re PR libstdc++/77537 (pair constructors do not properly SFINAE)

	PR libstdc++/77537
	Implement LWG 2729 for pair.
	* include/bits/stl_pair.h (_PCC): New.
	(_ConstructiblePair, _ImplicitlyConvertiblePair):
	Turn into static member functions of _PCC.
	(_MoveConstructiblePair, _ImplicitlyMoveConvertiblePair): Likewise.
	(_PCCP): New.
	(pair(const _T1&, const _T2&)): Adjust.
	(_PCCFP): New.
	(pair(const pair<_U1, _U2>&)): Adjust.
	(pair(_U1&&, const _T2&)): Likewise.
	(pair(const _T1&, _U2&&)): Likewise.
	(pair(_U1&&, _U2&&)): Likewise.
	(pair(pair<_U1, _U2>&&)): Likewise.
	(operator=(const pair&)): Make conditionally deleted.
	(operator=(pair&&)): Make conditionally suppressed.
	(operator=(const pair<_U1, _U2>&)): Constrain.
	(operator=(pair<_U1, _U2>&&): Likewise.
	* include/std/type_traits (__nonesuch): New.
	* testsuite/20_util/pair/traits.cc: New.

From-SVN: r240322

libstdc++-v3/ChangeLog

+2016-09-21  Ville Voutilainen  <ville.voutilainen@gmail.com>
+
+	PR libstdc++/77537
+	Implement LWG 2729 for pair.
+	* include/bits/stl_pair.h (_PCC): New.
+	(_ConstructiblePair, _ImplicitlyConvertiblePair):
+	Turn into static member functions of _PCC.
+	(_MoveConstructiblePair, _ImplicitlyMoveConvertiblePair): Likewise.
+	(_PCCP): New.
+	(pair(const _T1&, const _T2&)): Adjust.
+	(_PCCFP): New.
+	(pair(const pair<_U1, _U2>&)): Adjust.
+	(pair(_U1&&, const _T2&)): Likewise.
+	(pair(const _T1&, _U2&&)): Likewise.
+	(pair(_U1&&, _U2&&)): Likewise.
+	(pair(pair<_U1, _U2>&&)): Likewise.
+	(operator=(const pair&)): Make conditionally deleted.
+	(operator=(pair&&)): Make conditionally suppressed.
+	(operator=(const pair<_U1, _U2>&)): Constrain.
+	(operator=(pair<_U1, _U2>&&): Likewise.
+	* include/std/type_traits (__nonesuch): New.
+	* testsuite/20_util/pair/traits.cc: New.
+
 2016-09-20  Ville Voutilainen  <ville.voutilainen@gmail.com>
 
 	PR libstdc++/77619

libstdc++-v3/include/std/type_traits

@@ -2850,6 +2850,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
              __call_is_nothrow<result_of<_Fn(_Args...)>, _Fn, _Args...>>::type
     { };
 
+  struct __nonesuch {
+    __nonesuch() = delete;
+    ~__nonesuch() = delete;
+    __nonesuch(__nonesuch const&) = delete;
+    void operator=(__nonesuch const&) = delete;
+  };
+
 #if __cplusplus > 201402L
 # define __cpp_lib_is_callable 201603
 

libstdc++-v3/testsuite/20_util/pair/traits.cc

+// { dg-do compile { target c++11 } }
+
+// Copyright (C) 2016 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 <utility>
+
+#include <type_traits>
+#include <memory>
+
+using namespace std;
+
+struct Poison
+{
+	Poison(Poison&&) = delete;
+};
+
+struct ThrowingCopy
+{
+  ThrowingCopy(const ThrowingCopy&) {}
+  ThrowingCopy& operator=(const ThrowingCopy&) {}
+};
+
+int main()
+{
+	static_assert(!is_copy_constructible<Poison>::value, "");
+	static_assert(!is_move_constructible<Poison>::value, "");
+	static_assert(!is_copy_assignable<Poison>::value, "");
+	static_assert(!is_move_assignable<Poison>::value, "");
+	static_assert(!is_copy_constructible<std::pair<int, Poison>>::value,
+		      "");
+	static_assert(!is_move_constructible<std::pair<int, Poison>>::value,
+		      "");
+	static_assert(!is_copy_assignable<std::pair<int, Poison>>::value, "");
+	static_assert(!is_move_assignable<std::pair<int, Poison>>::value, "");
+	static_assert(!is_constructible<std::pair<int, Poison>&,
+		      std::pair<char, Poison>&>::value, "");
+	static_assert(!is_assignable<std::pair<int, Poison>&,
+		      std::pair<char, Poison>&>::value, "");
+	static_assert(!is_constructible<std::pair<int, Poison>&,
+		      std::pair<char, Poison>>::value, "");
+	static_assert(!is_assignable<std::pair<int, Poison>&,
+		      std::pair<char, Poison>>::value, "");
+	static_assert(!is_copy_constructible<std::pair<ThrowingCopy,
+		      std::unique_ptr<int>>>::value,
+		      "");
+	static_assert(is_move_constructible<std::pair<ThrowingCopy,
+		      std::unique_ptr<int>>>::value,
+		      "");
+	static_assert(!is_nothrow_move_constructible<std::pair<ThrowingCopy,
+		      std::unique_ptr<int>>>::value,
+		      "");
+	static_assert(!is_copy_assignable<std::pair<ThrowingCopy,
+		      std::unique_ptr<int>>>::value,
+		      "");
+	static_assert(is_move_assignable<std::pair<ThrowingCopy,
+		      std::unique_ptr<int>>>::value,
+		      "");
+	static_assert(!is_nothrow_move_assignable<std::pair<ThrowingCopy,
+		      std::unique_ptr<int>>>::value,
+		      "");
+}