$_

packages/pigeon/example/app/lib/src/messages.g.dart

@@ -98,111 +98,113 @@ class ExampleHostApi {
   /// available for dependency injection.  If it is left null, the default
   /// BinaryMessenger will be used which routes to the host platform.
   ExampleHostApi({BinaryMessenger? binaryMessenger})
-      : _binaryMessenger = binaryMessenger;
-  final BinaryMessenger? _binaryMessenger;
+      : $_binaryMessenger = binaryMessenger;
+  final BinaryMessenger? $_binaryMessenger;
 
-  static const MessageCodec<Object?> codec = _ExampleHostApiCodec();
+  static const MessageCodec<Object?> $_codec = _ExampleHostApiCodec();
 
   Future<String> getHostLanguage() async {
-    const String channelName =
+    const String $_channelName =
         'dev.flutter.pigeon.pigeon_example_package.ExampleHostApi.getHostLanguage';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> $_channel = BasicMessageChannel<Object?>(
+      $_channelName,
+      $_codec,
+      binaryMessenger: $_binaryMessenger,
     );
-    final List<Object?>? replyList = await channel.send(null) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? $_replyList =
+        await $_channel.send(null) as List<Object?>?;
+    if ($_replyList == null) {
+      throw _createConnectionError($_channelName);
+    } else if ($_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: $_replyList[0]! as String,
+        message: $_replyList[1] as String?,
+        details: $_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if ($_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as String?)!;
+      return ($_replyList[0] as String?)!;
     }
   }
 
   Future<int> add(int a, int b) async {
-    const String channelName =
+    const String $_channelName =
         'dev.flutter.pigeon.pigeon_example_package.ExampleHostApi.add';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> $_channel = BasicMessageChannel<Object?>(
+      $_channelName,
+      $_codec,
+      binaryMessenger: $_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[a, b]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? $_replyList =
+        await $_channel.send(<Object?>[a, b]) as List<Object?>?;
+    if ($_replyList == null) {
+      throw _createConnectionError($_channelName);
+    } else if ($_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: $_replyList[0]! as String,
+        message: $_replyList[1] as String?,
+        details: $_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if ($_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as int?)!;
+      return ($_replyList[0] as int?)!;
     }
   }
 
   Future<bool> sendMessage(MessageData message) async {
-    const String channelName =
+    const String $_channelName =
         'dev.flutter.pigeon.pigeon_example_package.ExampleHostApi.sendMessage';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> $_channel = BasicMessageChannel<Object?>(
+      $_channelName,
+      $_codec,
+      binaryMessenger: $_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[message]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? $_replyList =
+        await $_channel.send(<Object?>[message]) as List<Object?>?;
+    if ($_replyList == null) {
+      throw _createConnectionError($_channelName);
+    } else if ($_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: $_replyList[0]! as String,
+        message: $_replyList[1] as String?,
+        details: $_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if ($_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as bool?)!;
+      return ($_replyList[0] as bool?)!;
     }
   }
 }
 
 abstract class MessageFlutterApi {
-  static const MessageCodec<Object?> codec = StandardMessageCodec();
+  static const MessageCodec<Object?> $_codec = StandardMessageCodec();
 
   String flutterMethod(String? aString);
 
   static void setup(MessageFlutterApi? api,
       {BinaryMessenger? binaryMessenger}) {
     {
-      final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      final BasicMessageChannel<Object?> $_channel = BasicMessageChannel<
+              Object?>(
           'dev.flutter.pigeon.pigeon_example_package.MessageFlutterApi.flutterMethod',
-          codec,
+          $_codec,
           binaryMessenger: binaryMessenger);
       if (api == null) {
-        channel.setMessageHandler(null);
+        $_channel.setMessageHandler(null);
       } else {
-        channel.setMessageHandler((Object? message) async {
+        $_channel.setMessageHandler((Object? message) async {
           assert(message != null,
               'Argument for dev.flutter.pigeon.pigeon_example_package.MessageFlutterApi.flutterMethod was null.');
           final List<Object?> args = (message as List<Object?>?)!;

packages/pigeon/lib/ast.dart

@@ -284,22 +284,22 @@ class Parameter extends NamedType {
         isPositional = isPositional ?? true,
         isRequired = isRequired ?? true;
 
-  /// Return `true` if this parameter is a named parameter.
+  /// Whether this parameter is a named parameter.
   ///
   /// Defaults to `true`.
   final bool isNamed;
 
-  /// Return `true` if this parameter is an optional parameter.
+  /// Whether this parameter is an optional parameter.
   ///
   /// Defaults to `false`.
   final bool isOptional;
 
-  /// Return `true` if this parameter is a positional parameter.
+  /// Whether this parameter is a positional parameter.
   ///
   /// Defaults to `true`.
   final bool isPositional;
 
-  /// Return `true` if this parameter is a required parameter.
+  /// Whether this parameter is a required parameter.
   ///
   /// Defaults to `true`.
   final bool isRequired;

packages/pigeon/lib/dart_generator.dart

@@ -12,6 +12,8 @@ import 'generator_tools.dart';
 /// Documentation comment open symbol.
 const String _docCommentPrefix = '///';
 
+const String _varNamePrefix = r'$_';
+
 /// Documentation comment spec.
 const DocumentCommentSpecification _docCommentSpec =
     DocumentCommentSpecification(_docCommentPrefix);
@@ -324,8 +326,8 @@ $resultAt != null
         indent.writeln(
             'static TestDefaultBinaryMessengerBinding? get _testBinaryMessengerBinding => TestDefaultBinaryMessengerBinding.instance;');
       }
-      indent
-          .writeln('static const MessageCodec<Object?> codec = $codecName();');
+      indent.writeln(
+          'static const MessageCodec<Object?> ${_varNamePrefix}codec = $codecName();');
       indent.newln();
       for (final Method func in api.methods) {
         addDocumentationComments(
@@ -346,20 +348,20 @@ $resultAt != null
           indent.write('');
           indent.addScoped('{', '}', () {
             indent.writeln(
-              'final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(',
+              'final BasicMessageChannel<Object?> ${_varNamePrefix}channel = BasicMessageChannel<Object?>(',
             );
             final String channelName = channelNameFunc == null
                 ? makeChannelName(api, func, dartPackageName)
                 : channelNameFunc(func);
             indent.nest(2, () {
-              indent.writeln("'$channelName', codec,");
+              indent.writeln("'$channelName', ${_varNamePrefix}codec,");
               indent.writeln(
                 'binaryMessenger: binaryMessenger);',
               );
             });
             final String messageHandlerSetterWithOpeningParentheses = isMockHandler
-                ? '_testBinaryMessengerBinding!.defaultBinaryMessenger.setMockDecodedMessageHandler<Object?>(channel, '
-                : 'channel.setMessageHandler(';
+                ? '_testBinaryMessengerBinding!.defaultBinaryMessenger.setMockDecodedMessageHandler<Object?>(${_varNamePrefix}channel, '
+                : '${_varNamePrefix}channel.setMessageHandler(';
             indent.write('if (api == null) ');
             indent.addScoped('{', '}', () {
               indent.writeln(
@@ -499,12 +501,12 @@ $resultAt != null
 /// available for dependency injection.  If it is left null, the default
 /// BinaryMessenger will be used which routes to the host platform.
 ${api.name}({BinaryMessenger? binaryMessenger})
-\t\t: _binaryMessenger = binaryMessenger;
-final BinaryMessenger? _binaryMessenger;
+\t\t: ${_varNamePrefix}binaryMessenger = binaryMessenger;
+final BinaryMessenger? ${_varNamePrefix}binaryMessenger;
 ''');
 
-      indent
-          .writeln('static const MessageCodec<Object?> codec = $codecName();');
+      indent.writeln(
+          'static const MessageCodec<Object?> ${_varNamePrefix}codec = $codecName();');
       indent.newln();
       for (final Method func in api.methods) {
         if (!first) {
@@ -534,17 +536,18 @@ final BinaryMessenger? _binaryMessenger;
         );
         indent.addScoped('{', '}', () {
           indent.writeln(
-              "const String channelName = '${makeChannelName(api, func, dartPackageName)}';");
+              "const String ${_varNamePrefix}channelName = '${makeChannelName(api, func, dartPackageName)}';");
           indent.writeScoped(
-              'final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(',
+              'final BasicMessageChannel<Object?> ${_varNamePrefix}channel = BasicMessageChannel<Object?>(',
               ');', () {
-            indent.writeln('channelName,');
-            indent.writeln('codec,');
-            indent.writeln('binaryMessenger: _binaryMessenger,');
+            indent.writeln('${_varNamePrefix}channelName,');
+            indent.writeln('${_varNamePrefix}codec,');
+            indent
+                .writeln('binaryMessenger: ${_varNamePrefix}binaryMessenger,');
           });
           final String returnType = _makeGenericTypeArguments(func.returnType);
           final String genericCastCall = _makeGenericCastCall(func.returnType);
-          const String accessor = 'replyList[0]';
+          const String accessor = '${_varNamePrefix}replyList[0]';
           // Avoid warnings from pointlessly casting to `Object?`.
           final String nullablyTypedAccessor =
               returnType == 'Object' ? accessor : '($accessor as $returnType?)';
@@ -567,22 +570,22 @@ final BinaryMessenger? _binaryMessenger;
           returnStatement = '$returnStatement;';
 
           indent.format('''
-final List<Object?>? replyList =
-\t\tawait channel.send($sendArgument) as List<Object?>?;
-if (replyList == null) {
-\tthrow _createConnectionError(channelName);
-} else if (replyList.length > 1) {
+final List<Object?>? ${_varNamePrefix}replyList =
+\t\tawait ${_varNamePrefix}channel.send($sendArgument) as List<Object?>?;
+if (${_varNamePrefix}replyList == null) {
+\tthrow _createConnectionError(${_varNamePrefix}channelName);
+} else if (${_varNamePrefix}replyList.length > 1) {
 \tthrow PlatformException(
-\t\tcode: replyList[0]! as String,
-\t\tmessage: replyList[1] as String?,
-\t\tdetails: replyList[2],
+\t\tcode: ${_varNamePrefix}replyList[0]! as String,
+\t\tmessage: ${_varNamePrefix}replyList[1] as String?,
+\t\tdetails: ${_varNamePrefix}replyList[2],
 \t);''');
           // On iOS we can return nil from functions to accommodate error
           // handling.  Returning a nil value and not returning an error is an
           // exception.
           if (!func.returnType.isNullable && !func.returnType.isVoid) {
             indent.format('''
-} else if (replyList[0] == null) {
+} else if (${_varNamePrefix}replyList[0] == null) {
 \tthrow PlatformException(
 \t\tcode: 'null-error',
 \t\tmessage: 'Host platform returned null value for non-null return value.',

packages/pigeon/lib/pigeon_lib.dart

@@ -926,6 +926,7 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
         for (final Parameter param in func.parameters) {
           paramList.add(param.copyWithType(_attachClassesAndEnums(param.type)));
         }
+        func.parameters = paramList;
         func.returnType = _attachClassesAndEnums(func.returnType);
       }
     }
@@ -1129,17 +1130,13 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
       if (formalParameter is dart_ast.DefaultFormalParameter) {
         defaultValue = formalParameter.defaultValue?.toString();
       }
-      final bool isNamed = simpleFormalParameter.isNamed;
-      final bool isOptional = simpleFormalParameter.isOptional;
-      final bool isPositional = simpleFormalParameter.isPositional;
-      final bool isRequired = simpleFormalParameter.isRequired;
 
       return formalParameterToPigeonParameter(
         simpleFormalParameter,
-        isNamed: isNamed,
-        isOptional: isOptional,
-        isPositional: isPositional,
-        isRequired: isRequired,
+        isNamed: simpleFormalParameter.isNamed,
+        isOptional: simpleFormalParameter.isOptional,
+        isPositional: simpleFormalParameter.isPositional,
+        isRequired: simpleFormalParameter.isRequired,
         defaultValue: defaultValue,
       );
     } else {

packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/background_platform_channels.gen.dart

@@ -24,36 +24,36 @@ class BackgroundApi2Host {
   /// available for dependency injection.  If it is left null, the default
   /// BinaryMessenger will be used which routes to the host platform.
   BackgroundApi2Host({BinaryMessenger? binaryMessenger})
-      : _binaryMessenger = binaryMessenger;
-  final BinaryMessenger? _binaryMessenger;
+      : $_binaryMessenger = binaryMessenger;
+  final BinaryMessenger? $_binaryMessenger;
 
-  static const MessageCodec<Object?> codec = StandardMessageCodec();
+  static const MessageCodec<Object?> $_codec = StandardMessageCodec();
 
   Future<int> add(int x, int y) async {
-    const String channelName =
+    const String $_channelName =
         'dev.flutter.pigeon.pigeon_integration_tests.BackgroundApi2Host.add';
-    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
-      channelName,
-      codec,
-      binaryMessenger: _binaryMessenger,
+    final BasicMessageChannel<Object?> $_channel = BasicMessageChannel<Object?>(
+      $_channelName,
+      $_codec,
+      binaryMessenger: $_binaryMessenger,
     );
-    final List<Object?>? replyList =
-        await channel.send(<Object?>[x, y]) as List<Object?>?;
-    if (replyList == null) {
-      throw _createConnectionError(channelName);
-    } else if (replyList.length > 1) {
+    final List<Object?>? $_replyList =
+        await $_channel.send(<Object?>[x, y]) as List<Object?>?;
+    if ($_replyList == null) {
+      throw _createConnectionError($_channelName);
+    } else if ($_replyList.length > 1) {
       throw PlatformException(
-        code: replyList[0]! as String,
-        message: replyList[1] as String?,
-        details: replyList[2],
+        code: $_replyList[0]! as String,
+        message: $_replyList[1] as String?,
+        details: $_replyList[2],
       );
-    } else if (replyList[0] == null) {
+    } else if ($_replyList[0] == null) {
       throw PlatformException(
         code: 'null-error',
         message: 'Host platform returned null value for non-null return value.',
       );
     } else {
-      return (replyList[0] as int?)!;
+      return ($_replyList[0] as int?)!;
     }
   }
 }