Somewhat unrelated but I fantasised about creating an assembly language editor which uses binary executable to save code and some kind of attributes or whatever to save comments, identifiers and so on. Will not work with macroses, but an interesting idea IMO.

Might actually work with Java-like language (JVM bytecode is very close to Java AST).

(mods forgive me for double-posting this link!) https://twitter.com/PaniczGodek/status/1463860646253060104

(Scroll up in that thread for AST inspiration)