Fix bug with re-scoping arrow function parameter initializers

test/mjsunit/regress/regress-622663.js

Index: test/mjsunit/regress/regress-622663.js
diff --git a/test/mjsunit/regress/regress-622663.js b/test/mjsunit/regress/regress-622663.js
new file mode 100644
index 0000000000000000000000000000000000000000..9606bd86fae0367c477af475c8a85823fe7e25fb
--- /dev/null
+++ b/test/mjsunit/regress/regress-622663.js
@@ -0,0 +1,14 @@
++// Copyright 2016 the V8 project authors. All rights reserved.
++// Use of this source code is governed by a BSD-style license that can be
++// found in the LICENSE file.
++
++// Flags: --no-lazy
+
+(function() {
+  try { (y = [...[]]) => {} } catch(_) {}  // will core dump, if not fixed
+})();
+
+(function() {
+  try { ((y = [...[]]) => {})(); } catch(_) {}  // will core dump, if not fixed,
+                                                // even without --no-lazy
+})();