Support 'implements' clause on typedef mixin applications.

tests/language/mixin_implements_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.
+
+abstract class I0 {
+  foo();
+}
+
+abstract class I1 {
+  bar();
+}
+
+abstract class I2 implements I0, I1 {
+}
+
+class M {
+  foo() => 42;
+  bar() => 87;
+}
+
+typedef C0 = Object with M;
+typedef C1 = Object with M implements I0;
+typedef C2 = Object with M implements I1;
+typedef C3 = Object with M implements I0, I1;
+typedef C4 = Object with M implements I1, I0;
+typedef C5 = Object with M implements I2;
+
+main() {
+  var c0 = new C0();
+  Expect.equals(42, c0.foo());
+  Expect.equals(87, c0.bar());
+  Expect.isTrue(c0 is M);
+  Expect.isFalse(c0 is I0);
+  Expect.isFalse(c0 is I1);
+  Expect.isFalse(c0 is I2);
+
+  var c1 = new C1();
+  Expect.equals(42, c1.foo());
+  Expect.equals(87, c1.bar());
+  Expect.isTrue(c1 is M);
+  Expect.isTrue(c1 is I0);
+  Expect.isFalse(c1 is I1);
+  Expect.isFalse(c1 is I2);
+
+  var c2 = new C2();
+  Expect.equals(42, c2.foo());
+  Expect.equals(87, c2.bar());
+  Expect.isTrue(c2 is M);
+  Expect.isFalse(c2 is I0);
+  Expect.isTrue(c2 is I1);
+  Expect.isFalse(c1 is I2);
+
+  var c3 = new C3();
+  Expect.equals(42, c3.foo());
+  Expect.equals(87, c3.bar());
+  Expect.isTrue(c3 is M);
+  Expect.isTrue(c3 is I0);
+  Expect.isTrue(c3 is I1);
+  Expect.isFalse(c1 is I2);
+
+  var c4 = new C4();
+  Expect.equals(42, c4.foo());
+  Expect.equals(87, c4.bar());
+  Expect.isTrue(c4 is M);
+  Expect.isTrue(c4 is I0);
+  Expect.isTrue(c4 is I1);
+  Expect.isFalse(c1 is I2);
+
+  var c5 = new C5();
+  Expect.equals(42, c5.foo());
+  Expect.equals(87, c5.bar());
+  Expect.isTrue(c5 is M);
+  Expect.isTrue(c5 is I0);
+  Expect.isTrue(c5 is I1);
+  Expect.isTrue(c5 is I2);
+}