diff --git a/.github/workflows/codeql-analysis.yml b/.github/workflows/codeql-analysis.yml
index 3967cd447..1b8b4368e 100644
--- a/.github/workflows/codeql-analysis.yml
+++ b/.github/workflows/codeql-analysis.yml
@@ -33,7 +33,7 @@ jobs:
 
       # Initializes the CodeQL tools for scanning.
       - name: Initialize CodeQL
-        uses: github/codeql-action/init@c7f292ea4f542c473194b33813ccd4c207a6c725
+        uses: github/codeql-action/init@904260d7d935dff982205cbdb42025ce30b7a34f
         with:
           languages: ${{ matrix.language }}
           # If you wish to specify custom queries, you can do so here or in a config file.
@@ -44,7 +44,7 @@ jobs:
       # Autobuild attempts to build any compiled languages  (C/C++, C#, or Java).
       # If this step fails, then you should remove it and run the build manually (see below)
       - name: Autobuild
-        uses: github/codeql-action/autobuild@c7f292ea4f542c473194b33813ccd4c207a6c725
+        uses: github/codeql-action/autobuild@904260d7d935dff982205cbdb42025ce30b7a34f
 
       # ℹ️ Command-line programs to run using the OS shell.
       # 📚 https://git.io/JvXDl
@@ -58,4 +58,4 @@ jobs:
       #   make release
 
       - name: Perform CodeQL Analysis
-        uses: github/codeql-action/analyze@c7f292ea4f542c473194b33813ccd4c207a6c725
+        uses: github/codeql-action/analyze@904260d7d935dff982205cbdb42025ce30b7a34f
diff --git a/.github/workflows/scorecards-analysis.yml b/.github/workflows/scorecards-analysis.yml
index 725eac6d6..8f64919b5 100644
--- a/.github/workflows/scorecards-analysis.yml
+++ b/.github/workflows/scorecards-analysis.yml
@@ -17,6 +17,7 @@ jobs:
       security-events: write
       actions: read
       contents: read
+      id-token: write
 
     steps:
       - name: "Checkout code"
@@ -25,7 +26,7 @@ jobs:
           persist-credentials: false
 
       - name: "Run analysis"
-        uses: ossf/scorecard-action@ce330fde6b1a5c9c75b417e7efc510b822a35564
+        uses: ossf/scorecard-action@865b4092859256271290c77adbd10a43f4779972
         with:
           results_file: results.sarif
           results_format: sarif
@@ -48,6 +49,6 @@ jobs:
 
       # Upload the results to GitHub's code scanning dashboard.
       - name: "Upload to code-scanning"
-        uses: github/codeql-action/upload-sarif@c7f292ea4f542c473194b33813ccd4c207a6c725
+        uses: github/codeql-action/upload-sarif@904260d7d935dff982205cbdb42025ce30b7a34f
         with:
           sarif_file: results.sarif
diff --git a/Dockerfile b/Dockerfile
index 6018416e7..e37964a43 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -33,22 +33,22 @@ ENV PATH=$DART_SDK/bin:$PATH
 RUN set -eu; \
     case "$(dpkg --print-architecture)_${DART_CHANNEL}" in \
       amd64_stable) \
-        DART_SHA256="e391c4ed8f623b9748f897cb585d629057c1141f9eaf8e9b2be118932ba11632"; \
+        DART_SHA256="7369fcbfb3c96ed85511224580a8ce0e5ecfc8227af563d396ede2055cdf84e1"; \
         SDK_ARCH="x64";; \
       arm64_stable) \
-        DART_SHA256="06dd7c6eb6c903f5df8b23f9a35f7b1c35ccb869be6b5019c7dd93868ae2bfbf"; \
+        DART_SHA256="1c8d96c0b718873f9ae6d9aa7d866cddefdb86f8b1584cbdf589670d65b7c167"; \
         SDK_ARCH="arm64";; \
       amd64_beta) \
-        DART_SHA256="e391c4ed8f623b9748f897cb585d629057c1141f9eaf8e9b2be118932ba11632"; \
+        DART_SHA256="602d5936c3fad0776b999df2090c4c53354891f386fa71e0d7de9923e94c16e6"; \
         SDK_ARCH="x64";; \
       arm64_beta) \
-        DART_SHA256="06dd7c6eb6c903f5df8b23f9a35f7b1c35ccb869be6b5019c7dd93868ae2bfbf"; \
+        DART_SHA256="a1538410aed74e4f1c42962044ec7341b5ea6a74f815b049352f72c1f75e988b"; \
         SDK_ARCH="arm64";; \
       amd64_dev) \
-        DART_SHA256="688f8b5238632f53f6cbddee7ded17c665dccb00fb639ccab32a43437f18a4c8"; \
+        DART_SHA256="bb9bed8d193c5557f617eb4b89d4aee5894a806d5560157fbe6f5142ac1fadd0"; \
         SDK_ARCH="x64";; \
       arm64_dev) \
-        DART_SHA256="86c628337919bf7802a8551ce338046a95035dd7f075363811576e2828a0d415"; \
+        DART_SHA256="08379b473b7b9fd60ebafee20e4646053b0395e3d2eed49b243b93802a1ec201"; \
         SDK_ARCH="arm64";; \
     esac; \
     SDK="dartsdk-linux-${SDK_ARCH}-release.zip"; \
@@ -80,7 +80,7 @@ CMD ["./tool/test.sh"]
 FROM dart as node
 RUN set -eu; \
     NODE_PPA="node_ppa.sh"; \
-    NODE_SHA256=27932797347f900242caaaeba5c1d7c965b3da70566d81123b15be1c0b80cc2c; \
+    NODE_SHA256=99b85ba817cafd99b50e292a6690d8663b27a76630ac6339c2fc186e3333f4a3; \
     curl -fsSL https://deb.nodesource.com/setup_lts.x -o "$NODE_PPA"; \
     echo "$NODE_SHA256 $NODE_PPA" | sha256sum --check --status --strict - || (\
         echo -e "\n\nNODE CHECKSUM FAILED! Run tool/fetch-node-ppa-sum.sh for updated values.\n\n" && \
diff --git a/examples/async_await/lib/practice_errors/main.dart b/examples/async_await/lib/practice_errors/main.dart
new file mode 100644
index 000000000..f4c6813e3
--- /dev/null
+++ b/examples/async_await/lib/practice_errors/main.dart
@@ -0,0 +1,6 @@
+// ignore_for_file: always_declare_return_types, type_annotate_public_apis
+
+// #docregion
+// Implement changeUsername here
+changeUsername() {}
+// #enddocregion
diff --git a/examples/async_await/lib/practice_errors/solution.dart b/examples/async_await/lib/practice_errors/solution.dart
new file mode 100644
index 000000000..19ba318e0
--- /dev/null
+++ b/examples/async_await/lib/practice_errors/solution.dart
@@ -0,0 +1,11 @@
+import 'test.dart';
+
+// #docregion
+Future<String> changeUsername() async {
+  try {
+    return await fetchNewUsername();
+  } catch (err) {
+    return err.toString();
+  }
+}
+// #enddocregion
diff --git a/examples/async_await/lib/practice_errors/test.dart b/examples/async_await/lib/practice_errors/test.dart
new file mode 100644
index 000000000..b5fec94ba
--- /dev/null
+++ b/examples/async_await/lib/practice_errors/test.dart
@@ -0,0 +1,112 @@
+import 'package:examples_util/codelabs.dart';
+
+import 'solution.dart';
+
+const _result = result;
+
+// #docregion
+List<String> messages = [];
+bool logoutSucceeds = false;
+const passed = 'PASSED';
+const noCatch = 'NO_CATCH';
+const typoMessage = 'Test failed! Check for typos in your return value';
+const oneSecond = Duration(seconds: 1);
+
+class UserError implements Exception {
+  String errMsg() => 'New username is invalid';
+}
+
+Future<String> fetchNewUsername() {
+  var str = Future.delayed(oneSecond, () => throw UserError());
+  return str;
+}
+
+void main() async {
+  try {
+    messages
+      ..add(makeReadable(
+          testLabel: '',
+          testResult: await asyncDidCatchException(changeUsername),
+          readableErrors: {
+            typoMessage: typoMessage,
+            noCatch:
+                'Did you remember to call fetchNewUsername within a try/catch block?',
+          }))
+      ..add(makeReadable(
+          testLabel: '',
+          testResult: await asyncErrorEquals(changeUsername),
+          readableErrors: {
+            typoMessage: typoMessage,
+            noCatch:
+                'Did you remember to call fetchNewUsername within a try/catch block?',
+          }))
+      ..removeWhere((m) => m.contains(passed))
+      ..toList();
+
+    if (messages.isEmpty) {
+      _result(true);
+    } else {
+      _result(false, messages);
+    }
+  } catch (e) {
+    _result(false, ['Tried to run solution, but received an exception: $e']);
+  }
+}
+
+////////////////////////////////////////
+///////////// Test Helpers /////////////
+////////////////////////////////////////
+String makeReadable({
+  required String testResult,
+  required Map<String, String> readableErrors,
+  required String testLabel,
+}) {
+  if (readableErrors.containsKey(testResult)) {
+    var readable = readableErrors[testResult];
+    return '$testLabel $readable';
+  } else {
+    return '$testLabel $testResult';
+  }
+}
+
+void passIfNoMessages(List<String> messages, Map<String, String> readable) {
+  if (messages.isEmpty) {
+    _result(true);
+  } else {
+    final userMessages = messages
+        .where((message) => readable.containsKey(message))
+        .map((message) => readable[message]!)
+        .toList();
+    print(messages);
+
+    _result(false, userMessages);
+  }
+}
+
+///////////////////////////////////////
+//////////// Assertions ///////////////
+///////////////////////////////////////
+Future<String> asyncErrorEquals(Function fn) async {
+  var result = await fn();
+  if (result == UserError().toString()) {
+    return passed;
+  } else {
+    return 'Test failed! Did you stringify and return the caught error?';
+  }
+}
+
+Future<String> asyncDidCatchException(Function fn) async {
+  var caught = true;
+  try {
+    await fn();
+  } on UserError catch (_) {
+    caught = false;
+  }
+
+  if (caught == false) {
+    return noCatch;
+  } else {
+    return passed;
+  }
+}
+// #enddocregion
diff --git a/examples/async_await/lib/practice_using/main.dart b/examples/async_await/lib/practice_using/main.dart
new file mode 100644
index 000000000..24ee37700
--- /dev/null
+++ b/examples/async_await/lib/practice_using/main.dart
@@ -0,0 +1,17 @@
+// ignore_for_file: always_declare_return_types, type_annotate_public_apis
+import 'package:examples_util/codelabs.dart';
+
+// #docregion
+// Part 1
+// You can call the provided async function fetchRole()
+// to return the user role.
+Future<String> reportUserRole() async {
+  TODO('Your implementation goes here.');
+}
+
+// Part 2
+// Implement reportLogins here
+// You can call the provided async function fetchLoginAmount()
+// to return the number of times that the user has logged in.
+reportLogins() {}
+// #enddocregion
diff --git a/examples/async_await/lib/practice_using/solution.dart b/examples/async_await/lib/practice_using/solution.dart
new file mode 100644
index 000000000..84327a2b0
--- /dev/null
+++ b/examples/async_await/lib/practice_using/solution.dart
@@ -0,0 +1,13 @@
+import 'test.dart';
+
+// #docregion
+Future<String> reportUserRole() async {
+  var username = await fetchRole();
+  return 'User role: $username';
+}
+
+Future<String> reportLogins() async {
+  var logins = await fetchLoginAmount();
+  return 'Total number of logins: $logins';
+}
+// #enddocregion
diff --git a/examples/async_await/lib/practice_using/test.dart b/examples/async_await/lib/practice_using/test.dart
new file mode 100644
index 000000000..ea2fb8da2
--- /dev/null
+++ b/examples/async_await/lib/practice_using/test.dart
@@ -0,0 +1,117 @@
+import 'package:examples_util/codelabs.dart';
+
+import 'solution.dart';
+
+const _result = result;
+
+// #docregion
+const role = 'administrator';
+const logins = 42;
+const passed = 'PASSED';
+const testFailedMessage = 'Test failed for the function:';
+const typoMessage = 'Test failed! Check for typos in your return value';
+const didNotImplement =
+    'Test failed! Did you forget to implement or return from ';
+const oneSecond = Duration(seconds: 1);
+List<String> messages = [];
+Future<String> fetchRole() => Future.delayed(oneSecond, () => role);
+Future<int> fetchLoginAmount() => Future.delayed(oneSecond, () => logins);
+
+void main() async {
+  try {
+    messages
+      ..add(makeReadable(
+          testLabel: 'Part 1',
+          testResult: await asyncEquals(
+              expected: 'User role: administrator',
+              actual: await reportUserRole(),
+              typoKeyword: role),
+          readableErrors: {
+            typoMessage: typoMessage,
+            'null': '$didNotImplement reportUserRole?',
+            'User role: Instance of \'Future<String>\'':
+                '$testFailedMessage reportUserRole. Did you use the await keyword?',
+            'User role: Instance of \'_Future<String>\'':
+                '$testFailedMessage reportUserRole. Did you use the await keyword?',
+            'User role:':
+                '$testFailedMessage reportUserRole. Did you return a user role?',
+            'User role: ':
+                '$testFailedMessage reportUserRole. Did you return a user role?',
+            'User role: tester':
+                '$testFailedMessage reportUserRole. Did you invoke fetchRole to fetch the user\'s role?',
+          }))
+      ..add(makeReadable(
+          testLabel: 'Part 2',
+          testResult: await asyncEquals(
+              expected: 'Total number of logins: 42',
+              actual: await reportLogins(),
+              typoKeyword: logins.toString()),
+          readableErrors: {
+            typoMessage: typoMessage,
+            'null': '$didNotImplement reportLogins?',
+            'Total number of logins: Instance of \'Future<int>\'':
+                '$testFailedMessage reportLogins. Did you use the await keyword?',
+            'Total number of logins: Instance of \'_Future<int>\'':
+                '$testFailedMessage reportLogins. Did you use the await keyword?',
+            'Total number of logins: ':
+                '$testFailedMessage reportLogins. Did you return the number of logins?',
+            'Total number of logins:':
+                '$testFailedMessage reportLogins. Did you return the number of logins?',
+            'Total number of logins: 57':
+                '$testFailedMessage reportLogins. Did you invoke fetchLoginAmount to fetch the number of user logins?',
+          }))
+      ..removeWhere((m) => m.contains(passed))
+      ..toList();
+
+    if (messages.isEmpty) {
+      _result(true);
+    } else {
+      _result(false, messages);
+    }
+  } on UnimplementedError {
+    _result(false, [
+      '$didNotImplement reportUserRole?',
+    ]);
+  } catch (e) {
+    _result(false, ['Tried to run solution, but received an exception: $e']);
+  }
+}
+
+////////////////////////////////////////
+///////////// Test Helpers /////////////
+////////////////////////////////////////
+String makeReadable({
+  required String testResult,
+  required Map<String, String> readableErrors,
+  required String testLabel,
+}) {
+  if (readableErrors.containsKey(testResult)) {
+    var readable = readableErrors[testResult];
+    return '$testLabel $readable';
+  } else {
+    return '$testLabel $testResult';
+  }
+}
+
+///////////////////////////////////////
+//////////// Assertions ///////////////
+///////////////////////////////////////
+Future<String> asyncEquals({
+  required String expected,
+  required dynamic actual,
+  required String typoKeyword,
+}) async {
+  var strActual = actual is String ? actual : actual.toString();
+  try {
+    if (expected == actual) {
+      return passed;
+    } else if (strActual.contains(typoKeyword)) {
+      return typoMessage;
+    } else {
+      return strActual;
+    }
+  } catch (e) {
+    return e.toString();
+  }
+}
+// #enddocregion
diff --git a/examples/async_await/lib/putting_together/main.dart b/examples/async_await/lib/putting_together/main.dart
new file mode 100644
index 000000000..e32663157
--- /dev/null
+++ b/examples/async_await/lib/putting_together/main.dart
@@ -0,0 +1,16 @@
+// ignore_for_file: always_declare_return_types, type_annotate_public_apis
+
+// #docregion
+// Part 1
+addHello(String user) {}
+
+// Part 2
+// You can call the provided async function fetchUsername()
+// to return the username.
+greetUser() {}
+
+// Part 3
+// You can call the provided async function logoutUser()
+// to log out the user.
+sayGoodbye() {}
+// #enddocregion
diff --git a/examples/async_await/lib/putting_together/solution.dart b/examples/async_await/lib/putting_together/solution.dart
new file mode 100644
index 000000000..516ef5c08
--- /dev/null
+++ b/examples/async_await/lib/putting_together/solution.dart
@@ -0,0 +1,19 @@
+import 'test.dart';
+
+// #docregion
+String addHello(String user) => 'Hello $user';
+
+Future<String> greetUser() async {
+  var username = await fetchUsername();
+  return addHello(username);
+}
+
+Future<String> sayGoodbye() async {
+  try {
+    var result = await logoutUser();
+    return '$result Thanks, see you next time';
+  } catch (e) {
+    return 'Failed to logout user: $e';
+  }
+}
+// #enddocregion
diff --git a/examples/async_await/lib/putting_together/test.dart b/examples/async_await/lib/putting_together/test.dart
new file mode 100644
index 000000000..4e513f402
--- /dev/null
+++ b/examples/async_await/lib/putting_together/test.dart
@@ -0,0 +1,182 @@
+import 'package:examples_util/codelabs.dart';
+
+import 'solution.dart';
+
+const _result = result;
+
+// #docregion
+List<String> messages = [];
+bool logoutSucceeds = false;
+const passed = 'PASSED';
+const noCatch = 'NO_CATCH';
+const typoMessage = 'Test failed! Check for typos in your return value';
+const didNotImplement =
+    'Test failed! Did you forget to implement or return from ';
+const oneSecond = Duration(seconds: 1);
+
+Future<String> fetchUsername() => Future.delayed(oneSecond, () => 'Jean');
+String failOnce() {
+  if (logoutSucceeds) {
+    return 'Success!';
+  } else {
+    logoutSucceeds = true;
+    throw Exception('Logout failed');
+  }
+}
+
+Future<String> logoutUser() => Future.delayed(oneSecond, failOnce);
+
+void main() async {
+  try {
+    messages
+      ..add(makeReadable(
+          testLabel: 'Part 1',
+          testResult: await asyncEquals(
+              expected: 'Hello Jerry',
+              actual: addHello('Jerry'),
+              typoKeyword: 'Jerry'),
+          readableErrors: {
+            typoMessage: typoMessage,
+            'null': '$didNotImplement addHello?',
+            'Hello Instance of \'Future<String>\'':
+                'Looks like you forgot to use the \'await\' keyword!',
+            'Hello Instance of \'_Future<String>\'':
+                'Looks like you forgot to use the \'await\' keyword!',
+          }))
+      ..add(makeReadable(
+          testLabel: 'Part 2',
+          testResult: await asyncEquals(
+              expected: 'Hello Jean',
+              actual: await greetUser(),
+              typoKeyword: 'Jean'),
+          readableErrors: {
+            typoMessage: typoMessage,
+            'null': '$didNotImplement greetUser?',
+            'HelloJean':
+                'Looks like you forgot the space between \'Hello\' and \'Jean\'',
+            'Hello Instance of \'Future<String>\'':
+                'Looks like you forgot to use the \'await\' keyword!',
+            'Hello Instance of \'_Future<String>\'':
+                'Looks like you forgot to use the \'await\' keyword!',
+            '{Closure: (String) => dynamic from Function \'addHello\': static.(await fetchUsername())}':
+                'Did you place the \'\$\' character correctly?',
+            '{Closure \'addHello\'(await fetchUsername())}':
+                'Did you place the \'\$\' character correctly?',
+          }))
+      ..add(makeReadable(
+          testLabel: 'Part 3',
+          testResult: await asyncDidCatchException(sayGoodbye),
+          readableErrors: {
+            typoMessage:
+                '$typoMessage. Did you add the text \'Thanks, see you next time\'?',
+            'null': '$didNotImplement sayGoodbye?',
+            noCatch:
+                'Did you remember to call logoutUser within a try/catch block?',
+            'Instance of \'Future<String>\' Thanks, see you next time':
+                'Did you remember to use the \'await\' keyword in the sayGoodbye function?',
+            'Instance of \'_Future<String>\' Thanks, see you next time':
+                'Did you remember to use the \'await\' keyword in the sayGoodbye function?',
+          }))
+      ..add(makeReadable(
+          testLabel: 'Part 3',
+          testResult: await asyncEquals(
+              expected: 'Success! Thanks, see you next time',
+              actual: await sayGoodbye(),
+              typoKeyword: 'Success'),
+          readableErrors: {
+            typoMessage:
+                '$typoMessage. Did you add the text \'Thanks, see you next time\'?',
+            'null': '$didNotImplement sayGoodbye?',
+            noCatch:
+                'Did you remember to call logoutUser within a try/catch block?',
+            'Instance of \'Future<String>\' Thanks, see you next time':
+                'Did you remember to use the \'await\' keyword in the sayGoodbye function?',
+            'Instance of \'_Future<String>\' Thanks, see you next time':
+                'Did you remember to use the \'await\' keyword in the sayGoodbye function?',
+            'Instance of \'_Exception\'':
+                'CAUGHT Did you remember to return a string?',
+          }))
+      ..removeWhere((m) => m.contains(passed))
+      ..toList();
+
+    if (messages.isEmpty) {
+      _result(true);
+    } else {
+      _result(false, messages);
+    }
+  } catch (e) {
+    _result(false, ['Tried to run solution, but received an exception: $e']);
+  }
+}
+
+////////////////////////////////////////
+///////////// Test Helpers /////////////
+////////////////////////////////////////
+String makeReadable({
+  required String testResult,
+  required Map<String, String> readableErrors,
+  required String testLabel,
+}) {
+  String? readable;
+  if (readableErrors.containsKey(testResult)) {
+    readable = readableErrors[testResult];
+    return '$testLabel $readable';
+  } else if ((testResult != passed) && (testResult.length < 18)) {
+    readable = typoMessage;
+    return '$testLabel $readable';
+  } else {
+    return '$testLabel $testResult';
+  }
+}
+
+void passIfNoMessages(List<String> messages, Map<String, String> readable) {
+  if (messages.isEmpty) {
+    _result(true);
+  } else {
+    final userMessages = messages
+        .where((message) => readable.containsKey(message))
+        .map((message) => readable[message]!)
+        .toList();
+    print(messages);
+
+    _result(false, userMessages);
+  }
+}
+
+///////////////////////////////////////
+//////////// Assertions ///////////////
+///////////////////////////////////////
+Future<String> asyncEquals({
+  required String expected,
+  required dynamic actual,
+  required String typoKeyword,
+}) async {
+  var strActual = actual is String ? actual : actual.toString();
+  try {
+    if (expected == actual) {
+      return passed;
+    } else if (strActual.contains(typoKeyword)) {
+      return typoMessage;
+    } else {
+      return strActual;
+    }
+  } catch (e) {
+    return e.toString();
+  }
+}
+
+Future<String> asyncDidCatchException(Function fn) async {
+  var caught = true;
+  try {
+    await fn();
+  } on Exception catch (_) {
+    caught = false;
+  }
+
+  if (caught == true) {
+    return passed;
+  } else {
+    return noCatch;
+  }
+}
+// #enddocregion
diff --git a/examples/async_await/pubspec.yaml b/examples/async_await/pubspec.yaml
index 3c26c3683..aeccdf327 100644
--- a/examples/async_await/pubspec.yaml
+++ b/examples/async_await/pubspec.yaml
@@ -4,7 +4,9 @@ description: dart.dev example code.
 environment:
   sdk: '>=2.17.0 <3.0.0'
 
-dev_dependencies:
+dependencies:
   examples_util: {path: ../util}
+
+dev_dependencies:
   lints: ^2.0.0
   test: ^1.19.2
diff --git a/examples/util/lib/codelabs.dart b/examples/util/lib/codelabs.dart
new file mode 100644
index 000000000..ee6597820
--- /dev/null
+++ b/examples/util/lib/codelabs.dart
@@ -0,0 +1,11 @@
+const testKey = '__TESTRESULT__ ';
+
+void result(bool success, [List<String> messages = const []]) {
+  // Join messages into a comma-separated list for inclusion in the JSON array.
+  final joinedMessages = messages.map((m) => '"$m"').join(',');
+  print('$testKey{"success": \$success, "messages": [$joinedMessages]}');
+}
+
+// Placeholder for unimplemented methods in dart-pad exercises.
+// ignore: non_constant_identifier_names
+Never TODO([String message = '']) => throw UnimplementedError(message);
diff --git a/examples/vector_victor/analysis_options.yaml b/examples/vector_victor/analysis_options.yaml
new file mode 100644
index 000000000..5e2133eb6
--- /dev/null
+++ b/examples/vector_victor/analysis_options.yaml
@@ -0,0 +1 @@
+include: ../analysis_options.yaml
diff --git a/examples/vector_victor/lib/vector_victor.dart b/examples/vector_victor/lib/vector_victor.dart
new file mode 100644
index 000000000..1ad6c4c62
--- /dev/null
+++ b/examples/vector_victor/lib/vector_victor.dart
@@ -0,0 +1,9 @@
+// #docregion import
+import 'package:vector_math/vector_math.dart';
+// #enddocregion import
+
+void test() {
+  Vector3 x = Vector3.zero();
+  Vector4 y = Vector4.all(4.0);
+  x.zyx = y.xzz;
+}
diff --git a/examples/vector_victor/pubspec.yaml b/examples/vector_victor/pubspec.yaml
new file mode 100644
index 000000000..f79ff2abd
--- /dev/null
+++ b/examples/vector_victor/pubspec.yaml
@@ -0,0 +1,17 @@
+name: vector_victor
+description: A sample command-line application.
+version: 1.0.0
+# homepage: https://www.example.com
+
+environment:
+  sdk: '>=2.18.0 <3.0.0'
+
+# dependencies:
+#   path: ^1.8.0
+
+dev_dependencies:
+  lints: ^2.0.0
+  test: ^1.16.0
+
+dependencies:
+  vector_math: ^2.1.3
diff --git a/site-shared b/site-shared
index 8c92e5bdf..0fe3c62c7 160000
--- a/site-shared
+++ b/site-shared
@@ -1 +1 @@
-Subproject commit 8c92e5bdfdce14887605de6b5d9d0bd2615876b7
+Subproject commit 0fe3c62c70c0e8c4f1a051a5dec3bbc4eb6c8e57
diff --git a/src/_data/linter_rules.json b/src/_data/linter_rules.json
index 955885262..e0e636323 100644
--- a/src/_data/linter_rules.json
+++ b/src/_data/linter_rules.json
@@ -394,7 +394,7 @@
       "flutter"
     ],
     "fixStatus": "hasFix",
-    "details": "**DO** use key in widget constructors.\n\nIt's a good practice to expose the ability to provide a key when creating public\nwidgets.\n\n**BAD:**\n```dart\nclass MyPublicWidget extends StatelessWidget {\n}\n```\n\n**GOOD:**\n```dart\nclass MyPublicWidget extends StatelessWidget {\n  MyPublicWidget({Key? key}) : super(key: key);\n}\n```\n"
+    "details": "**DO** use key in widget constructors.\n\nIt's a good practice to expose the ability to provide a key when creating public\nwidgets.\n\n**BAD:**\n```dart\nclass MyPublicWidget extends StatelessWidget {\n}\n```\n\n**GOOD:**\n```dart\nclass MyPublicWidget extends StatelessWidget {\n  MyPublicWidget({super.key});\n}\n```\n"
   },
   {
     "name": "valid_regexps",
@@ -654,7 +654,7 @@
       "flutter"
     ],
     "fixStatus": "hasFix",
-    "details": "\n**AVOID** using `forEach` with a function literal.\n\n**BAD:**\n```dart\npeople.forEach((person) {\n  ...\n});\n```\n\n**GOOD:**\n```dart\nfor (var person in people) {\n  ...\n}\n\npeople.forEach(print);\n```\n"
+    "details": "\n**AVOID** using `forEach` with a function literal.\n\nThe `for` loop enables a developer to be clear and explicit as to their intent.\nA return in the body of the `for` loop returns from the body of the function, \nwhere as a return in the body of the `forEach` closure only returns a value \nfor that iteration of the `forEach`. The body of a `for` loop can contain \n`await`s, while the closure body of a `forEach` cannot.\n\n**BAD:**\n```dart\npeople.forEach((person) {\n  ...\n});\n```\n\n**GOOD:**\n```dart\nfor (var person in people) {\n  ...\n}\n```\n"
   },
   {
     "name": "avoid_implementing_value_types",
@@ -958,7 +958,7 @@
     "maturity": "stable",
     "incompatible": [],
     "sets": [],
-    "fixStatus": "needsEvaluation",
+    "fixStatus": "hasFix",
     "details": "\n**DO** sort combinator names alphabetically.\n\n**BAD:**\n```dart\nimport 'a.dart' show B, A hide D, C;\nexport 'a.dart' show B, A hide D, C;\n```\n\n**GOOD:**\n```dart\nimport 'a.dart' show A, B hide C, D;\nexport 'a.dart' show A, B hide C, D;\n```\n\n"
   },
   {
@@ -1266,7 +1266,7 @@
     "maturity": "stable",
     "incompatible": [],
     "sets": [],
-    "fixStatus": "needsEvaluation",
+    "fixStatus": "needsFix",
     "details": "\nSome operations on primitive types are idempotent and can be removed.\n\n**BAD:**\n\n```dart\ndoubleValue.toDouble();\n\nintValue.toInt();\nintValue.round();\nintValue.ceil();\nintValue.floor();\nintValue.truncate();\n\nstring.toString();\nstring = 'hello\\n'\n    'world\\n'\n    ''; // useless empty string\n\n'string with ${x.toString()}';\n```\n"
   },
   {
@@ -2298,6 +2298,16 @@
     "fixStatus": "needsEvaluation",
     "details": "\nUnnecessary `toList()` in spreads.\n\n**BAD:**\n```dart\nchildren: <Widget>[\n  ...['foo', 'bar', 'baz'].map((String s) => Text(s)).toList(),\n]\n```\n\n**GOOD:**\n```dart\nchildren: <Widget>[\n  ...['foo', 'bar', 'baz'].map((String s) => Text(s)),\n]\n```\n\n"
   },
+  {
+    "name": "unreachable_from_main",
+    "description": "Unreachable top-level members in executable libraries.",
+    "group": "style",
+    "maturity": "experimental",
+    "incompatible": [],
+    "sets": [],
+    "fixStatus": "needsEvaluation",
+    "details": "\nTop-level members in an executable library should be used directly inside this\nlibrary.  An executable library is a library that contains a `main` top-level\nfunction or that contains a top-level function annotated with\n`@pragma('vm:entry-point')`).  Executable libraries are not usually imported\nand it's better to avoid defining unused members.\n\nThis rule assumes that an executable library isn't imported by other files\nexcept to execute its `main` function.\n\n**BAD:**\n\n```dart\nmain() {}\nvoid f() {}\n```\n\n**GOOD:**\n\n```dart\nmain() {\n  f();\n}\nvoid f() {}\n```\n\n"
+  },
   {
     "name": "use_colored_box",
     "description": "Use `ColoredBox`.",
@@ -2439,6 +2449,16 @@
     "fixStatus": "needsEvaluation",
     "details": "\n**DO** use string buffers to compose strings.\n\nIn most cases, using a string buffer is preferred for composing strings due to\nits improved performance.\n\n**BAD:**\n```dart\nString foo() {\n  final buffer = '';\n  for (int i = 0; i < 10; i++) {\n    buffer += 'a'; // LINT\n  }\n  return buffer;\n}\n```\n\n**GOOD:**\n```dart\nString foo() {\n  final buffer = StringBuffer();\n  for (int i = 0; i < 10; i++) {\n    buffer.write('a');\n  }\n  return buffer.toString();\n}\n```\n\n"
   },
+  {
+    "name": "use_string_in_part_of_directives",
+    "description": "Use string in part of directives.",
+    "group": "style",
+    "maturity": "stable",
+    "incompatible": [],
+    "sets": [],
+    "fixStatus": "needsFix",
+    "details": "\nFrom [effective dart](https://dart.dev/guides/language/effective-dart/usage#do-use-strings-in-part-of-directives):\n\n**DO** use strings in `part of` directives.\n\n**BAD:**\n\n```dart\npart of my_library;\n```\n\n**GOOD:**\n\n```dart\npart of '../../my_library.dart';\n```\n\n"
+  },
   {
     "name": "use_super_parameters",
     "description": "Use super-initializer parameters where possible.",
diff --git a/src/_data/pkg-vers.json b/src/_data/pkg-vers.json
index c73a91331..08afd2d30 100644
--- a/src/_data/pkg-vers.json
+++ b/src/_data/pkg-vers.json
@@ -3,6 +3,6 @@
     "doc-path": "install",
     "channel": "stable",
     "prev-vers": "1.24.3",
-    "vers": "2.18.0"
+    "vers": "2.18.1"
   }
 }
diff --git a/src/_guides/libraries/c-interop.md b/src/_guides/libraries/c-interop.md
index 948568efb..25abeea43 100644
--- a/src/_guides/libraries/c-interop.md
+++ b/src/_guides/libraries/c-interop.md
@@ -281,9 +281,9 @@ For details, see the following:
 根据平台和库的类型的不同，捆绑（或 **打包** 和 **分发**）
 C 库到 package 或应用并进行加载的方式，有所不同。
 
-* [Flutter `dart:ffi` page][binding]
+* Flutter `dart:ffi` pages: [Android][android], [iOS][ios], and [macOS][macos] 
 
-  [Flutter `dart:ffi` 页面][binding]
+  Flutter 的 `dart:ffi` 页面: [Android][android]、[iOS][ios] 和 [macOS][macos]
 
 * [`dart:ffi` examples]({{page.samples}})
 
@@ -374,7 +374,9 @@ to automatically create FFI wrappers from C header files.
 
 [ABI]: {{site.dart-api}}/{{site.data.pkg-vers.SDK.channel}}/dart-ffi/Abi-class.html
 [AbiSpecificInteger]: {{site.dart-api}}/{{site.data.pkg-vers.SDK.channel}}/dart-ffi/AbiSpecificInteger-class.html
-[binding]: {{site.flutter-docs}}/development/platform-integration/c-interop
+[ios]: {{site.flutter-docs}}/development/platform-integration/ios/c-interop
+[android]: {{site.flutter-docs}}/development/platform-integration/android/c-interop
+[macos]: {{site.flutter-docs}}/development/platform-integration/macos/c-interop
 [FFI]: https://en.wikipedia.org/wiki/Foreign_function_interface
 [hello_world]: {{page.hw}}
 [primitives]: {{page.samples}}/primitives
diff --git a/src/_plugins/date_to_rfc2822.rb b/src/_plugins/date_to_rfc2822.rb
deleted file mode 100644
index 9fdf2fbe4..000000000
--- a/src/_plugins/date_to_rfc2822.rb
+++ /dev/null
@@ -1,14 +0,0 @@
-require 'time'
-
-module RFC2822Filter
-  def date_to_rfc2822(input)
-    if input == 'now'
-      Time.new.rfc2822
-    else
-      # input might be a date and not a string
-      Time.parse(input.to_s).rfc2822
-    end
-  end
-end
-
-Liquid::Template.register_filter(RFC2822Filter)
\ No newline at end of file
diff --git a/src/_plugins/format_num_filter.rb b/src/_plugins/format_num_filter.rb
deleted file mode 100644
index 9c2c87992..000000000
--- a/src/_plugins/format_num_filter.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-module FormatNumFilter
-  def format_num(input, fmt)
-    fmt % input
-  end
-end
-
-Liquid::Template.register_filter(FormatNumFilter)
\ No newline at end of file
diff --git a/src/_plugins/strip_html_filter.rb b/src/_plugins/strip_html_filter.rb
deleted file mode 100644
index a3dcb686c..000000000
--- a/src/_plugins/strip_html_filter.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-module StripHtmlFilter
-  def self.strip_html(input)
-    input.to_s.gsub(/<\/?[^>]*>/,"")
-  end
-end
-
-Liquid::Template.register_filter(StripHtmlFilter)
\ No newline at end of file
diff --git a/src/_tutorials/libraries/shared-pkgs.md b/src/_tutorials/libraries/shared-pkgs.md
index f16a0a1ff..a1e944a53 100644
--- a/src/_tutorials/libraries/shared-pkgs.md
+++ b/src/_tutorials/libraries/shared-pkgs.md
@@ -104,20 +104,11 @@ such as IntelliJ or WebStorm.
 你可以使用命令行工具来调用 Stagehand 工具，
 也可以使用类似 IntelliJ 或 WebStorm 这样的 IDE 来间接使用 Stagehand 工具。
 
-Install or update Stagehand using
-[pub global activate](/tools/pub/cmd/pub-global):
-
-你可以使用 [pub global activate](/tools/pub/cmd/pub-global)
-命令安装或更新 Stagehand 工具：
-
-```terminal
-$ pub global activate stagehand
-```
-
 Run the `dart create` command with the `--help` flag
 to see what kinds of template files it can generate:
 
-现在你可以运行 `dart create` 命令来查看它可以生成的模板文件：
+现在你可以运行 `dart create` 命令，使用
+`--help` 来查看它可以生成的模板文件：
 
 ```terminal
 $ dart create --help
@@ -147,8 +138,9 @@ The contents of your pubspec.yaml file should look something like this:
 
 pubspec.yaml 文件包含了由 YAML 语言撰写的 package 规格。
 （访问 <a href="/tools/pub/pubspec">Pubspec 格式 </a> 获取更多深入的介绍。）
-而你的 pubspec.yaml 文件看起来则应该是这样的：
+而你的 pubspec.yaml 文件看起来则应该是这样的
 
+<?code-excerpt "vector_victor/pubspec.yaml" to="test"?>
 ```yaml
 name: vector_victor
 description: A sample command-line application.
@@ -156,7 +148,7 @@ version: 1.0.0
 # homepage: https://www.example.com
 
 environment:
-  sdk: '>=2.12.0 <3.0.0'
+  sdk: '>=2.18.0 <3.0.0'
 
 # dependencies:
 #   path: ^1.8.0
@@ -182,58 +174,43 @@ of a package that your app uses.
 依赖中的每一项都指定了你应用所使用的 package 名称以及版本。
 
 Let's make the vector_victor app have a dependency
-on the vector_math package,
+on the `vector_math` package,
 which is available at the [pub.dev site]({{site.pub}}).
 
 下面让我们为 vector_victor 应用添加一个名为 vector_math 的 package，
 这个 package 可以在 [pub.dev 网站]({{site.pub}}) 中找到。
 
- 1. Get the current installation details for the package:
-
-    获取 package 当前的安装细节信息：
-
-    {: type="a"}
-     1. Go to [vector_math's entry on the Package
-        site.]({{site.pub-pkg}}/vector_math)
-
-        打开 [pub.dev 网站中 vector_math package 的网页。]({{site.pub-pkg}}/vector_math)
-
-     2. Click the **Installing** tab.
-
-        点击**Installing**标签。
+Run the [`dart pub add`](/tools/pub/cmd/pub-add) command 
+and specify `vector_math`
+to add a dependency on the package:
 
-     3. Copy the **vector_math** line from the sample **dependencies** entry.
-        The entry should look something like this:
+运行 [`dart pub add`](/tools/pub/cmd/pub-add) 命令并指定
+使用 `vector_math`，将其加入你的依赖中。
 
-        拷贝示例 _dependencies_ 实体中有 _vector_math_ 的那一行。 _dependencies_ 实体看起来像下面那样：
-
-        ```yaml
-        dependencies:
-          vector_math: ^2.0.8
-        ```
-
- 2. Edit `pubspec.yaml`.
-
-    编辑 `pubspec.yaml` 文件。
-
- 3. In the dependencies section, add the string you copied from the
-    pub.dev site. Be careful to keep the indentation the same; YAML is
-    picky! For example:
+```terminal
+$ dart pub add vector_math
+Resolving dependencies... 
++ vector_math 2.1.3
+Downloading vector_math 2.1.3...
+Changed 1 dependency!
+```
 
-    在 dependencies 部分，将上面你从 pub.dev 网站拷贝来的文本粘贴添加至这里。
-    这里要注意缩进；必须严格按照 YAML 语言规范！例如：
+This will add `vector_math` to the
+`dependencies` entry of your `pubspec.yaml`,
+resulting in the following:
 
-    ```yaml
-    environment:
-      sdk: '>=2.8.1 <3.0.0'
+这个命令将会将 `vector_math` 加入你工程文件中
+`pubspec.yaml` 的 `dependencies` 部分:
 
-    dependencies:
-      vector_math: ^2.0.8
+<?code-excerpt "vector_victor/pubspec.yaml" from="/^dependencies/"?>
+```yaml
+dependencies:
+  vector_math: ^2.1.3
+```
 
-    dev_dependencies:
-      pedantic: ^1.9.0
-      test: ^1.14.4
-    ```
+You can also find your desired version on the
+[`vector_math` page on pub.dev]({{site.pub-pkg}}/vector_math)
+and add it manually to the dependency section.
 
 For details of what version numbers mean
 and how you can format them,
@@ -259,10 +236,11 @@ as we have done here.
 
 ## 安装依赖的 package
 
-If you're using an IDE or Dart-savvy editor to edit `pubspec.yaml`,
+If you're using a Dart-savvy editor or `dart pub` to edit `pubspec.yaml`,
 it might automatically install the packages your app depends on.
 
-如果你使用 IDE 或适配了 Dart 语言开发的编辑器去编辑 `pubspec.yaml` 文件，
+如果你使用适配了 Dart 语言开发的编辑器或者
+`dart pub` 命令了编辑 `pubspec.yaml` 文件，
 其可能会在你编辑了该文件后自动下载安装相关依赖的 package。
 
 If not, do it yourself by running
@@ -274,7 +252,7 @@ If not, do it yourself by running
 ```terminal
 $ dart pub get
 Resolving dependencies...
-+ vector_math 2.0.8
++ vector_math 2.1.3
 Changed 1 dependency!
 ```
 
@@ -307,25 +285,26 @@ Pub 会创建一个名为 `pubspec.lock` 的文件来标识哪些 package 的哪
 ## 你可以从中获取（或不可获取）什么？
 
 Besides the Dart libraries,
-the vector_math package has other resources that might be useful to you
+the `vector_math` package has other resources that might be useful to you
 that do not get installed into your app directory.
 Let's take a step back for a moment to look at what
 you got and where it came from.
 
-除了 Dart 库以外，vector_math package
+除了 Dart 库以外，`vector_math` package
 可能包含其它对你有用但不会安装到你应用目录的资源。
 让我们后退一步看看你在获取依赖时得到了什么以及它们从何而来。
 
-To see the contents of the vector_math package,
+To see the contents of the `vector_math` package,
 visit the
-<a href="https://github.com/johnmccutchan/vector_math"
+<a href="https://github.com/google/vector_math"
 target="_blank" rel="noopener">Dart vector math repository</a>
-at GitHub.
+on GitHub.
 Although many files and directories are in the repository,
 only one, `lib`, was installed when you ran pub get.
 
-访问 <a href="https://github.com/johnmccutchan/vector_math" target="_blank">Dart 数学矢量仓库 </a>
-的 Github 仓库查看 vector_math package 的具体内容。
+访问 Github 仓库
+<a href="https://github.com/google/vector_math" target="_blank" rel="noopener">Dart 数学矢量仓库</a>
+来查看 `vector_math` package 的具体内容。
 尽管该仓库中有大量的文件和目录，
 但是只有 `lib` 目录下的文件会在你执行 pub get 命令时安装。
 
@@ -425,35 +404,34 @@ Dart SDK 库是内置的且由特殊的 `dart:` 前缀标识。
    获取 package 中主要库的导入流程：
 
    {: type="a"}
-   1. Go to [vector_math's entry on the Package
-      site.]({{site.pub-pkg}}/vector_math)
+   1. Go to the [`vector_math` page on pub.dev.]({{site.pub-pkg}}/vector_math)
 
-      打开
-      [pub.dev 网站中 vector_math package 的网页。]({{site.pub-pkg}}/vector_math)
+      打开 [pub.dev 网站中 `vector_math` package 的网页。]({{site.pub-pkg}}/vector_math)
 
    2. Click the **Installing** tab.
 
-      点击**Installing**标签。
+      点击 **Installing** 标签。
 
    3. Copy the **import** line. It should look something like this:
 
-      拷贝有**import**的这一行代码。其看起来像下面这样：
+      拷贝有 **import** 的这一行代码。其看起来像下面这样：
 
+      <?code-excerpt "vector_victor/lib/vector_victor.dart (import)"?>
       ```dart
       import 'package:vector_math/vector_math.dart';
       ```
 
 2. In your vector_victor app, edit `lib/vector_victor.dart`,
-   so that it imports the vector_math library and uses some of its API.
+   so that it imports the `vector_math` library and uses some of its API.
    For inspiration, look at the
-   [vector_math API
+   [`vector_math` API
    docs]({{site.pub-api}}/vector_math/latest),
    which you can find from the pub.dev site entry.
 
    在你的 vector_victor 应用中，编辑 `lib/vector_victor.dart` 文件，
    由此它导入 vector_math 库并使用了它的一些 API。
    你可以阅读
-   [vector_math API 文档]({{site.pub-api}}/documentation/vector_math/latest)
+   [vector_math API 文档]({{site.pub-api}}/vector_math/latest)
    获取更多相关信息。
 
    {{site.alert.note}}
diff --git a/src/codelabs/async-await.md b/src/codelabs/async-await.md
index 4e761ba16..a6a1bd6f5 100644
--- a/src/codelabs/async-await.md
+++ b/src/codelabs/async-await.md
@@ -449,8 +449,8 @@ Implement an `async` function `reportLogins()` so that it does the following:
   * Example return value from `reportLogins()`: `"Total number of logins: 57"`
 * Gets the number of logins by calling the provided function `fetchLoginAmount()`.
 
-```dart:run-dartpad:theme-dark:height-380px:ga_id-practice_using
-{$ begin main.dart $}
+<?code-excerpt "async_await/lib/practice_using/main.dart"?>
+```dart:start-dartpad:theme-dark:height-380px:ga_id-practice_using:file-main.dart
 // Part 1
 // You can call the provided async function fetchRole()
 // to return the user role.
@@ -463,8 +463,10 @@ Future<String> reportUserRole() async {
 // You can call the provided async function fetchLoginAmount()
 // to return the number of times that the user has logged in.
 reportLogins() {}
-{$ end main.dart $}
-{$ begin solution.dart $}
+```
+
+<?code-excerpt "async_await/lib/practice_using/solution.dart"?>
+```dart:file-solution.dart
 Future<String> reportUserRole() async {
   var username = await fetchRole();
   return 'User role: $username';
@@ -474,14 +476,17 @@ Future<String> reportLogins() async {
   var logins = await fetchLoginAmount();
   return 'Total number of logins: $logins';
 }
-{$ end solution.dart $}
-{$ begin test.dart $}
+```
+
+<?code-excerpt "async_await/lib/practice_using/test.dart"?>
+```dart:file-test.dart
 const role = 'administrator';
 const logins = 42;
 const passed = 'PASSED';
 const testFailedMessage = 'Test failed for the function:';
 const typoMessage = 'Test failed! Check for typos in your return value';
-const didNotImplement = 'Test failed! Did you forget to implement or return from ';
+const didNotImplement =
+    'Test failed! Did you forget to implement or return from ';
 const oneSecond = Duration(seconds: 1);
 List<String> messages = [];
 Future<String> fetchRole() => Future.delayed(oneSecond, () => role);
@@ -491,39 +496,45 @@ void main() async {
   try {
     messages
       ..add(makeReadable(
-
-        testLabel: 'Part 1',
-        testResult: await asyncEquals(
-          expected: 'User role: administrator',
-          actual: await reportUserRole(),
-          typoKeyword: role
-        ),
-        readableErrors: {
-          typoMessage: typoMessage,
-          'null': '$didNotImplement reportUserRole?',
-          'User role: Instance of \'Future<String>\'': '$testFailedMessage reportUserRole. Did you use the await keyword?',
-          'User role: Instance of \'_Future<String>\'': '$testFailedMessage reportUserRole. Did you use the await keyword?',
-          'User role:' : '$testFailedMessage reportUserRole. Did you return a user role?',
-          'User role: ' : '$testFailedMessage reportUserRole. Did you return a user role?',
-          'User role: tester' : '$testFailedMessage reportUserRole. Did you invoke fetchRole to fetch the user\'s role?',
-        }))
-
+          testLabel: 'Part 1',
+          testResult: await asyncEquals(
+              expected: 'User role: administrator',
+              actual: await reportUserRole(),
+              typoKeyword: role),
+          readableErrors: {
+            typoMessage: typoMessage,
+            'null': '$didNotImplement reportUserRole?',
+            'User role: Instance of \'Future<String>\'':
+                '$testFailedMessage reportUserRole. Did you use the await keyword?',
+            'User role: Instance of \'_Future<String>\'':
+                '$testFailedMessage reportUserRole. Did you use the await keyword?',
+            'User role:':
+                '$testFailedMessage reportUserRole. Did you return a user role?',
+            'User role: ':
+                '$testFailedMessage reportUserRole. Did you return a user role?',
+            'User role: tester':
+                '$testFailedMessage reportUserRole. Did you invoke fetchRole to fetch the user\'s role?',
+          }))
       ..add(makeReadable(
-        testLabel: 'Part 2',
-        testResult: await asyncEquals(
-          expected: 'Total number of logins: 42',
-          actual: await reportLogins(),
-          typoKeyword: logins.toString()
-        ),
-        readableErrors: {
-          typoMessage: typoMessage,
-          'null': '$didNotImplement reportLogins?',
-          'Total number of logins: Instance of \'Future<int>\'': '$testFailedMessage reportLogins. Did you use the await keyword?',
-          'Total number of logins: Instance of \'_Future<int>\'': '$testFailedMessage reportLogins. Did you use the await keyword?',
-          'Total number of logins: ': '$testFailedMessage reportLogins. Did you return the number of logins?',
-          'Total number of logins:': '$testFailedMessage reportLogins. Did you return the number of logins?',
-          'Total number of logins: 57': '$testFailedMessage reportLogins. Did you invoke fetchLoginAmount to fetch the number of user logins?',
-        }))
+          testLabel: 'Part 2',
+          testResult: await asyncEquals(
+              expected: 'Total number of logins: 42',
+              actual: await reportLogins(),
+              typoKeyword: logins.toString()),
+          readableErrors: {
+            typoMessage: typoMessage,
+            'null': '$didNotImplement reportLogins?',
+            'Total number of logins: Instance of \'Future<int>\'':
+                '$testFailedMessage reportLogins. Did you use the await keyword?',
+            'Total number of logins: Instance of \'_Future<int>\'':
+                '$testFailedMessage reportLogins. Did you use the await keyword?',
+            'Total number of logins: ':
+                '$testFailedMessage reportLogins. Did you return the number of logins?',
+            'Total number of logins:':
+                '$testFailedMessage reportLogins. Did you return the number of logins?',
+            'Total number of logins: 57':
+                '$testFailedMessage reportLogins. Did you invoke fetchLoginAmount to fetch the number of user logins?',
+          }))
       ..removeWhere((m) => m.contains(passed))
       ..toList();
 
@@ -546,7 +557,7 @@ void main() async {
 ////////////////////////////////////////
 String makeReadable({
   required String testResult,
-  required Map readableErrors,
+  required Map<String, String> readableErrors,
   required String testLabel,
 }) {
   if (readableErrors.containsKey(testResult)) {
@@ -561,8 +572,8 @@ String makeReadable({
 //////////// Assertions ///////////////
 ///////////////////////////////////////
 Future<String> asyncEquals({
-  expected,
-  actual,
+  required String expected,
+  required dynamic actual,
   required String typoKeyword,
 }) async {
   var strActual = actual is String ? actual : actual.toString();
@@ -574,18 +585,18 @@ Future<String> asyncEquals({
     } else {
       return strActual;
     }
-  } catch(e) {
+  } catch (e) {
     return e.toString();
   }
 }
-{$ end test.dart $}
-{$ begin hint.txt $}
+```
+
+```text:end-dartpad:file-hint.txt
 Did you remember to add the async keyword to the reportUserRole() function?
 
 Did you remember to use the await keyword before invoking fetchRole()?
 
 Remember: reportUserRole() needs to return a future!
-{$ end hint.txt $}
 ```
 
 {{site.alert.note}}
@@ -668,12 +679,14 @@ that does the following:
     and
     [Errors.]({{site.dart-api}}/{{site.data.pkg-vers.SDK.channel}}/dart-core/Error-class.html)
 
-```dart:run-dartpad:theme-dark:height-380px:ga_id-practice_errors
-{$ begin main.dart $}
+<?code-excerpt "async_await/lib/practice_errors/main.dart"?>
+```dart:start-dartpad:theme-dark:height-380px:ga_id-practice_errors:file-main.dart
 // Implement changeUsername here
 changeUsername() {}
-{$ end main.dart $}
-{$ begin solution.dart $}
+```
+
+<?code-excerpt "async_await/lib/practice_errors/solution.dart"?>
+```dart:file-solution.dart
 Future<String> changeUsername() async {
   try {
     return await fetchNewUsername();
@@ -681,8 +694,10 @@ Future<String> changeUsername() async {
     return err.toString();
   }
 }
-{$ end solution.dart $}
-{$ begin test.dart $}
+```
+
+<?code-excerpt "async_await/lib/practice_errors/test.dart"?>
+```dart:file-test.dart
 List<String> messages = [];
 bool logoutSucceeds = false;
 const passed = 'PASSED';
@@ -694,31 +709,30 @@ class UserError implements Exception {
   String errMsg() => 'New username is invalid';
 }
 
-Future fetchNewUsername() {
+Future<String> fetchNewUsername() {
   var str = Future.delayed(oneSecond, () => throw UserError());
   return str;
 }
 
 void main() async {
   try {
-    // ignore: cascade_invocations
     messages
       ..add(makeReadable(
           testLabel: '',
           testResult: await asyncDidCatchException(changeUsername),
           readableErrors: {
             typoMessage: typoMessage,
-            noCatch: 'Did you remember to call fetchNewUsername within a try/catch block?',
-          }
-      ))
+            noCatch:
+                'Did you remember to call fetchNewUsername within a try/catch block?',
+          }))
       ..add(makeReadable(
           testLabel: '',
           testResult: await asyncErrorEquals(changeUsername),
           readableErrors: {
             typoMessage: typoMessage,
-            noCatch: 'Did you remember to call fetchNewUsername within a try/catch block?',
-          }
-      ))
+            noCatch:
+                'Did you remember to call fetchNewUsername within a try/catch block?',
+          }))
       ..removeWhere((m) => m.contains(passed))
       ..toList();
 
@@ -737,7 +751,7 @@ void main() async {
 ////////////////////////////////////////
 String makeReadable({
   required String testResult,
-  required Map readableErrors,
+  required Map<String, String> readableErrors,
   required String testLabel,
 }) {
   if (readableErrors.containsKey(testResult)) {
@@ -748,13 +762,11 @@ String makeReadable({
   }
 }
 
-void passIfNoMessages(List<String> messages, Map<String, String> readable){
+void passIfNoMessages(List<String> messages, Map<String, String> readable) {
   if (messages.isEmpty) {
     _result(true);
   } else {
-
-    // ignore: omit_local_variable_types
-    List<String> userMessages = messages
+    final userMessages = messages
         .where((message) => readable.containsKey(message))
         .map((message) => readable[message]!)
         .toList();
@@ -763,6 +775,7 @@ void passIfNoMessages(List<String> messages, Map<String, String> readable){
     _result(false, userMessages);
   }
 }
+
 ///////////////////////////////////////
 //////////// Assertions ///////////////
 ///////////////////////////////////////
@@ -779,7 +792,7 @@ Future<String> asyncDidCatchException(Function fn) async {
   var caught = true;
   try {
     await fn();
-  } on UserError catch(_) {
+  } on UserError catch (_) {
     caught = false;
   }
 
@@ -789,12 +802,12 @@ Future<String> asyncDidCatchException(Function fn) async {
     return passed;
   }
 }
-{$ end test.dart $}
-{$ begin hint.txt $}
+```
+
+```text:end-dartpad:file-hint.txt
 Implement changeUsername() to return the string from fetchNewUsername() or
 (if that fails) the string value of any error that occurs.
 You'll need a try-catch statement to catch and handle errors.
-{$ end hint.txt $}
 ```
 
 {% comment %}
@@ -843,8 +856,8 @@ Write the following:
   `'<result> Thanks, see you next time'`, where `<result>` is
   the string value returned by calling `logoutUser()`.
 
-```dart:run-dartpad:theme-dark:height-380px:ga_id-putting_it_all_together
-{$ begin main.dart $}
+<?code-excerpt "async_await/lib/putting_together/main.dart"?>
+```dart:start-dartpad:theme-dark:height-380px:ga_id-putting_it_all_together:file-main.dart
 // Part 1
 addHello(String user) {}
 
@@ -857,8 +870,10 @@ greetUser() {}
 // You can call the provided async function logoutUser()
 // to log out the user.
 sayGoodbye() {}
-{$ end main.dart $}
-{$ begin solution.dart $}
+```
+
+<?code-excerpt "async_await/lib/putting_together/solution.dart"?>
+```dart:file-solution.dart
 String addHello(String user) => 'Hello $user';
 
 Future<String> greetUser() async {
@@ -874,18 +889,21 @@ Future<String> sayGoodbye() async {
     return 'Failed to logout user: $e';
   }
 }
-{$ end solution.dart $}
-{$ begin test.dart $}
+```
+
+<?code-excerpt "async_await/lib/putting_together/test.dart"?>
+```dart:file-test.dart
 List<String> messages = [];
 bool logoutSucceeds = false;
 const passed = 'PASSED';
 const noCatch = 'NO_CATCH';
 const typoMessage = 'Test failed! Check for typos in your return value';
-const didNotImplement = 'Test failed! Did you forget to implement or return from ';
+const didNotImplement =
+    'Test failed! Did you forget to implement or return from ';
 const oneSecond = Duration(seconds: 1);
 
 Future<String> fetchUsername() => Future.delayed(oneSecond, () => 'Jean');
-String failOnce () {
+String failOnce() {
   if (logoutSucceeds) {
     return 'Success!';
   } else {
@@ -894,72 +912,80 @@ String failOnce () {
   }
 }
 
-logoutUser() => Future.delayed(oneSecond, failOnce);
+Future<String> logoutUser() => Future.delayed(oneSecond, failOnce);
 
 void main() async {
   try {
-    // ignore: cascade_invocations
     messages
       ..add(makeReadable(
-
-        testLabel: 'Part 1',
-        testResult: await asyncEquals(
-          expected: 'Hello Jerry',
-          actual: addHello('Jerry'),
-          typoKeyword: 'Jerry'
-        ),
-        readableErrors: {
-          typoMessage: typoMessage,
-          'null': '$didNotImplement addHello?',
-          'Hello Instance of \'Future<String>\'': 'Looks like you forgot to use the \'await\' keyword!',
-          'Hello Instance of \'_Future<String>\'': 'Looks like you forgot to use the \'await\' keyword!',
-        }))
+          testLabel: 'Part 1',
+          testResult: await asyncEquals(
+              expected: 'Hello Jerry',
+              actual: addHello('Jerry'),
+              typoKeyword: 'Jerry'),
+          readableErrors: {
+            typoMessage: typoMessage,
+            'null': '$didNotImplement addHello?',
+            'Hello Instance of \'Future<String>\'':
+                'Looks like you forgot to use the \'await\' keyword!',
+            'Hello Instance of \'_Future<String>\'':
+                'Looks like you forgot to use the \'await\' keyword!',
+          }))
       ..add(makeReadable(
-
-        testLabel: 'Part 2',
-        testResult: await asyncEquals(
-          expected: 'Hello Jean',
-          actual: await greetUser(),
-          typoKeyword: 'Jean'
-        ),
-        readableErrors: {
-          typoMessage: typoMessage,
-          'null': '$didNotImplement greetUser?',
-          'HelloJean' : 'Looks like you forgot the space between \'Hello\' and \'Jean\'',
-          'Hello Instance of \'Future<String>\'': 'Looks like you forgot to use the \'await\' keyword!',
-          'Hello Instance of \'_Future<String>\'': 'Looks like you forgot to use the \'await\' keyword!',
-          '{Closure: (String) => dynamic from Function \'addHello\': static.(await fetchUsername())}': 'Did you place the \'\$\' character correctly?',
-          '{Closure \'addHello\'(await fetchUsername())}': 'Did you place the \'\$\' character correctly?', 
-        }))
+          testLabel: 'Part 2',
+          testResult: await asyncEquals(
+              expected: 'Hello Jean',
+              actual: await greetUser(),
+              typoKeyword: 'Jean'),
+          readableErrors: {
+            typoMessage: typoMessage,
+            'null': '$didNotImplement greetUser?',
+            'HelloJean':
+                'Looks like you forgot the space between \'Hello\' and \'Jean\'',
+            'Hello Instance of \'Future<String>\'':
+                'Looks like you forgot to use the \'await\' keyword!',
+            'Hello Instance of \'_Future<String>\'':
+                'Looks like you forgot to use the \'await\' keyword!',
+            '{Closure: (String) => dynamic from Function \'addHello\': static.(await fetchUsername())}':
+                'Did you place the \'\$\' character correctly?',
+            '{Closure \'addHello\'(await fetchUsername())}':
+                'Did you place the \'\$\' character correctly?',
+          }))
       ..add(makeReadable(
-        testLabel: 'Part 3',
-        testResult: await asyncDidCatchException(sayGoodbye),
-        readableErrors: {
-          typoMessage: '$typoMessage. Did you add the text \'Thanks, see you next time\'?',
-          'null': '$didNotImplement sayGoodbye?',
-          noCatch: 'Did you remember to call logoutUser within a try/catch block?',
-          'Instance of \'Future<String>\' Thanks, see you next time':'Did you remember to use the \'await\' keyword in the sayGoodbye function?',
-          'Instance of \'_Future<String>\' Thanks, see you next time':'Did you remember to use the \'await\' keyword in the sayGoodbye function?',
-        }
-      ))
+          testLabel: 'Part 3',
+          testResult: await asyncDidCatchException(sayGoodbye),
+          readableErrors: {
+            typoMessage:
+                '$typoMessage. Did you add the text \'Thanks, see you next time\'?',
+            'null': '$didNotImplement sayGoodbye?',
+            noCatch:
+                'Did you remember to call logoutUser within a try/catch block?',
+            'Instance of \'Future<String>\' Thanks, see you next time':
+                'Did you remember to use the \'await\' keyword in the sayGoodbye function?',
+            'Instance of \'_Future<String>\' Thanks, see you next time':
+                'Did you remember to use the \'await\' keyword in the sayGoodbye function?',
+          }))
       ..add(makeReadable(
-        testLabel: 'Part 3',
-        testResult: await asyncEquals(
-          expected: 'Success! Thanks, see you next time',
-          actual: await sayGoodbye(),
-          typoKeyword: 'Success'
-        ),
-        readableErrors: {
-          typoMessage: '$typoMessage. Did you add the text \'Thanks, see you next time\'?',
-          'null': '$didNotImplement sayGoodbye?',
-          noCatch: 'Did you remember to call logoutUser within a try/catch block?',
-          'Instance of \'Future<String>\' Thanks, see you next time':'Did you remember to use the \'await\' keyword in the sayGoodbye function?',
-          'Instance of \'_Future<String>\' Thanks, see you next time':'Did you remember to use the \'await\' keyword in the sayGoodbye function?',
-          'Instance of \'_Exception\'': 'CAUGHT Did you remember to return a string?',
-          }
-      ))
-    ..removeWhere((m) => m.contains(passed))
-    ..toList();
+          testLabel: 'Part 3',
+          testResult: await asyncEquals(
+              expected: 'Success! Thanks, see you next time',
+              actual: await sayGoodbye(),
+              typoKeyword: 'Success'),
+          readableErrors: {
+            typoMessage:
+                '$typoMessage. Did you add the text \'Thanks, see you next time\'?',
+            'null': '$didNotImplement sayGoodbye?',
+            noCatch:
+                'Did you remember to call logoutUser within a try/catch block?',
+            'Instance of \'Future<String>\' Thanks, see you next time':
+                'Did you remember to use the \'await\' keyword in the sayGoodbye function?',
+            'Instance of \'_Future<String>\' Thanks, see you next time':
+                'Did you remember to use the \'await\' keyword in the sayGoodbye function?',
+            'Instance of \'_Exception\'':
+                'CAUGHT Did you remember to return a string?',
+          }))
+      ..removeWhere((m) => m.contains(passed))
+      ..toList();
 
     if (messages.isEmpty) {
       _result(true);
@@ -991,13 +1017,11 @@ String makeReadable({
   }
 }
 
-void passIfNoMessages(List<String> messages, Map<String, String> readable){
+void passIfNoMessages(List<String> messages, Map<String, String> readable) {
   if (messages.isEmpty) {
     _result(true);
   } else {
-
-    // ignore: omit_local_variable_types
-    List<String> userMessages = messages
+    final userMessages = messages
         .where((message) => readable.containsKey(message))
         .map((message) => readable[message]!)
         .toList();
@@ -1006,12 +1030,13 @@ void passIfNoMessages(List<String> messages, Map<String, String> readable){
     _result(false, userMessages);
   }
 }
+
 ///////////////////////////////////////
 //////////// Assertions ///////////////
 ///////////////////////////////////////
 Future<String> asyncEquals({
-  expected,
-  actual,
+  required String expected,
+  required dynamic actual,
   required String typoKeyword,
 }) async {
   var strActual = actual is String ? actual : actual.toString();
@@ -1023,7 +1048,7 @@ Future<String> asyncEquals({
     } else {
       return strActual;
     }
-  } catch(e) {
+  } catch (e) {
     return e.toString();
   }
 }
@@ -1032,7 +1057,7 @@ Future<String> asyncDidCatchException(Function fn) async {
   var caught = true;
   try {
     await fn();
-  } on Exception catch(_) {
+  } on Exception catch (_) {
     caught = false;
   }
 
@@ -1042,11 +1067,11 @@ Future<String> asyncDidCatchException(Function fn) async {
     return noCatch;
   }
 }
-{$ end test.dart $}
-{$ begin hint.txt $}
+```
+
+```text:end-dartpad:file-hint.txt
 The greetUser() and sayGoodbye() functions are asynchronous;
 addHello() isn't.
-{$ end hint.txt $}
 ```
 
 ## What's next?
diff --git a/src/codelabs/dart-cheatsheet.md b/src/codelabs/dart-cheatsheet.md
index 78e6dc28b..72a2ede02 100644
--- a/src/codelabs/dart-cheatsheet.md
+++ b/src/codelabs/dart-cheatsheet.md
@@ -2488,7 +2488,7 @@ To make the constructor const, you'll need to make all the properties final.
 {$ end hint.txt $}
 ```
 
-## What next?
+## What's next?
 
 ## 下一步是什么？
 
diff --git a/src/null-safety/index.md b/src/null-safety/index.md
index d298a6262..d7bb5b52a 100644
--- a/src/null-safety/index.md
+++ b/src/null-safety/index.md
@@ -5,20 +5,72 @@ description: Information about Dart's null safety feature
 description: Dart 空安全的有关内容
 ---
 
-The Dart language now supports sound null safety!
+The Dart language comes with sound null safety.
+
+Dart 语言包含了健全的空安全特性。
+
+Null safety prevents errors that result from unintentional access
+of variables set to `null`.
+For example, if a method expects an integer but receives `null`,
+your app causes a runtime error. This type of error, a null dereference error,
+can be difficult to debug.
+
+空安全会在编译期防止意外访问 `null` 变量的错误的产生。
+例如，如果一个方法需要整型结果，却接收到了 `null`，你的应用会出现运行时错误。
+这类空引用错误在以前调试是非常困难的。
+
+With sound null safety variables are 'non-nullable' by default:
+They can be assigned only values of the declared type
+(e.g. `int i=42`), and never be assigned `null`.
+You can specify that a type of a variable is nullable
+(e.g. `int? i`),
+and only then can they contain either a `null` *or*
+a value of the defined type.
+
+有了健全的空安全体系，变量默认是「非空」的：
+它们可以赋予与定义的类型相同类型的任意值（例如 `int i = 42`），
+且永远不能被设置为 `null`。
+你可以指定一个类型为可空（例如 `int? i`），
+这类变量只能包含对应类型的值或者 `null`。
+
+Sound null safety changes potential **runtime errors**
+into **edit-time** analysis errors, by flagging when
+any non-nullable variable hasn't been initialized with a 
+non-null value or is being assigned a `null`.
+This allows you to fix these errors before deploying your app.
+
+健全的空安全通过对非空变量的未被初始化或以 `null` 初始化的情况进行标记，
+把潜在的 **运行时错误** 转变成了 **编辑时** 的分析错误。
+这样的特性让你在开发应用的过程中就可以修复这类错误。
+
+{{site.alert.warn}}
+
+  In Dart 2.x SDKs, you can enable or disable sound null safety 
+  through configuration of the project SDK constraint.
+  To learn more, see [Enabling/disabling null safety](#enable-null-safety).
+
+  在 Dart 2.x 版本的 SDK 里，你可以通过设置项目的 SDK 限制来控制是否启用空安全。
+  你可以通过 [启用/禁用空安全](#enable-null-safety) 小节来了解更多。
+
+  Dart 3--planned for a mid-2023 release--
+  will require sound null safety. It will prevent code from running without it.
+  All existing code must be [migrated](#migrate) to sound null safety
+  to be compatible with Dart 3.
+  To learn more, see the [Dart 3 sound null safety tracking issue][].
+
+  预计在 2023 年中发布的 Dart 3 计划强制使用空安全。
+  该版本不允许未使用空安全的代码运行。
+  所有的代码都需要 [迁移](#migrate) 至健全的空安全，以适配 Dart 3。
+  你可以通过 [Dart 3 空安全问题跟踪][Dart 3 sound null safety tracking issue]
+  来了解更多。
 
-Dart 语言已支持健全的空安全机制！
+{{site.alert.end}}
+
+[Dart 3 sound null safety tracking issue]: https://github.com/dart-lang/sdk/issues/49530
 
-When you opt into null safety,
-types in your code are non-nullable by default, meaning that
-variables can’t contain `null` _unless you say they can._
-With null safety, your **runtime** null-dereference errors
-turn into **edit-time** analysis errors.
+## Introduction through examples
 
-当你选择使用空安全时，代码中的类型将默认是非空的，
-意味着 **除非你声明它们可空**，它们的值都不能为空。
-有了空安全，原本处于你的 **运行时** 的空值引用错误
-将变为 **编辑时** 的分析错误。
+## 通过示例代码介绍空安全
 
 With null safety,
 all of the variables in the following code are non-nullable:
@@ -42,22 +94,15 @@ just add `?` to its type declaration:
 int? aNullableInt = null;
 ```
 
-You can
-[use null safety](#enable-null-safety) in your normal development environment,
-[migrate existing code][migration guide] to use null safety,
-or try null safety in [DartPad]({{site.dartpad}}).
+- To try an interactive example,
+  see the [null safety codelab][Null safety codelab].
 
-你可以在你的普通开发环境中 [使用空安全](#enable-null-safety)，
-也建议 [迁移你项目中的代码][migration guide] 至空安全，
-或者通过 [支持空安全的 DartPad]({{site.dartpad}}) 进行空安全特性实验。
+  你可以通过 [空安全 Codelab][Null safety codelab] 交互示例快速了解空安全。
 
-For an interactive, example-driven introduction to null safety language features,
-see the [null safety codelab][Null safety codelab].
-For an in-depth discussion, see
-[Understanding null safety](/null-safety/understanding-null-safety).
+- To learn more about this topic, see
+  [Understanding null safety](/null-safety/understanding-null-safety).
 
-若你想通过一个交互示例快速了解空安全，可以查看 [空安全 Codelab][Null safety codelab]。
-更深入的探讨，可以阅读 [深入理解空安全](/null-safety/understanding-null-safety)。
+  更深入的探讨，可以阅读文档 [深入理解空安全](/null-safety/understanding-null-safety)。
 
 ## Null safety principles
 
@@ -96,58 +141,56 @@ Dart 的空安全支持基于以下三条核心原则：
   你会享有健全性带来的所有优势&mdash;&mdash;
   更少的 BUG、更小的二进制文件以及更快的执行速度。
 
-## Enabling null safety {#enable-null-safety}
-
-## 启用空安全 {#enable-null-safety}
+## Enabling/disabling null safety {#enable-null-safety}
 
-Sound null safety is available in Dart 2.12 and Flutter 2.
+## 启用和禁用空安全 {#enable-null-safety}
 
-健全的空安全已在 Dart 2.12 和 Flutter 2 中可用。
+You can use sound null safety in Dart 2.12 and Flutter 2.0 or later.
+Dart 3 and later will [_only_ support sound null safety][Dart 3 sound null safety tracking issue].
 
-### Migrating an existing package or app {#migrate}
-
-### 迁移已有 package 或应用 {#migrate}
+健全的空安全已在 Dart 2.12 和 Flutter 2.0 及更高版本中可用。
+[Dart 3 及以后的版本将 **只支持** 健全的空安全][Dart 3 sound null safety tracking issue]。
 
-For instructions on how to migrate your code to null safety,
-see the [migration guide][].
+<a id="constraints"></a>
+To enable sound null safety, set the
+[SDK constraint lower-bound](/tools/pub/pubspec#sdk-constraints)
+to a [language version][] of 2.12 or later.
+For example, your `pubspec.yaml` file might have the following constraints:
 
-若你需要代码迁移的指导，请查看 [迁移至空安全][migration guide]。
+想要启用健全空安全，你需要将 [SDK 的最低版本约束](/tools/pub/pubspec#sdk-constraints)
+设定为 2.12 或者更高的 [语言版本][language version]。
+例如，你的 `pubspec.yaml` 可以设置为如下的限制：
 
-{{site.alert.version-note}}
+```yaml
+environment:
+  sdk: '>=2.12.0 <3.0.0'
+```
 
-  Before Dart 2.13, the templates used by the [`dart create`][] command
-  and IDEs aren't null safe, so you need to migrate the code they create.
-  For example:
+[language version]: /guides/language/evolution#language-versioning
 
-  使用 Dart 2.13 以前版本的 [`dart create`][] 命令或 IDE 创建的模板，
-  尚未迁移至空安全。在创建后你还需要对它们进行迁移。举个例子：
+### Migrating an existing package or app {#migrate}
 
-  ```terminal
-  $ dart create -t console my_cli
-  $ cd my_cli
-  $ dart migrate --apply-changes
-  ```
-{{site.alert.end}}
+### 迁移现有的 package 或应用 {#migrate}
 
-### Behind the scenes: SDK constraints {#constraints}
+The Dart SDK includes the `dart migrate` tool.
+This tool helps you migrate code that supports sound null safety. 
+Use `dart migrate` if you wrote Dart code with Dart 2.12 or earlier.
 
-### 幕后工作：SDK 限制 {#constraints}
+Dart SDK 内置了 `dart migrate` 工具。
+该工具会帮助你迁移你的代码至健全的空安全。
+如果你的代码是在 Dart 2.12 或更早前编写的（未完全支持空安全），
+你就可以使用这个工具进行迁移。
 
-To make Dart treat your code as null safe,
-the [SDK constraints](/tools/pub/pubspec#sdk-constraints)
-must require a [language version][] that has null safety support.
-For example, your `pubspec.yaml` file might have the following constraints:
+```terminal
+$ cd my_app
+$ dart migrate
+```
 
-将 [SDK 版本约束](/tools/pub/pubspec#sdk-constraints)
-设定为一个支持空安全的 SDK 版本。
-例如，你的 `pubspec.yaml` 可以设置为如下的限制：
+To learn how to migrate your code to null safety,
+see the [migration guide][].
 
-```yaml
-environment:
-  sdk: '>=2.12.0 <3.0.0'
-```
+你可以阅读 [迁移指南][migration guide] 来学习如何迁移你的代码至空安全。
 
-[language version]: /guides/language/evolution#language-versioning
 
 ## Where to learn more
 
diff --git a/src/tools/diagnostic-messages.md b/src/tools/diagnostic-messages.md
index 8631dcd6d..028dd8634 100644
--- a/src/tools/diagnostic-messages.md
+++ b/src/tools/diagnostic-messages.md
@@ -349,7 +349,7 @@ class [!C!] extends AbiSpecificInteger {
 }
 {% endprettify %}
 
-The following code produces this diagnostic because the class `C` defineS
+The following code produces this diagnostic because the class `C` defines
 a field:
 
 {% prettify dart tag=pre+code %}
@@ -468,8 +468,8 @@ class C extends AbiSpecificInteger {
 
 ### abi_specific_integer_mapping_unsupported
 
-_Only mappings to 'Int8', 'Int16', 'Int32', 'Int64', 'Uint8', 'Uint16',
-'UInt32', and 'Uint64' are supported._
+_Invalid mapping to '{0}'; only mappings to 'Int8', 'Int16', 'Int32', 'Int64',
+'Uint8', 'Uint16', 'UInt32', and 'Uint64' are supported._
 
 #### Description
 
@@ -493,7 +493,7 @@ entry is `Array<Uint8>`, which isn't a valid integer type:
 {% prettify dart tag=pre+code %}
 import 'dart:ffi';
 
-@[!AbiSpecificIntegerMapping!]({Abi.macosX64 : Array<Uint8>(4)})
+@AbiSpecificIntegerMapping({Abi.macosX64 : [!Array<Uint8>(4)!]})
 class C extends AbiSpecificInteger {
   const C();
 }
@@ -4158,7 +4158,7 @@ class C {
 {% endprettify %}
 
 If there are multiple named constructors and all except one of them are
-unneeded, then remove the constructorsthat aren't needed:
+unneeded, then remove the constructors that aren't needed:
 
 {% prettify dart tag=pre+code %}
 class C {
@@ -7310,8 +7310,6 @@ Given a [part file][] named `part.dart` containing the following:
 
 {% prettify dart tag=pre+code %}
 part of lib;
-
-class C{}
 {% endprettify %}
 
 The following code produces this diagnostic because imported files can't
@@ -7321,8 +7319,6 @@ have a part-of directive:
 library lib;
 
 import [!'part.dart'!];
-
-C c = C();
 {% endprettify %}
 
 #### Common fixes
@@ -12996,7 +12992,7 @@ class C {
 
 ### non_type_as_type_argument
 
-_The name '{0}' isn't a type so it can't be used as a type argument._
+_The name '{0}' isn't a type, so it can't be used as a type argument._
 
 #### Description
 
@@ -14117,88 +14113,6 @@ class C extends Struct {
 }
 {% endprettify %}
 
-### packed_nesting_non_packed
-
-_Nesting the non-packed or less tightly packed struct '{0}' in a packed struct
-'{1}' isn't supported._
-
-#### Description
-
-The analyzer produces this diagnostic when a subclass of `Struct` that is
-annotated as being `Packed` declares a field whose type is also a subclass
-of `Struct` and the field's type is either not packed or is packed less
-tightly.
-
-For more information about FFI, see [C interop using dart:ffi][ffi].
-
-#### Example
-
-The following code produces this diagnostic because the class `Outer`,
-which is a subclass of `Struct` and is packed on 1-byte boundaries,
-declared a field whose type (`Inner`) is packed on 8-byte boundaries:
-
-{% prettify dart tag=pre+code %}
-import 'dart:ffi';
-
-@Packed(8)
-class Inner extends Struct {
-  external Pointer<Uint8> notEmpty;
-}
-
-@Packed(1)
-class Outer extends Struct {
-  external Pointer<Uint8> notEmpty;
-
-  external [!Inner!] nestedLooselyPacked;
-}
-{% endprettify %}
-
-#### Common fixes
-
-If the inner struct should be packed more tightly, then change the
-argument to the inner struct's `Packed` annotation:
-
-{% prettify dart tag=pre+code %}
-import 'dart:ffi';
-
-@Packed(1)
-class Inner extends Struct {
-  external Pointer<Uint8> notEmpty;
-}
-
-@Packed(1)
-class Outer extends Struct {
-  external Pointer<Uint8> notEmpty;
-
-  external Inner nestedLooselyPacked;
-}
-{% endprettify %}
-
-If the outer struct should be packed less tightly, then change the
-argument to the outer struct's `Packed` annotation:
-
-{% prettify dart tag=pre+code %}
-import 'dart:ffi';
-
-@Packed(8)
-class Inner extends Struct {
-  external Pointer<Uint8> notEmpty;
-}
-
-@Packed(8)
-class Outer extends Struct {
-  external Pointer<Uint8> notEmpty;
-
-  external Inner nestedLooselyPacked;
-}
-{% endprettify %}
-
-If the inner struct doesn't have an annotation and should be packed, then
-add an annotation.
-
-If the inner struct doesn't have an annotation and the outer struct
-shouldn't be packed, then remove its annotation.
-
 ### part_of_different_library
 
 _Expected this library to be part of '{0}', not '{1}'._
@@ -16538,7 +16452,7 @@ class B extends a.A {}
 
 ### subtype_of_disallowed_type
 
-_''{0}' can't be used as a superclass constraint._
+_'{0}' can't be used as a superclass constraint._
 
 _Classes and mixins can't implement '{0}'._
 
@@ -17123,7 +17037,7 @@ _Invalid context for 'super' invocation._
 #### Description
 
 The analyzer produces this diagnostic when the keyword `super` is used
-outside of a instance method.
+outside of an instance method.
 
 #### Example
 
@@ -19484,11 +19398,19 @@ _The declaration '{0}' isn't referenced._
 The analyzer produces this diagnostic when a private declaration isn't
 referenced in the library that contains the declaration. The following
 kinds of declarations are analyzed:
-- Private top-level declarations, such as classes, enums, mixins, typedefs,
-  top-level variables, and top-level functions
-- Private static and instance methods
+- Private top-level declarations and all of their members
+- Private members of public declarations
 - Optional parameters of private functions for which a value is never
-  passed, even when the parameter doesn't have a private name
+  passed
+
+Not all references to an element will mark it as "used":
+- Assigning a value to a top-level variable (with a standard `=`
+  assignment, or a null-aware `??=` assignment) does not count as using
+  it.
+- Referring to an element in a doc comment reference does not count as
+  using it.
+- Referring to a class, mixin, or enum on the right side of an `is`
+  expression does not count as using it.
 
 #### Example
 
@@ -20371,5 +20293,3 @@ Iterable<String> get zero sync* {
   yield '0';
 }
 {% endprettify %}
-
-[C interop using dart:ffi]: /guides/libraries/c-interop
diff --git a/tool/analyze-and-test-examples.sh b/tool/analyze-and-test-examples.sh
index 1ca015787..8b27bb8e4 100755
--- a/tool/analyze-and-test-examples.sh
+++ b/tool/analyze-and-test-examples.sh
@@ -60,7 +60,7 @@ function toggle_in_file_analyzer_flags() {
   fi
   printf "\n$(blue "Toggling in-file flags: '$action'")\n"
   find $dir -name "*.dart" ! -path "**/.*" -exec perl \
-    -i -pe "s{//$mark(ignore(_for_file)?: .*?\b(stable|beta|dev)\b)}{//$toggle\$dir}g" {} \;
+    -i -pe "s{//$mark(ignore(_for_file)?: .*?\b(stable|beta|dev)\b)}{//$toggle\$1}g" {} \;
 }
 
 # Analyze and test code for arg $1