bug#32012: 27.0.50; jit-lock--run-functions broken

[Andreas Röhler]

On 30.06.2018 12:57, Eli Zaretskii wrote:
> > Cc: 32012@debbugs.gnu.org
> > From: Andreas Röhler <andreas.roehler@online.de>
> > Date: Sat, 30 Jun 2018 08:54:49 +0200
> >
> > On 30.06.2018 08:34, Eli Zaretskii wrote:
> > > > From: Andreas Röhler <andreas.roehler@online.de>
> > > > Date: Fri, 29 Jun 2018 22:16:55 +0200
> > > >
> > > > Running into it from ert-tests which call ‘jit-lock-fontify-now’
> > > >
> > > > When reproduced from emacs -Q in scratch-buffer:
> > > >
> > > > Debugger entered--Lisp error: (wrong-number-of-arguments (2 . 2) 0)
> > > >      jit-lock--run-functions()
> > > >      eval((jit-lock--run-functions) nil)
> > > >      elisp--eval-last-sexp(nil)
> > > >      eval-last-sexp(nil)
> > > >      funcall-interactively(eval-last-sexp nil)
> > > >      call-interactively(eval-last-sexp nil nil)
> > > >      command-execute(eval-last-sexp)
> > >
> > > Why did you think you can call that function tis way?
> >
> > Hmm, by looking at its signature
> >
> > (defun jit-lock-fontify-now (&optional start end)
> >
> > Why that shouldn't work?
>
> That's not what the backtrace suggests.  It suggests that you invoked
> jit-lock--run-functions via eval-last-sexp.

Right. But the arguments are optional.
Wherefrom to expect it failing?