bjoernager/rust
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Auto merge of #112422 - aliemjay:implied-bounds-placeholders, r=lcnr

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ignore implied bounds with placeholders

given the following code:
```rust
trait Trait {
    type Ty<'a> where Self: 'a;
}

impl<T> Trait for T {
    type Ty<'a> = () where Self: 'a;
}

struct Foo<T: Trait>(T)
where
    for<'x> T::Ty<'x>: Sized;
```

when computing the implied bounds from `Foo<X>` we incorrectly get the bound `X: !x` from the normalization of ` for<'x> <X as Trait>::Ty::<'x>: Sized`. This is a a known bug! we shouldn't use the constraints that arise from normalization as implied bounds. See #109628.

Ignore these bounds for now. This should prevent later ICEs.

Fixes #112250
Fixes #107409
This commit is contained in:
bors 2023-11-17 12:16:53 +00:00
commit 4d7f952a02
4 changed files with 81 additions and 3 deletions
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8
compiler/rustc_trait_selection/src/traits/outlives_bounds.rs
View file

@ -72,7 +72,7 @@ impl<'a, 'tcx: 'a> InferCtxtExt<'a, 'tcx> for InferCtxt<'tcx> {
};
let mut constraints = QueryRegionConstraints::default();
let Ok(InferOk { value, obligations }) = self
let Ok(InferOk { value: mut bounds, obligations }) = self
.instantiate_nll_query_response_and_region_obligations(
&ObligationCause::dummy(),
param_env,
@ -85,6 +85,10 @@ impl<'a, 'tcx: 'a> InferCtxtExt<'a, 'tcx> for InferCtxt<'tcx> {
};
assert_eq!(&obligations, &[]);
// Because of #109628, we may have unexpected placeholders. Ignore them!
// FIXME(#109628): panic in this case once the issue is fixed.
bounds.retain(|bound| !bound.has_placeholders());
if !constraints.is_empty() {
let span = self.tcx.def_span(body_id);
@ -114,7 +118,7 @@ impl<'a, 'tcx: 'a> InferCtxtExt<'a, 'tcx> for InferCtxt<'tcx> {
}
};
value
bounds
}
fn implied_bounds_tys(