Account for `impl Trait {` when `impl Trait for Type {` was intended
On editions where bare traits are never allowed, detect if the user has written `impl Trait` with no type, silence any dyn-compatibility errors, and provide a structured suggestion for the potentially missing type:
```
error[E0782]: trait objects must include the `dyn` keyword
--> $DIR/missing-for-type-in-impl.rs:8:6
|
LL | impl Foo<i64> {
| ^^^^^^^^
|
help: add `dyn` keyword before this trait
|
LL | impl dyn Foo<i64> {
| +++
help: you might have intended to implement this trait for a given type
|
LL | impl Foo<i64> for /* Type */ {
| ++++++++++++++
```
CC #131051.
08689af7b4