Tweak output of missing lifetime on associated type
Each commit can be reviewed independently. Address parts of #135589.
---
When an associated type is missing a lifetime, point at its enclosing `impl`, whether it has or doesn't have lifetimes defined. If it does have a lifetime, suggest using it.
```
error: in the trait associated type is declared without lifetime parameters, so using a borrowed type for them requires that lifetime to come from the implemented type
--> $DIR/missing-lifetime-in-assoc-type-1.rs:8:17
|
LL | impl<'a> IntoIterator for &S {
| ---- there is a named lifetime specified on the impl block you could use
...
LL | type Item = &T;
| ^ this lifetime must come from the implemented type
|
help: consider using the lifetime from the impl block
|
LL | type Item = &'a T;
| ++
```
```
error: in the trait associated type is declared without lifetime parameters, so using a borrowed type for them requires that lifetime to come from the implemented type
--> $DIR/missing-lifetime-in-assoc-type-2.rs:5:17
|
LL | impl IntoIterator for &S {
| - you could add a lifetime on the impl block, if the trait or the self type can have one
LL | type Item = &T;
| ^ this lifetime must come from the implemented type
```
---
On unconstrained lifetime on impl block, suggest using it if there's an implicit borrow in the self type
```
error[E0207]: the lifetime parameter `'a` is not constrained by the impl trait, self type, or predicates
--> $DIR/missing-lifetime-in-assoc-type-1.rs:4:6
|
LL | impl<'a> IntoIterator for &S {
| ^^ unconstrained lifetime parameter
|
help: consider using the named lifetime here instead of an implict lifetime
|
LL | impl<'a> IntoIterator for &'a S {
| ++
```
---
Do not suggest introducing lifetime in impl assoc type
---
Previously we only showed the trait's assoc item if the trait was local, because we were looking for a small span only for the generics, which we don't have for foreign traits. We now use `def_span` for the item, so we at least provide some context, even if its span is too wide.
```
error[E0195]: lifetime parameters or bounds on type `IntoIter` do not match the trait declaration
--> tests/ui/lifetimes/missing-lifetime-in-assoc-type-4.rs:7:18
|
7 | type IntoIter<'a> = std::collections::btree_map::Values<'a, i32, T>;
| ^^^^ lifetimes do not match type in trait
|
::: /home/gh-estebank/rust/library/core/src/iter/traits/collect.rs:292:5
|
292 | type IntoIter: Iterator<Item = Self::Item>;
| ------------------------------------------ lifetimes in impl do not match this type in trait
```
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