[PartiallyTyped]

Unsafe is concerned with unsafe blocks. NonZero::new_unchecked requires unsafe even though it’s not concerned with mem safety.

[vlovich123]

I believe the optimizer will do optimizations in response to the NonZero which can trigger UB if it does contain a 0, which is a traditional safety issue for Rust which can have no UB in safe code. But even the value being corrupt (ie NonZero returning 0) can cause memory safety issues. But yes, Rust also uses unsafe to bypass enforcing invariants, which std::mem::forget isn’t.