Comment by caim
3 days ago
Yep, that's true. But multiple immutable shared references are a form of contraction, while mutable references are actually affine.
Swift doesn't have references like Rust, and you can't even have unsafe raw pointers to variables without producing a dangling pointer, but this makes Swift more restrictive and less powerful than Rust.
> multiple immutable shared references are a form of contraction
No, they are not. You're not using a value more than once, you are borrowing it, which is an extension of affine logic but keeps true to the core principles of affinity. I have modeled multiple shared references in an affine logic (look up RustBelt), i.e. in a logic that doesn't have contraction, so we have very hard evidence for this claim.