Fix implicit casts (#49)

- Add some explicit casts.
- Cast a `Stream<dynamic>` to `Stream<List>` since we always expect to
  get a List out.

CHANGELOG.md

@@ -1,4 +1,4 @@
-## 2.1.0
+## 2.1.0-dev
 
 * Require Dart `2.2.0` or later.
 

analysis_options.yaml

@@ -1,5 +1,7 @@
 include: package:pedantic/analysis_options.yaml
 analyzer:
+  strong-mode:
+    implicit-casts: false
   # These are errors when building in Google
   errors:
     unused_import: error

lib/src/multi_channel.dart

@@ -140,8 +140,8 @@ class _MultiChannel<T> extends StreamChannelMixin<T>
         (message) => _inner.sink.add([0, message]),
         onDone: () => _closeChannel(0, 0));
 
-    _innerStreamSubscription = _inner.stream.listen((message) {
-      var id = message[0];
+    _innerStreamSubscription = _inner.stream.cast<List>().listen((message) {
+      var id = message[0] as int;
 
       // If the channel was closed before an incoming message was processed,
       // ignore that message.
@@ -156,7 +156,7 @@ class _MultiChannel<T> extends StreamChannelMixin<T>
       });
 
       if (message.length > 1) {
-        controller.local.sink.add(message[1]);
+        controller.local.sink.add(message[1] as T);
       } else {
         // A message without data indicates that the channel has been closed. We
         // can just close the sink here without doing any more cleanup, because