From fed14e1ce16ae24a99701012f5d26f1078bbab5e Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Tue, 15 Jul 2014 07:59:59 +0100
Subject: [PATCH] prop:evt: support chaperone when extracting field

Thanks to Sam for noticing this problem.
---
 .../racket-test/tests/racket/chaperone.rktl          | 12 ++++++++++++
 racket/src/racket/src/struct.c                       |  2 +-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/pkgs/racket-pkgs/racket-test/tests/racket/chaperone.rktl b/pkgs/racket-pkgs/racket-test/tests/racket/chaperone.rktl
index 7ac468e398..df57b03764 100644
--- a/pkgs/racket-pkgs/racket-test/tests/racket/chaperone.rktl
+++ b/pkgs/racket-pkgs/racket-test/tests/racket/chaperone.rktl
@@ -1258,6 +1258,18 @@
                             (set! checked? #t)
                             v)))
   (test #t values checked?))
+(let ()
+  (struct e (orig)
+    #:property prop:evt 0)
+  (define an-e (e always-evt))
+  (define checked? #f)
+  (test #t evt? an-e)
+  (sync (chaperone-struct an-e
+                          e-orig
+                          (lambda (self v)
+                            (set! checked? #t)
+                            v)))
+  (test #t values checked?))
 
 ;; ----------------------------------------
 ;; channel chaperones
diff --git a/racket/src/racket/src/struct.c b/racket/src/racket/src/struct.c
index ccb4c745ca..1e89f8c727 100644
--- a/racket/src/racket/src/struct.c
+++ b/racket/src/racket/src/struct.c
@@ -1521,7 +1521,7 @@ static int evt_struct_is_ready(Scheme_Object *o, Scheme_Schedule_Info *sinfo)
   }
 
   if (SCHEME_INTP(v))
-    v = ((Scheme_Structure *)o)->slots[SCHEME_INT_VAL(v)];
+    v = scheme_struct_ref(o, SCHEME_INT_VAL(v));
 
   if (scheme_is_evt(v)) {
     scheme_set_sync_target(sinfo, v, NULL, NULL, 0, 1, NULL);