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Assume we can normalize trait default method RPITITs in param-env instead

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This commit is contained in:
Michael Goulet 2023-02-17 17:16:43 +00:00
parent be55ad53a1
commit d42a3fbd69
3 changed files with 81 additions and 4 deletions
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22
compiler/rustc_middle/src/ty/util.rs
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@ -4,7 +4,7 @@ use crate::middle::codegen_fn_attrs::CodegenFnAttrFlags;
use crate::mir;
use crate::ty::layout::IntegerExt;
use crate::ty::{
self, ir::TypeFolder, DefIdTree, FallibleTypeFolder, Ty, TyCtxt, TypeFoldable,
self, ir::TypeFolder, DefIdTree, FallibleTypeFolder, ToPredicate, Ty, TyCtxt, TypeFoldable,
TypeSuperFoldable,
};
use crate::ty::{GenericArgKind, SubstsRef};
@ -865,6 +865,26 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for OpaqueTypeExpander<'tcx> {
}
t
}
fn fold_predicate(&mut self, p: ty::Predicate<'tcx>) -> ty::Predicate<'tcx> {
if let ty::PredicateKind::Clause(clause) = p.kind().skip_binder()
&& let ty::Clause::Projection(projection_pred) = clause
{
p.kind()
.rebind(ty::ProjectionPredicate {
projection_ty: projection_pred.projection_ty.fold_with(self),
// Don't fold the term on the RHS of the projection predicate.
// This is because for default trait methods with RPITITs, we
// install a `NormalizesTo(Projection(RPITIT) -> Opaque(RPITIT))`
// predicate, which would trivially cause a cycle when we do
// anything that requires `ParamEnv::with_reveal_all_normalized`.
term: projection_pred.term,
})
.to_predicate(self.tcx)
} else {
p.super_fold_with(self)
}
}
}
impl<'tcx> Ty<'tcx> {