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HACK: constrain yield type in check_fn so that projection is successful even with no yield

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This commit is contained in:
Michael Goulet 2023-12-07 18:36:55 +00:00
parent 44911b7c67
commit 4c77058562
1 changed files with 23 additions and 3 deletions
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26
compiler/rustc_hir_typeck/src/check.rs
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@ -59,9 +59,7 @@ pub(super) fn check_fn<'a, 'tcx>(
&& can_be_coroutine.is_some()
{
let yield_ty = match kind {
hir::CoroutineKind::Gen(..)
| hir::CoroutineKind::AsyncGen(..)
| hir::CoroutineKind::Coroutine => {
hir::CoroutineKind::Gen(..) | hir::CoroutineKind::Coroutine => {
let yield_ty = fcx.next_ty_var(TypeVariableOrigin {
kind: TypeVariableOriginKind::TypeInference,
span,
@ -69,6 +67,28 @@ pub(super) fn check_fn<'a, 'tcx>(
fcx.require_type_is_sized(yield_ty, span, traits::SizedYieldType);
yield_ty
}
// HACK(-Ztrait-solver=next): In the *old* trait solver, we must eagerly
// guide inference on the yield type so that we can handle `AsyncIterator`
// in this block in projection correctly. In the new trait solver, it is
// not a problem.
hir::CoroutineKind::AsyncGen(..) => {
let yield_ty = fcx.next_ty_var(TypeVariableOrigin {
kind: TypeVariableOriginKind::TypeInference,
span,
});
fcx.require_type_is_sized(yield_ty, span, traits::SizedYieldType);
Ty::new_adt(
tcx,
tcx.adt_def(tcx.require_lang_item(hir::LangItem::Poll, Some(span))),
tcx.mk_args(&[Ty::new_adt(
tcx,
tcx.adt_def(tcx.require_lang_item(hir::LangItem::Option, Some(span))),
tcx.mk_args(&[yield_ty.into()]),
)
.into()]),
)
}
hir::CoroutineKind::Async(..) => Ty::new_unit(tcx),
};