Provide more context on recursive `impl` evaluation overflow
When an associated type `Self::Assoc` is part of a `where` clause, we end up unable to evaluate the requirement and emit a E0275.
We now point at the associated type if specified in the `impl`. If so, we also suggest using that type instead of `Self::Assoc`. Otherwise, we explain that these are not allowed.
```
error[E0275]: overflow evaluating the requirement `<(T,) as Grault>::A == _`
--> $DIR/impl-wf-cycle-1.rs:15:1
|
LL | / impl<T: Grault> Grault for (T,)
LL | |
LL | | where
LL | | Self::A: Baz,
LL | | Self::B: Fiz,
| |_________________^
LL | {
LL | type A = ();
| ------ associated type `<(T,) as Grault>::A` is specified here
|
note: required for `(T,)` to implement `Grault`
--> $DIR/impl-wf-cycle-1.rs:15:17
|
LL | impl<T: Grault> Grault for (T,)
| ^^^^^^ ^^^^
...
LL | Self::A: Baz,
| --- unsatisfied trait bound introduced here
= note: 1 redundant requirement hidden
= note: required for `(T,)` to implement `Grault`
help: associated type for the current `impl` cannot be restricted in `where` clauses, remove this bound
|
LL - Self::A: Baz,
|
```
```
error[E0275]: overflow evaluating the requirement `<T as B>::Type == <T as B>::Type`
--> $DIR/impl-wf-cycle-3.rs:7:1
|
LL | / impl<T> B for T
LL | | where
LL | | T: A<Self::Type>,
| |_____________________^
LL | {
LL | type Type = bool;
| --------- associated type `<T as B>::Type` is specified here
|
note: required for `T` to implement `B`
--> $DIR/impl-wf-cycle-3.rs:7:9
|
LL | impl<T> B for T
| ^ ^
LL | where
LL | T: A<Self::Type>,
| ------------- unsatisfied trait bound introduced here
help: replace the associated type with the type specified in this `impl`
|
LL | T: A<bool>,
| ~~~~
```
```
error[E0275]: overflow evaluating the requirement `<T as Filter>::ToMatch == <T as Filter>::ToMatch`
--> $DIR/impl-wf-cycle-4.rs:5:1
|
LL | / impl<T> Filter for T
LL | | where
LL | | T: Fn(Self::ToMatch),
| |_________________________^
|
note: required for `T` to implement `Filter`
--> $DIR/impl-wf-cycle-4.rs:5:9
|
LL | impl<T> Filter for T
| ^^^^^^ ^
LL | where
LL | T: Fn(Self::ToMatch),
| ----------------- unsatisfied trait bound introduced here
note: associated types for the current `impl` cannot be restricted in `where` clauses
--> $DIR/impl-wf-cycle-4.rs:7:11
|
LL | T: Fn(Self::ToMatch),
| ^^^^^^^^^^^^^
```
Fix#116925
fd92d88c28