Also, Rust is not going to have it for the long run that pointers can be, in fact, disguised as integers. There is this thing called pointer provenance, and some day, all pointers are required to have provenance (i.e. a proof where they did come from) OR they are required to admit that POOF this is a pointer out of thin air, you can't assume anything about the pointee. As long as there are no POOF magicians, the GC can assume that it knows every reference!