From 4e7405a2339b0534c7975c850714174ba3fcfca1 Mon Sep 17 00:00:00 2001
From: Andrzej Krzemienski <akrzemi1@gmail.com>
Date: Mon, 18 May 2015 16:51:12 +0200
Subject: [PATCH] Sane swap() for rvalue-aware compilers

When we detect that compiler supports rvalue references, we implement swap() in term of moves (as intuition suggests).
Otherwise we fall back to old tricks with default constructor+swap
---
 include/boost/optional/optional.hpp | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/include/boost/optional/optional.hpp b/include/boost/optional/optional.hpp
index fd7cf73..f059e2e 100644
--- a/include/boost/optional/optional.hpp
+++ b/include/boost/optional/optional.hpp
@@ -1543,9 +1543,18 @@ struct swap_selector<false>
 
 } // namespace optional_detail
 
+#if (!defined BOOST_NO_CXX11_RVALUE_REFERENCES) && (!defined BOOST_CONFIG_RESTORE_OBSOLETE_SWAP_IMPLEMENTATION)
+
+template<class T>
+struct optional_swap_should_use_default_constructor : boost::false_type {} ;
+
+#else
+
 template<class T>
 struct optional_swap_should_use_default_constructor : has_nothrow_default_constructor<T> {} ;
 
+#endif //BOOST_NO_CXX11_RVALUE_REFERENCES
+
 template<class T> inline void swap ( optional<T>& x, optional<T>& y )
   //BOOST_NOEXCEPT_IF(::boost::is_nothrow_move_constructible<T>::value && BOOST_NOEXCEPT_EXPR(boost::swap(*x, *y)))
 {