The function ‘cl-set-difference’ might not be defined at runtime

[Jorge P. de Morais Neto]

Hi.  I have a small Elisp file that calls `cl-set-difference'.  Flycheck
complains

    the function ‘cl-set-difference’ might not be defined at runtime. 
(emacs-lisp)

This complaint makes no sense to me, because cl-set-difference is
autoloaded, according to `describe-function'.  I verified this by
looking at its definition in the file cl-seq.el.  It does have the
autoload cookie.  I then read more about autoload and found about the
function `autloadp'.  To my surprise,
`(describe-function #'cl-set-difference)` returns nil.  Then I checked a
few other autoloads:

(autoloadp #'markdown-mode)
(autoloadp #'js-mode)

All of them return nil!  What gives?

I am using Spacemacs develop (and just before testing I updated the
Spacemacs code and all packages), but the autoloadp invocations happened
within vanilla Emacs: emacs -q.  And I invoked `autoloadp` just after
invoking emacs -q.  Emacs is version 27.0.90, compiled from an updated
checkout of the emacs-27 branch some minutes ago.

Regards

-- 
- <https://jorgemorais.gitlab.io/justice-for-rms/>
- I am Brazilian.  I hope my English is correct and I welcome feedback.
- <https://www.defectivebydesign.org/>
- <https://www.gnu.org/>