Do not suggest bounds restrictions for synthesized RPITITs
Before this PR we were getting ...
```
warning: the feature `async_fn_in_trait` is incomplete and may not be safe to use and/or cause compiler crashes
--> tests/ui/async-await/in-trait/missing-send-bound.rs:5:12
|
5 | #![feature(async_fn_in_trait)]
| ^^^^^^^^^^^^^^^^^
|
= note: see issue #91611 <https://github.com/rust-lang/rust/issues/91611> for more information
= note: `#[warn(incomplete_features)]` on by default
error: future cannot be sent between threads safely
--> tests/ui/async-await/in-trait/missing-send-bound.rs:17:20
|
17 | assert_is_send(test::<T>());
| ^^^^^^^^^^^ future returned by `test` is not `Send`
|
= help: within `impl Future<Output = ()>`, the trait `Send` is not implemented for `impl Future<Output = ()>`
note: future is not `Send` as it awaits another future which is not `Send`
--> tests/ui/async-await/in-trait/missing-send-bound.rs:13:5
|
13 | T::bar().await;
| ^^^^^^^^ await occurs here on type `impl Future<Output = ()>`, which is not `Send`
note: required by a bound in `assert_is_send`
--> tests/ui/async-await/in-trait/missing-send-bound.rs:21:27
|
21 | fn assert_is_send(_: impl Send) {}
| ^^^^ required by this bound in `assert_is_send`
help: consider further restricting the associated type
|
16 | fn test2<T: Foo>() where impl Future<Output = ()>: Send {
| ++++++++++++++++++++++++++++++++++++
error: aborting due to previous error; 1 warning emitted
```
and we want this output ...
```
warning: the feature `async_fn_in_trait` is incomplete and may not be safe to use and/or cause compiler crashes
--> $DIR/missing-send-bound.rs:5:12
|
LL | #![feature(async_fn_in_trait)]
| ^^^^^^^^^^^^^^^^^
|
= note: see issue #91611 <https://github.com/rust-lang/rust/issues/91611> for more information
= note: `#[warn(incomplete_features)]` on by default
error: future cannot be sent between threads safely
--> $DIR/missing-send-bound.rs:17:20
|
LL | assert_is_send(test::<T>());
| ^^^^^^^^^^^ future returned by `test` is not `Send`
|
= help: within `impl Future<Output = ()>`, the trait `Send` is not implemented for `impl Future<Output = ()>`
note: future is not `Send` as it awaits another future which is not `Send`
--> $DIR/missing-send-bound.rs:13:5
|
LL | T::bar().await;
| ^^^^^^^^ await occurs here on type `impl Future<Output = ()>`, which is not `Send`
note: required by a bound in `assert_is_send`
--> $DIR/missing-send-bound.rs:21:27
|
LL | fn assert_is_send(_: impl Send) {}
| ^^^^ required by this bound in `assert_is_send`
error: aborting due to previous error; 1 warning emitted
```
r? `@compiler-errors`
94d2028abd