I don't understand this at all. JSON is a serialization format. So say you have an in-memory AST, and you want to serialize it: why not use JSON? If you don't

I don't understand this at all. JSON is a serialization format. So say you have an in-memory AST, and you want to serialize it: why not use JSON? If you don't want or need to serialize it, then of course don't use JSON. I can make up plenty of other reasons not to, but they're variations on some other format being better for the application, not JSON being inadequate in any way. I'd probably use JSON myself, and I don't care for it much. Or are we talking about building up an AST in JSON directly rather than taking some parser output and serializing it? Ok that's... not an AST then, it's a programming language with JSON compatible syntax, and yes I would try and prevent that from getting implemented as well.