[lacampbell]

I would say that at that point, it ceases to be a simple setter method (or set property). It's not a simple case of mutating some element of a data structure of filenames as strings. There'd be some validation and error handling involved. It's a perfectly valid high level message to send a file object.

As an aside, I'd probably make a method called "rename" that does this, as opposed to something like "setName".