diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/arrow-functions/precedence-4.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/arrow-functions/precedence-4.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,6 @@
+// Funny case that looks kind of like default arguments isn't.
+
+var f = (msg='hi', w=window => w.alert(a, b));  // sequence expression
+assertEq(msg, 'hi');
+assertEq(typeof w, 'function');
+assertEq(f, w);