Migrate test block 113 to Dart 2.0.

tests/language_2/generic_field_mixin6_test.dart

 // Copyright (c) 2014, 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 that generic types in mixins are handled.
 
 import 'package:expect/expect.dart';
 
 class M<T> {
-  var field = () {
-    return T;
-  }();
+  T field1 = 0; //# 01: compile-time error
+  T field2 = 0 as dynamic;
 }
 
 class A<U> {}
 
 class C1<V> = Object with M<V>;
 class C2 = Object with M<int>;
 class C3 = Object with M<String>;
 
 main() {
-  Expect.equals(int, new C1<int>().field);
-  Expect.equals(String, new C1<String>().field);
+  // no error: 0 is an int
+  new C1<int>();
+  new C2();
 
-  Expect.equals(int, new C2().field);
-
-  Expect.equals(String, new C3().field);
+  // type error: 0 is not a string
+  Expect.throws(() {
+    new C1<String>();
+  }, (e) => e is TypeError);
+  Expect.throws(() {
+    new C3();
+  }, (e) => e is TypeError);
 }