anchor.diff:      (:typeof
        (get-instance-node graph "String"))
       (:void
  -     (get-instance-node graph "undefined"))
  +     (get-location-node graph "undefined"))
       (otherwise
        (error "unrecognized unary operation ~A" (unary-operator-op-symbol elm)))))
       
  
positive.code:         for idx upfrom 0
          when (and (numberp env-min)
                    (>= idx env-min))
          do (add-assignment-edge param (get-instance-node graph "undefined" queue) queue))
  
    ;; Link corresponding arguments and parameters
    ;; TODO Deal with worse-than-quadratic nature of this operation, perhaps
  
negative.code:   (let ((left-node (get-location-node graph (var-decl-name elm))))
      (if (var-decl-initializer elm)
        (add-assignment-edge left-node (populate-nodes graph (var-decl-initializer elm)))
        (add-assignment-edge left-node (get-location-node graph "undefined")))))
  
  (defmethod populate-nodes (graph (elm fn-call))
    (let* ((target-node (populate-nodes graph (fn-call-fn elm)))
  