Re: ltree::text not immutable?

I wrote:
> More generally, it seems like we ought to have a test in the type_sanity
> regression script that checks that type I/O functions aren't volatile,
> because there are various embedded assumptions that this is so, cf
> commits aab353a60b95aadc00f81da0c6d99bde696c4b75 and
> 3db6524fe63f0598dcb2b307bb422bc126f2b15d.

> That wouldn't have directly caught this problem because we don't apply
> type_sanity or opr_sanity to contrib modules, only to core functions.
> I have done that manually in the past and think I'll go do it again
> to see what else crawls out ... but I wonder if anyone can think of
> a way to automate that?

Actually, the right thing to do if we want to enforce this is for
CREATE TYPE to check the marking. We'd still need a type_sanity
test to check erroneous declarations of built-in types, but a complaint
in CREATE TYPE would cover all the contrib modules as well as third-party
code.

I wouldn't propose back-patching such an error check, but it seems
reasonable to add it for 9.5. Any objections?

regards, tom lane