I would like to have completion-at-point for use-package. In particular, it would be great if there was a way to let emacs know that inside :custom, it should expect variables, not functions, even though point might look as if it was in a funcall position. If not easily fixable, could someone guide me in the correct direction to work on this?

#277 apparently tried to do something like this, but it didn't seem to lead anywhere.