Fix all strong-mode warnings.

lib/src/utils.dart

 // Copyright (c) 2013, 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 barback.utils;
 
 import 'dart:async';
 import 'dart:typed_data';
 
+import 'package:async/async.dart';
 import 'package:stack_trace/stack_trace.dart';
 
 /// A class that represents a value or an error.
 class Fallible<E> {
   /// Whether [this] has a [value], as opposed to an [error].
   final bool hasValue;
 
   /// Whether [this] has an [error], as opposed to a [value].
   bool get hasError => !hasValue;
 
@@ skipping 102 matching lines @@
     // TODO(nweiz): remove "as" when issue 11080 is fixed.
     return new Uint8List.view((input as TypedData).buffer);
   }
   return new Uint8List.fromList(input);
 }
 
 /// Group the elements in [iter] by the value returned by [fn].
 ///
 /// This returns a map whose keys are the return values of [fn] and whose values
 /// are lists of each element in [iter] for which [fn] returned that key.
-Map<Object, List> groupBy(Iterable iter, fn(element)) {
-  var map = {};
+Map<Object/*=T*/, List/*<S>*/> groupBy/*<S, T>*/(Iterable/*<S>*/ iter,
+    /*=T*/ fn(/*=S*/ element)) {
+  var map = /*<T, List<S>>*/{};
   for (var element in iter) {
     var list = map.putIfAbsent(fn(element), () => []);
     list.add(element);
   }
   return map;
 }
 
 /// Flattens nested lists inside an iterable into a single list containing only
 /// non-list elements.
 List flatten(Iterable nested) {
   var result = [];
   helper(list) {
     for (var element in list) {
       if (element is List) {
         helper(element);
       } else {
         result.add(element);
       }
     }
   }
   helper(nested);
   return result;
 }
 
 /// Returns the union of all elements in each set in [sets].
-Set unionAll(Iterable<Set> sets) =>
+Set/*<T>*/ unionAll/*<T>*/(Iterable<Set/*<T>*/> sets) =>
   sets.fold(new Set(), (union, set) => union.union(set));
 
 /// Creates a new map from [map] with new keys and values.
 ///
 /// The return values of [keyFn] are used as the keys and the return values of
 /// [valueFn] are used as the values for the new map.
-Map mapMap(Map map, keyFn(key, value), valueFn(key, value)) =>
+Map/*<K2, V2>*/ mapMap/*<K1, V1, K2, V2>*/(Map/*<K1, V1>*/ map,
+    /*=K2*/ keyFn(/*=K1*/ key, /*=V1*/ value),
+    /*=V2*/ valueFn(/*=K1*/ key, /*=V1*/ value)) =>
   new Map.fromIterable(map.keys,
-      key: (key) => keyFn(key, map[key]),
-      value: (key) => valueFn(key, map[key]));
+      key: (key) => keyFn(key as dynamic/*=K1*/, map[key]),
+      value: (key) => valueFn(key as dynamic/*=K1*/, map[key]));
 
 /// Creates a new map from [map] with the same keys.
 ///
 /// The return values of [fn] are used as the values for the new map.
-Map mapMapValues(Map map, fn(key, value)) => mapMap(map, (key, _) => key, fn);
+Map/*<K, V2>*/ mapMapValues/*<K, V1, V2>*/(Map/*<K, V1>*/ map,
+    /*=V2*/ fn(/*=K*/ key, /*=V1*/ value)) =>
+  // TODO(nweiz): Don't explicitly type [key] when sdk#25490 is fixed.
+  mapMap(map, (/*=K*/ key, _) => key, fn);
 
 /// Creates a new map from [map] with the same keys.
 ///
 /// The return values of [fn] are used as the keys for the new map.
-Map mapMapKeys(Map map, fn(key, value)) => mapMap(map, fn, (_, value) => value);
+Map/*<K2, V>*/ mapMapKeys/*<K1, V, K2>*/(Map/*<K1, V>*/ map,
+    /*=K2*/ fn(/*=K1*/ key, /*=V*/ value)) =>
+  // TODO(nweiz): Don't explicitly type [value] when sdk#25490 is fixed.
+  mapMap(map, fn, (_, /*=V*/ value) => value);
 
 /// Returns whether [set1] has exactly the same elements as [set2].
 bool setEquals(Set set1, Set set2) =>
   set1.length == set2.length && set1.containsAll(set2);
 
 /// Merges [streams] into a single stream that emits events from all sources.
 ///
 /// If [broadcast] is true, this will return a broadcast stream; otherwise, it
 /// will return a buffered stream.
-Stream mergeStreams(Iterable<Stream> streams, {bool broadcast: false}) {
+Stream/*<T>*/ mergeStreams/*<T>*/(Iterable<Stream/*<T>*/> streams,
+    {bool broadcast: false}) {
   streams = streams.toList();
   var doneCount = 0;
   // Use a sync stream to preserve the synchrony behavior of the input streams.
   // If the inputs are sync, then this will be sync as well; if the inputs are
   // async, then the events we receive will also be async, and forwarding them
   // sync won't change that.
-  var controller = broadcast ? new StreamController.broadcast(sync: true)
-      : new StreamController(sync: true);
+  var controller = broadcast
+      ? new StreamController/*<T>*/.broadcast(sync: true)
+      : new StreamController/*<T>*/(sync: true);
 
   for (var stream in streams) {
     stream.listen(
         controller.add,
         onError: controller.addError,
         onDone: () {
       doneCount++;
       if (doneCount == streams.length) controller.close();
     });
   }
@@ skipping 23 matching lines @@
   // We use a delayed future to allow microtask events to finish. The
   // Future.value or Future() constructors use scheduleMicrotask themselves and
   // would therefore not wait for microtask callbacks that are scheduled after
   // invoking this method.
   return new Future.delayed(Duration.ZERO, () => pumpEventQueue(times - 1));
 }
 
 /// Like `new Future`, but avoids issue 11911 by using `new Future.value` under
 /// the covers.
 // TODO(jmesserly): doc comment changed to due 14601.
-Future newFuture(callback()) => new Future.value().then((_) => callback());
-
-/// Like [Future.sync], but wraps the Future in [Chain.track] as well.
-Future syncFuture(callback()) => Chain.track(new Future.sync(callback));
+Future/*<T>*/ newFuture/*<T>*/(/*=T*/ callback()) async => await callback();
 
 /// Returns a buffered stream that will emit the same values as the stream
 /// returned by [future] once [future] completes.
 ///
 /// If [future] completes to an error, the return value will emit that error and
 /// then close.
 ///
 /// If [broadcast] is true, a broadcast stream is returned. This assumes that
 /// the stream returned by [future] will be a broadcast stream as well.
 /// [broadcast] defaults to false.
-Stream futureStream(Future<Stream> future, {bool broadcast: false}) {
-  var subscription;
-  var controller;
+Stream/*<T>*/ futureStream/*<T>*/(Future<Stream/*<T>*/> future,
+    {bool broadcast: false}) {
+  StreamSubscription/*<T>*/ subscription;
+  StreamController/*<T>*/ controller;
 
-  future = future.catchError((e, stackTrace) {
+  future = DelegatingFuture.typed(future.catchError((e, stackTrace) {
     // Since [controller] is synchronous, it's likely that emitting an error
     // will cause it to be cancelled before we call close.
     if (controller != null) controller.addError(e, stackTrace);
     if (controller != null) controller.close();
     controller = null;
-  });
+  }));
 
   onListen() {
     future.then((stream) {
       if (controller == null) return;
       subscription = stream.listen(
           controller.add,
           onError: controller.addError,
           onDone: controller.close);
     });
   }
 
   onCancel() {
     if (subscription != null) subscription.cancel();
     subscription = null;
     controller = null;
   }
 
   if (broadcast) {
-    controller = new StreamController.broadcast(
+    controller = new StreamController/*<T>*/.broadcast(
         sync: true, onListen: onListen, onCancel: onCancel);
   } else {
-    controller = new StreamController(
+    controller = new StreamController/*<T>*/(
         sync: true, onListen: onListen, onCancel: onCancel);
   }
   return controller.stream;
 }
 
 /// Returns a [Stream] that will emit the same values as the stream returned by
 /// [callback].
 ///
 /// [callback] will only be called when the returned [Stream] gets a subscriber.
-Stream callbackStream(Stream callback()) {
-  var subscription;
-  var controller;
-  controller = new StreamController(onListen: () {
+Stream/*<T>*/ callbackStream/*<T>*/(Stream/*<T>*/ callback()) {
+  StreamSubscription/*<T>*/ subscription;
+  StreamController/*<T>*/ controller;
+  controller = new StreamController/*<T>*/(onListen: () {
     subscription = callback().listen(controller.add,
         onError: controller.addError,
         onDone: controller.close);
   },
       onCancel: () => subscription.cancel(),
       onPause: () => subscription.pause(),
       onResume: () => subscription.resume(),
       sync: true);
   return controller.stream;
 }
 
 /// Creates a single-subscription stream from a broadcast stream.
 ///
 /// The returned stream will enqueue events from [broadcast] until a listener is
 /// attached, then pipe events to that listener.
-Stream broadcastToSingleSubscription(Stream broadcast) {
+Stream/*<T>*/ broadcastToSingleSubscription/*<T>*/(Stream/*<T>*/ broadcast) {
   if (!broadcast.isBroadcast) return broadcast;
 
   // TODO(nweiz): Implement this using a transformer when issues 18588 and 18586
   // are fixed.
   var subscription;
-  var controller = new StreamController(onCancel: () => subscription.cancel());
+  var controller = new StreamController/*<T>*/(
+      onCancel: () => subscription.cancel());
   subscription = broadcast.listen(controller.add,
       onError: controller.addError,
       onDone: controller.close);
   return controller.stream;
 }
 
 /// A regular expression to match the exception prefix that some exceptions'
 /// [Object.toString] values contain.
 final _exceptionPrefix = new RegExp(r'^([A-Z][a-zA-Z]*)?(Exception|Error): ');
 
 /// Get a string description of an exception.
 ///
 /// Many exceptions include the exception class name at the beginning of their
 /// [toString], so we remove that if it exists.
 String getErrorMessage(error) =>
   error.toString().replaceFirst(_exceptionPrefix, '');
 
 /// Returns a human-friendly representation of [duration].
 String niceDuration(Duration duration) {
   var result = duration.inMinutes > 0 ? "${duration.inMinutes}:" : "";
 
   var s = duration.inSeconds % 59;
   var ms = (duration.inMilliseconds % 1000) ~/ 100;
   return result + "$s.${ms}s";
 }