I like that in Rust pointers can't even be null, you have to wrap them in a kind of an "enum" (union, ish) of the pointer and Nil value.

Kinda like a Haskell 'Maybe' ?

I don't know Haskell, but looking quickly that's more like Rust's "Option" which is in std library, built using the odd "enum"

yeah, so Haskell Either seems to be more like Rust's language feature "enum" (only enum can take more than 2 choices...)

So rust's enum is an enumeration of types?

yes! which I guess is a really generic way of thinking about an enum... rustbyexample.com/custom_typ…