anchor.diff:     ;;; walker
      ;;;
      #:form
  +   #:walk-ast
      #:walk-form
      #:unwalk-form
      #:unwalk-forms
  
positive.code:    #:tag
     #:target-block-of
     #:jump-target-of
     #:then
     ;;#:type-of
     #:value-of
     #:values-form
     #:variable-name-of
     #:vars-form
  
     ))
  
negative.code:    #:keyword-function-argument-form
     #:allow-other-keys-function-argument-form
     #:rest-function-argument-form
  
     #:block-form
     #:return-from-form
     #:catch-form
  