Modifying an environment variable would make the function unsafe to
call.

…e line

In particular, lifetime-generic associated types often have a
`where Self: 'a` bound, which we can format on the same line.

Show an example that has bounds.

… decls

Suggested-by: Caleb Cartwright <[email protected]>

…-clause-same-line, r=compiler-errors

style-guide: Format single associated type `where` clauses on the same line

In particular, lifetime-generic associated types often have a
`where Self: 'a` bound, which we can format on the same line.

…ert-label, r=apiraino

[meta] Clarify prioritization alert

Apparently, there used to exist the label <kbd>I-nominated</kbd> judging from this entry:

https://github.com/rust-lang/rust/blob/8847bda592d940ae1f34d87d8cacdc09a9f787fa/triagebot.toml#L393

Since it was replaced with individual team labels, I think it makes sense to update the prioritization alert. Of course, it's not super important since the members of WG-prioritization already know that. This is just cleanup.

r? apiraino or wg-prioritization

…er-errors

elaborate obligations in coherence

The following test currently does not pass coherence:
```rust
trait Super {}
trait Sub<T>: Super {}

trait Overlap<T> {}
impl<T, U: Sub<T>> Overlap<T> for U {}
impl<T> Overlap<T> for () {}

fn main() {}
```

We check whether `(): Sub<?t>` holds. This stalls with ambiguity as downstream crates may add an impl for `(): Sub<Local>`. However, its super trait bound `(): Super` cannot be implemented downstream, so this one is known not to hold.

By elaborating the bounds in the implicit negative overlap check, this now compiles. This is necessary to prevent breakage from enabling `-Znext-solver=coherence` (rust-lang#121848), see tests/ui/coherence/super-traits/super-trait-knowable-2.rs for more details.

r? `@compiler-errors`

Use a proper probe for shadowing impl

r? lcnr

…lwoerister

Don't call `env::set_var` in `rustc_driver::install_ice_hook`

Modifying an environment variable would make the function unsafe to call.