Migrating a block of dart 1 tests to dart 2

tests/language_2/closure3_test.dart

 // Copyright (c) 2012, 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.
 
 import "package:expect/expect.dart";
 
 // Test that a NoSuchMethodError is thrown even when an expression
 // seems to be free of side-effects.
 
 test(x, y) {
   (() {
     x - y;
   })();
 }
 
 main() {
   Expect.throws(() {
     test(null, 2);
   }, (e) => e is NoSuchMethodError);
 }