Comment by thinkpad20

One advantage I could see of Rust over D for language stuff is sum types (enums in Rust). So for example you can write:

    enum MyLanguage {
      Var(String),
      Int(i32),
      Sum(Box<MyLang>, Box<MyLang>),
      Let(String, Box<MyLang>, Box<MyLang>)
    }

(Apologies if I got a few things wrong; I just mean the general idea)

Seems like without a construct like this, you'd have to use subclasses or something similar, which (to me) isn't quite as nice.