Well that's rather the point of being generic with any language, isn't it?

You can stop being generic when you have sufficient information to stop being generic. If you're writing a library, that can easily bubble up all the way to the top, because you may never have enough information.

ETA: I think I was using a definition of viral that wasn't entirely correct. I thought it was a casual term rather than a precise one. But it seems like you're saying something is viral if you _must_ pass it on. In which case I apologize, generics are "semiviral" (I'm trying to introduce this term - if it already exists & isn't this, I apologize) - you don't need to pass them on, there's just a tendency to. The result looks very similar.

Rust also has associated types, which are exposed to the implementer, but not to the consumer.

I mean, generics and associated types aren't equivalent, but they also are often exposed to the consumer. Eg, if you're accepting an Iterator, you'll want to populate the Item associated type.