From 9ca88083ac0d10da57797dd4e3be6108b604c4cd Mon Sep 17 00:00:00 2001
From: bolero-MURAKAMI <bolero.murakami@gmail.com>
Date: Mon, 1 Jul 2013 16:57:56 +0900
Subject: [PATCH] support for GCC4.7: optional in-place constructor

---
 sprout/optional/optional.hpp                 | 13 +++++++++----
 sprout/utility/value_holder/value_holder.hpp |  9 +++++++--
 2 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/sprout/optional/optional.hpp b/sprout/optional/optional.hpp
index f1d5f244..3a1d121d 100644
--- a/sprout/optional/optional.hpp
+++ b/sprout/optional/optional.hpp
@@ -42,6 +42,11 @@ namespace sprout {
 		typedef typename holder_type::reference_const_type reference_const_type;
 		typedef typename holder_type::pointer_type pointer_type;
 		typedef typename holder_type::pointer_const_type pointer_const_type;
+	public:
+		template<typename... Args>
+		struct is_constructible_args
+			: public std::is_constructible<T, Args&&...>
+		{};
 	public:
 		static SPROUT_CONSTEXPR reference_type get(optional& t) SPROUT_NOEXCEPT {
 			return sprout::get(t.val);
@@ -108,7 +113,7 @@ namespace sprout {
 		{}
 		template<
 			typename... Args,
-			typename = typename std::enable_if<std::is_constructible<T, Args&&...>::value>::type
+			typename = typename std::enable_if<is_constructible_args<Args...>::value>::type
 		>
 		explicit SPROUT_CONSTEXPR optional(sprout::in_place_t, Args&&... args)
 			: init(true)
@@ -116,7 +121,7 @@ namespace sprout {
 		{}
 		template<
 			typename U, typename... Args,
-			typename = typename std::enable_if<std::is_constructible<T, std::initializer_list<U>&, Args&&...>::value>::type
+			typename = typename std::enable_if<is_constructible_args<std::initializer_list<U>&, Args...>::value>::type
 		>
 		explicit SPROUT_CONSTEXPR optional(sprout::in_place_t, std::initializer_list<U> il, Args&&... args)
 			: init(true)
@@ -177,7 +182,7 @@ namespace sprout {
 
 		template<
 			typename... Args,
-			typename = typename std::enable_if<std::is_constructible<T, Args&&...>::value>::type
+			typename = typename std::enable_if<is_constructible_args<Args...>::value>::type
 		>
 		void emplace(Args&&... args) {
 			optional temp(sprout::in_place, sprout::forward<Args>(args)...);
@@ -185,7 +190,7 @@ namespace sprout {
 		}
 		template<
 			typename U, typename... Args,
-			typename = typename std::enable_if<std::is_constructible<T, std::initializer_list<U>&, Args&&...>::value>::type
+			typename = typename std::enable_if<is_constructible_args<std::initializer_list<U>&, Args...>::value>::type
 		>
 		void emplace(std::initializer_list<U> il, Args&&... args) {
 			optional temp(sprout::in_place, il, sprout::forward<Args>(args)...);
diff --git a/sprout/utility/value_holder/value_holder.hpp b/sprout/utility/value_holder/value_holder.hpp
index ce441d3f..f8b59fa2 100644
--- a/sprout/utility/value_holder/value_holder.hpp
+++ b/sprout/utility/value_holder/value_holder.hpp
@@ -174,6 +174,11 @@ namespace sprout {
 		typedef mutable_or_const_pointer pointer_const_type;
 		typedef param_type argument_type;
 		typedef movable_param_type movable_argument_type;
+	public:
+		template<typename... Args>
+		struct is_constructible_args
+			: public std::is_constructible<T, Args&&...>
+		{};
 	public:
 		static SPROUT_CONSTEXPR reference get(value_holder& t) SPROUT_NOEXCEPT {
 			return helper_type::ref(t.holder_);
@@ -209,14 +214,14 @@ namespace sprout {
 		{}
 		template<
 			typename... Args,
-			typename = typename std::enable_if<std::is_constructible<T, Args&&...>::value>::type
+			typename = typename std::enable_if<is_constructible_args<Args...>::value>::type
 		>
 		explicit SPROUT_CONSTEXPR value_holder(sprout::in_place_t, Args&&... args)
 			: holder_(sprout::forward<Args>(args)...)
 		{}
 		template<
 			typename U, typename... Args,
-			typename = typename std::enable_if<std::is_constructible<T, std::initializer_list<U>&, Args&&...>::value>::type
+			typename = typename std::enable_if<is_constructible_args<std::initializer_list<U>&, Args...>::value>::type
 		>
 		explicit SPROUT_CONSTEXPR value_holder(sprout::in_place_t, std::initializer_list<U> il, Args&&... args)
 			: holder_(il, sprout::forward<Args>(args)...)