[ChadNauseam]

> You can ignore `Clone`, but ignoring `Copy` destroys the premise, because without it Rust has no exponential types at all.

it somewhat strains the analogy because rust is implemented in a very elegant way (where references can be used multiple times because they implement Copy), but the analogy to exponentials in rust would be references. Just imagine clone and copy aren’t a thing, and that references have a special case that allow them to be used multiple times while owned values can be used at most once. The thing to note is that if you have an owned value, you can pass a reference to it to as many functions as you want (so long as those functions expect references). But if you have a reference, you can’t pass it to a function that expects an owned value unless the type provides you a way to make a copy.

You can imagine starting with this and then building up to rust in a nice way. You first implement passing an owned value as a move. Then first add types that can be used multiple times because they are still valid after a move. (the Copy trait.) And then you make references Copy since they meet that criteria.