diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/arrow-functions/associativity-3.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/arrow-functions/associativity-3.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,5 @@
+// Arrow right-associativity with +=
+
+var s = "";
+s += x => x.name;
+assertEq(s, "x => x.name");