bjoernager/rust
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marker_traits: require EvaluatedToOk

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This commit is contained in:
lcnr 2021-08-18 16:27:25 +02:00
parent 896f058f13
commit 3329f67f17
6 changed files with 93 additions and 3 deletions
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13
compiler/rustc_trait_selection/src/traits/select/mod.rs
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@ -1566,12 +1566,19 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
// See if we can toss out `victim` based on specialization.
// This requires us to know *for sure* that the `other` impl applies
// i.e., `EvaluatedToOk`.
//
// FIXME(@lcnr): Using `modulo_regions` here seems kind of scary
// to me but is required for `std` to compile, so I didn't change it
// for now.
let tcx = self.tcx();
if other.evaluation.must_apply_modulo_regions() {
let tcx = self.tcx();
if tcx.specializes((other_def, victim_def)) {
return true;
}
return match tcx.impls_are_allowed_to_overlap(other_def, victim_def) {
}
if other.evaluation.must_apply_considering_regions() {
match tcx.impls_are_allowed_to_overlap(other_def, victim_def) {
Some(ty::ImplOverlapKind::Permitted { marker: true }) => {
// Subtle: If the predicate we are evaluating has inference
// variables, do *not* allow discarding candidates due to
@ -1616,7 +1623,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
}
Some(_) => true,
None => false,
};
}
} else {
false
}