Signed-off-by: Yuki Okushi <jtitor@2k36.org>

As a workaround for the full `#[refine]` semantics not being implemented
yet, forbit returning a concrete future type like `Box<dyn Future>` or a
manually implemented Future.

`-> impl Future` is still permitted; while that can also cause
accidental refinement, that's behind a different feature gate
(`return_position_impl_trait_in_trait`) and that problem exists
regardless of whether the trait method is async, so will have to be
solved more generally.

Fixes rust-lang#102745

…f-id, r=estebank

Use impl's def id when calculating type to specify in UFCS

Fixes rust-lang#104327
Fixes rust-lang#104328

Also addresses rust-lang#102670 (comment)

…ler-errors

Ensure async trait impls are async (or otherwise return an opaque type)

As a workaround for the full `#[refine]` semantics not being implemented
yet, forbit returning a concrete future type like `Box<dyn Future>` or a
manually implemented Future.

`-> impl Future` is still permitted; while that can also cause
accidental refinement, that's behind a different feature gate
(`return_position_impl_trait_in_trait`) and that problem exists
regardless of whether the trait method is async, so will have to be
solved more generally.

Fixes rust-lang#102745

…env-2, r=estebank

Highlight conflicting param-env candidates, again

Un-reverts rust-lang#98794 (i.e. reverts rust-lang#99290).

The previous time I attempted to land this PR, it was because of an incremental issue (rust-lang#99233). The repro instructions in the issue is no longer manifest the ICE -- I think it's because this ambiguity code was refactored (I think by ````@lcnr)```` to no longer store the ambiguities in the fulfillment error, but instead recompute them on the fly.

The main motivation for trying to re-land this is that it fixes rust-lang#105131 by highlighting the root-cause of the issue, which is conflicting param-env candidates:

```
error[E0283]: type annotations needed: cannot satisfy `Self: Gen<'source>`
   |
note: multiple `impl`s or `where` clauses satisfying `Self: Gen<'source>` found
  --> $DIR/conflicting-bounds.rs:3:1
   |
LL | pub trait Gen<'source> {
   | ^^^^^^^^^^^^^^^^^^^^^^
...
LL |         Self: for<'s> Gen<'s, Output = T>;
   |               ^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to previous error

For more information about this error, try `rustc --explain E0283`.
```

Fixes rust-lang#105131.
Fixes (again) rust-lang#98786

…e-fix, r=Nilstrieb

Fix `-Z print-type-sizes` for generators with discriminant field ordered first

Fixes rust-lang#105589
Fixes rust-lang#105591

…le, r=davidtwco

Auto traits in `dyn Trait + Auto` are suggestable

Not  sure why I had made the `IsSuggestableVisitor` have that rule to not consider `dyn Trait + Auto` to be suggestable.

It's possible that this was done because of the fact that we don't print the right parentheses for `&(dyn Trait + Auto)`, but that's a problem with printing these types in general that we probably have tracked somewhere else...

…li-obk

Make `report_projection_error` more `Term` agnostic

Fixes rust-lang#105632

…-errors

Add regression test for rust-lang#104678

Closes rust-lang#104678
r? ````@compiler-errors````

Signed-off-by: Yuki Okushi <jtitor@2k36.org>

…rors

more clippy::complexity fixes

r? ``@compiler-errors``