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Auto merge of #85382 - Aaron1011:project-eval, r=nikomatsakis

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Always produce sub-obligations when using cached projection result

See https://github.com/rust-lang/rust/issues/85360

When we skip adding the sub-obligations to the `obligation` list, we can affect whether or not the final result is `EvaluatedToOk` or `EvaluatedToOkModuloObligations`. This creates problems for incremental compilation, since the projection cache is untracked shared state.

To solve this issue, we unconditionally process the sub-obligations. Surprisingly, this is a slight performance *win* in many cases.
This commit is contained in:
bors 2021-05-21 02:39:39 +00:00
parent 746ac21e48 8657bb251c
commit 6f5a198ffc
1 changed files with 1 additions and 9 deletions
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8
compiler/rustc_trait_selection/src/traits/project.rs
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@ -529,15 +529,7 @@ fn opt_normalize_projection_type<'a, 'b, 'tcx>(
// evaluation this is not the case, and dropping the trait
// evaluations can causes ICEs (e.g., #43132).
debug!(?ty, "found normalized ty");
// Once we have inferred everything we need to know, we
// can ignore the `obligations` from that point on.
if infcx.unresolved_type_vars(&ty.value).is_none() {
infcx.inner.borrow_mut().projection_cache().complete_normalized(cache_key, &ty);
// No need to extend `obligations`.
} else {
obligations.extend(ty.obligations);
}
return Ok(Some(ty.value));
}
Err(ProjectionCacheEntry::Error) => {