Fix redefining of attributes on aliased arguments.

test/mjsunit/object-define-property.js

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1035 matching lines @@
   { enumerable : false, configurable : false },
   { get: undefined, set: setter1, enumerable : false, configurable : false });
 
 
 // Regression test: Ensure that growing dictionaries are not ignored.
 o = {};
 for (var i = 0; i < 1000; i++) {
   // Non-enumerable property forces dictionary mode.
   Object.defineProperty(o, i, {value: i, enumerable: false});
 }
-assertEquals(999, o[999]);
+assertEquals(999, o[999]);
+
+
+// Regression test: Bizzare behavior on non-strict arguments object.
+(function test(arg0) {
+  // Here arguments[0] is a fast alias on arg0.
+  Object.defineProperty(arguments, "0", {
+    value:1,
+    enumerable:false
+  });
+  // Here arguments[0] is a slow alias on arg0.
+  Object.defineProperty(arguments, "0", {
+    value:2,
+    writable:false
+  });
+  // Here arguments[0] is no alias at all.
+  Object.defineProperty(arguments, "0", {
+    value:3
+  });
+  assertEquals(2, arg0);
+  assertEquals(3, arguments[0]);
+})(0);