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

//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

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

// template <class U> constexpr T optional<T>::value_or(U&& v) const&;

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

using std::optional;

struct Y
{
    int i_;

    constexpr Y(int i) : i_(i) {}
};

struct X
{
    int i_;

    constexpr X(int i) : i_(i) {}
    constexpr X(const Y& y) : i_(y.i_) {}
    constexpr X(Y&& y) : i_(y.i_+1) {}
    friend constexpr bool operator==(const X& x, const X& y)
        {return x.i_ == y.i_;}
};

int main(int, char**)
{
    {
        constexpr optional<X> opt(2);
        constexpr Y y(3);
        static_assert(opt.value_or(y) == 2, "");
    }
    {
        constexpr optional<X> opt(2);
        static_assert(opt.value_or(Y(3)) == 2, "");
    }
    {
        constexpr optional<X> opt;
        constexpr Y y(3);
        static_assert(opt.value_or(y) == 3, "");
    }
    {
        constexpr optional<X> opt;
        static_assert(opt.value_or(Y(3)) == 4, "");
    }
    {
        const optional<X> opt(2);
        const Y y(3);
        assert(opt.value_or(y) == 2);
    }
    {
        const optional<X> opt(2);
        assert(opt.value_or(Y(3)) == 2);
    }
    {
        const optional<X> opt;
        const Y y(3);
        assert(opt.value_or(y) == 3);
    }
    {
        const optional<X> opt;
        assert(opt.value_or(Y(3)) == 4);
    }

  return 0;
}