Retro68/gcc/libstdc++-v3/testsuite/20_util/hash/52931.cc

// { dg-options "-std=gnu++11" }
// { dg-do compile }

// Copyright (C) 2012-2015 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 <type_traits>
#include <functional>

class S{}; // No hash specialization

template<class T>
auto f(int) -> decltype(std::hash<T>(), std::true_type());

template<class T>
auto f(...) -> decltype(std::false_type());

static_assert(!decltype(f<S>(0))::value, "");