//===----------------------------------------------------------------------===//
//
// 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++03, c++11, c++14, c++17

// <span>

// constexpr span() noexcept;

#include <span>
#include <cassert>
#include <string>
#include <type_traits>

#include "test_macros.h"

void checkCV() {
  //  Types the same (dynamic sized)
  {
    std::span< int> s1;
    std::span<const int> s2;
    std::span< volatile int> s3;
    std::span<const volatile int> s4;
    assert(s1.size() + s2.size() + s3.size() + s4.size() == 0);
  }

  //  Types the same (static sized)
  {
    std::span< int, 0> s1;
    std::span<const int, 0> s2;
    std::span< volatile int, 0> s3;
    std::span<const volatile int, 0> s4;
    assert(s1.size() + s2.size() + s3.size() + s4.size() == 0);
  }
}

template <typename T>
constexpr bool testConstexprSpan() {
  std::span<const T> s1;
  std::span<const T, 0> s2;
  return s1.data() == nullptr && s1.size() == 0 && s2.data() == nullptr && s2.size() == 0;
}

template <typename T>
void testRuntimeSpan() {
  ASSERT_NOEXCEPT(T{});
  std::span<const T> s1;
  std::span<const T, 0> s2;
  assert(s1.data() == nullptr && s1.size() == 0);
  assert(s2.data() == nullptr && s2.size() == 0);
}

struct A {};

int main(int, char**) {
  static_assert(testConstexprSpan<int>(), "");
  static_assert(testConstexprSpan<long>(), "");
  static_assert(testConstexprSpan<double>(), "");
  static_assert(testConstexprSpan<A>(), "");

  testRuntimeSpan<int>();
  testRuntimeSpan<long>();
  testRuntimeSpan<double>();
  testRuntimeSpan<std::string>();
  testRuntimeSpan<A>();

  checkCV();

  static_assert(std::is_default_constructible_v<std::span<int, std::dynamic_extent>>, "");
  static_assert(std::is_default_constructible_v<std::span<int, 0>>, "");
  static_assert(!std::is_default_constructible_v<std::span<int, 2>>, "");

  return 0;
}