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-rw-r--r--compiler/rustc/Cargo.toml5
-rw-r--r--compiler/rustc/build.rs16
-rw-r--r--compiler/rustc_ast_lowering/src/expr.rs29
-rw-r--r--compiler/rustc_ast_lowering/src/lib.rs15
-rw-r--r--compiler/rustc_ast_passes/src/ast_validation.rs42
-rw-r--r--compiler/rustc_ast_passes/src/errors.rs4
-rw-r--r--compiler/rustc_attr_parsing/messages.ftl4
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/codegen_attrs.rs1
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/crate_level.rs148
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/prelude.rs5
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/repr.rs27
-rw-r--r--compiler/rustc_attr_parsing/src/context.rs25
-rw-r--r--compiler/rustc_attr_parsing/src/session_diagnostics.rs10
-rw-r--r--compiler/rustc_borrowck/src/region_infer/mod.rs2
-rw-r--r--compiler/rustc_borrowck/src/region_infer/opaque_types/mod.rs2
-rw-r--r--compiler/rustc_borrowck/src/type_check/mod.rs8
-rw-r--r--compiler/rustc_builtin_macros/src/format.rs27
-rw-r--r--compiler/rustc_codegen_gcc/src/back/lto.rs11
-rw-r--r--compiler/rustc_codegen_gcc/src/consts.rs2
-rw-r--r--compiler/rustc_codegen_gcc/src/lib.rs7
-rw-r--r--compiler/rustc_codegen_gcc/src/type_of.rs2
-rw-r--r--compiler/rustc_codegen_llvm/src/back/lto.rs27
-rw-r--r--compiler/rustc_codegen_llvm/src/back/write.rs2
-rw-r--r--compiler/rustc_codegen_llvm/src/consts.rs2
-rw-r--r--compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs11
-rw-r--r--compiler/rustc_codegen_llvm/src/lib.rs7
-rw-r--r--compiler/rustc_codegen_llvm/src/llvm/ffi.rs1
-rw-r--r--compiler/rustc_codegen_llvm/src/type_of.rs9
-rw-r--r--compiler/rustc_codegen_ssa/Cargo.toml2
-rw-r--r--compiler/rustc_codegen_ssa/src/back/write.rs49
-rw-r--r--compiler/rustc_codegen_ssa/src/traits/write.rs6
-rw-r--r--compiler/rustc_const_eval/src/interpret/eval_context.rs2
-rw-r--r--compiler/rustc_const_eval/src/interpret/memory.rs7
-rw-r--r--compiler/rustc_const_eval/src/interpret/traits.rs7
-rw-r--r--compiler/rustc_const_eval/src/interpret/util.rs11
-rw-r--r--compiler/rustc_const_eval/src/util/type_name.rs5
-rw-r--r--compiler/rustc_driver/Cargo.toml5
-rw-r--r--compiler/rustc_driver/build.rs21
-rw-r--r--compiler/rustc_expand/src/base.rs3
-rw-r--r--compiler/rustc_expand/src/errors.rs2
-rw-r--r--compiler/rustc_expand/src/expand.rs4
-rw-r--r--compiler/rustc_feature/src/builtin_attrs.rs1
-rw-r--r--compiler/rustc_feature/src/unstable.rs2
-rw-r--r--compiler/rustc_hir/src/attrs/data_structures.rs13
-rw-r--r--compiler/rustc_hir/src/attrs/encode_cross_crate.rs4
-rw-r--r--compiler/rustc_hir/src/attrs/pretty_printing.rs4
-rw-r--r--compiler/rustc_hir/src/hir.rs15
-rw-r--r--compiler/rustc_hir/src/lang_items.rs1
-rw-r--r--compiler/rustc_hir/src/lib.rs1
-rw-r--r--compiler/rustc_hir/src/limit.rs63
-rw-r--r--compiler/rustc_hir_analysis/src/autoderef.rs2
-rw-r--r--compiler/rustc_hir_analysis/src/check/mod.rs73
-rw-r--r--compiler/rustc_hir_analysis/src/check/wfcheck.rs2
-rw-r--r--compiler/rustc_hir_analysis/src/coherence/orphan.rs2
-rw-r--r--compiler/rustc_hir_analysis/src/collect/predicates_of.rs6
-rw-r--r--compiler/rustc_hir_analysis/src/errors.rs3
-rw-r--r--compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs144
-rw-r--r--compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs2
-rw-r--r--compiler/rustc_hir_typeck/src/cast.rs4
-rw-r--r--compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs7
-rw-r--r--compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs2
-rw-r--r--compiler/rustc_hir_typeck/src/inline_asm.rs2
-rw-r--r--compiler/rustc_hir_typeck/src/method/probe.rs8
-rw-r--r--compiler/rustc_hir_typeck/src/writeback.rs6
-rw-r--r--compiler/rustc_index/src/idx.rs15
-rw-r--r--compiler/rustc_index/src/interval.rs54
-rw-r--r--compiler/rustc_infer/src/infer/canonical/canonicalizer.rs34
-rw-r--r--compiler/rustc_infer/src/infer/canonical/mod.rs56
-rw-r--r--compiler/rustc_infer/src/infer/canonical/query_response.rs77
-rw-r--r--compiler/rustc_infer/src/infer/context.rs8
-rw-r--r--compiler/rustc_infer/src/infer/mod.rs9
-rw-r--r--compiler/rustc_infer/src/infer/outlives/test_type_match.rs2
-rw-r--r--compiler/rustc_infer/src/infer/outlives/verify.rs4
-rw-r--r--compiler/rustc_infer/src/infer/relate/generalize.rs47
-rw-r--r--compiler/rustc_infer/src/infer/snapshot/undo_log.rs4
-rw-r--r--compiler/rustc_infer/src/infer/type_variable.rs116
-rw-r--r--compiler/rustc_interface/messages.ftl4
-rw-r--r--compiler/rustc_interface/src/errors.rs10
-rw-r--r--compiler/rustc_interface/src/limits.rs88
-rw-r--r--compiler/rustc_interface/src/passes.rs54
-rw-r--r--compiler/rustc_lint/src/deref_into_dyn_supertrait.rs2
-rw-r--r--compiler/rustc_lint/src/for_loops_over_fallibles.rs2
-rw-r--r--compiler/rustc_lint/src/multiple_supertrait_upcastable.rs3
-rw-r--r--compiler/rustc_lint/src/types.rs2
-rw-r--r--compiler/rustc_llvm/Cargo.toml2
-rw-r--r--compiler/rustc_llvm/build.rs5
-rw-r--r--compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp11
-rw-r--r--compiler/rustc_log/Cargo.toml5
-rw-r--r--compiler/rustc_middle/src/error.rs2
-rw-r--r--compiler/rustc_middle/src/infer/canonical.rs1
-rw-r--r--compiler/rustc_middle/src/mir/interpret/allocation.rs5
-rw-r--r--compiler/rustc_middle/src/mir/interpret/allocation/provenance_map.rs16
-rw-r--r--compiler/rustc_middle/src/mir/interpret/mod.rs11
-rw-r--r--compiler/rustc_middle/src/mir/interpret/queries.rs12
-rw-r--r--compiler/rustc_middle/src/mir/pretty.rs12
-rw-r--r--compiler/rustc_middle/src/mir/visit.rs18
-rw-r--r--compiler/rustc_middle/src/query/mod.rs15
-rw-r--r--compiler/rustc_middle/src/ty/abstract_const.rs2
-rw-r--r--compiler/rustc_middle/src/ty/context.rs31
-rw-r--r--compiler/rustc_middle/src/ty/erase_regions.rs28
-rw-r--r--compiler/rustc_middle/src/ty/error.rs3
-rw-r--r--compiler/rustc_middle/src/ty/instance.rs4
-rw-r--r--compiler/rustc_middle/src/ty/layout.rs5
-rw-r--r--compiler/rustc_middle/src/ty/mod.rs1
-rw-r--r--compiler/rustc_middle/src/ty/normalize_erasing_regions.rs4
-rw-r--r--compiler/rustc_middle/src/ty/predicate.rs32
-rw-r--r--compiler/rustc_middle/src/ty/print/mod.rs12
-rw-r--r--compiler/rustc_middle/src/ty/print/pretty.rs6
-rw-r--r--compiler/rustc_middle/src/ty/util.rs13
-rw-r--r--compiler/rustc_middle/src/ty/visit.rs39
-rw-r--r--compiler/rustc_middle/src/ty/vtable.rs2
-rw-r--r--compiler/rustc_mir_build/src/check_tail_calls.rs6
-rw-r--r--compiler/rustc_mir_build/src/thir/cx/expr.rs13
-rw-r--r--compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs8
-rw-r--r--compiler/rustc_mir_dataflow/src/impls/liveness.rs37
-rw-r--r--compiler/rustc_mir_dataflow/src/impls/mod.rs3
-rw-r--r--compiler/rustc_mir_dataflow/src/points.rs68
-rw-r--r--compiler/rustc_mir_dataflow/src/value_analysis.rs11
-rw-r--r--compiler/rustc_mir_transform/src/add_subtyping_projections.rs4
-rw-r--r--compiler/rustc_mir_transform/src/cross_crate_inline.rs11
-rw-r--r--compiler/rustc_mir_transform/src/dest_prop.rs794
-rw-r--r--compiler/rustc_mir_transform/src/gvn.rs5
-rw-r--r--compiler/rustc_mir_transform/src/inline/cycle.rs2
-rw-r--r--compiler/rustc_mir_transform/src/promote_consts.rs3
-rw-r--r--compiler/rustc_mir_transform/src/ssa.rs4
-rw-r--r--compiler/rustc_monomorphize/src/collector.rs4
-rw-r--r--compiler/rustc_monomorphize/src/mono_checks/move_check.rs2
-rw-r--r--compiler/rustc_next_trait_solver/src/canonicalizer.rs50
-rw-r--r--compiler/rustc_next_trait_solver/src/coherence.rs16
-rw-r--r--compiler/rustc_next_trait_solver/src/delegate.rs6
-rw-r--r--compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs2
-rw-r--r--compiler/rustc_next_trait_solver/src/solve/assembly/structural_traits.rs6
-rw-r--r--compiler/rustc_next_trait_solver/src/solve/effect_goals.rs10
-rw-r--r--compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs70
-rw-r--r--compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs6
-rw-r--r--compiler/rustc_next_trait_solver/src/solve/mod.rs19
-rw-r--r--compiler/rustc_next_trait_solver/src/solve/normalizes_to/mod.rs21
-rw-r--r--compiler/rustc_next_trait_solver/src/solve/trait_goals.rs6
-rw-r--r--compiler/rustc_parse/messages.ftl3
-rw-r--r--compiler/rustc_parse/src/errors.rs4
-rw-r--r--compiler/rustc_parse/src/parser/expr.rs26
-rw-r--r--compiler/rustc_parse/src/parser/mod.rs5
-rw-r--r--compiler/rustc_passes/messages.ftl4
-rw-r--r--compiler/rustc_passes/src/check_attr.rs12
-rw-r--r--compiler/rustc_passes/src/errors.rs9
-rw-r--r--compiler/rustc_query_impl/Cargo.toml1
-rw-r--r--compiler/rustc_query_impl/src/plumbing.rs2
-rw-r--r--compiler/rustc_query_system/src/error.rs2
-rw-r--r--compiler/rustc_session/src/session.rs62
-rw-r--r--compiler/rustc_span/src/symbol.rs17
-rw-r--r--compiler/rustc_symbol_mangling/src/legacy.rs7
-rw-r--r--compiler/rustc_symbol_mangling/src/test.rs2
-rw-r--r--compiler/rustc_symbol_mangling/src/v0.rs7
-rw-r--r--compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs5
-rw-r--r--compiler/rustc_trait_selection/src/error_reporting/infer/need_type_info.rs3
-rw-r--r--compiler/rustc_trait_selection/src/error_reporting/infer/note_and_explain.rs6
-rw-r--r--compiler/rustc_trait_selection/src/error_reporting/infer/sub_relations.rs81
-rw-r--r--compiler/rustc_trait_selection/src/error_reporting/mod.rs4
-rw-r--r--compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs7
-rw-r--r--compiler/rustc_trait_selection/src/error_reporting/traits/mod.rs4
-rw-r--r--compiler/rustc_trait_selection/src/error_reporting/traits/overflow.rs4
-rw-r--r--compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs6
-rw-r--r--compiler/rustc_trait_selection/src/infer.rs5
-rw-r--r--compiler/rustc_trait_selection/src/solve/delegate.rs20
-rw-r--r--compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs2
-rw-r--r--compiler/rustc_trait_selection/src/traits/mod.rs8
-rw-r--r--compiler/rustc_trait_selection/src/traits/query/dropck_outlives.rs4
-rw-r--r--compiler/rustc_traits/src/codegen.rs2
-rw-r--r--compiler/rustc_traits/src/evaluate_obligation.rs2
-rw-r--r--compiler/rustc_traits/src/normalize_erasing_regions.rs2
-rw-r--r--compiler/rustc_transmute/src/layout/mod.rs2
-rw-r--r--compiler/rustc_transmute/src/layout/tree.rs37
-rw-r--r--compiler/rustc_ty_utils/src/instance.rs8
-rw-r--r--compiler/rustc_ty_utils/src/needs_drop.rs2
-rw-r--r--compiler/rustc_type_ir/Cargo.toml1
-rw-r--r--compiler/rustc_type_ir/src/canonical.rs109
-rw-r--r--compiler/rustc_type_ir/src/fast_reject.rs14
-rw-r--r--compiler/rustc_type_ir/src/infer_ctxt.rs2
-rw-r--r--compiler/rustc_type_ir/src/inherent.rs30
-rw-r--r--compiler/rustc_type_ir/src/interner.rs70
-rw-r--r--compiler/rustc_type_ir/src/lang_items.rs5
-rw-r--r--compiler/rustc_type_ir/src/relate.rs4
-rw-r--r--compiler/rustc_type_ir/src/search_graph/mod.rs4
-rw-r--r--compiler/rustc_type_ir/src/search_graph/stack.rs4
-rw-r--r--compiler/rustc_type_ir/src/solve/mod.rs2
-rw-r--r--compiler/rustc_type_ir/src/ty_kind.rs12
-rw-r--r--compiler/rustc_type_ir/src/ty_kind/closure.rs4
-rw-r--r--compiler/rustc_type_ir/src/visit.rs4
-rw-r--r--compiler/rustc_windows_rc/Cargo.toml11
-rw-r--r--compiler/rustc_windows_rc/rustc.rc.in40
-rw-r--r--compiler/rustc_windows_rc/src/lib.rs158
191 files changed, 2127 insertions, 1741 deletions
diff --git a/compiler/rustc/Cargo.toml b/compiler/rustc/Cargo.toml
index 3ca75235446..e3214d1ab9c 100644
--- a/compiler/rustc/Cargo.toml
+++ b/compiler/rustc/Cargo.toml
@@ -33,3 +33,8 @@ llvm = ['rustc_driver_impl/llvm']
 max_level_info = ['rustc_driver_impl/max_level_info']
 rustc_randomized_layouts = ['rustc_driver_impl/rustc_randomized_layouts']
 # tidy-alphabetical-end
+
+[build-dependencies]
+# tidy-alphabetical-start
+rustc_windows_rc = { path = "../rustc_windows_rc" }
+# tidy-alphabetical-end
diff --git a/compiler/rustc/build.rs b/compiler/rustc/build.rs
index 8b7d28d2b8a..9b5def53e3c 100644
--- a/compiler/rustc/build.rs
+++ b/compiler/rustc/build.rs
@@ -1,4 +1,6 @@
-use std::env;
+use std::{env, path};
+
+use rustc_windows_rc::{VersionInfoFileType, compile_windows_resource_file};
 
 fn main() {
     let target_os = env::var("CARGO_CFG_TARGET_OS");
@@ -13,6 +15,18 @@ fn main() {
 
 // Add a manifest file to rustc.exe.
 fn set_windows_exe_options() {
+    set_windows_resource();
+    set_windows_manifest();
+}
+
+fn set_windows_resource() {
+    let stem = path::PathBuf::from("rustc_main_resource");
+    let file_description = "rustc";
+    let res_file = compile_windows_resource_file(&stem, file_description, VersionInfoFileType::App);
+    println!("cargo:rustc-link-arg={}", res_file.display());
+}
+
+fn set_windows_manifest() {
     static WINDOWS_MANIFEST_FILE: &str = "Windows Manifest.xml";
 
     let mut manifest = env::current_dir().unwrap();
diff --git a/compiler/rustc_ast_lowering/src/expr.rs b/compiler/rustc_ast_lowering/src/expr.rs
index 3674814b796..bb6b25baf01 100644
--- a/compiler/rustc_ast_lowering/src/expr.rs
+++ b/compiler/rustc_ast_lowering/src/expr.rs
@@ -1536,7 +1536,13 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     hir::LangItem::Range
                 }
             }
-            (None, Some(..), Closed) => hir::LangItem::RangeToInclusive,
+            (None, Some(..), Closed) => {
+                if self.tcx.features().new_range() {
+                    hir::LangItem::RangeToInclusiveCopy
+                } else {
+                    hir::LangItem::RangeToInclusive
+                }
+            }
             (Some(e1), Some(e2), Closed) => {
                 if self.tcx.features().new_range() {
                     hir::LangItem::RangeInclusiveCopy
@@ -1560,13 +1566,26 @@ impl<'hir> LoweringContext<'_, 'hir> {
         };
 
         let fields = self.arena.alloc_from_iter(
-            e1.iter().map(|e| (sym::start, e)).chain(e2.iter().map(|e| (sym::end, e))).map(
-                |(s, e)| {
+            e1.iter()
+                .map(|e| (sym::start, e))
+                .chain(e2.iter().map(|e| {
+                    (
+                        if matches!(
+                            lang_item,
+                            hir::LangItem::RangeInclusiveCopy | hir::LangItem::RangeToInclusiveCopy
+                        ) {
+                            sym::last
+                        } else {
+                            sym::end
+                        },
+                        e,
+                    )
+                }))
+                .map(|(s, e)| {
                     let expr = self.lower_expr(e);
                     let ident = Ident::new(s, self.lower_span(e.span));
                     self.expr_field(ident, expr, e.span)
-                },
-            ),
+                }),
         );
 
         hir::ExprKind::Struct(
diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index 72f20a95ff0..4e2243e8787 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -2101,17 +2101,14 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                 {
                     return;
                 }
-                if self.tcx.features().more_maybe_bounds() {
-                    return;
-                }
             }
             RelaxedBoundPolicy::Forbidden(reason) => {
-                if self.tcx.features().more_maybe_bounds() {
-                    return;
-                }
-
                 match reason {
                     RelaxedBoundForbiddenReason::TraitObjectTy => {
+                        if self.tcx.features().more_maybe_bounds() {
+                            return;
+                        }
+
                         self.dcx().span_err(
                             span,
                             "relaxed bounds are not permitted in trait object types",
@@ -2119,6 +2116,10 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                         return;
                     }
                     RelaxedBoundForbiddenReason::SuperTrait => {
+                        if self.tcx.features().more_maybe_bounds() {
+                            return;
+                        }
+
                         let mut diag = self.dcx().struct_span_err(
                             span,
                             "relaxed bounds are not permitted in supertrait bounds",
diff --git a/compiler/rustc_ast_passes/src/ast_validation.rs b/compiler/rustc_ast_passes/src/ast_validation.rs
index 6133cc3548b..538918a890d 100644
--- a/compiler/rustc_ast_passes/src/ast_validation.rs
+++ b/compiler/rustc_ast_passes/src/ast_validation.rs
@@ -665,46 +665,42 @@ impl<'a> AstValidator<'a> {
     /// - Non-const
     /// - Either foreign, or free and `unsafe extern "C"` semantically
     fn check_c_variadic_type(&self, fk: FnKind<'a>) {
-        let variadic_spans: Vec<_> = fk
-            .decl()
-            .inputs
-            .iter()
-            .filter(|arg| matches!(arg.ty.kind, TyKind::CVarArgs))
-            .map(|arg| arg.span)
-            .collect();
+        // `...` is already rejected when it is not the final parameter.
+        let variadic_param = match fk.decl().inputs.last() {
+            Some(param) if matches!(param.ty.kind, TyKind::CVarArgs) => param,
+            _ => return,
+        };
 
-        if variadic_spans.is_empty() {
-            return;
-        }
+        let FnKind::Fn(fn_ctxt, _, Fn { sig, .. }) = fk else {
+            // Unreachable because the parser already rejects `...` in closures.
+            unreachable!("C variable argument list cannot be used in closures")
+        };
 
-        if let Some(header) = fk.header()
-            && let Const::Yes(const_span) = header.constness
-        {
-            let mut spans = variadic_spans.clone();
-            spans.push(const_span);
+        // C-variadics are not yet implemented in const evaluation.
+        if let Const::Yes(const_span) = sig.header.constness {
             self.dcx().emit_err(errors::ConstAndCVariadic {
-                spans,
+                spans: vec![const_span, variadic_param.span],
                 const_span,
-                variadic_spans: variadic_spans.clone(),
+                variadic_span: variadic_param.span,
             });
         }
 
-        match (fk.ctxt(), fk.header()) {
-            (Some(FnCtxt::Foreign), _) => return,
-            (Some(FnCtxt::Free), Some(header)) => match header.ext {
+        match fn_ctxt {
+            FnCtxt::Foreign => return,
+            FnCtxt::Free => match sig.header.ext {
                 Extern::Explicit(StrLit { symbol_unescaped: sym::C, .. }, _)
                 | Extern::Explicit(StrLit { symbol_unescaped: sym::C_dash_unwind, .. }, _)
                 | Extern::Implicit(_)
-                    if matches!(header.safety, Safety::Unsafe(_)) =>
+                    if matches!(sig.header.safety, Safety::Unsafe(_)) =>
                 {
                     return;
                 }
                 _ => {}
             },
-            _ => {}
+            FnCtxt::Assoc(_) => {}
         };
 
-        self.dcx().emit_err(errors::BadCVariadic { span: variadic_spans });
+        self.dcx().emit_err(errors::BadCVariadic { span: variadic_param.span });
     }
 
     fn check_item_named(&self, ident: Ident, kind: &str) {
diff --git a/compiler/rustc_ast_passes/src/errors.rs b/compiler/rustc_ast_passes/src/errors.rs
index ae8f056cb4e..476ed27a10e 100644
--- a/compiler/rustc_ast_passes/src/errors.rs
+++ b/compiler/rustc_ast_passes/src/errors.rs
@@ -322,7 +322,7 @@ pub(crate) struct ExternItemAscii {
 #[diag(ast_passes_bad_c_variadic)]
 pub(crate) struct BadCVariadic {
     #[primary_span]
-    pub span: Vec<Span>,
+    pub span: Span,
 }
 
 #[derive(Diagnostic)]
@@ -656,7 +656,7 @@ pub(crate) struct ConstAndCVariadic {
     #[label(ast_passes_const)]
     pub const_span: Span,
     #[label(ast_passes_variadic)]
-    pub variadic_spans: Vec<Span>,
+    pub variadic_span: Span,
 }
 
 #[derive(Diagnostic)]
diff --git a/compiler/rustc_attr_parsing/messages.ftl b/compiler/rustc_attr_parsing/messages.ftl
index 7fa1293463c..839a5d23c3b 100644
--- a/compiler/rustc_attr_parsing/messages.ftl
+++ b/compiler/rustc_attr_parsing/messages.ftl
@@ -247,3 +247,7 @@ attr_parsing_raw_dylib_only_windows =
 
 attr_parsing_whole_archive_needs_static =
     linking modifier `whole-archive` is only compatible with `static` linking kind
+
+attr_parsing_limit_invalid =
+    `limit` must be a non-negative integer
+    .label = {$error_str}
diff --git a/compiler/rustc_attr_parsing/src/attributes/codegen_attrs.rs b/compiler/rustc_attr_parsing/src/attributes/codegen_attrs.rs
index ffdacff7152..d5d51f2e79a 100644
--- a/compiler/rustc_attr_parsing/src/attributes/codegen_attrs.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/codegen_attrs.rs
@@ -218,6 +218,7 @@ impl<S: Stage> AttributeParser<S> for NakedParser {
             sym::rustc_std_internal_symbol,
             // FIXME(#82232, #143834): temporarily renamed to mitigate `#[align]` nameres ambiguity
             sym::rustc_align,
+            sym::rustc_align_static,
             // obviously compatible with self
             sym::naked,
             // documentation
diff --git a/compiler/rustc_attr_parsing/src/attributes/crate_level.rs b/compiler/rustc_attr_parsing/src/attributes/crate_level.rs
index 2fed09b85e8..d23a7ae72f8 100644
--- a/compiler/rustc_attr_parsing/src/attributes/crate_level.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/crate_level.rs
@@ -1,6 +1,40 @@
-use rustc_feature::AttributeType;
+use std::num::IntErrorKind;
+
+use rustc_hir::limit::Limit;
 
 use super::prelude::*;
+use crate::session_diagnostics::LimitInvalid;
+
+impl<S: Stage> AcceptContext<'_, '_, S> {
+    fn parse_limit_int(&self, nv: &NameValueParser) -> Option<Limit> {
+        let Some(limit) = nv.value_as_str() else {
+            self.expected_string_literal(nv.value_span, Some(nv.value_as_lit()));
+            return None;
+        };
+
+        let error_str = match limit.as_str().parse() {
+            Ok(i) => return Some(Limit::new(i)),
+            Err(e) => match e.kind() {
+                IntErrorKind::PosOverflow => "`limit` is too large",
+                IntErrorKind::Empty => "`limit` must be a non-negative integer",
+                IntErrorKind::InvalidDigit => "not a valid integer",
+                IntErrorKind::NegOverflow => {
+                    panic!(
+                        "`limit` should never negatively overflow since we're parsing into a usize and we'd get Empty instead"
+                    )
+                }
+                IntErrorKind::Zero => {
+                    panic!("zero is a valid `limit` so should have returned Ok() when parsing")
+                }
+                kind => panic!("unimplemented IntErrorKind variant: {:?}", kind),
+            },
+        };
+
+        self.emit_err(LimitInvalid { span: self.attr_span, value_span: nv.value_span, error_str });
+
+        None
+    }
+}
 
 pub(crate) struct CrateNameParser;
 
@@ -11,8 +45,8 @@ impl<S: Stage> SingleAttributeParser<S> for CrateNameParser {
     const TEMPLATE: AttributeTemplate = template!(NameValueStr: "name");
     const TYPE: AttributeType = AttributeType::CrateLevel;
 
-    // FIXME: crate name is allowed on all targets and ignored,
-    //        even though it should only be valid on crates of course
+    // because it's a crate-level attribute, we already warn about it.
+    // Putting target limitations here would give duplicate warnings
     const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(ALL_TARGETS);
 
     fn convert(cx: &mut AcceptContext<'_, '_, S>, args: &ArgParser<'_>) -> Option<AttributeKind> {
@@ -34,3 +68,111 @@ impl<S: Stage> SingleAttributeParser<S> for CrateNameParser {
         })
     }
 }
+
+pub(crate) struct RecursionLimitParser;
+
+impl<S: Stage> SingleAttributeParser<S> for RecursionLimitParser {
+    const PATH: &[Symbol] = &[sym::recursion_limit];
+    const ATTRIBUTE_ORDER: AttributeOrder = AttributeOrder::KeepOutermost;
+    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::WarnButFutureError;
+    const TEMPLATE: AttributeTemplate = template!(NameValueStr: "N", "https://doc.rust-lang.org/reference/attributes/limits.html#the-recursion_limit-attribute");
+    const TYPE: AttributeType = AttributeType::CrateLevel;
+
+    // because it's a crate-level attribute, we already warn about it.
+    // Putting target limitations here would give duplicate warnings
+    const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(ALL_TARGETS);
+
+    fn convert(cx: &mut AcceptContext<'_, '_, S>, args: &ArgParser<'_>) -> Option<AttributeKind> {
+        let ArgParser::NameValue(nv) = args else {
+            cx.expected_name_value(cx.attr_span, None);
+            return None;
+        };
+
+        Some(AttributeKind::RecursionLimit {
+            limit: cx.parse_limit_int(nv)?,
+            attr_span: cx.attr_span,
+            limit_span: nv.value_span,
+        })
+    }
+}
+
+pub(crate) struct MoveSizeLimitParser;
+
+impl<S: Stage> SingleAttributeParser<S> for MoveSizeLimitParser {
+    const PATH: &[Symbol] = &[sym::move_size_limit];
+    const ATTRIBUTE_ORDER: AttributeOrder = AttributeOrder::KeepOutermost;
+    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Error;
+    const TEMPLATE: AttributeTemplate = template!(NameValueStr: "N");
+    const TYPE: AttributeType = AttributeType::CrateLevel;
+
+    // because it's a crate-level attribute, we already warn about it.
+    // Putting target limitations here would give duplicate warnings
+    const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(ALL_TARGETS);
+
+    fn convert(cx: &mut AcceptContext<'_, '_, S>, args: &ArgParser<'_>) -> Option<AttributeKind> {
+        let ArgParser::NameValue(nv) = args else {
+            cx.expected_name_value(cx.attr_span, None);
+            return None;
+        };
+
+        Some(AttributeKind::MoveSizeLimit {
+            limit: cx.parse_limit_int(nv)?,
+            attr_span: cx.attr_span,
+            limit_span: nv.value_span,
+        })
+    }
+}
+
+pub(crate) struct TypeLengthLimitParser;
+
+impl<S: Stage> SingleAttributeParser<S> for TypeLengthLimitParser {
+    const PATH: &[Symbol] = &[sym::type_length_limit];
+    const ATTRIBUTE_ORDER: AttributeOrder = AttributeOrder::KeepOutermost;
+    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::WarnButFutureError;
+    const TEMPLATE: AttributeTemplate = template!(NameValueStr: "N");
+    const TYPE: AttributeType = AttributeType::CrateLevel;
+
+    // because it's a crate-level attribute, we already warn about it.
+    // Putting target limitations here would give duplicate warnings
+    const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(ALL_TARGETS);
+
+    fn convert(cx: &mut AcceptContext<'_, '_, S>, args: &ArgParser<'_>) -> Option<AttributeKind> {
+        let ArgParser::NameValue(nv) = args else {
+            cx.expected_name_value(cx.attr_span, None);
+            return None;
+        };
+
+        Some(AttributeKind::TypeLengthLimit {
+            limit: cx.parse_limit_int(nv)?,
+            attr_span: cx.attr_span,
+            limit_span: nv.value_span,
+        })
+    }
+}
+
+pub(crate) struct PatternComplexityLimitParser;
+
+impl<S: Stage> SingleAttributeParser<S> for PatternComplexityLimitParser {
+    const PATH: &[Symbol] = &[sym::pattern_complexity_limit];
+    const ATTRIBUTE_ORDER: AttributeOrder = AttributeOrder::KeepOutermost;
+    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Error;
+    const TEMPLATE: AttributeTemplate = template!(NameValueStr: "N");
+    const TYPE: AttributeType = AttributeType::CrateLevel;
+
+    // because it's a crate-level attribute, we already warn about it.
+    // Putting target limitations here would give duplicate warnings
+    const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(ALL_TARGETS);
+
+    fn convert(cx: &mut AcceptContext<'_, '_, S>, args: &ArgParser<'_>) -> Option<AttributeKind> {
+        let ArgParser::NameValue(nv) = args else {
+            cx.expected_name_value(cx.attr_span, None);
+            return None;
+        };
+
+        Some(AttributeKind::PatternComplexityLimit {
+            limit: cx.parse_limit_int(nv)?,
+            attr_span: cx.attr_span,
+            limit_span: nv.value_span,
+        })
+    }
+}
diff --git a/compiler/rustc_attr_parsing/src/attributes/prelude.rs b/compiler/rustc_attr_parsing/src/attributes/prelude.rs
index 6aef7e7a67b..8f040ffb9d4 100644
--- a/compiler/rustc_attr_parsing/src/attributes/prelude.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/prelude.rs
@@ -1,8 +1,7 @@
-// templates
-#[doc(hidden)]
-pub(super) use rustc_feature::{AttributeTemplate, template};
 // data structures
 #[doc(hidden)]
+pub(super) use rustc_feature::{AttributeTemplate, AttributeType, template};
+#[doc(hidden)]
 pub(super) use rustc_hir::attrs::AttributeKind;
 #[doc(hidden)]
 pub(super) use rustc_hir::lints::AttributeLintKind;
diff --git a/compiler/rustc_attr_parsing/src/attributes/repr.rs b/compiler/rustc_attr_parsing/src/attributes/repr.rs
index 23aabd15597..0330e2515c7 100644
--- a/compiler/rustc_attr_parsing/src/attributes/repr.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/repr.rs
@@ -331,3 +331,30 @@ impl<S: Stage> AttributeParser<S> for AlignParser {
         Some(AttributeKind::Align { align, span })
     }
 }
+
+#[derive(Default)]
+pub(crate) struct AlignStaticParser(AlignParser);
+
+impl AlignStaticParser {
+    const PATH: &'static [Symbol] = &[sym::rustc_align_static];
+    const TEMPLATE: AttributeTemplate = AlignParser::TEMPLATE;
+
+    fn parse<'c, S: Stage>(
+        &mut self,
+        cx: &'c mut AcceptContext<'_, '_, S>,
+        args: &'c ArgParser<'_>,
+    ) {
+        self.0.parse(cx, args)
+    }
+}
+
+impl<S: Stage> AttributeParser<S> for AlignStaticParser {
+    const ATTRIBUTES: AcceptMapping<Self, S> = &[(Self::PATH, Self::TEMPLATE, Self::parse)];
+    const ALLOWED_TARGETS: AllowedTargets =
+        AllowedTargets::AllowList(&[Allow(Target::Static), Allow(Target::ForeignStatic)]);
+
+    fn finalize(self, _cx: &FinalizeContext<'_, '_, S>) -> Option<AttributeKind> {
+        let (align, span) = self.0.0?;
+        Some(AttributeKind::Align { align, span })
+    }
+}
diff --git a/compiler/rustc_attr_parsing/src/context.rs b/compiler/rustc_attr_parsing/src/context.rs
index 7f5b810f244..d2b35090135 100644
--- a/compiler/rustc_attr_parsing/src/context.rs
+++ b/compiler/rustc_attr_parsing/src/context.rs
@@ -24,7 +24,10 @@ use crate::attributes::codegen_attrs::{
     UsedParser,
 };
 use crate::attributes::confusables::ConfusablesParser;
-use crate::attributes::crate_level::CrateNameParser;
+use crate::attributes::crate_level::{
+    CrateNameParser, MoveSizeLimitParser, PatternComplexityLimitParser, RecursionLimitParser,
+    TypeLengthLimitParser,
+};
 use crate::attributes::deprecation::DeprecationParser;
 use crate::attributes::dummy::DummyParser;
 use crate::attributes::inline::{InlineParser, RustcForceInlineParser};
@@ -47,7 +50,7 @@ use crate::attributes::proc_macro_attrs::{
     ProcMacroAttributeParser, ProcMacroDeriveParser, ProcMacroParser, RustcBuiltinMacroParser,
 };
 use crate::attributes::prototype::CustomMirParser;
-use crate::attributes::repr::{AlignParser, ReprParser};
+use crate::attributes::repr::{AlignParser, AlignStaticParser, ReprParser};
 use crate::attributes::rustc_internal::{
     RustcLayoutScalarValidRangeEnd, RustcLayoutScalarValidRangeStart,
     RustcObjectLifetimeDefaultParser,
@@ -149,6 +152,7 @@ attribute_parsers!(
     pub(crate) static ATTRIBUTE_PARSERS = [
         // tidy-alphabetical-start
         AlignParser,
+        AlignStaticParser,
         BodyStabilityParser,
         ConfusablesParser,
         ConstStabilityParser,
@@ -181,10 +185,13 @@ attribute_parsers!(
         Single<LinkOrdinalParser>,
         Single<LinkSectionParser>,
         Single<LinkageParser>,
+        Single<MoveSizeLimitParser>,
         Single<MustUseParser>,
         Single<OptimizeParser>,
         Single<PathAttributeParser>,
+        Single<PatternComplexityLimitParser>,
         Single<ProcMacroDeriveParser>,
+        Single<RecursionLimitParser>,
         Single<RustcBuiltinMacroParser>,
         Single<RustcForceInlineParser>,
         Single<RustcLayoutScalarValidRangeEnd>,
@@ -194,6 +201,7 @@ attribute_parsers!(
         Single<ShouldPanicParser>,
         Single<SkipDuringMethodDispatchParser>,
         Single<TransparencyParser>,
+        Single<TypeLengthLimitParser>,
         Single<WithoutArgs<AllowIncoherentImplParser>>,
         Single<WithoutArgs<AllowInternalUnsafeParser>>,
         Single<WithoutArgs<AsPtrParser>>,
@@ -346,7 +354,10 @@ impl<'f, 'sess: 'f, S: Stage> SharedContext<'f, 'sess, S> {
     /// must be delayed until after HIR is built. This method will take care of the details of
     /// that.
     pub(crate) fn emit_lint(&mut self, lint: AttributeLintKind, span: Span) {
-        if matches!(self.stage.should_emit(), ShouldEmit::Nothing) {
+        if !matches!(
+            self.stage.should_emit(),
+            ShouldEmit::ErrorsAndLints | ShouldEmit::EarlyFatal { also_emit_lints: true }
+        ) {
             return;
         }
         let id = self.target_id;
@@ -670,20 +681,20 @@ pub enum ShouldEmit {
     ///
     /// Only relevant when early parsing, in late parsing equivalent to `ErrorsAndLints`.
     /// Late parsing is never fatal, and instead tries to emit as many diagnostics as possible.
-    EarlyFatal,
+    EarlyFatal { also_emit_lints: bool },
     /// The operation will emit errors and lints.
     /// This is usually what you need.
     ErrorsAndLints,
     /// The operation will emit *not* errors and lints.
-    /// Use this if you are *sure* that this operation will be called at a different time with `ShouldEmit::Emit`.
+    /// Use this if you are *sure* that this operation will be called at a different time with `ShouldEmit::ErrorsAndLints`.
     Nothing,
 }
 
 impl ShouldEmit {
     pub(crate) fn emit_err(&self, diag: Diag<'_>) -> ErrorGuaranteed {
         match self {
-            ShouldEmit::EarlyFatal if diag.level() == Level::DelayedBug => diag.emit(),
-            ShouldEmit::EarlyFatal => diag.upgrade_to_fatal().emit(),
+            ShouldEmit::EarlyFatal { .. } if diag.level() == Level::DelayedBug => diag.emit(),
+            ShouldEmit::EarlyFatal { .. } => diag.upgrade_to_fatal().emit(),
             ShouldEmit::ErrorsAndLints => diag.emit(),
             ShouldEmit::Nothing => diag.delay_as_bug(),
         }
diff --git a/compiler/rustc_attr_parsing/src/session_diagnostics.rs b/compiler/rustc_attr_parsing/src/session_diagnostics.rs
index a9dee23bf6a..32ea9005a97 100644
--- a/compiler/rustc_attr_parsing/src/session_diagnostics.rs
+++ b/compiler/rustc_attr_parsing/src/session_diagnostics.rs
@@ -930,3 +930,13 @@ pub(crate) struct ImportNameTypeRaw {
     #[primary_span]
     pub span: Span,
 }
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_limit_invalid)]
+pub(crate) struct LimitInvalid<'a> {
+    #[primary_span]
+    pub span: Span,
+    #[label]
+    pub value_span: Span,
+    pub error_str: &'a str,
+}
diff --git a/compiler/rustc_borrowck/src/region_infer/mod.rs b/compiler/rustc_borrowck/src/region_infer/mod.rs
index 9990f4cb3f2..f57456949bb 100644
--- a/compiler/rustc_borrowck/src/region_infer/mod.rs
+++ b/compiler/rustc_borrowck/src/region_infer/mod.rs
@@ -615,7 +615,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             }
 
             // Type-test failed. Report the error.
-            let erased_generic_kind = infcx.tcx.erase_regions(type_test.generic_kind);
+            let erased_generic_kind = infcx.tcx.erase_and_anonymize_regions(type_test.generic_kind);
 
             // Skip duplicate-ish errors.
             if deduplicate_errors.insert((
diff --git a/compiler/rustc_borrowck/src/region_infer/opaque_types/mod.rs b/compiler/rustc_borrowck/src/region_infer/opaque_types/mod.rs
index 95c5366a6c8..0af636aa734 100644
--- a/compiler/rustc_borrowck/src/region_infer/opaque_types/mod.rs
+++ b/compiler/rustc_borrowck/src/region_infer/opaque_types/mod.rs
@@ -341,7 +341,7 @@ fn compute_concrete_types_from_defining_uses<'tcx>(
         //
         // FIXME(-Znext-solver): This isn't necessary after all. We can remove this check again.
         if let Some((prev_decl_key, prev_span)) = decls_modulo_regions.insert(
-            rcx.infcx.tcx.erase_regions(opaque_type_key),
+            rcx.infcx.tcx.erase_and_anonymize_regions(opaque_type_key),
             (opaque_type_key, hidden_type.span),
         ) && let Some((arg1, arg2)) = std::iter::zip(
             prev_decl_key.iter_captured_args(infcx.tcx).map(|(_, arg)| arg),
diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs
index 02be78f90b0..8c5447fe1e9 100644
--- a/compiler/rustc_borrowck/src/type_check/mod.rs
+++ b/compiler/rustc_borrowck/src/type_check/mod.rs
@@ -1892,7 +1892,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         if is_diverging {
             // The signature in this call can reference region variables,
             // so erase them before calling a query.
-            let output_ty = self.tcx().erase_regions(sig.output());
+            let output_ty = self.tcx().erase_and_anonymize_regions(sig.output());
             if !output_ty
                 .is_privately_uninhabited(self.tcx(), self.infcx.typing_env(self.infcx.param_env))
             {
@@ -1986,7 +1986,9 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
 
             let op_arg_ty = self.normalize(op_arg_ty, term_location);
             let category = if call_source.from_hir_call() {
-                ConstraintCategory::CallArgument(Some(self.infcx.tcx.erase_regions(func_ty)))
+                ConstraintCategory::CallArgument(Some(
+                    self.infcx.tcx.erase_and_anonymize_regions(func_ty),
+                ))
             } else {
                 ConstraintCategory::Boring
             };
@@ -2120,7 +2122,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         // Erase the regions from `ty` to get a global type. The
         // `Sized` bound in no way depends on precise regions, so this
         // shouldn't affect `is_sized`.
-        let erased_ty = tcx.erase_regions(ty);
+        let erased_ty = tcx.erase_and_anonymize_regions(ty);
         // FIXME(#132279): Using `Ty::is_sized` causes us to incorrectly handle opaques here.
         if !erased_ty.is_sized(tcx, self.infcx.typing_env(self.infcx.param_env)) {
             // in current MIR construction, all non-control-flow rvalue
diff --git a/compiler/rustc_builtin_macros/src/format.rs b/compiler/rustc_builtin_macros/src/format.rs
index 6415e55e0b0..a6c8e7d29cc 100644
--- a/compiler/rustc_builtin_macros/src/format.rs
+++ b/compiler/rustc_builtin_macros/src/format.rs
@@ -565,6 +565,7 @@ fn make_format_args(
             &used,
             &args,
             &pieces,
+            &invalid_refs,
             detect_foreign_fmt,
             str_style,
             fmt_str,
@@ -645,6 +646,7 @@ fn report_missing_placeholders(
     used: &[bool],
     args: &FormatArguments,
     pieces: &[parse::Piece<'_>],
+    invalid_refs: &[(usize, Option<Span>, PositionUsedAs, FormatArgPositionKind)],
     detect_foreign_fmt: bool,
     str_style: Option<usize>,
     fmt_str: &str,
@@ -762,6 +764,31 @@ fn report_missing_placeholders(
         diag.span_label(fmt_span, "formatting specifier missing");
     }
 
+    if !found_foreign && invalid_refs.is_empty() {
+        // Show example if user didn't use any format specifiers
+        let show_example = used.iter().all(|used| !used);
+
+        if !show_example {
+            if unused.len() > 1 {
+                diag.note(format!("consider adding {} format specifiers", unused.len()));
+            }
+        } else {
+            let original_fmt_str =
+                if fmt_str.len() >= 1 { &fmt_str[..fmt_str.len() - 1] } else { "" };
+
+            let msg = if unused.len() == 1 {
+                "a format specifier".to_string()
+            } else {
+                format!("{} format specifiers", unused.len())
+            };
+
+            let sugg = format!("\"{}{}\"", original_fmt_str, "{}".repeat(unused.len()));
+            let msg = format!("format specifiers use curly braces, consider adding {msg}");
+
+            diag.span_suggestion_verbose(fmt_span, msg, sugg, Applicability::MaybeIncorrect);
+        }
+    }
+
     diag.emit();
 }
 
diff --git a/compiler/rustc_codegen_gcc/src/back/lto.rs b/compiler/rustc_codegen_gcc/src/back/lto.rs
index 9d8ce2383f2..d29bba2570f 100644
--- a/compiler/rustc_codegen_gcc/src/back/lto.rs
+++ b/compiler/rustc_codegen_gcc/src/back/lto.rs
@@ -305,12 +305,9 @@ pub(crate) fn run_thin(
     )
 }
 
-pub(crate) fn prepare_thin(
-    module: ModuleCodegen<GccContext>,
-    _emit_summary: bool,
-) -> (String, ThinBuffer) {
+pub(crate) fn prepare_thin(module: ModuleCodegen<GccContext>) -> (String, ThinBuffer) {
     let name = module.name;
-    //let buffer = ThinBuffer::new(module.module_llvm.context, true, emit_summary);
+    //let buffer = ThinBuffer::new(module.module_llvm.context, true);
     let buffer = ThinBuffer::new(&module.module_llvm.context);
     (name, buffer)
 }
@@ -650,10 +647,6 @@ impl ThinBufferMethods for ThinBuffer {
     fn data(&self) -> &[u8] {
         &[]
     }
-
-    fn thin_link_data(&self) -> &[u8] {
-        unimplemented!();
-    }
 }
 
 pub struct ThinData; //(Arc<TempDir>);
diff --git a/compiler/rustc_codegen_gcc/src/consts.rs b/compiler/rustc_codegen_gcc/src/consts.rs
index 619277eba8b..7fe8fc122b3 100644
--- a/compiler/rustc_codegen_gcc/src/consts.rs
+++ b/compiler/rustc_codegen_gcc/src/consts.rs
@@ -81,6 +81,8 @@ impl<'gcc, 'tcx> StaticCodegenMethods for CodegenCx<'gcc, 'tcx> {
         if global.to_rvalue().get_type() != val_llty {
             global.to_rvalue().set_type(val_llty);
         }
+
+        // NOTE: Alignment from attributes has already been applied to the allocation.
         set_global_alignment(self, global, alloc.align);
 
         global.global_set_initializer_rvalue(value);
diff --git a/compiler/rustc_codegen_gcc/src/lib.rs b/compiler/rustc_codegen_gcc/src/lib.rs
index 2d7df79ba95..f76f933cad4 100644
--- a/compiler/rustc_codegen_gcc/src/lib.rs
+++ b/compiler/rustc_codegen_gcc/src/lib.rs
@@ -408,11 +408,8 @@ impl WriteBackendMethods for GccCodegenBackend {
         back::write::codegen(cgcx, module, config)
     }
 
-    fn prepare_thin(
-        module: ModuleCodegen<Self::Module>,
-        emit_summary: bool,
-    ) -> (String, Self::ThinBuffer) {
-        back::lto::prepare_thin(module, emit_summary)
+    fn prepare_thin(module: ModuleCodegen<Self::Module>) -> (String, Self::ThinBuffer) {
+        back::lto::prepare_thin(module)
     }
 
     fn serialize_module(_module: ModuleCodegen<Self::Module>) -> (String, Self::ModuleBuffer) {
diff --git a/compiler/rustc_codegen_gcc/src/type_of.rs b/compiler/rustc_codegen_gcc/src/type_of.rs
index 093f902bc3d..93202483eed 100644
--- a/compiler/rustc_codegen_gcc/src/type_of.rs
+++ b/compiler/rustc_codegen_gcc/src/type_of.rs
@@ -240,7 +240,7 @@ impl<'tcx> LayoutGccExt<'tcx> for TyAndLayout<'tcx> {
 
         // Make sure lifetimes are erased, to avoid generating distinct LLVM
         // types for Rust types that only differ in the choice of lifetimes.
-        let normal_ty = cx.tcx.erase_regions(self.ty);
+        let normal_ty = cx.tcx.erase_and_anonymize_regions(self.ty);
 
         let mut defer = None;
         let ty = if self.ty != normal_ty {
diff --git a/compiler/rustc_codegen_llvm/src/back/lto.rs b/compiler/rustc_codegen_llvm/src/back/lto.rs
index ad2e722cfef..f571716d9dd 100644
--- a/compiler/rustc_codegen_llvm/src/back/lto.rs
+++ b/compiler/rustc_codegen_llvm/src/back/lto.rs
@@ -185,12 +185,9 @@ pub(crate) fn run_thin(
     thin_lto(cgcx, dcx, modules, upstream_modules, cached_modules, &symbols_below_threshold)
 }
 
-pub(crate) fn prepare_thin(
-    module: ModuleCodegen<ModuleLlvm>,
-    emit_summary: bool,
-) -> (String, ThinBuffer) {
+pub(crate) fn prepare_thin(module: ModuleCodegen<ModuleLlvm>) -> (String, ThinBuffer) {
     let name = module.name;
-    let buffer = ThinBuffer::new(module.module_llvm.llmod(), true, emit_summary);
+    let buffer = ThinBuffer::new(module.module_llvm.llmod(), true);
     (name, buffer)
 }
 
@@ -687,9 +684,9 @@ unsafe impl Send for ThinBuffer {}
 unsafe impl Sync for ThinBuffer {}
 
 impl ThinBuffer {
-    pub(crate) fn new(m: &llvm::Module, is_thin: bool, emit_summary: bool) -> ThinBuffer {
+    pub(crate) fn new(m: &llvm::Module, is_thin: bool) -> ThinBuffer {
         unsafe {
-            let buffer = llvm::LLVMRustThinLTOBufferCreate(m, is_thin, emit_summary);
+            let buffer = llvm::LLVMRustThinLTOBufferCreate(m, is_thin);
             ThinBuffer(buffer)
         }
     }
@@ -698,21 +695,21 @@ impl ThinBuffer {
         let mut ptr = NonNull::new(ptr).unwrap();
         ThinBuffer(unsafe { ptr.as_mut() })
     }
-}
 
-impl ThinBufferMethods for ThinBuffer {
-    fn data(&self) -> &[u8] {
+    pub(crate) fn thin_link_data(&self) -> &[u8] {
         unsafe {
-            let ptr = llvm::LLVMRustThinLTOBufferPtr(self.0) as *const _;
-            let len = llvm::LLVMRustThinLTOBufferLen(self.0);
+            let ptr = llvm::LLVMRustThinLTOBufferThinLinkDataPtr(self.0) as *const _;
+            let len = llvm::LLVMRustThinLTOBufferThinLinkDataLen(self.0);
             slice::from_raw_parts(ptr, len)
         }
     }
+}
 
-    fn thin_link_data(&self) -> &[u8] {
+impl ThinBufferMethods for ThinBuffer {
+    fn data(&self) -> &[u8] {
         unsafe {
-            let ptr = llvm::LLVMRustThinLTOBufferThinLinkDataPtr(self.0) as *const _;
-            let len = llvm::LLVMRustThinLTOBufferThinLinkDataLen(self.0);
+            let ptr = llvm::LLVMRustThinLTOBufferPtr(self.0) as *const _;
+            let len = llvm::LLVMRustThinLTOBufferLen(self.0);
             slice::from_raw_parts(ptr, len)
         }
     }
diff --git a/compiler/rustc_codegen_llvm/src/back/write.rs b/compiler/rustc_codegen_llvm/src/back/write.rs
index 7ea2ae6673b..423f0da4878 100644
--- a/compiler/rustc_codegen_llvm/src/back/write.rs
+++ b/compiler/rustc_codegen_llvm/src/back/write.rs
@@ -837,7 +837,7 @@ pub(crate) fn codegen(
                         "LLVM_module_codegen_make_bitcode",
                         &*module.name,
                     );
-                    ThinBuffer::new(llmod, config.emit_thin_lto, false)
+                    ThinBuffer::new(llmod, config.emit_thin_lto)
                 };
                 let data = thin.data();
                 let _timer = cgcx
diff --git a/compiler/rustc_codegen_llvm/src/consts.rs b/compiler/rustc_codegen_llvm/src/consts.rs
index 9ec7b0f80ae..dc9bb743560 100644
--- a/compiler/rustc_codegen_llvm/src/consts.rs
+++ b/compiler/rustc_codegen_llvm/src/consts.rs
@@ -452,6 +452,8 @@ impl<'ll> CodegenCx<'ll, '_> {
             self.statics_to_rauw.borrow_mut().push((g, new_g));
             new_g
         };
+
+        // NOTE: Alignment from attributes has already been applied to the allocation.
         set_global_alignment(self, g, alloc.align);
         llvm::set_initializer(g, v);
 
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs b/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
index caa3369f413..dc3a84b6a15 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
@@ -103,16 +103,17 @@ fn build_fixed_size_array_di_node<'ll, 'tcx>(
     cx: &CodegenCx<'ll, 'tcx>,
     unique_type_id: UniqueTypeId<'tcx>,
     array_type: Ty<'tcx>,
+    span: Span,
 ) -> DINodeCreationResult<'ll> {
     let ty::Array(element_type, len) = array_type.kind() else {
         bug!("build_fixed_size_array_di_node() called with non-ty::Array type `{:?}`", array_type)
     };
 
-    let element_type_di_node = type_di_node(cx, *element_type);
+    let element_type_di_node = spanned_type_di_node(cx, *element_type, span);
 
     return_if_di_node_created_in_meantime!(cx, unique_type_id);
 
-    let (size, align) = cx.size_and_align_of(array_type);
+    let (size, align) = cx.spanned_size_and_align_of(array_type, span);
 
     let upper_bound = len
         .try_to_target_usize(cx.tcx)
@@ -447,7 +448,7 @@ pub(crate) fn spanned_type_di_node<'ll, 'tcx>(
             build_basic_type_di_node(cx, t)
         }
         ty::Tuple(elements) if elements.is_empty() => build_basic_type_di_node(cx, t),
-        ty::Array(..) => build_fixed_size_array_di_node(cx, unique_type_id, t),
+        ty::Array(..) => build_fixed_size_array_di_node(cx, unique_type_id, t, span),
         ty::Slice(_) | ty::Str => build_slice_type_di_node(cx, t, unique_type_id),
         ty::Dynamic(..) => build_dyn_type_di_node(cx, t, unique_type_id),
         ty::Foreign(..) => build_foreign_type_di_node(cx, t, unique_type_id),
@@ -1435,7 +1436,7 @@ fn build_vtable_type_di_node<'ll, 'tcx>(
 
     let vtable_entries = if let Some(poly_trait_ref) = poly_trait_ref {
         let trait_ref = poly_trait_ref.with_self_ty(tcx, ty);
-        let trait_ref = tcx.erase_regions(trait_ref);
+        let trait_ref = tcx.erase_and_anonymize_regions(trait_ref);
 
         tcx.vtable_entries(trait_ref)
     } else {
@@ -1562,7 +1563,7 @@ pub(crate) fn apply_vcall_visibility_metadata<'ll, 'tcx>(
     // Unwrap potential addrspacecast
     let vtable = find_vtable_behind_cast(vtable);
     let trait_ref_self = trait_ref.with_self_ty(cx.tcx, ty);
-    let trait_ref_self = cx.tcx.erase_regions(trait_ref_self);
+    let trait_ref_self = cx.tcx.erase_and_anonymize_regions(trait_ref_self);
     let trait_def_id = trait_ref_self.def_id;
     let trait_vis = cx.tcx.visibility(trait_def_id);
 
diff --git a/compiler/rustc_codegen_llvm/src/lib.rs b/compiler/rustc_codegen_llvm/src/lib.rs
index 628cb34fd9e..6fb23d09843 100644
--- a/compiler/rustc_codegen_llvm/src/lib.rs
+++ b/compiler/rustc_codegen_llvm/src/lib.rs
@@ -211,11 +211,8 @@ impl WriteBackendMethods for LlvmCodegenBackend {
     ) -> CompiledModule {
         back::write::codegen(cgcx, module, config)
     }
-    fn prepare_thin(
-        module: ModuleCodegen<Self::Module>,
-        emit_summary: bool,
-    ) -> (String, Self::ThinBuffer) {
-        back::lto::prepare_thin(module, emit_summary)
+    fn prepare_thin(module: ModuleCodegen<Self::Module>) -> (String, Self::ThinBuffer) {
+        back::lto::prepare_thin(module)
     }
     fn serialize_module(module: ModuleCodegen<Self::Module>) -> (String, Self::ModuleBuffer) {
         (module.name, back::lto::ModuleBuffer::new(module.module_llvm.llmod()))
diff --git a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
index b66fc157b3c..0679f55ab7f 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
@@ -2602,7 +2602,6 @@ unsafe extern "C" {
     pub(crate) fn LLVMRustThinLTOBufferCreate(
         M: &Module,
         is_thin: bool,
-        emit_summary: bool,
     ) -> &'static mut ThinLTOBuffer;
     pub(crate) fn LLVMRustThinLTOBufferFree(M: &'static mut ThinLTOBuffer);
     pub(crate) fn LLVMRustThinLTOBufferPtr(M: &ThinLTOBuffer) -> *const c_char;
diff --git a/compiler/rustc_codegen_llvm/src/type_of.rs b/compiler/rustc_codegen_llvm/src/type_of.rs
index 4e7096da502..84998b5499b 100644
--- a/compiler/rustc_codegen_llvm/src/type_of.rs
+++ b/compiler/rustc_codegen_llvm/src/type_of.rs
@@ -7,6 +7,7 @@ use rustc_middle::bug;
 use rustc_middle::ty::layout::{LayoutOf, TyAndLayout};
 use rustc_middle::ty::print::{with_no_trimmed_paths, with_no_visible_paths};
 use rustc_middle::ty::{self, CoroutineArgsExt, Ty, TypeVisitableExt};
+use rustc_span::{DUMMY_SP, Span};
 use tracing::debug;
 
 use crate::common::*;
@@ -149,7 +150,11 @@ impl<'a, 'tcx> CodegenCx<'a, 'tcx> {
     }
 
     pub(crate) fn size_and_align_of(&self, ty: Ty<'tcx>) -> (Size, Align) {
-        let layout = self.layout_of(ty);
+        self.spanned_size_and_align_of(ty, DUMMY_SP)
+    }
+
+    pub(crate) fn spanned_size_and_align_of(&self, ty: Ty<'tcx>, span: Span) -> (Size, Align) {
+        let layout = self.spanned_layout_of(ty, span);
         (layout.size, layout.align.abi)
     }
 }
@@ -226,7 +231,7 @@ impl<'tcx> LayoutLlvmExt<'tcx> for TyAndLayout<'tcx> {
 
         // Make sure lifetimes are erased, to avoid generating distinct LLVM
         // types for Rust types that only differ in the choice of lifetimes.
-        let normal_ty = cx.tcx.erase_regions(self.ty);
+        let normal_ty = cx.tcx.erase_and_anonymize_regions(self.ty);
 
         let mut defer = None;
         let llty = if self.ty != normal_ty {
diff --git a/compiler/rustc_codegen_ssa/Cargo.toml b/compiler/rustc_codegen_ssa/Cargo.toml
index 2dfbc581643..5462163f4ff 100644
--- a/compiler/rustc_codegen_ssa/Cargo.toml
+++ b/compiler/rustc_codegen_ssa/Cargo.toml
@@ -9,7 +9,7 @@ ar_archive_writer = "0.5"
 bitflags = "2.4.1"
 bstr = "1.11.3"
 # `cc` updates often break things, so we pin it here. Cargo enforces "max 1 semver-compat version
-# per crate", so if you change this, you need to also change it in `rustc_llvm`.
+# per crate", so if you change this, you need to also change it in `rustc_llvm` and `rustc_windows_rc`.
 cc = "=1.2.16"
 itertools = "0.12"
 pathdiff = "0.2.0"
diff --git a/compiler/rustc_codegen_ssa/src/back/write.rs b/compiler/rustc_codegen_ssa/src/back/write.rs
index 95e02a7c6db..cbaf67d7345 100644
--- a/compiler/rustc_codegen_ssa/src/back/write.rs
+++ b/compiler/rustc_codegen_ssa/src/back/write.rs
@@ -830,6 +830,8 @@ fn execute_optimize_work_item<B: ExtraBackendMethods>(
     cgcx: &CodegenContext<B>,
     mut module: ModuleCodegen<B::Module>,
 ) -> WorkItemResult<B> {
+    let _timer = cgcx.prof.generic_activity_with_arg("codegen_module_optimize", &*module.name);
+
     let dcx = cgcx.create_dcx();
     let dcx = dcx.handle();
 
@@ -862,7 +864,7 @@ fn execute_optimize_work_item<B: ExtraBackendMethods>(
             WorkItemResult::Finished(module)
         }
         ComputedLtoType::Thin => {
-            let (name, thin_buffer) = B::prepare_thin(module, false);
+            let (name, thin_buffer) = B::prepare_thin(module);
             if let Some(path) = bitcode {
                 fs::write(&path, thin_buffer.data()).unwrap_or_else(|e| {
                     panic!("Error writing pre-lto-bitcode file `{}`: {}", path.display(), e);
@@ -890,6 +892,10 @@ fn execute_copy_from_cache_work_item<B: ExtraBackendMethods>(
     cgcx: &CodegenContext<B>,
     module: CachedModuleCodegen,
 ) -> WorkItemResult<B> {
+    let _timer = cgcx
+        .prof
+        .generic_activity_with_arg("codegen_copy_artifacts_from_incr_cache", &*module.name);
+
     let incr_comp_session_dir = cgcx.incr_comp_session_dir.as_ref().unwrap();
 
     let mut links_from_incr_cache = Vec::new();
@@ -977,6 +983,8 @@ fn execute_fat_lto_work_item<B: ExtraBackendMethods>(
     mut needs_fat_lto: Vec<FatLtoInput<B>>,
     import_only_modules: Vec<(SerializedModule<B::ModuleBuffer>, WorkProduct)>,
 ) -> WorkItemResult<B> {
+    let _timer = cgcx.prof.generic_activity_with_arg("codegen_module_perform_lto", "everything");
+
     for (module, wp) in import_only_modules {
         needs_fat_lto.push(FatLtoInput::Serialized { name: wp.cgu_name, buffer: module })
     }
@@ -995,6 +1003,8 @@ fn execute_thin_lto_work_item<B: ExtraBackendMethods>(
     cgcx: &CodegenContext<B>,
     module: lto::ThinModule<B>,
 ) -> WorkItemResult<B> {
+    let _timer = cgcx.prof.generic_activity_with_arg("codegen_module_perform_lto", module.name());
+
     let module = B::optimize_thin(cgcx, module);
     let module = B::codegen(cgcx, module, &cgcx.module_config);
     WorkItemResult::Finished(module)
@@ -1714,38 +1724,21 @@ fn spawn_work<'a, B: ExtraBackendMethods>(
 
     B::spawn_named_thread(cgcx.time_trace, work.short_description(), move || {
         let result = std::panic::catch_unwind(AssertUnwindSafe(|| match work {
-            WorkItem::Optimize(m) => {
-                let _timer =
-                    cgcx.prof.generic_activity_with_arg("codegen_module_optimize", &*m.name);
-                execute_optimize_work_item(&cgcx, m)
-            }
-            WorkItem::CopyPostLtoArtifacts(m) => {
-                let _timer = cgcx
-                    .prof
-                    .generic_activity_with_arg("codegen_copy_artifacts_from_incr_cache", &*m.name);
-                execute_copy_from_cache_work_item(&cgcx, m)
-            }
+            WorkItem::Optimize(m) => execute_optimize_work_item(&cgcx, m),
+            WorkItem::CopyPostLtoArtifacts(m) => execute_copy_from_cache_work_item(&cgcx, m),
             WorkItem::FatLto {
                 exported_symbols_for_lto,
                 each_linked_rlib_for_lto,
                 needs_fat_lto,
                 import_only_modules,
-            } => {
-                let _timer =
-                    cgcx.prof.generic_activity_with_arg("codegen_module_perform_lto", "everything");
-                execute_fat_lto_work_item(
-                    &cgcx,
-                    &exported_symbols_for_lto,
-                    &each_linked_rlib_for_lto,
-                    needs_fat_lto,
-                    import_only_modules,
-                )
-            }
-            WorkItem::ThinLto(m) => {
-                let _timer =
-                    cgcx.prof.generic_activity_with_arg("codegen_module_perform_lto", m.name());
-                execute_thin_lto_work_item(&cgcx, m)
-            }
+            } => execute_fat_lto_work_item(
+                &cgcx,
+                &exported_symbols_for_lto,
+                &each_linked_rlib_for_lto,
+                needs_fat_lto,
+                import_only_modules,
+            ),
+            WorkItem::ThinLto(m) => execute_thin_lto_work_item(&cgcx, m),
         }));
 
         let msg = match result {
diff --git a/compiler/rustc_codegen_ssa/src/traits/write.rs b/compiler/rustc_codegen_ssa/src/traits/write.rs
index cc7c4e46d7b..1ac1d7ef2e2 100644
--- a/compiler/rustc_codegen_ssa/src/traits/write.rs
+++ b/compiler/rustc_codegen_ssa/src/traits/write.rs
@@ -50,16 +50,12 @@ pub trait WriteBackendMethods: Clone + 'static {
         module: ModuleCodegen<Self::Module>,
         config: &ModuleConfig,
     ) -> CompiledModule;
-    fn prepare_thin(
-        module: ModuleCodegen<Self::Module>,
-        want_summary: bool,
-    ) -> (String, Self::ThinBuffer);
+    fn prepare_thin(module: ModuleCodegen<Self::Module>) -> (String, Self::ThinBuffer);
     fn serialize_module(module: ModuleCodegen<Self::Module>) -> (String, Self::ModuleBuffer);
 }
 
 pub trait ThinBufferMethods: Send + Sync {
     fn data(&self) -> &[u8];
-    fn thin_link_data(&self) -> &[u8];
 }
 
 pub trait ModuleBufferMethods: Send + Sync {
diff --git a/compiler/rustc_const_eval/src/interpret/eval_context.rs b/compiler/rustc_const_eval/src/interpret/eval_context.rs
index 9681d89ce35..91ed71ac3e5 100644
--- a/compiler/rustc_const_eval/src/interpret/eval_context.rs
+++ b/compiler/rustc_const_eval/src/interpret/eval_context.rs
@@ -4,6 +4,7 @@ use either::{Left, Right};
 use rustc_abi::{Align, HasDataLayout, Size, TargetDataLayout};
 use rustc_errors::DiagCtxtHandle;
 use rustc_hir::def_id::DefId;
+use rustc_hir::limit::Limit;
 use rustc_middle::mir::interpret::{ErrorHandled, InvalidMetaKind, ReportedErrorInfo};
 use rustc_middle::query::TyCtxtAt;
 use rustc_middle::ty::layout::{
@@ -12,7 +13,6 @@ use rustc_middle::ty::layout::{
 };
 use rustc_middle::ty::{self, GenericArgsRef, Ty, TyCtxt, TypeFoldable, TypingEnv, Variance};
 use rustc_middle::{mir, span_bug};
-use rustc_session::Limit;
 use rustc_span::Span;
 use rustc_target::callconv::FnAbi;
 use tracing::{debug, trace};
diff --git a/compiler/rustc_const_eval/src/interpret/memory.rs b/compiler/rustc_const_eval/src/interpret/memory.rs
index 2c1e5087e1c..ebcdb9461d0 100644
--- a/compiler/rustc_const_eval/src/interpret/memory.rs
+++ b/compiler/rustc_const_eval/src/interpret/memory.rs
@@ -953,6 +953,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
 
         // # Global allocations
         if let Some(global_alloc) = self.tcx.try_get_global_alloc(id) {
+            // NOTE: `static` alignment from attributes has already been applied to the allocation.
             let (size, align) = global_alloc.size_and_align(*self.tcx, self.typing_env);
             let mutbl = global_alloc.mutability(*self.tcx, self.typing_env);
             let kind = match global_alloc {
@@ -1501,8 +1502,10 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         // `get_bytes_mut` will clear the provenance, which is correct,
         // since we don't want to keep any provenance at the target.
         // This will also error if copying partial provenance is not supported.
-        let provenance =
-            src_alloc.provenance().prepare_copy(src_range, dest_offset, num_copies, self);
+        let provenance = src_alloc
+            .provenance()
+            .prepare_copy(src_range, dest_offset, num_copies, self)
+            .map_err(|e| e.to_interp_error(src_alloc_id))?;
         // Prepare a copy of the initialization mask.
         let init = src_alloc.init_mask().prepare_copy(src_range);
 
diff --git a/compiler/rustc_const_eval/src/interpret/traits.rs b/compiler/rustc_const_eval/src/interpret/traits.rs
index e4b5c82853a..870f9a396ae 100644
--- a/compiler/rustc_const_eval/src/interpret/traits.rs
+++ b/compiler/rustc_const_eval/src/interpret/traits.rs
@@ -23,7 +23,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
     ) -> InterpResult<'tcx, Pointer<Option<M::Provenance>>> {
         trace!("get_vtable(ty={ty:?}, dyn_ty={dyn_ty:?})");
 
-        let (ty, dyn_ty) = self.tcx.erase_regions((ty, dyn_ty));
+        let (ty, dyn_ty) = self.tcx.erase_and_anonymize_regions((ty, dyn_ty));
 
         // All vtables must be monomorphic, bail out otherwise.
         ensure_monomorphic_enough(*self.tcx, ty)?;
@@ -53,8 +53,9 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
     ) -> &'tcx [VtblEntry<'tcx>] {
         if let Some(trait_) = trait_ {
             let trait_ref = trait_.with_self_ty(*self.tcx, dyn_ty);
-            let trait_ref =
-                self.tcx.erase_regions(self.tcx.instantiate_bound_regions_with_erased(trait_ref));
+            let trait_ref = self.tcx.erase_and_anonymize_regions(
+                self.tcx.instantiate_bound_regions_with_erased(trait_ref),
+            );
             self.tcx.vtable_entries(trait_ref)
         } else {
             TyCtxt::COMMON_VTABLE_ENTRIES
diff --git a/compiler/rustc_const_eval/src/interpret/util.rs b/compiler/rustc_const_eval/src/interpret/util.rs
index 72bee345406..f667823723c 100644
--- a/compiler/rustc_const_eval/src/interpret/util.rs
+++ b/compiler/rustc_const_eval/src/interpret/util.rs
@@ -1,6 +1,6 @@
 use rustc_hir::def_id::LocalDefId;
 use rustc_middle::mir;
-use rustc_middle::mir::interpret::{AllocInit, Allocation, InterpResult, Pointer};
+use rustc_middle::mir::interpret::{AllocInit, Allocation, GlobalAlloc, InterpResult, Pointer};
 use rustc_middle::ty::layout::TyAndLayout;
 use rustc_middle::ty::{TyCtxt, TypeVisitable, TypeVisitableExt};
 use tracing::debug;
@@ -38,7 +38,14 @@ pub(crate) fn create_static_alloc<'tcx>(
     static_def_id: LocalDefId,
     layout: TyAndLayout<'tcx>,
 ) -> InterpResult<'tcx, MPlaceTy<'tcx>> {
-    let alloc = Allocation::try_new(layout.size, layout.align.abi, AllocInit::Uninit, ())?;
+    // Inherit size and align from the `GlobalAlloc::Static` so we can avoid duplicating
+    // the alignment attribute logic.
+    let (size, align) =
+        GlobalAlloc::Static(static_def_id.into()).size_and_align(*ecx.tcx, ecx.typing_env);
+    assert_eq!(size, layout.size);
+    assert!(align >= layout.align.abi);
+
+    let alloc = Allocation::try_new(size, align, AllocInit::Uninit, ())?;
     let alloc_id = ecx.tcx.reserve_and_set_static_alloc(static_def_id.into());
     assert_eq!(ecx.machine.static_root_ids, None);
     ecx.machine.static_root_ids = Some((alloc_id, static_def_id));
diff --git a/compiler/rustc_const_eval/src/util/type_name.rs b/compiler/rustc_const_eval/src/util/type_name.rs
index 2ae6655901b..5bcf96abd8c 100644
--- a/compiler/rustc_const_eval/src/util/type_name.rs
+++ b/compiler/rustc_const_eval/src/util/type_name.rs
@@ -168,10 +168,11 @@ impl<'tcx> PrettyPrinter<'tcx> for TypeNamePrinter<'tcx> {
         // Bound regions are always printed (as `'_`), which gives some idea that they are special,
         // even though the `for` is omitted by the pretty printer.
         // E.g. `for<'a, 'b> fn(&'a u32, &'b u32)` is printed as "fn(&'_ u32, &'_ u32)".
+        let kind = region.kind();
         match region.kind() {
-            ty::ReErased | ty::ReEarlyParam(_) => false,
+            ty::ReErased | ty::ReEarlyParam(_) | ty::ReStatic => false,
             ty::ReBound(..) => true,
-            _ => unreachable!(),
+            _ => panic!("type_name unhandled region: {kind:?}"),
         }
     }
 
diff --git a/compiler/rustc_driver/Cargo.toml b/compiler/rustc_driver/Cargo.toml
index e3ee8351295..51909719827 100644
--- a/compiler/rustc_driver/Cargo.toml
+++ b/compiler/rustc_driver/Cargo.toml
@@ -10,3 +10,8 @@ crate-type = ["dylib"]
 # tidy-alphabetical-start
 rustc_driver_impl = { path = "../rustc_driver_impl" }
 # tidy-alphabetical-end
+
+[build-dependencies]
+# tidy-alphabetical-start
+rustc_windows_rc = { path = "../rustc_windows_rc" }
+# tidy-alphabetical-end
diff --git a/compiler/rustc_driver/build.rs b/compiler/rustc_driver/build.rs
new file mode 100644
index 00000000000..ba44fe7a86e
--- /dev/null
+++ b/compiler/rustc_driver/build.rs
@@ -0,0 +1,21 @@
+use std::{env, path};
+
+use rustc_windows_rc::{VersionInfoFileType, compile_windows_resource_file};
+
+fn main() {
+    let target_os = env::var("CARGO_CFG_TARGET_OS");
+    let target_env = env::var("CARGO_CFG_TARGET_ENV");
+    if Ok("windows") == target_os.as_deref() && Ok("msvc") == target_env.as_deref() {
+        set_windows_dll_options();
+    } else {
+        // Avoid rerunning the build script every time.
+        println!("cargo:rerun-if-changed=build.rs");
+    }
+}
+
+fn set_windows_dll_options() {
+    let stem = path::PathBuf::from("rustc_driver_resource");
+    let file_description = "rustc_driver";
+    let res_file = compile_windows_resource_file(&stem, file_description, VersionInfoFileType::Dll);
+    println!("cargo:rustc-link-arg={}", res_file.display());
+}
diff --git a/compiler/rustc_expand/src/base.rs b/compiler/rustc_expand/src/base.rs
index 8ff21509f4a..88f88f30a8c 100644
--- a/compiler/rustc_expand/src/base.rs
+++ b/compiler/rustc_expand/src/base.rs
@@ -18,13 +18,14 @@ use rustc_feature::Features;
 use rustc_hir as hir;
 use rustc_hir::attrs::{AttributeKind, CfgEntry, Deprecation};
 use rustc_hir::def::MacroKinds;
+use rustc_hir::limit::Limit;
 use rustc_hir::{Stability, find_attr};
 use rustc_lint_defs::RegisteredTools;
 use rustc_parse::MACRO_ARGUMENTS;
 use rustc_parse::parser::{ForceCollect, Parser};
+use rustc_session::Session;
 use rustc_session::config::CollapseMacroDebuginfo;
 use rustc_session::parse::ParseSess;
-use rustc_session::{Limit, Session};
 use rustc_span::def_id::{CrateNum, DefId, LocalDefId};
 use rustc_span::edition::Edition;
 use rustc_span::hygiene::{AstPass, ExpnData, ExpnKind, LocalExpnId, MacroKind};
diff --git a/compiler/rustc_expand/src/errors.rs b/compiler/rustc_expand/src/errors.rs
index ba9d76970f0..6eb5cd65846 100644
--- a/compiler/rustc_expand/src/errors.rs
+++ b/compiler/rustc_expand/src/errors.rs
@@ -2,8 +2,8 @@ use std::borrow::Cow;
 
 use rustc_ast::ast;
 use rustc_errors::codes::*;
+use rustc_hir::limit::Limit;
 use rustc_macros::{Diagnostic, Subdiagnostic};
-use rustc_session::Limit;
 use rustc_span::{Ident, MacroRulesNormalizedIdent, Span, Symbol};
 
 #[derive(Diagnostic)]
diff --git a/compiler/rustc_expand/src/expand.rs b/compiler/rustc_expand/src/expand.rs
index dbb4a9de9e0..38e057d2776 100644
--- a/compiler/rustc_expand/src/expand.rs
+++ b/compiler/rustc_expand/src/expand.rs
@@ -19,14 +19,15 @@ use rustc_errors::PResult;
 use rustc_feature::Features;
 use rustc_hir::Target;
 use rustc_hir::def::MacroKinds;
+use rustc_hir::limit::Limit;
 use rustc_parse::parser::{
     AttemptLocalParseRecovery, CommaRecoveryMode, ForceCollect, Parser, RecoverColon, RecoverComma,
     token_descr,
 };
+use rustc_session::Session;
 use rustc_session::lint::BuiltinLintDiag;
 use rustc_session::lint::builtin::{UNUSED_ATTRIBUTES, UNUSED_DOC_COMMENTS};
 use rustc_session::parse::feature_err;
-use rustc_session::{Limit, Session};
 use rustc_span::hygiene::SyntaxContext;
 use rustc_span::{ErrorGuaranteed, FileName, Ident, LocalExpnId, Span, Symbol, sym};
 use smallvec::SmallVec;
@@ -2529,6 +2530,7 @@ impl ExpansionConfig<'_> {
         ExpansionConfig {
             crate_name,
             features,
+            // FIXME should this limit be configurable?
             recursion_limit: Limit::new(1024),
             trace_mac: false,
             should_test: false,
diff --git a/compiler/rustc_feature/src/builtin_attrs.rs b/compiler/rustc_feature/src/builtin_attrs.rs
index e81003b1897..129ab7eccb5 100644
--- a/compiler/rustc_feature/src/builtin_attrs.rs
+++ b/compiler/rustc_feature/src/builtin_attrs.rs
@@ -621,6 +621,7 @@ pub static BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
     ),
     // FIXME(#82232, #143834): temporarily renamed to mitigate `#[align]` nameres ambiguity
     gated!(rustc_align, Normal, template!(List: &["alignment"]), DuplicatesOk, EncodeCrossCrate::No, fn_align, experimental!(rustc_align)),
+    gated!(rustc_align_static, Normal, template!(List: &["alignment"]), DuplicatesOk, EncodeCrossCrate::No, static_align, experimental!(rustc_align_static)),
     ungated!(
         unsafe(Edition2024) export_name, Normal,
         template!(NameValueStr: "name", "https://doc.rust-lang.org/reference/abi.html#the-export_name-attribute"),
diff --git a/compiler/rustc_feature/src/unstable.rs b/compiler/rustc_feature/src/unstable.rs
index 4f35bf63a1a..93e5588146e 100644
--- a/compiler/rustc_feature/src/unstable.rs
+++ b/compiler/rustc_feature/src/unstable.rs
@@ -632,6 +632,8 @@ declare_features! (
     (unstable, simd_ffi, "1.0.0", Some(27731)),
     /// Allows specialization of implementations (RFC 1210).
     (incomplete, specialization, "1.7.0", Some(31844)),
+    /// Allows using `#[rustc_align_static(...)]` on static items.
+    (unstable, static_align, "CURRENT_RUSTC_VERSION", Some(146177)),
     /// Allows attributes on expressions and non-item statements.
     (unstable, stmt_expr_attributes, "1.6.0", Some(15701)),
     /// Allows lints part of the strict provenance effort.
diff --git a/compiler/rustc_hir/src/attrs/data_structures.rs b/compiler/rustc_hir/src/attrs/data_structures.rs
index dd5565d6f90..b4c1b61b9b5 100644
--- a/compiler/rustc_hir/src/attrs/data_structures.rs
+++ b/compiler/rustc_hir/src/attrs/data_structures.rs
@@ -14,6 +14,7 @@ pub use rustc_target::spec::SanitizerSet;
 use thin_vec::ThinVec;
 
 use crate::attrs::pretty_printing::PrintAttribute;
+use crate::limit::Limit;
 use crate::{DefaultBodyStability, PartialConstStability, RustcVersion, Stability};
 
 #[derive(Copy, Clone, PartialEq, Encodable, Decodable, Debug, HashStable_Generic, PrintAttribute)]
@@ -565,6 +566,9 @@ pub enum AttributeKind {
     /// Represents [`#[may_dangle]`](https://std-dev-guide.rust-lang.org/tricky/may-dangle.html).
     MayDangle(Span),
 
+    /// Represents `#[move_size_limit]`
+    MoveSizeLimit { attr_span: Span, limit_span: Span, limit: Limit },
+
     /// Represents `#[must_use]`.
     MustUse {
         span: Span,
@@ -596,6 +600,9 @@ pub enum AttributeKind {
     /// Represents `#[path]`
     Path(Symbol, Span),
 
+    /// Represents `#[pattern_complexity_limit]`
+    PatternComplexityLimit { attr_span: Span, limit_span: Span, limit: Limit },
+
     /// Represents `#[pointee]`
     Pointee(Span),
 
@@ -611,6 +618,9 @@ pub enum AttributeKind {
     /// Represents `#[rustc_pub_transparent]` (used by the `repr_transparent_external_private_fields` lint).
     PubTransparent(Span),
 
+    /// Represents [`#[recursion_limit]`](https://doc.rust-lang.org/reference/attributes/limits.html#the-recursion_limit-attribute)
+    RecursionLimit { attr_span: Span, limit_span: Span, limit: Limit },
+
     /// Represents [`#[repr]`](https://doc.rust-lang.org/stable/reference/type-layout.html#representations).
     Repr { reprs: ThinVec<(ReprAttr, Span)>, first_span: Span },
 
@@ -661,6 +671,9 @@ pub enum AttributeKind {
     /// Represents `#[type_const]`.
     TypeConst(Span),
 
+    /// Represents `#[type_length_limit]`
+    TypeLengthLimit { attr_span: Span, limit_span: Span, limit: Limit },
+
     /// Represents `#[rustc_unsafe_specialization_marker]`.
     UnsafeSpecializationMarker(Span),
 
diff --git a/compiler/rustc_hir/src/attrs/encode_cross_crate.rs b/compiler/rustc_hir/src/attrs/encode_cross_crate.rs
index 3810bb6d003..0e208be3497 100644
--- a/compiler/rustc_hir/src/attrs/encode_cross_crate.rs
+++ b/compiler/rustc_hir/src/attrs/encode_cross_crate.rs
@@ -61,6 +61,7 @@ impl AttributeKind {
             MacroUse { .. } => No,
             Marker(..) => No,
             MayDangle(..) => No,
+            MoveSizeLimit { .. } => No,
             MustUse { .. } => Yes,
             Naked(..) => No,
             NoImplicitPrelude(..) => No,
@@ -70,11 +71,13 @@ impl AttributeKind {
             ParenSugar(..) => No,
             PassByValue(..) => Yes,
             Path(..) => No,
+            PatternComplexityLimit { .. } => No,
             Pointee(..) => No,
             ProcMacro(..) => No,
             ProcMacroAttribute(..) => No,
             ProcMacroDerive { .. } => No,
             PubTransparent(..) => Yes,
+            RecursionLimit { .. } => No,
             Repr { .. } => No,
             RustcBuiltinMacro { .. } => Yes,
             RustcLayoutScalarValidRangeEnd(..) => Yes,
@@ -89,6 +92,7 @@ impl AttributeKind {
             TargetFeature { .. } => No,
             TrackCaller(..) => Yes,
             TypeConst(..) => Yes,
+            TypeLengthLimit { .. } => No,
             UnsafeSpecializationMarker(..) => No,
             UnstableFeatureBound(..) => No,
             Used { .. } => No,
diff --git a/compiler/rustc_hir/src/attrs/pretty_printing.rs b/compiler/rustc_hir/src/attrs/pretty_printing.rs
index e65de25b451..d13cd3fd1da 100644
--- a/compiler/rustc_hir/src/attrs/pretty_printing.rs
+++ b/compiler/rustc_hir/src/attrs/pretty_printing.rs
@@ -9,6 +9,8 @@ use rustc_span::{ErrorGuaranteed, Ident, Span, Symbol};
 use rustc_target::spec::SanitizerSet;
 use thin_vec::ThinVec;
 
+use crate::limit::Limit;
+
 /// This trait is used to print attributes in `rustc_hir_pretty`.
 ///
 /// For structs and enums it can be derived using [`rustc_macros::PrintAttribute`].
@@ -146,7 +148,7 @@ macro_rules! print_tup {
 
 print_tup!(A B C D E F G H);
 print_skip!(Span, (), ErrorGuaranteed);
-print_disp!(u16, bool, NonZero<u32>);
+print_disp!(u16, bool, NonZero<u32>, Limit);
 print_debug!(
     Symbol,
     Ident,
diff --git a/compiler/rustc_hir/src/hir.rs b/compiler/rustc_hir/src/hir.rs
index ae03121e5f7..75551fe4c19 100644
--- a/compiler/rustc_hir/src/hir.rs
+++ b/compiler/rustc_hir/src/hir.rs
@@ -2616,6 +2616,18 @@ impl Expr<'_> {
             )
             | (
                 ExprKind::Struct(
+                    QPath::LangItem(LangItem::RangeToInclusiveCopy, _),
+                    [val1],
+                    StructTailExpr::None,
+                ),
+                ExprKind::Struct(
+                    QPath::LangItem(LangItem::RangeToInclusiveCopy, _),
+                    [val2],
+                    StructTailExpr::None,
+                ),
+            )
+            | (
+                ExprKind::Struct(
                     QPath::LangItem(LangItem::RangeFrom, _),
                     [val1],
                     StructTailExpr::None,
@@ -2705,7 +2717,8 @@ pub fn is_range_literal(expr: &Expr<'_>) -> bool {
                     | LangItem::RangeToInclusive
                     | LangItem::RangeCopy
                     | LangItem::RangeFromCopy
-                    | LangItem::RangeInclusiveCopy,
+                    | LangItem::RangeInclusiveCopy
+                    | LangItem::RangeToInclusiveCopy,
                 ..
             )
         ),
diff --git a/compiler/rustc_hir/src/lang_items.rs b/compiler/rustc_hir/src/lang_items.rs
index 0464665b41f..67d2f15d414 100644
--- a/compiler/rustc_hir/src/lang_items.rs
+++ b/compiler/rustc_hir/src/lang_items.rs
@@ -422,6 +422,7 @@ language_item_table! {
     RangeFromCopy,           sym::RangeFromCopy,       range_from_copy_struct,     Target::Struct,         GenericRequirement::None;
     RangeCopy,               sym::RangeCopy,           range_copy_struct,          Target::Struct,         GenericRequirement::None;
     RangeInclusiveCopy,      sym::RangeInclusiveCopy,  range_inclusive_copy_struct, Target::Struct,         GenericRequirement::None;
+    RangeToInclusiveCopy,    sym::RangeToInclusiveCopy,     range_to_inclusive_copy_struct, Target::Struct, GenericRequirement::None;
 
     String,                  sym::String,              string,                     Target::Struct,         GenericRequirement::None;
     CStr,                    sym::CStr,                c_str,                      Target::Struct,         GenericRequirement::None;
diff --git a/compiler/rustc_hir/src/lib.rs b/compiler/rustc_hir/src/lib.rs
index 78fc63753a2..eb630fc8018 100644
--- a/compiler/rustc_hir/src/lib.rs
+++ b/compiler/rustc_hir/src/lib.rs
@@ -25,6 +25,7 @@ mod hir;
 pub use rustc_hir_id::{self as hir_id, *};
 pub mod intravisit;
 pub mod lang_items;
+pub mod limit;
 pub mod lints;
 pub mod pat_util;
 mod stability;
diff --git a/compiler/rustc_hir/src/limit.rs b/compiler/rustc_hir/src/limit.rs
new file mode 100644
index 00000000000..7e6d23f51bd
--- /dev/null
+++ b/compiler/rustc_hir/src/limit.rs
@@ -0,0 +1,63 @@
+use std::fmt;
+use std::ops::{Div, Mul};
+
+use rustc_error_messages::{DiagArgValue, IntoDiagArg};
+use rustc_macros::{Decodable, Encodable, HashStable_Generic};
+
+/// New-type wrapper around `usize` for representing limits. Ensures that comparisons against
+/// limits are consistent throughout the compiler.
+#[derive(Clone, Copy, Debug, HashStable_Generic, Encodable, Decodable)]
+pub struct Limit(pub usize);
+
+impl Limit {
+    /// Create a new limit from a `usize`.
+    pub fn new(value: usize) -> Self {
+        Limit(value)
+    }
+
+    /// Create a new unlimited limit.
+    pub fn unlimited() -> Self {
+        Limit(usize::MAX)
+    }
+
+    /// Check that `value` is within the limit. Ensures that the same comparisons are used
+    /// throughout the compiler, as mismatches can cause ICEs, see #72540.
+    #[inline]
+    pub fn value_within_limit(&self, value: usize) -> bool {
+        value <= self.0
+    }
+}
+
+impl From<usize> for Limit {
+    fn from(value: usize) -> Self {
+        Self::new(value)
+    }
+}
+
+impl fmt::Display for Limit {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        self.0.fmt(f)
+    }
+}
+
+impl Div<usize> for Limit {
+    type Output = Limit;
+
+    fn div(self, rhs: usize) -> Self::Output {
+        Limit::new(self.0 / rhs)
+    }
+}
+
+impl Mul<usize> for Limit {
+    type Output = Limit;
+
+    fn mul(self, rhs: usize) -> Self::Output {
+        Limit::new(self.0 * rhs)
+    }
+}
+
+impl IntoDiagArg for Limit {
+    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+        self.to_string().into_diag_arg(&mut None)
+    }
+}
diff --git a/compiler/rustc_hir_analysis/src/autoderef.rs b/compiler/rustc_hir_analysis/src/autoderef.rs
index e27e68d3662..e8237471e1b 100644
--- a/compiler/rustc_hir_analysis/src/autoderef.rs
+++ b/compiler/rustc_hir_analysis/src/autoderef.rs
@@ -1,7 +1,7 @@
+use rustc_hir::limit::Limit;
 use rustc_infer::infer::InferCtxt;
 use rustc_infer::traits::PredicateObligations;
 use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitableExt};
-use rustc_session::Limit;
 use rustc_span::def_id::{LOCAL_CRATE, LocalDefId};
 use rustc_span::{ErrorGuaranteed, Span};
 use rustc_trait_selection::traits::ObligationCtxt;
diff --git a/compiler/rustc_hir_analysis/src/check/mod.rs b/compiler/rustc_hir_analysis/src/check/mod.rs
index b5c0ca4727c..63d0f400aef 100644
--- a/compiler/rustc_hir_analysis/src/check/mod.rs
+++ b/compiler/rustc_hir_analysis/src/check/mod.rs
@@ -85,7 +85,9 @@ use rustc_infer::traits::ObligationCause;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::error::{ExpectedFound, TypeError};
 use rustc_middle::ty::print::with_types_for_signature;
-use rustc_middle::ty::{self, GenericArgs, GenericArgsRef, Ty, TyCtxt, TypingMode};
+use rustc_middle::ty::{
+    self, GenericArgs, GenericArgsRef, GenericParamDefKind, Ty, TyCtxt, TypingMode,
+};
 use rustc_middle::{bug, span_bug};
 use rustc_session::parse::feature_err;
 use rustc_span::def_id::CRATE_DEF_ID;
@@ -233,8 +235,7 @@ fn missing_items_err(
     };
 
     // Obtain the level of indentation ending in `sugg_sp`.
-    let padding =
-        tcx.sess.source_map().indentation_before(sugg_sp).unwrap_or_else(|| String::new());
+    let padding = tcx.sess.source_map().indentation_before(sugg_sp).unwrap_or_else(String::new);
     let (mut missing_trait_item, mut missing_trait_item_none, mut missing_trait_item_label) =
         (Vec::new(), Vec::new(), Vec::new());
 
@@ -331,6 +332,7 @@ fn default_body_is_unstable(
 fn bounds_from_generic_predicates<'tcx>(
     tcx: TyCtxt<'tcx>,
     predicates: impl IntoIterator<Item = (ty::Clause<'tcx>, Span)>,
+    assoc: ty::AssocItem,
 ) -> (String, String) {
     let mut types: FxIndexMap<Ty<'tcx>, Vec<DefId>> = FxIndexMap::default();
     let mut projections = vec![];
@@ -354,34 +356,50 @@ fn bounds_from_generic_predicates<'tcx>(
     }
 
     let mut where_clauses = vec![];
-    let mut types_str = vec![];
-    for (ty, bounds) in types {
-        if let ty::Param(_) = ty.kind() {
-            let mut bounds_str = vec![];
-            for bound in bounds {
-                let mut projections_str = vec![];
-                for projection in &projections {
-                    let p = projection.skip_binder();
-                    if bound == tcx.parent(p.projection_term.def_id)
-                        && p.projection_term.self_ty() == ty
-                    {
-                        let name = tcx.item_name(p.projection_term.def_id);
-                        projections_str.push(format!("{} = {}", name, p.term));
+    let generics = tcx.generics_of(assoc.def_id);
+    let types_str = generics
+        .own_params
+        .iter()
+        .filter(|p| matches!(p.kind, GenericParamDefKind::Type { synthetic: false, .. }))
+        .map(|p| {
+            // we just checked that it's a type, so the unwrap can't fail
+            let ty = tcx.mk_param_from_def(p).as_type().unwrap();
+            if let Some(bounds) = types.get(&ty) {
+                let mut bounds_str = vec![];
+                for bound in bounds.iter().copied() {
+                    let mut projections_str = vec![];
+                    for projection in &projections {
+                        let p = projection.skip_binder();
+                        if bound == tcx.parent(p.projection_term.def_id)
+                            && p.projection_term.self_ty() == ty
+                        {
+                            let name = tcx.item_name(p.projection_term.def_id);
+                            projections_str.push(format!("{} = {}", name, p.term));
+                        }
+                    }
+                    let bound_def_path = tcx.def_path_str(bound);
+                    if projections_str.is_empty() {
+                        where_clauses.push(format!("{}: {}", ty, bound_def_path));
+                    } else {
+                        bounds_str.push(format!(
+                            "{}<{}>",
+                            bound_def_path,
+                            projections_str.join(", ")
+                        ));
                     }
                 }
-                let bound_def_path = tcx.def_path_str(bound);
-                if projections_str.is_empty() {
-                    where_clauses.push(format!("{}: {}", ty, bound_def_path));
+                if bounds_str.is_empty() {
+                    ty.to_string()
                 } else {
-                    bounds_str.push(format!("{}<{}>", bound_def_path, projections_str.join(", ")));
+                    format!("{}: {}", ty, bounds_str.join(" + "))
                 }
-            }
-            if bounds_str.is_empty() {
-                types_str.push(ty.to_string());
             } else {
-                types_str.push(format!("{}: {}", ty, bounds_str.join(" + ")));
+                ty.to_string()
             }
-        } else {
+        })
+        .collect::<Vec<_>>();
+    for (ty, bounds) in types.into_iter() {
+        if !matches!(ty.kind(), ty::Param(_)) {
             // Avoid suggesting the following:
             // fn foo<T, <T as Trait>::Bar>(_: T) where T: Trait, <T as Trait>::Bar: Other {}
             where_clauses.extend(
@@ -473,10 +491,10 @@ fn fn_sig_suggestion<'tcx>(
     let output = if !output.is_unit() { format!(" -> {output}") } else { String::new() };
 
     let safety = sig.safety.prefix_str();
-    let (generics, where_clauses) = bounds_from_generic_predicates(tcx, predicates);
+    let (generics, where_clauses) = bounds_from_generic_predicates(tcx, predicates, assoc);
 
     // FIXME: this is not entirely correct, as the lifetimes from borrowed params will
-    // not be present in the `fn` definition, not will we account for renamed
+    // not be present in the `fn` definition, nor will we account for renamed
     // lifetimes between the `impl` and the `trait`, but this should be good enough to
     // fill in a significant portion of the missing code, and other subsequent
     // suggestions can help the user fix the code.
@@ -512,6 +530,7 @@ fn suggestion_signature<'tcx>(
             let (generics, where_clauses) = bounds_from_generic_predicates(
                 tcx,
                 tcx.predicates_of(assoc.def_id).instantiate_own(tcx, args),
+                assoc,
             );
             format!("type {}{generics} = /* Type */{where_clauses};", assoc.name())
         }
diff --git a/compiler/rustc_hir_analysis/src/check/wfcheck.rs b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
index e6a1f6d8d8b..22a9446fd4c 100644
--- a/compiler/rustc_hir_analysis/src/check/wfcheck.rs
+++ b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
@@ -1047,7 +1047,7 @@ fn check_type_defn<'tcx>(
             let needs_drop_copy = || {
                 packed && {
                     let ty = tcx.type_of(variant.tail().did).instantiate_identity();
-                    let ty = tcx.erase_regions(ty);
+                    let ty = tcx.erase_and_anonymize_regions(ty);
                     assert!(!ty.has_infer());
                     ty.needs_drop(tcx, wfcx.infcx.typing_env(wfcx.param_env))
                 }
diff --git a/compiler/rustc_hir_analysis/src/coherence/orphan.rs b/compiler/rustc_hir_analysis/src/coherence/orphan.rs
index f707196c816..621431ae234 100644
--- a/compiler/rustc_hir_analysis/src/coherence/orphan.rs
+++ b/compiler/rustc_hir_analysis/src/coherence/orphan.rs
@@ -404,7 +404,7 @@ fn emit_orphan_check_error<'tcx>(
                     of_trait.trait_ref.path.span
                 };
 
-                ty = tcx.erase_regions(ty);
+                ty = tcx.erase_and_anonymize_regions(ty);
 
                 let is_foreign =
                     !trait_ref.def_id.is_local() && matches!(is_target_ty, IsFirstInputType::No);
diff --git a/compiler/rustc_hir_analysis/src/collect/predicates_of.rs b/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
index b59dc4bd132..126ffabd448 100644
--- a/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
+++ b/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
@@ -174,12 +174,6 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
         }
     };
 
-    if let Node::TraitItem(item) = node {
-        let mut bounds = Vec::new();
-        icx.lowerer().add_default_trait_item_bounds(item, &mut bounds);
-        predicates.extend(bounds);
-    }
-
     let generics = tcx.generics_of(def_id);
 
     // Below we'll consider the bounds on the type parameters (including `Self`)
diff --git a/compiler/rustc_hir_analysis/src/errors.rs b/compiler/rustc_hir_analysis/src/errors.rs
index 6565ad7cf53..3b6367219b7 100644
--- a/compiler/rustc_hir_analysis/src/errors.rs
+++ b/compiler/rustc_hir_analysis/src/errors.rs
@@ -6,6 +6,7 @@ use rustc_errors::{
     Applicability, Diag, DiagCtxtHandle, DiagSymbolList, Diagnostic, EmissionGuarantee, Level,
     MultiSpan,
 };
+use rustc_hir::limit::Limit;
 use rustc_macros::{Diagnostic, LintDiagnostic, Subdiagnostic};
 use rustc_middle::ty::Ty;
 use rustc_span::{Ident, Span, Symbol};
@@ -557,7 +558,7 @@ pub(crate) struct AutoDerefReachedRecursionLimit<'a> {
     #[label]
     pub span: Span,
     pub ty: Ty<'a>,
-    pub suggested_limit: rustc_session::Limit,
+    pub suggested_limit: Limit,
     pub crate_name: Symbol,
 }
 
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 d14aef8ace4..99dc8e6e522 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs
@@ -1,12 +1,13 @@
+use std::assert_matches::assert_matches;
 use std::ops::ControlFlow;
 
 use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_errors::codes::*;
 use rustc_errors::struct_span_code_err;
 use rustc_hir as hir;
+use rustc_hir::PolyTraitRef;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::{CRATE_DEF_ID, DefId, LocalDefId};
-use rustc_hir::{AmbigArg, PolyTraitRef};
 use rustc_middle::bug;
 use rustc_middle::ty::{
     self as ty, IsSuggestable, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitableExt,
@@ -230,122 +231,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         }
     }
 
-    /// Checks whether `Self: DefaultAutoTrait` bounds should be added on trait super bounds
-    /// or associated items.
-    ///
-    /// To keep backward compatibility with existing code, `experimental_default_bounds` bounds
-    /// should be added everywhere, including super bounds. However this causes a huge performance
-    /// costs. For optimization purposes instead of adding default supertraits, bounds
-    /// are added to the associated items:
-    ///
-    /// ```ignore(illustrative)
-    /// // Default bounds are generated in the following way:
-    /// trait Trait {
-    ///     fn foo(&self) where Self: Leak {}
-    /// }
-    ///
-    /// // instead of this:
-    /// trait Trait: Leak {
-    ///     fn foo(&self) {}
-    /// }
-    /// ```
-    /// It is not always possible to do this because of backward compatibility:
-    ///
-    /// ```ignore(illustrative)
-    /// pub trait Trait<Rhs = Self> {}
-    /// pub trait Trait1 : Trait {}
-    /// //~^ ERROR: `Rhs` requires `DefaultAutoTrait`, but `Self` is not `DefaultAutoTrait`
-    /// ```
-    ///
-    /// or:
-    ///
-    /// ```ignore(illustrative)
-    /// trait Trait {
-    ///     type Type where Self: Sized;
-    /// }
-    /// trait Trait2<T> : Trait<Type = T> {}
-    /// //~^ ERROR: `DefaultAutoTrait` required for `Trait2`, by implicit  `Self: DefaultAutoTrait` in `Trait::Type`
-    /// ```
-    ///
-    /// Therefore, `experimental_default_bounds` are still being added to supertraits if
-    /// the `SelfTyParam` or `AssocItemConstraint` were found in a trait header.
-    fn requires_default_supertraits(
-        &self,
-        hir_bounds: &'tcx [hir::GenericBound<'tcx>],
-        hir_generics: &'tcx hir::Generics<'tcx>,
-    ) -> bool {
-        struct TraitInfoCollector;
-
-        impl<'tcx> hir::intravisit::Visitor<'tcx> for TraitInfoCollector {
-            type Result = ControlFlow<()>;
-
-            fn visit_assoc_item_constraint(
-                &mut self,
-                _constraint: &'tcx hir::AssocItemConstraint<'tcx>,
-            ) -> Self::Result {
-                ControlFlow::Break(())
-            }
-
-            fn visit_ty(&mut self, t: &'tcx hir::Ty<'tcx, AmbigArg>) -> Self::Result {
-                if matches!(
-                    &t.kind,
-                    hir::TyKind::Path(hir::QPath::Resolved(
-                        _,
-                        hir::Path { res: hir::def::Res::SelfTyParam { .. }, .. },
-                    ))
-                ) {
-                    return ControlFlow::Break(());
-                }
-                hir::intravisit::walk_ty(self, t)
-            }
-        }
-
-        let mut found = false;
-        for bound in hir_bounds {
-            found |= hir::intravisit::walk_param_bound(&mut TraitInfoCollector, bound).is_break();
-        }
-        found |= hir::intravisit::walk_generics(&mut TraitInfoCollector, hir_generics).is_break();
-        found
-    }
-
-    /// Implicitly add `Self: DefaultAutoTrait` clauses on trait associated items if
-    /// they are not added as super trait bounds to the trait itself. See
-    /// `requires_default_supertraits` for more information.
-    pub(crate) fn add_default_trait_item_bounds(
-        &self,
-        trait_item: &hir::TraitItem<'tcx>,
-        bounds: &mut Vec<(ty::Clause<'tcx>, Span)>,
-    ) {
-        let tcx = self.tcx();
-        if !tcx.sess.opts.unstable_opts.experimental_default_bounds {
-            return;
-        }
-
-        let parent = tcx.local_parent(trait_item.hir_id().owner.def_id);
-        let hir::Node::Item(parent_trait) = tcx.hir_node_by_def_id(parent) else {
-            unreachable!();
-        };
-
-        let (trait_generics, trait_bounds) = match parent_trait.kind {
-            hir::ItemKind::Trait(_, _, _, _, generics, supertraits, _) => (generics, supertraits),
-            hir::ItemKind::TraitAlias(_, generics, supertraits) => (generics, supertraits),
-            _ => unreachable!(),
-        };
-
-        if !self.requires_default_supertraits(trait_bounds, trait_generics) {
-            let self_ty_where_predicates = (parent, trait_item.generics.predicates);
-            self.add_default_traits(
-                bounds,
-                tcx.types.self_param,
-                &[],
-                Some(self_ty_where_predicates),
-                trait_item.span,
-            );
-        }
-    }
-
-    /// Lazily sets `experimental_default_bounds` to true on trait super bounds.
-    /// See `requires_default_supertraits` for more information.
+    /// Adds `experimental_default_bounds` bounds to the supertrait bounds.
     pub(crate) fn add_default_super_traits(
         &self,
         trait_def_id: LocalDefId,
@@ -354,21 +240,21 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         hir_generics: &'tcx hir::Generics<'tcx>,
         span: Span,
     ) {
-        if !self.tcx().sess.opts.unstable_opts.experimental_default_bounds {
+        assert_matches!(self.tcx().def_kind(trait_def_id), DefKind::Trait | DefKind::TraitAlias);
+
+        // Supertraits for auto trait are unsound according to the unstable book:
+        // https://doc.rust-lang.org/beta/unstable-book/language-features/auto-traits.html#supertraits
+        if self.tcx().trait_is_auto(trait_def_id.to_def_id()) {
             return;
         }
 
-        assert!(matches!(self.tcx().def_kind(trait_def_id), DefKind::Trait | DefKind::TraitAlias));
-        if self.requires_default_supertraits(hir_bounds, hir_generics) {
-            let self_ty_where_predicates = (trait_def_id, hir_generics.predicates);
-            self.add_default_traits(
-                bounds,
-                self.tcx().types.self_param,
-                hir_bounds,
-                Some(self_ty_where_predicates),
-                span,
-            );
-        }
+        self.add_default_traits(
+            bounds,
+            self.tcx().types.self_param,
+            hir_bounds,
+            Some((trait_def_id, hir_generics.predicates)),
+            span,
+        );
     }
 
     pub(crate) fn add_default_traits(
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 93b82acf621..0cf9cb7193f 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
@@ -482,7 +482,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 .map(|header| header.trait_ref.instantiate_identity().self_ty())
                 // We don't care about blanket impls.
                 .filter(|self_ty| !self_ty.has_non_region_param())
-                .map(|self_ty| tcx.erase_regions(self_ty).to_string())
+                .map(|self_ty| tcx.erase_and_anonymize_regions(self_ty).to_string())
                 .collect()
         };
         // FIXME: also look at `tcx.generics_of(self.item_def_id()).params` any that
diff --git a/compiler/rustc_hir_typeck/src/cast.rs b/compiler/rustc_hir_typeck/src/cast.rs
index 3eeb0eac023..27540fd1a43 100644
--- a/compiler/rustc_hir_typeck/src/cast.rs
+++ b/compiler/rustc_hir_typeck/src/cast.rs
@@ -851,8 +851,8 @@ impl<'a, 'tcx> CastCheck<'tcx> {
         debug!("check_ptr_ptr_cast m_src={m_src:?} m_dst={m_dst:?}");
         // ptr-ptr cast. metadata must match.
 
-        let src_kind = fcx.tcx.erase_regions(fcx.pointer_kind(m_src.ty, self.span)?);
-        let dst_kind = fcx.tcx.erase_regions(fcx.pointer_kind(m_dst.ty, self.span)?);
+        let src_kind = fcx.tcx.erase_and_anonymize_regions(fcx.pointer_kind(m_src.ty, self.span)?);
+        let dst_kind = fcx.tcx.erase_and_anonymize_regions(fcx.pointer_kind(m_dst.ty, self.span)?);
 
         // We can't cast if target pointer kind is unknown
         let Some(dst_kind) = dst_kind else {
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs
index 74f27e85cba..7a060cafeab 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs
@@ -21,7 +21,6 @@ use rustc_middle::ty::{self, Const, Ty, TyCtxt, TypeVisitableExt};
 use rustc_session::Session;
 use rustc_span::{self, DUMMY_SP, ErrorGuaranteed, Ident, Span, sym};
 use rustc_trait_selection::error_reporting::TypeErrCtxt;
-use rustc_trait_selection::error_reporting::infer::sub_relations::SubRelations;
 use rustc_trait_selection::traits::{
     self, FulfillmentError, ObligationCause, ObligationCauseCode, ObligationCtxt,
 };
@@ -188,14 +187,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     ///
     /// [`InferCtxtErrorExt::err_ctxt`]: rustc_trait_selection::error_reporting::InferCtxtErrorExt::err_ctxt
     pub(crate) fn err_ctxt(&'a self) -> TypeErrCtxt<'a, 'tcx> {
-        let mut sub_relations = SubRelations::default();
-        sub_relations.add_constraints(
-            self,
-            self.fulfillment_cx.borrow_mut().pending_obligations().iter().map(|o| o.predicate),
-        );
         TypeErrCtxt {
             infcx: &self.infcx,
-            sub_relations: RefCell::new(sub_relations),
             typeck_results: Some(self.typeck_results.borrow()),
             fallback_has_occurred: self.fallback_has_occurred.get(),
             normalize_fn_sig: Box::new(|fn_sig| {
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs
index 84ea2ec0f8a..d7ddbcc8b53 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs
@@ -1358,7 +1358,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 .infcx
                 .type_implements_trait(
                     clone_trait_def,
-                    [self.tcx.erase_regions(expected_ty)],
+                    [self.tcx.erase_and_anonymize_regions(expected_ty)],
                     self.param_env,
                 )
                 .must_apply_modulo_regions()
diff --git a/compiler/rustc_hir_typeck/src/inline_asm.rs b/compiler/rustc_hir_typeck/src/inline_asm.rs
index b59c1752c25..c0cd23be690 100644
--- a/compiler/rustc_hir_typeck/src/inline_asm.rs
+++ b/compiler/rustc_hir_typeck/src/inline_asm.rs
@@ -44,7 +44,7 @@ impl<'a, 'tcx> InlineAsmCtxt<'a, 'tcx> {
         if ty.has_non_region_infer() {
             Ty::new_misc_error(self.tcx())
         } else {
-            self.tcx().erase_regions(ty)
+            self.tcx().erase_and_anonymize_regions(ty)
         }
     }
 
diff --git a/compiler/rustc_hir_typeck/src/method/probe.rs b/compiler/rustc_hir_typeck/src/method/probe.rs
index ab584eb7c90..52a8eff984b 100644
--- a/compiler/rustc_hir_typeck/src/method/probe.rs
+++ b/compiler/rustc_hir_typeck/src/method/probe.rs
@@ -403,15 +403,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 // special handling for this "trivial case" is a good idea.
 
                 let infcx = &self.infcx;
-                let (ParamEnvAnd { param_env: _, value: self_ty }, canonical_inference_vars) =
+                let (ParamEnvAnd { param_env: _, value: self_ty }, var_values) =
                     infcx.instantiate_canonical(span, &query_input.canonical);
                 debug!(?self_ty, ?query_input, "probe_op: Mode::Path");
                 MethodAutoderefStepsResult {
                     steps: infcx.tcx.arena.alloc_from_iter([CandidateStep {
-                        self_ty: self.make_query_response_ignoring_pending_obligations(
-                            canonical_inference_vars,
-                            self_ty,
-                        ),
+                        self_ty: self
+                            .make_query_response_ignoring_pending_obligations(var_values, self_ty),
                         autoderefs: 0,
                         from_unsafe_deref: false,
                         unsize: false,
diff --git a/compiler/rustc_hir_typeck/src/writeback.rs b/compiler/rustc_hir_typeck/src/writeback.rs
index d75bc9edab2..90301d1b391 100644
--- a/compiler/rustc_hir_typeck/src/writeback.rs
+++ b/compiler/rustc_hir_typeck/src/writeback.rs
@@ -802,7 +802,7 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
                         format!("unexpected inference variable after writeback: {predicate:?}"),
                     );
                 } else {
-                    let predicate = self.tcx().erase_regions(predicate);
+                    let predicate = self.tcx().erase_and_anonymize_regions(predicate);
                     if cause.has_infer() || cause.has_placeholders() {
                         // We can't use the the obligation cause as it references
                         // information local to this query.
@@ -984,8 +984,8 @@ impl<'cx, 'tcx> Resolver<'cx, 'tcx> {
         // borrowck, and specifically region constraints will be populated during
         // MIR typeck which is run on the new body.
         //
-        // We're not using `tcx.erase_regions` as that also anonymizes bound variables,
-        // regressing borrowck diagnostics.
+        // We're not using `tcx.erase_and_anonymize_regions` as that also
+        // anonymizes bound variables, regressing borrowck diagnostics.
         value = fold_regions(tcx, value, |_, _| tcx.lifetimes.re_erased);
 
         // Normalize consts in writeback, because GCE doesn't normalize eagerly.
diff --git a/compiler/rustc_index/src/idx.rs b/compiler/rustc_index/src/idx.rs
index 33f406e2113..9cd7134659c 100644
--- a/compiler/rustc_index/src/idx.rs
+++ b/compiler/rustc_index/src/idx.rs
@@ -130,7 +130,22 @@ impl<I: Idx, T> IntoSliceIdx<I, [T]> for core::range::RangeFrom<I> {
 impl<I: Idx, T> IntoSliceIdx<I, [T]> for core::range::RangeInclusive<I> {
     type Output = core::range::RangeInclusive<usize>;
     #[inline]
+    #[cfg(bootstrap)]
     fn into_slice_idx(self) -> Self::Output {
         core::range::RangeInclusive { start: self.start.index(), end: self.end.index() }
     }
+    #[inline]
+    #[cfg(not(bootstrap))]
+    fn into_slice_idx(self) -> Self::Output {
+        core::range::RangeInclusive { start: self.start.index(), last: self.last.index() }
+    }
+}
+
+#[cfg(all(feature = "nightly", not(bootstrap)))]
+impl<I: Idx, T> IntoSliceIdx<I, [T]> for core::range::RangeToInclusive<I> {
+    type Output = core::range::RangeToInclusive<usize>;
+    #[inline]
+    fn into_slice_idx(self) -> Self::Output {
+        core::range::RangeToInclusive { last: self.last.index() }
+    }
 }
diff --git a/compiler/rustc_index/src/interval.rs b/compiler/rustc_index/src/interval.rs
index 0225c5c4f32..dda5253e7c5 100644
--- a/compiler/rustc_index/src/interval.rs
+++ b/compiler/rustc_index/src/interval.rs
@@ -140,6 +140,30 @@ impl<I: Idx> IntervalSet<I> {
         result
     }
 
+    /// Specialized version of `insert` when we know that the inserted point is *after* any
+    /// contained.
+    pub fn append(&mut self, point: I) {
+        let point = point.index() as u32;
+
+        if let Some((_, last_end)) = self.map.last_mut() {
+            assert!(*last_end <= point);
+            if point == *last_end {
+                // The point is already in the set.
+            } else if point == *last_end + 1 {
+                *last_end = point;
+            } else {
+                self.map.push((point, point));
+            }
+        } else {
+            self.map.push((point, point));
+        }
+
+        debug_assert!(
+            self.check_invariants(),
+            "wrong intervals after append {point:?} to {self:?}"
+        );
+    }
+
     pub fn contains(&self, needle: I) -> bool {
         let needle = needle.index() as u32;
         let Some(last) = self.map.partition_point(|r| r.0 <= needle).checked_sub(1) else {
@@ -176,6 +200,32 @@ impl<I: Idx> IntervalSet<I> {
         })
     }
 
+    pub fn disjoint(&self, other: &IntervalSet<I>) -> bool
+    where
+        I: Step,
+    {
+        let helper = move || {
+            let mut self_iter = self.iter_intervals();
+            let mut other_iter = other.iter_intervals();
+
+            let mut self_current = self_iter.next()?;
+            let mut other_current = other_iter.next()?;
+
+            loop {
+                if self_current.end <= other_current.start {
+                    self_current = self_iter.next()?;
+                    continue;
+                }
+                if other_current.end <= self_current.start {
+                    other_current = other_iter.next()?;
+                    continue;
+                }
+                return Some(false);
+            }
+        };
+        helper().unwrap_or(true)
+    }
+
     pub fn is_empty(&self) -> bool {
         self.map.is_empty()
     }
@@ -325,6 +375,10 @@ impl<R: Idx, C: Step + Idx> SparseIntervalMatrix<R, C> {
         self.ensure_row(row).insert(point)
     }
 
+    pub fn append(&mut self, row: R, point: C) {
+        self.ensure_row(row).append(point)
+    }
+
     pub fn contains(&self, row: R, point: C) -> bool {
         self.row(row).is_some_and(|r| r.contains(point))
     }
diff --git a/compiler/rustc_infer/src/infer/canonical/canonicalizer.rs b/compiler/rustc_infer/src/infer/canonical/canonicalizer.rs
index 3ad14dc79d5..3c5e4a91c98 100644
--- a/compiler/rustc_infer/src/infer/canonical/canonicalizer.rs
+++ b/compiler/rustc_infer/src/infer/canonical/canonicalizer.rs
@@ -6,6 +6,7 @@
 //! [c]: https://rust-lang.github.io/chalk/book/canonical_queries/canonicalization.html
 
 use rustc_data_structures::fx::FxHashMap;
+use rustc_data_structures::sso::SsoHashMap;
 use rustc_index::Idx;
 use rustc_middle::bug;
 use rustc_middle::ty::{
@@ -17,7 +18,7 @@ use tracing::debug;
 
 use crate::infer::InferCtxt;
 use crate::infer::canonical::{
-    Canonical, CanonicalQueryInput, CanonicalTyVarKind, CanonicalVarKind, OriginalQueryValues,
+    Canonical, CanonicalQueryInput, CanonicalVarKind, OriginalQueryValues,
 };
 
 impl<'tcx> InferCtxt<'tcx> {
@@ -293,6 +294,13 @@ struct Canonicalizer<'cx, 'tcx> {
     // Note that indices is only used once `var_values` is big enough to be
     // heap-allocated.
     indices: FxHashMap<GenericArg<'tcx>, BoundVar>,
+    /// Maps each `sub_unification_table_root_var` to the index of the first
+    /// variable which used it.
+    ///
+    /// This means in case two type variables have the same sub relations root,
+    /// we set the `sub_root` of the second variable to the position of the first.
+    /// Otherwise the `sub_root` of each type variable is just its own position.
+    sub_root_lookup_table: SsoHashMap<ty::TyVid, usize>,
     canonicalize_mode: &'cx dyn CanonicalizeMode,
     needs_canonical_flags: TypeFlags,
 
@@ -361,10 +369,8 @@ impl<'cx, 'tcx> TypeFolder<TyCtxt<'tcx>> for Canonicalizer<'cx, 'tcx> {
                             // FIXME: perf problem described in #55921.
                             ui = ty::UniverseIndex::ROOT;
                         }
-                        self.canonicalize_ty_var(
-                            CanonicalVarKind::Ty(CanonicalTyVarKind::General(ui)),
-                            t,
-                        )
+                        let sub_root = self.get_or_insert_sub_root(vid);
+                        self.canonicalize_ty_var(CanonicalVarKind::Ty { ui, sub_root }, t)
                     }
                 }
             }
@@ -374,7 +380,7 @@ impl<'cx, 'tcx> TypeFolder<TyCtxt<'tcx>> for Canonicalizer<'cx, 'tcx> {
                 if nt != t {
                     return self.fold_ty(nt);
                 } else {
-                    self.canonicalize_ty_var(CanonicalVarKind::Ty(CanonicalTyVarKind::Int), t)
+                    self.canonicalize_ty_var(CanonicalVarKind::Int, t)
                 }
             }
             ty::Infer(ty::FloatVar(vid)) => {
@@ -382,7 +388,7 @@ impl<'cx, 'tcx> TypeFolder<TyCtxt<'tcx>> for Canonicalizer<'cx, 'tcx> {
                 if nt != t {
                     return self.fold_ty(nt);
                 } else {
-                    self.canonicalize_ty_var(CanonicalVarKind::Ty(CanonicalTyVarKind::Float), t)
+                    self.canonicalize_ty_var(CanonicalVarKind::Float, t)
                 }
             }
 
@@ -562,6 +568,7 @@ impl<'cx, 'tcx> Canonicalizer<'cx, 'tcx> {
             variables: SmallVec::from_slice(base.variables),
             query_state,
             indices: FxHashMap::default(),
+            sub_root_lookup_table: Default::default(),
             binder_index: ty::INNERMOST,
         };
         if canonicalizer.query_state.var_values.spilled() {
@@ -660,6 +667,13 @@ impl<'cx, 'tcx> Canonicalizer<'cx, 'tcx> {
         }
     }
 
+    fn get_or_insert_sub_root(&mut self, vid: ty::TyVid) -> ty::BoundVar {
+        let root_vid = self.infcx.unwrap().sub_unification_table_root_var(vid);
+        let idx =
+            *self.sub_root_lookup_table.entry(root_vid).or_insert_with(|| self.variables.len());
+        ty::BoundVar::from(idx)
+    }
+
     /// Replaces the universe indexes used in `var_values` with their index in
     /// `query_state.universe_map`. This minimizes the maximum universe used in
     /// the canonicalized value.
@@ -679,11 +693,11 @@ impl<'cx, 'tcx> Canonicalizer<'cx, 'tcx> {
         self.variables
             .iter()
             .map(|&kind| match kind {
-                CanonicalVarKind::Ty(CanonicalTyVarKind::Int | CanonicalTyVarKind::Float) => {
+                CanonicalVarKind::Int | CanonicalVarKind::Float => {
                     return kind;
                 }
-                CanonicalVarKind::Ty(CanonicalTyVarKind::General(u)) => {
-                    CanonicalVarKind::Ty(CanonicalTyVarKind::General(reverse_universe_map[&u]))
+                CanonicalVarKind::Ty { ui, sub_root } => {
+                    CanonicalVarKind::Ty { ui: reverse_universe_map[&ui], sub_root }
                 }
                 CanonicalVarKind::Region(u) => CanonicalVarKind::Region(reverse_universe_map[&u]),
                 CanonicalVarKind::Const(u) => CanonicalVarKind::Const(reverse_universe_map[&u]),
diff --git a/compiler/rustc_infer/src/infer/canonical/mod.rs b/compiler/rustc_infer/src/infer/canonical/mod.rs
index 79a2aa54ef8..f99f228e19d 100644
--- a/compiler/rustc_infer/src/infer/canonical/mod.rs
+++ b/compiler/rustc_infer/src/infer/canonical/mod.rs
@@ -24,7 +24,7 @@
 pub use instantiate::CanonicalExt;
 use rustc_index::IndexVec;
 pub use rustc_middle::infer::canonical::*;
-use rustc_middle::ty::{self, GenericArg, List, Ty, TyCtxt, TypeFoldable};
+use rustc_middle::ty::{self, GenericArg, Ty, TyCtxt, TypeFoldable};
 use rustc_span::Span;
 
 use crate::infer::{InferCtxt, RegionVariableOrigin};
@@ -67,30 +67,12 @@ impl<'tcx> InferCtxt<'tcx> {
             .chain((1..=canonical.max_universe.as_u32()).map(|_| self.create_next_universe()))
             .collect();
 
-        let canonical_inference_vars =
-            self.instantiate_canonical_vars(span, canonical.variables, |ui| universes[ui]);
-        let result = canonical.instantiate(self.tcx, &canonical_inference_vars);
-        (result, canonical_inference_vars)
-    }
-
-    /// Given the "infos" about the canonical variables from some
-    /// canonical, creates fresh variables with the same
-    /// characteristics (see `instantiate_canonical_var` for
-    /// details). You can then use `instantiate` to instantiate the
-    /// canonical variable with these inference variables.
-    fn instantiate_canonical_vars(
-        &self,
-        span: Span,
-        variables: &List<CanonicalVarKind<'tcx>>,
-        universe_map: impl Fn(ty::UniverseIndex) -> ty::UniverseIndex,
-    ) -> CanonicalVarValues<'tcx> {
-        CanonicalVarValues {
-            var_values: self.tcx.mk_args_from_iter(
-                variables
-                    .iter()
-                    .map(|kind| self.instantiate_canonical_var(span, kind, &universe_map)),
-            ),
-        }
+        let var_values =
+            CanonicalVarValues::instantiate(self.tcx, &canonical.variables, |var_values, info| {
+                self.instantiate_canonical_var(span, info, &var_values, |ui| universes[ui])
+            });
+        let result = canonical.instantiate(self.tcx, &var_values);
+        (result, var_values)
     }
 
     /// Given the "info" about a canonical variable, creates a fresh
@@ -105,21 +87,27 @@ impl<'tcx> InferCtxt<'tcx> {
         &self,
         span: Span,
         kind: CanonicalVarKind<'tcx>,
+        previous_var_values: &[GenericArg<'tcx>],
         universe_map: impl Fn(ty::UniverseIndex) -> ty::UniverseIndex,
     ) -> GenericArg<'tcx> {
         match kind {
-            CanonicalVarKind::Ty(ty_kind) => {
-                let ty = match ty_kind {
-                    CanonicalTyVarKind::General(ui) => {
-                        self.next_ty_var_in_universe(span, universe_map(ui))
+            CanonicalVarKind::Ty { ui, sub_root } => {
+                let vid = self.next_ty_vid_in_universe(span, universe_map(ui));
+                // If this inference variable is related to an earlier variable
+                // via subtyping, we need to add that info to the inference context.
+                if let Some(prev) = previous_var_values.get(sub_root.as_usize()) {
+                    if let &ty::Infer(ty::TyVar(sub_root)) = prev.expect_ty().kind() {
+                        self.sub_unify_ty_vids_raw(vid, sub_root);
+                    } else {
+                        unreachable!()
                     }
+                }
+                Ty::new_var(self.tcx, vid).into()
+            }
 
-                    CanonicalTyVarKind::Int => self.next_int_var(),
+            CanonicalVarKind::Int => self.next_int_var().into(),
 
-                    CanonicalTyVarKind::Float => self.next_float_var(),
-                };
-                ty.into()
-            }
+            CanonicalVarKind::Float => self.next_float_var().into(),
 
             CanonicalVarKind::PlaceholderTy(ty::PlaceholderType { universe, bound }) => {
                 let universe_mapped = universe_map(universe);
diff --git a/compiler/rustc_infer/src/infer/canonical/query_response.rs b/compiler/rustc_infer/src/infer/canonical/query_response.rs
index 09578598114..5d1b4be9e57 100644
--- a/compiler/rustc_infer/src/infer/canonical/query_response.rs
+++ b/compiler/rustc_infer/src/infer/canonical/query_response.rs
@@ -13,6 +13,7 @@ use std::iter;
 use rustc_index::{Idx, IndexVec};
 use rustc_middle::arena::ArenaAllocatable;
 use rustc_middle::bug;
+use rustc_middle::infer::canonical::CanonicalVarKind;
 use rustc_middle::ty::{self, BoundVar, GenericArg, GenericArgKind, Ty, TyCtxt, TypeFoldable};
 use tracing::{debug, instrument};
 
@@ -413,26 +414,27 @@ impl<'tcx> InferCtxt<'tcx> {
         let mut opt_values: IndexVec<BoundVar, Option<GenericArg<'tcx>>> =
             IndexVec::from_elem_n(None, query_response.variables.len());
 
-        // In terms of our example above, we are iterating over pairs like:
-        // [(?A, Vec<?0>), ('static, '?1), (?B, ?0)]
         for (original_value, result_value) in iter::zip(&original_values.var_values, result_values)
         {
             match result_value.kind() {
                 GenericArgKind::Type(result_value) => {
-                    // e.g., here `result_value` might be `?0` in the example above...
-                    if let ty::Bound(debruijn, b) = *result_value.kind() {
-                        // ...in which case we would set `canonical_vars[0]` to `Some(?U)`.
-
+                    // We disable the instantiation guess for inference variables
+                    // and only use it for placeholders. We need to handle the
+                    // `sub_root` of type inference variables which would make this
+                    // more involved. They are also a lot rarer than region variables.
+                    if let ty::Bound(debruijn, b) = *result_value.kind()
+                        && !matches!(
+                            query_response.variables[b.var.as_usize()],
+                            CanonicalVarKind::Ty { .. }
+                        )
+                    {
                         // We only allow a `ty::INNERMOST` index in generic parameters.
                         assert_eq!(debruijn, ty::INNERMOST);
                         opt_values[b.var] = Some(*original_value);
                     }
                 }
                 GenericArgKind::Lifetime(result_value) => {
-                    // e.g., here `result_value` might be `'?1` in the example above...
                     if let ty::ReBound(debruijn, b) = result_value.kind() {
-                        // ... in which case we would set `canonical_vars[0]` to `Some('static)`.
-
                         // We only allow a `ty::INNERMOST` index in generic parameters.
                         assert_eq!(debruijn, ty::INNERMOST);
                         opt_values[b.var] = Some(*original_value);
@@ -440,8 +442,6 @@ impl<'tcx> InferCtxt<'tcx> {
                 }
                 GenericArgKind::Const(result_value) => {
                     if let ty::ConstKind::Bound(debruijn, b) = result_value.kind() {
-                        // ...in which case we would set `canonical_vars[0]` to `Some(const X)`.
-
                         // We only allow a `ty::INNERMOST` index in generic parameters.
                         assert_eq!(debruijn, ty::INNERMOST);
                         opt_values[b.var] = Some(*original_value);
@@ -453,39 +453,36 @@ impl<'tcx> InferCtxt<'tcx> {
         // Create result arguments: if we found a value for a
         // given variable in the loop above, use that. Otherwise, use
         // a fresh inference variable.
-        let result_args = CanonicalVarValues {
-            var_values: self.tcx.mk_args_from_iter(
-                query_response.variables.iter().enumerate().map(|(index, var_kind)| {
-                    if var_kind.universe() != ty::UniverseIndex::ROOT {
-                        // A variable from inside a binder of the query. While ideally these shouldn't
-                        // exist at all, we have to deal with them for now.
-                        self.instantiate_canonical_var(cause.span, var_kind, |u| {
-                            universe_map[u.as_usize()]
-                        })
-                    } else if var_kind.is_existential() {
-                        match opt_values[BoundVar::new(index)] {
-                            Some(k) => k,
-                            None => self.instantiate_canonical_var(cause.span, var_kind, |u| {
-                                universe_map[u.as_usize()]
-                            }),
-                        }
-                    } else {
-                        // For placeholders which were already part of the input, we simply map this
-                        // universal bound variable back the placeholder of the input.
-                        opt_values[BoundVar::new(index)].expect(
-                            "expected placeholder to be unified with itself during response",
-                        )
-                    }
-                }),
-            ),
-        };
+        let tcx = self.tcx;
+        let variables = query_response.variables;
+        let var_values = CanonicalVarValues::instantiate(tcx, variables, |var_values, kind| {
+            if kind.universe() != ty::UniverseIndex::ROOT {
+                // A variable from inside a binder of the query. While ideally these shouldn't
+                // exist at all, we have to deal with them for now.
+                self.instantiate_canonical_var(cause.span, kind, &var_values, |u| {
+                    universe_map[u.as_usize()]
+                })
+            } else if kind.is_existential() {
+                match opt_values[BoundVar::new(var_values.len())] {
+                    Some(k) => k,
+                    None => self.instantiate_canonical_var(cause.span, kind, &var_values, |u| {
+                        universe_map[u.as_usize()]
+                    }),
+                }
+            } else {
+                // For placeholders which were already part of the input, we simply map this
+                // universal bound variable back the placeholder of the input.
+                opt_values[BoundVar::new(var_values.len())]
+                    .expect("expected placeholder to be unified with itself during response")
+            }
+        });
 
         let mut obligations = PredicateObligations::new();
 
         // Carry all newly resolved opaque types to the caller's scope
         for &(a, b) in &query_response.value.opaque_types {
-            let a = instantiate_value(self.tcx, &result_args, a);
-            let b = instantiate_value(self.tcx, &result_args, b);
+            let a = instantiate_value(self.tcx, &var_values, a);
+            let b = instantiate_value(self.tcx, &var_values, b);
             debug!(?a, ?b, "constrain opaque type");
             // We use equate here instead of, for example, just registering the
             // opaque type's hidden value directly, because the hidden type may have been an inference
@@ -502,7 +499,7 @@ impl<'tcx> InferCtxt<'tcx> {
             );
         }
 
-        Ok(InferOk { value: result_args, obligations })
+        Ok(InferOk { value: var_values, obligations })
     }
 
     /// Given a "guess" at the values for the canonical variables in
diff --git a/compiler/rustc_infer/src/infer/context.rs b/compiler/rustc_infer/src/infer/context.rs
index 8265fccabc9..14cc590720a 100644
--- a/compiler/rustc_infer/src/infer/context.rs
+++ b/compiler/rustc_infer/src/infer/context.rs
@@ -59,6 +59,10 @@ impl<'tcx> rustc_type_ir::InferCtxtLike for InferCtxt<'tcx> {
         self.root_var(var)
     }
 
+    fn sub_unification_table_root_var(&self, var: ty::TyVid) -> ty::TyVid {
+        self.sub_unification_table_root_var(var)
+    }
+
     fn root_const_var(&self, var: ty::ConstVid) -> ty::ConstVid {
         self.root_const_var(var)
     }
@@ -179,6 +183,10 @@ impl<'tcx> rustc_type_ir::InferCtxtLike for InferCtxt<'tcx> {
         self.inner.borrow_mut().type_variables().equate(a, b);
     }
 
+    fn sub_unify_ty_vids_raw(&self, a: ty::TyVid, b: ty::TyVid) {
+        self.sub_unify_ty_vids_raw(a, b);
+    }
+
     fn equate_int_vids_raw(&self, a: ty::IntVid, b: ty::IntVid) {
         self.inner.borrow_mut().int_unification_table().union(a, b);
     }
diff --git a/compiler/rustc_infer/src/infer/mod.rs b/compiler/rustc_infer/src/infer/mod.rs
index d105d24bed7..9d3886aff1c 100644
--- a/compiler/rustc_infer/src/infer/mod.rs
+++ b/compiler/rustc_infer/src/infer/mod.rs
@@ -764,6 +764,7 @@ impl<'tcx> InferCtxt<'tcx> {
         let r_b = self.shallow_resolve(predicate.skip_binder().b);
         match (r_a.kind(), r_b.kind()) {
             (&ty::Infer(ty::TyVar(a_vid)), &ty::Infer(ty::TyVar(b_vid))) => {
+                self.sub_unify_ty_vids_raw(a_vid, b_vid);
                 return Err((a_vid, b_vid));
             }
             _ => {}
@@ -1128,6 +1129,14 @@ impl<'tcx> InferCtxt<'tcx> {
         self.inner.borrow_mut().type_variables().root_var(var)
     }
 
+    pub fn sub_unify_ty_vids_raw(&self, a: ty::TyVid, b: ty::TyVid) {
+        self.inner.borrow_mut().type_variables().sub_unify(a, b);
+    }
+
+    pub fn sub_unification_table_root_var(&self, var: ty::TyVid) -> ty::TyVid {
+        self.inner.borrow_mut().type_variables().sub_unification_table_root_var(var)
+    }
+
     pub fn root_const_var(&self, var: ty::ConstVid) -> ty::ConstVid {
         self.inner.borrow_mut().const_unification_table().find(var).vid
     }
diff --git a/compiler/rustc_infer/src/infer/outlives/test_type_match.rs b/compiler/rustc_infer/src/infer/outlives/test_type_match.rs
index bfdd282d7e1..f06eb58a371 100644
--- a/compiler/rustc_infer/src/infer/outlives/test_type_match.rs
+++ b/compiler/rustc_infer/src/infer/outlives/test_type_match.rs
@@ -76,7 +76,7 @@ pub(super) fn can_match_erased_ty<'tcx>(
     erased_ty: Ty<'tcx>,
 ) -> bool {
     assert!(!outlives_predicate.has_escaping_bound_vars());
-    let erased_outlives_predicate = tcx.erase_regions(outlives_predicate);
+    let erased_outlives_predicate = tcx.erase_and_anonymize_regions(outlives_predicate);
     let outlives_ty = erased_outlives_predicate.skip_binder().0;
     if outlives_ty == erased_ty {
         // pointless micro-optimization
diff --git a/compiler/rustc_infer/src/infer/outlives/verify.rs b/compiler/rustc_infer/src/infer/outlives/verify.rs
index 69feecfe30a..f67b99cb3f8 100644
--- a/compiler/rustc_infer/src/infer/outlives/verify.rs
+++ b/compiler/rustc_infer/src/infer/outlives/verify.rs
@@ -96,7 +96,7 @@ impl<'cx, 'tcx> VerifyBoundCx<'cx, 'tcx> {
         &self,
         alias_ty: ty::AliasTy<'tcx>,
     ) -> Vec<ty::PolyTypeOutlivesPredicate<'tcx>> {
-        let erased_alias_ty = self.tcx.erase_regions(alias_ty.to_ty(self.tcx));
+        let erased_alias_ty = self.tcx.erase_and_anonymize_regions(alias_ty.to_ty(self.tcx));
         self.declared_generic_bounds_from_env_for_erased_ty(erased_alias_ty)
     }
 
@@ -241,7 +241,7 @@ impl<'cx, 'tcx> VerifyBoundCx<'cx, 'tcx> {
             }
 
             let p_ty = p.to_ty(tcx);
-            let erased_p_ty = self.tcx.erase_regions(p_ty);
+            let erased_p_ty = self.tcx.erase_and_anonymize_regions(p_ty);
             (erased_p_ty == erased_ty).then_some(ty::Binder::dummy(ty::OutlivesPredicate(p_ty, r)))
         }));
 
diff --git a/compiler/rustc_infer/src/infer/relate/generalize.rs b/compiler/rustc_infer/src/infer/relate/generalize.rs
index a000bb1123c..cc41957c110 100644
--- a/compiler/rustc_infer/src/infer/relate/generalize.rs
+++ b/compiler/rustc_infer/src/infer/relate/generalize.rs
@@ -6,8 +6,8 @@ use rustc_hir::def_id::DefId;
 use rustc_middle::bug;
 use rustc_middle::ty::error::TypeError;
 use rustc_middle::ty::{
-    self, AliasRelationDirection, InferConst, MaxUniverse, Term, Ty, TyCtxt, TypeVisitable,
-    TypeVisitableExt, TypingMode,
+    self, AliasRelationDirection, InferConst, Term, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable,
+    TypeVisitableExt, TypeVisitor, TypingMode,
 };
 use rustc_span::Span;
 use tracing::{debug, instrument, warn};
@@ -290,6 +290,45 @@ impl<'tcx> InferCtxt<'tcx> {
     }
 }
 
+/// Finds the max universe present
+struct MaxUniverse {
+    max_universe: ty::UniverseIndex,
+}
+
+impl MaxUniverse {
+    fn new() -> Self {
+        MaxUniverse { max_universe: ty::UniverseIndex::ROOT }
+    }
+
+    fn max_universe(self) -> ty::UniverseIndex {
+        self.max_universe
+    }
+}
+
+impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for MaxUniverse {
+    fn visit_ty(&mut self, t: Ty<'tcx>) {
+        if let ty::Placeholder(placeholder) = t.kind() {
+            self.max_universe = self.max_universe.max(placeholder.universe);
+        }
+
+        t.super_visit_with(self)
+    }
+
+    fn visit_const(&mut self, c: ty::Const<'tcx>) {
+        if let ty::ConstKind::Placeholder(placeholder) = c.kind() {
+            self.max_universe = self.max_universe.max(placeholder.universe);
+        }
+
+        c.super_visit_with(self)
+    }
+
+    fn visit_region(&mut self, r: ty::Region<'tcx>) {
+        if let ty::RePlaceholder(placeholder) = r.kind() {
+            self.max_universe = self.max_universe.max(placeholder.universe);
+        }
+    }
+}
+
 /// The "generalizer" is used when handling inference variables.
 ///
 /// The basic strategy for handling a constraint like `?A <: B` is to
@@ -519,6 +558,10 @@ impl<'tcx> TypeRelation<TyCtxt<'tcx>> for Generalizer<'_, 'tcx> {
                             let origin = inner.type_variables().var_origin(vid);
                             let new_var_id =
                                 inner.type_variables().new_var(self.for_universe, origin);
+                            // Record that `vid` and `new_var_id` have to be subtypes
+                            // of each other. This is currently only used for diagnostics.
+                            // To see why, see the docs in the `type_variables` module.
+                            inner.type_variables().sub_unify(vid, new_var_id);
                             // If we're in the new solver and create a new inference
                             // variable inside of an alias we eagerly constrain that
                             // inference variable to prevent unexpected ambiguity errors.
diff --git a/compiler/rustc_infer/src/infer/snapshot/undo_log.rs b/compiler/rustc_infer/src/infer/snapshot/undo_log.rs
index fcc0ab3af41..22c815fb87c 100644
--- a/compiler/rustc_infer/src/infer/snapshot/undo_log.rs
+++ b/compiler/rustc_infer/src/infer/snapshot/undo_log.rs
@@ -20,7 +20,7 @@ pub struct Snapshot<'tcx> {
 pub(crate) enum UndoLog<'tcx> {
     DuplicateOpaqueType,
     OpaqueTypes(OpaqueTypeKey<'tcx>, Option<OpaqueHiddenType<'tcx>>),
-    TypeVariables(sv::UndoLog<ut::Delegate<type_variable::TyVidEqKey<'tcx>>>),
+    TypeVariables(type_variable::UndoLog<'tcx>),
     ConstUnificationTable(sv::UndoLog<ut::Delegate<ConstVidKey<'tcx>>>),
     IntUnificationTable(sv::UndoLog<ut::Delegate<ty::IntVid>>),
     FloatUnificationTable(sv::UndoLog<ut::Delegate<ty::FloatVid>>),
@@ -49,6 +49,8 @@ impl_from! {
     RegionConstraintCollector(region_constraints::UndoLog<'tcx>),
 
     TypeVariables(sv::UndoLog<ut::Delegate<type_variable::TyVidEqKey<'tcx>>>),
+    TypeVariables(sv::UndoLog<ut::Delegate<type_variable::TyVidSubKey>>),
+    TypeVariables(type_variable::UndoLog<'tcx>),
     IntUnificationTable(sv::UndoLog<ut::Delegate<ty::IntVid>>),
     FloatUnificationTable(sv::UndoLog<ut::Delegate<ty::FloatVid>>),
 
diff --git a/compiler/rustc_infer/src/infer/type_variable.rs b/compiler/rustc_infer/src/infer/type_variable.rs
index 6f6791804d3..65f77fe8e25 100644
--- a/compiler/rustc_infer/src/infer/type_variable.rs
+++ b/compiler/rustc_infer/src/infer/type_variable.rs
@@ -13,12 +13,48 @@ use tracing::debug;
 
 use crate::infer::InferCtxtUndoLogs;
 
+/// Represents a single undo-able action that affects a type inference variable.
+#[derive(Clone)]
+pub(crate) enum UndoLog<'tcx> {
+    EqRelation(sv::UndoLog<ut::Delegate<TyVidEqKey<'tcx>>>),
+    SubRelation(sv::UndoLog<ut::Delegate<TyVidSubKey>>),
+}
+
+/// Convert from a specific kind of undo to the more general UndoLog
+impl<'tcx> From<sv::UndoLog<ut::Delegate<TyVidEqKey<'tcx>>>> for UndoLog<'tcx> {
+    fn from(l: sv::UndoLog<ut::Delegate<TyVidEqKey<'tcx>>>) -> Self {
+        UndoLog::EqRelation(l)
+    }
+}
+
+/// Convert from a specific kind of undo to the more general UndoLog
+impl<'tcx> From<sv::UndoLog<ut::Delegate<TyVidSubKey>>> for UndoLog<'tcx> {
+    fn from(l: sv::UndoLog<ut::Delegate<TyVidSubKey>>) -> Self {
+        UndoLog::SubRelation(l)
+    }
+}
+
 impl<'tcx> Rollback<sv::UndoLog<ut::Delegate<TyVidEqKey<'tcx>>>> for TypeVariableStorage<'tcx> {
     fn reverse(&mut self, undo: sv::UndoLog<ut::Delegate<TyVidEqKey<'tcx>>>) {
         self.eq_relations.reverse(undo)
     }
 }
 
+impl<'tcx> Rollback<sv::UndoLog<ut::Delegate<TyVidSubKey>>> for TypeVariableStorage<'tcx> {
+    fn reverse(&mut self, undo: sv::UndoLog<ut::Delegate<TyVidSubKey>>) {
+        self.sub_unification_table.reverse(undo)
+    }
+}
+
+impl<'tcx> Rollback<UndoLog<'tcx>> for TypeVariableStorage<'tcx> {
+    fn reverse(&mut self, undo: UndoLog<'tcx>) {
+        match undo {
+            UndoLog::EqRelation(undo) => self.eq_relations.reverse(undo),
+            UndoLog::SubRelation(undo) => self.sub_unification_table.reverse(undo),
+        }
+    }
+}
+
 #[derive(Clone, Default)]
 pub(crate) struct TypeVariableStorage<'tcx> {
     /// The origins of each type variable.
@@ -27,6 +63,25 @@ pub(crate) struct TypeVariableStorage<'tcx> {
     /// constraint `?X == ?Y`. This table also stores, for each key,
     /// the known value.
     eq_relations: ut::UnificationTableStorage<TyVidEqKey<'tcx>>,
+    /// Only used by `-Znext-solver` and for diagnostics. Tracks whether
+    /// type variables are related via subtyping at all, ignoring which of
+    /// the two is the subtype.
+    ///
+    /// When reporting ambiguity errors, we sometimes want to
+    /// treat all inference vars which are subtypes of each
+    /// others as if they are equal. For this case we compute
+    /// the transitive closure of our subtype obligations here.
+    ///
+    /// E.g. when encountering ambiguity errors, we want to suggest
+    /// specifying some method argument or to add a type annotation
+    /// to a local variable. Because subtyping cannot change the
+    /// shape of a type, it's fine if the cause of the ambiguity error
+    /// is only related to the suggested variable via subtyping.
+    ///
+    /// Even for something like `let x = returns_arg(); x.method();` the
+    /// type of `x` is only a supertype of the argument of `returns_arg`. We
+    /// still want to suggest specifying the type of the argument.
+    sub_unification_table: ut::UnificationTableStorage<TyVidSubKey>,
 }
 
 pub(crate) struct TypeVariableTable<'a, 'tcx> {
@@ -102,13 +157,24 @@ impl<'tcx> TypeVariableTable<'_, 'tcx> {
         self.storage.values[vid].origin
     }
 
-    /// Records that `a == b`, depending on `dir`.
+    /// Records that `a == b`.
     ///
     /// Precondition: neither `a` nor `b` are known.
     pub(crate) fn equate(&mut self, a: ty::TyVid, b: ty::TyVid) {
         debug_assert!(self.probe(a).is_unknown());
         debug_assert!(self.probe(b).is_unknown());
         self.eq_relations().union(a, b);
+        self.sub_unification_table().union(a, b);
+    }
+
+    /// Records that `a` and `b` are related via subtyping. We don't track
+    /// which of the two is the subtype.
+    ///
+    /// Precondition: neither `a` nor `b` are known.
+    pub(crate) fn sub_unify(&mut self, a: ty::TyVid, b: ty::TyVid) {
+        debug_assert!(self.probe(a).is_unknown());
+        debug_assert!(self.probe(b).is_unknown());
+        self.sub_unification_table().union(a, b);
     }
 
     /// Instantiates `vid` with the type `ty`.
@@ -142,6 +208,10 @@ impl<'tcx> TypeVariableTable<'_, 'tcx> {
         origin: TypeVariableOrigin,
     ) -> ty::TyVid {
         let eq_key = self.eq_relations().new_key(TypeVariableValue::Unknown { universe });
+
+        let sub_key = self.sub_unification_table().new_key(());
+        debug_assert_eq!(eq_key.vid, sub_key.vid);
+
         let index = self.storage.values.push(TypeVariableData { origin });
         debug_assert_eq!(eq_key.vid, index);
 
@@ -164,6 +234,18 @@ impl<'tcx> TypeVariableTable<'_, 'tcx> {
         self.eq_relations().find(vid).vid
     }
 
+    /// Returns the "root" variable of `vid` in the `sub_unification_table`
+    /// equivalence table. All type variables that have been are related via
+    /// equality or subtyping will yield the same root variable (per the
+    /// union-find algorithm), so `sub_unification_table_root_var(a)
+    /// == sub_unification_table_root_var(b)` implies that:
+    /// ```text
+    /// exists X. (a <: X || X <: a) && (b <: X || X <: b)
+    /// ```
+    pub(crate) fn sub_unification_table_root_var(&mut self, vid: ty::TyVid) -> ty::TyVid {
+        self.sub_unification_table().find(vid).vid
+    }
+
     /// Retrieves the type to which `vid` has been instantiated, if
     /// any.
     pub(crate) fn probe(&mut self, vid: ty::TyVid) -> TypeVariableValue<'tcx> {
@@ -181,6 +263,11 @@ impl<'tcx> TypeVariableTable<'_, 'tcx> {
         self.storage.eq_relations.with_log(self.undo_log)
     }
 
+    #[inline]
+    fn sub_unification_table(&mut self) -> super::UnificationTable<'_, 'tcx, TyVidSubKey> {
+        self.storage.sub_unification_table.with_log(self.undo_log)
+    }
+
     /// Returns a range of the type variables created during the snapshot.
     pub(crate) fn vars_since_snapshot(
         &mut self,
@@ -243,6 +330,33 @@ impl<'tcx> ut::UnifyKey for TyVidEqKey<'tcx> {
     }
 }
 
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub(crate) struct TyVidSubKey {
+    vid: ty::TyVid,
+}
+
+impl From<ty::TyVid> for TyVidSubKey {
+    #[inline] // make this function eligible for inlining - it is quite hot.
+    fn from(vid: ty::TyVid) -> Self {
+        TyVidSubKey { vid }
+    }
+}
+
+impl ut::UnifyKey for TyVidSubKey {
+    type Value = ();
+    #[inline]
+    fn index(&self) -> u32 {
+        self.vid.as_u32()
+    }
+    #[inline]
+    fn from_index(i: u32) -> TyVidSubKey {
+        TyVidSubKey { vid: ty::TyVid::from_u32(i) }
+    }
+    fn tag() -> &'static str {
+        "TyVidSubKey"
+    }
+}
+
 impl<'tcx> ut::UnifyValue for TypeVariableValue<'tcx> {
     type Error = ut::NoError;
 
diff --git a/compiler/rustc_interface/messages.ftl b/compiler/rustc_interface/messages.ftl
index 4b9c71d7172..d83b18cbc2d 100644
--- a/compiler/rustc_interface/messages.ftl
+++ b/compiler/rustc_interface/messages.ftl
@@ -30,10 +30,6 @@ interface_ignoring_out_dir = ignoring --out-dir flag due to -o flag
 interface_input_file_would_be_overwritten =
     the input file "{$path}" would be overwritten by the generated executable
 
-interface_limit_invalid =
-    `limit` must be a non-negative integer
-    .label = {$error_str}
-
 interface_mixed_bin_crate =
     cannot mix `bin` crate type with others
 
diff --git a/compiler/rustc_interface/src/errors.rs b/compiler/rustc_interface/src/errors.rs
index 6b39b4f1891..d1082eaf617 100644
--- a/compiler/rustc_interface/src/errors.rs
+++ b/compiler/rustc_interface/src/errors.rs
@@ -108,13 +108,3 @@ pub(crate) struct AbiRequiredTargetFeature<'a> {
     pub feature: &'a str,
     pub enabled: &'a str,
 }
-
-#[derive(Diagnostic)]
-#[diag(interface_limit_invalid)]
-pub(crate) struct LimitInvalid<'a> {
-    #[primary_span]
-    pub span: Span,
-    #[label]
-    pub value_span: Span,
-    pub error_str: &'a str,
-}
diff --git a/compiler/rustc_interface/src/limits.rs b/compiler/rustc_interface/src/limits.rs
index 8f01edec09f..10e58f32256 100644
--- a/compiler/rustc_interface/src/limits.rs
+++ b/compiler/rustc_interface/src/limits.rs
@@ -8,78 +8,32 @@
 //! Users can override these limits via an attribute on the crate like
 //! `#![recursion_limit="22"]`. This pass just looks for those attributes.
 
-use std::num::IntErrorKind;
-
-use rustc_ast::attr::AttributeExt;
-use rustc_middle::bug;
+use rustc_hir::attrs::AttributeKind;
+use rustc_hir::limit::Limit;
+use rustc_hir::{Attribute, find_attr};
 use rustc_middle::query::Providers;
-use rustc_session::{Limit, Limits, Session};
-use rustc_span::{Symbol, sym};
-
-use crate::errors::LimitInvalid;
+use rustc_session::Limits;
 
 pub(crate) fn provide(providers: &mut Providers) {
-    providers.limits = |tcx, ()| Limits {
-        recursion_limit: get_recursion_limit(tcx.hir_krate_attrs(), tcx.sess),
-        move_size_limit: get_limit(
-            tcx.hir_krate_attrs(),
-            tcx.sess,
-            sym::move_size_limit,
-            Limit::new(tcx.sess.opts.unstable_opts.move_size_limit.unwrap_or(0)),
-        ),
-        type_length_limit: get_limit(
-            tcx.hir_krate_attrs(),
-            tcx.sess,
-            sym::type_length_limit,
-            Limit::new(2usize.pow(24)),
-        ),
-        pattern_complexity_limit: get_limit(
-            tcx.hir_krate_attrs(),
-            tcx.sess,
-            sym::pattern_complexity_limit,
-            Limit::unlimited(),
-        ),
+    providers.limits = |tcx, ()| {
+        let attrs = tcx.hir_krate_attrs();
+        Limits {
+            recursion_limit: get_recursion_limit(tcx.hir_krate_attrs()),
+            move_size_limit:
+                find_attr!(attrs, AttributeKind::MoveSizeLimit { limit, .. } => *limit)
+                    .unwrap_or(Limit::new(tcx.sess.opts.unstable_opts.move_size_limit.unwrap_or(0))),
+            type_length_limit:
+                find_attr!(attrs, AttributeKind::TypeLengthLimit { limit, .. } => *limit)
+                    .unwrap_or(Limit::new(2usize.pow(24))),
+            pattern_complexity_limit:
+                find_attr!(attrs, AttributeKind::PatternComplexityLimit { limit, .. } => *limit)
+                    .unwrap_or(Limit::unlimited()),
+        }
     }
 }
 
 // This one is separate because it must be read prior to macro expansion.
-pub(crate) fn get_recursion_limit(krate_attrs: &[impl AttributeExt], sess: &Session) -> Limit {
-    get_limit(krate_attrs, sess, sym::recursion_limit, Limit::new(128))
-}
-
-fn get_limit(
-    krate_attrs: &[impl AttributeExt],
-    sess: &Session,
-    name: Symbol,
-    default: Limit,
-) -> Limit {
-    for attr in krate_attrs {
-        if !attr.has_name(name) {
-            continue;
-        }
-
-        if let Some(sym) = attr.value_str() {
-            match sym.as_str().parse() {
-                Ok(n) => return Limit::new(n),
-                Err(e) => {
-                    let error_str = match e.kind() {
-                        IntErrorKind::PosOverflow => "`limit` is too large",
-                        IntErrorKind::Empty => "`limit` must be a non-negative integer",
-                        IntErrorKind::InvalidDigit => "not a valid integer",
-                        IntErrorKind::NegOverflow => {
-                            bug!("`limit` should never negatively overflow")
-                        }
-                        IntErrorKind::Zero => bug!("zero is a valid `limit`"),
-                        kind => bug!("unimplemented IntErrorKind variant: {:?}", kind),
-                    };
-                    sess.dcx().emit_err(LimitInvalid {
-                        span: attr.span(),
-                        value_span: attr.value_span().unwrap(),
-                        error_str,
-                    });
-                }
-            }
-        }
-    }
-    default
+pub(crate) fn get_recursion_limit(attrs: &[Attribute]) -> Limit {
+    find_attr!(attrs, AttributeKind::RecursionLimit { limit, .. } => *limit)
+        .unwrap_or(Limit::new(128))
 }
diff --git a/compiler/rustc_interface/src/passes.rs b/compiler/rustc_interface/src/passes.rs
index cf81a125707..d39219bfd66 100644
--- a/compiler/rustc_interface/src/passes.rs
+++ b/compiler/rustc_interface/src/passes.rs
@@ -6,7 +6,7 @@ use std::sync::{Arc, LazyLock, OnceLock};
 use std::{env, fs, iter};
 
 use rustc_ast as ast;
-use rustc_attr_parsing::{AttributeParser, ShouldEmit, validate_attr};
+use rustc_attr_parsing::{AttributeParser, ShouldEmit};
 use rustc_codegen_ssa::traits::CodegenBackend;
 use rustc_data_structures::jobserver::Proxy;
 use rustc_data_structures::steal::Steal;
@@ -19,6 +19,7 @@ use rustc_fs_util::try_canonicalize;
 use rustc_hir::attrs::AttributeKind;
 use rustc_hir::def_id::{LOCAL_CRATE, StableCrateId, StableCrateIdMap};
 use rustc_hir::definitions::Definitions;
+use rustc_hir::limit::Limit;
 use rustc_incremental::setup_dep_graph;
 use rustc_lint::{BufferedEarlyLint, EarlyCheckNode, LintStore, unerased_lint_store};
 use rustc_metadata::EncodedMetadata;
@@ -31,12 +32,12 @@ use rustc_parse::lexer::StripTokens;
 use rustc_parse::{new_parser_from_file, new_parser_from_source_str, unwrap_or_emit_fatal};
 use rustc_passes::{abi_test, input_stats, layout_test};
 use rustc_resolve::{Resolver, ResolverOutputs};
+use rustc_session::Session;
 use rustc_session::config::{CrateType, Input, OutFileName, OutputFilenames, OutputType};
 use rustc_session::cstore::Untracked;
 use rustc_session::output::{collect_crate_types, filename_for_input};
 use rustc_session::parse::feature_err;
 use rustc_session::search_paths::PathKind;
-use rustc_session::{Limit, Session};
 use rustc_span::{
     DUMMY_SP, ErrorGuaranteed, ExpnKind, FileName, SourceFileHash, SourceFileHashAlgorithm, Span,
     Symbol, sym,
@@ -1255,7 +1256,8 @@ pub fn get_crate_name(sess: &Session, krate_attrs: &[ast::Attribute]) -> Symbol
     // in all code paths that require the crate name very early on, namely before
     // macro expansion.
 
-    let attr_crate_name = parse_crate_name(sess, krate_attrs, ShouldEmit::EarlyFatal);
+    let attr_crate_name =
+        parse_crate_name(sess, krate_attrs, ShouldEmit::EarlyFatal { also_emit_lints: true });
 
     let validate = |name, span| {
         rustc_session::output::validate_crate_name(sess, name, span);
@@ -1316,36 +1318,18 @@ pub(crate) fn parse_crate_name(
 }
 
 fn get_recursion_limit(krate_attrs: &[ast::Attribute], sess: &Session) -> Limit {
-    // We don't permit macro calls inside of the attribute (e.g., #![recursion_limit = `expand!()`])
-    // because that would require expanding this while in the middle of expansion, which needs to
-    // know the limit before expanding.
-    let _ = validate_and_find_value_str_builtin_attr(sym::recursion_limit, sess, krate_attrs);
-    crate::limits::get_recursion_limit(krate_attrs, sess)
-}
-
-/// Validate *all* occurrences of the given "[value-str]" built-in attribute and return the first find.
-///
-/// This validator is intended for built-in attributes whose value needs to be known very early
-/// during compilation (namely, before macro expansion) and it mainly exists to reject macro calls
-/// inside of the attributes, such as in `#![name = expand!()]`. Normal attribute validation happens
-/// during semantic analysis via [`TyCtxt::check_mod_attrs`] which happens *after* macro expansion
-/// when such macro calls (here: `expand`) have already been expanded and we can no longer check for
-/// their presence.
-///
-/// [value-str]: ast::Attribute::value_str
-fn validate_and_find_value_str_builtin_attr(
-    name: Symbol,
-    sess: &Session,
-    krate_attrs: &[ast::Attribute],
-) -> Option<(Symbol, Span)> {
-    let mut result = None;
-    // Validate *all* relevant attributes, not just the first occurrence.
-    for attr in ast::attr::filter_by_name(krate_attrs, name) {
-        let Some(value) = attr.value_str() else {
-            validate_attr::emit_fatal_malformed_builtin_attribute(&sess.psess, attr, name)
-        };
-        // Choose the first occurrence as our result.
-        result.get_or_insert((value, attr.span));
-    }
-    result
+    let attr = AttributeParser::parse_limited_should_emit(
+        sess,
+        &krate_attrs,
+        sym::recursion_limit,
+        DUMMY_SP,
+        rustc_ast::node_id::CRATE_NODE_ID,
+        None,
+        // errors are fatal here, but lints aren't.
+        // If things aren't fatal we continue, and will parse this again.
+        // That makes the same lint trigger again.
+        // So, no lints here to avoid duplicates.
+        ShouldEmit::EarlyFatal { also_emit_lints: false },
+    );
+    crate::limits::get_recursion_limit(attr.as_slice())
 }
diff --git a/compiler/rustc_lint/src/deref_into_dyn_supertrait.rs b/compiler/rustc_lint/src/deref_into_dyn_supertrait.rs
index 943fcc0801b..e1c51ff8299 100644
--- a/compiler/rustc_lint/src/deref_into_dyn_supertrait.rs
+++ b/compiler/rustc_lint/src/deref_into_dyn_supertrait.rs
@@ -78,7 +78,7 @@ impl<'tcx> LateLintPass<'tcx> for DerefIntoDynSupertrait {
         {
             // erase regions in self type for better diagnostic presentation
             let (self_ty, target_principal, supertrait_principal) =
-                tcx.erase_regions((self_ty, target_principal, supertrait_principal));
+                tcx.erase_and_anonymize_regions((self_ty, target_principal, supertrait_principal));
             let label2 = tcx
                 .associated_items(item.owner_id)
                 .find_by_ident_and_kind(
diff --git a/compiler/rustc_lint/src/for_loops_over_fallibles.rs b/compiler/rustc_lint/src/for_loops_over_fallibles.rs
index a56b753bda7..9e1fc598171 100644
--- a/compiler/rustc_lint/src/for_loops_over_fallibles.rs
+++ b/compiler/rustc_lint/src/for_loops_over_fallibles.rs
@@ -176,7 +176,7 @@ fn suggest_question_mark<'tcx>(
         cause,
         param_env,
         // Erase any region vids from the type, which may not be resolved
-        infcx.tcx.erase_regions(ty),
+        infcx.tcx.erase_and_anonymize_regions(ty),
         into_iterator_did,
     );
 
diff --git a/compiler/rustc_lint/src/multiple_supertrait_upcastable.rs b/compiler/rustc_lint/src/multiple_supertrait_upcastable.rs
index 5513c703f1d..93f067d0983 100644
--- a/compiler/rustc_lint/src/multiple_supertrait_upcastable.rs
+++ b/compiler/rustc_lint/src/multiple_supertrait_upcastable.rs
@@ -47,7 +47,8 @@ impl<'tcx> LateLintPass<'tcx> for MultipleSupertraitUpcastable {
                 .explicit_super_predicates_of(def_id)
                 .iter_identity_copied()
                 .filter_map(|(pred, _)| pred.as_trait_clause())
-                .filter(|pred| !cx.tcx.is_lang_item(pred.def_id(), hir::LangItem::MetaSized));
+                .filter(|pred| !cx.tcx.is_lang_item(pred.def_id(), hir::LangItem::MetaSized))
+                .filter(|pred| !cx.tcx.is_default_trait(pred.def_id()));
             if direct_super_traits_iter.count() > 1 {
                 cx.emit_span_lint(
                     MULTIPLE_SUPERTRAIT_UPCASTABLE,
diff --git a/compiler/rustc_lint/src/types.rs b/compiler/rustc_lint/src/types.rs
index a72b802eb5d..88527fa2e6e 100644
--- a/compiler/rustc_lint/src/types.rs
+++ b/compiler/rustc_lint/src/types.rs
@@ -935,7 +935,7 @@ impl<'tcx> LateLintPass<'tcx> for VariantSizeDifferences {
     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
         if let hir::ItemKind::Enum(_, _, ref enum_definition) = it.kind {
             let t = cx.tcx.type_of(it.owner_id).instantiate_identity();
-            let ty = cx.tcx.erase_regions(t);
+            let ty = cx.tcx.erase_and_anonymize_regions(t);
             let Ok(layout) = cx.layout_of(ty) else { return };
             let Variants::Multiple { tag_encoding: TagEncoding::Direct, tag, variants, .. } =
                 &layout.variants
diff --git a/compiler/rustc_llvm/Cargo.toml b/compiler/rustc_llvm/Cargo.toml
index cd352ce3d0f..0dfd1b13df5 100644
--- a/compiler/rustc_llvm/Cargo.toml
+++ b/compiler/rustc_llvm/Cargo.toml
@@ -11,7 +11,7 @@ libc = "0.2.73"
 [build-dependencies]
 # tidy-alphabetical-start
 # `cc` updates often break things, so we pin it here. Cargo enforces "max 1 semver-compat version
-# per crate", so if you change this, you need to also change it in `rustc_codegen_ssa`.
+# per crate", so if you change this, you need to also change it in `rustc_codegen_ssa` and `rustc_windows_rc`.
 cc = "=1.2.16"
 # tidy-alphabetical-end
 
diff --git a/compiler/rustc_llvm/build.rs b/compiler/rustc_llvm/build.rs
index 225ab8c846d..9d21d0d22e3 100644
--- a/compiler/rustc_llvm/build.rs
+++ b/compiler/rustc_llvm/build.rs
@@ -254,7 +254,10 @@ fn main() {
         println!("cargo:rustc-link-lib=kstat");
     }
 
-    if (target.starts_with("arm") && !target.contains("freebsd") && !target.contains("ohos"))
+    if (target.starts_with("arm")
+        && !target.starts_with("arm64")
+        && !target.contains("freebsd")
+        && !target.contains("ohos"))
         || target.starts_with("mips-")
         || target.starts_with("mipsel-")
         || target.starts_with("powerpc-")
diff --git a/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp b/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp
index dd492325814..3bb1533c2fe 100644
--- a/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp
+++ b/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp
@@ -1568,12 +1568,11 @@ extern "C" bool LLVMRustPrepareThinLTOImport(const LLVMRustThinLTOData *Data,
   return true;
 }
 
-extern "C" LLVMRustThinLTOBuffer *
-LLVMRustThinLTOBufferCreate(LLVMModuleRef M, bool is_thin, bool emit_summary) {
+extern "C" LLVMRustThinLTOBuffer *LLVMRustThinLTOBufferCreate(LLVMModuleRef M,
+                                                              bool is_thin) {
   auto Ret = std::make_unique<LLVMRustThinLTOBuffer>();
   {
     auto OS = raw_string_ostream(Ret->data);
-    auto ThinLinkOS = raw_string_ostream(Ret->thin_link_data);
     {
       if (is_thin) {
         PassBuilder PB;
@@ -1587,11 +1586,7 @@ LLVMRustThinLTOBufferCreate(LLVMModuleRef M, bool is_thin, bool emit_summary) {
         PB.registerLoopAnalyses(LAM);
         PB.crossRegisterProxies(LAM, FAM, CGAM, MAM);
         ModulePassManager MPM;
-        // We only pass ThinLinkOS to be filled in if we want the summary,
-        // because otherwise LLVM does extra work and may double-emit some
-        // errors or warnings.
-        MPM.addPass(
-            ThinLTOBitcodeWriterPass(OS, emit_summary ? &ThinLinkOS : nullptr));
+        MPM.addPass(ThinLTOBitcodeWriterPass(OS, nullptr));
         MPM.run(*unwrap(M), MAM);
       } else {
         WriteBitcodeToFile(*unwrap(M), OS);
diff --git a/compiler/rustc_log/Cargo.toml b/compiler/rustc_log/Cargo.toml
index 2332ff9b323..72f68d685cd 100644
--- a/compiler/rustc_log/Cargo.toml
+++ b/compiler/rustc_log/Cargo.toml
@@ -5,13 +5,12 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-# tracing > 0.1.37 have huge binary size / instructions regression
-tracing = "=0.1.37"
+tracing = "0.1.41"
 tracing-subscriber = { version = "0.3.3", default-features = false, features = ["fmt", "env-filter", "smallvec", "parking_lot", "ansi"] }
 tracing-tree = "0.3.1"
 # tidy-alphabetical-end
 
 [features]
 # tidy-alphabetical-start
-max_level_info = ['tracing/max_level_info']
+max_level_info = ['tracing/max_level_info', 'tracing/release_max_level_info']
 # tidy-alphabetical-end
diff --git a/compiler/rustc_middle/src/error.rs b/compiler/rustc_middle/src/error.rs
index 7520bc262c6..dad402ec696 100644
--- a/compiler/rustc_middle/src/error.rs
+++ b/compiler/rustc_middle/src/error.rs
@@ -72,7 +72,7 @@ pub enum TypeMismatchReason {
 #[help]
 pub(crate) struct RecursionLimitReached<'tcx> {
     pub ty: Ty<'tcx>,
-    pub suggested_limit: rustc_session::Limit,
+    pub suggested_limit: rustc_hir::limit::Limit,
 }
 
 #[derive(Diagnostic)]
diff --git a/compiler/rustc_middle/src/infer/canonical.rs b/compiler/rustc_middle/src/infer/canonical.rs
index 4fe4c2dadee..153605ee7f8 100644
--- a/compiler/rustc_middle/src/infer/canonical.rs
+++ b/compiler/rustc_middle/src/infer/canonical.rs
@@ -27,7 +27,6 @@ use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sync::Lock;
 use rustc_macros::{HashStable, TypeFoldable, TypeVisitable};
 pub use rustc_type_ir as ir;
-pub use rustc_type_ir::CanonicalTyVarKind;
 use smallvec::SmallVec;
 
 use crate::mir::ConstraintCategory;
diff --git a/compiler/rustc_middle/src/mir/interpret/allocation.rs b/compiler/rustc_middle/src/mir/interpret/allocation.rs
index 2ea92a39d48..67962813ae4 100644
--- a/compiler/rustc_middle/src/mir/interpret/allocation.rs
+++ b/compiler/rustc_middle/src/mir/interpret/allocation.rs
@@ -724,6 +724,11 @@ impl<Prov: Provenance, Extra, Bytes: AllocBytes> Allocation<Prov, Extra, Bytes>
             }
             // If we get here, we have to check per-byte provenance, and join them together.
             let prov = 'prov: {
+                if !Prov::OFFSET_IS_ADDR {
+                    // FIXME(#146291): We need to ensure that we don't mix different pointers with
+                    // the same provenance.
+                    return Err(AllocError::ReadPartialPointer(range.start));
+                }
                 // Initialize with first fragment. Must have index 0.
                 let Some((mut joint_prov, 0)) = self.provenance.get_byte(range.start, cx) else {
                     break 'prov None;
diff --git a/compiler/rustc_middle/src/mir/interpret/allocation/provenance_map.rs b/compiler/rustc_middle/src/mir/interpret/allocation/provenance_map.rs
index dbbd95408c8..720e58d7aa0 100644
--- a/compiler/rustc_middle/src/mir/interpret/allocation/provenance_map.rs
+++ b/compiler/rustc_middle/src/mir/interpret/allocation/provenance_map.rs
@@ -11,6 +11,7 @@ use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
 use tracing::trace;
 
 use super::{AllocRange, CtfeProvenance, Provenance, alloc_range};
+use crate::mir::interpret::{AllocError, AllocResult};
 
 /// Stores the provenance information of pointers stored in memory.
 #[derive(Clone, PartialEq, Eq, Hash, Debug)]
@@ -137,6 +138,11 @@ impl<Prov: Provenance> ProvenanceMap<Prov> {
         let Some(bytes) = self.bytes.as_deref_mut() else {
             return true;
         };
+        if !Prov::OFFSET_IS_ADDR {
+            // FIXME(#146291): We need to ensure that we don't mix different pointers with
+            // the same provenance.
+            return false;
+        }
         let ptr_size = cx.data_layout().pointer_size();
         while let Some((offset, (prov, _))) = bytes.iter().next().copied() {
             // Check if this fragment starts a pointer.
@@ -285,7 +291,7 @@ impl<Prov: Provenance> ProvenanceMap<Prov> {
         dest: Size,
         count: u64,
         cx: &impl HasDataLayout,
-    ) -> ProvenanceCopy<Prov> {
+    ) -> AllocResult<ProvenanceCopy<Prov>> {
         let shift_offset = move |idx, offset| {
             // compute offset for current repetition
             let dest_offset = dest + src.size * idx; // `Size` operations
@@ -363,6 +369,12 @@ impl<Prov: Provenance> ProvenanceMap<Prov> {
             }
             trace!("byte provenances: {bytes:?}");
 
+            if !bytes.is_empty() && !Prov::OFFSET_IS_ADDR {
+                // FIXME(#146291): We need to ensure that we don't mix different pointers with
+                // the same provenance.
+                return Err(AllocError::ReadPartialPointer(src.start));
+            }
+
             // And again a buffer for the new list on the target side.
             let mut dest_bytes = Vec::with_capacity(bytes.len() * (count as usize));
             for i in 0..count {
@@ -373,7 +385,7 @@ impl<Prov: Provenance> ProvenanceMap<Prov> {
             dest_bytes_box = Some(dest_bytes.into_boxed_slice());
         }
 
-        ProvenanceCopy { dest_ptrs: dest_ptrs_box, dest_bytes: dest_bytes_box }
+        Ok(ProvenanceCopy { dest_ptrs: dest_ptrs_box, dest_bytes: dest_bytes_box })
     }
 
     /// Applies a provenance copy.
diff --git a/compiler/rustc_middle/src/mir/interpret/mod.rs b/compiler/rustc_middle/src/mir/interpret/mod.rs
index bed99a4ff2a..9762e0f21da 100644
--- a/compiler/rustc_middle/src/mir/interpret/mod.rs
+++ b/compiler/rustc_middle/src/mir/interpret/mod.rs
@@ -386,7 +386,16 @@ impl<'tcx> GlobalAlloc<'tcx> {
                         .expect("statics should not have generic parameters");
                     let layout = tcx.layout_of(typing_env.as_query_input(ty)).unwrap();
                     assert!(layout.is_sized());
-                    (layout.size, layout.align.abi)
+
+                    // Take over-alignment from attributes into account.
+                    let align = match tcx.codegen_fn_attrs(def_id).alignment {
+                        Some(align_from_attribute) => {
+                            Ord::max(align_from_attribute, layout.align.abi)
+                        }
+                        None => layout.align.abi,
+                    };
+
+                    (layout.size, align)
                 }
             }
             GlobalAlloc::Memory(alloc) => {
diff --git a/compiler/rustc_middle/src/mir/interpret/queries.rs b/compiler/rustc_middle/src/mir/interpret/queries.rs
index e25f35c59c2..ecf35d9dd6d 100644
--- a/compiler/rustc_middle/src/mir/interpret/queries.rs
+++ b/compiler/rustc_middle/src/mir/interpret/queries.rs
@@ -41,7 +41,7 @@ impl<'tcx> TyCtxt<'tcx> {
         let instance = ty::Instance::new_raw(def_id, args);
         let cid = GlobalId { instance, promoted: None };
         let typing_env = ty::TypingEnv::post_analysis(self, def_id);
-        let inputs = self.erase_regions(typing_env.as_query_input(cid));
+        let inputs = self.erase_and_anonymize_regions(typing_env.as_query_input(cid));
         self.eval_to_allocation_raw(inputs)
     }
 
@@ -172,8 +172,9 @@ impl<'tcx> TyCtxt<'tcx> {
     ) -> EvalToConstValueResult<'tcx> {
         // Const-eval shouldn't depend on lifetimes at all, so we can erase them, which should
         // improve caching of queries.
-        let inputs =
-            self.erase_regions(typing_env.with_post_analysis_normalized(self).as_query_input(cid));
+        let inputs = self.erase_and_anonymize_regions(
+            typing_env.with_post_analysis_normalized(self).as_query_input(cid),
+        );
         if !span.is_dummy() {
             // The query doesn't know where it is being invoked, so we need to fix the span.
             self.at(span).eval_to_const_value_raw(inputs).map_err(|e| e.with_span(span))
@@ -192,8 +193,9 @@ impl<'tcx> TyCtxt<'tcx> {
     ) -> ConstToValTreeResult<'tcx> {
         // Const-eval shouldn't depend on lifetimes at all, so we can erase them, which should
         // improve caching of queries.
-        let inputs =
-            self.erase_regions(typing_env.with_post_analysis_normalized(self).as_query_input(cid));
+        let inputs = self.erase_and_anonymize_regions(
+            typing_env.with_post_analysis_normalized(self).as_query_input(cid),
+        );
         debug!(?inputs);
         let res = if !span.is_dummy() {
             // The query doesn't know where it is being invoked, so we need to fix the span.
diff --git a/compiler/rustc_middle/src/mir/pretty.rs b/compiler/rustc_middle/src/mir/pretty.rs
index a7d99f513a1..f9d0a5f0a3b 100644
--- a/compiler/rustc_middle/src/mir/pretty.rs
+++ b/compiler/rustc_middle/src/mir/pretty.rs
@@ -78,8 +78,9 @@ impl<'dis, 'de, 'tcx> MirDumper<'dis, 'de, 'tcx> {
     pub fn new(tcx: TyCtxt<'tcx>, pass_name: &'static str, body: &Body<'tcx>) -> Option<Self> {
         let dump_enabled = if let Some(ref filters) = tcx.sess.opts.unstable_opts.dump_mir {
             // see notes on #41697 below
-            let node_path =
-                ty::print::with_forced_impl_filename_line!(tcx.def_path_str(body.source.def_id()));
+            let node_path = ty::print::with_no_trimmed_paths!(
+                ty::print::with_forced_impl_filename_line!(tcx.def_path_str(body.source.def_id()))
+            );
             filters.split('|').any(|or_filter| {
                 or_filter.split('&').all(|and_filter| {
                     let and_filter_trimmed = and_filter.trim();
@@ -173,9 +174,10 @@ impl<'dis, 'de, 'tcx> MirDumper<'dis, 'de, 'tcx> {
     // trigger `type_of`, and this can run while we are already attempting to evaluate `type_of`.
     pub fn dump_mir_to_writer(&self, body: &Body<'tcx>, w: &mut dyn io::Write) -> io::Result<()> {
         // see notes on #41697 above
-        let def_path = ty::print::with_forced_impl_filename_line!(
-            self.tcx().def_path_str(body.source.def_id())
-        );
+        let def_path =
+            ty::print::with_no_trimmed_paths!(ty::print::with_forced_impl_filename_line!(
+                self.tcx().def_path_str(body.source.def_id())
+            ));
         // ignore-tidy-odd-backticks the literal below is fine
         write!(w, "// MIR for `{def_path}")?;
         match body.source.promoted {
diff --git a/compiler/rustc_middle/src/mir/visit.rs b/compiler/rustc_middle/src/mir/visit.rs
index 904d78d69b6..b498b7b8912 100644
--- a/compiler/rustc_middle/src/mir/visit.rs
+++ b/compiler/rustc_middle/src/mir/visit.rs
@@ -1415,6 +1415,24 @@ impl PlaceContext {
         )
     }
 
+    /// Returns `true` if this place context may be used to know the address of the given place.
+    #[inline]
+    pub fn may_observe_address(self) -> bool {
+        matches!(
+            self,
+            PlaceContext::NonMutatingUse(
+                NonMutatingUseContext::SharedBorrow
+                    | NonMutatingUseContext::RawBorrow
+                    | NonMutatingUseContext::FakeBorrow
+            ) | PlaceContext::MutatingUse(
+                MutatingUseContext::Drop
+                    | MutatingUseContext::Borrow
+                    | MutatingUseContext::RawBorrow
+                    | MutatingUseContext::AsmOutput
+            )
+        )
+    }
+
     /// Returns `true` if this place context represents a storage live or storage dead marker.
     #[inline]
     pub fn is_storage_marker(self) -> bool {
diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs
index 874cee54c7c..2aa32dfa0d8 100644
--- a/compiler/rustc_middle/src/query/mod.rs
+++ b/compiler/rustc_middle/src/query/mod.rs
@@ -135,7 +135,7 @@ use crate::traits::{
 };
 use crate::ty::fast_reject::SimplifiedType;
 use crate::ty::layout::ValidityRequirement;
-use crate::ty::print::{PrintTraitRefExt, describe_as_module};
+use crate::ty::print::PrintTraitRefExt;
 use crate::ty::util::AlwaysRequiresDrop;
 use crate::ty::{
     self, CrateInherentImpls, GenericArg, GenericArgsRef, PseudoCanonicalInput, SizedTraitKind, Ty,
@@ -761,9 +761,9 @@ rustc_queries! {
     }
 
     /// Erases regions from `ty` to yield a new type.
-    /// Normally you would just use `tcx.erase_regions(value)`,
+    /// Normally you would just use `tcx.erase_and_anonymize_regions(value)`,
     /// however, which uses this query as a kind of cache.
-    query erase_regions_ty(ty: Ty<'tcx>) -> Ty<'tcx> {
+    query erase_and_anonymize_regions_ty(ty: Ty<'tcx>) -> Ty<'tcx> {
         // This query is not expected to have input -- as a result, it
         // is not a good candidates for "replay" because it is essentially a
         // pure function of its input (and hence the expectation is that
@@ -2731,3 +2731,12 @@ rustc_queries! {
 
 rustc_with_all_queries! { define_callbacks! }
 rustc_feedable_queries! { define_feedable! }
+
+fn describe_as_module(def_id: impl Into<LocalDefId>, tcx: TyCtxt<'_>) -> String {
+    let def_id = def_id.into();
+    if def_id.is_top_level_module() {
+        "top-level module".to_string()
+    } else {
+        format!("module `{}`", tcx.def_path_str(def_id))
+    }
+}
diff --git a/compiler/rustc_middle/src/ty/abstract_const.rs b/compiler/rustc_middle/src/ty/abstract_const.rs
index c9b9ec771b3..463e4c58805 100644
--- a/compiler/rustc_middle/src/ty/abstract_const.rs
+++ b/compiler/rustc_middle/src/ty/abstract_const.rs
@@ -55,7 +55,7 @@ impl<'tcx> TyCtxt<'tcx> {
                     ty::ConstKind::Unevaluated(uv) => match self.tcx.thir_abstract_const(uv.def) {
                         Err(e) => ty::Const::new_error(self.tcx, e),
                         Ok(Some(bac)) => {
-                            let args = self.tcx.erase_regions(uv.args);
+                            let args = self.tcx.erase_and_anonymize_regions(uv.args);
                             let bac = bac.instantiate(self.tcx, args);
                             return bac.fold_with(self);
                         }
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index 97c8a0336c2..218ac2cfbc1 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -38,6 +38,7 @@ use rustc_hir::def_id::{CrateNum, DefId, LOCAL_CRATE, LocalDefId};
 use rustc_hir::definitions::{DefPathData, Definitions, DisambiguatorState};
 use rustc_hir::intravisit::VisitorExt;
 use rustc_hir::lang_items::LangItem;
+use rustc_hir::limit::Limit;
 use rustc_hir::{self as hir, Attribute, HirId, Node, TraitCandidate, find_attr};
 use rustc_index::IndexVec;
 use rustc_macros::{HashStable, TyDecodable, TyEncodable};
@@ -45,14 +46,14 @@ use rustc_query_system::cache::WithDepNode;
 use rustc_query_system::dep_graph::DepNodeIndex;
 use rustc_query_system::ich::StableHashingContext;
 use rustc_serialize::opaque::{FileEncodeResult, FileEncoder};
+use rustc_session::Session;
 use rustc_session::config::CrateType;
 use rustc_session::cstore::{CrateStoreDyn, Untracked};
 use rustc_session::lint::Lint;
-use rustc_session::{Limit, Session};
 use rustc_span::def_id::{CRATE_DEF_ID, DefPathHash, StableCrateId};
 use rustc_span::{DUMMY_SP, Ident, Span, Symbol, kw, sym};
 use rustc_type_ir::TyKind::*;
-use rustc_type_ir::lang_items::{SolverLangItem, SolverTraitLangItem};
+use rustc_type_ir::lang_items::{SolverAdtLangItem, SolverLangItem, SolverTraitLangItem};
 pub use rustc_type_ir::lift::Lift;
 use rustc_type_ir::{
     CollectAndApply, Interner, TypeFlags, TypeFoldable, WithCachedTypeInfo, elaborate, search_graph,
@@ -94,6 +95,13 @@ impl<'tcx> Interner for TyCtxt<'tcx> {
     type DefId = DefId;
     type LocalDefId = LocalDefId;
     type TraitId = DefId;
+    type ForeignId = DefId;
+    type FunctionId = DefId;
+    type ClosureId = DefId;
+    type CoroutineClosureId = DefId;
+    type CoroutineId = DefId;
+    type AdtId = DefId;
+    type ImplId = DefId;
     type Span = Span;
 
     type GenericArgs = ty::GenericArgsRef<'tcx>;
@@ -492,6 +500,10 @@ impl<'tcx> Interner for TyCtxt<'tcx> {
         self.require_lang_item(solver_trait_lang_item_to_lang_item(lang_item), DUMMY_SP)
     }
 
+    fn require_adt_lang_item(self, lang_item: SolverAdtLangItem) -> DefId {
+        self.require_lang_item(solver_adt_lang_item_to_lang_item(lang_item), DUMMY_SP)
+    }
+
     fn is_lang_item(self, def_id: DefId, lang_item: SolverLangItem) -> bool {
         self.is_lang_item(def_id, solver_lang_item_to_lang_item(lang_item))
     }
@@ -500,6 +512,10 @@ impl<'tcx> Interner for TyCtxt<'tcx> {
         self.is_lang_item(def_id, solver_trait_lang_item_to_lang_item(lang_item))
     }
 
+    fn is_adt_lang_item(self, def_id: DefId, lang_item: SolverAdtLangItem) -> bool {
+        self.is_lang_item(def_id, solver_adt_lang_item_to_lang_item(lang_item))
+    }
+
     fn is_default_trait(self, def_id: DefId) -> bool {
         self.is_default_trait(def_id)
     }
@@ -512,6 +528,10 @@ impl<'tcx> Interner for TyCtxt<'tcx> {
         lang_item_to_solver_trait_lang_item(self.lang_items().from_def_id(def_id)?)
     }
 
+    fn as_adt_lang_item(self, def_id: DefId) -> Option<SolverAdtLangItem> {
+        lang_item_to_solver_adt_lang_item(self.lang_items().from_def_id(def_id)?)
+    }
+
     fn associated_type_def_ids(self, def_id: DefId) -> impl IntoIterator<Item = DefId> {
         self.associated_items(def_id)
             .in_definition_order()
@@ -783,6 +803,13 @@ bidirectional_lang_item_map! {
     DynMetadata,
     FutureOutput,
     Metadata,
+// tidy-alphabetical-end
+}
+
+bidirectional_lang_item_map! {
+    SolverAdtLangItem, lang_item_to_solver_adt_lang_item, solver_adt_lang_item_to_lang_item;
+
+// tidy-alphabetical-start
     Option,
     Poll,
 // tidy-alphabetical-end
diff --git a/compiler/rustc_middle/src/ty/erase_regions.rs b/compiler/rustc_middle/src/ty/erase_regions.rs
index f4fead7e952..74b4adda7fd 100644
--- a/compiler/rustc_middle/src/ty/erase_regions.rs
+++ b/compiler/rustc_middle/src/ty/erase_regions.rs
@@ -6,20 +6,20 @@ use crate::ty::{
 };
 
 pub(super) fn provide(providers: &mut Providers) {
-    *providers = Providers { erase_regions_ty, ..*providers };
+    *providers = Providers { erase_and_anonymize_regions_ty, ..*providers };
 }
 
-fn erase_regions_ty<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Ty<'tcx> {
+fn erase_and_anonymize_regions_ty<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Ty<'tcx> {
     // N.B., use `super_fold_with` here. If we used `fold_with`, it
-    // could invoke the `erase_regions_ty` query recursively.
-    ty.super_fold_with(&mut RegionEraserVisitor { tcx })
+    // could invoke the `erase_and_anonymize_regions_ty` query recursively.
+    ty.super_fold_with(&mut RegionEraserAndAnonymizerVisitor { tcx })
 }
 
 impl<'tcx> TyCtxt<'tcx> {
-    /// Returns an equivalent value with all free regions removed (note
-    /// that late-bound regions remain, because they are important for
-    /// subtyping, but they are anonymized and normalized as well)..
-    pub fn erase_regions<T>(self, value: T) -> T
+    /// Returns an equivalent value with all free regions removed and
+    /// bound regions anonymized. (note that bound regions are important
+    /// for subtyping and generally type equality so *cannot* be removed)
+    pub fn erase_and_anonymize_regions<T>(self, value: T) -> T
     where
         T: TypeFoldable<TyCtxt<'tcx>>,
     {
@@ -27,18 +27,18 @@ impl<'tcx> TyCtxt<'tcx> {
         if !value.has_type_flags(TypeFlags::HAS_BINDER_VARS | TypeFlags::HAS_FREE_REGIONS) {
             return value;
         }
-        debug!("erase_regions({:?})", value);
-        let value1 = value.fold_with(&mut RegionEraserVisitor { tcx: self });
-        debug!("erase_regions = {:?}", value1);
+        debug!("erase_and_anonymize_regions({:?})", value);
+        let value1 = value.fold_with(&mut RegionEraserAndAnonymizerVisitor { tcx: self });
+        debug!("erase_and_anonymize_regions = {:?}", value1);
         value1
     }
 }
 
-struct RegionEraserVisitor<'tcx> {
+struct RegionEraserAndAnonymizerVisitor<'tcx> {
     tcx: TyCtxt<'tcx>,
 }
 
-impl<'tcx> TypeFolder<TyCtxt<'tcx>> for RegionEraserVisitor<'tcx> {
+impl<'tcx> TypeFolder<TyCtxt<'tcx>> for RegionEraserAndAnonymizerVisitor<'tcx> {
     fn cx(&self) -> TyCtxt<'tcx> {
         self.tcx
     }
@@ -49,7 +49,7 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for RegionEraserVisitor<'tcx> {
         } else if ty.has_infer() {
             ty.super_fold_with(self)
         } else {
-            self.tcx.erase_regions_ty(ty)
+            self.tcx.erase_and_anonymize_regions_ty(ty)
         }
     }
 
diff --git a/compiler/rustc_middle/src/ty/error.rs b/compiler/rustc_middle/src/ty/error.rs
index 3f854038651..66542525d28 100644
--- a/compiler/rustc_middle/src/ty/error.rs
+++ b/compiler/rustc_middle/src/ty/error.rs
@@ -7,6 +7,7 @@ use std::path::PathBuf;
 use rustc_errors::pluralize;
 use rustc_hir as hir;
 use rustc_hir::def::{CtorOf, DefKind};
+use rustc_hir::limit::Limit;
 use rustc_macros::extension;
 pub use rustc_type_ir::error::ExpectedFound;
 
@@ -233,7 +234,7 @@ impl<'tcx> TyCtxt<'tcx> {
         loop {
             // Look for the longest properly trimmed path that still fits in length_limit.
             short = with_forced_trimmed_paths!({
-                let mut p = FmtPrinter::new_with_limit(self, ns, rustc_session::Limit(type_limit));
+                let mut p = FmtPrinter::new_with_limit(self, ns, Limit(type_limit));
                 self.lift(t)
                     .expect("could not lift for printing")
                     .print(&mut p)
diff --git a/compiler/rustc_middle/src/ty/instance.rs b/compiler/rustc_middle/src/ty/instance.rs
index 3a51f79f121..e76993e0542 100644
--- a/compiler/rustc_middle/src/ty/instance.rs
+++ b/compiler/rustc_middle/src/ty/instance.rs
@@ -544,7 +544,9 @@ impl<'tcx> Instance<'tcx> {
 
         // All regions in the result of this query are erased, so it's
         // fine to erase all of the input regions.
-        tcx.resolve_instance_raw(tcx.erase_regions(typing_env.as_query_input((def_id, args))))
+        tcx.resolve_instance_raw(
+            tcx.erase_and_anonymize_regions(typing_env.as_query_input((def_id, args))),
+        )
     }
 
     pub fn expect_resolve(
diff --git a/compiler/rustc_middle/src/ty/layout.rs b/compiler/rustc_middle/src/ty/layout.rs
index aed94f9aa04..2114d080dfa 100644
--- a/compiler/rustc_middle/src/ty/layout.rs
+++ b/compiler/rustc_middle/src/ty/layout.rs
@@ -401,7 +401,10 @@ impl<'tcx> SizeSkeleton<'tcx> {
                 match tail.kind() {
                     ty::Param(_) | ty::Alias(ty::Projection | ty::Inherent, _) => {
                         debug_assert!(tail.has_non_region_param());
-                        Ok(SizeSkeleton::Pointer { non_zero, tail: tcx.erase_regions(tail) })
+                        Ok(SizeSkeleton::Pointer {
+                            non_zero,
+                            tail: tcx.erase_and_anonymize_regions(tail),
+                        })
                     }
                     ty::Error(guar) => {
                         // Fixes ICE #124031
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index e567ba05f61..da17ec1f9f3 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -109,7 +109,6 @@ pub use self::typeck_results::{
     CanonicalUserType, CanonicalUserTypeAnnotation, CanonicalUserTypeAnnotations, IsIdentity,
     Rust2024IncompatiblePatInfo, TypeckResults, UserType, UserTypeAnnotationIndex, UserTypeKind,
 };
-pub use self::visit::*;
 use crate::error::{OpaqueHiddenTypeMismatch, TypeMismatchReason};
 use crate::metadata::ModChild;
 use crate::middle::privacy::EffectiveVisibilities;
diff --git a/compiler/rustc_middle/src/ty/normalize_erasing_regions.rs b/compiler/rustc_middle/src/ty/normalize_erasing_regions.rs
index f2a4a5a4ecf..69c1eb9b345 100644
--- a/compiler/rustc_middle/src/ty/normalize_erasing_regions.rs
+++ b/compiler/rustc_middle/src/ty/normalize_erasing_regions.rs
@@ -51,7 +51,7 @@ impl<'tcx> TyCtxt<'tcx> {
 
         // Erase first before we do the real query -- this keeps the
         // cache from being too polluted.
-        let value = self.erase_regions(value);
+        let value = self.erase_and_anonymize_regions(value);
         debug!(?value);
 
         if !value.has_aliases() {
@@ -83,7 +83,7 @@ impl<'tcx> TyCtxt<'tcx> {
 
         // Erase first before we do the real query -- this keeps the
         // cache from being too polluted.
-        let value = self.erase_regions(value);
+        let value = self.erase_and_anonymize_regions(value);
         debug!(?value);
 
         if !value.has_aliases() {
diff --git a/compiler/rustc_middle/src/ty/predicate.rs b/compiler/rustc_middle/src/ty/predicate.rs
index 59e00f85957..69dcca54f46 100644
--- a/compiler/rustc_middle/src/ty/predicate.rs
+++ b/compiler/rustc_middle/src/ty/predicate.rs
@@ -638,21 +638,7 @@ impl<'tcx> Predicate<'tcx> {
         let predicate = self.kind();
         match predicate.skip_binder() {
             PredicateKind::Clause(ClauseKind::Trait(t)) => Some(predicate.rebind(t)),
-            PredicateKind::Clause(ClauseKind::Projection(..))
-            | PredicateKind::Clause(ClauseKind::HostEffect(..))
-            | PredicateKind::Clause(ClauseKind::ConstArgHasType(..))
-            | PredicateKind::Clause(ClauseKind::UnstableFeature(_))
-            | PredicateKind::NormalizesTo(..)
-            | PredicateKind::AliasRelate(..)
-            | PredicateKind::Subtype(..)
-            | PredicateKind::Coerce(..)
-            | PredicateKind::Clause(ClauseKind::RegionOutlives(..))
-            | PredicateKind::Clause(ClauseKind::WellFormed(..))
-            | PredicateKind::DynCompatible(..)
-            | PredicateKind::Clause(ClauseKind::TypeOutlives(..))
-            | PredicateKind::Clause(ClauseKind::ConstEvaluatable(..))
-            | PredicateKind::ConstEquate(..)
-            | PredicateKind::Ambiguous => None,
+            _ => None,
         }
     }
 
@@ -660,21 +646,7 @@ impl<'tcx> Predicate<'tcx> {
         let predicate = self.kind();
         match predicate.skip_binder() {
             PredicateKind::Clause(ClauseKind::Projection(t)) => Some(predicate.rebind(t)),
-            PredicateKind::Clause(ClauseKind::Trait(..))
-            | PredicateKind::Clause(ClauseKind::HostEffect(..))
-            | PredicateKind::Clause(ClauseKind::ConstArgHasType(..))
-            | PredicateKind::Clause(ClauseKind::UnstableFeature(_))
-            | PredicateKind::NormalizesTo(..)
-            | PredicateKind::AliasRelate(..)
-            | PredicateKind::Subtype(..)
-            | PredicateKind::Coerce(..)
-            | PredicateKind::Clause(ClauseKind::RegionOutlives(..))
-            | PredicateKind::Clause(ClauseKind::WellFormed(..))
-            | PredicateKind::DynCompatible(..)
-            | PredicateKind::Clause(ClauseKind::TypeOutlives(..))
-            | PredicateKind::Clause(ClauseKind::ConstEvaluatable(..))
-            | PredicateKind::ConstEquate(..)
-            | PredicateKind::Ambiguous => None,
+            _ => None,
         }
     }
 
diff --git a/compiler/rustc_middle/src/ty/print/mod.rs b/compiler/rustc_middle/src/ty/print/mod.rs
index 9e6f277ef77..d636e8ef31f 100644
--- a/compiler/rustc_middle/src/ty/print/mod.rs
+++ b/compiler/rustc_middle/src/ty/print/mod.rs
@@ -2,7 +2,7 @@ use hir::def::Namespace;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::sso::SsoHashSet;
 use rustc_hir as hir;
-use rustc_hir::def_id::{CrateNum, DefId, LocalDefId};
+use rustc_hir::def_id::{CrateNum, DefId};
 use rustc_hir::definitions::{DefPathData, DisambiguatedDefPathData};
 use tracing::{debug, instrument, trace};
 
@@ -396,16 +396,6 @@ impl<'tcx, P: Printer<'tcx>> Print<'tcx, P> for ty::Const<'tcx> {
     }
 }
 
-// This is only used by query descriptions
-pub fn describe_as_module(def_id: impl Into<LocalDefId>, tcx: TyCtxt<'_>) -> String {
-    let def_id = def_id.into();
-    if def_id.is_top_level_module() {
-        "top-level module".to_string()
-    } else {
-        format!("module `{}`", tcx.def_path_str(def_id))
-    }
-}
-
 impl<T> rustc_type_ir::ir_print::IrPrint<T> for TyCtxt<'_>
 where
     T: Copy + for<'a, 'tcx> Lift<TyCtxt<'tcx>, Lifted: Print<'tcx, FmtPrinter<'a, 'tcx>>>,
diff --git a/compiler/rustc_middle/src/ty/print/pretty.rs b/compiler/rustc_middle/src/ty/print/pretty.rs
index 74caee7336a..fc821ffdaa6 100644
--- a/compiler/rustc_middle/src/ty/print/pretty.rs
+++ b/compiler/rustc_middle/src/ty/print/pretty.rs
@@ -13,8 +13,8 @@ use rustc_hir::LangItem;
 use rustc_hir::def::{self, CtorKind, DefKind, Namespace};
 use rustc_hir::def_id::{DefIdMap, DefIdSet, LOCAL_CRATE, ModDefId};
 use rustc_hir::definitions::{DefKey, DefPathDataName};
+use rustc_hir::limit::Limit;
 use rustc_macros::{Lift, extension};
-use rustc_session::Limit;
 use rustc_session::cstore::{ExternCrate, ExternCrateSource};
 use rustc_span::{FileNameDisplayPreference, Ident, Symbol, kw, sym};
 use rustc_type_ir::{Upcast as _, elaborate};
@@ -1436,8 +1436,8 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                                 // anonymized regions, but the super projections can still
                                 // contain named regions. So we erase and anonymize everything
                                 // here to compare the types modulo regions below.
-                                let proj = p.tcx().erase_regions(proj);
-                                let super_proj = p.tcx().erase_regions(super_proj);
+                                let proj = p.tcx().erase_and_anonymize_regions(proj);
+                                let super_proj = p.tcx().erase_and_anonymize_regions(super_proj);
 
                                 proj == super_proj
                             });
diff --git a/compiler/rustc_middle/src/ty/util.rs b/compiler/rustc_middle/src/ty/util.rs
index a7d07adf78f..96fbdf44791 100644
--- a/compiler/rustc_middle/src/ty/util.rs
+++ b/compiler/rustc_middle/src/ty/util.rs
@@ -12,9 +12,9 @@ use rustc_hashes::Hash128;
 use rustc_hir as hir;
 use rustc_hir::def::{CtorOf, DefKind, Res};
 use rustc_hir::def_id::{CrateNum, DefId, LocalDefId};
+use rustc_hir::limit::Limit;
 use rustc_index::bit_set::GrowableBitSet;
 use rustc_macros::{HashStable, TyDecodable, TyEncodable, extension};
-use rustc_session::Limit;
 use rustc_span::sym;
 use rustc_type_ir::solve::SizedTraitKind;
 use smallvec::{SmallVec, smallvec};
@@ -131,10 +131,9 @@ impl<'tcx> TyCtxt<'tcx> {
     /// Creates a hash of the type `Ty` which will be the same no matter what crate
     /// context it's calculated within. This is used by the `type_id` intrinsic.
     pub fn type_id_hash(self, ty: Ty<'tcx>) -> Hash128 {
-        // We want the type_id be independent of the types free regions, so we
-        // erase them. The erase_regions() call will also anonymize bound
-        // regions, which is desirable too.
-        let ty = self.erase_regions(ty);
+        // We don't have region information, so we erase all free regions. Equal types
+        // must have the same `TypeId`, so we must anonymize all bound regions as well.
+        let ty = self.erase_and_anonymize_regions(ty);
 
         self.with_stable_hashing_context(|mut hcx| {
             let mut hasher = StableHasher::new();
@@ -1309,7 +1308,7 @@ impl<'tcx> Ty<'tcx> {
                 debug_assert!(!typing_env.param_env.has_infer());
                 let query_ty = tcx
                     .try_normalize_erasing_regions(typing_env, query_ty)
-                    .unwrap_or_else(|_| tcx.erase_regions(query_ty));
+                    .unwrap_or_else(|_| tcx.erase_and_anonymize_regions(query_ty));
 
                 tcx.needs_drop_raw(typing_env.as_query_input(query_ty))
             }
@@ -1346,7 +1345,7 @@ impl<'tcx> Ty<'tcx> {
                 debug_assert!(!typing_env.has_infer());
                 let query_ty = tcx
                     .try_normalize_erasing_regions(typing_env, query_ty)
-                    .unwrap_or_else(|_| tcx.erase_regions(query_ty));
+                    .unwrap_or_else(|_| tcx.erase_and_anonymize_regions(query_ty));
 
                 tcx.needs_async_drop_raw(typing_env.as_query_input(query_ty))
             }
diff --git a/compiler/rustc_middle/src/ty/visit.rs b/compiler/rustc_middle/src/ty/visit.rs
index 3853a804a92..f0c47f257cc 100644
--- a/compiler/rustc_middle/src/ty/visit.rs
+++ b/compiler/rustc_middle/src/ty/visit.rs
@@ -212,42 +212,3 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for LateBoundRegionsCollector {
         }
     }
 }
-
-/// Finds the max universe present
-pub struct MaxUniverse {
-    max_universe: ty::UniverseIndex,
-}
-
-impl MaxUniverse {
-    pub fn new() -> Self {
-        MaxUniverse { max_universe: ty::UniverseIndex::ROOT }
-    }
-
-    pub fn max_universe(self) -> ty::UniverseIndex {
-        self.max_universe
-    }
-}
-
-impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for MaxUniverse {
-    fn visit_ty(&mut self, t: Ty<'tcx>) {
-        if let ty::Placeholder(placeholder) = t.kind() {
-            self.max_universe = self.max_universe.max(placeholder.universe);
-        }
-
-        t.super_visit_with(self)
-    }
-
-    fn visit_const(&mut self, c: ty::consts::Const<'tcx>) {
-        if let ty::ConstKind::Placeholder(placeholder) = c.kind() {
-            self.max_universe = self.max_universe.max(placeholder.universe);
-        }
-
-        c.super_visit_with(self)
-    }
-
-    fn visit_region(&mut self, r: ty::Region<'tcx>) {
-        if let ty::RePlaceholder(placeholder) = r.kind() {
-            self.max_universe = self.max_universe.max(placeholder.universe);
-        }
-    }
-}
diff --git a/compiler/rustc_middle/src/ty/vtable.rs b/compiler/rustc_middle/src/ty/vtable.rs
index 6fc19c82342..e2f09fdcb4b 100644
--- a/compiler/rustc_middle/src/ty/vtable.rs
+++ b/compiler/rustc_middle/src/ty/vtable.rs
@@ -89,7 +89,7 @@ pub(super) fn vtable_allocation_provider<'tcx>(
 
     let vtable_entries = if let Some(poly_trait_ref) = poly_trait_ref {
         let trait_ref = poly_trait_ref.with_self_ty(tcx, ty);
-        let trait_ref = tcx.erase_regions(trait_ref);
+        let trait_ref = tcx.erase_and_anonymize_regions(trait_ref);
 
         tcx.vtable_entries(trait_ref)
     } else {
diff --git a/compiler/rustc_mir_build/src/check_tail_calls.rs b/compiler/rustc_mir_build/src/check_tail_calls.rs
index e0cbe8519ed..d40c77d145f 100644
--- a/compiler/rustc_mir_build/src/check_tail_calls.rs
+++ b/compiler/rustc_mir_build/src/check_tail_calls.rs
@@ -64,10 +64,10 @@ impl<'tcx> TailCallCkVisitor<'_, 'tcx> {
                 "`become` outside of functions should have been disallowed by hir_typeck"
             )
         };
-        // While the `caller_sig` does have its regions erased, it does not have its
-        // binders anonymized. We call `erase_regions` once again to anonymize any binders
+        // While the `caller_sig` does have its free regions erased, it does not have its
+        // binders anonymized. We call `erase_and_anonymize_regions` once again to anonymize any binders
         // within the signature, such as in function pointer or `dyn Trait` args.
-        let caller_sig = self.tcx.erase_regions(caller_sig);
+        let caller_sig = self.tcx.erase_and_anonymize_regions(caller_sig);
 
         let ExprKind::Scope { value, .. } = call.kind else {
             span_bug!(call.span, "expected scope, found: {call:?}")
diff --git a/compiler/rustc_mir_build/src/thir/cx/expr.rs b/compiler/rustc_mir_build/src/thir/cx/expr.rs
index 81b0e21a5f5..0b9bc018a09 100644
--- a/compiler/rustc_mir_build/src/thir/cx/expr.rs
+++ b/compiler/rustc_mir_build/src/thir/cx/expr.rs
@@ -792,10 +792,9 @@ impl<'tcx> ThirBuildCx<'tcx> {
                             let ty = self.typeck_results.node_type(anon_const.hir_id);
                             let did = anon_const.def_id.to_def_id();
                             let typeck_root_def_id = tcx.typeck_root_def_id(did);
-                            let parent_args = tcx.erase_regions(GenericArgs::identity_for_item(
-                                tcx,
-                                typeck_root_def_id,
-                            ));
+                            let parent_args = tcx.erase_and_anonymize_regions(
+                                GenericArgs::identity_for_item(tcx, typeck_root_def_id),
+                            );
                             let args =
                                 InlineConstArgs::new(tcx, InlineConstArgsParts { parent_args, ty })
                                     .args;
@@ -831,8 +830,10 @@ impl<'tcx> ThirBuildCx<'tcx> {
                 let ty = self.typeck_results.node_type(anon_const.hir_id);
                 let did = anon_const.def_id.to_def_id();
                 let typeck_root_def_id = tcx.typeck_root_def_id(did);
-                let parent_args =
-                    tcx.erase_regions(GenericArgs::identity_for_item(tcx, typeck_root_def_id));
+                let parent_args = tcx.erase_and_anonymize_regions(GenericArgs::identity_for_item(
+                    tcx,
+                    typeck_root_def_id,
+                ));
                 let args = InlineConstArgs::new(tcx, InlineConstArgsParts { parent_args, ty }).args;
 
                 ExprKind::ConstBlock { did, args }
diff --git a/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs b/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs
index d46c4678bcf..6316ccf1b8c 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs
@@ -105,9 +105,11 @@ impl<'tcx> ConstToPat<'tcx> {
         //
         // FIXME: `const_eval_resolve_for_typeck` should probably just modify the env itself
         // instead of having this logic here
-        let typing_env =
-            self.tcx.erase_regions(self.typing_env).with_post_analysis_normalized(self.tcx);
-        let uv = self.tcx.erase_regions(uv);
+        let typing_env = self
+            .tcx
+            .erase_and_anonymize_regions(self.typing_env)
+            .with_post_analysis_normalized(self.tcx);
+        let uv = self.tcx.erase_and_anonymize_regions(uv);
 
         // try to resolve e.g. associated constants to their definition on an impl, and then
         // evaluate the const.
diff --git a/compiler/rustc_mir_dataflow/src/impls/liveness.rs b/compiler/rustc_mir_dataflow/src/impls/liveness.rs
index 6ec1b03a34e..5eba474a60c 100644
--- a/compiler/rustc_mir_dataflow/src/impls/liveness.rs
+++ b/compiler/rustc_mir_dataflow/src/impls/liveness.rs
@@ -92,7 +92,7 @@ impl<'tcx> Visitor<'tcx> for TransferFunction<'_> {
         }
 
         match DefUse::for_place(*place, context) {
-            Some(DefUse::Def) => {
+            DefUse::Def => {
                 if let PlaceContext::MutatingUse(
                     MutatingUseContext::Call | MutatingUseContext::AsmOutput,
                 ) = context
@@ -105,8 +105,8 @@ impl<'tcx> Visitor<'tcx> for TransferFunction<'_> {
                     self.0.kill(place.local);
                 }
             }
-            Some(DefUse::Use) => self.0.gen_(place.local),
-            None => {}
+            DefUse::Use => self.0.gen_(place.local),
+            DefUse::PartialWrite | DefUse::NonUse => {}
         }
 
         self.visit_projection(place.as_ref(), context, location);
@@ -131,23 +131,29 @@ impl<'tcx> Visitor<'tcx> for YieldResumeEffect<'_> {
 }
 
 #[derive(Eq, PartialEq, Clone)]
-enum DefUse {
+pub enum DefUse {
+    /// Full write to the local.
     Def,
+    /// Read of any part of the local.
     Use,
+    /// Partial write to the local.
+    PartialWrite,
+    /// Non-use, like debuginfo.
+    NonUse,
 }
 
 impl DefUse {
     fn apply(state: &mut DenseBitSet<Local>, place: Place<'_>, context: PlaceContext) {
         match DefUse::for_place(place, context) {
-            Some(DefUse::Def) => state.kill(place.local),
-            Some(DefUse::Use) => state.gen_(place.local),
-            None => {}
+            DefUse::Def => state.kill(place.local),
+            DefUse::Use => state.gen_(place.local),
+            DefUse::PartialWrite | DefUse::NonUse => {}
         }
     }
 
-    fn for_place(place: Place<'_>, context: PlaceContext) -> Option<DefUse> {
+    pub fn for_place(place: Place<'_>, context: PlaceContext) -> DefUse {
         match context {
-            PlaceContext::NonUse(_) => None,
+            PlaceContext::NonUse(_) => DefUse::NonUse,
 
             PlaceContext::MutatingUse(
                 MutatingUseContext::Call
@@ -156,21 +162,20 @@ impl DefUse {
                 | MutatingUseContext::Store
                 | MutatingUseContext::Deinit,
             ) => {
+                // Treat derefs as a use of the base local. `*p = 4` is not a def of `p` but a use.
                 if place.is_indirect() {
-                    // Treat derefs as a use of the base local. `*p = 4` is not a def of `p` but a
-                    // use.
-                    Some(DefUse::Use)
+                    DefUse::Use
                 } else if place.projection.is_empty() {
-                    Some(DefUse::Def)
+                    DefUse::Def
                 } else {
-                    None
+                    DefUse::PartialWrite
                 }
             }
 
             // Setting the discriminant is not a use because it does no reading, but it is also not
             // a def because it does not overwrite the whole place
             PlaceContext::MutatingUse(MutatingUseContext::SetDiscriminant) => {
-                place.is_indirect().then_some(DefUse::Use)
+                if place.is_indirect() { DefUse::Use } else { DefUse::PartialWrite }
             }
 
             // All other contexts are uses...
@@ -188,7 +193,7 @@ impl DefUse {
                 | NonMutatingUseContext::PlaceMention
                 | NonMutatingUseContext::FakeBorrow
                 | NonMutatingUseContext::SharedBorrow,
-            ) => Some(DefUse::Use),
+            ) => DefUse::Use,
 
             PlaceContext::MutatingUse(MutatingUseContext::Projection)
             | PlaceContext::NonMutatingUse(NonMutatingUseContext::Projection) => {
diff --git a/compiler/rustc_mir_dataflow/src/impls/mod.rs b/compiler/rustc_mir_dataflow/src/impls/mod.rs
index 3f29b819a6d..6d573e1c00e 100644
--- a/compiler/rustc_mir_dataflow/src/impls/mod.rs
+++ b/compiler/rustc_mir_dataflow/src/impls/mod.rs
@@ -9,7 +9,8 @@ pub use self::initialized::{
     MaybeUninitializedPlaces, MaybeUninitializedPlacesDomain,
 };
 pub use self::liveness::{
-    MaybeLiveLocals, MaybeTransitiveLiveLocals, TransferFunction as LivenessTransferFunction,
+    DefUse, MaybeLiveLocals, MaybeTransitiveLiveLocals,
+    TransferFunction as LivenessTransferFunction,
 };
 pub use self::storage_liveness::{
     MaybeRequiresStorage, MaybeStorageDead, MaybeStorageLive, always_storage_live_locals,
diff --git a/compiler/rustc_mir_dataflow/src/points.rs b/compiler/rustc_mir_dataflow/src/points.rs
index 70d1a34b5fb..e3d1e04a319 100644
--- a/compiler/rustc_mir_dataflow/src/points.rs
+++ b/compiler/rustc_mir_dataflow/src/points.rs
@@ -1,9 +1,5 @@
-use rustc_index::bit_set::DenseBitSet;
-use rustc_index::interval::SparseIntervalMatrix;
 use rustc_index::{Idx, IndexVec};
-use rustc_middle::mir::{self, BasicBlock, Body, Location};
-
-use crate::framework::{Analysis, Results, ResultsVisitor, visit_results};
+use rustc_middle::mir::{BasicBlock, Body, Location};
 
 /// Maps between a `Location` and a `PointIndex` (and vice versa).
 pub struct DenseLocationMap {
@@ -93,65 +89,3 @@ rustc_index::newtype_index! {
     #[debug_format = "PointIndex({})"]
     pub struct PointIndex {}
 }
-
-/// Add points depending on the result of the given dataflow analysis.
-pub fn save_as_intervals<'tcx, N, A>(
-    elements: &DenseLocationMap,
-    body: &mir::Body<'tcx>,
-    mut analysis: A,
-    results: Results<A::Domain>,
-) -> SparseIntervalMatrix<N, PointIndex>
-where
-    N: Idx,
-    A: Analysis<'tcx, Domain = DenseBitSet<N>>,
-{
-    let values = SparseIntervalMatrix::new(elements.num_points());
-    let mut visitor = Visitor { elements, values };
-    visit_results(
-        body,
-        body.basic_blocks.reverse_postorder().iter().copied(),
-        &mut analysis,
-        &results,
-        &mut visitor,
-    );
-    visitor.values
-}
-
-struct Visitor<'a, N: Idx> {
-    elements: &'a DenseLocationMap,
-    values: SparseIntervalMatrix<N, PointIndex>,
-}
-
-impl<'tcx, A, N> ResultsVisitor<'tcx, A> for Visitor<'_, N>
-where
-    A: Analysis<'tcx, Domain = DenseBitSet<N>>,
-    N: Idx,
-{
-    fn visit_after_primary_statement_effect<'mir>(
-        &mut self,
-        _analysis: &mut A,
-        state: &A::Domain,
-        _statement: &'mir mir::Statement<'tcx>,
-        location: Location,
-    ) {
-        let point = self.elements.point_from_location(location);
-        // Use internal iterator manually as it is much more efficient.
-        state.iter().for_each(|node| {
-            self.values.insert(node, point);
-        });
-    }
-
-    fn visit_after_primary_terminator_effect<'mir>(
-        &mut self,
-        _analysis: &mut A,
-        state: &A::Domain,
-        _terminator: &'mir mir::Terminator<'tcx>,
-        location: Location,
-    ) {
-        let point = self.elements.point_from_location(location);
-        // Use internal iterator manually as it is much more efficient.
-        state.iter().for_each(|node| {
-            self.values.insert(node, point);
-        });
-    }
-}
diff --git a/compiler/rustc_mir_dataflow/src/value_analysis.rs b/compiler/rustc_mir_dataflow/src/value_analysis.rs
index 005e7973130..bf5ec8f459e 100644
--- a/compiler/rustc_mir_dataflow/src/value_analysis.rs
+++ b/compiler/rustc_mir_dataflow/src/value_analysis.rs
@@ -6,7 +6,7 @@ use rustc_data_structures::fx::{FxHashMap, FxIndexSet, StdEntry};
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_index::IndexVec;
 use rustc_index::bit_set::DenseBitSet;
-use rustc_middle::mir::visit::{MutatingUseContext, PlaceContext, Visitor};
+use rustc_middle::mir::visit::{PlaceContext, Visitor};
 use rustc_middle::mir::*;
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use tracing::debug;
@@ -891,7 +891,7 @@ pub fn iter_fields<'tcx>(
                     let field_ty = f_def.ty(tcx, args);
                     let field_ty = tcx
                         .try_normalize_erasing_regions(typing_env, field_ty)
-                        .unwrap_or_else(|_| tcx.erase_regions(field_ty));
+                        .unwrap_or_else(|_| tcx.erase_and_anonymize_regions(field_ty));
                     f(variant, f_index.into(), field_ty);
                 }
             }
@@ -917,12 +917,7 @@ pub fn excluded_locals(body: &Body<'_>) -> DenseBitSet<Local> {
 
     impl<'tcx> Visitor<'tcx> for Collector {
         fn visit_place(&mut self, place: &Place<'tcx>, context: PlaceContext, _location: Location) {
-            if (context.is_borrow()
-                || context.is_address_of()
-                || context.is_drop()
-                || context == PlaceContext::MutatingUse(MutatingUseContext::AsmOutput))
-                && !place.is_indirect()
-            {
+            if context.may_observe_address() && !place.is_indirect() {
                 // A pointer to a place could be used to access other places with the same local,
                 // hence we have to exclude the local completely.
                 self.result.insert(place.local);
diff --git a/compiler/rustc_mir_transform/src/add_subtyping_projections.rs b/compiler/rustc_mir_transform/src/add_subtyping_projections.rs
index 92ee80eaa35..be4f84d64d0 100644
--- a/compiler/rustc_mir_transform/src/add_subtyping_projections.rs
+++ b/compiler/rustc_mir_transform/src/add_subtyping_projections.rs
@@ -32,8 +32,8 @@ impl<'a, 'tcx> MutVisitor<'tcx> for SubTypeChecker<'a, 'tcx> {
         let mut rval_ty = rvalue.ty(self.local_decls, self.tcx);
         // Not erasing this causes `Free Regions` errors in validator,
         // when rval is `ReStatic`.
-        rval_ty = self.tcx.erase_regions(rval_ty);
-        place_ty = self.tcx.erase_regions(place_ty);
+        rval_ty = self.tcx.erase_and_anonymize_regions(rval_ty);
+        place_ty = self.tcx.erase_and_anonymize_regions(place_ty);
         if place_ty != rval_ty {
             let temp = self
                 .patcher
diff --git a/compiler/rustc_mir_transform/src/cross_crate_inline.rs b/compiler/rustc_mir_transform/src/cross_crate_inline.rs
index b186c2bd775..df98c07f549 100644
--- a/compiler/rustc_mir_transform/src/cross_crate_inline.rs
+++ b/compiler/rustc_mir_transform/src/cross_crate_inline.rs
@@ -135,7 +135,16 @@ impl<'tcx> Visitor<'tcx> for CostChecker<'_, 'tcx> {
                     }
                 }
             }
-            TerminatorKind::Call { unwind, .. } => {
+            TerminatorKind::Call { ref func, unwind, .. } => {
+                // We track calls because they make our function not a leaf (and in theory, the
+                // number of calls indicates how likely this function is to perturb other CGUs).
+                // But intrinsics don't have a body that gets assigned to a CGU, so they are
+                // ignored.
+                if let Some((fn_def_id, _)) = func.const_fn_def()
+                    && self.tcx.has_attr(fn_def_id, sym::rustc_intrinsic)
+                {
+                    return;
+                }
                 self.calls += 1;
                 if let UnwindAction::Cleanup(_) = unwind {
                     self.landing_pads += 1;
diff --git a/compiler/rustc_mir_transform/src/dest_prop.rs b/compiler/rustc_mir_transform/src/dest_prop.rs
index cf7425251e8..9ba2d274691 100644
--- a/compiler/rustc_mir_transform/src/dest_prop.rs
+++ b/compiler/rustc_mir_transform/src/dest_prop.rs
@@ -59,6 +59,12 @@
 //! The first two conditions are simple structural requirements on the `Assign` statements that can
 //! be trivially checked. The third requirement however is more difficult and costly to check.
 //!
+//! ## Current implementation
+//!
+//! The current implementation relies on live range computation to check for conflicts. We only
+//! allow to merge locals that have disjoint live ranges. The live range are defined with
+//! half-statement granularity, so as to make all writes be live for at least a half statement.
+//!
 //! ## Future Improvements
 //!
 //! There are a number of ways in which this pass could be improved in the future:
@@ -117,9 +123,8 @@
 //! - Layout optimizations for coroutines have been added to improve code generation for
 //!   async/await, which are very similar in spirit to what this optimization does.
 //!
-//! Also, rustc now has a simple NRVO pass (see `nrvo.rs`), which handles a subset of the cases that
-//! this destination propagation pass handles, proving that similar optimizations can be performed
-//! on MIR.
+//! [The next approach][attempt 4] computes a conflict matrix between locals by forbidding merging
+//! locals with competing writes or with one write while the other is live.
 //!
 //! ## Pre/Post Optimization
 //!
@@ -130,20 +135,18 @@
 //! [attempt 1]: https://github.com/rust-lang/rust/pull/47954
 //! [attempt 2]: https://github.com/rust-lang/rust/pull/71003
 //! [attempt 3]: https://github.com/rust-lang/rust/pull/72632
+//! [attempt 4]: https://github.com/rust-lang/rust/pull/96451
 
-use rustc_data_structures::fx::{FxIndexMap, IndexEntry, IndexOccupiedEntry};
+use rustc_data_structures::union_find::UnionFind;
 use rustc_index::bit_set::DenseBitSet;
 use rustc_index::interval::SparseIntervalMatrix;
-use rustc_middle::bug;
+use rustc_index::{IndexVec, newtype_index};
 use rustc_middle::mir::visit::{MutVisitor, PlaceContext, Visitor};
-use rustc_middle::mir::{
-    Body, HasLocalDecls, InlineAsmOperand, Local, LocalKind, Location, MirDumper, Operand,
-    PassWhere, Place, Rvalue, Statement, StatementKind, TerminatorKind, traversal,
-};
+use rustc_middle::mir::*;
 use rustc_middle::ty::TyCtxt;
-use rustc_mir_dataflow::Analysis;
-use rustc_mir_dataflow::impls::MaybeLiveLocals;
-use rustc_mir_dataflow::points::{DenseLocationMap, PointIndex, save_as_intervals};
+use rustc_mir_dataflow::impls::{DefUse, MaybeLiveLocals};
+use rustc_mir_dataflow::points::DenseLocationMap;
+use rustc_mir_dataflow::{Analysis, Results};
 use tracing::{debug, trace};
 
 pub(super) struct DestinationPropagation;
@@ -161,84 +164,81 @@ impl<'tcx> crate::MirPass<'tcx> for DestinationPropagation {
         sess.mir_opt_level() >= 3
     }
 
+    #[tracing::instrument(level = "trace", skip(self, tcx, body))]
     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
         let def_id = body.source.def_id();
-        let mut candidates = Candidates::default();
-        let mut write_info = WriteInfo::default();
-        trace!(func = ?tcx.def_path_str(def_id));
+        trace!(?def_id);
 
         let borrowed = rustc_mir_dataflow::impls::borrowed_locals(body);
 
+        let candidates = Candidates::find(body, &borrowed);
+        trace!(?candidates);
+        if candidates.c.is_empty() {
+            return;
+        }
+
         let live = MaybeLiveLocals.iterate_to_fixpoint(tcx, body, Some("MaybeLiveLocals-DestProp"));
+
         let points = DenseLocationMap::new(body);
-        let mut live = save_as_intervals(&points, body, live.analysis, live.results);
-
-        // In order to avoid having to collect data for every single pair of locals in the body, we
-        // do not allow doing more than one merge for places that are derived from the same local at
-        // once. To avoid missed opportunities, we instead iterate to a fixed point - we'll refer to
-        // each of these iterations as a "round."
-        //
-        // Reaching a fixed point could in theory take up to `min(l, s)` rounds - however, we do not
-        // expect to see MIR like that. To verify this, a test was run against `[rust-lang/regex]` -
-        // the average MIR body saw 1.32 full iterations of this loop. The most that was hit were 30
-        // for a single function. Only 80/2801 (2.9%) of functions saw at least 5.
-        //
-        // [rust-lang/regex]:
-        //     https://github.com/rust-lang/regex/tree/b5372864e2df6a2f5e543a556a62197f50ca3650
-        let mut round_count = 0;
-        loop {
-            // PERF: Can we do something smarter than recalculating the candidates and liveness
-            // results?
-            candidates.reset_and_find(body, &borrowed);
-            trace!(?candidates);
-            dest_prop_mir_dump(tcx, body, &points, &live, round_count);
-
-            FilterInformation::filter_liveness(
-                &mut candidates,
-                &points,
-                &live,
-                &mut write_info,
-                body,
-            );
-
-            // Because we only filter once per round, it is unsound to use a local for more than
-            // one merge operation within a single round of optimizations. We store here which ones
-            // we have already used.
-            let mut merged_locals: DenseBitSet<Local> =
-                DenseBitSet::new_empty(body.local_decls.len());
-
-            // This is the set of merges we will apply this round. It is a subset of the candidates.
-            let mut merges = FxIndexMap::default();
-
-            for (src, candidates) in candidates.c.iter() {
-                if merged_locals.contains(*src) {
-                    continue;
-                }
-                let Some(dest) = candidates.iter().find(|dest| !merged_locals.contains(**dest))
-                else {
-                    continue;
-                };
-
-                // Replace `src` by `dest` everywhere.
-                merges.insert(*src, *dest);
-                merged_locals.insert(*src);
-                merged_locals.insert(*dest);
-
-                // Update liveness information based on the merge we just performed.
-                // Every location where `src` was live, `dest` will be live.
-                live.union_rows(*src, *dest);
+        let mut relevant = RelevantLocals::compute(&candidates, body.local_decls.len());
+        let mut live = save_as_intervals(&points, body, &relevant, live.results);
+
+        dest_prop_mir_dump(tcx, body, &points, &live, &relevant);
+
+        let mut merged_locals = DenseBitSet::new_empty(body.local_decls.len());
+
+        for (src, dst) in candidates.c.into_iter() {
+            trace!(?src, ?dst);
+
+            let Some(mut src) = relevant.find(src) else { continue };
+            let Some(mut dst) = relevant.find(dst) else { continue };
+            if src == dst {
+                continue;
             }
-            trace!(merging = ?merges);
 
-            if merges.is_empty() {
-                break;
+            let Some(src_live_ranges) = live.row(src) else { continue };
+            let Some(dst_live_ranges) = live.row(dst) else { continue };
+            trace!(?src, ?src_live_ranges);
+            trace!(?dst, ?dst_live_ranges);
+
+            if src_live_ranges.disjoint(dst_live_ranges) {
+                // We want to replace `src` by `dst`.
+                let mut orig_src = relevant.original[src];
+                let mut orig_dst = relevant.original[dst];
+
+                // The return place and function arguments are required and cannot be renamed.
+                // This check cannot be made during candidate collection, as we may want to
+                // unify the same non-required local with several required locals.
+                match (is_local_required(orig_src, body), is_local_required(orig_dst, body)) {
+                    // Renaming `src` is ok.
+                    (false, _) => {}
+                    // Renaming `src` is wrong, but renaming `dst` is ok.
+                    (true, false) => {
+                        std::mem::swap(&mut src, &mut dst);
+                        std::mem::swap(&mut orig_src, &mut orig_dst);
+                    }
+                    // Neither local can be renamed, so skip this case.
+                    (true, true) => continue,
+                }
+
+                trace!(?src, ?dst, "merge");
+                merged_locals.insert(orig_src);
+                merged_locals.insert(orig_dst);
+
+                // Replace `src` by `dst`.
+                let head = relevant.union(src, dst);
+                live.union_rows(/* read */ src, /* write */ head);
+                live.union_rows(/* read */ dst, /* write */ head);
             }
-            round_count += 1;
+        }
+        trace!(?merged_locals);
+        trace!(?relevant.renames);
 
-            apply_merges(body, tcx, merges, merged_locals);
+        if merged_locals.is_empty() {
+            return;
         }
 
-        trace!(round_count);
+        apply_merges(body, tcx, relevant, merged_locals);
     }
 
     fn is_required(&self) -> bool {
@@ -246,30 +246,6 @@ impl<'tcx> crate::MirPass<'tcx> for DestinationPropagation {
     }
 }
 
-#[derive(Debug, Default)]
-struct Candidates {
-    /// The set of candidates we are considering in this optimization.
-    ///
-    /// We will always merge the key into at most one of its values.
-    ///
-    /// Whether a place ends up in the key or the value does not correspond to whether it appears as
-    /// the lhs or rhs of any assignment. As a matter of fact, the places in here might never appear
-    /// in an assignment at all. This happens because if we see an assignment like this:
-    ///
-    /// ```ignore (syntax-highlighting-only)
-    /// _1.0 = _2.0
-    /// ```
-    ///
-    /// We will still report that we would like to merge `_1` and `_2` in an attempt to allow us to
-    /// remove that assignment.
-    c: FxIndexMap<Local, Vec<Local>>,
-
-    /// A reverse index of the `c` set; if the `c` set contains `a => Place { local: b, proj }`,
-    /// then this contains `b => a`.
-    // PERF: Possibly these should be `SmallVec`s?
-    reverse: FxIndexMap<Local, Vec<Local>>,
-}
-
 //////////////////////////////////////////////////////////
 // Merging
 //
@@ -278,16 +254,16 @@ struct Candidates {
 fn apply_merges<'tcx>(
     body: &mut Body<'tcx>,
     tcx: TyCtxt<'tcx>,
-    merges: FxIndexMap<Local, Local>,
+    relevant: RelevantLocals,
     merged_locals: DenseBitSet<Local>,
 ) {
-    let mut merger = Merger { tcx, merges, merged_locals };
+    let mut merger = Merger { tcx, relevant, merged_locals };
     merger.visit_body_preserves_cfg(body);
 }
 
 struct Merger<'tcx> {
     tcx: TyCtxt<'tcx>,
-    merges: FxIndexMap<Local, Local>,
+    relevant: RelevantLocals,
     merged_locals: DenseBitSet<Local>,
 }
 
@@ -297,8 +273,8 @@ impl<'tcx> MutVisitor<'tcx> for Merger<'tcx> {
     }
 
     fn visit_local(&mut self, local: &mut Local, _: PlaceContext, _location: Location) {
-        if let Some(dest) = self.merges.get(local) {
-            *local = *dest;
+        if let Some(relevant) = self.relevant.find(*local) {
+            *local = self.relevant.original[relevant];
         }
     }
 
@@ -336,414 +312,95 @@ impl<'tcx> MutVisitor<'tcx> for Merger<'tcx> {
 }
 
 //////////////////////////////////////////////////////////
-// Liveness filtering
+// Relevant locals
 //
-// This section enforces bullet point 2
+// Small utility to reduce size of the conflict matrix by only considering locals that appear in
+// the candidates
 
-struct FilterInformation<'a, 'tcx> {
-    body: &'a Body<'tcx>,
-    points: &'a DenseLocationMap,
-    live: &'a SparseIntervalMatrix<Local, PointIndex>,
-    candidates: &'a mut Candidates,
-    write_info: &'a mut WriteInfo,
-    at: Location,
+newtype_index! {
+    /// Represent a subset of locals which appear in candidates.
+    struct RelevantLocal {}
 }
 
-// We first implement some utility functions which we will expose removing candidates according to
-// different needs. Throughout the liveness filtering, the `candidates` are only ever accessed
-// through these methods, and not directly.
-impl Candidates {
-    /// Collects the candidates for merging.
-    ///
-    /// This is responsible for enforcing the first and third bullet point.
-    fn reset_and_find<'tcx>(&mut self, body: &Body<'tcx>, borrowed: &DenseBitSet<Local>) {
-        self.c.clear();
-        self.reverse.clear();
-        let mut visitor = FindAssignments { body, candidates: &mut self.c, borrowed };
-        visitor.visit_body(body);
-        // Deduplicate candidates.
-        for (_, cands) in self.c.iter_mut() {
-            cands.sort();
-            cands.dedup();
-        }
-        // Generate the reverse map.
-        for (src, cands) in self.c.iter() {
-            for dest in cands.iter().copied() {
-                self.reverse.entry(dest).or_default().push(*src);
-            }
-        }
-    }
-
-    /// Just `Vec::retain`, but the condition is inverted and we add debugging output
-    fn vec_filter_candidates(
-        src: Local,
-        v: &mut Vec<Local>,
-        mut f: impl FnMut(Local) -> CandidateFilter,
-        at: Location,
-    ) {
-        v.retain(|dest| {
-            let remove = f(*dest);
-            if remove == CandidateFilter::Remove {
-                trace!("eliminating {:?} => {:?} due to conflict at {:?}", src, dest, at);
-            }
-            remove == CandidateFilter::Keep
-        });
-    }
-
-    /// `vec_filter_candidates` but for an `Entry`
-    fn entry_filter_candidates(
-        mut entry: IndexOccupiedEntry<'_, Local, Vec<Local>>,
-        p: Local,
-        f: impl FnMut(Local) -> CandidateFilter,
-        at: Location,
-    ) {
-        let candidates = entry.get_mut();
-        Self::vec_filter_candidates(p, candidates, f, at);
-        if candidates.len() == 0 {
-            // FIXME(#120456) - is `swap_remove` correct?
-            entry.swap_remove();
-        }
-    }
-
-    /// For all candidates `(p, q)` or `(q, p)` removes the candidate if `f(q)` says to do so
-    fn filter_candidates_by(
-        &mut self,
-        p: Local,
-        mut f: impl FnMut(Local) -> CandidateFilter,
-        at: Location,
-    ) {
-        // Cover the cases where `p` appears as a `src`
-        if let IndexEntry::Occupied(entry) = self.c.entry(p) {
-            Self::entry_filter_candidates(entry, p, &mut f, at);
-        }
-        // And the cases where `p` appears as a `dest`
-        let Some(srcs) = self.reverse.get_mut(&p) else {
-            return;
-        };
-        // We use `retain` here to remove the elements from the reverse set if we've removed the
-        // matching candidate in the forward set.
-        srcs.retain(|src| {
-            if f(*src) == CandidateFilter::Keep {
-                return true;
-            }
-            let IndexEntry::Occupied(entry) = self.c.entry(*src) else {
-                return false;
-            };
-            Self::entry_filter_candidates(
-                entry,
-                *src,
-                |dest| {
-                    if dest == p { CandidateFilter::Remove } else { CandidateFilter::Keep }
-                },
-                at,
-            );
-            false
-        });
-    }
+#[derive(Debug)]
+struct RelevantLocals {
+    original: IndexVec<RelevantLocal, Local>,
+    shrink: IndexVec<Local, Option<RelevantLocal>>,
+    renames: UnionFind<RelevantLocal>,
 }
 
-#[derive(Copy, Clone, PartialEq, Eq)]
-enum CandidateFilter {
-    Keep,
-    Remove,
-}
+impl RelevantLocals {
+    #[tracing::instrument(level = "trace", skip(candidates, num_locals), ret)]
+    fn compute(candidates: &Candidates, num_locals: usize) -> RelevantLocals {
+        let mut original = IndexVec::with_capacity(candidates.c.len());
+        let mut shrink = IndexVec::from_elem_n(None, num_locals);
 
-impl<'a, 'tcx> FilterInformation<'a, 'tcx> {
-    /// Filters the set of candidates to remove those that conflict.
-    ///
-    /// The steps we take are exactly those that are outlined at the top of the file. For each
-    /// statement/terminator, we collect the set of locals that are written to in that
-    /// statement/terminator, and then we remove all pairs of candidates that contain one such local
-    /// and another one that is live.
-    ///
-    /// We need to be careful about the ordering of operations within each statement/terminator
-    /// here. Many statements might write and read from more than one place, and we need to consider
-    /// them all. The strategy for doing this is as follows: We first gather all the places that are
-    /// written to within the statement/terminator via `WriteInfo`. Then, we use the liveness
-    /// analysis from *before* the statement/terminator (in the control flow sense) to eliminate
-    /// candidates - this is because we want to conservatively treat a pair of locals that is both
-    /// read and written in the statement/terminator to be conflicting, and the liveness analysis
-    /// before the statement/terminator will correctly report locals that are read in the
-    /// statement/terminator to be live. We are additionally conservative by treating all written to
-    /// locals as also being read from.
-    fn filter_liveness(
-        candidates: &mut Candidates,
-        points: &DenseLocationMap,
-        live: &SparseIntervalMatrix<Local, PointIndex>,
-        write_info: &mut WriteInfo,
-        body: &Body<'tcx>,
-    ) {
-        let mut this = FilterInformation {
-            body,
-            points,
-            live,
-            candidates,
-            // We don't actually store anything at this scope, we just keep things here to be able
-            // to reuse the allocation.
-            write_info,
-            // Doesn't matter what we put here, will be overwritten before being used
-            at: Location::START,
+        // Mark a local as relevant and record it into the maps.
+        let mut declare = |local| {
+            shrink.get_or_insert_with(local, || original.push(local));
         };
-        this.internal_filter_liveness();
-    }
 
-    fn internal_filter_liveness(&mut self) {
-        for (block, data) in traversal::preorder(self.body) {
-            self.at = Location { block, statement_index: data.statements.len() };
-            self.write_info.for_terminator(&data.terminator().kind);
-            self.apply_conflicts();
-
-            for (i, statement) in data.statements.iter().enumerate().rev() {
-                self.at = Location { block, statement_index: i };
-                self.write_info.for_statement(&statement.kind, self.body);
-                self.apply_conflicts();
-            }
+        for &(src, dest) in candidates.c.iter() {
+            declare(src);
+            declare(dest)
         }
-    }
 
-    fn apply_conflicts(&mut self) {
-        let writes = &self.write_info.writes;
-        for p in writes {
-            let other_skip = self.write_info.skip_pair.and_then(|(a, b)| {
-                if a == *p {
-                    Some(b)
-                } else if b == *p {
-                    Some(a)
-                } else {
-                    None
-                }
-            });
-            let at = self.points.point_from_location(self.at);
-            self.candidates.filter_candidates_by(
-                *p,
-                |q| {
-                    if Some(q) == other_skip {
-                        return CandidateFilter::Keep;
-                    }
-                    // It is possible that a local may be live for less than the
-                    // duration of a statement This happens in the case of function
-                    // calls or inline asm. Because of this, we also mark locals as
-                    // conflicting when both of them are written to in the same
-                    // statement.
-                    if self.live.contains(q, at) || writes.contains(&q) {
-                        CandidateFilter::Remove
-                    } else {
-                        CandidateFilter::Keep
-                    }
-                },
-                self.at,
-            );
-        }
+        let renames = UnionFind::new(original.len());
+        RelevantLocals { original, shrink, renames }
     }
-}
 
-/// Describes where a statement/terminator writes to
-#[derive(Default, Debug)]
-struct WriteInfo {
-    writes: Vec<Local>,
-    /// If this pair of locals is a candidate pair, completely skip processing it during this
-    /// statement. All other candidates are unaffected.
-    skip_pair: Option<(Local, Local)>,
-}
-
-impl WriteInfo {
-    fn for_statement<'tcx>(&mut self, statement: &StatementKind<'tcx>, body: &Body<'tcx>) {
-        self.reset();
-        match statement {
-            StatementKind::Assign(box (lhs, rhs)) => {
-                self.add_place(*lhs);
-                match rhs {
-                    Rvalue::Use(op) => {
-                        self.add_operand(op);
-                        self.consider_skipping_for_assign_use(*lhs, op, body);
-                    }
-                    Rvalue::Repeat(op, _) => {
-                        self.add_operand(op);
-                    }
-                    Rvalue::Cast(_, op, _)
-                    | Rvalue::UnaryOp(_, op)
-                    | Rvalue::ShallowInitBox(op, _) => {
-                        self.add_operand(op);
-                    }
-                    Rvalue::BinaryOp(_, ops) => {
-                        for op in [&ops.0, &ops.1] {
-                            self.add_operand(op);
-                        }
-                    }
-                    Rvalue::Aggregate(_, ops) => {
-                        for op in ops {
-                            self.add_operand(op);
-                        }
-                    }
-                    Rvalue::WrapUnsafeBinder(op, _) => {
-                        self.add_operand(op);
-                    }
-                    Rvalue::ThreadLocalRef(_)
-                    | Rvalue::NullaryOp(_, _)
-                    | Rvalue::Ref(_, _, _)
-                    | Rvalue::RawPtr(_, _)
-                    | Rvalue::Len(_)
-                    | Rvalue::Discriminant(_)
-                    | Rvalue::CopyForDeref(_) => {}
-                }
-            }
-            // Retags are technically also reads, but reporting them as a write suffices
-            StatementKind::SetDiscriminant { place, .. }
-            | StatementKind::Deinit(place)
-            | StatementKind::Retag(_, place) => {
-                self.add_place(**place);
-            }
-            StatementKind::Intrinsic(_)
-            | StatementKind::ConstEvalCounter
-            | StatementKind::Nop
-            | StatementKind::Coverage(_)
-            | StatementKind::StorageLive(_)
-            | StatementKind::StorageDead(_)
-            | StatementKind::BackwardIncompatibleDropHint { .. }
-            | StatementKind::PlaceMention(_) => {}
-            StatementKind::FakeRead(_) | StatementKind::AscribeUserType(_, _) => {
-                bug!("{:?} not found in this MIR phase", statement)
-            }
-        }
+    fn find(&mut self, src: Local) -> Option<RelevantLocal> {
+        let src = self.shrink[src]?;
+        let src = self.renames.find(src);
+        Some(src)
     }
 
-    fn consider_skipping_for_assign_use<'tcx>(
-        &mut self,
-        lhs: Place<'tcx>,
-        rhs: &Operand<'tcx>,
-        body: &Body<'tcx>,
-    ) {
-        let Some(rhs) = rhs.place() else { return };
-        if let Some(pair) = places_to_candidate_pair(lhs, rhs, body) {
-            self.skip_pair = Some(pair);
-        }
-    }
-
-    fn for_terminator<'tcx>(&mut self, terminator: &TerminatorKind<'tcx>) {
-        self.reset();
-        match terminator {
-            TerminatorKind::SwitchInt { discr: op, .. }
-            | TerminatorKind::Assert { cond: op, .. } => {
-                self.add_operand(op);
-            }
-            TerminatorKind::Call { destination, func, args, .. } => {
-                self.add_place(*destination);
-                self.add_operand(func);
-                for arg in args {
-                    self.add_operand(&arg.node);
-                }
-            }
-            TerminatorKind::TailCall { func, args, .. } => {
-                self.add_operand(func);
-                for arg in args {
-                    self.add_operand(&arg.node);
-                }
-            }
-            TerminatorKind::InlineAsm { operands, .. } => {
-                for asm_operand in operands {
-                    match asm_operand {
-                        InlineAsmOperand::In { value, .. } => {
-                            self.add_operand(value);
-                        }
-                        InlineAsmOperand::Out { place, .. } => {
-                            if let Some(place) = place {
-                                self.add_place(*place);
-                            }
-                        }
-                        // Note that the `late` field in `InOut` is about whether the registers used
-                        // for these things overlap, and is of absolutely no interest to us.
-                        InlineAsmOperand::InOut { in_value, out_place, .. } => {
-                            if let Some(place) = out_place {
-                                self.add_place(*place);
-                            }
-                            self.add_operand(in_value);
-                        }
-                        InlineAsmOperand::Const { .. }
-                        | InlineAsmOperand::SymFn { .. }
-                        | InlineAsmOperand::SymStatic { .. }
-                        | InlineAsmOperand::Label { .. } => {}
-                    }
-                }
-            }
-            TerminatorKind::Goto { .. }
-            | TerminatorKind::UnwindResume
-            | TerminatorKind::UnwindTerminate(_)
-            | TerminatorKind::Return
-            | TerminatorKind::Unreachable { .. } => (),
-            TerminatorKind::Drop { .. } => {
-                // `Drop`s create a `&mut` and so are not considered
-            }
-            TerminatorKind::Yield { .. }
-            | TerminatorKind::CoroutineDrop
-            | TerminatorKind::FalseEdge { .. }
-            | TerminatorKind::FalseUnwind { .. } => {
-                bug!("{:?} not found in this MIR phase", terminator)
-            }
-        }
-    }
-
-    fn add_place(&mut self, place: Place<'_>) {
-        self.writes.push(place.local);
-    }
-
-    fn add_operand<'tcx>(&mut self, op: &Operand<'tcx>) {
-        match op {
-            // FIXME(JakobDegen): In a previous version, the `Move` case was incorrectly treated as
-            // being a read only. This was unsound, however we cannot add a regression test because
-            // it is not possible to set this off with current MIR. Once we have that ability, a
-            // regression test should be added.
-            Operand::Move(p) => self.add_place(*p),
-            Operand::Copy(_) | Operand::Constant(_) => (),
-        }
-    }
-
-    fn reset(&mut self) {
-        self.writes.clear();
-        self.skip_pair = None;
+    fn union(&mut self, lhs: RelevantLocal, rhs: RelevantLocal) -> RelevantLocal {
+        let head = self.renames.unify(lhs, rhs);
+        // We need to ensure we keep the original local of the RHS, as it may be a required local.
+        self.original[head] = self.original[rhs];
+        head
     }
 }
 
 /////////////////////////////////////////////////////
 // Candidate accumulation
 
-/// If the pair of places is being considered for merging, returns the candidate which would be
-/// merged in order to accomplish this.
-///
-/// The contract here is in one direction - there is a guarantee that merging the locals that are
-/// outputted by this function would result in an assignment between the inputs becoming a
-/// self-assignment. However, there is no guarantee that the returned pair is actually suitable for
-/// merging - candidate collection must still check this independently.
-///
-/// This output is unique for each unordered pair of input places.
-fn places_to_candidate_pair<'tcx>(
-    a: Place<'tcx>,
-    b: Place<'tcx>,
-    body: &Body<'tcx>,
-) -> Option<(Local, Local)> {
-    let (mut a, mut b) = if a.projection.len() == 0 && b.projection.len() == 0 {
-        (a.local, b.local)
-    } else {
-        return None;
-    };
+#[derive(Debug, Default)]
+struct Candidates {
+    /// The set of candidates we are considering in this optimization.
+    ///
+    /// Whether a place ends up in the key or the value does not correspond to whether it appears as
+    /// the lhs or rhs of any assignment. As a matter of fact, the places in here might never appear
+    /// in an assignment at all. This happens because if we see an assignment like this:
+    ///
+    /// ```ignore (syntax-highlighting-only)
+    /// _1.0 = _2.0
+    /// ```
+    ///
+    /// We will still report that we would like to merge `_1` and `_2` in an attempt to allow us to
+    /// remove that assignment.
+    c: Vec<(Local, Local)>,
+}
 
-    // By sorting, we make sure we're input order independent
-    if a > b {
-        std::mem::swap(&mut a, &mut b);
-    }
+// We first implement some utility functions which we will expose removing candidates according to
+// different needs. Throughout the liveness filtering, the `candidates` are only ever accessed
+// through these methods, and not directly.
+impl Candidates {
+    /// Collects the candidates for merging.
+    ///
+    /// This is responsible for enforcing the first and third bullet point.
+    fn find(body: &Body<'_>, borrowed: &DenseBitSet<Local>) -> Candidates {
+        let mut visitor = FindAssignments { body, candidates: Default::default(), borrowed };
+        visitor.visit_body(body);
 
-    // We could now return `(a, b)`, but then we miss some candidates in the case where `a` can't be
-    // used as a `src`.
-    if is_local_required(a, body) {
-        std::mem::swap(&mut a, &mut b);
+        Candidates { c: visitor.candidates }
     }
-    // We could check `is_local_required` again here, but there's no need - after all, we make no
-    // promise that the candidate pair is actually valid
-    Some((a, b))
 }
 
 struct FindAssignments<'a, 'tcx> {
     body: &'a Body<'tcx>,
-    candidates: &'a mut FxIndexMap<Local, Vec<Local>>,
+    candidates: Vec<(Local, Local)>,
     borrowed: &'a DenseBitSet<Local>,
 }
 
@@ -753,11 +410,9 @@ impl<'tcx> Visitor<'tcx> for FindAssignments<'_, 'tcx> {
             lhs,
             Rvalue::CopyForDeref(rhs) | Rvalue::Use(Operand::Copy(rhs) | Operand::Move(rhs)),
         )) = &statement.kind
+            && let Some(src) = lhs.as_local()
+            && let Some(dest) = rhs.as_local()
         {
-            let Some((src, dest)) = places_to_candidate_pair(*lhs, *rhs, self.body) else {
-                return;
-            };
-
             // As described at the top of the file, we do not go near things that have
             // their address taken.
             if self.borrowed.contains(src) || self.borrowed.contains(dest) {
@@ -774,13 +429,8 @@ impl<'tcx> Visitor<'tcx> for FindAssignments<'_, 'tcx> {
                 return;
             }
 
-            // Also, we need to make sure that MIR actually allows the `src` to be removed
-            if is_local_required(src, self.body) {
-                return;
-            }
-
             // We may insert duplicates here, but that's fine
-            self.candidates.entry(src).or_default().push(dest);
+            self.candidates.push((src, dest));
         }
     }
 }
@@ -803,22 +453,162 @@ fn dest_prop_mir_dump<'tcx>(
     tcx: TyCtxt<'tcx>,
     body: &Body<'tcx>,
     points: &DenseLocationMap,
-    live: &SparseIntervalMatrix<Local, PointIndex>,
-    round: usize,
+    live: &SparseIntervalMatrix<RelevantLocal, TwoStepIndex>,
+    relevant: &RelevantLocals,
 ) {
     let locals_live_at = |location| {
-        let location = points.point_from_location(location);
-        live.rows().filter(|&r| live.contains(r, location)).collect::<Vec<_>>()
+        live.rows()
+            .filter(|&r| live.contains(r, location))
+            .map(|rl| relevant.original[rl])
+            .collect::<Vec<_>>()
     };
 
     if let Some(dumper) = MirDumper::new(tcx, "DestinationPropagation-dataflow", body) {
         let extra_data = &|pass_where, w: &mut dyn std::io::Write| {
             if let PassWhere::BeforeLocation(loc) = pass_where {
-                writeln!(w, "        // live: {:?}", locals_live_at(loc))?;
+                let location = TwoStepIndex::new(points, loc, Effect::Before);
+                let live = locals_live_at(location);
+                writeln!(w, "        // before: {:?} => {:?}", location, live)?;
+            }
+            if let PassWhere::AfterLocation(loc) = pass_where {
+                let location = TwoStepIndex::new(points, loc, Effect::After);
+                let live = locals_live_at(location);
+                writeln!(w, "        // after: {:?} => {:?}", location, live)?;
             }
             Ok(())
         };
 
-        dumper.set_disambiguator(&round).set_extra_data(extra_data).dump_mir(body)
+        dumper.set_extra_data(extra_data).dump_mir(body)
     }
 }
+
+#[derive(Copy, Clone, Debug)]
+enum Effect {
+    Before,
+    After,
+}
+
+rustc_index::newtype_index! {
+    /// A reversed `PointIndex` but with the lower bit encoding early/late inside the statement.
+    /// The reversed order allows to use the more efficient `IntervalSet::append` method while we
+    /// iterate on the statements in reverse order.
+    #[orderable]
+    #[debug_format = "TwoStepIndex({})"]
+    struct TwoStepIndex {}
+}
+
+impl TwoStepIndex {
+    fn new(elements: &DenseLocationMap, location: Location, effect: Effect) -> TwoStepIndex {
+        let point = elements.point_from_location(location);
+        let effect = match effect {
+            Effect::Before => 0,
+            Effect::After => 1,
+        };
+        let max_index = 2 * elements.num_points() as u32 - 1;
+        let index = 2 * point.as_u32() + (effect as u32);
+        // Reverse the indexing to use more efficient `IntervalSet::append`.
+        TwoStepIndex::from_u32(max_index - index)
+    }
+}
+
+struct VisitPlacesWith<F>(F);
+
+impl<'tcx, F> Visitor<'tcx> for VisitPlacesWith<F>
+where
+    F: FnMut(Place<'tcx>, PlaceContext),
+{
+    fn visit_local(&mut self, local: Local, ctxt: PlaceContext, _: Location) {
+        (self.0)(local.into(), ctxt);
+    }
+
+    fn visit_place(&mut self, place: &Place<'tcx>, ctxt: PlaceContext, location: Location) {
+        (self.0)(*place, ctxt);
+        self.visit_projection(place.as_ref(), ctxt, location);
+    }
+}
+
+/// Add points depending on the result of the given dataflow analysis.
+fn save_as_intervals<'tcx>(
+    elements: &DenseLocationMap,
+    body: &Body<'tcx>,
+    relevant: &RelevantLocals,
+    results: Results<DenseBitSet<Local>>,
+) -> SparseIntervalMatrix<RelevantLocal, TwoStepIndex> {
+    let mut values = SparseIntervalMatrix::new(2 * elements.num_points());
+    let mut state = MaybeLiveLocals.bottom_value(body);
+    let reachable_blocks = traversal::reachable_as_bitset(body);
+
+    let two_step_loc = |location, effect| TwoStepIndex::new(elements, location, effect);
+    let append_at =
+        |values: &mut SparseIntervalMatrix<_, _>, state: &DenseBitSet<Local>, twostep| {
+            for (relevant, &original) in relevant.original.iter_enumerated() {
+                if state.contains(original) {
+                    values.append(relevant, twostep);
+                }
+            }
+        };
+
+    // Iterate blocks in decreasing order, to visit locations in decreasing order. This
+    // allows to use the more efficient `append` method to interval sets.
+    for block in body.basic_blocks.indices().rev() {
+        if !reachable_blocks.contains(block) {
+            continue;
+        }
+
+        state.clone_from(&results[block]);
+
+        let block_data = &body.basic_blocks[block];
+        let loc = Location { block, statement_index: block_data.statements.len() };
+
+        let term = block_data.terminator();
+        let mut twostep = two_step_loc(loc, Effect::After);
+        append_at(&mut values, &state, twostep);
+        // Ensure we have a non-zero live range even for dead stores. This is done by marking all
+        // the written-to locals as live in the second half of the statement.
+        // We also ensure that operands read by terminators conflict with writes by that terminator.
+        // For instance a function call may read args after having written to the destination.
+        VisitPlacesWith(|place, ctxt| match DefUse::for_place(place, ctxt) {
+            DefUse::Def | DefUse::Use | DefUse::PartialWrite => {
+                if let Some(relevant) = relevant.shrink[place.local] {
+                    values.insert(relevant, twostep);
+                }
+            }
+            DefUse::NonUse => {}
+        })
+        .visit_terminator(term, loc);
+
+        twostep = TwoStepIndex::from_u32(twostep.as_u32() + 1);
+        debug_assert_eq!(twostep, two_step_loc(loc, Effect::Before));
+        MaybeLiveLocals.apply_early_terminator_effect(&mut state, term, loc);
+        MaybeLiveLocals.apply_primary_terminator_effect(&mut state, term, loc);
+        append_at(&mut values, &state, twostep);
+
+        for (statement_index, stmt) in block_data.statements.iter().enumerate().rev() {
+            let loc = Location { block, statement_index };
+            twostep = TwoStepIndex::from_u32(twostep.as_u32() + 1);
+            debug_assert_eq!(twostep, two_step_loc(loc, Effect::After));
+            append_at(&mut values, &state, twostep);
+            // Ensure we have a non-zero live range even for dead stores. This is done by marking
+            // all the written-to locals as live in the second half of the statement.
+            VisitPlacesWith(|place, ctxt| match DefUse::for_place(place, ctxt) {
+                DefUse::Def | DefUse::PartialWrite => {
+                    if let Some(relevant) = relevant.shrink[place.local] {
+                        values.insert(relevant, twostep);
+                    }
+                }
+                DefUse::Use | DefUse::NonUse => {}
+            })
+            .visit_statement(stmt, loc);
+
+            twostep = TwoStepIndex::from_u32(twostep.as_u32() + 1);
+            debug_assert_eq!(twostep, two_step_loc(loc, Effect::Before));
+            MaybeLiveLocals.apply_early_statement_effect(&mut state, stmt, loc);
+            MaybeLiveLocals.apply_primary_statement_effect(&mut state, stmt, loc);
+            // ... but reads from operands are marked as live here so they do not conflict with
+            // the all the writes we manually marked as live in the second half of the statement.
+            append_at(&mut values, &state, twostep);
+        }
+    }
+
+    values
+}
diff --git a/compiler/rustc_mir_transform/src/gvn.rs b/compiler/rustc_mir_transform/src/gvn.rs
index f867c130efb..bf6aa800d20 100644
--- a/compiler/rustc_mir_transform/src/gvn.rs
+++ b/compiler/rustc_mir_transform/src/gvn.rs
@@ -1644,6 +1644,11 @@ impl<'tcx> VnState<'_, 'tcx> {
                 let place =
                     Place { local, projection: self.tcx.mk_place_elems(projection.as_slice()) };
                 return Some(place);
+            } else if projection.last() == Some(&PlaceElem::Deref) {
+                // `Deref` can only be the first projection in a place.
+                // If we are here, we failed to find a local, and we already have a `Deref`.
+                // Trying to add projections will only result in an ill-formed place.
+                return None;
             } 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(self.ty(index), proj, loc)
diff --git a/compiler/rustc_mir_transform/src/inline/cycle.rs b/compiler/rustc_mir_transform/src/inline/cycle.rs
index 7f9234d1dc8..25a9baffe58 100644
--- a/compiler/rustc_mir_transform/src/inline/cycle.rs
+++ b/compiler/rustc_mir_transform/src/inline/cycle.rs
@@ -2,9 +2,9 @@ use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_data_structures::unord::UnordSet;
 use rustc_hir::def_id::{DefId, LocalDefId};
+use rustc_hir::limit::Limit;
 use rustc_middle::mir::TerminatorKind;
 use rustc_middle::ty::{self, GenericArgsRef, InstanceKind, TyCtxt, TypeVisitableExt};
-use rustc_session::Limit;
 use rustc_span::sym;
 use tracing::{instrument, trace};
 
diff --git a/compiler/rustc_mir_transform/src/promote_consts.rs b/compiler/rustc_mir_transform/src/promote_consts.rs
index 462ddfa3dd3..9ea2eb4f25d 100644
--- a/compiler/rustc_mir_transform/src/promote_consts.rs
+++ b/compiler/rustc_mir_transform/src/promote_consts.rs
@@ -875,7 +875,8 @@ impl<'a, 'tcx> Promoter<'a, 'tcx> {
             let mut promoted_operand = |ty, span| {
                 promoted.span = span;
                 promoted.local_decls[RETURN_PLACE] = LocalDecl::new(ty, span);
-                let args = tcx.erase_regions(GenericArgs::identity_for_item(tcx, def));
+                let args =
+                    tcx.erase_and_anonymize_regions(GenericArgs::identity_for_item(tcx, def));
                 let uneval =
                     mir::UnevaluatedConst { def, args, promoted: Some(next_promoted_index) };
 
diff --git a/compiler/rustc_mir_transform/src/ssa.rs b/compiler/rustc_mir_transform/src/ssa.rs
index cd9a7f4a39d..73c249a3c8c 100644
--- a/compiler/rustc_mir_transform/src/ssa.rs
+++ b/compiler/rustc_mir_transform/src/ssa.rs
@@ -225,6 +225,9 @@ impl SsaVisitor<'_, '_> {
 
 impl<'tcx> Visitor<'tcx> for SsaVisitor<'_, 'tcx> {
     fn visit_local(&mut self, local: Local, ctxt: PlaceContext, loc: Location) {
+        if ctxt.may_observe_address() {
+            self.borrowed_locals.insert(local);
+        }
         match ctxt {
             PlaceContext::MutatingUse(MutatingUseContext::Projection)
             | PlaceContext::NonMutatingUse(NonMutatingUseContext::Projection) => bug!(),
@@ -237,7 +240,6 @@ impl<'tcx> Visitor<'tcx> for SsaVisitor<'_, 'tcx> {
             PlaceContext::NonMutatingUse(
                 NonMutatingUseContext::SharedBorrow | NonMutatingUseContext::FakeBorrow,
             ) => {
-                self.borrowed_locals.insert(local);
                 self.check_dominates(local, loc);
                 self.direct_uses[local] += 1;
             }
diff --git a/compiler/rustc_monomorphize/src/collector.rs b/compiler/rustc_monomorphize/src/collector.rs
index cffeb6f9807..378d71cb1fc 100644
--- a/compiler/rustc_monomorphize/src/collector.rs
+++ b/compiler/rustc_monomorphize/src/collector.rs
@@ -217,6 +217,7 @@ use rustc_hir::attrs::InlineAttr;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{DefId, DefIdMap, LocalDefId};
 use rustc_hir::lang_items::LangItem;
+use rustc_hir::limit::Limit;
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use rustc_middle::mir::interpret::{AllocId, ErrorHandled, GlobalAlloc, Scalar};
 use rustc_middle::mir::mono::{CollectionMode, InstantiationMode, MonoItem};
@@ -231,7 +232,6 @@ use rustc_middle::ty::{
 };
 use rustc_middle::util::Providers;
 use rustc_middle::{bug, span_bug};
-use rustc_session::Limit;
 use rustc_session::config::{DebugInfo, EntryFnType};
 use rustc_span::source_map::{Spanned, dummy_spanned, respan};
 use rustc_span::{DUMMY_SP, Span};
@@ -1558,7 +1558,7 @@ impl<'v> RootCollector<'_, 'v> {
                         ty::Closure(def_id, args)
                         | ty::Coroutine(def_id, args)
                         | ty::CoroutineClosure(def_id, args) => {
-                            Instance::new_raw(def_id, self.tcx.erase_regions(args))
+                            Instance::new_raw(def_id, self.tcx.erase_and_anonymize_regions(args))
                         }
                         _ => unreachable!(),
                     };
diff --git a/compiler/rustc_monomorphize/src/mono_checks/move_check.rs b/compiler/rustc_monomorphize/src/mono_checks/move_check.rs
index 7251ef478c6..0adf1b089b5 100644
--- a/compiler/rustc_monomorphize/src/mono_checks/move_check.rs
+++ b/compiler/rustc_monomorphize/src/mono_checks/move_check.rs
@@ -1,10 +1,10 @@
 use rustc_abi::Size;
 use rustc_data_structures::fx::FxIndexSet;
 use rustc_hir::def_id::DefId;
+use rustc_hir::limit::Limit;
 use rustc_middle::mir::visit::Visitor as MirVisitor;
 use rustc_middle::mir::{self, Location, traversal};
 use rustc_middle::ty::{self, AssocTag, Instance, Ty, TyCtxt, TypeFoldable};
-use rustc_session::Limit;
 use rustc_session::lint::builtin::LARGE_ASSIGNMENTS;
 use rustc_span::source_map::Spanned;
 use rustc_span::{Ident, Span, sym};
diff --git a/compiler/rustc_next_trait_solver/src/canonicalizer.rs b/compiler/rustc_next_trait_solver/src/canonicalizer.rs
index da05c49756f..a8f2b4e8db6 100644
--- a/compiler/rustc_next_trait_solver/src/canonicalizer.rs
+++ b/compiler/rustc_next_trait_solver/src/canonicalizer.rs
@@ -2,9 +2,8 @@ use rustc_type_ir::data_structures::{HashMap, ensure_sufficient_stack};
 use rustc_type_ir::inherent::*;
 use rustc_type_ir::solve::{Goal, QueryInput};
 use rustc_type_ir::{
-    self as ty, Canonical, CanonicalParamEnvCacheEntry, CanonicalTyVarKind, CanonicalVarKind,
-    Flags, InferCtxtLike, Interner, TypeFlags, TypeFoldable, TypeFolder, TypeSuperFoldable,
-    TypeVisitableExt,
+    self as ty, Canonical, CanonicalParamEnvCacheEntry, CanonicalVarKind, Flags, InferCtxtLike,
+    Interner, TypeFlags, TypeFoldable, TypeFolder, TypeSuperFoldable, TypeVisitableExt,
 };
 
 use crate::delegate::SolverDelegate;
@@ -68,6 +67,13 @@ pub struct Canonicalizer<'a, D: SolverDelegate<Interner = I>, I: Interner> {
     variables: &'a mut Vec<I::GenericArg>,
     var_kinds: Vec<CanonicalVarKind<I>>,
     variable_lookup_table: HashMap<I::GenericArg, usize>,
+    /// Maps each `sub_unification_table_root_var` to the index of the first
+    /// variable which used it.
+    ///
+    /// This means in case two type variables have the same sub relations root,
+    /// we set the `sub_root` of the second variable to the position of the first.
+    /// Otherwise the `sub_root` of each type variable is just its own position.
+    sub_root_lookup_table: HashMap<ty::TyVid, usize>,
     binder_index: ty::DebruijnIndex,
 
     /// We only use the debruijn index during lookup. We don't need to
@@ -89,6 +95,7 @@ impl<'a, D: SolverDelegate<Interner = I>, I: Interner> Canonicalizer<'a, D, I> {
 
             variables,
             variable_lookup_table: Default::default(),
+            sub_root_lookup_table: Default::default(),
             var_kinds: Vec::new(),
             binder_index: ty::INNERMOST,
 
@@ -133,6 +140,7 @@ impl<'a, D: SolverDelegate<Interner = I>, I: Interner> Canonicalizer<'a, D, I> {
 
                         variables: &mut variables,
                         variable_lookup_table: Default::default(),
+                        sub_root_lookup_table: Default::default(),
                         var_kinds: Vec::new(),
                         binder_index: ty::INNERMOST,
 
@@ -140,6 +148,7 @@ impl<'a, D: SolverDelegate<Interner = I>, I: Interner> Canonicalizer<'a, D, I> {
                     };
                     let param_env = param_env.fold_with(&mut env_canonicalizer);
                     debug_assert_eq!(env_canonicalizer.binder_index, ty::INNERMOST);
+                    debug_assert!(env_canonicalizer.sub_root_lookup_table.is_empty());
                     CanonicalParamEnvCacheEntry {
                         param_env,
                         variable_lookup_table: env_canonicalizer.variable_lookup_table,
@@ -165,6 +174,7 @@ impl<'a, D: SolverDelegate<Interner = I>, I: Interner> Canonicalizer<'a, D, I> {
 
                 variables,
                 variable_lookup_table: Default::default(),
+                sub_root_lookup_table: Default::default(),
                 var_kinds: Vec::new(),
                 binder_index: ty::INNERMOST,
 
@@ -172,6 +182,7 @@ impl<'a, D: SolverDelegate<Interner = I>, I: Interner> Canonicalizer<'a, D, I> {
             };
             let param_env = param_env.fold_with(&mut env_canonicalizer);
             debug_assert_eq!(env_canonicalizer.binder_index, ty::INNERMOST);
+            debug_assert!(env_canonicalizer.sub_root_lookup_table.is_empty());
             (param_env, env_canonicalizer.variable_lookup_table, env_canonicalizer.var_kinds)
         }
     }
@@ -200,6 +211,7 @@ impl<'a, D: SolverDelegate<Interner = I>, I: Interner> Canonicalizer<'a, D, I> {
 
             variables,
             variable_lookup_table,
+            sub_root_lookup_table: Default::default(),
             var_kinds,
             binder_index: ty::INNERMOST,
 
@@ -266,6 +278,13 @@ impl<'a, D: SolverDelegate<Interner = I>, I: Interner> Canonicalizer<'a, D, I> {
         ty::BoundVar::from(idx)
     }
 
+    fn get_or_insert_sub_root(&mut self, vid: ty::TyVid) -> ty::BoundVar {
+        let root_vid = self.delegate.sub_unification_table_root_var(vid);
+        let idx =
+            *self.sub_root_lookup_table.entry(root_vid).or_insert_with(|| self.variables.len());
+        ty::BoundVar::from(idx)
+    }
+
     fn finalize(self) -> (ty::UniverseIndex, I::CanonicalVarKinds) {
         let mut var_kinds = self.var_kinds;
         // See the rustc-dev-guide section about how we deal with universes
@@ -313,18 +332,15 @@ impl<'a, D: SolverDelegate<Interner = I>, I: Interner> Canonicalizer<'a, D, I> {
                         "ty vid should have been resolved fully before canonicalization"
                     );
 
-                    match self.canonicalize_mode {
-                        CanonicalizeMode::Input { .. } => CanonicalVarKind::Ty(
-                            CanonicalTyVarKind::General(ty::UniverseIndex::ROOT),
-                        ),
-                        CanonicalizeMode::Response { .. } => {
-                            CanonicalVarKind::Ty(CanonicalTyVarKind::General(
-                                self.delegate.universe_of_ty(vid).unwrap_or_else(|| {
-                                    panic!("ty var should have been resolved: {t:?}")
-                                }),
-                            ))
-                        }
-                    }
+                    let sub_root = self.get_or_insert_sub_root(vid);
+                    let ui = match self.canonicalize_mode {
+                        CanonicalizeMode::Input { .. } => ty::UniverseIndex::ROOT,
+                        CanonicalizeMode::Response { .. } => self
+                            .delegate
+                            .universe_of_ty(vid)
+                            .unwrap_or_else(|| panic!("ty var should have been resolved: {t:?}")),
+                    };
+                    CanonicalVarKind::Ty { ui, sub_root }
                 }
                 ty::IntVar(vid) => {
                     debug_assert_eq!(
@@ -332,7 +348,7 @@ impl<'a, D: SolverDelegate<Interner = I>, I: Interner> Canonicalizer<'a, D, I> {
                         t,
                         "ty vid should have been resolved fully before canonicalization"
                     );
-                    CanonicalVarKind::Ty(CanonicalTyVarKind::Int)
+                    CanonicalVarKind::Int
                 }
                 ty::FloatVar(vid) => {
                     debug_assert_eq!(
@@ -340,7 +356,7 @@ impl<'a, D: SolverDelegate<Interner = I>, I: Interner> Canonicalizer<'a, D, I> {
                         t,
                         "ty vid should have been resolved fully before canonicalization"
                     );
-                    CanonicalVarKind::Ty(CanonicalTyVarKind::Float)
+                    CanonicalVarKind::Float
                 }
                 ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_) => {
                     panic!("fresh vars not expected in canonicalization")
diff --git a/compiler/rustc_next_trait_solver/src/coherence.rs b/compiler/rustc_next_trait_solver/src/coherence.rs
index 79219b34e29..b949deb1192 100644
--- a/compiler/rustc_next_trait_solver/src/coherence.rs
+++ b/compiler/rustc_next_trait_solver/src/coherence.rs
@@ -435,7 +435,21 @@ where
                 }
             }
             ty::Error(_) => ControlFlow::Break(OrphanCheckEarlyExit::LocalTy(ty)),
-            ty::Closure(did, ..) | ty::CoroutineClosure(did, ..) | ty::Coroutine(did, ..) => {
+            ty::Closure(did, ..) => {
+                if self.def_id_is_local(did) {
+                    ControlFlow::Break(OrphanCheckEarlyExit::LocalTy(ty))
+                } else {
+                    self.found_non_local_ty(ty)
+                }
+            }
+            ty::CoroutineClosure(did, ..) => {
+                if self.def_id_is_local(did) {
+                    ControlFlow::Break(OrphanCheckEarlyExit::LocalTy(ty))
+                } else {
+                    self.found_non_local_ty(ty)
+                }
+            }
+            ty::Coroutine(did, ..) => {
                 if self.def_id_is_local(did) {
                     ControlFlow::Break(OrphanCheckEarlyExit::LocalTy(ty))
                 } else {
diff --git a/compiler/rustc_next_trait_solver/src/delegate.rs b/compiler/rustc_next_trait_solver/src/delegate.rs
index 7b932010d49..41c2e5f60ec 100644
--- a/compiler/rustc_next_trait_solver/src/delegate.rs
+++ b/compiler/rustc_next_trait_solver/src/delegate.rs
@@ -57,12 +57,14 @@ pub trait SolverDelegate: Deref<Target = Self::Infcx> + Sized {
     where
         V: TypeFoldable<Self::Interner>;
 
-    fn instantiate_canonical_var_with_infer(
+    fn instantiate_canonical_var(
         &self,
         kind: ty::CanonicalVarKind<Self::Interner>,
         span: <Self::Interner as Interner>::Span,
+        var_values: &[<Self::Interner as Interner>::GenericArg],
         universe_map: impl Fn(ty::UniverseIndex) -> ty::UniverseIndex,
     ) -> <Self::Interner as Interner>::GenericArg;
+
     fn add_item_bounds_for_hidden_type(
         &self,
         def_id: <Self::Interner as Interner>::DefId,
@@ -76,7 +78,7 @@ pub trait SolverDelegate: Deref<Target = Self::Infcx> + Sized {
         &self,
         goal_trait_ref: ty::TraitRef<Self::Interner>,
         trait_assoc_def_id: <Self::Interner as Interner>::DefId,
-        impl_def_id: <Self::Interner as Interner>::DefId,
+        impl_def_id: <Self::Interner as Interner>::ImplId,
     ) -> Result<
         Option<<Self::Interner as Interner>::DefId>,
         <Self::Interner as Interner>::ErrorGuaranteed,
diff --git a/compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs b/compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs
index be7e4dd4cda..e3cf0330b14 100644
--- a/compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs
@@ -186,7 +186,7 @@ where
     fn consider_impl_candidate(
         ecx: &mut EvalCtxt<'_, D>,
         goal: Goal<I, Self>,
-        impl_def_id: I::DefId,
+        impl_def_id: I::ImplId,
     ) -> Result<Candidate<I>, NoSolution>;
 
     /// If the predicate contained an error, we want to avoid emitting unnecessary trait
diff --git a/compiler/rustc_next_trait_solver/src/solve/assembly/structural_traits.rs b/compiler/rustc_next_trait_solver/src/solve/assembly/structural_traits.rs
index 7c5940828da..f6eab286ba7 100644
--- a/compiler/rustc_next_trait_solver/src/solve/assembly/structural_traits.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/assembly/structural_traits.rs
@@ -605,7 +605,7 @@ fn coroutine_closure_to_certain_coroutine<I: Interner>(
     cx: I,
     goal_kind: ty::ClosureKind,
     goal_region: I::Region,
-    def_id: I::DefId,
+    def_id: I::CoroutineClosureId,
     args: ty::CoroutineClosureArgs<I>,
     sig: ty::CoroutineClosureSignature<I>,
 ) -> I::Ty {
@@ -629,7 +629,7 @@ fn coroutine_closure_to_ambiguous_coroutine<I: Interner>(
     cx: I,
     goal_kind: ty::ClosureKind,
     goal_region: I::Region,
-    def_id: I::DefId,
+    def_id: I::CoroutineClosureId,
     args: ty::CoroutineClosureArgs<I>,
     sig: ty::CoroutineClosureSignature<I>,
 ) -> I::Ty {
@@ -664,7 +664,7 @@ fn coroutine_closure_to_ambiguous_coroutine<I: Interner>(
 pub(in crate::solve) fn extract_fn_def_from_const_callable<I: Interner>(
     cx: I,
     self_ty: I::Ty,
-) -> Result<(ty::Binder<I, (I::FnInputTys, I::Ty)>, I::DefId, I::GenericArgs), NoSolution> {
+) -> Result<(ty::Binder<I, (I::FnInputTys, I::Ty)>, I::FunctionId, I::GenericArgs), NoSolution> {
     match self_ty.kind() {
         ty::FnDef(def_id, args) => {
             let sig = cx.fn_sig(def_id);
diff --git a/compiler/rustc_next_trait_solver/src/solve/effect_goals.rs b/compiler/rustc_next_trait_solver/src/solve/effect_goals.rs
index 229345065b1..6646857a136 100644
--- a/compiler/rustc_next_trait_solver/src/solve/effect_goals.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/effect_goals.rs
@@ -123,7 +123,7 @@ where
     fn consider_impl_candidate(
         ecx: &mut EvalCtxt<'_, D>,
         goal: Goal<I, Self>,
-        impl_def_id: I::DefId,
+        impl_def_id: I::ImplId,
     ) -> Result<Candidate<I>, NoSolution> {
         let cx = ecx.cx();
 
@@ -152,20 +152,20 @@ where
         }
 
         ecx.probe_trait_candidate(CandidateSource::Impl(impl_def_id)).enter(|ecx| {
-            let impl_args = ecx.fresh_args_for_item(impl_def_id);
+            let impl_args = ecx.fresh_args_for_item(impl_def_id.into());
             ecx.record_impl_args(impl_args);
             let impl_trait_ref = impl_trait_ref.instantiate(cx, impl_args);
 
             ecx.eq(goal.param_env, goal.predicate.trait_ref, impl_trait_ref)?;
             let where_clause_bounds = cx
-                .predicates_of(impl_def_id)
+                .predicates_of(impl_def_id.into())
                 .iter_instantiated(cx, impl_args)
                 .map(|pred| goal.with(cx, pred));
             ecx.add_goals(GoalSource::ImplWhereBound, where_clause_bounds);
 
             // For this impl to be `const`, we need to check its `[const]` bounds too.
             let const_conditions = cx
-                .const_conditions(impl_def_id)
+                .const_conditions(impl_def_id.into())
                 .iter_instantiated(cx, impl_args)
                 .map(|bound_trait_ref| {
                     goal.with(
@@ -240,7 +240,7 @@ where
             ty::TraitRef::new(cx, cx.require_trait_lang_item(SolverTraitLangItem::Sized), [output])
         });
         let requirements = cx
-            .const_conditions(def_id)
+            .const_conditions(def_id.into())
             .iter_instantiated(cx, args)
             .map(|trait_ref| {
                 (
diff --git a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs
index 6f9f4067384..169832ca5fb 100644
--- a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs
@@ -16,7 +16,8 @@ use rustc_type_ir::data_structures::HashSet;
 use rustc_type_ir::inherent::*;
 use rustc_type_ir::relate::solver_relating::RelateExt;
 use rustc_type_ir::{
-    self as ty, Canonical, CanonicalVarValues, InferCtxtLike, Interner, TypeFoldable,
+    self as ty, Canonical, CanonicalVarKind, CanonicalVarValues, InferCtxtLike, Interner,
+    TypeFoldable,
 };
 use tracing::{debug, instrument, trace};
 
@@ -336,7 +337,16 @@ where
         {
             match result_value.kind() {
                 ty::GenericArgKind::Type(t) => {
-                    if let ty::Bound(debruijn, b) = t.kind() {
+                    // We disable the instantiation guess for inference variables
+                    // and only use it for placeholders. We need to handle the
+                    // `sub_root` of type inference variables which would make this
+                    // more involved. They are also a lot rarer than region variables.
+                    if let ty::Bound(debruijn, b) = t.kind()
+                        && !matches!(
+                            response.variables.get(b.var().as_usize()).unwrap(),
+                            CanonicalVarKind::Ty { .. }
+                        )
+                    {
                         assert_eq!(debruijn, ty::INNERMOST);
                         opt_values[b.var()] = Some(*original_value);
                     }
@@ -355,39 +365,33 @@ where
                 }
             }
         }
-
-        let var_values = delegate.cx().mk_args_from_iter(
-            response.variables.iter().enumerate().map(|(index, var_kind)| {
-                if var_kind.universe() != ty::UniverseIndex::ROOT {
-                    // A variable from inside a binder of the query. While ideally these shouldn't
-                    // exist at all (see the FIXME at the start of this method), we have to deal with
-                    // them for now.
-                    delegate.instantiate_canonical_var_with_infer(var_kind, span, |idx| {
-                        prev_universe + idx.index()
-                    })
-                } else if var_kind.is_existential() {
-                    // As an optimization we sometimes avoid creating a new inference variable here.
-                    //
-                    // All new inference variables we create start out in the current universe of the caller.
-                    // This is conceptually wrong as these inference variables would be able to name
-                    // more placeholders then they should be able to. However the inference variables have
-                    // to "come from somewhere", so by equating them with the original values of the caller
-                    // later on, we pull them down into their correct universe again.
-                    if let Some(v) = opt_values[ty::BoundVar::from_usize(index)] {
-                        v
-                    } else {
-                        delegate
-                            .instantiate_canonical_var_with_infer(var_kind, span, |_| prev_universe)
-                    }
+        CanonicalVarValues::instantiate(delegate.cx(), response.variables, |var_values, kind| {
+            if kind.universe() != ty::UniverseIndex::ROOT {
+                // A variable from inside a binder of the query. While ideally these shouldn't
+                // exist at all (see the FIXME at the start of this method), we have to deal with
+                // them for now.
+                delegate.instantiate_canonical_var(kind, span, &var_values, |idx| {
+                    prev_universe + idx.index()
+                })
+            } else if kind.is_existential() {
+                // As an optimization we sometimes avoid creating a new inference variable here.
+                //
+                // All new inference variables we create start out in the current universe of the caller.
+                // This is conceptually wrong as these inference variables would be able to name
+                // more placeholders then they should be able to. However the inference variables have
+                // to "come from somewhere", so by equating them with the original values of the caller
+                // later on, we pull them down into their correct universe again.
+                if let Some(v) = opt_values[ty::BoundVar::from_usize(var_values.len())] {
+                    v
                 } else {
-                    // For placeholders which were already part of the input, we simply map this
-                    // universal bound variable back the placeholder of the input.
-                    original_values[var_kind.expect_placeholder_index()]
+                    delegate.instantiate_canonical_var(kind, span, &var_values, |_| prev_universe)
                 }
-            }),
-        );
-
-        CanonicalVarValues { var_values }
+            } else {
+                // For placeholders which were already part of the input, we simply map this
+                // universal bound variable back the placeholder of the input.
+                original_values[kind.expect_placeholder_index()]
+            }
+        })
     }
 
     /// Unify the `original_values` with the `var_values` returned by the canonical query..
diff --git a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs
index 443aebbdb4d..5cd597d4fe6 100644
--- a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs
@@ -900,6 +900,10 @@ where
             && goal.param_env.visit_with(&mut visitor).is_continue()
     }
 
+    pub(super) fn sub_unify_ty_vids_raw(&self, a: ty::TyVid, b: ty::TyVid) {
+        self.delegate.sub_unify_ty_vids_raw(a, b)
+    }
+
     #[instrument(level = "trace", skip(self, param_env), ret)]
     pub(super) fn eq<T: Relate<I>>(
         &mut self,
@@ -1092,7 +1096,7 @@ where
         &self,
         goal_trait_ref: ty::TraitRef<I>,
         trait_assoc_def_id: I::DefId,
-        impl_def_id: I::DefId,
+        impl_def_id: I::ImplId,
     ) -> Result<Option<I::DefId>, I::ErrorGuaranteed> {
         self.delegate.fetch_eligible_assoc_item(goal_trait_ref, trait_assoc_def_id, impl_def_id)
     }
diff --git a/compiler/rustc_next_trait_solver/src/solve/mod.rs b/compiler/rustc_next_trait_solver/src/solve/mod.rs
index 85f9d852d95..db3460c4ff6 100644
--- a/compiler/rustc_next_trait_solver/src/solve/mod.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/mod.rs
@@ -119,11 +119,15 @@ where
 
     #[instrument(level = "trace", skip(self))]
     fn compute_subtype_goal(&mut self, goal: Goal<I, ty::SubtypePredicate<I>>) -> QueryResult<I> {
-        if goal.predicate.a.is_ty_var() && goal.predicate.b.is_ty_var() {
-            self.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS)
-        } else {
-            self.sub(goal.param_env, goal.predicate.a, goal.predicate.b)?;
-            self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
+        match (goal.predicate.a.kind(), goal.predicate.b.kind()) {
+            (ty::Infer(ty::TyVar(a_vid)), ty::Infer(ty::TyVar(b_vid))) => {
+                self.sub_unify_ty_vids_raw(a_vid, b_vid);
+                self.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS)
+            }
+            _ => {
+                self.sub(goal.param_env, goal.predicate.a, goal.predicate.b)?;
+                self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
+            }
         }
     }
 
@@ -414,6 +418,11 @@ pub struct GoalEvaluation<I: Interner> {
     pub has_changed: HasChanged,
     /// If the [`Certainty`] was `Maybe`, then keep track of whether the goal has changed
     /// before rerunning it.
+    ///
+    /// We knowingly ignore the `sub_root` of our inference variables here. This means we
+    /// may not reevaluate a goal even though a change to the `sub_root` could cause a goal
+    /// to make progress. Tracking them adds additional complexity for an incredibly minor
+    /// type inference improvement. We could look into properly handling this in the future.
     pub stalled_on: Option<GoalStalledOn<I>>,
 }
 
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 cfdf2007391..6e6be829f52 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
@@ -5,7 +5,7 @@ mod opaque_types;
 
 use rustc_type_ir::fast_reject::DeepRejectCtxt;
 use rustc_type_ir::inherent::*;
-use rustc_type_ir::lang_items::{SolverLangItem, SolverTraitLangItem};
+use rustc_type_ir::lang_items::{SolverAdtLangItem, SolverLangItem, SolverTraitLangItem};
 use rustc_type_ir::solve::SizedTraitKind;
 use rustc_type_ir::{self as ty, Interner, NormalizesTo, PredicateKind, Upcast as _};
 use tracing::instrument;
@@ -193,7 +193,7 @@ where
     fn consider_impl_candidate(
         ecx: &mut EvalCtxt<'_, D>,
         goal: Goal<I, NormalizesTo<I>>,
-        impl_def_id: I::DefId,
+        impl_def_id: I::ImplId,
     ) -> Result<Candidate<I>, NoSolution> {
         let cx = ecx.cx();
 
@@ -217,13 +217,13 @@ where
         };
 
         ecx.probe_trait_candidate(CandidateSource::Impl(impl_def_id)).enter(|ecx| {
-            let impl_args = ecx.fresh_args_for_item(impl_def_id);
+            let impl_args = ecx.fresh_args_for_item(impl_def_id.into());
             let impl_trait_ref = impl_trait_ref.instantiate(cx, impl_args);
 
             ecx.eq(goal.param_env, goal_trait_ref, impl_trait_ref)?;
 
             let where_clause_bounds = cx
-                .predicates_of(impl_def_id)
+                .predicates_of(impl_def_id.into())
                 .iter_instantiated(cx, impl_args)
                 .map(|pred| goal.with(cx, pred));
             ecx.add_goals(GoalSource::ImplWhereBound, where_clause_bounds);
@@ -824,10 +824,10 @@ where
             // coroutine yield ty `Poll<Option<I>>`.
             let wrapped_expected_ty = Ty::new_adt(
                 cx,
-                cx.adt_def(cx.require_lang_item(SolverLangItem::Poll)),
+                cx.adt_def(cx.require_adt_lang_item(SolverAdtLangItem::Poll)),
                 cx.mk_args(&[Ty::new_adt(
                     cx,
-                    cx.adt_def(cx.require_lang_item(SolverLangItem::Option)),
+                    cx.adt_def(cx.require_adt_lang_item(SolverAdtLangItem::Option)),
                     cx.mk_args(&[expected_ty.into()]),
                 )
                 .into()]),
@@ -979,7 +979,7 @@ where
     fn translate_args(
         &mut self,
         goal: Goal<I, ty::NormalizesTo<I>>,
-        impl_def_id: I::DefId,
+        impl_def_id: I::ImplId,
         impl_args: I::GenericArgs,
         impl_trait_ref: rustc_type_ir::TraitRef<I>,
         target_container_def_id: I::DefId,
@@ -988,14 +988,15 @@ where
         Ok(if target_container_def_id == impl_trait_ref.def_id.into() {
             // Default value from the trait definition. No need to rebase.
             goal.predicate.alias.args
-        } else if target_container_def_id == impl_def_id {
+        } else if target_container_def_id == impl_def_id.into() {
             // Same impl, no need to fully translate, just a rebase from
             // the trait is sufficient.
             goal.predicate.alias.args.rebase_onto(cx, impl_trait_ref.def_id.into(), impl_args)
         } else {
             let target_args = self.fresh_args_for_item(target_container_def_id);
-            let target_trait_ref =
-                cx.impl_trait_ref(target_container_def_id).instantiate(cx, target_args);
+            let target_trait_ref = cx
+                .impl_trait_ref(target_container_def_id.try_into().unwrap())
+                .instantiate(cx, target_args);
             // Relate source impl to target impl by equating trait refs.
             self.eq(goal.param_env, impl_trait_ref, target_trait_ref)?;
             // Also add predicates since they may be needed to constrain the
diff --git a/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs b/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs
index cdcfebf2909..3e720a47f32 100644
--- a/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs
@@ -54,7 +54,7 @@ where
     fn consider_impl_candidate(
         ecx: &mut EvalCtxt<'_, D>,
         goal: Goal<I, TraitPredicate<I>>,
-        impl_def_id: I::DefId,
+        impl_def_id: I::ImplId,
     ) -> Result<Candidate<I>, NoSolution> {
         let cx = ecx.cx();
 
@@ -91,13 +91,13 @@ where
         };
 
         ecx.probe_trait_candidate(CandidateSource::Impl(impl_def_id)).enter(|ecx| {
-            let impl_args = ecx.fresh_args_for_item(impl_def_id);
+            let impl_args = ecx.fresh_args_for_item(impl_def_id.into());
             ecx.record_impl_args(impl_args);
             let impl_trait_ref = impl_trait_ref.instantiate(cx, impl_args);
 
             ecx.eq(goal.param_env, goal.predicate.trait_ref, impl_trait_ref)?;
             let where_clause_bounds = cx
-                .predicates_of(impl_def_id)
+                .predicates_of(impl_def_id.into())
                 .iter_instantiated(cx, impl_args)
                 .map(|pred| goal.with(cx, pred));
             ecx.add_goals(GoalSource::ImplWhereBound, where_clause_bounds);
diff --git a/compiler/rustc_parse/messages.ftl b/compiler/rustc_parse/messages.ftl
index 77dd313d9b8..72cd75f6d89 100644
--- a/compiler/rustc_parse/messages.ftl
+++ b/compiler/rustc_parse/messages.ftl
@@ -479,9 +479,6 @@ parse_invalid_identifier_with_leading_number = identifiers cannot start with a n
 
 parse_invalid_literal_suffix_on_tuple_index = suffixes on a tuple index are invalid
     .label = invalid suffix `{$suffix}`
-    .tuple_exception_line_1 = `{$suffix}` is *temporarily* accepted on tuple index fields as it was incorrectly accepted on stable for a few releases
-    .tuple_exception_line_2 = on proc macros, you'll want to use `syn::Index::from` or `proc_macro::Literal::*_unsuffixed` for code that will desugar to tuple field access
-    .tuple_exception_line_3 = see issue #60210 <https://github.com/rust-lang/rust/issues/60210> for more information
 
 parse_invalid_logical_operator = `{$incorrect}` is not a logical operator
     .note = unlike in e.g., Python and PHP, `&&` and `||` are used for logical operators
diff --git a/compiler/rustc_parse/src/errors.rs b/compiler/rustc_parse/src/errors.rs
index 797d4830c2f..00ca5acd84d 100644
--- a/compiler/rustc_parse/src/errors.rs
+++ b/compiler/rustc_parse/src/errors.rs
@@ -1017,10 +1017,6 @@ pub(crate) struct InvalidLiteralSuffixOnTupleIndex {
     #[label]
     pub span: Span,
     pub suffix: Symbol,
-    #[help(parse_tuple_exception_line_1)]
-    #[help(parse_tuple_exception_line_2)]
-    #[help(parse_tuple_exception_line_3)]
-    pub exception: bool,
 }
 
 #[derive(Diagnostic)]
diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index 4c02547357e..81a5d48d94e 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -1163,7 +1163,10 @@ impl<'a> Parser<'a> {
                         suffix,
                     }) => {
                         if let Some(suffix) = suffix {
-                            self.expect_no_tuple_index_suffix(current.span, suffix);
+                            self.dcx().emit_err(errors::InvalidLiteralSuffixOnTupleIndex {
+                                span: current.span,
+                                suffix,
+                            });
                         }
                         match self.break_up_float(symbol, current.span) {
                             // 1e2
@@ -1239,7 +1242,8 @@ impl<'a> Parser<'a> {
         suffix: Option<Symbol>,
     ) -> Box<Expr> {
         if let Some(suffix) = suffix {
-            self.expect_no_tuple_index_suffix(ident_span, suffix);
+            self.dcx()
+                .emit_err(errors::InvalidLiteralSuffixOnTupleIndex { span: ident_span, suffix });
         }
         self.mk_expr(lo.to(ident_span), ExprKind::Field(base, Ident::new(field, ident_span)))
     }
@@ -2225,24 +2229,6 @@ impl<'a> Parser<'a> {
         })
     }
 
-    pub(super) fn expect_no_tuple_index_suffix(&self, span: Span, suffix: Symbol) {
-        if [sym::i32, sym::u32, sym::isize, sym::usize].contains(&suffix) {
-            // #59553: warn instead of reject out of hand to allow the fix to percolate
-            // through the ecosystem when people fix their macros
-            self.dcx().emit_warn(errors::InvalidLiteralSuffixOnTupleIndex {
-                span,
-                suffix,
-                exception: true,
-            });
-        } else {
-            self.dcx().emit_err(errors::InvalidLiteralSuffixOnTupleIndex {
-                span,
-                suffix,
-                exception: false,
-            });
-        }
-    }
-
     /// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`).
     /// Keep this in sync with `Token::can_begin_literal_maybe_minus`.
     pub fn parse_literal_maybe_minus(&mut self) -> PResult<'a, Box<Expr>> {
diff --git a/compiler/rustc_parse/src/parser/mod.rs b/compiler/rustc_parse/src/parser/mod.rs
index 3bbca622975..ed4069dae93 100644
--- a/compiler/rustc_parse/src/parser/mod.rs
+++ b/compiler/rustc_parse/src/parser/mod.rs
@@ -1335,7 +1335,10 @@ impl<'a> Parser<'a> {
         if let token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) = self.token.kind
         {
             if let Some(suffix) = suffix {
-                self.expect_no_tuple_index_suffix(self.token.span, suffix);
+                self.dcx().emit_err(errors::InvalidLiteralSuffixOnTupleIndex {
+                    span: self.token.span,
+                    suffix,
+                });
             }
             self.bump();
             Ok(Ident::new(symbol, self.prev_token.span))
diff --git a/compiler/rustc_passes/messages.ftl b/compiler/rustc_passes/messages.ftl
index afd08319738..ab7885905a6 100644
--- a/compiler/rustc_passes/messages.ftl
+++ b/compiler/rustc_passes/messages.ftl
@@ -501,6 +501,10 @@ passes_repr_align_should_be_align =
     `#[repr(align(...))]` is not supported on {$item}
     .help = use `#[rustc_align(...)]` instead
 
+passes_repr_align_should_be_align_static =
+    `#[repr(align(...))]` is not supported on {$item}
+    .help = use `#[rustc_align_static(...)]` instead
+
 passes_repr_conflicting =
     conflicting representation hints
 
diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs
index 2cd4830b5d9..38a6b4b16c9 100644
--- a/compiler/rustc_passes/src/check_attr.rs
+++ b/compiler/rustc_passes/src/check_attr.rs
@@ -270,6 +270,10 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                     | AttributeKind::Linkage(..)
                     | AttributeKind::MustUse { .. }
                     | AttributeKind::CrateName { .. }
+                    | AttributeKind::RecursionLimit { .. }
+                    | AttributeKind::MoveSizeLimit { .. }
+                    | AttributeKind::TypeLengthLimit { .. }
+                    | AttributeKind::PatternComplexityLimit { .. }
                 ) => { /* do nothing  */ }
                 Attribute::Unparsed(attr_item) => {
                     style = Some(attr_item.style);
@@ -1602,12 +1606,18 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                 ReprAttr::ReprAlign(align) => {
                     match target {
                         Target::Struct | Target::Union | Target::Enum => {}
-                        Target::Fn | Target::Method(_) => {
+                        Target::Fn | Target::Method(_) if self.tcx.features().fn_align() => {
                             self.dcx().emit_err(errors::ReprAlignShouldBeAlign {
                                 span: *repr_span,
                                 item: target.plural_name(),
                             });
                         }
+                        Target::Static if self.tcx.features().static_align() => {
+                            self.dcx().emit_err(errors::ReprAlignShouldBeAlignStatic {
+                                span: *repr_span,
+                                item: target.plural_name(),
+                            });
+                        }
                         _ => {
                             self.dcx().emit_err(errors::AttrApplication::StructEnumUnion {
                                 hint_span: *repr_span,
diff --git a/compiler/rustc_passes/src/errors.rs b/compiler/rustc_passes/src/errors.rs
index 23dcabef1a1..2da4b6f52cf 100644
--- a/compiler/rustc_passes/src/errors.rs
+++ b/compiler/rustc_passes/src/errors.rs
@@ -1610,6 +1610,15 @@ pub(crate) struct ReprAlignShouldBeAlign {
 }
 
 #[derive(Diagnostic)]
+#[diag(passes_repr_align_should_be_align_static)]
+pub(crate) struct ReprAlignShouldBeAlignStatic {
+    #[primary_span]
+    #[help]
+    pub span: Span,
+    pub item: &'static str,
+}
+
+#[derive(Diagnostic)]
 #[diag(passes_custom_mir_phase_requires_dialect)]
 pub(crate) struct CustomMirPhaseRequiresDialect {
     #[primary_span]
diff --git a/compiler/rustc_query_impl/Cargo.toml b/compiler/rustc_query_impl/Cargo.toml
index e5cceacf15d..257785b10c8 100644
--- a/compiler/rustc_query_impl/Cargo.toml
+++ b/compiler/rustc_query_impl/Cargo.toml
@@ -13,7 +13,6 @@ rustc_index = { path = "../rustc_index" }
 rustc_middle = { path = "../rustc_middle" }
 rustc_query_system = { path = "../rustc_query_system" }
 rustc_serialize = { path = "../rustc_serialize" }
-rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
 tracing = "0.1"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_query_impl/src/plumbing.rs b/compiler/rustc_query_impl/src/plumbing.rs
index 55549cba737..4e601a6c594 100644
--- a/compiler/rustc_query_impl/src/plumbing.rs
+++ b/compiler/rustc_query_impl/src/plumbing.rs
@@ -9,6 +9,7 @@ use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::sync::{DynSend, DynSync};
 use rustc_data_structures::unord::UnordMap;
 use rustc_hashes::Hash64;
+use rustc_hir::limit::Limit;
 use rustc_index::Idx;
 use rustc_middle::bug;
 use rustc_middle::dep_graph::{
@@ -31,7 +32,6 @@ use rustc_query_system::query::{
 };
 use rustc_query_system::{QueryOverflow, QueryOverflowNote};
 use rustc_serialize::{Decodable, Encodable};
-use rustc_session::Limit;
 use rustc_span::def_id::LOCAL_CRATE;
 
 use crate::QueryConfigRestored;
diff --git a/compiler/rustc_query_system/src/error.rs b/compiler/rustc_query_system/src/error.rs
index 5108ecaeea3..2778b24e774 100644
--- a/compiler/rustc_query_system/src/error.rs
+++ b/compiler/rustc_query_system/src/error.rs
@@ -1,6 +1,6 @@
 use rustc_errors::codes::*;
+use rustc_hir::limit::Limit;
 use rustc_macros::{Diagnostic, Subdiagnostic};
-use rustc_session::Limit;
 use rustc_span::{Span, Symbol};
 
 #[derive(Subdiagnostic)]
diff --git a/compiler/rustc_session/src/session.rs b/compiler/rustc_session/src/session.rs
index 96767d05439..3525c7c1d1a 100644
--- a/compiler/rustc_session/src/session.rs
+++ b/compiler/rustc_session/src/session.rs
@@ -1,10 +1,9 @@
 use std::any::Any;
-use std::ops::{Div, Mul};
 use std::path::{Path, PathBuf};
 use std::str::FromStr;
 use std::sync::Arc;
 use std::sync::atomic::AtomicBool;
-use std::{env, fmt, io};
+use std::{env, io};
 
 use rand::{RngCore, rng};
 use rustc_ast::NodeId;
@@ -25,6 +24,7 @@ use rustc_errors::{
     Diag, DiagCtxt, DiagCtxtHandle, DiagMessage, Diagnostic, ErrorGuaranteed, FatalAbort,
     LintEmitter, TerminalUrl, fallback_fluent_bundle,
 };
+use rustc_hir::limit::Limit;
 use rustc_macros::HashStable_Generic;
 pub use rustc_span::def_id::StableCrateId;
 use rustc_span::edition::Edition;
@@ -62,64 +62,6 @@ pub enum CtfeBacktrace {
     Immediate,
 }
 
-/// New-type wrapper around `usize` for representing limits. Ensures that comparisons against
-/// limits are consistent throughout the compiler.
-#[derive(Clone, Copy, Debug, HashStable_Generic)]
-pub struct Limit(pub usize);
-
-impl Limit {
-    /// Create a new limit from a `usize`.
-    pub fn new(value: usize) -> Self {
-        Limit(value)
-    }
-
-    /// Create a new unlimited limit.
-    pub fn unlimited() -> Self {
-        Limit(usize::MAX)
-    }
-
-    /// Check that `value` is within the limit. Ensures that the same comparisons are used
-    /// throughout the compiler, as mismatches can cause ICEs, see #72540.
-    #[inline]
-    pub fn value_within_limit(&self, value: usize) -> bool {
-        value <= self.0
-    }
-}
-
-impl From<usize> for Limit {
-    fn from(value: usize) -> Self {
-        Self::new(value)
-    }
-}
-
-impl fmt::Display for Limit {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        self.0.fmt(f)
-    }
-}
-
-impl Div<usize> for Limit {
-    type Output = Limit;
-
-    fn div(self, rhs: usize) -> Self::Output {
-        Limit::new(self.0 / rhs)
-    }
-}
-
-impl Mul<usize> for Limit {
-    type Output = Limit;
-
-    fn mul(self, rhs: usize) -> Self::Output {
-        Limit::new(self.0 * rhs)
-    }
-}
-
-impl rustc_errors::IntoDiagArg for Limit {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> rustc_errors::DiagArgValue {
-        self.to_string().into_diag_arg(&mut None)
-    }
-}
-
 #[derive(Clone, Copy, Debug, HashStable_Generic)]
 pub struct Limits {
     /// The maximum recursion limit for potentially infinitely recursive
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index e5108d8b7e9..aedeb0e14ed 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -21,18 +21,17 @@ mod tests;
 
 // The proc macro code for this is in `compiler/rustc_macros/src/symbols.rs`.
 symbols! {
-    // This list includes things that are definitely keywords (e.g. `if`),
-    // a few things that are definitely not keywords (e.g. the empty symbol,
-    // `{{root}}`) and things where there is disagreement between people and/or
-    // documents (such as the Rust Reference) about whether it is a keyword
-    // (e.g. `_`).
+    // This list includes things that are definitely keywords (e.g. `if`), a
+    // few things that are definitely not keywords (e.g. `{{root}}`) and things
+    // where there is disagreement between people and/or documents (such as the
+    // Rust Reference) about whether it is a keyword (e.g. `_`).
     //
     // If you modify this list, adjust any relevant `Symbol::{is,can_be}_*`
     // predicates and `used_keywords`. Also consider adding new keywords to the
     // `ui/parser/raw/raw-idents.rs` test.
     Keywords {
-        // Special reserved identifiers used internally for elided lifetimes,
-        // unnamed method parameters, crate root module, error recovery etc.
+        // Special reserved identifiers used internally for unnamed method
+        // parameters, crate root module, etc.
         // Matching predicates: `is_special`/`is_reserved`
         //
         // tidy-alphabetical-start
@@ -326,6 +325,7 @@ symbols! {
         RangeSub,
         RangeTo,
         RangeToInclusive,
+        RangeToInclusiveCopy,
         Rc,
         RcWeak,
         Ready,
@@ -1280,6 +1280,7 @@ symbols! {
         lang,
         lang_items,
         large_assignments,
+        last,
         lateout,
         lazy_normalization_consts,
         lazy_type_alias,
@@ -1846,6 +1847,7 @@ symbols! {
         rustc_abi,
         // FIXME(#82232, #143834): temporary name to mitigate `#[align]` nameres ambiguity
         rustc_align,
+        rustc_align_static,
         rustc_allocator,
         rustc_allocator_zeroed,
         rustc_allocator_zeroed_variant,
@@ -2097,6 +2099,7 @@ symbols! {
         staged_api,
         start,
         state,
+        static_align,
         static_in_const,
         static_nobundle,
         static_recursion,
diff --git a/compiler/rustc_symbol_mangling/src/legacy.rs b/compiler/rustc_symbol_mangling/src/legacy.rs
index 4d9741f1d11..95a7ec61868 100644
--- a/compiler/rustc_symbol_mangling/src/legacy.rs
+++ b/compiler/rustc_symbol_mangling/src/legacy.rs
@@ -54,7 +54,7 @@ pub(super) fn mangle<'tcx>(
 
     // Erase regions because they may not be deterministic when hashed
     // and should not matter anyhow.
-    let instance_ty = tcx.erase_regions(instance_ty);
+    let instance_ty = tcx.erase_and_anonymize_regions(instance_ty);
 
     let hash = get_symbol_hash(tcx, instance, instance_ty, instantiating_crate);
 
@@ -422,7 +422,10 @@ impl<'tcx> Printer<'tcx> for LegacySymbolMangler<'tcx> {
             || &args[..generics.count()]
                 == self
                     .tcx
-                    .erase_regions(ty::GenericArgs::identity_for_item(self.tcx, impl_def_id))
+                    .erase_and_anonymize_regions(ty::GenericArgs::identity_for_item(
+                        self.tcx,
+                        impl_def_id,
+                    ))
                     .as_slice()
         {
             (
diff --git a/compiler/rustc_symbol_mangling/src/test.rs b/compiler/rustc_symbol_mangling/src/test.rs
index 0c6d1495e39..50935e7caf3 100644
--- a/compiler/rustc_symbol_mangling/src/test.rs
+++ b/compiler/rustc_symbol_mangling/src/test.rs
@@ -58,7 +58,7 @@ impl SymbolNamesTest<'_> {
             let def_id = def_id.to_def_id();
             let instance = Instance::new_raw(
                 def_id,
-                tcx.erase_regions(GenericArgs::identity_for_item(tcx, def_id)),
+                tcx.erase_and_anonymize_regions(GenericArgs::identity_for_item(tcx, def_id)),
             );
             let mangled = tcx.symbol_name(instance);
             tcx.dcx().emit_err(TestOutput {
diff --git a/compiler/rustc_symbol_mangling/src/v0.rs b/compiler/rustc_symbol_mangling/src/v0.rs
index 0655c2d5e81..1605b4958ba 100644
--- a/compiler/rustc_symbol_mangling/src/v0.rs
+++ b/compiler/rustc_symbol_mangling/src/v0.rs
@@ -329,7 +329,10 @@ impl<'tcx> Printer<'tcx> for V0SymbolMangler<'tcx> {
             || &args[..generics.count()]
                 == self
                     .tcx
-                    .erase_regions(ty::GenericArgs::identity_for_item(self.tcx, impl_def_id))
+                    .erase_and_anonymize_regions(ty::GenericArgs::identity_for_item(
+                        self.tcx,
+                        impl_def_id,
+                    ))
                     .as_slice()
         {
             (
@@ -339,7 +342,7 @@ impl<'tcx> Printer<'tcx> for V0SymbolMangler<'tcx> {
             )
         } else {
             assert!(
-                !args.has_non_region_param(),
+                !args.has_non_region_param() && !args.has_free_regions(),
                 "should not be mangling partially substituted \
                 polymorphic instance: {impl_def_id:?} {args:?}"
             );
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
index 812e20e4338..d71110521ff 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
@@ -91,7 +91,6 @@ mod suggest;
 pub mod need_type_info;
 pub mod nice_region_error;
 pub mod region;
-pub mod sub_relations;
 
 /// Makes a valid string literal from a string by escaping special characters (" and \),
 /// unless they are already escaped.
@@ -1617,8 +1616,8 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
             && let Some((e, f)) = values.ty()
             && let TypeError::ArgumentSorts(..) | TypeError::Sorts(_) = terr
         {
-            let e = self.tcx.erase_regions(e);
-            let f = self.tcx.erase_regions(f);
+            let e = self.tcx.erase_and_anonymize_regions(e);
+            let f = self.tcx.erase_and_anonymize_regions(f);
             let mut expected = with_forced_trimmed_paths!(e.sort_string(self.tcx));
             let mut found = with_forced_trimmed_paths!(f.sort_string(self.tcx));
             if let ObligationCauseCode::Pattern { span, .. } = cause.code()
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/need_type_info.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/need_type_info.rs
index ec2287ed516..edab530590b 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/need_type_info.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/need_type_info.rs
@@ -894,7 +894,8 @@ impl<'a, 'tcx> FindInferSourceVisitor<'a, 'tcx> {
                 use ty::{Infer, TyVar};
                 match (inner_ty.kind(), target_ty.kind()) {
                     (&Infer(TyVar(a_vid)), &Infer(TyVar(b_vid))) => {
-                        self.tecx.sub_relations.borrow_mut().unified(self.tecx, a_vid, b_vid)
+                        self.tecx.sub_unification_table_root_var(a_vid)
+                            == self.tecx.sub_unification_table_root_var(b_vid)
                     }
                     _ => false,
                 }
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/note_and_explain.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/note_and_explain.rs
index 40285e5d0e9..e042ce84955 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/note_and_explain.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/note_and_explain.rs
@@ -629,7 +629,11 @@ impl<T> Trait<T> for X {
         let tcx = self.tcx;
 
         // Don't suggest constraining a projection to something containing itself
-        if self.tcx.erase_regions(values.found).contains(self.tcx.erase_regions(values.expected)) {
+        if self
+            .tcx
+            .erase_and_anonymize_regions(values.found)
+            .contains(self.tcx.erase_and_anonymize_regions(values.expected))
+        {
             return;
         }
 
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/sub_relations.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/sub_relations.rs
deleted file mode 100644
index ef26a8ff7b8..00000000000
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/sub_relations.rs
+++ /dev/null
@@ -1,81 +0,0 @@
-use rustc_data_structures::fx::FxHashMap;
-use rustc_data_structures::undo_log::NoUndo;
-use rustc_data_structures::unify as ut;
-use rustc_middle::ty;
-
-use crate::infer::InferCtxt;
-
-#[derive(Debug, Copy, Clone, PartialEq)]
-struct SubId(u32);
-impl ut::UnifyKey for SubId {
-    type Value = ();
-    #[inline]
-    fn index(&self) -> u32 {
-        self.0
-    }
-    #[inline]
-    fn from_index(i: u32) -> SubId {
-        SubId(i)
-    }
-    fn tag() -> &'static str {
-        "SubId"
-    }
-}
-
-/// When reporting ambiguity errors, we sometimes want to
-/// treat all inference vars which are subtypes of each
-/// others as if they are equal. For this case we compute
-/// the transitive closure of our subtype obligations here.
-///
-/// E.g. when encountering ambiguity errors, we want to suggest
-/// specifying some method argument or to add a type annotation
-/// to a local variable. Because subtyping cannot change the
-/// shape of a type, it's fine if the cause of the ambiguity error
-/// is only related to the suggested variable via subtyping.
-///
-/// Even for something like `let x = returns_arg(); x.method();` the
-/// type of `x` is only a supertype of the argument of `returns_arg`. We
-/// still want to suggest specifying the type of the argument.
-#[derive(Default)]
-pub struct SubRelations {
-    map: FxHashMap<ty::TyVid, SubId>,
-    table: ut::UnificationTableStorage<SubId>,
-}
-
-impl SubRelations {
-    fn get_id<'tcx>(&mut self, infcx: &InferCtxt<'tcx>, vid: ty::TyVid) -> SubId {
-        let root_vid = infcx.root_var(vid);
-        *self.map.entry(root_vid).or_insert_with(|| self.table.with_log(&mut NoUndo).new_key(()))
-    }
-
-    pub fn add_constraints<'tcx>(
-        &mut self,
-        infcx: &InferCtxt<'tcx>,
-        obls: impl IntoIterator<Item = ty::Predicate<'tcx>>,
-    ) {
-        for p in obls {
-            let (a, b) = match p.kind().skip_binder() {
-                ty::PredicateKind::Subtype(ty::SubtypePredicate { a_is_expected: _, a, b }) => {
-                    (a, b)
-                }
-                ty::PredicateKind::Coerce(ty::CoercePredicate { a, b }) => (a, b),
-                _ => continue,
-            };
-
-            match (a.kind(), b.kind()) {
-                (&ty::Infer(ty::TyVar(a_vid)), &ty::Infer(ty::TyVar(b_vid))) => {
-                    let a = self.get_id(infcx, a_vid);
-                    let b = self.get_id(infcx, b_vid);
-                    self.table.with_log(&mut NoUndo).unify_var_var(a, b).unwrap();
-                }
-                _ => continue,
-            }
-        }
-    }
-
-    pub fn unified<'tcx>(&mut self, infcx: &InferCtxt<'tcx>, a: ty::TyVid, b: ty::TyVid) -> bool {
-        let a = self.get_id(infcx, a);
-        let b = self.get_id(infcx, b);
-        self.table.with_log(&mut NoUndo).unioned(a, b)
-    }
-}
diff --git a/compiler/rustc_trait_selection/src/error_reporting/mod.rs b/compiler/rustc_trait_selection/src/error_reporting/mod.rs
index 82695688ae8..cce20b05c79 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/mod.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/mod.rs
@@ -7,8 +7,6 @@ use rustc_macros::extension;
 use rustc_middle::bug;
 use rustc_middle::ty::{self, Ty};
 
-use crate::error_reporting::infer::sub_relations;
-
 pub mod infer;
 pub mod traits;
 
@@ -21,7 +19,6 @@ pub mod traits;
 /// methods which should not be used during the happy path.
 pub struct TypeErrCtxt<'a, 'tcx> {
     pub infcx: &'a InferCtxt<'tcx>,
-    pub sub_relations: std::cell::RefCell<sub_relations::SubRelations>,
 
     pub typeck_results: Option<std::cell::Ref<'a, ty::TypeckResults<'tcx>>>,
     pub fallback_has_occurred: bool,
@@ -38,7 +35,6 @@ impl<'tcx> InferCtxt<'tcx> {
     fn err_ctxt(&self) -> TypeErrCtxt<'_, 'tcx> {
         TypeErrCtxt {
             infcx: self,
-            sub_relations: Default::default(),
             typeck_results: None,
             fallback_has_occurred: false,
             normalize_fn_sig: Box::new(|fn_sig| fn_sig),
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 bc984f30472..c82043f0222 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
@@ -75,7 +75,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                 {
                     if let Some(cause) = self
                         .tcx
-                        .diagnostic_hir_wf_check((tcx.erase_regions(obligation.predicate), *wf_loc))
+                        .diagnostic_hir_wf_check((tcx.erase_and_anonymize_regions(obligation.predicate), *wf_loc))
                     {
                         obligation.cause = cause.clone();
                         span = obligation.cause.span;
@@ -2612,8 +2612,9 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
             }
 
             // Erase regions because layout code doesn't particularly care about regions.
-            let trait_pred =
-                self.tcx.erase_regions(self.tcx.instantiate_bound_regions_with_erased(trait_pred));
+            let trait_pred = self.tcx.erase_and_anonymize_regions(
+                self.tcx.instantiate_bound_regions_with_erased(trait_pred),
+            );
 
             let src_and_dst = rustc_transmute::Types {
                 dst: trait_pred.trait_ref.args.type_at(0),
diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/mod.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/mod.rs
index c8500b2d9d4..f794ff632c5 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/traits/mod.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/mod.rs
@@ -139,10 +139,6 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         &self,
         mut errors: Vec<FulfillmentError<'tcx>>,
     ) -> ErrorGuaranteed {
-        self.sub_relations
-            .borrow_mut()
-            .add_constraints(self, errors.iter().map(|e| e.obligation.predicate));
-
         #[derive(Debug)]
         struct ErrorDescriptor<'tcx> {
             goal: Goal<'tcx, ty::Predicate<'tcx>>,
diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/overflow.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/overflow.rs
index 4f1f5c330e5..a0876d8fe75 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/traits/overflow.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/overflow.rs
@@ -3,10 +3,10 @@ use std::fmt;
 use rustc_errors::{Diag, E0275, EmissionGuarantee, ErrorGuaranteed, struct_span_code_err};
 use rustc_hir::def::Namespace;
 use rustc_hir::def_id::LOCAL_CRATE;
+use rustc_hir::limit::Limit;
 use rustc_infer::traits::{Obligation, PredicateObligation};
 use rustc_middle::ty::print::{FmtPrinter, Print};
 use rustc_middle::ty::{self, TyCtxt, Upcast};
-use rustc_session::Limit;
 use rustc_span::Span;
 use tracing::debug;
 
@@ -67,7 +67,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                 // We don't need to save the type to a file, we will be talking about this type already
                 // in a separate note when we explain the obligation, so it will be available that way.
                 let mut p: FmtPrinter<'_, '_> =
-                    FmtPrinter::new_with_limit(tcx, Namespace::TypeNS, rustc_session::Limit(6));
+                    FmtPrinter::new_with_limit(tcx, Namespace::TypeNS, Limit(6));
                 value.print(&mut p).unwrap();
                 p.into_buffer()
             } else {
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 f6dbbeb51ca..cb84d583e6e 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
@@ -2442,7 +2442,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
 
         // Look for a type inside the coroutine interior that matches the target type to get
         // a span.
-        let target_ty_erased = self.tcx.erase_regions(target_ty);
+        let target_ty_erased = self.tcx.erase_and_anonymize_regions(target_ty);
         let ty_matches = |ty| -> bool {
             // Careful: the regions for types that appear in the
             // coroutine interior are not generally known, so we
@@ -2454,10 +2454,10 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
             // interior generally contain "bound regions" to
             // represent regions that are part of the suspended
             // coroutine frame. Bound regions are preserved by
-            // `erase_regions` and so we must also call
+            // `erase_and_anonymize_regions` and so we must also call
             // `instantiate_bound_regions_with_erased`.
             let ty_erased = self.tcx.instantiate_bound_regions_with_erased(ty);
-            let ty_erased = self.tcx.erase_regions(ty_erased);
+            let ty_erased = self.tcx.erase_and_anonymize_regions(ty_erased);
             let eq = ty_erased == target_ty_erased;
             debug!(?ty_erased, ?target_ty_erased, ?eq);
             eq
diff --git a/compiler/rustc_trait_selection/src/infer.rs b/compiler/rustc_trait_selection/src/infer.rs
index 7c6b7b14ecb..4c50c44b841 100644
--- a/compiler/rustc_trait_selection/src/infer.rs
+++ b/compiler/rustc_trait_selection/src/infer.rs
@@ -184,10 +184,9 @@ impl<'tcx> InferCtxtBuilder<'tcx> {
         R: Debug + TypeFoldable<TyCtxt<'tcx>>,
         Canonical<'tcx, QueryResponse<'tcx, R>>: ArenaAllocatable<'tcx>,
     {
-        let (infcx, key, canonical_inference_vars) =
-            self.build_with_canonical(DUMMY_SP, canonical_key);
+        let (infcx, key, var_values) = self.build_with_canonical(DUMMY_SP, canonical_key);
         let ocx = ObligationCtxt::new(&infcx);
         let value = operation(&ocx, key)?;
-        ocx.make_canonicalized_query_response(canonical_inference_vars, value)
+        ocx.make_canonicalized_query_response(var_values, value)
     }
 }
diff --git a/compiler/rustc_trait_selection/src/solve/delegate.rs b/compiler/rustc_trait_selection/src/solve/delegate.rs
index e6a2761db5a..b6bdf1067a3 100644
--- a/compiler/rustc_trait_selection/src/solve/delegate.rs
+++ b/compiler/rustc_trait_selection/src/solve/delegate.rs
@@ -126,13 +126,12 @@ impl<'tcx> rustc_next_trait_solver::delegate::SolverDelegate for SolverDelegate<
             }
             ty::PredicateKind::Subtype(ty::SubtypePredicate { a, b, .. })
             | ty::PredicateKind::Coerce(ty::CoercePredicate { a, b }) => {
-                if self.shallow_resolve(a).is_ty_var() && self.shallow_resolve(b).is_ty_var() {
-                    // FIXME: We also need to register a subtype relation between these vars
-                    // when those are added, and if they aren't in the same sub root then
-                    // we should mark this goal as `has_changed`.
-                    Some(Certainty::AMBIGUOUS)
-                } else {
-                    None
+                match (self.shallow_resolve(a).kind(), self.shallow_resolve(b).kind()) {
+                    (&ty::Infer(ty::TyVar(a_vid)), &ty::Infer(ty::TyVar(b_vid))) => {
+                        self.sub_unify_ty_vids_raw(a_vid, b_vid);
+                        Some(Certainty::AMBIGUOUS)
+                    }
+                    _ => None,
                 }
             }
             ty::PredicateKind::Clause(ty::ClauseKind::ConstArgHasType(ct, _)) => {
@@ -238,13 +237,14 @@ impl<'tcx> rustc_next_trait_solver::delegate::SolverDelegate for SolverDelegate<
         canonical.instantiate(self.tcx, &values)
     }
 
-    fn instantiate_canonical_var_with_infer(
+    fn instantiate_canonical_var(
         &self,
         kind: CanonicalVarKind<'tcx>,
         span: Span,
+        var_values: &[ty::GenericArg<'tcx>],
         universe_map: impl Fn(ty::UniverseIndex) -> ty::UniverseIndex,
     ) -> ty::GenericArg<'tcx> {
-        self.0.instantiate_canonical_var(span, kind, universe_map)
+        self.0.instantiate_canonical_var(span, kind, var_values, universe_map)
     }
 
     fn add_item_bounds_for_hidden_type(
@@ -300,7 +300,7 @@ impl<'tcx> rustc_next_trait_solver::delegate::SolverDelegate for SolverDelegate<
     ) -> Result<Certainty, NoSolution> {
         // Erase regions because we compute layouts in `rustc_transmute`,
         // which will ICE for region vars.
-        let (dst, src) = self.tcx.erase_regions((dst, src));
+        let (dst, src) = self.tcx.erase_and_anonymize_regions((dst, src));
 
         let Some(assume) = rustc_transmute::Assume::from_const(self.tcx, assume) else {
             return Err(NoSolution);
diff --git a/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs b/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
index 4b493c95d59..bcd11d6918d 100644
--- a/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
+++ b/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
@@ -759,7 +759,7 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for IllegalSelfTypeVisitor<'tcx> {
                                     )),
                                 )
                                 .map(|trait_ref| {
-                                    self.tcx.erase_regions(
+                                    self.tcx.erase_and_anonymize_regions(
                                         self.tcx.instantiate_bound_regions_with_erased(trait_ref),
                                     )
                                 })
diff --git a/compiler/rustc_trait_selection/src/traits/mod.rs b/compiler/rustc_trait_selection/src/traits/mod.rs
index a9fb16b8000..6fefac43699 100644
--- a/compiler/rustc_trait_selection/src/traits/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/mod.rs
@@ -576,7 +576,7 @@ pub fn try_evaluate_const<'tcx>(
                                     let args =
                                         replace_param_and_infer_args_with_placeholder(tcx, uv.args);
                                     let typing_env = infcx
-                                        .typing_env(tcx.erase_regions(param_env))
+                                        .typing_env(tcx.erase_and_anonymize_regions(param_env))
                                         .with_post_analysis_normalized(tcx);
                                     (args, typing_env)
                                 }
@@ -589,7 +589,7 @@ pub fn try_evaluate_const<'tcx>(
                         }
                     } else {
                         let typing_env = infcx
-                            .typing_env(tcx.erase_regions(param_env))
+                            .typing_env(tcx.erase_and_anonymize_regions(param_env))
                             .with_post_analysis_normalized(tcx);
                         (uv.args, typing_env)
                     }
@@ -634,14 +634,14 @@ pub fn try_evaluate_const<'tcx>(
                     }
 
                     let typing_env = infcx
-                        .typing_env(tcx.erase_regions(param_env))
+                        .typing_env(tcx.erase_and_anonymize_regions(param_env))
                         .with_post_analysis_normalized(tcx);
                     (uv.args, typing_env)
                 }
             };
 
             let uv = ty::UnevaluatedConst::new(uv.def, args);
-            let erased_uv = tcx.erase_regions(uv);
+            let erased_uv = tcx.erase_and_anonymize_regions(uv);
 
             use rustc_middle::mir::interpret::ErrorHandled;
             // FIXME: `def_span` will point at the definition of this const; ideally, we'd point at
diff --git a/compiler/rustc_trait_selection/src/traits/query/dropck_outlives.rs b/compiler/rustc_trait_selection/src/traits/query/dropck_outlives.rs
index de404532899..945ca7c3775 100644
--- a/compiler/rustc_trait_selection/src/traits/query/dropck_outlives.rs
+++ b/compiler/rustc_trait_selection/src/traits/query/dropck_outlives.rs
@@ -350,7 +350,9 @@ pub fn dtorck_constraint_for_ty_inner<'tcx>(
             // Note that we don't care about whether the resume type has any drops since this is
             // redundant; there is no storage for the resume type, so if it is actually stored
             // in the interior, we'll already detect the need for a drop by checking the interior.
-            let typing_env = tcx.erase_regions(typing_env);
+            //
+            // FIXME(@lcnr): Why do we erase regions in the env here? Seems odd
+            let typing_env = tcx.erase_and_anonymize_regions(typing_env);
             let needs_drop = tcx.mir_coroutine_witnesses(def_id).is_some_and(|witness| {
                 witness.field_tys.iter().any(|field| field.ty.needs_drop(tcx, typing_env))
             });
diff --git a/compiler/rustc_traits/src/codegen.rs b/compiler/rustc_traits/src/codegen.rs
index 7dd3c59edd0..4b05e2cc381 100644
--- a/compiler/rustc_traits/src/codegen.rs
+++ b/compiler/rustc_traits/src/codegen.rs
@@ -73,7 +73,7 @@ pub(crate) fn codegen_select_candidate<'tcx>(
     }
 
     let impl_source = infcx.resolve_vars_if_possible(impl_source);
-    let impl_source = tcx.erase_regions(impl_source);
+    let impl_source = tcx.erase_and_anonymize_regions(impl_source);
     if impl_source.has_non_region_infer() {
         // Unused generic types or consts on an impl get replaced with inference vars,
         // but never resolved, causing the return value of a query to contain inference
diff --git a/compiler/rustc_traits/src/evaluate_obligation.rs b/compiler/rustc_traits/src/evaluate_obligation.rs
index 819b8e3231c..8f72bdf0972 100644
--- a/compiler/rustc_traits/src/evaluate_obligation.rs
+++ b/compiler/rustc_traits/src/evaluate_obligation.rs
@@ -19,7 +19,7 @@ fn evaluate_obligation<'tcx>(
 ) -> Result<EvaluationResult, OverflowError> {
     assert!(!tcx.next_trait_solver_globally());
     debug!("evaluate_obligation(canonical_goal={:#?})", canonical_goal);
-    let (ref infcx, goal, _canonical_inference_vars) =
+    let (ref infcx, goal, _var_values) =
         tcx.infer_ctxt().build_with_canonical(DUMMY_SP, &canonical_goal);
     debug!("evaluate_obligation: goal={:#?}", goal);
     let ParamEnvAnd { param_env, value: predicate } = goal;
diff --git a/compiler/rustc_traits/src/normalize_erasing_regions.rs b/compiler/rustc_traits/src/normalize_erasing_regions.rs
index c1b848a2e79..c98b56abe9c 100644
--- a/compiler/rustc_traits/src/normalize_erasing_regions.rs
+++ b/compiler/rustc_traits/src/normalize_erasing_regions.rs
@@ -41,7 +41,7 @@ fn try_normalize_after_erasing_regions<'tcx, T: TypeFoldable<TyCtxt<'tcx>> + Par
             // fresh `InferCtxt`. If this assert does trigger, it will give
             // us a test case.
             debug_assert_eq!(normalized_value, resolved_value);
-            let erased = infcx.tcx.erase_regions(resolved_value);
+            let erased = infcx.tcx.erase_and_anonymize_regions(resolved_value);
             debug_assert!(!erased.has_infer(), "{erased:?}");
             Ok(erased)
         }
diff --git a/compiler/rustc_transmute/src/layout/mod.rs b/compiler/rustc_transmute/src/layout/mod.rs
index acbce258f39..4e548ff8fe2 100644
--- a/compiler/rustc_transmute/src/layout/mod.rs
+++ b/compiler/rustc_transmute/src/layout/mod.rs
@@ -163,7 +163,7 @@ pub mod rustc {
         ty: Ty<'tcx>,
     ) -> Result<Layout<'tcx>, &'tcx LayoutError<'tcx>> {
         use rustc_middle::ty::layout::LayoutOf;
-        let ty = cx.tcx().erase_regions(ty);
+        let ty = cx.tcx().erase_and_anonymize_regions(ty);
         cx.layout_of(ty).map(|tl| tl.layout)
     }
 }
diff --git a/compiler/rustc_transmute/src/layout/tree.rs b/compiler/rustc_transmute/src/layout/tree.rs
index 3f83b4d50aa..d7ea26a2ab1 100644
--- a/compiler/rustc_transmute/src/layout/tree.rs
+++ b/compiler/rustc_transmute/src/layout/tree.rs
@@ -426,24 +426,23 @@ pub(crate) mod rustc {
             assert!(def.is_enum());
 
             // Computes the layout of a variant.
-            let layout_of_variant =
-                |index, encoding: Option<TagEncoding<VariantIdx>>| -> Result<Self, Err> {
-                    let variant_layout = ty_variant(cx, (ty, layout), index);
-                    if variant_layout.is_uninhabited() {
-                        return Ok(Self::uninhabited());
-                    }
-                    let tag = cx.tcx().tag_for_variant(
-                        cx.typing_env.as_query_input((cx.tcx().erase_regions(ty), index)),
-                    );
-                    let variant_def = Def::Variant(def.variant(index));
-                    Self::from_variant(
-                        variant_def,
-                        tag.map(|tag| (tag, index, encoding.unwrap())),
-                        (ty, variant_layout),
-                        layout.size,
-                        cx,
-                    )
-                };
+            let layout_of_variant = |index, encoding: Option<_>| -> Result<Self, Err> {
+                let variant_layout = ty_variant(cx, (ty, layout), index);
+                if variant_layout.is_uninhabited() {
+                    return Ok(Self::uninhabited());
+                }
+                let tag = cx.tcx().tag_for_variant(
+                    cx.typing_env.as_query_input((cx.tcx().erase_and_anonymize_regions(ty), index)),
+                );
+                let variant_def = Def::Variant(def.variant(index));
+                Self::from_variant(
+                    variant_def,
+                    tag.map(|tag| (tag, index, encoding.unwrap())),
+                    (ty, variant_layout),
+                    layout.size,
+                    cx,
+                )
+            };
 
             match layout.variants() {
                 Variants::Empty => Ok(Self::uninhabited()),
@@ -634,7 +633,7 @@ pub(crate) mod rustc {
         (ty, layout): (Ty<'tcx>, Layout<'tcx>),
         i: VariantIdx,
     ) -> Layout<'tcx> {
-        let ty = cx.tcx().erase_regions(ty);
+        let ty = cx.tcx().erase_and_anonymize_regions(ty);
         TyAndLayout { ty, layout }.for_variant(&cx, i).layout
     }
 }
diff --git a/compiler/rustc_ty_utils/src/instance.rs b/compiler/rustc_ty_utils/src/instance.rs
index 5c3f7d491a5..e28ebaabc0a 100644
--- a/compiler/rustc_ty_utils/src/instance.rs
+++ b/compiler/rustc_ty_utils/src/instance.rs
@@ -176,7 +176,7 @@ fn resolve_associated_item<'tcx>(
                 args,
                 leaf_def.defining_node,
             );
-            let args = infcx.tcx.erase_regions(args);
+            let args = infcx.tcx.erase_and_anonymize_regions(args);
 
             // HACK: We may have overlapping `dyn Trait` built-in impls and
             // user-provided blanket impls. Detect that case here, and return
@@ -222,7 +222,7 @@ fn resolve_associated_item<'tcx>(
                 return Err(guar);
             }
 
-            let args = tcx.erase_regions(args);
+            let args = tcx.erase_and_anonymize_regions(args);
 
             // We check that the impl item is compatible with the trait item
             // because otherwise we may ICE in const eval due to type mismatches,
@@ -279,7 +279,7 @@ fn resolve_associated_item<'tcx>(
                     assert_eq!(name, sym::clone_from);
 
                     // Use the default `fn clone_from` from `trait Clone`.
-                    let args = tcx.erase_regions(rcvr_args);
+                    let args = tcx.erase_and_anonymize_regions(rcvr_args);
                     Some(ty::Instance::new_raw(trait_item_id, args))
                 }
             } else if tcx.is_lang_item(trait_ref.def_id, LangItem::FnPtrTrait) {
@@ -380,7 +380,7 @@ fn resolve_associated_item<'tcx>(
             } else if tcx.is_lang_item(trait_ref.def_id, LangItem::TransmuteTrait) {
                 let name = tcx.item_name(trait_item_id);
                 assert_eq!(name, sym::transmute);
-                let args = tcx.erase_regions(rcvr_args);
+                let args = tcx.erase_and_anonymize_regions(rcvr_args);
                 Some(ty::Instance::new_raw(trait_item_id, args))
             } else {
                 Instance::try_resolve_item_for_coroutine(tcx, trait_item_id, trait_id, rcvr_args)
diff --git a/compiler/rustc_ty_utils/src/needs_drop.rs b/compiler/rustc_ty_utils/src/needs_drop.rs
index 13d56889bd1..0ef435b1a0e 100644
--- a/compiler/rustc_ty_utils/src/needs_drop.rs
+++ b/compiler/rustc_ty_utils/src/needs_drop.rs
@@ -2,11 +2,11 @@
 
 use rustc_data_structures::fx::FxHashSet;
 use rustc_hir::def_id::DefId;
+use rustc_hir::limit::Limit;
 use rustc_middle::bug;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::util::{AlwaysRequiresDrop, needs_drop_components};
 use rustc_middle::ty::{self, EarlyBinder, GenericArgsRef, Ty, TyCtxt};
-use rustc_session::Limit;
 use rustc_span::sym;
 use tracing::{debug, instrument};
 
diff --git a/compiler/rustc_type_ir/Cargo.toml b/compiler/rustc_type_ir/Cargo.toml
index d55e9b3b1be..6ccddb17ff2 100644
--- a/compiler/rustc_type_ir/Cargo.toml
+++ b/compiler/rustc_type_ir/Cargo.toml
@@ -5,6 +5,7 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
+arrayvec = { version = "0.7", default-features = false }
 bitflags = "2.4.1"
 derive-where = "1.2.7"
 ena = "0.14.3"
diff --git a/compiler/rustc_type_ir/src/canonical.rs b/compiler/rustc_type_ir/src/canonical.rs
index de2a9186e7c..ecf3ae4f8b2 100644
--- a/compiler/rustc_type_ir/src/canonical.rs
+++ b/compiler/rustc_type_ir/src/canonical.rs
@@ -1,7 +1,7 @@
 use std::fmt;
-use std::hash::Hash;
 use std::ops::Index;
 
+use arrayvec::ArrayVec;
 use derive_where::derive_where;
 #[cfg(feature = "nightly")]
 use rustc_macros::{Decodable_NoContext, Encodable_NoContext, HashStable_NoContext};
@@ -91,8 +91,18 @@ impl<I: Interner, V: fmt::Display> fmt::Display for Canonical<I, V> {
     derive(Decodable_NoContext, Encodable_NoContext, HashStable_NoContext)
 )]
 pub enum CanonicalVarKind<I: Interner> {
-    /// Some kind of type inference variable.
-    Ty(CanonicalTyVarKind),
+    /// General type variable `?T` that can be unified with arbitrary types.
+    ///
+    /// We also store the index of the first type variable which is sub-unified
+    /// with this one. If there is no inference variable related to this one,
+    /// its `sub_root` just points to itself.
+    Ty { ui: UniverseIndex, sub_root: ty::BoundVar },
+
+    /// Integral type variable `?I` (that can only be unified with integral types).
+    Int,
+
+    /// Floating-point type variable `?F` (that can only be unified with float types).
+    Float,
 
     /// A "placeholder" that represents "any type".
     PlaceholderTy(I::PlaceholderTy),
@@ -117,15 +127,13 @@ impl<I: Interner> Eq for CanonicalVarKind<I> {}
 impl<I: Interner> CanonicalVarKind<I> {
     pub fn universe(self) -> UniverseIndex {
         match self {
-            CanonicalVarKind::Ty(CanonicalTyVarKind::General(ui)) => ui,
+            CanonicalVarKind::Ty { ui, sub_root: _ } => ui,
             CanonicalVarKind::Region(ui) => ui,
             CanonicalVarKind::Const(ui) => ui,
             CanonicalVarKind::PlaceholderTy(placeholder) => placeholder.universe(),
             CanonicalVarKind::PlaceholderRegion(placeholder) => placeholder.universe(),
             CanonicalVarKind::PlaceholderConst(placeholder) => placeholder.universe(),
-            CanonicalVarKind::Ty(CanonicalTyVarKind::Float | CanonicalTyVarKind::Int) => {
-                UniverseIndex::ROOT
-            }
+            CanonicalVarKind::Float | CanonicalVarKind::Int => UniverseIndex::ROOT,
         }
     }
 
@@ -135,9 +143,7 @@ impl<I: Interner> CanonicalVarKind<I> {
     /// the updated universe is not the root.
     pub fn with_updated_universe(self, ui: UniverseIndex) -> CanonicalVarKind<I> {
         match self {
-            CanonicalVarKind::Ty(CanonicalTyVarKind::General(_)) => {
-                CanonicalVarKind::Ty(CanonicalTyVarKind::General(ui))
-            }
+            CanonicalVarKind::Ty { ui: _, sub_root } => CanonicalVarKind::Ty { ui, sub_root },
             CanonicalVarKind::Region(_) => CanonicalVarKind::Region(ui),
             CanonicalVarKind::Const(_) => CanonicalVarKind::Const(ui),
 
@@ -150,7 +156,7 @@ impl<I: Interner> CanonicalVarKind<I> {
             CanonicalVarKind::PlaceholderConst(placeholder) => {
                 CanonicalVarKind::PlaceholderConst(placeholder.with_updated_universe(ui))
             }
-            CanonicalVarKind::Ty(CanonicalTyVarKind::Int | CanonicalTyVarKind::Float) => {
+            CanonicalVarKind::Int | CanonicalVarKind::Float => {
                 assert_eq!(ui, UniverseIndex::ROOT);
                 self
             }
@@ -159,19 +165,23 @@ impl<I: Interner> CanonicalVarKind<I> {
 
     pub fn is_existential(self) -> bool {
         match self {
-            CanonicalVarKind::Ty(_) => true,
-            CanonicalVarKind::PlaceholderTy(_) => false,
-            CanonicalVarKind::Region(_) => true,
-            CanonicalVarKind::PlaceholderRegion(..) => false,
-            CanonicalVarKind::Const(_) => true,
-            CanonicalVarKind::PlaceholderConst(_) => false,
+            CanonicalVarKind::Ty { .. }
+            | CanonicalVarKind::Int
+            | CanonicalVarKind::Float
+            | CanonicalVarKind::Region(_)
+            | CanonicalVarKind::Const(_) => true,
+            CanonicalVarKind::PlaceholderTy(_)
+            | CanonicalVarKind::PlaceholderRegion(..)
+            | CanonicalVarKind::PlaceholderConst(_) => false,
         }
     }
 
     pub fn is_region(self) -> bool {
         match self {
             CanonicalVarKind::Region(_) | CanonicalVarKind::PlaceholderRegion(_) => true,
-            CanonicalVarKind::Ty(_)
+            CanonicalVarKind::Ty { .. }
+            | CanonicalVarKind::Int
+            | CanonicalVarKind::Float
             | CanonicalVarKind::PlaceholderTy(_)
             | CanonicalVarKind::Const(_)
             | CanonicalVarKind::PlaceholderConst(_) => false,
@@ -180,7 +190,11 @@ impl<I: Interner> CanonicalVarKind<I> {
 
     pub fn expect_placeholder_index(self) -> usize {
         match self {
-            CanonicalVarKind::Ty(_) | CanonicalVarKind::Region(_) | CanonicalVarKind::Const(_) => {
+            CanonicalVarKind::Ty { .. }
+            | CanonicalVarKind::Int
+            | CanonicalVarKind::Float
+            | CanonicalVarKind::Region(_)
+            | CanonicalVarKind::Const(_) => {
                 panic!("expected placeholder: {self:?}")
             }
 
@@ -191,27 +205,6 @@ impl<I: Interner> CanonicalVarKind<I> {
     }
 }
 
-/// Rust actually has more than one category of type variables;
-/// notably, the type variables we create for literals (e.g., 22 or
-/// 22.) can only be instantiated with integral/float types (e.g.,
-/// usize or f32). In order to faithfully reproduce a type, we need to
-/// know what set of types a given type variable can be unified with.
-#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
-#[cfg_attr(
-    feature = "nightly",
-    derive(Decodable_NoContext, Encodable_NoContext, HashStable_NoContext)
-)]
-pub enum CanonicalTyVarKind {
-    /// General type variable `?T` that can be unified with arbitrary types.
-    General(UniverseIndex),
-
-    /// Integral type variable `?I` (that can only be unified with integral types).
-    Int,
-
-    /// Floating-point type variable `?F` (that can only be unified with float types).
-    Float,
-}
-
 /// A set of values corresponding to the canonical variables from some
 /// `Canonical`. You can give these values to
 /// `canonical_value.instantiate` to instantiate them into the canonical
@@ -287,7 +280,10 @@ impl<I: Interner> CanonicalVarValues<I> {
             var_values: cx.mk_args_from_iter(infos.iter().enumerate().map(
                 |(i, kind)| -> I::GenericArg {
                     match kind {
-                        CanonicalVarKind::Ty(_) | CanonicalVarKind::PlaceholderTy(_) => {
+                        CanonicalVarKind::Ty { .. }
+                        | CanonicalVarKind::Int
+                        | CanonicalVarKind::Float
+                        | CanonicalVarKind::PlaceholderTy(_) => {
                             Ty::new_anon_bound(cx, ty::INNERMOST, ty::BoundVar::from_usize(i))
                                 .into()
                         }
@@ -311,6 +307,37 @@ impl<I: Interner> CanonicalVarValues<I> {
         CanonicalVarValues { var_values: Default::default() }
     }
 
+    pub fn instantiate(
+        cx: I,
+        variables: I::CanonicalVarKinds,
+        mut f: impl FnMut(&[I::GenericArg], CanonicalVarKind<I>) -> I::GenericArg,
+    ) -> CanonicalVarValues<I> {
+        // Instantiating `CanonicalVarValues` is really hot, but limited to less than
+        // 4 most of the time. Avoid creating a `Vec` here.
+        if variables.len() <= 4 {
+            let mut var_values = ArrayVec::<_, 4>::new();
+            for info in variables.iter() {
+                var_values.push(f(&var_values, info));
+            }
+            CanonicalVarValues { var_values: cx.mk_args(&var_values) }
+        } else {
+            CanonicalVarValues::instantiate_cold(cx, variables, f)
+        }
+    }
+
+    #[cold]
+    fn instantiate_cold(
+        cx: I,
+        variables: I::CanonicalVarKinds,
+        mut f: impl FnMut(&[I::GenericArg], CanonicalVarKind<I>) -> I::GenericArg,
+    ) -> CanonicalVarValues<I> {
+        let mut var_values = Vec::with_capacity(variables.len());
+        for info in variables.iter() {
+            var_values.push(f(&var_values, info));
+        }
+        CanonicalVarValues { var_values: cx.mk_args(&var_values) }
+    }
+
     #[inline]
     pub fn len(&self) -> usize {
         self.var_values.len()
diff --git a/compiler/rustc_type_ir/src/fast_reject.rs b/compiler/rustc_type_ir/src/fast_reject.rs
index 5a05630e1bd..ed6416a7f55 100644
--- a/compiler/rustc_type_ir/src/fast_reject.rs
+++ b/compiler/rustc_type_ir/src/fast_reject.rs
@@ -122,7 +122,7 @@ pub fn simplify_type<I: Interner>(
         ty::Int(int_type) => Some(SimplifiedType::Int(int_type)),
         ty::Uint(uint_type) => Some(SimplifiedType::Uint(uint_type)),
         ty::Float(float_type) => Some(SimplifiedType::Float(float_type)),
-        ty::Adt(def, _) => Some(SimplifiedType::Adt(def.def_id())),
+        ty::Adt(def, _) => Some(SimplifiedType::Adt(def.def_id().into())),
         ty::Str => Some(SimplifiedType::Str),
         ty::Array(..) => Some(SimplifiedType::Array),
         ty::Slice(..) => Some(SimplifiedType::Slice),
@@ -135,11 +135,11 @@ pub fn simplify_type<I: Interner>(
             _ => Some(SimplifiedType::MarkerTraitObject),
         },
         ty::Ref(_, _, mutbl) => Some(SimplifiedType::Ref(mutbl)),
-        ty::FnDef(def_id, _) | ty::Closure(def_id, _) | ty::CoroutineClosure(def_id, _) => {
-            Some(SimplifiedType::Closure(def_id))
-        }
-        ty::Coroutine(def_id, _) => Some(SimplifiedType::Coroutine(def_id)),
-        ty::CoroutineWitness(def_id, _) => Some(SimplifiedType::CoroutineWitness(def_id)),
+        ty::FnDef(def_id, _) => Some(SimplifiedType::Closure(def_id.into())),
+        ty::Closure(def_id, _) => Some(SimplifiedType::Closure(def_id.into())),
+        ty::CoroutineClosure(def_id, _) => Some(SimplifiedType::Closure(def_id.into())),
+        ty::Coroutine(def_id, _) => Some(SimplifiedType::Coroutine(def_id.into())),
+        ty::CoroutineWitness(def_id, _) => Some(SimplifiedType::CoroutineWitness(def_id.into())),
         ty::Never => Some(SimplifiedType::Never),
         ty::Tuple(tys) => Some(SimplifiedType::Tuple(tys.len())),
         ty::FnPtr(sig_tys, _hdr) => {
@@ -161,7 +161,7 @@ pub fn simplify_type<I: Interner>(
             }
             TreatParams::AsRigid | TreatParams::InstantiateWithInfer => None,
         },
-        ty::Foreign(def_id) => Some(SimplifiedType::Foreign(def_id)),
+        ty::Foreign(def_id) => Some(SimplifiedType::Foreign(def_id.into())),
         ty::Error(_) => Some(SimplifiedType::Error),
         ty::Bound(..) | ty::Infer(_) => None,
     }
diff --git a/compiler/rustc_type_ir/src/infer_ctxt.rs b/compiler/rustc_type_ir/src/infer_ctxt.rs
index b4462294700..56962b4597b 100644
--- a/compiler/rustc_type_ir/src/infer_ctxt.rs
+++ b/compiler/rustc_type_ir/src/infer_ctxt.rs
@@ -158,6 +158,7 @@ pub trait InferCtxtLike: Sized {
     fn universe_of_ct(&self, ct: ty::ConstVid) -> Option<ty::UniverseIndex>;
 
     fn root_ty_var(&self, var: ty::TyVid) -> ty::TyVid;
+    fn sub_unification_table_root_var(&self, var: ty::TyVid) -> ty::TyVid;
     fn root_const_var(&self, var: ty::ConstVid) -> ty::ConstVid;
 
     fn opportunistic_resolve_ty_var(&self, vid: ty::TyVid) -> <Self::Interner as Interner>::Ty;
@@ -197,6 +198,7 @@ pub trait InferCtxtLike: Sized {
     ) -> U;
 
     fn equate_ty_vids_raw(&self, a: ty::TyVid, b: ty::TyVid);
+    fn sub_unify_ty_vids_raw(&self, a: ty::TyVid, b: ty::TyVid);
     fn equate_int_vids_raw(&self, a: ty::IntVid, b: ty::IntVid);
     fn equate_float_vids_raw(&self, a: ty::FloatVid, b: ty::FloatVid);
     fn equate_const_vids_raw(&self, a: ty::ConstVid, b: ty::ConstVid);
diff --git a/compiler/rustc_type_ir/src/inherent.rs b/compiler/rustc_type_ir/src/inherent.rs
index 64063b1a365..ecfc05a6e20 100644
--- a/compiler/rustc_type_ir/src/inherent.rs
+++ b/compiler/rustc_type_ir/src/inherent.rs
@@ -74,7 +74,7 @@ pub trait Ty<I: Interner<Ty = Self>>:
 
     fn new_adt(interner: I, adt_def: I::AdtDef, args: I::GenericArgs) -> Self;
 
-    fn new_foreign(interner: I, def_id: I::DefId) -> Self;
+    fn new_foreign(interner: I, def_id: I::ForeignId) -> Self;
 
     fn new_dynamic(
         interner: I,
@@ -83,17 +83,21 @@ pub trait Ty<I: Interner<Ty = Self>>:
         kind: ty::DynKind,
     ) -> Self;
 
-    fn new_coroutine(interner: I, def_id: I::DefId, args: I::GenericArgs) -> Self;
+    fn new_coroutine(interner: I, def_id: I::CoroutineId, args: I::GenericArgs) -> Self;
 
-    fn new_coroutine_closure(interner: I, def_id: I::DefId, args: I::GenericArgs) -> Self;
+    fn new_coroutine_closure(
+        interner: I,
+        def_id: I::CoroutineClosureId,
+        args: I::GenericArgs,
+    ) -> Self;
 
-    fn new_closure(interner: I, def_id: I::DefId, args: I::GenericArgs) -> Self;
+    fn new_closure(interner: I, def_id: I::ClosureId, args: I::GenericArgs) -> Self;
 
-    fn new_coroutine_witness(interner: I, def_id: I::DefId, args: I::GenericArgs) -> Self;
+    fn new_coroutine_witness(interner: I, def_id: I::CoroutineId, args: I::GenericArgs) -> Self;
 
     fn new_coroutine_witness_for_coroutine(
         interner: I,
-        def_id: I::DefId,
+        def_id: I::CoroutineId,
         coroutine_args: I::GenericArgs,
     ) -> Self;
 
@@ -112,7 +116,7 @@ pub trait Ty<I: Interner<Ty = Self>>:
         It: Iterator<Item = T>,
         T: CollectAndApply<Self, Self>;
 
-    fn new_fn_def(interner: I, def_id: I::DefId, args: I::GenericArgs) -> Self;
+    fn new_fn_def(interner: I, def_id: I::FunctionId, args: I::GenericArgs) -> Self;
 
     fn new_fn_ptr(interner: I, sig: ty::Binder<I, ty::FnSig<I>>) -> Self;
 
@@ -599,7 +603,7 @@ pub trait ParamLike: Copy + Debug + Hash + Eq {
 }
 
 pub trait AdtDef<I: Interner>: Copy + Debug + Hash + Eq {
-    fn def_id(self) -> I::DefId;
+    fn def_id(self) -> I::AdtId;
 
     fn is_struct(self) -> bool;
 
@@ -646,6 +650,16 @@ pub trait DefId<I: Interner>: Copy + Debug + Hash + Eq + TypeFoldable<I> {
     fn as_local(self) -> Option<I::LocalDefId>;
 }
 
+pub trait SpecificDefId<I: Interner>:
+    DefId<I> + Into<I::DefId> + TryFrom<I::DefId, Error: std::fmt::Debug>
+{
+}
+
+impl<I: Interner, T: DefId<I> + Into<I::DefId> + TryFrom<I::DefId, Error: std::fmt::Debug>>
+    SpecificDefId<I> for T
+{
+}
+
 pub trait BoundExistentialPredicates<I: Interner>:
     Copy + Debug + Hash + Eq + Relate<I> + SliceLike<Item = ty::Binder<I, ty::ExistentialPredicate<I>>>
 {
diff --git a/compiler/rustc_type_ir/src/interner.rs b/compiler/rustc_type_ir/src/interner.rs
index 3355c0c2104..3a83b1739ff 100644
--- a/compiler/rustc_type_ir/src/interner.rs
+++ b/compiler/rustc_type_ir/src/interner.rs
@@ -9,7 +9,7 @@ use rustc_index::bit_set::DenseBitSet;
 use crate::fold::TypeFoldable;
 use crate::inherent::*;
 use crate::ir_print::IrPrint;
-use crate::lang_items::{SolverLangItem, SolverTraitLangItem};
+use crate::lang_items::{SolverAdtLangItem, SolverLangItem, SolverTraitLangItem};
 use crate::relate::Relate;
 use crate::solve::{
     CanonicalInput, ExternalConstraintsData, PredefinedOpaquesData, QueryResult, inspect,
@@ -41,13 +41,20 @@ pub trait Interner:
 
     type DefId: DefId<Self>;
     type LocalDefId: Copy + Debug + Hash + Eq + Into<Self::DefId> + TypeFoldable<Self>;
-    /// A `DefId` of a trait.
-    ///
-    /// In rustc this is just a `DefId`, but rust-analyzer uses different types for different items.
-    ///
-    /// Note: The `TryFrom<DefId>` always succeeds (in rustc), so don't use it to check if some `DefId`
-    /// is a trait!
-    type TraitId: DefId<Self> + Into<Self::DefId> + TryFrom<Self::DefId, Error: std::fmt::Debug>;
+    // Various more specific `DefId`s.
+    //
+    // rustc just defines them all to be `DefId`, but rust-analyzer uses different types so this is convenient for it.
+    //
+    // Note: The `TryFrom<DefId>` always succeeds (in rustc), so don't use it to check if some `DefId`
+    // is of some specific type!
+    type TraitId: SpecificDefId<Self>;
+    type ForeignId: SpecificDefId<Self>;
+    type FunctionId: SpecificDefId<Self>;
+    type ClosureId: SpecificDefId<Self>;
+    type CoroutineClosureId: SpecificDefId<Self>;
+    type CoroutineId: SpecificDefId<Self>;
+    type AdtId: SpecificDefId<Self>;
+    type ImplId: SpecificDefId<Self>;
     type Span: Span<Self>;
 
     type GenericArgs: GenericArgs<Self>;
@@ -199,7 +206,7 @@ pub trait Interner:
     -> ty::EarlyBinder<Self, Self::Ty>;
 
     type AdtDef: AdtDef<Self>;
-    fn adt_def(self, adt_def_id: Self::DefId) -> Self::AdtDef;
+    fn adt_def(self, adt_def_id: Self::AdtId) -> Self::AdtDef;
 
     fn alias_ty_kind(self, alias: ty::AliasTy<Self>) -> ty::AliasTyKind;
 
@@ -240,17 +247,17 @@ pub trait Interner:
 
     fn coroutine_hidden_types(
         self,
-        def_id: Self::DefId,
+        def_id: Self::CoroutineId,
     ) -> ty::EarlyBinder<Self, ty::Binder<Self, ty::CoroutineWitnessTypes<Self>>>;
 
     fn fn_sig(
         self,
-        def_id: Self::DefId,
+        def_id: Self::FunctionId,
     ) -> ty::EarlyBinder<Self, ty::Binder<Self, ty::FnSig<Self>>>;
 
-    fn coroutine_movability(self, def_id: Self::DefId) -> Movability;
+    fn coroutine_movability(self, def_id: Self::CoroutineId) -> Movability;
 
-    fn coroutine_for_closure(self, def_id: Self::DefId) -> Self::DefId;
+    fn coroutine_for_closure(self, def_id: Self::CoroutineClosureId) -> Self::CoroutineId;
 
     fn generics_require_sized_self(self, def_id: Self::DefId) -> bool;
 
@@ -293,11 +300,11 @@ pub trait Interner:
     /// and filtering them to the outlives predicates. This is purely for performance.
     fn impl_super_outlives(
         self,
-        impl_def_id: Self::DefId,
+        impl_def_id: Self::ImplId,
     ) -> ty::EarlyBinder<Self, impl IntoIterator<Item = Self::Clause>>;
 
-    fn impl_is_const(self, def_id: Self::DefId) -> bool;
-    fn fn_is_const(self, def_id: Self::DefId) -> bool;
+    fn impl_is_const(self, def_id: Self::ImplId) -> bool;
+    fn fn_is_const(self, def_id: Self::FunctionId) -> bool;
     fn alias_has_const_conditions(self, def_id: Self::DefId) -> bool;
     fn const_conditions(
         self,
@@ -308,42 +315,49 @@ 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 impl_self_is_guaranteed_unsized(self, def_id: Self::ImplId) -> bool;
 
-    fn has_target_features(self, def_id: Self::DefId) -> bool;
+    fn has_target_features(self, def_id: Self::FunctionId) -> bool;
 
     fn require_lang_item(self, lang_item: SolverLangItem) -> Self::DefId;
 
     fn require_trait_lang_item(self, lang_item: SolverTraitLangItem) -> Self::TraitId;
 
+    fn require_adt_lang_item(self, lang_item: SolverAdtLangItem) -> Self::AdtId;
+
     fn is_lang_item(self, def_id: Self::DefId, lang_item: SolverLangItem) -> bool;
 
     fn is_trait_lang_item(self, def_id: Self::TraitId, lang_item: SolverTraitLangItem) -> bool;
 
+    fn is_adt_lang_item(self, def_id: Self::AdtId, lang_item: SolverAdtLangItem) -> bool;
+
     fn is_default_trait(self, def_id: Self::TraitId) -> bool;
 
     fn as_lang_item(self, def_id: Self::DefId) -> Option<SolverLangItem>;
 
     fn as_trait_lang_item(self, def_id: Self::TraitId) -> Option<SolverTraitLangItem>;
 
+    fn as_adt_lang_item(self, def_id: Self::AdtId) -> Option<SolverAdtLangItem>;
+
     fn associated_type_def_ids(self, def_id: Self::DefId) -> impl IntoIterator<Item = Self::DefId>;
 
     fn for_each_relevant_impl(
         self,
         trait_def_id: Self::TraitId,
         self_ty: Self::Ty,
-        f: impl FnMut(Self::DefId),
+        f: impl FnMut(Self::ImplId),
     );
 
     fn has_item_definition(self, def_id: Self::DefId) -> bool;
 
-    fn impl_specializes(self, impl_def_id: Self::DefId, victim_def_id: Self::DefId) -> bool;
+    fn impl_specializes(self, impl_def_id: Self::ImplId, victim_def_id: Self::ImplId) -> bool;
 
-    fn impl_is_default(self, impl_def_id: Self::DefId) -> bool;
+    fn impl_is_default(self, impl_def_id: Self::ImplId) -> bool;
 
-    fn impl_trait_ref(self, impl_def_id: Self::DefId) -> ty::EarlyBinder<Self, ty::TraitRef<Self>>;
+    fn impl_trait_ref(self, impl_def_id: Self::ImplId)
+    -> ty::EarlyBinder<Self, ty::TraitRef<Self>>;
 
-    fn impl_polarity(self, impl_def_id: Self::DefId) -> ty::ImplPolarity;
+    fn impl_polarity(self, impl_def_id: Self::ImplId) -> ty::ImplPolarity;
 
     fn trait_is_auto(self, trait_def_id: Self::TraitId) -> bool;
 
@@ -364,13 +378,13 @@ pub trait Interner:
 
     fn delay_bug(self, msg: impl ToString) -> Self::ErrorGuaranteed;
 
-    fn is_general_coroutine(self, coroutine_def_id: Self::DefId) -> bool;
-    fn coroutine_is_async(self, coroutine_def_id: Self::DefId) -> bool;
-    fn coroutine_is_gen(self, coroutine_def_id: Self::DefId) -> bool;
-    fn coroutine_is_async_gen(self, coroutine_def_id: Self::DefId) -> bool;
+    fn is_general_coroutine(self, coroutine_def_id: Self::CoroutineId) -> bool;
+    fn coroutine_is_async(self, coroutine_def_id: Self::CoroutineId) -> bool;
+    fn coroutine_is_gen(self, coroutine_def_id: Self::CoroutineId) -> bool;
+    fn coroutine_is_async_gen(self, coroutine_def_id: Self::CoroutineId) -> bool;
 
     type UnsizingParams: Deref<Target = DenseBitSet<u32>>;
-    fn unsizing_params_for_adt(self, adt_def_id: Self::DefId) -> Self::UnsizingParams;
+    fn unsizing_params_for_adt(self, adt_def_id: Self::AdtId) -> Self::UnsizingParams;
 
     fn anonymize_bound_vars<T: TypeFoldable<Self>>(
         self,
diff --git a/compiler/rustc_type_ir/src/lang_items.rs b/compiler/rustc_type_ir/src/lang_items.rs
index 31f8f5be588..5f503d8b912 100644
--- a/compiler/rustc_type_ir/src/lang_items.rs
+++ b/compiler/rustc_type_ir/src/lang_items.rs
@@ -11,6 +11,11 @@ pub enum SolverLangItem {
     DynMetadata,
     FutureOutput,
     Metadata,
+    // tidy-alphabetical-end
+}
+
+pub enum SolverAdtLangItem {
+    // tidy-alphabetical-start
     Option,
     Poll,
     // tidy-alphabetical-end
diff --git a/compiler/rustc_type_ir/src/relate.rs b/compiler/rustc_type_ir/src/relate.rs
index 223230fde9e..690a5f65e08 100644
--- a/compiler/rustc_type_ir/src/relate.rs
+++ b/compiler/rustc_type_ir/src/relate.rs
@@ -405,7 +405,7 @@ pub fn structurally_relate_tys<I: Interner, R: TypeRelation<I>>(
             Ok(if a_args.is_empty() {
                 a
             } else {
-                let args = relation.relate_item_args(a_def.def_id(), a_args, b_args)?;
+                let args = relation.relate_item_args(a_def.def_id().into(), a_args, b_args)?;
                 if args == a_args { a } else { Ty::new_adt(cx, a_def, args) }
             })
         }
@@ -524,7 +524,7 @@ pub fn structurally_relate_tys<I: Interner, R: TypeRelation<I>>(
             Ok(if a_args.is_empty() {
                 a
             } else {
-                let args = relation.relate_item_args(a_def_id, a_args, b_args)?;
+                let args = relation.relate_item_args(a_def_id.into(), a_args, b_args)?;
                 if args == a_args { a } else { Ty::new_fn_def(cx, a_def_id, args) }
             })
         }
diff --git a/compiler/rustc_type_ir/src/search_graph/mod.rs b/compiler/rustc_type_ir/src/search_graph/mod.rs
index dbbc0c217d7..8f8f019510f 100644
--- a/compiler/rustc_type_ir/src/search_graph/mod.rs
+++ b/compiler/rustc_type_ir/src/search_graph/mod.rs
@@ -1262,7 +1262,7 @@ impl<D: Delegate<Cx = X>, X: Cx> SearchGraph<D> {
             encountered_overflow |= stack_entry.encountered_overflow;
             debug_assert_eq!(stack_entry.input, input);
 
-            // If the current goal is not the root of a cycle, we are done.
+            // If the current goal is not a cycle head, we are done.
             //
             // There are no provisional cache entries which depend on this goal.
             let Some(usages) = stack_entry.usages else {
@@ -1278,7 +1278,7 @@ impl<D: Delegate<Cx = X>, X: Cx> SearchGraph<D> {
             //
             // Check whether we reached a fixpoint, either because the final result
             // is equal to the provisional result of the previous iteration, or because
-            // this was only the root of either coinductive or inductive cycles, and the
+            // this was only the head of either coinductive or inductive cycles, and the
             // final result is equal to the initial response for that case.
             if self.reached_fixpoint(cx, &stack_entry, usages, result) {
                 self.rebase_provisional_cache_entries(&stack_entry, |_, result| result);
diff --git a/compiler/rustc_type_ir/src/search_graph/stack.rs b/compiler/rustc_type_ir/src/search_graph/stack.rs
index 3fd8e2bd16e..8348666be41 100644
--- a/compiler/rustc_type_ir/src/search_graph/stack.rs
+++ b/compiler/rustc_type_ir/src/search_graph/stack.rs
@@ -13,7 +13,7 @@ rustc_index::newtype_index! {
     pub(super) struct StackDepth {}
 }
 
-/// Stack entries of the evaluation stack. Its fields tend to be lazily
+/// Stack entries of the evaluation stack. Its fields tend to be lazily updated
 /// when popping a child goal or completely immutable.
 #[derive_where(Debug; X: Cx)]
 pub(super) struct StackEntry<X: Cx> {
@@ -42,7 +42,7 @@ pub(super) struct StackEntry<X: Cx> {
     /// Whether evaluating this goal encountered overflow. Lazily updated.
     pub encountered_overflow: bool,
 
-    /// Whether and how this goal has been used as the root of a cycle. Lazily updated.
+    /// Whether and how this goal has been used as a cycle head. Lazily updated.
     pub usages: Option<HeadUsages>,
 
     /// We want to be able to ignore head usages if they happen inside of candidates
diff --git a/compiler/rustc_type_ir/src/solve/mod.rs b/compiler/rustc_type_ir/src/solve/mod.rs
index b6d362d77c4..b48a8f46ebe 100644
--- a/compiler/rustc_type_ir/src/solve/mod.rs
+++ b/compiler/rustc_type_ir/src/solve/mod.rs
@@ -136,7 +136,7 @@ pub enum CandidateSource<I: Interner> {
     ///     let y = x.clone();
     /// }
     /// ```
-    Impl(I::DefId),
+    Impl(I::ImplId),
     /// A builtin impl generated by the compiler. When adding a new special
     /// trait, try to use actual impls whenever possible. Builtin impls should
     /// only be used in cases where the impl cannot be manually be written.
diff --git a/compiler/rustc_type_ir/src/ty_kind.rs b/compiler/rustc_type_ir/src/ty_kind.rs
index bde506ffd93..225d85f79c3 100644
--- a/compiler/rustc_type_ir/src/ty_kind.rs
+++ b/compiler/rustc_type_ir/src/ty_kind.rs
@@ -101,7 +101,7 @@ pub enum TyKind<I: Interner> {
     Adt(I::AdtDef, I::GenericArgs),
 
     /// An unsized FFI type that is opaque to Rust. Written as `extern type T`.
-    Foreign(I::DefId),
+    Foreign(I::ForeignId),
 
     /// The pointee of a string slice. Written as `str`.
     Str,
@@ -137,7 +137,7 @@ pub enum TyKind<I: Interner> {
     /// fn foo() -> i32 { 1 }
     /// let bar = foo; // bar: fn() -> i32 {foo}
     /// ```
-    FnDef(I::DefId, I::GenericArgs),
+    FnDef(I::FunctionId, I::GenericArgs),
 
     /// A pointer to a function. Written as `fn() -> i32`.
     ///
@@ -172,21 +172,21 @@ pub enum TyKind<I: Interner> {
     /// Closure args contain both the - potentially instantiated - generic parameters
     /// of its parent and some synthetic parameters. See the documentation for
     /// `ClosureArgs` for more details.
-    Closure(I::DefId, I::GenericArgs),
+    Closure(I::ClosureId, I::GenericArgs),
 
     /// The anonymous type of a closure. Used to represent the type of `async |a| a`.
     ///
     /// Coroutine-closure args contain both the - potentially instantiated - generic
     /// parameters of its parent and some synthetic parameters. See the documentation
     /// for `CoroutineClosureArgs` for more details.
-    CoroutineClosure(I::DefId, I::GenericArgs),
+    CoroutineClosure(I::CoroutineClosureId, I::GenericArgs),
 
     /// The anonymous type of a coroutine. Used to represent the type of
     /// `|a| yield a`.
     ///
     /// For more info about coroutine args, visit the documentation for
     /// `CoroutineArgs`.
-    Coroutine(I::DefId, I::GenericArgs),
+    Coroutine(I::CoroutineId, I::GenericArgs),
 
     /// A type representing the types stored inside a coroutine.
     /// This should only appear as part of the `CoroutineArgs`.
@@ -211,7 +211,7 @@ pub enum TyKind<I: Interner> {
     /// }
     /// # ;
     /// ```
-    CoroutineWitness(I::DefId, I::GenericArgs),
+    CoroutineWitness(I::CoroutineId, I::GenericArgs),
 
     /// The never type `!`.
     Never,
diff --git a/compiler/rustc_type_ir/src/ty_kind/closure.rs b/compiler/rustc_type_ir/src/ty_kind/closure.rs
index a2e16d917a9..3a6d1acfa8d 100644
--- a/compiler/rustc_type_ir/src/ty_kind/closure.rs
+++ b/compiler/rustc_type_ir/src/ty_kind/closure.rs
@@ -391,7 +391,7 @@ impl<I: Interner> CoroutineClosureSignature<I> {
         cx: I,
         parent_args: I::GenericArgsSlice,
         coroutine_kind_ty: I::Ty,
-        coroutine_def_id: I::DefId,
+        coroutine_def_id: I::CoroutineId,
         tupled_upvars_ty: I::Ty,
     ) -> I::Ty {
         let coroutine_args = ty::CoroutineArgs::new(
@@ -418,7 +418,7 @@ impl<I: Interner> CoroutineClosureSignature<I> {
         self,
         cx: I,
         parent_args: I::GenericArgsSlice,
-        coroutine_def_id: I::DefId,
+        coroutine_def_id: I::CoroutineId,
         goal_kind: ty::ClosureKind,
         env_region: I::Region,
         closure_tupled_upvars_ty: I::Ty,
diff --git a/compiler/rustc_type_ir/src/visit.rs b/compiler/rustc_type_ir/src/visit.rs
index 5104484e9c4..6e62e1031a9 100644
--- a/compiler/rustc_type_ir/src/visit.rs
+++ b/compiler/rustc_type_ir/src/visit.rs
@@ -398,9 +398,9 @@ impl std::fmt::Debug for HasTypeFlagsVisitor {
 // looks, particular for `Ty`/`Predicate` where it's just a field access.
 //
 // N.B. The only case where this isn't totally true is binders, which also
-// add `HAS_{RE,TY,CT}_LATE_BOUND` flag depending on the *bound variables* that
+// add `HAS_BINDER_VARS` flag depending on the *bound variables* that
 // are present, regardless of whether those bound variables are used. This
-// is important for anonymization of binders in `TyCtxt::erase_regions`. We
+// is important for anonymization of binders in `TyCtxt::erase_and_anonymize_regions`. We
 // specifically detect this case in `visit_binder`.
 impl<I: Interner> TypeVisitor<I> for HasTypeFlagsVisitor {
     type Result = ControlFlow<FoundFlags>;
diff --git a/compiler/rustc_windows_rc/Cargo.toml b/compiler/rustc_windows_rc/Cargo.toml
new file mode 100644
index 00000000000..080acd35c38
--- /dev/null
+++ b/compiler/rustc_windows_rc/Cargo.toml
@@ -0,0 +1,11 @@
+[package]
+name = "rustc_windows_rc"
+version = "0.0.0"
+edition = "2024"
+
+[dependencies]
+#tidy-alphabetical-start
+# `cc` updates often break things, so we pin it here. Cargo enforces "max 1 semver-compat version
+# per crate", so if you change this, you need to also change it in `rustc_llvm` and `rustc_codegen_ssa`.
+cc = "=1.2.16"
+#tidy-alphabetical-end
diff --git a/compiler/rustc_windows_rc/rustc.rc.in b/compiler/rustc_windows_rc/rustc.rc.in
new file mode 100644
index 00000000000..10a00b9bd4e
--- /dev/null
+++ b/compiler/rustc_windows_rc/rustc.rc.in
@@ -0,0 +1,40 @@
+// A template for the rustc_driver and rustc Windows resource files.
+// This file is processed by the build script to produce rustc.rc and rustc_driver.rc
+// with the appropriate version information filled in.
+
+// All the strings are in UTF-8
+#pragma code_page(65001)
+
+#define RUSTC_FILEDESCRIPTION_STR "@RUSTC_FILEDESCRIPTION_STR@"
+#define RUSTC_FILETYPE @RUSTC_FILETYPE@
+#define RUSTC_FILEVERSION_QUAD @RUSTC_FILEVERSION_QUAD@
+#define RUSTC_FILEVERSION_STR "@RUSTC_FILEVERSION_STR@"
+
+#define RUSTC_PRODUCTNAME_STR "@RUSTC_PRODUCTNAME_STR@"
+#define RUSTC_PRODUCTVERSION_QUAD @RUSTC_PRODUCTVERSION_QUAD@
+#define RUSTC_PRODUCTVERSION_STR "@RUSTC_PRODUCTVERSION_STR@"
+
+
+1 VERSIONINFO
+FILEVERSION RUSTC_FILEVERSION_QUAD
+PRODUCTVERSION RUSTC_PRODUCTVERSION_QUAD
+FILEOS  0x00040004
+FILETYPE RUSTC_FILETYPE
+FILESUBTYPE 0
+FILEFLAGSMASK 0x3f
+FILEFLAGS 0x0
+{
+    BLOCK "StringFileInfo"
+    {
+        BLOCK "000004b0"
+        {
+            VALUE "FileDescription", RUSTC_FILEDESCRIPTION_STR
+            VALUE "FileVersion", RUSTC_FILEVERSION_STR
+            VALUE "ProductVersion", RUSTC_PRODUCTVERSION_STR
+            VALUE "ProductName", RUSTC_PRODUCTNAME_STR
+        }
+    }
+    BLOCK "VarFileInfo" {
+        VALUE "Translation", 0x0, 0x04b0
+    }
+}
diff --git a/compiler/rustc_windows_rc/src/lib.rs b/compiler/rustc_windows_rc/src/lib.rs
new file mode 100644
index 00000000000..caa5e5ef276
--- /dev/null
+++ b/compiler/rustc_windows_rc/src/lib.rs
@@ -0,0 +1,158 @@
+//! A build script dependency to create a Windows resource file for the compiler
+//!
+//! Uses values from the `CFG_VERSION` and `CFG_RELEASE` environment variables
+//! to set the product and file version information in the Windows resource file.
+use std::{env, ffi, fs, path, process};
+
+use cc::windows_registry;
+
+/// The template for the Windows resource file.
+const RESOURCE_TEMPLATE: &str = include_str!("../rustc.rc.in");
+
+/// A subset of the possible values for the `FILETYPE` field in a Windows resource file
+///
+/// See the `dwFileType` member of [VS_FIXEDFILEINFO](https://learn.microsoft.com/en-us/windows/win32/api/verrsrc/ns-verrsrc-vs_fixedfileinfo#members)
+#[derive(Debug, Clone, Copy)]
+#[repr(u32)]
+pub enum VersionInfoFileType {
+    /// `VFT_APP` - The file is an application.
+    App = 0x00000001,
+    /// `VFT_DLL` - The file is a dynamic link library.
+    Dll = 0x00000002,
+}
+
+/// Create and compile a Windows resource file with the product and file version information for the rust compiler.
+///
+/// Returns the path to the compiled resource file
+///
+/// Does not emit any cargo directives, the caller is responsible for that.
+pub fn compile_windows_resource_file(
+    file_stem: &path::Path,
+    file_description: &str,
+    filetype: VersionInfoFileType,
+) -> path::PathBuf {
+    let mut resources_dir = path::PathBuf::from(env::var_os("OUT_DIR").unwrap());
+    resources_dir.push("resources");
+    fs::create_dir_all(&resources_dir).unwrap();
+
+    let resource_compiler =
+        find_resource_compiler(&env::var("CARGO_CFG_TARGET_ARCH").unwrap()).expect("found rc.exe");
+
+    let rc_path = resources_dir.join(file_stem.with_extension("rc"));
+
+    write_resource_script_file(&rc_path, file_description, filetype);
+
+    let res_path = resources_dir.join(file_stem.with_extension("res"));
+
+    let status = process::Command::new(resource_compiler)
+        .arg("/fo")
+        .arg(&res_path)
+        .arg(&rc_path)
+        .status()
+        .expect("can execute resource compiler");
+    assert!(status.success(), "rc.exe failed with status {}", status);
+    assert!(
+        res_path.try_exists().unwrap_or(false),
+        "resource file {} was not created",
+        res_path.display()
+    );
+    res_path
+}
+
+/// Writes a Windows resource script file for the rust compiler with the product and file version information
+/// into `rc_path`
+fn write_resource_script_file(
+    rc_path: &path::Path,
+    file_description: &str,
+    filetype: VersionInfoFileType,
+) {
+    let mut resource_script = RESOURCE_TEMPLATE.to_string();
+
+    // Set the string product and file version to the same thing as `rustc --version`
+    let descriptive_version = env::var("CFG_VERSION").unwrap_or("unknown".to_string());
+
+    // Set the product name to "Rust Compiler" or "Rust Compiler (nightly)" etc
+    let product_name = product_name(env::var("CFG_RELEASE_CHANNEL").unwrap());
+
+    // For the numeric version we need `major,minor,patch,build`.
+    // Extract them from `CFG_RELEASE` which is "major.minor.patch" and a "-dev", "-nightly" or similar suffix
+    let cfg_release = env::var("CFG_RELEASE").unwrap();
+    // remove the suffix, if present and parse into [`ResourceVersion`]
+    let version = parse_version(cfg_release.split("-").next().unwrap_or("0.0.0"))
+        .expect("valid CFG_RELEASE version");
+
+    resource_script = resource_script
+        .replace("@RUSTC_FILEDESCRIPTION_STR@", file_description)
+        .replace("@RUSTC_FILETYPE@", &format!("{}", filetype as u32))
+        .replace("@RUSTC_FILEVERSION_QUAD@", &version.to_quad_string())
+        .replace("@RUSTC_FILEVERSION_STR@", &descriptive_version)
+        .replace("@RUSTC_PRODUCTNAME_STR@", &product_name)
+        .replace("@RUSTC_PRODUCTVERSION_QUAD@", &version.to_quad_string())
+        .replace("@RUSTC_PRODUCTVERSION_STR@", &descriptive_version);
+
+    fs::write(&rc_path, resource_script)
+        .unwrap_or_else(|_| panic!("failed to write resource file {}", rc_path.display()));
+}
+
+fn product_name(channel: String) -> String {
+    format!(
+        "Rust Compiler{}",
+        if channel == "stable" { "".to_string() } else { format!(" ({})", channel) }
+    )
+}
+
+/// Windows resources store versions as four 16-bit integers.
+struct ResourceVersion {
+    major: u16,
+    minor: u16,
+    patch: u16,
+    build: u16,
+}
+
+impl ResourceVersion {
+    /// Format the version as a comma-separated string of four integers
+    /// as expected by Windows resource scripts for the `FILEVERSION` and `PRODUCTVERSION` fields.
+    fn to_quad_string(&self) -> String {
+        format!("{},{},{},{}", self.major, self.minor, self.patch, self.build)
+    }
+}
+
+/// Parse a string in the format "major.minor.patch" into a [`ResourceVersion`].
+/// The build is set to 0.
+/// Returns `None` if the version string is not in the expected format.
+fn parse_version(version: &str) -> Option<ResourceVersion> {
+    let mut parts = version.split('.');
+    let major = parts.next()?.parse::<u16>().ok()?;
+    let minor = parts.next()?.parse::<u16>().ok()?;
+    let patch = parts.next()?.parse::<u16>().ok()?;
+    if parts.next().is_some() {
+        None
+    } else {
+        Some(ResourceVersion { major, minor, patch, build: 0 })
+    }
+}
+
+/// Find the Windows SDK resource compiler `rc.exe` for the given architecture or target triple.
+/// Returns `None` if the tool could not be found.
+fn find_resource_compiler(arch_or_target: &str) -> Option<path::PathBuf> {
+    find_windows_sdk_tool(arch_or_target, "rc.exe")
+}
+
+/// Find a Windows SDK tool for the given architecture or target triple.
+/// Returns `None` if the tool could not be found.
+fn find_windows_sdk_tool(arch_or_target: &str, tool_name: &str) -> Option<path::PathBuf> {
+    // windows_registry::find_tool can only find MSVC tools, not Windows SDK tools, but
+    // cc does include the Windows SDK tools in the PATH environment of MSVC tools.
+
+    let msvc_linker = windows_registry::find_tool(arch_or_target, "link.exe")?;
+    let path = &msvc_linker.env().iter().find(|(k, _)| k == "PATH")?.1;
+    find_tool_in_path(tool_name, path)
+}
+
+/// Find a tool in the directories in a given PATH-like string.
+fn find_tool_in_path<P: AsRef<ffi::OsStr>>(tool_name: &str, path: P) -> Option<path::PathBuf> {
+    env::split_paths(path.as_ref()).find_map(|p| {
+        let tool_path = p.join(tool_name);
+        if tool_path.try_exists().unwrap_or(false) { Some(tool_path) } else { None }
+    })
+}