Re: CREATE CAST allows creation of binary-coercible cast to range over domain

Peter Eisentraut <peter(at)eisentraut(dot)org> writes:
> CREATE CAST disallows creating a binary-coercible cast to a domain
> (because that would bypass checking the domain constraints). But it
> allows it if the domain is wrapped inside a range type:
> ...
> This particular case seems straightforward to fix, but maybe there are
> also cases with more nesting to consider.

I think it's an oversight that we allow binary-coercible casts
involving range types at all. There are no other nesting cases to
worry about, because CreateCast already rejects binary-coercible casts
applied to composites and arrays, explaining

* We know that composite, enum and array types are never binary-
* compatible with each other. They all have OIDs embedded in them.

But range types also embed their own OID, so I don't see why that
concern doesn't apply to them.

regards, tom lane