util.warn(
                            "Regular (i.e. not __special__) "
                            "attribute '%s.%s' uses @declared_attr, "
                            "but owning class %s is mapped - "
                            "not applying to subclass %s."
                            % (base.__name__, name, base, cls)
                        )
                    continue
                elif base is not cls:
                    # we're a mixin, abstract base, or something that is
                    # acting like that for now.
                    if isinstance(obj, (Column, MappedColumn)):
                        # already copied columns to the mapped class.
                        continue
                    elif isinstance(obj, MapperProperty):
                        raise exc.InvalidRequestError(
                            "Mapper properties (i.e. deferred,"
                            "column_property(), relationship(), etc.) must "
                            "be declared as @declared_attr callables "
                            "on declarative mixin classes.  For dataclass "
                            "field() objects, use a lambda:"
                        )
                    elif _is_declarative_props(obj):
                        # tried to get overloads to tell this to
                        # pylance, no luck
                        assert obj is not None
                        if obj._cascading:
                            if name in clsdict_view:
                                # unfortunately, while we can use the user-
                                # defined attribute here to allow a clean
                                # override, if there's another
                                # subclass below then it still tries to use
                                # this.  not sure if there is enough
                                # information here to add this as a feature
                                # later on.
                                util.warn(
                                    "Attribute '%s' on class %s cannot be "
                                    "processed due to "
                                    "@declared_attr.cascading; "
                                    "skipping" % (name, cls)
                                )