constexpr explicit outer-iterator(chunk_view& parent);
constexpr value_type operator*() const;
constexpr outer-iterator& operator++();
constexpr void operator++(int);
friend constexpr bool operator==(const outer-iterator& x, default_sentinel_t);
friend constexpr difference_type operator-(default_sentinel_t y, const outer-iterator& x)
requires sized_sentinel_for<sentinel_t<V>, iterator_t<V>>;
friend constexpr difference_type operator-(const outer-iterator& x, default_sentinel_t y)
requires sized_sentinel_for<sentinel_t<V>, iterator_t<V>>;