Rollup merge of #118736 - aliemjay:revert-ice-on-ambig, r=compiler-er…

…rors temporarily revert "ice on ambguity in mir typeck" Reverts #116530 as a temporary measure to fix #117577. That issue should be ultimately fixed by checking WF of type annotations prior to normalization, which is implemented in #104098 but this PR is intended to be backported to beta. r? ``@compiler-errors`` (the reviewer of the reverted PR)
rust-lang · Dec 8, 2023 · a255b52 · a255b52
2 parents 943fa33 5fdb648
commit a255b52
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diff --git a/compiler/rustc_trait_selection/src/traits/query/type_op/mod.rs b/compiler/rustc_trait_selection/src/traits/query/type_op/mod.rs
@@ -157,18 157,10 @@ where
  }
 
  let mut region_constraints = QueryRegionConstraints::default();
- let (output, error_info, mut obligations) =
- Q::fully_perform_into(self, infcx, &mut region_constraints)
- .map_err(|_| {
- infcx.tcx.sess.span_delayed_bug(span, format!("error performing {self:?}"))
- })
- .and_then(|(output, error_info, obligations, certainty)| match certainty {
- Certainty::Proven => Ok((output, error_info, obligations)),
- Certainty::Ambiguous => Err(infcx
- .tcx
- .sess
- .span_delayed_bug(span, format!("ambiguity performing {self:?}"))),
- })?;
  let (output, error_info, mut obligations, _) =
  Q::fully_perform_into(self, infcx, &mut region_constraints).map_err(|_| {
  infcx.tcx.sess.span_delayed_bug(span, format!("error performing {self:?}"))
  })?;
 
  // Typically, instantiating NLL query results does not
  // create obligations. However, in some cases there

diff --git a/tests/ui/wf/unnormalized-projection-guides-inference.rs b/tests/ui/wf/unnormalized-projection-guides-inference.rs
@@ -0,0 1,24 @@
 // The WF requirements of the *unnormalized* form of type annotations
 // can guide inference.
 // check-pass
 
 pub trait EqualTo {
  type Ty;
 }
 impl<X> EqualTo for X {
  type Ty = X;
 }
 
 trait MyTrait<U: EqualTo<Ty = Self>> {
  type Out;
 }
 impl<T, U: EqualTo<Ty = T>> MyTrait<U> for T {
  type Out = ();
 }
 
 fn main() {
  let _: <_ as MyTrait<u8>>::Out;
  // We shoud be able to infer a value for the inference variable above.
  // The WF of the unnormalized projection requires `u8: EqualTo<Ty = _>`,
  // which is sufficient to guide inference.
 }