boost::gil::dereference_iterator_adaptor::operator‐‐

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 */);

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 */);