+ ;; ANSI does not explicitly say that an error should
+ ;; be signalled, but the @ modifier is not explicitly
+ ;; allowed for ~> either.
+ (when (format-directive-atsignp close)
+ (error 'format-error
+ :complaint "@ modifier not allowed in close ~
+ directive of justification ~
+ block (i.e. ~~<...~~@>."
+ :offset (1- (format-directive-end close))
+ :references (list '(:ansi-cl :section (22 3 6 2)))))