From a3e995c0ce9a3fb447d78ad4ab3aeb6b83483607 Mon Sep 17 00:00:00 2001
From: Denis Blank <denis.blank@outlook.com>
Date: Mon, 12 Mar 2018 07:24:04 +0100
Subject: [PATCH] Improve order dependence for the coroutine detection

---
 include/continuable/continuable-base.hpp      |  6 +++-
 include/continuable/detail/awaiting.hpp       | 36 ++++---------------
 .../multi/test-continuable-await.cpp          |  5 +--
 3 files changed, 15 insertions(+), 32 deletions(-)

diff --git a/include/continuable/continuable-base.hpp b/include/continuable/continuable-base.hpp
index f270547..7b7cba5 100644
--- a/include/continuable/continuable-base.hpp
+++ b/include/continuable/continuable-base.hpp
@@ -36,7 +36,6 @@
 #include <type_traits>
 #include <utility>
 
-#include <continuable/detail/awaiting.hpp>
 #include <continuable/detail/base.hpp>
 #include <continuable/detail/composition-all.hpp>
 #include <continuable/detail/composition-any.hpp>
@@ -45,6 +44,11 @@
 #include <continuable/detail/traits.hpp>
 #include <continuable/detail/types.hpp>
 #include <continuable/detail/util.hpp>
+#include <continuable/detail/features.hpp>
+
+#ifdef CONTINUABLE_HAS_EXPERIMENTAL_COROUTINE
+#include <continuable/detail/awaiting.hpp>
+#endif // CONTINUABLE_HAS_EXPERIMENTAL_COROUTINE
 
 namespace cti {
 /// \defgroup Base Base
diff --git a/include/continuable/detail/awaiting.hpp b/include/continuable/detail/awaiting.hpp
index 6c4a922..683dc64 100644
--- a/include/continuable/detail/awaiting.hpp
+++ b/include/continuable/detail/awaiting.hpp
@@ -28,16 +28,13 @@
   SOFTWARE.
 **/
 
+// Exclude this header when coroutines are not available
 #ifndef CONTINUABLE_DETAIL_AWAITING_HPP_INCLUDED
 #define CONTINUABLE_DETAIL_AWAITING_HPP_INCLUDED
 
-// Exlude this header when coroutines are not available
-#ifdef CONTINUABLE_HAS_EXPERIMENTAL_COROUTINE
-
 #include <cassert>
 #include <experimental/coroutine>
 
-#include <continuable/detail/base.hpp>
 #include <continuable/detail/expected.hpp>
 #include <continuable/detail/features.hpp>
 #include <continuable/detail/hints.hpp>
@@ -133,32 +130,13 @@ template <typename Data, typename... Args, typename... FunctionArgs>
 struct coroutine_traits<
     cti::continuable_base<Data,
                           cti::detail::hints::signature_hint_tag<Args...>>,
-    FunctionArgs...> /*{
-  struct promise_type {
-    // boost::promise<R> p;
-    auto get_return_object() {
-      // return p.get_future();
-    }
-    suspend_always initial_suspend() {
-      return {};
-    }
-    suspend_never final_suspend() {
-      return {};
-    }
-    void set_exception(std::exception_ptr e) {
-      // p.set_exception(std::move(e));
-    }
-    void unhandled_exception() {
-      // p.set_exception(std::current_exception());
-    }
-    template <typename U>
-    void return_value(U&& u) {
-      // p.set_value(std::forward<U>(u));
-    }
-  };
-}*/;
+    FunctionArgs...> {
+
+  static_assert(cti::detail::traits::fail<Data>::value,
+                "Using a continuable as return value from co_return "
+                "expressions isn't supported yet!");
+};
 } // namespace experimental
 } // namespace std
 
-#endif // CONTINUABLE_HAS_EXPERIMENTAL_COROUTINE
 #endif // CONTINUABLE_DETAIL_UTIL_HPP_INCLUDED
diff --git a/test/unit-test/multi/test-continuable-await.cpp b/test/unit-test/multi/test-continuable-await.cpp
index f435f60..8bef212 100644
--- a/test/unit-test/multi/test-continuable-await.cpp
+++ b/test/unit-test/multi/test-continuable-await.cpp
@@ -21,6 +21,9 @@
   SOFTWARE.
 **/
 
+#include <test-continuable.hpp>
+
+#include <continuable/detail/features.hpp>
 #ifdef CONTINUABLE_HAS_EXPERIMENTAL_COROUTINE
 
 #ifndef CONTINUABLE_WITH_NO_EXCEPTIONS
@@ -29,8 +32,6 @@
 
 #include <tuple>
 
-#include <test-continuable.hpp>
-
 namespace std {
 namespace experimental {
 template <class... T>