test/std/utilities/optional/optional.object/optional.object.observe/value_const.pass.cpp

//===----------------------------------------------------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

// UNSUPPORTED: c++98, c++03, c++11, c++14
// <optional>

// constexpr const T& optional<T>::value() const &;

#include <optional>
#include <type_traits>
#include <cassert>

#include "test_macros.h"

using std::optional;
using std::in_place_t;
using std::in_place;
using std::bad_optional_access;

struct X
{
    X() = default;
    X(const X&) = delete;
    constexpr int test() const & {return 3;}
    int test() & {return 4;}
    constexpr int test() const && {return 5;}
    int test() && {return 6;}
};

int main()
{
    {
        const optional<X> opt; ((void)opt);
        ASSERT_NOT_NOEXCEPT(opt.value());
        ASSERT_SAME_TYPE(decltype(opt.value()), X const&);
    }
    {
        constexpr optional<X> opt(in_place);
        static_assert(opt.value().test() == 3, "");
    }
    {
        const optional<X> opt(in_place);
        assert(opt.value().test() == 3);
    }
#ifndef TEST_HAS_NO_EXCEPTIONS
    {
        const optional<X> opt;
        try
        {
            opt.value();
            assert(false);
        }
        catch (const bad_optional_access&)
        {
        }
    }
#endif
}