bug#50482: Unhelpful error message whilst byte-compiling a function.

[Alan Mackenzie <acm@muc.de>]

[-- Attachment #1: Type: text/plain, Size: 1975 bytes --]

Hello, Lars.

On Thu, Sep 09, 2021 at 16:42:29 +0200, Lars Ingebrigtsen wrote:
> Alan Mackenzie <acm@muc.de> writes:

> > I'm working on a function which begins thus:

> > ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
> > (defun jit-lock--run-functions-new (beg end &optional last-fun)
> >   (let ((tight-beg nil) (tight-end nil) ; The region we have fully fontified.
> >         (loose-beg beg) (loose-end end)) ; The maximum region we have fontified
> >                                         ; with at least some of
> >                                         ; `jit-lock-functions'.
> >     (run-hook-wrapped
> >      'jit-lock-functions
> > ......
> > ......
> > ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

> > On doing M-x compile-defun on this function, I get as sum total of the
> > output in *Compile-Log* this:

> > Buffer jit-lock.el:416:1: Error: Wrong number of arguments: #<subr
> > macroexp--warn-wrap>, 3

> If I just put that in a buffer (and add some closing parentheses), I
> don't get that warning.  Is there something else needed?

It would appear so.  On putting the entire function into *scratch*,
compile-defun gives the same error in scratch, so I'm attaching the file.
Note that lexical-binding was t in my *scratch*.

> > ..  I don't know what this means.  Line 416 is the line where the defun
> > starts.  I don't have `macroexp--warn-wrap' anywhere in my source code,
> > it's not clear to what form 3 arguments are being wrongly passed, or
> > where.

> The warn-wrap stuff comes from `with-suppressed-warnings', I think.

Just to be entirely clear, I'm not asking for help in debugging this
error message (although that wouldn't go amiss) - I'm asking that Emacs
be amended such that this unhelpful message cannot appear any more.

> -- 
> (domestic pets only, the antidote for overdose, milk.)
>    bloggy blog: http://lars.ingebrigtsen.no

-- 
Alan Mackenzie (Nuremberg, Germany).


[-- Attachment #2: jit-lock--run-functions-new.el --]
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(defun jit-lock--run-functions-new (beg end &optional last-fun)
  (let ((tight-beg nil) (tight-end nil) ; The region we have fully fontified.
        (loose-beg beg) (loose-end end)) ; The maximum region we have fontified
                                        ; with at least some of
                                        ; `jit-lock-functions'.
    (run-hook-wrapped
     'jit-lock-functions
     (lambda (fun)
       (if (eq fun last-fun)
           ;; If an earlier function in a recursive call has enlarged
           ;; the region being fontified, we need to re-run `last-fun'.
           (progn
             (when (< loose-beg beg)
               (pcase-let*
                   ((res (funcall fun loose-beg beg))
                    (`(,this-beg . ,this-end)
                     (if (eq (car-safe res) 'jit-lock-bounds)
                         (cdr res) (cons loose-beg beg))))
                 (setq loose-beg this-beg)))
             (when (> loose-end end)
               (pcase-let*
                   ((res (funcall fun end loose-end))
                    (`(,this-beg . ,this-end)
                     (if (eq (car-safe res) 'jit-lock-bounds)
                         (cdr res) (cons end loose-end))))
                 (setq loose-end this-end)))
             t)                         ; quit `run-hook-wrapped'.
         (pcase-let*
             ;; The first function in `jit-lock-functions' can expand
             ;; the region into `tight-beg' and `tight-end'.  These
             ;; arguments are passed to the next function (if any).
             ;; Subsequently, the expanded region from any function is
             ;; stored in `loose-beg' and `loose-end', and is likewise
             ;; passed to the next function.
             ((res (funcall fun loose-beg loose-end))
              (`(,this-beg . ,this-end)
               (if (eq (car-safe res) 'jit-lock-bounds)
                   (cdr res) (cons beg end))))
;;;; NEW STOUGH, 2021-09-07
           (when (< this-beg loose-beg)
             (let ((sub-beg (car (jit-lock--run-functions
                                  this-beg loose-beg fun))))
               (setq loose-beg this-beg)))
           (when (> this-end loose-end)
             (jit-lock--run-functions loose-end this-end)
             (setq loose-end this-end))
;;;; END OF NEW STOUGH
           (or tight-beg (setq tight-beg (min this-beg beg)))
           (or tight-end (setq tight-end (max this-end end)))
           (setq loose-beg (min loose-beg this-beg))
           (setq loose-end (max loose-end this-end))
           nil))))                      ; Carry on executing the hook.
    `(,(or tight-beg beg) ,(or tight-end end) ,loose-beg ,loose-end)))