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-rw-r--r--compiler/rustc_abi/Cargo.toml8
-rw-r--r--compiler/rustc_abi/src/layout.rs192
-rw-r--r--compiler/rustc_abi/src/layout/coroutine.rs320
-rw-r--r--compiler/rustc_abi/src/layout/simple.rs148
-rw-r--r--compiler/rustc_abi/src/layout/ty.rs6
-rw-r--r--compiler/rustc_abi/src/lib.rs49
-rw-r--r--compiler/rustc_arena/src/lib.rs26
-rw-r--r--compiler/rustc_ast/src/ast.rs17
-rw-r--r--compiler/rustc_ast/src/format.rs2
-rw-r--r--compiler/rustc_ast/src/mut_visit.rs23
-rw-r--r--compiler/rustc_ast/src/util/classify.rs2
-rw-r--r--compiler/rustc_ast/src/visit.rs15
-rw-r--r--compiler/rustc_ast_lowering/src/delegation.rs30
-rw-r--r--compiler/rustc_ast_lowering/src/expr.rs33
-rw-r--r--compiler/rustc_ast_lowering/src/format.rs2
-rw-r--r--compiler/rustc_ast_lowering/src/item.rs59
-rw-r--r--compiler/rustc_ast_lowering/src/lib.rs16
-rw-r--r--compiler/rustc_ast_lowering/src/pat.rs4
-rw-r--r--compiler/rustc_ast_passes/src/ast_validation.rs5
-rw-r--r--compiler/rustc_ast_passes/src/feature_gate.rs1
-rw-r--r--compiler/rustc_ast_pretty/src/pprust/state.rs11
-rw-r--r--compiler/rustc_ast_pretty/src/pprust/state/expr.rs9
-rw-r--r--compiler/rustc_ast_pretty/src/pprust/state/item.rs13
-rw-r--r--compiler/rustc_attr_data_structures/src/lib.rs96
-rw-r--r--compiler/rustc_attr_parsing/Cargo.toml1
-rw-r--r--compiler/rustc_attr_parsing/src/context.rs3
-rw-r--r--compiler/rustc_attr_parsing/src/lib.rs44
-rw-r--r--compiler/rustc_attr_parsing/src/parser.rs4
-rw-r--r--compiler/rustc_borrowck/src/borrowck_errors.rs1
-rw-r--r--compiler/rustc_borrowck/src/constraints/graph.rs128
-rw-r--r--compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs2
-rw-r--r--compiler/rustc_borrowck/src/lib.rs20
-rw-r--r--compiler/rustc_borrowck/src/region_infer/mod.rs97
-rw-r--r--compiler/rustc_borrowck/src/type_check/input_output.rs54
-rw-r--r--compiler/rustc_borrowck/src/type_check/liveness/mod.rs20
-rw-r--r--compiler/rustc_borrowck/src/type_check/liveness/trace.rs44
-rw-r--r--compiler/rustc_borrowck/src/type_check/mod.rs210
-rw-r--r--compiler/rustc_borrowck/src/type_check/opaque_types.rs1
-rw-r--r--compiler/rustc_builtin_macros/Cargo.toml4
-rw-r--r--compiler/rustc_builtin_macros/messages.ftl3
-rw-r--r--compiler/rustc_builtin_macros/src/alloc_error_handler.rs1
-rw-r--r--compiler/rustc_builtin_macros/src/assert/context.rs1
-rw-r--r--compiler/rustc_builtin_macros/src/autodiff.rs47
-rw-r--r--compiler/rustc_builtin_macros/src/define_opaque.rs54
-rw-r--r--compiler/rustc_builtin_macros/src/deriving/generic/mod.rs1
-rw-r--r--compiler/rustc_builtin_macros/src/errors.rs9
-rw-r--r--compiler/rustc_builtin_macros/src/format.rs4
-rw-r--r--compiler/rustc_builtin_macros/src/format_foreign.rs16
-rw-r--r--compiler/rustc_builtin_macros/src/global_allocator.rs1
-rw-r--r--compiler/rustc_builtin_macros/src/lib.rs2
-rw-r--r--compiler/rustc_builtin_macros/src/standard_library_imports.rs1
-rw-r--r--compiler/rustc_builtin_macros/src/test_harness.rs1
-rw-r--r--compiler/rustc_codegen_cranelift/example/issue-72793.rs24
-rw-r--r--compiler/rustc_codegen_cranelift/patches/0029-stdlib-Disable-f16-and-f128-in-compiler-builtins.patch6
-rw-r--r--compiler/rustc_codegen_cranelift/src/lib.rs13
-rw-r--r--compiler/rustc_codegen_gcc/src/abi.rs2
-rw-r--r--compiler/rustc_codegen_gcc/src/builder.rs6
-rw-r--r--compiler/rustc_codegen_gcc/src/common.rs4
-rw-r--r--compiler/rustc_codegen_gcc/src/consts.rs6
-rw-r--r--compiler/rustc_codegen_gcc/src/gcc_util.rs2
-rw-r--r--compiler/rustc_codegen_gcc/src/lib.rs68
-rw-r--r--compiler/rustc_codegen_gcc/src/type_.rs2
-rw-r--r--compiler/rustc_codegen_llvm/src/abi.rs2
-rw-r--r--compiler/rustc_codegen_llvm/src/allocator.rs156
-rw-r--r--compiler/rustc_codegen_llvm/src/asm.rs98
-rw-r--r--compiler/rustc_codegen_llvm/src/builder.rs141
-rw-r--r--compiler/rustc_codegen_llvm/src/builder/autodiff.rs4
-rw-r--r--compiler/rustc_codegen_llvm/src/common.rs9
-rw-r--r--compiler/rustc_codegen_llvm/src/consts.rs13
-rw-r--r--compiler/rustc_codegen_llvm/src/context.rs143
-rw-r--r--compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/covfun.rs2
-rw-r--r--compiler/rustc_codegen_llvm/src/declare.rs17
-rw-r--r--compiler/rustc_codegen_llvm/src/intrinsic.rs4
-rw-r--r--compiler/rustc_codegen_llvm/src/lib.rs11
-rw-r--r--compiler/rustc_codegen_llvm/src/llvm/enzyme_ffi.rs3
-rw-r--r--compiler/rustc_codegen_llvm/src/llvm/ffi.rs22
-rw-r--r--compiler/rustc_codegen_llvm/src/llvm_util.rs115
-rw-r--r--compiler/rustc_codegen_llvm/src/type_.rs54
-rw-r--r--compiler/rustc_codegen_ssa/messages.ftl28
-rw-r--r--compiler/rustc_codegen_ssa/src/back/link.rs31
-rw-r--r--compiler/rustc_codegen_ssa/src/back/linker.rs6
-rw-r--r--compiler/rustc_codegen_ssa/src/back/write.rs3
-rw-r--r--compiler/rustc_codegen_ssa/src/codegen_attrs.rs125
-rw-r--r--compiler/rustc_codegen_ssa/src/errors.rs104
-rw-r--r--compiler/rustc_codegen_ssa/src/mir/block.rs34
-rw-r--r--compiler/rustc_codegen_ssa/src/mir/place.rs2
-rw-r--r--compiler/rustc_codegen_ssa/src/mir/rvalue.rs7
-rw-r--r--compiler/rustc_codegen_ssa/src/target_features.rs2
-rw-r--r--compiler/rustc_codegen_ssa/src/traits/abi.rs2
-rw-r--r--compiler/rustc_codegen_ssa/src/traits/backend.rs9
-rw-r--r--compiler/rustc_codegen_ssa/src/traits/builder.rs2
-rw-r--r--compiler/rustc_codegen_ssa/src/traits/consts.rs4
-rw-r--r--compiler/rustc_codegen_ssa/src/traits/mod.rs2
-rw-r--r--compiler/rustc_codegen_ssa/src/traits/type_.rs9
-rw-r--r--compiler/rustc_const_eval/src/interpret/intern.rs2
-rw-r--r--compiler/rustc_const_eval/src/interpret/memory.rs4
-rw-r--r--compiler/rustc_data_structures/src/aligned.rs8
-rw-r--r--compiler/rustc_data_structures/src/obligation_forest/mod.rs1
-rw-r--r--compiler/rustc_data_structures/src/profiling.rs6
-rw-r--r--compiler/rustc_data_structures/src/sharded.rs4
-rw-r--r--compiler/rustc_error_codes/src/error_codes/E0792.md4
-rw-r--r--compiler/rustc_error_messages/src/lib.rs1
-rw-r--r--compiler/rustc_errors/src/diagnostic.rs2
-rw-r--r--compiler/rustc_errors/src/emitter.rs244
-rw-r--r--compiler/rustc_errors/src/lib.rs1
-rw-r--r--compiler/rustc_errors/src/markdown/parse.rs20
-rw-r--r--compiler/rustc_errors/src/styled_buffer.rs13
-rw-r--r--compiler/rustc_expand/src/expand.rs4
-rw-r--r--compiler/rustc_expand/src/mbe/quoted.rs2
-rw-r--r--compiler/rustc_feature/src/unstable.rs4
-rw-r--r--compiler/rustc_hir/src/def.rs22
-rw-r--r--compiler/rustc_hir/src/definitions.rs22
-rw-r--r--compiler/rustc_hir/src/hir.rs29
-rw-r--r--compiler/rustc_hir/src/intravisit.rs45
-rw-r--r--compiler/rustc_hir/src/lang_items.rs1
-rw-r--r--compiler/rustc_hir/src/stable_hash_impls.rs2
-rw-r--r--compiler/rustc_hir_analysis/messages.ftl9
-rw-r--r--compiler/rustc_hir_analysis/src/check/always_applicable.rs5
-rw-r--r--compiler/rustc_hir_analysis/src/check/check.rs20
-rw-r--r--compiler/rustc_hir_analysis/src/check/intrinsicck.rs110
-rw-r--r--compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs3
-rw-r--r--compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs80
-rw-r--r--compiler/rustc_hir_analysis/src/errors.rs10
-rw-r--r--compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs2
-rw-r--r--compiler/rustc_hir_analysis/src/hir_ty_lowering/lint.rs132
-rw-r--r--compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs25
-rw-r--r--compiler/rustc_hir_pretty/Cargo.toml2
-rw-r--r--compiler/rustc_hir_pretty/src/lib.rs118
-rw-r--r--compiler/rustc_hir_typeck/src/coercion.rs68
-rw-r--r--compiler/rustc_hir_typeck/src/expr.rs13
-rw-r--r--compiler/rustc_hir_typeck/src/expr_use_visitor.rs64
-rw-r--r--compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs24
-rw-r--r--compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs30
-rw-r--r--compiler/rustc_hir_typeck/src/pat.rs52
-rw-r--r--compiler/rustc_hir_typeck/src/upvar.rs89
-rw-r--r--compiler/rustc_incremental/Cargo.toml2
-rw-r--r--compiler/rustc_incremental/src/persist/file_format.rs2
-rw-r--r--compiler/rustc_incremental/src/persist/fs.rs4
-rw-r--r--compiler/rustc_index/src/bit_set.rs6
-rw-r--r--compiler/rustc_index/src/slice.rs41
-rw-r--r--compiler/rustc_index/src/vec.rs4
-rw-r--r--compiler/rustc_index/src/vec/tests.rs2
-rw-r--r--compiler/rustc_interface/src/util.rs8
-rw-r--r--compiler/rustc_lint/src/context.rs20
-rw-r--r--compiler/rustc_lint/src/dangling.rs5
-rw-r--r--compiler/rustc_lint/src/default_could_be_derived.rs2
-rw-r--r--compiler/rustc_lint/src/late.rs2
-rw-r--r--compiler/rustc_lint/src/opaque_hidden_inferred_bound.rs1
-rw-r--r--compiler/rustc_lint_defs/src/builtin.rs39
-rw-r--r--compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp8
-rw-r--r--compiler/rustc_macros/src/print_attribute.rs27
-rw-r--r--compiler/rustc_middle/Cargo.toml3
-rw-r--r--compiler/rustc_middle/src/hir/map.rs2
-rw-r--r--compiler/rustc_middle/src/middle/codegen_fn_attrs.rs2
-rw-r--r--compiler/rustc_middle/src/middle/stability.rs2
-rw-r--r--compiler/rustc_middle/src/mir/interpret/allocation.rs5
-rw-r--r--compiler/rustc_middle/src/mir/interpret/allocation/init_mask.rs4
-rw-r--r--compiler/rustc_middle/src/mir/interpret/mod.rs2
-rw-r--r--compiler/rustc_middle/src/mir/mod.rs4
-rw-r--r--compiler/rustc_middle/src/mir/mono.rs2
-rw-r--r--compiler/rustc_middle/src/mir/terminator.rs3
-rw-r--r--compiler/rustc_middle/src/query/erase.rs18
-rw-r--r--compiler/rustc_middle/src/query/mod.rs13
-rw-r--r--compiler/rustc_middle/src/query/plumbing.rs6
-rw-r--r--compiler/rustc_middle/src/thir.rs8
-rw-r--r--compiler/rustc_middle/src/thir/visit.rs3
-rw-r--r--compiler/rustc_middle/src/ty/adt.rs8
-rw-r--r--compiler/rustc_middle/src/ty/closure.rs7
-rw-r--r--compiler/rustc_middle/src/ty/consts/int.rs4
-rw-r--r--compiler/rustc_middle/src/ty/context.rs4
-rw-r--r--compiler/rustc_middle/src/ty/generic_args.rs7
-rw-r--r--compiler/rustc_middle/src/ty/instance.rs2
-rw-r--r--compiler/rustc_middle/src/ty/layout.rs47
-rw-r--r--compiler/rustc_middle/src/ty/list.rs4
-rw-r--r--compiler/rustc_middle/src/ty/mod.rs62
-rw-r--r--compiler/rustc_middle/src/ty/parameterized.rs8
-rw-r--r--compiler/rustc_middle/src/ty/print/pretty.rs4
-rw-r--r--compiler/rustc_middle/src/ty/significant_drop_order.rs6
-rw-r--r--compiler/rustc_middle/src/ty/util.rs12
-rw-r--r--compiler/rustc_mir_build/src/builder/expr/as_constant.rs7
-rw-r--r--compiler/rustc_mir_build/src/builder/expr/as_place.rs1
-rw-r--r--compiler/rustc_mir_build/src/builder/expr/as_rvalue.rs8
-rw-r--r--compiler/rustc_mir_build/src/builder/expr/category.rs1
-rw-r--r--compiler/rustc_mir_build/src/builder/expr/into.rs56
-rw-r--r--compiler/rustc_mir_build/src/builder/mod.rs7
-rw-r--r--compiler/rustc_mir_build/src/check_unsafety.rs1
-rw-r--r--compiler/rustc_mir_build/src/thir/cx/expr.rs17
-rw-r--r--compiler/rustc_mir_build/src/thir/cx/mod.rs2
-rw-r--r--compiler/rustc_mir_build/src/thir/pattern/check_match.rs1
-rw-r--r--compiler/rustc_mir_build/src/thir/pattern/mod.rs2
-rw-r--r--compiler/rustc_mir_build/src/thir/print.rs7
-rw-r--r--compiler/rustc_mir_build/src/thir/util.rs22
-rw-r--r--compiler/rustc_mir_transform/src/add_call_guards.rs61
-rw-r--r--compiler/rustc_mir_transform/src/coroutine/by_move_body.rs5
-rw-r--r--compiler/rustc_mir_transform/src/lib.rs4
-rw-r--r--compiler/rustc_parse/messages.ftl8
-rw-r--r--compiler/rustc_parse/src/errors.rs28
-rw-r--r--compiler/rustc_parse/src/parser/diagnostics.rs46
-rw-r--r--compiler/rustc_parse/src/parser/expr.rs30
-rw-r--r--compiler/rustc_parse/src/parser/item.rs65
-rw-r--r--compiler/rustc_parse/src/parser/mod.rs6
-rw-r--r--compiler/rustc_parse/src/parser/token_type.rs2
-rw-r--r--compiler/rustc_parse_format/src/lib.rs18
-rw-r--r--compiler/rustc_passes/src/check_attr.rs2
-rw-r--r--compiler/rustc_passes/src/input_stats.rs11
-rw-r--r--compiler/rustc_passes/src/liveness.rs11
-rw-r--r--compiler/rustc_passes/src/liveness/rwu_table.rs2
-rw-r--r--compiler/rustc_passes/src/naked_functions.rs1
-rw-r--r--compiler/rustc_privacy/src/lib.rs6
-rw-r--r--compiler/rustc_query_system/src/dep_graph/graph.rs3
-rw-r--r--compiler/rustc_query_system/src/dep_graph/serialized.rs11
-rw-r--r--compiler/rustc_resolve/src/def_collector.rs52
-rw-r--r--compiler/rustc_resolve/src/diagnostics.rs2
-rw-r--r--compiler/rustc_resolve/src/late.rs69
-rw-r--r--compiler/rustc_resolve/src/late/diagnostics.rs48
-rw-r--r--compiler/rustc_resolve/src/lib.rs2
-rw-r--r--compiler/rustc_serialize/src/leb128.rs2
-rw-r--r--compiler/rustc_session/src/config.rs56
-rw-r--r--compiler/rustc_session/src/filesearch.rs2
-rw-r--r--compiler/rustc_session/src/lib.rs1
-rw-r--r--compiler/rustc_session/src/session.rs5
-rw-r--r--compiler/rustc_span/src/edition.rs29
-rw-r--r--compiler/rustc_span/src/symbol.rs27
-rw-r--r--compiler/rustc_target/src/callconv/mod.rs7
-rw-r--r--compiler/rustc_target/src/callconv/x86.rs24
-rw-r--r--compiler/rustc_target/src/callconv/x86_win32.rs81
-rw-r--r--compiler/rustc_target/src/spec/base/linux_wasm.rs159
-rw-r--r--compiler/rustc_target/src/spec/base/mod.rs1
-rw-r--r--compiler/rustc_target/src/spec/mod.rs12
-rw-r--r--compiler/rustc_target/src/spec/targets/i586_pc_windows_msvc.rs9
-rw-r--r--compiler/rustc_target/src/spec/targets/wasm32_wali_linux_musl.rs29
-rw-r--r--compiler/rustc_target/src/target_features.rs12
-rw-r--r--compiler/rustc_trait_selection/src/error_reporting/infer/note_and_explain.rs27
-rw-r--r--compiler/rustc_trait_selection/src/infer.rs10
-rw-r--r--compiler/rustc_trait_selection/src/traits/const_evaluatable.rs2
-rw-r--r--compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs19
-rw-r--r--compiler/rustc_trait_selection/src/traits/select/mod.rs23
-rw-r--r--compiler/rustc_trait_selection/src/traits/specialize/mod.rs9
-rw-r--r--compiler/rustc_trait_selection/src/traits/specialize/specialization_graph.rs7
-rw-r--r--compiler/rustc_ty_utils/Cargo.toml1
-rw-r--r--compiler/rustc_ty_utils/messages.ftl2
-rw-r--r--compiler/rustc_ty_utils/src/assoc.rs6
-rw-r--r--compiler/rustc_ty_utils/src/common_traits.rs16
-rw-r--r--compiler/rustc_ty_utils/src/consts.rs5
-rw-r--r--compiler/rustc_ty_utils/src/errors.rs2
-rw-r--r--compiler/rustc_ty_utils/src/layout.rs615
-rw-r--r--compiler/rustc_ty_utils/src/opaque_types.rs132
-rw-r--r--compiler/rustc_ty_utils/src/ty.rs58
-rw-r--r--compiler/rustc_type_ir/Cargo.toml3
-rw-r--r--compiler/stable_mir/src/mir/alloc.rs4
250 files changed, 4071 insertions, 2831 deletions
diff --git a/compiler/rustc_abi/Cargo.toml b/compiler/rustc_abi/Cargo.toml
index 86dc84e2016..5f9afc46a1a 100644
--- a/compiler/rustc_abi/Cargo.toml
+++ b/compiler/rustc_abi/Cargo.toml
@@ -6,13 +6,13 @@ edition = "2024"
 [dependencies]
 # tidy-alphabetical-start
 bitflags = "2.4.1"
-rand = { version = "0.8.4", default-features = false, optional = true }
-rand_xoshiro = { version = "0.6.0", optional = true }
-rustc_data_structures = { path = "../rustc_data_structures", optional = true  }
+rand = { version = "0.9.0", default-features = false, optional = true }
+rand_xoshiro = { version = "0.7.0", optional = true }
+rustc_data_structures = { path = "../rustc_data_structures", optional = true }
 rustc_hashes = { path = "../rustc_hashes" }
 rustc_index = { path = "../rustc_index", default-features = false }
 rustc_macros = { path = "../rustc_macros", optional = true }
-rustc_serialize = { path = "../rustc_serialize", optional = true  }
+rustc_serialize = { path = "../rustc_serialize", optional = true }
 rustc_span = { path = "../rustc_span", optional = true }
 tracing = "0.1"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_abi/src/layout.rs b/compiler/rustc_abi/src/layout.rs
index d3ae6a29f10..7bffeaf4cc9 100644
--- a/compiler/rustc_abi/src/layout.rs
+++ b/compiler/rustc_abi/src/layout.rs
@@ -4,6 +4,7 @@ use std::{cmp, iter};
 
 use rustc_hashes::Hash64;
 use rustc_index::Idx;
+use rustc_index::bit_set::BitMatrix;
 use tracing::debug;
 
 use crate::{
@@ -12,6 +13,9 @@ use crate::{
     Variants, WrappingRange,
 };
 
+mod coroutine;
+mod simple;
+
 #[cfg(feature = "nightly")]
 mod ty;
 
@@ -60,17 +64,28 @@ pub enum LayoutCalculatorError<F> {
 
     /// The fields or variants have irreconcilable reprs
     ReprConflict,
+
+    /// The length of an SIMD type is zero
+    ZeroLengthSimdType,
+
+    /// The length of an SIMD type exceeds the maximum number of lanes
+    OversizedSimdType { max_lanes: u64 },
+
+    /// An element type of an SIMD type isn't a primitive
+    NonPrimitiveSimdType(F),
 }
 
 impl<F> LayoutCalculatorError<F> {
     pub fn without_payload(&self) -> LayoutCalculatorError<()> {
-        match self {
-            LayoutCalculatorError::UnexpectedUnsized(_) => {
-                LayoutCalculatorError::UnexpectedUnsized(())
-            }
-            LayoutCalculatorError::SizeOverflow => LayoutCalculatorError::SizeOverflow,
-            LayoutCalculatorError::EmptyUnion => LayoutCalculatorError::EmptyUnion,
-            LayoutCalculatorError::ReprConflict => LayoutCalculatorError::ReprConflict,
+        use LayoutCalculatorError::*;
+        match *self {
+            UnexpectedUnsized(_) => UnexpectedUnsized(()),
+            SizeOverflow => SizeOverflow,
+            EmptyUnion => EmptyUnion,
+            ReprConflict => ReprConflict,
+            ZeroLengthSimdType => ZeroLengthSimdType,
+            OversizedSimdType { max_lanes } => OversizedSimdType { max_lanes },
+            NonPrimitiveSimdType(_) => NonPrimitiveSimdType(()),
         }
     }
 
@@ -78,13 +93,15 @@ impl<F> LayoutCalculatorError<F> {
     ///
     /// Intended for use by rust-analyzer, as neither it nor `rustc_abi` depend on fluent infra.
     pub fn fallback_fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        use LayoutCalculatorError::*;
         f.write_str(match self {
-            LayoutCalculatorError::UnexpectedUnsized(_) => {
-                "an unsized type was found where a sized type was expected"
+            UnexpectedUnsized(_) => "an unsized type was found where a sized type was expected",
+            SizeOverflow => "size overflow",
+            EmptyUnion => "type is a union with no fields",
+            ReprConflict => "type has an invalid repr",
+            ZeroLengthSimdType | OversizedSimdType { .. } | NonPrimitiveSimdType(_) => {
+                "invalid simd type definition"
             }
-            LayoutCalculatorError::SizeOverflow => "size overflow",
-            LayoutCalculatorError::EmptyUnion => "type is a union with no fields",
-            LayoutCalculatorError::ReprConflict => "type has an invalid repr",
         })
     }
 }
@@ -102,41 +119,115 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
         Self { cx }
     }
 
-    pub fn scalar_pair<FieldIdx: Idx, VariantIdx: Idx>(
+    pub fn array_like<FieldIdx: Idx, VariantIdx: Idx, F>(
         &self,
-        a: Scalar,
-        b: Scalar,
-    ) -> LayoutData<FieldIdx, VariantIdx> {
-        let dl = self.cx.data_layout();
-        let b_align = b.align(dl);
-        let align = a.align(dl).max(b_align).max(dl.aggregate_align);
-        let b_offset = a.size(dl).align_to(b_align.abi);
-        let size = (b_offset + b.size(dl)).align_to(align.abi);
+        element: &LayoutData<FieldIdx, VariantIdx>,
+        count_if_sized: Option<u64>, // None for slices
+    ) -> LayoutCalculatorResult<FieldIdx, VariantIdx, F> {
+        let count = count_if_sized.unwrap_or(0);
+        let size =
+            element.size.checked_mul(count, &self.cx).ok_or(LayoutCalculatorError::SizeOverflow)?;
 
-        // HACK(nox): We iter on `b` and then `a` because `max_by_key`
-        // returns the last maximum.
-        let largest_niche = Niche::from_scalar(dl, b_offset, b)
-            .into_iter()
-            .chain(Niche::from_scalar(dl, Size::ZERO, a))
-            .max_by_key(|niche| niche.available(dl));
+        Ok(LayoutData {
+            variants: Variants::Single { index: VariantIdx::new(0) },
+            fields: FieldsShape::Array { stride: element.size, count },
+            backend_repr: BackendRepr::Memory { sized: count_if_sized.is_some() },
+            largest_niche: element.largest_niche.filter(|_| count != 0),
+            uninhabited: element.uninhabited && count != 0,
+            align: element.align,
+            size,
+            max_repr_align: None,
+            unadjusted_abi_align: element.align.abi,
+            randomization_seed: element.randomization_seed.wrapping_add(Hash64::new(count)),
+        })
+    }
 
-        let combined_seed = a.size(&self.cx).bytes().wrapping_add(b.size(&self.cx).bytes());
+    pub fn simd_type<
+        FieldIdx: Idx,
+        VariantIdx: Idx,
+        F: AsRef<LayoutData<FieldIdx, VariantIdx>> + fmt::Debug,
+    >(
+        &self,
+        element: F,
+        count: u64,
+        repr_packed: bool,
+    ) -> LayoutCalculatorResult<FieldIdx, VariantIdx, F> {
+        let elt = element.as_ref();
+        if count == 0 {
+            return Err(LayoutCalculatorError::ZeroLengthSimdType);
+        } else if count > crate::MAX_SIMD_LANES {
+            return Err(LayoutCalculatorError::OversizedSimdType {
+                max_lanes: crate::MAX_SIMD_LANES,
+            });
+        }
 
-        LayoutData {
+        let BackendRepr::Scalar(e_repr) = elt.backend_repr else {
+            return Err(LayoutCalculatorError::NonPrimitiveSimdType(element));
+        };
+
+        // Compute the size and alignment of the vector
+        let dl = self.cx.data_layout();
+        let size =
+            elt.size.checked_mul(count, dl).ok_or_else(|| LayoutCalculatorError::SizeOverflow)?;
+        let (repr, align) = if repr_packed && !count.is_power_of_two() {
+            // Non-power-of-two vectors have padding up to the next power-of-two.
+            // If we're a packed repr, remove the padding while keeping the alignment as close
+            // to a vector as possible.
+            (
+                BackendRepr::Memory { sized: true },
+                AbiAndPrefAlign {
+                    abi: Align::max_aligned_factor(size),
+                    pref: dl.llvmlike_vector_align(size).pref,
+                },
+            )
+        } else {
+            (BackendRepr::SimdVector { element: e_repr, count }, dl.llvmlike_vector_align(size))
+        };
+        let size = size.align_to(align.abi);
+
+        Ok(LayoutData {
             variants: Variants::Single { index: VariantIdx::new(0) },
             fields: FieldsShape::Arbitrary {
-                offsets: [Size::ZERO, b_offset].into(),
-                memory_index: [0, 1].into(),
+                offsets: [Size::ZERO].into(),
+                memory_index: [0].into(),
             },
-            backend_repr: BackendRepr::ScalarPair(a, b),
-            largest_niche,
+            backend_repr: repr,
+            largest_niche: elt.largest_niche,
             uninhabited: false,
-            align,
             size,
+            align,
             max_repr_align: None,
-            unadjusted_abi_align: align.abi,
-            randomization_seed: Hash64::new(combined_seed),
-        }
+            unadjusted_abi_align: elt.align.abi,
+            randomization_seed: elt.randomization_seed.wrapping_add(Hash64::new(count)),
+        })
+    }
+
+    /// Compute the layout for a coroutine.
+    ///
+    /// This uses dedicated code instead of [`Self::layout_of_struct_or_enum`], as coroutine
+    /// fields may be shared between multiple variants (see the [`coroutine`] module for details).
+    pub fn coroutine<
+        'a,
+        F: Deref<Target = &'a LayoutData<FieldIdx, VariantIdx>> + fmt::Debug + Copy,
+        VariantIdx: Idx,
+        FieldIdx: Idx,
+        LocalIdx: Idx,
+    >(
+        &self,
+        local_layouts: &IndexSlice<LocalIdx, F>,
+        prefix_layouts: IndexVec<FieldIdx, F>,
+        variant_fields: &IndexSlice<VariantIdx, IndexVec<FieldIdx, LocalIdx>>,
+        storage_conflicts: &BitMatrix<LocalIdx, LocalIdx>,
+        tag_to_layout: impl Fn(Scalar) -> F,
+    ) -> LayoutCalculatorResult<FieldIdx, VariantIdx, F> {
+        coroutine::layout(
+            self,
+            local_layouts,
+            prefix_layouts,
+            variant_fields,
+            storage_conflicts,
+            tag_to_layout,
+        )
     }
 
     pub fn univariant<
@@ -214,25 +305,6 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
         layout
     }
 
-    pub fn layout_of_never_type<FieldIdx: Idx, VariantIdx: Idx>(
-        &self,
-    ) -> LayoutData<FieldIdx, VariantIdx> {
-        let dl = self.cx.data_layout();
-        // This is also used for uninhabited enums, so we use `Variants::Empty`.
-        LayoutData {
-            variants: Variants::Empty,
-            fields: FieldsShape::Primitive,
-            backend_repr: BackendRepr::Memory { sized: true },
-            largest_niche: None,
-            uninhabited: true,
-            align: dl.i8_align,
-            size: Size::ZERO,
-            max_repr_align: None,
-            unadjusted_abi_align: dl.i8_align.abi,
-            randomization_seed: Hash64::ZERO,
-        }
-    }
-
     pub fn layout_of_struct_or_enum<
         'a,
         FieldIdx: Idx,
@@ -260,7 +332,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
             Some(present_first) => present_first,
             // Uninhabited because it has no variants, or only absent ones.
             None if is_enum => {
-                return Ok(self.layout_of_never_type());
+                return Ok(LayoutData::never_type(&self.cx));
             }
             // If it's a struct, still compute a layout so that we can still compute the
             // field offsets.
@@ -949,7 +1021,8 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
                     // Common prim might be uninit.
                     Scalar::Union { value: prim }
                 };
-                let pair = self.scalar_pair::<FieldIdx, VariantIdx>(tag, prim_scalar);
+                let pair =
+                    LayoutData::<FieldIdx, VariantIdx>::scalar_pair(&self.cx, tag, prim_scalar);
                 let pair_offsets = match pair.fields {
                     FieldsShape::Arbitrary { ref offsets, ref memory_index } => {
                         assert_eq!(memory_index.raw, [0, 1]);
@@ -1341,7 +1414,8 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
                             } else {
                                 ((j, b), (i, a))
                             };
-                            let pair = self.scalar_pair::<FieldIdx, VariantIdx>(a, b);
+                            let pair =
+                                LayoutData::<FieldIdx, VariantIdx>::scalar_pair(&self.cx, a, b);
                             let pair_offsets = match pair.fields {
                                 FieldsShape::Arbitrary { ref offsets, ref memory_index } => {
                                     assert_eq!(memory_index.raw, [0, 1]);
diff --git a/compiler/rustc_abi/src/layout/coroutine.rs b/compiler/rustc_abi/src/layout/coroutine.rs
new file mode 100644
index 00000000000..27e704d538c
--- /dev/null
+++ b/compiler/rustc_abi/src/layout/coroutine.rs
@@ -0,0 +1,320 @@
+//! Coroutine layout logic.
+//!
+//! When laying out coroutines, we divide our saved local fields into two
+//! categories: overlap-eligible and overlap-ineligible.
+//!
+//! Those fields which are ineligible for overlap go in a "prefix" at the
+//! beginning of the layout, and always have space reserved for them.
+//!
+//! Overlap-eligible fields are only assigned to one variant, so we lay
+//! those fields out for each variant and put them right after the
+//! prefix.
+//!
+//! Finally, in the layout details, we point to the fields from the
+//! variants they are assigned to. It is possible for some fields to be
+//! included in multiple variants. No field ever "moves around" in the
+//! layout; its offset is always the same.
+//!
+//! Also included in the layout are the upvars and the discriminant.
+//! These are included as fields on the "outer" layout; they are not part
+//! of any variant.
+
+use std::iter;
+
+use rustc_index::bit_set::{BitMatrix, DenseBitSet};
+use rustc_index::{Idx, IndexSlice, IndexVec};
+use tracing::{debug, trace};
+
+use crate::{
+    BackendRepr, FieldsShape, HasDataLayout, Integer, LayoutData, Primitive, ReprOptions, Scalar,
+    StructKind, TagEncoding, Variants, WrappingRange,
+};
+
+/// Overlap eligibility and variant assignment for each CoroutineSavedLocal.
+#[derive(Clone, Debug, PartialEq)]
+enum SavedLocalEligibility<VariantIdx, FieldIdx> {
+    Unassigned,
+    Assigned(VariantIdx),
+    Ineligible(Option<FieldIdx>),
+}
+
+/// Compute the eligibility and assignment of each local.
+fn coroutine_saved_local_eligibility<VariantIdx: Idx, FieldIdx: Idx, LocalIdx: Idx>(
+    nb_locals: usize,
+    variant_fields: &IndexSlice<VariantIdx, IndexVec<FieldIdx, LocalIdx>>,
+    storage_conflicts: &BitMatrix<LocalIdx, LocalIdx>,
+) -> (DenseBitSet<LocalIdx>, IndexVec<LocalIdx, SavedLocalEligibility<VariantIdx, FieldIdx>>) {
+    use SavedLocalEligibility::*;
+
+    let mut assignments: IndexVec<LocalIdx, _> = IndexVec::from_elem_n(Unassigned, nb_locals);
+
+    // The saved locals not eligible for overlap. These will get
+    // "promoted" to the prefix of our coroutine.
+    let mut ineligible_locals = DenseBitSet::new_empty(nb_locals);
+
+    // Figure out which of our saved locals are fields in only
+    // one variant. The rest are deemed ineligible for overlap.
+    for (variant_index, fields) in variant_fields.iter_enumerated() {
+        for local in fields {
+            match assignments[*local] {
+                Unassigned => {
+                    assignments[*local] = Assigned(variant_index);
+                }
+                Assigned(idx) => {
+                    // We've already seen this local at another suspension
+                    // point, so it is no longer a candidate.
+                    trace!(
+                        "removing local {:?} in >1 variant ({:?}, {:?})",
+                        local, variant_index, idx
+                    );
+                    ineligible_locals.insert(*local);
+                    assignments[*local] = Ineligible(None);
+                }
+                Ineligible(_) => {}
+            }
+        }
+    }
+
+    // Next, check every pair of eligible locals to see if they
+    // conflict.
+    for local_a in storage_conflicts.rows() {
+        let conflicts_a = storage_conflicts.count(local_a);
+        if ineligible_locals.contains(local_a) {
+            continue;
+        }
+
+        for local_b in storage_conflicts.iter(local_a) {
+            // local_a and local_b are storage live at the same time, therefore they
+            // cannot overlap in the coroutine layout. The only way to guarantee
+            // this is if they are in the same variant, or one is ineligible
+            // (which means it is stored in every variant).
+            if ineligible_locals.contains(local_b) || assignments[local_a] == assignments[local_b] {
+                continue;
+            }
+
+            // If they conflict, we will choose one to make ineligible.
+            // This is not always optimal; it's just a greedy heuristic that
+            // seems to produce good results most of the time.
+            let conflicts_b = storage_conflicts.count(local_b);
+            let (remove, other) =
+                if conflicts_a > conflicts_b { (local_a, local_b) } else { (local_b, local_a) };
+            ineligible_locals.insert(remove);
+            assignments[remove] = Ineligible(None);
+            trace!("removing local {:?} due to conflict with {:?}", remove, other);
+        }
+    }
+
+    // Count the number of variants in use. If only one of them, then it is
+    // impossible to overlap any locals in our layout. In this case it's
+    // always better to make the remaining locals ineligible, so we can
+    // lay them out with the other locals in the prefix and eliminate
+    // unnecessary padding bytes.
+    {
+        let mut used_variants = DenseBitSet::new_empty(variant_fields.len());
+        for assignment in &assignments {
+            if let Assigned(idx) = assignment {
+                used_variants.insert(*idx);
+            }
+        }
+        if used_variants.count() < 2 {
+            for assignment in assignments.iter_mut() {
+                *assignment = Ineligible(None);
+            }
+            ineligible_locals.insert_all();
+        }
+    }
+
+    // Write down the order of our locals that will be promoted to the prefix.
+    {
+        for (idx, local) in ineligible_locals.iter().enumerate() {
+            assignments[local] = Ineligible(Some(FieldIdx::new(idx)));
+        }
+    }
+    debug!("coroutine saved local assignments: {:?}", assignments);
+
+    (ineligible_locals, assignments)
+}
+
+/// Compute the full coroutine layout.
+pub(super) fn layout<
+    'a,
+    F: core::ops::Deref<Target = &'a LayoutData<FieldIdx, VariantIdx>> + core::fmt::Debug + Copy,
+    VariantIdx: Idx,
+    FieldIdx: Idx,
+    LocalIdx: Idx,
+>(
+    calc: &super::LayoutCalculator<impl HasDataLayout>,
+    local_layouts: &IndexSlice<LocalIdx, F>,
+    mut prefix_layouts: IndexVec<FieldIdx, F>,
+    variant_fields: &IndexSlice<VariantIdx, IndexVec<FieldIdx, LocalIdx>>,
+    storage_conflicts: &BitMatrix<LocalIdx, LocalIdx>,
+    tag_to_layout: impl Fn(Scalar) -> F,
+) -> super::LayoutCalculatorResult<FieldIdx, VariantIdx, F> {
+    use SavedLocalEligibility::*;
+
+    let (ineligible_locals, assignments) =
+        coroutine_saved_local_eligibility(local_layouts.len(), variant_fields, storage_conflicts);
+
+    // Build a prefix layout, including "promoting" all ineligible
+    // locals as part of the prefix. We compute the layout of all of
+    // these fields at once to get optimal packing.
+    let tag_index = prefix_layouts.len();
+
+    // `variant_fields` already accounts for the reserved variants, so no need to add them.
+    let max_discr = (variant_fields.len() - 1) as u128;
+    let discr_int = Integer::fit_unsigned(max_discr);
+    let tag = Scalar::Initialized {
+        value: Primitive::Int(discr_int, /* signed = */ false),
+        valid_range: WrappingRange { start: 0, end: max_discr },
+    };
+
+    let promoted_layouts = ineligible_locals.iter().map(|local| local_layouts[local]);
+    prefix_layouts.push(tag_to_layout(tag));
+    prefix_layouts.extend(promoted_layouts);
+    let prefix =
+        calc.univariant(&prefix_layouts, &ReprOptions::default(), StructKind::AlwaysSized)?;
+
+    let (prefix_size, prefix_align) = (prefix.size, prefix.align);
+
+    // Split the prefix layout into the "outer" fields (upvars and
+    // discriminant) and the "promoted" fields. Promoted fields will
+    // get included in each variant that requested them in
+    // CoroutineLayout.
+    debug!("prefix = {:#?}", prefix);
+    let (outer_fields, promoted_offsets, promoted_memory_index) = match prefix.fields {
+        FieldsShape::Arbitrary { mut offsets, memory_index } => {
+            let mut inverse_memory_index = memory_index.invert_bijective_mapping();
+
+            // "a" (`0..b_start`) and "b" (`b_start..`) correspond to
+            // "outer" and "promoted" fields respectively.
+            let b_start = FieldIdx::new(tag_index + 1);
+            let offsets_b = IndexVec::from_raw(offsets.raw.split_off(b_start.index()));
+            let offsets_a = offsets;
+
+            // Disentangle the "a" and "b" components of `inverse_memory_index`
+            // by preserving the order but keeping only one disjoint "half" each.
+            // FIXME(eddyb) build a better abstraction for permutations, if possible.
+            let inverse_memory_index_b: IndexVec<u32, FieldIdx> = inverse_memory_index
+                .iter()
+                .filter_map(|&i| i.index().checked_sub(b_start.index()).map(FieldIdx::new))
+                .collect();
+            inverse_memory_index.raw.retain(|&i| i.index() < b_start.index());
+            let inverse_memory_index_a = inverse_memory_index;
+
+            // Since `inverse_memory_index_{a,b}` each only refer to their
+            // respective fields, they can be safely inverted
+            let memory_index_a = inverse_memory_index_a.invert_bijective_mapping();
+            let memory_index_b = inverse_memory_index_b.invert_bijective_mapping();
+
+            let outer_fields =
+                FieldsShape::Arbitrary { offsets: offsets_a, memory_index: memory_index_a };
+            (outer_fields, offsets_b, memory_index_b)
+        }
+        _ => unreachable!(),
+    };
+
+    let mut size = prefix.size;
+    let mut align = prefix.align;
+    let variants = variant_fields
+        .iter_enumerated()
+        .map(|(index, variant_fields)| {
+            // Only include overlap-eligible fields when we compute our variant layout.
+            let variant_only_tys = variant_fields
+                .iter()
+                .filter(|local| match assignments[**local] {
+                    Unassigned => unreachable!(),
+                    Assigned(v) if v == index => true,
+                    Assigned(_) => unreachable!("assignment does not match variant"),
+                    Ineligible(_) => false,
+                })
+                .map(|local| local_layouts[*local]);
+
+            let mut variant = calc.univariant(
+                &variant_only_tys.collect::<IndexVec<_, _>>(),
+                &ReprOptions::default(),
+                StructKind::Prefixed(prefix_size, prefix_align.abi),
+            )?;
+            variant.variants = Variants::Single { index };
+
+            let FieldsShape::Arbitrary { offsets, memory_index } = variant.fields else {
+                unreachable!();
+            };
+
+            // Now, stitch the promoted and variant-only fields back together in
+            // the order they are mentioned by our CoroutineLayout.
+            // Because we only use some subset (that can differ between variants)
+            // of the promoted fields, we can't just pick those elements of the
+            // `promoted_memory_index` (as we'd end up with gaps).
+            // So instead, we build an "inverse memory_index", as if all of the
+            // promoted fields were being used, but leave the elements not in the
+            // subset as `invalid_field_idx`, which we can filter out later to
+            // obtain a valid (bijective) mapping.
+            let invalid_field_idx = promoted_memory_index.len() + memory_index.len();
+            let mut combined_inverse_memory_index =
+                IndexVec::from_elem_n(FieldIdx::new(invalid_field_idx), invalid_field_idx);
+
+            let mut offsets_and_memory_index = iter::zip(offsets, memory_index);
+            let combined_offsets = variant_fields
+                .iter_enumerated()
+                .map(|(i, local)| {
+                    let (offset, memory_index) = match assignments[*local] {
+                        Unassigned => unreachable!(),
+                        Assigned(_) => {
+                            let (offset, memory_index) = offsets_and_memory_index.next().unwrap();
+                            (offset, promoted_memory_index.len() as u32 + memory_index)
+                        }
+                        Ineligible(field_idx) => {
+                            let field_idx = field_idx.unwrap();
+                            (promoted_offsets[field_idx], promoted_memory_index[field_idx])
+                        }
+                    };
+                    combined_inverse_memory_index[memory_index] = i;
+                    offset
+                })
+                .collect();
+
+            // Remove the unused slots and invert the mapping to obtain the
+            // combined `memory_index` (also see previous comment).
+            combined_inverse_memory_index.raw.retain(|&i| i.index() != invalid_field_idx);
+            let combined_memory_index = combined_inverse_memory_index.invert_bijective_mapping();
+
+            variant.fields = FieldsShape::Arbitrary {
+                offsets: combined_offsets,
+                memory_index: combined_memory_index,
+            };
+
+            size = size.max(variant.size);
+            align = align.max(variant.align);
+            Ok(variant)
+        })
+        .collect::<Result<IndexVec<VariantIdx, _>, _>>()?;
+
+    size = size.align_to(align.abi);
+
+    let uninhabited = prefix.uninhabited || variants.iter().all(|v| v.is_uninhabited());
+    let abi = BackendRepr::Memory { sized: true };
+
+    Ok(LayoutData {
+        variants: Variants::Multiple {
+            tag,
+            tag_encoding: TagEncoding::Direct,
+            tag_field: tag_index,
+            variants,
+        },
+        fields: outer_fields,
+        backend_repr: abi,
+        // Suppress niches inside coroutines. If the niche is inside a field that is aliased (due to
+        // self-referentiality), getting the discriminant can cause aliasing violations.
+        // `UnsafeCell` blocks niches for the same reason, but we don't yet have `UnsafePinned` that
+        // would do the same for us here.
+        // See <https://github.com/rust-lang/rust/issues/63818>, <https://github.com/rust-lang/miri/issues/3780>.
+        // FIXME: Remove when <https://github.com/rust-lang/rust/issues/125735> is implemented and aliased coroutine fields are wrapped in `UnsafePinned`.
+        largest_niche: None,
+        uninhabited,
+        size,
+        align,
+        max_repr_align: None,
+        unadjusted_abi_align: align.abi,
+        randomization_seed: Default::default(),
+    })
+}
diff --git a/compiler/rustc_abi/src/layout/simple.rs b/compiler/rustc_abi/src/layout/simple.rs
new file mode 100644
index 00000000000..0d0706defc2
--- /dev/null
+++ b/compiler/rustc_abi/src/layout/simple.rs
@@ -0,0 +1,148 @@
+use std::num::NonZero;
+
+use rustc_hashes::Hash64;
+use rustc_index::{Idx, IndexVec};
+
+use crate::{
+    BackendRepr, FieldsShape, HasDataLayout, LayoutData, Niche, Primitive, Scalar, Size, Variants,
+};
+
+/// "Simple" layout constructors that cannot fail.
+impl<FieldIdx: Idx, VariantIdx: Idx> LayoutData<FieldIdx, VariantIdx> {
+    pub fn unit<C: HasDataLayout>(cx: &C, sized: bool) -> Self {
+        let dl = cx.data_layout();
+        LayoutData {
+            variants: Variants::Single { index: VariantIdx::new(0) },
+            fields: FieldsShape::Arbitrary {
+                offsets: IndexVec::new(),
+                memory_index: IndexVec::new(),
+            },
+            backend_repr: BackendRepr::Memory { sized },
+            largest_niche: None,
+            uninhabited: false,
+            align: dl.i8_align,
+            size: Size::ZERO,
+            max_repr_align: None,
+            unadjusted_abi_align: dl.i8_align.abi,
+            randomization_seed: Hash64::new(0),
+        }
+    }
+
+    pub fn never_type<C: HasDataLayout>(cx: &C) -> Self {
+        let dl = cx.data_layout();
+        // This is also used for uninhabited enums, so we use `Variants::Empty`.
+        LayoutData {
+            variants: Variants::Empty,
+            fields: FieldsShape::Primitive,
+            backend_repr: BackendRepr::Memory { sized: true },
+            largest_niche: None,
+            uninhabited: true,
+            align: dl.i8_align,
+            size: Size::ZERO,
+            max_repr_align: None,
+            unadjusted_abi_align: dl.i8_align.abi,
+            randomization_seed: Hash64::ZERO,
+        }
+    }
+
+    pub fn scalar<C: HasDataLayout>(cx: &C, scalar: Scalar) -> Self {
+        let largest_niche = Niche::from_scalar(cx, Size::ZERO, scalar);
+        let size = scalar.size(cx);
+        let align = scalar.align(cx);
+
+        let range = scalar.valid_range(cx);
+
+        // All primitive types for which we don't have subtype coercions should get a distinct seed,
+        // so that types wrapping them can use randomization to arrive at distinct layouts.
+        //
+        // Some type information is already lost at this point, so as an approximation we derive
+        // the seed from what remains. For example on 64-bit targets usize and u64 can no longer
+        // be distinguished.
+        let randomization_seed = size
+            .bytes()
+            .wrapping_add(
+                match scalar.primitive() {
+                    Primitive::Int(_, true) => 1,
+                    Primitive::Int(_, false) => 2,
+                    Primitive::Float(_) => 3,
+                    Primitive::Pointer(_) => 4,
+                } << 32,
+            )
+            // distinguishes references from pointers
+            .wrapping_add((range.start as u64).rotate_right(16))
+            // distinguishes char from u32 and bool from u8
+            .wrapping_add((range.end as u64).rotate_right(16));
+
+        LayoutData {
+            variants: Variants::Single { index: VariantIdx::new(0) },
+            fields: FieldsShape::Primitive,
+            backend_repr: BackendRepr::Scalar(scalar),
+            largest_niche,
+            uninhabited: false,
+            size,
+            align,
+            max_repr_align: None,
+            unadjusted_abi_align: align.abi,
+            randomization_seed: Hash64::new(randomization_seed),
+        }
+    }
+
+    pub fn scalar_pair<C: HasDataLayout>(cx: &C, a: Scalar, b: Scalar) -> Self {
+        let dl = cx.data_layout();
+        let b_align = b.align(dl);
+        let align = a.align(dl).max(b_align).max(dl.aggregate_align);
+        let b_offset = a.size(dl).align_to(b_align.abi);
+        let size = (b_offset + b.size(dl)).align_to(align.abi);
+
+        // HACK(nox): We iter on `b` and then `a` because `max_by_key`
+        // returns the last maximum.
+        let largest_niche = Niche::from_scalar(dl, b_offset, b)
+            .into_iter()
+            .chain(Niche::from_scalar(dl, Size::ZERO, a))
+            .max_by_key(|niche| niche.available(dl));
+
+        let combined_seed = a.size(dl).bytes().wrapping_add(b.size(dl).bytes());
+
+        LayoutData {
+            variants: Variants::Single { index: VariantIdx::new(0) },
+            fields: FieldsShape::Arbitrary {
+                offsets: [Size::ZERO, b_offset].into(),
+                memory_index: [0, 1].into(),
+            },
+            backend_repr: BackendRepr::ScalarPair(a, b),
+            largest_niche,
+            uninhabited: false,
+            align,
+            size,
+            max_repr_align: None,
+            unadjusted_abi_align: align.abi,
+            randomization_seed: Hash64::new(combined_seed),
+        }
+    }
+
+    /// Returns a dummy layout for an uninhabited variant.
+    ///
+    /// Uninhabited variants get pruned as part of the layout calculation,
+    /// so this can be used after the fact to reconstitute a layout.
+    pub fn uninhabited_variant<C: HasDataLayout>(cx: &C, index: VariantIdx, fields: usize) -> Self {
+        let dl = cx.data_layout();
+        LayoutData {
+            variants: Variants::Single { index },
+            fields: match NonZero::new(fields) {
+                Some(fields) => FieldsShape::Union(fields),
+                None => FieldsShape::Arbitrary {
+                    offsets: IndexVec::new(),
+                    memory_index: IndexVec::new(),
+                },
+            },
+            backend_repr: BackendRepr::Memory { sized: true },
+            largest_niche: None,
+            uninhabited: true,
+            align: dl.i8_align,
+            size: Size::ZERO,
+            max_repr_align: None,
+            unadjusted_abi_align: dl.i8_align.abi,
+            randomization_seed: Hash64::ZERO,
+        }
+    }
+}
diff --git a/compiler/rustc_abi/src/layout/ty.rs b/compiler/rustc_abi/src/layout/ty.rs
index 03f3f043c21..4f43c0e6f8e 100644
--- a/compiler/rustc_abi/src/layout/ty.rs
+++ b/compiler/rustc_abi/src/layout/ty.rs
@@ -150,6 +150,12 @@ impl<'a, Ty> Deref for TyAndLayout<'a, Ty> {
     }
 }
 
+impl<'a, Ty> AsRef<LayoutData<FieldIdx, VariantIdx>> for TyAndLayout<'a, Ty> {
+    fn as_ref(&self) -> &LayoutData<FieldIdx, VariantIdx> {
+        &*self.layout.0.0
+    }
+}
+
 /// Trait that needs to be implemented by the higher-level type representation
 /// (e.g. `rustc_middle::ty::Ty`), to provide `rustc_target::abi` functionality.
 pub trait TyAbiInterface<'a, C>: Sized + std::fmt::Debug {
diff --git a/compiler/rustc_abi/src/lib.rs b/compiler/rustc_abi/src/lib.rs
index a59dc870aa3..1b737582009 100644
--- a/compiler/rustc_abi/src/lib.rs
+++ b/compiler/rustc_abi/src/lib.rs
@@ -205,6 +205,13 @@ impl ReprOptions {
     }
 }
 
+/// The maximum supported number of lanes in a SIMD vector.
+///
+/// This value is selected based on backend support:
+/// * LLVM does not appear to have a vector width limit.
+/// * Cranelift stores the base-2 log of the lane count in a 4 bit integer.
+pub const MAX_SIMD_LANES: u64 = 1 << 0xF;
+
 /// Parsed [Data layout](https://llvm.org/docs/LangRef.html#data-layout)
 /// for a target, which contains everything needed to compute layouts.
 #[derive(Debug, PartialEq, Eq)]
@@ -1744,48 +1751,6 @@ impl<FieldIdx: Idx, VariantIdx: Idx> LayoutData<FieldIdx, VariantIdx> {
     pub fn is_uninhabited(&self) -> bool {
         self.uninhabited
     }
-
-    pub fn scalar<C: HasDataLayout>(cx: &C, scalar: Scalar) -> Self {
-        let largest_niche = Niche::from_scalar(cx, Size::ZERO, scalar);
-        let size = scalar.size(cx);
-        let align = scalar.align(cx);
-
-        let range = scalar.valid_range(cx);
-
-        // All primitive types for which we don't have subtype coercions should get a distinct seed,
-        // so that types wrapping them can use randomization to arrive at distinct layouts.
-        //
-        // Some type information is already lost at this point, so as an approximation we derive
-        // the seed from what remains. For example on 64-bit targets usize and u64 can no longer
-        // be distinguished.
-        let randomization_seed = size
-            .bytes()
-            .wrapping_add(
-                match scalar.primitive() {
-                    Primitive::Int(_, true) => 1,
-                    Primitive::Int(_, false) => 2,
-                    Primitive::Float(_) => 3,
-                    Primitive::Pointer(_) => 4,
-                } << 32,
-            )
-            // distinguishes references from pointers
-            .wrapping_add((range.start as u64).rotate_right(16))
-            // distinguishes char from u32 and bool from u8
-            .wrapping_add((range.end as u64).rotate_right(16));
-
-        LayoutData {
-            variants: Variants::Single { index: VariantIdx::new(0) },
-            fields: FieldsShape::Primitive,
-            backend_repr: BackendRepr::Scalar(scalar),
-            largest_niche,
-            uninhabited: false,
-            size,
-            align,
-            max_repr_align: None,
-            unadjusted_abi_align: align.abi,
-            randomization_seed: Hash64::new(randomization_seed),
-        }
-    }
 }
 
 impl<FieldIdx: Idx, VariantIdx: Idx> fmt::Debug for LayoutData<FieldIdx, VariantIdx>
diff --git a/compiler/rustc_arena/src/lib.rs b/compiler/rustc_arena/src/lib.rs
index b21ccba93bb..3b44e996358 100644
--- a/compiler/rustc_arena/src/lib.rs
+++ b/compiler/rustc_arena/src/lib.rs
@@ -93,7 +93,7 @@ impl<T> ArenaChunk<T> {
     #[inline]
     fn end(&mut self) -> *mut T {
         unsafe {
-            if mem::size_of::<T>() == 0 {
+            if size_of::<T>() == 0 {
                 // A pointer as large as possible for zero-sized elements.
                 ptr::without_provenance_mut(!0)
             } else {
@@ -151,7 +151,7 @@ impl<T> TypedArena<T> {
         }
 
         unsafe {
-            if mem::size_of::<T>() == 0 {
+            if size_of::<T>() == 0 {
                 self.ptr.set(self.ptr.get().wrapping_byte_add(1));
                 let ptr = ptr::NonNull::<T>::dangling().as_ptr();
                 // Don't drop the object. This `write` is equivalent to `forget`.
@@ -173,13 +173,13 @@ impl<T> TypedArena<T> {
         // FIXME: this should *likely* use `offset_from`, but more
         // investigation is needed (including running tests in miri).
         let available_bytes = self.end.get().addr() - self.ptr.get().addr();
-        let additional_bytes = additional.checked_mul(mem::size_of::<T>()).unwrap();
+        let additional_bytes = additional.checked_mul(size_of::<T>()).unwrap();
         available_bytes >= additional_bytes
     }
 
     #[inline]
     fn alloc_raw_slice(&self, len: usize) -> *mut T {
-        assert!(mem::size_of::<T>() != 0);
+        assert!(size_of::<T>() != 0);
         assert!(len != 0);
 
         // Ensure the current chunk can fit `len` objects.
@@ -213,7 +213,7 @@ impl<T> TypedArena<T> {
         // So we collect all the elements beforehand, which takes care of reentrancy and panic
         // safety. This function is much less hot than `DroplessArena::alloc_from_iter`, so it
         // doesn't need to be hyper-optimized.
-        assert!(mem::size_of::<T>() != 0);
+        assert!(size_of::<T>() != 0);
 
         let mut vec: SmallVec<[_; 8]> = iter.into_iter().collect();
         if vec.is_empty() {
@@ -236,7 +236,7 @@ impl<T> TypedArena<T> {
         unsafe {
             // We need the element size to convert chunk sizes (ranging from
             // PAGE to HUGE_PAGE bytes) to element counts.
-            let elem_size = cmp::max(1, mem::size_of::<T>());
+            let elem_size = cmp::max(1, size_of::<T>());
             let mut chunks = self.chunks.borrow_mut();
             let mut new_cap;
             if let Some(last_chunk) = chunks.last_mut() {
@@ -246,7 +246,7 @@ impl<T> TypedArena<T> {
                     // FIXME: this should *likely* use `offset_from`, but more
                     // investigation is needed (including running tests in miri).
                     let used_bytes = self.ptr.get().addr() - last_chunk.start().addr();
-                    last_chunk.entries = used_bytes / mem::size_of::<T>();
+                    last_chunk.entries = used_bytes / size_of::<T>();
                 }
 
                 // If the previous chunk's len is less than HUGE_PAGE
@@ -276,7 +276,7 @@ impl<T> TypedArena<T> {
         let end = self.ptr.get().addr();
         // We then calculate the number of elements to be dropped in the last chunk,
         // which is the filled area's length.
-        let diff = if mem::size_of::<T>() == 0 {
+        let diff = if size_of::<T>() == 0 {
             // `T` is ZST. It can't have a drop flag, so the value here doesn't matter. We get
             // the number of zero-sized values in the last and only chunk, just out of caution.
             // Recall that `end` was incremented for each allocated value.
@@ -284,7 +284,7 @@ impl<T> TypedArena<T> {
         } else {
             // FIXME: this should *likely* use `offset_from`, but more
             // investigation is needed (including running tests in miri).
-            (end - start) / mem::size_of::<T>()
+            (end - start) / size_of::<T>()
         };
         // Pass that to the `destroy` method.
         unsafe {
@@ -329,7 +329,7 @@ fn align_up(val: usize, align: usize) -> usize {
 
 // Pointer alignment is common in compiler types, so keep `DroplessArena` aligned to them
 // to optimize away alignment code.
-const DROPLESS_ALIGNMENT: usize = mem::align_of::<usize>();
+const DROPLESS_ALIGNMENT: usize = align_of::<usize>();
 
 /// An arena that can hold objects of multiple different types that impl `Copy`
 /// and/or satisfy `!mem::needs_drop`.
@@ -447,7 +447,7 @@ impl DroplessArena {
     #[inline]
     pub fn alloc<T>(&self, object: T) -> &mut T {
         assert!(!mem::needs_drop::<T>());
-        assert!(mem::size_of::<T>() != 0);
+        assert!(size_of::<T>() != 0);
 
         let mem = self.alloc_raw(Layout::new::<T>()) as *mut T;
 
@@ -471,7 +471,7 @@ impl DroplessArena {
         T: Copy,
     {
         assert!(!mem::needs_drop::<T>());
-        assert!(mem::size_of::<T>() != 0);
+        assert!(size_of::<T>() != 0);
         assert!(!slice.is_empty());
 
         let mem = self.alloc_raw(Layout::for_value::<[T]>(slice)) as *mut T;
@@ -546,7 +546,7 @@ impl DroplessArena {
         // Warning: this function is reentrant: `iter` could hold a reference to `&self` and
         // allocate additional elements while we're iterating.
         let iter = iter.into_iter();
-        assert!(mem::size_of::<T>() != 0);
+        assert!(size_of::<T>() != 0);
         assert!(!mem::needs_drop::<T>());
 
         let size_hint = iter.size_hint();
diff --git a/compiler/rustc_ast/src/ast.rs b/compiler/rustc_ast/src/ast.rs
index 11fc409cf43..1b831c454e6 100644
--- a/compiler/rustc_ast/src/ast.rs
+++ b/compiler/rustc_ast/src/ast.rs
@@ -1399,6 +1399,7 @@ impl Expr {
             // Never need parens
             ExprKind::Array(_)
             | ExprKind::Await(..)
+            | ExprKind::Use(..)
             | ExprKind::Block(..)
             | ExprKind::Call(..)
             | ExprKind::ConstBlock(_)
@@ -1588,6 +1589,8 @@ pub enum ExprKind {
     Gen(CaptureBy, P<Block>, GenBlockKind, Span),
     /// An await expression (`my_future.await`). Span is of await keyword.
     Await(P<Expr>, Span),
+    /// A use expression (`x.use`). Span is of use keyword.
+    Use(P<Expr>, Span),
 
     /// A try block (`try { ... }`).
     TryBlock(P<Block>),
@@ -1757,8 +1760,17 @@ pub enum CaptureBy {
         /// The span of the `move` keyword.
         move_kw: Span,
     },
-    /// `move` keyword was not specified.
+    /// `move` or `use` keywords were not specified.
     Ref,
+    /// `use |x| y + x`.
+    ///
+    /// Note that if you have a regular closure like `|| x.use`, this will *not* result
+    /// in a `Use` capture. Instead, the `ExprUseVisitor` will look at the type
+    /// of `x` and treat `x.use` as either a copy/clone/move as appropriate.
+    Use {
+        /// The span of the `use` keyword.
+        use_kw: Span,
+    },
 }
 
 /// Closure lifetime binder, `for<'a, 'b>` in `for<'a, 'b> |_: &'a (), _: &'b ()|`.
@@ -3454,6 +3466,7 @@ pub struct Fn {
     pub generics: Generics,
     pub sig: FnSig,
     pub contract: Option<P<FnContract>>,
+    pub define_opaque: Option<ThinVec<(NodeId, Path)>>,
     pub body: Option<P<Block>>,
 }
 
@@ -3751,7 +3764,7 @@ mod size_asserts {
     static_assert_size!(Block, 32);
     static_assert_size!(Expr, 72);
     static_assert_size!(ExprKind, 40);
-    static_assert_size!(Fn, 168);
+    static_assert_size!(Fn, 176);
     static_assert_size!(ForeignItem, 88);
     static_assert_size!(ForeignItemKind, 16);
     static_assert_size!(GenericArg, 24);
diff --git a/compiler/rustc_ast/src/format.rs b/compiler/rustc_ast/src/format.rs
index b93846c1fe6..b611ddea1d9 100644
--- a/compiler/rustc_ast/src/format.rs
+++ b/compiler/rustc_ast/src/format.rs
@@ -266,7 +266,7 @@ pub enum FormatAlignment {
 #[derive(Clone, Encodable, Decodable, Debug, PartialEq, Eq)]
 pub enum FormatCount {
     /// `{:5}` or `{:.5}`
-    Literal(usize),
+    Literal(u16),
     /// `{:.*}`, `{:.5$}`, or `{:a$}`, etc.
     Argument(FormatArgPosition),
 }
diff --git a/compiler/rustc_ast/src/mut_visit.rs b/compiler/rustc_ast/src/mut_visit.rs
index f14646b5a99..fc31912283a 100644
--- a/compiler/rustc_ast/src/mut_visit.rs
+++ b/compiler/rustc_ast/src/mut_visit.rs
@@ -973,7 +973,14 @@ fn walk_fn<T: MutVisitor>(vis: &mut T, kind: FnKind<'_>) {
             _ctxt,
             _ident,
             _vis,
-            Fn { defaultness, generics, contract, body, sig: FnSig { header, decl, span } },
+            Fn {
+                defaultness,
+                generics,
+                contract,
+                body,
+                sig: FnSig { header, decl, span },
+                define_opaque,
+            },
         ) => {
             // Identifier and visibility are visited as a part of the item.
             visit_defaultness(vis, defaultness);
@@ -987,6 +994,11 @@ fn walk_fn<T: MutVisitor>(vis: &mut T, kind: FnKind<'_>) {
                 vis.visit_block(body);
             }
             vis.visit_span(span);
+
+            for (id, path) in define_opaque.iter_mut().flatten() {
+                vis.visit_id(id);
+                vis.visit_path(path)
+            }
         }
         FnKind::Closure(binder, coroutine_kind, decl, body) => {
             vis.visit_closure_binder(binder);
@@ -1745,6 +1757,10 @@ pub fn walk_expr<T: MutVisitor>(vis: &mut T, Expr { kind, id, span, attrs, token
             vis.visit_expr(expr);
             vis.visit_span(await_kw_span);
         }
+        ExprKind::Use(expr, use_kw_span) => {
+            vis.visit_expr(expr);
+            vis.visit_span(use_kw_span);
+        }
         ExprKind::Assign(el, er, span) => {
             vis.visit_expr(el);
             vis.visit_expr(er);
@@ -1895,6 +1911,9 @@ fn walk_capture_by<T: MutVisitor>(vis: &mut T, capture_by: &mut CaptureBy) {
         CaptureBy::Value { move_kw } => {
             vis.visit_span(move_kw);
         }
+        CaptureBy::Use { use_kw } => {
+            vis.visit_span(use_kw);
+        }
     }
 }
 
@@ -1929,7 +1948,7 @@ impl DummyAstNode for Item {
                 span: Default::default(),
                 tokens: Default::default(),
             },
-            ident: Ident::empty(),
+            ident: Ident::dummy(),
             kind: ItemKind::ExternCrate(None),
             tokens: Default::default(),
         }
diff --git a/compiler/rustc_ast/src/util/classify.rs b/compiler/rustc_ast/src/util/classify.rs
index 64f2a98b8a6..e43d78f6e72 100644
--- a/compiler/rustc_ast/src/util/classify.rs
+++ b/compiler/rustc_ast/src/util/classify.rs
@@ -108,6 +108,7 @@ pub fn leading_labeled_expr(mut expr: &ast::Expr) -> bool {
             Assign(e, _, _)
             | AssignOp(_, e, _)
             | Await(e, _)
+            | Use(e, _)
             | Binary(_, e, _)
             | Call(e, _)
             | Cast(e, _)
@@ -224,6 +225,7 @@ pub fn expr_trailing_brace(mut expr: &ast::Expr) -> Option<TrailingBrace<'_>> {
             | Lit(_)
             | Type(_, _)
             | Await(_, _)
+            | Use(_, _)
             | Field(_, _)
             | Index(_, _, _)
             | Underscore
diff --git a/compiler/rustc_ast/src/visit.rs b/compiler/rustc_ast/src/visit.rs
index 37139e664f3..cfcb0e23cb5 100644
--- a/compiler/rustc_ast/src/visit.rs
+++ b/compiler/rustc_ast/src/visit.rs
@@ -892,7 +892,14 @@ pub fn walk_fn<'a, V: Visitor<'a>>(visitor: &mut V, kind: FnKind<'a>) -> V::Resu
             _ctxt,
             _ident,
             _vis,
-            Fn { defaultness: _, sig: FnSig { header, decl, span: _ }, generics, contract, body },
+            Fn {
+                defaultness: _,
+                sig: FnSig { header, decl, span: _ },
+                generics,
+                contract,
+                body,
+                define_opaque,
+            },
         ) => {
             // Identifier and visibility are visited as a part of the item.
             try_visit!(visitor.visit_fn_header(header));
@@ -900,6 +907,9 @@ pub fn walk_fn<'a, V: Visitor<'a>>(visitor: &mut V, kind: FnKind<'a>) -> V::Resu
             try_visit!(visitor.visit_fn_decl(decl));
             visit_opt!(visitor, visit_contract, contract);
             visit_opt!(visitor, visit_block, body);
+            for (id, path) in define_opaque.iter().flatten() {
+                try_visit!(visitor.visit_path(path, *id))
+            }
         }
         FnKind::Closure(binder, coroutine_kind, decl, body) => {
             try_visit!(visitor.visit_closure_binder(binder));
@@ -1203,7 +1213,7 @@ pub fn walk_expr<'a, V: Visitor<'a>>(visitor: &mut V, expression: &'a Expr) -> V
                 FnKind::Closure(binder, coroutine_kind, fn_decl, body),
                 *span,
                 *id
-            ))
+            ));
         }
         ExprKind::Block(block, opt_label) => {
             visit_opt!(visitor, visit_label, opt_label);
@@ -1211,6 +1221,7 @@ pub fn walk_expr<'a, V: Visitor<'a>>(visitor: &mut V, expression: &'a Expr) -> V
         }
         ExprKind::Gen(_capt, body, _kind, _decl_span) => try_visit!(visitor.visit_block(body)),
         ExprKind::Await(expr, _span) => try_visit!(visitor.visit_expr(expr)),
+        ExprKind::Use(expr, _span) => try_visit!(visitor.visit_expr(expr)),
         ExprKind::Assign(lhs, rhs, _span) => {
             try_visit!(visitor.visit_expr(lhs));
             try_visit!(visitor.visit_expr(rhs));
diff --git a/compiler/rustc_ast_lowering/src/delegation.rs b/compiler/rustc_ast_lowering/src/delegation.rs
index d8b7cb0c322..571172be4ed 100644
--- a/compiler/rustc_ast_lowering/src/delegation.rs
+++ b/compiler/rustc_ast_lowering/src/delegation.rs
@@ -60,25 +60,27 @@ pub(crate) struct DelegationResults<'hir> {
 }
 
 impl<'hir> LoweringContext<'_, 'hir> {
-    pub(crate) fn delegation_has_self(&self, item_id: NodeId, path_id: NodeId, span: Span) -> bool {
+    /// Defines whether the delegatee is an associated function whose first parameter is `self`.
+    pub(crate) fn delegatee_is_method(&self, item_id: NodeId, path_id: NodeId, span: Span) -> bool {
         let sig_id = self.get_delegation_sig_id(item_id, path_id, span);
         let Ok(sig_id) = sig_id else {
             return false;
         };
-        self.has_self(sig_id, span)
+        self.is_method(sig_id, span)
     }
 
-    fn has_self(&self, def_id: DefId, span: Span) -> bool {
-        if let Some(local_sig_id) = def_id.as_local() {
-            // The value may be missing due to recursive delegation.
-            // Error will be emitted later during HIR ty lowering.
-            self.resolver.delegation_fn_sigs.get(&local_sig_id).is_some_and(|sig| sig.has_self)
-        } else {
-            match self.tcx.def_kind(def_id) {
-                DefKind::Fn => false,
-                DefKind::AssocFn => self.tcx.associated_item(def_id).fn_has_self_parameter,
-                _ => span_bug!(span, "unexpected DefKind for delegation item"),
-            }
+    fn is_method(&self, def_id: DefId, span: Span) -> bool {
+        match self.tcx.def_kind(def_id) {
+            DefKind::Fn => false,
+            DefKind::AssocFn => match def_id.as_local() {
+                Some(local_def_id) => self
+                    .resolver
+                    .delegation_fn_sigs
+                    .get(&local_def_id)
+                    .is_some_and(|sig| sig.has_self),
+                None => self.tcx.associated_item(def_id).fn_has_self_parameter,
+            },
+            _ => span_bug!(span, "unexpected DefKind for delegation item"),
         }
     }
 
@@ -324,7 +326,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
 
         let call = if self
             .get_resolution_id(delegation.id, span)
-            .and_then(|def_id| Ok(self.has_self(def_id, span)))
+            .and_then(|def_id| Ok(self.is_method(def_id, span)))
             .unwrap_or_default()
             && delegation.qself.is_none()
             && !has_generic_args
diff --git a/compiler/rustc_ast_lowering/src/expr.rs b/compiler/rustc_ast_lowering/src/expr.rs
index c70fcdc84a3..5bb6704dde4 100644
--- a/compiler/rustc_ast_lowering/src/expr.rs
+++ b/compiler/rustc_ast_lowering/src/expr.rs
@@ -13,7 +13,7 @@ use rustc_middle::span_bug;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::errors::report_lit_error;
 use rustc_span::source_map::{Spanned, respan};
-use rustc_span::{DUMMY_SP, DesugaringKind, Ident, Span, Symbol, kw, sym};
+use rustc_span::{DUMMY_SP, DesugaringKind, Ident, Span, Symbol, sym};
 use thin_vec::{ThinVec, thin_vec};
 use visit::{Visitor, walk_expr};
 
@@ -207,6 +207,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     },
                 ),
                 ExprKind::Await(expr, await_kw_span) => self.lower_expr_await(*await_kw_span, expr),
+                ExprKind::Use(expr, use_kw_span) => self.lower_expr_use(*use_kw_span, expr),
                 ExprKind::Closure(box Closure {
                     binder,
                     capture_clause,
@@ -483,7 +484,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
             if legacy_args_idx.contains(&idx) {
                 let parent_def_id = self.current_hir_id_owner.def_id;
                 let node_id = self.next_node_id();
-                self.create_def(parent_def_id, node_id, kw::Empty, DefKind::AnonConst, f.span);
+                self.create_def(parent_def_id, node_id, None, DefKind::AnonConst, f.span);
                 let mut visitor = WillCreateDefIdsVisitor {};
                 let const_value = if let ControlFlow::Break(span) = visitor.visit_expr(&arg) {
                     AstP(Expr {
@@ -1067,6 +1068,10 @@ impl<'hir> LoweringContext<'_, 'hir> {
         )
     }
 
+    fn lower_expr_use(&mut self, use_kw_span: Span, expr: &Expr) -> hir::ExprKind<'hir> {
+        hir::ExprKind::Use(self.lower_expr(expr), use_kw_span)
+    }
+
     fn lower_expr_closure(
         &mut self,
         binder: &ClosureBinder,
@@ -2125,26 +2130,24 @@ impl<'hir> LoweringContext<'_, 'hir> {
         self.arena.alloc(self.expr(sp, hir::ExprKind::Tup(&[])))
     }
 
-    pub(super) fn expr_usize(&mut self, sp: Span, value: usize) -> hir::Expr<'hir> {
+    fn expr_uint(&mut self, sp: Span, ty: ast::UintTy, value: u128) -> hir::Expr<'hir> {
         let lit = self.arena.alloc(hir::Lit {
             span: sp,
-            node: ast::LitKind::Int(
-                (value as u128).into(),
-                ast::LitIntType::Unsigned(ast::UintTy::Usize),
-            ),
+            node: ast::LitKind::Int(value.into(), ast::LitIntType::Unsigned(ty)),
         });
         self.expr(sp, hir::ExprKind::Lit(lit))
     }
 
+    pub(super) fn expr_usize(&mut self, sp: Span, value: usize) -> hir::Expr<'hir> {
+        self.expr_uint(sp, ast::UintTy::Usize, value as u128)
+    }
+
     pub(super) fn expr_u32(&mut self, sp: Span, value: u32) -> hir::Expr<'hir> {
-        let lit = self.arena.alloc(hir::Lit {
-            span: sp,
-            node: ast::LitKind::Int(
-                u128::from(value).into(),
-                ast::LitIntType::Unsigned(ast::UintTy::U32),
-            ),
-        });
-        self.expr(sp, hir::ExprKind::Lit(lit))
+        self.expr_uint(sp, ast::UintTy::U32, value as u128)
+    }
+
+    pub(super) fn expr_u16(&mut self, sp: Span, value: u16) -> hir::Expr<'hir> {
+        self.expr_uint(sp, ast::UintTy::U16, value as u128)
     }
 
     pub(super) fn expr_char(&mut self, sp: Span, value: char) -> hir::Expr<'hir> {
diff --git a/compiler/rustc_ast_lowering/src/format.rs b/compiler/rustc_ast_lowering/src/format.rs
index 07b94dbc2ae..faa47274f96 100644
--- a/compiler/rustc_ast_lowering/src/format.rs
+++ b/compiler/rustc_ast_lowering/src/format.rs
@@ -292,7 +292,7 @@ fn make_count<'hir>(
                 hir::LangItem::FormatCount,
                 sym::Is,
             ));
-            let value = ctx.arena.alloc_from_iter([ctx.expr_usize(sp, *n)]);
+            let value = ctx.arena.alloc_from_iter([ctx.expr_u16(sp, *n)]);
             ctx.expr_call_mut(sp, count_is, value)
         }
         Some(FormatCount::Argument(arg)) => {
diff --git a/compiler/rustc_ast_lowering/src/item.rs b/compiler/rustc_ast_lowering/src/item.rs
index 5e89321e6ec..9adc8bdd361 100644
--- a/compiler/rustc_ast_lowering/src/item.rs
+++ b/compiler/rustc_ast_lowering/src/item.rs
@@ -3,10 +3,9 @@ use rustc_ast::ptr::P;
 use rustc_ast::visit::AssocCtxt;
 use rustc_ast::*;
 use rustc_errors::ErrorGuaranteed;
-use rustc_hir as hir;
-use rustc_hir::PredicateOrigin;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::{CRATE_DEF_ID, LocalDefId};
+use rustc_hir::{self as hir, HirId, PredicateOrigin};
 use rustc_index::{IndexSlice, IndexVec};
 use rustc_middle::span_bug;
 use rustc_middle::ty::{ResolverAstLowering, TyCtxt};
@@ -209,6 +208,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 generics,
                 body,
                 contract,
+                define_opaque,
                 ..
             }) => {
                 self.with_new_scopes(*fn_sig_span, |this| {
@@ -237,6 +237,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                         header: this.lower_fn_header(*header, hir::Safety::Safe, attrs),
                         span: this.lower_span(*fn_sig_span),
                     };
+                    this.lower_define_opaque(hir_id, &define_opaque);
                     hir::ItemKind::Fn { sig, generics, body: body_id, has_body: body.is_some() }
                 })
             }
@@ -779,7 +780,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 );
                 (generics, kind, expr.is_some())
             }
-            AssocItemKind::Fn(box Fn { sig, generics, body: None, .. }) => {
+            AssocItemKind::Fn(box Fn { sig, generics, body: None, define_opaque, .. }) => {
                 // FIXME(contracts): Deny contract here since it won't apply to
                 // any impl method or callees.
                 let names = self.lower_fn_params_to_names(&sig.decl);
@@ -791,9 +792,22 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     sig.header.coroutine_kind,
                     attrs,
                 );
+                if define_opaque.is_some() {
+                    self.dcx().span_err(
+                        i.span,
+                        "only trait methods with default bodies can define opaque types",
+                    );
+                }
                 (generics, hir::TraitItemKind::Fn(sig, hir::TraitFn::Required(names)), false)
             }
-            AssocItemKind::Fn(box Fn { sig, generics, body: Some(body), contract, .. }) => {
+            AssocItemKind::Fn(box Fn {
+                sig,
+                generics,
+                body: Some(body),
+                contract,
+                define_opaque,
+                ..
+            }) => {
                 let body_id = self.lower_maybe_coroutine_body(
                     sig.span,
                     i.span,
@@ -812,6 +826,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     sig.header.coroutine_kind,
                     attrs,
                 );
+                self.lower_define_opaque(hir_id, &define_opaque);
                 (generics, hir::TraitItemKind::Fn(sig, hir::TraitFn::Provided(body_id)), true)
             }
             AssocItemKind::Type(box TyAlias { generics, where_clauses, bounds, ty, .. }) => {
@@ -871,7 +886,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 hir::AssocItemKind::Fn { has_self: sig.decl.has_self() }
             }
             AssocItemKind::Delegation(box delegation) => hir::AssocItemKind::Fn {
-                has_self: self.delegation_has_self(i.id, delegation.id, i.span),
+                has_self: self.delegatee_is_method(i.id, delegation.id, i.span),
             },
             AssocItemKind::MacCall(..) | AssocItemKind::DelegationMac(..) => {
                 panic!("macros should have been expanded by now")
@@ -911,7 +926,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     hir::ImplItemKind::Const(ty, body)
                 },
             ),
-            AssocItemKind::Fn(box Fn { sig, generics, body, contract, .. }) => {
+            AssocItemKind::Fn(box Fn { sig, generics, body, contract, define_opaque, .. }) => {
                 let body_id = self.lower_maybe_coroutine_body(
                     sig.span,
                     i.span,
@@ -930,6 +945,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     sig.header.coroutine_kind,
                     attrs,
                 );
+                self.lower_define_opaque(hir_id, &define_opaque);
 
                 (generics, hir::ImplItemKind::Fn(sig, body_id))
             }
@@ -1000,7 +1016,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     hir::AssocItemKind::Fn { has_self: sig.decl.has_self() }
                 }
                 AssocItemKind::Delegation(box delegation) => hir::AssocItemKind::Fn {
-                    has_self: self.delegation_has_self(i.id, delegation.id, i.span),
+                    has_self: self.delegatee_is_method(i.id, delegation.id, i.span),
                 },
                 AssocItemKind::MacCall(..) | AssocItemKind::DelegationMac(..) => {
                     panic!("macros should have been expanded by now")
@@ -1657,6 +1673,35 @@ impl<'hir> LoweringContext<'_, 'hir> {
         (lowered_generics, res)
     }
 
+    pub(super) fn lower_define_opaque(
+        &mut self,
+        hir_id: HirId,
+        define_opaque: &Option<ThinVec<(NodeId, Path)>>,
+    ) {
+        assert_eq!(self.define_opaque, None);
+        assert!(hir_id.is_owner());
+        let Some(define_opaque) = define_opaque.as_ref() else {
+            return;
+        };
+        let define_opaque = define_opaque.iter().filter_map(|(id, path)| {
+            let res = self.resolver.get_partial_res(*id).unwrap();
+            let Some(did) = res.expect_full_res().opt_def_id() else {
+                self.dcx().span_delayed_bug(path.span, "should have errored in resolve");
+                return None;
+            };
+            let Some(did) = did.as_local() else {
+                self.dcx().span_err(
+                    path.span,
+                    "only opaque types defined in the local crate can be defined",
+                );
+                return None;
+            };
+            Some((self.lower_span(path.span), did))
+        });
+        let define_opaque = self.arena.alloc_from_iter(define_opaque);
+        self.define_opaque = Some(define_opaque);
+    }
+
     pub(super) fn lower_generic_bound_predicate(
         &mut self,
         ident: Ident,
diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index f5832068028..1bf85bbf26c 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -35,6 +35,7 @@
 #![doc(rust_logo)]
 #![feature(assert_matches)]
 #![feature(box_patterns)]
+#![feature(exact_size_is_empty)]
 #![feature(if_let_guard)]
 #![feature(let_chains)]
 #![feature(rustdoc_internals)]
@@ -98,6 +99,8 @@ struct LoweringContext<'a, 'hir> {
 
     /// Bodies inside the owner being lowered.
     bodies: Vec<(hir::ItemLocalId, &'hir hir::Body<'hir>)>,
+    /// `#[define_opaque]` attributes
+    define_opaque: Option<&'hir [(Span, LocalDefId)]>,
     /// Attributes inside the owner being lowered.
     attrs: SortedMap<hir::ItemLocalId, &'hir [hir::Attribute]>,
     /// Collect items that were created by lowering the current owner.
@@ -155,6 +158,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
 
             // HirId handling.
             bodies: Vec::new(),
+            define_opaque: None,
             attrs: SortedMap::default(),
             children: Vec::default(),
             contract_ensures: None,
@@ -494,7 +498,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         &mut self,
         parent: LocalDefId,
         node_id: ast::NodeId,
-        name: Symbol,
+        name: Option<Symbol>,
         def_kind: DefKind,
         span: Span,
     ) -> LocalDefId {
@@ -547,6 +551,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
 
         let current_attrs = std::mem::take(&mut self.attrs);
         let current_bodies = std::mem::take(&mut self.bodies);
+        let current_define_opaque = std::mem::take(&mut self.define_opaque);
         let current_ident_and_label_to_local_id =
             std::mem::take(&mut self.ident_and_label_to_local_id);
 
@@ -580,6 +585,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
 
         self.attrs = current_attrs;
         self.bodies = current_bodies;
+        self.define_opaque = current_define_opaque;
         self.ident_and_label_to_local_id = current_ident_and_label_to_local_id;
 
         #[cfg(debug_assertions)]
@@ -599,6 +605,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     fn make_owner_info(&mut self, node: hir::OwnerNode<'hir>) -> &'hir hir::OwnerInfo<'hir> {
         let attrs = std::mem::take(&mut self.attrs);
         let mut bodies = std::mem::take(&mut self.bodies);
+        let define_opaque = std::mem::take(&mut self.define_opaque);
         let trait_map = std::mem::take(&mut self.trait_map);
 
         #[cfg(debug_assertions)]
@@ -618,7 +625,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         let num_nodes = self.item_local_id_counter.as_usize();
         let (nodes, parenting) = index::index_hir(self.tcx, node, &bodies, num_nodes);
         let nodes = hir::OwnerNodes { opt_hash_including_bodies, nodes, bodies };
-        let attrs = hir::AttributeMap { map: attrs, opt_hash: attrs_hash };
+        let attrs = hir::AttributeMap { map: attrs, opt_hash: attrs_hash, define_opaque };
 
         self.arena.alloc(hir::OwnerInfo { nodes, parenting, attrs, trait_map })
     }
@@ -774,7 +781,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                 let _def_id = self.create_def(
                     self.current_hir_id_owner.def_id,
                     param,
-                    kw::UnderscoreLifetime,
+                    Some(kw::UnderscoreLifetime),
                     DefKind::LifetimeParam,
                     ident.span,
                 );
@@ -2089,8 +2096,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             // We're lowering a const argument that was originally thought to be a type argument,
             // so the def collector didn't create the def ahead of time. That's why we have to do
             // it here.
-            let def_id =
-                self.create_def(parent_def_id, node_id, kw::Empty, DefKind::AnonConst, span);
+            let def_id = self.create_def(parent_def_id, node_id, None, DefKind::AnonConst, span);
             let hir_id = self.lower_node_id(node_id);
 
             let path_expr = Expr {
diff --git a/compiler/rustc_ast_lowering/src/pat.rs b/compiler/rustc_ast_lowering/src/pat.rs
index 728981dea5f..07cc64a1358 100644
--- a/compiler/rustc_ast_lowering/src/pat.rs
+++ b/compiler/rustc_ast_lowering/src/pat.rs
@@ -7,7 +7,7 @@ use rustc_hir::def::{DefKind, Res};
 use rustc_hir::{self as hir, LangItem};
 use rustc_middle::span_bug;
 use rustc_span::source_map::{Spanned, respan};
-use rustc_span::{DesugaringKind, Ident, Span, kw};
+use rustc_span::{DesugaringKind, Ident, Span};
 
 use super::errors::{
     ArbitraryExpressionInPattern, ExtraDoubleDot, MisplacedDoubleDot, SubTupleBinding,
@@ -523,7 +523,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         // We're generating a range end that didn't exist in the AST,
         // so the def collector didn't create the def ahead of time. That's why we have to do
         // it here.
-        let def_id = self.create_def(parent_def_id, node_id, kw::Empty, DefKind::AnonConst, span);
+        let def_id = self.create_def(parent_def_id, node_id, None, DefKind::AnonConst, span);
         let hir_id = self.lower_node_id(node_id);
 
         let unstable_span = self.mark_span_with_reason(
diff --git a/compiler/rustc_ast_passes/src/ast_validation.rs b/compiler/rustc_ast_passes/src/ast_validation.rs
index f9f4035cb22..232d60be4eb 100644
--- a/compiler/rustc_ast_passes/src/ast_validation.rs
+++ b/compiler/rustc_ast_passes/src/ast_validation.rs
@@ -917,7 +917,10 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                 walk_list!(self, visit_attribute, &item.attrs);
                 return; // Avoid visiting again.
             }
-            ItemKind::Fn(func @ box Fn { defaultness, generics: _, sig, contract: _, body }) => {
+            ItemKind::Fn(
+                func
+                @ box Fn { defaultness, generics: _, sig, contract: _, body, define_opaque: _ },
+            ) => {
                 self.check_defaultness(item.span, *defaultness);
 
                 let is_intrinsic =
diff --git a/compiler/rustc_ast_passes/src/feature_gate.rs b/compiler/rustc_ast_passes/src/feature_gate.rs
index de11fe770c5..31ff102c127 100644
--- a/compiler/rustc_ast_passes/src/feature_gate.rs
+++ b/compiler/rustc_ast_passes/src/feature_gate.rs
@@ -489,6 +489,7 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session, features: &Features) {
     gate_all!(dyn_star, "`dyn*` trait objects are experimental");
     gate_all!(const_closures, "const closures are experimental");
     gate_all!(builtin_syntax, "`builtin #` syntax is unstable");
+    gate_all!(ergonomic_clones, "ergonomic clones are experimental");
     gate_all!(explicit_tail_calls, "`become` expression is experimental");
     gate_all!(generic_const_items, "generic const items are experimental");
     gate_all!(guard_patterns, "guard patterns are experimental", "consider using match arm guards");
diff --git a/compiler/rustc_ast_pretty/src/pprust/state.rs b/compiler/rustc_ast_pretty/src/pprust/state.rs
index 01fc272a458..a8eaff7346b 100644
--- a/compiler/rustc_ast_pretty/src/pprust/state.rs
+++ b/compiler/rustc_ast_pretty/src/pprust/state.rs
@@ -24,7 +24,6 @@ use rustc_span::edition::Edition;
 use rustc_span::source_map::{SourceMap, Spanned};
 use rustc_span::symbol::IdentPrinter;
 use rustc_span::{BytePos, CharPos, DUMMY_SP, FileName, Ident, Pos, Span, Symbol, kw, sym};
-use thin_vec::ThinVec;
 
 use crate::pp::Breaks::{Consistent, Inconsistent};
 use crate::pp::{self, Breaks};
@@ -1978,15 +1977,7 @@ impl<'a> State<'a> {
     ) {
         self.ibox(INDENT_UNIT);
         self.print_formal_generic_params(generic_params);
-        let generics = ast::Generics {
-            params: ThinVec::new(),
-            where_clause: ast::WhereClause {
-                has_where_token: false,
-                predicates: ThinVec::new(),
-                span: DUMMY_SP,
-            },
-            span: DUMMY_SP,
-        };
+        let generics = ast::Generics::default();
         let header = ast::FnHeader { safety, ext, ..ast::FnHeader::default() };
         self.print_fn(decl, header, name, &generics);
         self.end();
diff --git a/compiler/rustc_ast_pretty/src/pprust/state/expr.rs b/compiler/rustc_ast_pretty/src/pprust/state/expr.rs
index 496323a35b8..e3c41f117ab 100644
--- a/compiler/rustc_ast_pretty/src/pprust/state/expr.rs
+++ b/compiler/rustc_ast_pretty/src/pprust/state/expr.rs
@@ -574,6 +574,14 @@ impl<'a> State<'a> {
                 );
                 self.word(".await");
             }
+            ast::ExprKind::Use(expr, _) => {
+                self.print_expr_cond_paren(
+                    expr,
+                    expr.precedence() < ExprPrecedence::Unambiguous,
+                    fixup,
+                );
+                self.word(".use");
+            }
             ast::ExprKind::Assign(lhs, rhs, _) => {
                 self.print_expr_cond_paren(
                     lhs,
@@ -885,6 +893,7 @@ impl<'a> State<'a> {
     fn print_capture_clause(&mut self, capture_clause: ast::CaptureBy) {
         match capture_clause {
             ast::CaptureBy::Value { .. } => self.word_space("move"),
+            ast::CaptureBy::Use { .. } => self.word_space("use"),
             ast::CaptureBy::Ref => {}
         }
     }
diff --git a/compiler/rustc_ast_pretty/src/pprust/state/item.rs b/compiler/rustc_ast_pretty/src/pprust/state/item.rs
index ced0cbd2fef..6236f8ecfb5 100644
--- a/compiler/rustc_ast_pretty/src/pprust/state/item.rs
+++ b/compiler/rustc_ast_pretty/src/pprust/state/item.rs
@@ -650,7 +650,16 @@ impl<'a> State<'a> {
         attrs: &[ast::Attribute],
         func: &ast::Fn,
     ) {
-        let ast::Fn { defaultness, generics, sig, contract, body } = func;
+        let ast::Fn { defaultness, generics, sig, contract, body, define_opaque } = func;
+
+        if let Some(define_opaque) = define_opaque {
+            for (_, path) in define_opaque {
+                self.word("define opaques from ");
+                self.print_path(path, false, 0);
+                self.word(",");
+            }
+        }
+
         if body.is_some() {
             self.head("");
         }
@@ -698,7 +707,7 @@ impl<'a> State<'a> {
         }
         self.print_generic_params(&generics.params);
         self.print_fn_params_and_ret(decl, false);
-        self.print_where_clause(&generics.where_clause)
+        self.print_where_clause(&generics.where_clause);
     }
 
     pub(crate) fn print_fn_params_and_ret(&mut self, decl: &ast::FnDecl, is_closure: bool) {
diff --git a/compiler/rustc_attr_data_structures/src/lib.rs b/compiler/rustc_attr_data_structures/src/lib.rs
index e4bb459e6df..389d8c2413b 100644
--- a/compiler/rustc_attr_data_structures/src/lib.rs
+++ b/compiler/rustc_attr_data_structures/src/lib.rs
@@ -35,13 +35,17 @@ pub trait HashStableContext: rustc_ast::HashStableContext + rustc_abi::HashStabl
 /// like [`Span`]s and empty tuples, are gracefully skipped so they don't clutter the
 /// representation much.
 pub trait PrintAttribute {
-    fn print_something(&self) -> bool;
+    /// Whether or not this will render as something meaningful, or if it's skipped
+    /// (which will force the containing struct to also skip printing a comma
+    /// and the field name).
+    fn should_render(&self) -> bool;
+
     fn print_attribute(&self, p: &mut Printer);
 }
 
 impl<T: PrintAttribute> PrintAttribute for &T {
-    fn print_something(&self) -> bool {
-        T::print_something(self)
+    fn should_render(&self) -> bool {
+        T::should_render(self)
     }
 
     fn print_attribute(&self, p: &mut Printer) {
@@ -49,9 +53,10 @@ impl<T: PrintAttribute> PrintAttribute for &T {
     }
 }
 impl<T: PrintAttribute> PrintAttribute for Option<T> {
-    fn print_something(&self) -> bool {
-        self.as_ref().is_some_and(|x| x.print_something())
+    fn should_render(&self) -> bool {
+        self.as_ref().is_some_and(|x| x.should_render())
     }
+
     fn print_attribute(&self, p: &mut Printer) {
         if let Some(i) = self {
             T::print_attribute(i, p)
@@ -59,9 +64,10 @@ impl<T: PrintAttribute> PrintAttribute for Option<T> {
     }
 }
 impl<T: PrintAttribute> PrintAttribute for ThinVec<T> {
-    fn print_something(&self) -> bool {
-        self.is_empty() || self[0].print_something()
+    fn should_render(&self) -> bool {
+        self.is_empty() || self[0].should_render()
     }
+
     fn print_attribute(&self, p: &mut Printer) {
         let mut last_printed = false;
         p.word("[");
@@ -70,7 +76,7 @@ impl<T: PrintAttribute> PrintAttribute for ThinVec<T> {
                 p.word_space(",");
             }
             i.print_attribute(p);
-            last_printed = i.print_something();
+            last_printed = i.should_render();
         }
         p.word("]");
     }
@@ -78,7 +84,7 @@ impl<T: PrintAttribute> PrintAttribute for ThinVec<T> {
 macro_rules! print_skip {
     ($($t: ty),* $(,)?) => {$(
         impl PrintAttribute for $t {
-            fn print_something(&self) -> bool { false }
+            fn should_render(&self) -> bool { false }
             fn print_attribute(&self, _: &mut Printer) { }
         })*
     };
@@ -87,7 +93,7 @@ macro_rules! print_skip {
 macro_rules! print_disp {
     ($($t: ty),* $(,)?) => {$(
         impl PrintAttribute for $t {
-            fn print_something(&self) -> bool { true }
+            fn should_render(&self) -> bool { true }
             fn print_attribute(&self, p: &mut Printer) {
                 p.word(format!("{}", self));
             }
@@ -97,7 +103,7 @@ macro_rules! print_disp {
 macro_rules! print_debug {
     ($($t: ty),* $(,)?) => {$(
         impl PrintAttribute for $t {
-            fn print_something(&self) -> bool { true }
+            fn should_render(&self) -> bool { true }
             fn print_attribute(&self, p: &mut Printer) {
                 p.word(format!("{:?}", self));
             }
@@ -106,37 +112,39 @@ macro_rules! print_debug {
 }
 
 macro_rules! print_tup {
-    (num_print_something $($ts: ident)*) => { 0 $(+ $ts.print_something() as usize)* };
+    (num_should_render $($ts: ident)*) => { 0 $(+ $ts.should_render() as usize)* };
     () => {};
     ($t: ident $($ts: ident)*) => {
         #[allow(non_snake_case, unused)]
         impl<$t: PrintAttribute, $($ts: PrintAttribute),*> PrintAttribute for ($t, $($ts),*) {
-            fn print_something(&self) -> bool {
+            fn should_render(&self) -> bool {
                 let ($t, $($ts),*) = self;
-                print_tup!(num_print_something $t $($ts)*) != 0
+                print_tup!(num_should_render $t $($ts)*) != 0
             }
 
             fn print_attribute(&self, p: &mut Printer) {
                 let ($t, $($ts),*) = self;
-                let parens = print_tup!(num_print_something $t $($ts)*) > 1;
+                let parens = print_tup!(num_should_render $t $($ts)*) > 1;
                 if parens {
-                    p.word("(");
+                    p.popen();
                 }
 
-                let mut printed_anything = $t.print_something();
+                let mut printed_anything = $t.should_render();
 
                 $t.print_attribute(p);
 
                 $(
-                    if printed_anything && $ts.print_something() {
-                        p.word_space(",");
+                    if $ts.should_render() {
+                        if printed_anything {
+                            p.word_space(",");
+                        }
                         printed_anything = true;
                     }
                     $ts.print_attribute(p);
                 )*
 
                 if parens {
-                    p.word(")");
+                    p.pclose();
                 }
             }
         }
@@ -147,5 +155,49 @@ macro_rules! print_tup {
 
 print_tup!(A B C D E F G H);
 print_skip!(Span, ());
-print_disp!(Symbol, u16, bool, NonZero<u32>);
-print_debug!(UintTy, IntTy, Align, AttrStyle, CommentKind, Transparency);
+print_disp!(u16, bool, NonZero<u32>);
+print_debug!(Symbol, UintTy, IntTy, Align, AttrStyle, CommentKind, Transparency);
+
+/// Finds attributes in sequences of attributes by pattern matching.
+///
+/// A little like `matches` but for attributes.
+///
+/// ```rust,ignore (illustrative)
+/// // finds the repr attribute
+/// if let Some(r) = find_attr!(attrs, AttributeKind::Repr(r) => r) {
+///
+/// }
+///
+/// // checks if one has matched
+/// if find_attr!(attrs, AttributeKind::Repr(_)) {
+///
+/// }
+/// ```
+///
+/// Often this requires you to first end up with a list of attributes.
+/// A common way to get those is through `tcx.get_all_attrs(did)`
+#[macro_export]
+macro_rules! find_attr {
+    ($attributes_list: expr, $pattern: pat $(if $guard: expr)?) => {{
+        $crate::find_attr!($attributes_list, $pattern $(if $guard)? => ()).is_some()
+    }};
+
+    ($attributes_list: expr, $pattern: pat $(if $guard: expr)? => $e: expr) => {{
+        fn check_attribute_iterator<'a>(_: &'_ impl IntoIterator<Item = &'a rustc_hir::Attribute>) {}
+        check_attribute_iterator(&$attributes_list);
+
+        let find_attribute = |iter| {
+            for i in $attributes_list {
+                match i {
+                    rustc_hir::Attribute::Parsed($pattern) $(if $guard)? => {
+                        return Some($e);
+                    }
+                    _ => {}
+                }
+            }
+
+            None
+        };
+        find_attribute($attributes_list)
+    }};
+}
diff --git a/compiler/rustc_attr_parsing/Cargo.toml b/compiler/rustc_attr_parsing/Cargo.toml
index c335eeb5f71..6b4ce957630 100644
--- a/compiler/rustc_attr_parsing/Cargo.toml
+++ b/compiler/rustc_attr_parsing/Cargo.toml
@@ -16,6 +16,7 @@ rustc_fluent_macro = { path = "../rustc_fluent_macro" }
 rustc_hir = { path = "../rustc_hir" }
 rustc_lexer = { path = "../rustc_lexer" }
 rustc_macros = { path = "../rustc_macros" }
+rustc_middle = { path = "../rustc_middle" }
 rustc_serialize = { path = "../rustc_serialize" }
 rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
diff --git a/compiler/rustc_attr_parsing/src/context.rs b/compiler/rustc_attr_parsing/src/context.rs
index 0e6b0bab082..35541bb04bd 100644
--- a/compiler/rustc_attr_parsing/src/context.rs
+++ b/compiler/rustc_attr_parsing/src/context.rs
@@ -9,7 +9,6 @@ use rustc_errors::{DiagCtxtHandle, Diagnostic};
 use rustc_feature::Features;
 use rustc_hir::{AttrArgs, AttrItem, AttrPath, Attribute, HashIgnoredAttrId};
 use rustc_session::Session;
-use rustc_span::symbol::kw;
 use rustc_span::{DUMMY_SP, ErrorGuaranteed, Span, Symbol, sym};
 
 use crate::attributes::allow_unstable::{AllowConstFnUnstableParser, AllowInternalUnstableParser};
@@ -338,7 +337,7 @@ impl<'sess> AttributeParser<'sess> {
                         "expr in place where literal is expected (builtin attr parsing)",
                     );
                     ast::MetaItemLit {
-                        symbol: kw::Empty,
+                        symbol: sym::dummy,
                         suffix: None,
                         kind: ast::LitKind::Err(guar),
                         span: DUMMY_SP,
diff --git a/compiler/rustc_attr_parsing/src/lib.rs b/compiler/rustc_attr_parsing/src/lib.rs
index 9841166b37d..386f2c98447 100644
--- a/compiler/rustc_attr_parsing/src/lib.rs
+++ b/compiler/rustc_attr_parsing/src/lib.rs
@@ -95,47 +95,3 @@ pub use context::{AttributeParser, OmitDoc};
 pub use rustc_attr_data_structures::*;
 
 rustc_fluent_macro::fluent_messages! { "../messages.ftl" }
-
-/// Finds attributes in sequences of attributes by pattern matching.
-///
-/// A little like `matches` but for attributes.
-///
-/// ```rust,ignore (illustrative)
-/// // finds the repr attribute
-/// if let Some(r) = find_attr!(attrs, AttributeKind::Repr(r) => r) {
-///
-/// }
-///
-/// // checks if one has matched
-/// if find_attr!(attrs, AttributeKind::Repr(_)) {
-///
-/// }
-/// ```
-///
-/// Often this requires you to first end up with a list of attributes.
-/// A common way to get those is through `tcx.get_all_attrs(did)`
-#[macro_export]
-macro_rules! find_attr {
-    ($attributes_list: expr, $pattern: pat $(if $guard: expr)?) => {{
-        $crate::find_attr!($attributes_list, $pattern $(if $guard)? => ()).is_some()
-    }};
-
-    ($attributes_list: expr, $pattern: pat $(if $guard: expr)? => $e: expr) => {{
-        fn check_attribute_iterator<'a>(_: &'_ impl IntoIterator<Item = &'a rustc_hir::Attribute>) {}
-        check_attribute_iterator(&$attributes_list);
-
-        let find_attribute = |iter| {
-            for i in $attributes_list {
-                match i {
-                    rustc_hir::Attribute::Parsed($pattern) $(if $guard)? => {
-                        return Some($e);
-                    }
-                    _ => {}
-                }
-            }
-
-            None
-        };
-        find_attribute($attributes_list)
-    }};
-}
diff --git a/compiler/rustc_attr_parsing/src/parser.rs b/compiler/rustc_attr_parsing/src/parser.rs
index f0cce26f4e2..a8a1460591c 100644
--- a/compiler/rustc_attr_parsing/src/parser.rs
+++ b/compiler/rustc_attr_parsing/src/parser.rs
@@ -12,7 +12,7 @@ use rustc_ast::{AttrArgs, DelimArgs, Expr, ExprKind, LitKind, MetaItemLit, Norma
 use rustc_ast_pretty::pprust;
 use rustc_errors::DiagCtxtHandle;
 use rustc_hir::{self as hir, AttrPath};
-use rustc_span::symbol::{Ident, kw};
+use rustc_span::symbol::{Ident, kw, sym};
 use rustc_span::{ErrorGuaranteed, Span, Symbol};
 
 pub struct SegmentIterator<'a> {
@@ -360,7 +360,7 @@ fn expr_to_lit(dcx: DiagCtxtHandle<'_>, expr: &Expr, span: Span) -> MetaItemLit
             span,
             "expr in place where literal is expected (builtin attr parsing)",
         );
-        MetaItemLit { symbol: kw::Empty, suffix: None, kind: LitKind::Err(guar), span }
+        MetaItemLit { symbol: sym::dummy, suffix: None, kind: LitKind::Err(guar), span }
     }
 }
 
diff --git a/compiler/rustc_borrowck/src/borrowck_errors.rs b/compiler/rustc_borrowck/src/borrowck_errors.rs
index 30e94b0bec7..c9be5575da5 100644
--- a/compiler/rustc_borrowck/src/borrowck_errors.rs
+++ b/compiler/rustc_borrowck/src/borrowck_errors.rs
@@ -403,6 +403,7 @@ impl<'infcx, 'tcx> crate::MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                 .expect_closure();
             let span = match capture_clause {
                 rustc_hir::CaptureBy::Value { move_kw } => move_kw.shrink_to_lo(),
+                rustc_hir::CaptureBy::Use { use_kw } => use_kw.shrink_to_lo(),
                 rustc_hir::CaptureBy::Ref => fn_decl_span.shrink_to_lo(),
             };
             diag.span_suggestion_verbose(
diff --git a/compiler/rustc_borrowck/src/constraints/graph.rs b/compiler/rustc_borrowck/src/constraints/graph.rs
index 9d500586f08..1209d8bf596 100644
--- a/compiler/rustc_borrowck/src/constraints/graph.rs
+++ b/compiler/rustc_borrowck/src/constraints/graph.rs
@@ -1,11 +1,8 @@
 use rustc_data_structures::graph;
 use rustc_index::IndexVec;
-use rustc_middle::mir::ConstraintCategory;
-use rustc_middle::ty::{RegionVid, VarianceDiagInfo};
-use rustc_span::DUMMY_SP;
+use rustc_middle::ty::RegionVid;
 
 use crate::constraints::{OutlivesConstraint, OutlivesConstraintIndex, OutlivesConstraintSet};
-use crate::type_check::Locations;
 
 /// The construct graph organizes the constraints by their end-points.
 /// It can be used to view a `R1: R2` constraint as either an edge `R1
@@ -23,8 +20,8 @@ pub(crate) type ReverseConstraintGraph = ConstraintGraph<Reverse>;
 /// Marker trait that controls whether a `R1: R2` constraint
 /// represents an edge `R1 -> R2` or `R2 -> R1`.
 pub(crate) trait ConstraintGraphDirection: Copy + 'static {
-    fn start_region(c: &OutlivesConstraint<'_>) -> RegionVid;
-    fn end_region(c: &OutlivesConstraint<'_>) -> RegionVid;
+    fn start_region(sup: RegionVid, sub: RegionVid) -> RegionVid;
+    fn end_region(sup: RegionVid, sub: RegionVid) -> RegionVid;
     fn is_normal() -> bool;
 }
 
@@ -36,12 +33,12 @@ pub(crate) trait ConstraintGraphDirection: Copy + 'static {
 pub(crate) struct Normal;
 
 impl ConstraintGraphDirection for Normal {
-    fn start_region(c: &OutlivesConstraint<'_>) -> RegionVid {
-        c.sup
+    fn start_region(sup: RegionVid, _sub: RegionVid) -> RegionVid {
+        sup
     }
 
-    fn end_region(c: &OutlivesConstraint<'_>) -> RegionVid {
-        c.sub
+    fn end_region(_sup: RegionVid, sub: RegionVid) -> RegionVid {
+        sub
     }
 
     fn is_normal() -> bool {
@@ -57,12 +54,12 @@ impl ConstraintGraphDirection for Normal {
 pub(crate) struct Reverse;
 
 impl ConstraintGraphDirection for Reverse {
-    fn start_region(c: &OutlivesConstraint<'_>) -> RegionVid {
-        c.sub
+    fn start_region(_sup: RegionVid, sub: RegionVid) -> RegionVid {
+        sub
     }
 
-    fn end_region(c: &OutlivesConstraint<'_>) -> RegionVid {
-        c.sup
+    fn end_region(sup: RegionVid, _sub: RegionVid) -> RegionVid {
+        sup
     }
 
     fn is_normal() -> bool {
@@ -84,7 +81,7 @@ impl<D: ConstraintGraphDirection> ConstraintGraph<D> {
         let mut next_constraints = IndexVec::from_elem(None, &set.outlives);
 
         for (idx, constraint) in set.outlives.iter_enumerated().rev() {
-            let head = &mut first_constraints[D::start_region(constraint)];
+            let head = &mut first_constraints[D::start_region(constraint.sup, constraint.sub)];
             let next = &mut next_constraints[idx];
             debug_assert!(next.is_none());
             *next = *head;
@@ -105,63 +102,57 @@ impl<D: ConstraintGraphDirection> ConstraintGraph<D> {
         RegionGraph::new(set, self, static_region)
     }
 
+    pub(crate) fn is_normal(&self) -> bool {
+        D::is_normal()
+    }
+
     /// Given a region `R`, iterate over all constraints `R: R1`.
-    pub(crate) fn outgoing_edges<'a, 'tcx>(
+    pub(crate) fn outgoing_edges_from_graph<'a, 'tcx>(
         &'a self,
         region_sup: RegionVid,
         constraints: &'a OutlivesConstraintSet<'tcx>,
-        static_region: RegionVid,
-    ) -> Edges<'a, 'tcx, D> {
-        //if this is the `'static` region and the graph's direction is normal,
-        //then setup the Edges iterator to return all regions #53178
-        if region_sup == static_region && D::is_normal() {
-            Edges {
-                graph: self,
-                constraints,
-                pointer: None,
-                next_static_idx: Some(0),
-                static_region,
-            }
-        } else {
-            //otherwise, just setup the iterator as normal
-            let first = self.first_constraints[region_sup];
-            Edges { graph: self, constraints, pointer: first, next_static_idx: None, static_region }
-        }
+    ) -> EdgesFromGraph<'a, 'tcx, D> {
+        EdgesFromGraph { graph: self, constraints, pointer: self.first_constraints[region_sup] }
+    }
+
+    /// Returns all regions (#53178).
+    pub(crate) fn outgoing_edges_from_static(&self) -> EdgesFromStatic {
+        EdgesFromStatic { next_static_idx: 0, end_static_idx: self.first_constraints.len() }
     }
 }
 
-pub(crate) struct Edges<'a, 'tcx, D: ConstraintGraphDirection> {
+pub(crate) struct EdgesFromGraph<'a, 'tcx, D: ConstraintGraphDirection> {
     graph: &'a ConstraintGraph<D>,
     constraints: &'a OutlivesConstraintSet<'tcx>,
     pointer: Option<OutlivesConstraintIndex>,
-    next_static_idx: Option<usize>,
-    static_region: RegionVid,
 }
 
-impl<'a, 'tcx, D: ConstraintGraphDirection> Iterator for Edges<'a, 'tcx, D> {
-    type Item = OutlivesConstraint<'tcx>;
+impl<'a, 'tcx, D: ConstraintGraphDirection> Iterator for EdgesFromGraph<'a, 'tcx, D> {
+    type Item = &'a OutlivesConstraint<'tcx>;
 
     fn next(&mut self) -> Option<Self::Item> {
         if let Some(p) = self.pointer {
             self.pointer = self.graph.next_constraints[p];
+            Some(&self.constraints[p])
+        } else {
+            None
+        }
+    }
+}
+
+pub(crate) struct EdgesFromStatic {
+    next_static_idx: usize,
+    end_static_idx: usize,
+}
+
+impl Iterator for EdgesFromStatic {
+    type Item = RegionVid;
 
-            Some(self.constraints[p])
-        } else if let Some(next_static_idx) = self.next_static_idx {
-            self.next_static_idx = if next_static_idx == (self.graph.first_constraints.len() - 1) {
-                None
-            } else {
-                Some(next_static_idx + 1)
-            };
-
-            Some(OutlivesConstraint {
-                sup: self.static_region,
-                sub: next_static_idx.into(),
-                locations: Locations::All(DUMMY_SP),
-                span: DUMMY_SP,
-                category: ConstraintCategory::Internal,
-                variance_info: VarianceDiagInfo::default(),
-                from_closure: false,
-            })
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.next_static_idx < self.end_static_idx {
+            let ret = RegionVid::from_usize(self.next_static_idx);
+            self.next_static_idx += 1;
+            Some(ret)
         } else {
             None
         }
@@ -193,21 +184,38 @@ impl<'a, 'tcx, D: ConstraintGraphDirection> RegionGraph<'a, 'tcx, D> {
     /// Given a region `R`, iterate over all regions `R1` such that
     /// there exists a constraint `R: R1`.
     pub(crate) fn outgoing_regions(&self, region_sup: RegionVid) -> Successors<'a, 'tcx, D> {
-        Successors {
-            edges: self.constraint_graph.outgoing_edges(region_sup, self.set, self.static_region),
+        // If this is the `'static` region and the graph's direction is normal,
+        // then setup the Edges iterator to return all regions (#53178).
+        if region_sup == self.static_region && D::is_normal() {
+            Successors::FromStatic(self.constraint_graph.outgoing_edges_from_static())
+        } else {
+            // Otherwise, just setup the iterator as normal.
+            Successors::FromGraph(
+                self.constraint_graph.outgoing_edges_from_graph(region_sup, self.set),
+            )
         }
     }
 }
 
-pub(crate) struct Successors<'a, 'tcx, D: ConstraintGraphDirection> {
-    edges: Edges<'a, 'tcx, D>,
+pub(crate) enum Successors<'a, 'tcx, D: ConstraintGraphDirection> {
+    FromStatic(EdgesFromStatic),
+    FromGraph(EdgesFromGraph<'a, 'tcx, D>),
 }
 
 impl<'a, 'tcx, D: ConstraintGraphDirection> Iterator for Successors<'a, 'tcx, D> {
     type Item = RegionVid;
 
     fn next(&mut self) -> Option<Self::Item> {
-        self.edges.next().map(|c| D::end_region(&c))
+        match self {
+            Successors::FromStatic(edges) => {
+                // No `D::end_region` call needed here: static successors are only possible when
+                // the direction is `Normal`, so we can directly use what would be the `sub` value.
+                edges.next()
+            }
+            Successors::FromGraph(edges) => {
+                edges.next().map(|constraint| D::end_region(constraint.sup, constraint.sub))
+            }
+        }
     }
 }
 
diff --git a/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs b/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
index be4a7736b1c..145137f9236 100644
--- a/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
@@ -823,7 +823,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                             ) => {
                                 capture_reason = format!("mutable borrow of `{upvar}`");
                             }
-                            ty::UpvarCapture::ByValue => {
+                            ty::UpvarCapture::ByValue | ty::UpvarCapture::ByUse => {
                                 capture_reason = format!("possible mutation of `{upvar}`");
                             }
                             _ => bug!("upvar `{upvar}` borrowed, but not mutably"),
diff --git a/compiler/rustc_borrowck/src/lib.rs b/compiler/rustc_borrowck/src/lib.rs
index 68e0ab0933e..64a533e05ff 100644
--- a/compiler/rustc_borrowck/src/lib.rs
+++ b/compiler/rustc_borrowck/src/lib.rs
@@ -1490,14 +1490,20 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, '_, 'tcx> {
                         let stmt = &bbd.statements[loc.statement_index];
                         debug!("temporary assigned in: stmt={:?}", stmt);
 
-                        if let StatementKind::Assign(box (_, Rvalue::Ref(_, _, source))) = stmt.kind
-                        {
-                            propagate_closure_used_mut_place(self, source);
-                        } else {
-                            bug!(
-                                "closures should only capture user variables \
+                        match stmt.kind {
+                            StatementKind::Assign(box (
+                                _,
+                                Rvalue::Ref(_, _, source)
+                                | Rvalue::Use(Operand::Copy(source) | Operand::Move(source)),
+                            )) => {
+                                propagate_closure_used_mut_place(self, source);
+                            }
+                            _ => {
+                                bug!(
+                                    "closures should only capture user variables \
                                  or references to user variables"
-                            );
+                                );
+                            }
                         }
                     }
                     _ => propagate_closure_used_mut_place(self, place),
diff --git a/compiler/rustc_borrowck/src/region_infer/mod.rs b/compiler/rustc_borrowck/src/region_infer/mod.rs
index a00fce08c9b..bb209a95711 100644
--- a/compiler/rustc_borrowck/src/region_infer/mod.rs
+++ b/compiler/rustc_borrowck/src/region_infer/mod.rs
@@ -21,8 +21,8 @@ use rustc_middle::traits::{ObligationCause, ObligationCauseCode};
 use rustc_middle::ty::fold::fold_regions;
 use rustc_middle::ty::{self, RegionVid, Ty, TyCtxt, TypeFoldable, UniverseIndex};
 use rustc_mir_dataflow::points::DenseLocationMap;
-use rustc_span::Span;
 use rustc_span::hygiene::DesugaringKind;
+use rustc_span::{DUMMY_SP, Span};
 use tracing::{debug, instrument, trace};
 
 use crate::BorrowckInferCtxt;
@@ -311,9 +311,11 @@ enum RegionRelationCheckResult {
 }
 
 #[derive(Clone, PartialEq, Eq, Debug)]
-enum Trace<'tcx> {
+enum Trace<'a, 'tcx> {
     StartRegion,
-    FromOutlivesConstraint(OutlivesConstraint<'tcx>),
+    FromGraph(&'a OutlivesConstraint<'tcx>),
+    FromStatic(RegionVid),
+    FromMember(RegionVid, RegionVid, Span),
     NotVisited,
 }
 
@@ -1764,6 +1766,8 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         let mut context = IndexVec::from_elem(Trace::NotVisited, &self.definitions);
         context[from_region] = Trace::StartRegion;
 
+        let fr_static = self.universal_regions().fr_static;
+
         // Use a deque so that we do a breadth-first search. We will
         // stop at the first match, which ought to be the shortest
         // path (fewest constraints).
@@ -1783,13 +1787,39 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             if target_test(r) {
                 let mut result = vec![];
                 let mut p = r;
+                // This loop is cold and runs at the end, which is why we delay
+                // `OutlivesConstraint` construction until now.
                 loop {
-                    match context[p].clone() {
-                        Trace::NotVisited => {
-                            bug!("found unvisited region {:?} on path to {:?}", p, r)
+                    match context[p] {
+                        Trace::FromGraph(c) => {
+                            p = c.sup;
+                            result.push(*c);
                         }
 
-                        Trace::FromOutlivesConstraint(c) => {
+                        Trace::FromStatic(sub) => {
+                            let c = OutlivesConstraint {
+                                sup: fr_static,
+                                sub,
+                                locations: Locations::All(DUMMY_SP),
+                                span: DUMMY_SP,
+                                category: ConstraintCategory::Internal,
+                                variance_info: ty::VarianceDiagInfo::default(),
+                                from_closure: false,
+                            };
+                            p = c.sup;
+                            result.push(c);
+                        }
+
+                        Trace::FromMember(sup, sub, span) => {
+                            let c = OutlivesConstraint {
+                                sup,
+                                sub,
+                                locations: Locations::All(span),
+                                span,
+                                category: ConstraintCategory::OpaqueType,
+                                variance_info: ty::VarianceDiagInfo::default(),
+                                from_closure: false,
+                            };
                             p = c.sup;
                             result.push(c);
                         }
@@ -1798,6 +1828,10 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                             result.reverse();
                             return Some((result, r));
                         }
+
+                        Trace::NotVisited => {
+                            bug!("found unvisited region {:?} on path to {:?}", p, r)
+                        }
                     }
                 }
             }
@@ -1808,45 +1842,42 @@ impl<'tcx> RegionInferenceContext<'tcx> {
 
             // A constraint like `'r: 'x` can come from our constraint
             // graph.
-            let fr_static = self.universal_regions().fr_static;
-            let outgoing_edges_from_graph =
-                self.constraint_graph.outgoing_edges(r, &self.constraints, fr_static);
 
             // Always inline this closure because it can be hot.
-            let mut handle_constraint = #[inline(always)]
-            |constraint: OutlivesConstraint<'tcx>| {
-                debug_assert_eq!(constraint.sup, r);
-                let sub_region = constraint.sub;
-                if let Trace::NotVisited = context[sub_region] {
-                    context[sub_region] = Trace::FromOutlivesConstraint(constraint);
-                    deque.push_back(sub_region);
+            let mut handle_trace = #[inline(always)]
+            |sub, trace| {
+                if let Trace::NotVisited = context[sub] {
+                    context[sub] = trace;
+                    deque.push_back(sub);
                 }
             };
 
-            // This loop can be hot.
-            for constraint in outgoing_edges_from_graph {
-                if matches!(constraint.category, ConstraintCategory::IllegalUniverse) {
-                    debug!("Ignoring illegal universe constraint: {constraint:?}");
-                    continue;
+            // If this is the `'static` region and the graph's direction is normal, then set up the
+            // Edges iterator to return all regions (#53178).
+            if r == fr_static && self.constraint_graph.is_normal() {
+                for sub in self.constraint_graph.outgoing_edges_from_static() {
+                    handle_trace(sub, Trace::FromStatic(sub));
+                }
+            } else {
+                let edges = self.constraint_graph.outgoing_edges_from_graph(r, &self.constraints);
+                // This loop can be hot.
+                for constraint in edges {
+                    if matches!(constraint.category, ConstraintCategory::IllegalUniverse) {
+                        debug!("Ignoring illegal universe constraint: {constraint:?}");
+                        continue;
+                    }
+                    debug_assert_eq!(constraint.sup, r);
+                    handle_trace(constraint.sub, Trace::FromGraph(constraint));
                 }
-                handle_constraint(constraint);
             }
 
             // Member constraints can also give rise to `'r: 'x` edges that
             // were not part of the graph initially, so watch out for those.
             // (But they are extremely rare; this loop is very cold.)
             for constraint in self.applied_member_constraints(self.constraint_sccs.scc(r)) {
+                let sub = constraint.min_choice;
                 let p_c = &self.member_constraints[constraint.member_constraint_index];
-                let constraint = OutlivesConstraint {
-                    sup: r,
-                    sub: constraint.min_choice,
-                    locations: Locations::All(p_c.definition_span),
-                    span: p_c.definition_span,
-                    category: ConstraintCategory::OpaqueType,
-                    variance_info: ty::VarianceDiagInfo::default(),
-                    from_closure: false,
-                };
-                handle_constraint(constraint);
+                handle_trace(sub, Trace::FromMember(r, sub, p_c.definition_span));
             }
         }
 
diff --git a/compiler/rustc_borrowck/src/type_check/input_output.rs b/compiler/rustc_borrowck/src/type_check/input_output.rs
index f70b17e3362..c6b29fe36fd 100644
--- a/compiler/rustc_borrowck/src/type_check/input_output.rs
+++ b/compiler/rustc_borrowck/src/type_check/input_output.rs
@@ -24,9 +24,9 @@ use crate::universal_regions::DefiningTy;
 impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
     /// Check explicit closure signature annotation,
     /// e.g., `|x: FxIndexMap<_, &'static u32>| ...`.
-    #[instrument(skip(self, body), level = "debug")]
-    pub(super) fn check_signature_annotation(&mut self, body: &Body<'tcx>) {
-        let mir_def_id = body.source.def_id().expect_local();
+    #[instrument(skip(self), level = "debug")]
+    pub(super) fn check_signature_annotation(&mut self) {
+        let mir_def_id = self.body.source.def_id().expect_local();
 
         if !self.tcx().is_closure_like(mir_def_id.to_def_id()) {
             return;
@@ -38,9 +38,9 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         // (e.g., the `_` in the code above) with fresh variables.
         // Then replace the bound items in the fn sig with fresh variables,
         // so that they represent the view from "inside" the closure.
-        let user_provided_sig = self.instantiate_canonical(body.span, &user_provided_poly_sig);
+        let user_provided_sig = self.instantiate_canonical(self.body.span, &user_provided_poly_sig);
         let mut user_provided_sig = self.infcx.instantiate_binder_with_fresh_vars(
-            body.span,
+            self.body.span,
             BoundRegionConversionTime::FnCall,
             user_provided_sig,
         );
@@ -66,12 +66,13 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 Ty::new_tup(self.tcx(), user_provided_sig.inputs()),
                 args.tupled_upvars_ty(),
                 args.coroutine_captures_by_ref_ty(),
-                self.infcx.next_region_var(RegionVariableOrigin::MiscVariable(body.span), || {
-                    RegionCtxt::Unknown
-                }),
+                self.infcx
+                    .next_region_var(RegionVariableOrigin::MiscVariable(self.body.span), || {
+                        RegionCtxt::Unknown
+                    }),
             );
 
-            let next_ty_var = || self.infcx.next_ty_var(body.span);
+            let next_ty_var = || self.infcx.next_ty_var(self.body.span);
             let output_ty = Ty::new_coroutine(
                 self.tcx(),
                 self.tcx().coroutine_for_closure(mir_def_id),
@@ -107,9 +108,10 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         for (&user_ty, arg_decl) in user_provided_sig.inputs().iter().zip_eq(
             // In MIR, closure args begin with an implicit `self`.
             // Also, coroutines have a resume type which may be implicitly `()`.
-            body.args_iter()
+            self.body
+                .args_iter()
                 .skip(1 + if is_coroutine_with_implicit_resume_ty { 1 } else { 0 })
-                .map(|local| &body.local_decls[local]),
+                .map(|local| &self.body.local_decls[local]),
         ) {
             self.ascribe_user_type_skip_wf(
                 arg_decl.ty,
@@ -119,7 +121,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         }
 
         // If the user explicitly annotated the output type, enforce it.
-        let output_decl = &body.local_decls[RETURN_PLACE];
+        let output_decl = &self.body.local_decls[RETURN_PLACE];
         self.ascribe_user_type_skip_wf(
             output_decl.ty,
             ty::UserType::new(ty::UserTypeKind::Ty(user_provided_sig.output())),
@@ -127,12 +129,8 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         );
     }
 
-    #[instrument(skip(self, body), level = "debug")]
-    pub(super) fn equate_inputs_and_outputs(
-        &mut self,
-        body: &Body<'tcx>,
-        normalized_inputs_and_output: &[Ty<'tcx>],
-    ) {
+    #[instrument(skip(self), level = "debug")]
+    pub(super) fn equate_inputs_and_outputs(&mut self, normalized_inputs_and_output: &[Ty<'tcx>]) {
         let (&normalized_output_ty, normalized_input_tys) =
             normalized_inputs_and_output.split_last().unwrap();
 
@@ -141,18 +139,18 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
 
         // Equate expected input tys with those in the MIR.
         for (argument_index, &normalized_input_ty) in normalized_input_tys.iter().enumerate() {
-            if argument_index + 1 >= body.local_decls.len() {
+            if argument_index + 1 >= self.body.local_decls.len() {
                 self.tcx()
                     .dcx()
-                    .span_bug(body.span, "found more normalized_input_ty than local_decls");
+                    .span_bug(self.body.span, "found more normalized_input_ty than local_decls");
             }
 
             // In MIR, argument N is stored in local N+1.
             let local = Local::from_usize(argument_index + 1);
 
-            let mir_input_ty = body.local_decls[local].ty;
+            let mir_input_ty = self.body.local_decls[local].ty;
 
-            let mir_input_span = body.local_decls[local].source_info.span;
+            let mir_input_span = self.body.local_decls[local].source_info.span;
             self.equate_normalized_input_or_output(
                 normalized_input_ty,
                 mir_input_ty,
@@ -160,8 +158,8 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             );
         }
 
-        if let Some(mir_yield_ty) = body.yield_ty() {
-            let yield_span = body.local_decls[RETURN_PLACE].source_info.span;
+        if let Some(mir_yield_ty) = self.body.yield_ty() {
+            let yield_span = self.body.local_decls[RETURN_PLACE].source_info.span;
             self.equate_normalized_input_or_output(
                 self.universal_regions.yield_ty.unwrap(),
                 mir_yield_ty,
@@ -169,8 +167,8 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             );
         }
 
-        if let Some(mir_resume_ty) = body.resume_ty() {
-            let yield_span = body.local_decls[RETURN_PLACE].source_info.span;
+        if let Some(mir_resume_ty) = self.body.resume_ty() {
+            let yield_span = self.body.local_decls[RETURN_PLACE].source_info.span;
             self.equate_normalized_input_or_output(
                 self.universal_regions.resume_ty.unwrap(),
                 mir_resume_ty,
@@ -179,8 +177,8 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         }
 
         // Return types are a bit more complex. They may contain opaque `impl Trait` types.
-        let mir_output_ty = body.local_decls[RETURN_PLACE].ty;
-        let output_span = body.local_decls[RETURN_PLACE].source_info.span;
+        let mir_output_ty = self.body.local_decls[RETURN_PLACE].ty;
+        let output_span = self.body.local_decls[RETURN_PLACE].source_info.span;
         self.equate_normalized_input_or_output(normalized_output_ty, mir_output_ty, output_span);
     }
 
diff --git a/compiler/rustc_borrowck/src/type_check/liveness/mod.rs b/compiler/rustc_borrowck/src/type_check/liveness/mod.rs
index dcc17903002..f17ad23f4bf 100644
--- a/compiler/rustc_borrowck/src/type_check/liveness/mod.rs
+++ b/compiler/rustc_borrowck/src/type_check/liveness/mod.rs
@@ -31,7 +31,6 @@ mod trace;
 /// performed before
 pub(super) fn generate<'a, 'tcx>(
     typeck: &mut TypeChecker<'_, 'tcx>,
-    body: &Body<'tcx>,
     location_map: &DenseLocationMap,
     flow_inits: ResultsCursor<'a, 'tcx, MaybeInitializedPlaces<'a, 'tcx>>,
     move_data: &MoveData<'tcx>,
@@ -51,23 +50,16 @@ pub(super) fn generate<'a, 'tcx>(
     // We do record these regions in the polonius context, since they're used to differentiate
     // relevant and boring locals, which is a key distinction used later in diagnostics.
     if typeck.tcx().sess.opts.unstable_opts.polonius.is_next_enabled() {
-        let (_, boring_locals) = compute_relevant_live_locals(typeck.tcx(), &free_regions, body);
+        let (_, boring_locals) =
+            compute_relevant_live_locals(typeck.tcx(), &free_regions, typeck.body);
         typeck.polonius_liveness.as_mut().unwrap().boring_nll_locals =
             boring_locals.into_iter().collect();
         free_regions = typeck.universal_regions.universal_regions_iter().collect();
     }
     let (relevant_live_locals, boring_locals) =
-        compute_relevant_live_locals(typeck.tcx(), &free_regions, body);
-
-    trace::trace(
-        typeck,
-        body,
-        location_map,
-        flow_inits,
-        move_data,
-        relevant_live_locals,
-        boring_locals,
-    );
+        compute_relevant_live_locals(typeck.tcx(), &free_regions, typeck.body);
+
+    trace::trace(typeck, location_map, flow_inits, move_data, relevant_live_locals, boring_locals);
 
     // Mark regions that should be live where they appear within rvalues or within a call: like
     // args, regions, and types.
@@ -76,7 +68,7 @@ pub(super) fn generate<'a, 'tcx>(
         &mut typeck.constraints.liveness_constraints,
         &typeck.universal_regions,
         &mut typeck.polonius_liveness,
-        body,
+        typeck.body,
     );
 }
 
diff --git a/compiler/rustc_borrowck/src/type_check/liveness/trace.rs b/compiler/rustc_borrowck/src/type_check/liveness/trace.rs
index dc35d5eb89c..7718644b9a9 100644
--- a/compiler/rustc_borrowck/src/type_check/liveness/trace.rs
+++ b/compiler/rustc_borrowck/src/type_check/liveness/trace.rs
@@ -39,17 +39,15 @@ use crate::type_check::{NormalizeLocation, TypeChecker};
 /// this respects `#[may_dangle]` annotations).
 pub(super) fn trace<'a, 'tcx>(
     typeck: &mut TypeChecker<'_, 'tcx>,
-    body: &Body<'tcx>,
     location_map: &DenseLocationMap,
     flow_inits: ResultsCursor<'a, 'tcx, MaybeInitializedPlaces<'a, 'tcx>>,
     move_data: &MoveData<'tcx>,
     relevant_live_locals: Vec<Local>,
     boring_locals: Vec<Local>,
 ) {
-    let local_use_map = &LocalUseMap::build(&relevant_live_locals, location_map, body);
+    let local_use_map = &LocalUseMap::build(&relevant_live_locals, location_map, typeck.body);
     let cx = LivenessContext {
         typeck,
-        body,
         flow_inits,
         location_map,
         local_use_map,
@@ -69,14 +67,13 @@ pub(super) fn trace<'a, 'tcx>(
 /// Contextual state for the type-liveness coroutine.
 struct LivenessContext<'a, 'typeck, 'b, 'tcx> {
     /// Current type-checker, giving us our inference context etc.
+    ///
+    /// This also stores the body we're currently analyzing.
     typeck: &'a mut TypeChecker<'typeck, 'tcx>,
 
     /// Defines the `PointIndex` mapping
     location_map: &'a DenseLocationMap,
 
-    /// MIR we are analyzing.
-    body: &'a Body<'tcx>,
-
     /// Mapping to/from the various indices used for initialization tracking.
     move_data: &'a MoveData<'tcx>,
 
@@ -139,7 +136,7 @@ impl<'a, 'typeck, 'b, 'tcx> LivenessResults<'a, 'typeck, 'b, 'tcx> {
             self.compute_use_live_points_for(local);
             self.compute_drop_live_points_for(local);
 
-            let local_ty = self.cx.body.local_decls[local].ty;
+            let local_ty = self.cx.body().local_decls[local].ty;
 
             if !self.use_live_at.is_empty() {
                 self.cx.add_use_live_facts_for(local_ty, &self.use_live_at);
@@ -164,8 +161,8 @@ impl<'a, 'typeck, 'b, 'tcx> LivenessResults<'a, 'typeck, 'b, 'tcx> {
     /// and can therefore safely be dropped.
     fn dropck_boring_locals(&mut self, boring_locals: Vec<Local>) {
         for local in boring_locals {
-            let local_ty = self.cx.body.local_decls[local].ty;
-            let local_span = self.cx.body.local_decls[local].source_info.span;
+            let local_ty = self.cx.body().local_decls[local].ty;
+            let local_span = self.cx.body().local_decls[local].source_info.span;
             let drop_data = self.cx.drop_data.entry(local_ty).or_insert_with({
                 let typeck = &self.cx.typeck;
                 move || LivenessContext::compute_drop_data(typeck, local_ty, local_span)
@@ -173,7 +170,7 @@ impl<'a, 'typeck, 'b, 'tcx> LivenessResults<'a, 'typeck, 'b, 'tcx> {
 
             drop_data.dropck_result.report_overflows(
                 self.cx.typeck.infcx.tcx,
-                self.cx.body.local_decls[local].source_info.span,
+                self.cx.typeck.body.local_decls[local].source_info.span,
                 local_ty,
             );
         }
@@ -202,7 +199,7 @@ impl<'a, 'typeck, 'b, 'tcx> LivenessResults<'a, 'typeck, 'b, 'tcx> {
                 .var_dropped_at
                 .iter()
                 .filter_map(|&(local, location_index)| {
-                    let local_ty = self.cx.body.local_decls[local].ty;
+                    let local_ty = self.cx.body().local_decls[local].ty;
                     if relevant_live_locals.contains(&local) || !local_ty.has_free_regions() {
                         return None;
                     }
@@ -278,9 +275,9 @@ impl<'a, 'typeck, 'b, 'tcx> LivenessResults<'a, 'typeck, 'b, 'tcx> {
 
                 let block = self.cx.location_map.to_location(block_start).block;
                 self.stack.extend(
-                    self.cx.body.basic_blocks.predecessors()[block]
+                    self.cx.body().basic_blocks.predecessors()[block]
                         .iter()
-                        .map(|&pred_bb| self.cx.body.terminator_loc(pred_bb))
+                        .map(|&pred_bb| self.cx.body().terminator_loc(pred_bb))
                         .map(|pred_loc| self.cx.location_map.point_from_location(pred_loc)),
                 );
             }
@@ -305,7 +302,7 @@ impl<'a, 'typeck, 'b, 'tcx> LivenessResults<'a, 'typeck, 'b, 'tcx> {
         // Find the drops where `local` is initialized.
         for drop_point in self.cx.local_use_map.drops(local) {
             let location = self.cx.location_map.to_location(drop_point);
-            debug_assert_eq!(self.cx.body.terminator_loc(location.block), location,);
+            debug_assert_eq!(self.cx.body().terminator_loc(location.block), location,);
 
             if self.cx.initialized_at_terminator(location.block, mpi)
                 && self.drop_live_at.insert(drop_point)
@@ -351,7 +348,7 @@ impl<'a, 'typeck, 'b, 'tcx> LivenessResults<'a, 'typeck, 'b, 'tcx> {
         // block. One of them may be either a definition or use
         // live point.
         let term_location = self.cx.location_map.to_location(term_point);
-        debug_assert_eq!(self.cx.body.terminator_loc(term_location.block), term_location,);
+        debug_assert_eq!(self.cx.body().terminator_loc(term_location.block), term_location,);
         let block = term_location.block;
         let entry_point = self.cx.location_map.entry_point(term_location.block);
         for p in (entry_point..term_point).rev() {
@@ -376,7 +373,7 @@ impl<'a, 'typeck, 'b, 'tcx> LivenessResults<'a, 'typeck, 'b, 'tcx> {
             }
         }
 
-        let body = self.cx.body;
+        let body = self.cx.typeck.body;
         for &pred_block in body.basic_blocks.predecessors()[block].iter() {
             debug!("compute_drop_live_points_for_block: pred_block = {:?}", pred_block,);
 
@@ -403,7 +400,7 @@ impl<'a, 'typeck, 'b, 'tcx> LivenessResults<'a, 'typeck, 'b, 'tcx> {
                 continue;
             }
 
-            let pred_term_loc = self.cx.body.terminator_loc(pred_block);
+            let pred_term_loc = self.cx.body().terminator_loc(pred_block);
             let pred_term_point = self.cx.location_map.point_from_location(pred_term_loc);
 
             // If the terminator of this predecessor either *assigns*
@@ -463,6 +460,9 @@ impl<'a, 'typeck, 'b, 'tcx> LivenessResults<'a, 'typeck, 'b, 'tcx> {
 }
 
 impl<'tcx> LivenessContext<'_, '_, '_, 'tcx> {
+    fn body(&self) -> &Body<'tcx> {
+        self.typeck.body
+    }
     /// Returns `true` if the local variable (or some part of it) is initialized at the current
     /// cursor position. Callers should call one of the `seek` methods immediately before to point
     /// the cursor to the desired location.
@@ -481,7 +481,7 @@ impl<'tcx> LivenessContext<'_, '_, '_, 'tcx> {
     /// DROP of some local variable will have an effect -- note that
     /// drops, as they may unwind, are always terminators.
     fn initialized_at_terminator(&mut self, block: BasicBlock, mpi: MovePathIndex) -> bool {
-        self.flow_inits.seek_before_primary_effect(self.body.terminator_loc(block));
+        self.flow_inits.seek_before_primary_effect(self.body().terminator_loc(block));
         self.initialized_at_curr_loc(mpi)
     }
 
@@ -491,7 +491,7 @@ impl<'tcx> LivenessContext<'_, '_, '_, 'tcx> {
     /// **Warning:** Does not account for the result of `Call`
     /// instructions.
     fn initialized_at_exit(&mut self, block: BasicBlock, mpi: MovePathIndex) -> bool {
-        self.flow_inits.seek_after_primary_effect(self.body.terminator_loc(block));
+        self.flow_inits.seek_after_primary_effect(self.body().terminator_loc(block));
         self.initialized_at_curr_loc(mpi)
     }
 
@@ -526,7 +526,7 @@ impl<'tcx> LivenessContext<'_, '_, '_, 'tcx> {
             values::pretty_print_points(self.location_map, live_at.iter()),
         );
 
-        let local_span = self.body.local_decls()[dropped_local].source_info.span;
+        let local_span = self.body().local_decls()[dropped_local].source_info.span;
         let drop_data = self.drop_data.entry(dropped_ty).or_insert_with({
             let typeck = &self.typeck;
             move || Self::compute_drop_data(typeck, dropped_ty, local_span)
@@ -544,7 +544,7 @@ impl<'tcx> LivenessContext<'_, '_, '_, 'tcx> {
 
         drop_data.dropck_result.report_overflows(
             self.typeck.infcx.tcx,
-            self.body.source_info(*drop_locations.first().unwrap()).span,
+            self.typeck.body.source_info(*drop_locations.first().unwrap()).span,
             dropped_ty,
         );
 
@@ -610,7 +610,7 @@ impl<'tcx> LivenessContext<'_, '_, '_, 'tcx> {
             Err(ErrorGuaranteed { .. }) => {
                 // We don't run dropck on HIR, and dropck looks inside fields of
                 // types, so there's no guarantee that it succeeds. We also
-                // can't rely on the the `ErrorGuaranteed` from `fully_perform` here
+                // can't rely on the `ErrorGuaranteed` from `fully_perform` here
                 // because it comes from delay_span_bug.
                 //
                 // Do this inside of a probe because we don't particularly care (or want)
diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs
index c1e23cb5411..9d5022f2bef 100644
--- a/compiler/rustc_borrowck/src/type_check/mod.rs
+++ b/compiler/rustc_borrowck/src/type_check/mod.rs
@@ -174,11 +174,11 @@ pub(crate) fn type_check<'a, 'tcx>(
     let mut verifier = TypeVerifier { typeck: &mut typeck, promoted, last_span: body.span };
     verifier.visit_body(body);
 
-    typeck.typeck_mir(body);
-    typeck.equate_inputs_and_outputs(body, &normalized_inputs_and_output);
-    typeck.check_signature_annotation(body);
+    typeck.typeck_mir();
+    typeck.equate_inputs_and_outputs(&normalized_inputs_and_output);
+    typeck.check_signature_annotation();
 
-    liveness::generate(&mut typeck, body, &location_map, flow_inits, move_data);
+    liveness::generate(&mut typeck, &location_map, flow_inits, move_data);
 
     let opaque_type_values =
         opaque_types::take_opaques_and_register_member_constraints(&mut typeck);
@@ -485,6 +485,7 @@ impl<'a, 'b, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'tcx> {
 
     #[instrument(level = "debug", skip(self))]
     fn visit_body(&mut self, body: &Body<'tcx>) {
+        debug_assert!(std::ptr::eq(self.typeck.body, body));
         // We intentionally do not recurse into `body.required_consts` or
         // `body.mentioned_items` here as the MIR at this phase should still
         // refer to all items and we don't want to check them multiple times.
@@ -542,7 +543,7 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
 
         self.visit_body(promoted_body);
 
-        self.typeck.typeck_mir(promoted_body);
+        self.typeck.typeck_mir();
 
         self.typeck.body = parent_body;
         // Merge the outlives constraints back in, at the given location.
@@ -892,8 +893,8 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         self.infcx.tcx
     }
 
-    #[instrument(skip(self, body), level = "debug")]
-    fn check_stmt(&mut self, body: &Body<'tcx>, stmt: &Statement<'tcx>, location: Location) {
+    #[instrument(skip(self), level = "debug")]
+    fn check_stmt(&mut self, stmt: &Statement<'tcx>, location: Location) {
         let tcx = self.tcx();
         debug!("stmt kind: {:?}", stmt.kind);
         match &stmt.kind {
@@ -916,11 +917,14 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                         }
                     }
                     Some(l)
-                        if matches!(body.local_decls[l].local_info(), LocalInfo::AggregateTemp) =>
+                        if matches!(
+                            self.body.local_decls[l].local_info(),
+                            LocalInfo::AggregateTemp
+                        ) =>
                     {
                         ConstraintCategory::Usage
                     }
-                    Some(l) if !body.local_decls[l].is_user_variable() => {
+                    Some(l) if !self.body.local_decls[l].is_user_variable() => {
                         ConstraintCategory::Boring
                     }
                     _ => ConstraintCategory::Assignment,
@@ -928,14 +932,14 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 debug!(
                     "assignment category: {:?} {:?}",
                     category,
-                    place.as_local().map(|l| &body.local_decls[l])
+                    place.as_local().map(|l| &self.body.local_decls[l])
                 );
 
-                let place_ty = place.ty(body, tcx).ty;
+                let place_ty = place.ty(self.body, tcx).ty;
                 debug!(?place_ty);
                 let place_ty = self.normalize(place_ty, location);
                 debug!("place_ty normalized: {:?}", place_ty);
-                let rv_ty = rv.ty(body, tcx);
+                let rv_ty = rv.ty(self.body, tcx);
                 debug!(?rv_ty);
                 let rv_ty = self.normalize(rv_ty, location);
                 debug!("normalized rv_ty: {:?}", rv_ty);
@@ -972,7 +976,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                     }
                 }
 
-                self.check_rvalue(body, rv, location);
+                self.check_rvalue(rv, location);
                 if !self.unsized_feature_enabled() {
                     let trait_ref = ty::TraitRef::new(
                         tcx,
@@ -987,7 +991,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 }
             }
             StatementKind::AscribeUserType(box (place, projection), variance) => {
-                let place_ty = place.ty(body, tcx).ty;
+                let place_ty = place.ty(self.body, tcx).ty;
                 if let Err(terr) = self.relate_type_and_user_type(
                     place_ty,
                     *variance,
@@ -1029,13 +1033,8 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         }
     }
 
-    #[instrument(skip(self, body, term_location), level = "debug")]
-    fn check_terminator(
-        &mut self,
-        body: &Body<'tcx>,
-        term: &Terminator<'tcx>,
-        term_location: Location,
-    ) {
+    #[instrument(skip(self, term_location), level = "debug")]
+    fn check_terminator(&mut self, term: &Terminator<'tcx>, term_location: Location) {
         let tcx = self.tcx();
         debug!("terminator kind: {:?}", term.kind);
         match &term.kind {
@@ -1055,7 +1054,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             TerminatorKind::SwitchInt { discr, .. } => {
                 self.check_operand(discr, term_location);
 
-                let switch_ty = discr.ty(body, tcx);
+                let switch_ty = discr.ty(self.body, tcx);
                 if !switch_ty.is_integral() && !switch_ty.is_char() && !switch_ty.is_bool() {
                     span_mirbug!(self, term, "bad SwitchInt discr ty {:?}", switch_ty);
                 }
@@ -1074,7 +1073,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                     self.check_operand(&arg.node, term_location);
                 }
 
-                let func_ty = func.ty(body, tcx);
+                let func_ty = func.ty(self.body, tcx);
                 debug!("func_ty.kind: {:?}", func_ty.kind());
 
                 let sig = match func_ty.kind() {
@@ -1142,7 +1141,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 }
 
                 if let TerminatorKind::Call { destination, target, .. } = term.kind {
-                    self.check_call_dest(body, term, &sig, destination, target, term_location);
+                    self.check_call_dest(term, &sig, destination, target, term_location);
                 }
 
                 // The ordinary liveness rules will ensure that all
@@ -1157,21 +1156,21 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                     self.constraints.liveness_constraints.add_location(region_vid, term_location);
                 }
 
-                self.check_call_inputs(body, term, func, &sig, args, term_location, call_source);
+                self.check_call_inputs(term, func, &sig, args, term_location, call_source);
             }
             TerminatorKind::Assert { cond, msg, .. } => {
                 self.check_operand(cond, term_location);
 
-                let cond_ty = cond.ty(body, tcx);
+                let cond_ty = cond.ty(self.body, tcx);
                 if cond_ty != tcx.types.bool {
                     span_mirbug!(self, term, "bad Assert ({:?}, not bool", cond_ty);
                 }
 
                 if let AssertKind::BoundsCheck { len, index } = &**msg {
-                    if len.ty(body, tcx) != tcx.types.usize {
+                    if len.ty(self.body, tcx) != tcx.types.usize {
                         span_mirbug!(self, len, "bounds-check length non-usize {:?}", len)
                     }
-                    if index.ty(body, tcx) != tcx.types.usize {
+                    if index.ty(self.body, tcx) != tcx.types.usize {
                         span_mirbug!(self, index, "bounds-check index non-usize {:?}", index)
                     }
                 }
@@ -1179,10 +1178,10 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             TerminatorKind::Yield { value, resume_arg, .. } => {
                 self.check_operand(value, term_location);
 
-                match body.yield_ty() {
+                match self.body.yield_ty() {
                     None => span_mirbug!(self, term, "yield in non-coroutine"),
                     Some(ty) => {
-                        let value_ty = value.ty(body, tcx);
+                        let value_ty = value.ty(self.body, tcx);
                         if let Err(terr) = self.sub_types(
                             value_ty,
                             ty,
@@ -1201,10 +1200,10 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                     }
                 }
 
-                match body.resume_ty() {
+                match self.body.resume_ty() {
                     None => span_mirbug!(self, term, "yield in non-coroutine"),
                     Some(ty) => {
-                        let resume_ty = resume_arg.ty(body, tcx);
+                        let resume_ty = resume_arg.ty(self.body, tcx);
                         if let Err(terr) = self.sub_types(
                             ty,
                             resume_ty.ty,
@@ -1228,7 +1227,6 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
 
     fn check_call_dest(
         &mut self,
-        body: &Body<'tcx>,
         term: &Terminator<'tcx>,
         sig: &ty::FnSig<'tcx>,
         destination: Place<'tcx>,
@@ -1238,7 +1236,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         let tcx = self.tcx();
         match target {
             Some(_) => {
-                let dest_ty = destination.ty(body, tcx).ty;
+                let dest_ty = destination.ty(self.body, tcx).ty;
                 let dest_ty = self.normalize(dest_ty, term_location);
                 let category = match destination.as_local() {
                     Some(RETURN_PLACE) => {
@@ -1254,7 +1252,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                             ConstraintCategory::Return(ReturnConstraint::Normal)
                         }
                     }
-                    Some(l) if !body.local_decls[l].is_user_variable() => {
+                    Some(l) if !self.body.local_decls[l].is_user_variable() => {
                         ConstraintCategory::Boring
                     }
                     // The return type of a call is interesting for diagnostics.
@@ -1295,10 +1293,9 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         }
     }
 
-    #[instrument(level = "debug", skip(self, body, term, func, term_location, call_source))]
+    #[instrument(level = "debug", skip(self, term, func, term_location, call_source))]
     fn check_call_inputs(
         &mut self,
-        body: &Body<'tcx>,
         term: &Terminator<'tcx>,
         func: &Operand<'tcx>,
         sig: &ty::FnSig<'tcx>,
@@ -1310,7 +1307,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             span_mirbug!(self, term, "call to {:?} with wrong # of args", sig);
         }
 
-        let func_ty = func.ty(body, self.infcx.tcx);
+        let func_ty = func.ty(self.body, self.infcx.tcx);
         if let ty::FnDef(def_id, _) = *func_ty.kind() {
             // Some of the SIMD intrinsics are special: they need a particular argument to be a
             // constant. (Eventually this should use const-generics, but those are not up for the
@@ -1334,7 +1331,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         debug!(?func_ty);
 
         for (n, (fn_arg, op_arg)) in iter::zip(sig.inputs(), args).enumerate() {
-            let op_arg_ty = op_arg.node.ty(body, self.tcx());
+            let op_arg_ty = op_arg.node.ty(self.body, self.tcx());
 
             let op_arg_ty = self.normalize(op_arg_ty, term_location);
             let category = if call_source.from_hir_call() {
@@ -1358,16 +1355,16 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         }
     }
 
-    fn check_iscleanup(&mut self, body: &Body<'tcx>, block_data: &BasicBlockData<'tcx>) {
+    fn check_iscleanup(&mut self, block_data: &BasicBlockData<'tcx>) {
         let is_cleanup = block_data.is_cleanup;
         self.last_span = block_data.terminator().source_info.span;
         match block_data.terminator().kind {
             TerminatorKind::Goto { target } => {
-                self.assert_iscleanup(body, block_data, target, is_cleanup)
+                self.assert_iscleanup(block_data, target, is_cleanup)
             }
             TerminatorKind::SwitchInt { ref targets, .. } => {
                 for target in targets.all_targets() {
-                    self.assert_iscleanup(body, block_data, *target, is_cleanup);
+                    self.assert_iscleanup(block_data, *target, is_cleanup);
                 }
             }
             TerminatorKind::UnwindResume => {
@@ -1399,55 +1396,48 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 if is_cleanup {
                     span_mirbug!(self, block_data, "yield in cleanup block")
                 }
-                self.assert_iscleanup(body, block_data, resume, is_cleanup);
+                self.assert_iscleanup(block_data, resume, is_cleanup);
                 if let Some(drop) = drop {
-                    self.assert_iscleanup(body, block_data, drop, is_cleanup);
+                    self.assert_iscleanup(block_data, drop, is_cleanup);
                 }
             }
             TerminatorKind::Unreachable => {}
             TerminatorKind::Drop { target, unwind, .. }
             | TerminatorKind::Assert { target, unwind, .. } => {
-                self.assert_iscleanup(body, block_data, target, is_cleanup);
-                self.assert_iscleanup_unwind(body, block_data, unwind, is_cleanup);
+                self.assert_iscleanup(block_data, target, is_cleanup);
+                self.assert_iscleanup_unwind(block_data, unwind, is_cleanup);
             }
             TerminatorKind::Call { ref target, unwind, .. } => {
                 if let &Some(target) = target {
-                    self.assert_iscleanup(body, block_data, target, is_cleanup);
+                    self.assert_iscleanup(block_data, target, is_cleanup);
                 }
-                self.assert_iscleanup_unwind(body, block_data, unwind, is_cleanup);
+                self.assert_iscleanup_unwind(block_data, unwind, is_cleanup);
             }
             TerminatorKind::FalseEdge { real_target, imaginary_target } => {
-                self.assert_iscleanup(body, block_data, real_target, is_cleanup);
-                self.assert_iscleanup(body, block_data, imaginary_target, is_cleanup);
+                self.assert_iscleanup(block_data, real_target, is_cleanup);
+                self.assert_iscleanup(block_data, imaginary_target, is_cleanup);
             }
             TerminatorKind::FalseUnwind { real_target, unwind } => {
-                self.assert_iscleanup(body, block_data, real_target, is_cleanup);
-                self.assert_iscleanup_unwind(body, block_data, unwind, is_cleanup);
+                self.assert_iscleanup(block_data, real_target, is_cleanup);
+                self.assert_iscleanup_unwind(block_data, unwind, is_cleanup);
             }
             TerminatorKind::InlineAsm { ref targets, unwind, .. } => {
                 for &target in targets {
-                    self.assert_iscleanup(body, block_data, target, is_cleanup);
+                    self.assert_iscleanup(block_data, target, is_cleanup);
                 }
-                self.assert_iscleanup_unwind(body, block_data, unwind, is_cleanup);
+                self.assert_iscleanup_unwind(block_data, unwind, is_cleanup);
             }
         }
     }
 
-    fn assert_iscleanup(
-        &mut self,
-        body: &Body<'tcx>,
-        ctxt: &dyn fmt::Debug,
-        bb: BasicBlock,
-        iscleanuppad: bool,
-    ) {
-        if body[bb].is_cleanup != iscleanuppad {
+    fn assert_iscleanup(&mut self, ctxt: &dyn fmt::Debug, bb: BasicBlock, iscleanuppad: bool) {
+        if self.body[bb].is_cleanup != iscleanuppad {
             span_mirbug!(self, ctxt, "cleanuppad mismatch: {:?} should be {:?}", bb, iscleanuppad);
         }
     }
 
     fn assert_iscleanup_unwind(
         &mut self,
-        body: &Body<'tcx>,
         ctxt: &dyn fmt::Debug,
         unwind: UnwindAction,
         is_cleanup: bool,
@@ -1457,7 +1447,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 if is_cleanup {
                     span_mirbug!(self, ctxt, "unwind on cleanup block")
                 }
-                self.assert_iscleanup(body, ctxt, unwind, true);
+                self.assert_iscleanup(ctxt, unwind, true);
             }
             UnwindAction::Continue => {
                 if is_cleanup {
@@ -1468,8 +1458,8 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         }
     }
 
-    fn check_local(&mut self, body: &Body<'tcx>, local: Local, local_decl: &LocalDecl<'tcx>) {
-        match body.local_kind(local) {
+    fn check_local(&mut self, local: Local, local_decl: &LocalDecl<'tcx>) {
+        match self.body.local_kind(local) {
             LocalKind::ReturnPointer | LocalKind::Arg => {
                 // return values of normal functions are required to be
                 // sized by typeck, but return values of ADT constructors are
@@ -1598,23 +1588,23 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         }
     }
 
-    #[instrument(skip(self, body), level = "debug")]
-    fn check_rvalue(&mut self, body: &Body<'tcx>, rvalue: &Rvalue<'tcx>, location: Location) {
+    #[instrument(skip(self), level = "debug")]
+    fn check_rvalue(&mut self, rvalue: &Rvalue<'tcx>, location: Location) {
         let tcx = self.tcx();
-        let span = body.source_info(location).span;
+        let span = self.body.source_info(location).span;
 
         match rvalue {
             Rvalue::Aggregate(ak, ops) => {
                 for op in ops {
                     self.check_operand(op, location);
                 }
-                self.check_aggregate_rvalue(body, rvalue, ak, ops, location)
+                self.check_aggregate_rvalue(rvalue, ak, ops, location)
             }
 
             Rvalue::Repeat(operand, len) => {
                 self.check_operand(operand, location);
 
-                let array_ty = rvalue.ty(body.local_decls(), tcx);
+                let array_ty = rvalue.ty(self.body.local_decls(), tcx);
                 self.prove_predicate(
                     ty::PredicateKind::Clause(ty::ClauseKind::WellFormed(array_ty.into())),
                     Locations::Single(location),
@@ -1633,7 +1623,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                         }
                         Operand::Move(place) => {
                             // Make sure that repeated elements implement `Copy`.
-                            let ty = place.ty(body, tcx).ty;
+                            let ty = place.ty(self.body, tcx).ty;
                             let trait_ref = ty::TraitRef::new(
                                 tcx,
                                 tcx.require_lang_item(LangItem::Copy, Some(span)),
@@ -1688,7 +1678,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 match *cast_kind {
                     CastKind::PointerCoercion(PointerCoercion::ReifyFnPointer, coercion_source) => {
                         let is_implicit_coercion = coercion_source == CoercionSource::Implicit;
-                        let src_ty = op.ty(body, tcx);
+                        let src_ty = op.ty(self.body, tcx);
                         let mut src_sig = src_ty.fn_sig(tcx);
                         if let ty::FnDef(def_id, _) = src_ty.kind()
                             && let ty::FnPtr(_, target_hdr) = *ty.kind()
@@ -1697,7 +1687,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                             && let Some(safe_sig) = tcx.adjust_target_feature_sig(
                                 *def_id,
                                 src_sig,
-                                body.source.def_id(),
+                                self.body.source.def_id(),
                             )
                         {
                             src_sig = safe_sig;
@@ -1790,7 +1780,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                         PointerCoercion::ClosureFnPointer(safety),
                         coercion_source,
                     ) => {
-                        let sig = match op.ty(body, tcx).kind() {
+                        let sig = match op.ty(self.body, tcx).kind() {
                             ty::Closure(_, args) => args.as_closure().sig(),
                             _ => bug!(),
                         };
@@ -1819,7 +1809,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                         PointerCoercion::UnsafeFnPointer,
                         coercion_source,
                     ) => {
-                        let fn_sig = op.ty(body, tcx).fn_sig(tcx);
+                        let fn_sig = op.ty(self.body, tcx).fn_sig(tcx);
 
                         // The type that we see in the fcx is like
                         // `foo::<'a, 'b>`, where `foo` is the path to a
@@ -1853,7 +1843,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                         let trait_ref = ty::TraitRef::new(
                             tcx,
                             tcx.require_lang_item(LangItem::CoerceUnsized, Some(span)),
-                            [op.ty(body, tcx), ty],
+                            [op.ty(self.body, tcx), ty],
                         );
 
                         let is_implicit_coercion = coercion_source == CoercionSource::Implicit;
@@ -1879,7 +1869,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                             _ => panic!("Invalid dyn* cast_ty"),
                         };
 
-                        let self_ty = op.ty(body, tcx);
+                        let self_ty = op.ty(self.body, tcx);
 
                         let is_implicit_coercion = coercion_source == CoercionSource::Implicit;
                         self.prove_predicates(
@@ -1906,7 +1896,8 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                         PointerCoercion::MutToConstPointer,
                         coercion_source,
                     ) => {
-                        let ty::RawPtr(ty_from, hir::Mutability::Mut) = op.ty(body, tcx).kind()
+                        let ty::RawPtr(ty_from, hir::Mutability::Mut) =
+                            op.ty(self.body, tcx).kind()
                         else {
                             span_mirbug!(self, rvalue, "unexpected base type for cast {:?}", ty,);
                             return;
@@ -1934,7 +1925,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                     }
 
                     CastKind::PointerCoercion(PointerCoercion::ArrayToPointer, coercion_source) => {
-                        let ty_from = op.ty(body, tcx);
+                        let ty_from = op.ty(self.body, tcx);
 
                         let opt_ty_elem_mut = match ty_from.kind() {
                             ty::RawPtr(array_ty, array_mut) => match array_ty.kind() {
@@ -1997,7 +1988,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                     }
 
                     CastKind::PointerExposeProvenance => {
-                        let ty_from = op.ty(body, tcx);
+                        let ty_from = op.ty(self.body, tcx);
                         let cast_ty_from = CastTy::from_ty(ty_from);
                         let cast_ty_to = CastTy::from_ty(*ty);
                         match (cast_ty_from, cast_ty_to) {
@@ -2015,7 +2006,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                     }
 
                     CastKind::PointerWithExposedProvenance => {
-                        let ty_from = op.ty(body, tcx);
+                        let ty_from = op.ty(self.body, tcx);
                         let cast_ty_from = CastTy::from_ty(ty_from);
                         let cast_ty_to = CastTy::from_ty(*ty);
                         match (cast_ty_from, cast_ty_to) {
@@ -2032,7 +2023,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                         }
                     }
                     CastKind::IntToInt => {
-                        let ty_from = op.ty(body, tcx);
+                        let ty_from = op.ty(self.body, tcx);
                         let cast_ty_from = CastTy::from_ty(ty_from);
                         let cast_ty_to = CastTy::from_ty(*ty);
                         match (cast_ty_from, cast_ty_to) {
@@ -2049,7 +2040,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                         }
                     }
                     CastKind::IntToFloat => {
-                        let ty_from = op.ty(body, tcx);
+                        let ty_from = op.ty(self.body, tcx);
                         let cast_ty_from = CastTy::from_ty(ty_from);
                         let cast_ty_to = CastTy::from_ty(*ty);
                         match (cast_ty_from, cast_ty_to) {
@@ -2066,7 +2057,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                         }
                     }
                     CastKind::FloatToInt => {
-                        let ty_from = op.ty(body, tcx);
+                        let ty_from = op.ty(self.body, tcx);
                         let cast_ty_from = CastTy::from_ty(ty_from);
                         let cast_ty_to = CastTy::from_ty(*ty);
                         match (cast_ty_from, cast_ty_to) {
@@ -2083,7 +2074,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                         }
                     }
                     CastKind::FloatToFloat => {
-                        let ty_from = op.ty(body, tcx);
+                        let ty_from = op.ty(self.body, tcx);
                         let cast_ty_from = CastTy::from_ty(ty_from);
                         let cast_ty_to = CastTy::from_ty(*ty);
                         match (cast_ty_from, cast_ty_to) {
@@ -2100,7 +2091,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                         }
                     }
                     CastKind::FnPtrToPtr => {
-                        let ty_from = op.ty(body, tcx);
+                        let ty_from = op.ty(self.body, tcx);
                         let cast_ty_from = CastTy::from_ty(ty_from);
                         let cast_ty_to = CastTy::from_ty(*ty);
                         match (cast_ty_from, cast_ty_to) {
@@ -2117,7 +2108,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                         }
                     }
                     CastKind::PtrToPtr => {
-                        let ty_from = op.ty(body, tcx);
+                        let ty_from = op.ty(self.body, tcx);
                         let cast_ty_from = CastTy::from_ty(ty_from);
                         let cast_ty_to = CastTy::from_ty(*ty);
                         match (cast_ty_from, cast_ty_to) {
@@ -2193,7 +2184,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             }
 
             Rvalue::Ref(region, _borrow_kind, borrowed_place) => {
-                self.add_reborrow_constraint(body, location, *region, borrowed_place);
+                self.add_reborrow_constraint(location, *region, borrowed_place);
             }
 
             Rvalue::BinaryOp(
@@ -2203,12 +2194,13 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 self.check_operand(left, location);
                 self.check_operand(right, location);
 
-                let ty_left = left.ty(body, tcx);
+                let ty_left = left.ty(self.body, tcx);
                 match ty_left.kind() {
                     // Types with regions are comparable if they have a common super-type.
                     ty::RawPtr(_, _) | ty::FnPtr(..) => {
-                        let ty_right = right.ty(body, tcx);
-                        let common_ty = self.infcx.next_ty_var(body.source_info(location).span);
+                        let ty_right = right.ty(self.body, tcx);
+                        let common_ty =
+                            self.infcx.next_ty_var(self.body.source_info(location).span);
                         self.sub_types(
                             ty_left,
                             common_ty,
@@ -2237,7 +2229,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                     // For types with no regions we can just check that the
                     // both operands have the same type.
                     ty::Int(_) | ty::Uint(_) | ty::Bool | ty::Char | ty::Float(_)
-                        if ty_left == right.ty(body, tcx) => {}
+                        if ty_left == right.ty(self.body, tcx) => {}
                     // Other types are compared by trait methods, not by
                     // `Rvalue::BinaryOp`.
                     _ => span_mirbug!(
@@ -2245,7 +2237,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                         rvalue,
                         "unexpected comparison types {:?} and {:?}",
                         ty_left,
-                        right.ty(body, tcx)
+                        right.ty(self.body, tcx)
                     ),
                 }
             }
@@ -2326,7 +2318,6 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
 
     fn check_aggregate_rvalue(
         &mut self,
-        body: &Body<'tcx>,
         rvalue: &Rvalue<'tcx>,
         aggregate_kind: &AggregateKind<'tcx>,
         operands: &IndexSlice<FieldIdx, Operand<'tcx>>,
@@ -2359,7 +2350,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                     continue;
                 }
             };
-            let operand_ty = operand.ty(body, tcx);
+            let operand_ty = operand.ty(self.body, tcx);
             let operand_ty = self.normalize(operand_ty, location);
 
             if let Err(terr) = self.sub_types(
@@ -2389,7 +2380,6 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
     /// - `borrowed_place`: the place `P` being borrowed
     fn add_reborrow_constraint(
         &mut self,
-        body: &Body<'tcx>,
         location: Location,
         borrow_region: ty::Region<'tcx>,
         borrowed_place: &Place<'tcx>,
@@ -2428,7 +2418,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         let def = self.body.source.def_id().expect_local();
         let upvars = tcx.closure_captures(def);
         let field =
-            path_utils::is_upvar_field_projection(tcx, upvars, borrowed_place.as_ref(), body);
+            path_utils::is_upvar_field_projection(tcx, upvars, borrowed_place.as_ref(), self.body);
         let category = if let Some(field) = field {
             ConstraintCategory::ClosureUpvar(field)
         } else {
@@ -2440,7 +2430,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
 
             match elem {
                 ProjectionElem::Deref => {
-                    let base_ty = base.ty(body, tcx).ty;
+                    let base_ty = base.ty(self.body, tcx).ty;
 
                     debug!("add_reborrow_constraint - base_ty = {:?}", base_ty);
                     match base_ty.kind() {
@@ -2449,7 +2439,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                                 sup: ref_region.as_var(),
                                 sub: borrow_region.as_var(),
                                 locations: location.to_locations(),
-                                span: location.to_locations().span(body),
+                                span: location.to_locations().span(self.body),
                                 category,
                                 variance_info: ty::VarianceDiagInfo::default(),
                                 from_closure: false,
@@ -2634,27 +2624,27 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         tcx.predicates_of(def_id).instantiate(tcx, args)
     }
 
-    #[instrument(skip(self, body), level = "debug")]
-    fn typeck_mir(&mut self, body: &Body<'tcx>) {
-        self.last_span = body.span;
-        debug!(?body.span);
+    #[instrument(skip(self), level = "debug")]
+    fn typeck_mir(&mut self) {
+        self.last_span = self.body.span;
+        debug!(?self.body.span);
 
-        for (local, local_decl) in body.local_decls.iter_enumerated() {
-            self.check_local(body, local, local_decl);
+        for (local, local_decl) in self.body.local_decls.iter_enumerated() {
+            self.check_local(local, local_decl);
         }
 
-        for (block, block_data) in body.basic_blocks.iter_enumerated() {
+        for (block, block_data) in self.body.basic_blocks.iter_enumerated() {
             let mut location = Location { block, statement_index: 0 };
             for stmt in &block_data.statements {
                 if !stmt.source_info.span.is_dummy() {
                     self.last_span = stmt.source_info.span;
                 }
-                self.check_stmt(body, stmt, location);
+                self.check_stmt(stmt, location);
                 location.statement_index += 1;
             }
 
-            self.check_terminator(body, block_data.terminator(), location);
-            self.check_iscleanup(body, block_data);
+            self.check_terminator(block_data.terminator(), location);
+            self.check_iscleanup(block_data);
         }
     }
 }
diff --git a/compiler/rustc_borrowck/src/type_check/opaque_types.rs b/compiler/rustc_borrowck/src/type_check/opaque_types.rs
index 17482cc0cbd..94b3d0c2bbf 100644
--- a/compiler/rustc_borrowck/src/type_check/opaque_types.rs
+++ b/compiler/rustc_borrowck/src/type_check/opaque_types.rs
@@ -180,6 +180,7 @@ pub(super) fn take_opaques_and_register_member_constraints<'tcx>(
 /// // Equivalent to:
 /// # mod dummy { use super::*;
 /// type FooReturn<'a, T> = impl Foo<'a>;
+/// #[define_opaque(FooReturn)]
 /// fn foo<'a, T>(x: &'a u32, y: T) -> FooReturn<'a, T> {
 ///   (x, y)
 /// }
diff --git a/compiler/rustc_builtin_macros/Cargo.toml b/compiler/rustc_builtin_macros/Cargo.toml
index b5f4f2efd1f..1289d21308b 100644
--- a/compiler/rustc_builtin_macros/Cargo.toml
+++ b/compiler/rustc_builtin_macros/Cargo.toml
@@ -3,10 +3,6 @@ name = "rustc_builtin_macros"
 version = "0.0.0"
 edition = "2024"
 
-
-[lints.rust]
-unexpected_cfgs = { level = "warn", check-cfg = ['cfg(llvm_enzyme)'] }
-
 [lib]
 doctest = false
 
diff --git a/compiler/rustc_builtin_macros/messages.ftl b/compiler/rustc_builtin_macros/messages.ftl
index 4cac7cb93f5..3f03834f8d7 100644
--- a/compiler/rustc_builtin_macros/messages.ftl
+++ b/compiler/rustc_builtin_macros/messages.ftl
@@ -75,9 +75,10 @@ builtin_macros_autodiff_mode = unknown Mode: `{$mode}`. Use `Forward` or `Revers
 builtin_macros_autodiff_mode_activity = {$act} can not be used in {$mode} Mode
 builtin_macros_autodiff_not_build = this rustc version does not support autodiff
 builtin_macros_autodiff_number_activities = expected {$expected} activities, but found {$found}
+builtin_macros_autodiff_ret_activity = invalid return activity {$act} in {$mode} Mode
 builtin_macros_autodiff_ty_activity = {$act} can not be used for this type
-
 builtin_macros_autodiff_unknown_activity = did not recognize Activity: `{$act}`
+
 builtin_macros_bad_derive_target = `derive` may only be applied to `struct`s, `enum`s and `union`s
     .label = not applicable here
     .label2 = not a `struct`, `enum` or `union`
diff --git a/compiler/rustc_builtin_macros/src/alloc_error_handler.rs b/compiler/rustc_builtin_macros/src/alloc_error_handler.rs
index 78bf2195975..1c1b2c88f76 100644
--- a/compiler/rustc_builtin_macros/src/alloc_error_handler.rs
+++ b/compiler/rustc_builtin_macros/src/alloc_error_handler.rs
@@ -88,6 +88,7 @@ fn generate_handler(cx: &ExtCtxt<'_>, handler: Ident, span: Span, sig_span: Span
         generics: Generics::default(),
         contract: None,
         body,
+        define_opaque: None,
     }));
 
     let attrs = thin_vec![cx.attr_word(sym::rustc_std_internal_symbol, span)];
diff --git a/compiler/rustc_builtin_macros/src/assert/context.rs b/compiler/rustc_builtin_macros/src/assert/context.rs
index bb9dc651cec..a949ab94f3a 100644
--- a/compiler/rustc_builtin_macros/src/assert/context.rs
+++ b/compiler/rustc_builtin_macros/src/assert/context.rs
@@ -297,6 +297,7 @@ impl<'cx, 'a> Context<'cx, 'a> {
             | ExprKind::AssignOp(_, _, _)
             | ExprKind::Gen(_, _, _, _)
             | ExprKind::Await(_, _)
+            | ExprKind::Use(_, _)
             | ExprKind::Block(_, _)
             | ExprKind::Break(_, _)
             | ExprKind::Closure(_)
diff --git a/compiler/rustc_builtin_macros/src/autodiff.rs b/compiler/rustc_builtin_macros/src/autodiff.rs
index 6d9c3575657..dcd3c1ce8d9 100644
--- a/compiler/rustc_builtin_macros/src/autodiff.rs
+++ b/compiler/rustc_builtin_macros/src/autodiff.rs
@@ -8,7 +8,8 @@ mod llvm_enzyme {
     use std::string::String;
 
     use rustc_ast::expand::autodiff_attrs::{
-        AutoDiffAttrs, DiffActivity, DiffMode, valid_input_activity, valid_ty_for_activity,
+        AutoDiffAttrs, DiffActivity, DiffMode, valid_input_activity, valid_ret_activity,
+        valid_ty_for_activity,
     };
     use rustc_ast::ptr::P;
     use rustc_ast::token::{Token, TokenKind};
@@ -247,6 +248,7 @@ mod llvm_enzyme {
             generics: Generics::default(),
             contract: None,
             body: Some(d_body),
+            define_opaque: None,
         });
         let mut rustc_ad_attr =
             P(ast::NormalAttr::from_ident(Ident::with_dummy_span(sym::rustc_autodiff)));
@@ -286,7 +288,7 @@ mod llvm_enzyme {
         let orig_annotatable: Annotatable = match item {
             Annotatable::Item(ref mut iitem) => {
                 if !iitem.attrs.iter().any(|a| a.id == attr.id) {
-                    iitem.attrs.push(attr.clone());
+                    iitem.attrs.push(attr);
                 }
                 if !iitem.attrs.iter().any(|a| a.id == inline_never.id) {
                     iitem.attrs.push(inline_never.clone());
@@ -295,7 +297,7 @@ mod llvm_enzyme {
             }
             Annotatable::AssocItem(ref mut assoc_item, i @ Impl) => {
                 if !assoc_item.attrs.iter().any(|a| a.id == attr.id) {
-                    assoc_item.attrs.push(attr.clone());
+                    assoc_item.attrs.push(attr);
                 }
                 if !assoc_item.attrs.iter().any(|a| a.id == inline_never.id) {
                     assoc_item.attrs.push(inline_never.clone());
@@ -322,7 +324,7 @@ mod llvm_enzyme {
         let d_annotatable = if is_impl {
             let assoc_item: AssocItemKind = ast::AssocItemKind::Fn(asdf);
             let d_fn = P(ast::AssocItem {
-                attrs: thin_vec![d_attr.clone(), inline_never],
+                attrs: thin_vec![d_attr, inline_never],
                 id: ast::DUMMY_NODE_ID,
                 span,
                 vis,
@@ -332,12 +334,8 @@ mod llvm_enzyme {
             });
             Annotatable::AssocItem(d_fn, Impl)
         } else {
-            let mut d_fn = ecx.item(
-                span,
-                d_ident,
-                thin_vec![d_attr.clone(), inline_never],
-                ItemKind::Fn(asdf),
-            );
+            let mut d_fn =
+                ecx.item(span, d_ident, thin_vec![d_attr, inline_never], ItemKind::Fn(asdf));
             d_fn.vis = vis;
             Annotatable::Item(d_fn)
         };
@@ -446,7 +444,7 @@ mod llvm_enzyme {
 
         if primal_ret && n_active == 0 && x.mode.is_rev() {
             // We only have the primal ret.
-            body.stmts.push(ecx.stmt_expr(black_box_primal_call.clone()));
+            body.stmts.push(ecx.stmt_expr(black_box_primal_call));
             return body;
         }
 
@@ -471,7 +469,7 @@ mod llvm_enzyme {
         if primal_ret {
             // We have both primal ret and active floats.
             // primal ret is first, by construction.
-            exprs.push(primal_call.clone());
+            exprs.push(primal_call);
         }
 
         // Now construct default placeholder for each active float.
@@ -538,16 +536,11 @@ mod llvm_enzyme {
                 return body;
             }
             [arg] => {
-                ret = ecx.expr_call(
-                    new_decl_span,
-                    blackbox_call_expr.clone(),
-                    thin_vec![arg.clone()],
-                );
+                ret = ecx.expr_call(new_decl_span, blackbox_call_expr, thin_vec![arg.clone()]);
             }
             args => {
                 let ret_tuple: P<ast::Expr> = ecx.expr_tuple(span, args.into());
-                ret =
-                    ecx.expr_call(new_decl_span, blackbox_call_expr.clone(), thin_vec![ret_tuple]);
+                ret = ecx.expr_call(new_decl_span, blackbox_call_expr, thin_vec![ret_tuple]);
             }
         }
         assert!(has_ret(&d_sig.decl.output));
@@ -567,7 +560,7 @@ mod llvm_enzyme {
             let args: ThinVec<_> =
                 idents[1..].iter().map(|arg| ecx.expr_path(ecx.path_ident(span, *arg))).collect();
             let self_expr = ecx.expr_self(span);
-            ecx.expr_method_call(span, self_expr, primal, args.clone())
+            ecx.expr_method_call(span, self_expr, primal, args)
         } else {
             let args: ThinVec<_> =
                 idents.iter().map(|arg| ecx.expr_path(ecx.path_ident(span, *arg))).collect();
@@ -585,6 +578,8 @@ mod llvm_enzyme {
     //
     // Error handling: If the user provides an invalid configuration (incorrect numbers, types, or
     // both), we emit an error and return the original signature. This allows us to continue parsing.
+    // FIXME(Sa4dUs): make individual activities' span available so errors
+    // can point to only the activity instead of the entire attribute
     fn gen_enzyme_decl(
         ecx: &ExtCtxt<'_>,
         sig: &ast::FnSig,
@@ -632,10 +627,22 @@ mod llvm_enzyme {
                 errors = true;
             }
         }
+
+        if has_ret && !valid_ret_activity(x.mode, x.ret_activity) {
+            dcx.emit_err(errors::AutoDiffInvalidRetAct {
+                span,
+                mode: x.mode.to_string(),
+                act: x.ret_activity.to_string(),
+            });
+            // We don't set `errors = true` to avoid annoying type errors relative
+            // to the expanded macro type signature
+        }
+
         if errors {
             // This is not the right signature, but we can continue parsing.
             return (sig.clone(), new_inputs, idents, true);
         }
+
         let unsafe_activities = x
             .input_activity
             .iter()
diff --git a/compiler/rustc_builtin_macros/src/define_opaque.rs b/compiler/rustc_builtin_macros/src/define_opaque.rs
new file mode 100644
index 00000000000..9777e772cf2
--- /dev/null
+++ b/compiler/rustc_builtin_macros/src/define_opaque.rs
@@ -0,0 +1,54 @@
+use rustc_ast::{DUMMY_NODE_ID, ast};
+use rustc_expand::base::{Annotatable, ExtCtxt};
+use rustc_span::Span;
+
+pub(crate) fn expand(
+    ecx: &mut ExtCtxt<'_>,
+    _expand_span: Span,
+    meta_item: &ast::MetaItem,
+    mut item: Annotatable,
+) -> Vec<Annotatable> {
+    let define_opaque = match &mut item {
+        Annotatable::Item(p) => match &mut p.kind {
+            ast::ItemKind::Fn(f) => Some(&mut f.define_opaque),
+            _ => None,
+        },
+        Annotatable::AssocItem(i, _assoc_ctxt) => match &mut i.kind {
+            ast::AssocItemKind::Fn(func) => Some(&mut func.define_opaque),
+            _ => None,
+        },
+        Annotatable::Stmt(s) => match &mut s.kind {
+            ast::StmtKind::Item(p) => match &mut p.kind {
+                ast::ItemKind::Fn(f) => Some(&mut f.define_opaque),
+                _ => None,
+            },
+            _ => None,
+        },
+        _ => None,
+    };
+
+    let Some(list) = meta_item.meta_item_list() else {
+        ecx.dcx().span_err(meta_item.span, "expected list of type aliases");
+        return vec![item];
+    };
+
+    if let Some(define_opaque) = define_opaque {
+        *define_opaque = Some(
+            list.iter()
+                .filter_map(|entry| match entry {
+                    ast::MetaItemInner::MetaItem(meta_item) if meta_item.is_word() => {
+                        Some((DUMMY_NODE_ID, meta_item.path.clone()))
+                    }
+                    _ => {
+                        ecx.dcx().span_err(entry.span(), "expected path to type alias");
+                        None
+                    }
+                })
+                .collect(),
+        );
+    } else {
+        ecx.dcx().span_err(meta_item.span, "only functions and methods can define opaque types");
+    }
+
+    vec![item]
+}
diff --git a/compiler/rustc_builtin_macros/src/deriving/generic/mod.rs b/compiler/rustc_builtin_macros/src/deriving/generic/mod.rs
index 5402b5a1ae9..03ee59de70e 100644
--- a/compiler/rustc_builtin_macros/src/deriving/generic/mod.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/generic/mod.rs
@@ -1040,6 +1040,7 @@ impl<'a> MethodDef<'a> {
                 generics: fn_generics,
                 contract: None,
                 body: Some(body_block),
+                define_opaque: None,
             })),
             tokens: None,
         })
diff --git a/compiler/rustc_builtin_macros/src/errors.rs b/compiler/rustc_builtin_macros/src/errors.rs
index ab1e0d8ee89..30597944124 100644
--- a/compiler/rustc_builtin_macros/src/errors.rs
+++ b/compiler/rustc_builtin_macros/src/errors.rs
@@ -186,6 +186,15 @@ mod autodiff {
     }
 
     #[derive(Diagnostic)]
+    #[diag(builtin_macros_autodiff_ret_activity)]
+    pub(crate) struct AutoDiffInvalidRetAct {
+        #[primary_span]
+        pub(crate) span: Span,
+        pub(crate) mode: String,
+        pub(crate) act: String,
+    }
+
+    #[derive(Diagnostic)]
     #[diag(builtin_macros_autodiff_mode)]
     pub(crate) struct AutoDiffInvalidMode {
         #[primary_span]
diff --git a/compiler/rustc_builtin_macros/src/format.rs b/compiler/rustc_builtin_macros/src/format.rs
index 6dbd8a7ac01..12654001a1e 100644
--- a/compiler/rustc_builtin_macros/src/format.rs
+++ b/compiler/rustc_builtin_macros/src/format.rs
@@ -711,11 +711,9 @@ fn report_missing_placeholders(
                     };
 
                     let pos = sub.position();
-                    let sub = String::from(sub.as_str());
-                    if explained.contains(&sub) {
+                    if !explained.insert(sub.to_string()) {
                         continue;
                     }
-                    explained.insert(sub);
 
                     if !found_foreign {
                         found_foreign = true;
diff --git a/compiler/rustc_builtin_macros/src/format_foreign.rs b/compiler/rustc_builtin_macros/src/format_foreign.rs
index 866ec72f116..13d5b42942a 100644
--- a/compiler/rustc_builtin_macros/src/format_foreign.rs
+++ b/compiler/rustc_builtin_macros/src/format_foreign.rs
@@ -12,14 +12,16 @@ pub(crate) mod printf {
         Escape((usize, usize)),
     }
 
-    impl<'a> Substitution<'a> {
-        pub(crate) fn as_str(&self) -> &str {
+    impl ToString for Substitution<'_> {
+        fn to_string(&self) -> String {
             match self {
-                Substitution::Format(fmt) => fmt.span,
-                Substitution::Escape(_) => "%%",
+                Substitution::Format(fmt) => fmt.span.into(),
+                Substitution::Escape(_) => "%%".into(),
             }
         }
+    }
 
+    impl Substitution<'_> {
         pub(crate) fn position(&self) -> InnerSpan {
             match self {
                 Substitution::Format(fmt) => fmt.position,
@@ -627,15 +629,17 @@ pub(crate) mod shell {
         Escape((usize, usize)),
     }
 
-    impl Substitution<'_> {
-        pub(crate) fn as_str(&self) -> String {
+    impl ToString for Substitution<'_> {
+        fn to_string(&self) -> String {
             match self {
                 Substitution::Ordinal(n, _) => format!("${n}"),
                 Substitution::Name(n, _) => format!("${n}"),
                 Substitution::Escape(_) => "$$".into(),
             }
         }
+    }
 
+    impl Substitution<'_> {
         pub(crate) fn position(&self) -> InnerSpan {
             let (Self::Ordinal(_, pos) | Self::Name(_, pos) | Self::Escape(pos)) = self;
             InnerSpan::new(pos.0, pos.1)
diff --git a/compiler/rustc_builtin_macros/src/global_allocator.rs b/compiler/rustc_builtin_macros/src/global_allocator.rs
index 8fdbbf8e704..90d79235820 100644
--- a/compiler/rustc_builtin_macros/src/global_allocator.rs
+++ b/compiler/rustc_builtin_macros/src/global_allocator.rs
@@ -83,6 +83,7 @@ impl AllocFnFactory<'_, '_> {
             generics: Generics::default(),
             contract: None,
             body,
+            define_opaque: None,
         }));
         let item = self.cx.item(
             self.span,
diff --git a/compiler/rustc_builtin_macros/src/lib.rs b/compiler/rustc_builtin_macros/src/lib.rs
index ca16583a45d..c5d2a84fba4 100644
--- a/compiler/rustc_builtin_macros/src/lib.rs
+++ b/compiler/rustc_builtin_macros/src/lib.rs
@@ -39,6 +39,7 @@ mod compile_error;
 mod concat;
 mod concat_bytes;
 mod concat_idents;
+mod define_opaque;
 mod derive;
 mod deriving;
 mod edition_panic;
@@ -114,6 +115,7 @@ pub fn register_builtin_macros(resolver: &mut dyn ResolverExpand) {
         bench: test::expand_bench,
         cfg_accessible: cfg_accessible::Expander,
         cfg_eval: cfg_eval::expand,
+        define_opaque: define_opaque::expand,
         derive: derive::Expander { is_const: false },
         derive_const: derive::Expander { is_const: true },
         global_allocator: global_allocator::expand,
diff --git a/compiler/rustc_builtin_macros/src/standard_library_imports.rs b/compiler/rustc_builtin_macros/src/standard_library_imports.rs
index 6933ca09349..ba63b185e09 100644
--- a/compiler/rustc_builtin_macros/src/standard_library_imports.rs
+++ b/compiler/rustc_builtin_macros/src/standard_library_imports.rs
@@ -60,6 +60,7 @@ pub fn inject(
             Edition2018 => sym::rust_2018,
             Edition2021 => sym::rust_2021,
             Edition2024 => sym::rust_2024,
+            EditionFuture => sym::rust_future,
         }])
         .map(|&symbol| Ident::new(symbol, span))
         .collect();
diff --git a/compiler/rustc_builtin_macros/src/test_harness.rs b/compiler/rustc_builtin_macros/src/test_harness.rs
index 472e16e62d5..768b459ec5e 100644
--- a/compiler/rustc_builtin_macros/src/test_harness.rs
+++ b/compiler/rustc_builtin_macros/src/test_harness.rs
@@ -346,6 +346,7 @@ fn mk_main(cx: &mut TestCtxt<'_>) -> P<ast::Item> {
         generics: ast::Generics::default(),
         contract: None,
         body: Some(main_body),
+        define_opaque: None,
     }));
 
     // Honor the reexport_test_harness_main attribute
diff --git a/compiler/rustc_codegen_cranelift/example/issue-72793.rs b/compiler/rustc_codegen_cranelift/example/issue-72793.rs
index 2e08fbca8ef..95d58b90e79 100644
--- a/compiler/rustc_codegen_cranelift/example/issue-72793.rs
+++ b/compiler/rustc_codegen_cranelift/example/issue-72793.rs
@@ -2,23 +2,21 @@
 
 #![feature(type_alias_impl_trait)]
 
-mod helper {
-    pub trait T {
-        type Item;
-    }
+pub trait T {
+    type Item;
+}
 
-    pub type Alias<'a> = impl T<Item = &'a ()>;
+pub type Alias<'a> = impl T<Item = &'a ()>;
 
-    struct S;
-    impl<'a> T for &'a S {
-        type Item = &'a ();
-    }
+struct S;
+impl<'a> T for &'a S {
+    type Item = &'a ();
+}
 
-    pub fn filter_positive<'a>() -> Alias<'a> {
-        &S
-    }
+#[define_opaque(Alias)]
+pub fn filter_positive<'a>() -> Alias<'a> {
+    &S
 }
-use helper::*;
 
 fn with_positive(fun: impl Fn(Alias<'_>)) {
     fun(filter_positive());
diff --git a/compiler/rustc_codegen_cranelift/patches/0029-stdlib-Disable-f16-and-f128-in-compiler-builtins.patch b/compiler/rustc_codegen_cranelift/patches/0029-stdlib-Disable-f16-and-f128-in-compiler-builtins.patch
index c2027863b00..754025ff49d 100644
--- a/compiler/rustc_codegen_cranelift/patches/0029-stdlib-Disable-f16-and-f128-in-compiler-builtins.patch
+++ b/compiler/rustc_codegen_cranelift/patches/0029-stdlib-Disable-f16-and-f128-in-compiler-builtins.patch
@@ -12,15 +12,15 @@ index 7165c3e48af..968552ad435 100644
 --- a/library/alloc/Cargo.toml
 +++ b/library/alloc/Cargo.toml
 @@ -11,7 +11,7 @@ test = { path = "../test" }
- edition = "2021"
+ bench = false
  
  [dependencies]
  core = { path = "../core", public = true }
 -compiler_builtins = { version = "=0.1.151", features = ['rustc-dep-of-std'] }
 +compiler_builtins = { version = "=0.1.151", features = ['rustc-dep-of-std', 'no-f16-f128'] }
  
- [dev-dependencies]
- rand = { version = "0.8.5", default-features = false, features = ["alloc"] }
+ [features]
+ compiler-builtins-mem = ['compiler_builtins/mem']
 -- 
 2.34.1
 
diff --git a/compiler/rustc_codegen_cranelift/src/lib.rs b/compiler/rustc_codegen_cranelift/src/lib.rs
index a3f43744875..06939beb374 100644
--- a/compiler/rustc_codegen_cranelift/src/lib.rs
+++ b/compiler/rustc_codegen_cranelift/src/lib.rs
@@ -176,13 +176,9 @@ impl CodegenBackend for CraneliftCodegenBackend {
         }
     }
 
-    fn target_features_cfg(
-        &self,
-        sess: &Session,
-        _allow_unstable: bool,
-    ) -> Vec<rustc_span::Symbol> {
+    fn target_features_cfg(&self, sess: &Session) -> (Vec<Symbol>, Vec<Symbol>) {
         // FIXME return the actually used target features. this is necessary for #[cfg(target_feature)]
-        if sess.target.arch == "x86_64" && sess.target.os != "none" {
+        let target_features = if sess.target.arch == "x86_64" && sess.target.os != "none" {
             // x86_64 mandates SSE2 support and rustc requires the x87 feature to be enabled
             vec![sym::fsxr, sym::sse, sym::sse2, Symbol::intern("x87")]
         } else if sess.target.arch == "aarch64" {
@@ -196,7 +192,10 @@ impl CodegenBackend for CraneliftCodegenBackend {
             }
         } else {
             vec![]
-        }
+        };
+        // FIXME do `unstable_target_features` properly
+        let unstable_target_features = target_features.clone();
+        (target_features, unstable_target_features)
     }
 
     fn print_version(&self) {
diff --git a/compiler/rustc_codegen_gcc/src/abi.rs b/compiler/rustc_codegen_gcc/src/abi.rs
index 717baebcd8c..9fe6baa3d25 100644
--- a/compiler/rustc_codegen_gcc/src/abi.rs
+++ b/compiler/rustc_codegen_gcc/src/abi.rs
@@ -16,7 +16,7 @@ use crate::context::CodegenCx;
 use crate::intrinsic::ArgAbiExt;
 use crate::type_of::LayoutGccExt;
 
-impl<'a, 'gcc, 'tcx> AbiBuilderMethods<'tcx> for Builder<'a, 'gcc, 'tcx> {
+impl AbiBuilderMethods for Builder<'_, '_, '_> {
     fn get_param(&mut self, index: usize) -> Self::Value {
         let func = self.current_func();
         let param = func.get_param(index as i32);
diff --git a/compiler/rustc_codegen_gcc/src/builder.rs b/compiler/rustc_codegen_gcc/src/builder.rs
index c8b7616e645..6573b5b165e 100644
--- a/compiler/rustc_codegen_gcc/src/builder.rs
+++ b/compiler/rustc_codegen_gcc/src/builder.rs
@@ -2439,9 +2439,5 @@ fn get_maybe_pointer_size(value: RValue<'_>) -> u32 {
 #[cfg(not(feature = "master"))]
 fn get_maybe_pointer_size(value: RValue<'_>) -> u32 {
     let type_ = value.get_type();
-    if type_.get_pointee().is_some() {
-        std::mem::size_of::<*const ()>() as _
-    } else {
-        type_.get_size()
-    }
+    if type_.get_pointee().is_some() { size_of::<*const ()>() as _ } else { type_.get_size() }
 }
diff --git a/compiler/rustc_codegen_gcc/src/common.rs b/compiler/rustc_codegen_gcc/src/common.rs
index 628e34badf9..a63da6b6e27 100644
--- a/compiler/rustc_codegen_gcc/src/common.rs
+++ b/compiler/rustc_codegen_gcc/src/common.rs
@@ -59,7 +59,7 @@ pub fn type_is_pointer(typ: Type<'_>) -> bool {
     typ.get_pointee().is_some()
 }
 
-impl<'gcc, 'tcx> ConstCodegenMethods<'tcx> for CodegenCx<'gcc, 'tcx> {
+impl<'gcc, 'tcx> ConstCodegenMethods for CodegenCx<'gcc, 'tcx> {
     fn const_null(&self, typ: Type<'gcc>) -> RValue<'gcc> {
         if type_is_pointer(typ) { self.context.new_null(typ) } else { self.const_int(typ, 0) }
     }
@@ -257,7 +257,7 @@ impl<'gcc, 'tcx> ConstCodegenMethods<'tcx> for CodegenCx<'gcc, 'tcx> {
         }
     }
 
-    fn const_data_from_alloc(&self, alloc: ConstAllocation<'tcx>) -> Self::Value {
+    fn const_data_from_alloc(&self, alloc: ConstAllocation<'_>) -> Self::Value {
         const_alloc_to_gcc(self, alloc)
     }
 
diff --git a/compiler/rustc_codegen_gcc/src/consts.rs b/compiler/rustc_codegen_gcc/src/consts.rs
index fb0ca31c543..c514b7a428b 100644
--- a/compiler/rustc_codegen_gcc/src/consts.rs
+++ b/compiler/rustc_codegen_gcc/src/consts.rs
@@ -302,9 +302,9 @@ impl<'gcc, 'tcx> CodegenCx<'gcc, 'tcx> {
     }
 }
 
-pub fn const_alloc_to_gcc<'gcc, 'tcx>(
-    cx: &CodegenCx<'gcc, 'tcx>,
-    alloc: ConstAllocation<'tcx>,
+pub fn const_alloc_to_gcc<'gcc>(
+    cx: &CodegenCx<'gcc, '_>,
+    alloc: ConstAllocation<'_>,
 ) -> RValue<'gcc> {
     let alloc = alloc.inner();
     let mut llvals = Vec::with_capacity(alloc.provenance().ptrs().len() + 1);
diff --git a/compiler/rustc_codegen_gcc/src/gcc_util.rs b/compiler/rustc_codegen_gcc/src/gcc_util.rs
index 4e8c8aaaf5c..6eae0c24f48 100644
--- a/compiler/rustc_codegen_gcc/src/gcc_util.rs
+++ b/compiler/rustc_codegen_gcc/src/gcc_util.rs
@@ -48,7 +48,7 @@ pub(crate) fn global_gcc_features(sess: &Session, diagnostics: bool) -> Vec<Stri
     for feature in sess.opts.cg.target_feature.split(',') {
         if let Some(feature) = feature.strip_prefix('+') {
             all_rust_features.extend(
-                UnordSet::from(sess.target.implied_target_features(std::iter::once(feature)))
+                UnordSet::from(sess.target.implied_target_features(feature))
                     .to_sorted_stable_ord()
                     .iter()
                     .map(|&&s| (true, s)),
diff --git a/compiler/rustc_codegen_gcc/src/lib.rs b/compiler/rustc_codegen_gcc/src/lib.rs
index f090597f953..d478b2af46c 100644
--- a/compiler/rustc_codegen_gcc/src/lib.rs
+++ b/compiler/rustc_codegen_gcc/src/lib.rs
@@ -259,8 +259,8 @@ impl CodegenBackend for GccCodegenBackend {
             .join(sess)
     }
 
-    fn target_features_cfg(&self, sess: &Session, allow_unstable: bool) -> Vec<Symbol> {
-        target_features_cfg(sess, allow_unstable, &self.target_info)
+    fn target_features_cfg(&self, sess: &Session) -> (Vec<Symbol>, Vec<Symbol>) {
+        target_features_cfg(sess, &self.target_info)
     }
 }
 
@@ -486,35 +486,41 @@ fn to_gcc_opt_level(optlevel: Option<OptLevel>) -> OptimizationLevel {
 /// Returns the features that should be set in `cfg(target_feature)`.
 fn target_features_cfg(
     sess: &Session,
-    allow_unstable: bool,
     target_info: &LockedTargetInfo,
-) -> Vec<Symbol> {
+) -> (Vec<Symbol>, Vec<Symbol>) {
     // TODO(antoyo): use global_gcc_features.
-    sess.target
-        .rust_target_features()
-        .iter()
-        .filter_map(|&(feature, gate, _)| {
-            if allow_unstable
-                || (gate.in_cfg() && (sess.is_nightly_build() || gate.requires_nightly().is_none()))
-            {
-                Some(feature)
-            } else {
-                None
-            }
-        })
-        .filter(|feature| {
-            // TODO: we disable Neon for now since we don't support the LLVM intrinsics for it.
-            if *feature == "neon" {
-                return false;
-            }
-            target_info.cpu_supports(feature)
-            /*
-              adx, aes, avx, avx2, avx512bf16, avx512bitalg, avx512bw, avx512cd, avx512dq, avx512er, avx512f, avx512fp16, avx512ifma,
-              avx512pf, avx512vbmi, avx512vbmi2, avx512vl, avx512vnni, avx512vp2intersect, avx512vpopcntdq,
-              bmi1, bmi2, cmpxchg16b, ermsb, f16c, fma, fxsr, gfni, lzcnt, movbe, pclmulqdq, popcnt, rdrand, rdseed, rtm,
-              sha, sse, sse2, sse3, sse4.1, sse4.2, sse4a, ssse3, tbm, vaes, vpclmulqdq, xsave, xsavec, xsaveopt, xsaves
-            */
-        })
-        .map(Symbol::intern)
-        .collect()
+    let f = |allow_unstable| {
+        sess.target
+            .rust_target_features()
+            .iter()
+            .filter_map(|&(feature, gate, _)| {
+                if allow_unstable
+                    || (gate.in_cfg()
+                        && (sess.is_nightly_build() || gate.requires_nightly().is_none()))
+                {
+                    Some(feature)
+                } else {
+                    None
+                }
+            })
+            .filter(|feature| {
+                // TODO: we disable Neon for now since we don't support the LLVM intrinsics for it.
+                if *feature == "neon" {
+                    return false;
+                }
+                target_info.cpu_supports(feature)
+                /*
+                  adx, aes, avx, avx2, avx512bf16, avx512bitalg, avx512bw, avx512cd, avx512dq, avx512er, avx512f, avx512fp16, avx512ifma,
+                  avx512pf, avx512vbmi, avx512vbmi2, avx512vl, avx512vnni, avx512vp2intersect, avx512vpopcntdq,
+                  bmi1, bmi2, cmpxchg16b, ermsb, f16c, fma, fxsr, gfni, lzcnt, movbe, pclmulqdq, popcnt, rdrand, rdseed, rtm,
+                  sha, sse, sse2, sse3, sse4.1, sse4.2, sse4a, ssse3, tbm, vaes, vpclmulqdq, xsave, xsavec, xsaveopt, xsaves
+                */
+            })
+            .map(Symbol::intern)
+            .collect()
+    };
+
+    let target_features = f(false);
+    let unstable_target_features = f(true);
+    (target_features, unstable_target_features)
 }
diff --git a/compiler/rustc_codegen_gcc/src/type_.rs b/compiler/rustc_codegen_gcc/src/type_.rs
index cb08723431a..4e0a250b550 100644
--- a/compiler/rustc_codegen_gcc/src/type_.rs
+++ b/compiler/rustc_codegen_gcc/src/type_.rs
@@ -123,7 +123,7 @@ impl<'gcc, 'tcx> CodegenCx<'gcc, 'tcx> {
     }
 }
 
-impl<'gcc, 'tcx> BaseTypeCodegenMethods<'tcx> for CodegenCx<'gcc, 'tcx> {
+impl<'gcc, 'tcx> BaseTypeCodegenMethods for CodegenCx<'gcc, 'tcx> {
     fn type_i8(&self) -> Type<'gcc> {
         self.i8_type
     }
diff --git a/compiler/rustc_codegen_llvm/src/abi.rs b/compiler/rustc_codegen_llvm/src/abi.rs
index 8c75125e009..71059338151 100644
--- a/compiler/rustc_codegen_llvm/src/abi.rs
+++ b/compiler/rustc_codegen_llvm/src/abi.rs
@@ -654,7 +654,7 @@ impl<'ll, 'tcx> FnAbiLlvmExt<'ll, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
     }
 }
 
-impl<'tcx> AbiBuilderMethods<'tcx> for Builder<'_, '_, 'tcx> {
+impl AbiBuilderMethods for Builder<'_, '_, '_> {
     fn get_param(&mut self, index: usize) -> Self::Value {
         llvm::get_param(self.llfn(), index as c_uint)
     }
diff --git a/compiler/rustc_codegen_llvm/src/allocator.rs b/compiler/rustc_codegen_llvm/src/allocator.rs
index 66723cbf882..e614115f64b 100644
--- a/compiler/rustc_codegen_llvm/src/allocator.rs
+++ b/compiler/rustc_codegen_llvm/src/allocator.rs
@@ -3,33 +3,31 @@ use rustc_ast::expand::allocator::{
     ALLOCATOR_METHODS, AllocatorKind, AllocatorTy, NO_ALLOC_SHIM_IS_UNSTABLE,
     alloc_error_handler_name, default_fn_name, global_fn_name,
 };
+use rustc_codegen_ssa::traits::BaseTypeCodegenMethods as _;
 use rustc_middle::bug;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::config::{DebugInfo, OomStrategy};
 
-use crate::common::AsCCharPtr;
-use crate::llvm::{self, Context, False, Module, True, Type};
-use crate::{ModuleLlvm, attributes, debuginfo};
+use crate::builder::SBuilder;
+use crate::declare::declare_simple_fn;
+use crate::llvm::{self, False, True, Type};
+use crate::{SimpleCx, attributes, debuginfo};
 
 pub(crate) unsafe fn codegen(
     tcx: TyCtxt<'_>,
-    module_llvm: &mut ModuleLlvm,
+    cx: SimpleCx<'_>,
     module_name: &str,
     kind: AllocatorKind,
     alloc_error_handler_kind: AllocatorKind,
 ) {
-    let llcx = &*module_llvm.llcx;
-    let llmod = module_llvm.llmod();
-    let usize = unsafe {
-        match tcx.sess.target.pointer_width {
-            16 => llvm::LLVMInt16TypeInContext(llcx),
-            32 => llvm::LLVMInt32TypeInContext(llcx),
-            64 => llvm::LLVMInt64TypeInContext(llcx),
-            tws => bug!("Unsupported target word size for int: {}", tws),
-        }
+    let usize = match tcx.sess.target.pointer_width {
+        16 => cx.type_i16(),
+        32 => cx.type_i32(),
+        64 => cx.type_i64(),
+        tws => bug!("Unsupported target word size for int: {}", tws),
     };
-    let i8 = unsafe { llvm::LLVMInt8TypeInContext(llcx) };
-    let i8p = unsafe { llvm::LLVMPointerTypeInContext(llcx, 0) };
+    let i8 = cx.type_i8();
+    let i8p = cx.type_ptr();
 
     if kind == AllocatorKind::Default {
         for method in ALLOCATOR_METHODS {
@@ -58,15 +56,14 @@ pub(crate) unsafe fn codegen(
             let from_name = global_fn_name(method.name);
             let to_name = default_fn_name(method.name);
 
-            create_wrapper_function(tcx, llcx, llmod, &from_name, &to_name, &args, output, false);
+            create_wrapper_function(tcx, &cx, &from_name, &to_name, &args, output, false);
         }
     }
 
     // rust alloc error handler
     create_wrapper_function(
         tcx,
-        llcx,
-        llmod,
+        &cx,
         "__rust_alloc_error_handler",
         alloc_error_handler_name(alloc_error_handler_kind),
         &[usize, usize], // size, align
@@ -77,21 +74,21 @@ pub(crate) unsafe fn codegen(
     unsafe {
         // __rust_alloc_error_handler_should_panic
         let name = OomStrategy::SYMBOL;
-        let ll_g = llvm::LLVMRustGetOrInsertGlobal(llmod, name.as_c_char_ptr(), name.len(), i8);
+        let ll_g = cx.declare_global(name, i8);
         llvm::set_visibility(ll_g, llvm::Visibility::from_generic(tcx.sess.default_visibility()));
         let val = tcx.sess.opts.unstable_opts.oom.should_panic();
         let llval = llvm::LLVMConstInt(i8, val as u64, False);
         llvm::set_initializer(ll_g, llval);
 
         let name = NO_ALLOC_SHIM_IS_UNSTABLE;
-        let ll_g = llvm::LLVMRustGetOrInsertGlobal(llmod, name.as_c_char_ptr(), name.len(), i8);
+        let ll_g = cx.declare_global(name, i8);
         llvm::set_visibility(ll_g, llvm::Visibility::from_generic(tcx.sess.default_visibility()));
         let llval = llvm::LLVMConstInt(i8, 0, False);
         llvm::set_initializer(ll_g, llval);
     }
 
     if tcx.sess.opts.debuginfo != DebugInfo::None {
-        let dbg_cx = debuginfo::CodegenUnitDebugContext::new(llmod);
+        let dbg_cx = debuginfo::CodegenUnitDebugContext::new(cx.llmod);
         debuginfo::metadata::build_compile_unit_di_node(tcx, module_name, &dbg_cx);
         dbg_cx.finalize(tcx.sess);
     }
@@ -99,77 +96,64 @@ pub(crate) unsafe fn codegen(
 
 fn create_wrapper_function(
     tcx: TyCtxt<'_>,
-    llcx: &Context,
-    llmod: &Module,
+    cx: &SimpleCx<'_>,
     from_name: &str,
     to_name: &str,
     args: &[&Type],
     output: Option<&Type>,
     no_return: bool,
 ) {
-    unsafe {
-        let ty = llvm::LLVMFunctionType(
-            output.unwrap_or_else(|| llvm::LLVMVoidTypeInContext(llcx)),
-            args.as_ptr(),
-            args.len() as c_uint,
-            False,
-        );
-        let llfn = llvm::LLVMRustGetOrInsertFunction(
-            llmod,
-            from_name.as_c_char_ptr(),
-            from_name.len(),
-            ty,
-        );
-        let no_return = if no_return {
-            // -> ! DIFlagNoReturn
-            let no_return = llvm::AttributeKind::NoReturn.create_attr(llcx);
-            attributes::apply_to_llfn(llfn, llvm::AttributePlace::Function, &[no_return]);
-            Some(no_return)
-        } else {
-            None
-        };
-
-        llvm::set_visibility(llfn, llvm::Visibility::from_generic(tcx.sess.default_visibility()));
-
-        if tcx.sess.must_emit_unwind_tables() {
-            let uwtable =
-                attributes::uwtable_attr(llcx, tcx.sess.opts.unstable_opts.use_sync_unwind);
-            attributes::apply_to_llfn(llfn, llvm::AttributePlace::Function, &[uwtable]);
-        }
+    let ty = cx.type_func(args, output.unwrap_or_else(|| cx.type_void()));
+    let llfn = declare_simple_fn(
+        &cx,
+        from_name,
+        llvm::CallConv::CCallConv,
+        llvm::UnnamedAddr::Global,
+        llvm::Visibility::from_generic(tcx.sess.default_visibility()),
+        ty,
+    );
+    let no_return = if no_return {
+        // -> ! DIFlagNoReturn
+        let no_return = llvm::AttributeKind::NoReturn.create_attr(cx.llcx);
+        attributes::apply_to_llfn(llfn, llvm::AttributePlace::Function, &[no_return]);
+        Some(no_return)
+    } else {
+        None
+    };
 
-        let callee =
-            llvm::LLVMRustGetOrInsertFunction(llmod, to_name.as_c_char_ptr(), to_name.len(), ty);
-        if let Some(no_return) = no_return {
-            // -> ! DIFlagNoReturn
-            attributes::apply_to_llfn(callee, llvm::AttributePlace::Function, &[no_return]);
-        }
-        llvm::set_visibility(callee, llvm::Visibility::Hidden);
-
-        let llbb = llvm::LLVMAppendBasicBlockInContext(llcx, llfn, c"entry".as_ptr());
-
-        let llbuilder = llvm::LLVMCreateBuilderInContext(llcx);
-        llvm::LLVMPositionBuilderAtEnd(llbuilder, llbb);
-        let args = args
-            .iter()
-            .enumerate()
-            .map(|(i, _)| llvm::LLVMGetParam(llfn, i as c_uint))
-            .collect::<Vec<_>>();
-        let ret = llvm::LLVMBuildCallWithOperandBundles(
-            llbuilder,
-            ty,
-            callee,
-            args.as_ptr(),
-            args.len() as c_uint,
-            [].as_ptr(),
-            0 as c_uint,
-            c"".as_ptr(),
-        );
-        llvm::LLVMSetTailCall(ret, True);
-        if output.is_some() {
-            llvm::LLVMBuildRet(llbuilder, ret);
-        } else {
-            llvm::LLVMBuildRetVoid(llbuilder);
-        }
-        llvm::LLVMDisposeBuilder(llbuilder);
+    if tcx.sess.must_emit_unwind_tables() {
+        let uwtable =
+            attributes::uwtable_attr(cx.llcx, tcx.sess.opts.unstable_opts.use_sync_unwind);
+        attributes::apply_to_llfn(llfn, llvm::AttributePlace::Function, &[uwtable]);
+    }
+
+    let callee = declare_simple_fn(
+        &cx,
+        to_name,
+        llvm::CallConv::CCallConv,
+        llvm::UnnamedAddr::Global,
+        llvm::Visibility::Hidden,
+        ty,
+    );
+    if let Some(no_return) = no_return {
+        // -> ! DIFlagNoReturn
+        attributes::apply_to_llfn(callee, llvm::AttributePlace::Function, &[no_return]);
+    }
+    llvm::set_visibility(callee, llvm::Visibility::Hidden);
+
+    let llbb = unsafe { llvm::LLVMAppendBasicBlockInContext(cx.llcx, llfn, c"entry".as_ptr()) };
+
+    let mut bx = SBuilder::build(&cx, llbb);
+    let args = args
+        .iter()
+        .enumerate()
+        .map(|(i, _)| llvm::get_param(llfn, i as c_uint))
+        .collect::<Vec<_>>();
+    let ret = bx.call(ty, callee, &args, None);
+    llvm::LLVMSetTailCall(ret, True);
+    if output.is_some() {
+        bx.ret(ret);
+    } else {
+        bx.ret_void()
     }
 }
diff --git a/compiler/rustc_codegen_llvm/src/asm.rs b/compiler/rustc_codegen_llvm/src/asm.rs
index e8a69743157..88daa025740 100644
--- a/compiler/rustc_codegen_llvm/src/asm.rs
+++ b/compiler/rustc_codegen_llvm/src/asm.rs
@@ -1,6 +1,5 @@
 use std::assert_matches::assert_matches;
 
-use libc::{c_char, c_uint};
 use rustc_abi::{BackendRepr, Float, Integer, Primitive, Scalar};
 use rustc_ast::{InlineAsmOptions, InlineAsmTemplatePiece};
 use rustc_codegen_ssa::mir::operand::OperandValue;
@@ -483,12 +482,13 @@ pub(crate) fn inline_asm_call<'ll>(
 
     debug!("Asm Output Type: {:?}", output);
     let fty = bx.cx.type_func(&argtys, output);
-    unsafe {
-        // Ask LLVM to verify that the constraints are well-formed.
-        let constraints_ok = llvm::LLVMRustInlineAsmVerify(fty, cons.as_c_char_ptr(), cons.len());
-        debug!("constraint verification result: {:?}", constraints_ok);
-        if constraints_ok {
-            let v = llvm::LLVMRustInlineAsm(
+    // Ask LLVM to verify that the constraints are well-formed.
+    let constraints_ok =
+        unsafe { llvm::LLVMRustInlineAsmVerify(fty, cons.as_c_char_ptr(), cons.len()) };
+    debug!("constraint verification result: {:?}", constraints_ok);
+    if constraints_ok {
+        let v = unsafe {
+            llvm::LLVMRustInlineAsm(
                 fty,
                 asm.as_c_char_ptr(),
                 asm.len(),
@@ -498,54 +498,50 @@ pub(crate) fn inline_asm_call<'ll>(
                 alignstack,
                 dia,
                 can_throw,
-            );
-
-            let call = if !labels.is_empty() {
-                assert!(catch_funclet.is_none());
-                bx.callbr(fty, None, None, v, inputs, dest.unwrap(), labels, None, None)
-            } else if let Some((catch, funclet)) = catch_funclet {
-                bx.invoke(fty, None, None, v, inputs, dest.unwrap(), catch, funclet, None)
-            } else {
-                bx.call(fty, None, None, v, inputs, None, None)
-            };
+            )
+        };
 
-            // Store mark in a metadata node so we can map LLVM errors
-            // back to source locations. See #17552.
-            let key = "srcloc";
-            let kind = llvm::LLVMGetMDKindIDInContext(
-                bx.llcx,
-                key.as_ptr().cast::<c_char>(),
-                key.len() as c_uint,
-            );
+        let call = if !labels.is_empty() {
+            assert!(catch_funclet.is_none());
+            bx.callbr(fty, None, None, v, inputs, dest.unwrap(), labels, None, None)
+        } else if let Some((catch, funclet)) = catch_funclet {
+            bx.invoke(fty, None, None, v, inputs, dest.unwrap(), catch, funclet, None)
+        } else {
+            bx.call(fty, None, None, v, inputs, None, None)
+        };
 
-            // `srcloc` contains one 64-bit integer for each line of assembly code,
-            // where the lower 32 bits hold the lo byte position and the upper 32 bits
-            // hold the hi byte position.
-            let mut srcloc = vec![];
-            if dia == llvm::AsmDialect::Intel && line_spans.len() > 1 {
-                // LLVM inserts an extra line to add the ".intel_syntax", so add
-                // a dummy srcloc entry for it.
-                //
-                // Don't do this if we only have 1 line span since that may be
-                // due to the asm template string coming from a macro. LLVM will
-                // default to the first srcloc for lines that don't have an
-                // associated srcloc.
-                srcloc.push(llvm::LLVMValueAsMetadata(bx.const_u64(0)));
-            }
-            srcloc.extend(line_spans.iter().map(|span| {
-                llvm::LLVMValueAsMetadata(bx.const_u64(
-                    u64::from(span.lo().to_u32()) | (u64::from(span.hi().to_u32()) << 32),
-                ))
-            }));
-            let md = llvm::LLVMMDNodeInContext2(bx.llcx, srcloc.as_ptr(), srcloc.len());
-            let md = llvm::LLVMMetadataAsValue(&bx.llcx, md);
-            llvm::LLVMSetMetadata(call, kind, md);
+        // Store mark in a metadata node so we can map LLVM errors
+        // back to source locations. See #17552.
+        let key = "srcloc";
+        let kind = bx.get_md_kind_id(key);
 
-            Some(call)
-        } else {
-            // LLVM has detected an issue with our constraints, bail out
-            None
+        // `srcloc` contains one 64-bit integer for each line of assembly code,
+        // where the lower 32 bits hold the lo byte position and the upper 32 bits
+        // hold the hi byte position.
+        let mut srcloc = vec![];
+        if dia == llvm::AsmDialect::Intel && line_spans.len() > 1 {
+            // LLVM inserts an extra line to add the ".intel_syntax", so add
+            // a dummy srcloc entry for it.
+            //
+            // Don't do this if we only have 1 line span since that may be
+            // due to the asm template string coming from a macro. LLVM will
+            // default to the first srcloc for lines that don't have an
+            // associated srcloc.
+            srcloc.push(llvm::LLVMValueAsMetadata(bx.const_u64(0)));
         }
+        srcloc.extend(line_spans.iter().map(|span| {
+            llvm::LLVMValueAsMetadata(
+                bx.const_u64(u64::from(span.lo().to_u32()) | (u64::from(span.hi().to_u32()) << 32)),
+            )
+        }));
+        let md = unsafe { llvm::LLVMMDNodeInContext2(bx.llcx, srcloc.as_ptr(), srcloc.len()) };
+        let md = bx.get_metadata_value(md);
+        llvm::LLVMSetMetadata(call, kind, md);
+
+        Some(call)
+    } else {
+        // LLVM has detected an issue with our constraints, bail out
+        None
     }
 }
 
diff --git a/compiler/rustc_codegen_llvm/src/builder.rs b/compiler/rustc_codegen_llvm/src/builder.rs
index 3f20350d0ef..55d34f5f2ef 100644
--- a/compiler/rustc_codegen_llvm/src/builder.rs
+++ b/compiler/rustc_codegen_llvm/src/builder.rs
@@ -30,7 +30,7 @@ use tracing::{debug, instrument};
 
 use crate::abi::FnAbiLlvmExt;
 use crate::common::Funclet;
-use crate::context::{CodegenCx, SimpleCx};
+use crate::context::{CodegenCx, FullCx, GenericCx, SCx};
 use crate::llvm::{
     self, AtomicOrdering, AtomicRmwBinOp, BasicBlock, False, GEPNoWrapFlags, Metadata, True,
 };
@@ -40,15 +40,15 @@ use crate::value::Value;
 use crate::{attributes, llvm_util};
 
 #[must_use]
-pub(crate) struct GenericBuilder<'a, 'll, CX: Borrow<SimpleCx<'ll>>> {
+pub(crate) struct GenericBuilder<'a, 'll, CX: Borrow<SCx<'ll>>> {
     pub llbuilder: &'ll mut llvm::Builder<'ll>,
-    pub cx: &'a CX,
+    pub cx: &'a GenericCx<'ll, CX>,
 }
 
-pub(crate) type SBuilder<'a, 'll> = GenericBuilder<'a, 'll, SimpleCx<'ll>>;
-pub(crate) type Builder<'a, 'll, 'tcx> = GenericBuilder<'a, 'll, CodegenCx<'ll, 'tcx>>;
+pub(crate) type SBuilder<'a, 'll> = GenericBuilder<'a, 'll, SCx<'ll>>;
+pub(crate) type Builder<'a, 'll, 'tcx> = GenericBuilder<'a, 'll, FullCx<'ll, 'tcx>>;
 
-impl<'a, 'll, CX: Borrow<SimpleCx<'ll>>> Drop for GenericBuilder<'a, 'll, CX> {
+impl<'a, 'll, CX: Borrow<SCx<'ll>>> Drop for GenericBuilder<'a, 'll, CX> {
     fn drop(&mut self) {
         unsafe {
             llvm::LLVMDisposeBuilder(&mut *(self.llbuilder as *mut _));
@@ -57,7 +57,7 @@ impl<'a, 'll, CX: Borrow<SimpleCx<'ll>>> Drop for GenericBuilder<'a, 'll, CX> {
 }
 
 impl<'a, 'll> SBuilder<'a, 'll> {
-    fn call(
+    pub(crate) fn call(
         &mut self,
         llty: &'ll Type,
         llfn: &'ll Value,
@@ -87,79 +87,36 @@ impl<'a, 'll> SBuilder<'a, 'll> {
         };
         call
     }
+}
 
-    fn with_scx(scx: &'a SimpleCx<'ll>) -> Self {
+impl<'a, 'll, CX: Borrow<SCx<'ll>>> GenericBuilder<'a, 'll, CX> {
+    fn with_cx(scx: &'a GenericCx<'ll, CX>) -> Self {
         // Create a fresh builder from the simple context.
-        let llbuilder = unsafe { llvm::LLVMCreateBuilderInContext(scx.llcx) };
-        SBuilder { llbuilder, cx: scx }
+        let llbuilder = unsafe { llvm::LLVMCreateBuilderInContext(scx.deref().borrow().llcx) };
+        GenericBuilder { llbuilder, cx: scx }
     }
-}
-impl<'a, 'll, CX: Borrow<SimpleCx<'ll>>> GenericBuilder<'a, 'll, CX> {
+
     pub(crate) fn bitcast(&mut self, val: &'ll Value, dest_ty: &'ll Type) -> &'ll Value {
         unsafe { llvm::LLVMBuildBitCast(self.llbuilder, val, dest_ty, UNNAMED) }
     }
 
-    fn ret_void(&mut self) {
-        unsafe {
-            llvm::LLVMBuildRetVoid(self.llbuilder);
-        }
+    pub(crate) fn ret_void(&mut self) {
+        llvm::LLVMBuildRetVoid(self.llbuilder);
     }
 
-    fn ret(&mut self, v: &'ll Value) {
+    pub(crate) fn ret(&mut self, v: &'ll Value) {
         unsafe {
             llvm::LLVMBuildRet(self.llbuilder, v);
         }
     }
-}
-impl<'a, 'll> SBuilder<'a, 'll> {
-    fn build(cx: &'a SimpleCx<'ll>, llbb: &'ll BasicBlock) -> SBuilder<'a, 'll> {
-        let bx = SBuilder::with_scx(cx);
+
+    pub(crate) fn build(cx: &'a GenericCx<'ll, CX>, llbb: &'ll BasicBlock) -> Self {
+        let bx = Self::with_cx(cx);
         unsafe {
             llvm::LLVMPositionBuilderAtEnd(bx.llbuilder, llbb);
         }
         bx
     }
-
-    fn check_call<'b>(
-        &mut self,
-        typ: &str,
-        fn_ty: &'ll Type,
-        llfn: &'ll Value,
-        args: &'b [&'ll Value],
-    ) -> Cow<'b, [&'ll Value]> {
-        assert!(
-            self.cx.type_kind(fn_ty) == TypeKind::Function,
-            "builder::{typ} not passed a function, but {fn_ty:?}"
-        );
-
-        let param_tys = self.cx.func_params_types(fn_ty);
-
-        let all_args_match = iter::zip(&param_tys, args.iter().map(|&v| self.cx.val_ty(v)))
-            .all(|(expected_ty, actual_ty)| *expected_ty == actual_ty);
-
-        if all_args_match {
-            return Cow::Borrowed(args);
-        }
-
-        let casted_args: Vec<_> = iter::zip(param_tys, args)
-            .enumerate()
-            .map(|(i, (expected_ty, &actual_val))| {
-                let actual_ty = self.cx.val_ty(actual_val);
-                if expected_ty != actual_ty {
-                    debug!(
-                        "type mismatch in function call of {:?}. \
-                            Expected {:?} for param {}, got {:?}; injecting bitcast",
-                        llfn, expected_ty, i, actual_ty
-                    );
-                    self.bitcast(actual_val, expected_ty)
-                } else {
-                    actual_val
-                }
-            })
-            .collect();
-
-        Cow::Owned(casted_args)
-    }
 }
 
 /// Empty string, to be used where LLVM expects an instruction name, indicating
@@ -167,17 +124,17 @@ impl<'a, 'll> SBuilder<'a, 'll> {
 // FIXME(eddyb) pass `&CStr` directly to FFI once it's a thin pointer.
 const UNNAMED: *const c_char = c"".as_ptr();
 
-impl<'ll, 'tcx> BackendTypes for Builder<'_, 'll, 'tcx> {
-    type Value = <CodegenCx<'ll, 'tcx> as BackendTypes>::Value;
-    type Metadata = <CodegenCx<'ll, 'tcx> as BackendTypes>::Metadata;
-    type Function = <CodegenCx<'ll, 'tcx> as BackendTypes>::Function;
-    type BasicBlock = <CodegenCx<'ll, 'tcx> as BackendTypes>::BasicBlock;
-    type Type = <CodegenCx<'ll, 'tcx> as BackendTypes>::Type;
-    type Funclet = <CodegenCx<'ll, 'tcx> as BackendTypes>::Funclet;
-
-    type DIScope = <CodegenCx<'ll, 'tcx> as BackendTypes>::DIScope;
-    type DILocation = <CodegenCx<'ll, 'tcx> as BackendTypes>::DILocation;
-    type DIVariable = <CodegenCx<'ll, 'tcx> as BackendTypes>::DIVariable;
+impl<'ll, CX: Borrow<SCx<'ll>>> BackendTypes for GenericBuilder<'_, 'll, CX> {
+    type Value = <GenericCx<'ll, CX> as BackendTypes>::Value;
+    type Metadata = <GenericCx<'ll, CX> as BackendTypes>::Metadata;
+    type Function = <GenericCx<'ll, CX> as BackendTypes>::Function;
+    type BasicBlock = <GenericCx<'ll, CX> as BackendTypes>::BasicBlock;
+    type Type = <GenericCx<'ll, CX> as BackendTypes>::Type;
+    type Funclet = <GenericCx<'ll, CX> as BackendTypes>::Funclet;
+
+    type DIScope = <GenericCx<'ll, CX> as BackendTypes>::DIScope;
+    type DILocation = <GenericCx<'ll, CX> as BackendTypes>::DILocation;
+    type DIVariable = <GenericCx<'ll, CX> as BackendTypes>::DIVariable;
 }
 
 impl abi::HasDataLayout for Builder<'_, '_, '_> {
@@ -293,9 +250,7 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
     }
 
     fn ret_void(&mut self) {
-        unsafe {
-            llvm::LLVMBuildRetVoid(self.llbuilder);
-        }
+        llvm::LLVMBuildRetVoid(self.llbuilder);
     }
 
     fn ret(&mut self, v: &'ll Value) {
@@ -356,8 +311,8 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         // This function handles switch instructions with more than 2 targets and it needs to
         // emit branch weights metadata instead of using the intrinsic.
         // The values 1 and 2000 are the same as the values used by the `llvm.expect` intrinsic.
-        let cold_weight = unsafe { llvm::LLVMValueAsMetadata(self.cx.const_u32(1)) };
-        let hot_weight = unsafe { llvm::LLVMValueAsMetadata(self.cx.const_u32(2000)) };
+        let cold_weight = llvm::LLVMValueAsMetadata(self.cx.const_u32(1));
+        let hot_weight = llvm::LLVMValueAsMetadata(self.cx.const_u32(2000));
         let weight =
             |is_cold: bool| -> &Metadata { if is_cold { cold_weight } else { hot_weight } };
 
@@ -1476,26 +1431,12 @@ impl<'ll> StaticBuilderMethods for Builder<'_, 'll, '_> {
 }
 
 impl<'a, 'll, 'tcx> Builder<'a, 'll, 'tcx> {
-    fn build(cx: &'a CodegenCx<'ll, 'tcx>, llbb: &'ll BasicBlock) -> Builder<'a, 'll, 'tcx> {
-        let bx = Builder::with_cx(cx);
-        unsafe {
-            llvm::LLVMPositionBuilderAtEnd(bx.llbuilder, llbb);
-        }
-        bx
-    }
-
-    fn with_cx(cx: &'a CodegenCx<'ll, 'tcx>) -> Self {
-        // Create a fresh builder from the crate context.
-        let llbuilder = unsafe { llvm::LLVMCreateBuilderInContext(cx.llcx) };
-        Builder { llbuilder, cx }
-    }
-
     pub(crate) fn llfn(&self) -> &'ll Value {
         unsafe { llvm::LLVMGetBasicBlockParent(self.llbb()) }
     }
 }
 
-impl<'a, 'll, CX: Borrow<SimpleCx<'ll>>> GenericBuilder<'a, 'll, CX> {
+impl<'a, 'll, CX: Borrow<SCx<'ll>>> GenericBuilder<'a, 'll, CX> {
     fn position_at_start(&mut self, llbb: &'ll BasicBlock) {
         unsafe {
             llvm::LLVMRustPositionBuilderAtStart(self.llbuilder, llbb);
@@ -1525,7 +1466,7 @@ impl<'a, 'll, 'tcx> Builder<'a, 'll, 'tcx> {
         }
     }
 }
-impl<'a, 'll, CX: Borrow<SimpleCx<'ll>>> GenericBuilder<'a, 'll, CX> {
+impl<'a, 'll, CX: Borrow<SCx<'ll>>> GenericBuilder<'a, 'll, CX> {
     pub(crate) fn minnum(&mut self, lhs: &'ll Value, rhs: &'ll Value) -> &'ll Value {
         unsafe { llvm::LLVMRustBuildMinNum(self.llbuilder, lhs, rhs) }
     }
@@ -1626,9 +1567,7 @@ impl<'a, 'll, CX: Borrow<SimpleCx<'ll>>> GenericBuilder<'a, 'll, CX> {
         let ret = unsafe { llvm::LLVMBuildCatchRet(self.llbuilder, funclet.cleanuppad(), unwind) };
         ret.expect("LLVM does not have support for catchret")
     }
-}
 
-impl<'a, 'll, 'tcx> Builder<'a, 'll, 'tcx> {
     fn check_call<'b>(
         &mut self,
         typ: &str,
@@ -1643,7 +1582,7 @@ impl<'a, 'll, 'tcx> Builder<'a, 'll, 'tcx> {
 
         let param_tys = self.cx.func_params_types(fn_ty);
 
-        let all_args_match = iter::zip(&param_tys, args.iter().map(|&v| self.val_ty(v)))
+        let all_args_match = iter::zip(&param_tys, args.iter().map(|&v| self.cx.val_ty(v)))
             .all(|(expected_ty, actual_ty)| *expected_ty == actual_ty);
 
         if all_args_match {
@@ -1653,7 +1592,7 @@ impl<'a, 'll, 'tcx> Builder<'a, 'll, 'tcx> {
         let casted_args: Vec<_> = iter::zip(param_tys, args)
             .enumerate()
             .map(|(i, (expected_ty, &actual_val))| {
-                let actual_ty = self.val_ty(actual_val);
+                let actual_ty = self.cx.val_ty(actual_val);
                 if expected_ty != actual_ty {
                     debug!(
                         "type mismatch in function call of {:?}. \
@@ -1669,12 +1608,12 @@ impl<'a, 'll, 'tcx> Builder<'a, 'll, 'tcx> {
 
         Cow::Owned(casted_args)
     }
-}
-impl<'a, 'll, CX: Borrow<SimpleCx<'ll>>> GenericBuilder<'a, 'll, CX> {
+
     pub(crate) fn va_arg(&mut self, list: &'ll Value, ty: &'ll Type) -> &'ll Value {
         unsafe { llvm::LLVMBuildVAArg(self.llbuilder, list, ty, UNNAMED) }
     }
 }
+
 impl<'a, 'll, 'tcx> Builder<'a, 'll, 'tcx> {
     pub(crate) fn call_intrinsic(&mut self, intrinsic: &str, args: &[&'ll Value]) -> &'ll Value {
         let (ty, f) = self.cx.get_intrinsic(intrinsic);
@@ -1694,7 +1633,7 @@ impl<'a, 'll, 'tcx> Builder<'a, 'll, 'tcx> {
         self.call_intrinsic(intrinsic, &[self.cx.const_u64(size), ptr]);
     }
 }
-impl<'a, 'll, CX: Borrow<SimpleCx<'ll>>> GenericBuilder<'a, 'll, CX> {
+impl<'a, 'll, CX: Borrow<SCx<'ll>>> GenericBuilder<'a, 'll, CX> {
     pub(crate) fn phi(
         &mut self,
         ty: &'ll Type,
diff --git a/compiler/rustc_codegen_llvm/src/builder/autodiff.rs b/compiler/rustc_codegen_llvm/src/builder/autodiff.rs
index 2c7899975e3..71705ecb4d0 100644
--- a/compiler/rustc_codegen_llvm/src/builder/autodiff.rs
+++ b/compiler/rustc_codegen_llvm/src/builder/autodiff.rs
@@ -3,6 +3,7 @@ use std::ptr;
 use rustc_ast::expand::autodiff_attrs::{AutoDiffAttrs, AutoDiffItem, DiffActivity, DiffMode};
 use rustc_codegen_ssa::ModuleCodegen;
 use rustc_codegen_ssa::back::write::ModuleConfig;
+use rustc_codegen_ssa::traits::BaseTypeCodegenMethods as _;
 use rustc_errors::FatalError;
 use tracing::{debug, trace};
 
@@ -286,7 +287,8 @@ pub(crate) fn differentiate<'ll>(
     }
 
     let diag_handler = cgcx.create_dcx();
-    let cx = SimpleCx { llmod: module.module_llvm.llmod(), llcx: module.module_llvm.llcx };
+
+    let cx = SimpleCx::new(module.module_llvm.llmod(), module.module_llvm.llcx, cgcx.pointer_size);
 
     // First of all, did the user try to use autodiff without using the -Zautodiff=Enable flag?
     if !diff_items.is_empty()
diff --git a/compiler/rustc_codegen_llvm/src/common.rs b/compiler/rustc_codegen_llvm/src/common.rs
index f264e3419e4..457e5452ce9 100644
--- a/compiler/rustc_codegen_llvm/src/common.rs
+++ b/compiler/rustc_codegen_llvm/src/common.rs
@@ -1,5 +1,7 @@
 //! Code that is useful in various codegen modules.
 
+use std::borrow::Borrow;
+
 use libc::{c_char, c_uint};
 use rustc_abi as abi;
 use rustc_abi::Primitive::Pointer;
@@ -18,6 +20,7 @@ use tracing::debug;
 
 use crate::consts::const_alloc_to_llvm;
 pub(crate) use crate::context::CodegenCx;
+use crate::context::{GenericCx, SCx};
 use crate::llvm::{self, BasicBlock, Bool, ConstantInt, False, Metadata, True};
 use crate::type_::Type;
 use crate::value::Value;
@@ -81,7 +84,7 @@ impl<'ll> Funclet<'ll> {
     }
 }
 
-impl<'ll> BackendTypes for CodegenCx<'ll, '_> {
+impl<'ll, CX: Borrow<SCx<'ll>>> BackendTypes for GenericCx<'ll, CX> {
     type Value = &'ll Value;
     type Metadata = &'ll Metadata;
     // FIXME(eddyb) replace this with a `Function` "subclass" of `Value`.
@@ -118,7 +121,7 @@ impl<'ll> CodegenCx<'ll, '_> {
     }
 }
 
-impl<'ll, 'tcx> ConstCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
+impl<'ll, 'tcx> ConstCodegenMethods for CodegenCx<'ll, 'tcx> {
     fn const_null(&self, t: &'ll Type) -> &'ll Value {
         unsafe { llvm::LLVMConstNull(t) }
     }
@@ -342,7 +345,7 @@ impl<'ll, 'tcx> ConstCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
         }
     }
 
-    fn const_data_from_alloc(&self, alloc: ConstAllocation<'tcx>) -> Self::Value {
+    fn const_data_from_alloc(&self, alloc: ConstAllocation<'_>) -> Self::Value {
         const_alloc_to_llvm(self, alloc, /*static*/ false)
     }
 
diff --git a/compiler/rustc_codegen_llvm/src/consts.rs b/compiler/rustc_codegen_llvm/src/consts.rs
index 330e8a8f406..a4e5749b3ac 100644
--- a/compiler/rustc_codegen_llvm/src/consts.rs
+++ b/compiler/rustc_codegen_llvm/src/consts.rs
@@ -16,7 +16,6 @@ use rustc_middle::mir::mono::MonoItem;
 use rustc_middle::ty::Instance;
 use rustc_middle::ty::layout::{HasTypingEnv, LayoutOf};
 use rustc_middle::{bug, span_bug};
-use rustc_session::config::Lto;
 use tracing::{debug, instrument, trace};
 
 use crate::common::{AsCCharPtr, CodegenCx};
@@ -344,11 +343,11 @@ impl<'ll> CodegenCx<'ll, '_> {
                 // Local definitions can never be imported, so we must not apply
                 // the DLLImport annotation.
                 && !dso_local
-                // ThinLTO can't handle this workaround in all cases, so we don't
-                // emit the attrs. Instead we make them unnecessary by disallowing
-                // dynamic linking when linker plugin based LTO is enabled.
-                && !self.tcx.sess.opts.cg.linker_plugin_lto.enabled()
-                && self.tcx.sess.lto() != Lto::Thin;
+                // Linker plugin ThinLTO doesn't create the self-dllimport Rust uses for rlibs
+                // as the code generation happens out of process. Instead we assume static linkage
+                // and disallow dynamic linking when linker plugin based LTO is enabled.
+                // Regular in-process ThinLTO doesn't need this workaround.
+                && !self.tcx.sess.opts.cg.linker_plugin_lto.enabled();
 
             // If this assertion triggers, there's something wrong with commandline
             // argument validation.
@@ -490,7 +489,7 @@ impl<'ll> CodegenCx<'ll, '_> {
                         llvm::LLVMMDStringInContext2(self.llcx, bytes.as_c_char_ptr(), bytes.len());
                     let data = [section, alloc];
                     let meta = llvm::LLVMMDNodeInContext2(self.llcx, data.as_ptr(), data.len());
-                    let val = llvm::LLVMMetadataAsValue(self.llcx, meta);
+                    let val = self.get_metadata_value(meta);
                     llvm::LLVMAddNamedMetadataOperand(
                         self.llmod,
                         c"wasm.custom_sections".as_ptr(),
diff --git a/compiler/rustc_codegen_llvm/src/context.rs b/compiler/rustc_codegen_llvm/src/context.rs
index ed8426ae197..9f8ec0ea526 100644
--- a/compiler/rustc_codegen_llvm/src/context.rs
+++ b/compiler/rustc_codegen_llvm/src/context.rs
@@ -1,13 +1,13 @@
 use std::borrow::Borrow;
 use std::cell::{Cell, RefCell};
 use std::ffi::{CStr, c_char, c_uint};
+use std::marker::PhantomData;
 use std::ops::Deref;
 use std::str;
 
-use rustc_abi::{HasDataLayout, TargetDataLayout, VariantIdx};
+use rustc_abi::{HasDataLayout, Size, TargetDataLayout, VariantIdx};
 use rustc_codegen_ssa::back::versioned_llvm_target;
 use rustc_codegen_ssa::base::{wants_msvc_seh, wants_wasm_eh};
-use rustc_codegen_ssa::common::TypeKind;
 use rustc_codegen_ssa::errors as ssa_errors;
 use rustc_codegen_ssa::traits::*;
 use rustc_data_structures::base_n::{ALPHANUMERIC_ONLY, ToBaseN};
@@ -32,9 +32,9 @@ use smallvec::SmallVec;
 
 use crate::back::write::to_llvm_code_model;
 use crate::callee::get_fn;
-use crate::common::{self, AsCCharPtr};
+use crate::common::AsCCharPtr;
 use crate::debuginfo::metadata::apply_vcall_visibility_metadata;
-use crate::llvm::{Metadata, MetadataType};
+use crate::llvm::Metadata;
 use crate::type_::Type;
 use crate::value::Value;
 use crate::{attributes, coverageinfo, debuginfo, llvm, llvm_util};
@@ -43,18 +43,19 @@ use crate::{attributes, coverageinfo, debuginfo, llvm, llvm_util};
 /// However, there are various cx related functions which we want to be available to the builder and
 /// other compiler pieces. Here we define a small subset which has enough information and can be
 /// moved around more freely.
-pub(crate) struct SimpleCx<'ll> {
+pub(crate) struct SCx<'ll> {
     pub llmod: &'ll llvm::Module,
     pub llcx: &'ll llvm::Context,
+    pub isize_ty: &'ll Type,
 }
 
-impl<'ll> Borrow<SimpleCx<'ll>> for CodegenCx<'ll, '_> {
-    fn borrow(&self) -> &SimpleCx<'ll> {
+impl<'ll> Borrow<SCx<'ll>> for FullCx<'ll, '_> {
+    fn borrow(&self) -> &SCx<'ll> {
         &self.scx
     }
 }
 
-impl<'ll, 'tcx> Deref for CodegenCx<'ll, 'tcx> {
+impl<'ll, 'tcx> Deref for FullCx<'ll, 'tcx> {
     type Target = SimpleCx<'ll>;
 
     #[inline]
@@ -63,10 +64,25 @@ impl<'ll, 'tcx> Deref for CodegenCx<'ll, 'tcx> {
     }
 }
 
+pub(crate) struct GenericCx<'ll, T: Borrow<SCx<'ll>>>(T, PhantomData<SCx<'ll>>);
+
+impl<'ll, T: Borrow<SCx<'ll>>> Deref for GenericCx<'ll, T> {
+    type Target = T;
+
+    #[inline]
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+pub(crate) type SimpleCx<'ll> = GenericCx<'ll, SCx<'ll>>;
+
 /// There is one `CodegenCx` per codegen unit. Each one has its own LLVM
 /// `llvm::Context` so that several codegen units may be processed in parallel.
 /// All other LLVM data structures in the `CodegenCx` are tied to that `llvm::Context`.
-pub(crate) struct CodegenCx<'ll, 'tcx> {
+pub(crate) type CodegenCx<'ll, 'tcx> = GenericCx<'ll, FullCx<'ll, 'tcx>>;
+
+pub(crate) struct FullCx<'ll, 'tcx> {
     pub tcx: TyCtxt<'tcx>,
     pub scx: SimpleCx<'ll>,
     pub use_dll_storage_attrs: bool,
@@ -104,8 +120,6 @@ pub(crate) struct CodegenCx<'ll, 'tcx> {
     /// Mapping of scalar types to llvm types.
     pub scalar_lltypes: RefCell<FxHashMap<Ty<'tcx>, &'ll Type>>,
 
-    pub isize_ty: &'ll Type,
-
     /// Extra per-CGU codegen state needed when coverage instrumentation is enabled.
     pub coverage_cx: Option<coverageinfo::CguCoverageContext<'ll, 'tcx>>,
     pub dbg_cx: Option<debuginfo::CodegenUnitDebugContext<'ll, 'tcx>>,
@@ -579,33 +593,33 @@ impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {
             None
         };
 
-        let isize_ty = Type::ix_llcx(llcx, tcx.data_layout.pointer_size.bits());
-
-        CodegenCx {
-            tcx,
-            scx: SimpleCx { llcx, llmod },
-            use_dll_storage_attrs,
-            tls_model,
-            codegen_unit,
-            instances: Default::default(),
-            vtables: Default::default(),
-            const_str_cache: Default::default(),
-            const_globals: Default::default(),
-            statics_to_rauw: RefCell::new(Vec::new()),
-            used_statics: RefCell::new(Vec::new()),
-            compiler_used_statics: RefCell::new(Vec::new()),
-            type_lowering: Default::default(),
-            scalar_lltypes: Default::default(),
-            isize_ty,
-            coverage_cx,
-            dbg_cx,
-            eh_personality: Cell::new(None),
-            eh_catch_typeinfo: Cell::new(None),
-            rust_try_fn: Cell::new(None),
-            intrinsics: Default::default(),
-            local_gen_sym_counter: Cell::new(0),
-            renamed_statics: Default::default(),
-        }
+        GenericCx(
+            FullCx {
+                tcx,
+                scx: SimpleCx::new(llmod, llcx, tcx.data_layout.pointer_size),
+                use_dll_storage_attrs,
+                tls_model,
+                codegen_unit,
+                instances: Default::default(),
+                vtables: Default::default(),
+                const_str_cache: Default::default(),
+                const_globals: Default::default(),
+                statics_to_rauw: RefCell::new(Vec::new()),
+                used_statics: RefCell::new(Vec::new()),
+                compiler_used_statics: RefCell::new(Vec::new()),
+                type_lowering: Default::default(),
+                scalar_lltypes: Default::default(),
+                coverage_cx,
+                dbg_cx,
+                eh_personality: Cell::new(None),
+                eh_catch_typeinfo: Cell::new(None),
+                rust_try_fn: Cell::new(None),
+                intrinsics: Default::default(),
+                local_gen_sym_counter: Cell::new(0),
+                renamed_statics: Default::default(),
+            },
+            PhantomData,
+        )
     }
 
     pub(crate) fn statics_to_rauw(&self) -> &RefCell<Vec<(&'ll Value, &'ll Value)>> {
@@ -628,24 +642,32 @@ impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {
         llvm::set_section(g, c"llvm.metadata");
     }
 }
+
 impl<'ll> SimpleCx<'ll> {
-    pub(crate) fn val_ty(&self, v: &'ll Value) -> &'ll Type {
-        common::val_ty(v)
+    pub(crate) fn new(
+        llmod: &'ll llvm::Module,
+        llcx: &'ll llvm::Context,
+        pointer_size: Size,
+    ) -> Self {
+        let isize_ty = llvm::Type::ix_llcx(llcx, pointer_size.bits());
+        Self(SCx { llmod, llcx, isize_ty }, PhantomData)
     }
+}
 
+impl<'ll, CX: Borrow<SCx<'ll>>> GenericCx<'ll, CX> {
     pub(crate) fn get_metadata_value(&self, metadata: &'ll Metadata) -> &'ll Value {
-        unsafe { llvm::LLVMMetadataAsValue(self.llcx, metadata) }
+        llvm::LLVMMetadataAsValue(self.llcx(), metadata)
     }
 
     pub(crate) fn get_function(&self, name: &str) -> Option<&'ll Value> {
         let name = SmallCStr::new(name);
-        unsafe { llvm::LLVMGetNamedFunction(self.llmod, name.as_ptr()) }
+        unsafe { llvm::LLVMGetNamedFunction((**self).borrow().llmod, name.as_ptr()) }
     }
 
-    pub(crate) fn get_md_kind_id(&self, name: &str) -> u32 {
+    pub(crate) fn get_md_kind_id(&self, name: &str) -> llvm::MetadataKindId {
         unsafe {
             llvm::LLVMGetMDKindIDInContext(
-                self.llcx,
+                self.llcx(),
                 name.as_ptr() as *const c_char,
                 name.len() as c_uint,
             )
@@ -654,13 +676,9 @@ impl<'ll> SimpleCx<'ll> {
 
     pub(crate) fn create_metadata(&self, name: String) -> Option<&'ll Metadata> {
         Some(unsafe {
-            llvm::LLVMMDStringInContext2(self.llcx, name.as_ptr() as *const c_char, name.len())
+            llvm::LLVMMDStringInContext2(self.llcx(), name.as_ptr() as *const c_char, name.len())
         })
     }
-
-    pub(crate) fn type_kind(&self, ty: &'ll Type) -> TypeKind {
-        unsafe { llvm::LLVMRustGetTypeKind(ty).to_generic() }
-    }
 }
 
 impl<'ll, 'tcx> MiscCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
@@ -1203,27 +1221,18 @@ impl CodegenCx<'_, '_> {
         name.push_str(&(idx as u64).to_base(ALPHANUMERIC_ONLY));
         name
     }
-
-    /// A wrapper for [`llvm::LLVMSetMetadata`], but it takes `Metadata` as a parameter instead of `Value`.
-    pub(crate) fn set_metadata<'a>(&self, val: &'a Value, kind_id: MetadataType, md: &'a Metadata) {
-        unsafe {
-            let node = llvm::LLVMMetadataAsValue(&self.llcx, md);
-            llvm::LLVMSetMetadata(val, kind_id as c_uint, node);
-        }
-    }
 }
 
-// This is a duplication of the set_metadata function above. However, so far it's the only one
-// shared between both contexts, so it doesn't seem worth it to make the Cx generic like we did it
-// for the Builder.
-impl SimpleCx<'_> {
-    #[allow(unused)]
+impl<'ll, CX: Borrow<SCx<'ll>>> GenericCx<'ll, CX> {
     /// A wrapper for [`llvm::LLVMSetMetadata`], but it takes `Metadata` as a parameter instead of `Value`.
-    pub(crate) fn set_metadata<'a>(&self, val: &'a Value, kind_id: MetadataType, md: &'a Metadata) {
-        unsafe {
-            let node = llvm::LLVMMetadataAsValue(&self.llcx, md);
-            llvm::LLVMSetMetadata(val, kind_id as c_uint, node);
-        }
+    pub(crate) fn set_metadata<'a>(
+        &self,
+        val: &'a Value,
+        kind_id: impl Into<llvm::MetadataKindId>,
+        md: &'ll Metadata,
+    ) {
+        let node = self.get_metadata_value(md);
+        llvm::LLVMSetMetadata(val, kind_id.into(), node);
     }
 }
 
diff --git a/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/covfun.rs b/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/covfun.rs
index c53ea6d4666..80e54bf045e 100644
--- a/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/covfun.rs
+++ b/compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/covfun.rs
@@ -8,7 +8,7 @@ use std::ffi::CString;
 
 use rustc_abi::Align;
 use rustc_codegen_ssa::traits::{
-    BaseTypeCodegenMethods, ConstCodegenMethods, StaticCodegenMethods,
+    BaseTypeCodegenMethods as _, ConstCodegenMethods, StaticCodegenMethods,
 };
 use rustc_middle::mir::coverage::{
     BasicCoverageBlock, CovTerm, CoverageIdsInfo, Expression, FunctionCoverageInfo, Mapping,
diff --git a/compiler/rustc_codegen_llvm/src/declare.rs b/compiler/rustc_codegen_llvm/src/declare.rs
index e79662ebc64..2419ec1f888 100644
--- a/compiler/rustc_codegen_llvm/src/declare.rs
+++ b/compiler/rustc_codegen_llvm/src/declare.rs
@@ -11,6 +11,8 @@
 //! * Use define_* family of methods when you might be defining the Value.
 //! * When in doubt, define.
 
+use std::borrow::Borrow;
+
 use itertools::Itertools;
 use rustc_codegen_ssa::traits::TypeMembershipCodegenMethods;
 use rustc_data_structures::fx::FxIndexSet;
@@ -22,7 +24,7 @@ use tracing::debug;
 
 use crate::abi::FnAbiLlvmExt;
 use crate::common::AsCCharPtr;
-use crate::context::{CodegenCx, SimpleCx};
+use crate::context::{CodegenCx, GenericCx, SCx, SimpleCx};
 use crate::llvm::AttributePlace::Function;
 use crate::llvm::Visibility;
 use crate::type_::Type;
@@ -81,16 +83,25 @@ pub(crate) fn declare_raw_fn<'ll, 'tcx>(
     llfn
 }
 
-impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {
+impl<'ll, CX: Borrow<SCx<'ll>>> GenericCx<'ll, CX> {
     /// Declare a global value.
     ///
     /// If there’s a value with the same name already declared, the function will
     /// return its Value instead.
     pub(crate) fn declare_global(&self, name: &str, ty: &'ll Type) -> &'ll Value {
         debug!("declare_global(name={:?})", name);
-        unsafe { llvm::LLVMRustGetOrInsertGlobal(self.llmod, name.as_c_char_ptr(), name.len(), ty) }
+        unsafe {
+            llvm::LLVMRustGetOrInsertGlobal(
+                (**self).borrow().llmod,
+                name.as_c_char_ptr(),
+                name.len(),
+                ty,
+            )
+        }
     }
+}
 
+impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {
     /// Declare a C ABI function.
     ///
     /// Only use this for foreign function ABIs and glue. For Rust functions use
diff --git a/compiler/rustc_codegen_llvm/src/intrinsic.rs b/compiler/rustc_codegen_llvm/src/intrinsic.rs
index 0272667e223..660fc7ec4c4 100644
--- a/compiler/rustc_codegen_llvm/src/intrinsic.rs
+++ b/compiler/rustc_codegen_llvm/src/intrinsic.rs
@@ -649,7 +649,7 @@ impl<'ll, 'tcx> IntrinsicCallBuilderMethods<'tcx> for Builder<'_, 'll, 'tcx> {
     fn type_test(&mut self, pointer: Self::Value, typeid: Self::Metadata) -> Self::Value {
         // Test the called operand using llvm.type.test intrinsic. The LowerTypeTests link-time
         // optimization pass replaces calls to this intrinsic with code to test type membership.
-        let typeid = unsafe { llvm::LLVMMetadataAsValue(&self.llcx, typeid) };
+        let typeid = self.get_metadata_value(typeid);
         self.call_intrinsic("llvm.type.test", &[pointer, typeid])
     }
 
@@ -659,7 +659,7 @@ impl<'ll, 'tcx> IntrinsicCallBuilderMethods<'tcx> for Builder<'_, 'll, 'tcx> {
         vtable_byte_offset: u64,
         typeid: &'ll Metadata,
     ) -> Self::Value {
-        let typeid = unsafe { llvm::LLVMMetadataAsValue(&self.llcx, typeid) };
+        let typeid = self.get_metadata_value(typeid);
         let vtable_byte_offset = self.const_i32(vtable_byte_offset as i32);
         let type_checked_load =
             self.call_intrinsic("llvm.type.checked.load", &[llvtable, vtable_byte_offset, typeid]);
diff --git a/compiler/rustc_codegen_llvm/src/lib.rs b/compiler/rustc_codegen_llvm/src/lib.rs
index 8f72307eeba..dec93bbccc3 100644
--- a/compiler/rustc_codegen_llvm/src/lib.rs
+++ b/compiler/rustc_codegen_llvm/src/lib.rs
@@ -28,6 +28,7 @@ use std::mem::ManuallyDrop;
 
 use back::owned_target_machine::OwnedTargetMachine;
 use back::write::{create_informational_target_machine, create_target_machine};
+use context::SimpleCx;
 use errors::{AutoDiffWithoutLTO, ParseTargetMachineConfig};
 pub(crate) use llvm_util::target_features_cfg;
 use rustc_ast::expand::allocator::AllocatorKind;
@@ -115,9 +116,11 @@ impl ExtraBackendMethods for LlvmCodegenBackend {
         kind: AllocatorKind,
         alloc_error_handler_kind: AllocatorKind,
     ) -> ModuleLlvm {
-        let mut module_llvm = ModuleLlvm::new_metadata(tcx, module_name);
+        let module_llvm = ModuleLlvm::new_metadata(tcx, module_name);
+        let cx =
+            SimpleCx::new(module_llvm.llmod(), &module_llvm.llcx, tcx.data_layout.pointer_size);
         unsafe {
-            allocator::codegen(tcx, &mut module_llvm, module_name, kind, alloc_error_handler_kind);
+            allocator::codegen(tcx, cx, module_name, kind, alloc_error_handler_kind);
         }
         module_llvm
     }
@@ -338,8 +341,8 @@ impl CodegenBackend for LlvmCodegenBackend {
         llvm_util::print_version();
     }
 
-    fn target_features_cfg(&self, sess: &Session, allow_unstable: bool) -> Vec<Symbol> {
-        target_features_cfg(sess, allow_unstable)
+    fn target_features_cfg(&self, sess: &Session) -> (Vec<Symbol>, Vec<Symbol>) {
+        target_features_cfg(sess)
     }
 
     fn codegen_crate<'tcx>(
diff --git a/compiler/rustc_codegen_llvm/src/llvm/enzyme_ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/enzyme_ffi.rs
index 25ca3498803..f6b23862907 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/enzyme_ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/enzyme_ffi.rs
@@ -3,13 +3,14 @@
 
 use libc::{c_char, c_uint};
 
+use super::MetadataKindId;
 use super::ffi::{BasicBlock, Metadata, Module, Type, Value};
 use crate::llvm::Bool;
 
 #[link(name = "llvm-wrapper", kind = "static")]
 unsafe extern "C" {
     // Enzyme
-    pub(crate) fn LLVMRustHasMetadata(I: &Value, KindID: c_uint) -> bool;
+    pub(crate) safe fn LLVMRustHasMetadata(I: &Value, KindID: MetadataKindId) -> bool;
     pub(crate) fn LLVMRustEraseInstUntilInclusive(BB: &BasicBlock, I: &Value);
     pub(crate) fn LLVMRustGetLastInstruction<'a>(BB: &BasicBlock) -> Option<&'a Value>;
     pub(crate) fn LLVMRustDIGetInstMetadata(I: &Value) -> Option<&Metadata>;
diff --git a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
index e3d0b928c97..39087a4d6f4 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
@@ -976,6 +976,16 @@ pub type SelfProfileAfterPassCallback = unsafe extern "C" fn(*mut c_void);
 pub type GetSymbolsCallback = unsafe extern "C" fn(*mut c_void, *const c_char) -> *mut c_void;
 pub type GetSymbolsErrorCallback = unsafe extern "C" fn(*const c_char) -> *mut c_void;
 
+#[derive(Copy, Clone)]
+#[repr(transparent)]
+pub struct MetadataKindId(c_uint);
+
+impl From<MetadataType> for MetadataKindId {
+    fn from(value: MetadataType) -> Self {
+        Self(value as c_uint)
+    }
+}
+
 unsafe extern "C" {
     // Create and destroy contexts.
     pub(crate) fn LLVMContextDispose(C: &'static mut Context);
@@ -983,7 +993,7 @@ unsafe extern "C" {
         C: &Context,
         Name: *const c_char,
         SLen: c_uint,
-    ) -> c_uint;
+    ) -> MetadataKindId;
 
     // Create modules.
     pub(crate) fn LLVMModuleCreateWithNameInContext(
@@ -1050,9 +1060,9 @@ unsafe extern "C" {
     pub(crate) fn LLVMGetValueName2(Val: &Value, Length: *mut size_t) -> *const c_char;
     pub(crate) fn LLVMSetValueName2(Val: &Value, Name: *const c_char, NameLen: size_t);
     pub(crate) fn LLVMReplaceAllUsesWith<'a>(OldVal: &'a Value, NewVal: &'a Value);
-    pub(crate) fn LLVMSetMetadata<'a>(Val: &'a Value, KindID: c_uint, Node: &'a Value);
+    pub(crate) safe fn LLVMSetMetadata<'a>(Val: &'a Value, KindID: MetadataKindId, Node: &'a Value);
     pub(crate) fn LLVMGlobalSetMetadata<'a>(Val: &'a Value, KindID: c_uint, Metadata: &'a Metadata);
-    pub(crate) fn LLVMValueAsMetadata(Node: &Value) -> &Metadata;
+    pub(crate) safe fn LLVMValueAsMetadata(Node: &Value) -> &Metadata;
 
     // Operations on constants of any type
     pub(crate) fn LLVMConstNull(Ty: &Type) -> &Value;
@@ -1146,7 +1156,7 @@ unsafe extern "C" {
     pub(crate) fn LLVMSetThreadLocalMode(GlobalVar: &Value, Mode: ThreadLocalMode);
     pub(crate) fn LLVMIsGlobalConstant(GlobalVar: &Value) -> Bool;
     pub(crate) fn LLVMSetGlobalConstant(GlobalVar: &Value, IsConstant: Bool);
-    pub(crate) fn LLVMSetTailCall(CallInst: &Value, IsTailCall: Bool);
+    pub(crate) safe fn LLVMSetTailCall(CallInst: &Value, IsTailCall: Bool);
 
     // Operations on attributes
     pub(crate) fn LLVMCreateStringAttribute(
@@ -1203,7 +1213,7 @@ unsafe extern "C" {
     pub(crate) fn LLVMGetCurrentDebugLocation2<'a>(Builder: &Builder<'a>) -> Option<&'a Metadata>;
 
     // Terminators
-    pub(crate) fn LLVMBuildRetVoid<'a>(B: &Builder<'a>) -> &'a Value;
+    pub(crate) safe fn LLVMBuildRetVoid<'a>(B: &Builder<'a>) -> &'a Value;
     pub(crate) fn LLVMBuildRet<'a>(B: &Builder<'a>, V: &'a Value) -> &'a Value;
     pub(crate) fn LLVMBuildBr<'a>(B: &Builder<'a>, Dest: &'a BasicBlock) -> &'a Value;
     pub(crate) fn LLVMBuildCondBr<'a>(
@@ -1679,7 +1689,7 @@ unsafe extern "C" {
         Packed: Bool,
     );
 
-    pub(crate) fn LLVMMetadataAsValue<'a>(C: &'a Context, MD: &'a Metadata) -> &'a Value;
+    pub(crate) safe fn LLVMMetadataAsValue<'a>(C: &'a Context, MD: &'a Metadata) -> &'a Value;
 
     pub(crate) fn LLVMSetUnnamedAddress(Global: &Value, UnnamedAddr: UnnamedAddr);
 
diff --git a/compiler/rustc_codegen_llvm/src/llvm_util.rs b/compiler/rustc_codegen_llvm/src/llvm_util.rs
index 5cc4f4ab9e6..4a166b0872d 100644
--- a/compiler/rustc_codegen_llvm/src/llvm_util.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm_util.rs
@@ -306,45 +306,44 @@ pub(crate) fn to_llvm_features<'a>(sess: &Session, s: &'a str) -> Option<LLVMFea
 /// Must express features in the way Rust understands them.
 ///
 /// We do not have to worry about RUSTC_SPECIFIC_FEATURES here, those are handled outside codegen.
-pub(crate) fn target_features_cfg(sess: &Session, allow_unstable: bool) -> Vec<Symbol> {
-    let mut features: FxHashSet<Symbol> = Default::default();
-
+pub(crate) fn target_features_cfg(sess: &Session) -> (Vec<Symbol>, Vec<Symbol>) {
     // Add base features for the target.
     // We do *not* add the -Ctarget-features there, and instead duplicate the logic for that below.
     // The reason is that if LLVM considers a feature implied but we do not, we don't want that to
     // show up in `cfg`. That way, `cfg` is entirely under our control -- except for the handling of
-    // the target CPU, that is still expanded to target features (with all their implied features) by
-    // LLVM.
+    // the target CPU, that is still expanded to target features (with all their implied features)
+    // by LLVM.
     let target_machine = create_informational_target_machine(sess, true);
-    // Compute which of the known target features are enabled in the 'base' target machine.
-    // We only consider "supported" features; "forbidden" features are not reflected in `cfg` as of now.
-    features.extend(
-        sess.target
-            .rust_target_features()
-            .iter()
-            .filter(|(feature, _, _)| {
-                // skip checking special features, as LLVM may not understand them
-                if RUSTC_SPECIAL_FEATURES.contains(feature) {
-                    return true;
-                }
-                // check that all features in a given smallvec are enabled
-                if let Some(feat) = to_llvm_features(sess, feature) {
-                    for llvm_feature in feat {
-                        let cstr = SmallCStr::new(llvm_feature);
-                        if !unsafe { llvm::LLVMRustHasFeature(target_machine.raw(), cstr.as_ptr()) }
-                        {
-                            return false;
-                        }
+    // Compute which of the known target features are enabled in the 'base' target machine. We only
+    // consider "supported" features; "forbidden" features are not reflected in `cfg` as of now.
+    let mut features: FxHashSet<Symbol> = sess
+        .target
+        .rust_target_features()
+        .iter()
+        .filter(|(feature, _, _)| {
+            // skip checking special features, as LLVM may not understand them
+            if RUSTC_SPECIAL_FEATURES.contains(feature) {
+                return true;
+            }
+            if let Some(feat) = to_llvm_features(sess, feature) {
+                for llvm_feature in feat {
+                    let cstr = SmallCStr::new(llvm_feature);
+                    // `LLVMRustHasFeature` is moderately expensive. On targets with many
+                    // features (e.g. x86) these calls take a non-trivial fraction of runtime
+                    // when compiling very small programs.
+                    if !unsafe { llvm::LLVMRustHasFeature(target_machine.raw(), cstr.as_ptr()) } {
+                        return false;
                     }
-                    true
-                } else {
-                    false
                 }
-            })
-            .map(|(feature, _, _)| Symbol::intern(feature)),
-    );
+                true
+            } else {
+                false
+            }
+        })
+        .map(|(feature, _, _)| Symbol::intern(feature))
+        .collect();
 
-    // Add enabled features
+    // Add enabled and remove disabled features.
     for (enabled, feature) in
         sess.opts.cg.target_feature.split(',').filter_map(|s| match s.chars().next() {
             Some('+') => Some((true, Symbol::intern(&s[1..]))),
@@ -360,7 +359,7 @@ pub(crate) fn target_features_cfg(sess: &Session, allow_unstable: bool) -> Vec<S
             #[allow(rustc::potential_query_instability)]
             features.extend(
                 sess.target
-                    .implied_target_features(std::iter::once(feature.as_str()))
+                    .implied_target_features(feature.as_str())
                     .iter()
                     .map(|s| Symbol::intern(s)),
             );
@@ -371,11 +370,7 @@ pub(crate) fn target_features_cfg(sess: &Session, allow_unstable: bool) -> Vec<S
             // `features.contains` below.
             #[allow(rustc::potential_query_instability)]
             features.retain(|f| {
-                if sess
-                    .target
-                    .implied_target_features(std::iter::once(f.as_str()))
-                    .contains(&feature.as_str())
-                {
+                if sess.target.implied_target_features(f.as_str()).contains(&feature.as_str()) {
                     // If `f` if implies `feature`, then `!feature` implies `!f`, so we have to
                     // remove `f`. (This is the standard logical contraposition principle.)
                     false
@@ -387,25 +382,31 @@ pub(crate) fn target_features_cfg(sess: &Session, allow_unstable: bool) -> Vec<S
         }
     }
 
-    // Filter enabled features based on feature gates
-    sess.target
-        .rust_target_features()
-        .iter()
-        .filter_map(|(feature, gate, _)| {
-            // The `allow_unstable` set is used by rustc internally to determined which target
-            // features are truly available, so we want to return even perma-unstable "forbidden"
-            // features.
-            if allow_unstable
-                || (gate.in_cfg() && (sess.is_nightly_build() || gate.requires_nightly().is_none()))
-            {
-                Some(*feature)
-            } else {
-                None
-            }
-        })
-        .filter(|feature| features.contains(&Symbol::intern(feature)))
-        .map(|feature| Symbol::intern(feature))
-        .collect()
+    // Filter enabled features based on feature gates.
+    let f = |allow_unstable| {
+        sess.target
+            .rust_target_features()
+            .iter()
+            .filter_map(|(feature, gate, _)| {
+                // The `allow_unstable` set is used by rustc internally to determined which target
+                // features are truly available, so we want to return even perma-unstable
+                // "forbidden" features.
+                if allow_unstable
+                    || (gate.in_cfg()
+                        && (sess.is_nightly_build() || gate.requires_nightly().is_none()))
+                {
+                    Some(Symbol::intern(feature))
+                } else {
+                    None
+                }
+            })
+            .filter(|feature| features.contains(&feature))
+            .collect()
+    };
+
+    let target_features = f(false);
+    let unstable_target_features = f(true);
+    (target_features, unstable_target_features)
 }
 
 pub(crate) fn print_version() {
@@ -682,7 +683,7 @@ pub(crate) fn global_llvm_features(
         for feature in sess.opts.cg.target_feature.split(',') {
             if let Some(feature) = feature.strip_prefix('+') {
                 all_rust_features.extend(
-                    UnordSet::from(sess.target.implied_target_features(std::iter::once(feature)))
+                    UnordSet::from(sess.target.implied_target_features(feature))
                         .to_sorted_stable_ord()
                         .iter()
                         .map(|&&s| (true, s)),
diff --git a/compiler/rustc_codegen_llvm/src/type_.rs b/compiler/rustc_codegen_llvm/src/type_.rs
index d61ce417562..b89ce90d1a1 100644
--- a/compiler/rustc_codegen_llvm/src/type_.rs
+++ b/compiler/rustc_codegen_llvm/src/type_.rs
@@ -1,3 +1,4 @@
+use std::borrow::Borrow;
 use std::{fmt, ptr};
 
 use libc::{c_char, c_uint};
@@ -11,7 +12,7 @@ use rustc_middle::ty::{self, Ty};
 use rustc_target::callconv::{CastTarget, FnAbi};
 
 use crate::abi::{FnAbiLlvmExt, LlvmType};
-use crate::context::{CodegenCx, SimpleCx};
+use crate::context::{CodegenCx, GenericCx, SCx};
 pub(crate) use crate::llvm::Type;
 use crate::llvm::{Bool, False, Metadata, True};
 use crate::type_of::LayoutLlvmExt;
@@ -36,29 +37,29 @@ impl fmt::Debug for Type {
 }
 
 impl<'ll> CodegenCx<'ll, '_> {}
-impl<'ll> SimpleCx<'ll> {
+impl<'ll, CX: Borrow<SCx<'ll>>> GenericCx<'ll, CX> {
     pub(crate) fn type_named_struct(&self, name: &str) -> &'ll Type {
         let name = SmallCStr::new(name);
-        unsafe { llvm::LLVMStructCreateNamed(self.llcx, name.as_ptr()) }
+        unsafe { llvm::LLVMStructCreateNamed(self.llcx(), name.as_ptr()) }
     }
 
     pub(crate) fn set_struct_body(&self, ty: &'ll Type, els: &[&'ll Type], packed: bool) {
         unsafe { llvm::LLVMStructSetBody(ty, els.as_ptr(), els.len() as c_uint, packed as Bool) }
     }
     pub(crate) fn type_void(&self) -> &'ll Type {
-        unsafe { llvm::LLVMVoidTypeInContext(self.llcx) }
+        unsafe { llvm::LLVMVoidTypeInContext(self.llcx()) }
     }
     pub(crate) fn type_token(&self) -> &'ll Type {
-        unsafe { llvm::LLVMTokenTypeInContext(self.llcx) }
+        unsafe { llvm::LLVMTokenTypeInContext(self.llcx()) }
     }
 
     pub(crate) fn type_metadata(&self) -> &'ll Type {
-        unsafe { llvm::LLVMMetadataTypeInContext(self.llcx) }
+        unsafe { llvm::LLVMMetadataTypeInContext(self.llcx()) }
     }
 
     ///x Creates an integer type with the given number of bits, e.g., i24
     pub(crate) fn type_ix(&self, num_bits: u64) -> &'ll Type {
-        unsafe { llvm::LLVMIntTypeInContext(self.llcx, num_bits as c_uint) }
+        unsafe { llvm::LLVMIntTypeInContext(self.llcx(), num_bits as c_uint) }
     }
 
     pub(crate) fn type_vector(&self, ty: &'ll Type, len: u64) -> &'ll Type {
@@ -121,19 +122,28 @@ impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {
         self.type_array(self.type_from_integer(unit), size / unit_size)
     }
 }
-impl<'ll> SimpleCx<'ll> {
+
+impl<'ll, CX: Borrow<SCx<'ll>>> GenericCx<'ll, CX> {
+    pub(crate) fn llcx(&self) -> &'ll llvm::Context {
+        (**self).borrow().llcx
+    }
+
+    pub(crate) fn isize_ty(&self) -> &'ll Type {
+        (**self).borrow().isize_ty
+    }
+
     pub(crate) fn type_variadic_func(&self, args: &[&'ll Type], ret: &'ll Type) -> &'ll Type {
         unsafe { llvm::LLVMFunctionType(ret, args.as_ptr(), args.len() as c_uint, True) }
     }
 
     pub(crate) fn type_i1(&self) -> &'ll Type {
-        unsafe { llvm::LLVMInt1TypeInContext(self.llcx) }
+        unsafe { llvm::LLVMInt1TypeInContext(self.llcx()) }
     }
 
     pub(crate) fn type_struct(&self, els: &[&'ll Type], packed: bool) -> &'ll Type {
         unsafe {
             llvm::LLVMStructTypeInContext(
-                self.llcx,
+                self.llcx(),
                 els.as_ptr(),
                 els.len() as c_uint,
                 packed as Bool,
@@ -142,45 +152,45 @@ impl<'ll> SimpleCx<'ll> {
     }
 }
 
-impl<'ll, 'tcx> BaseTypeCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
+impl<'ll, CX: Borrow<SCx<'ll>>> BaseTypeCodegenMethods for GenericCx<'ll, CX> {
     fn type_i8(&self) -> &'ll Type {
-        unsafe { llvm::LLVMInt8TypeInContext(self.llcx) }
+        unsafe { llvm::LLVMInt8TypeInContext(self.llcx()) }
     }
 
     fn type_i16(&self) -> &'ll Type {
-        unsafe { llvm::LLVMInt16TypeInContext(self.llcx) }
+        unsafe { llvm::LLVMInt16TypeInContext(self.llcx()) }
     }
 
     fn type_i32(&self) -> &'ll Type {
-        unsafe { llvm::LLVMInt32TypeInContext(self.llcx) }
+        unsafe { llvm::LLVMInt32TypeInContext(self.llcx()) }
     }
 
     fn type_i64(&self) -> &'ll Type {
-        unsafe { llvm::LLVMInt64TypeInContext(self.llcx) }
+        unsafe { llvm::LLVMInt64TypeInContext(self.llcx()) }
     }
 
     fn type_i128(&self) -> &'ll Type {
-        unsafe { llvm::LLVMIntTypeInContext(self.llcx, 128) }
+        unsafe { llvm::LLVMIntTypeInContext(self.llcx(), 128) }
     }
 
     fn type_isize(&self) -> &'ll Type {
-        self.isize_ty
+        self.isize_ty()
     }
 
     fn type_f16(&self) -> &'ll Type {
-        unsafe { llvm::LLVMHalfTypeInContext(self.llcx) }
+        unsafe { llvm::LLVMHalfTypeInContext(self.llcx()) }
     }
 
     fn type_f32(&self) -> &'ll Type {
-        unsafe { llvm::LLVMFloatTypeInContext(self.llcx) }
+        unsafe { llvm::LLVMFloatTypeInContext(self.llcx()) }
     }
 
     fn type_f64(&self) -> &'ll Type {
-        unsafe { llvm::LLVMDoubleTypeInContext(self.llcx) }
+        unsafe { llvm::LLVMDoubleTypeInContext(self.llcx()) }
     }
 
     fn type_f128(&self) -> &'ll Type {
-        unsafe { llvm::LLVMFP128TypeInContext(self.llcx) }
+        unsafe { llvm::LLVMFP128TypeInContext(self.llcx()) }
     }
 
     fn type_func(&self, args: &[&'ll Type], ret: &'ll Type) -> &'ll Type {
@@ -196,7 +206,7 @@ impl<'ll, 'tcx> BaseTypeCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
     }
 
     fn type_ptr_ext(&self, address_space: AddressSpace) -> &'ll Type {
-        unsafe { llvm::LLVMPointerTypeInContext(self.llcx, address_space.0) }
+        unsafe { llvm::LLVMPointerTypeInContext(self.llcx(), address_space.0) }
     }
 
     fn element_type(&self, ty: &'ll Type) -> &'ll Type {
diff --git a/compiler/rustc_codegen_ssa/messages.ftl b/compiler/rustc_codegen_ssa/messages.ftl
index f15d6fba506..95912b01600 100644
--- a/compiler/rustc_codegen_ssa/messages.ftl
+++ b/compiler/rustc_codegen_ssa/messages.ftl
@@ -18,6 +18,8 @@ codegen_ssa_atomic_compare_exchange = Atomic compare-exchange intrinsic missing
 
 codegen_ssa_autodiff_without_lto = using the autodiff feature requires using fat-lto
 
+codegen_ssa_bare_instruction_set = `#[instruction_set]` requires an argument
+
 codegen_ssa_binary_output_to_tty = option `-o` or `--emit` is used to write binary output type `{$shorthand}` to stdout, but stdout is a tty
 
 codegen_ssa_cgu_not_recorded =
@@ -52,6 +54,10 @@ codegen_ssa_error_creating_remark_dir = failed to create remark directory: {$err
 codegen_ssa_error_writing_def_file =
     Error writing .DEF file: {$error}
 
+codegen_ssa_expected_name_value_pair = expected name value pair
+
+codegen_ssa_expected_one_argument = expected one argument
+
 codegen_ssa_expected_used_symbol = expected `used`, `used(compiler)` or `used(linker)`
 
 codegen_ssa_extern_funcs_not_found = some `extern` functions couldn't be found; some native libraries may need to be installed or have their path specified
@@ -88,9 +94,17 @@ codegen_ssa_incorrect_cgu_reuse_type =
 
 codegen_ssa_insufficient_vs_code_product = VS Code is a different product, and is not sufficient.
 
+codegen_ssa_invalid_argument = invalid argument
+    .help = valid inline arguments are `always` and `never`
+
+codegen_ssa_invalid_instruction_set = invalid instruction set specified
+
 codegen_ssa_invalid_link_ordinal_nargs = incorrect number of arguments to `#[link_ordinal]`
     .note = the attribute requires exactly one argument
 
+codegen_ssa_invalid_literal_value = invalid literal value
+    .label = value must be an integer between `0` and `255`
+
 codegen_ssa_invalid_monomorphization_basic_float_type = invalid monomorphization of `{$name}` intrinsic: expected basic float type, found `{$ty}`
 
 codegen_ssa_invalid_monomorphization_basic_integer_type = invalid monomorphization of `{$name}` intrinsic: expected basic integer type, found `{$ty}`
@@ -217,6 +231,8 @@ codegen_ssa_msvc_missing_linker = the msvc targets depend on the msvc linker but
 
 codegen_ssa_multiple_external_func_decl = multiple declarations of external function `{$function}` from library `{$library_name}` have different calling conventions
 
+codegen_ssa_multiple_instruction_set = cannot specify more than one instruction set
+
 codegen_ssa_multiple_main_functions = entry symbol `main` declared multiple times
     .help = did you use `#[no_mangle]` on `fn main`? Use `#![no_main]` to suppress the usual Rust-generated entry point
 
@@ -229,6 +245,11 @@ codegen_ssa_no_natvis_directory = error enumerating natvis directory: {$error}
 
 codegen_ssa_no_saved_object_file = cached cgu {$cgu_name} should have an object file, but doesn't
 
+codegen_ssa_null_on_export = `export_name` may not contain null characters
+
+codegen_ssa_out_of_range_integer = integer value out of range
+    .label = value must be between `0` and `255`
+
 codegen_ssa_processing_dymutil_failed = processing debug info with `dsymutil` failed: {$status}
     .note = {$output}
 
@@ -236,6 +257,8 @@ codegen_ssa_read_file = failed to read file: {$message}
 
 codegen_ssa_repair_vs_build_tools = the Visual Studio build tools may need to be repaired using the Visual Studio installer
 
+codegen_ssa_requires_rust_abi = `#[track_caller]` requires Rust ABI
+
 codegen_ssa_rlib_archive_build_failure = failed to build archive from rlib at `{$path}`: {$error}
 
 codegen_ssa_rlib_incompatible_dependency_formats = `{$ty1}` and `{$ty2}` do not have equivalent dependency formats (`{$list1}` vs `{$list2}`)
@@ -356,6 +379,9 @@ codegen_ssa_unable_to_run_dsymutil = unable to run `dsymutil`: {$error}
 
 codegen_ssa_unable_to_write_debugger_visualizer = Unable to write debugger visualizer file `{$path}`: {$error}
 
+codegen_ssa_unexpected_parameter_name = unexpected parameter name
+    .label = expected `{$prefix_nops}` or `{$entry_nops}`
+
 codegen_ssa_unknown_archive_kind =
     Don't know how to build archive of type: {$kind}
 
@@ -367,6 +393,8 @@ codegen_ssa_unknown_reuse_kind = unknown cgu-reuse-kind `{$kind}` specified
 
 codegen_ssa_unsupported_arch = unsupported arch `{$arch}` for os `{$os}`
 
+codegen_ssa_unsupported_instruction_set = target does not support `#[instruction_set]`
+
 codegen_ssa_unsupported_link_self_contained = option `-C link-self-contained` is not supported on this target
 
 codegen_ssa_use_cargo_directive = use the `cargo:rustc-link-lib` directive to specify the native libraries to link with Cargo (see https://doc.rust-lang.org/cargo/reference/build-scripts.html#rustc-link-lib)
diff --git a/compiler/rustc_codegen_ssa/src/back/link.rs b/compiler/rustc_codegen_ssa/src/back/link.rs
index a170b2e3b6a..7d9971c021d 100644
--- a/compiler/rustc_codegen_ssa/src/back/link.rs
+++ b/compiler/rustc_codegen_ssa/src/back/link.rs
@@ -1177,7 +1177,7 @@ mod win {
             let mut cp: u32 = 0;
             // We're using the `LOCALE_RETURN_NUMBER` flag to return a u32.
             // But the API requires us to pass the data as though it's a [u16] string.
-            let len = std::mem::size_of::<u32>() / std::mem::size_of::<u16>();
+            let len = size_of::<u32>() / size_of::<u16>();
             let data = std::slice::from_raw_parts_mut(&mut cp as *mut u32 as *mut u16, len);
             let len_written = GetLocaleInfoEx(
                 LOCALE_NAME_SYSTEM_DEFAULT,
@@ -3382,6 +3382,35 @@ fn add_lld_args(
     // this, `wasm-component-ld`, which is overridden if this option is passed.
     if !sess.target.is_like_wasm {
         cmd.cc_arg("-fuse-ld=lld");
+
+        // On ELF platforms like at least x64 linux, GNU ld and LLD have opposite defaults on some
+        // section garbage-collection features. For example, the somewhat popular `linkme` crate and
+        // its dependents rely in practice on this difference: when using lld, they need `-z
+        // nostart-stop-gc` to prevent encapsulation symbols and sections from being
+        // garbage-collected.
+        //
+        // More information about all this can be found in:
+        // - https://maskray.me/blog/2021-01-31-metadata-sections-comdat-and-shf-link-order
+        // - https://lld.llvm.org/ELF/start-stop-gc
+        //
+        // So when using lld, we restore, for now, the traditional behavior to help migration, but
+        // will remove it in the future.
+        // Since this only disables an optimization, it shouldn't create issues, but is in theory
+        // slightly suboptimal. However, it:
+        // - doesn't have any visible impact on our benchmarks
+        // - reduces the need to disable lld for the crates that depend on this
+        //
+        // Note that lld can detect some cases where this difference is relied on, and emits a
+        // dedicated error to add this link arg. We could make use of this error to emit an FCW. As
+        // of writing this, we don't do it, because lld is already enabled by default on nightly
+        // without this mitigation: no working project would see the FCW, so we do this to help
+        // stabilization.
+        //
+        // FIXME: emit an FCW if linking fails due its absence, and then remove this link-arg in the
+        // future.
+        if sess.target.llvm_target == "x86_64-unknown-linux-gnu" {
+            cmd.link_arg("-znostart-stop-gc");
+        }
     }
 
     if !flavor.is_gnu() {
diff --git a/compiler/rustc_codegen_ssa/src/back/linker.rs b/compiler/rustc_codegen_ssa/src/back/linker.rs
index 818edaf6603..a8405a2aec9 100644
--- a/compiler/rustc_codegen_ssa/src/back/linker.rs
+++ b/compiler/rustc_codegen_ssa/src/back/linker.rs
@@ -1655,9 +1655,9 @@ impl<'a> Linker for AixLinker<'a> {
         }
     }
 
-    fn link_dylib_by_name(&mut self, name: &str, _verbatim: bool, _as_needed: bool) {
+    fn link_dylib_by_name(&mut self, name: &str, verbatim: bool, _as_needed: bool) {
         self.hint_dynamic();
-        self.link_or_cc_arg(format!("-l{name}"));
+        self.link_or_cc_arg(if verbatim { String::from(name) } else { format!("-l{name}") });
     }
 
     fn link_dylib_by_path(&mut self, path: &Path, _as_needed: bool) {
@@ -1668,7 +1668,7 @@ impl<'a> Linker for AixLinker<'a> {
     fn link_staticlib_by_name(&mut self, name: &str, verbatim: bool, whole_archive: bool) {
         self.hint_static();
         if !whole_archive {
-            self.link_or_cc_arg(format!("-l{name}"));
+            self.link_or_cc_arg(if verbatim { String::from(name) } else { format!("-l{name}") });
         } else {
             let mut arg = OsString::from("-bkeepfile:");
             arg.push(find_native_static_library(name, verbatim, self.sess));
diff --git a/compiler/rustc_codegen_ssa/src/back/write.rs b/compiler/rustc_codegen_ssa/src/back/write.rs
index c8bb229998e..87992ce2e11 100644
--- a/compiler/rustc_codegen_ssa/src/back/write.rs
+++ b/compiler/rustc_codegen_ssa/src/back/write.rs
@@ -6,6 +6,7 @@ use std::sync::Arc;
 use std::sync::mpsc::{Receiver, Sender, channel};
 use std::{fs, io, mem, str, thread};
 
+use rustc_abi::Size;
 use rustc_ast::attr;
 use rustc_ast::expand::autodiff_attrs::AutoDiffItem;
 use rustc_data_structures::fx::{FxHashMap, FxIndexMap};
@@ -355,6 +356,7 @@ pub struct CodegenContext<B: WriteBackendMethods> {
     pub target_is_like_aix: bool,
     pub split_debuginfo: rustc_target::spec::SplitDebuginfo,
     pub split_dwarf_kind: rustc_session::config::SplitDwarfKind,
+    pub pointer_size: Size,
 
     /// All commandline args used to invoke the compiler, with @file args fully expanded.
     /// This will only be used within debug info, e.g. in the pdb file on windows
@@ -1216,6 +1218,7 @@ fn start_executing_work<B: ExtraBackendMethods>(
         split_debuginfo: tcx.sess.split_debuginfo(),
         split_dwarf_kind: tcx.sess.opts.unstable_opts.split_dwarf_kind,
         parallel: backend.supports_parallel() && !sess.opts.unstable_opts.no_parallel_backend,
+        pointer_size: tcx.data_layout.pointer_size,
     };
 
     // This is the "main loop" of parallel work happening for parallel codegen.
diff --git a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
index 673740b4aab..27b8be1022e 100644
--- a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
+++ b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
@@ -1,15 +1,11 @@
 use std::str::FromStr;
 
 use rustc_abi::ExternAbi;
-use rustc_ast::expand::autodiff_attrs::{
-    AutoDiffAttrs, DiffActivity, DiffMode, valid_input_activity, valid_ret_activity,
-};
+use rustc_ast::expand::autodiff_attrs::{AutoDiffAttrs, DiffActivity, DiffMode};
 use rustc_ast::{MetaItem, MetaItemInner, attr};
 use rustc_attr_parsing::ReprAttr::ReprAlign;
 use rustc_attr_parsing::{AttributeKind, InlineAttr, InstructionSetAttr, OptimizeAttr};
 use rustc_data_structures::fx::FxHashMap;
-use rustc_errors::codes::*;
-use rustc_errors::{DiagMessage, SubdiagMessage, struct_span_code_err};
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{DefId, LOCAL_CRATE, LocalDefId};
 use rustc_hir::weak_lang_items::WEAK_LANG_ITEMS;
@@ -236,13 +232,7 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
                     && let Some(fn_sig) = fn_sig()
                     && fn_sig.skip_binder().abi() != ExternAbi::Rust
                 {
-                    struct_span_code_err!(
-                        tcx.dcx(),
-                        attr.span(),
-                        E0737,
-                        "`#[track_caller]` requires Rust ABI"
-                    )
-                    .emit();
+                    tcx.dcx().emit_err(errors::RequiresRustAbi { span: attr.span() });
                 }
                 if is_closure
                     && !tcx.features().closure_track_caller()
@@ -263,13 +253,7 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
                     if s.as_str().contains('\0') {
                         // `#[export_name = ...]` will be converted to a null-terminated string,
                         // so it may not contain any null characters.
-                        struct_span_code_err!(
-                            tcx.dcx(),
-                            attr.span(),
-                            E0648,
-                            "`export_name` may not contain null characters"
-                        )
-                        .emit();
+                        tcx.dcx().emit_err(errors::NullOnExport { span: attr.span() });
                     }
                     codegen_fn_attrs.export_name = Some(s);
                     mixed_export_name_no_mangle_lint_state.track_export_name(attr.span());
@@ -394,47 +378,28 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
                                 [sym::arm, sym::a32 | sym::t32]
                                     if !tcx.sess.target.has_thumb_interworking =>
                                 {
-                                    struct_span_code_err!(
-                                        tcx.dcx(),
-                                        attr.span(),
-                                        E0779,
-                                        "target does not support `#[instruction_set]`"
-                                    )
-                                    .emit();
+                                    tcx.dcx().emit_err(errors::UnsuportedInstructionSet {
+                                        span: attr.span(),
+                                    });
                                     None
                                 }
                                 [sym::arm, sym::a32] => Some(InstructionSetAttr::ArmA32),
                                 [sym::arm, sym::t32] => Some(InstructionSetAttr::ArmT32),
                                 _ => {
-                                    struct_span_code_err!(
-                                        tcx.dcx(),
-                                        attr.span(),
-                                        E0779,
-                                        "invalid instruction set specified",
-                                    )
-                                    .emit();
+                                    tcx.dcx().emit_err(errors::InvalidInstructionSet {
+                                        span: attr.span(),
+                                    });
                                     None
                                 }
                             }
                         }
                         [] => {
-                            struct_span_code_err!(
-                                tcx.dcx(),
-                                attr.span(),
-                                E0778,
-                                "`#[instruction_set]` requires an argument"
-                            )
-                            .emit();
+                            tcx.dcx().emit_err(errors::BareInstructionSet { span: attr.span() });
                             None
                         }
                         _ => {
-                            struct_span_code_err!(
-                                tcx.dcx(),
-                                attr.span(),
-                                E0779,
-                                "cannot specify more than one instruction set"
-                            )
-                            .emit();
+                            tcx.dcx()
+                                .emit_err(errors::MultipleInstructionSet { span: attr.span() });
                             None
                         }
                     })
@@ -445,58 +410,38 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
                     let mut entry = None;
                     for item in l {
                         let Some(meta_item) = item.meta_item() else {
-                            tcx.dcx().span_err(item.span(), "expected name value pair");
+                            tcx.dcx().emit_err(errors::ExpectedNameValuePair { span: item.span() });
                             continue;
                         };
 
                         let Some(name_value_lit) = meta_item.name_value_literal() else {
-                            tcx.dcx().span_err(item.span(), "expected name value pair");
+                            tcx.dcx().emit_err(errors::ExpectedNameValuePair { span: item.span() });
                             continue;
                         };
 
-                        fn emit_error_with_label(
-                            tcx: TyCtxt<'_>,
-                            span: Span,
-                            error: impl Into<DiagMessage>,
-                            label: impl Into<SubdiagMessage>,
-                        ) {
-                            let mut err: rustc_errors::Diag<'_, _> =
-                                tcx.dcx().struct_span_err(span, error);
-                            err.span_label(span, label);
-                            err.emit();
-                        }
-
                         let attrib_to_write = match meta_item.name_or_empty() {
                             sym::prefix_nops => &mut prefix,
                             sym::entry_nops => &mut entry,
                             _ => {
-                                emit_error_with_label(
-                                    tcx,
-                                    item.span(),
-                                    "unexpected parameter name",
-                                    format!("expected {} or {}", sym::prefix_nops, sym::entry_nops),
-                                );
+                                tcx.dcx().emit_err(errors::UnexpectedParameterName {
+                                    span: item.span(),
+                                    prefix_nops: sym::prefix_nops,
+                                    entry_nops: sym::entry_nops,
+                                });
                                 continue;
                             }
                         };
 
                         let rustc_ast::LitKind::Int(val, _) = name_value_lit.kind else {
-                            emit_error_with_label(
-                                tcx,
-                                name_value_lit.span,
-                                "invalid literal value",
-                                "value must be an integer between `0` and `255`",
-                            );
+                            tcx.dcx().emit_err(errors::InvalidLiteralValue {
+                                span: name_value_lit.span,
+                            });
                             continue;
                         };
 
                         let Ok(val) = val.get().try_into() else {
-                            emit_error_with_label(
-                                tcx,
-                                name_value_lit.span,
-                                "integer value out of range",
-                                "value must be between `0` and `255`",
-                            );
+                            tcx.dcx()
+                                .emit_err(errors::OutOfRangeInteger { span: name_value_lit.span });
                             continue;
                         };
 
@@ -533,7 +478,7 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
         inline_span = Some(attr.span());
 
         let [item] = &items[..] else {
-            struct_span_code_err!(tcx.dcx(), attr.span(), E0534, "expected one argument").emit();
+            tcx.dcx().emit_err(errors::ExpectedOneArgument { span: attr.span() });
             return InlineAttr::None;
         };
 
@@ -542,9 +487,7 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
         } else if item.has_name(sym::never) {
             InlineAttr::Never
         } else {
-            struct_span_code_err!(tcx.dcx(), items[0].span(), E0535, "invalid argument")
-                .with_help("valid inline arguments are `always` and `never`")
-                .emit();
+            tcx.dcx().emit_err(errors::InvalidArgument { span: items[0].span() });
 
             InlineAttr::None
         }
@@ -575,9 +518,8 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
         if !attr.has_name(sym::optimize) {
             return ia;
         }
-        let err = |sp, s| struct_span_code_err!(tcx.dcx(), sp, E0722, "{}", s).emit();
         if attr.is_word() {
-            err(attr.span(), "expected one argument");
+            tcx.dcx().emit_err(errors::ExpectedOneArgumentOptimize { span: attr.span() });
             return ia;
         }
         let Some(ref items) = attr.meta_item_list() else {
@@ -586,7 +528,7 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
 
         inline_span = Some(attr.span());
         let [item] = &items[..] else {
-            err(attr.span(), "expected one argument");
+            tcx.dcx().emit_err(errors::ExpectedOneArgumentOptimize { span: attr.span() });
             return OptimizeAttr::Default;
         };
         if item.has_name(sym::size) {
@@ -596,7 +538,7 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
         } else if item.has_name(sym::none) {
             OptimizeAttr::DoNotOptimize
         } else {
-            err(item.span(), "invalid argument");
+            tcx.dcx().emit_err(errors::InvalidArgumentOptimize { span: item.span() });
             OptimizeAttr::Default
         }
     });
@@ -930,15 +872,6 @@ fn autodiff_attrs(tcx: TyCtxt<'_>, id: DefId) -> Option<AutoDiffAttrs> {
         }
     }
 
-    for &input in &arg_activities {
-        if !valid_input_activity(mode, input) {
-            span_bug!(attr.span(), "Invalid input activity {} for {} mode", input, mode);
-        }
-    }
-    if !valid_ret_activity(mode, ret_activity) {
-        span_bug!(attr.span(), "Invalid return activity {} for {} mode", ret_activity, mode);
-    }
-
     Some(AutoDiffAttrs { mode, ret_activity, input_activity: arg_activities })
 }
 
diff --git a/compiler/rustc_codegen_ssa/src/errors.rs b/compiler/rustc_codegen_ssa/src/errors.rs
index ccf6d12977f..394c80fcfbd 100644
--- a/compiler/rustc_codegen_ssa/src/errors.rs
+++ b/compiler/rustc_codegen_ssa/src/errors.rs
@@ -136,6 +136,110 @@ pub(crate) struct NoSavedObjectFile<'a> {
 }
 
 #[derive(Diagnostic)]
+#[diag(codegen_ssa_requires_rust_abi, code = E0737)]
+pub(crate) struct RequiresRustAbi {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(codegen_ssa_null_on_export, code = E0648)]
+pub(crate) struct NullOnExport {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(codegen_ssa_unsupported_instruction_set, code = E0779)]
+pub(crate) struct UnsuportedInstructionSet {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(codegen_ssa_invalid_instruction_set, code = E0779)]
+pub(crate) struct InvalidInstructionSet {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(codegen_ssa_bare_instruction_set, code = E0778)]
+pub(crate) struct BareInstructionSet {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(codegen_ssa_multiple_instruction_set, code = E0779)]
+pub(crate) struct MultipleInstructionSet {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(codegen_ssa_expected_name_value_pair)]
+pub(crate) struct ExpectedNameValuePair {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(codegen_ssa_unexpected_parameter_name)]
+pub(crate) struct UnexpectedParameterName {
+    #[primary_span]
+    #[label]
+    pub span: Span,
+    pub prefix_nops: Symbol,
+    pub entry_nops: Symbol,
+}
+
+#[derive(Diagnostic)]
+#[diag(codegen_ssa_invalid_literal_value)]
+pub(crate) struct InvalidLiteralValue {
+    #[primary_span]
+    #[label]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(codegen_ssa_out_of_range_integer)]
+pub(crate) struct OutOfRangeInteger {
+    #[primary_span]
+    #[label]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(codegen_ssa_expected_one_argument, code = E0534)]
+pub(crate) struct ExpectedOneArgument {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(codegen_ssa_expected_one_argument, code = E0722)]
+pub(crate) struct ExpectedOneArgumentOptimize {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(codegen_ssa_invalid_argument, code = E0535)]
+#[help]
+pub(crate) struct InvalidArgument {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(codegen_ssa_invalid_argument, code = E0722)]
+pub(crate) struct InvalidArgumentOptimize {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
 #[diag(codegen_ssa_copy_path_buf)]
 pub(crate) struct CopyPathBuf {
     pub source_file: PathBuf,
diff --git a/compiler/rustc_codegen_ssa/src/mir/block.rs b/compiler/rustc_codegen_ssa/src/mir/block.rs
index e2a9b540d30..6d1930a402d 100644
--- a/compiler/rustc_codegen_ssa/src/mir/block.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/block.rs
@@ -3,6 +3,7 @@ use std::cmp;
 use rustc_abi::{BackendRepr, ExternAbi, HasDataLayout, Reg, WrappingRange};
 use rustc_ast as ast;
 use rustc_ast::{InlineAsmOptions, InlineAsmTemplatePiece};
+use rustc_data_structures::packed::Pu128;
 use rustc_hir::lang_items::LangItem;
 use rustc_middle::mir::{self, AssertKind, InlineAsmMacro, SwitchTargets, UnwindTerminateReason};
 use rustc_middle::ty::layout::{HasTyCtxt, LayoutOf, ValidityRequirement};
@@ -406,6 +407,39 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 let cmp = bx.icmp(IntPredicate::IntEQ, discr_value, llval);
                 bx.cond_br_with_expect(cmp, lltarget, llotherwise, expect);
             }
+        } else if target_iter.len() == 2
+            && self.mir[targets.otherwise()].is_empty_unreachable()
+            && targets.all_values().contains(&Pu128(0))
+            && targets.all_values().contains(&Pu128(1))
+        {
+            // This is the really common case for `bool`, `Option`, etc.
+            // By using `trunc nuw` we communicate that other values are
+            // impossible without needing `switch` or `assume`s.
+            let true_bb = targets.target_for_value(1);
+            let false_bb = targets.target_for_value(0);
+            let true_ll = helper.llbb_with_cleanup(self, true_bb);
+            let false_ll = helper.llbb_with_cleanup(self, false_bb);
+
+            let expected_cond_value = if self.cx.sess().opts.optimize == OptLevel::No {
+                None
+            } else {
+                match (self.cold_blocks[true_bb], self.cold_blocks[false_bb]) {
+                    // Same coldness, no expectation
+                    (true, true) | (false, false) => None,
+                    // Different coldness, expect the non-cold one
+                    (true, false) => Some(false),
+                    (false, true) => Some(true),
+                }
+            };
+
+            let bool_ty = bx.tcx().types.bool;
+            let cond = if switch_ty == bool_ty {
+                discr_value
+            } else {
+                let bool_llty = bx.immediate_backend_type(bx.layout_of(bool_ty));
+                bx.unchecked_utrunc(discr_value, bool_llty)
+            };
+            bx.cond_br_with_expect(cond, true_ll, false_ll, expected_cond_value);
         } else if self.cx.sess().opts.optimize == OptLevel::No
             && target_iter.len() == 2
             && self.mir[targets.otherwise()].is_empty_unreachable()
diff --git a/compiler/rustc_codegen_ssa/src/mir/place.rs b/compiler/rustc_codegen_ssa/src/mir/place.rs
index 00e01e47fee..6988724b421 100644
--- a/compiler/rustc_codegen_ssa/src/mir/place.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/place.rs
@@ -133,7 +133,7 @@ impl<'a, 'tcx, V: CodegenObject> PlaceRef<'tcx, V> {
         Self::alloca(bx, ptr_layout)
     }
 
-    pub fn len<Cx: ConstCodegenMethods<'tcx, Value = V>>(&self, cx: &Cx) -> V {
+    pub fn len<Cx: ConstCodegenMethods<Value = V>>(&self, cx: &Cx) -> V {
         if let FieldsShape::Array { count, .. } = self.layout.fields {
             if self.layout.is_unsized() {
                 assert_eq!(count, 0);
diff --git a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
index ff555f4273c..95b108b1d33 100644
--- a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
@@ -364,6 +364,13 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
     ) -> Bx::Value {
         assert_eq!(from_scalar.size(self.cx), to_scalar.size(self.cx));
 
+        // While optimizations will remove no-op transmutes, they might still be
+        // there in debug or things that aren't no-op in MIR because they change
+        // the Rust type but not the underlying layout/niche.
+        if from_scalar == to_scalar && from_backend_ty == to_backend_ty {
+            return imm;
+        }
+
         use abi::Primitive::*;
         imm = bx.from_immediate(imm);
 
diff --git a/compiler/rustc_codegen_ssa/src/target_features.rs b/compiler/rustc_codegen_ssa/src/target_features.rs
index 95a5e96fe46..8058cd1b178 100644
--- a/compiler/rustc_codegen_ssa/src/target_features.rs
+++ b/compiler/rustc_codegen_ssa/src/target_features.rs
@@ -190,7 +190,7 @@ pub(crate) fn provide(providers: &mut Providers) {
         },
         implied_target_features: |tcx, feature: Symbol| {
             let feature = feature.as_str();
-            UnordSet::from(tcx.sess.target.implied_target_features(std::iter::once(feature)))
+            UnordSet::from(tcx.sess.target.implied_target_features(feature))
                 .into_sorted_stable_ord()
                 .into_iter()
                 .map(|s| Symbol::intern(s))
diff --git a/compiler/rustc_codegen_ssa/src/traits/abi.rs b/compiler/rustc_codegen_ssa/src/traits/abi.rs
index 60d8f2a9ece..49c51caa996 100644
--- a/compiler/rustc_codegen_ssa/src/traits/abi.rs
+++ b/compiler/rustc_codegen_ssa/src/traits/abi.rs
@@ -1,5 +1,5 @@
 use super::BackendTypes;
 
-pub trait AbiBuilderMethods<'tcx>: BackendTypes {
+pub trait AbiBuilderMethods: BackendTypes {
     fn get_param(&mut self, index: usize) -> Self::Value;
 }
diff --git a/compiler/rustc_codegen_ssa/src/traits/backend.rs b/compiler/rustc_codegen_ssa/src/traits/backend.rs
index ebcf118b903..65fd843e7a5 100644
--- a/compiler/rustc_codegen_ssa/src/traits/backend.rs
+++ b/compiler/rustc_codegen_ssa/src/traits/backend.rs
@@ -45,10 +45,13 @@ pub trait CodegenBackend {
 
     fn print(&self, _req: &PrintRequest, _out: &mut String, _sess: &Session) {}
 
-    /// Returns the features that should be set in `cfg(target_features)`.
+    /// Returns two feature sets:
+    /// - The first has the features that should be set in `cfg(target_features)`.
+    /// - The second is like the first, but also includes unstable features.
+    ///
     /// RUSTC_SPECIFIC_FEATURES should be skipped here, those are handled outside codegen.
-    fn target_features_cfg(&self, _sess: &Session, _allow_unstable: bool) -> Vec<Symbol> {
-        vec![]
+    fn target_features_cfg(&self, _sess: &Session) -> (Vec<Symbol>, Vec<Symbol>) {
+        (vec![], vec![])
     }
 
     fn print_passes(&self) {}
diff --git a/compiler/rustc_codegen_ssa/src/traits/builder.rs b/compiler/rustc_codegen_ssa/src/traits/builder.rs
index 99fd6b6510f..5f91133d5b4 100644
--- a/compiler/rustc_codegen_ssa/src/traits/builder.rs
+++ b/compiler/rustc_codegen_ssa/src/traits/builder.rs
@@ -40,7 +40,7 @@ pub trait BuilderMethods<'a, 'tcx>:
     + CoverageInfoBuilderMethods<'tcx>
     + DebugInfoBuilderMethods
     + ArgAbiBuilderMethods<'tcx>
-    + AbiBuilderMethods<'tcx>
+    + AbiBuilderMethods
     + IntrinsicCallBuilderMethods<'tcx>
     + AsmBuilderMethods<'tcx>
     + StaticBuilderMethods
diff --git a/compiler/rustc_codegen_ssa/src/traits/consts.rs b/compiler/rustc_codegen_ssa/src/traits/consts.rs
index dc6b68ceff7..d83a04d814b 100644
--- a/compiler/rustc_codegen_ssa/src/traits/consts.rs
+++ b/compiler/rustc_codegen_ssa/src/traits/consts.rs
@@ -3,7 +3,7 @@ use rustc_middle::mir::interpret::{ConstAllocation, Scalar};
 
 use super::BackendTypes;
 
-pub trait ConstCodegenMethods<'tcx>: BackendTypes {
+pub trait ConstCodegenMethods: BackendTypes {
     // Constant constructors
     fn const_null(&self, t: Self::Type) -> Self::Value;
     /// Generate an uninitialized value (matching uninitialized memory in MIR).
@@ -37,7 +37,7 @@ pub trait ConstCodegenMethods<'tcx>: BackendTypes {
     fn const_to_opt_uint(&self, v: Self::Value) -> Option<u64>;
     fn const_to_opt_u128(&self, v: Self::Value, sign_ext: bool) -> Option<u128>;
 
-    fn const_data_from_alloc(&self, alloc: ConstAllocation<'tcx>) -> Self::Value;
+    fn const_data_from_alloc(&self, alloc: ConstAllocation<'_>) -> Self::Value;
 
     fn scalar_to_backend(&self, cv: Scalar, layout: abi::Scalar, llty: Self::Type) -> Self::Value;
 
diff --git a/compiler/rustc_codegen_ssa/src/traits/mod.rs b/compiler/rustc_codegen_ssa/src/traits/mod.rs
index 90fcfbe4da7..239857a4298 100644
--- a/compiler/rustc_codegen_ssa/src/traits/mod.rs
+++ b/compiler/rustc_codegen_ssa/src/traits/mod.rs
@@ -55,7 +55,7 @@ pub trait CodegenObject = Copy + PartialEq + fmt::Debug;
 pub trait CodegenMethods<'tcx> = LayoutOf<'tcx, LayoutOfResult = TyAndLayout<'tcx>>
     + FnAbiOf<'tcx, FnAbiOfResult = &'tcx FnAbi<'tcx, Ty<'tcx>>>
     + TypeCodegenMethods<'tcx>
-    + ConstCodegenMethods<'tcx>
+    + ConstCodegenMethods
     + StaticCodegenMethods
     + DebugInfoCodegenMethods<'tcx>
     + AsmCodegenMethods<'tcx>
diff --git a/compiler/rustc_codegen_ssa/src/traits/type_.rs b/compiler/rustc_codegen_ssa/src/traits/type_.rs
index fbd927d0d66..32d9f27d32d 100644
--- a/compiler/rustc_codegen_ssa/src/traits/type_.rs
+++ b/compiler/rustc_codegen_ssa/src/traits/type_.rs
@@ -9,7 +9,7 @@ use super::misc::MiscCodegenMethods;
 use crate::common::TypeKind;
 use crate::mir::place::PlaceRef;
 
-pub trait BaseTypeCodegenMethods<'tcx>: BackendTypes {
+pub trait BaseTypeCodegenMethods: BackendTypes {
     fn type_i8(&self) -> Self::Type;
     fn type_i16(&self) -> Self::Type;
     fn type_i32(&self) -> Self::Type;
@@ -41,7 +41,7 @@ pub trait BaseTypeCodegenMethods<'tcx>: BackendTypes {
 }
 
 pub trait DerivedTypeCodegenMethods<'tcx>:
-    BaseTypeCodegenMethods<'tcx> + MiscCodegenMethods<'tcx> + HasTyCtxt<'tcx> + HasTypingEnv<'tcx>
+    BaseTypeCodegenMethods + MiscCodegenMethods<'tcx> + HasTyCtxt<'tcx> + HasTypingEnv<'tcx>
 {
     fn type_int(&self) -> Self::Type {
         match &self.sess().target.c_int_width[..] {
@@ -87,10 +87,7 @@ pub trait DerivedTypeCodegenMethods<'tcx>:
 }
 
 impl<'tcx, T> DerivedTypeCodegenMethods<'tcx> for T where
-    Self: BaseTypeCodegenMethods<'tcx>
-        + MiscCodegenMethods<'tcx>
-        + HasTyCtxt<'tcx>
-        + HasTypingEnv<'tcx>
+    Self: BaseTypeCodegenMethods + MiscCodegenMethods<'tcx> + HasTyCtxt<'tcx> + HasTypingEnv<'tcx>
 {
 }
 
diff --git a/compiler/rustc_const_eval/src/interpret/intern.rs b/compiler/rustc_const_eval/src/interpret/intern.rs
index 43631330f89..e4b2fe5d153 100644
--- a/compiler/rustc_const_eval/src/interpret/intern.rs
+++ b/compiler/rustc_const_eval/src/interpret/intern.rs
@@ -104,7 +104,7 @@ fn intern_as_new_static<'tcx>(
 ) {
     let feed = tcx.create_def(
         static_id,
-        sym::nested,
+        Some(sym::nested),
         DefKind::Static { safety: hir::Safety::Safe, mutability: alloc.0.mutability, nested: true },
     );
     tcx.set_nested_alloc_id_static(alloc_id, feed.def_id());
diff --git a/compiler/rustc_const_eval/src/interpret/memory.rs b/compiler/rustc_const_eval/src/interpret/memory.rs
index ce0b5a350e0..e5af0673629 100644
--- a/compiler/rustc_const_eval/src/interpret/memory.rs
+++ b/compiler/rustc_const_eval/src/interpret/memory.rs
@@ -982,6 +982,10 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                     todo.push(id);
                 }
             }
+            // Also expose the provenance of the interpreter-level allocation, so it can
+            // be read by FFI. The `black_box` is defensive programming as LLVM likes
+            // to (incorrectly) optimize away ptr2int casts whose result is unused.
+            std::hint::black_box(alloc.get_bytes_unchecked_raw().expose_provenance());
 
             // Prepare for possible write from native code if mutable.
             if info.mutbl.is_mut() {
diff --git a/compiler/rustc_data_structures/src/aligned.rs b/compiler/rustc_data_structures/src/aligned.rs
index 0e5ecfd9bff..a636d09fcae 100644
--- a/compiler/rustc_data_structures/src/aligned.rs
+++ b/compiler/rustc_data_structures/src/aligned.rs
@@ -2,10 +2,8 @@ use std::ptr::Alignment;
 
 /// Returns the ABI-required minimum alignment of a type in bytes.
 ///
-/// This is equivalent to [`mem::align_of`], but also works for some unsized
+/// This is equivalent to [`align_of`], but also works for some unsized
 /// types (e.g. slices or rustc's `List`s).
-///
-/// [`mem::align_of`]: std::mem::align_of
 pub const fn align_of<T: ?Sized + Aligned>() -> Alignment {
     T::ALIGN
 }
@@ -15,10 +13,10 @@ pub const fn align_of<T: ?Sized + Aligned>() -> Alignment {
 /// # Safety
 ///
 /// `Self::ALIGN` must be equal to the alignment of `Self`. For sized types it
-/// is [`mem::align_of<Self>()`], for unsized types it depends on the type, for
+/// is [`align_of::<Self>()`], for unsized types it depends on the type, for
 /// example `[T]` has alignment of `T`.
 ///
-/// [`mem::align_of<Self>()`]: std::mem::align_of
+/// [`align_of::<Self>()`]: align_of
 pub unsafe trait Aligned {
     /// Alignment of `Self`.
     const ALIGN: Alignment;
diff --git a/compiler/rustc_data_structures/src/obligation_forest/mod.rs b/compiler/rustc_data_structures/src/obligation_forest/mod.rs
index 78d69a66edc..ea3ac467340 100644
--- a/compiler/rustc_data_structures/src/obligation_forest/mod.rs
+++ b/compiler/rustc_data_structures/src/obligation_forest/mod.rs
@@ -315,6 +315,7 @@ mod helper {
     use super::*;
     pub type ObligationTreeIdGenerator = impl Iterator<Item = ObligationTreeId>;
     impl<O: ForestObligation> ObligationForest<O> {
+        #[cfg_attr(not(bootstrap), define_opaque(ObligationTreeIdGenerator))]
         pub fn new() -> ObligationForest<O> {
             ObligationForest {
                 nodes: vec![],
diff --git a/compiler/rustc_data_structures/src/profiling.rs b/compiler/rustc_data_structures/src/profiling.rs
index 39db551adfb..60f007083ba 100644
--- a/compiler/rustc_data_structures/src/profiling.rs
+++ b/compiler/rustc_data_structures/src/profiling.rs
@@ -863,15 +863,13 @@ fn get_thread_id() -> u32 {
 cfg_match! {
     windows => {
         pub fn get_resident_set_size() -> Option<usize> {
-            use std::mem;
-
             use windows::{
                 Win32::System::ProcessStatus::{K32GetProcessMemoryInfo, PROCESS_MEMORY_COUNTERS},
                 Win32::System::Threading::GetCurrentProcess,
             };
 
             let mut pmc = PROCESS_MEMORY_COUNTERS::default();
-            let pmc_size = mem::size_of_val(&pmc);
+            let pmc_size = size_of_val(&pmc);
             unsafe {
                 K32GetProcessMemoryInfo(
                     GetCurrentProcess(),
@@ -889,7 +887,7 @@ cfg_match! {
         pub fn get_resident_set_size() -> Option<usize> {
             use libc::{c_int, c_void, getpid, proc_pidinfo, proc_taskinfo, PROC_PIDTASKINFO};
             use std::mem;
-            const PROC_TASKINFO_SIZE: c_int = mem::size_of::<proc_taskinfo>() as c_int;
+            const PROC_TASKINFO_SIZE: c_int = size_of::<proc_taskinfo>() as c_int;
 
             unsafe {
                 let mut info: proc_taskinfo = mem::zeroed();
diff --git a/compiler/rustc_data_structures/src/sharded.rs b/compiler/rustc_data_structures/src/sharded.rs
index e6be9c256f0..3016348f224 100644
--- a/compiler/rustc_data_structures/src/sharded.rs
+++ b/compiler/rustc_data_structures/src/sharded.rs
@@ -1,7 +1,7 @@
 use std::borrow::Borrow;
 use std::collections::hash_map::RawEntryMut;
 use std::hash::{Hash, Hasher};
-use std::{iter, mem};
+use std::iter;
 
 use either::Either;
 
@@ -221,7 +221,7 @@ pub fn make_hash<K: Hash + ?Sized>(val: &K) -> u64 {
 /// consistently for each `Sharded` instance.
 #[inline]
 fn get_shard_hash(hash: u64) -> usize {
-    let hash_len = mem::size_of::<usize>();
+    let hash_len = size_of::<usize>();
     // Ignore the top 7 bits as hashbrown uses these and get the next SHARD_BITS highest bits.
     // hashbrown also uses the lowest bits, so we can't use those
     (hash >> (hash_len * 8 - 7 - SHARD_BITS)) as usize
diff --git a/compiler/rustc_error_codes/src/error_codes/E0792.md b/compiler/rustc_error_codes/src/error_codes/E0792.md
index 5e3dcc4aa72..033e1c65192 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0792.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0792.md
@@ -7,6 +7,7 @@ This means
 
 type Foo<T> = impl std::fmt::Debug;
 
+#[define_opaque(Foo)]
 fn foo() -> Foo<u32> {
     5u32
 }
@@ -19,6 +20,7 @@ is not accepted. If it were accepted, one could create unsound situations like
 
 type Foo<T> = impl Default;
 
+#[define_opaque(Foo)]
 fn foo() -> Foo<u32> {
     5u32
 }
@@ -36,6 +38,7 @@ Instead you need to make the function generic:
 
 type Foo<T> = impl std::fmt::Debug;
 
+#[define_opaque(Foo)]
 fn foo<U>() -> Foo<U> {
     5u32
 }
@@ -56,6 +59,7 @@ use std::fmt::Debug;
 
 type Foo<T: Debug> = impl Debug;
 
+#[define_opaque(Foo)]
 fn foo<U: Debug>() -> Foo<U> {
     Vec::<U>::new()
 }
diff --git a/compiler/rustc_error_messages/src/lib.rs b/compiler/rustc_error_messages/src/lib.rs
index ba1c3e185c2..6d02d6370fc 100644
--- a/compiler/rustc_error_messages/src/lib.rs
+++ b/compiler/rustc_error_messages/src/lib.rs
@@ -209,6 +209,7 @@ pub type LazyFallbackBundle = Arc<LazyLock<FluentBundle, impl FnOnce() -> Fluent
 
 /// Return the default `FluentBundle` with standard "en-US" diagnostic messages.
 #[instrument(level = "trace", skip(resources))]
+#[cfg_attr(not(bootstrap), define_opaque(LazyFallbackBundle))]
 pub fn fallback_fluent_bundle(
     resources: Vec<&'static str>,
     with_directionality_markers: bool,
diff --git a/compiler/rustc_errors/src/diagnostic.rs b/compiler/rustc_errors/src/diagnostic.rs
index 7fffeaddb86..9f4d2ea5c1a 100644
--- a/compiler/rustc_errors/src/diagnostic.rs
+++ b/compiler/rustc_errors/src/diagnostic.rs
@@ -490,7 +490,7 @@ pub struct Diag<'a, G: EmissionGuarantee = ErrorGuaranteed> {
 // would be bad.
 impl<G> !Clone for Diag<'_, G> {}
 
-rustc_data_structures::static_assert_size!(Diag<'_, ()>, 3 * std::mem::size_of::<usize>());
+rustc_data_structures::static_assert_size!(Diag<'_, ()>, 3 * size_of::<usize>());
 
 impl<G: EmissionGuarantee> Deref for Diag<'_, G> {
     type Target = DiagInner;
diff --git a/compiler/rustc_errors/src/emitter.rs b/compiler/rustc_errors/src/emitter.rs
index f7f84239308..21255fcca96 100644
--- a/compiler/rustc_errors/src/emitter.rs
+++ b/compiler/rustc_errors/src/emitter.rs
@@ -113,24 +113,11 @@ impl Margin {
         self.computed_left > 0
     }
 
-    fn was_cut_right(&self, line_len: usize) -> bool {
-        let right =
-            if self.computed_right == self.span_right || self.computed_right == self.label_right {
-                // FIXME: This comment refers to the only callsite of this method.
-                //        Rephrase it or refactor it, so it can stand on its own.
-                // Account for the "..." padding given above. Otherwise we end up with code lines
-                // that do fit but end in "..." as if they were trimmed.
-                // FIXME: Don't hard-code this offset. Is this meant to represent
-                //        `2 * str_width(self.margin())`?
-                self.computed_right - 6
-            } else {
-                self.computed_right
-            };
-        right < line_len && self.computed_left + self.column_width < line_len
-    }
-
     fn compute(&mut self, max_line_len: usize) {
         // When there's a lot of whitespace (>20), we want to trim it as it is useless.
+        // FIXME: this doesn't account for '\t', but to do so correctly we need to perform that
+        // calculation later, right before printing in order to be accurate with both unicode
+        // handling and trimming of long lines.
         self.computed_left = if self.whitespace_left > 20 {
             self.whitespace_left - 16 // We want some padding.
         } else {
@@ -616,7 +603,6 @@ pub struct HumanEmitter {
     #[setters(skip)]
     fallback_bundle: LazyFallbackBundle,
     short_message: bool,
-    teach: bool,
     ui_testing: bool,
     ignored_directories_in_source_blocks: Vec<String>,
     diagnostic_width: Option<usize>,
@@ -642,7 +628,6 @@ impl HumanEmitter {
             fluent_bundle: None,
             fallback_bundle,
             short_message: false,
-            teach: false,
             ui_testing: false,
             ignored_directories_in_source_blocks: Vec::new(),
             diagnostic_width: None,
@@ -670,43 +655,43 @@ impl HumanEmitter {
         width_offset: usize,
         code_offset: usize,
         margin: Margin,
-    ) {
-        // Tabs are assumed to have been replaced by spaces in calling code.
-        debug_assert!(!source_string.contains('\t'));
+    ) -> usize {
         let line_len = source_string.len();
         // Create the source line we will highlight.
         let left = margin.left(line_len);
         let right = margin.right(line_len);
         // FIXME: The following code looks fishy. See #132860.
         // On long lines, we strip the source line, accounting for unicode.
-        let mut taken = 0;
         let code: String = source_string
             .chars()
-            .skip(left)
-            .take_while(|ch| {
-                // Make sure that the trimming on the right will fall within the terminal width.
-                let next = char_width(*ch);
-                if taken + next > right - left {
-                    return false;
-                }
-                taken += next;
-                true
-            })
+            .enumerate()
+            .skip_while(|(i, _)| *i < left)
+            .take_while(|(i, _)| *i < right)
+            .map(|(_, c)| c)
             .collect();
+        let code = normalize_whitespace(&code);
+        let was_cut_right =
+            source_string.chars().enumerate().skip_while(|(i, _)| *i < right).next().is_some();
         buffer.puts(line_offset, code_offset, &code, Style::Quotation);
         let placeholder = self.margin();
         if margin.was_cut_left() {
             // We have stripped some code/whitespace from the beginning, make it clear.
             buffer.puts(line_offset, code_offset, placeholder, Style::LineNumber);
         }
-        if margin.was_cut_right(line_len) {
+        if was_cut_right {
             let padding = str_width(placeholder);
             // We have stripped some code after the rightmost span end, make it clear we did so.
-            buffer.puts(line_offset, code_offset + taken - padding, placeholder, Style::LineNumber);
+            buffer.puts(
+                line_offset,
+                code_offset + str_width(&code) - padding,
+                placeholder,
+                Style::LineNumber,
+            );
         }
         buffer.puts(line_offset, 0, &self.maybe_anonymized(line_index), Style::LineNumber);
 
         self.draw_col_separator_no_space(buffer, line_offset, width_offset - 2);
+        left
     }
 
     #[instrument(level = "trace", skip(self), ret)]
@@ -738,22 +723,16 @@ impl HumanEmitter {
             return Vec::new();
         }
 
-        let source_string = match file.get_line(line.line_index - 1) {
-            Some(s) => normalize_whitespace(&s),
-            None => return Vec::new(),
+        let Some(source_string) = file.get_line(line.line_index - 1) else {
+            return Vec::new();
         };
         trace!(?source_string);
 
         let line_offset = buffer.num_lines();
 
-        // Left trim
-        let left = margin.left(source_string.len());
-
+        // Left trim.
         // FIXME: This looks fishy. See #132860.
-        // Account for unicode characters of width !=0 that were removed.
-        let left = source_string.chars().take(left).map(|ch| char_width(ch)).sum();
-
-        self.draw_line(
+        let left = self.draw_line(
             buffer,
             &source_string,
             line.line_index,
@@ -784,7 +763,7 @@ impl HumanEmitter {
         let mut short_start = true;
         for ann in &line.annotations {
             if let AnnotationType::MultilineStart(depth) = ann.annotation_type {
-                if source_string.chars().take(ann.start_col.display).all(|c| c.is_whitespace()) {
+                if source_string.chars().take(ann.start_col.file).all(|c| c.is_whitespace()) {
                     let uline = self.underline(ann.is_primary);
                     let chr = uline.multiline_whole_line;
                     annotations.push((depth, uline.style));
@@ -903,11 +882,16 @@ impl HumanEmitter {
         //      |      x_span
         //      <EMPTY LINE>
         //
+        let mut overlap = vec![false; annotations.len()];
         let mut annotations_position = vec![];
         let mut line_len: usize = 0;
         let mut p = 0;
         for (i, annotation) in annotations.iter().enumerate() {
             for (j, next) in annotations.iter().enumerate() {
+                if overlaps(next, annotation, 0) && j > i {
+                    overlap[i] = true;
+                    overlap[j] = true;
+                }
                 if overlaps(next, annotation, 0)  // This label overlaps with another one and both
                     && annotation.has_label()     // take space (they have text and are not
                     && j > i                      // multiline lines).
@@ -1035,24 +1019,21 @@ impl HumanEmitter {
             let pos = pos + 1;
             match annotation.annotation_type {
                 AnnotationType::MultilineStart(depth) | AnnotationType::MultilineEnd(depth) => {
+                    let pre: usize = source_string
+                        .chars()
+                        .take(annotation.start_col.file)
+                        .skip(left)
+                        .map(|c| char_width(c))
+                        .sum();
                     self.draw_range(
                         buffer,
                         underline.multiline_horizontal,
                         line_offset + pos,
                         width_offset + depth,
-                        (code_offset + annotation.start_col.display).saturating_sub(left),
+                        code_offset + pre,
                         underline.style,
                     );
                 }
-                _ if self.teach => {
-                    buffer.set_style_range(
-                        line_offset,
-                        (code_offset + annotation.start_col.display).saturating_sub(left),
-                        (code_offset + annotation.end_col.display).saturating_sub(left),
-                        underline.style,
-                        annotation.is_primary,
-                    );
-                }
                 _ => {}
             }
         }
@@ -1072,11 +1053,18 @@ impl HumanEmitter {
             let underline = self.underline(annotation.is_primary);
             let pos = pos + 1;
 
+            let code_offset = code_offset
+                + source_string
+                    .chars()
+                    .take(annotation.start_col.file)
+                    .skip(left)
+                    .map(|c| char_width(c))
+                    .sum::<usize>();
             if pos > 1 && (annotation.has_label() || annotation.takes_space()) {
                 for p in line_offset + 1..=line_offset + pos {
                     buffer.putc(
                         p,
-                        (code_offset + annotation.start_col.display).saturating_sub(left),
+                        code_offset,
                         match annotation.annotation_type {
                             AnnotationType::MultilineLine(_) => underline.multiline_vertical,
                             _ => underline.vertical_text_line,
@@ -1087,7 +1075,7 @@ impl HumanEmitter {
                 if let AnnotationType::MultilineStart(_) = annotation.annotation_type {
                     buffer.putc(
                         line_offset + pos,
-                        (code_offset + annotation.start_col.display).saturating_sub(left),
+                        code_offset,
                         underline.bottom_right,
                         underline.style,
                     );
@@ -1097,7 +1085,7 @@ impl HumanEmitter {
                 {
                     buffer.putc(
                         line_offset + pos,
-                        (code_offset + annotation.start_col.display).saturating_sub(left),
+                        code_offset,
                         underline.multiline_bottom_right_with_text,
                         underline.style,
                     );
@@ -1155,13 +1143,30 @@ impl HumanEmitter {
             let style =
                 if annotation.is_primary { Style::LabelPrimary } else { Style::LabelSecondary };
             let (pos, col) = if pos == 0 {
-                if annotation.end_col.display == 0 {
-                    (pos + 1, (annotation.end_col.display + 2).saturating_sub(left))
+                let pre: usize = source_string
+                    .chars()
+                    .take(annotation.end_col.file)
+                    .skip(left)
+                    .map(|c| char_width(c))
+                    .sum();
+                if annotation.end_col.file == 0 {
+                    (pos + 1, (pre + 2))
                 } else {
-                    (pos + 1, (annotation.end_col.display + 1).saturating_sub(left))
+                    let pad = if annotation.end_col.file - annotation.start_col.file == 0 {
+                        2
+                    } else {
+                        1
+                    };
+                    (pos + 1, (pre + pad))
                 }
             } else {
-                (pos + 2, annotation.start_col.display.saturating_sub(left))
+                let pre: usize = source_string
+                    .chars()
+                    .take(annotation.start_col.file)
+                    .skip(left)
+                    .map(|c| char_width(c))
+                    .sum();
+                (pos + 2, pre)
             };
             if let Some(ref label) = annotation.label {
                 buffer.puts(line_offset + pos, code_offset + col, label, style);
@@ -1194,14 +1199,35 @@ impl HumanEmitter {
         //   |  _^  test
         for &(pos, annotation) in &annotations_position {
             let uline = self.underline(annotation.is_primary);
-            for p in annotation.start_col.display..annotation.end_col.display {
+            let width = annotation.end_col.file - annotation.start_col.file;
+            let previous: String =
+                source_string.chars().take(annotation.start_col.file).skip(left).collect();
+            let underlined: String =
+                source_string.chars().skip(annotation.start_col.file).take(width).collect();
+            debug!(?previous, ?underlined);
+            let code_offset = code_offset
+                + source_string
+                    .chars()
+                    .take(annotation.start_col.file)
+                    .skip(left)
+                    .map(|c| char_width(c))
+                    .sum::<usize>();
+            let ann_width: usize = source_string
+                .chars()
+                .skip(annotation.start_col.file)
+                .take(width)
+                .map(|c| char_width(c))
+                .sum();
+            let ann_width = if ann_width == 0
+                && matches!(annotation.annotation_type, AnnotationType::Singleline)
+            {
+                1
+            } else {
+                ann_width
+            };
+            for p in 0..ann_width {
                 // The default span label underline.
-                buffer.putc(
-                    line_offset + 1,
-                    (code_offset + p).saturating_sub(left),
-                    uline.underline,
-                    uline.style,
-                );
+                buffer.putc(line_offset + 1, code_offset + p, uline.underline, uline.style);
             }
 
             if pos == 0
@@ -1213,7 +1239,7 @@ impl HumanEmitter {
                 // The beginning of a multiline span with its leftward moving line on the same line.
                 buffer.putc(
                     line_offset + 1,
-                    (code_offset + annotation.start_col.display).saturating_sub(left),
+                    code_offset,
                     match annotation.annotation_type {
                         AnnotationType::MultilineStart(_) => uline.top_right_flat,
                         AnnotationType::MultilineEnd(_) => uline.multiline_end_same_line,
@@ -1231,7 +1257,7 @@ impl HumanEmitter {
                 // so we start going down first.
                 buffer.putc(
                     line_offset + 1,
-                    (code_offset + annotation.start_col.display).saturating_sub(left),
+                    code_offset,
                     match annotation.annotation_type {
                         AnnotationType::MultilineStart(_) => uline.multiline_start_down,
                         AnnotationType::MultilineEnd(_) => uline.multiline_end_up,
@@ -1241,11 +1267,37 @@ impl HumanEmitter {
                 );
             } else if pos != 0 && annotation.has_label() {
                 // The beginning of a span label with an actual label, we'll point down.
-                buffer.putc(
+                buffer.putc(line_offset + 1, code_offset, uline.label_start, uline.style);
+            }
+        }
+
+        // We look for individual *long* spans, and we trim the *middle*, so that we render
+        // LL | ...= [0, 0, 0, ..., 0, 0];
+        //    |      ^^^^^^^^^^...^^^^^^^ expected `&[u8]`, found `[{integer}; 1680]`
+        for (i, (_pos, annotation)) in annotations_position.iter().enumerate() {
+            // Skip cases where multiple spans overlap each other.
+            if overlap[i] {
+                continue;
+            };
+            let AnnotationType::Singleline = annotation.annotation_type else { continue };
+            let width = annotation.end_col.display - annotation.start_col.display;
+            if width > margin.column_width * 2 && width > 10 {
+                // If the terminal is *too* small, we keep at least a tiny bit of the span for
+                // display.
+                let pad = max(margin.column_width / 3, 5);
+                // Code line
+                buffer.replace(
+                    line_offset,
+                    annotation.start_col.file + pad,
+                    annotation.end_col.file - pad,
+                    self.margin(),
+                );
+                // Underline line
+                buffer.replace(
                     line_offset + 1,
-                    (code_offset + annotation.start_col.display).saturating_sub(left),
-                    uline.label_start,
-                    uline.style,
+                    annotation.start_col.file + pad,
+                    annotation.end_col.file - pad,
+                    self.margin(),
                 );
             }
         }
@@ -1702,17 +1754,11 @@ impl HumanEmitter {
                         // non-rustc_lexer::is_whitespace() chars are reported as an
                         // error (ex. no-break-spaces \u{a0}), and thus can't be considered
                         // for removal during error reporting.
+                        // FIXME: doesn't account for '\t' properly.
                         let leading_whitespace = source_string
                             .chars()
                             .take_while(|c| rustc_lexer::is_whitespace(*c))
-                            .map(|c| {
-                                match c {
-                                    // Tabs are displayed as 4 spaces
-                                    '\t' => 4,
-                                    _ => 1,
-                                }
-                            })
-                            .sum();
+                            .count();
                         if source_string.chars().any(|c| !rustc_lexer::is_whitespace(c)) {
                             whitespace_margin = min(whitespace_margin, leading_whitespace);
                         }
@@ -1726,8 +1772,8 @@ impl HumanEmitter {
                 let mut span_left_margin = usize::MAX;
                 for line in &annotated_file.lines {
                     for ann in &line.annotations {
-                        span_left_margin = min(span_left_margin, ann.start_col.display);
-                        span_left_margin = min(span_left_margin, ann.end_col.display);
+                        span_left_margin = min(span_left_margin, ann.start_col.file);
+                        span_left_margin = min(span_left_margin, ann.end_col.file);
                     }
                 }
                 if span_left_margin == usize::MAX {
@@ -1747,12 +1793,12 @@ impl HumanEmitter {
                             .map_or(0, |s| s.len()),
                     );
                     for ann in &line.annotations {
-                        span_right_margin = max(span_right_margin, ann.start_col.display);
-                        span_right_margin = max(span_right_margin, ann.end_col.display);
+                        span_right_margin = max(span_right_margin, ann.start_col.file);
+                        span_right_margin = max(span_right_margin, ann.end_col.file);
                         // FIXME: account for labels not in the same line
                         let label_right = ann.label.as_ref().map_or(0, |l| l.len() + 1);
                         label_right_margin =
-                            max(label_right_margin, ann.end_col.display + label_right);
+                            max(label_right_margin, ann.end_col.file + label_right);
                     }
                 }
 
@@ -1763,15 +1809,7 @@ impl HumanEmitter {
                     width_offset + annotated_file.multiline_depth + 1
                 };
 
-                let column_width = if let Some(width) = self.diagnostic_width {
-                    width.saturating_sub(code_offset)
-                } else if self.ui_testing || cfg!(miri) {
-                    DEFAULT_COLUMN_WIDTH
-                } else {
-                    termize::dimensions()
-                        .map(|(w, _)| w.saturating_sub(code_offset))
-                        .unwrap_or(DEFAULT_COLUMN_WIDTH)
-                };
+                let column_width = self.column_width(code_offset);
 
                 let margin = Margin::new(
                     whitespace_margin,
@@ -1928,6 +1966,18 @@ impl HumanEmitter {
         Ok(())
     }
 
+    fn column_width(&self, code_offset: usize) -> usize {
+        if let Some(width) = self.diagnostic_width {
+            width.saturating_sub(code_offset)
+        } else if self.ui_testing || cfg!(miri) {
+            DEFAULT_COLUMN_WIDTH
+        } else {
+            termize::dimensions()
+                .map(|(w, _)| w.saturating_sub(code_offset))
+                .unwrap_or(DEFAULT_COLUMN_WIDTH)
+        }
+    }
+
     fn emit_suggestion_default(
         &mut self,
         span: &MultiSpan,
diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index f69e756a3e1..86959b28e53 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -14,6 +14,7 @@
 #![feature(associated_type_defaults)]
 #![feature(box_into_inner)]
 #![feature(box_patterns)]
+#![feature(default_field_values)]
 #![feature(error_reporter)]
 #![feature(if_let_guard)]
 #![feature(let_chains)]
diff --git a/compiler/rustc_errors/src/markdown/parse.rs b/compiler/rustc_errors/src/markdown/parse.rs
index 7a991a2ace7..f02387d8335 100644
--- a/compiler/rustc_errors/src/markdown/parse.rs
+++ b/compiler/rustc_errors/src/markdown/parse.rs
@@ -40,11 +40,13 @@ type ParseResult<'a> = Option<Parsed<'a>>;
 
 /// Parsing context
 #[derive(Clone, Copy, Debug, PartialEq)]
+// The default values are the most common setting for non top-level parsing: not top block, not at
+// line start (yes leading whitespace, not escaped).
 struct Context {
     /// If true, we are at a the topmost level (not recursing a nested tt)
-    top_block: bool,
+    top_block: bool = false,
     /// Previous character
-    prev: Prev,
+    prev: Prev = Prev::Whitespace,
 }
 
 /// Character class preceding this one
@@ -57,14 +59,6 @@ enum Prev {
     Any,
 }
 
-impl Default for Context {
-    /// Most common setting for non top-level parsing: not top block, not at
-    /// line start (yes leading whitespace, not escaped)
-    fn default() -> Self {
-        Self { top_block: false, prev: Prev::Whitespace }
-    }
-}
-
 /// Flags to simple parser function
 #[derive(Clone, Copy, Debug, PartialEq)]
 enum ParseOpt {
@@ -248,7 +242,7 @@ fn parse_heading(buf: &[u8]) -> ParseResult<'_> {
     }
 
     let (txt, rest) = parse_to_newline(&buf[1..]);
-    let ctx = Context { top_block: false, prev: Prev::Whitespace };
+    let ctx = Context { .. };
     let stream = parse_recursive(txt, ctx);
 
     Some((MdTree::Heading(level.try_into().unwrap(), stream), rest))
@@ -257,7 +251,7 @@ fn parse_heading(buf: &[u8]) -> ParseResult<'_> {
 /// Bulleted list
 fn parse_unordered_li(buf: &[u8]) -> Parsed<'_> {
     let (txt, rest) = get_indented_section(&buf[2..]);
-    let ctx = Context { top_block: false, prev: Prev::Whitespace };
+    let ctx = Context { .. };
     let stream = parse_recursive(trim_ascii_start(txt), ctx);
     (MdTree::UnorderedListItem(stream), rest)
 }
@@ -266,7 +260,7 @@ fn parse_unordered_li(buf: &[u8]) -> Parsed<'_> {
 fn parse_ordered_li(buf: &[u8]) -> Parsed<'_> {
     let (num, pos) = ord_list_start(buf).unwrap(); // success tested in caller
     let (txt, rest) = get_indented_section(&buf[pos..]);
-    let ctx = Context { top_block: false, prev: Prev::Whitespace };
+    let ctx = Context { .. };
     let stream = parse_recursive(trim_ascii_start(txt), ctx);
     (MdTree::OrderedListItem(num, stream), rest)
 }
diff --git a/compiler/rustc_errors/src/styled_buffer.rs b/compiler/rustc_errors/src/styled_buffer.rs
index 5ca9e9b18f3..790efd0286e 100644
--- a/compiler/rustc_errors/src/styled_buffer.rs
+++ b/compiler/rustc_errors/src/styled_buffer.rs
@@ -89,6 +89,19 @@ impl StyledBuffer {
         }
     }
 
+    pub(crate) fn replace(&mut self, line: usize, start: usize, end: usize, string: &str) {
+        if start == end {
+            return;
+        }
+        if start > self.lines[line].len() || end > self.lines[line].len() {
+            return;
+        }
+        let _ = self.lines[line].drain(start..(end - string.chars().count()));
+        for (i, c) in string.chars().enumerate() {
+            self.lines[line][start + i] = StyledChar::new(c, Style::LineNumber);
+        }
+    }
+
     /// For given `line` inserts `string` with `style` before old content of that line,
     /// adding lines if needed
     pub(crate) fn prepend(&mut self, line: usize, string: &str, style: Style) {
diff --git a/compiler/rustc_expand/src/expand.rs b/compiler/rustc_expand/src/expand.rs
index c523bcece72..87f01be26c2 100644
--- a/compiler/rustc_expand/src/expand.rs
+++ b/compiler/rustc_expand/src/expand.rs
@@ -780,8 +780,8 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                             }
                         }
                         Err(err) => {
-                            let guar = err.emit();
-                            fragment_kind.dummy(span, guar)
+                            let _guar = err.emit();
+                            fragment_kind.expect_from_annotatables(iter::once(item))
                         }
                     }
                 }
diff --git a/compiler/rustc_expand/src/mbe/quoted.rs b/compiler/rustc_expand/src/mbe/quoted.rs
index 8cb001391c5..0ea53627fe7 100644
--- a/compiler/rustc_expand/src/mbe/quoted.rs
+++ b/compiler/rustc_expand/src/mbe/quoted.rs
@@ -274,7 +274,7 @@ fn parse_tree<'a>(
                     let msg =
                         format!("expected identifier, found `{}`", pprust::token_to_string(token),);
                     sess.dcx().span_err(token.span, msg);
-                    TokenTree::MetaVar(token.span, Ident::empty())
+                    TokenTree::MetaVar(token.span, Ident::dummy())
                 }
 
                 // There are no more tokens. Just return the `$` we already have.
diff --git a/compiler/rustc_feature/src/unstable.rs b/compiler/rustc_feature/src/unstable.rs
index c6e992573d6..3c61bfd1c93 100644
--- a/compiler/rustc_feature/src/unstable.rs
+++ b/compiler/rustc_feature/src/unstable.rs
@@ -240,7 +240,7 @@ declare_features! (
     /// Added for testing unstable lints; perma-unstable.
     (internal, test_unstable_lint, "1.60.0", None),
     /// Helps with formatting for `group_imports = "StdExternalCrate"`.
-    (unstable, unqualified_local_imports, "1.83.0", None),
+    (unstable, unqualified_local_imports, "1.83.0", Some(138299)),
     /// Use for stable + negative coherence and strict coherence depending on trait's
     /// rustc_strict_coherence value.
     (unstable, with_negative_coherence, "1.60.0", None),
@@ -474,6 +474,8 @@ declare_features! (
     (unstable, doc_masked, "1.21.0", Some(44027)),
     /// Allows `dyn* Trait` objects.
     (incomplete, dyn_star, "1.65.0", Some(102425)),
+    /// Allows the .use postfix syntax `x.use` and use closures `use |x| { ... }`
+    (incomplete, ergonomic_clones, "CURRENT_RUSTC_VERSION", Some(132290)),
     /// Allows exhaustive pattern matching on types that contain uninhabited types.
     (unstable, exhaustive_patterns, "1.13.0", Some(51085)),
     /// Allows explicit tail calls via `become` expression.
diff --git a/compiler/rustc_hir/src/def.rs b/compiler/rustc_hir/src/def.rs
index 7e3a8561da0..5f8941d4754 100644
--- a/compiler/rustc_hir/src/def.rs
+++ b/compiler/rustc_hir/src/def.rs
@@ -253,7 +253,9 @@ impl DefKind {
         }
     }
 
-    pub fn def_path_data(self, name: Symbol) -> DefPathData {
+    // Some `DefKind`s require a name, some don't. Panics if one is needed but
+    // not provided. (`AssocTy` is an exception, see below.)
+    pub fn def_path_data(self, name: Option<Symbol>) -> DefPathData {
         match self {
             DefKind::Mod
             | DefKind::Struct
@@ -264,9 +266,13 @@ impl DefKind {
             | DefKind::TyAlias
             | DefKind::ForeignTy
             | DefKind::TraitAlias
-            | DefKind::AssocTy
             | DefKind::TyParam
-            | DefKind::ExternCrate => DefPathData::TypeNs(name),
+            | DefKind::ExternCrate => DefPathData::TypeNs(Some(name.unwrap())),
+
+            // An associated type names will be missing for an RPITIT. It will
+            // later be given a name with `synthetic` in it, if necessary.
+            DefKind::AssocTy => DefPathData::TypeNs(name),
+
             // It's not exactly an anon const, but wrt DefPathData, there
             // is no difference.
             DefKind::Static { nested: true, .. } => DefPathData::AnonConst,
@@ -276,9 +282,9 @@ impl DefKind {
             | DefKind::Static { .. }
             | DefKind::AssocFn
             | DefKind::AssocConst
-            | DefKind::Field => DefPathData::ValueNs(name),
-            DefKind::Macro(..) => DefPathData::MacroNs(name),
-            DefKind::LifetimeParam => DefPathData::LifetimeNs(name),
+            | DefKind::Field => DefPathData::ValueNs(name.unwrap()),
+            DefKind::Macro(..) => DefPathData::MacroNs(name.unwrap()),
+            DefKind::LifetimeParam => DefPathData::LifetimeNs(name.unwrap()),
             DefKind::Ctor(..) => DefPathData::Ctor,
             DefKind::Use => DefPathData::Use,
             DefKind::ForeignMod => DefPathData::ForeignMod,
@@ -429,7 +435,7 @@ pub enum Res<Id = hir::HirId> {
         /// mention any generic parameters to allow the following with `min_const_generics`:
         /// ```
         /// # struct Foo;
-        /// impl Foo { fn test() -> [u8; std::mem::size_of::<Self>()] { todo!() } }
+        /// impl Foo { fn test() -> [u8; size_of::<Self>()] { todo!() } }
         ///
         /// struct Bar([u8; baz::<Self>()]);
         /// const fn baz<T>() -> usize { 10 }
@@ -439,7 +445,7 @@ pub enum Res<Id = hir::HirId> {
         /// compat lint:
         /// ```
         /// fn foo<T>() {
-        ///     let _bar = [1_u8; std::mem::size_of::<*mut T>()];
+        ///     let _bar = [1_u8; size_of::<*mut T>()];
         /// }
         /// ```
         // FIXME(generic_const_exprs): Remove this bodge once that feature is stable.
diff --git a/compiler/rustc_hir/src/definitions.rs b/compiler/rustc_hir/src/definitions.rs
index c4c309e77e1..61f5efd9978 100644
--- a/compiler/rustc_hir/src/definitions.rs
+++ b/compiler/rustc_hir/src/definitions.rs
@@ -271,8 +271,9 @@ pub enum DefPathData {
     Use,
     /// A global asm item.
     GlobalAsm,
-    /// Something in the type namespace.
-    TypeNs(Symbol),
+    /// Something in the type namespace. Will be empty for RPITIT associated
+    /// types, which are given a synthetic name later, if necessary.
+    TypeNs(Option<Symbol>),
     /// Something in the value namespace.
     ValueNs(Symbol),
     /// Something in the macro namespace.
@@ -410,8 +411,9 @@ impl DefPathData {
     pub fn get_opt_name(&self) -> Option<Symbol> {
         use self::DefPathData::*;
         match *self {
-            TypeNs(name) if name == kw::Empty => None,
-            TypeNs(name) | ValueNs(name) | MacroNs(name) | LifetimeNs(name) => Some(name),
+            TypeNs(name) => name,
+
+            ValueNs(name) | MacroNs(name) | LifetimeNs(name) => Some(name),
 
             Impl | ForeignMod | CrateRoot | Use | GlobalAsm | Closure | Ctor | AnonConst
             | OpaqueTy => None,
@@ -421,12 +423,14 @@ impl DefPathData {
     pub fn name(&self) -> DefPathDataName {
         use self::DefPathData::*;
         match *self {
-            TypeNs(name) if name == kw::Empty => {
-                DefPathDataName::Anon { namespace: sym::synthetic }
-            }
-            TypeNs(name) | ValueNs(name) | MacroNs(name) | LifetimeNs(name) => {
-                DefPathDataName::Named(name)
+            TypeNs(name) => {
+                if let Some(name) = name {
+                    DefPathDataName::Named(name)
+                } else {
+                    DefPathDataName::Anon { namespace: sym::synthetic }
+                }
             }
+            ValueNs(name) | MacroNs(name) | LifetimeNs(name) => DefPathDataName::Named(name),
             // Note that this does not show up in user print-outs.
             CrateRoot => DefPathDataName::Anon { namespace: kw::Crate },
             Impl => DefPathDataName::Anon { namespace: kw::Impl },
diff --git a/compiler/rustc_hir/src/hir.rs b/compiler/rustc_hir/src/hir.rs
index df305e6e769..d4dfb9f2973 100644
--- a/compiler/rustc_hir/src/hir.rs
+++ b/compiler/rustc_hir/src/hir.rs
@@ -243,7 +243,7 @@ impl<'hir> PathSegment<'hir> {
     }
 
     pub fn invalid() -> Self {
-        Self::new(Ident::empty(), HirId::INVALID, Res::Err)
+        Self::new(Ident::dummy(), HirId::INVALID, Res::Err)
     }
 
     pub fn args(&self) -> &GenericArgs<'hir> {
@@ -1307,13 +1307,18 @@ impl Attribute {
 #[derive(Debug)]
 pub struct AttributeMap<'tcx> {
     pub map: SortedMap<ItemLocalId, &'tcx [Attribute]>,
+    /// Preprocessed `#[define_opaque]` attribute.
+    pub define_opaque: Option<&'tcx [(Span, LocalDefId)]>,
     // Only present when the crate hash is needed.
     pub opt_hash: Option<Fingerprint>,
 }
 
 impl<'tcx> AttributeMap<'tcx> {
-    pub const EMPTY: &'static AttributeMap<'static> =
-        &AttributeMap { map: SortedMap::new(), opt_hash: Some(Fingerprint::ZERO) };
+    pub const EMPTY: &'static AttributeMap<'static> = &AttributeMap {
+        map: SortedMap::new(),
+        opt_hash: Some(Fingerprint::ZERO),
+        define_opaque: None,
+    };
 
     #[inline]
     pub fn get(&self, id: ItemLocalId) -> &'tcx [Attribute] {
@@ -2166,6 +2171,7 @@ impl Expr<'_> {
             | ExprKind::Tup(_)
             | ExprKind::Type(..)
             | ExprKind::UnsafeBinderCast(..)
+            | ExprKind::Use(..)
             | ExprKind::Err(_) => ExprPrecedence::Unambiguous,
 
             ExprKind::DropTemps(expr, ..) => expr.precedence(),
@@ -2212,6 +2218,7 @@ impl Expr<'_> {
             ExprKind::Path(QPath::TypeRelative(..))
             | ExprKind::Call(..)
             | ExprKind::MethodCall(..)
+            | ExprKind::Use(..)
             | ExprKind::Struct(..)
             | ExprKind::Tup(..)
             | ExprKind::If(..)
@@ -2285,7 +2292,9 @@ impl Expr<'_> {
 
     pub fn can_have_side_effects(&self) -> bool {
         match self.peel_drop_temps().kind {
-            ExprKind::Path(_) | ExprKind::Lit(_) | ExprKind::OffsetOf(..) => false,
+            ExprKind::Path(_) | ExprKind::Lit(_) | ExprKind::OffsetOf(..) | ExprKind::Use(..) => {
+                false
+            }
             ExprKind::Type(base, _)
             | ExprKind::Unary(_, base)
             | ExprKind::Field(base, _)
@@ -2547,6 +2556,8 @@ pub enum ExprKind<'hir> {
     ///
     /// [`type_dependent_def_id`]: ../../rustc_middle/ty/struct.TypeckResults.html#method.type_dependent_def_id
     MethodCall(&'hir PathSegment<'hir>, &'hir Expr<'hir>, &'hir [Expr<'hir>], Span),
+    /// An use expression (e.g., `var.use`).
+    Use(&'hir Expr<'hir>, Span),
     /// A tuple (e.g., `(a, b, c, d)`).
     Tup(&'hir [Expr<'hir>]),
     /// A binary operation (e.g., `a + b`, `a * b`).
@@ -4321,16 +4332,6 @@ pub enum OwnerNode<'hir> {
 }
 
 impl<'hir> OwnerNode<'hir> {
-    pub fn ident(&self) -> Option<Ident> {
-        match self {
-            OwnerNode::Item(Item { ident, .. })
-            | OwnerNode::ForeignItem(ForeignItem { ident, .. })
-            | OwnerNode::ImplItem(ImplItem { ident, .. })
-            | OwnerNode::TraitItem(TraitItem { ident, .. }) => Some(*ident),
-            OwnerNode::Crate(..) | OwnerNode::Synthetic => None,
-        }
-    }
-
     pub fn span(&self) -> Span {
         match self {
             OwnerNode::Item(Item { span, .. })
diff --git a/compiler/rustc_hir/src/intravisit.rs b/compiler/rustc_hir/src/intravisit.rs
index 41eb5b45bd1..3ef645a5f61 100644
--- a/compiler/rustc_hir/src/intravisit.rs
+++ b/compiler/rustc_hir/src/intravisit.rs
@@ -316,8 +316,8 @@ pub trait Visitor<'v>: Sized {
     fn visit_ident(&mut self, ident: Ident) -> Self::Result {
         walk_ident(self, ident)
     }
-    fn visit_mod(&mut self, m: &'v Mod<'v>, _s: Span, n: HirId) -> Self::Result {
-        walk_mod(self, m, n)
+    fn visit_mod(&mut self, m: &'v Mod<'v>, _s: Span, _n: HirId) -> Self::Result {
+        walk_mod(self, m)
     }
     fn visit_foreign_item(&mut self, i: &'v ForeignItem<'v>) -> Self::Result {
         walk_foreign_item(self, i)
@@ -363,7 +363,7 @@ pub trait Visitor<'v>: Sized {
     /// See the doc comments on [`Ty`] for an explanation of what it means for a type to be
     /// ambiguous.
     ///
-    /// The [`Visitor::visit_infer`] method should be overriden in order to handle infer vars.
+    /// The [`Visitor::visit_infer`] method should be overridden in order to handle infer vars.
     fn visit_ty(&mut self, t: &'v Ty<'v, AmbigArg>) -> Self::Result {
         walk_ty(self, t)
     }
@@ -374,7 +374,7 @@ pub trait Visitor<'v>: Sized {
     /// See the doc comments on [`ConstArg`] for an explanation of what it means for a const to be
     /// ambiguous.
     ///
-    /// The [`Visitor::visit_infer`] method should be overriden in order to handle infer vars.
+    /// The [`Visitor::visit_infer`] method should be overridden in order to handle infer vars.
     fn visit_const_arg(&mut self, c: &'v ConstArg<'v, AmbigArg>) -> Self::Result {
         walk_ambig_const_arg(self, c)
     }
@@ -464,8 +464,8 @@ pub trait Visitor<'v>: Sized {
     fn visit_field_def(&mut self, s: &'v FieldDef<'v>) -> Self::Result {
         walk_field_def(self, s)
     }
-    fn visit_enum_def(&mut self, enum_definition: &'v EnumDef<'v>, item_id: HirId) -> Self::Result {
-        walk_enum_def(self, enum_definition, item_id)
+    fn visit_enum_def(&mut self, enum_definition: &'v EnumDef<'v>) -> Self::Result {
+        walk_enum_def(self, enum_definition)
     }
     fn visit_variant(&mut self, v: &'v Variant<'v>) -> Self::Result {
         walk_variant(self, v)
@@ -532,28 +532,25 @@ pub fn walk_param<'v, V: Visitor<'v>>(visitor: &mut V, param: &'v Param<'v>) ->
 }
 
 pub fn walk_item<'v, V: Visitor<'v>>(visitor: &mut V, item: &'v Item<'v>) -> V::Result {
+    try_visit!(visitor.visit_id(item.hir_id()));
     try_visit!(visitor.visit_ident(item.ident));
     match item.kind {
         ItemKind::ExternCrate(orig_name) => {
-            try_visit!(visitor.visit_id(item.hir_id()));
             visit_opt!(visitor, visit_name, orig_name);
         }
         ItemKind::Use(ref path, _) => {
             try_visit!(visitor.visit_use(path, item.hir_id()));
         }
         ItemKind::Static(ref typ, _, body) => {
-            try_visit!(visitor.visit_id(item.hir_id()));
             try_visit!(visitor.visit_ty_unambig(typ));
             try_visit!(visitor.visit_nested_body(body));
         }
         ItemKind::Const(ref typ, ref generics, body) => {
-            try_visit!(visitor.visit_id(item.hir_id()));
             try_visit!(visitor.visit_ty_unambig(typ));
             try_visit!(visitor.visit_generics(generics));
             try_visit!(visitor.visit_nested_body(body));
         }
         ItemKind::Fn { sig, generics, body: body_id, .. } => {
-            try_visit!(visitor.visit_id(item.hir_id()));
             try_visit!(visitor.visit_fn(
                 FnKind::ItemFn(item.ident, generics, sig.header),
                 sig.decl,
@@ -562,19 +559,14 @@ pub fn walk_item<'v, V: Visitor<'v>>(visitor: &mut V, item: &'v Item<'v>) -> V::
                 item.owner_id.def_id,
             ));
         }
-        ItemKind::Macro(..) => {
-            try_visit!(visitor.visit_id(item.hir_id()));
-        }
+        ItemKind::Macro(..) => {}
         ItemKind::Mod(ref module) => {
-            // `visit_mod()` takes care of visiting the `Item`'s `HirId`.
             try_visit!(visitor.visit_mod(module, item.span, item.hir_id()));
         }
         ItemKind::ForeignMod { abi: _, items } => {
-            try_visit!(visitor.visit_id(item.hir_id()));
             walk_list!(visitor, visit_foreign_item_ref, items);
         }
         ItemKind::GlobalAsm { asm: _, fake_body } => {
-            try_visit!(visitor.visit_id(item.hir_id()));
             // Visit the fake body, which contains the asm statement.
             // Therefore we should not visit the asm statement again
             // outside of the body, or some visitors won't have their
@@ -582,14 +574,12 @@ pub fn walk_item<'v, V: Visitor<'v>>(visitor: &mut V, item: &'v Item<'v>) -> V::
             try_visit!(visitor.visit_nested_body(fake_body));
         }
         ItemKind::TyAlias(ref ty, ref generics) => {
-            try_visit!(visitor.visit_id(item.hir_id()));
             try_visit!(visitor.visit_ty_unambig(ty));
             try_visit!(visitor.visit_generics(generics));
         }
         ItemKind::Enum(ref enum_definition, ref generics) => {
             try_visit!(visitor.visit_generics(generics));
-            // `visit_enum_def()` takes care of visiting the `Item`'s `HirId`.
-            try_visit!(visitor.visit_enum_def(enum_definition, item.hir_id()));
+            try_visit!(visitor.visit_enum_def(enum_definition));
         }
         ItemKind::Impl(Impl {
             constness: _,
@@ -602,7 +592,6 @@ pub fn walk_item<'v, V: Visitor<'v>>(visitor: &mut V, item: &'v Item<'v>) -> V::
             self_ty,
             items,
         }) => {
-            try_visit!(visitor.visit_id(item.hir_id()));
             try_visit!(visitor.visit_generics(generics));
             visit_opt!(visitor, visit_trait_ref, of_trait);
             try_visit!(visitor.visit_ty_unambig(self_ty));
@@ -611,17 +600,14 @@ pub fn walk_item<'v, V: Visitor<'v>>(visitor: &mut V, item: &'v Item<'v>) -> V::
         ItemKind::Struct(ref struct_definition, ref generics)
         | ItemKind::Union(ref struct_definition, ref generics) => {
             try_visit!(visitor.visit_generics(generics));
-            try_visit!(visitor.visit_id(item.hir_id()));
             try_visit!(visitor.visit_variant_data(struct_definition));
         }
         ItemKind::Trait(.., ref generics, bounds, trait_item_refs) => {
-            try_visit!(visitor.visit_id(item.hir_id()));
             try_visit!(visitor.visit_generics(generics));
             walk_list!(visitor, visit_param_bound, bounds);
             walk_list!(visitor, visit_trait_item_ref, trait_item_refs);
         }
         ItemKind::TraitAlias(ref generics, bounds) => {
-            try_visit!(visitor.visit_id(item.hir_id()));
             try_visit!(visitor.visit_generics(generics));
             walk_list!(visitor, visit_param_bound, bounds);
         }
@@ -638,12 +624,7 @@ pub fn walk_ident<'v, V: Visitor<'v>>(visitor: &mut V, ident: Ident) -> V::Resul
     visitor.visit_name(ident.name)
 }
 
-pub fn walk_mod<'v, V: Visitor<'v>>(
-    visitor: &mut V,
-    module: &'v Mod<'v>,
-    mod_hir_id: HirId,
-) -> V::Result {
-    try_visit!(visitor.visit_id(mod_hir_id));
+pub fn walk_mod<'v, V: Visitor<'v>>(visitor: &mut V, module: &'v Mod<'v>) -> V::Result {
     walk_list!(visitor, visit_nested_item, module.item_ids.iter().copied());
     V::Result::output()
 }
@@ -821,6 +802,9 @@ pub fn walk_expr<'v, V: Visitor<'v>>(visitor: &mut V, expression: &'v Expr<'v>)
             try_visit!(visitor.visit_expr(receiver));
             walk_list!(visitor, visit_expr, arguments);
         }
+        ExprKind::Use(expr, _) => {
+            try_visit!(visitor.visit_expr(expr));
+        }
         ExprKind::Binary(_, ref left_expression, ref right_expression) => {
             try_visit!(visitor.visit_expr(left_expression));
             try_visit!(visitor.visit_expr(right_expression));
@@ -1145,7 +1129,6 @@ pub fn walk_use<'v, V: Visitor<'v>>(
     path: &'v UsePath<'v>,
     hir_id: HirId,
 ) -> V::Result {
-    try_visit!(visitor.visit_id(hir_id));
     let UsePath { segments, ref res, span } = *path;
     for &res in res {
         try_visit!(visitor.visit_path(&Path { segments, res, span }, hir_id));
@@ -1326,9 +1309,7 @@ pub fn walk_field_def<'v, V: Visitor<'v>>(
 pub fn walk_enum_def<'v, V: Visitor<'v>>(
     visitor: &mut V,
     enum_definition: &'v EnumDef<'v>,
-    item_id: HirId,
 ) -> V::Result {
-    try_visit!(visitor.visit_id(item_id));
     walk_list!(visitor, visit_variant, enum_definition.variants);
     V::Result::output()
 }
diff --git a/compiler/rustc_hir/src/lang_items.rs b/compiler/rustc_hir/src/lang_items.rs
index c3b14a4e06c..29f4d5b8076 100644
--- a/compiler/rustc_hir/src/lang_items.rs
+++ b/compiler/rustc_hir/src/lang_items.rs
@@ -171,6 +171,7 @@ language_item_table! {
     Copy,                    sym::copy,                copy_trait,                 Target::Trait,          GenericRequirement::Exact(0);
     Clone,                   sym::clone,               clone_trait,                Target::Trait,          GenericRequirement::None;
     CloneFn,                 sym::clone_fn,            clone_fn,                   Target::Method(MethodKind::Trait { body: false }), GenericRequirement::None;
+    UseCloned,               sym::use_cloned,          use_cloned_trait,           Target::Trait,          GenericRequirement::None;
     Sync,                    sym::sync,                sync_trait,                 Target::Trait,          GenericRequirement::Exact(0);
     DiscriminantKind,        sym::discriminant_kind,   discriminant_kind_trait,    Target::Trait,          GenericRequirement::None;
     /// The associated item of the `DiscriminantKind` trait.
diff --git a/compiler/rustc_hir/src/stable_hash_impls.rs b/compiler/rustc_hir/src/stable_hash_impls.rs
index 2709a826549..91ea88cae47 100644
--- a/compiler/rustc_hir/src/stable_hash_impls.rs
+++ b/compiler/rustc_hir/src/stable_hash_impls.rs
@@ -106,7 +106,7 @@ impl<'tcx, HirCtx: crate::HashStableContext> HashStable<HirCtx> for AttributeMap
     fn hash_stable(&self, hcx: &mut HirCtx, hasher: &mut StableHasher) {
         // We ignore the `map` since it refers to information included in `opt_hash` which is
         // hashed in the collector and used for the crate hash.
-        let AttributeMap { opt_hash, map: _ } = *self;
+        let AttributeMap { opt_hash, define_opaque: _, map: _ } = *self;
         opt_hash.unwrap().hash_stable(hcx, hasher);
     }
 }
diff --git a/compiler/rustc_hir_analysis/messages.ftl b/compiler/rustc_hir_analysis/messages.ftl
index 935f4de6c58..194f2cd04e4 100644
--- a/compiler/rustc_hir_analysis/messages.ftl
+++ b/compiler/rustc_hir_analysis/messages.ftl
@@ -504,12 +504,9 @@ hir_analysis_supertrait_item_shadowee = item from `{$supertrait}` is shadowed by
 
 hir_analysis_supertrait_item_shadowing = trait item `{$item}` from `{$subtrait}` shadows identically named item from supertrait
 
-hir_analysis_tait_forward_compat = item constrains opaque type that is not in its signature
-    .note = this item must mention the opaque type in its signature in order to be able to register hidden types
-
-hir_analysis_tait_forward_compat2 = item does not constrain `{$opaque_type}`, but has it in its signature
-    .note = consider moving the opaque type's declaration and defining uses into a separate module
-    .opaque = this opaque type is in the signature
+hir_analysis_tait_forward_compat2 = item does not constrain `{$opaque_type}`
+    .note = consider removing `#[define_opaque]` or adding an empty `#[define_opaque()]`
+    .opaque = this opaque type is supposed to be constrained
 
 hir_analysis_target_feature_on_main = `main` function is not allowed to have `#[target_feature]`
 
diff --git a/compiler/rustc_hir_analysis/src/check/always_applicable.rs b/compiler/rustc_hir_analysis/src/check/always_applicable.rs
index ba5b61d3fce..8a841a11556 100644
--- a/compiler/rustc_hir_analysis/src/check/always_applicable.rs
+++ b/compiler/rustc_hir_analysis/src/check/always_applicable.rs
@@ -124,7 +124,10 @@ pub(crate) fn check_negative_auto_trait_impl<'tcx>(
                 // be implemented here to handle non-ADT rigid types.
                 Ok(())
             } else {
-                span_bug!(tcx.def_span(impl_def_id), "incoherent impl of negative auto trait");
+                Err(tcx.dcx().span_delayed_bug(
+                    tcx.def_span(impl_def_id),
+                    "incoherent impl of negative auto trait",
+                ))
             }
         }
     }
diff --git a/compiler/rustc_hir_analysis/src/check/check.rs b/compiler/rustc_hir_analysis/src/check/check.rs
index 8f9997cb62c..8dc5d361750 100644
--- a/compiler/rustc_hir_analysis/src/check/check.rs
+++ b/compiler/rustc_hir_analysis/src/check/check.rs
@@ -392,6 +392,12 @@ fn best_definition_site_of_opaque<'tcx>(
                 return ControlFlow::Continue(());
             }
 
+            let opaque_types_defined_by = self.tcx.opaque_types_defined_by(item_def_id);
+            // Don't try to check items that cannot possibly constrain the type.
+            if !opaque_types_defined_by.contains(&self.opaque_def_id) {
+                return ControlFlow::Continue(());
+            }
+
             if let Some(hidden_ty) =
                 self.tcx.mir_borrowck(item_def_id).concrete_opaque_types.get(&self.opaque_def_id)
             {
@@ -451,19 +457,7 @@ fn best_definition_site_of_opaque<'tcx>(
             None
         }
         hir::OpaqueTyOrigin::TyAlias { in_assoc_ty: false, .. } => {
-            let scope = tcx.hir_get_defining_scope(tcx.local_def_id_to_hir_id(opaque_def_id));
-            let found = if scope == hir::CRATE_HIR_ID {
-                tcx.hir_walk_toplevel_module(&mut locator)
-            } else {
-                match tcx.hir_node(scope) {
-                    Node::Item(it) => locator.visit_item(it),
-                    Node::ImplItem(it) => locator.visit_impl_item(it),
-                    Node::TraitItem(it) => locator.visit_trait_item(it),
-                    Node::ForeignItem(it) => locator.visit_foreign_item(it),
-                    other => bug!("{:?} is not a valid scope for an opaque type item", other),
-                }
-            };
-            found.break_value()
+            tcx.hir_walk_toplevel_module(&mut locator).break_value()
         }
     }
 }
diff --git a/compiler/rustc_hir_analysis/src/check/intrinsicck.rs b/compiler/rustc_hir_analysis/src/check/intrinsicck.rs
index 590ade516ec..d63165f0f16 100644
--- a/compiler/rustc_hir_analysis/src/check/intrinsicck.rs
+++ b/compiler/rustc_hir_analysis/src/check/intrinsicck.rs
@@ -3,8 +3,11 @@ use rustc_ast::InlineAsmTemplatePiece;
 use rustc_data_structures::fx::FxIndexSet;
 use rustc_hir::def_id::DefId;
 use rustc_hir::{self as hir, LangItem};
+use rustc_infer::infer::InferCtxt;
 use rustc_middle::bug;
-use rustc_middle::ty::{self, Article, FloatTy, IntTy, Ty, TyCtxt, TypeVisitableExt, UintTy};
+use rustc_middle::ty::{
+    self, Article, FloatTy, IntTy, Ty, TyCtxt, TypeVisitableExt, TypeckResults, UintTy,
+};
 use rustc_session::lint;
 use rustc_span::def_id::LocalDefId;
 use rustc_span::{Symbol, sym};
@@ -14,12 +17,11 @@ use rustc_target::asm::{
 
 use crate::errors::RegisterTypeUnstable;
 
-pub struct InlineAsmCtxt<'a, 'tcx: 'a> {
-    tcx: TyCtxt<'tcx>,
+pub struct InlineAsmCtxt<'a, 'tcx> {
     typing_env: ty::TypingEnv<'tcx>,
     target_features: &'tcx FxIndexSet<Symbol>,
-    expr_ty: Box<dyn Fn(&hir::Expr<'tcx>) -> Ty<'tcx> + 'a>,
-    node_ty: Box<dyn Fn(hir::HirId) -> Ty<'tcx> + 'a>,
+    infcx: &'a InferCtxt<'tcx>,
+    typeck_results: &'a TypeckResults<'tcx>,
 }
 
 enum NonAsmTypeReason<'tcx> {
@@ -31,34 +33,38 @@ enum NonAsmTypeReason<'tcx> {
 
 impl<'a, 'tcx> InlineAsmCtxt<'a, 'tcx> {
     pub fn new(
-        tcx: TyCtxt<'tcx>,
         def_id: LocalDefId,
+        infcx: &'a InferCtxt<'tcx>,
         typing_env: ty::TypingEnv<'tcx>,
-        expr_ty: impl Fn(&hir::Expr<'tcx>) -> Ty<'tcx> + 'a,
-        node_ty: impl Fn(hir::HirId) -> Ty<'tcx> + 'a,
+        typeck_results: &'a TypeckResults<'tcx>,
     ) -> Self {
         InlineAsmCtxt {
-            tcx,
             typing_env,
-            target_features: tcx.asm_target_features(def_id),
-            expr_ty: Box::new(expr_ty),
-            node_ty: Box::new(node_ty),
+            target_features: infcx.tcx.asm_target_features(def_id),
+            infcx,
+            typeck_results,
         }
     }
 
-    fn expr_ty(&self, expr: &hir::Expr<'tcx>) -> Ty<'tcx> {
-        (self.expr_ty)(expr)
+    fn tcx(&self) -> TyCtxt<'tcx> {
+        self.infcx.tcx
     }
 
-    fn node_ty(&self, hir_id: hir::HirId) -> Ty<'tcx> {
-        (self.node_ty)(hir_id)
+    fn expr_ty(&self, expr: &hir::Expr<'tcx>) -> Ty<'tcx> {
+        let ty = self.typeck_results.expr_ty_adjusted(expr);
+        let ty = self.infcx.resolve_vars_if_possible(ty);
+        if ty.has_non_region_infer() {
+            Ty::new_misc_error(self.tcx())
+        } else {
+            self.tcx().erase_regions(ty)
+        }
     }
 
     // FIXME(compiler-errors): This could use `<$ty as Pointee>::Metadata == ()`
     fn is_thin_ptr_ty(&self, ty: Ty<'tcx>) -> bool {
         // Type still may have region variables, but `Sized` does not depend
         // on those, so just erase them before querying.
-        if ty.is_sized(self.tcx, self.typing_env) {
+        if ty.is_sized(self.tcx(), self.typing_env) {
             return true;
         }
         if let ty::Foreign(..) = ty.kind() {
@@ -68,7 +74,7 @@ impl<'a, 'tcx> InlineAsmCtxt<'a, 'tcx> {
     }
 
     fn get_asm_ty(&self, ty: Ty<'tcx>) -> Result<InlineAsmType, NonAsmTypeReason<'tcx>> {
-        let asm_ty_isize = match self.tcx.sess.target.pointer_width {
+        let asm_ty_isize = match self.tcx().sess.target.pointer_width {
             16 => InlineAsmType::I16,
             32 => InlineAsmType::I32,
             64 => InlineAsmType::I64,
@@ -97,12 +103,12 @@ impl<'a, 'tcx> InlineAsmCtxt<'a, 'tcx> {
             ty::Adt(adt, args) if adt.repr().simd() => {
                 let fields = &adt.non_enum_variant().fields;
                 let field = &fields[FieldIdx::ZERO];
-                let elem_ty = field.ty(self.tcx, args);
+                let elem_ty = field.ty(self.tcx(), args);
 
                 let (size, ty) = match elem_ty.kind() {
                     ty::Array(ty, len) => {
-                        let len = self.tcx.normalize_erasing_regions(self.typing_env, *len);
-                        if let Some(len) = len.try_to_target_usize(self.tcx) {
+                        let len = self.tcx().normalize_erasing_regions(self.typing_env, *len);
+                        if let Some(len) = len.try_to_target_usize(self.tcx()) {
                             (len, *ty)
                         } else {
                             return Err(NonAsmTypeReason::UnevaluatedSIMDArrayLength(
@@ -122,7 +128,7 @@ impl<'a, 'tcx> InlineAsmCtxt<'a, 'tcx> {
                         Ok(InlineAsmType::VecI128(size))
                     }
                     ty::Int(IntTy::Isize) | ty::Uint(UintTy::Usize) => {
-                        Ok(match self.tcx.sess.target.pointer_width {
+                        Ok(match self.tcx().sess.target.pointer_width {
                             16 => InlineAsmType::VecI16(size),
                             32 => InlineAsmType::VecI32(size),
                             64 => InlineAsmType::VecI64(size),
@@ -159,9 +165,9 @@ impl<'a, 'tcx> InlineAsmCtxt<'a, 'tcx> {
             // `!` is allowed for input but not for output (issue #87802)
             ty::Never if is_input => return None,
             _ if ty.references_error() => return None,
-            ty::Adt(adt, args) if self.tcx.is_lang_item(adt.did(), LangItem::MaybeUninit) => {
+            ty::Adt(adt, args) if self.tcx().is_lang_item(adt.did(), LangItem::MaybeUninit) => {
                 let fields = &adt.non_enum_variant().fields;
-                let ty = fields[FieldIdx::from_u32(1)].ty(self.tcx, args);
+                let ty = fields[FieldIdx::from_u32(1)].ty(self.tcx(), args);
                 // FIXME: Are we just trying to map to the `T` in `MaybeUninit<T>`?
                 // If so, just get it from the args.
                 let ty::Adt(ty, args) = ty.kind() else {
@@ -172,7 +178,7 @@ impl<'a, 'tcx> InlineAsmCtxt<'a, 'tcx> {
                     "expected first field of `MaybeUninit` to be `ManuallyDrop`"
                 );
                 let fields = &ty.non_enum_variant().fields;
-                let ty = fields[FieldIdx::ZERO].ty(self.tcx, args);
+                let ty = fields[FieldIdx::ZERO].ty(self.tcx(), args);
                 self.get_asm_ty(ty)
             }
             _ => self.get_asm_ty(ty),
@@ -183,9 +189,9 @@ impl<'a, 'tcx> InlineAsmCtxt<'a, 'tcx> {
                 match reason {
                     NonAsmTypeReason::UnevaluatedSIMDArrayLength(did, len) => {
                         let msg = format!("cannot evaluate SIMD vector length `{len}`");
-                        self.tcx
+                        self.infcx
                             .dcx()
-                            .struct_span_err(self.tcx.def_span(did), msg)
+                            .struct_span_err(self.tcx().def_span(did), msg)
                             .with_span_note(
                                 expr.span,
                                 "SIMD vector length needs to be known statically for use in `asm!`",
@@ -194,7 +200,7 @@ impl<'a, 'tcx> InlineAsmCtxt<'a, 'tcx> {
                     }
                     NonAsmTypeReason::Invalid(ty) => {
                         let msg = format!("cannot use value of type `{ty}` for inline assembly");
-                        self.tcx.dcx().struct_span_err(expr.span, msg).with_note(
+                        self.infcx.dcx().struct_span_err(expr.span, msg).with_note(
                             "only integers, floats, SIMD vectors, pointers and function pointers \
                             can be used as arguments for inline assembly",
                         ).emit();
@@ -203,7 +209,7 @@ impl<'a, 'tcx> InlineAsmCtxt<'a, 'tcx> {
                         let msg = format!(
                             "cannot use value of unsized pointer type `{ty}` for inline assembly"
                         );
-                        self.tcx
+                        self.infcx
                             .dcx()
                             .struct_span_err(expr.span, msg)
                             .with_note("only sized pointers can be used in inline assembly")
@@ -213,8 +219,8 @@ impl<'a, 'tcx> InlineAsmCtxt<'a, 'tcx> {
                         let msg = format!(
                             "cannot use SIMD vector with element type `{ty}` for inline assembly"
                         );
-                        self.tcx.dcx()
-                        .struct_span_err(self.tcx.def_span(did), msg).with_span_note(
+                        self.infcx.dcx()
+                        .struct_span_err(self.tcx().def_span(did), msg).with_span_note(
                             expr.span,
                             "only integers, floats, SIMD vectors, pointers and function pointers \
                             can be used as arguments for inline assembly",
@@ -227,9 +233,9 @@ impl<'a, 'tcx> InlineAsmCtxt<'a, 'tcx> {
 
         // Check that the type implements Copy. The only case where this can
         // possibly fail is for SIMD types which don't #[derive(Copy)].
-        if !self.tcx.type_is_copy_modulo_regions(self.typing_env, ty) {
+        if !self.tcx().type_is_copy_modulo_regions(self.typing_env, ty) {
             let msg = "arguments for inline assembly must be copyable";
-            self.tcx
+            self.infcx
                 .dcx()
                 .struct_span_err(expr.span, msg)
                 .with_note(format!("`{ty}` does not implement the Copy trait"))
@@ -249,7 +255,7 @@ impl<'a, 'tcx> InlineAsmCtxt<'a, 'tcx> {
             if in_asm_ty != asm_ty {
                 let msg = "incompatible types for asm inout argument";
                 let in_expr_ty = self.expr_ty(in_expr);
-                self.tcx
+                self.infcx
                     .dcx()
                     .struct_span_err(vec![in_expr.span, expr.span], msg)
                     .with_span_label(in_expr.span, format!("type `{in_expr_ty}`"))
@@ -268,21 +274,21 @@ impl<'a, 'tcx> InlineAsmCtxt<'a, 'tcx> {
 
         // Check the type against the list of types supported by the selected
         // register class.
-        let asm_arch = self.tcx.sess.asm_arch.unwrap();
-        let allow_experimental_reg = self.tcx.features().asm_experimental_reg();
+        let asm_arch = self.tcx().sess.asm_arch.unwrap();
+        let allow_experimental_reg = self.tcx().features().asm_experimental_reg();
         let reg_class = reg.reg_class();
         let supported_tys = reg_class.supported_types(asm_arch, allow_experimental_reg);
         let Some((_, feature)) = supported_tys.iter().find(|&&(t, _)| t == asm_ty) else {
             let mut err = if !allow_experimental_reg
                 && reg_class.supported_types(asm_arch, true).iter().any(|&(t, _)| t == asm_ty)
             {
-                self.tcx.sess.create_feature_err(
+                self.tcx().sess.create_feature_err(
                     RegisterTypeUnstable { span: expr.span, ty },
                     sym::asm_experimental_reg,
                 )
             } else {
                 let msg = format!("type `{ty}` cannot be used with this register class");
-                let mut err = self.tcx.dcx().struct_span_err(expr.span, msg);
+                let mut err = self.infcx.dcx().struct_span_err(expr.span, msg);
                 let supported_tys: Vec<_> =
                     supported_tys.iter().map(|(t, _)| t.to_string()).collect();
                 err.note(format!(
@@ -312,7 +318,7 @@ impl<'a, 'tcx> InlineAsmCtxt<'a, 'tcx> {
         if let Some(feature) = feature {
             if !self.target_features.contains(feature) {
                 let msg = format!("`{feature}` target feature is not enabled");
-                self.tcx
+                self.infcx
                     .dcx()
                     .struct_span_err(expr.span, msg)
                     .with_note(format!(
@@ -349,7 +355,7 @@ impl<'a, 'tcx> InlineAsmCtxt<'a, 'tcx> {
                     result: default_result,
                     size: default_size,
                 } = reg_class.default_modifier(asm_arch).unwrap();
-                self.tcx.node_span_lint(
+                self.tcx().node_span_lint(
                     lint::builtin::ASM_SUB_REGISTER,
                     expr.hir_id,
                     spans,
@@ -371,11 +377,11 @@ impl<'a, 'tcx> InlineAsmCtxt<'a, 'tcx> {
     }
 
     pub fn check_asm(&self, asm: &hir::InlineAsm<'tcx>) {
-        let Some(asm_arch) = self.tcx.sess.asm_arch else {
-            self.tcx.dcx().delayed_bug("target architecture does not support asm");
+        let Some(asm_arch) = self.tcx().sess.asm_arch else {
+            self.infcx.dcx().delayed_bug("target architecture does not support asm");
             return;
         };
-        let allow_experimental_reg = self.tcx.features().asm_experimental_reg();
+        let allow_experimental_reg = self.tcx().features().asm_experimental_reg();
         for (idx, &(op, op_sp)) in asm.operands.iter().enumerate() {
             // Validate register classes against currently enabled target
             // features. We check that at least one type is available for
@@ -398,13 +404,13 @@ impl<'a, 'tcx> InlineAsmCtxt<'a, 'tcx> {
                     }
                     if let Err(msg) = reg.validate(
                         asm_arch,
-                        self.tcx.sess.relocation_model(),
+                        self.tcx().sess.relocation_model(),
                         self.target_features,
-                        &self.tcx.sess.target,
+                        &self.tcx().sess.target,
                         op.is_clobber(),
                     ) {
                         let msg = format!("cannot use register `{}`: {}", reg.name(), msg);
-                        self.tcx.dcx().span_err(op_sp, msg);
+                        self.infcx.dcx().span_err(op_sp, msg);
                         continue;
                     }
                 }
@@ -444,7 +450,7 @@ impl<'a, 'tcx> InlineAsmCtxt<'a, 'tcx> {
                                 reg_class.name(),
                                 feature
                             );
-                            self.tcx.dcx().span_err(op_sp, msg);
+                            self.infcx.dcx().span_err(op_sp, msg);
                             // register isn't enabled, don't do more checks
                             continue;
                         }
@@ -458,7 +464,7 @@ impl<'a, 'tcx> InlineAsmCtxt<'a, 'tcx> {
                                     .intersperse(", ")
                                     .collect::<String>(),
                             );
-                            self.tcx.dcx().span_err(op_sp, msg);
+                            self.infcx.dcx().span_err(op_sp, msg);
                             // register isn't enabled, don't do more checks
                             continue;
                         }
@@ -493,16 +499,16 @@ impl<'a, 'tcx> InlineAsmCtxt<'a, 'tcx> {
                     }
                 }
                 hir::InlineAsmOperand::Const { anon_const } => {
-                    let ty = self.node_ty(anon_const.hir_id);
+                    let ty = self.expr_ty(self.tcx().hir_body(anon_const.body).value);
                     match ty.kind() {
                         ty::Error(_) => {}
                         _ if ty.is_integral() => {}
                         _ => {
-                            self.tcx
+                            self.infcx
                                 .dcx()
                                 .struct_span_err(op_sp, "invalid type for `const` operand")
                                 .with_span_label(
-                                    self.tcx.def_span(anon_const.def_id),
+                                    self.tcx().def_span(anon_const.def_id),
                                     format!("is {} `{}`", ty.kind().article(), ty),
                                 )
                                 .with_help("`const` operands must be of an integer type")
@@ -517,7 +523,7 @@ impl<'a, 'tcx> InlineAsmCtxt<'a, 'tcx> {
                         ty::FnDef(..) => {}
                         ty::Error(_) => {}
                         _ => {
-                            self.tcx
+                            self.infcx
                                 .dcx()
                                 .struct_span_err(op_sp, "invalid `sym` operand")
                                 .with_span_label(
diff --git a/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs b/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
index 6b61d317d3f..883a1acdb30 100644
--- a/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
+++ b/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
@@ -1462,7 +1462,8 @@ impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
         for &(opaque_def_id, captures) in opaque_capture_scopes.iter().rev() {
             let mut captures = captures.borrow_mut();
             let remapped = *captures.entry(lifetime).or_insert_with(|| {
-                let feed = self.tcx.create_def(opaque_def_id, ident.name, DefKind::LifetimeParam);
+                let feed =
+                    self.tcx.create_def(opaque_def_id, Some(ident.name), DefKind::LifetimeParam);
                 feed.def_span(ident.span);
                 feed.def_ident_span(Some(ident.span));
                 feed.def_id()
diff --git a/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs b/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
index 399c4fbe55a..142078900f0 100644
--- a/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
+++ b/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
@@ -1,14 +1,13 @@
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::LocalDefId;
-use rustc_hir::intravisit::{self, Visitor};
-use rustc_hir::{self as hir, Expr, ImplItem, Item, Node, TraitItem, def};
+use rustc_hir::{self as hir, Expr, ImplItem, Item, Node, TraitItem, def, intravisit};
 use rustc_middle::bug;
 use rustc_middle::hir::nested_filter;
 use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitableExt};
 use rustc_span::DUMMY_SP;
 use tracing::{debug, instrument, trace};
 
-use crate::errors::{TaitForwardCompat, TaitForwardCompat2, UnconstrainedOpaqueType};
+use crate::errors::{TaitForwardCompat2, UnconstrainedOpaqueType};
 
 /// Checks "defining uses" of opaque `impl Trait` in associated types.
 /// These can only be defined by associated items of the same trait.
@@ -82,38 +81,9 @@ pub(super) fn find_opaque_ty_constraints_for_impl_trait_in_assoc_type(
 /// ```
 #[instrument(skip(tcx), level = "debug")]
 pub(super) fn find_opaque_ty_constraints_for_tait(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Ty<'_> {
-    let hir_id = tcx.local_def_id_to_hir_id(def_id);
-    let scope = tcx.hir_get_defining_scope(hir_id);
     let mut locator = TaitConstraintLocator { def_id, tcx, found: None, typeck_types: vec![] };
 
-    debug!(?scope);
-
-    if scope == hir::CRATE_HIR_ID {
-        tcx.hir_walk_toplevel_module(&mut locator);
-    } else {
-        trace!("scope={:#?}", tcx.hir_node(scope));
-        match tcx.hir_node(scope) {
-            // We explicitly call `visit_*` methods, instead of using `intravisit::walk_*` methods
-            // This allows our visitor to process the defining item itself, causing
-            // it to pick up any 'sibling' defining uses.
-            //
-            // For example, this code:
-            // ```
-            // fn foo() {
-            //     type Blah = impl Debug;
-            //     let my_closure = || -> Blah { true };
-            // }
-            // ```
-            //
-            // requires us to explicitly process `foo()` in order
-            // to notice the defining usage of `Blah`.
-            Node::Item(it) => locator.visit_item(it),
-            Node::ImplItem(it) => locator.visit_impl_item(it),
-            Node::TraitItem(it) => locator.visit_trait_item(it),
-            Node::ForeignItem(it) => locator.visit_foreign_item(it),
-            other => bug!("{:?} is not a valid scope for an opaque type item", other),
-        }
-    }
+    tcx.hir_walk_toplevel_module(&mut locator);
 
     if let Some(hidden) = locator.found {
         // Only check against typeck if we didn't already error
@@ -137,12 +107,7 @@ pub(super) fn find_opaque_ty_constraints_for_tait(tcx: TyCtxt<'_>, def_id: Local
         let reported = tcx.dcx().emit_err(UnconstrainedOpaqueType {
             span: tcx.def_span(def_id),
             name: tcx.item_ident(parent_def_id.to_def_id()),
-            what: match tcx.hir_node(scope) {
-                _ if scope == hir::CRATE_HIR_ID => "module",
-                Node::Item(hir::Item { kind: hir::ItemKind::Mod(_), .. }) => "module",
-                Node::Item(hir::Item { kind: hir::ItemKind::Impl(_), .. }) => "impl",
-                _ => "item",
-            },
+            what: "crate",
         });
         Ty::new_error(tcx, reported)
     }
@@ -176,6 +141,13 @@ impl TaitConstraintLocator<'_> {
             return;
         }
 
+        let opaque_types_defined_by = self.tcx.opaque_types_defined_by(item_def_id);
+        // Don't try to check items that cannot possibly constrain the type.
+        if !opaque_types_defined_by.contains(&self.def_id) {
+            debug!("no constraint: no opaque types defined");
+            return;
+        }
+
         // Function items with `_` in their return type already emit an error, skip any
         // "non-defining use" errors for them.
         // Note that we use `Node::fn_sig` instead of `Node::fn_decl` here, because the former
@@ -215,8 +187,6 @@ impl TaitConstraintLocator<'_> {
             return;
         }
 
-        let opaque_types_defined_by = self.tcx.opaque_types_defined_by(item_def_id);
-
         let mut constrained = false;
         for (&opaque_type_key, &hidden_type) in &tables.concrete_opaque_types {
             if opaque_type_key.def_id != self.def_id {
@@ -224,20 +194,6 @@ impl TaitConstraintLocator<'_> {
             }
             constrained = true;
 
-            if !opaque_types_defined_by.contains(&self.def_id) {
-                let guar = self.tcx.dcx().emit_err(TaitForwardCompat {
-                    span: hidden_type.span,
-                    item_span: self
-                        .tcx
-                        .def_ident_span(item_def_id)
-                        .unwrap_or_else(|| self.tcx.def_span(item_def_id)),
-                });
-                // Avoid "opaque type not constrained" errors on the opaque itself.
-                self.found = Some(ty::OpaqueHiddenType {
-                    span: DUMMY_SP,
-                    ty: Ty::new_error(self.tcx, guar),
-                });
-            }
             let concrete_type =
                 self.tcx.erase_regions(hidden_type.remap_generic_params_to_declaration_params(
                     opaque_type_key,
@@ -309,19 +265,13 @@ impl<'tcx> intravisit::Visitor<'tcx> for TaitConstraintLocator<'tcx> {
     }
     fn visit_item(&mut self, it: &'tcx Item<'tcx>) {
         trace!(?it.owner_id);
-        // The opaque type itself or its children are not within its reveal scope.
-        if it.owner_id.def_id != self.def_id {
-            self.check(it.owner_id.def_id);
-            intravisit::walk_item(self, it);
-        }
+        self.check(it.owner_id.def_id);
+        intravisit::walk_item(self, it);
     }
     fn visit_impl_item(&mut self, it: &'tcx ImplItem<'tcx>) {
         trace!(?it.owner_id);
-        // The opaque type itself or its children are not within its reveal scope.
-        if it.owner_id.def_id != self.def_id {
-            self.check(it.owner_id.def_id);
-            intravisit::walk_impl_item(self, it);
-        }
+        self.check(it.owner_id.def_id);
+        intravisit::walk_impl_item(self, it);
     }
     fn visit_trait_item(&mut self, it: &'tcx TraitItem<'tcx>) {
         trace!(?it.owner_id);
diff --git a/compiler/rustc_hir_analysis/src/errors.rs b/compiler/rustc_hir_analysis/src/errors.rs
index 4c6c2504126..f2560f22874 100644
--- a/compiler/rustc_hir_analysis/src/errors.rs
+++ b/compiler/rustc_hir_analysis/src/errors.rs
@@ -425,16 +425,6 @@ pub(crate) struct UnconstrainedOpaqueType {
 }
 
 #[derive(Diagnostic)]
-#[diag(hir_analysis_tait_forward_compat)]
-#[note]
-pub(crate) struct TaitForwardCompat {
-    #[primary_span]
-    pub span: Span,
-    #[note]
-    pub item_span: Span,
-}
-
-#[derive(Diagnostic)]
 #[diag(hir_analysis_tait_forward_compat2)]
 #[note]
 pub(crate) struct TaitForwardCompat2 {
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 ace5e34b382..fa061c80618 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
@@ -1520,7 +1520,7 @@ fn generics_args_err_extend<'a>(
                 })
                 .collect();
             if args.len() > 1
-                && let Some(span) = args.into_iter().last()
+                && let Some(span) = args.into_iter().next_back()
             {
                 err.note(
                     "generic arguments are not allowed on both an enum and its variant's path \
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/lint.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/lint.rs
index f5e075367f3..e78801dd601 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/lint.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/lint.rs
@@ -78,15 +78,18 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         }
 
         if self_ty.span.edition().at_least_rust_2021() {
-            let msg = "expected a type, found a trait";
-            let label = "you can add the `dyn` keyword if you want a trait object";
-            let mut diag =
-                rustc_errors::struct_span_code_err!(self.dcx(), self_ty.span, E0782, "{}", msg);
+            let mut diag = rustc_errors::struct_span_code_err!(
+                self.dcx(),
+                self_ty.span,
+                E0782,
+                "{}",
+                "expected a type, found a trait"
+            );
             if self_ty.span.can_be_used_for_suggestions()
                 && !self.maybe_suggest_impl_trait(self_ty, &mut diag)
+                && !self.maybe_suggest_dyn_trait(self_ty, sugg, &mut diag)
             {
-                // FIXME: Only emit this suggestion if the trait is dyn-compatible.
-                diag.multipart_suggestion_verbose(label, sugg, Applicability::MachineApplicable);
+                self.maybe_suggest_add_generic_impl_trait(self_ty, &mut diag);
             }
             // Check if the impl trait that we are considering is an impl of a local trait.
             self.maybe_suggest_blanket_trait_impl(self_ty, &mut diag);
@@ -123,6 +126,64 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         }
     }
 
+    /// For a struct or enum with an invalid bare trait object field, suggest turning
+    /// it into a generic type bound.
+    fn maybe_suggest_add_generic_impl_trait(
+        &self,
+        self_ty: &hir::Ty<'_>,
+        diag: &mut Diag<'_>,
+    ) -> bool {
+        let tcx = self.tcx();
+
+        let parent_hir_id = tcx.parent_hir_id(self_ty.hir_id);
+        let parent_item = tcx.hir_get_parent_item(self_ty.hir_id).def_id;
+
+        let generics = match tcx.hir_node_by_def_id(parent_item) {
+            hir::Node::Item(hir::Item {
+                kind: hir::ItemKind::Struct(variant, generics), ..
+            }) => {
+                if !variant.fields().iter().any(|field| field.hir_id == parent_hir_id) {
+                    return false;
+                }
+                generics
+            }
+            hir::Node::Item(hir::Item { kind: hir::ItemKind::Enum(def, generics), .. }) => {
+                if !def
+                    .variants
+                    .iter()
+                    .flat_map(|variant| variant.data.fields().iter())
+                    .any(|field| field.hir_id == parent_hir_id)
+                {
+                    return false;
+                }
+                generics
+            }
+            _ => return false,
+        };
+
+        let Ok(rendered_ty) = tcx.sess.source_map().span_to_snippet(self_ty.span) else {
+            return false;
+        };
+
+        let param = "TUV"
+            .chars()
+            .map(|c| c.to_string())
+            .chain((0..).map(|i| format!("P{i}")))
+            .find(|s| !generics.params.iter().any(|param| param.name.ident().as_str() == s))
+            .expect("we definitely can find at least one param name to generate");
+        let mut sugg = vec![(self_ty.span, param.to_string())];
+        if let Some(insertion_span) = generics.span_for_param_suggestion() {
+            sugg.push((insertion_span, format!(", {param}: {}", rendered_ty)));
+        } else {
+            sugg.push((generics.where_clause_span, format!("<{param}: {}>", rendered_ty)));
+        }
+        diag.multipart_suggestion_verbose(
+            "you might be missing a type parameter",
+            sugg,
+            Applicability::MachineApplicable,
+        );
+        true
+    }
     /// Make sure that we are in the condition to suggest the blanket implementation.
     fn maybe_suggest_blanket_trait_impl<G: EmissionGuarantee>(
         &self,
@@ -171,6 +232,65 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         }
     }
 
+    /// Try our best to approximate when adding `dyn` would be helpful for a bare
+    /// trait object.
+    ///
+    /// Right now, this is if the type is either directly nested in another ty,
+    /// or if it's in the tail field within a struct. This approximates what the
+    /// user would've gotten on edition 2015, except for the case where we have
+    /// an *obvious* knock-on `Sized` error.
+    fn maybe_suggest_dyn_trait(
+        &self,
+        self_ty: &hir::Ty<'_>,
+        sugg: Vec<(Span, String)>,
+        diag: &mut Diag<'_>,
+    ) -> bool {
+        let tcx = self.tcx();
+
+        // Look at the direct HIR parent, since we care about the relationship between
+        // the type and the thing that directly encloses it.
+        match tcx.parent_hir_node(self_ty.hir_id) {
+            // These are all generally ok. Namely, when a trait object is nested
+            // into another expression or ty, it's either very certain that they
+            // missed the ty (e.g. `&Trait`) or it's not really possible to tell
+            // what their intention is, so let's not give confusing suggestions and
+            // just mention `dyn`. The user can make up their mind what to do here.
+            hir::Node::Ty(_)
+            | hir::Node::Expr(_)
+            | hir::Node::PatExpr(_)
+            | hir::Node::PathSegment(_)
+            | hir::Node::AssocItemConstraint(_)
+            | hir::Node::TraitRef(_)
+            | hir::Node::Item(_)
+            | hir::Node::WherePredicate(_) => {}
+
+            hir::Node::Field(field) => {
+                // Enums can't have unsized fields, fields can only have an unsized tail field.
+                if let hir::Node::Item(hir::Item {
+                    kind: hir::ItemKind::Struct(variant, _), ..
+                }) = tcx.parent_hir_node(field.hir_id)
+                    && variant
+                        .fields()
+                        .last()
+                        .is_some_and(|tail_field| tail_field.hir_id == field.hir_id)
+                {
+                    // Ok
+                } else {
+                    return false;
+                }
+            }
+            _ => return false,
+        }
+
+        // FIXME: Only emit this suggestion if the trait is dyn-compatible.
+        diag.multipart_suggestion_verbose(
+            "you can add the `dyn` keyword if you want a trait object",
+            sugg,
+            Applicability::MachineApplicable,
+        );
+        true
+    }
+
     fn add_generic_param_suggestion(
         &self,
         generics: &hir::Generics<'_>,
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
index dd6c40bfbb8..5f91f1d7b3e 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
@@ -2294,18 +2294,14 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         {
             let anon_const_type = tcx.type_of(param_def_id).instantiate(tcx, args);
 
-            // We must error if the instantiated type has any inference variables as we will
-            // use this type to feed the `type_of` and query results must not contain inference
-            // variables otherwise we will ICE.
-            //
+            // FIXME(generic_const_parameter_types): Ideally we remove these errors below when
+            // we have the ability to intermix typeck of anon const const args with the parent
+            // bodies typeck.
+
             // We also error if the type contains any regions as effectively any region will wind
             // up as a region variable in mir borrowck. It would also be somewhat concerning if
             // hir typeck was using equality but mir borrowck wound up using subtyping as that could
             // result in a non-infer in hir typeck but a region variable in borrowck.
-            //
-            // FIXME(generic_const_parameter_types): Ideally we remove these errors one day when
-            // we have the ability to intermix typeck of anon const const args with the parent
-            // bodies typeck.
             if tcx.features().generic_const_parameter_types()
                 && (anon_const_type.has_free_regions() || anon_const_type.has_erased_regions())
             {
@@ -2316,6 +2312,9 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 tcx.feed_anon_const_type(anon.def_id, ty::EarlyBinder::bind(Ty::new_error(tcx, e)));
                 return ty::Const::new_error(tcx, e);
             }
+            // We must error if the instantiated type has any inference variables as we will
+            // use this type to feed the `type_of` and query results must not contain inference
+            // variables otherwise we will ICE.
             if anon_const_type.has_non_region_infer() {
                 let e = tcx.dcx().span_err(
                     const_arg.span(),
@@ -2324,6 +2323,16 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 tcx.feed_anon_const_type(anon.def_id, ty::EarlyBinder::bind(Ty::new_error(tcx, e)));
                 return ty::Const::new_error(tcx, e);
             }
+            // We error when the type contains unsubstituted generics since we do not currently
+            // give the anon const any of the generics from the parent.
+            if anon_const_type.has_non_region_param() {
+                let e = tcx.dcx().span_err(
+                    const_arg.span(),
+                    "anonymous constants referencing generics are not yet supported",
+                );
+                tcx.feed_anon_const_type(anon.def_id, ty::EarlyBinder::bind(Ty::new_error(tcx, e)));
+                return ty::Const::new_error(tcx, e);
+            }
 
             tcx.feed_anon_const_type(
                 anon.def_id,
diff --git a/compiler/rustc_hir_pretty/Cargo.toml b/compiler/rustc_hir_pretty/Cargo.toml
index 86989d1e55b..91da8cb3fc5 100644
--- a/compiler/rustc_hir_pretty/Cargo.toml
+++ b/compiler/rustc_hir_pretty/Cargo.toml
@@ -8,7 +8,7 @@ edition = "2024"
 rustc_abi = { path = "../rustc_abi" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_ast_pretty = { path = "../rustc_ast_pretty" }
-rustc_attr_parsing = { path = "../rustc_attr_parsing" }
+rustc_attr_data_structures = { path = "../rustc_attr_data_structures" }
 rustc_hir = { path = "../rustc_hir" }
 rustc_span = { path = "../rustc_span" }
 # tidy-alphabetical-end
diff --git a/compiler/rustc_hir_pretty/src/lib.rs b/compiler/rustc_hir_pretty/src/lib.rs
index 147b42c0490..ae624fc253f 100644
--- a/compiler/rustc_hir_pretty/src/lib.rs
+++ b/compiler/rustc_hir_pretty/src/lib.rs
@@ -16,7 +16,7 @@ use rustc_ast_pretty::pp::Breaks::{Consistent, Inconsistent};
 use rustc_ast_pretty::pp::{self, Breaks};
 use rustc_ast_pretty::pprust::state::MacHeader;
 use rustc_ast_pretty::pprust::{Comments, PrintState};
-use rustc_attr_parsing::{AttributeKind, PrintAttribute};
+use rustc_attr_data_structures::{AttributeKind, PrintAttribute};
 use rustc_hir::{
     BindingMode, ByRef, ConstArgKind, GenericArg, GenericBound, GenericParam, GenericParamKind,
     HirId, ImplicitSelfKind, LifetimeParamKind, Node, PatKind, PreciseCapturingArg, RangeEnd, Term,
@@ -117,84 +117,10 @@ impl<'a> State<'a> {
                 ));
                 self.hardbreak()
             }
-            hir::Attribute::Parsed(AttributeKind::Deprecation { deprecation, .. }) => {
-                self.word("#[deprecated");
-
-                // There are three possible forms here:
-                // 1. a form with explicit components like
-                //    `#[deprecated(since = "1.2.3", note = "some note", suggestion = "something")]`
-                //    where each component may be present or absent.
-                // 2. `#[deprecated = "message"]`
-                // 3. `#[deprecated]`
-                //
-                // Let's figure out which we need.
-                // If there's a `since` or `suggestion` value, we're definitely in form 1.
-                if matches!(
-                    deprecation.since,
-                    rustc_attr_parsing::DeprecatedSince::RustcVersion(..)
-                        | rustc_attr_parsing::DeprecatedSince::Future
-                        | rustc_attr_parsing::DeprecatedSince::NonStandard(..)
-                ) || deprecation.suggestion.is_some()
-                {
-                    self.word("(");
-                    let mut use_comma = false;
-
-                    match &deprecation.since {
-                        rustc_attr_parsing::DeprecatedSince::RustcVersion(rustc_version) => {
-                            self.word("since = \"");
-                            self.word(format!(
-                                "{}.{}.{}",
-                                rustc_version.major, rustc_version.minor, rustc_version.patch
-                            ));
-                            self.word("\"");
-                            use_comma = true;
-                        }
-                        rustc_attr_parsing::DeprecatedSince::Future => {
-                            self.word("since = \"future\"");
-                            use_comma = true;
-                        }
-                        rustc_attr_parsing::DeprecatedSince::NonStandard(symbol) => {
-                            self.word("since = \"");
-                            self.word(symbol.to_ident_string());
-                            self.word("\"");
-                            use_comma = true;
-                        }
-                        _ => {}
-                    }
-
-                    if let Some(note) = &deprecation.note {
-                        if use_comma {
-                            self.word(", ");
-                        }
-                        self.word("note = \"");
-                        self.word(note.to_ident_string());
-                        self.word("\"");
-                        use_comma = true;
-                    }
-
-                    if let Some(suggestion) = &deprecation.suggestion {
-                        if use_comma {
-                            self.word(", ");
-                        }
-                        self.word("suggestion = \"");
-                        self.word(suggestion.to_ident_string());
-                        self.word("\"");
-                    }
-                } else if let Some(note) = &deprecation.note {
-                    // We're in form 2: `#[deprecated = "message"]`.
-                    self.word(" = \"");
-                    self.word(note.to_ident_string());
-                    self.word("\"");
-                } else {
-                    // We're in form 3: `#[deprecated]`. Nothing to do here.
-                }
-
-                self.word("]");
-            }
             hir::Attribute::Parsed(pa) => {
-                self.word("#[attr=\"");
+                self.word("#[attr = ");
                 pa.print_attribute(self);
-                self.word("\")]");
+                self.word("]");
                 self.hardbreak()
             }
         }
@@ -627,24 +553,6 @@ impl<'a> State<'a> {
         self.word(";")
     }
 
-    fn print_item_type(
-        &mut self,
-        item: &hir::Item<'_>,
-        generics: &hir::Generics<'_>,
-        inner: impl Fn(&mut Self),
-    ) {
-        self.head("type");
-        self.print_ident(item.ident);
-        self.print_generic_params(generics.params);
-        self.end(); // end the inner ibox
-
-        self.print_where_clause(generics);
-        self.space();
-        inner(self);
-        self.word(";");
-        self.end(); // end the outer ibox
-    }
-
     fn print_item(&mut self, item: &hir::Item<'_>) {
         self.hardbreak_if_not_bol();
         self.maybe_print_comment(item.span.lo());
@@ -757,10 +665,17 @@ impl<'a> State<'a> {
                 self.end()
             }
             hir::ItemKind::TyAlias(ty, generics) => {
-                self.print_item_type(item, generics, |state| {
-                    state.word_space("=");
-                    state.print_type(ty);
-                });
+                self.head("type");
+                self.print_ident(item.ident);
+                self.print_generic_params(generics.params);
+                self.end(); // end the inner ibox
+
+                self.print_where_clause(generics);
+                self.space();
+                self.word_space("=");
+                self.print_type(ty);
+                self.word(";");
+                self.end(); // end the outer ibox
             }
             hir::ItemKind::Enum(ref enum_definition, params) => {
                 self.print_enum_def(enum_definition, params, item.ident.name, item.span);
@@ -1544,6 +1459,10 @@ impl<'a> State<'a> {
             hir::ExprKind::MethodCall(segment, receiver, args, _) => {
                 self.print_expr_method_call(segment, receiver, args);
             }
+            hir::ExprKind::Use(expr, _) => {
+                self.print_expr(expr);
+                self.word(".use");
+            }
             hir::ExprKind::Binary(op, lhs, rhs) => {
                 self.print_expr_binary(op, lhs, rhs);
             }
@@ -2294,6 +2213,7 @@ impl<'a> State<'a> {
     fn print_capture_clause(&mut self, capture_clause: hir::CaptureBy) {
         match capture_clause {
             hir::CaptureBy::Value { .. } => self.word_space("move"),
+            hir::CaptureBy::Use { .. } => self.word_space("use"),
             hir::CaptureBy::Ref => {}
         }
     }
diff --git a/compiler/rustc_hir_typeck/src/coercion.rs b/compiler/rustc_hir_typeck/src/coercion.rs
index 67419fdf1c3..d7b5c1ed5e1 100644
--- a/compiler/rustc_hir_typeck/src/coercion.rs
+++ b/compiler/rustc_hir_typeck/src/coercion.rs
@@ -41,8 +41,8 @@ use rustc_abi::ExternAbi;
 use rustc_attr_parsing::InlineAttr;
 use rustc_errors::codes::*;
 use rustc_errors::{Applicability, Diag, struct_span_code_err};
-use rustc_hir as hir;
 use rustc_hir::def_id::{DefId, LocalDefId};
+use rustc_hir::{self as hir, LangItem};
 use rustc_hir_analysis::hir_ty_lowering::HirTyLowerer;
 use rustc_infer::infer::relate::RelateResult;
 use rustc_infer::infer::{Coercion, DefineOpaqueTypes, InferOk, InferResult};
@@ -56,7 +56,7 @@ use rustc_middle::ty::adjustment::{
 };
 use rustc_middle::ty::error::TypeError;
 use rustc_middle::ty::visit::TypeVisitableExt;
-use rustc_middle::ty::{self, GenericArgsRef, Ty, TyCtxt};
+use rustc_middle::ty::{self, AliasTy, GenericArgsRef, Ty, TyCtxt};
 use rustc_span::{BytePos, DUMMY_SP, DesugaringKind, Span};
 use rustc_trait_selection::infer::InferCtxtExt as _;
 use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt;
@@ -593,6 +593,63 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
 
         // Create an obligation for `Source: CoerceUnsized<Target>`.
         let cause = self.cause(self.cause.span, ObligationCauseCode::Coercion { source, target });
+        let root_obligation = Obligation::new(
+            self.tcx,
+            cause.clone(),
+            self.fcx.param_env,
+            ty::TraitRef::new(self.tcx, coerce_unsized_did, [coerce_source, coerce_target]),
+        );
+
+        // If the root `Source: CoerceUnsized<Target>` obligation can't possibly hold,
+        // we don't have to assume that this is unsizing coercion (it will always lead to an error)
+        //
+        // However, we don't want to bail early all the time, since the unholdable obligations
+        // may be interesting for diagnostics (such as trying to coerce `&T` to `&dyn Id<This = U>`),
+        // so we only bail if there (likely) is another way to convert the types.
+        if !self.infcx.predicate_may_hold(&root_obligation) {
+            if let Some(dyn_metadata_adt_def_id) = self.tcx.lang_items().get(LangItem::DynMetadata)
+                && let Some(metadata_type_def_id) = self.tcx.lang_items().get(LangItem::Metadata)
+            {
+                self.probe(|_| {
+                    let ocx = ObligationCtxt::new(&self.infcx);
+
+                    // returns `true` if `<ty as Pointee>::Metadata` is `DynMetadata<_>`
+                    let has_dyn_trait_metadata = |ty| {
+                        let metadata_ty: Result<_, _> = ocx.structurally_normalize_ty(
+                            &ObligationCause::dummy(),
+                            self.fcx.param_env,
+                            Ty::new_alias(
+                                self.tcx,
+                                ty::AliasTyKind::Projection,
+                                AliasTy::new(self.tcx, metadata_type_def_id, [ty]),
+                            ),
+                        );
+
+                        metadata_ty.is_ok_and(|metadata_ty| {
+                            metadata_ty
+                                .ty_adt_def()
+                                .is_some_and(|d| d.did() == dyn_metadata_adt_def_id)
+                        })
+                    };
+
+                    // If both types are raw pointers to a (wrapper over a) trait object,
+                    // this might be a cast like `*const W<dyn Trait> -> *const dyn Trait`.
+                    // So it's better to bail and try that. (even if the cast is not possible, for
+                    // example due to vtables not matching, cast diagnostic will likely still be better)
+                    //
+                    // N.B. use `target`, not `coerce_target` (the latter is a var)
+                    if let &ty::RawPtr(source_pointee, _) = coerce_source.kind()
+                        && let &ty::RawPtr(target_pointee, _) = target.kind()
+                        && has_dyn_trait_metadata(source_pointee)
+                        && has_dyn_trait_metadata(target_pointee)
+                    {
+                        return Err(TypeError::Mismatch);
+                    }
+
+                    Ok(())
+                })?;
+            }
+        }
 
         // Use a FIFO queue for this custom fulfillment procedure.
         //
@@ -601,12 +658,7 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
         // and almost never more than 3. By using a SmallVec we avoid an
         // allocation, at the (very small) cost of (occasionally) having to
         // shift subsequent elements down when removing the front element.
-        let mut queue: SmallVec<[PredicateObligation<'tcx>; 4]> = smallvec![Obligation::new(
-            self.tcx,
-            cause,
-            self.fcx.param_env,
-            ty::TraitRef::new(self.tcx, coerce_unsized_did, [coerce_source, coerce_target])
-        )];
+        let mut queue: SmallVec<[PredicateObligation<'tcx>; 4]> = smallvec![root_obligation];
 
         // Keep resolving `CoerceUnsized` and `Unsize` predicates to avoid
         // emitting a coercion in cases like `Foo<$1>` -> `Foo<$2>`, where
diff --git a/compiler/rustc_hir_typeck/src/expr.rs b/compiler/rustc_hir_typeck/src/expr.rs
index 2a89a03e0aa..7e4026db738 100644
--- a/compiler/rustc_hir_typeck/src/expr.rs
+++ b/compiler/rustc_hir_typeck/src/expr.rs
@@ -362,6 +362,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     // Any expression child of these expressions constitute reads.
                     ExprKind::Array(_)
                     | ExprKind::Call(_, _)
+                    | ExprKind::Use(_, _)
                     | ExprKind::MethodCall(_, _, _, _)
                     | ExprKind::Tup(_)
                     | ExprKind::Binary(_, _, _)
@@ -552,6 +553,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             ExprKind::Closure(closure) => self.check_expr_closure(closure, expr.span, expected),
             ExprKind::Block(body, _) => self.check_expr_block(body, expected),
             ExprKind::Call(callee, args) => self.check_expr_call(expr, callee, args, expected),
+            ExprKind::Use(used_expr, _) => self.check_expr_use(used_expr, expected),
             ExprKind::MethodCall(segment, receiver, args, _) => {
                 self.check_expr_method_call(expr, segment, receiver, args, expected)
             }
@@ -1616,6 +1618,15 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         )
     }
 
+    /// Checks use `x.use`.
+    fn check_expr_use(
+        &self,
+        used_expr: &'tcx hir::Expr<'tcx>,
+        expected: Expectation<'tcx>,
+    ) -> Ty<'tcx> {
+        self.check_expr_with_expectation(used_expr, expected)
+    }
+
     fn check_expr_cast(
         &self,
         e: &'tcx hir::Expr<'tcx>,
@@ -2922,7 +2933,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         }
 
         let guar = if field.name == kw::Empty {
-            self.dcx().span_delayed_bug(field.span, "field name with no name")
+            self.dcx().span_bug(field.span, "field name with no name")
         } else if self.method_exists_for_diagnostic(
             field,
             base_ty,
diff --git a/compiler/rustc_hir_typeck/src/expr_use_visitor.rs b/compiler/rustc_hir_typeck/src/expr_use_visitor.rs
index c0617119d67..9ff7eeb2368 100644
--- a/compiler/rustc_hir_typeck/src/expr_use_visitor.rs
+++ b/compiler/rustc_hir_typeck/src/expr_use_visitor.rs
@@ -47,6 +47,21 @@ pub trait Delegate<'tcx> {
     /// the id of the binding in the pattern `pat`.
     fn consume(&mut self, place_with_id: &PlaceWithHirId<'tcx>, diag_expr_id: HirId);
 
+    /// The value found at `place` is used, depending
+    /// on `mode`. Where `diag_expr_id` is the id used for diagnostics for `place`.
+    ///
+    /// Use of a `Copy` type in a ByUse context is considered a use
+    /// by `ImmBorrow` and `borrow` is called instead. This is because
+    /// a shared borrow is the "minimum access" that would be needed
+    /// to perform a copy.
+    ///
+    ///
+    /// The parameter `diag_expr_id` indicates the HIR id that ought to be used for
+    /// diagnostics. Around pattern matching such as `let pat = expr`, the diagnostic
+    /// id will be the id of the expression `expr` but the place itself will have
+    /// the id of the binding in the pattern `pat`.
+    fn use_cloned(&mut self, place_with_id: &PlaceWithHirId<'tcx>, diag_expr_id: HirId);
+
     /// The value found at `place` is being borrowed with kind `bk`.
     /// `diag_expr_id` is the id used for diagnostics (see `consume` for more details).
     fn borrow(
@@ -91,6 +106,10 @@ impl<'tcx, D: Delegate<'tcx>> Delegate<'tcx> for &mut D {
         (**self).consume(place_with_id, diag_expr_id)
     }
 
+    fn use_cloned(&mut self, place_with_id: &PlaceWithHirId<'tcx>, diag_expr_id: HirId) {
+        (**self).use_cloned(place_with_id, diag_expr_id)
+    }
+
     fn borrow(
         &mut self,
         place_with_id: &PlaceWithHirId<'tcx>,
@@ -143,6 +162,8 @@ pub trait TypeInformationCtxt<'tcx> {
 
     fn type_is_copy_modulo_regions(&self, ty: Ty<'tcx>) -> bool;
 
+    fn type_is_use_cloned_modulo_regions(&self, ty: Ty<'tcx>) -> bool;
+
     fn body_owner_def_id(&self) -> LocalDefId;
 
     fn tcx(&self) -> TyCtxt<'tcx>;
@@ -184,6 +205,10 @@ impl<'tcx> TypeInformationCtxt<'tcx> for &FnCtxt<'_, 'tcx> {
         self.infcx.type_is_copy_modulo_regions(self.param_env, ty)
     }
 
+    fn type_is_use_cloned_modulo_regions(&self, ty: Ty<'tcx>) -> bool {
+        self.infcx.type_is_use_cloned_modulo_regions(self.param_env, ty)
+    }
+
     fn body_owner_def_id(&self) -> LocalDefId {
         self.body_id
     }
@@ -230,6 +255,10 @@ impl<'tcx> TypeInformationCtxt<'tcx> for (&LateContext<'tcx>, LocalDefId) {
         self.0.type_is_copy_modulo_regions(ty)
     }
 
+    fn type_is_use_cloned_modulo_regions(&self, ty: Ty<'tcx>) -> bool {
+        self.0.type_is_use_cloned_modulo_regions(ty)
+    }
+
     fn body_owner_def_id(&self) -> LocalDefId {
         self.1
     }
@@ -295,6 +324,24 @@ impl<'tcx, Cx: TypeInformationCtxt<'tcx>, D: Delegate<'tcx>> ExprUseVisitor<'tcx
         }
     }
 
+    pub fn consume_clone_or_copy(&self, place_with_id: &PlaceWithHirId<'tcx>, diag_expr_id: HirId) {
+        debug!("delegate_consume_or_clone(place_with_id={:?})", place_with_id);
+
+        // `x.use` will do one of the following
+        // * if it implements `Copy`, it will be a copy
+        // * if it implements `UseCloned`, it will be a call to `clone`
+        // * otherwise, it is a move
+        //
+        // we do a conservative approximation of this, treating it as a move unless we know that it implements copy or `UseCloned`
+        if self.cx.type_is_copy_modulo_regions(place_with_id.place.ty()) {
+            self.delegate.borrow_mut().copy(place_with_id, diag_expr_id);
+        } else if self.cx.type_is_use_cloned_modulo_regions(place_with_id.place.ty()) {
+            self.delegate.borrow_mut().use_cloned(place_with_id, diag_expr_id);
+        } else {
+            self.delegate.borrow_mut().consume(place_with_id, diag_expr_id);
+        }
+    }
+
     fn consume_exprs(&self, exprs: &[hir::Expr<'_>]) -> Result<(), Cx::Error> {
         for expr in exprs {
             self.consume_expr(expr)?;
@@ -313,6 +360,15 @@ impl<'tcx, Cx: TypeInformationCtxt<'tcx>, D: Delegate<'tcx>> ExprUseVisitor<'tcx
         Ok(())
     }
 
+    pub fn consume_or_clone_expr(&self, expr: &hir::Expr<'_>) -> Result<(), Cx::Error> {
+        debug!("consume_or_clone_expr(expr={:?})", expr);
+
+        let place_with_id = self.cat_expr(expr)?;
+        self.consume_clone_or_copy(&place_with_id, place_with_id.hir_id);
+        self.walk_expr(expr)?;
+        Ok(())
+    }
+
     fn mutate_expr(&self, expr: &hir::Expr<'_>) -> Result<(), Cx::Error> {
         let place_with_id = self.cat_expr(expr)?;
         self.delegate.borrow_mut().mutate(&place_with_id, place_with_id.hir_id);
@@ -366,6 +422,10 @@ impl<'tcx, Cx: TypeInformationCtxt<'tcx>, D: Delegate<'tcx>> ExprUseVisitor<'tcx
                 self.consume_exprs(args)?;
             }
 
+            hir::ExprKind::Use(expr, _) => {
+                self.consume_or_clone_expr(expr)?;
+            }
+
             hir::ExprKind::MethodCall(.., receiver, args, _) => {
                 // callee.m(args)
                 self.consume_expr(receiver)?;
@@ -1085,6 +1145,9 @@ impl<'tcx, Cx: TypeInformationCtxt<'tcx>, D: Delegate<'tcx>> ExprUseVisitor<'tcx
                         ty::UpvarCapture::ByValue => {
                             self.consume_or_copy(&place_with_id, place_with_id.hir_id);
                         }
+                        ty::UpvarCapture::ByUse => {
+                            self.consume_clone_or_copy(&place_with_id, place_with_id.hir_id);
+                        }
                         ty::UpvarCapture::ByRef(upvar_borrow) => {
                             self.delegate.borrow_mut().borrow(
                                 &place_with_id,
@@ -1386,6 +1449,7 @@ impl<'tcx, Cx: TypeInformationCtxt<'tcx>, D: Delegate<'tcx>> ExprUseVisitor<'tcx
 
             hir::ExprKind::AddrOf(..)
             | hir::ExprKind::Call(..)
+            | hir::ExprKind::Use(..)
             | hir::ExprKind::Assign(..)
             | hir::ExprKind::AssignOp(..)
             | hir::ExprKind::Closure { .. }
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
index c46a42c5de1..da2d6579423 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
@@ -220,6 +220,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     ) {
         debug!("fcx {}", self.tag());
 
+        // Don't write user type annotations for const param types, since we give them
+        // identity args just so that we can trivially substitute their `EarlyBinder`.
+        // We enforce that they match their type in MIR later on.
+        if matches!(self.tcx.def_kind(def_id), DefKind::ConstParam) {
+            return;
+        }
+
         if Self::can_contain_user_lifetime_bounds((args, user_self_ty)) {
             let canonicalized = self.canonicalize_user_type_annotation(ty::UserType::new(
                 ty::UserTypeKind::TypeOf(def_id, UserArgs { args, user_self_ty }),
@@ -825,15 +832,14 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
                 let trait_missing_method =
                     matches!(error, method::MethodError::NoMatch(_)) && ty.normalized.is_trait();
-                if item_name.name != kw::Empty {
-                    self.report_method_error(
-                        hir_id,
-                        ty.normalized,
-                        error,
-                        Expectation::NoExpectation,
-                        trait_missing_method && span.edition().at_least_rust_2021(), // emits missing method for trait only after edition 2021
-                    );
-                }
+                assert_ne!(item_name.name, kw::Empty);
+                self.report_method_error(
+                    hir_id,
+                    ty.normalized,
+                    error,
+                    Expectation::NoExpectation,
+                    trait_missing_method && span.edition().at_least_rust_2021(), // emits missing method for trait only after edition 2021
+                );
 
                 result
             });
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
index db947b6744d..b8517701667 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
@@ -99,22 +99,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         debug!("FnCtxt::check_asm: {} deferred checks", deferred_asm_checks.len());
         for (asm, hir_id) in deferred_asm_checks.drain(..) {
             let enclosing_id = self.tcx.hir_enclosing_body_owner(hir_id);
-            let expr_ty = |expr: &hir::Expr<'tcx>| {
-                let ty = self.typeck_results.borrow().expr_ty_adjusted(expr);
-                let ty = self.resolve_vars_if_possible(ty);
-                if ty.has_non_region_infer() {
-                    Ty::new_misc_error(self.tcx)
-                } else {
-                    self.tcx.erase_regions(ty)
-                }
-            };
-            let node_ty = |hir_id: HirId| self.typeck_results.borrow().node_type(hir_id);
             InlineAsmCtxt::new(
-                self.tcx,
                 enclosing_id,
+                &self.infcx,
                 self.typing_env(self.param_env),
-                expr_ty,
-                node_ty,
+                &*self.typeck_results.borrow(),
             )
             .check_asm(asm);
         }
@@ -1647,7 +1636,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             ast::LitKind::Char(_) => tcx.types.char,
             ast::LitKind::Int(_, ast::LitIntType::Signed(t)) => Ty::new_int(tcx, ty::int_ty(t)),
             ast::LitKind::Int(_, ast::LitIntType::Unsigned(t)) => Ty::new_uint(tcx, ty::uint_ty(t)),
-            ast::LitKind::Int(_, ast::LitIntType::Unsuffixed) => {
+            ast::LitKind::Int(i, ast::LitIntType::Unsuffixed) => {
                 let opt_ty = expected.to_option(self).and_then(|ty| match ty.kind() {
                     ty::Int(_) | ty::Uint(_) => Some(ty),
                     // These exist to direct casts like `0x61 as char` to use
@@ -1656,6 +1645,19 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     ty::Char => Some(tcx.types.u8),
                     ty::RawPtr(..) => Some(tcx.types.usize),
                     ty::FnDef(..) | ty::FnPtr(..) => Some(tcx.types.usize),
+                    &ty::Pat(base, _) if base.is_integral() => {
+                        let layout = tcx
+                            .layout_of(self.typing_env(self.param_env).as_query_input(ty))
+                            .ok()?;
+                        assert!(!layout.uninhabited);
+
+                        match layout.backend_repr {
+                            rustc_abi::BackendRepr::Scalar(scalar) => {
+                                scalar.valid_range(&tcx).contains(u128::from(i.get())).then_some(ty)
+                            }
+                            _ => unreachable!(),
+                        }
+                    }
                     _ => None,
                 });
                 opt_ty.unwrap_or_else(|| self.next_int_var())
diff --git a/compiler/rustc_hir_typeck/src/pat.rs b/compiler/rustc_hir_typeck/src/pat.rs
index 19ae3e3899c..7e6973259fe 100644
--- a/compiler/rustc_hir_typeck/src/pat.rs
+++ b/compiler/rustc_hir_typeck/src/pat.rs
@@ -87,10 +87,10 @@ struct TopInfo<'tcx> {
 }
 
 #[derive(Copy, Clone)]
-struct PatInfo<'a, 'tcx> {
+struct PatInfo<'tcx> {
     binding_mode: ByRef,
     max_ref_mutbl: MutblCap,
-    top_info: &'a TopInfo<'tcx>,
+    top_info: TopInfo<'tcx>,
     decl_origin: Option<DeclOrigin<'tcx>>,
 
     /// The depth of current pattern
@@ -303,11 +303,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         origin_expr: Option<&'tcx hir::Expr<'tcx>>,
         decl_origin: Option<DeclOrigin<'tcx>>,
     ) {
-        let info = TopInfo { expected, origin_expr, span, hir_id: pat.hir_id };
+        let top_info = TopInfo { expected, origin_expr, span, hir_id: pat.hir_id };
         let pat_info = PatInfo {
             binding_mode: ByRef::No,
             max_ref_mutbl: MutblCap::Mut,
-            top_info: &info,
+            top_info,
             decl_origin,
             current_depth: 0,
         };
@@ -320,7 +320,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     /// Outside of this module, `check_pat_top` should always be used.
     /// Conversely, inside this module, `check_pat_top` should never be used.
     #[instrument(level = "debug", skip(self, pat_info))]
-    fn check_pat(&self, pat: &'tcx Pat<'tcx>, expected: Ty<'tcx>, pat_info: PatInfo<'_, 'tcx>) {
+    fn check_pat(&self, pat: &'tcx Pat<'tcx>, expected: Ty<'tcx>, pat_info: PatInfo<'tcx>) {
         let PatInfo { binding_mode, max_ref_mutbl, top_info: ti, current_depth, .. } = pat_info;
 
         let path_res = match pat.kind {
@@ -352,13 +352,15 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     qpath,
                     path_res.unwrap(),
                     expected,
-                    ti,
+                    &pat_info.top_info,
                 );
                 self.write_ty(*hir_id, ty);
                 ty
             }
-            PatKind::Expr(lt) => self.check_pat_lit(pat.span, lt, expected, ti),
-            PatKind::Range(lhs, rhs, _) => self.check_pat_range(pat.span, lhs, rhs, expected, ti),
+            PatKind::Expr(lt) => self.check_pat_lit(pat.span, lt, expected, &pat_info.top_info),
+            PatKind::Range(lhs, rhs, _) => {
+                self.check_pat_range(pat.span, lhs, rhs, expected, &pat_info.top_info)
+            }
             PatKind::Binding(ba, var_id, ident, sub) => {
                 self.check_pat_ident(pat, ba, var_id, ident, sub, expected, pat_info)
             }
@@ -818,7 +820,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         ident: Ident,
         sub: Option<&'tcx Pat<'tcx>>,
         expected: Ty<'tcx>,
-        pat_info: PatInfo<'_, 'tcx>,
+        pat_info: PatInfo<'tcx>,
     ) -> Ty<'tcx> {
         let PatInfo { binding_mode: def_br, top_info: ti, .. } = pat_info;
 
@@ -914,12 +916,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         };
 
         // We have a concrete type for the local, so we do not need to taint it and hide follow up errors *using* the local.
-        let _ = self.demand_eqtype_pat(pat.span, eq_ty, local_ty, ti);
+        let _ = self.demand_eqtype_pat(pat.span, eq_ty, local_ty, &ti);
 
         // If there are multiple arms, make sure they all agree on
         // what the type of the binding `x` ought to be.
         if var_id != pat.hir_id {
-            self.check_binding_alt_eq_ty(user_bind_annot, pat.span, var_id, local_ty, ti);
+            self.check_binding_alt_eq_ty(user_bind_annot, pat.span, var_id, local_ty, &ti);
         }
 
         if let Some(p) = sub {
@@ -1149,7 +1151,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         fields: &'tcx [hir::PatField<'tcx>],
         has_rest_pat: bool,
         expected: Ty<'tcx>,
-        pat_info: PatInfo<'_, 'tcx>,
+        pat_info: PatInfo<'tcx>,
     ) -> Ty<'tcx> {
         // Resolve the path and check the definition for errors.
         let (variant, pat_ty) = match self.check_struct_path(qpath, pat.hir_id) {
@@ -1164,7 +1166,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         };
 
         // Type-check the path.
-        let _ = self.demand_eqtype_pat(pat.span, expected, pat_ty, pat_info.top_info);
+        let _ = self.demand_eqtype_pat(pat.span, expected, pat_ty, &pat_info.top_info);
 
         // Type-check subpatterns.
         match self.check_struct_pat_fields(pat_ty, pat, variant, fields, has_rest_pat, pat_info) {
@@ -1353,7 +1355,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         subpats: &'tcx [Pat<'tcx>],
         ddpos: hir::DotDotPos,
         expected: Ty<'tcx>,
-        pat_info: PatInfo<'_, 'tcx>,
+        pat_info: PatInfo<'tcx>,
     ) -> Ty<'tcx> {
         let tcx = self.tcx;
         let on_error = |e| {
@@ -1403,7 +1405,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let pat_ty = pat_ty.no_bound_vars().expect("expected fn type");
 
         // Type-check the tuple struct pattern against the expected type.
-        let diag = self.demand_eqtype_pat_diag(pat.span, expected, pat_ty, pat_info.top_info);
+        let diag = self.demand_eqtype_pat_diag(pat.span, expected, pat_ty, &pat_info.top_info);
         let had_err = diag.map_err(|diag| diag.emit());
 
         // Type-check subpatterns.
@@ -1610,7 +1612,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         elements: &'tcx [Pat<'tcx>],
         ddpos: hir::DotDotPos,
         expected: Ty<'tcx>,
-        pat_info: PatInfo<'_, 'tcx>,
+        pat_info: PatInfo<'tcx>,
     ) -> Ty<'tcx> {
         let tcx = self.tcx;
         let mut expected_len = elements.len();
@@ -1625,7 +1627,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let element_tys_iter = (0..max_len).map(|_| self.next_ty_var(span));
         let element_tys = tcx.mk_type_list_from_iter(element_tys_iter);
         let pat_ty = Ty::new_tup(tcx, element_tys);
-        if let Err(reported) = self.demand_eqtype_pat(span, expected, pat_ty, pat_info.top_info) {
+        if let Err(reported) = self.demand_eqtype_pat(span, expected, pat_ty, &pat_info.top_info) {
             // Walk subpatterns with an expected type of `err` in this case to silence
             // further errors being emitted when using the bindings. #50333
             let element_tys_iter = (0..max_len).map(|_| Ty::new_error(tcx, reported));
@@ -1648,7 +1650,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         variant: &'tcx ty::VariantDef,
         fields: &'tcx [hir::PatField<'tcx>],
         has_rest_pat: bool,
-        pat_info: PatInfo<'_, 'tcx>,
+        pat_info: PatInfo<'tcx>,
     ) -> Result<(), ErrorGuaranteed> {
         let tcx = self.tcx;
 
@@ -2257,7 +2259,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         span: Span,
         inner: &'tcx Pat<'tcx>,
         expected: Ty<'tcx>,
-        pat_info: PatInfo<'_, 'tcx>,
+        pat_info: PatInfo<'tcx>,
     ) -> Ty<'tcx> {
         let tcx = self.tcx;
         let (box_ty, inner_ty) = self
@@ -2267,7 +2269,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 // think any errors can be introduced by using `demand::eqtype`.
                 let inner_ty = self.next_ty_var(inner.span);
                 let box_ty = Ty::new_box(tcx, inner_ty);
-                self.demand_eqtype_pat(span, expected, box_ty, pat_info.top_info)?;
+                self.demand_eqtype_pat(span, expected, box_ty, &pat_info.top_info)?;
                 Ok((box_ty, inner_ty))
             })
             .unwrap_or_else(|guar| {
@@ -2283,7 +2285,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         span: Span,
         inner: &'tcx Pat<'tcx>,
         expected: Ty<'tcx>,
-        pat_info: PatInfo<'_, 'tcx>,
+        pat_info: PatInfo<'tcx>,
     ) -> Ty<'tcx> {
         let tcx = self.tcx;
         // Register a `DerefPure` bound, which is required by all `deref!()` pats.
@@ -2324,7 +2326,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         inner: &'tcx Pat<'tcx>,
         pat_mutbl: Mutability,
         mut expected: Ty<'tcx>,
-        mut pat_info: PatInfo<'_, 'tcx>,
+        mut pat_info: PatInfo<'tcx>,
     ) -> Ty<'tcx> {
         let tcx = self.tcx;
 
@@ -2482,7 +2484,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             pat.span,
                             expected,
                             ref_ty,
-                            pat_info.top_info,
+                            &pat_info.top_info,
                         );
 
                         // Look for a case like `fn foo(&foo: u32)` and suggest
@@ -2605,7 +2607,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         slice: Option<&'tcx Pat<'tcx>>,
         after: &'tcx [Pat<'tcx>],
         expected: Ty<'tcx>,
-        pat_info: PatInfo<'_, 'tcx>,
+        pat_info: PatInfo<'tcx>,
     ) -> Ty<'tcx> {
         let expected = self.try_structurally_resolve_type(span, expected);
 
@@ -2767,7 +2769,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         &self,
         span: Span,
         expected_ty: Ty<'tcx>,
-        pat_info: PatInfo<'_, 'tcx>,
+        pat_info: PatInfo<'tcx>,
     ) -> ErrorGuaranteed {
         let PatInfo { top_info: ti, current_depth, .. } = pat_info;
 
diff --git a/compiler/rustc_hir_typeck/src/upvar.rs b/compiler/rustc_hir_typeck/src/upvar.rs
index 9a0b2247058..f570d0d8a0d 100644
--- a/compiler/rustc_hir_typeck/src/upvar.rs
+++ b/compiler/rustc_hir_typeck/src/upvar.rs
@@ -671,6 +671,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
                 let (place, capture_kind) = match capture_clause {
                     hir::CaptureBy::Value { .. } => adjust_for_move_closure(place, capture_kind),
+                    hir::CaptureBy::Use { .. } => adjust_for_use_closure(place, capture_kind),
                     hir::CaptureBy::Ref => adjust_for_non_move_closure(place, capture_kind),
                 };
 
@@ -1165,7 +1166,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         let ty = match closure_clause {
             hir::CaptureBy::Value { .. } => ty, // For move closure the capture kind should be by value
-            hir::CaptureBy::Ref => {
+            hir::CaptureBy::Ref | hir::CaptureBy::Use { .. } => {
                 // For non move closure the capture kind is the max capture kind of all captures
                 // according to the ordering ImmBorrow < UniqueImmBorrow < MutBorrow < ByValue
                 let mut max_capture_info = root_var_min_capture_list.first().unwrap().info;
@@ -1292,7 +1293,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         .insert(UpvarMigrationInfo::CapturingNothing { use_span: upvar.span });
                     return Some(diagnostics_info);
                 }
-                hir::CaptureBy::Ref => {}
+                hir::CaptureBy::Ref | hir::CaptureBy::Use { .. } => {}
             }
 
             return None;
@@ -1305,7 +1306,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         for captured_place in root_var_min_capture_list.iter() {
             match captured_place.info.capture_kind {
                 // Only care about captures that are moved into the closure
-                ty::UpvarCapture::ByValue => {
+                ty::UpvarCapture::ByValue | ty::UpvarCapture::ByUse => {
                     projections_list.push(captured_place.place.projections.as_slice());
                     diagnostics_info.insert(UpvarMigrationInfo::CapturingPrecise {
                         source_expr: captured_place.info.path_expr_id,
@@ -1689,10 +1690,32 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             //
             // If the data will be moved out of this place, then the place will be truncated
             // at the first Deref in `adjust_for_move_closure` and then moved into the closure.
+            //
+            // For example:
+            //
+            // struct Buffer<'a> {
+            //     x: &'a String,
+            //     y: Vec<u8>,
+            // }
+            //
+            // fn get<'a>(b: Buffer<'a>) -> impl Sized + 'a {
+            //     let c = move || b.x;
+            //     drop(b);
+            //     c
+            // }
+            //
+            // Even though the closure is declared as move, when we are capturing borrowed data (in
+            // this case, *b.x) we prefer to capture by reference.
+            // Otherwise you'd get an error in 2021 immediately because you'd be trying to take
+            // ownership of the (borrowed) String or else you'd take ownership of b, as in 2018 and
+            // before, which is also an error.
             hir::CaptureBy::Value { .. } if !place.deref_tys().any(Ty::is_ref) => {
                 ty::UpvarCapture::ByValue
             }
-            hir::CaptureBy::Value { .. } | hir::CaptureBy::Ref => {
+            hir::CaptureBy::Use { .. } if !place.deref_tys().any(Ty::is_ref) => {
+                ty::UpvarCapture::ByUse
+            }
+            hir::CaptureBy::Value { .. } | hir::CaptureBy::Use { .. } | hir::CaptureBy::Ref => {
                 ty::UpvarCapture::ByRef(BorrowKind::Immutable)
             }
         }
@@ -1927,7 +1950,7 @@ fn apply_capture_kind_on_capture_ty<'tcx>(
     region: ty::Region<'tcx>,
 ) -> Ty<'tcx> {
     match capture_kind {
-        ty::UpvarCapture::ByValue => ty,
+        ty::UpvarCapture::ByValue | ty::UpvarCapture::ByUse => ty,
         ty::UpvarCapture::ByRef(kind) => Ty::new_ref(tcx, region, ty, kind.to_mutbl_lossy()),
     }
 }
@@ -2024,6 +2047,21 @@ impl<'tcx> euv::Delegate<'tcx> for InferBorrowKind<'tcx> {
     }
 
     #[instrument(skip(self), level = "debug")]
+    fn use_cloned(&mut self, place_with_id: &PlaceWithHirId<'tcx>, diag_expr_id: HirId) {
+        let PlaceBase::Upvar(upvar_id) = place_with_id.place.base else { return };
+        assert_eq!(self.closure_def_id, upvar_id.closure_expr_id);
+
+        self.capture_information.push((
+            place_with_id.place.clone(),
+            ty::CaptureInfo {
+                capture_kind_expr_id: Some(diag_expr_id),
+                path_expr_id: Some(diag_expr_id),
+                capture_kind: ty::UpvarCapture::ByUse,
+            },
+        ));
+    }
+
+    #[instrument(skip(self), level = "debug")]
     fn borrow(
         &mut self,
         place_with_id: &PlaceWithHirId<'tcx>,
@@ -2164,6 +2202,20 @@ fn adjust_for_move_closure(
     (place, ty::UpvarCapture::ByValue)
 }
 
+/// Truncate deref of any reference.
+fn adjust_for_use_closure(
+    mut place: Place<'_>,
+    mut kind: ty::UpvarCapture,
+) -> (Place<'_>, ty::UpvarCapture) {
+    let first_deref = place.projections.iter().position(|proj| proj.kind == ProjectionKind::Deref);
+
+    if let Some(idx) = first_deref {
+        truncate_place_to_len_and_update_capture_kind(&mut place, &mut kind, idx);
+    }
+
+    (place, ty::UpvarCapture::ByUse)
+}
+
 /// Adjust closure capture just that if taking ownership of data, only move data
 /// from enclosing stack frame.
 fn adjust_for_non_move_closure(
@@ -2174,7 +2226,7 @@ fn adjust_for_non_move_closure(
         place.projections.iter().position(|proj| proj.kind == ProjectionKind::Deref);
 
     match kind {
-        ty::UpvarCapture::ByValue => {
+        ty::UpvarCapture::ByValue | ty::UpvarCapture::ByUse => {
             if let Some(idx) = contains_deref {
                 truncate_place_to_len_and_update_capture_kind(&mut place, &mut kind, idx);
             }
@@ -2219,6 +2271,7 @@ fn construct_capture_kind_reason_string<'tcx>(
 
     let capture_kind_str = match capture_info.capture_kind {
         ty::UpvarCapture::ByValue => "ByValue".into(),
+        ty::UpvarCapture::ByUse => "ByUse".into(),
         ty::UpvarCapture::ByRef(kind) => format!("{kind:?}"),
     };
 
@@ -2240,6 +2293,7 @@ fn construct_capture_info_string<'tcx>(
 
     let capture_kind_str = match capture_info.capture_kind {
         ty::UpvarCapture::ByValue => "ByValue".into(),
+        ty::UpvarCapture::ByUse => "ByUse".into(),
         ty::UpvarCapture::ByRef(kind) => format!("{kind:?}"),
     };
     format!("{place_str} -> {capture_kind_str}")
@@ -2335,8 +2389,11 @@ fn determine_capture_info(
     // expressions.
     let eq_capture_kind = match (capture_info_a.capture_kind, capture_info_b.capture_kind) {
         (ty::UpvarCapture::ByValue, ty::UpvarCapture::ByValue) => true,
+        (ty::UpvarCapture::ByUse, ty::UpvarCapture::ByUse) => true,
         (ty::UpvarCapture::ByRef(ref_a), ty::UpvarCapture::ByRef(ref_b)) => ref_a == ref_b,
-        (ty::UpvarCapture::ByValue, _) | (ty::UpvarCapture::ByRef(_), _) => false,
+        (ty::UpvarCapture::ByValue, _)
+        | (ty::UpvarCapture::ByUse, _)
+        | (ty::UpvarCapture::ByRef(_), _) => false,
     };
 
     if eq_capture_kind {
@@ -2346,10 +2403,20 @@ fn determine_capture_info(
         }
     } else {
         // We select the CaptureKind which ranks higher based the following priority order:
-        // ByValue > MutBorrow > UniqueImmBorrow > ImmBorrow
+        // (ByUse | ByValue) > MutBorrow > UniqueImmBorrow > ImmBorrow
         match (capture_info_a.capture_kind, capture_info_b.capture_kind) {
-            (ty::UpvarCapture::ByValue, _) => capture_info_a,
-            (_, ty::UpvarCapture::ByValue) => capture_info_b,
+            (ty::UpvarCapture::ByUse, ty::UpvarCapture::ByValue)
+            | (ty::UpvarCapture::ByValue, ty::UpvarCapture::ByUse) => {
+                bug!("Same capture can't be ByUse and ByValue at the same time")
+            }
+            (ty::UpvarCapture::ByValue, ty::UpvarCapture::ByValue)
+            | (ty::UpvarCapture::ByUse, ty::UpvarCapture::ByUse)
+            | (ty::UpvarCapture::ByValue | ty::UpvarCapture::ByUse, ty::UpvarCapture::ByRef(_)) => {
+                capture_info_a
+            }
+            (ty::UpvarCapture::ByRef(_), ty::UpvarCapture::ByValue | ty::UpvarCapture::ByUse) => {
+                capture_info_b
+            }
             (ty::UpvarCapture::ByRef(ref_a), ty::UpvarCapture::ByRef(ref_b)) => {
                 match (ref_a, ref_b) {
                     // Take LHS:
@@ -2401,7 +2468,7 @@ fn truncate_place_to_len_and_update_capture_kind<'tcx>(
         }
 
         ty::UpvarCapture::ByRef(..) => {}
-        ty::UpvarCapture::ByValue => {}
+        ty::UpvarCapture::ByValue | ty::UpvarCapture::ByUse => {}
     }
 
     place.projections.truncate(len);
diff --git a/compiler/rustc_incremental/Cargo.toml b/compiler/rustc_incremental/Cargo.toml
index 4939bfb3a1c..db0a5841887 100644
--- a/compiler/rustc_incremental/Cargo.toml
+++ b/compiler/rustc_incremental/Cargo.toml
@@ -5,7 +5,7 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-rand = "0.8.4"
+rand = "0.9.0"
 rustc_ast = { path = "../rustc_ast" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
diff --git a/compiler/rustc_incremental/src/persist/file_format.rs b/compiler/rustc_incremental/src/persist/file_format.rs
index 4c664ea6ba0..9cec2702a41 100644
--- a/compiler/rustc_incremental/src/persist/file_format.rs
+++ b/compiler/rustc_incremental/src/persist/file_format.rs
@@ -123,7 +123,7 @@ pub(crate) fn read_file(
 
     // Check HEADER_FORMAT_VERSION
     {
-        debug_assert!(::std::mem::size_of_val(&HEADER_FORMAT_VERSION) == 2);
+        debug_assert!(size_of_val(&HEADER_FORMAT_VERSION) == 2);
         let mut header_format_version = [0u8; 2];
         file.read_exact(&mut header_format_version)?;
         let header_format_version =
diff --git a/compiler/rustc_incremental/src/persist/fs.rs b/compiler/rustc_incremental/src/persist/fs.rs
index 19cca48af61..76a1ff3cf38 100644
--- a/compiler/rustc_incremental/src/persist/fs.rs
+++ b/compiler/rustc_incremental/src/persist/fs.rs
@@ -108,7 +108,7 @@ use std::io::{self, ErrorKind};
 use std::path::{Path, PathBuf};
 use std::time::{Duration, SystemTime, UNIX_EPOCH};
 
-use rand::{RngCore, thread_rng};
+use rand::{RngCore, rng};
 use rustc_data_structures::base_n::{BaseNString, CASE_INSENSITIVE, ToBaseN};
 use rustc_data_structures::fx::{FxHashSet, FxIndexSet};
 use rustc_data_structures::svh::Svh;
@@ -445,7 +445,7 @@ fn copy_files(sess: &Session, target_dir: &Path, source_dir: &Path) -> Result<bo
 fn generate_session_dir_path(crate_dir: &Path) -> PathBuf {
     let timestamp = timestamp_to_string(SystemTime::now());
     debug!("generate_session_dir_path: timestamp = {}", timestamp);
-    let random_number = thread_rng().next_u32();
+    let random_number = rng().next_u32();
     debug!("generate_session_dir_path: random_number = {}", random_number);
 
     // Chop the first 3 characters off the timestamp. Those 3 bytes will be zero for a while.
diff --git a/compiler/rustc_index/src/bit_set.rs b/compiler/rustc_index/src/bit_set.rs
index 6dc044a6d38..598409c9051 100644
--- a/compiler/rustc_index/src/bit_set.rs
+++ b/compiler/rustc_index/src/bit_set.rs
@@ -1,7 +1,9 @@
 use std::marker::PhantomData;
+#[cfg(not(feature = "nightly"))]
+use std::mem;
 use std::ops::{BitAnd, BitAndAssign, BitOrAssign, Bound, Not, Range, RangeBounds, Shl};
 use std::rc::Rc;
-use std::{fmt, iter, mem, slice};
+use std::{fmt, iter, slice};
 
 use Chunk::*;
 #[cfg(feature = "nightly")]
@@ -14,7 +16,7 @@ use crate::{Idx, IndexVec};
 mod tests;
 
 type Word = u64;
-const WORD_BYTES: usize = mem::size_of::<Word>();
+const WORD_BYTES: usize = size_of::<Word>();
 const WORD_BITS: usize = WORD_BYTES * 8;
 
 // The choice of chunk size has some trade-offs.
diff --git a/compiler/rustc_index/src/slice.rs b/compiler/rustc_index/src/slice.rs
index f17ea9e4b59..67ac805c2bf 100644
--- a/compiler/rustc_index/src/slice.rs
+++ b/compiler/rustc_index/src/slice.rs
@@ -1,6 +1,7 @@
 use std::fmt;
 use std::marker::PhantomData;
 use std::ops::{Index, IndexMut};
+use std::slice::GetDisjointMutError::*;
 use std::slice::{self, SliceIndex};
 
 use crate::{Idx, IndexVec, IntoSliceIdx};
@@ -65,6 +66,8 @@ impl<I: Idx, T> IndexSlice<I, T> {
 
     #[inline]
     pub fn iter_enumerated(&self) -> impl DoubleEndedIterator<Item = (I, &T)> + ExactSizeIterator {
+        // Allow the optimizer to elide the bounds checking when creating each index.
+        let _ = I::new(self.len());
         self.raw.iter().enumerate().map(|(n, t)| (I::new(n), t))
     }
 
@@ -72,6 +75,8 @@ impl<I: Idx, T> IndexSlice<I, T> {
     pub fn indices(
         &self,
     ) -> impl DoubleEndedIterator<Item = I> + ExactSizeIterator + Clone + 'static {
+        // Allow the optimizer to elide the bounds checking when creating each index.
+        let _ = I::new(self.len());
         (0..self.len()).map(|n| I::new(n))
     }
 
@@ -84,6 +89,8 @@ impl<I: Idx, T> IndexSlice<I, T> {
     pub fn iter_enumerated_mut(
         &mut self,
     ) -> impl DoubleEndedIterator<Item = (I, &mut T)> + ExactSizeIterator {
+        // Allow the optimizer to elide the bounds checking when creating each index.
+        let _ = I::new(self.len());
         self.raw.iter_mut().enumerate().map(|(n, t)| (I::new(n), t))
     }
 
@@ -115,32 +122,36 @@ impl<I: Idx, T> IndexSlice<I, T> {
 
     /// Returns mutable references to two distinct elements, `a` and `b`.
     ///
-    /// Panics if `a == b`.
+    /// Panics if `a == b` or if some of them are out of bounds.
     #[inline]
     pub fn pick2_mut(&mut self, a: I, b: I) -> (&mut T, &mut T) {
         let (ai, bi) = (a.index(), b.index());
-        assert!(ai != bi);
-
-        if ai < bi {
-            let (c1, c2) = self.raw.split_at_mut(bi);
-            (&mut c1[ai], &mut c2[0])
-        } else {
-            let (c2, c1) = self.pick2_mut(b, a);
-            (c1, c2)
+
+        match self.raw.get_disjoint_mut([ai, bi]) {
+            Ok([a, b]) => (a, b),
+            Err(OverlappingIndices) => panic!("Indices {ai:?} and {bi:?} are not disjoint!"),
+            Err(IndexOutOfBounds) => {
+                panic!("Some indices among ({ai:?}, {bi:?}) are out of bounds")
+            }
         }
     }
 
     /// Returns mutable references to three distinct elements.
     ///
-    /// Panics if the elements are not distinct.
+    /// Panics if the elements are not distinct or if some of them are out of bounds.
     #[inline]
     pub fn pick3_mut(&mut self, a: I, b: I, c: I) -> (&mut T, &mut T, &mut T) {
         let (ai, bi, ci) = (a.index(), b.index(), c.index());
-        assert!(ai != bi && bi != ci && ci != ai);
-        let len = self.raw.len();
-        assert!(ai < len && bi < len && ci < len);
-        let ptr = self.raw.as_mut_ptr();
-        unsafe { (&mut *ptr.add(ai), &mut *ptr.add(bi), &mut *ptr.add(ci)) }
+
+        match self.raw.get_disjoint_mut([ai, bi, ci]) {
+            Ok([a, b, c]) => (a, b, c),
+            Err(OverlappingIndices) => {
+                panic!("Indices {ai:?}, {bi:?} and {ci:?} are not disjoint!")
+            }
+            Err(IndexOutOfBounds) => {
+                panic!("Some indices among ({ai:?}, {bi:?}, {ci:?}) are out of bounds")
+            }
+        }
     }
 
     #[inline]
diff --git a/compiler/rustc_index/src/vec.rs b/compiler/rustc_index/src/vec.rs
index 7f3f3ead5f2..13f0dda180b 100644
--- a/compiler/rustc_index/src/vec.rs
+++ b/compiler/rustc_index/src/vec.rs
@@ -93,6 +93,8 @@ impl<I: Idx, T> IndexVec<I, T> {
     /// be allocated only once, with a capacity of at least `n`.)
     #[inline]
     pub fn from_fn_n(func: impl FnMut(I) -> T, n: usize) -> Self {
+        // Allow the optimizer to elide the bounds checking when creating each index.
+        let _ = I::new(n);
         IndexVec::from_raw((0..n).map(I::new).map(func).collect())
     }
 
@@ -128,6 +130,8 @@ impl<I: Idx, T> IndexVec<I, T> {
     pub fn into_iter_enumerated(
         self,
     ) -> impl DoubleEndedIterator<Item = (I, T)> + ExactSizeIterator {
+        // Allow the optimizer to elide the bounds checking when creating each index.
+        let _ = I::new(self.len());
         self.raw.into_iter().enumerate().map(|(n, t)| (I::new(n), t))
     }
 
diff --git a/compiler/rustc_index/src/vec/tests.rs b/compiler/rustc_index/src/vec/tests.rs
index 381d79c24fc..5b0ca4b2b92 100644
--- a/compiler/rustc_index/src/vec/tests.rs
+++ b/compiler/rustc_index/src/vec/tests.rs
@@ -9,8 +9,6 @@ crate::newtype_index! {
 
 #[test]
 fn index_size_is_optimized() {
-    use std::mem::size_of;
-
     assert_eq!(size_of::<MyIdx>(), 4);
     // Uses 0xFFFF_FFFB
     assert_eq!(size_of::<Option<MyIdx>>(), 4);
diff --git a/compiler/rustc_interface/src/util.rs b/compiler/rustc_interface/src/util.rs
index bc2aae7cd87..5cccab893bb 100644
--- a/compiler/rustc_interface/src/util.rs
+++ b/compiler/rustc_interface/src/util.rs
@@ -39,11 +39,11 @@ pub(crate) fn add_configuration(
 ) {
     let tf = sym::target_feature;
 
-    let unstable_target_features = codegen_backend.target_features_cfg(sess, true);
-    sess.unstable_target_features.extend(unstable_target_features.iter().cloned());
+    let (target_features, unstable_target_features) = codegen_backend.target_features_cfg(sess);
 
-    let target_features = codegen_backend.target_features_cfg(sess, false);
-    sess.target_features.extend(target_features.iter().cloned());
+    sess.unstable_target_features.extend(unstable_target_features.iter().copied());
+
+    sess.target_features.extend(target_features.iter().copied());
 
     cfg.extend(target_features.into_iter().map(|feat| (tf, Some(feat))));
 
diff --git a/compiler/rustc_lint/src/context.rs b/compiler/rustc_lint/src/context.rs
index 74663e6b4bb..017ae943e91 100644
--- a/compiler/rustc_lint/src/context.rs
+++ b/compiler/rustc_lint/src/context.rs
@@ -6,6 +6,7 @@
 use std::cell::Cell;
 use std::slice;
 
+use rustc_ast::BindingMode;
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_data_structures::sync;
 use rustc_data_structures::unord::UnordMap;
@@ -14,6 +15,7 @@ use rustc_feature::Features;
 use rustc_hir::def::Res;
 use rustc_hir::def_id::{CrateNum, DefId};
 use rustc_hir::definitions::{DefPathData, DisambiguatedDefPathData};
+use rustc_hir::{Pat, PatKind};
 use rustc_middle::bug;
 use rustc_middle::middle::privacy::EffectiveVisibilities;
 use rustc_middle::ty::layout::{LayoutError, LayoutOfHelpers, TyAndLayout};
@@ -683,6 +685,10 @@ impl<'tcx> LateContext<'tcx> {
         self.tcx.type_is_copy_modulo_regions(self.typing_env(), ty)
     }
 
+    pub fn type_is_use_cloned_modulo_regions(&self, ty: Ty<'tcx>) -> bool {
+        self.tcx.type_is_use_cloned_modulo_regions(self.typing_env(), ty)
+    }
+
     /// Gets the type-checking results for the current body,
     /// or `None` if outside a body.
     pub fn maybe_typeck_results(&self) -> Option<&'tcx ty::TypeckResults<'tcx>> {
@@ -886,7 +892,12 @@ impl<'tcx> LateContext<'tcx> {
             }
             && let Some(init) = match parent_node {
                 hir::Node::Expr(expr) => Some(expr),
-                hir::Node::LetStmt(hir::LetStmt { init, .. }) => *init,
+                hir::Node::LetStmt(hir::LetStmt {
+                    init,
+                    // Binding is immutable, init cannot be re-assigned
+                    pat: Pat { kind: PatKind::Binding(BindingMode::NONE, ..), .. },
+                    ..
+                }) => *init,
                 _ => None,
             }
         {
@@ -931,7 +942,12 @@ impl<'tcx> LateContext<'tcx> {
             }
             && let Some(init) = match parent_node {
                 hir::Node::Expr(expr) => Some(expr),
-                hir::Node::LetStmt(hir::LetStmt { init, .. }) => *init,
+                hir::Node::LetStmt(hir::LetStmt {
+                    init,
+                    // Binding is immutable, init cannot be re-assigned
+                    pat: Pat { kind: PatKind::Binding(BindingMode::NONE, ..), .. },
+                    ..
+                }) => *init,
                 hir::Node::Item(item) => match item.kind {
                     hir::ItemKind::Const(.., body_id) | hir::ItemKind::Static(.., body_id) => {
                         Some(self.tcx.hir_body(body_id).value)
diff --git a/compiler/rustc_lint/src/dangling.rs b/compiler/rustc_lint/src/dangling.rs
index fd6b3e90ada..91c7922638d 100644
--- a/compiler/rustc_lint/src/dangling.rs
+++ b/compiler/rustc_lint/src/dangling.rs
@@ -159,7 +159,10 @@ fn is_temporary_rvalue(expr: &Expr<'_>) -> bool {
         ExprKind::Path(..) => false,
 
         // Calls return rvalues.
-        ExprKind::Call(..) | ExprKind::MethodCall(..) | ExprKind::Binary(..) => true,
+        ExprKind::Call(..)
+        | ExprKind::MethodCall(..)
+        | ExprKind::Use(..)
+        | ExprKind::Binary(..) => true,
 
         // Inner blocks are rvalues.
         ExprKind::If(..) | ExprKind::Loop(..) | ExprKind::Match(..) | ExprKind::Block(..) => true,
diff --git a/compiler/rustc_lint/src/default_could_be_derived.rs b/compiler/rustc_lint/src/default_could_be_derived.rs
index 59e38a882dd..58efca5e994 100644
--- a/compiler/rustc_lint/src/default_could_be_derived.rs
+++ b/compiler/rustc_lint/src/default_could_be_derived.rs
@@ -133,7 +133,7 @@ impl<'tcx> LateLintPass<'tcx> for DefaultCouldBeDerived {
             return;
         }
 
-        // At least one of the fields with a default value have been overriden in
+        // At least one of the fields with a default value have been overridden in
         // the `Default` implementation. We suggest removing it and relying on `..`
         // instead.
         let any_default_field_given =
diff --git a/compiler/rustc_lint/src/late.rs b/compiler/rustc_lint/src/late.rs
index d22515d62d6..23d6efa0508 100644
--- a/compiler/rustc_lint/src/late.rs
+++ b/compiler/rustc_lint/src/late.rs
@@ -74,7 +74,7 @@ impl<'tcx, T: LateLintPass<'tcx>> LateContextAndPass<'tcx, T> {
 
     fn process_mod(&mut self, m: &'tcx hir::Mod<'tcx>, n: HirId) {
         lint_callback!(self, check_mod, m, n);
-        hir_visit::walk_mod(self, m, n);
+        hir_visit::walk_mod(self, m);
     }
 }
 
diff --git a/compiler/rustc_lint/src/opaque_hidden_inferred_bound.rs b/compiler/rustc_lint/src/opaque_hidden_inferred_bound.rs
index 7eaf83f5acf..659f6d98f03 100644
--- a/compiler/rustc_lint/src/opaque_hidden_inferred_bound.rs
+++ b/compiler/rustc_lint/src/opaque_hidden_inferred_bound.rs
@@ -43,6 +43,7 @@ declare_lint! {
     ///
     /// type Tait = impl Sized;
     ///
+    /// #[define_opaque(Tait)]
     /// fn test() -> impl Trait<Assoc = Tait> {
     ///     42
     /// }
diff --git a/compiler/rustc_lint_defs/src/builtin.rs b/compiler/rustc_lint_defs/src/builtin.rs
index 10b85be2cfb..592c934997c 100644
--- a/compiler/rustc_lint_defs/src/builtin.rs
+++ b/compiler/rustc_lint_defs/src/builtin.rs
@@ -73,7 +73,6 @@ declare_lint_pass! {
         NEVER_TYPE_FALLBACK_FLOWING_INTO_UNSAFE,
         NON_CONTIGUOUS_RANGE_ENDPOINTS,
         NON_EXHAUSTIVE_OMITTED_PATTERNS,
-        ORDER_DEPENDENT_TRAIT_OBJECTS,
         OUT_OF_SCOPE_MACRO_CALLS,
         OVERLAPPING_RANGE_ENDPOINTS,
         PATTERNS_IN_FNS_WITHOUT_BODY,
@@ -1502,42 +1501,6 @@ declare_lint! {
 }
 
 declare_lint! {
-    /// The `order_dependent_trait_objects` lint detects a trait coherency
-    /// violation that would allow creating two trait impls for the same
-    /// dynamic trait object involving marker traits.
-    ///
-    /// ### Example
-    ///
-    /// ```rust,compile_fail
-    /// pub trait Trait {}
-    ///
-    /// impl Trait for dyn Send + Sync { }
-    /// impl Trait for dyn Sync + Send { }
-    /// ```
-    ///
-    /// {{produces}}
-    ///
-    /// ### Explanation
-    ///
-    /// A previous bug caused the compiler to interpret traits with different
-    /// orders (such as `Send + Sync` and `Sync + Send`) as distinct types
-    /// when they were intended to be treated the same. This allowed code to
-    /// define separate trait implementations when there should be a coherence
-    /// error. This is a [future-incompatible] lint to transition this to a
-    /// hard error in the future. See [issue #56484] for more details.
-    ///
-    /// [issue #56484]: https://github.com/rust-lang/rust/issues/56484
-    /// [future-incompatible]: ../index.md#future-incompatible-lints
-    pub ORDER_DEPENDENT_TRAIT_OBJECTS,
-    Deny,
-    "trait-object types were treated as different depending on marker-trait order",
-    @future_incompatible = FutureIncompatibleInfo {
-        reason: FutureIncompatibilityReason::FutureReleaseErrorReportInDeps,
-        reference: "issue #56484 <https://github.com/rust-lang/rust/issues/56484>",
-    };
-}
-
-declare_lint! {
     /// The `coherence_leak_check` lint detects conflicting implementations of
     /// a trait that are only distinguished by the old leak-check code.
     ///
@@ -2710,7 +2673,7 @@ declare_lint! {
     ///
     /// ```rust
     /// const fn foo<T>() -> usize {
-    ///     if std::mem::size_of::<*mut T>() < 8 { // size of *mut T does not depend on T
+    ///     if size_of::<*mut T>() < 8 { // size of *mut T does not depend on T
     ///         4
     ///     } else {
     ///         8
diff --git a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
index aea2a8dd097..53df59930f4 100644
--- a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
+++ b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
@@ -152,8 +152,12 @@ extern "C" LLVMContextRef LLVMRustContextCreate(bool shouldDiscardNames) {
 }
 
 extern "C" void LLVMRustSetNormalizedTarget(LLVMModuleRef M,
-                                            const char *Triple) {
-  unwrap(M)->setTargetTriple(Triple::normalize(Triple));
+                                            const char *Target) {
+#if LLVM_VERSION_GE(21, 0)
+  unwrap(M)->setTargetTriple(Triple(Triple::normalize(Target)));
+#else
+  unwrap(M)->setTargetTriple(Triple::normalize(Target));
+#endif
 }
 
 extern "C" void LLVMRustPrintPassTimings(RustStringRef OutBuf) {
diff --git a/compiler/rustc_macros/src/print_attribute.rs b/compiler/rustc_macros/src/print_attribute.rs
index 3c6e30b851b..42d94e72ee9 100644
--- a/compiler/rustc_macros/src/print_attribute.rs
+++ b/compiler/rustc_macros/src/print_attribute.rs
@@ -16,12 +16,14 @@ fn print_fields(name: &Ident, fields: &Fields) -> (TokenStream, TokenStream, Tok
                 let name = field.ident.as_ref().unwrap();
                 let string_name = name.to_string();
                 disps.push(quote! {
-                    if __printed_anything && #name.print_something() {
-                        __p.word_space(",");
+                    if #name.should_render() {
+                        if __printed_anything {
+                            __p.word_space(",");
+                        }
+                        __p.word(#string_name);
+                        __p.word_space(":");
                         __printed_anything = true;
                     }
-                    __p.word(#string_name);
-                    __p.word_space(":");
                     #name.print_attribute(__p);
                 });
                 field_names.push(name);
@@ -31,10 +33,11 @@ fn print_fields(name: &Ident, fields: &Fields) -> (TokenStream, TokenStream, Tok
                 quote! { {#(#field_names),*} },
                 quote! {
                     __p.word(#string_name);
-                    if true #(&& !#field_names.print_something())* {
+                    if true #(&& !#field_names.should_render())* {
                         return;
                     }
 
+                    __p.nbsp();
                     __p.word("{");
                     #(#disps)*
                     __p.word("}");
@@ -48,8 +51,10 @@ fn print_fields(name: &Ident, fields: &Fields) -> (TokenStream, TokenStream, Tok
             for idx in 0..fields_unnamed.unnamed.len() {
                 let name = format_ident!("f{idx}");
                 disps.push(quote! {
-                    if __printed_anything && #name.print_something() {
-                        __p.word_space(",");
+                    if #name.should_render() {
+                        if __printed_anything {
+                            __p.word_space(",");
+                        }
                         __printed_anything = true;
                     }
                     #name.print_attribute(__p);
@@ -62,13 +67,13 @@ fn print_fields(name: &Ident, fields: &Fields) -> (TokenStream, TokenStream, Tok
                 quote! {
                     __p.word(#string_name);
 
-                    if true #(&& !#field_names.print_something())* {
+                    if true #(&& !#field_names.should_render())* {
                         return;
                     }
 
-                    __p.word("(");
+                    __p.popen();
                     #(#disps)*
-                    __p.word(")");
+                    __p.pclose();
                 },
                 quote! { true },
             )
@@ -138,7 +143,7 @@ pub(crate) fn print_attribute(input: Structure<'_>) -> TokenStream {
     input.gen_impl(quote! {
         #[allow(unused)]
         gen impl PrintAttribute for @Self {
-            fn print_something(&self) -> bool { #printed }
+            fn should_render(&self) -> bool { #printed }
             fn print_attribute(&self, __p: &mut rustc_ast_pretty::pp::Printer) { #code }
         }
     })
diff --git a/compiler/rustc_middle/Cargo.toml b/compiler/rustc_middle/Cargo.toml
index aebd2181f31..43c1af642dd 100644
--- a/compiler/rustc_middle/Cargo.toml
+++ b/compiler/rustc_middle/Cargo.toml
@@ -14,7 +14,8 @@ rustc_abi = { path = "../rustc_abi" }
 rustc_apfloat = "0.2.0"
 rustc_arena = { path = "../rustc_arena" }
 rustc_ast = { path = "../rustc_ast" }
-rustc_attr_parsing = { path = "../rustc_attr_parsing" }
+rustc_ast_ir = { path = "../rustc_ast_ir" }
+rustc_attr_data_structures = { path = "../rustc_attr_data_structures" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_error_messages = { path = "../rustc_error_messages" } # Used for intra-doc links
 rustc_errors = { path = "../rustc_errors" }
diff --git a/compiler/rustc_middle/src/hir/map.rs b/compiler/rustc_middle/src/hir/map.rs
index fad8c7dcbcb..c85af81ee25 100644
--- a/compiler/rustc_middle/src/hir/map.rs
+++ b/compiler/rustc_middle/src/hir/map.rs
@@ -1356,7 +1356,7 @@ impl<'hir> Visitor<'hir> for ItemCollector<'hir> {
             self.submodules.push(item.owner_id);
             // A module collector does not recurse inside nested modules.
             if self.crate_collector {
-                intravisit::walk_mod(self, module, item.hir_id());
+                intravisit::walk_mod(self, module);
             }
         } else {
             intravisit::walk_item(self, item)
diff --git a/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs b/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs
index 311bc60c3cd..a94ead161c3 100644
--- a/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs
+++ b/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs
@@ -1,6 +1,6 @@
 use rustc_abi::Align;
 use rustc_ast::expand::autodiff_attrs::AutoDiffAttrs;
-use rustc_attr_parsing::{InlineAttr, InstructionSetAttr, OptimizeAttr};
+use rustc_attr_data_structures::{InlineAttr, InstructionSetAttr, OptimizeAttr};
 use rustc_macros::{HashStable, TyDecodable, TyEncodable};
 use rustc_span::Symbol;
 use rustc_target::spec::SanitizerSet;
diff --git a/compiler/rustc_middle/src/middle/stability.rs b/compiler/rustc_middle/src/middle/stability.rs
index 2260cad41b9..ec128c8c478 100644
--- a/compiler/rustc_middle/src/middle/stability.rs
+++ b/compiler/rustc_middle/src/middle/stability.rs
@@ -4,7 +4,7 @@
 use std::num::NonZero;
 
 use rustc_ast::NodeId;
-use rustc_attr_parsing::{
+use rustc_attr_data_structures::{
     self as attr, ConstStability, DefaultBodyStability, DeprecatedSince, Deprecation, Stability,
 };
 use rustc_data_structures::unord::UnordMap;
diff --git a/compiler/rustc_middle/src/mir/interpret/allocation.rs b/compiler/rustc_middle/src/mir/interpret/allocation.rs
index ba65a711815..b24f6bc7770 100644
--- a/compiler/rustc_middle/src/mir/interpret/allocation.rs
+++ b/compiler/rustc_middle/src/mir/interpret/allocation.rs
@@ -679,6 +679,11 @@ impl<Prov: Provenance, Extra, Bytes: AllocBytes> Allocation<Prov, Extra, Bytes>
         // Set provenance of all bytes to wildcard.
         self.provenance.write_wildcards(self.len());
 
+        // Also expose the provenance of the interpreter-level allocation, so it can
+        // be written by FFI. The `black_box` is defensive programming as LLVM likes
+        // to (incorrectly) optimize away ptr2int casts whose result is unused.
+        std::hint::black_box(self.get_bytes_unchecked_raw_mut().expose_provenance());
+
         Ok(())
     }
 
diff --git a/compiler/rustc_middle/src/mir/interpret/allocation/init_mask.rs b/compiler/rustc_middle/src/mir/interpret/allocation/init_mask.rs
index cc6389e2989..fea5038e6dd 100644
--- a/compiler/rustc_middle/src/mir/interpret/allocation/init_mask.rs
+++ b/compiler/rustc_middle/src/mir/interpret/allocation/init_mask.rs
@@ -223,8 +223,8 @@ impl<D: TyDecoder> Decodable<D> for InitMaskMaterialized {
 // large.
 impl hash::Hash for InitMaskMaterialized {
     fn hash<H: hash::Hasher>(&self, state: &mut H) {
-        const MAX_BLOCKS_TO_HASH: usize = super::MAX_BYTES_TO_HASH / std::mem::size_of::<Block>();
-        const MAX_BLOCKS_LEN: usize = super::MAX_HASHED_BUFFER_LEN / std::mem::size_of::<Block>();
+        const MAX_BLOCKS_TO_HASH: usize = super::MAX_BYTES_TO_HASH / size_of::<Block>();
+        const MAX_BLOCKS_LEN: usize = super::MAX_HASHED_BUFFER_LEN / size_of::<Block>();
 
         // Partially hash the `blocks` buffer when it is large. To limit collisions with common
         // prefixes and suffixes, we hash the length and some slices of the buffer.
diff --git a/compiler/rustc_middle/src/mir/interpret/mod.rs b/compiler/rustc_middle/src/mir/interpret/mod.rs
index c48cfffa05c..2675b7e0fc5 100644
--- a/compiler/rustc_middle/src/mir/interpret/mod.rs
+++ b/compiler/rustc_middle/src/mir/interpret/mod.rs
@@ -573,7 +573,7 @@ pub fn write_target_uint(
 #[inline]
 pub fn read_target_uint(endianness: Endian, mut source: &[u8]) -> Result<u128, io::Error> {
     // This u128 holds an "any-size uint" (since smaller uints can fits in it)
-    let mut buf = [0u8; std::mem::size_of::<u128>()];
+    let mut buf = [0u8; size_of::<u128>()];
     // So we do not read exactly 16 bytes into the u128, just the "payload".
     let uint = match endianness {
         Endian::Little => {
diff --git a/compiler/rustc_middle/src/mir/mod.rs b/compiler/rustc_middle/src/mir/mod.rs
index ea0bb5feb12..83857ab6c5c 100644
--- a/compiler/rustc_middle/src/mir/mod.rs
+++ b/compiler/rustc_middle/src/mir/mod.rs
@@ -332,13 +332,13 @@ pub struct Body<'tcx> {
     ///
     /// ```rust
     /// fn test<T>() {
-    ///     let _ = [0; std::mem::size_of::<*mut T>()];
+    ///     let _ = [0; size_of::<*mut T>()];
     /// }
     /// ```
     ///
     /// **WARNING**: Do not change this flags after the MIR was originally created, even if an optimization
     /// removed the last mention of all generic params. We do not want to rely on optimizations and
-    /// potentially allow things like `[u8; std::mem::size_of::<T>() * 0]` due to this.
+    /// potentially allow things like `[u8; size_of::<T>() * 0]` due to this.
     pub is_polymorphic: bool,
 
     /// The phase at which this MIR should be "injected" into the compilation process.
diff --git a/compiler/rustc_middle/src/mir/mono.rs b/compiler/rustc_middle/src/mir/mono.rs
index 58d5c94d033..897119c0712 100644
--- a/compiler/rustc_middle/src/mir/mono.rs
+++ b/compiler/rustc_middle/src/mir/mono.rs
@@ -2,7 +2,7 @@ use std::fmt;
 use std::hash::Hash;
 
 use rustc_ast::expand::autodiff_attrs::AutoDiffItem;
-use rustc_attr_parsing::InlineAttr;
+use rustc_attr_data_structures::InlineAttr;
 use rustc_data_structures::base_n::{BaseNString, CASE_INSENSITIVE, ToBaseN};
 use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::fx::FxIndexMap;
diff --git a/compiler/rustc_middle/src/mir/terminator.rs b/compiler/rustc_middle/src/mir/terminator.rs
index bc77f22af67..b2c51ad8864 100644
--- a/compiler/rustc_middle/src/mir/terminator.rs
+++ b/compiler/rustc_middle/src/mir/terminator.rs
@@ -454,6 +454,7 @@ mod helper {
         /// Like [`SwitchTargets::target_for_value`], but returning the same type as
         /// [`Terminator::successors`].
         #[inline]
+        #[cfg_attr(not(bootstrap), define_opaque(Successors))]
         pub fn successors_for_value(&self, value: u128) -> Successors<'_> {
             let target = self.target_for_value(value);
             (&[]).into_iter().copied().chain(Some(target))
@@ -462,6 +463,7 @@ mod helper {
 
     impl<'tcx> TerminatorKind<'tcx> {
         #[inline]
+        #[cfg_attr(not(bootstrap), define_opaque(Successors))]
         pub fn successors(&self) -> Successors<'_> {
             use self::TerminatorKind::*;
             match *self {
@@ -500,6 +502,7 @@ mod helper {
         }
 
         #[inline]
+        #[cfg_attr(not(bootstrap), define_opaque(SuccessorsMut))]
         pub fn successors_mut(&mut self) -> SuccessorsMut<'_> {
             use self::TerminatorKind::*;
             match *self {
diff --git a/compiler/rustc_middle/src/query/erase.rs b/compiler/rustc_middle/src/query/erase.rs
index cbd60920bc5..7bbaa0496d5 100644
--- a/compiler/rustc_middle/src/query/erase.rs
+++ b/compiler/rustc_middle/src/query/erase.rs
@@ -24,10 +24,11 @@ pub trait EraseType: Copy {
 pub type Erase<T: EraseType> = Erased<impl Copy>;
 
 #[inline(always)]
+#[cfg_attr(not(bootstrap), define_opaque(Erase))]
 pub fn erase<T: EraseType>(src: T) -> Erase<T> {
     // Ensure the sizes match
     const {
-        if std::mem::size_of::<T>() != std::mem::size_of::<T::Result>() {
+        if size_of::<T>() != size_of::<T::Result>() {
             panic!("size of T must match erased type T::Result")
         }
     };
@@ -47,6 +48,7 @@ pub fn erase<T: EraseType>(src: T) -> Erase<T> {
 
 /// Restores an erased value.
 #[inline(always)]
+#[cfg_attr(not(bootstrap), define_opaque(Erase))]
 pub fn restore<T: EraseType>(value: Erase<T>) -> T {
     let value: Erased<<T as EraseType>::Result> = value;
     // See comment in `erase` for why we use `transmute_unchecked`.
@@ -231,9 +233,9 @@ trivial! {
     bool,
     Option<(rustc_span::def_id::DefId, rustc_session::config::EntryFnType)>,
     Option<rustc_ast::expand::allocator::AllocatorKind>,
-    Option<rustc_attr_parsing::ConstStability>,
-    Option<rustc_attr_parsing::DefaultBodyStability>,
-    Option<rustc_attr_parsing::Stability>,
+    Option<rustc_attr_data_structures::ConstStability>,
+    Option<rustc_attr_data_structures::DefaultBodyStability>,
+    Option<rustc_attr_data_structures::Stability>,
     Option<rustc_data_structures::svh::Svh>,
     Option<rustc_hir::def::DefKind>,
     Option<rustc_hir::CoroutineKind>,
@@ -256,10 +258,10 @@ trivial! {
     Result<rustc_middle::traits::EvaluationResult, rustc_middle::traits::OverflowError>,
     rustc_abi::ReprOptions,
     rustc_ast::expand::allocator::AllocatorKind,
-    rustc_attr_parsing::ConstStability,
-    rustc_attr_parsing::DefaultBodyStability,
-    rustc_attr_parsing::Deprecation,
-    rustc_attr_parsing::Stability,
+    rustc_attr_data_structures::ConstStability,
+    rustc_attr_data_structures::DefaultBodyStability,
+    rustc_attr_data_structures::Deprecation,
+    rustc_attr_data_structures::Stability,
     rustc_data_structures::svh::Svh,
     rustc_errors::ErrorGuaranteed,
     rustc_hir::Constness,
diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs
index 4ad4427594c..c8708857565 100644
--- a/compiler/rustc_middle/src/query/mod.rs
+++ b/compiler/rustc_middle/src/query/mod.rs
@@ -41,7 +41,7 @@ use rustc_span::def_id::LOCAL_CRATE;
 use rustc_span::source_map::Spanned;
 use rustc_span::{DUMMY_SP, Span, Symbol};
 use rustc_target::spec::PanicStrategy;
-use {rustc_abi as abi, rustc_ast as ast, rustc_attr_parsing as attr, rustc_hir as hir};
+use {rustc_abi as abi, rustc_ast as ast, rustc_attr_data_structures as attr, rustc_hir as hir};
 
 use crate::infer::canonical::{self, Canonical};
 use crate::lint::LintExpectation;
@@ -999,12 +999,6 @@ rustc_queries! {
         separate_provide_extern
     }
 
-    query self_ty_of_trait_impl_enabling_order_dep_trait_object_hack(
-        key: DefId
-    ) -> Option<ty::EarlyBinder<'tcx, ty::Ty<'tcx>>> {
-        desc { |tcx| "computing self type wrt issue #33140 `{}`", tcx.def_path_str(key) }
-    }
-
     /// Maps a `DefId` of a type to a list of its inherent impls.
     /// Contains implementations of methods that are inherent to a type.
     /// Methods in these implementations don't need to be exported.
@@ -1533,6 +1527,11 @@ rustc_queries! {
     query is_copy_raw(env: ty::PseudoCanonicalInput<'tcx, Ty<'tcx>>) -> bool {
         desc { "computing whether `{}` is `Copy`", env.value }
     }
+    /// Trait selection queries. These are best used by invoking `ty.is_use_cloned_modulo_regions()`,
+    /// `ty.is_use_cloned()`, etc, since that will prune the environment where possible.
+    query is_use_cloned_raw(env: ty::PseudoCanonicalInput<'tcx, Ty<'tcx>>) -> bool {
+        desc { "computing whether `{}` is `UseCloned`", env.value }
+    }
     /// Query backing `Ty::is_sized`.
     query is_sized_raw(env: ty::PseudoCanonicalInput<'tcx, Ty<'tcx>>) -> bool {
         desc { "computing whether `{}` is `Sized`", env.value }
diff --git a/compiler/rustc_middle/src/query/plumbing.rs b/compiler/rustc_middle/src/query/plumbing.rs
index 66a9e5fed4c..4834444ed1d 100644
--- a/compiler/rustc_middle/src/query/plumbing.rs
+++ b/compiler/rustc_middle/src/query/plumbing.rs
@@ -165,7 +165,7 @@ impl<'tcx> TyCtxt<'tcx> {
     }
 }
 
-#[inline]
+#[inline(always)]
 pub fn query_get_at<'tcx, Cache>(
     tcx: TyCtxt<'tcx>,
     execute_query: fn(TyCtxt<'tcx>, Span, Cache::Key, QueryMode) -> Option<Cache::Value>,
@@ -370,7 +370,7 @@ macro_rules! define_callbacks {
                 // Increase this limit if necessary, but do try to keep the size low if possible
                 #[cfg(target_pointer_width = "64")]
                 const _: () = {
-                    if mem::size_of::<Key<'static>>() > 88 {
+                    if size_of::<Key<'static>>() > 88 {
                         panic!("{}", concat!(
                             "the query `",
                             stringify!($name),
@@ -386,7 +386,7 @@ macro_rules! define_callbacks {
                 #[cfg(target_pointer_width = "64")]
                 #[cfg(not(feature = "rustc_randomized_layouts"))]
                 const _: () = {
-                    if mem::size_of::<Value<'static>>() > 64 {
+                    if size_of::<Value<'static>>() > 64 {
                         panic!("{}", concat!(
                             "the query `",
                             stringify!($name),
diff --git a/compiler/rustc_middle/src/thir.rs b/compiler/rustc_middle/src/thir.rs
index 72f31cec008..f7b98d935d4 100644
--- a/compiler/rustc_middle/src/thir.rs
+++ b/compiler/rustc_middle/src/thir.rs
@@ -315,6 +315,14 @@ pub enum ExprKind<'tcx> {
         /// (e.g. `foo(a, b)` in `x.foo(a, b)`).
         fn_span: Span,
     },
+    /// A use expression `x.use`.
+    ByUse {
+        /// The expression on which use is applied.
+        expr: ExprId,
+        /// The span of use, without the dot and receiver
+        /// (e.g. `use` in `x.use`).
+        span: Span,
+    },
     /// A *non-overloaded* dereference.
     Deref {
         arg: ExprId,
diff --git a/compiler/rustc_middle/src/thir/visit.rs b/compiler/rustc_middle/src/thir/visit.rs
index a9df4d1625b..d208692f4e7 100644
--- a/compiler/rustc_middle/src/thir/visit.rs
+++ b/compiler/rustc_middle/src/thir/visit.rs
@@ -59,6 +59,9 @@ pub fn walk_expr<'thir, 'tcx: 'thir, V: Visitor<'thir, 'tcx>>(
                 visitor.visit_expr(&visitor.thir()[arg]);
             }
         }
+        ByUse { expr, span: _ } => {
+            visitor.visit_expr(&visitor.thir()[expr]);
+        }
         Deref { arg } => visitor.visit_expr(&visitor.thir()[arg]),
         Binary { lhs, rhs, op: _ } | LogicalOp { lhs, rhs, op: _ } => {
             visitor.visit_expr(&visitor.thir()[lhs]);
diff --git a/compiler/rustc_middle/src/ty/adt.rs b/compiler/rustc_middle/src/ty/adt.rs
index 3585f28b4a5..c1dc6a894ca 100644
--- a/compiler/rustc_middle/src/ty/adt.rs
+++ b/compiler/rustc_middle/src/ty/adt.rs
@@ -53,8 +53,6 @@ bitflags::bitflags! {
         const IS_VARIANT_LIST_NON_EXHAUSTIVE = 1 << 8;
         /// Indicates whether the type is `UnsafeCell`.
         const IS_UNSAFE_CELL              = 1 << 9;
-        /// Indicates whether the type is anonymous.
-        const IS_ANONYMOUS                = 1 << 10;
     }
 }
 rustc_data_structures::external_bitflags_debug! { AdtFlags }
@@ -402,12 +400,6 @@ impl<'tcx> AdtDef<'tcx> {
         self.flags().contains(AdtFlags::IS_MANUALLY_DROP)
     }
 
-    /// Returns `true` if this is an anonymous adt
-    #[inline]
-    pub fn is_anonymous(self) -> bool {
-        self.flags().contains(AdtFlags::IS_ANONYMOUS)
-    }
-
     /// Returns `true` if this type has a destructor.
     pub fn has_dtor(self, tcx: TyCtxt<'tcx>) -> bool {
         self.destructor(tcx).is_some()
diff --git a/compiler/rustc_middle/src/ty/closure.rs b/compiler/rustc_middle/src/ty/closure.rs
index 3605f2402e7..5d9b1ddfa38 100644
--- a/compiler/rustc_middle/src/ty/closure.rs
+++ b/compiler/rustc_middle/src/ty/closure.rs
@@ -51,6 +51,9 @@ pub enum UpvarCapture {
     /// depending on inference.
     ByValue,
 
+    /// Upvar is captured by use. This is true when the closure is labeled `use`.
+    ByUse,
+
     /// Upvar is captured by reference.
     ByRef(BorrowKind),
 }
@@ -178,7 +181,7 @@ impl<'tcx> CapturedPlace<'tcx> {
 
     pub fn is_by_ref(&self) -> bool {
         match self.info.capture_kind {
-            ty::UpvarCapture::ByValue => false,
+            ty::UpvarCapture::ByValue | ty::UpvarCapture::ByUse => false,
             ty::UpvarCapture::ByRef(..) => true,
         }
     }
@@ -214,7 +217,7 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn closure_captures(self, def_id: LocalDefId) -> &'tcx [&'tcx ty::CapturedPlace<'tcx>] {
         if !self.is_closure_like(def_id.to_def_id()) {
             return &[];
-        };
+        }
         self.closure_typeinfo(def_id).captures
     }
 }
diff --git a/compiler/rustc_middle/src/ty/consts/int.rs b/compiler/rustc_middle/src/ty/consts/int.rs
index 7c9280fae16..9f5e31d894c 100644
--- a/compiler/rustc_middle/src/ty/consts/int.rs
+++ b/compiler/rustc_middle/src/ty/consts/int.rs
@@ -408,7 +408,7 @@ macro_rules! from_x_for_scalar_int {
                 fn from(u: $ty) -> Self {
                     Self {
                         data: u128::from(u),
-                        size: NonZero::new(std::mem::size_of::<$ty>() as u8).unwrap(),
+                        size: NonZero::new(size_of::<$ty>() as u8).unwrap(),
                     }
                 }
             }
@@ -424,7 +424,7 @@ macro_rules! from_scalar_int_for_x {
                 fn from(int: ScalarInt) -> Self {
                     // The `unwrap` cannot fail because to_bits (if it succeeds)
                     // is guaranteed to return a value that fits into the size.
-                    int.to_bits(Size::from_bytes(std::mem::size_of::<$ty>()))
+                    int.to_bits(Size::from_bytes(size_of::<$ty>()))
                        .try_into().unwrap()
                 }
             }
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index 4013f7b2c85..edba2a2530f 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -1890,7 +1890,7 @@ impl<'tcx> TyCtxtAt<'tcx> {
     pub fn create_def(
         self,
         parent: LocalDefId,
-        name: Symbol,
+        name: Option<Symbol>,
         def_kind: DefKind,
     ) -> TyCtxtFeed<'tcx, LocalDefId> {
         let feed = self.tcx.create_def(parent, name, def_kind);
@@ -1905,7 +1905,7 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn create_def(
         self,
         parent: LocalDefId,
-        name: Symbol,
+        name: Option<Symbol>,
         def_kind: DefKind,
     ) -> TyCtxtFeed<'tcx, LocalDefId> {
         let data = def_kind.def_path_data(name);
diff --git a/compiler/rustc_middle/src/ty/generic_args.rs b/compiler/rustc_middle/src/ty/generic_args.rs
index 27576a2ec4a..f24910477dc 100644
--- a/compiler/rustc_middle/src/ty/generic_args.rs
+++ b/compiler/rustc_middle/src/ty/generic_args.rs
@@ -2,7 +2,6 @@
 
 use core::intrinsics;
 use std::marker::PhantomData;
-use std::mem;
 use std::num::NonZero;
 use std::ptr::NonNull;
 
@@ -176,17 +175,17 @@ impl<'tcx> GenericArgKind<'tcx> {
         let (tag, ptr) = match self {
             GenericArgKind::Lifetime(lt) => {
                 // Ensure we can use the tag bits.
-                assert_eq!(mem::align_of_val(&*lt.0.0) & TAG_MASK, 0);
+                assert_eq!(align_of_val(&*lt.0.0) & TAG_MASK, 0);
                 (REGION_TAG, NonNull::from(lt.0.0).cast())
             }
             GenericArgKind::Type(ty) => {
                 // Ensure we can use the tag bits.
-                assert_eq!(mem::align_of_val(&*ty.0.0) & TAG_MASK, 0);
+                assert_eq!(align_of_val(&*ty.0.0) & TAG_MASK, 0);
                 (TYPE_TAG, NonNull::from(ty.0.0).cast())
             }
             GenericArgKind::Const(ct) => {
                 // Ensure we can use the tag bits.
-                assert_eq!(mem::align_of_val(&*ct.0.0) & TAG_MASK, 0);
+                assert_eq!(align_of_val(&*ct.0.0) & TAG_MASK, 0);
                 (CONST_TAG, NonNull::from(ct.0.0).cast())
             }
         };
diff --git a/compiler/rustc_middle/src/ty/instance.rs b/compiler/rustc_middle/src/ty/instance.rs
index 98ca71b86be..b99148f3368 100644
--- a/compiler/rustc_middle/src/ty/instance.rs
+++ b/compiler/rustc_middle/src/ty/instance.rs
@@ -203,7 +203,7 @@ impl<'tcx> Instance<'tcx> {
         if !tcx.sess.opts.share_generics()
             // However, if the def_id is marked inline(never), then it's fine to just reuse the
             // upstream monomorphization.
-            && tcx.codegen_fn_attrs(self.def_id()).inline != rustc_attr_parsing::InlineAttr::Never
+            && tcx.codegen_fn_attrs(self.def_id()).inline != rustc_attr_data_structures::InlineAttr::Never
         {
             return None;
         }
diff --git a/compiler/rustc_middle/src/ty/layout.rs b/compiler/rustc_middle/src/ty/layout.rs
index 272bb0cc915..ebb6a8c08a5 100644
--- a/compiler/rustc_middle/src/ty/layout.rs
+++ b/compiler/rustc_middle/src/ty/layout.rs
@@ -1,20 +1,17 @@
-use std::num::NonZero;
 use std::ops::Bound;
 use std::{cmp, fmt};
 
 use rustc_abi::{
-    AddressSpace, Align, BackendRepr, ExternAbi, FieldIdx, FieldsShape, HasDataLayout, LayoutData,
-    PointeeInfo, PointerKind, Primitive, ReprOptions, Scalar, Size, TagEncoding, TargetDataLayout,
+    AddressSpace, Align, ExternAbi, FieldIdx, FieldsShape, HasDataLayout, LayoutData, PointeeInfo,
+    PointerKind, Primitive, ReprOptions, Scalar, Size, TagEncoding, TargetDataLayout,
     TyAbiInterface, VariantIdx, Variants,
 };
 use rustc_error_messages::DiagMessage;
 use rustc_errors::{
     Diag, DiagArgValue, DiagCtxtHandle, Diagnostic, EmissionGuarantee, IntoDiagArg, Level,
 };
-use rustc_hashes::Hash64;
 use rustc_hir::LangItem;
 use rustc_hir::def_id::DefId;
-use rustc_index::IndexVec;
 use rustc_macros::{HashStable, TyDecodable, TyEncodable, extension};
 use rustc_session::config::OptLevel;
 use rustc_span::{DUMMY_SP, ErrorGuaranteed, Span, Symbol, sym};
@@ -185,12 +182,7 @@ pub const WIDE_PTR_ADDR: usize = 0;
 /// - For a slice, this is the length.
 pub const WIDE_PTR_EXTRA: usize = 1;
 
-/// The maximum supported number of lanes in a SIMD vector.
-///
-/// This value is selected based on backend support:
-/// * LLVM does not appear to have a vector width limit.
-/// * Cranelift stores the base-2 log of the lane count in a 4 bit integer.
-pub const MAX_SIMD_LANES: u64 = 1 << 0xF;
+pub const MAX_SIMD_LANES: u64 = rustc_abi::MAX_SIMD_LANES;
 
 /// Used in `check_validity_requirement` to indicate the kind of initialization
 /// that is checked to be valid
@@ -762,11 +754,9 @@ where
         variant_index: VariantIdx,
     ) -> TyAndLayout<'tcx> {
         let layout = match this.variants {
-            Variants::Single { index }
-                // If all variants but one are uninhabited, the variant layout is the enum layout.
-                if index == variant_index =>
-            {
-                this.layout
+            // If all variants but one are uninhabited, the variant layout is the enum layout.
+            Variants::Single { index } if index == variant_index => {
+                return this;
             }
 
             Variants::Single { .. } | Variants::Empty => {
@@ -783,29 +773,18 @@ where
                 }
 
                 let fields = match this.ty.kind() {
-                    ty::Adt(def, _) if def.variants().is_empty() =>
-                        bug!("for_variant called on zero-variant enum {}", this.ty),
+                    ty::Adt(def, _) if def.variants().is_empty() => {
+                        bug!("for_variant called on zero-variant enum {}", this.ty)
+                    }
                     ty::Adt(def, _) => def.variant(variant_index).fields.len(),
                     _ => bug!("`ty_and_layout_for_variant` on unexpected type {}", this.ty),
                 };
-                tcx.mk_layout(LayoutData {
-                    variants: Variants::Single { index: variant_index },
-                    fields: match NonZero::new(fields) {
-                        Some(fields) => FieldsShape::Union(fields),
-                        None => FieldsShape::Arbitrary { offsets: IndexVec::new(), memory_index: IndexVec::new() },
-                    },
-                    backend_repr: BackendRepr::Memory { sized: true },
-                    largest_niche: None,
-                    uninhabited: true,
-                    align: tcx.data_layout.i8_align,
-                    size: Size::ZERO,
-                    max_repr_align: None,
-                    unadjusted_abi_align: tcx.data_layout.i8_align.abi,
-                    randomization_seed: Hash64::ZERO,
-                })
+                tcx.mk_layout(LayoutData::uninhabited_variant(cx, variant_index, fields))
             }
 
-            Variants::Multiple { ref variants, .. } => cx.tcx().mk_layout(variants[variant_index].clone()),
+            Variants::Multiple { ref variants, .. } => {
+                cx.tcx().mk_layout(variants[variant_index].clone())
+            }
         };
 
         assert_eq!(*layout.variants(), Variants::Single { index: variant_index });
diff --git a/compiler/rustc_middle/src/ty/list.rs b/compiler/rustc_middle/src/ty/list.rs
index 6718493f6b3..0fd370a5619 100644
--- a/compiler/rustc_middle/src/ty/list.rs
+++ b/compiler/rustc_middle/src/ty/list.rs
@@ -93,7 +93,7 @@ impl<H, T> RawList<H, T> {
         T: Copy,
     {
         assert!(!mem::needs_drop::<T>());
-        assert!(mem::size_of::<T>() != 0);
+        assert!(size_of::<T>() != 0);
         assert!(!slice.is_empty());
 
         let (layout, _offset) =
@@ -155,7 +155,7 @@ macro_rules! impl_list_empty {
                 static EMPTY: ListSkeleton<$header_ty, MaxAlign> =
                     ListSkeleton { header: $header_init, len: 0, data: [] };
 
-                assert!(mem::align_of::<T>() <= mem::align_of::<MaxAlign>());
+                assert!(align_of::<T>() <= align_of::<MaxAlign>());
 
                 // SAFETY: `EMPTY` is sufficiently aligned to be an empty list for all
                 // types with `align_of(T) <= align_of(MaxAlign)`, which we checked above.
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index 527509af05f..97cfe5946af 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -17,7 +17,7 @@ use std::hash::{Hash, Hasher};
 use std::marker::PhantomData;
 use std::num::NonZero;
 use std::ptr::NonNull;
-use std::{fmt, mem, str};
+use std::{fmt, str};
 
 pub use adt::*;
 pub use assoc::*;
@@ -27,7 +27,8 @@ pub use intrinsic::IntrinsicDef;
 use rustc_abi::{Align, FieldIdx, Integer, IntegerType, ReprFlags, ReprOptions, VariantIdx};
 use rustc_ast::expand::StrippedCfgItem;
 use rustc_ast::node_id::NodeMap;
-use rustc_attr_parsing::AttributeKind;
+pub use rustc_ast_ir::{Movability, Mutability, try_visit};
+use rustc_attr_data_structures::AttributeKind;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap, FxIndexSet};
 use rustc_data_structures::intern::Interned;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
@@ -51,7 +52,7 @@ pub use rustc_type_ir::relate::VarianceDiagInfo;
 pub use rustc_type_ir::*;
 use tracing::{debug, instrument};
 pub use vtable::*;
-use {rustc_ast as ast, rustc_attr_parsing as attr, rustc_hir as hir};
+use {rustc_ast as ast, rustc_attr_data_structures as attr, rustc_hir as hir};
 
 pub use self::closure::{
     BorrowKind, CAPTURE_STRUCT_LOCAL, CaptureInfo, CapturedPlace, ClosureTypeInfo,
@@ -637,12 +638,12 @@ impl<'tcx> TermKind<'tcx> {
         let (tag, ptr) = match self {
             TermKind::Ty(ty) => {
                 // Ensure we can use the tag bits.
-                assert_eq!(mem::align_of_val(&*ty.0.0) & TAG_MASK, 0);
+                assert_eq!(align_of_val(&*ty.0.0) & TAG_MASK, 0);
                 (TYPE_TAG, NonNull::from(ty.0.0).cast())
             }
             TermKind::Const(ct) => {
                 // Ensure we can use the tag bits.
-                assert_eq!(mem::align_of_val(&*ct.0.0) & TAG_MASK, 0);
+                assert_eq!(align_of_val(&*ct.0.0) & TAG_MASK, 0);
                 (CONST_TAG, NonNull::from(ct.0.0).cast())
             }
         };
@@ -1150,7 +1151,7 @@ pub struct VariantDef {
     /// `DefId` that identifies the variant's constructor.
     /// If this variant is a struct variant, then this is `None`.
     pub ctor: Option<(CtorKind, DefId)>,
-    /// Variant or struct name, maybe empty for anonymous adt (struct or union).
+    /// Variant or struct name.
     pub name: Symbol,
     /// Discriminant of this variant.
     pub discr: VariantDiscr,
@@ -1414,39 +1415,6 @@ pub enum ImplOverlapKind {
         /// Whether or not the impl is permitted due to the trait being a `#[marker]` trait
         marker: bool,
     },
-    /// These impls are allowed to overlap, but that raises an
-    /// issue #33140 future-compatibility warning (tracked in #56484).
-    ///
-    /// Some background: in Rust 1.0, the trait-object types `Send + Sync` (today's
-    /// `dyn Send + Sync`) and `Sync + Send` (now `dyn Sync + Send`) were different.
-    ///
-    /// The widely-used version 0.1.0 of the crate `traitobject` had accidentally relied on
-    /// that difference, doing what reduces to the following set of impls:
-    ///
-    /// ```compile_fail,(E0119)
-    /// trait Trait {}
-    /// impl Trait for dyn Send + Sync {}
-    /// impl Trait for dyn Sync + Send {}
-    /// ```
-    ///
-    /// Obviously, once we made these types be identical, that code causes a coherence
-    /// error and a fairly big headache for us. However, luckily for us, the trait
-    /// `Trait` used in this case is basically a marker trait, and therefore having
-    /// overlapping impls for it is sound.
-    ///
-    /// To handle this, we basically regard the trait as a marker trait, with an additional
-    /// future-compatibility warning. To avoid accidentally "stabilizing" this feature,
-    /// it has the following restrictions:
-    ///
-    /// 1. The trait must indeed be a marker-like trait (i.e., no items), and must be
-    /// positive impls.
-    /// 2. The trait-ref of both impls must be equal.
-    /// 3. The trait-ref of both impls must be a trait object type consisting only of
-    /// marker traits.
-    /// 4. Neither of the impls can have any where-clauses.
-    ///
-    /// Once `traitobject` 0.1.0 is no longer an active concern, this hack can be removed.
-    FutureCompatOrderDepTraitObjects,
 }
 
 /// Useful source information about where a desugared associated type for an
@@ -1624,7 +1592,7 @@ impl<'tcx> TyCtxt<'tcx> {
         })
     }
 
-    /// Returns `true` if the impls are the same polarity and the trait either
+    /// Returns `Some` if the impls are the same polarity and the trait either
     /// has no items or is annotated `#[marker]` and prevents item overrides.
     #[instrument(level = "debug", skip(self), ret)]
     pub fn impls_are_allowed_to_overlap(
@@ -1665,18 +1633,6 @@ impl<'tcx> TyCtxt<'tcx> {
             return Some(ImplOverlapKind::Permitted { marker: true });
         }
 
-        if let Some(self_ty1) =
-            self.self_ty_of_trait_impl_enabling_order_dep_trait_object_hack(def_id1)
-            && let Some(self_ty2) =
-                self.self_ty_of_trait_impl_enabling_order_dep_trait_object_hack(def_id2)
-        {
-            if self_ty1 == self_ty2 {
-                return Some(ImplOverlapKind::FutureCompatOrderDepTraitObjects);
-            } else {
-                debug!("found {self_ty1:?} != {self_ty2:?}");
-            }
-        }
-
         None
     }
 
@@ -1757,7 +1713,7 @@ impl<'tcx> TyCtxt<'tcx> {
 
     /// Gets all attributes.
     ///
-    /// To see if an item has a specific attribute, you should use [`rustc_attr_parsing::find_attr!`] so you can use matching.
+    /// To see if an item has a specific attribute, you should use [`rustc_attr_data_structures::find_attr!`] so you can use matching.
     pub fn get_all_attrs(
         self,
         did: impl Into<DefId>,
diff --git a/compiler/rustc_middle/src/ty/parameterized.rs b/compiler/rustc_middle/src/ty/parameterized.rs
index 8eaf0a58f70..71fc38cb7ed 100644
--- a/compiler/rustc_middle/src/ty/parameterized.rs
+++ b/compiler/rustc_middle/src/ty/parameterized.rs
@@ -80,10 +80,10 @@ trivially_parameterized_over_tcx! {
     rustc_ast::Attribute,
     rustc_ast::DelimArgs,
     rustc_ast::expand::StrippedCfgItem<rustc_hir::def_id::DefIndex>,
-    rustc_attr_parsing::ConstStability,
-    rustc_attr_parsing::DefaultBodyStability,
-    rustc_attr_parsing::Deprecation,
-    rustc_attr_parsing::Stability,
+    rustc_attr_data_structures::ConstStability,
+    rustc_attr_data_structures::DefaultBodyStability,
+    rustc_attr_data_structures::Deprecation,
+    rustc_attr_data_structures::Stability,
     rustc_hir::Constness,
     rustc_hir::Defaultness,
     rustc_hir::Safety,
diff --git a/compiler/rustc_middle/src/ty/print/pretty.rs b/compiler/rustc_middle/src/ty/print/pretty.rs
index 34d85534d0a..2a3a7705b7b 100644
--- a/compiler/rustc_middle/src/ty/print/pretty.rs
+++ b/compiler/rustc_middle/src/ty/print/pretty.rs
@@ -569,7 +569,7 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
             // the children of the visible parent (as was done when computing
             // `visible_parent_map`), looking for the specific child we currently have and then
             // have access to the re-exported name.
-            DefPathData::TypeNs(ref mut name) if Some(visible_parent) != actual_parent => {
+            DefPathData::TypeNs(Some(ref mut name)) if Some(visible_parent) != actual_parent => {
                 // Item might be re-exported several times, but filter for the one
                 // that's public and whose identifier isn't `_`.
                 let reexport = self
@@ -590,7 +590,7 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
             }
             // Re-exported `extern crate` (#43189).
             DefPathData::CrateRoot => {
-                data = DefPathData::TypeNs(self.tcx().crate_name(def_id.krate));
+                data = DefPathData::TypeNs(Some(self.tcx().crate_name(def_id.krate)));
             }
             _ => {}
         }
diff --git a/compiler/rustc_middle/src/ty/significant_drop_order.rs b/compiler/rustc_middle/src/ty/significant_drop_order.rs
index 7f0d82d89fe..2d9e0331451 100644
--- a/compiler/rustc_middle/src/ty/significant_drop_order.rs
+++ b/compiler/rustc_middle/src/ty/significant_drop_order.rs
@@ -23,9 +23,11 @@ fn true_significant_drop_ty<'tcx>(
 
             match key.disambiguated_data.data {
                 rustc_hir::definitions::DefPathData::CrateRoot => {
-                    name_rev.push(tcx.crate_name(did.krate))
+                    name_rev.push(tcx.crate_name(did.krate));
+                }
+                rustc_hir::definitions::DefPathData::TypeNs(symbol) => {
+                    name_rev.push(symbol.unwrap());
                 }
-                rustc_hir::definitions::DefPathData::TypeNs(symbol) => name_rev.push(symbol),
                 _ => return None,
             }
             if let Some(parent) = key.parent {
diff --git a/compiler/rustc_middle/src/ty/util.rs b/compiler/rustc_middle/src/ty/util.rs
index 237aa66f486..0c68913904f 100644
--- a/compiler/rustc_middle/src/ty/util.rs
+++ b/compiler/rustc_middle/src/ty/util.rs
@@ -192,6 +192,18 @@ impl<'tcx> TyCtxt<'tcx> {
         ty.is_trivially_pure_clone_copy() || self.is_copy_raw(typing_env.as_query_input(ty))
     }
 
+    /// Checks whether `ty: UseCloned` holds while ignoring region constraints.
+    ///
+    /// This function should not be used if there is an `InferCtxt` available.
+    /// Use `InferCtxt::type_is_copy_modulo_regions` instead.
+    pub fn type_is_use_cloned_modulo_regions(
+        self,
+        typing_env: ty::TypingEnv<'tcx>,
+        ty: Ty<'tcx>,
+    ) -> bool {
+        ty.is_trivially_pure_clone_copy() || self.is_use_cloned_raw(typing_env.as_query_input(ty))
+    }
+
     /// Returns the deeply last field of nested structures, or the same type if
     /// not a structure at all. Corresponds to the only possible unsized field,
     /// and its type can be used to determine unsizing strategy.
diff --git a/compiler/rustc_mir_build/src/builder/expr/as_constant.rs b/compiler/rustc_mir_build/src/builder/expr/as_constant.rs
index 84c9297e658..f743ea60a45 100644
--- a/compiler/rustc_mir_build/src/builder/expr/as_constant.rs
+++ b/compiler/rustc_mir_build/src/builder/expr/as_constant.rs
@@ -117,7 +117,12 @@ fn lit_to_mir_constant<'tcx>(tcx: TyCtxt<'tcx>, lit_input: LitToConstInput<'tcx>
         ConstValue::Scalar(Scalar::from_uint(result, width))
     };
 
-    let value = match (lit, ty.kind()) {
+    let lit_ty = match *ty.kind() {
+        ty::Pat(base, _) => base,
+        _ => ty,
+    };
+
+    let value = match (lit, lit_ty.kind()) {
         (ast::LitKind::Str(s, _), ty::Ref(_, inner_ty, _)) if inner_ty.is_str() => {
             let s = s.as_str();
             let allocation = Allocation::from_bytes_byte_aligned_immutable(s.as_bytes());
diff --git a/compiler/rustc_mir_build/src/builder/expr/as_place.rs b/compiler/rustc_mir_build/src/builder/expr/as_place.rs
index 581f45db6c4..50ca924baf9 100644
--- a/compiler/rustc_mir_build/src/builder/expr/as_place.rs
+++ b/compiler/rustc_mir_build/src/builder/expr/as_place.rs
@@ -582,6 +582,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             | ExprKind::Yield { .. }
             | ExprKind::ThreadLocalRef(_)
             | ExprKind::Call { .. }
+            | ExprKind::ByUse { .. }
             | ExprKind::WrapUnsafeBinder { .. } => {
                 // these are not places, so we need to make a temporary.
                 debug_assert!(!matches!(Category::of(&expr.kind), Some(Category::Place)));
diff --git a/compiler/rustc_mir_build/src/builder/expr/as_rvalue.rs b/compiler/rustc_mir_build/src/builder/expr/as_rvalue.rs
index 2c9a1de7f99..97d34b85f50 100644
--- a/compiler/rustc_mir_build/src/builder/expr/as_rvalue.rs
+++ b/compiler/rustc_mir_build/src/builder/expr/as_rvalue.rs
@@ -572,6 +572,14 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 );
                 block.and(Rvalue::Use(operand))
             }
+
+            ExprKind::ByUse { expr, span: _ } => {
+                let operand = unpack!(
+                    block =
+                        this.as_operand(block, scope, expr, LocalInfo::Boring, NeedsTemporary::No)
+                );
+                block.and(Rvalue::Use(operand))
+            }
         }
     }
 
diff --git a/compiler/rustc_mir_build/src/builder/expr/category.rs b/compiler/rustc_mir_build/src/builder/expr/category.rs
index ca55d36bfc6..34524aed406 100644
--- a/compiler/rustc_mir_build/src/builder/expr/category.rs
+++ b/compiler/rustc_mir_build/src/builder/expr/category.rs
@@ -56,6 +56,7 @@ impl Category {
             | ExprKind::RawBorrow { .. }
             | ExprKind::Yield { .. }
             | ExprKind::Call { .. }
+            | ExprKind::ByUse { .. }
             | ExprKind::InlineAsm { .. } => Some(Category::Rvalue(RvalueFunc::Into)),
 
             ExprKind::Array { .. }
diff --git a/compiler/rustc_mir_build/src/builder/expr/into.rs b/compiler/rustc_mir_build/src/builder/expr/into.rs
index 72443e2f60d..333e69475c5 100644
--- a/compiler/rustc_mir_build/src/builder/expr/into.rs
+++ b/compiler/rustc_mir_build/src/builder/expr/into.rs
@@ -4,11 +4,14 @@ use rustc_ast::{AsmMacro, InlineAsmOptions};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_hir as hir;
+use rustc_hir::lang_items::LangItem;
 use rustc_middle::mir::*;
 use rustc_middle::span_bug;
 use rustc_middle::thir::*;
-use rustc_middle::ty::CanonicalUserTypeAnnotation;
+use rustc_middle::ty::{CanonicalUserTypeAnnotation, Ty};
+use rustc_span::DUMMY_SP;
 use rustc_span::source_map::Spanned;
+use rustc_trait_selection::infer::InferCtxtExt;
 use tracing::{debug, instrument};
 
 use crate::builder::expr::category::{Category, RvalueFunc};
@@ -289,6 +292,57 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 this.diverge_from(block);
                 success.unit()
             }
+            ExprKind::ByUse { expr, span } => {
+                let place = unpack!(block = this.as_place(block, expr));
+                let ty = place.ty(&this.local_decls, this.tcx).ty;
+
+                if this.tcx.type_is_copy_modulo_regions(this.infcx.typing_env(this.param_env), ty) {
+                    this.cfg.push_assign(
+                        block,
+                        source_info,
+                        destination,
+                        Rvalue::Use(Operand::Copy(place)),
+                    );
+                    block.unit()
+                } else if this.infcx.type_is_use_cloned_modulo_regions(this.param_env, ty) {
+                    // Convert `expr.use` to a call like `Clone::clone(&expr)`
+                    let success = this.cfg.start_new_block();
+                    let clone_trait = this.tcx.require_lang_item(LangItem::Clone, None);
+                    let clone_fn = this.tcx.associated_item_def_ids(clone_trait)[0];
+                    let func = Operand::function_handle(this.tcx, clone_fn, [ty.into()], expr_span);
+                    let ref_ty = Ty::new_imm_ref(this.tcx, this.tcx.lifetimes.re_erased, ty);
+                    let ref_place = this.temp(ref_ty, span);
+                    this.cfg.push_assign(
+                        block,
+                        source_info,
+                        ref_place,
+                        Rvalue::Ref(this.tcx.lifetimes.re_erased, BorrowKind::Shared, place),
+                    );
+                    this.cfg.terminate(
+                        block,
+                        source_info,
+                        TerminatorKind::Call {
+                            func,
+                            args: [Spanned { node: Operand::Move(ref_place), span: DUMMY_SP }]
+                                .into(),
+                            destination,
+                            target: Some(success),
+                            unwind: UnwindAction::Unreachable,
+                            call_source: CallSource::Misc,
+                            fn_span: expr_span,
+                        },
+                    );
+                    success.unit()
+                } else {
+                    this.cfg.push_assign(
+                        block,
+                        source_info,
+                        destination,
+                        Rvalue::Use(Operand::Move(place)),
+                    );
+                    block.unit()
+                }
+            }
             ExprKind::Use { source } => this.expr_into_dest(destination, block, source),
             ExprKind::Borrow { arg, borrow_kind } => {
                 // We don't do this in `as_rvalue` because we use `as_place`
diff --git a/compiler/rustc_mir_build/src/builder/mod.rs b/compiler/rustc_mir_build/src/builder/mod.rs
index 94955954934..f9fa750e750 100644
--- a/compiler/rustc_mir_build/src/builder/mod.rs
+++ b/compiler/rustc_mir_build/src/builder/mod.rs
@@ -37,7 +37,7 @@ pub(crate) fn closure_saved_names_of_captured_variables<'tcx>(
         .map(|captured_place| {
             let name = captured_place.to_symbol();
             match captured_place.info.capture_kind {
-                ty::UpvarCapture::ByValue => name,
+                ty::UpvarCapture::ByValue | ty::UpvarCapture::ByUse => name,
                 ty::UpvarCapture::ByRef(..) => Symbol::intern(&format!("_ref__{name}")),
             }
         })
@@ -612,7 +612,8 @@ fn construct_error(tcx: TyCtxt<'_>, def_id: LocalDefId, guar: ErrorGuaranteed) -
         | DefKind::AssocConst
         | DefKind::AnonConst
         | DefKind::InlineConst
-        | DefKind::Static { .. } => (vec![], tcx.type_of(def_id).instantiate_identity(), None),
+        | DefKind::Static { .. }
+        | DefKind::GlobalAsm => (vec![], tcx.type_of(def_id).instantiate_identity(), None),
         DefKind::Ctor(..) | DefKind::Fn | DefKind::AssocFn => {
             let sig = tcx.liberate_late_bound_regions(
                 def_id.to_def_id(),
@@ -871,7 +872,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 let mut projs = closure_env_projs.clone();
                 projs.push(ProjectionElem::Field(FieldIdx::new(i), ty));
                 match capture {
-                    ty::UpvarCapture::ByValue => {}
+                    ty::UpvarCapture::ByValue | ty::UpvarCapture::ByUse => {}
                     ty::UpvarCapture::ByRef(..) => {
                         projs.push(ProjectionElem::Deref);
                     }
diff --git a/compiler/rustc_mir_build/src/check_unsafety.rs b/compiler/rustc_mir_build/src/check_unsafety.rs
index c2eafd0a74e..d78c874c766 100644
--- a/compiler/rustc_mir_build/src/check_unsafety.rs
+++ b/compiler/rustc_mir_build/src/check_unsafety.rs
@@ -451,6 +451,7 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for UnsafetyVisitor<'a, 'tcx> {
             | ExprKind::Tuple { .. }
             | ExprKind::Unary { .. }
             | ExprKind::Call { .. }
+            | ExprKind::ByUse { .. }
             | ExprKind::Assign { .. }
             | ExprKind::AssignOp { .. }
             | ExprKind::Break { .. }
diff --git a/compiler/rustc_mir_build/src/thir/cx/expr.rs b/compiler/rustc_mir_build/src/thir/cx/expr.rs
index 7139516702e..e46e8c9871a 100644
--- a/compiler/rustc_mir_build/src/thir/cx/expr.rs
+++ b/compiler/rustc_mir_build/src/thir/cx/expr.rs
@@ -464,6 +464,10 @@ impl<'tcx> ThirBuildCx<'tcx> {
                 }
             }
 
+            hir::ExprKind::Use(expr, span) => {
+                ExprKind::ByUse { expr: self.mirror_expr(expr), span }
+            }
+
             hir::ExprKind::AddrOf(hir::BorrowKind::Ref, mutbl, arg) => {
                 ExprKind::Borrow { borrow_kind: mutbl.to_borrow_kind(), arg: self.mirror_expr(arg) }
             }
@@ -648,7 +652,7 @@ impl<'tcx> ThirBuildCx<'tcx> {
                 }
             },
 
-            hir::ExprKind::Closure { .. } => {
+            hir::ExprKind::Closure(hir::Closure { .. }) => {
                 let closure_ty = self.typeck_results.expr_ty(expr);
                 let (def_id, args, movability) = match *closure_ty.kind() {
                     ty::Closure(def_id, args) => (def_id, UpvarArgs::Closure(args), None),
@@ -1248,6 +1252,17 @@ impl<'tcx> ThirBuildCx<'tcx> {
 
         match upvar_capture {
             ty::UpvarCapture::ByValue => captured_place_expr,
+            ty::UpvarCapture::ByUse => {
+                let span = captured_place_expr.span;
+                let expr_id = self.thir.exprs.push(captured_place_expr);
+
+                Expr {
+                    temp_lifetime: TempLifetime { temp_lifetime, backwards_incompatible },
+                    ty: upvar_ty,
+                    span: closure_expr.span,
+                    kind: ExprKind::ByUse { expr: expr_id, span },
+                }
+            }
             ty::UpvarCapture::ByRef(upvar_borrow) => {
                 let borrow_kind = match upvar_borrow {
                     ty::BorrowKind::Immutable => BorrowKind::Shared,
diff --git a/compiler/rustc_mir_build/src/thir/cx/mod.rs b/compiler/rustc_mir_build/src/thir/cx/mod.rs
index 2e069cae426..3d55c1401b6 100644
--- a/compiler/rustc_mir_build/src/thir/cx/mod.rs
+++ b/compiler/rustc_mir_build/src/thir/cx/mod.rs
@@ -207,7 +207,7 @@ impl<'tcx> ThirBuildCx<'tcx> {
         &self,
         hir_id: HirId,
     ) -> Option<ty::CanonicalUserType<'tcx>> {
-        crate::thir::util::user_args_applied_to_ty_of_hir_id(self.typeck_results, hir_id)
+        crate::thir::util::user_args_applied_to_ty_of_hir_id(self.tcx, self.typeck_results, hir_id)
     }
 }
 
diff --git a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
index 954d0cf97ab..dadd1e85461 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
@@ -345,6 +345,7 @@ impl<'p, 'tcx> MatchVisitor<'p, 'tcx> {
             | Borrow { .. }
             | Box { .. }
             | Call { .. }
+            | ByUse { .. }
             | Closure { .. }
             | ConstBlock { .. }
             | ConstParam { .. }
diff --git a/compiler/rustc_mir_build/src/thir/pattern/mod.rs b/compiler/rustc_mir_build/src/thir/pattern/mod.rs
index 8dc3f998e09..4bfeab44bf4 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/mod.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/mod.rs
@@ -539,7 +539,7 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
         &self,
         hir_id: hir::HirId,
     ) -> Option<ty::CanonicalUserType<'tcx>> {
-        crate::thir::util::user_args_applied_to_ty_of_hir_id(self.typeck_results, hir_id)
+        crate::thir::util::user_args_applied_to_ty_of_hir_id(self.tcx, self.typeck_results, hir_id)
     }
 
     /// Takes a HIR Path. If the path is a constant, evaluates it and feeds
diff --git a/compiler/rustc_mir_build/src/thir/print.rs b/compiler/rustc_mir_build/src/thir/print.rs
index cd56d93afcf..16cef0ec3ac 100644
--- a/compiler/rustc_mir_build/src/thir/print.rs
+++ b/compiler/rustc_mir_build/src/thir/print.rs
@@ -246,6 +246,13 @@ impl<'a, 'tcx> ThirPrinter<'a, 'tcx> {
 
                 print_indented!(self, "}", depth_lvl);
             }
+            ByUse { expr, span } => {
+                print_indented!(self, "ByUse {", depth_lvl);
+                print_indented!(self, "expr:", depth_lvl + 1);
+                self.print_expr(*expr, depth_lvl + 2);
+                print_indented!(self, format!("span: {:?}", span), depth_lvl + 1);
+                print_indented!(self, "}", depth_lvl);
+            }
             Deref { arg } => {
                 print_indented!(self, "Deref {", depth_lvl);
                 self.print_expr(*arg, depth_lvl + 1);
diff --git a/compiler/rustc_mir_build/src/thir/util.rs b/compiler/rustc_mir_build/src/thir/util.rs
index 60a47a94e3a..457957f5fce 100644
--- a/compiler/rustc_mir_build/src/thir/util.rs
+++ b/compiler/rustc_mir_build/src/thir/util.rs
@@ -1,12 +1,16 @@
+use std::assert_matches::assert_matches;
+
 use rustc_hir as hir;
+use rustc_hir::def::DefKind;
 use rustc_middle::bug;
-use rustc_middle::ty::{self, CanonicalUserType};
+use rustc_middle::ty::{self, CanonicalUserType, TyCtxt};
 use tracing::debug;
 
 /// Looks up the type associated with this hir-id and applies the
 /// user-given generic parameters; the hir-id must map to a suitable
 /// type.
 pub(crate) fn user_args_applied_to_ty_of_hir_id<'tcx>(
+    tcx: TyCtxt<'tcx>,
     typeck_results: &ty::TypeckResults<'tcx>,
     hir_id: hir::HirId,
 ) -> Option<CanonicalUserType<'tcx>> {
@@ -16,7 +20,23 @@ pub(crate) fn user_args_applied_to_ty_of_hir_id<'tcx>(
     let ty = typeck_results.node_type(hir_id);
     match ty.kind() {
         ty::Adt(adt_def, ..) => {
+            // This "fixes" user type annotations for tupled ctor patterns for ADTs.
+            // That's because `type_of(ctor_did)` returns a FnDef, but we actually
+            // want to be annotating the type of the ADT itself. It's a bit goofy,
+            // but it's easier to adjust this here rather than in the path lowering
+            // code for patterns in HIR.
             if let ty::UserTypeKind::TypeOf(did, _) = &mut user_ty.value.kind {
+                // This is either already set up correctly (struct, union, enum, or variant),
+                // or needs adjusting (ctor). Make sure we don't start adjusting other
+                // user annotations like consts or fn calls.
+                assert_matches!(
+                    tcx.def_kind(*did),
+                    DefKind::Ctor(..)
+                        | DefKind::Struct
+                        | DefKind::Enum
+                        | DefKind::Union
+                        | DefKind::Variant
+                );
                 *did = adt_def.did();
             }
             Some(user_ty)
diff --git a/compiler/rustc_mir_transform/src/add_call_guards.rs b/compiler/rustc_mir_transform/src/add_call_guards.rs
index 55694cacd92..bc335cee147 100644
--- a/compiler/rustc_mir_transform/src/add_call_guards.rs
+++ b/compiler/rustc_mir_transform/src/add_call_guards.rs
@@ -40,6 +40,16 @@ impl<'tcx> crate::MirPass<'tcx> for AddCallGuards {
         let mut new_blocks = Vec::new();
 
         let cur_len = body.basic_blocks.len();
+        let mut new_block = |source_info: SourceInfo, is_cleanup: bool, target: BasicBlock| {
+            let block = BasicBlockData {
+                statements: vec![],
+                is_cleanup,
+                terminator: Some(Terminator { source_info, kind: TerminatorKind::Goto { target } }),
+            };
+            let idx = cur_len + new_blocks.len();
+            new_blocks.push(block);
+            BasicBlock::new(idx)
+        };
 
         for block in body.basic_blocks_mut() {
             match block.terminator {
@@ -47,25 +57,34 @@ impl<'tcx> crate::MirPass<'tcx> for AddCallGuards {
                     kind: TerminatorKind::Call { target: Some(ref mut destination), unwind, .. },
                     source_info,
                 }) if pred_count[*destination] > 1
-                    && (matches!(
-                        unwind,
-                        UnwindAction::Cleanup(_) | UnwindAction::Terminate(_)
-                    ) || self == &AllCallEdges) =>
+                    && (generates_invoke(unwind) || self == &AllCallEdges) =>
                 {
                     // It's a critical edge, break it
-                    let call_guard = BasicBlockData {
-                        statements: vec![],
-                        is_cleanup: block.is_cleanup,
-                        terminator: Some(Terminator {
-                            source_info,
-                            kind: TerminatorKind::Goto { target: *destination },
-                        }),
-                    };
-
-                    // Get the index it will be when inserted into the MIR
-                    let idx = cur_len + new_blocks.len();
-                    new_blocks.push(call_guard);
-                    *destination = BasicBlock::new(idx);
+                    *destination = new_block(source_info, block.is_cleanup, *destination);
+                }
+                Some(Terminator {
+                    kind:
+                        TerminatorKind::InlineAsm {
+                            asm_macro: InlineAsmMacro::Asm,
+                            ref mut targets,
+                            ref operands,
+                            unwind,
+                            ..
+                        },
+                    source_info,
+                }) if self == &CriticalCallEdges => {
+                    let has_outputs = operands.iter().any(|op| {
+                        matches!(op, InlineAsmOperand::InOut { .. } | InlineAsmOperand::Out { .. })
+                    });
+                    let has_labels =
+                        operands.iter().any(|op| matches!(op, InlineAsmOperand::Label { .. }));
+                    if has_outputs && (has_labels || generates_invoke(unwind)) {
+                        for target in targets.iter_mut() {
+                            if pred_count[*target] > 1 {
+                                *target = new_block(source_info, block.is_cleanup, *target);
+                            }
+                        }
+                    }
                 }
                 _ => {}
             }
@@ -80,3 +99,11 @@ impl<'tcx> crate::MirPass<'tcx> for AddCallGuards {
         true
     }
 }
+
+/// Returns true if this unwind action is code generated as an invoke as opposed to a call.
+fn generates_invoke(unwind: UnwindAction) -> bool {
+    match unwind {
+        UnwindAction::Continue | UnwindAction::Unreachable => false,
+        UnwindAction::Cleanup(_) | UnwindAction::Terminate(_) => true,
+    }
+}
diff --git a/compiler/rustc_mir_transform/src/coroutine/by_move_body.rs b/compiler/rustc_mir_transform/src/coroutine/by_move_body.rs
index 0f5fcb0d8eb..9cd7045a0a2 100644
--- a/compiler/rustc_mir_transform/src/coroutine/by_move_body.rs
+++ b/compiler/rustc_mir_transform/src/coroutine/by_move_body.rs
@@ -78,7 +78,6 @@ use rustc_middle::hir::place::{Projection, ProjectionKind};
 use rustc_middle::mir::visit::MutVisitor;
 use rustc_middle::mir::{self, dump_mir};
 use rustc_middle::ty::{self, InstanceKind, Ty, TyCtxt, TypeVisitableExt};
-use rustc_span::kw;
 
 pub(crate) fn coroutine_by_move_body_def_id<'tcx>(
     tcx: TyCtxt<'tcx>,
@@ -170,7 +169,7 @@ pub(crate) fn coroutine_by_move_body_def_id<'tcx>(
             // this when building the field projection in the MIR body later on.
             let mut parent_capture_ty = parent_capture.place.ty();
             parent_capture_ty = match parent_capture.info.capture_kind {
-                ty::UpvarCapture::ByValue => parent_capture_ty,
+                ty::UpvarCapture::ByValue | ty::UpvarCapture::ByUse => parent_capture_ty,
                 ty::UpvarCapture::ByRef(kind) => Ty::new_ref(
                     tcx,
                     tcx.lifetimes.re_erased,
@@ -214,7 +213,7 @@ pub(crate) fn coroutine_by_move_body_def_id<'tcx>(
     MakeByMoveBody { tcx, field_remapping, by_move_coroutine_ty }.visit_body(&mut by_move_body);
 
     // This will always be `{closure#1}`, since the original coroutine is `{closure#0}`.
-    let body_def = tcx.create_def(parent_def_id, kw::Empty, DefKind::SyntheticCoroutineBody);
+    let body_def = tcx.create_def(parent_def_id, None, DefKind::SyntheticCoroutineBody);
     by_move_body.source =
         mir::MirSource::from_instance(InstanceKind::Item(body_def.def_id().to_def_id()));
     dump_mir(tcx, false, "built", &"after", &by_move_body, |_, _| Ok(()));
diff --git a/compiler/rustc_mir_transform/src/lib.rs b/compiler/rustc_mir_transform/src/lib.rs
index 5df12ac4d8b..8aa14d15644 100644
--- a/compiler/rustc_mir_transform/src/lib.rs
+++ b/compiler/rustc_mir_transform/src/lib.rs
@@ -316,6 +316,10 @@ fn mir_keys(tcx: TyCtxt<'_>, (): ()) -> FxIndexSet<LocalDefId> {
     // All body-owners have MIR associated with them.
     let mut set: FxIndexSet<_> = tcx.hir_body_owners().collect();
 
+    // Remove the fake bodies for `global_asm!`, since they're not useful
+    // to be emitted (`--emit=mir`) or encoded (in metadata).
+    set.retain(|&def_id| !matches!(tcx.def_kind(def_id), DefKind::GlobalAsm));
+
     // Coroutine-closures (e.g. async closures) have an additional by-move MIR
     // body that isn't in the HIR.
     for body_owner in tcx.hir_body_owners() {
diff --git a/compiler/rustc_parse/messages.ftl b/compiler/rustc_parse/messages.ftl
index 1d5b5942170..6d4308cda1a 100644
--- a/compiler/rustc_parse/messages.ftl
+++ b/compiler/rustc_parse/messages.ftl
@@ -26,6 +26,11 @@ parse_async_move_block_in_2015 = `async move` blocks are only allowed in Rust 20
 parse_async_move_order_incorrect = the order of `move` and `async` is incorrect
     .suggestion = try switching the order
 
+parse_async_use_block_in_2015 = `async use` blocks are only allowed in Rust 2018 or later
+
+parse_async_use_order_incorrect = the order of `use` and `async` is incorrect
+    .suggestion = try switching the order
+
 parse_at_dot_dot_in_struct_pattern = `@ ..` is not supported in struct patterns
     .suggestion = bind to each field separately or, if you don't need them, just remove `{$ident} @`
 
@@ -348,6 +353,9 @@ parse_incorrect_use_of_await = incorrect use of `await`
 
 parse_incorrect_use_of_await_postfix_suggestion = `await` is a postfix operation
 
+parse_incorrect_use_of_use = incorrect use of `use`
+    .parentheses_suggestion = `use` is not a method call, try removing the parentheses
+
 parse_incorrect_visibility_restriction = incorrect visibility restriction
     .help = some possible visibility restrictions are:
             `pub(crate)`: visible only on the current crate
diff --git a/compiler/rustc_parse/src/errors.rs b/compiler/rustc_parse/src/errors.rs
index 8d2fd595942..e090d9cf760 100644
--- a/compiler/rustc_parse/src/errors.rs
+++ b/compiler/rustc_parse/src/errors.rs
@@ -106,6 +106,19 @@ pub(crate) struct IncorrectUseOfAwait {
     pub span: Span,
 }
 
+#[derive(Diagnostic)]
+#[diag(parse_incorrect_use_of_use)]
+pub(crate) struct IncorrectUseOfUse {
+    #[primary_span]
+    #[suggestion(
+        parse_parentheses_suggestion,
+        style = "verbose",
+        code = "",
+        applicability = "machine-applicable"
+    )]
+    pub span: Span,
+}
+
 #[derive(Subdiagnostic)]
 #[multipart_suggestion(
     parse_incorrect_use_of_await_postfix_suggestion,
@@ -1500,6 +1513,14 @@ pub(crate) struct AsyncMoveOrderIncorrect {
 }
 
 #[derive(Diagnostic)]
+#[diag(parse_async_use_order_incorrect)]
+pub(crate) struct AsyncUseOrderIncorrect {
+    #[primary_span]
+    #[suggestion(style = "verbose", code = "async use", applicability = "maybe-incorrect")]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
 #[diag(parse_double_colon_in_bound)]
 pub(crate) struct DoubleColonInBound {
     #[primary_span]
@@ -1668,6 +1689,13 @@ pub(crate) struct AsyncMoveBlockIn2015 {
 }
 
 #[derive(Diagnostic)]
+#[diag(parse_async_use_block_in_2015)]
+pub(crate) struct AsyncUseBlockIn2015 {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
 #[diag(parse_async_bound_modifier_in_2015)]
 pub(crate) struct AsyncBoundModifierIn2015 {
     #[primary_span]
diff --git a/compiler/rustc_parse/src/parser/diagnostics.rs b/compiler/rustc_parse/src/parser/diagnostics.rs
index 94db43bb59f..716ababb008 100644
--- a/compiler/rustc_parse/src/parser/diagnostics.rs
+++ b/compiler/rustc_parse/src/parser/diagnostics.rs
@@ -31,15 +31,15 @@ use super::{
     SeqSep, TokenType,
 };
 use crate::errors::{
-    AddParen, AmbiguousPlus, AsyncMoveBlockIn2015, AttributeOnParamType, AwaitSuggestion,
-    BadQPathStage2, BadTypePlus, BadTypePlusSub, ColonAsSemi, ComparisonOperatorsCannotBeChained,
-    ComparisonOperatorsCannotBeChainedSugg, ConstGenericWithoutBraces,
-    ConstGenericWithoutBracesSugg, DocCommentDoesNotDocumentAnything, DocCommentOnParamType,
-    DoubleColonInBound, ExpectedIdentifier, ExpectedSemi, ExpectedSemiSugg,
+    AddParen, AmbiguousPlus, AsyncMoveBlockIn2015, AsyncUseBlockIn2015, AttributeOnParamType,
+    AwaitSuggestion, BadQPathStage2, BadTypePlus, BadTypePlusSub, ColonAsSemi,
+    ComparisonOperatorsCannotBeChained, ComparisonOperatorsCannotBeChainedSugg,
+    ConstGenericWithoutBraces, ConstGenericWithoutBracesSugg, DocCommentDoesNotDocumentAnything,
+    DocCommentOnParamType, DoubleColonInBound, ExpectedIdentifier, ExpectedSemi, ExpectedSemiSugg,
     GenericParamsWithoutAngleBrackets, GenericParamsWithoutAngleBracketsSugg,
     HelpIdentifierStartsWithNumber, HelpUseLatestEdition, InInTypo, IncorrectAwait,
-    IncorrectSemicolon, IncorrectUseOfAwait, PatternMethodParamWithoutBody, QuestionMarkInType,
-    QuestionMarkInTypeSugg, SelfParamNotFirst, StructLiteralBodyWithoutPath,
+    IncorrectSemicolon, IncorrectUseOfAwait, IncorrectUseOfUse, PatternMethodParamWithoutBody,
+    QuestionMarkInType, QuestionMarkInTypeSugg, SelfParamNotFirst, StructLiteralBodyWithoutPath,
     StructLiteralBodyWithoutPathSugg, StructLiteralNeedingParens, StructLiteralNeedingParensSugg,
     SuggAddMissingLetStmt, SuggEscapeIdentifier, SuggRemoveComma, TernaryOperator,
     UnexpectedConstInGenericParam, UnexpectedConstParamDeclaration,
@@ -572,10 +572,17 @@ impl<'a> Parser<'a> {
             return Err(self.dcx().create_err(UseEqInstead { span: self.token.span }));
         }
 
-        if self.token.is_keyword(kw::Move) && self.prev_token.is_keyword(kw::Async) {
-            // The 2015 edition is in use because parsing of `async move` has failed.
+        if (self.token.is_keyword(kw::Move) || self.token.is_keyword(kw::Use))
+            && self.prev_token.is_keyword(kw::Async)
+        {
+            // The 2015 edition is in use because parsing of `async move` or `async use` has failed.
             let span = self.prev_token.span.to(self.token.span);
-            return Err(self.dcx().create_err(AsyncMoveBlockIn2015 { span }));
+            if self.token.is_keyword(kw::Move) {
+                return Err(self.dcx().create_err(AsyncMoveBlockIn2015 { span }));
+            } else {
+                // kw::Use
+                return Err(self.dcx().create_err(AsyncUseBlockIn2015 { span }));
+            }
         }
 
         let expect = tokens_to_string(&expected);
@@ -1991,7 +1998,7 @@ impl<'a> Parser<'a> {
             self.parse_expr()
         }
         .map_err(|mut err| {
-            err.span_label(await_sp, "while parsing this incorrect await expression");
+            err.span_label(await_sp, format!("while parsing this incorrect await expression"));
             err
         })?;
         Ok((expr.span, expr, is_question))
@@ -2030,6 +2037,21 @@ impl<'a> Parser<'a> {
             self.dcx().emit_err(IncorrectUseOfAwait { span });
         }
     }
+    ///
+    /// If encountering `x.use()`, consumes and emits an error.
+    pub(super) fn recover_from_use(&mut self) {
+        if self.token == token::OpenDelim(Delimiter::Parenthesis)
+            && self.look_ahead(1, |t| t == &token::CloseDelim(Delimiter::Parenthesis))
+        {
+            // var.use()
+            let lo = self.token.span;
+            self.bump(); // (
+            let span = lo.to(self.token.span);
+            self.bump(); // )
+
+            self.dcx().emit_err(IncorrectUseOfUse { span });
+        }
+    }
 
     pub(super) fn try_macro_suggestion(&mut self) -> PResult<'a, P<Expr>> {
         let is_try = self.token.is_keyword(kw::Try);
@@ -2085,7 +2107,7 @@ impl<'a> Parser<'a> {
                     ast::GenericBound::Trait(poly) => Some(poly),
                     _ => None,
                 })
-                .last()
+                .next_back()
         {
             err.span_suggestion_verbose(
                 poly.span.shrink_to_hi(),
diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index 0a08c6faeb4..b37dd64fbed 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -778,6 +778,7 @@ impl<'a> Parser<'a> {
                     ExprKind::MethodCall(_) => "a method call",
                     ExprKind::Call(_, _) => "a function call",
                     ExprKind::Await(_, _) => "`.await`",
+                    ExprKind::Use(_, _) => "`.use`",
                     ExprKind::Match(_, _, MatchKind::Postfix) => "a postfix match",
                     ExprKind::Err(_) => return Ok(with_postfix),
                     _ => unreachable!("parse_dot_or_call_expr_with_ shouldn't produce this"),
@@ -1296,6 +1297,12 @@ impl<'a> Parser<'a> {
             return Ok(self.mk_await_expr(self_arg, lo));
         }
 
+        if self.eat_keyword(exp!(Use)) {
+            let use_span = self.prev_token.span;
+            self.psess.gated_spans.gate(sym::ergonomic_clones, use_span);
+            return Ok(self.mk_use_expr(self_arg, lo));
+        }
+
         // Post-fix match
         if self.eat_keyword(exp!(Match)) {
             let match_span = self.prev_token.span;
@@ -1397,6 +1404,7 @@ impl<'a> Parser<'a> {
             } else if this.check_path() {
                 this.parse_expr_path_start()
             } else if this.check_keyword(exp!(Move))
+                || this.check_keyword(exp!(Use))
                 || this.check_keyword(exp!(Static))
                 || this.check_const_closure()
             {
@@ -2388,7 +2396,7 @@ impl<'a> Parser<'a> {
         Ok(closure)
     }
 
-    /// Parses an optional `move` prefix to a closure-like construct.
+    /// Parses an optional `move` or `use` prefix to a closure-like construct.
     fn parse_capture_clause(&mut self) -> PResult<'a, CaptureBy> {
         if self.eat_keyword(exp!(Move)) {
             let move_kw_span = self.prev_token.span;
@@ -2401,6 +2409,16 @@ impl<'a> Parser<'a> {
             } else {
                 Ok(CaptureBy::Value { move_kw: move_kw_span })
             }
+        } else if self.eat_keyword(exp!(Use)) {
+            let use_kw_span = self.prev_token.span;
+            self.psess.gated_spans.gate(sym::ergonomic_clones, use_kw_span);
+            // Check for `use async` and recover
+            if self.check_keyword(exp!(Async)) {
+                let use_async_span = self.token.span.with_lo(self.prev_token.span.data().lo);
+                Err(self.dcx().create_err(errors::AsyncUseOrderIncorrect { span: use_async_span }))
+            } else {
+                Ok(CaptureBy::Use { use_kw: use_kw_span })
+            }
         } else {
             Ok(CaptureBy::Ref)
         }
@@ -3415,7 +3433,7 @@ impl<'a> Parser<'a> {
         self.is_keyword_ahead(lookahead, &[kw])
             && ((
                 // `async move {`
-                self.is_keyword_ahead(lookahead + 1, &[kw::Move])
+                self.is_keyword_ahead(lookahead + 1, &[kw::Move, kw::Use])
                     && self.look_ahead(lookahead + 2, |t| {
                         *t == token::OpenDelim(Delimiter::Brace) || t.is_whole_block()
                     })
@@ -3818,6 +3836,13 @@ impl<'a> Parser<'a> {
         await_expr
     }
 
+    fn mk_use_expr(&mut self, self_arg: P<Expr>, lo: Span) -> P<Expr> {
+        let span = lo.to(self.prev_token.span);
+        let use_expr = self.mk_expr(span, ExprKind::Use(self_arg, self.prev_token.span));
+        self.recover_from_use();
+        use_expr
+    }
+
     pub(crate) fn mk_expr_with_attrs(&self, span: Span, kind: ExprKind, attrs: AttrVec) -> P<Expr> {
         P(Expr { kind, span, attrs, id: DUMMY_NODE_ID, tokens: None })
     }
@@ -3966,6 +3991,7 @@ impl MutVisitor for CondChecker<'_> {
             }
             ExprKind::Unary(_, _)
             | ExprKind::Await(_, _)
+            | ExprKind::Use(_, _)
             | ExprKind::AssignOp(_, _, _)
             | ExprKind::Range(_, _, _)
             | ExprKind::Try(_)
diff --git a/compiler/rustc_parse/src/parser/item.rs b/compiler/rustc_parse/src/parser/item.rs
index c3b1956ad2e..9e6cdfe59bb 100644
--- a/compiler/rustc_parse/src/parser/item.rs
+++ b/compiler/rustc_parse/src/parser/item.rs
@@ -209,7 +209,7 @@ impl<'a> Parser<'a> {
         let check_pub = def == &Defaultness::Final;
         let mut def_ = || mem::replace(def, Defaultness::Final);
 
-        let info = if self.eat_keyword_case(exp!(Use), case) {
+        let info = if !self.is_use_closure() && self.eat_keyword_case(exp!(Use), case) {
             self.parse_use_item()?
         } else if self.check_fn_front_matter(check_pub, case) {
             // FUNCTION ITEM
@@ -217,7 +217,14 @@ impl<'a> Parser<'a> {
                 self.parse_fn(attrs, fn_parse_mode, lo, vis, case)?;
             (
                 ident,
-                ItemKind::Fn(Box::new(Fn { defaultness: def_(), sig, generics, contract, body })),
+                ItemKind::Fn(Box::new(Fn {
+                    defaultness: def_(),
+                    sig,
+                    generics,
+                    contract,
+                    body,
+                    define_opaque: None,
+                })),
             )
         } else if self.eat_keyword(exp!(Extern)) {
             if self.eat_keyword(exp!(Crate)) {
@@ -639,7 +646,7 @@ impl<'a> Parser<'a> {
 
         let impl_items = self.parse_item_list(attrs, |p| p.parse_impl_item(ForceCollect::No))?;
 
-        let item_kind = match ty_second {
+        let (of_trait, self_ty) = match ty_second {
             Some(ty_second) => {
                 // impl Trait for Type
                 if !has_for {
@@ -672,31 +679,20 @@ impl<'a> Parser<'a> {
                 };
                 let trait_ref = TraitRef { path, ref_id: ty_first.id };
 
-                ItemKind::Impl(Box::new(Impl {
-                    safety,
-                    polarity,
-                    defaultness,
-                    constness,
-                    generics,
-                    of_trait: Some(trait_ref),
-                    self_ty: ty_second,
-                    items: impl_items,
-                }))
-            }
-            None => {
-                // impl Type
-                ItemKind::Impl(Box::new(Impl {
-                    safety,
-                    polarity,
-                    defaultness,
-                    constness,
-                    generics,
-                    of_trait: None,
-                    self_ty: ty_first,
-                    items: impl_items,
-                }))
+                (Some(trait_ref), ty_second)
             }
+            None => (None, ty_first), // impl Type
         };
+        let item_kind = ItemKind::Impl(Box::new(Impl {
+            safety,
+            polarity,
+            defaultness,
+            constness,
+            generics,
+            of_trait,
+            self_ty,
+            items: impl_items,
+        }));
 
         Ok((Ident::empty(), item_kind))
     }
@@ -1277,6 +1273,21 @@ impl<'a> Parser<'a> {
         None
     }
 
+    fn is_use_closure(&self) -> bool {
+        if self.token.is_keyword(kw::Use) {
+            // Check if this could be a closure.
+            self.look_ahead(1, |token| {
+                // Move or Async here would be an error but still we're parsing a closure
+                let dist =
+                    if token.is_keyword(kw::Move) || token.is_keyword(kw::Async) { 2 } else { 1 };
+
+                self.look_ahead(dist, |token| matches!(token.kind, token::Or | token::OrOr))
+            })
+        } else {
+            false
+        }
+    }
+
     fn is_unsafe_foreign_mod(&self) -> bool {
         self.token.is_keyword(kw::Unsafe)
             && self.is_keyword_ahead(1, &[kw::Extern])
@@ -1290,7 +1301,7 @@ impl<'a> Parser<'a> {
         if self.check_keyword(exp!(Static)) {
             // Check if this could be a closure.
             !self.look_ahead(1, |token| {
-                if token.is_keyword(kw::Move) {
+                if token.is_keyword(kw::Move) || token.is_keyword(kw::Use) {
                     return true;
                 }
                 matches!(token.kind, token::Or | token::OrOr)
diff --git a/compiler/rustc_parse/src/parser/mod.rs b/compiler/rustc_parse/src/parser/mod.rs
index 7dabc28c645..4ec8d9e5e49 100644
--- a/compiler/rustc_parse/src/parser/mod.rs
+++ b/compiler/rustc_parse/src/parser/mod.rs
@@ -813,9 +813,9 @@ impl<'a> Parser<'a> {
         self.is_keyword_ahead(0, &[kw::Const])
             && self.look_ahead(1, |t| match &t.kind {
                 // async closures do not work with const closures, so we do not parse that here.
-                token::Ident(kw::Move | kw::Static, IdentIsRaw::No) | token::OrOr | token::Or => {
-                    true
-                }
+                token::Ident(kw::Move | kw::Use | kw::Static, IdentIsRaw::No)
+                | token::OrOr
+                | token::Or => true,
                 _ => false,
             })
     }
diff --git a/compiler/rustc_parse/src/parser/token_type.rs b/compiler/rustc_parse/src/parser/token_type.rs
index 110546d0ba6..886438fd583 100644
--- a/compiler/rustc_parse/src/parser/token_type.rs
+++ b/compiler/rustc_parse/src/parser/token_type.rs
@@ -619,7 +619,7 @@ impl Iterator for TokenTypeSetIter {
     type Item = TokenType;
 
     fn next(&mut self) -> Option<TokenType> {
-        let num_bits: u32 = (std::mem::size_of_val(&self.0.0) * 8) as u32;
+        let num_bits: u32 = (size_of_val(&self.0.0) * 8) as u32;
         assert_eq!(num_bits, 128);
         let z = self.0.0.trailing_zeros();
         if z == num_bits {
diff --git a/compiler/rustc_parse_format/src/lib.rs b/compiler/rustc_parse_format/src/lib.rs
index 3b985621b57..e05cc6d29d8 100644
--- a/compiler/rustc_parse_format/src/lib.rs
+++ b/compiler/rustc_parse_format/src/lib.rs
@@ -190,7 +190,7 @@ pub enum DebugHex {
 #[derive(Copy, Clone, Debug, PartialEq)]
 pub enum Count<'a> {
     /// The count is specified explicitly.
-    CountIs(usize),
+    CountIs(u16),
     /// The count is specified by the argument with the given name.
     CountIsName(&'a str, InnerSpan),
     /// The count is specified by the argument at the given index.
@@ -565,7 +565,7 @@ impl<'a> Parser<'a> {
     /// consuming a macro argument, `None` if it's the case.
     fn position(&mut self) -> Option<Position<'a>> {
         if let Some(i) = self.integer() {
-            Some(ArgumentIs(i))
+            Some(ArgumentIs(i.into()))
         } else {
             match self.cur.peek() {
                 Some(&(lo, c)) if rustc_lexer::is_id_start(c) => {
@@ -771,7 +771,7 @@ impl<'a> Parser<'a> {
     /// width.
     fn count(&mut self, start: usize) -> Count<'a> {
         if let Some(i) = self.integer() {
-            if self.consume('$') { CountIsParam(i) } else { CountIs(i) }
+            if self.consume('$') { CountIsParam(i.into()) } else { CountIs(i) }
         } else {
             let tmp = self.cur.clone();
             let word = self.word();
@@ -822,15 +822,15 @@ impl<'a> Parser<'a> {
         word
     }
 
-    fn integer(&mut self) -> Option<usize> {
-        let mut cur: usize = 0;
+    fn integer(&mut self) -> Option<u16> {
+        let mut cur: u16 = 0;
         let mut found = false;
         let mut overflow = false;
         let start = self.current_pos();
         while let Some(&(_, c)) = self.cur.peek() {
             if let Some(i) = c.to_digit(10) {
                 let (tmp, mul_overflow) = cur.overflowing_mul(10);
-                let (tmp, add_overflow) = tmp.overflowing_add(i as usize);
+                let (tmp, add_overflow) = tmp.overflowing_add(i as u16);
                 if mul_overflow || add_overflow {
                     overflow = true;
                 }
@@ -847,11 +847,11 @@ impl<'a> Parser<'a> {
             let overflowed_int = &self.input[start..end];
             self.err(
                 format!(
-                    "integer `{}` does not fit into the type `usize` whose range is `0..={}`",
+                    "integer `{}` does not fit into the type `u16` whose range is `0..={}`",
                     overflowed_int,
-                    usize::MAX
+                    u16::MAX
                 ),
-                "integer out of range for `usize`",
+                "integer out of range for `u16`",
                 self.span(start, end),
             );
         }
diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs
index 91916b8f5fc..c6ae2c0fb9b 100644
--- a/compiler/rustc_passes/src/check_attr.rs
+++ b/compiler/rustc_passes/src/check_attr.rs
@@ -1998,7 +1998,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                     // catch `repr()` with no arguments, applied to an item (i.e. not `#![repr()]`)
                     if item.is_some() {
                         match target {
-                            Target::Struct | Target::Union | Target::Enum => {}
+                            Target::Struct | Target::Union | Target::Enum => continue,
                             Target::Fn | Target::Method(_) => {
                                 feature_err(
                                     &self.tcx.sess,
diff --git a/compiler/rustc_passes/src/input_stats.rs b/compiler/rustc_passes/src/input_stats.rs
index 92ea49f18e5..1278e98afcf 100644
--- a/compiler/rustc_passes/src/input_stats.rs
+++ b/compiler/rustc_passes/src/input_stats.rs
@@ -107,12 +107,12 @@ impl<'k> StatCollector<'k> {
 
         let node = self.nodes.entry(label1).or_insert(Node::new());
         node.stats.count += 1;
-        node.stats.size = std::mem::size_of_val(val);
+        node.stats.size = size_of_val(val);
 
         if let Some(label2) = label2 {
             let subnode = node.subnodes.entry(label2).or_insert(NodeStats::new());
             subnode.count += 1;
-            subnode.size = std::mem::size_of_val(val);
+            subnode.size = size_of_val(val);
         }
     }
 
@@ -255,9 +255,9 @@ impl<'v> hir_visit::Visitor<'v> for StatCollector<'v> {
         hir_visit::walk_body(self, b);
     }
 
-    fn visit_mod(&mut self, m: &'v hir::Mod<'v>, _s: Span, n: HirId) {
+    fn visit_mod(&mut self, m: &'v hir::Mod<'v>, _s: Span, _n: HirId) {
         self.record("Mod", None, m);
-        hir_visit::walk_mod(self, m, n)
+        hir_visit::walk_mod(self, m)
     }
 
     fn visit_foreign_item(&mut self, i: &'v hir::ForeignItem<'v>) {
@@ -328,6 +328,7 @@ impl<'v> hir_visit::Visitor<'v> for StatCollector<'v> {
                 Array,
                 Call,
                 MethodCall,
+                Use,
                 Tup,
                 Binary,
                 Unary,
@@ -626,7 +627,7 @@ impl<'v> ast_visit::Visitor<'v> for StatCollector<'v> {
             (self, e, e.kind, None, ast, Expr, ExprKind),
             [
                 Array, ConstBlock, Call, MethodCall, Tup, Binary, Unary, Lit, Cast, Type, Let,
-                If, While, ForLoop, Loop, Match, Closure, Block, Await, TryBlock, Assign,
+                If, While, ForLoop, Loop, Match, Closure, Block, Await, Use, TryBlock, Assign,
                 AssignOp, Field, Index, Range, Underscore, Path, AddrOf, Break, Continue, Ret,
                 InlineAsm, FormatArgs, OffsetOf, MacCall, Struct, Repeat, Paren, Try, Yield, Yeet,
                 Become, IncludedBytes, Gen, UnsafeBinderCast, Err, Dummy
diff --git a/compiler/rustc_passes/src/liveness.rs b/compiler/rustc_passes/src/liveness.rs
index 24dc018c661..822804893fe 100644
--- a/compiler/rustc_passes/src/liveness.rs
+++ b/compiler/rustc_passes/src/liveness.rs
@@ -426,6 +426,7 @@ impl<'tcx> Visitor<'tcx> for IrMaps<'tcx> {
             | hir::ExprKind::Array(..)
             | hir::ExprKind::Call(..)
             | hir::ExprKind::MethodCall(..)
+            | hir::ExprKind::Use(..)
             | hir::ExprKind::Tup(..)
             | hir::ExprKind::Binary(..)
             | hir::ExprKind::AddrOf(..)
@@ -705,7 +706,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
                             );
                             self.acc(self.exit_ln, var, ACC_READ | ACC_USE);
                         }
-                        ty::UpvarCapture::ByValue => {}
+                        ty::UpvarCapture::ByValue | ty::UpvarCapture::ByUse => {}
                     }
                 }
             }
@@ -1031,6 +1032,11 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
                 self.propagate_through_expr(receiver, succ)
             }
 
+            hir::ExprKind::Use(expr, _) => {
+                let succ = self.check_is_ty_uninhabited(expr, succ);
+                self.propagate_through_expr(expr, succ)
+            }
+
             hir::ExprKind::Tup(exprs) => self.propagate_through_exprs(exprs, succ),
 
             hir::ExprKind::Binary(op, ref l, ref r) if op.node.is_lazy() => {
@@ -1418,6 +1424,7 @@ fn check_expr<'tcx>(this: &mut Liveness<'_, 'tcx>, expr: &'tcx Expr<'tcx>) {
         // no correctness conditions related to liveness
         hir::ExprKind::Call(..)
         | hir::ExprKind::MethodCall(..)
+        | hir::ExprKind::Use(..)
         | hir::ExprKind::Match(..)
         | hir::ExprKind::Loop(..)
         | hir::ExprKind::Index(..)
@@ -1493,7 +1500,7 @@ impl<'tcx> Liveness<'_, 'tcx> {
         for (&var_hir_id, min_capture_list) in closure_min_captures {
             for captured_place in min_capture_list {
                 match captured_place.info.capture_kind {
-                    ty::UpvarCapture::ByValue => {}
+                    ty::UpvarCapture::ByValue | ty::UpvarCapture::ByUse => {}
                     ty::UpvarCapture::ByRef(..) => continue,
                 };
                 let span = captured_place.get_capture_kind_span(self.ir.tcx);
diff --git a/compiler/rustc_passes/src/liveness/rwu_table.rs b/compiler/rustc_passes/src/liveness/rwu_table.rs
index 6e2f976e5b0..4c1f6ea141e 100644
--- a/compiler/rustc_passes/src/liveness/rwu_table.rs
+++ b/compiler/rustc_passes/src/liveness/rwu_table.rs
@@ -39,7 +39,7 @@ impl RWUTable {
     /// Size of packed RWU in bits.
     const RWU_BITS: usize = 4;
     /// Size of a word in bits.
-    const WORD_BITS: usize = std::mem::size_of::<u8>() * 8;
+    const WORD_BITS: usize = size_of::<u8>() * 8;
     /// Number of packed RWUs that fit into a single word.
     const WORD_RWU_COUNT: usize = Self::WORD_BITS / Self::RWU_BITS;
 
diff --git a/compiler/rustc_passes/src/naked_functions.rs b/compiler/rustc_passes/src/naked_functions.rs
index cb17b0f6cf5..d35aedf9a56 100644
--- a/compiler/rustc_passes/src/naked_functions.rs
+++ b/compiler/rustc_passes/src/naked_functions.rs
@@ -182,6 +182,7 @@ impl CheckInlineAssembly {
             | ExprKind::Array(..)
             | ExprKind::Call(..)
             | ExprKind::MethodCall(..)
+            | ExprKind::Use(..)
             | ExprKind::Tup(..)
             | ExprKind::Binary(..)
             | ExprKind::Unary(..)
diff --git a/compiler/rustc_privacy/src/lib.rs b/compiler/rustc_privacy/src/lib.rs
index 5271d03a6f6..ff203b2938e 100644
--- a/compiler/rustc_privacy/src/lib.rs
+++ b/compiler/rustc_privacy/src/lib.rs
@@ -40,7 +40,7 @@ use rustc_middle::ty::{
 use rustc_middle::{bug, span_bug};
 use rustc_session::lint;
 use rustc_span::hygiene::Transparency;
-use rustc_span::{Ident, Span, Symbol, kw, sym};
+use rustc_span::{Ident, Span, Symbol, sym};
 use tracing::debug;
 use {rustc_attr_parsing as attr, rustc_hir as hir};
 
@@ -935,8 +935,8 @@ impl<'tcx> NamePrivacyVisitor<'tcx> {
         }
 
         // definition of the field
-        let ident = Ident::new(kw::Empty, use_ctxt);
-        let def_id = self.tcx.adjust_ident_and_get_scope(ident, def.did(), hir_id).1;
+        let ident = Ident::new(sym::dummy, use_ctxt);
+        let (_, def_id) = self.tcx.adjust_ident_and_get_scope(ident, def.did(), hir_id);
         !field.vis.is_accessible_from(def_id, self.tcx)
     }
 
diff --git a/compiler/rustc_query_system/src/dep_graph/graph.rs b/compiler/rustc_query_system/src/dep_graph/graph.rs
index 5e6bee1dbd5..6ece01c211b 100644
--- a/compiler/rustc_query_system/src/dep_graph/graph.rs
+++ b/compiler/rustc_query_system/src/dep_graph/graph.rs
@@ -1299,12 +1299,11 @@ impl Default for TaskDeps {
             #[cfg(debug_assertions)]
             node: None,
             reads: EdgesVec::new(),
-            read_set: FxHashSet::default(),
+            read_set: FxHashSet::with_capacity_and_hasher(128, Default::default()),
             phantom_data: PhantomData,
         }
     }
 }
-
 // A data structure that stores Option<DepNodeColor> values as a contiguous
 // array, using one u32 per entry.
 struct DepNodeColorMap {
diff --git a/compiler/rustc_query_system/src/dep_graph/serialized.rs b/compiler/rustc_query_system/src/dep_graph/serialized.rs
index bc78878a84a..2c6fd7d494f 100644
--- a/compiler/rustc_query_system/src/dep_graph/serialized.rs
+++ b/compiler/rustc_query_system/src/dep_graph/serialized.rs
@@ -63,7 +63,7 @@ rustc_index::newtype_index! {
     pub struct SerializedDepNodeIndex {}
 }
 
-const DEP_NODE_SIZE: usize = std::mem::size_of::<SerializedDepNodeIndex>();
+const DEP_NODE_SIZE: usize = size_of::<SerializedDepNodeIndex>();
 /// Amount of padding we need to add to the edge list data so that we can retrieve every
 /// SerializedDepNodeIndex with a fixed-size read then mask.
 const DEP_NODE_PAD: usize = DEP_NODE_SIZE - 1;
@@ -175,7 +175,7 @@ impl EdgeHeader {
 
 #[inline]
 fn mask(bits: usize) -> usize {
-    usize::MAX >> ((std::mem::size_of::<usize>() * 8) - bits)
+    usize::MAX >> ((size_of::<usize>() * 8) - bits)
 }
 
 impl SerializedDepGraph {
@@ -208,9 +208,8 @@ impl SerializedDepGraph {
         // for a node with length 64, which means the spilled 1-byte leb128 length is 1 byte of at
         // least (34 byte header + 1 byte len + 64 bytes edge data), which is ~1%. A 2-byte leb128
         // length is about the same fractional overhead and it amortizes for yet greater lengths.
-        let mut edge_list_data = Vec::with_capacity(
-            graph_bytes - node_count * std::mem::size_of::<SerializedNodeHeader<D>>(),
-        );
+        let mut edge_list_data =
+            Vec::with_capacity(graph_bytes - node_count * size_of::<SerializedNodeHeader<D>>());
 
         for _index in 0..node_count {
             // Decode the header for this edge; the header packs together as many of the fixed-size
@@ -300,7 +299,7 @@ struct Unpacked {
 // M..M+N  bytes per index
 // M+N..16 kind
 impl<D: Deps> SerializedNodeHeader<D> {
-    const TOTAL_BITS: usize = std::mem::size_of::<DepKind>() * 8;
+    const TOTAL_BITS: usize = size_of::<DepKind>() * 8;
     const LEN_BITS: usize = Self::TOTAL_BITS - Self::KIND_BITS - Self::WIDTH_BITS;
     const WIDTH_BITS: usize = DEP_NODE_WIDTH_BITS;
     const KIND_BITS: usize = Self::TOTAL_BITS - D::DEP_KIND_MAX.leading_zeros() as usize;
diff --git a/compiler/rustc_resolve/src/def_collector.rs b/compiler/rustc_resolve/src/def_collector.rs
index 95d637b6b22..33f529851ae 100644
--- a/compiler/rustc_resolve/src/def_collector.rs
+++ b/compiler/rustc_resolve/src/def_collector.rs
@@ -9,7 +9,7 @@ use rustc_hir as hir;
 use rustc_hir::def::{CtorKind, CtorOf, DefKind};
 use rustc_hir::def_id::LocalDefId;
 use rustc_span::hygiene::LocalExpnId;
-use rustc_span::{Span, Symbol, kw, sym};
+use rustc_span::{Span, Symbol, sym};
 use tracing::debug;
 
 use crate::{ImplTraitContext, InvocationParent, Resolver};
@@ -38,7 +38,7 @@ impl<'a, 'ra, 'tcx> DefCollector<'a, 'ra, 'tcx> {
     fn create_def(
         &mut self,
         node_id: NodeId,
-        name: Symbol,
+        name: Option<Symbol>,
         def_kind: DefKind,
         span: Span,
     ) -> LocalDefId {
@@ -89,7 +89,7 @@ impl<'a, 'ra, 'tcx> DefCollector<'a, 'ra, 'tcx> {
             self.visit_macro_invoc(field.id);
         } else {
             let name = field.ident.map_or_else(|| sym::integer(index(self)), |ident| ident.name);
-            let def = self.create_def(field.id, name, DefKind::Field, field.span);
+            let def = self.create_def(field.id, Some(name), DefKind::Field, field.span);
             self.with_parent(def, |this| visit::walk_field_def(this, field));
         }
     }
@@ -161,7 +161,7 @@ impl<'a, 'ra, 'tcx> visit::Visitor<'a> for DefCollector<'a, 'ra, 'tcx> {
                 return self.visit_macro_invoc(i.id);
             }
         };
-        let def_id = self.create_def(i.id, i.ident.name, def_kind, i.span);
+        let def_id = self.create_def(i.id, Some(i.ident.name), def_kind, i.span);
 
         if let Some(macro_data) = opt_macro_data {
             self.resolver.macro_map.insert(def_id.to_def_id(), macro_data);
@@ -175,7 +175,7 @@ impl<'a, 'ra, 'tcx> visit::Visitor<'a> for DefCollector<'a, 'ra, 'tcx> {
                         if let Some((ctor_kind, ctor_node_id)) = CtorKind::from_ast(struct_def) {
                             this.create_def(
                                 ctor_node_id,
-                                kw::Empty,
+                                None,
                                 DefKind::Ctor(CtorOf::Struct, ctor_kind),
                                 i.span,
                             );
@@ -211,20 +211,15 @@ impl<'a, 'ra, 'tcx> visit::Visitor<'a> for DefCollector<'a, 'ra, 'tcx> {
                 }
 
                 let (return_id, return_span) = coroutine_kind.return_id();
-                let return_def =
-                    self.create_def(return_id, kw::Empty, DefKind::OpaqueTy, return_span);
+                let return_def = self.create_def(return_id, None, DefKind::OpaqueTy, return_span);
                 self.with_parent(return_def, |this| this.visit_fn_ret_ty(output));
 
                 // If this async fn has no body (i.e. it's an async fn signature in a trait)
                 // then the closure_def will never be used, and we should avoid generating a
                 // def-id for it.
                 if let Some(body) = body {
-                    let closure_def = self.create_def(
-                        coroutine_kind.closure_id(),
-                        kw::Empty,
-                        DefKind::Closure,
-                        span,
-                    );
+                    let closure_def =
+                        self.create_def(coroutine_kind.closure_id(), None, DefKind::Closure, span);
                     self.with_parent(closure_def, |this| this.visit_block(body));
                 }
             }
@@ -235,7 +230,7 @@ impl<'a, 'ra, 'tcx> visit::Visitor<'a> for DefCollector<'a, 'ra, 'tcx> {
                 // Async closures desugar to closures inside of closures, so
                 // we must create two defs.
                 let coroutine_def =
-                    self.create_def(coroutine_kind.closure_id(), kw::Empty, DefKind::Closure, span);
+                    self.create_def(coroutine_kind.closure_id(), None, DefKind::Closure, span);
                 self.with_parent(coroutine_def, |this| this.visit_expr(body));
             }
             _ => visit::walk_fn(self, fn_kind),
@@ -243,7 +238,7 @@ impl<'a, 'ra, 'tcx> visit::Visitor<'a> for DefCollector<'a, 'ra, 'tcx> {
     }
 
     fn visit_use_tree(&mut self, use_tree: &'a UseTree, id: NodeId, _nested: bool) {
-        self.create_def(id, kw::Empty, DefKind::Use, use_tree.span);
+        self.create_def(id, None, DefKind::Use, use_tree.span);
         visit::walk_use_tree(self, use_tree, id);
     }
 
@@ -262,7 +257,7 @@ impl<'a, 'ra, 'tcx> visit::Visitor<'a> for DefCollector<'a, 'ra, 'tcx> {
             ForeignItemKind::MacCall(_) => return self.visit_macro_invoc(fi.id),
         };
 
-        let def = self.create_def(fi.id, fi.ident.name, def_kind, fi.span);
+        let def = self.create_def(fi.id, Some(fi.ident.name), def_kind, fi.span);
 
         self.with_parent(def, |this| visit::walk_item(this, fi));
     }
@@ -271,12 +266,12 @@ impl<'a, 'ra, 'tcx> visit::Visitor<'a> for DefCollector<'a, 'ra, 'tcx> {
         if v.is_placeholder {
             return self.visit_macro_invoc(v.id);
         }
-        let def = self.create_def(v.id, v.ident.name, DefKind::Variant, v.span);
+        let def = self.create_def(v.id, Some(v.ident.name), DefKind::Variant, v.span);
         self.with_parent(def, |this| {
             if let Some((ctor_kind, ctor_node_id)) = CtorKind::from_ast(&v.data) {
                 this.create_def(
                     ctor_node_id,
-                    kw::Empty,
+                    None,
                     DefKind::Ctor(CtorOf::Variant, ctor_kind),
                     v.span,
                 );
@@ -312,7 +307,7 @@ impl<'a, 'ra, 'tcx> visit::Visitor<'a> for DefCollector<'a, 'ra, 'tcx> {
             GenericParamKind::Type { .. } => DefKind::TyParam,
             GenericParamKind::Const { .. } => DefKind::ConstParam,
         };
-        self.create_def(param.id, param.ident.name, def_kind, param.ident.span);
+        self.create_def(param.id, Some(param.ident.name), def_kind, param.ident.span);
 
         // impl-Trait can happen inside generic parameters, like
         // ```
@@ -335,7 +330,7 @@ impl<'a, 'ra, 'tcx> visit::Visitor<'a> for DefCollector<'a, 'ra, 'tcx> {
             }
         };
 
-        let def = self.create_def(i.id, i.ident.name, def_kind, i.span);
+        let def = self.create_def(i.id, Some(i.ident.name), def_kind, i.span);
         self.with_parent(def, |this| visit::walk_assoc_item(this, i, ctxt));
     }
 
@@ -347,8 +342,7 @@ impl<'a, 'ra, 'tcx> visit::Visitor<'a> for DefCollector<'a, 'ra, 'tcx> {
     }
 
     fn visit_anon_const(&mut self, constant: &'a AnonConst) {
-        let parent =
-            self.create_def(constant.id, kw::Empty, DefKind::AnonConst, constant.value.span);
+        let parent = self.create_def(constant.id, None, DefKind::AnonConst, constant.value.span);
         self.with_parent(parent, |this| visit::walk_anon_const(this, constant));
     }
 
@@ -356,18 +350,14 @@ impl<'a, 'ra, 'tcx> visit::Visitor<'a> for DefCollector<'a, 'ra, 'tcx> {
         let parent_def = match expr.kind {
             ExprKind::MacCall(..) => return self.visit_macro_invoc(expr.id),
             ExprKind::Closure(..) | ExprKind::Gen(..) => {
-                self.create_def(expr.id, kw::Empty, DefKind::Closure, expr.span)
+                self.create_def(expr.id, None, DefKind::Closure, expr.span)
             }
             ExprKind::ConstBlock(ref constant) => {
                 for attr in &expr.attrs {
                     visit::walk_attribute(self, attr);
                 }
-                let def = self.create_def(
-                    constant.id,
-                    kw::Empty,
-                    DefKind::InlineConst,
-                    constant.value.span,
-                );
+                let def =
+                    self.create_def(constant.id, None, DefKind::InlineConst, constant.value.span);
                 self.with_parent(def, |this| visit::walk_anon_const(this, constant));
                 return;
             }
@@ -391,7 +381,7 @@ impl<'a, 'ra, 'tcx> visit::Visitor<'a> for DefCollector<'a, 'ra, 'tcx> {
                     ImplTraitContext::Existential => DefKind::OpaqueTy,
                     ImplTraitContext::InBinding => return visit::walk_ty(self, ty),
                 };
-                let id = self.create_def(*id, name, kind, ty.span);
+                let id = self.create_def(*id, Some(name), kind, ty.span);
                 match self.impl_trait_context {
                     // Do not nest APIT, as we desugar them as `impl_trait: bounds`,
                     // so the `impl_trait` node is not a parent to `bounds`.
@@ -495,7 +485,7 @@ impl<'a, 'ra, 'tcx> visit::Visitor<'a> for DefCollector<'a, 'ra, 'tcx> {
                 InlineAsmOperand::Const { anon_const } => {
                     let def = self.create_def(
                         anon_const.id,
-                        kw::Empty,
+                        None,
                         DefKind::InlineConst,
                         anon_const.value.span,
                     );
diff --git a/compiler/rustc_resolve/src/diagnostics.rs b/compiler/rustc_resolve/src/diagnostics.rs
index e3405c89b79..88d1126de1a 100644
--- a/compiler/rustc_resolve/src/diagnostics.rs
+++ b/compiler/rustc_resolve/src/diagnostics.rs
@@ -2266,7 +2266,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                     && !first.ident.is_path_segment_keyword() =>
             {
                 // Insert a placeholder that's later replaced by `self`/`super`/etc.
-                path.insert(0, Segment::from_ident(Ident::empty()));
+                path.insert(0, Segment::from_ident(Ident::dummy()));
             }
             _ => return None,
         }
diff --git a/compiler/rustc_resolve/src/late.rs b/compiler/rustc_resolve/src/late.rs
index 92f5fba1f9b..2c3e4bb505c 100644
--- a/compiler/rustc_resolve/src/late.rs
+++ b/compiler/rustc_resolve/src/late.rs
@@ -397,32 +397,37 @@ pub(crate) enum AliasPossibility {
 
 #[derive(Copy, Clone, Debug)]
 pub(crate) enum PathSource<'a> {
-    // Type paths `Path`.
+    /// Type paths `Path`.
     Type,
-    // Trait paths in bounds or impls.
+    /// Trait paths in bounds or impls.
     Trait(AliasPossibility),
-    // Expression paths `path`, with optional parent context.
+    /// Expression paths `path`, with optional parent context.
     Expr(Option<&'a Expr>),
-    // Paths in path patterns `Path`.
+    /// Paths in path patterns `Path`.
     Pat,
-    // Paths in struct expressions and patterns `Path { .. }`.
+    /// Paths in struct expressions and patterns `Path { .. }`.
     Struct,
-    // Paths in tuple struct patterns `Path(..)`.
+    /// Paths in tuple struct patterns `Path(..)`.
     TupleStruct(Span, &'a [Span]),
-    // `m::A::B` in `<T as m::A>::B::C`.
+    /// `m::A::B` in `<T as m::A>::B::C`.
     TraitItem(Namespace),
-    // Paths in delegation item
+    /// Paths in delegation item
     Delegation,
     /// An arg in a `use<'a, N>` precise-capturing bound.
     PreciseCapturingArg(Namespace),
-    // Paths that end with `(..)`, for return type notation.
+    /// Paths that end with `(..)`, for return type notation.
     ReturnTypeNotation,
+    /// Paths from `#[define_opaque]` attributes
+    DefineOpaques,
 }
 
 impl<'a> PathSource<'a> {
     fn namespace(self) -> Namespace {
         match self {
-            PathSource::Type | PathSource::Trait(_) | PathSource::Struct => TypeNS,
+            PathSource::Type
+            | PathSource::Trait(_)
+            | PathSource::Struct
+            | PathSource::DefineOpaques => TypeNS,
             PathSource::Expr(..)
             | PathSource::Pat
             | PathSource::TupleStruct(..)
@@ -443,6 +448,7 @@ impl<'a> PathSource<'a> {
             | PathSource::ReturnTypeNotation => true,
             PathSource::Trait(_)
             | PathSource::TraitItem(..)
+            | PathSource::DefineOpaques
             | PathSource::Delegation
             | PathSource::PreciseCapturingArg(..) => false,
         }
@@ -450,6 +456,7 @@ impl<'a> PathSource<'a> {
 
     fn descr_expected(self) -> &'static str {
         match &self {
+            PathSource::DefineOpaques => "type alias or associated type with opaqaue types",
             PathSource::Type => "type",
             PathSource::Trait(_) => "trait",
             PathSource::Pat => "unit struct, unit variant or constant",
@@ -493,6 +500,19 @@ impl<'a> PathSource<'a> {
 
     pub(crate) fn is_expected(self, res: Res) -> bool {
         match self {
+            PathSource::DefineOpaques => {
+                matches!(
+                    res,
+                    Res::Def(
+                        DefKind::Struct
+                            | DefKind::Union
+                            | DefKind::Enum
+                            | DefKind::TyAlias
+                            | DefKind::AssocTy,
+                        _
+                    ) | Res::SelfTyAlias { .. }
+                )
+            }
             PathSource::Type => matches!(
                 res,
                 Res::Def(
@@ -572,16 +592,16 @@ impl<'a> PathSource<'a> {
         match (self, has_unexpected_resolution) {
             (PathSource::Trait(_), true) => E0404,
             (PathSource::Trait(_), false) => E0405,
-            (PathSource::Type, true) => E0573,
-            (PathSource::Type, false) => E0412,
+            (PathSource::Type | PathSource::DefineOpaques, true) => E0573,
+            (PathSource::Type | PathSource::DefineOpaques, false) => E0412,
             (PathSource::Struct, true) => E0574,
             (PathSource::Struct, false) => E0422,
             (PathSource::Expr(..), true) | (PathSource::Delegation, true) => E0423,
             (PathSource::Expr(..), false) | (PathSource::Delegation, false) => E0425,
             (PathSource::Pat | PathSource::TupleStruct(..), true) => E0532,
             (PathSource::Pat | PathSource::TupleStruct(..), false) => E0531,
-            (PathSource::TraitItem(..), true) | (PathSource::ReturnTypeNotation, true) => E0575,
-            (PathSource::TraitItem(..), false) | (PathSource::ReturnTypeNotation, false) => E0576,
+            (PathSource::TraitItem(..) | PathSource::ReturnTypeNotation, true) => E0575,
+            (PathSource::TraitItem(..) | PathSource::ReturnTypeNotation, false) => E0576,
             (PathSource::PreciseCapturingArg(..), true) => E0799,
             (PathSource::PreciseCapturingArg(..), false) => E0800,
         }
@@ -2006,6 +2026,7 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
                 | PathSource::Pat
                 | PathSource::Struct
                 | PathSource::TupleStruct(..)
+                | PathSource::DefineOpaques
                 | PathSource::Delegation => true,
             };
             if inferred {
@@ -2619,7 +2640,7 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
                 );
             }
 
-            ItemKind::Fn(box Fn { ref generics, .. }) => {
+            ItemKind::Fn(box Fn { ref generics, ref define_opaque, .. }) => {
                 self.with_generic_param_rib(
                     &generics.params,
                     RibKind::Item(HasGenericParams::Yes(generics.span), def_kind),
@@ -2630,6 +2651,10 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
                     },
                     |this| visit::walk_item(this, item),
                 );
+
+                for (id, path) in define_opaque.iter().flatten() {
+                    self.smart_resolve_path(*id, &None, path, PathSource::DefineOpaques);
+                }
             }
 
             ItemKind::Enum(_, ref generics)
@@ -2995,7 +3020,7 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
     }
 
     // HACK(min_const_generics, generic_const_exprs): We
-    // want to keep allowing `[0; std::mem::size_of::<*mut T>()]`
+    // want to keep allowing `[0; size_of::<*mut T>()]`
     // with a future compat lint for now. We do this by adding an
     // additional special case for repeat expressions.
     //
@@ -3100,8 +3125,12 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
                         },
                     );
                 }
-                AssocItemKind::Fn(box Fn { generics, .. }) => {
+                AssocItemKind::Fn(box Fn { generics, define_opaque, .. }) => {
                     walk_assoc_item(self, generics, LifetimeBinderKind::Function, item);
+
+                    for (id, path) in define_opaque.iter().flatten() {
+                        self.smart_resolve_path(*id, &None, path, PathSource::DefineOpaques);
+                    }
                 }
                 AssocItemKind::Delegation(delegation) => {
                     self.with_generic_param_rib(
@@ -3311,7 +3340,7 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
                     },
                 );
             }
-            AssocItemKind::Fn(box Fn { generics, .. }) => {
+            AssocItemKind::Fn(box Fn { generics, define_opaque, .. }) => {
                 debug!("resolve_implementation AssocItemKind::Fn");
                 // We also need a new scope for the impl item type parameters.
                 self.with_generic_param_rib(
@@ -3338,6 +3367,10 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
                         visit::walk_assoc_item(this, item, AssocCtxt::Impl)
                     },
                 );
+
+                for (id, path) in define_opaque.iter().flatten() {
+                    self.smart_resolve_path(*id, &None, path, PathSource::DefineOpaques);
+                }
             }
             AssocItemKind::Type(box TyAlias { generics, .. }) => {
                 self.diag_metadata.in_non_gat_assoc_type = Some(generics.params.is_empty());
diff --git a/compiler/rustc_resolve/src/late/diagnostics.rs b/compiler/rustc_resolve/src/late/diagnostics.rs
index 67024f988a4..84858cfc1b1 100644
--- a/compiler/rustc_resolve/src/late/diagnostics.rs
+++ b/compiler/rustc_resolve/src/late/diagnostics.rs
@@ -24,7 +24,7 @@ use rustc_hir::def_id::{CRATE_DEF_ID, DefId};
 use rustc_hir::{MissingLifetimeKind, PrimTy};
 use rustc_middle::ty;
 use rustc_session::{Session, lint};
-use rustc_span::edit_distance::find_best_match_for_name;
+use rustc_span::edit_distance::{edit_distance, find_best_match_for_name};
 use rustc_span::edition::Edition;
 use rustc_span::hygiene::MacroKind;
 use rustc_span::{DUMMY_SP, Ident, Span, Symbol, kw, sym};
@@ -2919,23 +2919,35 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
             )
             .with_span_label(lifetime_ref.ident.span, "undeclared lifetime")
         };
-        self.suggest_introducing_lifetime(
-            &mut err,
-            Some(lifetime_ref.ident.name.as_str()),
-            |err, _, span, message, suggestion, span_suggs| {
-                err.multipart_suggestion_with_style(
-                    message,
-                    std::iter::once((span, suggestion)).chain(span_suggs.clone()).collect(),
-                    Applicability::MaybeIncorrect,
-                    if span_suggs.is_empty() {
-                        SuggestionStyle::ShowCode
-                    } else {
-                        SuggestionStyle::ShowAlways
-                    },
-                );
-                true
-            },
-        );
+
+        // Check if this is a typo of `'static`.
+        if edit_distance(lifetime_ref.ident.name.as_str(), "'static", 2).is_some() {
+            err.span_suggestion_verbose(
+                lifetime_ref.ident.span,
+                "you may have misspelled the `'static` lifetime",
+                "'static",
+                Applicability::MachineApplicable,
+            );
+        } else {
+            self.suggest_introducing_lifetime(
+                &mut err,
+                Some(lifetime_ref.ident.name.as_str()),
+                |err, _, span, message, suggestion, span_suggs| {
+                    err.multipart_suggestion_with_style(
+                        message,
+                        std::iter::once((span, suggestion)).chain(span_suggs.clone()).collect(),
+                        Applicability::MaybeIncorrect,
+                        if span_suggs.is_empty() {
+                            SuggestionStyle::ShowCode
+                        } else {
+                            SuggestionStyle::ShowAlways
+                        },
+                    );
+                    true
+                },
+            );
+        }
+
         err.emit();
     }
 
diff --git a/compiler/rustc_resolve/src/lib.rs b/compiler/rustc_resolve/src/lib.rs
index 4c5d4041022..ccdca855232 100644
--- a/compiler/rustc_resolve/src/lib.rs
+++ b/compiler/rustc_resolve/src/lib.rs
@@ -1340,7 +1340,7 @@ impl<'tcx> Resolver<'_, 'tcx> {
         &mut self,
         parent: LocalDefId,
         node_id: ast::NodeId,
-        name: Symbol,
+        name: Option<Symbol>,
         def_kind: DefKind,
         expn_id: ExpnId,
         span: Span,
diff --git a/compiler/rustc_serialize/src/leb128.rs b/compiler/rustc_serialize/src/leb128.rs
index aa7c2858466..4a475805697 100644
--- a/compiler/rustc_serialize/src/leb128.rs
+++ b/compiler/rustc_serialize/src/leb128.rs
@@ -7,7 +7,7 @@ use crate::serialize::Decoder;
 /// Returns the length of the longest LEB128 encoding for `T`, assuming `T` is an integer type
 pub const fn max_leb128_len<T>() -> usize {
     // The longest LEB128 encoding for an integer uses 7 bits per byte.
-    (std::mem::size_of::<T>() * 8 + 6) / 7
+    (size_of::<T>() * 8 + 6) / 7
 }
 
 /// Returns the length of the longest LEB128 encoding of all supported integer types.
diff --git a/compiler/rustc_session/src/config.rs b/compiler/rustc_session/src/config.rs
index e62a8fc0fc3..7af221c9607 100644
--- a/compiler/rustc_session/src/config.rs
+++ b/compiler/rustc_session/src/config.rs
@@ -681,10 +681,14 @@ impl OutputType {
 }
 
 /// The type of diagnostics output to generate.
-#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Default)]
 pub enum ErrorOutputType {
     /// Output meant for the consumption of humans.
-    HumanReadable(HumanReadableErrorType, ColorConfig),
+    #[default]
+    HumanReadable {
+        kind: HumanReadableErrorType = HumanReadableErrorType::Default,
+        color_config: ColorConfig = ColorConfig::Auto,
+    },
     /// Output that's consumed by other tools such as `rustfix` or the `RLS`.
     Json {
         /// Render the JSON in a human readable way (with indents and newlines).
@@ -696,12 +700,6 @@ pub enum ErrorOutputType {
     },
 }
 
-impl Default for ErrorOutputType {
-    fn default() -> Self {
-        Self::HumanReadable(HumanReadableErrorType::Default, ColorConfig::Auto)
-    }
-}
-
 #[derive(Clone, Hash, Debug)]
 pub enum ResolveDocLinks {
     /// Do not resolve doc links.
@@ -898,18 +896,13 @@ pub enum PrintKind {
     DeploymentTarget,
 }
 
-#[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
+#[derive(Debug, Copy, Clone, Hash, PartialEq, Eq, Default)]
 pub struct NextSolverConfig {
     /// Whether the new trait solver should be enabled in coherence.
-    pub coherence: bool,
+    pub coherence: bool = true,
     /// Whether the new trait solver should be enabled everywhere.
     /// This is only `true` if `coherence` is also enabled.
-    pub globally: bool,
-}
-impl Default for NextSolverConfig {
-    fn default() -> Self {
-        NextSolverConfig { coherence: true, globally: false }
-    }
+    pub globally: bool = false,
 }
 
 #[derive(Clone)]
@@ -1825,7 +1818,7 @@ pub fn parse_json(early_dcx: &EarlyDiagCtxt, matches: &getopts::Matches) -> Json
 pub fn parse_error_format(
     early_dcx: &mut EarlyDiagCtxt,
     matches: &getopts::Matches,
-    color: ColorConfig,
+    color_config: ColorConfig,
     json_color: ColorConfig,
     json_rendered: HumanReadableErrorType,
 ) -> ErrorOutputType {
@@ -1835,27 +1828,26 @@ pub fn parse_error_format(
     // `opt_present` because the latter will panic.
     let error_format = if matches.opts_present(&["error-format".to_owned()]) {
         match matches.opt_str("error-format").as_deref() {
-            None | Some("human") => {
-                ErrorOutputType::HumanReadable(HumanReadableErrorType::Default, color)
-            }
-            Some("human-annotate-rs") => {
-                ErrorOutputType::HumanReadable(HumanReadableErrorType::AnnotateSnippet, color)
-            }
+            None | Some("human") => ErrorOutputType::HumanReadable { color_config, .. },
+            Some("human-annotate-rs") => ErrorOutputType::HumanReadable {
+                kind: HumanReadableErrorType::AnnotateSnippet,
+                color_config,
+            },
             Some("json") => {
                 ErrorOutputType::Json { pretty: false, json_rendered, color_config: json_color }
             }
             Some("pretty-json") => {
                 ErrorOutputType::Json { pretty: true, json_rendered, color_config: json_color }
             }
-            Some("short") => ErrorOutputType::HumanReadable(HumanReadableErrorType::Short, color),
-            Some("human-unicode") => {
-                ErrorOutputType::HumanReadable(HumanReadableErrorType::Unicode, color)
+            Some("short") => {
+                ErrorOutputType::HumanReadable { kind: HumanReadableErrorType::Short, color_config }
             }
+            Some("human-unicode") => ErrorOutputType::HumanReadable {
+                kind: HumanReadableErrorType::Unicode,
+                color_config,
+            },
             Some(arg) => {
-                early_dcx.set_error_format(ErrorOutputType::HumanReadable(
-                    HumanReadableErrorType::Default,
-                    color,
-                ));
+                early_dcx.set_error_format(ErrorOutputType::HumanReadable { color_config, .. });
                 early_dcx.early_fatal(format!(
                     "argument for `--error-format` must be `human`, `human-annotate-rs`, \
                     `human-unicode`, `json`, `pretty-json` or `short` (instead was `{arg}`)"
@@ -1863,7 +1855,7 @@ pub fn parse_error_format(
             }
         }
     } else {
-        ErrorOutputType::HumanReadable(HumanReadableErrorType::Default, color)
+        ErrorOutputType::HumanReadable { color_config, .. }
     };
 
     match error_format {
@@ -1918,7 +1910,7 @@ fn check_error_format_stability(
     }
     let format = match format {
         ErrorOutputType::Json { pretty: true, .. } => "pretty-json",
-        ErrorOutputType::HumanReadable(format, _) => match format {
+        ErrorOutputType::HumanReadable { kind, .. } => match kind {
             HumanReadableErrorType::AnnotateSnippet => "human-annotate-rs",
             HumanReadableErrorType::Unicode => "human-unicode",
             _ => return,
diff --git a/compiler/rustc_session/src/filesearch.rs b/compiler/rustc_session/src/filesearch.rs
index ec83761da4a..cc2decc2fe4 100644
--- a/compiler/rustc_session/src/filesearch.rs
+++ b/compiler/rustc_session/src/filesearch.rs
@@ -92,7 +92,7 @@ fn current_dll_path() -> Result<PathBuf, String> {
             if libc::loadquery(
                 libc::L_GETINFO,
                 buffer.as_mut_ptr() as *mut u8,
-                (std::mem::size_of::<libc::ld_info>() * buffer.len()) as u32,
+                (size_of::<libc::ld_info>() * buffer.len()) as u32,
             ) >= 0
             {
                 break;
diff --git a/compiler/rustc_session/src/lib.rs b/compiler/rustc_session/src/lib.rs
index 112adde3740..d432e84fdb2 100644
--- a/compiler/rustc_session/src/lib.rs
+++ b/compiler/rustc_session/src/lib.rs
@@ -1,5 +1,6 @@
 // tidy-alphabetical-start
 #![allow(internal_features)]
+#![feature(default_field_values)]
 #![feature(iter_intersperse)]
 #![feature(let_chains)]
 #![feature(rustc_attrs)]
diff --git a/compiler/rustc_session/src/session.rs b/compiler/rustc_session/src/session.rs
index ecdf76d22fb..bcd9a73d9d3 100644
--- a/compiler/rustc_session/src/session.rs
+++ b/compiler/rustc_session/src/session.rs
@@ -913,7 +913,7 @@ fn default_emitter(
     let source_map = if sopts.unstable_opts.link_only { None } else { Some(source_map) };
 
     match sopts.error_format {
-        config::ErrorOutputType::HumanReadable(kind, color_config) => {
+        config::ErrorOutputType::HumanReadable { kind, color_config } => {
             let short = kind.short();
 
             if let HumanReadableErrorType::AnnotateSnippet = kind {
@@ -930,7 +930,6 @@ fn default_emitter(
                     .fluent_bundle(bundle)
                     .sm(source_map)
                     .short_message(short)
-                    .teach(sopts.unstable_opts.teach)
                     .diagnostic_width(sopts.diagnostic_width)
                     .macro_backtrace(macro_backtrace)
                     .track_diagnostics(track_diagnostics)
@@ -1430,7 +1429,7 @@ fn mk_emitter(output: ErrorOutputType) -> Box<DynEmitter> {
     let fallback_bundle =
         fallback_fluent_bundle(vec![rustc_errors::DEFAULT_LOCALE_RESOURCE], false);
     let emitter: Box<DynEmitter> = match output {
-        config::ErrorOutputType::HumanReadable(kind, color_config) => {
+        config::ErrorOutputType::HumanReadable { kind, color_config } => {
             let short = kind.short();
             Box::new(
                 HumanEmitter::new(stderr_destination(color_config), fallback_bundle)
diff --git a/compiler/rustc_span/src/edition.rs b/compiler/rustc_span/src/edition.rs
index 36f9b4cff60..da298080ed2 100644
--- a/compiler/rustc_span/src/edition.rs
+++ b/compiler/rustc_span/src/edition.rs
@@ -23,11 +23,27 @@ pub enum Edition {
     Edition2021,
     /// The 2024 edition
     Edition2024,
+    /// The future edition - this variant will always exist and features associated with this
+    /// edition can be moved to the next 20XX edition when it is established and it is confirmed
+    /// that those features will be part of that edition.
+    ///
+    /// This variant allows edition changes to be implemented before being assigned to a concrete
+    /// edition - primarily when there are two different unstable behaviours that need tested across
+    /// an edition boundary.
+    ///
+    /// This edition will be permanently unstable and any features associated with this edition
+    /// must also be behind a feature gate.
+    EditionFuture,
 }
 
 // Must be in order from oldest to newest.
-pub const ALL_EDITIONS: &[Edition] =
-    &[Edition::Edition2015, Edition::Edition2018, Edition::Edition2021, Edition::Edition2024];
+pub const ALL_EDITIONS: &[Edition] = &[
+    Edition::Edition2015,
+    Edition::Edition2018,
+    Edition::Edition2021,
+    Edition::Edition2024,
+    Edition::EditionFuture,
+];
 
 pub const EDITION_NAME_LIST: &str = "2015|2018|2021|2024";
 
@@ -42,6 +58,7 @@ impl fmt::Display for Edition {
             Edition::Edition2018 => "2018",
             Edition::Edition2021 => "2021",
             Edition::Edition2024 => "2024",
+            Edition::EditionFuture => "future",
         };
         write!(f, "{s}")
     }
@@ -54,6 +71,7 @@ impl Edition {
             Edition::Edition2018 => "rust_2018_compatibility",
             Edition::Edition2021 => "rust_2021_compatibility",
             Edition::Edition2024 => "rust_2024_compatibility",
+            Edition::EditionFuture => "edition_future_compatibility",
         }
     }
 
@@ -63,6 +81,7 @@ impl Edition {
             Edition::Edition2018 => true,
             Edition::Edition2021 => true,
             Edition::Edition2024 => true,
+            Edition::EditionFuture => false,
         }
     }
 
@@ -85,6 +104,11 @@ impl Edition {
     pub fn at_least_rust_2024(self) -> bool {
         self >= Edition::Edition2024
     }
+
+    /// Are we allowed to use features from the future edition?
+    pub fn at_least_edition_future(self) -> bool {
+        self >= Edition::EditionFuture
+    }
 }
 
 impl FromStr for Edition {
@@ -95,6 +119,7 @@ impl FromStr for Edition {
             "2018" => Ok(Edition::Edition2018),
             "2021" => Ok(Edition::Edition2021),
             "2024" => Ok(Edition::Edition2024),
+            "future" => Ok(Edition::EditionFuture),
             _ => Err(()),
         }
     }
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index 573c65a772c..8a8bec35d81 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -33,6 +33,15 @@ symbols! {
         // Special reserved identifiers used internally for elided lifetimes,
         // unnamed method parameters, crate root module, error recovery etc.
         // Matching predicates: `is_any_keyword`, `is_special`/`is_reserved`
+        //
+        // Notes about `kw::Empty`:
+        // - Its use can blur the lines between "empty symbol" and "no symbol".
+        //   Using `Option<Symbol>` is preferable, where possible, because that
+        //   is unambiguous.
+        // - For dummy symbols that are never used and absolutely must be
+        //   present, it's better to use `sym::dummy` than `kw::Empty`, because
+        //   it's clearer that it's intended as a dummy value, and more likely
+        //   to be detected if it accidentally does get used.
         Empty:              "",
         PathRoot:           "{{root}}",
         DollarCrate:        "$crate",
@@ -779,6 +788,7 @@ symbols! {
         default_method_body_is_const,
         default_type_parameter_fallback,
         default_type_params,
+        define_opaque,
         delayed_bug_from_inside_query,
         deny,
         deprecated,
@@ -833,6 +843,7 @@ symbols! {
         drop_types_in_const,
         dropck_eyepatch,
         dropck_parametricity,
+        dummy: "<!dummy!>", // use this instead of `kw::Empty` for symbols that won't be used
         dummy_cgu_name,
         dylib,
         dyn_compatible_for_dispatch,
@@ -862,6 +873,7 @@ symbols! {
         eprint_macro,
         eprintln_macro,
         eq,
+        ergonomic_clones,
         ermsb_target_feature,
         exact_div,
         except,
@@ -1015,6 +1027,7 @@ symbols! {
         from_residual,
         from_size_align_unchecked,
         from_str_method,
+        from_u16,
         from_usize,
         from_yeet,
         fs_create_dir,
@@ -1717,6 +1730,7 @@ symbols! {
         rust_cold_cc,
         rust_eh_catch_typeinfo,
         rust_eh_personality,
+        rust_future,
         rust_logo,
         rust_out,
         rustc,
@@ -2185,6 +2199,7 @@ symbols! {
         unwrap,
         unwrap_binder,
         unwrap_or,
+        use_cloned,
         use_extern_macros,
         use_nested_groups,
         used,
@@ -2300,11 +2315,23 @@ impl Ident {
         Ident::new(name, DUMMY_SP)
     }
 
+    /// This is best avoided, because it blurs the lines between "empty
+    /// identifier" and "no identifier". Using `Option<Ident>` is preferable,
+    /// where possible, because that is unambiguous.
     #[inline]
     pub fn empty() -> Ident {
         Ident::with_dummy_span(kw::Empty)
     }
 
+    // For dummy identifiers that are never used and absolutely must be
+    // present, it's better to use `Ident::dummy` than `Ident::Empty`, because
+    // it's clearer that it's intended as a dummy value, and more likely to be
+    // detected if it accidentally does get used.
+    #[inline]
+    pub fn dummy() -> Ident {
+        Ident::with_dummy_span(sym::dummy)
+    }
+
     /// Maps a string to an identifier with a dummy span.
     pub fn from_str(string: &str) -> Ident {
         Ident::with_dummy_span(Symbol::intern(string))
diff --git a/compiler/rustc_target/src/callconv/mod.rs b/compiler/rustc_target/src/callconv/mod.rs
index 198d08864be..6d0ee3c7ee5 100644
--- a/compiler/rustc_target/src/callconv/mod.rs
+++ b/compiler/rustc_target/src/callconv/mod.rs
@@ -31,6 +31,7 @@ mod sparc64;
 mod wasm;
 mod x86;
 mod x86_64;
+mod x86_win32;
 mod x86_win64;
 mod xtensa;
 
@@ -649,7 +650,11 @@ impl<'a, Ty> FnAbi<'a, Ty> {
                 };
                 let reg_struct_return = cx.x86_abi_opt().reg_struct_return;
                 let opts = x86::X86Options { flavor, regparm, reg_struct_return };
-                x86::compute_abi_info(cx, self, opts);
+                if spec.is_like_msvc {
+                    x86_win32::compute_abi_info(cx, self, opts);
+                } else {
+                    x86::compute_abi_info(cx, self, opts);
+                }
             }
             "x86_64" => match abi {
                 ExternAbi::SysV64 { .. } => x86_64::compute_abi_info(cx, self),
diff --git a/compiler/rustc_target/src/callconv/x86.rs b/compiler/rustc_target/src/callconv/x86.rs
index 73aff85a0ad..6f112b49400 100644
--- a/compiler/rustc_target/src/callconv/x86.rs
+++ b/compiler/rustc_target/src/callconv/x86.rs
@@ -36,7 +36,7 @@ where
             if t.abi_return_struct_as_int || opts.reg_struct_return {
                 // According to Clang, everyone but MSVC returns single-element
                 // float aggregates directly in a floating-point register.
-                if !t.is_like_msvc && fn_abi.ret.layout.is_single_fp_element(cx) {
+                if fn_abi.ret.layout.is_single_fp_element(cx) {
                     match fn_abi.ret.layout.size.bytes() {
                         4 => fn_abi.ret.cast_to(Reg::f32()),
                         8 => fn_abi.ret.cast_to(Reg::f64()),
@@ -64,31 +64,11 @@ where
             continue;
         }
 
-        // FIXME: MSVC 2015+ will pass the first 3 vector arguments in [XYZ]MM0-2
-        // See https://reviews.llvm.org/D72114 for Clang behavior
-
         let t = cx.target_spec();
         let align_4 = Align::from_bytes(4).unwrap();
         let align_16 = Align::from_bytes(16).unwrap();
 
-        if t.is_like_msvc
-            && arg.layout.is_adt()
-            && let Some(max_repr_align) = arg.layout.max_repr_align
-            && max_repr_align > align_4
-        {
-            // MSVC has special rules for overaligned arguments: https://reviews.llvm.org/D72114.
-            // Summarized here:
-            // - Arguments with _requested_ alignment > 4 are passed indirectly.
-            // - For backwards compatibility, arguments with natural alignment > 4 are still passed
-            //   on stack (via `byval`). For example, this includes `double`, `int64_t`,
-            //   and structs containing them, provided they lack an explicit alignment attribute.
-            assert!(
-                arg.layout.align.abi >= max_repr_align,
-                "abi alignment {:?} less than requested alignment {max_repr_align:?}",
-                arg.layout.align.abi,
-            );
-            arg.make_indirect();
-        } else if arg.layout.is_aggregate() {
+        if arg.layout.is_aggregate() {
             // We need to compute the alignment of the `byval` argument. The rules can be found in
             // `X86_32ABIInfo::getTypeStackAlignInBytes` in Clang's `TargetInfo.cpp`. Summarized
             // here, they are:
diff --git a/compiler/rustc_target/src/callconv/x86_win32.rs b/compiler/rustc_target/src/callconv/x86_win32.rs
new file mode 100644
index 00000000000..554a7368848
--- /dev/null
+++ b/compiler/rustc_target/src/callconv/x86_win32.rs
@@ -0,0 +1,81 @@
+use rustc_abi::{Align, HasDataLayout, Reg, TyAbiInterface};
+
+use crate::callconv::FnAbi;
+use crate::spec::HasTargetSpec;
+
+pub(crate) fn compute_abi_info<'a, Ty, C>(
+    cx: &C,
+    fn_abi: &mut FnAbi<'a, Ty>,
+    opts: super::x86::X86Options,
+) where
+    Ty: TyAbiInterface<'a, C> + Copy,
+    C: HasDataLayout + HasTargetSpec,
+{
+    if !fn_abi.ret.is_ignore() {
+        if fn_abi.ret.layout.is_aggregate() && fn_abi.ret.layout.is_sized() {
+            // Returning a structure. Most often, this will use
+            // a hidden first argument. On some platforms, though,
+            // small structs are returned as integers.
+            //
+            // Some links:
+            // https://www.angelcode.com/dev/callconv/callconv.html
+            // Clang's ABI handling is in lib/CodeGen/TargetInfo.cpp
+            let t = cx.target_spec();
+            // MSVC does not special-case 1-element float aggregates, unlike others.
+            // GCC used to apply the SysV rule here, breaking windows-gnu's ABI, but was fixed:
+            // - reported in https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82028
+            // - fixed in https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85667
+            if t.abi_return_struct_as_int || opts.reg_struct_return {
+                match fn_abi.ret.layout.size.bytes() {
+                    1 => fn_abi.ret.cast_to(Reg::i8()),
+                    2 => fn_abi.ret.cast_to(Reg::i16()),
+                    4 => fn_abi.ret.cast_to(Reg::i32()),
+                    8 => fn_abi.ret.cast_to(Reg::i64()),
+                    _ => fn_abi.ret.make_indirect(),
+                }
+            } else {
+                fn_abi.ret.make_indirect();
+            }
+        } else {
+            fn_abi.ret.extend_integer_width_to(32);
+        }
+    }
+
+    for arg in fn_abi.args.iter_mut() {
+        if arg.is_ignore() || !arg.layout.is_sized() {
+            continue;
+        }
+
+        // FIXME: MSVC 2015+ will pass the first 3 vector arguments in [XYZ]MM0-2
+        // See https://reviews.llvm.org/D72114 for Clang behavior
+
+        let align_4 = Align::from_bytes(4).unwrap();
+
+        if arg.layout.is_adt()
+            && let Some(max_repr_align) = arg.layout.max_repr_align
+            && max_repr_align > align_4
+        {
+            // MSVC has special rules for overaligned arguments: https://reviews.llvm.org/D72114.
+            // Summarized here:
+            // - Arguments with _requested_ alignment > 4 are passed indirectly.
+            // - For backwards compatibility, arguments with natural alignment > 4 are still passed
+            //   on stack (via `byval`). For example, this includes `double`, `int64_t`,
+            //   and structs containing them, provided they lack an explicit alignment attribute.
+            assert!(
+                arg.layout.align.abi >= max_repr_align,
+                "abi alignment {:?} less than requested alignment {max_repr_align:?}",
+                arg.layout.align.abi,
+            );
+            arg.make_indirect();
+        } else if arg.layout.is_aggregate() {
+            // Alignment of the `byval` argument.
+            // The rules can be found in `X86_32ABIInfo::getTypeStackAlignInBytes` in Clang's `TargetInfo.cpp`.
+            let byval_align = align_4;
+            arg.pass_by_stack_offset(Some(byval_align));
+        } else {
+            arg.extend_integer_width_to(32);
+        }
+    }
+
+    super::x86::fill_inregs(cx, fn_abi, opts, false);
+}
diff --git a/compiler/rustc_target/src/spec/base/linux_wasm.rs b/compiler/rustc_target/src/spec/base/linux_wasm.rs
new file mode 100644
index 00000000000..a8c137c22a9
--- /dev/null
+++ b/compiler/rustc_target/src/spec/base/linux_wasm.rs
@@ -0,0 +1,159 @@
+//! This target is a confluence of Linux and Wasm models, inheriting most
+//! aspects from their respective base targets
+
+use crate::spec::{
+    Cc, LinkSelfContainedDefault, LinkerFlavor, PanicStrategy, RelocModel, TargetOptions, TlsModel,
+    add_link_args, crt_objects, cvs,
+};
+
+pub(crate) fn opts() -> TargetOptions {
+    macro_rules! args {
+        ($prefix:literal) => {
+            &[
+                // By default LLD only gives us one page of stack (64k) which is a
+                // little small. Default to a larger stack closer to other PC platforms
+                // (1MB) and users can always inject their own link-args to override this.
+                concat!($prefix, "-z"),
+                concat!($prefix, "stack-size=1048576"),
+                // By default LLD's memory layout is:
+                //
+                // 1. First, a blank page
+                // 2. Next, all static data
+                // 3. Finally, the main stack (which grows down)
+                //
+                // This has the unfortunate consequence that on stack overflows you
+                // corrupt static data and can cause some exceedingly weird bugs. To
+                // help detect this a little sooner we instead request that the stack is
+                // placed before static data.
+                //
+                // This means that we'll generate slightly larger binaries as references
+                // to static data will take more bytes in the ULEB128 encoding, but
+                // stack overflow will be guaranteed to trap as it underflows instead of
+                // corrupting static data.
+                concat!($prefix, "--stack-first"),
+                // FIXME we probably shouldn't pass this but instead pass an explicit list
+                // of symbols we'll allow to be undefined. We don't currently have a
+                // mechanism of knowing, however, which symbols are intended to be imported
+                // from the environment and which are intended to be imported from other
+                // objects linked elsewhere. This is a coarse approximation but is sure to
+                // hide some bugs and frustrate someone at some point, so we should ideally
+                // work towards a world where we can explicitly list symbols that are
+                // supposed to be imported and have all other symbols generate errors if
+                // they remain undefined.
+                concat!($prefix, "--allow-undefined"),
+                // LLD only implements C++-like demangling, which doesn't match our own
+                // mangling scheme. Tell LLD to not demangle anything and leave it up to
+                // us to demangle these symbols later. Currently rustc does not perform
+                // further demangling, but tools like twiggy and wasm-bindgen are intended
+                // to do so.
+                concat!($prefix, "--no-demangle"),
+            ]
+        };
+    }
+
+    let mut pre_link_args = TargetOptions::link_args(LinkerFlavor::WasmLld(Cc::No), args!(""));
+    add_link_args(&mut pre_link_args, LinkerFlavor::WasmLld(Cc::Yes), args!("-Wl,"));
+
+    TargetOptions {
+        is_like_wasm: true,
+        families: cvs!["wasm", "unix"],
+        os: "linux".into(),
+        env: "musl".into(),
+
+        // we allow dynamic linking, but only cdylibs. Basically we allow a
+        // final library artifact that exports some symbols (a wasm module) but
+        // we don't allow intermediate `dylib` crate types
+        dynamic_linking: true,
+        only_cdylib: true,
+
+        // relatively self-explanatory!
+        exe_suffix: ".wasm".into(),
+        dll_prefix: "".into(),
+        dll_suffix: ".wasm".into(),
+        eh_frame_header: false,
+
+        max_atomic_width: Some(64),
+
+        // Unwinding doesn't work right now, so the whole target unconditionally
+        // defaults to panic=abort. Note that this is guaranteed to change in
+        // the future once unwinding is implemented. Don't rely on this as we're
+        // basically guaranteed to change it once WebAssembly supports
+        // exceptions.
+        panic_strategy: PanicStrategy::Abort,
+
+        // Symbol visibility takes care of this for the WebAssembly.
+        // Additionally the only known linker, LLD, doesn't support the script
+        // arguments just yet
+        limit_rdylib_exports: false,
+
+        // we use the LLD shipped with the Rust toolchain by default
+        linker: Some("rust-lld".into()),
+        linker_flavor: LinkerFlavor::WasmLld(Cc::No),
+
+        pre_link_args,
+
+        // FIXME: Figure out cases in which WASM needs to link with a native toolchain.
+        //
+        // rust-lang/rust#104137: cannot blindly remove this without putting in
+        // some other way to compensate for lack of `-nostartfiles` in linker
+        // invocation.
+        link_self_contained: LinkSelfContainedDefault::True,
+        pre_link_objects_self_contained: crt_objects::pre_wasi_self_contained(),
+        post_link_objects_self_contained: crt_objects::post_wasi_self_contained(),
+
+        // This has no effect in LLVM 8 or prior, but in LLVM 9 and later when
+        // PIC code is implemented this has quite a drastic effect if it stays
+        // at the default, `pic`. In an effort to keep wasm binaries as minimal
+        // as possible we're defaulting to `static` for now, but the hope is
+        // that eventually we can ship a `pic`-compatible standard library which
+        // works with `static` as well (or works with some method of generating
+        // non-relative calls and such later on).
+        relocation_model: RelocModel::Static,
+
+        // When the atomics feature is activated then these two keys matter,
+        // otherwise they're basically ignored by the standard library. In this
+        // mode, however, the `#[thread_local]` attribute works (i.e.
+        // `has_thread_local`) and we need to get it to work by specifying
+        // `local-exec` as that's all that's implemented in LLVM today for wasm.
+        has_thread_local: true,
+        tls_model: TlsModel::LocalExec,
+
+        // Supporting Linux requires multithreading supported by Wasm's thread
+        // proposal
+        singlethread: false,
+
+        // gdb scripts don't work on wasm blobs
+        emit_debug_gdb_scripts: false,
+
+        // There's more discussion of this at
+        // https://bugs.llvm.org/show_bug.cgi?id=52442 but the general result is
+        // that this isn't useful for wasm and has tricky issues with
+        // representation, so this is disabled.
+        generate_arange_section: false,
+
+        // Right now this is a bit of a workaround but we're currently saying that
+        // the target by default has a static crt which we're taking as a signal
+        // for "use the bundled crt". If that's turned off then the system's crt
+        // will be used, but this means that default usage of this target doesn't
+        // need an external compiler but it's still interoperable with an external
+        // compiler if configured correctly.
+        crt_static_default: true,
+        crt_static_respected: true,
+
+        // Allow `+crt-static` to create a "cdylib" output which is just a wasm file
+        // without a main function.
+        crt_static_allows_dylibs: true,
+
+        // Wasm start ignores arguments -- relies on API call from interface.
+        main_needs_argc_argv: false,
+
+        // Wasm toolchains mangle the name of "main" to distinguish between different
+        // signatures.
+        entry_name: "__main_void".into(),
+
+        // Wasm Feature flags for supporting Linux
+        features: "+atomics,+bulk-memory,+mutable-globals,+sign-ext".into(),
+
+        ..Default::default()
+    }
+}
diff --git a/compiler/rustc_target/src/spec/base/mod.rs b/compiler/rustc_target/src/spec/base/mod.rs
index 6f88be5d37f..e8fdc871785 100644
--- a/compiler/rustc_target/src/spec/base/mod.rs
+++ b/compiler/rustc_target/src/spec/base/mod.rs
@@ -18,6 +18,7 @@ pub(crate) mod linux_gnu;
 pub(crate) mod linux_musl;
 pub(crate) mod linux_ohos;
 pub(crate) mod linux_uclibc;
+pub(crate) mod linux_wasm;
 pub(crate) mod msvc;
 pub(crate) mod netbsd;
 pub(crate) mod nto_qnx;
diff --git a/compiler/rustc_target/src/spec/mod.rs b/compiler/rustc_target/src/spec/mod.rs
index 72202129f5b..1887134c575 100644
--- a/compiler/rustc_target/src/spec/mod.rs
+++ b/compiler/rustc_target/src/spec/mod.rs
@@ -1915,7 +1915,6 @@ supported_targets! {
     ("i686-pc-windows-msvc", i686_pc_windows_msvc),
     ("i686-uwp-windows-msvc", i686_uwp_windows_msvc),
     ("i686-win7-windows-msvc", i686_win7_windows_msvc),
-    ("i586-pc-windows-msvc", i586_pc_windows_msvc),
     ("thumbv7a-pc-windows-msvc", thumbv7a_pc_windows_msvc),
     ("thumbv7a-uwp-windows-msvc", thumbv7a_uwp_windows_msvc),
 
@@ -1925,6 +1924,7 @@ supported_targets! {
     ("wasm32-wasip1", wasm32_wasip1),
     ("wasm32-wasip2", wasm32_wasip2),
     ("wasm32-wasip1-threads", wasm32_wasip1_threads),
+    ("wasm32-wali-linux-musl", wasm32_wali_linux_musl),
     ("wasm64-unknown-unknown", wasm64_unknown_unknown),
 
     ("thumbv6m-none-eabi", thumbv6m_none_eabi),
@@ -3503,7 +3503,15 @@ impl Target {
                     return load_file(&p);
                 }
 
-                Err(format!("Could not find specification for target {target_tuple:?}"))
+                // Leave in a specialized error message for the removed target.
+                // FIXME: If you see this and it's been a few months after this has been released,
+                // you can probably remove it.
+                if target_tuple == "i586-pc-windows-msvc" {
+                    Err("the `i586-pc-windows-msvc` target has been removed. Use the `i686-pc-windows-msvc` target instead.\n\
+                        Windows 10 (the minimum required OS version) requires a CPU baseline of at least i686 so you can safely switch".into())
+                } else {
+                    Err(format!("Could not find specification for target {target_tuple:?}"))
+                }
             }
             TargetTuple::TargetJson { ref contents, .. } => {
                 let obj = serde_json::from_str(contents).map_err(|e| e.to_string())?;
diff --git a/compiler/rustc_target/src/spec/targets/i586_pc_windows_msvc.rs b/compiler/rustc_target/src/spec/targets/i586_pc_windows_msvc.rs
deleted file mode 100644
index 394e6f9e6bf..00000000000
--- a/compiler/rustc_target/src/spec/targets/i586_pc_windows_msvc.rs
+++ /dev/null
@@ -1,9 +0,0 @@
-use crate::spec::Target;
-
-pub(crate) fn target() -> Target {
-    let mut base = super::i686_pc_windows_msvc::target();
-    base.rustc_abi = None; // overwrite the SSE2 ABI set by the base target
-    base.cpu = "pentium".into();
-    base.llvm_target = "i586-pc-windows-msvc".into();
-    base
-}
diff --git a/compiler/rustc_target/src/spec/targets/wasm32_wali_linux_musl.rs b/compiler/rustc_target/src/spec/targets/wasm32_wali_linux_musl.rs
new file mode 100644
index 00000000000..a0eb4a254fc
--- /dev/null
+++ b/compiler/rustc_target/src/spec/targets/wasm32_wali_linux_musl.rs
@@ -0,0 +1,29 @@
+//! The `wasm32-wali-linux-musl` target is a wasm32 target compliant with the
+//! [WebAssembly Linux Interface](https://github.com/arjunr2/WALI).
+
+use crate::spec::{Cc, LinkerFlavor, Target, TargetMetadata, base};
+
+pub(crate) fn target() -> Target {
+    let mut options = base::linux_wasm::opts();
+
+    options
+        .add_pre_link_args(LinkerFlavor::WasmLld(Cc::No), &["--export-memory", "--shared-memory"]);
+    options.add_pre_link_args(
+        LinkerFlavor::WasmLld(Cc::Yes),
+        &["--target=wasm32-wasi-threads", "-Wl,--export-memory,", "-Wl,--shared-memory"],
+    );
+
+    Target {
+        llvm_target: "wasm32-wasi".into(),
+        metadata: TargetMetadata {
+            description: Some("WebAssembly Linux Interface with musl-libc".into()),
+            tier: Some(3),
+            host_tools: Some(false),
+            std: None,
+        },
+        pointer_width: 32,
+        data_layout: "e-m:e-p:32:32-p10:8:8-p20:8:8-i64:64-i128:128-n32:64-S128-ni:1:10:20".into(),
+        arch: "wasm32".into(),
+        options,
+    }
+}
diff --git a/compiler/rustc_target/src/target_features.rs b/compiler/rustc_target/src/target_features.rs
index d05466bb484..6d3b6608ea2 100644
--- a/compiler/rustc_target/src/target_features.rs
+++ b/compiler/rustc_target/src/target_features.rs
@@ -768,17 +768,15 @@ impl Target {
         }
     }
 
-    pub fn implied_target_features<'a>(
-        &self,
-        base_features: impl Iterator<Item = &'a str>,
-    ) -> FxHashSet<&'a str> {
+    // Note: the returned set includes `base_feature`.
+    pub fn implied_target_features<'a>(&self, base_feature: &'a str) -> FxHashSet<&'a str> {
         let implied_features =
             self.rust_target_features().iter().map(|(f, _, i)| (f, i)).collect::<FxHashMap<_, _>>();
 
-        // implied target features have their own implied target features, so we traverse the
-        // map until there are no more features to add
+        // Implied target features have their own implied target features, so we traverse the
+        // map until there are no more features to add.
         let mut features = FxHashSet::default();
-        let mut new_features = base_features.collect::<Vec<&str>>();
+        let mut new_features = vec![base_feature];
         while let Some(new_feature) = new_features.pop() {
             if features.insert(new_feature) {
                 if let Some(implied_features) = implied_features.get(&new_feature) {
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 514615735a5..51b2a0b36bb 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
@@ -395,11 +395,28 @@ impl<T> Trait<T> for X {
                             let sp = tcx
                                 .def_ident_span(body_owner_def_id)
                                 .unwrap_or_else(|| tcx.def_span(body_owner_def_id));
-                            diag.span_note(
-                                sp,
-                                "this item must have the opaque type in its signature in order to \
-                                 be able to register hidden types",
-                            );
+                            let mut alias_def_id = opaque_ty.def_id;
+                            while let DefKind::OpaqueTy = tcx.def_kind(alias_def_id) {
+                                alias_def_id = tcx.parent(alias_def_id);
+                            }
+                            let opaque_path = tcx.def_path_str(alias_def_id);
+                            // FIXME(type_alias_impl_trait): make this a structured suggestion
+                            match tcx.opaque_ty_origin(opaque_ty.def_id) {
+                                rustc_hir::OpaqueTyOrigin::FnReturn { .. } => {}
+                                rustc_hir::OpaqueTyOrigin::AsyncFn { .. } => {}
+                                rustc_hir::OpaqueTyOrigin::TyAlias {
+                                    in_assoc_ty: false, ..
+                                } => {
+                                    diag.span_note(
+                                        sp,
+                                        format!("this item must have a `#[define_opaque({opaque_path})]` \
+                                        attribute to be able to define hidden types"),
+                                    );
+                                }
+                                rustc_hir::OpaqueTyOrigin::TyAlias {
+                                    in_assoc_ty: true, ..
+                                } => {}
+                            }
                         }
                         // If two if arms can be coerced to a trait object, provide a structured
                         // suggestion.
diff --git a/compiler/rustc_trait_selection/src/infer.rs b/compiler/rustc_trait_selection/src/infer.rs
index f373706b296..5cf0600ade8 100644
--- a/compiler/rustc_trait_selection/src/infer.rs
+++ b/compiler/rustc_trait_selection/src/infer.rs
@@ -53,6 +53,16 @@ impl<'tcx> InferCtxt<'tcx> {
         traits::type_known_to_meet_bound_modulo_regions(self, param_env, ty, clone_def_id)
     }
 
+    fn type_is_use_cloned_modulo_regions(
+        &self,
+        param_env: ty::ParamEnv<'tcx>,
+        ty: Ty<'tcx>,
+    ) -> bool {
+        let ty = self.resolve_vars_if_possible(ty);
+        let use_cloned_def_id = self.tcx.require_lang_item(LangItem::UseCloned, None);
+        traits::type_known_to_meet_bound_modulo_regions(self, param_env, ty, use_cloned_def_id)
+    }
+
     fn type_is_sized_modulo_regions(&self, param_env: ty::ParamEnv<'tcx>, ty: Ty<'tcx>) -> bool {
         let lang_item = self.tcx.require_lang_item(LangItem::Sized, None);
         traits::type_known_to_meet_bound_modulo_regions(self, param_env, ty, lang_item)
diff --git a/compiler/rustc_trait_selection/src/traits/const_evaluatable.rs b/compiler/rustc_trait_selection/src/traits/const_evaluatable.rs
index 75f53b063d1..39333082acd 100644
--- a/compiler/rustc_trait_selection/src/traits/const_evaluatable.rs
+++ b/compiler/rustc_trait_selection/src/traits/const_evaluatable.rs
@@ -2,7 +2,7 @@
 //!
 //! For concrete constants, this is fairly simple as we can just try and evaluate it.
 //!
-//! When dealing with polymorphic constants, for example `std::mem::size_of::<T>() - 1`,
+//! When dealing with polymorphic constants, for example `size_of::<T>() - 1`,
 //! this is not as easy.
 //!
 //! In this case we try to build an abstract representation of this constant using
diff --git a/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs b/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
index d4502be6ccf..3fceada2510 100644
--- a/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
+++ b/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
@@ -24,7 +24,9 @@ use super::elaborate;
 use crate::infer::TyCtxtInferExt;
 pub use crate::traits::DynCompatibilityViolation;
 use crate::traits::query::evaluate_obligation::InferCtxtExt;
-use crate::traits::{MethodViolationCode, Obligation, ObligationCause, util};
+use crate::traits::{
+    MethodViolationCode, Obligation, ObligationCause, normalize_param_env_or_error, util,
+};
 
 /// Returns the dyn-compatibility violations that affect HIR ty lowering.
 ///
@@ -579,8 +581,8 @@ fn receiver_is_dispatchable<'tcx>(
     let unsized_receiver_ty =
         receiver_for_self_ty(tcx, receiver_ty, unsized_self_ty, method.def_id);
 
-    // create a modified param env, with `Self: Unsize<U>` and `U: Trait` added to caller bounds
-    // `U: ?Sized` is already implied here
+    // create a modified param env, with `Self: Unsize<U>` and `U: Trait` (and all of
+    // its supertraits) added to caller bounds. `U: ?Sized` is already implied here.
     let param_env = {
         let param_env = tcx.param_env(method.def_id);
 
@@ -598,10 +600,13 @@ fn receiver_is_dispatchable<'tcx>(
             ty::TraitRef::new_from_args(tcx, trait_def_id, args).upcast(tcx)
         };
 
-        let caller_bounds =
-            param_env.caller_bounds().iter().chain([unsize_predicate, trait_predicate]);
-
-        ty::ParamEnv::new(tcx.mk_clauses_from_iter(caller_bounds))
+        normalize_param_env_or_error(
+            tcx,
+            ty::ParamEnv::new(tcx.mk_clauses_from_iter(
+                param_env.caller_bounds().iter().chain([unsize_predicate, trait_predicate]),
+            )),
+            ObligationCause::dummy_with_span(tcx.def_span(method.def_id)),
+        )
     };
 
     // Receiver: DispatchFromDyn<Receiver[Self => U]>
diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
index 77dbb43465e..e1adabbeaa6 100644
--- a/compiler/rustc_trait_selection/src/traits/select/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -1925,9 +1925,9 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
         let mut impl_candidate = None;
         for c in impls {
             if let Some(prev) = impl_candidate.replace(c) {
-                if self.prefer_lhs_over_victim(has_non_region_infer, c, prev) {
+                if self.prefer_lhs_over_victim(has_non_region_infer, c, prev.0) {
                     // Ok, prefer `c` over the previous entry
-                } else if self.prefer_lhs_over_victim(has_non_region_infer, prev, c) {
+                } else if self.prefer_lhs_over_victim(has_non_region_infer, prev, c.0) {
                     // Ok, keep `prev` instead of the new entry
                     impl_candidate = Some(prev);
                 } else {
@@ -1986,7 +1986,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
         &self,
         has_non_region_infer: bool,
         (lhs, lhs_evaluation): (DefId, EvaluationResult),
-        (victim, victim_evaluation): (DefId, EvaluationResult),
+        victim: DefId,
     ) -> bool {
         let tcx = self.tcx();
         // See if we can toss out `victim` based on specialization.
@@ -2002,14 +2002,6 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
         }
 
         match tcx.impls_are_allowed_to_overlap(lhs, victim) {
-            // For #33140 the impl headers must be exactly equal, the trait must not have
-            // any associated items and there are no where-clauses.
-            //
-            // We can just arbitrarily drop one of the impls.
-            Some(ty::ImplOverlapKind::FutureCompatOrderDepTraitObjects) => {
-                assert_eq!(lhs_evaluation, victim_evaluation);
-                true
-            }
             // For candidates which already reference errors it doesn't really
             // matter what we do 🤷
             Some(ty::ImplOverlapKind::Permitted { marker: false }) => {
@@ -2239,15 +2231,6 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
                 }
             }
 
-            // `Copy` and `Clone` are automatically implemented for an anonymous adt
-            // if all of its fields are `Copy` and `Clone`
-            ty::Adt(adt, args) if adt.is_anonymous() => {
-                // (*) binder moved here
-                Where(obligation.predicate.rebind(
-                    adt.non_enum_variant().fields.iter().map(|f| f.ty(self.tcx(), args)).collect(),
-                ))
-            }
-
             ty::Adt(..) | ty::Alias(..) | ty::Param(..) | ty::Placeholder(..) => {
                 // Fallback to whatever user-defined impls exist in this case.
                 None
diff --git a/compiler/rustc_trait_selection/src/traits/specialize/mod.rs b/compiler/rustc_trait_selection/src/traits/specialize/mod.rs
index cb3e81f5477..448ac558cad 100644
--- a/compiler/rustc_trait_selection/src/traits/specialize/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/specialize/mod.rs
@@ -20,7 +20,7 @@ use rustc_middle::bug;
 use rustc_middle::query::LocalCrate;
 use rustc_middle::ty::print::PrintTraitRefExt as _;
 use rustc_middle::ty::{self, GenericArgsRef, Ty, TyCtxt, TypeVisitableExt, TypingMode};
-use rustc_session::lint::builtin::{COHERENCE_LEAK_CHECK, ORDER_DEPENDENT_TRAIT_OBJECTS};
+use rustc_session::lint::builtin::COHERENCE_LEAK_CHECK;
 use rustc_span::{DUMMY_SP, ErrorGuaranteed, Span, sym};
 use rustc_type_ir::solve::NoSolution;
 use specialization_graph::GraphExt;
@@ -557,13 +557,9 @@ fn report_conflicting_impls<'tcx>(
 
     let msg = || {
         format!(
-            "conflicting implementations of trait `{}`{}{}",
+            "conflicting implementations of trait `{}`{}",
             overlap.trait_ref.print_trait_sugared(),
             overlap.self_ty.map_or_else(String::new, |ty| format!(" for type `{ty}`")),
-            match used_to_be_allowed {
-                Some(FutureCompatOverlapErrorKind::OrderDepTraitObjects) => ": (E0119)",
-                _ => "",
-            }
         )
     };
 
@@ -588,7 +584,6 @@ fn report_conflicting_impls<'tcx>(
         }
         Some(kind) => {
             let lint = match kind {
-                FutureCompatOverlapErrorKind::OrderDepTraitObjects => ORDER_DEPENDENT_TRAIT_OBJECTS,
                 FutureCompatOverlapErrorKind::LeakCheck => COHERENCE_LEAK_CHECK,
             };
             tcx.node_span_lint(lint, tcx.local_def_id_to_hir_id(impl_def_id), impl_span, |err| {
diff --git a/compiler/rustc_trait_selection/src/traits/specialize/specialization_graph.rs b/compiler/rustc_trait_selection/src/traits/specialize/specialization_graph.rs
index 19d3561dd59..9452dca9a4f 100644
--- a/compiler/rustc_trait_selection/src/traits/specialize/specialization_graph.rs
+++ b/compiler/rustc_trait_selection/src/traits/specialize/specialization_graph.rs
@@ -12,7 +12,6 @@ use crate::traits;
 
 #[derive(Copy, Clone, Debug)]
 pub enum FutureCompatOverlapErrorKind {
-    OrderDepTraitObjects,
     LeakCheck,
 }
 
@@ -151,12 +150,6 @@ impl<'tcx> Children {
                 {
                     match overlap_kind {
                         ty::ImplOverlapKind::Permitted { marker: _ } => {}
-                        ty::ImplOverlapKind::FutureCompatOrderDepTraitObjects => {
-                            *last_lint_mut = Some(FutureCompatOverlapError {
-                                error: create_overlap_error(overlap),
-                                kind: FutureCompatOverlapErrorKind::OrderDepTraitObjects,
-                            });
-                        }
                     }
 
                     return Ok((false, false));
diff --git a/compiler/rustc_ty_utils/Cargo.toml b/compiler/rustc_ty_utils/Cargo.toml
index 4c7a57f2931..7e96b64408c 100644
--- a/compiler/rustc_ty_utils/Cargo.toml
+++ b/compiler/rustc_ty_utils/Cargo.toml
@@ -7,6 +7,7 @@ edition = "2024"
 # tidy-alphabetical-start
 itertools = "0.12"
 rustc_abi = { path = "../rustc_abi" }
+rustc_attr_parsing = { path = "../rustc_attr_parsing" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
 rustc_fluent_macro = { path = "../rustc_fluent_macro" }
diff --git a/compiler/rustc_ty_utils/messages.ftl b/compiler/rustc_ty_utils/messages.ftl
index de2c3b63997..8bc7bf10865 100644
--- a/compiler/rustc_ty_utils/messages.ftl
+++ b/compiler/rustc_ty_utils/messages.ftl
@@ -14,6 +14,8 @@ ty_utils_borrow_not_supported = borrowing is not supported in generic constants
 
 ty_utils_box_not_supported = allocations are not allowed in generic constants
 
+ty_utils_by_use_not_supported = .use is not allowed in generic constants
+
 ty_utils_closure_and_return_not_supported = closures and function keywords are not supported in generic constants
 
 ty_utils_const_block_not_supported = const blocks are not supported in generic constants
diff --git a/compiler/rustc_ty_utils/src/assoc.rs b/compiler/rustc_ty_utils/src/assoc.rs
index c8034f4e7b9..c84055f5b84 100644
--- a/compiler/rustc_ty_utils/src/assoc.rs
+++ b/compiler/rustc_ty_utils/src/assoc.rs
@@ -252,7 +252,8 @@ fn associated_type_for_impl_trait_in_trait(
     assert_eq!(tcx.def_kind(trait_def_id), DefKind::Trait);
 
     let span = tcx.def_span(opaque_ty_def_id);
-    let trait_assoc_ty = tcx.at(span).create_def(trait_def_id, kw::Empty, DefKind::AssocTy);
+    // No name because this is a synthetic associated type.
+    let trait_assoc_ty = tcx.at(span).create_def(trait_def_id, None, DefKind::AssocTy);
 
     let local_def_id = trait_assoc_ty.def_id();
     let def_id = local_def_id.to_def_id();
@@ -304,7 +305,8 @@ fn associated_type_for_impl_trait_in_impl(
         hir::FnRetTy::DefaultReturn(_) => tcx.def_span(impl_fn_def_id),
         hir::FnRetTy::Return(ty) => ty.span,
     };
-    let impl_assoc_ty = tcx.at(span).create_def(impl_local_def_id, kw::Empty, DefKind::AssocTy);
+    // No name because this is a synthetic associated type.
+    let impl_assoc_ty = tcx.at(span).create_def(impl_local_def_id, None, DefKind::AssocTy);
 
     let local_def_id = impl_assoc_ty.def_id();
     let def_id = local_def_id.to_def_id();
diff --git a/compiler/rustc_ty_utils/src/common_traits.rs b/compiler/rustc_ty_utils/src/common_traits.rs
index 2157ab3c402..20646cf9a82 100644
--- a/compiler/rustc_ty_utils/src/common_traits.rs
+++ b/compiler/rustc_ty_utils/src/common_traits.rs
@@ -10,6 +10,13 @@ fn is_copy_raw<'tcx>(tcx: TyCtxt<'tcx>, query: ty::PseudoCanonicalInput<'tcx, Ty
     is_item_raw(tcx, query, LangItem::Copy)
 }
 
+fn is_use_cloned_raw<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    query: ty::PseudoCanonicalInput<'tcx, Ty<'tcx>>,
+) -> bool {
+    is_item_raw(tcx, query, LangItem::UseCloned)
+}
+
 fn is_sized_raw<'tcx>(tcx: TyCtxt<'tcx>, query: ty::PseudoCanonicalInput<'tcx, Ty<'tcx>>) -> bool {
     is_item_raw(tcx, query, LangItem::Sized)
 }
@@ -33,5 +40,12 @@ fn is_item_raw<'tcx>(
 }
 
 pub(crate) fn provide(providers: &mut Providers) {
-    *providers = Providers { is_copy_raw, is_sized_raw, is_freeze_raw, is_unpin_raw, ..*providers };
+    *providers = Providers {
+        is_copy_raw,
+        is_use_cloned_raw,
+        is_sized_raw,
+        is_freeze_raw,
+        is_unpin_raw,
+        ..*providers
+    };
 }
diff --git a/compiler/rustc_ty_utils/src/consts.rs b/compiler/rustc_ty_utils/src/consts.rs
index ece796b3c71..b275cd382ab 100644
--- a/compiler/rustc_ty_utils/src/consts.rs
+++ b/compiler/rustc_ty_utils/src/consts.rs
@@ -230,7 +230,9 @@ fn recurse_build<'tcx>(
             error(GenericConstantTooComplexSub::LoopNotSupported(node.span))?
         }
         ExprKind::Box { .. } => error(GenericConstantTooComplexSub::BoxNotSupported(node.span))?,
-
+        ExprKind::ByUse { .. } => {
+            error(GenericConstantTooComplexSub::ByUseNotSupported(node.span))?
+        }
         ExprKind::Unary { .. } => unreachable!(),
         // we handle valid unary/binary ops above
         ExprKind::Binary { .. } => {
@@ -317,6 +319,7 @@ impl<'a, 'tcx> IsThirPolymorphic<'a, 'tcx> {
             | thir::ExprKind::Box { .. }
             | thir::ExprKind::If { .. }
             | thir::ExprKind::Call { .. }
+            | thir::ExprKind::ByUse { .. }
             | thir::ExprKind::Deref { .. }
             | thir::ExprKind::Binary { .. }
             | thir::ExprKind::LogicalOp { .. }
diff --git a/compiler/rustc_ty_utils/src/errors.rs b/compiler/rustc_ty_utils/src/errors.rs
index 8877bb45ceb..0298e7e0e95 100644
--- a/compiler/rustc_ty_utils/src/errors.rs
+++ b/compiler/rustc_ty_utils/src/errors.rs
@@ -55,6 +55,8 @@ pub(crate) enum GenericConstantTooComplexSub {
     BoxNotSupported(#[primary_span] Span),
     #[label(ty_utils_binary_not_supported)]
     BinaryNotSupported(#[primary_span] Span),
+    #[label(ty_utils_by_use_not_supported)]
+    ByUseNotSupported(#[primary_span] Span),
     #[label(ty_utils_logical_op_not_supported)]
     LogicalOpNotSupported(#[primary_span] Span),
     #[label(ty_utils_assign_not_supported)]
diff --git a/compiler/rustc_ty_utils/src/layout.rs b/compiler/rustc_ty_utils/src/layout.rs
index a53f0538c58..7334beb52c9 100644
--- a/compiler/rustc_ty_utils/src/layout.rs
+++ b/compiler/rustc_ty_utils/src/layout.rs
@@ -1,31 +1,25 @@
-use std::fmt::Debug;
-use std::iter;
-
 use hir::def_id::DefId;
 use rustc_abi::Integer::{I8, I32};
 use rustc_abi::Primitive::{self, Float, Int, Pointer};
 use rustc_abi::{
-    AbiAndPrefAlign, AddressSpace, Align, BackendRepr, FIRST_VARIANT, FieldIdx, FieldsShape,
-    HasDataLayout, Layout, LayoutCalculatorError, LayoutData, Niche, ReprOptions, Scalar, Size,
-    StructKind, TagEncoding, VariantIdx, Variants, WrappingRange,
+    AddressSpace, BackendRepr, FIRST_VARIANT, FieldIdx, FieldsShape, HasDataLayout, Layout,
+    LayoutCalculatorError, LayoutData, Niche, ReprOptions, Scalar, Size, StructKind, TagEncoding,
+    VariantIdx, Variants, WrappingRange,
 };
 use rustc_hashes::Hash64;
-use rustc_index::bit_set::DenseBitSet;
-use rustc_index::{IndexSlice, IndexVec};
+use rustc_index::IndexVec;
 use rustc_middle::bug;
-use rustc_middle::mir::{CoroutineLayout, CoroutineSavedLocal};
 use rustc_middle::query::Providers;
 use rustc_middle::ty::layout::{
-    FloatExt, HasTyCtxt, IntegerExt, LayoutCx, LayoutError, LayoutOf, MAX_SIMD_LANES, TyAndLayout,
+    FloatExt, HasTyCtxt, IntegerExt, LayoutCx, LayoutError, LayoutOf, TyAndLayout,
 };
 use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_middle::ty::{
-    self, AdtDef, CoroutineArgsExt, EarlyBinder, GenericArgsRef, PseudoCanonicalInput, Ty, TyCtxt,
-    TypeVisitableExt,
+    self, AdtDef, CoroutineArgsExt, EarlyBinder, PseudoCanonicalInput, Ty, TyCtxt, TypeVisitableExt,
 };
 use rustc_session::{DataTypeKind, FieldInfo, FieldKind, SizeKind, VariantInfo};
 use rustc_span::{Symbol, sym};
-use tracing::{debug, instrument, trace};
+use tracing::{debug, instrument};
 use {rustc_abi as abi, rustc_hir as hir};
 
 use crate::errors::{NonPrimitiveSimdType, OversizedSimdType, ZeroLengthSimdType};
@@ -124,20 +118,23 @@ fn map_error<'tcx>(
                 .delayed_bug(format!("computed impossible repr (packed enum?): {ty:?}"));
             LayoutError::ReferencesError(guar)
         }
+        LayoutCalculatorError::ZeroLengthSimdType => {
+            // Can't be caught in typeck if the array length is generic.
+            cx.tcx().dcx().emit_fatal(ZeroLengthSimdType { ty })
+        }
+        LayoutCalculatorError::OversizedSimdType { max_lanes } => {
+            // Can't be caught in typeck if the array length is generic.
+            cx.tcx().dcx().emit_fatal(OversizedSimdType { ty, max_lanes })
+        }
+        LayoutCalculatorError::NonPrimitiveSimdType(field) => {
+            // This error isn't caught in typeck, e.g., if
+            // the element type of the vector is generic.
+            cx.tcx().dcx().emit_fatal(NonPrimitiveSimdType { ty, e_ty: field.ty })
+        }
     };
     error(cx, err)
 }
 
-fn univariant_uninterned<'tcx>(
-    cx: &LayoutCx<'tcx>,
-    ty: Ty<'tcx>,
-    fields: &IndexSlice<FieldIdx, TyAndLayout<'tcx>>,
-    kind: StructKind,
-) -> Result<LayoutData<FieldIdx, VariantIdx>, &'tcx LayoutError<'tcx>> {
-    let repr = ReprOptions::default();
-    cx.calc.univariant(fields, &repr, kind).map_err(|err| map_error(cx, ty, err))
-}
-
 fn extract_const_value<'tcx>(
     cx: &LayoutCx<'tcx>,
     ty: Ty<'tcx>,
@@ -188,6 +185,10 @@ fn layout_of_uncached<'tcx>(
 
     let tcx = cx.tcx();
     let dl = cx.data_layout();
+    let map_layout = |result: Result<_, _>| match result {
+        Ok(layout) => Ok(tcx.mk_layout(layout)),
+        Err(err) => Err(map_error(cx, ty, err)),
+    };
     let scalar_unit = |value: Primitive| {
         let size = value.size(dl);
         assert!(size.bits() <= 128);
@@ -195,8 +196,10 @@ fn layout_of_uncached<'tcx>(
     };
     let scalar = |value: Primitive| tcx.mk_layout(LayoutData::scalar(cx, scalar_unit(value)));
 
-    let univariant = |fields: &IndexSlice<FieldIdx, TyAndLayout<'tcx>>, kind| {
-        Ok(tcx.mk_layout(univariant_uninterned(cx, ty, fields, kind)?))
+    let univariant = |tys: &[Ty<'tcx>], kind| {
+        let fields = tys.iter().map(|ty| cx.layout_of(*ty)).try_collect::<IndexVec<_, _>>()?;
+        let repr = ReprOptions::default();
+        map_layout(cx.calc.univariant(&fields, &repr, kind))
     };
     debug_assert!(!ty.has_non_region_infer());
 
@@ -217,6 +220,34 @@ fn layout_of_uncached<'tcx>(
                             .try_to_bits(tcx, cx.typing_env)
                             .ok_or_else(|| error(cx, LayoutError::Unknown(ty)))?;
 
+                        // FIXME(pattern_types): create implied bounds from pattern types in signatures
+                        // that require that the range end is >= the range start so that we can't hit
+                        // this error anymore without first having hit a trait solver error.
+                        // Very fuzzy on the details here, but pattern types are an internal impl detail,
+                        // so we can just go with this for now
+                        if scalar.is_signed() {
+                            let range = scalar.valid_range_mut();
+                            let start = layout.size.sign_extend(range.start);
+                            let end = layout.size.sign_extend(range.end);
+                            if end < start {
+                                let guar = tcx.dcx().err(format!(
+                                    "pattern type ranges cannot wrap: {start}..={end}"
+                                ));
+
+                                return Err(error(cx, LayoutError::ReferencesError(guar)));
+                            }
+                        } else {
+                            let range = scalar.valid_range_mut();
+                            if range.end < range.start {
+                                let guar = tcx.dcx().err(format!(
+                                    "pattern type ranges cannot wrap: {}..={}",
+                                    range.start, range.end
+                                ));
+
+                                return Err(error(cx, LayoutError::ReferencesError(guar)));
+                            }
+                        };
+
                         let niche = Niche {
                             offset: Size::ZERO,
                             value: scalar.primitive(),
@@ -258,7 +289,7 @@ fn layout_of_uncached<'tcx>(
         }
 
         // The never type.
-        ty::Never => tcx.mk_layout(cx.calc.layout_of_never_type()),
+        ty::Never => tcx.mk_layout(LayoutData::never_type(cx)),
 
         // Potentially-wide pointers.
         ty::Ref(_, pointee, _) | ty::RawPtr(pointee, _) => {
@@ -329,7 +360,7 @@ fn layout_of_uncached<'tcx>(
             };
 
             // Effectively a (ptr, meta) tuple.
-            tcx.mk_layout(cx.calc.scalar_pair(data_ptr, metadata))
+            tcx.mk_layout(LayoutData::scalar_pair(cx, data_ptr, metadata))
         }
 
         ty::Dynamic(_, _, ty::DynStar) => {
@@ -337,7 +368,7 @@ fn layout_of_uncached<'tcx>(
             data.valid_range_mut().start = 0;
             let mut vtable = scalar_unit(Pointer(AddressSpace::DATA));
             vtable.valid_range_mut().start = 1;
-            tcx.mk_layout(cx.calc.scalar_pair(data, vtable))
+            tcx.mk_layout(LayoutData::scalar_pair(cx, data, vtable))
         }
 
         // Arrays and slices.
@@ -347,96 +378,87 @@ fn layout_of_uncached<'tcx>(
                 .ok_or_else(|| error(cx, LayoutError::Unknown(ty)))?;
 
             let element = cx.layout_of(element)?;
-            let size = element
-                .size
-                .checked_mul(count, dl)
-                .ok_or_else(|| error(cx, LayoutError::SizeOverflow(ty)))?;
-
-            let abi = BackendRepr::Memory { sized: true };
-
-            let largest_niche = if count != 0 { element.largest_niche } else { None };
-            let uninhabited = if count != 0 { element.uninhabited } else { false };
-
-            tcx.mk_layout(LayoutData {
-                variants: Variants::Single { index: FIRST_VARIANT },
-                fields: FieldsShape::Array { stride: element.size, count },
-                backend_repr: abi,
-                largest_niche,
-                uninhabited,
-                align: element.align,
-                size,
-                max_repr_align: None,
-                unadjusted_abi_align: element.align.abi,
-                randomization_seed: element.randomization_seed.wrapping_add(Hash64::new(count)),
-            })
+            map_layout(cx.calc.array_like(&element, Some(count)))?
         }
         ty::Slice(element) => {
             let element = cx.layout_of(element)?;
-            tcx.mk_layout(LayoutData {
-                variants: Variants::Single { index: FIRST_VARIANT },
-                fields: FieldsShape::Array { stride: element.size, count: 0 },
-                backend_repr: BackendRepr::Memory { sized: false },
-                largest_niche: None,
-                uninhabited: false,
-                align: element.align,
-                size: Size::ZERO,
-                max_repr_align: None,
-                unadjusted_abi_align: element.align.abi,
-                // adding a randomly chosen value to distinguish slices
-                randomization_seed: element
-                    .randomization_seed
-                    .wrapping_add(Hash64::new(0x2dcba99c39784102)),
-            })
+            map_layout(cx.calc.array_like(&element, None).map(|mut layout| {
+                // a randomly chosen value to distinguish slices
+                layout.randomization_seed = Hash64::new(0x2dcba99c39784102);
+                layout
+            }))?
+        }
+        ty::Str => {
+            let element = scalar(Int(I8, false));
+            map_layout(cx.calc.array_like(&element, None).map(|mut layout| {
+                // another random value
+                layout.randomization_seed = Hash64::new(0xc1325f37d127be22);
+                layout
+            }))?
         }
-        ty::Str => tcx.mk_layout(LayoutData {
-            variants: Variants::Single { index: FIRST_VARIANT },
-            fields: FieldsShape::Array { stride: Size::from_bytes(1), count: 0 },
-            backend_repr: BackendRepr::Memory { sized: false },
-            largest_niche: None,
-            uninhabited: false,
-            align: dl.i8_align,
-            size: Size::ZERO,
-            max_repr_align: None,
-            unadjusted_abi_align: dl.i8_align.abi,
-            // another random value
-            randomization_seed: Hash64::new(0xc1325f37d127be22),
-        }),
 
         // Odd unit types.
-        ty::FnDef(..) => univariant(IndexSlice::empty(), StructKind::AlwaysSized)?,
-        ty::Dynamic(_, _, ty::Dyn) | ty::Foreign(..) => {
-            let mut unit =
-                univariant_uninterned(cx, ty, IndexSlice::empty(), StructKind::AlwaysSized)?;
-            match unit.backend_repr {
-                BackendRepr::Memory { ref mut sized } => *sized = false,
-                _ => bug!(),
-            }
-            tcx.mk_layout(unit)
+        ty::FnDef(..) | ty::Dynamic(_, _, ty::Dyn) | ty::Foreign(..) => {
+            let sized = matches!(ty.kind(), ty::FnDef(..));
+            tcx.mk_layout(LayoutData::unit(cx, sized))
         }
 
-        ty::Coroutine(def_id, args) => coroutine_layout(cx, ty, def_id, args)?,
+        ty::Coroutine(def_id, args) => {
+            use rustc_middle::ty::layout::PrimitiveExt as _;
+
+            let Some(info) = tcx.coroutine_layout(def_id, args.as_coroutine().kind_ty()) else {
+                return Err(error(cx, LayoutError::Unknown(ty)));
+            };
 
-        ty::Closure(_, args) => {
-            let tys = args.as_closure().upvar_tys();
-            univariant(
-                &tys.iter().map(|ty| cx.layout_of(ty)).try_collect::<IndexVec<_, _>>()?,
-                StructKind::AlwaysSized,
-            )?
+            let local_layouts = info
+                .field_tys
+                .iter()
+                .map(|local| {
+                    let field_ty = EarlyBinder::bind(local.ty);
+                    let uninit_ty = Ty::new_maybe_uninit(tcx, field_ty.instantiate(tcx, args));
+                    cx.spanned_layout_of(uninit_ty, local.source_info.span)
+                })
+                .try_collect::<IndexVec<_, _>>()?;
+
+            let prefix_layouts = args
+                .as_coroutine()
+                .prefix_tys()
+                .iter()
+                .map(|ty| cx.layout_of(ty))
+                .try_collect::<IndexVec<_, _>>()?;
+
+            let layout = cx
+                .calc
+                .coroutine(
+                    &local_layouts,
+                    prefix_layouts,
+                    &info.variant_fields,
+                    &info.storage_conflicts,
+                    |tag| TyAndLayout {
+                        ty: tag.primitive().to_ty(tcx),
+                        layout: tcx.mk_layout(LayoutData::scalar(cx, tag)),
+                    },
+                )
+                .map(|mut layout| {
+                    // this is similar to how ReprOptions populates its field_shuffle_seed
+                    layout.randomization_seed = tcx.def_path_hash(def_id).0.to_smaller_hash();
+                    debug!("coroutine layout ({:?}): {:#?}", ty, layout);
+                    layout
+                });
+            map_layout(layout)?
         }
 
+        ty::Closure(_, args) => univariant(args.as_closure().upvar_tys(), StructKind::AlwaysSized)?,
+
         ty::CoroutineClosure(_, args) => {
-            let tys = args.as_coroutine_closure().upvar_tys();
-            univariant(
-                &tys.iter().map(|ty| cx.layout_of(ty)).try_collect::<IndexVec<_, _>>()?,
-                StructKind::AlwaysSized,
-            )?
+            univariant(args.as_coroutine_closure().upvar_tys(), StructKind::AlwaysSized)?
         }
 
         ty::Tuple(tys) => {
             let kind =
                 if tys.len() == 0 { StructKind::AlwaysSized } else { StructKind::MaybeUnsized };
 
-            univariant(&tys.iter().map(|k| cx.layout_of(k)).try_collect::<IndexVec<_, _>>()?, kind)?
+            univariant(tys, kind)?
         }
 
         // SIMD vector types.
@@ -461,65 +483,9 @@ fn layout_of_uncached<'tcx>(
                 .try_to_target_usize(tcx)
                 .ok_or_else(|| error(cx, LayoutError::Unknown(ty)))?;
 
-            // SIMD vectors of zero length are not supported.
-            // Additionally, lengths are capped at 2^16 as a fixed maximum backends must
-            // support.
-            //
-            // Can't be caught in typeck if the array length is generic.
-            if e_len == 0 {
-                tcx.dcx().emit_fatal(ZeroLengthSimdType { ty });
-            } else if e_len > MAX_SIMD_LANES {
-                tcx.dcx().emit_fatal(OversizedSimdType { ty, max_lanes: MAX_SIMD_LANES });
-            }
-
-            // Compute the ABI of the element type:
             let e_ly = cx.layout_of(e_ty)?;
-            let BackendRepr::Scalar(e_abi) = e_ly.backend_repr else {
-                // This error isn't caught in typeck, e.g., if
-                // the element type of the vector is generic.
-                tcx.dcx().emit_fatal(NonPrimitiveSimdType { ty, e_ty });
-            };
 
-            // Compute the size and alignment of the vector:
-            let size = e_ly
-                .size
-                .checked_mul(e_len, dl)
-                .ok_or_else(|| error(cx, LayoutError::SizeOverflow(ty)))?;
-
-            let (abi, align) = if def.repr().packed() && !e_len.is_power_of_two() {
-                // Non-power-of-two vectors have padding up to the next power-of-two.
-                // If we're a packed repr, remove the padding while keeping the alignment as close
-                // to a vector as possible.
-                (
-                    BackendRepr::Memory { sized: true },
-                    AbiAndPrefAlign {
-                        abi: Align::max_aligned_factor(size),
-                        pref: dl.llvmlike_vector_align(size).pref,
-                    },
-                )
-            } else {
-                (
-                    BackendRepr::SimdVector { element: e_abi, count: e_len },
-                    dl.llvmlike_vector_align(size),
-                )
-            };
-            let size = size.align_to(align.abi);
-
-            tcx.mk_layout(LayoutData {
-                variants: Variants::Single { index: FIRST_VARIANT },
-                fields: FieldsShape::Arbitrary {
-                    offsets: [Size::ZERO].into(),
-                    memory_index: [0].into(),
-                },
-                backend_repr: abi,
-                largest_niche: e_ly.largest_niche,
-                uninhabited: false,
-                size,
-                align,
-                max_repr_align: None,
-                unadjusted_abi_align: align.abi,
-                randomization_seed: e_ly.randomization_seed.wrapping_add(Hash64::new(e_len)),
-            })
+            map_layout(cx.calc.simd_type(e_ly, e_len, def.repr().packed()))?
         }
 
         // ADTs.
@@ -545,11 +511,7 @@ fn layout_of_uncached<'tcx>(
                     return Err(error(cx, LayoutError::ReferencesError(guar)));
                 }
 
-                return Ok(tcx.mk_layout(
-                    cx.calc
-                        .layout_of_union(&def.repr(), &variants)
-                        .map_err(|err| map_error(cx, ty, err))?,
-                ));
+                return map_layout(cx.calc.layout_of_union(&def.repr(), &variants));
             }
 
             let get_discriminant_type =
@@ -677,335 +639,6 @@ fn layout_of_uncached<'tcx>(
     })
 }
 
-/// Overlap eligibility and variant assignment for each CoroutineSavedLocal.
-#[derive(Clone, Debug, PartialEq)]
-enum SavedLocalEligibility {
-    Unassigned,
-    Assigned(VariantIdx),
-    Ineligible(Option<FieldIdx>),
-}
-
-// When laying out coroutines, we divide our saved local fields into two
-// categories: overlap-eligible and overlap-ineligible.
-//
-// Those fields which are ineligible for overlap go in a "prefix" at the
-// beginning of the layout, and always have space reserved for them.
-//
-// Overlap-eligible fields are only assigned to one variant, so we lay
-// those fields out for each variant and put them right after the
-// prefix.
-//
-// Finally, in the layout details, we point to the fields from the
-// variants they are assigned to. It is possible for some fields to be
-// included in multiple variants. No field ever "moves around" in the
-// layout; its offset is always the same.
-//
-// Also included in the layout are the upvars and the discriminant.
-// These are included as fields on the "outer" layout; they are not part
-// of any variant.
-
-/// Compute the eligibility and assignment of each local.
-fn coroutine_saved_local_eligibility(
-    info: &CoroutineLayout<'_>,
-) -> (DenseBitSet<CoroutineSavedLocal>, IndexVec<CoroutineSavedLocal, SavedLocalEligibility>) {
-    use SavedLocalEligibility::*;
-
-    let mut assignments: IndexVec<CoroutineSavedLocal, SavedLocalEligibility> =
-        IndexVec::from_elem(Unassigned, &info.field_tys);
-
-    // The saved locals not eligible for overlap. These will get
-    // "promoted" to the prefix of our coroutine.
-    let mut ineligible_locals = DenseBitSet::new_empty(info.field_tys.len());
-
-    // Figure out which of our saved locals are fields in only
-    // one variant. The rest are deemed ineligible for overlap.
-    for (variant_index, fields) in info.variant_fields.iter_enumerated() {
-        for local in fields {
-            match assignments[*local] {
-                Unassigned => {
-                    assignments[*local] = Assigned(variant_index);
-                }
-                Assigned(idx) => {
-                    // We've already seen this local at another suspension
-                    // point, so it is no longer a candidate.
-                    trace!(
-                        "removing local {:?} in >1 variant ({:?}, {:?})",
-                        local, variant_index, idx
-                    );
-                    ineligible_locals.insert(*local);
-                    assignments[*local] = Ineligible(None);
-                }
-                Ineligible(_) => {}
-            }
-        }
-    }
-
-    // Next, check every pair of eligible locals to see if they
-    // conflict.
-    for local_a in info.storage_conflicts.rows() {
-        let conflicts_a = info.storage_conflicts.count(local_a);
-        if ineligible_locals.contains(local_a) {
-            continue;
-        }
-
-        for local_b in info.storage_conflicts.iter(local_a) {
-            // local_a and local_b are storage live at the same time, therefore they
-            // cannot overlap in the coroutine layout. The only way to guarantee
-            // this is if they are in the same variant, or one is ineligible
-            // (which means it is stored in every variant).
-            if ineligible_locals.contains(local_b) || assignments[local_a] == assignments[local_b] {
-                continue;
-            }
-
-            // If they conflict, we will choose one to make ineligible.
-            // This is not always optimal; it's just a greedy heuristic that
-            // seems to produce good results most of the time.
-            let conflicts_b = info.storage_conflicts.count(local_b);
-            let (remove, other) =
-                if conflicts_a > conflicts_b { (local_a, local_b) } else { (local_b, local_a) };
-            ineligible_locals.insert(remove);
-            assignments[remove] = Ineligible(None);
-            trace!("removing local {:?} due to conflict with {:?}", remove, other);
-        }
-    }
-
-    // Count the number of variants in use. If only one of them, then it is
-    // impossible to overlap any locals in our layout. In this case it's
-    // always better to make the remaining locals ineligible, so we can
-    // lay them out with the other locals in the prefix and eliminate
-    // unnecessary padding bytes.
-    {
-        let mut used_variants = DenseBitSet::new_empty(info.variant_fields.len());
-        for assignment in &assignments {
-            if let Assigned(idx) = assignment {
-                used_variants.insert(*idx);
-            }
-        }
-        if used_variants.count() < 2 {
-            for assignment in assignments.iter_mut() {
-                *assignment = Ineligible(None);
-            }
-            ineligible_locals.insert_all();
-        }
-    }
-
-    // Write down the order of our locals that will be promoted to the prefix.
-    {
-        for (idx, local) in ineligible_locals.iter().enumerate() {
-            assignments[local] = Ineligible(Some(FieldIdx::from_usize(idx)));
-        }
-    }
-    debug!("coroutine saved local assignments: {:?}", assignments);
-
-    (ineligible_locals, assignments)
-}
-
-/// Compute the full coroutine layout.
-fn coroutine_layout<'tcx>(
-    cx: &LayoutCx<'tcx>,
-    ty: Ty<'tcx>,
-    def_id: hir::def_id::DefId,
-    args: GenericArgsRef<'tcx>,
-) -> Result<Layout<'tcx>, &'tcx LayoutError<'tcx>> {
-    use SavedLocalEligibility::*;
-    let tcx = cx.tcx();
-    let instantiate_field = |ty: Ty<'tcx>| EarlyBinder::bind(ty).instantiate(tcx, args);
-
-    let Some(info) = tcx.coroutine_layout(def_id, args.as_coroutine().kind_ty()) else {
-        return Err(error(cx, LayoutError::Unknown(ty)));
-    };
-    let (ineligible_locals, assignments) = coroutine_saved_local_eligibility(info);
-
-    // Build a prefix layout, including "promoting" all ineligible
-    // locals as part of the prefix. We compute the layout of all of
-    // these fields at once to get optimal packing.
-    let tag_index = args.as_coroutine().prefix_tys().len();
-
-    // `info.variant_fields` already accounts for the reserved variants, so no need to add them.
-    let max_discr = (info.variant_fields.len() - 1) as u128;
-    let discr_int = abi::Integer::fit_unsigned(max_discr);
-    let tag = Scalar::Initialized {
-        value: Primitive::Int(discr_int, /* signed = */ false),
-        valid_range: WrappingRange { start: 0, end: max_discr },
-    };
-    let tag_layout = TyAndLayout {
-        ty: discr_int.to_ty(tcx, /* signed = */ false),
-        layout: tcx.mk_layout(LayoutData::scalar(cx, tag)),
-    };
-
-    let promoted_layouts = ineligible_locals.iter().map(|local| {
-        let field_ty = instantiate_field(info.field_tys[local].ty);
-        let uninit_ty = Ty::new_maybe_uninit(tcx, field_ty);
-        cx.spanned_layout_of(uninit_ty, info.field_tys[local].source_info.span)
-    });
-    let prefix_layouts = args
-        .as_coroutine()
-        .prefix_tys()
-        .iter()
-        .map(|ty| cx.layout_of(ty))
-        .chain(iter::once(Ok(tag_layout)))
-        .chain(promoted_layouts)
-        .try_collect::<IndexVec<_, _>>()?;
-    let prefix = univariant_uninterned(cx, ty, &prefix_layouts, StructKind::AlwaysSized)?;
-
-    let (prefix_size, prefix_align) = (prefix.size, prefix.align);
-
-    // Split the prefix layout into the "outer" fields (upvars and
-    // discriminant) and the "promoted" fields. Promoted fields will
-    // get included in each variant that requested them in
-    // CoroutineLayout.
-    debug!("prefix = {:#?}", prefix);
-    let (outer_fields, promoted_offsets, promoted_memory_index) = match prefix.fields {
-        FieldsShape::Arbitrary { mut offsets, memory_index } => {
-            let mut inverse_memory_index = memory_index.invert_bijective_mapping();
-
-            // "a" (`0..b_start`) and "b" (`b_start..`) correspond to
-            // "outer" and "promoted" fields respectively.
-            let b_start = FieldIdx::from_usize(tag_index + 1);
-            let offsets_b = IndexVec::from_raw(offsets.raw.split_off(b_start.as_usize()));
-            let offsets_a = offsets;
-
-            // Disentangle the "a" and "b" components of `inverse_memory_index`
-            // by preserving the order but keeping only one disjoint "half" each.
-            // FIXME(eddyb) build a better abstraction for permutations, if possible.
-            let inverse_memory_index_b: IndexVec<u32, FieldIdx> = inverse_memory_index
-                .iter()
-                .filter_map(|&i| i.as_u32().checked_sub(b_start.as_u32()).map(FieldIdx::from_u32))
-                .collect();
-            inverse_memory_index.raw.retain(|&i| i < b_start);
-            let inverse_memory_index_a = inverse_memory_index;
-
-            // Since `inverse_memory_index_{a,b}` each only refer to their
-            // respective fields, they can be safely inverted
-            let memory_index_a = inverse_memory_index_a.invert_bijective_mapping();
-            let memory_index_b = inverse_memory_index_b.invert_bijective_mapping();
-
-            let outer_fields =
-                FieldsShape::Arbitrary { offsets: offsets_a, memory_index: memory_index_a };
-            (outer_fields, offsets_b, memory_index_b)
-        }
-        _ => bug!(),
-    };
-
-    let mut size = prefix.size;
-    let mut align = prefix.align;
-    let variants = info
-        .variant_fields
-        .iter_enumerated()
-        .map(|(index, variant_fields)| {
-            // Only include overlap-eligible fields when we compute our variant layout.
-            let variant_only_tys = variant_fields
-                .iter()
-                .filter(|local| match assignments[**local] {
-                    Unassigned => bug!(),
-                    Assigned(v) if v == index => true,
-                    Assigned(_) => bug!("assignment does not match variant"),
-                    Ineligible(_) => false,
-                })
-                .map(|local| {
-                    let field_ty = instantiate_field(info.field_tys[*local].ty);
-                    Ty::new_maybe_uninit(tcx, field_ty)
-                });
-
-            let mut variant = univariant_uninterned(
-                cx,
-                ty,
-                &variant_only_tys.map(|ty| cx.layout_of(ty)).try_collect::<IndexVec<_, _>>()?,
-                StructKind::Prefixed(prefix_size, prefix_align.abi),
-            )?;
-            variant.variants = Variants::Single { index };
-
-            let FieldsShape::Arbitrary { offsets, memory_index } = variant.fields else {
-                bug!();
-            };
-
-            // Now, stitch the promoted and variant-only fields back together in
-            // the order they are mentioned by our CoroutineLayout.
-            // Because we only use some subset (that can differ between variants)
-            // of the promoted fields, we can't just pick those elements of the
-            // `promoted_memory_index` (as we'd end up with gaps).
-            // So instead, we build an "inverse memory_index", as if all of the
-            // promoted fields were being used, but leave the elements not in the
-            // subset as `INVALID_FIELD_IDX`, which we can filter out later to
-            // obtain a valid (bijective) mapping.
-            const INVALID_FIELD_IDX: FieldIdx = FieldIdx::MAX;
-            debug_assert!(variant_fields.next_index() <= INVALID_FIELD_IDX);
-
-            let mut combined_inverse_memory_index = IndexVec::from_elem_n(
-                INVALID_FIELD_IDX,
-                promoted_memory_index.len() + memory_index.len(),
-            );
-            let mut offsets_and_memory_index = iter::zip(offsets, memory_index);
-            let combined_offsets = variant_fields
-                .iter_enumerated()
-                .map(|(i, local)| {
-                    let (offset, memory_index) = match assignments[*local] {
-                        Unassigned => bug!(),
-                        Assigned(_) => {
-                            let (offset, memory_index) = offsets_and_memory_index.next().unwrap();
-                            (offset, promoted_memory_index.len() as u32 + memory_index)
-                        }
-                        Ineligible(field_idx) => {
-                            let field_idx = field_idx.unwrap();
-                            (promoted_offsets[field_idx], promoted_memory_index[field_idx])
-                        }
-                    };
-                    combined_inverse_memory_index[memory_index] = i;
-                    offset
-                })
-                .collect();
-
-            // Remove the unused slots and invert the mapping to obtain the
-            // combined `memory_index` (also see previous comment).
-            combined_inverse_memory_index.raw.retain(|&i| i != INVALID_FIELD_IDX);
-            let combined_memory_index = combined_inverse_memory_index.invert_bijective_mapping();
-
-            variant.fields = FieldsShape::Arbitrary {
-                offsets: combined_offsets,
-                memory_index: combined_memory_index,
-            };
-
-            size = size.max(variant.size);
-            align = align.max(variant.align);
-            Ok(variant)
-        })
-        .try_collect::<IndexVec<VariantIdx, _>>()?;
-
-    size = size.align_to(align.abi);
-
-    let uninhabited = prefix.uninhabited || variants.iter().all(|v| v.is_uninhabited());
-    let abi = BackendRepr::Memory { sized: true };
-
-    // this is similar to how ReprOptions populates its field_shuffle_seed
-    let def_hash = tcx.def_path_hash(def_id).0.to_smaller_hash();
-
-    let layout = tcx.mk_layout(LayoutData {
-        variants: Variants::Multiple {
-            tag,
-            tag_encoding: TagEncoding::Direct,
-            tag_field: tag_index,
-            variants,
-        },
-        fields: outer_fields,
-        backend_repr: abi,
-        // Suppress niches inside coroutines. If the niche is inside a field that is aliased (due to
-        // self-referentiality), getting the discriminant can cause aliasing violations.
-        // `UnsafeCell` blocks niches for the same reason, but we don't yet have `UnsafePinned` that
-        // would do the same for us here.
-        // See <https://github.com/rust-lang/rust/issues/63818>, <https://github.com/rust-lang/miri/issues/3780>.
-        // FIXME: Remove when <https://github.com/rust-lang/rust/issues/125735> is implemented and aliased coroutine fields are wrapped in `UnsafePinned`.
-        largest_niche: None,
-        uninhabited,
-        size,
-        align,
-        max_repr_align: None,
-        unadjusted_abi_align: align.abi,
-        randomization_seed: def_hash,
-    });
-    debug!("coroutine layout ({:?}): {:#?}", ty, layout);
-    Ok(layout)
-}
-
 fn record_layout_for_printing<'tcx>(cx: &LayoutCx<'tcx>, layout: TyAndLayout<'tcx>) {
     // Ignore layouts that are done with non-empty environments or
     // non-monomorphic layouts, as the user only wants to see the stuff
diff --git a/compiler/rustc_ty_utils/src/opaque_types.rs b/compiler/rustc_ty_utils/src/opaque_types.rs
index 98881905bcf..a107925fb18 100644
--- a/compiler/rustc_ty_utils/src/opaque_types.rs
+++ b/compiler/rustc_ty_utils/src/opaque_types.rs
@@ -1,8 +1,8 @@
 use rustc_data_structures::fx::FxHashSet;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::LocalDefId;
+use rustc_hir::intravisit;
 use rustc_hir::intravisit::Visitor;
-use rustc_hir::{CRATE_HIR_ID, intravisit};
 use rustc_middle::bug;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::util::{CheckRegions, NotUniqueParam};
@@ -30,14 +30,21 @@ enum CollectionMode {
     /// For impl trait in assoc types we only permit collecting them from
     /// associated types of the same impl block.
     ImplTraitInAssocTypes,
-    TypeAliasImplTraitTransition,
+    /// When collecting for an explicit `#[define_opaque]` attribute, find all TAITs
+    Taits,
+    /// The default case, only collect RPITs and AsyncFn return types, as these are
+    /// always defined by the current item.
+    RpitAndAsyncFnOnly,
 }
 
 impl<'tcx> OpaqueTypeCollector<'tcx> {
     fn new(tcx: TyCtxt<'tcx>, item: LocalDefId) -> Self {
-        let mode = match tcx.def_kind(tcx.local_parent(item)) {
-            DefKind::Impl { of_trait: true } => CollectionMode::ImplTraitInAssocTypes,
-            _ => CollectionMode::TypeAliasImplTraitTransition,
+        let mode = match tcx.def_kind(item) {
+            DefKind::AssocConst | DefKind::AssocFn | DefKind::AssocTy => {
+                CollectionMode::ImplTraitInAssocTypes
+            }
+            DefKind::TyAlias => CollectionMode::Taits,
+            _ => CollectionMode::RpitAndAsyncFnOnly,
         };
         Self { tcx, opaques: Vec::new(), item, seen: Default::default(), span: None, mode }
     }
@@ -73,40 +80,6 @@ impl<'tcx> OpaqueTypeCollector<'tcx> {
         }
     }
 
-    /// Returns `true` if `opaque_hir_id` is a sibling or a child of a sibling of `self.item`.
-    ///
-    /// Example:
-    /// ```ignore UNSOLVED (is this a bug?)
-    /// # #![feature(type_alias_impl_trait)]
-    /// pub mod foo {
-    ///     pub mod bar {
-    ///         pub trait Bar { /* ... */ }
-    ///         pub type Baz = impl Bar;
-    ///
-    ///         # impl Bar for () {}
-    ///         fn f1() -> Baz { /* ... */ }
-    ///     }
-    ///     fn f2() -> bar::Baz { /* ... */ }
-    /// }
-    /// ```
-    ///
-    /// and `opaque_def_id` is the `DefId` of the definition of the opaque type `Baz`.
-    /// For the above example, this function returns `true` for `f1` and `false` for `f2`.
-    #[instrument(level = "trace", skip(self), ret)]
-    fn check_tait_defining_scope(&self, opaque_def_id: LocalDefId) -> bool {
-        let mut hir_id = self.tcx.local_def_id_to_hir_id(self.item);
-        let opaque_hir_id = self.tcx.local_def_id_to_hir_id(opaque_def_id);
-
-        // Named opaque types can be defined by any siblings or children of siblings.
-        let scope = self.tcx.hir_get_defining_scope(opaque_hir_id);
-        // We walk up the node tree until we hit the root or the scope of the opaque type.
-        while hir_id != scope && hir_id != CRATE_HIR_ID {
-            hir_id = self.tcx.hir_get_parent_item(hir_id).into();
-        }
-        // Syntactically, we are allowed to define the concrete type if:
-        hir_id == scope
-    }
-
     #[instrument(level = "trace", skip(self))]
     fn collect_taits_declared_in_body(&mut self) {
         let body = self.tcx.hir_body_owned_by(self.item).value;
@@ -139,18 +112,31 @@ impl<'tcx> OpaqueTypeCollector<'tcx> {
         }
 
         // TAITs outside their defining scopes are ignored.
-        let origin = self.tcx.local_opaque_ty_origin(alias_ty.def_id.expect_local());
-        trace!(?origin);
-        match origin {
+        match self.tcx.local_opaque_ty_origin(alias_ty.def_id.expect_local()) {
             rustc_hir::OpaqueTyOrigin::FnReturn { .. }
             | rustc_hir::OpaqueTyOrigin::AsyncFn { .. } => {}
-            rustc_hir::OpaqueTyOrigin::TyAlias { in_assoc_ty, .. } => {
-                if !in_assoc_ty && !self.check_tait_defining_scope(alias_ty.def_id.expect_local()) {
-                    return;
+            rustc_hir::OpaqueTyOrigin::TyAlias { in_assoc_ty, .. } => match self.mode {
+                // If we are collecting opaques in an assoc method, we are only looking at assoc types
+                // mentioned in the assoc method and only at opaques defined in there. We do not
+                // want to collect TAITs
+                CollectionMode::ImplTraitInAssocTypes => {
+                    if !in_assoc_ty {
+                        return;
+                    }
                 }
-            }
+                // If we are collecting opaques referenced from a `define_opaque` attribute, we
+                // do not want to look at opaques defined in associated types. Those can only be
+                // defined by methods on the same impl.
+                CollectionMode::Taits => {
+                    if in_assoc_ty {
+                        return;
+                    }
+                }
+                CollectionMode::RpitAndAsyncFnOnly => return,
+            },
         }
 
+        trace!(?alias_ty, "adding");
         self.opaques.push(alias_ty.def_id.expect_local());
 
         let parent_count = self.tcx.generics_of(alias_ty.def_id).parent_count;
@@ -192,6 +178,32 @@ impl<'tcx> OpaqueTypeCollector<'tcx> {
             }
         }
     }
+
+    /// Checks the `#[define_opaque]` attributes on items and collectes opaques to define
+    /// from the referenced types.
+    #[instrument(level = "trace", skip(self))]
+    fn collect_taits_from_defines_attr(&mut self) {
+        let hir_id = self.tcx.local_def_id_to_hir_id(self.item);
+        if !hir_id.is_owner() {
+            return;
+        }
+        let Some(defines) = self.tcx.hir_attrs(hir_id.owner).define_opaque else {
+            return;
+        };
+        for &(span, define) in defines {
+            trace!(?define);
+            let mode = std::mem::replace(&mut self.mode, CollectionMode::Taits);
+            let n = self.opaques.len();
+            super::sig_types::walk_types(self.tcx, define, self);
+            if n == self.opaques.len() {
+                self.tcx.dcx().span_err(span, "item does not contain any opaque types");
+            }
+            self.mode = mode;
+        }
+        // Allow using `#[define_opaque]` on assoc methods and type aliases to override the default collection mode in
+        // case it was capturing too much.
+        self.mode = CollectionMode::RpitAndAsyncFnOnly;
+    }
 }
 
 impl<'tcx> super::sig_types::SpannedTypeVisitor<'tcx> for OpaqueTypeCollector<'tcx> {
@@ -210,6 +222,7 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for OpaqueTypeCollector<'tcx> {
                 self.visit_opaque_ty(alias_ty);
             }
             // Skips type aliases, as they are meant to be transparent.
+            // FIXME(type_alias_impl_trait): can we require mentioning nested type aliases explicitly?
             ty::Alias(ty::Weak, alias_ty) if alias_ty.def_id.is_local() => {
                 self.tcx
                     .type_of(alias_ty.def_id)
@@ -283,28 +296,6 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for OpaqueTypeCollector<'tcx> {
                     self.visit_opaque_ty(alias_ty);
                 }
             }
-            ty::Adt(def, _) if def.did().is_local() => {
-                if let CollectionMode::ImplTraitInAssocTypes = self.mode {
-                    return;
-                }
-                if !self.seen.insert(def.did().expect_local()) {
-                    return;
-                }
-                for variant in def.variants().iter() {
-                    for field in variant.fields.iter() {
-                        // Don't use the `ty::Adt` args, we either
-                        // * found the opaque in the args
-                        // * will find the opaque in the uninstantiated fields
-                        // The only other situation that can occur is that after instantiating,
-                        // some projection resolves to an opaque that we would have otherwise
-                        // not found. While we could instantiate and walk those, that would mean we
-                        // would have to walk all generic parameters of an Adt, which can quickly
-                        // degenerate into looking at an exponential number of types.
-                        let ty = self.tcx.type_of(field.did).instantiate_identity();
-                        self.visit_spanned(self.tcx.def_span(field.did), ty);
-                    }
-                }
-            }
             _ => trace!(kind=?t.kind()),
         }
     }
@@ -317,7 +308,9 @@ fn opaque_types_defined_by<'tcx>(
     let kind = tcx.def_kind(item);
     trace!(?kind);
     let mut collector = OpaqueTypeCollector::new(tcx, item);
+    collector.collect_taits_from_defines_attr();
     super::sig_types::walk_types(tcx, item, &mut collector);
+
     match kind {
         DefKind::AssocFn
         | DefKind::Fn
@@ -350,8 +343,7 @@ fn opaque_types_defined_by<'tcx>(
         | DefKind::GlobalAsm
         | DefKind::Impl { .. }
         | DefKind::SyntheticCoroutineBody => {}
-        // Closures and coroutines are type checked with their parent, so we need to allow all
-        // opaques from the closure signature *and* from the parent body.
+        // Closures and coroutines are type checked with their parent
         DefKind::Closure | DefKind::InlineConst => {
             collector.opaques.extend(tcx.opaque_types_defined_by(tcx.local_parent(item)));
         }
diff --git a/compiler/rustc_ty_utils/src/ty.rs b/compiler/rustc_ty_utils/src/ty.rs
index 8610c30ab70..bb61f4bee66 100644
--- a/compiler/rustc_ty_utils/src/ty.rs
+++ b/compiler/rustc_ty_utils/src/ty.rs
@@ -6,13 +6,11 @@ use rustc_index::bit_set::DenseBitSet;
 use rustc_middle::bug;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::fold::fold_regions;
-use rustc_middle::ty::{
-    self, EarlyBinder, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitor, Upcast,
-};
+use rustc_middle::ty::{self, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitor, Upcast};
 use rustc_span::DUMMY_SP;
 use rustc_span::def_id::{CRATE_DEF_ID, DefId, LocalDefId};
 use rustc_trait_selection::traits;
-use tracing::{debug, instrument};
+use tracing::instrument;
 
 #[instrument(level = "debug", skip(tcx), ret)]
 fn sized_constraint_for_ty<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Option<Ty<'tcx>> {
@@ -260,57 +258,6 @@ fn param_env_normalized_for_post_analysis(tcx: TyCtxt<'_>, def_id: DefId) -> ty:
     typing_env.with_post_analysis_normalized(tcx).param_env
 }
 
-/// If the given trait impl enables exploiting the former order dependence of trait objects,
-/// returns its self type; otherwise, returns `None`.
-///
-/// See [`ty::ImplOverlapKind::FutureCompatOrderDepTraitObjects`] for more details.
-#[instrument(level = "debug", skip(tcx))]
-fn self_ty_of_trait_impl_enabling_order_dep_trait_object_hack(
-    tcx: TyCtxt<'_>,
-    def_id: DefId,
-) -> Option<EarlyBinder<'_, Ty<'_>>> {
-    let impl_ =
-        tcx.impl_trait_header(def_id).unwrap_or_else(|| bug!("called on inherent impl {def_id:?}"));
-
-    let trait_ref = impl_.trait_ref.skip_binder();
-    debug!(?trait_ref);
-
-    let is_marker_like = impl_.polarity == ty::ImplPolarity::Positive
-        && tcx.associated_item_def_ids(trait_ref.def_id).is_empty();
-
-    // Check whether these impls would be ok for a marker trait.
-    if !is_marker_like {
-        debug!("not marker-like!");
-        return None;
-    }
-
-    // impl must be `impl Trait for dyn Marker1 + Marker2 + ...`
-    if trait_ref.args.len() != 1 {
-        debug!("impl has args!");
-        return None;
-    }
-
-    let predicates = tcx.predicates_of(def_id);
-    if predicates.parent.is_some() || !predicates.predicates.is_empty() {
-        debug!(?predicates, "impl has predicates!");
-        return None;
-    }
-
-    let self_ty = trait_ref.self_ty();
-    let self_ty_matches = match self_ty.kind() {
-        ty::Dynamic(data, re, _) if re.is_static() => data.principal().is_none(),
-        _ => false,
-    };
-
-    if self_ty_matches {
-        debug!("MATCHES!");
-        Some(EarlyBinder::bind(self_ty))
-    } else {
-        debug!("non-matching self type");
-        None
-    }
-}
-
 /// Check if a function is async.
 fn asyncness(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Asyncness {
     let node = tcx.hir_node_by_def_id(def_id);
@@ -370,7 +317,6 @@ pub(crate) fn provide(providers: &mut Providers) {
         adt_sized_constraint,
         param_env,
         param_env_normalized_for_post_analysis,
-        self_ty_of_trait_impl_enabling_order_dep_trait_object_hack,
         defaultness,
         unsizing_params_for_adt,
         ..*providers
diff --git a/compiler/rustc_type_ir/Cargo.toml b/compiler/rustc_type_ir/Cargo.toml
index 7b2593b96e3..4adf7157926 100644
--- a/compiler/rustc_type_ir/Cargo.toml
+++ b/compiler/rustc_type_ir/Cargo.toml
@@ -33,6 +33,3 @@ nightly = [
     "rustc_index/nightly",
     "rustc_ast_ir/nightly",
 ]
-
-[lints.rust]
-unexpected_cfgs = { level = "warn", check-cfg = ['cfg(bootstrap)'] }
diff --git a/compiler/stable_mir/src/mir/alloc.rs b/compiler/stable_mir/src/mir/alloc.rs
index 7e0c4a479b8..023807b76ae 100644
--- a/compiler/stable_mir/src/mir/alloc.rs
+++ b/compiler/stable_mir/src/mir/alloc.rs
@@ -58,7 +58,7 @@ impl IndexedVal for AllocId {
 
 /// Utility function used to read an allocation data into a unassigned integer.
 pub(crate) fn read_target_uint(mut bytes: &[u8]) -> Result<u128, Error> {
-    let mut buf = [0u8; std::mem::size_of::<u128>()];
+    let mut buf = [0u8; size_of::<u128>()];
     match MachineInfo::target_endianness() {
         Endian::Little => {
             bytes.read_exact(&mut buf[..bytes.len()])?;
@@ -73,7 +73,7 @@ pub(crate) fn read_target_uint(mut bytes: &[u8]) -> Result<u128, Error> {
 
 /// Utility function used to read an allocation data into an assigned integer.
 pub(crate) fn read_target_int(mut bytes: &[u8]) -> Result<i128, Error> {
-    let mut buf = [0u8; std::mem::size_of::<i128>()];
+    let mut buf = [0u8; size_of::<i128>()];
     match MachineInfo::target_endianness() {
         Endian::Little => {
             bytes.read_exact(&mut buf[..bytes.len()])?;