in gazebo/src/cell.rs [303:315]
fn test_ref_as_expected() {
let orig = RefCell::new("test".to_owned());
let p = orig.borrow();
let p2 = Ref::clone(&p);
let (pointer, cell): (usize, usize) = unsafe { mem::transmute(p) };
// We expect the first to be a pointer to the underlying string
assert_eq!(pointer, cast::ptr_to_usize(Ref::deref(&p2)));
// We want to make sure the second is never zero
assert_ne!(cell, 0);
// Put it back as it was, to make sure our test doesn't leak memory
let _ignore: Ref<String> = unsafe { mem::transmute((pointer, cell)) };
}