From b50c2bf8a8c2fbcb2cee2c438779b745e9d82533 Mon Sep 17 00:00:00 2001
From: Denis Blank <denis.blank@outlook.com>
Date: Fri, 9 Mar 2018 05:23:36 +0100
Subject: [PATCH] Fix non default constructible values in compositions * Add a
 test case for the non default constructible case

---
 include/continuable/detail/composition-all.hpp      |  5 +++--
 .../multi/test-continuable-connection-all-seq.hpp   | 13 +++++++++++++
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/include/continuable/detail/composition-all.hpp b/include/continuable/detail/composition-all.hpp
index 65f2d8a..186a7b3 100644
--- a/include/continuable/detail/composition-all.hpp
+++ b/include/continuable/detail/composition-all.hpp
@@ -56,13 +56,14 @@ struct all_hint_deducer {
 
   template <typename First>
   static constexpr auto deduce(hints::signature_hint_tag<First>) {
-    return First{};
+    return std::declval<First>();
   }
 
   template <typename First, typename Second, typename... Args>
   static constexpr auto
   deduce(hints::signature_hint_tag<First, Second, Args...>) {
-    return spread_this(First{}, Second{}, Args{}...);
+    return spread_this(std::declval<First>(), std::declval<Second>(),
+                       std::declval<Args>()...);
   }
 
   template <
diff --git a/test/unit-test/multi/test-continuable-connection-all-seq.hpp b/test/unit-test/multi/test-continuable-connection-all-seq.hpp
index f0eac07..fb32a4d 100644
--- a/test/unit-test/multi/test-continuable-connection-all-seq.hpp
+++ b/test/unit-test/multi/test-continuable-connection-all-seq.hpp
@@ -49,12 +49,25 @@ void test_all_seq_op(Supplier&& supply, OperatorConnector&& op) {
   }
 }
 
+class non_default_constructible {
+public:
+  explicit non_default_constructible(int) {
+  }
+};
+
 template <typename Supplier, typename AggregateConnector>
 void test_all_seq_aggregate(Supplier&& supply, AggregateConnector&& ag) {
   {
     auto chain = ag(supply(1, 2), supply(3, 4), supply(5, 6));
     EXPECT_ASYNC_RESULT(std::move(chain), 1, 2, 3, 4, 5, 6);
   }
+
+  {
+    auto chain =
+        ag(supply(1, 2), supply(non_default_constructible{1}), supply(5, 6));
+    ASSERT_ASYNC_TYPES(std::move(chain), int, int, non_default_constructible,
+                       int, int);
+  }
 }
 
 #endif // TEST_CONTINUABLE_CONNECTION_HPP__