constexpr
bool
operator==(
    iterator const& x,
    iterator const& y)
requires std::equality_comparable<std::ranges::iterator_t<Base> >;

template<bool OtherConst>
requires std::sentinel_for<
                std::ranges::sentinel_t<Base>,
                std::ranges::iterator_t<detail::maybe_const<OtherConst, V> > >
constexpr
bool
operator==(
    iterator<OtherConst> const& x,
    sentinel const& y);