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-rw-r--r--compiler/rustc_abi/src/lib.rs2
-rw-r--r--compiler/rustc_ast/src/expand/mod.rs4
-rw-r--r--compiler/rustc_ast_lowering/src/delegation.rs15
-rw-r--r--compiler/rustc_ast_lowering/src/item.rs6
-rw-r--r--compiler/rustc_ast_lowering/src/lib.rs8
-rw-r--r--compiler/rustc_ast_pretty/src/pprust/tests.rs4
-rw-r--r--compiler/rustc_borrowck/src/consumers.rs6
-rw-r--r--compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs6
-rw-r--r--compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs10
-rw-r--r--compiler/rustc_borrowck/src/diagnostics/mod.rs15
-rw-r--r--compiler/rustc_borrowck/src/diagnostics/region_errors.rs7
-rw-r--r--compiler/rustc_borrowck/src/diagnostics/region_name.rs10
-rw-r--r--compiler/rustc_borrowck/src/lib.rs258
-rw-r--r--compiler/rustc_borrowck/src/nll.rs27
-rw-r--r--compiler/rustc_borrowck/src/opaque_types.rs55
-rw-r--r--compiler/rustc_borrowck/src/polonius/dump.rs8
-rw-r--r--compiler/rustc_borrowck/src/region_infer/mod.rs15
-rw-r--r--compiler/rustc_borrowck/src/region_infer/opaque_types.rs14
-rw-r--r--compiler/rustc_borrowck/src/root_cx.rs101
-rw-r--r--compiler/rustc_borrowck/src/type_check/constraint_conversion.rs6
-rw-r--r--compiler/rustc_borrowck/src/type_check/mod.rs15
-rw-r--r--compiler/rustc_borrowck/src/type_check/opaque_types.rs2
-rw-r--r--compiler/rustc_borrowck/src/universal_regions.rs22
-rw-r--r--compiler/rustc_builtin_macros/src/autodiff.rs2
-rw-r--r--compiler/rustc_builtin_macros/src/proc_macro_harness.rs24
-rw-r--r--compiler/rustc_codegen_cranelift/src/driver/aot.rs78
-rw-r--r--compiler/rustc_codegen_cranelift/src/global_asm.rs3
-rw-r--r--compiler/rustc_codegen_cranelift/src/lib.rs2
-rw-r--r--compiler/rustc_codegen_cranelift/src/main_shim.rs2
-rw-r--r--compiler/rustc_codegen_gcc/src/back/write.rs29
-rw-r--r--compiler/rustc_codegen_llvm/src/back/write.rs64
-rw-r--r--compiler/rustc_codegen_llvm/src/common.rs16
-rw-r--r--compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs3
-rw-r--r--compiler/rustc_codegen_llvm/src/intrinsic.rs69
-rw-r--r--compiler/rustc_codegen_ssa/src/back/link.rs8
-rw-r--r--compiler/rustc_codegen_ssa/src/back/write.rs45
-rw-r--r--compiler/rustc_codegen_ssa/src/base.rs13
-rw-r--r--compiler/rustc_codegen_ssa/src/errors.rs4
-rw-r--r--compiler/rustc_codegen_ssa/src/lib.rs18
-rw-r--r--compiler/rustc_codegen_ssa/src/mir/mod.rs79
-rw-r--r--compiler/rustc_codegen_ssa/src/mir/operand.rs32
-rw-r--r--compiler/rustc_data_structures/Cargo.toml2
-rw-r--r--compiler/rustc_data_structures/src/marker.rs13
-rw-r--r--compiler/rustc_data_structures/src/obligation_forest/mod.rs2
-rw-r--r--compiler/rustc_data_structures/src/sync/freeze.rs2
-rw-r--r--compiler/rustc_data_structures/src/sync/parallel.rs104
-rw-r--r--compiler/rustc_data_structures/src/unord.rs10
-rw-r--r--compiler/rustc_driver_impl/Cargo.toml2
-rw-r--r--compiler/rustc_driver_impl/src/lib.rs22
-rw-r--r--compiler/rustc_error_codes/src/error_codes/E0622.md4
-rw-r--r--compiler/rustc_error_codes/src/lib.rs2
-rw-r--r--compiler/rustc_error_messages/src/lib.rs2
-rw-r--r--compiler/rustc_errors/src/diagnostic.rs8
-rw-r--r--compiler/rustc_errors/src/lib.rs70
-rw-r--r--compiler/rustc_expand/src/base.rs2
-rw-r--r--compiler/rustc_expand/src/expand.rs10
-rw-r--r--compiler/rustc_feature/src/accepted.rs4
-rw-r--r--compiler/rustc_feature/src/removed.rs2
-rw-r--r--compiler/rustc_feature/src/unstable.rs10
-rw-r--r--compiler/rustc_hir/src/def.rs15
-rw-r--r--compiler/rustc_hir/src/definitions.rs22
-rw-r--r--compiler/rustc_hir/src/hir.rs6
-rw-r--r--compiler/rustc_hir/src/intravisit.rs8
-rw-r--r--compiler/rustc_hir/src/tests.rs2
-rw-r--r--compiler/rustc_hir_analysis/messages.ftl11
-rw-r--r--compiler/rustc_hir_analysis/src/check/check.rs51
-rw-r--r--compiler/rustc_hir_analysis/src/check/compare_impl_item.rs10
-rw-r--r--compiler/rustc_hir_analysis/src/check/intrinsic.rs41
-rw-r--r--compiler/rustc_hir_analysis/src/check/wfcheck.rs4
-rw-r--r--compiler/rustc_hir_analysis/src/coherence/builtin.rs2
-rw-r--r--compiler/rustc_hir_analysis/src/collect.rs10
-rw-r--r--compiler/rustc_hir_analysis/src/collect/predicates_of.rs18
-rw-r--r--compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs8
-rw-r--r--compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs58
-rw-r--r--compiler/rustc_hir_analysis/src/constrained_generic_params.rs2
-rw-r--r--compiler/rustc_hir_analysis/src/errors.rs12
-rw-r--r--compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs4
-rw-r--r--compiler/rustc_hir_analysis/src/hir_ty_lowering/cmse.rs4
-rw-r--r--compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs14
-rw-r--r--compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs44
-rw-r--r--compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs41
-rw-r--r--compiler/rustc_hir_analysis/src/hir_wf_check.rs11
-rw-r--r--compiler/rustc_hir_analysis/src/outlives/implicit_infer.rs21
-rw-r--r--compiler/rustc_hir_analysis/src/outlives/utils.rs2
-rw-r--r--compiler/rustc_hir_analysis/src/variance/constraints.rs2
-rw-r--r--compiler/rustc_hir_analysis/src/variance/mod.rs10
-rw-r--r--compiler/rustc_hir_pretty/src/lib.rs30
-rw-r--r--compiler/rustc_hir_typeck/messages.ftl2
-rw-r--r--compiler/rustc_hir_typeck/src/errors.rs2
-rw-r--r--compiler/rustc_hir_typeck/src/expr.rs17
-rw-r--r--compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs14
-rw-r--r--compiler/rustc_hir_typeck/src/method/mod.rs6
-rw-r--r--compiler/rustc_hir_typeck/src/method/suggest.rs81
-rw-r--r--compiler/rustc_hir_typeck/src/pat.rs260
-rw-r--r--compiler/rustc_infer/src/infer/canonical/canonicalizer.rs8
-rw-r--r--compiler/rustc_infer/src/infer/canonical/query_response.rs2
-rw-r--r--compiler/rustc_infer/src/infer/freshen.rs2
-rw-r--r--compiler/rustc_infer/src/infer/lexical_region_resolve/mod.rs28
-rw-r--r--compiler/rustc_infer/src/infer/outlives/env.rs2
-rw-r--r--compiler/rustc_infer/src/infer/outlives/for_liveness.rs2
-rw-r--r--compiler/rustc_infer/src/infer/region_constraints/leak_check.rs2
-rw-r--r--compiler/rustc_infer/src/infer/region_constraints/mod.rs4
-rw-r--r--compiler/rustc_infer/src/infer/relate/generalize.rs2
-rw-r--r--compiler/rustc_infer/src/infer/resolve.rs4
-rw-r--r--compiler/rustc_interface/Cargo.toml1
-rw-r--r--compiler/rustc_interface/src/interface.rs5
-rw-r--r--compiler/rustc_interface/src/passes.rs5
-rw-r--r--compiler/rustc_interface/src/tests.rs2
-rw-r--r--compiler/rustc_interface/src/util.rs39
-rw-r--r--compiler/rustc_lint/src/builtin.rs4
-rw-r--r--compiler/rustc_lint/src/context.rs2
-rw-r--r--compiler/rustc_lint/src/impl_trait_overcaptures.rs4
-rw-r--r--compiler/rustc_lint/src/lints.rs2
-rw-r--r--compiler/rustc_lint/src/nonstandard_style.rs8
-rw-r--r--compiler/rustc_macros/src/symbols.rs25
-rw-r--r--compiler/rustc_metadata/src/rmeta/decoder.rs6
-rw-r--r--compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs2
-rw-r--r--compiler/rustc_metadata/src/rmeta/encoder.rs12
-rw-r--r--compiler/rustc_metadata/src/rmeta/mod.rs4
-rw-r--r--compiler/rustc_middle/src/arena.rs2
-rw-r--r--compiler/rustc_middle/src/hir/map.rs4
-rw-r--r--compiler/rustc_middle/src/hir/mod.rs16
-rw-r--r--compiler/rustc_middle/src/mir/query.rs158
-rw-r--r--compiler/rustc_middle/src/mir/syntax.rs2
-rw-r--r--compiler/rustc_middle/src/mir/terminator.rs6
-rw-r--r--compiler/rustc_middle/src/query/erase.rs4
-rw-r--r--compiler/rustc_middle/src/query/mod.rs23
-rw-r--r--compiler/rustc_middle/src/query/on_disk_cache.rs12
-rw-r--r--compiler/rustc_middle/src/ty/assoc.rs23
-rw-r--r--compiler/rustc_middle/src/ty/codec.rs2
-rw-r--r--compiler/rustc_middle/src/ty/context.rs4
-rw-r--r--compiler/rustc_middle/src/ty/erase_regions.rs2
-rw-r--r--compiler/rustc_middle/src/ty/error.rs2
-rw-r--r--compiler/rustc_middle/src/ty/flags.rs2
-rw-r--r--compiler/rustc_middle/src/ty/fold.rs4
-rw-r--r--compiler/rustc_middle/src/ty/mod.rs10
-rw-r--r--compiler/rustc_middle/src/ty/opaque_types.rs2
-rw-r--r--compiler/rustc_middle/src/ty/print/mod.rs2
-rw-r--r--compiler/rustc_middle/src/ty/print/pretty.rs19
-rw-r--r--compiler/rustc_middle/src/ty/region.rs37
-rw-r--r--compiler/rustc_middle/src/ty/significant_drop_order.rs2
-rw-r--r--compiler/rustc_middle/src/ty/typeck_results.rs2
-rw-r--r--compiler/rustc_middle/src/ty/visit.rs6
-rw-r--r--compiler/rustc_mir_build/src/builder/expr/into.rs2
-rw-r--r--compiler/rustc_mir_transform/src/gvn.rs74
-rw-r--r--compiler/rustc_mir_transform/src/instsimplify.rs192
-rw-r--r--compiler/rustc_mir_transform/src/lib.rs9
-rw-r--r--compiler/rustc_monomorphize/src/collector.rs2
-rw-r--r--compiler/rustc_monomorphize/src/mono_checks/move_check.rs35
-rw-r--r--compiler/rustc_next_trait_solver/src/lib.rs2
-rw-r--r--compiler/rustc_next_trait_solver/src/solve/normalizes_to/mod.rs32
-rw-r--r--compiler/rustc_parse/src/parser/expr.rs13
-rw-r--r--compiler/rustc_parse/src/parser/item.rs21
-rw-r--r--compiler/rustc_parse/src/parser/mod.rs20
-rw-r--r--compiler/rustc_passes/src/check_attr.rs1
-rw-r--r--compiler/rustc_pattern_analysis/src/rustc.rs40
-rw-r--r--compiler/rustc_query_system/src/dep_graph/graph.rs83
-rw-r--r--compiler/rustc_query_system/src/dep_graph/serialized.rs41
-rw-r--r--compiler/rustc_resolve/Cargo.toml1
-rw-r--r--compiler/rustc_resolve/src/build_reduced_graph.rs2
-rw-r--r--compiler/rustc_resolve/src/diagnostics.rs18
-rw-r--r--compiler/rustc_resolve/src/ident.rs3
-rw-r--r--compiler/rustc_resolve/src/imports.rs44
-rw-r--r--compiler/rustc_resolve/src/late.rs3
-rw-r--r--compiler/rustc_resolve/src/late/diagnostics.rs2
-rw-r--r--compiler/rustc_resolve/src/lib.rs33
-rw-r--r--compiler/rustc_resolve/src/macros.rs20
-rw-r--r--compiler/rustc_sanitizers/src/cfi/typeid/itanium_cxx_abi/encode.rs3
-rw-r--r--compiler/rustc_serialize/src/opaque.rs2
-rw-r--r--compiler/rustc_session/Cargo.toml1
-rw-r--r--compiler/rustc_session/src/config.rs63
-rw-r--r--compiler/rustc_session/src/session.rs17
-rw-r--r--compiler/rustc_span/src/lib.rs15
-rw-r--r--compiler/rustc_span/src/symbol.rs29
-rw-r--r--compiler/rustc_span/src/symbol/tests.rs2
-rw-r--r--compiler/rustc_symbol_mangling/src/v0.rs5
-rw-r--r--compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/util.rs2
-rw-r--r--compiler/rustc_trait_selection/src/error_reporting/infer/region.rs12
-rw-r--r--compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs76
-rw-r--r--compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs27
-rw-r--r--compiler/rustc_trait_selection/src/errors.rs2
-rw-r--r--compiler/rustc_trait_selection/src/errors/note_and_explain.rs2
-rw-r--r--compiler/rustc_trait_selection/src/opaque_types.rs2
-rw-r--r--compiler/rustc_trait_selection/src/solve/fulfill/derive_errors.rs97
-rw-r--r--compiler/rustc_trait_selection/src/solve/normalize.rs32
-rw-r--r--compiler/rustc_trait_selection/src/traits/auto_trait.rs2
-rw-r--r--compiler/rustc_trait_selection/src/traits/coherence.rs2
-rw-r--r--compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs2
-rw-r--r--compiler/rustc_trait_selection/src/traits/project.rs90
-rw-r--r--compiler/rustc_trait_selection/src/traits/query/normalize.rs2
-rw-r--r--compiler/rustc_trait_selection/src/traits/select/confirmation.rs44
-rw-r--r--compiler/rustc_trait_selection/src/traits/util.rs6
-rw-r--r--compiler/rustc_ty_utils/src/assoc.rs4
-rw-r--r--compiler/rustc_ty_utils/src/implied_bounds.rs33
-rw-r--r--compiler/rustc_ty_utils/src/opaque_types.rs20
-rw-r--r--compiler/rustc_ty_utils/src/sig_types.rs2
-rw-r--r--compiler/rustc_ty_utils/src/ty.rs57
-rw-r--r--compiler/rustc_type_ir/src/inherent.rs33
-rw-r--r--compiler/rustc_type_ir/src/interner.rs2
-rw-r--r--compiler/rustc_type_ir/src/lib.rs2
-rw-r--r--compiler/rustc_type_ir/src/solve/mod.rs7
201 files changed, 2439 insertions, 1697 deletions
diff --git a/compiler/rustc_abi/src/lib.rs b/compiler/rustc_abi/src/lib.rs
index 843d5ca61dd..59b74d29221 100644
--- a/compiler/rustc_abi/src/lib.rs
+++ b/compiler/rustc_abi/src/lib.rs
@@ -1829,7 +1829,7 @@ pub struct PointeeInfo {
     pub safe: Option<PointerKind>,
     /// If `safe` is `Some`, then the pointer is either null or dereferenceable for this many bytes.
     /// On a function argument, "dereferenceable" here means "dereferenceable for the entire duration
-    /// of this function call", i.e. it is UB for the memory that this pointer points to to be freed
+    /// of this function call", i.e. it is UB for the memory that this pointer points to be freed
     /// while this function is still running.
     /// The size can be zero if the pointer is not dereferenceable.
     pub size: Size,
diff --git a/compiler/rustc_ast/src/expand/mod.rs b/compiler/rustc_ast/src/expand/mod.rs
index 04c81629323..323a8fab6d5 100644
--- a/compiler/rustc_ast/src/expand/mod.rs
+++ b/compiler/rustc_ast/src/expand/mod.rs
@@ -13,12 +13,12 @@ pub mod typetree;
 #[derive(Debug, Clone, Encodable, Decodable, HashStable_Generic)]
 pub struct StrippedCfgItem<ModId = DefId> {
     pub parent_module: ModId,
-    pub name: Ident,
+    pub ident: Ident,
     pub cfg: MetaItem,
 }
 
 impl<ModId> StrippedCfgItem<ModId> {
     pub fn map_mod_id<New>(self, f: impl FnOnce(ModId) -> New) -> StrippedCfgItem<New> {
-        StrippedCfgItem { parent_module: f(self.parent_module), name: self.name, cfg: self.cfg }
+        StrippedCfgItem { parent_module: f(self.parent_module), ident: self.ident, cfg: self.cfg }
     }
 }
diff --git a/compiler/rustc_ast_lowering/src/delegation.rs b/compiler/rustc_ast_lowering/src/delegation.rs
index 9899ee03a51..2296b05f69b 100644
--- a/compiler/rustc_ast_lowering/src/delegation.rs
+++ b/compiler/rustc_ast_lowering/src/delegation.rs
@@ -47,7 +47,7 @@ use rustc_errors::ErrorGuaranteed;
 use rustc_hir::def_id::DefId;
 use rustc_middle::span_bug;
 use rustc_middle::ty::{Asyncness, ResolverAstLowering};
-use rustc_span::{Ident, Span};
+use rustc_span::{Ident, Span, Symbol};
 use {rustc_ast as ast, rustc_hir as hir};
 
 use super::{GenericArgsMode, ImplTraitContext, LoweringContext, ParamMode};
@@ -234,12 +234,13 @@ impl<'hir> LoweringContext<'_, 'hir> {
         hir::FnSig { decl, header, span }
     }
 
-    fn generate_param(&mut self, span: Span) -> (hir::Param<'hir>, NodeId) {
+    fn generate_param(&mut self, idx: usize, span: Span) -> (hir::Param<'hir>, NodeId) {
         let pat_node_id = self.next_node_id();
         let pat_id = self.lower_node_id(pat_node_id);
+        let ident = Ident::with_dummy_span(Symbol::intern(&format!("arg{idx}")));
         let pat = self.arena.alloc(hir::Pat {
             hir_id: pat_id,
-            kind: hir::PatKind::Binding(hir::BindingMode::NONE, pat_id, Ident::empty(), None),
+            kind: hir::PatKind::Binding(hir::BindingMode::NONE, pat_id, ident, None),
             span,
             default_binding_modes: false,
         });
@@ -247,9 +248,9 @@ impl<'hir> LoweringContext<'_, 'hir> {
         (hir::Param { hir_id: self.next_id(), pat, ty_span: span, span }, pat_node_id)
     }
 
-    fn generate_arg(&mut self, param_id: HirId, span: Span) -> hir::Expr<'hir> {
+    fn generate_arg(&mut self, idx: usize, param_id: HirId, span: Span) -> hir::Expr<'hir> {
         let segments = self.arena.alloc_from_iter(iter::once(hir::PathSegment {
-            ident: Ident::empty(),
+            ident: Ident::with_dummy_span(Symbol::intern(&format!("arg{idx}"))),
             hir_id: self.next_id(),
             res: Res::Local(param_id),
             args: None,
@@ -273,7 +274,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
             let mut args: Vec<hir::Expr<'_>> = Vec::with_capacity(param_count);
 
             for idx in 0..param_count {
-                let (param, pat_node_id) = this.generate_param(span);
+                let (param, pat_node_id) = this.generate_param(idx, span);
                 parameters.push(param);
 
                 let arg = if let Some(block) = block
@@ -289,7 +290,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     this.ident_and_label_to_local_id.insert(pat_node_id, param.pat.hir_id.local_id);
                     this.lower_target_expr(&block)
                 } else {
-                    this.generate_arg(param.pat.hir_id, span)
+                    this.generate_arg(idx, param.pat.hir_id, span)
                 };
                 args.push(arg);
             }
diff --git a/compiler/rustc_ast_lowering/src/item.rs b/compiler/rustc_ast_lowering/src/item.rs
index 958a6917dff..59099e5a554 100644
--- a/compiler/rustc_ast_lowering/src/item.rs
+++ b/compiler/rustc_ast_lowering/src/item.rs
@@ -645,7 +645,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                         (
                             // Disallow `impl Trait` in foreign items.
                             this.lower_fn_decl(fdec, i.id, sig.span, FnDeclKind::ExternFn, None),
-                            this.lower_fn_params_to_names(fdec),
+                            this.lower_fn_params_to_idents(fdec),
                         )
                     });
 
@@ -833,7 +833,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
             }) => {
                 // FIXME(contracts): Deny contract here since it won't apply to
                 // any impl method or callees.
-                let names = self.lower_fn_params_to_names(&sig.decl);
+                let idents = self.lower_fn_params_to_idents(&sig.decl);
                 let (generics, sig) = self.lower_method_sig(
                     generics,
                     sig,
@@ -851,7 +851,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 (
                     *ident,
                     generics,
-                    hir::TraitItemKind::Fn(sig, hir::TraitFn::Required(names)),
+                    hir::TraitItemKind::Fn(sig, hir::TraitFn::Required(idents)),
                     false,
                 )
             }
diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index 6aa6a18ee9a..22a293d9b50 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -1247,7 +1247,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     safety: self.lower_safety(f.safety, hir::Safety::Safe),
                     abi: self.lower_extern(f.ext),
                     decl: self.lower_fn_decl(&f.decl, t.id, t.span, FnDeclKind::Pointer, None),
-                    param_names: self.lower_fn_params_to_names(&f.decl),
+                    param_idents: self.lower_fn_params_to_idents(&f.decl),
                 }))
             }
             TyKind::UnsafeBinder(f) => {
@@ -1494,7 +1494,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         }))
     }
 
-    fn lower_fn_params_to_names(&mut self, decl: &FnDecl) -> &'hir [Option<Ident>] {
+    fn lower_fn_params_to_idents(&mut self, decl: &FnDecl) -> &'hir [Option<Ident>] {
         self.arena.alloc_from_iter(decl.inputs.iter().map(|param| match param.pat.kind {
             PatKind::Missing => None,
             PatKind::Ident(_, ident, _) => Some(self.lower_ident(ident)),
@@ -2034,7 +2034,9 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     }
 
     fn lower_array_length_to_const_arg(&mut self, c: &AnonConst) -> &'hir hir::ConstArg<'hir> {
-        match c.value.kind {
+        // We cannot just match on `ExprKind::Underscore` as `(_)` is represented as
+        // `ExprKind::Paren(ExprKind::Underscore)` and should also be lowered to `GenericArg::Infer`
+        match c.value.peel_parens().kind {
             ExprKind::Underscore => {
                 if !self.tcx.features().generic_arg_infer() {
                     feature_err(
diff --git a/compiler/rustc_ast_pretty/src/pprust/tests.rs b/compiler/rustc_ast_pretty/src/pprust/tests.rs
index 4c42dd1f202..bc7f22766a5 100644
--- a/compiler/rustc_ast_pretty/src/pprust/tests.rs
+++ b/compiler/rustc_ast_pretty/src/pprust/tests.rs
@@ -7,12 +7,12 @@ use super::*;
 fn fun_to_string(
     decl: &ast::FnDecl,
     header: ast::FnHeader,
-    name: Ident,
+    ident: Ident,
     generics: &ast::Generics,
 ) -> String {
     to_string(|s| {
         s.head("");
-        s.print_fn(decl, header, Some(name), generics);
+        s.print_fn(decl, header, Some(ident), generics);
         s.end(); // Close the head box.
         s.end(); // Close the outer box.
     })
diff --git a/compiler/rustc_borrowck/src/consumers.rs b/compiler/rustc_borrowck/src/consumers.rs
index 45cdd232564..1f087b09234 100644
--- a/compiler/rustc_borrowck/src/consumers.rs
+++ b/compiler/rustc_borrowck/src/consumers.rs
@@ -15,6 +15,7 @@ pub use super::polonius::legacy::{
     RichLocation, RustcFacts,
 };
 pub use super::region_infer::RegionInferenceContext;
+use crate::{BorrowCheckRootCtxt, do_mir_borrowck};
 
 /// Options determining the output behavior of [`get_body_with_borrowck_facts`].
 ///
@@ -97,8 +98,9 @@ pub struct BodyWithBorrowckFacts<'tcx> {
 /// *   Polonius is highly unstable, so expect regular changes in its signature or other details.
 pub fn get_body_with_borrowck_facts(
     tcx: TyCtxt<'_>,
-    def: LocalDefId,
+    def_id: LocalDefId,
     options: ConsumerOptions,
 ) -> BodyWithBorrowckFacts<'_> {
-    *super::do_mir_borrowck(tcx, def, Some(options)).1.unwrap()
+    let mut root_cx = BorrowCheckRootCtxt::new(tcx, def_id);
+    *do_mir_borrowck(&mut root_cx, def_id, Some(options)).1.unwrap()
 }
diff --git a/compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs b/compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs
index aa968a1e40f..134f30ed6f5 100644
--- a/compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs
@@ -406,8 +406,8 @@ impl<'tcx> TypeOpInfo<'tcx> for crate::type_check::InstantiateOpaqueType<'tcx> {
             // started MIR borrowchecking with, so the region
             // constraints have already been taken. Use the data from
             // our `mbcx` instead.
-            |vid| mbcx.regioncx.var_infos[vid].origin,
-            |vid| mbcx.regioncx.var_infos[vid].universe,
+            |vid| RegionVariableOrigin::Nll(mbcx.regioncx.definitions[vid].origin),
+            |vid| mbcx.regioncx.definitions[vid].universe,
         )
     }
 }
@@ -487,7 +487,7 @@ fn try_extract_error_from_region_constraints<'a, 'tcx>(
     let (sub_region, cause) = info?;
 
     debug!(?sub_region, "cause = {:#?}", cause);
-    let error = match (error_region, *sub_region) {
+    let error = match (error_region, sub_region.kind()) {
         (Some(error_region), ty::ReVar(vid)) => RegionResolutionError::SubSupConflict(
             vid,
             region_var_origin(vid),
diff --git a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
index 1f4eb0c449f..8a8ecc3b96e 100644
--- a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
@@ -2500,11 +2500,11 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
         );
         let ty::Tuple(params) = tupled_params.kind() else { return };
 
-        // Find the first argument with a matching type, get its name
-        let Some(this_name) = params.iter().zip(tcx.hir_body_param_names(closure.body)).find_map(
-            |(param_ty, name)| {
+        // Find the first argument with a matching type and get its identifier.
+        let Some(this_name) = params.iter().zip(tcx.hir_body_param_idents(closure.body)).find_map(
+            |(param_ty, ident)| {
                 // FIXME: also support deref for stuff like `Rc` arguments
-                if param_ty.peel_refs() == local_ty { name } else { None }
+                if param_ty.peel_refs() == local_ty { ident } else { None }
             },
         ) else {
             return;
@@ -3774,7 +3774,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                 method_args,
                 *fn_span,
                 call_source.from_hir_call(),
-                self.infcx.tcx.fn_arg_names(method_did)[0],
+                self.infcx.tcx.fn_arg_idents(method_did)[0],
             )
         {
             err.note(format!("borrow occurs due to deref coercion to `{deref_target_ty}`"));
diff --git a/compiler/rustc_borrowck/src/diagnostics/mod.rs b/compiler/rustc_borrowck/src/diagnostics/mod.rs
index 899e145c2c0..f9f63ae92a8 100644
--- a/compiler/rustc_borrowck/src/diagnostics/mod.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/mod.rs
@@ -8,9 +8,7 @@ use rustc_errors::{Applicability, Diag, EmissionGuarantee, MultiSpan, listify};
 use rustc_hir::def::{CtorKind, Namespace};
 use rustc_hir::{self as hir, CoroutineKind, LangItem};
 use rustc_index::IndexSlice;
-use rustc_infer::infer::{
-    BoundRegionConversionTime, NllRegionVariableOrigin, RegionVariableOrigin,
-};
+use rustc_infer::infer::{BoundRegionConversionTime, NllRegionVariableOrigin};
 use rustc_infer::traits::SelectionError;
 use rustc_middle::bug;
 use rustc_middle::mir::{
@@ -587,7 +585,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
         // this by hooking into the pretty printer and telling it to label the
         // lifetimes without names with the value `'0`.
         if let ty::Ref(region, ..) = ty.kind() {
-            match **region {
+            match region.kind() {
                 ty::ReBound(_, ty::BoundRegion { kind: br, .. })
                 | ty::RePlaceholder(ty::PlaceholderRegion {
                     bound: ty::BoundRegion { kind: br, .. },
@@ -607,7 +605,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
         let mut printer = ty::print::FmtPrinter::new(self.infcx.tcx, Namespace::TypeNS);
 
         let region = if let ty::Ref(region, ..) = ty.kind() {
-            match **region {
+            match region.kind() {
                 ty::ReBound(_, ty::BoundRegion { kind: br, .. })
                 | ty::RePlaceholder(ty::PlaceholderRegion {
                     bound: ty::BoundRegion { kind: br, .. },
@@ -633,9 +631,8 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
     ) {
         let predicate_span = path.iter().find_map(|constraint| {
             let outlived = constraint.sub;
-            if let Some(origin) = self.regioncx.var_infos.get(outlived)
-                && let RegionVariableOrigin::Nll(NllRegionVariableOrigin::Placeholder(_)) =
-                    origin.origin
+            if let Some(origin) = self.regioncx.definitions.get(outlived)
+                && let NllRegionVariableOrigin::Placeholder(_) = origin.origin
                 && let ConstraintCategory::Predicate(span) = constraint.category
             {
                 Some(span)
@@ -1029,7 +1026,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                 method_args,
                 *fn_span,
                 call_source.from_hir_call(),
-                self.infcx.tcx.fn_arg_names(method_did)[0],
+                self.infcx.tcx.fn_arg_idents(method_did)[0],
             );
 
             return FnSelfUse {
diff --git a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
index d1d783c22e3..8d530b51636 100644
--- a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
@@ -190,7 +190,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
     where
         T: TypeFoldable<TyCtxt<'tcx>>,
     {
-        fold_regions(tcx, ty, |region, _| match *region {
+        fold_regions(tcx, ty, |region, _| match region.kind() {
             ty::ReVar(vid) => self.to_error_region(vid).unwrap_or(region),
             _ => region,
         })
@@ -198,7 +198,8 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
 
     /// Returns `true` if a closure is inferred to be an `FnMut` closure.
     fn is_closure_fn_mut(&self, fr: RegionVid) -> bool {
-        if let Some(ty::ReLateParam(late_param)) = self.to_error_region(fr).as_deref()
+        if let Some(r) = self.to_error_region(fr)
+            && let ty::ReLateParam(late_param) = r.kind()
             && let ty::LateParamRegionKind::ClosureEnv = late_param.kind
             && let DefiningTy::Closure(_, args) = self.regioncx.universal_regions().defining_ty
         {
@@ -832,7 +833,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
         if let (Some(f), Some(outlived_f)) =
             (self.to_error_region(fr), self.to_error_region(outlived_fr))
         {
-            if *outlived_f != ty::ReStatic {
+            if outlived_f.kind() != ty::ReStatic {
                 return;
             }
             let suitable_region = self.infcx.tcx.is_suitable_region(self.mir_def_id(), f);
diff --git a/compiler/rustc_borrowck/src/diagnostics/region_name.rs b/compiler/rustc_borrowck/src/diagnostics/region_name.rs
index 45f5eaa514b..b08c10983bb 100644
--- a/compiler/rustc_borrowck/src/diagnostics/region_name.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/region_name.rs
@@ -288,7 +288,7 @@ impl<'tcx> MirBorrowckCtxt<'_, '_, 'tcx> {
         let tcx = self.infcx.tcx;
 
         debug!("give_region_a_name: error_region = {:?}", error_region);
-        match *error_region {
+        match error_region.kind() {
             ty::ReEarlyParam(ebr) => ebr.has_name().then(|| {
                 let def_id = tcx.generics_of(self.mir_def_id()).region_param(ebr, tcx).def_id;
                 let span = tcx.hir_span_if_local(def_id).unwrap_or(DUMMY_SP);
@@ -896,7 +896,7 @@ impl<'tcx> MirBorrowckCtxt<'_, '_, 'tcx> {
         &self,
         fr: RegionVid,
     ) -> Option<RegionName> {
-        let ty::ReEarlyParam(region) = *self.to_error_region(fr)? else {
+        let ty::ReEarlyParam(region) = self.to_error_region(fr)?.kind() else {
             return None;
         };
         if region.has_name() {
@@ -912,7 +912,7 @@ impl<'tcx> MirBorrowckCtxt<'_, '_, 'tcx> {
 
         let found = tcx
             .any_free_region_meets(&tcx.type_of(region_parent).instantiate_identity(), |r| {
-                *r == ty::ReEarlyParam(region)
+                r.kind() == ty::ReEarlyParam(region)
             });
 
         Some(RegionName {
@@ -931,7 +931,7 @@ impl<'tcx> MirBorrowckCtxt<'_, '_, 'tcx> {
         &self,
         fr: RegionVid,
     ) -> Option<RegionName> {
-        let ty::ReEarlyParam(region) = *self.to_error_region(fr)? else {
+        let ty::ReEarlyParam(region) = self.to_error_region(fr)?.kind() else {
             return None;
         };
         if region.has_name() {
@@ -1007,7 +1007,7 @@ impl<'tcx> MirBorrowckCtxt<'_, '_, 'tcx> {
                             if data.projection_term.self_ty() == ty => {}
                         _ => return false,
                     }
-                    tcx.any_free_region_meets(pred, |r| *r == ty::ReEarlyParam(region))
+                    tcx.any_free_region_meets(pred, |r| r.kind() == ty::ReEarlyParam(region))
                 })
             } else {
                 false
diff --git a/compiler/rustc_borrowck/src/lib.rs b/compiler/rustc_borrowck/src/lib.rs
index 240bd20053b..64ad1c96856 100644
--- a/compiler/rustc_borrowck/src/lib.rs
+++ b/compiler/rustc_borrowck/src/lib.rs
@@ -9,6 +9,7 @@
 #![feature(file_buffered)]
 #![feature(if_let_guard)]
 #![feature(let_chains)]
+#![feature(negative_impls)]
 #![feature(never_type)]
 #![feature(rustc_attrs)]
 #![feature(rustdoc_internals)]
@@ -21,6 +22,7 @@ use std::cell::RefCell;
 use std::marker::PhantomData;
 use std::ops::{ControlFlow, Deref};
 
+use root_cx::BorrowCheckRootCtxt;
 use rustc_abi::FieldIdx;
 use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_data_structures::graph::dominators::Dominators;
@@ -35,7 +37,9 @@ use rustc_infer::infer::{
 };
 use rustc_middle::mir::*;
 use rustc_middle::query::Providers;
-use rustc_middle::ty::{self, ParamEnv, RegionVid, TyCtxt, TypingMode};
+use rustc_middle::ty::{
+    self, ParamEnv, RegionVid, Ty, TyCtxt, TypeFoldable, TypeVisitable, TypingMode, fold_regions,
+};
 use rustc_middle::{bug, span_bug};
 use rustc_mir_dataflow::impls::{
     EverInitializedPlaces, MaybeInitializedPlaces, MaybeUninitializedPlaces,
@@ -45,7 +49,7 @@ use rustc_mir_dataflow::move_paths::{
 };
 use rustc_mir_dataflow::{Analysis, EntryStates, Results, ResultsVisitor, visit_results};
 use rustc_session::lint::builtin::{TAIL_EXPR_DROP_ORDER, UNUSED_MUT};
-use rustc_span::{Span, Symbol};
+use rustc_span::{ErrorGuaranteed, Span, Symbol};
 use smallvec::SmallVec;
 use tracing::{debug, instrument};
 
@@ -73,7 +77,6 @@ mod def_use;
 mod diagnostics;
 mod member_constraints;
 mod nll;
-mod opaque_types;
 mod path_utils;
 mod place_ext;
 mod places_conflict;
@@ -81,6 +84,7 @@ mod polonius;
 mod prefixes;
 mod region_infer;
 mod renumber;
+mod root_cx;
 mod session_diagnostics;
 mod type_check;
 mod universal_regions;
@@ -102,44 +106,202 @@ pub fn provide(providers: &mut Providers) {
     *providers = Providers { mir_borrowck, ..*providers };
 }
 
-fn mir_borrowck(tcx: TyCtxt<'_>, def: LocalDefId) -> &BorrowCheckResult<'_> {
+/// Provider for `query mir_borrowck`. Similar to `typeck`, this must
+/// only be called for typeck roots which will then borrowck all
+/// nested bodies as well.
+fn mir_borrowck(
+    tcx: TyCtxt<'_>,
+    def: LocalDefId,
+) -> Result<&ConcreteOpaqueTypes<'_>, ErrorGuaranteed> {
+    assert!(!tcx.is_typeck_child(def.to_def_id()));
     let (input_body, _) = tcx.mir_promoted(def);
+    debug!("run query mir_borrowck: {}", tcx.def_path_str(def));
+
     let input_body: &Body<'_> = &input_body.borrow();
-    if input_body.should_skip() || input_body.tainted_by_errors.is_some() {
-        debug!("Skipping borrowck because of injected body or tainted body");
-        // Let's make up a borrowck result! Fun times!
-        let result = BorrowCheckResult {
-            concrete_opaque_types: FxIndexMap::default(),
-            closure_requirements: None,
-            used_mut_upvars: SmallVec::new(),
-            tainted_by_errors: input_body.tainted_by_errors,
-        };
-        return tcx.arena.alloc(result);
+    if let Some(guar) = input_body.tainted_by_errors {
+        debug!("Skipping borrowck because of tainted body");
+        Err(guar)
+    } else if input_body.should_skip() {
+        debug!("Skipping borrowck because of injected body");
+        let opaque_types = ConcreteOpaqueTypes(Default::default());
+        Ok(tcx.arena.alloc(opaque_types))
+    } else {
+        let mut root_cx = BorrowCheckRootCtxt::new(tcx, def);
+        let PropagatedBorrowCheckResults { closure_requirements, used_mut_upvars } =
+            do_mir_borrowck(&mut root_cx, def, None).0;
+        debug_assert!(closure_requirements.is_none());
+        debug_assert!(used_mut_upvars.is_empty());
+        root_cx.finalize()
     }
+}
+
+/// Data propagated to the typeck parent by nested items.
+/// This should always be empty for the typeck root.
+#[derive(Debug)]
+struct PropagatedBorrowCheckResults<'tcx> {
+    closure_requirements: Option<ClosureRegionRequirements<'tcx>>,
+    used_mut_upvars: SmallVec<[FieldIdx; 8]>,
+}
+
+/// After we borrow check a closure, we are left with various
+/// requirements that we have inferred between the free regions that
+/// appear in the closure's signature or on its field types. These
+/// requirements are then verified and proved by the closure's
+/// creating function. This struct encodes those requirements.
+///
+/// The requirements are listed as being between various `RegionVid`. The 0th
+/// region refers to `'static`; subsequent region vids refer to the free
+/// regions that appear in the closure (or coroutine's) type, in order of
+/// appearance. (This numbering is actually defined by the `UniversalRegions`
+/// struct in the NLL region checker. See for example
+/// `UniversalRegions::closure_mapping`.) Note the free regions in the
+/// closure's signature and captures are erased.
+///
+/// Example: If type check produces a closure with the closure args:
+///
+/// ```text
+/// ClosureArgs = [
+///     'a,                                         // From the parent.
+///     'b,
+///     i8,                                         // the "closure kind"
+///     for<'x> fn(&'<erased> &'x u32) -> &'x u32,  // the "closure signature"
+///     &'<erased> String,                          // some upvar
+/// ]
+/// ```
+///
+/// We would "renumber" each free region to a unique vid, as follows:
+///
+/// ```text
+/// ClosureArgs = [
+///     '1,                                         // From the parent.
+///     '2,
+///     i8,                                         // the "closure kind"
+///     for<'x> fn(&'3 &'x u32) -> &'x u32,         // the "closure signature"
+///     &'4 String,                                 // some upvar
+/// ]
+/// ```
+///
+/// Now the code might impose a requirement like `'1: '2`. When an
+/// instance of the closure is created, the corresponding free regions
+/// can be extracted from its type and constrained to have the given
+/// outlives relationship.
+#[derive(Clone, Debug)]
+pub struct ClosureRegionRequirements<'tcx> {
+    /// The number of external regions defined on the closure. In our
+    /// example above, it would be 3 -- one for `'static`, then `'1`
+    /// and `'2`. This is just used for a sanity check later on, to
+    /// make sure that the number of regions we see at the callsite
+    /// matches.
+    pub num_external_vids: usize,
+
+    /// Requirements between the various free regions defined in
+    /// indices.
+    pub outlives_requirements: Vec<ClosureOutlivesRequirement<'tcx>>,
+}
 
-    let borrowck_result = do_mir_borrowck(tcx, def, None).0;
-    debug!("mir_borrowck done");
+/// Indicates an outlives-constraint between a type or between two
+/// free regions declared on the closure.
+#[derive(Copy, Clone, Debug)]
+pub struct ClosureOutlivesRequirement<'tcx> {
+    // This region or type ...
+    pub subject: ClosureOutlivesSubject<'tcx>,
 
-    tcx.arena.alloc(borrowck_result)
+    // ... must outlive this one.
+    pub outlived_free_region: ty::RegionVid,
+
+    // If not, report an error here ...
+    pub blame_span: Span,
+
+    // ... due to this reason.
+    pub category: ConstraintCategory<'tcx>,
+}
+
+// Make sure this enum doesn't unintentionally grow
+#[cfg(target_pointer_width = "64")]
+rustc_data_structures::static_assert_size!(ConstraintCategory<'_>, 16);
+
+/// The subject of a `ClosureOutlivesRequirement` -- that is, the thing
+/// that must outlive some region.
+#[derive(Copy, Clone, Debug)]
+pub enum ClosureOutlivesSubject<'tcx> {
+    /// Subject is a type, typically a type parameter, but could also
+    /// be a projection. Indicates a requirement like `T: 'a` being
+    /// passed to the caller, where the type here is `T`.
+    Ty(ClosureOutlivesSubjectTy<'tcx>),
+
+    /// Subject is a free region from the closure. Indicates a requirement
+    /// like `'a: 'b` being passed to the caller; the region here is `'a`.
+    Region(ty::RegionVid),
+}
+
+/// Represents a `ty::Ty` for use in [`ClosureOutlivesSubject`].
+///
+/// This abstraction is necessary because the type may include `ReVar` regions,
+/// which is what we use internally within NLL code, and they can't be used in
+/// a query response.
+#[derive(Copy, Clone, Debug)]
+pub struct ClosureOutlivesSubjectTy<'tcx> {
+    inner: Ty<'tcx>,
+}
+// DO NOT implement `TypeVisitable` or `TypeFoldable` traits, because this
+// type is not recognized as a binder for late-bound region.
+impl<'tcx, I> !TypeVisitable<I> for ClosureOutlivesSubjectTy<'tcx> {}
+impl<'tcx, I> !TypeFoldable<I> for ClosureOutlivesSubjectTy<'tcx> {}
+
+impl<'tcx> ClosureOutlivesSubjectTy<'tcx> {
+    /// All regions of `ty` must be of kind `ReVar` and must represent
+    /// universal regions *external* to the closure.
+    pub fn bind(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Self {
+        let inner = fold_regions(tcx, ty, |r, depth| match r.kind() {
+            ty::ReVar(vid) => {
+                let br = ty::BoundRegion {
+                    var: ty::BoundVar::from_usize(vid.index()),
+                    kind: ty::BoundRegionKind::Anon,
+                };
+                ty::Region::new_bound(tcx, depth, br)
+            }
+            _ => bug!("unexpected region in ClosureOutlivesSubjectTy: {r:?}"),
+        });
+
+        Self { inner }
+    }
+
+    pub fn instantiate(
+        self,
+        tcx: TyCtxt<'tcx>,
+        mut map: impl FnMut(ty::RegionVid) -> ty::Region<'tcx>,
+    ) -> Ty<'tcx> {
+        fold_regions(tcx, self.inner, |r, depth| match r.kind() {
+            ty::ReBound(debruijn, br) => {
+                debug_assert_eq!(debruijn, depth);
+                map(ty::RegionVid::from_usize(br.var.index()))
+            }
+            _ => bug!("unexpected region {r:?}"),
+        })
+    }
 }
 
 /// Perform the actual borrow checking.
 ///
 /// Use `consumer_options: None` for the default behavior of returning
-/// [`BorrowCheckResult`] only. Otherwise, return [`BodyWithBorrowckFacts`] according
-/// to the given [`ConsumerOptions`].
-#[instrument(skip(tcx), level = "debug")]
+/// [`PropagatedBorrowCheckResults`] only. Otherwise, return [`BodyWithBorrowckFacts`]
+/// according to the given [`ConsumerOptions`].
+///
+/// For nested bodies this should only be called through `root_cx.get_or_insert_nested`.
+#[instrument(skip(root_cx), level = "debug")]
 fn do_mir_borrowck<'tcx>(
-    tcx: TyCtxt<'tcx>,
+    root_cx: &mut BorrowCheckRootCtxt<'tcx>,
     def: LocalDefId,
     consumer_options: Option<ConsumerOptions>,
-) -> (BorrowCheckResult<'tcx>, Option<Box<BodyWithBorrowckFacts<'tcx>>>) {
+) -> (PropagatedBorrowCheckResults<'tcx>, Option<Box<BodyWithBorrowckFacts<'tcx>>>) {
+    let tcx = root_cx.tcx;
     let infcx = BorrowckInferCtxt::new(tcx, def);
     let (input_body, promoted) = tcx.mir_promoted(def);
     let input_body: &Body<'_> = &input_body.borrow();
     let input_promoted: &IndexSlice<_, _> = &promoted.borrow();
     if let Some(e) = input_body.tainted_by_errors {
         infcx.set_tainted_by_errors(e);
+        root_cx.set_tainted_by_errors(e);
     }
 
     let mut local_names = IndexVec::from_elem(None, &input_body.local_decls);
@@ -185,13 +347,13 @@ fn do_mir_borrowck<'tcx>(
     // Compute non-lexical lifetimes.
     let nll::NllOutput {
         regioncx,
-        concrete_opaque_types,
         polonius_input,
         polonius_output,
         opt_closure_req,
         nll_errors,
         polonius_diagnostics,
     } = nll::compute_regions(
+        root_cx,
         &infcx,
         free_regions,
         body,
@@ -210,26 +372,19 @@ fn do_mir_borrowck<'tcx>(
     // We also have a `#[rustc_regions]` annotation that causes us to dump
     // information.
     let diags_buffer = &mut BorrowckDiagnosticsBuffer::default();
-    nll::dump_annotation(
-        &infcx,
-        body,
-        &regioncx,
-        &opt_closure_req,
-        &concrete_opaque_types,
-        diags_buffer,
-    );
+    nll::dump_annotation(&infcx, body, &regioncx, &opt_closure_req, diags_buffer);
 
     let movable_coroutine =
-        // The first argument is the coroutine type passed by value
-        if let Some(local) = body.local_decls.raw.get(1)
-        // Get the interior types and args which typeck computed
-        && let ty::Coroutine(def_id, _) = *local.ty.kind()
-        && tcx.coroutine_movability(def_id) == hir::Movability::Movable
-    {
-        true
-    } else {
-        false
-    };
+    // The first argument is the coroutine type passed by value
+    if let Some(local) = body.local_decls.raw.get(1)
+    // Get the interior types and args which typeck computed
+    && let ty::Coroutine(def_id, _) = *local.ty.kind()
+    && tcx.coroutine_movability(def_id) == hir::Movability::Movable
+{
+    true
+} else {
+    false
+};
 
     // While promoteds should mostly be correct by construction, we need to check them for
     // invalid moves to detect moving out of arrays:`struct S; fn main() { &([S][0]); }`.
@@ -240,6 +395,7 @@ fn do_mir_borrowck<'tcx>(
         // this check out of `MirBorrowckCtxt`, actually doing so is far from trivial.
         let move_data = MoveData::gather_moves(promoted_body, tcx, |_| true);
         let mut promoted_mbcx = MirBorrowckCtxt {
+            root_cx,
             infcx: &infcx,
             body: promoted_body,
             move_data: &move_data,
@@ -280,6 +436,7 @@ fn do_mir_borrowck<'tcx>(
     }
 
     let mut mbcx = MirBorrowckCtxt {
+        root_cx,
         infcx: &infcx,
         body,
         move_data: &move_data,
@@ -347,13 +504,13 @@ fn do_mir_borrowck<'tcx>(
 
     debug!("mbcx.used_mut: {:?}", mbcx.used_mut);
     mbcx.lint_unused_mut();
-    let tainted_by_errors = mbcx.emit_errors();
+    if let Some(guar) = mbcx.emit_errors() {
+        mbcx.root_cx.set_tainted_by_errors(guar);
+    }
 
-    let result = BorrowCheckResult {
-        concrete_opaque_types: concrete_opaque_types.into_inner(),
+    let result = PropagatedBorrowCheckResults {
         closure_requirements: opt_closure_req,
         used_mut_upvars: mbcx.used_mut_upvars,
-        tainted_by_errors,
     };
 
     let body_with_facts = if consumer_options.is_some() {
@@ -488,6 +645,7 @@ impl<'tcx> Deref for BorrowckInferCtxt<'tcx> {
 }
 
 struct MirBorrowckCtxt<'a, 'infcx, 'tcx> {
+    root_cx: &'a mut BorrowCheckRootCtxt<'tcx>,
     infcx: &'infcx BorrowckInferCtxt<'tcx>,
     body: &'a Body<'tcx>,
     move_data: &'a MoveData<'tcx>,
@@ -1361,11 +1519,13 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, '_, 'tcx> {
                     | AggregateKind::CoroutineClosure(def_id, _)
                     | AggregateKind::Coroutine(def_id, _) => {
                         let def_id = def_id.expect_local();
-                        let BorrowCheckResult { used_mut_upvars, .. } =
-                            self.infcx.tcx.mir_borrowck(def_id);
+                        let used_mut_upvars = self.root_cx.used_mut_upvars(def_id);
                         debug!("{:?} used_mut_upvars={:?}", def_id, used_mut_upvars);
-                        for field in used_mut_upvars {
-                            self.propagate_closure_used_mut_upvar(&operands[*field]);
+                        // FIXME: We're cloning the `SmallVec` here to avoid borrowing `root_cx`
+                        // when calling `propagate_closure_used_mut_upvar`. This should ideally
+                        // be unnecessary.
+                        for field in used_mut_upvars.clone() {
+                            self.propagate_closure_used_mut_upvar(&operands[field]);
                         }
                     }
                     AggregateKind::Adt(..)
diff --git a/compiler/rustc_borrowck/src/nll.rs b/compiler/rustc_borrowck/src/nll.rs
index 8e7b6f083ac..8a2a34f207a 100644
--- a/compiler/rustc_borrowck/src/nll.rs
+++ b/compiler/rustc_borrowck/src/nll.rs
@@ -8,10 +8,7 @@ use std::str::FromStr;
 use polonius_engine::{Algorithm, Output};
 use rustc_index::IndexSlice;
 use rustc_middle::mir::pretty::{PrettyPrintMirOptions, dump_mir_with_options};
-use rustc_middle::mir::{
-    Body, ClosureOutlivesSubject, ClosureRegionRequirements, PassWhere, Promoted, create_dump_file,
-    dump_enabled, dump_mir,
-};
+use rustc_middle::mir::{Body, PassWhere, Promoted, create_dump_file, dump_enabled, dump_mir};
 use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_middle::ty::{self, TyCtxt};
 use rustc_mir_dataflow::ResultsCursor;
@@ -25,7 +22,6 @@ use tracing::{debug, instrument};
 use crate::borrow_set::BorrowSet;
 use crate::consumers::ConsumerOptions;
 use crate::diagnostics::{BorrowckDiagnosticsBuffer, RegionErrors};
-use crate::opaque_types::ConcreteOpaqueTypes;
 use crate::polonius::PoloniusDiagnosticsContext;
 use crate::polonius::legacy::{
     PoloniusFacts, PoloniusFactsExt, PoloniusLocationTable, PoloniusOutput,
@@ -33,13 +29,15 @@ use crate::polonius::legacy::{
 use crate::region_infer::RegionInferenceContext;
 use crate::type_check::{self, MirTypeckResults};
 use crate::universal_regions::UniversalRegions;
-use crate::{BorrowckInferCtxt, polonius, renumber};
+use crate::{
+    BorrowCheckRootCtxt, BorrowckInferCtxt, ClosureOutlivesSubject, ClosureRegionRequirements,
+    polonius, renumber,
+};
 
 /// The output of `nll::compute_regions`. This includes the computed `RegionInferenceContext`, any
 /// closure requirements to propagate, and any generated errors.
 pub(crate) struct NllOutput<'tcx> {
     pub regioncx: RegionInferenceContext<'tcx>,
-    pub concrete_opaque_types: ConcreteOpaqueTypes<'tcx>,
     pub polonius_input: Option<Box<PoloniusFacts>>,
     pub polonius_output: Option<Box<PoloniusOutput>>,
     pub opt_closure_req: Option<ClosureRegionRequirements<'tcx>>,
@@ -78,6 +76,7 @@ pub(crate) fn replace_regions_in_mir<'tcx>(
 ///
 /// This may result in errors being reported.
 pub(crate) fn compute_regions<'a, 'tcx>(
+    root_cx: &mut BorrowCheckRootCtxt<'tcx>,
     infcx: &BorrowckInferCtxt<'tcx>,
     universal_regions: UniversalRegions<'tcx>,
     body: &Body<'tcx>,
@@ -98,8 +97,6 @@ pub(crate) fn compute_regions<'a, 'tcx>(
 
     let location_map = Rc::new(DenseLocationMap::new(body));
 
-    let mut concrete_opaque_types = ConcreteOpaqueTypes::default();
-
     // Run the MIR type-checker.
     let MirTypeckResults {
         constraints,
@@ -107,6 +104,7 @@ pub(crate) fn compute_regions<'a, 'tcx>(
         opaque_type_values,
         polonius_context,
     } = type_check::type_check(
+        root_cx,
         infcx,
         body,
         promoted,
@@ -117,7 +115,6 @@ pub(crate) fn compute_regions<'a, 'tcx>(
         flow_inits,
         move_data,
         Rc::clone(&location_map),
-        &mut concrete_opaque_types,
     );
 
     // Create the region inference context, taking ownership of the
@@ -181,11 +178,10 @@ pub(crate) fn compute_regions<'a, 'tcx>(
         infcx.set_tainted_by_errors(guar);
     }
 
-    regioncx.infer_opaque_types(infcx, opaque_type_values, &mut concrete_opaque_types);
+    regioncx.infer_opaque_types(root_cx, infcx, opaque_type_values);
 
     NllOutput {
         regioncx,
-        concrete_opaque_types,
         polonius_input: polonius_facts.map(Box::new),
         polonius_output,
         opt_closure_req: closure_region_requirements,
@@ -301,7 +297,6 @@ pub(super) fn dump_annotation<'tcx, 'infcx>(
     body: &Body<'tcx>,
     regioncx: &RegionInferenceContext<'tcx>,
     closure_region_requirements: &Option<ClosureRegionRequirements<'tcx>>,
-    concrete_opaque_types: &ConcreteOpaqueTypes<'tcx>,
     diagnostics_buffer: &mut BorrowckDiagnosticsBuffer<'infcx, 'tcx>,
 ) {
     let tcx = infcx.tcx;
@@ -318,7 +313,7 @@ pub(super) fn dump_annotation<'tcx, 'infcx>(
     // better.
 
     let def_span = tcx.def_span(body.source.def_id());
-    let mut err = if let Some(closure_region_requirements) = closure_region_requirements {
+    let err = if let Some(closure_region_requirements) = closure_region_requirements {
         let mut err = infcx.dcx().struct_span_note(def_span, "external requirements");
 
         regioncx.annotate(tcx, &mut err);
@@ -344,9 +339,7 @@ pub(super) fn dump_annotation<'tcx, 'infcx>(
         err
     };
 
-    if !concrete_opaque_types.is_empty() {
-        err.note(format!("Inferred opaque type values:\n{concrete_opaque_types:#?}"));
-    }
+    // FIXME(@lcnr): We currently don't dump the inferred hidden types here.
 
     diagnostics_buffer.buffer_non_error(err);
 }
diff --git a/compiler/rustc_borrowck/src/opaque_types.rs b/compiler/rustc_borrowck/src/opaque_types.rs
deleted file mode 100644
index 5c78814abdd..00000000000
--- a/compiler/rustc_borrowck/src/opaque_types.rs
+++ /dev/null
@@ -1,55 +0,0 @@
-use rustc_data_structures::fx::FxIndexMap;
-use rustc_hir::def_id::LocalDefId;
-use rustc_middle::ty::{OpaqueHiddenType, Ty, TyCtxt};
-
-#[derive(Debug, Default)]
-pub(super) struct ConcreteOpaqueTypes<'tcx> {
-    concrete_opaque_types: FxIndexMap<LocalDefId, OpaqueHiddenType<'tcx>>,
-}
-
-impl<'tcx> ConcreteOpaqueTypes<'tcx> {
-    pub(super) fn is_empty(&self) -> bool {
-        self.concrete_opaque_types.is_empty()
-    }
-
-    pub(super) fn into_inner(self) -> FxIndexMap<LocalDefId, OpaqueHiddenType<'tcx>> {
-        self.concrete_opaque_types
-    }
-
-    /// Insert an opaque type into the list of opaque types defined by this function
-    /// after mapping the hidden type to the generic parameters of the opaque type
-    /// definition.
-    pub(super) fn insert(
-        &mut self,
-        tcx: TyCtxt<'tcx>,
-        def_id: LocalDefId,
-        hidden_ty: OpaqueHiddenType<'tcx>,
-    ) {
-        // Sometimes two opaque types are the same only after we remap the generic parameters
-        // back to the opaque type definition. E.g. we may have `OpaqueType<X, Y>` mapped to
-        // `(X, Y)` and `OpaqueType<Y, X>` mapped to `(Y, X)`, and those are the same, but we
-        // only know that once we convert the generic parameters to those of the opaque type.
-        if let Some(prev) = self.concrete_opaque_types.get_mut(&def_id) {
-            if prev.ty != hidden_ty.ty {
-                let (Ok(guar) | Err(guar)) =
-                    prev.build_mismatch_error(&hidden_ty, tcx).map(|d| d.emit());
-                prev.ty = Ty::new_error(tcx, guar);
-            }
-            // Pick a better span if there is one.
-            // FIXME(oli-obk): collect multiple spans for better diagnostics down the road.
-            prev.span = prev.span.substitute_dummy(hidden_ty.span);
-        } else {
-            self.concrete_opaque_types.insert(def_id, hidden_ty);
-        }
-    }
-
-    pub(super) fn extend_from_nested_body(
-        &mut self,
-        tcx: TyCtxt<'tcx>,
-        nested_body: &FxIndexMap<LocalDefId, OpaqueHiddenType<'tcx>>,
-    ) {
-        for (&def_id, &hidden_ty) in nested_body {
-            self.insert(tcx, def_id, hidden_ty);
-        }
-    }
-}
diff --git a/compiler/rustc_borrowck/src/polonius/dump.rs b/compiler/rustc_borrowck/src/polonius/dump.rs
index aa64a7c4e2a..eb53a98832c 100644
--- a/compiler/rustc_borrowck/src/polonius/dump.rs
+++ b/compiler/rustc_borrowck/src/polonius/dump.rs
@@ -5,7 +5,7 @@ use rustc_index::IndexVec;
 use rustc_middle::mir::pretty::{
     PassWhere, PrettyPrintMirOptions, create_dump_file, dump_enabled, dump_mir_to_writer,
 };
-use rustc_middle::mir::{Body, ClosureRegionRequirements, Location};
+use rustc_middle::mir::{Body, Location};
 use rustc_middle::ty::{RegionVid, TyCtxt};
 use rustc_mir_dataflow::points::PointIndex;
 use rustc_session::config::MirIncludeSpans;
@@ -17,7 +17,7 @@ use crate::polonius::{
 };
 use crate::region_infer::values::LivenessValues;
 use crate::type_check::Locations;
-use crate::{BorrowckInferCtxt, RegionInferenceContext};
+use crate::{BorrowckInferCtxt, ClosureRegionRequirements, RegionInferenceContext};
 
 /// `-Zdump-mir=polonius` dumps MIR annotated with NLL and polonius specific information.
 pub(crate) fn dump_polonius_mir<'tcx>(
@@ -334,7 +334,7 @@ fn emit_mermaid_nll_regions<'tcx>(
     writeln!(out, "flowchart TD")?;
 
     // Emit the region nodes.
-    for region in regioncx.var_infos.indices() {
+    for region in regioncx.definitions.indices() {
         write!(out, "{}[\"", region.as_usize())?;
         render_region(region, regioncx, out)?;
         writeln!(out, "\"]")?;
@@ -387,7 +387,7 @@ fn emit_mermaid_nll_sccs<'tcx>(
     // Gather and emit the SCC nodes.
     let mut nodes_per_scc: IndexVec<_, _> =
         regioncx.constraint_sccs().all_sccs().map(|_| Vec::new()).collect();
-    for region in regioncx.var_infos.indices() {
+    for region in regioncx.definitions.indices() {
         let scc = regioncx.constraint_sccs().scc(region);
         nodes_per_scc[scc].push(region);
     }
diff --git a/compiler/rustc_borrowck/src/region_infer/mod.rs b/compiler/rustc_borrowck/src/region_infer/mod.rs
index 5756a5e7c7c..569c46e6403 100644
--- a/compiler/rustc_borrowck/src/region_infer/mod.rs
+++ b/compiler/rustc_borrowck/src/region_infer/mod.rs
@@ -13,9 +13,8 @@ use rustc_infer::infer::region_constraints::{GenericKind, VarInfos, VerifyBound,
 use rustc_infer::infer::{InferCtxt, NllRegionVariableOrigin, RegionVariableOrigin};
 use rustc_middle::bug;
 use rustc_middle::mir::{
-    AnnotationSource, BasicBlock, Body, ClosureOutlivesRequirement, ClosureOutlivesSubject,
-    ClosureOutlivesSubjectTy, ClosureRegionRequirements, ConstraintCategory, Local, Location,
-    ReturnConstraint, TerminatorKind,
+    AnnotationSource, BasicBlock, Body, ConstraintCategory, Local, Location, ReturnConstraint,
+    TerminatorKind,
 };
 use rustc_middle::traits::{ObligationCause, ObligationCauseCode};
 use rustc_middle::ty::{self, RegionVid, Ty, TyCtxt, TypeFoldable, UniverseIndex, fold_regions};
@@ -24,7 +23,6 @@ use rustc_span::hygiene::DesugaringKind;
 use rustc_span::{DUMMY_SP, Span};
 use tracing::{Level, debug, enabled, instrument, trace};
 
-use crate::BorrowckInferCtxt;
 use crate::constraints::graph::{self, NormalConstraintGraph, RegionGraph};
 use crate::constraints::{ConstraintSccIndex, OutlivesConstraint, OutlivesConstraintSet};
 use crate::dataflow::BorrowIndex;
@@ -37,6 +35,10 @@ use crate::region_infer::values::{LivenessValues, RegionElement, RegionValues, T
 use crate::type_check::free_region_relations::UniversalRegionRelations;
 use crate::type_check::{Locations, MirTypeckRegionConstraints};
 use crate::universal_regions::UniversalRegions;
+use crate::{
+    BorrowckInferCtxt, ClosureOutlivesRequirement, ClosureOutlivesSubject,
+    ClosureOutlivesSubjectTy, ClosureRegionRequirements,
+};
 
 mod dump_mir;
 mod graphviz;
@@ -139,13 +141,11 @@ impl RegionTracker {
 }
 
 pub struct RegionInferenceContext<'tcx> {
-    pub var_infos: VarInfos,
-
     /// Contains the definition for every region variable. Region
     /// variables are identified by their index (`RegionVid`). The
     /// definition contains information about where the region came
     /// from as well as its final inferred value.
-    definitions: IndexVec<RegionVid, RegionDefinition<'tcx>>,
+    pub(crate) definitions: IndexVec<RegionVid, RegionDefinition<'tcx>>,
 
     /// The liveness constraints added to each region. For most
     /// regions, these start out empty and steadily grow, though for
@@ -453,7 +453,6 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             Rc::new(member_constraints.into_mapped(|r| constraint_sccs.scc(r)));
 
         let mut result = Self {
-            var_infos,
             definitions,
             liveness_constraints,
             constraints,
diff --git a/compiler/rustc_borrowck/src/region_infer/opaque_types.rs b/compiler/rustc_borrowck/src/region_infer/opaque_types.rs
index a098450352f..550c57338d3 100644
--- a/compiler/rustc_borrowck/src/region_infer/opaque_types.rs
+++ b/compiler/rustc_borrowck/src/region_infer/opaque_types.rs
@@ -10,7 +10,7 @@ use rustc_trait_selection::opaque_types::check_opaque_type_parameter_valid;
 use tracing::{debug, instrument};
 
 use super::RegionInferenceContext;
-use crate::opaque_types::ConcreteOpaqueTypes;
+use crate::BorrowCheckRootCtxt;
 use crate::session_diagnostics::LifetimeMismatchOpaqueParam;
 use crate::universal_regions::RegionClassification;
 
@@ -58,12 +58,12 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     ///
     /// [rustc-dev-guide chapter]:
     /// https://rustc-dev-guide.rust-lang.org/opaque-types-region-infer-restrictions.html
-    #[instrument(level = "debug", skip(self, infcx), ret)]
+    #[instrument(level = "debug", skip(self, root_cx, infcx), ret)]
     pub(crate) fn infer_opaque_types(
         &self,
+        root_cx: &mut BorrowCheckRootCtxt<'tcx>,
         infcx: &InferCtxt<'tcx>,
         opaque_ty_decls: FxIndexMap<OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>>,
-        concrete_opaque_types: &mut ConcreteOpaqueTypes<'tcx>,
     ) {
         let mut decls_modulo_regions: FxIndexMap<OpaqueTypeKey<'tcx>, (OpaqueTypeKey<'tcx>, Span)> =
             FxIndexMap::default();
@@ -140,11 +140,11 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                 }
             }
 
-            concrete_opaque_types.insert(
-                infcx.tcx,
+            root_cx.add_concrete_opaque_type(
                 opaque_type_key.def_id,
-                OpaqueHiddenType { ty, span: concrete_type.span },
+                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
@@ -186,7 +186,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     where
         T: TypeFoldable<TyCtxt<'tcx>>,
     {
-        fold_regions(tcx, ty, |region, _| match *region {
+        fold_regions(tcx, ty, |region, _| match region.kind() {
             ty::ReVar(vid) => {
                 let scc = self.constraint_sccs.scc(vid);
 
diff --git a/compiler/rustc_borrowck/src/root_cx.rs b/compiler/rustc_borrowck/src/root_cx.rs
new file mode 100644
index 00000000000..13daa5c7221
--- /dev/null
+++ b/compiler/rustc_borrowck/src/root_cx.rs
@@ -0,0 +1,101 @@
+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_span::ErrorGuaranteed;
+use smallvec::SmallVec;
+
+use crate::{ClosureRegionRequirements, ConcreteOpaqueTypes, PropagatedBorrowCheckResults};
+
+/// The shared context used by both the root as well as all its nested
+/// items.
+pub(super) struct BorrowCheckRootCtxt<'tcx> {
+    pub tcx: TyCtxt<'tcx>,
+    root_def_id: LocalDefId,
+    concrete_opaque_types: ConcreteOpaqueTypes<'tcx>,
+    nested_bodies: FxHashMap<LocalDefId, PropagatedBorrowCheckResults<'tcx>>,
+    tainted_by_errors: Option<ErrorGuaranteed>,
+}
+
+impl<'tcx> BorrowCheckRootCtxt<'tcx> {
+    pub(super) fn new(tcx: TyCtxt<'tcx>, root_def_id: LocalDefId) -> BorrowCheckRootCtxt<'tcx> {
+        BorrowCheckRootCtxt {
+            tcx,
+            root_def_id,
+            concrete_opaque_types: Default::default(),
+            nested_bodies: Default::default(),
+            tainted_by_errors: None,
+        }
+    }
+
+    /// 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.
+    pub(super) fn add_concrete_opaque_type(
+        &mut self,
+        def_id: LocalDefId,
+        hidden_ty: OpaqueHiddenType<'tcx>,
+    ) {
+        // Sometimes two opaque types are the same only after we remap the generic parameters
+        // back to the opaque type definition. E.g. we may have `OpaqueType<X, Y>` mapped to
+        // `(X, Y)` and `OpaqueType<Y, X>` mapped to `(Y, X)`, and those are the same, but we
+        // only know that once we convert the generic parameters to those of the opaque type.
+        if let Some(prev) = self.concrete_opaque_types.0.get_mut(&def_id) {
+            if prev.ty != hidden_ty.ty {
+                let guar = hidden_ty.ty.error_reported().err().unwrap_or_else(|| {
+                    let (Ok(e) | Err(e)) =
+                        prev.build_mismatch_error(&hidden_ty, self.tcx).map(|d| d.emit());
+                    e
+                });
+                prev.ty = Ty::new_error(self.tcx, guar);
+            }
+            // Pick a better span if there is one.
+            // FIXME(oli-obk): collect multiple spans for better diagnostics down the road.
+            prev.span = prev.span.substitute_dummy(hidden_ty.span);
+        } else {
+            self.concrete_opaque_types.0.insert(def_id, hidden_ty);
+        }
+    }
+
+    pub(super) fn set_tainted_by_errors(&mut self, guar: ErrorGuaranteed) {
+        self.tainted_by_errors = Some(guar);
+    }
+
+    fn get_or_insert_nested(&mut self, def_id: LocalDefId) -> &PropagatedBorrowCheckResults<'tcx> {
+        debug_assert_eq!(
+            self.tcx.typeck_root_def_id(def_id.to_def_id()),
+            self.root_def_id.to_def_id()
+        );
+        if !self.nested_bodies.contains_key(&def_id) {
+            let result = super::do_mir_borrowck(self, def_id, None).0;
+            if let Some(prev) = self.nested_bodies.insert(def_id, result) {
+                bug!("unexpected previous nested body: {prev:?}");
+            }
+        }
+
+        self.nested_bodies.get(&def_id).unwrap()
+    }
+
+    pub(super) fn closure_requirements(
+        &mut self,
+        nested_body_def_id: LocalDefId,
+    ) -> &Option<ClosureRegionRequirements<'tcx>> {
+        &self.get_or_insert_nested(nested_body_def_id).closure_requirements
+    }
+
+    pub(super) fn used_mut_upvars(
+        &mut self,
+        nested_body_def_id: LocalDefId,
+    ) -> &SmallVec<[FieldIdx; 8]> {
+        &self.get_or_insert_nested(nested_body_def_id).used_mut_upvars
+    }
+
+    pub(super) fn finalize(self) -> Result<&'tcx ConcreteOpaqueTypes<'tcx>, ErrorGuaranteed> {
+        if let Some(guar) = self.tainted_by_errors {
+            Err(guar)
+        } else {
+            Ok(self.tcx.arena.alloc(self.concrete_opaque_types))
+        }
+    }
+}
diff --git a/compiler/rustc_borrowck/src/type_check/constraint_conversion.rs b/compiler/rustc_borrowck/src/type_check/constraint_conversion.rs
index 6fbe1db6330..ccb257ae093 100644
--- a/compiler/rustc_borrowck/src/type_check/constraint_conversion.rs
+++ b/compiler/rustc_borrowck/src/type_check/constraint_conversion.rs
@@ -6,7 +6,6 @@ use rustc_infer::infer::region_constraints::{GenericKind, VerifyBound};
 use rustc_infer::infer::{self, InferCtxt, SubregionOrigin};
 use rustc_infer::traits::query::type_op::DeeplyNormalize;
 use rustc_middle::bug;
-use rustc_middle::mir::{ClosureOutlivesSubject, ClosureRegionRequirements, ConstraintCategory};
 use rustc_middle::ty::{
     self, GenericArgKind, Ty, TyCtxt, TypeFoldable, TypeVisitableExt, fold_regions,
 };
@@ -18,6 +17,7 @@ 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};
 
 pub(crate) struct ConstraintConversion<'a, 'tcx> {
     infcx: &'a InferCtxt<'tcx>,
@@ -205,7 +205,7 @@ impl<'a, 'tcx> ConstraintConversion<'a, 'tcx> {
     /// are dealt with during trait solving.
     fn replace_placeholders_with_nll<T: TypeFoldable<TyCtxt<'tcx>>>(&mut self, value: T) -> T {
         if value.has_placeholders() {
-            fold_regions(self.tcx, value, |r, _| match *r {
+            fold_regions(self.tcx, value, |r, _| match r.kind() {
                 ty::RePlaceholder(placeholder) => {
                     self.constraints.placeholder_region(self.infcx, placeholder)
                 }
@@ -227,7 +227,7 @@ impl<'a, 'tcx> ConstraintConversion<'a, 'tcx> {
     }
 
     fn to_region_vid(&mut self, r: ty::Region<'tcx>) -> ty::RegionVid {
-        if let ty::RePlaceholder(placeholder) = *r {
+        if let ty::RePlaceholder(placeholder) = r.kind() {
             self.constraints.placeholder_region(self.infcx, placeholder).as_var()
         } else {
             self.universal_regions.to_region_vid(r)
diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs
index f6144a25938..a17dff5d271 100644
--- a/compiler/rustc_borrowck/src/type_check/mod.rs
+++ b/compiler/rustc_borrowck/src/type_check/mod.rs
@@ -45,7 +45,6 @@ use crate::borrow_set::BorrowSet;
 use crate::constraints::{OutlivesConstraint, OutlivesConstraintSet};
 use crate::diagnostics::UniverseInfo;
 use crate::member_constraints::MemberConstraintSet;
-use crate::opaque_types::ConcreteOpaqueTypes;
 use crate::polonius::legacy::{PoloniusFacts, PoloniusLocationTable};
 use crate::polonius::{PoloniusContext, PoloniusLivenessContext};
 use crate::region_infer::TypeTest;
@@ -53,7 +52,7 @@ use crate::region_infer::values::{LivenessValues, PlaceholderIndex, PlaceholderI
 use crate::session_diagnostics::{MoveUnsized, SimdIntrinsicArgConst};
 use crate::type_check::free_region_relations::{CreateResult, UniversalRegionRelations};
 use crate::universal_regions::{DefiningTy, UniversalRegions};
-use crate::{BorrowckInferCtxt, path_utils};
+use crate::{BorrowCheckRootCtxt, BorrowckInferCtxt, path_utils};
 
 macro_rules! span_mirbug {
     ($context:expr, $elem:expr, $($message:tt)*) => ({
@@ -102,6 +101,7 @@ mod relate_tys;
 /// - `move_data` -- move-data constructed when performing the maybe-init dataflow analysis
 /// - `location_map` -- map between MIR `Location` and `PointIndex`
 pub(crate) fn type_check<'a, 'tcx>(
+    root_cx: &mut BorrowCheckRootCtxt<'tcx>,
     infcx: &BorrowckInferCtxt<'tcx>,
     body: &Body<'tcx>,
     promoted: &IndexSlice<Promoted, Body<'tcx>>,
@@ -112,7 +112,6 @@ pub(crate) fn type_check<'a, 'tcx>(
     flow_inits: ResultsCursor<'a, 'tcx, MaybeInitializedPlaces<'a, 'tcx>>,
     move_data: &MoveData<'tcx>,
     location_map: Rc<DenseLocationMap>,
-    concrete_opaque_types: &mut ConcreteOpaqueTypes<'tcx>,
 ) -> MirTypeckResults<'tcx> {
     let implicit_region_bound = ty::Region::new_var(infcx.tcx, universal_regions.fr_fn_body);
     let mut constraints = MirTypeckRegionConstraints {
@@ -153,6 +152,7 @@ pub(crate) fn type_check<'a, 'tcx>(
     };
 
     let mut typeck = TypeChecker {
+        root_cx,
         infcx,
         last_span: body.span,
         body,
@@ -167,7 +167,6 @@ pub(crate) fn type_check<'a, 'tcx>(
         polonius_facts,
         borrow_set,
         constraints: &mut constraints,
-        concrete_opaque_types,
         polonius_liveness,
     };
 
@@ -215,6 +214,7 @@ enum FieldAccessError {
 /// way, it accrues region constraints -- these can later be used by
 /// NLL region checking.
 struct TypeChecker<'a, 'tcx> {
+    root_cx: &'a mut BorrowCheckRootCtxt<'tcx>,
     infcx: &'a BorrowckInferCtxt<'tcx>,
     last_span: Span,
     body: &'a Body<'tcx>,
@@ -233,7 +233,6 @@ struct TypeChecker<'a, 'tcx> {
     polonius_facts: &'a mut Option<PoloniusFacts>,
     borrow_set: &'a BorrowSet<'tcx>,
     constraints: &'a mut MirTypeckRegionConstraints<'tcx>,
-    concrete_opaque_types: &'a mut ConcreteOpaqueTypes<'tcx>,
     /// When using `-Zpolonius=next`, the liveness helper data used to create polonius constraints.
     polonius_liveness: Option<PoloniusLivenessContext>,
 }
@@ -2503,11 +2502,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         args: GenericArgsRef<'tcx>,
         locations: Locations,
     ) -> ty::InstantiatedPredicates<'tcx> {
-        let closure_borrowck_results = tcx.mir_borrowck(def_id);
-        self.concrete_opaque_types
-            .extend_from_nested_body(tcx, &closure_borrowck_results.concrete_opaque_types);
-
-        if let Some(closure_requirements) = &closure_borrowck_results.closure_requirements {
+        if let Some(closure_requirements) = &self.root_cx.closure_requirements(def_id) {
             constraint_conversion::ConstraintConversion::new(
                 self.infcx,
                 self.universal_regions,
diff --git a/compiler/rustc_borrowck/src/type_check/opaque_types.rs b/compiler/rustc_borrowck/src/type_check/opaque_types.rs
index 8bab979a724..d41cbf757d7 100644
--- a/compiler/rustc_borrowck/src/type_check/opaque_types.rs
+++ b/compiler/rustc_borrowck/src/type_check/opaque_types.rs
@@ -271,7 +271,7 @@ where
     }
 
     fn visit_region(&mut self, r: ty::Region<'tcx>) {
-        match *r {
+        match r.kind() {
             // ignore bound regions, keep visiting
             ty::ReBound(_, _) => {}
             _ => (self.op)(r),
diff --git a/compiler/rustc_borrowck/src/universal_regions.rs b/compiler/rustc_borrowck/src/universal_regions.rs
index 8f6b405fcef..5c57ab99a85 100644
--- a/compiler/rustc_borrowck/src/universal_regions.rs
+++ b/compiler/rustc_borrowck/src/universal_regions.rs
@@ -909,19 +909,19 @@ impl<'tcx> UniversalRegionIndices<'tcx> {
     /// if it is a placeholder. Handling placeholders requires access to the
     /// `MirTypeckRegionConstraints`.
     fn to_region_vid(&self, r: ty::Region<'tcx>) -> RegionVid {
-        if let ty::ReVar(..) = *r {
-            r.as_var()
-        } else if let ty::ReError(guar) = *r {
-            self.tainted_by_errors.set(Some(guar));
-            // We use the `'static` `RegionVid` because `ReError` doesn't actually exist in the
-            // `UniversalRegionIndices`. This is fine because 1) it is a fallback only used if
-            // errors are being emitted and 2) it leaves the happy path unaffected.
-            self.fr_static
-        } else {
-            *self
+        match r.kind() {
+            ty::ReVar(..) => r.as_var(),
+            ty::ReError(guar) => {
+                self.tainted_by_errors.set(Some(guar));
+                // We use the `'static` `RegionVid` because `ReError` doesn't actually exist in the
+                // `UniversalRegionIndices`. This is fine because 1) it is a fallback only used if
+                // errors are being emitted and 2) it leaves the happy path unaffected.
+                self.fr_static
+            }
+            _ => *self
                 .indices
                 .get(&r)
-                .unwrap_or_else(|| bug!("cannot convert `{:?}` to a region vid", r))
+                .unwrap_or_else(|| bug!("cannot convert `{:?}` to a region vid", r)),
         }
     }
 
diff --git a/compiler/rustc_builtin_macros/src/autodiff.rs b/compiler/rustc_builtin_macros/src/autodiff.rs
index 351413dea49..4161829480d 100644
--- a/compiler/rustc_builtin_macros/src/autodiff.rs
+++ b/compiler/rustc_builtin_macros/src/autodiff.rs
@@ -234,7 +234,7 @@ mod llvm_enzyme {
         let meta_item_vec: ThinVec<MetaItemInner> = match meta_item.kind {
             ast::MetaItemKind::List(ref vec) => vec.clone(),
             _ => {
-                dcx.emit_err(errors::AutoDiffInvalidApplication { span: item.span() });
+                dcx.emit_err(errors::AutoDiffMissingConfig { span: item.span() });
                 return vec![item];
             }
         };
diff --git a/compiler/rustc_builtin_macros/src/proc_macro_harness.rs b/compiler/rustc_builtin_macros/src/proc_macro_harness.rs
index 8862965c053..a91f2d38a93 100644
--- a/compiler/rustc_builtin_macros/src/proc_macro_harness.rs
+++ b/compiler/rustc_builtin_macros/src/proc_macro_harness.rs
@@ -20,14 +20,14 @@ use crate::errors;
 struct ProcMacroDerive {
     id: NodeId,
     trait_name: Symbol,
-    function_name: Ident,
+    function_ident: Ident,
     span: Span,
     attrs: Vec<Symbol>,
 }
 
 struct ProcMacroDef {
     id: NodeId,
-    function_name: Ident,
+    function_ident: Ident,
     span: Span,
 }
 
@@ -95,7 +95,7 @@ impl<'a> CollectProcMacros<'a> {
     fn collect_custom_derive(
         &mut self,
         item: &'a ast::Item,
-        function_name: Ident,
+        function_ident: Ident,
         attr: &'a ast::Attribute,
     ) {
         let Some((trait_name, proc_attrs)) =
@@ -109,7 +109,7 @@ impl<'a> CollectProcMacros<'a> {
                 id: item.id,
                 span: item.span,
                 trait_name,
-                function_name,
+                function_ident,
                 attrs: proc_attrs,
             }));
         } else {
@@ -123,12 +123,12 @@ impl<'a> CollectProcMacros<'a> {
         }
     }
 
-    fn collect_attr_proc_macro(&mut self, item: &'a ast::Item, function_name: Ident) {
+    fn collect_attr_proc_macro(&mut self, item: &'a ast::Item, function_ident: Ident) {
         if self.in_root && item.vis.kind.is_pub() {
             self.macros.push(ProcMacro::Attr(ProcMacroDef {
                 id: item.id,
                 span: item.span,
-                function_name,
+                function_ident,
             }));
         } else {
             let msg = if !self.in_root {
@@ -141,12 +141,12 @@ impl<'a> CollectProcMacros<'a> {
         }
     }
 
-    fn collect_bang_proc_macro(&mut self, item: &'a ast::Item, function_name: Ident) {
+    fn collect_bang_proc_macro(&mut self, item: &'a ast::Item, function_ident: Ident) {
         if self.in_root && item.vis.kind.is_pub() {
             self.macros.push(ProcMacro::Bang(ProcMacroDef {
                 id: item.id,
                 span: item.span,
-                function_name,
+                function_ident,
             }));
         } else {
             let msg = if !self.in_root {
@@ -303,7 +303,7 @@ fn mk_decls(cx: &mut ExtCtxt<'_>, macros: &[ProcMacro]) -> P<ast::Item> {
                 ProcMacro::Derive(m) => m.span,
                 ProcMacro::Attr(m) | ProcMacro::Bang(m) => m.span,
             };
-            let local_path = |cx: &ExtCtxt<'_>, name| cx.expr_path(cx.path(span, vec![name]));
+            let local_path = |cx: &ExtCtxt<'_>, ident| cx.expr_path(cx.path(span, vec![ident]));
             let proc_macro_ty_method_path = |cx: &ExtCtxt<'_>, method| {
                 cx.expr_path(cx.path(
                     span.with_ctxt(harness_span.ctxt()),
@@ -327,7 +327,7 @@ fn mk_decls(cx: &mut ExtCtxt<'_>, macros: &[ProcMacro]) -> P<ast::Item> {
                                     .map(|&s| cx.expr_str(span, s))
                                     .collect::<ThinVec<_>>(),
                             ),
-                            local_path(cx, cd.function_name),
+                            local_path(cx, cd.function_ident),
                         ],
                     )
                 }
@@ -345,8 +345,8 @@ fn mk_decls(cx: &mut ExtCtxt<'_>, macros: &[ProcMacro]) -> P<ast::Item> {
                         harness_span,
                         proc_macro_ty_method_path(cx, ident),
                         thin_vec![
-                            cx.expr_str(span, ca.function_name.name),
-                            local_path(cx, ca.function_name),
+                            cx.expr_str(span, ca.function_ident.name),
+                            local_path(cx, ca.function_ident),
                         ],
                     )
                 }
diff --git a/compiler/rustc_codegen_cranelift/src/driver/aot.rs b/compiler/rustc_codegen_cranelift/src/driver/aot.rs
index 444dc441286..00136ac4a57 100644
--- a/compiler/rustc_codegen_cranelift/src/driver/aot.rs
+++ b/compiler/rustc_codegen_cranelift/src/driver/aot.rs
@@ -169,8 +169,11 @@ fn produce_final_output_artifacts(
         if codegen_results.modules.len() == 1 {
             // 1) Only one codegen unit. In this case it's no difficulty
             //    to copy `foo.0.x` to `foo.x`.
-            let module_name = Some(&codegen_results.modules[0].name[..]);
-            let path = crate_output.temp_path(output_type, module_name);
+            let path = crate_output.temp_path_for_cgu(
+                output_type,
+                &codegen_results.modules[0].name,
+                sess.invocation_temp.as_deref(),
+            );
             let output = crate_output.path(output_type);
             if !output_type.is_text_output() && output.is_tty() {
                 sess.dcx()
@@ -183,22 +186,16 @@ fn produce_final_output_artifacts(
                 ensure_removed(sess.dcx(), &path);
             }
         } else {
-            let extension = crate_output
-                .temp_path(output_type, None)
-                .extension()
-                .unwrap()
-                .to_str()
-                .unwrap()
-                .to_owned();
-
             if crate_output.outputs.contains_explicit_name(&output_type) {
                 // 2) Multiple codegen units, with `--emit foo=some_name`. We have
                 //    no good solution for this case, so warn the user.
-                sess.dcx().emit_warn(ssa_errors::IgnoringEmitPath { extension });
+                sess.dcx()
+                    .emit_warn(ssa_errors::IgnoringEmitPath { extension: output_type.extension() });
             } else if crate_output.single_output_file.is_some() {
                 // 3) Multiple codegen units, with `-o some_name`. We have
                 //    no good solution for this case, so warn the user.
-                sess.dcx().emit_warn(ssa_errors::IgnoringOutput { extension });
+                sess.dcx()
+                    .emit_warn(ssa_errors::IgnoringOutput { extension: output_type.extension() });
             } else {
                 // 4) Multiple codegen units, but no explicit name. We
                 //    just leave the `foo.0.x` files in place.
@@ -351,6 +348,7 @@ fn make_module(sess: &Session, name: String) -> UnwindModule<ObjectModule> {
 
 fn emit_cgu(
     output_filenames: &OutputFilenames,
+    invocation_temp: Option<&str>,
     prof: &SelfProfilerRef,
     name: String,
     module: UnwindModule<ObjectModule>,
@@ -366,6 +364,7 @@ fn emit_cgu(
 
     let module_regular = emit_module(
         output_filenames,
+        invocation_temp,
         prof,
         product.object,
         ModuleKind::Regular,
@@ -391,6 +390,7 @@ fn emit_cgu(
 
 fn emit_module(
     output_filenames: &OutputFilenames,
+    invocation_temp: Option<&str>,
     prof: &SelfProfilerRef,
     mut object: cranelift_object::object::write::Object<'_>,
     kind: ModuleKind,
@@ -409,7 +409,7 @@ fn emit_module(
         object.set_section_data(comment_section, producer, 1);
     }
 
-    let tmp_file = output_filenames.temp_path(OutputType::Object, Some(&name));
+    let tmp_file = output_filenames.temp_path_for_cgu(OutputType::Object, &name, invocation_temp);
     let file = match File::create(&tmp_file) {
         Ok(file) => file,
         Err(err) => return Err(format!("error creating object file: {}", err)),
@@ -449,8 +449,11 @@ fn reuse_workproduct_for_cgu(
     cgu: &CodegenUnit<'_>,
 ) -> Result<ModuleCodegenResult, String> {
     let work_product = cgu.previous_work_product(tcx);
-    let obj_out_regular =
-        tcx.output_filenames(()).temp_path(OutputType::Object, Some(cgu.name().as_str()));
+    let obj_out_regular = tcx.output_filenames(()).temp_path_for_cgu(
+        OutputType::Object,
+        cgu.name().as_str(),
+        tcx.sess.invocation_temp.as_deref(),
+    );
     let source_file_regular = rustc_incremental::in_incr_comp_dir_sess(
         &tcx.sess,
         &work_product.saved_files.get("o").expect("no saved object file in work product"),
@@ -595,13 +598,19 @@ fn module_codegen(
 
         let global_asm_object_file =
             profiler.generic_activity_with_arg("compile assembly", &*cgu_name).run(|| {
-                crate::global_asm::compile_global_asm(&global_asm_config, &cgu_name, &cx.global_asm)
+                crate::global_asm::compile_global_asm(
+                    &global_asm_config,
+                    &cgu_name,
+                    &cx.global_asm,
+                    cx.invocation_temp.as_deref(),
+                )
             })?;
 
         let codegen_result =
             profiler.generic_activity_with_arg("write object file", &*cgu_name).run(|| {
                 emit_cgu(
                     &global_asm_config.output_filenames,
+                    cx.invocation_temp.as_deref(),
                     &profiler,
                     cgu_name,
                     module,
@@ -626,8 +635,11 @@ fn emit_metadata_module(tcx: TyCtxt<'_>, metadata: &EncodedMetadata) -> Compiled
         .as_str()
         .to_string();
 
-    let tmp_file =
-        tcx.output_filenames(()).temp_path(OutputType::Metadata, Some(&metadata_cgu_name));
+    let tmp_file = tcx.output_filenames(()).temp_path_for_cgu(
+        OutputType::Metadata,
+        &metadata_cgu_name,
+        tcx.sess.invocation_temp.as_deref(),
+    );
 
     let symbol_name = rustc_middle::middle::exported_symbols::metadata_symbol_name(tcx);
     let obj = create_compressed_metadata_file(tcx.sess, metadata, &symbol_name);
@@ -657,6 +669,7 @@ fn emit_allocator_module(tcx: TyCtxt<'_>) -> Option<CompiledModule> {
 
         match emit_module(
             tcx.output_filenames(()),
+            tcx.sess.invocation_temp.as_deref(),
             &tcx.sess.prof,
             product.object,
             ModuleKind::Allocator,
@@ -728,26 +741,27 @@ pub(crate) fn run_aot(
 
     let concurrency_limiter = IntoDynSyncSend(ConcurrencyLimiter::new(todo_cgus.len()));
 
-    let modules = tcx.sess.time("codegen mono items", || {
-        let mut modules: Vec<_> = par_map(todo_cgus, |(_, cgu)| {
-            let dep_node = cgu.codegen_dep_node(tcx);
-            tcx.dep_graph
-                .with_task(
+    let modules: Vec<_> =
+        tcx.sess.time("codegen mono items", || {
+            let modules: Vec<_> = par_map(todo_cgus, |(_, cgu)| {
+                let dep_node = cgu.codegen_dep_node(tcx);
+                let (module, _) = tcx.dep_graph.with_task(
                     dep_node,
                     tcx,
                     (global_asm_config.clone(), cgu.name(), concurrency_limiter.acquire(tcx.dcx())),
                     module_codegen,
                     Some(rustc_middle::dep_graph::hash_result),
-                )
-                .0
-        });
-        modules.extend(
-            done_cgus
+                );
+                IntoDynSyncSend(module)
+            });
+            modules
                 .into_iter()
-                .map(|(_, cgu)| OngoingModuleCodegen::Sync(reuse_workproduct_for_cgu(tcx, cgu))),
-        );
-        modules
-    });
+                .map(|module| module.0)
+                .chain(done_cgus.into_iter().map(|(_, cgu)| {
+                    OngoingModuleCodegen::Sync(reuse_workproduct_for_cgu(tcx, cgu))
+                }))
+                .collect()
+        });
 
     let allocator_module = emit_allocator_module(tcx);
 
diff --git a/compiler/rustc_codegen_cranelift/src/global_asm.rs b/compiler/rustc_codegen_cranelift/src/global_asm.rs
index 9ea92c300f8..79cefb05de3 100644
--- a/compiler/rustc_codegen_cranelift/src/global_asm.rs
+++ b/compiler/rustc_codegen_cranelift/src/global_asm.rs
@@ -132,6 +132,7 @@ pub(crate) fn compile_global_asm(
     config: &GlobalAsmConfig,
     cgu_name: &str,
     global_asm: &str,
+    invocation_temp: Option<&str>,
 ) -> Result<Option<PathBuf>, String> {
     if global_asm.is_empty() {
         return Ok(None);
@@ -146,7 +147,7 @@ pub(crate) fn compile_global_asm(
     global_asm.push('\n');
 
     let global_asm_object_file = add_file_stem_postfix(
-        config.output_filenames.temp_path(OutputType::Object, Some(cgu_name)),
+        config.output_filenames.temp_path_for_cgu(OutputType::Object, cgu_name, invocation_temp),
         ".asm",
     );
 
diff --git a/compiler/rustc_codegen_cranelift/src/lib.rs b/compiler/rustc_codegen_cranelift/src/lib.rs
index e7afaff3b42..9d9e790289c 100644
--- a/compiler/rustc_codegen_cranelift/src/lib.rs
+++ b/compiler/rustc_codegen_cranelift/src/lib.rs
@@ -124,6 +124,7 @@ impl<F: Fn() -> String> Drop for PrintOnPanic<F> {
 /// inside a single codegen unit with the exception of the Cranelift [`Module`](cranelift_module::Module).
 struct CodegenCx {
     output_filenames: Arc<OutputFilenames>,
+    invocation_temp: Option<String>,
     should_write_ir: bool,
     global_asm: String,
     inline_asm_index: usize,
@@ -142,6 +143,7 @@ impl CodegenCx {
         };
         CodegenCx {
             output_filenames: tcx.output_filenames(()).clone(),
+            invocation_temp: tcx.sess.invocation_temp.clone(),
             should_write_ir: crate::pretty_clif::should_write_ir(tcx),
             global_asm: String::new(),
             inline_asm_index: 0,
diff --git a/compiler/rustc_codegen_cranelift/src/main_shim.rs b/compiler/rustc_codegen_cranelift/src/main_shim.rs
index 6d5df2b0043..3b48adb7e91 100644
--- a/compiler/rustc_codegen_cranelift/src/main_shim.rs
+++ b/compiler/rustc_codegen_cranelift/src/main_shim.rs
@@ -104,7 +104,7 @@ pub(crate) fn maybe_create_entry_wrapper(
                 let termination_trait = tcx.require_lang_item(LangItem::Termination, None);
                 let report = tcx
                     .associated_items(termination_trait)
-                    .find_by_name_and_kind(
+                    .find_by_ident_and_kind(
                         tcx,
                         Ident::from_str("report"),
                         AssocKind::Fn,
diff --git a/compiler/rustc_codegen_gcc/src/back/write.rs b/compiler/rustc_codegen_gcc/src/back/write.rs
index 51c5ba73e32..16c895322e8 100644
--- a/compiler/rustc_codegen_gcc/src/back/write.rs
+++ b/compiler/rustc_codegen_gcc/src/back/write.rs
@@ -24,19 +24,23 @@ pub(crate) unsafe fn codegen(
     {
         let context = &module.module_llvm.context;
 
-        let module_name = module.name.clone();
-
         let should_combine_object_files = module.module_llvm.should_combine_object_files;
 
-        let module_name = Some(&module_name[..]);
-
         // NOTE: Only generate object files with GIMPLE when this environment variable is set for
         // now because this requires a particular setup (same gcc/lto1/lto-wrapper commit as libgccjit).
         // TODO(antoyo): remove this environment variable.
         let fat_lto = env::var("EMBED_LTO_BITCODE").as_deref() == Ok("1");
 
-        let bc_out = cgcx.output_filenames.temp_path(OutputType::Bitcode, module_name);
-        let obj_out = cgcx.output_filenames.temp_path(OutputType::Object, module_name);
+        let bc_out = cgcx.output_filenames.temp_path_for_cgu(
+            OutputType::Bitcode,
+            &module.name,
+            cgcx.invocation_temp.as_deref(),
+        );
+        let obj_out = cgcx.output_filenames.temp_path_for_cgu(
+            OutputType::Object,
+            &module.name,
+            cgcx.invocation_temp.as_deref(),
+        );
 
         if config.bitcode_needed() {
             if fat_lto {
@@ -117,14 +121,22 @@ pub(crate) unsafe fn codegen(
         }
 
         if config.emit_ir {
-            let out = cgcx.output_filenames.temp_path(OutputType::LlvmAssembly, module_name);
+            let out = cgcx.output_filenames.temp_path_for_cgu(
+                OutputType::LlvmAssembly,
+                &module.name,
+                cgcx.invocation_temp.as_deref(),
+            );
             std::fs::write(out, "").expect("write file");
         }
 
         if config.emit_asm {
             let _timer =
                 cgcx.prof.generic_activity_with_arg("GCC_module_codegen_emit_asm", &*module.name);
-            let path = cgcx.output_filenames.temp_path(OutputType::Assembly, module_name);
+            let path = cgcx.output_filenames.temp_path_for_cgu(
+                OutputType::Assembly,
+                &module.name,
+                cgcx.invocation_temp.as_deref(),
+            );
             context.compile_to_file(OutputKind::Assembler, path.to_str().expect("path to str"));
         }
 
@@ -238,6 +250,7 @@ pub(crate) unsafe fn codegen(
         config.emit_asm,
         config.emit_ir,
         &cgcx.output_filenames,
+        cgcx.invocation_temp.as_deref(),
     ))
 }
 
diff --git a/compiler/rustc_codegen_llvm/src/back/write.rs b/compiler/rustc_codegen_llvm/src/back/write.rs
index 76d431a4975..18d221d232e 100644
--- a/compiler/rustc_codegen_llvm/src/back/write.rs
+++ b/compiler/rustc_codegen_llvm/src/back/write.rs
@@ -119,14 +119,18 @@ pub(crate) fn create_target_machine(tcx: TyCtxt<'_>, mod_name: &str) -> OwnedTar
         tcx.output_filenames(()).split_dwarf_path(
             tcx.sess.split_debuginfo(),
             tcx.sess.opts.unstable_opts.split_dwarf_kind,
-            Some(mod_name),
+            mod_name,
+            tcx.sess.invocation_temp.as_deref(),
         )
     } else {
         None
     };
 
-    let output_obj_file =
-        Some(tcx.output_filenames(()).temp_path(OutputType::Object, Some(mod_name)));
+    let output_obj_file = Some(tcx.output_filenames(()).temp_path_for_cgu(
+        OutputType::Object,
+        mod_name,
+        tcx.sess.invocation_temp.as_deref(),
+    ));
     let config = TargetMachineFactoryConfig { split_dwarf_file, output_obj_file };
 
     target_machine_factory(
@@ -330,8 +334,11 @@ pub(crate) fn save_temp_bitcode(
         return;
     }
     let ext = format!("{name}.bc");
-    let cgu = Some(&module.name[..]);
-    let path = cgcx.output_filenames.temp_path_ext(&ext, cgu);
+    let path = cgcx.output_filenames.temp_path_ext_for_cgu(
+        &ext,
+        &module.name,
+        cgcx.invocation_temp.as_deref(),
+    );
     write_bitcode_to_file(module, &path)
 }
 
@@ -694,11 +701,12 @@ pub(crate) unsafe fn optimize(
     let llcx = &*module.module_llvm.llcx;
     let _handlers = DiagnosticHandlers::new(cgcx, dcx, llcx, module, CodegenDiagnosticsStage::Opt);
 
-    let module_name = module.name.clone();
-    let module_name = Some(&module_name[..]);
-
     if config.emit_no_opt_bc {
-        let out = cgcx.output_filenames.temp_path_ext("no-opt.bc", module_name);
+        let out = cgcx.output_filenames.temp_path_ext_for_cgu(
+            "no-opt.bc",
+            &module.name,
+            cgcx.invocation_temp.as_deref(),
+        );
         write_bitcode_to_file(module, &out)
     }
 
@@ -743,8 +751,11 @@ pub(crate) unsafe fn optimize(
         if let Some(thin_lto_buffer) = thin_lto_buffer {
             let thin_lto_buffer = unsafe { ThinBuffer::from_raw_ptr(thin_lto_buffer) };
             module.thin_lto_buffer = Some(thin_lto_buffer.data().to_vec());
-            let bc_summary_out =
-                cgcx.output_filenames.temp_path(OutputType::ThinLinkBitcode, module_name);
+            let bc_summary_out = cgcx.output_filenames.temp_path_for_cgu(
+                OutputType::ThinLinkBitcode,
+                &module.name,
+                cgcx.invocation_temp.as_deref(),
+            );
             if config.emit_thin_lto_summary
                 && let Some(thin_link_bitcode_filename) = bc_summary_out.file_name()
             {
@@ -801,8 +812,6 @@ pub(crate) unsafe fn codegen(
         let llmod = module.module_llvm.llmod();
         let llcx = &*module.module_llvm.llcx;
         let tm = &*module.module_llvm.tm;
-        let module_name = module.name.clone();
-        let module_name = Some(&module_name[..]);
         let _handlers =
             DiagnosticHandlers::new(cgcx, dcx, llcx, &module, CodegenDiagnosticsStage::Codegen);
 
@@ -814,8 +823,16 @@ pub(crate) unsafe fn codegen(
         // copy it to the .o file, and delete the bitcode if it wasn't
         // otherwise requested.
 
-        let bc_out = cgcx.output_filenames.temp_path(OutputType::Bitcode, module_name);
-        let obj_out = cgcx.output_filenames.temp_path(OutputType::Object, module_name);
+        let bc_out = cgcx.output_filenames.temp_path_for_cgu(
+            OutputType::Bitcode,
+            &module.name,
+            cgcx.invocation_temp.as_deref(),
+        );
+        let obj_out = cgcx.output_filenames.temp_path_for_cgu(
+            OutputType::Object,
+            &module.name,
+            cgcx.invocation_temp.as_deref(),
+        );
 
         if config.bitcode_needed() {
             if config.emit_bc || config.emit_obj == EmitObj::Bitcode {
@@ -857,7 +874,11 @@ pub(crate) unsafe fn codegen(
         if config.emit_ir {
             let _timer =
                 cgcx.prof.generic_activity_with_arg("LLVM_module_codegen_emit_ir", &*module.name);
-            let out = cgcx.output_filenames.temp_path(OutputType::LlvmAssembly, module_name);
+            let out = cgcx.output_filenames.temp_path_for_cgu(
+                OutputType::LlvmAssembly,
+                &module.name,
+                cgcx.invocation_temp.as_deref(),
+            );
             let out_c = path_to_c_string(&out);
 
             extern "C" fn demangle_callback(
@@ -899,7 +920,11 @@ pub(crate) unsafe fn codegen(
         if config.emit_asm {
             let _timer =
                 cgcx.prof.generic_activity_with_arg("LLVM_module_codegen_emit_asm", &*module.name);
-            let path = cgcx.output_filenames.temp_path(OutputType::Assembly, module_name);
+            let path = cgcx.output_filenames.temp_path_for_cgu(
+                OutputType::Assembly,
+                &module.name,
+                cgcx.invocation_temp.as_deref(),
+            );
 
             // We can't use the same module for asm and object code output,
             // because that triggers various errors like invalid IR or broken
@@ -929,7 +954,9 @@ pub(crate) unsafe fn codegen(
                     .prof
                     .generic_activity_with_arg("LLVM_module_codegen_emit_obj", &*module.name);
 
-                let dwo_out = cgcx.output_filenames.temp_path_dwo(module_name);
+                let dwo_out = cgcx
+                    .output_filenames
+                    .temp_path_dwo_for_cgu(&module.name, cgcx.invocation_temp.as_deref());
                 let dwo_out = match (cgcx.split_debuginfo, cgcx.split_dwarf_kind) {
                     // Don't change how DWARF is emitted when disabled.
                     (SplitDebuginfo::Off, _) => None,
@@ -994,6 +1021,7 @@ pub(crate) unsafe fn codegen(
         config.emit_asm,
         config.emit_ir,
         &cgcx.output_filenames,
+        cgcx.invocation_temp.as_deref(),
     ))
 }
 
diff --git a/compiler/rustc_codegen_llvm/src/common.rs b/compiler/rustc_codegen_llvm/src/common.rs
index 457e5452ce9..a6f277e4455 100644
--- a/compiler/rustc_codegen_llvm/src/common.rs
+++ b/compiler/rustc_codegen_llvm/src/common.rs
@@ -4,8 +4,8 @@ use std::borrow::Borrow;
 
 use libc::{c_char, c_uint};
 use rustc_abi as abi;
+use rustc_abi::HasDataLayout;
 use rustc_abi::Primitive::Pointer;
-use rustc_abi::{AddressSpace, HasDataLayout};
 use rustc_ast::Mutability;
 use rustc_codegen_ssa::common::TypeKind;
 use rustc_codegen_ssa::traits::*;
@@ -269,7 +269,8 @@ impl<'ll, 'tcx> ConstCodegenMethods for CodegenCx<'ll, 'tcx> {
             }
             Scalar::Ptr(ptr, _size) => {
                 let (prov, offset) = ptr.into_parts();
-                let (base_addr, base_addr_space) = match self.tcx.global_alloc(prov.alloc_id()) {
+                let global_alloc = self.tcx.global_alloc(prov.alloc_id());
+                let base_addr = match global_alloc {
                     GlobalAlloc::Memory(alloc) => {
                         // For ZSTs directly codegen an aligned pointer.
                         // This avoids generating a zero-sized constant value and actually needing a
@@ -301,12 +302,10 @@ impl<'ll, 'tcx> ConstCodegenMethods for CodegenCx<'ll, 'tcx> {
                                     format!("alloc_{hash:032x}").as_bytes(),
                                 );
                             }
-                            (value, AddressSpace::DATA)
+                            value
                         }
                     }
-                    GlobalAlloc::Function { instance, .. } => {
-                        (self.get_fn_addr(instance), self.data_layout().instruction_address_space)
-                    }
+                    GlobalAlloc::Function { instance, .. } => self.get_fn_addr(instance),
                     GlobalAlloc::VTable(ty, dyn_ty) => {
                         let alloc = self
                             .tcx
@@ -319,14 +318,15 @@ impl<'ll, 'tcx> ConstCodegenMethods for CodegenCx<'ll, 'tcx> {
                             .unwrap_memory();
                         let init = const_alloc_to_llvm(self, alloc, /*static*/ false);
                         let value = self.static_addr_of_impl(init, alloc.inner().align, None);
-                        (value, AddressSpace::DATA)
+                        value
                     }
                     GlobalAlloc::Static(def_id) => {
                         assert!(self.tcx.is_static(def_id));
                         assert!(!self.tcx.is_thread_local_static(def_id));
-                        (self.get_static(def_id), AddressSpace::DATA)
+                        self.get_static(def_id)
                     }
                 };
+                let base_addr_space = global_alloc.address_space(self);
                 let llval = unsafe {
                     llvm::LLVMConstInBoundsGEP2(
                         self.type_i8(),
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs b/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
index 2eaaf127e41..1eb8f367c54 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
@@ -910,7 +910,8 @@ pub(crate) fn build_compile_unit_di_node<'ll, 'tcx>(
         && let Some(f) = output_filenames.split_dwarf_path(
             tcx.sess.split_debuginfo(),
             tcx.sess.opts.unstable_opts.split_dwarf_kind,
-            Some(codegen_unit_name),
+            codegen_unit_name,
+            tcx.sess.invocation_temp.as_deref(),
         ) {
         // We get a path relative to the working directory from split_dwarf_path
         Some(tcx.sess.source_map().path_mapping().to_real_filename(f))
diff --git a/compiler/rustc_codegen_llvm/src/intrinsic.rs b/compiler/rustc_codegen_llvm/src/intrinsic.rs
index 67135fcc308..d1d6bcebd33 100644
--- a/compiler/rustc_codegen_llvm/src/intrinsic.rs
+++ b/compiler/rustc_codegen_llvm/src/intrinsic.rs
@@ -1421,7 +1421,7 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
         return Ok(bx.shuffle_vector(args[0].immediate(), args[1].immediate(), indices));
     }
 
-    if name == sym::simd_insert {
+    if name == sym::simd_insert || name == sym::simd_insert_dyn {
         require!(
             in_elem == arg_tys[2],
             InvalidMonomorphization::InsertedType {
@@ -1432,40 +1432,49 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
                 out_ty: arg_tys[2]
             }
         );
-        let idx = bx
-            .const_to_opt_u128(args[1].immediate(), false)
-            .expect("typeck should have ensure that this is a const");
-        if idx >= in_len.into() {
-            return_error!(InvalidMonomorphization::SimdIndexOutOfBounds {
-                span,
-                name,
-                arg_idx: 1,
-                total_len: in_len.into(),
-            });
-        }
-        return Ok(bx.insert_element(
-            args[0].immediate(),
-            args[2].immediate(),
-            bx.const_i32(idx as i32),
-        ));
+
+        let index_imm = if name == sym::simd_insert {
+            let idx = bx
+                .const_to_opt_u128(args[1].immediate(), false)
+                .expect("typeck should have ensure that this is a const");
+            if idx >= in_len.into() {
+                return_error!(InvalidMonomorphization::SimdIndexOutOfBounds {
+                    span,
+                    name,
+                    arg_idx: 1,
+                    total_len: in_len.into(),
+                });
+            }
+            bx.const_i32(idx as i32)
+        } else {
+            args[1].immediate()
+        };
+
+        return Ok(bx.insert_element(args[0].immediate(), args[2].immediate(), index_imm));
     }
-    if name == sym::simd_extract {
+    if name == sym::simd_extract || name == sym::simd_extract_dyn {
         require!(
             ret_ty == in_elem,
             InvalidMonomorphization::ReturnType { span, name, in_elem, in_ty, ret_ty }
         );
-        let idx = bx
-            .const_to_opt_u128(args[1].immediate(), false)
-            .expect("typeck should have ensure that this is a const");
-        if idx >= in_len.into() {
-            return_error!(InvalidMonomorphization::SimdIndexOutOfBounds {
-                span,
-                name,
-                arg_idx: 1,
-                total_len: in_len.into(),
-            });
-        }
-        return Ok(bx.extract_element(args[0].immediate(), bx.const_i32(idx as i32)));
+        let index_imm = if name == sym::simd_extract {
+            let idx = bx
+                .const_to_opt_u128(args[1].immediate(), false)
+                .expect("typeck should have ensure that this is a const");
+            if idx >= in_len.into() {
+                return_error!(InvalidMonomorphization::SimdIndexOutOfBounds {
+                    span,
+                    name,
+                    arg_idx: 1,
+                    total_len: in_len.into(),
+                });
+            }
+            bx.const_i32(idx as i32)
+        } else {
+            args[1].immediate()
+        };
+
+        return Ok(bx.extract_element(args[0].immediate(), index_imm));
     }
 
     if name == sym::simd_select {
diff --git a/compiler/rustc_codegen_ssa/src/back/link.rs b/compiler/rustc_codegen_ssa/src/back/link.rs
index 1d05c4eee4d..8de68925cab 100644
--- a/compiler/rustc_codegen_ssa/src/back/link.rs
+++ b/compiler/rustc_codegen_ssa/src/back/link.rs
@@ -112,8 +112,12 @@ pub fn link_binary(
                 codegen_results.crate_info.local_crate_name,
             );
             let crate_name = format!("{}", codegen_results.crate_info.local_crate_name);
-            let out_filename =
-                output.file_for_writing(outputs, OutputType::Exe, Some(crate_name.as_str()));
+            let out_filename = output.file_for_writing(
+                outputs,
+                OutputType::Exe,
+                &crate_name,
+                sess.invocation_temp.as_deref(),
+            );
             match crate_type {
                 CrateType::Rlib => {
                     let _timer = sess.timer("link_rlib");
diff --git a/compiler/rustc_codegen_ssa/src/back/write.rs b/compiler/rustc_codegen_ssa/src/back/write.rs
index e816e71379a..0fd4ed8475b 100644
--- a/compiler/rustc_codegen_ssa/src/back/write.rs
+++ b/compiler/rustc_codegen_ssa/src/back/write.rs
@@ -306,14 +306,18 @@ impl TargetMachineFactoryConfig {
             cgcx.output_filenames.split_dwarf_path(
                 cgcx.split_debuginfo,
                 cgcx.split_dwarf_kind,
-                Some(module_name),
+                module_name,
+                cgcx.invocation_temp.as_deref(),
             )
         } else {
             None
         };
 
-        let output_obj_file =
-            Some(cgcx.output_filenames.temp_path(OutputType::Object, Some(module_name)));
+        let output_obj_file = Some(cgcx.output_filenames.temp_path_for_cgu(
+            OutputType::Object,
+            module_name,
+            cgcx.invocation_temp.as_deref(),
+        ));
         TargetMachineFactoryConfig { split_dwarf_file, output_obj_file }
     }
 }
@@ -344,6 +348,7 @@ pub struct CodegenContext<B: WriteBackendMethods> {
     pub crate_types: Vec<CrateType>,
     pub each_linked_rlib_for_lto: Vec<(CrateNum, PathBuf)>,
     pub output_filenames: Arc<OutputFilenames>,
+    pub invocation_temp: Option<String>,
     pub regular_module_config: Arc<ModuleConfig>,
     pub metadata_module_config: Arc<ModuleConfig>,
     pub allocator_module_config: Arc<ModuleConfig>,
@@ -582,8 +587,11 @@ fn produce_final_output_artifacts(
         if let [module] = &compiled_modules.modules[..] {
             // 1) Only one codegen unit. In this case it's no difficulty
             //    to copy `foo.0.x` to `foo.x`.
-            let module_name = Some(&module.name[..]);
-            let path = crate_output.temp_path(output_type, module_name);
+            let path = crate_output.temp_path_for_cgu(
+                output_type,
+                &module.name,
+                sess.invocation_temp.as_deref(),
+            );
             let output = crate_output.path(output_type);
             if !output_type.is_text_output() && output.is_tty() {
                 sess.dcx()
@@ -596,22 +604,15 @@ fn produce_final_output_artifacts(
                 ensure_removed(sess.dcx(), &path);
             }
         } else {
-            let extension = crate_output
-                .temp_path(output_type, None)
-                .extension()
-                .unwrap()
-                .to_str()
-                .unwrap()
-                .to_owned();
-
             if crate_output.outputs.contains_explicit_name(&output_type) {
                 // 2) Multiple codegen units, with `--emit foo=some_name`. We have
                 //    no good solution for this case, so warn the user.
-                sess.dcx().emit_warn(errors::IgnoringEmitPath { extension });
+                sess.dcx()
+                    .emit_warn(errors::IgnoringEmitPath { extension: output_type.extension() });
             } else if crate_output.single_output_file.is_some() {
                 // 3) Multiple codegen units, with `-o some_name`. We have
                 //    no good solution for this case, so warn the user.
-                sess.dcx().emit_warn(errors::IgnoringOutput { extension });
+                sess.dcx().emit_warn(errors::IgnoringOutput { extension: output_type.extension() });
             } else {
                 // 4) Multiple codegen units, but no explicit name. We
                 //    just leave the `foo.0.x` files in place.
@@ -967,7 +968,12 @@ fn execute_copy_from_cache_work_item<B: ExtraBackendMethods>(
         module.source.saved_files.get("dwo").as_ref().and_then(|saved_dwarf_object_file| {
             let dwarf_obj_out = cgcx
                 .output_filenames
-                .split_dwarf_path(cgcx.split_debuginfo, cgcx.split_dwarf_kind, Some(&module.name))
+                .split_dwarf_path(
+                    cgcx.split_debuginfo,
+                    cgcx.split_dwarf_kind,
+                    &module.name,
+                    cgcx.invocation_temp.as_deref(),
+                )
                 .expect(
                     "saved dwarf object in work product but `split_dwarf_path` returned `None`",
                 );
@@ -977,7 +983,11 @@ fn execute_copy_from_cache_work_item<B: ExtraBackendMethods>(
     let mut load_from_incr_cache = |perform, output_type: OutputType| {
         if perform {
             let saved_file = module.source.saved_files.get(output_type.extension())?;
-            let output_path = cgcx.output_filenames.temp_path(output_type, Some(&module.name));
+            let output_path = cgcx.output_filenames.temp_path_for_cgu(
+                output_type,
+                &module.name,
+                cgcx.invocation_temp.as_deref(),
+            );
             load_from_incr_comp_dir(output_path, &saved_file)
         } else {
             None
@@ -1222,6 +1232,7 @@ fn start_executing_work<B: ExtraBackendMethods>(
         split_dwarf_kind: tcx.sess.opts.unstable_opts.split_dwarf_kind,
         parallel: backend.supports_parallel() && !sess.opts.unstable_opts.no_parallel_backend,
         pointer_size: tcx.data_layout.pointer_size,
+        invocation_temp: sess.invocation_temp.clone(),
     };
 
     // This is the "main loop" of parallel work happening for parallel codegen.
diff --git a/compiler/rustc_codegen_ssa/src/base.rs b/compiler/rustc_codegen_ssa/src/base.rs
index 1985b3b7170..12b7a487455 100644
--- a/compiler/rustc_codegen_ssa/src/base.rs
+++ b/compiler/rustc_codegen_ssa/src/base.rs
@@ -10,7 +10,7 @@ use rustc_ast::expand::allocator::{ALLOCATOR_METHODS, AllocatorKind, global_fn_n
 use rustc_attr_parsing::OptimizeAttr;
 use rustc_data_structures::fx::{FxHashMap, FxIndexSet};
 use rustc_data_structures::profiling::{get_resident_set_size, print_time_passes_entry};
-use rustc_data_structures::sync::par_map;
+use rustc_data_structures::sync::{IntoDynSyncSend, par_map};
 use rustc_data_structures::unord::UnordMap;
 use rustc_hir::def_id::{DefId, LOCAL_CRATE};
 use rustc_hir::lang_items::LangItem;
@@ -640,8 +640,11 @@ pub fn codegen_crate<B: ExtraBackendMethods>(
         let metadata_cgu_name =
             cgu_name_builder.build_cgu_name(LOCAL_CRATE, &["crate"], Some("metadata")).to_string();
         tcx.sess.time("write_compressed_metadata", || {
-            let file_name =
-                tcx.output_filenames(()).temp_path(OutputType::Metadata, Some(&metadata_cgu_name));
+            let file_name = tcx.output_filenames(()).temp_path_for_cgu(
+                OutputType::Metadata,
+                &metadata_cgu_name,
+                tcx.sess.invocation_temp.as_deref(),
+            );
             let data = create_compressed_metadata_file(
                 tcx.sess,
                 &metadata,
@@ -757,7 +760,7 @@ pub fn codegen_crate<B: ExtraBackendMethods>(
 
             let pre_compiled_cgus = par_map(cgus, |(i, _)| {
                 let module = backend.compile_codegen_unit(tcx, codegen_units[i].name());
-                (i, module)
+                (i, IntoDynSyncSend(module))
             });
 
             total_codegen_time += start_time.elapsed();
@@ -777,7 +780,7 @@ pub fn codegen_crate<B: ExtraBackendMethods>(
         match cgu_reuse {
             CguReuse::No => {
                 let (module, cost) = if let Some(cgu) = pre_compiled_cgus.remove(&i) {
-                    cgu
+                    cgu.0
                 } else {
                     let start_time = Instant::now();
                     let module = backend.compile_codegen_unit(tcx, cgu.name());
diff --git a/compiler/rustc_codegen_ssa/src/errors.rs b/compiler/rustc_codegen_ssa/src/errors.rs
index b33de8802d8..42cea5c86d4 100644
--- a/compiler/rustc_codegen_ssa/src/errors.rs
+++ b/compiler/rustc_codegen_ssa/src/errors.rs
@@ -277,13 +277,13 @@ pub struct BinaryOutputToTty {
 #[derive(Diagnostic)]
 #[diag(codegen_ssa_ignoring_emit_path)]
 pub struct IgnoringEmitPath {
-    pub extension: String,
+    pub extension: &'static str,
 }
 
 #[derive(Diagnostic)]
 #[diag(codegen_ssa_ignoring_output)]
 pub struct IgnoringOutput {
-    pub extension: String,
+    pub extension: &'static str,
 }
 
 #[derive(Diagnostic)]
diff --git a/compiler/rustc_codegen_ssa/src/lib.rs b/compiler/rustc_codegen_ssa/src/lib.rs
index 67217927a87..153935f2531 100644
--- a/compiler/rustc_codegen_ssa/src/lib.rs
+++ b/compiler/rustc_codegen_ssa/src/lib.rs
@@ -105,13 +105,19 @@ impl<M> ModuleCodegen<M> {
         emit_asm: bool,
         emit_ir: bool,
         outputs: &OutputFilenames,
+        invocation_temp: Option<&str>,
     ) -> CompiledModule {
-        let object = emit_obj.then(|| outputs.temp_path(OutputType::Object, Some(&self.name)));
-        let dwarf_object = emit_dwarf_obj.then(|| outputs.temp_path_dwo(Some(&self.name)));
-        let bytecode = emit_bc.then(|| outputs.temp_path(OutputType::Bitcode, Some(&self.name)));
-        let assembly = emit_asm.then(|| outputs.temp_path(OutputType::Assembly, Some(&self.name)));
-        let llvm_ir =
-            emit_ir.then(|| outputs.temp_path(OutputType::LlvmAssembly, Some(&self.name)));
+        let object = emit_obj
+            .then(|| outputs.temp_path_for_cgu(OutputType::Object, &self.name, invocation_temp));
+        let dwarf_object =
+            emit_dwarf_obj.then(|| outputs.temp_path_dwo_for_cgu(&self.name, invocation_temp));
+        let bytecode = emit_bc
+            .then(|| outputs.temp_path_for_cgu(OutputType::Bitcode, &self.name, invocation_temp));
+        let assembly = emit_asm
+            .then(|| outputs.temp_path_for_cgu(OutputType::Assembly, &self.name, invocation_temp));
+        let llvm_ir = emit_ir.then(|| {
+            outputs.temp_path_for_cgu(OutputType::LlvmAssembly, &self.name, invocation_temp)
+        });
 
         CompiledModule {
             name: self.name.clone(),
diff --git a/compiler/rustc_codegen_ssa/src/mir/mod.rs b/compiler/rustc_codegen_ssa/src/mir/mod.rs
index 0758e5d0456..6a37889217a 100644
--- a/compiler/rustc_codegen_ssa/src/mir/mod.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/mod.rs
@@ -3,7 +3,7 @@ use std::iter;
 use rustc_index::IndexVec;
 use rustc_index::bit_set::DenseBitSet;
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
-use rustc_middle::mir::{Local, UnwindTerminateReason, traversal};
+use rustc_middle::mir::{Body, Local, UnwindTerminateReason, traversal};
 use rustc_middle::ty::layout::{FnAbiOf, HasTyCtxt, HasTypingEnv, TyAndLayout};
 use rustc_middle::ty::{self, Instance, Ty, TyCtxt, TypeFoldable, TypeVisitableExt};
 use rustc_middle::{bug, mir, span_bug};
@@ -170,19 +170,29 @@ pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
 ) {
     assert!(!instance.args.has_infer());
 
+    let tcx = cx.tcx();
     let llfn = cx.get_fn(instance);
 
-    let mir = cx.tcx().instance_mir(instance.def);
+    let mut mir = tcx.instance_mir(instance.def);
 
     let fn_abi = cx.fn_abi_of_instance(instance, ty::List::empty());
     debug!("fn_abi: {:?}", fn_abi);
 
-    if cx.tcx().codegen_fn_attrs(instance.def_id()).flags.contains(CodegenFnAttrFlags::NAKED) {
+    if tcx.codegen_fn_attrs(instance.def_id()).flags.contains(CodegenFnAttrFlags::NAKED) {
         crate::mir::naked_asm::codegen_naked_asm::<Bx>(cx, &mir, instance);
         return;
     }
 
-    let debug_context = cx.create_function_debug_context(instance, fn_abi, llfn, mir);
+    if tcx.features().ergonomic_clones() {
+        let monomorphized_mir = instance.instantiate_mir_and_normalize_erasing_regions(
+            tcx,
+            ty::TypingEnv::fully_monomorphized(),
+            ty::EarlyBinder::bind(mir.clone()),
+        );
+        mir = tcx.arena.alloc(optimize_use_clone::<Bx>(cx, monomorphized_mir));
+    }
+
+    let debug_context = cx.create_function_debug_context(instance, fn_abi, llfn, &mir);
 
     let start_llbb = Bx::append_block(cx, llfn, "start");
     let mut start_bx = Bx::build(cx, start_llbb);
@@ -194,7 +204,7 @@ pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
     }
 
     let cleanup_kinds =
-        base::wants_new_eh_instructions(cx.tcx().sess).then(|| analyze::cleanup_kinds(mir));
+        base::wants_new_eh_instructions(tcx.sess).then(|| analyze::cleanup_kinds(&mir));
 
     let cached_llbbs: IndexVec<mir::BasicBlock, CachedLlbb<Bx::BasicBlock>> =
         mir.basic_blocks
@@ -217,7 +227,7 @@ pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
         cleanup_kinds,
         landing_pads: IndexVec::from_elem(None, &mir.basic_blocks),
         funclets: IndexVec::from_fn_n(|_| None, mir.basic_blocks.len()),
-        cold_blocks: find_cold_blocks(cx.tcx(), mir),
+        cold_blocks: find_cold_blocks(tcx, mir),
         locals: locals::Locals::empty(),
         debug_context,
         per_local_var_debug_info: None,
@@ -233,7 +243,7 @@ pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
         fx.compute_per_local_var_debug_info(&mut start_bx).unzip();
     fx.per_local_var_debug_info = per_local_var_debug_info;
 
-    let traversal_order = traversal::mono_reachable_reverse_postorder(mir, cx.tcx(), instance);
+    let traversal_order = traversal::mono_reachable_reverse_postorder(mir, tcx, instance);
     let memory_locals = analyze::non_ssa_locals(&fx, &traversal_order);
 
     // Allocate variable and temp allocas
@@ -310,6 +320,61 @@ pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
     }
 }
 
+// FIXME: Move this function to mir::transform when post-mono MIR passes land.
+fn optimize_use_clone<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
+    cx: &'a Bx::CodegenCx,
+    mut mir: Body<'tcx>,
+) -> Body<'tcx> {
+    let tcx = cx.tcx();
+
+    if tcx.features().ergonomic_clones() {
+        for bb in mir.basic_blocks.as_mut() {
+            let mir::TerminatorKind::Call {
+                args,
+                destination,
+                target,
+                call_source: mir::CallSource::Use,
+                ..
+            } = &bb.terminator().kind
+            else {
+                continue;
+            };
+
+            // CallSource::Use calls always use 1 argument.
+            assert_eq!(args.len(), 1);
+            let arg = &args[0];
+
+            // These types are easily available from locals, so check that before
+            // doing DefId lookups to figure out what we're actually calling.
+            let arg_ty = arg.node.ty(&mir.local_decls, tcx);
+
+            let ty::Ref(_region, inner_ty, mir::Mutability::Not) = *arg_ty.kind() else { continue };
+
+            if !tcx.type_is_copy_modulo_regions(cx.typing_env(), inner_ty) {
+                continue;
+            }
+
+            let Some(arg_place) = arg.node.place() else { continue };
+
+            let destination_block = target.unwrap();
+
+            bb.statements.push(mir::Statement {
+                source_info: bb.terminator().source_info,
+                kind: mir::StatementKind::Assign(Box::new((
+                    *destination,
+                    mir::Rvalue::Use(mir::Operand::Copy(
+                        arg_place.project_deeper(&[mir::ProjectionElem::Deref], tcx),
+                    )),
+                ))),
+            });
+
+            bb.terminator_mut().kind = mir::TerminatorKind::Goto { target: destination_block };
+        }
+    }
+
+    mir
+}
+
 /// Produces, for each argument, a `Value` pointing at the
 /// argument's value. As arguments are places, these are always
 /// indirect.
diff --git a/compiler/rustc_codegen_ssa/src/mir/operand.rs b/compiler/rustc_codegen_ssa/src/mir/operand.rs
index 7e355b6406a..eade9e52de9 100644
--- a/compiler/rustc_codegen_ssa/src/mir/operand.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/operand.rs
@@ -9,6 +9,7 @@ use rustc_middle::mir::{self, ConstValue};
 use rustc_middle::ty::Ty;
 use rustc_middle::ty::layout::{LayoutOf, TyAndLayout};
 use rustc_middle::{bug, span_bug};
+use rustc_session::config::OptLevel;
 use tracing::{debug, instrument};
 
 use super::place::{PlaceRef, PlaceValue};
@@ -496,6 +497,18 @@ impl<'a, 'tcx, V: CodegenObject> OperandRef<'tcx, V> {
                     _ => (tag_imm, bx.cx().immediate_backend_type(tag_op.layout)),
                 };
 
+                // Layout ensures that we only get here for cases where the discriminant
+                // value and the variant index match, since that's all `Niche` can encode.
+                // But for emphasis and debugging, let's double-check one anyway.
+                debug_assert_eq!(
+                    self.layout
+                        .ty
+                        .discriminant_for_variant(bx.tcx(), untagged_variant)
+                        .unwrap()
+                        .val,
+                    u128::from(untagged_variant.as_u32()),
+                );
+
                 let relative_max = niche_variants.end().as_u32() - niche_variants.start().as_u32();
 
                 // We have a subrange `niche_start..=niche_end` inside `range`.
@@ -537,6 +550,21 @@ impl<'a, 'tcx, V: CodegenObject> OperandRef<'tcx, V> {
                         relative_discr,
                         bx.cx().const_uint(tag_llty, relative_max as u64),
                     );
+
+                    // Thanks to parameter attributes and load metadata, LLVM already knows
+                    // the general valid range of the tag. It's possible, though, for there
+                    // to be an impossible value *in the middle*, which those ranges don't
+                    // communicate, so it's worth an `assume` to let the optimizer know.
+                    if niche_variants.contains(&untagged_variant)
+                        && bx.cx().sess().opts.optimize != OptLevel::No
+                    {
+                        let impossible =
+                            u64::from(untagged_variant.as_u32() - niche_variants.start().as_u32());
+                        let impossible = bx.cx().const_uint(tag_llty, impossible);
+                        let ne = bx.icmp(IntPredicate::IntNE, relative_discr, impossible);
+                        bx.assume(ne);
+                    }
+
                     (is_niche, cast_tag, niche_variants.start().as_u32() as u128)
                 };
 
@@ -553,7 +581,9 @@ impl<'a, 'tcx, V: CodegenObject> OperandRef<'tcx, V> {
                 );
 
                 // In principle we could insert assumes on the possible range of `discr`, but
-                // currently in LLVM this seems to be a pessimization.
+                // currently in LLVM this isn't worth it because the original `tag` will
+                // have either a `range` parameter attribute or `!range` metadata,
+                // or come from a `transmute` that already `assume`d it.
 
                 discr
             }
diff --git a/compiler/rustc_data_structures/Cargo.toml b/compiler/rustc_data_structures/Cargo.toml
index fcaf2750507..f48c73b13b9 100644
--- a/compiler/rustc_data_structures/Cargo.toml
+++ b/compiler/rustc_data_structures/Cargo.toml
@@ -14,7 +14,7 @@ indexmap = "2.4.0"
 jobserver_crate = { version = "0.1.28", package = "jobserver" }
 measureme = "12.0.1"
 rustc-hash = "2.0.0"
-rustc-rayon = { version = "0.5.1", features = ["indexmap"] }
+rustc-rayon-core = { version = "0.5.0" }
 rustc-stable-hash = { version = "0.1.0", features = ["nightly"] }
 rustc_arena = { path = "../rustc_arena" }
 rustc_graphviz = { path = "../rustc_graphviz" }
diff --git a/compiler/rustc_data_structures/src/marker.rs b/compiler/rustc_data_structures/src/marker.rs
index 64c64bfa3c2..744ae9b6fe2 100644
--- a/compiler/rustc_data_structures/src/marker.rs
+++ b/compiler/rustc_data_structures/src/marker.rs
@@ -180,6 +180,12 @@ impl<T> FromDyn<T> {
     }
 
     #[inline(always)]
+    pub fn derive<O>(&self, val: O) -> FromDyn<O> {
+        // We already did the check for `sync::is_dyn_thread_safe()` when creating `Self`
+        FromDyn(val)
+    }
+
+    #[inline(always)]
     pub fn into_inner(self) -> T {
         self.0
     }
@@ -200,6 +206,13 @@ impl<T> std::ops::Deref for FromDyn<T> {
     }
 }
 
+impl<T> std::ops::DerefMut for FromDyn<T> {
+    #[inline(always)]
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.0
+    }
+}
+
 // A wrapper to convert a struct that is already a `Send` or `Sync` into
 // an instance of `DynSend` and `DynSync`, since the compiler cannot infer
 // it automatically in some cases. (e.g. Box<dyn Send / Sync>)
diff --git a/compiler/rustc_data_structures/src/obligation_forest/mod.rs b/compiler/rustc_data_structures/src/obligation_forest/mod.rs
index f63b201742d..2c62034c6e8 100644
--- a/compiler/rustc_data_structures/src/obligation_forest/mod.rs
+++ b/compiler/rustc_data_structures/src/obligation_forest/mod.rs
@@ -315,7 +315,7 @@ mod helper {
     use super::*;
     pub(super) type ObligationTreeIdGenerator = impl Iterator<Item = ObligationTreeId>;
     impl<O: ForestObligation> ObligationForest<O> {
-        #[cfg_attr(not(bootstrap), define_opaque(ObligationTreeIdGenerator))]
+        #[define_opaque(ObligationTreeIdGenerator)]
         pub fn new() -> ObligationForest<O> {
             ObligationForest {
                 nodes: vec![],
diff --git a/compiler/rustc_data_structures/src/sync/freeze.rs b/compiler/rustc_data_structures/src/sync/freeze.rs
index 9720b22ea7d..6338afb92c3 100644
--- a/compiler/rustc_data_structures/src/sync/freeze.rs
+++ b/compiler/rustc_data_structures/src/sync/freeze.rs
@@ -88,7 +88,7 @@ impl<T> FreezeLock<T> {
     #[inline]
     #[track_caller]
     pub fn write(&self) -> FreezeWriteGuard<'_, T> {
-        self.try_write().expect("still mutable")
+        self.try_write().expect("data should not be frozen if we're still attempting to mutate it")
     }
 
     #[inline]
diff --git a/compiler/rustc_data_structures/src/sync/parallel.rs b/compiler/rustc_data_structures/src/sync/parallel.rs
index 8ef8a3f3585..ba3c85ef5b1 100644
--- a/compiler/rustc_data_structures/src/sync/parallel.rs
+++ b/compiler/rustc_data_structures/src/sync/parallel.rs
@@ -7,7 +7,6 @@ use std::any::Any;
 use std::panic::{AssertUnwindSafe, catch_unwind, resume_unwind};
 
 use parking_lot::Mutex;
-use rayon::iter::{FromParallelIterator, IntoParallelIterator, ParallelIterator};
 
 use crate::FatalErrorMarker;
 use crate::sync::{DynSend, DynSync, FromDyn, IntoDynSyncSend, mode};
@@ -97,11 +96,11 @@ macro_rules! parallel {
 // This function only works when `mode::is_dyn_thread_safe()`.
 pub fn scope<'scope, OP, R>(op: OP) -> R
 where
-    OP: FnOnce(&rayon::Scope<'scope>) -> R + DynSend,
+    OP: FnOnce(&rayon_core::Scope<'scope>) -> R + DynSend,
     R: DynSend,
 {
     let op = FromDyn::from(op);
-    rayon::scope(|s| FromDyn::from(op.into_inner()(s))).into_inner()
+    rayon_core::scope(|s| FromDyn::from(op.into_inner()(s))).into_inner()
 }
 
 #[inline]
@@ -114,7 +113,7 @@ where
         let oper_a = FromDyn::from(oper_a);
         let oper_b = FromDyn::from(oper_b);
         let (a, b) = parallel_guard(|guard| {
-            rayon::join(
+            rayon_core::join(
                 move || guard.run(move || FromDyn::from(oper_a.into_inner()())),
                 move || guard.run(move || FromDyn::from(oper_b.into_inner()())),
             )
@@ -125,56 +124,103 @@ where
     }
 }
 
-pub fn par_for_each_in<I, T: IntoIterator<Item = I> + IntoParallelIterator<Item = I>>(
+fn par_slice<I: DynSend>(
+    items: &mut [I],
+    guard: &ParallelGuard,
+    for_each: impl Fn(&mut I) + DynSync + DynSend,
+) {
+    struct State<'a, F> {
+        for_each: FromDyn<F>,
+        guard: &'a ParallelGuard,
+        group: usize,
+    }
+
+    fn par_rec<I: DynSend, F: Fn(&mut I) + DynSync + DynSend>(
+        items: &mut [I],
+        state: &State<'_, F>,
+    ) {
+        if items.len() <= state.group {
+            for item in items {
+                state.guard.run(|| (state.for_each)(item));
+            }
+        } else {
+            let (left, right) = items.split_at_mut(items.len() / 2);
+            let mut left = state.for_each.derive(left);
+            let mut right = state.for_each.derive(right);
+            rayon_core::join(move || par_rec(*left, state), move || par_rec(*right, state));
+        }
+    }
+
+    let state = State {
+        for_each: FromDyn::from(for_each),
+        guard,
+        group: std::cmp::max(items.len() / 128, 1),
+    };
+    par_rec(items, &state)
+}
+
+pub fn par_for_each_in<I: DynSend, T: IntoIterator<Item = I>>(
     t: T,
-    for_each: impl Fn(I) + DynSync + DynSend,
+    for_each: impl Fn(&I) + DynSync + DynSend,
 ) {
     parallel_guard(|guard| {
         if mode::is_dyn_thread_safe() {
-            let for_each = FromDyn::from(for_each);
-            t.into_par_iter().for_each(|i| {
-                guard.run(|| for_each(i));
-            });
+            let mut items: Vec<_> = t.into_iter().collect();
+            par_slice(&mut items, guard, |i| for_each(&*i))
         } else {
             t.into_iter().for_each(|i| {
-                guard.run(|| for_each(i));
+                guard.run(|| for_each(&i));
             });
         }
     });
 }
 
-pub fn try_par_for_each_in<
-    T: IntoIterator + IntoParallelIterator<Item = <T as IntoIterator>::Item>,
-    E: Send,
->(
+/// This runs `for_each` in parallel for each iterator item. If one or more of the
+/// `for_each` calls returns `Err`, the function will also return `Err`. The error returned
+/// will be non-deterministic, but this is expected to be used with `ErrorGuaranteed` which
+/// are all equivalent.
+pub fn try_par_for_each_in<T: IntoIterator, E: DynSend>(
     t: T,
-    for_each: impl Fn(<T as IntoIterator>::Item) -> Result<(), E> + DynSync + DynSend,
-) -> Result<(), E> {
+    for_each: impl Fn(&<T as IntoIterator>::Item) -> Result<(), E> + DynSync + DynSend,
+) -> Result<(), E>
+where
+    <T as IntoIterator>::Item: DynSend,
+{
     parallel_guard(|guard| {
         if mode::is_dyn_thread_safe() {
-            let for_each = FromDyn::from(for_each);
-            t.into_par_iter()
-                .filter_map(|i| guard.run(|| for_each(i)))
-                .reduce(|| Ok(()), Result::and)
+            let mut items: Vec<_> = t.into_iter().collect();
+
+            let error = Mutex::new(None);
+
+            par_slice(&mut items, guard, |i| {
+                if let Err(err) = for_each(&*i) {
+                    *error.lock() = Some(err);
+                }
+            });
+
+            if let Some(err) = error.into_inner() { Err(err) } else { Ok(()) }
         } else {
-            t.into_iter().filter_map(|i| guard.run(|| for_each(i))).fold(Ok(()), Result::and)
+            t.into_iter().filter_map(|i| guard.run(|| for_each(&i))).fold(Ok(()), Result::and)
         }
     })
 }
 
-pub fn par_map<
-    I,
-    T: IntoIterator<Item = I> + IntoParallelIterator<Item = I>,
-    R: std::marker::Send,
-    C: FromIterator<R> + FromParallelIterator<R>,
->(
+pub fn par_map<I: DynSend, T: IntoIterator<Item = I>, R: DynSend, C: FromIterator<R>>(
     t: T,
     map: impl Fn(I) -> R + DynSync + DynSend,
 ) -> C {
     parallel_guard(|guard| {
         if mode::is_dyn_thread_safe() {
             let map = FromDyn::from(map);
-            t.into_par_iter().filter_map(|i| guard.run(|| map(i))).collect()
+
+            let mut items: Vec<(Option<I>, Option<R>)> =
+                t.into_iter().map(|i| (Some(i), None)).collect();
+
+            par_slice(&mut items, guard, |i| {
+                i.1 = Some(map(i.0.take().unwrap()));
+            });
+
+            items.into_iter().filter_map(|i| i.1).collect()
         } else {
             t.into_iter().filter_map(|i| guard.run(|| map(i))).collect()
         }
diff --git a/compiler/rustc_data_structures/src/unord.rs b/compiler/rustc_data_structures/src/unord.rs
index baa66cd7c85..3d44fb1fd48 100644
--- a/compiler/rustc_data_structures/src/unord.rs
+++ b/compiler/rustc_data_structures/src/unord.rs
@@ -109,6 +109,16 @@ impl<T, I: Iterator<Item = T>> UnordItems<T, I> {
     pub fn collect<C: From<UnordItems<T, I>>>(self) -> C {
         self.into()
     }
+
+    /// If the iterator has only one element, returns it, otherwise returns `None`.
+    #[track_caller]
+    pub fn get_only(mut self) -> Option<T> {
+        let item = self.0.next();
+        if self.0.next().is_some() {
+            return None;
+        }
+        item
+    }
 }
 
 impl<T> UnordItems<T, std::iter::Empty<T>> {
diff --git a/compiler/rustc_driver_impl/Cargo.toml b/compiler/rustc_driver_impl/Cargo.toml
index de643355f5f..c823d11126e 100644
--- a/compiler/rustc_driver_impl/Cargo.toml
+++ b/compiler/rustc_driver_impl/Cargo.toml
@@ -4,6 +4,7 @@ version = "0.0.0"
 edition = "2024"
 
 [dependencies]
+jiff = { version = "0.2.5", default-features = false, features = ["std"] }
 # tidy-alphabetical-start
 rustc_abi = { path = "../rustc_abi" }
 rustc_ast = { path = "../rustc_ast" }
@@ -50,7 +51,6 @@ rustc_trait_selection = { path = "../rustc_trait_selection" }
 rustc_ty_utils = { path = "../rustc_ty_utils" }
 serde_json = "1.0.59"
 shlex = "1.0"
-time = { version = "0.3.36", default-features = false, features = ["alloc", "formatting", "macros"] }
 tracing = { version = "0.1.35" }
 # tidy-alphabetical-end
 
diff --git a/compiler/rustc_driver_impl/src/lib.rs b/compiler/rustc_driver_impl/src/lib.rs
index 595ac1edd28..11d24dcf91d 100644
--- a/compiler/rustc_driver_impl/src/lib.rs
+++ b/compiler/rustc_driver_impl/src/lib.rs
@@ -30,7 +30,7 @@ use std::path::{Path, PathBuf};
 use std::process::{self, Command, Stdio};
 use std::sync::OnceLock;
 use std::sync::atomic::{AtomicBool, Ordering};
-use std::time::{Instant, SystemTime};
+use std::time::Instant;
 use std::{env, str};
 
 use rustc_ast as ast;
@@ -66,8 +66,6 @@ use rustc_span::FileName;
 use rustc_span::def_id::LOCAL_CRATE;
 use rustc_target::json::ToJson;
 use rustc_target::spec::{Target, TargetTuple};
-use time::OffsetDateTime;
-use time::macros::format_description;
 use tracing::trace;
 
 #[allow(unused_macros)]
@@ -264,6 +262,7 @@ pub fn run_compiler(at_args: &[String], callbacks: &mut (dyn Callbacks + Send))
         hash_untracked_state: None,
         register_lints: None,
         override_queries: None,
+        extra_symbols: Vec::new(),
         make_codegen_backend: None,
         registry: diagnostics_registry(),
         using_internal_features: &USING_INTERNAL_FEATURES,
@@ -348,10 +347,6 @@ pub fn run_compiler(at_args: &[String], callbacks: &mut (dyn Callbacks + Send))
             // Make sure name resolution and macro expansion is run.
             let _ = tcx.resolver_for_lowering();
 
-            if let Some(metrics_dir) = &sess.opts.unstable_opts.metrics_dir {
-                dump_feature_usage_metrics(tcx, metrics_dir);
-            }
-
             if callbacks.after_expansion(compiler, tcx) == Compilation::Stop {
                 return early_exit();
             }
@@ -370,6 +365,10 @@ pub fn run_compiler(at_args: &[String], callbacks: &mut (dyn Callbacks + Send))
 
             tcx.ensure_ok().analysis(());
 
+            if let Some(metrics_dir) = &sess.opts.unstable_opts.metrics_dir {
+                dump_feature_usage_metrics(tcx, metrics_dir);
+            }
+
             if callbacks.after_analysis(compiler, tcx) == Compilation::Stop {
                 return early_exit();
             }
@@ -1300,13 +1299,8 @@ fn ice_path_with_config(config: Option<&UnstableOptions>) -> &'static Option<Pat
                 .or_else(|| std::env::current_dir().ok())
                 .unwrap_or_default(),
         };
-        let now: OffsetDateTime = SystemTime::now().into();
-        let file_now = now
-            .format(
-                // Don't use a standard datetime format because Windows doesn't support `:` in paths
-                &format_description!("[year]-[month]-[day]T[hour]_[minute]_[second]"),
-            )
-            .unwrap_or_default();
+        // Don't use a standard datetime format because Windows doesn't support `:` in paths
+        let file_now = jiff::Zoned::now().strftime("%Y-%m-%dT%H_%M_%S");
         let pid = std::process::id();
         path.push(format!("rustc-ice-{file_now}-{pid}.txt"));
         Some(path)
diff --git a/compiler/rustc_error_codes/src/error_codes/E0622.md b/compiler/rustc_error_codes/src/error_codes/E0622.md
index e6ff949d3e9..9b8131a061e 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0622.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0622.md
@@ -1,8 +1,10 @@
+#### Note: this error code is no longer emitted by the compiler.
+
 An intrinsic was declared without being a function.
 
 Erroneous code example:
 
-```compile_fail,E0622
+```no_run
 #![feature(intrinsics)]
 #![allow(internal_features)]
 
diff --git a/compiler/rustc_error_codes/src/lib.rs b/compiler/rustc_error_codes/src/lib.rs
index dfeef5a957d..2488d870899 100644
--- a/compiler/rustc_error_codes/src/lib.rs
+++ b/compiler/rustc_error_codes/src/lib.rs
@@ -397,7 +397,7 @@ E0618: 0618,
 E0619: 0619,
 E0620: 0620,
 E0621: 0621,
-E0622: 0622,
+E0622: 0622, // REMOVED: rustc-intrinsic ABI was removed
 E0623: 0623,
 E0624: 0624,
 E0625: 0625,
diff --git a/compiler/rustc_error_messages/src/lib.rs b/compiler/rustc_error_messages/src/lib.rs
index 39e78ae8841..3c6df147b1b 100644
--- a/compiler/rustc_error_messages/src/lib.rs
+++ b/compiler/rustc_error_messages/src/lib.rs
@@ -208,7 +208,7 @@ pub type LazyFallbackBundle = Arc<LazyLock<FluentBundle, impl FnOnce() -> Fluent
 
 /// Return the default `FluentBundle` with standard "en-US" diagnostic messages.
 #[instrument(level = "trace", skip(resources))]
-#[cfg_attr(not(bootstrap), define_opaque(LazyFallbackBundle))]
+#[define_opaque(LazyFallbackBundle)]
 pub fn fallback_fluent_bundle(
     resources: Vec<&'static str>,
     with_directionality_markers: bool,
diff --git a/compiler/rustc_errors/src/diagnostic.rs b/compiler/rustc_errors/src/diagnostic.rs
index 794502d7aae..bd13c413a4d 100644
--- a/compiler/rustc_errors/src/diagnostic.rs
+++ b/compiler/rustc_errors/src/diagnostic.rs
@@ -647,9 +647,9 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
     #[rustc_lint_diagnostics]
     pub fn note_expected_found(
         &mut self,
-        expected_label: &dyn fmt::Display,
+        expected_label: &str,
         expected: DiagStyledString,
-        found_label: &dyn fmt::Display,
+        found_label: &str,
         found: DiagStyledString,
     ) -> &mut Self {
         self.note_expected_found_extra(
@@ -665,9 +665,9 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
     #[rustc_lint_diagnostics]
     pub fn note_expected_found_extra(
         &mut self,
-        expected_label: &dyn fmt::Display,
+        expected_label: &str,
         expected: DiagStyledString,
-        found_label: &dyn fmt::Display,
+        found_label: &str,
         found: DiagStyledString,
         expected_extra: DiagStyledString,
         found_extra: DiagStyledString,
diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index f5f7618285e..75bb0e8e7b4 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -589,7 +589,8 @@ struct DiagCtxtInner {
     /// add more information). All stashed diagnostics must be emitted with
     /// `emit_stashed_diagnostics` by the time the `DiagCtxtInner` is dropped,
     /// otherwise an assertion failure will occur.
-    stashed_diagnostics: FxIndexMap<(Span, StashKey), (DiagInner, Option<ErrorGuaranteed>)>,
+    stashed_diagnostics:
+        FxIndexMap<StashKey, FxIndexMap<Span, (DiagInner, Option<ErrorGuaranteed>)>>,
 
     future_breakage_diagnostics: Vec<DiagInner>,
 
@@ -912,8 +913,12 @@ impl<'a> DiagCtxtHandle<'a> {
         // FIXME(Centril, #69537): Consider reintroducing panic on overwriting a stashed diagnostic
         // if/when we have a more robust macro-friendly replacement for `(span, key)` as a key.
         // See the PR for a discussion.
-        let key = (span.with_parent(None), key);
-        self.inner.borrow_mut().stashed_diagnostics.insert(key, (diag, guar));
+        self.inner
+            .borrow_mut()
+            .stashed_diagnostics
+            .entry(key)
+            .or_default()
+            .insert(span.with_parent(None), (diag, guar));
 
         guar
     }
@@ -922,9 +927,10 @@ impl<'a> DiagCtxtHandle<'a> {
     /// and [`StashKey`] as the key. Panics if the found diagnostic is an
     /// error.
     pub fn steal_non_err(self, span: Span, key: StashKey) -> Option<Diag<'a, ()>> {
-        let key = (span.with_parent(None), key);
         // FIXME(#120456) - is `swap_remove` correct?
-        let (diag, guar) = self.inner.borrow_mut().stashed_diagnostics.swap_remove(&key)?;
+        let (diag, guar) = self.inner.borrow_mut().stashed_diagnostics.get_mut(&key).and_then(
+            |stashed_diagnostics| stashed_diagnostics.swap_remove(&span.with_parent(None)),
+        )?;
         assert!(!diag.is_error());
         assert!(guar.is_none());
         Some(Diag::new_diagnostic(self, diag))
@@ -943,9 +949,10 @@ impl<'a> DiagCtxtHandle<'a> {
     where
         F: FnMut(&mut Diag<'_>),
     {
-        let key = (span.with_parent(None), key);
         // FIXME(#120456) - is `swap_remove` correct?
-        let err = self.inner.borrow_mut().stashed_diagnostics.swap_remove(&key);
+        let err = self.inner.borrow_mut().stashed_diagnostics.get_mut(&key).and_then(
+            |stashed_diagnostics| stashed_diagnostics.swap_remove(&span.with_parent(None)),
+        );
         err.map(|(err, guar)| {
             // The use of `::<ErrorGuaranteed>` is safe because level is `Level::Error`.
             assert_eq!(err.level, Error);
@@ -966,9 +973,10 @@ impl<'a> DiagCtxtHandle<'a> {
         key: StashKey,
         new_err: Diag<'_>,
     ) -> ErrorGuaranteed {
-        let key = (span.with_parent(None), key);
         // FIXME(#120456) - is `swap_remove` correct?
-        let old_err = self.inner.borrow_mut().stashed_diagnostics.swap_remove(&key);
+        let old_err = self.inner.borrow_mut().stashed_diagnostics.get_mut(&key).and_then(
+            |stashed_diagnostics| stashed_diagnostics.swap_remove(&span.with_parent(None)),
+        );
         match old_err {
             Some((old_err, guar)) => {
                 assert_eq!(old_err.level, Error);
@@ -983,7 +991,14 @@ impl<'a> DiagCtxtHandle<'a> {
     }
 
     pub fn has_stashed_diagnostic(&self, span: Span, key: StashKey) -> bool {
-        self.inner.borrow().stashed_diagnostics.get(&(span.with_parent(None), key)).is_some()
+        let inner = self.inner.borrow();
+        if let Some(stashed_diagnostics) = inner.stashed_diagnostics.get(&key)
+            && !stashed_diagnostics.is_empty()
+        {
+            stashed_diagnostics.contains_key(&span.with_parent(None))
+        } else {
+            false
+        }
     }
 
     /// Emit all stashed diagnostics.
@@ -997,7 +1012,11 @@ impl<'a> DiagCtxtHandle<'a> {
         let inner = self.inner.borrow();
         inner.err_guars.len()
             + inner.lint_err_guars.len()
-            + inner.stashed_diagnostics.values().filter(|(_diag, guar)| guar.is_some()).count()
+            + inner
+                .stashed_diagnostics
+                .values()
+                .map(|a| a.values().filter(|(_, guar)| guar.is_some()).count())
+                .sum::<usize>()
     }
 
     /// This excludes lint errors and delayed bugs. Unless absolutely
@@ -1486,16 +1505,18 @@ impl DiagCtxtInner {
     fn emit_stashed_diagnostics(&mut self) -> Option<ErrorGuaranteed> {
         let mut guar = None;
         let has_errors = !self.err_guars.is_empty();
-        for (_, (diag, _guar)) in std::mem::take(&mut self.stashed_diagnostics).into_iter() {
-            if !diag.is_error() {
-                // Unless they're forced, don't flush stashed warnings when
-                // there are errors, to avoid causing warning overload. The
-                // stash would've been stolen already if it were important.
-                if !diag.is_force_warn() && has_errors {
-                    continue;
+        for (_, stashed_diagnostics) in std::mem::take(&mut self.stashed_diagnostics).into_iter() {
+            for (_, (diag, _guar)) in stashed_diagnostics {
+                if !diag.is_error() {
+                    // Unless they're forced, don't flush stashed warnings when
+                    // there are errors, to avoid causing warning overload. The
+                    // stash would've been stolen already if it were important.
+                    if !diag.is_force_warn() && has_errors {
+                        continue;
+                    }
                 }
+                guar = guar.or(self.emit_diagnostic(diag, None));
             }
-            guar = guar.or(self.emit_diagnostic(diag, None));
         }
         guar
     }
@@ -1688,6 +1709,7 @@ impl DiagCtxtInner {
             if let Some((_diag, guar)) = self
                 .stashed_diagnostics
                 .values()
+                .flat_map(|stashed_diagnostics| stashed_diagnostics.values())
                 .find(|(diag, guar)| guar.is_some() && diag.is_lint.is_none())
             {
                 *guar
@@ -1700,13 +1722,9 @@ impl DiagCtxtInner {
     fn has_errors(&self) -> Option<ErrorGuaranteed> {
         self.err_guars.get(0).copied().or_else(|| self.lint_err_guars.get(0).copied()).or_else(
             || {
-                if let Some((_diag, guar)) =
-                    self.stashed_diagnostics.values().find(|(_diag, guar)| guar.is_some())
-                {
-                    *guar
-                } else {
-                    None
-                }
+                self.stashed_diagnostics.values().find_map(|stashed_diagnostics| {
+                    stashed_diagnostics.values().find_map(|(_, guar)| *guar)
+                })
             },
         )
     }
diff --git a/compiler/rustc_expand/src/base.rs b/compiler/rustc_expand/src/base.rs
index d14e476ba32..49f6d58172f 100644
--- a/compiler/rustc_expand/src/base.rs
+++ b/compiler/rustc_expand/src/base.rs
@@ -1102,7 +1102,7 @@ pub trait ResolverExpand {
     /// HIR proc macros items back to their harness items.
     fn declare_proc_macro(&mut self, id: NodeId);
 
-    fn append_stripped_cfg_item(&mut self, parent_node: NodeId, name: Ident, cfg: ast::MetaItem);
+    fn append_stripped_cfg_item(&mut self, parent_node: NodeId, ident: Ident, cfg: ast::MetaItem);
 
     /// Tools registered with `#![register_tool]` and used by tool attributes and lints.
     fn registered_tools(&self) -> &RegisteredTools;
diff --git a/compiler/rustc_expand/src/expand.rs b/compiler/rustc_expand/src/expand.rs
index bca846d2ec4..1b539477d51 100644
--- a/compiler/rustc_expand/src/expand.rs
+++ b/compiler/rustc_expand/src/expand.rs
@@ -1169,9 +1169,9 @@ trait InvocationCollectorNode: HasAttrs + HasNodeId + Sized {
         collector.cx.dcx().emit_err(RemoveNodeNotSupported { span, descr: Self::descr() });
     }
 
-    /// All of the names (items) declared by this node.
+    /// All of the identifiers (items) declared by this node.
     /// This is an approximation and should only be used for diagnostics.
-    fn declared_names(&self) -> Vec<Ident> {
+    fn declared_idents(&self) -> Vec<Ident> {
         vec![]
     }
 }
@@ -1306,7 +1306,7 @@ impl InvocationCollectorNode for P<ast::Item> {
         res
     }
 
-    fn declared_names(&self) -> Vec<Ident> {
+    fn declared_idents(&self) -> Vec<Ident> {
         if let ItemKind::Use(ut) = &self.kind {
             fn collect_use_tree_leaves(ut: &ast::UseTree, idents: &mut Vec<Ident>) {
                 match &ut.kind {
@@ -2061,10 +2061,10 @@ impl<'a, 'b> InvocationCollector<'a, 'b> {
                         }
 
                         if let Some(meta_item) = meta_item {
-                            for name in node.declared_names() {
+                            for ident in node.declared_idents() {
                                 self.cx.resolver.append_stripped_cfg_item(
                                     self.cx.current_expansion.lint_node_id,
-                                    name,
+                                    ident,
                                     meta_item.clone(),
                                 )
                             }
diff --git a/compiler/rustc_feature/src/accepted.rs b/compiler/rustc_feature/src/accepted.rs
index 88e6593572b..8968c1771e4 100644
--- a/compiler/rustc_feature/src/accepted.rs
+++ b/compiler/rustc_feature/src/accepted.rs
@@ -63,7 +63,7 @@ declare_features! (
     /// Allows using `const` operands in inline assembly.
     (accepted, asm_const, "1.82.0", Some(93332)),
     /// Allows using `label` operands in inline assembly.
-    (accepted, asm_goto, "CURRENT_RUSTC_VERSION", Some(119364)),
+    (accepted, asm_goto, "1.87.0", Some(119364)),
     /// Allows using `sym` operands in inline assembly.
     (accepted, asm_sym, "1.66.0", Some(93333)),
     /// Allows the definition of associated constants in `trait` or `impl` blocks.
@@ -332,7 +332,7 @@ declare_features! (
     /// Allows `use<'a, 'b, A, B>` in `impl Trait + use<...>` for precise capture of generic args.
     (accepted, precise_capturing, "1.82.0", Some(123432)),
     /// Allows `use<..>` precise capturign on impl Trait in traits.
-    (accepted, precise_capturing_in_traits, "CURRENT_RUSTC_VERSION", Some(130044)),
+    (accepted, precise_capturing_in_traits, "1.87.0", Some(130044)),
     /// Allows procedural macros in `proc-macro` crates.
     (accepted, proc_macro, "1.29.0", Some(38356)),
     /// Allows multi-segment paths in attributes and derives.
diff --git a/compiler/rustc_feature/src/removed.rs b/compiler/rustc_feature/src/removed.rs
index 6ba7b22a0df..402e18c5d14 100644
--- a/compiler/rustc_feature/src/removed.rs
+++ b/compiler/rustc_feature/src/removed.rs
@@ -247,7 +247,7 @@ declare_features! (
     /// Allows unnamed fields of struct and union type
     (removed, unnamed_fields, "1.83.0", Some(49804), Some("feature needs redesign")),
     (removed, unsafe_no_drop_flag, "1.0.0", None, None),
-    (removed, unsized_tuple_coercion, "CURRENT_RUSTC_VERSION", Some(42877),
+    (removed, unsized_tuple_coercion, "1.87.0", Some(42877),
      Some("The feature restricts possible layouts for tuples, and this restriction is not worth it.")),
     /// Allows `union` fields that don't implement `Copy` as long as they don't have any drop glue.
     (removed, untagged_unions, "1.13.0", Some(55149),
diff --git a/compiler/rustc_feature/src/unstable.rs b/compiler/rustc_feature/src/unstable.rs
index 7edb05c7307..98213affc5b 100644
--- a/compiler/rustc_feature/src/unstable.rs
+++ b/compiler/rustc_feature/src/unstable.rs
@@ -474,7 +474,7 @@ declare_features! (
     /// Allows `dyn* Trait` objects.
     (incomplete, dyn_star, "1.65.0", Some(102425)),
     /// Allows the .use postfix syntax `x.use` and use closures `use |x| { ... }`
-    (incomplete, ergonomic_clones, "CURRENT_RUSTC_VERSION", Some(132290)),
+    (incomplete, ergonomic_clones, "1.87.0", Some(132290)),
     /// Allows exhaustive pattern matching on types that contain uninhabited types.
     (unstable, exhaustive_patterns, "1.13.0", Some(51085)),
     /// Allows explicit tail calls via `become` expression.
@@ -511,7 +511,7 @@ declare_features! (
     /// Allows generic parameters and where-clauses on free & associated const items.
     (incomplete, generic_const_items, "1.73.0", Some(113521)),
     /// Allows the type of const generics to depend on generic parameters
-    (incomplete, generic_const_parameter_types, "CURRENT_RUSTC_VERSION", Some(137626)),
+    (incomplete, generic_const_parameter_types, "1.87.0", Some(137626)),
     /// Allows any generic constants being used as pattern type range ends
     (incomplete, generic_pattern_types, "1.86.0", Some(136574)),
     /// Allows registering static items globally, possibly across crates, to iterate over at runtime.
@@ -602,7 +602,7 @@ declare_features! (
     /// Allows macro attributes on expressions, statements and non-inline modules.
     (unstable, proc_macro_hygiene, "1.30.0", Some(54727)),
     /// Allows the use of raw-dylibs on ELF platforms
-    (incomplete, raw_dylib_elf, "CURRENT_RUSTC_VERSION", Some(135694)),
+    (incomplete, raw_dylib_elf, "1.87.0", Some(135694)),
     /// 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
@@ -664,14 +664,14 @@ declare_features! (
     /// Allows using the `#[used(linker)]` (or `#[used(compiler)]`) attribute.
     (unstable, used_with_arg, "1.60.0", Some(93798)),
     /// Allows use of attributes in `where` clauses.
-    (unstable, where_clause_attrs, "CURRENT_RUSTC_VERSION", Some(115590)),
+    (unstable, where_clause_attrs, "1.87.0", Some(115590)),
     /// Allows use of x86 `AMX` target-feature attributes and intrinsics
     (unstable, x86_amx_intrinsics, "1.81.0", Some(126622)),
     /// Allows use of the `xop` target-feature
     (unstable, xop_target_feature, "1.81.0", Some(127208)),
     /// Allows `do yeet` expressions
     (unstable, yeet_expr, "1.62.0", Some(96373)),
-    (unstable, yield_expr, "CURRENT_RUSTC_VERSION", Some(43122)),
+    (unstable, yield_expr, "1.87.0", Some(43122)),
     // !!!!    !!!!    !!!!    !!!!   !!!!    !!!!    !!!!    !!!!    !!!!    !!!!    !!!!
     // Features are listed in alphabetical order. Tidy will fail if you don't keep it this way.
     // !!!!    !!!!    !!!!    !!!!   !!!!    !!!!    !!!!    !!!!    !!!!    !!!!    !!!!
diff --git a/compiler/rustc_hir/src/def.rs b/compiler/rustc_hir/src/def.rs
index dc00b52a593..9372ab532bf 100644
--- a/compiler/rustc_hir/src/def.rs
+++ b/compiler/rustc_hir/src/def.rs
@@ -267,11 +267,16 @@ impl DefKind {
             | DefKind::ForeignTy
             | DefKind::TraitAlias
             | DefKind::TyParam
-            | DefKind::ExternCrate => DefPathData::TypeNs(Some(name.unwrap())),
-
-            // An associated type names will be missing for an RPITIT. It will
-            // later be given a name with `synthetic` in it, if necessary.
-            DefKind::AssocTy => DefPathData::TypeNs(name),
+            | DefKind::ExternCrate => DefPathData::TypeNs(name.unwrap()),
+
+            // An associated type name will be missing for an RPITIT.
+            DefKind::AssocTy => {
+                if let Some(name) = name {
+                    DefPathData::TypeNs(name)
+                } else {
+                    DefPathData::AnonAssocTy
+                }
+            }
 
             // It's not exactly an anon const, but wrt DefPathData, there
             // is no difference.
diff --git a/compiler/rustc_hir/src/definitions.rs b/compiler/rustc_hir/src/definitions.rs
index c52954aa96f..34f3c169505 100644
--- a/compiler/rustc_hir/src/definitions.rs
+++ b/compiler/rustc_hir/src/definitions.rs
@@ -271,9 +271,8 @@ pub enum DefPathData {
     Use,
     /// A global asm item.
     GlobalAsm,
-    /// Something in the type namespace. Will be empty for RPITIT associated
-    /// types, which are given a synthetic name later, if necessary.
-    TypeNs(Option<Symbol>),
+    /// Something in the type namespace.
+    TypeNs(Symbol),
     /// Something in the value namespace.
     ValueNs(Symbol),
     /// Something in the macro namespace.
@@ -291,6 +290,8 @@ pub enum DefPathData {
     /// An existential `impl Trait` type node.
     /// Argument position `impl Trait` have a `TypeNs` with their pretty-printed name.
     OpaqueTy,
+    /// An anonymous associated type from an RPITIT.
+    AnonAssocTy,
     /// A synthetic body for a coroutine's by-move body.
     SyntheticCoroutineBody,
 }
@@ -413,9 +414,7 @@ impl DefPathData {
     pub fn get_opt_name(&self) -> Option<Symbol> {
         use self::DefPathData::*;
         match *self {
-            TypeNs(name) => name,
-
-            ValueNs(name) | MacroNs(name) | LifetimeNs(name) => Some(name),
+            TypeNs(name) | ValueNs(name) | MacroNs(name) | LifetimeNs(name) => Some(name),
 
             Impl
             | ForeignMod
@@ -426,6 +425,7 @@ impl DefPathData {
             | Ctor
             | AnonConst
             | OpaqueTy
+            | AnonAssocTy
             | SyntheticCoroutineBody => None,
         }
     }
@@ -433,14 +433,9 @@ impl DefPathData {
     pub fn name(&self) -> DefPathDataName {
         use self::DefPathData::*;
         match *self {
-            TypeNs(name) => {
-                if let Some(name) = name {
-                    DefPathDataName::Named(name)
-                } else {
-                    DefPathDataName::Anon { namespace: sym::synthetic }
-                }
+            TypeNs(name) | ValueNs(name) | MacroNs(name) | LifetimeNs(name) => {
+                DefPathDataName::Named(name)
             }
-            ValueNs(name) | MacroNs(name) | LifetimeNs(name) => DefPathDataName::Named(name),
             // Note that this does not show up in user print-outs.
             CrateRoot => DefPathDataName::Anon { namespace: kw::Crate },
             Impl => DefPathDataName::Anon { namespace: kw::Impl },
@@ -451,6 +446,7 @@ impl DefPathData {
             Ctor => DefPathDataName::Anon { namespace: sym::constructor },
             AnonConst => DefPathDataName::Anon { namespace: sym::constant },
             OpaqueTy => DefPathDataName::Anon { namespace: sym::opaque },
+            AnonAssocTy => DefPathDataName::Anon { namespace: sym::anon_assoc },
             SyntheticCoroutineBody => DefPathDataName::Anon { namespace: sym::synthetic },
         }
     }
diff --git a/compiler/rustc_hir/src/hir.rs b/compiler/rustc_hir/src/hir.rs
index c61477951c9..6455f33b9d1 100644
--- a/compiler/rustc_hir/src/hir.rs
+++ b/compiler/rustc_hir/src/hir.rs
@@ -1756,7 +1756,7 @@ pub enum PatKind<'hir> {
     Never,
 
     /// A tuple pattern (e.g., `(a, b)`).
-    /// If the `..` pattern fragment is present, then `Option<usize>` denotes its position.
+    /// If the `..` pattern fragment is present, then `DotDotPos` denotes its position.
     /// `0 <= position <= subpats.len()`
     Tuple(&'hir [Pat<'hir>], DotDotPos),
 
@@ -3399,9 +3399,9 @@ pub struct BareFnTy<'hir> {
     pub abi: ExternAbi,
     pub generic_params: &'hir [GenericParam<'hir>],
     pub decl: &'hir FnDecl<'hir>,
-    // `Option` because bare fn parameter names are optional. We also end up
+    // `Option` because bare fn parameter identifiers are optional. We also end up
     // with `None` in some error cases, e.g. invalid parameter patterns.
-    pub param_names: &'hir [Option<Ident>],
+    pub param_idents: &'hir [Option<Ident>],
 }
 
 #[derive(Debug, Clone, Copy, HashStable_Generic)]
diff --git a/compiler/rustc_hir/src/intravisit.rs b/compiler/rustc_hir/src/intravisit.rs
index ea3f396761b..93d20dfa799 100644
--- a/compiler/rustc_hir/src/intravisit.rs
+++ b/compiler/rustc_hir/src/intravisit.rs
@@ -652,10 +652,10 @@ pub fn walk_foreign_item<'v, V: Visitor<'v>>(
     try_visit!(visitor.visit_ident(foreign_item.ident));
 
     match foreign_item.kind {
-        ForeignItemKind::Fn(ref sig, param_names, ref generics) => {
+        ForeignItemKind::Fn(ref sig, param_idents, ref generics) => {
             try_visit!(visitor.visit_generics(generics));
             try_visit!(visitor.visit_fn_decl(sig.decl));
-            for ident in param_names.iter().copied() {
+            for ident in param_idents.iter().copied() {
                 visit_opt!(visitor, visit_ident, ident);
             }
         }
@@ -1169,9 +1169,9 @@ pub fn walk_trait_item<'v, V: Visitor<'v>>(
             try_visit!(visitor.visit_ty_unambig(ty));
             visit_opt!(visitor, visit_nested_body, default);
         }
-        TraitItemKind::Fn(ref sig, TraitFn::Required(param_names)) => {
+        TraitItemKind::Fn(ref sig, TraitFn::Required(param_idents)) => {
             try_visit!(visitor.visit_fn_decl(sig.decl));
-            for ident in param_names.iter().copied() {
+            for ident in param_idents.iter().copied() {
                 visit_opt!(visitor, visit_ident, ident);
             }
         }
diff --git a/compiler/rustc_hir/src/tests.rs b/compiler/rustc_hir/src/tests.rs
index 0837444ffdb..18c2bfdac8c 100644
--- a/compiler/rustc_hir/src/tests.rs
+++ b/compiler/rustc_hir/src/tests.rs
@@ -17,7 +17,7 @@ fn def_path_hash_depends_on_crate_id() {
     // the crate by changing the crate disambiguator (e.g. via bumping the
     // crate's version number).
 
-    create_session_globals_then(Edition::Edition2024, None, || {
+    create_session_globals_then(Edition::Edition2024, &[], None, || {
         let id0 = StableCrateId::new(Symbol::intern("foo"), false, vec!["1".to_string()], "");
         let id1 = StableCrateId::new(Symbol::intern("foo"), false, vec!["2".to_string()], "");
 
diff --git a/compiler/rustc_hir_analysis/messages.ftl b/compiler/rustc_hir_analysis/messages.ftl
index 194f2cd04e4..92701e3328e 100644
--- a/compiler/rustc_hir_analysis/messages.ftl
+++ b/compiler/rustc_hir_analysis/messages.ftl
@@ -1,5 +1,5 @@
-hir_analysis_ambiguous_assoc_item = ambiguous associated {$assoc_kind} `{$assoc_name}` in bounds of `{$qself}`
-    .label = ambiguous associated {$assoc_kind} `{$assoc_name}`
+hir_analysis_ambiguous_assoc_item = ambiguous associated {$assoc_kind} `{$assoc_ident}` in bounds of `{$qself}`
+    .label = ambiguous associated {$assoc_kind} `{$assoc_ident}`
 
 hir_analysis_ambiguous_lifetime_bound =
     ambiguous lifetime bound, explicit lifetime bound required
@@ -12,13 +12,13 @@ hir_analysis_assoc_item_is_private = {$kind} `{$name}` is private
     .label = private {$kind}
     .defined_here_label = the {$kind} is defined here
 
-hir_analysis_assoc_item_not_found = associated {$assoc_kind} `{$assoc_name}` not found for `{$qself}`
+hir_analysis_assoc_item_not_found = associated {$assoc_kind} `{$assoc_ident}` not found for `{$qself}`
 
 hir_analysis_assoc_item_not_found_found_in_other_trait_label = there is {$identically_named ->
         [true] an
         *[false] a similarly named
     } associated {$assoc_kind} `{$suggested_name}` in the trait `{$trait_name}`
-hir_analysis_assoc_item_not_found_label = associated {$assoc_kind} `{$assoc_name}` not found
+hir_analysis_assoc_item_not_found_label = associated {$assoc_kind} `{$assoc_ident}` not found
 hir_analysis_assoc_item_not_found_other_sugg = `{$qself}` has the following associated {$assoc_kind}
 hir_analysis_assoc_item_not_found_similar_in_other_trait_qpath_sugg =
     consider fully qualifying{$identically_named ->
@@ -486,6 +486,9 @@ hir_analysis_self_in_impl_self =
     `Self` is not valid in the self type of an impl block
     .note = replace `Self` with a different type
 
+hir_analysis_self_in_type_alias = `Self` is not allowed in type aliases
+    .label = `Self` is only available in impls, traits, and concrete type definitions
+
 hir_analysis_self_ty_not_captured = `impl Trait` must mention the `Self` type of the trait in `use<...>`
     .label = `Self` type parameter is implicitly captured by this `impl Trait`
     .note = currently, all type parameters are required to be mentioned in the precise captures list
diff --git a/compiler/rustc_hir_analysis/src/check/check.rs b/compiler/rustc_hir_analysis/src/check/check.rs
index e3ed20e1b31..f50746dd18d 100644
--- a/compiler/rustc_hir_analysis/src/check/check.rs
+++ b/compiler/rustc_hir_analysis/src/check/check.rs
@@ -397,8 +397,11 @@ fn best_definition_site_of_opaque<'tcx>(
                 return ControlFlow::Continue(());
             }
 
-            if let Some(hidden_ty) =
-                self.tcx.mir_borrowck(item_def_id).concrete_opaque_types.get(&self.opaque_def_id)
+            if let Some(hidden_ty) = self
+                .tcx
+                .mir_borrowck(item_def_id)
+                .ok()
+                .and_then(|opaque_types| opaque_types.0.get(&self.opaque_def_id))
             {
                 ControlFlow::Break((hidden_ty.span, item_def_id))
             } else {
@@ -413,9 +416,6 @@ fn best_definition_site_of_opaque<'tcx>(
             self.tcx
         }
         fn visit_expr(&mut self, ex: &'tcx hir::Expr<'tcx>) -> Self::Result {
-            if let hir::ExprKind::Closure(closure) = ex.kind {
-                self.check(closure.def_id)?;
-            }
             intravisit::walk_expr(self, ex)
         }
         fn visit_item(&mut self, it: &'tcx hir::Item<'tcx>) -> Self::Result {
@@ -719,7 +719,6 @@ pub(crate) fn check_item_type(tcx: TyCtxt<'_>, def_id: LocalDefId) {
                     def_id,
                     tcx.def_ident_span(def_id).unwrap(),
                     i.name,
-                    ExternAbi::Rust,
                 )
             }
         }
@@ -787,16 +786,6 @@ pub(crate) fn check_item_type(tcx: TyCtxt<'_>, def_id: LocalDefId) {
             for item in items {
                 let def_id = item.id.owner_id.def_id;
 
-                if tcx.has_attr(def_id, sym::rustc_intrinsic) {
-                    intrinsic::check_intrinsic_type(
-                        tcx,
-                        item.id.owner_id.def_id,
-                        item.span,
-                        item.ident.name,
-                        abi,
-                    );
-                }
-
                 let generics = tcx.generics_of(def_id);
                 let own_counts = generics.own_counts();
                 if generics.own_params.len() - own_counts.lifetimes != 0 {
@@ -937,31 +926,7 @@ fn check_impl_items_against_trait<'tcx>(
 
     let trait_def = tcx.trait_def(trait_ref.def_id);
 
-    let infcx = tcx.infer_ctxt().ignoring_regions().build(TypingMode::non_body_analysis());
-
-    let ocx = ObligationCtxt::new_with_diagnostics(&infcx);
-    let cause = ObligationCause::misc(tcx.def_span(impl_id), impl_id);
-    let param_env = tcx.param_env(impl_id);
-
-    let self_is_guaranteed_unsized = match tcx
-        .struct_tail_raw(
-            trait_ref.self_ty(),
-            |ty| {
-                ocx.structurally_normalize_ty(&cause, param_env, ty).unwrap_or_else(|_| {
-                    Ty::new_error_with_message(
-                        tcx,
-                        tcx.def_span(impl_id),
-                        "struct tail should be computable",
-                    )
-                })
-            },
-            || (),
-        )
-        .kind()
-    {
-        ty::Dynamic(_, _, ty::DynKind::Dyn) | ty::Slice(_) | ty::Str => true,
-        _ => false,
-    };
+    let self_is_guaranteed_unsize_self = tcx.impl_self_is_guaranteed_unsized(impl_id);
 
     for &impl_item in impl_item_refs {
         let ty_impl_item = tcx.associated_item(impl_item);
@@ -992,7 +957,7 @@ fn check_impl_items_against_trait<'tcx>(
             }
         }
 
-        if self_is_guaranteed_unsized && tcx.generics_require_sized_self(ty_trait_item.def_id) {
+        if self_is_guaranteed_unsize_self && tcx.generics_require_sized_self(ty_trait_item.def_id) {
             tcx.emit_node_span_lint(
                 rustc_lint_defs::builtin::DEAD_CODE,
                 tcx.local_def_id_to_hir_id(ty_impl_item.def_id.expect_local()),
@@ -1027,7 +992,7 @@ fn check_impl_items_against_trait<'tcx>(
             if !is_implemented
                 && tcx.defaultness(impl_id).is_final()
                 // unsized types don't need to implement methods that have `Self: Sized` bounds.
-                && !(self_is_guaranteed_unsized && tcx.generics_require_sized_self(trait_item_id))
+                && !(self_is_guaranteed_unsize_self && tcx.generics_require_sized_self(trait_item_id))
             {
                 missing_items.push(tcx.associated_item(trait_item_id));
             }
diff --git a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
index 5e68bb31001..29a9931696f 100644
--- a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
+++ b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
@@ -442,7 +442,7 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for RemapLateParam<'tcx> {
     }
 
     fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
-        if let ty::ReLateParam(fr) = *r {
+        if let ty::ReLateParam(fr) = r.kind() {
             ty::Region::new_late_param(
                 self.tcx,
                 fr.scope,
@@ -1046,11 +1046,11 @@ fn report_trait_method_mismatch<'tcx>(
             // argument pattern and type.
             let (sig, body) = tcx.hir_expect_impl_item(impl_m.def_id.expect_local()).expect_fn();
             let span = tcx
-                .hir_body_param_names(body)
+                .hir_body_param_idents(body)
                 .zip(sig.decl.inputs.iter())
-                .map(|(param_name, ty)| {
-                    if let Some(param_name) = param_name {
-                        param_name.span.to(ty.span)
+                .map(|(param_ident, ty)| {
+                    if let Some(param_ident) = param_ident {
+                        param_ident.span.to(ty.span)
                     } else {
                         ty.span
                     }
diff --git a/compiler/rustc_hir_analysis/src/check/intrinsic.rs b/compiler/rustc_hir_analysis/src/check/intrinsic.rs
index 0bf9e127989..ed8ca27d217 100644
--- a/compiler/rustc_hir_analysis/src/check/intrinsic.rs
+++ b/compiler/rustc_hir_analysis/src/check/intrinsic.rs
@@ -1,9 +1,8 @@
 //! Type-checking for the `#[rustc_intrinsic]` intrinsics that the compiler exposes.
 
 use rustc_abi::ExternAbi;
-use rustc_errors::codes::*;
-use rustc_errors::{DiagMessage, struct_span_code_err};
-use rustc_hir::{self as hir, Safety};
+use rustc_errors::DiagMessage;
+use rustc_hir::{self as hir};
 use rustc_middle::bug;
 use rustc_middle::traits::{ObligationCause, ObligationCauseCode};
 use rustc_middle::ty::{self, Ty, TyCtxt};
@@ -26,17 +25,10 @@ fn equate_intrinsic_type<'tcx>(
     sig: ty::PolyFnSig<'tcx>,
 ) {
     let (generics, span) = match tcx.hir_node_by_def_id(def_id) {
-        hir::Node::Item(hir::Item { kind: hir::ItemKind::Fn { generics, .. }, .. })
-        | hir::Node::ForeignItem(hir::ForeignItem {
-            kind: hir::ForeignItemKind::Fn(_, _, generics),
-            ..
-        }) => (tcx.generics_of(def_id), generics.span),
-        _ => {
-            struct_span_code_err!(tcx.dcx(), span, E0622, "intrinsic must be a function")
-                .with_span_label(span, "expected a function")
-                .emit();
-            return;
+        hir::Node::Item(hir::Item { kind: hir::ItemKind::Fn { generics, .. }, .. }) => {
+            (tcx.generics_of(def_id), generics.span)
         }
+        _ => tcx.dcx().span_bug(span, "intrinsic must be a function"),
     };
     let own_counts = generics.own_counts();
 
@@ -70,13 +62,7 @@ fn equate_intrinsic_type<'tcx>(
 }
 
 /// Returns the unsafety of the given intrinsic.
-pub fn intrinsic_operation_unsafety(tcx: TyCtxt<'_>, intrinsic_id: LocalDefId) -> hir::Safety {
-    let has_safe_attr = if tcx.has_attr(intrinsic_id, sym::rustc_intrinsic) {
-        tcx.fn_sig(intrinsic_id).skip_binder().safety()
-    } else {
-        // Old-style intrinsics are never safe
-        Safety::Unsafe
-    };
+fn intrinsic_operation_unsafety(tcx: TyCtxt<'_>, intrinsic_id: LocalDefId) -> hir::Safety {
     let is_in_list = match tcx.item_name(intrinsic_id.into()) {
         // When adding a new intrinsic to this list,
         // it's usually worth updating that intrinsic's documentation
@@ -148,7 +134,7 @@ pub fn intrinsic_operation_unsafety(tcx: TyCtxt<'_>, intrinsic_id: LocalDefId) -
         _ => hir::Safety::Unsafe,
     };
 
-    if has_safe_attr != is_in_list {
+    if tcx.fn_sig(intrinsic_id).skip_binder().safety() != is_in_list {
         tcx.dcx().struct_span_err(
             tcx.def_span(intrinsic_id),
             DiagMessage::from(format!(
@@ -163,12 +149,11 @@ pub fn intrinsic_operation_unsafety(tcx: TyCtxt<'_>, intrinsic_id: LocalDefId) -
 
 /// Remember to add all intrinsics here, in `compiler/rustc_codegen_llvm/src/intrinsic.rs`,
 /// and in `library/core/src/intrinsics.rs`.
-pub fn check_intrinsic_type(
+pub(crate) fn check_intrinsic_type(
     tcx: TyCtxt<'_>,
     intrinsic_id: LocalDefId,
     span: Span,
     intrinsic_name: Symbol,
-    abi: ExternAbi,
 ) {
     let generics = tcx.generics_of(intrinsic_id);
     let param = |n| {
@@ -674,8 +659,12 @@ pub fn check_intrinsic_type(
             sym::simd_masked_load => (3, 0, vec![param(0), param(1), param(2)], param(2)),
             sym::simd_masked_store => (3, 0, vec![param(0), param(1), param(2)], tcx.types.unit),
             sym::simd_scatter => (3, 0, vec![param(0), param(1), param(2)], tcx.types.unit),
-            sym::simd_insert => (2, 0, vec![param(0), tcx.types.u32, param(1)], param(0)),
-            sym::simd_extract => (2, 0, vec![param(0), tcx.types.u32], param(1)),
+            sym::simd_insert | sym::simd_insert_dyn => {
+                (2, 0, vec![param(0), tcx.types.u32, param(1)], param(0))
+            }
+            sym::simd_extract | sym::simd_extract_dyn => {
+                (2, 0, vec![param(0), tcx.types.u32], param(1))
+            }
             sym::simd_cast
             | sym::simd_as
             | sym::simd_cast_ptr
@@ -706,7 +695,7 @@ pub fn check_intrinsic_type(
         };
         (n_tps, 0, n_cts, inputs, output, safety)
     };
-    let sig = tcx.mk_fn_sig(inputs, output, false, safety, abi);
+    let sig = tcx.mk_fn_sig(inputs, output, false, safety, ExternAbi::Rust);
     let sig = ty::Binder::bind_with_vars(sig, bound_vars);
     equate_intrinsic_type(tcx, span, intrinsic_id, n_tps, n_lts, n_cts, sig)
 }
diff --git a/compiler/rustc_hir_analysis/src/check/wfcheck.rs b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
index 83d095ab72e..6292d03bf6a 100644
--- a/compiler/rustc_hir_analysis/src/check/wfcheck.rs
+++ b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
@@ -631,7 +631,7 @@ fn gather_gat_bounds<'tcx, T: TypeFoldable<TyCtxt<'tcx>>>(
         // Ignore `'static` lifetimes for the purpose of this lint: it's
         // because we know it outlives everything and so doesn't give meaningful
         // clues. Also ignore `ReError`, to avoid knock-down errors.
-        if let ty::ReStatic | ty::ReError(_) = **region_a {
+        if let ty::ReStatic | ty::ReError(_) = region_a.kind() {
             continue;
         }
         // For each region argument (e.g., `'a` in our example), check for a
@@ -672,7 +672,7 @@ fn gather_gat_bounds<'tcx, T: TypeFoldable<TyCtxt<'tcx>>>(
             // Again, skip `'static` because it outlives everything. Also, we trivially
             // know that a region outlives itself. Also ignore `ReError`, to avoid
             // knock-down errors.
-            if matches!(**region_b, ty::ReStatic | ty::ReError(_)) || region_a == region_b {
+            if matches!(region_b.kind(), ty::ReStatic | ty::ReError(_)) || region_a == region_b {
                 continue;
             }
             if region_known_to_outlive(tcx, item_def_id, param_env, wf_tys, *region_a, *region_b) {
diff --git a/compiler/rustc_hir_analysis/src/coherence/builtin.rs b/compiler/rustc_hir_analysis/src/coherence/builtin.rs
index 1f3f0b754bb..8ad9d80c6b5 100644
--- a/compiler/rustc_hir_analysis/src/coherence/builtin.rs
+++ b/compiler/rustc_hir_analysis/src/coherence/builtin.rs
@@ -656,7 +656,7 @@ fn infringing_fields_error<'tcx>(
                                 .entry((ty.clone(), predicate.clone()))
                                 .or_default()
                                 .push(origin.span());
-                            if let ty::RegionKind::ReEarlyParam(ebr) = *b
+                            if let ty::RegionKind::ReEarlyParam(ebr) = b.kind()
                                 && ebr.has_name()
                             {
                                 bounds.push((b.to_string(), a.to_string(), None));
diff --git a/compiler/rustc_hir_analysis/src/collect.rs b/compiler/rustc_hir_analysis/src/collect.rs
index e9cd22435d9..deded6904d4 100644
--- a/compiler/rustc_hir_analysis/src/collect.rs
+++ b/compiler/rustc_hir_analysis/src/collect.rs
@@ -14,6 +14,7 @@
 //! At present, however, we do run collection across all items in the
 //! crate as a kind of pass. This should eventually be factored away.
 
+use std::assert_matches::assert_matches;
 use std::cell::Cell;
 use std::iter;
 use std::ops::Bound;
@@ -438,9 +439,9 @@ impl<'tcx> HirTyLowerer<'tcx> for ItemCtxt<'tcx> {
         &self,
         span: Span,
         def_id: LocalDefId,
-        assoc_name: Ident,
+        assoc_ident: Ident,
     ) -> ty::EarlyBinder<'tcx, &'tcx [(ty::Clause<'tcx>, Span)]> {
-        self.tcx.at(span).type_param_predicates((self.item_def_id, def_id, assoc_name))
+        self.tcx.at(span).type_param_predicates((self.item_def_id, def_id, assoc_ident))
     }
 
     fn lower_assoc_shared(
@@ -1344,7 +1345,8 @@ fn fn_sig(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<'_, ty::PolyFn
             compute_sig_of_foreign_fn_decl(tcx, def_id, sig.decl, abi, sig.header.safety())
         }
 
-        Ctor(data) | Variant(hir::Variant { data, .. }) if data.ctor().is_some() => {
+        Ctor(data) => {
+            assert_matches!(data.ctor(), Some(_));
             let adt_def_id = tcx.hir_get_parent_item(hir_id).def_id.to_def_id();
             let ty = tcx.type_of(adt_def_id).instantiate_identity();
             let inputs = data.fields().iter().map(|f| tcx.type_of(f.def_id).instantiate_identity());
@@ -1416,7 +1418,7 @@ fn recover_infer_ret_ty<'tcx>(
         GenericParamKind::Lifetime { .. } => true,
         _ => false,
     });
-    let fn_sig = fold_regions(tcx, fn_sig, |r, _| match *r {
+    let fn_sig = fold_regions(tcx, fn_sig, |r, _| match r.kind() {
         ty::ReErased => {
             if has_region_params {
                 ty::Region::new_error_with_message(
diff --git a/compiler/rustc_hir_analysis/src/collect/predicates_of.rs b/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
index 320225a7a66..ce0f83d0ec2 100644
--- a/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
+++ b/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
@@ -359,7 +359,7 @@ fn compute_bidirectional_outlives_predicates<'tcx>(
 ) {
     for param in opaque_own_params {
         let orig_lifetime = tcx.map_opaque_lifetime_to_parent_lifetime(param.def_id.expect_local());
-        if let ty::ReEarlyParam(..) = *orig_lifetime {
+        if let ty::ReEarlyParam(..) = orig_lifetime.kind() {
             let dup_lifetime = ty::Region::new_early_param(
                 tcx,
                 ty::EarlyParamRegion { index: param.index, name: param.name },
@@ -584,12 +584,12 @@ pub(super) fn explicit_super_predicates_of<'tcx>(
 
 pub(super) fn explicit_supertraits_containing_assoc_item<'tcx>(
     tcx: TyCtxt<'tcx>,
-    (trait_def_id, assoc_name): (DefId, Ident),
+    (trait_def_id, assoc_ident): (DefId, Ident),
 ) -> ty::EarlyBinder<'tcx, &'tcx [(ty::Clause<'tcx>, Span)]> {
     implied_predicates_with_filter(
         tcx,
         trait_def_id,
-        PredicateFilter::SelfTraitThatDefines(assoc_name),
+        PredicateFilter::SelfTraitThatDefines(assoc_ident),
     )
 }
 
@@ -617,7 +617,7 @@ pub(super) fn implied_predicates_with_filter<'tcx>(
     filter: PredicateFilter,
 ) -> ty::EarlyBinder<'tcx, &'tcx [(ty::Clause<'tcx>, Span)]> {
     let Some(trait_def_id) = trait_def_id.as_local() else {
-        // if `assoc_name` is None, then the query should've been redirected to an
+        // if `assoc_ident` is None, then the query should've been redirected to an
         // external provider
         assert_matches!(filter, PredicateFilter::SelfTraitThatDefines(_));
         return tcx.explicit_super_predicates_of(trait_def_id);
@@ -834,11 +834,11 @@ pub(super) fn assert_only_contains_predicates_from<'tcx>(
 #[instrument(level = "trace", skip(tcx))]
 pub(super) fn type_param_predicates<'tcx>(
     tcx: TyCtxt<'tcx>,
-    (item_def_id, def_id, assoc_name): (LocalDefId, LocalDefId, Ident),
+    (item_def_id, def_id, assoc_ident): (LocalDefId, LocalDefId, Ident),
 ) -> ty::EarlyBinder<'tcx, &'tcx [(ty::Clause<'tcx>, Span)]> {
     match tcx.opt_rpitit_info(item_def_id.to_def_id()) {
         Some(ty::ImplTraitInTraitData::Trait { opaque_def_id, .. }) => {
-            return tcx.type_param_predicates((opaque_def_id.expect_local(), def_id, assoc_name));
+            return tcx.type_param_predicates((opaque_def_id.expect_local(), def_id, assoc_ident));
         }
         Some(ty::ImplTraitInTraitData::Impl { .. }) => {
             unreachable!("should not be lowering bounds on RPITIT in impl")
@@ -863,7 +863,7 @@ pub(super) fn type_param_predicates<'tcx>(
 
     let result = if let Some(parent) = parent {
         let icx = ItemCtxt::new(tcx, parent);
-        icx.probe_ty_param_bounds(DUMMY_SP, def_id, assoc_name)
+        icx.probe_ty_param_bounds(DUMMY_SP, def_id, assoc_ident)
     } else {
         ty::EarlyBinder::bind(&[] as &[_])
     };
@@ -889,7 +889,7 @@ pub(super) fn type_param_predicates<'tcx>(
     let extra_predicates = extend.into_iter().chain(icx.probe_ty_param_bounds_in_generics(
         hir_generics,
         def_id,
-        PredicateFilter::SelfTraitThatDefines(assoc_name),
+        PredicateFilter::SelfTraitThatDefines(assoc_ident),
     ));
 
     let bounds =
@@ -908,7 +908,7 @@ pub(super) fn type_param_predicates<'tcx>(
         _ => unreachable!(),
     };
     assert_only_contains_predicates_from(
-        PredicateFilter::SelfTraitThatDefines(assoc_name),
+        PredicateFilter::SelfTraitThatDefines(assoc_ident),
         bounds,
         self_ty,
     );
diff --git a/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs b/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
index 404753875ee..9bcda35ee87 100644
--- a/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
+++ b/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
@@ -1874,13 +1874,13 @@ impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
     fn supertrait_hrtb_vars(
         tcx: TyCtxt<'tcx>,
         def_id: DefId,
-        assoc_name: Ident,
+        assoc_ident: Ident,
         assoc_kind: ty::AssocKind,
     ) -> Option<(Vec<ty::BoundVariableKind>, &'tcx ty::AssocItem)> {
         let trait_defines_associated_item_named = |trait_def_id: DefId| {
-            tcx.associated_items(trait_def_id).find_by_name_and_kind(
+            tcx.associated_items(trait_def_id).find_by_ident_and_kind(
                 tcx,
-                assoc_name,
+                assoc_ident,
                 assoc_kind,
                 trait_def_id,
             )
@@ -1904,7 +1904,7 @@ impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
             if let Some(assoc_item) = trait_defines_associated_item_named(def_id) {
                 break Some((bound_vars.into_iter().collect(), assoc_item));
             }
-            let predicates = tcx.explicit_supertraits_containing_assoc_item((def_id, assoc_name));
+            let predicates = tcx.explicit_supertraits_containing_assoc_item((def_id, assoc_ident));
             let obligations = predicates.iter_identity_copied().filter_map(|(pred, _)| {
                 let bound_predicate = pred.kind();
                 match bound_predicate.skip_binder() {
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 3fe3d71b32d..772197a53ac 100644
--- a/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
+++ b/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
@@ -183,25 +183,23 @@ impl<'tcx> TaitConstraintLocator<'tcx> {
                     self.non_defining_use_in_defining_scope(item_def_id);
                 }
             }
-            DefiningScopeKind::MirBorrowck => {
-                let borrowck_result = tcx.mir_borrowck(item_def_id);
-                if let Some(guar) = borrowck_result.tainted_by_errors {
-                    self.insert_found(ty::OpaqueHiddenType::new_error(tcx, guar));
-                } else if let Some(&hidden_type) =
-                    borrowck_result.concrete_opaque_types.get(&self.def_id)
-                {
-                    debug!(?hidden_type, "found constraint");
-                    self.insert_found(hidden_type);
-                } else if let Err(guar) = tcx
-                    .type_of_opaque_hir_typeck(self.def_id)
-                    .instantiate_identity()
-                    .error_reported()
-                {
-                    self.insert_found(ty::OpaqueHiddenType::new_error(tcx, guar));
-                } else {
-                    self.non_defining_use_in_defining_scope(item_def_id);
+            DefiningScopeKind::MirBorrowck => match tcx.mir_borrowck(item_def_id) {
+                Err(guar) => self.insert_found(ty::OpaqueHiddenType::new_error(tcx, guar)),
+                Ok(concrete_opaque_types) => {
+                    if let Some(&hidden_type) = concrete_opaque_types.0.get(&self.def_id) {
+                        debug!(?hidden_type, "found constraint");
+                        self.insert_found(hidden_type);
+                    } else if let Err(guar) = tcx
+                        .type_of_opaque_hir_typeck(self.def_id)
+                        .instantiate_identity()
+                        .error_reported()
+                    {
+                        self.insert_found(ty::OpaqueHiddenType::new_error(tcx, guar));
+                    } else {
+                        self.non_defining_use_in_defining_scope(item_def_id);
+                    }
                 }
-            }
+            },
         }
     }
 }
@@ -264,20 +262,20 @@ pub(super) fn find_opaque_ty_constraints_for_rpit<'tcx>(
                 Ty::new_diverging_default(tcx)
             }
         }
-        DefiningScopeKind::MirBorrowck => {
-            let borrowck_result = tcx.mir_borrowck(owner_def_id);
-            if let Some(guar) = borrowck_result.tainted_by_errors {
-                Ty::new_error(tcx, guar)
-            } else if let Some(hidden_ty) = borrowck_result.concrete_opaque_types.get(&def_id) {
-                hidden_ty.ty
-            } else {
-                let hir_ty = tcx.type_of_opaque_hir_typeck(def_id).instantiate_identity();
-                if let Err(guar) = hir_ty.error_reported() {
-                    Ty::new_error(tcx, guar)
+        DefiningScopeKind::MirBorrowck => match tcx.mir_borrowck(owner_def_id) {
+            Ok(concrete_opaque_types) => {
+                if let Some(hidden_ty) = concrete_opaque_types.0.get(&def_id) {
+                    hidden_ty.ty
                 } else {
-                    hir_ty
+                    let hir_ty = tcx.type_of_opaque_hir_typeck(def_id).instantiate_identity();
+                    if let Err(guar) = hir_ty.error_reported() {
+                        Ty::new_error(tcx, guar)
+                    } else {
+                        hir_ty
+                    }
                 }
             }
-        }
+            Err(guar) => Ty::new_error(tcx, guar),
+        },
     }
 }
diff --git a/compiler/rustc_hir_analysis/src/constrained_generic_params.rs b/compiler/rustc_hir_analysis/src/constrained_generic_params.rs
index 53866aa27b1..951eda72ffe 100644
--- a/compiler/rustc_hir_analysis/src/constrained_generic_params.rs
+++ b/compiler/rustc_hir_analysis/src/constrained_generic_params.rs
@@ -80,7 +80,7 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for ParameterCollector {
     }
 
     fn visit_region(&mut self, r: ty::Region<'tcx>) {
-        if let ty::ReEarlyParam(data) = *r {
+        if let ty::ReEarlyParam(data) = r.kind() {
             self.parameters.push(Parameter::from(data));
         }
     }
diff --git a/compiler/rustc_hir_analysis/src/errors.rs b/compiler/rustc_hir_analysis/src/errors.rs
index f2560f22874..508970cf255 100644
--- a/compiler/rustc_hir_analysis/src/errors.rs
+++ b/compiler/rustc_hir_analysis/src/errors.rs
@@ -23,7 +23,7 @@ pub(crate) struct AmbiguousAssocItem<'a> {
     #[label]
     pub span: Span,
     pub assoc_kind: &'static str,
-    pub assoc_name: Ident,
+    pub assoc_ident: Ident,
     pub qself: &'a str,
 }
 
@@ -75,7 +75,7 @@ pub(crate) struct AssocItemIsPrivate {
 pub(crate) struct AssocItemNotFound<'a> {
     #[primary_span]
     pub span: Span,
-    pub assoc_name: Ident,
+    pub assoc_ident: Ident,
     pub assoc_kind: &'static str,
     pub qself: &'a str,
     #[subdiagnostic]
@@ -1707,3 +1707,11 @@ pub(crate) enum SupertraitItemShadowee {
         traits: DiagSymbolList,
     },
 }
+
+#[derive(Diagnostic)]
+#[diag(hir_analysis_self_in_type_alias, code = E0411)]
+pub(crate) struct SelfInTypeAlias {
+    #[primary_span]
+    #[label]
+    pub span: Span,
+}
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs
index 55087d1f400..24d05b49861 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs
@@ -363,10 +363,10 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         for hir_bound in hir_bounds {
             // In order to avoid cycles, when we're lowering `SelfTraitThatDefines`,
             // we skip over any traits that don't define the given associated type.
-            if let PredicateFilter::SelfTraitThatDefines(assoc_name) = predicate_filter {
+            if let PredicateFilter::SelfTraitThatDefines(assoc_ident) = predicate_filter {
                 if let Some(trait_ref) = hir_bound.trait_ref()
                     && let Some(trait_did) = trait_ref.trait_def_id()
-                    && self.tcx().trait_may_define_assoc_item(trait_did, assoc_name)
+                    && self.tcx().trait_may_define_assoc_item(trait_did, assoc_ident)
                 {
                     // Okay
                 } else {
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/cmse.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/cmse.rs
index ecb453bced0..d1ee5a5494c 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/cmse.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/cmse.rs
@@ -49,13 +49,13 @@ pub(crate) fn validate_cmse_abi<'tcx>(
                 Ok(Err(index)) => {
                     // fn(x: u32, u32, u32, u16, y: u16) -> u32,
                     //                           ^^^^^^
-                    let span = if let Some(ident) = bare_fn_ty.param_names[index] {
+                    let span = if let Some(ident) = bare_fn_ty.param_idents[index] {
                         ident.span.to(bare_fn_ty.decl.inputs[index].span)
                     } else {
                         bare_fn_ty.decl.inputs[index].span
                     }
                     .to(bare_fn_ty.decl.inputs.last().unwrap().span);
-                    let plural = bare_fn_ty.param_names.len() - index != 1;
+                    let plural = bare_fn_ty.param_idents.len() - index != 1;
                     dcx.emit_err(errors::CmseInputsStackSpill { span, plural, abi });
                 }
                 Err(layout_err) => {
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs
index aeebe45f881..e64cd8ec302 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs
@@ -16,6 +16,7 @@ use smallvec::{SmallVec, smallvec};
 use tracing::{debug, instrument};
 
 use super::HirTyLowerer;
+use crate::errors::SelfInTypeAlias;
 use crate::hir_ty_lowering::{
     GenericArgCountMismatch, GenericArgCountResult, PredicateFilter, RegionInferReason,
 };
@@ -125,6 +126,19 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         // ```
         let mut projection_bounds = FxIndexMap::default();
         for (proj, proj_span) in elaborated_projection_bounds {
+            let proj = proj.map_bound(|mut b| {
+                if let Some(term_ty) = &b.term.as_type() {
+                    let references_self = term_ty.walk().any(|arg| arg == dummy_self.into());
+                    if references_self {
+                        // With trait alias and type alias combined, type resolver
+                        // may not be able to catch all illegal `Self` usages (issue 139082)
+                        let guar = tcx.dcx().emit_err(SelfInTypeAlias { span });
+                        b.term = replace_dummy_self_with_error(tcx, b.term, guar);
+                    }
+                }
+                b
+            });
+
             let key = (
                 proj.skip_binder().projection_term.def_id,
                 tcx.anonymize_bound_vars(
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
index 6e9c178d33a..5a0524d33fd 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
@@ -117,7 +117,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         all_candidates: impl Fn() -> I,
         qself: AssocItemQSelf,
         assoc_kind: ty::AssocKind,
-        assoc_name: Ident,
+        assoc_ident: Ident,
         span: Span,
         constraint: Option<&hir::AssocItemConstraint<'tcx>>,
     ) -> ErrorGuaranteed
@@ -129,11 +129,15 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         // First and foremost, provide a more user-friendly & “intuitive” error on kind mismatches.
         if let Some(assoc_item) = all_candidates().find_map(|r| {
             tcx.associated_items(r.def_id())
-                .filter_by_name_unhygienic(assoc_name.name)
-                .find(|item| tcx.hygienic_eq(assoc_name, item.ident(tcx), r.def_id()))
+                .filter_by_name_unhygienic(assoc_ident.name)
+                .find(|item| tcx.hygienic_eq(assoc_ident, item.ident(tcx), r.def_id()))
         }) {
             return self.complain_about_assoc_kind_mismatch(
-                assoc_item, assoc_kind, assoc_name, span, constraint,
+                assoc_item,
+                assoc_kind,
+                assoc_ident,
+                span,
+                constraint,
             );
         }
 
@@ -142,18 +146,18 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
 
         // The fallback span is needed because `assoc_name` might be an `Fn()`'s `Output` without a
         // valid span, so we point at the whole path segment instead.
-        let is_dummy = assoc_name.span == DUMMY_SP;
+        let is_dummy = assoc_ident.span == DUMMY_SP;
 
         let mut err = errors::AssocItemNotFound {
-            span: if is_dummy { span } else { assoc_name.span },
-            assoc_name,
+            span: if is_dummy { span } else { assoc_ident.span },
+            assoc_ident,
             assoc_kind: assoc_kind_str,
             qself: &qself_str,
             label: None,
             sugg: None,
             // Try to get the span of the identifier within the path's syntax context
             // (if that's different).
-            within_macro_span: assoc_name.span.within_macro(span, tcx.sess.source_map()),
+            within_macro_span: assoc_ident.span.within_macro(span, tcx.sess.source_map()),
         };
 
         if is_dummy {
@@ -169,10 +173,10 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             .collect();
 
         if let Some(suggested_name) =
-            find_best_match_for_name(&all_candidate_names, assoc_name.name, None)
+            find_best_match_for_name(&all_candidate_names, assoc_ident.name, None)
         {
             err.sugg = Some(errors::AssocItemNotFoundSugg::Similar {
-                span: assoc_name.span,
+                span: assoc_ident.span,
                 assoc_kind: assoc_kind_str,
                 suggested_name,
             });
@@ -201,7 +205,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             .collect();
 
         if let Some(suggested_name) =
-            find_best_match_for_name(&wider_candidate_names, assoc_name.name, None)
+            find_best_match_for_name(&wider_candidate_names, assoc_ident.name, None)
         {
             if let [best_trait] = visible_traits
                 .iter()
@@ -215,11 +219,11 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             {
                 let trait_name = tcx.def_path_str(best_trait);
                 err.label = Some(errors::AssocItemNotFoundLabel::FoundInOtherTrait {
-                    span: assoc_name.span,
+                    span: assoc_ident.span,
                     assoc_kind: assoc_kind_str,
                     trait_name: &trait_name,
                     suggested_name,
-                    identically_named: suggested_name == assoc_name.name,
+                    identically_named: suggested_name == assoc_ident.name,
                 });
                 if let AssocItemQSelf::TyParam(ty_param_def_id, ty_param_span) = qself
                     // Not using `self.item_def_id()` here as that would yield the opaque type itself if we're
@@ -246,7 +250,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                         // The type param already has a bound for `trait_name`, we just need to
                         // change the associated item.
                         err.sugg = Some(errors::AssocItemNotFoundSugg::SimilarInOtherTrait {
-                            span: assoc_name.span,
+                            span: assoc_ident.span,
                             assoc_kind: assoc_kind_str,
                             suggested_name,
                         });
@@ -265,7 +269,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                         Applicability::MaybeIncorrect
                     };
 
-                    let identically_named = suggested_name == assoc_name.name;
+                    let identically_named = suggested_name == assoc_ident.name;
 
                     if let DefKind::TyAlias = tcx.def_kind(item_def_id)
                         && !tcx.type_alias_is_lazy(item_def_id)
@@ -273,7 +277,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                         err.sugg = Some(errors::AssocItemNotFoundSugg::SimilarInOtherTraitQPath {
                             lo: ty_param_span.shrink_to_lo(),
                             mi: ty_param_span.shrink_to_hi(),
-                            hi: (!identically_named).then_some(assoc_name.span),
+                            hi: (!identically_named).then_some(assoc_ident.span),
                             trait_ref,
                             identically_named,
                             suggested_name,
@@ -294,7 +298,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                             // We suggested constraining a type parameter, but the associated item on it
                             // was also not an exact match, so we also suggest changing it.
                             err.span_suggestion_verbose(
-                                assoc_name.span,
+                                assoc_ident.span,
                                 fluent::hir_analysis_assoc_item_not_found_similar_in_other_trait_with_bound_sugg,
                                 suggested_name,
                                 Applicability::MaybeIncorrect,
@@ -311,13 +315,13 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         // suggest using it.
         if let [candidate_name] = all_candidate_names.as_slice() {
             err.sugg = Some(errors::AssocItemNotFoundSugg::Other {
-                span: assoc_name.span,
+                span: assoc_ident.span,
                 qself: &qself_str,
                 assoc_kind: assoc_kind_str,
                 suggested_name: *candidate_name,
             });
         } else {
-            err.label = Some(errors::AssocItemNotFoundLabel::NotFound { span: assoc_name.span });
+            err.label = Some(errors::AssocItemNotFoundLabel::NotFound { span: assoc_ident.span });
         }
 
         self.dcx().emit_err(err)
@@ -805,7 +809,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                         return None;
                     };
 
-                    let assoc_item = tcx.associated_items(trait_def).find_by_name_and_kind(
+                    let assoc_item = tcx.associated_items(trait_def).find_by_ident_and_kind(
                         tcx,
                         ident,
                         ty::AssocKind::Type,
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
index b4a71edc118..83aa0d95620 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
@@ -147,7 +147,7 @@ pub trait HirTyLowerer<'tcx> {
         &self,
         span: Span,
         def_id: LocalDefId,
-        assoc_name: Ident,
+        assoc_ident: Ident,
     ) -> ty::EarlyBinder<'tcx, &'tcx [(ty::Clause<'tcx>, Span)]>;
 
     /// Lower an associated type/const (from a trait) to a projection.
@@ -933,11 +933,11 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         &self,
         trait_def_id: DefId,
         assoc_kind: ty::AssocKind,
-        assoc_name: Ident,
+        assoc_ident: Ident,
     ) -> bool {
         self.tcx()
             .associated_items(trait_def_id)
-            .find_by_name_and_kind(self.tcx(), assoc_name, assoc_kind, trait_def_id)
+            .find_by_ident_and_kind(self.tcx(), assoc_ident, assoc_kind, trait_def_id)
             .is_some()
     }
 
@@ -964,7 +964,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
     }
 
     /// Search for a trait bound on a type parameter whose trait defines the associated item
-    /// given by `assoc_name` and `kind`.
+    /// given by `assoc_ident` and `kind`.
     ///
     /// This fails if there is no such bound in the list of candidates or if there are multiple
     /// candidates in which case it reports ambiguity.
@@ -976,13 +976,13 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         ty_param_def_id: LocalDefId,
         ty_param_span: Span,
         kind: ty::AssocKind,
-        assoc_name: Ident,
+        assoc_ident: Ident,
         span: Span,
     ) -> Result<ty::PolyTraitRef<'tcx>, ErrorGuaranteed> {
-        debug!(?ty_param_def_id, ?assoc_name, ?span);
+        debug!(?ty_param_def_id, ?assoc_ident, ?span);
         let tcx = self.tcx();
 
-        let predicates = &self.probe_ty_param_bounds(span, ty_param_def_id, assoc_name);
+        let predicates = &self.probe_ty_param_bounds(span, ty_param_def_id, assoc_ident);
         debug!("predicates={:#?}", predicates);
 
         self.probe_single_bound_for_assoc_item(
@@ -990,17 +990,18 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 let trait_refs = predicates
                     .iter_identity_copied()
                     .filter_map(|(p, _)| Some(p.as_trait_clause()?.map_bound(|t| t.trait_ref)));
-                traits::transitive_bounds_that_define_assoc_item(tcx, trait_refs, assoc_name)
+                traits::transitive_bounds_that_define_assoc_item(tcx, trait_refs, assoc_ident)
             },
             AssocItemQSelf::TyParam(ty_param_def_id, ty_param_span),
             kind,
-            assoc_name,
+            assoc_ident,
             span,
             None,
         )
     }
 
-    /// Search for a single trait bound whose trait defines the associated item given by `assoc_name`.
+    /// Search for a single trait bound whose trait defines the associated item given by
+    /// `assoc_ident`.
     ///
     /// This fails if there is no such bound in the list of candidates or if there are multiple
     /// candidates in which case it reports ambiguity.
@@ -1010,7 +1011,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         all_candidates: impl Fn() -> I,
         qself: AssocItemQSelf,
         assoc_kind: ty::AssocKind,
-        assoc_name: Ident,
+        assoc_ident: Ident,
         span: Span,
         constraint: Option<&hir::AssocItemConstraint<'tcx>>,
     ) -> Result<ty::PolyTraitRef<'tcx>, ErrorGuaranteed>
@@ -1020,7 +1021,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         let tcx = self.tcx();
 
         let mut matching_candidates = all_candidates().filter(|r| {
-            self.probe_trait_that_defines_assoc_item(r.def_id(), assoc_kind, assoc_name)
+            self.probe_trait_that_defines_assoc_item(r.def_id(), assoc_kind, assoc_ident)
         });
 
         let Some(bound) = matching_candidates.next() else {
@@ -1028,7 +1029,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 all_candidates,
                 qself,
                 assoc_kind,
-                assoc_name,
+                assoc_ident,
                 span,
                 constraint,
             );
@@ -1044,7 +1045,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             let mut err = self.dcx().create_err(crate::errors::AmbiguousAssocItem {
                 span,
                 assoc_kind: assoc_kind_str,
-                assoc_name,
+                assoc_ident,
                 qself: &qself_str,
             });
             // Provide a more specific error code index entry for equality bindings.
@@ -1065,13 +1066,13 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 let bound_id = bound.def_id();
                 let bound_span = tcx
                     .associated_items(bound_id)
-                    .find_by_name_and_kind(tcx, assoc_name, assoc_kind, bound_id)
+                    .find_by_ident_and_kind(tcx, assoc_ident, assoc_kind, bound_id)
                     .and_then(|item| tcx.hir_span_if_local(item.def_id));
 
                 if let Some(bound_span) = bound_span {
                     err.span_label(
                         bound_span,
-                        format!("ambiguous `{assoc_name}` from `{}`", bound.print_trait_sugared(),),
+                        format!("ambiguous `{assoc_ident}` from `{}`", bound.print_trait_sugared(),),
                     );
                     if let Some(constraint) = constraint {
                         match constraint.kind {
@@ -1087,7 +1088,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                                 }
                                 // FIXME(#97583): This isn't syntactically well-formed!
                                 where_bounds.push(format!(
-                                    "        T: {trait}::{assoc_name} = {term}",
+                                    "        T: {trait}::{assoc_ident} = {term}",
                                     trait = bound.print_only_trait_path(),
                                 ));
                             }
@@ -1096,7 +1097,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                         }
                     } else {
                         err.span_suggestion_verbose(
-                            span.with_hi(assoc_name.span.lo()),
+                            span.with_hi(assoc_ident.span.lo()),
                             "use fully-qualified syntax to disambiguate",
                             format!("<{qself_str} as {}>::", bound.print_only_trait_path()),
                             Applicability::MaybeIncorrect,
@@ -1104,7 +1105,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                     }
                 } else {
                     err.note(format!(
-                        "associated {assoc_kind_str} `{assoc_name}` could derive from `{}`",
+                        "associated {assoc_kind_str} `{assoc_ident}` could derive from `{}`",
                         bound.print_only_trait_path(),
                     ));
                 }
@@ -2858,7 +2859,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
 
         let trait_ref = self.lower_impl_trait_ref(i.of_trait.as_ref()?, self.lower_ty(i.self_ty));
 
-        let assoc = tcx.associated_items(trait_ref.def_id).find_by_name_and_kind(
+        let assoc = tcx.associated_items(trait_ref.def_id).find_by_ident_and_kind(
             tcx,
             *ident,
             ty::AssocKind::Fn,
diff --git a/compiler/rustc_hir_analysis/src/hir_wf_check.rs b/compiler/rustc_hir_analysis/src/hir_wf_check.rs
index c01b81563dc..64c1a78bd1c 100644
--- a/compiler/rustc_hir_analysis/src/hir_wf_check.rs
+++ b/compiler/rustc_hir_analysis/src/hir_wf_check.rs
@@ -4,7 +4,7 @@ use rustc_infer::infer::TyCtxtInferExt;
 use rustc_infer::traits::{ObligationCause, WellFormedLoc};
 use rustc_middle::bug;
 use rustc_middle::query::Providers;
-use rustc_middle::ty::{self, TyCtxt, TypingMode, fold_regions};
+use rustc_middle::ty::{self, TyCtxt, TypeVisitableExt, TypingMode, fold_regions};
 use rustc_span::def_id::LocalDefId;
 use rustc_trait_selection::traits::{self, ObligationCtxt};
 use tracing::debug;
@@ -77,6 +77,15 @@ fn diagnostic_hir_wf_check<'tcx>(
             let tcx_ty = fold_regions(self.tcx, tcx_ty, |r, _| {
                 if r.is_bound() { self.tcx.lifetimes.re_erased } else { r }
             });
+
+            // We may be checking the WFness of a type in an opaque with a non-lifetime bound.
+            // Perhaps we could rebind all the escaping bound vars, but they're coming from
+            // arbitrary debruijn indices and aren't particularly important anyways, since they
+            // are only coming from `feature(non_lifetime_binders)` anyways.
+            if tcx_ty.has_escaping_bound_vars() {
+                return;
+            }
+
             let cause = traits::ObligationCause::new(
                 ty.span,
                 self.def_id,
diff --git a/compiler/rustc_hir_analysis/src/outlives/implicit_infer.rs b/compiler/rustc_hir_analysis/src/outlives/implicit_infer.rs
index a0faa5e8429..780c27d4595 100644
--- a/compiler/rustc_hir_analysis/src/outlives/implicit_infer.rs
+++ b/compiler/rustc_hir_analysis/src/outlives/implicit_infer.rs
@@ -24,8 +24,8 @@ pub(super) fn infer_predicates(
 
     // If new predicates were added then we need to re-calculate
     // all crates since there could be new implied predicates.
-    loop {
-        let mut predicates_added = false;
+    for i in 0.. {
+        let mut predicates_added = vec![];
 
         // Visit all the crates and infer predicates
         for id in tcx.hir_free_items() {
@@ -83,14 +83,27 @@ pub(super) fn infer_predicates(
                 .get(&item_did.to_def_id())
                 .map_or(0, |p| p.as_ref().skip_binder().len());
             if item_required_predicates.len() > item_predicates_len {
-                predicates_added = true;
+                predicates_added.push(item_did);
                 global_inferred_outlives
                     .insert(item_did.to_def_id(), ty::EarlyBinder::bind(item_required_predicates));
             }
         }
 
-        if !predicates_added {
+        if predicates_added.is_empty() {
+            // We've reached a fixed point.
             break;
+        } else if !tcx.recursion_limit().value_within_limit(i) {
+            let msg = if let &[id] = &predicates_added[..] {
+                format!("overflow computing implied lifetime bounds for `{}`", tcx.def_path_str(id),)
+            } else {
+                "overflow computing implied lifetime bounds".to_string()
+            };
+            tcx.dcx()
+                .struct_span_fatal(
+                    predicates_added.iter().map(|id| tcx.def_span(*id)).collect::<Vec<_>>(),
+                    msg,
+                )
+                .emit();
         }
     }
 
diff --git a/compiler/rustc_hir_analysis/src/outlives/utils.rs b/compiler/rustc_hir_analysis/src/outlives/utils.rs
index d0a2a2230ab..044fb64ca82 100644
--- a/compiler/rustc_hir_analysis/src/outlives/utils.rs
+++ b/compiler/rustc_hir_analysis/src/outlives/utils.rs
@@ -146,7 +146,7 @@ pub(crate) fn insert_outlives_predicate<'tcx>(
 
 fn is_free_region(region: Region<'_>) -> bool {
     // First, screen for regions that might appear in a type header.
-    match *region {
+    match region.kind() {
         // These correspond to `T: 'a` relationships:
         //
         //     struct Foo<'a, T> {
diff --git a/compiler/rustc_hir_analysis/src/variance/constraints.rs b/compiler/rustc_hir_analysis/src/variance/constraints.rs
index 8475903c68f..23223de918c 100644
--- a/compiler/rustc_hir_analysis/src/variance/constraints.rs
+++ b/compiler/rustc_hir_analysis/src/variance/constraints.rs
@@ -428,7 +428,7 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
         region: ty::Region<'tcx>,
         variance: VarianceTermPtr<'a>,
     ) {
-        match *region {
+        match region.kind() {
             ty::ReEarlyParam(ref data) => {
                 self.add_constraint(current, data.index, variance);
             }
diff --git a/compiler/rustc_hir_analysis/src/variance/mod.rs b/compiler/rustc_hir_analysis/src/variance/mod.rs
index 0800d99e945..dbba45dc7bb 100644
--- a/compiler/rustc_hir_analysis/src/variance/mod.rs
+++ b/compiler/rustc_hir_analysis/src/variance/mod.rs
@@ -44,13 +44,13 @@ fn variances_of(tcx: TyCtxt<'_>, item_def_id: LocalDefId) -> &[ty::Variance] {
         return &[];
     }
 
-    match tcx.def_kind(item_def_id) {
+    let kind = tcx.def_kind(item_def_id);
+    match kind {
         DefKind::Fn
         | DefKind::AssocFn
         | DefKind::Enum
         | DefKind::Struct
         | DefKind::Union
-        | DefKind::Variant
         | DefKind::Ctor(..) => {
             // These are inferred.
             let crate_map = tcx.crate_variances(());
@@ -89,7 +89,11 @@ fn variances_of(tcx: TyCtxt<'_>, item_def_id: LocalDefId) -> &[ty::Variance] {
     }
 
     // Variance not relevant.
-    span_bug!(tcx.def_span(item_def_id), "asked to compute variance for wrong kind of item");
+    span_bug!(
+        tcx.def_span(item_def_id),
+        "asked to compute variance for {}",
+        kind.descr(item_def_id.to_def_id())
+    );
 }
 
 #[derive(Debug, Copy, Clone)]
diff --git a/compiler/rustc_hir_pretty/src/lib.rs b/compiler/rustc_hir_pretty/src/lib.rs
index 865209b6a96..e5ab317685f 100644
--- a/compiler/rustc_hir_pretty/src/lib.rs
+++ b/compiler/rustc_hir_pretty/src/lib.rs
@@ -397,7 +397,7 @@ impl<'a> State<'a> {
                 self.pclose();
             }
             hir::TyKind::BareFn(f) => {
-                self.print_ty_fn(f.abi, f.safety, f.decl, None, f.generic_params, f.param_names);
+                self.print_ty_fn(f.abi, f.safety, f.decl, None, f.generic_params, f.param_idents);
             }
             hir::TyKind::UnsafeBinder(unsafe_binder) => {
                 self.print_unsafe_binder(unsafe_binder);
@@ -473,14 +473,14 @@ impl<'a> State<'a> {
         self.maybe_print_comment(item.span.lo());
         self.print_attrs_as_outer(self.attrs(item.hir_id()));
         match item.kind {
-            hir::ForeignItemKind::Fn(sig, arg_names, generics) => {
+            hir::ForeignItemKind::Fn(sig, arg_idents, generics) => {
                 self.head("");
                 self.print_fn(
                     sig.decl,
                     sig.header,
                     Some(item.ident.name),
                     generics,
-                    arg_names,
+                    arg_idents,
                     None,
                 );
                 self.end(); // end head-ibox
@@ -899,10 +899,10 @@ impl<'a> State<'a> {
         ident: Ident,
         m: &hir::FnSig<'_>,
         generics: &hir::Generics<'_>,
-        arg_names: &[Option<Ident>],
+        arg_idents: &[Option<Ident>],
         body_id: Option<hir::BodyId>,
     ) {
-        self.print_fn(m.decl, m.header, Some(ident.name), generics, arg_names, body_id);
+        self.print_fn(m.decl, m.header, Some(ident.name), generics, arg_idents, body_id);
     }
 
     fn print_trait_item(&mut self, ti: &hir::TraitItem<'_>) {
@@ -914,8 +914,8 @@ impl<'a> State<'a> {
             hir::TraitItemKind::Const(ty, default) => {
                 self.print_associated_const(ti.ident, ti.generics, ty, default);
             }
-            hir::TraitItemKind::Fn(ref sig, hir::TraitFn::Required(arg_names)) => {
-                self.print_method_sig(ti.ident, sig, ti.generics, arg_names, None);
+            hir::TraitItemKind::Fn(ref sig, hir::TraitFn::Required(arg_idents)) => {
+                self.print_method_sig(ti.ident, sig, ti.generics, arg_idents, None);
                 self.word(";");
             }
             hir::TraitItemKind::Fn(ref sig, hir::TraitFn::Provided(body)) => {
@@ -2122,7 +2122,7 @@ impl<'a> State<'a> {
         header: hir::FnHeader,
         name: Option<Symbol>,
         generics: &hir::Generics<'_>,
-        arg_names: &[Option<Ident>],
+        arg_idents: &[Option<Ident>],
         body_id: Option<hir::BodyId>,
     ) {
         self.print_fn_header_info(header);
@@ -2134,16 +2134,16 @@ impl<'a> State<'a> {
         self.print_generic_params(generics.params);
 
         self.popen();
-        // Make sure we aren't supplied *both* `arg_names` and `body_id`.
-        assert!(arg_names.is_empty() || body_id.is_none());
+        // Make sure we aren't supplied *both* `arg_idents` and `body_id`.
+        assert!(arg_idents.is_empty() || body_id.is_none());
         let mut i = 0;
         let mut print_arg = |s: &mut Self, ty: Option<&hir::Ty<'_>>| {
             if i == 0 && decl.implicit_self.has_implicit_self() {
                 s.print_implicit_self(&decl.implicit_self);
             } else {
-                if let Some(arg_name) = arg_names.get(i) {
-                    if let Some(arg_name) = arg_name {
-                        s.word(arg_name.to_string());
+                if let Some(arg_ident) = arg_idents.get(i) {
+                    if let Some(arg_ident) = arg_ident {
+                        s.word(arg_ident.to_string());
                         s.word(":");
                         s.space();
                     }
@@ -2452,7 +2452,7 @@ impl<'a> State<'a> {
         decl: &hir::FnDecl<'_>,
         name: Option<Symbol>,
         generic_params: &[hir::GenericParam<'_>],
-        arg_names: &[Option<Ident>],
+        arg_idents: &[Option<Ident>],
     ) {
         self.ibox(INDENT_UNIT);
         self.print_formal_generic_params(generic_params);
@@ -2467,7 +2467,7 @@ impl<'a> State<'a> {
             },
             name,
             generics,
-            arg_names,
+            arg_idents,
             None,
         );
         self.end();
diff --git a/compiler/rustc_hir_typeck/messages.ftl b/compiler/rustc_hir_typeck/messages.ftl
index 872861d6289..9e1b70f5767 100644
--- a/compiler/rustc_hir_typeck/messages.ftl
+++ b/compiler/rustc_hir_typeck/messages.ftl
@@ -148,7 +148,7 @@ hir_typeck_never_type_fallback_flowing_into_unsafe_path = never type fallback af
 hir_typeck_never_type_fallback_flowing_into_unsafe_union_field = never type fallback affects this union access
     .help = specify the type explicitly
 
-hir_typeck_no_associated_item = no {$item_kind} named `{$item_name}` found for {$ty_prefix} `{$ty_str}`{$trait_missing_method ->
+hir_typeck_no_associated_item = no {$item_kind} named `{$item_ident}` found for {$ty_prefix} `{$ty_str}`{$trait_missing_method ->
     [true] {""}
     *[other] {" "}in the current scope
 }
diff --git a/compiler/rustc_hir_typeck/src/errors.rs b/compiler/rustc_hir_typeck/src/errors.rs
index b73cd26927a..dfaa374592b 100644
--- a/compiler/rustc_hir_typeck/src/errors.rs
+++ b/compiler/rustc_hir_typeck/src/errors.rs
@@ -727,7 +727,7 @@ pub(crate) struct NoAssociatedItem {
     #[primary_span]
     pub span: Span,
     pub item_kind: &'static str,
-    pub item_name: Ident,
+    pub item_ident: Ident,
     pub ty_prefix: Cow<'static, str>,
     pub ty_str: String,
     pub trait_missing_method: bool,
diff --git a/compiler/rustc_hir_typeck/src/expr.rs b/compiler/rustc_hir_typeck/src/expr.rs
index 952a2e231e4..de2f039cb1c 100644
--- a/compiler/rustc_hir_typeck/src/expr.rs
+++ b/compiler/rustc_hir_typeck/src/expr.rs
@@ -2205,8 +2205,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 let fields = listify(&missing_mandatory_fields, |f| format!("`{f}`")).unwrap();
                 self.dcx()
                     .struct_span_err(
-                        span.shrink_to_hi(),
-                        format!("missing mandatory field{s} {fields}"),
+                        span.shrink_to_lo(),
+                        format!("missing field{s} {fields} in initializer"),
+                    )
+                    .with_span_label(
+                        span.shrink_to_lo(),
+                        "fields that do not have a defaulted value must be provided explicitly",
                     )
                     .emit();
                 return;
@@ -2916,8 +2920,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         }
         // We failed to check the expression, report an error.
 
-        // Emits an error if we deref an infer variable, like calling `.field` on a base type of &_.
-        self.structurally_resolve_type(autoderef.span(), autoderef.final_ty(false));
+        // Emits an error if we deref an infer variable, like calling `.field` on a base type
+        // of `&_`. We can also use this to suppress unnecessary "missing field" errors that
+        // will follow ambiguity errors.
+        let final_ty = self.structurally_resolve_type(autoderef.span(), autoderef.final_ty(false));
+        if let ty::Error(_) = final_ty.kind() {
+            return final_ty;
+        }
 
         if let Some((adjustments, did)) = private_candidate {
             // (#90483) apply adjustments to avoid ExprUseVisitor from
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
index f4bd7ec701f..81eb8510785 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
@@ -1136,7 +1136,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 && let self_implicit =
                     matches!(call_expr.kind, hir::ExprKind::MethodCall(..)) as usize
                 && let Some(Some(arg)) =
-                    self.tcx.fn_arg_names(fn_def_id).get(expected_idx.as_usize() + self_implicit)
+                    self.tcx.fn_arg_idents(fn_def_id).get(expected_idx.as_usize() + self_implicit)
                 && arg.name != kw::SelfLower
             {
                 format!("/* {} */", arg.name)
@@ -2619,7 +2619,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         is_method: bool,
     ) -> Option<(IndexVec<ExpectedIdx, (Option<GenericIdx>, FnParam<'_>)>, &hir::Generics<'_>)>
     {
-        let (sig, generics, body_id, param_names) = match self.tcx.hir_get_if_local(def_id)? {
+        let (sig, generics, body_id, params) = match self.tcx.hir_get_if_local(def_id)? {
             hir::Node::TraitItem(&hir::TraitItem {
                 generics,
                 kind: hir::TraitItemKind::Fn(sig, trait_fn),
@@ -2661,7 +2661,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 None
             }
         });
-        match (body_id, param_names) {
+        match (body_id, params) {
             (Some(_), Some(_)) | (None, None) => unreachable!(),
             (Some(body), None) => {
                 let params = self.tcx.hir_body(body).params;
@@ -2678,7 +2678,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     params.get(is_method as usize..params.len() - sig.decl.c_variadic as usize)?;
                 debug_assert_eq!(params.len(), fn_inputs.len());
                 Some((
-                    fn_inputs.zip(params.iter().map(|&ident| FnParam::Name(ident))).collect(),
+                    fn_inputs.zip(params.iter().map(|&ident| FnParam::Ident(ident))).collect(),
                     generics,
                 ))
             }
@@ -2709,14 +2709,14 @@ impl<'tcx> Visitor<'tcx> for FindClosureArg<'tcx> {
 #[derive(Clone, Copy)]
 enum FnParam<'hir> {
     Param(&'hir hir::Param<'hir>),
-    Name(Option<Ident>),
+    Ident(Option<Ident>),
 }
 
 impl FnParam<'_> {
     fn span(&self) -> Span {
         match self {
             Self::Param(param) => param.span,
-            Self::Name(ident) => {
+            Self::Ident(ident) => {
                 if let Some(ident) = ident {
                     ident.span
                 } else {
@@ -2738,7 +2738,7 @@ impl FnParam<'_> {
                     {
                         Some(ident.name)
                     }
-                    FnParam::Name(ident)
+                    FnParam::Ident(ident)
                         if let Some(ident) = ident
                             && ident.name != kw::Underscore =>
                     {
diff --git a/compiler/rustc_hir_typeck/src/method/mod.rs b/compiler/rustc_hir_typeck/src/method/mod.rs
index 4008021c3a8..ddfd27ccf6b 100644
--- a/compiler/rustc_hir_typeck/src/method/mod.rs
+++ b/compiler/rustc_hir_typeck/src/method/mod.rs
@@ -534,12 +534,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         Ok((def_kind, pick.item.def_id))
     }
 
-    /// Finds item with name `item_name` defined in impl/trait `def_id`
+    /// Finds item with name `item_ident` defined in impl/trait `def_id`
     /// and return it, or `None`, if no such item was defined there.
-    fn associated_value(&self, def_id: DefId, item_name: Ident) -> Option<ty::AssocItem> {
+    fn associated_value(&self, def_id: DefId, item_ident: Ident) -> Option<ty::AssocItem> {
         self.tcx
             .associated_items(def_id)
-            .find_by_name_and_namespace(self.tcx, item_name, Namespace::ValueNS, def_id)
+            .find_by_ident_and_namespace(self.tcx, item_ident, Namespace::ValueNS, def_id)
             .copied()
     }
 }
diff --git a/compiler/rustc_hir_typeck/src/method/suggest.rs b/compiler/rustc_hir_typeck/src/method/suggest.rs
index 246b23f11b6..68f13d654d6 100644
--- a/compiler/rustc_hir_typeck/src/method/suggest.rs
+++ b/compiler/rustc_hir_typeck/src/method/suggest.rs
@@ -25,6 +25,7 @@ use rustc_middle::bug;
 use rustc_middle::ty::fast_reject::{DeepRejectCtxt, TreatParams, simplify_type};
 use rustc_middle::ty::print::{
     PrintTraitRefExt as _, with_crate_prefix, with_forced_trimmed_paths,
+    with_no_visible_paths_if_doc_hidden,
 };
 use rustc_middle::ty::{self, GenericArgKind, IsSuggestable, Ty, TyCtxt, TypeVisitableExt};
 use rustc_span::def_id::DefIdSet;
@@ -584,7 +585,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         &self,
         mut span: Span,
         rcvr_ty: Ty<'tcx>,
-        item_name: Ident,
+        item_ident: Ident,
         expr_id: hir::HirId,
         source: SelfSource<'tcx>,
         args: Option<&'tcx [hir::Expr<'tcx>]>,
@@ -615,7 +616,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         } else if rcvr_ty.is_enum() {
             "variant or associated item"
         } else {
-            match (item_name.as_str().chars().next(), rcvr_ty.is_fresh_ty()) {
+            match (item_ident.as_str().chars().next(), rcvr_ty.is_fresh_ty()) {
                 (Some(name), false) if name.is_lowercase() => "function or associated item",
                 (Some(_), false) => "associated item",
                 (Some(_), true) | (None, false) => "variant or associated item",
@@ -630,7 +631,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             rcvr_ty,
             source,
             span,
-            item_name,
+            item_ident,
             &short_ty_str,
             &mut ty_file,
         ) {
@@ -642,13 +643,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             source,
             span,
             item_kind,
-            item_name,
+            item_ident,
             &short_ty_str,
             &mut ty_file,
         ) {
             return guar;
         }
-        span = item_name.span;
+        span = item_ident.span;
 
         // Don't show generic arguments when the method can't be found in any implementation (#81576).
         let mut ty_str_reported = ty_str.clone();
@@ -660,7 +661,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         self.tcx
                             .inherent_impls(adt_def.did())
                             .into_iter()
-                            .any(|def_id| self.associated_value(*def_id, item_name).is_some())
+                            .any(|def_id| self.associated_value(*def_id, item_ident).is_some())
                     } else {
                         false
                     }
@@ -677,14 +678,14 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let is_write = sugg_span.ctxt().outer_expn_data().macro_def_id.is_some_and(|def_id| {
             tcx.is_diagnostic_item(sym::write_macro, def_id)
                 || tcx.is_diagnostic_item(sym::writeln_macro, def_id)
-        }) && item_name.name == sym::write_fmt;
+        }) && item_ident.name == sym::write_fmt;
         let mut err = if is_write && let SelfSource::MethodCall(rcvr_expr) = source {
             self.suggest_missing_writer(rcvr_ty, rcvr_expr)
         } else {
             let mut err = self.dcx().create_err(NoAssociatedItem {
                 span,
                 item_kind,
-                item_name,
+                item_ident,
                 ty_prefix: if trait_missing_method {
                     // FIXME(mu001999) E0599 maybe not suitable here because it is for types
                     Cow::from("trait")
@@ -698,7 +699,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             if is_method {
                 self.suggest_use_shadowed_binding_with_method(
                     source,
-                    item_name,
+                    item_ident,
                     &ty_str_reported,
                     &mut err,
                 );
@@ -709,9 +710,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 && let hir::TyKind::Path(hir::QPath::Resolved(_, path)) = ty.kind
                 && let Res::SelfTyAlias { alias_to: impl_def_id, .. } = path.res
                 && let DefKind::Impl { .. } = self.tcx.def_kind(impl_def_id)
-                && let Some(candidate) = tcx.associated_items(impl_def_id).find_by_name_and_kind(
+                && let Some(candidate) = tcx.associated_items(impl_def_id).find_by_ident_and_kind(
                     self.tcx,
-                    item_name,
+                    item_ident,
                     ty::AssocKind::Type,
                     impl_def_id,
                 )
@@ -721,7 +722,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             {
                 let def_path = tcx.def_path_str(adt_def.did());
                 err.span_suggestion(
-                    ty.span.to(item_name.span),
+                    ty.span.to(item_ident.span),
                     format!("to construct a value of type `{}`, use the explicit path", def_path),
                     def_path,
                     Applicability::MachineApplicable,
@@ -749,7 +750,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             self.find_builder_fn(&mut err, rcvr_ty, expr_id);
         }
 
-        if tcx.ty_is_opaque_future(rcvr_ty) && item_name.name == sym::poll {
+        if tcx.ty_is_opaque_future(rcvr_ty) && item_ident.name == sym::poll {
             err.help(format!(
                 "method `poll` found on `Pin<&mut {ty_str}>`, \
                 see documentation for `std::pin::Pin`"
@@ -764,7 +765,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         {
             self.suggest_await_before_method(
                 &mut err,
-                item_name,
+                item_ident,
                 rcvr_ty,
                 cal,
                 span,
@@ -786,7 +787,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         if let SelfSource::MethodCall(rcvr_expr) = source
             && let ty::RawPtr(ty, ptr_mutbl) = *rcvr_ty.kind()
             && let Ok(pick) = self.lookup_probe_for_diagnostic(
-                item_name,
+                item_ident,
                 Ty::new_ref(tcx, ty::Region::new_error_misc(tcx), ty, ptr_mutbl),
                 self.tcx.hir_expect_expr(self.tcx.parent_hir_id(rcvr_expr.hir_id)),
                 ProbeScope::TraitsInScope,
@@ -807,7 +808,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             };
             err.span_note(
                 tcx.def_span(pick.item.def_id),
-                format!("the method `{item_name}` exists on the type `{ty}`", ty = pick.self_ty),
+                format!("the method `{item_ident}` exists on the type `{ty}`", ty = pick.self_ty),
             );
             let mut_str = ptr_mutbl.ptr_str();
             err.note(format!(
@@ -833,7 +834,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             self.suggest_fn_call(&mut err, rcvr_expr, rcvr_ty, |output_ty| {
                 let call_expr = self.tcx.hir_expect_expr(self.tcx.parent_hir_id(rcvr_expr.hir_id));
                 let probe = self.lookup_probe_for_diagnostic(
-                    item_name,
+                    item_ident,
                     output_ty,
                     call_expr,
                     ProbeScope::AllTraits,
@@ -872,13 +873,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 static_candidates,
                 rcvr_ty,
                 source,
-                item_name,
+                item_ident,
                 args,
                 sugg_span,
             );
             self.note_candidates_on_method_error(
                 rcvr_ty,
-                item_name,
+                item_ident,
                 source,
                 args,
                 span,
@@ -889,7 +890,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         } else if static_candidates.len() > 1 {
             self.note_candidates_on_method_error(
                 rcvr_ty,
-                item_name,
+                item_ident,
                 source,
                 args,
                 span,
@@ -903,7 +904,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let mut restrict_type_params = false;
         let mut suggested_derive = false;
         let mut unsatisfied_bounds = false;
-        if item_name.name == sym::count && self.is_slice_ty(rcvr_ty, span) {
+        if item_ident.name == sym::count && self.is_slice_ty(rcvr_ty, span) {
             let msg = "consider using `len` instead";
             if let SelfSource::MethodCall(_expr) = source {
                 err.span_suggestion_short(span, msg, "len", Applicability::MachineApplicable);
@@ -1348,7 +1349,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 };
                 let primary_message = primary_message.unwrap_or_else(|| {
                     format!(
-                        "the {item_kind} `{item_name}` exists for {actual_prefix} `{ty_str}`, \
+                        "the {item_kind} `{item_ident}` exists for {actual_prefix} `{ty_str}`, \
                          but its trait bounds were not satisfied"
                     )
                 });
@@ -1378,7 +1379,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // `Pin<&Self>`.
             if targs.len() == 1 {
                 let mut item_segment = hir::PathSegment::invalid();
-                item_segment.ident = item_name;
+                item_segment.ident = item_ident;
                 for t in [Ty::new_mut_ref, Ty::new_imm_ref, |_, _, t| t] {
                     let new_args =
                         tcx.mk_args_from_iter(targs.iter().map(|arg| match arg.as_type() {
@@ -1422,9 +1423,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     ty::Adt(adt, _) => self.tcx.is_lang_item(adt.did(), LangItem::String),
                     _ => false,
                 };
-                if is_string_or_ref_str && item_name.name == sym::iter {
+                if is_string_or_ref_str && item_ident.name == sym::iter {
                     err.span_suggestion_verbose(
-                        item_name.span,
+                        item_ident.span,
                         "because of the in-memory representation of `&str`, to obtain \
                          an `Iterator` over each of its codepoint use method `chars`",
                         "chars",
@@ -1438,7 +1439,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         .into_iter()
                         .copied()
                         .filter(|def_id| {
-                            if let Some(assoc) = self.associated_value(*def_id, item_name) {
+                            if let Some(assoc) = self.associated_value(*def_id, item_ident) {
                                 // Check for both mode is the same so we avoid suggesting
                                 // incorrect associated item.
                                 match (mode, assoc.fn_has_self_parameter, source) {
@@ -1499,7 +1500,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // If the method name is the name of a field with a function or closure type,
         // give a helping note that it has to be called as `(x.f)(...)`.
         if let SelfSource::MethodCall(expr) = source {
-            if !self.suggest_calling_field_as_fn(span, rcvr_ty, expr, item_name, &mut err)
+            if !self.suggest_calling_field_as_fn(span, rcvr_ty, expr, item_ident, &mut err)
                 && similar_candidate.is_none()
                 && !custom_span_label
             {
@@ -1512,7 +1513,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let confusable_suggested = self.confusable_method_name(
             &mut err,
             rcvr_ty,
-            item_name,
+            item_ident,
             args.map(|args| {
                 args.iter()
                     .map(|expr| {
@@ -1530,12 +1531,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 source,
                 span,
                 rcvr_ty,
-                item_name,
+                item_ident,
                 expected.only_has_type(self),
             );
         }
 
-        self.suggest_unwrapping_inner_self(&mut err, source, rcvr_ty, item_name);
+        self.suggest_unwrapping_inner_self(&mut err, source, rcvr_ty, item_ident);
 
         for (span, mut bounds) in bound_spans {
             if !tcx.sess.source_map().is_span_accessible(span) {
@@ -1546,7 +1547,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             let pre = if Some(span) == ty_span {
                 ty_span.take();
                 format!(
-                    "{item_kind} `{item_name}` not found for this {} because it ",
+                    "{item_kind} `{item_ident}` not found for this {} because it ",
                     rcvr_ty.prefix_string(self.tcx)
                 )
             } else {
@@ -1566,7 +1567,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             err.span_label(
                 span,
                 format!(
-                    "{item_kind} `{item_name}` not found for this {}",
+                    "{item_kind} `{item_ident}` not found for this {}",
                     rcvr_ty.prefix_string(self.tcx)
                 ),
             );
@@ -1578,7 +1579,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 &mut err,
                 span,
                 rcvr_ty,
-                item_name,
+                item_ident,
                 args.map(|args| args.len() + 1),
                 source,
                 no_match_data.out_of_scope_traits.clone(),
@@ -1595,7 +1596,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             let adt_def = rcvr_ty.ty_adt_def().expect("enum is not an ADT");
             if let Some(var_name) = edit_distance::find_best_match_for_name(
                 &adt_def.variants().iter().map(|s| s.name).collect::<Vec<_>>(),
-                item_name.name,
+                item_ident.name,
                 None,
             ) && let Some(variant) = adt_def.variants().iter().find(|s| s.name == var_name)
             {
@@ -1736,14 +1737,14 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         if !find_candidate_for_method {
             self.lookup_segments_chain_for_no_match_method(
                 &mut err,
-                item_name,
+                item_ident,
                 item_kind,
                 source,
                 no_match_data,
             );
         }
 
-        self.note_derefed_ty_has_method(&mut err, source, rcvr_ty, item_name, expected);
+        self.note_derefed_ty_has_method(&mut err, source, rcvr_ty, item_ident, expected);
         err.emit()
     }
 
@@ -3328,7 +3329,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             let path_strings = candidates.iter().map(|trait_did| {
                 format!(
                     "{prefix}{}{postfix}\n",
-                    with_crate_prefix!(self.tcx.def_path_str(*trait_did)),
+                    with_no_visible_paths_if_doc_hidden!(with_crate_prefix!(
+                        self.tcx.def_path_str(*trait_did)
+                    )),
                 )
             });
 
@@ -3336,7 +3339,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 let parent_did = parent_map.get(trait_did).unwrap();
                 format!(
                     "{prefix}{}::*{postfix} // trait {}\n",
-                    with_crate_prefix!(self.tcx.def_path_str(*parent_did)),
+                    with_no_visible_paths_if_doc_hidden!(with_crate_prefix!(
+                        self.tcx.def_path_str(*parent_did)
+                    )),
                     self.tcx.item_name(*trait_did),
                 )
             });
diff --git a/compiler/rustc_hir_typeck/src/pat.rs b/compiler/rustc_hir_typeck/src/pat.rs
index 8641348bffb..fbc783c0509 100644
--- a/compiler/rustc_hir_typeck/src/pat.rs
+++ b/compiler/rustc_hir_typeck/src/pat.rs
@@ -163,9 +163,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 enum AdjustMode {
     /// Peel off all immediate reference types.
     Peel,
-    /// Reset binding mode to the initial mode.
-    /// Used for destructuring assignment, where we don't want any match ergonomics.
-    Reset,
     /// Pass on the input binding mode and expected type.
     Pass,
 }
@@ -321,77 +318,14 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     /// Conversely, inside this module, `check_pat_top` should never be used.
     #[instrument(level = "debug", skip(self, pat_info))]
     fn check_pat(&self, pat: &'tcx Pat<'tcx>, expected: Ty<'tcx>, pat_info: PatInfo<'tcx>) {
-        let PatInfo { binding_mode, max_ref_mutbl, top_info: ti, current_depth, .. } = pat_info;
-
-        let path_res = match pat.kind {
+        let opt_path_res = match pat.kind {
             PatKind::Expr(PatExpr { kind: PatExprKind::Path(qpath), hir_id, span }) => {
                 Some(self.resolve_ty_and_res_fully_qualified_call(qpath, *hir_id, *span))
             }
             _ => None,
         };
-        let adjust_mode = self.calc_adjust_mode(pat, path_res.map(|(res, ..)| res));
-        let (expected, binding_mode, max_ref_mutbl) =
-            self.calc_default_binding_mode(pat, expected, binding_mode, adjust_mode, max_ref_mutbl);
-        let pat_info = PatInfo {
-            binding_mode,
-            max_ref_mutbl,
-            top_info: ti,
-            decl_origin: pat_info.decl_origin,
-            current_depth: current_depth + 1,
-        };
-
-        let ty = match pat.kind {
-            PatKind::Missing | PatKind::Wild | PatKind::Err(_) => expected,
-            // We allow any type here; we ensure that the type is uninhabited during match checking.
-            PatKind::Never => expected,
-            PatKind::Expr(PatExpr { kind: PatExprKind::Path(qpath), hir_id, span }) => {
-                let ty = self.check_pat_path(
-                    *hir_id,
-                    pat.hir_id,
-                    *span,
-                    qpath,
-                    path_res.unwrap(),
-                    expected,
-                    &pat_info.top_info,
-                );
-                self.write_ty(*hir_id, ty);
-                ty
-            }
-            PatKind::Expr(lt) => self.check_pat_lit(pat.span, lt, expected, &pat_info.top_info),
-            PatKind::Range(lhs, rhs, _) => {
-                self.check_pat_range(pat.span, lhs, rhs, expected, &pat_info.top_info)
-            }
-            PatKind::Binding(ba, var_id, ident, sub) => {
-                self.check_pat_ident(pat, ba, var_id, ident, sub, expected, pat_info)
-            }
-            PatKind::TupleStruct(ref qpath, subpats, ddpos) => {
-                self.check_pat_tuple_struct(pat, qpath, subpats, ddpos, expected, pat_info)
-            }
-            PatKind::Struct(ref qpath, fields, has_rest_pat) => {
-                self.check_pat_struct(pat, qpath, fields, has_rest_pat, expected, pat_info)
-            }
-            PatKind::Guard(pat, cond) => {
-                self.check_pat(pat, expected, pat_info);
-                self.check_expr_has_type_or_error(cond, self.tcx.types.bool, |_| {});
-                expected
-            }
-            PatKind::Or(pats) => {
-                for pat in pats {
-                    self.check_pat(pat, expected, pat_info);
-                }
-                expected
-            }
-            PatKind::Tuple(elements, ddpos) => {
-                self.check_pat_tuple(pat.span, elements, ddpos, expected, pat_info)
-            }
-            PatKind::Box(inner) => self.check_pat_box(pat.span, inner, expected, pat_info),
-            PatKind::Deref(inner) => self.check_pat_deref(pat.span, inner, expected, pat_info),
-            PatKind::Ref(inner, mutbl) => self.check_pat_ref(pat, inner, mutbl, expected, pat_info),
-            PatKind::Slice(before, slice, after) => {
-                self.check_pat_slice(pat.span, before, slice, after, expected, pat_info)
-            }
-        };
-
+        let adjust_mode = self.calc_adjust_mode(pat, opt_path_res.map(|(res, ..)| res));
+        let ty = self.check_pat_inner(pat, opt_path_res, adjust_mode, expected, pat_info);
         self.write_ty(pat.hir_id, ty);
 
         // (note_1): In most of the cases where (note_1) is referenced
@@ -437,27 +371,126 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // `regions-relate-bound-regions-on-closures-to-inference-variables.rs`,
     }
 
-    /// Compute the new expected type and default binding mode from the old ones
-    /// as well as the pattern form we are currently checking.
-    fn calc_default_binding_mode(
+    // Helper to avoid resolving the same path pattern several times.
+    fn check_pat_inner(
         &self,
         pat: &'tcx Pat<'tcx>,
-        expected: Ty<'tcx>,
-        def_br: ByRef,
+        opt_path_res: Option<(Res, Option<LoweredTy<'tcx>>, &'tcx [hir::PathSegment<'tcx>])>,
         adjust_mode: AdjustMode,
-        max_ref_mutbl: MutblCap,
-    ) -> (Ty<'tcx>, ByRef, MutblCap) {
+        expected: Ty<'tcx>,
+        pat_info: PatInfo<'tcx>,
+    ) -> Ty<'tcx> {
         #[cfg(debug_assertions)]
-        if def_br == ByRef::Yes(Mutability::Mut)
-            && max_ref_mutbl != MutblCap::Mut
+        if pat_info.binding_mode == ByRef::Yes(Mutability::Mut)
+            && pat_info.max_ref_mutbl != MutblCap::Mut
             && self.downgrade_mut_inside_shared()
         {
             span_bug!(pat.span, "Pattern mutability cap violated!");
         }
-        match adjust_mode {
-            AdjustMode::Pass => (expected, def_br, max_ref_mutbl),
-            AdjustMode::Reset => (expected, ByRef::No, MutblCap::Mut),
-            AdjustMode::Peel => self.peel_off_references(pat, expected, def_br, max_ref_mutbl),
+
+        // Resolve type if needed.
+        let expected = if let AdjustMode::Peel = adjust_mode
+            && pat.default_binding_modes
+        {
+            self.try_structurally_resolve_type(pat.span, expected)
+        } else {
+            expected
+        };
+        let old_pat_info = pat_info;
+        let pat_info = PatInfo { current_depth: old_pat_info.current_depth + 1, ..old_pat_info };
+
+        match pat.kind {
+            // Peel off a `&` or `&mut` from the scrutinee type. See the examples in
+            // `tests/ui/rfcs/rfc-2005-default-binding-mode`.
+            _ if let AdjustMode::Peel = adjust_mode
+                && pat.default_binding_modes
+                && let ty::Ref(_, inner_ty, inner_mutability) = *expected.kind() =>
+            {
+                debug!("inspecting {:?}", expected);
+
+                debug!("current discriminant is Ref, inserting implicit deref");
+                // Preserve the reference type. We'll need it later during THIR lowering.
+                self.typeck_results
+                    .borrow_mut()
+                    .pat_adjustments_mut()
+                    .entry(pat.hir_id)
+                    .or_default()
+                    .push(expected);
+
+                let mut binding_mode = ByRef::Yes(match pat_info.binding_mode {
+                    // If default binding mode is by value, make it `ref` or `ref mut`
+                    // (depending on whether we observe `&` or `&mut`).
+                    ByRef::No |
+                    // When `ref mut`, stay a `ref mut` (on `&mut`) or downgrade to `ref` (on `&`).
+                    ByRef::Yes(Mutability::Mut) => inner_mutability,
+                    // Once a `ref`, always a `ref`.
+                    // This is because a `& &mut` cannot mutate the underlying value.
+                    ByRef::Yes(Mutability::Not) => Mutability::Not,
+                });
+
+                let mut max_ref_mutbl = pat_info.max_ref_mutbl;
+                if self.downgrade_mut_inside_shared() {
+                    binding_mode = binding_mode.cap_ref_mutability(max_ref_mutbl.as_mutbl());
+                }
+                if binding_mode == ByRef::Yes(Mutability::Not) {
+                    max_ref_mutbl = MutblCap::Not;
+                }
+                debug!("default binding mode is now {:?}", binding_mode);
+
+                // Use the old pat info to keep `current_depth` to its old value.
+                let new_pat_info = PatInfo { binding_mode, max_ref_mutbl, ..old_pat_info };
+                // Recurse with the new expected type.
+                self.check_pat_inner(pat, opt_path_res, adjust_mode, inner_ty, new_pat_info)
+            }
+            PatKind::Missing | PatKind::Wild | PatKind::Err(_) => expected,
+            // We allow any type here; we ensure that the type is uninhabited during match checking.
+            PatKind::Never => expected,
+            PatKind::Expr(PatExpr { kind: PatExprKind::Path(qpath), hir_id, span }) => {
+                let ty = self.check_pat_path(
+                    *hir_id,
+                    pat.hir_id,
+                    *span,
+                    qpath,
+                    opt_path_res.unwrap(),
+                    expected,
+                    &pat_info.top_info,
+                );
+                self.write_ty(*hir_id, ty);
+                ty
+            }
+            PatKind::Expr(lt) => self.check_pat_lit(pat.span, lt, expected, &pat_info.top_info),
+            PatKind::Range(lhs, rhs, _) => {
+                self.check_pat_range(pat.span, lhs, rhs, expected, &pat_info.top_info)
+            }
+            PatKind::Binding(ba, var_id, ident, sub) => {
+                self.check_pat_ident(pat, ba, var_id, ident, sub, expected, pat_info)
+            }
+            PatKind::TupleStruct(ref qpath, subpats, ddpos) => {
+                self.check_pat_tuple_struct(pat, qpath, subpats, ddpos, expected, pat_info)
+            }
+            PatKind::Struct(ref qpath, fields, has_rest_pat) => {
+                self.check_pat_struct(pat, qpath, fields, has_rest_pat, expected, pat_info)
+            }
+            PatKind::Guard(pat, cond) => {
+                self.check_pat(pat, expected, pat_info);
+                self.check_expr_has_type_or_error(cond, self.tcx.types.bool, |_| {});
+                expected
+            }
+            PatKind::Or(pats) => {
+                for pat in pats {
+                    self.check_pat(pat, expected, pat_info);
+                }
+                expected
+            }
+            PatKind::Tuple(elements, ddpos) => {
+                self.check_pat_tuple(pat.span, elements, ddpos, expected, pat_info)
+            }
+            PatKind::Box(inner) => self.check_pat_box(pat.span, inner, expected, pat_info),
+            PatKind::Deref(inner) => self.check_pat_deref(pat.span, inner, expected, pat_info),
+            PatKind::Ref(inner, mutbl) => self.check_pat_ref(pat, inner, mutbl, expected, pat_info),
+            PatKind::Slice(before, slice, after) => {
+                self.check_pat_slice(pat.span, before, slice, after, expected, pat_info)
+            }
         }
     }
 
@@ -465,11 +498,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     ///
     /// When the pattern is a path pattern, `opt_path_res` must be `Some(res)`.
     fn calc_adjust_mode(&self, pat: &'tcx Pat<'tcx>, opt_path_res: Option<Res>) -> AdjustMode {
-        // When we perform destructuring assignment, we disable default match bindings, which are
-        // unintuitive in this context.
-        if !pat.default_binding_modes {
-            return AdjustMode::Reset;
-        }
         match &pat.kind {
             // Type checking these product-like types successfully always require
             // that the expected type be of those types and not reference types.
@@ -526,64 +554,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         }
     }
 
-    /// Peel off as many immediately nested `& mut?` from the expected type as possible
-    /// and return the new expected type and binding default binding mode.
-    /// The adjustments vector, if non-empty is stored in a table.
-    fn peel_off_references(
-        &self,
-        pat: &'tcx Pat<'tcx>,
-        expected: Ty<'tcx>,
-        mut def_br: ByRef,
-        mut max_ref_mutbl: MutblCap,
-    ) -> (Ty<'tcx>, ByRef, MutblCap) {
-        let mut expected = self.try_structurally_resolve_type(pat.span, expected);
-        // Peel off as many `&` or `&mut` from the scrutinee type as possible. For example,
-        // for `match &&&mut Some(5)` the loop runs three times, aborting when it reaches
-        // the `Some(5)` which is not of type Ref.
-        //
-        // For each ampersand peeled off, update the binding mode and push the original
-        // type into the adjustments vector.
-        //
-        // See the examples in `ui/match-defbm*.rs`.
-        let mut pat_adjustments = vec![];
-        while let ty::Ref(_, inner_ty, inner_mutability) = *expected.kind() {
-            debug!("inspecting {:?}", expected);
-
-            debug!("current discriminant is Ref, inserting implicit deref");
-            // Preserve the reference type. We'll need it later during THIR lowering.
-            pat_adjustments.push(expected);
-
-            expected = self.try_structurally_resolve_type(pat.span, inner_ty);
-            def_br = ByRef::Yes(match def_br {
-                // If default binding mode is by value, make it `ref` or `ref mut`
-                // (depending on whether we observe `&` or `&mut`).
-                ByRef::No |
-                // When `ref mut`, stay a `ref mut` (on `&mut`) or downgrade to `ref` (on `&`).
-                ByRef::Yes(Mutability::Mut) => inner_mutability,
-                // Once a `ref`, always a `ref`.
-                // This is because a `& &mut` cannot mutate the underlying value.
-                ByRef::Yes(Mutability::Not) => Mutability::Not,
-            });
-        }
-
-        if self.downgrade_mut_inside_shared() {
-            def_br = def_br.cap_ref_mutability(max_ref_mutbl.as_mutbl());
-        }
-        if def_br == ByRef::Yes(Mutability::Not) {
-            max_ref_mutbl = MutblCap::Not;
-        }
-
-        if !pat_adjustments.is_empty() {
-            debug!("default binding mode is now {:?}", def_br);
-            self.typeck_results
-                .borrow_mut()
-                .pat_adjustments_mut()
-                .insert(pat.hir_id, pat_adjustments);
-        }
-
-        (expected, def_br, max_ref_mutbl)
-    }
-
     fn check_pat_expr_unadjusted(&self, lt: &'tcx hir::PatExpr<'tcx>) -> Ty<'tcx> {
         let ty = match &lt.kind {
             rustc_hir::PatExprKind::Lit { lit, negated } => {
diff --git a/compiler/rustc_infer/src/infer/canonical/canonicalizer.rs b/compiler/rustc_infer/src/infer/canonical/canonicalizer.rs
index 307110d9fbc..a1a0926cd81 100644
--- a/compiler/rustc_infer/src/infer/canonical/canonicalizer.rs
+++ b/compiler/rustc_infer/src/infer/canonical/canonicalizer.rs
@@ -159,7 +159,7 @@ impl CanonicalizeMode for CanonicalizeQueryResponse {
     ) -> ty::Region<'tcx> {
         let infcx = canonicalizer.infcx.unwrap();
 
-        if let ty::ReVar(vid) = *r {
+        if let ty::ReVar(vid) = r.kind() {
             r = infcx
                 .inner
                 .borrow_mut()
@@ -171,7 +171,7 @@ impl CanonicalizeMode for CanonicalizeQueryResponse {
             );
         };
 
-        match *r {
+        match r.kind() {
             ty::ReLateParam(_) | ty::ReErased | ty::ReStatic | ty::ReEarlyParam(..) => r,
 
             ty::RePlaceholder(placeholder) => canonicalizer.canonical_var_for_region(
@@ -227,7 +227,7 @@ impl CanonicalizeMode for CanonicalizeUserTypeAnnotation {
         canonicalizer: &mut Canonicalizer<'_, 'tcx>,
         r: ty::Region<'tcx>,
     ) -> ty::Region<'tcx> {
-        match *r {
+        match r.kind() {
             ty::ReEarlyParam(_)
             | ty::ReLateParam(_)
             | ty::ReErased
@@ -321,7 +321,7 @@ impl<'cx, 'tcx> TypeFolder<TyCtxt<'tcx>> for Canonicalizer<'cx, 'tcx> {
     }
 
     fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
-        match *r {
+        match r.kind() {
             ty::ReBound(index, ..) => {
                 if index >= self.binder_index {
                     bug!("escaping late-bound region during canonicalization");
diff --git a/compiler/rustc_infer/src/infer/canonical/query_response.rs b/compiler/rustc_infer/src/infer/canonical/query_response.rs
index d53f631cc07..5220071c500 100644
--- a/compiler/rustc_infer/src/infer/canonical/query_response.rs
+++ b/compiler/rustc_infer/src/infer/canonical/query_response.rs
@@ -432,7 +432,7 @@ impl<'tcx> InferCtxt<'tcx> {
                 }
                 GenericArgKind::Lifetime(result_value) => {
                     // e.g., here `result_value` might be `'?1` in the example above...
-                    if let ty::ReBound(debruijn, br) = *result_value {
+                    if let ty::ReBound(debruijn, br) = result_value.kind() {
                         // ... in which case we would set `canonical_vars[0]` to `Some('static)`.
 
                         // We only allow a `ty::INNERMOST` index in generic parameters.
diff --git a/compiler/rustc_infer/src/infer/freshen.rs b/compiler/rustc_infer/src/infer/freshen.rs
index f2bb66ff736..cae674165f0 100644
--- a/compiler/rustc_infer/src/infer/freshen.rs
+++ b/compiler/rustc_infer/src/infer/freshen.rs
@@ -109,7 +109,7 @@ impl<'a, 'tcx> TypeFolder<TyCtxt<'tcx>> for TypeFreshener<'a, 'tcx> {
     }
 
     fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
-        match *r {
+        match r.kind() {
             ty::ReBound(..) => {
                 // leave bound regions alone
                 r
diff --git a/compiler/rustc_infer/src/infer/lexical_region_resolve/mod.rs b/compiler/rustc_infer/src/infer/lexical_region_resolve/mod.rs
index 91595de97f7..e3522137d83 100644
--- a/compiler/rustc_infer/src/infer/lexical_region_resolve/mod.rs
+++ b/compiler/rustc_infer/src/infer/lexical_region_resolve/mod.rs
@@ -218,7 +218,7 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> {
                                 true
                             }
                             VarValue::Value(cur_region) => {
-                                match *cur_region {
+                                match cur_region.kind() {
                                     // If this empty region is from a universe that can name the
                                     // placeholder universe, then the LUB is the Placeholder region
                                     // (which is the cur_region). Otherwise, the LUB is the Static
@@ -310,7 +310,7 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> {
 
         match *b_data {
             VarValue::Empty(empty_ui) => {
-                let lub = match *a_region {
+                let lub = match a_region.kind() {
                     RePlaceholder(placeholder) => {
                         // If this empty region is from a universe that can
                         // name the placeholder, then the placeholder is
@@ -350,7 +350,7 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> {
                 // tighter bound than `'static`.
                 //
                 // (This might e.g. arise from being asked to prove `for<'a> { 'b: 'a }`.)
-                if let ty::RePlaceholder(p) = *lub
+                if let ty::RePlaceholder(p) = lub.kind()
                     && b_universe.cannot_name(p.universe)
                 {
                     lub = self.tcx().lifetimes.re_static;
@@ -377,7 +377,7 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> {
                 a_ui.min(b_ui) == b_ui
             }
             (VarValue::Value(a), VarValue::Empty(_)) => {
-                match *a {
+                match a.kind() {
                     // this is always on an error path,
                     // so it doesn't really matter if it's shorter or longer than an empty region
                     ReError(_) => false,
@@ -410,7 +410,7 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> {
                 }
             }
             (VarValue::Empty(a_ui), VarValue::Value(b)) => {
-                match *b {
+                match b.kind() {
                     // this is always on an error path,
                     // so it doesn't really matter if it's shorter or longer than an empty region
                     ReError(_) => false,
@@ -479,7 +479,7 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> {
     /// term "concrete regions").
     #[instrument(level = "trace", skip(self), ret)]
     fn lub_concrete_regions(&self, a: Region<'tcx>, b: Region<'tcx>) -> Region<'tcx> {
-        match (*a, *b) {
+        match (a.kind(), b.kind()) {
             (ReBound(..), _) | (_, ReBound(..)) | (ReErased, _) | (_, ReErased) => {
                 bug!("cannot relate region: LUB({:?}, {:?})", a, b);
             }
@@ -725,7 +725,7 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> {
         // SubSupConflict(ReLateParam, ReLateParam) when reporting error, and so
         // the user will more likely get a specific suggestion.
         fn region_order_key(x: &RegionAndOrigin<'_>) -> u8 {
-            match *x.region {
+            match x.region.kind() {
                 ReEarlyParam(_) => 0,
                 ReLateParam(_) => 1,
                 _ => 2,
@@ -737,7 +737,7 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> {
         let node_universe = self.var_infos[node_idx].universe;
 
         for lower_bound in &lower_bounds {
-            let effective_lower_bound = if let ty::RePlaceholder(p) = *lower_bound.region {
+            let effective_lower_bound = if let ty::RePlaceholder(p) = lower_bound.region.kind() {
                 if node_universe.cannot_name(p.universe) {
                     self.tcx().lifetimes.re_static
                 } else {
@@ -785,7 +785,7 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> {
             .expect("lower_vid_bounds should at least include `node_idx`");
 
         for upper_bound in &upper_bounds {
-            if let ty::RePlaceholder(p) = *upper_bound.region {
+            if let ty::RePlaceholder(p) = upper_bound.region.kind() {
                 if min_universe.cannot_name(p.universe) {
                     let origin = self.var_infos[node_idx].origin;
                     errors.push(RegionResolutionError::UpperBoundUniverseConflict(
@@ -913,7 +913,7 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> {
         generic_ty: Ty<'tcx>,
         min: ty::Region<'tcx>,
     ) -> bool {
-        if let ty::ReError(_) = *min {
+        if let ty::ReError(_) = min.kind() {
             return true;
         }
 
@@ -931,18 +931,18 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> {
             }
 
             VerifyBound::OutlivedBy(r) => {
-                let a = match *min {
+                let a = match min.kind() {
                     ty::ReVar(rid) => var_values.values[rid],
                     _ => VarValue::Value(min),
                 };
-                let b = match **r {
+                let b = match r.kind() {
                     ty::ReVar(rid) => var_values.values[rid],
                     _ => VarValue::Value(*r),
                 };
                 self.sub_region_values(a, b)
             }
 
-            VerifyBound::IsEmpty => match *min {
+            VerifyBound::IsEmpty => match min.kind() {
                 ty::ReVar(rid) => match var_values.values[rid] {
                     VarValue::ErrorValue => false,
                     VarValue::Empty(_) => true,
@@ -989,7 +989,7 @@ impl<'tcx> LexicalRegionResolutions<'tcx> {
         tcx: TyCtxt<'tcx>,
         r: ty::Region<'tcx>,
     ) -> ty::Region<'tcx> {
-        let result = match *r {
+        let result = match r.kind() {
             ty::ReVar(rid) => match self.values[rid] {
                 VarValue::Empty(_) => r,
                 VarValue::Value(r) => r,
diff --git a/compiler/rustc_infer/src/infer/outlives/env.rs b/compiler/rustc_infer/src/infer/outlives/env.rs
index e924c974a02..cb5a33c5c97 100644
--- a/compiler/rustc_infer/src/infer/outlives/env.rs
+++ b/compiler/rustc_infer/src/infer/outlives/env.rs
@@ -69,7 +69,7 @@ impl<'tcx> OutlivesEnvironment<'tcx> {
                     region_bound_pairs
                         .insert(ty::OutlivesPredicate(GenericKind::Alias(alias_b), r_a));
                 }
-                OutlivesBound::RegionSubRegion(r_a, r_b) => match (*r_a, *r_b) {
+                OutlivesBound::RegionSubRegion(r_a, r_b) => match (r_a.kind(), r_b.kind()) {
                     (
                         ty::ReStatic | ty::ReEarlyParam(_) | ty::ReLateParam(_),
                         ty::ReStatic | ty::ReEarlyParam(_) | ty::ReLateParam(_),
diff --git a/compiler/rustc_infer/src/infer/outlives/for_liveness.rs b/compiler/rustc_infer/src/infer/outlives/for_liveness.rs
index 379410641fe..c44d9723f29 100644
--- a/compiler/rustc_infer/src/infer/outlives/for_liveness.rs
+++ b/compiler/rustc_infer/src/infer/outlives/for_liveness.rs
@@ -29,7 +29,7 @@ where
     }
 
     fn visit_region(&mut self, r: ty::Region<'tcx>) {
-        match *r {
+        match r.kind() {
             // ignore bound regions, keep visiting
             ty::ReBound(_, _) => {}
             _ => (self.op)(r),
diff --git a/compiler/rustc_infer/src/infer/region_constraints/leak_check.rs b/compiler/rustc_infer/src/infer/region_constraints/leak_check.rs
index 3cfc58dea05..e332b6d0447 100644
--- a/compiler/rustc_infer/src/infer/region_constraints/leak_check.rs
+++ b/compiler/rustc_infer/src/infer/region_constraints/leak_check.rs
@@ -155,7 +155,7 @@ impl<'a, 'tcx> LeakCheck<'a, 'tcx> {
             self.scc_universes[scc].take_min(universe, *region);
 
             // Detect those SCCs that directly contain a placeholder
-            if let ty::RePlaceholder(placeholder) = **region {
+            if let ty::RePlaceholder(placeholder) = region.kind() {
                 if self.outer_universe.cannot_name(placeholder.universe) {
                     // Update `scc_placeholders` to account for the fact that `P: S` must hold.
                     match self.scc_placeholders[scc] {
diff --git a/compiler/rustc_infer/src/infer/region_constraints/mod.rs b/compiler/rustc_infer/src/infer/region_constraints/mod.rs
index 57555db37ab..8366aa6ec42 100644
--- a/compiler/rustc_infer/src/infer/region_constraints/mod.rs
+++ b/compiler/rustc_infer/src/infer/region_constraints/mod.rs
@@ -463,7 +463,7 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
         // cannot add constraints once regions are resolved
         debug!("origin = {:#?}", origin);
 
-        match (*sub, *sup) {
+        match (sub.kind(), sup.kind()) {
             (ReBound(..), _) | (_, ReBound(..)) => {
                 span_bug!(origin.span(), "cannot relate bound region: {:?} <= {:?}", sub, sup);
             }
@@ -595,7 +595,7 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
     }
 
     pub fn universe(&mut self, region: Region<'tcx>) -> ty::UniverseIndex {
-        match *region {
+        match region.kind() {
             ty::ReStatic
             | ty::ReErased
             | ty::ReLateParam(..)
diff --git a/compiler/rustc_infer/src/infer/relate/generalize.rs b/compiler/rustc_infer/src/infer/relate/generalize.rs
index e16212955ff..b0ccd35e8f0 100644
--- a/compiler/rustc_infer/src/infer/relate/generalize.rs
+++ b/compiler/rustc_infer/src/infer/relate/generalize.rs
@@ -571,7 +571,7 @@ impl<'tcx> TypeRelation<TyCtxt<'tcx>> for Generalizer<'_, 'tcx> {
     ) -> RelateResult<'tcx, ty::Region<'tcx>> {
         assert_eq!(r, r2); // we are misusing TypeRelation here; both LHS and RHS ought to be ==
 
-        match *r {
+        match r.kind() {
             // Never make variables for regions bound within the type itself,
             // nor for erased regions.
             ty::ReBound(..) | ty::ReErased => {
diff --git a/compiler/rustc_infer/src/infer/resolve.rs b/compiler/rustc_infer/src/infer/resolve.rs
index 4a99c220975..245f1a4ac5e 100644
--- a/compiler/rustc_infer/src/infer/resolve.rs
+++ b/compiler/rustc_infer/src/infer/resolve.rs
@@ -89,7 +89,7 @@ impl<'a, 'tcx> TypeFolder<TyCtxt<'tcx>> for OpportunisticRegionResolver<'a, 'tcx
     }
 
     fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
-        match *r {
+        match r.kind() {
             ty::ReVar(vid) => self
                 .infcx
                 .inner
@@ -153,7 +153,7 @@ impl<'a, 'tcx> FallibleTypeFolder<TyCtxt<'tcx>> for FullTypeResolver<'a, 'tcx> {
     }
 
     fn try_fold_region(&mut self, r: ty::Region<'tcx>) -> Result<ty::Region<'tcx>, Self::Error> {
-        match *r {
+        match r.kind() {
             ty::ReVar(_) => Ok(self
                 .infcx
                 .lexical_region_resolutions
diff --git a/compiler/rustc_interface/Cargo.toml b/compiler/rustc_interface/Cargo.toml
index e3673935664..ff28dbeaee6 100644
--- a/compiler/rustc_interface/Cargo.toml
+++ b/compiler/rustc_interface/Cargo.toml
@@ -5,7 +5,6 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-rustc-rayon = { version = "0.5.0" }
 rustc-rayon-core = { version = "0.5.0" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_ast_lowering = { path = "../rustc_ast_lowering" }
diff --git a/compiler/rustc_interface/src/interface.rs b/compiler/rustc_interface/src/interface.rs
index 33b4a48b28d..708fe23b791 100644
--- a/compiler/rustc_interface/src/interface.rs
+++ b/compiler/rustc_interface/src/interface.rs
@@ -348,6 +348,10 @@ pub struct Config {
     /// the list of queries.
     pub override_queries: Option<fn(&Session, &mut Providers)>,
 
+    /// An extra set of symbols to add to the symbol interner, the symbol indices
+    /// will start at [`PREDEFINED_SYMBOLS_COUNT`](rustc_span::symbol::PREDEFINED_SYMBOLS_COUNT)
+    pub extra_symbols: Vec<&'static str>,
+
     /// This is a callback from the driver that is called to create a codegen backend.
     ///
     /// Has no uses within this repository, but is used by bjorn3 for "the
@@ -409,6 +413,7 @@ pub fn run_compiler<R: Send>(config: Config, f: impl FnOnce(&Compiler) -> R + Se
         &early_dcx,
         config.opts.edition,
         config.opts.unstable_opts.threads,
+        &config.extra_symbols,
         SourceMapInputs { file_loader, path_mapping, hash_kind, checksum_hash_kind },
         |current_gcx| {
             // The previous `early_dcx` can't be reused here because it doesn't
diff --git a/compiler/rustc_interface/src/passes.rs b/compiler/rustc_interface/src/passes.rs
index 747e36b6a1a..fde1872fb39 100644
--- a/compiler/rustc_interface/src/passes.rs
+++ b/compiler/rustc_interface/src/passes.rs
@@ -800,6 +800,7 @@ pub fn create_and_enter_global_ctxt<T, F: for<'tcx> FnOnce(TyCtxt<'tcx>) -> T>(
         sess.opts.cg.metadata.clone(),
         sess.cfg_version,
     );
+
     let outputs = util::build_output_filenames(&pre_configured_attrs, sess);
 
     let dep_type = DepsType { dep_names: rustc_query_impl::dep_kind_names() };
@@ -955,7 +956,9 @@ fn run_required_analyses(tcx: TyCtxt<'_>) {
             // Run unsafety check because it's responsible for stealing and
             // deallocating THIR.
             tcx.ensure_ok().check_unsafety(def_id);
-            tcx.ensure_ok().mir_borrowck(def_id)
+            if !tcx.is_typeck_child(def_id.to_def_id()) {
+                tcx.ensure_ok().mir_borrowck(def_id)
+            }
         });
     });
     sess.time("MIR_effect_checking", || {
diff --git a/compiler/rustc_interface/src/tests.rs b/compiler/rustc_interface/src/tests.rs
index a8e55663257..75a1b61b416 100644
--- a/compiler/rustc_interface/src/tests.rs
+++ b/compiler/rustc_interface/src/tests.rs
@@ -53,7 +53,7 @@ where
         checksum_hash_kind,
     });
 
-    rustc_span::create_session_globals_then(DEFAULT_EDITION, sm_inputs, || {
+    rustc_span::create_session_globals_then(DEFAULT_EDITION, &[], sm_inputs, || {
         let temps_dir = sessopts.unstable_opts.temps_dir.as_deref().map(PathBuf::from);
         let io = CompilerIO {
             input: Input::Str { name: FileName::Custom(String::new()), input: String::new() },
diff --git a/compiler/rustc_interface/src/util.rs b/compiler/rustc_interface/src/util.rs
index 83d80938b4e..c3a939f1ab0 100644
--- a/compiler/rustc_interface/src/util.rs
+++ b/compiler/rustc_interface/src/util.rs
@@ -117,6 +117,7 @@ fn run_in_thread_with_globals<F: FnOnce(CurrentGcx) -> R + Send, R: Send>(
     thread_stack_size: usize,
     edition: Edition,
     sm_inputs: SourceMapInputs,
+    extra_symbols: &[&'static str],
     f: F,
 ) -> R {
     // The "thread pool" is a single spawned thread in the non-parallel
@@ -134,9 +135,12 @@ fn run_in_thread_with_globals<F: FnOnce(CurrentGcx) -> R + Send, R: Send>(
         // name contains null bytes.
         let r = builder
             .spawn_scoped(s, move || {
-                rustc_span::create_session_globals_then(edition, Some(sm_inputs), || {
-                    f(CurrentGcx::new())
-                })
+                rustc_span::create_session_globals_then(
+                    edition,
+                    extra_symbols,
+                    Some(sm_inputs),
+                    || f(CurrentGcx::new()),
+                )
             })
             .unwrap()
             .join();
@@ -152,6 +156,7 @@ pub(crate) fn run_in_thread_pool_with_globals<F: FnOnce(CurrentGcx) -> R + Send,
     thread_builder_diag: &EarlyDiagCtxt,
     edition: Edition,
     threads: usize,
+    extra_symbols: &[&'static str],
     sm_inputs: SourceMapInputs,
     f: F,
 ) -> R {
@@ -168,18 +173,24 @@ pub(crate) fn run_in_thread_pool_with_globals<F: FnOnce(CurrentGcx) -> R + Send,
     let registry = sync::Registry::new(std::num::NonZero::new(threads).unwrap());
 
     if !sync::is_dyn_thread_safe() {
-        return run_in_thread_with_globals(thread_stack_size, edition, sm_inputs, |current_gcx| {
-            // Register the thread for use with the `WorkerLocal` type.
-            registry.register();
-
-            f(current_gcx)
-        });
+        return run_in_thread_with_globals(
+            thread_stack_size,
+            edition,
+            sm_inputs,
+            extra_symbols,
+            |current_gcx| {
+                // Register the thread for use with the `WorkerLocal` type.
+                registry.register();
+
+                f(current_gcx)
+            },
+        );
     }
 
     let current_gcx = FromDyn::from(CurrentGcx::new());
     let current_gcx2 = current_gcx.clone();
 
-    let builder = rayon::ThreadPoolBuilder::new()
+    let builder = rayon_core::ThreadPoolBuilder::new()
         .thread_name(|_| "rustc".to_string())
         .acquire_thread_handler(jobserver::acquire_thread)
         .release_thread_handler(jobserver::release_thread)
@@ -230,13 +241,13 @@ pub(crate) fn run_in_thread_pool_with_globals<F: FnOnce(CurrentGcx) -> R + Send,
     // pool. Upon creation, each worker thread created gets a copy of the
     // session globals in TLS. This is possible because `SessionGlobals` impls
     // `Send` in the parallel compiler.
-    rustc_span::create_session_globals_then(edition, Some(sm_inputs), || {
+    rustc_span::create_session_globals_then(edition, extra_symbols, Some(sm_inputs), || {
         rustc_span::with_session_globals(|session_globals| {
             let session_globals = FromDyn::from(session_globals);
             builder
                 .build_scoped(
                     // Initialize each new worker thread when created.
-                    move |thread: rayon::ThreadBuilder| {
+                    move |thread: rayon_core::ThreadBuilder| {
                         // Register the thread for use with the `WorkerLocal` type.
                         registry.register();
 
@@ -245,7 +256,9 @@ pub(crate) fn run_in_thread_pool_with_globals<F: FnOnce(CurrentGcx) -> R + Send,
                         })
                     },
                     // Run `f` on the first thread in the thread pool.
-                    move |pool: &rayon::ThreadPool| pool.install(|| f(current_gcx.into_inner())),
+                    move |pool: &rayon_core::ThreadPool| {
+                        pool.install(|| f(current_gcx.into_inner()))
+                    },
                 )
                 .unwrap()
         })
diff --git a/compiler/rustc_lint/src/builtin.rs b/compiler/rustc_lint/src/builtin.rs
index 38c2bf54432..e65f4beab24 100644
--- a/compiler/rustc_lint/src/builtin.rs
+++ b/compiler/rustc_lint/src/builtin.rs
@@ -1988,7 +1988,7 @@ impl ExplicitOutlivesRequirements {
 
         inferred_outlives
             .filter_map(|(clause, _)| match clause.kind().skip_binder() {
-                ty::ClauseKind::RegionOutlives(ty::OutlivesPredicate(a, b)) => match *a {
+                ty::ClauseKind::RegionOutlives(ty::OutlivesPredicate(a, b)) => match a.kind() {
                     ty::ReEarlyParam(ebr)
                         if item_generics.region_param(ebr, tcx).def_id == lifetime.to_def_id() =>
                     {
@@ -2038,7 +2038,7 @@ impl ExplicitOutlivesRequirements {
                 let is_inferred = match tcx.named_bound_var(lifetime.hir_id) {
                     Some(ResolvedArg::EarlyBound(def_id)) => inferred_outlives
                         .iter()
-                        .any(|r| matches!(**r, ty::ReEarlyParam(ebr) if { item_generics.region_param(ebr, tcx).def_id == def_id.to_def_id() })),
+                        .any(|r| matches!(r.kind(), ty::ReEarlyParam(ebr) if { item_generics.region_param(ebr, tcx).def_id == def_id.to_def_id() })),
                     _ => false,
                 };
 
diff --git a/compiler/rustc_lint/src/context.rs b/compiler/rustc_lint/src/context.rs
index 885a7308bdc..16c9e08c78d 100644
--- a/compiler/rustc_lint/src/context.rs
+++ b/compiler/rustc_lint/src/context.rs
@@ -859,7 +859,7 @@ impl<'tcx> LateContext<'tcx> {
     ) -> Option<Ty<'tcx>> {
         let tcx = self.tcx;
         tcx.associated_items(trait_id)
-            .find_by_name_and_kind(tcx, Ident::from_str(name), ty::AssocKind::Type, trait_id)
+            .find_by_ident_and_kind(tcx, Ident::from_str(name), ty::AssocKind::Type, trait_id)
             .and_then(|assoc| {
                 let proj = Ty::new_projection(tcx, assoc.def_id, [self_ty]);
                 tcx.try_normalize_erasing_regions(self.typing_env(), proj).ok()
diff --git a/compiler/rustc_lint/src/impl_trait_overcaptures.rs b/compiler/rustc_lint/src/impl_trait_overcaptures.rs
index 26481b97076..f1dc420aa3c 100644
--- a/compiler/rustc_lint/src/impl_trait_overcaptures.rs
+++ b/compiler/rustc_lint/src/impl_trait_overcaptures.rs
@@ -461,7 +461,7 @@ fn extract_def_id_from_arg<'tcx>(
     arg: ty::GenericArg<'tcx>,
 ) -> DefId {
     match arg.unpack() {
-        ty::GenericArgKind::Lifetime(re) => match *re {
+        ty::GenericArgKind::Lifetime(re) => match re.kind() {
             ty::ReEarlyParam(ebr) => generics.region_param(ebr, tcx).def_id,
             ty::ReBound(
                 _,
@@ -530,7 +530,7 @@ impl<'tcx> TypeRelation<TyCtxt<'tcx>> for FunctionalVariances<'tcx> {
         a: ty::Region<'tcx>,
         _: ty::Region<'tcx>,
     ) -> RelateResult<'tcx, ty::Region<'tcx>> {
-        let def_id = match *a {
+        let def_id = match a.kind() {
             ty::ReEarlyParam(ebr) => self.generics.region_param(ebr, self.tcx).def_id,
             ty::ReBound(
                 _,
diff --git a/compiler/rustc_lint/src/lints.rs b/compiler/rustc_lint/src/lints.rs
index 55d010e6d34..51214c8e8a4 100644
--- a/compiler/rustc_lint/src/lints.rs
+++ b/compiler/rustc_lint/src/lints.rs
@@ -513,7 +513,7 @@ impl Subdiagnostic for BuiltinClashingExternSub<'_> {
         expected_str.push(self.expected.fn_sig(self.tcx).to_string(), false);
         let mut found_str = DiagStyledString::new();
         found_str.push(self.found.fn_sig(self.tcx).to_string(), true);
-        diag.note_expected_found(&"", expected_str, &"", found_str);
+        diag.note_expected_found("", expected_str, "", found_str);
     }
 }
 
diff --git a/compiler/rustc_lint/src/nonstandard_style.rs b/compiler/rustc_lint/src/nonstandard_style.rs
index df567e80e55..a3e7c84584d 100644
--- a/compiler/rustc_lint/src/nonstandard_style.rs
+++ b/compiler/rustc_lint/src/nonstandard_style.rs
@@ -423,11 +423,11 @@ impl<'tcx> LateLintPass<'tcx> for NonSnakeCase {
     }
 
     fn check_trait_item(&mut self, cx: &LateContext<'_>, item: &hir::TraitItem<'_>) {
-        if let hir::TraitItemKind::Fn(_, hir::TraitFn::Required(pnames)) = item.kind {
+        if let hir::TraitItemKind::Fn(_, hir::TraitFn::Required(param_idents)) = item.kind {
             self.check_snake_case(cx, "trait method", &item.ident);
-            for param_name in pnames {
-                if let Some(param_name) = param_name {
-                    self.check_snake_case(cx, "variable", param_name);
+            for param_ident in param_idents {
+                if let Some(param_ident) = param_ident {
+                    self.check_snake_case(cx, "variable", param_ident);
                 }
             }
         }
diff --git a/compiler/rustc_macros/src/symbols.rs b/compiler/rustc_macros/src/symbols.rs
index 37200f62eb5..0400de62274 100644
--- a/compiler/rustc_macros/src/symbols.rs
+++ b/compiler/rustc_macros/src/symbols.rs
@@ -142,13 +142,13 @@ pub(super) fn symbols(input: TokenStream) -> TokenStream {
     output
 }
 
-struct Preinterned {
+struct Predefined {
     idx: u32,
     span_of_name: Span,
 }
 
 struct Entries {
-    map: HashMap<String, Preinterned>,
+    map: HashMap<String, Predefined>,
 }
 
 impl Entries {
@@ -163,7 +163,7 @@ impl Entries {
             prev.idx
         } else {
             let idx = self.len();
-            self.map.insert(s.to_string(), Preinterned { idx, span_of_name: span });
+            self.map.insert(s.to_string(), Predefined { idx, span_of_name: span });
             idx
         }
     }
@@ -295,10 +295,14 @@ fn symbols_with_errors(input: TokenStream) -> (TokenStream, Vec<syn::Error>) {
     }
 
     let symbol_digits_base = entries.map["0"].idx;
-    let preinterned_symbols_count = entries.len();
+    let predefined_symbols_count = entries.len();
     let output = quote! {
         const SYMBOL_DIGITS_BASE: u32 = #symbol_digits_base;
-        const PREINTERNED_SYMBOLS_COUNT: u32 = #preinterned_symbols_count;
+
+        /// The number of predefined symbols; this is the the first index for
+        /// extra pre-interned symbols in an Interner created via
+        /// [`Interner::with_extra_symbols`].
+        pub const PREDEFINED_SYMBOLS_COUNT: u32 = #predefined_symbols_count;
 
         #[doc(hidden)]
         #[allow(non_upper_case_globals)]
@@ -315,10 +319,13 @@ fn symbols_with_errors(input: TokenStream) -> (TokenStream, Vec<syn::Error>) {
         }
 
         impl Interner {
-            pub(crate) fn fresh() -> Self {
-                Interner::prefill(&[
-                    #prefill_stream
-                ])
+            /// Creates an `Interner` with the predefined symbols from the `symbols!` macro and
+            /// any extra symbols provided by external drivers such as Clippy
+            pub(crate) fn with_extra_symbols(extra_symbols: &[&'static str]) -> Self {
+                Interner::prefill(
+                    &[#prefill_stream],
+                    extra_symbols,
+                )
             }
         }
     };
diff --git a/compiler/rustc_metadata/src/rmeta/decoder.rs b/compiler/rustc_metadata/src/rmeta/decoder.rs
index 4610a571da0..4cc12ca2e0b 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder.rs
@@ -562,9 +562,9 @@ impl<'a, 'tcx> SpanDecoder for DecodeContext<'a, 'tcx> {
                     Symbol::intern(s)
                 })
             }
-            SYMBOL_PREINTERNED => {
+            SYMBOL_PREDEFINED => {
                 let symbol_index = self.read_u32();
-                Symbol::new_from_decoded(symbol_index)
+                Symbol::new(symbol_index)
             }
             _ => unreachable!(),
         }
@@ -1313,7 +1313,7 @@ impl<'a> CrateMetadataRef<'a> {
     fn get_fn_has_self_parameter(self, id: DefIndex, sess: &'a Session) -> bool {
         self.root
             .tables
-            .fn_arg_names
+            .fn_arg_idents
             .get(self, id)
             .expect("argument names not encoded for a function")
             .decode((self, sess))
diff --git a/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs b/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
index 3dc82ce9d18..ecc2dcc5318 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
@@ -286,7 +286,7 @@ provide! { tcx, def_id, other, cdata,
     rendered_const => { table }
     rendered_precise_capturing_args => { table }
     asyncness => { table_direct }
-    fn_arg_names => { table }
+    fn_arg_idents => { table }
     coroutine_kind => { table_direct }
     coroutine_for_closure => { table }
     coroutine_by_move_body_def_id => { table }
diff --git a/compiler/rustc_metadata/src/rmeta/encoder.rs b/compiler/rustc_metadata/src/rmeta/encoder.rs
index 167122a9793..5c8e2888ec9 100644
--- a/compiler/rustc_metadata/src/rmeta/encoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/encoder.rs
@@ -201,9 +201,9 @@ impl<'a, 'tcx> SpanEncoder for EncodeContext<'a, 'tcx> {
     }
 
     fn encode_symbol(&mut self, symbol: Symbol) {
-        // if symbol preinterned, emit tag and symbol index
-        if symbol.is_preinterned() {
-            self.opaque.emit_u8(SYMBOL_PREINTERNED);
+        // if symbol predefined, emit tag and symbol index
+        if symbol.is_predefined() {
+            self.opaque.emit_u8(SYMBOL_PREDEFINED);
             self.opaque.emit_u32(symbol.as_u32());
         } else {
             // otherwise write it as string or as offset to it
@@ -1099,7 +1099,6 @@ fn should_encode_variances<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, def_kind: Def
         DefKind::Struct
         | DefKind::Union
         | DefKind::Enum
-        | DefKind::Variant
         | DefKind::OpaqueTy
         | DefKind::Fn
         | DefKind::Ctor(..)
@@ -1109,6 +1108,7 @@ fn should_encode_variances<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, def_kind: Def
             matches!(tcx.opt_rpitit_info(def_id), Some(ty::ImplTraitInTraitData::Trait { .. }))
         }
         DefKind::Mod
+        | DefKind::Variant
         | DefKind::Field
         | DefKind::AssocConst
         | DefKind::TyParam
@@ -1469,7 +1469,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
             }
             if let DefKind::Fn | DefKind::AssocFn = def_kind {
                 self.tables.asyncness.set_some(def_id.index, tcx.asyncness(def_id));
-                record_array!(self.tables.fn_arg_names[def_id] <- tcx.fn_arg_names(def_id));
+                record_array!(self.tables.fn_arg_idents[def_id] <- tcx.fn_arg_idents(def_id));
             }
             if let Some(name) = tcx.intrinsic(def_id) {
                 record!(self.tables.intrinsic[def_id] <- name);
@@ -2199,7 +2199,7 @@ fn prefetch_mir(tcx: TyCtxt<'_>) {
     }
 
     let reachable_set = tcx.reachable_set(());
-    par_for_each_in(tcx.mir_keys(()), |&def_id| {
+    par_for_each_in(tcx.mir_keys(()), |&&def_id| {
         let (encode_const, encode_opt) = should_encode_mir(tcx, reachable_set, def_id);
 
         if encode_const {
diff --git a/compiler/rustc_metadata/src/rmeta/mod.rs b/compiler/rustc_metadata/src/rmeta/mod.rs
index 96a1f65eeb0..2f27e5f6c5d 100644
--- a/compiler/rustc_metadata/src/rmeta/mod.rs
+++ b/compiler/rustc_metadata/src/rmeta/mod.rs
@@ -451,7 +451,7 @@ define_tables! {
     rendered_const: Table<DefIndex, LazyValue<String>>,
     rendered_precise_capturing_args: Table<DefIndex, LazyArray<PreciseCapturingArgKind<Symbol, Symbol>>>,
     asyncness: Table<DefIndex, ty::Asyncness>,
-    fn_arg_names: Table<DefIndex, LazyArray<Option<Ident>>>,
+    fn_arg_idents: Table<DefIndex, LazyArray<Option<Ident>>>,
     coroutine_kind: Table<DefIndex, hir::CoroutineKind>,
     coroutine_for_closure: Table<DefIndex, RawDefId>,
     adt_destructor: Table<DefIndex, LazyValue<ty::Destructor>>,
@@ -586,7 +586,7 @@ impl SpanTag {
 // Tags for encoding Symbol's
 const SYMBOL_STR: u8 = 0;
 const SYMBOL_OFFSET: u8 = 1;
-const SYMBOL_PREINTERNED: u8 = 2;
+const SYMBOL_PREDEFINED: u8 = 2;
 
 pub fn provide(providers: &mut Providers) {
     encoder::provide(providers);
diff --git a/compiler/rustc_middle/src/arena.rs b/compiler/rustc_middle/src/arena.rs
index aef56ea46e9..98273a05446 100644
--- a/compiler/rustc_middle/src/arena.rs
+++ b/compiler/rustc_middle/src/arena.rs
@@ -28,7 +28,7 @@ macro_rules! arena_types {
                     rustc_middle::mir::Body<'tcx>
                 >,
             [decode] typeck_results: rustc_middle::ty::TypeckResults<'tcx>,
-            [decode] borrowck_result: rustc_middle::mir::BorrowCheckResult<'tcx>,
+            [decode] borrowck_result: rustc_middle::mir::ConcreteOpaqueTypes<'tcx>,
             [] resolver: rustc_data_structures::steal::Steal<(
                 rustc_middle::ty::ResolverAstLowering,
                 std::sync::Arc<rustc_ast::Crate>,
diff --git a/compiler/rustc_middle/src/hir/map.rs b/compiler/rustc_middle/src/hir/map.rs
index 21ab06c98a7..daf95420c43 100644
--- a/compiler/rustc_middle/src/hir/map.rs
+++ b/compiler/rustc_middle/src/hir/map.rs
@@ -281,7 +281,7 @@ impl<'tcx> TyCtxt<'tcx> {
         })
     }
 
-    pub fn hir_body_param_names(self, id: BodyId) -> impl Iterator<Item = Option<Ident>> {
+    pub fn hir_body_param_idents(self, id: BodyId) -> impl Iterator<Item = Option<Ident>> {
         self.hir_body(id).params.iter().map(|param| match param.pat.kind {
             PatKind::Binding(_, _, ident, _) => Some(ident),
             PatKind::Wild => Some(Ident::new(kw::Underscore, param.pat.span)),
@@ -343,7 +343,7 @@ impl<'tcx> TyCtxt<'tcx> {
 
     #[inline]
     pub fn par_hir_body_owners(self, f: impl Fn(LocalDefId) + DynSend + DynSync) {
-        par_for_each_in(&self.hir_crate_items(()).body_owners[..], |&def_id| f(def_id));
+        par_for_each_in(&self.hir_crate_items(()).body_owners[..], |&&def_id| f(def_id));
     }
 
     pub fn hir_ty_param_owner(self, def_id: LocalDefId) -> LocalDefId {
diff --git a/compiler/rustc_middle/src/hir/mod.rs b/compiler/rustc_middle/src/hir/mod.rs
index 74369b6636c..640ac70d3a7 100644
--- a/compiler/rustc_middle/src/hir/mod.rs
+++ b/compiler/rustc_middle/src/hir/mod.rs
@@ -83,35 +83,35 @@ impl ModuleItems {
         &self,
         f: impl Fn(ItemId) -> Result<(), ErrorGuaranteed> + DynSend + DynSync,
     ) -> Result<(), ErrorGuaranteed> {
-        try_par_for_each_in(&self.free_items[..], |&id| f(id))
+        try_par_for_each_in(&self.free_items[..], |&&id| f(id))
     }
 
     pub fn par_trait_items(
         &self,
         f: impl Fn(TraitItemId) -> Result<(), ErrorGuaranteed> + DynSend + DynSync,
     ) -> Result<(), ErrorGuaranteed> {
-        try_par_for_each_in(&self.trait_items[..], |&id| f(id))
+        try_par_for_each_in(&self.trait_items[..], |&&id| f(id))
     }
 
     pub fn par_impl_items(
         &self,
         f: impl Fn(ImplItemId) -> Result<(), ErrorGuaranteed> + DynSend + DynSync,
     ) -> Result<(), ErrorGuaranteed> {
-        try_par_for_each_in(&self.impl_items[..], |&id| f(id))
+        try_par_for_each_in(&self.impl_items[..], |&&id| f(id))
     }
 
     pub fn par_foreign_items(
         &self,
         f: impl Fn(ForeignItemId) -> Result<(), ErrorGuaranteed> + DynSend + DynSync,
     ) -> Result<(), ErrorGuaranteed> {
-        try_par_for_each_in(&self.foreign_items[..], |&id| f(id))
+        try_par_for_each_in(&self.foreign_items[..], |&&id| f(id))
     }
 
     pub fn par_opaques(
         &self,
         f: impl Fn(LocalDefId) -> Result<(), ErrorGuaranteed> + DynSend + DynSync,
     ) -> Result<(), ErrorGuaranteed> {
-        try_par_for_each_in(&self.opaques[..], |&id| f(id))
+        try_par_for_each_in(&self.opaques[..], |&&id| f(id))
     }
 }
 
@@ -215,9 +215,9 @@ pub fn provide(providers: &mut Providers) {
         let hir_id = tcx.local_def_id_to_hir_id(def_id);
         tcx.hir_opt_ident_span(hir_id)
     };
-    providers.fn_arg_names = |tcx, def_id| {
+    providers.fn_arg_idents = |tcx, def_id| {
         if let Some(body_id) = tcx.hir_node_by_def_id(def_id).body_id() {
-            tcx.arena.alloc_from_iter(tcx.hir_body_param_names(body_id))
+            tcx.arena.alloc_from_iter(tcx.hir_body_param_idents(body_id))
         } else if let Node::TraitItem(&TraitItem {
             kind: TraitItemKind::Fn(_, TraitFn::Required(idents)),
             ..
@@ -231,7 +231,7 @@ pub fn provide(providers: &mut Providers) {
         } else {
             span_bug!(
                 tcx.hir_span(tcx.local_def_id_to_hir_id(def_id)),
-                "fn_arg_names: unexpected item {:?}",
+                "fn_arg_idents: unexpected item {:?}",
                 def_id
             );
         }
diff --git a/compiler/rustc_middle/src/mir/query.rs b/compiler/rustc_middle/src/mir/query.rs
index 5a9fe10938a..3fc05f2caf2 100644
--- a/compiler/rustc_middle/src/mir/query.rs
+++ b/compiler/rustc_middle/src/mir/query.rs
@@ -6,14 +6,13 @@ use rustc_abi::{FieldIdx, VariantIdx};
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_errors::ErrorGuaranteed;
 use rustc_hir::def_id::LocalDefId;
+use rustc_index::IndexVec;
 use rustc_index::bit_set::BitMatrix;
-use rustc_index::{Idx, IndexVec};
 use rustc_macros::{HashStable, TyDecodable, TyEncodable, TypeFoldable, TypeVisitable};
 use rustc_span::{Span, Symbol};
-use smallvec::SmallVec;
 
 use super::{ConstValue, SourceInfo};
-use crate::ty::{self, CoroutineArgsExt, OpaqueHiddenType, Ty, TyCtxt, fold_regions};
+use crate::ty::{self, CoroutineArgsExt, OpaqueHiddenType, Ty};
 
 rustc_index::newtype_index! {
     #[derive(HashStable)]
@@ -85,16 +84,11 @@ impl Debug for CoroutineLayout<'_> {
     }
 }
 
-#[derive(Debug, TyEncodable, TyDecodable, HashStable)]
-pub struct BorrowCheckResult<'tcx> {
-    /// All the opaque types that are restricted to concrete types
-    /// by this function. Unlike the value in `TypeckResults`, this has
-    /// unerased regions.
-    pub concrete_opaque_types: FxIndexMap<LocalDefId, OpaqueHiddenType<'tcx>>,
-    pub closure_requirements: Option<ClosureRegionRequirements<'tcx>>,
-    pub used_mut_upvars: SmallVec<[FieldIdx; 8]>,
-    pub tainted_by_errors: Option<ErrorGuaranteed>,
-}
+/// All the opaque types that are restricted to concrete types
+/// by this function. Unlike the value in `TypeckResults`, this has
+/// unerased regions.
+#[derive(Default, Debug, TyEncodable, TyDecodable, HashStable)]
+pub struct ConcreteOpaqueTypes<'tcx>(pub FxIndexMap<LocalDefId, OpaqueHiddenType<'tcx>>);
 
 /// The result of the `mir_const_qualif` query.
 ///
@@ -108,84 +102,6 @@ pub struct ConstQualifs {
     pub needs_non_const_drop: bool,
     pub tainted_by_errors: Option<ErrorGuaranteed>,
 }
-
-/// After we borrow check a closure, we are left with various
-/// requirements that we have inferred between the free regions that
-/// appear in the closure's signature or on its field types. These
-/// requirements are then verified and proved by the closure's
-/// creating function. This struct encodes those requirements.
-///
-/// The requirements are listed as being between various `RegionVid`. The 0th
-/// region refers to `'static`; subsequent region vids refer to the free
-/// regions that appear in the closure (or coroutine's) type, in order of
-/// appearance. (This numbering is actually defined by the `UniversalRegions`
-/// struct in the NLL region checker. See for example
-/// `UniversalRegions::closure_mapping`.) Note the free regions in the
-/// closure's signature and captures are erased.
-///
-/// Example: If type check produces a closure with the closure args:
-///
-/// ```text
-/// ClosureArgs = [
-///     'a,                                         // From the parent.
-///     'b,
-///     i8,                                         // the "closure kind"
-///     for<'x> fn(&'<erased> &'x u32) -> &'x u32,  // the "closure signature"
-///     &'<erased> String,                          // some upvar
-/// ]
-/// ```
-///
-/// We would "renumber" each free region to a unique vid, as follows:
-///
-/// ```text
-/// ClosureArgs = [
-///     '1,                                         // From the parent.
-///     '2,
-///     i8,                                         // the "closure kind"
-///     for<'x> fn(&'3 &'x u32) -> &'x u32,         // the "closure signature"
-///     &'4 String,                                 // some upvar
-/// ]
-/// ```
-///
-/// Now the code might impose a requirement like `'1: '2`. When an
-/// instance of the closure is created, the corresponding free regions
-/// can be extracted from its type and constrained to have the given
-/// outlives relationship.
-#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable)]
-pub struct ClosureRegionRequirements<'tcx> {
-    /// The number of external regions defined on the closure. In our
-    /// example above, it would be 3 -- one for `'static`, then `'1`
-    /// and `'2`. This is just used for a sanity check later on, to
-    /// make sure that the number of regions we see at the callsite
-    /// matches.
-    pub num_external_vids: usize,
-
-    /// Requirements between the various free regions defined in
-    /// indices.
-    pub outlives_requirements: Vec<ClosureOutlivesRequirement<'tcx>>,
-}
-
-/// Indicates an outlives-constraint between a type or between two
-/// free regions declared on the closure.
-#[derive(Copy, Clone, Debug, TyEncodable, TyDecodable, HashStable)]
-pub struct ClosureOutlivesRequirement<'tcx> {
-    // This region or type ...
-    pub subject: ClosureOutlivesSubject<'tcx>,
-
-    // ... must outlive this one.
-    pub outlived_free_region: ty::RegionVid,
-
-    // If not, report an error here ...
-    pub blame_span: Span,
-
-    // ... due to this reason.
-    pub category: ConstraintCategory<'tcx>,
-}
-
-// Make sure this enum doesn't unintentionally grow
-#[cfg(target_pointer_width = "64")]
-rustc_data_structures::static_assert_size!(ConstraintCategory<'_>, 16);
-
 /// Outlives-constraints can be categorized to determine whether and why they
 /// are interesting (for error reporting). Order of variants indicates sort
 /// order of the category, thereby influencing diagnostic output.
@@ -253,66 +169,6 @@ pub enum AnnotationSource {
     GenericArg,
 }
 
-/// The subject of a `ClosureOutlivesRequirement` -- that is, the thing
-/// that must outlive some region.
-#[derive(Copy, Clone, Debug, TyEncodable, TyDecodable, HashStable)]
-pub enum ClosureOutlivesSubject<'tcx> {
-    /// Subject is a type, typically a type parameter, but could also
-    /// be a projection. Indicates a requirement like `T: 'a` being
-    /// passed to the caller, where the type here is `T`.
-    Ty(ClosureOutlivesSubjectTy<'tcx>),
-
-    /// Subject is a free region from the closure. Indicates a requirement
-    /// like `'a: 'b` being passed to the caller; the region here is `'a`.
-    Region(ty::RegionVid),
-}
-
-/// Represents a `ty::Ty` for use in [`ClosureOutlivesSubject`].
-///
-/// This abstraction is necessary because the type may include `ReVar` regions,
-/// which is what we use internally within NLL code, and they can't be used in
-/// a query response.
-///
-/// DO NOT implement `TypeVisitable` or `TypeFoldable` traits, because this
-/// type is not recognized as a binder for late-bound region.
-#[derive(Copy, Clone, Debug, TyEncodable, TyDecodable, HashStable)]
-pub struct ClosureOutlivesSubjectTy<'tcx> {
-    inner: Ty<'tcx>,
-}
-
-impl<'tcx> ClosureOutlivesSubjectTy<'tcx> {
-    /// All regions of `ty` must be of kind `ReVar` and must represent
-    /// universal regions *external* to the closure.
-    pub fn bind(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Self {
-        let inner = fold_regions(tcx, ty, |r, depth| match r.kind() {
-            ty::ReVar(vid) => {
-                let br = ty::BoundRegion {
-                    var: ty::BoundVar::new(vid.index()),
-                    kind: ty::BoundRegionKind::Anon,
-                };
-                ty::Region::new_bound(tcx, depth, br)
-            }
-            _ => bug!("unexpected region in ClosureOutlivesSubjectTy: {r:?}"),
-        });
-
-        Self { inner }
-    }
-
-    pub fn instantiate(
-        self,
-        tcx: TyCtxt<'tcx>,
-        mut map: impl FnMut(ty::RegionVid) -> ty::Region<'tcx>,
-    ) -> Ty<'tcx> {
-        fold_regions(tcx, self.inner, |r, depth| match r.kind() {
-            ty::ReBound(debruijn, br) => {
-                debug_assert_eq!(debruijn, depth);
-                map(ty::RegionVid::new(br.var.index()))
-            }
-            _ => bug!("unexpected region {r:?}"),
-        })
-    }
-}
-
 /// The constituent parts of a mir constant of kind ADT or array.
 #[derive(Copy, Clone, Debug, HashStable)]
 pub struct DestructuredConstant<'tcx> {
diff --git a/compiler/rustc_middle/src/mir/syntax.rs b/compiler/rustc_middle/src/mir/syntax.rs
index 707c8d04d55..ff9d32ebb71 100644
--- a/compiler/rustc_middle/src/mir/syntax.rs
+++ b/compiler/rustc_middle/src/mir/syntax.rs
@@ -652,6 +652,8 @@ pub enum CallSource {
     /// Other types of desugaring that did not come from the HIR, but we don't care about
     /// for diagnostics (yet).
     Misc,
+    /// Use of value, generating a clone function call
+    Use,
     /// Normal function call, no special source
     Normal,
 }
diff --git a/compiler/rustc_middle/src/mir/terminator.rs b/compiler/rustc_middle/src/mir/terminator.rs
index b2c51ad8864..82e8422c52d 100644
--- a/compiler/rustc_middle/src/mir/terminator.rs
+++ b/compiler/rustc_middle/src/mir/terminator.rs
@@ -454,7 +454,7 @@ mod helper {
         /// Like [`SwitchTargets::target_for_value`], but returning the same type as
         /// [`Terminator::successors`].
         #[inline]
-        #[cfg_attr(not(bootstrap), define_opaque(Successors))]
+        #[define_opaque(Successors)]
         pub fn successors_for_value(&self, value: u128) -> Successors<'_> {
             let target = self.target_for_value(value);
             (&[]).into_iter().copied().chain(Some(target))
@@ -463,7 +463,7 @@ mod helper {
 
     impl<'tcx> TerminatorKind<'tcx> {
         #[inline]
-        #[cfg_attr(not(bootstrap), define_opaque(Successors))]
+        #[define_opaque(Successors)]
         pub fn successors(&self) -> Successors<'_> {
             use self::TerminatorKind::*;
             match *self {
@@ -502,7 +502,7 @@ mod helper {
         }
 
         #[inline]
-        #[cfg_attr(not(bootstrap), define_opaque(SuccessorsMut))]
+        #[define_opaque(SuccessorsMut)]
         pub fn successors_mut(&mut self) -> SuccessorsMut<'_> {
             use self::TerminatorKind::*;
             match *self {
diff --git a/compiler/rustc_middle/src/query/erase.rs b/compiler/rustc_middle/src/query/erase.rs
index 6c6b9a5510c..5bd111fa2f2 100644
--- a/compiler/rustc_middle/src/query/erase.rs
+++ b/compiler/rustc_middle/src/query/erase.rs
@@ -25,7 +25,7 @@ pub trait EraseType: Copy {
 pub type Erase<T: EraseType> = Erased<impl Copy>;
 
 #[inline(always)]
-#[cfg_attr(not(bootstrap), define_opaque(Erase))]
+#[define_opaque(Erase)]
 pub fn erase<T: EraseType>(src: T) -> Erase<T> {
     // Ensure the sizes match
     const {
@@ -49,7 +49,7 @@ pub fn erase<T: EraseType>(src: T) -> Erase<T> {
 
 /// Restores an erased value.
 #[inline(always)]
-#[cfg_attr(not(bootstrap), define_opaque(Erase))]
+#[define_opaque(Erase)]
 pub fn restore<T: EraseType>(value: Erase<T>) -> T {
     let value: Erased<<T as EraseType>::Result> = value;
     // See comment in `erase` for why we use `transmute_unchecked`.
diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs
index aac1fdb3418..28a59d3e73e 100644
--- a/compiler/rustc_middle/src/query/mod.rs
+++ b/compiler/rustc_middle/src/query/mod.rs
@@ -1026,6 +1026,13 @@ rustc_queries! {
         separate_provide_extern
     }
 
+    /// Given an `impl_def_id`, return true if the self type is guaranteed to be unsized due
+    /// to either being one of the built-in unsized types (str/slice/dyn) or to be a struct
+    /// whose tail is one of those types.
+    query impl_self_is_guaranteed_unsized(impl_def_id: DefId) -> bool {
+        desc { |tcx| "computing whether `{}` has a guaranteed unsized self type", tcx.def_path_str(impl_def_id) }
+    }
+
     /// Maps a `DefId` of a type to a list of its inherent impls.
     /// Contains implementations of methods that are inherent to a type.
     /// Methods in these implementations don't need to be exported.
@@ -1153,11 +1160,10 @@ rustc_queries! {
         return_result_from_ensure_ok
     }
 
-    /// Borrow-checks the function body. If this is a closure, returns
-    /// additional requirements that the closure's creator must verify.
-    query mir_borrowck(key: LocalDefId) -> &'tcx mir::BorrowCheckResult<'tcx> {
+    /// Borrow-checks the given typeck root, e.g. functions, const/static items,
+    /// and its children, e.g. closures, inline consts.
+    query mir_borrowck(key: LocalDefId) -> Result<&'tcx mir::ConcreteOpaqueTypes<'tcx>, ErrorGuaranteed> {
         desc { |tcx| "borrow-checking `{}`", tcx.def_path_str(key) }
-        cache_on_disk_if(tcx) { tcx.is_typeck_child(key.to_def_id()) }
     }
 
     /// Gets a complete map from all types to their inherent impls.
@@ -1436,8 +1442,8 @@ rustc_queries! {
         desc { |tcx| "computing target features for inline asm of `{}`", tcx.def_path_str(def_id) }
     }
 
-    query fn_arg_names(def_id: DefId) -> &'tcx [Option<rustc_span::Ident>] {
-        desc { |tcx| "looking up function parameter names for `{}`", tcx.def_path_str(def_id) }
+    query fn_arg_idents(def_id: DefId) -> &'tcx [Option<rustc_span::Ident>] {
+        desc { |tcx| "looking up function parameter identifiers for `{}`", tcx.def_path_str(def_id) }
         separate_provide_extern
     }
 
@@ -1894,6 +1900,11 @@ rustc_queries! {
 
     // The macro which defines `rustc_metadata::provide_extern` depends on this query's name.
     // Changing the name should cause a compiler error, but in case that changes, be aware.
+    //
+    // The hash should not be calculated before the `analysis` pass is complete, specifically
+    // until `tcx.untracked().definitions.freeze()` has been called, otherwise if incremental
+    // compilation is enabled calculating this hash can freeze this structure too early in
+    // compilation and cause subsequent crashes when attempting to write to `definitions`
     query crate_hash(_: CrateNum) -> Svh {
         eval_always
         desc { "looking up the hash a crate" }
diff --git a/compiler/rustc_middle/src/query/on_disk_cache.rs b/compiler/rustc_middle/src/query/on_disk_cache.rs
index c6ecc679b7b..f78398c7c37 100644
--- a/compiler/rustc_middle/src/query/on_disk_cache.rs
+++ b/compiler/rustc_middle/src/query/on_disk_cache.rs
@@ -46,7 +46,7 @@ const TAG_EXPN_DATA: u8 = 1;
 // Tags for encoding Symbol's
 const SYMBOL_STR: u8 = 0;
 const SYMBOL_OFFSET: u8 = 1;
-const SYMBOL_PREINTERNED: u8 = 2;
+const SYMBOL_PREDEFINED: u8 = 2;
 
 /// Provides an interface to incremental compilation data cached from the
 /// previous compilation session. This data will eventually include the results
@@ -674,9 +674,9 @@ impl<'a, 'tcx> SpanDecoder for CacheDecoder<'a, 'tcx> {
                     Symbol::intern(s)
                 })
             }
-            SYMBOL_PREINTERNED => {
+            SYMBOL_PREDEFINED => {
                 let symbol_index = self.read_u32();
-                Symbol::new_from_decoded(symbol_index)
+                Symbol::new(symbol_index)
             }
             _ => unreachable!(),
         }
@@ -892,9 +892,9 @@ impl<'a, 'tcx> SpanEncoder for CacheEncoder<'a, 'tcx> {
 
     // copy&paste impl from rustc_metadata
     fn encode_symbol(&mut self, symbol: Symbol) {
-        // if symbol preinterned, emit tag and symbol index
-        if symbol.is_preinterned() {
-            self.encoder.emit_u8(SYMBOL_PREINTERNED);
+        // if symbol predefined, emit tag and symbol index
+        if symbol.is_predefined() {
+            self.encoder.emit_u8(SYMBOL_PREDEFINED);
             self.encoder.emit_u32(symbol.as_u32());
         } else {
             // otherwise write it as string or as offset to it
diff --git a/compiler/rustc_middle/src/ty/assoc.rs b/compiler/rustc_middle/src/ty/assoc.rs
index ce4c08aa485..bbaf735fbdb 100644
--- a/compiler/rustc_middle/src/ty/assoc.rs
+++ b/compiler/rustc_middle/src/ty/assoc.rs
@@ -98,10 +98,10 @@ impl AssocItem {
 
     pub fn descr(&self) -> &'static str {
         match self.kind {
-            ty::AssocKind::Const => "const",
+            ty::AssocKind::Const => "associated const",
             ty::AssocKind::Fn if self.fn_has_self_parameter => "method",
             ty::AssocKind::Fn => "associated function",
-            ty::AssocKind::Type => "type",
+            ty::AssocKind::Type => "associated type",
         }
     }
 
@@ -155,6 +155,8 @@ impl AssocKind {
 impl std::fmt::Display for AssocKind {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self {
+            // FIXME: fails to distinguish between "associated function" and
+            // "method" because `has_self` isn't known here.
             AssocKind::Fn => write!(f, "method"),
             AssocKind::Const => write!(f, "associated const"),
             AssocKind::Type => write!(f, "associated type"),
@@ -199,8 +201,9 @@ impl AssocItems {
         self.items.get_by_key(name)
     }
 
-    /// Returns the associated item with the given name and `AssocKind`, if one exists.
-    pub fn find_by_name_and_kind(
+    /// Returns the associated item with the given identifier and `AssocKind`, if one exists.
+    /// The identifier is matched hygienically.
+    pub fn find_by_ident_and_kind(
         &self,
         tcx: TyCtxt<'_>,
         ident: Ident,
@@ -212,8 +215,9 @@ impl AssocItems {
             .find(|item| tcx.hygienic_eq(ident, item.ident(tcx), parent_def_id))
     }
 
-    /// Returns the associated item with the given name and any of `AssocKind`, if one exists.
-    pub fn find_by_name_and_kinds(
+    /// Returns the associated item with the given identifier and any of `AssocKind`, if one
+    /// exists. The identifier is matched hygienically.
+    pub fn find_by_ident_and_kinds(
         &self,
         tcx: TyCtxt<'_>,
         ident: Ident,
@@ -221,11 +225,12 @@ impl AssocItems {
         kinds: &[AssocKind],
         parent_def_id: DefId,
     ) -> Option<&ty::AssocItem> {
-        kinds.iter().find_map(|kind| self.find_by_name_and_kind(tcx, ident, *kind, parent_def_id))
+        kinds.iter().find_map(|kind| self.find_by_ident_and_kind(tcx, ident, *kind, parent_def_id))
     }
 
-    /// Returns the associated item with the given name in the given `Namespace`, if one exists.
-    pub fn find_by_name_and_namespace(
+    /// Returns the associated item with the given identifier in the given `Namespace`, if one
+    /// exists. The identifier is matched hygienically.
+    pub fn find_by_ident_and_namespace(
         &self,
         tcx: TyCtxt<'_>,
         ident: Ident,
diff --git a/compiler/rustc_middle/src/ty/codec.rs b/compiler/rustc_middle/src/ty/codec.rs
index 74b34afe616..23927c112bc 100644
--- a/compiler/rustc_middle/src/ty/codec.rs
+++ b/compiler/rustc_middle/src/ty/codec.rs
@@ -501,7 +501,7 @@ impl_decodable_via_ref! {
     &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
     &'tcx traits::ImplSource<'tcx, ()>,
     &'tcx mir::Body<'tcx>,
-    &'tcx mir::BorrowCheckResult<'tcx>,
+    &'tcx mir::ConcreteOpaqueTypes<'tcx>,
     &'tcx ty::List<ty::BoundVariableKind>,
     &'tcx ty::ListWithCachedTypeInfo<ty::Clause<'tcx>>,
     &'tcx ty::List<FieldIdx>,
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index 162ca1f4af8..abf6cbbcd87 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -437,6 +437,10 @@ impl<'tcx> Interner for TyCtxt<'tcx> {
         )
     }
 
+    fn impl_self_is_guaranteed_unsized(self, impl_def_id: DefId) -> bool {
+        self.impl_self_is_guaranteed_unsized(impl_def_id)
+    }
+
     fn has_target_features(self, def_id: DefId) -> bool {
         !self.codegen_fn_attrs(def_id).target_features.is_empty()
     }
diff --git a/compiler/rustc_middle/src/ty/erase_regions.rs b/compiler/rustc_middle/src/ty/erase_regions.rs
index 8bddb5c0fd7..45a0b1288db 100644
--- a/compiler/rustc_middle/src/ty/erase_regions.rs
+++ b/compiler/rustc_middle/src/ty/erase_regions.rs
@@ -65,7 +65,7 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for RegionEraserVisitor<'tcx> {
         // We must not erase bound regions. `for<'a> fn(&'a ())` and
         // `fn(&'free ())` are different types: they may implement different
         // traits and have a different `TypeId`.
-        match *r {
+        match r.kind() {
             ty::ReBound(..) => r,
             _ => self.tcx.lifetimes.re_erased,
         }
diff --git a/compiler/rustc_middle/src/ty/error.rs b/compiler/rustc_middle/src/ty/error.rs
index a0e67929c52..5ecf1174def 100644
--- a/compiler/rustc_middle/src/ty/error.rs
+++ b/compiler/rustc_middle/src/ty/error.rs
@@ -279,7 +279,7 @@ impl<'tcx> TyCtxt<'tcx> {
         p.hash(&mut s);
         let hash = s.finish();
         *path = Some(path.take().unwrap_or_else(|| {
-            self.output_filenames(()).temp_path_ext(&format!("long-type-{hash}.txt"), None)
+            self.output_filenames(()).temp_path_for_diagnostic(&format!("long-type-{hash}.txt"))
         }));
         let Ok(mut file) =
             File::options().create(true).read(true).append(true).open(&path.as_ref().unwrap())
diff --git a/compiler/rustc_middle/src/ty/flags.rs b/compiler/rustc_middle/src/ty/flags.rs
index b0c442d28f0..2424923fb78 100644
--- a/compiler/rustc_middle/src/ty/flags.rs
+++ b/compiler/rustc_middle/src/ty/flags.rs
@@ -288,7 +288,7 @@ impl FlagComputation {
 
     fn add_region(&mut self, r: ty::Region<'_>) {
         self.add_flags(r.type_flags());
-        if let ty::ReBound(debruijn, _) = *r {
+        if let ty::ReBound(debruijn, _) = r.kind() {
             self.add_bound_var(debruijn);
         }
     }
diff --git a/compiler/rustc_middle/src/ty/fold.rs b/compiler/rustc_middle/src/ty/fold.rs
index dc2c9e3d9f1..8dc73e4ce85 100644
--- a/compiler/rustc_middle/src/ty/fold.rs
+++ b/compiler/rustc_middle/src/ty/fold.rs
@@ -145,10 +145,10 @@ where
     }
 
     fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
-        match *r {
+        match r.kind() {
             ty::ReBound(debruijn, br) if debruijn == self.current_index => {
                 let region = self.delegate.replace_region(br);
-                if let ty::ReBound(debruijn1, br) = *region {
+                if let ty::ReBound(debruijn1, br) = region.kind() {
                     // If the callback returns a bound region,
                     // that region should always use the INNERMOST
                     // debruijn index. Then we adjust it to the
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index 80f1bd7c6f4..a2b3acac3f2 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -1939,15 +1939,15 @@ impl<'tcx> TyCtxt<'tcx> {
     /// Hygienically compares a use-site name (`use_name`) for a field or an associated item with
     /// its supposed definition name (`def_name`). The method also needs `DefId` of the supposed
     /// definition's parent/scope to perform comparison.
-    pub fn hygienic_eq(self, use_name: Ident, def_name: Ident, def_parent_def_id: DefId) -> bool {
-        // We could use `Ident::eq` here, but we deliberately don't. The name
+    pub fn hygienic_eq(self, use_ident: Ident, def_ident: Ident, def_parent_def_id: DefId) -> bool {
+        // We could use `Ident::eq` here, but we deliberately don't. The identifier
         // comparison fails frequently, and we want to avoid the expensive
         // `normalize_to_macros_2_0()` calls required for the span comparison whenever possible.
-        use_name.name == def_name.name
-            && use_name
+        use_ident.name == def_ident.name
+            && use_ident
                 .span
                 .ctxt()
-                .hygienic_eq(def_name.span.ctxt(), self.expn_that_defined(def_parent_def_id))
+                .hygienic_eq(def_ident.span.ctxt(), self.expn_that_defined(def_parent_def_id))
     }
 
     pub fn adjust_ident(self, mut ident: Ident, scope: DefId) -> Ident {
diff --git a/compiler/rustc_middle/src/ty/opaque_types.rs b/compiler/rustc_middle/src/ty/opaque_types.rs
index c72efde0994..9445a18ad76 100644
--- a/compiler/rustc_middle/src/ty/opaque_types.rs
+++ b/compiler/rustc_middle/src/ty/opaque_types.rs
@@ -95,7 +95,7 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for ReverseMapper<'tcx> {
 
     #[instrument(skip(self), level = "debug")]
     fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
-        match *r {
+        match r.kind() {
             // Ignore bound regions and `'static` regions that appear in the
             // type, we only need to remap regions that reference lifetimes
             // from the function declaration.
diff --git a/compiler/rustc_middle/src/ty/print/mod.rs b/compiler/rustc_middle/src/ty/print/mod.rs
index 5904deaaaad..9172c5d3ab7 100644
--- a/compiler/rustc_middle/src/ty/print/mod.rs
+++ b/compiler/rustc_middle/src/ty/print/mod.rs
@@ -382,7 +382,7 @@ pub fn shrunk_instance_name<'tcx>(
             return (s, None);
         }
 
-        let path = tcx.output_filenames(()).temp_path_ext("long-type.txt", None);
+        let path = tcx.output_filenames(()).temp_path_for_diagnostic("long-type.txt");
         let written_to_path = std::fs::write(&path, s).ok().map(|_| path);
 
         (shrunk, written_to_path)
diff --git a/compiler/rustc_middle/src/ty/print/pretty.rs b/compiler/rustc_middle/src/ty/print/pretty.rs
index 3281cb4135a..2f93197bcef 100644
--- a/compiler/rustc_middle/src/ty/print/pretty.rs
+++ b/compiler/rustc_middle/src/ty/print/pretty.rs
@@ -63,6 +63,7 @@ thread_local! {
     static FORCE_TRIMMED_PATH: Cell<bool> = const { Cell::new(false) };
     static REDUCED_QUERIES: Cell<bool> = const { Cell::new(false) };
     static NO_VISIBLE_PATH: Cell<bool> = const { Cell::new(false) };
+    static NO_VISIBLE_PATH_IF_DOC_HIDDEN: Cell<bool> = const { Cell::new(false) };
     static RTN_MODE: Cell<RtnMode> = const { Cell::new(RtnMode::ForDiagnostic) };
 }
 
@@ -134,6 +135,8 @@ define_helper!(
     /// Prevent selection of visible paths. `Display` impl of DefId will prefer
     /// visible (public) reexports of types as paths.
     fn with_no_visible_paths(NoVisibleGuard, NO_VISIBLE_PATH);
+    /// Prevent selection of visible paths if the paths are through a doc hidden path.
+    fn with_no_visible_paths_if_doc_hidden(NoVisibleIfDocHiddenGuard, NO_VISIBLE_PATH_IF_DOC_HIDDEN);
 );
 
 #[must_use]
@@ -569,6 +572,10 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
             return Ok(false);
         };
 
+        if self.tcx().is_doc_hidden(visible_parent) && with_no_visible_paths_if_doc_hidden() {
+            return Ok(false);
+        }
+
         let actual_parent = self.tcx().opt_parent(def_id);
         debug!(
             "try_print_visible_def_path: visible_parent={:?} actual_parent={:?}",
@@ -613,7 +620,7 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
             // the children of the visible parent (as was done when computing
             // `visible_parent_map`), looking for the specific child we currently have and then
             // have access to the re-exported name.
-            DefPathData::TypeNs(Some(ref mut name)) if Some(visible_parent) != actual_parent => {
+            DefPathData::TypeNs(ref mut name) if Some(visible_parent) != actual_parent => {
                 // Item might be re-exported several times, but filter for the one
                 // that's public and whose identifier isn't `_`.
                 let reexport = self
@@ -634,7 +641,7 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
             }
             // Re-exported `extern crate` (#43189).
             DefPathData::CrateRoot => {
-                data = DefPathData::TypeNs(Some(self.tcx().crate_name(def_id.krate)));
+                data = DefPathData::TypeNs(self.tcx().crate_name(def_id.krate));
             }
             _ => {}
         }
@@ -2520,7 +2527,7 @@ impl<'tcx> PrettyPrinter<'tcx> for FmtPrinter<'_, 'tcx> {
 
         let identify_regions = self.tcx.sess.opts.unstable_opts.identify_regions;
 
-        match *region {
+        match region.kind() {
             ty::ReEarlyParam(ref data) => data.has_name(),
 
             ty::ReLateParam(ty::LateParamRegion { kind, .. }) => kind.is_named(),
@@ -2590,7 +2597,7 @@ impl<'tcx> FmtPrinter<'_, 'tcx> {
         // the user might want to diagnose an error, but there is basically no way
         // to fit that into a short string. Hence the recommendation to use
         // `explain_region()` or `note_and_explain_region()`.
-        match *region {
+        match region.kind() {
             ty::ReEarlyParam(data) => {
                 p!(write("{}", data.name));
                 return Ok(());
@@ -2680,7 +2687,7 @@ impl<'a, 'tcx> ty::TypeFolder<TyCtxt<'tcx>> for RegionFolder<'a, 'tcx> {
 
     fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
         let name = &mut self.name;
-        let region = match *r {
+        let region = match r.kind() {
             ty::ReBound(db, br) if db >= self.current_index => {
                 *self.region_map.entry(br).or_insert_with(|| name(Some(db), self.current_index, br))
             }
@@ -2704,7 +2711,7 @@ impl<'a, 'tcx> ty::TypeFolder<TyCtxt<'tcx>> for RegionFolder<'a, 'tcx> {
             }
             _ => return r,
         };
-        if let ty::ReBound(debruijn1, br) = *region {
+        if let ty::ReBound(debruijn1, br) = region.kind() {
             assert_eq!(debruijn1, ty::INNERMOST);
             ty::Region::new_bound(self.tcx, self.current_index, br)
         } else {
diff --git a/compiler/rustc_middle/src/ty/region.rs b/compiler/rustc_middle/src/ty/region.rs
index c78306f2ca3..3e4f7a79d53 100644
--- a/compiler/rustc_middle/src/ty/region.rs
+++ b/compiler/rustc_middle/src/ty/region.rs
@@ -1,5 +1,3 @@
-use std::ops::Deref;
-
 use rustc_data_structures::intern::Interned;
 use rustc_errors::MultiSpan;
 use rustc_hir::def_id::DefId;
@@ -22,7 +20,7 @@ impl<'tcx> rustc_type_ir::inherent::IntoKind for Region<'tcx> {
     type Kind = RegionKind<'tcx>;
 
     fn kind(self) -> RegionKind<'tcx> {
-        *self
+        *self.0.0
     }
 }
 
@@ -32,7 +30,7 @@ impl<'tcx> rustc_type_ir::Flags for Region<'tcx> {
     }
 
     fn outer_exclusive_binder(&self) -> ty::DebruijnIndex {
-        match **self {
+        match self.kind() {
             ty::ReBound(debruijn, _) => debruijn.shifted_in(1),
             _ => ty::INNERMOST,
         }
@@ -163,7 +161,7 @@ impl<'tcx> Region<'tcx> {
 
     pub fn get_name(self) -> Option<Symbol> {
         if self.has_name() {
-            match *self {
+            match self.kind() {
                 ty::ReEarlyParam(ebr) => Some(ebr.name),
                 ty::ReBound(_, br) => br.kind.get_name(),
                 ty::ReLateParam(fr) => fr.kind.get_name(),
@@ -185,7 +183,7 @@ impl<'tcx> Region<'tcx> {
 
     /// Is this region named by the user?
     pub fn has_name(self) -> bool {
-        match *self {
+        match self.kind() {
             ty::ReEarlyParam(ebr) => ebr.has_name(),
             ty::ReBound(_, br) => br.kind.is_named(),
             ty::ReLateParam(fr) => fr.kind.is_named(),
@@ -199,32 +197,32 @@ impl<'tcx> Region<'tcx> {
 
     #[inline]
     pub fn is_error(self) -> bool {
-        matches!(*self, ty::ReError(_))
+        matches!(self.kind(), ty::ReError(_))
     }
 
     #[inline]
     pub fn is_static(self) -> bool {
-        matches!(*self, ty::ReStatic)
+        matches!(self.kind(), ty::ReStatic)
     }
 
     #[inline]
     pub fn is_erased(self) -> bool {
-        matches!(*self, ty::ReErased)
+        matches!(self.kind(), ty::ReErased)
     }
 
     #[inline]
     pub fn is_bound(self) -> bool {
-        matches!(*self, ty::ReBound(..))
+        matches!(self.kind(), ty::ReBound(..))
     }
 
     #[inline]
     pub fn is_placeholder(self) -> bool {
-        matches!(*self, ty::RePlaceholder(..))
+        matches!(self.kind(), ty::RePlaceholder(..))
     }
 
     #[inline]
     pub fn bound_at_or_above_binder(self, index: ty::DebruijnIndex) -> bool {
-        match *self {
+        match self.kind() {
             ty::ReBound(debruijn, _) => debruijn >= index,
             _ => false,
         }
@@ -233,7 +231,7 @@ impl<'tcx> Region<'tcx> {
     pub fn type_flags(self) -> TypeFlags {
         let mut flags = TypeFlags::empty();
 
-        match *self {
+        match self.kind() {
             ty::ReVar(..) => {
                 flags = flags | TypeFlags::HAS_FREE_REGIONS;
                 flags = flags | TypeFlags::HAS_FREE_LOCAL_REGIONS;
@@ -275,14 +273,14 @@ impl<'tcx> Region<'tcx> {
 
     /// True for free regions other than `'static`.
     pub fn is_param(self) -> bool {
-        matches!(*self, ty::ReEarlyParam(_) | ty::ReLateParam(_))
+        matches!(self.kind(), ty::ReEarlyParam(_) | ty::ReLateParam(_))
     }
 
     /// True for free region in the current context.
     ///
     /// This is the case for `'static` and param regions.
     pub fn is_free(self) -> bool {
-        match *self {
+        match self.kind() {
             ty::ReStatic | ty::ReEarlyParam(..) | ty::ReLateParam(..) => true,
             ty::ReVar(..)
             | ty::RePlaceholder(..)
@@ -319,15 +317,6 @@ impl<'tcx> Region<'tcx> {
     }
 }
 
-impl<'tcx> Deref for Region<'tcx> {
-    type Target = RegionKind<'tcx>;
-
-    #[inline]
-    fn deref(&self) -> &RegionKind<'tcx> {
-        self.0.0
-    }
-}
-
 #[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
 #[derive(HashStable)]
 pub struct EarlyParamRegion {
diff --git a/compiler/rustc_middle/src/ty/significant_drop_order.rs b/compiler/rustc_middle/src/ty/significant_drop_order.rs
index ce4208f2c44..561f84192b4 100644
--- a/compiler/rustc_middle/src/ty/significant_drop_order.rs
+++ b/compiler/rustc_middle/src/ty/significant_drop_order.rs
@@ -26,7 +26,7 @@ fn true_significant_drop_ty<'tcx>(
                     name_rev.push(tcx.crate_name(did.krate));
                 }
                 rustc_hir::definitions::DefPathData::TypeNs(symbol) => {
-                    name_rev.push(symbol.unwrap());
+                    name_rev.push(symbol);
                 }
                 _ => return None,
             }
diff --git a/compiler/rustc_middle/src/ty/typeck_results.rs b/compiler/rustc_middle/src/ty/typeck_results.rs
index 7c437abfe24..90c6ef67fb8 100644
--- a/compiler/rustc_middle/src/ty/typeck_results.rs
+++ b/compiler/rustc_middle/src/ty/typeck_results.rs
@@ -758,7 +758,7 @@ impl<'tcx> IsIdentity for CanonicalUserType<'tcx> {
                             _ => false,
                         },
 
-                        GenericArgKind::Lifetime(r) => match *r {
+                        GenericArgKind::Lifetime(r) => match r.kind() {
                             ty::ReBound(debruijn, br) => {
                                 // We only allow a `ty::INNERMOST` index in generic parameters.
                                 assert_eq!(debruijn, ty::INNERMOST);
diff --git a/compiler/rustc_middle/src/ty/visit.rs b/compiler/rustc_middle/src/ty/visit.rs
index e3b7a258c39..b341b30af6a 100644
--- a/compiler/rustc_middle/src/ty/visit.rs
+++ b/compiler/rustc_middle/src/ty/visit.rs
@@ -77,7 +77,7 @@ impl<'tcx> TyCtxt<'tcx> {
             }
 
             fn visit_region(&mut self, r: ty::Region<'tcx>) -> Self::Result {
-                match *r {
+                match r.kind() {
                     ty::ReBound(debruijn, _) if debruijn < self.outer_index => {
                         ControlFlow::Continue(())
                     }
@@ -205,7 +205,7 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for LateBoundRegionsCollector {
     }
 
     fn visit_region(&mut self, r: ty::Region<'tcx>) {
-        if let ty::ReBound(debruijn, br) = *r {
+        if let ty::ReBound(debruijn, br) = r.kind() {
             if debruijn == self.current_index {
                 self.regions.insert(br.kind);
             }
@@ -250,7 +250,7 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for MaxUniverse {
     }
 
     fn visit_region(&mut self, r: ty::Region<'tcx>) {
-        if let ty::RePlaceholder(placeholder) = *r {
+        if let ty::RePlaceholder(placeholder) = r.kind() {
             self.max_universe = ty::UniverseIndex::from_u32(
                 self.max_universe.as_u32().max(placeholder.universe.as_u32()),
             );
diff --git a/compiler/rustc_mir_build/src/builder/expr/into.rs b/compiler/rustc_mir_build/src/builder/expr/into.rs
index 333e69475c5..a9a07997410 100644
--- a/compiler/rustc_mir_build/src/builder/expr/into.rs
+++ b/compiler/rustc_mir_build/src/builder/expr/into.rs
@@ -328,7 +328,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                             destination,
                             target: Some(success),
                             unwind: UnwindAction::Unreachable,
-                            call_source: CallSource::Misc,
+                            call_source: CallSource::Use,
                             fn_span: expr_span,
                         },
                     );
diff --git a/compiler/rustc_mir_transform/src/gvn.rs b/compiler/rustc_mir_transform/src/gvn.rs
index 68bc0ffce6b..8b8d1efbbd2 100644
--- a/compiler/rustc_mir_transform/src/gvn.rs
+++ b/compiler/rustc_mir_transform/src/gvn.rs
@@ -980,27 +980,17 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
             }
         }
 
-        let tcx = self.tcx;
-        let mut projection = SmallVec::<[PlaceElem<'tcx>; 1]>::new();
-        loop {
-            if let Some(local) = self.try_as_local(copy_from_local_value, location) {
-                projection.reverse();
-                let place = Place { local, projection: tcx.mk_place_elems(projection.as_slice()) };
-                if rvalue.ty(self.local_decls, tcx) == place.ty(self.local_decls, tcx).ty {
-                    self.reused_locals.insert(local);
-                    *rvalue = Rvalue::Use(Operand::Copy(place));
-                    return Some(copy_from_value);
-                }
-                return None;
-            } else if let Value::Projection(pointer, proj) = *self.get(copy_from_local_value)
-                && let Some(proj) = self.try_as_place_elem(proj, location)
-            {
-                projection.push(proj);
-                copy_from_local_value = pointer;
-            } else {
-                return None;
+        // Allow introducing places with non-constant offsets, as those are still better than
+        // reconstructing an aggregate.
+        if let Some(place) = self.try_as_place(copy_from_local_value, location, true) {
+            if rvalue.ty(self.local_decls, self.tcx) == place.ty(self.local_decls, self.tcx).ty {
+                self.reused_locals.insert(place.local);
+                *rvalue = Rvalue::Use(Operand::Copy(place));
+                return Some(copy_from_local_value);
             }
         }
+
+        None
     }
 
     fn simplify_aggregate(
@@ -1672,14 +1662,14 @@ fn op_to_prop_const<'tcx>(
 }
 
 impl<'tcx> VnState<'_, 'tcx> {
-    /// If either [`Self::try_as_constant`] as [`Self::try_as_local`] succeeds,
+    /// If either [`Self::try_as_constant`] as [`Self::try_as_place`] succeeds,
     /// returns that result as an [`Operand`].
     fn try_as_operand(&mut self, index: VnIndex, location: Location) -> Option<Operand<'tcx>> {
         if let Some(const_) = self.try_as_constant(index) {
             Some(Operand::Constant(Box::new(const_)))
-        } else if let Some(local) = self.try_as_local(index, location) {
-            self.reused_locals.insert(local);
-            Some(Operand::Copy(local.into()))
+        } else if let Some(place) = self.try_as_place(index, location, false) {
+            self.reused_locals.insert(place.local);
+            Some(Operand::Copy(place))
         } else {
             None
         }
@@ -1712,6 +1702,35 @@ impl<'tcx> VnState<'_, 'tcx> {
         Some(ConstOperand { span: DUMMY_SP, user_ty: None, const_ })
     }
 
+    /// Construct a place which holds the same value as `index` and for which all locals strictly
+    /// dominate `loc`. If you used this place, add its base local to `reused_locals` to remove
+    /// storage statements.
+    #[instrument(level = "trace", skip(self), ret)]
+    fn try_as_place(
+        &mut self,
+        mut index: VnIndex,
+        loc: Location,
+        allow_complex_projection: bool,
+    ) -> Option<Place<'tcx>> {
+        let mut projection = SmallVec::<[PlaceElem<'tcx>; 1]>::new();
+        loop {
+            if let Some(local) = self.try_as_local(index, loc) {
+                projection.reverse();
+                let place =
+                    Place { local, projection: self.tcx.mk_place_elems(projection.as_slice()) };
+                return Some(place);
+            } else if let Value::Projection(pointer, proj) = *self.get(index)
+                && (allow_complex_projection || proj.is_stable_offset())
+                && let Some(proj) = self.try_as_place_elem(proj, loc)
+            {
+                projection.push(proj);
+                index = pointer;
+            } else {
+                return None;
+            }
+        }
+    }
+
     /// If there is a local which is assigned `index`, and its assignment strictly dominates `loc`,
     /// return it. If you used this local, add it to `reused_locals` to remove storage statements.
     fn try_as_local(&mut self, index: VnIndex, loc: Location) -> Option<Local> {
@@ -1762,11 +1781,12 @@ impl<'tcx> MutVisitor<'tcx> for VnState<'_, 'tcx> {
             if let Some(value) = value {
                 if let Some(const_) = self.try_as_constant(value) {
                     *rvalue = Rvalue::Use(Operand::Constant(Box::new(const_)));
-                } else if let Some(local) = self.try_as_local(value, location)
-                    && *rvalue != Rvalue::Use(Operand::Move(local.into()))
+                } else if let Some(place) = self.try_as_place(value, location, false)
+                    && *rvalue != Rvalue::Use(Operand::Move(place))
+                    && *rvalue != Rvalue::Use(Operand::Copy(place))
                 {
-                    *rvalue = Rvalue::Use(Operand::Copy(local.into()));
-                    self.reused_locals.insert(local);
+                    *rvalue = Rvalue::Use(Operand::Copy(place));
+                    self.reused_locals.insert(place.local);
                 }
             }
         }
diff --git a/compiler/rustc_mir_transform/src/instsimplify.rs b/compiler/rustc_mir_transform/src/instsimplify.rs
index 2eff6b31372..a8d6aaa50a2 100644
--- a/compiler/rustc_mir_transform/src/instsimplify.rs
+++ b/compiler/rustc_mir_transform/src/instsimplify.rs
@@ -39,26 +39,26 @@ impl<'tcx> crate::MirPass<'tcx> for InstSimplify {
             attr::contains_name(tcx.hir_krate_attrs(), sym::rustc_preserve_ub_checks);
         for block in body.basic_blocks.as_mut() {
             for statement in block.statements.iter_mut() {
-                match statement.kind {
-                    StatementKind::Assign(box (_place, ref mut rvalue)) => {
-                        if !preserve_ub_checks {
-                            ctx.simplify_ub_check(rvalue);
-                        }
-                        ctx.simplify_bool_cmp(rvalue);
-                        ctx.simplify_ref_deref(rvalue);
-                        ctx.simplify_ptr_aggregate(rvalue);
-                        ctx.simplify_cast(rvalue);
-                        ctx.simplify_repeated_aggregate(rvalue);
-                        ctx.simplify_repeat_once(rvalue);
-                    }
-                    _ => {}
+                let StatementKind::Assign(box (.., rvalue)) = &mut statement.kind else {
+                    continue;
+                };
+
+                if !preserve_ub_checks {
+                    ctx.simplify_ub_check(rvalue);
                 }
+                ctx.simplify_bool_cmp(rvalue);
+                ctx.simplify_ref_deref(rvalue);
+                ctx.simplify_ptr_aggregate(rvalue);
+                ctx.simplify_cast(rvalue);
+                ctx.simplify_repeated_aggregate(rvalue);
+                ctx.simplify_repeat_once(rvalue);
             }
 
-            ctx.simplify_primitive_clone(block.terminator.as_mut().unwrap(), &mut block.statements);
-            ctx.simplify_intrinsic_assert(block.terminator.as_mut().unwrap());
-            ctx.simplify_nounwind_call(block.terminator.as_mut().unwrap());
-            simplify_duplicate_switch_targets(block.terminator.as_mut().unwrap());
+            let terminator = block.terminator.as_mut().unwrap();
+            ctx.simplify_primitive_clone(terminator, &mut block.statements);
+            ctx.simplify_intrinsic_assert(terminator);
+            ctx.simplify_nounwind_call(terminator);
+            simplify_duplicate_switch_targets(terminator);
         }
     }
 
@@ -105,43 +105,34 @@ impl<'tcx> InstSimplifyContext<'_, 'tcx> {
 
     /// Transform boolean comparisons into logical operations.
     fn simplify_bool_cmp(&self, rvalue: &mut Rvalue<'tcx>) {
-        match rvalue {
-            Rvalue::BinaryOp(op @ (BinOp::Eq | BinOp::Ne), box (a, b)) => {
-                let new = match (op, self.try_eval_bool(a), self.try_eval_bool(b)) {
-                    // Transform "Eq(a, true)" ==> "a"
-                    (BinOp::Eq, _, Some(true)) => Some(Rvalue::Use(a.clone())),
+        let Rvalue::BinaryOp(op @ (BinOp::Eq | BinOp::Ne), box (a, b)) = &*rvalue else { return };
+        *rvalue = match (op, self.try_eval_bool(a), self.try_eval_bool(b)) {
+            // Transform "Eq(a, true)" ==> "a"
+            (BinOp::Eq, _, Some(true)) => Rvalue::Use(a.clone()),
 
-                    // Transform "Ne(a, false)" ==> "a"
-                    (BinOp::Ne, _, Some(false)) => Some(Rvalue::Use(a.clone())),
+            // Transform "Ne(a, false)" ==> "a"
+            (BinOp::Ne, _, Some(false)) => Rvalue::Use(a.clone()),
 
-                    // Transform "Eq(true, b)" ==> "b"
-                    (BinOp::Eq, Some(true), _) => Some(Rvalue::Use(b.clone())),
+            // Transform "Eq(true, b)" ==> "b"
+            (BinOp::Eq, Some(true), _) => Rvalue::Use(b.clone()),
 
-                    // Transform "Ne(false, b)" ==> "b"
-                    (BinOp::Ne, Some(false), _) => Some(Rvalue::Use(b.clone())),
+            // Transform "Ne(false, b)" ==> "b"
+            (BinOp::Ne, Some(false), _) => Rvalue::Use(b.clone()),
 
-                    // Transform "Eq(false, b)" ==> "Not(b)"
-                    (BinOp::Eq, Some(false), _) => Some(Rvalue::UnaryOp(UnOp::Not, b.clone())),
+            // Transform "Eq(false, b)" ==> "Not(b)"
+            (BinOp::Eq, Some(false), _) => Rvalue::UnaryOp(UnOp::Not, b.clone()),
 
-                    // Transform "Ne(true, b)" ==> "Not(b)"
-                    (BinOp::Ne, Some(true), _) => Some(Rvalue::UnaryOp(UnOp::Not, b.clone())),
+            // Transform "Ne(true, b)" ==> "Not(b)"
+            (BinOp::Ne, Some(true), _) => Rvalue::UnaryOp(UnOp::Not, b.clone()),
 
-                    // Transform "Eq(a, false)" ==> "Not(a)"
-                    (BinOp::Eq, _, Some(false)) => Some(Rvalue::UnaryOp(UnOp::Not, a.clone())),
+            // Transform "Eq(a, false)" ==> "Not(a)"
+            (BinOp::Eq, _, Some(false)) => Rvalue::UnaryOp(UnOp::Not, a.clone()),
 
-                    // Transform "Ne(a, true)" ==> "Not(a)"
-                    (BinOp::Ne, _, Some(true)) => Some(Rvalue::UnaryOp(UnOp::Not, a.clone())),
-
-                    _ => None,
-                };
-
-                if let Some(new) = new {
-                    *rvalue = new;
-                }
-            }
+            // Transform "Ne(a, true)" ==> "Not(a)"
+            (BinOp::Ne, _, Some(true)) => Rvalue::UnaryOp(UnOp::Not, a.clone()),
 
-            _ => {}
-        }
+            _ => return,
+        };
     }
 
     fn try_eval_bool(&self, a: &Operand<'_>) -> Option<bool> {
@@ -151,64 +142,58 @@ impl<'tcx> InstSimplifyContext<'_, 'tcx> {
 
     /// Transform `&(*a)` ==> `a`.
     fn simplify_ref_deref(&self, rvalue: &mut Rvalue<'tcx>) {
-        if let Rvalue::Ref(_, _, place) | Rvalue::RawPtr(_, place) = rvalue {
-            if let Some((base, ProjectionElem::Deref)) = place.as_ref().last_projection() {
-                if rvalue.ty(self.local_decls, self.tcx) != base.ty(self.local_decls, self.tcx).ty {
-                    return;
-                }
-
-                *rvalue = Rvalue::Use(Operand::Copy(Place {
-                    local: base.local,
-                    projection: self.tcx.mk_place_elems(base.projection),
-                }));
-            }
+        if let Rvalue::Ref(_, _, place) | Rvalue::RawPtr(_, place) = rvalue
+            && let Some((base, ProjectionElem::Deref)) = place.as_ref().last_projection()
+            && rvalue.ty(self.local_decls, self.tcx) == base.ty(self.local_decls, self.tcx).ty
+        {
+            *rvalue = Rvalue::Use(Operand::Copy(Place {
+                local: base.local,
+                projection: self.tcx.mk_place_elems(base.projection),
+            }));
         }
     }
 
     /// Transform `Aggregate(RawPtr, [p, ()])` ==> `Cast(PtrToPtr, p)`.
     fn simplify_ptr_aggregate(&self, rvalue: &mut Rvalue<'tcx>) {
         if let Rvalue::Aggregate(box AggregateKind::RawPtr(pointee_ty, mutability), fields) = rvalue
+            && let meta_ty = fields.raw[1].ty(self.local_decls, self.tcx)
+            && meta_ty.is_unit()
         {
-            let meta_ty = fields.raw[1].ty(self.local_decls, self.tcx);
-            if meta_ty.is_unit() {
-                // The mutable borrows we're holding prevent printing `rvalue` here
-                let mut fields = std::mem::take(fields);
-                let _meta = fields.pop().unwrap();
-                let data = fields.pop().unwrap();
-                let ptr_ty = Ty::new_ptr(self.tcx, *pointee_ty, *mutability);
-                *rvalue = Rvalue::Cast(CastKind::PtrToPtr, data, ptr_ty);
-            }
+            // The mutable borrows we're holding prevent printing `rvalue` here
+            let mut fields = std::mem::take(fields);
+            let _meta = fields.pop().unwrap();
+            let data = fields.pop().unwrap();
+            let ptr_ty = Ty::new_ptr(self.tcx, *pointee_ty, *mutability);
+            *rvalue = Rvalue::Cast(CastKind::PtrToPtr, data, ptr_ty);
         }
     }
 
     fn simplify_ub_check(&self, rvalue: &mut Rvalue<'tcx>) {
-        if let Rvalue::NullaryOp(NullOp::UbChecks, _) = *rvalue {
-            let const_ = Const::from_bool(self.tcx, self.tcx.sess.ub_checks());
-            let constant = ConstOperand { span: DUMMY_SP, const_, user_ty: None };
-            *rvalue = Rvalue::Use(Operand::Constant(Box::new(constant)));
-        }
+        let Rvalue::NullaryOp(NullOp::UbChecks, _) = *rvalue else { return };
+
+        let const_ = Const::from_bool(self.tcx, self.tcx.sess.ub_checks());
+        let constant = ConstOperand { span: DUMMY_SP, const_, user_ty: None };
+        *rvalue = Rvalue::Use(Operand::Constant(Box::new(constant)));
     }
 
     fn simplify_cast(&self, rvalue: &mut Rvalue<'tcx>) {
-        if let Rvalue::Cast(kind, operand, cast_ty) = rvalue {
-            let operand_ty = operand.ty(self.local_decls, self.tcx);
-            if operand_ty == *cast_ty {
-                *rvalue = Rvalue::Use(operand.clone());
-            } else if *kind == CastKind::Transmute {
-                // Transmuting an integer to another integer is just a signedness cast
-                if let (ty::Int(int), ty::Uint(uint)) | (ty::Uint(uint), ty::Int(int)) =
-                    (operand_ty.kind(), cast_ty.kind())
-                    && int.bit_width() == uint.bit_width()
-                {
-                    // The width check isn't strictly necessary, as different widths
-                    // are UB and thus we'd be allowed to turn it into a cast anyway.
-                    // But let's keep the UB around for codegen to exploit later.
-                    // (If `CastKind::Transmute` ever becomes *not* UB for mismatched sizes,
-                    // then the width check is necessary for big-endian correctness.)
-                    *kind = CastKind::IntToInt;
-                    return;
-                }
-            }
+        let Rvalue::Cast(kind, operand, cast_ty) = rvalue else { return };
+
+        let operand_ty = operand.ty(self.local_decls, self.tcx);
+        if operand_ty == *cast_ty {
+            *rvalue = Rvalue::Use(operand.clone());
+        } else if *kind == CastKind::Transmute
+            // Transmuting an integer to another integer is just a signedness cast
+            && let (ty::Int(int), ty::Uint(uint)) | (ty::Uint(uint), ty::Int(int)) =
+                (operand_ty.kind(), cast_ty.kind())
+            && int.bit_width() == uint.bit_width()
+        {
+            // The width check isn't strictly necessary, as different widths
+            // are UB and thus we'd be allowed to turn it into a cast anyway.
+            // But let's keep the UB around for codegen to exploit later.
+            // (If `CastKind::Transmute` ever becomes *not* UB for mismatched sizes,
+            // then the width check is necessary for big-endian correctness.)
+            *kind = CastKind::IntToInt;
         }
     }
 
@@ -277,7 +262,7 @@ impl<'tcx> InstSimplifyContext<'_, 'tcx> {
     }
 
     fn simplify_nounwind_call(&self, terminator: &mut Terminator<'tcx>) {
-        let TerminatorKind::Call { func, unwind, .. } = &mut terminator.kind else {
+        let TerminatorKind::Call { ref func, ref mut unwind, .. } = terminator.kind else {
             return;
         };
 
@@ -290,7 +275,7 @@ impl<'tcx> InstSimplifyContext<'_, 'tcx> {
             ty::FnDef(..) => body_ty.fn_sig(self.tcx).abi(),
             ty::Closure(..) => ExternAbi::RustCall,
             ty::Coroutine(..) => ExternAbi::Rust,
-            _ => bug!("unexpected body ty: {:?}", body_ty),
+            _ => bug!("unexpected body ty: {body_ty:?}"),
         };
 
         if !layout::fn_can_unwind(self.tcx, Some(def_id), body_abi) {
@@ -299,10 +284,9 @@ impl<'tcx> InstSimplifyContext<'_, 'tcx> {
     }
 
     fn simplify_intrinsic_assert(&self, terminator: &mut Terminator<'tcx>) {
-        let TerminatorKind::Call { func, target, .. } = &mut terminator.kind else {
-            return;
-        };
-        let Some(target_block) = target else {
+        let TerminatorKind::Call { ref func, target: ref mut target @ Some(target_block), .. } =
+            terminator.kind
+        else {
             return;
         };
         let func_ty = func.ty(self.local_decls, self.tcx);
@@ -310,12 +294,10 @@ impl<'tcx> InstSimplifyContext<'_, 'tcx> {
             return;
         };
         // The intrinsics we are interested in have one generic parameter
-        if args.is_empty() {
-            return;
-        }
+        let [arg, ..] = args[..] else { return };
 
         let known_is_valid =
-            intrinsic_assert_panics(self.tcx, self.typing_env, args[0], intrinsic_name);
+            intrinsic_assert_panics(self.tcx, self.typing_env, arg, intrinsic_name);
         match known_is_valid {
             // We don't know the layout or it's not validity assertion at all, don't touch it
             None => {}
@@ -325,7 +307,7 @@ impl<'tcx> InstSimplifyContext<'_, 'tcx> {
             }
             Some(false) => {
                 // If we know the assert does not panic, turn the call into a Goto
-                terminator.kind = TerminatorKind::Goto { target: *target_block };
+                terminator.kind = TerminatorKind::Goto { target: target_block };
             }
         }
     }
@@ -346,9 +328,7 @@ fn resolve_rust_intrinsic<'tcx>(
     tcx: TyCtxt<'tcx>,
     func_ty: Ty<'tcx>,
 ) -> Option<(Symbol, GenericArgsRef<'tcx>)> {
-    if let ty::FnDef(def_id, args) = *func_ty.kind() {
-        let intrinsic = tcx.intrinsic(def_id)?;
-        return Some((intrinsic.name, args));
-    }
-    None
+    let ty::FnDef(def_id, args) = *func_ty.kind() else { return None };
+    let intrinsic = tcx.intrinsic(def_id)?;
+    Some((intrinsic.name, args))
 }
diff --git a/compiler/rustc_mir_transform/src/lib.rs b/compiler/rustc_mir_transform/src/lib.rs
index 6429d3f67ec..dfd07f0fb16 100644
--- a/compiler/rustc_mir_transform/src/lib.rs
+++ b/compiler/rustc_mir_transform/src/lib.rs
@@ -498,8 +498,11 @@ fn mir_drops_elaborated_and_const_checked(tcx: TyCtxt<'_>, def: LocalDefId) -> &
     }
 
     // We only need to borrowck non-synthetic MIR.
-    let tainted_by_errors =
-        if !tcx.is_synthetic_mir(def) { tcx.mir_borrowck(def).tainted_by_errors } else { None };
+    let tainted_by_errors = if !tcx.is_synthetic_mir(def) {
+        tcx.mir_borrowck(tcx.typeck_root_def_id(def.to_def_id()).expect_local()).err()
+    } else {
+        None
+    };
 
     let is_fn_like = tcx.def_kind(def).is_fn_like();
     if is_fn_like {
@@ -795,7 +798,7 @@ fn promoted_mir(tcx: TyCtxt<'_>, def: LocalDefId) -> &IndexVec<Promoted, Body<'_
     }
 
     if !tcx.is_synthetic_mir(def) {
-        tcx.ensure_done().mir_borrowck(def);
+        tcx.ensure_done().mir_borrowck(tcx.typeck_root_def_id(def.to_def_id()).expect_local());
     }
     let mut promoted = tcx.mir_promoted(def).1.steal();
 
diff --git a/compiler/rustc_monomorphize/src/collector.rs b/compiler/rustc_monomorphize/src/collector.rs
index 6e676ac6b8d..1dbb35f92c2 100644
--- a/compiler/rustc_monomorphize/src/collector.rs
+++ b/compiler/rustc_monomorphize/src/collector.rs
@@ -1689,7 +1689,7 @@ pub(crate) fn collect_crate_mono_items<'tcx>(
             let mut recursion_depths = DefIdMap::default();
             collect_items_rec(
                 tcx,
-                dummy_spanned(root),
+                dummy_spanned(*root),
                 &state,
                 &mut recursion_depths,
                 recursion_limit,
diff --git a/compiler/rustc_monomorphize/src/mono_checks/move_check.rs b/compiler/rustc_monomorphize/src/mono_checks/move_check.rs
index 838bfdab1ea..55d52d5075d 100644
--- a/compiler/rustc_monomorphize/src/mono_checks/move_check.rs
+++ b/compiler/rustc_monomorphize/src/mono_checks/move_check.rs
@@ -148,11 +148,7 @@ impl<'tcx> MoveCheckVisitor<'tcx> {
         span: Span,
     ) {
         let source_info = self.body.source_info(location);
-        for reported_span in &self.move_size_spans {
-            if reported_span.overlaps(span) {
-                return;
-            }
-        }
+
         let lint_root = source_info.scope.lint_root(&self.body.source_scopes);
         let Some(lint_root) = lint_root else {
             // This happens when the issue is in a function from a foreign crate that
@@ -162,19 +158,40 @@ impl<'tcx> MoveCheckVisitor<'tcx> {
             // but correct span? This would make the lint at least accept crate-level lint attributes.
             return;
         };
+
+        // If the source scope is inlined by the MIR inliner, report the lint on the call site.
+        let reported_span = self
+            .body
+            .source_scopes
+            .get(source_info.scope)
+            .and_then(|source_scope_data| source_scope_data.inlined)
+            .map(|(_, call_site)| call_site)
+            .unwrap_or(span);
+
+        for previously_reported_span in &self.move_size_spans {
+            if previously_reported_span.overlaps(reported_span) {
+                return;
+            }
+        }
+
         self.tcx.emit_node_span_lint(
             LARGE_ASSIGNMENTS,
             lint_root,
-            span,
-            LargeAssignmentsLint { span, size: too_large_size.bytes(), limit: limit as u64 },
+            reported_span,
+            LargeAssignmentsLint {
+                span: reported_span,
+                size: too_large_size.bytes(),
+                limit: limit as u64,
+            },
         );
-        self.move_size_spans.push(span);
+
+        self.move_size_spans.push(reported_span);
     }
 }
 
 fn assoc_fn_of_type<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, fn_ident: Ident) -> Option<DefId> {
     for impl_def_id in tcx.inherent_impls(def_id) {
-        if let Some(new) = tcx.associated_items(impl_def_id).find_by_name_and_kind(
+        if let Some(new) = tcx.associated_items(impl_def_id).find_by_ident_and_kind(
             tcx,
             fn_ident,
             AssocKind::Fn,
diff --git a/compiler/rustc_next_trait_solver/src/lib.rs b/compiler/rustc_next_trait_solver/src/lib.rs
index f575fe03019..92cdc28a37b 100644
--- a/compiler/rustc_next_trait_solver/src/lib.rs
+++ b/compiler/rustc_next_trait_solver/src/lib.rs
@@ -6,7 +6,7 @@
 
 // tidy-alphabetical-start
 #![allow(rustc::usage_of_type_ir_inherent)]
-#![cfg_attr(not(bootstrap), allow(rustc::usage_of_type_ir_traits))]
+#![allow(rustc::usage_of_type_ir_traits)]
 // tidy-alphabetical-end
 
 pub mod canonicalizer;
diff --git a/compiler/rustc_next_trait_solver/src/solve/normalizes_to/mod.rs b/compiler/rustc_next_trait_solver/src/solve/normalizes_to/mod.rs
index de6d21da0f5..2d027f16e5d 100644
--- a/compiler/rustc_next_trait_solver/src/solve/normalizes_to/mod.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/normalizes_to/mod.rs
@@ -134,7 +134,7 @@ where
                     // Add GAT where clauses from the trait's definition
                     // FIXME: We don't need these, since these are the type's own WF obligations.
                     ecx.add_goals(
-                        GoalSource::Misc,
+                        GoalSource::AliasWellFormed,
                         cx.own_predicates_of(goal.predicate.def_id())
                             .iter_instantiated(cx, goal.predicate.alias.args)
                             .map(|pred| goal.with(cx, pred)),
@@ -199,7 +199,7 @@ where
             // Add GAT where clauses from the trait's definition.
             // FIXME: We don't need these, since these are the type's own WF obligations.
             ecx.add_goals(
-                GoalSource::Misc,
+                GoalSource::AliasWellFormed,
                 cx.own_predicates_of(goal.predicate.def_id())
                     .iter_instantiated(cx, goal.predicate.alias.args)
                     .map(|pred| goal.with(cx, pred)),
@@ -232,7 +232,33 @@ where
             };
 
             if !cx.has_item_definition(target_item_def_id) {
-                return error_response(ecx, cx.delay_bug("missing item"));
+                // If the impl is missing an item, it's either because the user forgot to
+                // provide it, or the user is not *obligated* to provide it (because it
+                // has a trivially false `Sized` predicate). If it's the latter, we cannot
+                // delay a bug because we can have trivially false where clauses, so we
+                // treat it as rigid.
+                if cx.impl_self_is_guaranteed_unsized(impl_def_id) {
+                    match ecx.typing_mode() {
+                        ty::TypingMode::Coherence => {
+                            return ecx.evaluate_added_goals_and_make_canonical_response(
+                                Certainty::AMBIGUOUS,
+                            );
+                        }
+                        ty::TypingMode::Analysis { .. }
+                        | ty::TypingMode::Borrowck { .. }
+                        | ty::TypingMode::PostBorrowckAnalysis { .. }
+                        | ty::TypingMode::PostAnalysis => {
+                            ecx.structurally_instantiate_normalizes_to_term(
+                                goal,
+                                goal.predicate.alias,
+                            );
+                            return ecx
+                                .evaluate_added_goals_and_make_canonical_response(Certainty::Yes);
+                        }
+                    }
+                } else {
+                    return error_response(ecx, cx.delay_bug("missing item"));
+                }
             }
 
             let target_container_def_id = cx.parent(target_item_def_id);
diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index 9c457f150a3..d52e36fcfac 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -2166,10 +2166,15 @@ impl<'a> Parser<'a> {
                 let expr = self
                     .eat_metavar_seq(mv_kind, |this| this.parse_expr())
                     .expect("metavar seq expr");
-                let ast::ExprKind::Lit(token_lit) = expr.kind else {
-                    panic!("didn't reparse an expr");
-                };
-                Some(token_lit)
+                if let ast::ExprKind::Lit(token_lit) = expr.kind {
+                    Some(token_lit)
+                } else if let ast::ExprKind::Unary(UnOp::Neg, inner) = &expr.kind
+                    && let ast::Expr { kind: ast::ExprKind::Lit(_), .. } = **inner
+                {
+                    None
+                } else {
+                    panic!("unexpected reparsed expr: {:?}", expr.kind);
+                }
             }
             _ => None,
         }
diff --git a/compiler/rustc_parse/src/parser/item.rs b/compiler/rustc_parse/src/parser/item.rs
index 3647bf2c378..06501816340 100644
--- a/compiler/rustc_parse/src/parser/item.rs
+++ b/compiler/rustc_parse/src/parser/item.rs
@@ -602,21 +602,13 @@ impl<'a> Parser<'a> {
         let polarity = self.parse_polarity();
 
         // Parse both types and traits as a type, then reinterpret if necessary.
-        let err_path = |span| ast::Path::from_ident(Ident::new(kw::Empty, span));
         let ty_first = if self.token.is_keyword(kw::For) && self.look_ahead(1, |t| t != &token::Lt)
         {
             let span = self.prev_token.span.between(self.token.span);
-            self.dcx().emit_err(errors::MissingTraitInTraitImpl {
+            return Err(self.dcx().create_err(errors::MissingTraitInTraitImpl {
                 span,
                 for_span: span.to(self.token.span),
-            });
-
-            P(Ty {
-                kind: TyKind::Path(None, err_path(span)),
-                span,
-                id: DUMMY_NODE_ID,
-                tokens: None,
-            })
+            }));
         } else {
             self.parse_ty_with_generics_recovery(&generics)?
         };
@@ -657,6 +649,7 @@ impl<'a> Parser<'a> {
                     other => {
                         if let TyKind::ImplTrait(_, bounds) = other
                             && let [bound] = bounds.as_slice()
+                            && let GenericBound::Trait(poly_trait_ref) = bound
                         {
                             // Suggest removing extra `impl` keyword:
                             // `impl<T: Default> impl Default for Wrapper<T>`
@@ -666,12 +659,12 @@ impl<'a> Parser<'a> {
                                 extra_impl_kw,
                                 impl_trait_span: ty_first.span,
                             });
+                            poly_trait_ref.trait_ref.path.clone()
                         } else {
-                            self.dcx().emit_err(errors::ExpectedTraitInTraitImplFoundType {
-                                span: ty_first.span,
-                            });
+                            return Err(self.dcx().create_err(
+                                errors::ExpectedTraitInTraitImplFoundType { span: ty_first.span },
+                            ));
                         }
-                        err_path(ty_first.span)
                     }
                 };
                 let trait_ref = TraitRef { path, ref_id: ty_first.id };
diff --git a/compiler/rustc_parse/src/parser/mod.rs b/compiler/rustc_parse/src/parser/mod.rs
index 3b0861a9942..fafd1b1ae00 100644
--- a/compiler/rustc_parse/src/parser/mod.rs
+++ b/compiler/rustc_parse/src/parser/mod.rs
@@ -782,9 +782,16 @@ impl<'a> Parser<'a> {
             // Recovery is disabled when parsing macro arguments, so it must
             // also be disabled when reparsing pasted macro arguments,
             // otherwise we get inconsistent results (e.g. #137874).
-            let res = self.with_recovery(Recovery::Forbidden, |this| {
-                f(this).expect("failed to reparse {mv_kind:?}")
-            });
+            let res = self.with_recovery(Recovery::Forbidden, |this| f(this));
+
+            let res = match res {
+                Ok(res) => res,
+                Err(err) => {
+                    // This can occur in unusual error cases, e.g. #139445.
+                    err.delay_as_bug();
+                    return None;
+                }
+            };
 
             if let token::CloseDelim(delim) = self.token.kind
                 && let Delimiter::Invisible(InvisibleOrigin::MetaVar(mv_kind)) = delim
@@ -793,7 +800,12 @@ impl<'a> Parser<'a> {
                 self.bump();
                 Some(res)
             } else {
-                panic!("no close delim when reparsing {mv_kind:?}");
+                // This can occur when invalid syntax is passed to a decl macro. E.g. see #139248,
+                // where the reparse attempt of an invalid expr consumed the trailing invisible
+                // delimiter.
+                self.dcx()
+                    .span_delayed_bug(self.token.span, "no close delim with reparsing {mv_kind:?}");
+                None
             }
         } else {
             None
diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs
index 9161b23428a..c5142507812 100644
--- a/compiler/rustc_passes/src/check_attr.rs
+++ b/compiler/rustc_passes/src/check_attr.rs
@@ -1109,6 +1109,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
             ItemKind::Trait(_, _, _, generics, _, items)
                 if generics.params.len() != 0
                     || items.iter().any(|item| matches!(item.kind, AssocItemKind::Type)) => {}
+            ItemKind::TyAlias(_, _, generics) if generics.params.len() != 0 => {}
             _ => {
                 self.dcx().emit_err(errors::DocSearchUnboxInvalid { span: meta.span() });
             }
diff --git a/compiler/rustc_pattern_analysis/src/rustc.rs b/compiler/rustc_pattern_analysis/src/rustc.rs
index 88d45ead295..7c12f69f14c 100644
--- a/compiler/rustc_pattern_analysis/src/rustc.rs
+++ b/compiler/rustc_pattern_analysis/src/rustc.rs
@@ -1,5 +1,6 @@
 use std::fmt;
 use std::iter::once;
+use std::ops::ControlFlow;
 
 use rustc_abi::{FIRST_VARIANT, FieldIdx, Integer, VariantIdx};
 use rustc_arena::DroplessArena;
@@ -11,7 +12,8 @@ use rustc_middle::mir::{self, Const};
 use rustc_middle::thir::{self, Pat, PatKind, PatRange, PatRangeBoundary};
 use rustc_middle::ty::layout::IntegerExt;
 use rustc_middle::ty::{
-    self, FieldDef, OpaqueTypeKey, ScalarInt, Ty, TyCtxt, TypeVisitableExt, VariantDef,
+    self, FieldDef, OpaqueTypeKey, ScalarInt, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable,
+    TypeVisitableExt, TypeVisitor, VariantDef,
 };
 use rustc_middle::{bug, span_bug};
 use rustc_session::lint;
@@ -135,11 +137,22 @@ impl<'p, 'tcx: 'p> RustcPatCtxt<'p, 'tcx> {
     /// Returns the hidden type corresponding to this key if the body under analysis is allowed to
     /// know it.
     fn reveal_opaque_key(&self, key: OpaqueTypeKey<'tcx>) -> Option<Ty<'tcx>> {
-        self.typeck_results
-            .concrete_opaque_types
-            .get(&key.def_id)
-            .map(|x| ty::EarlyBinder::bind(x.ty).instantiate(self.tcx, key.args))
+        if let Some(hidden_ty) = self.typeck_results.concrete_opaque_types.get(&key.def_id) {
+            let ty = ty::EarlyBinder::bind(hidden_ty.ty).instantiate(self.tcx, key.args);
+            if ty.visit_with(&mut RecursiveOpaque { def_id: key.def_id.into() }).is_continue() {
+                Some(ty)
+            } else {
+                // HACK: We skip revealing opaque types which recursively expand
+                // to themselves. This is because we may infer hidden types like
+                // `Opaque<T> = Opaque<Opaque<T>>` or `Opaque<T> = Opaque<(T,)>`
+                // in hir typeck.
+                None
+            }
+        } else {
+            None
+        }
     }
+
     // This can take a non-revealed `Ty` because it reveals opaques itself.
     pub fn is_uninhabited(&self, ty: Ty<'tcx>) -> bool {
         !ty.inhabited_predicate(self.tcx).apply_revealing_opaque(
@@ -1105,3 +1118,20 @@ pub fn analyze_match<'p, 'tcx>(
 
     Ok(report)
 }
+
+struct RecursiveOpaque {
+    def_id: DefId,
+}
+impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for RecursiveOpaque {
+    type Result = ControlFlow<()>;
+
+    fn visit_ty(&mut self, t: Ty<'tcx>) -> Self::Result {
+        if let ty::Alias(ty::Opaque, alias_ty) = t.kind() {
+            if alias_ty.def_id == self.def_id {
+                return ControlFlow::Break(());
+            }
+        }
+
+        if t.has_opaque_types() { t.super_visit_with(self) } else { ControlFlow::Continue(()) }
+    }
+}
diff --git a/compiler/rustc_query_system/src/dep_graph/graph.rs b/compiler/rustc_query_system/src/dep_graph/graph.rs
index 9f34417973e..56fd3a660d0 100644
--- a/compiler/rustc_query_system/src/dep_graph/graph.rs
+++ b/compiler/rustc_query_system/src/dep_graph/graph.rs
@@ -141,7 +141,7 @@ impl<D: Deps> DepGraph<D> {
         let colors = DepNodeColorMap::new(prev_graph_node_count);
 
         // Instantiate a node with zero dependencies only once for anonymous queries.
-        let _green_node_index = current.alloc_node(
+        let _green_node_index = current.alloc_new_node(
             DepNode { kind: D::DEP_KIND_ANON_ZERO_DEPS, hash: current.anon_id_seed.into() },
             EdgesVec::new(),
             Fingerprint::ZERO,
@@ -149,7 +149,7 @@ impl<D: Deps> DepGraph<D> {
         assert_eq!(_green_node_index, DepNodeIndex::SINGLETON_ZERO_DEPS_ANON_NODE);
 
         // Instantiate a dependy-less red node only once for anonymous queries.
-        let red_node_index = current.alloc_node(
+        let red_node_index = current.alloc_new_node(
             DepNode { kind: D::DEP_KIND_RED, hash: Fingerprint::ZERO.into() },
             EdgesVec::new(),
             Fingerprint::ZERO,
@@ -438,7 +438,7 @@ impl<D: Deps> DepGraphData<D> {
                 // memory impact of this `anon_node_to_index` map remains tolerable, and helps
                 // us avoid useless growth of the graph with almost-equivalent nodes.
                 self.current.anon_node_to_index.get_or_insert_with(target_dep_node, || {
-                    self.current.alloc_node(target_dep_node, task_deps, Fingerprint::ZERO)
+                    self.current.alloc_new_node(target_dep_node, task_deps, Fingerprint::ZERO)
                 })
             }
         };
@@ -680,8 +680,8 @@ impl<D: Deps> DepGraphData<D> {
         qcx: Qcx,
         diagnostic: &DiagInner,
     ) -> DepNodeIndex {
-        // Use `send` so we get an unique index, even though the dep node is not.
-        let dep_node_index = self.current.encoder.send(
+        // Use `send_new` so we get an unique index, even though the dep node is not.
+        let dep_node_index = self.current.encoder.send_new(
             DepNode {
                 kind: D::DEP_KIND_SIDE_EFFECT,
                 hash: PackedFingerprint::from(Fingerprint::ZERO),
@@ -713,20 +713,22 @@ impl<D: Deps> DepGraphData<D> {
                 }
             }
 
-            // Manually recreate the node as `promote_node_and_deps_to_current` expects all
-            // green dependencies.
-            let dep_node_index = self.current.encoder.send(
+            // Use `send_and_color` as `promote_node_and_deps_to_current` expects all
+            // green dependencies. `send_and_color` will also prevent multiple nodes
+            // being encoded for concurrent calls.
+            let dep_node_index = self.current.encoder.send_and_color(
+                prev_index,
+                &self.colors,
                 DepNode {
                     kind: D::DEP_KIND_SIDE_EFFECT,
                     hash: PackedFingerprint::from(Fingerprint::ZERO),
                 },
                 Fingerprint::ZERO,
                 std::iter::once(DepNodeIndex::FOREVER_RED_NODE).collect(),
+                true,
             );
+            // This will just overwrite the same value for concurrent calls.
             qcx.store_side_effect(dep_node_index, side_effect);
-
-            // Mark the node as green.
-            self.colors.insert(prev_index, DepNodeColor::Green(dep_node_index));
         })
     }
 
@@ -736,38 +738,43 @@ impl<D: Deps> DepGraphData<D> {
         edges: EdgesVec,
         fingerprint: Option<Fingerprint>,
     ) -> DepNodeIndex {
-        let dep_node_index =
-            self.current.alloc_node(key, edges, fingerprint.unwrap_or(Fingerprint::ZERO));
-
         if let Some(prev_index) = self.previous.node_to_index_opt(&key) {
             // Determine the color and index of the new `DepNode`.
-            let color = if let Some(fingerprint) = fingerprint {
+            let is_green = if let Some(fingerprint) = fingerprint {
                 if fingerprint == self.previous.fingerprint_by_index(prev_index) {
                     // This is a green node: it existed in the previous compilation,
                     // its query was re-executed, and it has the same result as before.
-                    DepNodeColor::Green(dep_node_index)
+                    true
                 } else {
                     // This is a red node: it existed in the previous compilation, its query
                     // was re-executed, but it has a different result from before.
-                    DepNodeColor::Red
+                    false
                 }
             } else {
                 // This is a red node, effectively: it existed in the previous compilation
                 // session, its query was re-executed, but it doesn't compute a result hash
                 // (i.e. it represents a `no_hash` query), so we have no way of determining
                 // whether or not the result was the same as before.
-                DepNodeColor::Red
+                false
             };
 
-            debug_assert!(
-                self.colors.get(prev_index).is_none(),
-                "DepGraph::with_task() - Duplicate DepNodeColor insertion for {key:?}",
+            let fingerprint = fingerprint.unwrap_or(Fingerprint::ZERO);
+
+            let dep_node_index = self.current.encoder.send_and_color(
+                prev_index,
+                &self.colors,
+                key,
+                fingerprint,
+                edges,
+                is_green,
             );
 
-            self.colors.insert(prev_index, color);
-        }
+            self.current.record_node(dep_node_index, key, fingerprint);
 
-        dep_node_index
+            dep_node_index
+        } else {
+            self.current.alloc_new_node(key, edges, fingerprint.unwrap_or(Fingerprint::ZERO))
+        }
     }
 
     fn promote_node_and_deps_to_current(&self, prev_index: SerializedDepNodeIndex) -> DepNodeIndex {
@@ -1246,19 +1253,15 @@ impl<D: Deps> CurrentDepGraph<D> {
         assert_eq!(previous, fingerprint, "Unstable fingerprints for {:?}", key);
     }
 
-    /// Writes the node to the current dep-graph and allocates a `DepNodeIndex` for it.
-    /// Assumes that this is a node that has no equivalent in the previous dep-graph.
     #[inline(always)]
-    fn alloc_node(
+    fn record_node(
         &self,
+        dep_node_index: DepNodeIndex,
         key: DepNode,
-        edges: EdgesVec,
-        current_fingerprint: Fingerprint,
-    ) -> DepNodeIndex {
-        let dep_node_index = self.encoder.send(key, current_fingerprint, edges);
-
+        _current_fingerprint: Fingerprint,
+    ) {
         #[cfg(debug_assertions)]
-        self.record_edge(dep_node_index, key, current_fingerprint);
+        self.record_edge(dep_node_index, key, _current_fingerprint);
 
         if let Some(ref nodes_in_current_session) = self.nodes_in_current_session {
             outline(|| {
@@ -1267,6 +1270,20 @@ impl<D: Deps> CurrentDepGraph<D> {
                 }
             });
         }
+    }
+
+    /// Writes the node to the current dep-graph and allocates a `DepNodeIndex` for it.
+    /// Assumes that this is a node that has no equivalent in the previous dep-graph.
+    #[inline(always)]
+    fn alloc_new_node(
+        &self,
+        key: DepNode,
+        edges: EdgesVec,
+        current_fingerprint: Fingerprint,
+    ) -> DepNodeIndex {
+        let dep_node_index = self.encoder.send_new(key, current_fingerprint, edges);
+
+        self.record_node(dep_node_index, key, current_fingerprint);
 
         dep_node_index
     }
diff --git a/compiler/rustc_query_system/src/dep_graph/serialized.rs b/compiler/rustc_query_system/src/dep_graph/serialized.rs
index 7750d6d1fef..7556a2456aa 100644
--- a/compiler/rustc_query_system/src/dep_graph/serialized.rs
+++ b/compiler/rustc_query_system/src/dep_graph/serialized.rs
@@ -707,7 +707,8 @@ impl<D: Deps> GraphEncoder<D> {
         }
     }
 
-    pub(crate) fn send(
+    /// Encodes a node that does not exists in the previous graph.
+    pub(crate) fn send_new(
         &self,
         node: DepNode,
         fingerprint: Fingerprint,
@@ -718,6 +719,40 @@ impl<D: Deps> GraphEncoder<D> {
         self.status.lock().as_mut().unwrap().encode_node(&node, &self.record_graph)
     }
 
+    /// Encodes a node that exists in the previous graph, but was re-executed.
+    ///
+    /// This will also ensure the dep node is colored either red or green.
+    pub(crate) fn send_and_color(
+        &self,
+        prev_index: SerializedDepNodeIndex,
+        colors: &DepNodeColorMap,
+        node: DepNode,
+        fingerprint: Fingerprint,
+        edges: EdgesVec,
+        is_green: bool,
+    ) -> DepNodeIndex {
+        let _prof_timer = self.profiler.generic_activity("incr_comp_encode_dep_graph");
+        let node = NodeInfo { node, fingerprint, edges };
+
+        let mut status = self.status.lock();
+        let status = status.as_mut().unwrap();
+
+        // Check colors inside the lock to avoid racing when `send_promoted` is called concurrently
+        // on the same index.
+        match colors.get(prev_index) {
+            None => {
+                let dep_node_index = status.encode_node(&node, &self.record_graph);
+                colors.insert(
+                    prev_index,
+                    if is_green { DepNodeColor::Green(dep_node_index) } else { DepNodeColor::Red },
+                );
+                dep_node_index
+            }
+            Some(DepNodeColor::Green(dep_node_index)) => dep_node_index,
+            Some(DepNodeColor::Red) => panic!(),
+        }
+    }
+
     /// Encodes a node that was promoted from the previous graph. It reads the information directly from
     /// the previous dep graph and expects all edges to already have a new dep node index assigned.
     ///
@@ -733,8 +768,8 @@ impl<D: Deps> GraphEncoder<D> {
         let mut status = self.status.lock();
         let status = status.as_mut().unwrap();
 
-        // Check colors inside the lock to avoid racing when `send_promoted` is called concurrently
-        // on the same index.
+        // Check colors inside the lock to avoid racing when `send_promoted` or `send_and_color`
+        // is called concurrently on the same index.
         match colors.get(prev_index) {
             None => {
                 let dep_node_index =
diff --git a/compiler/rustc_resolve/Cargo.toml b/compiler/rustc_resolve/Cargo.toml
index 9ea9c58cfd1..0fcc3d8f6b3 100644
--- a/compiler/rustc_resolve/Cargo.toml
+++ b/compiler/rustc_resolve/Cargo.toml
@@ -18,7 +18,6 @@ rustc_expand = { path = "../rustc_expand" }
 rustc_feature = { path = "../rustc_feature" }
 rustc_fluent_macro = { path = "../rustc_fluent_macro" }
 rustc_hir = { path = "../rustc_hir" }
-rustc_index = { path = "../rustc_index" }
 rustc_macros = { path = "../rustc_macros" }
 rustc_metadata = { path = "../rustc_metadata" }
 rustc_middle = { path = "../rustc_middle" }
diff --git a/compiler/rustc_resolve/src/build_reduced_graph.rs b/compiler/rustc_resolve/src/build_reduced_graph.rs
index 4368f7882ff..cb328022c76 100644
--- a/compiler/rustc_resolve/src/build_reduced_graph.rs
+++ b/compiler/rustc_resolve/src/build_reduced_graph.rs
@@ -1207,7 +1207,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
             for (rule_i, rule_span) in &self.r.macro_map[&def_id.to_def_id()].rule_spans {
                 self.r
                     .unused_macro_rules
-                    .entry(def_id)
+                    .entry(node_id)
                     .or_default()
                     .insert(*rule_i, (ident, *rule_span));
             }
diff --git a/compiler/rustc_resolve/src/diagnostics.rs b/compiler/rustc_resolve/src/diagnostics.rs
index 6dc854758da..363a75911ad 100644
--- a/compiler/rustc_resolve/src/diagnostics.rs
+++ b/compiler/rustc_resolve/src/diagnostics.rs
@@ -170,10 +170,10 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
 
     fn report_with_use_injections(&mut self, krate: &Crate) {
         for UseError { mut err, candidates, def_id, instead, suggestion, path, is_call } in
-            self.use_injections.drain(..)
+            std::mem::take(&mut self.use_injections)
         {
             let (span, found_use) = if let Some(def_id) = def_id.as_local() {
-                UsePlacementFinder::check(krate, self.def_id_to_node_id[def_id])
+                UsePlacementFinder::check(krate, self.def_id_to_node_id(def_id))
             } else {
                 (None, FoundUse::No)
             };
@@ -1435,7 +1435,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         let import_suggestions =
             self.lookup_import_candidates(ident, Namespace::MacroNS, parent_scope, is_expected);
         let (span, found_use) = match parent_scope.module.nearest_parent_mod().as_local() {
-            Some(def_id) => UsePlacementFinder::check(krate, self.def_id_to_node_id[def_id]),
+            Some(def_id) => UsePlacementFinder::check(krate, self.def_id_to_node_id(def_id)),
             None => (None, FoundUse::No),
         };
         show_candidates(
@@ -2550,7 +2550,11 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                 .iter()
                 .filter_map(|item| {
                     let parent_module = self.opt_local_def_id(item.parent_module)?.to_def_id();
-                    Some(StrippedCfgItem { parent_module, name: item.name, cfg: item.cfg.clone() })
+                    Some(StrippedCfgItem {
+                        parent_module,
+                        ident: item.ident,
+                        cfg: item.cfg.clone(),
+                    })
                 })
                 .collect::<Vec<_>>();
             local_items.as_slice()
@@ -2558,12 +2562,12 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             self.tcx.stripped_cfg_items(module.krate)
         };
 
-        for &StrippedCfgItem { parent_module, name, ref cfg } in symbols {
-            if parent_module != module || name.name != *segment {
+        for &StrippedCfgItem { parent_module, ident, ref cfg } in symbols {
+            if parent_module != module || ident.name != *segment {
                 continue;
             }
 
-            let note = errors::FoundItemConfigureOut { span: name.span };
+            let note = errors::FoundItemConfigureOut { span: ident.span };
             err.subdiagnostic(note);
 
             if let MetaItemKind::List(nested) = &cfg.kind
diff --git a/compiler/rustc_resolve/src/ident.rs b/compiler/rustc_resolve/src/ident.rs
index 5f0a2a597e9..180d6af219d 100644
--- a/compiler/rustc_resolve/src/ident.rs
+++ b/compiler/rustc_resolve/src/ident.rs
@@ -296,9 +296,6 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
     ) -> Option<LexicalScopeBinding<'ra>> {
         assert!(ns == TypeNS || ns == ValueNS);
         let orig_ident = ident;
-        if ident.name == kw::Empty {
-            return Some(LexicalScopeBinding::Res(Res::Err));
-        }
         let (general_span, normalized_span) = if ident.name == kw::SelfUpper {
             // FIXME(jseyfried) improve `Self` hygiene
             let empty_span = ident.span.with_ctxt(SyntaxContext::root());
diff --git a/compiler/rustc_resolve/src/imports.rs b/compiler/rustc_resolve/src/imports.rs
index 0b3633a452c..3f3b455f4db 100644
--- a/compiler/rustc_resolve/src/imports.rs
+++ b/compiler/rustc_resolve/src/imports.rs
@@ -639,38 +639,38 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                 }
 
                 if let Some(glob_binding) = resolution.shadowed_glob {
-                    let binding_id = match binding.kind {
-                        NameBindingKind::Res(res) => {
-                            Some(self.def_id_to_node_id[res.def_id().expect_local()])
-                        }
-                        NameBindingKind::Module(module) => {
-                            Some(self.def_id_to_node_id[module.def_id().expect_local()])
-                        }
-                        NameBindingKind::Import { import, .. } => import.id(),
-                    };
-
                     if binding.res() != Res::Err
                         && glob_binding.res() != Res::Err
                         && let NameBindingKind::Import { import: glob_import, .. } =
                             glob_binding.kind
-                        && let Some(binding_id) = binding_id
                         && let Some(glob_import_id) = glob_import.id()
                         && let glob_import_def_id = self.local_def_id(glob_import_id)
                         && self.effective_visibilities.is_exported(glob_import_def_id)
                         && glob_binding.vis.is_public()
                         && !binding.vis.is_public()
                     {
-                        self.lint_buffer.buffer_lint(
-                            HIDDEN_GLOB_REEXPORTS,
-                            binding_id,
-                            binding.span,
-                            BuiltinLintDiag::HiddenGlobReexports {
-                                name: key.ident.name.to_string(),
-                                namespace: key.ns.descr().to_owned(),
-                                glob_reexport_span: glob_binding.span,
-                                private_item_span: binding.span,
-                            },
-                        );
+                        let binding_id = match binding.kind {
+                            NameBindingKind::Res(res) => {
+                                Some(self.def_id_to_node_id(res.def_id().expect_local()))
+                            }
+                            NameBindingKind::Module(module) => {
+                                Some(self.def_id_to_node_id(module.def_id().expect_local()))
+                            }
+                            NameBindingKind::Import { import, .. } => import.id(),
+                        };
+                        if let Some(binding_id) = binding_id {
+                            self.lint_buffer.buffer_lint(
+                                HIDDEN_GLOB_REEXPORTS,
+                                binding_id,
+                                binding.span,
+                                BuiltinLintDiag::HiddenGlobReexports {
+                                    name: key.ident.name.to_string(),
+                                    namespace: key.ns.descr().to_owned(),
+                                    glob_reexport_span: glob_binding.span,
+                                    private_item_span: binding.span,
+                                },
+                            );
+                        }
                     }
                 }
             }
diff --git a/compiler/rustc_resolve/src/late.rs b/compiler/rustc_resolve/src/late.rs
index 1389e8c811e..a7170edb986 100644
--- a/compiler/rustc_resolve/src/late.rs
+++ b/compiler/rustc_resolve/src/late.rs
@@ -5007,8 +5007,7 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
             return false;
         }
         let Some(local_did) = did.as_local() else { return true };
-        let Some(node_id) = self.r.def_id_to_node_id.get(local_did) else { return true };
-        !self.r.proc_macros.contains(node_id)
+        !self.r.proc_macros.contains(&local_did)
     }
 
     fn resolve_doc_links(&mut self, attrs: &[Attribute], maybe_exported: MaybeExported<'_>) {
diff --git a/compiler/rustc_resolve/src/late/diagnostics.rs b/compiler/rustc_resolve/src/late/diagnostics.rs
index b62bc6c45e0..c2761bd2717 100644
--- a/compiler/rustc_resolve/src/late/diagnostics.rs
+++ b/compiler/rustc_resolve/src/late/diagnostics.rs
@@ -2238,7 +2238,7 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
                                     .get(&def_id)
                                     .is_some_and(|sig| sig.has_self),
                                 None => {
-                                    self.r.tcx.fn_arg_names(def_id).first().is_some_and(|&ident| {
+                                    self.r.tcx.fn_arg_idents(def_id).first().is_some_and(|&ident| {
                                         matches!(ident, Some(Ident { name: kw::SelfLower, .. }))
                                     })
                                 }
diff --git a/compiler/rustc_resolve/src/lib.rs b/compiler/rustc_resolve/src/lib.rs
index 3ac66840d87..a92912c9639 100644
--- a/compiler/rustc_resolve/src/lib.rs
+++ b/compiler/rustc_resolve/src/lib.rs
@@ -56,7 +56,6 @@ use rustc_hir::def::{
 };
 use rustc_hir::def_id::{CRATE_DEF_ID, CrateNum, DefId, LOCAL_CRATE, LocalDefId, LocalDefIdMap};
 use rustc_hir::{PrimTy, TraitCandidate};
-use rustc_index::IndexVec;
 use rustc_metadata::creader::{CStore, CrateLoader};
 use rustc_middle::metadata::ModChild;
 use rustc_middle::middle::privacy::EffectiveVisibilities;
@@ -1141,7 +1140,7 @@ pub struct Resolver<'ra, 'tcx> {
     ast_transform_scopes: FxHashMap<LocalExpnId, Module<'ra>>,
     unused_macros: FxIndexMap<LocalDefId, (NodeId, Ident)>,
     /// A map from the macro to all its potentially unused arms.
-    unused_macro_rules: FxIndexMap<LocalDefId, UnordMap<usize, (Ident, Span)>>,
+    unused_macro_rules: FxIndexMap<NodeId, UnordMap<usize, (Ident, Span)>>,
     proc_macro_stubs: FxHashSet<LocalDefId>,
     /// Traces collected during macro resolution and validated when it's complete.
     single_segment_macro_resolutions:
@@ -1184,7 +1183,6 @@ pub struct Resolver<'ra, 'tcx> {
     next_node_id: NodeId,
 
     node_id_to_def_id: NodeMap<Feed<'tcx, LocalDefId>>,
-    def_id_to_node_id: IndexVec<LocalDefId, ast::NodeId>,
 
     /// Indices of unnamed struct or variant fields with unresolved attributes.
     placeholder_field_indices: FxHashMap<NodeId, usize>,
@@ -1202,7 +1200,7 @@ pub struct Resolver<'ra, 'tcx> {
     trait_impls: FxIndexMap<DefId, Vec<LocalDefId>>,
     /// A list of proc macro LocalDefIds, written out in the order in which
     /// they are declared in the static array generated by proc_macro_harness.
-    proc_macros: Vec<NodeId>,
+    proc_macros: Vec<LocalDefId>,
     confused_type_with_std_module: FxIndexMap<Span, Span>,
     /// Whether lifetime elision was successful.
     lifetime_elision_allowed: FxHashSet<NodeId>,
@@ -1339,12 +1337,12 @@ impl<'tcx> Resolver<'_, 'tcx> {
         expn_id: ExpnId,
         span: Span,
     ) -> TyCtxtFeed<'tcx, LocalDefId> {
-        let data = def_kind.def_path_data(name);
         assert!(
             !self.node_id_to_def_id.contains_key(&node_id),
-            "adding a def'n for node-id {:?} and data {:?} but a previous def'n exists: {:?}",
+            "adding a def for node-id {:?}, name {:?}, data {:?} but a previous def exists: {:?}",
             node_id,
-            data,
+            name,
+            def_kind,
             self.tcx.definitions_untracked().def_key(self.node_id_to_def_id[&node_id].key()),
         );
 
@@ -1369,7 +1367,6 @@ impl<'tcx> Resolver<'_, 'tcx> {
             debug!("create_def: def_id_to_node_id[{:?}] <-> {:?}", def_id, node_id);
             self.node_id_to_def_id.insert(node_id, feed.downgrade());
         }
-        assert_eq!(self.def_id_to_node_id.push(node_id), def_id);
 
         feed
     }
@@ -1385,6 +1382,19 @@ impl<'tcx> Resolver<'_, 'tcx> {
     pub fn tcx(&self) -> TyCtxt<'tcx> {
         self.tcx
     }
+
+    /// This function is very slow, as it iterates over the entire
+    /// [Resolver::node_id_to_def_id] map just to find the [NodeId]
+    /// that corresponds to the given [LocalDefId]. Only use this in
+    /// diagnostics code paths.
+    fn def_id_to_node_id(&self, def_id: LocalDefId) -> NodeId {
+        self.node_id_to_def_id
+            .items()
+            .filter(|(_, v)| v.key() == def_id)
+            .map(|(k, _)| *k)
+            .get_only()
+            .unwrap()
+    }
 }
 
 impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
@@ -1417,8 +1427,6 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             &mut Default::default(),
         );
 
-        let mut def_id_to_node_id = IndexVec::default();
-        assert_eq!(def_id_to_node_id.push(CRATE_NODE_ID), CRATE_DEF_ID);
         let mut node_id_to_def_id = NodeMap::default();
         let crate_feed = tcx.create_local_crate_def_id(crate_span);
 
@@ -1553,7 +1561,6 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             lint_buffer: LintBuffer::default(),
             next_node_id: CRATE_NODE_ID,
             node_id_to_def_id,
-            def_id_to_node_id,
             placeholder_field_indices: Default::default(),
             invocation_parents,
             legacy_const_generic_args: Default::default(),
@@ -1633,7 +1640,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
     }
 
     pub fn into_outputs(self) -> ResolverOutputs {
-        let proc_macros = self.proc_macros.iter().map(|id| self.local_def_id(*id)).collect();
+        let proc_macros = self.proc_macros;
         let expn_that_defined = self.expn_that_defined;
         let extern_crate_map = self.extern_crate_map;
         let maybe_unused_trait_imports = self.maybe_unused_trait_imports;
@@ -1648,7 +1655,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                 .filter_map(|item| {
                     let parent_module =
                         self.node_id_to_def_id.get(&item.parent_module)?.key().to_def_id();
-                    Some(StrippedCfgItem { parent_module, name: item.name, cfg: item.cfg })
+                    Some(StrippedCfgItem { parent_module, ident: item.ident, cfg: item.cfg })
                 })
                 .collect(),
         );
diff --git a/compiler/rustc_resolve/src/macros.rs b/compiler/rustc_resolve/src/macros.rs
index 9d6ae0aa9d1..749b7f24c50 100644
--- a/compiler/rustc_resolve/src/macros.rs
+++ b/compiler/rustc_resolve/src/macros.rs
@@ -323,8 +323,7 @@ impl<'ra, 'tcx> ResolverExpand for Resolver<'ra, 'tcx> {
     }
 
     fn record_macro_rule_usage(&mut self, id: NodeId, rule_i: usize) {
-        let did = self.local_def_id(id);
-        if let Some(rules) = self.unused_macro_rules.get_mut(&did) {
+        if let Some(rules) = self.unused_macro_rules.get_mut(&id) {
             rules.remove(&rule_i);
         }
     }
@@ -337,15 +336,12 @@ impl<'ra, 'tcx> ResolverExpand for Resolver<'ra, 'tcx> {
                 ident.span,
                 BuiltinLintDiag::UnusedMacroDefinition(ident.name),
             );
+            // Do not report unused individual rules if the entire macro is unused
+            self.unused_macro_rules.swap_remove(&node_id);
         }
 
-        for (&def_id, unused_arms) in self.unused_macro_rules.iter() {
+        for (&node_id, unused_arms) in self.unused_macro_rules.iter() {
             for (&arm_i, &(ident, rule_span)) in unused_arms.to_sorted_stable_ord() {
-                if self.unused_macros.contains_key(&def_id) {
-                    // We already lint the entire macro as unused
-                    continue;
-                }
-                let node_id = self.def_id_to_node_id[def_id];
                 self.lint_buffer.buffer_lint(
                     UNUSED_MACRO_RULES,
                     node_id,
@@ -466,11 +462,11 @@ impl<'ra, 'tcx> ResolverExpand for Resolver<'ra, 'tcx> {
     }
 
     fn declare_proc_macro(&mut self, id: NodeId) {
-        self.proc_macros.push(id)
+        self.proc_macros.push(self.local_def_id(id))
     }
 
-    fn append_stripped_cfg_item(&mut self, parent_node: NodeId, name: Ident, cfg: ast::MetaItem) {
-        self.stripped_cfg_items.push(StrippedCfgItem { parent_module: parent_node, name, cfg });
+    fn append_stripped_cfg_item(&mut self, parent_node: NodeId, ident: Ident, cfg: ast::MetaItem) {
+        self.stripped_cfg_items.push(StrippedCfgItem { parent_module: parent_node, ident, cfg });
     }
 
     fn registered_tools(&self) -> &RegisteredTools {
@@ -932,7 +928,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                             .invocation_parents
                             .get(&parent_scope.expansion)
                             .map_or(ast::CRATE_NODE_ID, |parent| {
-                                self.def_id_to_node_id[parent.parent_def]
+                                self.def_id_to_node_id(parent.parent_def)
                             });
                         self.lint_buffer.buffer_lint(
                             LEGACY_DERIVE_HELPERS,
diff --git a/compiler/rustc_sanitizers/src/cfi/typeid/itanium_cxx_abi/encode.rs b/compiler/rustc_sanitizers/src/cfi/typeid/itanium_cxx_abi/encode.rs
index d56ca9c2453..4b1b3903e40 100644
--- a/compiler/rustc_sanitizers/src/cfi/typeid/itanium_cxx_abi/encode.rs
+++ b/compiler/rustc_sanitizers/src/cfi/typeid/itanium_cxx_abi/encode.rs
@@ -721,7 +721,8 @@ fn encode_ty_name(tcx: TyCtxt<'_>, def_id: DefId) -> String {
             | hir::definitions::DefPathData::Use
             | hir::definitions::DefPathData::GlobalAsm
             | hir::definitions::DefPathData::MacroNs(..)
-            | hir::definitions::DefPathData::LifetimeNs(..) => {
+            | hir::definitions::DefPathData::LifetimeNs(..)
+            | hir::definitions::DefPathData::AnonAssocTy => {
                 bug!("encode_ty_name: unexpected `{:?}`", disambiguated_data.data);
             }
         });
diff --git a/compiler/rustc_serialize/src/opaque.rs b/compiler/rustc_serialize/src/opaque.rs
index 81f6266f8d1..0a55504a556 100644
--- a/compiler/rustc_serialize/src/opaque.rs
+++ b/compiler/rustc_serialize/src/opaque.rs
@@ -19,7 +19,7 @@ pub type FileEncodeResult = Result<usize, (PathBuf, io::Error)>;
 pub const MAGIC_END_BYTES: &[u8] = b"rust-end-file";
 
 /// The size of the buffer in `FileEncoder`.
-const BUF_SIZE: usize = 8192;
+const BUF_SIZE: usize = 64 * 1024;
 
 /// `FileEncoder` encodes data to file via fixed-size buffer.
 ///
diff --git a/compiler/rustc_session/Cargo.toml b/compiler/rustc_session/Cargo.toml
index a087725d34d..63772a32222 100644
--- a/compiler/rustc_session/Cargo.toml
+++ b/compiler/rustc_session/Cargo.toml
@@ -7,6 +7,7 @@ edition = "2024"
 # tidy-alphabetical-start
 bitflags = "2.4.1"
 getopts = "0.2"
+rand = "0.9.0"
 rustc_abi = { path = "../rustc_abi" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_data_structures = { path = "../rustc_data_structures" }
diff --git a/compiler/rustc_session/src/config.rs b/compiler/rustc_session/src/config.rs
index 56b3fe2ab4c..bdd54a15147 100644
--- a/compiler/rustc_session/src/config.rs
+++ b/compiler/rustc_session/src/config.rs
@@ -1015,11 +1015,14 @@ impl OutFileName {
         &self,
         outputs: &OutputFilenames,
         flavor: OutputType,
-        codegen_unit_name: Option<&str>,
+        codegen_unit_name: &str,
+        invocation_temp: Option<&str>,
     ) -> PathBuf {
         match *self {
             OutFileName::Real(ref path) => path.clone(),
-            OutFileName::Stdout => outputs.temp_path(flavor, codegen_unit_name),
+            OutFileName::Stdout => {
+                outputs.temp_path_for_cgu(flavor, codegen_unit_name, invocation_temp)
+            }
         }
     }
 
@@ -1094,40 +1097,59 @@ impl OutputFilenames {
     /// Gets the path where a compilation artifact of the given type for the
     /// given codegen unit should be placed on disk. If codegen_unit_name is
     /// None, a path distinct from those of any codegen unit will be generated.
-    pub fn temp_path(&self, flavor: OutputType, codegen_unit_name: Option<&str>) -> PathBuf {
+    pub fn temp_path_for_cgu(
+        &self,
+        flavor: OutputType,
+        codegen_unit_name: &str,
+        invocation_temp: Option<&str>,
+    ) -> PathBuf {
         let extension = flavor.extension();
-        self.temp_path_ext(extension, codegen_unit_name)
+        self.temp_path_ext_for_cgu(extension, codegen_unit_name, invocation_temp)
     }
 
     /// Like `temp_path`, but specifically for dwarf objects.
-    pub fn temp_path_dwo(&self, codegen_unit_name: Option<&str>) -> PathBuf {
-        self.temp_path_ext(DWARF_OBJECT_EXT, codegen_unit_name)
+    pub fn temp_path_dwo_for_cgu(
+        &self,
+        codegen_unit_name: &str,
+        invocation_temp: Option<&str>,
+    ) -> PathBuf {
+        self.temp_path_ext_for_cgu(DWARF_OBJECT_EXT, codegen_unit_name, invocation_temp)
     }
 
     /// Like `temp_path`, but also supports things where there is no corresponding
     /// OutputType, like noopt-bitcode or lto-bitcode.
-    pub fn temp_path_ext(&self, ext: &str, codegen_unit_name: Option<&str>) -> PathBuf {
-        let mut extension = String::new();
+    pub fn temp_path_ext_for_cgu(
+        &self,
+        ext: &str,
+        codegen_unit_name: &str,
+        invocation_temp: Option<&str>,
+    ) -> PathBuf {
+        let mut extension = codegen_unit_name.to_string();
 
-        if let Some(codegen_unit_name) = codegen_unit_name {
-            extension.push_str(codegen_unit_name);
+        // Append `.{invocation_temp}` to ensure temporary files are unique.
+        if let Some(rng) = invocation_temp {
+            extension.push('.');
+            extension.push_str(rng);
         }
 
+        // FIXME: This is sketchy that we're not appending `.rcgu` when the ext is empty.
+        // Append `.rcgu.{ext}`.
         if !ext.is_empty() {
-            if !extension.is_empty() {
-                extension.push('.');
-                extension.push_str(RUST_CGU_EXT);
-                extension.push('.');
-            }
-
+            extension.push('.');
+            extension.push_str(RUST_CGU_EXT);
+            extension.push('.');
             extension.push_str(ext);
         }
 
         let temps_directory = self.temps_directory.as_ref().unwrap_or(&self.out_directory);
-
         self.with_directory_and_extension(temps_directory, &extension)
     }
 
+    pub fn temp_path_for_diagnostic(&self, ext: &str) -> PathBuf {
+        let temps_directory = self.temps_directory.as_ref().unwrap_or(&self.out_directory);
+        self.with_directory_and_extension(temps_directory, &ext)
+    }
+
     pub fn with_extension(&self, extension: &str) -> PathBuf {
         self.with_directory_and_extension(&self.out_directory, extension)
     }
@@ -1144,10 +1166,11 @@ impl OutputFilenames {
         &self,
         split_debuginfo_kind: SplitDebuginfo,
         split_dwarf_kind: SplitDwarfKind,
-        cgu_name: Option<&str>,
+        cgu_name: &str,
+        invocation_temp: Option<&str>,
     ) -> Option<PathBuf> {
-        let obj_out = self.temp_path(OutputType::Object, cgu_name);
-        let dwo_out = self.temp_path_dwo(cgu_name);
+        let obj_out = self.temp_path_for_cgu(OutputType::Object, cgu_name, invocation_temp);
+        let dwo_out = self.temp_path_dwo_for_cgu(cgu_name, invocation_temp);
         match (split_debuginfo_kind, split_dwarf_kind) {
             (SplitDebuginfo::Off, SplitDwarfKind::Single | SplitDwarfKind::Split) => None,
             // Single mode doesn't change how DWARF is emitted, but does add Split DWARF attributes
diff --git a/compiler/rustc_session/src/session.rs b/compiler/rustc_session/src/session.rs
index fb4a437a487..1359f7eb7bb 100644
--- a/compiler/rustc_session/src/session.rs
+++ b/compiler/rustc_session/src/session.rs
@@ -6,6 +6,8 @@ use std::sync::Arc;
 use std::sync::atomic::AtomicBool;
 use std::{env, fmt, io};
 
+use rand::{RngCore, rng};
+use rustc_data_structures::base_n::{CASE_INSENSITIVE, ToBaseN};
 use rustc_data_structures::flock;
 use rustc_data_structures::fx::{FxHashMap, FxIndexSet};
 use rustc_data_structures::profiling::{SelfProfiler, SelfProfilerRef};
@@ -203,6 +205,14 @@ pub struct Session {
 
     target_filesearch: FileSearch,
     host_filesearch: FileSearch,
+
+    /// A random string generated per invocation of rustc.
+    ///
+    /// This is prepended to all temporary files so that they do not collide
+    /// during concurrent invocations of rustc, or past invocations that were
+    /// preserved with a flag like `-C save-temps`, since these files may be
+    /// hard linked.
+    pub invocation_temp: Option<String>,
 }
 
 #[derive(PartialEq, Eq, PartialOrd, Ord)]
@@ -1117,6 +1127,12 @@ pub fn build_session(
     let target_filesearch =
         filesearch::FileSearch::new(&sopts.search_paths, &target_tlib_path, &target);
     let host_filesearch = filesearch::FileSearch::new(&sopts.search_paths, &host_tlib_path, &host);
+
+    let invocation_temp = sopts
+        .incremental
+        .as_ref()
+        .map(|_| rng().next_u32().to_base_fixed_len(CASE_INSENSITIVE).to_string());
+
     let sess = Session {
         target,
         host,
@@ -1140,6 +1156,7 @@ pub fn build_session(
         expanded_args,
         target_filesearch,
         host_filesearch,
+        invocation_temp,
     };
 
     validate_commandline_args_with_session_available(&sess);
diff --git a/compiler/rustc_span/src/lib.rs b/compiler/rustc_span/src/lib.rs
index 9e6ba2e1b9c..c95c03b4e4f 100644
--- a/compiler/rustc_span/src/lib.rs
+++ b/compiler/rustc_span/src/lib.rs
@@ -116,9 +116,13 @@ pub struct SessionGlobals {
 }
 
 impl SessionGlobals {
-    pub fn new(edition: Edition, sm_inputs: Option<SourceMapInputs>) -> SessionGlobals {
+    pub fn new(
+        edition: Edition,
+        extra_symbols: &[&'static str],
+        sm_inputs: Option<SourceMapInputs>,
+    ) -> SessionGlobals {
         SessionGlobals {
-            symbol_interner: symbol::Interner::fresh(),
+            symbol_interner: symbol::Interner::with_extra_symbols(extra_symbols),
             span_interner: Lock::new(span_encoding::SpanInterner::default()),
             metavar_spans: Default::default(),
             hygiene_data: Lock::new(hygiene::HygieneData::new(edition)),
@@ -129,6 +133,7 @@ impl SessionGlobals {
 
 pub fn create_session_globals_then<R>(
     edition: Edition,
+    extra_symbols: &[&'static str],
     sm_inputs: Option<SourceMapInputs>,
     f: impl FnOnce() -> R,
 ) -> R {
@@ -137,7 +142,7 @@ pub fn create_session_globals_then<R>(
         "SESSION_GLOBALS should never be overwritten! \
          Use another thread if you need another SessionGlobals"
     );
-    let session_globals = SessionGlobals::new(edition, sm_inputs);
+    let session_globals = SessionGlobals::new(edition, extra_symbols, sm_inputs);
     SESSION_GLOBALS.set(&session_globals, f)
 }
 
@@ -156,7 +161,7 @@ where
     F: FnOnce(&SessionGlobals) -> R,
 {
     if !SESSION_GLOBALS.is_set() {
-        let session_globals = SessionGlobals::new(edition, None);
+        let session_globals = SessionGlobals::new(edition, &[], None);
         SESSION_GLOBALS.set(&session_globals, || SESSION_GLOBALS.with(f))
     } else {
         SESSION_GLOBALS.with(f)
@@ -172,7 +177,7 @@ where
 
 /// Default edition, no source map.
 pub fn create_default_session_globals_then<R>(f: impl FnOnce() -> R) -> R {
-    create_session_globals_then(edition::DEFAULT_EDITION, None, f)
+    create_session_globals_then(edition::DEFAULT_EDITION, &[], None, f)
 }
 
 // If this ever becomes non thread-local, `decode_syntax_context`
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index 31847ae3b46..986370f5019 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -454,6 +454,7 @@ symbols! {
         and_then,
         anon,
         anon_adt,
+        anon_assoc,
         anonymous_lifetime_in_impl_trait,
         any,
         append_const_msg,
@@ -1913,6 +1914,7 @@ symbols! {
         simd_eq,
         simd_expose_provenance,
         simd_extract,
+        simd_extract_dyn,
         simd_fabs,
         simd_fcos,
         simd_fexp,
@@ -1931,6 +1933,7 @@ symbols! {
         simd_ge,
         simd_gt,
         simd_insert,
+        simd_insert_dyn,
         simd_le,
         simd_lt,
         simd_masked_load,
@@ -2538,15 +2541,10 @@ rustc_index::newtype_index! {
 }
 
 impl Symbol {
-    const fn new(n: u32) -> Self {
+    pub const fn new(n: u32) -> Self {
         Symbol(SymbolIndex::from_u32(n))
     }
 
-    /// for use in Decoder only
-    pub fn new_from_decoded(n: u32) -> Self {
-        Self::new(n)
-    }
-
     /// Maps a string to its interned representation.
     #[rustc_diagnostic_item = "SymbolIntern"]
     pub fn intern(string: &str) -> Self {
@@ -2632,11 +2630,14 @@ struct InternerInner {
 }
 
 impl Interner {
-    fn prefill(init: &[&'static str]) -> Self {
-        Interner(Lock::new(InternerInner {
-            arena: Default::default(),
-            strings: init.iter().copied().collect(),
-        }))
+    fn prefill(init: &[&'static str], extra: &[&'static str]) -> Self {
+        let strings = FxIndexSet::from_iter(init.iter().copied().chain(extra.iter().copied()));
+        assert_eq!(
+            strings.len(),
+            init.len() + extra.len(),
+            "`init` or `extra` contain duplicate symbols",
+        );
+        Interner(Lock::new(InternerInner { arena: Default::default(), strings }))
     }
 
     #[inline]
@@ -2760,9 +2761,9 @@ impl Symbol {
         self != kw::Empty && self != kw::Underscore && !self.is_path_segment_keyword()
     }
 
-    /// Is this symbol was interned in compiler's `symbols!` macro
-    pub fn is_preinterned(self) -> bool {
-        self.as_u32() < PREINTERNED_SYMBOLS_COUNT
+    /// Was this symbol predefined in the compiler's `symbols!` macro
+    pub fn is_predefined(self) -> bool {
+        self.as_u32() < PREDEFINED_SYMBOLS_COUNT
     }
 }
 
diff --git a/compiler/rustc_span/src/symbol/tests.rs b/compiler/rustc_span/src/symbol/tests.rs
index c6aa7627b2b..660d0d7179a 100644
--- a/compiler/rustc_span/src/symbol/tests.rs
+++ b/compiler/rustc_span/src/symbol/tests.rs
@@ -3,7 +3,7 @@ use crate::create_default_session_globals_then;
 
 #[test]
 fn interner_tests() {
-    let i = Interner::prefill(&[]);
+    let i = Interner::prefill(&[], &[]);
     // first one is zero:
     assert_eq!(i.intern("dog"), Symbol::new(0));
     // re-use gets the same entry:
diff --git a/compiler/rustc_symbol_mangling/src/v0.rs b/compiler/rustc_symbol_mangling/src/v0.rs
index 99d44bcd7eb..d28f10ba9e3 100644
--- a/compiler/rustc_symbol_mangling/src/v0.rs
+++ b/compiler/rustc_symbol_mangling/src/v0.rs
@@ -368,7 +368,7 @@ impl<'tcx> Printer<'tcx> for SymbolMangler<'tcx> {
     }
 
     fn print_region(&mut self, region: ty::Region<'_>) -> Result<(), PrintError> {
-        let i = match *region {
+        let i = match region.kind() {
             // Erased lifetimes use the index 0, for a
             // shorter mangling of `L_`.
             ty::ReErased => 0,
@@ -858,7 +858,8 @@ impl<'tcx> Printer<'tcx> for SymbolMangler<'tcx> {
             | DefPathData::GlobalAsm
             | DefPathData::Impl
             | DefPathData::MacroNs(_)
-            | DefPathData::LifetimeNs(_) => {
+            | DefPathData::LifetimeNs(_)
+            | DefPathData::AnonAssocTy => {
                 bug!("symbol_names: unexpected DefPathData: {:?}", disambiguated_data.data)
             }
         };
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/util.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/util.rs
index 683b5b528c6..fd2d2fa7210 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/util.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/util.rs
@@ -42,7 +42,7 @@ pub fn find_param_with_region<'tcx>(
     anon_region: Region<'tcx>,
     replace_region: Region<'tcx>,
 ) -> Option<AnonymousParamInfo<'tcx>> {
-    let (id, kind) = match *anon_region {
+    let (id, kind) = match anon_region.kind() {
         ty::ReLateParam(late_param) => (late_param.scope, late_param.kind),
         ty::ReEarlyParam(ebr) => {
             let region_def = tcx.generics_of(generic_param_scope).region_param(ebr, tcx).def_id;
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/region.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/region.rs
index c7f0a88f951..49c6acedcfa 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/region.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/region.rs
@@ -299,7 +299,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                     self.tcx.param_env(generic_param_scope),
                     terr,
                 );
-                match (*sub, *sup) {
+                match (sub.kind(), sup.kind()) {
                     (ty::RePlaceholder(_), ty::RePlaceholder(_)) => {}
                     (ty::RePlaceholder(_), _) => {
                         note_and_explain_region(
@@ -391,7 +391,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                 })
             }
             infer::RelateParamBound(span, ty, opt_span) => {
-                let prefix = match *sub {
+                let prefix = match sub.kind() {
                     ty::ReStatic => note_and_explain::PrefixKind::TypeSatisfy,
                     _ => note_and_explain::PrefixKind::TypeOutlive,
                 };
@@ -967,7 +967,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                 format!("...so that the {}", sup_trace.cause.as_requirement_str()),
             );
 
-            err.note_expected_found(&"", sup_expected, &"", sup_found);
+            err.note_expected_found("", sup_expected, "", sup_found);
             return if sub_region.is_error() | sup_region.is_error() {
                 err.delay_as_bug()
             } else {
@@ -1048,7 +1048,7 @@ pub(super) fn note_and_explain_region<'tcx>(
     suffix: &str,
     alt_span: Option<Span>,
 ) {
-    let (description, span) = match *region {
+    let (description, span) = match region.kind() {
         ty::ReEarlyParam(_) | ty::ReLateParam(_) | ty::RePlaceholder(_) | ty::ReStatic => {
             msg_span_from_named_region(tcx, generic_param_scope, region, alt_span)
         }
@@ -1085,7 +1085,7 @@ fn msg_span_from_named_region<'tcx>(
     region: ty::Region<'tcx>,
     alt_span: Option<Span>,
 ) -> (String, Option<Span>) {
-    match *region {
+    match region.kind() {
         ty::ReEarlyParam(br) => {
             let param_def_id = tcx.generics_of(generic_param_scope).region_param(br, tcx).def_id;
             let span = tcx.def_span(param_def_id);
@@ -1185,7 +1185,7 @@ pub fn unexpected_hidden_region_diagnostic<'a, 'tcx>(
     });
 
     // Explain the region we are capturing.
-    match *hidden_region {
+    match hidden_region.kind() {
         ty::ReEarlyParam(_) | ty::ReLateParam(_) | ty::ReStatic => {
             // Assuming regionck succeeded (*), we ought to always be
             // capturing *some* region from the fn header, and hence it
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 bc45fc11e9b..5648021f613 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
@@ -2,6 +2,7 @@ use core::ops::ControlFlow;
 use std::borrow::Cow;
 use std::path::PathBuf;
 
+use rustc_abi::ExternAbi;
 use rustc_ast::TraitObjectSyntax;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::unord::UnordSet;
@@ -2799,32 +2800,57 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         }
 
         // Note any argument mismatches
-        let given_ty = params.skip_binder();
+        let ty::Tuple(given) = *params.skip_binder().kind() else {
+            return;
+        };
+
         let expected_ty = trait_pred.skip_binder().trait_ref.args.type_at(1);
-        if let ty::Tuple(given) = given_ty.kind()
-            && let ty::Tuple(expected) = expected_ty.kind()
-        {
-            if expected.len() != given.len() {
-                // Note number of types that were expected and given
-                err.note(
-                    format!(
-                        "expected a closure taking {} argument{}, but one taking {} argument{} was given",
-                        given.len(),
-                        pluralize!(given.len()),
-                        expected.len(),
-                        pluralize!(expected.len()),
-                    )
-                );
-            } else if !self.same_type_modulo_infer(given_ty, expected_ty) {
-                // Print type mismatch
-                let (expected_args, given_args) = self.cmp(given_ty, expected_ty);
-                err.note_expected_found(
-                    &"a closure with arguments",
-                    expected_args,
-                    &"a closure with arguments",
-                    given_args,
-                );
-            }
+        let ty::Tuple(expected) = *expected_ty.kind() else {
+            return;
+        };
+
+        if expected.len() != given.len() {
+            // Note number of types that were expected and given
+            err.note(format!(
+                "expected a closure taking {} argument{}, but one taking {} argument{} was given",
+                given.len(),
+                pluralize!(given.len()),
+                expected.len(),
+                pluralize!(expected.len()),
+            ));
+            return;
+        }
+
+        let given_ty = Ty::new_fn_ptr(
+            self.tcx,
+            params.rebind(self.tcx.mk_fn_sig(
+                given,
+                self.tcx.types.unit,
+                false,
+                hir::Safety::Safe,
+                ExternAbi::Rust,
+            )),
+        );
+        let expected_ty = Ty::new_fn_ptr(
+            self.tcx,
+            trait_pred.rebind(self.tcx.mk_fn_sig(
+                expected,
+                self.tcx.types.unit,
+                false,
+                hir::Safety::Safe,
+                ExternAbi::Rust,
+            )),
+        );
+
+        if !self.same_type_modulo_infer(given_ty, expected_ty) {
+            // Print type mismatch
+            let (expected_args, given_args) = self.cmp(expected_ty, given_ty);
+            err.note_expected_found(
+                "a closure with signature",
+                expected_args,
+                "a closure with signature",
+                given_args,
+            );
         }
     }
 
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 38fcba4ea62..b963e4a2c7c 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
@@ -1988,7 +1988,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         {
             let closure: Vec<_> = self
                 .tcx
-                .fn_arg_names(fn_def_id)
+                .fn_arg_idents(fn_def_id)
                 .iter()
                 .enumerate()
                 .map(|(i, ident)| {
@@ -3018,12 +3018,23 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                                 [] => span_bug!(ty.span, "trait object with no traits: {ty:?}"),
                             };
                             let needs_parens = traits.len() != 1;
-                            err.span_suggestion_verbose(
-                                span,
-                                "you can use `impl Trait` as the argument type",
-                                "impl ",
-                                Applicability::MaybeIncorrect,
-                            );
+                            // Don't recommend impl Trait as a closure argument
+                            if let Some(hir_id) = hir_id
+                                && matches!(
+                                    self.tcx.parent_hir_node(hir_id),
+                                    hir::Node::Item(hir::Item {
+                                        kind: hir::ItemKind::Fn { .. },
+                                        ..
+                                    })
+                                )
+                            {
+                                err.span_suggestion_verbose(
+                                    span,
+                                    "you can use `impl Trait` as the argument type",
+                                    "impl ",
+                                    Applicability::MaybeIncorrect,
+                                );
+                            }
                             let sugg = if !needs_parens {
                                 vec![(span.shrink_to_lo(), format!("&{kw}"))]
                             } else {
@@ -5397,7 +5408,7 @@ fn point_at_assoc_type_restriction<G: EmissionGuarantee>(
                 );
             }
             if let Some(new) =
-                tcx.associated_items(data.impl_or_alias_def_id).find_by_name_and_kind(
+                tcx.associated_items(data.impl_or_alias_def_id).find_by_ident_and_kind(
                     tcx,
                     Ident::with_dummy_span(name),
                     ty::AssocKind::Type,
diff --git a/compiler/rustc_trait_selection/src/errors.rs b/compiler/rustc_trait_selection/src/errors.rs
index 9f7bfe5101a..bb4aba9d29e 100644
--- a/compiler/rustc_trait_selection/src/errors.rs
+++ b/compiler/rustc_trait_selection/src/errors.rs
@@ -415,7 +415,7 @@ impl Subdiagnostic for RegionOriginNote<'_> {
                 label_or_note(span, fluent::trait_selection_subtype);
                 diag.arg("requirement", requirement);
 
-                diag.note_expected_found(&"", expected, &"", found);
+                diag.note_expected_found("", expected, "", found);
             }
             RegionOriginNote::WithRequirement { span, requirement, expected_found: None } => {
                 // FIXME: this really should be handled at some earlier stage. Our
diff --git a/compiler/rustc_trait_selection/src/errors/note_and_explain.rs b/compiler/rustc_trait_selection/src/errors/note_and_explain.rs
index 46622246a17..e4ab78b6247 100644
--- a/compiler/rustc_trait_selection/src/errors/note_and_explain.rs
+++ b/compiler/rustc_trait_selection/src/errors/note_and_explain.rs
@@ -20,7 +20,7 @@ impl<'a> DescriptionCtx<'a> {
         region: ty::Region<'tcx>,
         alt_span: Option<Span>,
     ) -> Option<Self> {
-        let (span, kind, arg) = match *region {
+        let (span, kind, arg) = match region.kind() {
             ty::ReEarlyParam(br) => {
                 let scope = tcx
                     .parent(tcx.generics_of(generic_param_scope).region_param(br, tcx).def_id)
diff --git a/compiler/rustc_trait_selection/src/opaque_types.rs b/compiler/rustc_trait_selection/src/opaque_types.rs
index c7b8f063196..309bf4dda3d 100644
--- a/compiler/rustc_trait_selection/src/opaque_types.rs
+++ b/compiler/rustc_trait_selection/src/opaque_types.rs
@@ -46,7 +46,7 @@ pub fn check_opaque_type_parameter_valid<'tcx>(
             GenericArgKind::Lifetime(lt) => match defining_scope_kind {
                 DefiningScopeKind::HirTypeck => continue,
                 DefiningScopeKind::MirBorrowck => {
-                    matches!(*lt, ty::ReEarlyParam(_) | ty::ReLateParam(_))
+                    matches!(lt.kind(), ty::ReEarlyParam(_) | ty::ReLateParam(_))
                         || (lt.is_static() && opaque_env.param_equal_static(i))
                 }
             },
diff --git a/compiler/rustc_trait_selection/src/solve/fulfill/derive_errors.rs b/compiler/rustc_trait_selection/src/solve/fulfill/derive_errors.rs
index 3a939df25e0..d8dcd12aecb 100644
--- a/compiler/rustc_trait_selection/src/solve/fulfill/derive_errors.rs
+++ b/compiler/rustc_trait_selection/src/solve/fulfill/derive_errors.rs
@@ -13,9 +13,9 @@ use rustc_next_trait_solver::solve::{GenerateProofTree, SolverDelegateEvalExt as
 use rustc_type_ir::solve::NoSolution;
 use tracing::{instrument, trace};
 
-use crate::solve::Certainty;
 use crate::solve::delegate::SolverDelegate;
 use crate::solve::inspect::{self, ProofTreeInferCtxtExt, ProofTreeVisitor};
+use crate::solve::{Certainty, deeply_normalize_for_diagnostics};
 use crate::traits::{FulfillmentError, FulfillmentErrorCode, wf};
 
 pub(super) fn fulfillment_error_for_no_solution<'tcx>(
@@ -151,7 +151,7 @@ fn find_best_leaf_obligation<'tcx>(
     //
     // We should probably fix the visitor to not do so instead, as this also
     // means the leaf obligation may be incorrect.
-    infcx
+    let obligation = infcx
         .fudge_inference_if_ok(|| {
             infcx
                 .visit_proof_tree(
@@ -161,7 +161,8 @@ fn find_best_leaf_obligation<'tcx>(
                 .break_value()
                 .ok_or(())
         })
-        .unwrap_or(obligation)
+        .unwrap_or(obligation);
+    deeply_normalize_for_diagnostics(infcx, obligation.param_env, obligation)
 }
 
 struct BestObligation<'tcx> {
@@ -291,6 +292,40 @@ impl<'tcx> BestObligation<'tcx> {
         }
     }
 
+    /// When a higher-ranked projection goal fails, check that the corresponding
+    /// higher-ranked trait goal holds or not. This is because the process of
+    /// instantiating and then re-canonicalizing the binder of the projection goal
+    /// forces us to be unable to see that the leak check failed in the nested
+    /// `NormalizesTo` goal, so we don't fall back to the rigid projection check
+    /// that should catch when a projection goal fails due to an unsatisfied trait
+    /// goal.
+    fn detect_trait_error_in_higher_ranked_projection(
+        &mut self,
+        goal: &inspect::InspectGoal<'_, 'tcx>,
+    ) -> ControlFlow<PredicateObligation<'tcx>> {
+        let tcx = goal.infcx().tcx;
+        if let Some(projection_clause) = goal.goal().predicate.as_projection_clause()
+            && !projection_clause.bound_vars().is_empty()
+        {
+            let pred = projection_clause.map_bound(|proj| proj.projection_term.trait_ref(tcx));
+            let obligation = Obligation::new(
+                tcx,
+                self.obligation.cause.clone(),
+                goal.goal().param_env,
+                deeply_normalize_for_diagnostics(goal.infcx(), goal.goal().param_env, pred),
+            );
+            self.with_derived_obligation(obligation, |this| {
+                goal.infcx().visit_proof_tree_at_depth(
+                    goal.goal().with(tcx, pred),
+                    goal.depth() + 1,
+                    this,
+                )
+            })
+        } else {
+            ControlFlow::Continue(())
+        }
+    }
+
     /// It is likely that `NormalizesTo` failed without any applicable candidates
     /// because the alias is not well-formed.
     ///
@@ -360,7 +395,8 @@ impl<'tcx> ProofTreeVisitor<'tcx> for BestObligation<'tcx> {
             (true, Ok(Certainty::Maybe(MaybeCause::Ambiguity))) | (false, Err(_)) => {}
             _ => return ControlFlow::Continue(()),
         }
-        let pred_kind = goal.goal().predicate.kind();
+
+        let pred = goal.goal().predicate;
 
         let candidates = self.non_trivial_candidates(goal);
         let candidate = match candidates.as_slice() {
@@ -374,7 +410,7 @@ impl<'tcx> ProofTreeVisitor<'tcx> for BestObligation<'tcx> {
             source: CandidateSource::Impl(impl_def_id),
             result: _,
         } = candidate.kind()
-            && goal.infcx().tcx.do_not_recommend_impl(impl_def_id)
+            && tcx.do_not_recommend_impl(impl_def_id)
         {
             trace!("#[do_not_recommend] -> exit");
             return ControlFlow::Break(self.obligation.clone());
@@ -382,12 +418,12 @@ impl<'tcx> ProofTreeVisitor<'tcx> for BestObligation<'tcx> {
 
         // FIXME: Also, what about considering >1 layer up the stack? May be necessary
         // for normalizes-to.
-        let child_mode = match pred_kind.skip_binder() {
-            ty::PredicateKind::Clause(ty::ClauseKind::Trait(pred)) => {
-                ChildMode::Trait(pred_kind.rebind(pred))
+        let child_mode = match pred.kind().skip_binder() {
+            ty::PredicateKind::Clause(ty::ClauseKind::Trait(trait_pred)) => {
+                ChildMode::Trait(pred.kind().rebind(trait_pred))
             }
-            ty::PredicateKind::Clause(ty::ClauseKind::HostEffect(pred)) => {
-                ChildMode::Host(pred_kind.rebind(pred))
+            ty::PredicateKind::Clause(ty::ClauseKind::HostEffect(host_pred)) => {
+                ChildMode::Host(pred.kind().rebind(host_pred))
             }
             ty::PredicateKind::NormalizesTo(normalizes_to)
                 if matches!(
@@ -395,7 +431,7 @@ impl<'tcx> ProofTreeVisitor<'tcx> for BestObligation<'tcx> {
                     ty::AliasTermKind::ProjectionTy | ty::AliasTermKind::ProjectionConst
                 ) =>
             {
-                ChildMode::Trait(pred_kind.rebind(ty::TraitPredicate {
+                ChildMode::Trait(pred.kind().rebind(ty::TraitPredicate {
                     trait_ref: normalizes_to.alias.trait_ref(tcx),
                     polarity: ty::PredicatePolarity::Positive,
                 }))
@@ -429,10 +465,12 @@ impl<'tcx> ProofTreeVisitor<'tcx> for BestObligation<'tcx> {
         for nested_goal in nested_goals {
             trace!(nested_goal = ?(nested_goal.goal(), nested_goal.source(), nested_goal.result()));
 
+            let nested_pred = nested_goal.goal().predicate;
+
             let make_obligation = |cause| Obligation {
                 cause,
                 param_env: nested_goal.goal().param_env,
-                predicate: nested_goal.goal().predicate,
+                predicate: nested_pred,
                 recursion_depth: self.obligation.recursion_depth + 1,
             };
 
@@ -482,30 +520,21 @@ impl<'tcx> ProofTreeVisitor<'tcx> for BestObligation<'tcx> {
 
         // alias-relate may fail because the lhs or rhs can't be normalized,
         // and therefore is treated as rigid.
-        if let Some(ty::PredicateKind::AliasRelate(lhs, rhs, _)) = pred_kind.no_bound_vars() {
-            if let Some(obligation) = goal
-                .infcx()
-                .visit_proof_tree_at_depth(
-                    goal.goal().with(goal.infcx().tcx, ty::ClauseKind::WellFormed(lhs.into())),
-                    goal.depth() + 1,
-                    self,
-                )
-                .break_value()
-            {
-                return ControlFlow::Break(obligation);
-            } else if let Some(obligation) = goal
-                .infcx()
-                .visit_proof_tree_at_depth(
-                    goal.goal().with(goal.infcx().tcx, ty::ClauseKind::WellFormed(rhs.into())),
-                    goal.depth() + 1,
-                    self,
-                )
-                .break_value()
-            {
-                return ControlFlow::Break(obligation);
-            }
+        if let Some(ty::PredicateKind::AliasRelate(lhs, rhs, _)) = pred.kind().no_bound_vars() {
+            goal.infcx().visit_proof_tree_at_depth(
+                goal.goal().with(tcx, ty::ClauseKind::WellFormed(lhs.into())),
+                goal.depth() + 1,
+                self,
+            )?;
+            goal.infcx().visit_proof_tree_at_depth(
+                goal.goal().with(tcx, ty::ClauseKind::WellFormed(rhs.into())),
+                goal.depth() + 1,
+                self,
+            )?;
         }
 
+        self.detect_trait_error_in_higher_ranked_projection(goal)?;
+
         ControlFlow::Break(self.obligation.clone())
     }
 }
diff --git a/compiler/rustc_trait_selection/src/solve/normalize.rs b/compiler/rustc_trait_selection/src/solve/normalize.rs
index 232357dc71a..79fb044a67f 100644
--- a/compiler/rustc_trait_selection/src/solve/normalize.rs
+++ b/compiler/rustc_trait_selection/src/solve/normalize.rs
@@ -253,20 +253,28 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for DeeplyNormalizeForDiagnosticsFolder<'_,
     }
 
     fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
-        deeply_normalize_with_skipped_universes(
-            self.at,
-            ty,
-            vec![None; ty.outer_exclusive_binder().as_usize()],
-        )
-        .unwrap_or_else(|_: Vec<ScrubbedTraitError<'tcx>>| ty.super_fold_with(self))
+        let infcx = self.at.infcx;
+        infcx
+            .commit_if_ok(|_| {
+                deeply_normalize_with_skipped_universes(
+                    self.at,
+                    ty,
+                    vec![None; ty.outer_exclusive_binder().as_usize()],
+                )
+            })
+            .unwrap_or_else(|_: Vec<ScrubbedTraitError<'tcx>>| ty.super_fold_with(self))
     }
 
     fn fold_const(&mut self, ct: ty::Const<'tcx>) -> ty::Const<'tcx> {
-        deeply_normalize_with_skipped_universes(
-            self.at,
-            ct,
-            vec![None; ct.outer_exclusive_binder().as_usize()],
-        )
-        .unwrap_or_else(|_: Vec<ScrubbedTraitError<'tcx>>| ct.super_fold_with(self))
+        let infcx = self.at.infcx;
+        infcx
+            .commit_if_ok(|_| {
+                deeply_normalize_with_skipped_universes(
+                    self.at,
+                    ct,
+                    vec![None; ct.outer_exclusive_binder().as_usize()],
+                )
+            })
+            .unwrap_or_else(|_: Vec<ScrubbedTraitError<'tcx>>| ct.super_fold_with(self))
     }
 }
diff --git a/compiler/rustc_trait_selection/src/traits/auto_trait.rs b/compiler/rustc_trait_selection/src/traits/auto_trait.rs
index 1fca2f4da7e..02521c9453d 100644
--- a/compiler/rustc_trait_selection/src/traits/auto_trait.rs
+++ b/compiler/rustc_trait_selection/src/traits/auto_trait.rs
@@ -382,7 +382,7 @@ impl<'tcx> AutoTraitFinder<'tcx> {
                     for (new_region, old_region) in
                         iter::zip(new_args.regions(), old_args.regions())
                     {
-                        match (*new_region, *old_region) {
+                        match (new_region.kind(), old_region.kind()) {
                             // If both predicates have an `ReBound` (a HRTB) in the
                             // same spot, we do nothing.
                             (ty::ReBound(_, _), ty::ReBound(_, _)) => {}
diff --git a/compiler/rustc_trait_selection/src/traits/coherence.rs b/compiler/rustc_trait_selection/src/traits/coherence.rs
index bcc247ba53c..93c7dae9c5b 100644
--- a/compiler/rustc_trait_selection/src/traits/coherence.rs
+++ b/compiler/rustc_trait_selection/src/traits/coherence.rs
@@ -537,7 +537,7 @@ fn plug_infer_with_placeholders<'tcx>(
         }
 
         fn visit_region(&mut self, r: ty::Region<'tcx>) {
-            if let ty::ReVar(vid) = *r {
+            if let ty::ReVar(vid) = r.kind() {
                 let r = self
                     .infcx
                     .inner
diff --git a/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs b/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
index fa6bbf1d6e5..bf9fcb0915a 100644
--- a/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
+++ b/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
@@ -797,7 +797,7 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for EraseEscapingBoundRegions<'tcx> {
     }
 
     fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
-        if let ty::ReBound(debruijn, _) = *r
+        if let ty::ReBound(debruijn, _) = r.kind()
             && debruijn < self.binder
         {
             r
diff --git a/compiler/rustc_trait_selection/src/traits/project.rs b/compiler/rustc_trait_selection/src/traits/project.rs
index 349569d750e..83591219b14 100644
--- a/compiler/rustc_trait_selection/src/traits/project.rs
+++ b/compiler/rustc_trait_selection/src/traits/project.rs
@@ -669,30 +669,11 @@ fn project<'cx, 'tcx>(
 
     match candidates {
         ProjectionCandidateSet::Single(candidate) => {
-            Ok(Projected::Progress(confirm_candidate(selcx, obligation, candidate)))
+            confirm_candidate(selcx, obligation, candidate)
         }
         ProjectionCandidateSet::None => {
             let tcx = selcx.tcx();
-            let term = match tcx.def_kind(obligation.predicate.def_id) {
-                DefKind::AssocTy => Ty::new_projection_from_args(
-                    tcx,
-                    obligation.predicate.def_id,
-                    obligation.predicate.args,
-                )
-                .into(),
-                DefKind::AssocConst => ty::Const::new_unevaluated(
-                    tcx,
-                    ty::UnevaluatedConst::new(
-                        obligation.predicate.def_id,
-                        obligation.predicate.args,
-                    ),
-                )
-                .into(),
-                kind => {
-                    bug!("unknown projection def-id: {}", kind.descr(obligation.predicate.def_id))
-                }
-            };
-
+            let term = obligation.predicate.to_term(tcx);
             Ok(Projected::NoProgress(term))
         }
         // Error occurred while trying to processing impls.
@@ -1244,18 +1225,16 @@ fn confirm_candidate<'cx, 'tcx>(
     selcx: &mut SelectionContext<'cx, 'tcx>,
     obligation: &ProjectionTermObligation<'tcx>,
     candidate: ProjectionCandidate<'tcx>,
-) -> Progress<'tcx> {
+) -> Result<Projected<'tcx>, ProjectionError<'tcx>> {
     debug!(?obligation, ?candidate, "confirm_candidate");
-    let mut progress = match candidate {
+    let mut result = match candidate {
         ProjectionCandidate::ParamEnv(poly_projection)
-        | ProjectionCandidate::Object(poly_projection) => {
-            confirm_param_env_candidate(selcx, obligation, poly_projection, false)
-        }
-
-        ProjectionCandidate::TraitDef(poly_projection) => {
-            confirm_param_env_candidate(selcx, obligation, poly_projection, true)
-        }
-
+        | ProjectionCandidate::Object(poly_projection) => Ok(Projected::Progress(
+            confirm_param_env_candidate(selcx, obligation, poly_projection, false),
+        )),
+        ProjectionCandidate::TraitDef(poly_projection) => Ok(Projected::Progress(
+            confirm_param_env_candidate(selcx, obligation, poly_projection, true),
+        )),
         ProjectionCandidate::Select(impl_source) => {
             confirm_select_candidate(selcx, obligation, impl_source)
         }
@@ -1266,23 +1245,26 @@ fn confirm_candidate<'cx, 'tcx>(
     // with new region variables, we need to resolve them to existing variables
     // when possible for this to work. See `auto-trait-projection-recursion.rs`
     // for a case where this matters.
-    if progress.term.has_infer_regions() {
+    if let Ok(Projected::Progress(progress)) = &mut result
+        && progress.term.has_infer_regions()
+    {
         progress.term = progress.term.fold_with(&mut OpportunisticRegionResolver::new(selcx.infcx));
     }
-    progress
+
+    result
 }
 
 fn confirm_select_candidate<'cx, 'tcx>(
     selcx: &mut SelectionContext<'cx, 'tcx>,
     obligation: &ProjectionTermObligation<'tcx>,
     impl_source: Selection<'tcx>,
-) -> Progress<'tcx> {
+) -> Result<Projected<'tcx>, ProjectionError<'tcx>> {
     match impl_source {
         ImplSource::UserDefined(data) => confirm_impl_candidate(selcx, obligation, data),
         ImplSource::Builtin(BuiltinImplSource::Misc | BuiltinImplSource::Trivial, data) => {
             let tcx = selcx.tcx();
             let trait_def_id = obligation.predicate.trait_def_id(tcx);
-            if tcx.is_lang_item(trait_def_id, LangItem::Coroutine) {
+            let progress = if tcx.is_lang_item(trait_def_id, LangItem::Coroutine) {
                 confirm_coroutine_candidate(selcx, obligation, data)
             } else if tcx.is_lang_item(trait_def_id, LangItem::Future) {
                 confirm_future_candidate(selcx, obligation, data)
@@ -1304,7 +1286,8 @@ fn confirm_select_candidate<'cx, 'tcx>(
                 confirm_async_fn_kind_helper_candidate(selcx, obligation, data)
             } else {
                 confirm_builtin_candidate(selcx, obligation, data)
-            }
+            };
+            Ok(Projected::Progress(progress))
         }
         ImplSource::Builtin(BuiltinImplSource::Object { .. }, _)
         | ImplSource::Param(..)
@@ -2000,7 +1983,7 @@ fn confirm_impl_candidate<'cx, 'tcx>(
     selcx: &mut SelectionContext<'cx, 'tcx>,
     obligation: &ProjectionTermObligation<'tcx>,
     impl_impl_source: ImplSourceUserDefinedData<'tcx, PredicateObligation<'tcx>>,
-) -> Progress<'tcx> {
+) -> Result<Projected<'tcx>, ProjectionError<'tcx>> {
     let tcx = selcx.tcx();
 
     let ImplSourceUserDefinedData { impl_def_id, args, mut nested } = impl_impl_source;
@@ -2011,19 +1994,33 @@ fn confirm_impl_candidate<'cx, 'tcx>(
     let param_env = obligation.param_env;
     let assoc_ty = match specialization_graph::assoc_def(tcx, impl_def_id, assoc_item_id) {
         Ok(assoc_ty) => assoc_ty,
-        Err(guar) => return Progress::error(tcx, guar),
+        Err(guar) => return Ok(Projected::Progress(Progress::error(tcx, guar))),
     };
+
+    // This means that the impl is missing a definition for the
+    // associated type. This is either because the associate item
+    // has impossible-to-satisfy predicates (since those were
+    // allowed in <https://github.com/rust-lang/rust/pull/135480>),
+    // or because the impl is literally missing the definition.
     if !assoc_ty.item.defaultness(tcx).has_value() {
-        // This means that the impl is missing a definition for the
-        // associated type. This error will be reported by the type
-        // checker method `check_impl_items_against_trait`, so here we
-        // just return Error.
         debug!(
             "confirm_impl_candidate: no associated type {:?} for {:?}",
             assoc_ty.item.name, obligation.predicate
         );
-        return Progress { term: Ty::new_misc_error(tcx).into(), obligations: nested };
+        if tcx.impl_self_is_guaranteed_unsized(impl_def_id) {
+            // We treat this projection as rigid here, which is represented via
+            // `Projected::NoProgress`. This will ensure that the projection is
+            // checked for well-formedness, and it's either satisfied by a trivial
+            // where clause in its env or it results in an error.
+            return Ok(Projected::NoProgress(obligation.predicate.to_term(tcx)));
+        } else {
+            return Ok(Projected::Progress(Progress {
+                term: Ty::new_misc_error(tcx).into(),
+                obligations: nested,
+            }));
+        }
     }
+
     // If we're trying to normalize `<Vec<u32> as X>::A<S>` using
     //`impl<T> X for Vec<T> { type A<Y> = Box<Y>; }`, then:
     //
@@ -2033,6 +2030,7 @@ fn confirm_impl_candidate<'cx, 'tcx>(
     let args = obligation.predicate.args.rebase_onto(tcx, trait_def_id, args);
     let args = translate_args(selcx.infcx, param_env, impl_def_id, args, assoc_ty.defining_node);
     let is_const = matches!(tcx.def_kind(assoc_ty.item.def_id), DefKind::AssocConst);
+
     let term: ty::EarlyBinder<'tcx, ty::Term<'tcx>> = if is_const {
         let did = assoc_ty.item.def_id;
         let identity_args = crate::traits::GenericArgs::identity_for_item(tcx, did);
@@ -2041,7 +2039,8 @@ fn confirm_impl_candidate<'cx, 'tcx>(
     } else {
         tcx.type_of(assoc_ty.item.def_id).map_bound(|ty| ty.into())
     };
-    if !tcx.check_args_compatible(assoc_ty.item.def_id, args) {
+
+    let progress = if !tcx.check_args_compatible(assoc_ty.item.def_id, args) {
         let err = Ty::new_error_with_message(
             tcx,
             obligation.cause.span,
@@ -2051,7 +2050,8 @@ fn confirm_impl_candidate<'cx, 'tcx>(
     } else {
         assoc_ty_own_obligations(selcx, obligation, &mut nested);
         Progress { term: term.instantiate(tcx, args), obligations: nested }
-    }
+    };
+    Ok(Projected::Progress(progress))
 }
 
 // Get obligations corresponding to the predicates from the where-clause of the
diff --git a/compiler/rustc_trait_selection/src/traits/query/normalize.rs b/compiler/rustc_trait_selection/src/traits/query/normalize.rs
index 5dbb4382fd1..507932699c7 100644
--- a/compiler/rustc_trait_selection/src/traits/query/normalize.rs
+++ b/compiler/rustc_trait_selection/src/traits/query/normalize.rs
@@ -144,7 +144,7 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for MaxEscapingBoundVarVisitor {
 
     #[inline]
     fn visit_region(&mut self, r: ty::Region<'tcx>) {
-        match *r {
+        match r.kind() {
             ty::ReBound(debruijn, _) if debruijn > self.outer_index => {
                 self.escaping =
                     self.escaping.max(debruijn.as_usize() - self.outer_index.as_usize());
diff --git a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
index 2cb7d2d8931..69e7b2a43ff 100644
--- a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
@@ -317,7 +317,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                     obligation.cause.clone(),
                     obligation.recursion_depth + 1,
                     obligation.param_env,
-                    obligation.predicate.rebind(trait_ref),
+                    trait_ref,
                 )
             };
 
@@ -343,7 +343,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                     obligation.cause.clone(),
                     obligation.recursion_depth + 1,
                     obligation.param_env,
-                    obligation.predicate.rebind(outlives),
+                    outlives,
                 )
             };
 
@@ -404,7 +404,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             }
         }
 
-        let predicate = obligation.predicate.skip_binder();
+        let predicate = self.infcx.enter_forall_and_leak_universe(obligation.predicate);
 
         let mut assume = predicate.trait_ref.args.const_at(2);
         // FIXME(mgca): We should shallowly normalize this.
@@ -1090,26 +1090,36 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             {
                 // See `assemble_candidates_for_unsizing` for more info.
                 // We already checked the compatibility of auto traits within `assemble_candidates_for_unsizing`.
-                let iter = data_a
-                    .principal()
-                    .filter(|_| {
-                        // optionally drop the principal, if we're unsizing to no principal
-                        data_b.principal().is_some()
-                    })
-                    .map(|b| b.map_bound(ty::ExistentialPredicate::Trait))
-                    .into_iter()
-                    .chain(
+                let existential_predicates = if data_b.principal().is_some() {
+                    tcx.mk_poly_existential_predicates_from_iter(
                         data_a
-                            .projection_bounds()
-                            .map(|b| b.map_bound(ty::ExistentialPredicate::Projection)),
+                            .principal()
+                            .map(|b| b.map_bound(ty::ExistentialPredicate::Trait))
+                            .into_iter()
+                            .chain(
+                                data_a
+                                    .projection_bounds()
+                                    .map(|b| b.map_bound(ty::ExistentialPredicate::Projection)),
+                            )
+                            .chain(
+                                data_b
+                                    .auto_traits()
+                                    .map(ty::ExistentialPredicate::AutoTrait)
+                                    .map(ty::Binder::dummy),
+                            ),
                     )
-                    .chain(
+                } else {
+                    // If we're unsizing to a dyn type that has no principal, then drop
+                    // the principal and projections from the type. We use the auto traits
+                    // from the RHS type since as we noted that we've checked for auto
+                    // trait compatibility during unsizing.
+                    tcx.mk_poly_existential_predicates_from_iter(
                         data_b
                             .auto_traits()
                             .map(ty::ExistentialPredicate::AutoTrait)
                             .map(ty::Binder::dummy),
-                    );
-                let existential_predicates = tcx.mk_poly_existential_predicates_from_iter(iter);
+                    )
+                };
                 let source_trait = Ty::new_dynamic(tcx, existential_predicates, r_b, dyn_a);
 
                 // Require that the traits involved in this upcast are **equal**;
diff --git a/compiler/rustc_trait_selection/src/traits/util.rs b/compiler/rustc_trait_selection/src/traits/util.rs
index 15f5cf916a4..9f20cd7eacb 100644
--- a/compiler/rustc_trait_selection/src/traits/util.rs
+++ b/compiler/rustc_trait_selection/src/traits/util.rs
@@ -289,7 +289,7 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for BoundVarReplacer<'_, 'tcx> {
     }
 
     fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
-        match *r {
+        match r.kind() {
             ty::ReBound(debruijn, _)
                 if debruijn.as_usize()
                     >= self.current_index.as_usize() + self.universe_indices.len() =>
@@ -407,7 +407,7 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for PlaceholderReplacer<'_, 'tcx> {
     }
 
     fn fold_region(&mut self, r0: ty::Region<'tcx>) -> ty::Region<'tcx> {
-        let r1 = match *r0 {
+        let r1 = match r0.kind() {
             ty::ReVar(vid) => self
                 .infcx
                 .inner
@@ -417,7 +417,7 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for PlaceholderReplacer<'_, 'tcx> {
             _ => r0,
         };
 
-        let r2 = match *r1 {
+        let r2 = match r1.kind() {
             ty::RePlaceholder(p) => {
                 let replace_var = self.mapped_regions.get(&p);
                 match replace_var {
diff --git a/compiler/rustc_ty_utils/src/assoc.rs b/compiler/rustc_ty_utils/src/assoc.rs
index b7684e85d41..9520d948f51 100644
--- a/compiler/rustc_ty_utils/src/assoc.rs
+++ b/compiler/rustc_ty_utils/src/assoc.rs
@@ -252,7 +252,7 @@ fn associated_type_for_impl_trait_in_trait(
     assert_eq!(tcx.def_kind(trait_def_id), DefKind::Trait);
 
     let span = tcx.def_span(opaque_ty_def_id);
-    // No name because this is a synthetic associated type.
+    // No name because this is an anonymous associated type.
     let trait_assoc_ty = tcx.at(span).create_def(trait_def_id, None, DefKind::AssocTy);
 
     let local_def_id = trait_assoc_ty.def_id();
@@ -305,7 +305,7 @@ fn associated_type_for_impl_trait_in_impl(
         hir::FnRetTy::DefaultReturn(_) => tcx.def_span(impl_fn_def_id),
         hir::FnRetTy::Return(ty) => ty.span,
     };
-    // No name because this is a synthetic associated type.
+    // No name because this is an anonymous associated type.
     let impl_assoc_ty = tcx.at(span).create_def(impl_local_def_id, None, DefKind::AssocTy);
 
     let local_def_id = impl_assoc_ty.def_id();
diff --git a/compiler/rustc_ty_utils/src/implied_bounds.rs b/compiler/rustc_ty_utils/src/implied_bounds.rs
index 088d5e76b86..6fa763f18ef 100644
--- a/compiler/rustc_ty_utils/src/implied_bounds.rs
+++ b/compiler/rustc_ty_utils/src/implied_bounds.rs
@@ -4,9 +4,9 @@ use rustc_data_structures::fx::FxHashMap;
 use rustc_hir as hir;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::LocalDefId;
-use rustc_middle::bug;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::{self, Ty, TyCtxt, fold_regions};
+use rustc_middle::{bug, span_bug};
 use rustc_span::Span;
 
 pub(crate) fn provide(providers: &mut Providers) {
@@ -21,7 +21,8 @@ pub(crate) fn provide(providers: &mut Providers) {
 }
 
 fn assumed_wf_types<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> &'tcx [(Ty<'tcx>, Span)] {
-    match tcx.def_kind(def_id) {
+    let kind = tcx.def_kind(def_id);
+    match kind {
         DefKind::Fn => {
             let sig = tcx.fn_sig(def_id).instantiate_identity();
             let liberated_sig = tcx.liberate_late_bound_regions(def_id.to_def_id(), sig);
@@ -75,7 +76,7 @@ fn assumed_wf_types<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> &'tcx [(Ty<'
                     {
                         let orig_lt =
                             tcx.map_opaque_lifetime_to_parent_lifetime(param.def_id.expect_local());
-                        if matches!(*orig_lt, ty::ReLateParam(..)) {
+                        if matches!(orig_lt.kind(), ty::ReLateParam(..)) {
                             mapping.insert(
                                 orig_lt,
                                 ty::Region::new_early_param(
@@ -121,32 +122,38 @@ fn assumed_wf_types<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> &'tcx [(Ty<'
             }
         }
         DefKind::AssocConst | DefKind::AssocTy => tcx.assumed_wf_types(tcx.local_parent(def_id)),
-        DefKind::OpaqueTy => bug!("implied bounds are not defined for opaques"),
-        DefKind::Mod
+        DefKind::Static { .. }
+        | DefKind::Const
+        | DefKind::AnonConst
+        | DefKind::InlineConst
         | DefKind::Struct
         | DefKind::Union
         | DefKind::Enum
-        | DefKind::Variant
         | DefKind::Trait
-        | DefKind::TyAlias
-        | DefKind::ForeignTy
         | DefKind::TraitAlias
+        | DefKind::TyAlias => ty::List::empty(),
+        DefKind::OpaqueTy
+        | DefKind::Mod
+        | DefKind::Variant
+        | DefKind::ForeignTy
         | DefKind::TyParam
-        | DefKind::Const
         | DefKind::ConstParam
-        | DefKind::Static { .. }
         | DefKind::Ctor(_, _)
         | DefKind::Macro(_)
         | DefKind::ExternCrate
         | DefKind::Use
         | DefKind::ForeignMod
-        | DefKind::AnonConst
-        | DefKind::InlineConst
         | DefKind::Field
         | DefKind::LifetimeParam
         | DefKind::GlobalAsm
         | DefKind::Closure
-        | DefKind::SyntheticCoroutineBody => ty::List::empty(),
+        | DefKind::SyntheticCoroutineBody => {
+            span_bug!(
+                tcx.def_span(def_id),
+                "`assumed_wf_types` not defined for {} `{def_id:?}`",
+                kind.descr(def_id.to_def_id())
+            );
+        }
     }
 }
 
diff --git a/compiler/rustc_ty_utils/src/opaque_types.rs b/compiler/rustc_ty_utils/src/opaque_types.rs
index 3aad97d86cc..cd730aeeea9 100644
--- a/compiler/rustc_ty_utils/src/opaque_types.rs
+++ b/compiler/rustc_ty_utils/src/opaque_types.rs
@@ -3,10 +3,10 @@ use rustc_hir::def::DefKind;
 use rustc_hir::def_id::LocalDefId;
 use rustc_hir::intravisit;
 use rustc_hir::intravisit::Visitor;
-use rustc_middle::bug;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::util::{CheckRegions, NotUniqueParam};
 use rustc_middle::ty::{self, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitor};
+use rustc_middle::{bug, span_bug};
 use rustc_span::Span;
 use tracing::{instrument, trace};
 
@@ -320,9 +320,12 @@ fn opaque_types_defined_by<'tcx>(
         | DefKind::AnonConst => {
             collector.collect_taits_declared_in_body();
         }
+        // Closures and coroutines are type checked with their parent
+        DefKind::Closure | DefKind::InlineConst => {
+            collector.opaques.extend(tcx.opaque_types_defined_by(tcx.local_parent(item)));
+        }
+        DefKind::AssocTy | DefKind::TyAlias | DefKind::GlobalAsm => {}
         DefKind::OpaqueTy
-        | DefKind::TyAlias
-        | DefKind::AssocTy
         | DefKind::Mod
         | DefKind::Struct
         | DefKind::Union
@@ -340,12 +343,13 @@ fn opaque_types_defined_by<'tcx>(
         | DefKind::ForeignMod
         | DefKind::Field
         | DefKind::LifetimeParam
-        | DefKind::GlobalAsm
         | DefKind::Impl { .. }
-        | DefKind::SyntheticCoroutineBody => {}
-        // Closures and coroutines are type checked with their parent
-        DefKind::Closure | DefKind::InlineConst => {
-            collector.opaques.extend(tcx.opaque_types_defined_by(tcx.local_parent(item)));
+        | DefKind::SyntheticCoroutineBody => {
+            span_bug!(
+                tcx.def_span(item),
+                "`opaque_types_defined_by` not defined for {} `{item:?}`",
+                kind.descr(item.to_def_id())
+            );
         }
     }
     tcx.mk_local_def_ids(&collector.opaques)
diff --git a/compiler/rustc_ty_utils/src/sig_types.rs b/compiler/rustc_ty_utils/src/sig_types.rs
index 5bb96f90029..dc6009116ac 100644
--- a/compiler/rustc_ty_utils/src/sig_types.rs
+++ b/compiler/rustc_ty_utils/src/sig_types.rs
@@ -116,7 +116,7 @@ pub fn walk_types<'tcx, V: SpannedTypeVisitor<'tcx>>(
                 "{kind:?} has not seen any uses of `walk_types` yet, ping oli-obk if you'd like any help"
             )
         }
-        // These don't have any types.
+        // These don't have any types, but are visited during privacy checking.
         | DefKind::ExternCrate
         | DefKind::ForeignMod
         | DefKind::ForeignTy
diff --git a/compiler/rustc_ty_utils/src/ty.rs b/compiler/rustc_ty_utils/src/ty.rs
index 9dc4f11e456..31d69eef5ec 100644
--- a/compiler/rustc_ty_utils/src/ty.rs
+++ b/compiler/rustc_ty_utils/src/ty.rs
@@ -3,6 +3,7 @@ use rustc_hir as hir;
 use rustc_hir::LangItem;
 use rustc_hir::def::DefKind;
 use rustc_index::bit_set::DenseBitSet;
+use rustc_infer::infer::TyCtxtInferExt;
 use rustc_middle::bug;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::{
@@ -312,6 +313,61 @@ fn unsizing_params_for_adt<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> DenseBitSe
     unsizing_params
 }
 
+fn impl_self_is_guaranteed_unsized<'tcx>(tcx: TyCtxt<'tcx>, impl_def_id: DefId) -> bool {
+    debug_assert_eq!(tcx.def_kind(impl_def_id), DefKind::Impl { of_trait: true });
+
+    let infcx = tcx.infer_ctxt().ignoring_regions().build(ty::TypingMode::non_body_analysis());
+
+    let ocx = traits::ObligationCtxt::new_with_diagnostics(&infcx);
+    let cause = traits::ObligationCause::dummy();
+    let param_env = tcx.param_env(impl_def_id);
+
+    let tail = tcx.struct_tail_raw(
+        tcx.type_of(impl_def_id).instantiate_identity(),
+        |ty| {
+            ocx.structurally_normalize_ty(&cause, param_env, ty).unwrap_or_else(|_| {
+                Ty::new_error_with_message(
+                    tcx,
+                    tcx.def_span(impl_def_id),
+                    "struct tail should be computable",
+                )
+            })
+        },
+        || (),
+    );
+
+    match tail.kind() {
+        ty::Dynamic(_, _, ty::Dyn) | ty::Slice(_) | ty::Str => true,
+        ty::Bool
+        | ty::Char
+        | ty::Int(_)
+        | ty::Uint(_)
+        | ty::Float(_)
+        | ty::Adt(_, _)
+        | ty::Foreign(_)
+        | ty::Array(_, _)
+        | ty::Pat(_, _)
+        | ty::RawPtr(_, _)
+        | ty::Ref(_, _, _)
+        | ty::FnDef(_, _)
+        | ty::FnPtr(_, _)
+        | ty::UnsafeBinder(_)
+        | ty::Closure(_, _)
+        | ty::CoroutineClosure(_, _)
+        | ty::Coroutine(_, _)
+        | ty::CoroutineWitness(_, _)
+        | ty::Never
+        | ty::Tuple(_)
+        | ty::Alias(_, _)
+        | ty::Param(_)
+        | ty::Bound(_, _)
+        | ty::Placeholder(_)
+        | ty::Infer(_)
+        | ty::Error(_)
+        | ty::Dynamic(_, _, ty::DynStar) => false,
+    }
+}
+
 pub(crate) fn provide(providers: &mut Providers) {
     *providers = Providers {
         asyncness,
@@ -320,6 +376,7 @@ pub(crate) fn provide(providers: &mut Providers) {
         param_env_normalized_for_post_analysis,
         defaultness,
         unsizing_params_for_adt,
+        impl_self_is_guaranteed_unsized,
         ..*providers
     };
 }
diff --git a/compiler/rustc_type_ir/src/inherent.rs b/compiler/rustc_type_ir/src/inherent.rs
index 59c2d3c2fc8..6e6c40580d8 100644
--- a/compiler/rustc_type_ir/src/inherent.rs
+++ b/compiler/rustc_type_ir/src/inherent.rs
@@ -155,6 +155,39 @@ pub trait Ty<I: Interner<Ty = Self>>:
     fn is_known_rigid(self) -> bool {
         self.kind().is_known_rigid()
     }
+
+    fn is_guaranteed_unsized_raw(self) -> bool {
+        match self.kind() {
+            ty::Dynamic(_, _, ty::Dyn) | ty::Slice(_) | ty::Str => true,
+            ty::Bool
+            | ty::Char
+            | ty::Int(_)
+            | ty::Uint(_)
+            | ty::Float(_)
+            | ty::Adt(_, _)
+            | ty::Foreign(_)
+            | ty::Array(_, _)
+            | ty::Pat(_, _)
+            | ty::RawPtr(_, _)
+            | ty::Ref(_, _, _)
+            | ty::FnDef(_, _)
+            | ty::FnPtr(_, _)
+            | ty::UnsafeBinder(_)
+            | ty::Closure(_, _)
+            | ty::CoroutineClosure(_, _)
+            | ty::Coroutine(_, _)
+            | ty::CoroutineWitness(_, _)
+            | ty::Never
+            | ty::Tuple(_)
+            | ty::Alias(_, _)
+            | ty::Param(_)
+            | ty::Bound(_, _)
+            | ty::Placeholder(_)
+            | ty::Infer(_)
+            | ty::Error(_)
+            | ty::Dynamic(_, _, ty::DynStar) => false,
+        }
+    }
 }
 
 pub trait Tys<I: Interner<Tys = Self>>:
diff --git a/compiler/rustc_type_ir/src/interner.rs b/compiler/rustc_type_ir/src/interner.rs
index fce93b735d7..a9e6764e218 100644
--- a/compiler/rustc_type_ir/src/interner.rs
+++ b/compiler/rustc_type_ir/src/interner.rs
@@ -255,6 +255,8 @@ pub trait Interner:
         def_id: Self::DefId,
     ) -> ty::EarlyBinder<Self, impl IntoIterator<Item = ty::Binder<Self, ty::TraitRef<Self>>>>;
 
+    fn impl_self_is_guaranteed_unsized(self, def_id: Self::DefId) -> bool;
+
     fn has_target_features(self, def_id: Self::DefId) -> bool;
 
     fn require_lang_item(self, lang_item: TraitSolverLangItem) -> Self::DefId;
diff --git a/compiler/rustc_type_ir/src/lib.rs b/compiler/rustc_type_ir/src/lib.rs
index 4e2baca2785..bdc61e956f8 100644
--- a/compiler/rustc_type_ir/src/lib.rs
+++ b/compiler/rustc_type_ir/src/lib.rs
@@ -1,12 +1,12 @@
 // tidy-alphabetical-start
 #![allow(rustc::usage_of_ty_tykind)]
 #![allow(rustc::usage_of_type_ir_inherent)]
+#![allow(rustc::usage_of_type_ir_traits)]
 #![cfg_attr(
     feature = "nightly",
     feature(associated_type_defaults, never_type, rustc_attrs, negative_impls)
 )]
 #![cfg_attr(feature = "nightly", allow(internal_features))]
-#![cfg_attr(not(bootstrap), allow(rustc::usage_of_type_ir_traits))]
 // tidy-alphabetical-end
 
 extern crate self as rustc_type_ir;
diff --git a/compiler/rustc_type_ir/src/solve/mod.rs b/compiler/rustc_type_ir/src/solve/mod.rs
index 3aec4804b27..4e9b87fdf74 100644
--- a/compiler/rustc_type_ir/src/solve/mod.rs
+++ b/compiler/rustc_type_ir/src/solve/mod.rs
@@ -83,8 +83,11 @@ pub enum GoalSource {
     /// Instantiating a higher-ranked goal and re-proving it.
     InstantiateHigherRanked,
     /// Predicate required for an alias projection to be well-formed.
-    /// This is used in two places: projecting to an opaque whose hidden type
-    /// is already registered in the opaque type storage, and for rigid projections.
+    /// This is used in three places:
+    /// 1. projecting to an opaque whose hidden type is already registered in
+    ///    the opaque type storage,
+    /// 2. for rigid projections's trait goal,
+    /// 3. for GAT where clauses.
     AliasWellFormed,
     /// In case normalizing aliases in nested goals cycles, eagerly normalizing these
     /// aliases in the context of the parent may incorrectly change the cycle kind.