let ptr = reference as *const _ as *mut i32; // raw ptr, with raw tag
let _mut_ref: &mut i32 = unsafe { mem::transmute(ptr) }; // &mut, with raw tag
// Now we retag, making our ref top-of-stack -- and, in particular, unfreezing.
- let _val = *reference; //~ ERROR is not frozen
+ let _val = *reference; //~ ERROR borrow stack
}