[epilys]

Nitpick, unsafe doesn't turn off the borrow checker. It just allows you to dereference raw pointers which are the things you must be careful about by reasoning about the actual safety yourself as a programmer. Everything else that uses safe pointers (references and mutable references) remain safe.

[nine_k]

But how passing around a (constant) raw pointer is not sidestepping borrow checker? Since the pointer (AFAICT) does need to be borrowed, because it's manifestly immutable, it could be passed into several functions that alter the pointed-at memory in arbitrary order.

[epilys]

Yeah it is sidestepping as you say! The distinction is that if you don't sidestep by dereferencing raw pointers, the borrow check still works. Observe that you can cast as raw pointers in safe rust. What unsafe {} changes is that you can dereference them. The borrow checker still works for regularly borrowed values (&var and &mut var etc). This is probably obvious for Rust users, but I find some people take the "turn the borrow checker off" literally by assuming they won't get lifetime errors if the put an unsafe { } around their code.