Hm, so trying to understand this, all things inside of the `last_private` map are either `Used` or `NotPresent`. If it's `Used` then this import resolved to something in that namespace, and if `NotPresent` it didn't resolve to anything?

And the this figures out whether `Used` should actually be `Unused`? OK this seems good. Does the `v_used == Used` condition overflow 80 characters? It'd be nice if the assignment and comparison weren't aligned with one another.