From f3fa7a1dc62aa5e7e60d1395b76ec7f08949820c Mon Sep 17 00:00:00 2001
From: Joel de Guzman <djowel@gmail.com>
Date: Sat, 15 Nov 2014 09:35:50 +0800
Subject: [PATCH] Fix for fusion pair to make the compiler select the proper
 copy constructor and remove a viable, but wrong, constructor. test added.

---
 include/boost/fusion/support/pair.hpp |  4 +++-
 test/sequence/map.cpp                 | 20 ++++++++++++++++++++
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/include/boost/fusion/support/pair.hpp b/include/boost/fusion/support/pair.hpp
index c547926e..97cac3c7 100644
--- a/include/boost/fusion/support/pair.hpp
+++ b/include/boost/fusion/support/pair.hpp
@@ -37,9 +37,11 @@ namespace boost { namespace fusion
             : second(rhs.second) {}
 
 #if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
+
         BOOST_FUSION_GPU_ENABLED
         pair(pair&& rhs)
             : second(std::forward<Second>(rhs.second)) {}
+
 #endif
 
         BOOST_FUSION_GPU_ENABLED
@@ -50,7 +52,7 @@ namespace boost { namespace fusion
 
         template <typename Second2>
         BOOST_FUSION_GPU_ENABLED
-        pair(Second2&& val
+        explicit pair(Second2&& val
           , typename boost::enable_if<is_convertible<Second2, Second> >::type* /*dummy*/ = 0
         ) : second(std::forward<Second2>(val)) {}
 
diff --git a/test/sequence/map.cpp b/test/sequence/map.cpp
index 58497b44..925d6720 100644
--- a/test/sequence/map.cpp
+++ b/test/sequence/map.cpp
@@ -25,6 +25,19 @@
 #include <iostream>
 #include <string>
 
+
+struct copy_all
+{
+    copy_all() {}
+    copy_all(copy_all const&) {}
+
+    template <typename T>
+    copy_all(T const& x)
+    {
+        foo(x); // should fail!
+    }
+};
+
 int
 main()
 {
@@ -119,6 +132,13 @@ main()
         BOOST_TEST(at_key<char>(make_map<char, int>('X', 123)) == 'X');
         BOOST_TEST(at_key<int>(make_map<char, int>('X', 123)) == 123);
     }
+    
+    {
+        // test for copy construction of fusion pairs
+        // make sure that the correct constructor is called
+        pair<int, copy_all> p1;
+        pair<int, copy_all> p2 = p1;
+    }
 
     return boost::report_errors();
 }