[coroutines] Make sure auto return type of await_resume is properly handled

Reviewers: rsmith, EricWF

Reviewed By: rsmith

Subscribers: javed.absar, cfe-commits

Differential Revision: https://reviews.llvm.org/D37454

llvm-svn: 312565

2 files changed, 12 insertions, 2 deletions

diff --git a/clang/lib/Sema/SemaCoroutine.cpp b/clang/lib/Sema/SemaCoroutine.cpp
index ae8744c07ba..e6b640f878c 100644
--- a/clang/lib/Sema/SemaCoroutine.cpp
+++ b/clang/lib/Sema/SemaCoroutine.cpp
@@ -438,14 +438,14 @@ static ReadySuspendResumeResult buildCoawaitCalls(Sema &S, VarDecl *CoroPromise,
     //   - await-suspend is the expression e.await_suspend(h), which shall be
     //     a prvalue of type void or bool.
     QualType RetType = AwaitSuspend->getCallReturnType(S.Context);
+
     // Experimental support for coroutine_handle returning await_suspend.
     if (Expr *TailCallSuspend = maybeTailCall(S, RetType, AwaitSuspend, Loc))
       Calls.Results[ACT::ACT_Suspend] = TailCallSuspend;
     else {
       // non-class prvalues always have cv-unqualified types
-      QualType AdjRetType = RetType.getUnqualifiedType();
       if (RetType->isReferenceType() ||
-          (AdjRetType != S.Context.BoolTy && AdjRetType != S.Context.VoidTy)) {
+          (!RetType->isBooleanType() && !RetType->isVoidType())) {
         S.Diag(AwaitSuspend->getCalleeDecl()->getLocation(),
                diag::err_await_suspend_invalid_return_type)
             << RetType;
diff --git a/clang/test/SemaCXX/coroutines.cpp b/clang/test/SemaCXX/coroutines.cpp
index 6394829f356..65e17abb11f 100644
--- a/clang/test/SemaCXX/coroutines.cpp
+++ b/clang/test/SemaCXX/coroutines.cpp
@@ -66,6 +66,12 @@ struct suspend_never {
   void await_resume() {}
 };
 
+struct auto_await_suspend {
+  bool await_ready();
+  template <typename F> auto await_suspend(F) {}
+  void await_resume();
+};
+
 struct DummyVoidTag {};
 DummyVoidTag no_specialization() { // expected-error {{this function cannot be a coroutine: 'std::experimental::coroutine_traits<DummyVoidTag>' has no member named 'promise_type'}}
   co_await a;
@@ -159,6 +165,10 @@ void yield() {
   co_yield yield; // expected-error {{no member named 'await_ready' in 'not_awaitable'}}
 }
 
+void check_auto_await_suspend() {
+  co_await auto_await_suspend{}; // Should compile successfully.
+}
+
 void coreturn(int n) {
   co_await a;
   if (n == 0)