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

["Andreas Röhler" <andreas.roehler@online.de>]

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?