From c0fcaae95159677eb7b5830f62d03f41b950ad89 Mon Sep 17 00:00:00 2001
From: Kohei Takahashi <flast@flast.jp>
Date: Wed, 1 Jul 2015 02:25:13 +0900
Subject: [PATCH] Prevent use of conversion ctor  for copy purpose.

Some compilers elect conversion ctor for copy purpose in implicitly defined copy ctor with derived class.
---
 include/boost/fusion/container/list/cons.hpp | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/boost/fusion/container/list/cons.hpp b/include/boost/fusion/container/list/cons.hpp
index d649068a..e05b62eb 100644
--- a/include/boost/fusion/container/list/cons.hpp
+++ b/include/boost/fusion/container/list/cons.hpp
@@ -23,6 +23,7 @@
 #include <boost/fusion/container/list/detail/value_at_impl.hpp>
 #include <boost/fusion/container/list/detail/empty_impl.hpp>
 #include <boost/type_traits/is_convertible.hpp>
+#include <boost/type_traits/is_base_of.hpp>
 #include <boost/utility/enable_if.hpp>
 #include <boost/fusion/support/sequence_base.hpp>
 #include <boost/fusion/support/is_sequence.hpp>
@@ -79,6 +80,7 @@ namespace boost { namespace fusion
           , typename boost::enable_if<
                 mpl::and_<
                     traits::is_sequence<Sequence>
+                  , mpl::not_<is_base_of<cons, Sequence> >
                   , mpl::not_<is_convertible<Sequence, Car> > > // use copy to car instead
             >::type* /*dummy*/ = 0
         )