llvm-project/libcxx/test/std/utilities/optional/optional.nullops/less_than.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>

// template <class T> constexpr bool operator<(const optional<T>& x, nullopt_t) noexcept;
// template <class T> constexpr bool operator<(nullopt_t, const optional<T>& x) noexcept;

#include <optional>

int main()
{
    using std::optional;
    using std::nullopt_t;
    using std::nullopt;

    {
    typedef int T;
    typedef optional<T> O;

    constexpr O o1;     // disengaged
    constexpr O o2{1};  // engaged

    static_assert ( !(nullopt < o1), "" );
    static_assert (  (nullopt < o2), "" );
    static_assert ( !(o1 < nullopt), "" );
    static_assert ( !(o2 < nullopt), "" );

    static_assert (noexcept(nullopt < o1), "");
    static_assert (noexcept(o1 < nullopt), "");
    }
}