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Rollup merge of #116257 - estebank:issue-101351, r=b-naber

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Suggest trait bounds for used associated type on type param

Fix #101351.

When an associated type on a type parameter is used, and the type parameter isn't constrained by the correct trait, suggest the appropriate trait bound:

```
error[E0220]: associated type `Associated` not found for `T`
 --> file.rs:6:15
  |
6 |     field: T::Associated,
  |               ^^^^^^^^^^ there is a similarly named associated type `Associated` in the trait `Foo`
  |
help: consider restricting type parameter `T`
  |
5 | struct Generic<T: Foo> {
  |                 +++++
  ```

When an associated type on a type parameter has a typo, suggest fixing
it:

```
error[E0220]: associated type `Baa` not found for `T`
  --> $DIR/issue-55673.rs:9:8
   |
LL |     T::Baa: std::fmt::Debug,
   |        ^^^ there is a similarly named associated type `Bar` in the trait `Foo`
   |
help: change the associated type name to use `Bar` from `Foo`
   |
LL |     T::Bar: std::fmt::Debug,
   |        ~~~
```
This commit is contained in:
Matthias Krüger 2023-10-16 19:10:49 +02:00 • committed by GitHub
commit 14663e09b7
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12 changed files with 152 additions and 23 deletions
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2
compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
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@ -364,7 +364,7 @@ fn predicate_constraint(generics: &hir::Generics<'_>, pred: ty::Predicate<'_>) -
/// Type parameter needs more bounds. The trivial case is `T` `where T: Bound`, but
/// it can also be an `impl Trait` param that needs to be decomposed to a type
/// param for cleaner code.
fn suggest_restriction<'tcx>(
pub fn suggest_restriction<'tcx>(
tcx: TyCtxt<'tcx>,
item_id: LocalDefId,
hir_generics: &hir::Generics<'tcx>,