diff --git a/dev/benchmarks/complex_layout/lib/main.dart b/dev/benchmarks/complex_layout/lib/main.dart
index 9b95c744f9a5ee50877095dfd7ddad4c093daafb..efae0a2e06c495a28a43a08b4e5c7100f8c982de 100644
--- a/dev/benchmarks/complex_layout/lib/main.dart
+++ b/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(
diff --git a/dev/bots/analyze.dart b/dev/bots/analyze.dart
index ec41f2c855313cb95ae5f363e47e8b946b450d51..20b70d92d1a3a62f82c808e1510c2aa2b299dd09 100644
--- a/dev/bots/analyze.dart
+++ b/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()),
-    stderr: utf8.decode((await savedStderr).expand((List<int> ints) => ints).toList()),
+    stdout: utf8.decode((await savedStdout).expand<int>((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),
diff --git a/dev/bots/prepare_package.dart b/dev/bots/prepare_package.dart
index b3b8fbbda119976651cc5da9e1110563b3d9d1eb..116018e7f9d1aa9107c4340b5db86f5417e96a12 100644
--- a/dev/bots/prepare_package.dart
+++ b/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(
diff --git a/dev/bots/run_command.dart b/dev/bots/run_command.dart
index 539192c97786fff55813040d0da24453d24157c5..0f32200513dae15c52946b7d12b471ab6697729f 100644
--- a/dev/bots/run_command.dart
+++ b/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()));
-      stderr.writeln(utf8.decode((await savedStderr).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<int>((List<int> ints) => ints).toList()));
     }
     print(
         '$redLine\n'
diff --git a/dev/bots/test/analyze-sample-code_test.dart b/dev/bots/test/analyze-sample-code_test.dart
index 7b50ad7fa600122e03c6ebec578d93089901cee2..41ac7c4775ceef23eb7b29ac6a1f475d4a00a725 100644
--- a/dev/bots/test/analyze-sample-code_test.dart
+++ b/dev/bots/test/analyze-sample-code_test.dart
@@ -13,8 +13,8 @@ void main() {
       '../../bin/cache/dart-sdk/bin/dart',
       <String>['analyze-sample-code.dart', 'test/analyze-sample-code-test-input'],
     );
-    final List<String> stdout = await process.stdout.transform(utf8.decoder).transform(const LineSplitter()).toList();
-    final List<String> stderr = await process.stderr.transform(utf8.decoder).transform(const LineSplitter()).toList();
+    final List<String> stdout = await process.stdout.transform<String>(utf8.decoder).transform<String>(const LineSplitter()).toList();
+    final List<String> stderr = await process.stderr.transform<String>(utf8.decoder).transform<String>(const LineSplitter()).toList();
     final Match line = RegExp(r'^(.+)/main\.dart:[0-9]+:[0-9]+: .+$').matchAsPrefix(stdout[1]);
     expect(line, isNot(isNull));
     final String directory = line.group(1);
diff --git a/dev/devicelab/bin/tasks/commands_test.dart b/dev/devicelab/bin/tasks/commands_test.dart
index f23f4b8e195778ee7eb53c707ca13b2555142ec5..a1e695d6f46167b4b8981d6506bdf192a2985a90 100644
--- a/dev/devicelab/bin/tasks/commands_test.dart
+++ b/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(const LineSplitter())
+        .transform<String>(utf8.decoder)
+        .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(const LineSplitter())
+        .transform<String>(utf8.decoder)
+        .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(const LineSplitter())
+        .transform<String>(utf8.decoder)
+        .transform<String>(const LineSplitter())
         .listen((String line) {
       print('drive:stdout: $line');
     });
     drive.stderr
-        .transform(utf8.decoder)
-        .transform(const LineSplitter())
+        .transform<String>(utf8.decoder)
+        .transform<String>(const LineSplitter())
         .listen((String line) {
       stderr.writeln('drive:stderr: $line');
     });
diff --git a/dev/devicelab/bin/tasks/dartdocs.dart b/dev/devicelab/bin/tasks/dartdocs.dart
index bac9d9b0ff051c61f4747f4073c0596462782dc5..174ca243bcb35ee3bcc24908f820277d1c20bbe1 100644
--- a/dev/devicelab/bin/tasks/dartdocs.dart
+++ b/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
diff --git a/dev/devicelab/bin/tasks/flutter_attach_test.dart b/dev/devicelab/bin/tasks/flutter_attach_test.dart
index 3c6641f42a9b985f748e50765ab8e6d17d3c0afb..f39faf21d225b47aa04957cb04238c9f69d8f1f6 100644
--- a/dev/devicelab/bin/tasks/flutter_attach_test.dart
+++ b/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(const LineSplitter())
+      .transform<String>(utf8.decoder)
+      .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(const LineSplitter())
+      .transform<String>(utf8.decoder)
+      .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 ]);
diff --git a/dev/devicelab/bin/tasks/flutter_test_performance.dart b/dev/devicelab/bin/tasks/flutter_test_performance.dart
index 2434680267bb833843fdbd7654861c764d4bfb12..0e5ef8d9796829f3b595c199000174d2ea9c1359 100644
--- a/dev/devicelab/bin/tasks/flutter_test_performance.dart
+++ b/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: $entry');
     badLines += 1;
   }
diff --git a/dev/devicelab/bin/tasks/gradle_plugin_test.dart b/dev/devicelab/bin/tasks/gradle_plugin_test.dart
index 32442d982e29fac9861299c78954f02332402888..8521314ea74e20c52ede99829354689abfd86e8d 100644
--- a/dev/devicelab/bin/tasks/gradle_plugin_test.dart
+++ b/dev/devicelab/bin/tasks/gradle_plugin_test.dart
@@ -297,7 +297,7 @@ class _Dependencies {
         .replaceAllMapped(_separatorExpr, (Match match) => '${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();
   }
diff --git a/dev/devicelab/bin/tasks/routing_test.dart b/dev/devicelab/bin/tasks/routing_test.dart
index d001aa536fa707f5efca03cd48251430ae3aad36..851d9dc23554c801b71d8d6edc46da216089ff4e 100644
--- a/dev/devicelab/bin/tasks/routing_test.dart
+++ b/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(const LineSplitter())
+        .transform<String>(utf8.decoder)
+        .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(const LineSplitter())
+        .transform<String>(utf8.decoder)
+        .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(const LineSplitter())
+        .transform<String>(utf8.decoder)
+        .transform<String>(const LineSplitter())
         .listen((String line) {
           print('drive:stdout: $line');
         });
       drive.stderr
-        .transform(utf8.decoder)
-        .transform(const LineSplitter())
+        .transform<String>(utf8.decoder)
+        .transform<String>(const LineSplitter())
         .listen((String line) {
           stderr.writeln('drive:stderr: $line');
         });
diff --git a/dev/devicelab/bin/tasks/run_machine_concurrent_hot_reload.dart b/dev/devicelab/bin/tasks/run_machine_concurrent_hot_reload.dart
index 19d48d331ed30b177e3ffadd2a03c2ce30ba5e77..aa441e50a8aa8e73982de9bf11d1d46bede44ce0 100644
--- a/dev/devicelab/bin/tasks/run_machine_concurrent_hot_reload.dart
+++ b/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]);
diff --git a/dev/devicelab/bin/tasks/run_release_test.dart b/dev/devicelab/bin/tasks/run_release_test.dart
index d3a8851ffd0c58a88e25831712fcf4a5db189ac3..7ebcb421825bcfd7a1713500b3ac6089e9a2a050 100644
--- a/dev/devicelab/bin/tasks/run_release_test.dart
+++ b/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(const LineSplitter())
+        .transform<String>(utf8.decoder)
+        .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(const LineSplitter())
+        .transform<String>(utf8.decoder)
+        .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.';
diff --git a/dev/devicelab/bin/tasks/service_extensions_test.dart b/dev/devicelab/bin/tasks/service_extensions_test.dart
index dda1676dec13845814a6445d1e9ff095e113551f..898d76f53066735bb3f866788f55ef6e614dcde2 100644
--- a/dev/devicelab/bin/tasks/service_extensions_test.dart
+++ b/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(const LineSplitter())
+          .transform<String>(utf8.decoder)
+          .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(const LineSplitter())
+          .transform<String>(utf8.decoder)
+          .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.';
diff --git a/dev/devicelab/bin/tasks/technical_debt__cost.dart b/dev/devicelab/bin/tasks/technical_debt__cost.dart
index dc2d076f7a371dfb371f932c547c42679176cfa8..7cc137d3018a41be51ca2e947c1a8f2ea11ea092 100644
--- a/dev/devicelab/bin/tasks/technical_debt__cost.dart
+++ b/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)
diff --git a/dev/devicelab/lib/framework/adb.dart b/dev/devicelab/lib/framework/adb.dart
index 8098d7091161237cc57773632fe11cee360d75e0..2ea21c8c4a3304f85fbb0689d343e366cf10fe6a 100644
--- a/dev/devicelab/lib/framework/adb.dart
+++ b/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(const LineSplitter())
+          .transform<String>(utf8.decoder)
+          .transform<String>(const LineSplitter())
           .listen((String line) {
             print('adb logcat: $line');
             stream.sink.add(line);
           }, onDone: () { stdoutDone.complete(); });
         process.stderr
-          .transform(utf8.decoder)
-          .transform(const LineSplitter())
+          .transform<String>(utf8.decoder)
+          .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)
diff --git a/dev/devicelab/lib/framework/manifest.dart b/dev/devicelab/lib/framework/manifest.dart
index f5e28545a5e6d13c59409656fedfdba54a6f3e44..dc0eca378ce980ce56a43f2bf9b271c8c5630ad9 100644
--- a/dev/devicelab/lib/framework/manifest.dart
+++ b/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) {
diff --git a/dev/devicelab/lib/framework/runner.dart b/dev/devicelab/lib/framework/runner.dart
index e836d9f57062ec484d76fdee95c381613ba8dbfd..87ad3190095e2e6f9e5ed2bcdf9bad080ca88a10 100644
--- a/dev/devicelab/lib/framework/runner.dart
+++ b/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(const LineSplitter())
+      .transform<String>(const Utf8Decoder())
+      .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(const LineSplitter())
+      .transform<String>(const Utf8Decoder())
+      .transform<String>(const LineSplitter())
       .listen((String line) {
     stderr.writeln('[$taskName] [STDERR] $line');
   });
diff --git a/dev/devicelab/lib/framework/utils.dart b/dev/devicelab/lib/framework/utils.dart
index c90adf481e65df464656b096a71c8a7cf59c9d36..8ec8345056b59dc03d2ad1ac0dd75cefea2baa9b 100644
--- a/dev/devicelab/lib/framework/utils.dart
+++ b/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(const LineSplitter())
+      .transform<String>(utf8.decoder)
+      .transform<String>(const LineSplitter())
       .listen((String line) {
         print('stdout: $line');
       }, onDone: () { stdoutDone.complete(); });
   process.stderr
-      .transform(utf8.decoder)
-      .transform(const LineSplitter())
+      .transform<String>(utf8.decoder)
+      .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(const LineSplitter())
+      .transform<String>(utf8.decoder)
+      .transform<String>(const LineSplitter())
       .listen((String line) {
         print('stdout: $line');
         output.writeln(line);
       }, onDone: () { stdoutDone.complete(); });
   process.stderr
-      .transform(utf8.decoder)
-      .transform(const LineSplitter())
+      .transform<String>(utf8.decoder)
+      .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]);
   });
 
diff --git a/dev/devicelab/lib/tasks/analysis.dart b/dev/devicelab/lib/tasks/analysis.dart
index 495935895d032f9817b5fc92e3a13089e2a08e15..cbf4366d5625509d33f1cbbbce10a004325641b9 100644
--- a/dev/devicelab/lib/tasks/analysis.dart
+++ b/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} / $targetIterations');
     final Stopwatch stopwatch = Stopwatch();
-    await inDirectory(directory, () async {
+    await inDirectory<void>(directory, () async {
       stopwatch.start();
       await flutter('analyze', options: options);
       stopwatch.stop();
diff --git a/dev/devicelab/lib/tasks/gallery.dart b/dev/devicelab/lib/tasks/gallery.dart
index 6044e4e19666cc4f6c07e63931f40aa578a71917..7fdc271466d2c8d41d53119ebf33f06338ccaf3f 100644
--- a/dev/devicelab/lib/tasks/gallery.dart
+++ b/dev/devicelab/lib/tasks/gallery.dart
@@ -28,7 +28,7 @@ class GalleryTransitionTest {
     final String deviceId = device.deviceId;
     final Directory galleryDirectory =
         dir('${flutterDirectory.path}/examples/flutter_gallery');
-    await inDirectory(galleryDirectory, () async {
+    await inDirectory<void>(galleryDirectory, () async {
       await flutter('packages', options: <String>['get']);
 
       if (deviceOperatingSystem == DeviceOperatingSystem.ios)
diff --git a/dev/devicelab/lib/tasks/hot_mode_tests.dart b/dev/devicelab/lib/tasks/hot_mode_tests.dart
index c938318bde4cc42b7eb3bb3feee92439244cc529..e24ff66d12cff4c31e8a578e59e57bc7715f803a 100644
--- a/dev/devicelab/lib/tasks/hot_mode_tests.dart
+++ b/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(const LineSplitter())
+              .transform<String>(utf8.decoder)
+              .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(const LineSplitter())
+              .transform<String>(utf8.decoder)
+              .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(const LineSplitter())
+              .transform<String>(utf8.decoder)
+              .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(const LineSplitter())
+              .transform<String>(utf8.decoder)
+              .transform<String>(const LineSplitter())
               .listen((String line) {
             print('stderr: $line');
           }, onDone: () {
diff --git a/dev/devicelab/lib/tasks/integration_tests.dart b/dev/devicelab/lib/tasks/integration_tests.dart
index 0064c1b5a466ef7098f400babec34f7dda58f836..05ec55642240be16e6c912e97cc19fe7c8fcd21e 100644
--- a/dev/devicelab/lib/tasks/integration_tests.dart
+++ b/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;
diff --git a/dev/devicelab/lib/tasks/integration_ui.dart b/dev/devicelab/lib/tasks/integration_ui.dart
index c40495ff08fa525794d38d77c4c7b493e5fe906d..335130fcc75efc35ca6b658530d464327f0de1f7 100644
--- a/dev/devicelab/lib/tasks/integration_ui.dart
+++ b/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)
diff --git a/dev/devicelab/lib/tasks/microbenchmarks.dart b/dev/devicelab/lib/tasks/microbenchmarks.dart
index ae96483bd2047600ffebb3e95a2db7cc35a60f7f..91892be2e6403544a13e4a027b3a0d4df21dd262 100644
--- a/dev/devicelab/lib/tasks/microbenchmarks.dart
+++ b/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(const LineSplitter())
+      .transform<String>(const Utf8Decoder())
+      .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(const LineSplitter())
+      .transform<String>(const Utf8Decoder())
+      .transform<String>(const LineSplitter())
       .listen((String line) async {
     print(line);
 
diff --git a/dev/devicelab/lib/tasks/perf_tests.dart b/dev/devicelab/lib/tasks/perf_tests.dart
index 345fd7c588d256e944a0456a112bc11813187bf2..1c0901201efd77848acac90ba41975cc9074b7a4 100644
--- a/dev/devicelab/lib/tasks/perf_tests.dart
+++ b/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.
 
diff --git a/dev/devicelab/lib/tasks/sample_catalog_generator.dart b/dev/devicelab/lib/tasks/sample_catalog_generator.dart
index ef52a3d6253da7e05056085e5c873c7ba608e6ec..376cc67abc03b4bc8953bc716acb35aa3ef11d30 100644
--- a/dev/devicelab/lib/tasks/sample_catalog_generator.dart
+++ b/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;
diff --git a/dev/devicelab/lib/tasks/save_catalog_screenshots.dart b/dev/devicelab/lib/tasks/save_catalog_screenshots.dart
index 727358bd19c0bd31685527d08fcd253f90823215..e1bd4d07019fe0939f7f19c3b7c4e92a7eb90c94 100644
--- a/dev/devicelab/lib/tasks/save_catalog_screenshots.dart
+++ b/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);
   }
 }
diff --git a/dev/integration_tests/android_semantics_testing/lib/main.dart b/dev/integration_tests/android_semantics_testing/lib/main.dart
index 1b7bf656e5ad4627c4225ed67f6c2c43c6abdc72..d0f52854ae92225cd1353bae8d3c9c0c632e27d4 100644
--- a/dev/integration_tests/android_semantics_testing/lib/main.dart
+++ b/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: () {
diff --git a/dev/integration_tests/android_views/lib/main.dart b/dev/integration_tests/android_views/lib/main.dart
index e1d0679a2d72e99ee6aa328d251068843f1ead3b..a9e79faf266e94142d377dd446941a75bbed95de 100644
--- a/dev/integration_tests/android_views/lib/main.dart
+++ b/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');
diff --git a/dev/manual_tests/lib/animated_icons.dart b/dev/manual_tests/lib/animated_icons.dart
index 3cf6f10e1f14d2277034f7822e3ac16413e7f2d1..b857423982b1d840021989f237ce17ee28ba44a5 100644
--- a/dev/manual_tests/lib/animated_icons.dart
+++ b/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(),
     );
   }
 }
diff --git a/dev/manual_tests/lib/material_arc.dart b/dev/manual_tests/lib/material_arc.dart
index 5b7fadaef35fea607144711d9817cc877324d22d..4d9ece5054061cdd0959a22758c9f0f64b8a993c 100644
--- a/dev/manual_tests/lib/material_arc.dart
+++ b/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()
         )
       )
     );
diff --git a/dev/manual_tests/lib/page_view.dart b/dev/manual_tests/lib/page_view.dart
index 5487f084b6ea10cb5ee42f167b1a91fd481bafe8..b882f3132f36156b4a8c0178cc93c441ae747bb9 100644
--- a/dev/manual_tests/lib/page_view.dart
+++ b/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,
     );
diff --git a/dev/manual_tests/lib/text.dart b/dev/manual_tests/lib/text.dart
index 938b532b02a9f1db99ebf9a41970b757b9b61688..0244f3e6c05de58f710b5509526a20608b9c2c8b 100644
--- a/dev/manual_tests/lib/text.dart
+++ b/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);
diff --git a/dev/manual_tests/test/card_collection_test.dart b/dev/manual_tests/test/card_collection_test.dart
index 3ed2a1b9f19ed9e84e8b5e0b3cb2615824c6d167..8de4efbf2b347fe4b5a3f74eb623a1041a89b3ad 100644
--- a/dev/manual_tests/test/card_collection_test.dart
+++ b/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
diff --git a/dev/manual_tests/test/color_testing_demo_test.dart b/dev/manual_tests/test/color_testing_demo_test.dart
index 9c3b16e18bd115a496650c2f977e367a44a63540..eca5509dbb335d6adba825af643e9b248abbea02 100644
--- a/dev/manual_tests/test/color_testing_demo_test.dart
+++ b/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
diff --git a/dev/tools/dartdoc.dart b/dev/tools/dartdoc.dart
index 20ca85d864999edb23340afc46539aa1ccf0e459..cde62e9205afc128bf2e88fb83f2de1ebf72cde5 100644
--- a/dev/tools/dartdoc.dart
+++ b/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(const LineSplitter())
+    .transform<String>(utf8.decoder)
+    .transform<String>(const LineSplitter())
     .listen((String line) {
       if (!filter.any((Pattern pattern) => line.contains(pattern)))
         print('$prefix$line'.trim());
diff --git a/dev/tools/gen_date_localizations.dart b/dev/tools/gen_date_localizations.dart
index 6a72ced3544a53df18a5cd5e063ab2261303863d..59c3a42b19c3bc1b44b4d35274a63df7380488f7 100644
--- a/dev/tools/gen_date_localizations.dart
+++ b/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>{');
diff --git a/dev/tools/gen_localizations.dart b/dev/tools/gen_localizations.dart
index da4a34c14436c93ff32ea03809eb5ba75d1ba869..7419912f65272c64a787504ced7a302576f27718 100644
--- a/dev/tools/gen_localizations.dart
+++ b/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`.
diff --git a/dev/tools/lib/roll_dev.dart b/dev/tools/lib/roll_dev.dart
index 143db305bba0b71ff1ccf0c2c94c7c39d1989ddd..d513ba0c0ad891115aca8d4b0bdc73392b29d6c3 100644
--- a/dev/tools/lib/roll_dev.dart
+++ b/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(".")}.');
diff --git a/dev/tools/localizations_utils.dart b/dev/tools/localizations_utils.dart
index bcfadd59515008a4f46e03ba5ce3a3e4eea52127..dfd7a83cffc98727b18d5728b6897db60544e7b9 100644
--- a/dev/tools/localizations_utils.dart
+++ b/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) {
diff --git a/dev/tools/update_icons.dart b/dev/tools/update_icons.dart
index 43a1f795c99e1a6234f36b3fe64752011b084878..1984cdf2ce1aa98ddb6deae97fb35ad7a27339c5 100644
--- a/dev/tools/update_icons.dart
+++ b/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();
 }
 
diff --git a/dev/tools/vitool/lib/vitool.dart b/dev/tools/vitool/lib/vitool.dart
index f89a93ac0ba995bbd73dd4dd2d1d0f5449dcce57..0e1ab4e9a8ee399804b91d51f776cb4e3aa013ff 100644
--- a/dev/tools/vitool/lib/vitool.dart
+++ b/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')
diff --git a/examples/catalog/bin/sample_page.dart b/examples/catalog/bin/sample_page.dart
index 42afe9288c1c74a0c52b8c6705cce250354a5a7a..d2780412f730973cbf0b25dd7fb902bd2c176e41 100644
--- a/examples/catalog/bin/sample_page.dart
+++ b/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'),
     },
diff --git a/examples/catalog/lib/app_bar_bottom.dart b/examples/catalog/lib/app_bar_bottom.dart
index fd6be4dd14c4dbba92f3f95d4b00c51059016d33..2fd1a60fe63bf9918a613fdf86a3f4bfcc90f41e 100644
--- a/examples/catalog/lib/app_bar_bottom.dart
+++ b/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),
diff --git a/examples/catalog/lib/basic_app_bar.dart b/examples/catalog/lib/basic_app_bar.dart
index 3638d64f6070c2325645ce911bc241a22d03ca67..6bf4cac2cc399e1a74dd7432dda6a37def983cfb 100644
--- a/examples/catalog/lib/basic_app_bar.dart
+++ b/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),
diff --git a/examples/catalog/lib/custom_semantics.dart b/examples/catalog/lib/custom_semantics.dart
index f9dc9e4316bdda071c1d1fd373e998057b18a918..e8bd86cb42aadb0895538dffe418e907e92bd75b 100644
--- a/examples/catalog/lib/custom_semantics.dart
+++ b/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),
diff --git a/examples/catalog/lib/expansion_tile_sample.dart b/examples/catalog/lib/expansion_tile_sample.dart
index 9e0264d0304ec9f6ba98bcdd067e67f6b8491d65..1d9fdfe3529533eaa2adb2201d94f88f88b64263 100644
--- a/examples/catalog/lib/expansion_tile_sample.dart
+++ b/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(),
     );
   }
 
diff --git a/examples/catalog/lib/tabbed_app_bar.dart b/examples/catalog/lib/tabbed_app_bar.dart
index 6bcfc1d326d9d659527fdd6e73e883b927eaf2d5..99aba1e52021be1ccbe19241f373a92f4094676f 100644
--- a/examples/catalog/lib/tabbed_app_bar.dart
+++ b/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),
diff --git a/examples/flutter_gallery/lib/demo/animation/home.dart b/examples/flutter_gallery/lib/demo/animation/home.dart
index 4a0de2d54b88293372cf845cc035a7a5f235c8aa..6f3d9e4cb5b5577568dbccff52c9f91786706f2a 100644
--- a/examples/flutter_gallery/lib/demo/animation/home.dart
+++ b/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(),
diff --git a/examples/flutter_gallery/lib/demo/colors_demo.dart b/examples/flutter_gallery/lib/demo/colors_demo.dart
index a38999ba2d639c50c65071caf4f0657ba2026117..59a94274f835ec732d7e34f361c312d66d3ed44b 100644
--- a/examples/flutter_gallery/lib/demo/colors_demo.dart
+++ b/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(),
         ),
diff --git a/examples/flutter_gallery/lib/demo/contacts_demo.dart b/examples/flutter_gallery/lib/demo/contacts_demo.dart
index 3ff7e6f80d1ce6730b4c30c405d9c1cd95f57d86..5566f8c25aaed88ecf2699682d85c93b470aa859 100644
--- a/examples/flutter_gallery/lib/demo/contacts_demo.dart
+++ b/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>[
diff --git a/examples/flutter_gallery/lib/demo/cupertino/cupertino_refresh_demo.dart b/examples/flutter_gallery/lib/demo/cupertino/cupertino_refresh_demo.dart
index cd4aecf1f14067db344116dbd71e7a1d9f68789f..84f8dc7bf741c8623a9dd3c668956a979ab6b649 100644
--- a/examples/flutter_gallery/lib/demo/cupertino/cupertino_refresh_demo.dart
+++ b/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());
                         }
diff --git a/examples/flutter_gallery/lib/demo/material/bottom_app_bar_demo.dart b/examples/flutter_gallery/lib/demo/material/bottom_app_bar_demo.dart
index 9b1d14dd801c35cdb2c71425e064f360bec6a15c..bf327f041bf7b27bf9c1d15f0b9832982320d127 100644
--- a/examples/flutter_gallery/lib/demo/material/bottom_app_bar_demo.dart
+++ b/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);
diff --git a/examples/flutter_gallery/lib/demo/material/bottom_navigation_demo.dart b/examples/flutter_gallery/lib/demo/material/bottom_navigation_demo.dart
index 479c81a85bf7fcde23b9abbd0649374a25ee4e31..3046c74b08d9d8bb2b0e0e80e0d79c23d13f9e7b 100644
--- a/examples/flutter_gallery/lib/demo/material/bottom_navigation_demo.dart
+++ b/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,
diff --git a/examples/flutter_gallery/lib/demo/material/buttons_demo.dart b/examples/flutter_gallery/lib/demo/material/buttons_demo.dart
index a590f1f5246f69f2d90cca92eef985361c71c434..9de0655709ace465efc9895ced5b0190e3f5410e 100644
--- a/examples/flutter_gallery/lib/demo/material/buttons_demo.dart
+++ b/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(),
       ),
     );
diff --git a/examples/flutter_gallery/lib/demo/material/cards_demo.dart b/examples/flutter_gallery/lib/demo/material/cards_demo.dart
index e318eb79de65435da6c585ff0e8ce234c56d6e75..2a09e8cabdae3182ad32bed9fa3db51f457bd3bf 100644
--- a/examples/flutter_gallery/lib/demo/material/cards_demo.dart
+++ b/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(
diff --git a/examples/flutter_gallery/lib/demo/material/chip_demo.dart b/examples/flutter_gallery/lib/demo/material/chip_demo.dart
index 48be2b1ea681393d094724d1a5c36db9f6e9f641..3590c0295c936c18123a61c4f7b640be4fbd7e84 100644
--- a/examples/flutter_gallery/lib/demo/material/chip_demo.dart
+++ b/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,
diff --git a/examples/flutter_gallery/lib/demo/material/date_and_time_picker_demo.dart b/examples/flutter_gallery/lib/demo/material/date_and_time_picker_demo.dart
index 76ccf441e25f3cc30070f82a025bc9a56cfed34b..64701fe2169e3f8083553d057e2b728e2d0236a2 100644
--- a/examples/flutter_gallery/lib/demo/material/date_and_time_picker_demo.dart
+++ b/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),
diff --git a/examples/flutter_gallery/lib/demo/material/dialog_demo.dart b/examples/flutter_gallery/lib/demo/material/dialog_demo.dart
index dc48a7e9a1fc5e5e5a4a3f6a6bb7d30b28169c9d..27c7bffc87539ce224d0cc2d9ac51c659ec70dcb 100644
--- a/examples/flutter_gallery/lib/demo/material/dialog_demo.dart
+++ b/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
diff --git a/examples/flutter_gallery/lib/demo/material/drawer_demo.dart b/examples/flutter_gallery/lib/demo/material/drawer_demo.dart
index 5590fd58fddae27727f9e821d11d68d341add096..3f08bdea837ba207d61177de9321ee2dddd8de6e 100644
--- a/examples/flutter_gallery/lib/demo/material/drawer_demo.dart
+++ b/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'),
diff --git a/examples/flutter_gallery/lib/demo/material/elevation_demo.dart b/examples/flutter_gallery/lib/demo/material/elevation_demo.dart
index 651854fc2ae203f1b5e4ae9cf55df4123e34b488..c2500a4ddd0b87048265a05b71ac7d9c09130d67 100644
--- a/examples/flutter_gallery/lib/demo/material/elevation_demo.dart
+++ b/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),
diff --git a/examples/flutter_gallery/lib/demo/material/expansion_panels_demo.dart b/examples/flutter_gallery/lib/demo/material/expansion_panels_demo.dart
index 861d578b51fe02f12c6a25e13107f8870a1c12f5..c3f2b86d078d6364ceedbd00340df26655b55b21 100644
--- a/examples/flutter_gallery/lib/demo/material/expansion_panels_demo.dart
+++ b/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,
diff --git a/examples/flutter_gallery/lib/demo/material/full_screen_dialog_demo.dart b/examples/flutter_gallery/lib/demo/material/full_screen_dialog_demo.dart
index 99db465b16728a50cf851092d53b0360da54a267..9d268feae040820fa311e9a927fb760febea98b0 100644
--- a/examples/flutter_gallery/lib/demo/material/full_screen_dialog_demo.dart
+++ b/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,
diff --git a/examples/flutter_gallery/lib/demo/material/grid_list_demo.dart b/examples/flutter_gallery/lib/demo/material/grid_list_demo.dart
index e6f2c6096848aeac936ea81efe6b369d65377242..eaa72b39181ebfa4bfc03b062e5e56df13da39d3 100644
--- a/examples/flutter_gallery/lib/demo/material/grid_list_demo.dart
+++ b/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,
diff --git a/examples/flutter_gallery/lib/demo/material/leave_behind_demo.dart b/examples/flutter_gallery/lib/demo/material/leave_behind_demo.dart
index 3cce01a3c3b8f73af24871abd3311c0ad7030137..c723baf92066f49c82ddcea5a0cbddf376239686 100644
--- a/examples/flutter_gallery/lib/demo/material/leave_behind_demo.dart
+++ b/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,
diff --git a/examples/flutter_gallery/lib/demo/material/list_demo.dart b/examples/flutter_gallery/lib/demo/material/list_demo.dart
index a3fdb96c76e63b56b955efeb89b9625c21f57119..0f35f96fdf8285fec246615136c0fcb8138684cc 100644
--- a/examples/flutter_gallery/lib/demo/material/list_demo.dart
+++ b/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);
 
diff --git a/examples/flutter_gallery/lib/demo/material/overscroll_demo.dart b/examples/flutter_gallery/lib/demo/material/overscroll_demo.dart
index 6720de9f90e6d48647c9fc72f1185f160ffac93d..58634444ca9adef71444695ebe3cc3e83a506146 100644
--- a/examples/flutter_gallery/lib/demo/material/overscroll_demo.dart
+++ b/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(
diff --git a/examples/flutter_gallery/lib/demo/material/page_selector_demo.dart b/examples/flutter_gallery/lib/demo/material/page_selector_demo.dart
index 3c9a47ceb395c06ba6f1d93066a09ac64f805db6..4a7dfe570e8dd7a6d3c68324cdcc99361554c2b3 100644
--- a/examples/flutter_gallery/lib/demo/material/page_selector_demo.dart
+++ b/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(
diff --git a/examples/flutter_gallery/lib/demo/material/progress_indicator_demo.dart b/examples/flutter_gallery/lib/demo/material/progress_indicator_demo.dart
index cdd086f510f2a6779a6703ad1ac784dac10f6bbf..edfa5496e4ad4628ca867c3ac8b00a3c6e4281a9 100644
--- a/examples/flutter_gallery/lib/demo/material/progress_indicator_demo.dart
+++ b/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(),
     );
   }
diff --git a/examples/flutter_gallery/lib/demo/material/reorderable_list_demo.dart b/examples/flutter_gallery/lib/demo/material/reorderable_list_demo.dart
index af386a7dd91a83ce4326b08e4987ce5287594355..4cda720dfcbacfa6e741093b7dfb856106f061f4 100644
--- a/examples/flutter_gallery/lib/demo/material/reorderable_list_demo.dart
+++ b/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(),
         ),
       ),
     );
diff --git a/examples/flutter_gallery/lib/demo/material/scrollable_tabs_demo.dart b/examples/flutter_gallery/lib/demo/material/scrollable_tabs_demo.dart
index 2d2364888f236ccfa3cb3f4d4bb9863d22882d0f..0135c30e3574204b15d94c2426907a25d907030f 100644
--- a/examples/flutter_gallery/lib/demo/material/scrollable_tabs_demo.dart
+++ b/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,
diff --git a/examples/flutter_gallery/lib/demo/material/search_demo.dart b/examples/flutter_gallery/lib/demo/material/search_demo.dart
index afc618616cfec4e3762adb4b8aefa7dbda9f9718..e1be3ea94ebb7ada51b25c25160ce59623df6794 100644
--- a/examples/flutter_gallery/lib/demo/material/search_demo.dart
+++ b/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);
diff --git a/examples/flutter_gallery/lib/demo/material/snack_bar_demo.dart b/examples/flutter_gallery/lib/demo/material/snack_bar_demo.dart
index 830ceba09b87541d8734564de9aa2453bdcc8783..6f135bf09665c2803ea9c6ec1873cc4d94583b3e 100644
--- a/examples/flutter_gallery/lib/demo/material/snack_bar_demo.dart
+++ b/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
diff --git a/examples/flutter_gallery/lib/demo/material/tabs_demo.dart b/examples/flutter_gallery/lib/demo/material/tabs_demo.dart
index 5cdfdcbb3a0ed94ffda4a0d3bcc7f16486e4be58..a9064b1513153ccef7904af9dba92d431199ba63 100644
--- a/examples/flutter_gallery/lib/demo/material/tabs_demo.dart
+++ b/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,
diff --git a/examples/flutter_gallery/lib/demo/material/tabs_fab_demo.dart b/examples/flutter_gallery/lib/demo/material/tabs_fab_demo.dart
index 2a7371a93485c37710d1160e9f1e342130dbe42b..0ebb592ef7800df2ffb6e0df9ae4aa69d815f2f7 100644
--- a/examples/flutter_gallery/lib/demo/material/tabs_fab_demo.dart
+++ b/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()
       ),
     );
   }
diff --git a/examples/flutter_gallery/lib/demo/material/tooltip_demo.dart b/examples/flutter_gallery/lib/demo/material/tooltip_demo.dart
index 69639085d9e8608d88e75ce3067475cc237a0ca9..20707a3801daaa4251949925678b50507d14a670 100644
--- a/examples/flutter_gallery/lib/demo/material/tooltip_demo.dart
+++ b/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
diff --git a/examples/flutter_gallery/lib/demo/pesto_demo.dart b/examples/flutter_gallery/lib/demo/pesto_demo.dart
index 29ed01f2fd73230d3cb6c6adb06f6f78ece487b9..8683c339752d4a2154aecf242af8228fc988809f 100644
--- a/examples/flutter_gallery/lib/demo/pesto_demo.dart
+++ b/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);
               }
diff --git a/examples/flutter_gallery/lib/demo/shrine/shrine_home.dart b/examples/flutter_gallery/lib/demo/shrine/shrine_home.dart
index 6e30227b4a0217cab941e69ca5d81d1d8e40ae32..9382df9f0fe82a8a501146a2e26ee657c128df35 100644
--- a/examples/flutter_gallery/lib/demo/shrine/shrine_home.dart
+++ b/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); },
diff --git a/examples/flutter_gallery/lib/demo/shrine/shrine_order.dart b/examples/flutter_gallery/lib/demo/shrine/shrine_order.dart
index 453b16e9b56bc42111c99237c4958dee568cbffb..45f0bb5362ffe22c4f6c7f5d04af5de2a3a79495 100644
--- a/examples/flutter_gallery/lib/demo/shrine/shrine_order.dart
+++ b/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(
diff --git a/examples/flutter_gallery/lib/demo/video_demo.dart b/examples/flutter_gallery/lib/demo/video_demo.dart
index ef4b9ff28bf23f781e239f917ffe47e4ded3b386..59bbc1cece090cd40ea1faf5f9afba678fd2fb37 100644
--- a/examples/flutter_gallery/lib/demo/video_demo.dart
+++ b/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;
     });
   }
diff --git a/examples/flutter_gallery/lib/gallery/demo.dart b/examples/flutter_gallery/lib/gallery/demo.dart
index d6e11683c523af68fcfecba5a2de7ac88c557b53..9b428b7595dd467544793d5aaea48a3352ebdd21 100644
--- a/examples/flutter_gallery/lib/gallery/demo.dart
+++ b/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,
diff --git a/examples/flutter_gallery/lib/gallery/example_code.dart b/examples/flutter_gallery/lib/gallery/example_code.dart
index 595b149f9acfdda83c43e4d26602045377d84409..96969393dbe03c112e5a83dfc6f6f21939f1c646 100644
--- a/examples/flutter_gallery/lib/gallery/example_code.dart
+++ b/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)
diff --git a/examples/flutter_gallery/lib/gallery/options.dart b/examples/flutter_gallery/lib/gallery/options.dart
index 29e09f2c4ec4a6ddc21c8a9ba0143b0fb77aa7cd..d40b31a0d6e0ffa7ed54f01f3b272004471ef47f 100644
--- a/examples/flutter_gallery/lib/gallery/options.dart
+++ b/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),
diff --git a/examples/layers/services/isolate.dart b/examples/layers/services/isolate.dart
index 6feeda9256adeca31a782cb329b5866ddb576fff..d7bfae7a60fbbe0b88853ebed4b008f2cebd2960 100644
--- a/examples/layers/services/isolate.dart
+++ b/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 {
diff --git a/examples/layers/widgets/media_query.dart b/examples/layers/widgets/media_query.dart
index 69ed7f349701b31e657a01574a3ccdbc8e4b7dd3..091fadb9c1c2a23ed549812f950837d4ea146ea9 100644
--- a/examples/layers/widgets/media_query.dart
+++ b/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(),
       );
     }
   }
diff --git a/examples/layers/widgets/sectors.dart b/examples/layers/widgets/sectors.dart
index b8fae26c00806a96f0b9d70c5721cce117c4b2b4..553e8af668e73884c925e79a3858fa44694631f0 100644
--- a/examples/layers/widgets/sectors.dart
+++ b/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;
diff --git a/examples/layers/widgets/styled_text.dart b/examples/layers/widgets/styled_text.dart
index b3dae6ca8f00a2c1f994abf49a9c44ba31fac084..633d55e722089b951a1919b9637d30efccffa12f 100644
--- a/examples/layers/widgets/styled_text.dart
+++ b/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);
diff --git a/examples/stocks/lib/stock_strings.dart b/examples/stocks/lib/stock_strings.dart
index 136d07926326f5aecfbb9da9916018166b271c18..ed1422476eeadc7d35195568dd02653ea4fcef70 100644
--- a/examples/stocks/lib/stock_strings.dart
+++ b/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);
       });
   }
diff --git a/packages/flutter/lib/src/cupertino/button.dart b/packages/flutter/lib/src/cupertino/button.dart
index 046cc113d46155a769d81e60cd8eab9d4fb90917..323d2c6cda162c6a4d87959bf9eaa44039e10cf2 100644
--- a/packages/flutter/lib/src/cupertino/button.dart
+++ b/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();
     });
diff --git a/packages/flutter/lib/src/cupertino/dialog.dart b/packages/flutter/lib/src/cupertino/dialog.dart
index 092beb0a14537632c26a76023c7b6841636bd001..4f5c7ce6d6362163d38aeff3f16ce6cf41600f3a 100644
--- a/packages/flutter/lib/src/cupertino/dialog.dart
+++ b/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(
diff --git a/packages/flutter/lib/src/foundation/isolates.dart b/packages/flutter/lib/src/foundation/isolates.dart
index 603e05239eba308ebb13d81785188561af7ae7d8..7eaf6181b01e97b08acf0afb0b88fd395f2c8dee 100644
--- a/packages/flutter/lib/src/foundation/isolates.dart
+++ b/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,
diff --git a/packages/flutter/lib/src/foundation/print.dart b/packages/flutter/lib/src/foundation/print.dart
index 2e8acd114f77d83006b2febc3d78e3a506eb5dd8..434dbb2436c50a9946c0c4d5b84fd5a6e9a8f5cb 100644
--- a/packages/flutter/lib/src/foundation/print.dart
+++ b/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'));
   }
diff --git a/packages/flutter/lib/src/material/animated_icons/animated_icons.dart b/packages/flutter/lib/src/material/animated_icons/animated_icons.dart
index 1077544c32fc31cc2519a3ad61b519a4cc70be34..6284d47248ffc85d55ca4bba7e8f62848d9ce8a0 100644
--- a/packages/flutter/lib/src/material/animated_icons/animated_icons.dart
+++ b/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 controlPoint2 = _interpolate(controlPoints2, progress, Offset.lerp);
-    final Offset targetPoint = _interpolate(targetPoints, progress, Offset.lerp);
+    final Offset controlPoint1 = _interpolate<Offset>(controlPoints1, progress, Offset.lerp);
+    final Offset controlPoint2 = _interpolate<Offset>(controlPoints2, 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);
   }
 }
diff --git a/packages/flutter/lib/src/material/bottom_navigation_bar.dart b/packages/flutter/lib/src/material/bottom_navigation_bar.dart
index 1116501fe6c6025cf2bfb245c39aa9a751544a6a..9024b5328f3c1027d447913c88a1929109af626f 100644
--- a/packages/flutter/lib/src/material/bottom_navigation_bar.dart
+++ b/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);
diff --git a/packages/flutter/lib/src/material/mergeable_material.dart b/packages/flutter/lib/src/material/mergeable_material.dart
index 5e333a2d8f326c00a485f67d5bb860e63315ddd6..757b6d31cccef6293cc7a598a5e3931e8290fc7e 100644
--- a/packages/flutter/lib/src/material/mergeable_material.dart
+++ b/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);
diff --git a/packages/flutter/lib/src/material/user_accounts_drawer_header.dart b/packages/flutter/lib/src/material/user_accounts_drawer_header.dart
index 7c37659f376733d4c7e8d7981a462ab5040419d6..3ca9773cf9c5ca713d2756bff53e7094ae057bd7 100644
--- a/packages/flutter/lib/src/material/user_accounts_drawer_header.dart
+++ b/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(
diff --git a/packages/flutter/lib/src/painting/image_resolution.dart b/packages/flutter/lib/src/painting/image_resolution.dart
index 7b9bb82f6351a475d5810b8fd1875ea9b91ea3d2..2061de09462aecb1080c8e0b19c94b7f886fc9a9 100644
--- a/packages/flutter/lib/src/painting/image_resolution.dart
+++ b/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);
   }
diff --git a/packages/flutter/lib/src/painting/text_span.dart b/packages/flutter/lib/src/painting/text_span.dart
index f2a08d5135f99af7c0543339f9434b6c2f41e23c..55a8f1530a0072d9f34ad92538addf3946be1ef7 100644
--- a/packages/flutter/lib/src/painting/text_span.dart
+++ b/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 {
diff --git a/packages/flutter/lib/src/rendering/custom_layout.dart b/packages/flutter/lib/src/rendering/custom_layout.dart
index 79f057785e62150e3242fc0b6e4f0118df404fbc..1b44d04408dce5efc2ad3c15dd36fc4150421687 100644
--- a/packages/flutter/lib/src/rendering/custom_layout.dart
+++ b/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 {
diff --git a/packages/flutter/lib/src/rendering/layer.dart b/packages/flutter/lib/src/rendering/layer.dart
index 2c12b3e989afa708bff38328dcf72743f79b275c..c0188192b626d543d7dcf51cab801929e1de879e 100644
--- a/packages/flutter/lib/src/rendering/layer.dart
+++ b/packages/flutter/lib/src/rendering/layer.dart
@@ -1140,7 +1140,7 @@ class LeaderLayer extends ContainerLayer {
 
   @override
   S find<S>(Offset regionOffset) {
-    return super.find(regionOffset - offset);
+    return super.find<S>(regionOffset - offset);
   }
 
   @override
diff --git a/packages/flutter/lib/src/rendering/platform_view.dart b/packages/flutter/lib/src/rendering/platform_view.dart
index dc87c7703e1b675a8376b7890f2883d2b8c65536..bf03b1296b2d6b935c1c6a4e09039877c2f6dba8 100644
--- a/packages/flutter/lib/src/rendering/platform_view.dart
+++ b/packages/flutter/lib/src/rendering/platform_view.dart
@@ -382,8 +382,8 @@ class _MotionEventsDispatcher {
         eventTime: event.timeStamp.inMilliseconds,
         action: action,
         pointerCount: pointerPositions.length,
-        pointerProperties: pointers.map((int i) => pointerProperties[i]).toList(),
-        pointerCoords: pointers.map((int i) => pointerPositions[i]).toList(),
+        pointerProperties: pointers.map<AndroidPointerProperties>((int i) => pointerProperties[i]).toList(),
+        pointerCoords: pointers.map<AndroidPointerCoords>((int i) => pointerPositions[i]).toList(),
         metaState: 0,
         buttonState: 0,
         xPrecision: 1.0,
diff --git a/packages/flutter/lib/src/scheduler/ticker.dart b/packages/flutter/lib/src/scheduler/ticker.dart
index a943a916d40c928e9145733f38e83ce3f13fa6cb..cd4d77ba338b2ecbe8dae29d45657104a554901c 100644
--- a/packages/flutter/lib/src/scheduler/ticker.dart
+++ b/packages/flutter/lib/src/scheduler/ticker.dart
@@ -389,7 +389,7 @@ class TickerFuture implements Future<Null> {
       callback();
       return null;
     }
-    orCancel.then(thunk, onError: thunk);
+    orCancel.then<Null>(thunk, onError: thunk);
   }
 
   /// A future that resolves when this future resolves or throws when the ticker
diff --git a/packages/flutter/lib/src/semantics/semantics.dart b/packages/flutter/lib/src/semantics/semantics.dart
index 6d956ba098d4bc186e749241d9c6a8afdccfcc42..9837cfbc89dd057a1e80a52dfd35e5c4080efbd3 100644
--- a/packages/flutter/lib/src/semantics/semantics.dart
+++ b/packages/flutter/lib/src/semantics/semantics.dart
@@ -1844,12 +1844,12 @@ class SemanticsNode extends AbstractNode with DiagnosticableTreeMixin {
       if (scale != null) {
         description = '$rect scaled by ${scale.toStringAsFixed(1)}x';
       } else if (transform != null && !MatrixUtils.isIdentity(transform)) {
-        final String matrix = transform.toString().split('\n').take(4).map((String line) => line.substring(4)).join('; ');
+        final String matrix = transform.toString().split('\n').take(4).map<String>((String line) => line.substring(4)).join('; ');
         description = '$rect with transform [$matrix]';
       }
       properties.add(DiagnosticsProperty<Rect>('rect', rect, description: description, showName: false));
     }
-    final List<String> actions = _actions.keys.map((SemanticsAction action) => describeEnum(action)).toList()..sort();
+    final List<String> actions = _actions.keys.map<String>((SemanticsAction action) => describeEnum(action)).toList()..sort();
     final List<String> customSemanticsActions = _customSemanticsActions.keys
       .map<String>((CustomSemanticsAction action) => action.label)
       .toList();
@@ -2118,7 +2118,7 @@ class _SemanticsSortGroup extends Comparable<_SemanticsSortGroup> {
       sortedIds.add(id);
     }
 
-    startNodes.map((SemanticsNode node) => node.id).forEach(search);
+    startNodes.map<int>((SemanticsNode node) => node.id).forEach(search);
     return sortedIds.map<SemanticsNode>((int id) => nodeMap[id]).toList().reversed.toList();
   }
 }
diff --git a/packages/flutter/lib/src/services/platform_views.dart b/packages/flutter/lib/src/services/platform_views.dart
index e015a985026c8d89d7bbb75a9a9f747832cbf374..0efb9c4bc8e9c02a00986895a2b84e99db7ef934 100644
--- a/packages/flutter/lib/src/services/platform_views.dart
+++ b/packages/flutter/lib/src/services/platform_views.dart
@@ -328,8 +328,8 @@ class AndroidMotionEvent {
       eventTime,
       action,
       pointerCount,
-      pointerProperties.map((AndroidPointerProperties p) => p._asList()).toList(),
-      pointerCoords.map((AndroidPointerCoords p) => p._asList()).toList(),
+      pointerProperties.map<List<int>>((AndroidPointerProperties p) => p._asList()).toList(),
+      pointerCoords.map<List<double>>((AndroidPointerCoords p) => p._asList()).toList(),
       metaState,
       buttonState,
       xPrecision,
diff --git a/packages/flutter/lib/src/services/text_formatter.dart b/packages/flutter/lib/src/services/text_formatter.dart
index 1eec81c9be9276ff35927db15e3e1e974f627380..e421143e18ac7ed8ea9cf25052d608dddd7d53d8 100644
--- a/packages/flutter/lib/src/services/text_formatter.dart
+++ b/packages/flutter/lib/src/services/text_formatter.dart
@@ -233,7 +233,7 @@ class WhitelistingTextInputFormatter extends TextInputFormatter {
       (String substring) {
         return whitelistedPattern
             .allMatches(substring)
-            .map((Match match) => match.group(0))
+            .map<String>((Match match) => match.group(0))
             .join();
       } ,
     );
diff --git a/packages/flutter/lib/src/widgets/image.dart b/packages/flutter/lib/src/widgets/image.dart
index 59232c0b0bc3663b53a03f7620b9c19005e20312..91e87ef841d74e55350b2f0e44b6ef6c87c06d0f 100644
--- a/packages/flutter/lib/src/widgets/image.dart
+++ b/packages/flutter/lib/src/widgets/image.dart
@@ -98,7 +98,7 @@ Future<Null> precacheImage(
     }
   }
   stream.addListener(listener, onError: errorListener);
-  completer.future.then((Null _) { stream.removeListener(listener); });
+  completer.future.then<void>((Null _) { stream.removeListener(listener); });
   return completer.future;
 }
 
diff --git a/packages/flutter/lib/src/widgets/list_wheel_scroll_view.dart b/packages/flutter/lib/src/widgets/list_wheel_scroll_view.dart
index 78a1af1003e58beb00e42db5f48742acbaa6d4e6..cf6c9a5cacb6077cd6735a018f336e35eb45b15f 100644
--- a/packages/flutter/lib/src/widgets/list_wheel_scroll_view.dart
+++ b/packages/flutter/lib/src/widgets/list_wheel_scroll_view.dart
@@ -266,7 +266,7 @@ class FixedExtentScrollController extends ScrollController {
         curve: curve,
       ));
     }
-    await Future.wait(futures);
+    await Future.wait<void>(futures);
   }
 
   /// Changes which item index is centered in the controlled scroll view.
diff --git a/packages/flutter/lib/src/widgets/localizations.dart b/packages/flutter/lib/src/widgets/localizations.dart
index 0b4124c2993f400bfeef0c874b73b0b7436b37d0..e960ec300562f7c9876884f22bd95593d3bedf21 100644
--- a/packages/flutter/lib/src/widgets/localizations.dart
+++ b/packages/flutter/lib/src/widgets/localizations.dart
@@ -74,7 +74,7 @@ Future<Map<Type, dynamic>> _loadAll(Locale locale, Iterable<LocalizationsDelegat
     return SynchronousFuture<Map<Type, dynamic>>(output);
 
   // Some of delegate.load() values were asynchronous futures. Wait for them.
-  return Future.wait<dynamic>(pendingList.map((_Pending p) => p.futureValue))
+  return Future.wait<dynamic>(pendingList.map<Future<dynamic>>((_Pending p) => p.futureValue))
     .then<Map<Type, dynamic>>((List<dynamic> values) {
       assert(values.length == pendingList.length);
       for (int i = 0; i < values.length; i += 1) {
@@ -502,7 +502,7 @@ class _LocalizationsState extends State<Localizations> {
 
     Map<Type, dynamic> typeToResources;
     final Future<Map<Type, dynamic>> typeToResourcesFuture = _loadAll(locale, delegates)
-      .then((Map<Type, dynamic> value) {
+      .then<Map<Type, dynamic>>((Map<Type, dynamic> value) {
         return typeToResources = value;
       });
 
@@ -516,7 +516,7 @@ class _LocalizationsState extends State<Localizations> {
       // - If we're running at app startup time then defer reporting the first
       // "useful" frame until after the async load has completed.
       WidgetsBinding.instance.deferFirstFrameReport();
-      typeToResourcesFuture.then((Map<Type, dynamic> value) {
+      typeToResourcesFuture.then<void>((Map<Type, dynamic> value) {
         WidgetsBinding.instance.allowFirstFrameReport();
         if (!mounted)
           return;
diff --git a/packages/flutter/lib/src/widgets/routes.dart b/packages/flutter/lib/src/widgets/routes.dart
index fd6d3dfadf8186ab570b089778d3c3c6f02acdee..9da5253da1c74d769eb2c660dfcec7cf022a772b 100644
--- a/packages/flutter/lib/src/widgets/routes.dart
+++ b/packages/flutter/lib/src/widgets/routes.dart
@@ -660,6 +660,7 @@ abstract class ModalRoute<T> extends TransitionRoute<T> with LocalHistoryRoute<T
   ///
   /// The given [BuildContext] will be rebuilt if the state of the route changes
   /// (specifically, if [isCurrent] or [canPop] change value).
+  @optionalTypeArgs
   static ModalRoute<T> of<T extends Object>(BuildContext context) {
     final _ModalScopeStatus widget = context.inheritFromWidgetOfExactType(_ModalScopeStatus);
     return widget?.route;
@@ -1519,7 +1520,7 @@ Future<T> showGeneralDialog<T>({
 }) {
   assert(pageBuilder != null);
   assert(!barrierDismissible || barrierLabel != null);
-  return Navigator.of(context, rootNavigator: true).push(_DialogRoute<T>(
+  return Navigator.of(context, rootNavigator: true).push<T>(_DialogRoute<T>(
     pageBuilder: pageBuilder,
     barrierDismissible: barrierDismissible,
     barrierLabel: barrierLabel,
diff --git a/packages/flutter/lib/src/widgets/scroll_controller.dart b/packages/flutter/lib/src/widgets/scroll_controller.dart
index 3c37682678cd8f0e4da8e7150b4df46a7cf6b09b..abaf543609d2ab03d890b7f72f7058f19ec65673 100644
--- a/packages/flutter/lib/src/widgets/scroll_controller.dart
+++ b/packages/flutter/lib/src/widgets/scroll_controller.dart
@@ -150,7 +150,7 @@ class ScrollController extends ChangeNotifier {
     final List<Future<Null>> animations = List<Future<Null>>(_positions.length);
     for (int i = 0; i < _positions.length; i += 1)
       animations[i] = _positions[i].animateTo(offset, duration: duration, curve: curve);
-    return Future.wait<Null>(animations).then((List<Null> _) => null);
+    return Future.wait<Null>(animations).then<Null>((List<Null> _) => null);
   }
 
   /// Jumps the scroll position from its current value to the given value,
diff --git a/packages/flutter/lib/src/widgets/scrollable.dart b/packages/flutter/lib/src/widgets/scrollable.dart
index fac04a306bf8304d43f28db452b4bb5145d84cac..d64c67a430613fbda92e5c695306435d4e8b36c5 100644
--- a/packages/flutter/lib/src/widgets/scrollable.dart
+++ b/packages/flutter/lib/src/widgets/scrollable.dart
@@ -213,7 +213,7 @@ class Scrollable extends StatefulWidget {
       return Future<Null>.value();
     if (futures.length == 1)
       return futures.single;
-    return Future.wait<Null>(futures).then((List<Null> _) => null);
+    return Future.wait<Null>(futures).then<Null>((List<Null> _) => null);
   }
 }
 
diff --git a/packages/flutter/lib/src/widgets/table.dart b/packages/flutter/lib/src/widgets/table.dart
index 9023b5725d7400e4a9ae4e1f64293b44e33837ea..85257f1b32bf28e827499ffbd3dc35029272dd45 100644
--- a/packages/flutter/lib/src/widgets/table.dart
+++ b/packages/flutter/lib/src/widgets/table.dart
@@ -141,7 +141,7 @@ class Table extends RenderObjectWidget {
                               : null,
        super(key: key) {
     assert(() {
-      final List<Widget> flatChildren = children.expand((TableRow row) => row.children).toList(growable: false);
+      final List<Widget> flatChildren = children.expand<Widget>((TableRow row) => row.children).toList(growable: false);
       if (debugChildrenHaveDuplicateKeys(this, flatChildren)) {
         throw FlutterError(
           'Two or more cells in this Table contain widgets with the same key.\n'
@@ -255,7 +255,7 @@ class _TableElement extends RenderObjectElement {
     super.mount(parent, newSlot);
     assert(!_debugWillReattachChildren);
     assert(() { _debugWillReattachChildren = true; return true; }());
-    _children = widget.children.map((TableRow row) {
+    _children = widget.children.map<_TableElementRow>((TableRow row) {
       return _TableElementRow(
         key: row.key,
         children: row.children.map<Element>((Widget child) {
@@ -351,7 +351,7 @@ class _TableElement extends RenderObjectElement {
 
   @override
   void visitChildren(ElementVisitor visitor) {
-    for (Element child in _children.expand((_TableElementRow row) => row.children)) {
+    for (Element child in _children.expand<Element>((_TableElementRow row) => row.children)) {
       if (!_forgottenChildren.contains(child))
         visitor(child);
     }
diff --git a/packages/flutter/lib/src/widgets/widget_inspector.dart b/packages/flutter/lib/src/widgets/widget_inspector.dart
index 9b7a6245badca9307038bcdd320e1c0eeb8c9d25..941de322b394111298d3a0e89c39300ae48bc047 100644
--- a/packages/flutter/lib/src/widgets/widget_inspector.dart
+++ b/packages/flutter/lib/src/widgets/widget_inspector.dart
@@ -1262,7 +1262,7 @@ class WidgetInspectorService {
     else
       throw FlutterError('Cannot get parent chain for node of type ${value.runtimeType}');
 
-    return path.map((_DiagnosticsPathNode node) => _pathNodeToJson(
+    return path.map<Object>((_DiagnosticsPathNode node) => _pathNodeToJson(
       node,
       _SerializeConfig(groupName: groupName),
     )).toList();
diff --git a/packages/flutter/test/cupertino/nav_bar_test.dart b/packages/flutter/test/cupertino/nav_bar_test.dart
index 3ccadc00ed0f95fbdbd72480a5b102f1a6014e8c..0855c7ed5effc8786faa7c863a8e6648049b3ca5 100644
--- a/packages/flutter/test/cupertino/nav_bar_test.dart
+++ b/packages/flutter/test/cupertino/nav_bar_test.dart
@@ -262,7 +262,7 @@ void main() {
           return aParagraph.text.style.fontSize.compareTo(bParagraph.text.style.fontSize);
         });
 
-    Iterable<double> opacities = titles.map((Element element) {
+    Iterable<double> opacities = titles.map<double>((Element element) {
       final RenderAnimatedOpacity renderOpacity = element.ancestorRenderObjectOfType(const TypeMatcher<RenderAnimatedOpacity>());
       return renderOpacity.opacity.value;
     });
@@ -287,7 +287,7 @@ void main() {
           return aParagraph.text.style.fontSize.compareTo(bParagraph.text.style.fontSize);
         });
 
-    opacities = titles.map((Element element) {
+    opacities = titles.map<double>((Element element) {
       final RenderAnimatedOpacity renderOpacity = element.ancestorRenderObjectOfType(const TypeMatcher<RenderAnimatedOpacity>());
       return renderOpacity.opacity.value;
     });
diff --git a/packages/flutter/test/cupertino/route_test.dart b/packages/flutter/test/cupertino/route_test.dart
index de721c5ef1871f45f782425d9dd131190102cf1b..fd706fc382ffe2524b35f8379ca48deedc4bcb0e 100644
--- a/packages/flutter/test/cupertino/route_test.dart
+++ b/packages/flutter/test/cupertino/route_test.dart
@@ -80,7 +80,7 @@ void main() {
           );
         });
 
-    final Iterable<double> opacities = titles.map((Element element) {
+    final Iterable<double> opacities = titles.map<double>((Element element) {
       final RenderAnimatedOpacity renderOpacity =
           element.ancestorRenderObjectOfType(const TypeMatcher<RenderAnimatedOpacity>());
       return renderOpacity.opacity.value;
diff --git a/packages/flutter/test/foundation/caching_iterable_test.dart b/packages/flutter/test/foundation/caching_iterable_test.dart
index f93229dce9d9969baf9eec556fae66e08c008980..39e345eee05b87fec75a4829bd551759a480c629 100644
--- a/packages/flutter/test/foundation/caching_iterable_test.dart
+++ b/packages/flutter/test/foundation/caching_iterable_test.dart
@@ -63,7 +63,7 @@ void main() {
     expect(integers.first, equals(1));
     expect(yieldCount, equals(2));
 
-    expect(evens.map((int i) => i + 1), equals(<int>[3, 5]));
+    expect(evens.map<int>((int i) => i + 1), equals(<int>[3, 5]));
     expect(yieldCount, equals(5));
 
     expect(evens, equals(<int>[2, 4]));
@@ -95,13 +95,13 @@ void main() {
     final Iterable<int> integers = CachingIterable<int>(range(1, 5).iterator);
     expect(yieldCount, equals(0));
 
-    final Iterable<int> expanded1 = integers.expand((int i) => <int>[i, i]);
+    final Iterable<int> expanded1 = integers.expand<int>((int i) => <int>[i, i]);
 
     expect(yieldCount, equals(0));
     expect(expanded1, equals(<int>[1, 1, 2, 2, 3, 3, 4, 4, 5, 5]));
     expect(yieldCount, equals(5));
 
-    final Iterable<int> expanded2 = integers.expand((int i) => <int>[i, i]);
+    final Iterable<int> expanded2 = integers.expand<int>((int i) => <int>[i, i]);
 
     expect(yieldCount, equals(5));
     expect(expanded2, equals(<int>[1, 1, 2, 2, 3, 3, 4, 4, 5, 5]));
diff --git a/packages/flutter/test/material/app_bar_test.dart b/packages/flutter/test/material/app_bar_test.dart
index b22df03bbd0172ecc6a8ee2f31f3674ecc4f74a4..39687a719abea96fde0d190f602645f4e04d1432 100644
--- a/packages/flutter/test/material/app_bar_test.dart
+++ b/packages/flutter/test/material/app_bar_test.dart
@@ -33,7 +33,7 @@ Widget buildSliverAppBarApp({ bool floating, bool pinned, double expandedHeight,
                   expandedHeight: expandedHeight,
                   snap: snap,
                   bottom: TabBar(
-                    tabs: <String>['A','B','C'].map((String t) => Tab(text: 'TAB $t')).toList(),
+                    tabs: <String>['A','B','C'].map<Widget>((String t) => Tab(text: 'TAB $t')).toList(),
                   ),
                 ),
                 SliverToBoxAdapter(
diff --git a/packages/flutter/test/material/colors_test.dart b/packages/flutter/test/material/colors_test.dart
index 243fb79cf75de40b6ad50f0eb28f08dee3401067..7414363c8343e4c4c4a1146f95eeab2d9b11bb08 100644
--- a/packages/flutter/test/material/colors_test.dart
+++ b/packages/flutter/test/material/colors_test.dart
@@ -54,12 +54,12 @@ void main() {
 
   test('Colors swatches do not contain duplicates', () {
     for (MaterialColor color in Colors.primaries)
-      expect(primaryKeys.map((int key) => color[key]).toSet().length, primaryKeys.length);
+      expect(primaryKeys.map<Color>((int key) => color[key]).toSet().length, primaryKeys.length);
 
-    expect(primaryKeys.map((int key) => Colors.grey[key]).toSet().length, primaryKeys.length);
+    expect(primaryKeys.map<Color>((int key) => Colors.grey[key]).toSet().length, primaryKeys.length);
 
     for (MaterialAccentColor color in Colors.accents)
-      expect(accentKeys.map((int key) => color[key]).toSet().length, accentKeys.length);
+      expect(accentKeys.map<Color>((int key) => color[key]).toSet().length, accentKeys.length);
   });
 
   test('All color swatch colors are opaque and equal their primary color', () {
diff --git a/packages/flutter/test/material/data_table_test.dart b/packages/flutter/test/material/data_table_test.dart
index 88cf8e6db4c404c74e40fe6c3d457bd7e841c5fe..d05561f6103fb4dc171a452c7a2bad6713741f77 100644
--- a/packages/flutter/test/material/data_table_test.dart
+++ b/packages/flutter/test/material/data_table_test.dart
@@ -32,7 +32,7 @@ void main() {
             }
           ),
         ],
-        rows: kDesserts.map((Dessert dessert) {
+        rows: kDesserts.map<DataRow>((Dessert dessert) {
           return DataRow(
             key: Key(dessert.name),
             onSelectChanged: (bool selected) {
diff --git a/packages/flutter/test/material/dropdown_test.dart b/packages/flutter/test/material/dropdown_test.dart
index a5fa90376cb324278c983082bf14a0b96e87494e..950629d9ed49a19458d9437f35b99e7ef2cbf70a 100644
--- a/packages/flutter/test/material/dropdown_test.dart
+++ b/packages/flutter/test/material/dropdown_test.dart
@@ -43,7 +43,7 @@ Widget buildFrame({
             onChanged: onChanged,
             isDense: isDense,
             isExpanded: isExpanded,
-            items: items.map((String item) {
+            items: items.map<DropdownMenuItem<String>>((String item) {
               return DropdownMenuItem<String>(
                 key: ValueKey<String>(item),
                 value: item,
@@ -407,7 +407,7 @@ void main() {
 
     // When isDense is true, the button's height is reduced. The menu items'
     // heights are not.
-    final double menuItemHeight = itemBoxes.map((RenderBox box) => box.size.height).reduce(math.max);
+    final double menuItemHeight = itemBoxes.map<double>((RenderBox box) => box.size.height).reduce(math.max);
     expect(menuItemHeight, greaterThan(buttonBox.size.height));
 
     for (RenderBox itemBox in itemBoxes) {
diff --git a/packages/flutter/test/material/list_tile_test.dart b/packages/flutter/test/material/list_tile_test.dart
index 39ecd205f23a35dc9e3d9fccb6587b51b6482efe..4102acc73ee13e9bd950383811bc4f6509d5c450 100644
--- a/packages/flutter/test/material/list_tile_test.dart
+++ b/packages/flutter/test/material/list_tile_test.dart
@@ -235,7 +235,7 @@ void main() {
             return ListView(
               children: ListTile.divideTiles(
                 context: context,
-                tiles: titles.map((String title) => ListTile(title: Text(title))),
+                tiles: titles.map<Widget>((String title) => ListTile(title: Text(title))),
               ).toList(),
             );
           },
diff --git a/packages/flutter/test/material/page_selector_test.dart b/packages/flutter/test/material/page_selector_test.dart
index 42a1ae06c472bd25d062da5b7467da0a68b74c49..8a4101324b200e468193bb130a20fbc67c0dddf9 100644
--- a/packages/flutter/test/material/page_selector_test.dart
+++ b/packages/flutter/test/material/page_selector_test.dart
@@ -52,7 +52,7 @@ List<Color> indicatorColors(WidgetTester tester) {
       matching: find.byType(TabPageSelectorIndicator)
     )
   );
-  return indicators.map((TabPageSelectorIndicator indicator) => indicator.backgroundColor).toList();
+  return indicators.map<Color>((TabPageSelectorIndicator indicator) => indicator.backgroundColor).toList();
 }
 
 void main() {
diff --git a/packages/flutter/test/material/refresh_indicator_test.dart b/packages/flutter/test/material/refresh_indicator_test.dart
index ea49f944300188918220aed2d5e12eb50f1492aa..4e6e0be66c5c45ad2ea1071fb811a7559af039db 100644
--- a/packages/flutter/test/material/refresh_indicator_test.dart
+++ b/packages/flutter/test/material/refresh_indicator_test.dart
@@ -29,7 +29,7 @@ void main() {
           onRefresh: refresh,
           child: ListView(
             physics: const AlwaysScrollableScrollPhysics(),
-            children: <String>['A', 'B', 'C', 'D', 'E', 'F'].map((String item) {
+            children: <String>['A', 'B', 'C', 'D', 'E', 'F'].map<Widget>((String item) {
               return SizedBox(
                 height: 200.0,
                 child: Text(item),
@@ -61,7 +61,7 @@ void main() {
               width: 600.0,
               child: ListView(
                 physics: const AlwaysScrollableScrollPhysics(),
-                children: <String>['A', 'B', 'C', 'D', 'E', 'F'].map((String item) {
+                children: <String>['A', 'B', 'C', 'D', 'E', 'F'].map<Widget>((String item) {
                   return SizedBox(
                     height: 200.0,
                     child: Text(item),
@@ -362,7 +362,7 @@ void main() {
           },
           child: ListView(
             physics: const AlwaysScrollableScrollPhysics(),
-            children: <String>['A', 'B', 'C', 'D', 'E', 'F'].map((String item) {
+            children: <String>['A', 'B', 'C', 'D', 'E', 'F'].map<Widget>((String item) {
               return SizedBox(
                 height: 200.0,
                 child: Text(item),
@@ -393,7 +393,7 @@ void main() {
           child: ListView(
             controller: controller,
             physics: const AlwaysScrollableScrollPhysics(),
-            children: <String>['A', 'B', 'C', 'D', 'E', 'F'].map((String item) {
+            children: <String>['A', 'B', 'C', 'D', 'E', 'F'].map<Widget>((String item) {
               return SizedBox(
                 height: 200.0,
                 child: Text(item),
diff --git a/packages/flutter/test/material/reorderable_list_test.dart b/packages/flutter/test/material/reorderable_list_test.dart
index bc21f799c0c0db65c92e580a2e9928cdf04a4ead..bab13e2904ddb3f94fd5f4e0eeec08df4e5fb3ab 100644
--- a/packages/flutter/test/material/reorderable_list_test.dart
+++ b/packages/flutter/test/material/reorderable_list_test.dart
@@ -39,7 +39,7 @@ void main() {
             width: itemHeight * 10,
             child: ReorderableListView(
               header: header,
-              children: listItems.map(listItemToWidget).toList(),
+              children: listItems.map<Widget>(listItemToWidget).toList(),
               scrollDirection: scrollDirection,
               onReorder: onReorder,
             ),
diff --git a/packages/flutter/test/material/tabs_test.dart b/packages/flutter/test/material/tabs_test.dart
index 81dc96b811ec1815d6e12fbedac6d220421a45ed..5eab06630c0354fb40e8be2350b838ce22ec4207 100644
--- a/packages/flutter/test/material/tabs_test.dart
+++ b/packages/flutter/test/material/tabs_test.dart
@@ -78,7 +78,7 @@ Widget buildFrame({
       length: tabs.length,
       child: TabBar(
         key: tabBarKey,
-        tabs: tabs.map((String tab) => Tab(text: tab)).toList(),
+        tabs: tabs.map<Widget>((String tab) => Tab(text: tab)).toList(),
         isScrollable: isScrollable,
         indicatorColor: indicatorColor,
       ),
@@ -134,7 +134,7 @@ Widget buildLeftRightApp({ List<String> tabs, String value }) {
         appBar: AppBar(
           title: const Text('tabs'),
           bottom: TabBar(
-            tabs: tabs.map((String tab) => Tab(text: tab)).toList(),
+            tabs: tabs.map<Widget>((String tab) => Tab(text: tab)).toList(),
           ),
         ),
         body: const TabBarView(
@@ -295,7 +295,7 @@ void main() {
           initialIndex: tabs.indexOf(value),
           length: tabs.length,
           child: TabBarView(
-            children: tabs.map((String name) {
+            children: tabs.map<Widget>((String name) {
               return StateMarker(
                 child: Text(name)
               );
@@ -483,11 +483,11 @@ void main() {
                   title: const Text('tabs'),
                   bottom: TabBar(
                     isScrollable: true,
-                    tabs: tabs.map((String tab) => Tab(text: tab)).toList(),
+                    tabs: tabs.map<Widget>((String tab) => Tab(text: tab)).toList(),
                   ),
                 ),
                 body: TabBarView(
-                  children: tabs.map((String name) => Text('${index++}')).toList(),
+                  children: tabs.map<Widget>((String name) => Text('${index++}')).toList(),
                 ),
               ),
             ),
@@ -550,7 +550,7 @@ void main() {
             title: const Text('tabs'),
             bottom: TabBar(
               controller: controller,
-              tabs: tabs.map((String tab) => Tab(text: tab)).toList(),
+              tabs: tabs.map<Widget>((String tab) => Tab(text: tab)).toList(),
             ),
           ),
           body: TabBarView(
@@ -609,7 +609,7 @@ void main() {
             title: const Text('tabs'),
             bottom: TabBar(
               controller: controller,
-              tabs: tabs.map((String tab) => Tab(text: tab)).toList(),
+              tabs: tabs.map<Widget>((String tab) => Tab(text: tab)).toList(),
             ),
           ),
           body: TabBarView(
@@ -1866,7 +1866,7 @@ void main() {
                 title: const Text('tabs'),
                 bottom: TabBar(
                   controller: controller,
-                  tabs: tabs.map((String tab) => Tab(text: tab)).toList(),
+                  tabs: tabs.map<Widget>((String tab) => Tab(text: tab)).toList(),
                 ),
               ),
               body: TabBarView(
diff --git a/packages/flutter/test/material/text_field_test.dart b/packages/flutter/test/material/text_field_test.dart
index 46979c5fb488a3c1094952af3b9dcafaf41cdbbf..0124ededa573ce3aa7641dcab0be60aa35b30449 100644
--- a/packages/flutter/test/material/text_field_test.dart
+++ b/packages/flutter/test/material/text_field_test.dart
@@ -145,7 +145,7 @@ void main() {
   }
 
   List<TextSelectionPoint> globalize(Iterable<TextSelectionPoint> points, RenderBox box) {
-    return points.map((TextSelectionPoint point) {
+    return points.map<TextSelectionPoint>((TextSelectionPoint point) {
       return TextSelectionPoint(
         box.localToGlobal(point.point),
         point.direction,
diff --git a/packages/flutter/test/material/theme_test.dart b/packages/flutter/test/material/theme_test.dart
index 8ea5f38eb37e3f820925270a091bf4d02b841b42..81f060d31956090ac7ecfbf4e3dde7ea706e03d5 100644
--- a/packages/flutter/test/material/theme_test.dart
+++ b/packages/flutter/test/material/theme_test.dart
@@ -388,7 +388,7 @@ void main() {
     }
 
     for (TextTheme textTheme in <TextTheme>[theme.textTheme, theme.primaryTextTheme, theme.accentTextTheme]) {
-      for (TextStyle style in extractStyles(textTheme).map((TextStyle style) => _TextStyleProxy(style))) {
+      for (TextStyle style in extractStyles(textTheme).map<TextStyle>((TextStyle style) => _TextStyleProxy(style))) {
         expect(style.inherit, false);
         expect(style.color, isNotNull);
         expect(style.fontFamily, isNotNull);
diff --git a/packages/flutter/test/scheduler/scheduler_test.dart b/packages/flutter/test/scheduler/scheduler_test.dart
index 60c5178191d26f5223a241900b0a47eb9bbe1e99..75eb269fdd53b67b1427de97eab0ddc55f7fcfb5 100644
--- a/packages/flutter/test/scheduler/scheduler_test.dart
+++ b/packages/flutter/test/scheduler/scheduler_test.dart
@@ -94,7 +94,7 @@ void main() {
   test('2 calls to scheduleWarmUpFrame just schedules it once', () {
     final List<VoidCallback> timerQueueTasks = <VoidCallback>[];
     bool taskExecuted = false;
-    runZoned(
+    runZoned<void>(
       () {
         // Run it twice without processing the queued tasks.
         scheduler.scheduleWarmUpFrame();
diff --git a/packages/flutter/test/widgets/custom_painter_test.dart b/packages/flutter/test/widgets/custom_painter_test.dart
index 52369b900a52302e23f82d5f37b40ee1d70e9e87..03455e53dcc9fffcbf4de95e6692a7e505102aba 100644
--- a/packages/flutter/test/widgets/custom_painter_test.dart
+++ b/packages/flutter/test/widgets/custom_painter_test.dart
@@ -363,7 +363,7 @@ void _defineTests() {
             TestSemantics.rootChild(
               id: expectedId,
               rect: TestSemantics.fullScreen,
-              actions: allActions.fold(0, (int previous, SemanticsAction action) => previous | action.index),
+              actions: allActions.fold<int>(0, (int previous, SemanticsAction action) => previous | action.index),
             ),
           ]
         ),
diff --git a/packages/flutter/test/widgets/dismissible_test.dart b/packages/flutter/test/widgets/dismissible_test.dart
index 71e19d832dfb3227208eff69f2f68aa695494e1b..084de05bdc98f046f2ad45dd6826ece82ac4934a 100644
--- a/packages/flutter/test/widgets/dismissible_test.dart
+++ b/packages/flutter/test/widgets/dismissible_test.dart
@@ -53,7 +53,7 @@ Widget buildTest({ double startToEndThreshold, TextDirection textDirection = Tex
             itemExtent: itemExtent,
             children: <int>[0, 1, 2, 3, 4]
               .where((int i) => !dismissedItems.contains(i))
-              .map(buildDismissibleItem).toList(),
+              .map<Widget>(buildDismissibleItem).toList(),
           ),
         );
       },
diff --git a/packages/flutter/test/widgets/grid_view_test.dart b/packages/flutter/test/widgets/grid_view_test.dart
index 1adc5e787a43cad9f5ac4f175354b28710b0c197..38b478630f361444e73f90709c0dbef2e65f17f8 100644
--- a/packages/flutter/test/widgets/grid_view_test.dart
+++ b/packages/flutter/test/widgets/grid_view_test.dart
@@ -29,7 +29,7 @@ void main() {
         textDirection: TextDirection.ltr,
         child: GridView.count(
           crossAxisCount: 4,
-          children: kStates.map((String state) {
+          children: kStates.map<Widget>((String state) {
             return GestureDetector(
               onTap: () {
                 log.add(state);
@@ -100,7 +100,7 @@ void main() {
         textDirection: TextDirection.ltr,
         child: GridView.extent(
           maxCrossAxisExtent: 200.0,
-          children: kStates.map((String state) {
+          children: kStates.map<Widget>((String state) {
             return GestureDetector(
               onTap: () {
                 log.add(state);
diff --git a/packages/flutter/test/widgets/heroes_test.dart b/packages/flutter/test/widgets/heroes_test.dart
index 850ae99f14aad82f0ab7e041f041b8622e06dd5c..45fd966c840ab3c0bf0c3c528bf6f66ac75bc285 100644
--- a/packages/flutter/test/widgets/heroes_test.dart
+++ b/packages/flutter/test/widgets/heroes_test.dart
@@ -948,7 +948,7 @@ void main() {
 
     // One Opacity widget per Hero, only one now has opacity 0.0
     final Iterable<RenderOpacity> renderers = tester.renderObjectList(find.byType(Opacity));
-    final Iterable<double> opacities = renderers.map((RenderOpacity r) => r.opacity);
+    final Iterable<double> opacities = renderers.map<double>((RenderOpacity r) => r.opacity);
     expect(opacities.singleWhere((double opacity) => opacity == 0.0), 0.0);
 
     // Hero BC's flight finishes normally.
diff --git a/packages/flutter/test/widgets/image_headers_test.dart b/packages/flutter/test/widgets/image_headers_test.dart
index a4dc552616e7892595ca5b4ea727a0df2edd2efa..c7f8de1325e0c632b37689581669c56342c5500e 100644
--- a/packages/flutter/test/widgets/image_headers_test.dart
+++ b/packages/flutter/test/widgets/image_headers_test.dart
@@ -18,7 +18,7 @@ void main() {
   final MockHttpHeaders headers = MockHttpHeaders();
 
   testWidgets('Headers', (WidgetTester tester) async {
-    HttpOverrides.runZoned(() async {
+    HttpOverrides.runZoned<Future<void>>(() async {
       await tester.pumpWidget(Image.network(
         'https://www.example.com/images/frame.png',
         headers: const <String, String>{'flutter': 'flutter'},
diff --git a/packages/flutter/test/widgets/list_view_horizontal_test.dart b/packages/flutter/test/widgets/list_view_horizontal_test.dart
index 8ed0474ff45ebe567505b8d4f735629dec22d333..fb425be03cb23e382ecb6ced414148aac95fda81 100644
--- a/packages/flutter/test/widgets/list_view_horizontal_test.dart
+++ b/packages/flutter/test/widgets/list_view_horizontal_test.dart
@@ -19,7 +19,7 @@ Widget buildFrame({ bool reverse = false, @required TextDirection textDirection
           scrollDirection: Axis.horizontal,
           reverse: reverse,
           physics: const BouncingScrollPhysics(),
-          children: items.map((int item) {
+          children: items.map<Widget>((int item) {
             return Container(
               child: Text('$item')
             );
diff --git a/packages/flutter/test/widgets/list_view_vertical_test.dart b/packages/flutter/test/widgets/list_view_vertical_test.dart
index ebc3fe298d5cf35a0cf26e97a17253b478f1dad5..617be7eb634c9a339fc3bec50616de0a85a1a513 100644
--- a/packages/flutter/test/widgets/list_view_vertical_test.dart
+++ b/packages/flutter/test/widgets/list_view_vertical_test.dart
@@ -13,7 +13,7 @@ Widget buildFrame() {
     child: ListView(
       itemExtent: 290.0,
       scrollDirection: Axis.vertical,
-      children: items.map((int item) {
+      children: items.map<Widget>((int item) {
         return Container(
           child: Text('$item')
         );
@@ -74,7 +74,7 @@ void main() {
           itemExtent: 290.0,
           padding: const EdgeInsets.only(top: 250.0),
           scrollDirection: Axis.vertical,
-          children: items.map((int item) {
+          children: items.map<Widget>((int item) {
             return Container(
               child: Text('$item')
             );
diff --git a/packages/flutter/test/widgets/nested_scroll_view_test.dart b/packages/flutter/test/widgets/nested_scroll_view_test.dart
index fd091f5d81df0c213505cab4e100b1cb32f6fb9b..b52360bc2a5214170ab9bad212afe62cf522183c 100644
--- a/packages/flutter/test/widgets/nested_scroll_view_test.dart
+++ b/packages/flutter/test/widgets/nested_scroll_view_test.dart
@@ -389,7 +389,7 @@ void main() {
                     forceElevated: innerBoxIsScrolled,
                     bottom: TabBar(
                       // These are the widgets to put in each tab in the tab bar.
-                      tabs: _tabs.map((String name) => Tab(text: name)).toList(),
+                      tabs: _tabs.map<Widget>((String name) => Tab(text: name)).toList(),
                     ),
                   ),
                 ),
@@ -397,7 +397,7 @@ void main() {
             },
             body: TabBarView(
               // These are the contents of the tab views, below the tabs.
-              children: _tabs.map((String name) {
+              children: _tabs.map<Widget>((String name) {
                 return SafeArea(
                   top: false,
                   bottom: false,
diff --git a/packages/flutter/test/widgets/pageable_list_test.dart b/packages/flutter/test/widgets/pageable_list_test.dart
index 670a23303ac928edc04607e37ba4f98b7ed08d2f..79f2dda8a32e63cb64d2ed377c3ee36d2ff50105 100644
--- a/packages/flutter/test/widgets/pageable_list_test.dart
+++ b/packages/flutter/test/widgets/pageable_list_test.dart
@@ -9,7 +9,7 @@ import 'package:meta/meta.dart';
 
 Size pageSize = const Size(600.0, 300.0);
 const List<int> defaultPages = <int>[0, 1, 2, 3, 4, 5];
-final List<GlobalKey> globalKeys = defaultPages.map((_) => GlobalKey()).toList();
+final List<GlobalKey> globalKeys = defaultPages.map<GlobalKey>((_) => GlobalKey()).toList();
 int currentPage;
 
 Widget buildPage(int page) {
@@ -30,7 +30,7 @@ Widget buildFrame({
     scrollDirection: Axis.horizontal,
     reverse: reverse,
     onPageChanged: (int page) { currentPage = page; },
-    children: pages.map(buildPage).toList(),
+    children: pages.map<Widget>(buildPage).toList(),
   );
 
   // The test framework forces the frame to be 800x600, so we need to create
diff --git a/packages/flutter/test/widgets/scrollable_list_hit_testing_test.dart b/packages/flutter/test/widgets/scrollable_list_hit_testing_test.dart
index 862873e9a2b71b98e860a7d27de4be41efc0e3b0..c06da6d576a016bd4787b28e0303457da002517f 100644
--- a/packages/flutter/test/widgets/scrollable_list_hit_testing_test.dart
+++ b/packages/flutter/test/widgets/scrollable_list_hit_testing_test.dart
@@ -20,7 +20,7 @@ void main() {
             child: ListView(
               itemExtent: 290.0,
               scrollDirection: Axis.horizontal,
-              children: items.map((int item) {
+              children: items.map<Widget>((int item) {
                 return Container(
                   child: GestureDetector(
                     onTap: () { tapped.add(item); },
@@ -62,7 +62,7 @@ void main() {
             child: ListView(
               itemExtent: 290.0,
               scrollDirection: Axis.vertical,
-              children: items.map((int item) {
+              children: items.map<Widget>((int item) {
                 return Container(
                   child: GestureDetector(
                     onTap: () { tapped.add(item); },
@@ -104,7 +104,7 @@ void main() {
         child: ListView(
           itemExtent: 290.0,
           padding: const EdgeInsets.fromLTRB(5.0, 20.0, 15.0, 10.0),
-          children: items.map((int item) {
+          children: items.map<Widget>((int item) {
             return Container(
               child: GestureDetector(
                 onTap: () { tapped.add(item); },
@@ -139,7 +139,7 @@ void main() {
           itemExtent: 290.0,
           reverse: true,
           padding: const EdgeInsets.fromLTRB(5.0, 20.0, 15.0, 10.0),
-          children: items.map((int item) {
+          children: items.map<Widget>((int item) {
             return Container(
               child: GestureDetector(
                 onTap: () { tapped.add(item); },
@@ -173,7 +173,7 @@ void main() {
         textDirection: TextDirection.ltr,
         child: ListView(
           itemExtent: 200.0,
-          children: items.map((int item) {
+          children: items.map<Widget>((int item) {
             return Container(
               child: GestureDetector(
                 onTap: () { tapped.add(item); },
diff --git a/packages/flutter/test/widgets/semantics_test.dart b/packages/flutter/test/widgets/semantics_test.dart
index 82ea8d606d46e5e7c3d1ab6df31160c80cb0d359..c2214c714ee9172f59fba35a02880f53df745deb 100644
--- a/packages/flutter/test/widgets/semantics_test.dart
+++ b/packages/flutter/test/widgets/semantics_test.dart
@@ -427,7 +427,7 @@ void main() {
         TestSemantics.rootChild(
           id: expectedId,
           rect: TestSemantics.fullScreen,
-          actions: allActions.fold(0, (int previous, SemanticsAction action) => previous | action.index),
+          actions: allActions.fold<int>(0, (int previous, SemanticsAction action) => previous | action.index),
         ),
       ],
     );
diff --git a/packages/flutter/test/widgets/semantics_tester.dart b/packages/flutter/test/widgets/semantics_tester.dart
index 455275a199b0270f2aed3e8acd69515822029ad2..c10779a6f72919321de8cccd53ed44381c1a68ba 100644
--- a/packages/flutter/test/widgets/semantics_tester.dart
+++ b/packages/flutter/test/widgets/semantics_tester.dart
@@ -325,7 +325,7 @@ class TestSemantics {
     if (rect != null)
       buf.writeln('$indent  rect: $rect,');
     if (transform != null)
-      buf.writeln('$indent  transform:\n${transform.toString().trim().split('\n').map((String line) => '$indent    $line').join('\n')},');
+      buf.writeln('$indent  transform:\n${transform.toString().trim().split('\n').map<String>((String line) => '$indent    $line').join('\n')},');
     buf.writeln('$indent  children: <TestSemantics>[');
     for (TestSemantics child in children) {
       buf.writeln('${child.toString(indentAmount + 2)},');
@@ -403,13 +403,13 @@ class SemanticsTester {
       if (textDirection != null && node.textDirection != textDirection)
         return false;
       if (actions != null) {
-        final int expectedActions = actions.fold(0, (int value, SemanticsAction action) => value | action.index);
+        final int expectedActions = actions.fold<int>(0, (int value, SemanticsAction action) => value | action.index);
         final int actualActions = node.getSemanticsData().actions;
         if (expectedActions != actualActions)
           return false;
       }
       if (flags != null) {
-        final int expectedFlags = flags.fold(0, (int value, SemanticsFlag flag) => value | flag.index);
+        final int expectedFlags = flags.fold<int>(0, (int value, SemanticsFlag flag) => value | flag.index);
         final int actualFlags = node.getSemanticsData().flags;
         if (expectedFlags != actualFlags)
           return false;
@@ -503,7 +503,7 @@ class SemanticsTester {
   }
 
   static String _tagsToSemanticsTagExpression(Set<SemanticsTag> tags) {
-    return '<SemanticsTag>[${tags.map((SemanticsTag tag) => 'const SemanticsTag(\'${tag.name}\')').join(', ')}]';
+    return '<SemanticsTag>[${tags.map<String>((SemanticsTag tag) => 'const SemanticsTag(\'${tag.name}\')').join(', ')}]';
   }
 
   static String _actionsToSemanticsActionExpression(dynamic actions) {
@@ -565,7 +565,7 @@ class SemanticsTester {
     }
 
     buf.write(')');
-    return buf.toString().split('\n').map((String l) => '$indent$l').join('\n');
+    return buf.toString().split('\n').map<String>((String l) => '$indent$l').join('\n');
   }
 }
 
@@ -614,7 +614,7 @@ class _HasSemantics extends Matcher {
   }
 
   String _indent(String text) {
-    return text.toString().trimRight().split('\n').map((String line) => '  $line').join('\n');
+    return text.toString().trimRight().split('\n').map<String>((String line) => '  $line').join('\n');
   }
 
   @override
diff --git a/packages/flutter/test/widgets/semantics_tester_generateTestSemanticsExpressionForCurrentSemanticsTree_test.dart b/packages/flutter/test/widgets/semantics_tester_generateTestSemanticsExpressionForCurrentSemanticsTree_test.dart
index 4b9202140736befc0f417ef0e970b647b4aad117..730d8307aab1d01836bf5f6f3872a49180a5b530 100644
--- a/packages/flutter/test/widgets/semantics_tester_generateTestSemanticsExpressionForCurrentSemanticsTree_test.dart
+++ b/packages/flutter/test/widgets/semantics_tester_generateTestSemanticsExpressionForCurrentSemanticsTree_test.dart
@@ -56,7 +56,7 @@ void _tests() {
     final String code = semantics
       .generateTestSemanticsExpressionForCurrentSemanticsTree(DebugSemanticsDumpOrder.inverseHitTest)
       .split('\n')
-      .map((String line) => line.trim())
+      .map<String>((String line) => line.trim())
       .join('\n')
       .trim() + ',';
 
@@ -82,7 +82,7 @@ void _tests() {
       expectedCode.indexOf('^' * 12) - 3,
     )
       .split('\n')
-      .map((String line) => line.trim())
+      .map<String>((String line) => line.trim())
       .join('\n')
       .trim();
     semantics.dispose();
diff --git a/packages/flutter/test/widgets/sliver_list_test.dart b/packages/flutter/test/widgets/sliver_list_test.dart
index 9ab78b700e70ca4f0ebeddff0bc024850a7eb429..9db3c881ceffd5fb2a444bc98b57135ac8e40017 100644
--- a/packages/flutter/test/widgets/sliver_list_test.dart
+++ b/packages/flutter/test/widgets/sliver_list_test.dart
@@ -76,7 +76,7 @@ void main() {
     expect(find.text('Tile 19'), findsOneWidget);
 
     await tester.pumpWidget(_buildSliverList(
-      items: items.map((int i) => i + 100).toList(),
+      items: items.map<int>((int i) => i + 100).toList(),
       controller: controller,
       itemHeight: itemHeight,
       viewportHeight: viewportHeight,
diff --git a/packages/flutter/test/widgets/slivers_block_global_key_test.dart b/packages/flutter/test/widgets/slivers_block_global_key_test.dart
index 92a28604c84ccebcaaa7841c4b94443c48910cf4..2aa787d84e4bb696238b550a619bbb8b43f4154b 100644
--- a/packages/flutter/test/widgets/slivers_block_global_key_test.dart
+++ b/packages/flutter/test/widgets/slivers_block_global_key_test.dart
@@ -34,7 +34,7 @@ Future<Null> test(WidgetTester tester, double offset, List<int> keys) {
         offset: ViewportOffset.fixed(offset),
         slivers: <Widget>[
           SliverList(
-            delegate: SliverChildListDelegate(keys.map((int key) {
+            delegate: SliverChildListDelegate(keys.map<Widget>((int key) {
               return SizedBox(key: GlobalObjectKey(key), height: 100.0, child: GenerationText(key));
             }).toList()),
           ),
diff --git a/packages/flutter_driver/lib/src/driver/driver.dart b/packages/flutter_driver/lib/src/driver/driver.dart
index 7e130d7776082ab99754bb9e4b8797d1a485759d..5aa1e47dc9b125478eaf2bb1074fd078fd966e6b 100644
--- a/packages/flutter_driver/lib/src/driver/driver.dart
+++ b/packages/flutter_driver/lib/src/driver/driver.dart
@@ -78,7 +78,7 @@ final Duration _kPauseBetweenReconnectAttempts = _kShortTimeout ~/ 5;
 
 // See https://github.com/dart-lang/sdk/blob/master/runtime/vm/timeline.cc#L32
 String _timelineStreamsToString(List<TimelineStream> streams) {
-  final String contents = streams.map((TimelineStream stream) {
+  final String contents = streams.map<String>((TimelineStream stream) {
     switch (stream) {
       case TimelineStream.all: return 'all';
       case TimelineStream.api: return 'API';
@@ -428,7 +428,7 @@ class FlutterDriver {
   /// The move events are generated at a given [frequency] in Hz (or events per
   /// second). It defaults to 60Hz.
   Future<Null> scroll(SerializableFinder finder, double dx, double dy, Duration duration, { int frequency = 60, Duration timeout }) async {
-    return await _sendCommand(Scroll(finder, dx, dy, duration, frequency, timeout: timeout)).then((Map<String, dynamic> _) => null);
+    return await _sendCommand(Scroll(finder, dx, dy, duration, frequency, timeout: timeout)).then<Null>((Map<String, dynamic> _) => null);
   }
 
   /// Scrolls the Scrollable ancestor of the widget located by [finder]
@@ -439,7 +439,7 @@ class FlutterDriver {
   /// then this method may fail because [finder] doesn't actually exist.
   /// The [scrollUntilVisible] method can be used in this case.
   Future<Null> scrollIntoView(SerializableFinder finder, { double alignment = 0.0, Duration timeout }) async {
-    return await _sendCommand(ScrollIntoView(finder, alignment: alignment, timeout: timeout)).then((Map<String, dynamic> _) => null);
+    return await _sendCommand(ScrollIntoView(finder, alignment: alignment, timeout: timeout)).then<Null>((Map<String, dynamic> _) => null);
   }
 
   /// Repeatedly [scroll] the widget located by [scrollable] by [dxScroll] and
@@ -483,7 +483,7 @@ class FlutterDriver {
     // the chance to complete if the item is already onscreen; if not, scroll
     // repeatedly until we either find the item or time out.
     bool isVisible = false;
-    waitFor(item, timeout: timeout).then((Null value) { isVisible = true; });
+    waitFor(item, timeout: timeout).then<void>((Null value) { isVisible = true; });
     await Future<Null>.delayed(const Duration(milliseconds: 500));
     while (!isVisible) {
       await scroll(scrollable, dxScroll, dyScroll, const Duration(milliseconds: 100));
diff --git a/packages/flutter_driver/lib/src/driver/timeline.dart b/packages/flutter_driver/lib/src/driver/timeline.dart
index 34be834abcf58da09ae2ae550569efe518abd26c..6bb3087659b4318eaa4f4cc235e9773ecb03f35e 100644
--- a/packages/flutter_driver/lib/src/driver/timeline.dart
+++ b/packages/flutter_driver/lib/src/driver/timeline.dart
@@ -129,6 +129,6 @@ List<TimelineEvent> _parseEvents(Map<String, dynamic> json) {
 
   // TODO(vegorov): use instance method version of castFrom when it is available.
   return Iterable.castFrom<dynamic, Map<String, dynamic>>(jsonEvents)
-    .map((Map<String, dynamic> eventJson) => TimelineEvent(eventJson))
+    .map<TimelineEvent>((Map<String, dynamic> eventJson) => TimelineEvent(eventJson))
     .toList();
 }
diff --git a/packages/flutter_driver/lib/src/driver/timeline_summary.dart b/packages/flutter_driver/lib/src/driver/timeline_summary.dart
index 09e61de8814073266fecf077ad0a0389517dd52c..64e7dc0056ea1076011a60c850b688f56d932df4 100644
--- a/packages/flutter_driver/lib/src/driver/timeline_summary.dart
+++ b/packages/flutter_driver/lib/src/driver/timeline_summary.dart
@@ -98,10 +98,10 @@ class TimelineSummary {
       'missed_frame_rasterizer_budget_count': computeMissedFrameRasterizerBudgetCount(),
       'frame_count': countFrames(),
       'frame_build_times': _extractFrameDurations()
-        .map((Duration duration) => duration.inMicroseconds)
+        .map<int>((Duration duration) => duration.inMicroseconds)
         .toList(),
       'frame_rasterizer_times': _extractGpuRasterizerDrawEvents()
-        .map((TimedEvent event) => event.duration.inMicroseconds)
+        .map<int>((TimedEvent event) => event.duration.inMicroseconds)
         .toList(),
     };
   }
@@ -143,7 +143,7 @@ class TimelineSummary {
   }
 
   List<Duration> _extractDurations(String name) {
-    return _extractNamedEvents(name).map((TimelineEvent event) => event.duration).toList();
+    return _extractNamedEvents(name).map<Duration>((TimelineEvent event) => event.duration).toList();
   }
 
   /// Extracts timed events that are reported as a pair of begin/end events.
@@ -199,7 +199,7 @@ class TimelineSummary {
   List<Duration> _extractFrameDurations() => _extractDurations('Frame');
 
   Iterable<Duration> _extractDuration(Iterable<TimedEvent> events) {
-    return events.map((TimedEvent e) => e.duration);
+    return events.map<Duration>((TimedEvent e) => e.duration);
   }
 }
 
diff --git a/packages/flutter_driver/test/flutter_driver_test.dart b/packages/flutter_driver/test/flutter_driver_test.dart
index d8d8adbd9934c6bf33dd4c45d3602e0a614087ca..eed263a2a9d210f297be054f0da902caa579f32a 100644
--- a/packages/flutter_driver/test/flutter_driver_test.dart
+++ b/packages/flutter_driver/test/flutter_driver_test.dart
@@ -28,7 +28,7 @@ void main() {
     MockPeer mockPeer;
 
     void expectLogContains(String message) {
-      expect(log.map((LogRecord r) => '$r'), anyElement(contains(message)));
+      expect(log.map<String>((LogRecord r) => '$r'), anyElement(contains(message)));
     }
 
     setUp(() {
diff --git a/packages/flutter_test/lib/src/binding.dart b/packages/flutter_test/lib/src/binding.dart
index 2d47644df92ae2d00f5d5317abc47f28aa6adea1..80c3fb8435f3017e04a469485b2e32d772db5352 100644
--- a/packages/flutter_test/lib/src/binding.dart
+++ b/packages/flutter_test/lib/src/binding.dart
@@ -228,7 +228,7 @@ abstract class TestWidgetsFlutterBinding extends BindingBase
   /// Artificially calls dispatchLocaleChanged on the Widget binding,
   /// then flushes microtasks.
   Future<Null> setLocale(String languageCode, String countryCode) {
-    return TestAsyncUtils.guard(() async {
+    return TestAsyncUtils.guard<Null>(() async {
       assert(inTest);
       final Locale locale = Locale(languageCode, countryCode);
       dispatchLocaleChanged(locale);
@@ -243,7 +243,7 @@ abstract class TestWidgetsFlutterBinding extends BindingBase
   ///
   /// Set to null to use the default surface size.
   Future<Null> setSurfaceSize(Size size) {
-    return TestAsyncUtils.guard(() async {
+    return TestAsyncUtils.guard<Null>(() async {
       assert(inTest);
       if (_surfaceSize == size)
         return null;
@@ -273,7 +273,7 @@ abstract class TestWidgetsFlutterBinding extends BindingBase
   /// to recursively schedule new microtasks. Will not run any timers scheduled
   /// after this method was invoked, even if they are zero-time timers.
   Future<Null> idle() {
-    return TestAsyncUtils.guard(() {
+    return TestAsyncUtils.guard<Null>(() {
       final Completer<Null> completer = Completer<Null>();
       Timer.run(() {
         completer.complete(null);
@@ -537,7 +537,7 @@ abstract class TestWidgetsFlutterBinding extends BindingBase
     );
     _parentZone = Zone.current;
     final Zone testZone = _parentZone.fork(specification: errorHandlingZoneSpecification);
-    testZone.runBinary(_runTestBody, testBody, invariantTester)
+    testZone.runBinary<Future<Null>, Future<Null> Function(), VoidCallback>(_runTestBody, testBody, invariantTester)
       .whenComplete(testCompletionHandler);
     timeout?.catchError(handleUncaughtError);
     return testCompleter.future;
@@ -689,7 +689,7 @@ class AutomatedTestWidgetsFlutterBinding extends TestWidgetsFlutterBinding {
 
   @override
   Future<Null> pump([ Duration duration, EnginePhase newPhase = EnginePhase.sendSemanticsUpdate ]) {
-    return TestAsyncUtils.guard(() {
+    return TestAsyncUtils.guard<Null>(() {
       assert(inTest);
       assert(_clock != null);
       if (duration != null)
@@ -741,7 +741,7 @@ class AutomatedTestWidgetsFlutterBinding extends TestWidgetsFlutterBinding {
 
     addTime(additionalTime);
 
-    return realAsyncZone.run(() {
+    return realAsyncZone.run<Future<T>>(() {
       _pendingAsyncTasks = Completer<void>();
       return callback().catchError((dynamic exception, StackTrace stack) {
         FlutterError.reportError(FlutterErrorDetails(
@@ -1197,7 +1197,7 @@ class LiveTestWidgetsFlutterBinding extends TestWidgetsFlutterBinding {
     assert(inTest);
     assert(!_expectingFrame);
     assert(_pendingFrame == null);
-    return TestAsyncUtils.guard(() {
+    return TestAsyncUtils.guard<Null>(() {
       if (duration != null) {
         Timer(duration, () {
           _expectingFrame = true;
diff --git a/packages/flutter_test/lib/src/controller.dart b/packages/flutter_test/lib/src/controller.dart
index d2c18d2694da8df7056dd10c0d032cfc559c6bf4..0d70e844392b2fe96f48f8bce202fe12927c36ba 100644
--- a/packages/flutter_test/lib/src/controller.dart
+++ b/packages/flutter_test/lib/src/controller.dart
@@ -46,7 +46,7 @@ abstract class WidgetController {
   Iterable<Widget> get allWidgets {
     TestAsyncUtils.guardSync();
     return allElements
-           .map((Element element) => element.widget);
+           .map<Widget>((Element element) => element.widget);
   }
 
   /// The matching widget in the widget tree.
@@ -137,7 +137,7 @@ abstract class WidgetController {
     TestAsyncUtils.guardSync();
     return allElements
            .whereType<StatefulElement>()
-           .map((StatefulElement element) => element.state);
+           .map<State>((StatefulElement element) => element.state);
   }
 
   /// The matching state in the widget tree.
@@ -173,7 +173,7 @@ abstract class WidgetController {
   /// * Use [firstState] if you expect to match several but only want the first.
   Iterable<T> stateList<T extends State>(Finder finder) {
     TestAsyncUtils.guardSync();
-    return finder.evaluate().map((Element element) => _stateOf<T>(element, finder));
+    return finder.evaluate().map<T>((Element element) => _stateOf<T>(element, finder));
   }
 
   T _stateOf<T extends State>(Element element, Finder finder) {
@@ -194,7 +194,7 @@ abstract class WidgetController {
   Iterable<RenderObject> get allRenderObjects {
     TestAsyncUtils.guardSync();
     return allElements
-           .map((Element element) => element.renderObject);
+           .map<RenderObject>((Element element) => element.renderObject);
   }
 
   /// The render object of the matching widget in the widget tree.
@@ -262,7 +262,7 @@ abstract class WidgetController {
 
   /// Dispatch a pointer down / pointer up sequence at the given location.
   Future<Null> tapAt(Offset location, { int pointer }) {
-    return TestAsyncUtils.guard(() async {
+    return TestAsyncUtils.guard<Null>(() async {
       final TestGesture gesture = await startGesture(location, pointer: pointer);
       await gesture.up();
       return null;
@@ -293,7 +293,7 @@ abstract class WidgetController {
   /// Dispatch a pointer down / pointer up sequence at the given location with
   /// a delay of [kLongPressTimeout] + [kPressTimeout] between the two events.
   Future<Null> longPressAt(Offset location, { int pointer }) {
-    return TestAsyncUtils.guard(() async {
+    return TestAsyncUtils.guard<Null>(() async {
       final TestGesture gesture = await startGesture(location, pointer: pointer);
       await pump(kLongPressTimeout + kPressTimeout);
       await gesture.up();
@@ -371,7 +371,7 @@ abstract class WidgetController {
   }) {
     assert(offset.distance > 0.0);
     assert(speed > 0.0); // speed is pixels/second
-    return TestAsyncUtils.guard(() async {
+    return TestAsyncUtils.guard<Null>(() async {
       final TestPointer testPointer = TestPointer(pointer ?? _getNextPointer());
       final HitTestResult result = hitTestOnBinding(startLocation);
       const int kMoveCount = 50; // Needs to be >= kHistorySize, see _LeastSquaresVelocityTrackerStrategy
@@ -428,7 +428,7 @@ abstract class WidgetController {
   /// system identifies the gesture as a fling, consider using [flingFrom]
   /// instead.
   Future<Null> dragFrom(Offset startLocation, Offset offset, { int pointer }) {
-    return TestAsyncUtils.guard(() async {
+    return TestAsyncUtils.guard<Null>(() async {
       final TestGesture gesture = await startGesture(startLocation, pointer: pointer);
       assert(gesture != null);
       await gesture.moveBy(offset);
@@ -469,7 +469,7 @@ abstract class WidgetController {
 
   /// Forwards the given pointer event to the binding.
   Future<Null> sendEventToBinding(PointerEvent event, HitTestResult result) {
-    return TestAsyncUtils.guard(() async {
+    return TestAsyncUtils.guard<Null>(() async {
       binding.dispatchEvent(event, result);
       return null;
     });
diff --git a/packages/flutter_test/lib/src/finders.dart b/packages/flutter_test/lib/src/finders.dart
index 6341190d4eb139f581ae960675e91a43438dcddb..2d41b0334c3ddb5d45e76c3cf0dd0c234747df25 100644
--- a/packages/flutter_test/lib/src/finders.dart
+++ b/packages/flutter_test/lib/src/finders.dart
@@ -633,7 +633,7 @@ class _DescendantFinder extends Finder {
   @override
   Iterable<Element> get allCandidates {
     final Iterable<Element> ancestorElements = ancestor.evaluate();
-    final List<Element> candidates = ancestorElements.expand(
+    final List<Element> candidates = ancestorElements.expand<Element>(
       (Element element) => collectAllElementsFrom(element, skipOffstage: skipOffstage)
     ).toSet().toList();
     if (matchRoot)
diff --git a/packages/flutter_test/lib/src/goldens.dart b/packages/flutter_test/lib/src/goldens.dart
index eeab00b7f56c63deb7c00fb6c51c465127add615..5ef149388eba911371bca32546402a4773936f6d 100644
--- a/packages/flutter_test/lib/src/goldens.dart
+++ b/packages/flutter_test/lib/src/goldens.dart
@@ -181,7 +181,7 @@ class LocalFileComparator implements GoldenFileComparator {
       throw test_package.TestFailure('Could not be compared against non-existent file: "$golden"');
     }
     final List<int> goldenBytes = await goldenFile.readAsBytes();
-    return _areListsEqual(imageBytes, goldenBytes);
+    return _areListsEqual<int>(imageBytes, goldenBytes);
   }
 
   @override
diff --git a/packages/flutter_test/lib/src/test_pointer.dart b/packages/flutter_test/lib/src/test_pointer.dart
index 063440e13901ea5f110017fc343bcdadb80eb545..56f20968e2068b75d69591455ba4e1e274862924 100644
--- a/packages/flutter_test/lib/src/test_pointer.dart
+++ b/packages/flutter_test/lib/src/test_pointer.dart
@@ -142,7 +142,7 @@ class TestGesture {
     assert(hitTester != null);
     assert(dispatcher != null);
     TestGesture result;
-    return TestAsyncUtils.guard(() async {
+    return TestAsyncUtils.guard<Null>(() async {
       // dispatch down event
       final HitTestResult hitTestResult = hitTester(downLocation);
       final TestPointer testPointer = TestPointer(pointer);
@@ -170,7 +170,7 @@ class TestGesture {
 
   /// Send a move event moving the pointer to the given location.
   Future<Null> moveTo(Offset location, { Duration timeStamp = Duration.zero }) {
-    return TestAsyncUtils.guard(() {
+    return TestAsyncUtils.guard<Null>(() {
       assert(_pointer._isDown);
       return _dispatcher(_pointer.move(location, timeStamp: timeStamp), _result);
     });
@@ -180,7 +180,7 @@ class TestGesture {
   ///
   /// The object is no longer usable after this method has been called.
   Future<Null> up() {
-    return TestAsyncUtils.guard(() async {
+    return TestAsyncUtils.guard<Null>(() async {
       assert(_pointer._isDown);
       await _dispatcher(_pointer.up(), _result);
       assert(!_pointer._isDown);
@@ -194,7 +194,7 @@ class TestGesture {
   ///
   /// The object is no longer usable after this method has been called.
   Future<Null> cancel() {
-    return TestAsyncUtils.guard(() async {
+    return TestAsyncUtils.guard<Null>(() async {
       assert(_pointer._isDown);
       await _dispatcher(_pointer.cancel(), _result);
       assert(!_pointer._isDown);
diff --git a/packages/flutter_test/lib/src/widget_tester.dart b/packages/flutter_test/lib/src/widget_tester.dart
index 4a766fc171c3ec202ce1af5fe9ad4e10b3147760..bcdee59e69933292eb7eb1356bfe9d0c09f31d34 100644
--- a/packages/flutter_test/lib/src/widget_tester.dart
+++ b/packages/flutter_test/lib/src/widget_tester.dart
@@ -221,7 +221,7 @@ class WidgetTester extends WidgetController implements HitTestDispatcher, Ticker
     Duration duration,
     EnginePhase phase = EnginePhase.sendSemanticsUpdate,
   ]) {
-    return TestAsyncUtils.guard(() {
+    return TestAsyncUtils.guard<Null>(() {
       binding.attachRootWidget(widget);
       binding.scheduleFrame();
       return binding.pump(duration, phase);
@@ -244,7 +244,7 @@ class WidgetTester extends WidgetController implements HitTestDispatcher, Ticker
     Duration duration,
     EnginePhase phase = EnginePhase.sendSemanticsUpdate,
   ]) {
-    return TestAsyncUtils.guard(() => binding.pump(duration, phase));
+    return TestAsyncUtils.guard<Null>(() => binding.pump(duration, phase));
   }
 
   /// Repeatedly calls [pump] with the given `duration` until there are no
@@ -292,7 +292,7 @@ class WidgetTester extends WidgetController implements HitTestDispatcher, Ticker
       return true;
     }());
     int count = 0;
-    return TestAsyncUtils.guard(() async {
+    return TestAsyncUtils.guard<Null>(() async {
       final DateTime endTime = binding.clock.fromNowBy(timeout);
       do {
         if (binding.clock.now().isAfter(endTime))
@@ -325,7 +325,7 @@ class WidgetTester extends WidgetController implements HitTestDispatcher, Ticker
   /// [TestFailure] error being thrown.
   Future<T> runAsync<T>(Future<T> callback(), {
     Duration additionalTime = const Duration(milliseconds: 250),
-  }) => binding.runAsync(callback, additionalTime: additionalTime);
+  }) => binding.runAsync<T>(callback, additionalTime: additionalTime);
 
   /// Whether there are any any transient callbacks scheduled.
   ///
@@ -351,7 +351,7 @@ class WidgetTester extends WidgetController implements HitTestDispatcher, Ticker
 
   @override
   Future<Null> sendEventToBinding(PointerEvent event, HitTestResult result) {
-    return TestAsyncUtils.guard(() async {
+    return TestAsyncUtils.guard<Null>(() async {
       binding.dispatchEvent(event, result, source: TestBindingEventSource.test);
       return null;
     });
@@ -485,7 +485,7 @@ class WidgetTester extends WidgetController implements HitTestDispatcher, Ticker
   /// Does not run timers. May result in an infinite loop or run out of memory
   /// if microtasks continue to recursively schedule new microtasks.
   Future<Null> idle() {
-    return TestAsyncUtils.guard(() => binding.idle());
+    return TestAsyncUtils.guard<Null>(() => binding.idle());
   }
 
   Set<Ticker> _tickers;
@@ -570,8 +570,8 @@ class WidgetTester extends WidgetController implements HitTestDispatcher, Ticker
   /// Tests that just need to add text to widgets like [TextField]
   /// or [TextFormField] only need to call [enterText].
   Future<Null> showKeyboard(Finder finder) async {
-    return TestAsyncUtils.guard(() async {
-      final EditableTextState editable = state(
+    return TestAsyncUtils.guard<Null>(() async {
+      final EditableTextState editable = state<EditableTextState>(
         find.descendant(
           of: finder,
           matching: find.byType(EditableText),
@@ -593,7 +593,7 @@ class WidgetTester extends WidgetController implements HitTestDispatcher, Ticker
   /// To just give [finder] the focus without entering any text,
   /// see [showKeyboard].
   Future<Null> enterText(Finder finder, String text) async {
-    return TestAsyncUtils.guard(() async {
+    return TestAsyncUtils.guard<Null>(() async {
       await showKeyboard(finder);
       testTextInput.enterText(text);
       await idle();
@@ -605,7 +605,7 @@ class WidgetTester extends WidgetController implements HitTestDispatcher, Ticker
   ///
   /// Will throw an error if there is no back button in the page.
   Future<void> pageBack() async {
-    return TestAsyncUtils.guard(() async {
+    return TestAsyncUtils.guard<void>(() async {
       Finder backButton = find.byTooltip('Back');
       if (backButton.evaluate().isEmpty) {
         backButton = find.byType(CupertinoNavigationBarBackButton);
diff --git a/packages/flutter_test/test/goldens_test.dart b/packages/flutter_test/test/goldens_test.dart
index 147ed2daea80c988c5aa47bacac6d3ebf661fb6c..0c084ad99c502f7ae2b35cfb3f24c514673e4926 100644
--- a/packages/flutter_test/test/goldens_test.dart
+++ b/packages/flutter_test/test/goldens_test.dart
@@ -34,7 +34,7 @@ void main() {
 
   void test(String description, FutureOr<void> body()) {
     test_package.test(description, () {
-      return io.IOOverrides.runZoned(
+      return io.IOOverrides.runZoned<FutureOr<void>>(
         body,
         createDirectory: (String path) => fs.directory(path),
         createFile: (String path) => fs.file(path),
diff --git a/packages/flutter_test/test/widget_tester_test.dart b/packages/flutter_test/test/widget_tester_test.dart
index ecb5ba050240236c1ec359212dbc43932c7d9595..924939826a52f0f8e2ff45a3e249caaf19353bff 100644
--- a/packages/flutter_test/test/widget_tester_test.dart
+++ b/packages/flutter_test/test/widget_tester_test.dart
@@ -24,7 +24,7 @@ void main() {
       final Completer<void> completer = Completer<void>();
       final Future<void> future = expectLater(null, FakeMatcher(completer));
       String value;
-      future.then((void _) {
+      future.then<void>((void _) {
         value = '123';
       });
       test_package.expect(value, isNull);
@@ -39,7 +39,7 @@ void main() {
       final Completer<void> completer = Completer<void>();
       final Future<void> future = expectLater(null, FakeMatcher(completer), skip: 'testing skip');
       bool completed = false;
-      future.then((void _) {
+      future.then<void>((void _) {
         completed = true;
       });
       test_package.expect(completed, isFalse);
@@ -498,7 +498,7 @@ void main() {
 
     testWidgets('maintains existing zone values', (WidgetTester tester) async {
       final Object key = Object();
-      await runZoned(() {
+      await runZoned<Future<void>>(() {
         expect(Zone.current[key], 'abczed');
         return tester.runAsync<void>(() async {
           expect(Zone.current[key], 'abczed');
diff --git a/packages/flutter_tools/bin/fuchsia_asset_builder.dart b/packages/flutter_tools/bin/fuchsia_asset_builder.dart
index e54702545a900bffc9e491a3bf237a063ea0f2a8..c659f846a50a4707274af52579430c45717061e6 100644
--- a/packages/flutter_tools/bin/fuchsia_asset_builder.dart
+++ b/packages/flutter_tools/bin/fuchsia_asset_builder.dart
@@ -77,7 +77,7 @@ Future<Null> run(List<String> args) async {
     final libfs.File outputFile = libfs.fs.file(libfs.fs.path.join(assetDir, fileName));
     calls.add(writeFile(outputFile, content));
   });
-  await Future.wait(calls);
+  await Future.wait<Null>(calls);
 
   final String outputMan = argResults[_kOptionAssetManifestOut];
   await writeFuchsiaManifest(assets, argResults[_kOptionAsset], outputMan, argResults[_kOptionComponentName]);
diff --git a/packages/flutter_tools/lib/src/android/android_device.dart b/packages/flutter_tools/lib/src/android/android_device.dart
index 339544209bba7372459ffc39d6d63a53c324888f..9f9545b53f3204e5765f6f772a00f9221e8fec5f 100644
--- a/packages/flutter_tools/lib/src/android/android_device.dart
+++ b/packages/flutter_tools/lib/src/android/android_device.dart
@@ -474,7 +474,7 @@ class AndroidDevice extends Device {
   @override
   Future<bool> stopApp(ApplicationPackage app) {
     final List<String> command = adbCommandForDevice(<String>['shell', 'am', 'force-stop', app.id]);
-    return runCommandAndStreamOutput(command).then((int exitCode) => exitCode == 0);
+    return runCommandAndStreamOutput(command).then<bool>((int exitCode) => exitCode == 0);
   }
 
   @override
@@ -673,8 +673,8 @@ class _AdbLogReader extends DeviceLogReader {
     runCommand(device.adbCommandForDevice(args)).then<Null>((Process process) {
       _process = process;
       const Utf8Decoder decoder = Utf8Decoder(allowMalformed: true);
-      _process.stdout.transform(decoder).transform(const LineSplitter()).listen(_onLine);
-      _process.stderr.transform(decoder).transform(const LineSplitter()).listen(_onLine);
+      _process.stdout.transform<String>(decoder).transform<String>(const LineSplitter()).listen(_onLine);
+      _process.stderr.transform<String>(decoder).transform<String>(const LineSplitter()).listen(_onLine);
       _process.exitCode.whenComplete(() {
         if (_linesController.hasListener)
           _linesController.close();
diff --git a/packages/flutter_tools/lib/src/android/android_emulator.dart b/packages/flutter_tools/lib/src/android/android_emulator.dart
index d0ea02dd2311892ceb4a24b77cd2f499fb570424..6a0e24de693d8288c55c94737d4b748e0b334815 100644
--- a/packages/flutter_tools/lib/src/android/android_emulator.dart
+++ b/packages/flutter_tools/lib/src/android/android_emulator.dart
@@ -112,13 +112,13 @@ Map<String, String> parseIniLines(List<String> contents) {
   final Map<String, String> results = <String, String>{};
 
   final Iterable<List<String>> properties = contents
-      .map((String l) => l.trim())
+      .map<String>((String l) => l.trim())
       // Strip blank lines/comments
       .where((String l) => l != '' && !l.startsWith('#'))
       // Discard anything that isn't simple name=value
       .where((String l) => l.contains('='))
       // Split into name/value
-      .map((String l) => l.split('='));
+      .map<List<String>>((String l) => l.split('='));
 
   for (List<String> property in properties) {
     results[property[0].trim()] = property[1].trim();
diff --git a/packages/flutter_tools/lib/src/android/android_sdk.dart b/packages/flutter_tools/lib/src/android/android_sdk.dart
index 72344d2b34bccea71780ca786c0fffaa456a7e79..4c9ea22918639d7a23b6811077e7bde009d7fbc1 100644
--- a/packages/flutter_tools/lib/src/android/android_sdk.dart
+++ b/packages/flutter_tools/lib/src/android/android_sdk.dart
@@ -382,7 +382,7 @@ class AndroidSdk {
     }
 
     // Match up platforms with the best corresponding build-tools.
-    _sdkVersions = platforms.map((Directory platformDir) {
+    _sdkVersions = platforms.map<AndroidSdkVersion>((Directory platformDir) {
       final String platformName = platformDir.basename;
       int platformVersion;
 
@@ -394,7 +394,7 @@ class AndroidSdk {
           final String buildProps = platformDir.childFile('build.prop').readAsStringSync();
           final String versionString = const LineSplitter()
               .convert(buildProps)
-              .map(_sdkVersionRe.firstMatch)
+              .map<Match>(_sdkVersionRe.firstMatch)
               .firstWhere((Match match) => match != null)
               .group(1);
           platformVersion = int.parse(versionString);
diff --git a/packages/flutter_tools/lib/src/android/android_studio.dart b/packages/flutter_tools/lib/src/android/android_studio.dart
index 9b416d7f36af9fe8ab7984595315df04ca3d6f06..4c3dc986960fe758f4e1d2c8ee33f6df57341480 100644
--- a/packages/flutter_tools/lib/src/android/android_studio.dart
+++ b/packages/flutter_tools/lib/src/android/android_studio.dart
@@ -188,7 +188,7 @@ class AndroidStudio implements Comparable<AndroidStudio> {
     }
 
     return candidatePaths
-        .map((FileSystemEntity e) => AndroidStudio.fromMacOSBundle(e.path))
+        .map<AndroidStudio>((FileSystemEntity e) => AndroidStudio.fromMacOSBundle(e.path))
         .where((AndroidStudio s) => s != null)
         .toList();
   }
diff --git a/packages/flutter_tools/lib/src/android/android_studio_validator.dart b/packages/flutter_tools/lib/src/android/android_studio_validator.dart
index fd59e4c392cb23d962ad4f0e7385e20f9607f258..3302e9430921392bd7046162e090a386aa4f0fbd 100644
--- a/packages/flutter_tools/lib/src/android/android_studio_validator.dart
+++ b/packages/flutter_tools/lib/src/android/android_studio_validator.dart
@@ -22,7 +22,7 @@ class AndroidStudioValidator extends DoctorValidator {
       validators.add(NoAndroidStudioValidator());
     } else {
       validators.addAll(studios
-          .map((AndroidStudio studio) => AndroidStudioValidator(studio)));
+          .map<DoctorValidator>((AndroidStudio studio) => AndroidStudioValidator(studio)));
     }
     return validators;
   }
@@ -46,11 +46,11 @@ class AndroidStudioValidator extends DoctorValidator {
     if (_studio.isValid) {
       type = ValidationType.installed;
       messages.addAll(_studio.validationMessages
-          .map((String m) => ValidationMessage(m)));
+          .map<ValidationMessage>((String m) => ValidationMessage(m)));
     } else {
       type = ValidationType.partial;
       messages.addAll(_studio.validationMessages
-          .map((String m) => ValidationMessage.error(m)));
+          .map<ValidationMessage>((String m) => ValidationMessage.error(m)));
       messages.add(ValidationMessage(
           'Try updating or re-installing Android Studio.'));
       if (_studio.configured != null) {
diff --git a/packages/flutter_tools/lib/src/android/android_workflow.dart b/packages/flutter_tools/lib/src/android/android_workflow.dart
index d3e428554f14486e2d727c43246f923d85f0908b..2a532a0c28b9b0233c1cdc7172db39689c1752cb 100644
--- a/packages/flutter_tools/lib/src/android/android_workflow.dart
+++ b/packages/flutter_tools/lib/src/android/android_workflow.dart
@@ -127,7 +127,7 @@ class AndroidValidator extends DoctorValidator {
 
     if (validationResult.isNotEmpty) {
       // Android SDK is not functional.
-      messages.addAll(validationResult.map((String message) {
+      messages.addAll(validationResult.map<ValidationMessage>((String message) {
         return ValidationMessage.error(message);
       }));
       messages.add(ValidationMessage(
@@ -200,13 +200,13 @@ class AndroidValidator extends DoctorValidator {
     );
     process.stdin.write('n\n');
     final Future<void> output = process.stdout
-      .transform(const Utf8Decoder(allowMalformed: true))
-      .transform(const LineSplitter())
+      .transform<String>(const Utf8Decoder(allowMalformed: true))
+      .transform<String>(const LineSplitter())
       .listen(_onLine)
       .asFuture<void>(null);
     final Future<void> errors = process.stderr
-      .transform(const Utf8Decoder(allowMalformed: true))
-      .transform(const LineSplitter())
+      .transform<String>(const Utf8Decoder(allowMalformed: true))
+      .transform<String>(const LineSplitter())
       .listen(_onLine)
       .asFuture<void>(null);
     try {
diff --git a/packages/flutter_tools/lib/src/asset.dart b/packages/flutter_tools/lib/src/asset.dart
index 22b7b2465c907f0b07c58d4dceb0d782a474edae..5052e5de1fb8f55716f45cb798080e451ffe148b 100644
--- a/packages/flutter_tools/lib/src/asset.dart
+++ b/packages/flutter_tools/lib/src/asset.dart
@@ -354,7 +354,7 @@ Future<DevFSContent> _obtainLicenses(
     printStatus(allPackagesList.join(', '));
   }
 
-  final List<String> combinedLicensesList = packageLicenses.keys.map(
+  final List<String> combinedLicensesList = packageLicenses.keys.map<String>(
     (String license) {
       final List<String> packageNames = packageLicenses[license].toList()
        ..sort();
@@ -444,7 +444,7 @@ List<Font> _parsePackageFonts(
 }
 
 List<Map<String, dynamic>> _createFontsDescriptor(List<Font> fonts) {
-  return fonts.map((Font font) => font.descriptor).toList();
+  return fonts.map<Map<String, dynamic>>((Font font) => font.descriptor).toList();
 }
 
 // Given an assets directory like this:
diff --git a/packages/flutter_tools/lib/src/base/fingerprint.dart b/packages/flutter_tools/lib/src/base/fingerprint.dart
index fed1cbf804ac6c96ea4a0eb2532e4e97fb227507..b898ed7c1b4e0923d55ab5a2dc5b4afed16dcf60 100644
--- a/packages/flutter_tools/lib/src/base/fingerprint.dart
+++ b/packages/flutter_tools/lib/src/base/fingerprint.dart
@@ -97,7 +97,7 @@ class Fingerprinter {
 /// See [Fingerprinter].
 class Fingerprint {
   Fingerprint.fromBuildInputs(Map<String, String> properties, Iterable<String> inputPaths) {
-    final Iterable<File> files = inputPaths.map(fs.file);
+    final Iterable<File> files = inputPaths.map<File>(fs.file);
     final Iterable<File> missingInputs = files.where((File file) => !file.existsSync());
     if (missingInputs.isNotEmpty)
       throw ArgumentError('Missing input files:\n' + missingInputs.join('\n'));
@@ -179,7 +179,7 @@ Future<Set<String>> readDepfile(String depfilePath) async {
   return dependencies
       .replaceAllMapped(_separatorExpr, (Match match) => '${match.group(1)}\n')
       .split('\n')
-      .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();
 }
diff --git a/packages/flutter_tools/lib/src/base/io.dart b/packages/flutter_tools/lib/src/base/io.dart
index fb9be5148140fd3a5bdfbd5e19afa39ef4a558d1..70ca4fe966519cfa0f372a46712bdea4c84b038e 100644
--- a/packages/flutter_tools/lib/src/base/io.dart
+++ b/packages/flutter_tools/lib/src/base/io.dart
@@ -127,7 +127,7 @@ class ProcessSignal implements io.ProcessSignal {
 
   @override
   Stream<ProcessSignal> watch() {
-    return _delegate.watch().map((io.ProcessSignal signal) => this);
+    return _delegate.watch().map<ProcessSignal>((io.ProcessSignal signal) => this);
   }
 
   @override
diff --git a/packages/flutter_tools/lib/src/base/logger.dart b/packages/flutter_tools/lib/src/base/logger.dart
index de9eabf9791251aeb1e31661c9790536df42107d..dd6f0a1d96df9f9ca2e0f3d53b72449e5376d17f 100644
--- a/packages/flutter_tools/lib/src/base/logger.dart
+++ b/packages/flutter_tools/lib/src/base/logger.dart
@@ -112,7 +112,7 @@ class StdoutLogger extends Logger {
       message = terminal.color(message, color);
     if (indent != null && indent > 0) {
       message = LineSplitter.split(message)
-          .map((String line) => ' ' * indent + line)
+          .map<String>((String line) => ' ' * indent + line)
           .join('\n');
     }
     if (newline != false)
diff --git a/packages/flutter_tools/lib/src/base/os.dart b/packages/flutter_tools/lib/src/base/os.dart
index 8c3b30dd696fac1a6289797c44499eb1db33a4d8..54f5964146208348e49b8dcdb8bf85956d132974 100644
--- a/packages/flutter_tools/lib/src/base/os.dart
+++ b/packages/flutter_tools/lib/src/base/os.dart
@@ -92,7 +92,7 @@ class _PosixUtils extends OperatingSystemUtils {
     if (result.exitCode != 0)
       return const <File>[];
     final String stdout = result.stdout;
-    return stdout.trim().split('\n').map((String path) => fs.file(path.trim())).toList();
+    return stdout.trim().split('\n').map<File>((String path) => fs.file(path.trim())).toList();
   }
 
   @override
@@ -166,7 +166,7 @@ class _WindowsUtils extends OperatingSystemUtils {
       return const <File>[];
     final List<String> lines = result.stdout.trim().split('\n');
     if (all)
-      return lines.map((String path) => fs.file(path.trim())).toList();
+      return lines.map<File>((String path) => fs.file(path.trim())).toList();
     return <File>[fs.file(lines.first.trim())];
   }
 
diff --git a/packages/flutter_tools/lib/src/base/process.dart b/packages/flutter_tools/lib/src/base/process.dart
index caf6349f814c57ac06deaeb23f8fb57e65ef5887..29029d4cebc3bd344088fe57d9d319bdddaea6f0 100644
--- a/packages/flutter_tools/lib/src/base/process.dart
+++ b/packages/flutter_tools/lib/src/base/process.dart
@@ -137,8 +137,8 @@ Future<int> runCommandAndStreamOutput(List<String> cmd, {
     environment: environment
   );
   final StreamSubscription<String> stdoutSubscription = process.stdout
-    .transform(utf8.decoder)
-    .transform(const LineSplitter())
+    .transform<String>(utf8.decoder)
+    .transform<String>(const LineSplitter())
     .where((String line) => filter == null ? true : filter.hasMatch(line))
     .listen((String line) {
       if (mapFunction != null)
@@ -152,8 +152,8 @@ Future<int> runCommandAndStreamOutput(List<String> cmd, {
       }
     });
   final StreamSubscription<String> stderrSubscription = process.stderr
-    .transform(utf8.decoder)
-    .transform(const LineSplitter())
+    .transform<String>(utf8.decoder)
+    .transform<String>(const LineSplitter())
     .where((String line) => filter == null ? true : filter.hasMatch(line))
     .listen((String line) {
       if (mapFunction != null)
diff --git a/packages/flutter_tools/lib/src/base/terminal.dart b/packages/flutter_tools/lib/src/base/terminal.dart
index 8e40c59a7799cd368917a19485f0f536a5a97193..65a5a466bf295b0b780c3d30401b42e4584bfa17 100644
--- a/packages/flutter_tools/lib/src/base/terminal.dart
+++ b/packages/flutter_tools/lib/src/base/terminal.dart
@@ -107,7 +107,7 @@ class AnsiTerminal {
   ///
   /// Useful when the console is in [singleCharMode].
   Stream<String> get onCharInput {
-    _broadcastStdInString ??= io.stdin.transform(const AsciiDecoder(allowInvalid: true)).asBroadcastStream();
+    _broadcastStdInString ??= io.stdin.transform<String>(const AsciiDecoder(allowInvalid: true)).asBroadcastStream();
     return _broadcastStdInString;
   }
 
diff --git a/packages/flutter_tools/lib/src/base/utils.dart b/packages/flutter_tools/lib/src/base/utils.dart
index 102a0ec5ad165dfd2bbbef85798fbc289bc814a6..ee485de5a5a034900fb8336ca4fa05144a81b8ab 100644
--- a/packages/flutter_tools/lib/src/base/utils.dart
+++ b/packages/flutter_tools/lib/src/base/utils.dart
@@ -202,7 +202,7 @@ class SettingsFile {
   final Map<String, String> values = <String, String>{};
 
   void writeContents(File file) {
-    file.writeAsStringSync(values.keys.map((String key) {
+    file.writeAsStringSync(values.keys.map<String>((String key) {
       return '$key=${values[key]}';
     }).join('\n'));
   }
diff --git a/packages/flutter_tools/lib/src/bundle.dart b/packages/flutter_tools/lib/src/bundle.dart
index db1b56945e515a7cbd12587a550328fa2d0648a4..4a531b29fe759b650404d9a1012ba6bc084c40b9 100644
--- a/packages/flutter_tools/lib/src/bundle.dart
+++ b/packages/flutter_tools/lib/src/bundle.dart
@@ -193,8 +193,8 @@ Future<void> writeBundle(
     bundleDir.deleteSync(recursive: true);
   bundleDir.createSync(recursive: true);
 
-  await Future.wait(
-      assetEntries.entries.map((MapEntry<String, DevFSContent> entry) async {
+  await Future.wait<void>(
+      assetEntries.entries.map<Future<void>>((MapEntry<String, DevFSContent> entry) async {
     final File file = fs.file(fs.path.join(bundleDir.path, entry.key));
     file.parent.createSync(recursive: true);
     await file.writeAsBytes(await entry.value.contentsAsBytes());
diff --git a/packages/flutter_tools/lib/src/cache.dart b/packages/flutter_tools/lib/src/cache.dart
index 8e2325c73e3080a65a0a9cc586a43cb7b3a09f21..8ab311c5ed18c97334d8175ebcba33eaf4bebaa2 100644
--- a/packages/flutter_tools/lib/src/cache.dart
+++ b/packages/flutter_tools/lib/src/cache.dart
@@ -560,7 +560,7 @@ String _flattenNameNoSubdirs(String fileName) {
 @visibleForTesting
 String flattenNameSubdirs(Uri url) {
   final List<String> pieces = <String>[url.host]..addAll(url.pathSegments);
-  final Iterable<String> convertedPieces = pieces.map(_flattenNameNoSubdirs);
+  final Iterable<String> convertedPieces = pieces.map<String>(_flattenNameNoSubdirs);
   return fs.path.joinAll(convertedPieces);
 }
 
diff --git a/packages/flutter_tools/lib/src/commands/analyze_once.dart b/packages/flutter_tools/lib/src/commands/analyze_once.dart
index ae14c97679b5f5e11e47bf101d6cc691e529cdd3..3d181ad58fb5b779efb7b7c4f68916a08c7acdf9 100644
--- a/packages/flutter_tools/lib/src/commands/analyze_once.dart
+++ b/packages/flutter_tools/lib/src/commands/analyze_once.dart
@@ -92,7 +92,7 @@ class AnalyzeOnce extends AnalyzeBase {
 
     await server.start();
     // Completing the future in the callback can't fail.
-    server.onExit.then((int exitCode) { // ignore: unawaited_futures
+    server.onExit.then<void>((int exitCode) { // ignore: unawaited_futures
       if (!analysisCompleter.isCompleted) {
         analysisCompleter.completeError('analysis server exited: $exitCode');
       }
diff --git a/packages/flutter_tools/lib/src/commands/build_aot.dart b/packages/flutter_tools/lib/src/commands/build_aot.dart
index fb07c2311c0bb6026e2299b6f18844ce861f60ed..dc5a79fafed8f2ff51eca5c3a901f47b73650cca 100644
--- a/packages/flutter_tools/lib/src/commands/build_aot.dart
+++ b/packages/flutter_tools/lib/src/commands/build_aot.dart
@@ -35,8 +35,8 @@ class BuildAotCommand extends BuildSubCommand {
       )
       ..addMultiOption('ios-arch',
         splitCommas: true,
-        defaultsTo: defaultIOSArchs.map(getNameForIOSArch),
-        allowed: IOSArch.values.map(getNameForIOSArch),
+        defaultsTo: defaultIOSArchs.map<String>(getNameForIOSArch),
+        allowed: IOSArch.values.map<String>(getNameForIOSArch),
         help: 'iOS architectures to build.',
       )
       ..addMultiOption(FlutterOptions.kExtraFrontEndOptions,
@@ -112,14 +112,14 @@ class BuildAotCommand extends BuildSubCommand {
             outputPath: outputPath,
             buildSharedLibrary: false,
             extraGenSnapshotOptions: argResults[FlutterOptions.kExtraGenSnapshotOptions],
-          ).then((int buildExitCode) {
+          ).then<int>((int buildExitCode) {
             return buildExitCode;
           });
         });
 
         // Merge arch-specific App.frameworks into a multi-arch App.framework.
-        if ((await Future.wait(exitCodes.values)).every((int buildExitCode) => buildExitCode == 0)) {
-          final Iterable<String> dylibs = iosBuilds.values.map((String outputDir) => fs.path.join(outputDir, 'App.framework', 'App'));
+        if ((await Future.wait<int>(exitCodes.values)).every((int buildExitCode) => buildExitCode == 0)) {
+          final Iterable<String> dylibs = iosBuilds.values.map<String>((String outputDir) => fs.path.join(outputDir, 'App.framework', 'App'));
           fs.directory(fs.path.join(outputPath, 'App.framework'))..createSync();
           await runCheckedAsync(<String>['lipo']
             ..addAll(dylibs)
diff --git a/packages/flutter_tools/lib/src/commands/config.dart b/packages/flutter_tools/lib/src/commands/config.dart
index a69655e592ada6e3f74f5b351d7d73b4dcd2bfe2..2d60e8a0b5583928f65e8c5bb382d5b4af4f68cf 100644
--- a/packages/flutter_tools/lib/src/commands/config.dart
+++ b/packages/flutter_tools/lib/src/commands/config.dart
@@ -47,7 +47,7 @@ class ConfigCommand extends FlutterCommand {
   @override
   String get usageFooter {
     // List all config settings.
-    String values = config.keys.map((String key) {
+    String values = config.keys.map<String>((String key) {
       return '  $key: ${config.getValue(key)}';
     }).join('\n');
     if (values.isNotEmpty)
diff --git a/packages/flutter_tools/lib/src/commands/daemon.dart b/packages/flutter_tools/lib/src/commands/daemon.dart
index 6189f2c3ec97d69e874ac5e856dbd05787b576f3..18d38bcd626c00250285e5668ec8be803e2d66e2 100644
--- a/packages/flutter_tools/lib/src/commands/daemon.dart
+++ b/packages/flutter_tools/lib/src/commands/daemon.dart
@@ -603,7 +603,7 @@ class DeviceDomain extends Domain {
 
   _DeviceEventHandler _onDeviceEvent(String eventName) {
     return (Device device) {
-      _serializeDeviceEvents = _serializeDeviceEvents.then((_) async {
+      _serializeDeviceEvents = _serializeDeviceEvents.then<Null>((_) async {
         sendEvent(eventName, await _deviceToMap(device));
       });
     };
@@ -679,10 +679,10 @@ class DeviceDomain extends Domain {
 }
 
 Stream<Map<String, dynamic>> get stdinCommandStream => stdin
-  .transform(utf8.decoder)
-  .transform(const LineSplitter())
+  .transform<String>(utf8.decoder)
+  .transform<String>(const LineSplitter())
   .where((String line) => line.startsWith('[{') && line.endsWith('}]'))
-  .map((String line) {
+  .map<Map<String, dynamic>>((String line) {
     line = line.substring(1, line.length - 1);
     return json.decode(line);
   });
@@ -829,7 +829,7 @@ class EmulatorDomain extends Domain {
 
   Future<List<Map<String, dynamic>>> getEmulators([Map<String, dynamic> args]) async {
     final List<Emulator> list = await emulators.getAllAvailableEmulators();
-    return list.map(_emulatorToMap).toList();
+    return list.map<Map<String, dynamic>>(_emulatorToMap).toList();
   }
 
   Future<Null> launch(Map<String, dynamic> args) async {
diff --git a/packages/flutter_tools/lib/src/commands/drive.dart b/packages/flutter_tools/lib/src/commands/drive.dart
index 419371a42387f6f2b22b7f20b6d4ea836c58240c..dcccb09e80b7968ee8714b6a9e7f67d2b201bc58 100644
--- a/packages/flutter_tools/lib/src/commands/drive.dart
+++ b/packages/flutter_tools/lib/src/commands/drive.dart
@@ -206,7 +206,7 @@ Future<Device> findTargetDevice() async {
     return null;
   } else if (devices.length > 1) {
     printStatus('Found multiple connected devices:');
-    printStatus(devices.map((Device d) => '  - ${d.name}\n').join(''));
+    printStatus(devices.map<String>((Device d) => '  - ${d.name}\n').join(''));
   }
   printStatus('Using device ${devices.first.name}.');
   return devices.first;
diff --git a/packages/flutter_tools/lib/src/commands/fuchsia_reload.dart b/packages/flutter_tools/lib/src/commands/fuchsia_reload.dart
index fab29884a7c994b0d0c5e9cee2ec32cad402a077..3979beb967d20ecc035cc4be86afce04ea637ad0 100644
--- a/packages/flutter_tools/lib/src/commands/fuchsia_reload.dart
+++ b/packages/flutter_tools/lib/src/commands/fuchsia_reload.dart
@@ -120,7 +120,7 @@ class FuchsiaReloadCommand extends FlutterCommand {
     // Wrap everything in try/finally to make sure we kill the ssh processes
     // doing the port forwarding.
     try {
-      final List<int> servicePorts = forwardedPorts.map(
+      final List<int> servicePorts = forwardedPorts.map<int>(
           (_PortForwarder pf) => pf.port).toList();
 
       if (_list) {
@@ -145,10 +145,10 @@ class FuchsiaReloadCommand extends FlutterCommand {
 
       // Set up a device and hot runner and attach the hot runner to the first
       // vm service we found.
-      final List<String> fullAddresses = targetPorts.map(
+      final List<String> fullAddresses = targetPorts.map<String>(
         (int p) => '$ipv4Loopback:$p'
       ).toList();
-      final List<Uri> observatoryUris = fullAddresses.map(
+      final List<Uri> observatoryUris = fullAddresses.map<Uri>(
         (String a) => Uri.parse('http://$a')
       ).toList();
       final FuchsiaDevice device = FuchsiaDevice(
@@ -168,7 +168,7 @@ class FuchsiaReloadCommand extends FlutterCommand {
       printStatus('Connecting to $_modName');
       await hotRunner.attach(viewFilter: isolateName);
     } finally {
-      await Future.wait(forwardedPorts.map((_PortForwarder pf) => pf.stop()));
+      await Future.wait<Null>(forwardedPorts.map<Future<Null>>((_PortForwarder pf) => pf.stop()));
     }
   }
 
@@ -474,11 +474,11 @@ class _PortForwarder {
     printTrace("_PortForwarder running '${command.join(' ')}'");
     final Process process = await processManager.start(command);
     process.stderr
-        .transform(utf8.decoder)
-        .transform(const LineSplitter())
+        .transform<String>(utf8.decoder)
+        .transform<String>(const LineSplitter())
         .listen((String data) { printTrace(data); });
     // Best effort to print the exit code.
-    process.exitCode.then((int c) { // ignore: unawaited_futures
+    process.exitCode.then<void>((int c) { // ignore: unawaited_futures
       printTrace("'${command.join(' ')}' exited with exit code $c");
     });
     printTrace('Set up forwarding from $localPort to $address:$remotePort');
diff --git a/packages/flutter_tools/lib/src/commands/run.dart b/packages/flutter_tools/lib/src/commands/run.dart
index 1f3bbc77620a321b9ea7440d66ae2a776ee23470..36efd98b7811e7a6952d1108e39bdee0db9bff5d 100644
--- a/packages/flutter_tools/lib/src/commands/run.dart
+++ b/packages/flutter_tools/lib/src/commands/run.dart
@@ -344,7 +344,7 @@ class RunCommand extends RunCommandBase {
       fs.file(pidFile).writeAsStringSync(pid.toString());
     }
 
-    final List<FlutterDevice> flutterDevices = devices.map((Device device) {
+    final List<FlutterDevice> flutterDevices = devices.map<FlutterDevice>((Device device) {
       return FlutterDevice(
         device,
         trackWidgetCreation: argResults['track-widget-creation'],
@@ -392,7 +392,7 @@ class RunCommand extends RunCommandBase {
     // Do not add more operations to the future.
     final Completer<void> appStartedTimeRecorder = Completer<void>.sync();
     // This callback can't throw.
-    appStartedTimeRecorder.future.then( // ignore: unawaited_futures
+    appStartedTimeRecorder.future.then<void>( // ignore: unawaited_futures
       (_) { appStartedTime = clock.now(); }
     );
 
diff --git a/packages/flutter_tools/lib/src/compile.dart b/packages/flutter_tools/lib/src/compile.dart
index c2b0352b037e97a9be4897f8824588f1db97fd6a..26c239a96382aa609e88459cd1f3e9d129d86f38 100644
--- a/packages/flutter_tools/lib/src/compile.dart
+++ b/packages/flutter_tools/lib/src/compile.dart
@@ -179,11 +179,11 @@ class KernelCompiler {
     final _StdoutHandler _stdoutHandler = _StdoutHandler();
 
     server.stderr
-      .transform(utf8.decoder)
+      .transform<String>(utf8.decoder)
       .listen((String message) { printError(message); });
     server.stdout
-      .transform(utf8.decoder)
-      .transform(const LineSplitter())
+      .transform<String>(utf8.decoder)
+      .transform<String>(const LineSplitter())
       .listen(_stdoutHandler.handler);
     final int exitCode = await server.exitCode;
     if (exitCode == 0) {
@@ -372,8 +372,8 @@ class ResidentCompiler {
     printTrace(command.join(' '));
     _server = await processManager.start(command);
     _server.stdout
-      .transform(utf8.decoder)
-      .transform(const LineSplitter())
+      .transform<String>(utf8.decoder)
+      .transform<String>(const LineSplitter())
       .listen(
         _stdoutHandler.handler,
         onDone: () {
@@ -385,8 +385,8 @@ class ResidentCompiler {
         });
 
     _server.stderr
-      .transform(utf8.decoder)
-      .transform(const LineSplitter())
+      .transform<String>(utf8.decoder)
+      .transform<String>(const LineSplitter())
       .listen((String message) { printError(message); });
 
     _server.stdin.writeln('compile $scriptFilename');
diff --git a/packages/flutter_tools/lib/src/dart/analysis.dart b/packages/flutter_tools/lib/src/dart/analysis.dart
index 0815190fe1a75dda0fde7432ca27ea0efedd1ea9..481e4cb66c26b9ddb2cdeede40f8273a2dc56d35 100644
--- a/packages/flutter_tools/lib/src/dart/analysis.dart
+++ b/packages/flutter_tools/lib/src/dart/analysis.dart
@@ -43,11 +43,11 @@ class AnalysisServer {
     _process.exitCode.whenComplete(() => _process = null); // ignore: unawaited_futures
 
     final Stream<String> errorStream =
-        _process.stderr.transform(utf8.decoder).transform(const LineSplitter());
+        _process.stderr.transform<String>(utf8.decoder).transform<String>(const LineSplitter());
     errorStream.listen(printError);
 
     final Stream<String> inStream =
-        _process.stdout.transform(utf8.decoder).transform(const LineSplitter());
+        _process.stdout.transform<String>(utf8.decoder).transform<String>(const LineSplitter());
     inStream.listen(_handleServerResponse);
 
     // Available options (many of these are obsolete):
diff --git a/packages/flutter_tools/lib/src/devfs.dart b/packages/flutter_tools/lib/src/devfs.dart
index 0594742d7f113e1d0eaf9e8a94b2e1614245fcd6..3dd881943cc4b95a86f7993d3e8f40917e81f10e 100644
--- a/packages/flutter_tools/lib/src/devfs.dart
+++ b/packages/flutter_tools/lib/src/devfs.dart
@@ -47,7 +47,7 @@ abstract class DevFSContent {
   Stream<List<int>> contentsAsStream();
 
   Stream<List<int>> contentsAsCompressedStream() {
-    return contentsAsStream().transform(gzip.encoder);
+    return contentsAsStream().transform<List<int>>(gzip.encoder);
   }
 
   /// Return the list of files this content depends on.
@@ -445,7 +445,7 @@ class DevFS {
       if (!content._exists) {
         final Future<Map<String, dynamic>> operation =
             _operations.deleteFile(fsName, deviceUri)
-            .then((dynamic v) => v?.cast<String,dynamic>());
+            .then<Map<String, dynamic>>((dynamic v) => v?.cast<String,dynamic>());
         if (operation != null)
           _pendingOperations.add(operation);
         toRemove.add(deviceUri);
@@ -458,7 +458,7 @@ class DevFS {
     if (toRemove.isNotEmpty) {
       printTrace('Removing deleted files');
       toRemove.forEach(_entries.remove);
-      await Future.wait(_pendingOperations);
+      await Future.wait<Map<String, dynamic>>(_pendingOperations);
       _pendingOperations.clear();
     }
 
@@ -542,11 +542,11 @@ class DevFS {
         dirtyEntries.forEach((Uri deviceUri, DevFSContent content) {
           final Future<Map<String, dynamic>> operation =
               _operations.writeFile(fsName, deviceUri, content)
-                  .then((dynamic v) => v?.cast<String, dynamic>());
+                  .then<Map<String, dynamic>>((dynamic v) => v?.cast<String, dynamic>());
           if (operation != null)
             _pendingOperations.add(operation);
         });
-        await Future.wait(_pendingOperations, eagerError: true);
+        await Future.wait<Map<String, dynamic>>(_pendingOperations, eagerError: true);
         _pendingOperations.clear();
       }
     }
diff --git a/packages/flutter_tools/lib/src/device.dart b/packages/flutter_tools/lib/src/device.dart
index 61ff0ab604721919fa0e579e8afd575610261095..29f5c272e695ca0f69c557f64971da369c16d0f8 100644
--- a/packages/flutter_tools/lib/src/device.dart
+++ b/packages/flutter_tools/lib/src/device.dart
@@ -315,14 +315,14 @@ abstract class Device {
 
     // Calculate column widths
     final List<int> indices = List<int>.generate(table[0].length - 1, (int i) => i);
-    List<int> widths = indices.map((int i) => 0).toList();
+    List<int> widths = indices.map<int>((int i) => 0).toList();
     for (List<String> row in table) {
-      widths = indices.map((int i) => math.max(widths[i], row[i].length)).toList();
+      widths = indices.map<int>((int i) => math.max(widths[i], row[i].length)).toList();
     }
 
     // Join columns into lines of text
     for (List<String> row in table) {
-      yield indices.map((int i) => row[i].padRight(widths[i])).join(' • ') + ' • ${row.last}';
+      yield indices.map<String>((int i) => row[i].padRight(widths[i])).join(' • ') + ' • ${row.last}';
     }
   }
 
diff --git a/packages/flutter_tools/lib/src/doctor.dart b/packages/flutter_tools/lib/src/doctor.dart
index 1c625b418122ad15cb2cb3080c457740e5778e6b..d0fcf2f693821c105fbd47dd5a2651b375d3e29e 100644
--- a/packages/flutter_tools/lib/src/doctor.dart
+++ b/packages/flutter_tools/lib/src/doctor.dart
@@ -569,9 +569,9 @@ class IntelliJValidatorOnMac extends IntelliJValidator {
 
     try {
       final Iterable<Directory> installDirs = installPaths
-              .map((String installPath) => fs.directory(installPath))
-              .map((Directory dir) => dir.existsSync() ? dir.listSync() : <FileSystemEntity>[])
-              .expand((List<FileSystemEntity> mappedDirs) => mappedDirs)
+              .map<Directory>((String installPath) => fs.directory(installPath))
+              .map<List<FileSystemEntity>>((Directory dir) => dir.existsSync() ? dir.listSync() : <FileSystemEntity>[])
+              .expand<FileSystemEntity>((List<FileSystemEntity> mappedDirs) => mappedDirs)
               .whereType<Directory>();
       for (Directory dir in installDirs) {
         checkForIntelliJ(dir);
@@ -626,13 +626,13 @@ class DeviceValidator extends DoctorValidator {
     if (devices.isEmpty) {
       final List<String> diagnostics = await deviceManager.getDeviceDiagnostics();
       if (diagnostics.isNotEmpty) {
-        messages = diagnostics.map((String message) => ValidationMessage(message)).toList();
+        messages = diagnostics.map<ValidationMessage>((String message) => ValidationMessage(message)).toList();
       } else {
         messages = <ValidationMessage>[ValidationMessage.hint('No devices available')];
       }
     } else {
       messages = await Device.descriptions(devices)
-          .map((String msg) => ValidationMessage(msg)).toList();
+          .map<ValidationMessage>((String msg) => ValidationMessage(msg)).toList();
     }
 
     if (devices.isEmpty) {
diff --git a/packages/flutter_tools/lib/src/emulator.dart b/packages/flutter_tools/lib/src/emulator.dart
index c40497c77afb428e4e3cfad1762f2804bbf25f91..42e63fe3033978463ba67120fa546130ae2a18e8 100644
--- a/packages/flutter_tools/lib/src/emulator.dart
+++ b/packages/flutter_tools/lib/src/emulator.dart
@@ -54,7 +54,7 @@ class EmulatorManager {
   /// Return the list of all available emulators.
   Future<List<Emulator>> getAllAvailableEmulators() async {
     final List<Emulator> emulators = <Emulator>[];
-    await Future.forEach(_platformDiscoverers, (EmulatorDiscovery discoverer) async {
+    await Future.forEach<EmulatorDiscovery>(_platformDiscoverers, (EmulatorDiscovery discoverer) async {
       emulators.addAll(await discoverer.emulators);
     });
     return emulators;
@@ -69,7 +69,7 @@ class EmulatorManager {
       // so we can keep adding suffixes until we miss.
       final List<Emulator> all = await getAllAvailableEmulators();
       final Set<String> takenNames = all
-          .map((Emulator e) => e.id)
+          .map<String>((Emulator e) => e.id)
           .where((String id) => id.startsWith(autoName))
           .toSet();
       int suffix = 1;
@@ -176,8 +176,8 @@ class EmulatorManager {
         .toList();
 
     final List<int> availableApiVersions = availableIDs
-        .map((String id) => androidApiVersion.firstMatch(id).group(1))
-        .map((String apiVersion) => int.parse(apiVersion))
+        .map<String>((String id) => androidApiVersion.firstMatch(id).group(1))
+        .map<int>((String apiVersion) => int.parse(apiVersion))
         .toList();
 
     // Get the highest Android API version or whats left
@@ -253,21 +253,21 @@ abstract class Emulator {
 
     // Calculate column widths
     final List<int> indices = List<int>.generate(table[0].length - 1, (int i) => i);
-    List<int> widths = indices.map((int i) => 0).toList();
+    List<int> widths = indices.map<int>((int i) => 0).toList();
     for (List<String> row in table) {
-      widths = indices.map((int i) => math.max(widths[i], row[i].length)).toList();
+      widths = indices.map<int>((int i) => math.max(widths[i], row[i].length)).toList();
     }
 
     // Join columns into lines of text
     final RegExp whiteSpaceAndDots = RegExp(r'[•\s]+$');
     return table
-        .map((List<String> row) {
+        .map<String>((List<String> row) {
           return indices
-                  .map((int i) => row[i].padRight(widths[i]))
+                  .map<String>((int i) => row[i].padRight(widths[i]))
                   .join(' • ') +
               ' • ${row.last}';
         })
-        .map((String line) => line.replaceAll(whiteSpaceAndDots, ''))
+        .map<String>((String line) => line.replaceAll(whiteSpaceAndDots, ''))
         .toList();
   }
 
diff --git a/packages/flutter_tools/lib/src/flutter_manifest.dart b/packages/flutter_tools/lib/src/flutter_manifest.dart
index 9e937f4ffcbe7912922c71faa484519584e502d5..6fa8efb4950dfc12256fdafb201bcf5598278346 100644
--- a/packages/flutter_tools/lib/src/flutter_manifest.dart
+++ b/packages/flutter_tools/lib/src/flutter_manifest.dart
@@ -224,7 +224,7 @@ class Font {
   Map<String, dynamic> get descriptor {
     return <String, dynamic>{
       'family': familyName,
-      'fonts': fontAssets.map((FontAsset a) => a.descriptor).toList(),
+      'fonts': fontAssets.map<Map<String, dynamic>>((FontAsset a) => a.descriptor).toList(),
     };
   }
 
diff --git a/packages/flutter_tools/lib/src/ios/devices.dart b/packages/flutter_tools/lib/src/ios/devices.dart
index 111b654153a650abb61ff3562d3696387dd73861..d9f4e2677ca61593296e2ff72328ea5504ba8980 100644
--- a/packages/flutter_tools/lib/src/ios/devices.dart
+++ b/packages/flutter_tools/lib/src/ios/devices.dart
@@ -477,8 +477,8 @@ class _IOSDeviceLogReader extends DeviceLogReader {
   void _start() {
     iMobileDevice.startLogger().then<Null>((Process process) {
       _process = process;
-      _process.stdout.transform(utf8.decoder).transform(const LineSplitter()).listen(_newLineHandler());
-      _process.stderr.transform(utf8.decoder).transform(const LineSplitter()).listen(_newLineHandler());
+      _process.stdout.transform<String>(utf8.decoder).transform<String>(const LineSplitter()).listen(_newLineHandler());
+      _process.stderr.transform<String>(utf8.decoder).transform<String>(const LineSplitter()).listen(_newLineHandler());
       _process.exitCode.whenComplete(() {
         if (_linesController.hasListener)
           _linesController.close();
diff --git a/packages/flutter_tools/lib/src/ios/mac.dart b/packages/flutter_tools/lib/src/ios/mac.dart
index d86bf9ba2b2d25ee5c59480e520a7a99c74cb671..d77a41de65896aebd2e2036c680c1baf78fd0869 100644
--- a/packages/flutter_tools/lib/src/ios/mac.dart
+++ b/packages/flutter_tools/lib/src/ios/mac.dart
@@ -662,7 +662,7 @@ Future<Null> _copyServiceFrameworks(List<Map<String, String>> services, Director
 
 void _copyServiceDefinitionsManifest(List<Map<String, String>> services, File manifest) {
   printTrace("Creating service definitions manifest at '${manifest.path}'");
-  final List<Map<String, String>> jsonServices = services.map((Map<String, String> service) => <String, String>{
+  final List<Map<String, String>> jsonServices = services.map<Map<String, String>>((Map<String, String> service) => <String, String>{
     'name': service['name'],
     // Since we have already moved it to the Frameworks directory. Strip away
     // the directory and basenames.
diff --git a/packages/flutter_tools/lib/src/ios/simulators.dart b/packages/flutter_tools/lib/src/ios/simulators.dart
index e4ba8301ed2a803388e5d1fad2ce92ac8778c8d6..77dd9d46636cf62ebd373f7db10c3c62c3ccafa7 100644
--- a/packages/flutter_tools/lib/src/ios/simulators.dart
+++ b/packages/flutter_tools/lib/src/ios/simulators.dart
@@ -46,7 +46,7 @@ class IOSSimulatorUtils {
     if (!xcode.isInstalledAndMeetsVersionCheck)
       return <IOSSimulator>[];
 
-    return SimControl.instance.getConnectedDevices().map((SimDevice device) {
+    return SimControl.instance.getConnectedDevices().map<IOSSimulator>((SimDevice device) {
       return IOSSimulator(device.udid, name: device.name, category: device.category);
     }).toList();
   }
@@ -339,7 +339,7 @@ class IOSSimulator extends Device {
   }
 
   Future<bool> _applicationIsInstalledAndRunning(ApplicationPackage app) async {
-    final List<bool> criteria = await Future.wait(<Future<bool>>[
+    final List<bool> criteria = await Future.wait<bool>(<Future<bool>>[
       isAppInstalled(app),
       exitsHappyAsync(<String>['/usr/bin/killall', 'Runner']),
     ]);
@@ -510,15 +510,15 @@ class _IOSSimulatorLogReader extends DeviceLogReader {
     // Device log.
     await device.ensureLogsExists();
     _deviceProcess = await launchDeviceLogTool(device);
-    _deviceProcess.stdout.transform(utf8.decoder).transform(const LineSplitter()).listen(_onDeviceLine);
-    _deviceProcess.stderr.transform(utf8.decoder).transform(const LineSplitter()).listen(_onDeviceLine);
+    _deviceProcess.stdout.transform<String>(utf8.decoder).transform<String>(const LineSplitter()).listen(_onDeviceLine);
+    _deviceProcess.stderr.transform<String>(utf8.decoder).transform<String>(const LineSplitter()).listen(_onDeviceLine);
 
     // Track system.log crashes.
     // ReportCrash[37965]: Saved crash report for FlutterRunner[37941]...
     _systemProcess = await launchSystemLogTool(device);
     if (_systemProcess != null) {
-      _systemProcess.stdout.transform(utf8.decoder).transform(const LineSplitter()).listen(_onSystemLine);
-      _systemProcess.stderr.transform(utf8.decoder).transform(const LineSplitter()).listen(_onSystemLine);
+      _systemProcess.stdout.transform<String>(utf8.decoder).transform<String>(const LineSplitter()).listen(_onSystemLine);
+      _systemProcess.stderr.transform<String>(utf8.decoder).transform<String>(const LineSplitter()).listen(_onSystemLine);
     }
 
     // We don't want to wait for the process or its callback. Best effort
@@ -629,8 +629,8 @@ class _IOSSimulatorLogReader extends DeviceLogReader {
 }
 
 int compareIosVersions(String v1, String v2) {
-  final List<int> v1Fragments = v1.split('.').map(int.parse).toList();
-  final List<int> v2Fragments = v2.split('.').map(int.parse).toList();
+  final List<int> v1Fragments = v1.split('.').map<int>(int.parse).toList();
+  final List<int> v2Fragments = v2.split('.').map<int>(int.parse).toList();
 
   int i = 0;
   while (i < v1Fragments.length && i < v2Fragments.length) {
diff --git a/packages/flutter_tools/lib/src/ios/xcodeproj.dart b/packages/flutter_tools/lib/src/ios/xcodeproj.dart
index 9e638650aa36817b1abff77a2362f6e9238bc79f..2bb2a20c5ee4d7458aa17f880f6c0cc755cc0db0 100644
--- a/packages/flutter_tools/lib/src/ios/xcodeproj.dart
+++ b/packages/flutter_tools/lib/src/ios/xcodeproj.dart
@@ -171,7 +171,7 @@ class XcodeProjectInterpreter {
 
 Map<String, String> parseXcodeBuildSettings(String showBuildSettingsOutput) {
   final Map<String, String> settings = <String, String>{};
-  for (Match match in showBuildSettingsOutput.split('\n').map(_settingExpr.firstMatch)) {
+  for (Match match in showBuildSettingsOutput.split('\n').map<Match>(_settingExpr.firstMatch)) {
     if (match != null) {
       settings[match[1]] = match[2];
     }
diff --git a/packages/flutter_tools/lib/src/plugins.dart b/packages/flutter_tools/lib/src/plugins.dart
index e9a16d7a1ec46b7d4c83e25390d1a631ba389737..2b959c794a30d8c3ffc825f944719d68b34ea2c6 100644
--- a/packages/flutter_tools/lib/src/plugins.dart
+++ b/packages/flutter_tools/lib/src/plugins.dart
@@ -94,7 +94,7 @@ bool _writeFlutterPluginsList(FlutterProject project, List<Plugin> plugins) {
   final File pluginsFile = project.flutterPluginsFile;
   final String oldContents = _readFlutterPluginsList(project);
   final String pluginManifest =
-      plugins.map((Plugin p) => '${p.name}=${escapePath(p.path)}').join('\n');
+      plugins.map<String>((Plugin p) => '${p.name}=${escapePath(p.path)}').join('\n');
   if (pluginManifest.isNotEmpty) {
     pluginsFile.writeAsStringSync('$pluginManifest\n', flush: true);
   } else {
@@ -147,7 +147,7 @@ public final class GeneratedPluginRegistrant {
 Future<void> _writeAndroidPluginRegistrant(FlutterProject project, List<Plugin> plugins) async {
   final List<Map<String, dynamic>> androidPlugins = plugins
       .where((Plugin p) => p.androidPackage != null && p.pluginClass != null)
-      .map((Plugin p) => <String, dynamic>{
+      .map<Map<String, dynamic>>((Plugin p) => <String, dynamic>{
           'name': p.name,
           'package': p.androidPackage,
           'class': p.pluginClass,
@@ -238,7 +238,7 @@ end
 Future<void> _writeIOSPluginRegistrant(FlutterProject project, List<Plugin> plugins) async {
   final List<Map<String, dynamic>> iosPlugins = plugins
       .where((Plugin p) => p.pluginClass != null)
-      .map((Plugin p) => <String, dynamic>{
+      .map<Map<String, dynamic>>((Plugin p) => <String, dynamic>{
     'name': p.name,
     'prefix': p.iosPrefix,
     'class': p.pluginClass,
diff --git a/packages/flutter_tools/lib/src/project.dart b/packages/flutter_tools/lib/src/project.dart
index 9df371afdd5e78d964bb5765980ee40dee18457e..065461158fdc52f7496c0671f02a43d40b8d2b3b 100644
--- a/packages/flutter_tools/lib/src/project.dart
+++ b/packages/flutter_tools/lib/src/project.dart
@@ -77,7 +77,7 @@ class FlutterProject {
       example.ios.productBundleIdentifier,
     ];
     return Set<String>.from(candidates
-        .map(_organizationNameFromPackageName)
+        .map<String>(_organizationNameFromPackageName)
         .where((String name) => name != null));
   }
 
diff --git a/packages/flutter_tools/lib/src/resident_runner.dart b/packages/flutter_tools/lib/src/resident_runner.dart
index 2824e20e9edcbf17e0476f9fdb7341d22a2d5c04..73cee56b591eca0831d7e3de867221846cac6da0 100644
--- a/packages/flutter_tools/lib/src/resident_runner.dart
+++ b/packages/flutter_tools/lib/src/resident_runner.dart
@@ -89,7 +89,7 @@ class FlutterDevice {
 
     return vmServices
       .where((VMService service) => !service.isClosed)
-      .expand((VMService service) => viewFilter != null
+      .expand<FlutterView>((VMService service) => viewFilter != null
           ? service.vm.allViewsWithName(viewFilter)
           : service.vm.views)
       .toList();
@@ -149,7 +149,7 @@ class FlutterDevice {
     final Uri deviceAssetsDirectoryUri = devFS.baseUri.resolveUri(
         fs.path.toUri(getAssetBuildDirectory()));
     assert(deviceAssetsDirectoryUri != null);
-    await Future.wait(views.map(
+    await Future.wait<Null>(views.map<Future<Null>>(
       (FlutterView view) => view.setAssetDirectory(deviceAssetsDirectoryUri)
     ));
   }
@@ -611,8 +611,8 @@ abstract class ResidentRunner {
   }
 
   Future<Null> stopEchoingDeviceLog() async {
-    await Future.wait(
-      flutterDevices.map((FlutterDevice device) => device.stopEchoingDeviceLog())
+    await Future.wait<Null>(
+      flutterDevices.map<Future<Null>>((FlutterDevice device) => device.stopEchoingDeviceLog())
     );
   }
 
diff --git a/packages/flutter_tools/lib/src/run_hot.dart b/packages/flutter_tools/lib/src/run_hot.dart
index f973c897e74830ec869ae45ce5d7dd48e49cf1c1..1d6a0a865a00abe3b8fa5523e845d74680f56011 100644
--- a/packages/flutter_tools/lib/src/run_hot.dart
+++ b/packages/flutter_tools/lib/src/run_hot.dart
@@ -582,11 +582,11 @@ class HotRunner extends ResidentRunner {
         );
         countExpectedReports += reports.length;
         await Future
-            .wait(reports)
+            .wait<Map<String, dynamic>>(reports)
             .catchError((dynamic error) {
               return <Map<String, dynamic>>[error];
             })
-            .then(
+            .then<void>(
               (List<Map<String, dynamic>> list) {
                 // TODO(aam): Investigate why we are validating only first reload report,
                 // which seems to be current behavior
diff --git a/packages/flutter_tools/lib/src/runner/flutter_command_runner.dart b/packages/flutter_tools/lib/src/runner/flutter_command_runner.dart
index edfc07433ca65774818dcc79d1cbb71a9ad7a24c..68cc46f2fca9f006d2620cfba9cd2474fa9bb6bf 100644
--- a/packages/flutter_tools/lib/src/runner/flutter_command_runner.dart
+++ b/packages/flutter_tools/lib/src/runner/flutter_command_runner.dart
@@ -425,7 +425,7 @@ class FlutterCommandRunner extends CommandRunner<Null> {
   List<String> getRepoRoots() {
     final String root = fs.path.absolute(Cache.flutterRoot);
     // not bin, and not the root
-    return <String>['dev', 'examples', 'packages'].map((String item) {
+    return <String>['dev', 'examples', 'packages'].map<String>((String item) {
       return fs.path.join(root, item);
     }).toList();
   }
@@ -434,7 +434,7 @@ class FlutterCommandRunner extends CommandRunner<Null> {
   List<Directory> getRepoPackages() {
     return getRepoRoots()
       .expand<String>((String root) => _gatherProjectPaths(root))
-      .map((String dir) => fs.directory(dir))
+      .map<Directory>((String dir) => fs.directory(dir))
       .toList();
   }
 
diff --git a/packages/flutter_tools/lib/src/services.dart b/packages/flutter_tools/lib/src/services.dart
index 2edceb70de77ac15b1c6db6549076ee9e71d66e1..bdc61d2c10e63922c82334b1bef2174426fa19d3 100644
--- a/packages/flutter_tools/lib/src/services.dart
+++ b/packages/flutter_tools/lib/src/services.dart
@@ -98,7 +98,7 @@ File generateServiceDefinitions(
   String dir, List<Map<String, String>> servicesIn
 ) {
   final List<Map<String, String>> services =
-      servicesIn.map((Map<String, String> service) => <String, String>{
+      servicesIn.map<Map<String, String>>((Map<String, String> service) => <String, String>{
         'name': service['name'],
         'class': service['android-class']
       }).toList();
diff --git a/packages/flutter_tools/lib/src/test/flutter_platform.dart b/packages/flutter_tools/lib/src/test/flutter_platform.dart
index 58ae3c6b664f0ee67e3d5c2dfeccf82bf588fa9b..e734fb28c9f354e0fd5ca4e5ffaf901537dd7a5e 100644
--- a/packages/flutter_tools/lib/src/test/flutter_platform.dart
+++ b/packages/flutter_tools/lib/src/test/flutter_platform.dart
@@ -526,7 +526,7 @@ class _FlutterPlatform extends PlatformPlugin {
           watcher?.handleStartedProcess(ProcessEvent(ourTestCount, process, processObservatoryUri));
         },
         startTimeoutTimer: () {
-          Future<_InitialResult>.delayed(_kTestStartupTimeout).then((_) => timeout.complete());
+          Future<_InitialResult>.delayed(_kTestStartupTimeout).then<void>((_) => timeout.complete());
         },
       );
 
@@ -536,7 +536,7 @@ class _FlutterPlatform extends PlatformPlugin {
       // The local test harness could get bored of us.
 
       printTrace('test $ourTestCount: awaiting initial result for pid ${process.pid}');
-      final _InitialResult initialResult = await Future.any(<Future<_InitialResult>>[
+      final _InitialResult initialResult = await Future.any<_InitialResult>(<Future<_InitialResult>>[
         process.exitCode.then<_InitialResult>((int exitCode) => _InitialResult.crashed),
         timeout.future.then<_InitialResult>((void value) => _InitialResult.timedOut),
         Future<_InitialResult>.delayed(_kTestProcessTimeout, () => _InitialResult.timedOut),
@@ -615,13 +615,13 @@ class _FlutterPlatform extends PlatformPlugin {
           );
 
           printTrace('test $ourTestCount: awaiting test result for pid ${process.pid}');
-          final _TestResult testResult = await Future.any(<Future<_TestResult>>[
+          final _TestResult testResult = await Future.any<_TestResult>(<Future<_TestResult>>[
             process.exitCode.then<_TestResult>((int exitCode) { return _TestResult.crashed; }),
             harnessDone.future.then<_TestResult>((void value) { return _TestResult.harnessBailed; }),
             testDone.future.then<_TestResult>((void value) { return _TestResult.testBailed; }),
           ]);
 
-          await Future.wait(<Future<void>>[
+          await Future.wait<void>(<Future<void>>[
             harnessToTest.cancel(),
             testToHarness.cancel(),
           ]);
@@ -870,8 +870,8 @@ class _FlutterPlatform extends PlatformPlugin {
     const String observatoryString = 'Observatory listening on ';
     for (Stream<List<int>> stream in
         <Stream<List<int>>>[process.stderr, process.stdout]) {
-      stream.transform(utf8.decoder)
-        .transform(const LineSplitter())
+      stream.transform<String>(utf8.decoder)
+        .transform<String>(const LineSplitter())
         .listen(
           (String line) {
             if (line == _kStartTimeoutTimerMessage) {
diff --git a/packages/flutter_tools/lib/src/tester/flutter_tester.dart b/packages/flutter_tools/lib/src/tester/flutter_tester.dart
index 2487d63fb2e4c02ae5df1f482838fb6f11d37777..4e5ff5ff5747dae5da73b43774ae6528898fd2c4 100644
--- a/packages/flutter_tools/lib/src/tester/flutter_tester.dart
+++ b/packages/flutter_tools/lib/src/tester/flutter_tester.dart
@@ -153,16 +153,16 @@ class FlutterTesterDevice extends Device {
         },
       );
       // Setting a bool can't fail in the callback.
-      _process.exitCode.then((_) => _isRunning = false); // ignore: unawaited_futures
+      _process.exitCode.then<void>((_) => _isRunning = false); // ignore: unawaited_futures
       _process.stdout
-          .transform(utf8.decoder)
-          .transform(const LineSplitter())
+          .transform<String>(utf8.decoder)
+          .transform<String>(const LineSplitter())
           .listen((String line) {
         _logReader.addLine(line);
       });
       _process.stderr
-          .transform(utf8.decoder)
-          .transform(const LineSplitter())
+          .transform<String>(utf8.decoder)
+          .transform<String>(const LineSplitter())
           .listen((String line) {
         _logReader.addLine(line);
       });
diff --git a/packages/flutter_tools/lib/src/version.dart b/packages/flutter_tools/lib/src/version.dart
index e1dea0e1ab55b385ce6c7a2a012a87f9c2408cd3..98612c0d19f79d07d80532e43aec72a193b9514a 100644
--- a/packages/flutter_tools/lib/src/version.dart
+++ b/packages/flutter_tools/lib/src/version.dart
@@ -161,7 +161,7 @@ class FlutterVersion {
   static Future<Null> _removeVersionCheckRemoteIfExists() async {
     final List<String> remotes = (await _run(<String>['git', 'remote']))
         .split('\n')
-        .map((String name) => name.trim()) // to account for OS-specific line-breaks
+        .map<String>((String name) => name.trim()) // to account for OS-specific line-breaks
         .toList();
     if (remotes.contains(_versionCheckRemote))
       await _run(<String>['git', 'remote', 'remove', _versionCheckRemote]);
diff --git a/packages/flutter_tools/lib/src/vmservice.dart b/packages/flutter_tools/lib/src/vmservice.dart
index 3fc389a96ce44d35ec94d69b5afc739955816750..ae7652efdef2deeb07fbde1867a686ced2c9ece1 100644
--- a/packages/flutter_tools/lib/src/vmservice.dart
+++ b/packages/flutter_tools/lib/src/vmservice.dart
@@ -289,7 +289,7 @@ class VMService {
     String method,
     Map<String, dynamic> params,
   ) {
-    return Future.any(<Future<Map<String, dynamic>>>[
+    return Future.any<Map<String, dynamic>>(<Future<Map<String, dynamic>>>[
       _peer.sendRequest(method, params).then<Map<String, dynamic>>(castStringKeyedMap),
       _connectionError.future,
     ]);
@@ -954,7 +954,7 @@ class VM extends ServiceObjectOwner {
       return;
     _viewCache.clear();
     for (Isolate isolate in isolates.toList()) {
-      await vmService.vm.invokeRpc('_flutter.listViews',
+      await vmService.vm.invokeRpc<ServiceObject>('_flutter.listViews',
           timeout: kLongRequestTimeout,
           params: <String, dynamic> {'isolateId': isolate.id});
     }
@@ -1208,7 +1208,7 @@ class Isolate extends ServiceObjectOwner {
       <Future<ProgramElement>>[];
     for (Map<String, dynamic> element in response['unused'])
       unusedElements.add(_describeElement(element));
-    return Future.wait(unusedElements);
+    return Future.wait<ProgramElement>(unusedElements);
   }
 
   /// Resumes the isolate.
@@ -1388,7 +1388,7 @@ class ServiceMap extends ServiceObject implements Map<String, dynamic> {
   @override
   void removeWhere(bool test(String key, dynamic value)) => _map.removeWhere(test);
   @override
-  Map<K2, V2> map<K2, V2>(MapEntry<K2, V2> transform(String key, dynamic value)) => _map.map(transform);
+  Map<K2, V2> map<K2, V2>(MapEntry<K2, V2> transform(String key, dynamic value)) => _map.map<K2, V2>(transform);
   @override
   Iterable<MapEntry<String, dynamic>> get entries => _map.entries;
   @override
@@ -1440,7 +1440,7 @@ class FlutterView extends ServiceObject {
 
   Future<Null> setAssetDirectory(Uri assetsDirectory) async {
     assert(assetsDirectory != null);
-    await owner.vmService.vm.invokeRpc('_flutter.setAssetBundlePath',
+    await owner.vmService.vm.invokeRpc<ServiceObject>('_flutter.setAssetBundlePath',
         params: <String, dynamic>{
           'isolateId': _uiIsolate.id,
           'viewId': id,
diff --git a/packages/flutter_tools/lib/src/vscode/vscode_validator.dart b/packages/flutter_tools/lib/src/vscode/vscode_validator.dart
index f68a3ec70e468b4b1289c56dda79c35f8607c58c..b93e1d02984d49608652c50c9f1f28acfed32d9f 100644
--- a/packages/flutter_tools/lib/src/vscode/vscode_validator.dart
+++ b/packages/flutter_tools/lib/src/vscode/vscode_validator.dart
@@ -18,7 +18,7 @@ class VsCodeValidator extends DoctorValidator {
   static Iterable<DoctorValidator> get installedValidators {
     return VsCode
         .allInstalled()
-        .map((VsCode vsCode) => VsCodeValidator(vsCode));
+        .map<DoctorValidator>((VsCode vsCode) => VsCodeValidator(vsCode));
   }
 
   @override
@@ -32,11 +32,11 @@ class VsCodeValidator extends DoctorValidator {
     if (_vsCode.isValid) {
       type = ValidationType.installed;
       messages.addAll(_vsCode.validationMessages
-          .map((String m) => ValidationMessage(m)));
+          .map<ValidationMessage>((String m) => ValidationMessage(m)));
     } else {
       type = ValidationType.partial;
       messages.addAll(_vsCode.validationMessages
-          .map((String m) => ValidationMessage.error(m)));
+          .map<ValidationMessage>((String m) => ValidationMessage.error(m)));
       messages.add(ValidationMessage(
           'Flutter extension not installed; install from\n$extensionMarketplaceUrl'));
     }
diff --git a/packages/flutter_tools/test/android/android_workflow_test.dart b/packages/flutter_tools/test/android/android_workflow_test.dart
index 73c9dc1a8025b85b0670c1e4a257f88c8dc91cd6..9564bd86c5fb27ae20ba0664e1c667c2531a1e95 100644
--- a/packages/flutter_tools/test/android/android_workflow_test.dart
+++ b/packages/flutter_tools/test/android/android_workflow_test.dart
@@ -33,7 +33,7 @@ void main() {
 
   MockProcess Function(List<String>) processMetaFactory(List<String> stdout) {
     final Stream<List<int>> stdoutStream = Stream<List<int>>.fromIterable(
-        stdout.map((String s) => s.codeUnits));
+        stdout.map<List<int>>((String s) => s.codeUnits));
     return (List<String> command) => MockProcess(stdout: stdoutStream);
   }
 
diff --git a/packages/flutter_tools/test/base/context_test.dart b/packages/flutter_tools/test/base/context_test.dart
index f7291dc3d0a41626ecfebfcedd9e1075a345cd68..94ec5675a79a04f7c11bac26feffc67193498e24 100644
--- a/packages/flutter_tools/test/base/context_test.dart
+++ b/packages/flutter_tools/test/base/context_test.dart
@@ -24,7 +24,7 @@ void main() {
       test('returns root context in child of root zone if zone was manually created', () {
         final Zone rootZone = Zone.current;
         final AppContext rootContext = context;
-        runZoned(() {
+        runZoned<void>(() {
           expect(Zone.current, isNot(rootZone));
           expect(Zone.current.parent, rootZone);
           expect(context, rootContext);
@@ -61,7 +61,7 @@ void main() {
         final AppContext rootContext = context;
         await rootContext.run<void>(name: 'child', body: () {
           final AppContext childContext = context;
-          runZoned(() {
+          runZoned<void>(() {
             expect(context, isNot(rootContext));
             expect(context, same(childContext));
             expect(context.name, 'child');
@@ -79,7 +79,7 @@ void main() {
         String value;
         await context.run<void>(
           body: () {
-            outer.future.then((_) {
+            outer.future.then<void>((_) {
               value = context[String];
               inner.complete();
             });
diff --git a/packages/flutter_tools/test/commands/daemon_test.dart b/packages/flutter_tools/test/commands/daemon_test.dart
index 15301da9ffe1606d5439d5712eebbad30514ca69..b1315ea304c7ed94aa1bf0b2d8f347a1c5c4a720 100644
--- a/packages/flutter_tools/test/commands/daemon_test.dart
+++ b/packages/flutter_tools/test/commands/daemon_test.dart
@@ -73,7 +73,7 @@ void main() {
     testUsingContext('printStatus should log to stdout when logToStdout is enabled', () async {
       final StringBuffer buffer = StringBuffer();
 
-      await runZoned(() async {
+      await runZoned<Future<void>>(() async {
         final StreamController<Map<String, dynamic>> commands = StreamController<Map<String, dynamic>>();
         final StreamController<Map<String, dynamic>> responses = StreamController<Map<String, dynamic>>();
         daemon = Daemon(
@@ -228,7 +228,7 @@ void main() {
       daemon.deviceDomain.addDeviceDiscoverer(discoverer);
       discoverer.addDevice(MockAndroidDevice());
 
-      return await responses.stream.skipWhile(_isConnectedEvent).first.then((Map<String, dynamic> response) async {
+      return await responses.stream.skipWhile(_isConnectedEvent).first.then<void>((Map<String, dynamic> response) async {
         expect(response['event'], 'device.added');
         expect(response['params'], isMap);
 
diff --git a/packages/flutter_tools/test/commands/packages_test.dart b/packages/flutter_tools/test/commands/packages_test.dart
index 95c7f461be10f6bf23cf78d6744c2c49f701b269..5f74b3a430d521a9510d736a4c03b37c1e28c857 100644
--- a/packages/flutter_tools/test/commands/packages_test.dart
+++ b/packages/flutter_tools/test/commands/packages_test.dart
@@ -159,7 +159,7 @@ void main() {
         pubOutput,
         pluginRegistrants,
         pluginWitnesses,
-      ].expand((List<String> list) => list);
+      ].expand<String>((List<String> list) => list);
       for (String path in allFiles) {
         final File file = fs.file(fs.path.join(projectPath, path));
         if (file.existsSync())
@@ -285,7 +285,7 @@ void main() {
       final Future<Null> simulateUserInput = Future<Null>(() {
         mockStdio.simulateStdin('y');
       });
-      await Future.wait(<Future<Null>>[runPackages, runPrompt, simulateUserInput]);
+      await Future.wait<Null>(<Future<Null>>[runPackages, runPrompt, simulateUserInput]);
       final List<String> commands = mockProcessManager.commands;
       expect(commands, hasLength(2));
       expect(commands[0], matches(r'dart-sdk[\\/]bin[\\/]pub'));
diff --git a/packages/flutter_tools/test/integration/test_driver.dart b/packages/flutter_tools/test/integration/test_driver.dart
index e70eb1573c3bf80060319144ffa3245449b7468a..b8503a2008c9e626e1db6adaf97ad581ba45a6e3 100644
--- a/packages/flutter_tools/test/integration/test_driver.dart
+++ b/packages/flutter_tools/test/integration/test_driver.dart
@@ -127,7 +127,7 @@ class FlutterTestDriver {
       // Proxy the stream/sink for the VM Client so we can debugPrint it.
       final StreamChannel<String> channel = IOWebSocketChannel.connect(_vmServiceWsUri)
           .cast<String>()
-          .changeStream((Stream<String> stream) => stream.map(_debugPrint))
+          .changeStream((Stream<String> stream) => stream.map<String>(_debugPrint))
           .changeSink((StreamSink<String> sink) =>
               StreamController<String>()
                 ..stream.listen((String s) => sink.add(_debugPrint(s))));
@@ -282,7 +282,7 @@ class FlutterTestDriver {
 
   Future<VMInstanceRef> evaluateExpression(String expression) async {
     final VMFrame topFrame = await getTopStackFrame();
-    return _timeoutWithMessages(() => topFrame.evaluate(expression),
+    return _timeoutWithMessages<VMInstanceRef>(() => topFrame.evaluate(expression),
         message: 'Timed out evaluating expression ($expression)');
   }
 
@@ -334,7 +334,7 @@ class FlutterTestDriver {
       }
     });
 
-    return _timeoutWithMessages(() => response.future,
+    return _timeoutWithMessages<Map<String, dynamic>>(() => response.future,
             timeout: timeout,
             message: event != null
                 ? 'Did not receive expected $event event.'
@@ -406,5 +406,5 @@ class FlutterTestDriver {
 }
 
 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());
 }
diff --git a/packages/flutter_tools/test/src/context.dart b/packages/flutter_tools/test/src/context.dart
index b20bac2a6d13089ecce48993e6fd0c4bb79fa5e5..e91e1559af7b09cf4cac8c30813771bccda79af1 100644
--- a/packages/flutter_tools/test/src/context.dart
+++ b/packages/flutter_tools/test/src/context.dart
@@ -85,7 +85,7 @@ void testUsingContext(String description, dynamic testMethod(), {
         body: () {
           final String flutterRoot = getFlutterRoot();
 
-          return runZoned(() {
+          return runZoned<Future<dynamic>>(() {
             try {
               return context.run<dynamic>(
                 // Apply the overrides to the test context in the zone since their
@@ -198,7 +198,7 @@ class MockDoctor extends Doctor {
   /// the Doctor.
   List<DoctorValidator> get validators {
     final List<DoctorValidator> superValidators = super.validators;
-    return superValidators.map((DoctorValidator v) {
+    return superValidators.map<DoctorValidator>((DoctorValidator v) {
       if (v is AndroidValidator) {
         return MockAndroidWorkflowValidator();
       }
diff --git a/packages/flutter_tools/test/src/mocks.dart b/packages/flutter_tools/test/src/mocks.dart
index d21cc91921ef76c839b8dee5ca34e910d2755942..5bcb4bcce9c214842b0892d2d6963df2524bef2c 100644
--- a/packages/flutter_tools/test/src/mocks.dart
+++ b/packages/flutter_tools/test/src/mocks.dart
@@ -303,8 +303,8 @@ class MockStdio extends Stdio {
     _stdin.add(utf8.encode('$line\n'));
   }
 
-  List<String> get writtenToStdout => _stdout.writes.map(_stdout.encoding.decode).toList();
-  List<String> get writtenToStderr => _stderr.writes.map(_stderr.encoding.decode).toList();
+  List<String> get writtenToStdout => _stdout.writes.map<String>(_stdout.encoding.decode).toList();
+  List<String> get writtenToStderr => _stderr.writes.map<String>(_stderr.encoding.decode).toList();
 }
 
 class MockPollingDeviceDiscovery extends PollingDeviceDiscovery {
diff --git a/packages/flutter_tools/tool/daemon_client.dart b/packages/flutter_tools/tool/daemon_client.dart
index 10f48959ef3bdaedccb196dd472d6a3dd7ad7ca4..d8a1d75994a935907c12a6affcdf862eab11ecf7 100644
--- a/packages/flutter_tools/tool/daemon_client.dart
+++ b/packages/flutter_tools/tool/daemon_client.dart
@@ -23,13 +23,13 @@ Future<Null> main() async {
   print('daemon process started, pid: ${daemon.pid}');
 
   daemon.stdout
-    .transform(utf8.decoder)
-    .transform(const LineSplitter())
+    .transform<String>(utf8.decoder)
+    .transform<String>(const LineSplitter())
     .listen((String line) => print('<== $line'));
   daemon.stderr.listen((dynamic data) => stderr.add(data));
 
   stdout.write('> ');
-  stdin.transform(utf8.decoder).transform(const LineSplitter()).listen((String line) {
+  stdin.transform<String>(utf8.decoder).transform<String>(const LineSplitter()).listen((String line) {
     final List<String> words = line.split(' ');
 
     if (line == 'version' || line == 'v') {
diff --git a/packages/fuchsia_remote_debug_protocol/lib/src/fuchsia_remote_connection.dart b/packages/fuchsia_remote_debug_protocol/lib/src/fuchsia_remote_connection.dart
index f9add30b9d54988d8e8ebc8fb8ccd1d91663d2aa..1fec7cac1bf109a6d221e4b96a4209f7ae32001d 100644
--- a/packages/fuchsia_remote_debug_protocol/lib/src/fuchsia_remote_connection.dart
+++ b/packages/fuchsia_remote_debug_protocol/lib/src/fuchsia_remote_connection.dart
@@ -306,9 +306,9 @@ class FuchsiaRemoteConnection {
       }
       isolates.add(vmService.getMainIsolatesByPattern(pattern));
     }
-    final List<IsolateRef> result = await Future.wait(isolates)
+    final List<IsolateRef> result = await Future.wait<List<IsolateRef>>(isolates)
         .timeout(timeout)
-        .then((List<List<IsolateRef>> listOfLists) {
+        .then<List<IsolateRef>>((List<List<IsolateRef>> listOfLists) {
       final List<List<IsolateRef>> mutableListOfLists =
           List<List<IsolateRef>>.from(listOfLists)
             ..retainWhere((List<IsolateRef> list) => list.isNotEmpty);
@@ -477,7 +477,7 @@ class FuchsiaRemoteConnection {
     await stop();
     final List<int> servicePorts = await getDeviceServicePorts();
     final List<PortForwarder> forwardedVmServicePorts =
-        await Future.wait(servicePorts.map((int deviceServicePort) {
+        await Future.wait<PortForwarder>(servicePorts.map<Future<PortForwarder>>((int deviceServicePort) {
       return fuchsiaPortForwardingFunction(
           _sshCommandRunner.address,
           deviceServicePort,