--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/g++.dg/coroutines/ramp-return.h	Mon May 25 07:50:57 2020 +0900
@@ -0,0 +1,64 @@
+#include "coro.h"
+
+#include <exception>
+#include <vector>
+
+template <typename T>
+struct promise {
+  T _value;
+  coro::coroutine_handle<> _continuation = nullptr;
+
+  struct final_awaitable {
+    bool _has_continuation;
+    final_awaitable(bool has_continuation)
+        : _has_continuation(has_continuation) {}
+
+    bool await_ready() const noexcept { return !_has_continuation; }
+
+    template <typename Promise>
+    coro::coroutine_handle<>
+    await_suspend(coro::coroutine_handle<Promise> coro) noexcept {
+      return coro.promise()._continuation;
+    }
+
+    void await_resume() noexcept {}
+  };
+
+  auto get_return_object() noexcept {
+    return coro::coroutine_handle<promise>::from_promise(*this);
+  }
+
+  auto initial_suspend() noexcept { return coro::suspend_always(); }
+
+  auto final_suspend() noexcept {
+    return final_awaitable(_continuation != nullptr);
+  }
+
+  void return_value(T value) { _value = value; }
+
+  void unhandled_exception() { std::terminate(); }
+};
+
+template <typename T> 
+struct task {
+  using promise_type = promise<T>;
+  std::coroutine_handle<promise<T>> _handle;
+
+  task (coro::coroutine_handle<promise<T>> handle) : _handle(handle) {}
+#if DELETE_COPY_CTOR
+ task (const task &) = delete; // no copying
+#endif
+#if DELETE_MOVE_CTOR
+ task(task&& t) noexcept
+    : _handle(t._handle) { t._handle = nullptr; }
+#endif
+  bool await_ready() noexcept { return _handle.done(); }
+
+  std::coroutine_handle<>
+  await_suspend(std::coroutine_handle<> handle) noexcept {
+    _handle.promise()._continuation = handle;
+    return _handle;
+  }
+
+  T await_resume() noexcept { return _handle.promise()._value; }
+};