diff -r 000000000000 -r 6474c204b198 js/src/tests/js1_7/extensions/regress-346021.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/tests/js1_7/extensions/regress-346021.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,45 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//-----------------------------------------------------------------------------
+var BUGNUMBER = 346021;
+var summary = 'Implementing __iterator__ as generator';
+var actual = '';
+var expect = '';
+
+
+//-----------------------------------------------------------------------------
+test();
+//-----------------------------------------------------------------------------
+
+function test()
+{
+  enterFunc ('test');
+  printBugNumber(BUGNUMBER);
+  printStatus (summary);
+ 
+  var o = { __iterator__: function () { print(12); yield 42; } };
+
+  expect = 42;
+  actual = 0;
+ 
+  for (let i in Iterator(o))
+  {
+    actual = i;
+  }
+
+  reportCompare(expect, actual, summary);
+
+  actual = 0;
+
+  for (let i in o)
+  {
+    actual = i; // this doesn't iterate 42
+  }
+
+  reportCompare(expect, actual, summary);
+
+  exitFunc ('test');
+}