add missing type parameter on methods (#22096)

dev/benchmarks/complex_layout/lib/main.dart

@@ -494,7 +494,7 @@ class ItemGalleryBox extends StatelessWidget {
           children: <Widget>[
             Expanded(
               child: TabBarView(
-                children: tabNames.map((String tabName) {
+                children: tabNames.map<Widget>((String tabName) {
                   return Container(
                     key: PageStorageKey<String>(tabName),
                     child: Padding(

dev/bots/analyze.dart

@@ -207,8 +207,8 @@ Future<EvalResult> _evalCommand(String executable, List<String> arguments, {
   final Future<List<List<int>>> savedStderr = process.stderr.toList();
   final int exitCode = await process.exitCode;
   final EvalResult result = EvalResult(
-    stdout: utf8.decode((await savedStdout).expand((List<int> ints) => ints).toList()),
+    stdout: utf8.decode((await savedStdout).expand<int>((List<int> ints) => ints).toList()),
-    stderr: utf8.decode((await savedStderr).expand((List<int> ints) => ints).toList()),
+    stderr: utf8.decode((await savedStderr).expand<int>((List<int> ints) => ints).toList()),
     exitCode: exitCode,
   );
 
@@ -328,13 +328,13 @@ Future<Null> _verifyNoBadImportsInFlutter(String workingDirectory) async {
     .whereType<Directory>()
     .map<String>((Directory entity) => path.basename(entity.path))
     .toList()..sort();
-  if (!_matches(packages, directories)) {
+  if (!_matches<String>(packages, directories)) {
     errors.add(
       'flutter/lib/*.dart does not match flutter/lib/src/*/:\n'
       'These are the exported packages:\n' +
-      packages.map((String path) => '  lib/$path.dart').join('\n') +
+      packages.map<String>((String path) => '  lib/$path.dart').join('\n') +
       'These are the directories:\n' +
-      directories.map((String path) => '  lib/src/$path/').join('\n')
+      directories.map<String>((String path) => '  lib/src/$path/').join('\n')
     );
   }
   // Verify that the imports are well-ordered.
@@ -350,7 +350,7 @@ Future<Null> _verifyNoBadImportsInFlutter(String workingDirectory) async {
     }
   }
   for (String package in dependencyMap.keys) {
-    final List<String> loop = _deepSearch(dependencyMap, package);
+    final List<String> loop = _deepSearch<String>(dependencyMap, package);
     if (loop != null) {
       errors.add(
         '${yellow}Dependency loop:$reset ' +
@@ -421,7 +421,7 @@ List<T> _deepSearch<T>(Map<T, Set<T>> map, T start, [ Set<T> seen ]) {
       continue; // we catch these separately
     if (seen != null && seen.contains(key))
       return <T>[start, key];
-    final List<T> result = _deepSearch(
+    final List<T> result = _deepSearch<T>(
       map,
       key,
       (seen == null ? Set<T>.from(<T>[start]) : Set<T>.from(seen))..add(key),

dev/bots/prepare_package.dart

@@ -587,7 +587,7 @@ Future<Null> main(List<String> argList) async {
   argParser.addOption(
     'branch',
     defaultsTo: null,
-    allowed: Branch.values.map((Branch branch) => getBranchName(branch)),
+    allowed: Branch.values.map<String>((Branch branch) => getBranchName(branch)),
     help: 'The Flutter branch to build the archive with. Required.',
   );
   argParser.addOption(

dev/bots/run_command.dart

@@ -56,7 +56,7 @@ Future<Null> runCommand(String executable, List<String> arguments, {
 
   Future<List<List<int>>> savedStdout, savedStderr;
   if (printOutput) {
-    await Future.wait(<Future<void>>[
+    await Future.wait<void>(<Future<void>>[
       stdout.addStream(process.stdout),
       stderr.addStream(process.stderr)
     ]);
@@ -75,8 +75,8 @@ Future<Null> runCommand(String executable, List<String> arguments, {
       print(failureMessage);
     }
     if (!printOutput) {
-      stdout.writeln(utf8.decode((await savedStdout).expand((List<int> ints) => ints).toList()));
+      stdout.writeln(utf8.decode((await savedStdout).expand<int>((List<int> ints) => ints).toList()));
-      stderr.writeln(utf8.decode((await savedStderr).expand((List<int> ints) => ints).toList()));
+      stderr.writeln(utf8.decode((await savedStderr).expand<int>((List<int> ints) => ints).toList()));
     }
     print(
         '$redLine\n'

dev/bots/test/analyze-sample-code_test.dart

@@ -13,8 +13,8 @@ void main() {
       '../../bin/cache/dart-sdk/bin/dart',
       <String>['analyze-sample-code.dart', 'test/analyze-sample-code-test-input'],
     );
-    final List<String> stdout = await process.stdout.transform(utf8.decoder).transform(const LineSplitter()).toList();
+    final List<String> stdout = await process.stdout.transform<String>(utf8.decoder).transform<String>(const LineSplitter()).toList();
-    final List<String> stderr = await process.stderr.transform(utf8.decoder).transform(const LineSplitter()).toList();
+    final List<String> stderr = await process.stderr.transform<String>(utf8.decoder).transform<String>(const LineSplitter()).toList();
     final Match line = RegExp(r'^(.+)/main\.dart:[0-9]+:[0-9]+: .+$').matchAsPrefix(stdout[1]);
     expect(line, isNot(isNull));
     final String directory = line.group(1);

dev/devicelab/bin/tasks/commands_test.dart

@@ -30,8 +30,8 @@ void main() {
       );
       final StreamController<String> stdout = StreamController<String>.broadcast();
       run.stdout
-        .transform(utf8.decoder)
+        .transform<String>(utf8.decoder)
-        .transform(const LineSplitter())
+        .transform<String>(const LineSplitter())
         .listen((String line) {
           print('run:stdout: $line');
           stdout.add(line);
@@ -46,12 +46,12 @@ void main() {
           }
         });
       run.stderr
-        .transform(utf8.decoder)
+        .transform<String>(utf8.decoder)
-        .transform(const LineSplitter())
+        .transform<String>(const LineSplitter())
         .listen((String line) {
           stderr.writeln('run:stderr: $line');
         });
-      run.exitCode.then((int exitCode) { ok = false; });
+      run.exitCode.then<void>((int exitCode) { ok = false; });
       await Future.any<dynamic>(<Future<dynamic>>[ ready.future, run.exitCode ]);
       if (!ok)
         throw 'Failed to run test app.';
@@ -114,14 +114,14 @@ class DriveHelper {
       <String>['drive', '--use-existing-app', 'http://127.0.0.1:$vmServicePort/', '--keep-app-running', '--driver', 'test_driver/commands_${name}_test.dart'],
     );
     drive.stdout
-        .transform(utf8.decoder)
+        .transform<String>(utf8.decoder)
-        .transform(const LineSplitter())
+        .transform<String>(const LineSplitter())
         .listen((String line) {
       print('drive:stdout: $line');
     });
     drive.stderr
-        .transform(utf8.decoder)
+        .transform<String>(utf8.decoder)
-        .transform(const LineSplitter())
+        .transform<String>(const LineSplitter())
         .listen((String line) {
       stderr.writeln('drive:stderr: $line');
     });

dev/devicelab/bin/tasks/dartdocs.dart

@@ -21,7 +21,7 @@ Future<Null> main() async {
     int publicMembers = 0;
     int otherErrors = 0;
     int otherLines = 0;
-    await for (String entry in analysis.stdout.transform(utf8.decoder).transform(const LineSplitter())) {
+    await for (String entry in analysis.stdout.transform<String>(utf8.decoder).transform<String>(const LineSplitter())) {
       entry = entry.trim();
       print('analyzer stdout: $entry');
       if (entry == 'Building flutter tool...') {
@@ -36,7 +36,7 @@ Future<Null> main() async {
         otherLines += 1;
       }
     }
-    await for (String entry in analysis.stderr.transform(utf8.decoder).transform(const LineSplitter())) {
+    await for (String entry in analysis.stderr.transform<String>(utf8.decoder).transform<String>(const LineSplitter())) {
       print('analyzer stderr: $entry');
       if (entry.startsWith('[lint] ')) {
         // ignore this line

dev/devicelab/bin/tasks/flutter_attach_test.dart

@@ -26,8 +26,8 @@ Future<void> testReload(Process process, { Future<void> Function() onListening }
 
   int exitCode;
   process.stdout
-      .transform(utf8.decoder)
+      .transform<String>(utf8.decoder)
-      .transform(const LineSplitter())
+      .transform<String>(const LineSplitter())
       .listen((String line) {
     print('attach:stdout: $line');
     stdout.add(line);
@@ -43,14 +43,14 @@ Future<void> testReload(Process process, { Future<void> Function() onListening }
       finished.complete();
   });
   process.stderr
-      .transform(utf8.decoder)
+      .transform<String>(utf8.decoder)
-      .transform(const LineSplitter())
+      .transform<String>(const LineSplitter())
       .listen((String line) {
     print('run:stderr: $line');
     stdout.add(line);
   });
 
-  process.exitCode.then((int processExitCode) { exitCode = processExitCode; });
+  process.exitCode.then<void>((int processExitCode) { exitCode = processExitCode; });
 
   Future<dynamic> eventOrExit(Future<Null> event) {
     return Future.any<dynamic>(<Future<dynamic>>[ event, process.exitCode ]);

dev/devicelab/bin/tasks/flutter_test_performance.dart

@@ -45,7 +45,7 @@ Future<int> runTest() async {
   );
   int badLines = 0;
   TestStep step = TestStep.starting;
-  await for (String entry in analysis.stdout.transform(utf8.decoder).transform(const LineSplitter())) {
+  await for (String entry in analysis.stdout.transform<String>(utf8.decoder).transform<String>(const LineSplitter())) {
     print('test stdout ($step): $entry');
     if (step == TestStep.starting && entry == 'Building flutter tool...') {
       // ignore this line
@@ -76,7 +76,7 @@ Future<int> runTest() async {
       }
     }
   }
-  await for (String entry in analysis.stderr.transform(utf8.decoder).transform(const LineSplitter())) {
+  await for (String entry in analysis.stderr.transform<String>(utf8.decoder).transform<String>(const LineSplitter())) {
     print('test stderr: $entry');
     badLines += 1;
   }

dev/devicelab/bin/tasks/gradle_plugin_test.dart

@@ -297,7 +297,7 @@ class _Dependencies {
         .replaceAllMapped(_separatorExpr, (Match match) => '${match.group(1)}\n')
         .split('\n')
         // Expand escape sequences, so that '\ ', for example,ß becomes ' '
-        .map((String path) => path.replaceAllMapped(_escapeExpr, (Match match) => match.group(1)).trim())
+        .map<String>((String path) => path.replaceAllMapped(_escapeExpr, (Match match) => match.group(1)).trim())
         .where((String path) => path.isNotEmpty)
         .toSet();
   }

dev/devicelab/bin/tasks/routing_test.dart

@@ -37,8 +37,8 @@ void main() {
         <String>['run', '--verbose', '-d', device.deviceId, '--route', '/smuggle-it', 'lib/route.dart'],
       );
       run.stdout
-        .transform(utf8.decoder)
+        .transform<String>(utf8.decoder)
-        .transform(const LineSplitter())
+        .transform<String>(const LineSplitter())
         .listen((String line) {
           print('run:stdout: $line');
           if (vmServicePort == null) {
@@ -52,12 +52,12 @@ void main() {
           }
         });
       run.stderr
-        .transform(utf8.decoder)
+        .transform<String>(utf8.decoder)
-        .transform(const LineSplitter())
+        .transform<String>(const LineSplitter())
         .listen((String line) {
           stderr.writeln('run:stderr: $line');
         });
-      run.exitCode.then((int exitCode) { ok = false; });
+      run.exitCode.then<void>((int exitCode) { ok = false; });
       await Future.any<dynamic>(<Future<dynamic>>[ ready.future, run.exitCode ]);
       if (!ok)
         throw 'Failed to run test app.';
@@ -67,14 +67,14 @@ void main() {
         <String>['drive', '--use-existing-app', 'http://127.0.0.1:$vmServicePort/', '--no-keep-app-running', 'lib/route.dart'],
       );
       drive.stdout
-        .transform(utf8.decoder)
+        .transform<String>(utf8.decoder)
-        .transform(const LineSplitter())
+        .transform<String>(const LineSplitter())
         .listen((String line) {
           print('drive:stdout: $line');
         });
       drive.stderr
-        .transform(utf8.decoder)
+        .transform<String>(utf8.decoder)
-        .transform(const LineSplitter())
+        .transform<String>(const LineSplitter())
         .listen((String line) {
           stderr.writeln('drive:stderr: $line');
         });

dev/devicelab/bin/tasks/run_machine_concurrent_hot_reload.dart

@@ -27,7 +27,7 @@ void main() {
   }
 
   Stream<String> transformToLines(Stream<List<int>> byteStream) {
-    return byteStream.transform(utf8.decoder).transform(const LineSplitter());
+    return byteStream.transform<String>(utf8.decoder).transform<String>(const LineSplitter());
   }
 
   task(() async {
@@ -74,7 +74,7 @@ void main() {
       transformToLines(run.stderr).listen((String line) {
         stderr.writeln('run:stderr: $line');
       });
-      run.exitCode.then((int exitCode) {
+      run.exitCode.then<void>((int exitCode) {
         ok = false;
       });
       await Future.any<dynamic>(<Future<dynamic>>[ready.future, run.exitCode]);

dev/devicelab/bin/tasks/run_release_test.dart

@@ -29,8 +29,8 @@ void main() {
       final List<String> stderr = <String>[];
       int runExitCode;
       run.stdout
-        .transform(utf8.decoder)
+        .transform<String>(utf8.decoder)
-        .transform(const LineSplitter())
+        .transform<String>(const LineSplitter())
         .listen((String line) {
           print('run:stdout: $line');
           stdout.add(line);
@@ -38,13 +38,13 @@ void main() {
             ready.complete();
         });
       run.stderr
-        .transform(utf8.decoder)
+        .transform<String>(utf8.decoder)
-        .transform(const LineSplitter())
+        .transform<String>(const LineSplitter())
         .listen((String line) {
           print('run:stderr: $line');
           stdout.add(line);
         });
-      run.exitCode.then((int exitCode) { runExitCode = exitCode; });
+      run.exitCode.then<void>((int exitCode) { runExitCode = exitCode; });
       await Future.any<dynamic>(<Future<dynamic>>[ ready.future, run.exitCode ]);
       if (runExitCode != null)
         throw 'Failed to run test app; runner unexpected exited, with exit code $runExitCode.';

dev/devicelab/bin/tasks/service_extensions_test.dart

@@ -29,8 +29,8 @@ void main() {
         <String>['run', '--verbose', '-d', device.deviceId, 'lib/main.dart'],
       );
       run.stdout
-          .transform(utf8.decoder)
+          .transform<String>(utf8.decoder)
-          .transform(const LineSplitter())
+          .transform<String>(const LineSplitter())
           .listen((String line) {
         print('run:stdout: $line');
         if (vmServicePort == null) {
@@ -44,12 +44,12 @@ void main() {
         }
       });
       run.stderr
-          .transform(utf8.decoder)
+          .transform<String>(utf8.decoder)
-          .transform(const LineSplitter())
+          .transform<String>(const LineSplitter())
           .listen((String line) {
         stderr.writeln('run:stderr: $line');
       });
-      run.exitCode.then((int exitCode) { ok = false; });
+      run.exitCode.then<void>((int exitCode) { ok = false; });
       await Future.any<dynamic>(<Future<dynamic>>[ ready.future, run.exitCode ]);
       if (!ok)
         throw 'Failed to run test app.';

dev/devicelab/bin/tasks/technical_debt__cost.dart

@@ -54,7 +54,7 @@ Future<double> findCostsForRepo() async {
     workingDirectory: flutterDirectory.path,
   );
   double total = 0.0;
-  await for (String entry in git.stdout.transform(utf8.decoder).transform(const LineSplitter()))
+  await for (String entry in git.stdout.transform<String>(utf8.decoder).transform<String>(const LineSplitter()))
     total += await findCostsForFile(File(path.join(flutterDirectory.path, entry)));
   final int gitExitCode = await git.exitCode;
   if (gitExitCode != 0)

dev/devicelab/lib/framework/adb.dart

@@ -129,7 +129,7 @@ class AndroidDeviceDiscovery implements DeviceDiscovery {
   @override
   Future<Null> chooseWorkingDevice() async {
     final List<Device> allDevices = (await discoverDevices())
-      .map((String id) => AndroidDevice(deviceId: id))
+      .map<Device>((String id) => AndroidDevice(deviceId: id))
       .toList();
 
     if (allDevices.isEmpty)
@@ -298,19 +298,19 @@ class AndroidDevice implements Device {
         await adb(<String>['logcat', '--clear']);
         final Process process = await startProcess(adbPath, <String>['-s', deviceId, 'logcat']);
         process.stdout
-          .transform(utf8.decoder)
+          .transform<String>(utf8.decoder)
-          .transform(const LineSplitter())
+          .transform<String>(const LineSplitter())
           .listen((String line) {
             print('adb logcat: $line');
             stream.sink.add(line);
           }, onDone: () { stdoutDone.complete(); });
         process.stderr
-          .transform(utf8.decoder)
+          .transform<String>(utf8.decoder)
-          .transform(const LineSplitter())
+          .transform<String>(const LineSplitter())
           .listen((String line) {
             print('adb logcat stderr: $line');
           }, onDone: () { stderrDone.complete(); });
-        process.exitCode.then((int exitCode) {
+        process.exitCode.then<void>((int exitCode) {
           print('adb logcat process terminated with exit code $exitCode');
           if (!aborted) {
             stream.addError(BuildFailedError('adb logcat failed with exit code $exitCode.'));
@@ -374,7 +374,7 @@ class IosDeviceDiscovery implements DeviceDiscovery {
   @override
   Future<Null> chooseWorkingDevice() async {
     final List<IosDevice> allDevices = (await discoverDevices())
-      .map((String id) => IosDevice(deviceId: id))
+      .map<IosDevice>((String id) => IosDevice(deviceId: id))
       .toList();
 
     if (allDevices.isEmpty)
@@ -387,7 +387,7 @@ class IosDeviceDiscovery implements DeviceDiscovery {
   @override
   Future<List<String>> discoverDevices() async {
     final List<String> iosDeviceIDs = LineSplitter.split(await eval('idevice_id', <String>['-l']))
-      .map((String line) => line.trim())
+      .map<String>((String line) => line.trim())
       .where((String line) => line.isNotEmpty)
       .toList();
     if (iosDeviceIDs.isEmpty)

dev/devicelab/lib/framework/manifest.dart

@@ -83,7 +83,7 @@ Manifest _validateAndParseManifest(Map<dynamic, dynamic> manifestYaml) {
 List<ManifestTask> _validateAndParseTasks(dynamic tasksYaml) {
   _checkType(tasksYaml is Map, tasksYaml, 'Value of "tasks"', 'dictionary');
   final List<dynamic> sortedKeys = tasksYaml.keys.toList()..sort();
-  return sortedKeys.map((dynamic taskName) => _validateAndParseTask(taskName, tasksYaml[taskName])).toList();
+  return sortedKeys.map<ManifestTask>((dynamic taskName) => _validateAndParseTask(taskName, tasksYaml[taskName])).toList();
 }
 
 ManifestTask _validateAndParseTask(dynamic taskName, dynamic taskYaml) {

dev/devicelab/lib/framework/runner.dart

@@ -44,8 +44,8 @@ Future<Map<String, dynamic>> runTask(String taskName, { bool silent = false }) a
   final Completer<int> port = Completer<int>();
 
   final StreamSubscription<String> stdoutSub = runner.stdout
-      .transform(const Utf8Decoder())
+      .transform<String>(const Utf8Decoder())
-      .transform(const LineSplitter())
+      .transform<String>(const LineSplitter())
       .listen((String line) {
     if (!port.isCompleted) {
       final int portValue = parseServicePort(line, prefix: 'Observatory listening on ');
@@ -58,8 +58,8 @@ Future<Map<String, dynamic>> runTask(String taskName, { bool silent = false }) a
   });
 
   final StreamSubscription<String> stderrSub = runner.stderr
-      .transform(const Utf8Decoder())
+      .transform<String>(const Utf8Decoder())
-      .transform(const LineSplitter())
+      .transform<String>(const LineSplitter())
       .listen((String line) {
     stderr.writeln('[$taskName] [STDERR] $line');
   });

dev/devicelab/lib/framework/utils.dart

@@ -172,14 +172,14 @@ Future<String> getCurrentFlutterRepoCommit() {
     return null;
   }
 
-  return inDirectory(flutterDirectory, () {
+  return inDirectory<String>(flutterDirectory, () {
     return eval('git', <String>['rev-parse', 'HEAD']);
   });
 }
 
 Future<DateTime> getFlutterRepoCommitTimestamp(String commit) {
   // git show -s --format=%at 4b546df7f0b3858aaaa56c4079e5be1ba91fbb65
-  return inDirectory(flutterDirectory, () async {
+  return inDirectory<DateTime>(flutterDirectory, () async {
     final String unixTimestamp = await eval('git', <String>[
       'show',
       '-s',
@@ -235,7 +235,7 @@ Future<Process> startProcess(
   final ProcessInfo processInfo = ProcessInfo(command, process);
   _runningProcesses.add(processInfo);
 
-  process.exitCode.then((int exitCode) {
+  process.exitCode.then<void>((int exitCode) {
     print('"$executable" exit code: $exitCode');
     _runningProcesses.remove(processInfo);
   });
@@ -273,14 +273,14 @@ Future<int> exec(
   final Completer<Null> stdoutDone = Completer<Null>();
   final Completer<Null> stderrDone = Completer<Null>();
   process.stdout
-      .transform(utf8.decoder)
+      .transform<String>(utf8.decoder)
-      .transform(const LineSplitter())
+      .transform<String>(const LineSplitter())
       .listen((String line) {
         print('stdout: $line');
       }, onDone: () { stdoutDone.complete(); });
   process.stderr
-      .transform(utf8.decoder)
+      .transform<String>(utf8.decoder)
-      .transform(const LineSplitter())
+      .transform<String>(const LineSplitter())
       .listen((String line) {
         print('stderr: $line');
       }, onDone: () { stderrDone.complete(); });
@@ -310,15 +310,15 @@ Future<String> eval(
   final Completer<Null> stdoutDone = Completer<Null>();
   final Completer<Null> stderrDone = Completer<Null>();
   process.stdout
-      .transform(utf8.decoder)
+      .transform<String>(utf8.decoder)
-      .transform(const LineSplitter())
+      .transform<String>(const LineSplitter())
       .listen((String line) {
         print('stdout: $line');
         output.writeln(line);
       }, onDone: () { stdoutDone.complete(); });
   process.stderr
-      .transform(utf8.decoder)
+      .transform<String>(utf8.decoder)
-      .transform(const LineSplitter())
+      .transform<String>(const LineSplitter())
       .listen((String line) {
         print('stderr: $line');
       }, onDone: () { stderrDone.complete(); });
@@ -427,11 +427,11 @@ Future<Null> getFlutter(String revision) async {
     flutterDirectory.deleteSync(recursive: true);
   }
 
-  await inDirectory(flutterDirectory.parent, () async {
+  await inDirectory<void>(flutterDirectory.parent, () async {
     await exec('git', <String>['clone', 'https://github.com/flutter/flutter.git']);
   });
 
-  await inDirectory(flutterDirectory, () async {
+  await inDirectory<void>(flutterDirectory, () async {
     await exec('git', <String>['checkout', revision]);
   });
 

dev/devicelab/lib/tasks/analysis.dart

@@ -22,7 +22,7 @@ const int _kRunsPerBenchmark = 3;
 Directory get _megaGalleryDirectory => dir(path.join(Directory.systemTemp.path, 'mega_gallery'));
 
 Future<TaskResult> analyzerBenchmarkTask() async {
-  await inDirectory(flutterDirectory, () async {
+  await inDirectory<void>(flutterDirectory, () async {
     rmTree(_megaGalleryDirectory);
     mkdirs(_megaGalleryDirectory);
     await dart(<String>['dev/tools/mega_gallery.dart', '--out=${_megaGalleryDirectory.path}']);
@@ -74,7 +74,7 @@ abstract class _Benchmark {
   Future<double> execute(int iteration, int targetIterations) async {
     section('Analyze $title ${watch ? 'with watcher' : ''} - ${iteration + 1} / $targetIterations');
     final Stopwatch stopwatch = Stopwatch();
-    await inDirectory(directory, () async {
+    await inDirectory<void>(directory, () async {
       stopwatch.start();
       await flutter('analyze', options: options);
       stopwatch.stop();

dev/devicelab/lib/tasks/gallery.dart

@@ -28,7 +28,7 @@ class GalleryTransitionTest {
     final String deviceId = device.deviceId;
     final Directory galleryDirectory =
         dir('${flutterDirectory.path}/examples/flutter_gallery');
-    await inDirectory(galleryDirectory, () async {
+    await inDirectory<void>(galleryDirectory, () async {
       await flutter('packages', options: <String>['get']);
 
       if (deviceOperatingSystem == DeviceOperatingSystem.ios)

dev/devicelab/lib/tasks/hot_mode_tests.dart

@@ -29,11 +29,11 @@ TaskFunction createHotModeTest() {
     int hotReloadCount = 0;
     Map<String, dynamic> twoReloadsData;
     Map<String, dynamic> freshRestartReloadsData;
-    await inDirectory(flutterDirectory, () async {
+    await inDirectory<void>(flutterDirectory, () async {
       rmTree(_editedFlutterGalleryDir);
       mkdirs(_editedFlutterGalleryDir);
       recursiveCopy(flutterGalleryDir, _editedFlutterGalleryDir);
-      await inDirectory(_editedFlutterGalleryDir, () async {
+      await inDirectory<void>(_editedFlutterGalleryDir, () async {
         if (deviceOperatingSystem == DeviceOperatingSystem.ios)
           await prepareProvisioningCertificates(_editedFlutterGalleryDir.path);
         {
@@ -46,8 +46,8 @@ TaskFunction createHotModeTest() {
           final Completer<Null> stdoutDone = Completer<Null>();
           final Completer<Null> stderrDone = Completer<Null>();
           process.stdout
-              .transform(utf8.decoder)
+              .transform<String>(utf8.decoder)
-              .transform(const LineSplitter())
+              .transform<String>(const LineSplitter())
               .listen((String line) {
             if (line.contains('\] Reloaded ')) {
               if (hotReloadCount == 0) {
@@ -72,8 +72,8 @@ TaskFunction createHotModeTest() {
             stdoutDone.complete();
           });
           process.stderr
-              .transform(utf8.decoder)
+              .transform<String>(utf8.decoder)
-              .transform(const LineSplitter())
+              .transform<String>(const LineSplitter())
               .listen((String line) {
             print('stderr: $line');
           }, onDone: () {
@@ -99,8 +99,8 @@ TaskFunction createHotModeTest() {
           final Completer<Null> stdoutDone = Completer<Null>();
           final Completer<Null> stderrDone = Completer<Null>();
           process.stdout
-              .transform(utf8.decoder)
+              .transform<String>(utf8.decoder)
-              .transform(const LineSplitter())
+              .transform<String>(const LineSplitter())
               .listen((String line) {
             if (line.contains('\] Reloaded ')) {
               process.stdin.writeln('q');
@@ -110,8 +110,8 @@ TaskFunction createHotModeTest() {
             stdoutDone.complete();
           });
           process.stderr
-              .transform(utf8.decoder)
+              .transform<String>(utf8.decoder)
-              .transform(const LineSplitter())
+              .transform<String>(const LineSplitter())
               .listen((String line) {
             print('stderr: $line');
           }, onDone: () {

dev/devicelab/lib/tasks/integration_tests.dart

@@ -73,7 +73,7 @@ class DriverTest {
   final List<String> extraOptions;
 
   Future<TaskResult> call() {
-    return inDirectory(testDirectory, () async {
+    return inDirectory<TaskResult>(testDirectory, () async {
       final Device device = await devices.workingDevice;
       await device.unlock();
       final String deviceId = device.deviceId;

dev/devicelab/lib/tasks/integration_ui.dart

@@ -15,7 +15,7 @@ Future<TaskResult> runEndToEndTests() async {
   await device.unlock();
   final String deviceId = device.deviceId;
   final Directory testDirectory = dir('${flutterDirectory.path}/dev/integration_tests/ui');
-  await inDirectory(testDirectory, () async {
+  await inDirectory<void>(testDirectory, () async {
     await flutter('packages', options: <String>['get']);
 
     if (deviceOperatingSystem == DeviceOperatingSystem.ios)

dev/devicelab/lib/tasks/microbenchmarks.dart

@@ -78,8 +78,8 @@ Future<Map<String, double>> _readJsonResults(Process process) {
   final Completer<Map<String, double>> completer = Completer<Map<String, double>>();
 
   final StreamSubscription<String> stderrSub = process.stderr
-      .transform(const Utf8Decoder())
+      .transform<String>(const Utf8Decoder())
-      .transform(const LineSplitter())
+      .transform<String>(const LineSplitter())
       .listen((String line) {
         stderr.writeln('[STDERR] $line');
       });
@@ -87,8 +87,8 @@ Future<Map<String, double>> _readJsonResults(Process process) {
   bool processWasKilledIntentionally = false;
   bool resultsHaveBeenParsed = false;
   final StreamSubscription<String> stdoutSub = process.stdout
-      .transform(const Utf8Decoder())
+      .transform<String>(const Utf8Decoder())
-      .transform(const LineSplitter())
+      .transform<String>(const LineSplitter())
       .listen((String line) async {
     print(line);
 

dev/devicelab/lib/tasks/perf_tests.dart

@@ -75,7 +75,7 @@ TaskFunction createBasicMaterialCompileTest() {
 
     rmTree(sampleDir);
 
-    await inDirectory(Directory.systemTemp, () async {
+    await inDirectory<void>(Directory.systemTemp, () async {
       await flutter('create', options: <String>[sampleAppName]);
     });
 
@@ -95,7 +95,7 @@ class StartupTest {
   final bool reportMetrics;
 
   Future<TaskResult> run() async {
-    return await inDirectory(testDirectory, () async {
+    return await inDirectory<TaskResult>(testDirectory, () async {
       final String deviceId = (await devices.workingDevice).deviceId;
       await flutter('packages', options: <String>['get']);
 
@@ -131,7 +131,7 @@ class PerfTest {
   final String timelineFileName;
 
   Future<TaskResult> run() {
-    return inDirectory(testDirectory, () async {
+    return inDirectory<TaskResult>(testDirectory, () async {
       final Device device = await devices.workingDevice;
       await device.unlock();
       final String deviceId = device.deviceId;
@@ -183,7 +183,7 @@ class CompileTest {
   final bool reportPackageContentSizes;
 
   Future<TaskResult> run() async {
-    return await inDirectory(testDirectory, () async {
+    return await inDirectory<TaskResult>(testDirectory, () async {
       final Device device = await devices.workingDevice;
       await device.unlock();
       await flutter('packages', options: <String>['get']);
@@ -402,7 +402,7 @@ class MemoryTest {
   Device _device;
 
   Future<TaskResult> run() {
-    return inDirectory(project, () async {
+    return inDirectory<TaskResult>(project, () async {
       // This test currently only works on Android, because device.logcat,
       // device.getMemoryStats, etc, aren't implemented for iOS.
 

dev/devicelab/lib/tasks/sample_catalog_generator.dart

@@ -18,7 +18,7 @@ Future<TaskResult> samplePageCatalogGenerator(String authorizationToken) async {
   final String deviceId = device.deviceId;
 
   final Directory catalogDirectory = dir('${flutterDirectory.path}/examples/catalog');
-  await inDirectory(catalogDirectory, () async {
+  await inDirectory<void>(catalogDirectory, () async {
     await flutter('packages', options: <String>['get']);
 
     final bool isIosDevice = deviceOperatingSystem == DeviceOperatingSystem.ios;

dev/devicelab/lib/tasks/save_catalog_screenshots.dart

@@ -65,7 +65,7 @@ class Upload {
       } else {
         // TODO(hansmuller): only retry on 5xx and 429 responses
         logMessage('Request to save "$name" (length ${content.length}) failed with status ${response.statusCode}, will retry');
-        logMessage(await response.transform(utf8.decoder).join());
+        logMessage(await response.transform<String>(utf8.decoder).join());
       }
       return response.statusCode == HttpStatus.ok;
     } on TimeoutException catch (_) {
@@ -104,7 +104,7 @@ Future<Null> saveScreenshots(List<String> fromPaths, List<String> largeNames, Li
   while (uploads.any(Upload.isNotComplete)) {
     final HttpClient client = HttpClient();
     uploads = uploads.where(Upload.isNotComplete).toList();
-    await Future.wait(uploads.map((Upload upload) => upload.run(client)));
+    await Future.wait<bool>(uploads.map<Future<bool>>((Upload upload) => upload.run(client)));
     client.close(force: true);
   }
 }

dev/integration_tests/android_semantics_testing/lib/main.dart

@@ -59,7 +59,7 @@ class TestApp extends StatelessWidget {
         builder: (BuildContext context) {
           return Scaffold(
             body: ListView(
-              children: routes.map((String value) {
+              children: routes.map<Widget>((String value) {
                 return MaterialButton(
                   child: Text(value),
                   onPressed: () {

dev/integration_tests/android_views/lib/main.dart

@@ -123,7 +123,7 @@ class PlatformViewState extends State<PlatformViewPage> {
       final List<dynamic> unTypedRecordedEvents = codec.decodeMessage(data);
       final List<Map<String, dynamic>> recordedEvents = unTypedRecordedEvents
           .cast<Map<dynamic, dynamic>>()
-          .map((Map<dynamic, dynamic> e) =>e.cast<String, dynamic>())
+          .map<Map<String, dynamic>>((Map<dynamic, dynamic> e) =>e.cast<String, dynamic>())
           .toList();
       await channel.invokeMethod('pipeFlutterViewEvents');
       await viewChannel.invokeMethod('pipeTouchEvents');

dev/manual_tests/lib/animated_icons.dart

@@ -22,7 +22,7 @@ class IconsList extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     return ListView(
-      children: samples.map((IconSample s) => IconSampleRow(s)).toList(),
+      children: samples.map<IconSampleRow>((IconSample s) => IconSampleRow(s)).toList(),
     );
   }
 }

dev/manual_tests/lib/material_arc.dart

@@ -452,7 +452,7 @@ class _AnimationDemoState extends State<AnimationDemo> with TickerProviderStateM
         appBar: AppBar(
           title: const Text('Animation'),
           bottom: TabBar(
-            tabs: _allDemos.map((_ArcDemo demo) => Tab(text: demo.title)).toList(),
+            tabs: _allDemos.map<Tab>((_ArcDemo demo) => Tab(text: demo.title)).toList(),
           ),
         ),
         floatingActionButton: Builder(
@@ -466,7 +466,7 @@ class _AnimationDemoState extends State<AnimationDemo> with TickerProviderStateM
           },
         ),
         body: TabBarView(
-          children: _allDemos.map((_ArcDemo demo) => demo.builder(demo)).toList()
+          children: _allDemos.map<Widget>((_ArcDemo demo) => demo.builder(demo)).toList()
         )
       )
     );

dev/manual_tests/lib/page_view.dart

@@ -119,7 +119,7 @@ class PageViewAppState extends State<PageViewApp> {
 
   Widget _buildBody(BuildContext context) {
     return PageView(
-      children: cardModels.map(buildCard).toList(),
+      children: cardModels.map<Widget>(buildCard).toList(),
       // TODO(abarth): itemsWrap: itemsWrap,
       scrollDirection: scrollDirection,
     );

dev/manual_tests/lib/text.dart

@@ -189,7 +189,7 @@ class _FuzzerState extends State<Fuzzer> with SingleTickerProviderStateMixin {
     switch (_random.nextInt(10)) {
       case 0:
         if (value == null)
-          return pickFromList(_random, Colors.primaries)[(_random.nextInt(9) + 1) * 100];
+          return pickFromList<MaterialColor>(_random, Colors.primaries)[(_random.nextInt(9) + 1) * 100];
         switch (_random.nextInt(4)) {
           case 0:
             return value.withAlpha(value.alpha + _random.nextInt(10) - 5);
@@ -240,7 +240,7 @@ class _FuzzerState extends State<Fuzzer> with SingleTickerProviderStateMixin {
       case 0:
         return null;
       case 1:
-        return pickFromList(_random, TextDecorationStyle.values);
+        return pickFromList<TextDecorationStyle>(_random, TextDecorationStyle.values);
     }
     return value;
   }
@@ -250,7 +250,7 @@ class _FuzzerState extends State<Fuzzer> with SingleTickerProviderStateMixin {
       case 0:
         return null;
       case 1:
-        return pickFromList(_random, FontWeight.values);
+        return pickFromList<FontWeight>(_random, FontWeight.values);
     }
     return value;
   }
@@ -260,7 +260,7 @@ class _FuzzerState extends State<Fuzzer> with SingleTickerProviderStateMixin {
       case 0:
         return null;
       case 1:
-        return pickFromList(_random, FontStyle.values);
+        return pickFromList<FontStyle>(_random, FontStyle.values);
     }
     return value;
   }
@@ -938,7 +938,7 @@ class _PaintingState extends State<Painting> with SingleTickerProviderStateMixin
       if (mounted && intrinsicKey.currentContext.size.height != controlKey.currentContext.size.height) {
         debugPrint('Found some text that unexpectedly renders at different heights.');
         debugPrint('Text: $_text');
-        debugPrint(_text.runes.map((int index) => 'U+' + index.toRadixString(16).padLeft(4, '0')).join(' '));
+        debugPrint(_text.runes.map<String>((int index) => 'U+' + index.toRadixString(16).padLeft(4, '0')).join(' '));
         setState(() {
           _ticker.stop();
         });
@@ -1045,7 +1045,7 @@ class _PaintingState extends State<Painting> with SingleTickerProviderStateMixin
                     FlatButton(
                       onPressed: _ticker.isActive ? null : () {
                         print('The currently visible text is: $_text');
-                        print(_text.runes.map((int value) => 'U+${value.toRadixString(16).padLeft(4, '0').toUpperCase()}').join(' '));
+                        print(_text.runes.map<String>((int value) => 'U+${value.toRadixString(16).padLeft(4, '0').toUpperCase()}').join(' '));
                       },
                       child: const Text('DUMP TEXT TO LOGS'),
                     ),
@@ -2109,7 +2109,7 @@ int randomCharacter(math.Random random) {
     Range(0x2ceb0, 0x2ebe0),
     Range(0x2f800, 0x2fa1d),
   ];
-  final Range range = pickFromList(random, characterRanges);
+  final Range range = pickFromList<Range>(random, characterRanges);
   if (range.start == range.end)
     return range.start;
   return range.start + random.nextInt(range.end - range.start);

dev/manual_tests/test/card_collection_test.dart

@@ -12,7 +12,7 @@ import 'mock_image_http.dart';
 
 void main() {
   testWidgets('Card Collection smoke test', (WidgetTester tester) async {
-    HttpOverrides.runZoned(() async {
+    HttpOverrides.runZoned<Future<void>>(() async {
       card_collection.main(); // builds the app and schedules a frame but doesn't trigger one
       await tester.pump(); // see https://github.com/flutter/flutter/issues/1865
       await tester.pump(); // triggers a frame

dev/manual_tests/test/color_testing_demo_test.dart

@@ -12,7 +12,7 @@ import 'mock_image_http.dart';
 
 void main() {
   testWidgets('Color testing demo smoke test', (WidgetTester tester) async {
-    HttpOverrides.runZoned(() async {
+    HttpOverrides.runZoned<Future<void>>(() async {
       color_testing_demo.main(); // builds the app and schedules a frame but doesn't trigger one
       await tester.pump(); // see https://github.com/flutter/flutter/issues/1865
       await tester.pump(); // triggers a frame

dev/tools/dartdoc.dart

@@ -146,7 +146,7 @@ Future<Null> main(List<String> arguments) async {
   }
 
   String quote(String arg) => arg.contains(' ') ? "'$arg'" : arg;
-  print('Executing: (cd dev/docs ; $pubExecutable ${dartdocArgs.map(quote).join(' ')})');
+  print('Executing: (cd dev/docs ; $pubExecutable ${dartdocArgs.map<String>(quote).join(' ')})');
 
   process = await Process.start(
     pubExecutable,
@@ -302,7 +302,7 @@ void putRedirectInOldIndexLocation() {
 }
 
 List<String> findPackageNames() {
-  return findPackages().map((FileSystemEntity file) => path.basename(file.path)).toList();
+  return findPackages().map<String>((FileSystemEntity file) => path.basename(file.path)).toList();
 }
 
 /// Finds all packages in the Flutter SDK
@@ -350,8 +350,8 @@ void printStream(Stream<List<int>> stream, { String prefix = '', List<Pattern> f
   assert(prefix != null);
   assert(filter != null);
   stream
-    .transform(utf8.decoder)
+    .transform<String>(utf8.decoder)
-    .transform(const LineSplitter())
+    .transform<String>(const LineSplitter())
     .listen((String line) {
       if (!filter.any((Pattern pattern) => line.contains(pattern)))
         print('$prefix$line'.trim());

dev/tools/gen_date_localizations.dart

@@ -135,7 +135,7 @@ String _jsonToMap(dynamic json) {
   }
 
   if (json is Iterable)
-    return '<dynamic>[${json.map(_jsonToMap).join(',')}]';
+    return '<dynamic>[${json.map<String>(_jsonToMap).join(',')}]';
 
   if (json is Map<String, dynamic>) {
     final StringBuffer buffer = StringBuffer('<String, dynamic>{');

dev/tools/gen_localizations.dart

@@ -202,7 +202,7 @@ String generateTranslationBundles() {
 ///
 ///  * [getTranslation], whose documentation describes these values.
 final Set<String> kSupportedLanguages = HashSet<String>.from(const <String>[
-${languageCodes.map((String value) => "  '$value', // ${describeLocale(value)}").toList().join('\n')}
+${languageCodes.map<String>((String value) => "  '$value', // ${describeLocale(value)}").toList().join('\n')}
 ]);
 
 /// Creates a [GlobalMaterialLocalizations] instance for the given `locale`.

dev/tools/lib/roll_dev.dart

@@ -105,7 +105,7 @@ void main(List<String> args) {
     exit(1);
   }
 
-  final List<int> parts = match.groups(<int>[1, 2, 3]).map(int.parse).toList();
+  final List<int> parts = match.groups(<int>[1, 2, 3]).map<int>(int.parse).toList();
 
   if (match.group(4) == '0') {
     print('This commit has already been released, as version ${parts.join(".")}.');

dev/tools/localizations_utils.dart

@@ -29,7 +29,7 @@ void checkCwdIsRepoRoot(String commandName) {
 String camelCase(String locale) {
   return locale
     .split('_')
-    .map((String part) => part.substring(0, 1).toUpperCase() + part.substring(1).toLowerCase())
+    .map<String>((String part) => part.substring(0, 1).toUpperCase() + part.substring(1).toLowerCase())
     .join('');
 }
 
@@ -91,7 +91,7 @@ Future<void> precacheLanguageAndRegionTags() async {
   final HttpClient client = HttpClient();
   final HttpClientRequest request = await client.getUrl(Uri.parse(registry));
   final HttpClientResponse response = await request.close();
-  final String body = (await response.transform(utf8.decoder).toList()).join('');
+  final String body = (await response.transform<String>(utf8.decoder).toList()).join('');
   client.close(force: true);
   final List<Map<String, List<String>>> sections = body.split('%%').skip(1).map<Map<String, List<String>>>(_parseSection).toList();
   for (Map<String, List<String>> section in sections) {

dev/tools/update_icons.dart

@@ -199,9 +199,9 @@ String regenerateIconsFile(String iconData, String codepointData) {
 
 String generateIconDeclarations(String codepointData) {
   return LineSplitter.split(codepointData)
-      .map((String l) => l.trim())
+      .map<String>((String l) => l.trim())
       .where((String l) => l.isNotEmpty)
-      .map(getIconDeclaration)
+      .map<String>(getIconDeclaration)
       .join();
 }
 

dev/tools/vitool/lib/vitool.dart

@@ -314,7 +314,7 @@ class SvgPath {
 
   SvgPath applyTransform(_Transform transform) {
     final List<SvgPathCommand> transformedCommands =
-      commands.map((SvgPathCommand c) => c.applyTransform(transform)).toList();
+      commands.map<SvgPathCommand>((SvgPathCommand c) => c.applyTransform(transform)).toList();
     return SvgPath(id, transformedCommands, opacity: opacity * transform.opacity);
   }
 
@@ -400,7 +400,7 @@ class SvgPathCommandBuilder {
   SvgPathCommand build(String type, List<Point<double>> points) {
     List<Point<double>> absPoints = points;
     if (_isRelativeCommand(type)) {
-      absPoints = points.map((Point<double> p) => p + lastPoint).toList();
+      absPoints = points.map<Point<double>>((Point<double> p) => p + lastPoint).toList();
     }
 
     if (type == 'M' || type == 'm')

examples/catalog/bin/sample_page.dart

@@ -89,7 +89,7 @@ class SampleInfo {
     final String classNames = commentValues['classes'];
     if (classNames == null)
       return const <String>[];
-    return classNames.split(',').map((String s) => s.trim()).where((String s) => s.isNotEmpty);
+    return classNames.split(',').map<String>((String s) => s.trim()).where((String s) => s.isNotEmpty);
   }
 
   // The relative import path for this sample, like '../lib/foo.dart'.
@@ -163,7 +163,7 @@ void generate(String commit) {
   final String entryTemplate = inputFile('bin', 'entry.md.template').readAsStringSync();
 
   // Write the sample catalog's home page: index.md
-  final Iterable<String> entries = samples.map((SampleInfo sample) {
+  final Iterable<String> entries = samples.map<String>((SampleInfo sample) {
     return expandTemplate(entryTemplate, sample.commentValues);
   });
   writeExpandedTemplate(
@@ -195,7 +195,7 @@ void generate(String commit) {
     }
   }
   for (String className in classToSamples.keys) {
-    final Iterable<String> entries = classToSamples[className].map((SampleInfo sample) {
+    final Iterable<String> entries = classToSamples[className].map<String>((SampleInfo sample) {
       return expandTemplate(entryTemplate, sample.commentValues);
     });
     writeExpandedTemplate(
@@ -215,10 +215,10 @@ void generate(String commit) {
     outputFile('screenshot.dart', driverDirectory),
     inputFile('bin', 'screenshot.dart.template').readAsStringSync(),
     <String, String>{
-      'imports': samples.map((SampleInfo page) {
+      'imports': samples.map<String>((SampleInfo page) {
         return "import '${page.importPath}' show ${page.sampleClass};\n";
       }).toList().join(),
-      'widgets': samples.map((SampleInfo sample) {
+      'widgets': samples.map<String>((SampleInfo sample) {
         return 'new ${sample.sampleClass}(),\n';
       }).toList().join(),
     },
@@ -230,7 +230,7 @@ void generate(String commit) {
     outputFile('screenshot_test.dart', driverDirectory),
     inputFile('bin', 'screenshot_test.dart.template').readAsStringSync(),
     <String, String>{
-      'paths': samples.map((SampleInfo sample) {
+      'paths': samples.map<String>((SampleInfo sample) {
         return "'${outputFile(sample.sourceName + '.png').path}'";
       }).toList().join(',\n'),
     },

examples/catalog/lib/app_bar_bottom.dart

@@ -63,7 +63,7 @@ class _AppBarBottomSampleState extends State<AppBarBottomSample> with SingleTick
         ),
         body: TabBarView(
           controller: _tabController,
-          children: choices.map((Choice choice) {
+          children: choices.map<Widget>((Choice choice) {
             return Padding(
               padding: const EdgeInsets.all(16.0),
               child: ChoiceCard(choice: choice),

examples/catalog/lib/basic_app_bar.dart

@@ -37,7 +37,7 @@ class _BasicAppBarSampleState extends State<BasicAppBarSample> {
             PopupMenuButton<Choice>( // overflow menu
               onSelected: _select,
               itemBuilder: (BuildContext context) {
-                return choices.skip(2).map((Choice choice) {
+                return choices.skip(2).map<PopupMenuItem<Choice>>((Choice choice) {
                   return PopupMenuItem<Choice>(
                     value: choice,
                     child: Text(choice.title),

examples/catalog/lib/custom_semantics.dart

@@ -50,7 +50,7 @@ class AdjustableDropdownListTile extends StatelessWidget {
           trailing: DropdownButton<String>(
             value: value,
             onChanged: onChanged,
-            items: items.map((String item) {
+            items: items.map<DropdownMenuItem<String>>((String item) {
               return DropdownMenuItem<String>(
                 value: item,
                 child: Text(item),

examples/catalog/lib/expansion_tile_sample.dart

@@ -78,7 +78,7 @@ class EntryItem extends StatelessWidget {
     return ExpansionTile(
       key: PageStorageKey<Entry>(root),
       title: Text(root.title),
-      children: root.children.map(_buildTiles).toList(),
+      children: root.children.map<Widget>(_buildTiles).toList(),
     );
   }
 

examples/catalog/lib/tabbed_app_bar.dart

@@ -15,7 +15,7 @@ class TabbedAppBarSample extends StatelessWidget {
             title: const Text('Tabbed AppBar'),
             bottom: TabBar(
               isScrollable: true,
-              tabs: choices.map((Choice choice) {
+              tabs: choices.map<Widget>((Choice choice) {
                 return Tab(
                   text: choice.title,
                   icon: Icon(choice.icon),
@@ -24,7 +24,7 @@ class TabbedAppBarSample extends StatelessWidget {
             ),
           ),
           body: TabBarView(
-            children: choices.map((Choice choice) {
+            children: choices.map<Widget>((Choice choice) {
               return Padding(
                 padding: const EdgeInsets.all(16.0),
                 child: ChoiceCard(choice: choice),

examples/flutter_gallery/lib/demo/animation/home.dart

@@ -493,7 +493,7 @@ class _AnimationDemoHomeState extends State<AnimationDemoHome> {
   }
 
   Iterable<Widget> _detailItemsFor(Section section) {
-    final Iterable<Widget> detailItems = section.details.map((SectionDetail detail) {
+    final Iterable<Widget> detailItems = section.details.map<Widget>((SectionDetail detail) {
       return SectionDetailView(detail: detail);
     });
     return ListTile.divideTiles(context: context, tiles: detailItems);
@@ -591,7 +591,7 @@ class _AnimationDemoHomeState extends State<AnimationDemoHome> {
                       },
                       child: PageView(
                         controller: _detailsPageController,
-                        children: allSections.map((Section section) {
+                        children: allSections.map<Widget>((Section section) {
                           return Column(
                             crossAxisAlignment: CrossAxisAlignment.stretch,
                             children: _detailItemsFor(section).toList(),

examples/flutter_gallery/lib/demo/colors_demo.dart

@@ -99,7 +99,7 @@ class PaletteTabView extends StatelessWidget {
     final TextTheme textTheme = Theme.of(context).textTheme;
     final TextStyle whiteTextStyle = textTheme.body1.copyWith(color: Colors.white);
     final TextStyle blackTextStyle = textTheme.body1.copyWith(color: Colors.black);
-    final List<Widget> colorItems = primaryKeys.map((int index) {
+    final List<Widget> colorItems = primaryKeys.map<Widget>((int index) {
       return DefaultTextStyle(
         style: index > colors.threshold ? whiteTextStyle : blackTextStyle,
         child: ColorItem(index: index, color: colors.primary[index]),
@@ -107,7 +107,7 @@ class PaletteTabView extends StatelessWidget {
     }).toList();
 
     if (colors.accent != null) {
-      colorItems.addAll(accentKeys.map((int index) {
+      colorItems.addAll(accentKeys.map<Widget>((int index) {
         return DefaultTextStyle(
           style: index > colors.threshold ? whiteTextStyle : blackTextStyle,
           child: ColorItem(index: index, color: colors.accent[index], prefix: 'A'),
@@ -135,11 +135,11 @@ class ColorsDemo extends StatelessWidget {
           title: const Text('Colors'),
           bottom: TabBar(
             isScrollable: true,
-            tabs: allPalettes.map((Palette swatch) => Tab(text: swatch.name)).toList(),
+            tabs: allPalettes.map<Widget>((Palette swatch) => Tab(text: swatch.name)).toList(),
           ),
         ),
         body: TabBarView(
-          children: allPalettes.map((Palette colors) {
+          children: allPalettes.map<Widget>((Palette colors) {
             return PaletteTabView(colors: colors);
           }).toList(),
         ),

examples/flutter_gallery/lib/demo/contacts_demo.dart

@@ -54,7 +54,7 @@ class _ContactItem extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     final ThemeData themeData = Theme.of(context);
-    final List<Widget> columnChildren = lines.sublist(0, lines.length - 1).map((String line) => Text(line)).toList();
+    final List<Widget> columnChildren = lines.sublist(0, lines.length - 1).map<Widget>((String line) => Text(line)).toList();
     columnChildren.add(Text(lines.last, style: themeData.textTheme.caption));
 
     final List<Widget> rowChildren = <Widget>[

examples/flutter_gallery/lib/demo/cupertino/cupertino_refresh_demo.dart

@@ -58,7 +58,7 @@ class _CupertinoRefreshControlDemoState extends State<CupertinoRefreshControlDem
               CupertinoSliverRefreshControl(
                 onRefresh: () {
                   return Future<void>.delayed(const Duration(seconds: 2))
-                      ..then((_) {
+                      ..then<void>((_) {
                         if (mounted) {
                           setState(() => repopulateList());
                         }

examples/flutter_gallery/lib/demo/material/bottom_app_bar_demo.dart

@@ -281,7 +281,7 @@ class _ColorsItem extends StatelessWidget {
   Widget build(BuildContext context) {
     return Row(
       mainAxisAlignment: MainAxisAlignment.spaceEvenly,
-      children: colors.map((_NamedColor namedColor) {
+      children: colors.map<Widget>((_NamedColor namedColor) {
         return RawMaterialButton(
           onPressed: () {
             onChanged(namedColor.color);

examples/flutter_gallery/lib/demo/material/bottom_navigation_demo.dart

@@ -194,7 +194,7 @@ class _BottomNavigationDemoState extends State<BottomNavigationDemo>
   Widget build(BuildContext context) {
     final BottomNavigationBar botNavBar = BottomNavigationBar(
       items: _navigationViews
-          .map((NavigationIconView navigationView) => navigationView.item)
+          .map<BottomNavigationBarItem>((NavigationIconView navigationView) => navigationView.item)
           .toList(),
       currentIndex: _currentIndex,
       type: _type,

examples/flutter_gallery/lib/demo/material/buttons_demo.dart

@@ -280,7 +280,7 @@ class _ButtonsDemoState extends State<ButtonsDemo> {
                   dropdown1Value = newValue;
                 });
               },
-              items: <String>['One', 'Two', 'Free', 'Four'].map((String value) {
+              items: <String>['One', 'Two', 'Free', 'Four'].map<DropdownMenuItem<String>>((String value) {
                 return DropdownMenuItem<String>(
                   value: value,
                   child: Text(value),
@@ -301,7 +301,7 @@ class _ButtonsDemoState extends State<ButtonsDemo> {
                   dropdown2Value = newValue;
                 });
               },
-              items: <String>['One', 'Two', 'Free', 'Four'].map((String value) {
+              items: <String>['One', 'Two', 'Free', 'Four'].map<DropdownMenuItem<String>>((String value) {
                 return DropdownMenuItem<String>(
                   value: value,
                   child: Text(value),
@@ -325,7 +325,7 @@ class _ButtonsDemoState extends State<ButtonsDemo> {
                   'One', 'Two', 'Free', 'Four', 'Can', 'I', 'Have', 'A', 'Little',
                   'Bit', 'More', 'Five', 'Six', 'Seven', 'Eight', 'Nine', 'Ten'
                  ]
-                .map((String value) {
+                .map<DropdownMenuItem<String>>((String value) {
                   return DropdownMenuItem<String>(
                     value: value,
                     child: Text(value),
@@ -365,7 +365,7 @@ class _ButtonsDemoState extends State<ButtonsDemo> {
             onPressed: null,
           )
         ]
-        .map((Widget button) => SizedBox(width: 64.0, height: 64.0, child: button))
+        .map<Widget>((Widget button) => SizedBox(width: 64.0, height: 64.0, child: button))
         .toList(),
       ),
     );

examples/flutter_gallery/lib/demo/material/cards_demo.dart

@@ -191,7 +191,7 @@ class _CardsDemoState extends State<CardsDemo> {
       body: ListView(
         itemExtent: TravelDestinationItem.height,
         padding: const EdgeInsets.only(top: 8.0, left: 8.0, right: 8.0),
-        children: destinations.map((TravelDestination destination) {
+        children: destinations.map<Widget>((TravelDestination destination) {
           return Container(
             margin: const EdgeInsets.only(bottom: 8.0),
             child: TravelDestinationItem(

examples/flutter_gallery/lib/demo/material/chip_demo.dart

@@ -92,7 +92,7 @@ class _ChipsTile extends StatelessWidget {
     ];
     if (children.isNotEmpty) {
       cardChildren.add(Wrap(
-        children: children.map((Widget chip) {
+        children: children.map<Widget>((Widget chip) {
         return Padding(
           padding: const EdgeInsets.all(2.0),
           child: chip,

examples/flutter_gallery/lib/demo/material/date_and_time_picker_demo.dart

@@ -201,7 +201,7 @@ class _DateAndTimePickerDemoState extends State<DateAndTimePickerDemo> {
                       _activity = newValue;
                     });
                   },
-                  items: _allActivities.map((String value) {
+                  items: _allActivities.map<DropdownMenuItem<String>>((String value) {
                     return DropdownMenuItem<String>(
                       value: value,
                       child: Text(value),

examples/flutter_gallery/lib/demo/material/dialog_demo.dart

@@ -201,7 +201,7 @@ class DialogDemoState extends State<DialogDemo> {
           ),
         ]
         // Add a little space between the buttons
-        .map((Widget button) {
+        .map<Widget>((Widget button) {
           return Container(
             padding: const EdgeInsets.symmetric(vertical: 8.0),
             child: button

examples/flutter_gallery/lib/demo/material/drawer_demo.dart

@@ -159,7 +159,7 @@ class _DrawerDemoState extends State<DrawerDemo> with TickerProviderStateMixin {
                           child: Column(
                             mainAxisSize: MainAxisSize.min,
                             crossAxisAlignment: CrossAxisAlignment.stretch,
-                            children: _drawerContents.map((String id) {
+                            children: _drawerContents.map<Widget>((String id) {
                               return ListTile(
                                 leading: CircleAvatar(child: Text(id)),
                                 title: Text('Drawer item $id'),

examples/flutter_gallery/lib/demo/material/elevation_demo.dart

@@ -25,7 +25,7 @@ class _ElevationDemoState extends State<ElevationDemo> {
       24.0,
     ];
 
-    return elevations.map((double elevation) {
+    return elevations.map<Widget>((double elevation) {
       return Center(
         child: Card(
           margin: const EdgeInsets.all(20.0),

examples/flutter_gallery/lib/demo/material/expansion_panels_demo.dart

@@ -356,7 +356,7 @@ class _ExpansionPanelsDemoState extends State<ExpansionPanelsDemo> {
                   _demoItems[index].isExpanded = !isExpanded;
                 });
               },
-              children: _demoItems.map((DemoItem<dynamic> item) {
+              children: _demoItems.map<ExpansionPanel>((DemoItem<dynamic> item) {
                 return ExpansionPanel(
                   isExpanded: item.isExpanded,
                   headerBuilder: item.headerBuilder,

examples/flutter_gallery/lib/demo/material/full_screen_dialog_demo.dart

@@ -251,7 +251,7 @@ class FullScreenDialogDemoState extends State<FullScreenDialogDemo> {
               )
             )
           ]
-          .map((Widget child) {
+          .map<Widget>((Widget child) {
             return Container(
               padding: const EdgeInsets.symmetric(vertical: 8.0),
               height: 96.0,

examples/flutter_gallery/lib/demo/material/grid_list_demo.dart

@@ -374,7 +374,7 @@ class GridListDemoState extends State<GridListDemo> {
                 crossAxisSpacing: 4.0,
                 padding: const EdgeInsets.all(4.0),
                 childAspectRatio: (orientation == Orientation.portrait) ? 1.0 : 1.3,
-                children: photos.map((Photo photo) {
+                children: photos.map<Widget>((Photo photo) {
                   return GridDemoPhotoItem(
                     photo: photo,
                     tileStyle: _tileStyle,

examples/flutter_gallery/lib/demo/material/leave_behind_demo.dart

@@ -126,7 +126,7 @@ class LeaveBehindDemoState extends State<LeaveBehindDemo> {
       );
     } else {
       body = ListView(
-        children: leaveBehindItems.map((LeaveBehindItem item) {
+        children: leaveBehindItems.map<Widget>((LeaveBehindItem item) {
           return _LeaveBehindListItem(
             item: item,
             onArchive: _handleArchive,

examples/flutter_gallery/lib/demo/material/list_demo.dart

@@ -209,7 +209,7 @@ class _ListDemoState extends State<ListDemo> {
         break;
     }
 
-    Iterable<Widget> listTiles = items.map((String item) => buildListTile(context, item));
+    Iterable<Widget> listTiles = items.map<Widget>((String item) => buildListTile(context, item));
     if (_showDividers)
       listTiles = ListTile.divideTiles(context: context, tiles: listTiles);
 

examples/flutter_gallery/lib/demo/material/overscroll_demo.dart

@@ -29,7 +29,7 @@ class OverscrollDemoState extends State<OverscrollDemo> {
   Future<Null> _handleRefresh() {
     final Completer<Null> completer = Completer<Null>();
     Timer(const Duration(seconds: 3), () { completer.complete(null); });
-    return completer.future.then((_) {
+    return completer.future.then<Null>((_) {
        _scaffoldKey.currentState?.showSnackBar(SnackBar(
          content: const Text('Refresh complete'),
          action: SnackBarAction(

examples/flutter_gallery/lib/demo/material/page_selector_demo.dart

@@ -54,7 +54,7 @@ class _PageSelector extends StatelessWidget {
                 color: color,
               ),
               child: TabBarView(
-                children: icons.map((Icon icon) {
+                children: icons.map<Widget>((Icon icon) {
                   return Container(
                     padding: const EdgeInsets.all(12.0),
                     child: Card(

examples/flutter_gallery/lib/demo/material/progress_indicator_demo.dart

@@ -94,7 +94,7 @@ class _ProgressIndicatorDemoState extends State<ProgressIndicatorDemo> with Sing
     ];
     return Column(
       children: indicators
-        .map((Widget c) => Container(child: c, margin: const EdgeInsets.symmetric(vertical: 15.0, horizontal: 20.0)))
+        .map<Widget>((Widget c) => Container(child: c, margin: const EdgeInsets.symmetric(vertical: 15.0, horizontal: 20.0)))
         .toList(),
     );
   }

examples/flutter_gallery/lib/demo/material/reorderable_list_demo.dart

@@ -44,7 +44,7 @@ class _ListDemoState extends State<ReorderableListDemo> {
   bool _reverseSort = false;
   final List<_ListItem> _items = <String>[
     'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N',
-  ].map((String item) => _ListItem(item, false)).toList();
+  ].map<_ListItem>((String item) => _ListItem(item, false)).toList();
 
   void changeItemType(_ReorderableListType type) {
     setState(() {
@@ -191,7 +191,7 @@ class _ListDemoState extends State<ReorderableListDemo> {
           onReorder: _onReorder,
           scrollDirection: _itemType == _ReorderableListType.horizontalAvatar ? Axis.horizontal : Axis.vertical,
           padding: const EdgeInsets.symmetric(vertical: 8.0),
-          children: _items.map(buildListTile).toList(),
+          children: _items.map<Widget>(buildListTile).toList(),
         ),
       ),
     );

examples/flutter_gallery/lib/demo/material/scrollable_tabs_demo.dart

@@ -174,7 +174,7 @@ class ScrollableTabsDemoState extends State<ScrollableTabsDemo> with SingleTicke
       ),
       body: TabBarView(
         controller: _controller,
-        children: _allPages.map((_Page page) {
+        children: _allPages.map<Widget>((_Page page) {
           return SafeArea(
             top: false,
             bottom: false,

examples/flutter_gallery/lib/demo/material/search_demo.dart

@@ -160,7 +160,7 @@ class _SearchDemoSearchDelegate extends SearchDelegate<int> {
 
     return _SuggestionList(
       query: query,
-      suggestions: suggestions.map((int i) => '$i').toList(),
+      suggestions: suggestions.map<String>((int i) => '$i').toList(),
       onSelected: (String suggestion) {
         query = suggestion;
         showResults(context);

examples/flutter_gallery/lib/demo/material/snack_bar_demo.dart

@@ -60,7 +60,7 @@ class _SnackBarDemoState extends State<SnackBarDemo> {
           ),
           const Text(_text3),
         ]
-        .map((Widget child) {
+        .map<Widget>((Widget child) {
           return Container(
             margin: const EdgeInsets.symmetric(vertical: 12.0),
             child: child

examples/flutter_gallery/lib/demo/material/tabs_demo.dart

@@ -157,7 +157,7 @@ class TabsDemo extends StatelessWidget {
                   expandedHeight: 150.0,
                   forceElevated: innerBoxIsScrolled,
                   bottom: TabBar(
-                    tabs: _allPages.keys.map(
+                    tabs: _allPages.keys.map<Widget>(
                       (_Page page) => Tab(text: page.label),
                     ).toList(),
                   ),
@@ -166,7 +166,7 @@ class TabsDemo extends StatelessWidget {
             ];
           },
           body: TabBarView(
-            children: _allPages.keys.map((_Page page) {
+            children: _allPages.keys.map<Widget>((_Page page) {
               return SafeArea(
                 top: false,
                 bottom: false,

examples/flutter_gallery/lib/demo/material/tabs_fab_demo.dart

@@ -136,7 +136,7 @@ class _TabsFabDemoState extends State<TabsFabDemo> with SingleTickerProviderStat
         title: const Text('FAB per tab'),
         bottom: TabBar(
           controller: _controller,
-          tabs: _allPages.map((_Page page) => Tab(text: page.label.toUpperCase())).toList(),
+          tabs: _allPages.map<Widget>((_Page page) => Tab(text: page.label.toUpperCase())).toList(),
         ),
         actions: <Widget>[
           MaterialDemoDocumentationButton(TabsFabDemo.routeName),
@@ -153,7 +153,7 @@ class _TabsFabDemoState extends State<TabsFabDemo> with SingleTickerProviderStat
       floatingActionButton: buildFloatingActionButton(_selectedPage),
       body: TabBarView(
         controller: _controller,
-        children: _allPages.map(buildTabView).toList()
+        children: _allPages.map<Widget>(buildTabView).toList()
       ),
     );
   }

examples/flutter_gallery/lib/demo/material/tooltip_demo.dart

@@ -59,7 +59,7 @@ class TooltipDemo extends StatelessWidget {
                   )
                 )
               ]
-              .map((Widget widget) {
+              .map<Widget>((Widget widget) {
                 return Padding(
                   padding: const EdgeInsets.only(top: 16.0, left: 16.0, right: 16.0),
                   child: widget

examples/flutter_gallery/lib/demo/pesto_demo.dart

@@ -492,7 +492,7 @@ class RecipeSheet extends StatelessWidget {
                   ),
                 ]
               ),
-            ]..addAll(recipe.ingredients.map(
+            ]..addAll(recipe.ingredients.map<TableRow>(
               (RecipeIngredient ingredient) {
                 return _buildItemRow(ingredient.amount, ingredient.description);
               }
@@ -506,7 +506,7 @@ class RecipeSheet extends StatelessWidget {
                   ),
                 ]
               )
-            )..addAll(recipe.steps.map(
+            )..addAll(recipe.steps.map<TableRow>(
               (RecipeStep step) {
                 return _buildItemRow(step.duration ?? '', step.description);
               }

examples/flutter_gallery/lib/demo/shrine/shrine_home.dart

@@ -395,7 +395,7 @@ class _ShrineHomeState extends State<ShrineHome> {
             sliver: SliverGrid(
               gridDelegate: gridDelegate,
               delegate: SliverChildListDelegate(
-                _products.map((Product product) {
+                _products.map<Widget>((Product product) {
                   return _ProductItem(
                     product: product,
                     onPressed: () { _showOrderPage(product); },

examples/flutter_gallery/lib/demo/shrine/shrine_order.dart

@@ -46,7 +46,7 @@ class _ProductItem extends StatelessWidget {
                 ),
               ),
               child: DropdownButton<int>(
-                items: <int>[0, 1, 2, 3, 4, 5].map((int value) {
+                items: <int>[0, 1, 2, 3, 4, 5].map<DropdownMenuItem<int>>((int value) {
                   return DropdownMenuItem<int>(
                     value: value,
                     child: Padding(

examples/flutter_gallery/lib/demo/video_demo.dart

@@ -381,7 +381,7 @@ class _VideoDemoState extends State<VideoDemo>
 
     initController(butterflyController);
     initController(beeController);
-    isIOSSimulator().then((bool result) {
+    isIOSSimulator().then<void>((bool result) {
       isSupported = !result;
     });
   }

examples/flutter_gallery/lib/gallery/demo.dart

@@ -96,11 +96,11 @@ class TabbedComponentDemoScaffold extends StatelessWidget {
           ),
           bottom: TabBar(
             isScrollable: true,
-            tabs: demos.map((ComponentDemoTabData data) => Tab(text: data.tabName)).toList(),
+            tabs: demos.map<Widget>((ComponentDemoTabData data) => Tab(text: data.tabName)).toList(),
           ),
         ),
         body: TabBarView(
-          children: demos.map((ComponentDemoTabData demo) {
+          children: demos.map<Widget>((ComponentDemoTabData demo) {
             return SafeArea(
               top: false,
               bottom: false,

examples/flutter_gallery/lib/gallery/example_code.dart

@@ -104,7 +104,7 @@ DropdownButton<String>(
     });
   },
   items: <String>['One', 'Two', 'Free', 'Four']
-    .map((String value) {
+    .map<DropdownMenuItem<String>>((String value) {
       return DropdownMenuItem<String>(
         value: value,
         child: Text(value));
@@ -263,7 +263,7 @@ GridView.count(
     'https://example.com/image-2.jpg',
     '...',
     'https://example.com/image-n.jpg'
-  ].map((String url) {
+  ].map<Widget>((String url) {
     return GridTile(
       footer: GridTileBar(
         title: Text(url)

examples/flutter_gallery/lib/gallery/options.dart

@@ -252,7 +252,7 @@ class _TextScaleFactorItem extends StatelessWidget {
             padding: const EdgeInsetsDirectional.only(end: 16.0),
             icon: const Icon(Icons.arrow_drop_down),
             itemBuilder: (BuildContext context) {
-              return kAllGalleryTextScaleValues.map((GalleryTextScaleValue scaleValue) {
+              return kAllGalleryTextScaleValues.map<PopupMenuItem<GalleryTextScaleValue>>((GalleryTextScaleValue scaleValue) {
                 return PopupMenuItem<GalleryTextScaleValue>(
                   value: scaleValue,
                   child: Text(scaleValue.label),

examples/layers/services/isolate.dart

@@ -141,7 +141,7 @@ class CalculationManager {
         final CalculationMessage message = CalculationMessage(data, _receivePort.sendPort);
         // Spawn an isolate to JSON-parse the file contents. The JSON parsing
         // is synchronous, so if done in the main isolate, the UI would block.
-        Isolate.spawn(_calculate, message).then<Null>((Isolate isolate) {
+        Isolate.spawn<CalculationMessage>(_calculate, message).then<Null>((Isolate isolate) {
           if (!isRunning) {
             isolate.kill(priority: Isolate.immediate);
           } else {

examples/layers/widgets/media_query.dart

@@ -74,12 +74,12 @@ class AdaptiveContainer extends StatelessWidget {
     if (MediaQuery.of(context).size.width < _kGridViewBreakpoint) {
       return ListView(
         itemExtent: _kListItemExtent,
-        children: names.map((String name) => AdaptedListItem(name: name)).toList(),
+        children: names.map<Widget>((String name) => AdaptedListItem(name: name)).toList(),
       );
     } else {
       return GridView.extent(
         maxCrossAxisExtent: _kMaxTileWidth,
-        children: names.map((String name) => AdaptedGridItem(name: name)).toList(),
+        children: names.map<Widget>((String name) => AdaptedGridItem(name: name)).toList(),
       );
     }
   }

examples/layers/widgets/sectors.dart

@@ -28,7 +28,7 @@ class SectorAppState extends State<SectorApp> {
 
   List<double> wantedSectorSizes = <double>[];
   List<double> actualSectorSizes = <double>[];
-  double get currentTheta => wantedSectorSizes.fold(0.0, (double total, double value) => total + value);
+  double get currentTheta => wantedSectorSizes.fold<double>(0.0, (double total, double value) => total + value);
 
   void addSector() {
     final double currentTheta = this.currentTheta;

examples/layers/widgets/styled_text.dart

@@ -20,7 +20,7 @@ HAL: This mission is too important for me to allow you to jeopardize it.''';
 // [["Dave", "Open the pod bay..."] ...]
 final List<List<String>> _kNameLines = _kDialogText
   .split('\n')
-  .map((String line) => line.split(':'))
+  .map<List<String>>((String line) => line.split(':'))
   .toList();
 
 final TextStyle _kDaveStyle = TextStyle(color: Colors.indigo.shade400, height: 1.8);

examples/stocks/lib/stock_strings.dart

@@ -19,7 +19,7 @@ class StockStrings {
 
   static Future<StockStrings> load(Locale locale) {
     return initializeMessages(locale.toString())
-      .then((Object _) {
+      .then<StockStrings>((Object _) {
         return StockStrings(locale);
       });
   }

packages/flutter/lib/src/cupertino/button.dart

@@ -191,7 +191,7 @@ class _CupertinoButtonState extends State<CupertinoButton> with SingleTickerProv
     final Future<Null> ticker = _buttonHeldDown
         ? _animationController.animateTo(1.0, duration: kFadeOutDuration)
         : _animationController.animateTo(0.0, duration: kFadeInDuration);
-    ticker.then((Null value) {
+    ticker.then<void>((Null value) {
       if (mounted && wasHeldDown != _buttonHeldDown)
         _animate();
     });

packages/flutter/lib/src/cupertino/dialog.dart

@@ -1564,7 +1564,7 @@ class _RenderCupertinoDialogActions extends RenderBox
         )
       : Rect.zero;
 
-    final List<Rect> pressedButtonRects = _pressedButtons.map((RenderBox pressedButton) {
+    final List<Rect> pressedButtonRects = _pressedButtons.map<Rect>((RenderBox pressedButton) {
       final MultiChildLayoutParentData buttonParentData = pressedButton.parentData;
 
       return Rect.fromLTWH(

packages/flutter/lib/src/foundation/isolates.dart

@@ -50,7 +50,7 @@ Future<R> compute<Q, R>(ComputeCallback<Q, R> callback, Q message, { String debu
   Timeline.startSync('$debugLabel: start', flow: flow);
   final ReceivePort resultPort = ReceivePort();
   Timeline.finishSync();
-  final Isolate isolate = await Isolate.spawn(
+  final Isolate isolate = await Isolate.spawn<_IsolateConfiguration<Q, R>>(
     _spawn,
     _IsolateConfiguration<Q, R>(
       callback,

packages/flutter/lib/src/foundation/print.dart

@@ -32,7 +32,7 @@ DebugPrintCallback debugPrint = debugPrintThrottled;
 /// Used by tests.
 void debugPrintSynchronously(String message, { int wrapWidth }) {
   if (wrapWidth != null) {
-    print(message.split('\n').expand((String line) => debugWordWrap(line, wrapWidth)).join('\n'));
+    print(message.split('\n').expand<String>((String line) => debugWordWrap(line, wrapWidth)).join('\n'));
   } else {
     print(message);
   }
@@ -42,7 +42,7 @@ void debugPrintSynchronously(String message, { int wrapWidth }) {
 /// messages on platforms that rate-limit their logging (for example, Android).
 void debugPrintThrottled(String message, { int wrapWidth }) {
   if (wrapWidth != null) {
-    _debugPrintBuffer.addAll(message.split('\n').expand((String line) => debugWordWrap(line, wrapWidth)));
+    _debugPrintBuffer.addAll(message.split('\n').expand<String>((String line) => debugWordWrap(line, wrapWidth)));
   } else {
     _debugPrintBuffer.addAll(message.split('\n'));
   }

packages/flutter/lib/src/material/animated_icons/animated_icons.dart

@@ -195,7 +195,7 @@ class _PathFrames {
   final List<double> opacities;
 
   void paint(ui.Canvas canvas, Color color, _UiPathFactory uiPathFactory, double progress) {
-    final double opacity = _interpolate(opacities, progress, lerpDouble);
+    final double opacity = _interpolate<double>(opacities, progress, lerpDouble);
     final ui.Paint paint = ui.Paint()
       ..style = PaintingStyle.fill
       ..color = color.withOpacity(color.opacity * opacity);
@@ -227,7 +227,7 @@ class _PathMoveTo extends _PathCommand {
 
   @override
   void apply(Path path, double progress) {
-    final Offset offset = _interpolate(points, progress, Offset.lerp);
+    final Offset offset = _interpolate<Offset>(points, progress, Offset.lerp);
     path.moveTo(offset.dx, offset.dy);
   }
 }
@@ -241,9 +241,9 @@ class _PathCubicTo extends _PathCommand {
 
   @override
   void apply(Path path, double progress) {
-    final Offset controlPoint1 = _interpolate(controlPoints1, progress, Offset.lerp);
+    final Offset controlPoint1 = _interpolate<Offset>(controlPoints1, progress, Offset.lerp);
-    final Offset controlPoint2 = _interpolate(controlPoints2, progress, Offset.lerp);
+    final Offset controlPoint2 = _interpolate<Offset>(controlPoints2, progress, Offset.lerp);
-    final Offset targetPoint = _interpolate(targetPoints, progress, Offset.lerp);
+    final Offset targetPoint = _interpolate<Offset>(targetPoints, progress, Offset.lerp);
     path.cubicTo(
       controlPoint1.dx, controlPoint1.dy,
       controlPoint2.dx, controlPoint2.dy,
@@ -260,7 +260,7 @@ class _PathLineTo extends _PathCommand {
 
   @override
   void apply(Path path, double progress) {
-    final Offset point = _interpolate(points, progress, Offset.lerp);
+    final Offset point = _interpolate<Offset>(points, progress, Offset.lerp);
     path.lineTo(point.dx, point.dy);
   }
 }

packages/flutter/lib/src/material/bottom_navigation_bar.dart

@@ -582,7 +582,7 @@ class _Circle {
     double weightSum(Iterable<Animation<double>> animations) {
       // We're adding flex values instead of animation values to produce correct
       // ratios.
-      return animations.map(state._evaluateFlex).fold(0.0, (double sum, double value) => sum + value);
+      return animations.map<double>(state._evaluateFlex).fold<double>(0.0, (double sum, double value) => sum + value);
     }
 
     final double allWeights = weightSum(state._animations);

packages/flutter/lib/src/material/mergeable_material.dart

@@ -278,10 +278,10 @@ class _MergeableMaterialState extends State<MergeableMaterial> with TickerProvid
   void didUpdateWidget(MergeableMaterial oldWidget) {
     super.didUpdateWidget(oldWidget);
 
-    final Set<LocalKey> oldKeys = oldWidget.children.map(
+    final Set<LocalKey> oldKeys = oldWidget.children.map<LocalKey>(
       (MergeableMaterialItem child) => child.key
     ).toSet();
-    final Set<LocalKey> newKeys = widget.children.map(
+    final Set<LocalKey> newKeys = widget.children.map<LocalKey>(
       (MergeableMaterialItem child) => child.key
     ).toSet();
     final Set<LocalKey> newOnly = newKeys.difference(oldKeys);

packages/flutter/lib/src/material/user_accounts_drawer_header.dart

@@ -30,7 +30,7 @@ class _AccountPictures extends StatelessWidget {
           top: 0.0,
           end: 0.0,
           child: Row(
-            children: (otherAccountsPictures ?? <Widget>[]).take(3).map((Widget picture) {
+            children: (otherAccountsPictures ?? <Widget>[]).take(3).map<Widget>((Widget picture) {
               return Padding(
                 padding: const EdgeInsetsDirectional.only(start: 8.0),
                 child: Semantics(

packages/flutter/lib/src/painting/image_resolution.dart

@@ -223,7 +223,7 @@ class AssetImage extends AssetBundleImageProvider {
     final Iterable<String> keys = parsedJson.keys;
     final Map<String, List<String>> parsedManifest =
         Map<String, List<String>>.fromIterables(keys,
-          keys.map((String key) => List<String>.from(parsedJson[key])));
+          keys.map<List<String>>((String key) => List<String>.from(parsedJson[key])));
     // TODO(ianh): convert that data structure to the right types.
     return SynchronousFuture<Map<String, List<String>>>(parsedManifest);
   }

packages/flutter/lib/src/painting/text_span.dart

@@ -355,7 +355,7 @@ class TextSpan extends DiagnosticableTree {
   List<DiagnosticsNode> debugDescribeChildren() {
     if (children == null)
       return const <DiagnosticsNode>[];
-    return children.map((TextSpan child) {
+    return children.map<DiagnosticsNode>((TextSpan child) {
       if (child != null) {
         return child.toDiagnosticsNode();
       } else {

packages/flutter/lib/src/rendering/custom_layout.dart

@@ -214,7 +214,7 @@ abstract class MultiChildLayoutDelegate {
           if (_debugChildrenNeedingLayout.length > 1) {
             throw FlutterError(
               'The $this custom multichild layout delegate forgot to lay out the following children:\n'
-              '  ${_debugChildrenNeedingLayout.map(_debugDescribeChild).join("\n  ")}\n'
+              '  ${_debugChildrenNeedingLayout.map<String>(_debugDescribeChild).join("\n  ")}\n'
               'Each child must be laid out exactly once.'
             );
           } else {