re PR libstdc++/13860 (Poor error messages on invalid template parameters for basic_filebuf)

	PR libstdc++/13860
	* include/std/fstream (basic_filebuf): Enforce requirements on traits.

From-SVN: r210231

libstdc++-v3/ChangeLog

@@ -11,6 +11,9 @@
 	(swap(basic_streambuf&)): Define for C++11.
 	* testsuite/27_io/basic_streambuf/cons/57394.cc: New.
 
+	PR libstdc++/13860
+	* include/std/fstream (basic_filebuf): Enforce requirements on traits.
+
 2014-05-08  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	* acinclude.m4 ([GLIBCXX_ENABLE_C99]): Avoid -Wwrite-strings warning.

libstdc++-v3/include/std/fstream

@@ -71,6 +71,20 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   template<typename _CharT, typename _Traits>
     class basic_filebuf : public basic_streambuf<_CharT, _Traits>
     {
+#if __cplusplus >= 201103L
+      template<typename _Tp>
+	using __chk_state = __and_<is_copy_assignable<_Tp>,
+				   is_copy_constructible<_Tp>,
+				   is_default_constructible<_Tp>>;
+
+      static_assert(__chk_state<typename _Traits::state_type>::value,
+		    "state_type must be CopyAssignable, CopyConstructible"
+		    " and DefaultConstructible");
+
+      static_assert(is_same<typename _Traits::pos_type,
+			    fpos<typename _Traits::state_type>>::value,
+		    "pos_type must be fpos<state_type>");
+#endif
     public:
       // Types:
       typedef _CharT                     	        char_type;