[seanmcdirmid]

Speaking out of complete ignorance of what Rust's situation actually is, I think the key is to have a gentle slope from "bad program" to "good program" that allows for the IDE to provide bits of feedback along the way to get to the "good program" state along with helping out with much of the mental computation that the programmer otherwise does in their head.

Rust's type system doesn't really seem to be there yet: there are just "wrong programs" and "right programs" with not much in between. Gradual typing on the other hand works very well here.