Migrate test block 9 to Dart 2.0

tests/corelib_strong/hash_set_type_check_test.dart

-// Copyright (c) 2015, 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.
-
-// Tests of hash set type checking.
-
-library hash_set_type_check_test;
-
-import "package:expect/expect.dart";
-import 'dart:collection';
-
-testSet(Set<String> newSet()) {
-  Set<String> s = newSet();
-  Expect.throws(() => s.add(1), (e) => e is Error);
-  Expect.isNull(s.lookup(1));
-}
-
-void testIdentitySet(Set create()) {
-  Set<String> s = create();
-  Expect.throws(() => s.add(1), (e) => e is Error);
-  Expect.isNull(s.lookup(1));
-}
-
-bool get inCheckedMode {
-  try {
-    var i = 1;
-    String j = i;
-  } catch (_) {
-    return true;
-  }
-  return false;
-}
-
-void main() {
-  if (!inCheckedMode) return;
-
-  testSet(() => new Set<String>());
-  testSet(() => new HashSet<String>());
-  testSet(() => new LinkedHashSet<String>());
-  testIdentitySet(() => new Set<String>.identity());
-  testIdentitySet(() => new HashSet<String>.identity());
-  testIdentitySet(() => new LinkedHashSet<String>.identity());
-  testIdentitySet(() => new HashSet<String>(
-      equals: (x, y) => identical(x, y), hashCode: (x) => identityHashCode(x)));
-  testIdentitySet(() => new LinkedHashSet<String>(
-      equals: (x, y) => identical(x, y), hashCode: (x) => identityHashCode(x)));
-}