bjoernager/rust
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Only prevent TAITs from defining each other, RPIT and async are fine, they only ever have one defining site, and it is ordered correctly around expected and actual type in type comparisons

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This commit is contained in:
Oli Scherer 2022-02-02 15:03:44 +00:00
parent 7f608eb9ed
commit be153f0976
3 changed files with 10 additions and 21 deletions
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9
compiler/rustc_infer/src/infer/opaque_types.rs
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@ -82,7 +82,14 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
let process = |a: Ty<'tcx>, b: Ty<'tcx>| match *a.kind() {
ty::Opaque(def_id, substs) => {
if let ty::Opaque(did2, _) = *b.kind() {
if self.opaque_type_origin(did2, cause.span).is_some() {
// We could accept this, but there are various ways to handle this situation, and we don't
// want to make a decision on it right now. Likely this case is so super rare anyway, that
// no one encounters it in practice.
// It does occur however in `fn fut() -> impl Future<Output = i32> { async { 42 } }`,
// where it is of no concern, so we only check for TAITs.
if let Some(OpaqueTyOrigin::TyAlias) =
self.opaque_type_origin(did2, cause.span)
{
self.tcx
.sess
.struct_span_err(