mirror of git://gcc.gnu.org/git/gcc.git
46 lines
1.4 KiB
C++
46 lines
1.4 KiB
C++
// Copyright (C) 2015-2016 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/>.
|
|
|
|
// { dg-options "-std=gnu++1z" }
|
|
// { dg-do compile }
|
|
|
|
#include <type_traits>
|
|
|
|
#ifndef __cpp_lib_void_t
|
|
# error "Feature-test macro for void_t missing"
|
|
#elif __cpp_lib_void_t != 201411
|
|
# error "Feature-test macro for void_t has wrong value"
|
|
#endif
|
|
|
|
static_assert( std::is_same<std::void_t<int, long, double>, void>::value,
|
|
"void_t is a synonym for void" );
|
|
|
|
struct X { };
|
|
X operator+(const X& x) { return x; }
|
|
|
|
template<typename T, typename U = std::void_t<>>
|
|
struct has_unary_plus
|
|
: std::false_type
|
|
{ };
|
|
|
|
template<typename T>
|
|
struct has_unary_plus<T, std::void_t<decltype(+std::declval<X>())>>
|
|
: std::true_type
|
|
{ };
|
|
|
|
static_assert( has_unary_plus<X>::value, "void_t detects valid expressions" );
|