boost::gil::position_iterator::operator++

constexpr
position_iterator&
operator++() noexcept;

template<typename D = Derived>
requires !v1_dtl::plus_eq<D, difference_type>::value
constexpr
decltype(++access::base(std::declval<D &>()), std::declval<D &>())
operator++() noexcept(/* see-below */);

template<typename D = Derived>
constexpr
decltype(std::declval<D &>() += difference_type(1), std::declval<D &>())
operator++() noexcept(/* see-below */);

constexpr
position_iterator
operator++(int) noexcept;

template<typename D = Derived>
constexpr
std::remove_reference_t<decltype(D(std::declval<D &>()),
                ++std::declval<D &>(),
                std::declval<D &>())>
operator++(int) noexcept(/* see-below */);