libcxx/test/std/utilities/intseq/intseq.binding/structured_binding.pass.cpp

//===----------------------------------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//

// REQUIRES: std-at-least-c++26

// <utility>

// template<size_t I, class T, T... Values>
//   struct tuple_element<I, integer_sequence<T, Values...>>;
// template<size_t I, class T, T... Values>
//   struct tuple_element<I, const integer_sequence<T, Values...>>;
// template<size_t I, class T, T... Values>
//   constexpr T get(integer_sequence<T, Values...>) noexcept;

#include <cassert>
#include <utility>

constexpr bool test() {
  auto [elt0, elt1, elt2, elt3] = std::make_index_sequence<4>();

  assert(elt0 == 0);
  assert(elt1 == 1);
  assert(elt2 == 2);
  assert(elt3 == 3);

// TODO: remove this macro guard once GCC16 is available
#if __cpp_structured_bindings >= 202411L
  []<typename...> {
    auto [... empty] = std::make_index_sequence<0>();
    static_assert(sizeof...(empty) == 0);

    auto [... size4] = std::make_index_sequence<4>();
    static_assert(sizeof...(size4) == 4);

    assert(size4...[0] == 0);
    assert(size4...[1] == 1);
    assert(size4...[2] == 2);
    assert(size4...[3] == 3);
  }();
#endif

  return true;
}

int main(int, char**) {
  test();
  static_assert(test());
  return 0;
}