Fix testsuite failures caused by the patch implementing LWG 2534.

* include/std/istream (__is_convertible_to_basic_istream):
Change the return types of __check, introduce istream_type.
(operator>>(_Istream&&, _Tp&&)):
Use __is_convertible_to_basic_istream::istream_type as the return type.
* include/std/ostream (__is_convertible_to_basic_ostream):
Change the return types of __check, introduce ostream_type.
(operator>>(_Ostream&&, _Tp&&)):
Use __is_convertible_to_basic_ostream::ostream_type as the return type.

From-SVN: r243036

libstdc++-v3/ChangeLog

+2016-11-30  Ville Voutilainen  <ville.voutilainen@gmail.com>
+
+	Fix testsuite failures caused by the patch implementing LWG 2534.
+	* include/std/istream (__is_convertible_to_basic_istream):
+	Change the return types of __check, introduce istream_type.
+	(operator>>(_Istream&&, _Tp&&)):
+	Use __is_convertible_to_basic_istream::istream_type as the return type.
+	* include/std/ostream (__is_convertible_to_basic_ostream):
+	Change the return types of __check, introduce ostream_type.
+	(operator>>(_Ostream&&, _Tp&&)):
+	Use __is_convertible_to_basic_ostream::ostream_type as the return type.
+
 2016-11-30  Tim Shen  <timshen@google.com>
 
 	* include/bits/shared_ptr_base.h

libstdc++-v3/include/std/istream

@@ -913,11 +913,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     struct __is_convertible_to_basic_istream
     {
       template<typename _Ch, typename _Up>
-      static true_type __check(basic_istream<_Ch, _Up>*);
+      static basic_istream<_Ch, _Up>& __check(basic_istream<_Ch, _Up>*);
 
-      static false_type __check(void*);
+      static void __check(void*);
     public:
-      using type = decltype(__check(declval<_Tp*>()));
+      using istream_type =
+	decltype(__check(declval<typename remove_reference<_Tp>::type*>()));
+      using type = __not_<is_same<istream_type, void>>;
       constexpr static bool value = type::value;
   };
 
@@ -946,10 +948,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   template<typename _Istream, typename _Tp>
     inline
     typename enable_if<__and_<__not_<is_lvalue_reference<_Istream>>,
-			      __is_convertible_to_basic_istream<
-				typename remove_reference<_Istream>::type>,
+			      __is_convertible_to_basic_istream<_Istream>,
 			      __is_extractable<_Istream&, _Tp&&>>::value,
-		       _Istream&>::type
+		       typename __is_convertible_to_basic_istream<
+			 _Istream>::istream_type>::type
     operator>>(_Istream&& __is, _Tp&& __x)
     {
       __is >> std::forward<_Tp>(__x);

libstdc++-v3/include/std/ostream

@@ -617,11 +617,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     struct __is_convertible_to_basic_ostream
   {
     template<typename _Ch, typename _Up>
-    static true_type __check(basic_ostream<_Ch, _Up>*);
+    static basic_ostream<_Ch, _Up>& __check(basic_ostream<_Ch, _Up>*);
 
-    static false_type __check(void*);
+    static void __check(void*);
   public:
-    using type = decltype(__check(declval<_Tp*>()));
+    using ostream_type =
+      decltype(__check(declval<typename remove_reference<_Tp>::type*>()));
+    using type = __not_<is_same<ostream_type, void>>;
     constexpr static bool value = type::value;
   };
 
@@ -647,11 +649,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   template<typename _Ostream, typename _Tp>
     inline
     typename enable_if<__and_<__not_<is_lvalue_reference<_Ostream>>,
-			      __is_convertible_to_basic_ostream<
-				typename remove_reference<_Ostream>::type>,
+			      __is_convertible_to_basic_ostream<_Ostream>,
 			      __is_insertable<_Ostream&, const _Tp&>>::value,
-		       _Ostream&>::type
-				      //basic_ostream<_CharT, _Traits>&
+		       typename __is_convertible_to_basic_ostream<
+			 _Ostream>::ostream_type>::type
     operator<<(_Ostream&& __os, const _Tp& __x)
     {
       __os << __x;