Renaming tables to other schemas

Hello!

The following SQL works:

ALTER TABLE a.foo RENAME TO bar;

But the following doesn't:

ALTER TABLE a.foo RENAME TO b.bar;

The capability to move objects to other schemas
would be quite useful.

Apparently, everything works OK if you change
pg_class.relnamespace with UPDATE, but this is
not very nice.

Are there any problems to be expected with this that
I am missing and if not, would it make sense to support
changing schemas with ALTER TABLE?