anchor.diff:    };
   }
   
  -/// Converts a serializable map into an [Asset].
  -Asset _deserializeAsset(Map asset) {
  -  return new Asset.fromStream(
  -      _deserializeId(asset['id']),
  -      _deserializeStream(asset['stream']));
  -}
  -
  -/// The body of a [StreamTransformer] that deserializes the values in a stream
  -/// sent by [_serializeStream].
  -StreamSubscription _deserializeTransformer(Stream input, bool cancelOnError) {
  -  var subscription;
  -  var transformed = input.transform(new StreamTransformer.fromHandlers(
  -      handleData: (data, sink) {
  -    if (data['type'] == 'data') {
  -      sink.add(data['data']);
  -    } else if (data['type'] == 'error') {
  -      sink.addError(CrossIsolateException.deserialize(data['error']));
  -    } else {
  -      assert(data['type'] == 'done');
  -      sink.close();
  -      subscription.cancel();
  -    }
  -  }));
  -  subscription = transformed.listen(null, cancelOnError: cancelOnError);
  -  return subscription;
  -}
  -
  -/// Convert a [SendPort] whose opposite is waiting to send us a stream into a
  -/// [Stream].
  -///
  -/// No stream data will actually be sent across the isolate boundary until
  -/// someone subscribes to the returned stream.
  -Stream _deserializeStream(SendPort sendPort) {
  -  return callbackStream(() {
  -    var receivePort = new ReceivePort();
  -    sendPort.send(receivePort.sendPort);
  -    return receivePort.transform(
  -        const StreamTransformer(_deserializeTransformer));
  -  });
  -}
  -
   /// Converts a serializable map into an [AssetId].
   AssetId _deserializeId(Map id) => new AssetId(id['package'], id['path']);
  -
  -/// Converts [asset] into a serializable map.
  -Map _serializeAsset(Asset asset) {
  -  return {
  -    'id': _serializeId(asset.id),
  -    'stream': _serializeStream(asset.read())
  -  };
  -}
  -
  -/// Converts [stream] into a [SendPort] with which another isolate can request
  -/// the data from [stream].
  -SendPort _serializeStream(Stream stream) {
  -  var receivePort = new ReceivePort();
  -  receivePort.first.then((sendPort) {
  -    stream.listen((data) => sendPort.send({'type': 'data', 'data': data}),
  -        onDone: () => sendPort.send({'type': 'done'}),
  -        onError: (error, stackTrace) {
  -      sendPort.send({
  -        'type': 'error',
  -        'error': CrossIsolateException.serialize(error, stackTrace)
  -      });
  -    });
  -  });
  -
  -  return receivePort.sendPort;
  -}
   
   /// Converts [id] into a serializable map.
   Map _serializeId(AssetId id) => {'package': id.package, 'path': id.path};
  
positive.code: import 'dart:isolate';
  
  import 'package:barback/barback.dart';
  import 'package:source_maps/source_maps.dart';
  
  import '../barback.dart';
  
negative.code: 
    return {
      'port': receivePort.sendPort,
      'primaryInput': serializeAsset(transform.primaryInput)
    };
  }
  
  /// Converts a serializable map into an [AssetId].
  