Remote returns for function expression inferred return type void. (#61582)

packages/flutter/test/services/default_binary_messenger_test.dart

@@ -26,7 +26,6 @@ void main() {
     ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage(
         channel, _makeByteData('bar'), (ByteData message) async {
       count += 1;
-      return null;
     });
     expect(count, equals(0));
     await ui.channelBuffers.drain(channel,

packages/flutter_tools/lib/src/devfs.dart

@@ -271,7 +271,7 @@ class _DevFSHttpWriter {
         );
         await request.addStream(contents);
         final HttpClientResponse response = await request.close();
-        response.listen((_) => null,
+        response.listen((_) {},
           onError: (dynamic error) {
             _logger.printTrace('error: $error');
           },

packages/flutter_tools/test/commands.shard/hermetic/attach_test.dart

@@ -85,7 +85,7 @@ void main() {
         when(portForwarder.forwardedPorts)
           .thenReturn(<ForwardedPort>[ForwardedPort(hostPort, devicePort)]);
         when(portForwarder.unforward(any))
-          .thenAnswer((_) async => null);
+          .thenAnswer((_) async {});
 
         final HttpClientRequest httpClientRequest = MockHttpClientRequest();
         httpClient = MockHttpClient();
@@ -296,7 +296,7 @@ void main() {
       when(portForwarder.forwardedPorts)
         .thenReturn(<ForwardedPort>[ForwardedPort(hostPort, devicePort)]);
       when(portForwarder.unforward(any))
-        .thenAnswer((_) async => null);
+        .thenAnswer((_) async {});
       when(mockHotRunner.attach(appStartedCompleter: anyNamed('appStartedCompleter')))
         .thenAnswer((_) async => 0);
       when(mockHotRunnerFactory.build(
@@ -370,7 +370,7 @@ void main() {
       when(portForwarder.forwardedPorts)
         .thenReturn(<ForwardedPort>[ForwardedPort(hostPort, devicePort)]);
       when(portForwarder.unforward(any))
-        .thenAnswer((_) async => null);
+        .thenAnswer((_) async {});
       when(mockHotRunner.attach(appStartedCompleter: anyNamed('appStartedCompleter')))
         .thenAnswer((_) async => 0);
       when(mockHotRunnerFactory.build(
@@ -424,7 +424,7 @@ void main() {
         when(portForwarder.forwardedPorts)
           .thenReturn(<ForwardedPort>[ForwardedPort(hostPort, devicePort)]);
         when(portForwarder.unforward(any))
-          .thenAnswer((_) async => null);
+          .thenAnswer((_) async {});
       });
 
       testUsingContext('succeeds in ipv4 mode', () async {

packages/flutter_tools/test/commands.shard/hermetic/drive_test.dart

@@ -202,7 +202,6 @@ void main() {
         expect(environment, <String, String>{
           'VM_SERVICE_URL': 'null',
         });
-        return null;
       });
       appStopper = expectAsync1((DriveCommand command) async {
         return true;

packages/flutter_tools/test/general.shard/application_package_test.dart

@@ -295,7 +295,7 @@ void main() {
       when(os.unzip(any, any)).thenAnswer((Invocation invocation) {
         final File zipFile = invocation.positionalArguments[0] as File;
         if (zipFile.path != 'app.ipa') {
-          return null;
+          return;
         }
         final Directory targetDirectory = invocation.positionalArguments[1] as Directory;
         final String bundlePath1 =
@@ -316,7 +316,7 @@ void main() {
       when(os.unzip(any, any)).thenAnswer((Invocation invocation) {
         final File zipFile = invocation.positionalArguments[0] as File;
         if (zipFile.path != 'app.ipa') {
-          return null;
+          return;
         }
         final Directory targetDirectory = invocation.positionalArguments[1] as Directory;
         final Directory bundleAppDir = globals.fs.directory(

packages/flutter_tools/test/general.shard/version_test.dart

@@ -655,7 +655,7 @@ void fakeData(
 
     if (expectSetStamp) {
       stamp = VersionCheckStamp.fromJson(castStringKeyedMap(json.decode(invocation.positionalArguments[1] as String)));
-      return null;
+      return;
     }
 
     throw StateError('Unexpected call to Cache.setStampFor(${invocation.positionalArguments}, ${invocation.namedArguments})');