Auto merge of #142071 - lcnr:revealing-use, r=compiler-errors

2025-08-15T18:52:12+00:00

`apply_member_constraints`: fix placeholder check Checking whether the member region is *an existential region from a higher universe* is just wrong and I am pretty sure we've added that check by accident as the naming was just horribly confusing before rust-lang/rust#140466. I've encountered this issue separately while working on rust-lang/rust#139587, but feel like it's probably easier to separately FCP this change. This allows the following code to compile ```rust trait Proj<'a> { type Assoc; } impl<'a, 'b, F: FnOnce() -> &'b ()> Proj<'a> for F { type Assoc = (); } fn is_proj Proj<'a>>(f: F) {} fn define<'a>() -> impl Sized + use<'a> { // This adds a use of `opaque::<'a>` with hidden type `&'unconstrained_b ()`. // 'unconstrained_b is an inference variable from a higher universe as it gets // created inside of the binder of `F: for<'a> Proj<'a>`. This previously // caused us to not apply member constraints. We now do, constraining // it to `'a`. is_proj(define::<'a>); &() } fn main() {} ``` This should not be breaking change, even in theory. Applying member constraints is incomplete in rare circumstances which means that applying them in more cases can cause spurious errors, cc rust-lang/rust#140569/rust-lang/rust#142073. However, as we always skipped these member regions in `apply_member_constraints` the skipped region is guaranteed to cause an error in `check_member_constraints` later on.

apply_member_constraints: fix placeholder check

2025-08-08T12:32:35+00:00

move member-constraints tests

2025-08-07T12:20:19+00:00

UI tests: add missing diagnostic kinds where possible

2025-04-08T20:06:31+00:00

Bless test fallout

2024-08-17T16:43:25+00:00

[AUTO-GENERATED] Migrate ui tests from `//` to `//@` directives

2024-02-16T20:02:50+00:00

remove trailing dots

2023-10-08T10:06:17+00:00

always show and explain sub region

2023-10-08T09:59:51+00:00

vars are ?

2023-04-25T19:53:09+00:00

Label opaque type for 'captures lifetime' error message

2023-03-03T05:02:34+00:00

rust/tests/ui/nll/member-constraints, branch try-perf