//===----------------------------------------------------------------------===//
//
//                     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, class U> constexpr bool operator==(const optional<T>& x, const optional<U>& y);

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

using std::optional;

struct X {
  int i_;

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

constexpr bool operator==(const X& lhs, const X& rhs) {
  return lhs.i_ == rhs.i_;
}

int main() {
  {
    typedef X T;
    typedef optional<T> O;

    constexpr O o1;    // disengaged
    constexpr O o2;    // disengaged
    constexpr O o3{1}; // engaged
    constexpr O o4{2}; // engaged
    constexpr O o5{1}; // engaged

    static_assert(o1 == o1, "");
    static_assert(o1 == o2, "");
    static_assert(!(o1 == o3), "");
    static_assert(!(o1 == o4), "");
    static_assert(!(o1 == o5), "");

    static_assert(o2 == o1, "");
    static_assert(o2 == o2, "");
    static_assert(!(o2 == o3), "");
    static_assert(!(o2 == o4), "");
    static_assert(!(o2 == o5), "");

    static_assert(!(o3 == o1), "");
    static_assert(!(o3 == o2), "");
    static_assert(o3 == o3, "");
    static_assert(!(o3 == o4), "");
    static_assert(o3 == o5, "");

    static_assert(!(o4 == o1), "");
    static_assert(!(o4 == o2), "");
    static_assert(!(o4 == o3), "");
    static_assert(o4 == o4, "");
    static_assert(!(o4 == o5), "");

    static_assert(!(o5 == o1), "");
    static_assert(!(o5 == o2), "");
    static_assert(o5 == o3, "");
    static_assert(!(o5 == o4), "");
    static_assert(o5 == o5, "");
  }
  {
    using O1 = optional<int>;
    using O2 = optional<long>;
    constexpr O1 o1(42);
    static_assert(o1 == O2(42), "");
    static_assert(!(O2(101) == o1), "");
  }
  {
    using O1 = optional<int>;
    using O2 = optional<const int>;
    constexpr O1 o1(42);
    static_assert(o1 == O2(42), "");
    static_assert(!(O2(101) == o1), "");
  }
}