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Short circuit full corherence check when dealing with types with different reference mutability

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This commit is contained in:
Ryan Levick 2021-02-12 14:04:09 +01:00
parent cdfc52fbd6
commit 8ea0973725
2 changed files with 15 additions and 5 deletions
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11
compiler/rustc_trait_selection/src/traits/coherence.rs
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@ -75,18 +75,19 @@ where
let impl1_ref = tcx.impl_trait_ref(impl1_def_id);
let impl2_ref = tcx.impl_trait_ref(impl2_def_id);
// Check if any of the input types definitely mismatch.
// Check if any of the input types definitely do not unify.
if impl1_ref
.iter()
.flat_map(|tref| tref.substs.types())
.zip(impl2_ref.iter().flat_map(|tref| tref.substs.types()))
.chain(iter::once((impl1_self, impl2_self)))
.any(|(ty1, ty2)| {
let ty1 = fast_reject::simplify_type(tcx, ty1, false);
let ty2 = fast_reject::simplify_type(tcx, ty2, false);
if let (Some(ty1), Some(ty2)) = (ty1, ty2) {
let t1 = fast_reject::simplify_type(tcx, ty1, false);
let t2 = fast_reject::simplify_type(tcx, ty2, false);
if let (Some(t1), Some(t2)) = (t1, t2) {
// Simplified successfully
ty1 != ty2
// Types cannot unify if they differ in their reference mutability or simplify to different types
ty1.ref_mutability() != ty2.ref_mutability() || t1 != t2
} else {
// Types might unify
false