diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/closures/closure-pluseq.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/closures/closure-pluseq.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,31 @@
+actual = '';
+expected = '3,6,9,12,15,18,';
+
+function slice(a, b)
+{
+  //return { x: a + ':' + b };
+  return b;
+}
+
+function f()
+{
+  var length = 20;
+  var index = 0;
+
+  function get3() {
+    //appendToActual("get3 " + index);
+    if (length - index < 3)
+      return null;
+    return slice(index, index += 3);
+  }
+
+  var bytes = null;
+  while (bytes = get3()) {
+    appendToActual(bytes);
+  }
+}
+
+f();
+
+
+assertEq(actual, expected)