anchor.diff:    "True if WARNING is about an unused variable."
     #+sbcl
     (when (typep warning '(and warning simple-condition))     ; not really a simple-warning
  -    (let ((control (simple-condition-format-control warning)))
  +    (let ((control (format-control-string-or-nil warning)))
         (and (search "variable" control :test #'char-equal)
              (search "defined but never used" control :test #'char-equal)))))
   
  
positive.code: Returns two values: a boolean and a name symbol of the thing."
    #+sbcl
    (when (typep warning '(and warning simple-condition))     ; not really a simple-warning
      (let ((control (simple-condition-format-control warning))
            (args (simple-condition-format-arguments warning)))
        (cond ((equal control "undefined ~(~A~): ~S")
               (and (eq (first args) kind)
                    (values t (second args))))
              ((equal control "~W more use~:P of undefined ~(~A~) ~S")
  
negative.code:   (declare (ignorable note))
    #+sbcl
    (when (typep note 'sb-ext:compiler-note)
      (let ((control (format-control-string-or-nil note)))
        (and (or (search "could" control) (search "can" control))
             (search "not stack allocate" control)))))
  
  ;;;
  