anchor.diff:    
   (defmethod convert-compound
       ((symbol (eql 'setq)) form environment)
  -  (check-special-form-proper-list form)
  +  (sicl-code-utilities:check-form-proper-list form)
     (unless (oddp (length form))
       (error 'setq-must-have-even-number-of-arguments
   	   :expr form))
  
positive.code: (defclass go-ast (ast)
    ((%binding :initarg :binding :reader binding)))
  
  (define-condition go-must-have-exactly-one-argument
      (compilation-program-error)
    ())
  
  (defmethod convert-compound
      ((symbol (eql 'go)) form environment)
    (check-special-form-proper-list form)
    (unless (= (length form) 2)
      (error 'go-must-have-exactly-one-argument
  	   :expr form))
    (let ((binding (find-if (lambda (entry)
  			    (and (typep entry 'go-tag-entry)
  				 (eq (name entry) (cadr form))))
  
negative.code: 
  (defmethod convert-compound
      ((symbol (eql 'flet)) form environment)
    (sicl-code-utilities:check-form-proper-list form)
    (sicl-code-utilities:check-argcount form 1 nil)
    (unless (sicl-code-utilities:proper-list-p (cadr form))
      (error 'flet-functions-must-be-proper-list
  	   :expr form))
  