anchor.diff:            (t
              (values nil t)))))
   
  -(defun %skip-comment-backward (point)
  +(defun %skip-block-comment-backward (point)
     (multiple-value-bind (n pair)
         (syntax-end-block-comment-p point)
       (if n
  
positive.code: (defun %skip-list-backward (point depth)
    (loop :with paren-stack := '()
          :do
          (unless (skip-space-and-comment-backward point)
            (return nil))
          (when (start-buffer-p point)
            (return nil))
          (let ((c (character-at point -1))
  
negative.code:                 ((syntax-fence-char-p c)
                   (%skip-fence-backward point))
                  (t
                   (multiple-value-bind (p win)
                       (%skip-block-comment-backward point)
                     (unless win
                       (return nil))
                     (unless p
                       (character-offset point -1))))))))
  
  (defun %form-offset-positive (point)
    (skip-space-and-comment-forward point)
  