missing make_pair() for r-value refs (#264)

* missing make_pair() for r-value refs

hello guys!

the `make_pair()` for r-value refs is required for r-value, otherwise `non-copyable` but `movable` can be constructed.


thanks!

* fix for prev commit

conditional support for r-values was fixed

* the test case was added

* fix for prev commit

* Update Jamfile

* one more fix for Jamfile

* the forgotten r-value ctor was added

* ah, they should be conditional

include/boost/fusion/support/pair.hpp

@@ -120,6 +120,17 @@ namespace boost { namespace fusion
         return pair<First, typename detail::as_fusion_element<Second>::type>(val);
     }
 
+#if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
+    template <typename First, typename Second>
+    BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
+    inline typename result_of::make_pair<First,Second>::type
+    make_pair(Second&& val)
+    {
+        return pair<First, typename detail::as_fusion_element<Second>::type>(
+            BOOST_FUSION_FWD_ELEM(Second, val));
+    }
+#endif
+
     template <typename First, typename Second>
     inline std::ostream&
     operator<<(std::ostream& os, pair<First, Second> const& p)

test/Jamfile

@@ -273,6 +273,10 @@ project
     [ compile support/unused.cpp ]
     [ compile support/detail/tag_of_fallback.cpp ]
 
+    [ compile-fail support/make_pair_r-value.cpp ]
+    [ compile support/make_pair_r-value.cpp
+        : [ requires cxx11_rvalue_references ] ]
+
 #   [ compile-fail xxx.cpp  ]
 
     ;

test/support/make_pair_r-value.cpp

@@ -0,0 +1,24 @@
+/*=============================================================================
+    Copyright (c) 2022 niXman (github dot nixman at pm.me)
+    Distributed under the Boost Software License, Version 1.0. (See accompanying
+    file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+==============================================================================*/
+
+#include <boost/fusion/support/pair.hpp>
+
+struct noncopyable_type {
+    noncopyable_type(const noncopyable_type &) = delete;
+    noncopyable_type& operator=(const noncopyable_type &) = delete;
+#if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
+    noncopyable_type(noncopyable_type &&) = default;
+    noncopyable_type& operaotr=(noncopyable_type &&) = default;
+#endif
+};
+
+int main() {
+    using namespace boost::fusion;
+
+    pair<int, noncopyable_type> val = make_pair<int>(noncopyable_type{});
+
+    return 0;
+}