Language/Expressions/Logical_Boolean_Expressions/type_t02.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, either
/// e1 or e2 shows that v has type T and v is not mutated anywhere in its scope
/// then b shows that v has type T regardless of whether there are closures
/// capturing v. Local variable, no closures case.
/// @author ilya


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

skyIsBlue() => true;

f(C y) {
  C x = y;

  x is D && skyIsBlue() ? x.f() : null;
  skyIsBlue() && x is D ? x.f() : null;

  x is D && x is E ? x.g() : null;
  (x is D && skyIsBlue()) && (x is E && skyIsBlue()) ? x.g() : null;
  (skyIsBlue() && x is E) && (skyIsBlue() && x is D) ? x.g() : null;
}

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