;; Error checking still required.

(defgeneric migrate-methods (source-generic-function target-generic-function)
  (:method (source target)
    (let ((methods (closer-mop:generic-function-methods source)))
      (dolist (m methods)
        (remove-method source m)
        (add-method target m)))))

(defgeneric replace-generic-function-using-class (generic-function class)
  (:method ((name symbol) (class symbol))
    (let ((gf (fdefinition name)))
      (fmakunbound name)
      (migrate-methods
       gf
       (ensure-generic-function
        name
        :generic-function-class class
        :lambda-list (closer-mop:generic-function-lambda-list gf)
        :name name)))))