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lub: don't bail out due to empty binders

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This commit is contained in:
lcnr 2022-06-08 12:39:14 +02:00
parent 64a7aa7016
commit c7b6e1de66
5 changed files with 193 additions and 12 deletions
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20
compiler/rustc_infer/src/infer/glb.rs
View file

@ -95,12 +95,20 @@ impl<'tcx> TypeRelation<'tcx> for Glb<'_, '_, 'tcx> {
T: Relate<'tcx>,
{
debug!("binders(a={:?}, b={:?})", a, b);
// When higher-ranked types are involved, computing the LUB is
// very challenging, switch to invariance. This is obviously
// overly conservative but works ok in practice.
self.relate_with_variance(ty::Variance::Invariant, ty::VarianceDiagInfo::default(), a, b)?;
Ok(a)
if a.skip_binder().has_escaping_bound_vars() || b.skip_binder().has_escaping_bound_vars() {
// When higher-ranked types are involved, computing the GLB is
// very challenging, switch to invariance. This is obviously
// overly conservative but works ok in practice.
self.relate_with_variance(
ty::Variance::Invariant,
ty::VarianceDiagInfo::default(),
a,
b,
)?;
Ok(a)
} else {
Ok(ty::Binder::dummy(self.relate(a.skip_binder(), b.skip_binder())?))
}
}
}

20
compiler/rustc_infer/src/infer/lub.rs
View file

@ -95,12 +95,20 @@ impl<'tcx> TypeRelation<'tcx> for Lub<'_, '_, 'tcx> {
T: Relate<'tcx>,
{
debug!("binders(a={:?}, b={:?})", a, b);
// When higher-ranked types are involved, computing the LUB is
// very challenging, switch to invariance. This is obviously
// overly conservative but works ok in practice.
self.relate_with_variance(ty::Variance::Invariant, ty::VarianceDiagInfo::default(), a, b)?;
Ok(a)
if a.skip_binder().has_escaping_bound_vars() || b.skip_binder().has_escaping_bound_vars() {
// When higher-ranked types are involved, computing the LUB is
// very challenging, switch to invariance. This is obviously
// overly conservative but works ok in practice.
self.relate_with_variance(
ty::Variance::Invariant,
ty::VarianceDiagInfo::default(),
a,
b,
)?;
Ok(a)
} else {
Ok(ty::Binder::dummy(self.relate(a.skip_binder(), b.skip_binder())?))
}
}
}