+ ,@(when (or prefixp per-line-prefix-p)
+ `((unless (typep ,(or prefix per-line-prefix) 'string)
+ (error 'type-error
+ :datum ,(or prefix per-line-prefix)
+ :expected-type 'string))))
+ ,@(when suffixp
+ `((unless (typep ,suffix 'string)
+ (error 'type-error
+ :datum ,suffix
+ :expected-type 'string))))