text: //===----------------------------------------------------------------------===//
  //
  // 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
  // UNSUPPORTED: libcpp-has-no-incomplete-ranges
  
  // friend constexpr void iter_swap(const iterator& x, const iterator& y);
  
  #include <cassert>
  #include <ranges>
  
  #include "../types.h"
  
  using NonSwappableView = BufferView<copying_iterator<int*>>;
  static_assert(std::ranges::input_range<NonSwappableView>);
  static_assert(!std::indirectly_swappable<std::ranges::iterator_t<NonSwappableView>>);
  
  constexpr bool test() {
    int buffer[4][4] = {{1, 2, 3, 4}, {5, 6, 7, 8}, {9, 10, 11, 12}, {13, 14, 15, 16}};
  
    {
      std::ranges::join_view jv(buffer);
      auto iter1 = jv.begin();
      auto iter2 = std::next(jv.begin());
      assert(buffer[0][0] == 1);
      assert(buffer[0][1] == 2);
      std::ranges::iter_swap(iter1, iter2);
      assert(buffer[0][0] == 2);
      assert(buffer[0][1] == 1);
  
      static_assert(noexcept(std::ranges::iter_swap(iter1, iter2)));
    }
  
    {
      // iter_move calls inner's iter_swap
      IterMoveSwapAwareView inners[1] = {buffer[0]};
      std::ranges::join_view jv(inners);
      auto it1 = jv.begin();
      auto it2 = std::ranges::next(it1);
  
      const auto& iter_swap_called_times = jv.base().begin()->iter_swap_called;
  
      assert(iter_swap_called_times == 0);
      assert(buffer[0][0] == 2);
      assert(buffer[0][1] == 1);
  
      std::ranges::iter_swap(it1, it2);
  
      assert(buffer[0][0] == 1);
      assert(buffer[0][1] == 2);
      assert(iter_swap_called_times == 1);
    }
  
    {
      // LWG3517 `join_view::iterator`'s `iter_swap` is underconstrained
      // `iter_swap` should not be defined if Inner's iterator does not indirectly_swappable
      NonSwappableView inners[2] = {buffer[0], buffer[1]};
      std::ranges::join_view jv(inners);
      using Iter = std::ranges::iterator_t<decltype(jv)>;
      static_assert(!std::indirectly_swappable<Iter>);
    }
    return true;
  }
  
  int main(int, char**) {
    test();
    static_assert(test());
  
    return 0;
  }
  