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Only make GAT ambiguous in match_projection_projections considering shallow resolvability

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This commit is contained in:
Michael Goulet 2024-05-17 11:14:36 -04:00
parent ddba1dc97e
commit fa829feb2f
2 changed files with 30 additions and 1 deletions
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12
compiler/rustc_trait_selection/src/traits/select/mod.rs
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@ -1778,9 +1778,19 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
// If this type is a GAT, and of the GAT args resolve to something new,
// that means that we must have newly inferred something about the GAT.
// We should give up in that case.
// FIXME(generic-associated-types): This only detects one layer of inference,
// which is probably not what we actually want, but fixing it causes some ambiguity:
// <https://github.com/rust-lang/rust/issues/125196>.
if !generics.own_params.is_empty()
&& obligation.predicate.args[generics.parent_count..].iter().any(|&p| {
p.has_non_region_infer() && self.infcx.resolve_vars_if_possible(p) != p
p.has_non_region_infer()
&& match p.unpack() {
ty::GenericArgKind::Const(ct) => {
self.infcx.shallow_resolve_const(ct) != ct
}
ty::GenericArgKind::Type(ty) => self.infcx.shallow_resolve(ty) != ty,
ty::GenericArgKind::Lifetime(_) => false,
}
})
{
ProjectionMatchesProjection::Ambiguous