anchor.diff:  
   (eval-when (:compile-toplevel :load-toplevel :execute)
     (defun (setf macro-function) (new-function symbol &optional environment)
  -    (unless (null environment)
  -      (error 'type-error :datum environment :expected-type 'null))
  -    (unless (symbolp symbol)
  -      (error 'type-error :datum symbol :expected-type 'symbol))
  -    (unless (functionp new-function)
  -      (error 'type-error :datum new-function 'function))
  +    (declare (cl:type null environment)
  +	     (cl:type symbol symbol)
  +	     (cl:type function new-function)
  +	     (ignore environment))
       ;; First check whether there is a global function entry with
       ;; this name.
       (let ((function-entry
  
positive.code: ;;; of that entry does not contain +unbound+.
  
  (defun boundp (symbol)
    (unless (symbolp symbol)
      (error 'type-error :datum symbol :expected-type 'symbol))
    (not (null (or (find symbol (constant-variables *global-environment*)
  		       :key #'name :test #'eq)
  		 (find symbol (symbol-macros *global-environment*)
  
negative.code: ;;; attempt is made to make a constant variable unbound.
  
  (defun makunbound (symbol)
    (declare (cl:type symbol symbol))
    ;; Check whether the symbol has a definition as a constant variable.
    (let ((constant-variable-entry
  	  (find symbol (constant-variables *global-environment*)
  