[Gankro]

Ultimately it boils down to the fact that there's basically no interesting difference between an immutable reference to a primitive and the primitive itself in Rust. It can't dangle. The immutability can't be casted away. They just have a different ABI if the references don't get completely optimized away. You could do pointer equality checks on them if you really want?

Swift has taken the observation further and is investigating ways to avoid ever having a immutable+shared-reference-to-primitive vs primitive distinction in the language, while still introducing this distinction for types where it is interesting. (e.g. reference counted classes or atomics)