add a constructor arity test

Closes #2390

pkgs/racket-test-core/tests/racket/struct.rktl

@@ -1253,6 +1253,20 @@
   (test 'nope g 5 (lambda () 'nope))
   (test 'nope g struct:arity-at-least (lambda () 'nope)))
 
+;; ----------------------------------------
+;; Make sure an indirect struct constructor reports
+;; the right arity when there are more than 6 fields
+
+(let ()
+  (struct b (case-sensitive 
+             printing-style 
+             fraction-style
+             show-sharing
+             insert-newlines
+             annotations))
+  (struct a (x y) #:super struct:b)
+  (test 8 procedure-arity a))
+
 ;; ----------------------------------------
 
 (report-errs)