The following union:

/**
 * @brief Timer event details.
 */
typedef union
{
    /**
     * @brief Event details for an event of type.
     */
    uint8_t timeout;
} timer_event_details_t;

When documented with doxygenunion:: and :members: it does not display at all nor seems to raise any error. When I switch to doxygenstruct an error is raised stating that the structure can't be found, which is what I would expect since it is an union.

When :members: is not included it seems to work, however I do not understand why the #include ... part is displayed.

.. doxygenunion:: timer_event_details_t

If I add :outline:, it displays without the #include ..., but it also removes the documentation, so I do not think there is a workaround:

.. doxygenunion:: timer_event_details_t
    :outline:

Is doxygenunion working as expected?