anchor.diff:        (incf (lexical-variable-use-count tag))
         (pushnew *current-lambda* (lexical-variable-used-in tag))
         (make-instance 'ast-return-from
  +                     :optimize (optimize-qualities-in-environment env)
                        :target tag
                        :value (pass1-form result env)
                        :info tag))))
  
positive.code:         ((null (cddr form))
           (pass1-form (cadr form) env))
          (t (make-instance 'ast-progn
                            :forms (pass1-implicit-progn (rest form) env)))))
  
  ;; Turn PROGV into a call to %PROGV.
  
negative.code:     (if (eql declared-type 't)
          converted
          (make-instance 'ast-the
                         :optimize (optimize-qualities-in-environment env)
                         :type (sys.int::typeexpand declared-type env)
                         :value converted))))
  
  