anchor.diff:                                 ((and (not default-p)
                                        (eq label :optional)
                                        ;; Use unbound for booleans only
  -                                     (not (eq pclass 'boolean)))
  +                                     (not (eq type 'boolean)))
                                   nil)
                                  (default-p `,default)))))
                  (field (make-instance
  
positive.code:                 (if default-p
                      default
                      $empty-default))
                 (pclass (if (member type (list 'cl:keyword 'cl:symbol))
                             'symbol
                             type))
                 (cslot (unless alias-for
                          (make-field-data
                           :internal-slot-name internal-slot-name
  
negative.code:                        :name  (or name (slot-name->proto slot))
                         :type type
                         :kind kind
                         :class type
                         :qualified-name (make-qualified-name *current-message-descriptor*
                                                              (or name (slot-name->proto slot)))
                         :label label
  