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Unrolled build for rust-lang#126968
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Rollup merge of rust-lang#126968 - lqd:issue-126670, r=compiler-errors

Don't ICE during RPITIT refinement checking for resolution errors after normalization

rust-lang#126670 shows a case where resolution errors after normalization can happen during RPITIT refinement checking. Our tests didn't reach this path before, and we explicitly ICEd until we had a test. We can now delay a bug since we're sure it is reachable and have the test from the isue.

The comment I added likely still needs more expert wordsmithing.

r? ``@compiler-errors`` who's making me work during vacation (j/k).
Fixes rust-lang#126670
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rust-timer authored Jun 26, 2024
2 parents a299aa5 + 6402909 commit a2a8312
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Showing 3 changed files with 43 additions and 4 deletions.
Original file line number Diff line number Diff line change
Expand Up @@ -171,10 +171,10 @@ pub(super) fn check_refining_return_position_impl_trait_in_trait<'tcx>(
}
// Resolve any lifetime variables that may have been introduced during normalization.
let Ok((trait_bounds, impl_bounds)) = infcx.fully_resolve((trait_bounds, impl_bounds)) else {
// This code path is not reached in any tests, but may be reachable. If
// this is triggered, it should be converted to `delayed_bug` and the
// triggering case turned into a test.
tcx.dcx().bug("encountered errors when checking RPITIT refinement (resolution)");
// If resolution didn't fully complete, we cannot continue checking RPITIT refinement, and
// delay a bug as the original code contains load-bearing errors.
tcx.dcx().delayed_bug("encountered errors when checking RPITIT refinement (resolution)");
return;
};

// For quicker lookup, use an `IndexSet` (we don't use one earlier because
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23 changes: 23 additions & 0 deletions tests/ui/impl-trait/in-trait/refine-resolution-errors.rs
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@@ -0,0 +1,23 @@
// This is a non-regression test for issue #126670 where RPITIT refinement checking encountered
// errors during resolution and ICEd.

//@ edition: 2018

pub trait Mirror {
type Assoc;
}
impl<T: ?Sized> Mirror for () {
//~^ ERROR the type parameter `T` is not constrained
type Assoc = T;
}

pub trait First {
async fn first() -> <() as Mirror>::Assoc;
//~^ ERROR type annotations needed
}

impl First for () {
async fn first() {}
}

fn main() {}
16 changes: 16 additions & 0 deletions tests/ui/impl-trait/in-trait/refine-resolution-errors.stderr
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error[E0207]: the type parameter `T` is not constrained by the impl trait, self type, or predicates
--> $DIR/refine-resolution-errors.rs:9:6
|
LL | impl<T: ?Sized> Mirror for () {
| ^ unconstrained type parameter

error[E0282]: type annotations needed
--> $DIR/refine-resolution-errors.rs:15:5
|
LL | async fn first() -> <() as Mirror>::Assoc;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ cannot infer type

error: aborting due to 2 previous errors

Some errors have detailed explanations: E0207, E0282.
For more information about an error, try `rustc --explain E0207`.

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