Stop mapping indexOf/lastIndexOf directly to the JavaScript native on indexable primitives.

tests/corelib/list_test.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 class ListTest {
 
   static testMain() {
     testList();
     testExpandableList();
   }
@@ skipping 47 matching lines @@
     expectValues(list, 4, val, null, null);
     double d = 2.0;
     list[3] = d;
     expectValues(list, 4, val, null, d);
 
     for (int i = 0; i < list.length; i++) {
       list[i] = i;
     }
 
     for (int i = 0; i < 4; i++) {
-      Expect.equals(list[i], i);
+      Expect.equals(i, list[i]);
+      Expect.equals(i, list.indexOf(i));
+      Expect.equals(i, list.lastIndexOf(i));
     }
 
+    Expect.equals(-1, list.indexOf(100));
+    Expect.equals(-1, list.lastIndexOf(100));
+    list[2] = new Yes();
+    Expect.equals(2, list.indexOf(100));
+    Expect.equals(2, list.lastIndexOf(100));
+    list[3] = new Yes();
+    Expect.equals(2, list.indexOf(100));
+    Expect.equals(3, list.lastIndexOf(100));
+    list[2] = 2;
+    Expect.equals(3, list.indexOf(100));
+    Expect.equals(3, list.lastIndexOf(100));
+    list[3] = 3;
+    Expect.equals(-1, list.indexOf(100));
+    Expect.equals(-1, list.lastIndexOf(100));
+
     testClosures(list);
 
     var exception = null;
     try {
       list.clear();
     } catch (UnsupportedOperationException e) {
       exception = e;
     }
     Expect.equals(true, exception != null);
   }
 
   static void testExpandableList() {
     List list = new List();
     Expect.equals(true, list.isEmpty());
     Expect.equals(list.length, 0);
     list.add(4);
     Expect.equals(1, list.length);
     Expect.equals(true, !list.isEmpty());
     Expect.equals(list.length, 1);
     Expect.equals(list.length, 1);
     Expect.equals(list.removeLast(), 4);
 
     for (int i = 0; i < 10; i++) {
       list.add(i);
     }
 
     Expect.equals(list.length, 10);
     for (int i = 0; i < 10; i++) {
-      Expect.equals(list[i], i);
+      Expect.equals(i, list[i]);
+      Expect.equals(i, list.indexOf(i));
+      Expect.equals(i, list.lastIndexOf(i));
     }
 
+    Expect.equals(-1, list.indexOf(100));
+    Expect.equals(-1, list.lastIndexOf(100));
+    list[2] = new Yes();
+    Expect.equals(2, list.indexOf(100));
+    Expect.equals(2, list.lastIndexOf(100));
+    list[3] = new Yes();
+    Expect.equals(2, list.indexOf(100));
+    Expect.equals(3, list.lastIndexOf(100));
+    list[2] = 2;
+    Expect.equals(3, list.indexOf(100));
+    Expect.equals(3, list.lastIndexOf(100));
+    list[3] = 3;
+    Expect.equals(-1, list.indexOf(100));
+    Expect.equals(-1, list.lastIndexOf(100));
+
     testClosures(list);
 
     Expect.equals(list.removeLast(), 9);
     list.clear();
     Expect.equals(list.length, 0);
     Expect.equals(list.length, 0);
     Expect.equals(true, list.isEmpty());
   }
 }
 
+class Yes {
+  operator ==(var other) => true;
+}
+
 main() {
   ListTest.testMain();
 }