bjoernager/rust
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Winnow specializing impls

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This commit is contained in:
Michael Goulet 2023-07-04 18:06:41 +00:00
parent 9227ff28af
commit d2a1803d6f
3 changed files with 37 additions and 4 deletions
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15
compiler/rustc_trait_selection/src/solve/eval_ctxt/select.rs
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@ -52,7 +52,11 @@ impl<'tcx> InferCtxtSelectExt<'tcx> for InferCtxt<'tcx> {
let mut i = 0;
while i < candidates.len() {
let should_drop_i = (0..candidates.len()).filter(|&j| i != j).any(|j| {
candidate_should_be_dropped_in_favor_of(&candidates[i], &candidates[j])
candidate_should_be_dropped_in_favor_of(
ecx.tcx(),
&candidates[i],
&candidates[j],
)
});
if should_drop_i {
candidates.swap_remove(i);
@ -160,12 +164,19 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
}
fn candidate_should_be_dropped_in_favor_of<'tcx>(
tcx: TyCtxt<'tcx>,
victim: &Candidate<'tcx>,
other: &Candidate<'tcx>,
) -> bool {
match (victim.source, other.source) {
(CandidateSource::ParamEnv(i), CandidateSource::ParamEnv(j)) => i >= j,
(CandidateSource::ParamEnv(victim_idx), CandidateSource::ParamEnv(other_idx)) => {
victim_idx >= other_idx
}
(_, CandidateSource::ParamEnv(_)) => true,
(CandidateSource::Impl(victim_def_id), CandidateSource::Impl(other_def_id)) => {
tcx.specializes((other_def_id, victim_def_id))
&& other.result.value.certainty == Certainty::Yes
}
_ => false,
}
}