It seems all fixes are done. I tested the patch and regression tests passed.
I think here Alvaro means that you should keep original comment without the ROW. Like this:
/* XXX perhaps allow REC here? */
I tried rewording this comment
By the way, these functions are misnamed after this patch. They are called "wordtype" and "cwordtype" originally because they accept "word%TYPE" and "compositeword%TYPE", but after the patch they not only accept TYPE at the right of the percent sign but also ELEMENTTYPE and ARRAYTYPE. Not sure that this is something we want to be too strict about.
Understand - used name ***reftype instead ****type
I am not sure, but it seems that new names is a little worse. I think original names are good too. They accept a word and return the PLpgSQL_type structure.
The "TYPE" word in this name was related to syntax %TYPE. And because new syntax allows more constructs, then the change name is correct. I am think. But choosing names is hard work. The new name little bit more strongly show relation to work with referenced types.
I noticed a little typo in the comment in the derive_type(): /* Return base_type, when it is a array already */
should be: /* Return base_type, when it is an array already */
