Fix all strong-mode warnings.

lib/src/utils.dart

Index: lib/src/utils.dart
diff --git a/lib/src/utils.dart b/lib/src/utils.dart
index 7ce6724e17c31d67239f2754e61c1757c2532b1e..c9975e5f9ae769a030c2dfa729dcd03a21c44863 100644
--- a/lib/src/utils.dart
+++ b/lib/src/utils.dart
@@ -7,6 +7,7 @@ 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.
@@ -129,8 +130,9 @@ Uint8List toUint8List(List<int> input) {
 ///
 /// 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);
@@ -156,27 +158,35 @@ List flatten(Iterable nested) {
 }
 
 /// 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) =>
@@ -186,15 +196,17 @@ bool setEquals(Set set1, Set set2) =>
 ///
 /// 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(
@@ -238,10 +250,7 @@ Future pumpEventQueue([int times=20]) {
 /// 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.
@@ -252,17 +261,18 @@ Future syncFuture(callback()) => Chain.track(new Future.sync(callback));
 /// 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) {
@@ -281,10 +291,10 @@ Stream futureStream(Future<Stream> future, {bool broadcast: false}) {
   }
 
   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;
@@ -294,10 +304,10 @@ Stream futureStream(Future<Stream> future, {bool broadcast: false}) {
 /// [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);
@@ -313,13 +323,14 @@ Stream callbackStream(Stream callback()) {
 ///
 /// 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);