successful and gives the same result
             // (e.g. if the macro is re-imported), then silence the lint.
             let no_macro_rules = self.arenas.alloc_macro_rules_scope(MacroRulesScope::Empty);
-            let fallback_binding = self.reborrow().early_resolve_ident_in_lexical_scope(
+            let fallback_binding = self.reborrow().resolve_ident_in_scope_set(
                 path.segments[0].ident,
                 ScopeSet::Macro(MacroKind::Bang),
                 &ParentScope { macro_rules: no_macro_rules, ..*parent_scope },
diff --git a/compiler/rustc_session/Cargo.toml b/compiler/rustc_session/Cargo.toml
index 0516982aeab..60d56b1b808 100644
--- a/compiler/rustc_session/Cargo.toml
+++ b/compiler/rustc_session/Cargo.toml
@@ -27,8 +27,10 @@ tracing = "0.1"
 # tidy-alphabetical-end
 
 [target.'cfg(unix)'.dependencies]
+# FIXME: Remove this pin once this rustix issue is resolved
+# https://github.com/bytecodealliance/rustix/issues/1496
 # tidy-alphabetical-start
-libc = "0.2"
+libc = "=0.2.174"
 # tidy-alphabetical-end
 
 [target.'cfg(windows)'.dependencies.windows]
diff --git a/compiler/rustc_session/messages.ftl b/compiler/rustc_session/messages.ftl
index 528c52eace7..b46e8ab4fdc 100644
--- a/compiler/rustc_session/messages.ftl
+++ b/compiler/rustc_session/messages.ftl
@@ -49,6 +49,8 @@ session_hexadecimal_float_literal_not_supported = hexadecimal float literal is n
 session_incompatible_linker_flavor = linker flavor `{$flavor}` is incompatible with the current target
     .note = compatible flavors are: {$compatible_list}
 
+session_indirect_branch_cs_prefix_requires_x86_or_x86_64 = `-Zindirect-branch-cs-prefix` is only supported on x86 and x86_64
+
 session_instrumentation_not_supported = {$us} instrumentation is not supported for this target
 
 session_int_literal_too_large = integer literal is too large
@@ -129,6 +131,10 @@ session_target_small_data_threshold_not_supported = `-Z small-data-threshold` is
 
 session_target_stack_protector_not_supported = `-Z stack-protector={$stack_protector}` is not supported for target {$target_triple} and will be ignored
 
+session_unexpected_builtin_cfg = unexpected `--cfg {$cfg}` flag
+    .controlled_by = config `{$cfg_name}` is only supposed to be controlled by `{$controlled_by}`
+    .incoherent = manually setting a built-in cfg can and does create incoherent behaviors
+
 session_unleashed_feature_help_named = skipping check for `{$gate}` feature
 session_unleashed_feature_help_unnamed = skipping check that does not even have a feature gate
 
diff --git a/compiler/rustc_session/src/config/cfg.rs b/compiler/rustc_session/src/config/cfg.rs
index 62891eb4f26..8f63ce6f0ae 100644
--- a/compiler/rustc_session/src/config/cfg.rs
+++ b/compiler/rustc_session/src/config/cfg.rs
@@ -26,13 +26,12 @@ use std::iter;
 use rustc_abi::Align;
 use rustc_ast::ast;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
-use rustc_lint_defs::BuiltinLintDiag;
 use rustc_lint_defs::builtin::EXPLICIT_BUILTIN_CFGS_IN_FLAGS;
 use rustc_span::{Symbol, sym};
 use rustc_target::spec::{PanicStrategy, RelocModel, SanitizerSet, Target};
 
-use crate::Session;
 use crate::config::{CrateType, FmtDebug};
+use crate::{Session, errors};
 
 /// The parsed `--cfg` options that define the compilation environment of the
 /// crate, used to drive conditional compilation.
@@ -99,7 +98,7 @@ pub(crate) fn disallow_cfgs(sess: &Session, user_cfgs: &Cfg) {
             EXPLICIT_BUILTIN_CFGS_IN_FLAGS,
             None,
             ast::CRATE_NODE_ID,
-            BuiltinLintDiag::UnexpectedBuiltinCfg { cfg, cfg_name, controlled_by },
+            errors::UnexpectedBuiltinCfg { cfg, cfg_name, controlled_by }.into(),
         )
     };
 
diff --git a/compiler/rustc_session/src/errors.rs b/compiler/rustc_session/src/errors.rs
index bf95014843d..34da54a20bf 100644
--- a/compiler/rustc_session/src/errors.rs
+++ b/compiler/rustc_session/src/errors.rs
@@ -7,7 +7,7 @@ use rustc_errors::{
     Diag, DiagCtxtHandle, DiagMessage, Diagnostic, EmissionGuarantee, ErrorGuaranteed, Level,
     MultiSpan,
 };
-use rustc_macros::{Diagnostic, Subdiagnostic};
+use rustc_macros::{Diagnostic, LintDiagnostic, Subdiagnostic};
 use rustc_span::{Span, Symbol};
 use rustc_target::spec::{SplitDebuginfo, StackProtector, TargetTuple};
 
@@ -472,6 +472,10 @@ pub(crate) struct FunctionReturnRequiresX86OrX8664;
 pub(crate) struct FunctionReturnThunkExternRequiresNonLargeCodeModel;
 
 #[derive(Diagnostic)]
+#[diag(session_indirect_branch_cs_prefix_requires_x86_or_x86_64)]
+pub(crate) struct IndirectBranchCsPrefixRequiresX86OrX8664;
+
+#[derive(Diagnostic)]
 #[diag(session_unsupported_regparm)]
 pub(crate) struct UnsupportedRegparm {
     pub(crate) regparm: u32,
@@ -501,3 +505,13 @@ pub(crate) struct SoftFloatIgnored;
 #[note]
 #[note(session_soft_float_deprecated_issue)]
 pub(crate) struct SoftFloatDeprecated;
+
+#[derive(LintDiagnostic)]
+#[diag(session_unexpected_builtin_cfg)]
+#[note(session_controlled_by)]
+#[note(session_incoherent)]
+pub(crate) struct UnexpectedBuiltinCfg {
+    pub(crate) cfg: String,
+    pub(crate) cfg_name: Symbol,
+    pub(crate) controlled_by: &'static str,
+}
diff --git a/compiler/rustc_session/src/options.rs b/compiler/rustc_session/src/options.rs
index 0e112edc733..6d5be2d92cd 100644
--- a/compiler/rustc_session/src/options.rs
+++ b/compiler/rustc_session/src/options.rs
@@ -2295,6 +2295,8 @@ options! {
         - hashes of green query instances
         - hash collisions of query keys
         - hash collisions when creating dep-nodes"),
+    indirect_branch_cs_prefix: bool = (false, parse_bool, [TRACKED TARGET_MODIFIER],
+        "add `cs` prefix to `call` and `jmp` to indirect thunks (default: no)"),
     inline_llvm: bool = (true, parse_bool, [TRACKED],
         "enable LLVM inlining (default: yes)"),
     inline_mir: Option<bool> = (None, parse_opt_bool, [TRACKED],
diff --git a/compiler/rustc_session/src/parse.rs b/compiler/rustc_session/src/parse.rs
index 426480f0dba..9048c51d5b4 100644
--- a/compiler/rustc_session/src/parse.rs
+++ b/compiler/rustc_session/src/parse.rs
@@ -11,8 +11,8 @@ use rustc_data_structures::sync::{AppendOnlyVec, Lock};
 use rustc_errors::emitter::{FatalOnlyEmitter, HumanEmitter, stderr_destination};
 use rustc_errors::translation::Translator;
 use rustc_errors::{
-    ColorConfig, Diag, DiagCtxt, DiagCtxtHandle, DiagMessage, EmissionGuarantee, MultiSpan,
-    StashKey,
+    BufferedEarlyLint, ColorConfig, DecorateDiagCompat, Diag, DiagCtxt, DiagCtxtHandle,
+    DiagMessage, EmissionGuarantee, MultiSpan, StashKey,
 };
 use rustc_feature::{GateIssue, UnstableFeatures, find_feature_issue};
 use rustc_span::edition::Edition;
@@ -27,7 +27,7 @@ use crate::errors::{
     FeatureDiagnosticSuggestion, FeatureGateError, SuggestUpgradeCompiler,
 };
 use crate::lint::builtin::UNSTABLE_SYNTAX_PRE_EXPANSION;
-use crate::lint::{BufferedEarlyLint, BuiltinLintDiag, Lint, LintId};
+use crate::lint::{Lint, LintId};
 
 /// Collected spans during parsing for places where a certain feature was
 /// used and should be feature gated accordingly in `check_crate`.
@@ -342,17 +342,17 @@ impl ParseSess {
         lint: &'static Lint,
         span: impl Into<MultiSpan>,
         node_id: NodeId,
-        diagnostic: BuiltinLintDiag,
+        diagnostic: impl Into<DecorateDiagCompat>,
     ) {
-        self.opt_span_buffer_lint(lint, Some(span.into()), node_id, diagnostic)
+        self.opt_span_buffer_lint(lint, Some(span.into()), node_id, diagnostic.into())
     }
 
-    pub fn opt_span_buffer_lint(
+    pub(crate) fn opt_span_buffer_lint(
         &self,
         lint: &'static Lint,
         span: Option<MultiSpan>,
         node_id: NodeId,
-        diagnostic: BuiltinLintDiag,
+        diagnostic: DecorateDiagCompat,
     ) {
         self.buffered_lints.with_lock(|buffered_lints| {
             buffered_lints.push(BufferedEarlyLint {
diff --git a/compiler/rustc_session/src/session.rs b/compiler/rustc_session/src/session.rs
index c6956cf5f23..96767d05439 100644
--- a/compiler/rustc_session/src/session.rs
+++ b/compiler/rustc_session/src/session.rs
@@ -7,6 +7,7 @@ use std::sync::atomic::AtomicBool;
 use std::{env, fmt, io};
 
 use rand::{RngCore, rng};
+use rustc_ast::NodeId;
 use rustc_data_structures::base_n::{CASE_INSENSITIVE, ToBaseN};
 use rustc_data_structures::flock;
 use rustc_data_structures::fx::{FxHashMap, FxIndexSet};
@@ -22,7 +23,7 @@ use rustc_errors::timings::TimingSectionHandler;
 use rustc_errors::translation::Translator;
 use rustc_errors::{
     Diag, DiagCtxt, DiagCtxtHandle, DiagMessage, Diagnostic, ErrorGuaranteed, FatalAbort,
-    TerminalUrl, fallback_fluent_bundle,
+    LintEmitter, TerminalUrl, fallback_fluent_bundle,
 };
 use rustc_macros::HashStable_Generic;
 pub use rustc_span::def_id::StableCrateId;
@@ -44,6 +45,7 @@ use crate::config::{
     SwitchWithOptPath,
 };
 use crate::filesearch::FileSearch;
+use crate::lint::LintId;
 use crate::parse::{ParseSess, add_feature_diagnostics};
 use crate::search_paths::SearchPath;
 use crate::{errors, filesearch, lint};
@@ -139,7 +141,10 @@ pub struct CompilerIO {
     pub temps_dir: Option<PathBuf>,
 }
 
-pub trait LintStoreMarker: Any + DynSync + DynSend {}
+pub trait DynLintStore: Any + DynSync + DynSend {
+    /// Provides a way to access lint groups without depending on `rustc_lint`
+    fn lint_groups_iter(&self) -> Box<dyn Iterator<Item = LintGroup> + '_>;
+}
 
 /// Represents the data associated with a compilation
 /// session for a single crate.
@@ -164,7 +169,7 @@ pub struct Session {
     pub code_stats: CodeStats,
 
     /// This only ever stores a `LintStore` but we don't want a dependency on that type here.
-    pub lint_store: Option<Arc<dyn LintStoreMarker>>,
+    pub lint_store: Option<Arc<dyn DynLintStore>>,
 
     /// Cap lint level specified by a driver specifically.
     pub driver_lint_caps: FxHashMap<lint::LintId, lint::Level>,
@@ -219,6 +224,20 @@ pub struct Session {
     pub invocation_temp: Option<String>,
 }
 
+impl LintEmitter for &'_ Session {
+    type Id = NodeId;
+
+    fn emit_node_span_lint(
+        self,
+        lint: &'static rustc_lint_defs::Lint,
+        node_id: Self::Id,
+        span: impl Into<rustc_errors::MultiSpan>,
+        decorator: impl for<'a> rustc_errors::LintDiagnostic<'a, ()> + DynSend + 'static,
+    ) {
+        self.psess.buffer_lint(lint, span, node_id, decorator);
+    }
+}
+
 #[derive(Clone, Copy)]
 pub enum CodegenUnits {
     /// Specified by the user. In this case we try fairly hard to produce the
@@ -240,6 +259,12 @@ impl CodegenUnits {
     }
 }
 
+pub struct LintGroup {
+    pub name: &'static str,
+    pub lints: Vec<LintId>,
+    pub is_externally_loaded: bool,
+}
+
 impl Session {
     pub fn miri_unleashed_feature(&self, span: Span, feature_gate: Option<Symbol>) {
         self.miri_unleashed_features.lock().push((span, feature_gate));
@@ -596,6 +621,13 @@ impl Session {
             (&*self.target.staticlib_prefix, &*self.target.staticlib_suffix)
         }
     }
+
+    pub fn lint_groups_iter(&self) -> Box<dyn Iterator<Item = LintGroup> + '_> {
+        match self.lint_store {
+            Some(ref lint_store) => lint_store.lint_groups_iter(),
+            None => Box::new(std::iter::empty()),
+        }
+    }
 }
 
 // JUSTIFICATION: defn of the suggested wrapper fns
@@ -1368,6 +1400,12 @@ fn validate_commandline_args_with_session_available(sess: &Session) {
         }
     }
 
+    if sess.opts.unstable_opts.indirect_branch_cs_prefix {
+        if sess.target.arch != "x86" && sess.target.arch != "x86_64" {
+            sess.dcx().emit_err(errors::IndirectBranchCsPrefixRequiresX86OrX8664);
+        }
+    }
+
     if let Some(regparm) = sess.opts.unstable_opts.regparm {
         if regparm > 3 {
             sess.dcx().emit_err(errors::UnsupportedRegparm { regparm });
diff --git a/compiler/rustc_span/src/caching_source_map_view.rs b/compiler/rustc_span/src/caching_source_map_view.rs
index a887b50ec1e..41cfaa3ee34 100644
--- a/compiler/rustc_span/src/caching_source_map_view.rs
+++ b/compiler/rustc_span/src/caching_source_map_view.rs
@@ -123,27 +123,25 @@ impl<'sm> CachingSourceMapView<'sm> {
 
         if lo_cache_idx != -1 && hi_cache_idx != -1 {
             // Cache hit for span lo and hi. Check if they belong to the same file.
-            let result = {
-                let lo = &self.line_cache[lo_cache_idx as usize];
-                let hi = &self.line_cache[hi_cache_idx as usize];
+            let lo_file_index = self.line_cache[lo_cache_idx as usize].file_index;
+            let hi_file_index = self.line_cache[hi_cache_idx as usize].file_index;
 
-                if lo.file_index != hi.file_index {
-                    return None;
-                }
-
-                (
-                    lo.file.stable_id,
-                    lo.line_number,
-                    span_data.lo - lo.line.start,
-                    hi.line_number,
-                    span_data.hi - hi.line.start,
-                )
-            };
+            if lo_file_index != hi_file_index {
+                return None;
+            }
 
             self.line_cache[lo_cache_idx as usize].touch(self.time_stamp);
             self.line_cache[hi_cache_idx as usize].touch(self.time_stamp);
 
-            return Some(result);
+            let lo = &self.line_cache[lo_cache_idx as usize];
+            let hi = &self.line_cache[hi_cache_idx as usize];
+            return Some((
+                lo.file.stable_id,
+                lo.line_number,
+                span_data.lo - lo.line.start,
+                hi.line_number,
+                span_data.hi - hi.line.start,
+            ));
         }
 
         // No cache hit or cache hit for only one of span lo and hi.
diff --git a/compiler/rustc_span/src/source_map.rs b/compiler/rustc_span/src/source_map.rs
index d9315149798..8270de1e917 100644
--- a/compiler/rustc_span/src/source_map.rs
+++ b/compiler/rustc_span/src/source_map.rs
@@ -911,12 +911,13 @@ impl SourceMap {
 
     /// Returns a new span representing just the last character of this span.
     pub fn end_point(&self, sp: Span) -> Span {
-        let pos = sp.hi().0;
+        let sp = sp.data();
+        let pos = sp.hi.0;
 
         let width = self.find_width_of_character_at_span(sp, false);
         let corrected_end_position = pos.checked_sub(width).unwrap_or(pos);
 
-        let end_point = BytePos(cmp::max(corrected_end_position, sp.lo().0));
+        let end_point = BytePos(cmp::max(corrected_end_position, sp.lo.0));
         sp.with_lo(end_point)
     }
 
@@ -930,8 +931,9 @@ impl SourceMap {
         if sp.is_dummy() {
             return sp;
         }
-        let start_of_next_point = sp.hi().0;
 
+        let sp = sp.data();
+        let start_of_next_point = sp.hi.0;
         let width = self.find_width_of_character_at_span(sp, true);
         // If the width is 1, then the next span should only contain the next char besides current ending.
         // However, in the case of a multibyte character, where the width != 1, the next span should
@@ -940,7 +942,7 @@ impl SourceMap {
             start_of_next_point.checked_add(width).unwrap_or(start_of_next_point);
 
         let end_of_next_point = BytePos(cmp::max(start_of_next_point + 1, end_of_next_point));
-        Span::new(BytePos(start_of_next_point), end_of_next_point, sp.ctxt(), None)
+        Span::new(BytePos(start_of_next_point), end_of_next_point, sp.ctxt, None)
     }
 
     /// Check whether span is followed by some specified expected string in limit scope
@@ -963,9 +965,7 @@ impl SourceMap {
     /// Finds the width of the character, either before or after the end of provided span,
     /// depending on the `forwards` parameter.
     #[instrument(skip(self, sp))]
-    fn find_width_of_character_at_span(&self, sp: Span, forwards: bool) -> u32 {
-        let sp = sp.data();
-
+    fn find_width_of_character_at_span(&self, sp: SpanData, forwards: bool) -> u32 {
         if sp.lo == sp.hi && !forwards {
             debug!("early return empty span");
             return 1;
diff --git a/compiler/rustc_span/src/span_encoding.rs b/compiler/rustc_span/src/span_encoding.rs
index a4a47dc99b0..e34efa784de 100644
--- a/compiler/rustc_span/src/span_encoding.rs
+++ b/compiler/rustc_span/src/span_encoding.rs
@@ -74,9 +74,8 @@ use crate::{BytePos, SPAN_TRACK, SpanData};
 ///   because `parent` isn't currently used by default.
 ///
 /// In order to reliably use parented spans in incremental compilation,
-/// the dependency to the parent definition's span. This is performed
-/// using the callback `SPAN_TRACK` to access the query engine.
-///
+/// accesses to `lo` and `hi` must introduce a dependency to the parent definition's span.
+/// This is performed using the callback `SPAN_TRACK` to access the query engine.
 #[derive(Clone, Copy, Eq, PartialEq, Hash)]
 #[rustc_pass_by_value]
 pub struct Span {
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index 65a52b27d3b..5d140cc6117 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -901,6 +901,7 @@ symbols! {
         dynamic_no_pic: "dynamic-no-pic",
         e,
         edition_panic,
+        effective_target_features,
         effects,
         eh_catch_typeinfo,
         eh_personality,
@@ -1061,6 +1062,7 @@ symbols! {
         fn_ptr_addr,
         fn_ptr_trait,
         forbid,
+        force_target_feature,
         forget,
         format,
         format_args,
@@ -1754,6 +1756,7 @@ symbols! {
         readonly,
         realloc,
         reason,
+        reborrow,
         receiver,
         receiver_target,
         recursion_limit,
@@ -1837,6 +1840,7 @@ symbols! {
         rustc_align,
         rustc_allocator,
         rustc_allocator_zeroed,
+        rustc_allocator_zeroed_variant,
         rustc_allow_const_fn_unstable,
         rustc_allow_incoherent_impl,
         rustc_allowed_through_unstable_modules,
@@ -2532,10 +2536,16 @@ impl fmt::Debug for Ident {
 /// except that AST identifiers don't keep the rawness flag, so we have to guess it.
 impl fmt::Display for Ident {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        fmt::Display::fmt(&IdentPrinter::new(self.name, self.is_raw_guess(), None), f)
+        fmt::Display::fmt(&IdentPrinter::new(self.name, self.guess_print_mode(), None), f)
     }
 }
 
+pub enum IdentPrintMode {
+    Normal,
+    RawIdent,
+    RawLifetime,
+}
+
 /// The most general type to print identifiers.
 ///
 /// AST pretty-printer is used as a fallback for turning AST structures into token streams for
@@ -2551,7 +2561,7 @@ impl fmt::Display for Ident {
 /// done for a token stream or a single token.
 pub struct IdentPrinter {
     symbol: Symbol,
-    is_raw: bool,
+    mode: IdentPrintMode,
     /// Span used for retrieving the crate name to which `$crate` refers to,
     /// if this field is `None` then the `$crate` conversion doesn't happen.
     convert_dollar_crate: Option<Span>,
@@ -2559,32 +2569,51 @@ pub struct IdentPrinter {
 
 impl IdentPrinter {
     /// The most general `IdentPrinter` constructor. Do not use this.
-    pub fn new(symbol: Symbol, is_raw: bool, convert_dollar_crate: Option<Span>) -> IdentPrinter {
-        IdentPrinter { symbol, is_raw, convert_dollar_crate }
+    pub fn new(
+        symbol: Symbol,
+        mode: IdentPrintMode,
+        convert_dollar_crate: Option<Span>,
+    ) -> IdentPrinter {
+        IdentPrinter { symbol, mode, convert_dollar_crate }
     }
 
     /// This implementation is supposed to be used when printing identifiers
     /// as a part of pretty-printing for larger AST pieces.
     /// Do not use this either.
-    pub fn for_ast_ident(ident: Ident, is_raw: bool) -> IdentPrinter {
-        IdentPrinter::new(ident.name, is_raw, Some(ident.span))
+    pub fn for_ast_ident(ident: Ident, mode: IdentPrintMode) -> IdentPrinter {
+        IdentPrinter::new(ident.name, mode, Some(ident.span))
     }
 }
 
 impl fmt::Display for IdentPrinter {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        if self.is_raw {
-            f.write_str("r#")?;
-        } else if self.symbol == kw::DollarCrate {
-            if let Some(span) = self.convert_dollar_crate {
+        let s = match self.mode {
+            IdentPrintMode::Normal
+                if self.symbol == kw::DollarCrate
+                    && let Some(span) = self.convert_dollar_crate =>
+            {
                 let converted = span.ctxt().dollar_crate_name();
                 if !converted.is_path_segment_keyword() {
                     f.write_str("::")?;
                 }
-                return fmt::Display::fmt(&converted, f);
+                converted
             }
-        }
-        fmt::Display::fmt(&self.symbol, f)
+            IdentPrintMode::Normal => self.symbol,
+            IdentPrintMode::RawIdent => {
+                f.write_str("r#")?;
+                self.symbol
+            }
+            IdentPrintMode::RawLifetime => {
+                f.write_str("'r#")?;
+                let s = self
+                    .symbol
+                    .as_str()
+                    .strip_prefix("'")
+                    .expect("only lifetime idents should be passed with RawLifetime mode");
+                Symbol::intern(s)
+            }
+        };
+        s.fmt(f)
     }
 }
 
@@ -3019,6 +3048,29 @@ impl Ident {
         self.name.can_be_raw() && self.is_reserved()
     }
 
+    /// Given the name of a lifetime without the first quote (`'`),
+    /// returns whether the lifetime name is reserved (therefore invalid)
+    pub fn is_reserved_lifetime(self) -> bool {
+        self.is_reserved() && ![kw::Underscore, kw::Static].contains(&self.name)
+    }
+
+    pub fn is_raw_lifetime_guess(self) -> bool {
+        let name_without_apostrophe = self.without_first_quote();
+        name_without_apostrophe.name != self.name
+            && name_without_apostrophe.name.can_be_raw()
+            && name_without_apostrophe.is_reserved_lifetime()
+    }
+
+    pub fn guess_print_mode(self) -> IdentPrintMode {
+        if self.is_raw_lifetime_guess() {
+            IdentPrintMode::RawLifetime
+        } else if self.is_raw_guess() {
+            IdentPrintMode::RawIdent
+        } else {
+            IdentPrintMode::Normal
+        }
+    }
+
     /// Whether this would be the identifier for a tuple field like `self.0`, as
     /// opposed to a named field like `self.thing`.
     pub fn is_numeric(self) -> bool {
diff --git a/compiler/rustc_symbol_mangling/src/lib.rs b/compiler/rustc_symbol_mangling/src/lib.rs
index f3c96f64190..d97ee956525 100644
--- a/compiler/rustc_symbol_mangling/src/lib.rs
+++ b/compiler/rustc_symbol_mangling/src/lib.rs
@@ -193,29 +193,20 @@ fn compute_symbol_name<'tcx>(
         // defining crate.
         // Weak lang items automatically get #[rustc_std_internal_symbol]
         // applied by the code computing the CodegenFnAttrs.
-        // We are mangling all #[rustc_std_internal_symbol] items that don't
-        // also have #[no_mangle] as a combination of the rustc version and the
-        // unmangled linkage name. This is to ensure that if we link against a
-        // staticlib compiled by a different rustc version, we don't get symbol
-        // conflicts or even UB due to a different implementation/ABI. Rust
-        // staticlibs currently export all symbols, including those that are
-        // hidden in cdylibs.
+        // We are mangling all #[rustc_std_internal_symbol] items as a
+        // combination of the rustc version and the unmangled linkage name.
+        // This is to ensure that if we link against a staticlib compiled by a
+        // different rustc version, we don't get symbol conflicts or even UB
+        // due to a different implementation/ABI. Rust staticlibs currently
+        // export all symbols, including those that are hidden in cdylibs.
         // We are using the v0 symbol mangling scheme here as we need to be
         // consistent across all crates and in some contexts the legacy symbol
         // mangling scheme can't be used. For example both the GCC backend and
         // Rust-for-Linux don't support some of the characters used by the
         // legacy symbol mangling scheme.
-        let name = if tcx.is_foreign_item(def_id) {
-            if let Some(name) = attrs.link_name { name } else { tcx.item_name(def_id) }
-        } else {
-            if let Some(name) = attrs.export_name { name } else { tcx.item_name(def_id) }
-        };
+        let name = if let Some(name) = attrs.symbol_name { name } else { tcx.item_name(def_id) };
 
-        if attrs.flags.contains(CodegenFnAttrFlags::NO_MANGLE) {
-            return name.to_string();
-        } else {
-            return v0::mangle_internal_symbol(tcx, name.as_str());
-        }
+        return v0::mangle_internal_symbol(tcx, name.as_str());
     }
 
     let wasm_import_module_exception_force_mangling = {
@@ -240,23 +231,16 @@ fn compute_symbol_name<'tcx>(
             && tcx.wasm_import_module_map(LOCAL_CRATE).contains_key(&def_id.into())
     };
 
-    if let Some(name) = attrs.link_name
-        && !wasm_import_module_exception_force_mangling
-    {
-        // Use provided name
-        return name.to_string();
-    }
-
-    if let Some(name) = attrs.export_name {
-        // Use provided name
-        return name.to_string();
-    }
+    if !wasm_import_module_exception_force_mangling {
+        if let Some(name) = attrs.symbol_name {
+            // Use provided name
+            return name.to_string();
+        }
 
-    if attrs.flags.contains(CodegenFnAttrFlags::NO_MANGLE)
-        && !wasm_import_module_exception_force_mangling
-    {
-        // Don't mangle
-        return tcx.item_name(def_id).to_string();
+        if attrs.flags.contains(CodegenFnAttrFlags::NO_MANGLE) {
+            // Don't mangle
+            return tcx.item_name(def_id).to_string();
+        }
     }
 
     // If we're dealing with an instance of a function that's inlined from
diff --git a/compiler/rustc_target/Cargo.toml b/compiler/rustc_target/Cargo.toml
index 56932c24922..57c90a703f1 100644
--- a/compiler/rustc_target/Cargo.toml
+++ b/compiler/rustc_target/Cargo.toml
@@ -8,6 +8,7 @@ edition = "2024"
 bitflags = "2.4.1"
 rustc_abi = { path = "../rustc_abi" }
 rustc_data_structures = { path = "../rustc_data_structures" }
+rustc_error_messages = { path = "../rustc_error_messages" }
 rustc_fs_util = { path = "../rustc_fs_util" }
 rustc_macros = { path = "../rustc_macros" }
 rustc_serialize = { path = "../rustc_serialize" }
diff --git a/compiler/rustc_target/src/callconv/mod.rs b/compiler/rustc_target/src/callconv/mod.rs
index 63e56744aec..5f2a6f7ba38 100644
--- a/compiler/rustc_target/src/callconv/mod.rs
+++ b/compiler/rustc_target/src/callconv/mod.rs
@@ -119,6 +119,7 @@ mod attr_impl {
             const ReadOnly  = 1 << 4;
             const InReg     = 1 << 5;
             const NoUndef = 1 << 6;
+            const CapturesReadOnly = 1 << 7;
         }
     }
     rustc_data_structures::external_bitflags_debug! { ArgAttribute }
diff --git a/compiler/rustc_target/src/spec/mod.rs b/compiler/rustc_target/src/spec/mod.rs
index 2aa8ab5d317..a67795e3e93 100644
--- a/compiler/rustc_target/src/spec/mod.rs
+++ b/compiler/rustc_target/src/spec/mod.rs
@@ -50,6 +50,7 @@ use rustc_abi::{
     Align, CanonAbi, Endian, ExternAbi, Integer, Size, TargetDataLayout, TargetDataLayoutErrors,
 };
 use rustc_data_structures::fx::{FxHashSet, FxIndexSet};
+use rustc_error_messages::{DiagArgValue, IntoDiagArg, into_diag_arg_using_display};
 use rustc_fs_util::try_canonicalize;
 use rustc_macros::{Decodable, Encodable, HashStable_Generic};
 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
@@ -875,6 +876,12 @@ impl FromStr for PanicStrategy {
 
 crate::json::serde_deserialize_from_str!(PanicStrategy);
 
+impl IntoDiagArg for PanicStrategy {
+    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+        DiagArgValue::Str(Cow::Owned(self.desc().to_string()))
+    }
+}
+
 impl ToJson for PanicStrategy {
     fn to_json(&self) -> Json {
         match *self {
@@ -1518,6 +1525,8 @@ impl fmt::Display for SplitDebuginfo {
     }
 }
 
+into_diag_arg_using_display!(SplitDebuginfo);
+
 #[derive(Clone, Debug, PartialEq, Eq, serde_derive::Deserialize)]
 #[serde(tag = "kind")]
 #[serde(rename_all = "kebab-case")]
@@ -1795,6 +1804,8 @@ impl fmt::Display for StackProtector {
     }
 }
 
+into_diag_arg_using_display!(StackProtector);
+
 #[derive(PartialEq, Clone, Debug)]
 pub enum BinaryFormat {
     Coff,
@@ -2105,6 +2116,7 @@ supported_targets! {
 
     ("msp430-none-elf", msp430_none_elf),
 
+    ("aarch64_be-unknown-hermit", aarch64_be_unknown_hermit),
     ("aarch64-unknown-hermit", aarch64_unknown_hermit),
     ("riscv64gc-unknown-hermit", riscv64gc_unknown_hermit),
     ("x86_64-unknown-hermit", x86_64_unknown_hermit),
@@ -3806,3 +3818,5 @@ impl fmt::Display for TargetTuple {
         write!(f, "{}", self.debug_tuple())
     }
 }
+
+into_diag_arg_using_display!(&TargetTuple);
diff --git a/compiler/rustc_target/src/spec/targets/aarch64_be_unknown_hermit.rs b/compiler/rustc_target/src/spec/targets/aarch64_be_unknown_hermit.rs
new file mode 100644
index 00000000000..cad57abc2b1
--- /dev/null
+++ b/compiler/rustc_target/src/spec/targets/aarch64_be_unknown_hermit.rs
@@ -0,0 +1,25 @@
+use rustc_abi::Endian;
+
+use crate::spec::{StackProbeType, Target, TargetMetadata, TargetOptions, base};
+
+pub(crate) fn target() -> Target {
+    Target {
+        llvm_target: "aarch64_be-unknown-hermit".into(),
+        metadata: TargetMetadata {
+            description: Some("ARM64 Hermit (big-endian)".into()),
+            tier: Some(3),
+            host_tools: Some(false),
+            std: Some(true),
+        },
+        pointer_width: 64,
+        arch: "aarch64".into(),
+        data_layout: "E-m:e-p270:32:32-p271:32:32-p272:64:64-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128-Fn32".into(),
+        options: TargetOptions {
+            features: "+v8a,+strict-align,+neon,+fp-armv8".into(),
+            max_atomic_width: Some(128),
+            stack_probes: StackProbeType::Inline,
+            endian: Endian::Big,
+            ..base::hermit::opts()
+        },
+    }
+}
diff --git a/compiler/rustc_target/src/spec/targets/aarch64_nintendo_switch_freestanding.rs b/compiler/rustc_target/src/spec/targets/aarch64_nintendo_switch_freestanding.rs
index 9b81362b27d..61e4cad3fa2 100644
--- a/compiler/rustc_target/src/spec/targets/aarch64_nintendo_switch_freestanding.rs
+++ b/compiler/rustc_target/src/spec/targets/aarch64_nintendo_switch_freestanding.rs
@@ -19,7 +19,7 @@ pub(crate) fn target() -> Target {
         data_layout: "e-m:e-p270:32:32-p271:32:32-p272:64:64-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128-Fn32".into(),
         arch: "aarch64".into(),
         options: TargetOptions {
-            features: "+v8a".into(),
+            features: "+v8a,+neon,+crypto,+crc".into(),
             linker_flavor: LinkerFlavor::Gnu(Cc::No, Lld::Yes),
             linker: Some("rust-lld".into()),
             link_script: Some(LINKER_SCRIPT.into()),
diff --git a/compiler/rustc_target/src/spec/targets/armv7a_vex_v5_linker_script.ld b/compiler/rustc_target/src/spec/targets/armv7a_vex_v5_linker_script.ld
index a4783de0183..0f3e6eeee19 100644
--- a/compiler/rustc_target/src/spec/targets/armv7a_vex_v5_linker_script.ld
+++ b/compiler/rustc_target/src/spec/targets/armv7a_vex_v5_linker_script.ld
@@ -17,15 +17,25 @@ PROVIDE(__vcodesig_type = 0);               /* V5_SIG_TYPE_USER     */
 PROVIDE(__vcodesig_owner = 2);              /* V5_SIG_OWNER_PARTNER */
 PROVIDE(__vcodesig_options = 0);            /* none (0)             */
 
-PROVIDE(__user_ram_start = 0x03800000);
-PROVIDE(__user_ram_length = 48M);
-PROVIDE(__user_ram_end = __user_ram_start + __user_ram_length); /* 0x8000000 */
+__user_ram_start = 0x03800000;
+__user_ram_end   = 0x08000000;
+/* (0x48 =) 72 MiB length */
+__user_ram_length = __user_ram_start - __user_ram_end;
 
-PROVIDE(__code_signature_length = 0x20);
+/*
+ * VEXos provides a method for pre-loading a "linked file" at a specified
+ * address in User RAM, conventionally near the end, after the primary
+ * program binary. We need to be sure not to place any data in that location,
+ * so we allow the user of this linker script to inform the start address of
+ * this blob.
+ */
+PROVIDE(__linked_file_length = 0);
+PROVIDE(__linked_file_end = __user_ram_end);
+PROVIDE(__linked_file_start = __linked_file_end - __linked_file_length);
 
 PROVIDE(__stack_length = 4M);
-PROVIDE(__heap_end = __user_ram_end - __stack_length);
-PROVIDE(__user_length = __heap_start - __user_ram_start);
+PROVIDE(__stack_top = __linked_file_start);
+PROVIDE(__stack_bottom = __linked_file_start - __stack_length);
 
 MEMORY {
     USER_RAM (RWX) : ORIGIN = __user_ram_start, LENGTH = __user_ram_length
@@ -44,7 +54,7 @@ SECTIONS {
         LONG(__vcodesig_options)
 
         FILL(0)
-        . = __user_ram_start + __code_signature_length;
+        . = __user_ram_start + 0x20;
     } > USER_RAM
 
     /*
@@ -125,7 +135,8 @@ SECTIONS {
      */
     .heap (NOLOAD) : {
         __heap_start = .;
-        . = __heap_end;
+        . = __stack_bottom;
+        __heap_end = .;
     } > USER_RAM
 
     .stack (NOLOAD) : ALIGN(8) {
diff --git a/compiler/rustc_target/src/spec/targets/x86_64_apple_darwin.rs b/compiler/rustc_target/src/spec/targets/x86_64_apple_darwin.rs
index 53e2cb469ee..8892c50d844 100644
--- a/compiler/rustc_target/src/spec/targets/x86_64_apple_darwin.rs
+++ b/compiler/rustc_target/src/spec/targets/x86_64_apple_darwin.rs
@@ -7,7 +7,7 @@ pub(crate) fn target() -> Target {
         llvm_target,
         metadata: TargetMetadata {
             description: Some("x86_64 Apple macOS (10.12+, Sierra+)".into()),
-            tier: Some(1),
+            tier: Some(2),
             host_tools: Some(true),
             std: Some(true),
         },
diff --git a/compiler/rustc_target/src/target_features.rs b/compiler/rustc_target/src/target_features.rs
index 507e938d5cc..e45300b59cc 100644
--- a/compiler/rustc_target/src/target_features.rs
+++ b/compiler/rustc_target/src/target_features.rs
@@ -767,6 +767,7 @@ static CSKY_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
 
 static LOONGARCH_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
     // tidy-alphabetical-start
+    ("32s", Unstable(sym::loongarch_target_feature), &[]),
     ("d", Stable, &["f"]),
     ("div32", Unstable(sym::loongarch_target_feature), &[]),
     ("f", Stable, &[]),
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 f31a85ec07a..40285e5d0e9 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
@@ -537,7 +537,7 @@ impl<T> Trait<T> for X {
                 }
             }
             TypeError::TargetFeatureCast(def_id) => {
-                let target_spans = find_attr!(tcx.get_all_attrs(def_id), AttributeKind::TargetFeature(.., span) => *span);
+                let target_spans = find_attr!(tcx.get_all_attrs(def_id), AttributeKind::TargetFeature{attr_span: span, was_forced: false, ..} => *span);
                 diag.note(
                     "functions with `#[target_feature]` can only be coerced to `unsafe` function pointers"
                 );
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 214a6e86d39..d768e0bf63f 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
@@ -275,8 +275,9 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                         *err.long_ty_path() = long_ty_file;
 
                         let mut suggested = false;
+                        let mut noted_missing_impl = false;
                         if is_try_conversion || is_question_mark {
-                            suggested = self.try_conversion_context(&obligation, main_trait_predicate, &mut err);
+                            (suggested, noted_missing_impl) = self.try_conversion_context(&obligation, main_trait_predicate, &mut err);
                         }
 
                         if let Some(ret_span) = self.return_type_span(&obligation) {
@@ -335,6 +336,11 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                             return err.emit();
                         }
 
+                        let ty_span = match leaf_trait_predicate.self_ty().skip_binder().kind() {
+                            ty::Adt(def, _) if def.did().is_local()
+                                && !self.can_suggest_derive(&obligation, leaf_trait_predicate) => self.tcx.def_span(def.did()),
+                            _ => DUMMY_SP,
+                        };
                         if let Some(s) = label {
                             // If it has a custom `#[rustc_on_unimplemented]`
                             // error message, let's display it as the label!
@@ -347,15 +353,28 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                                     // Don't say "the trait `FromResidual<Option<Infallible>>` is
                                     // not implemented for `Result<T, E>`".
                             {
-                                err.help(explanation);
+                                // We do this just so that the JSON output's `help` position is the
+                                // right one and not `file.rs:1:1`. The render is the same.
+                                if ty_span == DUMMY_SP {
+                                    err.help(explanation);
+                                } else {
+                                    err.span_help(ty_span, explanation);
+                                }
                             }
                         } else if let Some(custom_explanation) = safe_transmute_explanation {
                             err.span_label(span, custom_explanation);
-                        } else if explanation.len() > self.tcx.sess.diagnostic_width() {
+                        } else if (explanation.len() > self.tcx.sess.diagnostic_width() || ty_span != DUMMY_SP) && !noted_missing_impl {
                             // Really long types don't look good as span labels, instead move it
                             // to a `help`.
                             err.span_label(span, "unsatisfied trait bound");
-                            err.help(explanation);
+
+                            // We do this just so that the JSON output's `help` position is the
+                            // right one and not `file.rs:1:1`. The render is the same.
+                            if ty_span == DUMMY_SP {
+                                err.help(explanation);
+                            } else {
+                                err.span_help(ty_span, explanation);
+                            }
                         } else {
                             err.span_label(span, explanation);
                         }
@@ -939,7 +958,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         obligation: &PredicateObligation<'tcx>,
         trait_pred: ty::PolyTraitPredicate<'tcx>,
         err: &mut Diag<'_>,
-    ) -> bool {
+    ) -> (bool, bool) {
         let span = obligation.cause.span;
         /// Look for the (direct) sub-expr of `?`, and return it if it's a `.` method call.
         struct FindMethodSubexprOfTry {
@@ -959,21 +978,22 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
             }
         }
         let hir_id = self.tcx.local_def_id_to_hir_id(obligation.cause.body_id);
-        let Some(body_id) = self.tcx.hir_node(hir_id).body_id() else { return false };
+        let Some(body_id) = self.tcx.hir_node(hir_id).body_id() else { return (false, false) };
         let ControlFlow::Break(expr) =
             (FindMethodSubexprOfTry { search_span: span }).visit_body(self.tcx.hir_body(body_id))
         else {
-            return false;
+            return (false, false);
         };
         let Some(typeck) = &self.typeck_results else {
-            return false;
+            return (false, false);
         };
         let ObligationCauseCode::QuestionMark = obligation.cause.code().peel_derives() else {
-            return false;
+            return (false, false);
         };
         let self_ty = trait_pred.skip_binder().self_ty();
         let found_ty = trait_pred.skip_binder().trait_ref.args.get(1).and_then(|a| a.as_type());
-        self.note_missing_impl_for_question_mark(err, self_ty, found_ty, trait_pred);
+        let noted_missing_impl =
+            self.note_missing_impl_for_question_mark(err, self_ty, found_ty, trait_pred);
 
         let mut prev_ty = self.resolve_vars_if_possible(
             typeck.expr_ty_adjusted_opt(expr).unwrap_or(Ty::new_misc_error(self.tcx)),
@@ -1137,7 +1157,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
             }
             prev = Some(err_ty);
         }
-        suggested
+        (suggested, noted_missing_impl)
     }
 
     fn note_missing_impl_for_question_mark(
@@ -1146,7 +1166,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         self_ty: Ty<'_>,
         found_ty: Option<Ty<'_>>,
         trait_pred: ty::PolyTraitPredicate<'tcx>,
-    ) {
+    ) -> bool {
         match (self_ty.kind(), found_ty) {
             (ty::Adt(def, _), Some(ty))
                 if let ty::Adt(found, _) = ty.kind()
@@ -1187,8 +1207,9 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                     format!("`{ty}` needs to implement `Into<{self_ty}>`"),
                 );
             }
-            _ => {}
+            _ => return false,
         }
+        true
     }
 
     fn report_const_param_not_wf(
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 bc8c8a44405..e31ff8b8729 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
@@ -2878,7 +2878,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                                 // we check if `TraitB` can be reachable from `S`
                                 // to determine whether to note `TraitA` is sealed trait.
                                 if let ty::Adt(adt, _) = ty.kind() {
-                                    let visibilities = tcx.effective_visibilities(());
+                                    let visibilities = &tcx.resolutions(()).effective_visibilities;
                                     visibilities.effective_vis(local).is_none_or(|v| {
                                         v.at_level(Level::Reexported)
                                             .is_accessible_from(adt.did(), tcx)
@@ -3853,59 +3853,71 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         }
     }
 
-    pub fn suggest_derive(
+    pub fn can_suggest_derive(
         &self,
         obligation: &PredicateObligation<'tcx>,
-        err: &mut Diag<'_>,
         trait_pred: ty::PolyTraitPredicate<'tcx>,
-    ) {
+    ) -> bool {
         if trait_pred.polarity() == ty::PredicatePolarity::Negative {
-            return;
+            return false;
         }
         let Some(diagnostic_name) = self.tcx.get_diagnostic_name(trait_pred.def_id()) else {
-            return;
+            return false;
         };
         let (adt, args) = match trait_pred.skip_binder().self_ty().kind() {
             ty::Adt(adt, args) if adt.did().is_local() => (adt, args),
-            _ => return,
+            _ => return false,
         };
-        let can_derive = {
-            let is_derivable_trait = match diagnostic_name {
-                sym::Default => !adt.is_enum(),
-                sym::PartialEq | sym::PartialOrd => {
-                    let rhs_ty = trait_pred.skip_binder().trait_ref.args.type_at(1);
-                    trait_pred.skip_binder().self_ty() == rhs_ty
-                }
-                sym::Eq | sym::Ord | sym::Clone | sym::Copy | sym::Hash | sym::Debug => true,
-                _ => false,
-            };
-            is_derivable_trait &&
-                // Ensure all fields impl the trait.
-                adt.all_fields().all(|field| {
-                    let field_ty = ty::GenericArg::from(field.ty(self.tcx, args));
-                    let trait_args = match diagnostic_name {
-                        sym::PartialEq | sym::PartialOrd => {
-                            Some(field_ty)
-                        }
-                        _ => None,
-                    };
-                    let trait_pred = trait_pred.map_bound_ref(|tr| ty::TraitPredicate {
-                        trait_ref: ty::TraitRef::new(self.tcx,
-                            trait_pred.def_id(),
-                            [field_ty].into_iter().chain(trait_args),
-                        ),
-                        ..*tr
-                    });
-                    let field_obl = Obligation::new(
-                        self.tcx,
-                        obligation.cause.clone(),
-                        obligation.param_env,
-                        trait_pred,
-                    );
-                    self.predicate_must_hold_modulo_regions(&field_obl)
-                })
+        let is_derivable_trait = match diagnostic_name {
+            sym::Default => !adt.is_enum(),
+            sym::PartialEq | sym::PartialOrd => {
+                let rhs_ty = trait_pred.skip_binder().trait_ref.args.type_at(1);
+                trait_pred.skip_binder().self_ty() == rhs_ty
+            }
+            sym::Eq | sym::Ord | sym::Clone | sym::Copy | sym::Hash | sym::Debug => true,
+            _ => false,
+        };
+        is_derivable_trait &&
+            // Ensure all fields impl the trait.
+            adt.all_fields().all(|field| {
+                let field_ty = ty::GenericArg::from(field.ty(self.tcx, args));
+                let trait_args = match diagnostic_name {
+                    sym::PartialEq | sym::PartialOrd => {
+                        Some(field_ty)
+                    }
+                    _ => None,
+                };
+                let trait_pred = trait_pred.map_bound_ref(|tr| ty::TraitPredicate {
+                    trait_ref: ty::TraitRef::new(self.tcx,
+                        trait_pred.def_id(),
+                        [field_ty].into_iter().chain(trait_args),
+                    ),
+                    ..*tr
+                });
+                let field_obl = Obligation::new(
+                    self.tcx,
+                    obligation.cause.clone(),
+                    obligation.param_env,
+                    trait_pred,
+                );
+                self.predicate_must_hold_modulo_regions(&field_obl)
+            })
+    }
+
+    pub fn suggest_derive(
+        &self,
+        obligation: &PredicateObligation<'tcx>,
+        err: &mut Diag<'_>,
+        trait_pred: ty::PolyTraitPredicate<'tcx>,
+    ) {
+        let Some(diagnostic_name) = self.tcx.get_diagnostic_name(trait_pred.def_id()) else {
+            return;
+        };
+        let adt = match trait_pred.skip_binder().self_ty().kind() {
+            ty::Adt(adt, _) if adt.did().is_local() => adt,
+            _ => return,
         };
-        if can_derive {
+        if self.can_suggest_derive(obligation, trait_pred) {
             err.span_suggestion_verbose(
                 self.tcx.def_span(adt.did()).shrink_to_lo(),
                 format!(
diff --git a/compiler/rustc_trait_selection/src/opaque_types.rs b/compiler/rustc_trait_selection/src/opaque_types.rs
index d5bde9192d5..bc7bdd372ba 100644
--- a/compiler/rustc_trait_selection/src/opaque_types.rs
+++ b/compiler/rustc_trait_selection/src/opaque_types.rs
@@ -4,8 +4,8 @@ use rustc_hir::def_id::LocalDefId;
 use rustc_infer::infer::outlives::env::OutlivesEnvironment;
 use rustc_infer::infer::{InferCtxt, TyCtxtInferExt};
 use rustc_middle::ty::{
-    self, DefiningScopeKind, GenericArgKind, GenericArgs, OpaqueTypeKey, TyCtxt, TypeVisitableExt,
-    TypingMode, fold_regions,
+    self, DefiningScopeKind, GenericArgKind, GenericArgs, OpaqueTypeKey, Ty, TyCtxt,
+    TypeVisitableExt, TypingMode, fold_regions,
 };
 use rustc_span::{ErrorGuaranteed, Span};
 
@@ -13,22 +13,23 @@ use crate::errors::NonGenericOpaqueTypeParam;
 use crate::regions::OutlivesEnvironmentBuildExt;
 use crate::traits::ObligationCtxt;
 
-pub enum InvalidOpaqueTypeArgs<'tcx> {
-    AlreadyReported(ErrorGuaranteed),
+#[derive(Debug)]
+pub enum NonDefiningUseReason<'tcx> {
+    Tainted(ErrorGuaranteed),
     NotAParam { opaque_type_key: OpaqueTypeKey<'tcx>, param_index: usize, span: Span },
     DuplicateParam { opaque_type_key: OpaqueTypeKey<'tcx>, param_indices: Vec<usize>, span: Span },
 }
-impl From<ErrorGuaranteed> for InvalidOpaqueTypeArgs<'_> {
+impl From<ErrorGuaranteed> for NonDefiningUseReason<'_> {
     fn from(guar: ErrorGuaranteed) -> Self {
-        InvalidOpaqueTypeArgs::AlreadyReported(guar)
+        NonDefiningUseReason::Tainted(guar)
     }
 }
-impl<'tcx> InvalidOpaqueTypeArgs<'tcx> {
+impl<'tcx> NonDefiningUseReason<'tcx> {
     pub fn report(self, infcx: &InferCtxt<'tcx>) -> ErrorGuaranteed {
         let tcx = infcx.tcx;
         match self {
-            InvalidOpaqueTypeArgs::AlreadyReported(guar) => guar,
-            InvalidOpaqueTypeArgs::NotAParam { opaque_type_key, param_index, span } => {
+            NonDefiningUseReason::Tainted(guar) => guar,
+            NonDefiningUseReason::NotAParam { opaque_type_key, param_index, span } => {
                 let opaque_generics = tcx.generics_of(opaque_type_key.def_id);
                 let opaque_param = opaque_generics.param_at(param_index, tcx);
                 let kind = opaque_param.kind.descr();
@@ -39,7 +40,7 @@ impl<'tcx> InvalidOpaqueTypeArgs<'tcx> {
                     param_span: tcx.def_span(opaque_param.def_id),
                 })
             }
-            InvalidOpaqueTypeArgs::DuplicateParam { opaque_type_key, param_indices, span } => {
+            NonDefiningUseReason::DuplicateParam { opaque_type_key, param_indices, span } => {
                 let opaque_generics = tcx.generics_of(opaque_type_key.def_id);
                 let descr = opaque_generics.param_at(param_indices[0], tcx).kind.descr();
                 let spans: Vec<_> = param_indices
@@ -57,15 +58,17 @@ impl<'tcx> InvalidOpaqueTypeArgs<'tcx> {
 }
 
 /// Opaque type parameter validity check as documented in the [rustc-dev-guide chapter].
+/// With the new solver, uses which fail this check are simply treated as non-defining
+/// and we only emit an error if no defining use exists.
 ///
 /// [rustc-dev-guide chapter]:
 /// https://rustc-dev-guide.rust-lang.org/opaque-types-region-infer-restrictions.html
-pub fn check_opaque_type_parameter_valid<'tcx>(
+pub fn opaque_type_has_defining_use_args<'tcx>(
     infcx: &InferCtxt<'tcx>,
     opaque_type_key: OpaqueTypeKey<'tcx>,
     span: Span,
     defining_scope_kind: DefiningScopeKind,
-) -> Result<(), InvalidOpaqueTypeArgs<'tcx>> {
+) -> Result<(), NonDefiningUseReason<'tcx>> {
     let tcx = infcx.tcx;
     let opaque_env = LazyOpaqueTyEnv::new(tcx, opaque_type_key.def_id);
     let mut seen_params: FxIndexMap<_, Vec<_>> = FxIndexMap::default();
@@ -104,13 +107,13 @@ pub fn check_opaque_type_parameter_valid<'tcx>(
         } else {
             // Prevent `fn foo() -> Foo<u32>` from being defining.
             opaque_env.param_is_error(i)?;
-            return Err(InvalidOpaqueTypeArgs::NotAParam { opaque_type_key, param_index: i, span });
+            return Err(NonDefiningUseReason::NotAParam { opaque_type_key, param_index: i, span });
         }
     }
 
     for (_, param_indices) in seen_params {
         if param_indices.len() > 1 {
-            return Err(InvalidOpaqueTypeArgs::DuplicateParam {
+            return Err(NonDefiningUseReason::DuplicateParam {
                 opaque_type_key,
                 param_indices,
                 span,
@@ -205,3 +208,27 @@ impl<'tcx> LazyOpaqueTyEnv<'tcx> {
         canonical_args
     }
 }
+
+pub fn report_item_does_not_constrain_error<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    item_def_id: LocalDefId,
+    def_id: LocalDefId,
+    non_defining_use: Option<(OpaqueTypeKey<'tcx>, Span)>,
+) -> ErrorGuaranteed {
+    let span = tcx.def_ident_span(item_def_id).unwrap_or_else(|| tcx.def_span(item_def_id));
+    let opaque_type_span = tcx.def_span(def_id);
+    let opaque_type_name = tcx.def_path_str(def_id);
+
+    let mut err =
+        tcx.dcx().struct_span_err(span, format!("item does not constrain `{opaque_type_name}`"));
+    err.note("consider removing `#[define_opaque]` or adding an empty `#[define_opaque()]`");
+    err.span_note(opaque_type_span, "this opaque type is supposed to be constrained");
+    if let Some((key, span)) = non_defining_use {
+        let opaque_ty = Ty::new_opaque(tcx, key.def_id.into(), key.args);
+        err.span_note(
+            span,
+            format!("this use of `{opaque_ty}` does not have unique universal generic arguments"),
+        );
+    }
+    err.emit()
+}
diff --git a/compiler/rustc_trait_selection/src/solve/fulfill.rs b/compiler/rustc_trait_selection/src/solve/fulfill.rs
index 3f628d80662..575e0472e0e 100644
--- a/compiler/rustc_trait_selection/src/solve/fulfill.rs
+++ b/compiler/rustc_trait_selection/src/solve/fulfill.rs
@@ -252,7 +252,9 @@ where
                         // 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() {
+                        if infcx.in_hir_typeck
+                            && (obligation.has_non_region_infer() || obligation.has_free_regions())
+                        {
                             infcx.push_hir_typeck_potentially_region_dependent_goal(obligation);
                         }
                     }
diff --git a/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs b/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
index ea1eed95723..4b493c95d59 100644
--- a/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
+++ b/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
@@ -106,6 +106,10 @@ fn dyn_compatibility_violations_for_trait(
     if !spans.is_empty() {
         violations.push(DynCompatibilityViolation::SupertraitNonLifetimeBinder(spans));
     }
+    let spans = super_predicates_are_unconditionally_const(tcx, trait_def_id);
+    if !spans.is_empty() {
+        violations.push(DynCompatibilityViolation::SupertraitConst(spans));
+    }
 
     violations
 }
@@ -247,16 +251,31 @@ fn super_predicates_have_non_lifetime_binders(
     tcx: TyCtxt<'_>,
     trait_def_id: DefId,
 ) -> SmallVec<[Span; 1]> {
-    // If non_lifetime_binders is disabled, then exit early
-    if !tcx.features().non_lifetime_binders() {
-        return SmallVec::new();
-    }
     tcx.explicit_super_predicates_of(trait_def_id)
         .iter_identity_copied()
         .filter_map(|(pred, span)| pred.has_non_region_bound_vars().then_some(span))
         .collect()
 }
 
+/// Checks for `const Trait` supertraits. We're okay with `[const] Trait`,
+/// supertraits since for a non-const instantiation of that trait, the
+/// conditionally-const supertrait is also not required to be const.
+fn super_predicates_are_unconditionally_const(
+    tcx: TyCtxt<'_>,
+    trait_def_id: DefId,
+) -> SmallVec<[Span; 1]> {
+    tcx.explicit_super_predicates_of(trait_def_id)
+        .iter_identity_copied()
+        .filter_map(|(pred, span)| {
+            if let ty::ClauseKind::HostEffect(_) = pred.kind().skip_binder() {
+                Some(span)
+            } else {
+                None
+            }
+        })
+        .collect()
+}
+
 fn trait_has_sized_self(tcx: TyCtxt<'_>, trait_def_id: DefId) -> bool {
     tcx.generics_require_sized_self(trait_def_id)
 }
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 0ca2d216228..6ce68507d65 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
@@ -1,6 +1,7 @@
 use std::fmt;
 
 use rustc_errors::ErrorGuaranteed;
+use rustc_hir::def_id::LocalDefId;
 use rustc_infer::infer::region_constraints::RegionConstraintData;
 use rustc_middle::traits::query::NoSolution;
 use rustc_middle::ty::{TyCtxt, TypeFoldable};
@@ -42,13 +43,14 @@ where
     fn fully_perform(
         self,
         infcx: &InferCtxt<'tcx>,
+        root_def_id: LocalDefId,
         span: Span,
     ) -> Result<TypeOpOutput<'tcx, Self>, ErrorGuaranteed> {
         if cfg!(debug_assertions) {
             info!("fully_perform({:?})", self);
         }
 
-        Ok(scrape_region_constraints(infcx, self.closure, self.description, span)?.0)
+        Ok(scrape_region_constraints(infcx, root_def_id, self.description, span, self.closure)?.0)
     }
 }
 
@@ -62,9 +64,10 @@ impl<F> fmt::Debug for CustomTypeOp<F> {
 /// constraints that result, creating query-region-constraints.
 pub fn scrape_region_constraints<'tcx, Op, R>(
     infcx: &InferCtxt<'tcx>,
-    op: impl FnOnce(&ObligationCtxt<'_, 'tcx>) -> Result<R, NoSolution>,
+    root_def_id: LocalDefId,
     name: &'static str,
     span: Span,
+    op: impl FnOnce(&ObligationCtxt<'_, 'tcx>) -> Result<R, NoSolution>,
 ) -> Result<(TypeOpOutput<'tcx, Op>, RegionConstraintData<'tcx>), ErrorGuaranteed>
 where
     R: TypeFoldable<TyCtxt<'tcx>>,
@@ -94,6 +97,8 @@ where
         let errors = ocx.select_all_or_error();
         if errors.is_empty() {
             Ok(value)
+        } else if let Err(guar) = infcx.tcx.check_potentially_region_dependent_goals(root_def_id) {
+            Err(guar)
         } else {
             Err(infcx
                 .dcx()
diff --git a/compiler/rustc_trait_selection/src/traits/query/type_op/mod.rs b/compiler/rustc_trait_selection/src/traits/query/type_op/mod.rs
index 018e9748cf0..4b8bf868123 100644
--- a/compiler/rustc_trait_selection/src/traits/query/type_op/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/query/type_op/mod.rs
@@ -1,6 +1,7 @@
 use std::fmt;
 
 use rustc_errors::ErrorGuaranteed;
+use rustc_hir::def_id::LocalDefId;
 use rustc_infer::traits::PredicateObligations;
 use rustc_middle::traits::query::NoSolution;
 use rustc_middle::ty::{ParamEnvAnd, TyCtxt, TypeFoldable};
@@ -37,6 +38,7 @@ pub trait TypeOp<'tcx>: Sized + fmt::Debug {
     fn fully_perform(
         self,
         infcx: &InferCtxt<'tcx>,
+        root_def_id: LocalDefId,
         span: Span,
     ) -> Result<TypeOpOutput<'tcx, Self>, ErrorGuaranteed>;
 }
@@ -140,6 +142,7 @@ where
     fn fully_perform(
         self,
         infcx: &InferCtxt<'tcx>,
+        root_def_id: LocalDefId,
         span: Span,
     ) -> Result<TypeOpOutput<'tcx, Self>, ErrorGuaranteed> {
         // In the new trait solver, query type ops are performed locally. This
@@ -152,9 +155,10 @@ where
         if infcx.next_trait_solver() {
             return Ok(scrape_region_constraints(
                 infcx,
-                |ocx| QueryTypeOp::perform_locally_with_next_solver(ocx, self, span),
+                root_def_id,
                 "query type op",
                 span,
+                |ocx| QueryTypeOp::perform_locally_with_next_solver(ocx, self, span),
             )?
             .0);
         }
@@ -166,19 +170,15 @@ where
         // we sometimes end up with `Opaque<'a> = Opaque<'b>` instead of an actual hidden type. In that case we don't register a
         // hidden type but just equate the lifetimes. Thus we need to scrape the region constraints even though we're also manually
         // collecting region constraints via `region_constraints`.
-        let (mut output, _) = scrape_region_constraints(
-            infcx,
-            |ocx| {
+        let (mut output, _) =
+            scrape_region_constraints(infcx, root_def_id, "fully_perform", span, |ocx| {
                 let (output, ei, obligations, _) =
                     Q::fully_perform_into(self, infcx, &mut region_constraints, span)?;
                 error_info = ei;
 
                 ocx.register_obligations(obligations);
                 Ok(output)
-            },
-            "fully_perform",
-            span,
-        )?;
+            })?;
         output.error_info = error_info;
         if let Some(QueryRegionConstraints { outlives, assumptions }) = output.constraints {
             region_constraints.outlives.extend(outlives.iter().cloned());
diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
index 468c42abf48..1dd31990ab7 100644
--- a/compiler/rustc_trait_selection/src/traits/select/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -4,9 +4,9 @@
 
 use std::assert_matches::assert_matches;
 use std::cell::{Cell, RefCell};
+use std::cmp;
 use std::fmt::{self, Display};
 use std::ops::ControlFlow;
-use std::{cmp, iter};
 
 use hir::def::DefKind;
 use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
@@ -2185,32 +2185,23 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
                 ty::Binder::dummy(vec![ty])
             }
 
-            ty::Coroutine(coroutine_def_id, args) => {
-                match self.tcx().coroutine_movability(coroutine_def_id) {
-                    hir::Movability::Static => {
-                        unreachable!("tried to assemble `Sized` for static coroutine")
-                    }
-                    hir::Movability::Movable => {
-                        if self.tcx().features().coroutine_clone() {
-                            ty::Binder::dummy(
-                                args.as_coroutine()
-                                    .upvar_tys()
-                                    .iter()
-                                    .chain([Ty::new_coroutine_witness(
-                                        self.tcx(),
-                                        coroutine_def_id,
-                                        self.tcx().mk_args(args.as_coroutine().parent_args()),
-                                    )])
-                                    .collect::<Vec<_>>(),
-                            )
-                        } else {
-                            unreachable!(
-                                "tried to assemble `Sized` for coroutine without enabled feature"
-                            )
-                        }
+            ty::Coroutine(def_id, args) => match self.tcx().coroutine_movability(def_id) {
+                hir::Movability::Static => {
+                    unreachable!("tried to assemble `Clone` for static coroutine")
+                }
+                hir::Movability::Movable => {
+                    if self.tcx().features().coroutine_clone() {
+                        ty::Binder::dummy(vec![
+                            args.as_coroutine().tupled_upvars_ty(),
+                            Ty::new_coroutine_witness_for_coroutine(self.tcx(), def_id, args),
+                        ])
+                    } else {
+                        unreachable!(
+                            "tried to assemble `Clone` for coroutine without enabled feature"
+                        )
                     }
                 }
-            }
+            },
 
             ty::CoroutineWitness(def_id, args) => self
                 .infcx
@@ -2334,25 +2325,9 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
             ty::Coroutine(def_id, args) => {
                 let ty = self.infcx.shallow_resolve(args.as_coroutine().tupled_upvars_ty());
                 let tcx = self.tcx();
-                let witness = Ty::new_coroutine_witness(
-                    tcx,
-                    def_id,
-                    ty::GenericArgs::for_item(tcx, def_id, |def, _| match def.kind {
-                        // HACK: Coroutine witnesse types are lifetime erased, so they
-                        // never reference any lifetime args from the coroutine. We erase
-                        // the regions here since we may get into situations where a
-                        // coroutine is recursively contained within itself, leading to
-                        // witness types that differ by region args. This means that
-                        // cycle detection in fulfillment will not kick in, which leads
-                        // to unnecessary overflows in async code. See the issue:
-                        // <https://github.com/rust-lang/rust/issues/145151>.
-                        ty::GenericParamDefKind::Lifetime => tcx.lifetimes.re_erased.into(),
-                        ty::GenericParamDefKind::Type { .. }
-                        | ty::GenericParamDefKind::Const { .. } => args[def.index as usize],
-                    }),
-                );
+                let witness = Ty::new_coroutine_witness_for_coroutine(tcx, def_id, args);
                 ty::Binder::dummy(AutoImplConstituents {
-                    types: [ty].into_iter().chain(iter::once(witness)).collect(),
+                    types: vec![ty, witness],
                     assumptions: vec![],
                 })
             }
diff --git a/compiler/rustc_trait_selection/src/traits/util.rs b/compiler/rustc_trait_selection/src/traits/util.rs
index 83c0969762f..335942d5bcc 100644
--- a/compiler/rustc_trait_selection/src/traits/util.rs
+++ b/compiler/rustc_trait_selection/src/traits/util.rs
@@ -9,8 +9,8 @@ pub use rustc_infer::traits::util::*;
 use rustc_middle::bug;
 use rustc_middle::ty::fast_reject::DeepRejectCtxt;
 use rustc_middle::ty::{
-    self, PolyTraitPredicate, SizedTraitKind, TraitPredicate, TraitRef, Ty, TyCtxt, TypeFoldable,
-    TypeFolder, TypeSuperFoldable, TypeVisitableExt,
+    self, PolyTraitPredicate, PredicatePolarity, SizedTraitKind, TraitPredicate, TraitRef, Ty,
+    TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable, TypeVisitableExt,
 };
 pub use rustc_next_trait_solver::placeholder::BoundVarReplacer;
 use rustc_span::Span;
@@ -427,7 +427,9 @@ pub(crate) fn lazily_elaborate_sizedness_candidate<'tcx>(
         return candidate;
     }
 
-    if obligation.predicate.polarity() != candidate.polarity() {
+    if obligation.predicate.polarity() != PredicatePolarity::Positive
+        || candidate.polarity() != PredicatePolarity::Positive
+    {
         return candidate;
     }
 
diff --git a/compiler/rustc_traits/Cargo.toml b/compiler/rustc_traits/Cargo.toml
index 04aef4e7b9e..9f40f4d5c23 100644
--- a/compiler/rustc_traits/Cargo.toml
+++ b/compiler/rustc_traits/Cargo.toml
@@ -6,7 +6,6 @@ edition = "2024"
 [dependencies]
 # tidy-alphabetical-start
 rustc_data_structures = { path = "../rustc_data_structures" }
-rustc_hir = { path = "../rustc_hir" }
 rustc_infer = { path = "../rustc_infer" }
 rustc_middle = { path = "../rustc_middle" }
 rustc_span = { path = "../rustc_span" }
diff --git a/compiler/rustc_traits/src/coroutine_witnesses.rs b/compiler/rustc_traits/src/coroutine_witnesses.rs
index 8a2a0832ddb..20f9b013724 100644
--- a/compiler/rustc_traits/src/coroutine_witnesses.rs
+++ b/compiler/rustc_traits/src/coroutine_witnesses.rs
@@ -1,9 +1,9 @@
-use rustc_hir::def_id::DefId;
 use rustc_infer::infer::TyCtxtInferExt;
 use rustc_infer::infer::canonical::query_response::make_query_region_constraints;
 use rustc_infer::infer::resolve::OpportunisticRegionResolver;
 use rustc_infer::traits::{Obligation, ObligationCause};
 use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable, TypeVisitableExt, fold_regions};
+use rustc_span::def_id::DefId;
 use rustc_trait_selection::traits::{ObligationCtxt, with_replaced_escaping_bound_vars};
 
 /// Return the set of types that should be taken into account when checking
diff --git a/compiler/rustc_traits/src/dropck_outlives.rs b/compiler/rustc_traits/src/dropck_outlives.rs
index 5eddad39e2b..d33ade7a9e1 100644
--- a/compiler/rustc_traits/src/dropck_outlives.rs
+++ b/compiler/rustc_traits/src/dropck_outlives.rs
@@ -1,5 +1,4 @@
 use rustc_data_structures::fx::FxHashSet;
-use rustc_hir::def_id::DefId;
 use rustc_infer::infer::TyCtxtInferExt;
 use rustc_infer::infer::canonical::{Canonical, QueryResponse};
 use rustc_middle::bug;
@@ -7,6 +6,7 @@ use rustc_middle::query::Providers;
 use rustc_middle::traits::query::{DropckConstraint, DropckOutlivesResult};
 use rustc_middle::ty::{self, GenericArgs, TyCtxt};
 use rustc_span::DUMMY_SP;
+use rustc_span::def_id::DefId;
 use rustc_trait_selection::infer::InferCtxtBuilderExt;
 use rustc_trait_selection::traits::query::dropck_outlives::{
     compute_dropck_outlives_inner, dtorck_constraint_for_ty_inner,
diff --git a/compiler/rustc_ty_utils/src/abi.rs b/compiler/rustc_ty_utils/src/abi.rs
index 89d1dd8cf23..e4ed084b073 100644
--- a/compiler/rustc_ty_utils/src/abi.rs
+++ b/compiler/rustc_ty_utils/src/abi.rs
@@ -356,6 +356,7 @@ fn arg_attrs_for_rust_scalar<'tcx>(
 
             if matches!(kind, PointerKind::SharedRef { frozen: true }) && !is_return {
                 attrs.set(ArgAttribute::ReadOnly);
+                attrs.set(ArgAttribute::CapturesReadOnly);
             }
         }
     }
diff --git a/compiler/rustc_type_ir/Cargo.toml b/compiler/rustc_type_ir/Cargo.toml
index e7fee574dd4..d55e9b3b1be 100644
--- a/compiler/rustc_type_ir/Cargo.toml
+++ b/compiler/rustc_type_ir/Cargo.toml
@@ -12,6 +12,7 @@ indexmap = "2.0.0"
 rustc-hash = "2.0.0"
 rustc_ast_ir = { path = "../rustc_ast_ir", default-features = false }
 rustc_data_structures = { path = "../rustc_data_structures", optional = true }
+rustc_error_messages = { path = "../rustc_error_messages", optional = true }
 rustc_index = { path = "../rustc_index", default-features = false }
 rustc_macros = { path = "../rustc_macros", optional = true }
 rustc_serialize = { path = "../rustc_serialize", optional = true }
@@ -27,6 +28,7 @@ tracing = "0.1"
 default = ["nightly"]
 nightly = [
     "dep:rustc_data_structures",
+    "dep:rustc_error_messages",
     "dep:rustc_macros",
     "dep:rustc_serialize",
     "dep:rustc_span",
diff --git a/compiler/rustc_type_ir/src/infer_ctxt.rs b/compiler/rustc_type_ir/src/infer_ctxt.rs
index e39b99e992b..b4462294700 100644
--- a/compiler/rustc_type_ir/src/infer_ctxt.rs
+++ b/compiler/rustc_type_ir/src/infer_ctxt.rs
@@ -148,10 +148,6 @@ 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 1a6c99ce7de..569570b5783 100644
--- a/compiler/rustc_type_ir/src/inherent.rs
+++ b/compiler/rustc_type_ir/src/inherent.rs
@@ -91,6 +91,12 @@ pub trait Ty<I: Interner<Ty = Self>>:
 
     fn new_coroutine_witness(interner: I, def_id: I::DefId, args: I::GenericArgs) -> Self;
 
+    fn new_coroutine_witness_for_coroutine(
+        interner: I,
+        def_id: I::DefId,
+        coroutine_args: I::GenericArgs,
+    ) -> Self;
+
     fn new_ptr(interner: I, ty: Self, mutbl: Mutability) -> Self;
 
     fn new_ref(interner: I, region: I::Region, ty: Self, mutbl: Mutability) -> Self;
diff --git a/compiler/rustc_type_ir/src/ir_print.rs b/compiler/rustc_type_ir/src/ir_print.rs
index 388ad09cb20..82bb8791b84 100644
--- a/compiler/rustc_type_ir/src/ir_print.rs
+++ b/compiler/rustc_type_ir/src/ir_print.rs
@@ -1,9 +1,9 @@
 use std::fmt;
 
 use crate::{
-    AliasTerm, AliasTy, Binder, CoercePredicate, ExistentialProjection, ExistentialTraitRef, FnSig,
-    HostEffectPredicate, Interner, NormalizesTo, OutlivesPredicate, PatternKind,
-    ProjectionPredicate, SubtypePredicate, TraitPredicate, TraitRef,
+    AliasTerm, AliasTy, Binder, ClosureKind, CoercePredicate, ExistentialProjection,
+    ExistentialTraitRef, FnSig, HostEffectPredicate, Interner, NormalizesTo, OutlivesPredicate,
+    PatternKind, ProjectionPredicate, SubtypePredicate, TraitPredicate, TraitRef, UnevaluatedConst,
 };
 
 pub trait IrPrint<T> {
@@ -70,3 +70,46 @@ where
         <I as IrPrint<OutlivesPredicate<I, T>>>::print(self, fmt)
     }
 }
+
+#[cfg(feature = "nightly")]
+mod into_diag_arg_impls {
+    use rustc_error_messages::{DiagArgValue, IntoDiagArg};
+
+    use super::*;
+
+    impl<I: Interner> IntoDiagArg for TraitRef<I> {
+        fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+            self.to_string().into_diag_arg(path)
+        }
+    }
+
+    impl<I: Interner> IntoDiagArg for ExistentialTraitRef<I> {
+        fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+            self.to_string().into_diag_arg(path)
+        }
+    }
+
+    impl<I: Interner> IntoDiagArg for UnevaluatedConst<I> {
+        fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+            format!("{self:?}").into_diag_arg(path)
+        }
+    }
+
+    impl<I: Interner> IntoDiagArg for FnSig<I> {
+        fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+            format!("{self:?}").into_diag_arg(path)
+        }
+    }
+
+    impl<I: Interner, T: IntoDiagArg> IntoDiagArg for Binder<I, T> {
+        fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+            self.skip_binder().into_diag_arg(path)
+        }
+    }
+
+    impl IntoDiagArg for ClosureKind {
+        fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+            DiagArgValue::Str(self.as_str().into())
+        }
+    }
+}
diff --git a/compiler/rustc_type_ir/src/region_kind.rs b/compiler/rustc_type_ir/src/region_kind.rs
index cca81dcb4a0..06048af0436 100644
--- a/compiler/rustc_type_ir/src/region_kind.rs
+++ b/compiler/rustc_type_ir/src/region_kind.rs
@@ -154,7 +154,7 @@ pub enum RegionKind<I: Interner> {
     /// parameters via `tcx.liberate_late_bound_regions`. They are then treated
     /// the same way as `ReEarlyParam` while inside of the function.
     ///
-    /// See <https://rustc-dev-guide.rust-lang.org/early-late-bound-params/early-late-bound-summary.html> for
+    /// See <https://rustc-dev-guide.rust-lang.org/early_late_parameters.html> for
     /// more info about early and late bound lifetime parameters.
     ReLateParam(I::LateParamRegion),