The return-value of 'asFuture' isn't necessarily related to the Stream's type.

tests/lib/async/stream_subscription_as_future_test.dart

Index: tests/lib/async/stream_subscription_as_future_test.dart
diff --git a/tests/lib/async/stream_subscription_as_future_test.dart b/tests/lib/async/stream_subscription_as_future_test.dart
index ef868e28fc7308d7399a8d89e28e9e14af7f7d51..ac1293b0297ba9b8c1f9d429c89b22e9f0d21680 100644
--- a/tests/lib/async/stream_subscription_as_future_test.dart
+++ b/tests/lib/async/stream_subscription_as_future_test.dart
@@ -40,6 +40,18 @@ main() {
     }));
   });
 
+  test("subscription.asStream different type", () {
+    Stream stream = new Stream<int>.fromIterable([1, 2, 3]);
+    var asyncCallback = expectAsync(() => {});
+    var output = [];
+    var subscription = stream.listen((x) { output.add(x); });
+    subscription.asFuture("string").then((String o) {
+      Expect.listEquals([1, 2, 3], output);
+      Expect.equals("string", o);
+      asyncCallback();
+    });
+  });
+
   test("subscription.asStream failure", () {
     StreamController controller = new StreamController(sync: true);
     [1, 2, 3].forEach(controller.add);