Language/12_Expressions/20_Logical_Boolean_Expressions_A06_t31.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 A logical boolean expression b of the form e1 && e2 shows that a
 * variable v has type T if all of the following conditions hold:
 * - Either e1 shows that v has type T or e2 shows that v has type T.
 * - v is a local variable or formal parameter.
 * - The variable v is not mutated in e2 or within a closure.
 * Furthermore, if all of the following hold:
 * - e1 shows that v has type T .
 * - v is not mutated in either e1 , e2 or within a closure.
 * - If the variable v is accessed by a closure in e2 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 e2 .
 * @description Checks that if v is local variable or formal parameter, 
 * e1 shows that v has type T, v is not mutated in either e1, e2 or within a
 * closure, v is captured by a closure in e2, but v is potentially mutated
 * elsewhere in its scope,
 * then the type of v is not known to be T in e2. Formal parameter case.
 * @static-warning
 * @author ilya
 */
import "../../Utils/expect.dart";

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

skyIsBlue(_) => true;

f(C x) {
  var closure;
  x is D && skyIsBlue(closure = () => x.f() /*throws*/);

  x = new C();
  closure();
}

main() {
  Expect.throws(() => f(new D()));
}