1 files changed, 19 insertions, 0 deletions
diff --git a/test/SemaCXX/coroutine-traits-undefined-template.cpp b/test/SemaCXX/coroutine-traits-undefined-template.cpp
new file mode 100644
index 0000000000000..4687ed245ac84
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+++ b/test/SemaCXX/coroutine-traits-undefined-template.cpp
@@ -0,0 +1,19 @@
+// This file contains references to sections of the Coroutines TS, which can be
+// found at http://wg21.link/coroutines.
+
+// RUN: %clang_cc1 -std=c++14 -fcoroutines-ts -verify %s -fcxx-exceptions -fexceptions -Wunused-result
+
+namespace std {
+namespace experimental {
+
+template<typename ...T>
+struct coroutine_traits {
+  struct promise_type {};
+};
+
+template<> struct coroutine_traits<void>; // expected-note {{forward declaration of 'std::experimental::coroutine_traits<void>'}}
+}} // namespace std::experimental
+
+void uses_forward_declaration() {
+  co_return; // expected-error {{this function cannot be a coroutine: missing definition of specialization 'coroutine_traits<void>'}}
+}