> Casting *mut to &mut in a safe function is unsound, and UB if the result is used alternatingly with an earlier &mut to the save object This is a very differe

> Casting *mut to &mut in a safe function is unsound, and UB if the result is used alternatingly with an earlier &mut to the save object This is a very different statement than your first comment, and still wrong. Casting *mut to &mut is not, itself, unsound or UB- it is, for example, how `Mutex` and `RefCell` are implemented in the standard library! Alternating &muts is of course UB, but that has nothing to do with raw pointers- that's just the definition of &mut, however you obtain one. Even if it were not strictly UB, it would still need to be forbidden, because thread safety and library code (like `Mutex`) relies on it. > I find compile-time lifetime safety to be a tradeoff Yes, this is exactly what I said in the first place- my further point was that the other side of the trade-off is not fixed, and the ergonomics of raw pointers and interior mutability can, have, and will continue to improve over time. Or in other words, the Rust language developers are not "on a crusade to stop programmers from writing code in unsafe languages." Rather, they looked (and continue to look) for ways to expand the space of programs that can be written in safe languages. This is an important distinction, and you appear to be causing yourself a lot of grief ("stop at nothing"? really?) by conflating one with the other.