template<input_or_output_iterator I> constexpr I ranges::next(I x);
template<input_or_output_iterator I> constexpr I ranges::next(I x, iter_difference_t<I> n);
template<input_or_output_iterator I, sentinel_for<I> S> constexpr I ranges::next(I x, S bound);
template<input_or_output_iterator I, sentinel_for<I> S> constexpr I ranges::next(I x, iter_difference_t<I> n, S bound);