diff -r 000000000000 -r 6474c204b198 js/src/tests/js1_8_5/extensions/regress-627859.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/tests/js1_8_5/extensions/regress-627859.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,23 @@
+// -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+// Any copyright is dedicated to the Public Domain.
+// http://creativecommons.org/licenses/publicdomain/
+
+var x = 42;
+function a() { 
+    var x;
+    function b() {
+        x = 43;
+        // When jsparse.cpp's CompExprTransplanter transplants the
+        // comprehension expression 'x' into the scope of the 'for' loop,
+        // it must not bring the placeholder definition node for the
+        // assignment to x above along with it. If it does, x won't appear
+        // in b's lexdeps, we'll never find out that the assignment refers
+        // to a's x, and we'll generate an assignment to the global x.
+        (x for (x in []));
+    }
+    b();
+}
+a();
+assertEq(x, 42);
+
+reportCompare(true, true);