Comment by zamalek

Right, if references were meant to be pointers then they would simply be called pointers.

Some abstractions are meant to be treated as a black box. It's bloody trivial to realize and point out that references are represented as pointers internally. The actually intelligent step is to figure out how to use that knowledge correctly. Do we pass small bittable types around by-value because we skip the dereference? Hell yes (pending profiling). Do we treat references as pointers? No.

As a plausible scenario, rustc could use tagged pointers for some purpose in refs. Your code could seem to be working in tests, but segfault when rustc sets the MSB for some reason.