DarwinAwardWinner/ido-ubiquitous — comment on commit fb6210ff86cbc039da05d7356810ab4e1da67653
File:  line 0
By milkypostman:

For some reason, when I use this as a package with package.el, and I have it byte compiled, it causes an error saying that `set-difference` is not defined. No matter how I start emacs, the problem is that packages automatically get loaded and `cl` does not, by default, get loaded. I don't understand why it is not using the byte-compiled version though.

It compiles fine.