third_party/llvm-project/libcxx/test/std/ranges/range.adaptors/range.lazy.split/range.lazy.split.inner/increment.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
//
//===----------------------------------------------------------------------===//

// UNSUPPORTED: c++03, c++11, c++14, c++17

// constexpr inner-iterator& inner-iterator::operator++();
//
// constexpr decltype(auto) inner-iterator::operator++(int);

#include <ranges>

#include <cassert>
#include <type_traits>
#include "test_macros.h"
#include "../types.h"

struct EmptyView : std::ranges::view_base {
  constexpr int* begin() const { return nullptr; }
  constexpr int* end() const { return nullptr; }
  constexpr static std::size_t size() { return 0; }
};
static_assert(std::ranges::forward_range<EmptyView>);
static_assert(std::ranges::view<EmptyView>);
LIBCPP_STATIC_ASSERT(std::ranges::__tiny_range<EmptyView>);

constexpr bool test() {
  // Can call `inner-iterator::operator++`; `View` is a forward range.
  {
    SplitViewForward v("abc def", " ");
    auto val = *v.begin();

    // ++i
    {
      auto i = val.begin();
      assert(*i == 'a');

      decltype(auto) i2 = ++i;
      static_assert(std::is_lvalue_reference_v<decltype(i2)>);
      assert(&i2 == &i);
      assert(*i2 == 'b');
    }

    // i++
    {
      auto i = val.begin();
      assert(*i == 'a');

      decltype(auto) i2 = i++;
      static_assert(!std::is_reference_v<decltype(i2)>);
      assert(*i2 == 'a');
      assert(*i == 'b');
    }
  }

  // Can call `inner-iterator::operator++`; `View` is an input range.
  {
    // ++i
    {
      SplitViewInput v("abc def", ' ');
      auto val = *v.begin();

      auto i = val.begin();
      assert(*i == 'a');

      decltype(auto) i2 = ++i;
      static_assert(std::is_lvalue_reference_v<decltype(i2)>);
      assert(&i2 == &i);
      assert(*i2 == 'b');
    }

    // i++
    {
      SplitViewInput v("abc def", ' ');
      auto val = *v.begin();

      auto i = val.begin();
      assert(*i == 'a');

      static_assert(std::is_void_v<decltype(i++)>);
      i++;
      assert(*i == 'b');
    }
  }

  // Can call `inner-iterator::operator++`; `View` is an input range and `Pattern` is an "empty" range.
  {
    // ++i
    {
      std::ranges::lazy_split_view<InputView, EmptyView> v("a", EmptyView());
      auto val = *v.begin();

      auto i = val.begin();
      assert(*i.base() == 'a');
      assert(i != std::default_sentinel);

      // The iterator doesn't move to the next character but is considered to point to the end.
      decltype(auto) i2 = ++i;
      assert(&i2 == &i);
      assert(*i2.base() == 'a');
      assert(i2 == std::default_sentinel);
    }

    // i++
    {
      std::ranges::lazy_split_view<InputView, EmptyView> v("a", EmptyView());
      auto val = *v.begin();

      auto i = val.begin();
      assert(*i.base() == 'a');
      assert(i != std::default_sentinel);

      // The iterator doesn't move to the next character but is considered to point to the end.
      i++;
      assert(*i.base() == 'a');
      assert(i == std::default_sentinel);
    }
  }

  return true;
}

int main(int, char**) {
  test();
  static_assert(test());

  return 0;
}