N3887 Consistent Metafunction Aliases

	* include/std/tuple (tuple_element_t): Define.
	* testsuite/20_util/tuple/tuple_element.cc: Change to compile-only
	test.
	* testsuite/20_util/tuple/tuple_element_t.cc: New.

From-SVN: r209395

libstdc++-v3/ChangeLog

@@ -13,6 +13,11 @@
 	* include/std/tuple (get): Qualify calls to prevent ADL.
 	* testsuite/20_util/tuple/60497.cc: New.
 
+	* include/std/tuple (tuple_element_t): Define.
+	* testsuite/20_util/tuple/tuple_element.cc: Change to compile-only
+	test.
+	* testsuite/20_util/tuple/tuple_element_t.cc: New.
+
 2014-04-11  Marc Glisse  <marc.glisse@inria.fr>
 
 	PR libstdc++/59434

libstdc++-v3/include/std/tuple

@@ -710,6 +710,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       add_cv<typename tuple_element<__i, _Tp>::type>::type type;
     };
 
+#if __cplusplus > 201103L
+  template<std::size_t __i, typename _Tp>
+    using tuple_element_t = typename tuple_element<__i, _Tp>::type;
+#endif
+
   /// Finds the size of a given tuple type.
   template<typename _Tp>
     struct tuple_size;

libstdc++-v3/testsuite/20_util/tuple/tuple_element.cc

-// { dg-options "-std=gnu++0x" }
+// { dg-options "-std=gnu++11" }
+// { dg-do compile }
 
 // Copyright (C) 2007-2014 Free Software Foundation, Inc.
 //

libstdc++-v3/testsuite/20_util/tuple/tuple_element_t.cc

+// { dg-options "-std=gnu++14" }
+// { dg-do compile }
+
+// Copyright (C) 2014 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#include <tuple>
+
+using namespace std;
+
+struct foo
+{ };
+
+int
+main()
+{
+  // As foo isn't constructible from anything else, this
+  // lets us check if the alias is returning foo when it should
+  foo q1;
+  tuple_element_t<0,tuple<foo,void,int> > q2(q1);
+  tuple_element_t<2,tuple<void,int,foo> > q3(q1);
+}