2 Checks for casts of `&T` to `&mut T` anywhere in the code.
5 It’s basically guaranteed to be undefined behavior.
6 `UnsafeCell` is the only way to obtain aliasable data that is considered
13 *(r as *const _ as *mut _) += 1;
18 Instead consider using interior mutability types.
21 use std::cell::UnsafeCell;
23 fn x(r: &UnsafeCell<i32>) {