[Bug libstdc++/49058] [C++0x] Bind no-arguments functor failed using std::bind with -pedantic option.

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49058

--- Comment #15 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-05-22 22:30:55 UTC ---
This is something which actually passes the testsuite, and the tests here and
the new test explained by Jon. Maybe something even more clean along the same
lines is possible, but I would be already pretty happy for now... assuming Jon
isn't able to figure out yet another regression ;)

////////////////////

Index: include/std/functional
===================================================================
--- include/std/functional    (revision 174044)
+++ include/std/functional    (working copy)
@@ -1210,7 +1210,8 @@

       // Call as const
       template<typename... _Args, typename _Result
-    = decltype( std::declval<const _Functor>()(
+    = decltype( std::declval<typename conditional<(sizeof...(_Args) >= 0),
+               typename add_const<_Functor>::type, void>::type>()(
           _Mu<_Bound_args>()( std::declval<const _Bound_args&>(),
                   std::declval<tuple<_Args...>&>() )... ) )>
     _Result
@@ -1223,7 +1224,8 @@

       // Call as volatile
       template<typename... _Args, typename _Result
-    = decltype( std::declval<volatile _Functor>()(
+    = decltype( std::declval<typename conditional<(sizeof...(_Args) >= 0),
+                       typename add_volatile<_Functor>::type, void>::type>()(
           _Mu<_Bound_args>()( std::declval<volatile _Bound_args&>(),
                   std::declval<tuple<_Args...>&>() )... ) )>
     _Result
@@ -1236,7 +1238,8 @@

       // Call as const volatile
       template<typename... _Args, typename _Result
-    = decltype( std::declval<const volatile _Functor>()(
+    = decltype( std::declval<typename conditional<(sizeof...(_Args) >= 0),
+                       typename add_cv<_Functor>::type, void>::type>()(
           _Mu<_Bound_args>()( std::declval<const volatile _Bound_args&>(),
                   std::declval<tuple<_Args...>&>() )... ) )>
     _Result