> One group loves fast compile times and quickly validating hypotheses

In Rust, it’s sufficient to type check (if it type/borrow checks, it will probably work) and Rust can type check in real time via rust-analyzer. This is much faster feedback than running your program or even its tests.

Of course, Rust’s type/borrow checker is also choosier than many others, and you still spend more time fighting with errors that don’t actually improve your code’s correctness (e.g., borrow checker errors are rarely indicative of a bug in a single-threaded context). So Rust’s iteration loop is quite fast but it’s development velocity is still relatively low (even when adjusting for quality), but it’s improving all the time.