Add expansion info to assoc type implied bounds

oli-obk · oli-obk · commit 44d45cfbe33d · 2026-06-10T13:31:00.000+02:00
diff --git a/compiler/rustc_hir_analysis/src/collect/item_bounds.rs b/compiler/rustc_hir_analysis/src/collect/item_bounds.rs
@@ -59,15 +59,15 @@ fn associated_type_bounds<'tcx>(
                     item_ty,
                     hir_bounds,
                     &[],
-                    ImpliedBoundsContext::AssociatedTypeOrImplTrait,
+                    ImpliedBoundsContext::AssociatedType(assoc_item_def_id),
                     span,
                 );
                 icx.lowerer().add_default_traits(
                     &mut bounds,
                     item_ty,
                     hir_bounds,
                     &[],
-                    ImpliedBoundsContext::AssociatedTypeOrImplTrait,
+                    ImpliedBoundsContext::AssociatedType(assoc_item_def_id),
                     span,
                 );
 
@@ -387,15 +387,15 @@ fn opaque_type_bounds<'tcx>(
                     item_ty,
                     hir_bounds,
                     &[],
-                    ImpliedBoundsContext::AssociatedTypeOrImplTrait,
+                    ImpliedBoundsContext::ImplTrait,
                     span,
                 );
                 icx.lowerer().add_default_traits(
                     &mut bounds,
                     item_ty,
                     hir_bounds,
                     &[],
-                    ImpliedBoundsContext::AssociatedTypeOrImplTrait,
+                    ImpliedBoundsContext::ImplTrait,
                     span,
                 );
             }
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs
@@ -181,8 +181,11 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                     return;
                 }
             }
-            ImpliedBoundsContext::TyParam(..) | ImpliedBoundsContext::AssociatedTypeOrImplTrait => {
-            }
+            ImpliedBoundsContext::TyParam(..)
+            | ImpliedBoundsContext::AssociatedType(..)
+            | ImpliedBoundsContext::TraitObject
+            | ImpliedBoundsContext::TraitAscription
+            | ImpliedBoundsContext::ImplTrait => {}
         }
         let collected = collect_sizedness_bounds(tcx, hir_bounds, where_bounds, context, span);
         if let Some(span) = collected.sized.maybe.or(collected.sized.negative)
@@ -195,7 +198,9 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             add_trait_bound(tcx, bounds, self_ty, meta_sized_did, span);
         } else if !collected.any() {
             let span = match context {
-                ImpliedBoundsContext::TyParam(def) => {
+                ImpliedBoundsContext::TraitDef(def)
+                | ImpliedBoundsContext::TyParam(def)
+                | ImpliedBoundsContext::AssociatedType(def) => {
                     self.tcx().with_stable_hashing_context(|hcx| {
                         span.mark_with_reason(
                             None,
@@ -214,7 +219,10 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                     add_trait_bound(tcx, bounds, self_ty, meta_sized_did, span);
                 }
                 ImpliedBoundsContext::TyParam(..)
-                | ImpliedBoundsContext::AssociatedTypeOrImplTrait => {
+                | ImpliedBoundsContext::AssociatedType(..)
+                | ImpliedBoundsContext::TraitObject
+                | ImpliedBoundsContext::TraitAscription
+                | ImpliedBoundsContext::ImplTrait => {
                     // If there are no explicit sizedness bounds on a parameter then add a default
                     // `Sized` bound.
                     let sized_did = tcx.require_lang_item(hir::LangItem::Sized, span);
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
@@ -84,7 +84,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 .map(|&trait_ref| hir::GenericBound::Trait(trait_ref))
                 .collect::<Vec<_>>(),
             &[],
-            ImpliedBoundsContext::AssociatedTypeOrImplTrait,
+            ImpliedBoundsContext::TraitObject,
             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
@@ -65,8 +65,11 @@ pub(crate) enum ImpliedBoundsContext {
     TraitDef(LocalDefId),
     /// An implied bound is added to a type parameter
     TyParam(LocalDefId),
-    /// An implied bound being added in any other context
-    AssociatedTypeOrImplTrait,
+    /// Associated type bounds
+    AssociatedType(LocalDefId),
+    ImplTrait,
+    TraitObject,
+    TraitAscription,
 }
 
 /// A path segment that is semantically allowed to have generic arguments.
@@ -3064,7 +3067,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                     self_ty,
                     hir_bounds,
                     &[],
-                    ImpliedBoundsContext::AssociatedTypeOrImplTrait,
+                    ImpliedBoundsContext::TraitAscription,
                     hir_ty.span,
                 );
                 self.register_trait_ascription_bounds(bounds, hir_ty.hir_id, hir_ty.span);
diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
@@ -3571,7 +3571,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                     }
                 }
                 let mut a = "a";
-                let mut this = "this bound";
+                let mut this = "this bound".to_owned();
                 let mut note = None;
                 let mut help = None;
                 if let ty::PredicateKind::Clause(clause) = predicate.kind().skip_binder() {
@@ -3598,12 +3598,14 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                                 tcx.visible_parent_map(()).get(&def_id).is_some()
                             };
                             if tcx.is_lang_item(def_id, LangItem::Sized) {
-                                if let Some(DesugaringKind::ImpliedBound { .. }) =
+                                if let Some(DesugaringKind::ImpliedBound { def }) =
                                     span.desugaring_kind()
                                 {
                                     a = "an implicit `Sized`";
-                                    this =
-                                        "the implicit `Sized` requirement on this type parameter";
+                                    this = format!(
+                                        "the implicit `Sized` requirement on this {}",
+                                        tcx.def_kind(def).descr(def)
+                                    );
                                 }
                                 if let Some(hir::Node::TraitItem(hir::TraitItem {
                                     generics,
diff --git a/tests/ui/associated-types/issue-63593.current.stderr b/tests/ui/associated-types/issue-63593.current.stderr
@@ -4,11 +4,11 @@ error[E0277]: the size for values of type `Self` cannot be known at compilation
 LL |     type This = Self;
    |                 ^^^^ doesn't have a size known at compile-time
    |
-note: required by a bound in `MyTrait::This`
+note: required by an implicit `Sized` bound in `MyTrait::This`
   --> $DIR/issue-63593.rs:13:5
    |
 LL |     type This = Self;
-   |     ^^^^^^^^^^^^^^^^^ required by this bound in `MyTrait::This`
+   |     ^^^^^^^^^^^^^^^^^ required by the implicit `Sized` requirement on this associated type in `MyTrait::This`
 help: consider further restricting `Self`
    |
 LL | trait MyTrait: Sized {
diff --git a/tests/ui/associated-types/issue-63593.next.stderr b/tests/ui/associated-types/issue-63593.next.stderr
@@ -4,11 +4,11 @@ error[E0277]: the size for values of type `Self` cannot be known at compilation
 LL |     type This = Self;
    |                 ^^^^ doesn't have a size known at compile-time
    |
-note: required by a bound in `MyTrait::This`
+note: required by an implicit `Sized` bound in `MyTrait::This`
   --> $DIR/issue-63593.rs:13:5
    |
 LL |     type This = Self;
-   |     ^^^^^^^^^^^^^^^^^ required by this bound in `MyTrait::This`
+   |     ^^^^^^^^^^^^^^^^^ required by the implicit `Sized` requirement on this associated type in `MyTrait::This`
 help: consider further restricting `Self`
    |
 LL | trait MyTrait: Sized {
diff --git a/tests/ui/drop/dropck-normalize-errors.nll.stderr b/tests/ui/drop/dropck-normalize-errors.nll.stderr
@@ -47,11 +47,11 @@ note: required because it appears within the type `BDecoder`
    |
 LL | pub struct BDecoder {
    |            ^^^^^^^^
-note: required by a bound in `Decode::Decoder`
+note: required by an implicit `Sized` bound in `Decode::Decoder`
   --> $DIR/dropck-normalize-errors.rs:8:5
    |
 LL |     type Decoder;
-   |     ^^^^^^^^^^^^^ required by this bound in `Decode::Decoder`
+   |     ^^^^^^^^^^^^^ required by the implicit `Sized` requirement on this associated type in `Decode::Decoder`
 help: consider relaxing the implicit `Sized` restriction
    |
 LL |     type Decoder: ?Sized;
diff --git a/tests/ui/drop/dropck-normalize-errors.polonius.stderr b/tests/ui/drop/dropck-normalize-errors.polonius.stderr
@@ -47,11 +47,11 @@ note: required because it appears within the type `BDecoder`
    |
 LL | pub struct BDecoder {
    |            ^^^^^^^^
-note: required by a bound in `Decode::Decoder`
+note: required by an implicit `Sized` bound in `Decode::Decoder`
   --> $DIR/dropck-normalize-errors.rs:8:5
    |
 LL |     type Decoder;
-   |     ^^^^^^^^^^^^^ required by this bound in `Decode::Decoder`
+   |     ^^^^^^^^^^^^^ required by the implicit `Sized` requirement on this associated type in `Decode::Decoder`
 help: consider relaxing the implicit `Sized` restriction
    |
 LL |     type Decoder: ?Sized;
diff --git a/tests/ui/dyn-compatibility/assoc_type_bounds_implicit_sized.stderr b/tests/ui/dyn-compatibility/assoc_type_bounds_implicit_sized.stderr
@@ -5,11 +5,11 @@ LL |     type Item = dyn Trait;
    |                 ^^^^^^^^^ doesn't have a size known at compile-time
    |
    = help: the trait `Sized` is not implemented for `(dyn Trait + 'static)`
-note: required by a bound in `TraitWithAType::Item`
+note: required by an implicit `Sized` bound in `TraitWithAType::Item`
   --> $DIR/assoc_type_bounds_implicit_sized.rs:4:5
    |
 LL |     type Item;
-   |     ^^^^^^^^^^ required by this bound in `TraitWithAType::Item`
+   |     ^^^^^^^^^^ required by the implicit `Sized` requirement on this associated type in `TraitWithAType::Item`
 help: consider relaxing the implicit `Sized` restriction
    |
 LL |     type Item: ?Sized;
diff --git a/tests/ui/generic-associated-types/issue-119942-unsatisified-gat-bound-during-assoc-ty-selection.stderr b/tests/ui/generic-associated-types/issue-119942-unsatisified-gat-bound-during-assoc-ty-selection.stderr
@@ -5,11 +5,11 @@ LL |     type Pointer<T> = dyn Deref<Target = T>;
    |                       ^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
    |
    = help: the trait `Sized` is not implemented for `(dyn Deref<Target = T> + 'static)`
-note: required by a bound in `PointerFamily::Pointer`
+note: required by an implicit `Sized` bound in `PointerFamily::Pointer`
   --> $DIR/issue-119942-unsatisified-gat-bound-during-assoc-ty-selection.rs:4:5
    |
 LL |     type Pointer<T>: Deref<Target = T>;
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `PointerFamily::Pointer`
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by the implicit `Sized` requirement on this associated type in `PointerFamily::Pointer`
 help: consider relaxing the implicit `Sized` restriction
    |
 LL |     type Pointer<T>: Deref<Target = T> + ?Sized;
diff --git a/tests/ui/generic-associated-types/issue-74816.current.stderr b/tests/ui/generic-associated-types/issue-74816.current.stderr
@@ -20,11 +20,11 @@ error[E0277]: the size for values of type `Self` cannot be known at compilation
 LL |     type Associated: Trait1 = Self;
    |                               ^^^^ doesn't have a size known at compile-time
    |
-note: required by a bound in `Trait2::Associated`
+note: required by an implicit `Sized` bound in `Trait2::Associated`
   --> $DIR/issue-74816.rs:12:5
    |
 LL |     type Associated: Trait1 = Self;
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `Trait2::Associated`
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by the implicit `Sized` requirement on this associated type in `Trait2::Associated`
 help: consider further restricting `Self`
    |
 LL | trait Trait2: Sized {
diff --git a/tests/ui/generic-associated-types/issue-74816.next.stderr b/tests/ui/generic-associated-types/issue-74816.next.stderr
@@ -20,11 +20,11 @@ error[E0277]: the size for values of type `Self` cannot be known at compilation
 LL |     type Associated: Trait1 = Self;
    |                               ^^^^ doesn't have a size known at compile-time
    |
-note: required by a bound in `Trait2::Associated`
+note: required by an implicit `Sized` bound in `Trait2::Associated`
   --> $DIR/issue-74816.rs:12:5
    |
 LL |     type Associated: Trait1 = Self;
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `Trait2::Associated`
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by the implicit `Sized` requirement on this associated type in `Trait2::Associated`
 help: consider further restricting `Self`
    |
 LL | trait Trait2: Sized {
diff --git a/tests/ui/impl-trait/in-trait/refine-resolution-errors.stderr b/tests/ui/impl-trait/in-trait/refine-resolution-errors.stderr
@@ -13,11 +13,11 @@ LL |
 LL |     type Assoc = T;
    |                  ^ doesn't have a size known at compile-time
    |
-note: required by a bound in `Mirror::Assoc`
+note: required by an implicit `Sized` bound in `Mirror::Assoc`
   --> $DIR/refine-resolution-errors.rs:7:5
    |
 LL |     type Assoc;
-   |     ^^^^^^^^^^^ required by this bound in `Mirror::Assoc`
+   |     ^^^^^^^^^^^ required by the implicit `Sized` requirement on this associated type in `Mirror::Assoc`
 help: consider removing the `?Sized` bound to make the type parameter `Sized`
    |
 LL - impl<T: ?Sized> Mirror for () {
diff --git a/tests/ui/trait-bounds/suggest-maybe-sized-bound.stderr b/tests/ui/trait-bounds/suggest-maybe-sized-bound.stderr
@@ -22,11 +22,11 @@ LL |         type P<X> = [u8];
    |                     ^^^^ doesn't have a size known at compile-time
    |
    = help: the trait `Sized` is not implemented for `[u8]`
-note: required by a bound in `main::Trait::P`
+note: required by an implicit `Sized` bound in `main::Trait::P`
   --> $DIR/suggest-maybe-sized-bound.rs:13:9
    |
 LL |         type P<X>;
-   |         ^^^^^^^^^^ required by this bound in `Trait::P`
+   |         ^^^^^^^^^^ required by the implicit `Sized` requirement on this associated type in `Trait::P`
 help: consider relaxing the implicit `Sized` restriction
    |
 LL |         type P<X>: ?Sized;
diff --git a/tests/ui/traits/cycle-cache-err-60010.stderr b/tests/ui/traits/cycle-cache-err-60010.stderr
@@ -80,11 +80,11 @@ note: required because it appears within the type `SalsaStorage`
    |
 LL | struct SalsaStorage {
    |        ^^^^^^^^^^^^
-note: required by a bound in `Database::Storage`
+note: required by an implicit `Sized` bound in `Database::Storage`
   --> $DIR/cycle-cache-err-60010.rs:7:5
    |
 LL |     type Storage;
-   |     ^^^^^^^^^^^^^ required by this bound in `Database::Storage`
+   |     ^^^^^^^^^^^^^ required by the implicit `Sized` requirement on this associated type in `Database::Storage`
 help: consider relaxing the implicit `Sized` restriction
    |
 LL |     type Storage: ?Sized;
diff --git a/tests/ui/traits/normalize/unconstrained-projection-normalization-2.current.stderr b/tests/ui/traits/normalize/unconstrained-projection-normalization-2.current.stderr
@@ -22,11 +22,11 @@ LL |
 LL |     type Assoc = T;
    |                  ^ doesn't have a size known at compile-time
    |
-note: required by a bound in `Every::Assoc`
+note: required by an implicit `Sized` bound in `Every::Assoc`
   --> $DIR/unconstrained-projection-normalization-2.rs:12:5
    |
 LL |     type Assoc;
-   |     ^^^^^^^^^^^ required by this bound in `Every::Assoc`
+   |     ^^^^^^^^^^^ required by the implicit `Sized` requirement on this associated type in `Every::Assoc`
 help: consider removing the `?Sized` bound to make the type parameter `Sized`
    |
 LL - impl<T: ?Sized> Every for Thing {
diff --git a/tests/ui/traits/normalize/unconstrained-projection-normalization-2.next.stderr b/tests/ui/traits/normalize/unconstrained-projection-normalization-2.next.stderr
@@ -22,11 +22,11 @@ LL |
 LL |     type Assoc = T;
    |                  ^ doesn't have a size known at compile-time
    |
-note: required by a bound in `Every::Assoc`
+note: required by an implicit `Sized` bound in `Every::Assoc`
   --> $DIR/unconstrained-projection-normalization-2.rs:12:5
    |
 LL |     type Assoc;
-   |     ^^^^^^^^^^^ required by this bound in `Every::Assoc`
+   |     ^^^^^^^^^^^ required by the implicit `Sized` requirement on this associated type in `Every::Assoc`
 help: consider removing the `?Sized` bound to make the type parameter `Sized`
    |
 LL - impl<T: ?Sized> Every for Thing {
diff --git a/tests/ui/traits/normalize/unconstrained-projection-normalization.current.stderr b/tests/ui/traits/normalize/unconstrained-projection-normalization.current.stderr
@@ -22,11 +22,11 @@ LL |
 LL |     type Assoc = T;
    |                  ^ doesn't have a size known at compile-time
    |
-note: required by a bound in `Every::Assoc`
+note: required by an implicit `Sized` bound in `Every::Assoc`
   --> $DIR/unconstrained-projection-normalization.rs:11:5
    |
 LL |     type Assoc;
-   |     ^^^^^^^^^^^ required by this bound in `Every::Assoc`
+   |     ^^^^^^^^^^^ required by the implicit `Sized` requirement on this associated type in `Every::Assoc`
 help: consider removing the `?Sized` bound to make the type parameter `Sized`
    |
 LL - impl<T: ?Sized> Every for Thing {
diff --git a/tests/ui/traits/normalize/unconstrained-projection-normalization.next.stderr b/tests/ui/traits/normalize/unconstrained-projection-normalization.next.stderr
@@ -22,11 +22,11 @@ LL |
 LL |     type Assoc = T;
    |                  ^ doesn't have a size known at compile-time
    |
-note: required by a bound in `Every::Assoc`
+note: required by an implicit `Sized` bound in `Every::Assoc`
   --> $DIR/unconstrained-projection-normalization.rs:11:5
    |
 LL |     type Assoc;
-   |     ^^^^^^^^^^^ required by this bound in `Every::Assoc`
+   |     ^^^^^^^^^^^ required by the implicit `Sized` requirement on this associated type in `Every::Assoc`
 help: consider removing the `?Sized` bound to make the type parameter `Sized`
    |
 LL - impl<T: ?Sized> Every for Thing {

Original file line number	Diff line number	Diff line change
@@ -4,11 +4,11 @@ error[E0277]: the size for values of type `Self` cannot be known at compilation
`4`	`4`	`LL \| type This = Self;`
`5`	`5`	`\| ^^^^ doesn't have a size known at compile-time`
`6`	`6`	`\|`
`7`		-note: required by a bound in `MyTrait::This`
	`7`	+note: required by an implicit `Sized` bound in `MyTrait::This`
`8`	`8`	`--> $DIR/issue-63593.rs:13:5`
`9`	`9`	`\|`
`10`	`10`	`LL \| type This = Self;`
`11`		- \| ^^^^^^^^^^^^^^^^^ required by this bound in `MyTrait::This`
	`11`	+ \| ^^^^^^^^^^^^^^^^^ required by the implicit `Sized` requirement on this associated type in `MyTrait::This`
`12`	`12`	help: consider further restricting `Self`
`13`	`13`	`\|`
`14`	`14`	`LL \| trait MyTrait: Sized {`
Original file line number	Diff line number	Diff line change
@@ -47,11 +47,11 @@ note: required because it appears within the type `BDecoder`
`47`	`47`	`\|`
`48`	`48`	`LL \| pub struct BDecoder {`
`49`	`49`	`\| ^^^^^^^^`
`50`		-note: required by a bound in `Decode::Decoder`
	`50`	+note: required by an implicit `Sized` bound in `Decode::Decoder`
`51`	`51`	`--> $DIR/dropck-normalize-errors.rs:8:5`
`52`	`52`	`\|`
`53`	`53`	`LL \| type Decoder;`
`54`		- \| ^^^^^^^^^^^^^ required by this bound in `Decode::Decoder`
	`54`	+ \| ^^^^^^^^^^^^^ required by the implicit `Sized` requirement on this associated type in `Decode::Decoder`
`55`	`55`	help: consider relaxing the implicit `Sized` restriction
`56`	`56`	`\|`
`57`	`57`	`LL \| type Decoder: ?Sized;`
Original file line number	Diff line number	Diff line change
`@@ -5,11 +5,11 @@ LL \| type Item = dyn Trait;`
`5`	`5`	`\| ^^^^^^^^^ doesn't have a size known at compile-time`
`6`	`6`	`\|`
`7`	`7`	= help: the trait `Sized` is not implemented for `(dyn Trait + 'static)`
`8`		-note: required by a bound in `TraitWithAType::Item`
	`8`	+note: required by an implicit `Sized` bound in `TraitWithAType::Item`
`9`	`9`	`--> $DIR/assoc_type_bounds_implicit_sized.rs:4:5`
`10`	`10`	`\|`
`11`	`11`	`LL \| type Item;`
`12`		- \| ^^^^^^^^^^ required by this bound in `TraitWithAType::Item`
	`12`	+ \| ^^^^^^^^^^ required by the implicit `Sized` requirement on this associated type in `TraitWithAType::Item`
`13`	`13`	help: consider relaxing the implicit `Sized` restriction
`14`	`14`	`\|`
`15`	`15`	`LL \| type Item: ?Sized;`