Tom Lane wrote:
> That's an artifact of the fact that the patch tries to piggyback on
> the DOMAIN infrastructure instead of implementing its own statement
> type etc.
This piggybacking is intentional in some way. If you read the
commentary on the SQL99 standard, distinct types were specifically
invented as a better replacement for the domains introduced in SQL92,
with the only functional difference being the casting behavior (and that
you can use distinct types as function argument types, but PostgreSQL
supports that for domains as well). So even though the names of the
object classes are different, they are really intended to be quite similar.