// { dg-do compile { target c++17 }  }

// Copyright (C) 2013-2023 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/>.

#include <optional>

struct value_type
{
  int i;
};

void test01()
{
  constexpr std::optional<value_type> o { value_type { 51 } };
  constexpr value_type fallback { 3 };
  static_assert( o.value_or(fallback).i == 51 );
  static_assert( o.value_or(fallback).i == (*o).i );
}

void test02()
{
  constexpr std::optional<value_type> o;
  constexpr value_type fallback { 3 };
  static_assert( o.value_or(fallback).i == 3 );
}

template<typename T>
  constexpr std::optional<value_type>
  make_rvalue(T t)
  { return std::optional<value_type>{t}; }

void test03()
{
  constexpr value_type fallback { 3 };
  static_assert( make_rvalue(value_type{51}).value_or(fallback).i == 51 );
}

void test04()
{
  constexpr value_type fallback { 3 };
  static_assert( make_rvalue(std::nullopt).value_or(fallback).i == 3 );
}

int main()
{
  test01();
  test02();
  test03();
  test04();
}