Use destructuring assignments for named parameters (#180)

lib/runtime/dart/async.js

 dart_library.library('dart/async', null, /* Imports */[
   "dart/_runtime",
   'dart/core',
   'dart/_internal',
   'dart/collection'
 ], /* Lazy imports */[
   'dart/_isolate_helper'
 ], function(exports, dart, core, _internal, collection, _isolate_helper) {
   'use strict';
   let dartx = dart.dartx;
@@ skipping 124 matching lines @@
             timer = null;
           })});
         return controller.stream;
       }
       static eventTransformed(source, mapSink) {
         return new (_BoundSinkStream$(dart.dynamic, T))(source, dart.as(mapSink, _SinkMapper));
       }
       get isBroadcast() {
         return false;
       }
-      asBroadcastStream(opts) {
-        let onListen = opts && 'onListen' in opts ? opts.onListen : null;
+      asBroadcastStream({onListen = null, onCancel = null} = {}) {
         dart.as(onListen, dart.functionType(dart.void, [StreamSubscription$(T)]));
-        let onCancel = opts && 'onCancel' in opts ? opts.onCancel : null;
         dart.as(onCancel, dart.functionType(dart.void, [StreamSubscription$(T)]));
         return new (_AsBroadcastStream$(T))(this, dart.as(onListen, __CastType12), dart.as(onCancel, dart.functionType(dart.void, [StreamSubscription])));
       }
       where(test) {
         dart.as(test, dart.functionType(core.bool, [T]));
         return new (_WhereStream$(T))(this, test);
       }
       map(convert) {
         dart.as(convert, dart.functionType(dart.dynamic, [T]));
         return new (_MapStream$(T, dart.dynamic))(this, convert);
@@ skipping 75 matching lines @@
           controller = StreamController.new({onListen: onListen, onPause: dart.fn(() => {
               subscription.pause();
             }), onResume: dart.fn(() => {
               subscription.resume();
             }), onCancel: dart.fn(() => {
               subscription.cancel();
             }), sync: true});
         }
         return controller.stream;
       }
-      handleError(onError, opts) {
-        let test = opts && 'test' in opts ? opts.test : null;
+      handleError(onError, {test = null} = {}) {
         dart.as(test, dart.functionType(core.bool, [dart.dynamic]));
         return new (_HandleErrorStream$(T))(this, onError, test);
       }
       expand(convert) {
         dart.as(convert, dart.functionType(core.Iterable, [T]));
         return new (_ExpandStream$(T, dart.dynamic))(this, convert);
       }
       pipe(streamConsumer) {
         dart.as(streamConsumer, StreamConsumer$(T));
         return streamConsumer.addStream(this).then(dart.fn(_ => streamConsumer.close(), Future, [dart.dynamic]));
@@ skipping 273 matching lines @@
             try {
               dart.throw(_internal.IterableElementError.noElement());
             } catch (e) {
               let s = dart.stackTrace(e);
               _completeWithErrorCallback(future, e, s);
             }
 
           }), cancelOnError: true});
         return future;
       }
-      firstWhere(test, opts) {
+      firstWhere(test, {defaultValue = null} = {}) {
         dart.as(test, dart.functionType(core.bool, [T]));
-        let defaultValue = opts && 'defaultValue' in opts ? opts.defaultValue : null;
         dart.as(defaultValue, dart.functionType(core.Object, []));
         let future = new _Future();
         let subscription = null;
         subscription = this.listen(dart.fn(value => {
           dart.as(value, T);
           _runUserCode(dart.fn(() => test(value), core.bool, []), dart.fn(isMatch => {
             if (dart.notNull(isMatch)) {
               _cancelAndValue(subscription, future, value);
             }
           }, dart.dynamic, [core.bool]), dart.as(_cancelAndErrorClosure(subscription, future), dart.functionType(dart.dynamic, [dart.dynamic, core.StackTrace])));
         }, dart.dynamic, [T]), {onError: dart.bind(future, _completeError), onDone: dart.fn(() => {
             if (defaultValue != null) {
               _runUserCode(defaultValue, dart.bind(future, _complete), dart.bind(future, _completeError));
               return;
             }
             try {
               dart.throw(_internal.IterableElementError.noElement());
             } catch (e) {
               let s = dart.stackTrace(e);
               _completeWithErrorCallback(future, e, s);
             }
 
           }), cancelOnError: true});
         return future;
       }
-      lastWhere(test, opts) {
+      lastWhere(test, {defaultValue = null} = {}) {
         dart.as(test, dart.functionType(core.bool, [T]));
-        let defaultValue = opts && 'defaultValue' in opts ? opts.defaultValue : null;
         dart.as(defaultValue, dart.functionType(core.Object, []));
         let future = new _Future();
         let result = null;
         let foundResult = false;
         let subscription = null;
         subscription = this.listen(dart.fn(value => {
           dart.as(value, T);
           _runUserCode(dart.fn(() => true == test(value), core.bool, []), dart.fn(isMatch => {
             if (dart.notNull(isMatch)) {
               foundResult = true;
@@ skipping 69 matching lines @@
           if (index == elementIndex) {
             _cancelAndValue(subscription, future, value);
             return;
           }
           elementIndex = dart.notNull(elementIndex) + 1;
         }, dart.dynamic, [T]), {onError: dart.bind(future, _completeError), onDone: dart.fn((() => {
             future[_completeError](core.RangeError.index(index, this, "index", null, elementIndex));
           }).bind(this)), cancelOnError: true});
         return future;
       }
-      timeout(timeLimit, opts) {
-        let onTimeout = opts && 'onTimeout' in opts ? opts.onTimeout : null;
+      timeout(timeLimit, {onTimeout = null} = {}) {
         dart.as(onTimeout, dart.functionType(dart.void, [EventSink]));
         let controller = null;
         let subscription = null;
         let timer = null;
         let zone = null;
         let timeout2 = null;
         function onData(event) {
           dart.as(event, T);
           timer.cancel();
           controller.add(event);
@@ skipping 92 matching lines @@
     return Stream;
   });
   let Stream = Stream$();
   const _createSubscription = Symbol('_createSubscription');
   const _onListen = Symbol('_onListen');
   const _StreamImpl$ = dart.generic(function(T) {
     class _StreamImpl extends Stream$(T) {
       _StreamImpl() {
         super.Stream();
       }
-      listen(onData, opts) {
+      listen(onData, {onError = null, onDone = null, cancelOnError = null} = {}) {
         dart.as(onData, dart.functionType(dart.void, [T]));
-        let onError = opts && 'onError' in opts ? opts.onError : null;
-        let onDone = opts && 'onDone' in opts ? opts.onDone : null;
         dart.as(onDone, dart.functionType(dart.void, []));
-        let cancelOnError = opts && 'cancelOnError' in opts ? opts.cancelOnError : null;
         cancelOnError = core.identical(true, cancelOnError);
         let subscription = this[_createSubscription](onData, onError, onDone, cancelOnError);
         this[_onListen](subscription);
         return dart.as(subscription, StreamSubscription$(T));
       }
       [_createSubscription](onData, onError, onDone, cancelOnError) {
         dart.as(onData, dart.functionType(dart.void, [T]));
         dart.as(onDone, dart.functionType(dart.void, []));
         return new (_BufferingStreamSubscription$(T))(onData, onError, onDone, cancelOnError);
       }
@@ skipping 658 matching lines @@
         if (!dart.notNull(this[_mayAddEvent]))
           dart.throw(this[_addEventError]());
         this[_state] = dart.notNull(this[_state]) | dart.notNull(_BroadcastStreamController$()._STATE_CLOSED);
         let doneFuture = this[_ensureDoneFuture]();
         this[_sendDone]();
         return doneFuture;
       }
       get done() {
         return this[_ensureDoneFuture]();
       }
-      addStream(stream, opts) {
+      addStream(stream, {cancelOnError = true} = {}) {
         dart.as(stream, Stream$(T));
-        let cancelOnError = opts && 'cancelOnError' in opts ? opts.cancelOnError : true;
         if (!dart.notNull(this[_mayAddEvent]))
           dart.throw(this[_addEventError]());
         this[_state] = dart.notNull(this[_state]) | dart.notNull(_BroadcastStreamController$()._STATE_ADDSTREAM);
         this[_addStreamState] = new (_AddStreamState$(T))(this, stream, cancelOnError);
         return this[_addStreamState].addStreamFuture;
       }
       [_add](data) {
         dart.as(data, T);
         this[_sendData](data);
       }
@@ skipping 300 matching lines @@
     });
     return _DoneSubscription;
   });
   let _DoneSubscription = _DoneSubscription$();
   const __CastType2$ = dart.generic(function(T) {
     const __CastType2 = dart.typedef('__CastType2', () => dart.functionType(dart.void, [_BufferingStreamSubscription$(T)]));
     return __CastType2;
   });
   let __CastType2 = __CastType2$();
   class DeferredLibrary extends core.Object {
-    DeferredLibrary(libraryName, opts) {
-      let uri = opts && 'uri' in opts ? opts.uri : null;
+    DeferredLibrary(libraryName, {uri = null} = {}) {
       this.libraryName = libraryName;
       this.uri = uri;
     }
     load() {
       dart.throw('DeferredLibrary not supported. ' + 'please use the `import "lib.dart" deferred as lib` syntax.');
     }
   }
   dart.setSignature(DeferredLibrary, {
     constructors: () => ({DeferredLibrary: [DeferredLibrary, [core.String], {uri: core.String}]}),
     methods: () => ({load: [Future$(core.Null), []]})
@@ skipping 77 matching lines @@
           try {
             result[_complete](computation == null ? null : computation());
           } catch (e) {
             let s = dart.stackTrace(e);
             _completeWithErrorCallback(result, e, s);
           }
 
         }));
         return dart.as(result, Future$(T));
       }
-      static wait(futures, opts) {
-        let eagerError = opts && 'eagerError' in opts ? opts.eagerError : false;
-        let cleanUp = opts && 'cleanUp' in opts ? opts.cleanUp : null;
+      static wait(futures, {eagerError = false, cleanUp = null} = {}) {
         dart.as(cleanUp, dart.functionType(dart.void, [dart.dynamic]));
         let result = new (_Future$(core.List))();
         let values = null;
         let remaining = 0;
         let error = null;
         let stackTrace = null;
         function handleError(theError, theStackTrace) {
           remaining = dart.notNull(remaining) - 1;
           if (values != null) {
             if (cleanUp != null) {
@@ skipping 368 matching lines @@
       }
       set [_isChained](value) {
         if (dart.notNull(value)) {
           dart.assert(!dart.notNull(this[_isComplete]));
           this[_state] = _Future$()._CHAINED;
         } else {
           dart.assert(this[_isChained]);
           this[_state] = _Future$()._INCOMPLETE;
         }
       }
-      then(f, opts) {
+      then(f, {onError = null} = {}) {
         dart.as(f, dart.functionType(dart.dynamic, [T]));
-        let onError = opts && 'onError' in opts ? opts.onError : null;
         let result = new (_Future$())();
         if (!dart.notNull(core.identical(result[_zone], _ROOT_ZONE))) {
           f = dart.as(result[_zone].registerUnaryCallback(f), __CastType6$(T));
           if (onError != null) {
             onError = _registerErrorHandler(onError, result[_zone]);
           }
         }
         this[_addListener](new _FutureListener.then(result, f, onError));
         return result;
       }
-      catchError(onError, opts) {
-        let test = opts && 'test' in opts ? opts.test : null;
+      catchError(onError, {test = null} = {}) {
         dart.as(test, dart.functionType(core.bool, [dart.dynamic]));
         let result = new (_Future$())();
         if (!dart.notNull(core.identical(result[_zone], _ROOT_ZONE))) {
           onError = _registerErrorHandler(onError, result[_zone]);
           if (test != null)
             test = dart.as(result[_zone].registerUnaryCallback(test), __CastType8);
         }
         this[_addListener](new _FutureListener.catchError(result, onError, test));
         return result;
       }
@@ skipping 299 matching lines @@
           listeners = result[_removeListeners]();
           if (dart.notNull(listenerHasValue)) {
             result[_setValue](listenerValueOrError);
           } else {
             let asyncError = dart.as(listenerValueOrError, AsyncError);
             result[_setErrorObject](asyncError);
           }
           source = result;
         }
       }
-      timeout(timeLimit, opts) {
-        let onTimeout = opts && 'onTimeout' in opts ? opts.onTimeout : null;
+      timeout(timeLimit, {onTimeout = null} = {}) {
         dart.as(onTimeout, dart.functionType(dart.dynamic, []));
         if (dart.notNull(this[_isComplete]))
           return new (_Future$()).immediate(this);
         let result = new (_Future$())();
         let timer = null;
         if (onTimeout == null) {
           timer = Timer.new(timeLimit, dart.fn(() => {
             result[_completeError](new TimeoutException("Future not completed", timeLimit));
           }));
         } else {
@@ skipping 235 matching lines @@
   const _stream = Symbol('_stream');
   const StreamView$ = dart.generic(function(T) {
     class StreamView extends Stream$(T) {
       StreamView(stream) {
         this[_stream] = stream;
         super.Stream();
       }
       get isBroadcast() {
         return this[_stream].isBroadcast;
       }
-      asBroadcastStream(opts) {
-        let onListen = opts && 'onListen' in opts ? opts.onListen : null;
+      asBroadcastStream({onListen = null, onCancel = null} = {}) {
         dart.as(onListen, dart.functionType(dart.void, [StreamSubscription$(T)]));
-        let onCancel = opts && 'onCancel' in opts ? opts.onCancel : null;
         dart.as(onCancel, dart.functionType(dart.void, [StreamSubscription$(T)]));
         return this[_stream].asBroadcastStream({onListen: onListen, onCancel: onCancel});
       }
-      listen(onData, opts) {
+      listen(onData, {onError = null, onDone = null, cancelOnError = null} = {}) {
         dart.as(onData, dart.functionType(dart.void, [T]));
-        let onError = opts && 'onError' in opts ? opts.onError : null;
-        let onDone = opts && 'onDone' in opts ? opts.onDone : null;
         dart.as(onDone, dart.functionType(dart.void, []));
-        let cancelOnError = opts && 'cancelOnError' in opts ? opts.cancelOnError : null;
         return this[_stream].listen(onData, {onError: onError, onDone: onDone, cancelOnError: cancelOnError});
       }
     }
     dart.setSignature(StreamView, {
       constructors: () => ({StreamView: [StreamView$(T), [Stream$(T)]]}),
       methods: () => ({
         asBroadcastStream: [Stream$(T), [], {onListen: dart.functionType(dart.void, [StreamSubscription$(T)]), onCancel: dart.functionType(dart.void, [StreamSubscription$(T)])}],
         listen: [StreamSubscription$(T), [dart.functionType(dart.void, [T])], {onError: core.Function, onDone: dart.functionType(dart.void, []), cancelOnError: core.bool}]
       })
     });
@@ skipping 70 matching lines @@
     });
     return _ControllerEventSinkWrapper;
   });
   let _ControllerEventSinkWrapper = _ControllerEventSinkWrapper$();
   const __CastType12 = dart.typedef('__CastType12', () => dart.functionType(dart.void, [StreamSubscription]));
   const __CastType14 = dart.typedef('__CastType14', () => dart.functionType(dart.dynamic, [dart.dynamic, core.StackTrace]));
   const __CastType17 = dart.typedef('__CastType17', () => dart.functionType(dart.void, []));
   const __CastType18 = dart.typedef('__CastType18', () => dart.functionType(dart.void, [EventSink]));
   const StreamController$ = dart.generic(function(T) {
     class StreamController extends core.Object {
-      static new(opts) {
-        let onListen = opts && 'onListen' in opts ? opts.onListen : null;
-        let onPause = opts && 'onPause' in opts ? opts.onPause : null;
-        let onResume = opts && 'onResume' in opts ? opts.onResume : null;
-        let onCancel = opts && 'onCancel' in opts ? opts.onCancel : null;
-        let sync = opts && 'sync' in opts ? opts.sync : false;
+      static new({onListen = null, onPause = null, onResume = null, onCancel = null, sync = false} = {}) {
         if (onListen == null && onPause == null && onResume == null && onCancel == null) {
           return dart.as(dart.notNull(sync) ? new _NoCallbackSyncStreamController() : new _NoCallbackAsyncStreamController(), StreamController$(T));
         }
         return dart.notNull(sync) ? new (_SyncStreamController$(T))(onListen, onPause, onResume, onCancel) : new (_AsyncStreamController$(T))(onListen, onPause, onResume, onCancel);
       }
-      static broadcast(opts) {
-        let onListen = opts && 'onListen' in opts ? opts.onListen : null;
-        let onCancel = opts && 'onCancel' in opts ? opts.onCancel : null;
-        let sync = opts && 'sync' in opts ? opts.sync : false;
+      static broadcast({onListen = null, onCancel = null, sync = false} = {}) {
         return dart.notNull(sync) ? new (_SyncBroadcastStreamController$(T))(onListen, onCancel) : new (_AsyncBroadcastStreamController$(T))(onListen, onCancel);
       }
     }
     StreamController[dart.implements] = () => [StreamSink$(T)];
     dart.setSignature(StreamController, {
       constructors: () => ({
         new: [StreamController$(T), [], {onListen: dart.functionType(dart.void, []), onPause: dart.functionType(dart.void, []), onResume: dart.functionType(dart.void, []), onCancel: dart.functionType(dart.dynamic, []), sync: core.bool}],
         broadcast: [StreamController$(T), [], {onListen: dart.functionType(dart.void, []), onCancel: dart.functionType(dart.void, []), sync: core.bool}]
       })
     });
@@ skipping 91 matching lines @@
         }
         return dart.as(this[_varData], _ControllerSubscription);
       }
       [_badEventState]() {
         if (dart.notNull(this.isClosed)) {
           return new core.StateError("Cannot add event after closing");
         }
         dart.assert(this[_isAddingStream]);
         return new core.StateError("Cannot add event while adding a stream");
       }
-      addStream(source, opts) {
+      addStream(source, {cancelOnError = true} = {}) {
         dart.as(source, Stream$(T));
-        let cancelOnError = opts && 'cancelOnError' in opts ? opts.cancelOnError : true;
         if (!dart.notNull(this[_mayAddEvent]))
           dart.throw(this[_badEventState]());
         if (dart.notNull(this[_isCanceled]))
           return new _Future.immediate(null);
         let addState = new _StreamControllerAddStreamState(this, this[_varData], source, cancelOnError);
         this[_varData] = addState;
         this[_state] = dart.notNull(this[_state]) | dart.notNull(_StreamController$()._STATE_ADDSTREAM);
         return addState.addStreamFuture;
       }
       get done() {
@@ skipping 299 matching lines @@
         this[_target].add(data);
       }
       addError(error, stackTrace) {
         if (stackTrace === void 0)
           stackTrace = null;
         this[_target].addError(error, stackTrace);
       }
       close() {
         return this[_target].close();
       }
-      addStream(source, opts) {
+      addStream(source, {cancelOnError = true} = {}) {
         dart.as(source, Stream$(T));
-        let cancelOnError = opts && 'cancelOnError' in opts ? opts.cancelOnError : true;
         return this[_target].addStream(source, {cancelOnError: cancelOnError});
       }
       get done() {
         return this[_target].done;
       }
     }
     _StreamSinkWrapper[dart.implements] = () => [StreamSink$(T)];
     dart.setSignature(_StreamSinkWrapper, {
       constructors: () => ({_StreamSinkWrapper: [_StreamSinkWrapper$(T), [StreamController]]}),
       methods: () => ({
@@ skipping 453 matching lines @@
         this[_onCancelHandler] = dart.as(Zone.current.registerUnaryCallback(onCancelHandler), _broadcastCallback);
         this[_zone] = Zone.current;
         this[_controller] = null;
         this[_subscription] = null;
         super.Stream();
         this[_controller] = new (_AsBroadcastStreamController$(T))(dart.bind(this, _onListen), dart.bind(this, _onCancel));
       }
       get isBroadcast() {
         return true;
       }
-      listen(onData, opts) {
+      listen(onData, {onError = null, onDone = null, cancelOnError = null} = {}) {
         dart.as(onData, dart.functionType(dart.void, [T]));
-        let onError = opts && 'onError' in opts ? opts.onError : null;
-        let onDone = opts && 'onDone' in opts ? opts.onDone : null;
         dart.as(onDone, dart.functionType(dart.void, []));
-        let cancelOnError = opts && 'cancelOnError' in opts ? opts.cancelOnError : null;
         if (this[_controller] == null || dart.notNull(this[_controller].isClosed)) {
           return new (_DoneStreamSubscription$(T))(onDone);
         }
         if (this[_subscription] == null) {
           this[_subscription] = this[_source].listen(dart.bind(this[_controller], 'add'), {onError: dart.bind(this[_controller], 'addError'), onDone: dart.bind(this[_controller], 'close')});
         }
         cancelOnError = core.identical(true, cancelOnError);
         return this[_controller][_subscribe](onData, onError, onDone, cancelOnError);
       }
       [_onCancel]() {
@@ skipping 297 matching lines @@
   const _handleDone = Symbol('_handleDone');
   const _ForwardingStream$ = dart.generic(function(S, T) {
     class _ForwardingStream extends Stream$(T) {
       _ForwardingStream(source) {
         this[_source] = source;
         super.Stream();
       }
       get isBroadcast() {
         return this[_source].isBroadcast;
       }
-      listen(onData, opts) {
+      listen(onData, {onError = null, onDone = null, cancelOnError = null} = {}) {
         dart.as(onData, dart.functionType(dart.void, [T]));
-        let onError = opts && 'onError' in opts ? opts.onError : null;
-        let onDone = opts && 'onDone' in opts ? opts.onDone : null;
         dart.as(onDone, dart.functionType(dart.void, []));
-        let cancelOnError = opts && 'cancelOnError' in opts ? opts.cancelOnError : null;
         cancelOnError = core.identical(true, cancelOnError);
         return this[_createSubscription](onData, onError, onDone, cancelOnError);
       }
       [_createSubscription](onData, onError, onDone, cancelOnError) {
         dart.as(onData, dart.functionType(dart.void, [T]));
         dart.as(onDone, dart.functionType(dart.void, []));
         return new (_ForwardingStreamSubscription$(S, T))(this, onData, onError, onDone, cancelOnError);
       }
       [_handleData](data, sink) {
         dart.as(data, S);
@@ skipping 568 matching lines @@
   const _BoundSinkStream$ = dart.generic(function(S, T) {
     class _BoundSinkStream extends Stream$(T) {
       get isBroadcast() {
         return this[_stream].isBroadcast;
       }
       _BoundSinkStream(stream, sinkMapper) {
         this[_stream] = stream;
         this[_sinkMapper] = sinkMapper;
         super.Stream();
       }
-      listen(onData, opts) {
+      listen(onData, {onError = null, onDone = null, cancelOnError = null} = {}) {
         dart.as(onData, dart.functionType(dart.void, [T]));
-        let onError = opts && 'onError' in opts ? opts.onError : null;
-        let onDone = opts && 'onDone' in opts ? opts.onDone : null;
         dart.as(onDone, dart.functionType(dart.void, []));
-        let cancelOnError = opts && 'cancelOnError' in opts ? opts.cancelOnError : null;
         cancelOnError = core.identical(true, cancelOnError);
         let subscription = new (_SinkTransformerStreamSubscription$(dart.dynamic, T))(this[_stream], dart.as(this[_sinkMapper], _SinkMapper), onData, onError, onDone, cancelOnError);
         return subscription;
       }
     }
     dart.setSignature(_BoundSinkStream, {
       constructors: () => ({_BoundSinkStream: [_BoundSinkStream$(S, T), [Stream$(S), _SinkMapper$(S, T)]]}),
       methods: () => ({listen: [StreamSubscription$(T), [dart.functionType(dart.void, [T])], {onError: core.Function, onDone: dart.functionType(dart.void, []), cancelOnError: core.bool}]})
     });
     return _BoundSinkStream;
@@ skipping 42 matching lines @@
         add: [dart.void, [S]],
         addError: [dart.void, [core.Object], [core.StackTrace]],
         close: [dart.void, []]
       })
     });
     return _HandlerEventSink;
   });
   let _HandlerEventSink = _HandlerEventSink$();
   const _StreamHandlerTransformer$ = dart.generic(function(S, T) {
     class _StreamHandlerTransformer extends _StreamSinkTransformer$(S, T) {
-      _StreamHandlerTransformer(opts) {
-        let handleData = opts && 'handleData' in opts ? opts.handleData : null;
-        let handleError = opts && 'handleError' in opts ? opts.handleError : null;
-        let handleDone = opts && 'handleDone' in opts ? opts.handleDone : null;
+      _StreamHandlerTransformer({handleData = null, handleError = null, handleDone = null} = {}) {
         super._StreamSinkTransformer(dart.as(dart.fn(outputSink => {
           dart.as(outputSink, EventSink$(T));
           if (handleData == null)
             handleData = dart.as(_StreamHandlerTransformer$()._defaultHandleData, __CastType27$(S, T));
           if (handleError == null)
             handleError = dart.as(_StreamHandlerTransformer$()._defaultHandleError, __CastType30$(T));
           if (handleDone == null)
             handleDone = _StreamHandlerTransformer$()._defaultHandleDone;
           return new (_HandlerEventSink$(S, T))(handleData, handleError, handleDone, outputSink);
         }, dart.dynamic, [EventSink$(T)]), _SinkMapper$(S, T)));
@@ skipping 49 matching lines @@
     return _StreamSubscriptionTransformer;
   });
   let _StreamSubscriptionTransformer = _StreamSubscriptionTransformer$();
   const _BoundSubscriptionStream$ = dart.generic(function(S, T) {
     class _BoundSubscriptionStream extends Stream$(T) {
       _BoundSubscriptionStream(stream, transformer) {
         this[_stream] = stream;
         this[_transformer] = transformer;
         super.Stream();
       }
-      listen(onData, opts) {
+      listen(onData, {onError = null, onDone = null, cancelOnError = null} = {}) {
         dart.as(onData, dart.functionType(dart.void, [T]));
-        let onError = opts && 'onError' in opts ? opts.onError : null;
-        let onDone = opts && 'onDone' in opts ? opts.onDone : null;
         dart.as(onDone, dart.functionType(dart.void, []));
-        let cancelOnError = opts && 'cancelOnError' in opts ? opts.cancelOnError : null;
         cancelOnError = core.identical(true, cancelOnError);
         let result = this[_transformer](this[_stream], cancelOnError);
         result.onData(onData);
         result.onError(onError);
         result.onDone(onDone);
         return result;
       }
     }
     dart.setSignature(_BoundSubscriptionStream, {
       constructors: () => ({_BoundSubscriptionStream: [_BoundSubscriptionStream$(S, T), [Stream$(S), _SubscriptionTransformer$(S, T)]]}),
@@ skipping 76 matching lines @@
       this.function = func;
     }
   }
   dart.setSignature(_ZoneFunction, {
     constructors: () => ({_ZoneFunction: [_ZoneFunction, [_Zone, core.Function]]})
   });
   class ZoneSpecification extends core.Object {
     static new(opts) {
       return new _ZoneSpecification(opts);
     }
-    static from(other, opts) {
-      let handleUncaughtError = opts && 'handleUncaughtError' in opts ? opts.handleUncaughtError : null;
-      let run = opts && 'run' in opts ? opts.run : null;
-      let runUnary = opts && 'runUnary' in opts ? opts.runUnary : null;
-      let runBinary = opts && 'runBinary' in opts ? opts.runBinary : null;
-      let registerCallback = opts && 'registerCallback' in opts ? opts.registerCallback : null;
-      let registerUnaryCallback = opts && 'registerUnaryCallback' in opts ? opts.registerUnaryCallback : null;
-      let registerBinaryCallback = opts && 'registerBinaryCallback' in opts ? opts.registerBinaryCallback : null;
-      let errorCallback = opts && 'errorCallback' in opts ? opts.errorCallback : null;
-      let scheduleMicrotask = opts && 'scheduleMicrotask' in opts ? opts.scheduleMicrotask : null;
-      let createTimer = opts && 'createTimer' in opts ? opts.createTimer : null;
-      let createPeriodicTimer = opts && 'createPeriodicTimer' in opts ? opts.createPeriodicTimer : null;
-      let print = opts && 'print' in opts ? opts.print : null;
-      let fork = opts && 'fork' in opts ? opts.fork : null;
+    static from(other, {handleUncaughtError = null, run = null, runUnary = null, runBinary = null, registerCallback = null, registerUnaryCallback = null, registerBinaryCallback = null, errorCallback = null, scheduleMicrotask = null, createTimer = null, createPeriodicTimer = null, print = null, fork = null} = {}) {
       return ZoneSpecification.new({handleUncaughtError: handleUncaughtError != null ? handleUncaughtError : other.handleUncaughtError, run: run != null ? run : other.run, runUnary: runUnary != null ? runUnary : other.runUnary, runBinary: runBinary != null ? runBinary : other.runBinary, registerCallback: registerCallback != null ? registerCallback : other.registerCallback, registerUnaryCallback: registerUnaryCallback != null ? registerUnaryCallback : other.registerUnaryCallback, registerBinaryCallback: registerBinaryCallback != null ? registerBinaryCallback : other.registerBinaryCallback, errorCallback: errorCallback != null ? errorCallback : other.errorCallback, scheduleMicrotask: scheduleMicrotask != null ? scheduleMicrotask : other.scheduleMicrotask, createTimer: createTimer != null ? createTimer : other.createTimer, createPeriodicTimer: createPeriodicTimer != null ? createPeriodicTimer : other.createPeriodicTimer, print: print != null ? print : other.print, fork: fork != null ? fork : other.fork});
     }
   }
   dart.setSignature(ZoneSpecification, {
     constructors: () => ({
       new: [ZoneSpecification, [], {handleUncaughtError: dart.functionType(dart.dynamic, [Zone, ZoneDelegate, Zone, dart.dynamic, core.StackTrace]), run: dart.functionType(dart.dynamic, [Zone, ZoneDelegate, Zone, dart.functionType(dart.dynamic, [])]), runUnary: dart.functionType(dart.dynamic, [Zone, ZoneDelegate, Zone, dart.functionType(dart.dynamic, [dart.dynamic]), dart.dynamic]), runBinary: dart.functionType(dart.dynamic, [Zone, ZoneDelegate, Zone, dart.functionType(dart.dynamic, [dart.dynamic, dart.dynamic]), dart.dynamic, dart.dynamic]), registerCallback: dart.functionType(ZoneCallback, [Zone, ZoneDelegate, Zone, dart.functionType(dart.dynamic, [])]), registerUnaryCallback: dart.functionType(ZoneUnaryCallback, [Zone, ZoneDelegate, Zone, dart.functionType(dart.dynamic, [dart.dynamic])]), registerBinaryCallback: dart.functionType(ZoneBinaryCallback, [Zone, ZoneDelegate, Zone, dart.functionType(dart.dynamic, [dart.dynamic, dart.dynamic])]), errorCallback: dart.functionType(AsyncError, [Zone, ZoneDelegate, Zone, core.Object, core.StackTrace]), scheduleMicrotask: dart.functionType(dart.void, [Zone, ZoneDelegate, Zone, dart.functionType(dart.dynamic, [])]), createTimer: dart.functionType(Timer, [Zone, ZoneDelegate, Zone, core.Duration, dart.functionType(dart.void, [])]), createPeriodicTimer: dart.functionType(Timer, [Zone, ZoneDelegate, Zone, core.Duration, dart.functionType(dart.void, [Timer])]), print: dart.functionType(dart.void, [Zone, ZoneDelegate, Zone, core.String]), fork: dart.functionType(Zone, [Zone, ZoneDelegate, Zone, ZoneSpecification, core.Map])}],
       from: [ZoneSpecification, [ZoneSpecification], {handleUncaughtError: dart.functionType(dart.dynamic, [Zone, ZoneDelegate, Zone, dart.dynamic, core.StackTrace]), run: dart.functionType(dart.dynamic, [Zone, ZoneDelegate, Zone, dart.functionType(dart.dynamic, [])]), runUnary: dart.functionType(dart.dynamic, [Zone, ZoneDelegate, Zone, dart.functionType(dart.dynamic, [dart.dynamic]), dart.dynamic]), runBinary: dart.functionType(dart.dynamic, [Zone, ZoneDelegate, Zone, dart.functionType(dart.dynamic, [dart.dynamic, dart.dynamic]), dart.dynamic, dart.dynamic]), registerCallback: dart.functionType(ZoneCallback, [Zone, ZoneDelegate, Zone, dart.functionType(dart.dynamic, [])]), registerUnaryCallback: dart.functionType(ZoneUnaryCallback, [Zone, ZoneDelegate, Zone, dart.functionType(dart.dynamic, [dart.dynamic])]), registerBinaryCallback: dart.functionType(ZoneBinaryCallback, [Zone, ZoneDelegate, Zone, dart.functionType(dart.dynamic, [dart.dynamic, dart.dynamic])]), errorCallback: dart.functionType(AsyncError, [Zone, ZoneDelegate, Zone, core.Object, core.StackTrace]), scheduleMicrotask: dart.functionType(dart.void, [Zone, ZoneDelegate, Zone, dart.functionType(dart.dynamic, [])]), createTimer: dart.functionType(Timer, [Zone, ZoneDelegate, Zone, core.Duration, dart.functionType(dart.void, [])]), createPeriodicTimer: dart.functionType(Timer, [Zone, ZoneDelegate, Zone, core.Duration, dart.functionType(dart.void, [Timer])]), print: dart.functionType(dart.void, [Zone, ZoneDelegate, Zone, core.String]), fork: dart.functionType(Zone, [Zone, ZoneDelegate, Zone, ZoneSpecification, core.Map])}]
     })
   });
   class _ZoneSpecification extends core.Object {
-    _ZoneSpecification(opts) {
-      let handleUncaughtError = opts && 'handleUncaughtError' in opts ? opts.handleUncaughtError : null;
-      let run = opts && 'run' in opts ? opts.run : null;
-      let runUnary = opts && 'runUnary' in opts ? opts.runUnary : null;
-      let runBinary = opts && 'runBinary' in opts ? opts.runBinary : null;
-      let registerCallback = opts && 'registerCallback' in opts ? opts.registerCallback : null;
-      let registerUnaryCallback = opts && 'registerUnaryCallback' in opts ? opts.registerUnaryCallback : null;
-      let registerBinaryCallback = opts && 'registerBinaryCallback' in opts ? opts.registerBinaryCallback : null;
-      let errorCallback = opts && 'errorCallback' in opts ? opts.errorCallback : null;
-      let scheduleMicrotask = opts && 'scheduleMicrotask' in opts ? opts.scheduleMicrotask : null;
-      let createTimer = opts && 'createTimer' in opts ? opts.createTimer : null;
-      let createPeriodicTimer = opts && 'createPeriodicTimer' in opts ? opts.createPeriodicTimer : null;
-      let print = opts && 'print' in opts ? opts.print : null;
-      let fork = opts && 'fork' in opts ? opts.fork : null;
+    _ZoneSpecification({handleUncaughtError = null, run = null, runUnary = null, runBinary = null, registerCallback = null, registerUnaryCallback = null, registerBinaryCallback = null, errorCallback = null, scheduleMicrotask = null, createTimer = null, createPeriodicTimer = null, print = null, fork = null} = {}) {
       this.handleUncaughtError = handleUncaughtError;
       this.run = run;
       this.runUnary = runUnary;
       this.runBinary = runBinary;
       this.registerCallback = registerCallback;
       this.registerUnaryCallback = registerUnaryCallback;
       this.registerBinaryCallback = registerBinaryCallback;
       this.errorCallback = errorCallback;
       this.scheduleMicrotask = scheduleMicrotask;
       this.createTimer = createTimer;
@@ skipping 147 matching lines @@
         if (dart.notNull(core.identical(_ROOT_ZONE, Zone._current))) {
           return dart.dcall(f, arg1, arg2);
         }
         return _rootRunBinary(null, null, this, f, arg1, arg2);
       } catch (e) {
         let s = dart.stackTrace(e);
         return this.handleUncaughtError(e, s);
       }
 
     }
-    bindCallback(f, opts) {
-      let runGuarded = opts && 'runGuarded' in opts ? opts.runGuarded : true;
+    bindCallback(f, {runGuarded = true} = {}) {
       if (dart.notNull(runGuarded)) {
         return dart.fn((() => this.runGuarded(f)).bind(this));
       } else {
         return dart.fn((() => this.run(f)).bind(this));
       }
     }
-    bindUnaryCallback(f, opts) {
-      let runGuarded = opts && 'runGuarded' in opts ? opts.runGuarded : true;
+    bindUnaryCallback(f, {runGuarded = true} = {}) {
       if (dart.notNull(runGuarded)) {
         return dart.fn((arg => this.runUnaryGuarded(f, arg)).bind(this));
       } else {
         return dart.fn((arg => this.runUnary(f, arg)).bind(this));
       }
     }
-    bindBinaryCallback(f, opts) {
-      let runGuarded = opts && 'runGuarded' in opts ? opts.runGuarded : true;
+    bindBinaryCallback(f, {runGuarded = true} = {}) {
       if (dart.notNull(runGuarded)) {
         return dart.fn(((arg1, arg2) => this.runBinaryGuarded(f, arg1, arg2)).bind(this));
       } else {
         return dart.fn(((arg1, arg2) => this.runBinary(f, arg1, arg2)).bind(this));
       }
     }
     get(key) {
       return null;
     }
     handleUncaughtError(error, stackTrace) {
       return _rootHandleUncaughtError(null, null, this, error, stackTrace);
     }
-    fork(opts) {
-      let specification = opts && 'specification' in opts ? opts.specification : null;
-      let zoneValues = opts && 'zoneValues' in opts ? opts.zoneValues : null;
+    fork({specification = null, zoneValues = null} = {}) {
       return _rootFork(null, null, this, specification, zoneValues);
     }
     run(f) {
       if (dart.notNull(core.identical(Zone._current, _ROOT_ZONE)))
         return f();
       return _rootRun(null, null, this, f);
     }
     runUnary(f, arg) {
       if (dart.notNull(core.identical(Zone._current, _ROOT_ZONE)))
         return dart.dcall(f, arg);
@@ skipping 218 matching lines @@
     }
     runBinaryGuarded(f, arg1, arg2) {
       try {
         return this.runBinary(f, arg1, arg2);
       } catch (e) {
         let s = dart.stackTrace(e);
         return this.handleUncaughtError(e, s);
       }
 
     }
-    bindCallback(f, opts) {
-      let runGuarded = opts && 'runGuarded' in opts ? opts.runGuarded : true;
+    bindCallback(f, {runGuarded = true} = {}) {
       let registered = this.registerCallback(f);
       if (dart.notNull(runGuarded)) {
         return dart.fn((() => this.runGuarded(registered)).bind(this));
       } else {
         return dart.fn((() => this.run(registered)).bind(this));
       }
     }
-    bindUnaryCallback(f, opts) {
-      let runGuarded = opts && 'runGuarded' in opts ? opts.runGuarded : true;
+    bindUnaryCallback(f, {runGuarded = true} = {}) {
       let registered = this.registerUnaryCallback(f);
       if (dart.notNull(runGuarded)) {
         return dart.fn((arg => this.runUnaryGuarded(registered, arg)).bind(this));
       } else {
         return dart.fn((arg => this.runUnary(registered, arg)).bind(this));
       }
     }
-    bindBinaryCallback(f, opts) {
-      let runGuarded = opts && 'runGuarded' in opts ? opts.runGuarded : true;
+    bindBinaryCallback(f, {runGuarded = true} = {}) {
       let registered = this.registerBinaryCallback(f);
       if (dart.notNull(runGuarded)) {
         return dart.fn(((arg1, arg2) => this.runBinaryGuarded(registered, arg1, arg2)).bind(this));
       } else {
         return dart.fn(((arg1, arg2) => this.runBinary(registered, arg1, arg2)).bind(this));
       }
     }
     get(key) {
       let result = this[_map].get(key);
       if (result != null || dart.notNull(this[_map].containsKey(key)))
         return result;
       if (this.parent != null) {
         let value = this.parent.get(key);
         if (value != null) {
           this[_map].set(key, value);
         }
         return value;
       }
       dart.assert(dart.equals(this, _ROOT_ZONE));
       return null;
     }
     handleUncaughtError(error, stackTrace) {
       let implementation = this[_handleUncaughtError];
       dart.assert(implementation != null);
       let parentDelegate = _parentDelegate(implementation.zone);
       return dart.dcall(implementation.function, implementation.zone, parentDelegate, this, error, stackTrace);
     }
-    fork(opts) {
-      let specification = opts && 'specification' in opts ? opts.specification : null;
-      let zoneValues = opts && 'zoneValues' in opts ? opts.zoneValues : null;
+    fork({specification = null, zoneValues = null} = {}) {
       let implementation = this[_fork];
       dart.assert(implementation != null);
       let parentDelegate = _parentDelegate(implementation.zone);
       return dart.as(dart.dcall(implementation.function, implementation.zone, parentDelegate, this, specification, zoneValues), Zone);
     }
     run(f) {
       let implementation = this[_run];
       dart.assert(implementation != null);
       let parentDelegate = _parentDelegate(implementation.zone);
       return dart.dcall(implementation.function, implementation.zone, parentDelegate, this, f);
@@ skipping 234 matching lines @@
     }
   }
   _RootZoneSpecification[dart.implements] = () => [ZoneSpecification];
   _RootZone._rootDelegate = null;
   dart.defineLazyProperties(_RootZone, {
     get _rootMap() {
       return collection.HashMap.new();
     },
     set _rootMap(_) {}
   });
-  function runZoned(body, opts) {
-    let zoneValues = opts && 'zoneValues' in opts ? opts.zoneValues : null;
-    let zoneSpecification = opts && 'zoneSpecification' in opts ? opts.zoneSpecification : null;
-    let onError = opts && 'onError' in opts ? opts.onError : null;
+  function runZoned(body, {zoneValues = null, zoneSpecification = null, onError = null} = {}) {
     let errorHandler = null;
     if (onError != null) {
       errorHandler = dart.fn((self, parent, zone, error, stackTrace) => {
         try {
           if (dart.is(onError, ZoneBinaryCallback)) {
             return self.parent.runBinary(onError, error, stackTrace);
           }
           return self.parent.runUnary(dart.as(onError, __CastType38), error);
         } catch (e) {
           let s = dart.stackTrace(e);
@@ skipping 69 matching lines @@
   exports.ScheduleMicrotaskHandler = ScheduleMicrotaskHandler;
   exports.CreateTimerHandler = CreateTimerHandler;
   exports.CreatePeriodicTimerHandler = CreatePeriodicTimerHandler;
   exports.PrintHandler = PrintHandler;
   exports.ForkHandler = ForkHandler;
   exports.ZoneSpecification = ZoneSpecification;
   exports.ZoneDelegate = ZoneDelegate;
   exports.Zone = Zone;
   exports.runZoned = runZoned;
 });