- let ret_ty = if tcx.generator_is_async(did) {
- let state_did = tcx.require_lang_item(LangItem::Poll, None);
- let state_adt_ref = tcx.adt_def(state_did);
- let state_substs = tcx.intern_substs(&[sig.return_ty.into()]);
- tcx.mk_adt(state_adt_ref, state_substs)
+ let (resume_ty, ret_ty) = if tcx.generator_is_async(did) {
+ // The signature should be `Future::poll(_, &mut Context<'_>) -> Poll<Output>`
+ let poll_did = tcx.require_lang_item(LangItem::Poll, None);
+ let poll_adt_ref = tcx.adt_def(poll_did);
+ let poll_substs = tcx.intern_substs(&[sig.return_ty.into()]);
+ let ret_ty = tcx.mk_adt(poll_adt_ref, poll_substs);
+
+ // We have to replace the `ResumeTy` that is used for type and borrow checking
+ // with `&mut Context<'_>` which is used in codegen.
+ #[cfg(debug_assertions)]
+ {
+ if let ty::Adt(resume_ty_adt, _) = sig.resume_ty.kind() {
+ let expected_adt =
+ tcx.adt_def(tcx.require_lang_item(LangItem::ResumeTy, None));
+ assert_eq!(*resume_ty_adt, expected_adt);
+ } else {
+ panic!("expected `ResumeTy`, found `{:?}`", sig.resume_ty);
+ };
+ }
+ let context_mut_ref = tcx.mk_task_context();
+
+ (context_mut_ref, ret_ty)