Test for PR 10946.

original commit: 0e3c2b71cc827236f4695e0271b869c416489557

collects/tests/typed-scheme/succeed/poly-struct-union.rkt

@@ -0,0 +1,31 @@
+
+#lang racket/load
+
+
+(module test typed/racket
+
+
+ (provide a:list-helper)
+
+ (define-type (Append-List+ elem) (U (a:singleton elem) (a:join elem)))
+
+ (define-struct: (elem) a:join
+   ((left : (Append-List+ elem)) (right : (Append-List+ elem)))
+   #:transparent)
+
+ (define-struct: (elem) a:singleton
+   ((elem : elem)) #:transparent)
+
+ (: a:list-helper (All (elem) ((Pair elem (Listof elem)) -> (Append-List+ elem))))
+ (define (a:list-helper elems)
+   (cond
+     ((empty? (cdr elems)) (make-a:singleton (car elems)))
+     (else (make-a:join (make-a:singleton (car elems))
+                        (a:list-helper (cdr elems))))))
+ )
+
+(module test2 racket
+ (require 'test)
+ (a:list-helper (list 1 2)))
+
+(require 'test2)