Language/Expressions/Identifier_Reference/static_type_t03.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 The static type of e is determined as follows:
 * • If d is a class, type alias or type parameter the static type of e is Type.
 * • If d is a local variable or formal parameter the static type of e is the
 *   type of the variable id, unless id is known to have some type T, in which
 *   case the static type of e is T, provided that T is more specic than any
 *   other type S such that v is known to have type S.
 * • If d is a static method, top-level function or local function the static
 *   type of e the function type defined by d.
 * • If d is the declaration of a static variable, static getter or static
 *   setter declared in class C, the static type of e the static type of the
 *   getter invocation C.id.
 * • If d is the declaration of a library variable, top-level getter or
 *   top-level setter, the static type of e is the static type of the top level
 *   getter invocation id.
 * • Otherwise, if e occurs inside a top level or static function (be it
 *   function, method, getter, or setter) or variable initializer, the static
 *   type of e is dynamic.
 * • Otherwise, the static type of e is the type of the property extraction
 *   this.id.
 * @description Checks that if d is a local variable or formal parameter, and
 * a type promotion is in effect, then the static type of e is the most
 * specific type that id is known to have.
 * @static-clean
 * @author ilya
 */

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

f1(C x) {
  x is D ? (x is E ? x.g() : x.f()) : null;
  x is D && x.f() == null && x is E && x.g() == null ? x.g() : null;
  x is D && x is E ? x.g() : null;
}

f2(C y) {
  C x = y;
  x is D ? (x is E ? x.g() : x.f()) : null;
  x is D && x.f() == null && x is E && x.g() == null ? x.g() : null;
  x is D && x is E ? x.g() : null;
}

main() {
  f1(new E());
  f2(new E());
}