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-rw-r--r--compiler/rustc_borrowck/src/borrowck_errors.rs4
-rw-r--r--compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs8
-rw-r--r--compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs20
-rw-r--r--compiler/rustc_borrowck/src/lib.rs4
-rw-r--r--compiler/rustc_borrowck/src/region_infer/mod.rs4
-rw-r--r--compiler/rustc_borrowck/src/region_infer/opaque_types/mod.rs76
-rw-r--r--compiler/rustc_borrowck/src/root_cx.rs22
-rw-r--r--compiler/rustc_codegen_llvm/src/context.rs6
-rw-r--r--compiler/rustc_codegen_llvm/src/coverageinfo/llvm_cov.rs15
-rw-r--r--compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs8
-rw-r--r--compiler/rustc_codegen_llvm/src/llvm/ffi.rs72
-rw-r--r--compiler/rustc_codegen_llvm/src/llvm/metadata_kind.rs71
-rw-r--r--compiler/rustc_codegen_llvm/src/llvm/mod.rs3
-rw-r--r--compiler/rustc_codegen_llvm/src/type_.rs8
-rw-r--r--compiler/rustc_error_codes/src/error_codes/E0719.md14
-rw-r--r--compiler/rustc_hir_analysis/src/check/check.rs4
-rw-r--r--compiler/rustc_hir_analysis/src/collect/item_bounds.rs20
-rw-r--r--compiler/rustc_hir_analysis/src/collect/predicates_of.rs18
-rw-r--r--compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs12
-rw-r--r--compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs32
-rw-r--r--compiler/rustc_hir_analysis/src/hir_ty_lowering/cmse.rs1
-rw-r--r--compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_trait.rs10
-rw-r--r--compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs18
-rw-r--r--compiler/rustc_hir_typeck/src/opaque_types.rs19
-rw-r--r--compiler/rustc_hir_typeck/src/writeback.rs28
-rw-r--r--compiler/rustc_infer/src/infer/outlives/obligations.rs4
-rw-r--r--compiler/rustc_interface/src/util.rs74
-rw-r--r--compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp52
-rw-r--r--compiler/rustc_middle/src/arena.rs2
-rw-r--r--compiler/rustc_middle/src/mir/query.rs7
-rw-r--r--compiler/rustc_middle/src/query/mod.rs2
-rw-r--r--compiler/rustc_middle/src/ty/typeck_results.rs4
-rw-r--r--compiler/rustc_pattern_analysis/src/rustc.rs4
-rw-r--r--compiler/rustc_target/src/spec/base/apple/mod.rs16
-rw-r--r--compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs17
-rw-r--r--compiler/rustc_trait_selection/src/error_reporting/traits/mod.rs45
-rw-r--r--compiler/rustc_trait_selection/src/traits/query/type_op/implied_outlives_bounds.rs8
-rw-r--r--compiler/rustc_trait_selection/src/traits/select/mod.rs2
-rw-r--r--compiler/rustc_type_ir/src/infer_ctxt.rs2
-rw-r--r--library/alloc/src/rc.rs4
-rw-r--r--library/alloc/src/sync.rs16
-rw-r--r--library/proc_macro/src/bridge/client.rs19
-rw-r--r--library/proc_macro/src/bridge/closure.rs4
-rw-r--r--library/proc_macro/src/bridge/mod.rs28
-rw-r--r--library/proc_macro/src/bridge/server.rs16
-rw-r--r--library/proc_macro/src/lib.rs1
-rw-r--r--library/std/src/path.rs187
-rw-r--r--library/std/src/thread/current.rs24
-rw-r--r--library/std/src/thread/mod.rs4
-rw-r--r--library/std/tests/path.rs38
-rw-r--r--src/bootstrap/src/core/build_steps/doc.rs21
-rw-r--r--src/bootstrap/src/core/builder/cargo.rs12
-rw-r--r--src/bootstrap/src/core/builder/tests.rs18
-rw-r--r--src/etc/lldb_providers.py5
-rw-r--r--tests/ui/associated-type-bounds/duplicate-bound-err.rs114
-rw-r--r--tests/ui/associated-type-bounds/duplicate-bound-err.stderr268
-rw-r--r--tests/ui/associated-type-bounds/duplicate-bound.rs240
-rw-r--r--tests/ui/associated-type-bounds/duplicate.rs278
-rw-r--r--tests/ui/associated-type-bounds/duplicate.stderr751
-rw-r--r--tests/ui/associated-types/associated-types-overridden-binding-2.stderr2
-rw-r--r--tests/ui/associated-types/associated-types-overridden-binding.stderr2
-rw-r--r--tests/ui/async-await/async-closures/without-precise-captures-we-are-powerless.rs14
-rw-r--r--tests/ui/async-await/async-closures/without-precise-captures-we-are-powerless.stderr63
-rw-r--r--tests/ui/borrowck/fn-item-check-type-params.stderr12
-rw-r--r--tests/ui/borrowck/implementation-not-general-enough-ice-133252.stderr6
-rw-r--r--tests/ui/borrowck/issue-17545.stderr3
-rw-r--r--tests/ui/cmse-nonsecure/cmse-nonsecure-call/undeclared-lifetime.rs20
-rw-r--r--tests/ui/cmse-nonsecure/cmse-nonsecure-call/undeclared-lifetime.stderr19
-rw-r--r--tests/ui/error-codes/E0719.rs5
-rw-r--r--tests/ui/error-codes/E0719.stderr34
-rw-r--r--tests/ui/errors/span-format_args-issue-140578.rs32
-rw-r--r--tests/ui/errors/span-format_args-issue-140578.stderr43
-rw-r--r--tests/ui/generic-associated-types/bugs/hrtb-implied-1.stderr5
-rw-r--r--tests/ui/impl-trait/precise-capturing/migration-note.rs2
-rw-r--r--tests/ui/impl-trait/precise-capturing/migration-note.stderr54
-rw-r--r--tests/ui/implied-bounds/bevy_world_query.rs6
-rw-r--r--tests/ui/inference/need_type_info/issue-107745-avoid-expr-from-macro-expansion.stderr6
-rw-r--r--tests/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-comparing-against-free.stderr6
-rw-r--r--tests/ui/nll/closure-requirements/propagate-multiple-requirements.stderr6
-rw-r--r--tests/ui/nll/local-outlives-static-via-hrtb.stderr10
-rw-r--r--tests/ui/nll/polonius/location-insensitive-scopes-issue-117146.nll.stderr5
-rw-r--r--tests/ui/nll/polonius/location-insensitive-scopes-issue-117146.polonius.stderr5
-rw-r--r--tests/ui/proc-macro/quote/not-quotable.stderr4
-rw-r--r--tests/ui/regions/multiple-sources-for-outlives-requirement.rs11
-rw-r--r--tests/ui/regions/multiple-sources-for-outlives-requirement.stderr20
-rw-r--r--tests/ui/regions/regions-infer-proc-static-upvar.stderr6
-rw-r--r--tests/ui/regions/regions-pattern-typing-issue-19552.stderr6
-rw-r--r--tests/ui/static/static-lifetime-bound.stderr6
-rw-r--r--tests/ui/static/static-region-bound.stderr6
-rw-r--r--tests/ui/suggestions/auxiliary/hidden-struct.rs26
-rw-r--r--tests/ui/suggestions/dont-suggest-foreign-doc-hidden.rs18
-rw-r--r--tests/ui/suggestions/dont-suggest-foreign-doc-hidden.stderr44
-rw-r--r--tests/ui/traits/trait-upcasting/illegal-upcast-to-impl-opaque.rs7
-rw-r--r--tests/ui/wf/wf-in-where-clause-static.current.stderr6
-rw-r--r--tests/ui/wf/wf-in-where-clause-static.next.stderr6
95 files changed, 1858 insertions, 1452 deletions
diff --git a/compiler/rustc_borrowck/src/borrowck_errors.rs b/compiler/rustc_borrowck/src/borrowck_errors.rs
index c9be5575da5..7c9011505d6 100644
--- a/compiler/rustc_borrowck/src/borrowck_errors.rs
+++ b/compiler/rustc_borrowck/src/borrowck_errors.rs
@@ -426,7 +426,7 @@ impl<'infcx, 'tcx> crate::MirBorrowckCtxt<'_, 'infcx, 'tcx> {
     }
 
     pub(crate) fn path_does_not_live_long_enough(&self, span: Span, path: &str) -> Diag<'infcx> {
-        struct_span_code_err!(self.dcx(), span, E0597, "{} does not live long enough", path,)
+        struct_span_code_err!(self.dcx(), span, E0597, "{} does not live long enough", path)
     }
 
     pub(crate) fn cannot_return_reference_to_local(
@@ -480,7 +480,7 @@ impl<'infcx, 'tcx> crate::MirBorrowckCtxt<'_, 'infcx, 'tcx> {
     }
 
     pub(crate) fn temporary_value_borrowed_for_too_long(&self, span: Span) -> Diag<'infcx> {
-        struct_span_code_err!(self.dcx(), span, E0716, "temporary value dropped while borrowed",)
+        struct_span_code_err!(self.dcx(), span, E0716, "temporary value dropped while borrowed")
     }
 }
 
diff --git a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
index 7e20a5133e0..efb622e2155 100644
--- a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
@@ -2992,6 +2992,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
         self.buffer_error(err);
     }
 
+    #[tracing::instrument(level = "debug", skip(self, explanation))]
     fn report_local_value_does_not_live_long_enough(
         &self,
         location: Location,
@@ -3001,13 +3002,6 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
         borrow_spans: UseSpans<'tcx>,
         explanation: BorrowExplanation<'tcx>,
     ) -> Diag<'infcx> {
-        debug!(
-            "report_local_value_does_not_live_long_enough(\
-             {:?}, {:?}, {:?}, {:?}, {:?}\
-             )",
-            location, name, borrow, drop_span, borrow_spans
-        );
-
         let borrow_span = borrow_spans.var_or_use_path_span();
         if let BorrowExplanation::MustBeValidFor {
             category,
diff --git a/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs b/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
index 7ca07bb9b43..638d89f5bcb 100644
--- a/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
@@ -416,6 +416,26 @@ impl<'tcx> BorrowExplanation<'tcx> {
                 {
                     self.add_object_lifetime_default_note(tcx, err, unsize_ty);
                 }
+
+                let mut preds = path
+                    .iter()
+                    .filter_map(|constraint| match constraint.category {
+                        ConstraintCategory::Predicate(pred) if !pred.is_dummy() => Some(pred),
+                        _ => None,
+                    })
+                    .collect::<Vec<Span>>();
+                preds.sort();
+                preds.dedup();
+                if !preds.is_empty() {
+                    let s = if preds.len() == 1 { "" } else { "s" };
+                    err.span_note(
+                        preds,
+                        format!(
+                            "requirement{s} that the value outlives `{region_name}` introduced here"
+                        ),
+                    );
+                }
+
                 self.add_lifetime_bound_suggestion_to_diagnostic(err, &category, span, region_name);
             }
             _ => {}
diff --git a/compiler/rustc_borrowck/src/lib.rs b/compiler/rustc_borrowck/src/lib.rs
index 4c380ddcf70..268cb47fd12 100644
--- a/compiler/rustc_borrowck/src/lib.rs
+++ b/compiler/rustc_borrowck/src/lib.rs
@@ -119,7 +119,7 @@ pub fn provide(providers: &mut Providers) {
 fn mir_borrowck(
     tcx: TyCtxt<'_>,
     def: LocalDefId,
-) -> Result<&ConcreteOpaqueTypes<'_>, ErrorGuaranteed> {
+) -> Result<&DefinitionSiteHiddenTypes<'_>, ErrorGuaranteed> {
     assert!(!tcx.is_typeck_child(def.to_def_id()));
     let (input_body, _) = tcx.mir_promoted(def);
     debug!("run query mir_borrowck: {}", tcx.def_path_str(def));
@@ -130,7 +130,7 @@ fn mir_borrowck(
         Err(guar)
     } else if input_body.should_skip() {
         debug!("Skipping borrowck because of injected body");
-        let opaque_types = ConcreteOpaqueTypes(Default::default());
+        let opaque_types = DefinitionSiteHiddenTypes(Default::default());
         Ok(tcx.arena.alloc(opaque_types))
     } else {
         let mut root_cx = BorrowCheckRootCtxt::new(tcx, def, None);
diff --git a/compiler/rustc_borrowck/src/region_infer/mod.rs b/compiler/rustc_borrowck/src/region_infer/mod.rs
index 0910e8ef4b3..e98c60e6338 100644
--- a/compiler/rustc_borrowck/src/region_infer/mod.rs
+++ b/compiler/rustc_borrowck/src/region_infer/mod.rs
@@ -1382,10 +1382,10 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     }
 
     /// The constraints we get from equating the hidden type of each use of an opaque
-    /// with its final concrete type may end up getting preferred over other, potentially
+    /// with its final hidden type may end up getting preferred over other, potentially
     /// longer constraint paths.
     ///
-    /// Given that we compute the final concrete type by relying on this existing constraint
+    /// Given that we compute the final hidden type by relying on this existing constraint
     /// path, this can easily end up hiding the actual reason for why we require these regions
     /// to be equal.
     ///
diff --git a/compiler/rustc_borrowck/src/region_infer/opaque_types/mod.rs b/compiler/rustc_borrowck/src/region_infer/opaque_types/mod.rs
index 0af636aa734..8d89f3e0d87 100644
--- a/compiler/rustc_borrowck/src/region_infer/opaque_types/mod.rs
+++ b/compiler/rustc_borrowck/src/region_infer/opaque_types/mod.rs
@@ -8,7 +8,7 @@ use rustc_infer::infer::outlives::env::RegionBoundPairs;
 use rustc_infer::infer::{InferCtxt, NllRegionVariableOrigin, OpaqueTypeStorageEntries};
 use rustc_infer::traits::ObligationCause;
 use rustc_macros::extension;
-use rustc_middle::mir::{Body, ConcreteOpaqueTypes, ConstraintCategory};
+use rustc_middle::mir::{Body, ConstraintCategory, DefinitionSiteHiddenTypes};
 use rustc_middle::ty::{
     self, DefiningScopeKind, EarlyBinder, FallibleTypeFolder, GenericArg, GenericArgsRef,
     OpaqueHiddenType, OpaqueTypeKey, Region, RegionVid, Ty, TyCtxt, TypeFoldable,
@@ -129,9 +129,9 @@ fn nll_var_to_universal_region<'tcx>(
 /// Collect all defining uses of opaque types inside of this typeck root. This
 /// expects the hidden type to be mapped to the definition parameters of the opaque
 /// and errors if we end up with distinct hidden types.
-fn add_concrete_opaque_type<'tcx>(
+fn add_hidden_type<'tcx>(
     tcx: TyCtxt<'tcx>,
-    concrete_opaque_types: &mut ConcreteOpaqueTypes<'tcx>,
+    hidden_types: &mut DefinitionSiteHiddenTypes<'tcx>,
     def_id: LocalDefId,
     hidden_ty: OpaqueHiddenType<'tcx>,
 ) {
@@ -139,7 +139,7 @@ fn add_concrete_opaque_type<'tcx>(
     // back to the opaque type definition. E.g. we may have `OpaqueType<X, Y>` mapped to
     // `(X, Y)` and `OpaqueType<Y, X>` mapped to `(Y, X)`, and those are the same, but we
     // only know that once we convert the generic parameters to those of the opaque type.
-    if let Some(prev) = concrete_opaque_types.0.get_mut(&def_id) {
+    if let Some(prev) = hidden_types.0.get_mut(&def_id) {
         if prev.ty != hidden_ty.ty {
             let guar = hidden_ty.ty.error_reported().err().unwrap_or_else(|| {
                 let (Ok(e) | Err(e)) = prev.build_mismatch_error(&hidden_ty, tcx).map(|d| d.emit());
@@ -151,15 +151,15 @@ fn add_concrete_opaque_type<'tcx>(
         // FIXME(oli-obk): collect multiple spans for better diagnostics down the road.
         prev.span = prev.span.substitute_dummy(hidden_ty.span);
     } else {
-        concrete_opaque_types.0.insert(def_id, hidden_ty);
+        hidden_types.0.insert(def_id, hidden_ty);
     }
 }
 
-fn get_concrete_opaque_type<'tcx>(
-    concrete_opaque_types: &ConcreteOpaqueTypes<'tcx>,
+fn get_hidden_type<'tcx>(
+    hidden_types: &DefinitionSiteHiddenTypes<'tcx>,
     def_id: LocalDefId,
 ) -> Option<EarlyBinder<'tcx, OpaqueHiddenType<'tcx>>> {
-    concrete_opaque_types.0.get(&def_id).map(|ty| EarlyBinder::bind(*ty))
+    hidden_types.0.get(&def_id).map(|ty| EarlyBinder::bind(*ty))
 }
 
 #[derive(Debug)]
@@ -173,22 +173,22 @@ struct DefiningUse<'tcx> {
 }
 
 /// This computes the actual hidden types of the opaque types and maps them to their
-/// definition sites. Outside of registering the computed concrete types this function
+/// definition sites. Outside of registering the computed hidden types this function
 /// does not mutate the current borrowck state.
 ///
 /// While it may fail to infer the hidden type and return errors, we always apply
-/// the computed concrete hidden type to all opaque type uses to check whether they
+/// the computed hidden type to all opaque type uses to check whether they
 /// are correct. This is necessary to support non-defining uses of opaques in their
 /// defining scope.
 ///
 /// It also means that this whole function is not really soundness critical as we
 /// recheck all uses of the opaques regardless.
-pub(crate) fn compute_concrete_opaque_types<'tcx>(
+pub(crate) fn compute_definition_site_hidden_types<'tcx>(
     infcx: &BorrowckInferCtxt<'tcx>,
     universal_region_relations: &Frozen<UniversalRegionRelations<'tcx>>,
     constraints: &MirTypeckRegionConstraints<'tcx>,
     location_map: Rc<DenseLocationMap>,
-    concrete_opaque_types: &mut ConcreteOpaqueTypes<'tcx>,
+    hidden_types: &mut DefinitionSiteHiddenTypes<'tcx>,
     opaque_types: &[(OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>)],
 ) -> Vec<DeferredOpaqueTypeError<'tcx>> {
     let mut errors = Vec::new();
@@ -201,8 +201,7 @@ pub(crate) fn compute_concrete_opaque_types<'tcx>(
     // We start by checking each use of an opaque type during type check and
     // check whether the generic arguments of the opaque type are fully
     // universal, if so, it's a defining use.
-    let defining_uses =
-        collect_defining_uses(&mut rcx, concrete_opaque_types, opaque_types, &mut errors);
+    let defining_uses = collect_defining_uses(&mut rcx, hidden_types, opaque_types, &mut errors);
 
     // We now compute and apply member constraints for all regions in the hidden
     // types of each defining use. This mutates the region values of the `rcx` which
@@ -210,11 +209,11 @@ pub(crate) fn compute_concrete_opaque_types<'tcx>(
     apply_member_constraints(&mut rcx, &defining_uses);
 
     // After applying member constraints, we now check whether all member regions ended
-    // up equal to one of their choice regions and compute the actual concrete type of
+    // up equal to one of their choice regions and compute the actual hidden type of
     // the opaque type definition. This is stored in the `root_cx`.
-    compute_concrete_types_from_defining_uses(
+    compute_definition_site_hidden_types_from_defining_uses(
         &rcx,
-        concrete_opaque_types,
+        hidden_types,
         &defining_uses,
         &mut errors,
     );
@@ -224,7 +223,7 @@ pub(crate) fn compute_concrete_opaque_types<'tcx>(
 #[instrument(level = "debug", skip_all, ret)]
 fn collect_defining_uses<'tcx>(
     rcx: &mut RegionCtxt<'_, 'tcx>,
-    concrete_opaque_types: &mut ConcreteOpaqueTypes<'tcx>,
+    hidden_types: &mut DefinitionSiteHiddenTypes<'tcx>,
     opaque_types: &[(OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>)],
     errors: &mut Vec<DeferredOpaqueTypeError<'tcx>>,
 ) -> Vec<DefiningUse<'tcx>> {
@@ -244,9 +243,9 @@ fn collect_defining_uses<'tcx>(
             // with `TypingMode::Borrowck`.
             if infcx.tcx.use_typing_mode_borrowck() {
                 match err {
-                    NonDefiningUseReason::Tainted(guar) => add_concrete_opaque_type(
+                    NonDefiningUseReason::Tainted(guar) => add_hidden_type(
                         infcx.tcx,
-                        concrete_opaque_types,
+                        hidden_types,
                         opaque_type_key.def_id,
                         OpaqueHiddenType::new_error(infcx.tcx, guar),
                     ),
@@ -277,9 +276,9 @@ fn collect_defining_uses<'tcx>(
     defining_uses
 }
 
-fn compute_concrete_types_from_defining_uses<'tcx>(
+fn compute_definition_site_hidden_types_from_defining_uses<'tcx>(
     rcx: &RegionCtxt<'_, 'tcx>,
-    concrete_opaque_types: &mut ConcreteOpaqueTypes<'tcx>,
+    hidden_types: &mut DefinitionSiteHiddenTypes<'tcx>,
     defining_uses: &[DefiningUse<'tcx>],
     errors: &mut Vec<DeferredOpaqueTypeError<'tcx>>,
 ) {
@@ -358,9 +357,9 @@ fn compute_concrete_types_from_defining_uses<'tcx>(
                 },
             ));
         }
-        add_concrete_opaque_type(
+        add_hidden_type(
             tcx,
-            concrete_opaque_types,
+            hidden_types,
             opaque_type_key.def_id,
             OpaqueHiddenType { span: hidden_type.span, ty },
         );
@@ -489,20 +488,20 @@ impl<'tcx> FallibleTypeFolder<TyCtxt<'tcx>> for ToArgRegionsFolder<'_, 'tcx> {
 ///
 /// It does this by equating the hidden type of each use with the instantiated final
 /// hidden type of the opaque.
-pub(crate) fn apply_computed_concrete_opaque_types<'tcx>(
+pub(crate) fn apply_definition_site_hidden_types<'tcx>(
     infcx: &BorrowckInferCtxt<'tcx>,
     body: &Body<'tcx>,
     universal_regions: &UniversalRegions<'tcx>,
     region_bound_pairs: &RegionBoundPairs<'tcx>,
     known_type_outlives_obligations: &[ty::PolyTypeOutlivesPredicate<'tcx>],
     constraints: &mut MirTypeckRegionConstraints<'tcx>,
-    concrete_opaque_types: &mut ConcreteOpaqueTypes<'tcx>,
+    hidden_types: &mut DefinitionSiteHiddenTypes<'tcx>,
     opaque_types: &[(OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>)],
 ) -> Vec<DeferredOpaqueTypeError<'tcx>> {
     let tcx = infcx.tcx;
     let mut errors = Vec::new();
     for &(key, hidden_type) in opaque_types {
-        let Some(expected) = get_concrete_opaque_type(concrete_opaque_types, key.def_id) else {
+        let Some(expected) = get_hidden_type(hidden_types, key.def_id) else {
             if !tcx.use_typing_mode_borrowck() {
                 if let ty::Alias(ty::Opaque, alias_ty) = hidden_type.ty.kind()
                     && alias_ty.def_id == key.def_id.to_def_id()
@@ -521,12 +520,7 @@ pub(crate) fn apply_computed_concrete_opaque_types<'tcx>(
                 hidden_type.span,
                 "non-defining use in the defining scope with no defining uses",
             );
-            add_concrete_opaque_type(
-                tcx,
-                concrete_opaque_types,
-                key.def_id,
-                OpaqueHiddenType::new_error(tcx, guar),
-            );
+            add_hidden_type(tcx, hidden_types, key.def_id, OpaqueHiddenType::new_error(tcx, guar));
             continue;
         };
 
@@ -566,18 +560,13 @@ pub(crate) fn apply_computed_concrete_opaque_types<'tcx>(
                 "equating opaque types",
             ),
         ) {
-            add_concrete_opaque_type(
-                tcx,
-                concrete_opaque_types,
-                key.def_id,
-                OpaqueHiddenType::new_error(tcx, guar),
-            );
+            add_hidden_type(tcx, hidden_types, key.def_id, OpaqueHiddenType::new_error(tcx, guar));
         }
     }
     errors
 }
 
-/// In theory `apply_concrete_opaque_types` could introduce new uses of opaque types.
+/// In theory `apply_definition_site_hidden_types` could introduce new uses of opaque types.
 /// We do not check these new uses so this could be unsound.
 ///
 /// We detect any new uses and simply delay a bug if they occur. If this results in
@@ -682,13 +671,6 @@ impl<'tcx> InferCtxt<'tcx> {
     ///
     /// (*) C1 and C2 were introduced in the comments on
     /// `register_member_constraints`. Read that comment for more context.
-    ///
-    /// # Parameters
-    ///
-    /// - `def_id`, the `impl Trait` type
-    /// - `args`, the args used to instantiate this opaque type
-    /// - `instantiated_ty`, the inferred type C1 -- fully resolved, lifted version of
-    ///   `opaque_defn.concrete_ty`
     #[instrument(level = "debug", skip(self))]
     fn infer_opaque_definition_from_instantiation(
         &self,
diff --git a/compiler/rustc_borrowck/src/root_cx.rs b/compiler/rustc_borrowck/src/root_cx.rs
index cd4e9683f2d..21c11e12873 100644
--- a/compiler/rustc_borrowck/src/root_cx.rs
+++ b/compiler/rustc_borrowck/src/root_cx.rs
@@ -12,12 +12,12 @@ use smallvec::SmallVec;
 use crate::consumers::BorrowckConsumer;
 use crate::nll::compute_closure_requirements_modulo_opaques;
 use crate::region_infer::opaque_types::{
-    apply_computed_concrete_opaque_types, clone_and_resolve_opaque_types,
-    compute_concrete_opaque_types, detect_opaque_types_added_while_handling_opaque_types,
+    apply_definition_site_hidden_types, clone_and_resolve_opaque_types,
+    compute_definition_site_hidden_types, detect_opaque_types_added_while_handling_opaque_types,
 };
 use crate::type_check::{Locations, constraint_conversion};
 use crate::{
-    ClosureRegionRequirements, CollectRegionConstraintsResult, ConcreteOpaqueTypes,
+    ClosureRegionRequirements, CollectRegionConstraintsResult, DefinitionSiteHiddenTypes,
     PropagatedBorrowCheckResults, borrowck_check_region_constraints,
     borrowck_collect_region_constraints,
 };
@@ -27,7 +27,7 @@ use crate::{
 pub(super) struct BorrowCheckRootCtxt<'tcx> {
     pub tcx: TyCtxt<'tcx>,
     root_def_id: LocalDefId,
-    concrete_opaque_types: ConcreteOpaqueTypes<'tcx>,
+    hidden_types: DefinitionSiteHiddenTypes<'tcx>,
     /// The region constraints computed by [borrowck_collect_region_constraints]. This uses
     /// an [FxIndexMap] to guarantee that iterating over it visits nested bodies before
     /// their parents.
@@ -49,7 +49,7 @@ impl<'tcx> BorrowCheckRootCtxt<'tcx> {
         BorrowCheckRootCtxt {
             tcx,
             root_def_id,
-            concrete_opaque_types: Default::default(),
+            hidden_types: Default::default(),
             collect_region_constraints_results: Default::default(),
             propagated_borrowck_results: Default::default(),
             tainted_by_errors: None,
@@ -72,11 +72,11 @@ impl<'tcx> BorrowCheckRootCtxt<'tcx> {
         &self.propagated_borrowck_results[&nested_body_def_id].used_mut_upvars
     }
 
-    pub(super) fn finalize(self) -> Result<&'tcx ConcreteOpaqueTypes<'tcx>, ErrorGuaranteed> {
+    pub(super) fn finalize(self) -> Result<&'tcx DefinitionSiteHiddenTypes<'tcx>, ErrorGuaranteed> {
         if let Some(guar) = self.tainted_by_errors {
             Err(guar)
         } else {
-            Ok(self.tcx.arena.alloc(self.concrete_opaque_types))
+            Ok(self.tcx.arena.alloc(self.hidden_types))
         }
     }
 
@@ -88,12 +88,12 @@ impl<'tcx> BorrowCheckRootCtxt<'tcx> {
                 &input.universal_region_relations,
                 &mut input.constraints,
             );
-            input.deferred_opaque_type_errors = compute_concrete_opaque_types(
+            input.deferred_opaque_type_errors = compute_definition_site_hidden_types(
                 &input.infcx,
                 &input.universal_region_relations,
                 &input.constraints,
                 Rc::clone(&input.location_map),
-                &mut self.concrete_opaque_types,
+                &mut self.hidden_types,
                 &opaque_types,
             );
             per_body_info.push((num_entries, opaque_types));
@@ -103,14 +103,14 @@ impl<'tcx> BorrowCheckRootCtxt<'tcx> {
             self.collect_region_constraints_results.values_mut().zip(per_body_info)
         {
             if input.deferred_opaque_type_errors.is_empty() {
-                input.deferred_opaque_type_errors = apply_computed_concrete_opaque_types(
+                input.deferred_opaque_type_errors = apply_definition_site_hidden_types(
                     &input.infcx,
                     &input.body_owned,
                     &input.universal_region_relations.universal_regions,
                     &input.region_bound_pairs,
                     &input.known_type_outlives_obligations,
                     &mut input.constraints,
-                    &mut self.concrete_opaque_types,
+                    &mut self.hidden_types,
                     &opaque_types,
                 );
             }
diff --git a/compiler/rustc_codegen_llvm/src/context.rs b/compiler/rustc_codegen_llvm/src/context.rs
index aa5c17269fb..b1da6f7c740 100644
--- a/compiler/rustc_codegen_llvm/src/context.rs
+++ b/compiler/rustc_codegen_llvm/src/context.rs
@@ -34,7 +34,7 @@ use smallvec::SmallVec;
 use crate::back::write::to_llvm_code_model;
 use crate::callee::get_fn;
 use crate::debuginfo::metadata::apply_vcall_visibility_metadata;
-use crate::llvm::Metadata;
+use crate::llvm::{Metadata, MetadataKindId};
 use crate::type_::Type;
 use crate::value::Value;
 use crate::{attributes, common, coverageinfo, debuginfo, llvm, llvm_util};
@@ -1006,11 +1006,11 @@ impl<'ll, CX: Borrow<SCx<'ll>>> GenericCx<'ll, CX> {
     pub(crate) fn set_metadata<'a>(
         &self,
         val: &'a Value,
-        kind_id: impl Into<llvm::MetadataKindId>,
+        kind_id: MetadataKindId,
         md: &'ll Metadata,
     ) {
         let node = self.get_metadata_value(md);
-        llvm::LLVMSetMetadata(val, kind_id.into(), node);
+        llvm::LLVMSetMetadata(val, kind_id, node);
     }
 }
 
diff --git a/compiler/rustc_codegen_llvm/src/coverageinfo/llvm_cov.rs b/compiler/rustc_codegen_llvm/src/coverageinfo/llvm_cov.rs
index bc4f6bb6a82..d50eb533ffd 100644
--- a/compiler/rustc_codegen_llvm/src/coverageinfo/llvm_cov.rs
+++ b/compiler/rustc_codegen_llvm/src/coverageinfo/llvm_cov.rs
@@ -2,26 +2,25 @@
 
 use std::ffi::CString;
 
-use crate::common::AsCCharPtr;
 use crate::coverageinfo::ffi;
 use crate::llvm;
 
 pub(crate) fn covmap_var_name() -> CString {
-    CString::new(llvm::build_byte_buffer(|s| unsafe {
+    CString::new(llvm::build_byte_buffer(|s| {
         llvm::LLVMRustCoverageWriteCovmapVarNameToString(s);
     }))
     .expect("covmap variable name should not contain NUL")
 }
 
 pub(crate) fn covmap_section_name(llmod: &llvm::Module) -> CString {
-    CString::new(llvm::build_byte_buffer(|s| unsafe {
+    CString::new(llvm::build_byte_buffer(|s| {
         llvm::LLVMRustCoverageWriteCovmapSectionNameToString(llmod, s);
     }))
     .expect("covmap section name should not contain NUL")
 }
 
 pub(crate) fn covfun_section_name(llmod: &llvm::Module) -> CString {
-    CString::new(llvm::build_byte_buffer(|s| unsafe {
+    CString::new(llvm::build_byte_buffer(|s| {
         llvm::LLVMRustCoverageWriteCovfunSectionNameToString(llmod, s);
     }))
     .expect("covfun section name should not contain NUL")
@@ -34,7 +33,7 @@ pub(crate) fn create_pgo_func_name_var<'ll>(
     unsafe {
         llvm::LLVMRustCoverageCreatePGOFuncNameVar(
             llfn,
-            mangled_fn_name.as_c_char_ptr(),
+            mangled_fn_name.as_ptr(),
             mangled_fn_name.len(),
         )
     }
@@ -44,7 +43,7 @@ pub(crate) fn write_filenames_to_buffer(filenames: &[impl AsRef<str>]) -> Vec<u8
     let (pointers, lengths) = filenames
         .into_iter()
         .map(AsRef::as_ref)
-        .map(|s: &str| (s.as_c_char_ptr(), s.len()))
+        .map(|s: &str| (s.as_ptr(), s.len()))
         .unzip::<_, _, Vec<_>, Vec<_>>();
 
     llvm::build_byte_buffer(|buffer| unsafe {
@@ -89,12 +88,12 @@ pub(crate) fn write_function_mappings_to_buffer(
 /// Hashes some bytes into a 64-bit hash, via LLVM's `IndexedInstrProf::ComputeHash`,
 /// as required for parts of the LLVM coverage mapping format.
 pub(crate) fn hash_bytes(bytes: &[u8]) -> u64 {
-    unsafe { llvm::LLVMRustCoverageHashBytes(bytes.as_c_char_ptr(), bytes.len()) }
+    unsafe { llvm::LLVMRustCoverageHashBytes(bytes.as_ptr(), bytes.len()) }
 }
 
 /// Returns LLVM's `coverage::CovMapVersion::CurrentVersion` (CoverageMapping.h)
 /// as a raw numeric value. For historical reasons, the numeric value is 1 less
 /// than the number in the version's name, so `Version7` is actually `6u32`.
 pub(crate) fn mapping_version() -> u32 {
-    unsafe { llvm::LLVMRustCoverageMappingVersion() }
+    llvm::LLVMRustCoverageMappingVersion()
 }
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs b/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
index 1e4ace4ca92..bc20c759413 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
@@ -1611,16 +1611,12 @@ pub(crate) fn apply_vcall_visibility_metadata<'ll, 'tcx>(
         let v = [llvm::LLVMValueAsMetadata(cx.const_usize(0)), typeid];
         llvm::LLVMRustGlobalAddMetadata(
             vtable,
-            llvm::MD_type as c_uint,
+            llvm::MD_type,
             llvm::LLVMMDNodeInContext2(cx.llcx, v.as_ptr(), v.len()),
         );
         let vcall_visibility = llvm::LLVMValueAsMetadata(cx.const_u64(vcall_visibility as u64));
         let vcall_visibility_metadata = llvm::LLVMMDNodeInContext2(cx.llcx, &vcall_visibility, 1);
-        llvm::LLVMGlobalSetMetadata(
-            vtable,
-            llvm::MetadataType::MD_vcall_visibility as c_uint,
-            vcall_visibility_metadata,
-        );
+        llvm::LLVMGlobalSetMetadata(vtable, llvm::MD_vcall_visibility, vcall_visibility_metadata);
     }
 }
 
diff --git a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
index afd2991a09c..e9f92267a7d 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
@@ -29,6 +29,7 @@ use super::debuginfo::{
     DITemplateTypeParameter, DIType, DebugEmissionKind, DebugNameTableKind,
 };
 use crate::llvm;
+use crate::llvm::MetadataKindId;
 
 /// In the LLVM-C API, boolean values are passed as `typedef int LLVMBool`,
 /// which has a different ABI from Rust or C++ `bool`.
@@ -513,31 +514,6 @@ pub(crate) enum FileType {
     ObjectFile,
 }
 
-/// LLVMMetadataType
-#[derive(Copy, Clone)]
-#[repr(C)]
-#[expect(dead_code, reason = "Some variants are unused, but are kept to match LLVM-C")]
-pub(crate) enum MetadataType {
-    MD_dbg = 0,
-    MD_tbaa = 1,
-    MD_prof = 2,
-    MD_fpmath = 3,
-    MD_range = 4,
-    MD_tbaa_struct = 5,
-    MD_invariant_load = 6,
-    MD_alias_scope = 7,
-    MD_noalias = 8,
-    MD_nontemporal = 9,
-    MD_mem_parallel_loop_access = 10,
-    MD_nonnull = 11,
-    MD_unpredictable = 15,
-    MD_align = 17,
-    MD_type = 19,
-    MD_vcall_visibility = 28,
-    MD_noundef = 29,
-    MD_kcfi_type = 36,
-}
-
 /// Must match the layout of `LLVMInlineAsmDialect`.
 #[derive(Copy, Clone, PartialEq)]
 #[repr(C)]
@@ -1035,16 +1011,6 @@ pub(crate) type GetSymbolsCallback =
     unsafe extern "C" fn(*mut c_void, *const c_char) -> *mut c_void;
 pub(crate) type GetSymbolsErrorCallback = unsafe extern "C" fn(*const c_char) -> *mut c_void;
 
-#[derive(Copy, Clone)]
-#[repr(transparent)]
-pub(crate) 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);
@@ -1139,7 +1105,11 @@ unsafe extern "C" {
     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) 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 LLVMGlobalSetMetadata<'a>(
+        Val: &'a Value,
+        KindID: MetadataKindId,
+        Metadata: &'a Metadata,
+    );
     pub(crate) safe fn LLVMValueAsMetadata(Node: &Value) -> &Metadata;
 
     // Operations on constants of any type
@@ -2059,7 +2029,7 @@ unsafe extern "C" {
     // Operations on all values
     pub(crate) fn LLVMRustGlobalAddMetadata<'a>(
         Val: &'a Value,
-        KindID: c_uint,
+        KindID: MetadataKindId,
         Metadata: &'a Metadata,
     );
     pub(crate) fn LLVMRustIsNonGVFunctionPointerTy(Val: &Value) -> bool;
@@ -2256,8 +2226,11 @@ unsafe extern "C" {
         ConstraintsLen: size_t,
     ) -> bool;
 
+    /// A list of pointer-length strings is passed as two pointer-length slices,
+    /// one slice containing pointers and one slice containing their corresponding
+    /// lengths. The implementation will check that both slices have the same length.
     pub(crate) fn LLVMRustCoverageWriteFilenamesToBuffer(
-        Filenames: *const *const c_char,
+        Filenames: *const *const c_uchar, // See "PTR_LEN_STR".
         FilenamesLen: size_t,
         Lengths: *const size_t,
         LengthsLen: size_t,
@@ -2280,18 +2253,25 @@ unsafe extern "C" {
 
     pub(crate) fn LLVMRustCoverageCreatePGOFuncNameVar(
         F: &Value,
-        FuncName: *const c_char,
+        FuncName: *const c_uchar, // See "PTR_LEN_STR".
         FuncNameLen: size_t,
     ) -> &Value;
-    pub(crate) fn LLVMRustCoverageHashBytes(Bytes: *const c_char, NumBytes: size_t) -> u64;
-
-    pub(crate) fn LLVMRustCoverageWriteCovmapSectionNameToString(M: &Module, OutStr: &RustString);
+    pub(crate) fn LLVMRustCoverageHashBytes(
+        Bytes: *const c_uchar, // See "PTR_LEN_STR".
+        NumBytes: size_t,
+    ) -> u64;
 
-    pub(crate) fn LLVMRustCoverageWriteCovfunSectionNameToString(M: &Module, OutStr: &RustString);
-
-    pub(crate) fn LLVMRustCoverageWriteCovmapVarNameToString(OutStr: &RustString);
+    pub(crate) safe fn LLVMRustCoverageWriteCovmapSectionNameToString(
+        M: &Module,
+        OutStr: &RustString,
+    );
+    pub(crate) safe fn LLVMRustCoverageWriteCovfunSectionNameToString(
+        M: &Module,
+        OutStr: &RustString,
+    );
+    pub(crate) safe fn LLVMRustCoverageWriteCovmapVarNameToString(OutStr: &RustString);
 
-    pub(crate) fn LLVMRustCoverageMappingVersion() -> u32;
+    pub(crate) safe fn LLVMRustCoverageMappingVersion() -> u32;
     pub(crate) fn LLVMRustDebugMetadataVersion() -> u32;
     pub(crate) fn LLVMRustVersionMajor() -> u32;
     pub(crate) fn LLVMRustVersionMinor() -> u32;
diff --git a/compiler/rustc_codegen_llvm/src/llvm/metadata_kind.rs b/compiler/rustc_codegen_llvm/src/llvm/metadata_kind.rs
new file mode 100644
index 00000000000..a8a671b5c85
--- /dev/null
+++ b/compiler/rustc_codegen_llvm/src/llvm/metadata_kind.rs
@@ -0,0 +1,71 @@
+use libc::c_uint;
+
+pub(crate) use self::fixed_kinds::*;
+
+#[derive(Copy, Clone)]
+#[repr(transparent)]
+pub(crate) struct MetadataKindId(c_uint);
+
+macro_rules! declare_fixed_metadata_kinds {
+    (
+        $(
+            FIXED_MD_KIND($variant:ident, $value:literal)
+        )*
+    ) => {
+        // Use a submodule to group all declarations into one `#[expect(..)]`.
+        #[expect(dead_code)]
+        mod fixed_kinds {
+            use super::MetadataKindId;
+            $(
+                #[expect(non_upper_case_globals)]
+                pub(crate) const $variant: MetadataKindId = MetadataKindId($value);
+            )*
+        }
+    };
+}
+
+// Must be kept in sync with the corresponding static assertions in `RustWrapper.cpp`.
+declare_fixed_metadata_kinds! {
+    FIXED_MD_KIND(MD_dbg, 0)
+    FIXED_MD_KIND(MD_tbaa, 1)
+    FIXED_MD_KIND(MD_prof, 2)
+    FIXED_MD_KIND(MD_fpmath, 3)
+    FIXED_MD_KIND(MD_range, 4)
+    FIXED_MD_KIND(MD_tbaa_struct, 5)
+    FIXED_MD_KIND(MD_invariant_load, 6)
+    FIXED_MD_KIND(MD_alias_scope, 7)
+    FIXED_MD_KIND(MD_noalias, 8)
+    FIXED_MD_KIND(MD_nontemporal, 9)
+    FIXED_MD_KIND(MD_mem_parallel_loop_access, 10)
+    FIXED_MD_KIND(MD_nonnull, 11)
+    FIXED_MD_KIND(MD_dereferenceable, 12)
+    FIXED_MD_KIND(MD_dereferenceable_or_null, 13)
+    FIXED_MD_KIND(MD_make_implicit, 14)
+    FIXED_MD_KIND(MD_unpredictable, 15)
+    FIXED_MD_KIND(MD_invariant_group, 16)
+    FIXED_MD_KIND(MD_align, 17)
+    FIXED_MD_KIND(MD_loop, 18)
+    FIXED_MD_KIND(MD_type, 19)
+    FIXED_MD_KIND(MD_section_prefix, 20)
+    FIXED_MD_KIND(MD_absolute_symbol, 21)
+    FIXED_MD_KIND(MD_associated, 22)
+    FIXED_MD_KIND(MD_callees, 23)
+    FIXED_MD_KIND(MD_irr_loop, 24)
+    FIXED_MD_KIND(MD_access_group, 25)
+    FIXED_MD_KIND(MD_callback, 26)
+    FIXED_MD_KIND(MD_preserve_access_index, 27)
+    FIXED_MD_KIND(MD_vcall_visibility, 28)
+    FIXED_MD_KIND(MD_noundef, 29)
+    FIXED_MD_KIND(MD_annotation, 30)
+    FIXED_MD_KIND(MD_nosanitize, 31)
+    FIXED_MD_KIND(MD_func_sanitize, 32)
+    FIXED_MD_KIND(MD_exclude, 33)
+    FIXED_MD_KIND(MD_memprof, 34)
+    FIXED_MD_KIND(MD_callsite, 35)
+    FIXED_MD_KIND(MD_kcfi_type, 36)
+    FIXED_MD_KIND(MD_pcsections, 37)
+    FIXED_MD_KIND(MD_DIAssignID, 38)
+    FIXED_MD_KIND(MD_coro_outside_frame, 39)
+    FIXED_MD_KIND(MD_mmra, 40)
+    FIXED_MD_KIND(MD_noalias_addrspace, 41)
+}
diff --git a/compiler/rustc_codegen_llvm/src/llvm/mod.rs b/compiler/rustc_codegen_llvm/src/llvm/mod.rs
index 1115d82fa85..9a53dacb1df 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/mod.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/mod.rs
@@ -11,13 +11,14 @@ use rustc_llvm::RustString;
 
 pub(crate) use self::CallConv::*;
 pub(crate) use self::CodeGenOptSize::*;
-pub(crate) use self::MetadataType::*;
 pub(crate) use self::ffi::*;
+pub(crate) use self::metadata_kind::*;
 use crate::common::AsCCharPtr;
 
 pub(crate) mod diagnostic;
 pub(crate) mod enzyme_ffi;
 mod ffi;
+mod metadata_kind;
 
 pub(crate) use self::enzyme_ffi::*;
 
diff --git a/compiler/rustc_codegen_llvm/src/type_.rs b/compiler/rustc_codegen_llvm/src/type_.rs
index 9ecaf5f24fe..5b97898a4b8 100644
--- a/compiler/rustc_codegen_llvm/src/type_.rs
+++ b/compiler/rustc_codegen_llvm/src/type_.rs
@@ -306,7 +306,7 @@ impl<'ll, 'tcx> TypeMembershipCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
             let v = [llvm::LLVMValueAsMetadata(self.const_usize(0)), typeid_metadata];
             llvm::LLVMRustGlobalAddMetadata(
                 function,
-                llvm::MD_type as c_uint,
+                llvm::MD_type,
                 llvm::LLVMMDNodeInContext2(self.llcx, v.as_ptr(), v.len()),
             )
         }
@@ -318,7 +318,7 @@ impl<'ll, 'tcx> TypeMembershipCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
             let v = [llvm::LLVMValueAsMetadata(self.const_usize(0)), typeid_metadata];
             llvm::LLVMGlobalSetMetadata(
                 function,
-                llvm::MD_type as c_uint,
+                llvm::MD_type,
                 llvm::LLVMMDNodeInContext2(self.llcx, v.as_ptr(), v.len()),
             )
         }
@@ -333,7 +333,7 @@ impl<'ll, 'tcx> TypeMembershipCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
         unsafe {
             llvm::LLVMRustGlobalAddMetadata(
                 function,
-                llvm::MD_kcfi_type as c_uint,
+                llvm::MD_kcfi_type,
                 llvm::LLVMMDNodeInContext2(
                     self.llcx,
                     &llvm::LLVMValueAsMetadata(kcfi_type_metadata),
@@ -348,7 +348,7 @@ impl<'ll, 'tcx> TypeMembershipCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
         unsafe {
             llvm::LLVMGlobalSetMetadata(
                 function,
-                llvm::MD_kcfi_type as c_uint,
+                llvm::MD_kcfi_type,
                 llvm::LLVMMDNodeInContext2(
                     self.llcx,
                     &llvm::LLVMValueAsMetadata(kcfi_type_metadata),
diff --git a/compiler/rustc_error_codes/src/error_codes/E0719.md b/compiler/rustc_error_codes/src/error_codes/E0719.md
index cd981db1058..6aec38b42a3 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0719.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0719.md
@@ -1,4 +1,4 @@
-An associated type value was specified more than once.
+An associated item was specified more than once in a trait object.
 
 Erroneous code example:
 
@@ -7,21 +7,15 @@ trait FooTrait {}
 trait BarTrait {}
 
 // error: associated type `Item` in trait `Iterator` is specified twice
-struct Foo<T: Iterator<Item: FooTrait, Item: BarTrait>> { f: T }
+type Foo = dyn Iterator<Item = u32, Item = u32>;
 ```
 
-`Item` in trait `Iterator` cannot be specified multiple times for struct `Foo`.
-To fix this, create a new trait that is a combination of the desired traits and
-specify the associated type with the new trait.
+To fix this, remove the duplicate specifier:
 
 Corrected example:
 
 ```
-trait FooTrait {}
-trait BarTrait {}
-trait FooBarTrait: FooTrait + BarTrait {}
-
-struct Foo<T: Iterator<Item: FooBarTrait>> { f: T } // ok!
+type Foo = dyn Iterator<Item = u32>; // ok!
 ```
 
 For more information about associated types, see [the book][bk-at]. For more
diff --git a/compiler/rustc_hir_analysis/src/check/check.rs b/compiler/rustc_hir_analysis/src/check/check.rs
index 886ebddc75c..e1e6860e430 100644
--- a/compiler/rustc_hir_analysis/src/check/check.rs
+++ b/compiler/rustc_hir_analysis/src/check/check.rs
@@ -219,7 +219,7 @@ fn check_opaque(tcx: TyCtxt<'_>, def_id: LocalDefId) {
 
     // HACK(jynelson): trying to infer the type of `impl trait` breaks documenting
     // `async-std` (and `pub async fn` in general).
-    // Since rustdoc doesn't care about the concrete type behind `impl Trait`, just don't look at it!
+    // Since rustdoc doesn't care about the hidden type behind `impl Trait`, just don't look at it!
     // See https://github.com/rust-lang/rust/issues/75100
     if tcx.sess.opts.actually_rustdoc {
         return;
@@ -252,7 +252,7 @@ pub(super) fn check_opaque_for_cycles<'tcx>(
     Ok(())
 }
 
-/// Check that the concrete type behind `impl Trait` actually implements `Trait`.
+/// Check that the hidden type behind `impl Trait` actually implements `Trait`.
 ///
 /// This is mostly checked at the places that specify the opaque type, but we
 /// check those cases in the `param_env` of that function, which may have
diff --git a/compiler/rustc_hir_analysis/src/collect/item_bounds.rs b/compiler/rustc_hir_analysis/src/collect/item_bounds.rs
index ba54fa8cc0d..9841fafc82c 100644
--- a/compiler/rustc_hir_analysis/src/collect/item_bounds.rs
+++ b/compiler/rustc_hir_analysis/src/collect/item_bounds.rs
@@ -12,7 +12,7 @@ use tracing::{debug, instrument};
 
 use super::ItemCtxt;
 use super::predicates_of::assert_only_contains_predicates_from;
-use crate::hir_ty_lowering::{HirTyLowerer, PredicateFilter};
+use crate::hir_ty_lowering::{HirTyLowerer, OverlappingAsssocItemConstraints, PredicateFilter};
 
 /// For associated types we include both bounds written on the type
 /// (`type X: Trait`) and predicates from the trait: `where Self::X: Trait`.
@@ -37,7 +37,14 @@ fn associated_type_bounds<'tcx>(
 
         let icx = ItemCtxt::new(tcx, assoc_item_def_id);
         let mut bounds = Vec::new();
-        icx.lowerer().lower_bounds(item_ty, hir_bounds, &mut bounds, ty::List::empty(), filter);
+        icx.lowerer().lower_bounds(
+            item_ty,
+            hir_bounds,
+            &mut bounds,
+            ty::List::empty(),
+            filter,
+            OverlappingAsssocItemConstraints::Allowed,
+        );
 
         match filter {
             PredicateFilter::All
@@ -347,7 +354,14 @@ fn opaque_type_bounds<'tcx>(
     ty::print::with_reduced_queries!({
         let icx = ItemCtxt::new(tcx, opaque_def_id);
         let mut bounds = Vec::new();
-        icx.lowerer().lower_bounds(item_ty, hir_bounds, &mut bounds, ty::List::empty(), filter);
+        icx.lowerer().lower_bounds(
+            item_ty,
+            hir_bounds,
+            &mut bounds,
+            ty::List::empty(),
+            filter,
+            OverlappingAsssocItemConstraints::Allowed,
+        );
         // Implicit bounds are added to opaque types unless a `?Trait` bound is found
         match filter {
             PredicateFilter::All
diff --git a/compiler/rustc_hir_analysis/src/collect/predicates_of.rs b/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
index dd3590f9ac5..ffdf2a2f4c0 100644
--- a/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
+++ b/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
@@ -18,7 +18,9 @@ use super::item_bounds::explicit_item_bounds_with_filter;
 use crate::collect::ItemCtxt;
 use crate::constrained_generic_params as cgp;
 use crate::delegation::inherit_predicates_for_delegation_item;
-use crate::hir_ty_lowering::{HirTyLowerer, PredicateFilter, RegionInferReason};
+use crate::hir_ty_lowering::{
+    HirTyLowerer, OverlappingAsssocItemConstraints, PredicateFilter, RegionInferReason,
+};
 
 /// Returns a list of all type predicates (explicit and implicit) for the definition with
 /// ID `def_id`. This includes all predicates returned by `explicit_predicates_of`, plus
@@ -187,6 +189,7 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
             &mut bounds,
             ty::List::empty(),
             PredicateFilter::All,
+            OverlappingAsssocItemConstraints::Allowed,
         );
         icx.lowerer().add_sizedness_bounds(
             &mut bounds,
@@ -289,6 +292,7 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
                     &mut bounds,
                     bound_vars,
                     PredicateFilter::All,
+                    OverlappingAsssocItemConstraints::Allowed,
                 );
                 predicates.extend(bounds);
             }
@@ -659,7 +663,14 @@ pub(super) fn implied_predicates_with_filter<'tcx>(
 
     let self_param_ty = tcx.types.self_param;
     let mut bounds = Vec::new();
-    icx.lowerer().lower_bounds(self_param_ty, superbounds, &mut bounds, ty::List::empty(), filter);
+    icx.lowerer().lower_bounds(
+        self_param_ty,
+        superbounds,
+        &mut bounds,
+        ty::List::empty(),
+        filter,
+        OverlappingAsssocItemConstraints::Allowed,
+    );
     match filter {
         PredicateFilter::All
         | PredicateFilter::SelfOnly
@@ -984,6 +995,7 @@ impl<'tcx> ItemCtxt<'tcx> {
                 &mut bounds,
                 bound_vars,
                 filter,
+                OverlappingAsssocItemConstraints::Allowed,
             );
         }
 
@@ -1063,6 +1075,7 @@ pub(super) fn const_conditions<'tcx>(
                     &mut bounds,
                     bound_vars,
                     PredicateFilter::ConstIfConst,
+                    OverlappingAsssocItemConstraints::Allowed,
                 );
             }
             _ => {}
@@ -1083,6 +1096,7 @@ pub(super) fn const_conditions<'tcx>(
             &mut bounds,
             ty::List::empty(),
             PredicateFilter::ConstIfConst,
+            OverlappingAsssocItemConstraints::Allowed,
         );
     }
 
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 b6d898886ac..a02990fe4ab 100644
--- a/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
+++ b/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
@@ -177,7 +177,7 @@ impl<'tcx> TaitConstraintLocator<'tcx> {
                 let tables = tcx.typeck(item_def_id);
                 if let Some(guar) = tables.tainted_by_errors {
                     self.insert_found(ty::OpaqueHiddenType::new_error(tcx, guar));
-                } else if let Some(&hidden_type) = tables.concrete_opaque_types.get(&self.def_id) {
+                } else if let Some(&hidden_type) = tables.hidden_types.get(&self.def_id) {
                     self.insert_found(hidden_type);
                 } else {
                     self.non_defining_use_in_defining_scope(item_def_id);
@@ -185,8 +185,8 @@ impl<'tcx> TaitConstraintLocator<'tcx> {
             }
             DefiningScopeKind::MirBorrowck => match tcx.mir_borrowck(item_def_id) {
                 Err(guar) => self.insert_found(ty::OpaqueHiddenType::new_error(tcx, guar)),
-                Ok(concrete_opaque_types) => {
-                    if let Some(&hidden_type) = concrete_opaque_types.0.get(&self.def_id) {
+                Ok(hidden_types) => {
+                    if let Some(&hidden_type) = hidden_types.0.get(&self.def_id) {
                         debug!(?hidden_type, "found constraint");
                         self.insert_found(hidden_type);
                     } else if let Err(guar) = tcx
@@ -247,7 +247,7 @@ pub(super) fn find_opaque_ty_constraints_for_rpit<'tcx>(
             let tables = tcx.typeck(owner_def_id);
             if let Some(guar) = tables.tainted_by_errors {
                 Ty::new_error(tcx, guar)
-            } else if let Some(hidden_ty) = tables.concrete_opaque_types.get(&def_id) {
+            } else if let Some(hidden_ty) = tables.hidden_types.get(&def_id) {
                 hidden_ty.ty
             } else {
                 assert!(!tcx.next_trait_solver_globally());
@@ -261,8 +261,8 @@ pub(super) fn find_opaque_ty_constraints_for_rpit<'tcx>(
             }
         }
         DefiningScopeKind::MirBorrowck => match tcx.mir_borrowck(owner_def_id) {
-            Ok(concrete_opaque_types) => {
-                if let Some(hidden_ty) = concrete_opaque_types.0.get(&def_id) {
+            Ok(hidden_types) => {
+                if let Some(hidden_ty) = hidden_types.0.get(&def_id) {
                     hidden_ty.ty
                 } else {
                     let hir_ty = tcx.type_of_opaque_hir_typeck(def_id).instantiate_identity();
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs
index 99dc8e6e522..8682fdc5494 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs
@@ -21,7 +21,8 @@ use tracing::{debug, instrument};
 use super::errors::GenericsArgsErrExtend;
 use crate::errors;
 use crate::hir_ty_lowering::{
-    AssocItemQSelf, FeedConstTy, HirTyLowerer, PredicateFilter, RegionInferReason,
+    AssocItemQSelf, FeedConstTy, HirTyLowerer, OverlappingAsssocItemConstraints, PredicateFilter,
+    RegionInferReason,
 };
 
 #[derive(Debug, Default)]
@@ -338,6 +339,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         bounds: &mut Vec<(ty::Clause<'tcx>, Span)>,
         bound_vars: &'tcx ty::List<ty::BoundVariableKind>,
         predicate_filter: PredicateFilter,
+        overlapping_assoc_constraints: OverlappingAsssocItemConstraints,
     ) where
         'tcx: 'hir,
     {
@@ -362,6 +364,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                         param_ty,
                         bounds,
                         predicate_filter,
+                        overlapping_assoc_constraints,
                     );
                 }
                 hir::GenericBound::Outlives(lifetime) => {
@@ -402,7 +405,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         trait_ref: ty::PolyTraitRef<'tcx>,
         constraint: &hir::AssocItemConstraint<'tcx>,
         bounds: &mut Vec<(ty::Clause<'tcx>, Span)>,
-        duplicates: &mut FxIndexMap<DefId, Span>,
+        duplicates: Option<&mut FxIndexMap<DefId, Span>>,
         path_span: Span,
         predicate_filter: PredicateFilter,
     ) -> Result<(), ErrorGuaranteed> {
@@ -458,17 +461,19 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             )
             .expect("failed to find associated item");
 
-        duplicates
-            .entry(assoc_item.def_id)
-            .and_modify(|prev_span| {
-                self.dcx().emit_err(errors::ValueOfAssociatedStructAlreadySpecified {
-                    span: constraint.span,
-                    prev_span: *prev_span,
-                    item_name: constraint.ident,
-                    def_path: tcx.def_path_str(assoc_item.container_id(tcx)),
-                });
-            })
-            .or_insert(constraint.span);
+        if let Some(duplicates) = duplicates {
+            duplicates
+                .entry(assoc_item.def_id)
+                .and_modify(|prev_span| {
+                    self.dcx().emit_err(errors::ValueOfAssociatedStructAlreadySpecified {
+                        span: constraint.span,
+                        prev_span: *prev_span,
+                        item_name: constraint.ident,
+                        def_path: tcx.def_path_str(assoc_item.container_id(tcx)),
+                    });
+                })
+                .or_insert(constraint.span);
+        }
 
         let projection_term = if let ty::AssocTag::Fn = assoc_tag {
             let bound_vars = tcx.late_bound_vars(constraint.hir_id);
@@ -600,6 +605,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                             bounds,
                             projection_ty.bound_vars(),
                             predicate_filter,
+                            OverlappingAsssocItemConstraints::Allowed,
                         );
                     }
                     PredicateFilter::SelfOnly
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/cmse.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/cmse.rs
index 0458fa1204e..0a41659ec66 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/cmse.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/cmse.rs
@@ -134,6 +134,7 @@ fn is_valid_cmse_inputs<'tcx>(
 
     // this type is only used for layout computation, which does not rely on regions
     let fn_sig = tcx.instantiate_bound_regions_with_erased(fn_sig);
+    let fn_sig = tcx.erase_and_anonymize_regions(fn_sig);
 
     for (index, ty) in fn_sig.inputs().iter().enumerate() {
         let layout = tcx.layout_of(ty::TypingEnv::fully_monomorphized().as_query_input(*ty))?;
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_trait.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_trait.rs
index c248cd7fec2..c0b13773089 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_trait.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_trait.rs
@@ -23,7 +23,9 @@ use tracing::{debug, instrument};
 
 use super::HirTyLowerer;
 use crate::errors::SelfInTypeAlias;
-use crate::hir_ty_lowering::{GenericArgCountMismatch, PredicateFilter, RegionInferReason};
+use crate::hir_ty_lowering::{
+    GenericArgCountMismatch, OverlappingAsssocItemConstraints, PredicateFilter, RegionInferReason,
+};
 
 impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
     /// Lower a trait object type from the HIR to our internal notion of a type.
@@ -60,6 +62,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 dummy_self,
                 &mut user_written_bounds,
                 PredicateFilter::SelfOnly,
+                OverlappingAsssocItemConstraints::Forbidden,
             );
             if let Err(GenericArgCountMismatch { invalid_args, .. }) = result.correct {
                 potential_assoc_types.extend(invalid_args);
@@ -157,10 +160,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 self.dcx()
                     .struct_span_err(
                         span,
-                        format!(
-                            "conflicting associated type bounds for `{item}` when \
-                            expanding trait alias"
-                        ),
+                        format!("conflicting associated type bounds for `{item}`"),
                     )
                     .with_span_label(
                         old_proj_span,
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 9b198d04454..eb660804c2b 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
@@ -332,6 +332,15 @@ pub(crate) enum GenericArgPosition {
     MethodCall,
 }
 
+/// Whether to allow duplicate associated iten constraints in a trait ref, e.g.
+/// `Trait<Assoc = Ty, Assoc = Ty>`. This is forbidden in `dyn Trait<...>`
+/// but allowed everywhere else.
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub(crate) enum OverlappingAsssocItemConstraints {
+    Allowed,
+    Forbidden,
+}
+
 /// A marker denoting that the generic arguments that were
 /// provided did not match the respective generic parameters.
 #[derive(Clone, Debug)]
@@ -752,6 +761,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         self_ty: Ty<'tcx>,
         bounds: &mut Vec<(ty::Clause<'tcx>, Span)>,
         predicate_filter: PredicateFilter,
+        overlapping_assoc_item_constraints: OverlappingAsssocItemConstraints,
     ) -> GenericArgCountResult {
         let tcx = self.tcx();
 
@@ -908,7 +918,10 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             }
         }
 
-        let mut dup_constraints = FxIndexMap::default();
+        let mut dup_constraints = (overlapping_assoc_item_constraints
+            == OverlappingAsssocItemConstraints::Forbidden)
+            .then_some(FxIndexMap::default());
+
         for constraint in trait_segment.args().constraints {
             // Don't register any associated item constraints for negative bounds,
             // since we should have emitted an error for them earlier, and they
@@ -927,7 +940,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 poly_trait_ref,
                 constraint,
                 bounds,
-                &mut dup_constraints,
+                dup_constraints.as_mut(),
                 constraint.span,
                 predicate_filter,
             );
@@ -2484,6 +2497,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                     &mut bounds,
                     ty::List::empty(),
                     PredicateFilter::All,
+                    OverlappingAsssocItemConstraints::Allowed,
                 );
                 self.add_sizedness_bounds(
                     &mut bounds,
diff --git a/compiler/rustc_hir_typeck/src/opaque_types.rs b/compiler/rustc_hir_typeck/src/opaque_types.rs
index 5cefa506b5a..4c1fe69405e 100644
--- a/compiler/rustc_hir_typeck/src/opaque_types.rs
+++ b/compiler/rustc_hir_typeck/src/opaque_types.rs
@@ -15,7 +15,7 @@ use crate::FnCtxt;
 
 impl<'tcx> FnCtxt<'_, 'tcx> {
     /// This takes all the opaque type uses during HIR typeck. It first computes
-    /// the concrete hidden type by iterating over all defining uses.
+    /// the hidden type by iterating over all defining uses.
     ///
     /// A use during HIR typeck is defining if all non-lifetime arguments are
     /// unique generic parameters and the hidden type does not reference any
@@ -35,8 +35,8 @@ impl<'tcx> FnCtxt<'_, 'tcx> {
         }
         debug!(?opaque_types);
 
-        self.compute_concrete_opaque_types(&opaque_types);
-        self.apply_computed_concrete_opaque_types(&opaque_types);
+        self.compute_definition_site_hidden_types(&opaque_types);
+        self.apply_definition_site_hidden_types(&opaque_types);
     }
 }
 
@@ -71,7 +71,7 @@ impl<'tcx> UsageKind<'tcx> {
 }
 
 impl<'tcx> FnCtxt<'_, 'tcx> {
-    fn compute_concrete_opaque_types(
+    fn compute_definition_site_hidden_types(
         &mut self,
         opaque_types: &[(OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>)],
     ) {
@@ -142,7 +142,7 @@ impl<'tcx> FnCtxt<'_, 'tcx> {
 
             self.typeck_results
                 .borrow_mut()
-                .concrete_opaque_types
+                .hidden_types
                 .insert(def_id, OpaqueHiddenType::new_error(tcx, guar));
             self.set_tainted_by_errors(guar);
         }
@@ -161,7 +161,7 @@ impl<'tcx> FnCtxt<'_, 'tcx> {
         ) {
             match err {
                 NonDefiningUseReason::Tainted(guar) => {
-                    self.typeck_results.borrow_mut().concrete_opaque_types.insert(
+                    self.typeck_results.borrow_mut().hidden_types.insert(
                         opaque_type_key.def_id,
                         OpaqueHiddenType::new_error(self.tcx, guar),
                     );
@@ -197,20 +197,19 @@ impl<'tcx> FnCtxt<'_, 'tcx> {
         let prev = self
             .typeck_results
             .borrow_mut()
-            .concrete_opaque_types
+            .hidden_types
             .insert(opaque_type_key.def_id, hidden_type);
         assert!(prev.is_none());
         UsageKind::HasDefiningUse
     }
 
-    fn apply_computed_concrete_opaque_types(
+    fn apply_definition_site_hidden_types(
         &mut self,
         opaque_types: &[(OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>)],
     ) {
         let tcx = self.tcx;
         for &(key, hidden_type) in opaque_types {
-            let expected =
-                *self.typeck_results.borrow_mut().concrete_opaque_types.get(&key.def_id).unwrap();
+            let expected = *self.typeck_results.borrow_mut().hidden_types.get(&key.def_id).unwrap();
 
             let expected = EarlyBinder::bind(expected.ty).instantiate(tcx, key.args);
             self.demand_eqtype(hidden_type.span, expected, hidden_type.ty);
diff --git a/compiler/rustc_hir_typeck/src/writeback.rs b/compiler/rustc_hir_typeck/src/writeback.rs
index d01eeb9a4b6..697029e55f7 100644
--- a/compiler/rustc_hir_typeck/src/writeback.rs
+++ b/compiler/rustc_hir_typeck/src/writeback.rs
@@ -550,13 +550,12 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
     fn visit_opaque_types_next(&mut self) {
         let mut fcx_typeck_results = self.fcx.typeck_results.borrow_mut();
         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
-        for hidden_ty in fcx_typeck_results.concrete_opaque_types.values() {
+        for hidden_ty in fcx_typeck_results.hidden_types.values() {
             assert!(!hidden_ty.has_infer());
         }
 
-        assert_eq!(self.typeck_results.concrete_opaque_types.len(), 0);
-        self.typeck_results.concrete_opaque_types =
-            mem::take(&mut fcx_typeck_results.concrete_opaque_types);
+        assert_eq!(self.typeck_results.hidden_types.len(), 0);
+        self.typeck_results.hidden_types = mem::take(&mut fcx_typeck_results.hidden_types);
     }
 
     #[instrument(skip(self), level = "debug")]
@@ -588,7 +587,7 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
                 hidden_type.span,
                 DefiningScopeKind::HirTypeck,
             ) {
-                self.typeck_results.concrete_opaque_types.insert(
+                self.typeck_results.hidden_types.insert(
                     opaque_type_key.def_id,
                     ty::OpaqueHiddenType::new_error(tcx, err.report(self.fcx)),
                 );
@@ -600,16 +599,11 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
                 DefiningScopeKind::HirTypeck,
             );
 
-            if let Some(prev) = self
-                .typeck_results
-                .concrete_opaque_types
-                .insert(opaque_type_key.def_id, hidden_type)
+            if let Some(prev) =
+                self.typeck_results.hidden_types.insert(opaque_type_key.def_id, hidden_type)
             {
-                let entry = &mut self
-                    .typeck_results
-                    .concrete_opaque_types
-                    .get_mut(&opaque_type_key.def_id)
-                    .unwrap();
+                let entry =
+                    &mut self.typeck_results.hidden_types.get_mut(&opaque_type_key.def_id).unwrap();
                 if prev.ty != hidden_type.ty {
                     if let Some(guar) = self.typeck_results.tainted_by_errors {
                         entry.ty = Ty::new_error(tcx, guar);
@@ -628,7 +622,7 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
 
         let recursive_opaques: Vec<_> = self
             .typeck_results
-            .concrete_opaque_types
+            .hidden_types
             .iter()
             .filter(|&(&def_id, hidden_ty)| {
                 hidden_ty
@@ -636,7 +630,7 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
                     .visit_with(&mut HasRecursiveOpaque {
                         def_id,
                         seen: Default::default(),
-                        opaques: &self.typeck_results.concrete_opaque_types,
+                        opaques: &self.typeck_results.hidden_types,
                         tcx,
                     })
                     .is_break()
@@ -651,7 +645,7 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
                 .with_code(E0720)
                 .emit();
             self.typeck_results
-                .concrete_opaque_types
+                .hidden_types
                 .insert(def_id, OpaqueHiddenType { span, ty: Ty::new_error(tcx, guar) });
         }
     }
diff --git a/compiler/rustc_infer/src/infer/outlives/obligations.rs b/compiler/rustc_infer/src/infer/outlives/obligations.rs
index b989d419057..a640dcb1b4e 100644
--- a/compiler/rustc_infer/src/infer/outlives/obligations.rs
+++ b/compiler/rustc_infer/src/infer/outlives/obligations.rs
@@ -170,6 +170,10 @@ impl<'tcx> InferCtxt<'tcx> {
         std::mem::take(&mut self.inner.borrow_mut().region_obligations)
     }
 
+    pub fn clone_registered_region_obligations(&self) -> Vec<TypeOutlivesConstraint<'tcx>> {
+        self.inner.borrow().region_obligations.clone()
+    }
+
     pub fn register_region_assumption(&self, assumption: ty::ArgOutlivesPredicate<'tcx>) {
         let mut inner = self.inner.borrow_mut();
         inner.undo_log.push(UndoLog::PushRegionAssumption);
diff --git a/compiler/rustc_interface/src/util.rs b/compiler/rustc_interface/src/util.rs
index 58ec72b5b45..be2fd0787b9 100644
--- a/compiler/rustc_interface/src/util.rs
+++ b/compiler/rustc_interface/src/util.rs
@@ -1,3 +1,4 @@
+use std::any::Any;
 use std::env::consts::{DLL_PREFIX, DLL_SUFFIX};
 use std::path::{Path, PathBuf};
 use std::sync::atomic::{AtomicBool, Ordering};
@@ -6,13 +7,20 @@ use std::{env, thread};
 
 use rustc_ast as ast;
 use rustc_attr_parsing::{ShouldEmit, validate_attr};
+use rustc_codegen_ssa::back::archive::ArArchiveBuilderBuilder;
+use rustc_codegen_ssa::back::link::link_binary;
 use rustc_codegen_ssa::traits::CodegenBackend;
+use rustc_codegen_ssa::{CodegenResults, CrateInfo};
+use rustc_data_structures::fx::FxIndexMap;
 use rustc_data_structures::jobserver::Proxy;
 use rustc_data_structures::sync;
 use rustc_errors::LintBuffer;
-use rustc_metadata::{DylibError, load_symbol_from_dylib};
-use rustc_middle::ty::CurrentGcx;
-use rustc_session::config::{Cfg, OutFileName, OutputFilenames, OutputTypes, Sysroot, host_tuple};
+use rustc_metadata::{DylibError, EncodedMetadata, load_symbol_from_dylib};
+use rustc_middle::dep_graph::{WorkProduct, WorkProductId};
+use rustc_middle::ty::{CurrentGcx, TyCtxt};
+use rustc_session::config::{
+    Cfg, CrateType, OutFileName, OutputFilenames, OutputTypes, Sysroot, host_tuple,
+};
 use rustc_session::output::{CRATE_TYPES, categorize_crate_type};
 use rustc_session::{EarlyDiagCtxt, Session, filesearch, lint};
 use rustc_span::edit_distance::find_best_match_for_name;
@@ -316,12 +324,13 @@ pub fn get_codegen_backend(
         let backend = backend_name
             .or(target.default_codegen_backend.as_deref())
             .or(option_env!("CFG_DEFAULT_CODEGEN_BACKEND"))
-            .unwrap_or("llvm");
+            .unwrap_or("dummy");
 
         match backend {
             filename if filename.contains('.') => {
                 load_backend_from_dylib(early_dcx, filename.as_ref())
             }
+            "dummy" => || Box::new(DummyCodegenBackend),
             #[cfg(feature = "llvm")]
             "llvm" => rustc_codegen_llvm::LlvmCodegenBackend::new,
             backend_name => get_codegen_sysroot(early_dcx, sysroot, backend_name),
@@ -334,6 +343,63 @@ pub fn get_codegen_backend(
     unsafe { load() }
 }
 
+struct DummyCodegenBackend;
+
+impl CodegenBackend for DummyCodegenBackend {
+    fn locale_resource(&self) -> &'static str {
+        ""
+    }
+
+    fn name(&self) -> &'static str {
+        "dummy"
+    }
+
+    fn codegen_crate<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Box<dyn Any> {
+        Box::new(CodegenResults {
+            modules: vec![],
+            allocator_module: None,
+            crate_info: CrateInfo::new(tcx, String::new()),
+        })
+    }
+
+    fn join_codegen(
+        &self,
+        ongoing_codegen: Box<dyn Any>,
+        _sess: &Session,
+        _outputs: &OutputFilenames,
+    ) -> (CodegenResults, FxIndexMap<WorkProductId, WorkProduct>) {
+        (*ongoing_codegen.downcast().unwrap(), FxIndexMap::default())
+    }
+
+    fn link(
+        &self,
+        sess: &Session,
+        codegen_results: CodegenResults,
+        metadata: EncodedMetadata,
+        outputs: &OutputFilenames,
+    ) {
+        // JUSTIFICATION: TyCtxt no longer available here
+        #[allow(rustc::bad_opt_access)]
+        if sess.opts.crate_types.iter().any(|&crate_type| crate_type != CrateType::Rlib) {
+            #[allow(rustc::untranslatable_diagnostic)]
+            #[allow(rustc::diagnostic_outside_of_impl)]
+            sess.dcx().fatal(format!(
+                "crate type {} not supported by the dummy codegen backend",
+                sess.opts.crate_types[0],
+            ));
+        }
+
+        link_binary(
+            sess,
+            &ArArchiveBuilderBuilder,
+            codegen_results,
+            metadata,
+            outputs,
+            self.name(),
+        );
+    }
+}
+
 // This is used for rustdoc, but it uses similar machinery to codegen backend
 // loading, so we leave the code here. It is potentially useful for other tools
 // that want to invoke the rustc binary while linking to rustc as well.
diff --git a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
index 4a778125918..2b83ea24ac6 100644
--- a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
+++ b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
@@ -1824,3 +1824,55 @@ extern "C" size_t LLVMRustEnzymeGetMaxTypeDepth() {
   return 6; // Default fallback depth
 }
 #endif
+
+// Statically assert that the fixed metadata kind IDs declared in
+// `metadata_kind.rs` match the ones actually used by LLVM.
+#define FIXED_MD_KIND(VARIANT, VALUE)                                          \
+  static_assert(::llvm::LLVMContext::VARIANT == VALUE);
+// Must be kept in sync with the corresponding list in `metadata_kind.rs`.
+FIXED_MD_KIND(MD_dbg, 0)
+FIXED_MD_KIND(MD_tbaa, 1)
+FIXED_MD_KIND(MD_prof, 2)
+FIXED_MD_KIND(MD_fpmath, 3)
+FIXED_MD_KIND(MD_range, 4)
+FIXED_MD_KIND(MD_tbaa_struct, 5)
+FIXED_MD_KIND(MD_invariant_load, 6)
+FIXED_MD_KIND(MD_alias_scope, 7)
+FIXED_MD_KIND(MD_noalias, 8)
+FIXED_MD_KIND(MD_nontemporal, 9)
+FIXED_MD_KIND(MD_mem_parallel_loop_access, 10)
+FIXED_MD_KIND(MD_nonnull, 11)
+FIXED_MD_KIND(MD_dereferenceable, 12)
+FIXED_MD_KIND(MD_dereferenceable_or_null, 13)
+FIXED_MD_KIND(MD_make_implicit, 14)
+FIXED_MD_KIND(MD_unpredictable, 15)
+FIXED_MD_KIND(MD_invariant_group, 16)
+FIXED_MD_KIND(MD_align, 17)
+FIXED_MD_KIND(MD_loop, 18)
+FIXED_MD_KIND(MD_type, 19)
+FIXED_MD_KIND(MD_section_prefix, 20)
+FIXED_MD_KIND(MD_absolute_symbol, 21)
+FIXED_MD_KIND(MD_associated, 22)
+FIXED_MD_KIND(MD_callees, 23)
+FIXED_MD_KIND(MD_irr_loop, 24)
+FIXED_MD_KIND(MD_access_group, 25)
+FIXED_MD_KIND(MD_callback, 26)
+FIXED_MD_KIND(MD_preserve_access_index, 27)
+FIXED_MD_KIND(MD_vcall_visibility, 28)
+FIXED_MD_KIND(MD_noundef, 29)
+FIXED_MD_KIND(MD_annotation, 30)
+FIXED_MD_KIND(MD_nosanitize, 31)
+FIXED_MD_KIND(MD_func_sanitize, 32)
+FIXED_MD_KIND(MD_exclude, 33)
+FIXED_MD_KIND(MD_memprof, 34)
+FIXED_MD_KIND(MD_callsite, 35)
+FIXED_MD_KIND(MD_kcfi_type, 36)
+FIXED_MD_KIND(MD_pcsections, 37)
+FIXED_MD_KIND(MD_DIAssignID, 38)
+FIXED_MD_KIND(MD_coro_outside_frame, 39)
+FIXED_MD_KIND(MD_mmra, 40)
+FIXED_MD_KIND(MD_noalias_addrspace, 41)
+// If some fixed metadata kinds are not present and consistent in all supported
+// LLVM versions, it's fine to omit them from this list; in that case Rust-side
+// code cannot declare them as fixed IDs and must look them up by name instead.
+#undef FIXED_MD_KIND
diff --git a/compiler/rustc_middle/src/arena.rs b/compiler/rustc_middle/src/arena.rs
index fa6a2db38ef..feaad5bb96e 100644
--- a/compiler/rustc_middle/src/arena.rs
+++ b/compiler/rustc_middle/src/arena.rs
@@ -27,7 +27,7 @@ macro_rules! arena_types {
                     rustc_middle::mir::Body<'tcx>
                 >,
             [decode] typeck_results: rustc_middle::ty::TypeckResults<'tcx>,
-            [decode] borrowck_result: rustc_middle::mir::ConcreteOpaqueTypes<'tcx>,
+            [decode] borrowck_result: rustc_middle::mir::DefinitionSiteHiddenTypes<'tcx>,
             [] resolver: rustc_data_structures::steal::Steal<(
                 rustc_middle::ty::ResolverAstLowering,
                 std::sync::Arc<rustc_ast::Crate>,
diff --git a/compiler/rustc_middle/src/mir/query.rs b/compiler/rustc_middle/src/mir/query.rs
index a509c40c89c..2e6c9f207e2 100644
--- a/compiler/rustc_middle/src/mir/query.rs
+++ b/compiler/rustc_middle/src/mir/query.rs
@@ -84,11 +84,10 @@ impl Debug for CoroutineLayout<'_> {
     }
 }
 
-/// All the opaque types that are restricted to concrete types
-/// by this function. Unlike the value in `TypeckResults`, this has
-/// unerased regions.
+/// All the opaque types that have had their hidden type fully computed.
+/// Unlike the value in `TypeckResults`, this has unerased regions.
 #[derive(Default, Debug, TyEncodable, TyDecodable, HashStable)]
-pub struct ConcreteOpaqueTypes<'tcx>(pub FxIndexMap<LocalDefId, OpaqueHiddenType<'tcx>>);
+pub struct DefinitionSiteHiddenTypes<'tcx>(pub FxIndexMap<LocalDefId, OpaqueHiddenType<'tcx>>);
 
 /// The result of the `mir_const_qualif` query.
 ///
diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs
index 326df9239aa..895c8c0295a 100644
--- a/compiler/rustc_middle/src/query/mod.rs
+++ b/compiler/rustc_middle/src/query/mod.rs
@@ -1244,7 +1244,7 @@ rustc_queries! {
 
     /// Borrow-checks the given typeck root, e.g. functions, const/static items,
     /// and its children, e.g. closures, inline consts.
-    query mir_borrowck(key: LocalDefId) -> Result<&'tcx mir::ConcreteOpaqueTypes<'tcx>, ErrorGuaranteed> {
+    query mir_borrowck(key: LocalDefId) -> Result<&'tcx mir::DefinitionSiteHiddenTypes<'tcx>, ErrorGuaranteed> {
         desc { |tcx| "borrow-checking `{}`", tcx.def_path_str(key) }
     }
 
diff --git a/compiler/rustc_middle/src/ty/typeck_results.rs b/compiler/rustc_middle/src/ty/typeck_results.rs
index 8dd80aab946..944bd9756a9 100644
--- a/compiler/rustc_middle/src/ty/typeck_results.rs
+++ b/compiler/rustc_middle/src/ty/typeck_results.rs
@@ -167,7 +167,7 @@ pub struct TypeckResults<'tcx> {
     /// We also store the type here, so that the compiler can use it as a hint
     /// for figuring out hidden types, even if they are only set in dead code
     /// (which doesn't show up in MIR).
-    pub concrete_opaque_types: FxIndexMap<LocalDefId, ty::OpaqueHiddenType<'tcx>>,
+    pub hidden_types: FxIndexMap<LocalDefId, ty::OpaqueHiddenType<'tcx>>,
 
     /// Tracks the minimum captures required for a closure;
     /// see `MinCaptureInformationMap` for more details.
@@ -250,7 +250,7 @@ impl<'tcx> TypeckResults<'tcx> {
             coercion_casts: Default::default(),
             used_trait_imports: Default::default(),
             tainted_by_errors: None,
-            concrete_opaque_types: Default::default(),
+            hidden_types: Default::default(),
             closure_min_captures: Default::default(),
             closure_fake_reads: Default::default(),
             rvalue_scopes: Default::default(),
diff --git a/compiler/rustc_pattern_analysis/src/rustc.rs b/compiler/rustc_pattern_analysis/src/rustc.rs
index d9f8085083e..0652461e975 100644
--- a/compiler/rustc_pattern_analysis/src/rustc.rs
+++ b/compiler/rustc_pattern_analysis/src/rustc.rs
@@ -120,7 +120,7 @@ impl<'p, 'tcx: 'p> fmt::Debug for RustcPatCtxt<'p, 'tcx> {
 impl<'p, 'tcx: 'p> RustcPatCtxt<'p, 'tcx> {
     /// Type inference occasionally gives us opaque types in places where corresponding patterns
     /// have more specific types. To avoid inconsistencies as well as detect opaque uninhabited
-    /// types, we use the corresponding concrete type if possible.
+    /// types, we use the corresponding hidden type if possible.
     // FIXME(#132279): This will be unnecessary once we have a TypingMode which supports revealing
     // opaque types defined in a body.
     #[inline]
@@ -146,7 +146,7 @@ impl<'p, 'tcx: 'p> RustcPatCtxt<'p, 'tcx> {
     /// know it.
     fn reveal_opaque_key(&self, key: OpaqueTypeKey<'tcx>) -> Option<Ty<'tcx>> {
         self.typeck_results
-            .concrete_opaque_types
+            .hidden_types
             .get(&key.def_id)
             .map(|x| ty::EarlyBinder::bind(x.ty).instantiate(self.tcx, key.args))
     }
diff --git a/compiler/rustc_target/src/spec/base/apple/mod.rs b/compiler/rustc_target/src/spec/base/apple/mod.rs
index ecc74264160..39e604bcce7 100644
--- a/compiler/rustc_target/src/spec/base/apple/mod.rs
+++ b/compiler/rustc_target/src/spec/base/apple/mod.rs
@@ -158,12 +158,22 @@ pub(crate) fn base(
             SplitDebuginfo::Off,
         ]),
 
+        // Tell the linker that we would like it to avoid irreproducible binaries.
+        //
         // This environment variable is pretty magical but is intended for
         // producing deterministic builds. This was first discovered to be used
         // by the `ar` tool as a way to control whether or not mtime entries in
-        // the archive headers were set to zero or not. It appears that
-        // eventually the linker got updated to do the same thing and now reads
-        // this environment variable too in recent versions.
+        // the archive headers were set to zero or not.
+        //
+        // In `ld64-351.8`, shipped with Xcode 9.3, the linker was updated to
+        // read this flag too. Linker versions that don't support this flag
+        // may embed modification timestamps in binaries (especially in debug
+        // information).
+        //
+        // A cleaner alternative would be to pass the `-reproducible` flag,
+        // though that is only supported since `ld64-819.6` shipped with Xcode
+        // 14, which is too new for our minimum supported version:
+        // https://doc.rust-lang.org/rustc/platform-support/apple-darwin.html#host-tooling
         //
         // For some more info see the commentary on #47086
         link_env: Cow::Borrowed(&[(Cow::Borrowed("ZERO_AR_DATE"), Cow::Borrowed("1"))]),
diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs
index d485eb7266b..bec12750728 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs
@@ -1897,6 +1897,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         other: bool,
         param_env: ty::ParamEnv<'tcx>,
     ) -> bool {
+        let parent_map = self.tcx.visible_parent_map(());
         let alternative_candidates = |def_id: DefId| {
             let mut impl_candidates: Vec<_> = self
                 .tcx
@@ -1921,7 +1922,21 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                         // FIXME(compiler-errors): This could be generalized, both to
                         // be more granular, and probably look past other `#[fundamental]`
                         // types, too.
-                        self.tcx.visibility(def.did()).is_accessible_from(body_def_id, self.tcx)
+                        let mut did = def.did();
+                        if self.tcx.visibility(did).is_accessible_from(body_def_id, self.tcx) {
+                            // don't suggest foreign `#[doc(hidden)]` types
+                            if !did.is_local() {
+                                while let Some(parent) = parent_map.get(&did) {
+                                    if self.tcx.is_doc_hidden(did) {
+                                        return false;
+                                    }
+                                    did = *parent;
+                                }
+                            }
+                            true
+                        } else {
+                            false
+                        }
                     } else {
                         true
                     }
diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/mod.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/mod.rs
index b3d1b8e3888..9052031ce4f 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/traits/mod.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/mod.rs
@@ -21,7 +21,7 @@ use rustc_infer::traits::{
 };
 use rustc_middle::ty::print::{PrintTraitRefExt as _, with_no_trimmed_paths};
 use rustc_middle::ty::{self, Ty, TyCtxt};
-use rustc_span::{ErrorGuaranteed, ExpnKind, Span};
+use rustc_span::{DesugaringKind, ErrorGuaranteed, ExpnKind, Span};
 use tracing::{info, instrument};
 
 pub use self::overflow::*;
@@ -154,9 +154,20 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
             })
             .collect();
 
-        // Ensure `T: Sized`, `T: MetaSized`, `T: PointeeSized` and `T: WF` obligations come last.
+        // Ensure `T: Sized`, `T: MetaSized`, `T: PointeeSized` and `T: WF` obligations come last,
+        // and `Subtype` obligations from `FormatLiteral` desugarings come first.
         // This lets us display diagnostics with more relevant type information and hide redundant
         // E0282 errors.
+        #[derive(Debug, PartialEq, Eq, PartialOrd, Ord)]
+        enum ErrorSortKey {
+            SubtypeFormat(usize, usize),
+            OtherKind,
+            SizedTrait,
+            MetaSizedTrait,
+            PointeeSizedTrait,
+            Coerce,
+            WellFormed,
+        }
         errors.sort_by_key(|e| {
             let maybe_sizedness_did = match e.obligation.predicate.kind().skip_binder() {
                 ty::PredicateKind::Clause(ty::ClauseKind::Trait(pred)) => Some(pred.def_id()),
@@ -165,12 +176,30 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
             };
 
             match e.obligation.predicate.kind().skip_binder() {
-                _ if maybe_sizedness_did == self.tcx.lang_items().sized_trait() => 1,
-                _ if maybe_sizedness_did == self.tcx.lang_items().meta_sized_trait() => 2,
-                _ if maybe_sizedness_did == self.tcx.lang_items().pointee_sized_trait() => 3,
-                ty::PredicateKind::Coerce(_) => 4,
-                ty::PredicateKind::Clause(ty::ClauseKind::WellFormed(_)) => 5,
-                _ => 0,
+                ty::PredicateKind::Subtype(_)
+                    if matches!(
+                        e.obligation.cause.span.desugaring_kind(),
+                        Some(DesugaringKind::FormatLiteral { .. })
+                    ) =>
+                {
+                    let (_, row, col, ..) =
+                        self.tcx.sess.source_map().span_to_location_info(e.obligation.cause.span);
+                    ErrorSortKey::SubtypeFormat(row, col)
+                }
+                _ if maybe_sizedness_did == self.tcx.lang_items().sized_trait() => {
+                    ErrorSortKey::SizedTrait
+                }
+                _ if maybe_sizedness_did == self.tcx.lang_items().meta_sized_trait() => {
+                    ErrorSortKey::MetaSizedTrait
+                }
+                _ if maybe_sizedness_did == self.tcx.lang_items().pointee_sized_trait() => {
+                    ErrorSortKey::PointeeSizedTrait
+                }
+                ty::PredicateKind::Coerce(_) => ErrorSortKey::Coerce,
+                ty::PredicateKind::Clause(ty::ClauseKind::WellFormed(_)) => {
+                    ErrorSortKey::WellFormed
+                }
+                _ => ErrorSortKey::OtherKind,
             }
         });
 
diff --git a/compiler/rustc_trait_selection/src/traits/query/type_op/implied_outlives_bounds.rs b/compiler/rustc_trait_selection/src/traits/query/type_op/implied_outlives_bounds.rs
index 7540cbe3fd1..e55ffb4d5fd 100644
--- a/compiler/rustc_trait_selection/src/traits/query/type_op/implied_outlives_bounds.rs
+++ b/compiler/rustc_trait_selection/src/traits/query/type_op/implied_outlives_bounds.rs
@@ -55,6 +55,12 @@ pub fn compute_implied_outlives_bounds_inner<'tcx>(
     span: Span,
     disable_implied_bounds_hack: bool,
 ) -> Result<Vec<OutlivesBound<'tcx>>, NoSolution> {
+    // Inside mir borrowck, each computation starts with an empty list.
+    assert!(
+        ocx.infcx.inner.borrow().region_obligations().is_empty(),
+        "compute_implied_outlives_bounds assumes region obligations are empty before starting"
+    );
+
     let normalize_ty = |ty| -> Result<_, NoSolution> {
         // We must normalize the type so we can compute the right outlives components.
         // for example, if we have some constrained param type like `T: Trait<Out = U>`,
@@ -143,7 +149,7 @@ pub fn compute_implied_outlives_bounds_inner<'tcx>(
         && ty.visit_with(&mut ContainsBevyParamSet { tcx: ocx.infcx.tcx }).is_break()
     {
         for TypeOutlivesConstraint { sup_type, sub_region, .. } in
-            ocx.infcx.take_registered_region_obligations()
+            ocx.infcx.clone_registered_region_obligations()
         {
             let mut components = smallvec![];
             push_outlives_components(ocx.infcx.tcx, sup_type, &mut components);
diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
index 1dd31990ab7..fb4f28412d4 100644
--- a/compiler/rustc_trait_selection/src/traits/select/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -2359,7 +2359,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
                 if self.infcx.can_define_opaque_ty(def_id) {
                     unreachable!()
                 } else {
-                    // We can resolve the `impl Trait` to its concrete type,
+                    // We can resolve the opaque type to its hidden type,
                     // which enforces a DAG between the functions requiring
                     // the auto trait bounds in question.
                     match self.tcx().type_of_opaque(def_id) {
diff --git a/compiler/rustc_type_ir/src/infer_ctxt.rs b/compiler/rustc_type_ir/src/infer_ctxt.rs
index f743b84bce6..feafcee7bad 100644
--- a/compiler/rustc_type_ir/src/infer_ctxt.rs
+++ b/compiler/rustc_type_ir/src/infer_ctxt.rs
@@ -80,7 +80,7 @@ pub enum TypingMode<I: Interner> {
     /// the old solver as well.
     PostBorrowckAnalysis { defined_opaque_types: I::LocalDefIds },
     /// After analysis, mostly during codegen and MIR optimizations, we're able to
-    /// reveal all opaque types. As the concrete type should *never* be observable
+    /// reveal all opaque types. As the hidden type should *never* be observable
     /// directly by the user, this should not be used by checks which may expose
     /// such details to the user.
     ///
diff --git a/library/alloc/src/rc.rs b/library/alloc/src/rc.rs
index 627e5c7f976..023238a00db 100644
--- a/library/alloc/src/rc.rs
+++ b/library/alloc/src/rc.rs
@@ -277,7 +277,9 @@ use crate::vec::Vec;
 // This is repr(C) to future-proof against possible field-reordering, which
 // would interfere with otherwise safe [into|from]_raw() of transmutable
 // inner types.
-#[repr(C)]
+// repr(align(2)) (forcing alignment to at least 2) is required because usize
+// has 1-byte alignment on AVR.
+#[repr(C, align(2))]
 struct RcInner<T: ?Sized> {
     strong: Cell<usize>,
     weak: Cell<usize>,
diff --git a/library/alloc/src/sync.rs b/library/alloc/src/sync.rs
index 3a8695d34a8..6432bdfbbed 100644
--- a/library/alloc/src/sync.rs
+++ b/library/alloc/src/sync.rs
@@ -341,7 +341,7 @@ pub struct Weak<
     // but it is not necessarily a valid pointer.
     // `Weak::new` sets this to `usize::MAX` so that it doesn’t need
     // to allocate space on the heap. That's not a value a real pointer
-    // will ever have because RcInner has alignment at least 2.
+    // will ever have because ArcInner has alignment at least 2.
     ptr: NonNull<ArcInner<T>>,
     alloc: A,
 }
@@ -366,7 +366,9 @@ impl<T: ?Sized, A: Allocator> fmt::Debug for Weak<T, A> {
 // This is repr(C) to future-proof against possible field-reordering, which
 // would interfere with otherwise safe [into|from]_raw() of transmutable
 // inner types.
-#[repr(C)]
+// Unlike RcInner, repr(align(2)) is not strictly required because atomic types
+// have the alignment same as its size, but we use it for consistency and clarity.
+#[repr(C, align(2))]
 struct ArcInner<T: ?Sized> {
     strong: Atomic<usize>,
 
@@ -1613,9 +1615,9 @@ impl<T: ?Sized, A: Allocator> Arc<T, A> {
     pub fn as_ptr(this: &Self) -> *const T {
         let ptr: *mut ArcInner<T> = NonNull::as_ptr(this.ptr);
 
-        // SAFETY: This cannot go through Deref::deref or RcInnerPtr::inner because
+        // SAFETY: This cannot go through Deref::deref or ArcInnerPtr::inner because
         // this is required to retain raw/mut provenance such that e.g. `get_mut` can
-        // write through the pointer after the Rc is recovered through `from_raw`.
+        // write through the pointer after the Arc is recovered through `from_raw`.
         unsafe { &raw mut (*ptr).data }
     }
 
@@ -2450,7 +2452,7 @@ impl<T: ?Sized, A: Allocator> Arc<T, A> {
     /// If any other `Arc` or [`Weak`] pointers to the same allocation exist, then
     /// they must not be dereferenced or have active borrows for the duration
     /// of the returned borrow, and their inner type must be exactly the same as the
-    /// inner type of this Rc (including lifetimes). This is trivially the case if no
+    /// inner type of this Arc (including lifetimes). This is trivially the case if no
     /// such pointers exist, for example immediately after `Arc::new`.
     ///
     /// # Examples
@@ -3022,7 +3024,7 @@ impl<T: ?Sized, A: Allocator> Weak<T, A> {
             // Otherwise, we're guaranteed the pointer came from a nondangling Weak.
             // SAFETY: data_offset is safe to call, as ptr references a real (potentially dropped) T.
             let offset = unsafe { data_offset(ptr) };
-            // Thus, we reverse the offset to get the whole RcInner.
+            // Thus, we reverse the offset to get the whole ArcInner.
             // SAFETY: the pointer originated from a Weak, so this offset is safe.
             unsafe { ptr.byte_sub(offset) as *mut ArcInner<T> }
         };
@@ -4015,7 +4017,7 @@ impl<T: ?Sized, A: Allocator> Unpin for Arc<T, A> {}
 /// valid instance of T, but the T is allowed to be dropped.
 unsafe fn data_offset<T: ?Sized>(ptr: *const T) -> usize {
     // Align the unsized value to the end of the ArcInner.
-    // Because RcInner is repr(C), it will always be the last field in memory.
+    // Because ArcInner is repr(C), it will always be the last field in memory.
     // SAFETY: since the only unsized types possible are slices, trait objects,
     // and extern types, the input safety requirement is currently enough to
     // satisfy the requirements of align_of_val_raw; this is an implementation
diff --git a/library/proc_macro/src/bridge/client.rs b/library/proc_macro/src/bridge/client.rs
index e7d547966a5..92558f2b7d9 100644
--- a/library/proc_macro/src/bridge/client.rs
+++ b/library/proc_macro/src/bridge/client.rs
@@ -26,18 +26,16 @@ macro_rules! define_client_handles {
         $(
             pub(crate) struct $oty {
                 handle: handle::Handle,
-                // Prevent Send and Sync impls. `!Send`/`!Sync` is the usual
-                // way of doing this, but that requires unstable features.
-                // rust-analyzer uses this code and avoids unstable features.
-                _marker: PhantomData<*mut ()>,
             }
 
+            impl !Send for $oty {}
+            impl !Sync for $oty {}
+
             // Forward `Drop::drop` to the inherent `drop` method.
             impl Drop for $oty {
                 fn drop(&mut self) {
                     $oty {
                         handle: self.handle,
-                        _marker: PhantomData,
                     }.drop();
                 }
             }
@@ -64,7 +62,6 @@ macro_rules! define_client_handles {
                 fn decode(r: &mut Reader<'_>, s: &mut S) -> Self {
                     $oty {
                         handle: handle::Handle::decode(r, s),
-                        _marker: PhantomData,
                     }
                 }
             }
@@ -74,12 +71,11 @@ macro_rules! define_client_handles {
             #[derive(Copy, Clone, PartialEq, Eq, Hash)]
             pub(crate) struct $ity {
                 handle: handle::Handle,
-                // Prevent Send and Sync impls. `!Send`/`!Sync` is the usual
-                // way of doing this, but that requires unstable features.
-                // rust-analyzer uses this code and avoids unstable features.
-                _marker: PhantomData<*mut ()>,
             }
 
+            impl !Send for $ity {}
+            impl !Sync for $ity {}
+
             impl<S> Encode<S> for $ity {
                 fn encode(self, w: &mut Writer, s: &mut S) {
                     self.handle.encode(w, s);
@@ -90,7 +86,6 @@ macro_rules! define_client_handles {
                 fn decode(r: &mut Reader<'_>, s: &mut S) -> Self {
                     $ity {
                         handle: handle::Handle::decode(r, s),
-                        _marker: PhantomData,
                     }
                 }
             }
@@ -144,7 +139,7 @@ macro_rules! define_client_side {
 
                     buf.clear();
                     api_tags::Method::$name(api_tags::$name::$method).encode(&mut buf, &mut ());
-                    reverse_encode!(buf; $($arg),*);
+                    $($arg.encode(&mut buf, &mut ());)*
 
                     buf = bridge.dispatch.call(buf);
 
diff --git a/library/proc_macro/src/bridge/closure.rs b/library/proc_macro/src/bridge/closure.rs
index e0e688434dc..e5133907854 100644
--- a/library/proc_macro/src/bridge/closure.rs
+++ b/library/proc_macro/src/bridge/closure.rs
@@ -6,9 +6,7 @@ use std::marker::PhantomData;
 pub(super) struct Closure<'a, A, R> {
     call: unsafe extern "C" fn(*mut Env, A) -> R,
     env: *mut Env,
-    // Prevent Send and Sync impls. `!Send`/`!Sync` is the usual way of doing
-    // this, but that requires unstable features. rust-analyzer uses this code
-    // and avoids unstable features.
+    // Prevent Send and Sync impls.
     //
     // The `'a` lifetime parameter represents the lifetime of `Env`.
     _marker: PhantomData<*mut &'a mut ()>,
diff --git a/library/proc_macro/src/bridge/mod.rs b/library/proc_macro/src/bridge/mod.rs
index d60a76fff5d..1b09deb6bfe 100644
--- a/library/proc_macro/src/bridge/mod.rs
+++ b/library/proc_macro/src/bridge/mod.rs
@@ -119,26 +119,6 @@ macro_rules! with_api_handle_types {
     };
 }
 
-// FIXME(eddyb) this calls `encode` for each argument, but in reverse,
-// to match the ordering in `reverse_decode`.
-macro_rules! reverse_encode {
-    ($writer:ident;) => {};
-    ($writer:ident; $first:ident $(, $rest:ident)*) => {
-        reverse_encode!($writer; $($rest),*);
-        $first.encode(&mut $writer, &mut ());
-    }
-}
-
-// FIXME(eddyb) this calls `decode` for each argument, but in reverse,
-// to avoid borrow conflicts from borrows started by `&mut` arguments.
-macro_rules! reverse_decode {
-    ($reader:ident, $s:ident;) => {};
-    ($reader:ident, $s:ident; $first:ident: $first_ty:ty $(, $rest:ident: $rest_ty:ty)*) => {
-        reverse_decode!($reader, $s; $($rest: $rest_ty),*);
-        let $first = <$first_ty>::decode(&mut $reader, $s);
-    }
-}
-
 #[allow(unsafe_code)]
 mod arena;
 #[allow(unsafe_code)]
@@ -180,13 +160,11 @@ pub struct BridgeConfig<'a> {
 
     /// If 'true', always invoke the default panic hook
     force_show_panics: bool,
-
-    // Prevent Send and Sync impls. `!Send`/`!Sync` is the usual way of doing
-    // this, but that requires unstable features. rust-analyzer uses this code
-    // and avoids unstable features.
-    _marker: marker::PhantomData<*mut ()>,
 }
 
+impl !Send for BridgeConfig<'_> {}
+impl !Sync for BridgeConfig<'_> {}
+
 #[forbid(unsafe_code)]
 #[allow(non_camel_case_types)]
 mod api_tags {
diff --git a/library/proc_macro/src/bridge/server.rs b/library/proc_macro/src/bridge/server.rs
index 5beda7c3c96..0bb30698aa1 100644
--- a/library/proc_macro/src/bridge/server.rs
+++ b/library/proc_macro/src/bridge/server.rs
@@ -178,7 +178,7 @@ macro_rules! define_dispatcher_impl {
                     $(api_tags::Method::$name(m) => match m {
                         $(api_tags::$name::$method => {
                             let mut call_method = || {
-                                reverse_decode!(reader, handle_store; $($arg: $arg_ty),*);
+                                $(let $arg = <$arg_ty>::decode(&mut reader, handle_store);)*
                                 $name::$method(server, $($arg),*)
                             };
                             // HACK(eddyb) don't use `panic::catch_unwind` in a panic.
@@ -295,12 +295,7 @@ impl ExecutionStrategy for SameThread {
 
         let mut dispatch = |buf| dispatcher.dispatch(buf);
 
-        run_client(BridgeConfig {
-            input,
-            dispatch: (&mut dispatch).into(),
-            force_show_panics,
-            _marker: marker::PhantomData,
-        })
+        run_client(BridgeConfig { input, dispatch: (&mut dispatch).into(), force_show_panics })
     }
 }
 
@@ -331,12 +326,7 @@ where
                 client.recv().expect("server died while client waiting for reply")
             };
 
-            run_client(BridgeConfig {
-                input,
-                dispatch: (&mut dispatch).into(),
-                force_show_panics,
-                _marker: marker::PhantomData,
-            })
+            run_client(BridgeConfig { input, dispatch: (&mut dispatch).into(), force_show_panics })
         });
 
         while let Some(b) = server.recv() {
diff --git a/library/proc_macro/src/lib.rs b/library/proc_macro/src/lib.rs
index 162b4fdcc8a..613abd7024e 100644
--- a/library/proc_macro/src/lib.rs
+++ b/library/proc_macro/src/lib.rs
@@ -27,7 +27,6 @@
 #![feature(panic_can_unwind)]
 #![feature(restricted_std)]
 #![feature(rustc_attrs)]
-#![feature(stmt_expr_attributes)]
 #![feature(extend_one)]
 #![recursion_limit = "256"]
 #![allow(internal_features)]
diff --git a/library/std/src/path.rs b/library/std/src/path.rs
index 718c7c2e3b1..6e3b1e6e47d 100644
--- a/library/std/src/path.rs
+++ b/library/std/src/path.rs
@@ -1412,6 +1412,99 @@ impl PathBuf {
         }
     }
 
+    /// Sets whether the path has a trailing [separator](MAIN_SEPARATOR).
+    ///
+    /// The value returned by [`has_trailing_sep`](Path::has_trailing_sep) will be equivalent to
+    /// the provided value if possible.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(path_trailing_sep)]
+    /// use std::path::PathBuf;
+    ///
+    /// let mut p = PathBuf::from("dir");
+    ///
+    /// assert!(!p.has_trailing_sep());
+    /// p.set_trailing_sep(false);
+    /// assert!(!p.has_trailing_sep());
+    /// p.set_trailing_sep(true);
+    /// assert!(p.has_trailing_sep());
+    /// p.set_trailing_sep(false);
+    /// assert!(!p.has_trailing_sep());
+    ///
+    /// p = PathBuf::from("/");
+    /// assert!(p.has_trailing_sep());
+    /// p.set_trailing_sep(false);
+    /// assert!(p.has_trailing_sep());
+    /// ```
+    #[unstable(feature = "path_trailing_sep", issue = "142503")]
+    pub fn set_trailing_sep(&mut self, trailing_sep: bool) {
+        if trailing_sep { self.push_trailing_sep() } else { self.pop_trailing_sep() }
+    }
+
+    /// Adds a trailing [separator](MAIN_SEPARATOR) to the path.
+    ///
+    /// This acts similarly to [`Path::with_trailing_sep`], but mutates the underlying `PathBuf`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(path_trailing_sep)]
+    /// use std::ffi::OsStr;
+    /// use std::path::PathBuf;
+    ///
+    /// let mut p = PathBuf::from("dir");
+    ///
+    /// assert!(!p.has_trailing_sep());
+    /// p.push_trailing_sep();
+    /// assert!(p.has_trailing_sep());
+    /// p.push_trailing_sep();
+    /// assert!(p.has_trailing_sep());
+    ///
+    /// p = PathBuf::from("dir/");
+    /// p.push_trailing_sep();
+    /// assert_eq!(p.as_os_str(), OsStr::new("dir/"));
+    /// ```
+    #[unstable(feature = "path_trailing_sep", issue = "142503")]
+    pub fn push_trailing_sep(&mut self) {
+        if !self.has_trailing_sep() {
+            self.push("");
+        }
+    }
+
+    /// Removes a trailing [separator](MAIN_SEPARATOR) from the path, if possible.
+    ///
+    /// This acts similarly to [`Path::trim_trailing_sep`], but mutates the underlying `PathBuf`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(path_trailing_sep)]
+    /// use std::ffi::OsStr;
+    /// use std::path::PathBuf;
+    ///
+    /// let mut p = PathBuf::from("dir//");
+    ///
+    /// assert!(p.has_trailing_sep());
+    /// assert_eq!(p.as_os_str(), OsStr::new("dir//"));
+    /// p.pop_trailing_sep();
+    /// assert!(!p.has_trailing_sep());
+    /// assert_eq!(p.as_os_str(), OsStr::new("dir"));
+    /// p.pop_trailing_sep();
+    /// assert!(!p.has_trailing_sep());
+    /// assert_eq!(p.as_os_str(), OsStr::new("dir"));
+    ///
+    /// p = PathBuf::from("/");
+    /// assert!(p.has_trailing_sep());
+    /// p.pop_trailing_sep();
+    /// assert!(p.has_trailing_sep());
+    /// ```
+    #[unstable(feature = "path_trailing_sep", issue = "142503")]
+    pub fn pop_trailing_sep(&mut self) {
+        self.inner.truncate(self.trim_trailing_sep().as_os_str().len());
+    }
+
     /// Updates [`self.file_name`] to `file_name`.
     ///
     /// If [`self.file_name`] was [`None`], this is equivalent to pushing
@@ -1610,7 +1703,7 @@ impl PathBuf {
         let new = extension.as_encoded_bytes();
         if !new.is_empty() {
             // truncate until right after the file name
-            // this is necessary for trimming the trailing slash
+            // this is necessary for trimming the trailing separator
             let end_file_name = file_name[file_name.len()..].as_ptr().addr();
             let start = self.inner.as_encoded_bytes().as_ptr().addr();
             self.inner.truncate(end_file_name.wrapping_sub(start));
@@ -2755,6 +2848,94 @@ impl Path {
         self.file_name().map(rsplit_file_at_dot).and_then(|(before, after)| before.and(after))
     }
 
+    /// Checks whether the path ends in a trailing [separator](MAIN_SEPARATOR).
+    ///
+    /// This is generally done to ensure that a path is treated as a directory, not a file,
+    /// although it does not actually guarantee that such a path is a directory on the underlying
+    /// file system.
+    ///
+    /// Despite this behavior, two paths are still considered the same in Rust whether they have a
+    /// trailing separator or not.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(path_trailing_sep)]
+    /// use std::path::Path;
+    ///
+    /// assert!(Path::new("dir/").has_trailing_sep());
+    /// assert!(!Path::new("file.rs").has_trailing_sep());
+    /// ```
+    #[unstable(feature = "path_trailing_sep", issue = "142503")]
+    #[must_use]
+    #[inline]
+    pub fn has_trailing_sep(&self) -> bool {
+        self.as_os_str().as_encoded_bytes().last().copied().is_some_and(is_sep_byte)
+    }
+
+    /// Ensures that a path has a trailing [separator](MAIN_SEPARATOR),
+    /// allocating a [`PathBuf`] if necessary.
+    ///
+    /// The resulting path will return true for [`has_trailing_sep`](Self::has_trailing_sep).
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(path_trailing_sep)]
+    /// use std::ffi::OsStr;
+    /// use std::path::Path;
+    ///
+    /// assert_eq!(Path::new("dir//").with_trailing_sep().as_os_str(), OsStr::new("dir//"));
+    /// assert_eq!(Path::new("dir/").with_trailing_sep().as_os_str(), OsStr::new("dir/"));
+    /// assert!(!Path::new("dir").has_trailing_sep());
+    /// assert!(Path::new("dir").with_trailing_sep().has_trailing_sep());
+    /// ```
+    #[unstable(feature = "path_trailing_sep", issue = "142503")]
+    #[must_use]
+    #[inline]
+    pub fn with_trailing_sep(&self) -> Cow<'_, Path> {
+        if self.has_trailing_sep() { Cow::Borrowed(self) } else { Cow::Owned(self.join("")) }
+    }
+
+    /// Trims a trailing [separator](MAIN_SEPARATOR) from a path, if possible.
+    ///
+    /// The resulting path will return false for [`has_trailing_sep`](Self::has_trailing_sep) for
+    /// most paths.
+    ///
+    /// Some paths, like `/`, cannot be trimmed in this way.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(path_trailing_sep)]
+    /// use std::ffi::OsStr;
+    /// use std::path::Path;
+    ///
+    /// assert_eq!(Path::new("dir//").trim_trailing_sep().as_os_str(), OsStr::new("dir"));
+    /// assert_eq!(Path::new("dir/").trim_trailing_sep().as_os_str(), OsStr::new("dir"));
+    /// assert_eq!(Path::new("dir").trim_trailing_sep().as_os_str(), OsStr::new("dir"));
+    /// assert_eq!(Path::new("/").trim_trailing_sep().as_os_str(), OsStr::new("/"));
+    /// assert_eq!(Path::new("//").trim_trailing_sep().as_os_str(), OsStr::new("//"));
+    /// ```
+    #[unstable(feature = "path_trailing_sep", issue = "142503")]
+    #[must_use]
+    #[inline]
+    pub fn trim_trailing_sep(&self) -> &Path {
+        if self.has_trailing_sep() && (!self.has_root() || self.parent().is_some()) {
+            let mut bytes = self.inner.as_encoded_bytes();
+            while let Some((last, init)) = bytes.split_last()
+                && is_sep_byte(*last)
+            {
+                bytes = init;
+            }
+
+            // SAFETY: Trimming trailing ASCII bytes will retain the validity of the string.
+            Path::new(unsafe { OsStr::from_encoded_bytes_unchecked(bytes) })
+        } else {
+            self
+        }
+    }
+
     /// Creates an owned [`PathBuf`] with `path` adjoined to `self`.
     ///
     /// If `path` is absolute, it replaces the current path.
@@ -2907,7 +3088,7 @@ impl Path {
     ///   `a/b` all have `a` and `b` as components, but `./a/b` starts with
     ///   an additional [`CurDir`] component.
     ///
-    /// * A trailing slash is normalized away, `/a/b` and `/a/b/` are equivalent.
+    /// * Trailing separators are normalized away, so `/a/b` and `/a/b/` are equivalent.
     ///
     /// Note that no other normalization takes place; in particular, `a/c`
     /// and `a/b/../c` are distinct, to account for the possibility that `b`
@@ -3718,7 +3899,7 @@ impl Error for NormalizeError {}
 ///
 /// On POSIX platforms, the path is resolved using [POSIX semantics][posix-semantics],
 /// except that it stops short of resolving symlinks. This means it will keep `..`
-/// components and trailing slashes.
+/// components and trailing separators.
 ///
 /// On Windows, for verbatim paths, this will simply return the path as given. For other
 /// paths, this is currently equivalent to calling
diff --git a/library/std/src/thread/current.rs b/library/std/src/thread/current.rs
index 7da1621da45..f00212bfcb6 100644
--- a/library/std/src/thread/current.rs
+++ b/library/std/src/thread/current.rs
@@ -133,12 +133,32 @@ pub(super) fn set_current(thread: Thread) -> Result<(), Thread> {
     Ok(())
 }
 
-/// Gets the id of the thread that invokes it.
+/// Gets the unique identifier of the thread which invokes it.
+///
+/// Calling this function may be more efficient than accessing the current
+/// thread id through the current thread handle. i.e. `thread::current().id()`.
 ///
 /// This function will always succeed, will always return the same value for
 /// one thread and is guaranteed not to call the global allocator.
+///
+/// # Examples
+///
+/// ```
+/// #![feature(current_thread_id)]
+///
+/// use std::thread;
+///
+/// let other_thread = thread::spawn(|| {
+///     thread::current_id()
+/// });
+///
+/// let other_thread_id = other_thread.join().unwrap();
+/// assert_ne!(thread::current_id(), other_thread_id);
+/// ```
 #[inline]
-pub(crate) fn current_id() -> ThreadId {
+#[must_use]
+#[unstable(feature = "current_thread_id", issue = "147194")]
+pub fn current_id() -> ThreadId {
     // If accessing the persistent thread ID takes multiple TLS accesses, try
     // to retrieve it from the current thread handle, which will only take one
     // TLS access.
diff --git a/library/std/src/thread/mod.rs b/library/std/src/thread/mod.rs
index 4d09b2b4e9d..1768369792a 100644
--- a/library/std/src/thread/mod.rs
+++ b/library/std/src/thread/mod.rs
@@ -183,7 +183,9 @@ mod current;
 
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use current::current;
-pub(crate) use current::{current_id, current_or_unnamed, current_os_id, drop_current};
+#[unstable(feature = "current_thread_id", issue = "147194")]
+pub use current::current_id;
+pub(crate) use current::{current_or_unnamed, current_os_id, drop_current};
 use current::{set_current, try_with_current};
 
 mod spawnhook;
diff --git a/library/std/tests/path.rs b/library/std/tests/path.rs
index 837a14b808f..c60edbdf961 100644
--- a/library/std/tests/path.rs
+++ b/library/std/tests/path.rs
@@ -1,4 +1,9 @@
-#![feature(clone_to_uninit, maybe_uninit_slice, normalize_lexically)]
+// tidy-alphabetical-start
+#![feature(clone_to_uninit)]
+#![feature(maybe_uninit_slice)]
+#![feature(normalize_lexically)]
+#![feature(path_trailing_sep)]
+// tidy-alphabetical-end
 
 use std::clone::CloneToUninit;
 use std::ffi::OsStr;
@@ -2542,3 +2547,34 @@ fn compare_path_like_to_str_like() {
     assert!(path_buf == s);
     assert!(s == path_buf);
 }
+
+#[test]
+fn test_trim_trailing_sep() {
+    assert_eq!(Path::new("/").trim_trailing_sep().as_os_str(), OsStr::new("/"));
+    assert_eq!(Path::new("//").trim_trailing_sep().as_os_str(), OsStr::new("//"));
+    assert_eq!(Path::new("").trim_trailing_sep().as_os_str(), OsStr::new(""));
+    assert_eq!(Path::new(".").trim_trailing_sep().as_os_str(), OsStr::new("."));
+    assert_eq!(Path::new("./").trim_trailing_sep().as_os_str(), OsStr::new("."));
+    assert_eq!(Path::new(".//").trim_trailing_sep().as_os_str(), OsStr::new("."));
+    assert_eq!(Path::new("..").trim_trailing_sep().as_os_str(), OsStr::new(".."));
+    assert_eq!(Path::new("../").trim_trailing_sep().as_os_str(), OsStr::new(".."));
+    assert_eq!(Path::new("..//").trim_trailing_sep().as_os_str(), OsStr::new(".."));
+
+    #[cfg(any(windows, target_os = "cygwin"))]
+    {
+        assert_eq!(Path::new("\\").trim_trailing_sep().as_os_str(), OsStr::new("\\"));
+        assert_eq!(Path::new("\\\\").trim_trailing_sep().as_os_str(), OsStr::new("\\\\"));
+        assert_eq!(Path::new("c:/").trim_trailing_sep().as_os_str(), OsStr::new("c:/"));
+        assert_eq!(Path::new("c://").trim_trailing_sep().as_os_str(), OsStr::new("c://"));
+        assert_eq!(Path::new("c:./").trim_trailing_sep().as_os_str(), OsStr::new("c:."));
+        assert_eq!(Path::new("c:.//").trim_trailing_sep().as_os_str(), OsStr::new("c:."));
+        assert_eq!(Path::new("c:../").trim_trailing_sep().as_os_str(), OsStr::new("c:.."));
+        assert_eq!(Path::new("c:..//").trim_trailing_sep().as_os_str(), OsStr::new("c:.."));
+        assert_eq!(Path::new("c:\\").trim_trailing_sep().as_os_str(), OsStr::new("c:\\"));
+        assert_eq!(Path::new("c:\\\\").trim_trailing_sep().as_os_str(), OsStr::new("c:\\\\"));
+        assert_eq!(Path::new("c:.\\").trim_trailing_sep().as_os_str(), OsStr::new("c:."));
+        assert_eq!(Path::new("c:.\\\\").trim_trailing_sep().as_os_str(), OsStr::new("c:."));
+        assert_eq!(Path::new("c:..\\").trim_trailing_sep().as_os_str(), OsStr::new("c:.."));
+        assert_eq!(Path::new("c:..\\\\").trim_trailing_sep().as_os_str(), OsStr::new("c:.."));
+    }
+}
diff --git a/src/bootstrap/src/core/build_steps/doc.rs b/src/bootstrap/src/core/build_steps/doc.rs
index 7865b685659..37462c63f1b 100644
--- a/src/bootstrap/src/core/build_steps/doc.rs
+++ b/src/bootstrap/src/core/build_steps/doc.rs
@@ -1024,12 +1024,9 @@ macro_rules! tool_doc {
                         run.builder.ensure(Rustc::from_build_compiler(run.builder, compilers.build_compiler(), target));
                         compilers.build_compiler()
                     }
-                    Mode::ToolBootstrap => {
-                        // bootstrap/host tools should be documented with the stage 0 compiler
-                        prepare_doc_compiler(run.builder, run.builder.host_target, 1)
-                    }
                     Mode::ToolTarget => {
-                        // target tools should be documented with the in-tree compiler
+                        // when shipping multiple docs together in one folder,
+                        // they all need to use the same rustdoc version
                         prepare_doc_compiler(run.builder, run.builder.host_target, run.builder.top_stage)
                     }
                     _ => {
@@ -1132,7 +1129,11 @@ macro_rules! tool_doc {
 tool_doc!(
     BuildHelper,
     "src/build_helper",
-    mode = Mode::ToolBootstrap,
+    // ideally, this would use ToolBootstrap,
+    // but we distribute these docs together in the same folder
+    // as a bunch of stage1 tools, and you can't mix rustdoc versions
+    // because that breaks cross-crate data (particularly search)
+    mode = Mode::ToolTarget,
     is_library = true,
     crates = ["build_helper"]
 );
@@ -1175,25 +1176,25 @@ tool_doc!(
     // "specialization" feature in its build script when it detects a nightly toolchain.
     allow_features: "specialization"
 );
-tool_doc!(Tidy, "src/tools/tidy", mode = Mode::ToolBootstrap, crates = ["tidy"]);
+tool_doc!(Tidy, "src/tools/tidy", mode = Mode::ToolTarget, crates = ["tidy"]);
 tool_doc!(
     Bootstrap,
     "src/bootstrap",
-    mode = Mode::ToolBootstrap,
+    mode = Mode::ToolTarget,
     is_library = true,
     crates = ["bootstrap"]
 );
 tool_doc!(
     RunMakeSupport,
     "src/tools/run-make-support",
-    mode = Mode::ToolBootstrap,
+    mode = Mode::ToolTarget,
     is_library = true,
     crates = ["run_make_support"]
 );
 tool_doc!(
     Compiletest,
     "src/tools/compiletest",
-    mode = Mode::ToolBootstrap,
+    mode = Mode::ToolTarget,
     is_library = true,
     crates = ["compiletest"]
 );
diff --git a/src/bootstrap/src/core/builder/cargo.rs b/src/bootstrap/src/core/builder/cargo.rs
index 9fc4ce669c2..a404aec5120 100644
--- a/src/bootstrap/src/core/builder/cargo.rs
+++ b/src/bootstrap/src/core/builder/cargo.rs
@@ -10,7 +10,7 @@ use crate::core::config::flags::Color;
 use crate::utils::build_stamp;
 use crate::utils::helpers::{self, LldThreads, check_cfg_arg, linker_args, linker_flags};
 use crate::{
-    BootstrapCommand, CLang, Compiler, Config, DocTests, DryRun, EXTRA_CHECK_CFGS, GitRepo, Mode,
+    BootstrapCommand, CLang, Compiler, Config, DryRun, EXTRA_CHECK_CFGS, GitRepo, Mode,
     RemapScheme, TargetSelection, command, prepare_behaviour_dump_dir, t,
 };
 
@@ -851,8 +851,6 @@ impl Builder<'_> {
 
         rustflags.arg("-Zmacro-backtrace");
 
-        let want_rustdoc = self.doc_tests != DocTests::No;
-
         // Clear the output directory if the real rustc we're using has changed;
         // Cargo cannot detect this as it thinks rustc is bootstrap/debug/rustc.
         //
@@ -881,7 +879,8 @@ impl Builder<'_> {
             .env("RUSTC_REAL", self.rustc(compiler))
             .env("RUSTC_STAGE", build_compiler_stage.to_string())
             .env("RUSTC_SYSROOT", sysroot)
-            .env("RUSTC_LIBDIR", libdir)
+            .env("RUSTC_LIBDIR", &libdir)
+            .env("RUSTDOC_LIBDIR", libdir)
             .env("RUSTDOC", self.bootstrap_out.join("rustdoc"))
             .env("RUSTDOC_REAL", rustdoc_path)
             .env("RUSTC_ERROR_METADATA_DST", self.extended_error_dir());
@@ -919,11 +918,6 @@ impl Builder<'_> {
             rustflags.arg(&format!("-Zstack-protector={stack_protector}"));
         }
 
-        if !matches!(cmd_kind, Kind::Build | Kind::Check | Kind::Clippy | Kind::Fix) && want_rustdoc
-        {
-            cargo.env("RUSTDOC_LIBDIR", self.rustc_libdir(compiler));
-        }
-
         let debuginfo_level = match mode {
             Mode::Rustc | Mode::Codegen => self.config.rust_debuginfo_level_rustc,
             Mode::Std => self.config.rust_debuginfo_level_std,
diff --git a/src/bootstrap/src/core/builder/tests.rs b/src/bootstrap/src/core/builder/tests.rs
index 88df469e9a0..3306435758b 100644
--- a/src/bootstrap/src/core/builder/tests.rs
+++ b/src/bootstrap/src/core/builder/tests.rs
@@ -1158,13 +1158,12 @@ mod snapshot {
         [doc] embedded-book (book) <host>
         [doc] edition-guide (book) <host>
         [doc] style-guide (book) <host>
-        [build] rustdoc 0 <host>
-        [doc] rustc 0 <host> -> Tidy 1 <host>
-        [doc] rustc 0 <host> -> Bootstrap 1 <host>
+        [doc] rustc 1 <host> -> Tidy 2 <host>
+        [doc] rustc 1 <host> -> Bootstrap 2 <host>
         [doc] rustc 1 <host> -> releases 2 <host>
-        [doc] rustc 0 <host> -> RunMakeSupport 1 <host>
-        [doc] rustc 0 <host> -> BuildHelper 1 <host>
-        [doc] rustc 0 <host> -> Compiletest 1 <host>
+        [doc] rustc 1 <host> -> RunMakeSupport 2 <host>
+        [doc] rustc 1 <host> -> BuildHelper 2 <host>
+        [doc] rustc 1 <host> -> Compiletest 2 <host>
         [build] rustc 0 <host> -> RustInstaller 1 <host>
         "
         );
@@ -2686,8 +2685,11 @@ mod snapshot {
                 .path("src/tools/compiletest")
                 .stage(2)
                 .render_steps(), @r"
-        [build] rustdoc 0 <host>
-        [doc] rustc 0 <host> -> Compiletest 1 <host>
+        [build] llvm <host>
+        [build] rustc 0 <host> -> rustc 1 <host>
+        [build] rustc 1 <host> -> std 1 <host>
+        [build] rustdoc 1 <host>
+        [doc] rustc 1 <host> -> Compiletest 2 <host>
         ");
     }
 
diff --git a/src/etc/lldb_providers.py b/src/etc/lldb_providers.py
index 65f18baa937..3eb964d2fba 100644
--- a/src/etc/lldb_providers.py
+++ b/src/etc/lldb_providers.py
@@ -761,7 +761,8 @@ class MSVCTupleSyntheticProvider:
 
     def get_child_at_index(self, index: int) -> SBValue:
         child: SBValue = self.valobj.GetChildAtIndex(index)
-        return child.CreateChildAtOffset(str(index), 0, child.GetType())
+        offset = self.valobj.GetType().GetFieldAtIndex(index).byte_offset
+        return self.valobj.CreateChildAtOffset(str(index), offset, child.GetType())
 
     def update(self):
         pass
@@ -772,7 +773,7 @@ class MSVCTupleSyntheticProvider:
     def get_type_name(self) -> str:
         name = self.valobj.GetTypeName()
         # remove "tuple$<" and ">", str.removeprefix and str.removesuffix require python 3.9+
-        name = name[7:-1]
+        name = name[7:-1].strip()
         return "(" + name + ")"
 
 
diff --git a/tests/ui/associated-type-bounds/duplicate-bound-err.rs b/tests/ui/associated-type-bounds/duplicate-bound-err.rs
new file mode 100644
index 00000000000..01cc05f2545
--- /dev/null
+++ b/tests/ui/associated-type-bounds/duplicate-bound-err.rs
@@ -0,0 +1,114 @@
+//@ edition: 2024
+
+#![feature(associated_const_equality, type_alias_impl_trait, return_type_notation)]
+#![allow(refining_impl_trait_internal)]
+
+use std::iter;
+
+fn rpit1() -> impl Iterator<Item: Copy, Item: Send> {
+    iter::empty()
+    //~^ ERROR type annotations needed
+}
+fn rpit2() -> impl Iterator<Item: Copy, Item: Copy> {
+    iter::empty()
+    //~^ ERROR type annotations needed
+}
+fn rpit3() -> impl Iterator<Item: 'static, Item: 'static> {
+    iter::empty()
+    //~^ ERROR type annotations needed
+}
+
+type Tait1<T: Iterator<Item: Copy, Item: Send>> = impl Copy;
+//~^ ERROR unconstrained opaque type
+type Tait2<T: Iterator<Item: Copy, Item: Copy>> = impl Copy;
+//~^ ERROR unconstrained opaque type
+type Tait3<T: Iterator<Item: 'static, Item: 'static>> = impl Copy;
+//~^ ERROR unconstrained opaque type
+
+type Tait4 = impl Iterator<Item: Copy, Item: Send>;
+//~^ ERROR unconstrained opaque type
+type Tait5 = impl Iterator<Item: Copy, Item: Copy>;
+//~^ ERROR unconstrained opaque type
+type Tait6 = impl Iterator<Item: 'static, Item: 'static>;
+//~^ ERROR unconstrained opaque type
+
+fn mismatch() -> impl Iterator<Item: Copy, Item: Send> {
+    //~^ ERROR [E0277]
+    iter::empty::<*const ()>()
+}
+
+fn mismatch_2() -> impl Iterator<Item: Copy, Item: Send> {
+    //~^ ERROR [E0277]
+    iter::empty::<String>()
+}
+
+trait Trait {
+    type Gat<T>;
+
+    const ASSOC: i32;
+
+    fn foo() -> impl Sized;
+}
+
+impl Trait for () {
+    type Gat<T> = ();
+
+    const ASSOC: i32 = 3;
+
+    fn foo() {}
+}
+
+impl Trait for u32 {
+    type Gat<T> = ();
+
+    const ASSOC: i32 = 4;
+
+    fn foo() -> u32 {
+        42
+    }
+}
+
+fn uncallable(_: impl Iterator<Item = i32, Item = u32>) {}
+
+fn uncallable_const(_: impl Trait<ASSOC = 3, ASSOC = 4>) {}
+
+fn uncallable_rtn(_: impl Trait<foo(..): Trait<ASSOC = 3>, foo(..): Trait<ASSOC = 4>>) {}
+
+type MustFail = dyn Iterator<Item = i32, Item = u32>;
+//~^ ERROR [E0719]
+//~| ERROR conflicting associated type bounds
+
+trait Trait2 {
+    const ASSOC: u32;
+}
+
+type MustFail2 = dyn Trait2<ASSOC = 3u32, ASSOC = 4u32>;
+//~^ ERROR [E0719]
+//~| ERROR conflicting associated type bounds
+
+type MustFail3 = dyn Iterator<Item = i32, Item = i32>;
+//~^ ERROR [E0719]
+
+type MustFail4 = dyn Trait2<ASSOC = 3u32, ASSOC = 3u32>;
+//~^ ERROR [E0719]
+
+trait Trait3 {
+    fn foo() -> impl Iterator<Item = i32, Item = u32>;
+}
+
+impl Trait3 for () {
+    fn foo() -> impl Iterator<Item = i32, Item = u32> {
+        //~^ ERROR[E0271]
+        //~| ERROR[E0271]
+        [2u32].into_iter()
+    }
+}
+
+fn main() {
+    uncallable(iter::empty::<u32>()); //~ ERROR [E0271]
+    uncallable(iter::empty::<i32>()); //~ ERROR [E0271]
+    uncallable_const(()); //~ ERROR [E0271]
+    uncallable_const(4u32); //~ ERROR [E0271]
+    uncallable_rtn(()); //~ ERROR [E0271]
+    uncallable_rtn(17u32); //~ ERROR [E0271]
+}
diff --git a/tests/ui/associated-type-bounds/duplicate-bound-err.stderr b/tests/ui/associated-type-bounds/duplicate-bound-err.stderr
new file mode 100644
index 00000000000..1737d0dc5a3
--- /dev/null
+++ b/tests/ui/associated-type-bounds/duplicate-bound-err.stderr
@@ -0,0 +1,268 @@
+error[E0282]: type annotations needed
+  --> $DIR/duplicate-bound-err.rs:9:5
+   |
+LL |     iter::empty()
+   |     ^^^^^^^^^^^ cannot infer type of the type parameter `T` declared on the function `empty`
+   |
+help: consider specifying the generic argument
+   |
+LL |     iter::empty::<T>()
+   |                +++++
+
+error[E0282]: type annotations needed
+  --> $DIR/duplicate-bound-err.rs:13:5
+   |
+LL |     iter::empty()
+   |     ^^^^^^^^^^^ cannot infer type of the type parameter `T` declared on the function `empty`
+   |
+help: consider specifying the generic argument
+   |
+LL |     iter::empty::<T>()
+   |                +++++
+
+error[E0282]: type annotations needed
+  --> $DIR/duplicate-bound-err.rs:17:5
+   |
+LL |     iter::empty()
+   |     ^^^^^^^^^^^ cannot infer type of the type parameter `T` declared on the function `empty`
+   |
+help: consider specifying the generic argument
+   |
+LL |     iter::empty::<T>()
+   |                +++++
+
+error: unconstrained opaque type
+  --> $DIR/duplicate-bound-err.rs:21:51
+   |
+LL | type Tait1<T: Iterator<Item: Copy, Item: Send>> = impl Copy;
+   |                                                   ^^^^^^^^^
+   |
+   = note: `Tait1` must be used in combination with a concrete type within the same crate
+
+error: unconstrained opaque type
+  --> $DIR/duplicate-bound-err.rs:23:51
+   |
+LL | type Tait2<T: Iterator<Item: Copy, Item: Copy>> = impl Copy;
+   |                                                   ^^^^^^^^^
+   |
+   = note: `Tait2` must be used in combination with a concrete type within the same crate
+
+error: unconstrained opaque type
+  --> $DIR/duplicate-bound-err.rs:25:57
+   |
+LL | type Tait3<T: Iterator<Item: 'static, Item: 'static>> = impl Copy;
+   |                                                         ^^^^^^^^^
+   |
+   = note: `Tait3` must be used in combination with a concrete type within the same crate
+
+error: unconstrained opaque type
+  --> $DIR/duplicate-bound-err.rs:28:14
+   |
+LL | type Tait4 = impl Iterator<Item: Copy, Item: Send>;
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `Tait4` must be used in combination with a concrete type within the same crate
+
+error: unconstrained opaque type
+  --> $DIR/duplicate-bound-err.rs:30:14
+   |
+LL | type Tait5 = impl Iterator<Item: Copy, Item: Copy>;
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `Tait5` must be used in combination with a concrete type within the same crate
+
+error: unconstrained opaque type
+  --> $DIR/duplicate-bound-err.rs:32:14
+   |
+LL | type Tait6 = impl Iterator<Item: 'static, Item: 'static>;
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `Tait6` must be used in combination with a concrete type within the same crate
+
+error[E0277]: `*const ()` cannot be sent between threads safely
+  --> $DIR/duplicate-bound-err.rs:35:18
+   |
+LL | fn mismatch() -> impl Iterator<Item: Copy, Item: Send> {
+   |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `*const ()` cannot be sent between threads safely
+LL |
+LL |     iter::empty::<*const ()>()
+   |     -------------------------- return type was inferred to be `std::iter::Empty<*const ()>` here
+   |
+   = help: the trait `Send` is not implemented for `*const ()`
+
+error[E0277]: the trait bound `String: Copy` is not satisfied
+  --> $DIR/duplicate-bound-err.rs:40:20
+   |
+LL | fn mismatch_2() -> impl Iterator<Item: Copy, Item: Send> {
+   |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Copy` is not implemented for `String`
+LL |
+LL |     iter::empty::<String>()
+   |     ----------------------- return type was inferred to be `std::iter::Empty<String>` here
+
+error[E0271]: expected `IntoIter<u32, 1>` to be an iterator that yields `i32`, but it yields `u32`
+  --> $DIR/duplicate-bound-err.rs:100:17
+   |
+LL |     fn foo() -> impl Iterator<Item = i32, Item = u32> {
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `i32`, found `u32`
+...
+LL |         [2u32].into_iter()
+   |         ------------------ return type was inferred to be `std::array::IntoIter<u32, 1>` here
+
+error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
+  --> $DIR/duplicate-bound-err.rs:77:42
+   |
+LL | type MustFail = dyn Iterator<Item = i32, Item = u32>;
+   |                              ----------  ^^^^^^^^^^ re-bound here
+   |                              |
+   |                              `Item` bound here first
+
+error: conflicting associated type bounds for `Item`
+  --> $DIR/duplicate-bound-err.rs:77:17
+   |
+LL | type MustFail = dyn Iterator<Item = i32, Item = u32>;
+   |                 ^^^^^^^^^^^^^----------^^----------^
+   |                              |           |
+   |                              |           `Item` is specified to be `u32` here
+   |                              `Item` is specified to be `i32` here
+
+error[E0719]: the value of the associated type `ASSOC` in trait `Trait2` is already specified
+  --> $DIR/duplicate-bound-err.rs:85:43
+   |
+LL | type MustFail2 = dyn Trait2<ASSOC = 3u32, ASSOC = 4u32>;
+   |                             ------------  ^^^^^^^^^^^^ re-bound here
+   |                             |
+   |                             `ASSOC` bound here first
+
+error: conflicting associated type bounds for `ASSOC`
+  --> $DIR/duplicate-bound-err.rs:85:18
+   |
+LL | type MustFail2 = dyn Trait2<ASSOC = 3u32, ASSOC = 4u32>;
+   |                  ^^^^^^^^^^^------------^^------------^
+   |                             |             |
+   |                             |             `ASSOC` is specified to be `4` here
+   |                             `ASSOC` is specified to be `3` here
+
+error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
+  --> $DIR/duplicate-bound-err.rs:89:43
+   |
+LL | type MustFail3 = dyn Iterator<Item = i32, Item = i32>;
+   |                               ----------  ^^^^^^^^^^ re-bound here
+   |                               |
+   |                               `Item` bound here first
+
+error[E0719]: the value of the associated type `ASSOC` in trait `Trait2` is already specified
+  --> $DIR/duplicate-bound-err.rs:92:43
+   |
+LL | type MustFail4 = dyn Trait2<ASSOC = 3u32, ASSOC = 3u32>;
+   |                             ------------  ^^^^^^^^^^^^ re-bound here
+   |                             |
+   |                             `ASSOC` bound here first
+
+error[E0271]: expected `impl Iterator<Item = u32>` to be an iterator that yields `i32`, but it yields `u32`
+  --> $DIR/duplicate-bound-err.rs:100:17
+   |
+LL |     fn foo() -> impl Iterator<Item = i32, Item = u32> {
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `i32`, found `u32`
+   |
+note: required by a bound in `Trait3::foo::{anon_assoc#0}`
+  --> $DIR/duplicate-bound-err.rs:96:31
+   |
+LL |     fn foo() -> impl Iterator<Item = i32, Item = u32>;
+   |                               ^^^^^^^^^^ required by this bound in `Trait3::foo::{anon_assoc#0}`
+
+error[E0271]: expected `Empty<u32>` to be an iterator that yields `i32`, but it yields `u32`
+  --> $DIR/duplicate-bound-err.rs:108:16
+   |
+LL |     uncallable(iter::empty::<u32>());
+   |     ---------- ^^^^^^^^^^^^^^^^^^^^ expected `i32`, found `u32`
+   |     |
+   |     required by a bound introduced by this call
+   |
+note: required by a bound in `uncallable`
+  --> $DIR/duplicate-bound-err.rs:71:32
+   |
+LL | fn uncallable(_: impl Iterator<Item = i32, Item = u32>) {}
+   |                                ^^^^^^^^^^ required by this bound in `uncallable`
+
+error[E0271]: expected `Empty<i32>` to be an iterator that yields `u32`, but it yields `i32`
+  --> $DIR/duplicate-bound-err.rs:109:16
+   |
+LL |     uncallable(iter::empty::<i32>());
+   |     ---------- ^^^^^^^^^^^^^^^^^^^^ expected `u32`, found `i32`
+   |     |
+   |     required by a bound introduced by this call
+   |
+note: required by a bound in `uncallable`
+  --> $DIR/duplicate-bound-err.rs:71:44
+   |
+LL | fn uncallable(_: impl Iterator<Item = i32, Item = u32>) {}
+   |                                            ^^^^^^^^^^ required by this bound in `uncallable`
+
+error[E0271]: type mismatch resolving `<() as Trait>::ASSOC == 4`
+  --> $DIR/duplicate-bound-err.rs:110:22
+   |
+LL |     uncallable_const(());
+   |     ---------------- ^^ expected `4`, found `3`
+   |     |
+   |     required by a bound introduced by this call
+   |
+   = note: expected constant `4`
+              found constant `3`
+note: required by a bound in `uncallable_const`
+  --> $DIR/duplicate-bound-err.rs:73:46
+   |
+LL | fn uncallable_const(_: impl Trait<ASSOC = 3, ASSOC = 4>) {}
+   |                                              ^^^^^^^^^ required by this bound in `uncallable_const`
+
+error[E0271]: type mismatch resolving `<u32 as Trait>::ASSOC == 3`
+  --> $DIR/duplicate-bound-err.rs:111:22
+   |
+LL |     uncallable_const(4u32);
+   |     ---------------- ^^^^ expected `3`, found `4`
+   |     |
+   |     required by a bound introduced by this call
+   |
+   = note: expected constant `3`
+              found constant `4`
+note: required by a bound in `uncallable_const`
+  --> $DIR/duplicate-bound-err.rs:73:35
+   |
+LL | fn uncallable_const(_: impl Trait<ASSOC = 3, ASSOC = 4>) {}
+   |                                   ^^^^^^^^^ required by this bound in `uncallable_const`
+
+error[E0271]: type mismatch resolving `<() as Trait>::ASSOC == 4`
+  --> $DIR/duplicate-bound-err.rs:112:20
+   |
+LL |     uncallable_rtn(());
+   |     -------------- ^^ expected `4`, found `3`
+   |     |
+   |     required by a bound introduced by this call
+   |
+   = note: expected constant `4`
+              found constant `3`
+note: required by a bound in `uncallable_rtn`
+  --> $DIR/duplicate-bound-err.rs:75:75
+   |
+LL | fn uncallable_rtn(_: impl Trait<foo(..): Trait<ASSOC = 3>, foo(..): Trait<ASSOC = 4>>) {}
+   |                                                                           ^^^^^^^^^ required by this bound in `uncallable_rtn`
+
+error[E0271]: type mismatch resolving `<u32 as Trait>::ASSOC == 3`
+  --> $DIR/duplicate-bound-err.rs:113:20
+   |
+LL |     uncallable_rtn(17u32);
+   |     -------------- ^^^^^ expected `3`, found `4`
+   |     |
+   |     required by a bound introduced by this call
+   |
+   = note: expected constant `3`
+              found constant `4`
+note: required by a bound in `uncallable_rtn`
+  --> $DIR/duplicate-bound-err.rs:75:48
+   |
+LL | fn uncallable_rtn(_: impl Trait<foo(..): Trait<ASSOC = 3>, foo(..): Trait<ASSOC = 4>>) {}
+   |                                                ^^^^^^^^^ required by this bound in `uncallable_rtn`
+
+error: aborting due to 25 previous errors
+
+Some errors have detailed explanations: E0271, E0277, E0282, E0719.
+For more information about an error, try `rustc --explain E0271`.
diff --git a/tests/ui/associated-type-bounds/duplicate-bound.rs b/tests/ui/associated-type-bounds/duplicate-bound.rs
new file mode 100644
index 00000000000..696710d76f6
--- /dev/null
+++ b/tests/ui/associated-type-bounds/duplicate-bound.rs
@@ -0,0 +1,240 @@
+//@ edition: 2024
+//@ run-pass
+
+#![feature(associated_const_equality, return_type_notation)]
+#![allow(dead_code, refining_impl_trait_internal, type_alias_bounds)]
+
+use std::iter;
+use std::mem::ManuallyDrop;
+
+struct Si1<T: Iterator<Item: Copy, Item: Send>> {
+    f: T,
+}
+struct Si2<T: Iterator<Item: Copy, Item: Copy>> {
+    f: T,
+}
+struct Si3<T: Iterator<Item: 'static, Item: 'static>> {
+    f: T,
+}
+struct Sw1<T>
+where
+    T: Iterator<Item: Copy, Item: Send>,
+{
+    f: T,
+}
+struct Sw2<T>
+where
+    T: Iterator<Item: Copy, Item: Copy>,
+{
+    f: T,
+}
+struct Sw3<T>
+where
+    T: Iterator<Item: 'static, Item: 'static>,
+{
+    f: T,
+}
+
+enum Ei1<T: Iterator<Item: Copy, Item: Send>> {
+    V(T),
+}
+enum Ei2<T: Iterator<Item: Copy, Item: Copy>> {
+    V(T),
+}
+enum Ei3<T: Iterator<Item: 'static, Item: 'static>> {
+    V(T),
+}
+enum Ew1<T>
+where
+    T: Iterator<Item: Copy, Item: Send>,
+{
+    V(T),
+}
+enum Ew2<T>
+where
+    T: Iterator<Item: Copy, Item: Copy>,
+{
+    V(T),
+}
+enum Ew3<T>
+where
+    T: Iterator<Item: 'static, Item: 'static>,
+{
+    V(T),
+}
+
+union Ui1<T: Iterator<Item: Copy, Item: Send>> {
+    f: ManuallyDrop<T>,
+}
+union Ui2<T: Iterator<Item: Copy, Item: Copy>> {
+    f: ManuallyDrop<T>,
+}
+union Ui3<T: Iterator<Item: 'static, Item: 'static>> {
+    f: ManuallyDrop<T>,
+}
+union Uw1<T>
+where
+    T: Iterator<Item: Copy, Item: Send>,
+{
+    f: ManuallyDrop<T>,
+}
+union Uw2<T>
+where
+    T: Iterator<Item: Copy, Item: Copy>,
+{
+    f: ManuallyDrop<T>,
+}
+union Uw3<T>
+where
+    T: Iterator<Item: 'static, Item: 'static>,
+{
+    f: ManuallyDrop<T>,
+}
+
+fn fi1<T: Iterator<Item: Copy, Item: Send>>() {}
+fn fi2<T: Iterator<Item: Copy, Item: Copy>>() {}
+fn fi3<T: Iterator<Item: 'static, Item: 'static>>() {}
+fn fw1<T>()
+where
+    T: Iterator<Item: Copy, Item: Send>,
+{
+}
+fn fw2<T>()
+where
+    T: Iterator<Item: Copy, Item: Copy>,
+{
+}
+fn fw3<T>()
+where
+    T: Iterator<Item: 'static, Item: 'static>,
+{
+}
+
+fn rpit1() -> impl Iterator<Item: Copy, Item: Send> {
+    iter::empty::<u32>()
+}
+fn rpit2() -> impl Iterator<Item: Copy, Item: Copy> {
+    iter::empty::<u32>()
+}
+fn rpit3() -> impl Iterator<Item: 'static, Item: 'static> {
+    iter::empty::<u32>()
+}
+fn apit1(_: impl Iterator<Item: Copy, Item: Send>) {}
+fn apit2(_: impl Iterator<Item: Copy, Item: Copy>) {}
+fn apit3(_: impl Iterator<Item: 'static, Item: 'static>) {}
+
+type Tait1<T: Iterator<Item: Copy, Item: Send>> = T;
+type Tait2<T: Iterator<Item: Copy, Item: Copy>> = T;
+type Tait3<T: Iterator<Item: 'static, Item: 'static>> = T;
+type Taw1<T>
+where
+    T: Iterator<Item: Copy, Item: Send>,
+= T;
+type Taw2<T>
+where
+    T: Iterator<Item: Copy, Item: Copy>,
+= T;
+type Taw3<T>
+where
+    T: Iterator<Item: 'static, Item: 'static>,
+= T;
+
+trait Tri1<T: Iterator<Item: Copy, Item: Send>> {}
+trait Tri2<T: Iterator<Item: Copy, Item: Copy>> {}
+trait Tri3<T: Iterator<Item: 'static, Item: 'static>> {}
+trait Trs1: Iterator<Item: Copy, Item: Send> {}
+trait Trs2: Iterator<Item: Copy, Item: Copy> {}
+trait Trs3: Iterator<Item: 'static, Item: 'static> {}
+trait Trw1<T>
+where
+    T: Iterator<Item: Copy, Item: Send>,
+{
+}
+trait Trw2<T>
+where
+    T: Iterator<Item: Copy, Item: Copy>,
+{
+}
+trait Trw3<T>
+where
+    T: Iterator<Item: 'static, Item: 'static>,
+{
+}
+trait Trsw1
+where
+    Self: Iterator<Item: Copy, Item: Send>,
+{
+}
+trait Trsw2
+where
+    Self: Iterator<Item: Copy, Item: Copy>,
+{
+}
+trait Trsw3
+where
+    Self: Iterator<Item: 'static, Item: 'static>,
+{
+}
+trait Tra1 {
+    type A: Iterator<Item: Copy, Item: Send>;
+}
+trait Tra2 {
+    type A: Iterator<Item: Copy, Item: Copy>;
+}
+trait Tra3 {
+    type A: Iterator<Item: 'static, Item: 'static>;
+}
+
+trait Trait {
+    type Gat<T>;
+
+    const ASSOC: i32;
+
+    fn foo() -> impl Sized;
+}
+
+impl Trait for () {
+    type Gat<T> = ();
+
+    const ASSOC: i32 = 3;
+
+    fn foo() {}
+}
+
+trait Subtrait: Trait<Gat<u32> = u32, Gat<u64> = u64> {}
+
+fn f<T: Trait<Gat<i32> = (), Gat<i64> = ()>>() {
+    let _: T::Gat<i32> = ();
+    let _: T::Gat<i64> = ();
+}
+
+fn g<T: Trait<Gat<i32> = (), Gat<i64> = &'static str>>() {
+    let _: T::Gat<i32> = ();
+    let _: T::Gat<i64> = "";
+}
+
+fn uncallable(_: impl Iterator<Item = i32, Item = u32>) {}
+
+fn callable(_: impl Iterator<Item = i32, Item = i32>) {}
+
+fn uncallable_const(_: impl Trait<ASSOC = 3, ASSOC = 4>) {}
+
+fn callable_const(_: impl Trait<ASSOC = 3, ASSOC = 3>) {}
+
+fn uncallable_rtn(_: impl Trait<foo(..): Trait<ASSOC = 3>, foo(..): Trait<ASSOC = 4>>) {}
+
+fn callable_rtn(_: impl Trait<foo(..): Send, foo(..): Send, foo(..): Eq>) {}
+
+trait Trait2 {
+    const ASSOC: u32;
+}
+
+trait Trait3 {
+    fn foo() -> impl Iterator<Item = i32, Item = u32>;
+}
+
+fn main() {
+    callable(iter::empty::<i32>());
+    callable_const(());
+    callable_rtn(());
+}
diff --git a/tests/ui/associated-type-bounds/duplicate.rs b/tests/ui/associated-type-bounds/duplicate.rs
deleted file mode 100644
index e9d94787e98..00000000000
--- a/tests/ui/associated-type-bounds/duplicate.rs
+++ /dev/null
@@ -1,278 +0,0 @@
-#![feature(type_alias_impl_trait)]
-
-use std::iter;
-use std::mem::ManuallyDrop;
-
-struct SI1<T: Iterator<Item: Copy, Item: Send>> {
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    f: T,
-}
-struct SI2<T: Iterator<Item: Copy, Item: Copy>> {
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    f: T,
-}
-struct SI3<T: Iterator<Item: 'static, Item: 'static>> {
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    f: T,
-}
-struct SW1<T>
-where
-    T: Iterator<Item: Copy, Item: Send>,
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-{
-    f: T,
-}
-struct SW2<T>
-where
-    T: Iterator<Item: Copy, Item: Copy>,
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-{
-    f: T,
-}
-struct SW3<T>
-where
-    T: Iterator<Item: 'static, Item: 'static>,
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-{
-    f: T,
-}
-
-enum EI1<T: Iterator<Item: Copy, Item: Send>> {
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    V(T),
-}
-enum EI2<T: Iterator<Item: Copy, Item: Copy>> {
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    V(T),
-}
-enum EI3<T: Iterator<Item: 'static, Item: 'static>> {
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    V(T),
-}
-enum EW1<T>
-where
-    T: Iterator<Item: Copy, Item: Send>,
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-{
-    V(T),
-}
-enum EW2<T>
-where
-    T: Iterator<Item: Copy, Item: Copy>,
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-{
-    V(T),
-}
-enum EW3<T>
-where
-    T: Iterator<Item: 'static, Item: 'static>,
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-{
-    V(T),
-}
-
-union UI1<T: Iterator<Item: Copy, Item: Send>> {
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    f: ManuallyDrop<T>,
-}
-union UI2<T: Iterator<Item: Copy, Item: Copy>> {
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    f: ManuallyDrop<T>,
-}
-union UI3<T: Iterator<Item: 'static, Item: 'static>> {
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    f: ManuallyDrop<T>,
-}
-union UW1<T>
-where
-    T: Iterator<Item: Copy, Item: Send>,
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-{
-    f: ManuallyDrop<T>,
-}
-union UW2<T>
-where
-    T: Iterator<Item: Copy, Item: Copy>,
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-{
-    f: ManuallyDrop<T>,
-}
-union UW3<T>
-where
-    T: Iterator<Item: 'static, Item: 'static>,
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-{
-    f: ManuallyDrop<T>,
-}
-
-fn FI1<T: Iterator<Item: Copy, Item: Send>>() {}
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-fn FI2<T: Iterator<Item: Copy, Item: Copy>>() {}
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-fn FI3<T: Iterator<Item: 'static, Item: 'static>>() {}
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-fn FW1<T>()
-where
-    T: Iterator<Item: Copy, Item: Send>,
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-{
-}
-fn FW2<T>()
-where
-    T: Iterator<Item: Copy, Item: Copy>,
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-{
-}
-fn FW3<T>()
-where
-    T: Iterator<Item: 'static, Item: 'static>,
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-{
-}
-
-fn FRPIT1() -> impl Iterator<Item: Copy, Item: Send> {
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    //~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    iter::empty()
-    //~^ ERROR type annotations needed
-}
-fn FRPIT2() -> impl Iterator<Item: Copy, Item: Copy> {
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    //~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    iter::empty()
-    //~^ ERROR type annotations needed
-}
-fn FRPIT3() -> impl Iterator<Item: 'static, Item: 'static> {
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    //~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    iter::empty()
-    //~^ ERROR type annotations needed
-}
-fn FAPIT1(_: impl Iterator<Item: Copy, Item: Send>) {}
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-fn FAPIT2(_: impl Iterator<Item: Copy, Item: Copy>) {}
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-fn FAPIT3(_: impl Iterator<Item: 'static, Item: 'static>) {}
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-
-type TAI1<T: Iterator<Item: Copy, Item: Send>> = T;
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-type TAI2<T: Iterator<Item: Copy, Item: Copy>> = T;
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-type TAI3<T: Iterator<Item: 'static, Item: 'static>> = T;
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-type TAW1<T>
-where
-    T: Iterator<Item: Copy, Item: Send>,
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-= T;
-type TAW2<T>
-where
-    T: Iterator<Item: Copy, Item: Copy>,
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-= T;
-type TAW3<T>
-where
-    T: Iterator<Item: 'static, Item: 'static>,
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-= T;
-
-type ETAI1<T: Iterator<Item: Copy, Item: Send>> = impl Copy;
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-//~| ERROR unconstrained opaque type
-type ETAI2<T: Iterator<Item: Copy, Item: Copy>> = impl Copy;
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-//~| ERROR unconstrained opaque type
-type ETAI3<T: Iterator<Item: 'static, Item: 'static>> = impl Copy;
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-//~| ERROR unconstrained opaque type
-type ETAI4 = impl Iterator<Item: Copy, Item: Send>;
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-//~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-//~| ERROR unconstrained opaque type
-type ETAI5 = impl Iterator<Item: Copy, Item: Copy>;
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-//~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-//~| ERROR unconstrained opaque type
-type ETAI6 = impl Iterator<Item: 'static, Item: 'static>;
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-//~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-//~| ERROR unconstrained opaque type
-
-trait TRI1<T: Iterator<Item: Copy, Item: Send>> {}
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-trait TRI2<T: Iterator<Item: Copy, Item: Copy>> {}
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-trait TRI3<T: Iterator<Item: 'static, Item: 'static>> {}
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-trait TRS1: Iterator<Item: Copy, Item: Send> {}
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-//~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-//~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-trait TRS2: Iterator<Item: Copy, Item: Copy> {}
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-//~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-//~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-trait TRS3: Iterator<Item: 'static, Item: 'static> {}
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-//~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-//~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-trait TRW1<T>
-where
-    T: Iterator<Item: Copy, Item: Send>,
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-{
-}
-trait TRW2<T>
-where
-    T: Iterator<Item: Copy, Item: Copy>,
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-{
-}
-trait TRW3<T>
-where
-    T: Iterator<Item: 'static, Item: 'static>,
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-{
-}
-trait TRSW1
-where
-    Self: Iterator<Item: Copy, Item: Send>,
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    //~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    //~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-{
-}
-trait TRSW2
-where
-    Self: Iterator<Item: Copy, Item: Copy>,
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    //~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    //~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-{
-}
-trait TRSW3
-where
-    Self: Iterator<Item: 'static, Item: 'static>,
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    //~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    //~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-{
-}
-trait TRA1 {
-    type A: Iterator<Item: Copy, Item: Send>;
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    //~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-}
-trait TRA2 {
-    type A: Iterator<Item: Copy, Item: Copy>;
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    //~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-}
-trait TRA3 {
-    type A: Iterator<Item: 'static, Item: 'static>;
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    //~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-}
-
-fn main() {}
diff --git a/tests/ui/associated-type-bounds/duplicate.stderr b/tests/ui/associated-type-bounds/duplicate.stderr
deleted file mode 100644
index 68fbb345f6f..00000000000
--- a/tests/ui/associated-type-bounds/duplicate.stderr
+++ /dev/null
@@ -1,751 +0,0 @@
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:6:36
-   |
-LL | struct SI1<T: Iterator<Item: Copy, Item: Send>> {
-   |                        ----------  ^^^^^^^^^^ re-bound here
-   |                        |
-   |                        `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:10:36
-   |
-LL | struct SI2<T: Iterator<Item: Copy, Item: Copy>> {
-   |                        ----------  ^^^^^^^^^^ re-bound here
-   |                        |
-   |                        `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:14:39
-   |
-LL | struct SI3<T: Iterator<Item: 'static, Item: 'static>> {
-   |                        -------------  ^^^^^^^^^^^^^ re-bound here
-   |                        |
-   |                        `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:20:29
-   |
-LL |     T: Iterator<Item: Copy, Item: Send>,
-   |                 ----------  ^^^^^^^^^^ re-bound here
-   |                 |
-   |                 `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:27:29
-   |
-LL |     T: Iterator<Item: Copy, Item: Copy>,
-   |                 ----------  ^^^^^^^^^^ re-bound here
-   |                 |
-   |                 `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:34:32
-   |
-LL |     T: Iterator<Item: 'static, Item: 'static>,
-   |                 -------------  ^^^^^^^^^^^^^ re-bound here
-   |                 |
-   |                 `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:40:34
-   |
-LL | enum EI1<T: Iterator<Item: Copy, Item: Send>> {
-   |                      ----------  ^^^^^^^^^^ re-bound here
-   |                      |
-   |                      `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:44:34
-   |
-LL | enum EI2<T: Iterator<Item: Copy, Item: Copy>> {
-   |                      ----------  ^^^^^^^^^^ re-bound here
-   |                      |
-   |                      `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:48:37
-   |
-LL | enum EI3<T: Iterator<Item: 'static, Item: 'static>> {
-   |                      -------------  ^^^^^^^^^^^^^ re-bound here
-   |                      |
-   |                      `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:54:29
-   |
-LL |     T: Iterator<Item: Copy, Item: Send>,
-   |                 ----------  ^^^^^^^^^^ re-bound here
-   |                 |
-   |                 `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:61:29
-   |
-LL |     T: Iterator<Item: Copy, Item: Copy>,
-   |                 ----------  ^^^^^^^^^^ re-bound here
-   |                 |
-   |                 `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:68:32
-   |
-LL |     T: Iterator<Item: 'static, Item: 'static>,
-   |                 -------------  ^^^^^^^^^^^^^ re-bound here
-   |                 |
-   |                 `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:74:35
-   |
-LL | union UI1<T: Iterator<Item: Copy, Item: Send>> {
-   |                       ----------  ^^^^^^^^^^ re-bound here
-   |                       |
-   |                       `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:78:35
-   |
-LL | union UI2<T: Iterator<Item: Copy, Item: Copy>> {
-   |                       ----------  ^^^^^^^^^^ re-bound here
-   |                       |
-   |                       `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:82:38
-   |
-LL | union UI3<T: Iterator<Item: 'static, Item: 'static>> {
-   |                       -------------  ^^^^^^^^^^^^^ re-bound here
-   |                       |
-   |                       `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:88:29
-   |
-LL |     T: Iterator<Item: Copy, Item: Send>,
-   |                 ----------  ^^^^^^^^^^ re-bound here
-   |                 |
-   |                 `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:95:29
-   |
-LL |     T: Iterator<Item: Copy, Item: Copy>,
-   |                 ----------  ^^^^^^^^^^ re-bound here
-   |                 |
-   |                 `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:102:32
-   |
-LL |     T: Iterator<Item: 'static, Item: 'static>,
-   |                 -------------  ^^^^^^^^^^^^^ re-bound here
-   |                 |
-   |                 `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:108:32
-   |
-LL | fn FI1<T: Iterator<Item: Copy, Item: Send>>() {}
-   |                    ----------  ^^^^^^^^^^ re-bound here
-   |                    |
-   |                    `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:110:32
-   |
-LL | fn FI2<T: Iterator<Item: Copy, Item: Copy>>() {}
-   |                    ----------  ^^^^^^^^^^ re-bound here
-   |                    |
-   |                    `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:112:35
-   |
-LL | fn FI3<T: Iterator<Item: 'static, Item: 'static>>() {}
-   |                    -------------  ^^^^^^^^^^^^^ re-bound here
-   |                    |
-   |                    `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:116:29
-   |
-LL |     T: Iterator<Item: Copy, Item: Send>,
-   |                 ----------  ^^^^^^^^^^ re-bound here
-   |                 |
-   |                 `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:122:29
-   |
-LL |     T: Iterator<Item: Copy, Item: Copy>,
-   |                 ----------  ^^^^^^^^^^ re-bound here
-   |                 |
-   |                 `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:128:32
-   |
-LL |     T: Iterator<Item: 'static, Item: 'static>,
-   |                 -------------  ^^^^^^^^^^^^^ re-bound here
-   |                 |
-   |                 `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:133:42
-   |
-LL | fn FRPIT1() -> impl Iterator<Item: Copy, Item: Send> {
-   |                              ----------  ^^^^^^^^^^ re-bound here
-   |                              |
-   |                              `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:139:42
-   |
-LL | fn FRPIT2() -> impl Iterator<Item: Copy, Item: Copy> {
-   |                              ----------  ^^^^^^^^^^ re-bound here
-   |                              |
-   |                              `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:145:45
-   |
-LL | fn FRPIT3() -> impl Iterator<Item: 'static, Item: 'static> {
-   |                              -------------  ^^^^^^^^^^^^^ re-bound here
-   |                              |
-   |                              `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:151:40
-   |
-LL | fn FAPIT1(_: impl Iterator<Item: Copy, Item: Send>) {}
-   |                            ----------  ^^^^^^^^^^ re-bound here
-   |                            |
-   |                            `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:153:40
-   |
-LL | fn FAPIT2(_: impl Iterator<Item: Copy, Item: Copy>) {}
-   |                            ----------  ^^^^^^^^^^ re-bound here
-   |                            |
-   |                            `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:155:43
-   |
-LL | fn FAPIT3(_: impl Iterator<Item: 'static, Item: 'static>) {}
-   |                            -------------  ^^^^^^^^^^^^^ re-bound here
-   |                            |
-   |                            `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:158:35
-   |
-LL | type TAI1<T: Iterator<Item: Copy, Item: Send>> = T;
-   |                       ----------  ^^^^^^^^^^ re-bound here
-   |                       |
-   |                       `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:160:35
-   |
-LL | type TAI2<T: Iterator<Item: Copy, Item: Copy>> = T;
-   |                       ----------  ^^^^^^^^^^ re-bound here
-   |                       |
-   |                       `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:162:38
-   |
-LL | type TAI3<T: Iterator<Item: 'static, Item: 'static>> = T;
-   |                       -------------  ^^^^^^^^^^^^^ re-bound here
-   |                       |
-   |                       `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:166:29
-   |
-LL |     T: Iterator<Item: Copy, Item: Send>,
-   |                 ----------  ^^^^^^^^^^ re-bound here
-   |                 |
-   |                 `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:171:29
-   |
-LL |     T: Iterator<Item: Copy, Item: Copy>,
-   |                 ----------  ^^^^^^^^^^ re-bound here
-   |                 |
-   |                 `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:176:32
-   |
-LL |     T: Iterator<Item: 'static, Item: 'static>,
-   |                 -------------  ^^^^^^^^^^^^^ re-bound here
-   |                 |
-   |                 `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:180:36
-   |
-LL | type ETAI1<T: Iterator<Item: Copy, Item: Send>> = impl Copy;
-   |                        ----------  ^^^^^^^^^^ re-bound here
-   |                        |
-   |                        `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:183:36
-   |
-LL | type ETAI2<T: Iterator<Item: Copy, Item: Copy>> = impl Copy;
-   |                        ----------  ^^^^^^^^^^ re-bound here
-   |                        |
-   |                        `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:186:39
-   |
-LL | type ETAI3<T: Iterator<Item: 'static, Item: 'static>> = impl Copy;
-   |                        -------------  ^^^^^^^^^^^^^ re-bound here
-   |                        |
-   |                        `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:202:36
-   |
-LL | trait TRI1<T: Iterator<Item: Copy, Item: Send>> {}
-   |                        ----------  ^^^^^^^^^^ re-bound here
-   |                        |
-   |                        `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:204:36
-   |
-LL | trait TRI2<T: Iterator<Item: Copy, Item: Copy>> {}
-   |                        ----------  ^^^^^^^^^^ re-bound here
-   |                        |
-   |                        `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:206:39
-   |
-LL | trait TRI3<T: Iterator<Item: 'static, Item: 'static>> {}
-   |                        -------------  ^^^^^^^^^^^^^ re-bound here
-   |                        |
-   |                        `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:208:34
-   |
-LL | trait TRS1: Iterator<Item: Copy, Item: Send> {}
-   |                      ----------  ^^^^^^^^^^ re-bound here
-   |                      |
-   |                      `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:208:34
-   |
-LL | trait TRS1: Iterator<Item: Copy, Item: Send> {}
-   |                      ----------  ^^^^^^^^^^ re-bound here
-   |                      |
-   |                      `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:208:34
-   |
-LL | trait TRS1: Iterator<Item: Copy, Item: Send> {}
-   |                      ----------  ^^^^^^^^^^ re-bound here
-   |                      |
-   |                      `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:212:34
-   |
-LL | trait TRS2: Iterator<Item: Copy, Item: Copy> {}
-   |                      ----------  ^^^^^^^^^^ re-bound here
-   |                      |
-   |                      `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:212:34
-   |
-LL | trait TRS2: Iterator<Item: Copy, Item: Copy> {}
-   |                      ----------  ^^^^^^^^^^ re-bound here
-   |                      |
-   |                      `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:212:34
-   |
-LL | trait TRS2: Iterator<Item: Copy, Item: Copy> {}
-   |                      ----------  ^^^^^^^^^^ re-bound here
-   |                      |
-   |                      `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:216:37
-   |
-LL | trait TRS3: Iterator<Item: 'static, Item: 'static> {}
-   |                      -------------  ^^^^^^^^^^^^^ re-bound here
-   |                      |
-   |                      `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:216:37
-   |
-LL | trait TRS3: Iterator<Item: 'static, Item: 'static> {}
-   |                      -------------  ^^^^^^^^^^^^^ re-bound here
-   |                      |
-   |                      `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:216:37
-   |
-LL | trait TRS3: Iterator<Item: 'static, Item: 'static> {}
-   |                      -------------  ^^^^^^^^^^^^^ re-bound here
-   |                      |
-   |                      `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:222:29
-   |
-LL |     T: Iterator<Item: Copy, Item: Send>,
-   |                 ----------  ^^^^^^^^^^ re-bound here
-   |                 |
-   |                 `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:228:29
-   |
-LL |     T: Iterator<Item: Copy, Item: Copy>,
-   |                 ----------  ^^^^^^^^^^ re-bound here
-   |                 |
-   |                 `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:234:32
-   |
-LL |     T: Iterator<Item: 'static, Item: 'static>,
-   |                 -------------  ^^^^^^^^^^^^^ re-bound here
-   |                 |
-   |                 `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:240:32
-   |
-LL |     Self: Iterator<Item: Copy, Item: Send>,
-   |                    ----------  ^^^^^^^^^^ re-bound here
-   |                    |
-   |                    `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:240:32
-   |
-LL |     Self: Iterator<Item: Copy, Item: Send>,
-   |                    ----------  ^^^^^^^^^^ re-bound here
-   |                    |
-   |                    `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:240:32
-   |
-LL |     Self: Iterator<Item: Copy, Item: Send>,
-   |                    ----------  ^^^^^^^^^^ re-bound here
-   |                    |
-   |                    `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:248:32
-   |
-LL |     Self: Iterator<Item: Copy, Item: Copy>,
-   |                    ----------  ^^^^^^^^^^ re-bound here
-   |                    |
-   |                    `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:248:32
-   |
-LL |     Self: Iterator<Item: Copy, Item: Copy>,
-   |                    ----------  ^^^^^^^^^^ re-bound here
-   |                    |
-   |                    `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:248:32
-   |
-LL |     Self: Iterator<Item: Copy, Item: Copy>,
-   |                    ----------  ^^^^^^^^^^ re-bound here
-   |                    |
-   |                    `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:256:35
-   |
-LL |     Self: Iterator<Item: 'static, Item: 'static>,
-   |                    -------------  ^^^^^^^^^^^^^ re-bound here
-   |                    |
-   |                    `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:256:35
-   |
-LL |     Self: Iterator<Item: 'static, Item: 'static>,
-   |                    -------------  ^^^^^^^^^^^^^ re-bound here
-   |                    |
-   |                    `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:256:35
-   |
-LL |     Self: Iterator<Item: 'static, Item: 'static>,
-   |                    -------------  ^^^^^^^^^^^^^ re-bound here
-   |                    |
-   |                    `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:263:34
-   |
-LL |     type A: Iterator<Item: Copy, Item: Send>;
-   |                      ----------  ^^^^^^^^^^ re-bound here
-   |                      |
-   |                      `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:263:34
-   |
-LL |     type A: Iterator<Item: Copy, Item: Send>;
-   |                      ----------  ^^^^^^^^^^ re-bound here
-   |                      |
-   |                      `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:268:34
-   |
-LL |     type A: Iterator<Item: Copy, Item: Copy>;
-   |                      ----------  ^^^^^^^^^^ re-bound here
-   |                      |
-   |                      `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:268:34
-   |
-LL |     type A: Iterator<Item: Copy, Item: Copy>;
-   |                      ----------  ^^^^^^^^^^ re-bound here
-   |                      |
-   |                      `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:273:37
-   |
-LL |     type A: Iterator<Item: 'static, Item: 'static>;
-   |                      -------------  ^^^^^^^^^^^^^ re-bound here
-   |                      |
-   |                      `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:273:37
-   |
-LL |     type A: Iterator<Item: 'static, Item: 'static>;
-   |                      -------------  ^^^^^^^^^^^^^ re-bound here
-   |                      |
-   |                      `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:133:42
-   |
-LL | fn FRPIT1() -> impl Iterator<Item: Copy, Item: Send> {
-   |                              ----------  ^^^^^^^^^^ re-bound here
-   |                              |
-   |                              `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0282]: type annotations needed
-  --> $DIR/duplicate.rs:136:5
-   |
-LL |     iter::empty()
-   |     ^^^^^^^^^^^ cannot infer type of the type parameter `T` declared on the function `empty`
-   |
-help: consider specifying the generic argument
-   |
-LL |     iter::empty::<T>()
-   |                +++++
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:139:42
-   |
-LL | fn FRPIT2() -> impl Iterator<Item: Copy, Item: Copy> {
-   |                              ----------  ^^^^^^^^^^ re-bound here
-   |                              |
-   |                              `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0282]: type annotations needed
-  --> $DIR/duplicate.rs:142:5
-   |
-LL |     iter::empty()
-   |     ^^^^^^^^^^^ cannot infer type of the type parameter `T` declared on the function `empty`
-   |
-help: consider specifying the generic argument
-   |
-LL |     iter::empty::<T>()
-   |                +++++
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:145:45
-   |
-LL | fn FRPIT3() -> impl Iterator<Item: 'static, Item: 'static> {
-   |                              -------------  ^^^^^^^^^^^^^ re-bound here
-   |                              |
-   |                              `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0282]: type annotations needed
-  --> $DIR/duplicate.rs:148:5
-   |
-LL |     iter::empty()
-   |     ^^^^^^^^^^^ cannot infer type of the type parameter `T` declared on the function `empty`
-   |
-help: consider specifying the generic argument
-   |
-LL |     iter::empty::<T>()
-   |                +++++
-
-error: unconstrained opaque type
-  --> $DIR/duplicate.rs:180:51
-   |
-LL | type ETAI1<T: Iterator<Item: Copy, Item: Send>> = impl Copy;
-   |                                                   ^^^^^^^^^
-   |
-   = note: `ETAI1` must be used in combination with a concrete type within the same crate
-
-error: unconstrained opaque type
-  --> $DIR/duplicate.rs:183:51
-   |
-LL | type ETAI2<T: Iterator<Item: Copy, Item: Copy>> = impl Copy;
-   |                                                   ^^^^^^^^^
-   |
-   = note: `ETAI2` must be used in combination with a concrete type within the same crate
-
-error: unconstrained opaque type
-  --> $DIR/duplicate.rs:186:57
-   |
-LL | type ETAI3<T: Iterator<Item: 'static, Item: 'static>> = impl Copy;
-   |                                                         ^^^^^^^^^
-   |
-   = note: `ETAI3` must be used in combination with a concrete type within the same crate
-
-error: unconstrained opaque type
-  --> $DIR/duplicate.rs:189:14
-   |
-LL | type ETAI4 = impl Iterator<Item: Copy, Item: Send>;
-   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: `ETAI4` must be used in combination with a concrete type within the same crate
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:189:40
-   |
-LL | type ETAI4 = impl Iterator<Item: Copy, Item: Send>;
-   |                            ----------  ^^^^^^^^^^ re-bound here
-   |                            |
-   |                            `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:189:40
-   |
-LL | type ETAI4 = impl Iterator<Item: Copy, Item: Send>;
-   |                            ----------  ^^^^^^^^^^ re-bound here
-   |                            |
-   |                            `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error: unconstrained opaque type
-  --> $DIR/duplicate.rs:193:14
-   |
-LL | type ETAI5 = impl Iterator<Item: Copy, Item: Copy>;
-   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: `ETAI5` must be used in combination with a concrete type within the same crate
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:193:40
-   |
-LL | type ETAI5 = impl Iterator<Item: Copy, Item: Copy>;
-   |                            ----------  ^^^^^^^^^^ re-bound here
-   |                            |
-   |                            `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:193:40
-   |
-LL | type ETAI5 = impl Iterator<Item: Copy, Item: Copy>;
-   |                            ----------  ^^^^^^^^^^ re-bound here
-   |                            |
-   |                            `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error: unconstrained opaque type
-  --> $DIR/duplicate.rs:197:14
-   |
-LL | type ETAI6 = impl Iterator<Item: 'static, Item: 'static>;
-   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: `ETAI6` must be used in combination with a concrete type within the same crate
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:197:43
-   |
-LL | type ETAI6 = impl Iterator<Item: 'static, Item: 'static>;
-   |                            -------------  ^^^^^^^^^^^^^ re-bound here
-   |                            |
-   |                            `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:197:43
-   |
-LL | type ETAI6 = impl Iterator<Item: 'static, Item: 'static>;
-   |                            -------------  ^^^^^^^^^^^^^ re-bound here
-   |                            |
-   |                            `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error: aborting due to 87 previous errors
-
-Some errors have detailed explanations: E0282, E0719.
-For more information about an error, try `rustc --explain E0282`.
diff --git a/tests/ui/associated-types/associated-types-overridden-binding-2.stderr b/tests/ui/associated-types/associated-types-overridden-binding-2.stderr
index 71a4a2610aa..e96a2446b6c 100644
--- a/tests/ui/associated-types/associated-types-overridden-binding-2.stderr
+++ b/tests/ui/associated-types/associated-types-overridden-binding-2.stderr
@@ -1,4 +1,4 @@
-error: conflicting associated type bounds for `Item` when expanding trait alias
+error: conflicting associated type bounds for `Item`
   --> $DIR/associated-types-overridden-binding-2.rs:6:13
    |
 LL | trait I32Iterator = Iterator<Item = i32>;
diff --git a/tests/ui/associated-types/associated-types-overridden-binding.stderr b/tests/ui/associated-types/associated-types-overridden-binding.stderr
index 3b20015dfca..08ab9b63ee9 100644
--- a/tests/ui/associated-types/associated-types-overridden-binding.stderr
+++ b/tests/ui/associated-types/associated-types-overridden-binding.stderr
@@ -22,7 +22,7 @@ note: required by a bound in `I32Iterator`
 LL | trait I32Iterator = Iterator<Item = i32>;
    |                              ^^^^^^^^^^ required by this bound in `I32Iterator`
 
-error: conflicting associated type bounds for `Item` when expanding trait alias
+error: conflicting associated type bounds for `Item`
   --> $DIR/associated-types-overridden-binding.rs:10:13
    |
 LL | trait I32Iterator = Iterator<Item = i32>;
diff --git a/tests/ui/async-await/async-closures/without-precise-captures-we-are-powerless.rs b/tests/ui/async-await/async-closures/without-precise-captures-we-are-powerless.rs
index 19a31d1889b..f97ec779b32 100644
--- a/tests/ui/async-await/async-closures/without-precise-captures-we-are-powerless.rs
+++ b/tests/ui/async-await/async-closures/without-precise-captures-we-are-powerless.rs
@@ -44,4 +44,18 @@ fn through_field_and_ref_move<'a>(x: &S<'a>) {
     outlives::<'a>(call_once(c)); //~ ERROR explicit lifetime required in the type of `x`
 }
 
+struct T;
+impl T {
+    fn outlives<'a>(&'a self, _: impl Sized + 'a) {}
+}
+fn through_method<'a>(x: &'a i32) {
+    let c = async || { println!("{}", *x); }; //~ ERROR `x` does not live long enough
+    T.outlives::<'a>(c());
+    T.outlives::<'a>(call_once(c));
+
+    let c = async move || { println!("{}", *x); };
+    T.outlives::<'a>(c()); //~ ERROR `c` does not live long enough
+    T.outlives::<'a>(call_once(c));
+}
+
 fn main() {}
diff --git a/tests/ui/async-await/async-closures/without-precise-captures-we-are-powerless.stderr b/tests/ui/async-await/async-closures/without-precise-captures-we-are-powerless.stderr
index b7259074bf6..4aae9807dd2 100644
--- a/tests/ui/async-await/async-closures/without-precise-captures-we-are-powerless.stderr
+++ b/tests/ui/async-await/async-closures/without-precise-captures-we-are-powerless.stderr
@@ -28,6 +28,12 @@ LL |     outlives::<'a>(c());
 LL |     outlives::<'a>(call_once(c));
 LL | }
    | - `c` dropped here while still borrowed
+   |
+note: requirement that the value outlives `'a` introduced here
+  --> $DIR/without-precise-captures-we-are-powerless.rs:7:33
+   |
+LL | fn outlives<'a>(_: impl Sized + 'a) {}
+   |                                 ^^
 
 error[E0597]: `x` does not live long enough
   --> $DIR/without-precise-captures-we-are-powerless.rs:26:13
@@ -73,6 +79,12 @@ LL |     outlives::<'a>(c());
 LL |     outlives::<'a>(call_once(c));
 LL | }
    | - `c` dropped here while still borrowed
+   |
+note: requirement that the value outlives `'a` introduced here
+  --> $DIR/without-precise-captures-we-are-powerless.rs:7:33
+   |
+LL | fn outlives<'a>(_: impl Sized + 'a) {}
+   |                                 ^^
 
 error[E0505]: cannot move out of `c` because it is borrowed
   --> $DIR/without-precise-captures-we-are-powerless.rs:32:30
@@ -89,6 +101,12 @@ LL |     outlives::<'a>(c());
    |     argument requires that `c` is borrowed for `'a`
 LL |     outlives::<'a>(call_once(c));
    |                              ^ move out of `c` occurs here
+   |
+note: requirement that the value outlives `'a` introduced here
+  --> $DIR/without-precise-captures-we-are-powerless.rs:7:33
+   |
+LL | fn outlives<'a>(_: impl Sized + 'a) {}
+   |                                 ^^
 
 error[E0597]: `x` does not live long enough
   --> $DIR/without-precise-captures-we-are-powerless.rs:36:13
@@ -129,6 +147,12 @@ LL |     outlives::<'a>(c());
 LL |     outlives::<'a>(call_once(c));
 LL | }
    | - `c` dropped here while still borrowed
+   |
+note: requirement that the value outlives `'a` introduced here
+  --> $DIR/without-precise-captures-we-are-powerless.rs:7:33
+   |
+LL | fn outlives<'a>(_: impl Sized + 'a) {}
+   |                                 ^^
 
 error[E0621]: explicit lifetime required in the type of `x`
   --> $DIR/without-precise-captures-we-are-powerless.rs:44:5
@@ -141,7 +165,44 @@ help: add explicit lifetime `'a` to the type of `x`
 LL | fn through_field_and_ref_move<'a>(x: &'a S<'a>) {
    |                                       ++
 
-error: aborting due to 10 previous errors
+error[E0597]: `x` does not live long enough
+  --> $DIR/without-precise-captures-we-are-powerless.rs:52:13
+   |
+LL | fn through_method<'a>(x: &'a i32) {
+   |                   -- lifetime `'a` defined here
+LL |     let c = async || { println!("{}", *x); };
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ borrowed value does not live long enough
+LL |     T.outlives::<'a>(c());
+LL |     T.outlives::<'a>(call_once(c));
+   |     ------------------------------ argument requires that `x` is borrowed for `'a`
+...
+LL | }
+   |  - `x` dropped here while still borrowed
+
+error[E0597]: `c` does not live long enough
+  --> $DIR/without-precise-captures-we-are-powerless.rs:57:22
+   |
+LL | fn through_method<'a>(x: &'a i32) {
+   |                   -- lifetime `'a` defined here
+...
+LL |     let c = async move || { println!("{}", *x); };
+   |         - binding `c` declared here
+LL |     T.outlives::<'a>(c());
+   |     -----------------^---
+   |     |                |
+   |     |                borrowed value does not live long enough
+   |     argument requires that `c` is borrowed for `'a`
+LL |     T.outlives::<'a>(call_once(c));
+LL | }
+   | - `c` dropped here while still borrowed
+   |
+note: requirement that the value outlives `'a` introduced here
+  --> $DIR/without-precise-captures-we-are-powerless.rs:49:47
+   |
+LL |     fn outlives<'a>(&'a self, _: impl Sized + 'a) {}
+   |                                               ^^
+
+error: aborting due to 12 previous errors
 
 Some errors have detailed explanations: E0505, E0597, E0621.
 For more information about an error, try `rustc --explain E0505`.
diff --git a/tests/ui/borrowck/fn-item-check-type-params.stderr b/tests/ui/borrowck/fn-item-check-type-params.stderr
index aafb7e66ef5..7a0a7752a14 100644
--- a/tests/ui/borrowck/fn-item-check-type-params.stderr
+++ b/tests/ui/borrowck/fn-item-check-type-params.stderr
@@ -27,6 +27,12 @@ LL |     want(&String::new(), extend_lt);
    |     |     |
    |     |     creates a temporary value which is freed while still in use
    |     argument requires that borrow lasts for `'static`
+   |
+note: requirement that the value outlives `'static` introduced here
+  --> $DIR/fn-item-check-type-params.rs:47:33
+   |
+LL |     fn want<I, O>(_: I, _: impl Fn(I) -> O) {}
+   |                                 ^^^^^^^^^^
 
 error[E0716]: temporary value dropped while borrowed
   --> $DIR/fn-item-check-type-params.rs:54:26
@@ -36,6 +42,12 @@ LL |     let val = extend_lt(&String::from("blah blah blah"));
    |               |          |
    |               |          creates a temporary value which is freed while still in use
    |               argument requires that borrow lasts for `'static`
+   |
+note: requirement that the value outlives `'static` introduced here
+  --> $DIR/fn-item-check-type-params.rs:22:21
+   |
+LL |     (T, Option<U>): Displayable,
+   |                     ^^^^^^^^^^^
 
 error: aborting due to 4 previous errors
 
diff --git a/tests/ui/borrowck/implementation-not-general-enough-ice-133252.stderr b/tests/ui/borrowck/implementation-not-general-enough-ice-133252.stderr
index 5389226f7a7..7b840d54ed0 100644
--- a/tests/ui/borrowck/implementation-not-general-enough-ice-133252.stderr
+++ b/tests/ui/borrowck/implementation-not-general-enough-ice-133252.stderr
@@ -22,6 +22,12 @@ LL |         force_send(async_load(&not_static));
 ...
 LL |     }
    |     - `not_static` dropped here while still borrowed
+   |
+note: requirement that the value outlives `'1` introduced here
+  --> $DIR/implementation-not-general-enough-ice-133252.rs:16:18
+   |
+LL | fn force_send<T: Send>(_: T) {}
+   |                  ^^^^
 
 error: aborting due to 2 previous errors
 
diff --git a/tests/ui/borrowck/issue-17545.stderr b/tests/ui/borrowck/issue-17545.stderr
index 45e977e3947..63fd57cd233 100644
--- a/tests/ui/borrowck/issue-17545.stderr
+++ b/tests/ui/borrowck/issue-17545.stderr
@@ -10,6 +10,9 @@ LL | |     ));
    | |      -- temporary value is freed at the end of this statement
    | |______|
    |        argument requires that borrow lasts for `'a`
+   |
+note: requirement that the value outlives `'a` introduced here
+  --> $SRC_DIR/core/src/ops/function.rs:LL:COL
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/cmse-nonsecure/cmse-nonsecure-call/undeclared-lifetime.rs b/tests/ui/cmse-nonsecure/cmse-nonsecure-call/undeclared-lifetime.rs
new file mode 100644
index 00000000000..5fa5b74c0c0
--- /dev/null
+++ b/tests/ui/cmse-nonsecure/cmse-nonsecure-call/undeclared-lifetime.rs
@@ -0,0 +1,20 @@
+//@ add-core-stubs
+//@ compile-flags: --target thumbv8m.main-none-eabi --crate-type lib -Cincremental=true
+//@ needs-llvm-components: arm
+#![feature(abi_cmse_nonsecure_call, no_core)]
+#![no_core]
+
+extern crate minicore;
+use minicore::*;
+
+// A regression test for https://github.com/rust-lang/rust/issues/131639.
+// NOTE: -Cincremental=true was required for triggering the bug.
+
+fn foo() {
+    id::<extern "cmse-nonsecure-call" fn(&'a ())>(PhantomData);
+    //~^ ERROR use of undeclared lifetime name `'a`
+}
+
+fn id<T>(x: PhantomData<T>) -> PhantomData<T> {
+    x
+}
diff --git a/tests/ui/cmse-nonsecure/cmse-nonsecure-call/undeclared-lifetime.stderr b/tests/ui/cmse-nonsecure/cmse-nonsecure-call/undeclared-lifetime.stderr
new file mode 100644
index 00000000000..4aca17e7354
--- /dev/null
+++ b/tests/ui/cmse-nonsecure/cmse-nonsecure-call/undeclared-lifetime.stderr
@@ -0,0 +1,19 @@
+error[E0261]: use of undeclared lifetime name `'a`
+  --> $DIR/undeclared-lifetime.rs:14:43
+   |
+LL |     id::<extern "cmse-nonsecure-call" fn(&'a ())>(PhantomData);
+   |                                           ^^ undeclared lifetime
+   |
+   = note: for more information on higher-ranked polymorphism, visit https://doc.rust-lang.org/nomicon/hrtb.html
+help: consider making the type lifetime-generic with a new `'a` lifetime
+   |
+LL |     id::<for<'a> extern "cmse-nonsecure-call" fn(&'a ())>(PhantomData);
+   |          +++++++
+help: consider introducing lifetime `'a` here
+   |
+LL | fn foo<'a>() {
+   |       ++++
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0261`.
diff --git a/tests/ui/error-codes/E0719.rs b/tests/ui/error-codes/E0719.rs
index 0ea6d19000b..d7b4b876d1b 100644
--- a/tests/ui/error-codes/E0719.rs
+++ b/tests/ui/error-codes/E0719.rs
@@ -1,8 +1,3 @@
-trait Foo: Iterator<Item = i32, Item = i32> {}
-//~^ ERROR is already specified
-//~| ERROR is already specified
-//~| ERROR is already specified
-
 type Unit = ();
 
 fn test() -> Box<dyn Iterator<Item = (), Item = Unit>> {
diff --git a/tests/ui/error-codes/E0719.stderr b/tests/ui/error-codes/E0719.stderr
index 7e8329db1f4..f4817568924 100644
--- a/tests/ui/error-codes/E0719.stderr
+++ b/tests/ui/error-codes/E0719.stderr
@@ -1,33 +1,5 @@
 error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/E0719.rs:1:33
-   |
-LL | trait Foo: Iterator<Item = i32, Item = i32> {}
-   |                     ----------  ^^^^^^^^^^ re-bound here
-   |                     |
-   |                     `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/E0719.rs:1:33
-   |
-LL | trait Foo: Iterator<Item = i32, Item = i32> {}
-   |                     ----------  ^^^^^^^^^^ re-bound here
-   |                     |
-   |                     `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/E0719.rs:1:33
-   |
-LL | trait Foo: Iterator<Item = i32, Item = i32> {}
-   |                     ----------  ^^^^^^^^^^ re-bound here
-   |                     |
-   |                     `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/E0719.rs:8:42
+  --> $DIR/E0719.rs:3:42
    |
 LL | fn test() -> Box<dyn Iterator<Item = (), Item = Unit>> {
    |                               ---------  ^^^^^^^^^^^ re-bound here
@@ -35,13 +7,13 @@ LL | fn test() -> Box<dyn Iterator<Item = (), Item = Unit>> {
    |                               `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/E0719.rs:14:38
+  --> $DIR/E0719.rs:9:38
    |
 LL |     let _: &dyn Iterator<Item = i32, Item = i32>;
    |                          ----------  ^^^^^^^^^^ re-bound here
    |                          |
    |                          `Item` bound here first
 
-error: aborting due to 5 previous errors
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0719`.
diff --git a/tests/ui/errors/span-format_args-issue-140578.rs b/tests/ui/errors/span-format_args-issue-140578.rs
new file mode 100644
index 00000000000..8c91ded8337
--- /dev/null
+++ b/tests/ui/errors/span-format_args-issue-140578.rs
@@ -0,0 +1,32 @@
+fn check_format_args() {
+  print!("{:?} {a} {a:?}", [], a = 1 + 1);
+  //~^ ERROR type annotations needed
+}
+
+fn check_format_args_nl() {
+  println!("{:?} {a} {a:?}", [], a = 1 + 1);
+  //~^ ERROR type annotations needed
+}
+
+fn check_multi1() {
+  println!("{:?} {:?} {a} {a:?}", [], [], a = 1 + 1);
+  //~^ ERROR type annotations needed
+}
+
+fn check_multi2() {
+  println!("{:?} {:?} {a} {a:?} {b:?}", [], [], a = 1 + 1, b = []);
+  //~^ ERROR type annotations needed
+}
+
+fn check_unformatted() {
+  println!("
+  {:?} {:?}
+{a}
+{a:?}",
+        [],
+        //~^ ERROR type annotations needed
+ [],
+a = 1 + 1);
+}
+
+fn main() {}
diff --git a/tests/ui/errors/span-format_args-issue-140578.stderr b/tests/ui/errors/span-format_args-issue-140578.stderr
new file mode 100644
index 00000000000..6a273e5cd51
--- /dev/null
+++ b/tests/ui/errors/span-format_args-issue-140578.stderr
@@ -0,0 +1,43 @@
+error[E0282]: type annotations needed
+  --> $DIR/span-format_args-issue-140578.rs:2:28
+   |
+LL |   print!("{:?} {a} {a:?}", [], a = 1 + 1);
+   |                            ^^ cannot infer type
+   |
+   = note: this error originates in the macro `$crate::format_args` which comes from the expansion of the macro `print` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0282]: type annotations needed
+  --> $DIR/span-format_args-issue-140578.rs:7:30
+   |
+LL |   println!("{:?} {a} {a:?}", [], a = 1 + 1);
+   |                              ^^ cannot infer type
+   |
+   = note: this error originates in the macro `$crate::format_args_nl` which comes from the expansion of the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0282]: type annotations needed
+  --> $DIR/span-format_args-issue-140578.rs:12:35
+   |
+LL |   println!("{:?} {:?} {a} {a:?}", [], [], a = 1 + 1);
+   |                                   ^^ cannot infer type
+   |
+   = note: this error originates in the macro `$crate::format_args_nl` which comes from the expansion of the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0282]: type annotations needed
+  --> $DIR/span-format_args-issue-140578.rs:17:41
+   |
+LL |   println!("{:?} {:?} {a} {a:?} {b:?}", [], [], a = 1 + 1, b = []);
+   |                                         ^^ cannot infer type
+   |
+   = note: this error originates in the macro `$crate::format_args_nl` which comes from the expansion of the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0282]: type annotations needed
+  --> $DIR/span-format_args-issue-140578.rs:26:9
+   |
+LL |         [],
+   |         ^^ cannot infer type
+   |
+   = note: this error originates in the macro `$crate::format_args_nl` which comes from the expansion of the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to 5 previous errors
+
+For more information about this error, try `rustc --explain E0282`.
diff --git a/tests/ui/generic-associated-types/bugs/hrtb-implied-1.stderr b/tests/ui/generic-associated-types/bugs/hrtb-implied-1.stderr
index 8bb72833e30..77a637c470c 100644
--- a/tests/ui/generic-associated-types/bugs/hrtb-implied-1.stderr
+++ b/tests/ui/generic-associated-types/bugs/hrtb-implied-1.stderr
@@ -14,6 +14,11 @@ note: due to a current limitation of the type system, this implies a `'static` l
    |
 LL |     for<'a> I::Item<'a>: Debug,
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
+note: requirement that the value outlives `'static` introduced here
+  --> $DIR/hrtb-implied-1.rs:26:26
+   |
+LL |     for<'a> I::Item<'a>: Debug,
+   |                          ^^^^^
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/impl-trait/precise-capturing/migration-note.rs b/tests/ui/impl-trait/precise-capturing/migration-note.rs
index 7587e89409a..412d8af9884 100644
--- a/tests/ui/impl-trait/precise-capturing/migration-note.rs
+++ b/tests/ui/impl-trait/precise-capturing/migration-note.rs
@@ -32,6 +32,7 @@ fn needs_static() {
     //~| NOTE borrowed value does not live long enoug
 
     fn needs_static(_: impl Sized + 'static) {}
+    //~^ NOTE requirement that the value outlives `'static` introduced here
     needs_static(a);
     //~^ NOTE argument requires that `x` is borrowed for `'static`
 }
@@ -79,6 +80,7 @@ fn needs_static_mut() {
     //~| NOTE borrowed value does not live long enough
 
     fn needs_static(_: impl Sized + 'static) {}
+    //~^ NOTE requirement that the value outlives `'static` introduced here
     needs_static(a);
     //~^ NOTE argument requires that `x` is borrowed for `'static`
 }
diff --git a/tests/ui/impl-trait/precise-capturing/migration-note.stderr b/tests/ui/impl-trait/precise-capturing/migration-note.stderr
index aa0f6400091..880e7878477 100644
--- a/tests/ui/impl-trait/precise-capturing/migration-note.stderr
+++ b/tests/ui/impl-trait/precise-capturing/migration-note.stderr
@@ -1,5 +1,5 @@
 error[E0597]: `x` does not live long enough
-  --> $DIR/migration-note.rs:182:17
+  --> $DIR/migration-note.rs:184:17
    |
 LL |     let x = vec![0];
    |         - binding `x` declared here
@@ -50,6 +50,11 @@ LL |
 LL | }
    | - `x` dropped here while still borrowed
    |
+note: requirement that the value outlives `'static` introduced here
+  --> $DIR/migration-note.rs:34:37
+   |
+LL |     fn needs_static(_: impl Sized + 'static) {}
+   |                                     ^^^^^^^
 note: this call may capture more lifetimes than intended, because Rust 2024 has adjusted the `impl Trait` lifetime capture rules
   --> $DIR/migration-note.rs:29:13
    |
@@ -61,7 +66,7 @@ LL | fn display_len<T>(x: &Vec<T>) -> impl Display + use<T> {
    |                                               ++++++++
 
 error[E0505]: cannot move out of `x` because it is borrowed
-  --> $DIR/migration-note.rs:48:8
+  --> $DIR/migration-note.rs:49:8
    |
 LL |     let x = vec![1];
    |         - binding `x` declared here
@@ -76,7 +81,7 @@ LL | }
    | - borrow might be used here, when `a` is dropped and runs the destructor for type `impl std::fmt::Display`
    |
 note: this call may capture more lifetimes than intended, because Rust 2024 has adjusted the `impl Trait` lifetime capture rules
-  --> $DIR/migration-note.rs:43:13
+  --> $DIR/migration-note.rs:44:13
    |
 LL |     let a = display_len(&x);
    |             ^^^^^^^^^^^^^^^
@@ -90,7 +95,7 @@ LL |     let a = display_len(&x.clone());
    |                           ++++++++
 
 error[E0499]: cannot borrow `x` as mutable more than once at a time
-  --> $DIR/migration-note.rs:66:5
+  --> $DIR/migration-note.rs:67:5
    |
 LL |     let a = display_len_mut(&mut x);
    |                             ------ first mutable borrow occurs here
@@ -102,7 +107,7 @@ LL |     println!("{a}");
    |                - first borrow later used here
    |
 note: this call may capture more lifetimes than intended, because Rust 2024 has adjusted the `impl Trait` lifetime capture rules
-  --> $DIR/migration-note.rs:63:13
+  --> $DIR/migration-note.rs:64:13
    |
 LL |     let a = display_len_mut(&mut x);
    |             ^^^^^^^^^^^^^^^^^^^^^^^
@@ -112,7 +117,7 @@ LL | fn display_len_mut<T>(x: &mut Vec<T>) -> impl Display + use<T> {
    |                                                       ++++++++
 
 error[E0597]: `x` does not live long enough
-  --> $DIR/migration-note.rs:76:29
+  --> $DIR/migration-note.rs:77:29
    |
 LL |     let mut x = vec![1];
    |         ----- binding `x` declared here
@@ -126,8 +131,13 @@ LL |
 LL | }
    | - `x` dropped here while still borrowed
    |
+note: requirement that the value outlives `'static` introduced here
+  --> $DIR/migration-note.rs:82:37
+   |
+LL |     fn needs_static(_: impl Sized + 'static) {}
+   |                                     ^^^^^^^
 note: this call may capture more lifetimes than intended, because Rust 2024 has adjusted the `impl Trait` lifetime capture rules
-  --> $DIR/migration-note.rs:76:13
+  --> $DIR/migration-note.rs:77:13
    |
 LL |     let a = display_len_mut(&mut x);
    |             ^^^^^^^^^^^^^^^^^^^^^^^
@@ -137,7 +147,7 @@ LL | fn display_len_mut<T>(x: &mut Vec<T>) -> impl Display + use<T> {
    |                                                       ++++++++
 
 error[E0505]: cannot move out of `x` because it is borrowed
-  --> $DIR/migration-note.rs:95:8
+  --> $DIR/migration-note.rs:97:8
    |
 LL |     let mut x = vec![1];
    |         ----- binding `x` declared here
@@ -152,7 +162,7 @@ LL | }
    | - borrow might be used here, when `a` is dropped and runs the destructor for type `impl std::fmt::Display`
    |
 note: this call may capture more lifetimes than intended, because Rust 2024 has adjusted the `impl Trait` lifetime capture rules
-  --> $DIR/migration-note.rs:90:13
+  --> $DIR/migration-note.rs:92:13
    |
 LL |     let a = display_len_mut(&mut x);
    |             ^^^^^^^^^^^^^^^^^^^^^^^
@@ -166,7 +176,7 @@ LL |     let a = display_len_mut(&mut x.clone());
    |                                   ++++++++
 
 error[E0506]: cannot assign to `s.f` because it is borrowed
-  --> $DIR/migration-note.rs:115:5
+  --> $DIR/migration-note.rs:117:5
    |
 LL |     let a = display_field(&s.f);
    |                           ---- `s.f` is borrowed here
@@ -178,7 +188,7 @@ LL |     println!("{a}");
    |                - borrow later used here
    |
 note: this call may capture more lifetimes than intended, because Rust 2024 has adjusted the `impl Trait` lifetime capture rules
-  --> $DIR/migration-note.rs:112:13
+  --> $DIR/migration-note.rs:114:13
    |
 LL |     let a = display_field(&s.f);
    |             ^^^^^^^^^^^^^^^^^^^
@@ -188,7 +198,7 @@ LL | fn display_field<T: Copy + Display>(t: &T) -> impl Display + use<T> {
    |                                                            ++++++++
 
 error[E0506]: cannot assign to `s.f` because it is borrowed
-  --> $DIR/migration-note.rs:131:5
+  --> $DIR/migration-note.rs:133:5
    |
 LL |     let a = display_field(&mut s.f);
    |                           -------- `s.f` is borrowed here
@@ -200,7 +210,7 @@ LL |     println!("{a}");
    |                - borrow later used here
    |
 note: this call may capture more lifetimes than intended, because Rust 2024 has adjusted the `impl Trait` lifetime capture rules
-  --> $DIR/migration-note.rs:128:13
+  --> $DIR/migration-note.rs:130:13
    |
 LL |     let a = display_field(&mut s.f);
    |             ^^^^^^^^^^^^^^^^^^^^^^^
@@ -210,7 +220,7 @@ LL | fn display_field<T: Copy + Display>(t: &T) -> impl Display + use<T> {
    |                                                            ++++++++
 
 error[E0503]: cannot use `s.f` because it was mutably borrowed
-  --> $DIR/migration-note.rs:143:5
+  --> $DIR/migration-note.rs:145:5
    |
 LL |     let a = display_field(&mut s.f);
    |                           -------- `s.f` is borrowed here
@@ -222,7 +232,7 @@ LL |     println!("{a}");
    |                - borrow later used here
    |
 note: this call may capture more lifetimes than intended, because Rust 2024 has adjusted the `impl Trait` lifetime capture rules
-  --> $DIR/migration-note.rs:140:13
+  --> $DIR/migration-note.rs:142:13
    |
 LL |     let a = display_field(&mut s.f);
    |             ^^^^^^^^^^^^^^^^^^^^^^^
@@ -232,7 +242,7 @@ LL | fn display_field<T: Copy + Display>(t: &T) -> impl Display + use<T> {
    |                                                            ++++++++
 
 error[E0597]: `z.f` does not live long enough
-  --> $DIR/migration-note.rs:159:25
+  --> $DIR/migration-note.rs:161:25
    |
 LL |         let z = Z { f: vec![1] };
    |             - binding `z` declared here
@@ -248,7 +258,7 @@ LL | }
    |
    = note: values in a scope are dropped in the opposite order they are defined
 note: this call may capture more lifetimes than intended, because Rust 2024 has adjusted the `impl Trait` lifetime capture rules
-  --> $DIR/migration-note.rs:159:13
+  --> $DIR/migration-note.rs:161:13
    |
 LL |         x = display_len(&z.f);
    |             ^^^^^^^^^^^^^^^^^
@@ -258,7 +268,7 @@ LL | fn display_len<T>(x: &Vec<T>) -> impl Display + use<T> {
    |                                               ++++++++
 
 error[E0716]: temporary value dropped while borrowed
-  --> $DIR/migration-note.rs:170:40
+  --> $DIR/migration-note.rs:172:40
    |
 LL |     let x = { let x = display_len(&mut vec![0]); x };
    |                                        ^^^^^^^ - - borrow later used here
@@ -268,7 +278,7 @@ LL |     let x = { let x = display_len(&mut vec![0]); x };
    |
    = note: consider using a `let` binding to create a longer lived value
 note: this call may capture more lifetimes than intended, because Rust 2024 has adjusted the `impl Trait` lifetime capture rules
-  --> $DIR/migration-note.rs:170:23
+  --> $DIR/migration-note.rs:172:23
    |
 LL |     let x = { let x = display_len(&mut vec![0]); x };
    |                       ^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -279,7 +289,7 @@ LL | fn display_len<T>(x: &Vec<T>) -> impl Display + use<T> {
    |                                               ++++++++
 
 error[E0505]: cannot move out of `x` because it is borrowed
-  --> $DIR/migration-note.rs:198:10
+  --> $DIR/migration-note.rs:200:10
    |
 LL |     let x = String::new();
    |         - binding `x` declared here
@@ -294,12 +304,12 @@ LL | }
    | - borrow might be used here, when `y` is dropped and runs the destructor for type `impl Sized`
    |
 note: this call may capture more lifetimes than intended, because Rust 2024 has adjusted the `impl Trait` lifetime capture rules
-  --> $DIR/migration-note.rs:195:13
+  --> $DIR/migration-note.rs:197:13
    |
 LL |     let y = capture_apit(&x);
    |             ^^^^^^^^^^^^^^^^
 note: you could use a `use<...>` bound to explicitly specify captures, but argument-position `impl Trait`s are not nameable
-  --> $DIR/migration-note.rs:189:21
+  --> $DIR/migration-note.rs:191:21
    |
 LL | fn capture_apit(x: &impl Sized) -> impl Sized {}
    |                     ^^^^^^^^^^
diff --git a/tests/ui/implied-bounds/bevy_world_query.rs b/tests/ui/implied-bounds/bevy_world_query.rs
index 6548c03d1b0..e2750bcf957 100644
--- a/tests/ui/implied-bounds/bevy_world_query.rs
+++ b/tests/ui/implied-bounds/bevy_world_query.rs
@@ -1,6 +1,8 @@
-#![crate_name = "bevy_ecs"]
-
 //@ check-pass
+//@ revisions: current next
+//@ ignore-compare-mode-next-solver (explicit revisions)
+//@[next] compile-flags: -Znext-solver
+#![crate_name = "bevy_ecs"]
 
 // We currently special case bevy from erroring on incorrect implied bounds
 // from normalization (issue #109628).
diff --git a/tests/ui/inference/need_type_info/issue-107745-avoid-expr-from-macro-expansion.stderr b/tests/ui/inference/need_type_info/issue-107745-avoid-expr-from-macro-expansion.stderr
index a78941f9e11..3de317d2af6 100644
--- a/tests/ui/inference/need_type_info/issue-107745-avoid-expr-from-macro-expansion.stderr
+++ b/tests/ui/inference/need_type_info/issue-107745-avoid-expr-from-macro-expansion.stderr
@@ -1,10 +1,10 @@
 error[E0282]: type annotations needed
-  --> $DIR/issue-107745-avoid-expr-from-macro-expansion.rs:17:5
+  --> $DIR/issue-107745-avoid-expr-from-macro-expansion.rs:17:22
    |
 LL |     println!("{:?}", []);
-   |     ^^^^^^^^^^^^^^^^^^^^ cannot infer type
+   |                      ^^ cannot infer type
    |
-   = note: this error originates in the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `$crate::format_args_nl` which comes from the expansion of the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-comparing-against-free.stderr b/tests/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-comparing-against-free.stderr
index e13653f3423..af07745a00a 100644
--- a/tests/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-comparing-against-free.stderr
+++ b/tests/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-comparing-against-free.stderr
@@ -69,6 +69,12 @@ LL |         cell_x.set(cell_a.get()); // forces 'a: 'x, implies 'a = 'static ->
 LL |     })
 LL | }
    | - `a` dropped here while still borrowed
+   |
+note: requirement that the value outlives `'static` introduced here
+  --> $DIR/propagate-approximated-shorter-to-static-comparing-against-free.rs:13:8
+   |
+LL |     F: for<'x> FnOnce(Cell<&'a u32>, Cell<&'x u32>),
+   |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to 2 previous errors
 
diff --git a/tests/ui/nll/closure-requirements/propagate-multiple-requirements.stderr b/tests/ui/nll/closure-requirements/propagate-multiple-requirements.stderr
index 15f48d88c37..4136ac418de 100644
--- a/tests/ui/nll/closure-requirements/propagate-multiple-requirements.stderr
+++ b/tests/ui/nll/closure-requirements/propagate-multiple-requirements.stderr
@@ -13,6 +13,12 @@ LL |         z = &local_arr;
 ...
 LL | }
    | - `local_arr` dropped here while still borrowed
+   |
+note: requirement that the value outlives `'static` introduced here
+  --> $DIR/propagate-multiple-requirements.rs:4:21
+   |
+LL | fn once<S, T, U, F: FnOnce(S, T) -> U>(f: F, s: S, t: T) -> U {
+   |                     ^^^^^^^^^^^^^^^^^
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/nll/local-outlives-static-via-hrtb.stderr b/tests/ui/nll/local-outlives-static-via-hrtb.stderr
index a98f11ce513..263d271b6b3 100644
--- a/tests/ui/nll/local-outlives-static-via-hrtb.stderr
+++ b/tests/ui/nll/local-outlives-static-via-hrtb.stderr
@@ -17,6 +17,11 @@ note: due to a current limitation of the type system, this implies a `'static` l
    |
 LL | fn assert_static_via_hrtb<G>(_: G) where for<'a> G: Outlives<'a> {}
    |                                          ^^^^^^^^^^^^^^^^^^^^^^^
+note: requirement that the value outlives `'static` introduced here
+  --> $DIR/local-outlives-static-via-hrtb.rs:15:53
+   |
+LL | fn assert_static_via_hrtb<G>(_: G) where for<'a> G: Outlives<'a> {}
+   |                                                     ^^^^^^^^^^^^
 
 error[E0597]: `local` does not live long enough
   --> $DIR/local-outlives-static-via-hrtb.rs:25:45
@@ -37,6 +42,11 @@ note: due to a current limitation of the type system, this implies a `'static` l
    |
 LL |     for<'a> &'a T: Reference<AssociatedType = &'a ()>,
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+note: requirement that the value outlives `'static` introduced here
+  --> $DIR/local-outlives-static-via-hrtb.rs:19:30
+   |
+LL |     for<'a> &'a T: Reference<AssociatedType = &'a ()>,
+   |                              ^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to 2 previous errors
 
diff --git a/tests/ui/nll/polonius/location-insensitive-scopes-issue-117146.nll.stderr b/tests/ui/nll/polonius/location-insensitive-scopes-issue-117146.nll.stderr
index 6e47b8e59f5..804b3f00a26 100644
--- a/tests/ui/nll/polonius/location-insensitive-scopes-issue-117146.nll.stderr
+++ b/tests/ui/nll/polonius/location-insensitive-scopes-issue-117146.nll.stderr
@@ -18,6 +18,11 @@ note: due to a current limitation of the type system, this implies a `'static` l
    |
 LL | fn bad<F: Fn(&()) -> &()>(_: F) {}
    |           ^^^^^^^^^^^^^^
+note: requirement that the value outlives `'static` introduced here
+  --> $DIR/location-insensitive-scopes-issue-117146.rs:20:22
+   |
+LL | fn bad<F: Fn(&()) -> &()>(_: F) {}
+   |                      ^^^
 
 error: implementation of `Fn` is not general enough
   --> $DIR/location-insensitive-scopes-issue-117146.rs:13:5
diff --git a/tests/ui/nll/polonius/location-insensitive-scopes-issue-117146.polonius.stderr b/tests/ui/nll/polonius/location-insensitive-scopes-issue-117146.polonius.stderr
index 6e47b8e59f5..804b3f00a26 100644
--- a/tests/ui/nll/polonius/location-insensitive-scopes-issue-117146.polonius.stderr
+++ b/tests/ui/nll/polonius/location-insensitive-scopes-issue-117146.polonius.stderr
@@ -18,6 +18,11 @@ note: due to a current limitation of the type system, this implies a `'static` l
    |
 LL | fn bad<F: Fn(&()) -> &()>(_: F) {}
    |           ^^^^^^^^^^^^^^
+note: requirement that the value outlives `'static` introduced here
+  --> $DIR/location-insensitive-scopes-issue-117146.rs:20:22
+   |
+LL | fn bad<F: Fn(&()) -> &()>(_: F) {}
+   |                      ^^^
 
 error: implementation of `Fn` is not general enough
   --> $DIR/location-insensitive-scopes-issue-117146.rs:13:5
diff --git a/tests/ui/proc-macro/quote/not-quotable.stderr b/tests/ui/proc-macro/quote/not-quotable.stderr
index d1c3d06f2b6..62a02638e54 100644
--- a/tests/ui/proc-macro/quote/not-quotable.stderr
+++ b/tests/ui/proc-macro/quote/not-quotable.stderr
@@ -15,8 +15,8 @@ LL |     let _ = quote! { $ip };
              Cow<'_, T>
              Option<T>
              Rc<T>
-             RepInterp<T>
-           and 25 others
+             bool
+           and 24 others
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/regions/multiple-sources-for-outlives-requirement.rs b/tests/ui/regions/multiple-sources-for-outlives-requirement.rs
new file mode 100644
index 00000000000..720cd1cf6ee
--- /dev/null
+++ b/tests/ui/regions/multiple-sources-for-outlives-requirement.rs
@@ -0,0 +1,11 @@
+fn outlives_indir<'a: 'b, 'b, T: 'a>(_x: T) {}
+//~^ NOTE: requirements that the value outlives `'b` introduced here
+
+fn foo<'b>() { //~ NOTE: lifetime `'b` defined here
+    outlives_indir::<'_, 'b, _>(&mut 1u32); //~ ERROR: temporary value dropped while borrowed
+    //~^ NOTE: argument requires that borrow lasts for `'b`
+    //~| NOTE: creates a temporary value which is freed while still in use
+    //~| NOTE: temporary value is freed at the end of this statement
+}
+
+fn main() {}
diff --git a/tests/ui/regions/multiple-sources-for-outlives-requirement.stderr b/tests/ui/regions/multiple-sources-for-outlives-requirement.stderr
new file mode 100644
index 00000000000..4cdaf950e15
--- /dev/null
+++ b/tests/ui/regions/multiple-sources-for-outlives-requirement.stderr
@@ -0,0 +1,20 @@
+error[E0716]: temporary value dropped while borrowed
+  --> $DIR/multiple-sources-for-outlives-requirement.rs:5:38
+   |
+LL | fn foo<'b>() {
+   |        -- lifetime `'b` defined here
+LL |     outlives_indir::<'_, 'b, _>(&mut 1u32);
+   |     ---------------------------------^^^^-- temporary value is freed at the end of this statement
+   |     |                                |
+   |     |                                creates a temporary value which is freed while still in use
+   |     argument requires that borrow lasts for `'b`
+   |
+note: requirements that the value outlives `'b` introduced here
+  --> $DIR/multiple-sources-for-outlives-requirement.rs:1:23
+   |
+LL | fn outlives_indir<'a: 'b, 'b, T: 'a>(_x: T) {}
+   |                       ^^         ^^
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0716`.
diff --git a/tests/ui/regions/regions-infer-proc-static-upvar.stderr b/tests/ui/regions/regions-infer-proc-static-upvar.stderr
index 919fcffdc53..158d74ed06d 100644
--- a/tests/ui/regions/regions-infer-proc-static-upvar.stderr
+++ b/tests/ui/regions/regions-infer-proc-static-upvar.stderr
@@ -11,6 +11,12 @@ LL | |     });
    | |______- argument requires that `x` is borrowed for `'static`
 LL |   }
    |   - `x` dropped here while still borrowed
+   |
+note: requirement that the value outlives `'static` introduced here
+  --> $DIR/regions-infer-proc-static-upvar.rs:4:19
+   |
+LL | fn foo<F:FnOnce()+'static>(_p: F) { }
+   |                   ^^^^^^^
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/regions/regions-pattern-typing-issue-19552.stderr b/tests/ui/regions/regions-pattern-typing-issue-19552.stderr
index 1d3d5e831c3..a8fd827bc69 100644
--- a/tests/ui/regions/regions-pattern-typing-issue-19552.stderr
+++ b/tests/ui/regions/regions-pattern-typing-issue-19552.stderr
@@ -10,6 +10,12 @@ LL |         [ word ] => { assert_static(word); }
 LL |     }
 LL | }
    | - `line` dropped here while still borrowed
+   |
+note: requirement that the value outlives `'static` introduced here
+  --> $DIR/regions-pattern-typing-issue-19552.rs:1:21
+   |
+LL | fn assert_static<T: 'static>(_t: T) {}
+   |                     ^^^^^^^
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/static/static-lifetime-bound.stderr b/tests/ui/static/static-lifetime-bound.stderr
index 8b0d3a0bf4c..51be79be5db 100644
--- a/tests/ui/static/static-lifetime-bound.stderr
+++ b/tests/ui/static/static-lifetime-bound.stderr
@@ -10,6 +10,12 @@ LL |     f(&x);
    |     argument requires that `x` is borrowed for `'static`
 LL | }
    | - `x` dropped here while still borrowed
+   |
+note: requirement that the value outlives `'static` introduced here
+  --> $DIR/static-lifetime-bound.rs:1:10
+   |
+LL | fn f<'a: 'static>(_: &'a i32) {}
+   |          ^^^^^^^
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/static/static-region-bound.stderr b/tests/ui/static/static-region-bound.stderr
index a47c9457102..8472738daa4 100644
--- a/tests/ui/static/static-region-bound.stderr
+++ b/tests/ui/static/static-region-bound.stderr
@@ -7,6 +7,12 @@ LL |     f(x);
    |     ---- argument requires that borrow lasts for `'static`
 LL | }
    | - temporary value is freed at the end of this statement
+   |
+note: requirement that the value outlives `'static` introduced here
+  --> $DIR/static-region-bound.rs:3:8
+   |
+LL | fn f<T:'static>(_: T) {}
+   |        ^^^^^^^
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/suggestions/auxiliary/hidden-struct.rs b/tests/ui/suggestions/auxiliary/hidden-struct.rs
index 30d69acac20..1f495a9f222 100644
--- a/tests/ui/suggestions/auxiliary/hidden-struct.rs
+++ b/tests/ui/suggestions/auxiliary/hidden-struct.rs
@@ -1,3 +1,5 @@
+// `Foo` and `Bar` should not be suggested in diagnostics of dependents
+
 #[doc(hidden)]
 pub mod hidden {
     pub struct Foo;
@@ -5,13 +7,29 @@ pub mod hidden {
 
 pub mod hidden1 {
     #[doc(hidden)]
-    pub struct Foo;
+    pub struct Bar;
 }
 
+// `Baz` and `Quux` *should* be suggested in diagnostics of dependents
 
 #[doc(hidden)]
-pub(crate) mod hidden2 {
-    pub struct Bar;
+pub mod hidden2 {
+    pub struct Baz;
+}
+
+pub use hidden2::Baz;
+
+#[doc(hidden)]
+pub(crate) mod hidden3 {
+    pub struct Quux;
 }
 
-pub use hidden2::Bar;
+pub use hidden3::Quux;
+
+pub trait Marker {}
+
+impl Marker for Option<u32> {}
+impl Marker for hidden::Foo {}
+impl Marker for hidden1::Bar {}
+impl Marker for Baz {}
+impl Marker for Quux {}
diff --git a/tests/ui/suggestions/dont-suggest-foreign-doc-hidden.rs b/tests/ui/suggestions/dont-suggest-foreign-doc-hidden.rs
index 281975dcc2f..a83e496f270 100644
--- a/tests/ui/suggestions/dont-suggest-foreign-doc-hidden.rs
+++ b/tests/ui/suggestions/dont-suggest-foreign-doc-hidden.rs
@@ -1,5 +1,4 @@
 //@ aux-build:hidden-struct.rs
-//@ compile-flags: --crate-type lib
 
 extern crate hidden_struct;
 
@@ -9,7 +8,20 @@ mod local {
 }
 
 pub fn test(_: Foo) {}
-//~^ ERROR cannot find type `Foo` in this scope
+//~^ ERROR [E0412]
 
 pub fn test2(_: Bar) {}
-//~^ ERROR cannot find type `Bar` in this scope
+//~^ ERROR [E0412]
+
+pub fn test3(_: Baz) {}
+//~^ ERROR [E0412]
+
+pub fn test4(_: Quux) {}
+//~^ ERROR [E0412]
+
+fn test5<T: hidden_struct::Marker>() {}
+
+fn main() {
+    test5::<i32>();
+    //~^ ERROR [E0277]
+}
diff --git a/tests/ui/suggestions/dont-suggest-foreign-doc-hidden.stderr b/tests/ui/suggestions/dont-suggest-foreign-doc-hidden.stderr
index 7fb4d95ff9b..7036708756d 100644
--- a/tests/ui/suggestions/dont-suggest-foreign-doc-hidden.stderr
+++ b/tests/ui/suggestions/dont-suggest-foreign-doc-hidden.stderr
@@ -1,5 +1,5 @@
 error[E0412]: cannot find type `Foo` in this scope
-  --> $DIR/dont-suggest-foreign-doc-hidden.rs:11:16
+  --> $DIR/dont-suggest-foreign-doc-hidden.rs:10:16
    |
 LL | pub fn test(_: Foo) {}
    |                ^^^ not found in this scope
@@ -10,16 +10,50 @@ LL + use local::Foo;
    |
 
 error[E0412]: cannot find type `Bar` in this scope
-  --> $DIR/dont-suggest-foreign-doc-hidden.rs:14:17
+  --> $DIR/dont-suggest-foreign-doc-hidden.rs:13:17
    |
 LL | pub fn test2(_: Bar) {}
    |                 ^^^ not found in this scope
+
+error[E0412]: cannot find type `Baz` in this scope
+  --> $DIR/dont-suggest-foreign-doc-hidden.rs:16:17
+   |
+LL | pub fn test3(_: Baz) {}
+   |                 ^^^ not found in this scope
    |
 help: consider importing this struct
    |
-LL + use hidden_struct::Bar;
+LL + use hidden_struct::Baz;
+   |
+
+error[E0412]: cannot find type `Quux` in this scope
+  --> $DIR/dont-suggest-foreign-doc-hidden.rs:19:17
+   |
+LL | pub fn test4(_: Quux) {}
+   |                 ^^^^ not found in this scope
+   |
+help: consider importing this struct
+   |
+LL + use hidden_struct::Quux;
+   |
+
+error[E0277]: the trait bound `i32: Marker` is not satisfied
+  --> $DIR/dont-suggest-foreign-doc-hidden.rs:25:13
+   |
+LL |     test5::<i32>();
+   |             ^^^ the trait `Marker` is not implemented for `i32`
+   |
+   = help: the following other types implement trait `Marker`:
+             Baz
+             Option<u32>
+             Quux
+note: required by a bound in `test5`
+  --> $DIR/dont-suggest-foreign-doc-hidden.rs:22:13
    |
+LL | fn test5<T: hidden_struct::Marker>() {}
+   |             ^^^^^^^^^^^^^^^^^^^^^ required by this bound in `test5`
 
-error: aborting due to 2 previous errors
+error: aborting due to 5 previous errors
 
-For more information about this error, try `rustc --explain E0412`.
+Some errors have detailed explanations: E0277, E0412.
+For more information about an error, try `rustc --explain E0277`.
diff --git a/tests/ui/traits/trait-upcasting/illegal-upcast-to-impl-opaque.rs b/tests/ui/traits/trait-upcasting/illegal-upcast-to-impl-opaque.rs
index 2760c1696b5..f603ff1ec80 100644
--- a/tests/ui/traits/trait-upcasting/illegal-upcast-to-impl-opaque.rs
+++ b/tests/ui/traits/trait-upcasting/illegal-upcast-to-impl-opaque.rs
@@ -1,12 +1,5 @@
 //@ revisions: current next
 //@[next] compile-flags: -Znext-solver
-//@[next] failure-status: 101
-//@[next] known-bug: unknown
-//@[next] normalize-stderr: "note: .*\n\n" -> ""
-//@[next] normalize-stderr: "thread 'rustc' panicked.*\n.*\n" -> ""
-//@[next] normalize-stderr: "(error: internal compiler error: [^:]+):\d+:\d+: " -> "$1:LL:CC: "
-//@[next] normalize-stderr: "delayed at .*" -> ""
-//@[next] rustc-env:RUST_BACKTRACE=0
 //@ check-pass
 
 trait Super {
diff --git a/tests/ui/wf/wf-in-where-clause-static.current.stderr b/tests/ui/wf/wf-in-where-clause-static.current.stderr
index d0bb89884c6..788fe2c3faa 100644
--- a/tests/ui/wf/wf-in-where-clause-static.current.stderr
+++ b/tests/ui/wf/wf-in-where-clause-static.current.stderr
@@ -6,6 +6,12 @@ LL |     let s = foo(&String::from("blah blah blah"));
    |             |    |
    |             |    creates a temporary value which is freed while still in use
    |             argument requires that borrow lasts for `'static`
+   |
+note: requirement that the value outlives `'static` introduced here
+  --> $DIR/wf-in-where-clause-static.rs:12:17
+   |
+LL |     &'static S: Static,
+   |                 ^^^^^^
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/wf/wf-in-where-clause-static.next.stderr b/tests/ui/wf/wf-in-where-clause-static.next.stderr
index d0bb89884c6..788fe2c3faa 100644
--- a/tests/ui/wf/wf-in-where-clause-static.next.stderr
+++ b/tests/ui/wf/wf-in-where-clause-static.next.stderr
@@ -6,6 +6,12 @@ LL |     let s = foo(&String::from("blah blah blah"));
    |             |    |
    |             |    creates a temporary value which is freed while still in use
    |             argument requires that borrow lasts for `'static`
+   |
+note: requirement that the value outlives `'static` introduced here
+  --> $DIR/wf-in-where-clause-static.rs:12:17
+   |
+LL |     &'static S: Static,
+   |                 ^^^^^^
 
 error: aborting due to 1 previous error