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pkg/dev_compiler/tool/input_sdk/lib/core/expando.dart

-// Copyright (c) 2012, 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.
-
-part of dart.core;
-
-/**
- * An [Expando] allows adding new properties to objects.
- *
- * Does not work on numbers, strings, booleans or null.
- *
- * An `Expando` does not hold on to the added property value after an object
- * becomes inacessible.
- *
- * Since you can always create a new number that is identical to an existing
- * number, it means that an expando property on a number could never be
- * released. To avoid this, expando properties cannot be added to numbers.
- * The same argument applies to strings, booleans and null, which also have
- * literals that evaluate to identical values when they occur more than once.
- *
- * There is no restriction on other classes, even for compile time constant
- * objects. Be careful if adding expando properties to compile time constants,
- * since they will stay alive forever.
- */
-class Expando<T> {
-
-  /**
-   * The name of the this [Expando] as passed to the constructor. If
-   * no name was passed to the constructor, the name is [:null:].
-   */
-  final String name;
-
-  /**
-   * Creates a new [Expando]. The optional name is only used for
-   * debugging purposes and creating two different [Expando]s with the
-   * same name yields two [Expando]s that work on different properties
-   * of the objects they are used on.
-   */
-  external Expando([String name]);
-
-  /**
-   * Expando toString method override.
-   */
-  String toString() => "Expando:$name";
-
-  /**
-   * Gets the value of this [Expando]'s property on the given
-   * object. If the object hasn't been expanded, the method returns
-   * [:null:].
-   *
-   * The object must not be a number, a string, a boolean or null.
-   */
-  external T operator [](Object object);
-
-  /**
-   * Sets the value of this [Expando]'s property on the given
-   * object. Properties can effectively be removed again by setting
-   * their value to null.
-   *
-   * The object must not be a number, a string, a boolean or null.
-   */
-  external void operator []=(Object object, T value);
-
-}