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Don't arbitrarily choose one upper bound for hidden captured region

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This commit is contained in:
Michael Goulet 2024-08-06 15:43:28 -04:00
parent 60d146580c
commit c656ce7aeb
6 changed files with 68 additions and 36 deletions
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35
compiler/rustc_borrowck/src/region_infer/opaque_types.rs
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@ -225,21 +225,26 @@ impl<'tcx> RegionInferenceContext<'tcx> {
// Find something that we can name
let upper_bound = self.approx_universal_upper_bound(vid);
let upper_bound = &self.definitions[upper_bound];
match upper_bound.external_name {
Some(reg) => reg,
None => {
// Nothing exact found, so we pick the first one that we find.
let scc = self.constraint_sccs.scc(vid);
for vid in self.rev_scc_graph.as_ref().unwrap().upper_bounds(scc) {
match self.definitions[vid].external_name {
None => {}
Some(region) if region.is_static() => {}
Some(region) => return region,
}
}
region
}
if let Some(universal_region) = self.definitions[upper_bound].external_name {
return universal_region;
}
// Nothing exact found, so we pick a named upper bound, if there's only one.
// If there's >1 universal region, then we probably are dealing w/ an intersection
// region which cannot be mapped back to a universal.
// FIXME: We could probably compute the LUB if there is one.
let scc = self.constraint_sccs.scc(vid);
let upper_bounds: Vec<_> = self
.rev_scc_graph
.as_ref()
.unwrap()
.upper_bounds(scc)
.filter_map(|vid| self.definitions[vid].external_name)
.filter(|r| !r.is_static())
.collect();
match &upper_bounds[..] {
[universal_region] => *universal_region,
_ => region,
}
}
_ => region,