CleanUpVisitor doesn't do much.

[71]

The point of the CleanUpVisitor is to remove every single dependency to Cometary. That means namespaces, classes, attributes, metadata references, etc. It currently only removes usings that start with Cometary, and destroys the program as it does it.

It should also be smarter -- not only should it remove references to Cometary, but also to packages that depend on it.

[71]

The CleanUpVisitor was renamed to CleanUpRewriter in 2cc21e8.
Now, extensions should manually add Hooks to clean up their code, thanks to the new CleanUp static class.

This is a big change, but right now, the source code still doesn't clean up everything. Also, references aren't deleted correctly either, which is why I'm letting this issue open.