Fix language/duplicate_implements_test.

tests/language/duplicate_implements_test.dart

Index: tests/language/duplicate_implements_test.dart
diff --git a/tests/language/duplicate_implements_test.dart b/tests/language/duplicate_implements_test.dart
index 5baf45f9d91e2c8c2d584a7c69c5e006d0a4499f..e9ff103dcfa786055cd5231e53399cd54403bd2a 100644
--- a/tests/language/duplicate_implements_test.dart
+++ b/tests/language/duplicate_implements_test.dart
@@ -15,5 +15,8 @@ abstract class Z implements I, J, J { }              /// 03: compile-time error
 abstract class Z implements K<int>, K<int> { }       /// 04: compile-time error
 
 main() {
-  return null;
+  X x = new X();  /// 01: continued
+  X x = new X();  /// 02: continued
+  Z z = new Z();  /// 03: continued
+  Z z = new Z();  /// 04: continued
 }