anchor.diff:                       ;; TODO(cgay): this should probably refer to the external field name but I'll
                        ;; wait since I've no idea if that slot is bound at this point.
                        (proto-internal-field-name field) (proto-class msg-desc))
  -             ;; todo(benkuehnert: What does this do?
  -             (setq index idx)
                (when slot
                  (collect-slot slot))
                (push field (proto-fields msg-desc))))))
  
positive.code:                                   :conc-name conc-name
                                    :options   (remove-options options "default" "packed")
                                    :documentation documentation))
           (index 0)
           (field-offset 0)
           (top-level-form-p (top-level-p *protobuf*))
           (*protobuf* msg-desc)
  
negative.code:              (assert (not (find-field message (proto-index field))) ()
                       "The field ~S overlaps with another field in ~S"
                       (proto-internal-field-name field) (proto-class message))
               (when slot
                 (collect-slot slot))
               (appendf (proto-fields message) (list field))))))
  