anchor.diff:        (intern (symbol-name (name-of k)) :keyword)))
   
   (defun walk-keyword-argument (form parent env)
  -  (destructuring-bind (name &optional default-value supplied-p-parameter)
  +  (destructuring-bind (name &optional (default-value nil default-value-supplied?) supplied-p-parameter)
         (ensure-list form)
       (let ((name (if (consp name)
                       (second name)
  
positive.code: 
  (defclass keyword-function-argument-form (function-argument-form)
    ((keyword-name :accessor keyword-name-of :initarg :keyword-name)
     (default-value :accessor default-value-of :initarg :default-value)
     (supplied-p-parameter :accessor supplied-p-parameter :initarg :supplied-p-parameter)))
  
  (defun effective-keyword-name-of (k)
  
negative.code:                              :name name
                               :keyword-name keyword
                               :supplied-p-parameter supplied-p-parameter)
          (when default-value-supplied?
            (setf (default-value-of arg) (walk-form default-value arg env)))))))
  
  (defunwalker-handler keyword-function-argument-form (keyword-name name default-value supplied-p-parameter)
    (let ((default-value (unwalk-form (default-value-of -form-))))
  