I just uploaded jpatest.zip, which supersedes the earlier persist.zip test case.

Gail, while JSR 338 does not have an example that directly matches my use case, it's clear from examples that it should be possible to project downcasted properties in the select clause (6.5.7, example 1). Downcasting the root entity is also supported (example 3). The test case testTreatInWhereClause exercises the equivalent of example 3 in JSR 338 6.5.7. As with the earlier test case, the logged Hibernate query shows that it is using inner joins on the downcasted entities. This makes queries such as example 3 in 6.5.7 impossible: Hibernate will always return an empty set, which is wrong.