All objects update their reference after a renaming. If you rename a column, foreign keys referencing that column have the name updated.
It's kind of surprising in some cases when I haven't seen it before (like views) but is consistent and the alternative would be a lot harder to work with.
Allow SQL-language functions and procedures to use SQL-standard function bodies (Peter Eisentraut)
Previously only string-literal function bodies were supported. When writing a function or procedure in SQL-standard syntax, the body is parsed immediately and stored as a parse tree. This allows better tracking of function dependencies, and can have security benefits.
[1]: https://www.postgresql.org/docs/14/release-14.htmlif so that's form interpretation right, you could build a powerful lisp-style macro system that way I think.
On me for not testing better, but it was some quick and dirty work in a quick and dirty environment that doesn't even have a dev instance.