mrdocs::cast_or_null

template<
    class To,
    class From>
requires ( std::derived_from<std::remove_cvref_t<To>, std::remove_cvref_t<From>> )
[[nodiscard]]
std::add_pointer_t<std::remove_reference_t<To> const>
cast_or_null(Polymorphic<From> const* pp);