Migrate language/arithmetic2_test ... language/async_await_syntax_test.

tests/language/assign_to_type_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.
-
-// Verify that an attempt to assign to a class, enum, typedef, or type
-// parameter produces a static warning and runtime error.
-
-import "package:expect/expect.dart";
-
-noMethod(e) => e is NoSuchMethodError;
-
-class C<T> {
-  f() {
-    Expect.throws(() => T = null, noMethod); //# 01: static type warning
-  }
-}
-
-class D {}
-
-enum E { e0 }
-
-typedef void F();
-
-main() {
-  new C<D>().f();
-  Expect.throws(() => D = null, noMethod); //# 02: static type warning
-  Expect.throws(() => E = null, noMethod); //# 03: static type warning
-  Expect.throws(() => F = null, noMethod); //# 04: static type warning
-}