anchor.diff:  }
   
   /// A widget that copies the appearance of another widget.
  +///
  +/// The other widget should be specified (via the [original] property) by
  +/// providing a [MimicableHandle] obtained from [MimicableState.startMimic].
   class Mimic extends StatelessWidget {
     /// Creates a widget that copies the appearance of another widget.
     Mimic({ Key key, this.original }) : super(key: key);
   
     /// A handle to the widget that this widget should copy.
  +  ///
  +  /// Obtained from [MimicableState.startMimic].
     final MimicableHandle original;
   
     @override
  
positive.code: 
    /// Start the mimicking process.
    ///
    /// The child of this object will no longer be built at this
    /// location in the tree. Instead, this widget will build a
    /// transparent placeholder with the same dimensions as the widget
    /// had when the mimicking process started.
    ///
    /// If you use startMimic(), it is your responsibility to do
    /// something with the returned [MimicableHandle]; typically,
    /// passing it to a [Mimic] widget. To mimic the child in the
    /// [Overlay], consider using [liftToOverlay()] instead.
    MimicableHandle startMimic() {
      assert(() {
        if (_placeholderSize != null) {
  
negative.code: import 'overlay.dart';
  
  /// An opaque reference to a widget that can be mimicked.
  ///
  /// Obtained from [MimicableState.startMimic].
  ///
  /// This handle should be passed to a [Mimic] widget via its [Mimic.original]
  /// property.
  class MimicableHandle {
    MimicableHandle._(this._state);
  
  