>> Stefan Monnier <monnier@iro.umontreal.ca>
  >> on Thu, 15 Nov 2012 13:40:37 -0500 wrote:

  >> In elisp mode completion-at-point-functions is set to
  >> (lisp-completion-at-point t).  If I set it to (t), filename completion
  >> works as expected.  So, it's the lisp-completion-at-point that is not
  >> handing the completion over.

  SM> Indeed, lisp-completion-at-point should return nil when it determines
  SM> that it cannot provide completion information for the text around point.
  SM> Problem is: how should it determine that?


There is an inbuilt facility (:exclusive 'no). Why is that not the default?

This solves the problem: