Answer:

sqlRestriction should directly use {alias}.COLUMNNAME

so

 criteria.add(Restrictions.sqlRestriction("trim(" + alias + "bar) like %" + filter.getBar()));

becomes

 criteria.add(Restrictions.sqlRestriction(
                    "trim({alias}.IDBAR) like ?",
                    "%" + filter.getBar(),
                    Hibernate.STRING
            ));