anchor.diff:  
   (def form-class auxiliary-function-argument-form (function-argument-form-with-default-value)
     ())
  -
  -(defun walk-auxiliary-argument (form parent env)
  -  (destructuring-bind (name &optional (default-value nil default-value-supplied?))
  -      (ensure-list form)
  -    (with-form-object (arg 'auxiliary-function-argument-form parent :name name)
  -      (when default-value-supplied?
  -        (setf (default-value-of arg) (walk-form default-value :parent arg :environment env))))))
   
   (def unwalker auxiliary-function-argument-form (name supplied-p-parameter)
     (bind ((default-value (awhen (default-value-of -form-)
  
positive.code: 
  (def form-class optional-function-argument-form (function-argument-form-with-supplied-p-parameter)
    ())
  
  (defun walk-optional-argument (form parent env)
    ;; TODO report bind bug: (bind (((name &optional (default-value nil default-value-supplied?) supplied-p-parameter) (ensure-list form))) )
    (destructuring-bind (name &optional (default-value nil default-value-supplied?) supplied-p-parameter-name)
        (ensure-list form)
      (with-form-object (arg 'optional-function-argument-form parent
                             :name name
                             :supplied-p-parameter-name supplied-p-parameter-name)
        (when default-value-supplied?
          (setf (default-value-of arg) (walk-form default-value :parent arg :environment env))))))
  
  (def unwalker optional-function-argument-form (name supplied-p-parameter-name)
    (bind ((default-value (awhen (default-value-of -form-)
  
negative.code: (def (function e) effective-keyword-name-of (k)
    (or (keyword-name-of k)
        (intern (symbol-name (name-of k)) :keyword)))
  
  (def unwalker keyword-function-argument-form (keyword-name name default-value supplied-p-parameter-name)
    (bind ((default-value (awhen (default-value-of -form-)
  