Implement complex super assignment.

tests/language/super_operator_index6_test.dart

+// Copyright (c) 2013, 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.
+
+// Test for unresolved super[].
+
+class A {
+  var indexField = new List(2);
+  operator[]=(index, value) { indexField[index] = value; }
+
+  noSuchMethod(InvocationMirror im) {
+    if (im.memberName == '[]') {
+      Expect.equals(1, im.positionalArguments.length);
+      return indexField[im.positionalArguments[0]];
+    } else {
+      Expect.fail('Should not reach here');
+    }
+  }
+}
+
+class B extends A {
+  test() {
+    Expect.equals(42, super[0] = 42);
+    Expect.equals(42, super[0]);
+    Expect.equals(43, super[0] += 1);
+    Expect.equals(43, super[0]);
+    Expect.equals(43, super[0]++);
+    Expect.equals(44, super[0]);
+
+    Expect.equals(2, super[0] = 2);
+    Expect.equals(2, super[0]);
+    Expect.equals(3, super[0] += 1);
+    Expect.equals(3, super[0]);
+    Expect.equals(3, super[0]++);
+    Expect.equals(4, super[0]);
+  }
+}
+
+main() {
+  new B().test();
+}