When treating the root of a criteria query on a type that does not have subtypes, an invalid null = null is rendered in the query, causing the query to never return any rows. I understand this is a rather strange query, and quite easy to work around (do not treat), but I suspect it is also quite easy to fix. I've attached a testcase that performs the following criteria query:

		CriteriaBuilder cb = entityManager.getCriteriaBuilder();
		CriteriaQuery<MyEntity> query = cb.createQuery(MyEntity.class);
		Root<MyEntity> root = query.from(MyEntity.class);
		query.select(cb.treat(root, MyEntity.class));

This results in the following SQL:

    select
        myentity0_.id as id1_0_ 
    from
        MyEntity myentity0_ 
    where
        null=null