anchor.diff:    (cond
       (initial-element-p
        (once-only (vector)
  -       `(free-vector-if-error (,vector)
  +       `(free-vector-on-error (,vector)
             ,@(if (and (constantp element-type env)
                        (constantp initial-element env))
                   (check-initial-element (eval-constant element-type env) initial-element)
  
positive.code:   (declare (ignore length element-type))
    (cond
      (initial-element-p
       (free-vector-if-error (vector)
         (fill vector initial-element)))
      (initial-contents-p
       (free-vector-if-error (vector)
         (replace vector initial-contents))))
    vector)
  
  
negative.code:           ,vector)))
      (initial-contents-p
       (once-only (vector)
         `(free-vector-on-error (,vector)
            ,@(if (and (constantp length env)
                       (constantp initial-contents env))
                  (check-initial-contents length (eval-constant initial-contents env))
  