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Auto merge of #104765 - chenyukang:yukang-fix-104639-lifetime-check, r=oli-obk

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Find the right lower bound region in the scenario of partial order relations

Fixes #104639
This commit is contained in:
bors 2022-12-15 01:28:16 +00:00
commit 939a3ddf94
2 changed files with 17 additions and 20 deletions
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27
compiler/rustc_borrowck/src/region_infer/mod.rs
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@ -747,27 +747,14 @@ impl<'tcx> RegionInferenceContext<'tcx> {
// Otherwise, we need to find the minimum remaining choice, if
// any, and take that.
debug!("choice_regions remaining are {:#?}", choice_regions);
let min = |r1: ty::RegionVid, r2: ty::RegionVid| -> Option<ty::RegionVid> {
let r1_outlives_r2 = self.universal_region_relations.outlives(r1, r2);
let r2_outlives_r1 = self.universal_region_relations.outlives(r2, r1);
match (r1_outlives_r2, r2_outlives_r1) {
(true, true) => Some(r1.min(r2)),
(true, false) => Some(r2),
(false, true) => Some(r1),
(false, false) => None,
}
let Some(&min_choice) = choice_regions.iter().find(|&r1| {
choice_regions.iter().all(|&r2| {
self.universal_region_relations.outlives(r2, *r1)
})
}) else {
debug!("no choice region outlived by all others");
return false;
};
let mut min_choice = choice_regions[0];
for &other_option in &choice_regions[1..] {
debug!(?min_choice, ?other_option,);
match min(min_choice, other_option) {
Some(m) => min_choice = m,
None => {
debug!(?min_choice, ?other_option, "incomparable; no min choice",);
return false;
}
}
}
let min_choice_scc = self.constraint_sccs.scc(min_choice);
debug!(?min_choice, ?min_choice_scc);