template<bool OtherConst>
requires std::sized_sentinel_for<
                std::ranges::sentinel_t<Base>,
                std::ranges::iterator_t<detail::maybe_const<OtherConst, V> > >
constexpr
std::ranges::range_difference_t</* implementation-defined */>
operator‐(
    iterator<OtherConst> const& x,
    sentinel const& y);