Right but it wasn’t obvious to me (at the time) what a change to the source code would do to the ast, so it wasn’t easy to know all the cases to handle, especia

Right but it wasn’t obvious to me (at the time) what a change to the source code would do to the ast, so it wasn’t easy to know all the cases to handle, especially with quasiquotation (I think double-backtick style programming was basically impossible). For example, maybe you want to handle something that looks like: foo ~~> bar In lisp syntax (and recall that is what the Julia ast is: everything is a head and then arguments) it might look like: (~~> foo bar) ; or (op ~~> foo bar) But if you change to e.g. foo ~~> bar + 5 You might get (+ (~~> foo bar) 5) Or (~~> foo (progn (+ bar 5))) I don’t remember what you got or which cases were tricky, only that I could never guess what the output of dump would be.