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Equate fn outputs when inferring RPITIT hidden types

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This commit is contained in:
Michael Goulet 2022-09-09 14:59:54 +00:00
parent 98f3001eec
commit 022e3fe550
1 changed files with 17 additions and 2 deletions
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19
compiler/rustc_typeck/src/check/compare_method.rs
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@ -295,12 +295,26 @@ pub(super) fn compare_predicates_and_trait_impl_trait_tys<'tcx>(
// type would be more appropriate. In other places we have a `Vec<Span>`
// corresponding to their `Vec<Predicate>`, but we don't have that here.
// Fixing this would improve the output of test `issue-83765.rs`.
let sub_result = infcx
let mut result = infcx
.at(&cause, param_env)
.sup(trait_fty, impl_fty)
.map(|infer_ok| ocx.register_infer_ok_obligations(infer_ok));
if let Err(terr) = sub_result {
// HACK(RPITIT): #101614. When we are trying to infer the hidden types for
// RPITITs, we need to equate the output tys instead of just subtyping. If
// we just use `sup` above, we'll end up `&'static str <: _#1t`, which causes
// us to infer `_#1t = #'_#2r str`, where `'_#2r` is unconstrained, which gets
// fixed up to `ReEmpty`, and which is certainly not what we want.
if trait_fty.has_infer_types() {
result = result.and_then(|()| {
infcx
.at(&cause, param_env)
.eq(trait_sig.output(), impl_sig.output())
.map(|infer_ok| ocx.register_infer_ok_obligations(infer_ok))
});
}
if let Err(terr) = result {
debug!("sub_types failed: impl ty {:?}, trait ty {:?}", impl_fty, trait_fty);
let (impl_err_span, trait_err_span) =
@ -445,6 +459,7 @@ pub(super) fn compare_predicates_and_trait_impl_trait_tys<'tcx>(
region
}
});
debug!(%ty);
collected_tys.insert(def_id, ty);
}
Err(err) => {