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Rollup merge of #121435 - estebank:rpitit-static-119773, r=compiler-errors

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Account for RPITIT in E0310 explicit lifetime constraint suggestion

When given

```rust
trait Original {
    fn f() -> impl Fn();
}

trait Erased {
    fn f(&self) -> Box<dyn Fn()>;
}

impl<T: Original> Erased for T {
    fn f(&self) -> Box<dyn Fn()> {
        Box::new(<T as Original>::f())
    }
}
```

emit do not emit an invalid suggestion restricting the `Trait::{opaque}` type in a `where` clause:

```
error[E0310]: the associated type `<T as Original>::{opaque#0}` may not live long enough
  --> $DIR/missing-static-bound-from-impl.rs:11:9
   |
LL |         Box::new(<T as Original>::f())
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |         |
   |         the associated type `<T as Original>::{opaque#0}` must be valid for the static lifetime...
   |         ...so that the type `impl Fn()` will meet its required lifetime bounds
```

Partially address #119773. Ideally we'd suggest modifying `Erased::f` instead.

r? `@compiler-errors`
This commit is contained in:
Matthias Krüger 2024-02-24 15:35:12 +01:00 • committed by GitHub
commit b10ef3c6bc
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4 changed files with 36 additions and 2 deletions
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8
compiler/rustc_infer/src/infer/error_reporting/mod.rs
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@ -2437,6 +2437,14 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
let suggestion =
if has_lifetimes { format!(" + {lt_name}") } else { format!(": {lt_name}") };
suggs.push((sp, suggestion))
} else if let GenericKind::Alias(ref p) = bound_kind
&& let ty::Projection = p.kind(self.tcx)
&& let DefKind::AssocTy = self.tcx.def_kind(p.def_id)
&& let Some(ty::ImplTraitInTraitData::Trait { .. }) =
self.tcx.opt_rpitit_info(p.def_id)
{
// The lifetime found in the `impl` is longer than the one on the RPITIT.
// Do not suggest `<Type as Trait>::{opaque}: 'static`.
} else if let Some(generics) = self.tcx.hir().get_generics(suggestion_scope) {
let pred = format!("{bound_kind}: {lt_name}");
let suggestion = format!("{} {}", generics.add_where_or_trailing_comma(), pred);