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// Copyright (C) 2019-2023 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++2a" }
// { dg-do compile { target c++2a } }
#include <concepts>
static_assert( std::same_as<int, int> );
static_assert( !std::same_as<int&, int> );
static_assert( !std::same_as<int, int&> );
static_assert( !std::same_as<int&&, int&> );
static_assert( !std::same_as<const int, int> );
static_assert( std::same_as<const int, const int> );
struct A { };
static_assert( std::same_as<A, A> );
static_assert( !std::same_as<A, const A> );
static_assert( std::same_as<A const, const A> );
static_assert( !std::same_as<volatile A, const A> );
struct B : A { };
static_assert( !std::same_as<A, B> );
template<typename T, typename U>
constexpr int
check_subsumption()
{ return 0; }
template<typename T, typename U>
requires std::same_as<T, U>
constexpr int
check_subsumption()
{ return 1; }
template<typename T, typename U>
requires std::same_as<U, T> && std::is_const_v<T>
constexpr int
check_subsumption()
{ return 2; }
template<typename T, typename U>
requires std::same_as<U, T> && std::is_volatile_v<T>
constexpr int
check_subsumption()
{ return 3; }
static_assert( check_subsumption<short, long>() == 0 );
static_assert( check_subsumption<unsigned, unsigned>() == 1 );
// These will be ambiguous if same_as<T,U> doesn't subsume same_as<U,T>:
static_assert( check_subsumption<const char, const char>() == 2 );
static_assert( check_subsumption<volatile int, volatile int>() == 3 );
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