internal: add implicit : Sized bound to type parameters.

crates/hir_ty/src/lower.rs

@@ -1024,7 +1024,7 @@ pub(crate) fn generic_predicates_for_param_query(
     let ctx =
         TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
     let generics = generics(db.upcast(), param_id.parent);
-    resolver
+    let mut predicates: Vec<_> = resolver
         .where_predicates_in_scope()
         // we have to filter out all other predicates *first*, before attempting to lower them
         .filter(|pred| match pred {
@@ -1038,7 +1038,15 @@ pub(crate) fn generic_predicates_for_param_query(
             WherePredicate::Lifetime { .. } => false,
         })
         .flat_map(|pred| ctx.lower_where_predicate(pred, true).map(|p| make_binders(&generics, p)))
-        .collect()
+        .collect();
+
+    let subst = generics.bound_vars_subst(DebruijnIndex::INNERMOST);
+    let explicitly_unsized_tys = ctx.unsized_types.into_inner();
+    let implicitly_sized_predicates =
+        implicitly_sized_clauses(db, param_id.parent, &explicitly_unsized_tys, &subst, &resolver)
+            .map(|p| make_binders(&generics, crate::wrap_empty_binders(p)));
+    predicates.extend(implicitly_sized_predicates);
+    predicates.into()
 }
 
 pub(crate) fn generic_predicates_for_param_recover(

crates/ide/src/hover.rs

@@ -3520,15 +3520,15 @@ fn foo() {
             r#"
 //- minicore: sized
 struct Foo<T>(T);
-trait Copy {}
+trait TraitA {}
-trait Clone {}
+trait TraitB {}
-impl<T: Copy + Clone> Foo<T$0> where T: Sized {}
+impl<T: TraitA + TraitB> Foo<T$0> where T: Sized {}
 "#,
             expect![[r#"
                 *T*
 
                 ```rust
-                T: Copy + Clone
+                T: TraitA + TraitB
                 ```
             "#]],
         );
@@ -3562,20 +3562,35 @@ impl<T: 'static> Foo<T$0> {}
     }
 
     #[test]
-    fn hover_type_param_not_sized() {
+    fn hover_type_param_sized_bounds() {
+        // implicit `: Sized` bound
         check(
             r#"
 //- minicore: sized
+trait Trait {}
 struct Foo<T>(T);
-trait Copy {}
+impl<T: Trait> Foo<T$0> {}
-trait Clone {}
-impl<T: Copy + Clone> Foo<T$0> where T: ?Sized {}
 "#,
             expect![[r#"
                 *T*
 
                 ```rust
-                T: Copy + Clone + ?Sized
+                T: Trait
+                ```
+            "#]],
+        );
+        check(
+            r#"
+//- minicore: sized
+trait Trait {}
+struct Foo<T>(T);
+impl<T: Trait + ?Sized> Foo<T$0> {}
+"#,
+            expect![[r#"
+                *T*
+
+                ```rust
+                T: Trait + ?Sized
                 ```
             "#]],
         );