tbh the on-disk storage format is pretty irrelevant, its all just bits and bytes on disk anyways. for many cases you can consider source text a serialization of ast; no matter how you store it you still need to parse the data somehow. Sure some formats are easier to parse than others (hello sexprs), but that is just minor perf aspect, conceptually its all the same.

this closely relates to the missing type discussion, there is no universal "tree" type, and as such it is also difficult to construct any universal "ast" type; different uses need trees structured in different ways: https://news.ycombinator.com/item?id=39592444