fix propertyIsEnumerable when using an index to access string; closes #…

…582

src/org/mozilla/javascript/NativeString.java

@@ -574,6 +574,18 @@ public boolean has(int index, Scriptable start) {
         return super.has(index, start);
     }
 
+    @Override
+    public int getAttributes(int index) {
+        if (0 <= index && index < string.length()) {
+          int attribs = READONLY | PERMANENT;
+          if (Context.getContext().getLanguageVersion() < Context.VERSION_ES6) {
+              attribs |= DONTENUM;
+          }
+          return attribs;
+        }
+        return super.getAttributes(index);
+    }
+
     @Override
     protected Object[] getIds(boolean nonEnumerable, boolean getSymbols)
     {

testsrc/jstests/es6/string.js

@@ -0,0 +1,13 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+load("testsrc/assert.js");
+
+(function TestIsEnumerable() {
+  var obj = new Object("z");
+
+  assertTrue(obj.propertyIsEnumerable('0'));
+})();
+
+"success";

testsrc/org/mozilla/javascript/tests/es6/NativeStringTest.java

@@ -0,0 +1,16 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package org.mozilla.javascript.tests.es6;
+
+import org.mozilla.javascript.Context;
+import org.mozilla.javascript.drivers.LanguageVersion;
+import org.mozilla.javascript.drivers.RhinoTest;
+import org.mozilla.javascript.drivers.ScriptTestsBase;
+
+@RhinoTest("testsrc/jstests/es6/string.js")
+@LanguageVersion(Context.VERSION_ES6)
+public class NativeStringTest extends ScriptTestsBase
+{
+}