Language/Expressions/Type_Cast/evaluation_t01.dart

// Copyright (c) 2011, 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.

/**
 * @assertion Evaluation of the cast expression e as T proceeds as follows:
 * The expression e is evaluated to a value v.
 * Then, if T is malformed or deferred type, a dynamic error occurs.
 * Otherwise, if the interface of the class of v is a subtype of T, the cast
 * expression evaluates to v.
 * Otherwise, if v is null, the cast expression evaluates to v.
 * In all other cases, a CastError is thrown.
 * @description Checks that the type cast operator works as specified when the
 * type of v is a subtype of T.
 * @author rodionov
 */
import '../../../Utils/expect.dart';

abstract class I {}

class C implements I {
  C(this.x);
  int x;
}

main() {
  Expect.equals(1, 1 as int);
  Expect.equals(0, 0 as num);
  Expect.equals("foo", "foo" as String);
  Expect.equals("bar", "bar" as Pattern);

  var c = null;
  Expect.equals(null, c as num?);

  c = C(1);
  Expect.identical(c, c as I);

  Expect.throws(() { c = 1 as I; }, (e) => e is TypeError);
}