To elaborate on the other reply to your comment: In Rust, if you don't use `unsafe` and still manage to trigger UB, then that's a bug in the compiler or the library code you called (which in turn has to have used unsafe somewhere to trigger UB).

So the fact that `unreachable!()` does not require the use of the keyword `unsafe` means that it can't be like C++ `std::unreachable()`.