anchor.diff:  
   ;;; If the type specifier is a symbol for which there is deftype
   ;;; expander or a list whose CAR is such a symbol, we apply the
  -;;; expander and try again. 
  +;;; expander and try again.
   ;;;
   ;;; If not, and if the type specifier is a class C or a symbol that is
   ;;; the name of a class C, we check whether the CLASS-OF the object is
  
positive.code: ;;; standard-generic-function, class, standard-class, built-in-class,
  ;;; structure-class, standard-object, structure-object, method,
  ;;; standard-method, method-combination,
  ;;; 
  ;;; Others: t, null, nil, atom, hash-table, keyword, logical-pathname,
  ;;; list, compiled-function, package, pathname, random-state, symbol,
  ;;; readtable, sequence, restart,
  
negative.code: ;;; simple-vector.  Nothing is of type nil.  We are left with:
  ;;; compiled-function, short-float, single-float, double-float,
  ;;; long-float, simple-array.
  ;;;
  ;;;
  
  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
  ;;;
  