.. change::
    :tags: bug, orm
    :tickets: 9350

    Fields that are declared on Declarative Mixins and then combined with
    classes that make use of :class:`_orm.MappedAsDataclass`, where those mixin
    fields are not themselves part of a dataclass, now emit a deprecation
    warning as these fields will be ignored in a future release, as Python
    dataclasses behavior is to ignore these fields. Type checkers will not see
    these fields under pep-681.

    .. seealso::

        :ref:`error_dcmx` - background on rationale

        :ref:`orm_declarative_dc_mixins`
