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crater: drop implied bound with non-universal region #159706

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crater: drop implied bound with non-universal region #159706

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f897262
Drop implied bound with non-universal region
tiif Jul 22, 2026
380b76b
fmt
tiif Jul 22, 2026
e11f8d5
assert
tiif Aug 29, 2026
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19 changes: 16 additions & 3 deletions compiler/rustc_borrowck/src/type_check/free_region_relations.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -572,19 +572,32 @@ impl<'tcx> UniversalRegionRelationsBuilder<'_, 'tcx> {
debug!("add_outlives_bounds(bound={:?})", outlives_bound);

match outlives_bound {
OutlivesBound::RegionSubRegion(r1, r2) => {
OutlivesBound::RegionSubRegion(ra, rb) => {
// The bound says that `r1 <= r2`; we store `r2: r1`.
let r1 = self.universal_regions.to_region_vid(r1);
let r2 = self.universal_regions.to_region_vid(r2);
let r1 = self.universal_regions.to_region_vid(ra);
let r2 = self.universal_regions.to_region_vid(rb);
if !(self.universal_regions.is_universal_region(r1)
|| self.universal_regions.is_universal_region(r2))
{
assert!(false, "case one: {} <= {}", ra, rb);
}
Comment on lines +577 to +583

@tiif tiif Aug 29, 2026 •
edited by rustbot
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Looking at this again, I noticed I missed the case where r1 xor r2 is non-universal region, I will open a follow-up PR with crater run that only includes this case that I missed.

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@tiif tiif Aug 30, 2026 •
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There isn't any case in our test suite where r1 xor r2 is non-universal region, I guess we can just safely ignore it?

self.relate_universal_regions(r2, r1);
}

OutlivesBound::RegionSubParam(r_a, param_b) => {
let r1 = self.universal_regions.to_region_vid(r_a);
if !self.universal_regions.is_universal_region(r1) {
assert!(false, "case two: {} <= {}", r_a, param_b);
}
self.region_bound_pairs
.insert(ty::OutlivesClause(GenericKind::Param(param_b), r_a));
}

OutlivesBound::RegionSubAlias(r_a, alias_b) => {
let r1 = self.universal_regions.to_region_vid(r_a);
if !self.universal_regions.is_universal_region(r1) {
assert!(false, "case three: {} <= {}", r_a, alias_b);
}
self.region_bound_pairs
.insert(ty::OutlivesClause(GenericKind::Alias(alias_b), r_a));
}
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