diff --git a/pkg/front_end/test/spell_checking_list_tests.txt b/pkg/front_end/test/spell_checking_list_tests.txt
index af163706629..32567bde15e 100644
--- a/pkg/front_end/test/spell_checking_list_tests.txt
+++ b/pkg/front_end/test/spell_checking_list_tests.txt
@@ -306,6 +306,7 @@ extern
 f\u
 fa
 fac
+failsafe
 faking
 falling
 faults
@@ -835,6 +836,7 @@ walt
 warmup
 week
 weekly
+went
 wherever
 whiskers
 wildcards
diff --git a/pkg/front_end/tool/_fasta/generate_messages.dart b/pkg/front_end/tool/_fasta/generate_messages.dart
index 6642de10027..978359d6d57 100644
--- a/pkg/front_end/tool/_fasta/generate_messages.dart
+++ b/pkg/front_end/tool/_fasta/generate_messages.dart
@@ -2,16 +2,14 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'dart:io' show File, exitCode;
-
-import "package:_fe_analyzer_shared/src/messages/severity.dart"
-    show severityEnumNames;
+import 'dart:io' show File;
 
 import 'package:dart_style/dart_style.dart' show DartFormatter;
 
-import 'package:yaml/yaml.dart' show loadYaml;
-
 import '../../test/utils/io_utils.dart' show computeRepoDirUri;
+import 'generate_messages_lib.dart';
+
+export 'generate_messages_lib.dart';
 
 void main(List<String> arguments) {
   final Uri repoDir = computeRepoDirUri();
@@ -28,451 +26,7 @@ void main(List<String> arguments) {
   }
 }
 
-Uri computeSharedGeneratedFile(Uri repoDir) {
-  return repoDir
-      .resolve("pkg/_fe_analyzer_shared/lib/src/messages/codes_generated.dart");
-}
-
-Uri computeCfeGeneratedFile(Uri repoDir) {
-  return repoDir
-      .resolve("pkg/front_end/lib/src/fasta/fasta_codes_cfe_generated.dart");
-}
-
-class Messages {
-  final String sharedMessages;
-  final String cfeMessages;
-
-  Messages(this.sharedMessages, this.cfeMessages);
-}
-
 Messages generateMessagesFiles(Uri repoDir) {
-  Uri messagesFile = repoDir.resolve("pkg/front_end/messages.yaml");
-  Map<dynamic, dynamic> yaml =
-      loadYaml(new File.fromUri(messagesFile).readAsStringSync());
-  StringBuffer sharedMessages = new StringBuffer();
-  StringBuffer cfeMessages = new StringBuffer();
-
-  const String preamble1 = """
-// Copyright (c) 2021, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-""";
-
-  const String preamble2 = """
-
-// NOTE: THIS FILE IS GENERATED. DO NOT EDIT.
-//
-// Instead modify 'pkg/front_end/messages.yaml' and run
-// 'pkg/front_end/tool/fasta generate-messages' to update.
-
-// ignore_for_file: lines_longer_than_80_chars
-""";
-
-  sharedMessages.writeln(preamble1);
-  sharedMessages.writeln(preamble2);
-  sharedMessages.writeln("""
-part of _fe_analyzer_shared.messages.codes;
-""");
-
-  cfeMessages.writeln(preamble1);
-  cfeMessages.writeln("""
-
-""");
-  cfeMessages.writeln(preamble2);
-  cfeMessages.writeln("""
-part of fasta.codes;
-""");
-
-  bool hasError = false;
-  int largestIndex = 0;
-  final indexNameMap = new Map<int, String>();
-
-  List<String> keys = yaml.keys.cast<String>().toList()..sort();
-  for (String name in keys) {
-    var description = yaml[name];
-    while (description is String) {
-      description = yaml[description];
-    }
-    Map<dynamic, dynamic>? map = description;
-    if (map == null) {
-      throw "No 'problemMessage:' in key $name.";
-    }
-    var index = map['index'];
-    if (index != null) {
-      if (index is! int || index < 1) {
-        print('Error: Expected positive int for "index:" field in $name,'
-            ' but found $index');
-        hasError = true;
-        index = -1;
-        // Continue looking for other problems.
-      } else {
-        String? otherName = indexNameMap[index];
-        if (otherName != null) {
-          print('Error: The "index:" field must be unique, '
-              'but is the same for $otherName and $name');
-          hasError = true;
-          // Continue looking for other problems.
-        } else {
-          indexNameMap[index] = name;
-          if (largestIndex < index) {
-            largestIndex = index;
-          }
-        }
-      }
-    }
-    Template template = compileTemplate(name, index, map['problemMessage'],
-        map['correctionMessage'], map['analyzerCode'], map['severity']);
-    if (template.isShared) {
-      sharedMessages.writeln(template.text);
-    } else {
-      cfeMessages.writeln(template.text);
-    }
-  }
-  if (largestIndex > indexNameMap.length) {
-    print('Error: The "index:" field values should be unique, consecutive'
-        ' whole numbers starting with 1.');
-    hasError = true;
-    // Fall through to print more information.
-  }
-  if (hasError) {
-    exitCode = 1;
-    print('The largest index is $largestIndex');
-    final sortedIndices = indexNameMap.keys.toList()..sort();
-    int nextAvailableIndex = largestIndex + 1;
-    for (int index = 1; index <= sortedIndices.length; ++index) {
-      if (sortedIndices[index - 1] != index) {
-        nextAvailableIndex = index;
-        break;
-      }
-    }
-    print('The next available index is ${nextAvailableIndex}');
-    return new Messages('', '');
-  }
-
-  return new Messages(new DartFormatter().format("$sharedMessages"),
-      new DartFormatter().format("$cfeMessages"));
-}
-
-final RegExp placeholderPattern =
-    new RegExp("#\([-a-zA-Z0-9_]+\)(?:%\([0-9]*\)\.\([0-9]+\))?");
-
-class Template {
-  final String text;
-  final isShared;
-
-  Template(this.text, {this.isShared}) : assert(isShared != null);
-}
-
-Template compileTemplate(String name, int? index, String? problemMessage,
-    String? correctionMessage, Object? analyzerCode, String? severity) {
-  if (problemMessage == null) {
-    print('Error: missing problemMessage for message: $name');
-    exitCode = 1;
-    return new Template('', isShared: true);
-  }
-  // Remove trailing whitespace. This is necessary for templates defined with
-  // `|` (verbatim) as they always contain a trailing newline that we don't
-  // want.
-  problemMessage = problemMessage.trimRight();
-  var parameters = new Set<String>();
-  var conversions = new Set<String>();
-  var conversions2 = new Set<String>();
-  var arguments = new Set<String>();
-  bool hasLabeler = false;
-  bool canBeShared = true;
-  void ensureLabeler() {
-    if (hasLabeler) return;
-    conversions
-        .add("TypeLabeler labeler = new TypeLabeler(isNonNullableByDefault);");
-    hasLabeler = true;
-    canBeShared = false;
-  }
-
-  for (Match match in placeholderPattern
-      .allMatches("$problemMessage\n${correctionMessage ?? ''}")) {
-    String name = match[1]!;
-    String? padding = match[2];
-    String? fractionDigits = match[3];
-
-    String format(String name) {
-      String conversion;
-      if (fractionDigits == null) {
-        conversion = "'\$$name'";
-      } else {
-        conversion = "$name.toStringAsFixed($fractionDigits)";
-      }
-      if (padding!.isNotEmpty) {
-        if (padding.startsWith("0")) {
-          conversion += ".padLeft(${int.parse(padding)}, '0')";
-        } else {
-          conversion += ".padLeft(${int.parse(padding)})";
-        }
-      }
-      return conversion;
-    }
-
-    switch (name) {
-      case "character":
-        parameters.add("String character");
-        conversions.add("if (character.runes.length != 1)"
-            "throw \"Not a character '\${character}'\";");
-        arguments.add("'$name': character");
-        break;
-
-      case "unicode":
-        // Write unicode value using at least four (but otherwise no more than
-        // necessary) hex digits, using uppercase letters.
-        // http://www.unicode.org/versions/Unicode10.0.0/appA.pdf
-        parameters.add("int codePoint");
-        conversions.add("String unicode = \"U+\${codePoint.toRadixString(16)"
-            ".toUpperCase().padLeft(4, '0')}\";");
-        arguments.add("'$name': codePoint");
-        break;
-
-      case "name":
-        parameters.add("String name");
-        conversions.add("if (name.isEmpty) throw 'No name provided';");
-        arguments.add("'$name': name");
-        conversions.add("name = demangleMixinApplicationName(name);");
-        break;
-
-      case "name2":
-        parameters.add("String name2");
-        conversions.add("if (name2.isEmpty) throw 'No name provided';");
-        arguments.add("'$name': name2");
-        conversions.add("name2 = demangleMixinApplicationName(name2);");
-        break;
-
-      case "name3":
-        parameters.add("String name3");
-        conversions.add("if (name3.isEmpty) throw 'No name provided';");
-        arguments.add("'$name': name3");
-        conversions.add("name3 = demangleMixinApplicationName(name3);");
-        break;
-
-      case "name4":
-        parameters.add("String name4");
-        conversions.add("if (name4.isEmpty) throw 'No name provided';");
-        arguments.add("'$name': name4");
-        conversions.add("name4 = demangleMixinApplicationName(name4);");
-        break;
-
-      case "nameOKEmpty":
-        parameters.add("String nameOKEmpty");
-        conversions.add("if (nameOKEmpty.isEmpty) "
-            "nameOKEmpty = '(unnamed)';");
-        arguments.add("'nameOKEmpty': nameOKEmpty");
-        break;
-
-      case "names":
-        parameters.add("List<String> _names");
-        conversions.add("if (_names.isEmpty) throw 'No names provided';");
-        arguments.add("'$name': _names");
-        conversions.add("String names = itemizeNames(_names);");
-        break;
-
-      case "lexeme":
-        parameters.add("Token token");
-        conversions.add("String lexeme = token.lexeme;");
-        arguments.add("'$name': token");
-        break;
-
-      case "lexeme2":
-        parameters.add("Token token2");
-        conversions.add("String lexeme2 = token2.lexeme;");
-        arguments.add("'$name': token2");
-        break;
-
-      case "string":
-        parameters.add("String string");
-        conversions.add("if (string.isEmpty) throw 'No string provided';");
-        arguments.add("'$name': string");
-        break;
-
-      case "string2":
-        parameters.add("String string2");
-        conversions.add("if (string2.isEmpty) throw 'No string provided';");
-        arguments.add("'$name': string2");
-        break;
-
-      case "string3":
-        parameters.add("String string3");
-        conversions.add("if (string3.isEmpty) throw 'No string provided';");
-        arguments.add("'$name': string3");
-        break;
-
-      case "stringOKEmpty":
-        parameters.add("String stringOKEmpty");
-        conversions.add("if (stringOKEmpty.isEmpty) "
-            "stringOKEmpty = '(empty)';");
-        arguments.add("'$name': stringOKEmpty");
-        break;
-
-      case "type":
-      case "type2":
-      case "type3":
-      case "type4":
-        parameters.add("DartType _${name}");
-        ensureLabeler();
-        conversions
-            .add("List<Object> ${name}Parts = labeler.labelType(_${name});");
-        conversions2.add("String ${name} = ${name}Parts.join();");
-        arguments.add("'${name}': _${name}");
-        break;
-
-      case "uri":
-        parameters.add("Uri uri_");
-        conversions.add("String? uri = relativizeUri(uri_);");
-        arguments.add("'$name': uri_");
-        break;
-
-      case "uri2":
-        parameters.add("Uri uri2_");
-        conversions.add("String? uri2 = relativizeUri(uri2_);");
-        arguments.add("'$name': uri2_");
-        break;
-
-      case "uri3":
-        parameters.add("Uri uri3_");
-        conversions.add("String? uri3 = relativizeUri(uri3_);");
-        arguments.add("'$name': uri3_");
-        break;
-
-      case "count":
-        parameters.add("int count");
-        arguments.add("'$name': count");
-        break;
-
-      case "count2":
-        parameters.add("int count2");
-        arguments.add("'$name': count2");
-        break;
-
-      case "constant":
-        parameters.add("Constant _constant");
-        ensureLabeler();
-        conversions.add(
-            "List<Object> ${name}Parts = labeler.labelConstant(_${name});");
-        conversions2.add("String ${name} = ${name}Parts.join();");
-        arguments.add("'$name': _constant");
-        break;
-
-      case "num1":
-        parameters.add("num _num1");
-        conversions.add("String num1 = ${format('_num1')};");
-        arguments.add("'$name': _num1");
-        break;
-
-      case "num2":
-        parameters.add("num _num2");
-        conversions.add("String num2 = ${format('_num2')};");
-        arguments.add("'$name': _num2");
-        break;
-
-      case "num3":
-        parameters.add("num _num3");
-        conversions.add("String num3 = ${format('_num3')};");
-        arguments.add("'$name': _num3");
-        break;
-
-      default:
-        throw "Unhandled placeholder in template: '$name'";
-    }
-  }
-
-  if (hasLabeler) {
-    parameters.add("bool isNonNullableByDefault");
-  }
-
-  conversions.addAll(conversions2);
-
-  String interpolate(String text) {
-    text = text
-        .replaceAll(r"$", r"\$")
-        .replaceAllMapped(placeholderPattern, (Match m) => "\${${m[1]}}");
-    return "\"\"\"$text\"\"\"";
-  }
-
-  List<String> codeArguments = <String>[];
-  if (index != null) {
-    codeArguments.add('index: $index');
-  } else if (analyzerCode != null) {
-    if (analyzerCode is String) {
-      analyzerCode = <String>[analyzerCode];
-    }
-    List<Object?> codes = analyzerCode as List<Object?>;
-    // If "index:" is defined, then "analyzerCode:" should not be generated
-    // in the front end. See comment in messages.yaml
-    codeArguments.add('analyzerCodes: <String>["${codes.join('", "')}"]');
-  }
-  if (severity != null) {
-    String? severityEnumName = severityEnumNames[severity];
-    if (severityEnumName == null) {
-      throw "Unknown severity '$severity'";
-    }
-    codeArguments.add('severity: Severity.$severityEnumName');
-  }
-
-  if (parameters.isEmpty && conversions.isEmpty && arguments.isEmpty) {
-    codeArguments.add('problemMessage: r"""$problemMessage"""');
-    if (correctionMessage != null) {
-      codeArguments.add('correctionMessage: r"""$correctionMessage"""');
-    }
-
-    return new Template("""
-// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
-const Code<Null> code$name = message$name;
-
-// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
-const MessageCode message$name =
-    const MessageCode(\"$name\", ${codeArguments.join(', ')},);
-""", isShared: canBeShared);
-  }
-
-  List<String> templateArguments = <String>[];
-  templateArguments.add('\"$name\"');
-  templateArguments.add('problemMessageTemplate: r"""$problemMessage"""');
-  if (correctionMessage != null) {
-    templateArguments
-        .add('correctionMessageTemplate: r"""$correctionMessage"""');
-  }
-
-  templateArguments.add("withArguments: _withArguments$name");
-
-  List<String> messageArguments = <String>[];
-  String message = interpolate(problemMessage);
-  if (hasLabeler) {
-    message += " + labeler.originMessages";
-  }
-  messageArguments.add("problemMessage: ${message}");
-  if (correctionMessage != null) {
-    messageArguments
-        .add("correctionMessage: ${interpolate(correctionMessage)}");
-  }
-  messageArguments.add("arguments: { ${arguments.join(', ')}, }");
-
-  if (codeArguments.isNotEmpty) {
-    codeArguments.add("");
-  }
-
-  return new Template("""
-// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
-const Template<Message Function(${parameters.join(', ')})> template$name =
-    const Template<Message Function(${parameters.join(', ')})>(
-        ${templateArguments.join(', ')},);
-
-// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
-const Code<Message Function(${parameters.join(', ')})> code$name =
-    const Code<Message Function(${parameters.join(', ')})>(
-        \"$name\", ${codeArguments.join(', ')});
-
-// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
-Message _withArguments$name(${parameters.join(', ')}) {
-  ${conversions.join('\n  ')}
-  return new Message(
-     code$name,
-     ${messageArguments.join(', ')},);
-}
-""", isShared: canBeShared);
+  return generateMessagesFilesRaw(
+      repoDir, (s) => new DartFormatter().format(s));
 }
diff --git a/pkg/front_end/tool/_fasta/generate_messages_failsafe.dart b/pkg/front_end/tool/_fasta/generate_messages_failsafe.dart
new file mode 100644
index 00000000000..4b6fa63a0e6
--- /dev/null
+++ b/pkg/front_end/tool/_fasta/generate_messages_failsafe.dart
@@ -0,0 +1,39 @@
+// Copyright (c) 2024, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:io';
+
+import '../../test/utils/io_utils.dart' show computeRepoDirUri;
+
+import 'generate_messages_lib.dart';
+
+void main(List<String> arguments) {
+  print("Running the fail-safe version.");
+  final Uri repoDir = computeRepoDirUri();
+  Messages message = generateMessagesFilesRaw(repoDir, (s) => s);
+  if (message.sharedMessages.trim().isEmpty ||
+      message.cfeMessages.trim().isEmpty) {
+    print("Bailing because of errors: "
+        "Refusing to overwrite with empty file!");
+  } else {
+    new File.fromUri(computeSharedGeneratedFile(repoDir))
+        .writeAsStringSync(message.sharedMessages, flush: true);
+    new File.fromUri(computeCfeGeneratedFile(repoDir))
+        .writeAsStringSync(message.cfeMessages, flush: true);
+  }
+
+  if (exitCode != 0) {
+    print("Something went wrong.");
+    return;
+  }
+
+  print("Now executing the non-failsafe version.");
+
+  ProcessResult run = Process.runSync(Platform.resolvedExecutable,
+      [Platform.script.resolve("generate_messages.dart").toFilePath()]);
+  stderr.writeln(run.stderr);
+  stdout.writeln(run.stdout);
+  if (run.exitCode != 0) exitCode = 1;
+  print("Done with exit code $exitCode");
+}
diff --git a/pkg/front_end/tool/_fasta/generate_messages_lib.dart b/pkg/front_end/tool/_fasta/generate_messages_lib.dart
new file mode 100644
index 00000000000..84f2c4affa0
--- /dev/null
+++ b/pkg/front_end/tool/_fasta/generate_messages_lib.dart
@@ -0,0 +1,459 @@
+// Copyright (c) 2024, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:io' show File, exitCode;
+
+import "package:_fe_analyzer_shared/src/messages/severity.dart"
+    show severityEnumNames;
+
+import 'package:yaml/yaml.dart' show loadYaml;
+
+Uri computeSharedGeneratedFile(Uri repoDir) {
+  return repoDir
+      .resolve("pkg/_fe_analyzer_shared/lib/src/messages/codes_generated.dart");
+}
+
+Uri computeCfeGeneratedFile(Uri repoDir) {
+  return repoDir
+      .resolve("pkg/front_end/lib/src/fasta/fasta_codes_cfe_generated.dart");
+}
+
+class Messages {
+  final String sharedMessages;
+  final String cfeMessages;
+
+  Messages(this.sharedMessages, this.cfeMessages);
+}
+
+Messages generateMessagesFilesRaw(
+    Uri repoDir, String Function(String) formatter) {
+  Uri messagesFile = repoDir.resolve("pkg/front_end/messages.yaml");
+  Map<dynamic, dynamic> yaml =
+      loadYaml(new File.fromUri(messagesFile).readAsStringSync());
+  StringBuffer sharedMessages = new StringBuffer();
+  StringBuffer cfeMessages = new StringBuffer();
+
+  const String preamble1 = """
+// Copyright (c) 2021, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+""";
+
+  const String preamble2 = """
+
+// NOTE: THIS FILE IS GENERATED. DO NOT EDIT.
+//
+// Instead modify 'pkg/front_end/messages.yaml' and run
+// 'pkg/front_end/tool/fasta generate-messages' to update.
+
+// ignore_for_file: lines_longer_than_80_chars
+""";
+
+  sharedMessages.writeln(preamble1);
+  sharedMessages.writeln(preamble2);
+  sharedMessages.writeln("""
+part of _fe_analyzer_shared.messages.codes;
+""");
+
+  cfeMessages.writeln(preamble1);
+  cfeMessages.writeln("""
+
+""");
+  cfeMessages.writeln(preamble2);
+  cfeMessages.writeln("""
+part of fasta.codes;
+""");
+
+  bool hasError = false;
+  int largestIndex = 0;
+  final indexNameMap = new Map<int, String>();
+
+  List<String> keys = yaml.keys.cast<String>().toList()..sort();
+  for (String name in keys) {
+    var description = yaml[name];
+    while (description is String) {
+      description = yaml[description];
+    }
+    Map<dynamic, dynamic>? map = description;
+    if (map == null) {
+      throw "No 'problemMessage:' in key $name.";
+    }
+    var index = map['index'];
+    if (index != null) {
+      if (index is! int || index < 1) {
+        print('Error: Expected positive int for "index:" field in $name,'
+            ' but found $index');
+        hasError = true;
+        index = -1;
+        // Continue looking for other problems.
+      } else {
+        String? otherName = indexNameMap[index];
+        if (otherName != null) {
+          print('Error: The "index:" field must be unique, '
+              'but is the same for $otherName and $name');
+          hasError = true;
+          // Continue looking for other problems.
+        } else {
+          indexNameMap[index] = name;
+          if (largestIndex < index) {
+            largestIndex = index;
+          }
+        }
+      }
+    }
+    Template template = compileTemplate(name, index, map['problemMessage'],
+        map['correctionMessage'], map['analyzerCode'], map['severity']);
+    if (template.isShared) {
+      sharedMessages.writeln(template.text);
+    } else {
+      cfeMessages.writeln(template.text);
+    }
+  }
+  if (largestIndex > indexNameMap.length) {
+    print('Error: The "index:" field values should be unique, consecutive'
+        ' whole numbers starting with 1.');
+    hasError = true;
+    // Fall through to print more information.
+  }
+  if (hasError) {
+    exitCode = 1;
+    print('The largest index is $largestIndex');
+    final sortedIndices = indexNameMap.keys.toList()..sort();
+    int nextAvailableIndex = largestIndex + 1;
+    for (int index = 1; index <= sortedIndices.length; ++index) {
+      if (sortedIndices[index - 1] != index) {
+        nextAvailableIndex = index;
+        break;
+      }
+    }
+    print('The next available index is ${nextAvailableIndex}');
+    return new Messages('', '');
+  }
+
+  return new Messages(formatter("$sharedMessages"), formatter("$cfeMessages"));
+}
+
+final RegExp placeholderPattern =
+    new RegExp("#\([-a-zA-Z0-9_]+\)(?:%\([0-9]*\)\.\([0-9]+\))?");
+
+class Template {
+  final String text;
+  final isShared;
+
+  Template(this.text, {this.isShared}) : assert(isShared != null);
+}
+
+Template compileTemplate(String name, int? index, String? problemMessage,
+    String? correctionMessage, Object? analyzerCode, String? severity) {
+  if (problemMessage == null) {
+    print('Error: missing problemMessage for message: $name');
+    exitCode = 1;
+    return new Template('', isShared: true);
+  }
+  // Remove trailing whitespace. This is necessary for templates defined with
+  // `|` (verbatim) as they always contain a trailing newline that we don't
+  // want.
+  problemMessage = problemMessage.trimRight();
+  var parameters = new Set<String>();
+  var conversions = new Set<String>();
+  var conversions2 = new Set<String>();
+  var arguments = new Set<String>();
+  bool hasLabeler = false;
+  bool canBeShared = true;
+  void ensureLabeler() {
+    if (hasLabeler) return;
+    conversions
+        .add("TypeLabeler labeler = new TypeLabeler(isNonNullableByDefault);");
+    hasLabeler = true;
+    canBeShared = false;
+  }
+
+  for (Match match in placeholderPattern
+      .allMatches("$problemMessage\n${correctionMessage ?? ''}")) {
+    String name = match[1]!;
+    String? padding = match[2];
+    String? fractionDigits = match[3];
+
+    String format(String name) {
+      String conversion;
+      if (fractionDigits == null) {
+        conversion = "'\$$name'";
+      } else {
+        conversion = "$name.toStringAsFixed($fractionDigits)";
+      }
+      if (padding!.isNotEmpty) {
+        if (padding.startsWith("0")) {
+          conversion += ".padLeft(${int.parse(padding)}, '0')";
+        } else {
+          conversion += ".padLeft(${int.parse(padding)})";
+        }
+      }
+      return conversion;
+    }
+
+    switch (name) {
+      case "character":
+        parameters.add("String character");
+        conversions.add("if (character.runes.length != 1)"
+            "throw \"Not a character '\${character}'\";");
+        arguments.add("'$name': character");
+        break;
+
+      case "unicode":
+        // Write unicode value using at least four (but otherwise no more than
+        // necessary) hex digits, using uppercase letters.
+        // http://www.unicode.org/versions/Unicode10.0.0/appA.pdf
+        parameters.add("int codePoint");
+        conversions.add("String unicode = \"U+\${codePoint.toRadixString(16)"
+            ".toUpperCase().padLeft(4, '0')}\";");
+        arguments.add("'$name': codePoint");
+        break;
+
+      case "name":
+        parameters.add("String name");
+        conversions.add("if (name.isEmpty) throw 'No name provided';");
+        arguments.add("'$name': name");
+        conversions.add("name = demangleMixinApplicationName(name);");
+        break;
+
+      case "name2":
+        parameters.add("String name2");
+        conversions.add("if (name2.isEmpty) throw 'No name provided';");
+        arguments.add("'$name': name2");
+        conversions.add("name2 = demangleMixinApplicationName(name2);");
+        break;
+
+      case "name3":
+        parameters.add("String name3");
+        conversions.add("if (name3.isEmpty) throw 'No name provided';");
+        arguments.add("'$name': name3");
+        conversions.add("name3 = demangleMixinApplicationName(name3);");
+        break;
+
+      case "name4":
+        parameters.add("String name4");
+        conversions.add("if (name4.isEmpty) throw 'No name provided';");
+        arguments.add("'$name': name4");
+        conversions.add("name4 = demangleMixinApplicationName(name4);");
+        break;
+
+      case "nameOKEmpty":
+        parameters.add("String nameOKEmpty");
+        conversions.add("if (nameOKEmpty.isEmpty) "
+            "nameOKEmpty = '(unnamed)';");
+        arguments.add("'nameOKEmpty': nameOKEmpty");
+        break;
+
+      case "names":
+        parameters.add("List<String> _names");
+        conversions.add("if (_names.isEmpty) throw 'No names provided';");
+        arguments.add("'$name': _names");
+        conversions.add("String names = itemizeNames(_names);");
+        break;
+
+      case "lexeme":
+        parameters.add("Token token");
+        conversions.add("String lexeme = token.lexeme;");
+        arguments.add("'$name': token");
+        break;
+
+      case "lexeme2":
+        parameters.add("Token token2");
+        conversions.add("String lexeme2 = token2.lexeme;");
+        arguments.add("'$name': token2");
+        break;
+
+      case "string":
+        parameters.add("String string");
+        conversions.add("if (string.isEmpty) throw 'No string provided';");
+        arguments.add("'$name': string");
+        break;
+
+      case "string2":
+        parameters.add("String string2");
+        conversions.add("if (string2.isEmpty) throw 'No string provided';");
+        arguments.add("'$name': string2");
+        break;
+
+      case "string3":
+        parameters.add("String string3");
+        conversions.add("if (string3.isEmpty) throw 'No string provided';");
+        arguments.add("'$name': string3");
+        break;
+
+      case "stringOKEmpty":
+        parameters.add("String stringOKEmpty");
+        conversions.add("if (stringOKEmpty.isEmpty) "
+            "stringOKEmpty = '(empty)';");
+        arguments.add("'$name': stringOKEmpty");
+        break;
+
+      case "type":
+      case "type2":
+      case "type3":
+      case "type4":
+        parameters.add("DartType _${name}");
+        ensureLabeler();
+        conversions
+            .add("List<Object> ${name}Parts = labeler.labelType(_${name});");
+        conversions2.add("String ${name} = ${name}Parts.join();");
+        arguments.add("'${name}': _${name}");
+        break;
+
+      case "uri":
+        parameters.add("Uri uri_");
+        conversions.add("String? uri = relativizeUri(uri_);");
+        arguments.add("'$name': uri_");
+        break;
+
+      case "uri2":
+        parameters.add("Uri uri2_");
+        conversions.add("String? uri2 = relativizeUri(uri2_);");
+        arguments.add("'$name': uri2_");
+        break;
+
+      case "uri3":
+        parameters.add("Uri uri3_");
+        conversions.add("String? uri3 = relativizeUri(uri3_);");
+        arguments.add("'$name': uri3_");
+        break;
+
+      case "count":
+        parameters.add("int count");
+        arguments.add("'$name': count");
+        break;
+
+      case "count2":
+        parameters.add("int count2");
+        arguments.add("'$name': count2");
+        break;
+
+      case "constant":
+        parameters.add("Constant _constant");
+        ensureLabeler();
+        conversions.add(
+            "List<Object> ${name}Parts = labeler.labelConstant(_${name});");
+        conversions2.add("String ${name} = ${name}Parts.join();");
+        arguments.add("'$name': _constant");
+        break;
+
+      case "num1":
+        parameters.add("num _num1");
+        conversions.add("String num1 = ${format('_num1')};");
+        arguments.add("'$name': _num1");
+        break;
+
+      case "num2":
+        parameters.add("num _num2");
+        conversions.add("String num2 = ${format('_num2')};");
+        arguments.add("'$name': _num2");
+        break;
+
+      case "num3":
+        parameters.add("num _num3");
+        conversions.add("String num3 = ${format('_num3')};");
+        arguments.add("'$name': _num3");
+        break;
+
+      default:
+        throw "Unhandled placeholder in template: '$name'";
+    }
+  }
+
+  if (hasLabeler) {
+    parameters.add("bool isNonNullableByDefault");
+  }
+
+  conversions.addAll(conversions2);
+
+  String interpolate(String text) {
+    text = text
+        .replaceAll(r"$", r"\$")
+        .replaceAllMapped(placeholderPattern, (Match m) => "\${${m[1]}}");
+    return "\"\"\"$text\"\"\"";
+  }
+
+  List<String> codeArguments = <String>[];
+  if (index != null) {
+    codeArguments.add('index: $index');
+  } else if (analyzerCode != null) {
+    if (analyzerCode is String) {
+      analyzerCode = <String>[analyzerCode];
+    }
+    List<Object?> codes = analyzerCode as List<Object?>;
+    // If "index:" is defined, then "analyzerCode:" should not be generated
+    // in the front end. See comment in messages.yaml
+    codeArguments.add('analyzerCodes: <String>["${codes.join('", "')}"]');
+  }
+  if (severity != null) {
+    String? severityEnumName = severityEnumNames[severity];
+    if (severityEnumName == null) {
+      throw "Unknown severity '$severity'";
+    }
+    codeArguments.add('severity: Severity.$severityEnumName');
+  }
+
+  if (parameters.isEmpty && conversions.isEmpty && arguments.isEmpty) {
+    codeArguments.add('problemMessage: r"""$problemMessage"""');
+    if (correctionMessage != null) {
+      codeArguments.add('correctionMessage: r"""$correctionMessage"""');
+    }
+
+    return new Template("""
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const Code<Null> code$name = message$name;
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const MessageCode message$name =
+    const MessageCode(\"$name\", ${codeArguments.join(', ')},);
+""", isShared: canBeShared);
+  }
+
+  List<String> templateArguments = <String>[];
+  templateArguments.add('\"$name\"');
+  templateArguments.add('problemMessageTemplate: r"""$problemMessage"""');
+  if (correctionMessage != null) {
+    templateArguments
+        .add('correctionMessageTemplate: r"""$correctionMessage"""');
+  }
+
+  templateArguments.add("withArguments: _withArguments$name");
+
+  List<String> messageArguments = <String>[];
+  String message = interpolate(problemMessage);
+  if (hasLabeler) {
+    message += " + labeler.originMessages";
+  }
+  messageArguments.add("problemMessage: ${message}");
+  if (correctionMessage != null) {
+    messageArguments
+        .add("correctionMessage: ${interpolate(correctionMessage)}");
+  }
+  messageArguments.add("arguments: { ${arguments.join(', ')}, }");
+
+  if (codeArguments.isNotEmpty) {
+    codeArguments.add("");
+  }
+
+  return new Template("""
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const Template<Message Function(${parameters.join(', ')})> template$name =
+    const Template<Message Function(${parameters.join(', ')})>(
+        ${templateArguments.join(', ')},);
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const Code<Message Function(${parameters.join(', ')})> code$name =
+    const Code<Message Function(${parameters.join(', ')})>(
+        \"$name\", ${codeArguments.join(', ')});
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+Message _withArguments$name(${parameters.join(', ')}) {
+  ${conversions.join('\n  ')}
+  return new Message(
+     code$name,
+     ${messageArguments.join(', ')},);
+}
+""", isShared: canBeShared);
+}