diff --git a/analysis_options.yaml b/analysis_options.yaml
index a73c3a63e1bb..51b9c0d266d8 100644
--- a/analysis_options.yaml
+++ b/analysis_options.yaml
@@ -112,7 +112,6 @@ linter:
     # - prefer_interpolation_to_compose_strings # not yet tested
     - prefer_is_empty
     - prefer_is_not_empty
-    - prefer_void_to_null
     # - recursive_getters # https://github.com/dart-lang/linter/issues/452
     - slash_for_doc_comments
     - sort_constructors_first
diff --git a/packages/android_alarm_manager/example/lib/main.dart b/packages/android_alarm_manager/example/lib/main.dart
index 0c7fc2a2cd7e..8424920ddd4e 100644
--- a/packages/android_alarm_manager/example/lib/main.dart
+++ b/packages/android_alarm_manager/example/lib/main.dart
@@ -12,7 +12,7 @@ import 'package:flutter/widgets.dart';
 final FirebaseAuth firebaseAuth = FirebaseAuth.instance;
 FirebaseUser firebaseUser;
 
-Future<void> ensureFirebaseUser() async {
+Future<Null> ensureFirebaseUser() async {
   if (firebaseUser == null) {
     firebaseUser = await firebaseAuth.currentUser();
     if (firebaseUser == null) {
@@ -67,7 +67,7 @@ void printOneShot() {
   printHelloMessage("Hello, once!");
 }
 
-Future<void> main() async {
+Future<Null> main() async {
   final int helloAlarmID = 0;
   final int goodbyeAlarmID = 1;
   final int oneShotID = 2;
diff --git a/packages/android_intent/lib/android_intent.dart b/packages/android_intent/lib/android_intent.dart
index 962bc5f849ba..5409d857713c 100644
--- a/packages/android_intent/lib/android_intent.dart
+++ b/packages/android_intent/lib/android_intent.dart
@@ -42,7 +42,7 @@ class AndroidIntent {
   ///
   /// This works only on Android platforms. Please guard the call so that your
   /// iOS app does not crash. Checked mode will throw an assert exception.
-  Future<void> launch() async {
+  Future<Null> launch() async {
     assert(_platform.isAndroid);
     final Map<String, dynamic> args = <String, dynamic>{'action': action};
     if (category != null) {
diff --git a/packages/battery/example/lib/main.dart b/packages/battery/example/lib/main.dart
index 250d458d5190..4bf9a58939fc 100644
--- a/packages/battery/example/lib/main.dart
+++ b/packages/battery/example/lib/main.dart
@@ -63,7 +63,7 @@ class _MyHomePageState extends State<MyHomePage> {
         child: const Icon(Icons.battery_unknown),
         onPressed: () async {
           final int batteryLevel = await _battery.batteryLevel;
-          showDialog<void>(
+          showDialog<Null>(
             context: context,
             builder: (_) => AlertDialog(
                   content: Text('Battery: $batteryLevel%'),
diff --git a/packages/camera/README.md b/packages/camera/README.md
index 58d30bdfb894..7d10149c7628 100644
--- a/packages/camera/README.md
+++ b/packages/camera/README.md
@@ -48,7 +48,7 @@ import 'package:camera/camera.dart';
 
 List<CameraDescription> cameras;
 
-Future<void> main() async {
+Future<Null> main() async {
   cameras = await availableCameras();
   runApp(CameraApp());
 }
diff --git a/packages/camera/example/lib/main.dart b/packages/camera/example/lib/main.dart
index ca01a7ac0f57..a0eed3ca7de6 100644
--- a/packages/camera/example/lib/main.dart
+++ b/packages/camera/example/lib/main.dart
@@ -356,7 +356,7 @@ class CameraApp extends StatelessWidget {
 
 List<CameraDescription> cameras;
 
-Future<void> main() async {
+Future<Null> main() async {
   // Fetch the available cameras before initializing the app.
   try {
     cameras = await availableCameras();
diff --git a/packages/camera/lib/camera.dart b/packages/camera/lib/camera.dart
index 153bbeb69b98..baae0f9634cc 100644
--- a/packages/camera/lib/camera.dart
+++ b/packages/camera/lib/camera.dart
@@ -185,17 +185,17 @@ class CameraController extends ValueNotifier<CameraValue> {
   int _textureId;
   bool _isDisposed = false;
   StreamSubscription<dynamic> _eventSubscription;
-  Completer<void> _creatingCompleter;
+  Completer<Null> _creatingCompleter;
 
   /// Initializes the camera on the device.
   ///
   /// Throws a [CameraException] if the initialization fails.
-  Future<void> initialize() async {
+  Future<Null> initialize() async {
     if (_isDisposed) {
-      return Future<void>.value();
+      return Future<Null>.value(null);
     }
     try {
-      _creatingCompleter = Completer<void>();
+      _creatingCompleter = Completer<Null>();
       final Map<dynamic, dynamic> reply = await _channel.invokeMethod(
         'initialize',
         <String, dynamic>{
@@ -218,7 +218,7 @@ class CameraController extends ValueNotifier<CameraValue> {
         EventChannel('flutter.io/cameraPlugin/cameraEvents$_textureId')
             .receiveBroadcastStream()
             .listen(_listener);
-    _creatingCompleter.complete();
+    _creatingCompleter.complete(null);
     return _creatingCompleter.future;
   }
 
@@ -250,7 +250,7 @@ class CameraController extends ValueNotifier<CameraValue> {
   /// The file can be read as this function returns.
   ///
   /// Throws a [CameraException] if the capture fails.
-  Future<void> takePicture(String path) async {
+  Future<Null> takePicture(String path) async {
     if (!value.isInitialized || _isDisposed) {
       throw CameraException(
         'Uninitialized CameraController.',
@@ -286,7 +286,7 @@ class CameraController extends ValueNotifier<CameraValue> {
   /// The file can be read as soon as [stopVideoRecording] returns.
   ///
   /// Throws a [CameraException] if the capture fails.
-  Future<void> startVideoRecording(String filePath) async {
+  Future<Null> startVideoRecording(String filePath) async {
     if (!value.isInitialized || _isDisposed) {
       throw CameraException(
         'Uninitialized CameraController',
@@ -311,7 +311,7 @@ class CameraController extends ValueNotifier<CameraValue> {
   }
 
   /// Stop recording.
-  Future<void> stopVideoRecording() async {
+  Future<Null> stopVideoRecording() async {
     if (!value.isInitialized || _isDisposed) {
       throw CameraException(
         'Uninitialized CameraController',
@@ -337,19 +337,22 @@ class CameraController extends ValueNotifier<CameraValue> {
 
   /// Releases the resources of this camera.
   @override
-  Future<void> dispose() async {
+  Future<Null> dispose() async {
     if (_isDisposed) {
-      return;
+      return Future<Null>.value(null);
     }
     _isDisposed = true;
     super.dispose();
-    if (_creatingCompleter != null) {
-      await _creatingCompleter.future;
-      await _channel.invokeMethod(
-        'dispose',
-        <String, dynamic>{'textureId': _textureId},
-      );
-      await _eventSubscription?.cancel();
+    if (_creatingCompleter == null) {
+      return Future<Null>.value(null);
+    } else {
+      return _creatingCompleter.future.then((_) async {
+        await _channel.invokeMethod(
+          'dispose',
+          <String, dynamic>{'textureId': _textureId},
+        );
+        await _eventSubscription?.cancel();
+      });
     }
   }
 }
diff --git a/packages/cloud_firestore/example/lib/main.dart b/packages/cloud_firestore/example/lib/main.dart
index 27138f2fbd9e..7fde45e1edeb 100755
--- a/packages/cloud_firestore/example/lib/main.dart
+++ b/packages/cloud_firestore/example/lib/main.dart
@@ -57,7 +57,7 @@ class MyHomePage extends StatelessWidget {
   final Firestore firestore;
   CollectionReference get messages => firestore.collection('messages');
 
-  Future<void> _addMessage() async {
+  Future<Null> _addMessage() async {
     await messages.add(<String, dynamic>{
       'message': 'Hello world!',
       'created_at': FieldValue.serverTimestamp(),
diff --git a/packages/cloud_firestore/lib/src/write_batch.dart b/packages/cloud_firestore/lib/src/write_batch.dart
index ea1f0851d1c3..b9ffc14f34bf 100644
--- a/packages/cloud_firestore/lib/src/write_batch.dart
+++ b/packages/cloud_firestore/lib/src/write_batch.dart
@@ -25,11 +25,11 @@ class WriteBatch {
   /// Commits all of the writes in this write batch as a single atomic unit.
   ///
   /// Calling this method prevents any future operations from being added.
-  Future<void> commit() async {
+  Future<Null> commit() async {
     if (!_committed) {
       _committed = true;
       await Future.wait<dynamic>(_actions);
-      await Firestore.channel.invokeMethod(
+      return await Firestore.channel.invokeMethod(
           'WriteBatch#commit', <String, dynamic>{'handle': await _handle});
     } else {
       throw StateError("This batch has already been committed.");
diff --git a/packages/cloud_firestore/test/cloud_firestore_test.dart b/packages/cloud_firestore/test/cloud_firestore_test.dart
index 08dcde54a0aa..f0c9828a0d8b 100755
--- a/packages/cloud_firestore/test/cloud_firestore_test.dart
+++ b/packages/cloud_firestore/test/cloud_firestore_test.dart
@@ -279,7 +279,7 @@ void main() {
         expect(document.reference.path, equals('foo/0'));
         expect(document.data, equals(kMockDocumentSnapshotData));
         // Flush the async removeListener call
-        await Future<void>.delayed(Duration.zero);
+        await Future<Null>.delayed(Duration.zero);
         expect(log, <Matcher>[
           isMethodCall(
             'Query#addSnapshotListener',
@@ -305,7 +305,7 @@ void main() {
                 .snapshots()
                 .listen((QuerySnapshot querySnapshot) {});
         subscription.cancel();
-        await Future<void>.delayed(Duration.zero);
+        await Future<Null>.delayed(Duration.zero);
         expect(
           log,
           equals(<Matcher>[
@@ -336,7 +336,7 @@ void main() {
                 .snapshots()
                 .listen((QuerySnapshot querySnapshot) {});
         subscription.cancel();
-        await Future<void>.delayed(Duration.zero);
+        await Future<Null>.delayed(Duration.zero);
         expect(
           log,
           equals(<Matcher>[
@@ -367,7 +367,7 @@ void main() {
                 .snapshots()
                 .listen((QuerySnapshot querySnapshot) {});
         subscription.cancel();
-        await Future<void>.delayed(Duration.zero);
+        await Future<Null>.delayed(Duration.zero);
         expect(
           log,
           equals(<Matcher>[
@@ -401,7 +401,7 @@ void main() {
         expect(snapshot.reference.path, equals('path/to/foo'));
         expect(snapshot.data, equals(kMockDocumentSnapshotData));
         // Flush the async removeListener call
-        await Future<void>.delayed(Duration.zero);
+        await Future<Null>.delayed(Duration.zero);
         expect(
           log,
           <Matcher>[
diff --git a/packages/connectivity/example/lib/main.dart b/packages/connectivity/example/lib/main.dart
index ccb4ebe5001b..35696fc10131 100644
--- a/packages/connectivity/example/lib/main.dart
+++ b/packages/connectivity/example/lib/main.dart
@@ -57,7 +57,7 @@ class _MyHomePageState extends State<MyHomePage> {
   }
 
   // Platform messages are asynchronous, so we initialize in an async method.
-  Future<void> initConnectivity() async {
+  Future<Null> initConnectivity() async {
     String connectionStatus;
     // Platform messages may fail, so we use a try/catch PlatformException.
     try {
diff --git a/packages/device_info/example/lib/main.dart b/packages/device_info/example/lib/main.dart
index 6ffae432c48b..58cf460334f8 100644
--- a/packages/device_info/example/lib/main.dart
+++ b/packages/device_info/example/lib/main.dart
@@ -33,7 +33,7 @@ class _MyAppState extends State<MyApp> {
     initPlatformState();
   }
 
-  Future<void> initPlatformState() async {
+  Future<Null> initPlatformState() async {
     Map<String, dynamic> deviceData;
 
     try {
diff --git a/packages/firebase_admob/lib/firebase_admob.dart b/packages/firebase_admob/lib/firebase_admob.dart
index aca3ee53bbf8..7b7ad9eb9900 100644
--- a/packages/firebase_admob/lib/firebase_admob.dart
+++ b/packages/firebase_admob/lib/firebase_admob.dart
@@ -501,7 +501,7 @@ class FirebaseAdMob {
       }
     }
 
-    return Future<dynamic>.value(null);
+    return Future<Null>(null);
   }
 }
 
diff --git a/packages/firebase_analytics/example/lib/main.dart b/packages/firebase_analytics/example/lib/main.dart
index 644955283730..6864e594439a 100755
--- a/packages/firebase_analytics/example/lib/main.dart
+++ b/packages/firebase_analytics/example/lib/main.dart
@@ -61,7 +61,7 @@ class _MyHomePageState extends State<MyHomePage> {
     });
   }
 
-  Future<void> _sendAnalyticsEvent() async {
+  Future<Null> _sendAnalyticsEvent() async {
     await analytics.logEvent(
       name: 'test_event',
       parameters: <String, dynamic>{
@@ -75,12 +75,12 @@ class _MyHomePageState extends State<MyHomePage> {
     setMessage('logEvent succeeded');
   }
 
-  Future<void> _testSetUserId() async {
+  Future<Null> _testSetUserId() async {
     await analytics.setUserId('some-user');
     setMessage('setUserId succeeded');
   }
 
-  Future<void> _testSetCurrentScreen() async {
+  Future<Null> _testSetCurrentScreen() async {
     await analytics.setCurrentScreen(
       screenName: 'Analytics Demo',
       screenClassOverride: 'AnalyticsDemo',
@@ -88,28 +88,28 @@ class _MyHomePageState extends State<MyHomePage> {
     setMessage('setCurrentScreen succeeded');
   }
 
-  Future<void> _testSetAnalyticsCollectionEnabled() async {
+  Future<Null> _testSetAnalyticsCollectionEnabled() async {
     await analytics.android?.setAnalyticsCollectionEnabled(false);
     await analytics.android?.setAnalyticsCollectionEnabled(true);
     setMessage('setAnalyticsCollectionEnabled succeeded');
   }
 
-  Future<void> _testSetMinimumSessionDuration() async {
+  Future<Null> _testSetMinimumSessionDuration() async {
     await analytics.android?.setMinimumSessionDuration(20000);
     setMessage('setMinimumSessionDuration succeeded');
   }
 
-  Future<void> _testSetSessionTimeoutDuration() async {
+  Future<Null> _testSetSessionTimeoutDuration() async {
     await analytics.android?.setSessionTimeoutDuration(2000000);
     setMessage('setSessionTimeoutDuration succeeded');
   }
 
-  Future<void> _testSetUserProperty() async {
+  Future<Null> _testSetUserProperty() async {
     await analytics.setUserProperty(name: 'regular', value: 'indeed');
     setMessage('setUserProperty succeeded');
   }
 
-  Future<void> _testAllEventTypes() async {
+  Future<Null> _testAllEventTypes() async {
     await analytics.logAddPaymentInfo();
     await analytics.logAddToCart(
       currency: 'USD',
diff --git a/packages/firebase_analytics/lib/firebase_analytics.dart b/packages/firebase_analytics/lib/firebase_analytics.dart
index e9764df855c1..034968f03261 100755
--- a/packages/firebase_analytics/lib/firebase_analytics.dart
+++ b/packages/firebase_analytics/lib/firebase_analytics.dart
@@ -41,7 +41,7 @@ class FirebaseAnalytics {
   final FirebaseAnalyticsAndroid android;
 
   /// Logs a custom Flutter Analytics event with the given [name] and event [parameters].
-  Future<void> logEvent(
+  Future<Null> logEvent(
       {@required String name, Map<String, dynamic> parameters}) async {
     if (_reservedEventNames.contains(name)) {
       throw ArgumentError.value(
@@ -66,7 +66,7 @@ class FirebaseAnalytics {
   /// This feature must be used in accordance with [Google's Privacy Policy][1].
   ///
   /// [1]: https://www.google.com/policies/privacy/
-  Future<void> setUserId(String id) async {
+  Future<Null> setUserId(String id) async {
     if (id == null) {
       throw ArgumentError.notNull('id');
     }
@@ -91,7 +91,7 @@ class FirebaseAnalytics {
   ///
   /// https://firebase.google.com/docs/reference/android/com/google/firebase/analytics/FirebaseAnalytics.html#setCurrentScreen(android.app.Activity, java.lang.String, java.lang.String)
   /// https://firebase.google.com/docs/reference/ios/firebaseanalytics/api/reference/Classes/FIRAnalytics#setscreennamescreenclass
-  Future<void> setCurrentScreen(
+  Future<Null> setCurrentScreen(
       {@required String screenName,
       String screenClassOverride = 'Flutter'}) async {
     if (screenName == null) {
@@ -116,7 +116,7 @@ class FirebaseAnalytics {
   /// alphanumeric characters or underscores and must start with an alphabetic
   /// character. The "firebase_" prefix is reserved and should not be used for
   /// user property names.
-  Future<void> setUserProperty(
+  Future<Null> setUserProperty(
       {@required String name, @required String value}) async {
     if (name == null) {
       throw ArgumentError.notNull('name');
@@ -144,7 +144,7 @@ class FirebaseAnalytics {
   /// to your app.
   ///
   /// See: https://firebase.google.com/docs/reference/android/com/google/firebase/analytics/FirebaseAnalytics.Event.html#ADD_PAYMENT_INFO
-  Future<void> logAddPaymentInfo() {
+  Future<Null> logAddPaymentInfo() {
     return logEvent(name: 'add_payment_info');
   }
 
@@ -157,7 +157,7 @@ class FirebaseAnalytics {
   /// revenue metrics can be computed accurately.
   ///
   /// See: https://firebase.google.com/docs/reference/android/com/google/firebase/analytics/FirebaseAnalytics.Event.html#ADD_TO_CART
-  Future<void> logAddToCart({
+  Future<Null> logAddToCart({
     @required String itemId,
     @required String itemName,
     @required String itemCategory,
@@ -200,7 +200,7 @@ class FirebaseAnalytics {
   /// revenue metrics can be computed accurately.
   ///
   /// See: https://firebase.google.com/docs/reference/android/com/google/firebase/analytics/FirebaseAnalytics.Event.html#ADD_TO_WISHLIST
-  Future<void> logAddToWishlist({
+  Future<Null> logAddToWishlist({
     @required String itemId,
     @required String itemName,
     @required String itemCategory,
@@ -230,7 +230,7 @@ class FirebaseAnalytics {
   /// Logs the standard `app_open` event.
   ///
   /// See: https://firebase.google.com/docs/reference/android/com/google/firebase/analytics/FirebaseAnalytics.Event.html#APP_OPEN
-  Future<void> logAppOpen() {
+  Future<Null> logAppOpen() {
     return logEvent(name: 'app_open');
   }
 
@@ -243,7 +243,7 @@ class FirebaseAnalytics {
   /// revenue metrics can be computed accurately.
   ///
   /// See: https://firebase.google.com/docs/reference/android/com/google/firebase/analytics/FirebaseAnalytics.Event.html#BEGIN_CHECKOUT
-  Future<void> logBeginCheckout({
+  Future<Null> logBeginCheckout({
     double value,
     String currency,
     String transactionId,
@@ -281,7 +281,7 @@ class FirebaseAnalytics {
   /// Log this event to supply the referral details of a re-engagement campaign.
   ///
   /// See: https://firebase.google.com/docs/reference/android/com/google/firebase/analytics/FirebaseAnalytics.Event.html#CAMPAIGN_DETAILS
-  Future<void> logCampaignDetails({
+  Future<Null> logCampaignDetails({
     @required String source,
     @required String medium,
     @required String campaign,
@@ -311,7 +311,7 @@ class FirebaseAnalytics {
   /// economy.
   ///
   /// See: https://firebase.google.com/docs/reference/android/com/google/firebase/analytics/FirebaseAnalytics.Event.html#EARN_VIRTUAL_CURRENCY
-  Future<void> logEarnVirtualCurrency({
+  Future<Null> logEarnVirtualCurrency({
     @required String virtualCurrencyName,
     @required num value,
   }) {
@@ -333,7 +333,7 @@ class FirebaseAnalytics {
   /// be computed accurately.
   ///
   /// See: https://firebase.google.com/docs/reference/android/com/google/firebase/analytics/FirebaseAnalytics.Event.html#ECOMMERCE_PURCHASE
-  Future<void> logEcommercePurchase({
+  Future<Null> logEcommercePurchase({
     String currency,
     double value,
     String transactionId,
@@ -382,7 +382,7 @@ class FirebaseAnalytics {
   /// parameter so that revenue metrics can be computed accurately.
   ///
   /// See: https://firebase.google.com/docs/reference/android/com/google/firebase/analytics/FirebaseAnalytics.Event.html#GENERATE_LEAD
-  Future<void> logGenerateLead({
+  Future<Null> logGenerateLead({
     String currency,
     double value,
   }) {
@@ -404,7 +404,7 @@ class FirebaseAnalytics {
   /// are in your app.
   ///
   /// See: https://firebase.google.com/docs/reference/android/com/google/firebase/analytics/FirebaseAnalytics.Event.html#JOIN_GROUP
-  Future<void> logJoinGroup({
+  Future<Null> logJoinGroup({
     @required String groupId,
   }) {
     return logEvent(
@@ -422,7 +422,7 @@ class FirebaseAnalytics {
   /// identify certain levels that are difficult to pass.
   ///
   /// See: https://firebase.google.com/docs/reference/android/com/google/firebase/analytics/FirebaseAnalytics.Event.html#LEVEL_UP
-  Future<void> logLevelUp({
+  Future<Null> logLevelUp({
     @required int level,
     String character,
   }) {
@@ -441,7 +441,7 @@ class FirebaseAnalytics {
   /// has logged in.
   ///
   /// See: https://firebase.google.com/docs/reference/android/com/google/firebase/analytics/FirebaseAnalytics.Event.html#LOGIN
-  Future<void> logLogin() {
+  Future<Null> logLogin() {
     return logEvent(name: 'login');
   }
 
@@ -453,7 +453,7 @@ class FirebaseAnalytics {
   /// behaviors.
   ///
   /// See: https://firebase.google.com/docs/reference/android/com/google/firebase/analytics/FirebaseAnalytics.Event.html#POST_SCORE
-  Future<void> logPostScore({
+  Future<Null> logPostScore({
     @required int score,
     int level,
     String character,
@@ -477,7 +477,7 @@ class FirebaseAnalytics {
   /// parameter so that revenue metrics can be computed accurately.
   ///
   /// See: https://firebase.google.com/docs/reference/android/com/google/firebase/analytics/FirebaseAnalytics.Event.html#PRESENT_OFFER
-  Future<void> logPresentOffer({
+  Future<Null> logPresentOffer({
     @required String itemId,
     @required String itemName,
     @required String itemCategory,
@@ -511,7 +511,7 @@ class FirebaseAnalytics {
   /// parameter so that revenue metrics can be computed accurately.
   ///
   /// See: https://firebase.google.com/docs/reference/android/com/google/firebase/analytics/FirebaseAnalytics.Event.html#PURCHASE_REFUND
-  Future<void> logPurchaseRefund({
+  Future<Null> logPurchaseRefund({
     String currency,
     double value,
     String transactionId,
@@ -535,7 +535,7 @@ class FirebaseAnalytics {
   /// This event can help you identify the most popular content in your app.
   ///
   /// See: https://firebase.google.com/docs/reference/android/com/google/firebase/analytics/FirebaseAnalytics.Event.html#SEARCH
-  Future<void> logSearch({
+  Future<Null> logSearch({
     @required String searchTerm,
     int numberOfNights,
     int numberOfRooms,
@@ -570,7 +570,7 @@ class FirebaseAnalytics {
   /// of content in your app.
   ///
   /// See: https://firebase.google.com/docs/reference/android/com/google/firebase/analytics/FirebaseAnalytics.Event.html#SELECT_CONTENT
-  Future<void> logSelectContent({
+  Future<Null> logSelectContent({
     @required String contentType,
     @required String itemId,
   }) {
@@ -589,7 +589,7 @@ class FirebaseAnalytics {
   /// viral content.
   ///
   /// See: https://firebase.google.com/docs/reference/android/com/google/firebase/analytics/FirebaseAnalytics.Event.html#SHARE
-  Future<void> logShare({
+  Future<Null> logShare({
     @required String contentType,
     @required String itemId,
   }) {
@@ -610,7 +610,7 @@ class FirebaseAnalytics {
   /// logged out users.
   ///
   /// See: https://firebase.google.com/docs/reference/android/com/google/firebase/analytics/FirebaseAnalytics.Event.html#SIGN_UP
-  Future<void> logSignUp({
+  Future<Null> logSignUp({
     @required String signUpMethod,
   }) {
     return logEvent(
@@ -627,7 +627,7 @@ class FirebaseAnalytics {
   /// identify which virtual goods are the most popular objects of purchase.
   ///
   /// See: https://firebase.google.com/docs/reference/android/com/google/firebase/analytics/FirebaseAnalytics.Event.html#SPEND_VIRTUAL_CURRENCY
-  Future<void> logSpendVirtualCurrency({
+  Future<Null> logSpendVirtualCurrency({
     @required String itemName,
     @required String virtualCurrencyName,
     @required num value,
@@ -649,7 +649,7 @@ class FirebaseAnalytics {
   /// users complete this process and move on to the full app experience.
   ///
   /// See: https://firebase.google.com/docs/reference/android/com/google/firebase/analytics/FirebaseAnalytics.Event.html#TUTORIAL_BEGIN
-  Future<void> logTutorialBegin() {
+  Future<Null> logTutorialBegin() {
     return logEvent(name: 'tutorial_begin');
   }
 
@@ -660,7 +660,7 @@ class FirebaseAnalytics {
   /// completion rate of your on-boarding process.
   ///
   /// See: https://firebase.google.com/docs/reference/android/com/google/firebase/analytics/FirebaseAnalytics.Event.html#TUTORIAL_COMPLETE
-  Future<void> logTutorialComplete() {
+  Future<Null> logTutorialComplete() {
     return logEvent(name: 'tutorial_complete');
   }
 
@@ -673,7 +673,7 @@ class FirebaseAnalytics {
   /// experiencing all that your game has to offer.
   ///
   /// See: https://firebase.google.com/docs/reference/android/com/google/firebase/analytics/FirebaseAnalytics.Event.html#UNLOCK_ACHIEVEMENT
-  Future<void> logUnlockAchievement({
+  Future<Null> logUnlockAchievement({
     @required String id,
   }) {
     return logEvent(
@@ -694,7 +694,7 @@ class FirebaseAnalytics {
   /// that revenue metrics can be computed accurately.
   ///
   /// See: https://firebase.google.com/docs/reference/android/com/google/firebase/analytics/FirebaseAnalytics.Event.html#VIEW_ITEM
-  Future<void> logViewItem({
+  Future<Null> logViewItem({
     @required String itemId,
     @required String itemName,
     @required String itemCategory,
@@ -747,7 +747,7 @@ class FirebaseAnalytics {
   /// certain category.
   ///
   /// See: https://firebase.google.com/docs/reference/android/com/google/firebase/analytics/FirebaseAnalytics.Event.html#VIEW_ITEM_LIST
-  Future<void> logViewItemList({
+  Future<Null> logViewItemList({
     @required String itemCategory,
   }) {
     return logEvent(
@@ -764,7 +764,7 @@ class FirebaseAnalytics {
   /// search.
   ///
   /// See: https://firebase.google.com/docs/reference/android/com/google/firebase/analytics/FirebaseAnalytics.Event.html#VIEW_SEARCH_RESULTS
-  Future<void> logViewSearchResults({
+  Future<Null> logViewSearchResults({
     @required String searchTerm,
   }) {
     return logEvent(
@@ -786,7 +786,7 @@ class FirebaseAnalyticsAndroid {
   /// Sets whether analytics collection is enabled for this app on this device.
   ///
   /// This setting is persisted across app sessions. By default it is enabled.
-  Future<void> setAnalyticsCollectionEnabled(bool enabled) async {
+  Future<Null> setAnalyticsCollectionEnabled(bool enabled) async {
     if (enabled == null) {
       throw ArgumentError.notNull('enabled');
     }
@@ -797,7 +797,7 @@ class FirebaseAnalyticsAndroid {
   /// Sets the minimum engagement time required before starting a session.
   ///
   /// The default value is 10000 (10 seconds).
-  Future<void> setMinimumSessionDuration(int milliseconds) async {
+  Future<Null> setMinimumSessionDuration(int milliseconds) async {
     if (milliseconds == null) {
       throw ArgumentError.notNull('milliseconds');
     }
@@ -808,7 +808,7 @@ class FirebaseAnalyticsAndroid {
   /// Sets the duration of inactivity that terminates the current session.
   ///
   /// The default value is 1800000 (30 minutes).
-  Future<void> setSessionTimeoutDuration(int milliseconds) async {
+  Future<Null> setSessionTimeoutDuration(int milliseconds) async {
     if (milliseconds == null) {
       throw ArgumentError.notNull('milliseconds');
     }
diff --git a/packages/firebase_analytics/test/firebase_analytics_test.dart b/packages/firebase_analytics/test/firebase_analytics_test.dart
index 67372733bd26..a4718c1b2b0a 100755
--- a/packages/firebase_analytics/test/firebase_analytics_test.dart
+++ b/packages/firebase_analytics/test/firebase_analytics_test.dart
@@ -155,7 +155,7 @@ void main() {
       expect(analytics.logEvent(name: 'firebase_foo'), throwsArgumentError);
     });
 
-    void smokeTest(String testFunctionName, Future<void> testFunction()) {
+    void smokeTest(String testFunctionName, Future<Null> testFunction()) {
       test('$testFunctionName works', () async {
         await testFunction();
         expect(name, testFunctionName);
@@ -301,7 +301,7 @@ void main() {
             ));
 
     void testRequiresValueAndCurrencyTogether(
-        String methodName, Future<void> testFn()) {
+        String methodName, Future<Null> testFn()) {
       test('$methodName requires value and currency together', () async {
         try {
           testFn();
diff --git a/packages/firebase_auth/lib/firebase_auth.dart b/packages/firebase_auth/lib/firebase_auth.dart
index 45a177331b91..5b5328b2302d 100755
--- a/packages/firebase_auth/lib/firebase_auth.dart
+++ b/packages/firebase_auth/lib/firebase_auth.dart
@@ -474,7 +474,7 @@ class FirebaseAuth {
     });
   }
 
-  Future<dynamic> _callHandler(MethodCall call) async {
+  Future<Null> _callHandler(MethodCall call) async {
     switch (call.method) {
       case 'onAuthStateChanged':
         _onAuthStageChangedHandler(call);
@@ -514,6 +514,7 @@ class FirebaseAuth {
         codeAutoRetrievalTimeout(verificationId);
         break;
     }
+    return null;
   }
 
   void _onAuthStageChangedHandler(MethodCall call) {
diff --git a/packages/firebase_auth/test/firebase_auth_test.dart b/packages/firebase_auth/test/firebase_auth_test.dart
index d5f0e3146ee7..06b0814ce052 100755
--- a/packages/firebase_auth/test/firebase_auth_test.dart
+++ b/packages/firebase_auth/test/firebase_auth_test.dart
@@ -453,7 +453,7 @@ void main() {
     test('onAuthStateChanged', () async {
       mockHandleId = 42;
 
-      Future<void> simulateEvent(Map<String, dynamic> user) async {
+      Future<Null> simulateEvent(Map<String, dynamic> user) async {
         await BinaryMessages.handlePlatformMessage(
           FirebaseAuth.channel.name,
           FirebaseAuth.channel.codec.encodeMethodCall(
@@ -471,7 +471,7 @@ void main() {
       // Subscribe and allow subscription to complete.
       final StreamSubscription<FirebaseUser> subscription =
           auth.onAuthStateChanged.listen(events.add);
-      await Future<void>.delayed(const Duration(seconds: 0));
+      await Future<Null>.delayed(const Duration(seconds: 0));
 
       await simulateEvent(null);
       await simulateEvent(mockFirebaseUser());
@@ -484,7 +484,7 @@ void main() {
 
       // Cancel subscription and allow cancellation to complete.
       subscription.cancel();
-      await Future<void>.delayed(const Duration(seconds: 0));
+      await Future<Null>.delayed(const Duration(seconds: 0));
 
       expect(
         log,
diff --git a/packages/firebase_core/example/lib/main.dart b/packages/firebase_core/example/lib/main.dart
index de231536c911..f0e603a4ff3e 100644
--- a/packages/firebase_core/example/lib/main.dart
+++ b/packages/firebase_core/example/lib/main.dart
@@ -12,7 +12,7 @@ class MyApp extends StatelessWidget {
     apiKey: 'AIzaSyBq6mcufFXfyqr79uELCiqM_O_1-G72PVU',
   );
 
-  Future<void> _configure() async {
+  Future<Null> _configure() async {
     final FirebaseApp app = await FirebaseApp.configure(
       name: name,
       options: options,
@@ -21,12 +21,12 @@ class MyApp extends StatelessWidget {
     print('Configured $app');
   }
 
-  Future<void> _allApps() async {
+  Future<Null> _allApps() async {
     final List<FirebaseApp> apps = await FirebaseApp.allApps();
     print('Currently configured apps: $apps');
   }
 
-  Future<void> _options() async {
+  Future<Null> _options() async {
     final FirebaseApp app = await FirebaseApp.appNamed(name);
     final FirebaseOptions options = await app?.options;
     print('Current options for app $name: $options');
diff --git a/packages/firebase_database/example/lib/main.dart b/packages/firebase_database/example/lib/main.dart
index 0430e66434b7..79865c9c5411 100755
--- a/packages/firebase_database/example/lib/main.dart
+++ b/packages/firebase_database/example/lib/main.dart
@@ -92,7 +92,7 @@ class _MyHomePageState extends State<MyHomePage> {
     _counterSubscription.cancel();
   }
 
-  Future<void> _increment() async {
+  Future<Null> _increment() async {
     // Increment counter in transaction.
     final TransactionResult transactionResult =
         await _counterRef.runTransaction((MutableData mutableData) async {
diff --git a/packages/firebase_database/test/firebase_database_test.dart b/packages/firebase_database/test/firebase_database_test.dart
index 653fc2a484ea..bb79a1cdc0f4 100755
--- a/packages/firebase_database/test/firebase_database_test.dart
+++ b/packages/firebase_database/test/firebase_database_test.dart
@@ -36,7 +36,7 @@ void main() {
             return true;
           case 'DatabaseReference#runTransaction':
             Map<String, dynamic> updatedValue;
-            Future<void> simulateEvent(
+            Future<Null> simulateEvent(
                 int transactionKey, final MutableData mutableData) async {
               await BinaryMessages.handlePlatformMessage(
                 channel.name,
@@ -454,7 +454,7 @@ void main() {
         const int errorCode = 12;
         const String errorDetails = 'Some details';
         final Query query = database.reference().child('some path');
-        Future<void> simulateError(String errorMessage) async {
+        Future<Null> simulateError(String errorMessage) async {
           await BinaryMessages.handlePlatformMessage(
             channel.name,
             channel.codec.encodeMethodCall(
@@ -476,7 +476,7 @@ void main() {
         // Subscribe and allow subscription to complete.
         final StreamSubscription<Event> subscription =
             query.onValue.listen((_) {}, onError: errors.add);
-        await Future<void>.delayed(const Duration(seconds: 0));
+        await Future<Null>.delayed(const Duration(seconds: 0));
 
         await simulateError('Bad foo');
         await simulateError('Bad bar');
@@ -494,7 +494,7 @@ void main() {
         mockHandleId = 87;
         final String path = 'foo';
         final Query query = database.reference().child(path);
-        Future<void> simulateEvent(String value) async {
+        Future<Null> simulateEvent(String value) async {
           await BinaryMessages.handlePlatformMessage(
             channel.name,
             channel.codec.encodeMethodCall(
@@ -515,7 +515,7 @@ void main() {
         // Subscribe and allow subscription to complete.
         final StreamSubscription<Event> subscription =
             query.onValue.listen(events.add);
-        await Future<void>.delayed(const Duration(seconds: 0));
+        await Future<Null>.delayed(const Duration(seconds: 0));
 
         await simulateEvent('1');
         await simulateEvent('2');
@@ -528,7 +528,7 @@ void main() {
 
         // Cancel subscription and allow cancellation to complete.
         subscription.cancel();
-        await Future<void>.delayed(const Duration(seconds: 0));
+        await Future<Null>.delayed(const Duration(seconds: 0));
 
         expect(
           log,
diff --git a/packages/firebase_messaging/example/lib/main.dart b/packages/firebase_messaging/example/lib/main.dart
index 8a24b939cc9d..ab464ee84e6d 100644
--- a/packages/firebase_messaging/example/lib/main.dart
+++ b/packages/firebase_messaging/example/lib/main.dart
@@ -29,12 +29,12 @@ class Item {
     _controller.add(this);
   }
 
-  static final Map<String, Route<void>> routes = <String, Route<void>>{};
-  Route<void> get route {
+  static final Map<String, Route<Null>> routes = <String, Route<Null>>{};
+  Route<Null> get route {
     final String routeName = '/detail/$itemId';
     return routes.putIfAbsent(
       routeName,
-      () => MaterialPageRoute<void>(
+      () => MaterialPageRoute<Null>(
             settings: RouteSettings(name: routeName),
             builder: (BuildContext context) => DetailPage(itemId),
           ),
diff --git a/packages/firebase_messaging/lib/firebase_messaging.dart b/packages/firebase_messaging/lib/firebase_messaging.dart
index 5822039121d5..4cacff8b3b3a 100644
--- a/packages/firebase_messaging/lib/firebase_messaging.dart
+++ b/packages/firebase_messaging/lib/firebase_messaging.dart
@@ -96,7 +96,7 @@ class FirebaseMessaging {
     _channel.invokeMethod('unsubscribeFromTopic', topic);
   }
 
-  Future<dynamic> _handleMethod(MethodCall call) async {
+  Future<Null> _handleMethod(MethodCall call) async {
     switch (call.method) {
       case "onToken":
         final String token = call.arguments;
diff --git a/packages/firebase_storage/example/lib/main.dart b/packages/firebase_storage/example/lib/main.dart
index 553ee8301642..5125e95e09fa 100755
--- a/packages/firebase_storage/example/lib/main.dart
+++ b/packages/firebase_storage/example/lib/main.dart
@@ -55,7 +55,7 @@ class _MyHomePageState extends State<MyHomePage> {
   GlobalKey<ScaffoldState> _scaffoldKey = GlobalKey();
   List<StorageUploadTask> _tasks = <StorageUploadTask>[];
 
-  Future<void> _uploadFile() async {
+  Future<Null> _uploadFile() async {
     final String uuid = Uuid().v1();
     final Directory systemTempDir = Directory.systemTemp;
     final File file = await File('${systemTempDir.path}/foo$uuid.txt').create();
@@ -76,7 +76,7 @@ class _MyHomePageState extends State<MyHomePage> {
     });
   }
 
-  Future<void> _downloadFile(StorageReference ref) async {
+  Future<Null> _downloadFile(StorageReference ref) async {
     final String url = await ref.getDownloadURL();
     final String uuid = Uuid().v1();
     final http.Response downloadData = await http.get(url);
diff --git a/packages/google_maps_flutter/lib/src/controller.dart b/packages/google_maps_flutter/lib/src/controller.dart
index 629ab2a348ea..01b05b4fe2db 100644
--- a/packages/google_maps_flutter/lib/src/controller.dart
+++ b/packages/google_maps_flutter/lib/src/controller.dart
@@ -74,7 +74,7 @@ class GoogleMapController extends ChangeNotifier {
 
   final int _id;
 
-  Future<dynamic> _handleMethodCall(MethodCall call) async {
+  Future<void> _handleMethodCall(MethodCall call) async {
     switch (call.method) {
       case 'infoWindow#onTap':
         final String markerId = call.arguments['marker'];
diff --git a/packages/google_sign_in/README.md b/packages/google_sign_in/README.md
index 8abeae5b1729..64268008a9ee 100755
--- a/packages/google_sign_in/README.md
+++ b/packages/google_sign_in/README.md
@@ -72,7 +72,7 @@ GoogleSignIn _googleSignIn = GoogleSignIn(
 You can now use the `GoogleSignIn` class to authenticate in your Dart code, e.g.
 
 ```
-Future<void> _handleSignIn() async {
+Future<Null> _handleSignIn() async {
   try {
     await _googleSignIn.signIn();
   } catch (error) {
diff --git a/packages/google_sign_in/example/lib/main.dart b/packages/google_sign_in/example/lib/main.dart
index 390bba367e02..75b2f4ca3808 100755
--- a/packages/google_sign_in/example/lib/main.dart
+++ b/packages/google_sign_in/example/lib/main.dart
@@ -48,7 +48,7 @@ class SignInDemoState extends State<SignInDemo> {
     _googleSignIn.signInSilently();
   }
 
-  Future<void> _handleGetContact() async {
+  Future<Null> _handleGetContact() async {
     setState(() {
       _contactText = "Loading contact info...";
     });
@@ -94,7 +94,7 @@ class SignInDemoState extends State<SignInDemo> {
     return null;
   }
 
-  Future<void> _handleSignIn() async {
+  Future<Null> _handleSignIn() async {
     try {
       await _googleSignIn.signIn();
     } catch (error) {
@@ -102,7 +102,7 @@ class SignInDemoState extends State<SignInDemo> {
     }
   }
 
-  Future<void> _handleSignOut() async {
+  Future<Null> _handleSignOut() async {
     _googleSignIn.disconnect();
   }
 
diff --git a/packages/local_auth/example/lib/main.dart b/packages/local_auth/example/lib/main.dart
index 6d0d9f7f1f9c..0d79acd86203 100644
--- a/packages/local_auth/example/lib/main.dart
+++ b/packages/local_auth/example/lib/main.dart
@@ -22,7 +22,7 @@ class _MyAppState extends State<MyApp> {
   List<BiometricType> _availableBiometrics;
   String _authorized = 'Not Authorized';
 
-  Future<void> _checkBiometrics() async {
+  Future<Null> _checkBiometrics() async {
     bool canCheckBiometrics;
     try {
       canCheckBiometrics = await auth.canCheckBiometrics;
@@ -36,7 +36,7 @@ class _MyAppState extends State<MyApp> {
     });
   }
 
-  Future<void> _getAvailableBiometrics() async {
+  Future<Null> _getAvailableBiometrics() async {
     List<BiometricType> availableBiometrics;
     try {
       availableBiometrics = await auth.getAvailableBiometrics();
@@ -50,7 +50,7 @@ class _MyAppState extends State<MyApp> {
     });
   }
 
-  Future<void> _authenticate() async {
+  Future<Null> _authenticate() async {
     bool authenticated = false;
     try {
       authenticated = await auth.authenticateWithBiometrics(
diff --git a/packages/package_info/example/lib/main.dart b/packages/package_info/example/lib/main.dart
index 9edbce152657..dca6908035dc 100644
--- a/packages/package_info/example/lib/main.dart
+++ b/packages/package_info/example/lib/main.dart
@@ -45,7 +45,7 @@ class _MyHomePageState extends State<MyHomePage> {
     _initPackageInfo();
   }
 
-  Future<void> _initPackageInfo() async {
+  Future<Null> _initPackageInfo() async {
     final PackageInfo info = await PackageInfo.fromPlatform();
     setState(() {
       _packageInfo = info;
diff --git a/packages/quick_actions/lib/quick_actions.dart b/packages/quick_actions/lib/quick_actions.dart
index 7747495d37b8..4d2acf99874f 100644
--- a/packages/quick_actions/lib/quick_actions.dart
+++ b/packages/quick_actions/lib/quick_actions.dart
@@ -49,14 +49,14 @@ class QuickActions {
   }
 
   /// Sets the [ShortcutItem]s to become the app's quick actions.
-  Future<void> setShortcutItems(List<ShortcutItem> items) async {
+  Future<Null> setShortcutItems(List<ShortcutItem> items) async {
     final List<Map<String, String>> itemsList =
         items.map(_serializeItem).toList();
     await _kChannel.invokeMethod('setShortcutItems', itemsList);
   }
 
   /// Removes all [ShortcutItem]s registered for the app.
-  Future<void> clearShortcutItems() =>
+  Future<Null> clearShortcutItems() =>
       _kChannel.invokeMethod('clearShortcutItems');
 
   Map<String, String> _serializeItem(ShortcutItem item) {
diff --git a/packages/sensors/test/sensors_test.dart b/packages/sensors/test/sensors_test.dart
index 9bbbb49c6315..0867b3566bef 100644
--- a/packages/sensors/test/sensors_test.dart
+++ b/packages/sensors/test/sensors_test.dart
@@ -40,7 +40,7 @@ void main() {
     expect(event.y, 2.0);
     expect(event.z, 3.0);
 
-    await Future<void>.delayed(Duration.zero);
+    await Future<Null>.delayed(Duration.zero);
     expect(isCanceled, isTrue);
   });
 }
diff --git a/packages/shared_preferences/example/lib/main.dart b/packages/shared_preferences/example/lib/main.dart
index 34347f89b844..97d22f8c662e 100644
--- a/packages/shared_preferences/example/lib/main.dart
+++ b/packages/shared_preferences/example/lib/main.dart
@@ -32,7 +32,7 @@ class SharedPreferencesDemoState extends State<SharedPreferencesDemo> {
   Future<SharedPreferences> _prefs = SharedPreferences.getInstance();
   Future<int> _counter;
 
-  Future<void> _incrementCounter() async {
+  Future<Null> _incrementCounter() async {
     final SharedPreferences prefs = await _prefs;
     final int counter = (prefs.getInt('counter') ?? 0) + 1;
 
diff --git a/packages/url_launcher/example/lib/main.dart b/packages/url_launcher/example/lib/main.dart
index f330bc56a3f2..d29aaa35342d 100644
--- a/packages/url_launcher/example/lib/main.dart
+++ b/packages/url_launcher/example/lib/main.dart
@@ -33,9 +33,9 @@ class MyHomePage extends StatefulWidget {
 }
 
 class _MyHomePageState extends State<MyHomePage> {
-  Future<void> _launched;
+  Future<Null> _launched;
 
-  Future<void> _launchInBrowser(String url) async {
+  Future<Null> _launchInBrowser(String url) async {
     if (await canLaunch(url)) {
       await launch(url, forceSafariVC: false, forceWebView: false);
     } else {
@@ -43,7 +43,7 @@ class _MyHomePageState extends State<MyHomePage> {
     }
   }
 
-  Future<void> _launchInWebViewOrVC(String url) async {
+  Future<Null> _launchInWebViewOrVC(String url) async {
     if (await canLaunch(url)) {
       await launch(url, forceSafariVC: true, forceWebView: true);
     } else {
@@ -51,7 +51,7 @@ class _MyHomePageState extends State<MyHomePage> {
     }
   }
 
-  Future<void> _launchInWebViewWithJavaScript(String url) async {
+  Future<Null> _launchInWebViewWithJavaScript(String url) async {
     if (await canLaunch(url)) {
       await launch(
         url,
@@ -64,7 +64,7 @@ class _MyHomePageState extends State<MyHomePage> {
     }
   }
 
-  Widget _launchStatus(BuildContext context, AsyncSnapshot<void> snapshot) {
+  Widget _launchStatus(BuildContext context, AsyncSnapshot<Null> snapshot) {
     if (snapshot.hasError) {
       return Text('Error: ${snapshot.error}');
     } else {
@@ -108,7 +108,7 @@ class _MyHomePageState extends State<MyHomePage> {
               child: const Text('Launch in app(JavaScript ON)'),
             ),
             const Padding(padding: EdgeInsets.all(16.0)),
-            FutureBuilder<void>(future: _launched, builder: _launchStatus),
+            FutureBuilder<Null>(future: _launched, builder: _launchStatus),
           ],
         ),
       ),
diff --git a/packages/webview_flutter/test/webview_flutter_test.dart b/packages/webview_flutter/test/webview_flutter_test.dart
index 7a586b2c5533..9768b26fa190 100644
--- a/packages/webview_flutter/test/webview_flutter_test.dart
+++ b/packages/webview_flutter/test/webview_flutter_test.dart
@@ -122,7 +122,7 @@ class FakePlatformWebView {
     switch (call.method) {
       case 'loadUrl':
         lastUrlLoaded = call.arguments;
-        return Future<void>.sync(() {});
+        return Future<Null>.sync(() => null);
       case 'updateSettings':
         if (call.arguments['jsMode'] == null) {
           break;
@@ -130,7 +130,7 @@ class FakePlatformWebView {
         javaScriptMode = JavaScriptMode.values[call.arguments['jsMode']];
         break;
     }
-    return Future<void>.sync(() {});
+    return Future<Null>.sync(() => null);
   }
 }
 
@@ -148,7 +148,7 @@ class _FakePlatformViewsController {
         );
         return Future<int>.sync(() => 1);
       default:
-        return Future<void>.sync(() {});
+        return Future<Null>.sync(() => null);
     }
   }