Language/Statements/If/type_t06.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 An if statement of the form if (b) s1 else s2.
 * If:
 * • b shows that a variable v has type T .
 * • v is not potentially mutated in s1 or within a closure.
 * • If the variable v is accessed by a closure in s1 then the variable v is
 *   not potentially mutated anywhere in the scope of v.
 * Then the type of v is known to be T in s1.
 * @description Checks that if b does not show that v has any type T, then the
 * type of v is not known to be any promoted type in s1.
 * @compile-error
 * @author ilya
 */

class C {}
class D extends C {
  f() {}
}
class E extends C {
  f() {}
}

f(C x) {
  if (x is D || x is E)
    x.f();
}

main() {
  f(new D());
}