From 22363636965d2268340e797dfd22f63fc1e5ee58 Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Thu, 28 Feb 2013 10:03:41 -0700
Subject: [PATCH] fix bug in hashing shortcut for transparency

---
 collects/tests/racket/basic.rktl | 10 ++++++++++
 src/racket/src/struct.c          |  2 +-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/collects/tests/racket/basic.rktl b/collects/tests/racket/basic.rktl
index 39cfd2d63f..76571fcc5d 100644
--- a/collects/tests/racket/basic.rktl
+++ b/collects/tests/racket/basic.rktl
@@ -2562,6 +2562,16 @@
   (equal-hash-code ht)
   (equal-secondary-hash-code ht))
 
+;; Check that an equal hash code on an
+;;  mutable, opaque structure does not
+;;  see mutation.
+(let ()
+  (struct a (x [y #:mutable]))
+  (define an-a (a 1 2))
+  (define v (equal-hash-code an-a))
+  (set-a-y! an-a 8)
+  (test v equal-hash-code an-a))
+
 ;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;; Misc
 
diff --git a/src/racket/src/struct.c b/src/racket/src/struct.c
index b085de8a1d..ca985d53ba 100644
--- a/src/racket/src/struct.c
+++ b/src/racket/src/struct.c
@@ -3061,7 +3061,7 @@ int scheme_struct_is_transparent(Scheme_Object *s)
 
   stype = ((Scheme_Structure *)s)->stype;
 
-  for (p = stype->name_pos; p--; ) {
+  for (p = stype->name_pos + 1; p--; ) {
     if (SCHEME_TRUEP(stype->parent_types[p]->inspector))
       return 0;
   }