Mock up code completion.

dart/site/try/src/user_option.dart

+// Copyright (c) 2014, 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.
+
+library trydart.userOption;
+
+class UserOption {
+  final String name;
+
+  final bool isHidden;
+
+  static var storage;
+
+  const UserOption(this.name, {this.isHidden: false});
+
+  get value => storage[name];
+
+  void set value(newValue) {
+    storage[name] = newValue;
+  }
+}
+
+class BooleanUserOption extends UserOption {
+  const BooleanUserOption(String name, {bool isHidden: false})
+      : super(name, isHidden: isHidden);
+
+  bool get value => super.value == 'true';
+
+  void set value(bool newValue) {
+    super.value = '$newValue';
+  }
+}
+
+class StringUserOption extends UserOption {
+  const StringUserOption(String name, {bool isHidden: false})
+      : super(name, isHidden: isHidden);
+
+  String get value => super.value == null ? '' : super.value;
+
+  void set value(String newValue) {
+    super.value = newValue;
+  }
+}