which kind of ASTs can have scopes?

[thautwarm]

https://github.com/thautwarm/JuliaVariables.jl/blob/b66db8e1f1efc84406b073ad2a8c03efe34c6b62/src/JuliaVariables.jl#L233

This is relevant to https://github.com/thautwarm/GeneralizedGenerated.jl/issues/44 .

It seems that at least Expr and Symbol can have scopes, while a literal, or QuoteNode cannot.

I'll update the code once I make sure all possibilities.