From 4a5136427bdd9d1f7f759b5fb664655553de897d Mon Sep 17 00:00:00 2001
From: Denis Blank <denis.blank@outlook.com>
Date: Wed, 28 Feb 2018 17:28:41 +0100
Subject: [PATCH] Avoid using SFINAE inside the materializer

---
 include/continuable/continuable-base.hpp      | 25 +++----------------
 .../continuable/detail/composition-all.hpp    |  4 +--
 include/continuable/detail/composition.hpp    | 21 ++++++++++++++++
 3 files changed, 26 insertions(+), 24 deletions(-)

diff --git a/include/continuable/continuable-base.hpp b/include/continuable/continuable-base.hpp
index c950c60..384d94f 100644
--- a/include/continuable/continuable-base.hpp
+++ b/include/continuable/continuable-base.hpp
@@ -115,7 +115,8 @@ using detail::base::is_continuable;
 ///
 /// \since 1.0.0
 template <typename Data, typename Annotation>
-class continuable_base {
+class continuable_base
+    : detail::composition::materializer<continuable_base<Data, Annotation>> {
 
   /// \cond false
   template <typename, typename>
@@ -625,28 +626,8 @@ private:
     ownership_.release();
   }
 
-  auto materialize() &&
-      noexcept(std::is_nothrow_move_constructible<Data>::value) {
-    assert_acquired();
-    return materializeImpl(std::move(*this));
-  }
-
-  template <typename OData, typename OAnnotation,
-            std::enable_if_t<!detail::composition::is_composition_strategy<
-                OAnnotation>::value>* = nullptr>
-  static auto
-  materializeImpl(continuable_base<OData, OAnnotation>&& continuable) {
-    return std::move(continuable);
-  }
-  template <typename OData, typename OAnnotation,
-            std::enable_if_t<detail::composition::is_composition_strategy<
-                OAnnotation>::value>* = nullptr>
-  static auto
-  materializeImpl(continuable_base<OData, OAnnotation>&& continuable) {
-    return detail::composition::finalize_composition(std::move(continuable));
-  }
-
   Data&& consume_data() && {
+    assert_acquired();
     release();
     return std::move(data_);
   }
diff --git a/include/continuable/detail/composition-all.hpp b/include/continuable/detail/composition-all.hpp
index 66049fb..12bf654 100644
--- a/include/continuable/detail/composition-all.hpp
+++ b/include/continuable/detail/composition-all.hpp
@@ -262,13 +262,13 @@ struct composition_finalizer<composition_strategy_all_tag> {
     };
   }
 
-  template <typename Composition>
+  /*template <typename Composition>
   static auto finalize_new(Composition&& composition) {
     return [composition = std::forward<Composition>(composition)](
         auto&& callback) mutable {
       // TODO
     };
-  }
+  }*/
 };
 } // namespace composition
 } // namespace detail
diff --git a/include/continuable/detail/composition.hpp b/include/continuable/detail/composition.hpp
index 341c100..b2e8b26 100644
--- a/include/continuable/detail/composition.hpp
+++ b/include/continuable/detail/composition.hpp
@@ -159,6 +159,27 @@ auto finalize_composition(continuable_base<Data, Strategy>&& continuation) {
                                 signature, std::move(ownership));
 }
 
+/// A base class from which the continuable may inherit in order to
+/// provide a materializer method which will finalize an oustanding strategy.
+template <typename Continuable, typename = void>
+struct materializer {
+protected:
+  constexpr auto&& materialize() && {
+    return std::move(*static_cast<Continuable*>(this));
+  }
+};
+template <typename Data, typename Strategy>
+struct materializer<
+    continuable_base<Data, Strategy>,
+    std::enable_if_t<is_composition_strategy<Strategy>::value>> {
+
+protected:
+  constexpr auto materialize() && {
+    return finalize_composition(
+        std::move(*static_cast<continuable_base<Data, Strategy>*>(this)));
+  }
+};
+
 struct prepare_continuables {
   util::ownership& ownership_;