Tree Borrows

From the paper:

> The problem with unsafe code is that it can do things like this:

    fn main() {
        let mut x = 42;
        let ptr = &mut x as *mut i32;
        let val = unsafe { write_both(&mut *ptr, &mut *ptr) };
        println!("{val}");
    }

No it can't? Using pointers to coexist multiple mutable references to the same variable is undefined behavior. Unless I'm just misunderstanding the point they're trying to make here.

"can do things" in this case doesn't mean "is allowed to do things".

"Unsafe code allows to express the following, which is UB:"