test/std/utilities/time/time.cal/time.cal.day/time.cal.day.nonmembers/plus.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++03, c++11, c++14, c++17

// <chrono>
// class day;

// constexpr day operator+(const day& x, const days& y) noexcept;
//   Returns: day(unsigned{x} + y.count()).
//
// constexpr day operator+(const days& x, const day& y) noexcept;
//   Returns: y + x.


#include <chrono>
#include <type_traits>
#include <cassert>

#include "test_macros.h"

template <typename D, typename Ds>
constexpr bool testConstexpr()
{
    D d{1};
    Ds offset{23};
    if (d + offset != D{24}) return false;
    if (offset + d != D{24}) return false;
    return true;
}

int main()
{
    using day  = std::chrono::day;
    using days = std::chrono::days;

    ASSERT_NOEXCEPT(std::declval<day>() + std::declval<days>());
    ASSERT_NOEXCEPT(std::declval<days>() + std::declval<day>());

    ASSERT_SAME_TYPE(day, decltype(std::declval<day>() + std::declval<days>()));
    ASSERT_SAME_TYPE(day, decltype(std::declval<days>() + std::declval<day>()));
    
    static_assert(testConstexpr<day, days>(), "");

    day dy{12};
    for (unsigned i = 0; i <= 10; ++i)
    {
        day d1 = dy + days{i};
        day d2 = days{i} + dy;
        assert(d1 == d2);
        assert(static_cast<unsigned>(d1) == i + 12);
        assert(static_cast<unsigned>(d2) == i + 12);
    }
}