Migrating another batch of tests to dart 2.

tests/language/closure_type_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.
-
-// Dart test for a closure result type test that cannot be eliminated at compile
-// time.
-
-library closure_type_test;
-
-import "package:expect/expect.dart";
-import 'dart:math' as math;
-
-class Math {
-  static
-  int // //# 01: static type warning
-      sqrt(x) => math.sqrt(x);
-}
-
-isCheckedMode() {
-  try {
-    var i = 1;
-    String s = i;
-    return false;
-  } catch (e) {
-    return true;
-  }
-}
-
-void test(int func(int value), int value) {
-  bool got_type_error = false;
-  try {
-    // Because of function subtyping rules, the static return type of a closure
-    // call cannot be relied upon for static type analysis. For example, a
-    // function returning dynamic (function 'root') can be assigned to a closure
-    // variable declared to return int (closure 'func') and may actually return
-    // a double at run-time.
-    // Therefore, eliminating the run-time type check would be wrong.
-    int x = func(value);
-    Expect.equals(value, x * x);
-  } on TypeError catch (error) {
-    got_type_error = true;
-  }
-  // Type error expected in checked mode only.
-  Expect.isTrue(got_type_error == isCheckedMode());
-}
-
-root(x) => Math.sqrt(x);
-
-main() => test(root, 4);