anchor.diff:  
   (defun get-drawing-options (highlighting-rules syntax parse-symbol)
     "Get the drawing options with which `parse-symbol' should be
  -drawn. If `parse-symbol' is NIL, return NIL."
  -  (when parse-symbol
  +drawn. If `parse-symbol' or the stack-top of syntax, return NIL."
  +  (when (and parse-symbol (not (eq (stack-top syntax) parse-symbol)))
       (funcall highlighting-rules syntax parse-symbol)))
   
   (defstruct (pump-state
  
positive.code:                               (finish (line-end-offset line) start-symbol))
                               ((and (typep symbol 'literal-object-mixin))
                                (finish (start-offset symbol) symbol
                                        (or (get-drawing-options highlighting-rules syntax symbol)
                                            (make-drawing-options :function (object-drawer)))))
                               ((and (> (start-offset symbol) offset)
                                     (not (drawing-options-equal (or symbol-drawing-options
  
negative.code:    (preceding-parse-tree :initform nil :reader preceding-parse-tree)
     (parser-state :initform nil :initarg :parser-state :reader parser-state)))
  
  (defmethod print-object ((object parser-symbol) stream)
    (print-unreadable-object (object stream :type t :identity t)
      (format stream "~s ~s" (start-offset object) (end-offset object))))
  
  (defclass literal-object-mixin () ()
    (:documentation "Mixin for parser symbols representing
  literal (non-character) objects in the buffer."))
  