// Copyright (C) 2020-2023 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING3.  If not see
// <http://www.gnu.org/licenses/>.

// { dg-options "-std=gnu++2a" }
// { dg-do compile { target c++2a } }

#include <ranges>

using std::ranges::__detail::__box;

using T = decltype([] { return 0; });
static_assert(std::is_empty_v<__box<T>>);
static_assert(std::is_nothrow_copy_constructible_v<__box<T>>);
static_assert(std::is_nothrow_move_constructible_v<__box<T>>);
static_assert(std::is_nothrow_constructible_v<__box<T>, std::in_place_t>);
static_assert(requires (__box<T> a) {
  a = a;
  a = std::move(a);
  a.operator*();
  a.operator->();
  a.has_value();
});

struct S
{
  S();
  ~S();
  S(const S&);
  S(S&&);
  S& operator=(const S&);
  S& operator=(S&&);
};
static_assert(std::is_empty_v<__box<S>>);
static_assert(!std::is_nothrow_copy_constructible_v<__box<S>>
	      && std::is_copy_constructible_v<__box<S>>);
static_assert(!std::is_nothrow_move_constructible_v<__box<S>>
	      && std::is_move_constructible_v<__box<S>>);
static_assert(!std::is_nothrow_constructible_v<__box<S>, std::in_place_t>
	      && std::is_constructible_v<__box<S>, std::in_place_t>);
static_assert(requires (__box<S> a) {
  a = a;
  a = std::move(a);
  a.operator*();
  a.operator->();
  a.has_value();
});

using U = decltype([i=0] { return 0; });
static_assert(!std::is_empty_v<__box<U>>);
static_assert(std::is_nothrow_copy_constructible_v<__box<U>>);
static_assert(std::is_nothrow_move_constructible_v<__box<U>>);
static_assert(!std::is_nothrow_constructible_v<__box<U>, std::in_place_t>);
static_assert(requires (__box<U> a) {
  a = a;
  a = std::move(a);
  a.operator*();
  a.operator->();
  a.has_value();
});

constexpr bool
test01()
{
  // Verify the default constructor value-initializes the underlying object.
  __box<int> x;
  __glibcxx_assert(*x == 0);
  return true;
}
static_assert(test01());

template<bool make_copyable>
  struct A {
    A(const A&) = default;
    A& operator=(const A&) requires make_copyable;
    A(int, int);
    A(std::initializer_list<int>) = delete;
  };

void
test02()
{
  // PR libstdc++/100475
  static_assert(std::copyable<A<true>>);
  __box<A<true>> x2(std::in_place, 0, 0);

  static_assert(!std::copyable<A<false>>);
  __box<A<false>> x1(std::in_place, 0, 0);
}

constexpr bool
test03()
{
  // Verify correctness of the non-defaulted operator= for the partial
  // specialization of __box.
  struct B {
    constexpr B(int* p) : p(p) { }
    constexpr ~B() { ++*p; };
    B(const B&) = default;
    B& operator=(const B&) = delete;
    int* p;
  };
  static_assert(!std::copyable<B>);
  static_assert(std::is_nothrow_copy_constructible_v<B>);
  static_assert(sizeof(__box<B>) == sizeof(B));

  int m = 0;
  __box<B> x(std::in_place, &m);
  __glibcxx_assert(m == 0);
  x = x;
  __glibcxx_assert(m == 0);
  x = std::move(x);
  __glibcxx_assert(m == 0);

  int n = 0;
  __box<B> y(std::in_place, &n);
  auto z = x;
  x = y;
  __glibcxx_assert(m == 1);
  __glibcxx_assert(n == 0);
  __glibcxx_assert(x->p == &n);
  __glibcxx_assert(y->p == &n);
  y = std::move(z);
  __glibcxx_assert(m == 1);
  __glibcxx_assert(n == 1);
  __glibcxx_assert(y->p == &m);
  __glibcxx_assert(z->p == &m);

  return true;
}
static_assert(test03());