None of the things you mentioned, other than the slice type, which i don’t see how it would work on raw memory, are a language feature.
Generics and privacy are definitely language features, and they're core to the ease with which one can create abstractions. Rust is a systems language, it tries to give programmers the power to create their own safe abstractions as needed.
> though i don't see how that differs from a generic accessor method or an overloaded operator
Err, it does all the bounds checking automatically? I thought you wanted these features without having to implement them yourself, but apparently writing accessor methods or an overloaded operator is OK too?!?
We actually used to implement Vec as a language feature, and it was a lot of work to write things like growth in raw LLVM IR (which is a miserable programming language) instead of just using a real programming language—Rust—to do it.