[lr1970]

> Borrow checker tracks who is using what over time.

This is a very imprecise statement. Do you mean tracks at "compile time" or at "run time"?

A more accurate statement would be -- the borrow checker enforces a specific set of rules and constraints at _compile time_ only. But this set of constraints guarantees memory safety at run time (with the exception of unsafe code). In fact, Rust's runtime is minimal -- it handles panics but has no GC or other bells and whistles. The fancy things are in libraries.