Downward inference

lib/runtime/dart/async.js

 var async;
 (function(exports) {
   'use strict';
   // Function _invokeErrorHandler: (Function, Object, StackTrace) → dynamic
   function _invokeErrorHandler(errorHandler, error, stackTrace) {
     if (dart.is(errorHandler, ZoneBinaryCallback)) {
       return dart.dinvokef(errorHandler, error, stackTrace);
     } else {
       return dart.dinvokef(errorHandler, error);
     }
@@ skipping 42 matching lines @@
   let _onListen = Symbol('_onListen');
   let _addError = Symbol('_addError');
   let _completeError = Symbol('_completeError');
   let _complete = Symbol('_complete');
   let _sink = Symbol('_sink');
   let Stream$ = dart.generic(function(T) {
     class Stream extends core.Object {
       Stream() {
       }
       fromFuture(future) {
-        let controller = dart.as(new StreamController({sync: true}), _StreamController$(T));
+        let controller = new StreamController({sync: true});
         future.then(dart.closureWrap(((value) => {
           controller._add(dart.as(value, T));
           controller._closeUnchecked();
         }).bind(this), "(T) → dynamic"), {onError: ((error, stackTrace) => {
             controller._addError(error, dart.as(stackTrace, core.StackTrace));
             controller._closeUnchecked();
           }).bind(this)});
         return controller.stream;
       }
       fromIterable(data) {
@@ skipping 1646 matching lines @@
         return doneSignal;
       }
     }
     dart.defineNamedConstructor(Future, 'microtask');
     dart.defineNamedConstructor(Future, 'sync');
     dart.defineNamedConstructor(Future, 'value');
     dart.defineNamedConstructor(Future, 'error');
     dart.defineNamedConstructor(Future, 'delayed');
     dart.defineLazyProperties(Future, {
       get _nullFuture() {
-        return dart.as(new Future.value(null), _Future);
+        return new Future.value(null);
       }
     });
     return Future;
   });
   let Future = Future$(dart.dynamic);
   class TimeoutException extends core.Object {
     TimeoutException(message, duration) {
       if (duration === void 0)
         duration = null;
       this.message = message;
@@ skipping 2356 matching lines @@
       _BoundSinkStream(stream$, sinkMapper) {
         this[_stream] = stream$;
         this[_sinkMapper] = sinkMapper;
         super.Stream();
       }
       listen(onData, opts) {
         let onError = opts && 'onError' in opts ? opts.onError : null;
         let onDone = opts && 'onDone' in opts ? opts.onDone : null;
         let cancelOnError = opts && 'cancelOnError' in opts ? opts.cancelOnError : null;
         cancelOnError = core.identical(true, cancelOnError);
-        let subscription = dart.as(new _SinkTransformerStreamSubscription(this[_stream], dart.closureWrap(this[_sinkMapper], "(EventSink<dynamic>) → EventSink"), onData, onError, onDone, cancelOnError), StreamSubscription$(T));
+        let subscription = new _SinkTransformerStreamSubscription(this[_stream], dart.closureWrap(this[_sinkMapper], "(EventSink<dynamic>) → EventSink"), onData, onError, onDone, cancelOnError);
         return subscription;
       }
     }
     return _BoundSinkStream;
   });
   let _BoundSinkStream = _BoundSinkStream$(dart.dynamic, dart.dynamic);
   let _HandlerEventSink$ = dart.generic(function(S, T) {
     class _HandlerEventSink extends core.Object {
       _HandlerEventSink(handleData$, handleError$, handleDone$, sink$) {
         this[_handleData] = handleData$;
@@ skipping 894 matching lines @@
   exports.StreamIterator = StreamIterator;
   exports.StreamIterator$ = StreamIterator$;
   exports.StreamController = StreamController;
   exports.StreamController$ = StreamController$;
   exports.Timer = Timer;
   exports.ZoneSpecification = ZoneSpecification;
   exports.ZoneDelegate = ZoneDelegate;
   exports.Zone = Zone;
   exports.runZoned = runZoned;
 })(async || (async = {}));