[Boost-commit] svn:boost r74934 - trunk/boost/fusion/support

Subject: [Boost-commit] svn:boost r74934 - trunk/boost/fusion/support
From: joel_at_[hidden]
Date: 2011-10-12 20:23:41

Author: djowel
Date: 2011-10-12 20:23:40 EDT (Wed, 12 Oct 2011)
New Revision: 74934
URL: http://svn.boost.org/trac/boost/changeset/74934

Log:
+ Fixes Ticket #6016 using a two-level specialization such that specialization is preferred over SFINAE. 
+ Removes tag_of_fallback. It's not needed anymore. The proper way is to specialize tag_of.
Text files modified: 
   trunk/boost/fusion/support/tag_of.hpp     |    27 ++++++++++++++-------------             
   trunk/boost/fusion/support/tag_of_fwd.hpp |     3 ---                                     
   2 files changed, 14 insertions(+), 16 deletions(-)

Modified: trunk/boost/fusion/support/tag_of.hpp
==============================================================================
--- trunk/boost/fusion/support/tag_of.hpp	(original)
+++ trunk/boost/fusion/support/tag_of.hpp	2011-10-12 20:23:40 EDT (Wed, 12 Oct 2011)
@@ -46,30 +46,31 @@
     namespace detail
     {
         BOOST_MPL_HAS_XXX_TRAIT_DEF(fusion_tag)
-    }
-
-    namespace traits
-    {
-        template <typename Sequence, typename Active>
-        struct tag_of_fallback
-        {
-            typedef non_fusion_tag type;
-        };
 
         template <typename Sequence, typename Active>
-        struct tag_of
-          : mpl::if_< fusion::detail::is_mpl_sequence<Sequence>,
+        struct tag_of_impl
+          : mpl::if_<fusion::detail::is_mpl_sequence<Sequence>,
               mpl::identity<mpl_sequence_tag>,
-              tag_of_fallback<Sequence> >::type
+              mpl::identity<non_fusion_tag> >::type
         {};
 
         template <typename Sequence>
-        struct tag_of<Sequence, typename boost::enable_if<detail::has_fusion_tag<Sequence> >::type>
+        struct tag_of_impl<
+            Sequence
+          , typename boost::enable_if<detail::has_fusion_tag<Sequence> >::type>
         {
             typedef typename Sequence::fusion_tag type;
         };
     }
 
+    namespace traits
+    {
+        template <typename Sequence, typename Active>
+        struct tag_of
+            : boost::fusion::detail::tag_of_impl<Sequence, Active>
+        {};
+    }
+
     namespace detail
     {
         template<typename T>

Modified: trunk/boost/fusion/support/tag_of_fwd.hpp
==============================================================================
--- trunk/boost/fusion/support/tag_of_fwd.hpp	(original)
+++ trunk/boost/fusion/support/tag_of_fwd.hpp	2011-10-12 20:23:40 EDT (Wed, 12 Oct 2011)
@@ -12,9 +12,6 @@
 {
     namespace traits
     {
-        template <typename Sequence, typename Active = void>
-        struct tag_of_fallback;
-
         template<typename T, typename Active = void>
         struct tag_of;
     }