Implement Hash for Expression

[TitanNano]

I'm trying to store data associated with an expression. Unfortunately Expression doesn't implement Hash which makes it impossible for me to store the data inside a HashMap. Would it be possible to derive or implement Hash for Expression so an expression can be used as a HashMap key?

[Yoric]

Associating arbitrary data to arbitrary nodes is indeed something commonly useful. It's useful to store comments, lines of code, transformation data, etc.

One solution would be to have all nodes carry on a unique integer or a Rc::Weak<Any>. Or to parameterize all nodes by a payload type T.

[TitanNano]

Is this something that could be done in the near future? I'd be happy to, but I don't know how. So if someone could give me some pointers into the right direction, then I'd be happy to work on it.